• 대한금속재료학회지
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• 제47권8호
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• pp.482-487
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• 2009

In order to investigate the effects of intermediate heat treatment between cold rolling passes on the hardness and corrosion properties of a Zr alloy incorporating Nb (Zr-1.49Nb-0.38Sn-0.20Fe-0.11Cr) strip, three different intermediate heat treatment processes ($580^{\circ}C{\times}4hrs$, $600^{\circ}C{\times}2hrs$ and $620^{\circ}{\times}1hrs$) were designed based on a recrystallization map and an accumulated annealing parameter. Test samples from the different processes were investigated by a hardness test, corrosion test, and microstructure analysis and appropriate heat-treatment conditions were thereupon proposed. The sample subjected to an intermediate heat treatment of $580^{\circ}C{\times}4hrs$ was harder than that undergoing $600^{\circ}C{\times}2hrs$ and $620^{\circ}C{\times}1hr$ while the corrosion resistance of the sample that received an intermediate heat treatment of $580^{\circ}C{\times}4hrs$ was superior to that of the other specimens. Considering the trade-off of hardness and corrosion resistance, an intermediate heat treatment process of $600^{\circ}C{\times}2hrs$ is proposed to improve the manufacturing process of the alloy strip.

• 한국시뮬레이션학회논문지
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• 제30권1호
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• pp.65-73
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• 2021

일반적으로 유도탄 정비의 핵심적인 군수지원요소는 수리부속 재고수량과 정비 소요시간이며, 본 연구는 정비 소요시간과 가동률 간의 상관관계 영향을 분석하였다. 본 연구의 목적은 하푼 유도탄 정비인력 기술수준을 고려하여 정비팀을 분류하고 정비 소요시간 변화에 따라 유도탄 가동률에 미치는 영향을 분석하여 정량적인 분석 결과를 제시하는 것이다. 먼저, 하푼 유도탄에 대한 정비데이터와 정비 소요시간을 측정한 데이터를 바탕으로 실제 유도탄 정비절차와 유사한 시뮬레이션 모델을 구성하고 결과값을 분석하였다. 정비인력 기술수준을 고려하여 정비팀을 구성하였을 때, 전문성이 높은 팀일수록 정비 소요시간이 단축되었으며 가동률에 미치는 영향이 크다는 것을 시뮬레이션 결과값을 통해 확인할 수 있었다. 이러한 정량적 분석결과값은 유도탄 정비인력 구성 및 운영방안에 대한 정책결정에 기여할 수 있을 것이다.

• 한국지진공학회논문집
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• 제25권2호
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• pp.59-69
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• 2021

Historical records of earthquakes are generally used as a basis to extrapolate the instrumental earthquake catalog in time and space during the probabilistic seismic hazard analysis (PSHA). However, the historical catalogs' input parameters determined through historical descriptions rather than any quantitative measurements are accompanied by considerable uncertainty in PSHA. Therefore, quantitative assessment to verify the historical earthquake parameters is essential for refining the reliability of PSHA. This study presents an approach and its application to constrain reliable ranges of the magnitude and corresponding epicenter of historical earthquakes. First, ranges rather than specific values of ground motion intensities are estimated at multiple locations with distances between each other for selected historical earthquakes by reviewing observed co-seismic natural phenomena, structural damage levels, or felt areas described in their historical records. Based on specific objective criteria, this study selects only one earthquake (July 24, 1643), which is potentially one of the largest historical earthquakes. Then, ground motion simulations are performed for sufficiently broadly distributed epicenters, with a regular grid to prevent one from relying on strong assumptions. Calculated peak ground accelerations and velocities in areas with the historical descriptions on corresponding earthquakes are converted to intensities with an empirical ground motion-intensity conversion equation to compare them with historical descriptions. For the ground motion simulation, ground motion prediction equations and a frequency-wavenumber method are used to consider the effects of possible source mechanisms and stress drop. From these quantitative calculations, reliable ranges of epicenters and magnitudes and the trade-off between them are inferred for the earthquake that can conservatively match the upper and lower boundaries of intensity values from historical descriptions.

