Judul: Evaluation of the Production Process and Physical  Quality of Gempol (Nauclea orientalis) Seedlings at Nursery Park PT Bukit Asam,  South Sumatra
Abstrak: Keberhasilan revegetasi di pertambangan dipengaruhi oleh ketersediaan bibit yang berkualitas. Kualitas bibit yang baik dapat dinilai dari proses produksi dan mutu fisiknya. Penelitian ini bertujuan mengevaluasi proses produksi dan menilai mutu fisik bibit gempol yang diproduksi oleh nursery park PT Bukit Asam (BA), Sumatera Selatan. Data proses produksi bibit gempol didapatkan dari hasil wawancara dengan pihak nursery park PT BA. Penilaian mutu fisik bibit gempol dilakukan berdasarkan Standar Nasional Indonesia (SNI) Bibit Tanaman Hutan (8420:2018) yang terdiri atas evaluasi persyaratan umum dan persyaratan khusus. Hasil penelitian menunjukkan bahwa proses produksi dan pemeliharaan bibit gempol di nursery park PT BA sudah cukup baik karena bibit gempol yang diproduksi oleh nursery park PT BA cukup untuk memenuhi kebutuhan kegiatan revegetasi lahan dan melayani permintaan bibit gratis. Selain itu, juga ditandai dengan hasil evaluasi mutu fisik bibit gempol pada persyaratan khusus yang telah memenuhi standar SNI. Namun, untuk evaluasi mutu fisik bibit gempol pada persyaratan umum masih perlu dilakukan perbaikan karena tidak memenuhi standar SNI, terkhusus pada kriteria kelurusan batang dan kondisi kesehatan bibit (terserang hama penyakit). Perbaikan bibit dapat dilakukan dengan monitoring hama dan penyakit secara rutin, serta melakukan penjarangan di bedengan open area nursery park PT BA., The success of revegetation in mining is greatly influenced by the availability of quality seeds. This research evaluates the production process and physical quality of gempol seeds in the PT Bukit Asam (BA) nursery, South Sumatra. Gempol seed production data was obtained from interviews with PT BA. Evaluation of the physical quality of seeds refers to the Indonesian National Standard (SNI) for Forest Plant Seeds (8420:2018). The research results show that the production and maintenance process for gempol seeds at PT BA is good, meeting revegetation needs and demand for free seeds. Apart from that, it is also marked by the results of evaluating the physical quality of gempol seeds according to special requirements that meet SNI standards. However, the physical quality of gempol seeds needs to be improved, especially the straightness of the stems and the health of the seeds which do not yet meet SNI standards. Improvements can be made by monitoring pests and diseases as well as thinning the beds in the open areas of PT BA's nursery gardens.
Keyword: kesehatan bibit, kualitas bibit, persyaratan khusus, persyaratan umum, Standar Nasional Indonesia 8420:2018

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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