Locked segments are recognized as a critical role that controls the stability of rock slopes but remain an unclear and challenging problem with respect to their role incorporated into the failure mechanism.In order to...Locked segments are recognized as a critical role that controls the stability of rock slopes but remain an unclear and challenging problem with respect to their role incorporated into the failure mechanism.In order to study the effect of the locked segments on the initial failure process of rockslides,thirty-six groups of locked segment specimens with three different lithologies were prepared,direct shear tests were carried out to obtain the accelerations caused by brittle failure of the locked segment specimens.Experiment results showed that the maximum accelerations caused by the brittle failure of locked segment specimens was 2.91 g in the horizontal direction,and 3.18 g in the vertical direction.We took the Wangjiayan rockslide in 2008 Wenchuan earthquake as an example,the critical balance condition of the sliding mass under combined effect of gravity and accelerations induced by brittle failure of locked segment was analyzed,which indicated that the initial failure process of the Wangjiayan rockslides was notably influenced by the existence of the locked segment.The departure acceleration and direction of the Wangjiayan rockslide were proposed.The study results can provide a new insight into the understanding of the initial failure mechanism of rockslides with locked segments.展开更多
Grain composition plays a vital role in impact pressure of debris flow. Current approaches treat debris flow as uniform fluid and almost ignore its granular effects. A series of flume experiments have been carried out...Grain composition plays a vital role in impact pressure of debris flow. Current approaches treat debris flow as uniform fluid and almost ignore its granular effects. A series of flume experiments have been carried out to explore the granular influence on the impact process of debris flow by using a contact surface pressure gauge sensor(Tactilus~?, produced by Sensor Products LLC). It is found that the maximum impact pressure for debris flow of low density fluctuates drastically with a long duration time while the fluctuation for flow of high density is short in time, respectively presenting logarithmic and linear form in longitudinal attenuation. This can be ascribed to the turbulence effect in the former and grain collisions and grainfluid interaction in the latter. The horizontal distribution of the impact pressure can be considered as the equivalent distribution. For engineering purposes, the longitudinal distribution of the pressure can be generalized to a triangular distribution, from which a new impact method considering granular effects is proposed.展开更多
Drainage canals are engineering structures widely used for debris flow mitigation.When passing through a drainage canal,debris flow usually scours the gully bed at the back of the rib sill of the drainage canal,which ...Drainage canals are engineering structures widely used for debris flow mitigation.When passing through a drainage canal,debris flow usually scours the gully bed at the back of the rib sill of the drainage canal,which leads to failure of the rib sill.Therefore,the scour depth at the back of the rib sill is an important design problem and it is related to the economic benefits of engineering and service years.To explore the law of the depth of the scour pit after debris flow through drainage canal ribs,we first proposed a formula for the calculation of the maximum scour depth at the back of a rib sill based on energy conservation.We then conducted a series of simulation experiments to test the proposed formula.The experimental results show that the scour depth,trench slope and the distance between ribs all increase with a decrease in debris flow density.We then compared the results of experiments and formula calculations.Through the testing analysis,we found that the calculation results of the conductedformula correspond with the experimental results better.Finally,taking Qipan Gully as an example,we designed the ultimate depth of a drainage canal for debris flow using the calculation formula.展开更多
Strain-compensated Ge/Si0.15Ge0.85 multiple quantum wells were grown on an Si0.1 Ge0.9 virtual substrate using ultrahigh vacuum chemical vapor deposition technology on an n＋-Si（001） substrate. Photoluminescence mea...Strain-compensated Ge/Si0.15Ge0.85 multiple quantum wells were grown on an Si0.1 Ge0.9 virtual substrate using ultrahigh vacuum chemical vapor deposition technology on an n＋-Si（001） substrate. Photoluminescence measurements were performed at room temperature, and the quantum confinement effect of the direct-bandgap transitions of a Ge quantum well was observed, which is in good agreement with the calculated results. The luminescence mechanism was discussed by recombination rate analysis and the temperature dependence of the luminescence spectrum.展开更多
