The vortex-induced nonlinear vibration of casing pipes in the deep water was studied considering the loads of current and combined wave-current. The vortex-induced vibration equation of a casing pipe was set up consid...The vortex-induced nonlinear vibration of casing pipes in the deep water was studied considering the loads of current and combined wave-current. The vortex-induced vibration equation of a casing pipe was set up considering the beam mode and Morison’s nonlinear fluid loads as well as the vortex-excited loads. The approach of calculating vortex-excited nonlinear vibration by Galerkin’s method was proposed. The natural vibration frequencies and modes were obtained, and the response including primary resonance induced by current and the composite resonance under combined wave-current for the 170 m long casing pipe in the 160m depth of water were investigated. The results show that the dynamics response of casing pipe obviously increases, and the complicated response behaviors of casing pipe are described under combined wave-current.展开更多
Au/Co3O4/CeO2 materials are prepared using conventional deposition-precipitation method. The effects of calcination temperatures and pretreatment conditions on the catalytic performance of Au/Co3O4/CeO2 for CO low-tem...Au/Co3O4/CeO2 materials are prepared using conventional deposition-precipitation method. The effects of calcination temperatures and pretreatment conditions on the catalytic performance of Au/Co3O4/CeO2 for CO low-temperature oxidation in humid circumstance are investigated. The sample calcines at 443 K in flowing air exhibited good activity and stability for CO oxidation. 80% CO conversion rate can be achieved after 3 000 min with a feed gas contained 3.1%(φw) of water vapor. The physical and chemical properties of the Au/Co3O4/CeO2 samples are characterized by X-ray diffraction (XRD),temperature-programmed reduction (H2-TPR),and transmission electron microscopy (TEM) techniques. The characterized results show that the prepared material calcined at 443 K has a weak diffraction peak of gold species observed by XRD,the grain diameter of 3 nm by TEM and best redox property and the highest activity for CO oxidation by H2-TPR at prope calcined temperature.展开更多
Effective thermal performance of oscillating heat pipe(OHP)is driven by inside pressure distribution.Heat transfer phenomena were reported in terms of pressure and frequency of pressure fluctuation in multi loop OHP c...Effective thermal performance of oscillating heat pipe(OHP)is driven by inside pressure distribution.Heat transfer phenomena were reported in terms of pressure and frequency of pressure fluctuation in multi loop OHP charged with aqueous Al2O3 and MWCNTs/Al2O3 nanoparticles.The influences on thermal resistance of aqueous Al2O3,MWCNTs as well as the hybrid of them in OHP having 3 mm in inner diameter were investigated at 60% filling ratio.Experimental results show that thermal characteristics are significantly inter-related with pressure distribution and strongly depend upon the number of pressure fluctuations with time.Frequency of pressure depends upon the power input in evaporative section.A little inclusion of MWCNTs into aqueous Al2O3 at 60% filling ratio achieves the highest fluctuation frequency and the lowest thermal resistance at any evaporator power input though different nanofluids cause different thermal performances of OHPs.展开更多
Since the amplitude and frequency of irregular waves change with time,great difficulties are brought for solving ship load responses in random waves.To take the effect of various frequencies of irregular waves into co...Since the amplitude and frequency of irregular waves change with time,great difficulties are brought for solving ship load responses in random waves.To take the effect of various frequencies of irregular waves into consideration in load responses of hull,the wave memory effect is necessary.A semi-analytical method is introduced for the time-domain retardation functions,and then a nonlinear hydroelastic method considering memory effect for ships in irregular waves is proposed.Segmented self-propelling model experiments of a container ship were carried out in a towing tank,a ship motion measuring device for self-propelling model test was designed.Whipping responses of the ship in regular and irregular waves are analyzed.Finally,the calculation results are compared with those measured by segmented model experiments,and the result indicates that the memory effect has little effect on load responses of ship in regular waves,but pronounced effect on results in irregular waves.Moreover,the presented method is reasonable for the prediction of ship load responses in irregular waves.展开更多
This paper presents an approach to the challenging is- sue of passive source localization in shallow water using a mobile short horizontal linear array with length less than ten meters. The short array can be convenie...This paper presents an approach to the challenging is- sue of passive source localization in shallow water using a mobile short horizontal linear array with length less than ten meters. The short array can be conveniently placed on autonomous underwa- ter vehicles and deployed for adaptive spatial sampling. However, the use of such small aperture passive sonar systems makes it difficult to acquire sufficient spatial gain for localizing long-range sources. To meet the requirement, a localization approach that employs matched-field based techniques that enable the short ho- rizontal linear array is used to passively localize acoustic sources in shallow water. Furthermore, the broadband processing and inter-position processing provide robustness against ocean en- vironmental mismatch and enhance the stability of the estimation process. The proposed approach＇s ability to localize acoustic sources in shallow water at different signal-to-noise ratios is examined through the synthetic test cases where the sources are located at the endfire and some other bearing of the mobile short horizontal linear array. The presented results demonstrate that the positional parameters of the estimated source build up over time as the array moves at a low speed along a straight line at a constant depth.展开更多
基金Project supported by the National Natural Science Foundation of China (No.50279026) andthe National985Engineering Project in China
文摘The vortex-induced nonlinear vibration of casing pipes in the deep water was studied considering the loads of current and combined wave-current. The vortex-induced vibration equation of a casing pipe was set up considering the beam mode and Morison’s nonlinear fluid loads as well as the vortex-excited loads. The approach of calculating vortex-excited nonlinear vibration by Galerkin’s method was proposed. The natural vibration frequencies and modes were obtained, and the response including primary resonance induced by current and the composite resonance under combined wave-current for the 170 m long casing pipe in the 160m depth of water were investigated. The results show that the dynamics response of casing pipe obviously increases, and the complicated response behaviors of casing pipe are described under combined wave-current.
