First-principles study of the local structure and crystal field of Yb^(2+) in sodium and potassium halides

The local coordination structures around the doping Yb2＋ ions in sodium and potassium halides were calculated by using the first-principles supercell model. Both the cases with and without the charge compensation vacancy in the local environment of the doping Yb2＋ were calculated to study the effect of the doping on the local coordination structures of Yb2＋. Using the calculated local structures, we obtained the crystal-field parameters for the Yb2＋ ions doped in sodium and potassium halides by a method based on the combination of the quantum-chemical calculations and the effective Hamiltonian method. The calculated crystal-field parameters were analyzed and compared with the fitted results.

High power disk laser

The mono-module disk laser concept is an effective design for diode-pumped solid-state lasers, which allows the realization of lasers with super-high output power, having very good efficiency and also excellent beam quality. Since the first demonstration of the principle in 1964 the output power of mono-module disk has been increased to the level of few kW in continuous wave (CW) mode of operation. “Zig-Zag” disk laser geometry does not look like as a perspective one for further output parameters growing. The scaling laws for mono-module disk laser design show that the limits for CW mode of operation are far beyond 100 kW for output power and the energy can be higher than 100 J in pulsed mode of operation. Due to the efficient porous cooling technology and possibility of amplified spontaneous emission (ASE) suppression the operation of the mono-module disk laser geometry is possible in CW and pulse-periodical (P-P) modes at extremely high output power.

Influence of Zr and Mn additions on microstructure and properties of Mg-2.5wt%Cu-Xwt%Zn(X=2.5,5 and 6.5)alloys

This work studied the effects of adding Zr and Mn in amounts less than 1wt%on the microstructure,mechanical properties,casting properties,and corrosion resistance of Mg-Zn-Cu alloys containing 2.5wt%Cu and 2.5wt%-6.5wt%Zn.The hardness and electrical conductivity measurements were used to find an optimal heat treatment schedule with the best mechanical properties.It has been established that Zr significantly increases the yield strength of the alloys due to a strong grain refinement effect.However,the presence of Mn and Zr has a detrimental effect on alloy’s elongation at fracture.It was shown that the precipitation of the Mg_(2)Cu cathodic phase in the alloy structure negatively affects the corrosion behavior.Nevertheless,the addition of Mn decreases the corrosion rate of the investigated alloys.The best combination of the mechanical,casting,and corrosion properties were achieved in the alloys containing 2.5wt%Cu and 5wt%Zn.However,the Mn or Zr addition can improve the properties of the alloys;for example,the addition of Mn or Zr increases the fluidity of the alloys.

High power optics and its new manifestations

The advent of the laser has placed stringent requirements on the fabrication, performance and quality of optical elements employed within systems for most practical applications. Their high power performance is generally governed by three distinct steps, firstly the absorption of incident optical radiation (governed primarily by various absorption mechanisms);secondly, followed by a temperature increase and response governed primarily by thermal properties and finally the elements thermo-optical and thermomechanical response, e.g., distortion, stress birefringenous fracture, etc. All of which needs to be understood in the design as efficient, compact, reliable and useful for many applications high power systems, under a variety of operating conditions, pulsed and continuous wave, rep-rated or burst mode of varying duty cycles.

The Mass and Size of Photons in the 5-Dimensional Extended Space Model

We propose the generalization of Einstein’s special theory of relativity (STR). In our model, we use the (1 + 4)-dimensional space G, which is the extension of the (1 + 3)-dimensional Minkowski space M. As a fifth additional coordinate, the interval S is used. This value is constant under the usual Lorentz transformations in M, but it changes when the transformations in the extended space G are used. We call this model the Extended space model (ESM). From a physical point of view, our expansion means that processes in which the rest mass of the particles changes are acceptable now. In the ESM, gravity and electromagnetism are combined in one field. In the ESM, a photon can have a nonzero mass and this mass can be either positive or negative. It is also possible to establish in the frame of ESM connection between mass of a particle and its size.

Low Temperature Growth of SWNTs on a Nickel Catalyst by Thermal Chemical Vapor Deposition

围单人赛的碳 nanotubes (SWNT ) 在支持硅石的一金属的镍(Ni ) 上被种了在温度从的催化剂象 450 一样低 ? 偅 ???  ???? 慮潮潣灭獯瑩獥吗？？