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61.
When the underexpanded supersonic jet impinges on the obstacle, it is well known that the self-induced flow oscillation occurs at the specific condition of the pressure ratio in the flowfield, the position of an obstacle and so on. This oscillation is related with the noise problems of aeronautical and other industrial engineering so that the characteristic and the mechanism of self-induced flow oscillation have to be cleared to control the various noise problems. But, it seems that the characteristics of t... 相似文献
62.
Due to the disadvantages of complexity,high maintenance and vast investment of the electro-hydraulic servo oscillator,a new mechanical device synchronously driven by double servomotors was proposed.The working principle of the non-sinusoidal oscillator was analyzed and the model of the oscillator was validated via simulation software.Then,taking advantage of resonance technology,the hinging force and moment were calculated.The results showed that the hinging force and driving moment reduced,which was useful in reducing the impact of the hinge and prolonging the service life of the bearing.Besides,the best initial spring pressure was 0.9 times the mold gravity,which improved the oscillation system stability and reduced the load fluctuation and servomotor driving power. 相似文献
63.
运用非线性分析方法,探讨了B-Z化学振荡系统的复杂现象及机理。研究了以凉茶(潘高寿)、8%的硫酸、5%的丙酮、1.67%的硫酸锰、1.07%的溴酸钠形成的反应振荡体系。通过只改变凉茶的量(其他条件均不变),温度为(37.5±0.1)℃,测定离子选择性电极上的电势U随时间(t)变化的U-t曲线。由B-Z振荡曲线可以了解其反应随时间作周期性的变化,即可得到以下振荡参数:振荡诱导期、振荡周期、振荡寿命、振荡△E等等。结果表明:随着凉茶的量的增加,其振荡的时间逐渐缩短,诱导期缩短,周期也逐渐缩短且趋于稳定。但振幅的改变率不明显。初步说明了反应物与电极电势之间存在良好的线性关系。当加入氧化剂溴酸钠时,振荡图形整体向上漂移。 相似文献
64.
Single‐chamber fuel cells (SCFCs) are an alternative way to conventional SOFCs. Effectively, they do not require any more sealing between anodic and cathodic compartment's as the cell is fed with a mixture of hydrocarbon and oxygen. This paper deals with voltage oscillations observed with an SCFC composed of GDC (Ce0.9Gd0.1O1.95) supported electrolyte, Ni‐GDC anode and a BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3–δ) cathode, operating in the temperature range 500–600 °C and under various propane and oxygen mixtures, with a C3H8/O2 ratio between 0.2 and 0.66. Electrical and Thermo‐Programmed Oxidation (TPO) measurements combined with SEM observations allowed us proving that these oscillations are due to carbon nanowires deposition/oxidation cycles. A mechanism is proposed to explain this behavior. 相似文献
65.
针对电子元件的测量问题,提出了一种简易测量方法。采用555多谐振荡电路,通过C8051F060单片机控制测量电阻、电容对应振荡电路所产生的频率实现各个参数的测量,一方面测量精度较高,另一方面便于使仪表实现自动化,并可语音播报使其更加智能化。应用结果表明:该测量方法所用元器件少、电路简单,误差在±5%以内,满足实际测量要求。 相似文献
66.
Bulent Yesilata 《Polymer-Plastics Technology and Engineering》2013,52(7):723-729
Polymeric (viscoelastic) fluids have nonlinear mechanical properties and therefore the flow of a sufficiently elastic polymer solution may become irregular even at very low Re. Experimental evidences of these flow irregularities occurred near pipe exit at Re << 1 are presented here for Poiseuille flow of a highly elastic polymer solution. Although the Re is extremely low, the measured instantaneous pressures show turbulent-like fluctuations induced by elasticity of the fluid. Temporal nature of these fluctuations is analyzed in terms of Deborah number (De) that provides an appropriate measure for degree of nonlinearity in a polymeric flow. 相似文献
67.
SUMMARY An apparatus for the accurate determination of reaction kinetics by the stirred flow technique is described. A 2- to 3-ml stirred reactor is fed by solutions injected from screw-driven syringes. The flow rates vary between 8 × 10-4 and 58 ml/min and are controlled to ±0.1%. The pH is determined directly from an electrode inserted into the reactor cell. An auxiliary unit for continuous variation of concentration over a specified range is provided. The progress of the reaction is followed by direct spectro-photometric observation and other techniques. The stirred flow reactor is particularly useful for complex reactions and for the detection of short-lived intermediates. It should find use for the study of enzyme kinetics. 相似文献
68.
板坯结晶器与振动台振动特征分析 总被引:3,自引:0,他引:3
应用自行开发的软硬件系统,对板坯连铸机结晶器及振动台进行测试与分析,发现其振动特征随拉速而变化的规律,提出了用相位分析判定振型的方法。 相似文献
69.
X. B. Li T. S. Lok J. Zhao P. J. Zhao 《International Journal of Rock Mechanics and Mining Sciences》2000,37(7)
This paper highlights an improved experimental approach for eliminating oscillation that exists in the dynamic stress–strain response of rocks and other brittle materials obtained from tests using a split Hopkinson pressure bar (SHPB). Both analytical and experimental results for a number of rock types are presented to verify the idea. Results from the investigation indicate that oscillation in the dynamic stress–strain response of these materials originates from the Pochhammer–Chree dispersion of the loading incident wave, and more evidently from the relatively low strength and elastic modulus of the samples compared with metallic materials. In order to control the oscillation effectively, it is proposed that a half-sine loading waveform should be used instead of the conventional rectangular loading waveform in SHPB tests. Experimental results obtained from both the conventional and the improved methods are presented, including dynamic complete stress–strain curves for granite, sandstone and limestone. The improved method eliminates oscillation in the tests, provides better stability of strain rate and more representative results than those obtained from the conventional rectangular loading waveform shape. 相似文献
70.