Taking the sectional area and the bending moment of inertia as variables for each beam element, the plane frame will possess a stiffness matrix containing parameters.In terms of the symbolic computation software, the ...Taking the sectional area and the bending moment of inertia as variables for each beam element, the plane frame will possess a stiffness matrix containing parameters.In terms of the symbolic computation software, the inverse matrix is solved to obtain the new analytical solution with respect ic characteristics of elements cross-section.The general program is coded in the microcomputer and corresponding exmpales are computed.展开更多
Simulating the dynamic response of trucks requires that a model be constructed and subjected to road inputs. Inclusion or omission of flexible frame effects is often based on intuition or assumption. If frame vibratio...Simulating the dynamic response of trucks requires that a model be constructed and subjected to road inputs. Inclusion or omission of flexible frame effects is often based on intuition or assumption. If frame vibration is assumed to be significant, it is typically incorporated in one of two ways. Either a complex finite element model of the frame is used, or a simplified linear modal expansion model (which assumes small motions) is employed. The typical low-order modal expansion model, while computationally efficient and easier to use, is limited by the fact that 1) large rigid body motions and road grade changes are not supported, and 2) longitudinal dynamics are not coupled to vertical and bounce dynamics. In this paper, a bond graph model is presented which includes coupled pitch and bounce motions, longitudinal dynamics, and transverse frame vibration. Large rigid body motions are allowed, onto which small flexible vibrations are superimposed. Frame flexibility is incorporated using modal expansion of a free-free beam. The model allows for a complete pitch-plane representation in which motive forces can propel the truck forward over varying terrain, including hills. The effect of frame flexibility on vehicle dynamics can then be studied. This is an extension of the typical half-car model in which suspension motion is assumed vertical, pitch angles are small, and longitudinal dynamics are completely decoupled or omitted. Model output shows the effect of frame flexibility on vehicle responses such as forward velocity, pitch angle, and payload acceleration. Participation of individual modes can be seen to increase as road input approaches their natural frequency. The bond graph formalism allows for any or all flexible frame modes to be easily removed from the model if their effects are negligible, and for inclusion of more complex submodels for components such as suspension and engine if desired.展开更多
The rotation of skew bridges in the plane is a common phenomenon in engineering. Traditional measure is to setup pins or limiting displacement with lateral bearings, but the result is not satisfactory. In order to sol...The rotation of skew bridges in the plane is a common phenomenon in engineering. Traditional measure is to setup pins or limiting displacement with lateral bearings, but the result is not satisfactory. In order to solve this problem, the reason for the rotation in the plane is found by philosophy analysis and an idea regarding the application of slantleg frame skew bridges without abutment is brought forward in this paper. Theory and engineering practices indicate that slant-leg rigid frame bridges without abutment can restrain the rotation of skew bridges in the plane to the utmost extent because of its structural characteristics and can fundamentally solve the tough defect of skew bridges.展开更多
A novel technique called physical frame time-slot switching （PFTS） is discussed and its technical and application aspects are analyzed. The format of the ethernet media access control （MAC） frame is borrowed in de...A novel technique called physical frame time-slot switching （PFTS） is discussed and its technical and application aspects are analyzed. The format of the ethernet media access control （MAC） frame is borrowed in defining the physical frame for PFTS and the transmission time for the maximum size of the MAC frame is defined as a physical frame time-slot （PFT）. Consequently, user data can be fed into PFTS and switched in a single layer sub-network in an asynchronous mode.展开更多
为提升非制冷红外焦平面探测器在动态成像应用场景下的综合性能,文中围绕品质因子(Figure of Merit,FOM)开展系统性优化研究。FOM作为衡量探测器噪声等效温差(Noise Equivalent Temperature Difference,NETD)与热时间常数(Thermal Time ...为提升非制冷红外焦平面探测器在动态成像应用场景下的综合性能,文中围绕品质因子(Figure of Merit,FOM)开展系统性优化研究。FOM作为衡量探测器噪声等效温差(Noise Equivalent Temperature Difference,NETD)与热时间常数(Thermal Time Constant,τ)综合性能的关键指标,其优化对于实现快速动态成像具有重要意义。研究首先通过理论分析,识别出影响FOM的关键参数,包括探测器噪声、热容及红外有效吸收率等,并进一步明确桥面面积是调控这些参数以实现灵敏度与响应速度协同优化的关键结构变量。在此基础上,提出以桥面面积调控为核心的优化策略,设计并制备了多种不同尺寸的微桥结构器件,系统研究其对上述FOM关键参数的影响规律。实验结果表明,适当减小桥面面积可显著降低热时间常数,同时对NET D影响可控。最终成功研制出像元尺寸为12μm、阵列规模为640×512的低热时间常数探测器,其实测噪声等效温差为32.4 mK,热时间常数低至5.1 ms,FOM达到165 mK·ms,支持最高120 frame/s的工作帧频。成像测试显示,该探测器在观测快速运动目标时,有效抑制了图像拖尾与果冻效应,显著提升了动态成像的清晰度与实时性。研究表明,通过桥面面积优化可实现FOM的显著改善,为高性能、高帧频非制冷红外成像系统的工程化应用提供了可行的技术方案。展开更多
文摘Taking the sectional area and the bending moment of inertia as variables for each beam element, the plane frame will possess a stiffness matrix containing parameters.In terms of the symbolic computation software, the inverse matrix is solved to obtain the new analytical solution with respect ic characteristics of elements cross-section.The general program is coded in the microcomputer and corresponding exmpales are computed.
