As the basic of a deeper investigation on the turbulent transport, the fluctuation property in the boundary of the newly-reconstructed Joint Texas Experimental Tokamak （J- TEXT） is studied experimentally using the r...As the basic of a deeper investigation on the turbulent transport, the fluctuation property in the boundary of the newly-reconstructed Joint Texas Experimental Tokamak （J- TEXT） is studied experimentally using the reciprocating Langmuir four-tip probe, which has been built and operated as the primary diagnostic tool in the boundary of J-TEXT tokamak. In this paper, spatial profiles of the plasma-edge parameters are obtained, such as electron temperature, plasma density, plasma potential, poloidal electric field and their fluctuations. The results indicate the existence of a Er ×BT shear layer at the vicinity of last closed flux surface （LCFS）, with the fluctuations suppressed in varying degrees. The turbulence-induced particle and energy fluxes can be calculated by the local plasma parameters above. Convection dominates the cross-field turbulent transport in boundary plasma. Electrostatic fluctuations properties are also studied in detail with the help of numerical analysis. Statistical analysis on density fluctuation shows that, the intermittency can affect the turbulence in the scrape-off layer （SOL）.展开更多
Organic-rich shale resources remain an important source of hydrocarbons considering their substantial contribution to crude oil and natural gas production around the world. Moreover, as part of mitigating the greenhou...Organic-rich shale resources remain an important source of hydrocarbons considering their substantial contribution to crude oil and natural gas production around the world. Moreover, as part of mitigating the greenhouse gas effects due to the emissions of carbon dioxide （CO2） gas, organic-rich shales are considered a possible alternate geologic storage. This is due to the adsorptive properties of organic ke- rogen and clay minerals within the shale matrix. Therefore, this research looks at evaluating the seques- tration potential of carbon dioxide （CO2） gas in kerogen nanopores with the use of the lattice Boltzmann method under varying experimental pressures and different pore sizes. Gas flow in micro/nano pores differ in hydrodynamics due to the dominant pore wall effects, as the mean free path （λ） of the gas molecules become comparable to the characteristic length （H） of the pores. In so doing, the traditional computational methods break down beyond the continuum region, and the lattice Boltzmann method （LBM） is employed. The lattice Boltzmann method is a mesoscopic numerical method for fluid system, where a unit of gas particles is assigned a discrete distribution function （/）. The particles stream along de- fined lattice links and collide locally at the lattice sites to conserve mass and momentum. The effects of gas-wall collisions （Knudsen layer effects） is incorporated into the LBM through an effective-relaxation- time model, and the discontinuous velocity at the pore walls is resolved with a slip boundary condition. Above all, the time lag （slip effect） created by CO2 gas molecules due to adsorption and desorption over a time period, and the surface diffusion as a result of the adsorption-gradient are captured by an adsorption isotherm and included in our LBM. Implementing the Langmuir adsorption isotherm at the pore walls for both CO2 gas revealed the underlying flow mechanism for CO2 gas in a typical kerogen nano-pore is dominated by the slip flow regime. Increasing the e展开更多
Fractional-order differentiator is a principal component of the fractional-order controller.Discretization of fractional-order differentiator is essential to implement the fractionalorder controller digitally.Discreti...Fractional-order differentiator is a principal component of the fractional-order controller.Discretization of fractional-order differentiator is essential to implement the fractionalorder controller digitally.Discretization methods generally include indirect approach and direct approach to find the discrete-time approximation of fractional-order differentiator in the Z-domain as evident from the existing literature.In this paper,a direct approach is proposed for discretization of fractional-order differentiator in delta-domain instead of the conventional Z-domain as the delta operator unifies both analog system and digital system together at a high sampling frequency.The discretization of fractional-order differentiator is accomplished in two stages.In the first stage,the generating function is framed by reformulating delta operator using trapezoidal rule or Tustin approximation and in the next stage,the fractional-order differentiator has been approximated by expanding the generating function using continued fraction expansion method.The proposed method has been compared with two well-known direct discretization methods taken from the existing literature.Two examples are presented in this context to show the efficacy of the proposed discretization method using simulation results obtained from MATLAB.展开更多
