The implementation of sinusoidal PWM on single phase 5-level cascaded H-bridge multilevel inverter

In the new millennium era of technology, modern industrial devices are mostly based on electronic devices that are very sensitive to harmonics. The needs for a free-harmonics and high rating power source is extremely increased in the past few years to meet the requirement from the industries. An inverter which converts DC power to AC power is one of the power electronic devices that have been in the researchers’ radar for further improvement to generate a clean power source. An inverter can be broadly classified into single level inverter and multilevel inverter. A multilevel inverter as compared to a single level inverter has advantages like minimum harmonics distortion and higher power output. An implementation of cascaded h-bridge topology and a sinusoidal pulse�width modulation, synthesize a higher quality output power especially with multilevel configuration

The effect of vortex trap on helicopter blade lift

The 5-seater Aerospatiale AS350B helicopter has been chosen in this analysis in order to investigate the capabilities of the vortex trap in increasing the helicopter blade lift. Blade Element Theory (BET) was applied to scrutinize the lift force and angle of attack distribution along the helicopter blade. From BET, the retreating blade must operate at a higher coefficient of lift for the purpose to balance the lift force on both sides of the rotor. In the process of designing and analyzing the grooyer, , commercial CFD, Fluent 6.3 and pre-processor Gambit were utilised in order to investigate the effect of groove which was applied on the upper surface of the helicopter airfoil. The Shear-Stress Transport (SST) k - o turbulence model was utilized in this analysis because of its capability in producing the flow inside the groove and the ability on predicting the separation of the airfoil. The mesh sensitivity analysis had also been accounted in the numerical study. The optimization of the groove was done by analyzing the numbers and locations of the grooves, the design depth and length of the groove and modification of the groove shape to smoothen the velocities flow. Finally, the data from BET was used with data from numerical analysis to obtain the lift force achieved by the vortex trap method to increase the lift of helicopter blade. Thus, the small increment of lift was achieved when applying groove on the upper surface of the retreating blade due to the small area contribution at high angle of attac

Terjemahan kembang ilmu

Terjemahan tidak hanya membabitkan pemindahan perkataan antara dua bahasa, bahkan turut membawa pemikiran, kebudayaan dan kemajuan intelektual ke dalam bahasa sasaran, lalu menguntungkan kedua-dua bahasa

Genotypic Characterization of Vibrio Sp. Isolated from Cockles Obtained in Padang, Indonesia

Vibrio parahaemoi'yticus is a gram negative bacterium that naturally found in warm marine environments. They commonly live in shellfish, oysters and cockles and cause gastrointestinal illness in humans. Most people become infected by eating raw or undercooked shellfish. In this study, 32 isolates of V: parahaemolyticus were isolated Erom cockles obtained from Padang, Indonesia. Presumptive identification of the isolates was performed by the following analysis: antibiotic resistance, plasmid profiling, specific PCR, random amplified polymorphic DNA (RAPD)-PCR and enternbacterial repetitive intergenic consensus (ERIC)-PCR. In the antibiotic resistance test, 16 types of antibiotics were tested against this bacterium. The isolates of V: parahemolyticus showed variable antibiotic resistance pattern. They are most commonly resistant to amoxycillin, bacitracin, penicillin, teicoplanin, ampicillin and carbenicillin. In the plasmid profiling analysis, 14 different profiles were determined. The most common profiles for the isolates is profile 110.2 which contains 4 plasmids with 5.6,7.2,42.4 and 54.0 kilobase pairs respectively. For toxR detection, all of the isolates were positive but they gave negative results in both tdh and trh detection. This indicated that they have less potential to cause diseases. They also showed high diversity in RAPD-PCR and also ERIC-PCR analysis. They showed many differences in the polymorphism pattern and can be divided into 5 major clusters in RAPD-PCR and 4 major clusters in ERIC-PCR. Application of phenotype and genotype based methods provides information about distribution, epidemiology and pathogenesis of V. parasympathetics. The data is important to identify sources of infection of this bacterium in the case of outbreaks occurrence in humans. This study also gives us preliminary information in monitoring the potential infection risk. It also can increase our awareness about the infection potential of these bacteria

Synthesis And Physico-Mechanical Analysis Of Graphene Nanoplatelets (GNPs) Filled Natural Rubber/Ethylene Propylene Diene Monomer (NR/EPDM) For Vibration Resistance

