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1.
埋地管道现场激震试验研究 总被引：1，自引：0，他引：1
为了验证我国长输管道抗震设计规范的振动参数，分析软硬地基上的地震应力，进行了现场激震试验和理论分析，详细介绍了利用火箭燃料做能源的地震动激震系统在埋地管道现场模拟地震动来研究埋地管道在地震波作用下所产生的应变，这在地下管道抗振研究中是一种新的尝试，也为今年地下管道现场试验提供了一种新的激震方法，通过实测管道应变与我国规范简化计算应变的对比，验证了我国规范的取值，确定了埋地管道抗震计算的振动参数，经 相似文献
2.
针对柴油机燃油系统精密偶件磨损后的油压波形变化，采用高压油管压力波形识别的方法，测取磨损状态下的柱塞副、出油阀副、喷油器针阀副工作压力波形，研究高压油管压力波形所反映的偶件磨损状况。 相似文献
3.
The phenomenon of ocean waves breaking on a beach is analogous to shock waves in the atmosphere of a pulsating star. In both cases a velocity discontinuity is clearly present. In stars the upper, expanding layer halts and falls back so as to interact with the rising gas at a shock. Similarly, a bore on a beach reaches its maximum extension before sliding back onto the next incoming wave. Analogous quantities such as the surface gravity of the star and the beach gradient in the ocean have similar effects on the flows and the nature of the discontinuity between them. Phenomena that are not analogous include the thermodynamic properties of the two media. Ocean observations may help solve some problems in shock phenomena associated with stellar pulsation. 相似文献
4.
黄敬党 《福建农林大学学报(自然科学版)》1998,(1)
采用一台ＲｉｃａｒｄｏＥ６可变压缩比四冲程单缸试验机为样机，配以示功图、温度、排气成分测量仪器以及自制的气体燃料混合及调节装置，组成了模拟生物质气发动机试验台架及数据测录系统．实践证明，该系统工作正常，能满足研究需要． 相似文献
5.
Eyring H 《Science (New York, N.Y.)》1978,199(4330):740-743
Reactions that take place in shock waves are slow compared to the energy present in the translational degrees of freedom. One explanation for the slow burning in a detonation is that successive surface layers of the solid or liquid must react sequentially. Another mechanism, which can also account for the slowness of reactions in shock waves in gases, is the basis for starvation kinetics: the bond that is breaking must draw its activation energy from a vibrational reservoir in disequilibrium with the translational degrees of freedom of the reacting molecule. 相似文献
6.
The Voyager 1 plasma wave instrument detected many familiar types of plasma waves during the encounter with Saturn, including ion-acoustic waves and electron plasma oscillations upstream of the bow shock, an intense burst of electrostatic noise at the shock, and chorus, hiss, electrostatic electron cyclotron waves, and upper hybrid resonance emissions in the inner magnetosphere. A clocklike Saturn rotational control of low-frequency radio emissions was observed, and evidence was obtained of possible control by the moon Dione. Strong plasma wave emissions were detected at the Titan encounter indicating the presence of a turbulent sheath extending around Titan, and upper hybrid resonance measurements of the electron density show the existence of a dense plume of plasma being carried downstream of Titan by the interaction with the rapidly rotating magnetosphere of Saturn. 相似文献
7.
Explosive volcanic eruptions generate pressure disturbances in the atmosphere that propagate away either as acoustic or as shock waves, depending on the explosivity of the eruption. Both types of waves are recorded on microbarographs as 1- to 0.1-hertz N-shaped signals followed by a longer period coda. These waveforms can be used to estimate burst pressures and gas concentrations in explosive volcanic eruptions and provide estimates of eruption magnitudes. 相似文献
8.
Dunne BB 《Science (New York, N.Y.)》1970,167(3921):1124-1126
By the use of a metal indentation techinque, microscopic transverse or side-running shock waves can be detected in composition C-4, an explosive consisting largely of cyclonite (RDX) with organic plasticizers. The minimum wave spacing observed is approximately 0.05 millimeters. with a lateral velocity of about 6.5 millimeters per microsecond. The instability was demnostrated in cylindrically divergent detonation waves. 相似文献
9.
The Voyager I plasma wave instrument detected low-frequency radio emissions, ion acoustic waves, and electron plasma oscillations for a period of months before encountering Jupiter's bow shock. In the outer magnetosphere, measurements of trapped radio waves were used to derive an electron density profile. Near and within the Io plasma torus the instrument detected high-frequency electrostatic waves, strong whistler mode turbulence, and discrete whistlers, apparently associated with lightning. Some strong emissions in the tail region and some impulsive signals have not yet been positively identified. 相似文献
10.
Gurnett DA Kurth WS Poynter RL Granroth LJ Cairns IH Macek WM Moses SL Coroniti FV Kennel CF Barbosa DD 《Science (New York, N.Y.)》1989,246(4936):1494-1498
The Voyager 2 plasma wave instrument detected many familiar plasma waves during the encounter with Neptune, including electron plasma oscillations in the solar wind upstream of the bow shock, electrostatic turbulence at the bow shock, and chorus, hiss, electron cyclotron waves, and upper hybrid resonance waves in the inner magnetosphere. Low-frequency radio emissions, believed to be generated by mode conversion from the upper hybrid resonance emissions, were also observed propagating outward in a disklike beam along the magnetic equatorial plane. At the two ring plane crossings many small micrometer-sized dust particles were detected striking the spacecraft. The maximum impact rates were about 280 impacts per second at the inbound ring plane crossing, and about 110 impacts per second at the outbound ring plane crossing. Most of the particles are concentrated in a dense disk, about 1000 kilometers thick, centered on the equatorial plane. However, a broader, more tenuous distribution also extends many tens of thousands of kilometers from the equatorial plane, including over the northern polar region. 相似文献
11.
