The cutting properties of the functionally gradient ceramic cutting tools relate closely to the gradient distribution. A cutting model of the functionally gradient ceramic tool is firstly designed in the present paper...The cutting properties of the functionally gradient ceramic cutting tools relate closely to the gradient distribution. A cutting model of the functionally gradient ceramic tool is firstly designed in the present paper. The optimum of gradient distribution is obtained by way of the FEM analyses.展开更多
Based on the deep understanding of the requirements of cutting conditions on ceramic tools, a design model for functionally gradient ceramic tool materials with symmetrical composition distribution was presented in th...Based on the deep understanding of the requirements of cutting conditions on ceramic tools, a design model for functionally gradient ceramic tool materials with symmetrical composition distribution was presented in this paper, according to which an Al 2O 3-TiC functionally gradient ceramic tool material FG-1 was synthesized by powder-laminating and uniaxially hot-pressing technique. The thermal shock resistance of the Al 2O 3-TiC functionally gradient ceramics FG-1 was evaluated by water quenching and subsequent three-point bending tests of flexural strength diminution. Comparisons were made with results from parallel experiments conducted using a homogeneous Al 2O 3-TiC ceramics. Functionally gradient ceramics exhibited higher retained strength under all thermal shock temperature differences compared to homogeneous ceramics, indicating the higher thermal shock resistance. The experimental results were supported by the calculation of transient thermal stress field. The cutting performance of the Al 2O 3-TiC functionally gradient ceramic tool FG-1 was also investigated in rough turning the cylindrical surface of exhaust valve of diesel engine in comparison with that of a common Al 2O 3-TiC ceramic tool LT55. The results indicated that the tool life of FG-1 increased by 50 percent over that of LT55. Tool life of LT55 was mainly controlled by thermal shock cracking which was accompanied by mechanical shock. While tool life of FG-1 was mainly controlled by mechanical fatigue crack extension rather than thermal shock cracking, revealing the less thermal shock susceptibility of functionally gradient ceramics than that of common ceramics.展开更多
Based on the analyses of the severity of cutting process as well as the failure mechanisms of ceramic tools, a model for designing functionally gradient ceramic tool materials with symmetrical distribution is presente...Based on the analyses of the severity of cutting process as well as the failure mechanisms of ceramic tools, a model for designing functionally gradient ceramic tool materials with symmetrical distribution is presented, by which a Al 2O 3/(W,Ti)C ceramic tool material FG 2 was developed. Multi objective optimization method was employed in designing the compositional distribution of this ceramic tool material. The results of both continuous and intermittent cutting tests are indicative of the much better cutting behavior of the functionally gradient ceramic tool FG 2 than that of the common ceramic tool SG 4.展开更多
目的基于健康测量工具选择的共识标准指南系统评价慢性阻塞性肺疾病(简称慢阻肺)患者呼吸功能评估工具的方法学质量和测量属性质量,为临床工作者选择最佳评估工具提供依据。方法计算机检索PubMed、Web of Science、Embase、中国知网、...目的基于健康测量工具选择的共识标准指南系统评价慢性阻塞性肺疾病(简称慢阻肺)患者呼吸功能评估工具的方法学质量和测量属性质量,为临床工作者选择最佳评估工具提供依据。方法计算机检索PubMed、Web of Science、Embase、中国知网、维普数据库、万方数据库中有关慢阻肺患者肺功能评估工具的研究,检索时限为建库至2024年4月。由2名研究者按照文献纳入及排除标准独立获取和筛选文献。基于COSIMIN指南对纳入的评估工具进行评价,形成对于工具的最终推荐意见。结果共纳入18项研究,包含14项慢阻肺患者呼吸症状评估工具。其中SOBDA、PFSDQ-M、汉化Dyspnoea-12、挪威版Dyspnoea-12、RSQ为A级推荐,汉化PFSDQ修订版、SOBQ-USCD版、S-CRQ、CRQ-SR、C-MRADLQ、BCSS为B级推荐,阿拉伯语版Dyspnoea-12、汉化COPD-MSD、C-SOBQ为C级推荐。结论SOBDA、PFSDQ-M、汉化Dyspnoea-12、挪威版Dyspnoea-12和RSQ量表的各个测量学属性得到了较为全面地评价,具有较好的信效度。针对我国国情,暂推荐使用汉化Dyspnoea-12,但其他测量学特性仍有待验证。展开更多
HEST is a practical integrated expert system tool. Its basis is a knowledge programming language FFLL, characterized by a combination of fuzzy logic and function paradigms. The tool integrates alot of important knowle...HEST is a practical integrated expert system tool. Its basis is a knowledge programming language FFLL, characterized by a combination of fuzzy logic and function paradigms. The tool integrates alot of important knowledge processing capabilities such as fuzzy reasoning, function computation, knowledge compilation and explanation, knowledge base maintenance, as well as practical programming functions, e.g., editing, filing, compiling, module imbedding, etc., constructing, a user--friendly knowledge application environment, HEST can enable expert system development in various domaills quickly and easily.This paper gives an outline of the design and implementation of HEST.展开更多
