Judul: Photothermal Unit Approach for Determination of Development Phases and Harvest Time of Eight Bambara Groundnut (Vigna subterranea L.)
Abstrak: Terbatasnya benih bermutu merupakan salah satu permasalahan yang sering dihadapi oleh petani kacang Bambara. Benih mencapai mutu maksimum saat masak fisiologis. Waktu masak fisiologis tanaman berbeda pada setiap lokasi penanaman dan faktor lingkungan yang mempengaruhinya, terutama suhu harian dan lama penyinaran sinar matahari. Photothermal unit merupakan konsep yang menjelaskan hubungan antara perkembangan tanaman dengan suhu dan lama penyinaran. Penelitian ini bertujuan mempelajari photothermal unit tiap fase perkembangan serta waktu panen terbaik delapan lanras kacang Bambara. Rancangan percobaan yang digunakan yaitu rancangan kelompok lengkap teracak satu faktor yakni lanras yang dilakukan pada dua lokasi dengan masing-masing 5 lima taraf dan 3 taraf berupa lanras tanaman. Lokasi percobaan pertama beada pada Kebun Percobaan Cikabayan dengan lima taraf : Bogor, Sukabumi, Sumedang testa hitam kecil, Sumedang testa cokelat. Lokasi kedua di Kebun Percobaan Sawah Baru dengan tiga taraf : Sumedang testa hitam besar, Tasikmalaya testa hitam kecil, Tasikmalaya testa hitam besar, dan Gresik. Hasil penelitian menunjukkan bahwa setiap lanras tanaman kacang Bambara membutuhkan waktu yang berbeda untuk mencapai setiap fase perkembangan dan akumulasi nilai photothermal unit nya. Nilai photothermal unit yang dibutuhkan untuk mencapai waktu panen lanras Bogor, Gresik, dan Tasikmalaya testa hitam kecil 10710 ℃ d h, lanras Sukabumi 10760 ℃ d h, Sumedang testa hitam kecil dan Tasikmalaya testa hitam besar 10342,72 ℃ d h, lanras Sumedang testa cokelat 11540 ℃ d h dan lanras Sumedang testa hitam kecil 11756,7 ℃ d h., Lack of quality seeds is one of the problems often faced by Bambara groundnut farmers. Seed reaches its maximum quality at physiological maturity. The physiological maturity time is different for each planting location and environmental factors that influence it, especially daily temperature and duration of irradiation. A photothermal unit is a concept that explains relationship between plant development, temperature, and duration of irradiation. This experiment aimed to study the photothermal unit of each developmental phase and the best harvest time for eight landraces of Bambara groundnut. The experimental design used was a one-factor randomized complete block design, namely landraces conducted at two locations, each with five levels and three levels consisting of plant varieties. The first experiment location was at the Cikabayan Experimental Garden with five levels: Bogor, Sukabumi, small Sumedang black testa, Sumedang brown testa. The second location was at the Sawah Baru Experimental Garden with three levels: large Sumedang black testa, small Tasikmalaya black testa, and large Tasikmalaya black testa. The results showed that each landrace of the Bambara groundnut plant required a different time to reach the stage of development and to accumulate the photothermal unit requirement. The photothermal unit needed to achieve the harvest time of the Bogor, Gresik, and small Tasikmalaya black testa were 10710 ℃ d h, Sukabumi 10760 ℃ d h, small Sumedang black testa and large Tasikmalaya black testa 10342.72 ℃ d h, Sumedang brown testa 11540 ℃ d h and small Sumedang black testa 11756.7 ℃ d h.
Keyword: daily temperature, duration of irradiation, physiological maturity, seed quality, yield component

Judul: Seed Production of Several Bambara Groundnut (Vigna subterranea L. Verdcourt) Landraces in Different Plant Spacing
Abstrak: Rendahnya minat petani untuk membudidayakan kacang Bambara salah satunya disebabkan terbatasnya ketersediaan benih. Salah satu upaya yang dapat dilakukan dalam meningkatkan ketersediaan benih adalah dengan menentukan teknik budidaya yang tepat agar memperoleh hasil yang maksimal. Penelitian ini bertujuan untuk mempelajari pengaruh lanras dan jarak tanam terhadap produksi dan mutu benih kacang bambara. Percobaan disusun dalam rancangan kelompok lengkap teracak faktorial dengan dua faktor yaitu lanras (Sumedang, Sukabumi, Bogor, dan Gresik) dan jarak tanam (60 cm x 25 cm dan 50 cm x 25 cm). Pertumbuhan vegetatif tertinggi ditunjukkan oleh lanras Sumedang (tinggi tanaman dan lebar kanopi) dan Gresik (jumlah tangkai daun dan jumlah daun). Jarak tanam 60 cm x 25 cm meningkatkan tinggi tanaman dan lebar kanopi pada seluruh lanras. Pertanaman dengan jarak tanam 60 cm x 25 cm mengalami laju fotosintesis yang lebih tinggi dan meningkatkan jumlah polong per tanaman pada seluruh lanras dibandingkan 50 cm x 25 cm. Bobot kering polong per tanaman lanras Sumedang, Sukabumi dan Bogor tidak menunjukkan perbedaan nyata pada kedua jarak tanam. Lanras Gresik pada jarak tanam 60 cm x 25 cm menghasilkan bobot kering polong nyata lebih tinggi (79,32 g) dibandingkan ketiga lanras lainnya, dan dibandingkan pada jarak tanam 50 cm x 25 cm (36,65 g). Keempat lanras menghasilkan bobot kering benih per tanaman yang nyata lebih tinggi pada jarak tanam 60 cm x 25 cm dibandingkan 50 cm x 25 cm. Lanras Sumedang menghasilkan bobot kering benih per tanaman terendah (39,10 g) dan berbeda nyata dengan ketiga lanras lainnya (42,15 – 43,68 g) pada jarak tanam 60 cm x 25 cm. Lanras Bogor pada jarak tanam 50 cm x 25 cm menghasilkan bobot benih per tanaman tertinggi (37,75 g) yang berbeda nyata dari ketiga lanras lainnya, sedangkan lanras Gresik terendah (23,70 g). Lanras Sumedang, Sukabumi, dan Bogor menghasilkan bobot kering benih per petak yang lebih tinggi (0,96; 0,94; 0,91 kg) dibandingkan Gresik (0,53 kg). Lanras Sumedang menghasilkan bobot kering 100 butir benih tertinggi (72,61 g), sedangkan lanras Gresik terendah (59,58 g). Jarak tanam tidak berpengaruh pada mutu benih yang dihasilkan., The low interest of farmers to cultivate Bambara groundnut is partly due to the lack of seed availability. One of the efforts to increase the availability of seeds is to determine the proper cultivation techniques to produce maximum yields. This study aimed to evaluate the effect of landraces and plant spacing on the production and quality of Bambara groundnut seeds. The experiment was arranged in a factorial randomized complete block design with two factors: landraces (Sumedang, Sukabumi, and Bogor) and spacing (60 cm x 25 cm and 50 cm x 25 cm). The best vegetative growth was shown by the Sumedang landrace (plant height and canopy width) and Gresik (number of petioles and leaves). The 60 cm x 25 cm spacing increased plant height and canopy width in all landraces. The spacing of 60 cm x 25 cm resulted in a higher rate of photosynthesis and increased the number of pods per plant in all landraces than 50 cm x 25 cm. The dry weight of pods per plant from Sumedang, Sukabumi, and Bogor
Keyword: canopy width, photosynthetic rate, plant height, pod weight, seed  weight

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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