Let ΡΥ（X） be the semigroup of all partial transformations on X, Υ（X） and Ι（X） be the subsemigroups of ΡΥ（X） of all full transformations on X and of all injective partial transformations on X, respectivel...Let ΡΥ（X） be the semigroup of all partial transformations on X, Υ（X） and Ι（X） be the subsemigroups of ΡΥ（X） of all full transformations on X and of all injective partial transformations on X, respectively. Given a non-empty subset Y of X, let ΡΥ（X, Y） = {α∈ ΡΥ（X） ： Xα Y}, Υ（X, Y） = ΡΥ（X, Y） ∩Υ（X） and Ι（X, Y） = ΡΥ（X, Y） ∩ Ι（X）. In 2008, Sanwong and Sommanee described the largest regular subsemigroup and determined Green＇s relations of Υ（X,Y）. In this paper, we present analogous results for bothΡ Υ（X, Y） and Ι（X, Y）. For a finite set X with ｜x｜≥ 3, the ranks of ΡΥ（X） = ΡΥ（X, X）, Υ（X） = Υ（X, X） and.Ι（X） = Ι（X, X） are well known to be 4, 3 and 3, respectively. In this paper, we also compute the ranks of ΡΥ（X,Y）, Υ（X, Y） and Ι（X, Y） for any proper non-empty subset Y of X.展开更多
Recently, the 1-bit compressive sensing （1-bit CS） has been studied in the field of sparse signal recovery. Since the amplitude information of sparse signals in 1-bit CS is not available, it is often the support or ...Recently, the 1-bit compressive sensing （1-bit CS） has been studied in the field of sparse signal recovery. Since the amplitude information of sparse signals in 1-bit CS is not available, it is often the support or the sign of a signal that can be exactly recovered with a decoding method. We first show that a necessary assumption （that has been overlooked in the literature） should be made for some existing theories and discussions for 1-bit CS. Without such an assumption, the found solution by some existing decoding algorithms might be inconsistent with 1-bit measurements. This motivates us to pursue a new direction to develop uniform and nonuniform recovery theories for 1-bit CS with a new decoding method which always generates a solution consistent with 1-bit measurements. We focus on an extreme case of 1-bit CS, in which the measurements capture only the sign of the product of a sensing matrix and a signal. We show that the 1-bit CS model can be reformulated equivalently as an t0-minimization problem with linear constraints. This reformulation naturally leads to a new linear-program-based decoding method, referred to as the 1-bit basis pursuit, which is remarkably different from existing formulations. It turns out that the uniqueness condition for the solution of the 1-bit basis pursuit yields the so-called restricted range space property （RRSP） of the transposed sensing matrix. This concept provides a basis to develop sign recovery conditions for sparse signals through 1-bit measurements. We prove that if the sign of a sparse signal can be exactly recovered from 1-bit measurements with 1-bit basis pursuit, then the sensing matrix must admit a certain RRSP, and that if the sensing matrix admits a slightly enhanced RRSP, then the sign of a k-sparse signal can be exactly recovered with 1-bit basis pursuit.展开更多
The advantage of solar sails in deep space exploration is that no fuel consumption is required. The heliocentric distance is one factor influencing the solar radiation pressure force exerted on solar sails. In additio...The advantage of solar sails in deep space exploration is that no fuel consumption is required. The heliocentric distance is one factor influencing the solar radiation pressure force exerted on solar sails. In addition, the solar radiation pressure force is also related to the solar sail orientation with respect to the sunlight direction. For an ideal flat solar sail, the cone angle between the sail normal and the sunlight direction determines the magnitude and direction of solar radiation pressure force. In general, the cone angle can change from 0° to 90°. However, in practical applications, a large cone angle may reduce the efficiency of solar radiation pressure force and there is a strict requirement on the attitude control. Usually, the cone angle range is restricted less more than an acute angle （for example, not more than 40°） in engineering practice. In this paper, the time-optimal transfer trajectory is designed over a restricted range of the cone angle, and an indirect method is used to solve the two point boundary value problem associated to the optimal control problem. Relevant numerical examples are provided to compare with the case of an unrestricted case, and the effects of different maximum restricted cone angles are discussed. The results indicate that （1） for the condition of a restricted cone-angle range the transfer time is longer than that for the unrestricted case and （2） the optimal transfer time increases as the maximum restricted cone angle decreases.展开更多
