• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.139-145
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• 1999

The objective of this study is to provide the information on the small-scale model mix proportion when the behavior of prototype concrete pavement is studied through small-scale model experiments. However it is difficult to obtain a model material to simulate the prototype concrete by scaling the individual components according to the laws of similitude. In this paper, the stress-strain behavior in uniaxial compression is used as a means to correlate material similitude between the prototype and the model concrete. Based on the results of experiments, we compared the stress-strain curves of prototype and model concrete mixes using a nondimensional basis. In order to simulate the stress-stain curves of prototype concrete, it is important that various mix proportions of model concrete selected properly which are varied from aggregate grading, cement-aggregate and sand-aggregate ratio.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.8
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• pp.3523-3531
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• 2011

This study was intended to measure the quality of sleep according to the job stress contents among nurses working for an university hospital. The self-administered questionnaires were given to 482 nurses employed in an university hospital during the period from June 1st to July 31st, 2011. As a results, the quality of sleep was significantly lower in the group with higher job demand, lower job control, lower supervisor and coworker support. In correlation, the level of quality of sleep was positively correlated with job demand, but it was negatively correlated with job control, supervisor and coworker support. In logistic regression analysis, the adjusted odds ratio of the quality of sleep was significantly increased in higher group of job demand than in lower group. But it was significantly decreased in higher group of supervisor and coworker support. The study results may explain that the quality of sleep is independently associated with the job stress contents.

• Journal of the Korean GEO-environmental Society
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• v.12 no.7
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• pp.57-65
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• 2011

Numerical simulations by three-dimensional Particle Flow Code($PFC^{3D}$, Itasca) considering distinct element method (DEM) were carried out for prediction of triaxial compression test with sand material. The effect of scale conditions for numerical model and distinct material on final prediction results was analyzed by numerical models under various scale conditions, and following observations were made from the numerical experiments. It is very useful to model the initial material condition without any porosity conversion from 2-D to 3-D DEM. Numerical experiments have shown that in all cases considered, 3D distinct element modeling could provide good agreement on stress-strain behavior, volume change and strength properties with laboratory testing results. It was important thing to assess reasonable scale ratio of numerical model and distinct elements for saving calculation time and securing calculation efficiency under condition with accuracy and appropriateness as numerical laboratory. As results of DEM simulations under various scale conditions, most of results show that shear strength properties as cohesion and internal friction angle are similar in condition of $D_{mod}/D_{gmax}$ < 10. It shows that 3-D distinct element method could be used as efficient tool to assess strength properties by numerical laboratory technique.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.409-417
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• 2010

This paper discusses a series of experiments including material improvement in order to ensure quality of grouting for the post-tensioned structure. In prestressed concrete, grouting refers to the construction procedure of filling empty space of duct enclosing with strands using cementitious material, To date, adequate quality control of the grouting has not been established in Korea because the relationship between the grouting and durability of post-tensioned structure is not well-recognized. The Korean standard does not consider the important material characteristic, wick effect, which is caused by strands in the ducts and current standard testing method unlikely quantify reasonable material segregation. As a result, the grout material, which meets the current material standards, may exhibit excessive bleeding water or shrinkage during construction. In this study, international codes and standards related to grouting were surveyed. The ratio of constituents and novel admixtures were suggested to meet equivalently with these standards. Performance of this enhanced grout was compared to common domestic grout using the international standard testing method. A series of mock-up specimens considering geometry of PC beam was constructed and grout flow pattern was observed as the grout was injected. It was observed that the grouting performance was highly influenced by material properties and filling characteristic can be varied depending on geometry of ducts.

• Journal of Korea Society of Industrial Information Systems
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• v.15 no.4
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• pp.71-81
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• 2010

The purpose of this study is to examine the moderating effects of the Leader-member exchange(LMX) on relationship between the interpersonal conflict and turnover intention. Since effective management of IS personnel is important issue for the IS related researchers and practitioners since their turnover rate has been known to be high and skilled personnel have been in short supply. We develop the hypotheses from the prior studies and empirically testing them in the context of IS personnels from various companies located in vicinity of capital city of Korea. This empirical study show interesting results. Good leader-member exchange has the moderating effect on the management of interpersonal conflict level and drastic reduction of the turnover behavior. Based on the analyzed results, we discussed the theoretical implications and limitations.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.1
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• pp.118-122
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• 2016

