CJ6水平强度磁力仪的观测与讨论

ＣＪ６水平强度磁力仪的观测与讨论叶富华（中国四川１６１１７３０成都地震台）１引言ＣＪ６水平强度磁力仪（以下简称Ｃ仪）存在着系统误差大、仪器重新调整前后测值重复性差的缺点，所以，实际投人到台站观测使用的并不多。成都台自１９８２年使用该仪器观测以来，除１...

磁性耐磨材料在烧结球团生产中应用的探讨

磁性耐磨材料的抗磨原理是在自身与含铁物料之间形成一层“保护膜” ,从而避免材料的磨损。济钢烧结厂采用磁性材料作成品矿仓内衬 ,不仅衬板寿命延长 ,而且烧结转运过程中的减粒现象减轻 。

飞机电排斥除冰器件设计与仿真

结冰是飞机飞行中的重大安全隐患。电排斥除冰器利用电磁排斥力除去冻结在飞机表面的积冰,具有低功耗、高效率、对飞机气动性能影响小、安装简易等优点。本文采用ANSYS仿真软件,利用磁矢量位有限元仿真方法,构建了飞机电排斥除冰器单组排斥元件有限元模型,通过对模型进行电磁—结构瞬态耦合,分析了单组元件尺寸及通入电流峰值对元件运动层所受电磁排斥力强度的影响,得到了单组元件不同尺寸和电流峰值的电磁力强度曲线,进而提出了电排斥除冰系统的设计思路。本文模拟结果与实验吻合度高,较该种除冰器设计时常用的经验公式的计算结果更精确,为电排斥除冰器件的设计提供了精确的理论指导。

Mode II fracture analysis of double edge cracked circular disk subjected to different diametral compression

A detailed analysis of mode II stress intensity factors(SIFs) for the double edge cracked Brazilian disk subjected to different diametral compression is presented using a weight function method. The mode II SIFs at crack tips can be obtained by simply calculating an integral of the product of mode II weight function and the shear stress on the prospective crack faces of uncracked disk loaded by a diametral compression. A semi-analytical formula for the calculation of normalized mode II SIF, f _Ⅱ, is derived for different crack lengths (from 0.1 to 0.7) and inclination angles (from 10° to 75°) with respect to loading direction. Comparison between the obtained results and finite element method solutions shows that the weight function method is of high precision. Combined with the authors previous work on mode I fracture analysis, the new specimen geometry can be used to study fracture through any combination of mode I and mode II loading by a simple alignment of the crack relative to the diameter of compression loading, and to obtain pure mode II crack extension. Another advantage of this specimen geometry is that it is available directly from rock core and is also easy to fabricate.

Microstructure and magnetic properties of FeAs with coarse-grain and nanocrystalline structure

The microstructure and magnetic properties of iron arsenide(FeAs) with coarse-grain and nanocrystalline structure were investigated. Coarse-grain FeAs was synthesized through high-energy ball milling and heat treatment. Nanocrystalline FeAs was obtained by ball milling of coarse-grain FeAs. The results suggest that the reduced grain size of FeAs(from >100 to 32.4 nm) is accompanied by the introduction of internal strains up to 0.568% with ball milling time from 0 to 32 h. The magnetic properties of FeAs show that the coercivity is reduced from 29.2 to 15.6 kA/m and the magnetization is increased over time of milling. The low coercivity is mainly due to the small grain size stemmed from ball milling, while the increase of magnetization is primarily caused by the change of lattice parameters of FeAs and the emergence of superparamagnetic phase at the same time.

Correlation of electromagnetic radiation emitted from coal or rock to supporting resistance

More accurate forecasting of rock burst might be possible from observations of electromagnetic radiation emitted in the mine.We analyzed experimental observations and field data from the Muchengjian coal mine to study the relationship between electromagnetic radiation signal intensity and stress during the fracturing of coal, or rock, and samples under load.The results show that the signal intensity is positively correlated with stress.In addition, we investigated the change in the electromagnetic radiation intensity, the supporting resistance in a real coal mine environment, and the coal or rock stress in the mining area.The data analysis indicates that:1) electromagnetic radiation intensity can accurately reflect the distribution of stress in the mining area;and, 2) there is a correlation between electromagnetic radiation intensity and supporting resistance.The research has some practical guiding significance for rock burst forecasting and for the prevention of accidents in coal mines.

Magnetization and coercivity in Co/Pt multilayers with constant total Co layer thickness

Co/Pt multilayers with perpendicular anisotropy were deposited using a dc magnetron sputtering system under high vacuum.Magnetization process was investigated by the measurement of magnetic components parallel and perpendicular to the applied field.A dependence of the coercivity of Co/Pt multilayers on the Co layer thickness was reported,in which the total thickness of Co layers kept constant.It is observed that the coercivity increases with the increment of Co layer thickness.For the samples with the same Co layer thickness while different total Co layer thickness,the coercivity first increases and then decreases with the increase of the total thickness of Co layers.This effect could be attributed to the competition between the reduction of HC related to incoherent reversal and the step-up of HC contributed by the magnetic polarization of Pt atoms at the interface of Co and Pt layers during magnetization reversal.The results show that the change of the coercivity is strongly related to the Co layer thickness,but not the total thickness of Co layers.The dependence of the coercivity on the angle between an applied field and the easy axis shows that the nucleation mode is dominant in magnetization reversal process of the samples.

Influence of solar wind dynamic pressure on geomagnetic Dst index during various magnetic storms

The Dst index,designed as a proxy of ring current intensity,is known to be also affected by other magnetospheric current systems,e.g.magnetopause current.The pressure-corrected Dst index is obtained by removing the effects of the solar wind dynamic pressure and the quiet time ring current.However,all previous studies treated the correction coefficient as an averaged parameter for storms of different intensity.In this paper,based on the Burton's equations and employing two independent methods,we will show a positive correlation between pressure-correction coefficient b and the intensity of the storms.We divided our storm database(872 storms in total) into three categories according to the intensity of storms.In order to improve the accuracy of calculating,we also used the higher-resolution SYM-H index data instead of Dst index to compute the corrected Dst index during different storms.Furthermore,we are able to provide corrected magnetic storm index with high-time resolution(-1 min).

Large magnetocaloric effect in metamagnetic HoPdAl

Magnetic properties and magnetocaloric effects （MCEs） of the HoPdA1 compounds with the hexagonal ZrNiAl-type and the orthorhombic TiNiSi-type structures are investigated. Both the compounds are found to be antiferromagnet with the Nrel tem- perature TN=12 and 10 K, respectively. A field-induced metamagnetic transition from antiferromagnetic （AFM） state to ferro- magnetic （FM） state is observed below TN. For the hexagonal HoPdA1, a small magnetic field can induce an FM-like state due to a weak AFM coupling, which leads to a high saturation magnetization and gives rise to a large MCE around TN. The maxi- mal value of magnetic entropy change （ASM） is -20.6 J/kg K with a refrigerant capacity （RC） value of 386 J/kg for a field change of 0-5 T. For the orthorhombic HoPdA1, the critical field required for metamagnetic transition is estimated to be about 1.5 T, showing a strong AFM coupling. However, the maximal ASM value is still -13.7 J/kg K around TN for a field change of 0-5 T. The large reversible ASM and considerable RC suggest that HoPdA1 may be an appropriate candidate for magnetic re- frigerant in a low temperature range.