CFD Analysis of Flow, Pollutant Dispersion and Thermal Effects in Street Canyons

Aim of this study is to investigate the pollutant dispersion inside an urban street canyon so that the understanding of the characteristics of air flow subjected to the dispersion of pollutant can help achieve greater air quality urban areas, sustainably for improving the health and comfort of the people. Using numerical method through Computational Fluid Dynamic Software ANSYS Fluent, a simplified two dimensional street canyon is modeled to simulate the flow of pollutant subjected to building geometry as well as wind speed. The building height and street width were manipulated throughout the study. A series of multiphase analysis were conducted with different building height to street width ratio to examine the pollutant dispersion rate. With the volume fraction gradually decrease from Φ=1 to a certain value that indicates the pollutant has disperse. The result presented the relation between the street canyon geometry and the pollutant dispersion rate, with wider streets proves to have a better pollution dispersion rate as well as when the wind speed is higher. The significant of the study is to see effect of the street canyon geometry to the rate of pollutant dispersion

Effects of High and Low Temperature on the Tensile Strength of Glass Fiber Reinforced Polymer Composites

In this paper, the tensile performance of glass fiber reinforced polymer (GFRP) composites at high and low temperature was experimentally evaluated. GFRP laminates were manufactured using the wet hand lay-up assisted by vacuum bag, which has resulted in average fibre volume fraction of 0.45. Using simultaneous heating/cooling and loading, glass fiber epoxy and polyester laminates were evaluated for their mechanical performance in static tensile loading. In the elevated temperature environment test, the tension mechanical properties; stress and modulus were reduced with increasing temperature from 25oC to 80oC. Results of low temperature environment from room temperature to a minimum temperature of -20oC, indicated that there is no considerable effect on the tensile strength, however a slight decrease of tensile modulus were observed on the GFRP laminates. The results obtained from the research highlight the structural survivability on tensile properties at low and high temperature of the GFRP laminates

Ambit determination method in estimating rice plant population density

Rice plant population density is a key indicator in determining the crop setting and fertilizer application rate. It is therefore essential that the population density is monitored to ensure that a correct crop management decision is taken. The conventional method of determining plant population is by manually counting the total number of rice plant tillers in a 25 cm x 25 cm square frame. Sampling is done by randomly choosing several different locations within a plot to perform tiller counting. This sampling method is time consuming, labour intensive and costly. An alternative fast estimating method was developed to overcome this issue. The method relies on measuring the outer circumference or ambit of the contained rice plants in a 25 cm x 25 cm square frame to determine the number of tillers within that square frame. Data samples of rice variety MR219 were collected from rice plots in the Muda granary area, Sungai Limau Dalam, Kedah. The data were taken at 50 days and 70 days after seeding (DAS). A total of 100 data samples were collected for each sampling day. A good correlation was obtained for the variety of 50 DAS and 70 DAS. The model was then verified by taking 100 samples with the latching strap for 50 DAS and 70 DAS. As a result, this technique can be used as a fast, economical and practical alternative to manual tiller counting. The technique can potentially be used in the development of an electronic sensing system to estimate paddy plant population density

High impedance fault location in 11 kV underground distribution systems using wavelet transforms

Detecting and locating high impedance fault (HIF) in distribution system is a crucial task. HIF causes insulation degradation and over time will lead to supply interruptions. However, it is quite challenging to locate HIF since changes of voltage or current signal during the fault is insignificant and not able to trigger protection system. Besides, the complexity of the distribution system such as non-homogenous line and lateral with branches increase the difficulty in detecting and locating HIF. Considering these issues, this paper presents a method to detect and locate HIF based on Discrete Wavelet Transform (DWT) Multi-Resolution Analysis. In the method, fault features from voltages measured at primary substation are extracted using DWT and matched with the pre-developed database from simulation. Due to single measurement and multiple branches, the matching will produce multiple possible faulted sections. This problem is then solved by applying ranking analysis to rank the possible faulted sections from the most likely to the least likely faulted section. The proposed method has been tested with all types of faults on a 38-node distribution network system in Malaysia using the PSCAD/EMTDC software. The test results revealed the effectiveness of the method. Since only single measurement of voltage signal is needed, the method is considered economical for practical implementation