Germanium-tin(Ge_(1-x)Sn_(x))p-type metal-oxide-semiconductor field effect transistors(pMOSFETs)were fabricated using a strained Ge_(0.985)Sn_(0.015) thin film that was epitaxially grown on a silicon-on-insulator subs...Germanium-tin(Ge_(1-x)Sn_(x))p-type metal-oxide-semiconductor field effect transistors(pMOSFETs)were fabricated using a strained Ge_(0.985)Sn_(0.015) thin film that was epitaxially grown on a silicon-on-insulator substrate with a relaxed Ge buffer layer.The Ge buffer was deposited using a two-step chemical vapor deposition growth technique.The high quality Ge_(0.985)Sn_(0.015) layer was grown by solid source molecular beam epitaxy.Ge_(0.985)Sn_(0.015) pMOSFETs with Si surface passivation,TaN/HfO_(2) gate stack,and nickel stanogermanide[Ni(Ge_(1-x)Sn_(x))]source/drain were fabricated on the grown substrate.The device achieves an effective hole mobility of 182 cm^(2)/V·s at an inversion carrier density of 1×10^(13) cm^(-2).展开更多
High performance InP/InGaAs heterojunction bipolar transistors（HBTs） have been widely used in hlgh-speed electronic devices and optoelectronic integrated circuits. InP-based HBTs were fabricated by low pressure meta...High performance InP/InGaAs heterojunction bipolar transistors（HBTs） have been widely used in hlgh-speed electronic devices and optoelectronic integrated circuits. InP-based HBTs were fabricated by low pressure metal organic chemical vapor deposition（MOCVD） and wet chemical etching. The sub-collector and collector were grown at 655 ℃ and other layers at 550 ℃. To suppress the Zn out-diffusion in HBT, base layer was grown with a 16-minute growth interruption. Fabricated HBTs with emitter size of 2.5×20μm^2 showed current gain of 70-90, breakdown voltage（BVCE0 ）〉2 V, cut-off frequency（fτ ） of 60 G Hz and the maximum relaxation frequency（f MAX） of 70 GHz.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 41672295)
文摘Locked segments are recognized as a critical role that controls the stability of rock slopes but remain an unclear and challenging problem with respect to their role incorporated into the failure mechanism.In order to study the effect of the locked segments on the initial failure process of rockslides,thirty-six groups of locked segment specimens with three different lithologies were prepared,direct shear tests were carried out to obtain the accelerations caused by brittle failure of the locked segment specimens.Experiment results showed that the maximum accelerations caused by the brittle failure of locked segment specimens was 2.91 g in the horizontal direction,and 3.18 g in the vertical direction.We took the Wangjiayan rockslide in 2008 Wenchuan earthquake as an example,the critical balance condition of the sliding mass under combined effect of gravity and accelerations induced by brittle failure of locked segment was analyzed,which indicated that the initial failure process of the Wangjiayan rockslides was notably influenced by the existence of the locked segment.The departure acceleration and direction of the Wangjiayan rockslide were proposed.The study results can provide a new insight into the understanding of the initial failure mechanism of rockslides with locked segments.
基金funded by the Research on Prevention and Control Technology of Ecological Debris Flow Disasters from Department of Land and Resources of Sichuan Province (Grant No. KJ2018-24)the Natural Science Foundation of China (Grant No. 41772343)+2 种基金the Chinese Academy of Sciences and Organization Department of Sichuan Provincial Party Committee "Light of West China" Program (the key control techniques of glacial debris flow along the Sichuan-Tibet Railway)the Key International S&T Cooperation Projects (Grant No. 2016YFE0122400)the Natural Science Foundation of China (Grant No. 41471011)
文摘Grain composition plays a vital role in impact pressure of debris flow. Current approaches treat debris flow as uniform fluid and almost ignore its granular effects. A series of flume experiments have been carried out to explore the granular influence on the impact process of debris flow by using a contact surface pressure gauge sensor(Tactilus~?, produced by Sensor Products LLC). It is found that the maximum impact pressure for debris flow of low density fluctuates drastically with a long duration time while the fluctuation for flow of high density is short in time, respectively presenting logarithmic and linear form in longitudinal attenuation. This can be ascribed to the turbulence effect in the former and grain collisions and grainfluid interaction in the latter. The horizontal distribution of the impact pressure can be considered as the equivalent distribution. For engineering purposes, the longitudinal distribution of the pressure can be generalized to a triangular distribution, from which a new impact method considering granular effects is proposed.
