Judul: Tree Felling of Agroforestry Private Forest with Sandat  Technique in Private Forest in Probolinggo, East Java
Abstrak: Hutan rakyat memiliki peranan penting sebagai pemasok kayu bulat pada industri perkayuan, sumber pendapatan masyarakat, dan menjaga fungsi lingkungan. Hutan rakyat agroforestri membutuhkan teknik penebangan yang berbeda jika dibandingkan dengan hutan rakyat monokultur dan campuran. Penelitian ini bertujuan untuk menganalisis cara kerja dan kinerja teknik penebangan sandat di hutan rakyat agroforestri. Penelitian dilakukan di dua lahan hutan rakyat. Indikator kinerja teknik sandat yang diukur adalah kesalahan arah rebah (felling error), menyangkut pada tanaman lain (hang up), unusan (barber chair), dan tinggi tunggak. Data yang dikumpulkan di lapangan kemudian dilakukan analisis secara deskriptif yang disajikan dalam bentuk tabel dan gambar. Hasil penelitian menunjukkan bahwa kesalahan arah rebah (felling error) pada penebangan teknik sandat pada masing-masing lahan sebesar 0% dan 34,78%, menyangkut pada tanaman lain (hang up) sebesar 0% dan 26,09% dan tidak ditemukan unusan (barber chair) pada kedua lahan. Tinggi tunggak sisa penebangan pada lahan memiliki rata-rata sebesar 17,13 cm dan sebesar 16,35 cm., Private forests have an essential role as a supplier of logs in the timber industry, a source of income for the community, and maintain environmental functions. Agroforestry private forests require different felling techniques than monoculture and mixed private forests. This study aims to analyze the workings and performance of sandat felling techniques in private agroforestry forests. The study was conducted on two private forest lands. The performance indicators of the sandat technique measured are felling error, involving other plants (hang up), barber chair, and arrears height. The data collected in the field is then analyzed descriptive, which is present in the form of tables and figures. The results showed that felling errors in felling sandat techniques on each land amounted to 0% and 34,78%, concerned other crops (hang up) by 0% and 26,09%, and no barber chairs were found in both fields. The height of the remaining felling arrears on the land has an average of 17,13 cm and 16,35 cm.
Keyword: agroforestry, private forest, felling, sandat

Judul: Techniques, Productivity, and Costs of Tree Felling in Private Forests Kostajasa, Central Java
Abstrak: Penebangan pohon di hutan rakyat memerlukan teknik yang tepat untuk meminimalkan kerusakan yang ditimbulkan dan sesuai dengan kondisi lokal. Penelitian ini bertujuan untuk mengidentifikasi teknik-teknik penebangan pohon, menghitung produktivitas, dan biaya penebangan di hutan rakyat Kostajasa. Penelitian ini dilakukan di empat lahan hutan rakyat di Kostajasa, yang mana setiap lahan dikerjakan oleh tim penebang yang berbeda. Pengukuran waktu kerja dilakukan menggunakan metode null stop. Produktivitas dihitung dengan membagi volume pohon berdiri dengan waktu kerja. Data biaya diperoleh melalui wawancara dengan tim penebang dan data sekunder. Hasil penelitian menunjukkan bahwa teknik penebangan yang digunakan di hutan rakyat Kostajasa adalah bervariasi, yaitu teknik tebang konvensional, teknik penebangan dengan bantuan tali, dan teknik tebang dengan pemangkasan dahan. Produktivitas penebangan di lahan 1, 2, 3, dan 4 berturut-turut adalah 2,9 m3/jam; 2,5 m3/jam; 8,9 m3/jam; dan 6,8 m3/jam. Biaya penebangan per unit untuk lahan 1, 2, 3, dan 4 berturut-turut sebesar Rp 22.435/m3; Rp 28.854/m3; Rp 7.987/m3; dan Rp 10.087/m3., Forest harvesting in private forests requires appropriate techniques to minimize the damage caused and suitable with local situations. This study aims to identify tree felling techniques, calculate productivity, and costs in the Kostajasa private forest. This study was conducted in four areas of the Kostajasa private forest, each of which was worked on by different team of loggers. Working time was measured using the null-stop method. Productivity was obtained through a comparison between the volume of standing tree and time of work produced. Costs were obtained from direct interviews with the felling team on each land. The results of the study show that the logging techniques used in Kostajasa private forests are varied, namely conventional logging techniques, logging techniques with the help of ropes, and cutting techniques with pruning branches. The productivity produced on land 1, 2, 3, and 4 is, respectively, 2,9 m3 /hour; 2,5 m3 /hour; 8,9 m3 /hour; and 6,8 m3 /hour. With the cost per unit used on land 1, 2, 3, and 4, respectively, amounting to Rp 22.435/m3; Rp 28.854/m3; Rp 7.987/m3; and Rp 10.087/m3.
Keyword: cost, logging, private forests, productivity, working time

Judul: Dynamical System of Hepatitis B in Three Groups with Vaccination
Abstrak: The aim of this study is to modify the hepatitis B transmission model in three age groups involving vaccination from the model conducted by Zhoe and Zhang.The method used is to analyze the stability of the fixed point and its basic reproduction number (R_0). Performed stability analysis and numerical simulation to see population dynamics. Next, a sensitivity analysis of the parameters was carried out to see its effect on R_0. From the analysis obtained two fixed points, namely non-endemic and endemic fixed points. Non-endemic fixed points are locally asymptotically stable if R_0 <1 Meanwhile, the endemic fixed point is locally asymptotically stable if R_0 > 1. Hepatitis vaccination affects the number of susceptible population, because the more successful the vaccination, the smaller the number of susceptible populations so that the smaller the population will be infected.
Keyword: Dynamic, Hepatitis B, Vaccine, Mathematical model