Judul: Optimization of thin-layer drying of temu putih and temu lawak based on energy analysis
Abstrak: Temu putih or zedoary (Curcuma zedoaria Rosc.) and temu lawak or java turmeric (Curcuma xanthorrhiza Roxb.) are two of some important medicinal plants in Indonesia. The dried slices of their rhizome are called simplicia and used as raw materials for jamu or traditional herbal medicine. The aim of this research were (a) to study the influence of drying process conditions on simplicia drying characteristics, quality and exergy eficiency during the drying, and (b) to determine the optimum process conditions to get the best quality. In the first study, the influence of drying air temperature, relative humidity (RH) and flow rate on the thin layer drying of temu putih and temu lawak slices were investigated. A laboratory air dryer was designed and used for drying experiments. The system was operated in an air temperature range of 40–70o C, relative humidity range of 20–80% and air flow rate 0.2-0.9 m/s. Three mathematical models available in the literature were fitted to the experimental data. It was found that drying of temu putih and temu lawak took place in the falling rate period. Higher drying air temperature and flow rate and lower drying air relative humidity resulted in a lower final moisture content and shorter drying time. By statistical comparison of the three models, it was concluded that the Page model represents drying characteristics was better than the other equations for describing single layer drying of both temu putih and temu lawak. In the second part, the effects of drying conditions on shrinkage and quality of temu putih and temu lawak were studied. A thin-layer dryer with machine vision system and image analysis software were used. Temu putih and temu lawak slices were dried at temperatures of 50, 60 and 70 oC and relative humidities of 20%, 30% and 40%. Changes in area of the slice were measured continuously during the drying. Shrinkage showed almost linear relation with moisture content. It was found that air temperature and relative humidity had no significant effect on shrinkage. Slices dried in a higher temperature showed more bend than a lower one. Lower drying air temperature resulted higher quantity of curcumin of temulawak and worse visually performance of sample. The last part was concerned with the energy and exergy analysis of the thin layer drying process of temu putih and temu lawak at different air temperatures and humidities using a laboratory dryer. Using the first law of thermodynamics, energy analysis was carried to estimate the amounts of energy gained from air drying and the ratios of energy utilization. Exergy analysis was accomplished to determine exergy destroyed and exergy efficiencies during the drying process by applying the second law of thermodynamics. The optimum process conditions for temu putih drying were at a temperature of 50 oC 20% RH and air flow rate of 0.2-0.3 m/s, while for temu lawak drying were at a temperature of 50 oC and 30% RH.
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Judul: The relationship of  shrinkage with thin layer drying characteristics of  Curcuma xanthorriza Roxb simplicia
Abstrak: Experiments were undertaken to study the relationship of shrinkage with thin layer drying characteristics of Curcuma xanthorrhiza Roxb simplicia. In order to estimate and select a suitable drying curve, three different thin layer drying models were fitted to experimental data. Experiment were performed at the air temperature of 50, 60, and 70 ⁰C with relative humidity ranging from 30 to 50%. At each performed level, velocity of drying was adjusted 0.8-0.9 m/s. All of model were investigated by comparing the coefficient of determination (R2), root mean square error (RMSE), and chi square (χ2). Among all the selected drying models, the Page model was found as the best mathematical model for describing the characteristics of ginger simplicia, where the shrinkage of Curcuma linearly decreased with a reduction of the moisture content and increased of temperature.
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Judul: Cycle Hamilton pada Graf Lengkap, Graf Regular, dan Graf 2-Connected 4-Regular Berorder Kurang dari Sepuluh.
Abstrak: Suatu graf disebut graf Hamilton apabila graf tersebut memuat cycle Hamilton, yaitu cycle yang melewati setiap vertex tepat satu kali. Menentukan keberadaan cycle Hamilton pada suatu graf dapat menggunakan syarat cukup yang berupa teorema-teorema yang telah diperkenalkan sejak tahun 1950-an. Beberapa syarat cukup yang dibahas dalam karya ilmiah ini adalah syarat cukup yang berhubungan dengan graf lengkap dan graf regular. ,,,
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular.