• Corrosion Science and Technology
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• 제4권2호
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• pp.56-59
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• 2005

In rebar concrete structure, the corrosion of rebar can arise the deterioration of concrete structure and may affect the safety of the whole system. Recently, several methods for corrosion protection have been used and are more important for concrete structure using the sand including chloride ion. Among several protections, electrical cathodic protection has been expected to be one of the most useful methods in corrosion protection for reinforcement of concrete structures. The anode for cathodic protection needs high current density, high corrosion resistance and low overvoltage. To fill up the special qualities, the insoluble anodes were developed and these anodes were coated with metal oxide of $TiO_2$, $ZrO_2$, $RuO_2$, and $IrO_2$. Lifetime of these anodes can be one of the important factors affecting the lifetime of concrete structure in cathodic protection. In this work, several anodes were made by sol-gel method and thermal decomposition method and the lifetime of these anodes was evaluated by NACE international standard test method, TM 0294-94. Also, we did analyze the properties of coated metal oxides.

• 한국안전학회지
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• 제18권4호
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• pp.35-38
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• 2003

The wire rope, one of the component of the elevator, is extremely important for the sage operation of the elevator. That is why the wire rope is replaced at a specific interval regradless of the operating conditions or the degree of damage to prevent the breakage of the wire rope. This is the waste of resources, causing economic and environmental loss. This paper has surveyed and analyzed and analyzed the status of replacing wire-rope by buildings that use elevators, in order to compare the replacement cycles of the wire rope under each operating conditions.

• Journal of Information Processing Systems
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• 제16권1호
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• pp.83-95
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• 2020

Because sensor nodes have limited resources in wireless sensor networks, data aggregation can efficiently reduce communication overhead and extend the network lifetime. Although many existing methods are particularly useful for data aggregation applications, they incur unbalanced communication cost and waste lots of sensors' energy. In this paper, we propose a privacy-preserving, energy-saving data aggregation scheme (EBPP). Our method can efficiently reduce the communication cost and provide privacy preservation to protect useful information. Meanwhile, the balanced energy of the nodes can extend the network lifetime in our scheme. Through many simulation experiments, we use several performance criteria to evaluate the method. According to the simulation and analysis results, this method can more effectively balance energy dissipation and provide privacy preservation compared to the existing schemes.

• 한국해안·해양공학회논문집
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• 제32권3호
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• pp.147-160
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• 2020

추계학적 WP을 이용하여 불확실성을 고려하면서 항만 구조물의 실시간에 따른 피해와 파괴확률 그리고 잔류수명을 해석할 수 있는 모형을 수립하였다. 과거부터 현재까지의 피해상태와 미래에 발생될 피해 진행 과정에 포함되는 불확실성을 고려할 수 있는 추계학적 확률모형이다. 피해경로를 추적할 수 있으며 누적피해의 밀도함수도 산정하여 파괴확률을 추정할 수 있다. 또한 구조물의 잔류수명에 대한 밀도함수도 구할 수 있다. 최소자승법과 최우도법을 이용하여 모형의 파라미터를 추정할 수 있는 방법도 제시하였다. 검증을 위해 시간의 진행에 따른 누적피해와 잔류수명에 대한 밀도함수를 산정하고 해석하였는데 이론적인 결과가 MCS 기법의 수치적인 결과와 매우 잘 일치하였다. 또한 내구수명이나 잔류수명에 대한 밀도함수의 거동과 MTTF와 MRL이 정량적으로 잘 일치하였다. 한편 본 연구에 수립된 모형을 경사제에 적용하기 위하여 피복재 피해에 대한 수리모형 실험자료를 활용하여 모형의 파라미터들을 추정하였다. 시간의 진행에 따른 피복재 누적피해의 밀도함수와 파괴확률을 산정하였는데 MCS의 결과와 이론적인 결과가 매우 잘 일치하였다. 경과시간이 클수록 밀도함수가 우측으로 이동하면서 불확실성이 커지면서 파괴확률이 급격하게 증가하였다. 또한 재령에 따른 잔류수명의 거동특성을 해석하였는데, 잔류수명의 분포함수에서 좌측보다는 우측 꼬리 부분이 길게 형성되어 MRL이 급격하게 감소하는 경향을 보였다. 이는 경사제 피복재의 피해가 완만하게 증가하는 현상을 반영한 것으로 판단된다. 특히 재령과 내구수명 그리고 잔류수명의 관계를 해석하였는데, 재령이 오래될수록 재령과 MRL의 합이 MTTF와 큰 차이를 보이고 있다. 이는 재령이 증가하면 잔류수명의 평균인 MRL이 불확실성에 의하여 급격히 감소하기 때문이다.