“Come to the woods, for here is rest,” wrote John Muir,the 19th Century Scottish-American naturalist who was one of the earliest advocates of US national parks. Muir spent large chunks of his life exploring Yosemite...“Come to the woods, for here is rest,” wrote John Muir,the 19th Century Scottish-American naturalist who was one of the earliest advocates of US national parks. Muir spent large chunks of his life exploring Yosemite and the Sierra Nevada, and wrote abundantly of his belief in nature’s nourishing role,saying:“Everybody needs beauty as well as bread, places to play in and pray in, where nature may heal and give strength to body and soul alike.”展开更多
Faced with the problems of natural resources and ecological environment caused by the early modernization in the late 19^th and early 20^th centuries,John Muir combined the natural science knowledge as well as the obs...Faced with the problems of natural resources and ecological environment caused by the early modernization in the late 19^th and early 20^th centuries,John Muir combined the natural science knowledge as well as the observation and perception of nature,constructed the preservation thoughts which advocated the overall preservation concept by highlighting the aesthetics value,spiritual value and intrinsic value of nature,and perfected the cognition of the natural multi-value system and the relationship between man and nature.At the same time,the preservationists like Muir actively put preservation into practice,promoted the establishment of Yosemite and other national parks,contributing to the construction of the U.S.national park system.However,in the process of the management of national parks and forest reserves,it was difficult to really implement preservation because there existed the tension between it and the mainstream values such as the concept of development and progress.展开更多
目的 应用高分辨率固态测压技术(HRM)检测Passy-Muir说话瓣膜(PMV)对脑卒中气管切开患者吞咽生物力学的作用,探讨利用咽腔与食管上括约肌(UES)压力参数评估PMV治疗效果的应用价值。方法 2020年1月至2024年1月,新疆维吾尔自治区人民医院...目的 应用高分辨率固态测压技术(HRM)检测Passy-Muir说话瓣膜(PMV)对脑卒中气管切开患者吞咽生物力学的作用,探讨利用咽腔与食管上括约肌(UES)压力参数评估PMV治疗效果的应用价值。方法 2020年1月至2024年1月,新疆维吾尔自治区人民医院100例脑卒中气管切开患者随机分为对照组(n=50)和PMV组(n=50),对照组给予常规吞咽康复,PMV组在此基础上佩戴PMV,共2周。治疗前后,采用改良曼恩吞咽能力评估量表(MMASA)进行临床吞咽功能评估;并进行HRM检查,收集腭咽收缩压力峰值、腭咽收缩时长、UES松弛残余压和UES松弛时间等数据。将PMV组治疗后的MMASA评分与HRM压力参数值进行相关性分析。结果 两组各脱落4例。治疗后,两组UES松弛残余压显著降低(t> 47.403, P <0.001),MMASA评分、腭咽收缩压力峰值、腭咽收缩时长和UES松弛时间均显著增加(t> 19.621, P <0.001);PMV组均优于对照组(t>2.050, P <0.05)。治疗后PMV组腭咽收缩压力峰值(r=0.924, P <0.001)、腭咽收缩时长(r=0.948, P <0.001)和UES松弛残余时间(r=0.954, P <0.001)与MMASA评分呈正相关,UES松弛残余压与MMASA评分呈负相关(r=-0.939, P <0.001)。结论 佩戴PMV治疗能增强脑卒中气管切开患者的吞咽功能,提高咽腔和UES区域的吞咽生物力学水平。利用咽腔和UES区域的压力参数可预测佩戴PMV治疗后患者吞咽功能的改善情况。展开更多
基金supported by Open Research Program from Key Laboratory of Geospace Environment, Chinese Academy of Sciences
文摘As the basic of a deeper investigation on the turbulent transport, the fluctuation property in the boundary of the newly-reconstructed Joint Texas Experimental Tokamak （J- TEXT） is studied experimentally using the reciprocating Langmuir four-tip probe, which has been built and operated as the primary diagnostic tool in the boundary of J-TEXT tokamak. In this paper, spatial profiles of the plasma-edge parameters are obtained, such as electron temperature, plasma density, plasma potential, poloidal electric field and their fluctuations. The results indicate the existence of a Er ×BT shear layer at the vicinity of last closed flux surface （LCFS）, with the fluctuations suppressed in varying degrees. The turbulence-induced particle and energy fluxes can be calculated by the local plasma parameters above. Convection dominates the cross-field turbulent transport in boundary plasma. Electrostatic fluctuations properties are also studied in detail with the help of numerical analysis. Statistical analysis on density fluctuation shows that, the intermittency can affect the turbulence in the scrape-off layer （SOL）.
