Chiral adsorption of phenylalanine by α-, β-cyclodextrin modified layered double hydroxides

Xiaolei Liu,Lili Meng 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.4

The chiral adsorption of racemic phenylalanine (Phe) by carboxymethyl-α/β-cyclodextrin-intercalated Zn-Al layered double hydroxides (CM-α/β-CD-LDHs) has been studied. The adsorption isotherms of chiral excess adsorption and the total adsorption of Phe by these CM-α/β-CD-LDHs have been investigated. CM--CD-LDHs were found to be more suitable for chiral recognition of Phe than CM--CD-LDHs. Furthermore, the intraparticle diffusion model is successfully validated in this work. Intraparticle effective diffusivities (Deff) of Phe in these CM-α/β-CD-LDHs macroparticles were determined from the homogeneous Fickian diffusion model at various temperatures.

Effect of Vacuum Thermal Annealing on a Molybdenum Bilayer Back Contact Deposited by Radio-Frequency Magnetron Sputtering for Chalcogenide- and Kesterite-Based Solar Cells

Xiaolei Liu,Hongtao Cui,Xiaojing Hao,Shujuan Huang,Gavin Conibeer 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.71 No.12

Molybdenum (Mo) thin films are still a dominant choice for the back contact layer of Cu(In,Ga)Se2 (CIGS) and Cu2ZnSnS4 (CZTS) solar cells. This paper presents a review of Mo back contacts for CIGS and CZTS solar cells, including the requirements for a good back contact, the reason for the choice of Mo, and post-treatment. Additionally, a Mo bilayer back contact was fabricated by varying the argon (Ar) pressure during sputtering to provide both low resistivity and good adhesion to the soda-lime glass substrate. The effects of vacuum thermal annealing on the electrical, morphological and structural properties of the Mo bilayer were also investigated. Vacuum thermal annealing was seen to densify the Mo bilayer, reduce the sheet resistance, and improve the bilayer’s adhesion to the soda-lime glass. The Mo bilayer back contact with a low sheet resistance of 0.132 / and strong adhesion was made for chalcogenide- and kesterite-based solar cells.

Reliable Localization for Wireless Sensor Networks in Complex Environments

Xiaolei Liu,Yongji Ren,Xuguang Xin,Liping Zhang,Jixiang Chen 보안공학연구지원센터 2014 International Journal of Control and Automation Vol.7 No.10

Although localization has been widely studied for Wireless Sensor Networks (WSNs), the complex environments and the large network scale pose severe challenges and make it necessary to develop new reliable localization algorithms. In this paper, we propose a novel Multi-Hop Localization Algorithm for large-scale WSNs in complex environments. This work is based on the consideration that the localization process would encounter several kinds of adverse factors with different nature at the same time (e.g. anisotropic network characteristics, ranging uncertainty, link quality of multihop paths, etc.), which lead to obvious degradation of localization performance. Unlike most of the existing schemes, we transform the localization problem in complex environments into a hybrid constraint satisfaction problem (CSP) which is composed of three different kinds of constraints, i.e. spatial constraint, network situation constraint, and confidence constraint. Set-membership approach and interval analysis method have been utilized to deal with the CSP and determine the positions of sensor nodes. Simulation results show that our scheme is an effective and efficient approach to localization in large-scale WSNs.

Dynamic Power Optimization of Pilot and Data for Downlink OFDMA Systems

Yong Liu,Fei Liu,Guang Zhu,Xiaolei Wang,Yuechao Jiao 한국통신학회 2021 Journal of communications and networks Vol.23 No.4

In this paper, we investigate the power allocation prob lem in downlink orthogonal frequency-division multiple access(OFDMA) networks. Different from previous researches on powerallocation, we take into account various practical factors, such asthe stochastic traffic arrival, the time-varying channel, the queuestability requirements of all users, the channel estimation cost andthe corresponding effect of imperfect channel state information(CSI) on data transmission rate. The power allocation problemis formulated as maximizing the time-averaged data transmissionrate by optimizing pilot and data power allocation subject to thequeue stability and the maximum transmit power constraints. Thedata transmission rate is defined in terms of the pilot transmitpower, the data transmit power and the channel estimation er ror, which is non-concave. To solve the non-concave and stochas tic optimization problem, a dynamic pilot and data power alloca tion (DPDPA) algorithm is proposed with the aids of approximatetransformation, Lyapunov optimization and Lagrange dual formu lation. Moreover, we derive the bounds of performances, in termsof the time-averaged data transmission rate and queue length.

