HL-2M装置真空室预装阶段检漏试验

通过在加工现场和安装现场搭建的真空辅助系统、四极质谱计及氦检漏仪组成的检漏系统,运用残余气体分析和氦质谱检漏方法在冷态下对HL-2M真空室扇形段及真空室整体进行了真空检漏试验.对漏点进行修复后,测试了真空室的极限真空度和总漏气率等.真空室经过72h的抽气后,真空度达到3.7×10?5Pa,超过了1.0×10?4Pa的预...     

The lowest electronic states of Ne2 +, Ar2 + and Kr2 +: comparison of theory and experiment

Non-relativistic configuration interaction (CI) ab initio calculations using large basis sets have been carried out to determine the potential curves of the first electronic states of Ne₂ ⁺, Ar₂ ⁺ and Kr₂ ⁺. The spin—orbit interaction was treated assuming that the spin—orbit coupling constant is independent of the internuclear separation (R). For Ar₂ ⁺, calculated dissociation energies and equilibrium separations are in good agreement with experimental results. The calculations for Ne₂ ⁺ suggest that the lowest vibrational level of the I(1/2u) ground state observed by threshold photoelectron spectroscopy by Hall et al. [1995, J. Phys. B: At. molec. opt. Phys., 28, 2435] and assigned to either ν = 0 or ν = 2 actually corresponds to ν = 4. The calculations also predict the I(1/2g) state of Ne₂ ⁺ and Ar₂ ⁺ to possess a double-well potential and that of Kr₂ ⁺ to be repulsive at short range and to only possess a single shallow well at large internuclear separation. The ab initio calculations provide an explanation for the observation made by Yoshii et al. [2002, J. chem. Phys., 117, 1517] that Kr₂ ⁺ and Xe₂ ⁺ dissociate after photoemission from the II(1/2u) state to the I(1/2g) state whereas Ar₂ ⁺ does not.     

Two-photon annihilation rate of the positronic HCN molecule

Positron binding by the HCN molecule was studied within a modified adiabatic approximation. This approach, in which the positron is treated as a light pseudonucleus with fractional charge, leads to the binding energy of 0.65?mHartree. Using effective positron mass which reproduces the Quantum Monte Carlo binding energy gives an estimation of the two-photon annihilation rate of e ⁺HCN, equal to 0.091?ns^?1.     

Time-series analysis of foreign exchange rates using time-dependent pattern entropy

Time-dependent pattern entropy is a method that reduces variations to binary symbolic dynamics and considers the pattern of symbols in a sliding temporal window. We use this method to analyze the instability of daily variations in foreign exchange rates, in particular, the dollar–yen rate. The time-dependent pattern entropy of the dollar–yen rate was found to be high in the following periods: before and after the turning points of the yen from strong to weak or from weak to strong, and the period after the Lehman shock.     

A short walk through quantum optomechanics

This paper gives a brief review of the basic physics of quantum optomechanics and provides an overview of some of its recent developments and current areas of focus. It first outlines the basic theory of cavity optomechanical cooling and gives a brief status report of the experimental state‐of‐the‐art. It then turns to the deep quantum regime of operation of optomechanical oscillators and covers selected aspects of quantum state preparation, control and characterization, including mechanical squeezing and pulsed optomechanics. This is followed by a discussion of the “bottom‐up” approach that exploits ultracold atomic samples instead of nanoscale systems. It concludes with an outlook that concentrates largely on the functionalization of quantum optomechanical systems and their promise in metrology applications.     

Hydrophobic Bimetallic Catalysts for H/D Exchange Reaction between Hydrogen and Water

Hydrophobic bimetallic catalysts of Pt-M on styrenedivinylbenzene were prepared, where M represents successively: Ir, Rh, Pd, Cu and Ag. The total metal loading was 0.5 wt% and the weight fractions of the metal M were: 0.0,0.05,0.1,0.25,0.5,0.75 and 1.0. For each sample, the catalytic activity for H/D exchange between hydrogen and water vapor was measured. In case of monometallic catalysts, no activity was detected for M = Cu and M = Ag, and the order of the activity values for the other metals was: Pt < Ir < Rh < Pd. For each bimetallic catalyst, the activity measurements indicated a clear interaction between the platinum and the second metal, thus the activity was significantly increased for M = Ir, increased for M = Rh, decreased for M = Pd, drastically decreased for M = Cu and M = Ag.     