• Journal of Photoscience
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• 제11권1호
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• pp.35-40
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• 2004

[Ru(2,2'-bipyridine)$_2$(4,4'-dicarboxy-2,2'-bipyridine)]$^{2+}$(RuBDc) is a very photostable probe that possesses favorable photophysical properties including long lifetime, high quantum yield, large Stokes' shift, and highly polarized emission. To evaluate the usefulness of this luminophore (RuBDc) for studying macromolecular dynamics, its intensity and anisotropy decays when conjugated to RNA bacteriophage MS2 were examined using frequency-domain fluorometry with a high-intensity, blue light-emitting diode (LED) as the modulated light source. The intensity decays were best fit by a sum of two exponentials, and the mean intensity decay time was 442.2 ns. The anisotropy decay data showed a single rotational correlation time (2334.9 ns), which is typical for a spherical molecule. The use of RuBDc enabled us to measure the rotational correlation time up to several microseconds. These results indicate that RuBDc can be useful for studying rotational diffusion of biological macromolecules.s.

• 한국정밀공학회지
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• 제19권6호
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• pp.145-154
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• 2002

CMP (Chemical mechanical polishing) process was used to control the fine grinding process induced mechanical damage of Cz Silicon wafer. Characterization of mechanical damage was carried out using Nomarski microscope, magic mirror and also using angle lapping and lifetime scanner evaluation after heat treatment. Magic mirror and lifetime scanner were very useful for the residual damage pattern characterization and CMP process was effective on the reduction of fine grinding induced mechanical damage.

• 한국전기전자재료학회논문지
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• 제22권9호
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• pp.732-736
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• 2009

Protons are irradiated into SOl wafers under total dose of 100 krad, 500 krad, 1 Mrad and 2 Mrad to analyze the irradiation effect. The electrical properties are analyzed by pseudo MOSFET technology after proton irradiation. The wafers are annealed to stabilize generated defects in a nitrogen atmosphere at $300^{\circ}C$ for 1 hour because proton irradiation induces a lot of unstable defects in the surface silicon film. Both negative and positive turn-on voltages are shifted to negative direction after the irradiation. The more proton total dose, the more turn on voltage shifts. It means that positive oxide trap charge is generated in the buried oxide(BOX). The minority carrier lifetime which is analyzed by the drain current transient characteristics decreases with the increase of proton total dose. The proton irradiation makes crystal defects in the silicon film, and consequently, the crystal defects reduce the carrier lifetime and mobility. As these results, it can be concluded that pseudo MOSFET is a useful technology for the analysis of irradiated SOI wafer.

• Journal of Photoscience
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• 제7권4호
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• pp.155-159
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• 2000

