EMC用大损耗NiCuZn铁氧体吸收瓦材料研究

３０～１０００ＭＨｚ铁氧体吸收瓦（尺寸为１００ｍｍ ×１００ｍｍ×厚度）在电磁兼容（ＥＭＣ）领域具有广泛的应用。本文采用氧化物工艺制备ＮｉＣｕＺｎ尖晶石铁氧体,测试并分析了用Ｃｕ２＋取代Ｎｉ２＋及Ｃｏ２＋掺杂对材料复磁导率的影响。在９００℃／２ｈ预烧,１１５０℃／２ｂ烧结,得到ＮｉＣｕＺｎ铁氧体相对复磁导率（μｒ＝μ′ｒ－ｊμ″）μ＇ｒ＞１１０,μ″ｒ＞２００（频率ｆ＝３００ＭＨｚ）;通过对该材料优化设计,当铁氧体吸收瓦厚度 ｄ＝５．５ｍｍ,在 ３０～１０００ＭＨｚ,反射率 Ｒ＜－１２ｄＢ,在 ｆ＝５０～８００ＭＨｚ,Ｒ＜－１５ｄＢ。     

感应加热卷烟烟具用电磁屏蔽材料

本研究采用COMSOL有限元软件仿真能量转换效率随屏蔽材料磁导率的变化规律,结果表明,当μ″=0时,μ′越大,能量转换效率越高;当μ″≠0,则存在μ′与μ″的最佳匹配值。根据仿真结果,选取合适的屏蔽材料,在感应加热卷烟烟具保持谐振状态,且发热体温度满足要求的基础上,采用功率分析仪测试烟具1个工作循环的能耗。测试结果表明：在240～320 kHz频率范围内,采用铁氧体材料,μ′越高,效果越优。当μ′为220时,可将1个工作循环能耗由978.14 J降至833.40 J,能量转转效率提升14.80%。采用纳米晶材料,当μ=2064-j349时,性能最优,1个工作循环能耗可降至811.30 J,能量转换效率提升17.06%,随μ′及μ″的进一步提高,能耗逐渐增大,此规律与仿真结果一致。因此,通过合理选择电磁屏蔽材料可提高感应加热卷烟烟具的能量转换效率。     

Ni／聚乙烯复合材料复磁导率研究

研究了电磁波屏蔽材料Ｎｉ／聚乙类复合材料在５０ＭＨｚ－１ＧＨｚ频率范围内的电磁选择性。研究结果表明：Ｎｉ含量小于７０ｗｔ％时，频率和成分对磁导率部实μ’的影响；Ｎｉ含量大于７０ｗｔ％时，因材料中非磁性材料聚乙烯形成的等效气隙足够长，使Ｎｉ／聚乙烯复合材料的磁导率实部μ’随着频率的增加而降低。Ｎｉ含量小于７０ｗｔ％时，频率和含量对磁导率虚部μ’’的影响较小，μ’’值较小；Ｎｉ含量大于７０ｗｔ％时，μ     

氧化锌形态及含量对ZnO/Ni-Zn铁氧体复合材料电磁特性的影响

研究了氧化锌形态及含量在１～１０００ＭＨｚ范围内对ＺｎＯ／Ｎｉ－Ｚｎ铁氧体复合材料电磁特性的影响。结果表明，复合材料的等效介电常数（ε＇，ε＂）和等效磁导率（μ＇，μ＂）均随着ＺｎＯ（颗粒或晶须）含量的增加而逐渐减小。在１～１０００ＭＨｚ范围内，相同成份配比条件下添加晶须状ＺｎＯ比添加颗粒状ＺｎＯ所得复合材料的电磁参量（ε＇，ε＂，μ＇，μ＂）值要高。     

十字形碳化硅纤维的制备与微波电磁特性(英文)