This paper is concerned with the problem of the best restricted range approximations of complex-valued continuous functions. Several properties for the approximating set PΩ such that the classical characterization re...This paper is concerned with the problem of the best restricted range approximations of complex-valued continuous functions. Several properties for the approximating set PΩ such that the classical characterization results and/or the uniqueness results of the best approximations hold are introduced. Under the very mild conditions, we prove that these properties are equivalent that P is a Haar subspce.展开更多
设 f 是线性赋范空间 R 中给定的函数,K 为广义多项式集合 V^n(?)R 中满足某种线性约束条件的多项式所成的子集合。本文研究了 K 对 f 的最佳逼近的特征。我们在较一般的情况下,即对空间 R 的范数,函数 f 的性质,以及 K 所满足的线性约...设 f 是线性赋范空间 R 中给定的函数,K 为广义多项式集合 V^n(?)R 中满足某种线性约束条件的多项式所成的子集合。本文研究了 K 对 f 的最佳逼近的特征。我们在较一般的情况下,即对空间 R 的范数,函数 f 的性质,以及 K 所满足的线性约束条件不作任何规定的情况下,获得了一种适用范围很广的特征定理,前人已证明的多种常见的约束逼近特征定理都是本文结果的特例,特别。展开更多
文章在Cadot et al.(2006)的政治经济学模型基础之上,首先构建了适用于中澳FTA的理论框架,进而分析中澳优惠原产地规则制定的影响因素。研究表明,缔约方进行FTA原产地规则谈判时,产业发展水平、优惠关税幅度是缔约方考量的重要因素。一...文章在Cadot et al.(2006)的政治经济学模型基础之上,首先构建了适用于中澳FTA的理论框架,进而分析中澳优惠原产地规则制定的影响因素。研究表明,缔约方进行FTA原产地规则谈判时,产业发展水平、优惠关税幅度是缔约方考量的重要因素。一国产业发展水平越高,另一国就越有动力在FTA谈判中提出制定严格的原产地规则,限制对方优势产业进入本国,以达到保护本国产业的目的。FTA优惠关税幅度越高,缔约方防止第三国"搭便车"和贸易偏转的动机就越强,越倾向制定严格的优惠原产地规则。进一步研究发现,对本国价值含量较高的产品而言,厂商为满足本国消费和销出余量进行产业游说以获取严格优惠原产地规则的可能性较低。因此,为制定合理、合情、合利的优惠原产地规则,有必要从内生贸易政策视角理解优惠原产地规则发挥的政策优势。展开更多
This paper investigates urban traffic data by analysing the long-range correlation with detrended fluctuation analysis. Through a large number of real data collected by the travel time detection system in Beijing, the...This paper investigates urban traffic data by analysing the long-range correlation with detrended fluctuation analysis. Through a large number of real data collected by the travel time detection system in Beijing, the variation of flow in different time periods and intersections is studied. According to the long-range correlation in different time scales, it mainly discuss the effect of intersection location in road net, people activity customs and special traffic controls on urban traffic flow. As demonstrated by obtained results, the urban traffic flow represents three-phase characters similar to highway traffic. Moreover, compared by the two groups of data obtained before and after the special traffic restrictions （vehicles with special numbered plates only run in a special workday） enforcement, it indicates that the rules not only reduce the flow but also avoid irregular fluctuation.展开更多
Purpose: Belt electrode skeletal muscle electrical stimulation (B-SES) can stimulate large portions of muscles including deep sites without localisation of the stimulation area. The purpose of this study is to investi...Purpose: Belt electrode skeletal muscle electrical stimulation (B-SES) can stimulate large portions of muscles including deep sites without localisation of the stimulation area. The purpose of this study is to investigate both immediate treatment effects of B-SES and long-term treatment effects of B-SES with passive exercise on range of motion (ROM) and muscle tone of lower extremities in bedridden elderly patients. Methods: Outcome measures before and after B-SES treatment alone (4 Hz, 20 min, both lower extremities) were examined for the immediate effect. Outcome measures were: ROM and Modified Ashworth scale (MAS) of hip flexion and adduction;knee flexion and extension;and knee joint distance at position of flexion abduction in hip (distance of knee). A randomized crossover trial was conducted to examine the long-term effect of adding B-SES to passive exercise on ROM and MAS. Results and Discussion: The immediate effect study had 18 patients. ROM and MAS of 4 joint angles in 2 joints and distance of knee significantly improved after B-SES treatment. The long-term effect study had 11 patients. Friedman test revealed ROM and MAS of 4 joint angles in 2 joints and distance of knee significantly improved during B-SES intervention but not control intervention. B-SES in addition to passive stretch has a more statistically significant effect on contracture and spasticity in large portions of the lower extremities of bedridden elderly patients than passive stretching alone. Conclusions: We consider B-SES a useful tool to improve the ROM in lower extremities of bedridden patients.展开更多
