高效切削加工对机床的要求

在木材加工中生产率的提高,降低制造成本,至今主要依靠数控技术减少辅助时间.高效切削加工的目标是减少加工时间同时没有舍弃质量要求.这方面初期研究工作可以追溯到20年代以前,60年代后高速切削开始发展,在80年代加工技术进步和更加坚硬的刀具材料使高速切削有重大进展.内容丰富的研究计划致力于高速切削的各种金属合金和纤维增强刀具材料.对于每一种工件材料,高速切削的概念必须有一个明确的定义范围.结果表明,加工时间的优化将比通常值有明显的改变,在改善表面质量的同时还可以达到大大降低加工成本的目标.部分仍然进行的木材加工研究计划希望有类似的有益结果.     

Controlled p-doping of pigment layers by cosublimation: Basic mechanisms and implications for their use in organic photovoltaic cells

We present a systematic study on doping of vanadyl- and zinc-pathalocyanine by a fully fluorinated form of tetracyano-quinodimethane as an example of controlled doping of thin organic films by cosublimation of matrix and dopant. The films are characterized in situ by temperature dependent Seebeck and conductivity measurements. We observe a drastic increase of conductivity and a corresponding shift of the Fermi level towards the valence states with increasing dopant concentration. We thus conclude that doping has the potential of both reducing the series resistance and increasing the photovoltage of organic solar cells. As a first step to exploit this potential, we present two different ways of preparing diodes with rectification ratios in excess of 10⁴ using doped phthalocyanines. By adding an undoped interlayer between the contact and the doped layer, we have produced diodes which work already in the strict absence of oxygen and are stable in air. To increase the efficiency of charge carrier generation in photovoltaic cells, we need to use photoactive donor–acceptor-heterojunctions. We present here first examples of pn- and pin-type heterojunctions combining p-doped and nominally undoped layers.     

Dioxins, dioxin-like PCBs and non-dioxin-like PCBs in dairy products on the German market and the temporal tendency in Schleswig-Holstein

140 Milcherzeugnisse aus verschiedenen Regionen Deutschlands wurden 2006 auf Dioxine, dioxin?hnliche PCB und nicht dioxin?hnliche PCB untersucht. Insgesamt wurden 66 K?se-, 23 Butter- und 51 Quark- bzw. Joghurterzeugnisse analysiert. Die Probenahme erfolgte in Superm?rkten und Einzelhandelsgesch?ften auf der Basis der Produktionsmengen in den einzelnen Bundesl?ndern der Bundesrepublik Deutschland. Die Dioxinkonzentrationen und die Summe der WHO-TEQ blieben weit unter den EU-Grenzwerten von 3 pg WHO-PCDD/F-TEQ/g Fett und 6 pg WHO-PCDD/F-PCB-TEQ/g Fett. Die Dioxingehalte lagen bei niedrigen 0,07–0,53 pg WHO-PCDD/F-TEQ/g Fett mit einem arithmetischen Mittelwert von 0,19 pg WHO-PCDD/F-TEQ/kg Fett. Die WHO-PCDD/F-PCB-TEQ Gehalte lagen zwischen 0,21 und 2,1 pg WHO-TEQ/g Fett, mit einem mittleren Gehalt von 0,76 pg WHO-TEQ/g Fett. Regionale Abh?ngigkeiten und Unterschiede zwischen den einzelnen Produktgruppen konnten nicht festgestellt werden. Langj?hrige Messungen der Dioxingehalte in Butter und K?se aus Schleswig-Holstein zeigen über den Zeitraum von 13 Jahren eine deutliche Abnahme der Gehalte von 0,43 auf 0,19 pg WHO-PCDD/F-TEQ/g Fett.     

drupa 2004展示印刷的前景

被誉为全球印刷业界“奥林匹克”盛会的drupa 2004国际印刷媒体、出版和纸品加工展览会将于今年5月6日在德国杜塞尔多夫展览中心拉开帷幕。据有关方面预计,届时我国印刷及设备器材行业将有5000余人前往参观。即使是没有机会亲临现场的业内人士,也无疑会对这一盛会给予极大的关注。为了使国内印刷业同仁能够在展会开幕前就对本届drupa展会有更好的了解,本刊于本期推出了“drupa观展指南”专题。本专题由二部分组成,前一部分是10篇国外印刷界专家撰写的文章,从各不同角度介绍和分析了当前印刷业各相关技术的发展趋势,也提示参观者在展会上看什么,怎么看?本专题的后一部分是国内外的一些知名参展商将在展会上推出的热点产品;穿插在专题当中的还有与本届展览相关的各种信息,可供参观人员参考。愿本专题能为即将赴德参观drupa2004的人士以及虽然不能亲临展会现场但密切关注drupa2004的本刊广大读者提供有益的帮助。这即是本刊编辑这一专题的初衷。     