In short-wavelength optics,millimetre spot-sized ion beam figuring(IBF)is an effective method to eliminate form errors with spatial wavelengths ranging from 10 mm to 1 mm.In this case,the full width at half maximum(FW...In short-wavelength optics,millimetre spot-sized ion beam figuring(IBF)is an effective method to eliminate form errors with spatial wavelengths ranging from 10 mm to 1 mm.In this case,the full width at half maximum(FWHM)of the tool influence function(TIF)is typically below 2 mm.In IBF,accurate measurement of a small-sized TIF is critical in determining the removal rate and distribution.In existing research,the online measurement of the TIF has been achieved by scanning the beam current density(BCD)distribution with the Faraday cup(FC).However,due to the convolution effect during scanning,this method is not sufficiently accurate for small-sized TIFs,posing considerable limitations to high-precision applications.This paper presents an in-depth analysis of the convolution effect in TIF measurements.The obtained findings are applied to a corrective TIF measurement method and verified by calculation,simulation,and experiment.The results demonstrate that the proposed method can effectively reduce the measurement error.Specifically,for TIFs with FWHMs ranging from 0.5 to 1 mm,the average measurement error of the peak removal rate(PRR)is reduced from 47.4%to 3.1%,and the average error in the FWHM is reduced from 51.7%to 2.6%.The application of this method to a polishing experiment reduces the rootmean-square(RMS)of the aspherical optical mirror from 1.7 nm to 0.4 nm;moreover,the average convergence rate is 76.4%,which is within the target spatial wavelength range of 15 mm to 3.6 mm.Thus,this paper provides practical guidance for millimetre spot-sized IBF,and is promising for application in high-precision optics.展开更多
构造一种适用于反向传播(backpropagation,BP)神经网络的新型激活函数Lfun(logarithmic series function),并使用基于该函数的BP神经网络进行机床能耗状态的预测。首先,分析Sigmoid系列和ReLU系列激活函数的特点和缺陷,结合对数函数,构...构造一种适用于反向传播(backpropagation,BP)神经网络的新型激活函数Lfun(logarithmic series function),并使用基于该函数的BP神经网络进行机床能耗状态的预测。首先,分析Sigmoid系列和ReLU系列激活函数的特点和缺陷,结合对数函数,构造了一种非线性分段含参数激活函数。该函数可导且光滑、导数形式简单、单调递增、输出均值为零,且通过可变参数使函数形式更灵活;其次,通过数值仿真实验在公共数据集上将Lfun函数与Sigmoid、ReLU、tanh、Leaky_ReLU和ELU函数的性能进行对比;最后,使用基于Lfun函数的BP神经网络进行机床能耗状态的预测。实验结果表明,使用Lfun函数的BP神经网络相较于使用其他几种常用激活函数的网络具有更好的性能。展开更多
This paper presents the notion of the global execution context of a task as a representational construct for analysing complexity in software evolution. Based on this notion a visual notation and a supporting tool are...This paper presents the notion of the global execution context of a task as a representational construct for analysing complexity in software evolution. Based on this notion a visual notation and a supporting tool are presented to support specification of a system’s global execution context. A system’s global execution context is conceived as an evolving network of use scenarios depicted by nodes and links designating semantic relationships between scenarios. A node represents either a base or a growth scenario. Directed links characterize the transition from one node to another by means of semantic scenario relationships. Each growth scenario is generated following a critique (or screening) of one or more base or reference scenarios. Subsequently, representative growth scenarios are compiled and consolidated in the global execution context graph. The paper describes the stages of this process, presents the tool designed to facilitate the construction of the global execution context graph and elaborates on recent practice and experience.展开更多
基金supported by the National Natural Science Foundation of China(59875091)
文摘The cutting properties of the functionally gradient ceramic cutting tools relate closely to the gradient distribution. A cutting model of the functionally gradient ceramic tool is firstly designed in the present paper. The optimum of gradient distribution is obtained by way of the FEM analyses.
