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: Productivity and Cost of Felling with Rope Technique at Agroforestri Private Forest in Probolinggo, East Java
Abstrak: Jarak tanam yang rapat dan batas lahan yang sempit menyebabkan risiko tingkat kerusakan tanaman bawah akibat kegiatan penebangan konvensional di hutan rakyat agroforestri cukup tinggi, sehingga diperlukan teknik penebangan yang dapat mengurangi kerusakan tanaman bawah. Teknik penebangan sandat digunakan oleh masyarakat untuk mengatasi hal tersebut. Tujuan penelitian adalah menganalisis produktivitas dan biaya penebangan teknik sandat pada hutan rakyat agroforestri. Analisis waktu dan elemen kerja berbasis video. Produktivitas didapatkan melalui volume dan waktu kerja yang dihasilkan setiap tahapan. Biaya didapatkan dari hasil wawancara dengan regu penebang untuk menentukan biaya tetap dan biaya variabel. Tahapan teknik penebangan sandat terdiri atas pemasangan sandat, penebangan, dan pembagian batang. Produktivitas pada tahapan pemasangan sandat, penebangan, dan pembagian batang berturut-turut adalah sebesar 11,80 m3/jam, 3,77 m3/jam, dan 5,33 m3/jam. Biaya per unit yang dikeluarkan pada tahapan pemasangan sandat, penebangan, dan pembagian batang berturut-turut adalah sebesar Rp2.600,63/ m3, Rp11.875,65/ m3, dan Rp10.699,34/m3., Close planting distances and narrow land boundaries cause the risk of damage to bottom crops due to conventional felling activities in agroforestry private forests being quite high, so felling technique are needed to solve it. Rope felling technique are used by communities to overcome this problem. The study aimed to analyze the productivity and cost of felling with rope technique in agroforestry private forests. The video-based analysis uses to determine time and work elements. Productivity is obtained through the volume and time of work produced by each stage. Costs are obtained from interviews with logger teams to determine fixed costs and variable costs. The stages of the felling with rope technique consist of rope installation, felling, and bucking. Productivity at the stages of rope installation, felling, and bucking was 11,80 m3/hour, 3,77 m3/hour, and 5,33 m3/hour. The cost per unit incurred at the stages of rope installation, felling, and bucking is Rp2.600,63/m3, Rp11.875,65/m3, and Rp10.699,34/m3.
Keyword: cost, felling, productivity, rope technique, 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