Dislocation Density-Based Constitutive Model and Processing Map for T2 Copper During Isothermal and Time-Variant Deformation

Gang Chen,Yu Jin,Jing Wang,Cheng Zhang,Qiang Chen,Hongming Zhang,Xingjian Zhao,Zhiyong Li,Changhai Xie,Zhiming Du 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.9

Isothermal compression tests were carried out to study the hot deformation behavior of T2 copper under various conditions. The deformation parameters, such as temperature and strain rate, have strong influence on flow stress and microstructureevolution of the alloy. A unified dislocation density-based model considering dynamic recovery and recrystallization wasestablished. And material parameters of the developed model were optimized by genetic algorithm. Comparisons betweenthe experimental and model data demonstrates that the developed model can precisely describe the flow behavior at quitewide range of deformation conditions. Meanwhile, the designed iterative procedure allows the model to be applied in timevariantdeformation conditions. Processing map and microstructure examination were constructed to optimize the processingwindow of the studied alloy. According to the processing maps, flow instability mainly appeared at low temperatures of500–650 °C and strain rates higher than 0.1 s−1. The optimum deformation parameters of T2 copper was concluded as thetemperature range of 700–800 °C and the strain rate of 0.1–1 s−1.

Workspace analysis of 3-CPS parallel micro-manipulator for mirror active adjusting platform

Gang Cheng,Bing-jing Qiu,De-hua Yang,Hou-guang Liu 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.12

In order to adjust telescope mirrors with high precision, a 3 cylindrical-prismatic-spherical (CPS) parallel micro-manipulator with 6 degrees-of-freedom (DOF) and partial decoupling is proposed. Structure characteristics of the micro-manipulator were analyzed and the kinematic equations were derived based on Euler method. To avoid tedious derivation, Jacobian matrix with screw theory representing the input and output relation of micro-manipulator is established by using velocity influence coefficient method. Combining topological structure characteristics of the 3-CPS parallel micro-manipulator, the solving procedures of workspace are obtained. Moreover, the position workspace with a given orientation and the orientation workspace with a given translation position are constructed by numerical simulations. The workspace range is chosen as the optimization goal of structure parameters, and the circumcircle radius ratio of base and moving platform and the lengths of each sub-link are optimized. The maximum condition number and the minimum singular value are chosen as the precision indexes to analyze the precision performance of the workspace. Then, the properties of the position workspaces with various orientations and the orientation workspaces with various positions are simulated numerically, and the simulation results prove that the 3-CPS parallel micro-manipulator has an ability to achieve high precision operations. This research provides a workspace modeling and optimization method for the practical application in telescope mirror adjustment or other fields requiring high precision.

Theoretical Studies on Mechanism and Kinetics of the Hydrogen-Abstraction Reaction of CF_3CH_2CHO with OH Radicals

Cheng-gang Ci,Hong-bo Yu,Su-qin Wan,Jing-yao Liu,Chia-Chung Sun 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.4

The hydrogen abstraction reaction of CF_3CH_2CHO + OH has been studied theoretically by dual-level direct dynamics method. Two stable conformers, trans- and cis-CF_3CH_2CHO, have been located, and there are four distinct OH hydrogen-abstraction channels from t-CF_3CH_2CHO and two channels from c-CF_3CH_2CHO. The required potential energy surface information for the kinetic calculation was obtained at the MCG3-MPWB//M06-2X/aug-cc-pVDZ level. The rate constants, which were calculated using improved canonical transitionstate theory with small-curvature tunneling correction (ICVT/SCT) were fitted by a four-parameter Arrhenius equation. It is shown that the reaction proceeds predominantly via the H-abstraction from the -CHO group over the temperature range 200-2000 K. The calculated rate constants were in good agreement with the experimental data between 263 and 358 K.

