The SHARC framework for data quality in Web archiving

Web archives preserve the history of born-digital content and offer great potential for sociologists, business analysts, and legal experts on intellectual property and compliance issues. Data quality is crucial for these purposes. Ideally, crawlers should gather coherent captures of entire Web sites, but the politeness etiquette and completeness requirement mandate very slow, long-duration crawling while Web sites undergo changes. This paper presents the SHARC framework for assessing the data quality in Web archives and for tuning capturing strategies toward better quality with given resources. We define data quality measures, characterize their properties, and develop a suite of quality-conscious scheduling strategies for archive crawling. Our framework includes single-visit and visit?Crevisit crawls. Single-visit crawls download every page of a site exactly once in an order that aims to minimize the ??blur?? in capturing the site. Visit?Crevisit strategies revisit pages after their initial downloads to check for intermediate changes. The revisiting order aims to maximize the ??coherence?? of the site capture(number pages that did not change during the capture). The quality notions of blur and coherence are formalized in the paper. Blur is a stochastic notion that reflects the expected number of page changes that a time-travel access to a site capture would accidentally see, instead of the ideal view of a instantaneously captured, ??sharp?? site. Coherence is a deterministic quality measure that counts the number of unchanged and thus coherently captured pages in a site snapshot. Strategies that aim to either minimize blur or maximize coherence are based on prior knowledge of or predictions for the change rates of individual pages. Our framework includes fairly accurate classifiers for change predictions. All strategies are fully implemented in a testbed and shown to be effective by experiments with both synthetically generated sites and a periodic crawl series for different Web sites.     

On some weight functions admitting (0, 2) quadrature formulae with a high algebraic degree of precision

The purpose of this paper is to find a class of weight functions μ for which there exist quadrature formulae of the form (1) $$\int_{ - 1}^1 {\mu (x) f(x) dx \approx \sum\limits_{k = 1}^n {(a_k f(x_k ) + b_k f''(x_k ))} }$$ , which are precise for every polynomial of degree 2n.     

On the geometrical dependence of low-frequency noise in SiGe HBTs

We present an investigation of the dependence of low-frequency noise on device geometry in advanced npn silicon–germanium (SiGe) heterojunction bipolar transistors (HBTs). The devices examined in this work have fixed emitter width (W_E = 0.4 μm), but varying emitter length (0.5 μm  L_E  20.0 μm), and thus the ratio of the emitter perimeter (P_E) to the emitter area (A_E) varies widely, making it ideal for examining geometrical effects. The SPICE noise parameter A_F extracted from these devices decreases with increasing L_E. Furthermore, the low-frequency noise measured on SiGe HBTs with significantly different P_E/A_E ratios suggests a possibility that the fundamental noise source for the diffusion base current may be located at the emitter periphery. Transistors with different distances between the emitter edge and the shallow trench edge (XEC), and shallow trench edge to deep trench edge (XTC), are also investigated. The SiGe HBTs with a smaller value of XEC have higher low-frequency noise, but no significant difference is found in devices with varying XTC. Explanations of the observed noise behavior are suggested.     

绿色能源与绿色工业

<正>A New AUsing the Modified Four Point Probe (Mo4PP) as a Tool for Monitoring Processing of Solar Cell Wafers 1 Modified Four Point Probe The aim of this report is to present and justify a new tool (Mo4PP) for Monitoring processing of solar cells.     

互联网的业务融合及可信度研究

互联网融合多种业务过程中面临服务质量、信息安全和网络可信度等问题带来的挑战。实行实名制,层次结构,测量、监控与审计,流量规划和准入控制,地址空间扩充,网络可信度综合评价是有效的治理措施。从驻地网开始治理,使得每一个驻地网都有良好的品质,可为互联网提供良好的服务创造条件。     

Catalytic activity of Fe/AC, obtained by impregnation of activated carbon in aqueous and non-aqueous media, to neutralize NO

The influence of the nature of the impregnating solutions media (aqueous or non-aqueous) on the forming of active phases is investigated in case of preparing iron catalysts, supported on activated carbon with respect to their catalytic activity in the reaction of NO reduction by CO. The catalysts are characterized by chemical analysis (AAS), BET surface area, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), magnetic susceptibility, and Mössbauer spectroscopy (MS). The catalytic investigations and TPD are carried out in a flow apparatus. Three peculiarities are observed with respect to this influence—the ratio between the separate iron species in different oxidation state of Fe species, which build up the catalytic active complexes (CAC), common participation of superficial groups of the carbon support and Fe components of the impregnating solutions as well as different dispersion of the active phase on the surface of the samples. As a result the highest catalytic activity was observed with the sample, obtained by impregnation with an aqueous solution, while with the other samples, obtained from organic solutions, the catalytic activity decreases in the order of: Methanol > Ethyl Ether > Acetone. It was assumed that the different catalytic activities are connected most probably with the process of forming of CAC during the process of preparation of the samples.     

