In 2005,Gogu,a Frenchman,analyzed 35 different existing formulas for mobility calculation and pointed that the formulas for quick mobility calculation had some limitations and were not general.Therefore,looking for a ...In 2005,Gogu,a Frenchman,analyzed 35 different existing formulas for mobility calculation and pointed that the formulas for quick mobility calculation had some limitations and were not general.Therefore,looking for a general and simple mobility formula is still a hot topic in mechanisms.At the meantime,it is also an important topic to complete the mechanism theory.Gogu proposed a new method that can avoid determining virtual constraints in 2008,but the method is still not general.To solve the problem,this paper defines the new concepts of link-group rank,general-kinematic-pair rank,virtual pair,virtual loop,and virtual-loop rank,and gives a new simple and general formula.Our method converts multi-loop mechanisms into some independent virtual loops,simplifies the problem,avoids calculating virtual constraints,and reduces the calculation difficulty.It is proved that the new formula is simple,general and effective through the mobility analysis of several different kinds of mechanisms.The application of this formula will provide great convenience for general engineers in mobility calculation.展开更多
We construct a class of modules for the twisted multi-loop algebra of type A1 × A1 by applying Wakimoto free bosonic realization. We also discuss the structures and the irreducibility of the Fock space.
在SIP(System In a Package)系统中集成具有LVDS(Low-Voltage Differential Signal)接口的多通道高速模数转换器(Analog-to-Digital Converter,ADC)时,面临不同LVDS输出通道延时不同所导致的数据采集错误的问题,为此设计了一个多通道自...在SIP(System In a Package)系统中集成具有LVDS(Low-Voltage Differential Signal)接口的多通道高速模数转换器(Analog-to-Digital Converter,ADC)时,面临不同LVDS输出通道延时不同所导致的数据采集错误的问题,为此设计了一个多通道自适应LVDS接收器。通过采用数据时钟恢复技术产生一个多相位的采样时钟,并结合ADC的测试模式来确认每一个通道的采样相位,能够自动对每一个通道的延时分别进行调整,以达到对齐各通道采样相位点,保证数据正确采集的目的。最后,基于先进CMOS工艺进行了接收器的设计、仿真、后端设计实现和流片测试,仿真和流片后的板级测试结果均表明该接收器能够对通道延迟进行自动调节以对齐采样相位,且最大的采样相位调节范围为±3 bit,信噪比大于65 dB,满足了设计要求和应用需求。展开更多
In-situ stress is a critical factor influencing the permeability of coal reservoirs and the production capacity of coalbed methane(CBM)wells.Accurate prediction of in-situ stress and investigation of its influence on ...In-situ stress is a critical factor influencing the permeability of coal reservoirs and the production capacity of coalbed methane(CBM)wells.Accurate prediction of in-situ stress and investigation of its influence on coal reservoir permeability and production capacity are significant for CBM development.This study investigated the CBM development zone in the Zhengzhuang area of the Qinshui Basin.According to the low mechanical strength of coal reservoirs,this study derived a calculation model of the in-situ stress of coal reservoirs based on the multi-loop hydraulic fracturing method and analyzed the impacts of initial fractures on the calculated results.Moreover,by combining the data such as the in-situ stress,permeability,and drainage and recovery data of CBM wells,this study revealed the spatial distribution patterns of the current in-situ stress of the coal reservoirs and discussed the impacts of the insitu stress on the permeability and production capacity.The results are as follows.(1)Under given fracturing pressure,longer initial fractures are associated with higher calculated maximum horizontal principal stress values.Therefore,ignoring the effects of the initial fractures will cause the calculated values of the in-situ stress to be less than the actual values.(2)As the burial depth increases,the fracturing pressure,closure pressure,and the maximum and minimum horizontal principal stress of the coal reservoirs in the Zhengzhuang area constantly increase.The average gradients of the maximum and minimum horizontal principal stress are 3.17 MPa/100 m and 2.05 MPa/100 m,respectively.(3)Coal reservoir permeability is significantly controlled by the magnitude and state of the current in-situ stress.The coal reservoir permeability decreases exponentially with an increase in the effective principal stress.Moreover,a low lateral pressure coefficient(less than 1)is associated with minor horizontal compressive effects and high coal reservoir permeability.(4)Under similar conditions,such as resource endowments,CBM well capacity is higher in primary structural coal regions with moderate paleotectonic stress modification,low current in-situ stress,and lateral pressure coefficient of less than 1.展开更多
文摘In 2005,Gogu,a Frenchman,analyzed 35 different existing formulas for mobility calculation and pointed that the formulas for quick mobility calculation had some limitations and were not general.Therefore,looking for a general and simple mobility formula is still a hot topic in mechanisms.At the meantime,it is also an important topic to complete the mechanism theory.Gogu proposed a new method that can avoid determining virtual constraints in 2008,but the method is still not general.To solve the problem,this paper defines the new concepts of link-group rank,general-kinematic-pair rank,virtual pair,virtual loop,and virtual-loop rank,and gives a new simple and general formula.Our method converts multi-loop mechanisms into some independent virtual loops,simplifies the problem,avoids calculating virtual constraints,and reduces the calculation difficulty.It is proved that the new formula is simple,general and effective through the mobility analysis of several different kinds of mechanisms.The application of this formula will provide great convenience for general engineers in mobility calculation.
