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Journal of Thermal Science 2015年第1期24卷 49-57页

作者： Wan Aizon W Ghopa Zambri Harun Ken-ichi Funazaki Takemitsu Miura Department of Mechanical and Materials Engineering Universiti Kebangsaan Malaysia Department of Mechanical Engineering Iwate University

The existence of a gap between combustor and turbine endwall in the real gas turbine induces to the leakages phenomenon. However, the leakages could be used as a coolant to protect the endwaU surfaces from the hot gas since it could not be completely prevented. Thus, present study investigated the potential of leakage flows as a function of film cooling. In present study, the flow field at the downstream of high-pressure turbine blade has been investigated by 5-holes pitot tube. This is to reveal the aerodynamic performances under the influenced of leakage flows while the temperature measurement was conducted by thermoehromic liquid crystal （TLC）. Expe- rimental has significantly captured theaerodynamics effect of leakage flows near the blade downstream. Further- more, TLC measurement illustrated that the film cooling effectiveness contours were strongly influenced by the secondary flows behavior on the endwall region. Aero-thermal results were validated by the numerical simulation adopted by commercial sottware, ANSYS CFX 13. Both experimental and numerical simulation indicated almost similar trendinaero and also thermal behavior as the amount of leakage flows increases.

关键词： endwall fllmcooling leakage flows secondary flows aerodynamic loss film cooling effectiveness

Comparative study of effectiveness of different var compensation devices in large-scale power networks

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Journal of Central South university 2013年第3期20卷 715-723页

作者： Reza Sirjani Azah Mohamed Hussain Shareef Department of Electrical Electronic and Systems Engineering Universiti KebangsaanBangi 43600Malaysia

A comparison of the effectiveness of installing reactive power compensators,such as shunt capacitors,static var compensators(SVCs),and static synchronous compensators(STATCOMs),was presented in large-scale power networks.A suitable bus was first identified using modal analysis *** single shunt capacitor,single SVC,and single STATCOM were installed separately on the most critical *** effects of the installation of different devices on power loss reduction,voltage profile improvement,and voltage stability margin enhancement were examined and compared for 57-and 118-bus transmission *** comparative study results show that SVC,and STATCOM are expensive compared to shunt capacitor,yet the effect of installing STATCOM is better than SVC and the effect of installing SVC is better than that of shunt capacitor in achieving power loss reduction,voltage profile improvement and voltage stability margin enhancement.

关键词： shunt capacitor static var compensator static synchronous compensator power loss voltage profile voltage stability

Stress intensity factors under combined bending and torsion moments

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Journal of Zhejiang university-Science A(Applied Physics & Engineering) 2012年第1期13卷 1-8页

作者： Al Emran ISMAIL Ahmad Kamal ARIFFIN Shahrum ABDULLAH Mariyam Jameelah GHAZALI Mohammed ABDULRAZZAQ Ruslizam DAUD Faculty of Mechanical & Manufacturing Engineering Universiti Tun Hussein Onn Malaysia Faculty of Engineering & Built Environment Universiti Kebangsaan Malaysia School of Mechatronic Engineering Universiti Malaysia Perlis

This paper discusses stress intensity factor （SIF） calculations for surface cracks in round bars subjected to combined torsion and bending loadings. Different crack aspect ratios, a/b, ranging from 0.0 to 1.2 and relative crack depths, a/D, ranging from 0.1 to 0.6 were considered. Since the loading was non-symmetrical for torsion loadings, a whole finite element model was constructed. Then, the individual and combined bending and torsion loadings were remotely applied to the model. The equivalent SIF method, F＊EQ, was then used explicitly to combine the individual SIFs from the bending and torsion loadings. A comparison was then carried out with the combined SIF, F＊FE, obtained using the finite element analysis （FEA） under similar loadings. It was found that the equivalent SIF method successfully predicted the combined SIF for Mode I. However, discrepancies between the results determined from the different approaches occurred when Fm was involved. It was also noted that the predicted F＊ EE using FEA was higher than the F＊EQ predicted through the equivalent SIF method due to the difference in crack face interactions.

