• Geomechanics and Engineering
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• v.11 no.6
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• pp.867-877
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• 2016

Collapse shape of tunnel roof in layered Hoek-Brown rock media is investigated within the framework of upper bound theorem. The traditional collapse mechanism for homogeneous stratum is no longer suitable for the present analysis of roof stability, and it would be necessary to propose a curve failure mode to describe the velocity discontinuity surface in layered media. What is discussed in the paper is that the failure mechanism of tunnel roofs, consisting of two different functions, is proposed for layered rock media. Then it is employed to investigate the impending roof failure. Based on the nonlinear Hoek-Brown failure criterion, the collapse volume of roof blocks are derived with the upper bound theorem and variational principle. Numerical calculations and parametric analysis are carried out to illustrate the effects of different parameters on the shape of failure mechanism, which is of overriding significance to the stability analysis of tunnel roof in layered rock media.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.4
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• pp.302-306
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• 2019

We investigated a solution-derived $Y_2O_3$ film treated by ion beam (IB) irradiation as a liquid crystal (LC) alignment layer. With IB irradiation, homogeneous LC alignment was achieved irrespective of the annealing temperature. To verify the effect of IB irradiation, we conducted surface analyses such as X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). As $Y_2O_3$ is a high-k material, the electro-optical properties of the twisted nematic (TN) cells were superior to those of conventional TN cells based on a rubbed polymer, with an LC rising time of 4.1ms and falling time of 2.9ms. The IB-irradiated $Y_2O_3$ is a good alternative as an alignment layer for fast-switching TN LC displays.

• Journal of muscle and joint health
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• v.2 no.1
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• pp.41-72
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• 1995

The purpose of this study is to examine the effects of assertiveness training and value clarification training on nurse's conflict and conflict management mode. Fifty seven registered nurses participated in the study ; they were employed by three general hospital located in Daegu, Korea. The study employs two treatment groups. The assertiveness training group consisted of subjects who participated in 90-120 minutes sessions of assertiveness training nine times over five weeks. The other treatment group, was adiministed nine, 90-120 minutes sessions of value clarification during the same period. For the control group, nursing subjects were appointed the training after five weeks. Pre-test evaluation were administered to all subjects in three groups prior to one week of the treatment. Role conflict Inventory-general(RCI-G) and Communication Conflict Inventory-general (CCI-G) measure nurse's conflict management mode. Post-test evaluation were administered to all subjects in three groups two weeks after the last session by Role Conflict Inventory-Specific(RCI-S), Communication Conflict Inventory-Specific (CCI-S), Management Model-Specific(CMMI-S). The analysis of variance(ANOVA) and covariance(ANCOVA) on gain scores were running the SPSS program. In order to test statistical differences among mean scores of the scales obtained after treatment, multiple comparisons were carried out by Turkey method. Conclusions obtained from the results are as follows. 1. The assertiveness training and the value clarification training were effective in decreasing the nurse's role conflict. The value clarification was more effective than the assertiveness training in decreasing the nurse's role conflict. 2. Both assertiveness training and value clarification training were effective in decreasing nurse's communication conflict. There was, however, no differences between assertiveness training and value clarification training in decreasing the nurse's communication conflict. 3. The assertiveness training and the value clarification training were quite effective in compromizing and collaborating conflict management mode, to reducing the withdrawl and accomodate, force and accomodate conflict management mode to conflict. There was no difference in the effectiveness of assertiveness training and value clarification. In assessing the effects of the treatments, this study employed different measurements. It is unclear whether the measurement affected the test results. It is worth conducting a further test using the same measurements. The results of future studies can be compared with those of this study. The homogeneity of the control group and treatment group is questionable. Futher studies may employ homogeneous sample group to evaluate whether the sample characteristics bias the test results. Assertiveness training or value clarification training for nurses can be utilized in nursing intervention.

