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SIM JAE HOON
No full text학위논문(석사)----아주대학교 산업대학원 :기계공학과,2007. 8경유는 압력이 가해지는 연소실에서 점화를 좋게 하기 위하여 여러 종류의 왁스와 파라핀을 포함하고 있다. 이러한 종류의 구성물은 저온 시에 쉽게 고형화 되고 연료필터 내부의 엘리멘트의 작은 구멍을 막음으로써 연료의 흐름을 방해하여 고압펌프가 연료를 인젝터까지 보내는 것을 어렵게 한다. CRDI 엔진과 같은 경우에 연료인 경유를 이용 고압펌프 등과 같은 구성부품의 윤활작용도 하기 때문에 연료의 흐름이 방해되어 필요한 양의 연료가 공급이 되지 않는다면 심각한 손상을 입을 수 있다. 플런저와 바렐의 사이의 간격은 매우 작기 때문에 연료의 흐름이 없는 건조한 상태로 서로 접촉을 하게 된다면 펌프의 작동에 문제가 생길 것이다. 이러한 문제를 해소하기 위하여 연료필터에는 여러 종류의 히터를 사용하고 있다. 이번 실험에서는 현재 사용하는 다양한 종류의 히터 중 몇 가지를 선정하여 평가 하고, 추가로 새로운 콘셉트를 적용한 사양도 함께 평가를 하여 동절기와 같은 저온환경에서 연료의 흐름 장애를 극복할 수 있는 최선의 방법을 찾고자 하였다.1. 서론 ………………………………………………………………………… 1
1.1 연구배경 ………………………………………………………………… 1
1.2 연구목적과 방법 ……………………………………………………… 4
2. 디젤 연료 필터의 개요 …………………………………………………… 5
2.1 디젤엔진의 연료 공급 시스템에서의 연료 필터의 구성과 기능 … 5
2.2 연료 필터에서의 연료 가열 방법 …………………………………… 9
2.2.1 전기식 연료 히터 …………………………………………………… 9
가) PTC 히터 …………………………………………………………… 10
나) 저항체 히터 ………………………………………………………… 14
2.2.2 Coolant 히터 ………………………………………………………… 16
2.2.3 순환연료 히터 ………………………………………………………… 17
3. 실험장치 및 방법 ………………………………………………………… 18
3.1 PTC 방식 히터와 저항체 방식 히터의 성능 실험 결과 ………… 18
3.1.1 유체의 흐름이 없고 저온시 히터의 작동에 따른 온도 변화 ……18
1) PTC 방식 히터 ………………………………………………………… 19
2) 저항체 방식 히터 ……………………………………………………… 20
3) 실험결과 비교 ………………………………………………………… 22
3.1.2 저온 상태에서 히터 작동시 연료의 질에 따른 유체의 흐름 … 23
1) 지방 주유소 경유 …………………………………………………… 25
2) H사 연구소 사용 경유 ……………………………………………… 26
3) 실험결과의 비교 ……………………………………………………… 27
3.1.3 등유를 사용하는 히터의 성능 실험 ……………………………… 28
1) PTC 방식 히터 ……………………………………………………… 28
2) 저항체 방식 히터 ……………………………………………………… 29
3) 실험결과 비교 ………………………………………………………… 29
3.2 콘셉트 적용 시작품 히터제작 성능실험 결과 ……………………… 30
1) PTC Pill 2개 사용 …………………………………………………… 31
2) PTC Pill 3개 사용 …………………………………………………… 33
3) 실험결과 비교 ………………………………………………………… 33
4. 결과 및 고찰 ……………………………………………………………… 34
4.1 각 히터의 성능실험 결과 ……………………………………………… 34
5. 결론 ………………………………………………………………………… 37
참고문헌 ………………………………………………………………………… 39Maste
A New Stapes-Head Coupler for the Vibrant Soundbridge System
Get PDFIntroduction: The Vibrant Soundbridge (MED-EL Medical Electronics, Austria) is an active middle ear implant with a floating mass transducer (FMT) for patients with conductive, sensorineural, or mixed hearing loss. While the FMT is vertically aligned above the stapes head (SH) with the current Vibroplasty Clip coupler (MED-EL Medical Electronics), the new SH coupler was developed to mount the FMT on the inferior side of the stapes and to fit in the reduced middle ear space after canal-wall-down mastoidectomy. Methods: Using 11 human cadaveric temporal bones (TBs), placements of the new SH couplers on the stapes were examined, and effective stimuli to the cochlea were evaluated by measuring piston-like motion of the stapes footplate with a current of 1 mA on the FMT. The results were assessed in comparison with the Vibroplasty Clip coupler. Results: The new SH coupler showed perfect coupling on the stapes in 9 out of 11 TBs. A small gap between the SH and the plate of the connection link part was unavoidable in 2 TBs but had negligible effect on vibrational motion of the stapes. Vibrational motion of the stapes with the new SH coupler was reduced at frequencies above 3 kHz compared to the corresponding motion with the current Vibroplasty Clip coupler, but the relative attenuation over all 11 cadaveric temporal bones was <10 dB. Conclusions: The new SH coupler provides an alternative with more stable fixation when placement of the current Vibroplasty Clip coupler is limited due to insufficient space after canal-wall-down mastoidectomy, while still delivering effective stimuli to the cochlea
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“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
Get PDFWe 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
Analysis of dynamic characteristics of three-wheeled vehicle considering mass center shift rollover prevention control
