Geometrical model and experimental evidence for the growth of Ag-doped YBa2Cu3O7?x thin films

The improvement in the properties of laser-ablated Ag-doped YBa₂Cu₃O_7–x (YBCO) thin films in both normal and superconducting states has been interpreted using a growth model. The model is simple and is based on the widely accepted characteristics of Ag such as its flux action at high temperature and nonreactivity with YBCO phase.     

LaNiO3: A promising material for contact with YBa2Cu3O7− δ thin films

Epitaxial LaNiO₃ metallic oxide thin films have been grown onc-axis oriented YBa₂Cu₃O_7?δ thin films on 〈100〉 LaAlO₃ substrates by pulsed laser deposition technique and the interface formed between the two films has been exmained by measuring the contact conductance of the same. The high value of specific contact conductance indicates the existence of a clean interface at the LaNiO₃?YBaO₂CuO₃OO_7?δ thin film contact.     

Global intraurban intake fractions for primary air pollutants from vehicles and other distributed sources

We model intraurban intake fraction (iF) values for distributed ground-level emissions in all 3646 global cities with more than 100,000 inhabitants, encompassing a total population of 2.0 billion. For conserved primary pollutants, population-weighted median, mean, and interquartile range iF values are 26, 39, and 14-52 ppm, respectively, where 1 ppm signifies 1 g inhaled/t emitted. The global mean urban iF reported here is roughly twice as large as previous estimates for cities in the United States and Europe. Intake fractions vary among cities owing to differences in population size, population density, and meteorology. Sorting by size, population-weighted mean iF values are 65, 35, and 15 ppm, respectively, for cities with populations larger than 3, 0.6-3, and 0.1-0.6 million. The 20 worldwide megacities (each >10 million people) have a population-weighted mean iF of 83 ppm. Mean intraurban iF values are greatest in Asia and lowest in land-rich high-income regions. Country-average iF values vary by a factor of 3 among the 10 nations with the largest urban populations.     

Physical mixtures as simple and efficient alternative to alloy carriers in chemical looping processes

Chemical looping combustion is a clean combustion technology for fossil or renewable fuels. In a previous demonstration, chemical looping was applied to CO₂ activation via reduction to CO with concurrent production of synthesis gas (CO + H₂) from CH₄ via rationally designed Fe‐Ni alloys. Here, it is demonstrated that that a simple physical mixture can even outperform the equivalent alloy based on an intricate gas phase mediated coupling between the two metals: Ni cracks methane to carbon and H₂. The latter then reduces iron oxide carrier, forming steam, which gasifies the carbon deposits on Ni to produce a mixture of CO + H₂, thus regenerating the active Ni surface. It was suggested that the principle demonstrated here—the gas phase‐mediated coupling of two solid reactants with distinct functionalities—should be applicable broadly toward oxidation reactions and hence opens a new avenue for rational design of chemical looping processes. © 2016 American Institute of Chemical Engineers AIChE J, 63: 51–59, 2017     

Application of the Taguchi Method in Establishing Criticality of Parameters that Influence Cracking Characteristics of Fine-Grained Soils

Extensive studies have been conducted by earlier researchers to understand cracking characteristics of fine-grained soils. Based on these studies, several theories and models which facilitate understanding the effect of various soil- and environment-specific parameters (viz., clay content, plasticity, free swelling index, specimen dimensions, boundary conditions, temperature, and humidity) that influence cracking characteristics of such soils have been proposed. A critical synthesis of the existing literature reveals that selection of any crack sealing/arresting technique would largely depend on the most critical of these parameters. However, studies related to identification of this critical parameter(s) and its (their) influence on cracking characteristics of fine-grained soils are not available in the existing literature. Hence, efforts have been made in the present study to establish the effect of each of these parameters on the cracking characteristics of fine-grained soils and the most critical parameter(s) has/have been identified. To achieve this, the Taguchi method, which is basically a statistical method and has been widely adopted for designing experiments and optimizing and/or detecting the most influential parameter(s) from the set of parameters of any multi-variant problem, has been employed. From the present study, it has been demonstrated that temperature, humidity, and mineralogy are the most critical parameters that affect cracking behavior of fine-grained soils.     

Silver doping: A potential means to grow high quality YBa2Cu3O7?x thin films on bare sapphire

High qualityAg-doped YBa₂Cu₃O_7–x (YBCO) thin films have been grown by laser ablation on ¯1012 bare sapphire. This work demonstrates thatAg-doping can be used as very convenient means to realize good quality YBCO films on highly coveted sapphire substrates for microwave applications of highT _c thin films.     

Evaluation of complex and dynamic safety tasks in human learning using the ACT-R and SOAR skill acquisition theories

This paper provides a human-centered analytical approach to learning dynamic and complex tasks using the Adaptive Control of Thought-Rational (ACT-R) and the State, Operator And Result (SOAR) models by comparing the task times of the model and the subjects. Twenty-one full time assembly line workers at a local computer company (14 men and 7 women) from ages 18-32 (Mean = 19.86 years, SD = 0.96 years) were randomly selected for this analysis. The task involved the placement of printed circuit board (PCB) components on the flow line of the desktop computer mother board manufacturing process. The overall timed performance of the subjects indicated that the match between the model and the subjects was good, resulting in an R² - value of 0.94. At the unit task level performance, and R² - value of 0.96 for placing the PCBs on the flow line. For tasks involving picking and searching of PCBs, the obtained R² - value was 0.76 and R² of 0.68 at the keystroke level. Findings revealed that the model already started out with a complete strategy of performing the task, whereas the human participants had to acquire additional learning information during the trials. Efforts will be made in the future to determine how the performance of the human subjects could be enhanced to meet or the same level as the model performance.     

An approach to expert control of interactive software systems

Expert problem-solving strategies in many domains require the use of detailed mathematical techniques coupled with experiential knowledge about how and when to use the appropriate techniques. In many of these domains, such techniques are made available to experts in large software packages. In attempting to build expert systems for these domains, we wish to make use of these packages, and are therefore faced with an important problem: how to integrate the existing software, and knowledge about its use, into a practical expert system. The expert knowledge is used, in dynamic selection and interpretation of appropriate programs and parameters, to reach a successful goal in the problem solving. We describe the framework of a hybrid expert system for representing problem-solving knowledge in these domains. This hybrid system may be characterized as consisting of a production system and mathematical methods. The software package is reorganized as necessary to map it into the mathematical-method representation of a hybrid system. This approach has evolved out of an effort to build an expert system for performing well-log analysis, ELAS (expert log analysis system).     

Application of the Taguchi analytical method for optimization of effective parameters of the chemical vapor deposition process controlling the production of nanotubes/nanobeads

Seven variable parameters of the chemical vapor deposition system have been optimized with the help of the Taguchi analytical method for getting a desired product, e.g., carbon nanotubes or carbon nanobeads. It is observed that almost all selected parameters influence the growth of carbon nanotubes. However, among them, the nature of precursor (racemic, R or Technical grade camphor) and the carrier gas (hydrogen, argon and mixture of argon/hydrogen) seem to be more important parameters affecting the growth of carbon nanotubes. Whereas, for the growth of nanobeads, out of seven parameters, only two, i.e., catalyst (powder of iron, cobalt, and nickel) and temperature (1023 K, 1123 K, and 1273 K), are the most influential parameters. Systematic defects or islands on the substrate surface enhance nucleation of novel carbon materials. Quantitative contributions of process parameters as well as optimum factor levels are obtained by performing analysis of variance (ANOVA) and analysis of mean (ANOM), respectively.