电磁学单位制的沿革

本文介绍了电磁学创立之初各种电磁学量的定义和单位的命名,电磁学量的绝对测量,电磁学发展史上曾经使用过的几种主要的单位体系,各种电磁学单位体系之间互相融合的过程,电磁学单位的有理化,绝对电磁学单位制的建立和演变,以及在ＭＫＳＡ单位制基础上建立的国际单位制     

瑞利和略布欣斯基的一场争论

瑞利用量纲法讨论流动的流体导热问题，他的推理后来招到许多人的批评。笔者认为瑞利的结论是正确的，他的答辩指明了批评者略布欣斯基的论证中忽视的东西。     

电磁学单位制集合

首次提出了单位制集合的概念，并以此作为论述的基础，文中由单位定义方程逐步代入引入理纲式的方法，阐明了量纲式的度量本质，证明了关于单位变换的两条定理，，由它们可以很好地导出各种单位制之间的变换公式，这曾是许多人想要解决的问题。     

国际单位制和高斯单位制之间方程转换的一种简单方法

0 引言电磁学中的单位制相当繁杂,用得比较多的是国际单位制和高斯单位制。每个物理公式或物理定律只适用于一定的单位制,公式中各符号代表的是该物理量用此单位制中的单位量度时的数值,公式本身代表的是这些数值之间的关系。在不同单位制中,反映同一物理规律的公式,一般来说,具有不同的数学形式(通常是公式中出现不同的系数)。国际单位制是世界上公认的比较先进的单位制,但高斯单位制在理论物理及有关文献中还常常被采用。因此掌握物理     

《热力学·统计物理》练习中单位制问题的讨论

本文针对汪志诚先生的《热力学·统计物理》教材中的两个练习题进行分析,对采用不同单位制计算得到不同结果进行讨论,并给出了解释。     

国企“单位制”变迁中的职工行动模式转换——制度与行动关系的研究

国企改革主要是"浓缩"在具有计划经济特征的"单位制"中的。改革改变了国企单位的组织特征和行动模式,改变了职工的角色、身份、地位和利益,改变了他们的思想、观念和意识。因此,他们也必然改变原有的、已经不适应社会情境要求的行动,去寻找和转换那些有利于获取自身利益的、更适合生存和发展的行动。     

科技型中介机构转型发展的思考

随着国家事业单位制度的改革，部分科技型中介机构逐渐从事业单位转为企业单位，在转型过程中，在人员聘用方面起了较大的变化，存在着一些问题。因而，建立良好的人员聘用制更有利于推动科技中介机构的发展。     

量纲分析在物理学中的应用

本文引入量细的概念，阐述量纲在物理学中的作用，并说明物理学中的量钢分析方法实际上是一种半定量的分析方法。     

基本物理常数与计量基本单位

基本物理常数的发现和测量，不仅在物理学的发展中起到了很大的作用，而且在计量学的发展上也起到了重要的作用，设法把计量单位的定义与基本物理常数相联系，详细分析了长度单位、电压单位、电阻单位以及质量单位与基本物理常数的关系，由于基本物理常数是不会变化的，因此这样定义的计量单位极为稳定，不会随着时间而发生漂移。     

一种启迪思维、拓广思路的物理学方法：—标度分析与变换

物质世界时空结构上的自相似性（即无穷嵌套现象）证实了自界的许多性质及其部分运动规律只取决于于物质世界自身结构的拓扑性质，而与空间绝对大小无关，因此可利用对已有的“大（或小）物理世界”的认识和物理空间基准量（特征量）选择的自由来预测并进而发现未知的 “小（或大）物理世界”的运动规律，这一过程称之为标度分析与变换，利用对事物某一标度层次上的认识和具有启迪思维和拓广思路的标度分析与变换方法可以去把握事物各个标度层次上的运动特性。     

