Zusammenhang zwischen der im instrumentierten Kerbschlagbiegeversuch ermittelten Bruchverformungsarbeit und der dynamischen Rißzähigkeit hochfester Stähle in Abhängigkeit von Temperatur und Kerbschärfe

An den Stählen St 52-3 und 35 NiCrMoV 12 5 wurden im instrumentierten Kerbschlagbiegeversuch bei einer Schlaggeschwindigkeit von 5 m/s die Bruchverformungsarbeit und die dynamische Rißzähigkeit bei unterschiedlicher Kerbschärfe und Prüftemperatur bestimmt. Es wurden die Einflüsse aufgezeigt, die bei der Bestimmung der wahren Bruchverformungsarbeit E_d gegenüber dem beim Kerbschlagbiegeversuch aufgenommenen Arbeitsverbrauch a_K berücksichtigt werden müssen. Die Versuchsergebnisse wurden verglichen und diskutiert, wobei auch die Gültigkeit einer Modellvorstellung von A. S. Tetelman zur Bestimmung der Rißzähigkeit an endlich gekerbten Proben überprüft wird.     

源于共同的机械、电气和自动化设计的薄板坯连铸连轧工艺开发

西马克德马格公司在冶金工业方面是一个领先的工业工厂解决方案提供商.统一设计的机械、电气和自动化方案使我们的用户无论是在产品质量、产量、生产的灵活性、工艺的稳定性以及易维护性方面,拥有了生产具有高性能的高级材料的技术.在薄板坯连铸连轧领域,这样的共同开发的例子如下①CSP薄板坯连铸.结晶器液面控制,液压结晶器振动,用于楔形和速度优化的自动导航,带有LCR3(液芯压下)的液压扇形段调整,动态二冷水和结晶器监视系统;②CSP轧机.用于带材板形、连续凸度、平直度控制和自由轧制,采用了特定的磨辊以及相配套的串辊策略的CVC+技术;③用于实现厚度小于1mm带钢高效热轧的"薄规格技术包",包括采用"张力差活套"或"张力计活套"以及快速液压机构配合相应的自动化模块,如自动调平控制,以活套测量为基础的平直度控制,尾部监控或以楔形测量为基础的调平预设定.不仅是机械和电气的共同设计,还有共同的项目执行都将使工厂的运营者受益.例如,对于现代化改造项目和新安装的工厂,通过在交货之前在实验室内的联合测试,项目的投产时间得以优化."工厂回路测试(PILT)"将仿真或甚至机械部件本身与真实的自动化系统(1级,2级和人机界面HMI)结合在一起.通过这样的共同解决方案,西马克德马格公司在电气和自动化领域已发展成"从电机轴一直到生产计划系统"的成套供货商和系统集成商,其目标就是致力于与其用户的长期伙伴关系,并与用户分享其所拥有的工艺经验.     

Design and characterization of the balloon-borne Michelson Interferometer for Passive Atmospheric Sounding (MIPAS-B2)

MIPAS-B2 is a balloon-borne limb-emission sounder for atmospheric research. The heart of the instrument is a Fourier spectrometer that covers the mid-infrared spectral range (4-14 microns) and operates at cryogenic temperatures. Essential for this application is the sophisticated line-of-sight stabilization system, which is based on an inertial navigation system and is supplemented with an additional star reference system. The major scientific benefit of the instrument is the simultaneous detection of complete trace gas families in the stratosphere without restrictions concerning the time of day and viewing directions. The specifications, the design considerations, the actual realization of the instrument, and the results of characterization measurements that have been performed are described.     

Biological tissue characterization by magnetic induction spectroscopy (MIS): requirements and limitations

Magnetic induction spectroscopy (MIS) aims at the contactless measurement of the passive electrical properties (PEP) sigma, epsilon, and mu of biological tissues via magnetic fields at multiple frequencies. Whereas previous publications focus on either the conductive or the magnetic aspect of inductive measurements, this article provides a synthesis of both concepts by discussing two different applications with the same measurement system: 1) monitoring of brain edema and 2) the estimation of hepatic iron stores in certain pathologies. We derived the equations to estimate the sensitivity of MIS as a function of the PEP of biological objects. The system requirements and possible systematic errors are analyzed for a MIS-channel using a planar gradiometer (PGRAD) as detector. We studied 4 important error sources: 1) moving conductors near the PGRAD; 2) thermal drifts of the PGRAD-parameters; 3) lateral displacements of the PGRAD; and 4) phase drifts in the receiver. All errors were compared with the desirable resolution. All errors affect the detected imaginary part (mainly related to sigma) of the measured complex field much less than the real part (mainly related to epsilon and mu). Hence, the presented technique renders possible the resolution of (patho-) physiological changes of the electrical conductivity when applying highly resolving hardware and elaborate signal processing. Changes of the magnetic permeability and permittivity in biological tissues are more complicated to deal with and may require chopping techniques, e.g., periodic movement of the object.     

