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101.
C.C.H.Rosen 《计算机教育》2010,(9):94-96
Students at the University of Derby are required to complete a year in industry as part of their Bachelor of Science degrees.This is a daunting prospect for some of them,and they can be reluctant to engage in the process of finding a placement position.As part of a second year module,students seeking placement are paired with students already on placement in a mentee/mentor relationship to support the second year students in their search for an internship.This arrangement helps the mentees by introducing them to potential role models close to their experience,receiving encouragement from peers and the inculcation of belief that it is possible to find a placement.The mentors also benefit from a recognition of how much they have learnt.However,there are difficulties in establishing and managing the scheme which should be recognised.This paper reports our experience over the last three years. 相似文献
102.
The bootstrap method is a computer intensive statistical method that is widely used in performing nonparametric inference. Categorical data analysis, in particular the analysis of contingency tables, is commonly used in applied field. This work considers nonparametric bootstrap tests for the analysis of contingency tables. There are only a few research papers which exploit this field. The p-values of tests in contingency tables are discrete and should be uniformly distributed under the null hypothesis. The results of this article show that corresponding bootstrap versions work better than the standard tests. Properties of the proposed tests are illustrated and discussed using Monte Carlo simulations. This article concludes with an analytical example that examines the performance of the proposed tests and the confidence interval of the association coefficient. 相似文献
103.
We consider packet networks and make use of the "adversarial queuing theory" model [10]. We are interested in the question
of guaranteeing that all packets are
actually delivered to destination, and of having an upper bound on the delivery times
of all packets. Whether this is possible against all adversarial queuing theory
rate-1 adversaries was previously posed as an open question [13],[10]. Among other things, we give a queuing policy that guarantees
bounded delivery time whenever the rate-1 adversary injects a sequence of packets for which there exists a schedule with a
finite upper bound on the delivery times of all packets, and adheres to certain additional conditions. On the negative side
we show that there exist rate-1 sequences of packets for which there is no schedule with a finite upper bound on the delivery
times of all packets. We thus answer an open question posed by Gamarnik [13]. We further show that delivering all packets
while maintaining stability (we coin the term "reliability" for this property) can be done by an offline scheduler whenever
the injection of packets is done at rate of at most 1. However, on the other hand, we also show that there is no online protocol
(even centralized) that can achieve that property against all rate-1 adversaries. We thus answer an open question of Borodin
et al. [10]. 相似文献
104.
AD Gouliamos DS Kontogiannis J Androulidakis AE Kalovidouris LJ Vlahos CG Papavasiliou 《Canadian Metallurgical Quarterly》1993,17(3):446-448
The MR studies of three histologically proven spinal neurilemmomas and neurofibromas were reviewed retrospectively. There were two benign neurilemmomas (schwannomas) and one neurofibroma. The common characteristic of these cases was a central low intensity focus ("dot") seen on postcontrast T1-weighted imaging. The low intensity foci corresponded histologically to a congeries of changes including edema, microcysts, foam cells, hyalinization of blood vessels, old hemorrhage, and dystrophic calcification. 相似文献
105.
A theoretical analysis was carried out on the change of composition of a deposit obtained by the dual pulse method of forming laminar metal foils, with transition from a low current to a high current pulse, both in the galvanostatic and the potentiostatic mode of deposition. It was shown that the existence of a transition layer of varying composition between a layer of pure metal 1 and a layer consisting predominantly of the metal 2 is an inherent consequence of the electrochemical process, primarily because of an induction period in the concentration polarization with respect to ions of metal 1. The importance of this transition layer increases as the thickness of the layers of the two metals decreases. Eventually this limits the possibility of obtaining a sharp boundary between the layers, when the nanometre region of layer thickness is reached. Equations are given for calculating the deposition current density and rate of stirring of the electrolyte which provide a deposit of a required level of metal 1 in the layer of metal 2, as well as a required sharpness of the boundary between two layers. Experimental proof of the correctness of the analysis was sought. It was found that significant changes in the properties of the deposit occur in the same range of layer thickness in which the transition of the composition takes places.Nomenclature c,1, ac,2
transfer coefficient of the cathodic processes
-
C
interfacial capacitance
- C1, C2
concentration of the ions of metals 1 and 2 at the interface r
- C
0
1
, C
0
2
concentration of ions of the metals 1 and 2 in solution
-
D
1
diffusion coefficient for the diffusion of ions of the metal 1
-
E
r,1,E
r,2
reversible potentials of metals 1 and 2, respectively
-
F
the Faraday constant
-
J
0
1
,J
0
2
exchange current density of the metals 1 and 2, respectively
-
M
1,M
2
atomic weights of the metals 1 and 2, respectively
-
kinematic viscosity of solution
- 1, 2
densities of the metals 1 and 2 respectively
-
rotation speed (r.p.s.)
