• Journal of the Korea Institute of Information Security & Cryptology
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• v.33 no.2
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• pp.211-222
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• 2023

Multivariate quadratic equations (MQ)-based public-key cryptographic algorithms are one of promising post-quantumreplacements for currently used public-key cryptography. After selecting to NIST Post-Quantum Cryptography StandardizationRound 3 as one of digital signature finalists, Rainbow was cryptanalyzed by advanced algebraic attacks due to its multiple layered structure. The researches on MQ-based schemes are focusing on UOV with a single layer. In this paper, we propose a new MQ-signature scheme based on UOV using the combinations of the special structure of linear equations, spare polynomials and random polynomials to reduce the secret key size. Our scheme uses the block inversion method using half-sized blockmatrices to improve signing performance. We then provide security analysis, suggest secure parameters at three security levels and investigate their key sizes and signature sizes. Our scheme has the shortest signature length among post-quantumsignature schemes based on other hard problems and its secret key size is reduced by up to 97% compared to UOV.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.603-610
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• 2016

Over 12 years have passed since the first commercial operation of a Korean high-speed train. Since then, the transport capacity of the high-speed lines has become almost saturated. Therefore, studies have been carried out to increase the operating speed of the trains in order to increase their transportation capacity. This study was carried out to improve the critical speed of the KTX-Sancheon, Korean high-speed train, in order to increase its operating speed. A dynamic analysis of the KTX-Sancheon train was performed using the contact data obtained from the wheel wear profiles that were measured from a KTX-Sancheon train in commercial operation. The analysis results were verified by comparing them with the measurement acceleration data obtained from KTX-Sancheon. The suspension parameters were optimized to improve the operation speed. The critical speed of KTX-Sancheon was increased by 9.4% after the optimization by the response surface method. The optimized suspension parameters are expected to be used for the new bogie design to increase the operating speed of KTX-Sancheon from 300km/h to 350km/h.

• Journal of Engineering Education Research
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• v.11 no.1
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• pp.64-75
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• 2008

A new product development and product realization process (PRP) is a circulating and feedback process by generating ideas through creative problem solving process. The early stages of PRP correspond to conceptual design and product development, in which a large portion of product life cycle cost can be saved. The optimal design method for this stage is a robust design suggested by Taguchi. Quality must be 'engineered in' since it can not be 'inspected out.' A robust design is an engineering methodology to improve the quality of a product by minimizing the efforts of variations without eliminating the causes. The objective of this study is to propose a scheme and a case study of robust design for exploring design parameters, and introduce a creative problem solving process. Major research subjects include a creative problem solving process, robust design procedure and their implementation. For the experiment of Taguchi method, a toy catapult is adopted. For the creativity development, a short project is assigned to devise a similar tool with the toy catapult. A reference model is suggested to compare and evaluate their ideas.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.4
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• pp.232-237
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• 2015

Complex dynamic systems are composed of several subsystems. Each subsystems affect the dynamics of other subsystems since they are connected to each other in the whole system. Theoretically, we can derive the exact mass and stiffness matrix of a system if we have the natural frequencies and mode shapes of that system. In real situation, the modal parameters for the higher modes are not available and the number of degree of freedom concerned are not so high. This paper shows a simple method to derive the mass and stiffness matrix of a system considering the connecting points of subsystems. Since the accuracy of reconstructed structure depends on the selection of node and mode, the rule for selection of node and mode are derived from the numerical examples.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.4
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• pp.496-503
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• 1999

In this paper, the improvement of cap tilting system in heavy truck and the development of program for automatic design are discussed. Cab tilting system takes some important roles in heavy truck, absorbing discomfort vibration from load, increasing repair efficiency and making sure of safety. Common manual cab tilting system cannot be easily tilt up in sloped road, giving difficulty to driver as cal tilting up/down. So recently hydraulic cab tilting system is in wide use. But some problem such as tilting up/down speed is not constant and sudden swing of cab has brought discredit from user. Therefore, this paper presents advanced cab tilting system which prevents sudden swing of cab and development of program for selecting design parameters automatically.

• Proceedings of the KIEE Conference
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• 2008.04c
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• pp.143-145
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• 2008

본 논문에서는 산간벽지 또는 낙도와 같이 중앙계통으로부터 송 배전선을 이용한 전력공급이 어려운 약 계통(Weak grid)에 주로 사용되는 계통연계형 분산전원시스템의 설계 방법을 설명한다. Weak grid에서는 계통의 전압변동의 폭이 매우 크기 때문에 부하에 안정적으로 정전압을 공급할 수 있는 전압제어형 전압원인버터(VCVSI: Voltage-Controlled Voltage Source Inverter)를 주로 사용한다. 따라서 본 연구에서는 계통의 전압에 변동에 따른 각각의 시스템 파라미터 특성을 분석하고 이에 따른 최적의 시스템 용량의 선정방법을 제시한다.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.691-694
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• 2009

전세계적으로 운전자의 주행시 차선변경이나 정지시 돌발적으로 지나가는 옆차선의 차량을 감시함으로서 교통사고발생율을 대폭 감소시킬 수 있기 때문에 많은 시스템들이 개발되고 있다. 그러나 대부분 비젼시스템과 연결되는 고정형 타입으로서 운전자의 시각을 지원해 주는 경우가 많았다. 본 연구에서는 회전형으로 제작되어 사용자가 원하는 대로 감시영역을 축소시키거나 확대시킬 수 있는 방식으로서 사각지대 감지를 위한 서보모터의 회전속도/각도와 초음파센서의 측정거리 및 LED의 ON-OFF 등 각종 파라미터를 조절함으로서 최적의 사양을 선정하였고 시험을 통해 그 타당성을 증명하였다.

• Journal of Power System Engineering
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• v.16 no.2
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• pp.60-65
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• 2012

Pneumatic actuators are clean, lightweight, and can be easily serviced, whereas low energy efficiency has been considered as a critical shortcoming compared with corresponding hydraulic and electrical actuators. This study describes a new design method of pneumatic cylinder driving apparatus by lowering a supply pressure. The simulation study demonstrates that the designed system with the proposed method can operate at the smaller energy consumption state compare to the designed system with the conventional method for the specified working conditions.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.8
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• pp.1353-1359
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• 2010

This paper presents the determination of synchronous compensator(S.C) rating and parameter in Cheju AC network. The role of S.C is to supply Inertia and reactive power to HVDC system which is a kind of a generator without the function of reactive power control and Inertia. Therefore, the parameters of S,C have to be determined by considering HVDC operating characteristics. The background of this paper is the determination of S.C parameters in Cheju AC network in the case of replacing current operating S,C to new S.C type.

• Journal of the Korean Society of Systems Engineering
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• v.5 no.1
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• pp.49-56
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• 2009

This research attempts to acquire technical performance measure information based on identifying the Critical To Quality(CTQ) parameters of user requirement by using Quality Function Deployment(QFD) methodology in the initial phase of a defense R&D project. This results will contribute to the integration of technical progress to the Work Breakdown Structure(WBS) based project performance tracking. It also improve the bridging of systems engineering activities to the project management and the project decision making process.