12.
Gurnett DA Kurth WS Roux A Gendrin R Kennel CF Bolton SJ 《Science (New York, N.Y.)》1991,253(5027):1522-1525
During the Galileo flyby of Venus the plasma wave instrument was used to search for impulsive radio signals from lightning and to investigate locally generated plasma waves. A total of nine events were detected in the frequency range from 100 kilohertz to 5.6 megahertz. Although the signals are weak, lightning is the only known source of these signals. Near the bow shock two types of locally generated plasma waves were observed, low-frequency electromagnetic waves from about 5 to 50 hertz and electron plasma oscillation at about 45 kilohertz. The plasma oscillations have considerable fine structure, possibly because of the formation of soliton-like wave packets. 相似文献
13.
Particle acceleration is one of the most important topics in plasma astrophysics as well as in cosmic-ray astrophysics. The heliosphere is an ideal astrophysical laboratory, wherein one can observe in situ the elementary mechanisms involved in the particle acceleration processes. Two phenomena of special interest are stochastic acceleration in the magnetohydrodynamic turbulence around comets and stochastic shock acceleration at interplanetary shock waves. 相似文献
14.
Electron plasma oscillations have been detected upstream of the solar wind termination shock by the plasma wave instrument on the Voyager 1 spacecraft. These waves were first observed on 11 February 2004, at a heliocentric radial distance of 91.0 astronomical units, and continued sporadically with a gradually increasing occurrence rate for nearly a year. The last event occurred on 15 December 2004, at 94.1 astronomical units, just before the spacecraft crossed the termination shock. Since then, no further electron plasma oscillations have been observed, consistent with the spacecraft having crossed the termination shock into the heliosheath. 相似文献
15.
An understanding of interstellar shock waves is crucial in determining the structure of the interstellar medium. By causing the gas to radiate, interstellar shocks provide astronomers with valuable diagnostics on both the physical conditions in the interstellar medium and the energy source that produced the shock. The complexity of the interstellar plasma-its degree of ionization, its molecular content, the presence of small dust grains and cosmic rays, and the magnetic field-leads to a rich variety of structures for interstellar shocks, which are being actively investigated both observationally and theoretically. 相似文献
16.
[目的]对海栖热袍菌电转化技术进行研究。[方法]采用不同参数即不同的方型电脉冲参数、指数衰退型电脉冲参数和高电压电击参数对海栖热袍菌感受态细胞进行电转化,得到的转化子进行PCR验证。[结果]试验中发现以150V的低压方形电脉冲,室温厌氧条件下电击25ms、1次,有利于T.maritima MS8的转化,但这种以整合质粒进行的转化效率极低。[结论]为提高T.maritima MS8的基因转化效率奠定了基础。 相似文献
17.
Kivelson MG Kennel CF McPherron RL Russell CT Southwood DJ Walker RJ Hammond CM Khurana KK Strangeway RJ Coleman PJ 《Science (New York, N.Y.)》1991,253(5027):1518-1522
During the 10 February 1990 flyby of Venus, the Galileo spacecraft skimmed the downstream flank of the planetary bow shock. This provided an opportunity to examine both the global and the local structure of the shock in an interval during which conditions in the solar wind plasma were quite steady. The data show that the cross section of the shock in planes transverse to the flow is smaller in directions aligned with the projection of the interplanetary magnetic field than in directions not so aligned. Ultralow-frequency waves were present in the unshocked solar wind, and their amplitude peaked when the spacecraft was downstream of the foreshock. At large distances down the tail, the Mach number of the flow normal to the shock is low, thus providing the opportunity to study repeated crossings of the collisionless shock in an interesting parameter regime. Some of the shock crossings reveal structure that comes close to the theoretically predicted form of intermediate shocks, whose existence in collisionless plasmas has not been confirmed. 相似文献
18.
液压实验台工作时，其油箱温度在一定范围内波动，将对液压元件测试精度造成不利影响，本文以单片机为核心研制成一种恒温装置，用于稳定油温，以使液压系统工作稳定。 相似文献
19.
In the current paradigm of cold dark matter cosmology, large-scale structures are assembling through hierarchical clustering of matter. In this process, an important role is played by megaparsec (Mpc)-scale cosmic shock waves, arising in gravity-driven supersonic flows of intergalactic matter onto dark matter-dominated collapsing structures such as pancakes, filaments, and clusters of galaxies. Here, we report Very Large Array telescope observations of giant ( approximately 2 Mpc by 1.6 Mpc), ring-shaped nonthermal radio-emitting structures, found at the outskirts of the rich cluster of galaxies Abell 3376. These structures may trace the elusive shock waves of cosmological large-scale matter flows, which are energetic enough to power them. These radio sources may also be the acceleration sites where magnetic shocks are possibly boosting cosmic-ray particles with energies of up to 10(18) to 10(19) electron volts. 相似文献