• 국제학술발표논문집
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• The 1th International Conference on Construction Engineering and Project Management
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• pp.672-680
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• 2005

There are a lot of reasons to use In-place tests. Construction schedules often require that operations such as form removal, post-tensioning, termination of curing, and removal of reshores be carried out as early as possible. To enable these operations to proceed safely as soon as possible requires the use of reliable in-place tests to estimate the in-place strength. In-place test results are not reliable for engineering judgment. These results should be interpreted and correlated to standard compressive strength, based on the test method. In this paper some of these test procedures and their limitations are discussed. In this study we will go on for Rebound number, Pullout, Ultrasonic pulse velocity, and Cast-in-place cylinder methods which are most useful methods in the Asia.

• Structural Engineering and Mechanics
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• 제58권1호
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• pp.39-58
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• 2016

Since the publication of ACI 318-02, the concrete capacity design (CCD) method has been used to determine the resistance of unreinforced concrete anchors. The regulation of steel-reinforced anchors was proposed in ACI 318-08. Until ACI 318-08, the shear resistance of concrete breakout for an unreinforced anchor during an earthquake was reduced to 75% of the static shear strength, but this reduction has been eliminated since ACI 318-11. In addition, the resistance of a hairpin-reinforced anchor was calculated using only the strength of the steel, and a regulation on the dynamic strength was not given for reinforced anchors. In this study, shaking table tests were performed to evaluate the dynamic shear strength of unreinforced and hairpin-reinforced cast-in-place (CIP) anchors during earthquakes. The anchors used in this study were 30 mm in diameter, with edge distances of 150 mm and embedment depths of 240 mm. The diameter of the hairpin steel was 10 mm. Shaking table tests were carried out on two specimens using the artificial earthquake, based on the United States Nuclear Regulatory Commission (US NRC)'s Regulatory Guide 1.60, and the Northridge earthquake. The experimental results were compared to the current ACI 318 and ETAG 001 design codes.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.1125-1131
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• 2008

In this study, Calibration Chamber Tests for cast-in-place piles in sand were performed for measuring behavior properties of piles. These tests were examined effects of various parameters of soil conditions including the relative density($D_R$), the coefficient of earth pressure, and investigated differences between cylindrical pile and taper-shaped pile with the same volumes. The important effect factors of foundation behavior were investigated by considering embedded depth of piles and shapes of piles, and inspected details of lateral behavior of piles. These results were verified reliabilities of each methods for comparing the results estimated with tests and the results by proposed estimating solutions in the past.

• 복식문화연구
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• 제27권6호
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• pp.569-581
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• 2019

This study investigated differences in cosmetic buying behavior and personal characteristics between cosmetic involvement groups. Cosmetics buying behavior refers to reason for using cosmetics, use of information sources, selection criteria, place of purchase, use/non-use of cosmetics, purchase propensity, purchase frequency, purchase amount, and satisfaction with cosmetics. Personal characteristic contains pursuing image, age, residence area, job, and average household monthly income. Data was collected from 5-10 December 2016, from 308 females in their 20s using an internet survey. The analysis included descriptive statistics, t-tests, Mann-Whitney U tests, and chi-square tests. The respondents were divided into two groups (a high cosmetic involvement group and a low cosmetic involvement group) according to the degree of cosmetic involvement. The results of t-tests revealed significant differences between groups in terms of reasons for using cosmetics, use of information sources, selection criteria, purchase frequency, place of purchase, use/non-use of cosmetics, and satisfaction with cosmetics. The results of Mann-Whitney U tests highlighted a significant difference in purchase frequency between both groups. The results of chi-square tests indicated significant differences in purchase frequency, purchase amount, pursuing image, and average household monthly income. However, no significant differences were evident in terms of purchase propensity, age, job, and area of residence between groups.

