Judul: Sebaran Lokal Asteroidea (Echinodermata) di Pulau Tikus, Gugusan Pulau Pari, Kepulauan Seribu
Abstrak: Penelitian ekologis tentang bintang laut anggota famili Asteroidea dilakukan pada tahun 2007 di Pulau Tikus Kepulauan Seribu. Tujuan penelitian adalah membandingkan densitas Asteroidea berdasarkan metode transek dan metode pemetaan, serta memperkirakan jumlah dan habitat Archaster typicus. Hasil penelitian menunjukkan bahwa di P. Tikus sebelah selatan terdapat 4 jenis Asteroidrea yaitu A. typicus, Linckia laevigata, Culcita novaeguinea dan Nordoa tuberculata. A. typicus merupakan spesies yang dominan. Densitas Asteroidea yang diperoleh dari metode pemetaan lebih tinggi dibandingkan dengan densitas hasil teknik transek. Selain itu, penggunaan metode pemetaan memungkinkan diperolehnya informasi tipe sebaran dari setiap jenis Asteroidea. A.typicus cenderung menempati area berdekatan dengan darat, dengan tutupan lamun 0- 30% dan ukuran partikel substrat 0,5-2 mm. Studi ini menunjukkan bahwa teknik pemetaan memberikan data jumlah individu yang lebih akurat dan pola penyebaran tiap populasi di Pulau Tikus.
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Judul: Kepadatan Archaster typicus Pada Ekosistem Lamun di Pulau Pari, Kepulauan Seribu
Abstrak: Ekosistem lamun tumbuh subur di perairan besubstrat lumpur, pasir dan kerikil bahkan patahan karang. Pulau Pari memiliki karakteristik substrat pasir putih yang halus. Berdasarkan kondisi karakteristik Pulau Pari dapat ditemui berbagai macam jenis biota laut salah satunya bintang laut dengan jenis A. typicus. Penelitian ini bertujuan menganalisis kepadatan A. typicus yang hidup pada ekosistem lamun di Pulau Pari, Kepulauan Seribu. Pengambilan data A. typicus dan lamun dilakukan pada tiga stasiun yaitu Stasiun Perawan, Stasiun Bintang, Stasiun Kresek di Pulau Pari, Kepulauan Seribu dengan menggunakan metode transek kuadrat berukuran 50 cm x 50 cm dengan panjang garis transek 50 m. Pengukuran dilakukan sebanyak tiga kali pengulangan dan jarak antar garis transek sebesar 25 m. Komposisi lamun pada Stasiun Perawan di dominasi T. hemprichii senilai 97,7%, pada Stasiun Bintang di dominasi oleh T. hemprichii senilai 66,1% dan pada Stasiun Kresek didominasi oleh E. acoroides dan T. hemprichii senilai 47,2%. Kerapatan lamun di Pulau Pari pada Stasiun Perawan sebesar 88 individu/m2, pada Stasiun Bintang sebesar 78 individu/m2 dan pada Stasiun Kresek bernilai 76 individu/m2. Kepadatan A. typicus pada Stasiun Bintang kepadatan bernilai 5 individu/m2 dan pada Stasiun Kresek kepadatan bernilai 2 individu/m2.
Keyword: A. Typicus, density, composition, quadratic transect, seagrass

Judul: Exergy Analysis of Membrane Utilization for Solution Separation in LiBr-H2O Absorbtion Refrigeration System
Abstrak: Absorbtion refrigeration system provides prominent advantages in tems of environmental impact and energy consumption. Absorbtion refrigeration system uses natural refrigerant, such as water, which gives no harm to the environment. In terms of energy consumption, it requires heat to regenerate refrigerant from its absorber and provide the refrigeration effect. This form of energy is preferred since heat can be supplied from various sources, including waste heat and renewable energy, and thermodynamically categorized as low quality energy. However, effectiveness of refrigerant regeneration could only be obtained if the temperature is high enough. In this study, the heat utilization in the regeneration process will be eliminated by introducing membranes for separating the refrigerant from the absorber. Specifically, the objectives of this research are to :1) to study the absorbtion mechanism of water vapor by LiBr-H2O solution in a controlled condition, 2) to study the regeneration process of LiBr-H2O using reverse osmosis (RO) membrane and vacuum membrane distillation (VMD) when applied in LiBr-H2O absorbtion refrigeration system, 3) to perform the energy and exergy analysis in LiBr-H2O absorbtion refrigeration system using RO membrane. The membrane was used as a tool to separate the refrigerant from absorbent which performs as regeneration process in conventional absorbtion system. As separation component, RO membrane employs pressure to oppose the osmotic pressure and pass certain component through the pores. While, VMD employs vacuum pressure and thermal, so that the substance to be transported through the membrane is in form of vapor. The result shows that absorbtion rate of water vapor by LiBr-H2O solution was influenced by solution concentration, temperature, humidity and pressure. The highest absorbtion rate was 0.031 g/minute which was occurred at temperature 40°C, RH 70% and solution concentration 60%. Prediction model was developed to calculate the absorbtion parameter inspite of P-T-X diagram.The highest water vapor absorbtion in absorber using spiral wound module-based RO membrane occurred at initial concentration of 30%, wich is the highest concentration used in the experiment. Increasing of operation pressure during separation process will increase permeation flux but decrease rejection factor.Unexpectedly, permeate of the RO membrane still contain LiBr at concentration 7w/w %-9w/w%, which affect the achievable cooling temperature and cooling capacity. Optimization of regeneration using VMD was conducted with response surface methodology (RSM) and the result show that highest permeate flux (0.93 kg.m-2.s-1) can be achived at initial concentration of 47.5%, temperature of 80°C and flow rate of 1.9 L.min-1.COP obtained in absorbtion refrigeration system using RO membran with initial concentration 20% was in the range of 1.147-1.171. Exergy analysis shows that increasing pressure of RO membrane at concentration 20% increased the irreversibity.On the other hand, exergy analysis on VMD shows that higher concentration and temperature will increased irreversibility.
Keyword: refrigeration, absorbtion, reverse osmosis, vacuum membrane distillation, energy, exergy