Experimental and Theoretical Investigation on the Forming Limit of 2024-O Aluminum Alloy Sheet at Cryogenic Temperatures

Chenguang Wang,Youping Yi,Shiquan Huang,Fei Dong,Hailin He,Ke Huang,Yanzhen Jia 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.12

Cryogenic forming, a new technology used to manufacture aluminum alloy thin-walled parts, has attracted much attentionin recent years. This work presents an experimental and theoretical study of 2024-O aluminum alloy sheet forming limit atcryogenic temperatures and provides an effective method for accurate prediction of forming limit curves (FLCs) at cryogenictemperatures. Uniaxial tensile experiments at different temperatures were carried out between 20 °C and − 196 °C to obtainthe constitutive equation of the material at cryogenic temperatures. The Marciniak–Kuczynski (M–K) model was used topredict FLCs at cryogenic and room temperatures. The constitutive equation and yield functions are used in the model. Theeffects of different yield criteria (Mises, Hill-48, Barlat89, Gotoh, and Yld2000-2d) on the prediction results of FLC areanalyzed. These prediction results were verified by the Nakazima test, and it was found that the Yld2000-2d yield criterion isthe most accurate for FLC prediction. Finally, the M–K model is combined with this criterion to predict the FLC at differenttemperatures. It was found that the lower the temperature, the higher the FLC curve and the better the sheet formability, andthe increase is more obvious at extremely low temperatures.

Application of model reduction technique and structural subsection technique on optimal sensor placement of truss structures

Chenguang Huang,Lingling Lu,Lijuan Liao,Yanpeng Wei,Yanchi Liu,Xi Wang 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.15 No.2

An optimal sensor placement (OSP) method based on structural subsection technique (SST) and model reduction technique was proposed for modal identification of truss structures, which was conducted using genetic algorithm (GA). The constraints of GA variables were determined by SST in advance. Subsequently, according to model reduction technique, the optimal group of master degrees of freedom and the optimal objective function value were obtained using GA in a case of the given number of sensors. Correspondingly, the optimal number of sensors was determined according to optimal objective function values in cases of the different number of sensors. The proposed method was applied on a scaled jacket offshore platform to get its optimal number of sensors and the corresponding optimal sensor layout. Then modal kinetic energy and modal assurance criterion were adopted to evaluate vibration energy and mode independence property. The experiment was also conducted to verify the effectiveness of the selected optimal sensor layout. The results showed that experimental modes agreed reasonably well with numerical results. Moreover the influence of the proposed method using different optimal algorithms and model reduction technique on optimal results was also compared. The results showed that the influence was very little.

Robust Transmission Waveform Design for Distributed Multiple-Radar Systems Based on Low Probability of Intercept

Chenguang Shi,Fei Wang,Mathini Sellathurai,Jianjiang Zhou,Huan Zhang 한국전자통신연구원 2016 ETRI Journal Vol.38 No.1

This paper addresses the problem of robust waveform design for distributed multiple-radar systems (DMRSs) based on low probability of intercept (LPI), where signal-to-interference-plus-noise ratio (SINR) and mutual information (MI) are utilized as the metrics for target detection and information extraction, respectively. Recognizing that a precise characterization of a target spectrum is impossible to capture in practice, we consider that a target spectrum lies in an uncertainty class bounded by known upper and lower bounds. Based on this model, robust waveform design approaches for the DMRS are developed based on LPI-SINR and LPI-MI criteria, where the total transmitting energy is minimized for a given system performance. Numerical results show the effectiveness of the proposed approaches.

The growth improvement of DvGS2-transgenic Arabidopsis thaliana arises from the higher efficiency of nitrogen and carbon assimilation

Chenguang Zhu,Shilin Chen,Guimin Zhang,Wei Wang,Yuanping Tang,Bing Mei,Rentao Song 한국식물생명공학회 2015 Plant biotechnology reports Vol.9 No.4

The overexpression of algal glutamine synthetase (GS) gene DvGS2 in Arabidopsis thaliana resulted in higher plant biomass and better growth phenotype. The purpose of this study was to understand the biological mechanism for the improvement of growth phenotype of DvGS2-transgenic Arabidopsis. A series of molecular and biochemical investigation related to nitrogen and carbon metabolism in DvGS2-transgenic line was, respectively, conducted. Analysis of nitrogen use efficiency (NUE)-related gene expression and enzymatic activity revealed that the transcriptional level and enzymatic activity of genes encoding glutamate synthase, glutamate dehydrogenase and alanine aminotransferase were significantly up-regulated especially under low nitrate condition. The DvGS2- transgenic line showed higher total nitrogen content and lower carbon: nitrogen ratio than the wild type. Significant reduced concentration of leaf free ammonium, higher concentrations of total amino acids, individual amino acid (glutamine, methionine, alanine, asparagine) together with increased concentrations of glucose, fructose and starch, confirmed the higher efficiency of nitrogen and carbon assimilation. These improved metabolisms of nitrogen and carbon conferred the DvGS2-transgenic Arabidopsis more biomass, better growth phenotype and higher NUE compared with the wild type plant.

