• 한국도로학회논문집
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• 제19권6호
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• pp.165-173
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• 2017

PURPOSES : The current practice in car headlight visibility performance evaluation is based on the luminous intensity and illuminance of headlight. Such practice can be inappropriate from a visibility point of view where visibility indicates abilities to perceive an object ahead on the road. This study aimed at evaluating the appropriateness of current headlight evaluation method. METHODS : This study measured the luminance of object and road surface at unlit roadways. The variables were measured by vehicle type and by headlight lamp type. Based on the measurements, the distance where drivers can perceive an object ahead was calculated and then compared against such distance obtained by conventional visibility performance evaluation. RESULTS : The evaluation method based on illuminance of headlight is not appropriate when viewed from the visibility concept that is based on object-perceivable distance. Further, the results indicated a shorter object-perceiving distance even when road surface luminance is higher, thereby suggesting that illuminance of headlight and luminance of road surface are not the representative indices of nighttime visibility. CONCLUSIONS : Considering that this study utilized limited vehicle types and that road surface (background) luminance can vary depending on the characteristics of the given road surface, it would likely go too far to argue that this study's visibility performance evaluation results can get generalized to other conditions. Regardless, there is little doubt that the current performance evaluation criterion which is based on illuminance, is unreasonable. There should be future endeavors on the current subject which will need to explore study conditions further, under which more experiments should be conducted and effective methodologies developed for evaluating automotive headlight visibility performance. Needs are recognized particularly in the development of headlight visibility performance evaluation methodology which will take into account road surface (background) luminance and luminance contrast from various perspectives as the former indicates the driver's perception of the front road alignment and the latter being indicative of object perception performance.

• 설비공학논문집
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• 제9권4호
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• pp.552-560
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• 1997

Analysis is performed to determine the optimal lengths or cross-sectional areas of refrigerator-cooled current leads that can be applied to the conduction-cooled superconducting systems. The binary current lead is composed of the series combination of a normal metal at the upper(warm) part and a high $T_c$ superconductor(HTS) at the lower(cold) part. The heat conduction toward the cold end of HTS part constitutes a major refrigeration load. In addition, the joint between the parts should be cooled by a refrigerator in order to reduce the load at the low end and maintain the HTS part in a superconducting state. The sum of the work inputs required for the two refrigeration loads needs to be minimized for an optimal operation. In this design, three simple models that depict the refrigeration performance as functions of cooling temperature are developed based on some of the existing refrigerators. By solving one-dimensional conduction equation that take into account the temperature-dependent properties of the materials, the refrigeration works are numerically calculated for various values of the joint temperature and the sizes of two parts. The results show that for given size of HTS, there exist the optimal values for the joint temperature and the size of the normal metal. It is also found that the refrigeration work decreases as the length of HTS increases and that the optimal size of normal metal is quite independent of the size of HTS. For a given length of HTS, there is an optimal cross-sectional area and it increases as the length increases. The dependence of the optimal sizes on the refrigerator models employed are presented for 1kA leads.

• 국제지역연구
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• 제13권1호
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• pp.39-51
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• 2009

물가상승률과 실업률을 합한 수치를 미저리 지수(misery index)라고 칭한다. 미저리 지수가 높을수록 국민경제의 성과는 저조한 것을 나타낸다. Lee and Cheong (2007)은 미저리 지수에 경상수지의 GDP대비 비율(%)을 합한 수치를 개방 미저리 지수로 정의하였으며, 동 지수가 개방도가 높은 경제의 성과를 잘 나타낼 수 있다고 주장하였다. 본 논문은 미국에서 개방 미저리 지수가 증가하는 시기는 미국경제의 성과가 저조한 때와 일치한다는 것을 보인다. 특히 2008년에 시작된 현재의 경제위기 이전에 약 10년간 지속적으로 개방 미저리 지수가 상승하는 추세임을 보여준다. 이는, 미국의 현 경제위기에 앞서 지난 10여년간 미국경제의 내부 및 외부불균형이 누적되어 왔음을 보여주는 것이다. 본 논문은 이와 같이 최근의 증가하는 추세의 개방 미저리 지수를 현재의 경제위기의 전조로 해석한다.

• Journal of Power Electronics
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• 제14권1호
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• pp.92-104
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• 2014

To insure stable operation and eliminate twice torque ripple, a topology for a six phase permanent magnet synchronous generator (SP-PMSG) with a neutral point connected together was analyzed in this paper. By adopting an extended transformation matrix, the mathematic model of the space vector control was established. The voltage and torque equations were deduced while considering the third harmonic flux and inductance. In addition, the suppression third harmonic method and the closed loop control strategy were proposed. A comparison analysis indicates that the cooper loss minimum method and the current magnitude minimum method can meet different application requirements. The voltage compensation amount for each of the methods was deduced which also takes into account the third harmonic effect. A simulation and experimental result comparison validates the consistency through theoretical derivation. It can be seen that all of the two control strategies can meet the requirements of post-fault.

• 대한교통학회:학술대회논문집
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• 대한교통학회 1999년도 제36회 학술발표회논문집
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• pp.47-52
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• 1999

The methods currently in use to evaluate traffic impacts on the transportation network involve some fundamental shortcomings. First, the methodss do not properly take into account regional and local traffic impacts on the transportation network simultaneously. Second, temporal distribution of traffic, a major contributor to transportation problems, is not accurately accounted for. Third, traffic impact studies require costly and labor-intensive efforts to collect necessary data and to establish to collect necessary data and to establish traffic impact models. In this research, a new method called AMIS is developed for congestion management, access control, and impact simulation to overcome the shortcomings involved in the current methods. The new method is designed for a variety of scenarios such as access management strategies, land use policies, traffic impacts, and other congestion management strategies. This method can effectively be used, with little modification, anywhere in the United States. It is an improvement over the current traffic impact simulation methods that produces more reliable and accurate traffic impact estimates. The case studies conducted in this research have offered evidence that the new method, AMIS, is a credible congestion management tool. Most importantly, a case study presented in this paper illustrates how the new method can be used not only to estimate regional and local impacts of alternate supply management policies in the course of a day, but virtually on an hour-by-hour basis.

