Combined effects of Soret(thermal-diffusion) and Dufour(diffusion-thermo) in MHD stagnation point flow by a permeable stretching cylinder were studied. Analysis was examined in the presence of heat generation/absorpti...Combined effects of Soret(thermal-diffusion) and Dufour(diffusion-thermo) in MHD stagnation point flow by a permeable stretching cylinder were studied. Analysis was examined in the presence of heat generation/absorption and chemical reaction. The laws of conservation of mass, momentum, energy and concentration are found to lead to the mathematical development of the problem. Suitable transformations were used to convert the nonlinear partial differential equations into the ordinary differential equations. The series solutions of boundary layer equations through momentum, energy and concentration equations were obtained.Convergence of the developed series solutions was discussed via plots and numerical values. The behaviors of different physical parameters on the velocity components, temperature and concentration were obtained. Numerical values of Nusselt number, skin friction and Sherwood number with different parameters were computed and analyzed. It is found that Dufour and Soret numbers result in the enhancement of temperature and concentration distributions, respectively.展开更多
Finite element simulations for metal powder compaction of a clutch plate were performed to examine the stresses during compaction,unloading,and ejection.To describe the mechanical behavior of compacted green body,a mo...Finite element simulations for metal powder compaction of a clutch plate were performed to examine the stresses during compaction,unloading,and ejection.To describe the mechanical behavior of compacted green body,a modified densitydependent Drucker-Prager Cap model was utilized to predict the stress and density distribution of the compacted clutch plate during loading and ejection stages.The results indicate that maximum tensile principal stress was a main driving force for the tensile crack initiation during ejection stage,and shear stress may be another driving force in both compaction and ejection stages for shear crack initiation.There were peak value of the stresses during ejection stage,and the stresses are in compressive state only during compaction stage.Therefore,the tensile crack initiation is not possible during compaction except shear crack.Hoop stress in the clutch plate is of less contribution to the crack initiation during compaction,unloading and ejection.Study of criteria of the crack initiation and fracture is necessary in order to obtain uniform density and crackfree components in the manufacturing of metal powder compaction.展开更多
Due to native character of thermal expansion coefficient(CTE)mismatch between C_(f)/SiC and GH3536,achieving high strength joint was a huge challenge for C_(f)/SiC-GH3536 joints.Herein,a composite filler metal of Ag-C...Due to native character of thermal expansion coefficient(CTE)mismatch between C_(f)/SiC and GH3536,achieving high strength joint was a huge challenge for C_(f)/SiC-GH3536 joints.Herein,a composite filler metal of Ag-Cu-Ti+Sc_(2)(WO_(4))_(3) was developed to join C_(f)/SiC and GH3536.This work introduced Sc_(2)(WO_(4))_(3) to Ag-Cu-Ti system as a negative thermal expansion(NTE)reinforcing phase to release joint residual stress.Sc_(2)(WO_(4))_(3) was evenly distributed in the brazing seam and reacted with Ti to form Ti_(3)O_(5) reaction layer.The results of finite element analysis showed that the residual stress of the joints was effectively released by introducing Sc_(2)(WO_(4))_(3) reinforcing phase,and the mises stress was decreased from447 to 401 MPa.The maximum shear strength of the C_(f)/SiC-GH3536 joint brazed with Ag-Cu-Ti+6 vol%Sc_(2)(WO_(4))_(3) filler alloys was 64 MPa,which was about 2.6 times higher than that of Ag-Cu-Ti alloys.The results of this study provide a promising strategy for the introduction of new Sc_(2)(WO_(4))_(3) reinforcing phase in Ag-Cu-Ti system,and improve the reliability and feasibility of composite brazing alloy in brazing filed.展开更多
The establishment of a possible connection between neutrino emission and gravitational-wave(GW)bursts is important to our understanding of the physical processes that occur when black holes or neutron stars merge.In t...The establishment of a possible connection between neutrino emission and gravitational-wave(GW)bursts is important to our understanding of the physical processes that occur when black holes or neutron stars merge.In the Daya Bay experiment,using the data collected from December 2011 to August 2017,a search was per-formed for electron-antineutrino signals that coincided with detected GW events,including GW150914,GW151012,GW151226,GW170104,GW170608,GW 170814,and GW 170817.We used three time windows of±10,±500,and±1000 s relative to the occurrence of the GW events and a neutrino energy range of 1.8 to 100 MeV to search for correlated neutrino candidates.The detected electron-antineutrino candidates were consistent with the expected background rates for all the three time windows.Assuming monochromatic spectra,we found upper limits(90%confidence level)of the electron-antineutrino fluence of(1.13-2.44)×10^(11)cm^(-2)at 5 MeV to 8.0×10^(7)cm^(-2)at 100 MeV for the three time w indows.Under the assumption of a Fermi-Dirac spectrum,the upper limits were found to be(5.4-7.0)×10^(9)cm^(2)for the three time windows.展开更多
