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Articles by Suwarno
Total Records ( 7 ) for Suwarno
  Caribu Hadi Prayitno , Suwarno , Agus Susanto and Anuraga Jayanegara
  Background and Objective: The objective of this study was to evaluate supplementation of garlic (Allium sativum) extract and organic minerals (1.5 ppm organic Cr, 0.3 ppm organic Se and 40 ppm Zn-lysinat) on milk yield, milk quality and feed digestibility of lactating dairy cows. Materials and Methods: Fifteen multiparous, one month pre-partum Friesian Holstein cows with an average body weigth of 638±72 kg were used as the experimental units and therefore, there were 5 replicates for each treatment. The cows were fed with a Total Mixed Ration (TMR) consisted of Napier grass: Concentrate mixture (60:40 w/w, dry matter basis) as the basal diet. The experiment was conducted with three treatments, namely control feed (CTL), control feed+Organic Minerals (OM) and OM+garlic extract (OM-G). Variables measured were nutrient intake, nutrient digestibility, milk yield and milk composition. Data were analyzed by analysis of variance with a completely randomized design. Results: Supplementation of garlic extract significantly influenced the digestibility of Crude Fiber (CF), Neutral Detergent Fiber (NDF ), milk yield and milk efficiency (p<0.05). However, the supplementation had no effect on nutrient intake (dry matter, organic matter and total digestible nutrient) and milk composition (fat, protein, lactose and solid non-fat). Supplementation of garlic extract and organic mineral resulted in better feed digestibility, milk production and milk efficiency than those of the control diet and control diet supplemented with organic mineral (p<0.05). Conclusion: Supplementation of combined garlic extract and organic mineral (Se, Cr and Zn) in dairy cows increases feed digestibility, milk production and milk efficiency.
  High voltage apparatuses play an important role in transmitting a huge amount of electrical energy. In order to keep the apparatuses in normal condition, the insulation system should be maintained. Solid as well liquid insulating materials are widely used in high voltage apparatuses. During operation of the apparatuses, the insulation may experience ageing. Appearance of electrical discharges in high voltage apparatuses with reasonable magnitude and frequency can be interpreted as abnormal condition. In order to know the origin of the discharges it is necessary to investigate the characteristics of the discharge. This study reports the experimental results on the characteristics of Partial Discharges (PD) in Low Density Polyethylene (LDPE) under sinusoidal, triangular and rectangular voltages. Electrode used in the experiment was steel needle-plane arrangement with tip radius of curvature of 3 μm. This sharp needle allow to produce a very high electric field of several MV m-1 at the needle tip. The PD in LDPE was generated around the tip of needle electrode when an electrical tree appeared. The PD pulses were measured using a personal computer-based measurement system. Discharges occurred in the sample were detected with an RC detector with a lower cut off frequency of 250 kHz. The output of the detector was measured by PD analyzer and digitized. Using the measuring system the discharge magnitude, frequency as well as the phase of discharge occurrence in the applied voltage cycles is measured and the digital data are stored in the PC. The analysis was focused on the φ-q-n pattern and the time sequence between consecutive pulses. Here, φ is the phase angle of PD occurrence, q is the PD magnitude and n is the number of PD pulses. The experimental results showed that the applied voltage greatly affected the PD in the LDPE. Under sinusoidal applied voltage, the PD pulses due to electrical tree in LDPE distributed around the zero cross. The occurrence is strongly related to the time derivative of the applied voltage. This was clarified under triangular applied voltage where PD pulses distributed almost uniformly as can bee seen in PD pulse sequences. φ-q-n pattern under rectangular applied voltage made more clearly where PD pulses only took place around the zero cross where the value of dv/dv was high. The PD magnitude of the electrical tree reflected the instantaneous applied voltage. This was clarified under triangular applied voltage where triangular patterns were obtained. The experimental results under rectangular voltage strongly supported the findings under sinusoidal and triangular applied voltage. Based on the experimental results equivalent circuits for electrical treeing PD in LDPE is proposed.