No full text학위논문(석사) - 한국과학기술원 : 기계공학전공, 2014.2, [ ii, 64 p. ]세바퀴 자동차는 기존의 자동차와 비교하여 여러 장점을 가지고 있어서 미래형 교통수단으로 각광받고 있다. 샤시 구조가 작기 때문에 제작비용이 적게 들고 연비 효율 측면에서 유리하다. 하지만 전복 위험성과 같은 안정성 문제를 가지고 있다. 게다가 만약 세바퀴 자동차가 개인형 자동차의 사이즈에 맞게 더욱더 가벼워 질 경우 많은 문제를 야기할 수 있다. 작은 무게 때문에, 무거운 사람이나 무거운 짐은 자동차의 무게중심을 변하게 하고, 이는 세바퀴 자동차의 안정성에 큰 영향을 미칠 수 있다. 따라서 본 연구의 목표는 세바퀴 자동차의 동적 특성을 분석하고 안전을 보장하기 위한 전복방지 제어기를 설계하는 것이다. 우리는 이전에 연구된 앞바퀴는 스키드스티어링을 하고 뒷바퀴는 아크만 스티어링을 하는 자동차를 목표로 하였다. 또한 기존의 모델을 질량중심 변화를 고려하여 수정하였고 그 동적 특성이 분석되었다. 각 변수가 얼만큼 동적 특성에 변화를 미치는지를 연구하기 위하여 민감도 분석이 수행되었다.
자동차의 롤 안정성을 향상시키기 위하여 전복방지제어기가 설계되었다. 이를 위해서는 전복현상이 일어나기 전에 전복을 예측하는 것이 중요하다. 이 때문에 많은 연구자들이 전복 인자를 개발하였다. 우리는 전복인자들을 질량중심이 변하였을 경우에 대하여 수정하였고 이 성능을 시뮬레이션을 통하여 확인하였다. 또한 전복방지제어를 하기 위하여 제동력을 이용하여 자동차의 앞방향 속도를 줄였고, 시뮬레이션을 통하여 또한 그 성능을 확인하였다.한국과학기술원 : 기계공학전공
강한 스핀-궤도 결합을 갖는 강상관 물질에 대한 제일원리 기반 방법의 개발 및 응용
No full text학위논문(박사) - 한국과학기술원 : 물리학과, 2018.8,[v, 62 p. :]The first-principles studies within the density functional theory (DFT) framework have been successfully applied to a wide range of materials in condensed matter physics. Despite the success of DFT, there exists a class of materials for which DFT fails to describe, even qualitatively. Most of these materials contain localized d and f electrons with strong Coulomb interactions. Beyond DFT methods are essential to account for electron-electron interactions of the localized orbitals correctly. DFT+U and DFT+dynamical mean field theory (DMFT) are widely used. In the +U and +DMFT frameworks, Kohn-Sham Hamiltonian is corrected by the local self-energy terms in static and dynamical mean-field level, respectively.
In this thesis, we present the theoretical backgrounds, practical implementations, and its applications of the first-principles based methods. Focusing on the metal-insulator transition for strongly correlated materials, we analyze the role of the spin-orbit coupling and degeneracy of the bands near the Fermi level. Firstly, for systematic study, we have implemented full band DFT+DMFT based on OpenMX, a non-orthogonal pseudo-atomic orbital basis DFT code. While the different projection methods are tested, the natural atomic orbital orthogonalization is stable to basis set change. We also have developed new analytic continuation methods, so-called maximum quantum entropy method. This continuation method is developed to obtain spectral functions for the case of multi-band Hamiltonian and real material research.
Second, We also suggest the newly developed method and physical concept based on first-principles calculation. These methods are introduced to compare the calculation results with the experimental data and to provide useful insights to understand the results, e.g., metal-insulator transition. The DFT+U and +DMFT calculations are performed to apply our method to real materials. The calculation results for iridate and other transition-metal oxides are presented. The calculation results for , a prototype Mott insulator, and superlattice shows the importance of the interplay between the spin-orbit coupling and electronic correlations for the 5d orbitals. In this regards, we applied a simple technique to calculate spin-orbit coupling and branching ratio measured in x-ray absorption spectroscopy. Calculated and branching ratio of the several different iridates are in good agreement with experimental data. We also suggest a way to quantify the `effective degeneracy' relevant to metal-insulator transition by introducing entropy-like terms. Calculating effective degeneracy, we show that the degeneracy lifting due to the spin-orbit coupling plays a central role in stabilizing `spin-orbit coupling assisted Mott insulator'. This quantified `effective degeneracy' concept is applied to not only 5d iridate but also 3d titanates, namely superlattice, suggesting a novel `degeneracy control' metal-insulator transition.한국과학기술원 :물리학과
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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