Electrical and thermophysical properties of mechanochemically obtained lanthanide hafnates

This contribution presents the synthesis and thermophysical characterization of seven lanthanide hafnates Ln₂Hf₂O₇ (Ln=Sm³⁺, Eu³⁺, Gd³⁺, Dy³⁺, Y³⁺, Ho³⁺, Yb³⁺); the title samples were prepared at room temperature by mechanically milling stoichiometric mixtures of the corresponding elemental oxides. Irrespective of the lanthanide ion involved, milling promotes the formation of highly disordered fluoritelike materials. Postmilling thermal treatments facilitate the formation of the fluorite ordered derivative, the pyrochlore structure, but only for the larger lanthanides (Sm³⁺, Eu³⁺, Gd³⁺). Impedance spectroscopy measurements revealed that these materials show a moderate‐to‐good oxygen ion conductivity at high temperatures; furthermore, those adopting the pyrochlore structure give higher σ_dc and lower E_dc than their fluorite analogues (σ_dc at 750°C>10^?3 S·cm^?1 vs <5·10^?4 S·cm^?1, respectively). The same trend also holds for the thermal resistivity at high temperatures; the highest thermal resistivity and thus, lowest κ was obtained for Eu₂Hf₂O₇ (κ~1.3·W·m^?1·K^?1 at 800°C). Therefore, Ln₂Hf₂O₇ phases might be attractive component materials for electrochemical devices and thermal insulating coatings.     

Effect of spark timing and load on a DISI engine fuelled with 2,5-dimethylfuran

Currently, bioethanol leads the automotive fuel market as the main substitute for gasoline in spark-ignition engines. However, worldwide interest has been triggered in the potential of 2,5-dimethylfuran, known as DMF, since the discovery of improved production methods. Although the energy content of DMF is comparable to that of gasoline, little is known about its combustion characteristics and emissions. Therefore, this work examines the effect of DMF in a single cylinder direct-injection spark-ignition engine. The results are compared to ethanol and gasoline using the optimized spark timings for gasoline and the respective fuel. In summary, DMF produces competitive combustion and emissions qualities to gasoline, which, in some cases surpass ethanol. The two biofuels have a higher burning rate and lower initial combustion duration than gasoline. They also produce greater combustion efficiency, which helps to lower hydrocarbon and carbon monoxide emissions. These initial results highlight how DMF, which was originally only considered as an octane improver, has the potential to become a competitive renewable gasoline alternative.     

On resource allocation in multistage interconnection network-based systems

A resource allocation problem in a reconfigurable multicomputer architecture based on rectangular banyan multistage interconnection network with arbitrary fanout and arbitrary number of levels is studied. Four commonly used problem structures such as ring, pipeline, broadcast, and macropipeline are introduced and the mapping problem of these structures on the system model, which is equivalent to the resource allocation problem, is discussed. Analytic solutions to several mapping questions are given and generalization of the results to other networks is presented.     

Multi-CMP system with data communication on the fly

The paper concerns new communication solutions for hierarchical Chip Multiprocessor (CMP) systems composed of many CMP modules interconnected by a global data exchange network. New architectural solutions for internal module data communication are presented in the presence of hierarchical data caches in CMP modules. Inside CMP modules, dynamic shared memory core clusters are organized around L1–L2 data cache busses. Such clusters enable a group-oriented data communication based on reads on the fly to L1 banks of data present on the busses by many cores at a time. Dynamic switching of cores between such L1–L2 busses is done with porting data in core’s L1 caches. Together with data reads on the fly, it provides a very efficient intercluster “communication on the fly,” especially useful for transfers of strongly shared data. It provides fast cache to cache group data transmissions and eliminates standard transactions based on shared memory in the system. Comparative experimental results based on automatic scheduling of program data flow graphs and execution in a simulator of the proposed architecture evaluate the assumed architectural solutions. The multi-CMP system structure is assessed while taking into account technological limitations of the size of the single CMP module.     

An ergonomic analysis framework for construction tasks

This paper presents a new methodology for obtaining a quantitative measure of human task performance complexity and effort on the construction site. An example application of the developed methodology to the analysis of concrete placement tasks is provided. The developed method can be used to aid construction equipment manufacturers in understanding and assessing the automation potential for a variety of construction work tasks.     

Influence of Plasma Waves on the Photoacoustic Signal of Silicon Samples

This article presents the results of theoretical and experimental studies of the influence of plasma waves on the photoacoustic signals of Si samples. The aim of these investigations was to find and examine the sensitive measurement configurations and the configurations of the sample in the photoacoustic cell for detection and measurement of the lifetime of excess carriers. Two measurement configurations were examined: transmission and phase lag and two configurations of the sample in the photoacoustic cell. This article demonstrates that both configurations for samples with differently prepared surfaces are effective for observation and detection of plasma waves with the photoacoustic method.     

