Judul: Rekayasa Pengaturan Udara Berdasarkan Perubahan Kandungan Metana pada Biogas Umpan ke Motor Bakar Bensin
Abstrak: Pembakaran metana dengan jumlah udara yang tidak sesuai mengakibatkan konversi energi kimia ke mekanik pada motor bakar tidak optimum. Sementara itu, kandungan metana di dalam biogas umumnya beragam sehingga diperlukan rekayasa pengaturan udara agar pembakaran menjadi sempurna. Hasil pengukuran kinerja motor bakar dengan perlakuan yang dilakukan menunjukkan daya tertinggi 4.086 kW terjadi pada biogas dengan kandungan metana 92 % di putaran 3000 rpm dan nilai daya terendah adalah 3.236 kW pada biogas dengan kandungan metana 57 % di putaran 3000 rpm. Penggunaan bahan bakar paling hemat terjadi pada kandungan metana 92 % sedangkan penggunaan bahan bakar yang boros terjadi pada kandungan metana 57 %. Berdasarkan perhitungan stoikiometri kandungan 57 %, 62 %, 77%, 82% dan 92 % berturut-turut memiliki air fuel ratio 1: 13.54, 1: 13.97, 1: 15.26, 1: 15.69, 1: 16.55. Efisiensi termal paling tinggi terdapat pada power maksimum pada masing masing bahan bakar, nilai dari efisiensi termal mendekati efisiensi termal dari motor bakar bensin yaitu 25 %.
Keyword: biogas, amda, metana, motor bakar, power

Judul: Optimasi Kinerja Mesin Bensin Berbahan Bakar Campuran Bensin Metanol Dengan Pengaturan Ignition Timing Dan Injection Duration
Abstrak: Metanol adalah salah satu bahan bakar alternatif yang dapat diproduksi dari sumber energi terbarukan. Metanol dapat digunakan sebagai campuran untuk bahan bakar bensin, dan memiliki keunggulan yaitu nilai oktan yang tinggi dan menghasilkan pembakaran yang lebih bersih. Pada penelitian ini telah dilakukan pengujian kinerja mesin bensin menggunakan bahan bakar campuran bensin RON 90 dengan metanol, dengan persentase metanol sebesar 5% dan 10% (M5 dan M10). Optimasi kinerja mesin dilakukan dengan mengatur ignition timing dan injection duration pada mesin. Pengujian dilakukan menggunakan mesin bensin 4 langkah dengan kapasitas 150 cc, yang telah terpasang engine control unit. Uji kinerja dilakukan pada dinamometer mesin dan uji emisi menggunakan emission analyzer. Berdasarkan hasil pengujian dan analisis data, pengaturan mesin yang optimal yaitu pada penggunaan bahan bakar M5 dengan ignition timing 24 °bTDC dan injection duration +10%. Pada pengaturan tersebut terjadi kenaikan daya sebesar 0,59%, kenaikan torsi sebesar 13%, dan penurunan konsumsi bahan bakar spesifik sebesar 7,3%. Pada pengaturan mesin tersebut juga kadar karbon monoksida dalam emisi gas buang mengalami penurunan, sementara kadar hidrokarbon mengalami peningkatan., Methanol is an alternative fuel that can be produced from renewable energy sources. Methanol can be used as a mixture for gasoline fuel, and has the advantage of a high octane value and results in cleaner combustion. This research has tested the performance of a gasoline engine using a mixture of gasoline RON 90 and methanol, with a methanol percentage of 5% and 10% (M5 and M10). The engine performance optimization is done by adjusting the ignition timing and injection duration on the engine. The test was carried out using a 4 stroke gasoline engine with a capacity of 150 cc, which had an engine control unit installed. The performance test is carried out on the engine dynamometer and the emission test using an emission analyzer. Based on the test results and data analysis, the optimal engine setting is the use of M5 fuel with an ignition timing of 24 °bTDC and injection duration + 10%. In this setting there is an increase in power by 0.59%, an increase in torque by 13%, and a decrease in specific fuel consumption by 7.3%. Also in that engine setting, the carbon monoxide level in the exhaust emission decreases, while there was an increase in hydrocarbon level.
