• Nuclear Engineering and Technology
• /
• 제39권5호
• /
• pp.637-646
• /
• 2007

An UET (ultrasound excited thermography) has been used for several years for a remote non-destructive testing in the automotive and aircraft industry. It provides a thermo sonic image for a defect detection. A thermograhy is based On a propagation and a reflection of a thermal wave, which is launched from the surface into the inspected sample by an absorption of a modulated radiation. For an energy deposition to a sample, the UET uses an ultrasound excited vibration energy as an internal heat source. In this paper the applicability of the UET for a realtime defect detection is described. Measurements were performed on two kinds of pipes made from a copper and a CFRP material. In the interior of the CFRP pipe (70mm diameter), a groove (width - 6mm, depth - 2.7mm, and length - 70mm) was engraved by a milling. In the case of the copper pipe, a defect was made with a groove (width - 2mm, depth - 1mm, and length - 110 mm) by the same method. An ultrasonic vibration energy of a pulsed type is injected into the exterior side of the pipe. A hot spot, which is a small area around the defect was considerably heated up when compared to the other intact areas, was observed. A test On a damaged copper pipe produced a thermo sonic image, which was an excellent image contrast when compared to a CFRP pipe. Test on a CFRP pipe with a subsurface defect revealed a thermo sonic image at the groove position which was a relatively weak contrast.

• International Journal of Concrete Structures and Materials
• /
• 제11권2호
• /
• pp.343-363
• /
• 2017

The objective of this work was finding out the most advisable testing conditions for an effective and robust characterization of the tensile strength (TS) of concrete disks. The independent variables were the loading geometry, the angle subtended by the contact area, disk diameter and thickness, maximum aggregate size, and the sample compression strength (CS). The effect of the independent variables was studied in a three groups of experiments using a factorial design with two levels and four factors. The likeliest location where failure beginning was calculated using the equations that account for the stress-strain field developed within the disk. The theoretical outcome shows that for failure beginning at the geometric center of the sample, it is necessary for the contact angle in the loading setup to be larger than or equal to a threshold value. Nevertheless, the measured indirect tensile strength must be adjusted to get a close estimate of the uniaxial TS of the material. The correction depends on the loading geometry, and we got their mathematical expression and cross-validated them with the reported in the literature. The experimental results show that a loading geometry with a curved contact area, uniform load distribution over the contact area, loads projected parallel to one another within the disk, and a contact angle bigger of $12^{\circ}$ is the most advisable and robust setup for implementation of BT on concrete disks. This work provides a description of the BT carries on concrete disks and put forward a characterization technique to study costly samples of cement based material that have been enabled to display new and improved properties with nanomaterials.

• 한국지반공학회논문집
• /
• 제22권12호
• /
• pp.57-65
• /
• 2006

낙동강 하구지역에는 부산점토라고 불리는 연약점토가 두텁게 분포하고 있다. 과거 10년 동안에 대단위 지반개량 사업이 수행되어 왔지만, 주로 시료교란 때문에 압밀침하량과 시간을 아주 과소평가하여 왔었다. 이를 극복하기 위하여 부산점토에 대한 체계적인 지반조사에 의하여 압축특성을 규명할 필요가 요구되었다. 따라서 본 연구에서는 해안지역의 두 현장에서 개선된 시료채취기술을 적용하여 얻어진 시료에 대하여 지질조사, 불교란 및 교란 시료에 대한 압밀실험이 수행되었다. 이 결과를 이용하여 각종 압축정수의 산정과 그들의 상관성을 규명하였으며, 특히 퇴적환경에 따라 물리적 특성, 구조수준, 교란도 및 압축정수의 변화를 분석하였다.