文摘Based on the deep understanding of the requirements of cutting conditions on ceramic tools, a design model for functionally gradient ceramic tool materials with symmetrical composition distribution was presented in this paper, according to which an Al 2O 3-TiC functionally gradient ceramic tool material FG-1 was synthesized by powder-laminating and uniaxially hot-pressing technique. The thermal shock resistance of the Al 2O 3-TiC functionally gradient ceramics FG-1 was evaluated by water quenching and subsequent three-point bending tests of flexural strength diminution. Comparisons were made with results from parallel experiments conducted using a homogeneous Al 2O 3-TiC ceramics. Functionally gradient ceramics exhibited higher retained strength under all thermal shock temperature differences compared to homogeneous ceramics, indicating the higher thermal shock resistance. The experimental results were supported by the calculation of transient thermal stress field. The cutting performance of the Al 2O 3-TiC functionally gradient ceramic tool FG-1 was also investigated in rough turning the cylindrical surface of exhaust valve of diesel engine in comparison with that of a common Al 2O 3-TiC ceramic tool LT55. The results indicated that the tool life of FG-1 increased by 50 percent over that of LT55. Tool life of LT55 was mainly controlled by thermal shock cracking which was accompanied by mechanical shock. While tool life of FG-1 was mainly controlled by mechanical fatigue crack extension rather than thermal shock cracking, revealing the less thermal shock susceptibility of functionally gradient ceramics than that of common ceramics.
文摘Based on the analyses of the severity of cutting process as well as the failure mechanisms of ceramic tools, a model for designing functionally gradient ceramic tool materials with symmetrical distribution is presented, by which a Al 2O 3/(W,Ti)C ceramic tool material FG 2 was developed. Multi objective optimization method was employed in designing the compositional distribution of this ceramic tool material. The results of both continuous and intermittent cutting tests are indicative of the much better cutting behavior of the functionally gradient ceramic tool FG 2 than that of the common ceramic tool SG 4.
文摘目的基于健康测量工具选择的共识标准指南系统评价慢性阻塞性肺疾病(简称慢阻肺)患者呼吸功能评估工具的方法学质量和测量属性质量,为临床工作者选择最佳评估工具提供依据。方法计算机检索PubMed、Web of Science、Embase、中国知网、维普数据库、万方数据库中有关慢阻肺患者肺功能评估工具的研究,检索时限为建库至2024年4月。由2名研究者按照文献纳入及排除标准独立获取和筛选文献。基于COSIMIN指南对纳入的评估工具进行评价,形成对于工具的最终推荐意见。结果共纳入18项研究,包含14项慢阻肺患者呼吸症状评估工具。其中SOBDA、PFSDQ-M、汉化Dyspnoea-12、挪威版Dyspnoea-12、RSQ为A级推荐,汉化PFSDQ修订版、SOBQ-USCD版、S-CRQ、CRQ-SR、C-MRADLQ、BCSS为B级推荐,阿拉伯语版Dyspnoea-12、汉化COPD-MSD、C-SOBQ为C级推荐。结论SOBDA、PFSDQ-M、汉化Dyspnoea-12、挪威版Dyspnoea-12和RSQ量表的各个测量学属性得到了较为全面地评价,具有较好的信效度。针对我国国情,暂推荐使用汉化Dyspnoea-12,但其他测量学特性仍有待验证。
文摘HEST is a practical integrated expert system tool. Its basis is a knowledge programming language FFLL, characterized by a combination of fuzzy logic and function paradigms. The tool integrates alot of important knowledge processing capabilities such as fuzzy reasoning, function computation, knowledge compilation and explanation, knowledge base maintenance, as well as practical programming functions, e.g., editing, filing, compiling, module imbedding, etc., constructing, a user--friendly knowledge application environment, HEST can enable expert system development in various domaills quickly and easily.This paper gives an outline of the design and implementation of HEST.
