Mössbauer effect study of antiferromagnetic Fe–Mn–Si alloys

Antiferromagnetic Fe–30Mn–Si alloys containing 2.0–8.7 at.% Si are known to exhibit several attractive physical properties at Néel temperatures which render them candidate materials for functional alloys applications. The Néel transitions and anomalous transport phenomena have been studied extensively in a wide temperature range. In the present work, the hyperfine interactions are studied by Mössbauer spectroscopy measured at temperatures 95–623 K. It is found that the Mössbauer spectra are singlets at temperatures above the Néel temperature and doublets below the Néel temperature. The alloys have a small hyperfine field around the Fe nuclei below the Néel temperature and the hyperfine field increases linearly with increasing silicon concentration. This can be explained by the presence of a localised net magnetic moment on the Fe nuclei which is induced by the silicon atoms. A decrease in isomer shift with increasing silicon concentration is observed and this can be accounted for by the change in the occupation of the Fe 3d shell. There is a small quadrupole splitting, it increases with increasing silicon concentration, and is consistent with the lattice shrinking and magnetostriction.     

Asymptotic Behavior of Nodal Solutions for Semilinear Elliptic Equationsin R~n

§１．　ＩｎｔｒｏｄｕｃｔｉｏｎＲｅｃｅｎｔｌｙ，ｔｈｅｓｅｍｉｌｉｎｅａｒｅｌｌｉｐｔｉｃｅｑｕａｔｉｏｎｓ△ｕ＋ｆ（ｕ）＝０（１．１）ｕ（ｘ）→０ａｓ｜ｘ｜→∞（１．２）ｉｎＲｎｗｅｒｅｃｏｎｓｉｄｅｒｅｄｗｉｄｅｌｙ（ｓｅｅ［１］－［７］）．Ｉｎｔｈｅｎｉｃｅｐａｐｅｒｓ［１］ａｎｄ［２］，ｉｔｗａｓｐｒｏｖｅｄｔｈａｔａｎｙｐｏｓｉｔｉｖｅｓｏｌｕｔｉｏｎｏｆ（１．１）ｍｕｓｔｂｅｒａｄｉａｌｉｎｃａｓｅｆ（ｕ）∈Ｃ１＋δ（δ＞０）．Ｔｈｅｒｅｆｏｒｅ，ａｎｙｐｏｓｉｔｉｖｅｓｏｌｕｔｉ…     

次线性条件下奇异三阶微分方程周期边值问题解的全局结构

讨论三阶微分方程周期边值问题解的全局结构,其中ρ∈(0,1/3~(1/2))为常数,λ∈R~+=[0,+∞)为参数,f在t=0,t=2π和u=0处有奇异性,关于u处满足次线性增长条件。     

BOUNDEDNESS,ASYMPTOTIC BEHAVIOR AND OSCILLATORY PROPERTIES FOR THE MODELS OF SINGLE-SPECIES POPULATION GROWTH WITH IMPULSIVE EFFECT

1. IntroductionThe models of single-species population growth can be described as the following ordinary differelltial equations(IVP) X' ~ f(x,K(t)), x(to) = xo 2 0, (1.1)where K(t) > 0 is the carrying capacity of the environment. Much has been done underthe assumption that K(t) is either constant or changed periodicallyll-3]. However, onemay easily visualize in nature where abruput changes such as harvesting, and disajsters mayoccur. Consequently, we consider such model with impulses. It …     

MULTIPLE POSITIVE SOLUTIONS OF SINGULAR THIRD-ORDER PERIODIC BOUNDARY VALUE PROBLEM

This paper deals with the singular nonlinear third-order periodic boundary value problem u‘‘‘ ρ^3u = f(t,u), 0 ≤ t ≤ 2π, with u^(i)(0) = u^(i)(2π), i = 0,1,2, where ρ ∈ (0, 1 /√3) and f is singular at t = 0, t = 1 and u = 0. Under suitable weaker conditions than those of [1], it is proved by constructing a special cone in C[0, 2π] and employing the fixed point index theory that the problem has at least one or at least two positive solutions.     

含能材料装药的损伤及力学性能研究进展

研究含能材料的损伤和力学性能对于指导含能材料配方和结构件设计,以及对含能材料进行安全性评估和寿命预测等都具有重要的意义.损伤一方面使含能材料的力学性能劣化,另一方面还影响含能材料的感度、燃烧甚至爆炸性能.本文对含能材料损伤和力学性能的研究现状进行了综述和归纳.对含能材料损伤的产生、实验模拟、主要损伤模式,损伤对含能材料的感度和燃烧性能等的影响,炸药单相材料的性质,影响含能材料力学性能的因素以及损伤本构关系等进行了介绍.对其中的一些关键问题和热点问题进行了分析,并对今后需要开展的工作发表了一些看法.      

改变相比/顶空气相色谱法测定变压器油中溶解气体的分配常数

采用改变相比/顶空气相色谱法测定了甲烷、乙炔、乙烯、乙烷和丙烷在变压器油中的分配常数。顶空瓶中的气体样品经石英毛细管送到气相色谱仪的六通进样阀样品管中,然后进行分离和定量。采用标准曲线法定量,通过测定5个不同相比时轻烃组分的顶空浓度,计算顶空浓度倒数与相比之间的线性回归方程,测定了20 ℃和50 ℃时烃类气体在变压器油中溶解气体的分配常数。除甲烷外,计算所得的分配常数与文献值基本吻合,油中溶解气体浓度的实验值与实际值之间的相对误差小于4.14%,表明用此方法可以测定不同温度下变压器油中溶解气体的分     

On the uniqueness of the positive solution for a second-order integral boundary value problem with switched nonlinearity

Applying a fixed point theorem for a concave operator on a cone, this work presents a sufficient condition for the existence and uniqueness of a positive solution for a second-order integral boundary value problem with switched nonlinearity. An example is worked out to illustrate the main results.     

Preparation and Characterization of Carbonate-type Mg–Al Layered Double Hydroxides by Ion Exchange Resins

Russian Journal of Physical Chemistry A - Carbonate-type Mg–Al layered double hydroxides were successfully prepared using ion exchange resins. Based on XRD patterns, 8 h and 40°C were...     

边界润滑条件下离子渗氮与极压抗磨添加剂的协同作用

利用球－盘摩擦磨损试验机系统地研究了边界润滑条件下４５＃钢离子渗氮与极压抗磨添加剂硫化烯烃及磷酸三甲酚酯的协同作用，结果表明，离子渗氮与这两种添加剂不仅在提高承载能力方面都有明显的协同作用，而且在减小摩擦磨损方面也都有较好的协同作用，其中以与磷酸三甲酚酯的协同作用效果更好。此外，还利用Ｘ射线光电子能谱仪和俄歇电子能谱仪等表面分析手段分析研究了产生这种协同作用的机理。