Judul: Development of Regional Scale Tree Volume Models in Indonesia
Abstrak: Pengukuran volume pohon memiliki peranan penting untuk pengelolaan hutan lestari, perkiraan biomassa dan karbon, dan inventarisasi hutan nasional. Model volume yang telah dikembangkan terdahulu kadang terdapat bias dan tidak mencakup semua jenis dan lokasi. Pemodelan dapat menggunakan model spesifik dan model umum, yaitu multilvel model. Penelitian ini membangun model spesifik berdasarkan pulau dan tipe ekosistem hutan di Indonesia; dan membangun model umum dengan multilevel model untuk mengevaluasi efek data hirarki pada volume pohon. Hasil menunjukkan bahwa model spesifik dan model umum dengan multilevel model memiliki kemampuan prediksi yang hampir sama. Multilevel model dengan dua peubah MDH2MM memiliki uji statistik model yang lebih baik, koefisien determinasi lebih besar dan BIC lebih kecil, dibandingkan model satu peubah MD1MM. Multilevel model sangat membantu dalam penilaian stok hutan skala besar, seperti program inventarisasi nasional dengan menyusun satu model untuk memprediksi setiap jenis tegakan., Measuring tree volume has an important role for sustainable forest management and national forest inventories. Volume models that have been developed previously use a relatively small number of trees or do not include trees with larger diameters, which can cause bias in tree volume estimates. Modeling can use specific models and general models, namely multilevel models. This research builds a specific model based on islands and forest ecosystem types in Indonesia; and building a general model with a multilevel model to evaluate the effect of hierarchical data on tree volume. The results show that the specific model and the general model with multilevel models have almost the same predictive ability. The multilevel model with two variables MDH2MM has a better model statistical test, a larger coefficient of determination and a smaller BIC, compared to the one variable model MD1MM. Multilevel models are very helpful in large-scale forest stock assessments, such as national inventory programs by developing one model to predict each type of stand.
Keyword: ekosistem hutan, model spesifik, multilevel model, volume pohon

Judul: Penyusunan model penduga volume pohon jenis Keruing (Dipterocarpus sp.) di IUPHHK-HA PT. Salaki Summa Sejahtera, Pulau Siberut, Sumatera Barat
Abstrak: A careful, rational and directional forest planning should be conducted to achieve sustainable forest management. Periodic Census Inventory of Forest/Inventarisasi Hutan Menyeluruh Berkala (IHMB) is important to arrange ten years of Work Planning on Timber Utilization/Rencana Kerja Usaha Pemanfaatan Hasil Hutan Kayu (RKUPHHK). Providing aid of inventory is one of important things to support IHMB and reduce error in measurement. One of the methods to estimate trees’ volume is by using table of volume. The table of volume is useful to estimate volume of certain trees in a stand forest then to estimate their standing stock. The aims of this research are to arrange and obtain equality model of trees’ volume estimation from species of Dipterocarpus sp. In this research, the trees were selected purposively by diameter consideration, those which have normal growth and representative diameter. The total of samples was 55 trees; 45 trees were for model construction and 10 trees for validation purpose those trees were determined randomly. Data was analyzed using the least square method and the estimation of trees volume was based on measurement parameters of standing trees and felled trees. Based on regression analysis, the appropriate equality model to estimate volume of Dipterocarpus sp. with bark is V = 0,00014 D2,49 (R2 = 98,00%, s = 0,08). This model is proposed to estimate volume of Dipterocarpus sp. in order to support forest planning in PT. Salaki Summa Sejahtera, West Sumatera.
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Judul: Characterizations of low alloy steel sae 4422  plated with chromic acid (Cro3)
Abstrak: Characterizations of low alloy steel SAE 4422 plated with chromic acid (CrOrO3) was use Optical Microscopy (OM), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), RD),Energy Dispersive Analysis of X-Ray (EDAX), Hardness Test and Roughness Test. Microstructures analysis exhibits cracks and grain boundaries microcracks as a characteristics of chrome metal found at plating metal. Perlite and Ferrite as grains of steel found at base metal with grain boundaries around it. Phase analysis of plating metal appropriate to chrome metal with lattice constant (a) is 2.559 Å and phase analysis of base metal appropriate to iron ferrite with lattice constant (a) is 3.318 Å. Both plating and base metal have cubic system. Chemical analysis of plating metal at surface section exhibits that cracks area have highest value of carbon element compare with grains and grains boundaries area. While chemical analysis of base metal at cross section exhibits that perlite have highest value of carbon element compare with ferrite and grain boundaries. The hardness value of plating metal at surface section and cross section are 753 and 637 VHN. While, the hardness value of base metal and interface area at cross section are 205 and 373 VHN. The roughness value at measurement points of chrome surface for as received sample are 0.445 μm. Observation used Optical Microscopy and Scanning Electron Microscopy exhibits surface irregularities combine to form surface texture of plating metal at surface section.
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