• Geomechanics and Engineering
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• 제22권4호
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• pp.339-348
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• 2020

The uncertain geotechnical properties of frozen soil are important evidence for the design, operation and maintenance of the frozen ground. The complex geological, environmental and physical effects can lead to the spatial variations of the frozen soil, and the uncertain mechanical properties are the key factors for the uncertain analysis of frozen soil engineering. In this study, the elastic modulus, strength and Poisson ratio of warm frozen soil were measured, and the statistical characteristics under different temperature conditions are obtained. The autocorrelation distance (ACD) and autocorrelation function (ACF) of uncertain mechanical properties are estimated by random field (RF) method. The results show that the mean elastic modulus and mean strength decrease with the increase of temperature while the mean Poisson ratio increases with the increase of temperature. The average values of the ACD for the elastic modulus, strength and Poisson ratio are 0.64m, 0.53m and 0.48m, respectively. The standard deviation of the ACD for the elastic modulus, strength and Poisson ratio are 0.03m, 0.07m and 0.03m, respectively. The ACFs of elastic modulus, strength and Poisson ratio decrease with the increase of ratio of local average distance and scale of fluctuation. The ACF of uncertain mechanical properties is different when the temperature is different. This study can improve our understanding of the spatial autocorrelation variations of uncertain geotechnical properties and provide a basis and reference for the uncertain settlement analysis of frozen soil foundation.

• 한국산학기술학회논문지
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• 제9권2호
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• pp.370-378
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• 2008

공인전자문서보관소는 전자문서 보관의 법적 효력을 부여해 문서를 안전하게 보관하고, 전자문서의 내용과 송수신 여부 등을 증명해 주는 신뢰할 수 있는 제3의 기관을 말한다. 본 논문에서는 공인전자문서보관소 구축 핵심기능인 송수신 보안 기능에 초점을 맞추고 있으며, 공인전자문서보관소 업무 서버와 이용자간에 각 시스템간의 데이터 송수신시 안전하게 메시지를 보낼 수 있도록 공개키를 이용한 암호화 시스템을 제안 및 구현하였다. ITU-T의 X.509 기본 원칙을 준수하며, 대량의 데이터를 속도 향상을 위해 대칭키 암호화 알고리즘을 사용하였으며, 여기에 사용된 키만을 개인키로 암호화 시켰으며, 데이터의 무결성을 위해 메시지를 전자서명을 통해 수정하는 것을 방지하였다. 또한 시스템간의 인증을 하기 위해 인증서를 통해 서로 인증할 수 있도록 하였다.

• 대한지역사회영양학회지
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• 제18권2호
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• pp.154-164
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• 2013

The objectives of this study were to assign reasonability to importance of weight selection issue in key performance indicator for performance evaluation of Centers for Child-care Foodservice Management (CCFSM) developed by using Balanced Scorecard (BSC), to draw key performance indicator (KPI) by perspective and to analyze differences in recognition on importance. From September 25 to October 9, 2012, we conducted a questionnaire-based study via e-mail, targeting chiefs and team leaders of nationwide 21 CCFSMs (43 persons), officials of local governments where CCFSM was established (21 persons), officials of Korea Food and Drug Administration (2 persons) and foodservice management experts (27 persons) in order to estimate the relative importance on 4 perspectives and 14 KPIs and analyzed its results by using 61 collected data. The results showed that relative importance of perspectives was estimated in order of importance as follows: business performance (0.3519), customer (0.3393), resource (0.1557), learning and growth (0.1531). Relative importance of KPIs was in order of importance as follows: Evaluation of sanitary management level in child-care foodservice facilities (0.1327), Level of customer recognition and behavior improvement (0.1153), performances of round visiting inspection on foodservice, sanitary, safety management, and foodservice consulting (0.0913). Our results showed that the recognition differences exist on the relative importance of perspectives and KPIs between officials of CCFSM, KFDA, local government and foodservice management experts. These observations will form the basis for developing evaluation systems, and it is considered that performance indicators developed on this basis will suggest direction of operation which CCFSM will have to perform.