[Ru(bpy)$_2$(dppz)]$^2$$^{+}$ (bpy = 2,2'-bipyridine, dppz = dipyrido[3,2-a:2',3'-c]phenazine)(RuBD), a long-lifetime metal-ligand complex displays photophysical properties including long lifetime, polarized emission, and very little background fluorescence. To further show the usefulness of this luminophore(RuBD) for probing nucleic acid dynamics, its intensity and anisotropy decays when bound to tRN $A^{val}$ were examined using frequency-domain fluorometry with a blue light-emitting diode(LED)as the modulated light source. Unexpectedly much longer mean lifetime was obtained at 4$^{\circ}C$(<$\tau$>=178.3 ns) as compared to at $25^{\circ}C$(<$\tau$>=117.0 ns), suggesting more favorable conformation of tRN $A^{val}$ for RuBD when intercalated at 4$^{\circ}C$. The anisotropy decay data showed longer rotational correlation times at 4$^{\circ}C$(52.7 and 13.0 ns) than at $25^{\circ}C$ (32.9 and 10.3 ns). The presence of two rotational correlation times suggests that RuBD reveals both local and overall rotational motion of tRN $A^{val}$. Due to long lifetime of RuBD and small size of tRN $A^{val}$, very low steady-state anisotropy values were observed, 0.048 and 0.036 at 4 and $25^{\circ}C$, respectively. However, a clear difference in the modulated anisotropy values was seen between 4 and $25^{\circ}C$. These results indicate that RuBD can be useful for studying hydrodynamics of small nucleic acids such as tRN $A^{val}$.^{val}$.>.$.>.

• 한국정보과학회논문지:정보통신
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• 제31권1호
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• pp.27-36
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• 2004

사용자의 이동성을 지원하는 Mobile IP 환경에서, 빈번한 바인딩 갱신 메시지의 발생은 상당한 부하를 초래할 수 있다. 따라서 이를 감소시키기 위한 알고리즘 개발이 필요하다. 이를 위해, 본 논문에서는 사용자의 이동성과 관련된 지역적 특성을 고려한 동적 바인딩 갱신을 위한 라이프타임 할당 기법을 제안한다. 각 이동 노드는 방문한 서브넷과 관련된 로그 정보를 이용하여 프로파일을 유지하고 있다. 즉, 방문한 서브넷별로 평균 상주시간을 기반으로 하여 적응적 라이프타임을 결정하여 다음 방문 시에 이 값을 바인딩 갱신의 라이프타임으로 사용한다. 또한 각 이동 노드가 동일한 서브넷을 방문하더라도 방문 시간대에 따라 평균 상주시간이 차이가 날 수 있다는 사실을 기반으로 하여, 동일한 서브넷에 대하여 방문 시각에 따라 별개의 라이프타임을 결정하는 알고리즘도 제안한다. 제안한 기법의 성능 향상을 보이기 위하여 기존 Mobile IPv6과 비교 실험을 수행하였으며, 이 과정에서 다음의 두 가지 인자를 주로 비교하였다: 바인딩 갱신 메시지의 수 및 바인딩 요청 메시지의 수. 실험 결과, 제안한 기법은 기존 Mobile IPv6에 비해 위 메시지의 수를 줄임으로써 상당한 통신비용 절감효과를 보여주었다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제16권1호
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• pp.56-63
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• 2016

Purpose: The purpose of this study is to point out that the Kaplan-Meier method is not valid to calculate the survival probability or failure probability (risk) in the presence of competing risks and to introduce more valid method of cumulative incidence function. Methods: Survival analysis methods have been widely used in biostatistics division. However the same methods have not been utilized in reliability division. Especially competing risks cases, where several causes of failure occur and the occurrence of one event precludes the occurrence of the other events, are scattered in reliability field. But they are not noticed in the realm of reliability expertism or they are analysed in the wrong way. Specifically Kaplan-Meier method which assumes that the censoring times and failure times are independent is used to calculate the probability of failure in the presence of competing risks, thereby overestimating the real probability of failure. Hence, cumulative incidence function is introduced and sample competing risks data are analysed using cumulative incidence function and some graphs. Finally comparison of cumulative incidence functions and regression type analysis are mentioned briefly. Results: Cumulative incidence function is used to calculate the survival probability or failure probability (risk) in the presence of competing risks and some useful graphs depicting the failure trend over the lifetime are introduced. Conclusion: This paper shows that Kaplan-Meier method is not appropriate for the evaluation of survival or failure over the course of lifetime. In stead, cumulative incidence function is shown to be useful. Some graphs using the cumulative incidence functions are also shown to be informative.