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71.
Elias Penelope K.; Elias Merrill F.; Robbins Michael A.; Gage Paulette 《Canadian Metallurgical Quarterly》1987,2(4):340
A total of 45 subjects in three age groups (younger, middle-age, older) were trained to word process on microcomputers using a commercial training program and an experimenter-designed test and evaluation protocol. Although all of the subjects mastered the essentials of word processing, the older group took significantly longer to complete the training and evaluation procedures and performed more poorly on a review examination that tested their knowledge of the word-processing commands and techniques. The results are discussed in relation to requirements for trainer assistance, motivational factors, and the need to design training protocols that meet the needs of older adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
72.
C. Santos L.H.P. Teixeira J.K.M.F. Daguano S.O. Rogero K. Strecker C.N. Elias 《Ceramics International》2009,35(2):709-718
The influence of Al2O3 addition and sintering parameters on the mechanical properties and cytotoxicity of tetragonal ZrO2–3 mol% Y2O3 ceramics was evaluated. Samples containing 0, 10, 20 and 30 wt.% of Al2O3 particles were prepared by cold uniaxial pressing (80 MPa) and sintered in air at 1500, 1550 and 1600 °C for 120 min. The effects of the sintering conditions on the microstructure were analyzed by X-ray diffraction analysis and scanning electron microscopy. Hardness and fracture toughness were determined by the Vickers indentation method and the mechanical resistance by four-point bending tests. As a preliminary biological evaluation, “in vitro” cytotoxicity tests were realized to determine the cytotoxic level of the ZrO2–Al2O3 composites, using the neutral red uptake method with NCTC clones L929 from the American Type Culture Collection (ATCC) bank. Fully dense ceramic materials were obtained with a hardness ranging between 1340 HV and 1585 HV, depending on the amount of Al2O3 in the ZrO2 matrix. On the other hand, no significant influence of the Al2O3 addition on fracture toughness was observed, exhibiting values near 8 MPa m1/2 for all compositions and sintering conditions studied. The non-cytotoxic behavior, the elevated fracture toughness, the good bending strength (σf = 690 MPa) and the elevated Weibull's modulus (m = 11) exhibited by the material, show that these ceramic composites are highly suitable biomaterials for dental implant applications. 相似文献
73.
George Z. Voyiadjis Babur Deliktas Elias C. Aifantis 《Canadian Metallurgical Quarterly》2001,127(7):636-645
Thermodynamically consistent constitutive equations are derived here in order to investigate size effects on the strength of composite, strain, and damage localization effects on the macroscopic response of the composite, and statistical inhomogeneity of the evolution-related damage variables associated with the representative volume element. This approach is based on a gradient-dependent theory of plasticity and damage over multiple scales that incorporates mesoscale interstate variables and their higher order gradients at both the macro- and mesoscales. This theory provides the bridging of length scales. The interaction of the length scales is a paramount factor in understanding and controlling material defects such as dislocation, voids, and cracks at the mesoscale and interpreting them at the macroscale. The behavior of these defects is captured not only individually, but also the interaction between them and their ability to create spatiotemporal patterns under different loading conditions. The proposed work introduces gradients at both the meso- and macroscales. The combined coupled concept of introducing gradients at the mesoscale and the macroscale enables one to address two issues simultaneously. The mesoscale gradients allow one to address issues such as lack of statistical homogeneous state variables at the macroscale level such as debonding of fibers in composite materials, cracks, voids, and so forth. On the other hand, the macroscale gradients allow one to address nonlocal behavior of materials and interpret the collective behavior of defects such as dislocations and cracks. The capability of the proposed model is to properly simulate the size-dependent behavior of the materials together with the localization problem. Consequently, the boundary-value problem of a standard continuum model remains well-posed even in the softening regime. The enhanced gradient continuum results in additional partial differential equations that are satisfied in a weak form. Additional nodal degrees of freedom are introduced that leads to a modified finite-element formulation. The governing equations can be linearized consistently and solved within the incremental iterative Newton-Raphson solution procedure. 相似文献
74.
