• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.2 s.54
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• pp.27-38
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• 2007

A series of forced vibration tests and ambient vibration measurement was conducted on a four-story reinforced concrete building damaged in the 1994 Northridge earthquake. Both low amplitude broadband and moderate amplitude harmonic excitation were applied using a linear shaker and two eccentric mass shakers, respectively, and ambient vibrations were measured before and after each forced vibration test. Accelerations, interstory displacements, and curvature distributions were monitored using accelerometers, LVDTs and concrete strain gauges. Natural frequencies and the associated mode shapes fur the first 7 modes were identified. Fundamental frequencies determined from the eccentric mass shaker tests were 70% to 75% of the values determined using ambient vibration data, and 92% to 93% of the values determined using the linear shaker test data. Larger frequency drops were observed in the NS direction of the building, apparently due to damage that was induced during the Northridge earthquake.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.25-30
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• 2006

When wet soil overlies dry soil, which can be found in the infiltration test, the radar wave is not attenuated and guided within wet soil layer. This phenomenon is known to be the dispersive guided wave and happens when the thickness of upper wet layer is less than or comparable to the wavelength of radar wave. In this study, we have conducted the FDTD modeling and obtained the velocity dispersion curve to identify the dispersive guided wave through F-K analysis. This guided wave can be explained by modal propagation theory and a simple inversion code was developed to obtain the two layer's dielectric constants as well as layer thickness. By inverting the dispersion curve from synthetic modeling data, we could obtain the accurate dielectric constants and layer thickness. Moreover, we could enhance the accuracy by including the higher mode data. We expect this method will be very useful to get the quantitative property of subsurface when the condition is similar.

• Journal of Korean Academy of Nursing
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• v.40 no.5
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• pp.736-746
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• 2010

Purpose: This study was done to identify the distribution and related factors for stage of change for wearing hearing protection devices (HPDs) by workers in environments with high noise. Predictors of Use of Hearing Protection Model and Trans-theoretical Model were tested. Methods: The participants were 755 workers from 20 noisy work places in Busan and Gyeongnam. Data were collected from January to April 2008 using self-administered questionnaires, and analyzed using multiple logistic regression. Results: There were significant differences in social mode (OR=1.35, 95% CI: 1.06-1.73) between precontemplation/contemplation and preparation stage, in males (OR=2.36, 95% CI: 1.24-4.51), workers with high school education or less (OR=1.39, 95% CI: 1.28-2.78), shift workers (OR=1.50, 95% CI: 1.02-2.21), workers who previously worked in noisy places (OR=1.39, 95% CI: 1.20-2.34), and workers who had previous hearing examinations (OR=1.89, 95% CI: 1.25-2.85), in the social model (OR=1.59, 95% CI: 1.42-1.78), and self-efficacy (OR=1.05, 95% CI: 1.02-1.08) between workers in preparation and action stages, in length of time working in noisy work places (OR=2.26, 95% CI: 1.17-4.39), social model (OR=1.66, 95% CI: 1.33-2.08), and perceived benefit (OR=0.95, 95% CI: 0.93-0.97) between action and maintenance stage. Conclusion: Social model was a common factor showing differences between two adjacent stages for wearing HPDs. The results provide data for developing programs to encourage workers to wear HPDs and application of these programs in work settings.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1287-1292
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• 2010

In this paper, a hybrid technique is presented. First, the isochromatic fringe data of a given set of points are calculated by the finite element method and are used as input data in complex variable formulations. Then the numerical model of the specimen with a central inclined crack is transformed from the physical plane to the complex plane by conformal mapping. The stress field is analyzed and the mixed-mode stress intensity factors are calculated for this complex plane. The stress intensity factors are calculated by the finite element method as well as by a theoretical method and compared with each other. In order to conveniently compare these values with each other, both actual and regenerated photoelastic fringe patterns are multiplied by a factor of two and sharpened by digital image processing.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.34 no.4
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• pp.431-441
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• 2016