具有良好可再生性的新型二氧化硅磁性氧化石墨烯纳米复合材料

Graphene oxide (GO) wrapped Fe₃O₄ nanoparticles (NPs) were prepared by coating the Fe₃O₄ NPs with a SiO₂ layer, and then modifying by amino groups, which interact with the GO nanosheets to form covalent bonding. The SiO₂ coating layer plays a key role in integrating the magnetic nanoparticles with the GO nanosheets. The effect of the amount of SiO₂ on the morphology, structure, adsorption, and regenerability of the composites was studied in detail. An appropriate SiO₂ layer can effectively induce the GO nanosheets to completely wrap the Fe₃O₄ NPs, forming a core-shell Fe₃O₄@SiO₂@GO composite where Fe₃O₄@SiO₂ NPs are firmly encapsulated by GO nanosheets. The optimized Fe₃O₄@SiO₂@GO sample exhibits a high saturated adsorption capacity of 253 mg·g?1 Pb(II) cations from wastewater, and the adsorption process is well fitted by Langmuir adsorption model. Notably, the composite displays excellent regeneration, maintaining a ~90% adsorption capacity for five cycles, while other samples decrease their adsorption capacity rapidly. This work provides a theoretical guidance to improve the regeneration of the GO-based adsorbents.     

微波预处理对复杂铜矿磨矿及浮选动力学的影响

The effect of CaCO₃, Na₂CO₃, and CaF₂ on the reduction roasting and magnetic separation of high-phosphorus iron ore containing phosphorus in the form of Fe₃PO₇ and apatite was investigated. The results revealed that Na₂CO₃ had the most significant effect on iron recovery and dephosphorization, followed by CaCO₃, the effect of CaF₂ was negligible. The mechanisms of CaCO₃, Na₂CO₃, and CaF₂ were investigated using X-ray diffraction (XRD), scanning electron microscopy and energy dispersive spectrometry (SEM–EDS). Without additives, Fe₃PO₇ was reduced to elemental phosphorus and formed an iron–phosphorus alloy with metallic iron. The addition of CaCO₃ reacted with Fe₃PO₇ to generate an enormous amount of Ca₃(PO₄)₂ and promoted the reduction of iron oxides. However, the growth of iron particles was inhibited. With the addition of Na₂CO₃, the phosphorus in Fe₃PO₇ migrated to nepheline and Na₂CO₃ improved the reduction of iron oxides and growth of iron particles. Therefore, the recovery of iron and the separation of iron and phosphorus were the best. In contrast, CaF₂ reacted with Fe₃PO₇ to form fine Ca₃(PO₄)₂ particles scattered around the iron particles, making the separation of iron and phosphorus difficult.     

不同硅饱和系数水榴石的碳酸化分解动力学

Carbonated decomposition of hydrogarnet is one of the vital reactions of the calcification–carbonation method, which is designed to dispose of low-grade bauxite and Bayer red mud and is a novel eco-friendly method. In this study, the effect of the silica saturation coefficient (x) on the carbonation of hydrogarnet was investigated from the kinetic perspective. The results indicated that the carbonation of hydrogarnets with different x values (x = 0.27, 0.36, 0.70, and 0.73) underwent two stages with significantly different rates, and the kinetic mechanisms of the two stages can be described by the kinetic functions R3 and D3. The apparent activation energies at Stages 1 and 2 were 41.96–81.64 and 14.80–34.84 kJ/mol, respectively. Moreover, the corresponding limiting steps of the two stages were interfacial chemical reaction and diffusion.     

一种超重力燃烧合成制备高性能高熵合金的新方法

A new method of high-gravity combustion synthesis (HGCS) followed by post-treatment (PT) is reported for preparing high-performance high-entropy alloys (HEAs), Cr_0.9FeNi_2.5V_0.2Al_0.5 alloy, whereby cheap thermite powder is used as the raw material. In this process, the HEA melt and the ceramic melt are rapidly formed by a strong exothermic combustion synthesis reaction and completely separated under a high-gravity field. Then, the master alloy is obtained after cooling. Subsequently, the master alloy is sequentially subjected to conventional vacuum arc melting (VAM), homogenization treatment, cold rolling, and annealing treatment to realize a tensile strength, yield strength, and elongation of 1250 MPa, 1075 MPa, and 2.9%, respectively. The present method is increasingly attractive due to its low cost of raw materials and the intermediate product obtained without high-temperature heating. Based on the calculation of phase separation kinetics in the high-temperature melt, it is expected that the final alloys with high performance can be prepared directly across master alloys with higher high-gravity coefficients.     

