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排序方式: 共有250条查询结果,搜索用时 15 毫秒
101.
102.
We present a method of representing some classes of default theories as normal logic programs. The main point is that the standart semantics (i.e., SLDNF-resolution) computes answer substitutions that correspond exactly to the extensions of the represented default theory. This means that we give a correct implementation of default logic. We explain the steps of constructing a logic program LogProg(P, D) from a given default theory (P, D), give some examples, and derive soundness and completeness results. 相似文献
103.
Deissenboeck Florian Juergens Elmar Hummel Benjamin Wagner Stefan Parareda Benedikt Mas y Pizka Markus 《Software, IEEE》2008,25(5):60-67
Over time, software systems suffer gradual quality decay and therefore costs can rise if organizations fail to take proactive countermeasures. Quality control is the first step to avoiding this cost trap. Continuous quality assessments help users identify quality problems early, when their removal is still inexpensive; they also aid decision making by providing an integrated view of a software system's current status. As a side effect, continuous and timely feedback helps developers and maintenance personnel improve their skills and thereby decreases the likelihood of future quality defects. To make regular quality control feasible, it must be highly automated, and assessment results must be presented in an aggregated manner to avoid overwhelming users with data. This article offers an overview of tools that aim to address these issues. The authors also discuss their own flexible, open-source toolkit, which supports the creation of dashboards for quality control. 相似文献
104.
This paper introduces an accurate real‐time soft shadow algorithm that uses sample based visibility. Initially, we present a GPU‐based alias‐free hard shadow map algorithm that typically requires only a single render pass from the light, in contrast to using depth peeling and one pass per layer. For closed objects, we also suppress the need for a bias. The method is extended to soft shadow sampling for an arbitrarily shaped area‐/volumetric light source using 128‐1024 light samples per screen pixel. The alias‐free shadow map guarantees that the visibility is accurately sampled per screen‐space pixel, even for arbitrarily shaped (e.g. non‐planar) surfaces or solid objects. Another contribution is a smooth coherent shading model to avoid common light leakage near shadow borders due to normal interpolation. 相似文献
105.
Shape‐Memory Topographies on Nickel–Titanium Alloys Trained by Embossing and Pulse Electrochemical Machining 下载免费PDF全文
Mareike Frensemeier Dominik Schirra Martin Weinmann Olivier Weber Elmar Kroner 《Advanced Engineering Materials》2016,18(8):1388-1395
The two‐way shape‐memory effect (TWSME) in Nickel–titanium (NiTi) alloys is of interest for applications in aerospace, biomedicine, and microengineering due to its reversible shape recovery. In this study, the authors demonstrate two approaches to obtain switchable surface structures using the TWSME. Samples are structured using two surface geometries by either cold embossing, or pulse electrochemical machining (PECM). After planarization, a change from optically smooth to structured and vice versa is observed. The switch is induced through heating and cooling the sample above and below the phase transformation temperature. The protrusions reflect the pattern applied by the two processes. Both methods are promising for preparation of switchable metallic surfaces on larger areas. 相似文献
106.
Klaus Reichmann Elmar Völkl Martin Ahrens Jürgen Fleig Jürgen Vötsch 《Journal of Materials Science》2010,45(6):1473-1477
The influence of SrO–WO3 additive on the piezoelectric properties and electric conductivity of lead zirconate–titanate (PZT) near the morphotropic phase boundary was investigated. Starting from the composition 0.995 Pb(Zr0.525Ti0.475)O3 + 0.015 SrO + 0.005 WO3 (corresponding to 0.5 mol% of Sr3WO6) the fraction of WO3 was increased until Sr:W = 1:1. These samples were compared to a set of samples of PZT with WO3 addition but without SrO. Sr3WO6 has pseudocubic K2NaAlF6 structure with part of the strontium being octahedrally coordinated. In a solid solution with PZT this opens the possibility of realizing Sr on a B-site adjacent to a B-site occupied by W. Piezoelectric properties were measured on sintered disc samples under high field conditions. Impedance spectroscopy was used to investigate the conductivity and dielectric properties of the ceramics at various temperatures. The combined addition of SrO and WO3 increases the piezoelectric strain compared to samples of PZT with WO3 addition only. The results in polarization and conductivity indicate that the donor effect of WO3 is counteracted by the addition of SrO. 相似文献
107.
