47 resultados para inter-item correlations
Resumo:
Purpose: This paper seeks to measure in a quantitative way the degree of alignment among a set of performance measures between two organizations. Design/methodology/approach: This paper extends Venkatraman's test of coalignment to assess the alignment of a set of performance measures governing a contractual inter-organizational relationship. The authors applied the test and present coefficients of misalignment across three sets of measures: those used by a service provider involved in the research, those used by customers contracting the services, and those documented in 11 contracts studied. Findings: Results confirmed a high degree of alignment between target and actual operational performance in the contracts. The alignment of customers' financial objectives and contracts' operational metrics was low. Calculations show poor alignment between the objectives of the provider and the contribution received from the contracts. Research limitations/implications: Some limitations of the conclusions include the small sample of contracts used in the calculations. Further research should include not only actual contracts, but also failed ones. Practical implications: It is possible that misaligned goals, represented in misaligned performance measures, lead to tensions in intra-firm relationships. If these tensions are not addressed properly the relationship could be unstable or terminated prematurely. This method of measuring alignment could detect early potential dangers in intra-firm relationships. Originality/value: This paper extends Venkatraman's test of coalignment to assess the alignment of a set of performance measures governing a contractual inter-organizational relationship. Management researchers and business professionals may use this methodology when exploring degrees of alignment of performance measures in intra-functional and inter-firm relationships. © Emerald Group Publishing Limited.
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This chapter focuses on relationships between plastic deformation structures and mechanical properties in metals and alloys deforming by dislocation glide. We start by summarizing plastic deformation processes, then look at the fundamental mechanisms of plastic deformation and explore how deformation structures evolve. We then turn to experimental techniques for characterization which have allowed deformation microstructures to be quantified in terms of common structural parameters. The microstructural evolution has been described over many length scales and analyzed theoretically based on general principles. The deformation microstructures are related to work hardening stages. Finally we identify correlations between a wide range of microstructural features and mechanical properties, particularly flow stress, and use experimental observations to illustrate their inter-relationships.
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This paper reports the modeling and characterization of interdigitated rows of carbon nanotube electrodes used to address a liquid crystal media. Finite Element Method modeling of the nanotube arrays was performed to analyze the static electric Fields produced to Find suitable electrode geometry. A device was fabricated based on the simulation results and electro optics characteristics of the device are presented. This Finding has applications in the development of micron and submicron pixels, precise beem steering and nanotube based active back planes.
Resumo:
Change detection is a classic paradigm that has been used for decades to argue that working memory can hold no more than a fixed number of items ("item-limit models"). Recent findings force us to consider the alternative view that working memory is limited by the precision in stimulus encoding, with mean precision decreasing with increasing set size ("continuous-resource models"). Most previous studies that used the change detection paradigm have ignored effects of limited encoding precision by using highly discriminable stimuli and only large changes. We conducted two change detection experiments (orientation and color) in which change magnitudes were drawn from a wide range, including small changes. In a rigorous comparison of five models, we found no evidence of an item limit. Instead, human change detection performance was best explained by a continuous-resource model in which encoding precision is variable across items and trials even at a given set size. This model accounts for comparison errors in a principled, probabilistic manner. Our findings sharply challenge the theoretical basis for most neural studies of working memory capacity.
Resumo:
Atomic force microscopy (AFM) and scanning electron microscopy (SEM) with cathodoluminescence (CL) were performed on exactly the same defects in a blue-emitting InGaN/GaN multiple quantum well (QW) sample enabling the direct correlation of the morphology of an individual defect with its emission properties. The defects in question are observed in AFM and SEM as a trench partially or fully enclosing a region of the QW having altered emission properties. Their sub-surface structure has previously been shown to consist of a basal plane stacking fault (BSF) in the plane of the QW stack, and a stacking mismatch boundary (SMB) which opens up into a trench at the sample surface. In CL, the material enclosed by the trench may emit more or less intensely than the surrounding material, but always exhibits a redshift relative to the surrounding material. A strong correlation exists between the width of the trench and both the redshift and the intensity ratio, with the widest trenches surrounding regions which exhibit the brightest and most redshifted emission. Based on studies of the evolution of the trench width with the number of QWs from four additional MQW samples, we conclude that in order for a trench defect to emit intense, strongly redshifted light, the BSF must be formed in the early stages of the growth of the QW stack. The data suggest that the SMB may act as a non-radiative recombination center. © 2013 American Institute of Physics.