关键词： Stress intensity factor (SIF) Combined loadings Finite element analysis (FEA) Surface cracks Round solid bars

Influence of surface treatments on fatigue life of a two-stroke free piston linear engine component using random loading

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Journal of Zhejiang university-Science A(Applied Physics & Engineering) 2006年第11期7卷 1819-1830页

作者： RAHMAN M.M. ARIFFIN A.K. JAMALUDIN N. HARON C.H.C. Department of Mechanical and Materials Engineering Faculty of Engineering Universiti Kebangsaan Malaysia 43600 UKM Bangi Selangor DE Malaysia

This paper describes the finite element (FE) analysis technique to predict fatigue life using the narrow band frequency response approach. The life prediction results are useful for improving the component design methodology at the very early development stage. The approach is found to be suitable for a periodic loading but requires very large time records to accurately describe random loading processes. This paper is aimed at investigating the effects of surface treatments on the fatigue life of the free piston linear engine’s components. Finite element modelling and frequency response analysis were conducted using computer aided design and finite element analysis commercial codes, respectively. In addition, the fatigue life prediction was carried out using finite element based fatigue analysis commercial code. Narrow band approach was specially applied to predict the fatigue life of the free piston linear engine cylinder block. Significant variation was observed between the surface treatments and untreated cylinder block of free piston engine. The obtained results indicated that nitrided treatment yielded the longest life. This approach can determine premature products failure phenomena, and therefore can reduce time to market, improve product reliability and customer confidence.

关键词： Vibration fatigue Finite element (FE) Power spectral density function Frequency response Surface treatment

De Broglie–Bohm Interpretation of Canonical Quantum Cosmology Implies Early Stages of the universe Dominated by Radiation

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Communications in Theoretical Physics 2013年第12期60卷 691-694页

作者： Ch’ng Han Siong Shahidan Radiman School of Applied Physics Faculty of Science and Technology Universiti Kebangsaan Malaysia

The Einstein＇s genera/relativity is formulated in the Hamiltonian form for a spatia/ly Bat, isotropic and homogeneous universe. Subsequently, we perform the canonical quantization procedure to the Hamiltonian to obtain the Wheeler-DeWitt equation. Solving the Wheeler-DeWitt equation and employing the de Broglie-Bohm interpretation to the wave function of the universe, we obtain a new version of spatia/ly fiat Friedmann equation for the early universe where the scale factor of the universe is taken to be sufilcientlv small.

关键词： de Broglie-Bohm interpretation canonical quantum cosmology Friedmann equation Wheeler-DeWitt equation

Metamaterial-Based Compact Antenna with Defected Ground Structure for 5G and Beyond

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Computers, Materials & Continua 2022年第5期71卷 2383-2399页

作者： Md.Mushfiqur Rahman Md.Shabiul Islam Mohammad Tariqul Islam Samir Salem Al-Bawri Wong Hin Yong Faculty of Engineering Multimedia UniversityPersiaran MultimediaCyberjaya63100SelangorMalaysia Department of Electrical Electronic and Systems EngineeringFaculty of Engineering and Built EnvironmentUniversiti Kebangsaan MalaysiaBangi43600Malaysia Space Science Centre Climate Change InstituteUniversiti Kebangsaan Malaysia(UKM)Bangi43600Malaysia

In this paper,a unit cell of a single-negative metamaterial structure loaded with a meander line and defected ground structure(DGS)is investigated as the principle radiating element of an *** unit cell antenna causes even or odd mode resonances similar to the unit cell structure depending on the orientation of the microstrip feed used to excite the unit ***,the orientation which gives low-frequency resonance is considered *** unit cell antenna is then loaded with a meander line which is parallel to the split bearing side and connects the other two sides orthogonal to the split bearing *** modified structure excites another mode of resonance at high frequency when a meander line defect is loaded on the metallic ground *** parameters of the meander line structure,the DGS shape,and the unit cell are optimized to place these two resonances at different frequencies with proper frequency intervals to enhance the ***,the feed is placed in an offset position for better impedance matching without affecting the bandwidth The compact dimension of the antenna is 0.25λL×0.23λL×0.02λL,whereλL is the free space wavelength with respect to the center frequency of the impedance *** proposed antenna is fabricated and *** results reveal that the modified design gives monopole like radiation patterns which achieves a fractional operating bandwidth of 26.6%,from 3.26 to 4.26 GHz for|S11|<−10 dB and a pick gain of 1.26 dBi is *** addition,the simulated and measured crosspolarization levels are both less than−15 dB in the horizontal plane.

