Judul: Hydroponic vegetable production planning at pt. Kebun sayur segar (parung farm), bogor, west java
Abstrak: Seiring meningkatnya kesadaran dan kepedulian masyarakat terhadap kesehatan, sayuran kini menjadi alternatif pilihan dalam pola konsumsi masyarakat Indonesia. Pertumbuhan konsumsi sayuran pada tahun 2008 hingga 2011 mengalami penurunan, namun pada tahun 2012 pertumbuhan bernilai positif. Hal tersebut berarti bahwa ada kecenderungan perubahan dalam tingkat konsumsi sayuran masyarakat Indonesia yang akan berimplikasi pada peramalan permintaan dan perencanaan produksi yang akan dilakukan oleh suatu perusahaan. Salah satu perusahaan yang bergerak di bidang agribisnis ialah PT. Kebun Sayur Segar (Parung Farm) yang memproduksi beberapa sayuran hidroponik, seperti bayam hijau, kangkung, romaine dan sebagainya. Berdasarkan hasil ramalan untuk lima bulan kedepan, permintaan bayam hijau berkisar antara 300 hingga 400 pak perhari, permintaan kangkung berkisar antara 220 hingga 270 pak perhari, dan permintaan romaine berkisar antara 100 hingga 148 pak perhari. Puncak permintaan ketiga komoditi terjadi pada hari-hari akhir di bulan Juli 2014, yakni tanggal 24 dan 25 Juli 2014. Jika ditarik mundur dari tanggal tersebut, maka secara umum berdasarkan karakteristik masing-masing komoditi, perencanaan produksi akan dimulai pada bulan Juni 2014 dengan memperhatikan masa N1, N2 serta N3 dari masing-masing komoditi., By increasing awareness and public awareness of the health, now vegetables is as alternative patterns of consumption in Indonesia. Vegetables consumption growth in 2008 and 2011 has decreased, but in 2012 growth is positive. This means that there is a trend of change in the rate of Indonesian society vegetables consumption which will have implications for demand forecasting and production planning will be done by a company. One of the agribusiness companies is PT. Kebun Sayur Segar (Parung Farm) which produces some hydroponic vegetables, such as green spinach, kale, romaine, and so on. Based on the results of the forecast for the next five months, demand for green spinach ranged from 300 to 400 packs per day, demand kale ranged from 220 to 270 packs per day, and romaine demand ranged from 100 to 148 packs per day. Peak demand occurs in the third commodity these days in the month end of July 2014, which is dated 24 and 25 July 2014. If pulled backwards from that date, it is generally based on the characteristics of each commodity, production planning will begin in June 2014 with regard period N1, N2 and N3 of each commodity.
Keyword: hidroponik, Parung Farm, peramalan, perencanaan produksi

Judul: Optimize Hydroponic Vegetable Production Plan at PT Sumber Agro Semesta (PT SAS), Tanjung Sari District, Bogor Regency
Abstrak: Perencanaan jadwal tanam sayur hidroponik di PT Sumber Agro Semesta (PT SAS) masih dilakukan secara subjektif oleh PIC hidroponik, yaitu dengan menggunakan prakiraan rata-rata permintaan sayur pada siklus sebelumnya. Perencanaan jadwal tanam belum dilakukan berdasarkan prakiraan permintaan sehingga terjadi perbedaan antara rencana tanam dan permintaan aktual. Kapasitas greenhouse produksi sebesar 38.556 lubang tanam juga belum digunakan secara maksimal sehingga banyak lubang tanam yang tidak terisi. Adapun tujuan dari penelitian ini adalah menentukan prakiraan permintaan, serta menentukan rencana produksi yang optimal berdasarkan prakiraan permintaan dan penggunaan maksimal kapasitas greenhouse. Prakiraan permintaan pada pakcoy, bayam hijau, caisim, kangkung dan kailan dilakukan melalui dua metode, yaitu menggunakan metode ARIMA dan asumsi peningkatan permintaan sebesar 10% dari permintaan aktual yang terakhir. Hasil optimasi dengan teknik linear programming pada kedua kondisi tersebut menghasilkan keuntungan masing-masing sebesar Rp. 71.296.390 untuk hasil optimasi berdasarkan metode ARIMA dan Rp. 70.690.398 untuk hasil optimasi berdasarkan asumsi peningkatan permintaan sebesar 10%. Selain itu, dilakukan pula optimasi produksi berdasarkan penggunaan maksimal kapasitas greenhouse produksi. Sayur yang dioptimasi penjadwalannya adalah pakcoy, bayam hijau, caisim, kangkung, kailan, siomak, pagoda, bayam merah, romain, selada, dan kale. Hasil optimasi dengan teknik linear programming pada kondisi tersebut menghasilkan keuntungan sebesar Rp. 70.904.345 dan total bobot produksi sekitar 1,5 ton., The planning of the hydroponic vegetable planting schedule at PT Sumber Agro Semesta (PT SAS) is still subjectively to hydroponic PIC, using the forecast of the average vegetable demand in the previous cycle. The planting schedule has not been planned based on the demand forecast, so there is a difference between the planting plan and the actual demand. The greenhouse production capacity of 38,556 planting holes has not been used optimally, so many planting holes are not filled. The purpose of this research is to determine the demand forecast and determine the optimal production plan based on the demand forecast and the maximum use of a greenhouse. Forecasting demand for pakcoy, green spinach, caisim, kangkung, and kailan is made through two methods, namely using the ARIMA method and the assumption of an increase in demand by 10% from the last actual demand. Techniques of linear programming in both conditions produce a profit of Rp. 71,296,390 for optimization results based on the ARIMA method and Rp. 70,690,398 for optimization results based on the assumption of a 10% increase in demand. In addition, production optimization is also carried out based on the maximum use of greenhouse production capacity. Vegetables that are optimized for scheduling are pakcoy, green spinach, caisim, kale, kailan, dumplings, pagoda, red spinach, romain, lettuce, and kale. Techniques of linear programming in these conditions generate a profit of Rp. 70,904,345 and a total production weight of about 1.5 tons.
Keyword: ARIMA, demand forecasting, linear programming, production plan

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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