The spectral observation of decimetric spikes with very high spectral resolution

Thousands of decimetric spikes were observed with a new spectrometer of Yunnan Observatory on June 24, 2001. The statistical analyses of the bandwidth, polarization degree, and half power duration of these spikes were made. We found that the absolute bandwidth of the spikes is down to the low limit of the instrument's spectral resolution (about 1.4 MHz). 76% of the total spikes have the polarization degree greater than 70%. The distribution of the half power durations concentrates on less than 16 milliseconds. These results support the interpretation of the electron cyclotron maser (ECM) mechanism for the decimetric spikes.     

TCP在光突发交换试验网络中性能的实验研究

在光突发交换试验网络中对TCP的性能进行了实验研究.首先研究了丢包对网络性能的影响,表明突发包丢失将导致TCP吞吐量的快速下降,并且丢包率越高,可用的TCP传输带宽越窄.然后分别详细研究了OBS试验网络中的延时损伤和报文段关联增益,以及对TCP传输性能的影响.最后综合考虑这些因素.实验结果表明,在本OBS试验网络中存在一个不随丢包率变化的最优化突发包组装时间250us使得可用TCP带宽最大化.为了最大限度地提高TCP的传输性能,组包时间应该选择等于或稍大于这个最优值.     

Luminescence of silver chloride microcrystals upon photoexcitation by different methods

The luminescence spectra of AgCl microcrystals were measured in two different regimes: in the regime of excitation of stationary luminescence and in the regime of photostimulated burst of luminescence. Differences between the spectra of stationary luminescence and the spectra of photostimulated-luminescence burst in the range between 430 and 590 nm have been found. The luminescence spectra are complex; the ratio of intensities for elementary components changes with the technique of excitation. Differences in the form and composition of complex luminescence bands obtained under different conditions of registration are attributed to the recombination interaction of the luminescence centers. It is shown that analysis of the dependences of intensity ratios for the elementary components of a complex luminescence band on the exciting-radiation intensity allows one to evaluate the mechanism of recombination in elementary bands provided that the mechanism is known for at least one luminescence band.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 1, pp. 85–89. January–February, 2005.     

NON-OCCURRENCE OF TRAPPED SURFACES AND BLACK HOLES IN SPHERICAL GRAVITATIONAL COLLAPSE

By using the most general form of Einstein equations for General Relativistic (GTR) spherical collapse of an isolated fluid having arbitrary equation of state and radiation transport properties, we show that they obey a Global Constraint, 2GM(r, t)/R(r, t)c ²1, where R is the invariant circumference radius, t is the comoving time, and M(r, t) is the gravitational mass enclosed within a comoving shell r. This inequality specifically shows that, contrary to the traditional intuitive Newtonian idea, which equates the total gravitational mass (M _b) with the fixed baryonic mass (M ₀), the trapped surfaces are not allowed in general theory of relativity (GTR), and therefore, for continued collapse, the final gravitational mass M _f0 as R0. This result should be valid for all spherical collapse scenarios including that of collapse of a spherical homogeneous dust as enunciated by Oppenheimer and Snyder (OS). Since the argument of a logarithmic function cannot be negative, the Eq. (36) of the O–S paper (TIn ) categorically demands that y _b=R _b/R _gb1, or 2GM _b/R _b c ²1, where R _b referes to the invariant radius at the outer boundary. Unfortunately, OS worked with an approximate form of Eq. (36) [Eq. 37], where this fundamentalconstraint got obfuscated. And although OS noted that for a finite value of M(r, t) the spatial metric coefficient for an internal point fails to blow up even when the collapse is complete for R0, they, nevertheless, ignored it, and, failed to realize that such a problem was occurring because they were assuming a finite value ofM _f, where M _f is the value of the finite gravitational mass, in violation of their Eq. (36).Additionally, irrespective of the gravitational collapse problem, by analyzing the properties of the Kruskal transformations we show that in order that the actual radial geodesics remain timelike, finite mass Schwarzschild Black Holes can not exist at all.Our work shows that as one attempts to arrive at the singularity, R0, the proper radial length l= dr (even though r and R are finite), and the collapse process continues indefinitely. During this indefinite journey, naturally, the system radiates out all available energy, QM _i c ², because trapped surfaces are not formed. And this categorically shows that GTR is not only the most beautiful physical theory, but also, is the only, naturally, singularity free theory (atleast for isolated bodies), as intended by its founder, Einstein. However, this derivation need not rule out the initial singularity of big bang cosmology because the universe may not be treated as an isolated body.There is a widespread misconception, that recent astrophysical observations have proved the existence of Black Holes. Actually, observations suggest existence of compact objects having masses greater than the upper limit of static Neutron Stars. The present work also allows to have such massive compact objects. It is also argued that there is evidence that part of the mass-energy accreting onto several stellar mass (binary) compact objects or massive Active Galactic Nuclei is getting lost, indicating the presence of an Event Horizon. Since, we are showing here that the collapse process continues indefinitely with local 3-speed Vc, accretion onto such Eternally Collapsing Objects (ECO) may generate little collisional energy out put. But, in the frame work of existence of static central compact objects, this small output of accretion energy would be misinterpreted as an evidence for Event Horizons. Thus the supposed BHs are actually massive compact ECOs.     

