Judul: Kajian Morfologi, Produktivitas, dan Kualitas Nira Aren pada Beberapa Tingkat Umur Sadap di Banjarnegara
Abstrak: Arenga pinnata (Wurmb) Merr. merupakan pohon serbaguna yang bermanfaat sebagai bahan makanan dan non makanan, serta sebagai konservasi tanah dan air. Produk utamanya adalah nira aren yang mengandung gula yang dikumpulkan dari penyadapan infloresen jantan. Tujuan penelitian ini adalah mempelajari karakter morfologi, produktivitas, dan kualitas nira aren pada beberapa tingkat umur sadap. Hal ini penting dilakukan untuk mendapatkan informasi mengenai karakter agronomi, produktivitas, dan kualitas nira aren untuk pembuatan gula kristal. Gula aren memiliki prospek pasar yang tinggi di level domestik dan internasional, namun belum dapat dimanfaatkan dengan baik oleh masyarakat. Penelitian ini telah dilaksanakan bulan Agustus 2016 sampai April 2017 di Desa Pringamba, Kecamatan Pandanarum, Kabupaten Banjarnegara. Teknik sampling yang digunakan adalah non probability sampling jenis purposive sampling. Hasil sampling mendapatkan 15 pohon dengan rincian: 3 pohon pada tingkat umur sadap awal, 9 pohon tingkat umur sadap tengah, dan 3 pohon tingkat umur sadap akhir. Penelitian ini menggunakan metode studi deskriptif dengan melibatkan para petani. Analisis tanah telah dilakukan di laboratorium Ilmu Tanah Universitas Jenderal Soedirman dan pengujian kadar gula telah dilakukan di Laboratorium Terpadu Institut Pertanian Bogor menggunakan High Performance Liquid Cromatography. Hasil penelitian menunjukkan bahwa karakter morfologi pada tiga tingkat umur sadap dijabarkan sebagai berikut: tinggi tanaman berkisar 9.90 sampai 18.50 m, lingkar batang 0.50 dan 1.50 m di atas permukaan tanah berkisar 60.0 sampai 195.0 cm dan 70.0 sampai 210.0 cm, jumlah infloresen betina berkisar 2 sampai 4, jumlah daun berkisar 7 sampai 12, lingkar tangkai tandan sadap berkisar 20.0 sampai 35.0 cm, posisi nomor infloresen yang disadap berkisar 2 sampai 12, dan tinggi infloresen jantan yang disadap berkisar 5.20 sampai 16.20 m. Komponen produksi nira pada tiga tingkat umur sadap dijabarkan sebagai berikut: jumlah hari sadap berkisar 15 sampai 214 hari, volume nira pagi berkisar 41.30 sampai 1 511.00 l/infloresen, volume nira sore berkisar 34.80 sampai 1 139.00 l/infloresen, debit nira pagi berkisar 0.20-0.96 l/infloresen/jam, debit nira sore berkisar 0.23-0.67 l/infloresen/jam, volume total berkisar 76.10 sampai 2 650.00 l/infloresen, dan produktivitas nira berkisar 4.47-14.62 l/infloresen/hari. Kualitas nira aren pada tiga tingkat umur sadap dijabarkan sebagai berikut: padatan total terlarut berkisar 11.00 sampai 16.80 %, keasaman nira berkisar 7.00 sampai 7.10, dan kadar gula nira aren berkisar 8.09 sampai 13.52%.
Keyword: infloresen jantan, lama penyadapan nira, volume nira

Judul: Karakter Agronomi Tanaman Aren (Arenga pinnata (Wurmb) Merr.) untuk Produksi Nira
Abstrak: This research was aimed to study the agronomic performance of tapped sugar palm tree and their sap production. Experiment used 15 productive trees of sugar palm that were tapped by 3 farmers. The observation including volume of sap every morning and evening for each male infloresence while brown sugar was observed everyday per farmer. Results showed that sugar palm trees in the research site of Desa Salagedang, Kecamatan Cibeber, Kabupaten Cianjur, have range of trunk height between 6.9 – 20.3 m, with a trunk circumference of 0.5–1.53 m and up to the 14th position of the male infloresence, it can still be taped for 50 days and producing sap with volume until 233.3 liters. Growth environment of sugar palm in the research sites had a pH range of 5.0–6.4, range of the light intensity under the canopy near the soil surface from 1243–49012 lux, and range of the temperature from 25.7–31.3 oC with a relative humidity of 53.7–78%. Sap production of male infloresence varied in the range of 6.5–1045.7 liters with an average 5.4 liters per infloresence perday, with tapping period range between 2–167 days. Morning tapping (with an average 118 liters/infloresence and averaging 3.1 liters per day per infloresence) generally 40.3% higher than evening tapping (with an average 84.1 liters/infloresence and averaging 2.2 liters per day per infloresence). Brown sugar that was produced has a yield approximately 14.2% of brown sugar weight of sap volume. Arenga sap has content 0.12% of fructose, 0.16% of glucose, and 12.47% of sucrose with a total 12.75%.
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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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