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Amorphous structure in a laser clad Ni-Cr-Al coating on Al-Si alloy

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中国有色金属学会会刊：英文版 2000年第2期10卷 220-223页

作者：梁工英苏俊义黄俊达胡仲豪 Xi An Jiao Tong Univ Sch Mech Engn Xian 710049 Peoples R China hong kong polytech Univ Dept Mech Engn Hong Kong Hong Kong Peoples R China

A mixing microstructure containing Ni based amorphous structures was observed by TEM in the laser clad zones. As the uniformity of chemical composition and temperature is poor in the laser cladding, the amorphous structure with some Ni 3Al crystals coexists in the cladding. The microhardness of the mixing amorphous structure is HV 600～800, which is lower than that of crystal phases in the coating. Differential thermal analysis (DTA) shows that Ni based amorphous structure exhibits a higher initial crystallizing temperature (about 588 ℃), which is slightly higher than that of the eutectic temperature of Al Si alloy. The wear test results indicate that there are some amorphous structures in the laser clad coating, which reduces the peeling of the granular phases from matrix, and improves the wear resistance.

关键词： laser surface treatment aluminum alloy amorphous structures

Skin Impedance at Acupuncture Point Dingchuan in Subjects with and without Asthma

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中国康复医学杂志 2009年第6期24卷 481-484页

作者： Ngai Shirley Pui-ching Jones Alice Yee-men Department of Rehabilitation Sciences The Hong Kong Polytech- nic University Hong Kong

Objective:Asthma can be a disabling disease and despite advances in pharmacology,the prevalence of this condition globally remains high and accounts for a significant proportion of public health care *** pharmacology is the mainstay of asthma management,drug side effects have promoted alternative therapeutic interventions,such as *** points have a lower skin impedance compared to non-acupuncture *** impairment is associated with changes in skin impedance at system-specific acupuncture *** of skin impedance changes may assist in the early diagnosis of asthma and monitoring the effectiveness of therapeutic interventions for this ***:This study compared skin impedance at acupuncture point Dingchuan(EX-B1),in 92 subjects with normal health(47 subjects,age 32.6 ±1.67yr) and those diagnosed with asthma(45 subjects,age 42.4 ±1.80 yr).Skin impedance was measured using a 2-electrode impedance meter bilaterally at EX-B1,0.5 "cun" lateral to the lower border of 7th cervical ***:The study showed that skin impedance was significantly higher at acupuncture point EX-B1 in subjects with asthma(29.4 ± 21 kΩ) compared to subjects with normal health(13.8±7.9 kΩ)(P=0.013).Skin impedance was negatively correlated to forced expiratory volume in 1 second(FEV1,r=-0.59,P=0.012 in females;and r=-0.68,P=0.015 in males).A receiver operator characteristic(ROC) curve revealed an optimum cut-off point of 35 kΩ for male and 10 kΩ for female ***:We conclude that EX-B1 skin impedance is higher in patients with asthma and skin impedance might be a possible adjunctive parameter for assisting diagnosis and monitoring asthmatic status.

关键词：哮喘治疗方法临床分析诊断方法

FINITE ELEMENT ANALYSIS OF A LOCAL EXPONENTIALLYFITTED SCHEME FOR TIME-DEPENDENTCONVECTION-DIFFUSION PROBLEMS

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Journal of Computational Mathematics 1999年第3期17卷 225-232页

作者： Yue, XY Jiang, LS Shih, TM Suzhou Univ Dept Math Suzhou 215006 Peoples R China Tongji Univ Inst Math Shanghai 200092 Peoples R China hong kong polytech Univ Dept Appl Math Hong Kong Hong Kong

In [16], Stynes and O' Riordan(91) introduced a local exponentially fitted finite element (FE) scheme for a singularly perturbed two-point boundary value problem without turning-point. An E-uniform h(1/2)-order accuracy was obtain for the epsilon-weighted energy norm. And this uniform order is known as an optimal one for global exponentially fitted FE schemes (see [6, 7, 12]). In present paper, this scheme is used to a parabolic singularly perturbed problem. After some subtle analysis, a uniformly in epsilon convergent order h\ln h\(1/2) + tau is achieved (h is the space step and tau is the time step), which sharpens the results in present literature. Furthermore, it implies that the accuracy order in [16] is actuallay h\ln h\(1/2) rather than h(1/2).

关键词： singularly perturbed exponentially fitted uniformly in epsilon convergent Petrov-Galerkin finite element method

Wear resistance and hot corrosion behaviour of laser cladding Co-based alloy

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Transactions of Nonferrous Metals Society of China 2001年第6期11卷 838-842页

作者：张松张春华吴维 文効忠王茂才 Shenyang polytech Univ Sch Mat Sci & Engn Shenyang 110023 Peoples R China Chinese Acad Sci State Key Lab Corros & Protect Met Shenyang 110016 Peoples R China hong kong polytech Univ Dept Mfg Engn Hong Kong Hong Kong Peoples R China

Cr13 stainless steel was surface cladded with Co based alloy using a high power carbon dioxide laser. The microstructure, wear resistance and corrosion properties of the clad layer were investigated. It is found that the high temperature corrosion behavior and wearing resistant property of the clad layer are 3 and 2.5 times higher than those of the parent metal. Under the high temperature molten lead sulphate salt corrosion condition, the clad layer fails by spalling which is caused by intergrannular corrosion within the clad layer. The fine dendritic structure and the oxide help to retard the penetration of the sulphur ion that induces the intergrannular corrosion.