文摘Au/Co3O4/CeO2 materials are prepared using conventional deposition-precipitation method. The effects of calcination temperatures and pretreatment conditions on the catalytic performance of Au/Co3O4/CeO2 for CO low-temperature oxidation in humid circumstance are investigated. The sample calcines at 443 K in flowing air exhibited good activity and stability for CO oxidation. 80% CO conversion rate can be achieved after 3 000 min with a feed gas contained 3.1%(φw) of water vapor. The physical and chemical properties of the Au/Co3O4/CeO2 samples are characterized by X-ray diffraction (XRD),temperature-programmed reduction (H2-TPR),and transmission electron microscopy (TEM) techniques. The characterized results show that the prepared material calcined at 443 K has a weak diffraction peak of gold species observed by XRD,the grain diameter of 3 nm by TEM and best redox property and the highest activity for CO oxidation by H2-TPR at prope calcined temperature.
基金Project(NRF-2012R1A1A4A01002052)supported by Basic Science Research Program through the National Research Foundation(NRF)funded by the Ministry of Education,Science and Technology of Korea
文摘Effective thermal performance of oscillating heat pipe(OHP)is driven by inside pressure distribution.Heat transfer phenomena were reported in terms of pressure and frequency of pressure fluctuation in multi loop OHP charged with aqueous Al2O3 and MWCNTs/Al2O3 nanoparticles.The influences on thermal resistance of aqueous Al2O3,MWCNTs as well as the hybrid of them in OHP having 3 mm in inner diameter were investigated at 60% filling ratio.Experimental results show that thermal characteristics are significantly inter-related with pressure distribution and strongly depend upon the number of pressure fluctuations with time.Frequency of pressure depends upon the power input in evaporative section.A little inclusion of MWCNTs into aqueous Al2O3 at 60% filling ratio achieves the highest fluctuation frequency and the lowest thermal resistance at any evaporator power input though different nanofluids cause different thermal performances of OHPs.
基金Project(51509062)supported by the National Natural Science Foundation of ChinaProject(ZR2014EEP024)supported by the Shandong Provincial Natural Science Foundation,ChinaProject(HIT.NSRIF.201727)supported by the Fundamental Research Funds for the Central Universities,China
文摘Since the amplitude and frequency of irregular waves change with time,great difficulties are brought for solving ship load responses in random waves.To take the effect of various frequencies of irregular waves into consideration in load responses of hull,the wave memory effect is necessary.A semi-analytical method is introduced for the time-domain retardation functions,and then a nonlinear hydroelastic method considering memory effect for ships in irregular waves is proposed.Segmented self-propelling model experiments of a container ship were carried out in a towing tank,a ship motion measuring device for self-propelling model test was designed.Whipping responses of the ship in regular and irregular waves are analyzed.Finally,the calculation results are compared with those measured by segmented model experiments,and the result indicates that the memory effect has little effect on load responses of ship in regular waves,but pronounced effect on results in irregular waves.Moreover,the presented method is reasonable for the prediction of ship load responses in irregular waves.
基金supported by the State Scholarship Fund(2011611091)supported by China Shipbuilding Industry Corporation
文摘This paper presents an approach to the challenging is- sue of passive source localization in shallow water using a mobile short horizontal linear array with length less than ten meters. The short array can be conveniently placed on autonomous underwa- ter vehicles and deployed for adaptive spatial sampling. However, the use of such small aperture passive sonar systems makes it difficult to acquire sufficient spatial gain for localizing long-range sources. To meet the requirement, a localization approach that employs matched-field based techniques that enable the short ho- rizontal linear array is used to passively localize acoustic sources in shallow water. Furthermore, the broadband processing and inter-position processing provide robustness against ocean en- vironmental mismatch and enhance the stability of the estimation process. The proposed approach＇s ability to localize acoustic sources in shallow water at different signal-to-noise ratios is examined through the synthetic test cases where the sources are located at the endfire and some other bearing of the mobile short horizontal linear array. The presented results demonstrate that the positional parameters of the estimated source build up over time as the array moves at a low speed along a straight line at a constant depth.
