共查询到20条相似文献,搜索用时 31 毫秒
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J.P. Protzen 《Design Studies》1982,3(2):85-91
This paper discusses whar are the proper criteria for decision-making in planning and design. A parable introduces three principles by which to justify decisions: the principle of indifference or chance, the principle of absolute truth and the principle of idoneity, where the idoneus is ‘that which is proper to, and conforms with, the ends and intentions’. 相似文献
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为了研究采煤机截割过程中的动力学特性及其对截割载荷的影响,采用含滚筒振动量的锋利截齿截割阻力模型描述滚筒截割载荷,采用含间隙齿轮啮合模型描述行走轮驱动载荷,采用库伦摩擦模型描述平滑靴摩擦载荷,建立了采煤机整机五自由度动力学模型,利用ode45对模型求解.结果表明:当煤岩硬度f=3,行走速度为3m/min时,采煤机右摇臂振动幅值约为0.8×10~(-4)rad,左摇臂振动幅值约为0.4×10~(-5)rad;机身振动速度在-1.4~+1.4mm/s间波动,右、左摇臂的振动角速度分别在-1×10~(-3)~+1×10~(-3) rad/s和-4.5×10~(-4)~+4.5×10~(-4) rad/s间波动;通过对比考虑滚筒振动和未考虑滚筒振动时的截割载荷,表明滚筒的振动有利于对煤岩的截割;对右侧摇臂的振动量进行了实验测量,其大小及波动范围与仿真值较为接近,说明采煤机的动力学模型具有一定的准确性. 相似文献
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Jun Shen Jianping Hou Hengzhi Fu Junyi Su 《Science and Technology of Advanced Materials》2013,14(1):213-217
Based on analyses for the electromagnetic pressure on the melt and the heat induced in the melt, the ratio of heat to pressure Q0/Pm is defined, to give the relationship between Qo/Pm and the thickness a, the electromagnetic parameter (μγ) of the melt and the electric current frequency/under the electromagnetic confinement and shaping process. If Qo/Pm is large, any adjustment to the melt shape will easily cause a variation of the temperature in the melt. In this situation, there appears to be a more sensitive interaction between the shape and the temperature field and a more narrow adjustment range for the process. Experiments on thin plate samples with a cross-section of 6 mm × 18 mm are done with two kinds of induction coils. The results show that when a coil with a trumpet inside wall is used and the positions of the melt top and the S/L interface are properly selected, the melt periphery is nearly vertical and the temperature gradient ahead of the S/L interface is high. Under these conditions, a more stable and wider coupling between the shape and the temperature field is continuously maintained and samples with a smooth surface and unidirectional crystals are successfully obtained. 相似文献
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Based on the method of successive substitutions, an integral equation is derived in which multiple reflections are explicitly
identified. This equation is used provide simple methods of estimating the local effective radiation of two-dimensional and
three-dimensional systems of surfaces, with due regard for the anisotropy of their optical properties. A cylindrical cavity
confined by the surface of a right circular cylinder with a side pyrometric hole is treated as an example. The results obtained
by the suggested method are compared with the data of direct solution of an integral equation for the two-dimensional problem. 相似文献
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The dependence of the coefficient of concentration jump on the coefficient of vaporization for a diluted binary mixture, when
the concentrations of the components are significantly different, has been investigated. The analytical expression of the
concentration jump for the case where the frequency of collisions of molecules is in proportion to their velocity has been
obtained.
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Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 2, pp. 121–126, March–April, 2007. 相似文献
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论知觉对象与背景的关系 总被引:3,自引:2,他引:1
通过将"万绿丛中一点红"中的哲学原理在广告的创意、制作中的运用得到的经验,阐述了这样的原理:知觉对象与背景是通过对比与协调达到和谐统一的,它们通过色彩与造型的差异性和互补性,产生奇特的视觉效果,给人以鲜明的印象和强大的视觉冲击力,从而达到吸引消费者的目的.这在广告学中有着至关重要的作用,也是众多广告设计中都遵守的原则之一. 相似文献
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以家具的风格、造型形态、装饰、色彩、材料、功能、价格定位等方面作为主要的评价项目,针对消费者和设计师分别设计了感性意象的调查问卷并进行问卷调查。通过对调查数据的研究分析,获得消费者和设计师在家具感性意象上的共同点和差异性,并构建了消费者和设计师的家具产品感性意象的偏好模型,模型可用于指导家具方案设计,避免家具设计的盲目性,从而降低了设计风险,提高家具方案设计的成功性。 相似文献
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《Science and Technology of Advanced Materials》2001,2(1):213-217
Based on analyses for the electromagnetic pressure on the melt and the heat induced in the melt, the ratio of heat to pressure Q0/Pm is defined, to give the relationship between Q0/Pm and the thickness a, the electromagnetic parameter (μγ) of the melt and the electric current frequency f under the electromagnetic confinement and shaping process. If Q0/Pm is large, any adjustment to the melt shape will easily cause a variation of the temperature in the melt. In this situation, there appears to be a more sensitive interaction between the shape and the temperature field and a more narrow adjustment range for the process. Experiments on thin plate samples with a cross-section of 6 mm×18 mm are done with two kinds of induction coils. The results show that when a coil with a trumpet inside wall is used and the positions of the melt top and the S/L interface are properly selected, the melt periphery is nearly vertical and the temperature gradient ahead of the S/L interface is high. Under these conditions, a more stable and wider coupling between the shape and the temperature field is continuously maintained and samples with a smooth surface and unidirectional crystals are successfully obtained. 相似文献
