Judul: Optimization of Gold Fish (Carassius auratus) Aquaculture  in Ciseeng Village, Ciseeng District, Bogor Regency
Abstrak: Sektor perikanan merupakan sektor penting dalam pembangunan ekonomi nasional. Perikanan budidaya memiliki produksi dan pertumbuhan lebih besar dibandingkan perikanan tangkap. Budidaya ikan mas koki memiliki peluang yang besar untuk dikembangkan, namun sistem produksi budidaya komoditas tersebut belum optimal. Penelitian ini bertujuan (1) mengidentifikasi faktor-faktor yang memengaruhi produksi ikan mas koki (2) menganalisis tingkat optimal faktor produksi ikan mas koki (3) mengkaji kelayakan finansial usaha budidaya ikan mas koki (4) merumuskan alternatif kebijakan dalam budidaya ikan mas koki. Metode penelitian yang digunakan adalah metode survei. Jenis data yang digunakan adalah data primer dan sekunder. Metode sensus dan purposive sampling digunakan sebagai metode pengambilan contoh. Metode analisis data menggunakan analisis regresi berganda, analisis optimalisasi produksi, cost-benefit analysis, dan Weighted Sum Model. Hasil penelitian menunjukkan bahwa faktor yang berpengaruh nyata adalah benih, pakan, pupuk, dan lama pengalaman. Tingkat penggunaan input optimal ikan mas koki untuk satu siklus budidaya pada rata-rata luas kolam 3.231,7 m2 dengan kedalaman 1 m yaitu benih sebanyak 65.799,69 ekor atau sebesar 526,39 kg, pakan sebanyak 168,41 kg, dan pupuk sebanyak 990,96 kg. Produksi optimal ikan mas koki di Desa Ciseeng jika menggunakan input optimal pada tahun 2020 adalah 35.563,19 ekor atau 142,48 kg. Pengalaman pembudidaya rata-rata 10,7 tahun. Budidaya ikan mas koki pada kondisi aktual layak untuk dilakukan berdasarkan kriteria kelayakan investasi yaitu Net Present Value sebesar Rp 49.897.474, Net B/C sebesar 2,78, Internal Rate of Return sebesar 24%, dan Payback Period sebesar 4 tahun 6 bulan. Prioritas utama alternatif kebijakan dalam mengatasi hambatan budidaya adalah meningkatkan kapasitas kelompok pembudidaya ikan., The fisheries sector plays an important role in national economic development. Aquaculture has higher growth rate production compared to capture fisheries. Gold fish aquaculture has a great opportunity to be developed, however the aquaculture production has not been optimal yet. Based on that problem, the objectives of this research are (1) to identify the factors that affect the production of goldfish aquaculture (2) to analyze the optimal level of goldfish production factors (3) to examine the financial feasibility of goldfish aquaculture (4) to formulate and recommend alternative policies in goldfish aquaculture. The research method used is survey method. The type of data used are primary and secondary data. Census and purposive sampling are used in this research technique sampling. Data analysis methods used are multiple regression analysis, optimization of production, cost-benefit analysis, and Weighted Sum Model. The results of this research showed that factors which significantly affected the production were seeds, feed, fertilizer, and the length of experience. The optimal level used of input for one aquaculture cycle with an average area of pond 3.231,7 m2 and a depth of 1 meter are 65.799,69 fish or 526,39 kg, 168,41 kg of feed, and 990,96 kg of fertilizers. The optimal production of gold fish aquaculture in Ciseeng Village using optimal input in 2020 is calculated by 35.563,19 fish or 142,48 kg. The average experience farmers of fish is 10,7 years. The aquaculture of goldfish in actual condition is feasible based on financial feasibility criteria, respectively Net Present Value of Rp 49.897.474, Net B/C of 2,78, Internal Rate of Return of 24%,
Keyword: cost-benefit analysis, Cobb-Douglas function, aquaculture groups, optimal input, Weighted Sum Model

Judul: Study of the Effectiveness of Polyculture-Based Aquaponic  Systems of Koi Ornamental Fish (Cyprinus rubrofuscus) and Goldfish (Carassius auratus)
Abstrak: Sistem akuaponik telah banyak diterapkan dalam kegiatan budidaya ikan, namun masih jarang yang menerapkan sistem budidaya akuaponik berbasis polikultur. Penelitian kajian ini dilakukan dengan tujuan untuk mengetahui kinerja produksi ikan koi (Cyprinus rubrofuscus) dan koki (Carassius auratus) pada sistem akuaponik polikultur menggunakan tanaman kangkung air (Ipomoea aquatica). Metode pada penelitian kajian ini yaitu non eksperimental menggunakan dua jurnal ilmiah dengan pendekatan penelitian berupa metode studi pustaka. Penelitian pada kedua sumber pustaka dirancang dengan menggunakan metode RAL dengan tiga perlakuan. Perlakuan pada sumber pustaka pertama terdiri dari K (laju aliran air sebesar 0 L/menit), L1 (laju aliran air sebesar 0,8 L/menit), L2 (laju aliran air sebesar 2,4 L/menit), dan L3 (laju aliran air sebesar 4 L/menit) dengan masa pemeliharaan 45 hari. Perlakuan pada sumber pustaka kedua terdiri dari K (Rasio koi dan koki 1:1 (tanpa akuaponik), R1 (Rasio koi dan koki 1:1), R2 (Rasio koi dan koki 1:2), dan R3 (Rasio koi dan koki 2:1) dengan masa pemeliharaan 60 hari. Ikan koi dan koki memiliki pertumbuhan yang baik pada lingkungan dengan laju aliran air 2,4 L/menit dengan rasio padat tebar 1:2. Kinerja produksi dipengaruhi oleh ukuran tebar ikan, rasio padat tebar ikan, dan laju aliran air., The aquaponics system has been widely applied in fish farming activities, but it is still rare to apply a poly-culture based aquaponic cultivation system. This research study was conducted with the aim of knowing the production performance of koi (Cyprinus rubrofuscus) and goldfish (Carassius auratus) fish in a polyculture aquaponic system using water spinach (Ipomoea aquatica). The method in this study research is non-experimental using two scientific journals with a research approach in the form of a literature study method. Research on both sources of literature was designed using the RAL method with three treatments. The treatments at the first library source consisted of K (water flow rate of 0 L / min), L1 (water flow rate of 0.8 L / min), L2 (water flow rate of 2.4 L / min), and L3 (water flow rate of 4 L / min) with a maintenance period of 45 days. The treatments in the second library source consisted of K (Koi and goldfish ratio 1: 1 (without aquaponics), R1 (Koi to goldfish ratio 1: 1), R2 (Koi to goldfish ratio 1: 2), and R3 (Koi to goldfish ratio. 2: 1) with a maintenance period of 60 days. Koi fish and goldfish have good growth in the environment with a water flow rate of 2.4 L / minute with a stocking density ratio of 1: 2. Production performance is influenced by the stocking size of the fish, the stocking density ratio of the fish, and the water flow rate.
Keyword: aquaponics, Carassius auratus, Cyprinus rubrofuscus, Ipomoea aquatica, polyculture

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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