关键词： Split ring resonator(SRR) meander line defected ground structure compact antenna bandwidth enhancement 5G technology

Observed Trends in Extreme Temperature over the Klang Valley, malaysia

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Advances in Atmospheric Sciences 2019年第12期36卷 1355-1370页

作者： Ahmad Norazhar Mohd YATIM Mohd Talib LATIF Fatimah AHAMAD Md Firoz KHAN Mohd Shahrul Mohd NADZIR Liew JUNENG Space Science Centre Institute of Climate ChangeUniversiti Kebangsaan Malaysia43600 BangiSelangorMalaysia Faculty of Science and Natural Resources Universiti Malaysia Sabah88400 Kota KinabaluSabahMalaysia School of Environmental and Natural Resource Sciences Faculty of Science and TechnologyUniversiti Kebangsaan Malaysia43600 BangiSelangorMalaysia Centre for Tropical Climate Change System Institute of Climate ChangeUniversiti Kebangsaan Malaysia43600 BangiSelangorMalaysia Department of Chemistry Faculty of ScienceUniversity of Malaya50603 Kuala LumpurMalaysia

This study investigates the recent extreme temperature trends across 19 stations in the Klang Valley, malaysia, over the period 2006^-16. Fourteen extreme index trends were analyzed using the Mann-Kendall non-parametric test, with Sen’s slope as a magnitude estimator. Generally, the annual daily mean temperature, daily mean maximum temperature, and daily mean minimum temperature in the Klang Valley increased significantly, by 0.07°C yr^-1, 0.07°C yr^-1 and 0.08°C yr^-1, respectively. For the warm temperature indices, the results indicated a significant upward trend for the annual maximum of maximum temperature, by 0.09°C yr^-1, and the annual maximum of minimum temperature, by 0.11°C yr^-1. The results for the total number of warm days and warm nights showed significant increasing trends of 5.02 d yr^-1 and 6.92 d yr^-1, respectively. For the cold temperature indices, there were upward trends for the annual minimum of maximum temperature, by 0.09°C yr^-1, and the annual minimum of minimum temperature, by 0.03°C yr^-1, concurrent with the decreases in the total number cold days (TX10P), with -3.80 d yr^-1, and cold nights (TN10P), with -4.33 d yr^-1. The 34°C and 37°C summer days results showed significant upward trends of 4.10 d yr^-1 and 0.25 d yr^-1, respectively. Overall, these findings showed upward warming trends in the Klang Valley, with the minimum temperature rate increasing more than that of the maximum temperature, especially in urban areas.

关键词： climate change extreme temperature trend urban environment tropical area

Psychosocial impact of mothers with perinatal loss and its contributing factors:an insight

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Journal of Zhejiang university-Science B(Biomedicine & Biotechnology) 2010年第3期11卷 209-217页

作者： Rosnah SUTAN Rosnah Mohamad AMIN Khatija Banu ARIFFIN Tang Zoun TENG Mohd Faiz KAMAL Rusli Zaim RUSLI Department of Community Health University Kebangsaan Malaysia Medical CentreBandar Tun RazakCheras 56000KLMalaysia

Objective:To evaluate the psychosocial impact among mothers with perinatal loss and its contributing ***:A cross sectional study was conducted in university kebangsaan malaysia Medical Centre (UKMMC) from April 2008 to May 2009 using Edinburgh Postnatal Depression Scale (EPDS) and self administered ***:Sixty-two respondents were included and most of them were working mothers (77.4%).The mean age of the respondents was (31.0±5.6) years and a majority of the subjects aged between 20-34 years (77.4%).According to the EPDS score,53.2% of the respondents had a psychosocial impact with a total score of >9,out of *** was a significant relationship between psychosocial impact after perinatal loss and support from friends (P=0.019).However,there were no significant differences between psychosocial impact and history of previous perinatal loss,ethnicity,occupation,educational level,age or total ***:Mothers with perinatal loss should be screened for psychosocial impact and offered support when *** and friends should continue to provide emotional *** who have experienced similar problem before will be able to provide better support than those who have not.

