Pt-V2O5-WO3/TiO2 catalysts supported on SiC filter for NO reduction at low temperature

The catalytic filter, V₂O₅-WO₃-TiO₂ supported on a ceramic filter, is known as a promising material for treating particulates and NO _x simultaneously at optimum temperatures around 320°C. In order to improve its catalytic activity at low temperatures, the effect of Pt addition on the catalytic filter has been investigated. Catalytic filters, Pt-V₂O₅-WO₃-TiO₂/SiC, were prepared by co-impregnation of Pt, V, and W precursors on TiO₂ coated-SiC filter by vacuum aided-dip coating. The Pt-added catalytic filter shifted the optimum working temperature from 280–330°C (for the non Pt-impregnated filter) to 180–230°C, providing N _x slip concentration less than 20 ppm for the treatment of 700 ppm NO at a face velocity of 2 cm/s with the same value over the non Pt-added catalytic filters. The promotional effect following the addition of Pt is believed to result from electrical modification of the catalyst maintaining a high electron transfer state. Ammonia oxidation was also observed to be dominant above the optimal temperature for SCR.     

Classification of time series by shapelet transformation

Time-series classification (TSC) problems present a specific challenge for classification algorithms: how to measure similarity between series. A shapelet is a time-series subsequence that allows for TSC based on local, phase-independent similarity in shape. Shapelet-based classification uses the similarity between a shapelet and a series as a discriminatory feature. One benefit of the shapelet approach is that shapelets are comprehensible, and can offer insight into the problem domain. The original shapelet-based classifier embeds the shapelet-discovery algorithm in a decision tree, and uses information gain to assess the quality of candidates, finding a new shapelet at each node of the tree through an enumerative search. Subsequent research has focused mainly on techniques to speed up the search. We examine how best to use the shapelet primitive to construct classifiers. We propose a single-scan shapelet algorithm that finds the best $k$ shapelets, which are used to produce a transformed dataset, where each of the $k$ features represent the distance between a time series and a shapelet. The primary advantages over the embedded approach are that the transformed data can be used in conjunction with any classifier, and that there is no recursive search for shapelets. We demonstrate that the transformed data, in conjunction with more complex classifiers, gives greater accuracy than the embedded shapelet tree. We also evaluate three similarity measures that produce equivalent results to information gain in less time. Finally, we show that by conducting post-transform clustering of shapelets, we can enhance the interpretability of the transformed data. We conduct our experiments on 29 datasets: 17 from the UCR repository, and 12 we provide ourselves.     

Authorized workflow schemas: deciding realizability through \mathsf{LTL }(\mathsf{F }) model checking

Many business processes are modeled as workflows, which often need to comply with business rules, legal requirements, and authorization policies. Workflow satisfiability is the problem of determining whether there exists a workflow instance that realizes the workflow specification while simultaneously complying with such constraints. This problem has already been studied by the computer security community, with the development of algorithms and the study of their worst-case complexity. These solutions are often tailored to a particular workflow model and are, therefore, of little or no use in analyzing different models; their worst-case complexities are likely to be an unreliable judge of their feasibility; and they lack support for other forms of analysis such as the determination of the smallest number of users required to satisfy a workflow specification. We propose model checking of an NP-complete fragment $\mathsf{LTL }(\mathsf{F })$ of propositional linear-time temporal logic as an alternative solution. We report encodings in LTL(F) that can compute a set of solutions (thus deciding satisfiability), compute minimal user bases and a safe bound on the resiliency of satisfiability under the removal of users. These theoretical contributions are validated through detailed experiments whose results attest to the viability of our proposed approach.     