基金financially supported by the key Projects of the Chinese Academy of Sciences (Grant No.KZZD-EW-05-01-04)the National Science and Technology Support Program (Grant No.2012BAC06B02)the sub-program of Science and technology research and development plan from China Railway (Grant No.2014G004-A-5)
文摘Drainage canals are engineering structures widely used for debris flow mitigation.When passing through a drainage canal,debris flow usually scours the gully bed at the back of the rib sill of the drainage canal,which leads to failure of the rib sill.Therefore,the scour depth at the back of the rib sill is an important design problem and it is related to the economic benefits of engineering and service years.To explore the law of the depth of the scour pit after debris flow through drainage canal ribs,we first proposed a formula for the calculation of the maximum scour depth at the back of a rib sill based on energy conservation.We then conducted a series of simulation experiments to test the proposed formula.The experimental results show that the scour depth,trench slope and the distance between ribs all increase with a decrease in debris flow density.We then compared the results of experiments and formula calculations.Through the testing analysis,we found that the calculation results of the conductedformula correspond with the experimental results better.Finally,taking Qipan Gully as an example,we designed the ultimate depth of a drainage canal for debris flow using the calculation formula.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61036003,61176013,61177038,and 60906035)the High Technology Research and Development Program of China(Grant No.2011AA010302)
文摘Strain-compensated Ge/Si0.15Ge0.85 multiple quantum wells were grown on an Si0.1 Ge0.9 virtual substrate using ultrahigh vacuum chemical vapor deposition technology on an n＋-Si（001） substrate. Photoluminescence measurements were performed at room temperature, and the quantum confinement effect of the direct-bandgap transitions of a Ge quantum well was observed, which is in good agreement with the calculated results. The luminescence mechanism was discussed by recombination rate analysis and the temperature dependence of the luminescence spectrum.
基金Supported by the National Basic Research Program of China under Grant Nos 2013CB632103 and 2011CBA00608the National Natural Science Foundation of China under Grant Nos 61036003,61177038 and 61176013the Science Research Foundation of Huaqiao University under Grant 12BS221.
文摘Germanium-tin(Ge_(1-x)Sn_(x))p-type metal-oxide-semiconductor field effect transistors(pMOSFETs)were fabricated using a strained Ge_(0.985)Sn_(0.015) thin film that was epitaxially grown on a silicon-on-insulator substrate with a relaxed Ge buffer layer.The Ge buffer was deposited using a two-step chemical vapor deposition growth technique.The high quality Ge_(0.985)Sn_(0.015) layer was grown by solid source molecular beam epitaxy.Ge_(0.985)Sn_(0.015) pMOSFETs with Si surface passivation,TaN/HfO_(2) gate stack,and nickel stanogermanide[Ni(Ge_(1-x)Sn_(x))]source/drain were fabricated on the grown substrate.The device achieves an effective hole mobility of 182 cm^(2)/V·s at an inversion carrier density of 1×10^(13) cm^(-2).
基金Chinese High Technology Developing Plan(2002AA312040)
文摘High performance InP/InGaAs heterojunction bipolar transistors（HBTs） have been widely used in hlgh-speed electronic devices and optoelectronic integrated circuits. InP-based HBTs were fabricated by low pressure metal organic chemical vapor deposition（MOCVD） and wet chemical etching. The sub-collector and collector were grown at 655 ℃ and other layers at 550 ℃. To suppress the Zn out-diffusion in HBT, base layer was grown with a 16-minute growth interruption. Fabricated HBTs with emitter size of 2.5×20μm^2 showed current gain of 70-90, breakdown voltage（BVCE0 ）〉2 V, cut-off frequency（fτ ） of 60 G Hz and the maximum relaxation frequency（f MAX） of 70 GHz.