• 사물인터넷융복합논문지
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• 제6권2호
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• pp.25-29
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• 2020

타원곡선 암호 알고리즘은 RSA 공개키 알고리즘에 비해 짧은 키의 길이와 적은 통신 부하 때문에 IoT 환경에서 인증용으로 많이 사용되고 있다. 타원곡선 암호 알고리즘의 핵심연산인 스칼라 곱셈이 안전하게 구현되지 않으면, 공격자가 단순 전력분석이나 차분 전력분석을 사용하여 비밀 키를 찾을 수 있다. 본 논문에서는 스칼라 난수화와 타원곡선점 가리기를 함께 적용하고, 연산의 효율성이 크게 떨어지지 않으며 전력분석 공격법에 대응하는 결합 난수 타원곡선 스칼라 알고리즘을 제안한다. 난수 r과 랜덤 타원곡선 점 R에 대해 변형된 Shamir의 두 배 사다리 알고리즘을 사용하여 타원곡선 스칼라 곱셈 kP = u(P+R)-vR을 계산한다. 여기에서 위수 n=2^l±c일 때, 2^lP=∓cP를 이용하여 l+20 비트 정도의 u≡rn+k(modn)과 ν≡rn-k(modn)를 구한다.

• Structural Engineering and Mechanics
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• 제66권1호
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• pp.15-25
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• 2018

Post-construction subgrade settlement especially differential settlement, has become a key issue in construction and operation of non-ballasted track on high-speed railway soil subgrade, which may also affect the dynamic performance of passing trains. To estimate the effect of differential subgrade settlement on the mechanical behaviors of the vehicle-slab track system, a detailed model considering nonlinear subgrade support and initial track state due to track self-weight is developed. Accordingly, analysis aiming at a typical high-speed vehicle coupled with a deteriorated slab track owing to differential subgrade settlement is carried out, in terms of two aspects: (i) determination of an initial mapping relationship between subgrade settlement and track deflections as well as contact state between track and subgrade based on a semi-analytical method; (ii) simulation of dynamic performance of the coupled system by employing a time integration approach. The investigation indicates that subgrade settlement results in additional track irregularity, and locally, the contact between the concrete track and the soil subgrade is prone to failure. Moreover, wheel-rail interaction is significantly exacerbated by the track degradation and abnormal responses occur as a result of the unsupported areas. Distributions of interlaminar contact forces in track system vary dramatically due to the combined effect of track deterioration and dynamic load. These may not only intensify the dynamic responses of the coupled system, but also have impacts on the long-term behavior of the track components.

• 한국광학회지
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• 제14권6호
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• pp.623-629
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• 2003

본 논문에서는 XOR 연산을 위상 변조하여 만든 위상 변조 XOR(phase-encoded exclusive-OR) 연산이라는 개념을 기본으로 그레이 영상을 암호화 한 새로운 광 암호화 방법을 제안하였다 그레이 원 영상을 이진 영상들의 합으로 분리한 후 각각의 이진 영상들을 이진 무작위 영상들과 위상변조 XOR 연산 방법을 이용해 암호화하고, 이를 위상 변조하여 암호화된 데이터를 만들었다. 그리고 복호화에 필요한 키 데이터는 암호화 시 사용한 무작위 이진 영상들로 만든 무작위 그레이 영상을 위상 변조하여 구하였다 암호화된 데이터는 위상 변조로 인한 비선형성과 비가시적 특성을 가지므로 기본적으로 높은 정보보호의 특성이 있으나, 여기에 위상정보 자체를 암호화함으로써 보다 높은 수준의 정보 보호를 가능하게 하였다. 또한, 복호화 과정은 암호화 데이터와 키 데이터의 단순 곱과 기준파와 간섭을 이용하므로, 원 영상 복원 시 간단한 위상 시각화 시스템(phase-visualization system)으로 구현할 수 있다. 컴퓨터 시뮬레이션을 통해 제안한 방법의 구현 가능성과 타당성을 확인하였다.

• Journal of Power Electronics
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• 제19권1호
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• pp.190-200
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• 2019

The flyback converter, which can be regarded as a nonlinear time-varying system, has complex dynamics and nonlinear behaviors. These phenomena can affect the stability of the converter. To simplify the modeling process and retain the information of the output capacitor branch, a special sampled-data model of a peak current-mode (PCM) controlled flyback converter is established in this paper. Based on this, its dynamic behaviors are analyzed, which provides guidance for designing the circuit parameters of the converter. With the critical stability boundary equation derived by a Jacobian matrix, the stable operation range with a varied output capacitor, proportional coefficient of error the amplifier, input voltage, reference voltage and slope of the compensation ramp of a PCM controlled flyback converter are investigated in detail. Research results show that the duty ratio should be less than 0.5 for a PCM controlled flyback converter without ramp compensation to operate in a stable state. The stability regions in the parameter space between the output capacitor and the proportional coefficient of the error amplifier are enlarged by increasing the input voltage or by decreasing the reference voltage. Furthermore, the ramp compensation also can extend to the stable region. Finally, time-domain simulations and experimental results are presented to verify the theoretical analysis results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권6호
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• pp.2148-2167
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• 2021