文摘Let ΡΥ（X） be the semigroup of all partial transformations on X, Υ（X） and Ι（X） be the subsemigroups of ΡΥ（X） of all full transformations on X and of all injective partial transformations on X, respectively. Given a non-empty subset Y of X, let ΡΥ（X, Y） = {α∈ ΡΥ（X） ： Xα Y}, Υ（X, Y） = ΡΥ（X, Y） ∩Υ（X） and Ι（X, Y） = ΡΥ（X, Y） ∩ Ι（X）. In 2008, Sanwong and Sommanee described the largest regular subsemigroup and determined Green＇s relations of Υ（X,Y）. In this paper, we present analogous results for bothΡ Υ（X, Y） and Ι（X, Y）. For a finite set X with ｜x｜≥ 3, the ranks of ΡΥ（X） = ΡΥ（X, X）, Υ（X） = Υ（X, X） and.Ι（X） = Ι（X, X） are well known to be 4, 3 and 3, respectively. In this paper, we also compute the ranks of ΡΥ（X,Y）, Υ（X, Y） and Ι（X, Y） for any proper non-empty subset Y of X.
基金supported by the Engineering and Physical Sciences Research Council of UK (Grant No. #EP/K00946X/1)
文摘Recently, the 1-bit compressive sensing （1-bit CS） has been studied in the field of sparse signal recovery. Since the amplitude information of sparse signals in 1-bit CS is not available, it is often the support or the sign of a signal that can be exactly recovered with a decoding method. We first show that a necessary assumption （that has been overlooked in the literature） should be made for some existing theories and discussions for 1-bit CS. Without such an assumption, the found solution by some existing decoding algorithms might be inconsistent with 1-bit measurements. This motivates us to pursue a new direction to develop uniform and nonuniform recovery theories for 1-bit CS with a new decoding method which always generates a solution consistent with 1-bit measurements. We focus on an extreme case of 1-bit CS, in which the measurements capture only the sign of the product of a sensing matrix and a signal. We show that the 1-bit CS model can be reformulated equivalently as an t0-minimization problem with linear constraints. This reformulation naturally leads to a new linear-program-based decoding method, referred to as the 1-bit basis pursuit, which is remarkably different from existing formulations. It turns out that the uniqueness condition for the solution of the 1-bit basis pursuit yields the so-called restricted range space property （RRSP） of the transposed sensing matrix. This concept provides a basis to develop sign recovery conditions for sparse signals through 1-bit measurements. We prove that if the sign of a sparse signal can be exactly recovered from 1-bit measurements with 1-bit basis pursuit, then the sensing matrix must admit a certain RRSP, and that if the sensing matrix admits a slightly enhanced RRSP, then the sign of a k-sparse signal can be exactly recovered with 1-bit basis pursuit.
基金supported by the National Natural Science Foundation of China(11272004 and 11302112)China’s Civil Space Funding
文摘The advantage of solar sails in deep space exploration is that no fuel consumption is required. The heliocentric distance is one factor influencing the solar radiation pressure force exerted on solar sails. In addition, the solar radiation pressure force is also related to the solar sail orientation with respect to the sunlight direction. For an ideal flat solar sail, the cone angle between the sail normal and the sunlight direction determines the magnitude and direction of solar radiation pressure force. In general, the cone angle can change from 0° to 90°. However, in practical applications, a large cone angle may reduce the efficiency of solar radiation pressure force and there is a strict requirement on the attitude control. Usually, the cone angle range is restricted less more than an acute angle （for example, not more than 40°） in engineering practice. In this paper, the time-optimal transfer trajectory is designed over a restricted range of the cone angle, and an indirect method is used to solve the two point boundary value problem associated to the optimal control problem. Relevant numerical examples are provided to compare with the case of an unrestricted case, and the effects of different maximum restricted cone angles are discussed. The results indicate that （1） for the condition of a restricted cone-angle range the transfer time is longer than that for the unrestricted case and （2） the optimal transfer time increases as the maximum restricted cone angle decreases.