Prion diseases: from molecular biology to intervention strategies

Prion diseases are fatal neurodegenerative infectious disorders for which no therapeutic or prophylactic regimens exist. Understanding the molecular process of conformational conversion of the cellular prion protein (PrP(c)) into its pathological isoform (PrP(Sc)) will be necessary to devise effective antiprion strategies. In recent years, new findings in the cell biology of PrP(c), in the molecular pathogenesis of PrP(Sc), and in the cellular quality control mechanisms involved in these scenarios have accumulated. A function of the prion protein in signalling, the possible impact of the proteasome, and aggresomes as intracellular waste deposits have been described. Here, important pathogenetic similarities with the more frequent neurodegenerative disorders are evident. The need for therapeutic, postexposure, and prophylactic possibilities was drastically illustrated by the emergence of variant Creutzfeldt-Jakob disease (vCJD), a new human prion disease caused by bovine spongiform encephalopathy (BSE) derived prions. Although prion infectivity in humans is usually restricted to the central nervous system, in vCJD patients prions are present in the lympho-reticular system, posing a theoretical risk of accidental human-to-human transmission. A variety of chemical antiprion substances have been reported in in vitro and cell culture based assays or in animal studies. Occasionally, they have also made their way into the first human trials. In addition, various promising interference strategies have been devised in transgenic models, although they are usually hard to transfer into nontransgenic in vivo situations. New findings in the fields of peripheral prion pathogenesis and immune system involvement fuelled the search for antiprion strategies formerly considered to be entirely impossible. This opened the door towards classical immunological interference techniques. Remarkably, passive and even active vaccination approaches now seem to be realistic goals.     

Variability, covariation, and invariance with respect to coordinate systems in motor control: Reply to Smeets and Louw (2007).

In their comment on the tolerance-noise covariation (TNC) method for decomposing variability by H. Müller and D. Sternad (2003, 2004b), J. B. J. Smeets and S. Louw (see record 2007-01135-017) show that covariation (C), as defined within the TNC method, is not invariant with respect to coordinate transformations and contend that it is, therefore, meaningless. Although the observation is correct, their interpretation is misleading in the following ways: (a) They equate covariation C with the known statistical quantity covariance and noise (N) with standard deviations. The two quantities C and N are conceptually different statistical measures. (b) Dependency on the reference frame is not only a feature of C but of all 3 components. However, such dependency is ubiquitous in motor control. (c) As the frame of reference in biological systems is poorly understood, the TNC method may afford evaluation of different coordinates for control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Quasicrystal–crystal structural transformation in Al–5 wt.% Mn alloy

The atomic structure of Al–5 wt.%Mn (Al–5Mn) alloy, prepared by rapid solidification, and pre-annealed at 623 and 773 K for 5 and 1 h, respectively, were characterized by X-ray powder diffraction (XRD) and extended X-ray absorption fine structure (XAFS) techniques. The sample in as-quenched stage was found crystalline, consisting of metastable α-Al (Al–Mn solid solution) and icosahedral quasicrystalline I-Al₆Mn phases. Five hours annealing at 623 K proved thermal stability of both the phases. Pre-annealing at 773 K/1 h on the other hand leads to α-Al phase decomposition and structural transformation of metastable I-Al₆Mn to stable orthorhombic Al₆Mn phase. The EXAFS results indicate that Mn atoms are located preferably on the outer shell of icosahedrons. During the I-Al₆Mn→o-Al₆Mn transformation the total Al atoms coordinating one Mn were found to be constant (∼10). Based on the results, only distance/symmetry changes in atomic arrangement around Mn atoms were suggested.     

Microflow-based control of near-wall fluctuations for large viscous drag reduction

The stabilizing effect of microgroove surface morphology on viscous drag reduction was studied experimentally in the inlet region of a plane channel flow. The stabilization is thought to be due to the ability of a microgrooved surface pattern to suppress the velocity fluctuations in the spanwise direction on a restricted portion of the wetted surface, which prevents vorticity development at the wall and consequently across the entire flow field. This smart microflow control strategy, which works successfully only under very particular circumstances, was implemented in a microgroove-modified channel flow in which the front part has a microgrooved surface topology. The results of pressure drop measurements indicate that microgrooved surfaces can effectively stabilize laminar boundary layer development, leading to a significant reduction in the viscous drag. In the rear flat part of the microgroove-modified channel test section, a maximum drag reduction of DR @ 35%{\rm DR\simeq 35\%} was measured. This corresponds to an overall drag reduction of DR @ 16%{\rm DR\simeq 16\%} at a length Reynolds number of Re_x @ 10⁶.Re_x\simeq 10^6. The drag reduction effect persisted in a narrow range of flow velocities and for the reported experimental conditions corresponds to microgroove dimensions between 1.5 and 2.5 viscous length-scales.