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《振动与冲击》2018,(21)
为了改善摆线转子泵流场脉动特性,建立一种具有增加极限进出油面积的凸舌油槽结构模型。采用数值模拟方法,对凸舌油槽结构的摆线转子泵模型内部流场进行计算,分析了凸舌油槽结构对转子流体内部齿顶处、齿根处及最大啮合容积处压力脉动的影响,研究了转子轴向压力不均匀度以及轴向流场特性。结果表明:凸舌油槽结构能够有效改善摆线转子泵流场压力脉动;在齿根处压力脉动下降约25%,最大啮合容积处压力脉动下降约54. 2%,对齿顶影响不大;齿根处轴向不均匀度约3. 5%,齿顶处约17. 9%,最大啮合容积处约3. 1%;齿间容积越小,轴向流动阻力越大,使得高压流体沉积,导致轴向存在不均匀度。 相似文献
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C~3连续的保凸T-B插值曲线及保形插值算法 总被引:1,自引:0,他引:1
基于三角函数的T-B样条曲线虽然具有保凸性,但曲线不通过任何控制点.现在在两个相邻控制点之间插入两个新的控制点,使改造后新的T-B样条曲线插值能够通过原来的控制点,不仅保凸、C~3连续,而且曲线的形状还可作局部修改.给出了T-B样条曲线保形插值算法的保形性条件,并给出了数值计算例子. 相似文献
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为实现直齿圆柱齿轮精密成形,并克服传统工艺存在的成形力大、模具结构复杂等一些不足,在已有齿形凸模双向镦挤成形直齿圆柱齿轮的基础上提出了另外2种改进的成形工艺,分析了不同成形工艺下端面摩擦力对载荷的影响,利用有限元模拟软件DEFORM-3D分别对3种成形工艺进行了数值模拟研究,并提出了一种优化的成形新工艺——无齿凸模双向镦挤精密成形.结果表明:采用无齿凸模镦挤成形直齿圆柱齿轮在载荷及模具结构方面优于有齿凸模镦挤成形,其中,无齿凸模双向镦挤较有齿凸模双向镦挤,上、下凸模载荷下降约55%;无齿凸模双向镦挤较非对称凸模双向镦挤,上、下凸模载荷分别下降约50%、38%;无齿模具加工制造更容易,强度更高;新工艺的等效应力最大值为3种方案中最小,而且等效应力变化正常,无破坏现象出现.对优化后的成形工艺进行了试验研究,得到了齿形轮廓清晰、充填饱满、无折叠、开裂等缺陷的铅质试件,试验结果与模拟结果基本吻合. 相似文献
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The lubrication approximation is used to investigate slender dry patches in an infinitely wide film of viscous fluid flowing steadily on an inclined plane that is either heated or cooled relative to the surrounding atmosphere. Four non-isothermal situations in which thermocapillary effects play a significant role are considered.Similarity solutions describing a thermocapillary-driven flow with a dry patch that is widening or narrowing due to either gravitational or surface-tension effects on a non-uniformly heated or cooled substrate are obtained, and examples of these solutions, when the substrate temperature gradient depends on the longitudinal coordinate according to a general power law, are presented. When gravitational effects are strong, the solution contains a free parameter, and for each value of this parameter there is a unique solution representing both a narrowing pendent dry patch and a widening sessile dry patch, whose transverse profile has a monotonically increasing shape. When surface-tension effects are strong, the solution also contains a free parameter, and for each value of this parameter there is both a unique solution representing a narrowing dry patch, whose transverse profile has a monotonically increasing shape, and a one-parameter family of solutions representing a widening dry patch, whose transverse profile has a capillary ridge near the contact line and decays in an oscillatory manner far from it.Similarity solutions are also obtained for both a gravity-driven and a constant-surface-shear-stress-driven flow with a dry patch that is widening or narrowing due to thermocapillarity on a uniformly heated or cooled substrate. The solutions in both cases contain a free parameter, and for each value of this parameter there is a unique solution representing both a narrowing dry patch on a heated substrate and a widening dry patch on a cooled substrate, whose transverse profile has a monotonically increasing shape. 相似文献
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该文对不同参数下的正六边形孔蜂窝梁和蜂窝组合梁抗剪性能进行了试验与有限元分析研究。以试验研究为基础,基于有限元软件ABAQUS 建立非线性有限元模型,对不同开孔率、不同翼缘宽度和厚度的蜂窝梁和蜂窝组合梁进行分析比较,发现蜂窝梁和蜂窝组合梁抗剪承载力大小与翼缘厚度、开孔率和连接程度均有关。结果表明:蜂窝梁翼缘厚度变化对其抗剪承载力影响较大,而蜂窝组合梁中翼缘厚度的变化对其抗剪性能影响相对较小;混凝土板提高了蜂窝梁的抗剪极限承载能力;最后,给出蜂窝梁和蜂窝组合梁抗剪计算公式。 相似文献
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利用共旋坐标法提出了一种预应力钢筋混凝土梁非线性分析的混合单元模型,在随转坐标系内,采用分层梁单元来模拟混凝土结构,带初应变的杆单元来模拟预应力钢筋,预应力钢筋杆元和混凝土梁元的变形协调则通过非线性刚臂来实现,通过刚臂单元两端节点位移和力的关系形成预应力钢筋对混合单元刚度矩阵的贡献,从而导出随转坐标系下预应力混凝土梁考虑材料非线性的切线刚度矩阵,几何非线性则由单元随转坐标系到结构坐标系的转换矩阵及其微分来体现,从而获得结构坐标系下混合单元模型的几何与材料双非线性切线刚度矩阵。数个钢筋混凝土及预应力钢筋混凝土梁非线性分析算例表明:所提出的混合单元模型能较好地分析预应力钢筋混凝土梁非线性性能,具有一定的实用价值。 相似文献
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Mohd Faizal B. Ismail Mohamad Dernaika Amin Khodaei Sulaiman Wadi Harun 《Journal of Modern Optics》2013,60(11):892-896
This study describes a proposal and experimental demonstration of a tunable thulium-doped fiber laser with a multi-wavelength output operating at 1.8 μm. The introduction of a multi-mode non-adiabatic taper fiber into a single-mode cavity induces spatial-mode beating and a consequent narrow band filter mechanism. The fiber laser can be tuned by changing the state of the polarization in a ring cavity via adjustment of a polarization controller. The resulting outputs for single and dual wavelengths with different spacing are reported in detail. 相似文献
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Nicola Manca Luca Pellegrino Teruo Kanki Warner J. Venstra Giordano Mattoni Yoshiyuki Higuchi Hidekazu Tanaka Andrea D. Caviglia Daniele Marré 《Advanced materials (Deerfield Beach, Fla.)》2017,29(35)
