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: Evaluasi Kesehatan Pohon Peneduh di Kota Bandar Lampung Berbasis Sonic Tomography
Abstrak: Shade trees take an important role in urban ecosystem for its function on social, economy and ecology. It also have worth value to provide aesthetic, cool, and enjoyment in urban area. On the other hand the condition of this shade trees were lost attention. Therefor monitoring and evaluation of tree health is became important as a part of tree management. A study was conducted to evaluate health condition of shade trees in Bandar Lampung using visual assesment as well as sonic wave propagation measurement. Eighteen road were choosen as the sample road based on density of shade trees. The result showed that angsana (Pterocarpus indicus) was the dominant species that found 53% of one hundred sample of shade trees. The major deterioration symptoms that appear in trees were epiphytes attack (1%), hollow (1%), cavity (2%), and cancer (2%). Non-destructive evaluation by using PiCUS Sonic Tomograph showed that 70% of shade trees were in healthy condition as indicated with solid wood persentage above 75% from tomogram image.
Keyword: visual assesment, tomogram image, shade trees, NDT

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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