• Smart Structures and Systems
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• v.13 no.4
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• pp.615-636
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• 2014

Aluminium Foam Sandwich (AFS) panels are becoming always more attractive in transportation applications thanks to the excellent combination of mechanical properties, high strength and stiffness, with functional ones, thermo-acoustic isolation and vibration damping. These properties strongly depend on the density of the foam, the morphology of the pores, the type (open or closed cells) and the size of the gas bubbles enclosed in the solid material. In this paper, the vibrational performances of two classes of sandwich panels with an Alulight(R) foam core are studied. Experimental tests, in terms of frequency response function and modal analysis, are performed in order to investigate the effect of different percentage of porosity in the foam, as well as the effect of the random distribution of the gas bubbles. Experimental results are used as a reference for developing numerical models using finite element approach. Firstly, a sensitivity analysis is performed in order to obtain a limit-but-bounded dynamic response, modelling the foam core as a homogeneous one. The experimental-numerical correlation is evaluated in terms of natural frequencies and mode shapes. Afterwards, an update of the previous numerical model is presented, in which the core is not longer modelled as homogeneous. Mass and stiffness are randomly distributed in the core volume, exploring the space of the eigenvectors.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.68.1-68.1
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• 2019

Turbulence plays a crucial role in controlling star formation as it produces density fluctuation as well as non-thermal pressure against gravity. Therefore, turbulence controls the mode and tempo of star formation. However, despite a plenty of previous studies, the properties of turbulence remain poorly understood. As part of the Taeduk Radio Astronomy Observatory (TRAO) Key Science Program (KSP), "mapping Turbulent properties In star-forming MolEcular clouds down to the Sonic scale (TIMES; PI: Jeong-Eun Lee)", we mapped the Orion A and the Ophiuchus clouds, in three sets of lines (13CO 1-0/C18O 1-0, HCN 1-0/HCO+ 1-0, and CS 2-1/N2H+ 1-0) with a high-velocity resolution (~0.1 km/s) using the TRAO 14-m telescope. The mean Trms for the observed maps are less than 0.25 K, and all these maps show uniform Trms values throughout the observed area. These homogeneous and high signal-to-noise ratio data provide the best chance to probe the nature of turbulence in two different star-forming clouds, the Orion A and Ophiuchus clouds. We present comparisons between the line intensities of different molecular tracers as well as the results of a Principal Component Analysis (PCA).

• Journal of Biomedical Engineering Research
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• v.19 no.6
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• pp.551-562
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• 1998

Amultiresolution filtering algorithm based on the physical SPECT lesion detachability provides and optimal solution for SPECT reconstruction problem. Related to the previous study, we estimated the SPECT lesion detection capability by m minimum detectable lesion sizes (MDLSs), and generated m reconstruction filters which are designed to maximize the smoothing effect at a fixed MDLS-dependent resolution level $\frac{MDLS}{4\sqrt{2In2}}$. The proposed multiresolution filtering algorithm used a coarse-to-fine approach for the m-level resolution filter images obtained from these m filters for a given projection image. First, the local homogeneity is determined for every pixel of the filter images, by comparing the local variance value computed in a window centered at the pixel and the mode determined from the distribution of the local variances. Based on the local homogeneity, the pixels declared as homogeneous are chosen from the filter image of the lowest resolution, and for the other pixels the same process is repeated for the higher resolution filter images. For the non-homogeneous pixels after this pixels after this repetition process ends, the pixel values of the highest resolution filter image are substituted. From the results of the simulated experiments, the proposed multiresolution filtering algorithm showed a strong smoothing effect in the homogeneous regions and a significant resolution improvement near the edge regions of the projection images, and so produced good adaptability effects in the reconstructed images.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5D
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• pp.709-716
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• 2006