文摘We construct a class of modules for the twisted multi-loop algebra of type A1 × A1 by applying Wakimoto free bosonic realization. We also discuss the structures and the irreducibility of the Fock space.
文摘在SIP(System In a Package)系统中集成具有LVDS(Low-Voltage Differential Signal)接口的多通道高速模数转换器(Analog-to-Digital Converter,ADC)时,面临不同LVDS输出通道延时不同所导致的数据采集错误的问题,为此设计了一个多通道自适应LVDS接收器。通过采用数据时钟恢复技术产生一个多相位的采样时钟,并结合ADC的测试模式来确认每一个通道的采样相位,能够自动对每一个通道的延时分别进行调整,以达到对齐各通道采样相位点,保证数据正确采集的目的。最后,基于先进CMOS工艺进行了接收器的设计、仿真、后端设计实现和流片测试,仿真和流片后的板级测试结果均表明该接收器能够对通道延迟进行自动调节以对齐采样相位,且最大的采样相位调节范围为±3 bit,信噪比大于65 dB,满足了设计要求和应用需求。
基金sponsored by the National Natural Science Foundation of China(42002181)projecta public bidding project of 2020 Shanxi Provincial Science and Technology Program(20201101002-03).
文摘In-situ stress is a critical factor influencing the permeability of coal reservoirs and the production capacity of coalbed methane(CBM)wells.Accurate prediction of in-situ stress and investigation of its influence on coal reservoir permeability and production capacity are significant for CBM development.This study investigated the CBM development zone in the Zhengzhuang area of the Qinshui Basin.According to the low mechanical strength of coal reservoirs,this study derived a calculation model of the in-situ stress of coal reservoirs based on the multi-loop hydraulic fracturing method and analyzed the impacts of initial fractures on the calculated results.Moreover,by combining the data such as the in-situ stress,permeability,and drainage and recovery data of CBM wells,this study revealed the spatial distribution patterns of the current in-situ stress of the coal reservoirs and discussed the impacts of the insitu stress on the permeability and production capacity.The results are as follows.(1)Under given fracturing pressure,longer initial fractures are associated with higher calculated maximum horizontal principal stress values.Therefore,ignoring the effects of the initial fractures will cause the calculated values of the in-situ stress to be less than the actual values.(2)As the burial depth increases,the fracturing pressure,closure pressure,and the maximum and minimum horizontal principal stress of the coal reservoirs in the Zhengzhuang area constantly increase.The average gradients of the maximum and minimum horizontal principal stress are 3.17 MPa/100 m and 2.05 MPa/100 m,respectively.(3)Coal reservoir permeability is significantly controlled by the magnitude and state of the current in-situ stress.The coal reservoir permeability decreases exponentially with an increase in the effective principal stress.Moreover,a low lateral pressure coefficient(less than 1)is associated with minor horizontal compressive effects and high coal reservoir permeability.(4)Under similar conditions,such as resource endowments,CBM well capacity is higher in primary structural coal regions with moderate paleotectonic stress modification,low current in-situ stress,and lateral pressure coefficient of less than 1.
