The document describes the steps to set up and run a 1 ns molecular dynamics simulation of a polyvaline peptide using NAMD. The steps include: 1) initializing the topology, coordinate, and force field files; 2) minimizing the energy of the initial structure to relax steric clashes; 3) heating the system to 300K; 4) equilibrating the system at 300K; and 5) running a 1 ns production simulation to obtain conformational properties of the peptide.
Optimal and Power Aware BIST for Delay Testing of System-On-ChipIDES Editor
Test engineering for fault tolerant VLSI systems is
encumbered with optimization requisites for hardware
overhead, test power and test time. The high level quality of
these complex high-speed VLSI circuits can be assured only
through delay testing, which involves checking for accurate
temporal behavior. In the present paper, a data-path based
built-in test pattern generator (TPG) that generates iterative
pseudo-exhaustive two-patterns (IPET) for parallel delay
testing of modules with different input cone capacities is
implemented. Further, in the present study a CMOS
implementation of low power architecture (LPA) for scan based
built-in self test (BIST) for delay testing and combinational
testing is carried out. This reduces test power dissipation in
the circuit under test (CUT). Experimental results and
comparisons with pre-existing methods prove the reduction
in hardware overhead and test-time.
Breaking the 49 qubit barrier in the simulation of quantum circuitshquynh
This paper presents a new method for classically simulating quantum circuits with up to 56 qubits. The method uses a tensor representation rather than a matrix representation, allowing quantum circuits to be decomposed and simulated in arbitrary order. The authors demonstrate the method by simulating a 49-qubit circuit with depth 27 and a 56-qubit circuit with depth 23. These simulations required 4.5TB and 3.0TB of memory respectively, within the capabilities of existing supercomputers, whereas previous methods would have required impractical amounts of memory. The simulations confirm theoretical predictions about the distribution of output probabilities.
This document contains 9 tutorials related to the subject of Advanced Computer Architecture for a BTech course at M.M.M. Engineering College in Gorakhpur, India during the 2007-2008 session. Each tutorial contains 2 questions related to topics such as instruction set architecture, performance analysis, parallelization, pipelining, multiprocessing, parallel algorithms and synchronization techniques.
This document discusses placement in VLSI physical design. It defines placement as arranging modules on a layout surface with fixed shapes and pin locations. The key goals of placement are to minimize area, reduce critical net lengths, and ensure routability. Different placement problems are discussed at the system, board and chip levels. Common placement algorithms described include simulated annealing, genetic algorithms, and force-directed placement.
Optimal Unate Decomposition Method for Synthesis of Mixed CMOS VLSI CircuitsVLSICS Design
Static CMOS logic style is often the choice of designers for synthesizing low power circuits. This style is
robust in terms of noise integrity however, it offers less speed. Domino logic style, as an alternative is often
found in critical paths of various large scale high performance circuits. Yet, due to high switching activity
they are not suitable for synthesis of low power circuits. To achieve both power and speed benefits, we
propose a method of designing circuit using mixed CMOS logic style, taking advantages of both static and
Domino logic styles. For a given circuit, we extract the unate and binate components using a unate
decomposition algorithm. These are optimized such that the resulting circuit is optimum in terms of power,
area and delay. To do this, a multi-objective genetic algorithm is employed. The optimized unate and binate
blocks are mapped using Domino and static cell libraries, respectively. Testing the efficacy of our
approach with ISCAS85 and MCNC89 benchmark circuits showed an improvement of 25% in delay and
22% in transistor count with 12% more power dissipation compared to circuits with only static CMOS
logic. Thus, mixed CMOS circuits are promising in high speed and area constraint applications.
Regulation Analysis using Restricted Boltzmann MachinesPatrick Michl
This document summarizes a presentation on using restricted Boltzmann machines to model the regulation of metabolism. It discusses using RBMs as a graphical model to represent topological network structures and preserve dependencies between transcription factors, signals, and enzymes in metabolic pathways. The document outlines how an RBM represents the network as visible and hidden units, learns the dependencies through an energy-based model and stochastic gradient descent, and validates the results on simulated data representing simple regulatory relationships.
This document discusses profiling and optimization of sparse matrix-vector multiplication (SpMV). It proposes a system that uses performance modeling to predict execution times of different SpMV kernels for a given sparse matrix stored in various formats. An auto-selection algorithm then identifies the optimal storage format and predicted execution time based on the performance modeling. The system was evaluated on NVIDIA GPUs and achieved accurate performance predictions to select the best SpMV solution for a target sparse matrix.
Optimal and Power Aware BIST for Delay Testing of System-On-ChipIDES Editor
Test engineering for fault tolerant VLSI systems is
encumbered with optimization requisites for hardware
overhead, test power and test time. The high level quality of
these complex high-speed VLSI circuits can be assured only
through delay testing, which involves checking for accurate
temporal behavior. In the present paper, a data-path based
built-in test pattern generator (TPG) that generates iterative
pseudo-exhaustive two-patterns (IPET) for parallel delay
testing of modules with different input cone capacities is
implemented. Further, in the present study a CMOS
implementation of low power architecture (LPA) for scan based
built-in self test (BIST) for delay testing and combinational
testing is carried out. This reduces test power dissipation in
the circuit under test (CUT). Experimental results and
comparisons with pre-existing methods prove the reduction
in hardware overhead and test-time.
Breaking the 49 qubit barrier in the simulation of quantum circuitshquynh
This paper presents a new method for classically simulating quantum circuits with up to 56 qubits. The method uses a tensor representation rather than a matrix representation, allowing quantum circuits to be decomposed and simulated in arbitrary order. The authors demonstrate the method by simulating a 49-qubit circuit with depth 27 and a 56-qubit circuit with depth 23. These simulations required 4.5TB and 3.0TB of memory respectively, within the capabilities of existing supercomputers, whereas previous methods would have required impractical amounts of memory. The simulations confirm theoretical predictions about the distribution of output probabilities.
This document contains 9 tutorials related to the subject of Advanced Computer Architecture for a BTech course at M.M.M. Engineering College in Gorakhpur, India during the 2007-2008 session. Each tutorial contains 2 questions related to topics such as instruction set architecture, performance analysis, parallelization, pipelining, multiprocessing, parallel algorithms and synchronization techniques.
This document discusses placement in VLSI physical design. It defines placement as arranging modules on a layout surface with fixed shapes and pin locations. The key goals of placement are to minimize area, reduce critical net lengths, and ensure routability. Different placement problems are discussed at the system, board and chip levels. Common placement algorithms described include simulated annealing, genetic algorithms, and force-directed placement.
Optimal Unate Decomposition Method for Synthesis of Mixed CMOS VLSI CircuitsVLSICS Design
Static CMOS logic style is often the choice of designers for synthesizing low power circuits. This style is
robust in terms of noise integrity however, it offers less speed. Domino logic style, as an alternative is often
found in critical paths of various large scale high performance circuits. Yet, due to high switching activity
they are not suitable for synthesis of low power circuits. To achieve both power and speed benefits, we
propose a method of designing circuit using mixed CMOS logic style, taking advantages of both static and
Domino logic styles. For a given circuit, we extract the unate and binate components using a unate
decomposition algorithm. These are optimized such that the resulting circuit is optimum in terms of power,
area and delay. To do this, a multi-objective genetic algorithm is employed. The optimized unate and binate
blocks are mapped using Domino and static cell libraries, respectively. Testing the efficacy of our
approach with ISCAS85 and MCNC89 benchmark circuits showed an improvement of 25% in delay and
22% in transistor count with 12% more power dissipation compared to circuits with only static CMOS
logic. Thus, mixed CMOS circuits are promising in high speed and area constraint applications.
Regulation Analysis using Restricted Boltzmann MachinesPatrick Michl
This document summarizes a presentation on using restricted Boltzmann machines to model the regulation of metabolism. It discusses using RBMs as a graphical model to represent topological network structures and preserve dependencies between transcription factors, signals, and enzymes in metabolic pathways. The document outlines how an RBM represents the network as visible and hidden units, learns the dependencies through an energy-based model and stochastic gradient descent, and validates the results on simulated data representing simple regulatory relationships.
