http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Dual-Buck AC–AC Converter With Inverting and Non-Inverting Operations
Khan, Usman Ali,Khan, Ashraf Ali,Cha, Honnyong,Kim, Heung-Geun,Kim, Juyong,Baek, Ju-Won Institute of Electrical and Electronics Engineers 2018 IEEE transactions on power electronics Vol.33 No.11
<P>In this paper, a novel buck–boost ac–ac converter is proposed. The basic switching unit of the proposed converter is a unidirectional buck circuit; therefore, it has no shoot-through worries. It can achieve safe commutation without using <I>RC</I> snubbers or soft commutation strategies. It can be implemented with power MOSFETs without their body diodes conducting and, for current freewheeling external diodes, can be used to minimize the reverse recovery issues and related loss. It has a bipolar voltage gain with both inverting and non-inverting operations. The non-inverting operation can be used to compensate voltage sag, and inverting operation can be used to compensate voltage swell. Therefore, the proposed converter as a dynamic voltage restorer is capable of compensating for both voltage sag and swell in a wide range. The detailed theoretical analysis followed by detailed experimental results of a 300-W prototype converter is provided.</P>
An Analysis of Spot Cloud in Cloud Computing
( Usman Mansoor ),( Usman Mehmood ),( Faraz Idris Khan ),( Ki-hyung Kim ) 한국정보처리학회 2011 한국정보처리학회 학술대회논문집 Vol.18 No.1
Cloud Computing is a fast developing domain in computer system architecture which enables dynamically scalable and virtualized resources to its users. Spot Cloud is the next evolutionary step in this field which allows the cloud computing resources to be treated as a market commodity. Cloud computing vendors will now be able to put their un used computational resources for sale using the singular access platform provided by Spot Cloud. Meanwhile customers will be able to buy/sell these resources according to their requirements. This paper analyzes the idea of Spot Cloud and the anticipated impact it will have on Cloud Computing globally. The paper also presents the risks and inherent barriers associated with this idea and how they might hinder the development of Spot Cloud to its full potential.
Khan, Nabiullah,Nadeem, Raghib,Usman, Talha,Khan, Abdul Hakim The Honam Mathematical Society 2019 호남수학학술지 Vol.41 No.1
In the last decades, various integral formulas associated with Bessel functions of different kinds as well as Bessel functions themselves, have been studied and a noteworthy amount of work can be found in the literature. Following up, we present two definite integral formulas involving the product of generalized Bessel function associated with orthogonal polynomials. Also, some intriguing special cases of our main results have been discussed.
Usman, Muhammad Rehan,Khan, Arsla,Usman, Muhammad Arslan,Shin, Soo Young China Communications Magazine Co. Ltd. 2018 China communications Vol.15 No.9
<P>Non-orthogonal multiple access (NOMA) is a new access method to achieve high performance gains in terms of capacity and throughput, so it is currently under consideration as one of the candidates for fifth generation (5G) technologies. NOMA utilizes power domain in order to superimpose signals of multiple users in a single transmitted signal. This creates a lot of interference at the receive side. Although the use of successive interference cancellation (SIC) technique reduces the interference, but to further improve the receiver performance, in this paper, we have proposed a joint Walsh-Hadamard transform (WHT) and NOMA approach for achieving better performance gains than the conventional NOMA. WHT is a well-known code used in communication systems and is used as an orthogonal variable spreading factor (OVSF) in communication systems. Application of WHT to NOMA results in low bit error rate (BER) and high throughput performance for both low and high channel gain users. Further, it also reduces peak to average power ratio (PAPR) of the user signal. The results are discussed in terms of comparison between the conventional NOMA and the proposed technique, which shows that it offers high performance gains in terms of low BER at different SNR levels, reduced PAPR, high user throughput performance and better spectral efficiency.</P>
Fiscal Convergence and Total Factor Productivity: Firm-Level Evidence from Pakistan
KHAN, Usman Shaukat,KHAN, Muhammad Arshad,NAWAZ, Saima,RAHMAN, Abdul Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.10
This study examines the impact of corporate tax, a fiscal measure along with trade liberalization and research and development on total factor productivity for a panel of 153 industrial firms listed on the Pakistan Stock Exchange over the period 1997-2017. For empirical analysis, we employ the system generalized method of moment estimator. In the first step, we estimate industrial production function and the results reveal that raw material, industrial labour force and energy play vital role in enhancing industrial production. Whereas, industrial capital exerts negative impact on industrial output. We also measured total factor productivity using the production elasticities. In the second step, we examine the impact of corporate tax, trade liberalization and research and development on total factor productivity. The results indicate that higher level of corporate tax exerts negative impact on total factor productivity. The findings reveal that higher corporate taxation discourages industrial firms to undertake research and development thereby exerting adverse impact on total factor productivity of firms. The impact of trade liberalization proxied by average tariff is positive while customs duty and sales tax negatively impact firm-level total factor productivity. These findings provide useful insights for managers, investors and policy makers in Pakistan.
