Fabrication and Interface Structural Behavior of Mg/Al Thickness-Oriented Bonding Sheet via Direct Extrusion

Lei Gao,Feng Li,Ye Wang,Xing Mao Xiao,Peng Da Huo 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8

Solid-state bonding of heterogeneous materials is one of the effective ways to achieve light weight. An extrusion formingprocess for Mg/Al thickness-oriented bonding sheet was carried out. Due to triaxial compressive stress in the extrusion container,the AZ31 and AA6061 billets were deformed and the bonding and forming of Mg/Al thickness-oriented sheet can berealized by this method. The observation results of the bonding position by using XRD, SEM and EDS showed that: at theforming temperature with 360–420 °C, it had a good bonding interface, and the width of the transition layer increased withthe increase of the forming temperature. The presence of brittle intermetallic compounds in the transition layer indicated thatmetallurgical bonding had occurred at the interface. Considering all factors comprehensively, when the forming temperaturewas 390 °C, the bonding quality was appropriate. Its tensile-shear strength was 42 MPa, the width of the interface transitionlayer was about 10 μm, and the microhardness was about 164.3 HV. This method provided scientific guidance and technicalreserves for green forming of Mg/Al sheets.

A Study of the Satisfaction with the operation of design courses-Based on PJBL(Project Based Learning): An analysis of a University of Applied Sciences in China

WANG LEI(LEI WANG),Choi Wonjae(Wonjae Choi) 한국스마트미디어학회 2023 스마트미디어저널 Vol.12 No.5

As the definition and role of design changes over time with the times and society, design education needs to update teaching methods to match it. The course design in this study began with an optimisation of the learning model based on previous research and analysis, followed by in-depth interviews, the application of the interview results to the final curriculum design, and finally a questionnaire to verify the positive effects of this teaching model. This teaching model has been applied to teach a pilot class in a university of applied sciences in China. The main characteristics of the course design are Project-Based Learning (PJBL) oriented, team cooperation centric, and an educational model developed based on peer assessment. In every stage of the UI design course, realistic project simulations are adopted, enhancing students' abilities through practical experience, teamwork, and peer assessment. The innovation lies in validating the effectiveness and advantages of this model at every stage of the UI design course, innovating existing teaching methods, optimizing learning models, and combining practice with evaluation. This research found that a project-oriented team course design based on PJBL has a high degree of effectiveness and relevance in each stage of the UI design course, significantly improving students' overall competence. It is expected that the results of this study can be applied in various ways to the course design of the courses that similar to design majors.

Research on Large‑scale Photovoltaic Planning Based on Risk Assessment in Distribution Network

Lei Wang,Minyu Yuan,Fan Zhang,Xuli Wang,Jing Ma,Lei Dai,Xianjun Qi,Rui Bi 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.3

Risks caused by large amounts of distributed photovoltaic (PV) feeding into distribution networks, have an impact on PV planning, which has become a critical consideration for distribution networks’ operation. In this paper, a large-scale PV planning method is proposed which based on risk assessment in distribution networks. Cluster division is used to group large-scale distributed PVs. A risk assessment is performed on the distribution network, considering the correlation between PVs and loads. The efects of load fuctuations, PV quantity, capacity and location on the operational risk of the distribution network are analyzed and discussed. A large-scale PV planning model is established with the goal of maximizing the comprehensive benefts, considering the penalty cost of node voltage over-limit and branch power fow over-limit risk. Finally, the genetic algorithm is used to solve the planning model. The simulation results demonstrate the efectiveness of the proposed method.

LiFePO₄ quantum-dots composite synthesized by a general microreactor strategy for ultra-high-rate lithium ion batteries

Wang, Bo,Xie, Ying,Liu, Tong,Luo, Hao,Wang, Bin,Wang, Chunhui,Wang, Lei,Wang, Dianlong,Dou, Shixue,Zhou, Yu Elsevier 2017 Nano energy Vol.42 No.-

