• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.2
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• pp.58-64
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• 2012

Due to the influence of global oil prices, industrial productivity, which oil consumption is high, was significantly reduced. AC type of high-strength PHC piles is being manufactured through twice the steam curing process and this have resulted in a significant rise for product's manufacturing costs. NAC way other types of file manufacturing process has the advantage of reducing manufacturing costs by a turn of the steam curing. Nevertheless, because the initial strength be poor than that of AC method, shipment is being after the curing period of approximately three days. In addition, the growth of the product enhance with curing period can not be avoided, as a result, cost of inventory is acting as the rise. Piles by the AC method is immediately shipped after curing, damaging problems does not occur when they are introduced to the field site (for example, pile on-site). In the case of NAC, however, at least after the curing period of three days and after expressing the strength of 80 MPa or more, they are shipped on the scene. Therefore, NAC type has problems as follows: (1) increase in moderate inventory holding costs with type and (2) breakage in the field due to lack of strength. In this study, for NAC-typed PHC files, mixing characteristics research for the strength development at 1 day equivalent to AC method were conducted and strength characteristics with changes of original materials were evaluated were also identified.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.8-11
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• 2009

NAC(Network Access Control) technology is intended for authentication of internal networks access through various paths. In this paper, we build computer network platform using NAC and Extreme switch and confirm authentication for the platform. The platform consists of PIX, NAC and authentication server.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.39 no.6
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• pp.9-19
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• 2002

An NAC(Natural Admittance Control) system design is presented for interaction controller that achieves high-performance and guarantees stability. The NAC can be classified as a particular flavor of impedance control similar to control schemes that have velocity compensator and force compensator. The NAC significantly improves the response characteristics when Coulomb friction is presented in One-link Robot System and guarantees stability when robot contacts with environment. Pragmatic rules for NAC synthesis are derived. It shows method to choose a target impedance for realizable force compensator. Important parameters are found experimentally. It is demonstrated, by the experimental result, that NAC algorithm is successful in rejecting Coulomb friction through velocity compensator and guarantees stability through force compensator. We implement an experimental set-up consisting of environment-generated one-link robot system and DSP system for controller development. We apply the natural admittance controller to the One-link robot system, and show the good performance on desired force control in case of contacting with arbitrary environment.

• Corrosion Science and Technology
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• v.7 no.6
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• pp.350-361
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• 2008

Canada's oil sands contain one of the largest reserves of oil in the world. According to recent estimates, there are nearly 180 billion barrels of oil in the Canadian oil sands trapped in a complex mixture of sand, water and clay. More than 40 companies have been currently operating or developing oil sands facilities since the first production in 1967. The process of oil sands upgrading is similar with down stream refinery, but the corrosion environment in upgrading refinery is often more severe than in the refinery because of high chlorides, mineral contents, carbonic acid, heavy viscosity and fouling, higher naphthenic acid [$NA-R(CH_{2})nCOOH$], and greater sulfur contents. Naphthenic acid corrosion (NAC) which is one of the most critical corrosion issues in up & downstream refinery plants was observed for the first time in 1920's in refinery distillation processes of Rumania, Azerbaizan (Baku), Venezuela, and California. As a first API report, the 11th annual meeting stated sources and mechanism of NAC in early 1930's. API has been developing the risk base standards, such as API RP580, 571, and Publication 581 which are based on the worst NAC damage in the world since 2000. Nevertheless not only the NAC phenomena and control in Canadian sands oil process are not much widely known but also there are still no engineering guidances for the Canadian sands oil in API standards. This paper will give NAC phenomina and materials selection guidance against NA environment in Canadian oil sands upgrading processes.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.703-705
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• 2011

내부 네트워크의 IP관리를 위해 많은 네트워크 관리 방안 및 솔루션들이 기 구축되어 운영 중이고, 이를 위해 내부 네트워크에 연결된 모든 단말에 특정 Agent를 설치하여 IP를 관리하고 있어 단말(PC, IPT전화기 등)의 OS에 따른 기종별 Agent의 호환문제 및 단말에 기 설치 운영중인 응용프로그램과의 충돌문제가 발생한다. 본 연구에서는 이러한 네트워크 IP관리를 위해 Agent가 필요 없는 네트워크 관리 방식을 제안한다. 네트워크 Switch장비 Firmware의 포트차단 설정을 이용한 기법으로 Agent의 설치없이 Switch장비의 Firmware를 이용하여 네트워크의 접근제어가 가능함을 제안한다. 이를 위하여 인가되지 않은 IP를 Switch장비의 Firmware로 차단하여 네트워크의 접근제어가 가능함을 증명하였다.

• Review of KIISC
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• v.34 no.3
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• pp.13-19
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• 2024

제로트러스트는 전세계적으로 사이버 보안의 패러다임 변화를 가져오고 있다. 이러한 환경에서 세부화 된 워크로드 별로 안전하게 접속하기 위한 방법으로 SDP가 적용되거나 SDP 기술을 활용하는 방법이 소개되고 있다. 본 논문에서는 이러한 SDP의 최근 기술 동향을 분석하기 위하여, SDP v1, v2를 분석, 비교하였으며, SDP가 적용된 기술 논문들을 분석하였다. SDP는 '선 접속 후 인증'의 접근 방식을 가진 기존의 VPN과는 달리 '선 인증 후 접속'의 절차를 거쳐 네트워크에 접근하는 방식으로 경계망 위주의 보안을 제공했던 VPN과 NAC(Netwrok Access Control), 방화벽 등의 솔루션이 해결하지 못하는 보안적 한계를 완화한다. 이러한 SDP 기숭을 바탕으로 추후 제로트러스트 환경에서 안전한 네트워크 접속 환경을 위한 방법들을 소개한다.

• The Journal of the Acoustical Society of Korea
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• v.36 no.3
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• pp.172-178
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• 2017

Ultrasound has been widely used for biological and medical applications including induction of cell death, but a precise mechanism of induced cell death by ultrasound is controversial. In this study, an irradiation system with 40 kHz ultrasound was developed for a suitable cell death test of a representative unicellular organism, yeast, and used to study the biological effect of ultrasound on inducing cell death. Potassium Iodide (KI) dosimetry was used to devise an optimal system that successfully delivers 40 kHz ultrasound and produces reactive oxygen species in a 1.5 ml Eppendorf tube. Cell death was observed in an ultrasound transmission time-dependent fashion in this system. Thermal effect during irradiation was not observable in ultrasound induced cell death. Co-treatment of 40 kHz ultrasound and hydrogen peroxide showed a synergistic effect in inducing cell death. This finding suggests that 40 kHz ultrasound is related to reactive oxygen species formation. However, NAC (N-acetyl-L-cysteine) oxygen scavenger slightly inhibited the cell death by 40 kHz ultrasound. It was also found that 40 kHz ultrasound induced cell death was slightly inhibited by inhibitors of necrosis or apoptosis (glycyrrhizin or zVAD-fmk). This study suggests that cell death induced by 40 kHz ultrasound may not be exclusively related to reactive oxygen species formation and thermal effects in irradiated yeast cells.