Variations on a Constant Theme

We describe how theories incorporating time-varying coupling constants can drive the Universe to a late-time near-flat attractor in which the cosmological constant is very small. We also discuss some consequences of allowing time-varying constants to vary in space as well.     

方位词“左”的修辞阐释

从方位词＂左＂的语义入手,结合史料,对＂尊左＂＂卑左＂现象加以归纳和分析,认为＂卑左＂和＂尊左＂的现象在古代中国同时并存,适用于不同的范围、情景。这种现象反映出中国古人把握世界时的多元和灵活特性。     

基于热丝法对CaO-SiO_2-Al_2O_3保护渣结晶性能与凝固分数的研究

针对髙铝包晶钢连铸设计了Ca O-Si O2-Al2O3系保护渣.采用单丝法研究w(Ca O)/w(Al2O3)对保护渣结晶性能的影响;采用双丝法模拟了保护渣渣膜形成及凝固过程,研究了w(Ca O)/w(Al2O3)对保护渣固相体积分数φ的影响.结果表明:实验保护渣系结晶能力随w(Ca O)/w(Al2O3)增大而增强,按结晶能力分为两个区间,w(Ca O)/w(Al2O3)1.30时保护渣结晶能力强于w(Ca O)/w(Al2O3)≤1.30的保护渣;在等温结晶过程中,w(Ca O)/w(Al2O3)=1.00的实验保护渣中析出枪晶石,w(Ca O)/w(Al2O3)=2.50时渣中析出硅酸二钙;w(Ca O)/w(Al2O3)增大使保护渣渣膜双丝间固相体积分数增大,结晶层增厚,不利于保证结晶器内润滑.与浇注常规包晶钢的Ca O-Si O2系保护渣性能对比表明,Ca O-Si O2-Al2O3系保护渣在w(Ca O)/w(Al2O3)≤1.30时的结晶能力和固相体积分数都与对照渣相近,设计的Ca O-Si O2-Al2O3系保护渣适用于高铝包晶钢连铸.     

Effect of Porous Coatings on Stability of Hypersonic Boundary Layers

The influence of ultrasoundw15w8p3238/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">absorbing coatings on stability of hypersonic boundary layers is considered. Two types of coatings were used in experiments: feltw15w8p3238/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">metal with a random porous microstructure and a sheet perforated by blind cylindrical microchannels. The experiments were performed in a wind tunnel at a Mach number M = 5.95 on sharp cones with a 7° apex halfw15w8p3238/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">angle. Evolution of natural disturbances and artificially induced wave packets in the boundary layer was studied with the help of hotw15w8p3238/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">wire anemometry. Spatial characteristics of artificial disturbances were obtained. It is demonstrated that such coatings exert a stabilizing effect on secondw15w8p3238/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">mode disturbances.     

Biomechanical effects of shock waves onEscherichia coli and λphage DNA

Escherichia coli (recombinant cells) and w7467118/xxlarge955.gif" alt="lambda" align="BASELINE" BORDER="0">phage DNA in suspension liquid were exposed to pressure pulses of about 20w7467118/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">s duration and amplitude of up to 14 MPa. These pulses were generated by a diaphragmless shock tube. The destruction of cells was monitored by the assay of phenylalanine dehydrogenase leaking from the recombinant cells and was found to increase remarkably at the peak pressure of higher than 12 MPa. A probability relation for the cell destruction expressed as a function of pressure was proposed. It is most likely that there exists a threshold pressure for the cell destruction. Fragmentation effects of shock waves on w7467118/xxlarge955.gif" alt="lambda" align="BASELINE" BORDER="0">phage DNA were analyzed by electrophoresis. They were enhanced by increasing the shock wave strength and the number of shots. Probability for the DNA fragmentation as a function of pressure and molecular size was estimated with HPLC. The larger size of the DNA was more easily fragmented. A threshold pressure does not seem to exist for the DNA fragmentation.     

Independent‐Stress Method for Analysis of Nonlinear Antiplane Strain

The stress field in a cylindrical body under antiplane strains is studied using the nonlinear theory of elasticity in actual variables under assumptions of the absence of body forces and weak nonlinearity of the elastic potential. The stresses are determined by solving the nonlinear boundaryw3/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">value problem for two independent stresses in polar coordinates of the physical and stress planes. Analytical solutions of the nonlinear problems are obtained. The effect of potential nonlinearity is studied. It is shown that the nonlinear problem can be solved using the harmonicw3/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">equation solution corresponding to the linear potential.     

Plane Problem of Vibrations of an Elastic Floating Plate under Periodic External Loading

The Wiener–Hopf technique is used to construct an analytical solution of the problem of vibrations of a semiw/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">infinite elastic floating plate under periodic external loading. The solution is obtained in explicit form ignoring draft. The dependences of the amplitudes of surface waves and icew/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">plate deflection on the loading distribution and frequency, ice thickness, and liquid depth are studied numerically. It is established that for some types of acting load, no waves propagate in the plate and liquid and the plate vibrations are standing waves localized near the loading region. An example of such vibrations is given and a condition for the occurrence of localized vibrations is found.     

S波段气象雷达天线馈线设计与测量

馈线是雷达系统的重要组成部分。介绍了S波段8.54m天气雷达天线馈线的基本特性,提出了S波段天气雷达天线波导馈线的设计方案,论述了其设计原则及性能估算方法。最后,描述了波导馈线插入损耗和电压驻波比的测试原理和方法程序,给出了S波段8.54m天气雷达天线馈线插入损耗和电压驻波比的实测结果,测量结果满足理论设计的技术要求。     

Non‐relativistic Eigen spectra with q‐deformed physical potentials by using the SUSY approach

The Schrödinger equation is solved for some of the q‐deformed physical potentials within the framework of supersymmetric approach and supersymmetric Wentzel–Kramers–Brillouin approximation method. The energy levels are obtained with the corresponding normalized wave functions in terms of hypergeometric functions. The energy equations for some special cases of these potentials are discussed, and some of the thermodynamic quantities of the canonical system and the optical quantities of the two‐level system are calculated for one of the potentials. Some of the numerical results are shown, too. Copyright © 2016 John Wiley & Sons, Ltd.     

Investigation of Selected Properties of Injection-Molded Parts Subjected to Natural Aging

This article provides general information about the aging process of polymer plastics. It also reports the experimental results of investigations undertaken to determine changes in the mechanical properties of polypropylene injection-molded samples with the oxo-biodegradable additive d2w which were subjected to natural aging for two years. A decrease of tensile strength and elongation at yield as well as an increase of hardness were observed during the experiment.