Load characteristics are the main factor to affect voltage stability. In addition, load modeling reflecting the actual load characteristics has been a well—known difficult problem and unsolved so far, It is mainly du...Load characteristics are the main factor to affect voltage stability. In addition, load modeling reflecting the actual load characteristics has been a well—known difficult problem and unsolved so far, It is mainly due to the fact that the load composition, amount and characteristics are always changing. This paper introduces the slip into the equivalent impedance load model to analyze load characteristic, the varying slip is employed to indicate?time-varying load characteristic precisely, and considering the dissimilar load behaviors, discusses node voltage, power during the changes of load characteristic, obtains voltage inflexion and power inflexion, and then analyzes the mechanism of power system voltage instability based on static voltage stability region. An example indicates the feasibility of the method.展开更多
The rubber circular plate is considered as a kind of membrane. Based on the character that there exists no bending moment inside a membrane, the geometric behavior of the rubber circular plate in expanding state was d...The rubber circular plate is considered as a kind of membrane. Based on the character that there exists no bending moment inside a membrane, the geometric behavior of the rubber circular plate in expanding state was described with the aid of a group of mathematic method. The relationship between deflection and load was attained by means of calculating stress and strain inside the curved surface of rubber plate. Meantime, based on Hencky method, the relationship between deflection and load was attained and considered as the Hencky solution. The different results given rise by the two different resolving methods were compared. The deviation results from the Hencky method was discussed, and a kind of correcting method was put forward.展开更多
To investigate the mechanical properties of a dowel action under fatigue loads, nine reinforced concrete specimens were fabricated, and the monotonic and fatigue loadings were performed on these specimens, respectivel...To investigate the mechanical properties of a dowel action under fatigue loads, nine reinforced concrete specimens were fabricated, and the monotonic and fatigue loadings were performed on these specimens, respectively. All of these specimens were divided into two series. Six specimens in SeriesⅠwith different bar diameters of 12, 20 and 25 mm were subjected to monotonic loads and were used to confirm the ultimate bearing capacity. The remaining three specimens in Series Ⅱ were subjected to fatigue loads and were designed to investigate the attenuation character of dowel action and the fatigue failure modes. The test results show that the accumulated fatigue damage due to fatigue loads can reduce the ultimate bearing capacity of specimens. With the increase in fatigue loads, the failure mode can transform to fatigue rupture of the dowel bar under the serviceability loading state,i. e. 55% of the monotonic capacity. The fatigue life is determined by the fatigue properties of steel and concrete.Based on the test data, the failure process of dowel action can be divided into two stages： the accumulation of fatigue damage and the fatigue rupture of dowel bar.展开更多
With annually increased coal mining depth,gas extraction becomes more and more problematic.The gas extraction efect depends on coal seam permeability,which,in turn,is afected by many factors,including loading and unlo...With annually increased coal mining depth,gas extraction becomes more and more problematic.The gas extraction efect depends on coal seam permeability,which,in turn,is afected by many factors,including loading and unloading stresses and strains in the coal seam.Stresses induce internal cracks,resulting in cleats and gas emission channels,the coal seam permeability permanently changes accordingly.To clarify the stress-induced efects on coal seam permeability,this survey summarized the available approaches used to link the stress path and seepage law in the coal body seepage law,which can be classifed into two design methods:single load variation and combined feld mining method.The characterization methods used to observe the surface of coal samples and three-dimensional reconstruction include electron microscopy,CT scanning,and Nuclear Magnetic Resonance(NMR).According to the stress paths designed by the above two approaches,the seepage laws and similarities of three kinds of coal samples with the fractured structure were summarized in this paper.The following directions are recommended to study the seepage law of coal bodies with three kinds of fractured structures under stress.Firstly,the stress path of the experimental coal body should be designed by the combined feld mining method.The stressed environment of a deep coal seam is complicated,and the axial and confning pressures change simultaneously.Therefore,one cannot fully refect the real situation on-site by studying permeability evolution alone.Secondly,during the coal seam mining,the stressed state changes from time to time,and the development of coal seam fractures is afected by mining.When studying the stress efect on seepage of coal samples,the fractured structure of coal samples should be considered.Finally,the available structural characterization methods of coal samples can be combined with the 3D printing technology,which would produce artifcial samples with the fractured structure characteristics of natural coal.展开更多