The rapid changes of family structure such as singles, working couples and so on have effects on a travel behaviour. One of the characteristics from this is the increasing portion of trip-chain, in which plural activities were conducted in a "single outgoing" travel. Therefore travel must be considered as location change to conduct various activities instead of pursuing single travel purpose. This paper specifies a behavioral homogeneous person group by a job, a possession of cars. Based on this classification of person groups and their activity diary, the sequence, time and travel mode of activities in a day can be verified. As a case study household survey was conducted in city Kongju. The survey result shows that the classification of behavioral homogeneous person group based on criteria like employment status and car ownership bring a good result to forecast trip generation in traffic zone.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.4
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• pp.423-431
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• 2004

For the fracture mechanics analysis of cracks in welds of dissimilar steels, residual stress analysis and fracture analysis must be performed simultaneously. The standard definition of the J -integral leads to a path dependent value in the presence of a residual stress field. And unlike cracks in homogeneous materials, a bimaterial interface crack always induces both opening and shearing modes of stress in the vicinity of the crack tip. Therefore, it is necessary to develope a path independent J-integral definition for a crack in a residual stress field generated by welding of dissimilar steels. This paper addresses the modification of the Rice-J-integral to produce a path independent J -integral when residual stresses due to welding of dissimilar steels and external forces are present. The residual stress problem is treated as an initial strain problem and the J-integral proposed for this class of problems is used. And a program which can evaluate the J -integral for a crack in a weld of dissimialr steels is developed using proposed J integral definition.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.1
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• pp.193-200
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• 2007

Natural gas is one of the most promising alternatives to gasoline and diesel fuels because of its lower harmful emissions, including $CO_2$, and high thermal efficiency. In particular, natural gas is seen as an alternative fuel for heavy-duty Diesel Engines because of the lower resulting emissions of PM, $CO_2$ and $NO_x$. Almost all CNG vehicles use the PFI-type Engine. However, PFI-type CNG Engines have a lower brake horse power, because of reduced volumetric efficiency and lower burning speed. This is a result of gaseous charge and the time losses increase as compared with the DI-type. This study was conducted to investigate the effect of injection conditions (early injection mode, late injection mode) on the combustion phenomena and performances in the or CNG Engine. A DI Diesel Engine with the same specifications used in a previous study was modified to a DI CNG Engine, and injection pressure was constantly kept at 60bar by a two-stage pressure-reducing type regulator. In this study, excess air ratios were varied from 1.0 to the lean limit, at the load conditions 50% throttle open rate and 1700rpm. The combustion characteristics of the or CNG Engine - such as in-cylinder pressure, indicated thermal efficiency, cycle-by-cycle variation, combustion duration and emissions - were investigated. Through this method, it was possible to verify that the combustion duration, the lean limit and the emissions were improved by control of injection timing and the stratified mixture conditions. And combustion duration is affected by not only excess air ratio, injection timing and position of piston but gas flow condition.

• Journal of the korean society of oceanography
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• v.31 no.4
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• pp.164-172
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• 1996

CREAMS (Circulation Research of the East Asian Marginal Seas) Expeditions have provided a rare opportunity to carry out precise measurements of salinity, temperature and chemical tracers extensively in all major basins of the East Sea (Japan Sea) in 1993-1996 for the first time in more than 60 years since Uda's investigation (Uda, 1934). Studies revealed unequivocal evidence that the East Sea Proper Water (ESPW), previously known as a single homogeneous water mass, is indeed made of several distinct water masses. CREAMS data further confirmed the earlier observations of Gamo et al. (1986) that properties in Deep Waters in the East Sea have been changing during at least the last 25 years. There is evidence, especially from the analysis of the DO profile, that these changes may result from a major change in the mode of deep water formation: from bottom water formation in the past to intermediate/deep water formation in recent years. The causes for these changes are not clear at the present time, but nay include natural variation and may also reflect recent global changes in regional scale. A moving-boundary box model is presented to describe current observations, predicting the turnover time of the total deep and bottom waters to the cold surface waters to be ${\sim}$80 years in 1996.