共查询到20条相似文献，搜索用时 225 毫秒
1.
Overconstraints exist widely in planar closed chain mechanisms and mechanical systems result in a series of detrimental influences on behavior of machines, and attention is given to them by machine designer. Some analysis methods of overconstraints in planar closed chain mechanisms are presented, and more study due to the faultiness of these methods. In accordance with faultiness of two common kind of methods, formulas method and loop analysis method of degrees of freedom, and by combining these two methods, an useful mechanism overconstraints analysis method which is convenient for computer aided overconstraints analysis is gained via research on the two methods thoroughly and systematically, and some new views about mechanism overconstraints analysis are presented. 相似文献
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改进遗传算法在饲料配方设计中的应用 总被引：1，自引：1，他引：0
针对现有饲料配方软件的局限性,以白绒山羊饲料配方为例,提出一种基于改进遗传算法的求解方法。与标准遗传算法相比,采用随机联赛选择替代轮盘赌模型,优化了选择策略;采用不同的随机数交叉和高斯变异,改进了交叉算子与变异算子。测试结果表明,该方法具有良好的运算效率,拓宽了搜索空间,提高了对重点区域的搜索能力,降低了成本,为复杂问题的优化提供了一种新的思路。 相似文献
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Response Spectrum Method for Seismic Response Calculation of Pipeline System Multiply Supported on Structures 总被引：1，自引：0，他引：1
In order to ensure the function of building in the earthquake, reduce economic losses and facilitate post-disaster relief, it is necessary to accurately evaluate the seismic performance of pipeline system on the structure under seismic excitation. Considering this practical need, seismic response calculation methods of piping systems on structures were systematically studied. Firstly, theoretical derivation was performed based on the pseudo-excitation method for seismic response of pipeline system. It is found that the formula in previous studies has obvious defect: the accurate relative displacement values of degree of freedom near the supports can not be obtained in the formula. Thereby, the theoretical basis for derivation was mended to correct the defect, and the uniform combination expressions available for pipeline's seismic response calculation which is in the form of ground response spectrum or floor response spectrum were presented. Moreover, the simplified formulas and calculation method of correlation coefficients in the obtained expressions were put forward according to the assumption of white noise earthquake excitation. Finally, case studies were adopted to verify the proposed method's effectiveness and applicability in the seismic response calculation of pipeline system. 相似文献
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By using advanced accuracy design concept,Nano-CMM's structure is designed,which is set-up by choosing high degree of accuracy components.The traditional Abbe error is solved due to the design of the structure of the Nano-CMM.By studying the modern accuracy ensuring theory and technique,the nanometer level's analysis of total error source of the Nano-CMM is processed.The uncertainty calculating formula is deduced.The reasonable error distributing and design are done according to the given accuracy target.The needed nanometer level calibrating instruments' technic index are put forward.The result of accuracy design meets the measuring accuracy demand of Nano-CMM is made. 相似文献
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Xiao Pendong Zhang Rongrui Huang Yumin Department of Mechanical Electrical Engineering 《保鲜与加工》1991,(2)
In this paper,a new method of using vector-matrix tosolving a dimensional chain in plane is presented.A mathematical modelis established by means of Rodrig's formula,and the computer programof this method is provided.It is more general and convenient than thegeometric calculation.The numerical calculation is presented in connec-tion with a practical example.The result is the same as that of geometricmethod. 相似文献
8.