针对未充分考虑气象因子交互作用、模型非线性表达能力存在局限性等问题,基于复合因子构造提出一种结合科尔莫戈洛夫-阿诺德网络(Kolmogorov-Arnold network,KAN)与双向长短期记忆(bidirectional long short-term memory,BiLSTM)网络的...针对未充分考虑气象因子交互作用、模型非线性表达能力存在局限性等问题,基于复合因子构造提出一种结合科尔莫戈洛夫-阿诺德网络(Kolmogorov-Arnold network,KAN)与双向长短期记忆(bidirectional long short-term memory,BiLSTM)网络的电力负荷预测方法。首先,通过高斯混合模型(Gaussian mixture model,GMM)将有相似特征的用电负荷曲线归类。其次,提出复合因子构造策略,通过皮尔逊相关性分析量化气象因子与负荷的线性关联度,筛选关键气象变量并构造交互项,充分挖掘气象因素间潜在交互作用,结合最大信息系数(maximal information coefficient,MIC)进一步提取非线性依赖特征。最后,针对传统BiLSTM模型全连接层对高维非线性特征学习能力受限的问题,引入KAN替代全连接层,利用其非线性映射能力,构建KAN-BiLSTM混合预测模型。基于某地区实际数据进行算例分析,实验结果表明,在春秋日、夏季常温日、夏季高温日、冬季日4类不同负荷模式下所提方法均具有较高的预测准确率和普适性,可为多气象耦合场景下的电力负荷精准预测提供一种可行的解决方案。展开更多
试件尺度的岩石受载破裂过程中,其本身结构发生变形、破坏的同时,包含了地球物理属性参数信息的变化,如应变量、电阻率、波速等。通过对受载中的岩石试件进行地球物理参数测试,可定性或定量地感知其内部结构、强度等特征变化,有助于了...试件尺度的岩石受载破裂过程中,其本身结构发生变形、破坏的同时,包含了地球物理属性参数信息的变化,如应变量、电阻率、波速等。通过对受载中的岩石试件进行地球物理参数测试,可定性或定量地感知其内部结构、强度等特征变化,有助于了解岩石试件破裂机理,进而解决一系列岩体工程测试问题。基于Web of Science论文检索系统搜索出岩石试件加载测试的文献资料,利用CiteSpace软件对岩石试件加载测试现状进行分析,并详细阐述了几种常用测试方法的原理及研究进展。结合煤系地层深部采场领域研究现状,分析、总结岩石试件受载测试研究过程中存在的不足,并对地球物理参数采集、装置研发与微-宏观测试融合等方面提出展望。展开更多
Characterization of power transistors is an indispensable step in the design of radio frequency and mi- crowave power amplifiers. A full harmonic load-pull measurement setup is normally required for the accurate and c...Characterization of power transistors is an indispensable step in the design of radio frequency and mi- crowave power amplifiers. A full harmonic load-pull measurement setup is normally required for the accurate and comprehensive characterization of RF power transistors. The setup is usually highly complex, leading to a rela- tively high hardware cost and low measurement throughput. This paper presents X-parameter measurement on a gallium nitride （GaN） high-electron-mobility transistor and studies the potential of utilizing an X-parameter-based modeling technique to highly reduce the complexity of the harmonic load-pull measurement setup for transistor characterization. During the X-parameter measurement and characterization, load impedance of the device is tuned and controlled only at the fundamental frequency and is left uncontrolled at other higher harmonics. However, it proves preliminarily that the extracted X-parameters can still predict the behavior of the device with moderate to high accuracy, when the load impedance is tuned up to the third-order harmonic frequency. It means that a fundamental-only load-pull test setup is already enough even though the device is to be characterized under load tuning up to the third-order harmonic frequency, by utilizing X-parameters.展开更多
文摘Load characteristics are the main factor to affect voltage stability. In addition, load modeling reflecting the actual load characteristics has been a well—known difficult problem and unsolved so far, It is mainly due to the fact that the load composition, amount and characteristics are always changing. This paper introduces the slip into the equivalent impedance load model to analyze load characteristic, the varying slip is employed to indicate?time-varying load characteristic precisely, and considering the dissimilar load behaviors, discusses node voltage, power during the changes of load characteristic, obtains voltage inflexion and power inflexion, and then analyzes the mechanism of power system voltage instability based on static voltage stability region. An example indicates the feasibility of the method.
文摘The rubber circular plate is considered as a kind of membrane. Based on the character that there exists no bending moment inside a membrane, the geometric behavior of the rubber circular plate in expanding state was described with the aid of a group of mathematic method. The relationship between deflection and load was attained by means of calculating stress and strain inside the curved surface of rubber plate. Meantime, based on Hencky method, the relationship between deflection and load was attained and considered as the Hencky solution. The different results given rise by the two different resolving methods were compared. The deviation results from the Hencky method was discussed, and a kind of correcting method was put forward.
基金The Fund of the National Key Laboratory in China(No.2015-Ky-01)the National Key Technology R&D Program of China(No.2015BAB07B07)
文摘To investigate the mechanical properties of a dowel action under fatigue loads, nine reinforced concrete specimens were fabricated, and the monotonic and fatigue loadings were performed on these specimens, respectively. All of these specimens were divided into two series. Six specimens in SeriesⅠwith different bar diameters of 12, 20 and 25 mm were subjected to monotonic loads and were used to confirm the ultimate bearing capacity. The remaining three specimens in Series Ⅱ were subjected to fatigue loads and were designed to investigate the attenuation character of dowel action and the fatigue failure modes. The test results show that the accumulated fatigue damage due to fatigue loads can reduce the ultimate bearing capacity of specimens. With the increase in fatigue loads, the failure mode can transform to fatigue rupture of the dowel bar under the serviceability loading state,i. e. 55% of the monotonic capacity. The fatigue life is determined by the fatigue properties of steel and concrete.Based on the test data, the failure process of dowel action can be divided into two stages： the accumulation of fatigue damage and the fatigue rupture of dowel bar.
