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Optimizing Concurrent Product Development Process Using Genetic Algorithm

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Systems Science and Systems Engineering 2000年第4期10卷 503-510页

作者： YAN Ji\|hong,\ wu Cheng CIMS Center, Department of Automation, tsinghua university, {2., {2.

Scheduling concurrent activities is of great significance to shorten development lead time and minimize the cost, a heuristic optimization scheduling approach therefore is proposed for concurrent product development process, in which some uncertain crucial parameters are determined by genetic algorithm (GA). To ensure the optimal concurrent scheduling and the effective utilization of resources along with the fluent delivery of information, some key factors such as time order, information, resources, lead time and overlapping time of activities are taken into account adequately, and the weights of these factors are fixed by GA. In addition, role allocation and feedback revision process are realized in optimization module. The simulation example is a part of a certain product development process, and the results show the feasibility of the algorithm.

关键词： concurrent engineering product development process optimization scheduling

DEVELOPMENT AND APPLICATION OF ADAPTIVE MESH TECHNIQUE IN THREE DIMENSIONAL NUMERICAL SIMULATION OF WELDING PROCESS

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Acta Metallurgica Sinica(English Letters) 2000年第1期13卷 33-39页

作者： Q. Y.Shi A. L. Lu H. Y.Zhao A.P. wu (Department of Mechanical Engineering, tsinghua university, {2., {2.)

The adaptive mesh mesh technique is developed and applied in three dimensional numerical simulation of welding process on the base of the commercial software. Special user subroutine is worked out to accom- plish this *** technique can make the dense mesh moving simultaneously with the heat source while the other area of the structure with much coarser mesh, greatly reducing the number of nodes and elements in the *** field,displacement and stress distributions during welding pro- cess me analyzed by FEM method with adaptive mesh and the analysis is also conducted with normal FEM method. The temperature field,displacement and stress distributions obtained with both methods are shown in contrast. The results show that the temperature fields and the displacement distributions of simulation on adaptive mesh correspond wery well with that of without adaptive mesh. Though the stress distributions have some difference,but the trends of the stress distribution are *** com- parison of the computing time of the two meshes indicates that the adaptive that the adaptive mesh can greatly reduce the calculation time when used for welding process.

关键词： adaptive mesh numerical simulation,temperature distribution,welding stress,welding displacement

Microstructure evolution and phase transformation of the mushy zone in a quenchedβ-solidifying TiAl alloy

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Journal of Materials Science & Technology 2024年第2期169卷 28-41页

作者： Fuqiang Zhang Xianfei Ding Leming Xu Xin Feng Hai Nan jianping He Yongfeng Liang Junpin Lin State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China Cast Titanium Alloy R&D Center Beijing Institute of Aeronautical MaterialsBeijing 100095China

This study investigates the phase constitutions and transformations that occur in the mushy zone and in the adjacent phase fields of a directionally solidified Ti-44Al-8Nb-1Cr alloy via quenching *** results indicate that the mushy zone consists of unmeltedβdendrites and interdendritic liquid,whose formation can be attributed to the difference in melting point aroused by local heterogeneity in ***βdendrite is composed of numerous subgrains with various *** quenching,theβdendrite transforms into Widmanstättenαvia a precipitation reaction,owing to the decreasing cooling rate caused by heat transfer from the surrounding ***,after quenching,the interdendritic liquid is transformed intoγ*** the singleβphase field and the lower part of the mushy zone,a massive transformation ofβtoγ***,in theβ+αphase field,bothβandαphases are retained to ambient *** the heating process,the transformation ofα→βgives rise to the formation ofβvariants,which affects the orientation ofβdendrites in the mushy *** growth kinematics of theα→βtransformation was elucidated,revealing the preferential growth directions of111and112.forβ***,this study presents an illustration of the formation process of the mushy zone and the microstructural evolution during the heating and quenching process.

