透波层厚度对结构吸波材料吸收峰的影响

采用弓形法测试反射率,研究透波层的厚度对结构吸波复合材料吸收峰的影响。结果显示,在4~18 GHz范围内,厚度对其吸波性能具有显著影响:透波层厚度为0.95 mm时,结构吸波材料的吸收峰值最高,达-22.6 d B;其吸收峰值先随透波层厚度的增加而增强,而后逐渐减弱,透波层厚度对吸收峰值的影响可用二次多项式描述;吸收峰的位置随透波层的厚度增加向低频方向漂移,其漂移位移与透波层厚度线性相关,满足一次线性方程。     

结构吸波复合材料的吸波性能

本文制备了以石墨粉为添加剂的结构吸波复合材料,研究了吸波剂含量和材料厚度对材料吸波性能的影响并分析了其相关机理。结果表明:随着石墨粉含量、材料厚度的增加,复合材料的最大吸收峰均向低频方向移动,实验试样中最大反射率可达-16.8dB,有效带宽约3GHz,具有一定的工程实用价值。复合材料的吸波性能与石墨粉含量、材料厚度密切相关,含量、厚度引起材料的电磁参数发生改变,进而导致吸波性能发生变化,电磁参数与吸波性能的规律有待进一步深入探讨。     

含电路模拟结构吸波复合材料

研究了电路模拟结构材质、电路模拟结构尺寸、介质层电磁参数等对电阻渐变型和"陷阱"式结构吸波复合材料的吸波性能和力学性能的影响。结果表明:通过合理的结构设计,在其它条件相同的情况下含电路模拟结构电阻渐变吸波复合材料的吸波性能在8~18 GHz范围内有3~5 dB的提高;含电路模拟结构"陷阱"式吸波复合材料在厚度≤4 mm条件下,实现了吸波性能在8~18 GHz频率范围内吸收率≥12 dB。在提高吸波复合材料吸波性能的同时,电路模拟结构的引入使复合材料力学性能有一定的提高,有利于实现吸波复合材料的吸波/承载一体化。      

螺旋形碳纤维结构吸波材料的制备及其吸波性能研究

用基板法以乙炔为碳源,镍板为催化剂,PCl3为助催化剂,通过化学气相沉积制备了螺旋形碳纤维手性吸收剂,并研究了其在2～18GHz的微波电磁特性:具有较高的介电损耗,电磁参数随频率的增大有减小的趋势,有利于实现宽频吸波。以螺旋形碳纤维作为吸收剂制备了Nomex蜂窝夹芯结构吸波材料,复合材料的厚度为9.5mm时,在3.76～18GHz反射率R<-10dB,反射率<-10dB的频宽为14.24GHz;最大吸收峰在10.4GHz,反射率R为-21.62dB。探讨了螺旋形碳纤维的吸波机理,螺旋形碳纤维是一种非常有发展前景的手性吸收剂和吸波材料。     

碳纤维/羰基铁粉复合涂层吸波效果及机理分析

在碳纤维表面化学镀镍,再将其与羰基铁粉混合制备成吸波涂层,对其吸波性能进行了测试.结果表明:在2～18 GHz内,碳纤维/羰基铁粉吸波涂层,最大吸收峰在5.92 GHz,此时反射率为-8.89 dB,反射率小于-5.00 dB的频宽为9.50 GHz;单层羰基铁粉涂层在相同厚度下,最大吸收峰为7.94 GHz,对应的反射率为-10.36 dB,反射率小于-5.00 dB的频宽为6.90 GHz;碳纤维与羰基铁粉混合后,涂层反射率小于-5.00 dB的频宽增大,有利于吸收雷达波.最后,对碳纤维/羰基铁粉吸波涂层的吸波机理进行了初步分析.     

羰基铁/三元乙丙橡胶复合材料的吸波性能

为了探明吸波材料的厚度、吸收剂的含量与吸波性能之间的关系,以羰基铁为吸收剂、三元乙丙橡胶为基体制备了复合橡胶吸波材料,采用矢量网络分析仪研究了在2.6~18 GHz范围内羰基铁含量和吸波材料厚度对吸波性能的影响,并利用电磁理论分析了吸波材料的吸波性能.对于3 mm吸波材料,当羰基铁体积分数为45%时,在3.5 GHz处其反射率的最小值达-21.7 dB;在羰基铁含量一定的条件下,微波吸收性能与吸波材料的厚度并不成正比关系,当厚度<2 mm时,吸波材料的吸波效果较差;当厚度>2 mm时,随着吸波材料厚度的增加,最大吸收峰的位置向低频移动,并且最大吸收峰的峰值和指定反射率的频率带宽也呈减小的趋势.在相同厚度下,随着羰基铁含量的增加,吸波材料在电磁波吸收峰处的反射率不断减小,而且吸波材料吸收峰的位置也向低频移动;输入阻抗与空气阻抗越接近,吸波材料的吸波性能越好.     