Khan Zafar H,Makinde Oluwole D,Usman Muhammad,Ahmad Rashid,Khan Waqar A,Huang Zaitang 한국CDE학회 2023 Journal of computational design and engineering Vol.10 No.5
This study focuses on fractional-order derivatives for the unsteady flow of magnetohydrodynamic (MHD) methanol-iron oxide (CH3OH-Fe3O4) nanofluid over a permeable vertical plate. The utilization of fractional-order derivatives provides a mathematical representation of the flow model. The concluding model, consisting of a system of fractional-order transient partial differential equations, has been solved using the finite difference method, and graphical illustrations demonstrate the effects of key parameters on the flow field. Velocity and temperature profiles provide insights into nanofluid behavior. Additionally, essential quantities such as skin friction coefficient, Nusselt number, Bejan number, and entropy generation rate have been depicted graphically. Comparison with previous studies authenticates the accuracy of the anticipated model, contributing to new intuitions into MHD nanofluid flow over a permeable vertical plate. It is worth noting that the current model, incorporating fractional-order derivatives, contributes to understanding the physical characteristics of MHD CH3OH-Fe3O4 nanofluid flow over a permeable vertical plate, research that has not been extensively explored before.
Talha Usman,Nabiullah Khan,Raghib Nadeem,Abdul Hakim Khan 호남수학회 2019 호남수학학술지 Vol.41 No.1
In the last decades, various integral formulas associated with Bessel functions of different kinds as well as Bessel functions themselves, have been studied and a noteworthy amount of work can be found in the literature. Following up, we present two definite integral formulas involving the product of generalized Bessel function associated with orthogonal polynomials. Also, some intriguing special cases of our main results have been discussed.
Influence of tungsten doping concentration on the electronic and optical properties of anatase TiO2
Matiullah Khan,Wenbin Cao,Ning Chen,Zahid Usman,Dil Faraz Khan,Arbab Mohammad Toufiq,Murad Ali Khaskheli 한국물리학회 2013 Current Applied Physics Vol.13 No.7
The structural, electronic and optical properties of tungsten-doped TiO2 have been investigated using density functional theory with plane wave basis sets and ultrasoft pseuodopotential. Substitutional W doping at Ti sites create W 5d states just below the conduction band minimum while interstitial W doping gives isolatedW5d states in the middle of forbidden region. Averaged bond lengths show that W doping at Ti sites produce minimum structural distortion as compared to the interstitial W-doped TiO2. Substitutional W-doped TiO2 has better visible light absorption compared to interstitial W-doped TiO2and has stable configuration which provide reasonable explanation for the experimental findings. Tungsten doping in TiO2 with different doping concentrations is investigated as an enabling concept for enhancing the visible light absorption. Optical properties show that optimal W doping concentration would improve the visible light absorption. 2.08% W doping concentration gives strong visible and ultraviolet light absorption among all doped models found consistent with experiments.