Influence of the presence of Co on the rare earth solubility in M-type hexaferrite powders

Sr_1−xRE_xFe₁₂O₁₉ and Sr_1−xRE_xFe_12−xCo_xO₁₉ (x=0–0.4 and RE=Pr, Nd) M-type hexaferrite powders were produced according to a conventional ceramic process. The X-ray diffraction analysis of the calcinated material reveals the presence of secondary α-Fe₂O₃, PrFeO₃ or NdFeO₃ and CoFe₂O₄ phases in substituted samples, with proportions that increase with x. However, for the same x value, the proportion of secondary phases is lower in Co-containing powders than in Co-free powders. This indicates that the presence of Co in the M-type phase increases the solubility of the rare earth. The results of the Mössbauer investigation indicate that the solubility of Pr is higher than that of Nd in Co-containing samples.     

对沉降明挖隧道的结构安全评估及修复措施

目前国内对于隧道变形和开裂的研究较少,经验积累不多。本文介绍了某地区明挖地铁隧道的沉降情况,分析了沉降发生的原因,指出临近隧道的基坑开挖及工程降水是沉降发生的两个原因,针对沉降隧道进行了结构安全评估,并给出了修复措施,为类似工程修复提供参考。     

关于条形磁体穿过线圈时线圈中的感应电流的思考简

揭示并分析了当条形磁体的一端进入线圈（单匝）时．线圈中感应电流方向与磁体外侧磁感应强度方向之间的矛盾,同时对条形磁体内外的轴向磁场的大小和变化率的分布也进行了深入地分析,并据此进一步的论述了条形磁体匀速地穿过线圈（单匝）的全过程中线圈中的感应电流的方向和大小的变化规律。     

教学机房通风系统的模糊控制方法研究

为满足教学机房的通风需求,同时也为了降低维护成本,提高安全,设计了一种基于模糊控制技术的自动通风系统。系统地采集了实验室内外的空气指标,如 CO2质量分数、温度、湿度,通过模糊控制器推理运算来控制系统的换气和通风,本系统具备投资少、可拓展性强的特点,并在教学机房中成功实施和验证。     

Nonradiative relaxation processes in molecular crystals

Internal conversion is the dominant relaxation channel from higher lying excited states in molecular crystals and involves the transfer of energy from the electronic system to the lattice. In this work, we present results from simulations of the nonradiative relaxation process with an emphasis on both intra- and interband transitions. We find the internal conversion process to be strongly nonadiabatic and the associated relaxation time in the case of large energy excitations to be limited by the transitions made between states of different bands.     

Magnetic and Distribution of Magnetic Moments in Amorphous Fe89.7P10.3 Alloy Nanowire Arrays

Binary amorphous Fe89.7P10.3 alloy nanowire arrays in been fabricated in an anodic aluminium oxide template diameter of about 40nm and length of about 3μm have by electrodeposition. Magnetic properties of the samples are investigated by mean of vibrating sample magnetometer, transmission Mossbauer spectroscopy and conversion electron Mossbauer spectroscopy at room temperature. It is found that the nanowire arrays have obvious perpendicular magnetic anisotropy, and are ferromagnetic at room temperature, with its Mossbauer spectra consisting of six broad lines. The average angles between the Fe and 28° at the end of the amorphous Fe89.7P10.3 alloy magnetic moment and the wire axis are about 14°inside nanowire arrays, respectively. The magnetic behaviour is decided by the shape anisotropy and the dipolar interaction between wires. In addition, the magnetic moments distribution is theoretically demonstrated by using the symmetric fanning mechanism of the spheres chain model.     

Suprathreshold Stochastic Resonance in Mechanoelectrical Transduction of Hair Cells

Hair cell, the sound signal sensor in the auditory system, works in an environment full of noise. This noise has been demonstrated before to be a factor beneficial to the transfer of subthreshold weak signal. We further theoretically demonstrate that in suprathreshold signal situation, noise can still be a beneficial factor and enhance the haircell nonlinear transfer of suprathreshoM signal. This reveals an additional constructive function of noise in hearing and provides theoretic foundation for relevant applications.     

Numerical simulation of magnetic interactions in polycrystalline YFeO3

The magnetic behavior of polycrystalline yttrium orthoferrite was studied from the experimental and theoretical points of view. Magnetization measurements up to 170 kOe were carried out on a single-phase YFeO₃ sample synthesized from heterobimetallic alkoxides. The complex interplay between weak-ferromagnetic and antiferromagnetic interactions, observed in the experimental M(H) curves, was successfully simulated by locally minimizing the magnetic energy of two interacting Fe sublattices. The resulting values of exchange field (H_E=5590 kOe), anisotropy field (H_A=0.5 kOe) and Dzyaloshinsky–Moriya antisymmetric field (H_D=149 kOe) are in good agreement with previous reports on this system.     

The role of iron in the formation of the magnetic structure and related properties of La0.8Sr0.2Co1−xFexO3 (x=0.15, 0.2, 0.3)

La_0.8Sr_0.2Co_1−xFe_xO₃ (x=0.15, 0.2, 0.3) samples were studied by means of AC magnetic susceptibility, magnetization, magnetoresistance and ⁵⁷Fe Mössbauer spectrometry. Iron was found to take on a high spin 3d^5−α electronic state in each of the samples, where α refers to a partly delocalized 3d electron. The compounds were found to exhibit a spin-cluster glass transition with a common transition temperature of ∼53 K. The spin-cluster glass transition is visualized in the ⁵⁷Fe Mössbauer spectra as the slowing down of magnetic relaxation below ∼70 K, thereby showing that iron takes part in the formation of the glassy magnetic phase. The paramagnetic-like phase found at higher temperatures is identified below T_c≈195 K as being composed of weakly interacting, magnetically ordered nanosized clusters of magnetic ions in part with a magnetic moment oriented opposite to the net magnetic moment of the cluster. For each of the samples a considerable low-temperature negative magnetoresistance was found, whose magnitude in the studied range decreases with increasing iron concentration. The observed results obtained on the present compounds are qualitatively explained assuming that the absolute strengths of magnetic exchange interactions are subject to the relation ∣J_Co–Co∣<∣J_Fe–Co∣<∣J_Fe–Fe∣.     

Texture measurement of grain-oriented electrical steels after secondary recrystallization

The measurement of the final Goss texture sharpness in grain-oriented electrical steels is a challenging task due to the immense grain size ranging from millimeters to centimeters. Although, it is widely claimed in the literature that the orientation deviations from the ideal Goss orientation lie in the range of about 7° for conventional grain-oriented steel and in the range of about 3° for high permeability grades, no precise investigation with an appropriate statistical relevance is known to the authors.