This document discusses profiling and optimization of sparse matrix-vector multiplication (SpMV). It proposes a system that uses performance modeling to predict execution times of different SpMV kernels for a given sparse matrix stored in various formats. An auto-selection algorithm then identifies the optimal storage format and predicted execution time based on the performance modeling. The system was evaluated on NVIDIA GPUs and achieved accurate performance predictions to select the best SpMV solution for a target sparse matrix.
This document discusses trends in embedded systems and multiprocessor system-on-chips (MPSoCs). It summarizes issues with traditional bus and crossbar networks for SoCs like latency, priority, bandwidth limitation, and cost. It then describes a routing congestion-aware and power-aware mapping algorithm for MPSoCs that arranges task graphs by latency constraint severity and maps cores to tiles to minimize congestion while meeting latency constraints.
This document discusses trends in embedded systems and multiprocessor system-on-chips (MPSoCs). MPSoCs integrate multiple processors into a single chip to improve performance. This is necessary as system needs increase and more components are integrated onto chips. MPSoCs address issues with traditional bus and crossbar interconnects like latency, bandwidth limitations, and routing congestion. The document then describes algorithms for mapping tasks to cores in an MPSoC while considering latency constraints, network congestion, and communication power.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Study and Development of an Energy Saving Mechanical SystemIDES Editor
A new energy-saving mechanical system with
automatically controlled air valves has been proposed by
investigator and the preliminary model setup has been tested.
The testing results indicated the proper function of this
energy-saving mechanical system. This mechanical system
model has been simulated and analyzed by the computational
aided engineering solution. The major advantages of this
mechanical system include: simple and compact in design,
higher efficiency in mechanical functioning, quiet in
manufacturing operation, less energy losses due to less
frictional forces in this free piston-cylinder setup, selfadjustable
in operational parameter to improve the system
performance, and etc.
logical effort based dual mode logic gates by mallikaMallika Naidu
Logic optimization and timing estimations are basic tasks for digital circuit designers. Dual Mode Logic (DML) allows operation in two modes such as static and dynamic modes. DML gates can be switched between these two modes on feature very low power dissipation in the static mode and high speed of operation in dynamic mode which is achieved at the expense of increased power dissipation. We introduce the logical effort (LE) methodology for the CMOS-based family. The proposed methodology allows path length, delay and power optimization for number of stages with load. Logical effort is the transistor sizing optimization methodology reduces the delay and power with number of stages with any static logic gate. The proposed optimization is shown for dual mode logic gates with logical effort using Digital Schematic Tool (DSCH).
This document describes the process of global routing in VLSI physical design. Global routing assigns wiring paths between circuit components at a coarse level of granularity by partitioning the chip into routing regions and assigning nets to these regions. It aims to minimize total wirelength and reduce delays on critical nets. Routing regions are represented using graphs to model available routing resources. Common algorithms discussed include rectilinear Steiner tree construction and sequential Steiner tree heuristics to find minimum path routes between pins in the global routing stage.
This document discusses the theoretical and experimental study of dynamics and control of a two-link flexible robot arm. It presents the following:
1) A linear dynamic model of the robot arm is constructed using Ritz's approach and validated experimentally.
2) Three active control schemes are designed using pole placement technique for path tracking and vibration suppression, and tested via simulation.
3) A discrete-time state variable feedback control scheme is presented and designed to control the robot arm's motion using three sensors for position and curvature feedback.
Speech recognition using hidden markov model mee 03_19NGUYEN_SPKT
This document describes the implementation of a speech recognition system using hidden Markov models (HMMs) on a DSK-ADSP-BF533 EZ-KIT LITE REV 1.5 digital signal processor board. The key steps taken are:
1. Feature extraction from speech signals by calculating mel frequency cepstrum coefficients (MFCCs). This involves preprocessing the signal, framing and windowing, Fourier transform, mel filtering, and discrete cosine transform.
2. Training HMMs to create models of words using an iterative process that calculates mean, variance, state transition probabilities, and output distributions from multiple utterances of words.
3. Testing utterances against trained models using the Viterbi
A Novel Flipflop Topology for High Speed and Area Efficient Logic Structure D...IOSR Journals
In high speed data path network flop is one of the major functional elements to store intermediate
results and data at different stages. But the most important problem is huge power utilization due to switching
activity and increase in clock period that is Timing Latency; causes the performance of data path in digital
design is decreased. The existing works implement various Flipflop topology in data path structure design such
as conventional Transmission Gate Based Master Slave Filpflop (TGMS FF), Write Port Master Slave Flip-flop
(WPMS) and Clocked Complementary Metal Oxide Semiconductor (C2MOS). In WPMS method, area is
minimized but delay is increased. In C2MOS technique Power consumption and delay is reduced, but there is a
definite scope to reduce Power, area and delay. In this paper a Modified Clocked Complementary Metal Oxide
Semiconductor Latch (mC2MOS Latch) is proposed and delay, power is again reduced up to 60% and the area
of the circuit is also reduced while comparing with previous methods.
A High Speed Pipelined Dynamic Circuit Implementation Using Modified TSPC Log...IDES Editor
This document presents a modified True Single Phase Clock (TSPC) logic design style to implement high-speed pipelined circuits with improved performance. The modified style reduces transistor count by 40-50% compared to the standard TSPC style by allowing logic functions to be implemented using either the N-block or P-block. A 3-bit pipelined adder was designed using the modified style and showed a 46-47% reduction in transistors and 50% reduction in clock cycles compared to the standard style. The modified style offers benefits like lower transistor count, reduced latency, increased throughput, and lower power consumption for pipelined circuits.
This document summarizes the development of a multi-level reduced order modeling (MLROM) methodology. MLROM uses a physics-informed approach to extract an active subspace by executing a high-fidelity model on sub-domains, like a pin cell, rather than the full domain like the whole core. This reduces computational cost. Error bounds for the reduced model are established using the pin-cell determined active subspace and verified against full-order lattice simulations. Future work will apply MLROM to core-wide calculations using representative lattices to capture the core-wide active subspace.
The document describes an efficient FPGA-based architecture for implementing a delayed least mean square (DLMS) adaptive filter using fixed-point arithmetic. The proposed architecture aims to reduce adaptation delay and optimize area, delay, and power efficiency. It uses a novel partial product generator and balanced pipelining across computation blocks to minimize critical path delays. Synthesis results show the proposed design offers lower area and higher maximum frequency than existing systolic structures for various filter lengths. The design was implemented on a Spartan-3 FPGA and results matched simulations for an 8-tap filter.
1) The document contains solutions to chapter 8 homework problems involving page tables, page replacement policies, working set size, and memory management with both paging and segmentation.
2) Key concepts covered include virtual to physical address translation using page tables, page replacement algorithms like FIFO and LRU, calculating memory access rates, and addressing with multiple levels of page tables and segmentation.
3) Memory management techniques like page tables, page replacement, and multi-level addressing schemes are analyzed to solve problems involving virtual memory configuration, address translation, and modeling memory access patterns.
This document summarizes a research paper that proposes a Model Reference Adaptive Controller (MRAC) for online estimation of rotor time constant and speed for indirect field oriented control of an induction motor drive. The MRAC design is based on reactive power concepts and consists of a reference model that is independent of slip speed and an adjustable model that depends on slip speed. The difference between the instantaneous reactive power computed by the reference model and the steady-state reactive power computed by the adjustable model is used as an error signal for an adaptation mechanism to estimate the slip speed and rotor resistance. Simulation results show the proposed MRAC approach can accurately estimate rotor time constant and speed.
HIGH SPEED REVERSE CONVERTER FOR HIGH DYNAMIC RANGE MODULI SETP singh
In this paper a new reverse converter architecture for the five moduli set {2n, 2n/2-1, 2n/2+1, 2n+1, 22n-1-1} is presented. The proposed converter is designed in two levels architecture by using of New Chinese Reminder Theorem-I (New CRT-I) and Mixed Radix Conversion (MRC). The proposed architecture has achieved significant improvement in terms of delay of the reverse converter compared to state-of-the-art reverse converters.
This document summarizes a seminar presentation on using linear matrix inequalities (LMIs) to optimally adjust power system stabilizers (PSSs) to guarantee power system stability and performance under varying operating conditions. The presentation discusses modeling power systems and PSS control structures, using LMIs to place closed-loop system poles in desired regions to meet performance criteria, constraining controller gains, and ensuring robustness to operating point variations through a polytopic modeling approach. Experimental results applying these LMI techniques to a 9-machine New England power system model are also summarized.