• 아태비즈니스연구
• /
• 제14권1호
• /
• pp.149-169
• /
• 2023

Purpose - The main purpose of this study is to develop the stress test model for Korean banks by exploring the optimal Monte Carlo simulation and BIS forecasting model. Design/methodology/approach - This study selects 15 Korean banks as sample financial firms and collects relevant 76 quarterly data for the period between year 2000 and 2018 from KRX(Korea Excange), Bank of Korea, and FnGuide. The Regression analysis, Unit-root test, and Monte Carlo simulation are hired to analyze the data. Findings - First, most of the sample banks failed to keep 8% BIS ratio for the adverse and severely Adverse Scenarios, implying that Korean banks must make every effort to realize better BIS ratios under adverse market conditions. Second, we suggest the better Monte Carlo simulation model for the Korean banks by finding that the more appropriate volatility should be different depending on variables rather than simple two-sigma which has been used in the previous studies. Third, we find that the stepwise regression model is better fitted than simple regression model in forecasting macro-economic variables for the BIS variables. Fourth, we find that, for the more robust and significant statistical results in designing stress tests, Korean banks are required to construct more valid time-series and cross-sectional data-base. Research implications or Originality - The above results all together show that the optimal volatility in designing optimal Monte Carlo simulation varies depending on the country, and many Korean banks fail to pass sress test under the adverse and severely adverse scenarios, implying that Korean banks need to make improvement in the BIS ratio.

• Macromolecular Research
• /
• 제17권8호
• /
• pp.616-622
• /
• 2009

In-depth understanding of the influence of hot pressing and melt processing on the properties of thermoplastic polyurethane (TPU) is critical for effective mechanical recycling of TPU scraps. Therefore, this study focused on the effects of hot pressing and melt mixing on molecular weight (MW), polydispersity index (PDI), melt index (MI), characteristic IR peaks, hardness, thermal degradation and mechanical properties of TPU. The original TPU pellet (o-TPU) showed two broad peaks at lower and higher MW regions. However, four TPU film samples, TPU-0 prepared only by hot pressing of o-TPU pellet and TPU-1, TPU-2 and TPU-3 obtained by hot pressing of melt mixed TPUs (where the numbers indicate the run number of melt mixing), exhibited only a single peak at higher MW region. The TPU-0 film sample had the highest $M_n$ and the lowest PDI and hardness. The TPU-1 film sample had the highest $M_w$ and tensile modulus. As the run number of melt mixing increased, the peak-intensity of hydrogen bonded C=O stretching increased, however, the free C=O peak intensity, tensile strength/elongation at break and average MW decreased. All the samples showed two stage degradations. The degradation temperatures of TPU-0 sample (359 $^{\circ}C$ and 394 $^{\circ}C$)were higher than those of o-TPU (342 $^{\circ}C$ and 391 $^{\circ}C$). While all the melt mixed samples degraded at almost the same temperature (365 $^{\circ}C$ and 381 $^{\circ}C$). The first round of hot pressing and melt mixing was found to be the critical condition which led to the significant changes of $M_n$/$M_w$/PDI, MI, mechanical property and thermal degradation of TPU.

• International Journal of Human Ecology
• /
• 제6권2호
• /
• pp.25-35
• /
• 2005

The purpose of this study was to examine the effects of family-school relations on children's school adjustment with divorced mothers. Subcategories of the family-school relations were family participation in decision making, family help for schools, learning activities at home, school help for families, and school-home communication adopted from Epstein's parent involvement theory. Sub categories of children's school adjustment were delinquent behavior and academic achievement. The sample of this study included 3,367 children from first to fifth grade who lived either in a two-parent or one-parent home. Among them, 411 children with divorced mothers were analyzed. Independent t-test, Pearson's correlations, stepwise regression analysis were all conducted. Findings suggested that children with divorced mothers showed higher delinquency and lower academic achievement than children in intact families. Sub categories of family involvement and school involvement were correlated in divorced families. Children's delinquency was predicted by three of the family-school relation factors, which were school-home communication, family help for schools, and school help for families. Children's academic achievement was predicted by ail factors.