The proliferation of the Internet of Things (IoT) technologies and applications, especially the rapid rise in the use of mobile devices, from individuals to organizations, has led to the fundamental role of secure wireless networks in all aspects of services that presented with many opportunities and challenges. To ensure the CIA (confidentiality, integrity and accessibility) security model of the networks security and high efficiency of performance results in various resource-constrained applications and environments of the IoT platform, DDO-(data-driven operation) based constructions have been introduced as a primitive design that meet the demand of high speed encryption systems. Among of them, the TMN-family ciphers which were proposed by Tuan P.M., Do Thi B., etc., in 2016, are entirely suitable approaches for various communication applications of wireless mobile networks (WMNs) and advanced wireless sensor networks (WSNs) with high flexibility, applicability and mobility shown in two different algorithm selections, TMN64 and TMN128. The two ciphers provide strong security against known cryptanalysis, such as linear attacks and differential attacks. In this study, we demonstrate new probability results on the security of the two TMN construction versions - TMN64 and TMN128, by proposing efficient related-key recovery attacks. The high probability characteristics (DCs) are constructed under the related-key differential properties on a full number of function rounds of TMN64 and TMN128, as 10-rounds and 12-rounds, respectively. Hence, the amplified boomerang attacks can be applied to break these two ciphers with appropriate complexity of data and time consumptions. The work is expected to be extended and improved with the latest BCT technique for better cryptanalytic results in further research.

• 정보보호학회논문지
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• 제19권3호
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• pp.73-82
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• 2009

본 논문에서는 SIP UA와 서버 사이에서 HTTP Digest 인증과 TLS를 대신하여 효율적이고 안전한 사용자 인증 및 키 교환 기술을 제안한다. 기존에 다양한 SIP 인증 및 키 교환 기술들이 연구되었지만, 이동 단말과 같이 자원 활용이 한정적인 SIP UA에서 암호학적 연산량에 대한 부담이 여전히 존재한다. 제안 기술은 HTTP Digest 인증 기법의 사전 공격 문제를 해결하고 홉 간 보안을 위하여 Diffie-Hellman 키 교환 알고리즘을 사용하여 보안성을 강화하였다. 또한 자원이 충분하지 않은 SIP UA에서 수행해야 하는 Diffie-Hellman 알고리즘의 지수 모듈러 연산을 SIP 서버에게 위임하는 방법을 사용하여 보안성을 강화하였다. 또한 SIP 서버에게 위임하는 방법을 사용하여 제안 기뎁이 기존 기법틀보다 암호학적 연산량에 대한 에너지 소모량이 적다. 제안 기술은 SIP 포준 인증 절차를 크게 수정하지 않고 필요한 인증 파라미터만을 추가하여 간단하게 구현할 수 있기 때문에 이미 널리 사용되고 있는 SIP 환경에 쉽게 적용할 수 있다.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.1599-1607
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• 2009

In order to deal with severe competition in the construction market of developing countries, large contractors must continually improve their own performance and operation. Performance measurement is the heart of ceaseless improvement in organizations. Key performance indicators (KPIs) play a key role in measuring project management performance (PMP) of large contractors in developing countries. The main objective of this paper is to identify KPIs, which can be used to measure PMP of contractors, and then analyze the underlying relationships of these KPIs in order to gain insight into PMP of large construction firms in Vietnam construction industry (VCI). Literature reviews and the pilot survey provided 30 KPIs. Fourteen KPIs, which have the mean values higher than 3.0, were considered as important KPIs through a questionnaire survey of 32 professionals. Factor analysis of these KPIs was employed to categorize them. The results of the survey revealed that top six KPIs are construction time and cost, owner satisfaction on services and products, and quality management and project team performance. Factor analysis uncovered that 14 top-ranked KPIs can be grouped under six categories, namely: (1) construction input management, (2) owner satisfaction, (3) cost and quality, (4) manpower management, (5) subcontractor performance and (6) equipment management. The findings of this research can be used as a guideline to measure PMP of contractors in Vietnam as well as in other developing countries. Since contractors from a country to the other country may have the same manner to manage construction projects, the results of this study may be useful not only to practitioners and researchers in Vietnam but also to participants in other developing countries.