• Geomechanics and Engineering
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• 제19권2호
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• pp.115-126
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• 2019

The long-term settlement characteristics for the cast-in-place bored pile in the deep-thick soft soil are investigated by post-grouting field tests. Six cast-in-place bored engineering piles and three cast-in-place bored test piles are installed to study the long-term settlement characteristics. Three post-grouting methods (i.e., post-tip-grouting, post-side-grouting, and tip and side post-grouting) are designed and carried out by field tests. Results of the local test show that decreased settlements for the post-side-grouted pile, the post-tip-grouted pile and the tip and side post-grouted pile are 22.2%~25.8%, 30.10%~35.98% and 32.40%~35.50%, respectively, compared with non-grouted piles. The side friction resistance for non-grouted piles, post-side-grouted pile, post-tip-grouted pile and the tip and side post-grouted pile undertakes 89.6~91.3%, 94.6%, 92.4%~93.0%, 95.7% of the total loading, respectively. At last, the parameters back analysis method and numerical calculation are adopted to predict the long-term settlement characteristics of the cast-in-place bored pile in the deep-thick soft soil. Determined Bulk modulus (K) and a creep parameter (Ks) are used for the back analysis of the long-term settlement of the post-grouted pile. The settlement difference between the back analysis and the measurement data is about 1.11%-7.41%. Long-term settlement of the post-grouted piles are predicted by the back analysis method, and the predicted results show that the settlement of the post-grouted pile are less than 6 mm and will be stable in 30 days.

• 한국농공학회지
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• 제16권2호
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• pp.3410-3419
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• 1974

The purpose of this study is to find out the correlation between pumping rates and influential factors in the tube wells for irrigation through the analysis of various statistical data of the existing tube wells for irrigation and pumping tests. Statistical data of the existing tube wells for irrigation were collected from the authorities concerned, and pumping tests were carried out for twelve tube wells. The results of this study are summarized as follows: 1. The drilled tube wells are the most useful among various tube wells in securing pumping rates. 2. The enlargement of well diameter or the improvement of pumping equipments is necessary in drilled tube wells with pumping rates more than 806 ㎥/day, and the adjustment of foot valves or the special control of pumping equipments is necessary in tube wells with pumping rates less than 300 ㎥/day. 3. The choking of aquifer and slits can be prevented by removing earth and sand piled in tube wells. 4. The increase of well loss and the destruction of aquifer can be prevented by determining the optimum pumping rates through the step draw down tests. 5. The thickness of gravel packing is rather thin in drilled tube tube wells. 6. High pamping rates can be gained by deepening the depth of tube wells in the place the ground water storage is abundant, the thickness of aquifer is thick. and the depth of tube wells is deep. 7. Higher pumping rates can be obtained by constructing tube wells in the place where the drawdown is little and the coefficient of transmissibility is large.

• Smart Structures and Systems
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• 제4권1호
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• pp.1-17
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• 2008

This study proposes a conceptual framework of in-situ vibration tests and analyses for quality appraisal of non-slender, cast-in-place piles with irregular cross-section configuration. It evaluates a frequency index from vibration recordings to a series of impulse loadings that is related to total soil-resistance forces around a pile, so as to assess if the pile achieves the design requirement in terms of bearing capacity. In particular, in-situ pile-vibration tests in sequential are carried out, in which dropping a weight from different heights generates series impulse loadings with low-to-high amplitudes. The high-amplitude impulse is designed in way that the load will generate equivalent static load that is equal to or larger than the designed bearing capacity of the pile. This study then uses empirical mode decomposition and Hilbert spectral analysis for processing the nonstationary, short-period recordings, so as to single out with accuracy the frequency index. Comparison of the frequency indices identified from the recordings to the series loadings with the design-based one would tell if the total soil resistance force remains linear or nonlinear and subsequently for the quality appraisal of the pile. As an example, this study investigates six data sets collected from the in-situ tests of two piles in Taipu water pump project, Jiangshu Province of China. It concludes that the two piles have the actual axial load capacity higher than the designed bearing capacity. The true bearing capacity of the piles under investigation can be estimated with accuracy if the amplitude of impact loadings is further increased and the analyses are calibrated with the static testing results.

