Judul: Systematic Review: Timber Harvesting Waste in Indonesia (Quantity, Source, and Utilization)
Abstrak: Pemanfaatan kayu yang kurang efisien terjadi karena jumlah kayu yang dimanfaatkan pada umumnya masih rendah dibandingkan dengan volume kayu yang ditebang. Dalam arti lain, kegiatan pemanenan masih banyak menimbulkan limbah kayu. Penelitian mengenai limbah pemanenan kayu sudah banyak dilakukan di Indonesia. Penelitian ini bertujuan untuk menghimpun dan menganalisis hasil penelitian terkait kuantitas, sumber, dan pemanfaatan limbah pemanenan kayu di Indonesia. Penelitian ini menggunakan data sekunder yang dihimpun menggunakan metode systematic review yang kemudian dilakukan analisis secara deskriptif. Hasil pencarian secara online mendapatkan 32 artikel penelitian mengenai limbah pemanenan kayu di Indonesia dari tahun 1984 hingga tahun 2020 yang terbagi atas dua jenis hutan, yaitu hutan alam dan hutan tanaman. Penelitian paling banyak dilakukan di hutan alam dengan teknik pemanenan yang digunakan adalah Reduce Impact Logging (RIL) dan konvensional. Limbah kayu berupa tunggak merupakan jenis yang paling banyak dihasilkan dengan kondisi cacat mekanis berupa pecah. Keterampilan operator chainsaw, topografi, kelas umur pohon, diameter pohon, kerapatan tegakan, dan penentuan arah rebah pohon sangat memengaruhi limbah kayu yang terjadi dalam kegiatan pemanenan kayu., Inefficient use of wood occurs because the amount of wood used is generally still low compared to the volume of wood cut. In another sense, harvesting activities still generate a lot of wood waste. Research on wood harvesting waste has been widely carried out in Indonesia. This study aims to collect and analyze research results related to the quantity, source, and utilization of wood harvesting waste in Indonesia. This research uses secondary data collected using a systematic review method which is then analyzed descriptively. The online search results found 32 research articles on wood harvesting waste in Indonesia from 1984 to 2020 which were divided into two types of forest, namely natural forest and plantation forest. Most research is conducted in natural forests with the harvesting techniques used are Reduce Impact Logging (RIL) and conventional. Wood waste in the form of stumps is the type that is mostly produced with mechanical defects in the form of breaking. The skills of chainsaw operators, topography, tree age class, tree diameter, stand density, and determining the direction of tree fall greatly affect the wood waste that occurs in wood harvesting activities.
Keyword: harvesting waste, harvesting waste wood, wood waste.

Judul: Systematic Review: Techniques, Produvtivity, and Costs of Harvesting Forest in Indonesia
Abstrak: Pasokan kayu selama ini berasal dari hasil pemanenan hutan alam dan hutan tanaman. Penelitian mengenai pemanenan kayu sudah banyak dilakukan di Indonesia dengan variasi hasil yang berbeda. Penelitian ini bertujuan untuk menghimpun hasil penelitian mengenai teknik, produktivitas, dan biaya pemanenan hutan di Indonesia. Data sekunder dihimpun menggunakan metode Systematic Review kemudian dianalisis menggunakan analisis deskriptif. Berdasarkan hasil pencarian secara online terhimpun 51 artikel penelitian mengenai pemanenan kayu di Indonesia yang kemudian dikelompokan menjadi tiga tipe hutan yaitu, hutan tanaman lahan basah, hutan tanaman lahan kering, dan hutan alam. Hutan tanaman lahan kering merupakan jenis hutan yang paling banyak diteliti. Kegiatan pemanenan dibagi menjadi beberapa tahapan antara lain penebangan, penyaradan, muat bongkar, dan pengangkutan. Kegiatan yang paling banyak diteliti adalah penyaradan. Produktivitas pemanenan dipengaruhi oleh peralatan pemanenan, kondisi lapang, teknik pemanenan, keterampilan pekerja, beban kerja, dan cuaca. Besarnya biaya pemanenan di pengaruhi oleh produktivitas, biaya pemilikan, biaya operasional, dan upah pekerja., The supply of wood so far has come from harvesting natural forests and plantation forests. Many studies on timber harvesting have been carried out in Indonesia with varying results. This study aims to compile research results on techniques, productivity, and costs of forest harvesting in Indonesia. Secondary data was collected using the Systematic Review method and then analyzed using descriptive analysis. Based on the results of an online search, 51 research articles on timber harvesting in Indonesia were collected which were then grouped into three types of forest, namely, wetland plantation forest, dry land plantation forest, and natural forest. Dryland plantation forest is the most studied forest type. Harvesting activities are divided into several stages, including logging, skidding, loading and unloading, and transportation. The most researched activity is skidding. Harvesting productivity is influenced by harvesting equipment, field conditions, harvesting techniques, worker skills, workload, and weather. The amount of harvesting costs is influenced by productivity, ownership costs, operational costs, and worker wages.
Keyword: biaya pemanenan, produktivitas pemanenan kayu, teknik pemanenan

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
Keyword: