Cross-Layer Resource Allocation Scheme for WLANs with Multipacket Reception

Lei Xu,Dazhuan Xu,Xiaofei Zhang,Shufang Xu 한국전자통신연구원 2011 ETRI Journal Vol.33 No.2

Tailored for wireless local area networks, the present paper proposes a cross-layer resource allocation scheme for multiple-input multiple-output orthogonal frequency-division multiplexing systems. Our cross-layer resource allocation scheme consists of three stages. Firstly, the condition of sharing the subchannel by more than one user is studied. Secondly, the subchannel allocation policy which depends on the data packets’ lengths and the admissible combination of users per subchannel is proposed. Finally, the bits and corresponding power are allocated to users based on a greedy algorithm and the data packets’ lengths. The analysis and simulation results demonstrate that our proposed scheme not only achieves significant improvement in system throughput and average packet delay compared with conventional schemes but also has low computational complexity.

Numerical Analysis on Mechanical Property of Concrete Filled Steel Tube Reinforced Concrete (CFSTRC) Columns Subjected to ISO-834 Standard Fire

Lei Xu,Lei Xu,Wen-Da Wang,Jian-Gang Sun 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.4

The present study established a numerical investigation on the behavior of concrete filled steel tube reinforced concrete (CFSTRC) columns subjected to fire. A finite element analysis (FEA) model was built to simulate the performance of CFSTRC columns under combined loading and fire. The FEA model was verified by the experimental results of CFSTRC columns subjected to fire. The comparison demonstrated an acceptable accuracy for the proposed FEA model. Afterwards, the FEA model was used to analyze the failure modes, the redistribution of internal force, the changes and development of the stress and strain, and the contact stress between the tube and concrete of CFSTRC columns subjected to fire. Influencing factors that may affect the bearing capacity of the CFSTRC columns subjected to fire were analyzed. The bearing capacity and stiffness of the CFSTRC columns gradually decreased in the fire; the parameters such as the fire duration time, sectional dimension, slenderness ratio, and sectional core area ratio significantly influenced the bearing capacity of the CFSTRC columns. Finally, a simplified calculating formula was proposed to calculate the influence factors of the bearing capacity of the CFSTRC columns subjected to ISO-834 standard fire. The formula-calculated results were well in agreement with the finite element analysis results, which provide a simple and feasible method for evaluating the fire-resistance design of these types of components in practical engineering.

A metal oxide TFT gate driver with a single negative power source employing a boosting module

Yangang Xu,Jun-Wei Chen,Wen-Xing Xu,Lei Zhou,Wei-Jing Wu,Jianhua Zou,Miao Xu,Lei Wang,Junbiao Peng 한국정보디스플레이학회 2020 Journal of information display Vol.21 No.1

This paper presents a new gate driver integrated by In-Zn-O thin-film transistors (IZO TFTs) with the etch stop layer (ESL) structure, in which only a single negative power source is used on account of a new boosting module. The boosting module is controlled only by the VIN signal for generating a lower level than VSS. The proposed gate driver with 15 stages is fabricated through the IZO TFT process on a glass substrate to verify its function. The experiment results showed that the proposed gate driver can successfully output full-swing waveforms with resistive load RL=2 kΩ and capacitive load CL=30 pF at the 16.7 and 66.7 kHz clock frequencies, and can also output as small as 3.2 μs pulse width with little distortion, revealing good stability.

Uniform Side Illumination Generated from LEDs Arranged by an Annealing Algorithm

Xu Wang,Panling Lei,Chaoyi Qian,Zhiping Wang,Xuefen Xu,Zhouping Su 한국광학회 2022 Current Optics and Photonics Vol.6 No.3

Given a cubic space, it is easy to uniformly illuminate the floor with light sources placed on top. However, little has been reported about uniform illumination on walls with the same configuration of light sources. Here we present a luminaire consisting of nine light-emitting diodes (LEDs) with perfect Lambertian distribution, placed on the top as a 3 × 3 rectangular LED array. The distances between LEDs and tilt angles of each individual LED are adjustable and optimized by an annealing algorithm. After optimization, the array produces a rectangular illumination pattern on one wall with a uniformity of about 89%. Analysis shows that the tilt angles of individual LEDs are key parameters for uniform side illumination. In a scenario that is more practical, the tilt angles of all the LEDs are set to be the same, only decreasing the uniformity to 83%.

Numerical Analysis on Structural Behaviors of Concrete Filled Steel Tube Reinforced Concrete (CFSTRC) Columns Subjected To 3-side Fire

Lei Xu,Ming-Tao Wang,Yan-Hong Bao,Wen-Da Wang 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.4

The structural behaviors of concrete filled steel tube reinforced concrete (CFSTRC) columns, which were exposed to a 3- side fire were discussed by using the non-linear finite element analysis (FEA) software ABAQUS. Details of the temperature distribution, fire resistance, failure modes, redistribution of internal force, contact stress between the steel tube and the concrete (both inside and outside of the steel tube), and the development of stress and strain within the CFSTRC columns subjected to a 3-side fire were revealed. The factors that may have affected the fire resistance of the CFSTRC columns exposed to threeside fire were analyzed. Based on the above research, the present study observed uniaxial symmetry on the cross-sectional thermal distribution of the CFSTRC, wherein a significantly lower temperature on the unexposed side was observed as compared to the exposed side. The two side verges of the surface, which were not exposed to fire, exhibited the lowest temperature. Following the end of the heating, the maximum temperature difference reached about 1065oC. The large temperature difference would bring non-uniform thermal stress and strain, and accidental eccentricity. In addition, the existence of concrete inside and outside of the steel tube prevented the steel tube from occurring local buckling, and the failure modes of CFSTRC columns acted as overall bucking. Parameters such as the fire load ratio, sectional dimension, slenderness ratio, sectional core area ratio, and external concrete compression strength significantly influenced the fire resistance of the CFSTRC columns. Finally, a simplified calculating formula was proposed to calculate the fire resistance influence factors of the CFSTRC columns subjected to three-sid fire. The formula-calculated results were well in agreement with the finite element analysis results, thereby providing a simple and feasible method for evaluating the fire-resistance design of these types of components in practical engineering.