• 산업경영시스템학회지
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• 제45권4호
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• pp.109-117
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• 2022

Most of real-world decision-making processes are used to optimize problems with many objectives of conflicting. Since the betterment of some objectives requires the sacrifice of other objectives, different objectives may not be optimized simultaneously. Consequently, Pareto solution can be considered as candidates of a solution with respect to a multi-objective optimization (MOP). Such problem involves two main procedures: finding Pareto solutions and choosing one solution among them. So-called multi-objective genetic algorithms have been proved to be effective for finding many Pareto solutions. In this study, we suggest a fitness evaluation method based on the achievement level up to the target value to improve the solution search performance by the multi-objective genetic algorithm. Using numerical examples and benchmark problems, we compare the proposed method, which considers the achievement level, with conventional Pareto ranking methods. Based on the comparison, it is verified that the proposed method can generate a highly convergent and diverse solution set. Most of the existing multi-objective genetic algorithms mainly focus on finding solutions, however the ultimate aim of MOP is not to find the entire set of Pareto solutions, but to choose one solution among many obtained solutions. We further propose an interactive decision-making process based on a visualized trade-off analysis that incorporates the satisfaction of the decision maker. The findings of the study will serve as a reference to build a multi-objective decision-making support system.

• 국제학술발표논문집
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• The 5th International Conference on Construction Engineering and Project Management
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• pp.252-259
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• 2013

Building Information Modeling (BIM) is utilizing CAD technology in a way that ultimately ties all the components of a building together as objects imbedded with information, and has been changing the way we design and build over the last 20-30 years. In Polytechnic Institute of NYU, there are four BIM courses offered which provide students with different levels of knowledge regarding BIM Technique, BIM Standards, BIM Guideline and Roadmap for Private and Public Implementation, BIM Application in Real Projects, the Cooperation of BIM and IPD for Public Works in New York City. With advanced BIM technology, BIM's integration into the construction process and its incorporation into project delivery systems, especially Integrated Project Delivery (IPD) are the bridges between technology, industry and research. This paper presents an integrated BIM curriculum with three modules: 1) BIM functions and Bid Preparation; 2) Time-Cost Trade-off Analysis; and 3) Problems Solving in BIM/IPD Environment. In this project-based curriculum developed by the common efforts of academia, public agency and industry, the objectives are: (1) to provide the information and skills needed to successfully implement BIM into the construction phase; (2) to identify BIM's role in construction and the project delivery system; (3) to develop a module in conjunction with leading BIM into project delivery system, particularly coordination between BIM and IPD; (4) to connect technology and research into industry. The course assessment was conducted and the results indicate that it is a successful reform in construction management education.

• International Journal of Internet, Broadcasting and Communication
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• 제16권1호
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• pp.17-28
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• 2024

As listed as one of the most important requirements for Post-Quantum Cryptography standardization process by National Institute of Standards and Technology, the resistance to various side-channel attacks is considered very critical in deploying cryptosystems in practice. In fact, cryptosystems can easily be broken by side-channel attacks, even though they are considered to be secure in the mathematical point of view. The timing attack(TA) and the simple power analysis attack(SPA) are such side-channel attack methods which can reveal sensitive information by analyzing the timing behavior or the power consumption pattern of cryptographic operations. Thus, appropriate measures against such attacks must carefully be considered in the early stage of cryptosystem's implementation process. The Montgomery multiplier is a commonly used and classical gadget in implementing big-number-based cryptosystems including RSA and ECC. And, as recently proposed as an alternative of building blocks for implementing post quantum cryptography such as lattice-based cryptography, the big-number multiplier including the Montgomery multiplier still plays a role in modern cryptography. However, in spite of its effectiveness and wide-adoption, the multiplier is known to be vulnerable to TA and SPA. And this paper proposes a new countermeasure for the Montgomery multiplier against TA and SPA. Briefly speaking, the new measure first represents a multiplication operand without 0 digits, so the resulting multiplication operation behaves in a very regular manner. Also, the new algorithm removes the extra final reduction (which is intrinsic to the modular multiplication) to make the resulting multiplier more timing-independent. Consequently, the resulting multiplier operates in constant time so that it totally removes any TA and SPA vulnerabilities. Since the proposed method can process multi bits at a time, implementers can also trade-off the performance with the resource usage to get desirable implementation characteristics.