  Suwarno and P. Juniko
  Since long time ago, ceramic insulators are widely being used in power systems. During operation, the insulators may severe a certain degree of pollution, which may reduce their performances such as surface resistance and flash over voltages. The pollution may arise in the form of fogs. A large Leakage Current (LC) may flow on the surface and degradation may take place. In long term the degradation may lead to the flash over of the insulators. This study reports the experimental results on the effects of humidity and fog conductivity on leakage current characteristics of ceramics. The samples used are blocks of ceramics with dimension of 250x50x20 mm3. The samples were made from same materials for outdoor ceramic insulators. The samples were put in a test chamber with controlled humidity and artificial pollution conditions. AC voltage with frequency of 50 Hz was applied. The tests were conducted according to IEC 60-1 and IEC 507 (fog test). The magnitudes as well as harmonic content of the LC were analyzed. The experimental results indicated that under fog condition, LC magnitude increase with fog conductivity. At high fog conductivity the oscillation behaviour of LC magnitude dependence on applied voltage was observed due to the wetting effect of sample surface by the fog and drying effect caused by the higher LC. The THD of leakage current under salt fog increased with the applied voltage. LC amplitude increases with applied voltage and RH. LC waveforms distortion significantly decreased with the salt fog conductivity resulting in smaller THD. At given applied voltage the harmonic components decrease with the increase of fog conductivity.
  Dahelmi , Evy Sriganti and Suwarno
  Background and Objective: Larvae of the genus Cethosia is known associate with plants of the family Passifloraceae. The aim of this study was to obtain preliminary data on the life cycle of Cethosia hypsea that reared on Adenia macrophylla. Methodology: The immature stages (egg, larvae and pupae) were reared in the laboratory condition at temperature ranging between 26-30°C and relative humidity of 65-75%. Results: The incubation period of egg was 6-7 days. There are five instars stage of larva, the duration of instar 1st, 2nd, 3rd, 4th and 5th are 3, 3, 3, 3 and 4 days, respectively. Total larval phase is about 16 days, pupae formed after 1 day of the pre pupa period. Pupae period is about 7 days. Conclusion: The larvae of C. hypsea passed through five instars. The total development time from egg to adult eclosion ranged between 30-31 days. The life cycle duration of C. hypsea was about 34-35 days. This is the first study describing life cycle of Chetosia in Indonesia and this species capable of producing multiple generations per year.
  Liquid insulations are widely used in high voltage equipments such as transformers. Under high electric stress and the presence of impurities or defects streamer discharges may take place in the liquid insulation. This study reports the experimental results on the characteristics of Partial Discharges (PD) silicone oil under sinusoidal and triangular voltages and a proposal for equivalent circuit for explaining the characteristics. Electrode used in the experiment was steel needle-plane arrangement with needle tip radius of curvature of 3 μm. Discharges occurred in the sample were detected with an RC detector. The experimental results shown that the PD inception voltage in silicone oil increased with viscosity. Negative PD pulses appeared at applied voltage of slightly higher than the inception voltage. At higher voltage PD took place at both positive and negative half cycles where the negative PD pulse number was higher but with smaller magnitude. This shown that initiation of negative PD from needle tip was easier to happen compared to those of positive PD from the oil side. PD in silicone oil took place around the peak of the applied voltage under both sinusoidal and triangular applied voltage which indicated that PD occurrence in silicone oil was strongly dependent on the instantaneous applied voltage. The magnitude of the PD also reflected the waveform of the applied voltage. Based on the experimental results equivalent circuits for PD in silicone oil is proposed. In order to obtain more deeply understanding of the streamer discharges in insulating liquid, a computer simulation was done by utilizing the proposed equivalent circuit. The simulation results were compared to discharge patterns obtained from the experiment. The results indicated that simulated discharge patterns were strongly similar to those obtained from experiment. This shown the validity of the proposed equivalent circuit.
  Suwarno and Santosh
  Arcing is one of the most dangerous faults in a power transformer because it release large amount of energy. Arcing result in scission in chemical bonds of liquid insulation and afterward the recombination of those broken bonds create solid contaminants such as carbon oxides and gases. The appearance of these substances enhances the degradation of the liquid insulation. In long term it may cause failure. This study reports the experimental results on the effects of electric arc on dielectric characteristics such as breakdown voltage, resistivity, dissipation factor and dissolved gases in mineral transformer oil. The electric arc was generated using multi needles-plane electrode system under AC applied voltage with frequency of 50 Hz. The arc magnitude was adjusted using different gap between electrodes. The amount of arc energy was also adjusted by using different arcing period from 0-30 min. The experimental results indicated that breakdown voltage significantly reduced by applying electric arc. Similar behavior was observed for oil resistivity. The arc application enhanced the dielectric losses factor (tan δ). Very small change was observed on dielectric constant.
  Dianto Mampanini , M. Pudjihardjo , Susilo , Asfi Manzilati , Sabarno Dwirianto and Suwarno
  This study was aims to analyze the dynamics BUMDes in the process of economic empowerment of rural communities in Indragiri Hilirregency through BUMDes. The approach used in this study was a case study with qualitative research methods phenomenology perspective. The research was conducted in Indragiri Hilir by involving some stake holders who participated in the activities BUMDes with economic empowerment.
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