Advanced Materials Research Vols. 931-932

Abstract: Using actual solar cells for laboratory study may encounter some problems related to uncontrollable test environment and large operating area. Artificial solar cells which can provide electric properties similar to the actual cells but with controllable test features and less operating area therefore are usually used instead. However, most artificial solar cells relatively have high cost and complex. This paper presents an alternative structure of artificial cells. The proposed artificial solar cell consists of a DC current source, a string of series diodes, a diode and two resistors. As only few elements are used for the cell, the proposed cell can achieve simple configuration, small in size, light in weight and inexpensive. The experimental results show that the proposed cell can generate correct electrical outputs with the error less than 5% compared to the actual cell.

Abstract: This paper presents the flashover between the electrodes conducted the current by the water drop on insulating surfaces. It causes ageing to the insulator and leads to deterioration when the insulator is used for over years. In the experiments, epoxy resin with the water drop is tested by using direct current until flashover of 70 kV. Besides that, the effect of the water volume, the number of the water drop and the water types - tap and aqua water on flashover are investigated. The flashover of tap water grows faster when increases the volume of water drop. The flashover of aqua water does not depend on the volume of water drop. The deformation and elongate of water drop is in the direction of electric field line. The results lead to protect the damage of insulator caused by the humidity and the loss of their efficiency insulators.

Abstract: The partial discharge on the insulator surfaces usually occurred in the distribution system. The influence of water droplets is investigated in this paper. This experiment used a circular resin specimen under High Voltage Alternating Current (HVAC) field stress that was applied to the electrodes with a diameter of 2 mm and with a distance between both electrodes of 35 mm. For this methodology, both a single droplet and also double droplets were used on surfaces and the voltage level was adjusted by 15 kV. Results showed that, firstly, the corona phenomenon occurred around the circular electrode after the water droplets on the specimen surface were stretched to each other, but the double drops took a lower voltage level for the stretching than the single drop. In addition, the double drops acted as a bridge, allowing an electrical field to be generated from both electrodes. This pulled them, easily resulting in arcing. In conclusion, water droplets are a main factor to the aging that occurred on the insulators surfaces and this effect is presented in this experiment.

Abstract: Multilayer polarization beam splitters (MPBSs) are important optical components in optical communication systems and optical devices. The components of transverse electric (TE) and transverse magnetic (TM) light plane wave in MPBSs are separated in different ways. In this paper, the Pareto optimization (multiobjective evolutionary and genetic algorithms) is used to design MPBSs on C-band frequency. The reflectances of TM light plane wave for Pareto optimization are the lowest and zero at the wavelength of 1.535 μm. The degree of polarization for Pareto optimization is the highest at wavelength from 1.528 - 1.54 μm and reaches 100% at wavelength of 1.535 μm.

Abstract: This paper presents the effect of the flashover on insulating surface under alternative current (AC) electric field stressed by humidity factor. It is obviously demonstrated about the insulator deterioration due to an ageing, partial discharge (PD) when it is used in services. Epoxy resin with the water droplets is brought to test by high voltage AC until flashover voltage levels. The flashover level on insulator surface depends on the volume and the number of the water droplets. The highest flashover voltage is 52.2 kV for the insulator surface without humidity, but the lowest voltage is 43.5 kV for water droplets of 1, 2, 3 and 4 drops (0.5, 1.0, 1.5 and 2.0 ml). Consequently, it leads to use the lower voltage respectively. The deformation of the water drop was oscillated, moved, elongated and broken up in to a several small drops on insulating surface. PD was the result of the flashover phenomena which causes the damage of the insulator. These results lead to protect the insulator surface under humidity effect from flashover phenomena.

Abstract: A new mismatch model of temperature and narrow channel dependence on threshold voltage of MOSFETs and the parameter extraction method are proposed. A new model is developed from spice level3 and BSIM3 model. The I_DS -V_GS in linear region was used with a different of channel width. The threshold voltage parameters extraction procedure is based on the measurement of the tranconductance characteristics of MOSFET in linear region. In this predicted model, the temperature coefficient for threshold voltage and the body-bias coefficient of threshold voltage of a big MOSFET at various narrow channel width of MOSFET are determined. The results show that the deviations of experimentally measured threshold voltages of both devices from the predicted model are around 3%.

