• 한국재료학회지
• /
• 제23권12호
• /
• pp.695-701
• /
• 2013

To understand how reactivity between reinforcing nanoparticles and aqueous solution affects electrodeposited Cu thin films, two types of commercialized cerium oxide (ceria, $CeO_2$) nanoparticles were used with copper sulfate electrolyte to form in-situ nanocomposite films. During this process, we observed variation in colors and pH of the electrolyte depending on the manufacturer. Ceria aqueous solution and nickel sulfate ($NiSO_4$) aqueous solutions were also used for comparison. We checked several parameters which could be key factors contributing to the changes, such as the oxidation number of Cu, chemical impurities of ceria nanoparticles, and so on. Oxidation number was checked by salt formation by chemical reaction between $CuSO_4$ solution and sodium hydroxide (NaOH) solution. We observed that the color changed when $H_2SO_4$ was added to the $CuSO_4$ solution. The same effect was obtained when $H_2SO_4$ was mixed with ceria solution; the color of ceria solution changed from white to yellow. However, the color of $NiSO_4$ solution did not show any significant changes. We did observe slight changes in the pH of the solutions in this study. We did not obtain firm evidence to explain the changes observed in this study, but changes in the color of the electrolyte might be caused by interaction of Cu ion and the by-product of ceria. The mechanical properties of the films were examined by nanoindentation, and reaction between ceria and electrolyte presumably affect the mechanical properties of electrodeposited copper films. We also examined their crystal structures and optical properties by X-ray diffraction (XRD) and UV-Vis spectroscopy.

• 한국구조물진단유지관리공학회 논문집
• /
• 제16권1호
• /
• pp.110-119
• /
• 2012

최근 고부식 환경에 놓여 있는 철근 콘크리트 구조물의 철근 부식 문제를 해결할 수 있는 방안 중 하나로 뛰어난 내부식성을 가진 섬유복합체(Fiber Reinforced Polymer, FRP)로 제작된 보강근이 주목받고 있다. 유리섬유복합체로 제작된 보강근이 상용화된 상태이나 가격, 철근보다 낮은 탄성계수, 취성파괴 특성 등의 이유로 사용 실적은 많지 않은 것이 현실이다. 이러한 문제점을 해결하기 위한 방편 중 하나는 유리섬유복합체 보강근의 성능을 고도화하는 것이다. 성능 고도화를 통해 강도 대비 가격을 낮출 수 있으며, 인장성능을 향상시킬 수 있다. 본 연구는 주어진 재료와 조건 하에서 보강근 성능에 영향을 미치는 인자들의 효율성 향상을 통한 고인장 성능 유리섬유복합체 보강근의 개발에 관한 것이다. 이를 위해 구성재료와 제작방법 등 유리섬유복합체 보강근의 인장성능에 영향을 미치는 인자들에 대해 분석을 수행하여 개선 방안을 제안하였으며, 이를 통해 보강근의 주재료인 유리섬유의 성능을 기존 제품보다 더욱 효율적으로 활용하는 보강근을 제작하였으며, 다양한 변수에 대한 인장시험을 통하여 그 성능을 비교 분석함으로써 개선 방안의 적절성을 검증하였다.

• 예술인문사회 융합 멀티미디어 논문지
• /
• 제8권7호
• /
• pp.137-147
• /
• 2018

우리나라는 OECD 회원국 가운데에서도 정부규제의 수준이 가장 높은 나라들 중의 하나로 인식되고 있다. 정부규제가 강할수록 민간부문의 경제 및 각종 사회활동들이 위축되고 이러한 현상은 국가 경쟁력을 약화시키는 요인으로 인식되고 있다. 정부규제는 여러 가지 형태로 수행될 수 있는 바, 이러한 정부규제는 정부경쟁력에 영향을 미치고 정부경쟁력은 국가경쟁력에 영향을 미칠 수 있다. 본 연구에서는 정부규제와 국가경쟁력 간에 작용하는 많은 요소들을 인과관계론적으로 검토하고, 이를 시스템사고 관점에서 인과지도를 작성한다. 이를 통하여 정부규제와 국가경쟁력 간에 작용하는 피이드 백 루프를 탐색하고 향후 정부규제와 국가경쟁력이 균형을 이루면서 선 순환적으로 강화될 수 있는 정책적 제안을 하는데 연구의 목적이 있다. 연구결과 강화루프 (Reinforcing Loop) 2개와 균형루프(Balancing Loop) 4개가 각각 발견되었다. 이러한 루프들은 규제와 국가경쟁력간의 관계에서 실질적으로 중요한 역할을 하는 관계라는 점이며, 정책결정자 입장에서는 이러한 루프들을 잘 활용하여 양자간의 관계를 균형있게 발전시킬 수 있도록 노력할 필요가 있다는 점을 시사해 준다.

