松花江冰下声学试验技术研究

北极区域极具战略意义与商业价值,随着各国的广泛关注,针对北极地区开展的科考科研活动逐渐增多。其中北极海域的相关研究尤为重要,特别是北极水声学,是保障北极军事存在以及正常科考科研活动的重要支撑。课题组于2015年1月在哈尔滨松花江进行了冰下声学试验,主要内容包括冰下信道测试、冰层散射系数测量以及冰下水声通信试验,实现了冰下半波导现象的初步观测、冰层前向散射系数的测量、基于能量检测器的低信噪比扩频通信、基于时反镜判决反馈均衡技术的高速水声通信以及冰下12用户多址水声通信等内容。本文对本次冰下声学试验情况进行介绍,并给出了相应的试验结果及经验总结。     

Environmentally benign oxidation reaction of aldehydes to their corresponding carboxylic acids using Pd/C with NaBH4 and KOH

Pd/C catalyst in aqueous methanol with sodium borohydride and potassium hydroxide under the air efficiently oxidized aldehydes to their corresponding carboxylic acids at room temperature. The utilization of room temperature reaction, aqueous methanol solvent, and the open-air conditions make this manipulation very interesting for economic and environmental perspectives.     

Process and performance of hot dip zinc coatings containing ZnO and Ni-P under layers as barrier protection

A new coating system of under layer for hot dip zinc coating was explored as an effective coating for steel especially for application in relatively high aggressive environments. The influence of different barrier layers formed prior to hot dip galvanization was investigated to optimize high performance protective galvanic coatings. The deposition of ZnO and Ni-P inner layers and characteristics of hotdip zinc coatings were explored in this study. The coating morphology was characterized by scanning electron microscope (SEM) analysis. The hot dip zinc coatings containing under layer showed substantial improvement in their properties such as good adhesion, and high hardness. In addition, a decrease in the thickness of the coating layer and an enhancement of the corrosion resistance were found. Open circuit potential (OCP) of different galvanized layers in different corrosive media viz. 5% NaCl and 0.5 M H₂SO₄ solutions at 25 ± 1 °C was measured as a function of time. A nobler OCP was exhibited for samples treated with ZnO and Ni than sample of pure Zn; this indicates a dissolution process followed by passivation due to the surface oxide formation. The high negative OCP can be attributed to the better alloying reaction between Zn and Fe and to the sacrificial nature of the top pure zinc layer.     

Ge掺杂β-Ga2O3晶体的发光性能研究

采用浮区法(FZ)生长Ge掺杂β-Ga2O3晶体,利用XRD和Raman光谱研究了掺杂对晶体结构的影响.透射光谱测试表明,随着Ge离子掺杂浓度增加,Ge∶ β-Ga2O3晶体光学带隙增大.在4.67 eV紫外光激发下,Ge∶ β-Ga2O3晶体的发光强度与β-Ga2O3晶体相当,发光衰减时间比β-Ga2O3晶体更快.     

Electrochemical Designing of Au/Pt Core Shell Nanoparticles as Nanostructured Catalyst with Tunable Activity for Oxygen Reduction

Au/Pt core shell nanoparticles (NPs) have been prepared via a layer‐by‐layer growth of Pt layers on Au NPs using underpotential deposition (UPD) redox replacement technique. A single UPD Cu monolayer replacement with Pt(II) yielded a uniform Pt film on Au NPs, and the shell thickness can be tuned by controlling the number of UPD redox replacement cycles. Oxygen reduction reaction (ORR) in air‐saturated 0.1 M H₂SO₄ was used to investigate the electrocatalytic behavior of the as‐prepared core shell NPs. Cyclic voltammograms of ORR show that the peak potentials shift positively from 0.32 V to 0.48 V with the number of Pt layers increasing from one to five, suggesting the electrocatalytic activity increases with increasing the thickness of Pt shell. The increase in electrocatalytic activity may originate mostly from the large decrease of electronic influence of Au cores on surface Pt atoms. Rotating ring‐disk electrode voltammetry and rotating disk electrode voltammetry demonstrate that ORR is mainly a four‐electron reduction on the as‐prepared modified electrode with 5 Pt layers and first charge transfer is the rate‐determining step.     

High Pressure Optical Absorption in Cs 2 TCNQ 3 Complexes Grown Under the Influence of Magnetic Field

Crystals of the organic semiconductor Cs 2 TCNQ 3 have been grown under the influence of magnetic field of 5 T and their optical properties have been compared with the crystals grown without magnetic field. The magnetic field effect manifests itself as the enhancement of the intradimer charge transfer band S 1 , which appears at around 1.3 eV in the E//a polarization. The high-pressure optical absorption measurements have shown that the S 1 band of the crystal grown at 5 T contains a new component, which is significantly intensified with increasing pressure up to 1 GPa, but diminishes as pressure increases further up to 4 GPa, and remains constant at higher pressures. This new component is additional to the component of S 1 band which has similar properties to that of the crystals grown without magnetic filed, which continuously grows up to 3 GPa and abruptly broadens out at higher pressures. The new component of S 1 is strongly linked to the ferromagnetism in this substance.     

Performance evaluation of fault-tolerant routing algorithms: an optimization problem

In this paper, we present a new theoretical approach for studying the behaviour and the performance of shortest paths fault-tolerant distributed algorithms of a certain class. The behaviour of each processor is modeled by means of a stochastic matrix. We show that achieving the optimal behaviour of Nprocessors is equivalent to solvingan optimization problem of a function of 2N variables under constraints; this function is neither convex nor concave. Solutions for which such a type of algorithms has an optimal behaviour are derived. Using that result, we build a fuzzy set of solutions which provides a global overview (a sort of “relief”): each solution of the fuzzy set has value ? ranging between 0 and 1, which may be regarded as its“bench-mark” so (1 -?) points out the proximity of any solution from the optimal solution     

New insights on structural dynamics of electrochemical interface by time-resolved surface X-ray diffraction

Many time-resolved measurements of electrochemical interface have been developed in conformity with the time scale of various transition. X-ray diffraction using synchrotron radiation is a powerful tool for structural determination of electrical double layer in real time. This short review describes structural dynamics of interfacial ions during the faraday and non-faraday processes in the time scale from microsecond to second.     

Pressure-induced closure of the jahn-teller distortion in Rb2CuCl4(H2O)2

This work investigates the pressure-induced variation of the local structure around Cu²⁺ as well as the crystal structure in Rb₂CuCl₄(H₂O)₂ through XAS and XRD techniques. The application of pressure induces a structural change in the Jahn-Teller (JT) [Formula: See Text] complex from axially elongated to compressed. This change leads to the closing of the 2D JT distortion related to the four in-plane Cl^? ligands, which are responsible for the antiferrodistortive structure displayed by the crystal. It is shown that the presence of water ligands enhances a JT release. Their associated axial ligand-field favours the occurrence of such a local structural transition below the metallization pressure. The results are compared with recent pressure experiments on A₂CuCl₄ systems.     

气相下材料真空放气性能的理论研究

气相下,材料表面气体分子的脱附速率会大大增加。文中对这方面的研究进行了总结,并应用分子动力学理论,从气相空间分子间的碰撞、气相空间分子与材料表面的碰撞、气相空间分子与材料表面的相互作用、材料表面气体分子的徙动、材料表面气体分子的脱附几个方面,从理论上研究气相下材料的真空放气性能。