大脉冲热负荷下HL-2A偏滤器靶板的热分析

HL－2A安装完成后,将以ASDEX最终的运行参数水平进行工程调试。本文研究了,在仅有欧姆加热和3.5MW中性束注入条件下,当HL－2A发生大不稳定性或巨ELMs爆发时,有水冷却和辐射冷却两种情况下不同板材料偏滤器板的温升和冷却时间。     

Determination of Gravitomagnetic Field Through GRBs or X-ray Pulsars

In gauge theory of gravity, there is direct coupling between the spin of a particle and gravitomagnetic field, which will affect Landau level. In the surface of a neutron star or near a black hole, the coupling energy between spin and gravitomagnetic field can be large and detectable. Precise measurement of the position of spectrum lines of the corresponding emission or absorption can help us to determine the gravitomagnetic field and electromagnetic field simultaneously. The ratio ΔE_e/ΔE_p can be served as a quantitative criteria of black hole. In GRBs or X-ray pulsar, absorption spectral lines of electron were observed. If the absorption spectral lines of electron, neutron and proton can be observed simultaneously, using the method given in this paper, we can determine the gravitomagnetic field in the surface of the star, and discriminate black hole from neutron star.     

In situ observation of cascade damage under heavy ion irradiation

Abstract

Collision cascades initiated from high energy PKAs produce defect clusters in crystalline solids irradiated with fast neutrons or energetic ions. They will affect not only an early stage of microstructural evolution but that at high fluence by changing free defect survival rate. To elucidate fundamental processes of cascade damage evolution, in situ observation of microstructure in FCC metals under heavy ion irradiation has been carried out using a combined facility of a 400 kV accelerator and a 200 kV transmission electron microscope installed in the University of Tokyo, Tokai. Defect clusters produced by individual energetic ions are observed during irradiation to examine subcascade formation, interaction of point-defects from cascade damage and related point-defect processes.     

Effect of chemical functionalization on the mechanical properties of polypropylene hollow fiber membranes

Chemical treatment of polymeric hollow fiber membranes (HFMs) is used to prepare their exterior surfaces for coatings. Typical treatments can cleave both C? C and C? H bonds of polypropylene, leading to lower mechanical strength of the fibers. This study evaluated the yield strength, maximum strain, ultimate tensile strength, and burst strength of HFMs treated with each of three common oxidizing reagents: ozone as a gas phase system, aqueous solutions of potassium persulfate, and ammonium persulfate for liquid phase systems. The yield strength and ultimate tensile strength of HFMs decreased continuously with increasing ozonation time. Batch treatments with aqueous oxidizing systems showed limiting values of the yield and ultimate tensile strengths with time. Swelling the hollow fibers with methanol prior to oxidation caused less reduction of the mechanical properties after persulfate treatment. Fibers pretreated with methanol showed lower losses of mechanical properties strength with aqueous oxidation systems. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1366–1373     

恒稳推进的煤与瓦斯突出

本文建立理想的一维运动模型,对煤与瓦斯突出的机理进行了探讨,指出煤的破碎起动与瓦斯渗流的耦合是煤与瓦斯突出的内在因素,大型突出相应于恒稳推进的情况,通过分析给出了讨论煤与瓦斯突出的重要的无量纲参数以及突出判据的近似形式。     

壁面加热湍流相干结构的实验研究

用热线风速仪测量了风洞中壁面加热平板湍流边界层不同法向位置的流向脉动速度,用条件采样方法中的m-u-level法和VITA法研究了壁面加热对壁湍流相干结构猝发条件平均波形的影响,发现壁面另热能够提高猝发强度,缩短喷射时间,使一次猝发中出现多次喷射事件的现象明显增多,增强猝发的间歇性。