Since the use of UAV (Unmanned Aerial Vehicle) is convenient for the acquisition of data on broad or inaccessible regions, it is nowadays used to establish spatial information for various fields, such as the environment, ecosystem, forest, or for military purposes. In this study, the process of estimating FVC (Fractional Vegetation Cover), based on multi-spectral UAV, to overcome the limitations of conventional methods is suggested. Hence, we propose that the FVC map is generated by using multi-spectral imaging. First, two types of result classifications were obtained based on RF (Random Forest) using RGB images and NDVI (Normalized Difference Vegetation Index) with RGB images. Then, the result map was reclassified into vegetation and non-vegetation. Finally, an FVC map-based RF were generated by using pixel calculation and FVC map-based GI (Gutman and Ignatov) model were indirectly made by fixed parameters. The method of adding NDVI shows a relatively higher accuracy compared to that of adding only RGB, and in particular, the GI model shows a lower RMSE (Root Mean Square Error) with 0.182 than RF. In this regard, the availability of the GI model which uses only the values of NDVI is higher than that of RF whose accuracy varies according to the results of classification. Our results showed that the GI mode ensures the quality of the FVC if the NDVI maintained at a uniform level. This can be easily achieved by using a UAV, which can provide vegetation data to improve the estimation of FVC.

• Korean Journal of Ecology and Environment
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• v.41 no.2
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• pp.247-263
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• 2008

A two-dimensional (2D) reservoir hydrodynamics and water quality model, CE-QUAL-W2, is employed to simulate the hydrothermal behavior and density current regime in Andong Reservoir. Observed data used for model forcing and calibration includes: surface water level, water temperature, dissolved oxygen and suspended solids concentration. The model was calibrated to the year of 2003 and verified with continuous run from 2000 till 2004. Without major adjustments, the model accurately simulated surface water levels including the events of large storm. Deep-water reservoirs, like Andong Reservoir, located in the Asian Monsoon region begin to stratify in summer and overturn in fall. This mixing pattern as well as the descending thermocline, onset and duration of stratification and timing of turnover phenomenon were well reproduced by the Andong Model. The temperature field and distinct thermocline are simulated to within $2^{\circ}C$ of observed data. The model performed well in simulating not only the dissolved oxygen profiles but also the metalimnetic dissolved minima phenomenon, a common1y occurring phenomenon in deep reservoirs of temperate regions. The Root Mean Square Error (RMSE) values of model calibration for surface water elevation, temperature and dissolved oxygen were 0.0095 m, $1.82^{\circ}C$, and $1.13\;mg\;L^{-1}$, respectively. The turbid storm runoff, during the summer monsoon, formed an intermediate layer of about 15 m thickness, moved along the metalimnion until being finally discharged from the dam. This mode of transport of density current, a common characteristic of various other large reservoirs in the Asian summer monsoon region, was well tracked by the model.

• Economic and Environmental Geology
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• v.27 no.4
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• pp.325-333
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• 1994

Gold and/or silver mineralization in the southeast province, Korea, occurred in hydrothermal quartz vein that fills fracture zones in Cretaceous volcanic and sedimentary rocks of the Gyeongsang basin or granites and Precambrian gneiss. Most of the gold-silver-bearing veins in the province occur in Hapcheon, Suncheon and Haman-Gunbuk area where they are associated with Cretaceous Bulgugsa granites. On the basis of the Ag/Au ratio on amounts produced and ore grades, mode of occurrence, and associated mineral assemblages, hydrothermal Au-Ag deposits in southeast province, Korea, can be classified as follows: pyrite-type gold deposit (Group IIB, Samjeong and Sangchon deposits), antimony-type gold-silver deposit (Group IV, Gisan and Geochang deposits), and antimony-type silver deposit (Group V, Sanggo, Seweon, Seongju and Gahoe deposits). All of the gold-silver deposits in the province are generally characteristics of the gold-silver or silver-dominant type deposit which contains more silver-bearing minerals than those deposits in central Korea. The gold-silver mineralization in the deposits consist of two generation; the early characterized by gold precipitation and the late represented by silver-rich (as silver-bearing sulfosalts minerals) mineralization. All but one deposit (Samjeong deposit) having relatively lower Au content in electrum values between ${\approx}20$ and ${\approx}50$ atomic %. The mineralogical data on electrum-sphalerite and/or arsenopyrite geothermometry and fluid inclusion data indicate that the gold and silver mineralizations were occurred at temperatures of $190{\sim}280^{\circ}C$ and $150{\sim}180^{\circ}C$, respectively. These suggest that the gold-silver mineralization in the province occurred in the lower temperature and pressure conditions as epithermal-type hydrothermal vein deposit.

