Chronological Decomposition Heuristic: A Temporal Divide-and-Conquer Strateg...Alkis Vazacopoulos
The chronological decomposition heuristic (CDH) is a simple divide-and-conquer strategy intended to find rapidly, integer-feasible solutions to production scheduling optimization problems of practical scale. It is not an exact algorithm in that it will not find the global optimum although it does use either branch-and-bound or branch-and-cut. The CDH is specifically designed for production scheduling optimization problems which are formulated using a uniform discretization of time where a time grid is pre-specified with fixed time-period spacing. The basic premise of the CDH is to slice the scheduling time horizon into aggregate time-intervals or “time-chunks” which are some multiple of the base time-period. Each time-chunk is solved using mixed-integer linear programming (MILP) techniques starting from the first time-chunk and moving forward in time using the technique of chronological backtracking if required (Marriott and Stuckey, 1998; for more details see the extensive literature on constraint logic programming). The efficiency of the heuristic is that it decomposes the temporal dimension into smaller size time-chunks which are solved in succession instead of solving one large problem over the entire scheduling horizon. The basic idea of such a decomposition strategy was partially presented in Bassett et. al. (1996) whereby they provided a hierarchical interaction or collaboration between a planning layer and a temporally decomposed scheduling layer. For the CDH, we focus on the time-based decomposition of the scheduling layer without the need for a higher-level coordinating or planning layer.
For many industrial size problems, solving the MILP using commercial branch-and-bound or branch-and-cut optimization can be a somewhat futile exercise even for well-formulated problems of practical interest. Instead, many researchers such as Kudva et. al. (1994), Wolsey (1998), Nott and Lee (1999), Blomer and Gunther (2000) and Kelly (2002) have devised elaborate primal heuristic techniques to enable the solution of problems of large scale and complexity; these techniques can also be augmented by other decomposition strategies such as Lagrangean and Bender’s relaxation. Unfortunately with these heuristics global optimality or even global feasibility cannot be guaranteed, however these methods and others not mentioned, have proven useful for problems which are sometimes too large to be solved using conventional methods alone. Therefore, the CDH should be considered as a step in the direction of aiding the scheduling user in finding integer-feasible solutions of reasonable quality quickly.
Women Executives Correlates to Startup Successgordonkaren
This Dow Jones research study shows female executives positively
helps VC-backed companies. Particularly at VP and director levels, the participation from female executives makes a significant difference in pushing a company to its success.
Chronological Decomposition Heuristic: A Temporal Divide-and-Conquer Strateg...Alkis Vazacopoulos
The chronological decomposition heuristic (CDH) is a simple divide-and-conquer strategy intended to find rapidly, integer-feasible solutions to production scheduling optimization problems of practical scale. It is not an exact algorithm in that it will not find the global optimum although it does use either branch-and-bound or branch-and-cut. The CDH is specifically designed for production scheduling optimization problems which are formulated using a uniform discretization of time where a time grid is pre-specified with fixed time-period spacing. The basic premise of the CDH is to slice the scheduling time horizon into aggregate time-intervals or “time-chunks” which are some multiple of the base time-period. Each time-chunk is solved using mixed-integer linear programming (MILP) techniques starting from the first time-chunk and moving forward in time using the technique of chronological backtracking if required (Marriott and Stuckey, 1998; for more details see the extensive literature on constraint logic programming). The efficiency of the heuristic is that it decomposes the temporal dimension into smaller size time-chunks which are solved in succession instead of solving one large problem over the entire scheduling horizon. The basic idea of such a decomposition strategy was partially presented in Bassett et. al. (1996) whereby they provided a hierarchical interaction or collaboration between a planning layer and a temporally decomposed scheduling layer. For the CDH, we focus on the time-based decomposition of the scheduling layer without the need for a higher-level coordinating or planning layer.
For many industrial size problems, solving the MILP using commercial branch-and-bound or branch-and-cut optimization can be a somewhat futile exercise even for well-formulated problems of practical interest. Instead, many researchers such as Kudva et. al. (1994), Wolsey (1998), Nott and Lee (1999), Blomer and Gunther (2000) and Kelly (2002) have devised elaborate primal heuristic techniques to enable the solution of problems of large scale and complexity; these techniques can also be augmented by other decomposition strategies such as Lagrangean and Bender’s relaxation. Unfortunately with these heuristics global optimality or even global feasibility cannot be guaranteed, however these methods and others not mentioned, have proven useful for problems which are sometimes too large to be solved using conventional methods alone. Therefore, the CDH should be considered as a step in the direction of aiding the scheduling user in finding integer-feasible solutions of reasonable quality quickly.
Women Executives Correlates to Startup Successgordonkaren
This Dow Jones research study shows female executives positively
helps VC-backed companies. Particularly at VP and director levels, the participation from female executives makes a significant difference in pushing a company to its success.