Resumo:
Due to the Fermi-Dirac statistics of electrons the temporal correlations of tunneling events in a double barrier setup are typically negative. Here, we investigate the shot noise behavior of a system of two capacitively coupled quantum dot states by means of a Master equation model. In an asymmetric setup positive correlations in the tunneling current can arise due to the bunching of tunneling events. The underlying mechanism will be discussed in detail in terms of the current-current correlation function and the frequency-dependent Fano factor.
Resumo:
The present paper considers the problem of autonomous synchronization of attitudes in a swarm of spacecraft. Building upon our recent results on consensus on manifolds, we model the spacecraft as particles on SO(3) and drive these particles to a common point in SO(3). Unlike the Euler angle or quaternion descriptions, this model suffers no singularities nor double-points. Our approach is fully cooperative and autonomous: we use no leader nor external reference. We present two types of control laws, in terms of applied control torques, that globally drive the swarm towards attitude synchronization: one that requires tree-like or all-to-all inter-satellite communication (most efficient) and one that works with nearly arbitrary communication (most robust).
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The vortical wake structure produced by a three-dimensional shock control bump (SCB) is thought to be useful for controlling transonic buffet on airfoils. However, at present the vorticity produced is relatively weak and the production mechanism is not well understood. Using a combined experimental and computational approach, a preliminary investigation on the wake vorticity for different bump geometries has been carried out. The structure of the wake for on and off-design conditions are considered, and the effects on the downstream boundary layer demonstrated. Three main vortical structures are observed: a primary vortex pair, weak inter-bump vortices and shear flow in the lambda-shock region. The effect of pressure gradients on vortex strength is examined and it is found that spanwise pressure gradients on the front section of the bump are the most significant parameter influencing vortex strength. © 2013 by S.P. Colliss et al.
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Against a background of increasing energy demand and rising fuel prices, hybrid-electric propulsion systems (HEPS) have the potential to significantly reduce fuel consumption in the aviation industry, particularly in the lighter sectors. By taking advantage of both Electric Motor (EM) and Internal Combustion Engine (ICE), HEPS provide not only a benefit in fuel saving but also a reduction in take-off noise and the emission levels. This research considers the design and sizing process of a hybrid-electric propulsion system for a single-seat demonstrator aircraft, the experimental derivation of the ICE map and the EM parameters. In addition to the experimental data, a novel modeling approach including several linked desktop PC software packages is presented to analyze and optimize hybrid-electric technology for aircraft. Further to the analysis of a parallel hybrid-electric, mid-scale aircraft, this paper also presents a scaling approach for a 20 kg UAV and a 50 tonne inter-city airliner. At the smaller scale, two different mission profiles are analyzed: an ISR mission profile, where the simulation routine optimizes the component size of the hybrid-electric propulsion system with respect to fuel saving, and a maximum duration profile; where the flight endurance is determined as a function of payload weight. At the larger scale, the performance of a 50 tonne inter-city airliner is modeled, based on a hybrid-electric gas-turbine, assuming a range of electric boost powers and battery masses.
Resumo:
In the first part of the paper steady two-phase flow predictions have been performed for the last stage of a model steam turbine to examine the influence of drag between condensed fog droplets and the continuous vapour phase. In general, droplets due to homogeneous condensation are small and thus kinematic relaxation provides only a minor contribution to the wetness losses. Different droplet size distributions have been investigated to estimate at which size inter-phase friction becomes more important. The second part of the paper deals with the deposition of fog droplets on stator blades. Results from several references are repeated to introduce the two main deposition mechanisms which are inertia and turbulent diffusion. Extensive postprocessing routines have been programmed to calculate droplet deposition due to these effects for a last stage stator blade in three-dimensions. In principle the method to determine droplet deposition by turbulent diffusion equates to that of Yau and Young [1] and the advantages and disadvantages of this relatively simple method are discussed. The investigation includes the influence of different droplet sizes on droplet deposition rates and shows that for small fog droplets turbulent diffusion is the main deposition mechanism. If the droplets size is increased inertial effects become more and more important and for droplets around 1 μm inertial deposition dominates. Assuming realistic droplet sizes the overall deposition equates to about 1% to 3% of the incoming wetness for the investigated guide vane at normal operating conditions. Copyright © 2013 by Solar Turbines Incorporated.