文摘Simulating the dynamic response of trucks requires that a model be constructed and subjected to road inputs. Inclusion or omission of flexible frame effects is often based on intuition or assumption. If frame vibration is assumed to be significant, it is typically incorporated in one of two ways. Either a complex finite element model of the frame is used, or a simplified linear modal expansion model (which assumes small motions) is employed. The typical low-order modal expansion model, while computationally efficient and easier to use, is limited by the fact that 1) large rigid body motions and road grade changes are not supported, and 2) longitudinal dynamics are not coupled to vertical and bounce dynamics. In this paper, a bond graph model is presented which includes coupled pitch and bounce motions, longitudinal dynamics, and transverse frame vibration. Large rigid body motions are allowed, onto which small flexible vibrations are superimposed. Frame flexibility is incorporated using modal expansion of a free-free beam. The model allows for a complete pitch-plane representation in which motive forces can propel the truck forward over varying terrain, including hills. The effect of frame flexibility on vehicle dynamics can then be studied. This is an extension of the typical half-car model in which suspension motion is assumed vertical, pitch angles are small, and longitudinal dynamics are completely decoupled or omitted. Model output shows the effect of frame flexibility on vehicle responses such as forward velocity, pitch angle, and payload acceleration. Participation of individual modes can be seen to increase as road input approaches their natural frequency. The bond graph formalism allows for any or all flexible frame modes to be easily removed from the model if their effects are negligible, and for inclusion of more complex submodels for components such as suspension and engine if desired.
文摘The rotation of skew bridges in the plane is a common phenomenon in engineering. Traditional measure is to setup pins or limiting displacement with lateral bearings, but the result is not satisfactory. In order to solve this problem, the reason for the rotation in the plane is found by philosophy analysis and an idea regarding the application of slantleg frame skew bridges without abutment is brought forward in this paper. Theory and engineering practices indicate that slant-leg rigid frame bridges without abutment can restrain the rotation of skew bridges in the plane to the utmost extent because of its structural characteristics and can fundamentally solve the tough defect of skew bridges.
基金Supported by National Natural Science Foundation of China (No. 60372065)
文摘A novel technique called physical frame time-slot switching （PFTS） is discussed and its technical and application aspects are analyzed. The format of the ethernet media access control （MAC） frame is borrowed in defining the physical frame for PFTS and the transmission time for the maximum size of the MAC frame is defined as a physical frame time-slot （PFT）. Consequently, user data can be fed into PFTS and switched in a single layer sub-network in an asynchronous mode.
文摘为提升非制冷红外焦平面探测器在动态成像应用场景下的综合性能,文中围绕品质因子(Figure of Merit,FOM)开展系统性优化研究。FOM作为衡量探测器噪声等效温差(Noise Equivalent Temperature Difference,NETD)与热时间常数(Thermal Time Constant,τ)综合性能的关键指标,其优化对于实现快速动态成像具有重要意义。研究首先通过理论分析,识别出影响FOM的关键参数,包括探测器噪声、热容及红外有效吸收率等,并进一步明确桥面面积是调控这些参数以实现灵敏度与响应速度协同优化的关键结构变量。在此基础上,提出以桥面面积调控为核心的优化策略,设计并制备了多种不同尺寸的微桥结构器件,系统研究其对上述FOM关键参数的影响规律。实验结果表明,适当减小桥面面积可显著降低热时间常数,同时对NET D影响可控。最终成功研制出像元尺寸为12μm、阵列规模为640×512的低热时间常数探测器,其实测噪声等效温差为32.4 mK,热时间常数低至5.1 ms,FOM达到165 mK·ms,支持最高120 frame/s的工作帧频。成像测试显示,该探测器在观测快速运动目标时,有效抑制了图像拖尾与果冻效应,显著提升了动态成像的清晰度与实时性。研究表明,通过桥面面积优化可实现FOM的显著改善,为高性能、高帧频非制冷红外成像系统的工程化应用提供了可行的技术方案。
