Judul: Keanekaragaman dan Distribusi Bivalvia dan Gastropoda (Moluska) di Pesisir Glayem Juntinyuat, Indramayu, Jawa Barat
Abstrak: There are several species of molluscs from bivalves and gastropods living in the coastal area of Glayem, Indramayu, West Java. They are used by people for animal feed ingredients, craft materials and other economic activities. The aims of the research were to study diversity and distribution of molluscs in the coastal area and influencing abiotic factors. The research was conducted on January-May 2012. Mollusc samples were collected from 3 stations randomly by using quadrat transect method from the coast line to the reef edge. Generally, the water quality in the coastal of Glayem is fair good, but the ammonia level at all three stations exceeded the standard quality. We found 15 species; 6 species belongs to bivalve, and 9 species belongs to gastropod. The highest Important Value Index (IVI) was showed by Donax incarnatus with 51.28%. The lowest IVI of 1% was displayed by three species of molluscs from class gastropod. The diversity index (H’) ranged from 1.17-1.41, the Evenness index (E) ranged from 0.43-0.52, the dominancy index (C) at each stations of 0.01. The highest density of bivalve at station 3 was 16.4 ind/m2, and the highest density of gastropod at station 1 was 8 ind/m2. The highest Similarity index found in station 2 and 3 was 0.875. Meanwhile, the distribution of 11 species of molluscs was clump and the other 4 species was distributed randomly.
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Judul: Keanekaragaman dan Distribusi Gastropoda dan Bivalvia (Moluska) di Muara Karang Tirta, Pangandaran
Abstrak: Karang Tirta estuary is an estuarine zone located in Pangandaran, West Java. Substrate of the area was dominated by coarse sand and its salinity ranges from 10-25 ‰. The aim of the reaserch was to know the diversity and distribution of gastropod and bivalve in the estuary of Karang Tirta, Pangandaran and environmental factors affecting them. Samples of molluscs were collected from 3 stations choosen randomly by using quadrat method. Seventeen species were found in the study sties, 12 species belong to gastropod and 5 species of bivalve. The highest Importance Value Index (IVI) among the species was observed on Tellina radiata with 47.449 %. The lowest IVI was observed on four species belong to gastropod and bivalve with 1.949 %. The diversity index (H') ranged from 0.536 to 2.429, the evenness index (E) was from 0.189 to 0.857, and the dominant index (C) was from 0.001 to 0.037. The highest diversity index (H’ = 2.429) was found at station 2 and the lowest (H’ = 0.536) was at station 1. The similarity ranged from 0.235 to 0.522. The distribution patterns of molluscs occured mostly in clumps (Id > 1).
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Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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