• 산업경영시스템학회지
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• 제42권1호
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• pp.151-157
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• 2019

This study is about the process capability index (PCI). In this study, we introduce several indices including the index $C_{PR}$ and present the characteristics of the $C_{PR}$ as well as its validity. The difference between the other indices and the $C_{PR}$ is the way we use to estimate the standard deviation. Calculating the index, most indices use sample standard deviation while the index $C_{PR}$ uses range R. The sample standard deviation is generally a better estimator than the range R. But in the case of the panel process, the $C_{PR}$ has more consistency than the other indices at the point of non-conforming ratio which is an important term in quality control. The reason why the $C_{PR}$ using the range has better consistency is explained by introducing the concept of 'flatness ratio'. At least one million cells are present in one panel, so we can't inspect all of them. In estimating the PCI, it is necessary to consider the inspection cost together with the consistency. Even though we want smaller sample size at the point of inspection cost, the small sample size makes the PCI unreliable. There is 'trade off' between the inspection cost and the accuracy of the PCI. Therefore, we should obtain as large a sample size as possible under the allowed inspection cost. In order for $C_{PR}$ to be used throughout the industry, it is necessary to analyze the characteristics of the $C_{PR}$. Because the $C_{PR}$ is a kind of index including subgroup concept, the analysis should be done at the point of sample size of the subgroup. We present numerical analysis results of $C_{PR}$ by the data from the random number generating method. In this study, we also show the difference between the $C_{PR}$ using the range and the $C_P$ which is a representative index using the sample standard deviation. Regression analysis was used for the numerical analysis of the sample data. In addition, residual analysis and equal variance analysis was also conducted.

• 대한교통학회:학술대회논문집
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• 대한교통학회 1995년도 제27회 학술발표회
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• pp.3-32
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• 1995

The Highway Capacity Manual specifies procedures for evaluating intersection performance in terms of delay per vehicle. What is lacking in the current methodology is a comparable quantitative procedure for ass~ssing the safety-based level of service provided to motorists. The objective of the research described herein was to develop a computational procedure for evaluating the safety-based level of service of signalized intersections based on the relative hazard of alternative intersection designs and signal timing plans. Conflict opportunity models were developed for those crossing, diverging, and stopping maneuvers which are associated with left-turn and rear-end accidents. Safety¬based level-of-service criteria were then developed based on the distribution of conflict opportunities computed from the developed models. A case study evaluation of the level of service analysis methodology revealed that the developed safety-based criteria were not as sensitive to changes in prevailing traffic, roadway, and signal timing conditions as the traditional delay-based measure. However, the methodology did permit a quantitative assessment of the trade-off between delay reduction and safety improvement. The Highway Capacity Manual (HCM) specifies procedures for evaluating intersection performance in terms of a wide variety of prevailing conditions such as traffic composition, intersection geometry, traffic volumes, and signal timing (1). At the present time, however, performance is only measured in terms of delay per vehicle. This is a parameter which is widely accepted as a meaningful and useful indicator of the efficiency with which an intersection is serving traffic needs. What is lacking in the current methodology is a comparable quantitative procedure for assessing the safety-based level of service provided to motorists. For example, it is well¬known that the change from permissive to protected left-turn phasing can reduce left-turn accident frequency. However, the HCM only permits a quantitative assessment of the impact of this alternative phasing arrangement on vehicle delay. It is left to the engineer or planner to subjectively judge the level of safety benefits, and to evaluate the trade-off between the efficiency and safety consequences of the alternative phasing plans. Numerous examples of other geometric design and signal timing improvements could also be given. At present, the principal methods available to the practitioner for evaluating the relative safety at signalized intersections are: a) the application of engineering judgement, b) accident analyses, and c) traffic conflicts analysis. Reliance on engineering judgement has obvious limitations, especially when placed in the context of the elaborate HCM procedures for calculating delay. Accident analyses generally require some type of before-after comparison, either for the case study intersection or for a large set of similar intersections. In e.ither situation, there are problems associated with compensating for regression-to-the-mean phenomena (2), as well as obtaining an adequate sample size. Research has also pointed to potential bias caused by the way in which exposure to accidents is measured (3, 4). Because of the problems associated with traditional accident analyses, some have promoted the use of tqe traffic conflicts technique (5). However, this procedure also has shortcomings in that it.requires extensive field data collection and trained observers to identify the different types of conflicts occurring in the field. The objective of the research described herein was to develop a computational procedure for evaluating the safety-based level of service of signalized intersections that would be compatible and consistent with that presently found in the HCM for evaluating efficiency-based level of service as measured by delay per vehicle (6). The intent was not to develop a new set of accident prediction models, but to design a methodology to quantitatively predict the relative hazard of alternative intersection designs and signal timing plans.