不同培养料配方对双孢菇产量的影响 总被引：2，自引：1，他引：1
为充分利用农业秸秆资源,在双孢蘑菇隧道培养料传统麦草配方的基础上,分别添加菇渣和玉米秸秆,对培养料堆制过程中的含水量、pH、含氮量、碳氮比等指标变化趋势进行监测,并对双孢蘑菇产量及农艺学性状进行统计。结果表明,培养料建堆至二次发酵结束均以添加玉米秸秆的配方含水量最高,以传统麦草配方含氮量最高,3个处理的pH差异不大。传统麦草鸡粪配方的产量为18.31 kg/m2,添加菇渣的处理产量为11.43 kg/m2,添加玉米秸秆的处理产量为14.48 kg/m2,添加玉米秸秆还可以显著提高头潮菇所占产量的比重。此外,二次发酵结束后的培养料碳氮比与产量有一定的相关性。 相似文献
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区块链技术及其在农产品质量安全追溯应用的研究进展 总被引：1，自引：1，他引：0
农产品质量安全是一个备受关注的公共卫生问题,追溯应用已成为保障农产品质量安全的有效手段。确保溯源数据的真实性和安全性,成为追溯应用研究的重点和亟需解决的问题。区块链是一个综合多种技术并确保完全去中心化点对点系统完备性的完整技术方案,具有去中心化、透明化、去信任和数据不可篡改等优点,不受传统中心式技术的制约,在农产品质量安全追溯应用上有很大的发展空间。文章概述了区块链技术的基础架构、关键技术及其在追溯应用上的特点,以及区块链技术和农产品质量追溯的内在关系;通过分析基于公有链、联盟链和改良模式的农产品质量安全追溯研究进展和技术特点,总结了区块链技术在农产品质量安全追溯研究中存在的问题,结合区块链发展趋势,提出了注重横向技术融合、加强监测数据信息上链、建立农产品追溯激励惩罚机制等研究展望。 相似文献
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Aimed at the limitations of total fluctuating wind-induced response with combination of background and resonant components using Square Root of the Sum of Squares (SRSS) method, the theoretical combination formulas of fluctuating wind-induced responses and ESWLs are derived based on structural dynamics and random vibration theory. Meanwhile, the refined analysis method is firstly presented by four components formula to compensate the coupling component between background and resonant modes. The proposed procedure avoids the integration process of calculating elastic restoring force and completely considers the modal coupling effects, which can be used to calculate the ESWL for any complex structures. Taking the steel grid roof structure of a large museum as an example, the new method was used to calculate its wind-induced response. Compared with results of complete quadratic combination (CQC), the effectiveness and accuracy of the present approach has been revealed. 相似文献
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Zhang Peiyuan 《保鲜与加工》1988,(2)
Using the flaw-detecting with ultrasonic wave one may know the equivalant area of a crack that burys in the member. If the crack is ellipse shaped, the equivalant area is constant, and the distribution function of its major semiaxle and the plane strain fracture toughness of the material are given, then we would get the probability of reliability of the member under the uniform tension. In this condition, a formula of calculating the probability would be provided in this paper. Because a simple and enough precise approximate function has been introduced the formula in the paper is simple in shape and easy to use. 相似文献
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DYNAMIC ANALYSIS AND NUMERICAL METHOD IN PHE DRIVE MECHANISMS OF THE STEEL-TUBE COLD-ROLLING MACHINE
Wang Hongen 《保鲜与加工》1988,(3)
In this paper, the calculating formulas for partial dynamic balance of crankslider mechanisms are derived in terms of the limear independent vector theory. The driving torque and the optimum selections for partial dynamic balance in drive mechanism of the steeltube cold-rolling machine are carried out. The method in this paper has a universal reference meaning for the partial dynamic balances of crankslider mechanisms. 相似文献
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In the field of signal analyies for time frequency, the DFT is a familiar term. Especially,when its efficient algorithm FFT given, the other operations in signal analyses are also usually translated to DFT as soon as possible so as to enhance the calculating speed. But in our exploning the virtual instrument for time frequency analyzing, two sorts of formulas to calculate DFT and its inverse transform (IDFT) are found. These results are in different value of operation from different signal analysts or from different instruments for time frequency analyzing, their physical meaning are also not clear enough.The period extent theory some previous document based on when defined DFT is firstly expatiated. Then, separately with future defining coefficient method and analogy evolvement method, the authors argue that, based on the period extent theory, it is more rational to calculate DFT with the formula given. A shortage is pointed out and corrected is appeared in some previous documents when having given the formula of DFT. The improper view is also clarified that the reason why there are two sorts of formulas is make by custom.The rationality of the authors view with three examples is visually verified in the end. 相似文献
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According to the field theory of additional deformation on pre - stressed configuration , in the paper , the ordinary expression of the governing equation and variational equation of elastic buckling are brought forward . Under the theory system, through lowering dimensions, the governing equation and variational equation for the critical condition solution of elastic buckling of a plane arch are deduced, and the eigenvalues problem of the linear homogeneous differential equations corresponding to the equations are concluded While Abandoning the plane assumption and considering shearing deformation, the linear finite element method arithmetic of bending bar's cross section containing six degree of freedom is given. The process of derivation and calculational results show that, under this system info, the finite element equations of bending bar deduced are accurate and easy to be used to numeric calculations, and the conclusion achieved is more practical. 相似文献