• 한국IT서비스학회지
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• 제19권1호
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• pp.113-127
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• 2020

Current web accessibility checks and automatic assessments have been pointed out that the assessment items and scores are evaluated from the developer's point of view rather than from the user's one. In addition, although most of the grades of an automatic assessment on the public web sites are excellent because they are built in accordance with the web accessibility development guidelines, not a few web sites shows relatively low grades in evaluating their usability test made by those users. Taking into account the inadequacy of these web accessibility assessments, this study has identified the differences between the grades of usability evaluations and automatic evaluations for people with low vision and analyzed the major factors affecting web accessibility usability evaluations using Repertory Grid Techniques. Also, the Hard Laddering method of the Means-End Chain theory was adopted to visualize the relationship between Attributes-Conferences-Value and a hierarchical value system analysis based on FGI(Focused Group Interview) to people with the low vision. This study proposed the measures to improve the current web accessibility automatic assessment allocation, expert evaluation criteria, and user task assessment. In particular, it is a web accessibility user evaluation model that can consider the web accessibility quality certification criteria and user review assessment by directly analyzing the user cognitive structure and value system. This study is expected to be useful as a research to enhance the quality of web accessibility assessment.

• 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
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• 제25권4호
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• pp.93-104
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• 2019

Purpose: To establish the building guidelines and to analyze the function of Regional Public Hospitals, the survey was conducted primarily on the current status focusing on the location and relationship of the department, area composition ratio, area per bed, and area per operating room. Methods: The research methods of this paper are as follows. 1) A literature survey on the function of the operating and related departments, 2) A drawing analysis for spatial composition and net area calculation. Results: The area of the Operation Department in the Regional Public Hospitals with 200 to 300 beds are as follows. Area ratio: 3.35%, area per Bed: 2.53㎡/bed, the number of beds per operating room: 64.37bed, area per operating room: 146.46㎡/n, area per operating room by plan type: integration corridor 133.84㎡/n, separation corridor 184.82㎡/n. Implications: This paper analyzed data on the current state of Operation Departments for setting up the function and role for the Regional Public Hospital. In the future, it is also required to provide size that takes into account user behavior and the user's psychological aspect in order to suggest appropriate area.

• 한국소음진동공학회논문집
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• 제27권1호
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• pp.20-27
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• 2017

This study investigated the problems in current practice of drive-train resonance analysis procedure and suggested solutions. The first problem is the resonance occurrence at the un-identified resonance point by the current practice, as for a solution the force spectrum analysis for each critical force transmitting component was suggested. The second one is the inaccurate estimation of potential resonance point in eigenfrequency analysis because of the non-consideration about the eigenfrequency dependency on rotor-speed, the fine linearization at each rotor speed point all over operational range was proposed to account for the affection. Lastly the insufficient time for resonance activation under run-up simulation condition was recognized as a problem in resonance load increasing analysis, as an alternative, steady state condition was suggested to estimate the maximum load increasing level.

• Earthquakes and Structures
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• 제10권4호
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• pp.849-865
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• 2016

Beside the invaluable advancements in constructing more secure buildings, the post-earthquake inspections have reported considerable damages. In other words, the modern buildings satisfactorily decrease fatalities but the monetary impacts still mostly remain an unsolved concern of the stakeholders, the insurance companies and society together. Therefore, the fundamental target of the researches shifted from current force-based seismic design regulations to the Performance-Based earthquake engineering (PBEE). At the moment, some probabilistic approaches, such as PEER framework have been developed to predict the performance of building at any desired hazard levels. These procedures are so time-consuming, to which many details are needed to be assigned. It causes their usage to be limited. On that account, developing more straightforward methods seems indispensable. The main objective of the present paper is to adapt an equivalent static method in different damage states. Consequently, constant damage spectrums corresponding to different limit states, soil types, ductility and fundamental periods are plotted and tri-linear formulas are proposed for further applications. Moreover, the sensitivity of outcomes to the employed hysteresis model, ductility, viscous damping and site soil type is investigated. Finally, a case study building with moment-resisting R.C. frame is evaluated based on the both of new and current methods to ensure applicability of the proposed method.

• Structural Engineering and Mechanics
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• 제68권2호
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• pp.171-182
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• 2018

For the first time, nonlocal damped vibration and buckling analyses of arbitrary tapered bidirectional functionally graded solid circular nano-plate (BDFGSCNP) are presented by employing modified spectral Ritz method. The energy method based on Love-Kirchhoff plate theory assumptions is applied to derive neutral equilibrium equation. The Eringen's nonlocal continuum theory is taken into account to capture small-scale effects. The characteristic equations and corresponding first mode shapes are calculated by using a novel modified basis in spectral Ritz method. The modified basis is in terms of orthogonal shifted Chebyshev polynomials of the first kind to avoid employing adhesive functions in the spectral Ritz method. The fast convergence and compatibility with various conditions are advantages of the modified spectral Ritz method. A more accurate multivariable function is used to model two-directional variations of elasticity modulus and mass density. The effects of nanoscale, in-plane pre-load, distributed dashpot, arbitrary tapering, pinned and clamped boundary conditions on natural frequencies and buckling loads are investigated. Observing an excellent agreement between results of current work and outcomes of previously published works in literature, indicates the results' accuracy in current work.