On effects of rail fastener failure on vehicle/track interactions

Xu, Lei,Gao, Jianmin,Zhai, Wanming Techno-Press 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.63 No.5

Rail support failure is inevitably subjected to track geometric deformations. Due to the randomness and evolvements of track irregularities, it is naturally a hard work to grasp the trajectories of dynamic responses of railway systems. This work studies the influence of rail fastener failure on dynamic behaviours of wheel/rail interactions and the railway tracks by jointly considering the effects of track random irregularities. The failure of rail fastener is simulated by setting the stiffness and damping of rail fasteners to be zeroes in the compiled vehicle-track coupled model. While track random irregularities will be transformed from the PSD functions using a developed probabilistic method. The novelty of this work lays on providing a method to completely reveal the possible responses of railway systems under jointly excitation of track random irregularities and rail support failure. The numerical results show that rail fastener failure has a great influence on both the wheel/rail interactions and the track vibrations if the number of rail fastener failure is over three. Besides, the full views of time-dependent amplitudes and probabilities of dynamic indices can be clearly presented against different failing status.

Wave propagation of graphene platelets reinforced metal foams circular plates

Lei-Lei Gan,Jia-Qin Xu,Gui-Lin She 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.85 No.5

Based on first-order shear deformation theory, a wave propagation model of graphene platelets reinforced metal foams (GPLRMFs) circular plates is built in this paper. The expressions of phase-/group- velocities and wave number are obtained by using Laplace integral transformation and Hankel integral transformation. The effects of GPLs pattern, foams distribution, GPLs weight fraction and foam coefficient on the phase and group velocity of GPLRMFs circular plates are discussed in detail. It can be inferred that GPLs distribution have great impacts on the wave propagation problems, and Porosity- I type distribution has the largest phase velocity and group velocity, followed by Porosity-III, and finally Porosity-II; With the increase of the GPLs weight fraction, the phase- and group- velocities for the GPLRMFs circular plate will be increased; With the increase of the foam coefficient, the phase- and group- velocities for the GPLRMFs circular plate will be decreased.

Herd Behavior in the Chinese Growth Enterprise Market

Xu Lei,박광수 성균관대학교 경영연구소 2018 자산운용연구 Vol.6 No.2

This paper analyzes herd behavior in the growth enterprise market(GEM) of China. Herd behavior means that sheep or other animals move together at the same time when they are in a herd. This paper provides the brief reviews of theory of herd behavior and empirically tests the existence of herd behavior in the GEM by two regression models(non-linear model and transaction volume model) using the cross-section absolute deviation(CSAD) measure. The main results of this paper are as follows. First, there is strong herd behavior in the Chinese GEM in all the three periods ; flat market, bull market and bear market. Second, the herd behavior in the GEM is more obvious in the bull market and relatively weak in the bear market. Third, we infer the strong herd behavior in the GEM is caused by imperfection of information disclosure system, excessive government intervention on the GEM, and speculative factors in GEM. Based on above findings, we suggest that the GEM investors need to invest based on the more fundamental approach than market sentiment, and Chinese financial authority should minimize market intervention and supplement the operational systems of the GEM, such as information disclosure and short selling, in order to increase the efficiency of the GEM.

Beyond PCA Learnings : From Linear to Nonlinear and From Global Representation to Local Representation

Lei Xu 대한전자공학회 1994 ICONIP : International Conference On Neural Inform Vol.3 No.2

Homosexual film creation under the influence of queer theory

Xu Lei(쉬레이),Hyun-seok Lee(이현석) 한국정보통신학회 2021 한국정보통신학회 여성 ICT 학술대회 논문집 Vol.2021 No.8

퀴어 이론은 성적 권리의 관점에서 생물학적 젠더, 사회적 젠더 및 성적 지향 간의 관계를 해체하고 구성하는 혁명적인 이론이다. 게이 그룹은 퀴어 이론을 자신의 권리를 위해 싸울 이론적 무기로 사용한다. 현재 퀴어 이론에 기반한 많은 영화가 제작되고 있으며, 대부분은 동성 간의 관계를 다루고 있다. 이는, 영화의 전통적인 젠더 개념에 반하는 장르이다. 본 논문은 주로 현대 동성애 영화에 대한 퀴어 이론의 중요성을 논의하고 현재 영화 산업에서 게이 영화의 향방을 예측하고자 한다. Queer theory is a powerful and revolutionary theory, which deconstructs and constructs the relationship among biological gender, social gender and sexual orientation from the perspective of sexual rights. Gay groups take queer theory as a theoretical weapon to fight for their rights. At present, there are many movies based on queer theory, most of which are about the relationship between the same sex, and these movies are a challenge to the traditional gender concept. This paper mainly discusses the significance of queer theory to contemporary homosexual film and analyze the survival status of these excellent gay films in the current film industry.