Judul: Productivity Increasing of Robusta Coffee (Coffea canephora Pierre ex. A. Froehner) through Maintenance Pruning at Bangelan Plantation, PT Perkebunan Nusantara XII, Malang, East Java
Abstrak: Kopi merupakan komoditas sub sektor perkebunan yang berperan penting terhadap pendapatan negara. Pemangkasan pemeliharaan merupakan teknik budidaya yang berperan penting terhadap produktivitas kopi. Tujuan kegiatan magang, yaitu mempelajari, melatih keterampilan, memperoleh pengalaman kerja di lapangan mengenai pengusahaan tanaman kopi di perkebunan, baik dari aspek teknis maupun aspek manajerial, terutama mempelajari pengaruh pemangkasan pemeliharaan terhadap produktivitas. Pelaksanaan magang di Kebun Bangelan PTPN XII, Malang berlangsung dari bulan Januari hingga Juni 2021. Pengamatan peubah-peubah terkait aspek khusus pemangkasan dilakukan untuk memperoleh data primer. Pengumpulan data sekunder dari laporan manajemen perusahaan. Peubah-peubah yang diamati adalah tinggi tanaman, jumlah cabang produktif, tunas air, jumlah dompolan dan buah kopi gelondong. Tanaman kopi yang diamati dari 3 blok berbeda yang mewakili kelas kebun dengan tahun tanam yang sama, yaitu tahun tanam 2013. Pemangkasan pemeliharaan meliputi wiwil kasar dan wiwil halus yang dilakukan dengan teknik dan manajemen yang baik dapat berpengaruh positif pada cabang produktif. Pemangkasan pemeliharan dapat meningkatkan produktivitas sebesar 73%., Coffee is a commodity of the plantation sub sector that plays important role in state income. Maintenance pruning is a cultivation technique that plays an important role in coffee productivity. The purpose of the internship activity is to learn, train skills, gain work experience in the field regarding the exploitation of coffee plants in plantations, both from the technical and managerial aspects, especially studying the effect of pruning maintenance on productivity. The internship at Bangelan Plantation PTPN XII, Malang was started from January to June 2021. Observations of variables related to special aspects of pruning are carried out to obtain primary data. Secondary data collection is obtained from company management reports. The variables observed were plant height, number of productive branches, water shoots, number of dompolan and coffee fruits. Coffee plants were observed from 3 different blocks representing each garden class with the same planting year, namely the planting year 2013. Pruning maintenance, namely coarse wiwil and fine wiwil which is carried out with good and correct techniques and management can have a positive effect on productive branches. Pruning maintenance can increase productivity by 73%.
Keyword: Bangelan Plantation, maintenance pruning, productive branches, productivity, Robusta

Judul: Harvest and Postharvest Management of Robusta Coffee (Coffea canephora Pierre ex Froehner) at Bangelan Plantation, PT Perkebunan Nusantara XII, Malang, East Java
Abstrak: Kopi merupakan salah satu komoditas perkebunan yang banyak dibudidayakan di Indonesia. Kegiatan panen merupakan faktor yang sangat berepengaruh dalam kualitas dan citarasa kopi sehingga perlu dilakukan manajemen panen yang baik. Kegiatan magang dilaksanakan di PT Perkebunan Negara XII Kebun Bangelan, Malang, Jawa Timur pada 18 Januari hingga 9 Juni 2021. Kegiatan magang memiliki tujuan untuk menambah pengetahuan, memperoleh pengalaman, dan keterampilan kerja tentang budidaya kopi robusta dengan aspek khusus yang diamati tentang manajemen pemanenan kopi robusta. Aspek khusus yang diamati meliputi persiapan panen, pelaksanaan panen, dan pasca panen. Data yang diamati dianalisis secara kuantitatif dan deskriptif dengan menggunakan rata-rata, persentase, dan uji komparasi (t-student). Kegiatan panen di Afdeling Besaran Kebun Bangelan sudah cukup baik terlihat dari produksi yang sudah sesuai dengan taksasi serta kualitas petik yang sudah memenuhi standar perusahaan. Walaupun demikian beberapa hal perlu ditingkatkan seperti persiapan areal yang akan dipanen, persiapan tenaga kerja panen, kehilangan hasil yang sangat tinggi, terdapat buah hijau yang ikut terpetik sebesar 1,35%, serta persentase bubuk buah (buah terserang PBKo) yang mencapai 23,41%., Coffee is one of the plantation comodities that is widely cultivated in Indonesia. Harvesting activity is a infulential factor in the quality and taste of coffee so it is necessary to do a good harvest management. Internship was held at Bangelan Plantation, PT Perkebunan Nusantara XII, Malang, East Java from January 18th until June 9th 2021. The internship activity aims to increase knowledge, gain experience, and work skill regarding robusta coffee cultivation with specific aspect observed about harvest management of robusta coffee. Specific aspect were observed include harvest preparation, harvest implementation, and post harvest management. Observation data were analyzed quantitatively and descriptively using averages, percentages, and comparative test (t-student). Harvest activities in Besaran Section Bangelan Plantation its quite well as seen from production result already in accordance with production estimate and harvest quality was reach the company standard. However several things need to be improved such as preparation of the area to be harvested, preparation of labor for harvesting, very high yield loss, 13,5% of unripe fruit harvested, and 23,41% fruit affected by Cherry Berry Borrer (CBB)
Keyword: kopi robusta, manajemen panen, pascapanen, taksasi produksi

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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