In recent years, polymer nanocomposites have attracted great interest due to their remarkable improvements in materials properties when compared with virgin polymer or conventional micro and macro-composites. This research is an effort to explore the potential of graphene nanoplatelets (GNPs) filled natural rubber/ethylene-propylene-diene rubber (NR/EPDM) as mount rubber based on their physico-mechanical and vibration damping properties. At stage 1, the effects of compatibilizer and processing parameters on the properties of NR/EPDM (70: 30 phr) blends were studied. The blends were prepared by melt compounding using Haake Internal Mixer. Using Response Surface Methodology (RSM) of two-level full factorial, the effects of epoxidized natural rubber, ENR-50 contents (-1:5 phr; +1:10 phr), mixing temperature (-1:50 °C; +1:110 °C), rotor speed (-1:40 rpm; +1: 80 rpm) and mixing time (-1:5 min; +1:9 min) in NR/EPDM blends were evaluated. Cure characteristics and tensile properties were selected as the responses. The coefficient of determination, R2 values above 0.90 were accurate to represent the actual system. The findings were further supported by swelling behaviour, thermal and morphological characteristics. At stage 2, a facile method for surface treatment of GNPs was demonstrated. In stage 3 and 4, the effects of unfunctionalized and functionalized GNPs loading (0, 0.25, 0.50, 1, 3 and 5 wt%) on cure characteristics, physico-mechanical, structural, vibration, thermal properties of the composites as well as on their morphologies were studied. The studies were carried out through Monsanto rheometer analysis, tensile test, swelling test, X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), vibration test, dynamic mechanical analysis (DMA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis. The GNPs show good compatibility with NR/EPDM matrix due to their improvement observed in cure characteristics, tensile properties and crosslink density compared with unfilled vulcanized NR/EPDM. It was in line with the observation on structural and chemical properties of GNPs dispersed in NR/EPDM matrix. XRD and FTIR pattern have provided sufficient explanation regarding the state of dispersion of GNPs filled NR/EPDM matrix. The morphology of the unfunctionalized and functionalized GNPs in the NR/EPDM matrix revealed uniform distribution of GNPs up to 3 wt% loading, whereas, GNPs agglomerates were observed at 5 wt%. The vibration test via free vibration test had proven the potential of GNPs filled NR/EPDM as mount rubber in which their amplitude decays faster than the vulcanized NR/EPDM. The storage modulus, loss modulus and tan δ showed good agreement with the vibrational damping behaviours. TEM analysis revealed the existence of intercalated and exfoliated structure of GNPs which resulted in improved vibration damping characteristics and mechanical properties. In overall, GNPs filled NR/EPDM are capable to absorb vibrational energy particularly for a mount rubber

Hubungan di antara Kekhuatiran Berkomunikasi dan Kesepaduan Kumpulan dengan Persepsi terhadap Kejayaan Pengurusan Projek di Kalangan Warga Kerja Jabatan Kerja Raya Selangor

Communication skills and cohesiveness are important for task group in any organization in achieving its goals and mission. However, communication apprehension often become obstacles to some individuals. In order to achieve the organization’s objectives, the level of communication apprehension must be low and group cohesiveness must be effective and established. This research intended to answer the question what is the level of communication apprehension of the staff of Public Works Department of Selangor; whether significant relationship exist between all the dimension of communication apprehension with the perception on project management success; whether significant relationship exist between group cohesiveness with the perception on project management success; and whether there exist any differences among the demographic factors between the comnnunication apprehension, group cohesiveness and perception on project management success. A total of 140 respondents selected using purposive sampling method from the engineers, assistant engineers and technical assistant supervising the projects. There exists a significant, positive but weak relationship between communication apprehension and group cohesiveness with the perception on project management success. There are no significant differences between demographic factors and communication apprehension. There exist significant differences between genders and both group cohesiveness and perception on project management success. In conclusion, the research has answered all pertaining questions regarding communication apprehension traits and group cohesiveness through quantitative research and hypothesis testing

Job motivation and performance of secondary school teachers

Performance can be regarded as almost any behavior, which is directed toward task or goal accomplishment. Despite extensive research, discussion and debate on how to predict employees' performance, teachers performance is complex and remains difficult to predict and evaluate. Teachers are still uncertain whether they can rely on some specific characteristics of performance. In view of this practice and in evaluating teachers' performance at the work place, it is therefore the interest of the researcher to conduct a study on secondary school teachers, so as to determine their job motivation and job performance. The second objective of this study is to compare job motivation with job performance and the third one is to compare teaching performance with job performance of secondary school teachers. This correlation study involved a total of 245 secondary school teachers throughout Kedah. Data will be analyzed using the t-test and ANOV

Why They Choose Teaching: a Factor Analysis of Motives of Malaysian Teacher Trainees

A study was carried out on 210 fourth semester teacher trainees specializing in primary school teaching from a teachers' college in Kuala Lumpur for the 1986/87 academic year to seek out their motives for taking up teaching. Results off actor analysis produced six factors, five of which were interpreted. Factor 1 touches on personal considerations for teaching; Factor 2 on the values of teaching; Factor 3 is altruistic in nature; Factor 4 refers to agreeable working conditions and Factor 5, influence 'received from key persons. Results are discussed in relation to Goldberg's theory of occupational choice and other 'related literature. The findings of the study have several implications on the selection of teacher trainees