Judul: Keanekaragaman Tumbuhan Bawah pada Tegakan Sengon Buto (Enterolobium cylocarpum Griseb.) dan Trembesi (Samanea saman Merr.) di Lahan Pasca Tambang Batubara PT Kitadin Embalut, Kutai Kartanegara, Kalimantan Timur
Abstrak: Mining activities have a negative impact on the environment, as the Minister of Energy and Mineral Resources Regulation No. 18 of 2008 regarding the Mine Closure Plan in which requires mining companies to conduct reclamation activities on any pit mine. The research was carried out aimed to assess the composition and diversity of plant species, especially in the areas under coal mine revegetation after PT Kitadin Embalut, Kutai Kartanegara, East Kalimantan. This research conducted on the revegetation area PT Kitadin of sengon buto and trembesi stand planted on the year of 2006 for four month period of observation. Data collection methods used was step undergrowth vegetation, and data analysis is the INP of undergrowth species and analysis of plant diversity. Results showed that the total species found in both stand is 24 species from 20 families which scattered in the stands of sengon buto as many as 22 species from 19 families and the trembesi stands as many as 17 species from 13 families. The most dominated species in both stands is Paspalum conjugatum and Solanum torvum. Diversity level of undergrowth plant under stands of sengon buto and trembesi classified as medium. Richness level of undergrowth plant species is relatively low with a value of Richness (R1) on the stands of sengon buto is 2.56 and richness on the trembesi stands is 1.96. Evenness of undergrowth species under sengon buto and trembesi stands is categorized high because both the values level (E) > 0.6. The similarity index of undergrowth in sengon buto and trembesi stands can be considered as the same because the value of the IS> 75%.
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Judul: Growth Analysis of Sengon Buto (Enterolobium cyclocarpum G.) Revegetation Results at PT Bukit Asam Tbk, South Sumatera
Abstrak: Batu bara merupakan salah satu sumber energi alternatif yang telah lama digunakan sebagai pengganti hidrokarbon seperti minyak bumi. Penambangan batu bara yang dilakukan dapat menyebabkan degradasi lahan yaitu penurunan kualitas dari lahan tersebut. Tujuan penelitian ini adalah menganalisis pertumbuhan sengon buto di lahan hasil revegetasi tambang batu bara PT Bukit Asam Tbk. Data penelitian diambil dengan cara membuat 3 plot berukuran 25 m × 40 m dengan metode penentuan plot systematic sampling with random start pada setiap tahun tanam (2011, 2013, dan 2015). Intensitas sampling yang digunakan sebesar 10% pada lahan revegetasi seluas 3 ha. Hasil penelitian menunjukkan revegetasi yang dilakukan oleh PT Bukit Asam Tbk dinyatakan berhasil karena memiliki persentase hidup yang tinggi (>90%). Tahun tanam dan jarak tanam sangat berpengaruh nyata terhadap pertumbuhan tinggi total, tinggi bebas cabang, diameter batang, dan live crown ratio. Semakin tua umur tanam dan semakin lebar jarak tanam, maka semakin tinggi nilai tinggi total, tinggi bebas cabang, dan diameter batang; namun semakin rendah nilai live crown ratio., Coal is one alternative energy source that has long been used as a substitute for hydrocarbons such as petroleum. Coal mining carried out can cause land degradation, namely a decrease in the quality of the land. The purpose of this study was to analyze the growth of sengon buto in revegetated land of PT Bukit Asam Tbk. The research data was taken by making 3 plots measuring 25 m × 40 m with a systematic plot sampling method with random start in each planting year (2011, 2013, and 2015). The sampling intensity used was 10% on 3 ha of revegetated land. The results showed that the revegetation carried out by PT Bukit Asam Tbk was declared successful because it had a high percentage of life (>90%). Planting year and spacing have a significant effect on total height growth, branch-free height, trunk diameter, and live crown ratio. The older the planting age and the wider the planting distance, the higher the total height value, branch-free height, and trunk diameter; But the lower the value of the Live Crown Ratio.
Keyword: coal, branch free height, live crown ratio, trunk diameter, tree height

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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