This document provides an overview of protein structure analysis tools and techniques:
1) It describes exploring the Protein Data Bank (PDB) to view and analyze X-ray crystallography and NMR protein structures, comparing similar structures, and using tools like FoldX for in silico mutagenesis and homology modeling.
2) Key concepts covered include PDB file formats, atomic coordinates, B-factors, resolution, RMSD, and the principles of X-ray crystallography, NMR structure determination, and homology modeling.
3) Visualization software like YASARA, SwissPDBViewer and PyMOL are introduced for viewing protein structures from the PDB.
Quantum Espresso is a suite of open-source computer codes for electronic structure calculations and materials modeling based on density functional theory and plane waves. It can be used to calculate material properties including ground-state energy, atomic forces, stresses, molecular dynamics, and more. The document provides an introduction and overview of Quantum Espresso, including examples of input files for defining crystal structures, pseudopotentials, k-points, and performing calculations of total energy and phonon frequencies. Convergence of key parameters like the plane wave cutoff energy and k-point sampling is also discussed.
This document provides the analysis and settings for installing two three-phase reclosers to improve protection of two site power transformers. The reclosers will be located between the secondary side of the transformers and downstream disconnect switches. Coordination studies were performed to select settings for the reclosers' phase and ground protection elements. These settings allow the reclosers to clear faults without operating any downstream protective devices and ensures coordination between the reclosers and other relays. Attachments include the coordination plot verifying selective operation and the selected recloser settings.
The document describes experiments to be conducted in the VLSI Design laboratory at K J Somaiya College of Engineering. The experiments include SPICE simulation of various NMOS inverter circuits, layout and simulation of CMOS inverter, NAND/NOR gates using Magic and SPICE, Boolean expression and transmission gate layout using Microwind, and Verilog programming and simulation of multiplexers, decoders, flip-flops, counters and state machines. The document also provides theory and methodology for each experiment.
This document summarizes the design and testing of circuits to generate the waveforms used in external defibrillators. It describes the Lown monophasic waveform and the biphasic truncated exponential waveform (BTEW), which are the two main waveforms used. Circuits were designed using basic electrical components to generate each waveform, and were simulated and tested experimentally. The results showed that the BTEW circuit more closely matched the original waveform specifications, was cheaper to produce, and had advantages for defibrillation effectiveness. Therefore, the biphasic truncated exponential waveform is recommended for use in defibrillators.
This document discusses trends in embedded systems and multiprocessor system-on-chips (MPSoCs). It summarizes issues with traditional bus and crossbar networks for SoCs like latency, priority, bandwidth limitation, and cost. It then describes a routing congestion-aware and power-aware mapping algorithm for MPSoCs that arranges task graphs by latency constraint severity and maps cores to tiles to minimize congestion while meeting latency constraints.
This document discusses trends in embedded systems and multiprocessor system-on-chips (MPSoCs). MPSoCs integrate multiple processors into a single chip to improve performance. This is necessary as system needs increase and more components are integrated onto chips. MPSoCs address issues with traditional bus and crossbar interconnects like latency, bandwidth limitations, and routing congestion. The document then describes algorithms for mapping tasks to cores in an MPSoC while considering latency constraints, network congestion, and communication power.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Study and Development of an Energy Saving Mechanical SystemIDES Editor
A new energy-saving mechanical system with
automatically controlled air valves has been proposed by
investigator and the preliminary model setup has been tested.
The testing results indicated the proper function of this
energy-saving mechanical system. This mechanical system
model has been simulated and analyzed by the computational
aided engineering solution. The major advantages of this
mechanical system include: simple and compact in design,
higher efficiency in mechanical functioning, quiet in
manufacturing operation, less energy losses due to less
frictional forces in this free piston-cylinder setup, selfadjustable
in operational parameter to improve the system
performance, and etc.
logical effort based dual mode logic gates by mallikaMallika Naidu
Logic optimization and timing estimations are basic tasks for digital circuit designers. Dual Mode Logic (DML) allows operation in two modes such as static and dynamic modes. DML gates can be switched between these two modes on feature very low power dissipation in the static mode and high speed of operation in dynamic mode which is achieved at the expense of increased power dissipation. We introduce the logical effort (LE) methodology for the CMOS-based family. The proposed methodology allows path length, delay and power optimization for number of stages with load. Logical effort is the transistor sizing optimization methodology reduces the delay and power with number of stages with any static logic gate. The proposed optimization is shown for dual mode logic gates with logical effort using Digital Schematic Tool (DSCH).
This document describes the process of global routing in VLSI physical design. Global routing assigns wiring paths between circuit components at a coarse level of granularity by partitioning the chip into routing regions and assigning nets to these regions. It aims to minimize total wirelength and reduce delays on critical nets. Routing regions are represented using graphs to model available routing resources. Common algorithms discussed include rectilinear Steiner tree construction and sequential Steiner tree heuristics to find minimum path routes between pins in the global routing stage.
This document discusses the theoretical and experimental study of dynamics and control of a two-link flexible robot arm. It presents the following:
1) A linear dynamic model of the robot arm is constructed using Ritz's approach and validated experimentally.
2) Three active control schemes are designed using pole placement technique for path tracking and vibration suppression, and tested via simulation.
3) A discrete-time state variable feedback control scheme is presented and designed to control the robot arm's motion using three sensors for position and curvature feedback.
Speech recognition using hidden markov model mee 03_19NGUYEN_SPKT
This document describes the implementation of a speech recognition system using hidden Markov models (HMMs) on a DSK-ADSP-BF533 EZ-KIT LITE REV 1.5 digital signal processor board. The key steps taken are:
1. Feature extraction from speech signals by calculating mel frequency cepstrum coefficients (MFCCs). This involves preprocessing the signal, framing and windowing, Fourier transform, mel filtering, and discrete cosine transform.
2. Training HMMs to create models of words using an iterative process that calculates mean, variance, state transition probabilities, and output distributions from multiple utterances of words.
3. Testing utterances against trained models using the Viterbi
A Novel Flipflop Topology for High Speed and Area Efficient Logic Structure D...IOSR Journals
In high speed data path network flop is one of the major functional elements to store intermediate
results and data at different stages. But the most important problem is huge power utilization due to switching
activity and increase in clock period that is Timing Latency; causes the performance of data path in digital
design is decreased. The existing works implement various Flipflop topology in data path structure design such
as conventional Transmission Gate Based Master Slave Filpflop (TGMS FF), Write Port Master Slave Flip-flop
(WPMS) and Clocked Complementary Metal Oxide Semiconductor (C2MOS). In WPMS method, area is
minimized but delay is increased. In C2MOS technique Power consumption and delay is reduced, but there is a
definite scope to reduce Power, area and delay. In this paper a Modified Clocked Complementary Metal Oxide
Semiconductor Latch (mC2MOS Latch) is proposed and delay, power is again reduced up to 60% and the area
of the circuit is also reduced while comparing with previous methods.
A High Speed Pipelined Dynamic Circuit Implementation Using Modified TSPC Log...IDES Editor
This document presents a modified True Single Phase Clock (TSPC) logic design style to implement high-speed pipelined circuits with improved performance. The modified style reduces transistor count by 40-50% compared to the standard TSPC style by allowing logic functions to be implemented using either the N-block or P-block. A 3-bit pipelined adder was designed using the modified style and showed a 46-47% reduction in transistors and 50% reduction in clock cycles compared to the standard style. The modified style offers benefits like lower transistor count, reduced latency, increased throughput, and lower power consumption for pipelined circuits.
This document summarizes the development of a multi-level reduced order modeling (MLROM) methodology. MLROM uses a physics-informed approach to extract an active subspace by executing a high-fidelity model on sub-domains, like a pin cell, rather than the full domain like the whole core. This reduces computational cost. Error bounds for the reduced model are established using the pin-cell determined active subspace and verified against full-order lattice simulations. Future work will apply MLROM to core-wide calculations using representative lattices to capture the core-wide active subspace.