Lazaros Elias Mavromatidis Pierre Michel Mohamed El Mankibi Mat Santamouris 《Building Simulation》2010,3(4):279-294
This paper reports on a numerical and experimental study of heat transfer phenomena through two different multilayer fibrous
insulations for building applications. The investigated samples were composed of different layers of fibrous materials and
aluminium foils, placed between one or two air gaps in the vertical dimension. An experimental apparatus (a guarded hot box)
has been used to measure heat transfer through the samples, while a finite volume numerical model combined radiation/conduction
heat transfer was developed to predict the temperature distribution and heat transfer in such insulation systems comprised
of the materials separated by multiple reflective foils. The model takes into account the coupling between the solid conduction
of the fibrous system and the gaseous conduction and radiation. The radiation heat transfer through the insulation system
has been modelled via the two flux approximation. The numerical results were compared with the experimental data from the
guarded hot box for model validation, as well as to assess the effectiveness of the reflective foils in changing the resistance
of the insulations. The comparative verification of the model showed that the numerical results were consistent with the experimental
data through the environmental conditions under examination. 相似文献
75.
Wardah Fatimah Mohammad Yusoff Elias Salleh Nor Mariah Adam Abdul Razak Sapian Mohamad Yusof Sulaiman 《Building and Environment》2010
In the hot and humid climate, stack ventilation is inefficient due to small temperature difference between the inside and outside of naturally ventilated buildings. Hence, solar induced ventilation is a feasible alternative in enhancing the stack ventilation. This paper aims to investigate the effectiveness of a proposed solar induced ventilation strategy, which combines a roof solar collector and a vertical stack, in enhancing the stack ventilation performance in the hot and humid climate. The methodology selected for the investigation is physical experimental modelling which was carried out in the actual environment. The results are presented and discussed in terms of two performance variables: air temperature and air velocity. The findings indicate that the proposed strategy is able to enhance the stack ventilation, both in semi-clear sky and overcast sky conditions. The highest air temperature difference between the air inside the stack and the ambient air (Ti−To) is achieved in the semi-clear sky condition, which is about 9.9 °C (45.8 °C–35.9 °C). Meanwhile, in the overcast sky condition, the highest air temperature difference (Ti−To) is 6.2 °C (39.3 °C–33.1 °C). The experimental results also indicate good agreement with the theoretical results for the glass temperature, the air temperature in the roof solar collector’s channel and the absorber temperature. The findings also show that wind has significant effect to the induced air velocity by the proposed strategy. 相似文献
76.
The subunit structure of human macrophage migration inhibitory factor: evidence for a trimer 总被引:1,自引:0,他引:1
Sun Hong-Wei; Swope Melissa; Craig Cinquina; Bedarkar Sudhir; Bernhagen Jurgen; Bucala Richard; Lolis Elias 《Protein engineering, design & selection : PEDS》1996,9(8):631-635
The subunit structure of human macrophage migration inhibitoryfactor (MIF) has been studied by preliminary X-ray analysisof wild-type and selenomethionine-MIF and dynamic light scattering.Crystal form I of MIF belongs to space group P212121 and isgrown from 2 M ammonium sulfate at pH 8.5. A native data sethas been collected to 2.4 Å resolution. Self-rotationstudies and Vm values indicate that three molecules per asymmetricunit are present A data set to 2.8 Å resolution has beencollected for crystal form II, which belongs to space groupP3121 or P3221 and grows from 2 M ammonium sulfate, 2% polyethyleneglycol (average molecular mass 400), 0.1 M HEPES, pH 7.5. Three,four, five or six monomers in the asymmetric unit are consistentwith Vm values for this crystal form. Analysis of crystal formII containing selenomethionine-MIF indicates nine selenium sitesare present per asymmetric unit. Dynamic light scattering ofMIF suggests that the major form of the protein in solutionis a trimer. The results of these studies are in contrast toprevious reports indicating that MIF is a monomer or dimer.The subunit arrangement of MIF is similar to that of tumor necrosisfactor and suggests that signal transduction might require trimerizationof receptor subunits. 相似文献
77.
