Saturation Effects and the Colored Pump Noise in a Dye Laser

We investigate the statistical properties of two single-mode dye-laser models-the colored-loss-noise model and the colored-gain-noise model. Analytic expressions of the probability,the mean and the variance of the steady-state laser intensity are obtained through the unified expansion theory [Phys. Rev. A43 (1991) 700]. By comparison we find that when the cavity decay rate for the electric field is large and the pump parameter a₀ is small, the differences of the results of the two laser models are small. Otherwise, the differences are large. And the correlation time of the noise has very obvious influence on the results of the two models.     

Quasi-stationäre Schwingungen einer rotierenden Welle,die an einem Hindernis streift — Spiral Vibration

Übersicht Das Streifen einer rotierenden Welle an einem stehenden Hindernis wird unter vereinfachenden Annahmen durch nichtlineare Vektordifferentialgleichungen beschrieben. Als Hindernis kommen Schleifringe, Kollektoren und Dichtungsringe bei elektrischen Maschinen oder Statoren und Gehäuse bei Turbomaschinen in Frage. Der Schwingungsvektor der rotierenden Welle ist im rotierenden System zeitlich veränderlich. Die Spitze beschreibt eine kreisformähnliche Kurve, und der Betrag kann nach genügend langer Zeit und Wärmeentwicklung rasch unzulässige Werte annehmen. Der Vorgang kann somit zu einer Instabilität führen. Das langsame Drehen des Schwingungsvektors kann mit guter Näherung einer gewöhnlichen Vektorgleichung entnommen werden. Die theoretischen Resultate erklären alte und neue Beobachtungen an laufenden Maschinen.

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Summary The rubbing of a rotating shaft on a stationary interference is represented, subject to some simplifying assumptions, by a system of nonlinear vector differential equations. Sliprings, collectors and sealing rings are typical interference elements in electrical machines, as are stators and housings in turbines. The vibration vector of the rotating shaft varies with time in the rotating coordinate system. The locus of the vibration vector point is approximately circular and its magnitude can quickly rise to an unacceptable value after a sufficiently long time and heat dissipation. The process can therefore become unstable. To a good approximation the slow rotation of the vibration vector can be derived from an ordinary vector equation. The theoretical results cast light on both former and recent observations on machines in operation.

     

网络上两类物资联合最大流问题的极流特征

当网络上(诸如交通网络、通讯网络)有多种不同物资或信息同时分别从相应的发点输送到相应的收点,要求每条线路上各类物资或信息的输送量总和不超过线路的容量时,寻求所有物资的最大输送量的问题,就是所谓网络多种物资的最大流问题,这个问题在生产实际和理论上都有着重要的意义,1963年T.C.Hu提出了求两类物资联合最大流的标号方法,但是为了保证有限步达到最大流,要求边的容量是偶数。 本文是文献[3]的继续,用图论的语言描述了两类物资最大流问题极流的特征,并对标号方法作了一点修改,使得有限步得到最大流,或者在某一步得到极流后,保证以后的迭代是从极流到极流.这样因极流的个数是有限的,并且最大流总可以在极流上达到,从而保证了有限步内得到所要求的最大流,无须对边的容量作任何限制, 本文所提的算法是使图形特征很强的标号算法和线性规划的极点迭代结合起来,这就使得有可能把这种方法,推广到更大的一类问题中,例如,研究容量的改变对最大流量的影响。     

分子束研究GaAs和InP与氯的激光化学反应动态学

本文采用CW超声分子束和时间分辨质谱技术,研究了在紫外和可见(355nm和560nm)脉冲激光辐照下GaAs(100)和InP(100)表面与氯的激光化学反应动态学。由质谱和飞行时间谱测得反应的主要产物为GaCl_x和InCl_x(x=1,2),研究了激光波长和能量密度对产物飞行时间谱的影响,首次发现提高入射Cl₂分子的平动能对上述激光诱导气-固相反应有明显的增强作用。     

A Study of Synthesis, Immobilization and Catalytic Capability of Metalloporphyrin

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Dense particle cloud dispersion by a shock wave

A dense particle flow is generated by the interaction of a shock wave with an initially stationary packed granular bed. High-speed particle dispersion research is motivated by the energy release enhancement of explosives containing solid particles. The initial packed granular bed is produced by compressing loose powder into a wafer with a particle volume fraction of $\phi _\mathrm{p} = 0.48$ . The wafer is positioned inside the shock tube, uniformly filling the entire cross-section. This results in a clean experiment where no flow obstructing support structures are present. Through high-speed shadowgraph imaging and pressure measurements along the length of the channel, detailed information about the particle shock interaction was obtained. Due to the limited strength of the incident shock wave, no transmitted shock wave is produced. The initial solid-like response of the particle wafer acceleration forms a series of compression waves that eventually coalesce to form a shock wave. Breakup is initiated along the periphery of the wafer as the result of shear that forms due to the fixed boundary condition. Particle breakup is initiated by local failure sites that result in the formation of particle jets that extend ahead of the accelerating, largely intact, wafer core. In a circular tube, the failure sites are uniformly distributed along the wafer circumference. In a square channel, the failure sites, and the subsequent particle jets, initially form at the corners due to the enhanced shear. The wafer breakup subsequently spreads to the edges forming a highly non-uniform particle cloud.     

Biegeschwingungen einer unrunden,rotierenden Welle in horizontaler Lage

Ohne Zusammenfassung     

非结构网格上一种新型的高分辨率高精度无波动的有限元格式

在非结构网格上构造出无波动无自由参数耗散性有限元格式 ,即NND有限元格式 .通过若干个典型二维跨音速和超音速可压缩无粘定常流动的算例证明这确是一个高精度的 ,对激波具有高分辨率的无波动的新型有限元格式 .特别与网格自适应相结合 ,可得到十分满意的结果