The document describes an efficient FPGA-based architecture for implementing a delayed least mean square (DLMS) adaptive filter using fixed-point arithmetic. The proposed architecture aims to reduce adaptation delay and optimize area, delay, and power efficiency. It uses a novel partial product generator and balanced pipelining across computation blocks to minimize critical path delays. Synthesis results show the proposed design offers lower area and higher maximum frequency than existing systolic structures for various filter lengths. The design was implemented on a Spartan-3 FPGA and results matched simulations for an 8-tap filter.
1) The document contains solutions to chapter 8 homework problems involving page tables, page replacement policies, working set size, and memory management with both paging and segmentation.
2) Key concepts covered include virtual to physical address translation using page tables, page replacement algorithms like FIFO and LRU, calculating memory access rates, and addressing with multiple levels of page tables and segmentation.
3) Memory management techniques like page tables, page replacement, and multi-level addressing schemes are analyzed to solve problems involving virtual memory configuration, address translation, and modeling memory access patterns.
This document summarizes a research paper that proposes a Model Reference Adaptive Controller (MRAC) for online estimation of rotor time constant and speed for indirect field oriented control of an induction motor drive. The MRAC design is based on reactive power concepts and consists of a reference model that is independent of slip speed and an adjustable model that depends on slip speed. The difference between the instantaneous reactive power computed by the reference model and the steady-state reactive power computed by the adjustable model is used as an error signal for an adaptation mechanism to estimate the slip speed and rotor resistance. Simulation results show the proposed MRAC approach can accurately estimate rotor time constant and speed.
HIGH SPEED REVERSE CONVERTER FOR HIGH DYNAMIC RANGE MODULI SETP singh
In this paper a new reverse converter architecture for the five moduli set {2n, 2n/2-1, 2n/2+1, 2n+1, 22n-1-1} is presented. The proposed converter is designed in two levels architecture by using of New Chinese Reminder Theorem-I (New CRT-I) and Mixed Radix Conversion (MRC). The proposed architecture has achieved significant improvement in terms of delay of the reverse converter compared to state-of-the-art reverse converters.
This document summarizes a seminar presentation on using linear matrix inequalities (LMIs) to optimally adjust power system stabilizers (PSSs) to guarantee power system stability and performance under varying operating conditions. The presentation discusses modeling power systems and PSS control structures, using LMIs to place closed-loop system poles in desired regions to meet performance criteria, constraining controller gains, and ensuring robustness to operating point variations through a polytopic modeling approach. Experimental results applying these LMI techniques to a 9-machine New England power system model are also summarized.
This document provides an overview of protein structure analysis tools and techniques:
1) It describes exploring the Protein Data Bank (PDB) to view and analyze X-ray crystallography and NMR protein structures, comparing similar structures, and using tools like FoldX for in silico mutagenesis and homology modeling.
2) Key concepts covered include PDB file formats, atomic coordinates, B-factors, resolution, RMSD, and the principles of X-ray crystallography, NMR structure determination, and homology modeling.
3) Visualization software like YASARA, SwissPDBViewer and PyMOL are introduced for viewing protein structures from the PDB.
Quantum Espresso is a suite of open-source computer codes for electronic structure calculations and materials modeling based on density functional theory and plane waves. It can be used to calculate material properties including ground-state energy, atomic forces, stresses, molecular dynamics, and more. The document provides an introduction and overview of Quantum Espresso, including examples of input files for defining crystal structures, pseudopotentials, k-points, and performing calculations of total energy and phonon frequencies. Convergence of key parameters like the plane wave cutoff energy and k-point sampling is also discussed.
This document provides the analysis and settings for installing two three-phase reclosers to improve protection of two site power transformers. The reclosers will be located between the secondary side of the transformers and downstream disconnect switches. Coordination studies were performed to select settings for the reclosers' phase and ground protection elements. These settings allow the reclosers to clear faults without operating any downstream protective devices and ensures coordination between the reclosers and other relays. Attachments include the coordination plot verifying selective operation and the selected recloser settings.
The document describes experiments to be conducted in the VLSI Design laboratory at K J Somaiya College of Engineering. The experiments include SPICE simulation of various NMOS inverter circuits, layout and simulation of CMOS inverter, NAND/NOR gates using Magic and SPICE, Boolean expression and transmission gate layout using Microwind, and Verilog programming and simulation of multiplexers, decoders, flip-flops, counters and state machines. The document also provides theory and methodology for each experiment.
This document summarizes the design and testing of circuits to generate the waveforms used in external defibrillators. It describes the Lown monophasic waveform and the biphasic truncated exponential waveform (BTEW), which are the two main waveforms used. Circuits were designed using basic electrical components to generate each waveform, and were simulated and tested experimentally. The results showed that the BTEW circuit more closely matched the original waveform specifications, was cheaper to produce, and had advantages for defibrillation effectiveness. Therefore, the biphasic truncated exponential waveform is recommended for use in defibrillators.
Refurbishment of a Three-Phase Induction Motor Reflecting Local Voltage Condi...IOSR Journals
This document summarizes the refurbishment of a 3-phase induction motor originally designed for 415V but operating in an area with a maximum supply of 380V. Key steps included:
1. Calculating new winding parameters for 380V operation, including number of poles, coils per phase, turns, etc.
2. Measuring the motor dimensions to inform the calculations.
3. Developing a double-layer lap winding with 12 phase groups of 44 turns each for the 380V design.
4. Rewinding the stator with the new winding configuration and testing the motor, which achieved satisfactory no-load speed.
The document describes a method and system for determining the number of load coils in a transmission line. It involves calculating the impulse response of the transmission line based on its characteristic impedance. It then determines the number of complex conjugate pole pairs in the transfer function of the impulse response. The number of pole pairs equals the number of load coils in the transmission line. This allows the load coils to be detected by analyzing the impulse response rather than directly examining variations in the characteristic impedance.
SPECTRAL-BASED FATIGUE ASSESSMENT OF FSOSUMARDIONO .
The document discusses fatigue analysis of an offshore floating storage vessel (FSO) hull construction using spectral-based fatigue analysis methods. It outlines the objectives to determine long-term wave load characteristics, stress distributions, and fatigue life of critical locations. The methodology involves regular wave load analysis, finite element modeling, spectral analysis of long-term wave loads and stresses, and fatigue analysis to estimate the fatigue life. Critical locations on the hull are identified for further stress analysis and fatigue life estimation.
The document describes the design of an operational amplifier using MOSFET transistors. It specifies the design rules and parameters to be used, including junction geometries, device properties, and operating specifications. It then presents the design of a common-source gain stage, where the input voltage is calculated to be 0.881 mV for an output of 2.5 V, which is verified through simulation and analytical calculation.
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Disclaimer: No one is perfect, so please mind that there might be mistakes and typos.
dtubbenhauer@gmail.com
Corrected slides: dtubbenhauer.com/talks.html
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1. Part I. Strategy for running molecular dynamics simulations
This part of the lecture describes the general steps in setting and running molecular
dynamics (MD) simulations using NAMD for a short polyvaline peptide (VVVV) capped
with acetyl and amide groups. This peptide is one of the two peptides to be examined in
the MD project. More information on running MD simulations with NAMD can be found
at www.ks.uiuc.edu/Research/namd/current/ug/.
Stages in a typical MD trajectory
The stages in MD simulations are shown in Fig. 1.
Initial input
Energy minimization
Heating to 300K
Equilibration
Production
NVE MD simulations
Figure 1. Strategy for performing generic MD simulations.
1
2. In what follows it is assumed that the initial solvated structure of polyvaline (the file
val_solv.pdb) and the topology file val_solv.psf are already prepared. The goal of MD
simulations is to obtain a single 1 ns production trajectory, from which conformational
properties of polyvaline can be computed.
1. Initialization: structure/topology/force field files
Three input files are needed to start the simulations. These are the topology file
val_solv.psf, the coordinate file val_solv.pdb, and the force field file
par_all22_prot.inp (part of CHARMM22 force field). The topology file contains all the
information about the structure and connectivity of atoms in the system as well as few
parameters of the force field (i.e., those which are incorporated in the top_all22_prot.inp
file). In all, the solvated polyvaline system contains 2476 atoms and 805 residues, which
include peptide amino acids, capping terminals, and water molecules. The peptide itself
contains only 73 atoms in four residues and two terminal groups.
