Judul: Simulasi Numerik untuk Pola Sebaran Suhu Kolektor Surya Pelat Datar Tipe Back-pass Cover Semi Tertutup
Abstrak: Solar energy is abundantly available, so this energy is very potential to be developed, especially in Indonesia. One of the alternative to utilize solar energy is using back-pass flat plate solar collector. The thermal energy produced by the collector can be used for crop drying. In this study, the back-pass flat plate solar collector with semi-closed cover was connected to a drying box and the thermal energy will flow into it. The effect of variation of the length of cover percentage at several tilt angle to the collector performance (temperature distribution and mass flow rate) were investigated experimentally and numerically. Numerical simulation result showed that cover of 60% had adequated to produce the air temperature above 40oC that can be used for drying most of agricultural products. Increasing percentage of cover to 80% or 100% did not improve air temperature significantly. Even the effect would increase collector manufacturing cost. The results of numerical simulations showed that tilt angle 45o had optimum mass flow rate, it was about 0.009 kg/s. Validation with experiment data showed that total error was below 10% and R2 varied from 0.76 until 0.98. Simulation of temperature distribution in drying box showed that temperature varied from 41 oC until 51 oC with error below 10% and R2 varied from 0.93-0.98.
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Judul: Uji Performansi Alat Pengering dengan Kolektor Surya Pelat Datar Tipe Back Pass Menggunakan Cover Semi Tertutup untuk Pengeringan Mangga (Mangifera indica, L.)
Abstrak: Kolektor surya pelat datar terdiri atas cover transparan, pelat absorber dan insulasi. Kolektor surya dapat digolongkan menjadi dua kategori yaitu unglazed air collector dan glazed air collector. Peniadaaan cover akan meningkatkan kinerja kolektor karena sinar matahari langsung diserap oleh absorber, namun akan meningkatkan koefisien kehilangan panas. Sedangkan penggunaan cover akan memerangkap panas yang lebih baik di dalam kolektor namun menghambat transmisivitas, maka diperlukan kolektor dengan cover semi tertutup. Pada kolektor terjadi efek chimney karena adanya perbedaan temperatur yang menyebabkan terjadinya aliran udara secara alami. Tujuan penelitian ini adalah merancang kolektor surya untuk udara dengan berbagai variasi ukuran cover dan kemiringan. Diharapkan dengan disain yang dimaksud dapat diketahui kolektor yang menghasilkan energi berguna terbesar dan dapat digunakan untuk pengeringan produk pertanian. Penelitian ini dibagi menjadi dua tahap. Tahap pertama yaitu merancang kolektor dengan berbagai variasi ukuran cover kemudian menguji kinerja kolektor. Tahap kedua yaitu merancang alat pengering kemudian melakukan pengujian alat pengering yang telah dibuat menggunakan mangga sebagai bahan percobaan. Kolektor yang dirancang terdiri atas enam kolektor dengan variasi cover yaitu cover 100%, cover 80%, cover 60%, cover 40%, cover 20% dan kolektor tanpa cover. Bagian utama kolektor yaitu cover (kaca transparan) menggunakan kaca indofigur tipe mislite FM5 untuk memerangkap radiasi yang masuk ke dalam kolektor dan mengurangi kehilangan panas secara konveksi. Kemudian pelat absorber menggunakan pelat alumunium dengan ketebalan 0.8 mm yang dicat hitam. Pemberian warna hitam agar dapat menyerap panas lebih banyak. Insulasi menggunakan armaflex untuk mengurangi kehilangan panas. Kemiringan kolektor dapat diatur dengan sudut 6°, 15°, 30°, 45° dan 60°. Pengujian kinerja kolektor dilakukan lima kali percobaan yaitu percobaan 1 (kemiringan 6°), percobaan 2 (kemiringan 15°), percobaan 3 (kemiringan 30°), percobaan 4 (kemiringan 45°) dan percobaan 5 (kemiringan 60°). Kolektor menghadap ke arah utara karena pada bulan Maret sampai September matahari berada pada bumi belahan utara.
Keyword: Flat plate collector, Solar air heater, Drying

Judul: Inhibitory Control of Former Drug Users.
Abstrak: Inhibitory control is one of the characteristic functions of the prefrontal cortex by which inappropriate responses to extrinsic stimuli are avoided. On the other hand, poor inhibitory control and perseveration are the common symptoms among drug users. A little known study related to the inhibitory control, including the perseveration among former drug users in Indonesia. The Go/ NoGo task was used during the research. Seventeen former drug users and seventeen controls with no record in drug abuse were asked to do the Go/ NoGo task. Former drug users show the same ability to recognize the meaning of the cue, i.e Go cue and NoGo cue, as well as in controls. However, we found the difficulty to stop Go response in NoGo trials in former drug users, which means the failure of inhibitory response. The perseveration to the old meaning of cue was also found during the reversal phase of the task. Our study suggests that less inhibitory control and perseveration behavior occurred in former drug users. These findings suggest that even the former drug users already finished or in progress of rehabilitation program, they may still have the tendency to initiate the drug abuse. Keyword: former drug users, Go/ NoGo task, inhibitory control, perseveration
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