Grouting to Prevent Sulfate Corrosion on Coal Mine Shaft

Gang-Gang Xu,Shuan-Cheng Gu,Xiao-Dong Wang,Hai Wang,Shi-Bin Zhu 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.11

In the area of high sulfate concentration in China, the problem of sulfate corrosion in coal mine shaft is increasingly prominent. Currently, shaft repair methods are limited to diversion, interception, and backwall grouting. However, after conventional cement stabilization, shafts still must contend with poor durability and weak resistance to sulfate corrosion. To solve these problems, this study combined theoretical research, laboratory tests, and field tests to reveal the corrosion mechanism of shafts, explored novel anti-sulfate corrosion grout, and built a model for the migration of sulfate ions (SO42−) in strata and shafts. According to the results of this study, shaft corrosion was a process of continuous penetration towards the concrete interior following a cycle of concrete compaction, expansion, and cracking. Laboratory tests show that the specimens of ordinary Portland cement mortar with 20 – 30% fly ash not only have good long-term strength, but also have a significantly improved resistance capacity to sulfate solution. Based on the laboratory test results, the HSR42.5 mixed with 20% fly ash was used for wall grouting, and the water-cement ratio of the slurry was 1:1. After wall grouting, the water inflow was effectively controlled in the grouting area in the main shaft, auxiliary shaft, and air shaft, reducing from 18.5 m3/h, 20.9 m3/h, and 10.0 m3/h to 3.5 m3/h, 4.6 m3/h, and 3.2 m3/h, respectively. Moreover, after nearly three years of continuous monitoring, the water inflow did not show any significant increase in the shafts. Based on the migration law of SO42− in concrete, a shaft geological model and a salt solution migration model after grouting reinforcement under sulfate corrosion conditions were constructed. In addition, the analysis of the migration law of sulfate ion in the shaft and grouting reinforcement formation revealed that the service period of the grouting shaft can be extended for approximately 6 – 8 years.

Novel Preparation of Anatase TiO₂@Reduced Graphene Oxide Hybrids for High-Performance Dye-Sensitized Solar Cells

Cheng, Gang,Akhtar, M. Shaheer,Yang, O-Bong,Stadler, Florian J. American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.14

<P>An effective method was developed to prepare hybrid materials of TiO<SUB>2</SUB> nanoparticles on reduced graphene oxide (RGO) sheets for application in solar cells. The morphology, size, and crystal phase of the TiO<SUB>2</SUB> nanoparticles and TiO<SUB>2</SUB>@reduced graphene oxide (TiO<SUB>2</SUB>@RGO) hybrids were investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), Raman, and UV-vis diffuse reflectance spectroscopy. A possible growth mechanism of TiO<SUB>2</SUB>@RGO hybrids is proposed based on observations of the TiO<SUB>2</SUB> nanoparticles obtained from the hydrolysis process under different conditions. The effects of different reduced graphene oxide contents on the energy conversion efficiency of the dye-sensitized solar cells (DSSCs) based on <I>J</I>–<I>V</I> and incident photon-to-current conversion efficiency (IPCE) spectra are also discussed. DSSCs based on TiO<SUB>2</SUB>@RGO hybrid photoanodes with a graphene content of 1.6 wt % showed an overall light-to-electricity conversion efficiency of 7.68%, which is much higher than that of pure anatase nanoparticles (4.78%) accompanied by a short-circuit current density of 18.39 mA cm<SUP>2</SUP>, an open-circuit voltage of 0.682 V, and a fill factor of 61.2%.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-14/am4013374/production/images/medium/am-2013-013374_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am4013374'>ACS Electronic Supporting Info</A></P>

Generation of Selenoprotein with Glutathione Peroxidase Activity by Chemical Modification of the Single-chain Variable Fragment Expressed in a Single-protein Production System and Its Antioxidant Ability

Cheng Wang,Gang-Lin Yan,Shao-Wu Lü,Chun-Hong Sui,Yang Zhao,Ya-Wei Xu,Gang Zhao,Jun-jie Xu,Ping-Sheng Gong,Gui-Min Luo,Ying Mu 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.1