• Journal of the Institute of Convergence Signal Processing
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• v.8 no.2
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• pp.106-112
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• 2007

This paper proposes a hybrid architecture algorithm for fast computation of DCT and DFT via recursive factorization. Recursive factorization of DCT-II and DFT transform matrix leads to a similar architectural structure so that common architectural base may be used by simply adding a switching device. Linking between two transforms was derived based on matrix recursion formula. Hybrid acrchitectural design for DCT and DFT matrix decomposition were derived using the generation matrix and the trigonometric identities and relations. Data flow diagram for high-speed architecture of Cooley-Tukey type was drawn to accommodate DCT/DFT hybrid architecture. From this data flow diagram computational complexity is comparable to that of the fast DCT algorithms for moderate size of N. Further investigation is needed for multi-mode operation use of FFT architecture in other orthogonal transform computation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.153-164
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• 2010

In this paper, we propose a multi-channel MAC protocol to improve the channel efficiency and network performance in wireless ad hoc networks. There are two main problems encountered in designing multi-channel MAC protocols. The first problem is the rendezvous problem and the second is multi-channel hidden node problem. In order to solve these problems, most of previous researches that have considered multi-channel MAC protocols use a common control channel to exchange control packets. However, they have a bottleneck problem at common control channel as increasing the number of data channels. The proposed MAC protocol solves the multi-channel hidden node problem using a TDMA scheme and increases the network throughput because transmitting and receiving data at the same time is possible. Also, since there is no common control channel, the network does not suffer from the common control channel saturation problem. Moreover, it achieves energy savings by allowing nodes that are not involved in communication to go into sleep mode. Simulation results show that the proposed MAC protocol improves the network throughput and channel efficiency and provides energy savings.

• Women's Health Nursing
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• v.9 no.2
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• pp.161-169
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• 2003

The purpose of this study was to identify menstrual symptoms, coping and Relief of Symptoms used by female college students. A convenience sample of 202 students were obtained from two colleges in Seoul. Data were collected through questionnaires from September 10 to December 18, 2001, Three instruments were used in this study, the Menstrual Symptoms Questionnaire by Park K. R(1988) and Menstrual Coping Questionnaire and Relief of Symptoms by Billings & Moos(1981) modified for this study. 1)Part time instructor, Department of Nursing, Pochon CHA University The data were analyzed by descriptive statistics, t-test, ANOVA with the SPSS 10.0 program. The result of this study are as follows. 1. Prevalence rate of dysmenorrhea was 91.6%. 2. The total mean score for menstrual symptoms was 1.89 of a possible total of 5 and mean score for each category was, 2.26 for water retention, 2.11 for negative affect, 2.02 for pain, 1.83 behavioral change, 1.69 for autonomic reactions, and 1.53 for concentration. 3. According to the result of this study, statistical differences were found for age (F=3.76, p=0.01), menstrual fear (t=2.02, p=0.04), dysmenorrhea (t=7.73, p=0.02), and taking medication (t=5.95, p=0.00). 4. The coping mode with the highest scores were 'rest and go to bed (83.7%)', 'regard mensturation as a physiological and temporary phenomenon (68.3%)', 'take a warm shower(66.8%)'. The most frequently used methods to relief of symptoms were 'take pain killers (99.9%)', 'to apply hot water bag on painful parts of the body (96.6%)' and 'rest and go to bed (88.8%)'.