The prediction of reactor antineutrino spectra will play a crucial role as reactor experiments enter the precision era.The positron energy spectrum of 3.5 million antineutrino inverse beta decay reactions observed by ...The prediction of reactor antineutrino spectra will play a crucial role as reactor experiments enter the precision era.The positron energy spectrum of 3.5 million antineutrino inverse beta decay reactions observed by the Daya Bay experiment,in combination with the fission rates of fissile isotopes in the reactor,is used to extract the positron energy spectra resulting from the fission of specific isotopes.This information can be used to produce a precise,data-based prediction of the antineutrino energy spectrum in other reactor antineutrino experiments with different fission fractions than Daya Bay.The positron energy spectra are unfolded to obtain the antineutrino energy spectra by removing the contribution from detector response with the Wiener-SVD unfolding method.Consistent results are obtained with other unfolding methods.A technique to construct a data-based prediction of the reactor antineutrino energy spectrum is proposed and investigated.Given the reactor fission fractions,the technique can predict the energy spectrum to a 2%precision.In addition,we illustrate how to perform a rigorous comparison between the unfolded antineutrino spectrum and a theoretical model prediction that avoids the input model bias of the unfolding method.展开更多
文摘Combined effects of Soret(thermal-diffusion) and Dufour(diffusion-thermo) in MHD stagnation point flow by a permeable stretching cylinder were studied. Analysis was examined in the presence of heat generation/absorption and chemical reaction. The laws of conservation of mass, momentum, energy and concentration are found to lead to the mathematical development of the problem. Suitable transformations were used to convert the nonlinear partial differential equations into the ordinary differential equations. The series solutions of boundary layer equations through momentum, energy and concentration equations were obtained.Convergence of the developed series solutions was discussed via plots and numerical values. The behaviors of different physical parameters on the velocity components, temperature and concentration were obtained. Numerical values of Nusselt number, skin friction and Sherwood number with different parameters were computed and analyzed. It is found that Dufour and Soret numbers result in the enhancement of temperature and concentration distributions, respectively.
基金The authors gratefully acknowledge the financial supports of State Key Lab of Advanced Welding and Joining,Harbin Institute of Technology(Nos.AWJ-19Z05).
文摘Finite element simulations for metal powder compaction of a clutch plate were performed to examine the stresses during compaction,unloading,and ejection.To describe the mechanical behavior of compacted green body,a modified densitydependent Drucker-Prager Cap model was utilized to predict the stress and density distribution of the compacted clutch plate during loading and ejection stages.The results indicate that maximum tensile principal stress was a main driving force for the tensile crack initiation during ejection stage,and shear stress may be another driving force in both compaction and ejection stages for shear crack initiation.There were peak value of the stresses during ejection stage,and the stresses are in compressive state only during compaction stage.Therefore,the tensile crack initiation is not possible during compaction except shear crack.Hoop stress in the clutch plate is of less contribution to the crack initiation during compaction,unloading and ejection.Study of criteria of the crack initiation and fracture is necessary in order to obtain uniform density and crackfree components in the manufacturing of metal powder compaction.
基金the National Natural Science Foundation of China(Grant Nos.51575135 and 51622503)Natural Science Foundation of Heilongjiang Province of China(YQ2019E023)。
文摘Due to native character of thermal expansion coefficient(CTE)mismatch between C_(f)/SiC and GH3536,achieving high strength joint was a huge challenge for C_(f)/SiC-GH3536 joints.Herein,a composite filler metal of Ag-Cu-Ti+Sc_(2)(WO_(4))_(3) was developed to join C_(f)/SiC and GH3536.This work introduced Sc_(2)(WO_(4))_(3) to Ag-Cu-Ti system as a negative thermal expansion(NTE)reinforcing phase to release joint residual stress.Sc_(2)(WO_(4))_(3) was evenly distributed in the brazing seam and reacted with Ti to form Ti_(3)O_(5) reaction layer.The results of finite element analysis showed that the residual stress of the joints was effectively released by introducing Sc_(2)(WO_(4))_(3) reinforcing phase,and the mises stress was decreased from447 to 401 MPa.The maximum shear strength of the C_(f)/SiC-GH3536 joint brazed with Ag-Cu-Ti+6 vol%Sc_(2)(WO_(4))_(3) filler alloys was 64 MPa,which was about 2.6 times higher than that of Ag-Cu-Ti alloys.The results of this study provide a promising strategy for the introduction of new Sc_(2)(WO_(4))_(3) reinforcing phase in Ag-Cu-Ti system,and improve the reliability and feasibility of composite brazing alloy in brazing filed.