• Structural Engineering and Mechanics
• /
• 제90권4호
• /
• pp.371-390
• /
• 2024

Investigating the impact of openings on the structural behavior of ferrocement I-beams with two distinct types of reinforcing metallic and non-metallic meshes is the primary goal of the current study. Up until failure, eight 250x200x2200 mm reinforced concrete I-beams were tested under flexural loadings. Depending on the kind of meshes used for reinforcement, the beams are split into two series. A control I-beam with no openings and three beams with one, two, and three openings, respectively, are found in each series. The two series are reinforced with three layers of welded steel meshes and two layers of tensar meshes, respectively, in order to maintain a constant reinforcement ratio. Structural parameters of investigated beams, including first crack, ultimate load, deflection, ductility index, energy absorption, strain characteristics, crack pattern, and failure mode were reported. The number of mesh layers, the volume fraction of reinforcement, and the kind of reinforcing materials are the primary factors that vary. This article presents the outcomes of a study that examined the experimental and numerical performance of ferrocement reinforced concrete I-beams with and without openings reinforced with welded steel mesh and tensar mesh separately. Utilizing ANSYS-16.0 software, nonlinear finite element analysis (NLFEA) was applied to illustrate how composite RC I-beams with openings behaved. In addition, a parametric study is conducted to explore the variables that can most significantly impact the mechanical behavior of the proposed model, such as the number of openings. The FE simulations produced an acceptable degree of experimental value estimation, as demonstrated by the obtained experimental and numerical results. It is also noteworthy to demonstrate that the strength gained by specimens without openings reinforced with tensar meshes was, on average, 22% less than that of specimens reinforced with welded steel meshes. For specimens with openings, this value is become on average 10%.

• 한국시스템다이내믹스연구
• /
• 제8권2호
• /
• pp.141-173
• /
• 2007

In Korean context, the innovative cities imply new towns or urban clusters in the Non Capital Regions, all of which would accommodate the relocated Capital based public organizations. The central government-initiated innovative cities have provoked pros and cons towards their effectiveness and efficacy for the balanced territorial development. From a broader prospective, this paper firstly examines the current status quo of the innovative cities. Based on their master plans, it analyzes physical and non physical factors which would exert significant impact on the innovative cities. Secondly, it pays attention to how key factors strengthen or weaken their behavioral patterns in terms of dynamic location and implementation policies of the innovative cities. Using System dynamics approaches, it sets up couples of scenarios, categorizing between supporting and opposing arguments towards the innovative cities. Lastly, after divulging systematic structure of the innovative cities, it proposes a series of practical alternatives which would contribute to minimizing unexpected side effects or unwanted social cost in the long run. In order to guarantee reinforcing structure of the innovative cities, the paper suggests that QOL (quality of life) variables, which would require continuous investment in the social infrastructure, are pivotal in achieving original goals of the innovative cities. Otherwise, the innovative cities would not be innovative per se. In the worst case, they might be degraded into the unpopular ghost towns.

• International Journal of Concrete Structures and Materials
• /
• 제4권2호
• /
• pp.89-96
• /
• 2010

This paper focuses on the effect of creep on the critical compressive strain (CCS) of concrete. The strain of concrete corresponding to the peak compressive stress is crucial in the selection of the ultimate yield strength of the reinforcing bar used in reinforced concrete columns. Among the various influencing factors, such as the creep, shrinkage, loading rate and confinement, the effect of creep and shrinkage is the most significant. So far, investigations into how these factors can affect the CCS of concrete have been rare. Therefore, to investigate the effect of creep and shrinkage on CCS, an experimental (part I) and a parametric study (part II) were conducted, as presented in these papers (part I considers creep effect, part II considers effect of creep and shrinkage). In part I, experiments pertaining to the loading age, loading rate, loading duration and loading and creep levels were conducted to study the effect of these variables on the CCS of concrete. It was found that the effects of the loading rate, loading age, and level and duration on the CCS of concrete were negligible. However, it is very important to consider the effect of creep.

