Experimental and Theoretical Study of the Torsional Mechanism of a Hybrid FRP-aluminum Triangular Deck-truss Structure

Dongdong Zhang,Qilin Zhao,Fei Li,Feng Li 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.6

This paper investigates the torsional mechanism of a hybrid FRP-aluminum triangular deck-truss structure composed of modular structural units. A pure torsion test was conducted on a 6-m cantilever specimen to characterize the structural responses. Based on the experimental results and structural layout, a simplified analytical model is established to predict the torsional stiffness of the hybrid triangular deck-truss structure. The derivation procedures and formulae are experimentally calibrated, finding that the formulae can be conveniently used with satisfactory accuracy. It is ultimately confirmed that the torsional center of the entire triangular truss collocates with the center of the orthotropic deck. The external torsional moment is primarily resisted by the FRP lower chords and the aluminum longitudinal beams, particularly for the FRP lower chords which should be given a great consideration in the torsion design.

Characterization of a Thermophilic Lignocellulose-Degrading Microbial Consortium with High Extracellular Xylanase Activity

( Dongdong Zhang ),( Yi Wang ),( Chunfang Zhang ),( Dan Zheng ),( Peng Guo ),( Zongjun Cui ) 한국미생물생명공학회(구 한국산업미생물학회) 2018 Journal of microbiology and biotechnology Vol.28 No.2

A microbial consortium, TMC7, was enriched for the degradation of natural lignocellulosic materials under high temperature. TMC7 degraded 79.7% of rice straw during 15 days of incubation at 65°C. Extracellular xylanase was effectively secreted and hemicellulose was mainly degraded in the early stage (first 3 days), whereas primary decomposition of cellulose was observed as of day 3. The optimal temperature and initial pH for extracellular xylanase activity and lignocellulose degradation were 65°C and between 7.0 and 9.0, respectively. Extracellular xylanase activity was maintained above 80% and 85% over a wide range of temperature (50-75°C) and pH values (6.0-11.0), respectively. Clostridium likely had the largest contribution to lignocellulose conversion in TMC7 initially, and Geobacillus, Aeribacillus, and Thermoanaerobacterium might have also been involved in the later phase. These results demonstrate the potential practical application of TMC7 for lignocellulosic biomass utilization in the biotechnological industry under hot and alkaline conditions.

A Comparative Study on the Characteristics of Dancing Props and Dancing Costumes in Angga

Zhang Dongdong,Zhang Yanan,Kim Mina,Lim Jeonghee 부산대학교 중국연구소 2018 Journal of China Studies Vol.21 No.4

Asymmetric coaxial three‑coil wireless power transmission system optimization

Dongdong Zhang,Xuesong Li,Jie Yang,Xiang Li,Thomas Wu 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.9

With the rapid development of wireless power transmission (WPT) technology and the demand for a wide range of applications, the common two-coil system is becoming increasingly mature. However, the monotonous structure of two-coil systems limits their development. By incorporating relay coils, the distance of power transmission, efficiency, and electromagnetic field (EMF) leakage can be effectively improved. In this paper, the three-coil system is analyzed, and the relay coil parameters are optimized by an evolutionary algorithm. After that, based on the coil optimization, the compensation capacitance of the relay coil is analyzed and an analytical formula of the compensation capacitance of the optimized relay coil is obtained. The results show that the parameter-optimized system reduces current by 86.9%, increases efficiency by 10%, and suppresses EMF leakage by 18 dB. Meanwhile, the capacitor optimization further improves the transmission efficiency of the system.

Evaluation of Equivalent Bending Stiffness by Simplified Theoretical Solution for an FRP–aluminum Deck–truss Structure

Dongdong Zhang,Feng Li,Fei Shao,Chengfei Fan 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.1

A hybrid Fiber-Reinforced Polymer (FRP)–aluminum spatial deck–truss structure that incorporates an innovative structural form and advanced extrusion-type FRP profiles has the advantages of a lightweight, high-bearing capacity, and faster installation. In this study, a design-oriented investigation was conducted with a simplified theoretical solution to conveniently evaluate the equivalent bending stiffness of the above-mentioned unique structure. The simplified theoretical solution was derived using the equivalent continuum beam method based on the homogenization concept and shearing equivalence principle. The theoretical prediction enabled a direct format and simple calculation process convenient for engineers in terms of the calculation and design. The theoretical solution was experimentally and numerically calibrated to ensure that the formulae have the satisfactory accuracy. The accuracy of the predicted bending stiffness exceeded 90%. The derivation procedures and formulae further indicated that the FRP web diagonals played a key role in resisting the global bending stiffness of the unique structure, and thus, the shear deformation should be considered in the structural design in terms of stiffness-driven. When compared with the conventional calculation method for obtaining the bending stiffness of steel solid-web beams and planar trusses, the proposed method was more accurate and applicable for the unique hybrid structures.

