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31.
Phonon relaxation and heat conduction in one-dimensional Fermi-Pasta-Ulam β lattices by molecular dynamics simulations 下载免费PDF全文
The phonon relaxation and heat conduction in one-dimensional Fermi-Pasta-Ulam (FPU) β lattices are studied by using molecular dynamics simulations.The phonon relaxation rate,which dominates the length dependence of the FPU β lattice,is first calculated from the energy autocorrelation function for different modes at various temperatures through equilibrium molecular dynamics simulations.We find that the relaxation rate as a function of wave number k is proportional to k 1.688,which leads to a N 0.41 divergence of the thermal conductivity in the framework of Green-Kubo relation.This is also in good agreement with the data obtained by non-equilibrium molecular dynamics simulations which estimate the length dependence exponent of the thermal conductivity as 0.415.Our results confirm the N 2/5 divergence in one-dimensional FPU β lattices.The effects of the heat flux on the thermal conductivity are also studied by imposing different temperature differences on the two ends of the lattices.We find that the thermal conductivity is insensitive to the heat flux under our simulation conditions.It implies that the linear response theory is applicable towards the heat conduction in one-dimensional FPU β lattices. 相似文献
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This study investigates the academic and clinical preparation a speech-language pathologist receives in the area of voice. The purpose is to determine how to structure continuing education and specialty training in vocology, defined as the science and practice of voice habilitation. Surveys were sent to the graduate programs in speech-language pathology accredited by the American Speech-Language-Hearing Association (ASHA) in 1994, and again in 1999. Results from the 1994 survey indicated that students received limited information and clinical experience in handling typical voice cases. Although most programs required a voice disorders course, fewer mandated coursework in normal voice production or clinical experience with voice patients. The follow-up survey showed that the educational environment in 1999 is similar to that in 1994. It is evident that the programs are in compliance with the Educational Training Board model developed by ASHA for basic clinical competence, but no structure for specialty training has yet emerged. 相似文献
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Niels-Christian F. Bagger Matias Sørensen Thomas R. Stidsen 《European Journal of Operational Research》2019,272(2):430-446
In this paper, we considered the problem of Curriculum-Based Course Timetabling, i.e., assigning weekly lectures to a time schedule and rooms. We developed a Column Generation algorithm based on a pattern formulation of the time scheduling part of the problem by Bagger et al. (2016). The pattern formulation is an enumeration of all schedules by which each course can be assigned on each day; it is a lower bounding model. Pattern enumeration has also been considered in Burke (2008), where the authors enumerated all schedules to which each curriculum can be assigned on each day. We applied the Dantzig–Wolfe reformulation, so each column corresponded to a schedule for an entire day.We solved the reformulation with the Column Generation algorithm, where each pricing problem generated a full schedule for a single day. We provided a pre-processing technique that, on average, removed approximately 45% of the pattern variables in the pricing problems. We then extended the pre-processing technique into inequalities that we added to the model. Lastly, we describe how we applied Local Branching to the pricing problem by using the columns generated in previous iterations.We compare the lower bounds we obtained, with other methods from literature, on 20 data instances of real-world applications. For 16 instances the optimal solutions are known, but the remaining four are still open. Our approach improved the best-known lower bound for all four open instances, and decreased the average gap from 24 to 11%. 相似文献
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Yannis Siskos Evangelos Grigoroudis Evangelia Krassadaki Nikolaos Matsatsinis 《European Journal of Operational Research》2007
Employees must acquire new competences and qualifications throughout their lives, in order to be able to deal with the multiple changes in the labour market. The specific knowledge and competences, acquired either formally or non-formally, must be recognized so that they can be transferred and utilized. The existing titles of studies and accreditation mechanisms do not generally cover this need. This paper aims to propose an integrated approach for the evaluation of information technology knowledge and skills, regardless of where and how they have been acquired, so as to apply a continuous education and training policy. The proposed multicriteria methodology for the evaluation of qualifications and skills concerns candidates wishing to be accredited in an information technology specialization or profession. The methodology refers to the evaluation of the professional experience, studies and vocational training of the candidates for accreditation. It contains the analysis and modelling of the qualitative criteria as well as the implementation of multicriteria aggregation–disaggregation techniques attributing value to each criterion. Then, the candidates are classified in categories of professionals using the Electre Tri method, accepting as input data the multicriteria assessments on each criterion. The proposed evaluation approach has been adapted to the Greek educational system and is applied to a specific example of candidate. 相似文献
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对中国作者在英国《化学教育研究与实践》上的发文情况进行了较为全面的统计分析,包括发文数量、作者区域、作者机构、合作程度以及论文内容等;旨在揭示我国化学教育的国际化程度及其特点,以期为我国化学学科教育研究提供一些参考与启示,提升我国化学教育研究的国际化水平。 相似文献
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Konstantina Kamvysi Katerina Gotzamani Andreas Andronikidis Andreas C. Georgiou 《European Journal of Operational Research》2014
Customer requirements play a vital and important role in the design of products and services. Quality Function Deployment (QFD) is a popular, widely used method that helps translate customer requirements into design specifications. Thus, the foundation for a successful QFD implementation lies in the accurate capturing and prioritization of these requirements. This paper proposes and tests the use of an alternative framework for prioritizing students’ requirements within QFD. More specifically, Fuzzy Analytic Hierarchy Process (Fuzzy-AHP) and the linear programming method (LP-GW-AHP) based on Data Envelopment Analysis (DEA) are embedded into QFD (QFD-LP-GW-Fuzzy AHP) in order to account for inherent subjectivity of human judgements. The effectiveness of the proposed framework is assessed in capturing and prioritizing students’ requirements regarding courses’ learning outcomes within the process of an academic course design. Sensitivity analysis evaluates the robustness of the prioritization solution and implications for course design specifications are discussed. 相似文献
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Chun-Xue Zhao Bing-Qian Li Zhao-Xiang Shao Da-Hong Li Yong-Kui Jing Zhan-Lin Li Hui-Ming Hua 《Tetrahedron letters》2019,60(43):151154
A new cephalotane diterpenoid glucoside, cephasinenoside A (1), was isolated from the twigs and leaves of Cephalotaxus sinensis (Rehd. et Wils.) Li. The structure of 1 was established on the basis of spectroscopic analyses and ECD calculations. Compound 1 represents the first cephalotane diterpenoid glycoside which inhibits the proliferation of human acute myeloid leukemia HL-60 cells with a GI50 value of 7.17 ± 1.03 μM. 相似文献