• Journal of Information Processing Systems
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• v.7 no.4
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• pp.691-706
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• 2011

Since security and privacy problems in RFID systems have attracted much attention, numerous RFID authentication protocols have been suggested. One of the various design approaches is to use light-weight logics such as bitwise Boolean operations and addition modulo $2^m$ between m-bits words. Because these operations can be implemented in a small chip area, that is the major requirement in RFID protocols, a series of protocols have been suggested conforming to this approach. In this paper, we present new attacks on these lightweight RFID authentication protocols by using the Gr$\ddot{o}$bner basis. Our attacks are superior to previous ones for the following reasons: since we do not use the specific characteristics of target protocols, they are generally applicable to various ones. Furthermore, they are so powerful that we can recover almost all secret information of the protocols. For concrete examples, we show that almost all secret variables of six RFID protocols, LMAP, $M^2AP$, EMAP, SASI, Lo et al.'s protocol, and Lee et al.'s protocol, can be recovered within a few seconds on a single PC.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1025-1026
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• 2007

Recently study on components for a electric golf car and a utility car driven by a electric motor has been performed actively, and the study on a drive motor, a inverter and a battery focuses on a small, light weight and high power density source to improve fuel efficiency using limited electric energy. Especially, since a utility car such as a golf car performance depends on initial acceleration and maximum speed capability, a drive system requires high power and large and wide operation area, This study therefore investigates on the interior permanent magnet synchronous motor with high power density and wide operation, and is verified with the test result after design and characteristic analysis is performed

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.558-559
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• 2005

Recently, polymer insulators that are used for high voltage applications have some advantages such as light weight, small size, vandalism resistance, hydrophobicity and easy making process. During outdoor service of polymer insulators, the surface of the insulating material is frequently subjected to moisture and contamination that lead to dry band arcing. Their tracking resistance, erosion resistance, end sealing and shed design are very important because dry band arcing causes degradation of polymer surface. In this paper, the tracking property of polymer suspension insulator for power transmission is investigated with CEA tracking wheel test. The diagnosis of insulator sample in tracking test has been analyzed by leakage current, STRI Guide, SEM, FTIR and thermal image.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.848-851
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• 2003

Display devices are becoming increasingly important as an interface between humans and machines in the growing information society In display device, PDP(Plasma Display Panel) has many advantages in that wide screen, light weight, thin, wide viewing angle and unaffected by magnetic field. In this paper, modified ramp waveform is suggested by Vt Close Curve, and PDP driving circuit is designed by modified ramp waveform, this modified ramp waveform have more addressing wall voltage better then the old ramp waveform.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.155-161
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• 2000

To improve the vehicle fuel economy, various technologies such as improvement of power train efficiency, use of light weight material, improvement of aerodynamic design, have been studied. One of the possible way to improve the vehicle fuel economy is to reduce the engine friction loss by improving the engine oil characteristics. In the present paper, it was examined the effect of the engine oil viscosity and the addition of friction modifier to engine oil on vehicle fuel economy improvements. Moreover, the effect of engine oil degradation on vehicle fuel economy was examined with two gasoline vehicles and one diesel vehicle by using the fuel economy test facility.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.325-328
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• 2008

In recent years, developments of light weight vehicle are one of the most important issues in automotive industry. It is important to know the variations of the mechanical properties in the hydro forming process for the safe and durable design purposes. Generally, tube hydroforming process consists of three main processes such as bending, preforming, and hydroforming. It means that the strain hardening histories of final products are nonlinear. In this study, strain hardening behavior during hydroforming has been investigated by hydroforming of engine cradle as a model process. The variation of mechanical properties such as local hardness and strength were used as an index of strain hardening during respective processes. The correlationship between strength and hardness obtained from tensile test has been equivalently converted into correlation between hardness and measured strain.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.377-384
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• 2003

Recently, there are much concerns about new and innovative transverse materials which could be used instead of conventional transverse steel in reinforced concrete bridge piers. FRP materials could be substituted for conventional transverse steel because of their sufficient strength, light weight, easy fabrication, and useful applicability to any shapes of pier sections, such as rectangular or circular sections. The objective of this research is to evaluate the seismic performance of reinforced concrete bridge pier specimens with FRP transverse reinforcement by means of the Quasi-Static test. In the first task, test columns were made using FRP rope, but these specimens appeared to fail at low displacement ductility levels due to insufficient confinement of strand extension itself. Therefore, the second task was to evaluate the seismic performance of test specimens transversely confined with FRP band. Although FRP banded specimens showed lower seismic performance than the specimen with spiral reinforcing steel, it satisfied with the response modification factor, 3, required for the single column of Korea bridge roadway design code. It was concluded that FRP band could be efficiently substituted for conventional reinforcing steel.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.4
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• pp.80-86
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• 2021

Plastics are widely used in mechanical and other fields due to their light weight, design flexibility, and molding processability. In processing plastics, defective products are mixed and reprocessed to improve production efficiency and reduce costs. In this study, an experiment was conducted to confirm the coefficient of thermal expansion of HDPE during this reprocessing. The coefficient of thermal expansion was measured at different measurement directions and heating rates. As a result, we observed that the coefficient of thermal expansion in the direction perpendicular to the injection direction is greater than that in the horizontal direction.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.11a
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• pp.1106-1109
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• 2013

미래 육군의 대대급이하 NCW 핵심은 기반통신장비인 TMMR(Tactical Multi Function Terminal)과 전투지휘를 위한 전장단말기인 대대급이하 전투지휘체계(B2CS)로 대표할 수 있다. 이중 TMMR은 음성과 데이터 통신이 가능토록 개발중인 무전기이다. 하지만, 군 무전기 특성상 은 엄폐 지역에서의 통신 보장을 위해 낮은 주파수 대역을 사용함에 따라 최대 지원 가능한 전송속도는 매우 한정적이다. 따라서 TMMR을 기반 통신장비로 활용하는 B2CS는 이 낮은 대역폭을 어떻게 효율적으로 사용할 것인가가 핵심이다. 따라서 본고에서는 이를 위해 군 운용환경에서의 TMMR 기반하 B2CS 운용 시 필요한 TMMR의 요구대역폭을 분석, 데이터 경량화 설계가 필요함을 확인하고, 이에 따른 B2CS에서 적용하고 있는 데이터 경량화 설계 방안을 제시하고자 한다.

• Journal of the Korean Society of Mechanical Technology
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• v.20 no.6
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• pp.912-916
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• 2018

Crawling robots are advantageous in overcoming obstacles. These robots have characteristics such as light weight and outstanding mobility. In case of large robots, they have difficulties passing narrow gaps or entering the cave. In this paper, we propose a milli-scale hexapedal robot using 4-bar linkages. Two conditions are necessary to enable efficient walking. In short, the trajectory of the foot must be elliptical, and the lowest point of the foot should be the same. These conditions are satisfied with a novel leg design. The robot has a pair of three legs and the legs are coupled to operate simultaneously. Each set of the legs are installed to robot's both sides and the legs satisfy the equal lowest foot point and elliptical trajectory. As a result, this hexapedal robot can crawl with 0.56m/s speed.