• 한국정보시스템학회지:정보시스템연구
• /
• 제19권4호
• /
• pp.111-136
• /
• 2010

This study examined the difference in the usage of internet banking users between Korea and China. This model tests various theoretical research hypotheses relating to internet banking, The Unified Theory of Acceptance and Use of Technology(UTAUT). The factors influencing on the use intention of Internet banking have been classified as performance expectancy, effort expectancy, social influence and facilitating conditions. The proposed model was empirically tested using data collected from a survey of internet banking users in Korea and China. The model is used by SPSS 15.0 and AMOS 7.0 for analysis on the sample collected from 272 respondents. The result of hypothesis testing are as follows. First, performance expectancy and social influence positively influence use intention of internet banking user both Korea and China. Second, facilitating conditions only positively influence on the usage of internet banking users in Korea. On the other side, effort expectancy do not influence the use intention of internet banking users in both two countries. The results of study will provide practical implications on the internet banking in Korea and China.

• Asian Journal for Public Opinion Research
• /
• 제4권2호
• /
• pp.73-87
• /
• 2017

The Korean Academic Multimode Open Survey (KAMOS) is a national survey first conducted in 2016. Stratified cluster random sampling was used in an initial face-to-face survey during which panel members were recruited. The second survey allowed invited panel members to answer online or by phone. KAMOS includes both longitudinal items and omnibus items, i.e., researchers can propose questions to include on KAMOS. This paper seeks to establish that KAMOS is representative of the South Korean adult population. The demographic variables from the first survey were comparable to demographic variables from two well-respected surveys in South Korea: the KOSTAT Social Survey and the Gallup Korea Omnibus Survey. To ensure that there was no substantial difference between those who answered the first survey and those who answered the second survey, we compared the results of 22 items from the first survey. The 2,000 panel members who were invited to participate in the second survey had similar responses to the 1,008 of those who responded to the second survey. Based on our findings, KAMOS can be considered a representative sample.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2005년도 춘계 학술발표회 논문집
• /
• pp.627-632
• /
• 2005

In this study, a series of large-scale oedometer tests was performed to investigate the compressibility of rock fill materials. The testing samples were prepared to have three different grain size distributions and for each distribution, exist in two different states(dried and saturated). The test results indicated that particle breakages occurred mainly for the particles larger than 4.75mm in size and increased with increasing grain sizes. Also, it was found that, for a dry sample as it became well-graged, its compressibility decreased and accordingly, its tangent constrained modulus increased. A comparion between the samples in dry and saturated states revealed that compressibility of the materials increases with increasing water content. The values of tangent constrained modulus calculated for the tested dry samples were larger by about 10 to 20%, on average, than those for the saturated samples.

• 유통과학연구
• /
• 제18권10호
• /
• pp.101-110
• /
• 2020

Purpose: The study investigates the implementation of corporate social responsibility (CSR) in the real estate sector of the UAE by collecting the opinions of both the real estate companies and different tenants on the execution of CSR. Research design, data, and methodology: Using a sample of 300 different types of UAE real estate consumers and twenty real estate firms, the researchers collected the opinions of targeted subjects by administering two types of questionnaires. The Cronbach's Alpha and the Kaiser-Meyer-Olkin (KMO) tests were employed to check the internal consistency and validity of the questionnaires. The selected hypotheses were tested using the Kruskal-Wallis (K-W) hypothesis testing technique. Results: The findings revealed that all types of UAE real estate consumers expressed their discontentment over the implementation of socially responsible actions by the real estate companies. Whereas UAE real estate companies expressed their confidence in the ideal implementation of social actions towards all stakeholders in general and tenants. Conclusion: Even though more than 50 percent of realty customers are dissatisfied with the company's implementation of CSR, a little over 54.80 percent are willing to recommend the company to their family and friends. Implications have been provided for UAE real estate companies who wish to promote their business to all categories of UAE real estate consumers successfully.