Investigation on laser brazing AA6056 Al alloy to XC18 low-carbon steel

Based on the studies of influence of YAG laser heating conditions for Al alloy melt and steel on wettability,the mechanics of the laser overlap braze welding of 6056 Al and XC18 steel sheet has been investigated.Under the temperature range which is above the melting point of the Al alloy and below the melting point of the steel, two dissimilar metals can be joined by means of laser braze welding. There is no crack observed in the joining area, i.e. Al-Fe intermetallic phase (Fe3Al/FeAl/FeAl3/Fe2Al5) layer formed by solution and diffusion between liquid-solid interface. The temperature range can be defined as the process temperatures of laser braze welding of Al-Fe materials. Selecting a higher laser heating temperature can improve the wettability of Al melt to steel surface, but the intermetallic phase layer is also thicker. When the laser heating temperature is so high that the joining surface of steel is melted, there is a crack trend in the joining area.     

与两个更新过程有关的某些联合分布

本文讨论的两个时偶问题涉及来一个泊松过程与一个更新过程穿越时间和更新数的联合分布．利用向量马氏过程方法得到了这些联合分布的变换，给出了一个与分布均值有关量的数值结果．     

光栅子结构对光纤光栅特性的影响

用传输矩阵法对具有不同参数的λ／４移相结构，多节λ／４移相结构，有效折射率调制结构，耦合系数调制结构和“缝合”误差结构等五种光栅子结构进行了数值模拟计算，模拟结果解释了作者研制的均匀光纤光栅，相移光纤光栅的传输谱，也验证了其他研究小组发表的实验结果，通过对各种结构的系统研究了，提出了一些新的利用光纤光栅的设想。     

关于Poincare—Hopf的奇点指数公式

在一般的文献中，Poincare-Hopf的曲面奇点指数公式的证明需要利用Euler的曲面示性数公式。本文将通过微分方程的定性方法，直接证明了Poincare-Hopf的奇点指数公式，然后作为简单的应用可得到Euler的曲面示性数公式。     

新型富勒烯衍生物的光限幅研究

应用倍频Ｎｄ∶ＹＡＧ脉冲激光，在波长为５３２ｎｍ、脉冲宽度分别为８ｎｓ和２３ｐｓ的条件下，研究了新型富勒氮烯乙酰氨衍生物（Ｎ－ａｃｅｔａｍｉｄｅ１，２－ｄｉｈｙｄｒｏ－１，２－ａｚａ－ｆｕｌｅｒｅｎｅ［６０］）的反饱和吸收与光限幅特性。实验结果表明，同脉宽为纳秒的激发脉冲相比，富勒烯乙酰氨衍生物对脉宽为皮秒的脉冲限幅效果比较好。     

TA on Mo(W)/Cu(Ag)/S clusters derived with [Cp*MS3]- Kinetics of [PPh4]2[Cp*WS3(CuBr)3]2 and [PPh4]2[Cp*MoS3(CuBr)3]2

Thermal analysis on two new heterometallic sulfide clusters, [PPh4]2[WS3(CuBr)3]2 and [PPh4]2[MoS3(CuBr)3]2 (where PPh4=tetraphenyl phosphonium, =pentamethylcyclopenta- dienyl), was carried out using a simultaneous TG-DTA unit in an atmosphere of flowing nitrogen and at various heating rates. Supplemented using EDS method, their thermal behavior and properties, together with the composition of their intermediate product, were examined and discussed in connection with their distinctive molecular structure as a dianion, which provided some theoretically and practically significant information. Both clusters decomposed in a two-step mode, but without a stable new phase composed of Mo/W-Cu-S formed during their decomposition process as we expected. Based on TG-DTG data, four methods, i.e. Achar-Brindley-Sharp, Coats-Redfern, Kissinger and Flynn- Wall-Ozawa equation, were used to calculate the non-isothermal kinetic parameters and to determine the most probable mechanisms. This revised version was published online in July 2006 with corrections to the Cover Date.     

The 1-Lipschitz mapping between the unit spheres of two Hilbert spaces can be extended to a real linear isometry of the whole space

LetE andF be Hilbert spaces with unit spheresS ₁(E) andS ₁(F). Suppose thatV ₀ S₁(E) →S ₁(F) is a Lipschitz mapping with Lipschitz constantk=1 such that −V ₀[S ₁(E)] ⊂V ₀[S ₁(E)]. Then V₀ can be extended to a real linear isometric mappingV fromE intoF. In particular, every isometric mapping fromS ₁(E) ontoS ₁(F) can be extended to a real linear isometric mapping fromE ontoF.     

Twisted parafermions

A new type of nonlocal currents (quasi-particles), which we call twisted parafermions, and its corresponding twisted Z-algebra are found. The system consists of one spin-1 bosonic field and six nonlocal fields of fractional spins. Jacobi-type identities for the twisted parafermions are derived, and a new conformal field theory is constructed from these currents. As an application, a parafermionic representation of the twisted affine current algebra A⁽²⁾₂ is given.     

超声雾化法制取金属粉末方法研究

本文介绍了利用超声振动能量制取超细金属粉末的超声雾化方法，提出了超声制粉雾化室，等离子枪，阴极、阳极喷咀及换能器振动系统的最佳尺寸和工作参数，给出了实验结果及制得的粉末显微结构照片．实验结果表明，用本文所述方法制得的金属粉末组成为：－80目粉占84呢，－120目粉占63．7啪，而用PREP方法制得的粉末分别占19．5％和11．7％，由此看来，用本方法制取超细金属粉，在粒度组成方面优于PREP方法．文中还对粉末冷却速度做了估算，得到了粉末平均冷却速度大于1×10_5k/5     

金属线性热膨胀系数的研究

 从温度T时的压强表达式出发，结合普适状态方程（UEOS）、Debye模型和热力学关系式，给出了计算金属线性热膨胀系数的普遍公式。并对Al、Cu、Pb的这一物理量进行了具体计算。结果表明，理论与实验符合较好。