• 대한수학교육학회지:수학교육학연구
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• 제25권3호
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• pp.347-366
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• 2015

초등 수학에서 학습부진의 원인은 다양하지만, 선수학습요소의 결여가 하나의 원인으로 주목되고 있다. 본 연구에서는 초등 수학 학습부진의 원인으로 자릿값 이해의 결여 가능성을 고려하여, 초등 수학 학습부진아의 자릿값 이해 수준을 분석하고, 그들이 어려움을 느끼는 자릿값 개념의 과제 유형을 파악하는 것을 목적으로 한다. 이를 위해 수학 학습에서 지속적으로 어려움을 보이는 초등학교 3학년 학습부진아 10명을 대상으로 자릿값 개념 이해 검사인 SToPV를 개별적으로 적용함으로써 학생들의 반응을 분석하였다. 분석 결과, 초등학교 3학년 시기의 수학 학습부진아들은 이전 학년에서 자릿값을 학습하였음에도 불구하고 자릿값을 이해하고 활용하는 데 어려움을 느끼며, 어려움을 느끼는 과제 유형에 있어서도 경향성이 있음이 파악되었다. 분석 결과 및 그에 대한 논의를 통해 초등 수학 학습부진아의 자릿값 개념 진단과 지도를 위한 교수학적 시사점을 도출하였다.

• 대한토목학회논문집
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• 제35권2호
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• pp.361-375
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• 2015

에너지파일은 기존의 수직밀폐형 지중열교환기를 경제적으로 대체할 수 있는 새로운 형태의 지중열교환기이다. 즉, 에너지파일은 건물의 기초 구조물과 지중열교환기의 역할을 동시에 수행하는 에너지 구조체로서, 말뚝 기초 내부에 열교환 파이프를 삽입하고 파이프를 통해 유체를 순환시켜 지반과의 열교환을 유도한다. 본 연구에서는 병렬 U형(5쌍, 8쌍, 10쌍)의 열교환 파이프를 대구경 현장타설 에너지파일에 삽입하여, 3본의 에너지파일을 실규모로 시공하였다. 또한 현장 열응답 시험(In-situ thermal response tests, TRTs)을 수행하고 시공된 현장타설 에너지파일과의 열교환 효율을 비교하기 위하여 30m 깊이의 수직밀폐형 지중열교환기를 별도로 시공하였다. 병렬 U형 현장타설 에너지파일에 대해서는 냉난방 부하를 인공적으로 주입하는 열교환 성능 평가시험을 수행하여 열교환 성능(heat exchange rate)을 평가하였다. 마지막으로 현장타설 에너지파일의 적용성 평가를 위해 산정된 상대 열교환 효율(relative heat exchange efficiency) 및 열교환 성능을 선행 연구 결과와 비교하였으며, 본 연구에서 시공된 현장타설 에너지파일은 안정적이고 효율적인 열성능을 보이는 것으로 나타났다.

• The Journal of Asian Finance, Economics and Business
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• 제7권5호
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• pp.305-314
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• 2020

The paper explores the return migration choice of graduates, which takes place during the transition from higher education to the labor market. Graduate students, after a short time in temporary migration to cities for studying, have to make a decision of returning back home or staying in migration in urban areas for working. Drawing on the mechanism identified in the literature on internal migration, this empirical research tests the effects of two factors: place attractiveness and social supports factors on graduates' decision to return migration to hometown. A binary logit regression analysis was conducted with data from 502 surveyed graduates in Hanoi, Vietnam. The analysis of the motives reported by graduates indicates that return migration decisions cannot be reduced to a single dimension. Perceived attractiveness of a region such as quality of living environment, job opportunities, and social context of individuals positively impact on student' decision to return migration after graduation. The research results imply that, in a collectivistic country like Vietnam, students' choice of future career is strongly influenced by their social context, and choosing a place to work is not simply a matter of earning a higher salary or enjoying better working conditions, but is also related to family issues.