基金supported by the National Natural Science Foundation of China(52174129,52104155,51704274)Independent Research Project of State Key Laboratory of Coal Resources and Safe Mining,CUMT(SKLCRSM22X006)Jiangsu Province Scientifc Research and Practice Innovation Project(KYCX21_2390).
文摘With annually increased coal mining depth,gas extraction becomes more and more problematic.The gas extraction efect depends on coal seam permeability,which,in turn,is afected by many factors,including loading and unloading stresses and strains in the coal seam.Stresses induce internal cracks,resulting in cleats and gas emission channels,the coal seam permeability permanently changes accordingly.To clarify the stress-induced efects on coal seam permeability,this survey summarized the available approaches used to link the stress path and seepage law in the coal body seepage law,which can be classifed into two design methods:single load variation and combined feld mining method.The characterization methods used to observe the surface of coal samples and three-dimensional reconstruction include electron microscopy,CT scanning,and Nuclear Magnetic Resonance(NMR).According to the stress paths designed by the above two approaches,the seepage laws and similarities of three kinds of coal samples with the fractured structure were summarized in this paper.The following directions are recommended to study the seepage law of coal bodies with three kinds of fractured structures under stress.Firstly,the stress path of the experimental coal body should be designed by the combined feld mining method.The stressed environment of a deep coal seam is complicated,and the axial and confning pressures change simultaneously.Therefore,one cannot fully refect the real situation on-site by studying permeability evolution alone.Secondly,during the coal seam mining,the stressed state changes from time to time,and the development of coal seam fractures is afected by mining.When studying the stress efect on seepage of coal samples,the fractured structure of coal samples should be considered.Finally,the available structural characterization methods of coal samples can be combined with the 3D printing technology,which would produce artifcial samples with the fractured structure characteristics of natural coal.
文摘针对未充分考虑气象因子交互作用、模型非线性表达能力存在局限性等问题,基于复合因子构造提出一种结合科尔莫戈洛夫-阿诺德网络(Kolmogorov-Arnold network,KAN)与双向长短期记忆(bidirectional long short-term memory,BiLSTM)网络的电力负荷预测方法。首先,通过高斯混合模型(Gaussian mixture model,GMM)将有相似特征的用电负荷曲线归类。其次,提出复合因子构造策略,通过皮尔逊相关性分析量化气象因子与负荷的线性关联度,筛选关键气象变量并构造交互项,充分挖掘气象因素间潜在交互作用,结合最大信息系数(maximal information coefficient,MIC)进一步提取非线性依赖特征。最后,针对传统BiLSTM模型全连接层对高维非线性特征学习能力受限的问题,引入KAN替代全连接层,利用其非线性映射能力,构建KAN-BiLSTM混合预测模型。基于某地区实际数据进行算例分析,实验结果表明,在春秋日、夏季常温日、夏季高温日、冬季日4类不同负荷模式下所提方法均具有较高的预测准确率和普适性,可为多气象耦合场景下的电力负荷精准预测提供一种可行的解决方案。
文摘试件尺度的岩石受载破裂过程中,其本身结构发生变形、破坏的同时,包含了地球物理属性参数信息的变化,如应变量、电阻率、波速等。通过对受载中的岩石试件进行地球物理参数测试,可定性或定量地感知其内部结构、强度等特征变化,有助于了解岩石试件破裂机理,进而解决一系列岩体工程测试问题。基于Web of Science论文检索系统搜索出岩石试件加载测试的文献资料,利用CiteSpace软件对岩石试件加载测试现状进行分析,并详细阐述了几种常用测试方法的原理及研究进展。结合煤系地层深部采场领域研究现状,分析、总结岩石试件受载测试研究过程中存在的不足,并对地球物理参数采集、装置研发与微-宏观测试融合等方面提出展望。
文摘Characterization of power transistors is an indispensable step in the design of radio frequency and mi- crowave power amplifiers. A full harmonic load-pull measurement setup is normally required for the accurate and comprehensive characterization of RF power transistors. The setup is usually highly complex, leading to a rela- tively high hardware cost and low measurement throughput. This paper presents X-parameter measurement on a gallium nitride （GaN） high-electron-mobility transistor and studies the potential of utilizing an X-parameter-based modeling technique to highly reduce the complexity of the harmonic load-pull measurement setup for transistor characterization. During the X-parameter measurement and characterization, load impedance of the device is tuned and controlled only at the fundamental frequency and is left uncontrolled at other higher harmonics. However, it proves preliminarily that the extracted X-parameters can still predict the behavior of the device with moderate to high accuracy, when the load impedance is tuned up to the third-order harmonic frequency. It means that a fundamental-only load-pull test setup is already enough even though the device is to be characterized under load tuning up to the third-order harmonic frequency, by utilizing X-parameters.