Gas-phase photoinduced graft polymerization of acrylic acid onto polyacrylonitrile ultrafiltration membranes

Heterogeneous surface modification of polyacrylonitrile (PAN) ultrafiltration (UF) membranes is realized with UV irradiation-initiated graft polymerization of acrylic acid (AA) from the gas phase onto photoinitiator (benzophenone, BP)-coated samples. In the absence of monomer, PAN functionalization by ketyl radicals dominates after UV excitation of sorbed BP. With AA, graft and total polymer yield increase with BP loading and UV irradiation time. Average molecular weight and distribution of PAA homopolymer—formed in parallel during graft polymerization—are analyzed with gel permeation chromatography. Morphology of PAN-gr-AA UF membranes is checked with scanning electron micrographs (SEMs) and atomic force microscopy. Chemical changes are characterized with FTIR-ATR spectroscopy and SEM/EDX analyses, indicating a pronounced surface selctivity of the graft polymer modification (localized in the upper 5-μm membrane thickness). The amount of grafted PAA systematically reduces membrane permeability and increases dextrane retention, as verified in UF experiments. Photo graft polymer modificationof UF membranes will be applied to adjust membrane performance by controlling surface hydrophilicity and permeability using other monomers and/or further graft polymer functionalization. © 1995 John Wiley & Sons, Inc.     

Novel Potential Enantioselective Phase Transfer Catalysts Based on Lupinine

Ten N-alkylated lupininium derivatives 5–8 were prepared as potential enantioselective phase transfer catalysts. Compounds 5a–d , 6a–d contain four asymmetric centers (including one in the side chain) with known configuration resting on an X-ray structure. Preliminary PT catalytic experiments in several reactions gave high chemical yields but relatively disappointing enantioselectivities.     

Progress in Understanding Plasma‐Propellant Interaction

To explore the phenomena of the plasma‐propellant interaction (PPI) and to point out the role of radiation, a series of experiments have been performed at the U.S. Army Research Laboratory. For this, the plasma radiation to the propellant has been separated from all other energy transfer mechanisms. The results clearly indicate that the observed structural damage of translucent JA2 samples is due to radiation only. An other aim of this work is to clarify some misunderstandings in analyzing plasma‐propellant interaction. By variation of the electrical pulse length it will be shown that electrical energy is in no way a useful parameter to characterize propellant response to variable plasma igniter systems.     

Comparative Analysis of Volatile Constituents from Mice and their Urine

We report the volatile composition of the body scent of male C57BL/6J mice in comparison to the volatile composition of their urine. From a total of 67 components, nitromethane, propanoic acid, dimethyldisulfide, 1-octene, 1-hexanol, hexanoic acid, indole, α- and β-farnesene, and one unidentified component were observed only in the volatiles from the body of mice. On the other hand, 3-penten-2-one, 3-methyl-2-buten-1-ol, 3-methyl-cyclopentanone, p-xylene, 3-hepten-2-one, 2,3-dehydro-exo-brevicomin, benzylmethylketone, and 13 unidentified components were only found in urine volatiles. All other substances were present in the volatiles of both mice and their urine. Aliphatic aldehydes from pentanal to decanal were prominent mouse odor components. Because receptors for these aldehydes have been extensively characterized in the main olfactory organ, these components may be important for mice in recognizing their conspecifics.Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Delamination of organo-modified layered double hydroxides in polyamide 6 by melt processing

Layered double hydroxides (LDH) are a class of readily synthesizable layered crystals that can be used as an alternative to the commonly used silicate crystals for the preparation of polymeric nanocomposites. In this work layered double hydroxide/polyamide 6 nanocomposites (LDH/PA6) were prepared from organo-modified LDH by melt processing. The anionic exchange capacity of LDH was varied in order to investigate its influence on the degree of exfoliation. LDH were dispersed by a twin screw micro-extruder at a variety of processing conditions. The nanocomposites were characterized by wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), transmission electron microscopy, dynamic scanning calorimetry, and thermogravimetric analysis. It was found that exfoliated nanocomposites were successfully prepared by melt processing with a low exchange capacity LDH, whereas residue tactoids were observed with a high exchange capacity LDH. Shear, together with the exchange capacity, seems to be the key factor for the delamination in LDH/PA6. No major change in the crystalline phase or in the rate of crystallization was observed in the nanocomposite as compared to the neat polymer. A reduction in the onset of thermal decomposition temperature was observed in PA6/LDH compared to neat PA6, likely due to a nucleophilic attack mechanism. The properties of this nanocomposite system are discussed with connections to the current understanding within the broader nanocomposite field.