Theoretical investigations on the methylation of NH bond using CO2 and hydrosilane catalyzed by ZincII complexes: Mechanism and ligand effect

Li, Weiyi,Kim, Chan Kyung Elsevier Science B.V. Amsterdam 2017 Journal of CO₂ utilization Vol.2017 No.20

Research on Optimization Adjustment Strategy for SaaS Multi-tenant Data Placement

Li Xiaona,Li Qingzhong,Zhu Weiyi,Li Hui 보안공학연구지원센터 2015 International Journal of Grid and Distributed Comp Vol.8 No.2

In order to meet the requirements for data access by tenants and management by service providers, the multi-tenant data stored in cloud using replica technology must be reasonably placed. For the outweight nodes and the ultra light nodes, according to characteristics of the multi-tenant data and the load of nodes, through adjusting the number and position of the replicas to maintenance and optimization the strategy so that meet the SLA requirements meanwhile minimize the overall cost. Experimental results through comparison with random placement strategy and greedy placement policy demonstrate the feasibility and effectiveness of the proposed strategy.

A Theoretical Study on the Mechanism of Methylation of N-methylaniline with CO2 and Silyl Hydrides

Weiyi Li,김찬경 대한화학회 2017 Bulletin of the Korean Chemical Society Vol.38 No.1

The mechanism of methylation of N-methylaniline with CO2 and the phenylsilane (PhSiH3) was studied using density functional theory (DFT) at the M05-2X(THF, SMD)/6-311++G**//M05-2X/6-31G* level. The calculations show that the three-component reaction takes place from the reduction of CO2 with PhSiH3, forming the formoxysilane (FOS) species. This hydrosilylation step requires the highest activation free energy barrier (41.6 kcal/mol), and thus can be regarded as the rate-determining step (RDS) for the entire reaction. Once the FOS species is formed, its subsequent formylation with the amine to formamide (FA) species and the two successive reductions of the FA species to the desired methylamine (MA) product are easy to proceed. Furthermore, our calculations show that 1,3-diphenyldisiloxan-1-ol (PhSiH2OSiHOHPh) is together formed with the product MA. The Si–H bond activity in PhSiH2OSiHOHPh is higher than that in reactant PhSiH3 and intermediate phenylsilanol (PhSiH2OH). Thus, there exists a product catalysis as the activation free energy barrier for the FOS species formation is lowered to 36.9 kcal/mol when this species is used as a reducing agent.

Bandgap Engineering of Monolayer MoS2 under Strain: A DFT Study

Can Li,Bowen Fan,Weiyi Li,Luowei Wen,Yan Liu,Tao Wang,Kuang Sheng,You Yin 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.11

In this paper, density functional theory calculations are used to investigate the monolayer MoS2 in terms of the strain by analyzing the structure parameters: the bandgap, the density of states (DOS) and the Milliken charges. The calculations indicate that an increasing external stain tends to depress the ripple structure with a shorter S-S interlayer spacing and to enlarge the length of the Mo-S bond. Tensile strain dramatically alteres the bandgap; however, compressive strain almost does not. The change in the bandgap is explained by an analysis of the DOS, the partial density of states (PDOS), the structure parameters and the Mulliken charge distribution. The effects of strain on the Mulliken charge and the length of the Mo-S band cause bandgap differences under tensile and compressive strain.

A Correlation Evaluation Method of PV Power Output Based on ITOPSIS

Xia Weiyi,Ren Zhouyang,Li Hui,Song Yue,Hu Xiuqiong,Hu Bo 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.4

Based on the Improved Technique for Order Preference by Similarity to an Ideal Solution (ITOPSIS), an evaluation method is proposed to quantify the contribution of each photovoltaic (PV) plant on the randomness and sequential characteristics of regional PV power. It can provide valuable information for the operators and planners of power systems, as well as the dealers in electricity market. First, a correlation index system is constructed to evaluate the correlation between the power outputs of individual PV plants and the regional PV power. Next, ITOPSIS is proposed to synthesize the proposed indices. Group standardization and theoretical optimal value avert the decrease of diff erence between plants and make the results applicable for comparing correlations in diff erent cluster. The historical data collected from 16 PV plants were used to verify the eff ectiveness and correctness of the proposed method

MICRO INJECTOR BASED ON DIGITAL DRIVE AND CONTROL FOR BIOMEDICAL ENGINEERING

Liya Hou,Weiyi Zhang,Lili Mu,Li Zhu 제어로봇시스템학회 2003 제어로봇시스템학회 국제학술대회 논문집 Vol.2003 No.10

Efficacy of Interventions Based on Applied Behavior Analysis for Autism Spectrum Disorder: A Meta-Analysis

Yu Qian,Li Enyao,Li Liguo,Liang Weiyi 대한신경정신의학회 2020 PSYCHIATRY INVESTIGATION Vol.17 No.5