Nyawade Shadrack O. Karanja Nancy N. Gachene Charles K. K. Gitari Harun I. Schulte-Geldermann Elmar Parker Monica 《Nutrient Cycling in Agroecosystems》2020,117(1):43-59
Nutrient Cycling in Agroecosystems - Negative nitrogen balance represents a major factor causing low potato yield in potato growing areas of Kenya while its excessive surplus poses a significant... 相似文献
108.
Abbas H. K. Al Temimi Dr. Michael Martin Dr. Qingxi Meng Danny C. Lenstra Dr. Ping Qian Prof. Dr. Hong Guo Prof. Dr. Elmar Weinhold Prof. Dr. Jasmin Mecinović 《Chembiochem : a European journal of chemical biology》2020,21(3):392-400
Biomedicinally important histone lysine methyltransferases (KMTs) catalyze the transfer of a methyl group from S-adenosylmethionine (AdoMet) cosubstrate to lysine residues in histones and other proteins. Herein, experimental and computational investigations on human KMT-catalyzed ethylation of histone peptides by using S-adenosylethionine (AdoEth) and Se-adenosylselenoethionine (AdoSeEth) cosubstrates are reported. MALDI-TOF MS experiments reveal that, unlike monomethyltransferases SETD7 and SETD8, methyltransferases G9a and G9a-like protein (GLP) do have the capacity to ethylate lysine residues in histone peptides, and that cosubstrates follow the efficiency trend AdoMet>AdoSeEth>AdoEth. G9a and GLP can also catalyze AdoSeEth-mediated ethylation of ornithine and produce histone peptides bearing lysine residues with different alkyl groups, such as H3K9meet and H3K9me2et. Molecular dynamics and free energy simulations based on quantum mechanics/molecular mechanics potential supported the experimental findings by providing an insight into the geometry and energetics of the enzymatic methyl/ethyl transfer process. 相似文献
109.
Shepherd M. Tichapondwa Walter W. Focke Olinto DelFabbro Elmar Muller 《Propellants, Explosives, Pyrotechnics》2013,38(1):48-55
Aqueous silicon dispersions are used to produce pyrotechnic time delay compositions. The propensity of silicon to react with water and to produce hazardous hydrogen gas must be suppressed. To this end, the effect of air heat treatment temperature on the rate of corrosion of silicon was investigated. It was found that four hour heat treatments at temperatures below 350 °C provided significant passivation. This is attributed to the removal of the hydroxyl groups present on the SiO2 surface scale layer. It was found that thickening the silica layer, by heat treatment at higher temperatures, causes a further reduction in the amount of hydrogen released. However, differential thermal analysis (DTA) studies showed that excessive silicon surface oxidation increased the ignition temperature and reduced the heat release of a near‐stoichiometric silicon‐lead chromate pyrotechnic composition. 相似文献
110.
Walter W. Focke Sfiso S. Mkhize Rowan Storey Olinto Del Fabbro Elmar Muller 《Chemical Engineering Communications》2013,200(2):153-159
Copper antimonite, CuSb2O4, is a candidate oxidant for use in time delays for mining detonators. A facile process for the synthesis of copper antimonite comprises the reaction of antimony trioxide with copper-ammonia complex with excess ammonia at reflux conditions (ca. 65°C) for about 1 h. Thereafter the reaction is driven to completion by driving off the ammonia by distillation. A well-crystallized product with a cuboid crystal habit approximately 4 µm in size is obtained. 相似文献