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: Diversity of Molluscs (Bivalve and Gastropod) in Carita Beach, Pandeglang, Banten.
Abstrak: Carita beach is one of a beach ecosystem that has variety of substrates. Substrates were dominated by sand and corral reef flat. There were vegetations such as seagrass and seaweed. The aim of the research was to know species richness and diversity of Bilvave and Gastropod in Carita beach, Pandeglang, Banten. The research was conducted on May 2008. Molluscs sample were collected from 4 stations randomly by using quadrat method. There were 34 species molluscs that had been observed, 3 species belong to Bivalves and 31 species belong to Gastropods. The highest Important Value Index (IVI) of all station was found in Donax cuneatus with 55.21%. The lowest IVI was found in thirteen species of Bivalve and Gastropod with 0.83%. The diversity index (H’) ranged from 0.130 to 2.216, the evenness index (E) was 0.072 to 0.717, and the dominant index (C) was 0.198 to 0.960. The highest diversity index (2.216) was found at station 4 and the lowest (0.130) was at station 1. The similarity index ranged from 0 to 0.744. Key word : diversity, quadrat method, Carita beach
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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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