When a geometric size of moonpool and an inflow velocity are determined based on the similarity of Froude number, Reynolds number is depending on the scale ratio of moonpool geometry. It means that different characteristics of flow fluctuations in moonpool can be observed depending on the scale ratio of moonpool even though Froude number is the same. In the present study two dimensional numerical simulations were performed to investigate the influence of scale ratios on the flow characteristics inside the moonpool. The inflow velocity at several scale ratios was determined to keep Froude number constant. A periodic response was observed in a small size of moonpool while a large moonpool showed complicated fluctuations with various amplitudes and frequencies, which made it difficult to distinguish the statistical steady-state response from the temporal responses in the case of large moonpool. The similarity of Froude number gave rise to a spectral characteristic which was inversely proportional to the square root of scale ratios ($f_{0.5}{\approx}{\sqrt{2}}f_1{\approx}2f_{2.0}$) but a low frequent occurrence of strong vortex ($f_{2.0}=0.07$)which is observed inside the large moonpool was characterized depending on scale ratios.

• Journal of Korea Water Resources Association
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• v.31 no.4
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• pp.459-467
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• 1998

The existing methods to analyze the heterogeneous porous media based on the similar media concept are the microscopic Miller similitude(MiS), the macroscopic Miller similitude(MaS) and the Warrick similitude(WS). The inter-relationship is found such that MiS ⊂ MaS ⊂ (⊂:subset). The proposed method is based ont eh assumption that the scale variables $\alpha$=w and the moisture content is dimensionless by introducing the effective degree of saturation instead of the degree of saturation into WS. The method, without the loss of generality in view of the inspectional analysis, can explain the heterogeneity of the media by using the scale variable $\alpha$ only. The media of $\alpha$=1 (average of $\alpha$) means the equivalent media corresponding to the heterogeneous media, while the standard deviation of $\alpha$ may explain the degree of the heterogeneity of the media under consideration. The hydraulic conductivity of the media with $\alpha$>1 is greater than that of the equivalent media, and the effective moisture content of the media with $\alpha$>1 is also greater. Based on these properties of the scale variable $\alpha$, the ideal vertical one-dimensional heterogeneous porous media is generated by using the technique of random number generation.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.6_2
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• pp.613-623
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• 2007

The main purpose of this study is to investigate the coordinate transformation based on two different systems between local geodetic datum(tokyo datum) and international geocentric datum(new Korea geodetic datum). For this purpose, three methods were used to determine seven parameters as follows: Bursa-Wolf model, Molodensky-Badekas model, and Veis model. Also, we adopted multiple regression equation method to convert from Tokyo datum to KTRF. We used 935 control points as a common points and applied gross error analysis for detecting the outlier among those control points. The coordinate transformation was carried out using similarity transformation applied the obtained seven parameters and the precision of transformed coordinate was evaluated about 9,917 third or forth order control points. From these results, it was found that Bursa-Wolf model and Molodensky-Badekas model are more suitable than other for the determination of transformation parameters in Korea. And, transforming accuracy using MRE is lower than other similarity transformation model.

• Magazine of the Korea Concrete Institute
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• v.7 no.2
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• pp.165-174
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• 1995

It is well known that the behavior of R /C members under static cyclic loading is somewhat different from that under dynamic cyclic loading, such as earthquake loading, because static loading rate is substantially lower than that corresponding to the Frequencies of seismic excitation. The purpose of this research is to estabilish the reliance for modeling techniques of small-scale specirr~ens subjected to dynamic cyclic loading. This research focused on the similitude requirements for reinforced concrete frame structures subjeced to dynamic cyclic loading. Length scale ratio of specimens were 1 : 2 : 4, and eleven specimens were tested at the frequencies of 0.0025Hz-2.OHz. It was confirmed that rnode1ir.g techniques based on the similitude requirements were useful methods to evaluate the behavior of full-size R /C structures subjected to earthquake type loading.

• Journal of Digital Convergence
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• v.12 no.12
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• pp.427-439
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• 2014

This study analyzed the effects of job stress, job burnout, and social support on turnover intention for beauty salon workers in Busan. First, the younger, the higher levels of emotional labor; the younger, the lower education levels, the shorter career, and the lower position, the higher job stress and the higher job burnout; and the younger, the lower education levels, and the fewer days off, the higher turnover intention. Second, directors, designers and the staff had emotional labor, job stress, job burnout, and social support associated with turnover intention. Third, owners and designers had their turnover intention in general affected by emotional control, role stress, supervisor support, and colleague support and had their workplace-related turnover intention affected by emotional control, role stress, colleague support, and depersonalization, while the staff had their turnover intention in general and workplace-related turnover intention affected by supervisor support, colleague support, and depersonalization and had their job-related turnover intention affected by supervisor support.