Abstract: This paper reports the Joule heating and Peltier effects in thermoelectric spin-transfer torque MRAMs (TSTT-MRAMs). The simulation was undertaken based on the current-induced magnetization switching at the MgO/CoFe magnetic tunnel junction. Thermal and heat flux distributions of the TSTT-MRAM cells were simulated and analyzed using finite-element modeling. The Joule heating and Peltier effects lead to the increases in the temperature and heat flux distributions at the magnetic tunnel junction (MTJ) as well as the thermoelectric module. The maximum temperature of Peltier effect is higher than Joule heating effect when voltage amplitude below 0.77V. Some practical data for the STT-MRAM were also reported.

Abstract: This research represents a design and analysis of Automatic loading copper wire machine for the actuator arm (ALCM). The process of copper wire placement on a single actuator arm type compensates human workers. In this research, copper wire placement set is made as a 3D model by computer program before undergoes arrangement analysis via explicit dynamic finite element method to study a suitable speed for copper wire placing. It is considered by characteristics of copper wire after placed and failures occurred during the process that will define suitable speed of motor rotation. The suitable speed is corresponding to copper wire characteristic as preferred, prevent copper wire fracture and time reduction compare to human work.

Abstract: From the theoretical point of view, network localization can be viewed as finding a unique solution from distances constraint among points. The one of the difficulties is that even if the network is uniquely localizable, it is proven to be an NP-Hard [1]. It is also true that the network graph has to be sufficiently dense [2]. This poses even more challenges to the original problem as we often work on sparse networks. To cope with this, in [3], we introduce priori knowledge to assist the process of finding the unique localization solution. It helps to speed up the searching algorithm; however, the ambiguity still exists among sparse networks. In this paper we try to bring as much priori knowledge as possible to assist or to be used as constraints. Hopefully this will reduce search space and reach the unique solution quickly. In clean environment, this extra info will, by some magnitude, bring the graph closer to the unique answer. We start from integer-coordinate noise-free position and then add sources of priori knowledge. Then we examine the case where assisted data can be noisy. A search is used within the noisy but useful constraint. The justification of using the assisted knowledge is from the practical uses of some networks, e.g. sensor network, where other measurements are available and they are often correlated and can be helpful in determining the positions.

Abstract: From the test study of the use of biodiesel B10 in a diesel pick-up truck with an engine size not over 2500 cc, it showed that biodiesel B10 can be effectively used as an alternative fuel giving low polluted emission. On dynamometer performance test of the Isuzu TFR 2500 Di pick-up truck used over 200,000 kilometers, it resulted that the maximum power output from the use of diesel was 60.9 hp@3,630 rpm whereas from the use of biodiesel B10 was 58.1 hp@3,700 rpm which was about 4.6% lower. Considering the heating value of diesel of 35,970 kJ/l, it was 8.4% higher than that of the pure biodiesel (32,940 kJ/l). Since biodiesel B10 is a mixture of 10% pure biodiesel and 90% diesel fuel, and the molecular structure of biodiesel contains 11%wt oxygen gives better combustion. However, biodiesel was more viscous compared to diesel at the same fuel injection pressure of 180 kg_f/cm², therefore, the fuel nozzle injector was changed to a 5-hole nozzle from the original 4-hole nozzle for better fuel spray and atomization in the combustion chamber. The maximum power output of 58.6 hp@3,685 rpm was achieved but the fuel consumption rate and soot emission were lower. Comparing the road test results at the average speed of 90 km/h, the average consumption rate of biodiesel B10 was 16.4 km/l which was about 5.2% higher than that of diesel of 17.3 km/l. When changing to 5-hole fuel injector, the average consumption rate of biodiesel B10 was 18.4 km/l, about 12.2% saver than from the original 4-hole nozzle use. Similarly the average consumption rate of diesel when using the 5-hole nozzle injector was saver to 18.6 km/l. It clearly provided better fuel atomization in the combustion chamber. From the random emission measurements, it showed that there was 33.7% soot from using biodiesel B10 which was lower than the use of diesel of 34.2% for 4-hole fuel injector, and decreased to 31.2% when switching to the 5-hole fuel injector. Keywords: biodiesel, B10, alternative fuel, diesel pick-up truck, fuel nozzle injector