-
z
number of electrons exchanged in the deposition process
This paper is dedicated to Professor Brian E. Conway on the occasion of his 65th birthday, and in recognition of his outstanding contribution to electrochemistry. 相似文献
106.
Oxidation of formic acid at a high surface area supported platinum modified by foreign metal adatoms
The anodic oxidation of formic acid was studied on platinum distributed in the form of small particles in a porous substrate modified by metal adatoms deposited at underpotentials. The rate of the reaction was greatly enhanced on the commercial catalyst Powercat 3000 (PC 3000). The hydrogen adsorption and the underpotential deposition of several metals at PC 3000 were shown to be dissimilar to that at smooth polycrystalline Pt. Steady-state and long-term experiments were performed to determine the stability of this electrode. 相似文献
107.
Taylor Joy L.; O'Hara Ruth; Mumenthaler Martin S.; Rosen Allyson C.; Yesavage Jerome A. 《Canadian Metallurgical Quarterly》2005,20(1):117
Differences in cognitive ability and domain-specific expertise may help explain age differences in pilot performance. Pilots heard air-traffic controller messages and then executed them while "flying" in a simulator. Messages varied in length and speech rate. Age was associated with lower accuracy, but the expected Age x Message Difficulty interactions were not obtained. Expertise, as indexed by pilot ratings, was associated with higher accuracy; yet expertise did not reduce age differences in accuracy. The effect of age on communication task accuracy was largely explainable as an age-associated decrease in working memory span, which in turn was explainable as decreases in both speed and interference control. Results are discussed within frameworks of deliberate practice and cognitive mediation of age differences. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
108.
Integration of material composition, microstructure, and mechanical properties with geometry information enables design and analysis of materials and products in a computer-aided design (CAD) environment. In this paper, we propose a method for the construction of material models from microstructure images, that can be integrated into a heterogeneous CAD representation. The method utilizes Radon and wavelet transforms to compute a surfacelet representation. A novel feature recognition method was developed to identify microstructure features, including embedded fibers and grain boundaries, from the surfacelet representation. The models and methods were demonstrated with examples of synthetic and engineered polymer nanocomposites, a metal alloy, and a medical dataset of human feet. 相似文献
109.
An economic model and optimization procedure is developed in this paper for grid-connected hybrid wind–hydrogen combined heat and power systems for residential applications in northeastern Iran. The model considers various significant factors: energy production cost, electrical trade with local grid, electrical power generation from the wind/hydrogen energy system, thermal recovery from the fuel cell, and maintenance. Also, various tariffs for purchasing and selling electrical energy from the local grid are considered for the hybrid system operation. The optimization objective is to minimize the system total cost subject to relevant constraints for residential applications. To achieve this aim, an efficient optimization method is proposed based on particle swarm optimization. The proposed algorithm performance is compared with that for the imperialist competition algorithm. The results show that the hybrid system is the most cost-effective for the residential load, and the results of the proposed algorithm are more promising than those for the alternative algorithm. 相似文献
110.
Julie A. Rosen 《Natural Gas \u0026amp; Electricity》2015,31(11):25-29
For nearly a century, the Migratory Bird Treaty Act has been a tool used by the federal government to protect migratory bird species.1 相似文献