Static performance of a new GFRP–metal string truss bridge subjected to unsymmetrical loads

Dongdong Zhang,Jiaxin Yuan,Qilin Zhao,Feng Li,Yifeng Gao,Ruijie Zhu,Zhiqin Zhao 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.35 No.5

A unique lightweight string truss deployable bridge assembled by thin-walled fiber reinforced polymer (FRP) and metal profiles was designed for emergency applications. As a new structure, investigations into the static structural performance under the serviceability limit state are desired for examining the structural integrity of the developed bridge when subjected to unsymmetrical loadings characterized by combined torsion and bending. In this study, a full-scale experimental inspection was conducted on a fabricated bridge, and the combined flexural–torsional behavior was examined in terms of displacement and strains. The experimental structure showed favorable strength and rigidity performances to function as deployable bridge under unsymmetrical loading conditions and should be designed in accordance with the stiffness criterion, the same as that under symmetrical loads. In addition, a finite element model (FEM) with a simple modeling process, which considered the multi segments of the FRP members and realistic nodal stiffness of the complex unique hybrid nodal joints, was constructed and compared against experiments, demonstrating good agreement. A FEM-based numerical analysis was thereafter performed to explore the effect of the change in elastic modulus of different FRP elements on the static deformation of the bridge. The results confirmed that the change in elastic modulus of different types of FRP element members caused remarkable differences on the bending and torsional stiffness of the hybrid bridge. The global stiffness of such a unique bridge can be significantly enhanced by redesigning the critical lower string pull bars using designable FRP profiles with high elastic modulus.

관광지 브랜드 자산의 추진요인 모델 및 구성에 관한 연구

장동동(Dongdong Zhang) 융합관광콘텐츠학회 2022 융합관광콘텐츠학회 학술대회 발표집 Vol.2022 No.-

Dual NURBS Path Smoothing for 5-Axis Linear Path of Flank Milling

Dongdong Li,Weimin Zhang,Wei Zhou,Tengfei Shang,Jürgen Fleischer 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.12

Linear path is still widely used to describe the five-axis machining trajectory. Five-axis tool path consists of two parts, one trajectory describes the tool tip position, and the other one represents the second point on tool axis to define the tool orientation. The natural disadvantages of G01 path are tangential and curvature discontinuities at freeform surface, which will lead to feedrate fluctuation and accuracy decrease due to the drive constraints of machine tool. In this study, a path smoothing method is proposed to smooth and optimize the linear path by using dual NURBS curves. Firstly, according to the accuracy requirements, the tool tip spline can be fitted. Secondly, the tool orientation spline can also be obtained by a coordinate system mapping method. Then, the synchronization equation of the two spline parameters is established to achieve interpolation synchronization of cutter location points. Finally, the smoothing dual NURBS tool path can be obtained with continuous curvature to improve the surface quality, motion stability and machining efficiency. Simulations and experiments validate its practicability and reliability. This method is no need to upgrade the CAM, and also could be integrated into CAM system to perform the 5-axis path smoothing.

Time-Delay and Amplitude Modified BP Imaging Algorithm of Multiple Targets for UWB Through-the-Wall Radar Imaging

Zhang, Huamei,Li, Dongdong,Zhao, Jinlong,Wang, Haitao Korea Information Processing Society 2017 Journal of information processing systems Vol.13 No.4

In order to solve the undetected probability of multiple targets in ultra-wideband (UWB) through-the-wall radar imaging (TWRI), a time-delay and amplitude modified back projection (BP) algorithm is proposed. The refraction point is found by Fermat's principle in the presence of a wall, and the time-delay is correctly compensated. On this basis, transmission loss of the electromagnetic wave, the absorption loss of the refraction wave, and the diffusion loss of the spherical wave are analyzed in detail. Amplitude compensation is deduced and tested on a model with a single-layer wall. The simulating results by finite difference time domain (FDTD) show that it is effective in increasing the scattering intensity of the targets behind the wall. Compensation for the diffusion loss in the spherical wave also plays a main role. Additionally, the two-layer wall model is simulated. Then, the calculating time and the imaging quality are compared between a single-layer wall model and a two-layer wall model. The results illustrate the performance of the time-delay and amplitude-modified BP algorithm with multiple targets and multiple-layer walls of UWB TWRI.

Application of Archimedean Copulas to the Analysis of Drought Decadal Variation in China

Dongdong Zuo,Guolin Feng,Zengping Zhang,Wei Hou 한국기상학회 2018 Asia-Pacific Journal of Atmospheric Sciences Vol.54 No.2

The joint probability and return period were calculated to analyze the drought characteristics and decadal variation. According to the fit analysis, the Gumbel-Hougaard copula provided the best fit to the observed data. Based on four drought duration classifications and four severity classifications, the drought events were divided into 16 drought types according to the different combinations of duration and severity classifications, and the probability and return period were analyzed for different drought types. The results showed that the occurring probability of six common drought types (0 < D ≤ 1 and 0.5 < S ≤ 1, 1 < D ≤ 3 and 0.5 < S ≤ 1, 1 < D ≤ 3 and 1 < S ≤ 1.5, 1 < D ≤ 3 and 1.5 < S ≤ 2, 1 < D ≤ 3 and 2 < S, and 3 < D ≤ 6 and 2 < S) accounted for 76% of the total probability of all types.