NUMERICAL STUDY ON CAVITATION FLOW CHARACTERISTICS IN DIESEL FUEL INJECTOR CONTROL VALVE

Zhenming Liu,Jingbin Liu,Jiechang Wu,Xiaolei Gu 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.4

The flow and cavitation in the flow passage of the control valve are calculated, and the effects of operating conditions (including injection pulse width, rail pressure and ball valve lift) on the flow and cavitation characteristics are analyzed under dynamic boundary conditions. The simulation results show that the cavitation in the outflowing control-orifice (OA) and the guide-hole are almost unaffected by these operating conditions. In contrast, the cavitation process in the ball valve chamber has two distinct stages, which can be classified as violent and relatively smooth. The shorter the pulse width, the more severe the average degree of cavitation in the ball valve chamber; however, the risk of cavitation erosion on the ball valve and the ball valve seat surface does not increase too much. The increase of rail pressure and the increase of ball valve lift will aggravate the cavitation, and the cavitation position will move forward closer to the sealing annular surface.

Solidification of uranium mill tailings by MBS-MICP and environmental implications

Niu Qianjin,Li Chunguang,Liu Zhenzhong,Li Yongmei,Meng Shuo,He Xinqi,Liu Xinfeng,Wang Wenji,He Meijiao,Yang Xiaolei,Liu Qi,Liu Longcheng 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.10

Uranium mill tailing ponds (UMTPs) are risk source of debris flow and a critical source of environmental U and Rn pollution. The technology of microbial induced calcium carbonate precipitation (MICP) has been extensively studied on reinforcement of UMTs, while little attention has been paid to the effects of MICP on U & Rn release, especially when incorporation of metakaolin and bacillus subtilis (MBS). In this study, the reinforcement and U & Rn immobilization role of MBS -MICP solidification in different grouting cycle for uranium mill tailings (UMTs) was comprehensively investigated. The results showed that under the action of about 166.7 g/L metakaolin and ~50% bacillus subtilis, the solidification cycle of MICP was shortened by 50%, the solidified bodies became brittle, and the axial stress increased by up to 7.9%, and U immobilization rates and Rn exhalation rates decrease by 12.6% and 0.8%, respectively. Therefore, the incorporation of MBS can enhance the triaxial compressive strength and improve the immobilization capacity of U and Rn of the UMTs bodies solidified during MICP, due to the reduction of pore volume and surface area, the formation of more crystals general gypsum and gismondine, as well as the enhancing of coprecipitation and encapsulation capacity

Numerical Analysis of Leakage Performance of Brush Seal Based on a 2-D Tube Bank Model and Porous Medium Model Considering the Effect of Compressible Gas

Xiaolei Song,Meihong Liu,Jingyao Yang 한국유체기계학회 2022 International journal of fluid machinery and syste Vol.15 No.3

This paper presented a formula for calculating the resistance coefficient of porous medium model of brush seals considering the effect of gas compressibility. Firstly, the 2-D tube bank model is used to calculate the axial resistance coefficient of brush seals. Secondly, the feasibility of the method is validated according to the existing experiment results. The validation results show that this formula is effective for brush seals. Lastly, the pressure distribution and leakage rate of the test brush seal are analyzed. With the presented porous medium model, the pressure drop through the bristle is computed, and the effect of groove of the back plate is addressed. The pressure drop is mainly concentrated on the downstream side of the bristle pack. The groove in the back plate can keep the pressure balance of the bristles back, causing the recovering of the pressure in the last row of bristles. The leakage rate of porous medium model is higher than the 2-d tube bank model, because the 2-D tube bank model only considers the leakage rate of the zone of the fence height. The rotation speed has a little effect on the reduction of the leakage rate.