关键词： Titanium aluminides Mushy zone Quenching Electron backscattering diffraction Phase transformation

NUMERICAL INVESTIGATION OF THE VENTILATED CAVITATING FLOW AROUND AN UNDER-WATER VEHICLE BASED ON A THREE-COMPONENT CAVITATION MODEL

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Journal of Hydrodynamics 2010年第6期22卷 753-759页

作者： JI Bin LUO Xian-wu PENG Xiao-xing ZHANG Yao wu Yu-lin XU Hong-yuan State Key Laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 China china Ship Scientific Research Center Wuxi 214082 China State Key Laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 China

Based on the Reynolds-Averaged Navier-Stokes equations and mass transfer model, an approach, where a three-component cavitation model is proposed, is presented to simulate ventilated cavitating flow as well as natural cavitation. In the proposed cavitation model, the initial content of nucleus in the local flow field is updated instantaneously, and is coupled with the Rayleigh-Plesset equation to capture the cavity development. The proposed model is applied to simulate the cavitating flow around an under-water vehicle in different cavitation conditions. The results indicate that for the natural and ventilated cavitation simulation, the predicted cavitation characteristics including the cavity length, cavity diameter and cavity shape agree satisfactorily with the analytic and experimental results, for the ventilated cavitation, the proposed methods reproduce the special behavior that the axial line of the cavity bends and rises at the tail part. The study concludes that the ventilated flow rate of the non-condensate gas influences the development of natural cavitation as well as ventilated cavitation, and the vapor cavity is suppressed remarkably by the gas cavity with the increase of the gas ventilation.

关键词： under-water vehicle natural cavitation ventilated cavitation three-component model

FORMATION OF HEXAGONAL Co_(2.3)C IN Co BY CARBON ION IMPLANTATION

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Acta Metallurgica Sinica(English Letters) 1992年第2期5卷 137-140页

作者： WANG Jian wu Xingfang CHEN Xunping CAI Jun university of Science and Technology {2.,{2.,china LIU Baixin tsinghua university,{2.,china FANG Zhengzhi {2. Institute of Space Physics,Academia Sinica,{2.,china Univ of Science and Technology Beijing Beijing China

Co thin films were subjected to 50 keV carbon ion *** the dose of 2.5× 10^(17)/cm^2.a hexagonal Co-carbide phase was observed for the first *** lattice con- stants from electron diffraction are a=0.2.85 nm and c=0.4335 *** phase does not dis- appear until the dose of 9×10^(17)/cm^*** spectra showed that the stoichiometry was Co_(2.3)*** behavior of the ferromagnetic carbides along the descending sequence of Ni-Fe-Co by Fermi energy of solids was ***,based on the kinetic con- dition of phase transformation and the band theory of solids,a possible explanation about the difference of the results of ion-metallurgy and thermal metallurgy was proposed.

关键词： ion implantation phase Fermi energy Co Co_(2.3)C

Peripheral carbazole units-decorated MR emitter containing B−N covalent bond for highly efficient green OLEDs with low roll-off

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Journal of Semiconductors 2024年第8期45卷 59-66页

作者： Danrui Wan jianping Zhou Guoyun Meng Ning Su Dongdong Zhang Lian Duan Junqiao Ding School of Chemical Science and Technology Yunnan UniversityKunming 650091China Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education Department of ChemistryTsinghua UniversityBeijing 100084China Southwest United Graduate School Kunming 650092China

Boron−nitrogen doped multiple resonance(BN-MR)emitters,characterized by B−N covalent bonds,offer distinctive advantages as pivotal building blocks for facile access to novel MR emitters featuring narrowband spectra and high ***,there remains a scarcity of exploration concerning synthetic methods and structural derivations to expand the library of novel BN-MR ***,we present the synthesis of a BN-MR emitter,tCz[B−N]N,through a one-pot borylation reaction directed by the amine group,achieving an impressive yield of 94%.The emitter is decorated by incorporating two 3,6-di-tbutylcarbazole(tCz)units into a B−N covalent bond doped BN-MR parent molecule via para-C−π−D and para-N−π−D *** peripheral decoration strategy enhances the reverse intersystem crossing process and shifts the emission band towards the pure green region,peaking at 52. nm with a narrowband full-width at half maximum(FWHM)of 41 ***,organic light emitting diodes(OLEDs)employing this emitter achieved a maximum external quantum efficiency(EQEmax)value of 2..7%,with minimal efficiency *** at a practical luminance of 1000 cd·m^(−2.,the device maintains a high EQE value of 2..6%.

