排序方式： 共有34条查询结果，搜索用时 15 毫秒
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
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Mohammad Mohsen Shahmardan Mahmood Norouzi Mohammad Hassan Kayhani Amin Amiri Delouei 《浙江大学学报(A卷英文版)》2012,13(10):768-781
An exact analytical solution is obtained for convective heat transfer in straight ducts with rectangular cross-sections for the first time. This solution is valid for both H1 and H2 boundary conditions, which are related to fully developed convective heat transfer under constant heat flux at the duct walls. The separation of variables method and various other mathematical techniques are used to find the closed form of the temperature distribution. The local and mean Nusselt numbers are also obtained as functions of the aspect ratio. A new physical constraint is presented to solve the Neumann problem in non-dimensional analysis for the H2 boundary conditions. This is one of the major innovations of the current study. The analytical results indicate a singularity occurs at a critical aspect ratio of 2.4912 when calculating the local and mean Nusselt numbers. 相似文献
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A quantitative research study was conducted to examine the knowledge of girls aged 12-14 years regarding reproductive health in five cities in Iran with different ethnic and cultural majorities. A cross-sectional study using a self-administrated questionnaire was conducted among guide school (middle school) pupils. Data analysis was based on 1,893 questionnaires. The internal consistency of the items was 0.80. Overall, knowledge level was unsatisfactory. An association between age and knowledge about reproductive health was found. Additionally, there was a statistically significant difference in the knowledge of reproductive health between cities. The findings suggest that reproductive health education initiatives that involve mothers may be most appro priate in terms of cultural and religious sensitivities, and be in keeping with the wishes of the girls themselves. 相似文献
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Mohsen Saghapour Mohammad Iranmanesh Suhaiza Zailani Gerald Guan Gan Goh 《Education and Information Technologies》2018,23(2):777-795
This study has determined the determinants of the perceived ease of use and perceived usefulness and their influence on campus portal usage. A quantitative approach was employed, using a five-point Likert scale questionnaire, adapted from previous studies. Data were gathered through a survey conducted with 341 staff working in the University of Malaya and were analysed using the partial least squares technique. The results indicate that the ease of finding and ease of understanding have a positive impact on the perceived ease of use of the campus portal. Furthermore, this study also reported a significant positive effect of service quality, information, and process on perceived usefulness of the campus portal. Our study suggests that the perceived ease of use and usefulness are vital towards enhancing the usage frequency and volume of the campus portal. This study broadens the knowledge concerning factors that increase campus portal usage which will enable academic institutions to refine the campus portal thus enhancing the portal usage. 相似文献
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Sadegh Fattahi Mohammad Karimi Alivije Farhang Babamahmoodi Masomeh Bayani Mahmoud Sadeghi Haddad Zavareh Mohsen Asouri Maryam Lotfi Galia Amirbozorgi Haleh Akhavan-Niaki 《Indian journal of clinical biochemistry : IJCB》2018,33(4):467-472
Hepatitis B virus (HBV) infection is a worldwide health concern which is associated with significant morbidity and mortality. Both viral and host factors have a significant effect on infection, replication and pathogenesis of HBV. The aim of this study was to investigate the effect of CYP2E1 and CYP1A1 genetic variants on susceptibility to HBV. 143 individuals including 54 chronic HBV patients and 89 healthy controls were enrolled in the genotyping procedure. rs2031920 and rs3813867 at CYP2E1 as well as rs4646421 and rs2198843 at CYP1A1 loci were studied in all subjects using PCR–RFLP (restriction fragment length polymorphism) analysis. Both variants at CYP2E1 locus were monomorphic in all studied subjects. Genotype frequency of rs4646421 was significantly different between chronic HBV patients and healthy blood donors (P = 0.04, OR 4.31; 95% CI 1.04–17.7). Furthermore, individuals carrying at least one C allele (CC or CT genotypes) for rs4646421 seemed to have a decrease risk of hepatitis in comparison with TT genotype (P = 0.039). Our results showed a relationship between rs4646421 TT genotype (rare genotype) and the risk for developing chronic HBV infection (four times higher). Further studies are needed to examine the role of CYP1A1 polymorphism in susceptibility to chronic HBV infection. 相似文献
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In this paper, we propose a technique for lowering the latency of the communication in a NoC （network on chip）. The technique, which can support two qualities of service （QoS）, i.e., the guaranteed throughput （GT） and best effort （BE）, is based on splitting a wider link into narrower links to increase throughput and decrease latency in the NoC. In addition, to ease the synchronization and reduce the crosstalk, we use the l-of-4 encoding for the smaller buses. The use of the encoding in the proposed NoC architecture considerably lowers the latency for both BE and GT packets. In addition, the bandwidth is increased while the power consumption of the links is reduced. 相似文献
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提出一种在车辆自组织网络(VANET)中应用的无线多跳视频传输实验系统的设计和实现方案及其对应的传输控制和路由选择协议.该系统将嵌入式Linux与IEEE 802.11n传输协议集成到ARM内核,由S3C6410主控模块、无线局域网网卡及LCD屏等构成.针对VANET的无线多跳视频传输场景,对视频编译码分别采用H.264和JPEG两种标准实现并对它们的压缩比、时延、传输丢包率等性能进行了理论分析和实验比较,进行了室内室外多种不同场景的实际测试.结果表明:所设计的多跳视频传输实验系统方案能够适应VANET等多种场景的应用,所提出的传输控制和路由选择协议能够保证视频传输的多跳和实时性要求. 相似文献
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Van-Quang-Binh Ngo Mohsen Latifi Rabeh Abbassi Houssem Jerbi Kentaro Ohshima Mehrdad khaksar 《Journal of The Franklin Institute》2021,358(7):3491-3511
In recent years, Photovoltaic (PV) systems have been received great attention all over the words as they are sustainable, unlimited and environmentally friendly energy. However, it is required for the PV system to apply a tracking controller to guarantee efficient operation by extracting the maximum power, which named maximum power point tracking (MPPT) method. Due to the simple structure, the conventional perturb and observe (P&O) MPPT algorithm is very popular in the literature. Nevertheless, conventional methods show inaccurate performance, particularly when high variations occur in irradiance, resulting in fluctuations around the MPP. To deal with these challenges, a novel technique on the basis of the variable-step size of P&O MPPT and sliding mode controller (SMC) adjusted by the θ-modified krill herd (θ-MKH) algorithm is presented. The θ-MKH algorithm is utilized to fine-tune the optimal SMC parameters to drive the variable step of the classical P&O algorithm. Simulations are prepared to compare the performance of the suggested scheme with conventional methods by considering simultaneous fast changes of irradiance and temperature. The results show that the suggested scheme have proper performance in both transient and steady-state, particularly under quickly varying climate circumstances. 相似文献