Comparison between the apparent chemical diffusion coefficient evaluated from relaxation experiments by means of electrical conductivity changes and the corresponding theoretical value for a pure and doped p-type oxide

The chemical diffusion coefficient for a p-type oxide either pure or doped with an aliovalent impurity as evaluated from electrical conductivity changes in simulated relaxation experiments is compared with the corresponding theoretical values obtained on the basis of Fick's first law using a convenient model to represent the defect structure of the oxide. It is found that if the relaxation process is purely diffusion controlled, the experimental value of obtained ( ) is in rather good agreement with the theoretical value calculated by considering the diffusion of lattice defects rather than with that obtained by considering the diffusion of the prevailing electronic defects , even when the latter two values differ. This is shown to be the result of relatively small departures from a proportionality (for the pure oxide) or from a linear dependence (for a doped oxide) in the relationship between the deviation from stoichiometry and the concentration of the electron holes in restricted range of oxygen activity as used in relaxation experiments.     

Facets of work values: A structural analysis of work outcomes.

Attempted to analyze contents of work value items and to construct an explicit definition of the work values domain. A facet definition of work values is suggested that provides guidelines for selection items and the formulation of hypotheses about the structure of interrelationships among components of work values. Interview data were obtained from 2 samples of Israeli adults containing 489 Ss (median age 35 yrs) and 546 Ss (median age 38 yrs), respectively. Results of Guttman's smallest space analysis support the hypotheses. An empirical double-ordered conceptual system, a radex structure, was obtained that reflects the 2 facets of the definition: modality of outcome—material, social, and psychological—and type of outcome—performance relations (reward, resource). The fact that essentially the same structure was obtained in 2 independent samples lends substantial support to the definitional framework of work values suggested. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Determining production sequences for single-stage multifunctional machining systems based on the tradeoff between fixture cost, re-fixturing and tool replenishment

The main advantage of a Single-Stage Multifunctional machining System (SSMS) is its ability to combine many operations and processes, previously done on different machines in several stages, into a single stage. The flexibility and process variety these machining systems offer have ensured their widespread adoption in industry. As a result SSMSs frequently constitute the bottleneck of a manufacturing system and therefore control system throughput. Hence, it is imperative to use these resources efficiently. This study considers three possible costs and the tradeoffs between them that are pertinent to any job sequence: (i) the Tool Magazine Replenishment (TMR) cost; (ii) the Re-Fixturing (RF) cost; and (iii) the fixture cost. A job sequencing algorithm that minimizes these costs as well as the machine non-operational time, which stems from TMRs and RFs, is developed. The algorithm takes into account the tools and fixture requirements as well as the tool magazine capacity. The algorithm also recommends purchasing additional fixtures when economically justified. The algorithm is used to solve a job sequencing problem that occurs in a real industrial setting.     

Chemorheological changes in crosslinked epoxy resins subjected to large strains

Chemorheological changes in epoxy resins subjected to large strains while heated were observed earlier, but the subject was not treated quantitatively. This paper describes the investigation of an epoxy resin—Epon 826, of known chemical, structure, crosslinked with two different amines. By means of a simple calibrated apparatus, the epoxide samples were subjected to large strains in a non-oxidizing atmosphere and in air. They were heated to different temperatures for various times; the results were compared with data obtained from unstrained samples kept in otherwise the same conditions. The results show a linear-logarithmic relation between the torsion modulus, G₍₁₀₎ and the time of applied strain at a certain temperature and also a linear relation between G₍₁₀₎, and 1/T°K, both above T₍₁₀₎. The results obtained in swelling experiments support the data from 10 sec torsional modulus vs temperature measurements. An increase in the amount of solubles and in M_c is observed on extending the time of heating. A clear difference in properties between the strained and unstrained samples, kept in otherwise the sane conditions, is observed and the contribution of the applied strain to chemorheology has been shown. Both systems of crosslinked Epon 826 showed the same general behavior, although the specific data were different.     

Implicit leadership theory as a determinant of the factor structure underlying supervisory behavior scales.