Keyword: bensin, ignition timing, injection duration, mesin bensin, metanol

Judul: Systematics of Desmos (Annonaceae) in Malesia
Abstrak: Desmos is a woody climbing genus of Annonaceae which has been widely used as traditional medicine in several countries such as China, Indo-China, Thailand, and Peninsular Malaysia to treat dysentery, vertigo, fever, and postpartum. Phylogenetic studies on Desmos showed a close relationship between Desmos and Dasymaschalon. They share similar moniliform monocarpic fruits, but their flowers are different. It has been debated among Annonaceae researchers whether both genera should be treated as the same or distinct genus. Therefore, investigation on the taxonomic delimitation of Desmos species and Dasymaschalon will be necessary. Plastid genome (plastome) identification, leaf epidermal section of Desmos species and Dasymaschalon species, a taxonomic revision of Desmos in Malesia using morphological data, the spatial distribution of Desmos species in Malesia, and morphological and genetic variation in Desmos chinensis population using ISSR marker were used to investigate taxonomic delimitation of Desmos. Plastome study of Desmos chinensis and Dasymaschalon dasymaschalum was carried out to determine the origin, evolution, phylogenomics, and identify marker candidates for Desmos and Dasymaschalon or with other genera in Annonaceae. We discovered that the plastome of Desmos chinensis was circular with the size of 167,677 bp (smaller than Dasymaschalon dasymaschalum), consist of 111 genes, including 78 protein-coding genes, 29 transfer RNAs, and 4 ribosomal RNAs. The plastome showed a typical quadripartite structure, i.e., large single copy (LSC), small single copy (SSC), and two inverted repeats (IRs). The plastome of Dasymaschalon dasymaschalum was 191,488 bp in length, which also exhibited a typical quadripartite structure (LSC, SSC, and two IRs). Desmos chinensis and Dasymaschalon dasymaschalum showed different copies of accD, ndhD, ndhF, rps18, and ycf2. Protein coding genes of rpoB, rpoC1, rbcL, matK, rpl32, infA, and rpl36 were identified based on nucleotide diversity, sequence variability, and parsimony-informative sites. The genes are defined as molecular marker candidates of plastome for phylogenetic, barcoding, and population genetic research. We predicted that Desmos chinensis and Dasymaschalon dasymaschalum separated at ca. 64 million years ago during the Paleocene. Leaf anatomical feature study was carried to support the taxonomic delimitation of interspecific Desmos and intergeneric of Desmos and Dasymaschalon. Leaf anatomy in the paradermal section of 20 taxa (12 species of Desmos, eight species of Dasymaschalon) have been carried out. According to the leaf epidermal section, Desmos and Dasymaschalon are two distinct genera mainly distinguished based on the anticlinal wall undulation of epidermal cells and supported by variation of the crystal type and size. The anticlinal wall undulation of Desmos was almost straight to slightly wavy and never sinuous; meanwhile, Dasymaschalon varies from almost straight to deeply sinusoid. The crystals of Desmos consist of rhombohedral, druse type A, and druse type B crystals, whereas Dasymaschalon has prism, druse type A, druse type B, and druse type C crystals. The recent taxonomic revision using the morphological data was mainly based on the examination of about 1374 specimens from BO, L, WAN, ANDA, SING, SAN, K, P, HUH herbaria. The Desmos species in Malesia consists of eight species: D. acutus, D. chinensis, D. chryseus, D. dunalii, D. pedunculosus, D. subbiglandulosus, two new records: D. lawii and D. macrocarpus, and one
Keyword: Dasymaschalon, Desmoid clade, Magnoliid, plastid genome, phylogenomics analysis