1,721,580 research outputs found
Temperature-dependent phonon anharmonicity and thermal transport in CuInTe2
No full textThe Cu-based chalcopyrite compounds are good thermoelectrics for waste heat harvesting, partially due to the dramatic reduction of the thermal conductivity above Debye temperature, whereas the mechanism of this drop is still elusive. By Raman measurements from 7 to 780 K, we have investigated the anharmonicity of the phonon modes B12, A1, and B32 in CuInTe2. The fourth-order anharmonicity of B12 and B32 modes is greatly enhanced with increasing temperature and becomes dominant above 400 K. The phonon dynamics is calculated from 10 to 800 K. The fourth-order anharmonicity is predominant over the third-order ones for the phonon modes at low ( 70 cm???1) and high ( 130 cm???1) frequency domains, confirmed by the enhanced weighted phase space and scattering rate of the four-phonon processes above 300 K. The phonon avoided-crossing is found to take place around 40 cm???1 between the lowest-optical mode and acoustic modes. Counting on the fourth-order phonon anharmonicity, the calculated lattice thermal conductivity agrees well with experiment. The results unveil that the dramatic thermal conductivity reduction, about 83% from 300 to 800 K, originates from the enhanced four-phonon process. Our insights on the thermal transport mechanisms might benefit the materials design of thermoelectrics and thermal control.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dependency and correlation analysis of specifications and parameters of products for supporting design decisions
No full textDesign changes often occur during product development processes and some design changes may require significant modifications of product specifications and design parameters, which may affect life cycle performances of the product. Due to complexities and possibly unknown relationships among specifications and parameters of products, the design change decisions must be carefully evaluated. This paper proposes a systematic method for modeling and analysis of dependencies and correlations among product specifications and critical design parameters for supporting design decisions. A case study illustrates the feasibility and effectiveness of the proposed approac
Microscopic optimization model and algorithm for integrating train timetabling and track maintenance task scheduling
No full textThis paper addresses the problem of improving the integration between passenger timetabling and track maintenance scheduling. We propose a microscopic optimization model and an iterative algorithm for solving this problem efficiently. Block sections are considered as the basic microscopic elements for train movements in a railway network. A mixed-integer linear programming formulation is proposed for the integrated optimization problem in which train timing, sequencing and routing are the timetabling variables, while timing and sequencing of maintenance tasks are the track maintenance variables. The objective function is to minimize the total train travel time and the maintenance tardiness cost. The constraints proposed in this work address the practical specifications of the INFORMS RAS 2016 Problem Solving Competition (2016 PSC). In this context, the main decision variables are the entrance and exit times of the trains on each block section plus the start and end times of each maintenance task. Since the integrated optimization problem is strongly NP-hard, an iterative algorithm is proposed to compute near-optimal solutions in a short computation time. The algorithm is based on a decomposition of the overall problem into sub-problems related to train scheduling and/or routing with or without track maintenance task scheduling. The connecting information between the two sub-problems concerns the selected train routes plus the start and end times of the maintenance tasks. Computational experiments are performed on a set of realistic railway instances, which were introduced during the 2016 PSC. The iterative algorithm outperforms a standard MILP solver and the first-place team of this competition in terms of both solution quality and time to deliver the new best-known solutions. The scalability of the iterative algorithm is investigated when increasing the number of trains and track maintenance tasks
Simultaneous node and link districting in transportation networks: Model, algorithms and railway application
No full textPartitioning a large network into multiple subnetworks is adopted extensively in various practical applications involving the architecture of distributed management. In this study, we consider strategic simultaneous node and link districting to partition the nodes and links of a given transportation network into a fixed number of mutually disjoint districts, based on the districting criteria of integrity, contiguity, balance, and independence. We first formulate the resulting problem as a mixed integer linear programming model to minimize the weighted sum of the total size deviation of districts and total cooperation between districts. An improved network flow-based technique is proposed to incorporate the complicated contiguity criterion by using a polynomial number of constraints. Valid inequalities, which break the symmetry within and between districts, are designed to strengthen the model. To solve this challenge problem, we reformulate it as a binary linear programming model, and develop a column generation-based algorithm to find tight lower bounds and good-quality solutions. Then, an iterative search algorithm is designed to obtain good-quality solutions rapidly. Furthermore, a more efficient hybrid algorithm is proposed by using the results of the iterative search algorithm to initialize the column generation-based algorithm. We assess the proposed model and algorithms by using various scales of instances derived from the train dispatcher desk districting problem, which is a practical application of the investigated problem in the context of railway. The computational results reveal that our approaches outperform existing approaches and a commercial solver, and our best algorithm can solve almost all the investigated instances to optimality within a considerably short average computation time. The districting solutions of our approaches are also better than the empirical solutions designed by railway managers mainly based on experience
The heterogeneity of mast cell tryptase from human lung and skin
No full textThere has long been conjecture over the degree to which there may be structural and functional heterogeneity in the tetrameric serine protease tryptase (EC 3.4.21.59), a major mediator of allergic inflammation. We have applied 2D gel electrophoresis to analyze the extent, nature, and variability of this heterogeneity in lysates of mast cells isolated from lung and skin, and in preparations of purified tryptase. Gels were silver stained, or the proteins transferred to nitrocellulose blots and probed with either tryptase-specific monoclonal antibodies or various lectins. Tryptase was the major protein constituent in mast cell lysates, and presented as an array of 9–12 diffuse immunoreactive spots with molecular masses ranging from 29 to 40 kDa, and pI values from 5.1 to 6.3. Although the patterns obtained for lung and skin tryptase were broadly similar, differences were observed between tissues and between individual donors. Lectin binding studies indicated the presence of mono-antennary or bi-antennary complex-type oligosaccharide with varying degrees of sialylation. Deglycosylation with protein-N-glycosidase F (PNGase F) reduced the size of both lung and skin tryptase, while incubation with PNGase F or neuraminidase narrowed the pI range, indicating variable degrees of glycosylation as a major contributor to the size and charge heterogeneity. Comparison of different purified preparations of lung and skin tryptase revealed no significant difference in pH profiles, but differences were seen in reactivity towards a range of chromogenic substrates, with substantial differences in Km, kcat and degree of cooperativity. Mathematical modeling indicated that the variety in kinetics parameters could not result solely from the sum of varying amounts of isoforms obeying Michaelis–Menten kinetics but with different values of Km and kcat. The heterogeneity demonstrated for tryptase in these studies suggests that there are important differences in tryptase function in different tissues
Joint rolling stock rotation planning and depot deadhead scheduling in complicated urban rail transit lines
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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