(10 22) pojok riset, asosiasi ikan target. okasyawalarkan
Floating net cages (KJA) is one means of marine aquaculture (mariculture) are placed in water will act as FADs or fish aggregating devices (FAD) as a gathering place for various types of fish. Similarly to the artificial reef will serve as the breeding (nursery grounds) for various types of fish.
In general, the target fish belonging -Fish economically important fishes associated with artificial reefs and floating net which interact in the mornings and afternoons differ in amount and kind, this is because of differences in the nature and behavior based on the type of fish species. The target fish population changes from day to night fish in diurnal seen mostly during the day will take refuge in the reef and replaced by a nocturnal species that are not visible during the day. The fish-eating plankton are usually widely spread around the reefs during the day and hide or take refuge in the crevices of the reef at night, it is a cause of differences in the amount of the target fish species associated with artificial reefs and floating net. Thus the association structure of the target fish around the artificial reefs and floating net can be concluded that as a shelter and as a visitor species.
Transformasi Sosial Ekonomi Masyarakat Pesisir & Pedalaman di KalimantanTri Widodo W. UTOMO
Mencari Sebuah Model Kebijakan Pembangunan yang Memberdayakan
(Socio-Economic Transformation for Coastal and Remote Society in Kalimantan: A Search for Enabling Developmental Policy)
(10 22) pojok riset, asosiasi ikan target. okasyawalarkan
Floating net cages (KJA) is one means of marine aquaculture (mariculture) are placed in water will act as FADs or fish aggregating devices (FAD) as a gathering place for various types of fish. Similarly to the artificial reef will serve as the breeding (nursery grounds) for various types of fish.
In general, the target fish belonging -Fish economically important fishes associated with artificial reefs and floating net which interact in the mornings and afternoons differ in amount and kind, this is because of differences in the nature and behavior based on the type of fish species. The target fish population changes from day to night fish in diurnal seen mostly during the day will take refuge in the reef and replaced by a nocturnal species that are not visible during the day. The fish-eating plankton are usually widely spread around the reefs during the day and hide or take refuge in the crevices of the reef at night, it is a cause of differences in the amount of the target fish species associated with artificial reefs and floating net. Thus the association structure of the target fish around the artificial reefs and floating net can be concluded that as a shelter and as a visitor species.
2. Karakteristik Sosial Budaya Masyarakat Nelayan
Sektor Perikanan : 1. Budidaya Ikan
2. Penangkapan Ikan
Dalam pola kerjanya budidaya lebih menyerupai pertanian
dan peternakan daripada penangkapan ikan. Biasanya
seorang yg membudidaya ikan memperbaiki daerah
tertentu untuk meningkatkan pertumbuhan ikan dan
memperoleh hak atas ikan. Pemilikan ikan menyerupai
apa yg ada dalam pertanian.Sedangkan penangkapan
ikan bergantung pada kemudahan bersama (open access)
para nelayan yang mempunyai hak yang sama thd SD
karena tengkapan tergolong liar, berpindah dari satu
tempat ke tempat lain, ada elemen resiko yg dihadapi dan
nelayan harus berpindah-pindah. Sebaliknya memanen
hasil budidaya ikan lebih terkontrol.
3. Sumberdaya perikanan tangkap biasanya ditandai oleh
suatu tingkat kemampuan berubah yang tinggi.
Kemampuan berubah ini ada tiga macam, yaitu:
1. Jangka panjang, dapat diperkirakan (musiman).
2. Jangka panjang, tidak dapat diperkirakan (karena
perubahan populasi yg berkaitan dengan
penangkapan ikan yg berlebihan, iklim, atau faktor2
luar).
3. Jangka pendek, tidak dapat diperkirakan (bervariasi
dalam penangkapan sehari-hari).
Hal ini mengakibatkan kebanyakan masyarakat nelayan
telah membangun sifat khusus sosial budaya.
4. Karakteristik Sosial Budaya Masyarakat Nelayan:
1. Keterasingan Relatif
Dalam banyak hal nelayan sering seperti subbudaya
matapencaharian lainnya, membentuk masyarakat sendiri.
Nelayan juga sering terasing karena mereka harus hidup di
sepanjang tepi danau, sungai dan laut. Keterasingan relatif
ini semakin besar krn nelayan semakin terpisah dari
masyarakat daratan ketika menangkap ikan. Di samping itu,
krn banyak nelayan bekerja pd malam hari atau pagi buta, pd
saat orang lain masih tidur, nelayan sering dipandang sbg
orang yg terpencil dari masyarakat.
Tempat tinggal dan keterasingan sosial mempengaruhi
variabel sosial budaya, yg pd gilirannya mempengaruhi
pembangunan. Hal ini mungkin ikut mendukung rendahnya
tingkat pendidikan sebagian besar nelayan. Bahkan apabila
keterasingan tempat tinggal begitu besar, keterasingan
sosial mungkin mengakibatkan nelayan dan keluarganya
membentuk sikap negatif terhadap pendidikan formal pada
masyarakat bukan penangkap ikan. Misalnya ejekan thd
anak2 nelayan karena berpakaian jelek dan keluarga yang
secara relatif miskin membuat mereka gagal dari sekolah.