Objective To systematically evaluate evidence for the use of interventions based on appied behavior analysis (ABA) to manage various symptoms of children with autism spectrum disorder (ASD). Methods Sensitivity analyses were conducted by removing any outlying studies and subgroup analyses were performed to compare the effectiveness of ABA and early start denver model (ESDM), picture exchange communication systems (PECS) and discrete trial training (DTT). Results 14 randomized control trials of 555 participants were included in this meta-analysis. The overall standardized mean difference was d=-0.36 (95% CI -1.31, 0.58; Z=0.75, p=0.45) for autism general symptoms, d=0.11 (95% CI -0.31, 0.54; Z=0.52, p=0.60) for socialization, d=0.30 (95% CI -0.02, 0.61; Z=1.84, p=0.07) for communication and d=-3.52 (95% CI -6.31, -0.72; Z=2.47, p=0.01) for expressive language, d=-0.04 (95% CI -0.44, 0.36; Z=0.20, p=0.84) for receptive language. Those results suggested outcomes of socialization, communication and expressive language may be promising targets for ABA-based interventions involving children with ASD. However, significant effects for the outcomes of autism general symptoms, receptive language, adaptive behavior, daily living skills, IQ, verbal IQ, nenverbal IQ, restricted and repetitive behavior, motor and cognition were not observed. Conclusion The small number of studies included in the present study limited the ability to make inferences when comparing ABA, ESDM, PECS and DTT interventions for children with ASD.

Aqueous two-phase extraction to separate alpha-ketoglutaric acid from fermentation broth by combining crystallization

Xueqi Shi,Weiyi Su,Hongyu Zhang,Jing Fang,Ning Xu,Yanjun Jiang,Hao Li 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.115 No.-

Alpha-ketoglutaric acid (a-KG) is a crucial intermediate with broad application prospects. However, thedownstream separation of a-KG from fermentation broth with low concentration and complex componentshas become the bottleneck of large-scale production. In this study, a-KG was separated from theactual fermentation broth by aqueous two-phase system (ATPS) and crystallization. The optimal ATPScomposed of acetone/(NH4)2SO4 was selected by studying the phase diagram and a-KG distributionbehavior in different organic solvents and salts/sugars. Under the optimized conditions, the purity ofa-KG products from crude fermentation broth reached 98.08%, and the one-pass extraction efficiencywas 90.52%. The removal of cell debris and soluble proteins increased with the increase of acetone and(NH4)2SO4 concentrations, with the removal ratios reaching up to 99.44% and 86.54%. In addition,92.56% of the glucose was distributed in the aqueous phase. Although the a-KG fermentation broth ismore complex than the whole-cell biotransformation, impurities in the crude fermentation broth couldbe efficiently removed and a higher a-KG distribution coefficient was obtained. Meanwhile, the recovered(NH4)2SO4 could be reused for fermentation medium. This strategy provides an economical and effectivemethod combined with upstream biosynthesis to recover a-KG and other bioproducts from crude fermentationbroth.

Flow and heat transfer characteristics in a channel having furrowed wall based on sinusoidal wave

Jiansheng Wang,Xiaoming Gao,Weiyi Li 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.11

The effect of wall geometry on the flow and heat transfer in a channel with one lower furrowed and an upper flat wall kept at a uniform temperature is investigated by large eddy simulation. Three channels, one with sinusoidal wavy surface having the ratio (amplitude to wavelength) α/λ=0.05 and the other two with furrowed surface derived from the sinusoidal curve, are considered. The numerical results show that the streamwise vortices center is located near the lower wall and vary along the streamwise on various furrow surfaces. The furrow geometry increases the pressure drag and decreases the friction drag of the furrowed surface compared with that of the smooth surface; consequently, the total drag is increased for the augment of pressure drag. As expected, the heat transfer performance has been improved. Finally, a thermal performance factor is defined to evaluate the performance of the furrowed wall.

Residual Shear Capacity of Reinforced Concrete Beams after Fire Exposure

Yamin Song,Chuanguo Fu,Shuting Liang,Dong Li,Longji Dang,Chongfang Sun,Weiyi Kong 대한토목학회 2020 KSCE Journal of Civil Engineering Vol.24 No.11

The mechanical properties of concrete and steel are seriously degraded under high temperature, so that reinforced concrete (RC) members after fire may not be able to satisfy the prescribed performance. In this study, 27 full-scale RC beams were carried out shear tests to investigate the shear behaviour after fire. A total of 20 beams were subjected to fire on three sides in accordance with ISO 834 standard fire curve, and the remaining 7 beams (which were not subjected to fire) were employed as a reference. The influences of fire time, stirrup ratio, shear span ratio, longitudinal reinforcement ratio, and preloading (40% loading level) were considered. The experimental results indicated that the shear failure mode of the RC specimens after fire exposure was similar to that of the reference specimens. Both the residual shear load bearing capacity and stiffness of the RC beams decreased after being subjected to fire. The loss of shear bearing capacity increased with the heating time. In addition, the ultimate load bearing capacity of specimens with stirrups subjected to the same fire exposure time decreased with an increasing shear span ratio.