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分析了电加热器对流动氦气的加热过程,从能量平衡和热传导的角度建立了系统数学模型,用解析的方法表达了热量的传递过程,得到了传递函数。用Matlab的Simulink模块搭建了PID的控制框架,用积分分离的策略改进了温度控制的效果。仿真结果显示流体在进口温度不断变化的情况下,通过加热器的功率调节获得了比较稳定的气体出口温度,表现出了良好的控制结果。 相似文献
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众所周知,伊萨克•牛顿(IsaacNewton,1642~1727)是英国伟大的科学家,其研究领域包括了物理学、数学、天文学、自然哲学、炼金术和神学。牛顿发明了微积分,发现了万有引力定律,创建了经典力学,设计并制造了第一架反射式望远镜等,被誉为人类历史上最有影响力的科学家。正如恩格斯所说:"牛顿由于发明了万有引力定律而创立了科学的天文学;由于进行了光的分解,而创立了科学的光学;由于创立了二项式定理和无限理论而创立了科学的数学;由于认识了力的本质,而创立了科学的力学"。假如牛顿生活的时代就有诺贝尔奖的话,他无疑会多次获得诺贝尔奖。为了纪念牛顿的杰出成就,以牛顿的姓氏命名力的单位,国际天文学联合会还把662号小行星命名为牛顿小行星。 相似文献
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武振有 《工程物理研究院科技年报》2008,(1)
1 工程设计技术
利用有限元软件和采用CAD设计方法,对复杂结构进行了优化设计,达到了提高产品可靠性的目的。开展了五层阻尼圆板的优化设计,达到了阻尼板具有更佳的减振效果;整机三维立体布线设计,实现了整机布线可视化装配;控制系统的集成化设计,提高了产品的可靠性和降低了电源能耗;Kα波段短脉冲检波器设计,为毫米波短脉冲的检测技术提供了重要的设计经验。 相似文献
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分析了电加热器对流动氦气的加热过程,从能量平衡和热传导的角度建立了系统数学模型,用解析的方法表达了热量的传递过程,得到了传递函数。用Matlab 的Simulink 模块搭建了PID 的控制框架,用积分分离的策略改进了温度控制的效果。仿真结果显示流体在进口温度不断变化的情况下,通过加热器的功率调节获得了比较稳定的气体出口温度,表现出了良好的控制结果。 相似文献
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本文在8根水力直径均为186ìm的硅微平行通道的入口端加工了限制装置,抑制了通道间的相互作用,得到了稳定的气液两相流动,并借助于可视化技术,揭示了通道内部不同区段典型的流型特点.分析了经过通道的压降和局部换热系数的变化规律,并用经验关系式和试验结果进行了比较. 相似文献
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S. G. Nedel’ko M. A. Krysyuk A. L. Apanasenko L. N. Lymarenko Z. T. Moroz 《Journal of Applied Spectroscopy》1997,64(1):55-61
Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped
with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly
described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation
(5.5·104 Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum
cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics
of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure
crystals is analyzed (preliminarily).
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997. 相似文献
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In order to understand the viscoelasticity of material, this research has been conducted to study the propagation characteristics of viscoelastic Rayleigh wave theoretically. A model is presented for the pulsed laser generation of ultrasound on viscoelastic medium surface. Referred to the Kelvin model, the frequency equation and the normal displacement of viscoelastic Rayleigh wave were derived, the influence of the viscoelastic modulus on dispersion and attenuation was discussed. From the theoretical calculation, it is shown that the effect of viscoelasticity on the attenuation of Rayleigh wave is more than that on its dispersion. In the case of a weak viscosity, the attenuation of viscoelastic Rayleigh wave is directly proportional to viscosity modulus; the effect of shear viscosity on the attenuation is much more than that of bulk viscosity. The transient response of viscoelastic Rayleigh wave was also simulated using Laplace and Hankel inversion transform, which are showed in good agreement with the theoretic predictions. The model provides a useful tool for the determination of viscoelastic parameters of medium. 相似文献
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The nonlinear dynamics of a waveguide CO2 laser with combined periodic loss and pumping modulation is investigated theoretically and experimentally. The possibilities
of controlling time and energy parameters of the output radiation using the corresponding selection of the detuning of the
cavity's longitudinal mode from the center of the amplification line, the amplitude, and the frequency of loss modulation
are demonstrated. The observed asymmetric dependence of the lasing-radiation density on the detuning of the cavity frequency
is explained by the attendant modulation of the refractive index of the loss modulator.
To whom correspondence should be addressed.