关键词： multi-resonance narrowband emission B−N covalent bond organic light emitting diodes

The effects of shock wave and quasi-traveling wave in the mechanical impact test

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Science china(Technological Sciences) 2010年第9期53卷 2535-2541页

作者： wu Mei1,5,SUN ZhongFeng2.ZHANG LuMei3,CHEN Yong1 & JI LinHong4 1 Institute of High Energy Physics,Chinese Academy of Sciences,beijing 100049,{2. 2.School of Mathematical Sciences,Peking {2.,beijing 100871,{2. 3 High School of Central {2. for Nationalities,beijing 100081,{2. 4 Institute of Mechanical Design,Department of Precision Instruments and Mechanology,tsinghua university,beijing 100084,{2. 5 Academy of Opto-electronics,Chinese Academy of Sciences,beijing 100190,{2. 1. Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China5. Academy of Opto-electronics Chinese Academy of Sciences Beijing 100190 China2. School of Mathematical Sciences Peking University Beijing 100871 China3. High School of Central University for Nationalities Beijing 100081 China4. Institute of Mechanical Design Department of Precision Instruments and Mechanology Tsinghua University Beijing 100084 China

It is well-known that the numerical value is always larger than the measured value,amounting to many times,if we calculate the stress of the specimen in the impulse test using the NASTRAN and ANSYS (N-A) *** believe that the impact induces shock wave or quasi-traveling wave in the specimen,which can qualitatively explain the discrepancy of the two *** order to verify it,the Lax-Friedrichs (L-F) scheme is taken to simulate the transmission of shock wave and quasi-traveling wave in *** results show that the action area of the stress wave is small and the action time is very short,so the resulting stress and actual work are not *** addition,the distribution of the impact values obtained by the numerical simulation is in accordance with the trend of the measured impact values.

关键词： aerospace environment test shock wave quasi-traveling wave

^(2.4)Th/^(2.8)U disequilibrium and particulate organic carbon export in the northwestern South china Sea

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Acta Oceanologica Sinica 2011年第3期30卷 55-62页

作者： MA Hao ZENG Zhi YU Wen HE Jianhua CHEN Liqi CHENG jianping YIN Mingduan ZENG Shi Department of Engineering Physics Tsinghua University Beijing 100084 China Key Laboratory of Global Change and Marine-Atmospheric Chemistry State Oceanic Administration Xiamen 361005 China Key Laboratory of Particle ＆ Radiation Imaging （tsinghua university） Ministry of Education Beijing 100084 China Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense Beijing 100084 China

2.4Th was utilized as a tracer of particulate organic carbon （POC） export in the northwestern South china Sea （SCS） on the basis of the data collected at four stations during a spring cruise. Depth profiles of dissolved and particulate 2.4Th activities were measured in the upper 60m, showing a significant deficit relative to 2.Su over the investigated stations. A stratified structure of 2.4Th-2.su disequilibrium was in general observed in the upper 60 m water column, indicating that the euphotic zone of the northwestern SCS in this reason can be divided into two layers, an upper and lower layer, with different export rates. POC export fluxes were estimated from a one-dimensional steady state model of 2.4Th fluxes in combination with the measurement of POC/2.4Th ratios on suspended particles. The POC export in this region ranged from 8.2.to 2..0 mmol/（m2.d）, with an average of 16.0 mmol/（m2.d）, and was slightly higher than those previously reported in the southern SCS.

关键词： 2.4Th 2.su disequilibrium POC export South china Sea

Invariant Joint Transform CorrelatorⅠ: Mapping Filter

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Chinese Journal of Lasers 1997年第1期B6卷 64-70页

作者： FENG Jihong wu Minxian JIN Guofan YAN Shuhua(Tainghua university, Precision Department,{2. {2., china) tsinghua Univ Beijing China

A joint transform correlator incorporating coordinate transformation technique is propescd to perform invariant pattern recognition. Instead of an input image or its Fourier transform intensity, the Fourier transform of the input image is directly transformed from rectangular into logarithmic-polar coordinate. All of information is saved, and as a result, multiple objects can be proceased simulataneously. A binary optical component is designed and fabricated to perform coordinate transformation in high efficiency.

关键词： invariant optical pattern recognition cyclic shift joint transform correlator binary optical component