No abstract

Abstract-Radio Direction Finder (RDF) had been used as a part of the system in order to determine the direction of the Radio Frequency (RF) source. This research had used three different RDF stations without any mobile human operator. The direction data were collected from the each RDF station, it would be calculated using the triangle-centroid-algorithm. Therefore, the RF source position had been automatically determined. This experiment result of the RF source imaginary was compared with the real RF source at about 3.2 meters for latitude, and 3.3 meters for longitude. The results of this method and experiment are very useful for scientist and engineers in application of RF engineering.

Guiding and triggering of discharges from a three phase Tesla coil type 280 kHz AC high voltage source using filaments created by a femtosecond Terawatt laser pulse. Without the laser the discharges were maximum 30 cm long. With the laser straight, guided discharges up to 110 cm length were detected. The discharge length was limited by the voltage amplitude of the Tesla coil. A significant reduction of the breakdown voltage threshold due to the pre-ionization of the air gap by laser pulse filamentation was observed. The lifetime of filaments is measured by using time-resolved fluorescence spectrum, and the lifetime of filaments generated by dual fs laser pulses was doubled due to the re-ionization by the succeeding pulse

<p><em>In recent years, domestic c</em><em>arbage </em><em>become a serious problem since </em><em>not all waste is managed properly. </em><em>The organic waste has a potential as a feedstock for biogas production. </em><em>Before the fermentation process</em><em> of biogas production</em><em>, it is necessary to enumerate organic waste with the help of a multi-function chopper. </em><em>In the present work, dual function machine (chopping and milling process) is designed and fabricated. The machine is driven with </em><em>a 5.5 HP gasoline </em><em>engine</em><em> with a two-way transmission system connecting to each process. The first line transmission system on the </em><em>chopping</em><em> with a pulley size of 2 inch diameter, two grooves mounted on the motor and a 3 inch pulley mounted on the </em><em>chopper axis </em><em>with a rotation</em><em> speed</em><em> of 2400 rpm. The second line transmission system on the </em><em>milling</em><em> uses a 12 inch diameter pulley with a rotation of 600 rpm. </em><em>The test results show that the capacity of the machine was 60 kg/h with 1 cm chopping size.</em><em></em></p>

The topography of Gunungkidul area in the Province of Yogyakarta, Indonesia, consisting of hills and limestone mountains. It becomes the potential factor of landslide occurrences. Especially in the rainy season, the soils in the hills become softer and it increases the possibility to cause a landslide. This condition has became the concern of many people, especially the residents who live in the landslide-prone area. This topography is also one of the factors for health centre in a certain area becomes isolated due to the inability of telecommunication signal services from the provider to reach that area, which is called a blank area. That situation makes an inability to contact the nearest district hospital to ask for support in an emergency case. This research focuses on the performance test of the emergency data communication system by using several types of data. The system uses Very High Frequency (VHF) 144 MHz and High Frequency (HF) 7.08 MHz as the data carrier and a software to interpret the text and image to be modulated onto the data carrier. That system is called a virtual hospital, means that even though the health center is located in a blank area, but specialists from the Sardjito Hospital can still deliver advices to support the health center in maintaining the medical service quality by using the VHF-HF-based emergency data communication system. Based on the results of the system's performance test between the Wonosari Gunungkidul District Hospital and the Sardjito Hospital with the distance of 40 km, the receiving quality of the data transmission for text and image are 95% and 55.33%, respectively.