关键词： laser cladding Co based alloy wear resistance hot corrosion

Facile Synthesis of Chiral Conjugated Polymer Based on BINOL Skeleton

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Chinese Chemical Letters 2000年第1期11卷 29-30页

作者： Chun E DONG Yong Gang ZHI Zuo Long YU Liang Fu ZHANG Albert. S. C. CHAN (Chengdu institute of organic chemistry Academ Sinica Chengdu 610041 hong kong polytechnic University, hongkong) Acad Sinica Chengdu Inst Organ Chem Chengdu 610041 Peoples R China hong kong polytech Hong Kong Peoples R China

A new type of chiral conjugated polymers 6a-d has been synthesized by the reaction of (R)-2,2'-dihydroxy-1,1'-binaphthyl-6,6'-dicarbaldehyde 5 with corresponding diamine in the presence of acetic acid.

关键词： chiral conjugated polymers synthesis BINOL

Characterization of Deformations of Multiaxial Warp Knitted Fabrics during Forming Process

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Journal of China Textile University(English Edition) 2000年第3期17卷 20-26页

作者： Hu JinlianInstitute of Textiles and Clothing, The hong kong polytechnic UniversityJiang YamingComposites Research Institute, Tianjin polytechnic University, Tianjin, 300191 Inst. of Textiles and Clothing Hong Kong Polytech. Univ. Hong Kong Comp. Res. Inst. Tianjin Polytech. Univ. Tianjin 300191 China

The typical structure(with four inserting yarn systems) of multi-axial warp knitted fabrics shows unsatisfactory conformability according to hemisphere pressing *** structure containing only two bias inserting yarn systems(TBMWK fabric),however,proves to possess good *** paper characterized in detail the forming behavior of TBMWK *** was found that the two bias inserting yarn systems tend to gather always along the weft direction,and the angles between them along this direction are basically linear to the perpendicular distances from the measured points to the longitudinal axis of the ***

关键词： MWK fabric conformability forming and characteristics .

Special Issue on Resilience in Steel Structures

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Frontiers of Structural and Civil Engineering 2016年第3期10卷 237-238页

作者： Wang, Wei Chan, Tak-Ming Zhang, Yunfeng Tongji Univ Struct Engn Shanghai Peoples R China hong kong polytech Univ Struct Engn Hong Kong Hong Kong Peoples R China Univ Maryland Struct Engn College Pk MD 20742 USA

This special issue of Frontiers of Structural and Civil Engineering features nine technical papers focusing on resilience in steel structures with authors from Canada, China, Italy, Portugal, Singapore and the United States. Through their contributions, they have shared their technical expertise in innovative solution towards resilience in steel structures by conducting experimental investigation, formulating analytical modelling and developing finite-element simulation. Papers also addressed the topical issue on life-cycle costing, constructability and reparability. Current design provisions were also assessed and new design concepts and solutions were proposed. The following are the highlights of each of the technical contributions.

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Interpretable gradient boosting based ensemble learning and African vultures optimization algorithm optimization for estimating deflection induced by excavation

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FRONTIERS OF STRUCTURAL AND CIVIL ENGINEERING 2024年第11期18卷 1698-1712页

作者： Liang, Zenglong Lin, Shan Dong, Miao Cao, Xitailang Guo, hongwei Zheng, hong Beijing Univ Technol Key Lab Urban Secur & Disaster Engn Minist Educ Beijing 100124 Peoples R China hong kong polytech Univ PolyU Dept Civil & Environm Engn Hong Kong 999077 Peoples R China

Intelligent construction has become an inevitable trend in the development of the construction industry. In the excavation project, using machine learning methods for early warning can improve construction efficiency and quality and reduce the chances of damage in the excavation process. An interpretable gradient boosting based ensemble learning framework enhanced by the African Vultures Optimization Algorithm (AVOA) was proposed and evaluated in estimating the diaphragm wall deflections induced by excavation. We investigated and compared the performance of machine learning models in predicting deflections induced by excavation based on a database generated by finite element simulations. First, we exploratively analyzed these data to discover the relationship between features. We used several state-of-the-art intelligent models based on gradient boosting and several simple models for model selection. The hyperparameters for all models in evaluation are optimized using AVOA, and then the optimized models are assembled into a unified framework for fairness assessment. The comprehensive evaluation results show that the AVOA-CatBoost built in this paper performs well (RMSE = 1.84, MAE = 1.18, R2 = 0.9993) and cross-validation (RMSE = 2.65 +/- 1.54, MAE = 1.17 +/- 0.23, R2 = 0.998 +/- 0.002). In the end, in order to improve the transparency and usefulness of the model, we constructed an interpretable model from both global and local perspectives.

关键词： African vultures optimization algorithm gradient boosting ensemble learning interpretable model wall deflection prediction

THE DEFECT ITERATION OF THE FINITE ELEMENT FOR ELLIPTIC BOUNDARY VALUE PROBLEMS AND PETROV-GALERKIN APPROXIMATION

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Journal of Computational Mathematics 1998年第2期16卷 152-164页

作者： Gao, JB Yang, YD Shih, TM Huazhong Univ Sci & Technol Dept Math Wuhan 430074 Peoples R China Guizhou Normal Univ Dept Math Guiyang 550001 Peoples R China hong kong polytech Univ Dept Math Appl Hong Kong Peoples R China

In this paper we introduce a Petrov-Galerkin approximation model to the solution of linear and semi-linear elliptic boundary value problems in which piecewise quadratic polynomial space and piecewise linear polynomial space are used as the shape function space and the test function space, respectively. We prove that the approximation order of the standard quadratic finite element can be attained in this Petrov-Galerkin model. Based on the so-called 'contractivity' of the interpolation operator, we further prove that the defect iterative sequence of the linear finite element solution converge to the proposed Petrov-Galerkin approximate solution.

关键词： Petrov-Galerkin approximation defect iteration correction interpolation operator