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Experimental methods for determination of mechanical behaviors of materials at high temperatures via the split Hopkinson bars

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Acta Mechanica Sinica 2020年第6期36卷 1275-1293,I0003页

作者： Q.B.Dou K.R.wu T.Suo C.zhang X.Guo Y.z.Guo w.G.Guo Y.L.Li School of Aeronautics Northwestern Polytechnical UniversityXi’an710072China Joint International Research Laboratory of Impact Dynamics and its Engineering Application Xi’an710072China Shaanxi Key Laboratory of Impact Dynamics and its Engineering Application Xi’an710072China State Key Laboratory for Strength and Vibration of Mechanical Structures School of AerospaceXi’an Jiaotong UniversityXi’an710049China

Full understanding of the thermomechanical behaviors of materials at high strain rates and high temperatures are of great importance from not only scientific meaning but also practical value in engineering structure design and safety *** efforts have been made for abilities of operation the split Hopkinson bars,the most popular technique for experimental determination of mechanical behaviors of materials over the strain rates from 10^2 to 10^4 s^−1 over the past 70 years,at high temperatures since 1960s.A review of experiment work is presented in this paper to give an overview of the development of experimental techniques at high temperatures based on Hopkinson bar *** principles of the split Hopkinson bar requires the loading bars avoiding temperature gradient or keeping relatively low temperature when performing high temperature *** such as performing temperature gradient corrections,rapid heating or using special designed automatically assembled systems were proposed by researchers to enable the operation of the split Hopkinson bars at temperature as high as ***,to the application of high speed photographic technique for capturing the dynamic deformation process of the specimen in high temperature Hopkinson bar testing,some key issues of eliminating the strong thermal radiation induced lights oversaturation and de-blurring of images due to insufficient exposure at high temperature and high strain rate condition,as well as fabrication of high contrast speckle pattern for high temperature digital image correlation measurement were also *** technique can now enable the split Hopkinson bar testing to be performed at high temperature up to 1873 K under the loading conditions of compression or tension with the in situ observation and full field measurement of deformation as *** paper concludes with summaries of the most important achievements and highlighting of the prospects,trends and remaining challenge

关键词： Mechanical behaviors Split Hopkinson bar High strain rate High temperature

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Influence of Rotor Iron Bridge Position on DC-winding-induced Voltage in wound Field Switched Flux Machine Having Partitioned Stators

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Chinese Journal of Electrical Engineering 2021年第3期7卷 20-28页

作者： zhongze wu z.Q.zhu Chao wang wei Hua Kai wang wentao zhang School of Electrical Engineering Southeast UniversityNanjing 210096China Department of Electronic and Electrical Engineering University of SheffieldSheffield S102TNUK College of Automation Nanjing University of Aeronautics and AstronauticsNanjing 211106China

In this study,the influence of the position of the rotor iron bridge on the DC-winding-induced voltage pulsation in a partitioned stator wound field switched flux machine is *** and finite element(FE)analyses show that both the open-circuit and on-load DC-winding-induced voltages can be minimized by positioning the rotor iron bridge adjacent to the inner air gap closer to the DC *** is due to a smoother inner air-gap magnetic reluctance while maintaining the average electromagnetic torque at 92.59%of the maximum *** analyzed machine with the rotor iron bridge adjacent to the inner air gap is prototyped,and the experimental results validate the analytical and FE results.

关键词： DC winding induced voltage flux switching iron bridge partitioned stator switched flux wound field

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Exact Penalty Function and Asymptotic Strong Nonlinear Duality in Integer Programming

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Acta Mathematicae Applicatae Sinica 2004年第1期20卷 45-52页

作者： Fu-shengBai z.Y.wu L.S.zhang DepartmentofMathematics ShanghaiUniversityShanghai200436China DepartmentofMathematicsandComputerScience ChongqingNormalUniversityChongqing400047China

In this paper, a logarithmic-exponential penalty function with two parameters for integer programming is discussed. we obtain the exact penalty properties and then establish the asymptotic strong nonlinear duality in the corresponding logarithmic-exponential dual formulation by using the obtained exact penalty properties. The discussion is based on the logarithmic-exponential nonlinear dual formulation proposed in [6].

关键词： Integer programming exact penalty function asymptotic strong duality

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Experimental Study of the Temperature Distribution of Solar Collector Pavement

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武汉理工大学学报 2010年第17期32卷 227-230页

作者： zHANG J z wu S P CHEN M Y Key Laboratory of Silicate Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China

Black asphalt road have excellent properties to collect the solar radiation and good use of asphalt absorb solar energy is a new energy technology. Asphalt is a sticky plastic material,its modulus and strength will change with temperature and the actual bearing capacity of pavement structure will change as well. A new method was used to evaluate the temperature change of asphalt pavement. By simulate solar radiation on asphalt sample to study the change of the temperature field. The temperature distribution of the asphalt concrete under the same light radiation and circulating water was also studied. The results indicate that this method can be a good simulation of solar collectors on the surface temperature field.