<P><B>Abstract</B></P> <P>Due to the relatively slow, diffusion-controlled faradaic reaction mechanisms of conventional LiFePO<SUB>4</SUB> (LFP) materials, which is hard to deliver satisfied capacity for high rate applications. In this work, ultrafine LFP quantum dots (LFP-QDs) co-modified by two types of carbonaceous materials - amorphous carbon and graphitized conductive carbon (graphene) have been successfully synthesized through a novel microreactor strategy. Because of the very limited area constructed by the dual-carbon microreactor for the growth of LFP crystal, it's demension was furthest suppressed to a very small level (~ 6.5nm). Such a designed nano-composite possesses a large specific surface area for charge adsorption and abundant active sites for faradaic reactions, as well as ideal kinetic features for both electron and ion transport, and thus exhibits ultra-fast, surface-reaction-controlled lithium storage behavior, mimicking the pseudocapacitive mechanisms for supercapacitor materials, in terms of extraordinary rate capability (78mAhg<SUP>−1</SUP> at 200C) and remarkable cycling stability (~ 99% over 1000 cycles at 20C). On the other side, due to the quasi-2D structure of the synthesized LFP-QDs composite, which can be used as the basic unit to further fabricate free-standing film, aerogel and fiber electrode without the addition of binder and conductive agent for different practical applications. In addition, to deeper understand its electrochemical behavior, a combined experimental and density functional theoretical (DFT) calculation study is also introduced.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A general microreactor strategy has been developed for structure-optimized Li-contained electrode materials. </LI> <LI> Ultrafine LiFePO<SUB>4</SUB> quantum dots are first reported through the designed microreactor strategy. </LI> <LI> The synthesized G/LFP-QDs@C exhibits ultra-fast, surface-reaction-controlled Li storage behavior. </LI> <LI> A combined experimental and DFT calculation study is introduced to reveal the energy storage mechanism of G/LFP-QDs@C. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Ultrafine LiFePO<SUB>4</SUB> quantum dots (~ 6.5nm) co-modified by two types of carbonaceous materials - amorphous carbon and graphitized conductive carbon (graphene) have been successfully synthesized through a novel microreactor strategy, which exhibit ultra-fast, surface-reaction-controlled energy storage behavior, mimicking the pseudocapacitive mechanisms for supercapacitor materials, in terms of excellent rate capability and outstanding cycling stability.</P> <P>[DISPLAY OMISSION]</P>

증강현실을 이용한 패턴 인식

왕레이(Wang Lei),신성윤(Wang Lei),이양원(Seong-Yoon Shin) 한국컴퓨터정보학회 2009 한국컴퓨터정보학회 학술발표논문집 Vol.16 No.2

분 논문은 카메라 장비와 마커, DB를 이용하여 문자의 색감과 모음, 자음을 인식하여 문자에 해당되는 이미지 및 영상을 HMD 및 모니터, 가정에서 사용하는 화상 카메라 등을 이용하여 보다 구체적인 정보를 전달할 수 있게 해준다. DB에는 각 텍스트의 모음과 자음에 관한 텍스트가 등록되어 있으며, 각각의 색과 텍스트를 비교하여 해당하는 이미지를 출력하게 된다. 기존의 증강현실 기법은 해당 마크에 관한 패턴을 인식하여 그에 해당하는 이미지 및 영상을 출력하는데, DB를 이용한 문자인식을 사용할 경우 사용자에게 텍스트를 인식하여 연관된 많은 정보를 제공할 수 있게 된다. 제안된 인터페이스는 다양한 모습을 어려 시야를 통해 기존의 카탈로그보다 사용자의 접근성을 향상시키고, 미리 정의된 DB에 접근하여 해당 문자에 관한 여러가지 정보를 사용자에게 전달한다. 여러 전달 매체를 이용, 가상현실 및 증강현실 등을 다양한 카탈로그 뿐만 아니라 교육 및 신문 잡지, 광고 등 문자가 등장하는 여러 분야에 활용이 가능하다.

Bending ratcheting behavior of pressurized straight Z2CND18.12N stainless steel pipe

Wang, Lei,Chen, Gang,Zhu, Jianbei,Sun, Xiuhu,Mei, Yunhui,Ling, Xiang,Chen, Xu Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.6

The ratcheting effect greatly challenges the design of piping components. With the assistance of the quasi-three point bending apparatus, ratcheting and the ratcheting boundary of pressurized straight Z2CND18.12N stainless steel pipe under bending loading and vertical displacement control were studied experimentally. The characteristics of progressive inelastic deformation in axial and hoop directions of the Z2CND18.12N stainless steel pipes were investigated. The experiment results show that the ratcheting strain occurs mainly in the hoop direction while there is less ratcheting strain in the axial direction. The characteristics of the bending ratcheting behavior of the pressure pipes were derived and compared under load control and displacement control, respectively. The results show that the cyclic bending loading and the internal pressure affect the ratcheting behavior of the pressurized straight pipe significantly under load control. In the meantime, the ratcheting characteristics are also highly associated with the cyclic displacement and the internal pressure under displacement control. All these factors affect not only the saturation of the ratcheting strain but the ratcheting strain rate. A series of multi-step bending ratcheting experiments were conducted under both control modes. It was found that the hardening effect of Z2CND18.12N stainless steel pipe under previous cyclic loadings no matter with high or low displacement amplitudes is significant, and the prior loading histories greatly retard the ratcheting strain and its rate under subsequent loadings. Finally, the ratcheting boundaries of the pressurized straight Z2CND18.12N stainless steel pipe were determined and compared based on KTA/ASME, RCC-MR and the experimental results.