Structure of the topology file is as follows:
2476 !NATOM
(a) (b) (c) (d) (e) (f) (g) (h) (i)
1 VAL4 1 VAL CAY CT3 -0.270000 12.0110 0
2 VAL4 1 VAL HY1 HA 0.090000 1.0080 0
3 VAL4 1 VAL HY2 HA 0.090000 1.0080 0
4 VAL4 1 VAL HY3 HA 0.090000 1.0080 0
5 VAL4 1 VAL CY C 0.510000 12.0110 0
6 VAL4 1 VAL OY O -0.510000 15.9990 0
7 VAL4 1 VAL N NH1 -0.470000 14.0070 0
8 VAL4 1 VAL HN H 0.310000 1.0080 0
9 VAL4 1 VAL CA CT1 0.070000 12.0110 0
10 VAL4 1 VAL HA HB 0.090000 1.0080 0
11 VAL4 1 VAL CB CT1 -0.090000 12.0110 0
12 VAL4 1 VAL HB HA 0.090000 1.0080 0
13 VAL4 1 VAL CG1 CT3 -0.270000 12.0110 0
14 VAL4 1 VAL HG11 HA 0.090000 1.0080 0
15 VAL4 1 VAL HG12 HA 0.090000 1.0080 0
16 VAL4 1 VAL HG13 HA 0.090000 1.0080 0
17 VAL4 1 VAL CG2 CT3 -0.270000 12.0110 0
18 VAL4 1 VAL HG21 HA 0.090000 1.0080 0
19 VAL4 1 VAL HG22 HA 0.090000 1.0080 0
20 VAL4 1 VAL HG23 HA 0.090000 1.0080 0
21 VAL4 1 VAL C C 0.510000 12.0110 0
22 VAL4 1 VAL O O -0.510000 15.9990 0
………………………………………………………………………………
2
3. 302 SOLV 81 TIP3 OH2 OT -0.834000 15.9994 0
303 SOLV 81 TIP3 H1 HT 0.417000 1.0080 0
304 SOLV 81 TIP3 H2 HT 0.417000 1.0080 0
………………………………………………………………………………
(a) atom number;
(b) segment name, e.g., VAL4 is the name of peptide segment in the solvated system.
The other segment is solvent (SOLV);
(c) residue number (may not be sequential);
(d) residue name;
(e) atom name;
(f) atom type;
(g) partial charge;
(h) atomic mass;
(i) flag used to indicate constrained atom
Note that the first six atoms correspond to acetyl cap (CH3-CO-), which is incorporated
by CHARMM convention into the first residue. The amide cap (-NH2) is included in the
last residue. The N- and C-terminal caps are distinguished by the letters “Y” and “T” in
the atom names, respectively. Topology file also contains information (atom numbers),
which defines covalent bonds, bond angles, dihedral angles, and improper torsion angles.
Bond lengths (defined by pairs of atom numbers)………………………..
2475 !NBOND: bonds # number of bonds
1 2 1 3 1 4 5 1
5 7 6 5 7 8 7 9
9 10 11 9 11 12 13 11
Bond angles (defined by triplets of atom numbers)……………………………..
933 !NTHETA: bond angles # number of bond angles
1 5 6 1 5 7 2 1 4
2 1 3 3 1 4 5 7 9
5 7 8 5 1 4 5 1 3
Dihedral angles (defined by sets of four atom numbers)……………………..
183 !NPHI: dihedrals # number of dihedral angles
1 5 7 8 1 5 7 9
2 1 5 7 2 1 5 6
Improper torsion angles (sets of four atom numbers)………………………………..
12 !NIMPHI: impropers # number of improper torsions
5 1 7 6 7 5 9 8
21 9 23 22 23 21 25 24
…………………………………………………………………..
3
4. The coordinates of the initial structure are taken from val_solv.pdb file (written
according to PDB format):
(a) (b) (c) (d) _______(e)________ (f) (g) (h)
ATOM 1 CAY VAL 1 -3.881 -1.044 -2.178 0.00 0.00 VAL4
ATOM 2 HY1 VAL 1 -3.778 -1.657 -1.394 0.00 0.00 VAL4
ATOM 3 HY2 VAL 1 -3.019 -0.986 -2.681 0.00 0.00 VAL4
ATOM 4 HY3 VAL 1 -4.605 -1.380 -2.780 0.00 0.00 VAL4
ATOM 5 CY VAL 1 -4.128 -0.133 -1.848 0.00 0.00 VAL4
ATOM 6 OY VAL 1 -4.231 0.480 -2.632 0.00 0.00 VAL4
ATOM 7 N VAL 1 -4.185 -0.152 -0.850 1.00 0.00 VAL4
ATOM 8 HN VAL 1 -4.049 -0.874 -0.158 1.00 0.00 VAL4
……………………………………………………………………………………….
ATOM 254 OH2 TIP3 65 0.440 13.787 -14.273 1.00 0.00 SOLV
ATOM 255 H1 TIP3 65 0.953 14.520 -13.933 1.00 0.00 SOLV
ATOM 256 H2 TIP3 65 0.764 13.660 -15.165 1.00 0.00 SOLV
…………………………………………………………………………………………
Notes:
(a) atom number;
(b) atom name;
(c) residue name;
(d) residue number (may not be consequent);
(e) xyz coordinates;
(f) occupancy (confidence in determination the atom position in X-ray diffraction).
In NAMD package, the value of 0.0 is assigned to all positions “guessed” during
generation of psf file;
(g) temperature factor (uncertainty due to thermal disorder);
(h) segment name
The third input file is par_all22_prot.inp, which provides virtually all the parameters for
CHARMM force field (not included in val_solv.psf file). These include the parameters
for bond angle, length, dihedral angle, improper and Lennard-Jones potentials. This file is
obtained from www.pharmacy.umaryland.edu/faculty/amackere/force_fields.htm.
Download the file toppar_c31b1.tar.gz and extract files par_all22_prot.inp and
top_all22_prot.inp.
2. Energy minimization
The first “real” step in preparing the system for production MD simulations involves
energy minimization. The purpose of this stage is not to find a true global energy
minimum, but to adjust the structure to the force field, particular distribution of solvent
molecules, and to relax possible steric clashes created by guessing coordinates of atoms
4
5. during generation of psf file. The following NAMD configuration file is used to
minimize the potential energy of val_solv.pdb structure. Fig. 2 shows the decrease in
the potential energy Ep of the peptide + solvent system.
# input topology and initial structure…………..
structure val_solv.psf # Reading topology file
coordinates val_solv.pdb # Reading initial structure coordinates
#..force field block ........................
paratypecharmm on # Selecting the type of force field (CHARMM)
parameters par_all22_prot.inp #Getting the force field parameters for proteins (a)
exclude scaled1-4 # Exclude/scale local (along the sequence)
# non-bonded interactions (b)
1-4scaling 1.0 # Scale factor for (i,i+3) EL interactions
dielectric 1.0 # Value of the dielectric constant
# dealing with long-range interactions…………..
switching on # Switch VdW interactions and partition EL into
# local and nonlocal terms
switchdist 8.0 # Distance (=a), at which the switching function is
# first applied (c)
cutoff 12.0 #Distance (=b), at which VdW interactions become
# zero and electrostatics becomes purely nonlocal
pairlistdist 13.5 # Maximum distance used for generating Verlet
# lists (aka in NAMD as pair list) of atoms
margin 0.0 # Extra distance used in selecting the patches (d)
stepspercycle 20 # Frequency of updating Verlet list (in integration
# steps)
rigidBonds all # Apply SHAKE algorithm to all covalent bonds
# involving hydrogens
rigidTolerance 0.00001 # Desired accuracy in maintaining SHAKEed bond
# lengths
rigidIterations 500 # Maximum number of SHAKE iterations
# this block specifies the Ewald electrostatics.........................
PME on # Use Particle-Mesh Ewald summation for long-
# range electrostatics
PMETolerance 0.000001 # The accuracy of computing the Ewald real space
# (direct) term
PMEGridSizeX 32 # Setting the grids of points for
PMEGridSizeY 32 # fast calculation of reciprocal term
PMEGridSizeZ 32 # along x,y and z directions
minimization on # Do conjugate gradient minimization of potential
# energy (instead of MD run)
5
6. # this block specifies the output….
outputenergies 1000 # Interval in integration steps of writing energies
# to stdout
outputtiming 1000 # Interval of writing timing (basically, speed,
# memory allocation, etc) to stdout
binaryoutput no # Are binary files used for saving last structure?
outputname output/val_min # The file name (without extension!), to which final
# coordinates and velocities are to be saved
# (appended extensions are *.coor or *.vel)
restartname output/vali # The file name (without extension), which holds
# the restart structure and velocities
# (appended extensions are *.coor or *.vel)
restartfreq 10000 # Interval between writing out the restart
# coordinates and velocities
binaryrestart no # Are restart files binary?