关键词： Perinatal loss Stillbirth Neonatal death Psychosocial impact Edinburgh Postnatal Depression Scale (EPDS)

Ontogenetic changes in feeding and food preferences of the dog conch Laevistrombus canarium Linnaeus 1758 (Mollusca： Gastropoda) from Merambong shoal, malaysia

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Chinese Journal of Oceanology and Limnology 2017年第5期35卷 1230-1238页

作者： HUSNA Wan Nurul Wan Hassan MAZLAN Abd Ghaffar COB Zaidi Che School of Environmental and Natural Resource Science Faculty of Science and Technology Universiti Kebangsaan Malaysia 43600 Bangi Selangor Malaysia Marine Ecosystem Research Centre (EKOMAR) Faculty of Science and Technology Universiti Kebangsaan Malaysia 43600 Bangi Selangor Malaysia School of Fisheries andAquaculture Sciences Universiti Malaysia Terengganu 21030 Kuala Terengganu Terengganu Malaysia

Laevistrombus canarium is one of the marine gastropod mollusks that have high commercial value, particularly in the aquaculture sector in malaysia. This study was conducted to determine the feeding and food items of L. canarium at different ontogenetic stages （juveniles, sub-adults and adults） from Merambong shoals, malaysia. Field observations on feeding activity were conducted, followed by detailed laboratory analysis on the stomach content. Five-minutes observations on randomly selected individuals were conducted at the field sampling site and their feeding activities were recorded with reference to age stage. Various shell sizes from each ontogenetic stage were randomly collected and quickly anaesthetized with ice and preserved in 10% formalin before being transported to the laboratory for stomach content analyses. Field observations showed that L. canarium mainly grazed on epiphytes occurring on seagrass （46.67%）, followed by sediment surface （40%） and epiphytes occurring on macroalgae （13.33%）. Stomach content analyses showed a significant difference （P〈0.05） in gastro-somatic index （Gasi） between the juveniles （0.39±0.05）, sub-adults （0.68±0.09） and adults （0.70±0.05）（P〈0.05）. Food items found in the conch stomach include diatoms, detritus, foraminifera, seagrass and macroalgae fragments, sand particles and shell fragments. The Index of Relative Importance （%IRI） indicates three main types of food dominated the three ontogenetic stages namely diatoms, sand particles and detritus. However, no significant difference （P〉0.05） was detected between the three main food items （diatoms, sand particles and detritus） among the ontogenetic stages. Therefore, feeding activity revealed the role of the dog conch in the marine food network. While, classification of the types of food consumed by L. canarium through stomach content analysis determines the particular position of the gastropod in the food chain. Further studies are needed to provide a better insight between tr

关键词： Laevistrombus canarium feeding activity gut contents Merambong shoal

Optimized synthesis and photovoltaic performance of TiO_2 nanoparticles for dye-sensitized solar cell

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Particuology 2013年第6期11卷 753-759页

作者： Siti Nur Fadhilah Zainudin Masturah Markom Huda Abdullah Renata Adami Siti Masrinda Tasirin Department of Chemical Engineering and Process Faculty of Engineering and Built EnvironmentUniversiti Kebangsaan Malaysia Department of Electrical Electronic and System EngineeringFaculty of Engineering and Built EnvironmentUniversiti Kebangsaan Malaysia Department of Chemical and Food Engineering University of Salerno

This paper presents response surface methodology （RSM） as an efficient approach for modeling and optimizing TiO2 nanoparticles preparation via co-precipitation for dye-sensitized solar cell （DSSC） perfor- mance. Titanium （IV） bis-（acetylacetonate） di-isopropoxide （DIPBAT）, isopropanol and water were used as precursor, solvent and co-solvent, respectively. Molar ratio of water, aging temperature and calcina- tion temperature as preparation factors with main and interaction effects on particle characteristics and performances were investigated, Particle characteristics in terms of primary and secondary sizes, crys- tal orientation and morphology were determined by X-ray diffractometry （XRD） and scanning electron microscopy （SEM）. Band gap energy and power conversion efficiency of DSSCs were used for perfor- mance studies. According to analysis of variance （ANOVA） in response surface methodology （RSM）, all three independent parameters were statistically significant and the final model was accurate. The model predicted maximum power conversion efficiency （0.14%） under the optimal condition of molar ratio of DIPBAT-to-isopropanol-to-water of 1 ： 10：500, aging temperature of 36 C and calcination temperature of 400 ℃. A second set of data was adopted to validate the model at optimal conditions and was found to be 0.14 ± 0.015%, which was very close to the predicted value. This study proves the reliability of the model in identi（ving the optimal condition for maximum performance.

关键词： Titanium dioxide Hydrolysis precipitation Dye-sensitized solar cell Optimization Response surface methodology