Design, Synthesis and Catalytic Property of L-Proline Derivatives as Organocatalysts for Direct Aldol Reaction

Wang, Lei,Tang, Ruiren,Yang, Hua Korean Chemical Society 2013 대한화학회지 Vol.57 No.5

A series of chiral prolinamide compounds with pyridine-2, 6-dicarboxylic acid moieties derived from L-proline have been designed and synthesized, their catalytic properties for direct asymmetric aldol reactions were also studied in this article. These catalysts gave the aldol product in high yield (87%) and high enantioselectivity, up to 85%, of the anti-structure at room temperature but gave disappointing results at a lower temperature or when additive was added. Conditions, including solvents, temperature and additives were screened for the reactions. Moreover, the influence of presence of water on yield and stereoselectivity was also discussed.

Study on the Reaction Mechanism and Magnetic Properties of Metal/Ferrites Nanocomposite

Lei Wang,Qin Wang,Yan Chen,Hua Yang 한국자기학회 2008 한국자기학회 학술연구발표회 논문개요집 Vol.- No.-

Photoinduced degradation of 2,4-dichlorophenol in water: influence of various Fe(III) carboxylates

Wang, Lei,Zhang, Changbo,Mestankova, Hana,Wu, Feng,Deng, Nansheng,Pan, Gang,Bolte, Michele,Mailhot, Gilles Korean Society of Photoscience 2009 Photochemical & photobiological sciences Vol.8 No.7

Fe(III)-carboxylate complexes were investigated with respect to tri-carboxylic (citric), di-carboxylic (tartaric) and mono-carboxylic (pyruvic) acids. In agreement with the chemical structure, results demonstrated that Fe(III) was complexed by citric acid with a ratio of 1 : 1 (Fe/ligand), tartaric acid (D or L) with a ratio of 1 : 2 and by pyruvic acid with a ratio of 1 : 3. The iron concentration was fixed at 0.3 mmol $L^{-1}$ and the ligand concentration ranged from 0 to 1.0 mmol $L^{-1}$. The primary stage of 2,4-dichlorophenol (2,4-DCP) degradation photoinduced by these Fe(III) complexes was investigated under monochromatic irradiation (${\lambda}$ = 365, 313 and 296 nm). The values of initial quantum yields of 2,4-DCP disappearance (between 0.01 and 0.135) and Fe(II) formation (between 0.002 and 0.47) were evaluated and are presented in detail. Short irradiation wavelength (296 nm), low pH (3.0) and high oxygen concentration favoured the pollutant degradation. The disappearance of 2,4-DCP was complete under these favourable conditions.

Analysis of vortex induced vibration frequency of super tall building based on wind tunnel tests of MDOF aero-elastic model

Wang, Lei,Liang, Shuguo,Song, Jie,Wang, Shuliang Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.21 No.5

To study the vibration frequency of super high-rise buildings in the process of vortex induced vibration (VIV), wind tunnel tests of multi-degree-of-freedom (MDOF) aero-elastic models were carried out to measure the vibration frequency of the system directly. The effects of structural damping, wind field category, mass density, reduced wind velocity ($V_r$), as well as VIV displacement on the VIV frequency were investigated systematically. It was found that the frequency drift phenomenon cannot be ignored when the building is very high and flexible. When $V_r$ is less than 8, the drift magnitude of the frequency is typically positive. When $V_r$ is close to the critical wind velocity of resonance, the frequency drift magnitude becomes negative and reaches a minimum at the critical wind velocity. When $V_r$ is larger than12, the frequency drift magnitude almost maintains a stable value that is slightly smaller than the fundamental frequency of the aero-elastic model. Furthermore, the vibration frequency does not lock in the vortex shedding frequency completely, and it can even be significantly modified by the vortex shedding frequency when the reduced wind velocity is close to 10.5.