1,720,974 research outputs found
Selective charge transfer to dioxygen on KPF6-modified carbon nitride for photocatalytic synthesis of H2O2 under visible light
No full textPhotochemical production of H2O2 through O-2 reduction has been proposed as an alternative method of solar energy storage. A carbon nitride (CN) photocatalyst was selected for this purpose. The incorporation of KPF6 into the CN structure greatly enhanced the apparent quantum yield (AQY) of H2O2 production in the UV and visible light region. The AQY of KPF6-modified CN was measured to be 35.9% and 24.3% under monochromatic irradiation at 370 and 420 nm, respectively, which are 8.3 and 26.1 times higher than for bare CN. The KPF6-enhanced activity is ascribed to several factors including (i) enhanced absorption of UV and visible light, (ii) higher charge carrier density, (iii) retarded radiative recombination of charge pairs, (iv) highly selective two-electron transfer to O-2, and (v) hindered photodecomposition of in-situ generated H2O2. The markedly high selectivity of KPF6-modified CN toward the two-electron reduction of O-2 (leading to H2O2) was demonstrated in comparision with other photoreductive conversions such as the reduction of polyoxometalate (POM -> POM-), hexavalent chromium (Cr-VI -> Cr-III), CCl4 (dechlorination), and protons (H-2 production). This study developed a simple method of efficient production of H2O2 using visible light, which could be utilized for a variety of applications that employ H2O2 as a solar fuel or a green oxidant. (C) 2017 Elsevier Inc. All rights reserved.
다수 무인기 화물 운송 시스템의 임무 할당을 위한 공동 구매 알고리듬
No full text학위논문(석사) - 한국과학기술원 : 항공우주공학전공, 2014.2, [ vi, 68 p. ]A rotary wing aircraft, so that can be vertical takeoff and landing, it is suitable for the transporting goods in the downtown area and the mountainous area. In particular, a plurality of aircraft are possible to transport a freight, which exceeds the load capacity of each aircraft, in slung load form. As the use of un-manned aircraft is getting diverse, and private usage of UAV increases, the research for the multi-agents task assignment of unmanned cargo transport system is required.
This work specifies the task unit as a cargo transport by defining the task tuples, and formulate the multiple cooperative task assignment (MCTA) problem as a utility optimal problem. In addition, the thesis expressed the task assignment of the multiple agents load transport system as the MCTA problem that the initiation of the task is constrained by the critical agents.
For the task assignment of the multiple agents load transport system, this thesis proposed a group buying algorithm based on the sequential greedy algorithm. The group buying algorithm has a particular property, which is different from the original sequential greedy algorithm, of being more robust to the impact of the winner’s curse by running the market to maximize the utilities of the critical agents of each task. For the two common problem that can be held in the group buying algorithm, the incentive strategy for resolving the over concentration problem and the additional algorithm for resolving the cross deployment are consid-ered.
To obtain the optimal task assignment for the performance analysis, a complete enumeration method that visits all feasible solution and finds the optimal solution is made. Then the cross deployment problem that can occurs when the MCTA is constrained on the initiation of the task by the critical agent is defined mathematically, and proposed an algorithm that can inspect whether the given path is cross-deployed or not.
The author conducted the Monte-Carlo Simulation and the analy...한국과학기술원 : 항공우주공학전공
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
예측 기반 종말속도제어 유도 기법
No full text학위논문(박사) - 한국과학기술원 : 항공우주공학과, 2019.2,[vi, 100 p. :]This dissertation addresses the prediction based terminal velocity control guidance law which can control the terminal velocity of an aerial vehicle. Terminal velocity control problem is formulated into the two-point boundary value problem, and the guidance command is given by the acceleration command. This dissertation proposes a guidance law that satisfies the terminal velocity constraint through the pitch plane maneuver. It is inspired from the augmented polynomial guidance that can adjust the trajectory by changing a guidance constant without violating any other constraints. A terminal speed prediction method is provided that approximates the flight path into a polynomial function with the downrange-to-go terms to the power of (n+2), (m+2), 2, and 1, and a constant term. It assumes the acceleration command does not saturated along the path, then it is possible to integrate just velocity along the downrange to go. The proposed method keeps finding the guidance parameter updating periodically and controlling the terminal speed using the terminal speed prediction method. The acceleration to follow a parameterized curve is derived, and the polynomial approximating the path is employed to calculate the acceleration command in the terminal speed prediction process. Three strategies are proposed to determine the guidance parameter of APG according to the flight phase: First, it employs some numerical root finding algorithms to find the parameter. Second, the parameter is frequently updated using the predicted terminal velocity sensitivity and the slope of sensitivity. Third, if the terminal speed is unreachable, the guidance parameter is decided to maximize the terminal speed. Throughout the simulations, the sensitivity studies to the initial condition is studied in various conditions, and verified the terminal speed prediction accuracy. Finally it is demonstrated that the proposed guidance law can control the terminal speed.한국과학기술원 :항공우주공학과
Variations 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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
High Altitude Long Endurance UAV Longitudinal Controller Design using Co-Evolutionary Augmented Lagrangian Method
No full text
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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