基金support of the Tertiary Oil Recovery Program (TORP)the Kansas Interdisciplinary Carbonates Consortium (KICC) at the University of Kansas
文摘Organic-rich shale resources remain an important source of hydrocarbons considering their substantial contribution to crude oil and natural gas production around the world. Moreover, as part of mitigating the greenhouse gas effects due to the emissions of carbon dioxide （CO2） gas, organic-rich shales are considered a possible alternate geologic storage. This is due to the adsorptive properties of organic ke- rogen and clay minerals within the shale matrix. Therefore, this research looks at evaluating the seques- tration potential of carbon dioxide （CO2） gas in kerogen nanopores with the use of the lattice Boltzmann method under varying experimental pressures and different pore sizes. Gas flow in micro/nano pores differ in hydrodynamics due to the dominant pore wall effects, as the mean free path （λ） of the gas molecules become comparable to the characteristic length （H） of the pores. In so doing, the traditional computational methods break down beyond the continuum region, and the lattice Boltzmann method （LBM） is employed. The lattice Boltzmann method is a mesoscopic numerical method for fluid system, where a unit of gas particles is assigned a discrete distribution function （/）. The particles stream along de- fined lattice links and collide locally at the lattice sites to conserve mass and momentum. The effects of gas-wall collisions （Knudsen layer effects） is incorporated into the LBM through an effective-relaxation- time model, and the discontinuous velocity at the pore walls is resolved with a slip boundary condition. Above all, the time lag （slip effect） created by CO2 gas molecules due to adsorption and desorption over a time period, and the surface diffusion as a result of the adsorption-gradient are captured by an adsorption isotherm and included in our LBM. Implementing the Langmuir adsorption isotherm at the pore walls for both CO2 gas revealed the underlying flow mechanism for CO2 gas in a typical kerogen nano-pore is dominated by the slip flow regime. Increasing the e
文摘Fractional-order differentiator is a principal component of the fractional-order controller.Discretization of fractional-order differentiator is essential to implement the fractionalorder controller digitally.Discretization methods generally include indirect approach and direct approach to find the discrete-time approximation of fractional-order differentiator in the Z-domain as evident from the existing literature.In this paper,a direct approach is proposed for discretization of fractional-order differentiator in delta-domain instead of the conventional Z-domain as the delta operator unifies both analog system and digital system together at a high sampling frequency.The discretization of fractional-order differentiator is accomplished in two stages.In the first stage,the generating function is framed by reformulating delta operator using trapezoidal rule or Tustin approximation and in the next stage,the fractional-order differentiator has been approximated by expanding the generating function using continued fraction expansion method.The proposed method has been compared with two well-known direct discretization methods taken from the existing literature.Two examples are presented in this context to show the efficacy of the proposed discretization method using simulation results obtained from MATLAB.
文摘“Come to the woods, for here is rest,” wrote John Muir,the 19th Century Scottish-American naturalist who was one of the earliest advocates of US national parks. Muir spent large chunks of his life exploring Yosemite and the Sierra Nevada, and wrote abundantly of his belief in nature’s nourishing role,saying:“Everybody needs beauty as well as bread, places to play in and pray in, where nature may heal and give strength to body and soul alike.”
基金the support from the National Social Science Fund of China(Project No.17CSS022).
文摘Faced with the problems of natural resources and ecological environment caused by the early modernization in the late 19^th and early 20^th centuries,John Muir combined the natural science knowledge as well as the observation and perception of nature,constructed the preservation thoughts which advocated the overall preservation concept by highlighting the aesthetics value,spiritual value and intrinsic value of nature,and perfected the cognition of the natural multi-value system and the relationship between man and nature.At the same time,the preservationists like Muir actively put preservation into practice,promoted the establishment of Yosemite and other national parks,contributing to the construction of the U.S.national park system.However,in the process of the management of national parks and forest reserves,it was difficult to really implement preservation because there existed the tension between it and the mainstream values such as the concept of development and progress.
文摘目的 应用高分辨率固态测压技术(HRM)检测Passy-Muir说话瓣膜(PMV)对脑卒中气管切开患者吞咽生物力学的作用,探讨利用咽腔与食管上括约肌(UES)压力参数评估PMV治疗效果的应用价值。方法 2020年1月至2024年1月,新疆维吾尔自治区人民医院100例脑卒中气管切开患者随机分为对照组(n=50)和PMV组(n=50),对照组给予常规吞咽康复,PMV组在此基础上佩戴PMV,共2周。治疗前后,采用改良曼恩吞咽能力评估量表(MMASA)进行临床吞咽功能评估;并进行HRM检查,收集腭咽收缩压力峰值、腭咽收缩时长、UES松弛残余压和UES松弛时间等数据。将PMV组治疗后的MMASA评分与HRM压力参数值进行相关性分析。结果 两组各脱落4例。治疗后,两组UES松弛残余压显著降低(t> 47.403, P <0.001),MMASA评分、腭咽收缩压力峰值、腭咽收缩时长和UES松弛时间均显著增加(t> 19.621, P <0.001);PMV组均优于对照组(t>2.050, P <0.05)。治疗后PMV组腭咽收缩压力峰值(r=0.924, P <0.001)、腭咽收缩时长(r=0.948, P <0.001)和UES松弛残余时间(r=0.954, P <0.001)与MMASA评分呈正相关,UES松弛残余压与MMASA评分呈负相关(r=-0.939, P <0.001)。结论 佩戴PMV治疗能增强脑卒中气管切开患者的吞咽功能,提高咽腔和UES区域的吞咽生物力学水平。利用咽腔和UES区域的压力参数可预测佩戴PMV治疗后患者吞咽功能的改善情况。