Shock cooling of liquid nitrogen and superfluid helium

Abstract

Superfluid Helium (11) and liquid nitrogen are the only liquids which have been shown experimentally, to exhibit shock cooling. In the present paper we use the Landau model to demonstrate theoretically that the roton gap, which decreases with increasing density, plays the same role leading to shock cooling in liquid helium as the dissociation energy does in liquid nitrogen.     

Evaluation of the mechanical properties of PMC interface using slice compression test — Analysis of transfer mechanism of interfacial shear stress

Properties of the fiber/matrix interface in SiO₂/epoxy and SiC/epoxy composite are investigated using the slice compression test (SCT) for the single fiber, where the specimen is loaded and unloaded between a plate which has different mechanical properties. It is found that the interfacial debonding proceeds from the polished surface at a soft plate side and that the fiber protrusion occurs after unloading. The fiber-protrusion length is directly measured at each applied stress level using a scanning electron microscope. Interfacial shear-sliding stress is obtained based on the constant shear-sliding stress analysis employing the obtained protrusion length. It is demonstrated that the value of interfacial shear-sliding stress shows good agreement with that obtained from another technique, the push-out test, on the same system. The relation between the fiber-protrusion length and applied stress is proportional to a certain extent. From this result, it is analytically pointed out that the applied stress has a limiting value in this SCT because of Poisson's effect. Also, two interfacial debonding criteria, which are determined analytically for the PMC, are discussed.     

Influence of gamma radiation on morphology structure,electrochemical corrosion behavior and hardness of Ni–Cr based alloys

This study evaluates the effects of gamma radiation on structure, electrochemical corrosion behavior and Vickers hardness of commercial dental Nikkeli–Kromi–Polttosekoitus [Ni_65.2Cr_22.5Mo_9.5X_2.8 (X=Nb, Si, Fe and Mn)] alloy. The corrosion rate of Ni_65.2Cr_22.5Mo_9.5X_2.8 (X=Nb, Si, Fe and Mn) alloy with 0.5 M HCl is increased with increasing the exposure rate of gamma radiation. The corrosion resistance of Ni_65.2Cr_22.5Mo_9.5X_2.8 (X=Nb, Si, Fe and Mn) is varied and reaches a minimum value at 30 KGy. The corrosion potential value also is varied and reaches its highest value at 30 KGy. The Vickers hardness value of Ni_65.2Cr_22.5Mo_9.5X_2.8 (X=Nb, Si, Fe and Mn) alloy is decreased by increasing the gamma radiation dose. Also it is obvious from our results that the effects of gamma radiation at the surface are much higher as compared with deeper parts and the structure of the alloy is changed due to its exposure to gamma radiation.     

A theoretical and numerical evaluation of the steady-state burning rate of vertically oriented PMMA slabs

The steady state burning rate of vertically oriented slabs of poly-methyl-methacrylate (PMMA) is numerically investigated. Model predictions are compared with measurements and results of the laminar boundary layer (LBL) theory. The numerical model provides a solution of the Favre-averaged Navier–Stokes equations coupled with sub-models for turbulence, combustion, soot production and radiation. The modelling of condensed phase processes is based on the one-dimensional heat transfer equation and pyrolysis is treated as a phase change using the latent heat approach. Results show that the pyrolysing region can be divided into three regions. In the laminar part of the flow (Gr _x < 4.3 × 10⁷), the predicted normalised burning rate, [mdot]″ _p x/μ_∞, is a power-law function of Gr _x with an exponent close to that of the LBL theory, surface re-radiation being the primary source of discrepancies. From the LBL theory for free flow, it is demonstrated that the local burning rate is inversely proportional to the shear velocity gradient. This is globally confirmed by numerical model results. At Gr _x = 4.3 × 10⁷ the change in slope of the burning rate observed experimentally, which indicates the end of the laminar flow region, is reproduced numerically. From Gr _x = 2.5 × 10⁹ model results show that the surface mass flux of pyrolyzate increases with x, in agreement with experimental data in literature.