DCDfile output/val_min.dcd # Trajectory filename (binary file)
dcdfreq 1000 # Frequency of writing structural snapshots to
# trajectory file
numsteps 2000 # Number of minimization steps
# this block defines periodic boundary conditions......
cellBasisVector1 29.4 0.0 0.0 # Direction of the x basis vector for a unit cell
cellBasisVector2 0.0 29.4 0.0 # Direction of the y basis vector for a unit cell
cellBasisVector3 0.0 0.0 29.4 # Direction of the z basis vector for a unit cell
cellOrigin 0.0 0.0 0.0 # Position of the unit cell center
wrapWater on # Are water molecules translated back to the unit
# cell (purely cosmetic option, has no effect on
# simulations)
Notes:
(a) CHARMM22 force field is used;
(b) This setting implies exclusion of all non-bonded interactions for the atoms
(i,i+1,i+2) and scaling the EL interactions between (i,i+3) by the factor 1-
4scaling. The scaling of van-der-Waals (VdW) interactions between the atoms i
and i+3 is set in par_all22_prot.inp file;
(c) All distances are in angstroms. All “times” are expressed in the number of
integration steps;
(d) This distance is used for generating patches or groups of atoms, which should not
be separated by Verlet lists.
6
7. Figure 2. The decrease in potential energy of polyvaline peptide during minimization.
3. Heating the simulation system
During this stage the temperature of the system is linearly increased from 0K to 300K
within 300 ps. At each integration step velocities are reassigned (i.e., drawn) from a new
Maxwell distribution and the temperature is incremented by 0.001K. Fig. 3 shows the
increase in the temperature T(t) (upper panel) and potential energy Ep (lower panel) as a
function of time. Note that instantaneous temperature T(t) and energy Ep fluctuate due to
finite system size. The keywords, which have not been changed compared to previous
simulations stage, are marked in grey.
# input topology and initial structure……
structure val_solv.psf
coordinates ./output/val_min.coor # Start heating simulations from the minimized
# structure (a)
#..force field block........................
paratypecharmm on
parameters par_all22_prot.inp
exclude scaled1-4
1-4scaling 1.0
dielectric 1.0
7
8. # dealing with long-range interactions…………..
switching on
switchdist 8.0
cutoff 12.0
pairlistdist 13.5
margin 0.0
stepspercycle 20
rigidBonds all
rigidTolerance 0.00001
rigidIterations 100
# this block specifies the Ewald electrostatics.........................
PME on
PMETolerance 0.000001
PMEGridSizeX 32
PMEGridSizeY 32
PMEGridSizeZ 32
#block specifying the parameters for integrator and MTS
timestep 1.0 # Integration time step in fs
fullElectFrequency 4 # The interval between calculation of long-
# range electrostatics using PME method.
# Short-range nonbonded interactions are
# computed at every integration step by default (b)
# this block specifies the output….
outputenergies 1000
outputtiming 1000
binaryoutput no
outputname output/val_heat010 #The file name (without extension) to which final
# coordinates and velocities are to be saved
# (appended extensions are *.coor or *.vel)
restartname output/vali_heat010 # The file name (without extension), which holds
# the restart structure and velocities
# (appended extensions are *.coor or *.vel)
restartfreq 10000
binaryrestart yes # Use binary restart files (c)
DCDfile output/val_heat010.dcd # Trajectory filename (binary file)
dcdfreq 1000
#MD protocol block ………………….
seed 1010 # Random number seed used to generate initial
# Maxwell distribution of velocities (d)
numsteps 300000 # Number of integration steps
temperature 0 # Initial temperature (in K), at which initial velocity
# distribution is generated
8
9. reassignFreq 1 # Number of steps between reassignment of
# velocities
reassignIncr 0.001 # Increment used to adjust temperature
# during temperature reassignment
reassignHold 300 # The value of temperature to be kept after heating is
# completed
# this block defines periodic boundary conditions......
cellBasisVector1 29.4 0.0 0.0
cellBasisVector2 0.0 29.4 0.0
cellBasisVector3 0.0 0.0 29.4
cellOrigin 0.0 0.0 0.0
wrapWater on
Notes:
(a) binary format for input files is not used here;
(b) multisteping (r-RESPA) integration of equations of motion is used by default;
(c) restrart files (*.coor and *.vel) are saved in binary format. This option provides
better numerical accuracy during writing out/reading in of restart files;
(d) Seed should “identify” (i.e., be unique) for a given trajectory. Only applicable if
temperature keyword is present
Figure 3. Increase in instantaneous temperature (upper panel) and potential energy
(lower panel) during heating
9
10. 4. Equilibration at constant temperature
Equilibration stage is used to equilibrate kinetic and potential energies, i.e., to distribute
the kinetic energy “pumped” into the system during heating among all degrees of
freedom. This usually implies that the potential energy “lags on” and must be equilibrated
with the kinetic energy. In other words, the kinetic energy must be transferred to potential
energy. As soon as potential energy levels off the equilibration stage is completed. Fig. 4
shows the temperature T(t) (upper panel) and the potential energy Ep (lower panel) as a
function of time. After initial rapid increase from about -8000 kcal/mol the potential
energy Ep fluctuates near the constant level. This behavior suggests that the system is
equilibrated on a timescale much shorter than 300 ps.
# input topology and initial structure……..
structure val_solv.psf
coordinates ./output/val_heat010.coor # Start equilibration with the final structure
# from the heating stage of MD trajectory
#..force field block........................
paratypecharmm on
parameters par_all22_prot.inp
exclude scaled1-4
1-4scaling 1.0
dielectric 1.0
# dealing with long-range interactions…………..
switching on
switchdist 8.0
cutoff 12.0
pairlistdist 13.5
margin 0.0
stepspercycle 20
rigidBonds all
rigidTolerance 0.00001
rigidIterations 100
# this block specifies the Ewald electrostatics.........................
PME on
PMETolerance 0.000001
PMEGridSizeX 32
PMEGridSizeY 32
PMEGridSizeZ 32
# this block specifies the parameters for integrator and MTS
timestep 1.0
fullElectFrequency 4
10
11. # this block deternines the output….
outputenergies 1000
outputtiming 1000
binaryoutput no
outputname output/val_equil010 #The file name (without extension) to which final
# coordinates and velocities are to be saved
# (appended extensions are *.coor or *.vel)
restartname output/vali_equil010 #The file name (without extension), which holds
# the restart structure and velocities
# (appended extensions are *.coor or *.vel)
restartfreq 10000
binaryrestart yes
DCDfile output/val_equil010.dcd # Trajectory filename (binary file)
dcdfreq 1000
#MD protocol block ………………….
seed 2010 # Random number seed used to generate initial
# Maxwell distribution of velocities
numsteps 300000
temperature 300 # Temperature of initial velocity generation
rescaleFreq 1 # Number of integration steps between rescaling
# velocities to a given temperature
rescaleTemp 300 # Temperature, to which velocities are rescaled
# this block defines periodic boundary conditions......
cellBasisVector1 29.4 0.0 0.0
cellBasisVector2 0.0 29.4 0.0
cellBasisVector3 0.0 0.0 29.4
cellOrigin 0.0 0.0 0.0
wrapWater on
11
12. Figure 4. Time dependence of instantaneous temperature (upper panel) and potential
energy (lower panel) during equilibration stage.
Note that the potential energy in Fig. 4 is leveled off at about -7800 kcal/mol, whereas the
final energy during heating stage is somewhat smaller (≈-8000 kcal/mol). Although all
velocities are rescaled to 300K at every integration step, fluctuations in temperature are
still visible in Fig. 4, because the temperatures are plotted after advancing the velocities
using Verlet algorithm, but before actual rescaling.