窄板坯结晶器内连铸工艺参数对钢液流场的影响

Computational simulations and high-temperature measurements of velocities near the surface of a mold were carried out by using the rod deflection method to study the effects of various operating parameters on the flow field in slab continuous casting (CC) molds with narrow widths for the production of automobile exposed panels. Reasonable agreement between the calculated results and measured subsurface velocities of liquid steel was obtained under different operating parameters of the CC process. The simulation results reveal that the flow field in the horizontal plane located 50 mm from the meniscus can be used as the characteristic flow field to optimize the flow field of molten steel in the mold. Increases in casting speed can increase the subsurface velocity of molten steel and shift the position of the vortex core downward in the downward circulation zone. The flow field of liquid steel in a 1040 mm-wide slab CC mold can be improved by an Ar gas flow rate of 7 L·min?1 and casting speed of 1.7 m·min?1. Under the present experimental conditions, the double-roll flow pattern is generally stable at a submerged entry nozzle immersion depth of 170 mm.     

电渣重熔脱硫技术研究进展

Electroslag remelting (ESR) gives a combination of liquid metal refining and solidification structure control. One of the typical aspects of liquid metal refining during ESR for the advanced steel and alloy production is desulfurization. It involves two patterns, i.e., slag–metal reaction and gas–slag reaction (gasifying desulfurization). In this paper, the advances in desulfurization practices of ESR are reviewed. The effects of processing parameters, including the initial sulfur level of consumable electrode, remelting atmosphere, deoxidation schemes of ESR, slag composition, melting rate, and electrical parameters on the desulfurization in ESR are assessed. The interrelation between desulfurization and sulfide inclusion evolution during ESR is discussed, and advancements in the production of sulfur-bearing steel at a high-sulfur level during ESR are described. The remaining challenges for future work are also proposed.     

利用皮秒激光烧蚀制备非球形铝纳米颗粒

We report the picosecond laser ablation of aluminum targets immersed in a polar organic liquid (chloroform, CHCl₃) with ~2 ps laser pulses at an input energy of ~350 μJ. The synthesized aluminum nanoparticles exhibited a surface plasmon resonance peak at ~340 nm. Scanning electron microscopy images of Al nanoparticles demonstrated the spherical morphology with an average size of (27 ± 3.6) nm. The formation of smaller spherical Al nanoparticles and the diminished growth could be from the formation of electric double layers on the Al nanoparticles. In addition to spherical aluminum nanoparticles, triangular/pentagonal/hexagonal nanoparticles were also observed in the colloidal solution. Field emission scanning electron microscopy images of ablated Al targets demonstrated laser induced periodic surface structures (LIPSSs), which were the high spatial frequency LIPSSs (HSF-LIPSSs) since their grating period was ~280 nm. Additionally, coarse structures with a period of ~700 nm were observed.     

Mineral transition and formation mechanism of calcium aluminate compounds in CaO?Al2O3?Na2O system during high-temperature sintering

The mineral transition and formation mechanism of calcium aluminate compounds in CaO?Al₂O₃?Na₂O system during the high-temperature sintering process were systematically investigated using DSC?TG, XRD, SEM?EDS, FTIR, and Raman spectra, and the crystal structure of Na₄Ca₃(AlO₂)₁₀ was also simulated by Material Studio software. The results indicated that the minerals formed during the sintering process included Na₄Ca₃(AlO₂)₁₀, CaO·Al₂O₃, and 12CaO·7Al₂O₃, and the content of Na₄Ca₃(AlO₂)₁₀ could reach 92wt% when sintered at 1200°C for 30 min. The main formation stage of Na₄Ca₃(AlO₂)₁₀ occurred at temperatures from 970 to 1100°C, and the content could reach 82wt% when the reaction temperature increased to 1100°C. The crystal system of Na₄Ca₃(AlO₂)₁₀ was tetragonal, and the cells preferred to grow along crystal planes (110) and (210). The formation of Na₄Ca₃(AlO₂)₁₀ was an exothermic reaction that followed a secondary reaction model, and its activation energy was 223.97 kJ/mol.