隐晶质石墨/LDPE复合材料的吸波性能

为了研究隐晶质石墨在吸波材料方面的应用,从隐晶质石墨微观形貌、粒径大小、晶体结构、杂质成分入手,深入探讨隐晶质石墨含量对隐晶质石墨/低密度聚乙烯(LDPE)复合材料吸波性能的影响.结果表明,固定碳含量为85.69％的微米级隐晶质石墨可显著提高低频吸波效果,且其含量对吸波材料吸波性能有很大影响;随着隐晶质石墨吸波剂含量的增加,最大吸收峰值均向低频方向移动,在隐晶质石墨含量为60％时的反射率在频段2～18GHz达到最大峰值-25.19 dB,小于-5dB和-10 dB的有效带宽分别为4.31 GHz和2.57 GHz.研究表明,隐晶质石墨/LDPE复合材料具有较好的吸波性能.     

双层吸波材料吸波特性研究

依据阻抗匹配原理与电磁波传播规律,设计了具有阻抗渐变结构的双层吸波材料.实验表明,匹配层对提高吸收率起着重要作用;需精确控制其吸波剂含量,以实现吸波效果.经测试:4#试样厚度为6mm,测试频段为8-18GHz,最大吸收峰值在14.1GHz(R=-28.14dB),R＜-10dB的频宽为6.7GHz;7#试样厚度为5.5mm,最大吸收峰值在9.6GHz(R=-27.48dB),R＜10dB的频宽为8.6GHz,R＜-15dB的频宽为7.6GHz;8#试样厚度为6mm,最大吸收峰值在16.8GHz(R=-24.24dB),R＜-10dB的频宽为8.6Hz.该结果具有一定工程应用价值.     

中间相沥青基碳纤维镀镍制备吸波材料

为制备中间相沥青基镀镍碳纤维,本文对比研究了电磁搅拌法和超声波法两种镀镍工艺,结果表明,两种工艺均可制备出表面镍含量较高的碳纤维,但超声波法制备的镀镍碳纤维的连续性优于电磁搅拌法,适合后续结构型吸波复合材料的制备。对镀镍碳纤维的电磁性能的研究发现,镀镍后碳纤维的电损耗参数下降,磁导率提高,利于低频带吸收。利用中间相沥青基镀镍碳纤维制备出树脂基复合材料,对其吸波性能进行测试,研究结果发现:以镀镍纤维层间全平行排布铺层制备的复合材料与未加镀镍碳纤维的相比,同时提高了在低频带和高频带的吸波效果,在14.88GHz吸收峰峰值为-27.62dB,低于-5dB的累积频宽约为14GHz,低于-10dB的累积频宽约为6.5GHz,吸波效果明显。     

碳纤维增强莫来石陶瓷的介电性能和吸波性能研究

采用模压成型工艺和固相反应烧结制备了碳纤维/莫来石（Cf /Mullite）复合材料。对Cf /Mullite复合材料的物相组成、微观结构进行了表征,使用矢量网络分析仪研究了碳纤维（Cf）含量对莫来石（3Al2O3 2SiO2）陶瓷在X波段（8.2~12.4 GHz）的介电性能和吸波性能的影响。结果表明：Al2O3和SiO2在高温下充分反应生成了莫来石陶瓷,Cf /Mullite复合材料具有相对致密结构,Cf /Mullite复合材料的介电常数和介电损耗角正切值（tan δ）均随碳纤维添加量的增加而增大,且Cf的加入使得莫来石陶瓷具有更优的电磁波吸收性能。Cf体积分数为1.2%、Cf /Mullite复合材料厚度d=1.5 mm时,反射损耗最大吸收峰为-33.3 dB,反射损耗优于-5 dB的吸收频宽达3.675 GHz,反射损耗优于-10 dB的频宽达到2.205 GHz。Cf的加入显著提高了莫来石陶瓷的吸波性能。     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

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.……     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

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.     

Mechanism Study on the Wear of CrAlTiN Coated High-Speed Steel Twist Drills Under Dry Cutting Conditions

As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.