Salvador M. Aceves Francisco Espinosa-Loza Elias Ledesma-Orozco Timothy O. Ross Andrew H. Weisberg Tobias C. Brunner Oliver Kircher 《International Journal of Hydrogen Energy》2010
LLNL is developing cryogenic capable pressure vessels with thermal endurance 5–10 times greater than conventional liquid hydrogen (LH2) tanks that can eliminate evaporative losses in routine usage of (L)H2 automobiles. In a joint effort BMW is working on a proof of concept for a first automotive cryo-compressed hydrogen storage system that can fulfill automotive requirements on system performance, life cycle, safety and cost. Cryogenic pressure vessels can be fueled with ambient temperature compressed gaseous hydrogen (CGH2), LH2 or cryogenic hydrogen at elevated supercritical pressure (cryo-compressed hydrogen, CcH2). When filled with LH2 or CcH2, these vessels contain 2–3 times more fuel than conventional ambient temperature compressed H2 vessels. LLNL has demonstrated fueling with LH2 onboard two vehicles. The generation 2 vessel, installed onboard an H2-powered Toyota Prius and fueled with LH2 demonstrated the longest unrefueled driving distance and the longest cryogenic H2 hold time without evaporative losses. A third generation vessel will be installed, reducing weight and volume by minimizing insulation thickness while still providing acceptable thermal endurance. Based on its long experience with cryogenic hydrogen storage, BMW has developed its cryo-compressed hydrogen storage concept, which is now undergoing a thorough system and component validation to prove compliance with automotive requirements before it can be demonstrated in a BMW test vehicle. 相似文献
78.
Extrusion of Rice,Bean and Corn Starches: Extrudate Structure and Molecular Changes in Amylose and Amylopectin 总被引:1,自引:0,他引:1 下载免费PDF全文
Nathan Levien Vanier Varatharajan Vamadevan Graziella Pinheiro Bruni Cristiano Dietrich Ferreira Vânia Zanella Pinto Koushik Seetharaman Elessandra da Rosa Zavareze Moacir Cardoso Elias Jose De J. Berrios 《Journal of food science》2016,81(12):E2932-E2938
The objective of this study was to evaluate the effects of starch source and amylose content on the expansion ratio, density, and texture of expanded extrudates, as well as to investigate the structural and molecular changes that occur in starch granules as a function of extrusion. The starches employed were rice starches (8%, 20%, and 32% amylose), carioca bean starch (35% amylose), and Hylon V® corn starch (55% amylose). The extrudates from rice starches containing 20% and 32% amylose exhibited the highest expansion ratio, while, extrudates from Hylon V® corn starch containing 55% amylose exhibited the lowest expansion ratio. The hardness values of the extrudates with 55% amylose were twice those of the extrudates with 20%, 32%, and 35% amylose. An additional finding was that although the amylopectin promoted the expansion of the gelatinized starch matrix, it failed to strengthen and sustain the walls of the extrudate bubbles during expansion. 相似文献
79.
Beierlein Dennis Häussermann Dorothea Traa Yvonne Klemm Elias 《Catalysis Letters》2022,152(10):2908-2919
Catalysis Letters - We developed a rapid aging method for Ni/Al2O3 methanation catalysts mimicking the real aging in the actual application. The method is based on hydrothermal deactivation of the... 相似文献
80.
Daniel Walgraef Elias C. Aifantis 《International Journal of Engineering Science》1985,23(12):1351-1358
By distinguishing among mobile and immobile dislocations and operating within the framework of continuum mechanics it is possible to derive a set of partial differential equations of the diffusion-reaction type for the evolution of dislocation species. On examining the competition between gradient dependent terms modelling the motion of dislocations and nonlinear terms modelling their interactions, it is shown that stable solutions are possible. The wavelength turns out to be a material property in agreement with observations. The discussion is limited to one dimension, that is to glide of straight dislocations in the slip direction, and the model corresponds physically to the ladder-like structure of persistent slip bands. 相似文献