Multi-objective Optimal Allocation of TCSC for Power Systems with Wind Power Considering Load Randomness

Liu Wenli,Yang Xiaolei,Zhang Tao,Abu-Siada A. 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.2

Optimum allocation of flexible AC transmission system (FACTS) can improve the power grids performances such as available transmission capacity (ATC) and voltage stability. Optimal allocation of FACTS with multiple optimization objectives for power systems comprise multiple random variables is still a challenging task to be solved. This paper derives a scenario generation method for systems containing multiple random variables first. Then, a thyristor-controlled series capacitor (TCSC) multi-objective optimal allocation model with ATC and voltage stability L index as an objective function is established. By adding the chaos initialization and the variable inertia weight setting, an improved multi-objective particle swarm optimization (MOPSO) algorithm is also proposed to easily solve the established model. Finally, based on the improved IEEE-30 bus system, the non-inferior solutions of multiple system scenarios are compared and analyzed. Simulation results show that the proposed scenario processing method, the TCSC multi-objective optimal allocation model and the improved MOPSO algorithm are effective in solving related problems.

Flower-like MoS2 Nanospheres: A Promising Material with Good Microwave Absorption Property in the Frequency Range of 8.2–12.4 GHz

XIAOLEI SU,Jing Ning,YAN JIA,Yi Liu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.7

MoS2 nanospheres have been synthesized by a hydrothermal method at various reaction times using sodium molybdate and thioacetamide as the sulfur source and reducing agent, respectively. The prepared MoS2 nanospheres have been characterized by XRD, SEM and vector network analyzer, respectively. Results show that the prepared MoS2 samples were the flower-like nanospheres and the powder size increased with increasing reaction time. The real part (ε') and imaginary part (ε") of permittivity of the prepared MoS2 nanospheres increased as the reaction time increased initially and decreased afterwards. When the reaction time was 20 h, the ε' and ε" reached the maximum values, 8.25–8.05 and 4.1–3.85, respectively. The minimum reflection loss value of -45 dB was achieved at 8.3 GHz for the synthesized MoS2 nanospheres with reaction time of 16 h. All the samples with matching thicknesses of 2–4mm presented wider effective absorption bandwidths (RL < -10 dB) in the frequency range of 8.2–12.4 GHz.

Complexity science of multiscale materials via stochastic computations

Liu, Wing Kam,Siad, Larbi,Tian, Rong,Lee, Sanghoon,Lee, Dockjin,Yin, Xiaolei,Chen, Wei,Chan, Stephanie,Olson, Gregory B.,Lindgen, Lars-Erik,Horstemeyer, Mark F.,Chang, Yoon-Suk,Choi, Jae-Boong,Kim, Yo John Wiley Sons, Ltd. 2009 International Journal for Numerical Methods in Eng Vol.80 No.6

<P>New technological advances today allow for a range of advanced composite materials, including multilayer materials and nanofiber-matrix composites. In this context, the key to developing advanced materials is the understanding of the interplay between the various physical scales present, from the atomic level interactions to the microstructural composition and the macroscale behavior. Using the developing ‘multiresolution data sets mechanics’, the ‘predictive science-based governing laws of the materials microstructure evolutions’ are derived and melted into a ‘stochastic multiresolution design framework.’ Under such a framework, the governing laws of the materials microstructure evolution will be essential to assess, across multiple scales, the impact of multiscale material design, geometry design of a structure, and the manufacturing process conditions, by following the cause–effect relationships from structure to property and then to performance.</P><P>The future integrated multiscale analysis system will be constructed based on a probabilistic complexity science-based mathematical framework. Its verification, validation and uncertainty quantification are done through carefully designed experiments, and the life-cycled materials design for products design and manufacturing is performed through the use of petascale computing. The various techniques of microstructure reconstruction result in the generation of model microstructures that, at some level, has the same statistical properties as the real heterogeneous media. Having reconstructed the heterogeneous medium, one can then evaluate its effective properties via direct numerical simulation and compare these values with experimentally measured properties of the actual medium. The proposed analysis will be dynamic in nature to capture the multi-stage historical evolvement of material/structure performance over the life span of a product. In addition to providing more accurate assessment of structure performance with stochastic multiscale analysis, our development will provide the capability of predicting structure failures and system reliability to enable more reliable design and manufacturing decisions in product development. Copyright © 2009 John Wiley & Sons, Ltd.</P>