关键词： temperature field asphalt sample solar collector fluorescent lamp analog

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Effect of forced-air cooling on the microstructure and age-hardening response of extruded Mg-Gd-Y-zn-zr alloy full with LPSO lamella

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Journal of Materials Science & Technology 2021年第14期73卷 66-75页

作者： S.z.wu T.Nakata G.z.Tang C.Xu X.J.wang X.w.Li X.G.Qiao M.Y.zheng L.Geng S.Kamado G.H.Fan School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China Research Center for Advanced Magnesium Technology Nagaoka University of TechnologyNagaoka 940-2188Japan School of Material Science and Engineering Harbin University of Science and TechnologyHarbin 150040China Key Laboratory for Light-weight Materials Nanjing Tech UniversityNanjing 211816China

The homogenized Mg-8.2 Gd-3.8 Y-1.0 zn-0.4 zr(wt.%)alloy full of plate-shaped long period stacking ordered(LPSO)phases was hot extruded in the atmosphere and cooled by the forced-air,then the effect of forced-air cooling on the microstructure and age-hardening response of the alloy was investigated in this *** results show that in comparison with the extruded sample cooling in the atmosphere,the forced-air cooling restricts dynamic recrystallization(DRX)and brings about finer dynamic recrystallized(DRXed)grain size,stronger basal texture and higher dislocation ***,the forced-air cooling promotes the dynamic precipitation in the DRXed regions and facilitates formation of plate-shaped LPSO phases andγ’phases with smaller interspacing in the unrecrystallized(un DRXed)regions,then slightly restricts the precipitation ofβphases during *** peak-ageing treatment,the extruded sample with forced-air cooling shows superior tensile properties with a tensile yield strength of 439 MPa,an ultimate tensile strength of 493 MPa,and elongation to failure of 18.6%.

关键词： Mg-RE alloy LPSO phase Dynamic recrystallization Precipitation Mechanical properties

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ATOMIC　FORCE　MICROSCOPY　OBSERVATION　OF　MAGNETRON　SPUTTERED　ALUMINUM－SILICON　ALLOY　FILMS

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Acta Metallurgica Sinica(English Letters) 1996年第4期9卷 263-266页

作者： J.w.wu,J.H. Fang and z.H.Lu (National Laboratory of Molecule and Biomolecule Electronics,Southeast University,Nanjing 210096, China

wo different surface morphology characteristics of magnetron sputtered aluminumsilicon(Al-Si)alloy films deposited at 0 and 200℃ were observed by atomic force microscopy(AFM).One is irregularly shaped grains put togther on a *** other is irregularly shaped grains Piled up in space. Nanometer-sized particles with heights from 1.6 to 2.9 nm were first observed. On the basis of these observations the growth mechanism of magnetron sputtered films is discussed.

关键词： magnetron sputtering Al-Si alloy surface morphology,atomic force microscopy,film growth mechanism

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LOw CYCLE FATIGUE AND DEFORMATION BEHAVIOR IN AN 8090 Al-Li ALLOY

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Acta Metallurgica Sinica(English Letters) 1998年第1期11卷 1-11页

作者： S.H.Ai Y.Q.wu z.G.wang Y.zhang Chinese Acad of Sciences Shenyang China

Low cycle fatigue (LCF)tests under different total strain amplitudes have been conducted in order to ascertain the effect of precipitate sizes on LCF behavior of 8090 Al-Li alloy. A constant strain rate of 3×10-3s-1 and symmetrical triangular waveform were employed for all tests. It is found that the cyclic stress response of the alloy varied with the precipitate sizes and strain amplitudes. The materials in all conditions cyclically handen at first and the higher the strain amplitude, the greater the amount of hardening. The low cyclic flow stress is the highest in the peakaged condition. TEM and SEM observations demonstrated that cyclic stress-strain behavior and fracture mode of Al-Li alloy are closely related to an increase in the dislocation density and interaction between the precipitates and dislocations, sizes of δ particles and pricipitate free zone (PFz) at grain boundaries.