基金supported by National Natural Science Foundation of China(62127901,12103054,62405314,62305333,62375260)National Key Research and Development Program of China(2022YFB3403405)+4 种基金Scientific and Technological Development Program of Jilin(SKL202402021)Youth Innovation Promotion Association of the Chinese Academy of Sciences(2019221,Y2023062)Youth Elite Scientists Sponsorship Program of CAST(2022QNRC001)Young Elite Scientists Sponsorship Program of Jilin Province(QT202222)Scientific and Technological Program of Changchun(2024GZZ19).
文摘In short-wavelength optics,millimetre spot-sized ion beam figuring(IBF)is an effective method to eliminate form errors with spatial wavelengths ranging from 10 mm to 1 mm.In this case,the full width at half maximum(FWHM)of the tool influence function(TIF)is typically below 2 mm.In IBF,accurate measurement of a small-sized TIF is critical in determining the removal rate and distribution.In existing research,the online measurement of the TIF has been achieved by scanning the beam current density(BCD)distribution with the Faraday cup(FC).However,due to the convolution effect during scanning,this method is not sufficiently accurate for small-sized TIFs,posing considerable limitations to high-precision applications.This paper presents an in-depth analysis of the convolution effect in TIF measurements.The obtained findings are applied to a corrective TIF measurement method and verified by calculation,simulation,and experiment.The results demonstrate that the proposed method can effectively reduce the measurement error.Specifically,for TIFs with FWHMs ranging from 0.5 to 1 mm,the average measurement error of the peak removal rate(PRR)is reduced from 47.4%to 3.1%,and the average error in the FWHM is reduced from 51.7%to 2.6%.The application of this method to a polishing experiment reduces the rootmean-square(RMS)of the aspherical optical mirror from 1.7 nm to 0.4 nm;moreover,the average convergence rate is 76.4%,which is within the target spatial wavelength range of 15 mm to 3.6 mm.Thus,this paper provides practical guidance for millimetre spot-sized IBF,and is promising for application in high-precision optics.
文摘构造一种适用于反向传播(backpropagation,BP)神经网络的新型激活函数Lfun(logarithmic series function),并使用基于该函数的BP神经网络进行机床能耗状态的预测。首先,分析Sigmoid系列和ReLU系列激活函数的特点和缺陷,结合对数函数,构造了一种非线性分段含参数激活函数。该函数可导且光滑、导数形式简单、单调递增、输出均值为零,且通过可变参数使函数形式更灵活;其次,通过数值仿真实验在公共数据集上将Lfun函数与Sigmoid、ReLU、tanh、Leaky_ReLU和ELU函数的性能进行对比;最后,使用基于Lfun函数的BP神经网络进行机床能耗状态的预测。实验结果表明,使用Lfun函数的BP神经网络相较于使用其他几种常用激活函数的网络具有更好的性能。
文摘This paper presents the notion of the global execution context of a task as a representational construct for analysing complexity in software evolution. Based on this notion a visual notation and a supporting tool are presented to support specification of a system’s global execution context. A system’s global execution context is conceived as an evolving network of use scenarios depicted by nodes and links designating semantic relationships between scenarios. A node represents either a base or a growth scenario. Directed links characterize the transition from one node to another by means of semantic scenario relationships. Each growth scenario is generated following a critique (or screening) of one or more base or reference scenarios. Subsequently, representative growth scenarios are compiled and consolidated in the global execution context graph. The paper describes the stages of this process, presents the tool designed to facilitate the construction of the global execution context graph and elaborates on recent practice and experience.
