Low-Gas Detonation in Low-Density Mechanically Activated Powder Mixtures

Technical Physics - We have analyzed experimental data on supersonic self-sustained propagation of an energy-release wave in low-density mechanically activated mixtures. Various mechanisms that can...     

Appearance potential spectroscopy of CuZr and CuTi metallic glasses

The local density of empty electronic states at the Cu sites in CuZr and CuTi has been derived from soft X-ray appearance potential spectroscopy (SXAPS) on glassy Cu₆₀Zr₄₀ and Cu₄₀Ti₆₀ samples. An energetically narrow d-like density of states is found just above the Fermi level. Results are discussed in terms of d-band hybridization.     

Crystallization Kinetics Study on Magnetron-Sputtered Amorphous TiA1 Alloy Thin Films

Crystallization kinetics of magnetron-sputtered amorphous TiAl ahoy thin films is investigated by differential scanning calorimetry through isothermal analysis and non-isotherm analysis. In non-isothermai analysis, the Kissinger method and the Ozawa method are used to calculate the apparent activation energy and local activation energy, respectively, in the crystallization processes of amorphous TiA1 thin films. Furthermore, the crystallization mechanism is discussed from the investigation of the A vrami exponent by isothermal analysis. In addition, x-ray diffraction is utilized to reveal the grain orientation and evolution during the crystallization of TiA1 thin fihns.     

Surface and Bulk Crystallization of Fe61Co21Nb3B15 Alloy

Surface and bulk crystallization of Fe₆₁Co₂₁Nb₃B₁₅ alloy has been studied. Crystallization (surface and bulk) of specimens starts after annealing at 400°C. Differences in crystalline fraction, order in crystalline phase and environment around Fe-atom are observed at the surface and in the bulk. Crystalline component appearance (both at the surface and in the bulk) after annealing at 480°C is attributed to Fe₃Co. This revised version was published online in August 2006 with corrections to the Cover Date.     

Crystallization of a quasi-two-dimensional granular fluid

We experimentally investigate the crystallization of a uniformly heated quasi-2D granular fluid as a function of the filling fraction. Our experimental results for the Lindemann melting criterion, the radial distribution function, the bond order parameter, and the statistics of topological changes at the particle level are the same as those found in simulations of equilibrium hard disks. This direct mapping suggests that the study of equilibrium systems can be effectively applied to study nonequilibrium steady states such as those found in our driven and dissipative granular system.     

Mechanically scanned leaky-wave antenna based on a topological one-way waveguide

We propose a uniform backfire-to-endfire leaky-wave antenna (LWA) based on a topological one-way waveguide under external bias magnetic field. We systematically analyze the dispersion, showing that the proposed structure supports leaky mode arisen from total internal reflection. By means of tuning frequency or magnetic field, we obtain fixed-bias frequency and fixed-frequency bias LWA with continuous beam scanning from backward, broadside to forward direction. More importantly, we, for the first time, demonstrate that this proposed LWA shows mechanical tunability, allowing us to manipulate the radiation direction from backward, broadside to forward direction by mechanically tuning the air layer thickness. The simulated results show that our system exhibits super low 3dB beam width, high radiation efficiency as well as high antenna gain. Being provided such multiple controlled (especially mechanically) beam scanning manners, the present LWA paves an advanced approach for continuous beam scanning, holding a great potential for applications in modern communication and radar system.     

无机械连接方位角测量系统中磁光调制的温度适应性研究

在无机械连接的方位角测量系统的研制中,通过对磁光材料的特性及磁旋光温漂的成因分析,采用直接读出解调和方位随动测角的方法,有效的降低了由Verdet常数变化引起的磁旋光漂移导致的方位失调角变化.使得系统可以在无需补偿和预热的情况下实时测量,方位测角精度3δ小于5″.     

Crystallization of electrons confined to a lattice

A necessary condition for electron crystallization is the dominance of the electronic Coulomb repulsion as compared with the kinetic energy. We show that 4f systems are good candidates for electron or hole crystallization to occur since the small radius of the 4f shell leads to small hybridizations and hence kinetic energy of the f electrons. Crystallization may take place in lattices with several equivalent 4f sites per unit cell when the electron or hole number is less than the number of sites. We give evidence that charge ordering in Yb₄As₃ is an example of the mechanism considered here. We also compare it with those considered by Wigner, Verwey, Mott and Hubbard.     

Crystallization in the Presence of a Flow

Physics of the Solid State - A method of calculating the size distribution of supercritical nuclei in the presence of flows in a melt or in a vapor for the first-order phase transition, namely, for...     

Crystallization in a One-Dimensional Periodic Landscape

Journal of Statistical Physics - We consider the crystallization problem for a finite one-dimensional collection of identical hard spheres in a periodic energy landscape. This issue arises in...     

Crystallization waves in a dusty plasma

Crystallization waves in the dusty component of a complex plasma, which were recently observed experimentally, have been investigated numerically. The evolution of the system of charged microparticles whose interaction between each other is described by a screened Coulomb potential (Yukawa potential) has been numerically simulated using the molecular dynamics method. It has been shown that the process of the formation and propagation of a crystallization wave in such a system is fundamentally three-dimensional. Analysis of the local structure of dust particles behind the crystallization wave front indicates the coexistence of different types of the crystal lattice including the metastable phase, i.e., a nonequilibrium phase transition.     

Proton Crystallization in a Dense Hydrogen Plasma

We perform a first‐principle analysis of Coulomb crystallization in neutral two‐component mass asymmetric plasmas by large‐scale path integral Monte Carlo simulations for a dense hydrogen plasma in a broad density range. We observe two large jumps in the relative distance fluctuations of protons that are connected with qualitative changes in the behavior of the proton pair distribution function and are attributed to the formation of a spatially ordered state. A third smaller jump inside the ordered phase indicates a structural transition (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Algebraic Time Crystallization in a Two-Dimensional Superfluid

Journal of Experimental and Theoretical Physics - Time crystallization is a hallmark of superfluidity, indicative of the fundamental fact that along with breaking the global U(1) symmetry,...     

Crystallization in a dense suspension of self-propelled particles

Using Brownian dynamics computer simulations, we show that a two-dimensional suspension of self-propelled ("active") colloidal particles crystallizes at sufficiently high densities. Compared to the equilibrium freezing of passive particles, the freezing density is both significantly shifted and depends on the structural or dynamical criterion employed. In nonequilibrium the transition is accompanied by pronounced structural heterogeneities. This leads to a transition region between liquid and solid in which the suspension is globally ordered but unordered liquidlike "bubbles" still persist.     

Mechanically controlled DNA extrusion from a palindromic sequence by single molecule micromanipulation

A magnetic tweezers setup is used to control both the stretching force and the relative linking number DeltaLk of a palindromic DNA molecule. We show here, in absence of divalent ions, that twisting negatively the molecule while stretching it at approximately 1 pN induces the formation of a cruciform DNA structure. Furthermore, once the cruciform DNA structure is formed, the extrusion of several kilo-base pairs of palindromic DNA sequence is directly and reversibly controlled by varying DeltaLk. Indeed the branch point behaves as a nanomechanical gear that links rotation with translation, a feature related to the helicity of DNA. We obtain experimentally a very good linear relationship between the extension of the molecule and DeltaLk. We use then this experiment to obtain a precise measurement of the pitch of B-DNA in solution: 3.61 +/- 0.03 nm/turn.