Plastic deformation of ZnO thin films through edge and screw dislocation movements

Columnar wurtzite grains were formed in sputtered ZnO thin films deposited on a plastic polyethylene terephthalate substrate. Selected-area diffraction patterns reveal that the columnar grains in the sputtered films present two preferred growth planes, namely, the basal (0002) and prismatic (100) growth planes. The diffraction patterns obtained also confirm that the microstructure of sputtered indium tin oxide thin films is amorphous in nature. Tensile tests indicate that the fracture strain of the ZnO thin film occurs between 1.73% and 2.14%, while the fracture strain of the indium tin oxide thin film occurs between 0.24% and 0.67%. Thus, the fracture toughness of the sputtered ZnO thin film is greater than that of the sputtered indium tin oxide thin film. High-resolution transmission electron microscopic images demonstrate that edge and screw dislocations could be identified in the sputtered ZnO thin films. Moreover, edge and screw dislocation movements may, respectively, be observed in the basal- and prismatic-oriented ZnO columnar grains of the sputtered ZnO thin films. Our results indicate that movements of the edge and screw dislocations in the basal- and prismatic-oriented ZnO columnar grains account for the plastic deformation of the investigated ZnO thin films under tensile stress.     

A new model for evaluating the electrical conductivity of nonferrous slag

Electrical conductivity of molten slag is an important physicochemical property for designing the refining process in electric smelting furnaces.Though conductivities of many slag systems have been measured,the quantitative relationships of conductivity with slag composition and temperature are still very limited.In this article,the Arrhenius law was used to describe the experimental data of conductivities for CaO-MgO-Al2O3-SiO2,CaO-Al2O3-SiO2,CaO-MnO-Al2O3-SiO2,as well as CaO-MgO-MnO-Al2O3-SiO2 systems,and...     

Associations between apolipoprotein E genotype and circulating F<Subscript>2</Subscript>-isoprostane levels in humans

Apolipoprotein E (apoE), an important determinant of plasma lipoprotein metabolism, has three common alleles (ε2, ε3, and ε4). Population studies have shown that the risk of diseases characterized by oxidative damage, such as coronary heart disease and Alzheimer’s disease, is significantly higher in ɛ4 carriers. We evaluated the association between apoE genotypes and plasma F₂-isoprostane levels, an index of lipid peroxidation, in humans. Two hundred seventy-four healthy subjects (104 males, 170 females; 46.9±13.0 yr; 200 whites, 74 blacks; 81 nonsmokers, 64 passive smokers, and 129 active smokers) recruited for a randomized clinical antioxidant intervention trial were included in this analysis. ApoE genotype was determined by PCR and restriction enzyme digestion. Free plasma F₂-isoprostane was measured by GC-MS. Genotype groups were compared using multiple regression analysis with adjustment for sex, age, race, smoking status, body mass index, plasma ascorbic acid, and β-carotene. Subjects with ε3/ε4 and ε4/ε4 genotype (ε4-carriers) and with ε2/ε3 and ε3/ε3 (non-ε4-carriers) were pooled for analysis. In subjects with high cholesterol levels (total cholesterol above 200 mg/dl), plasma F₂-isoprostane levels were 29% higher in ε4 carriers than in non-ε4-carriers (P=0.0056). High-cholesterol subjects that are ε4 carriers have significantly higher levels of lipid peroxidation as assessed by circulating F₂-isoprostane levels.     

Cation interdiffusion between thick film of YBa2Cu3O7-δ and ceramic substrate

Thick films of superconducting oxides, YBa₂Cu₃O_7-, were successfully made by conventional screen-printing technology on Al₂O₃, MgO, and ZrO₂ substrates. Interdiffusion between the superconductive film and substrate was investigated using analytical electron microscopy. The results indicate that MgO and ZrO₂ are superior to Al₂O₃ for substrate materials.     