5. 2. Organisasi Kerja
Banyak perhatian telah diberikan pada kesaling-
tergantungan dan sifat kerja sama dalam kegiatan
penangkapan ikan. Koordinasi di antara awak kapal
penangkapan ikan, perlu ada dan dikombinasikan. Adanya
resiko fisik yang berkaitan dengan lingkungan laut,
menambah pentingnya kesaling-tergantungan setiap
pekerja. Bersamaan dengan cepatnya peralatan menyusut
dan kemungkinan hilangnya peralatan, kerja sama ini
mengurangi jarak sosial dan ekonomi antara pemilik dan
buruhnya.
Keselamatan dan keuntungan operasi suatu kapal/perahu
ikan tergantung pada saling ketergantungan dan kerja
sama awaknya. Keanggotaan sanak keluarga dalam suatu
regu mempertinggi kerja sama di dalam kelompok kerja
dan merupakan suatu praktik yang umum di banyak
tempat di dunia ini.
6. 3. Pembagian Tenaga Kerja
Pada beberapa sistem perekonomian wanita dapat
mengombinasikan fungsi subsistem dan mengasuh anak,
dalam penangkapan, khususnya penangkapan ikan di laut
dalam atau danau dengan perahu, sulit bagi wanita untuk
ikut terlibat di dalamnya. Oleh karena itu wanita biasanya
dibatasi pada kegiatan2 di tepi pantai (termasuk
penangkapan ikan dan kerang di air dangkal) dimana
pekerjaan tidak akan bertentangan dengan mengasuh
anak.
Pada banyak masyarakat penangkap ikan, wanita
mengambil alih fungsi membeli dan menjual ikan.
Pembagian kerja ini dapat membantu menyimpan sedikit
keuntungan keluarga, dimana pria penangkap ikan dan
anggota keluarga yang wanita menjual produk. Peranan
wanita sebagai pedagang ikan menstabilkan ekonomi pada
beberapa masyarakat penangkap ikan karena pria
mungkin hanya kadang2 menangkap ikan, tetapi wanita
bekerja sepanjang tahun.
7. 4. Hak-hak Atas Sumberdaya Laut
Satu organisasi sosial yang sangat penting adalah
pengawasan dan pemilikan sumberdaya alam. Pentingnya
sistem penguasaan lahan pertanian telah diakui secara
luas, tetapi penguasaan laut hingga saat ini jarang
diperhatikan apabila membahas masyarakat nelayan. Di
samping itu, sifat laut dan danau yang secara relatif sama
menyebabkan pembuatan batas di laut tidak sama dengan
lahan pertanian.
Singkatnya, aspek masyarakat dan budaya tentang
nelayan tersebut sungguh penting diketahui demi
terlaksananya pembangunan;
Pertama, perubahan sumberdaya secara musiman dan
ketidaksuburan daerah pesisir sering mengakibatkan
nelayan memutuskan untuk pindah tempat tinggal.
Perubahan jangka pendek yg tidak dapat diramalkan
mengakibatkan jam kerja tidak teratur dan perubahan
pendapatan yang memerlukan adanya penyesuaian
khusus mengenai keuangan.
8. Kedua, tempat tingga di sepanjang tepi aliran sungai,
danau, atau laut dan karakteristik yang tidak biasa dari
matapencahariannya (jam kerja tidak teratur, terpisah dari
masyarakat daratan) sering mengakibatkan nelayan
menjadi terasing secara sosial. Keterasingan sosial ini
menyulitkan mereka mencapai pendidikan formal dan juga
mempengaruhi sikapnya thd anggota lain dalam kelompok
masyarakat.
Ketiga, risiko fisik yang berkaitan dengan beberapa bentuk
penangkapan ikan, perlunya koordinasi di antara awak
perahu dan cepatnya alat2 menjadi menyusut, menuntut
kepercayaan awak perahu mengenai persamaan setiap
orang, mandiri dan bekerja sama, yg sering didasarkan
pada hubungan kekerabatan. Di samping itu
penanggulangan perselisihan hingga sekecil mungkin di
antara para awak perahu tergolong cepat. Jadi risiko fisik
akibat kebutuhan yang dibarengi dengan cepatnya
pengambilan keputusan menciptakan nelayan secara
relatif mandiri.
9. Keempat, penanganan secara khusus, pengolahan dan
pemasaran ikan membutuhkan para spesialis. Dalam
banyak hal, pembagian tenaga kerja ini didasarkan pada
jenis kelamin karena terbatasnya tempat kerja, lagi pula
pekerjaan ini berbahaya bagi anak2. wanita seringkali
mengambil alih kegiatan pengolahan dan pemasaran ikan
sambil mengasuh anak.
SELESAI….