B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072, Belarus.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 471–478, July–August, 1999. 相似文献
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Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains. 相似文献
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The beam dynamic code PARMELA was used to simulate the transportation process of accelerating electrons in S-band SW linacs with different energies of 2.5, 6 and 20 MeV. The results indicated that in the ideal condition, the percentage of electron beam loss was 50% in accelerator tubes. Also we calculated the spectrum, the location and angular distribution of the lost electrons. Calculation performed by Monte Carlo code MCNP demonstrated that the radiation distribution of lost electrons was nearly uniform along the tube axis, the angular distributions of the radiation dose rates of the three tubes were similar, and the highest leaking dose was at the angle of 160° with respect to the axis. The lower the energy of the accelerator, the higher the radiation relative leakage. For the 2.5 MeV accelerator, the maximum dose rate reached 5% of the main dose and the one on the head of the electron gun was 1%, both of which did not meet the eligible protection requirement for accelerators. We adopted different shielding designs for different accelerators. The simulated result showed that the shielded radiation leaking dose rates fulfilled the requirement. 相似文献
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Krzysztof Drozdowicz Barbara Gabańska Andrzej Igielski Ewa Krynicka Urszula Woźnicka 《Central European Journal of Physics》2003,1(2):210-234
The structure of a heterogeneous system influences diffusion of thermal neutrons. The thermal-neutron absorption in grained
media is considered in the paper. A simple theory is presented for a two-component medium treated as grains embedded in the
matrix or as a system built of two types of grains (of strongly differing absorption cross-sections). A grain parameter is
defined as the ratio of the effective macroscopic absorption cross-section of the heterogeneous medium to the absorption cross-section
of the corresponding homogeneous medium (consisting of the same components in the same proportions). The grain parameter depends
on the ratio of the absorption cross-sections and contributions of the components and on the size of grains. The theoretical
approach has been verified in experiments on prepared dedicated models which have kept required geometrical and physical conditions
(silver grains distributed regularly in Plexiglas). The effective absorption cross-sections have been measured and compared
with the results of calculations. A very good agreement has been observed. In certain cases the differences between the absorption
in the heterogeneous and homogeneous media are very significant. A validity of an extension of the theoretical model on natural,
two-component, heterogeneous mixtures has been tested experimentally. Aqueous solutions of boric acid have been used as the
strongly absorbing component. Fine- and coarse-grained pure silicon has been used as the second component with well-defined
thermal-neutron parameters. Small and large grains of diabase have been used as the second natural component. The theoretical
predictions have been confirmed in these experiments. 相似文献
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To predict sound-absorbing performance of anechoic materials,the acoustic reflection problem of a viscoelastic layer backed with periodically rib-stiffened infinite double plates is studied in this paper.The reason why structural theories of plates are not applicable to viscoelastic plates is explained through comparing dispersion and attenuation curves of flexural waves with those of Lamb waves.As a result,(visco-)elastic theory is adopted to deal with(visco-)elastic plates,and ribs are treated by structural theories of plates.The coupling between ribs and plates are solved by Hull's method,and solution of the reflected field is obtained.The accuracy of present method is validated by comparing with the results by the structural theories of plates.The influence of a backing on the acoustic reflection of the viscoelatic layer is analyzed by computing reflection coefficients.Performances of different viscoelastic materials are evaluated by the average reflection coefficients.The computational results show that,influence of a backing on the acoustic reflection cannot be suppressed by the viscoelastic materials in low frequencies.The resonance is determined by the coupling of the fluid layer and the double plates.And ribs,which are coupled with the double plates,mainly reduce the acoustic reflection. 相似文献
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Quantum-chemical calculations of the excited electronic states of a porphyrin dication have been performed by the CNDO/S method
for different angles determining the saddle-like and ruffled distortions of the porphyrin macroring. It is shown that saddle-like
distortions arising as a result of a tilt of the pyrrole rings have a significant influence on the energies of the molecular
orbitals and energies of the excited electronic states of porphyrin molecules, especially on the oscillator strength of the
G→Q transition. The results of the calculations performed are in good agreement with the experimental spectra of porphyrin
dications.
To whom correspondence should be addressed.
Reported at the VIIIth International Conference on Spectroscopy of Porphyrins and Their Analogs, Minsk, September 22–26, 1998.
Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 559–562, July–August, 1999. 相似文献
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D. K. Buslov E. V. Korolik R. G. Zhbankov F. N. Kaputskii T. L. Yurkshtovich V. A. Alinovskaya L. V. Plenina S. V. Khlyustov 《Journal of Applied Spectroscopy》1999,66(6):890-895
By the method of IR spectroscopy it is established that the process of sorption of celiase, trypsin, chymotrypsin, streptase,
plasminogen, and plasmin by monocarboxylcellulose (the content of COOH groups is 15 wt.%) is mainly identical. The determining
role in the mechanism of binding of monocarboxylcellulose with the considered medicinal enzymes belongs to electrostatic interactions
with the formation of ionic bonds between the COO− groups of the matrix and charged amine groups of protein molecules. It is established that the process of interaction of
plasmin with oxidized cellulose takes a more active course than with other investigated enzymes. It is shown that the activity
of interaction of the enzymes with monocarboxylcellulose can be evaluated by a change in the relative intensity of the band
of stretching vibrations of C=O groups.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 6, pp. 771–774, November–December, 1999. 相似文献
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E. A. Yanovskaya Yu. N. Chiberkus A. F. Yanovskii 《Journal of Applied Spectroscopy》1997,64(5):658-662
We present the results of comprehensive investigations that include remote spectral measurements under field conditions, laboratory
experiments, and mathematical simulation of the radiative regime of winter rye sowings.
B. I. Stepanov Institute of Physics, Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072, Belarus. Translated
from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 5, pp. 646–650, September–October, 1997. 相似文献