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By means of symbol operation of Matlab and the convergent condition of the linear muhistp method formula, the authors attained the well posed convergent formulas directly for all linear 2-step methods. Some convergent formulas are gotten after screening and the fraction coefficients, errors coefficients, orders and intervals of absolute stability are calculated. Then figure of region of absolute stability of the absolute stability formula is drawn by means of root locus method. The performance of those formulas simply is analyzed. One new A - stable formula of linear 2-step methods of order 2 is derived and proved. 相似文献
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Based on the principle of interactive analysis,the deformation equation of hybrid structure which contains rigid character value is established using the analysis of the frame - shear wall structure for reference, considering the rigid zone between concrete beam and concrete - tube, the shear deformation of concrete - tube, axial deformation of steel frames and semi - rigid connection between steel columns and concrete beams. Assuming the hybrid structure to be a continuous elastic structure with infinite degree of freedom, a free vibration equation has been built and the formula for calculating free vibration period has been deduced. The influences of various parameters to the coefficient of free vibration period relating to rigid character value are discussed according to some diagrams. It is shown that the rigid zone can lessen the free vibration period but the shear deformation of concrete - tube, axial deformation of steel frames, and the semi -rigid connection between steel columns and concrete beams can enhance the free vibration period. 相似文献
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We calculated the elastic plastic finite element method (FEM) of three adobe walls and three composite adobe walls of differing thicknesses, and analyzed their lateral resistance capacities, crack shapes and ductility. Based on the results, a simplified formula is put forward for calculating the lateral resistance capacities of composite adobe walls. The formula provides a basis for designing composite adobe walls. In addition, we estimated the seismic effects of earthquakes of varying degrees and frequency of intensity (basic and rare intensity) on composite adobe walls. The results indicate that traditional adobe walls with timber columns and beams can satisfy the criterion of rare earthquakes of seismic zone 9. The results provide a basis for the transformation and seismic reinforcement of traditional residential buildings in Xinjiang. 相似文献
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The flow of people changes very greatly in the public areas of public buildings, so the energy demand should also change with the flow of people. However, under the traditional model, the pedestrian flow is rarely considered when accounting energy output, which causes some of the energy invalid. How to assess the energy efficiency to reduce energy waste is an emergent problem to be solved for building energy conservation. The concept of energy utilization efficiency is put forward to judge the degree of utilization of energy, and the formula for calculating energy utilization efficiency is also provided. In a hospital public waiting area, a lot of experiments have been carried out. By comparing the energy consumption before and after the experiments, it is found that energy utilization efficiency can assess the effectiveness of energy. And to improve the energy efficiency of buildings greatly in public areas can be realized by promoting the energy utilization efficiency. 相似文献
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This paper develops a new method of extra degree of freedom (extra DOF) for the beam element with end release. Based on the strain matrix with extra DOFs, it derives the stiffness transformation matrix of released element, which can be applied to situations along global coordinate system or element local coordinate system. The effects of end release processing method for beams with large displacement are analyzed, and the results compared with those from other existing methods show that the extra DOF processing method has higher performance and accuracy. 相似文献
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不同配方基质对日光温室辣椒果实品质及产量的影响 总被引：3，自引：1，他引：2
为筛选出适合当地日光温室辣椒的栽培基质,以‘陇椒3号’辣椒为试材,以腐熟的作物秸秆、羊粪、牛粪、菇渣为主要原料,复配草炭、蛭石、河沙,按照不同体积比制成8种不同配方栽培基质,以当地传统基质和商品基质作为对照,研究不同配方基质的理化性状以及对辣椒品质和产量的影响。结果表明：配方G（玉米秆:牛粪:草炭:蛭石:河沙=2:3.5:1:1:2.5）、配方H（玉米秆:牛粪:草炭:河沙=2:3.5:1:3.5）、配方J（玉米秆:牛粪:草炭:蛭石:河沙:菇渣=2:2.5:1:1:2.5:1）基质具有优良的理化性状,其EC、容重、孔隙度、气水比均在最适范围内,通气和持水能力强;并且这3种基质栽培的辣椒果实可溶性糖和Vc含量高,硝酸盐含量符合国家蔬菜标准,品质优异,产量分别为60492.06、59809.52、56939.68 kg/hm2,显著高于传统基质（配方A）。综上所述,G、H、J配方基质理化性状优良,辣椒果实品质良好、产量高,同时以农业废弃物和河沙为主要原料,成本较低,可在当地推广使用。 相似文献