铸态Al-7Si-0．3Mg合金的连续冷却析出图

采用冷却速率为0．01～3K／s的差示扫描量热法（DSC）和冷却速率更高的淬火膨胀法研究铸态Al-7Si-0．3Mg合金淬火的析出行为。在合金冷却的过程中发生了两种析出反应,高温反应开始于淬火起始温度540℃,低温反应始于400℃左右。3K／s的淬火冷却速率已经显著抑制淬火过程中相的析出。合金T6态的硬度随着淬火速率的增快而增加,这是由合金过饱和固溶度增加而导致的。通过膨胀实验和硬度实验的结果可以估计临界冷却速率大约为60K／s。通过光学显微镜观察淬火态的铸态Al-7Si-0．3Mg合金的显微组织。结果表明：根据淬火冷却速率的不同合金的显微组织由铝一硅共晶组织、铝固溶体枝晶及枝晶间的析出相组成。     

TiO2-coated foams as a medium for solar catalysis

Sunlight irradiating the surface of the Earth represents a maximum input available for a solar catalytic process of 50 W_UV m⁻². We propose using high-porosity, metallic, reticulated foams as the support medium for the photocatalyst in order to improve the apparent quantum yield. The layer of TiO₂ was applied by dip-coating. The measurement of the degradation kinetics was carried out on a model target molecule, 2,4 dichlorophenol, at an initial concentration of 10 mg l⁻¹. The aim was to assess the efficiency of the foams as a photocatalytic media compared to that of a suspension of catalytic powder (Degussa P25) and the flat 2D support (Ahlstrom cellulose media). The apparent quantum yield of the foam scaffold carrying the TiO₂ was high, showing that, as with the powder suspension, foam makes good use of the UV rays to break down molecules. It is noteworthy that the apparent quantum yield of the foam tended towards that observed for suspensions which form the ideal support thanks to their optimal ability to harness the light.     

Fast and exact synthesis of stationary multivariate Gaussian time series using circulant embedding

A fast and exact procedure for the numerical synthesis of stationary multivariate Gaussian time series with a priori prescribed and well controlled auto- and cross-covariance functions is proposed. It is based on extending the circulant embedding technique to the multivariate case and can be viewed as a modification and variation around the Chan and Wood algorithm proposed earlier to solve the same problem. The procedure is shown to yield time series possessing exactly the desired covariance structure, when sufficient conditions are satisfied. Such conditions are discussed theoretically and examined on several examples of multivariate time series models. Issues related to prescribing a priori the spectral structure rather than the covariance one are also discussed. Matlab routines implementing this procedure are publicly available at http://www.hermir.org.     

Computational modeling of age-differences in a visually demandingdriving task: vehicle detection

The visual task of detecting an approaching vehicle was modeled with a neurophysiologically motivated computational vision model, the National Automotive Center-visual perception model (NAC-VPM). The scientific literature documenting age-related changes in early vision was reviewed in relationship to the components of the NAC-VPM, and the model was fit to laboratory data from older observers. The model fit the older observers' data adequately, particularly when the data was partitioned into subsets based on viewing conditions. Model fits were compared to calibrations based on younger observers' data. The calibrations based on older observers were substantially different from calibrations based on younger observers, indicating that the model can capture age-related differences in visual perception. When calibrated to the older adults' data, the model successfully predicted conditions under which vehicle detection was particularly difficult for older adults     

Verhaltensbasierte Verkettung von Internetsitzungen

Die Analyse der Aktivit?ten eines Internet-Nutzers ist über l?ngere Zeit in der Regel nur mit Kenntnis der bei vielen Internet-Zugangsprovidern mindestens einmal t?glich wechselnden IP-Adressen m?glich. Verwendet der Nutzer zudem einen Anonymisierungsdienst, sollte eine Verkettung der Nutzer-Aktivit?ten auch für den Zugangsprovider unm?glich sein. Der Beitrag zeigt, dass eine verhaltensbasierte Verkettung dennoch m?glich ist und verbreitete Anonymisierungsl?sungen in der Praxis einen deutlich geringeren Schutz vor Beobachtung bieten, als bisher angenommen.     

Fracture resistance of a doped PZT ceramic for multilayer piezoelectric actuators: Effect of mechanical load and temperature

The fracture resistance behaviour of a doped lead zirconate titanate (PZT) ceramic after combined thermo-mechanical loading is investigated between room temperature (RT) and 400 °C, i.e. above the Curie temperature (T_C). The thermal- and stress-induced depolarisation effects due to domain switching have been assessed by the indentation method on bulk PZTs. This has been extended to multilayered actuators. Experimental findings show a depolarisation effect with the temperature, which is significantly enhanced when combined with mechanical loading. This partial or even full depolarisation of the PZT material below T_C leads to important anisotropy effects in the fracture resistance of the piezo-ceramic, which should be taking into account in the design of multilayer actuators where the direction of crack propagation (i.e. parallel or normal to electrodes) can affect the actuator functionality.     

Selective impairments of memory functioning in unmedicated adults with Gilles de la Tourette's syndrome.

Different forms of memory linked to specific brain regions were assessed in unmedicated adults with Gilles de la Tourette's syndrome (TS) and in normal controls of equivalent age and educational attainment. TS patients were impaired on measures of strategic, working, and procedural memory associated with fronto-striatal function. In contrast, their performance was intact on measures of immediate, semantic, and declarative memory associated with temporal-diencephalic functioning. These findings are consistent with radiological evidence of fronto-striatal abnormalities in TS and provide convergent evidence that a fronto-striatal memory system mediates working memory in humans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electron holography and AFM studies on styrenic block copolymers and a high impact polystyrene

Many of the artifacts of conventional electron microscopy can be avoided if the unstained polymers are studied by electron holography and atomic force microscopy (AFM). Holograms of thin sections (50–70 nm) of organic block copolymers were recorded, and the corresponding phase images were reconstructed. In this way, typical structures such as lamellae and cylinders could be imaged without any staining. In addition, we successfully recorded holograms and performed Lorentz microscopy of an impact‐modified polystyrene (high‐impact polystyrene). The results were compared with the tapping mode AFM phase images. Electron holography and AFM have been demonstrated as suitable tools to image unstained heterogeneous polymers, leading to the understanding of their structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1573–1583, 2005     

Forced Relocation vs. Voluntary Mobility: The Effects of Dispersal Programmes on Households

The deconcentration of poverty in the US has involved both voluntary mobility programmes for low-income households and involuntary relocation of families through government action. This paper examines the effects on families of these two different strategies. Using data on over 600 families in the Twin Cities region of Minneapolis/Saint Paul, the study reveals only sporadic support for the hypothesis that voluntary or involuntary participants in the deconcentration effort will report improvements in their living conditions, or report better conditions than a control group of public housing and Section 8 residents. Several possible explanations for the lack of programme effects are offered.