• 한국경제지리학회지
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• 제12권4호
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• pp.507-520
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• 2009

본 연구는 저소득층을 대상으로 주거이동을 통한 주거 불안정성의 변화를 분석하는데 목적을 두었다. 주거 불안정성은 주택의 노후도, 이사 횟수, 무주택 기간, 주거비 지불능력 등의 지표를 통해 측정하였다. 분석 결과 빈곤층 가구 중 자가 가구는 노후화된 주택의 물리적인 측면에서, 차가 가구는 주거비 부담 측면에서 주거 불안정성이 매우 심각한 것으로 나타났다. 주거이동을 통한 주거 불안정성 변화 요인을 다항로짓모형을 이용하여 추정한 결과 차가 가구의 경우 여성 가구주에 비해 남성 가구주일수록, 소득이 높을수록, 연령이 높을수록 상향이동할 확률이 높아지는 것으로 나타났다. 거주지별로 보면 비수도권 시 도에 비해 광역시 및 수도권에서 자가 가구의 하향이동 비율이 높아지고 차가 가구의 상향이동 비율이 낮아지는 것으로 나타나 대도시에 거주하고 있는 빈곤층 가구들이 자력으로 주거 불안정성을 개선하는데 더 많은 어려움을 겪는 것으로 나타났다. 또한 이전 거주지의 일반주택비율이 높을수록 빈곤층 자가 가구와 차가 가구 모두 하향이동 확률이 낮아지며, 특히 차가 가구의 상향이동 비율이 높아지는 것으로 나타났다. 이는 빈곤층의 주거 불안정성 개선을 위해서는 아파트 위주의 주택공급보다 저소득층이 지불가능한 저렴한 주택 재고량을 유지시키는 정책이 더 효과적일 수 있음을 시사 해준다.

• 대한전자공학회논문지TC
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• 제37권2호
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• pp.32-45
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• 2000

본 논문에서는 CDMA 기지국에 선형 어레이 안테나를 적용하고자 할 경우, beamforming(BF) 성능과 관련된 두 가지 주요지표인 주 빔 폭의 좁은 정도를 지칭하는 direction selectivity와 사용자 신호의 방향추정 정확도가 BF의 SINR(Signal to interference and noise ratio) 성능에 미치는 영향과 이들 상호간의 관련성을 해석적으로 유도하였으며, 이를 수신 동작 시뮬레이션을 통하여 확인하였다. BF에 내포된 사용자 방향추정 기능과 간섭 사용자 신호 억제기능에 대하여 이들의 오차가 SINR에 미치는 영향을 구분하여 알아보기 위한 목적으로 방향추정 기능만을 포함한 steering BF 알고리즘과 간섭 사용자 전력을 최소화시키는 기능이 포함된 MVDR(Minimum variance distortionless response) BF 알고리즘을 대상으로 해석 및 동작 시뮬레이션을 수행하였다. 이 과정에 BF 알고리즘의 방향추정 기능에 직접적으로 오차를 유발하는 전파의 공간적 scattering 현상에 대한 모델을 새로이 제시하여 적용하도록 하였다. 본 연구의 결과, 종래의 군사적 목적의 BF와는 달리 셀룰러 CDMA 기지국에 array 안테나를 적용하고자 할 경우는 direction selectivity 및 사용자 방향추정 정확도를 향상시키고자 하는 것이 구현의 경제성 및 오차요인들에 대한 robustness 측면에서는 적합하지 않다는 것을 확인하였다. 이러한 특성은 BF 성능열화에는 크게 영향을 주지 않으면서 복잡도를 최소화하고 오차요인에 대한 robustness 특성을 갖는 경제적인 BF 알고리즘의 구현을 가능케 하여주는 중요한 사실이다. 이에 본 연구에서 제시한 해석의 결과는 셀룰러 CDMA기지국에 대한 BF 알고리즘 개발 및 적용의 설계지표로서 의미가 크다하겠다.