Hydrocarbon condensation modelling to mitigate fluid coker cyclone fouling

FLUID COKING is a continuous process that thermally converts heavy hydrocarbons, such as oil sands bitumen, to lighter and higher‐value products by horizontal spray injection onto a fluidized bed of hot coke particles. The cyclone sections of commercial fluid coker reactors experience fouling during typical operation, which limits unit run lengths. The main objective of this work is to improve fluid coker reliability by proposing cyclone fouling mitigation strategies based on practical operation modifications. This study developed a process simulation in Aspen Plus to establish the combined impact of vapour‐liquid equilibrium, endothermic thermal cracking reactions, pressure changes, and overall fluid dynamics in the selected fluid coker control volumes. The hydrocarbon composition was defined by applying an assay characterization of distillation data for representative hydrocarbon streams. Case studies were performed to determine the sensitivity of the predicted temperatures and hydrocarbon condensate flow rates for: (a) the burner‐to‐fluid coker transfer line temperature; (b) the hot coke flow rate; (c) hot coke entrainment from the freeboard region; and (d) scouring coke flow rate in the horn chamber. The scouring coke flow rate was identified as the most promising process lever to mitigate fluid coker cyclone fouling.     

A STUDY OF THE STRESS CORROSION CRACKING OF SENSITIZED 1Cr18Ni9Ti STAINLESS STEEL IN HIGH TEMPERATURE HIGH PRESSURE WATER

从环境角度研究了敏化1Cr18Ni9Ti不锈钢在高温水中的腐蚀行为.研究指出,在一定浓度Cl~-和(或)O_2存在情况下,在酸性和中性高温高压水中都会出现应力腐蚀破裂.断口电子金相表明,在氯离子为主的环境中,破裂系晶间型;在氧为主的环境中,破裂系以解理为主的混合型.给出了1Cr18Ni9Ti在高温水中腐蚀的表观和真实动力学曲线,表明腐蚀包含溶解和湿氧化两部分,而以湿氧化为主.借Mossbauer内转换电子谱研究了氧化膜结构与腐蚀的关系,指出在一般腐蚀条件下,膜的主要组分为Fe_3O_4,而在应力腐蚀条件下,膜的主要组分为Fe_2O_3,并且系Fe_2O_3和Fe_3O_4多层重叠结构.当水中添加了一定量的硼,在氧化膜中会局部出现FeBO_3相,既不会引起也不会抑制应力腐蚀.硼的这种“惰性”作用和膜结构中Fe_3O_4相的非化学计量比,膜具有阴离子选择性有关.根据腐蚀电化学,认为应力腐蚀系发生在钝化/过钝化区域,增高Cl~-或O_2含量,从不同角度都会使合金的电位接近过钝化区.Cl~-的作用在于改变阳极极化曲线,O_2的作用在于改变阴极极化曲线.在含Cl~-水中,晶界TiC的迅速溶解是应力腐蚀的主要原因,而在含氧水中,晶粒Fe-Cr-Ni中Cr的选择性溶解是应力腐蚀的主要原因.在分析应力腐蚀的特征后,指出应力既是某些严重腐蚀点形     

Microstructure and tensile properties of squeeze cast magnesium alloy AM50

High-pressure die cast magnesium alloy AM50 is currently used extensively in large and complex shaped thin-wall automotive components. For further expansion of the alloy usage in automobiles, novelmanufacturing processes need to be developed. In this study, squeeze casting of AM50 alloy with a relatively thick cross section was carried out using a hydraulic press with an applied pressure of 70 MPa. Microstructure and mechanical properties of the squeeze cast AM50 with a cross-section thickness of 10 mm were characterized in comparison with the die cast counterpart. The squeeze cast AM50 alloy exhibits virtually no porosity in the microstructure as evaluated by both optical microscopy and the density measurement technique. The results of tensile testing indicate the improved tensile properties, specifically ultimate tensile strength and elongation, for the squeeze cast samples over the conventional high-pressure die cast parts. The analysis of tensile behavior show that the strain-hardening rate during the plastic deformation of the squeeze cast specimens is constantly higher than that of the die cast specimens. The scanning electron microscopy fractography evidently reveals the ductile fracture features of the squeeze cast alloy AM50.