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The results of an investigation of different types of tungsten lamps in order to estimate the components of the error budget of spectrum-pyrometer apparatus are presented. Quantitative relations are considered and the results of experimental research, which enable systematic methods to be developed for eliminating the influence of polarization of the radiation of the lamps in standard radiation thermometry, are analyzed.Translated from Izmeritelnaya Tekhnika, No. 9, pp. 42–45, September, 2004. 相似文献
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A general equation has been derived for the threshold pressure of infiltration of liquids into porous solids. From this equation all the known equations for the threshold pressure can be obtained, using different assumptions on the morphology of the porous solid and on the way how the liquid infiltrates the solid. Particularly, the Young-Laplace equation, the Carman-equation, and the modification of the Carman equation, suggested by White and later by Mortensen and Cornie have been reproduced as particular cases of the general equation. A new particular solution of this general equation is also suggested, taking into account that the original solid/gas interface inside the porous body is not fully replaced by the solid/liquid interface during infiltration, especially for the case of non-wetting liquids. The new, general equation consists of three semi-empirical parameters, which should be found experimentally for a given type of morphology of the porous solid and for the given ratio of the surface tension to the density of the infiltrating liquid metal. The new equation provides a value of the threshold contact angle to be between 65.5° and 90°, depending on the morphology of the porous solid. Consequently, the threshold pressure appears to be an asymmetrical function of the contact angle. Based on the new equation, the practical constancy of the threshold pressure is predicted in the interval of the contact angles between 120° and 180°. 相似文献
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M. R. Romanovskii 《Journal of Engineering Physics and Thermophysics》1982,42(3):351-357
We consider the problems of unambiguous determination of coefficients of the linear heat-conduction equation from measurements on a temperature field.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 3, pp. 476–483, March, 1982. 相似文献
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S. I. Starchenko 《Measurement Techniques》1998,41(4):375-377
The effect of the shape of the radiation pattern of the difference channel of a monopulse antenna on the accuracy of angular-coordinate
measurements is estimated. The least root mean square deviation is obtained using a radiation pattern with a Chebyshev amplitude
distribution. Of the practical amplitude distributions a “parabola on a pedestal” of 0.1–0.316 is preferable.
Translated from Izmeritel'naya Tekhnika, No. 4, pp. 53–54, April, 1998. 相似文献
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本文研究用8098单片机对密闭大贮槽的贮液容量进行自动检测的应用系统,解决了把贮槽液位测量传感器输出的电流信号直接转换成贮液重量进行显示,从而使显示直观、清晰. 相似文献
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资源型城市产业转型中接续产业选择问题分析 总被引:1,自引:0,他引:1
提出以判定工业化发展阶段、产业竞争力分析、产业发展趋势与结构调整效益分析、区位分析相结合的方法,研究资源型城市接续产业选择问题,并以东营为例,演示该方法的有效性.其中,在判定工业化发展阶段中采用四项指标综合评判;在产业竞争力分析中采用因子分析法;在结构调整效益分析中采用SS模型;在区位分析时着重考虑区位经济互补问题.在实证基础上,提出资源型城市选择接续产业时需着力避免跟风攀比、盲目照搬和飞地经济三种倾向. 相似文献
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Karl F. Warnick Weng Cho Chew 《International journal for numerical methods in engineering》2001,51(1):31-56
Existing convergence estimates for numerical scattering methods based on boundary integral equations are asymptotic in the limit of vanishing discretization length, and break down as the electrical size of the problem grows. In order to analyse the efficiency and accuracy of numerical methods for the large scattering problems of interest in computational electromagnetics, we study the spectrum of the electric field integral equation (EFIE) for an infinite, conducting strip for both the TM (weakly singular kernel) and TE polarizations (hypersingular kernel). Due to the self‐coupling of surface wave modes, the condition number of the discretized integral equation increases as the square root of the electrical size of the strip for both polarizations. From the spectrum of the EFIE, the solution error introduced by discretization of the integral equation can also be estimated. Away from the edge singularities of the solution, the error is second order in the discretization length for low‐order bases with exact integration of matrix elements, and is first order if an approximate quadrature rule is employed. Comparison with numerical results demonstrates the validity of these condition number and solution error estimates. The spectral theory offers insights into the behaviour of numerical methods commonly observed in computational electromagnetics. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献