5. Production stage of MD trajectory (NVE ensemble)
This stage of MD trajectory is used to sample the structural characteristics and dynamics
of polyvaline peptide at 300K. Velocity reassigning or rescaling must now be turned off.
The fluctuations in instantaneous temperature and nearly constant total energy (kinetic
plus potential energies) are shown in Fig. 5.
12
13. # input topology and initial structure……..
structure val_solv.psf
coordinates ./output/val_equil010.coor # Reading the final structure from
bincoordinates./output/vali_equil010.coor # equilibration stage in a binary format (a)
#binvelocities ./output/vali_equil010.vel # Initial velocities from restart file (b)
#..force field block........................
paratypecharmm on
parameters par_all22_prot.inp
exclude scaled1-4
1-4scaling 1.0
dielectric 1.0
# dealing with long-range interactions…………..
switching on
switchdist 8.0
cutoff 12.0
pairlistdist 13.5
margin 0.0
stepspercycle 20
rigidBonds all
rigidTolerance 0.00001
rigidIterations 100
# this block specifies the Ewald electrostatics.........................
PME on
PMETolerance 0.000001
PMEGridSizeX 32
PMEGridSizeY 32
PMEGridSizeZ 32
# this block specifies the parameters for integrator and MTS
timestep 1.0
fullElectFrequency 4
# this block determines the output….
outputenergies 1000
outputtiming 1000
binaryoutput no
outputname output/val_quench010 # The file name (without extension) to which final
# coordinates and velocities are to be saved
# (appended extensions are .coor or vel)
restartname output/vali_quench010 # The file name (without extension), which holds
# the restart structure and velocities
# (appended extensions are *.coor or *.vel)
restartfreq 10000
13
14. binaryrestart yes
DCDfile output/val_quench010.dcd # Trajectory filename (binary file)
dcdfreq 1000
#MD protocol block..............
seed 3010 # Random number seed used to generate initial
# Maxwell distribution of velocities
numsteps 1000000 # Number of integration steps during
# production simulations
temperature 300 # see also (b)
# this block defines periodic boundary conditions......
cellBasisVector1 29.4 0.0 0.0
cellBasisVector2 0.0 29.4 0.0
cellBasisVector3 0.0 0.0 29.4
cellOrigin 0.0 0.0 0.0
wrapWater on
Notes:
(a) Initial coordinates are read from equilibration restart file in a binary format. The
keyword coordinates has no meaning, although must be used as per NAMD
specifications
(b) This particular configuration file forces NAMD to generate a new Maxwell
distribution of velocities during initialization of production run (the keyword
temperature is present). An alternative option is to read the velocities saved in a
binary form from previous simulation stage. In this case the temperature is
“imported” with the velocities and the keyword temperature must be omitted,
whereas the keyword binvelocities must be uncommented.
14
15. Figure 5. Fluctuations in instantaneous temperature (upper panel) and approximately
constant total energy (lower panel) are shown for production NVE simulations of
polyvaline.
Part II. Molecular dynamics project: Simulations of peptides
in explicit water
The purpose of this project is to perform MD simulations for short peptides and explore
their secondary structure propensities. Two peptides, acetyl-VVVV-NH2 and acetyl-
AAAAAAAAA-NH2, are to be used in the simulations. From the analysis of secondary
structure propensities of proteins in structural databases it is known that valine and
alanine generally favor β-strand and α-helix conformations, respectively. Therefore, MD
simulations at normal physiological conditions (300K, normal pH, no salt) are expected
to reflect these propensities.
Note that polyvaline sequence is shorter than polyalanine, because β-strand conformation
usually does not rely on interresidue contacts (other than steric clashes). In contrast,
15
16. helical structures draw their stability, at least partially, from the (i,i+4) interactions
(usually, hydrogen bonds). Accordingly, polyalanine sequence must be long enough to
form at least two full helical turns. Because there are usually 3.6 residues per turn in an α-
helix and polyalanine sequence is nine residues long, a short α-helix is expected to form in these
simulations.
Secondary structure propensities can be examined by computing the distribution of (φ,ψ)
backbone dihedral angles collected during production MD simulations. The best way to
visualize the distribution P(φ,ψ) is to plot the Ramachandran plots for both peptides. All
data are to be obtained from standard microcanonical (NVE) MD simulations of 1 ns long
using NAMD program.
Input files: There are three input files for each peptide. For polyvaline the topology file
and the file with the solvated peptide coordinates are val_solv.psf and val_solv.pdb,
respectively. For polyalanine the corresponding files are ala2_solv.psf and
ala2_solv.pdb. For both peptides the CHARMM22 parameter file par_all22_prot.inp
is used. The density of water is approximately 1.0 g/cm3
for both peptides. The sizes of
the unit cells for solvated polyvaline and polyalanine are 29.4 x 29.4 x 29.4 A and 34.7 x
34.7 x 34.7 A, respectively.
Energy minimization: Because the initial structures of the peptides were generated using
a template based on the structure of other protein and initial distribution of water
molecules may create steric clashes, energy minimization is required to relax “strained”
local conformations. The NAMD configuration files for performing energy minimization
for polyvaline and polyalanine peptides are val_min.namd and ala2_min.namd,
respectively. After completing minimization the potential energy of the system Ep must
be plotted as a function of minimization steps to assure that Ep nearly levels off by the
end of minimization stage.
The energy can be extracted from the stdout produced by NAMD. For convenience, the
output should be redirected to, e.g., val_min.out file, the part of which is given below. In
general, various energy terms are output by NAMD. Specifically, look for the lines
starting with “ENERGY:’ and a single line “ETITLE:”, which describes the “identity” of
the energy terms in the line “ENERGY:”. The total energy (kinetic Ek+potential Ep)
corresponds to the eleventh term, while the kinetic energy is given by the tenth term.
During minimization total energy coincides with the potential energy.
To start NAMD minimization first copy all input files into a dedicated directory. Then
create a subdirectory output, in which trajectory (*.dcd), coordinate (*.coor), and
velocity (*.vel) files will be output by NAMD.
To start NAMD minimization type the following command in the terminal window:
namd2 val_min.namd > val_min.out &
For polyalanine use ala2_min.namd.
16
17. Fragment of the file val_min.out (created as a result of redirection of stdout) is shown
below:
…………
ETITLE: TS BOND ANGLE DIHED IMPRP
ELECT VDW BOUNDARY MISC KINETIC
TOTAL TEMP TOTAL2 TOTAL3 TEMPAVG
PRESSURE GPRESSURE VOLUME PRESSAVG GPRESSAVG
ENERGY: 0 213.4650 82.1573 11.9522 2.8768
-8786.9485 1018.5613 0.0000 0.0000 0.0000
-7457.9359 0.0000 -7457.9359 -7457.9359 0.0000
21899.6229 1661.0030 25412.1840 21899.6229 1661.0030
………………
Heating to 300K: Once energy minimization is completed, the system is to be heated
from 0 to 300K as described in the section “Part I. Strategy for running molecular
dynamics simulations”. The configuration file for polyvaline system is
val_heat010.namd. Modify this file to obtain similar configuration file for heating the
polyalanine peptide ala2_heat010.namd. Remember to change names of input/output
files, random seed value, and the size of the unit cell.
Plot the instantaneous temperature T(t) and the potential energy Ep(t) to verify the system
behavior. T(t) can be extracted from, e.g., val_heat010.out file. Remember to subtract
kinetic energy (the tenth term in “ENERGY:” line) from the total energy to get Ep(t). Set
the length of heating trajectory to 300 ps.
To start NAMD heating simulations use the command:
namd2 val_heat010.namd > val_heat010.out &
For polyalanine use ala2_heat010.namd.
Equilibration at 300K: Perform equilibration of both polypeptides at 300 K by rescaling
velocities at every integration step for 300 ps as described in the section “Part I. Strategy
for running molecular dynamics simulations”. It is likely that the systems will be
equilibrated much faster than 300 ps, but this long equilibration stage provides an
opportunity to monitor instantaneous temperatures T(t) and energies Ep(t).
Plot these quantities to demonstrate that their baselines have no apparent time
dependence. The configuration file for equilibrating polyvaline is val_equil010.namd.
Modify this file to obtain the configuration file for polyalanine peptide.