通过先驱体法制备出十字形SiC纤维, 纤维外接圆直径为34μm左右, 纤维叶片长度为12μm左右, 宽度为8μm左右。使用同轴环方法测试了十字形SiC纤维的复介电常数和复磁导率, 测试表明纤维是介电损耗材料, 纤维的介电常数实部（ε′）、虚部（ε″）和介电损耗角正切值（tanδ=ε″/ε′）分别为2. 77~7. 93、1. 38~6. 41和0. 49~0. 81, 磁导率实部（μ′）和虚部（μ″）分别为0. 96~1. 12和-0. 05~0. 08。在2~18GHz频率范围内, 纤维/石蜡复合材料的反射率衰减大于10dB的频率为9. 12~18GHz, 最大衰减为28. 47dB, 对应频率为12GHz。反射率衰减大于10dB的频宽为8. 88GHz。     

微波铁氧体吸收剂复磁导率和复介电常数的温度特性研究

本文对（Ｚｎ＿（１－ｘ）Ｃｏ＿ｘ）＿２－ｗ型六角晶系铁氧体吸波材料的复磁导率μ＿ｒ和复介电常数ε＿ｒ的温度特性进行了研究。实验发现当温度从－２５℃升至１００℃时，复磁导率的实部μ＇＿ｒ值从１．５１降至１．３０，虚部μ″＿ｒ值从０．１９降至０．１４，复介电常数的实部ε′＿ｒ值从６．５０升至７．１０，虚部ε″＿ｒ值从１．７０升至１．８０，理论上对电磁参数随温度变化特性进行了分析讨论。     

磁场强度对FeCuNbSiB合金μ-T曲线的影响*

研究了不同温度（350－620℃）退火后Fe73.5Cu1Nb3Si13.5B9合金在不同磁场强度（0.4-3.2A/m)条件下,磁导率μ与温度T的关系（μ－T曲线）。实验结果表明：磁场强度对μ－T曲线的形状有明显的影响,在非晶状态时,随着磁场强度的增加,μ－T曲线上尖锐的Hopkinson峰消失。     

乳液聚合条件对纳米磁性导电聚苯胺电磁性能的影响

以十二烷基苯磺酸（DBSA）为乳化剂和掺杂剂，过硫酸铵（APS）为氧化剂，采用乳液聚合的方法合成了导电聚苯胺包覆磁性四氧化三铁的核-壳纳米复合材料，其粒径在120nm左右。利用3cm波导式测量线法分别研究了聚合反应中Fe3O4的含量、DBSA和APS与苯胺的相对含量对复合材料的介电常数（ε′，ε″）和磁导率（μ′，μ″）的影响。结果表明，Fe2O3的加入能够在提高复合材料磁损耗的同时，提高其介电损耗，μ″和ε″分别提高到0．72和9．62，扩展高频时的吸收频带，通过调整聚合反应中Fe3O4、DBSA和APS的相对含量可以调节材料的电磁参数，设计多层的梯度吸波结构，从而满足阻抗匹配定律和对入射电磁波实现最大限度的吸收。     

Fe—47wt%Ni纳米晶粉芯磁谱及其压力效应

用蒸发冷凝法，制备成不同平均粒径的Ｆｅ－４７ｗｔ％／Ｎｉ纳米晶粉。将其压成小圆环，测其室温磁谱。结果表明，Ｆｅ４７ｗｔ％Ｎｉ纳主晶粉芯具有较好的高频特性。在（１－３００）ＭＨｚ频率范围内，其复数磁导率实部μ１〉１００，虚部μ２〈２０，损耗解正切ｔｇδ〈０．１，共振频率ｆｒ〉３００ＭＨｚ。当１ＭＨｚ〉ｆ〉４００ＭＨｚ时，μ２及ｔｇδ激剧上升。在（１－３００ＭＨｚ）范围，形成一个很宽的通频带。它有可能     

Nb含量对FeCuNbSiB超微晶合金的结构和磁性的影响

FeCuNbSiB超微晶合金中晶化相－α-Fe(Si)固溶体（α相）的体积份数，尺寸和成分（Si含量）与合金中Nb含量有关。Nb含量的增加使FeCuNbSiB非晶合金在最佳温度退火后α相的体积份数减少，尺寸减小及Si含量降低。α相的体积份数，尺寸及成分（Si含量）对合金的起始磁导率有综合影响。对于合金获得最高起始磁导率，α相的体积份数为64％－70％，尺寸为9．4－11．0nm,含Si量约为16－19（at)%，此时，合金中Nb含量为3－5（at)%.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...