Relaxation oscillators consist of periodic variations of a physical quantity triggered by a static excitation. They are a typical consequence of nonlinear dynamics and can be observed in a variety of systems. VO2 is a correlated oxide with a solid‐state phase transition above room temperature, where both electrical resistance and lattice parameters undergo a drastic change in a narrow temperature range. This strong nonlinear response allows to realize spontaneous electrical oscillations in the megahertz range under a DC voltage bias. These electrical oscillations are employed to set into mechanical resonance a microstructure without the need of any active electronics, with small power consumption and with the possibility to selectively excite specific flexural modes by tuning the value of the DC electrical bias in a range of few hundreds of millivolts. This actuation method is robust and flexible and can be implemented in a variety of autonomous DC‐powered devices. 相似文献
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Hollow sphere-like and other shaped mesoporous silicas were prepared using reformer naphtha as a swelling agent via a hydrothermal synthesis process. The mesoporous silicas underwent a complicated process in which their morphology was transformed from a red blood cell-like shape to a golf-ball sphere-like shape, and then from a golf-ball-like shape to a hollow sphere-like shape in response to various synthesis temperatures. Under the control of using reformer naphtha, the mesoporous silica was transformed from a wheat-like shape to a sphere-like shape, and then from a sphere-like shape to a hollow sphere-like shape. The effects of temperature and the swelling agent may have contributed to the formation of reformer naphtha microemulsions in the copolymer aqueous solution, followed by the self-assembly of block copolymer micelles and silica around the emulsions. 相似文献
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A. Braem C. Joram J. Sguinot P. Lavoute C. Moussant 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2007,570(3):467-474
We present the results of a conceptual study demonstrating the feasibility of a large spherical hybrid photodetector with central anode. A prototype tube with 208 mm diameter and an anode in form of a metallic cube has been fabricated. In the final version of the so-called X-HPD concept the anode will be a scintillator cube with plated faces and a small photodetector to readout the bottom. The bialkali photocathode covers three quarters of the sphere surface. Combined use of this cathode in transmissive and reflective mode leads to effective quantum efficiency values exceeding those obtained in conventional hemispherical PMT designs. Further features of the concept are a photoelectron collection efficiency approaching 100% and a photon amplification in the scintillator crystal leading to a distinct single photoelectron signal.
Using a custom built electron accelerator based on a CsI transmissive photocathode, LSO and YAP block crystals in geometries adapted to the anode of an X-HPD have been tested with single photoelectrons in the 10–30 keV energy range. The scintillation light was readout with a conventional PMT or a Si-PM. More than 30 photoelectrons per incident electron could be detected with the PMT. 相似文献
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R Heide 《International Journal of Refrigeration》1997,20(7):496-503
The surface tension of the refrigerants R32, R125, R134a, R143a and R152a, as well as the binary refrigerant mixtures R32-R125, R32-R134a, R125-R134a, R125-R143a, R125- R152a, R143a-R134a and R134a-R152a, and the commercially available ternary mixtures R404A and R407C was measured across the temperature range from −50 to 60°C using a measuring unit based on the capillary rise method. Different formulations for calculation of the surface tension of the binary and ternary mixtures on the basis of the surface tension of the pure refrigerants were tested. With an approach based on mass proportions in the mixture, a good correspondence between the measured and calculated values was achieved. 相似文献
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In this paper, we consider a dynamic supply chain where a manufacturer produces and distributes a featured product through an exclusive retailer to end consumers. The manufacturer decides the product quality and wholesale price, while the retailer sets the retail price in the presence of a revenue-sharing contract and consumers’ reference quality effects. The objective of this study is to investigate the impacts of myopic behaviour regarding the reference quality on the product quality and pricing strategies and profits of both members. Our results suggest that the manufacturer’s myopia leads to a higher quality, higher price strategy and a higher quality–price ratio which benefits consumers. Meanwhile, relative to the far-sighted behaviour, myopia results in a more quality-sensitive but less price-sensitive market demand. What’s more, we find that the manufacturer is apt to act in a far-sighted way, but the retailer isn’t always willing to cooperate with a far-sighted manufacturer. Taking myopic strategies for both members is likely to gain a high profit of the whole supply chain for a relatively high marginal contribution of product quality on demand and a relatively low revenue-sharing proportion. 相似文献