Japanese larch is one of the main plantation tree species in China.A lack of engineered wood products made by Japanese larch,however,limits its application in wood stnuctures.In this study,based on optimum process par...Japanese larch is one of the main plantation tree species in China.A lack of engineered wood products made by Japanese larch,however,limits its application in wood stnuctures.In this study,based on optimum process parameters,such as pressure(12 MPa),adhesive spread rate(200 g/m^(2))and adhesive(one-component polyurethane),the mechanical properties of Japanese larch-made cross-laminated timber(CLT)with different lay-ups were evaluated by means of the static method.Results of this study showed that variations in lay-ups significantly affected the mechanical properties of CLT.The strength and modulus of bending and parallel compression for CLT increased with the thickness of lumber,while that of bending,parallel compression and rolling shear all decreased with the number of layers.Thickness,layup orientation and the number of layers all had an impact on the strength of CLT.Failure modes obtained from numerical simulation were basically the same as those of experimental tests.There was also strong alignment between theoretical value and test value for effective bending stifness and shear stifness.Thus,the shear analogy method can be used to predict the mechanical properties of CLT effectively.This study proved great potential in using Japanese larch wood for manufacturing CLT due to its good mechanical properties.展开更多
Yielding behaviors of waxy crude oil is one of the key issues of flow assurance challenges. The yielding of waxy crude under constant stress is actually a creep process of strain accumulation to structural failure,to ...Yielding behaviors of waxy crude oil is one of the key issues of flow assurance challenges. The yielding of waxy crude under constant stress is actually a creep process of strain accumulation to structural failure,to describe the process completely and accurately is the basis of numerical simulation of restart process of the pipeline. The creep and yield behaviors of two gelled waxy crudes were investigated experimentally under different constant applied stresses. The results clearly show that the creep process of waxy crude is related to the applied stress and time. The greater the applied stress, and the longer the loaded time, the more obvious the nonlinear features. Based on the fractional calculus theory, a fractional viscous element was developed to describe the decelerated and steady creep process of gelled waxy crude. On the basis of the damage theory, an elastic damage element was proposed to describe the accelerated creep after the yielding. According to the idea of mechanical analogy, a nonlinear creep model was established by a fractional viscous element, an elastic damaged element, and an elastic element in series, which can accurately describe the whole creep and yielding process of gelled waxy crude.展开更多
针对传统压电型声矢量传感器无法兼顾小体积与高灵敏度的问题,利用MEMS电容加速度计作为拾振器,实现矢量传感器的小型化设计。首先采用机电类比分析的方法得到内置加速度计的刚硬球体的声致振动响应;然后进行硅微电容加速度计选型和参...针对传统压电型声矢量传感器无法兼顾小体积与高灵敏度的问题,利用MEMS电容加速度计作为拾振器,实现矢量传感器的小型化设计。首先采用机电类比分析的方法得到内置加速度计的刚硬球体的声致振动响应;然后进行硅微电容加速度计选型和参数分析、设定,并设计制作了一只二维球形矢量传感器样机;最后对样机进行了参数测试,结果表明两矢量通道均具有良好的方向性,声压灵敏度分别为?185 d B和-186 d B(1 k Hz,0 d B ref 1 V/μPa),通道间相位差与理论值保持一致,验证了利用MEMS电容加速度计设计矢量传感器的可行性。展开更多
基金by basic operating budget of scientific research institutes for public welfare at the central level(CAFBB2018SY032)China Postdoctoral Science Foundation (No.2018M641225).
文摘Japanese larch is one of the main plantation tree species in China.A lack of engineered wood products made by Japanese larch,however,limits its application in wood stnuctures.In this study,based on optimum process parameters,such as pressure(12 MPa),adhesive spread rate(200 g/m^(2))and adhesive(one-component polyurethane),the mechanical properties of Japanese larch-made cross-laminated timber(CLT)with different lay-ups were evaluated by means of the static method.Results of this study showed that variations in lay-ups significantly affected the mechanical properties of CLT.The strength and modulus of bending and parallel compression for CLT increased with the thickness of lumber,while that of bending,parallel compression and rolling shear all decreased with the number of layers.Thickness,layup orientation and the number of layers all had an impact on the strength of CLT.Failure modes obtained from numerical simulation were basically the same as those of experimental tests.There was also strong alignment between theoretical value and test value for effective bending stifness and shear stifness.Thus,the shear analogy method can be used to predict the mechanical properties of CLT effectively.This study proved great potential in using Japanese larch wood for manufacturing CLT due to its good mechanical properties.
基金the financial support from the National Natural Science Foundation of China (No.52174066)。
文摘Yielding behaviors of waxy crude oil is one of the key issues of flow assurance challenges. The yielding of waxy crude under constant stress is actually a creep process of strain accumulation to structural failure,to describe the process completely and accurately is the basis of numerical simulation of restart process of the pipeline. The creep and yield behaviors of two gelled waxy crudes were investigated experimentally under different constant applied stresses. The results clearly show that the creep process of waxy crude is related to the applied stress and time. The greater the applied stress, and the longer the loaded time, the more obvious the nonlinear features. Based on the fractional calculus theory, a fractional viscous element was developed to describe the decelerated and steady creep process of gelled waxy crude. On the basis of the damage theory, an elastic damage element was proposed to describe the accelerated creep after the yielding. According to the idea of mechanical analogy, a nonlinear creep model was established by a fractional viscous element, an elastic damaged element, and an elastic element in series, which can accurately describe the whole creep and yielding process of gelled waxy crude.
文摘针对传统压电型声矢量传感器无法兼顾小体积与高灵敏度的问题,利用MEMS电容加速度计作为拾振器,实现矢量传感器的小型化设计。首先采用机电类比分析的方法得到内置加速度计的刚硬球体的声致振动响应;然后进行硅微电容加速度计选型和参数分析、设定,并设计制作了一只二维球形矢量传感器样机;最后对样机进行了参数测试,结果表明两矢量通道均具有良好的方向性,声压灵敏度分别为?185 d B和-186 d B(1 k Hz,0 d B ref 1 V/μPa),通道间相位差与理论值保持一致,验证了利用MEMS电容加速度计设计矢量传感器的可行性。