基金This work was partially supported by the National Natural Science Foundation of China(Grant No.10671175)the Program for New Century Excellent Talents in University and the Scientific Research Fund of Hunan Provincial Education Department(Grant No.06C651)
文摘This paper is concerned with the problem of the best restricted range approximations of complex-valued continuous functions. Several properties for the approximating set PΩ such that the classical characterization results and/or the uniqueness results of the best approximations hold are introduced. Under the very mild conditions, we prove that these properties are equivalent that P is a Haar subspce.
文摘设 f 是线性赋范空间 R 中给定的函数,K 为广义多项式集合 V^n(?)R 中满足某种线性约束条件的多项式所成的子集合。本文研究了 K 对 f 的最佳逼近的特征。我们在较一般的情况下,即对空间 R 的范数,函数 f 的性质,以及 K 所满足的线性约束条件不作任何规定的情况下,获得了一种适用范围很广的特征定理,前人已证明的多种常见的约束逼近特征定理都是本文结果的特例,特别。
文摘文章在Cadot et al.(2006)的政治经济学模型基础之上,首先构建了适用于中澳FTA的理论框架,进而分析中澳优惠原产地规则制定的影响因素。研究表明,缔约方进行FTA原产地规则谈判时,产业发展水平、优惠关税幅度是缔约方考量的重要因素。一国产业发展水平越高,另一国就越有动力在FTA谈判中提出制定严格的原产地规则,限制对方优势产业进入本国,以达到保护本国产业的目的。FTA优惠关税幅度越高,缔约方防止第三国"搭便车"和贸易偏转的动机就越强,越倾向制定严格的优惠原产地规则。进一步研究发现,对本国价值含量较高的产品而言,厂商为满足本国消费和销出余量进行产业游说以获取严格优惠原产地规则的可能性较低。因此,为制定合理、合情、合利的优惠原产地规则,有必要从内生贸易政策视角理解优惠原产地规则发挥的政策优势。
基金Project supported by the National High Technology Research and Development Program of China(Grant Nos.2008AA01Z208 and 2009AA01Z405)the Applied Basic Research Program of Sichuan Province of China(Grant No.2010JY0013)the Youth Foundation of Sichuan Province of China(Grant No.2009-28-419)
文摘This paper investigates urban traffic data by analysing the long-range correlation with detrended fluctuation analysis. Through a large number of real data collected by the travel time detection system in Beijing, the variation of flow in different time periods and intersections is studied. According to the long-range correlation in different time scales, it mainly discuss the effect of intersection location in road net, people activity customs and special traffic controls on urban traffic flow. As demonstrated by obtained results, the urban traffic flow represents three-phase characters similar to highway traffic. Moreover, compared by the two groups of data obtained before and after the special traffic restrictions （vehicles with special numbered plates only run in a special workday） enforcement, it indicates that the rules not only reduce the flow but also avoid irregular fluctuation.
文摘Purpose: Belt electrode skeletal muscle electrical stimulation (B-SES) can stimulate large portions of muscles including deep sites without localisation of the stimulation area. The purpose of this study is to investigate both immediate treatment effects of B-SES and long-term treatment effects of B-SES with passive exercise on range of motion (ROM) and muscle tone of lower extremities in bedridden elderly patients. Methods: Outcome measures before and after B-SES treatment alone (4 Hz, 20 min, both lower extremities) were examined for the immediate effect. Outcome measures were: ROM and Modified Ashworth scale (MAS) of hip flexion and adduction;knee flexion and extension;and knee joint distance at position of flexion abduction in hip (distance of knee). A randomized crossover trial was conducted to examine the long-term effect of adding B-SES to passive exercise on ROM and MAS. Results and Discussion: The immediate effect study had 18 patients. ROM and MAS of 4 joint angles in 2 joints and distance of knee significantly improved after B-SES treatment. The long-term effect study had 11 patients. Friedman test revealed ROM and MAS of 4 joint angles in 2 joints and distance of knee significantly improved during B-SES intervention but not control intervention. B-SES in addition to passive stretch has a more statistically significant effect on contracture and spasticity in large portions of the lower extremities of bedridden elderly patients than passive stretching alone. Conclusions: We consider B-SES a useful tool to improve the ROM in lower extremities of bedridden patients.