Modeling participatory learning as a control mechanism

We discuss the participatory learning model originally introduced by Yager [IEEE Trans. Syst. Man Cybern. SMC-20 , 1229–1234 (1990)]. We analyze the learning mechanism as a stable control strategy. We show how the learning mechanism used in participatory learning can be expressed in the form of a fuzzy rule base. We use this rule base formulation to provide new learning rules. We modify the Widrow-Hoff rule to include a participatory learning mechanism. © 1993 John Wiley & Sons, Inc.     

Xylose fermentation to biofuels (hydrogen and ethanol) by extreme thermophilic (70 °C) mixed culture

Combined biohydrogen and bioethanol (CHE) production from xylose was achieved by an extreme thermophilic (70 °C) mixed culture. Effect of initial pH, xylose, peptone, FeSO₄, NaHCO₃, yeast extract, trace mineral salts, vitamins, and phosphate buffer concentrations on bioethanol and biohydrogen yield was investigated in batch experiments. Results obtained showed that initial pH, concentration of xylose, peptone, and FeSO₄ significantly affected biohydrogen and bioethanol production, while the concentration of NaHCO₃ was only significant for bioethanol production. By changing cultivation conditions the culture could be directed to mainly produce ethanol with maximum ethanol yield of 1.60 mol ethanol/mol-xylose corresponding to 95.8% of the theoretical ethanol yield based on degradation of xylose through ethanologenic pathway, or mainly hydrogen with maximum hydrogen yield of 1.84 mol H₂/mol-xylose corresponding to 55% of the theoretical hydrogen yield based on acetate metabolic pathway. An empirical model was established to reveal the quantitative effect of factors significant for biohydrogen (quadratic model) production and for bioethanol (linear model) production. Changes in hydrogen/ethanol yields observed were due to the shift of the metabolic pathway between ethanol or hydrogen production, rather than changes in bacterial community composition at genus level. Thermoanaerobacter related bacteria were found to be the dominant hydrogen/ethanol producers.     

Heavy metals (Pb,Cu, Zn and Cd) in the system soil – grapevine – grape

An Erratum has been published for this article in Journal of the Science of Food and Agriculture 79(15)1999, 2122. The investigation was carried out in the period 1991–1995 in a region with a major industrial pollutant, the Non‐Ferrous‐Metal Works, and a region with no industrial pollutants (as a control). The heavy metal content in soil, roots, annual shoots and perennial parts of grapevine, leaves, grapes and wine, was determined. Soil samples and roots of the rootstock Kober 5BB were taken at 10 cm intervals from depths of 0–100 cm. Roots were divided by thickness in fractions at 1 mm intervals. The shoots, bark, vascular tissue, wood, core and diaphragm were investigated. The leaf analyses included leaf blade and leaf petioles, and those of grapes, berry‐free raceme (washed in a lot of water and unwashed). Berries were analysed (the berry skin, the pulp and the seeds). The results obtained for the Pb, Cu, Zn and Cd contents in the grapevine roots show that they depend significantly both on their amounts in the soil and the age of the roots. The main parts of the heavy metal amounts taken by the roots of the grapevine from the soil are fixed and accumulated in the young feed rootlets (with diameters of 1 mm), and small amounts of them move through the conducting system to the older, larger diameter root system. The experimental data obtained for the presence of Pb, Cu, Zn and Cd in the separate tissues and organs of grapevines grown in an industrially polluted region showed that their amounts were mainly due to the heavy‐metal‐containing aerosols falling from the atmosphere. Part of them, however, got into the soil, and from there, even if in minimal amounts, penetrated via the root system into the grapevine plants and accumulated into their different overground parts. © 1999 Society of Chemical Industry     

Mechanochemical Synthesis and Characterization of Nanocrystalline Copper-Cobalt Ferrites

Nanocrystalline copper-cobalt ferrites with composition Cu_(1-x)Co_xFe_2O_4,where x = 0.2 and 0.8,were synthesized by mechanochemical treatment of co-precipitated precursors.The ferrite powders were characterized by XRD and Mossbauer spectroscopy.Results proved obtaining of spinel ferrites with crystallite size smaller than 10 nm.Increasing of crystallite size of samples with increasing of mechanochemical treatment duration was established,too.Catalytic properties of obtained ferrites were tested in reactions of oxidation of CO,methanol and dimethyl ether.High catalytic activity of nanocrystalline copper-cobalt ferrites toward CO and CH_3OH(about 100% conversions of CO and CH_3OH at 160 ℃)and moderate activity toward(CH_3)_2O oxidation were established.The results obtained revealed that the Co/Cu atomic ratio is an important factor determinant the behavior of catalysts toward methanol and DME oxidation.