To start NAMD equilibration simulations for polyvaline use the command:
namd2 val_equil010.namd > val_equil010.out &
For polyalanine use ala2_equil010.namd.
17
18. Production stage (NVE ensemble): Generate 1 ns trajectories for both peptides using
microcanonical (NVE) ensemble. The configuration file for polyvaline simulations is
val_quench010.namd (modify this file accordingly to run simulations for polyalanine
peptide).
The structural snapshots (trajectory) will be saved in a “DCD” file in the directory
./output. Make the plots and check that the total energy Ep(t)+ Ek(t) and instantaneous
temperatures T(t) in the stdout files for both peptides (such as val_quench010.out)
remain constant or the baseline remains approximately constant for T(t).
To start NAMD NVE simulations for polyvaline use the command:
namd2 val_quench010.namd > val_quench010.out &
For polyalanine use ala2_quench010.namd.
If for some unforeseen reason simulations crash (power outage etc), repeat the stage
affected by the crash.
Computing the distribution of dihedral angles: The backbone dihedral angles (φ,ψ) are
to be computed using the positions of heavy backbone atoms saved every 1 ps. To this
end the coordinates of peptide backbone in pdb format must be first extracted from binary
DCD files. Use for this purpose VMD program, which may be downloaded from
http://www.ks.uiuc.edu/Research/vmd/ (use version 1.8.3).
Manual is available at http://www.ks.uiuc.edu/Research/vmd/current/ug/ug.html and an
excellent tutorial can be found at http://www.ks.uiuc.edu/Training/Tutorials/vmd/tutorial-
html/index.html. VMD will be installed on Linux machines in the computer lab. Type
vmd in the terminal window to start the program.
How to extract backbone coordinates:
1. Place tcl script getpdb.tcl in the directory, where dcd files are located.
2. Start vmd program and load in the VMD Main window two files val_solv.psf
and val_quench010.dcd.
3. Select File menu and then New Molecule. Browse for the psf (in the directory
one level up) and dcd files and load both in this particular order.
4. Open Extensions menu from the VMD Main window and choose Tk console
(tcl console), which will open in a new window.
5. Change the directory in Tcl console to that of the dcd file and start tcl script
getpdb.tcl using the command source getpdb.tcl. This script reads dcd file and
saves the coordinates of N, Ca, and C backbone atoms into pdb file.
18
19. For polyvaline peptide this procedure will output pdb file val_quench010.pdb. For
polyalanine replace val_quench010.pdb in the tcl script with ala2_quench010.pdb.
Compute the backbone dihedral angles (φ,ψ) for polyvaline and polyalanine using the
extracted pdb files and the program for calculating dihedral angles. Plot the distributions
of dihedral angles P(φ,ψ) on the Ramachandran plot (Fig. 6). Note that for the first and
last residues only one angle (φ or ψ) is defined. These residues must be excluded from
calculations. For example, for four residue polyvaline only two pairs of (φ,ψ) are to be
plotted from each conformational snapshot. When the distributions P(φ,ψ) is computed,
compare them with the typical β-strand and α-helix regions. Use the following
definitions (see also Proteins: Struct. Funct. Gen. 20, 301 (1994) and Proc. Natl. Acad.
Sci USA 96, 9074 (1999)).
β-strand is defined by a polygon with the vertices:
(-180,180),(-180,126),(-162,126),(-162,108),(-144,108),(-144,90),(-50,90),(-50,180)
α-helix is defined by a polygon with the vertices:
(-90,0),(-90,-54),(-72,-54),(-72,-72),(-36,-72),(-36,-18),(-54,-18),(-54,0)
Visualization of simulations: It is instructive to visualize each step of MD simulations
using VMD. Once a stage of the MD project is completed, start VMD in the directory
output. Load psf and dcd files as described above. The animation will start automatically
in the VMD display window. Although the default molecular representation is rather
poor, there are many more advanced graphical representations available in VMD. Here a
VDW option is illustrated.
1. Select Graphics menu in VMD Main window and choose Representations.
There clear the Selected Atoms line, type “protein”, and press Enter.
2. Select VDW for the Drawing method. Choose Coloring method and select,
e.g., Type. Protein atoms will be colored according to their type.
3. You may want to adjust the size of atom spheres by changing the Sphere Scale.
Click Create Representation to store currently created view as a separate
representation. Then clear the Selected Atoms line again, type “water”, and
press Enter.
4. Keep VDW as the Drawing method. Select Coloring Method and choose
ResName. Click Create Representation to store the water view as a separate
representation.
5. To save the current view (protein+water) in the script file, select File menu in the
VMD Main window and choose Save State option. The saved VMD script will
have the extension *.vmd. Before loading at a later time a saved state make sure
that VMD Main window show no other loaded molecules.
19
20. 6. If there are loaded molecules, highlight them, select Molecule menu and choose
Delete Molecule. As a result for each MD stage there will be a separate VMD
script file, containing a graphical representation.
7. Animations of the full system (peptide+water) may be slow depending on CPU
power. In this case, either reduce the sphere size or eliminate the water
representation.
8. The snapshots may be saved as postscript pictures using the option Render in the
File menu.
Project report: The project report must contain a full description and explanation of all
the simulation steps taken. The following plots must be included for both polyvaline and
polyalanine peptides:
1. Dependence of the potential energy on minimization step
2. Time dependencies of the potential energy and temperature for heating and
equilibration stages
3. Time dependence of the total energy and temperature during production run
4. Ramachandran plots showing dihedral angle distributions and boundaries of
helical and strand structure (as in Fig. 6)
5. Include pictures of the final production structure (peptide plus water) for each
peptide visualized using VMD.
Figure 6. Ramachandran plot for polyvaline peptide. The probability of dihedral angles
P(φ,ψ) is color coded. All dihedral angles are localized in the β-strand region.
20
21. Part III. Solvation of peptide structure
In most MD simulations the very first step involves the solvation of a protein structure
with solvent (usually water). This means that water molecules must be randomly
distributed with some density around a protein to fill the entire unit cell. In what follows
the preparation of solvated polyvaline peptide is considered. Initial polyvaline peptide
structure (with no water around) is contained in the file val0.pdb. (Note that this file
contains only heavy atoms and no hydrogen atoms.) The easy way to solvate this
structure is to use VMD program.
There are two main steps in preparing solvated system:
1. In the command line window of VMD (vmd console) type the command play
build.vmd. The script build.vmd loads the pdb file and call in the psfgen
program, which serves as a plugin for VMD. psfgen is a tcl interpreter, which
reads in a CHARMM topology file top_all22_prot.inp and based on the
sequence information in pdb file creates a psf peptide topology file. psfgen adds
missing atoms (hydrogens) as well as adds terminals (acetyl terminal ACE and
standard NH2 terminal CT2). The resulting peptide topology file is saved to
val.psf. psfgen then loads again pdb file and guesses the positions of missing
atoms. The all-atom structure is finally saved to val.pdb (no water).
2. The next step is to distribute water molecules around the peptide. This is
accomplished by the script solv.vmd. This script first reads the topology and the
coordinates of polyvaline and then calls the program solvate, which distributes
waters around the peptide. (Note solvate is a plugin for VMD and as psfgen
comes with VMD package).
The following options determine the details of peptide solvation:
(1) –o val_solv specifies the name for final (pepetide+water) topology and
coordinate files;
(2) –s WT indicates the name of the water box to be used for peptide solvation (water
box is also included in VMD distribution);
(3) -b 2.4 gives the minimum distance between peptide and waters. All waters
positioned closer than 2.4 A to the peptide are deleted;
(4) –minmax { {-15 -15 -15} {15 15 15} } specifies the dimensions of the solvated
system using the format {{–xmin –ymin –zmin} {xmax ymax zmax} }.
The final solvated system val_solv.pdb has the dimensions 30 x 30 x 30 Å and contains
2422 atoms (or 787 residues). Because of slightly different water boxes, the dimensions
and the number of atoms in this version of solvated polyvaline do not coincide with the
21
22. ones used in MD simulations. For polyvaline peptide the scripts build.vmd and solv.vmd
can be used without any modifications. For polyalanine remember to change the
following:
1. all names val must be replaced with ala2
2. change the name of the segment VAL4 with ALA9
3. to obtain proper size of solvation box set the (x,y,z)min and (x,y,z)max to 18 Å
22