基金Daya Bay is supported in part by the Ministry of Science and Technology o f China, the U.S. Department o f Energy, the Chinese Academy of Sciences, the CASCenter for Excellence in Particle Physics, the National Natural Science Foundation of China, the Guangdong provincial government, the Shenzhen municipal government,the China General Nuclear Power Group, Key Laboratory of Particle and Radiation Imaging (Tsinghua University), the Ministry of Education, Key Laboratory ofParticle Physics and Particle Irradiation (Shandong University), the Ministry o f Education, Shanghai Laboratory for Particle Physics and Cosmology, the ResearchGrants Council o f the Hong Kong Special Administrative Region of China, the University Development Fund of the University of Hong Kong, the MOE program forResearch of Excellence at National Taiwan University, National Chiao-Tung University, NSC fund support from Taiwan, the U.S. National Science Foundation, the AlfredP. Sloan Foundation, the Ministry o f Education, Youth, and Sports of the Czech Republic, the Charles University GAUK (284317), the Joint Institute o f NuclearResearch in Dubna, Russia, the National Commission of Scientific and Technological Research of Chile, and the Tsinghua University Initiative Scientific Research Program.
文摘The establishment of a possible connection between neutrino emission and gravitational-wave(GW)bursts is important to our understanding of the physical processes that occur when black holes or neutron stars merge.In the Daya Bay experiment,using the data collected from December 2011 to August 2017,a search was per-formed for electron-antineutrino signals that coincided with detected GW events,including GW150914,GW151012,GW151226,GW170104,GW170608,GW 170814,and GW 170817.We used three time windows of±10,±500,and±1000 s relative to the occurrence of the GW events and a neutrino energy range of 1.8 to 100 MeV to search for correlated neutrino candidates.The detected electron-antineutrino candidates were consistent with the expected background rates for all the three time windows.Assuming monochromatic spectra,we found upper limits(90%confidence level)of the electron-antineutrino fluence of(1.13-2.44)×10^(11)cm^(-2)at 5 MeV to 8.0×10^(7)cm^(-2)at 100 MeV for the three time w indows.Under the assumption of a Fermi-Dirac spectrum,the upper limits were found to be(5.4-7.0)×10^(9)cm^(2)for the three time windows.
基金Supported in part by the Ministry of Science and Technology of Chinathe U.S.Department of Energy,the Chinese Academy of Sciences,the CAS Center for Excellence in Particle Physics,the National Natural Science Foundation of China+3 种基金the Guangdong provincial governmentthe Shenzhen municipal government,the China General Nuclear Power Group,the Research Grants Council of the Hong Kong Special Administrative Region of China,the Ministry of Education in TWthe U.S.National Science Foundation,the Ministry of Education,Youth,and Sports of the Czech Republic,the Charles University Research Centre UNCE,the Joint Institute of Nuclear Research in Dubna,Russiathe National Commission of Scientific and Technological Research of Chile。
文摘The prediction of reactor antineutrino spectra will play a crucial role as reactor experiments enter the precision era.The positron energy spectrum of 3.5 million antineutrino inverse beta decay reactions observed by the Daya Bay experiment,in combination with the fission rates of fissile isotopes in the reactor,is used to extract the positron energy spectra resulting from the fission of specific isotopes.This information can be used to produce a precise,data-based prediction of the antineutrino energy spectrum in other reactor antineutrino experiments with different fission fractions than Daya Bay.The positron energy spectra are unfolded to obtain the antineutrino energy spectra by removing the contribution from detector response with the Wiener-SVD unfolding method.Consistent results are obtained with other unfolding methods.A technique to construct a data-based prediction of the reactor antineutrino energy spectrum is proposed and investigated.Given the reactor fission fractions,the technique can predict the energy spectrum to a 2%precision.In addition,we illustrate how to perform a rigorous comparison between the unfolded antineutrino spectrum and a theoretical model prediction that avoids the input model bias of the unfolding method.