• 성인간호학회지
• /
• 제27권2호
• /
• pp.127-134
• /
• 2015

Purpose: The purpose of this study is to identify health beliefs and knowledge related to hepatitis A vaccination (HAV). Preventative behaviors related to HAV were also examined. Methods: The convenience sample of 332 students were drawn from a university in Chung-nam province. The results were analyzed using descriptive statistics, t-test, ANOVA, Scheff$\acute{e}$ test, Pearson's correlation coefficient, and stepwise multiple regression with SPSS for Windows 21.0 software. Results: Vaccination rates for hepatitis A were 23.4%. The mean scores of health beliefs, knowledge and preventative behaviors related to hepatitis A were $2.38{\pm}0.25$, $0.34{\pm}0.30$, and $3.15{\pm}0.40$ respectively. The factors found to be related to hepatitis A preventative behaviors were HAV, having the HAV antibody and health beliefs. Conclusion: An experience of HAV, having HAV antibody, and positive health beliefs related to hepatitis A may be necessary to increase voluntary hepatitis A preventive behaviors among university students. It is essential to develop the strategy of educating university students about HAV and having HAV antibody as well as reinforcing health beliefs about hepatitis A which prevent the hepatitis A occurrence.

• 콘크리트학회지
• /
• 제9권4호
• /
• pp.207-214
• /
• 1997

본 연구는변형구속에 의해 생기는 축력이 철근콘크리트 휨부재의 역학적 거동과 평균 균열간격에 미치는 영향을 검토하기 위해 수행되었다. 이를 위하여 변형구속 및 무구속 조건하에서의 휨강도와 휨강성을 실험으로 구하였으며, 또한 축방향 구속을 받는 휨부재의 평균 균열간격을 예측하는 식을 제안하였다.

• 한국시스템다이내믹스연구
• /
• 제13권4호
• /
• pp.33-55
• /
• 2012

The research is to identify important diffusion factors and their effects on green car diffusion process using system dynamics perspectives and a causal-loop analysis. Through a deep review on previous research, we have found the important factors of green car diffusion process. Price, driving range, network effect, recharge system, fuel cost had important facilitation on consumer attraction and green car diffusion. Based on the review, we have constructed a causal loop diagram explaining hybrid car diffusion process. We have found 3 important reinforcing loops in the causal loop diagram. Loop for learning & economies of scale(supply side), loop for network effect(consumer side), and loop for battery development(technology side) had most significant roles in the whole diffusion process. Through a deliberate analysis on the 3 causal loops, we have found meaningful results. First, there seems to exist a critical mass in the diffusion. Second, of the 3 loops, the battery technology had most significant role. Third, not consumer installed base but sales must be a standard to decide whether the critical mass is achieved or not. Based on these findings, several meaningful implications are suggested for the government and corporations related to the green car industries.

• Steel and Composite Structures
• /
• 제22권1호
• /
• pp.203-216
• /
• 2016

To study the stress concentration factors (SCFs) of concrete-filled tubular Y-joints subject to in-plane bending, experiments were used to investigate the hot spot stress distribution along the intersection between chord and brace. Three concrete-filled tubular chords forming Y-joints were tested with different reinforcing components, including doubler-plate, sleeve, and haunch-plate reinforcement. In addition, an unreinforced joint was also tested for comparison. Test results indicate that the three different forms of reinforcement effectively reduce the peak SCFs compared with the unreinforced joint. The current research suggests that the linear extrapolation method can be used for chords, whereas the quadratic extrapolation method must be used for braces. The SCF is effectively reduced and more evenly distributed when the value of the axial compression ratio in the chord is increased. Furthermore, the SCFs obtained from the test results were compared to predictions from some well-established SCF equations. Generally, the predictions from those equations are very consistent for braces, but very conservative for concrete-filled chords.