Examined implicit leadership theory (preconceptions about the patterning of leadership variables) in 235 college students. Ss completed the Survey of Organizations questionnnaire on a fictitious "Plant X" about which they were given little information. Factor analysis, performed on the items purported to measure 4 leadership factors, resulted in the conceptualized factor structure. Since no information was given regarding supervisory behavior in Plant X, the factor structure was attributed to an implicit leadership theory. Factor analysis on subsamples indicated the factor structure could not be attributed to either experience in organizations or previous instruction in management. It is suggested that responses to questionnaires regarding organizational variables may be contaminated by implicit theory and that multitrait-multimethod procedures may be required to validate questionnaires. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An equivalent pressure source for the heart

A technique is described for the representation of the left ventricle as a one-port source characterized by a generator pressure and an internal impedance. The Fourier components of the pressure and impedance are determined from phasor analysis performed on recorded time-domain functions of pressure and flow under two conditions of loading. One condition is the quiescent state corresponding to normal operation of the circulatory system, and the other is obtained by use of a phase-shift balloon pump situated in the descending thoracic aorta. The use of the balloon pump for determining source parameters is novel. The Fourier components of pressure and impedance are determined for the first five harmonics of the quiescent pulse rate. Heart failure is simulated by ligation of all branches of the anterior descending coronary artery. The source parameters have been found to vary considerably between normal and failing hearts. Valve impedance and the impedance at the root of the aorta were also measured. The generator time-domain pressure waveforms were determined from the Fourier components. Effects of long duration pumping, upon the source parameters were found. The ratio of the calculated magnitudes of internal to external or load impedance indicates the possibility of considering the heart as a pressure source.     

General Analytical Framework for Design of Flexible Reinforced Earth Structures

Current design methods divide reinforced earth structures into walls and slopes by using an arbitrary face inclination of 70° as the boundary. The required maximum strength of reinforcement computed for reinforced walls are significantly higher than that computed for reinforced slopes even if the inclination is practically the same. Presented is a general analytical framework for design of flexible reinforced earth structures regardless of the slope face inclination. In fact, the framework is consistent for any structural geometry and any applicable slope stability analysis although, for demonstration purposes, the simple Culmann formulation is utilized for simple geometry with zero batter. Using an adequate slope stability formulation, the required tensile resistance of reinforcement for a given layout is calculated so as to produce the same prescribed factor of safety anywhere within the reinforced zone. That is, using the design shear strength of the soil, the required reinforcement resistance along each layer is computed to fully mobilize this shear strength for all possible slip surfaces. That is, a baseline solution is produced for an ideal long-term strength of reinforcement at any location. Consequently, the required strength of the connection between each reinforcement layer and the facing unit can also be determined. This connection strength, however, assumes small facing units with negligibly small shear and moment resistance. Parametric study is conducted to demonstrate the reasonableness of the presented framework. It is shown that the required tensile resistance and connection strength depend on factors such as: reinforcement length; intermediate reinforcement; percent coverage; and quality of fill. When compared with the current AASHTO design for walls, the required maximum long-term strength of the reinforcement as well as the required connection strength in the proposed approach are substantially smaller.     

Microwave pulses compressed in a quasi-optical resonator with corrugated mirror

A microwave pulse compressor, representing a three-mirror resonator supplied with a radiation beam reflected from a corrugated mirror, was constructed and experimentally tested. A fivefold compression of microwave pulses with a 70% efficiency was obtained in a 9-mm wavelength range.     

3D effects of turning corner on stability of geosynthetic-reinforced soil structures

Current design procedures of Geosynthetic-Reinforced Soil Structures (GRSS's) are for walls/slopes with long straight alignments. When two GRSS segments intersect, an abrupt change in the alignment forms a turning corner. Experience indicate potential instability problems occurring at corners. The purpose of this study is to explore the effects of turning corner on the stability of reinforced slopes. Three-dimensional (3D) slope stability analysis, based on limit equilibrium, resulted in the maximum tensile force of reinforcement. Parametric studies required numerous computations considering various geometrical parameters and material properties. The computed results produced efficient practical format of stability charts. For long-term stability of reinforced slopes with turning corner, the influences of pore water pressure and seismic loading are also considered. Turning corner can improve the stability of reinforced slopes by virtue of inclusion of end effects. However, localized increase of pore water pressure or directional seismic amplification may decrease locally thus stability requiring strength of reinforcement larger than in two-dimensional (2D) plane-strain. While using 2D analysis for non-localized conditions may require stronger reinforcement, it also requires shorter reinforcement than in 3D analysis; i.e., 2D analysis may be unconservative in terms of reinforcement length.