关键词： Al-Li alloy low cycle fatigue aged condition

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A DCPD TECHNIQUE FOR LOCALIzED CREEP DAMAGE IN NOTCHED BARS

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Acta Metallurgica Sinica(English Letters) 1998年第6期11卷 456-462页

作者： z.D.wang Y.Qiao B.S.zhou D.O.wu East China Univ of Science and Technology Shanghai China

Localized creep damage in a notched round specimen has been investigated in this paper based on the creep damage mechanics and the DCPD technique. Expressions of creep damage equivalent stress under multi-axial state are given to describe the validity for localized damage in ductile materials. A DCPD method is introduced into the measurement of local creep damage near the tip of V-type notch of round bar. The technique with instrument configuration, selection of probe position and measuring calibration is also presented in the paper. Some results of creep damage estimation are shown on 2.25Cr-1Mo at 550℃.

关键词： creep damage mechanics notched round bar creep damage measurement

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EFFECT OF THE DEFECT STATES DENSITY ON OPTICAL BAND GAP OF CdIn_(2)O_(4)THIN FILM

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Acta Metallurgica Sinica(English Letters) 2005年第3期18卷 403-410页

作者： H.S.San z.G.wu B.Li B.X.Feng KeyLaboratoryforMagnetismandMagneticMaterialofMinistryofEducation LanzhouUniversityLanzhou730000China ShanghaiInstituteofTechnicalPhysics TheChineseAcademyofSciencesShanghai200083China

Transparent conducting oxides CdIn2O4 thin films were prepared by radio-frequenc y reactive sputtering from a Cd-In alloy target in Ar+O2 atmosphere. By transmis sion spectrum and Hall measurement for different samples prepared at different s ubstrate temperatures, it could be found that the carrier concentration would in crease with the decrease of substrate temperature, but absorption edge showed an abrupt variation from a blue shift to a red shift. Theoretically, the paper for mulated the effect of high-density point defects on band structures; it embodied the formation of band tailing, Burstein-Moss shift and band-gap narrowing. The density of holes will influence the magnitude of optical band gap and transmitta nce of light. Since extrapolation method does not fit degenerate semiconductor m aterials, a more accurate method of obtaining optical band gap is curve fitting. In addition, ionized impurities scattering is the main damping mechanism of the free electrons in CdIn2O4 films, the density of ionized impurities induced by a ltering substrate temperature will affect the carriers mobility.

关键词： sputtering CdIn2O4 thin film electrical property optical property

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Study of the mechanisms of acupuncture and moxibustion treatmentfor ulcerative colitis ratsinview of the gene expression of cytokines

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world Journal of Gastroenterology 1999年第6期5卷 515-517页

作者： wu HG zhou LB Pan YY Huang C Chen HP Shi z Hua XG Shanghai Inst Acupuncture Moxibust & Meridians Shanghai 200030 Peoples R China

AIM:To observe the effect of acupuncture and moxibustion on the expression of IL-1beta and IL-6 mRNA in ulcerative colitis ***:The SD rat ulcerative colitis model was created by immunological method associated with local stimulation. Colonic mucosa was prepared from human fresh surgical colonic specimens, homogenized by adding appropriate amount of normal saline and centrifuged at 3000r/min. The supernatant was collected for measurement of protein conentration and then mixed with Freund adjuvant. This antigen fluid was first injected into the plantae of the model group rats, and then into their plantae, dorsa, inguina and abdominal cavities (noFreund adjuvant for the last injection) again on the 10th, 17th, 24th and 31st day. when a certain titer of serum anti colonic antibody was reached, 2% formalin and antigen fluid (no Freund adjuvant) were administered separately by enema. The ulcerative colitis rat model was thus set up. The animals were randomly divided into four groups: model control group (MC, n = 8), electro acupuncture group (EA, n = 8), herbs partition moxibustion group (HPM 8), normal control group (NC,n = 8). HPM: Moxa cones made of refined mugwort floss were placed on the medicinal pad (medicinal pad dispensing: Radix Aconiti praeparata, cortex Cinnamomi, etc) for Qihai (RN 6) and Tianshu (ST 25, bilateral) and ignited. Two moxa cones were used for each acupoint once a day and 14 times in all. EA: Tianshu (bilateral) and Qihai were stimulated by the intermittent pulse with 2Hz frequency, 4mA intensity for 20 minutes once a day and 14 times in all. After treatment, rats of all four groups were killed simultaneously. The spleen was separated and the distal colon was dissected. Total tissue RNA was isolated by the guanidinium thiocyanate phenol chloroform extraction method. RT-PCR technique was used to study the expression of IL-1 beta and IL-6 ***:IL-1 beta and IL-6 mRNAs were not detected in the spleen and colonic mucosa of the NC rat

关键词： colitis, ulcerative/therapy acupuncture and moxibustion therapy gene expression cytokines interleukin-1 beta interleukin-6

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