Redesigning the active site of Geotrichum candidum lipase

Attempts to engineer enzymes with unique catalytic propertieshave largely focused on altering the existing specificitiesby reshaping the substrate binding pockets. Few experimentshave aimed at modifying the configuration of the residues essentialfor catalysis. The difference in the topological location ofthe triad acids of Geotrichum candidum lipase (GCL) and thecatalytic domain of human pancreatic lipase (HPL), despite greatsimilarities in their topologies and 3-D structures, suggestthat these are related enzymes whose catalytic triads have beenrearranged in the course of evolution (Schrag et aL, 1992).In this study we prepared a double mutant GCL in which the catalytictriad acid is shifted to the position equivalent to the locationof the triad acid of HPL. The double mutant maintains 10% ofthe wild type activity against triglycerides and the fluorogenicester 4-methylumbelliferyl-oleate. The only significant differencesbetween the 3-D structures of the double mutant and wild typeGCL are at the mutated sites. Even the water structure in theregion of the triad is unchanged. The hydrogen bonding patternof the catalytic triad of the double mutant is very similarto that of pancreatic lipase. The acid of the double mutantis stabilized by only two hydrogen bonds, whereas three hydrogenbonds are observed in the wild type enzyme. These results stronglysupport the hypothesis that the pancreatic Upases are evolutionaryswitchpoints between the two observed arrangements of the catalytictriads supported by the /ß hydrolase fold and suggestthat this fold provides a stable protein core for engineeringenzymes with unique catalytic properties.     

The relation between structural,rugometric and fractal characteristics of hard dental tissues at micro and nano levels

Human tooth exhibits a structure of a mixture of inorganic hydroxyapatite nanocrystals and organic phases. The aim of this study is to investigate different tissues of human canine teeth surface along with the micro structure parameters of each tissue. X‐ray diffraction (XRD) is used to study the amorphous or crystalline nature of each tissue with different mineral compositions and crystalline structures where the highest crystalline quality is related to enamel. The surfaces are also examined by energy‐dispersive X‐ray spectrometry. Moreover, crystalline quality factor is carried out to estimate the crystallinity of the tissues. Also, based on the basic Scherrer equation, the Williamson–Hall equation is applied to extend the formula for the XRD. Enamel and cementum tissues of a typical human tooth, which look similar, are composed of a large variety of wide lines with different widths through Raman spectra analysis. In addition, the applied scanning electron microscopy extracts similar morphology for all tissues with round granular structures which are denser in the cementum. Atomic force microscopy is finally used for investigation of micro‐morphologies of the different tissues and the results are compared with the fractal analysis which ends to the bifractal and anisotropic nature of enamel and cementum along with monofractal and isotropic nature of dentin.     

An update on thoron exposure in Canada with simultaneous ²²²Rn and ²²⁰Rn measurements in Fredericton and Halifax

Naturally occurring isotopes of radon in indoor air are identified as the second leading cause of lung cancer after tobacco smoking. Radon-222 (radon gas) and radon-220 (thoron gas) are the most common isotopes of radon. While extensive radon surveys have been conducted, indoor thoron data are very limited. To better assess thoron exposure in Canada, radon/thoron discriminating detectors were deployed in 45 homes in Fredericton and 65 homes in Halifax for a period of 3 months. In this study, radon concentrations ranged from 16 to 1374 Bq m(-3) with a geometric mean (GM) of 82 Bq m(-3) and a geometric standard deviation (GSD) of 2.56 in Fredericton, and from 4 to 2341 Bq m(-3) with a GM of 107 Bq m(-3) and a GSD of 3.67 in Halifax. It is estimated that 18 % of Fredericton homes and 32 % of Halifax homes could have radon concentrations above the Canadian indoor radon guideline of 200 Bq m(-3). This conclusion is significantly higher than the previous estimates made 30 y ago with short-term radon measurements. Thoron concentrations were below the detection limit in 62 % of homes in both cities. Among the homes with detectable thoron concentrations, the values varied from 12 to 1977 Bq m(-3) in Fredericton and from 6 to 206 Bq m(-3) in Halifax. The GM and GSD were 86 Bq m(-3) and 3.19 for Fredericton, and 35 Bq m(-3) and 2.35 for Halifax, respectively. On the basis of these results, together with previous measurements in Ottawa, Winnipeg and the Mont-Laurier region of Quebec, it is estimated that thoron contributes ～8 % of the radiation dose due to indoor radon exposure in Canada.     

Prospective safety performance evaluation on construction sites

This paper presents a systematic Structural Equation Modeling (SEM) based approach for Prospective Safety Performance Evaluation (PSPE) on construction sites, with causal relationships and interactions between enablers and the goals of PSPE taken into account. According to a sample of 450 valid questionnaire surveys from 30 Chinese construction enterprises, a SEM model with 26 items included for PSPE in the context of Chinese construction industry is established and then verified through the goodness-of-fit test. Three typical types of construction enterprises, namely the state-owned enterprise, private enterprise and Sino-foreign joint venture, are selected as samples to measure the level of safety performance given the enterprise scale, ownership and business strategy are different. Results provide a full understanding of safety performance practice in the construction industry, and indicate that the level of overall safety performance situation on working sites is rated at least a level of III (Fair) or above. This phenomenon can be explained that the construction industry has gradually matured with the norms, and construction enterprises should improve the level of safety performance as not to be eliminated from the government-led construction industry. The differences existing in the safety performance practice regarding different construction enterprise categories are compared and analyzed according to evaluation results. This research provides insights into cause–effect relationships among safety performance factors and goals, which, in turn, can facilitate the improvement of high safety performance in the construction industry.