Mechanical, thermal and morphological properties of epoxy resin toughened with epoxidized soybean oil

Biobased toughened thermosetting polymer blend was prepared by incorporating epoxidized soybean oil (ESO) into a petroleum-based epoxy (DGEBA) in different composition ratios. The mechanical properties (tensile and flexural tests) of the ESO/DGEBA thermoset blends were determined. Thermal properties of the blends were characterized using thermogravimetric analysis. The result showed that, the tensile and flexural properties decreased with increasing of ESO content. However, a slight increase in the strength properties was observed at 10% of ESO content. A significant enhancement in impact strength proves the role of ESO acting as a plasticizer in the blends as well as improve the toughness properties of ESO/DGEBA thermoset blend. As the ESO content increase, the thermal stability of ESO/DGEBA thermoset blend has decreased might be due to reduced cross-linking density of the epoxy network. Further investigations on morphological properties were also done to correlate the mechanical properties of ESO/DGEBA thermoset blend

High-impedance fault location using matching technique and wavelet transform for underground cable distribution network

Locating the faulty section of a high-impedance fault (HIF) is quite challenging for the underground distribution network of a power system. The complexity of the distribution network, such as branches, nonhomogenous lines, and HIF, contributes to the difficulties in locating the faulty section. In this paper, the shortest distance (SD) technique and a database approach have been proposed to determine the faulty section. A multiresolution analysis based on discrete wavelet transforms is chosen to extract the unique features from voltage signals during the HIF event. The output coefficients from the decomposition process is stored in a database and used as the input data for the SD algorithm. The first, second, and third level of detailed coefficients of the post-disturbance voltage signal were utilized for the identification of the faulty section using the proposed method. A ranking analysis was created to provide a number of possibilities of faulty section. In this paper, a 38-node underground distribution network system in a national grid in Malaysia was modeled using the PSCAD software. The proposed method was able to successfully determine the faulty section

High impedance fault localization in a distribution network using the discrete wavelet transform

Basic guidelines for the preparation of a technical work for the Locating the faulty section for High Impedance Fault (HIF) in a power system is a major challenge especially for a radial distribution network. This is due to the effect of the complexity of the distribution network such as branches; non-homogenous lines and high impedance fault that results in a variation of fault location. In this paper, analysis of fault location using the discrete wavelet transform based Multi-Resolution Analysis (MRA) and database approach is proposed. The three-phase voltage signal at the main substation to be analyzed was measured. The 1 st, 2 nd and 3 rd level of detail coefficients were extracted for each phase and were used for the identification of faulty section using the proposed method. The simulation on a 38 nodes distribution network system in a national grid in Malaysia using PSCAD software was simulated. The proposed method has successfully determined the faulty section

AC susceptibility and electrical properties of rare-earth- and alkali metal-substituted (Tl0.7M0.3)Sr2CaCu2O7 with M = Er, Gd, La, Na, K and Rb

The effects of rare-earth elements M = Er, Gd and La, and alkali metals M = Na, K and Rb substitution on (Tl0.7M0.3)Sr2CaCu2O7 (Tl-1212) are reported. The rare-earth elements were chosen by considering the ionic radius, i.e., from the smallest (Er+3) to the largest (La+3) ion. The samples were prepared via the solid-state reaction method. X-ray diffraction patterns showed the presence of major Tl-1212 and minor Tl-1201 and Ca0.3Sr0.7CuO2 phase in almost all samples. The resistance versus temperature curves for the rare-earth-substituted samples showed onset temperature between 87 and 90 K and zero resistance temperature between 69 and 81 K. Alkali metal substitutions exhibited Tl-1212 phase but showed no superconducting transition although the electrical resistivity was much lower than the rare-earth-substituted samples. AC susceptibility measurement showed superconducting transition Tcχ, between 59 and 80 K for the rare-earth element-substituted samples. The average grain size, the transition temperature, Tcχ and the peak temperature Tp of the imaginary part of the susceptibility χ″ decreased as the ionic radius of the rare earths was reduced