Glutathione peroxidase (GPX) is one of the important members of the antioxidant enzyme family. It can catalyze the reduction of hydroperoxides with glutathione to protect cells against oxidative damage. Single-chain variable fragment (scFv) can be converted into seleniumcontaining single-chain variable fragment (Se-scFv) by chemical modification of the hydroxyl groups in scFv, thus Se-scFv possesses GPX activity and becomes a prodrug. To improve the expression of scFv and simplify its purification steps, Single-protein production (SPP) system was used to express scFv and chemical modification was used to synthesize Se-scFv. Therefore, we must construct a new scFv-WCD1-lessACA gene, which can express its mRNA not containing any ACA sequences and express its amino acid sequence of target protein (scFv) being same to scFv-WCD1. In this way, the scFv-WCD1-lessACA can be only expressed in SPP system and no other background proteins in the cells could be expressed. The expression results showed that high level of scFv-WCD1-lessACA synthesis was at least sustained for 96 h in the virtual absence of background protein synthesis. Then, selenocysteine (Sec) was incorporated into the scFv-WCD1-lessACA by chemical modification and resulted in Se-scFv-WCD1-lessACA. The enzymatic characteristics of Se-scFv-WCD1-lessACA were determined. GPX activity was 2,563 U/μmol,its binding constant for GSH was 0.687 ×105/mol. Moreover,Se-scFv-WCD1-lessACA was confirmed to have a strong antioxidant ability to protect mitochondria against oxidative damage induced by Vc/Fe2+ (mitochondrial damage model),suggesting that Se-scFv-WCD1-lessACA has potential application for protection of mitochondrial damage induced by reactive oxygen species (ROS).

Sensitivity analysis and kinematic calibration of 3-UCR symmetrical parallel robot leg

Gang Cheng,Shi-Rong Ge,Jing-Li Yu 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.7

Based on the complete differential-coefficient theory, the model of the pose errors expressed by the Rodrigues Parameters was established. By normalizing all error sources, the statistical model of sensitivity coefficients was obtained. Considering the sensitivity percentages,a kinematic calibration model with the successive approximation algorithm was achieved. The simulation shows that the algorithm is effective to study the calibration question and has concrete directivity, reducing the kinematic errors with high sensitivity percentage when optimizing iteratively.

ERRATUM Bull. Korean Chem. Soc. 2011, Vol. 32, No. 4, pp 1187~1194

Cheng-gang Ci,Hong-bo Yu,Su-qin Wan,Jing-yao Liu,Chia-Chung Sun 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.7

Kinematic analysis of a 3SPS+1PS parallel hip joint simulator based on Rodrigues parameters

Gang Cheng,Wei Gu,Shi-Rong Ge 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.10

To overcome defects in complex motion simulation and variable dynamic loading of hip joint simulators available in literature, a parallel hip joint simulator with a spatial parallel manipulator as core module is proposed. The simulator has four degrees of freedom (DOFs)including three rotational freedoms which replicate abduction/adduction (AA), flexion/extension (FE) and internal/external rotation (IER)motions in various human motion states and one translational freedom designed for specimen replacement. First, the mobility properties of the simulator were analyzed based on screw theory. Second, its kinematics was analyzed and its active/constrained forces were solved based on Rodrigues parameters. Some analytic formulae were derived for solving the inverse/forward displacements, velocities, accelerations and forces. Third, according to ISO 14242-1:2002(E), a numerical simulation of the inverse kinematics was conducted, the motion configuration scheme of the simulator was determined and the selection of actuators was validated. Then the numerical simulation was validated by an experiment. Finally, higher calculation efficiency of the Rodrigues parameters against the Quaternion was proved. It is shown that the simulator proposed here can replicate motions of a natural hip joint under various motion states via changing control programs but mechanical structure.

열간압연 중 HSS를 내부응력분포 및 압하력 고찰

손성강(Cheng-Gang Sum),황상무(Sang-Moo Hwang) 한국소성가공학회 1996 압연 심포지엄 Vol.1996 No.9