Enhanced and broadband absorber with surface pattern design for X-Band

Chenguang Wu,Shuwen Chen,Xisheng Gu,Renchao Hu,Shuomin Zhong,Guoguo Tan,Qikui Man,Chuntao Chang,Xinmin Wang,Run-Wei Li 한국물리학회 2018 Current Applied Physics Vol.18 No.1

A broadband and thin-layer microwave absorber is designed based on surface pattern design made by carbonyl iron and rubber composite. The bandwidth with reflection less than 10 dB covers the full Xband owing to two absorption peaks appeared simultaneously in both the simulation results and experimental results. In this work, the power loss and power flow diagram were present by CST simulation, which clearly explain the broadband absorption caused by double l/4 matching absorption and interfacial scattering synergistic effect. A facile splicing method was provided to extend the absorption bandwidth for the magnetic absorbing materials.

Ultrasound guided breast cancer surgery & VABB experiences in China

Chenguang Zhang,Yongtao Li,Xiowen Wang,Weihua Jiang,Lina Yi,Jianghua Ou 대한외과학회 2016 대한외과학회 학술대회 초록집 Vol.2016 No.11

Nonstructural Influence Factors of Dynamic Load Allowance for Concrete Beam Bridges

Chenguang Liu,Zonglin Wang,Qingfei Gao 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.5

Studies show that nonstructural parameters, such as pavement conditions or load patterns, have greater influences on the dynamic load allowance (DLA) of bridges than structural parameters. For pavement roughness effects, the values of DLA caused by roughness profiles are calculated by a self-compiled program. The results showed that the values of DLA are discrete even if they are caused by roughness profiles that belong to the same power spectral density (PSD) grade. The PSD grade method for pavement conditions has limitations when it is used in the analysis of DLA. Statistical analysis was also carried out on these DLA results. The statistical analysis indicated that the values of DLA followed a normal distribution when they were excited by roughness profiles that belong to the same grade. For the influence of vehicle string loads on DLA, an improved optimization approach based on a genetic algorithm for the largest DLA is presented. A new method is used to calculate the fitness value in the genetic algorithm (GA) method, which could substantially reduce calculation time. The new approach is able to obtain the most unfavorable arrangement of the vehicle string and estimate the largest DLA caused by it.

Research on Natural Gas Leakage Diffusion of Urban Underground Pipeline and its Explosion Hazard

Dai Wang,Peng Liu,Chenguang Hua,Hai Zhang,Chenyang Shi,Jianmei Du 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.2

For the risk of gas leakage and explosion that may occur during the serviceability of urban natural gas pipeline, based on the numerical simulation conducted by FLACS, the gas leakage, explosion and disaster risk under the different speed of wind are mainly studied with local climate characteristics for actual urban street. The results show that the wind speed has an obvious effect on the gas leakage and diffusion, the deviation of gas leakage direction is not obvious for the smaller speed of wind at the initial stage, the horizontal diffusion range gradually increases with the increase of wind speed, while the vertical diffusion range gradually decreases, and the volume of gas at the limit concentration of combustion and explosion gradually decreases. In urban buildings, the overpressure load of higher buildings is lower. After the explosion, the peak overpressure at the same monitoring point decreases with the increase of wind speed. With the increase of distance from the building to the explosion location, the overpressure load on the building decreases and the oscillation effect of overpressure load is relatively gentle. The thermal radiation after burning has great influence on the surrounding buildings and downwind position, especially the buildings around the leakage point.

Online Robot Reference Trajectory Adaptation for Haptic Identification of Unknown Force Field

Dianye Huang,Chenguang Yang,Ning Wang,Andy Annamalai,Chun-Yi Su 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.1

In this paper, a novel online reference trajectory adaptation algorithm is developed, which aims to balance the interactive force and the deviation when the robots interact with an unknown environment. The algorithm first estimates the online parameters of the environmental dynamic model using the Lyapunov-based method. The desired trajectory is then derived by obtaining a tradeoff between the cost of strictly tracking the reference trajectory and the cost of tracking deviation. Simulation studies are carried out to verify the validity of the proposed algorithm. Simulations show that the desired trajectory tends to go around the contour of the force field when more weight is placed on the cost of interaction force, which can be used for haptic identification; identifying contours of the force field.

Application of model reduction technique and structural subsection technique on optimal sensor placement of truss structures

Lu, Lingling,Wang, Xi,Liao, Lijuan,Wei, Yanpeng,Huang, Chenguang,Liu, Yanchi Techno-Press 2015 Smart Structures and Systems, An International Jou Vol.15 No.2

An optimal sensor placement (OSP) method based on structural subsection technique (SST) and model reduction technique was proposed for modal identification of truss structures, which was conducted using genetic algorithm (GA). The constraints of GA variables were determined by SST in advance. Subsequently, according to model reduction technique, the optimal group of master degrees of freedom and the optimal objective function value were obtained using GA in a case of the given number of sensors. Correspondingly, the optimal number of sensors was determined according to optimal objective function values in cases of the different number of sensors. The proposed method was applied on a scaled jacket offshore platform to get its optimal number of sensors and the corresponding optimal sensor layout. Then modal kinetic energy and modal assurance criterion were adopted to evaluate vibration energy and mode independence property. The experiment was also conducted to verify the effectiveness of the selected optimal sensor layout. The results showed that experimental modes agreed reasonably well with numerical results. Moreover the influence of the proposed method using different optimal algorithms and model reduction technique on optimal results was also compared. The results showed that the influence was very little.