Judul: Evaluasi Kesehatan Pohon Peneduh Jenis Angsana (Pterocarpus indicus Willd.) secara Sonic Tomography di Kota Surabaya
Abstrak: Shade trees in urban areas have very important roles for social, economic, ecological and aesthetics benefits. The health of shade trees could be detected by visual assessment as well as by non-destructive method. The internal condition of trunk is assessed by Sonic Tomography which is based on sound waves propagation in the wood. The objective of this research was to understand the health of shade trees in median street of Surabaya city. Ten street samples were chosen by purposive sampling according to the median paths. The result of this research shows that angsana (Pterocarpus indicus Willd.) was the dominant species found in Surabaya city. The results of sonic tomograph found that 75 trees were healthy trees with more than 75% of solid wood with sound wave propagation above 900 m / sec. Meanwhile there were four trees which suffered severe damage below 50% of solid wood.Visual observation showed that 44% healthy trees and 56% unhealthy conditions
Keyword: visual assessment, sound wave, shade trees, non-destructive test

Judul: Ornamental Tree Health Evaluation in City of Bogor Using Visual Observation and Ultrasonic Wave Based Technique
Abstrak: Pohon ornamental dalam ekosistem perkotaan (urban trees) tidak saja memiliki fungsi ekologis, tetapi juga memiliki fungsi sosial dan ekonomis yang sangat penting. Oleh karena itu keberadaan dan kondisi kesehatannya selayaknya mendapat perhatian yang memadai. Cara paling sederhana untuk mengetahui kesehatan pohon adalah dengan pengamatan visual terhadap kondisi fisik pohon tersebut. Akan tetapi dengan metode ini tidak dimungkinkan mengetahui kondisi bagian dalam batang pohon, seperti adanya busuk hati dan kerusakan dalam batang lainnya. Sementara itu sejak beberapa tahun yang lalu telah berkembang teknik evaluasi kesehatan pohon dengan menggunakan gelombang suara, khususnya gelombang ultrasonik. Teknik ini termasuk ke dalam kategori tanpa merusak (non destructive testing/evaluation). Suatu penelitian telah dilakukan untuk mengetahui kesehatan pohon ornamental di sepanjang Jalan Raya Pajajaran Kota Bogor, Jawa Barat, baik secara visual maupun dengan memanfaatkan rambatan gelombang ultrasonik yang dihasilkan dari alat Sylvatest Duo® (frekuensi 22 KHz). Pengamatan secara visual dilakukan terhadap ada tidaknya gejala deteriorasi pada pohon sasaran, dari pangkal batang hingga tajuk pohon. Sedangkan penilaian kesehatan pohon dengan alat Sylvatest Duo® didasarkan atas kecepatan rambatan gelombang.
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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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