• Journal of the Korean Geotechnical Society
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• v.32 no.8
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• pp.5-14
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• 2016

The leakage of water under sewer pipelines is one of main sources of sinkholes in urban areas. We performed laboratory model tests to investigate the presence of cavities using impact-echo method, which is a nondestructive test method. To simulate a concrete sewer pipe, a thin concrete plate was built and placed over container filled with sand. The cavity was modeled as an extruded polystyrene foam box. Two sets of tests were performed, one over sand and the other on cavity. A new impact device was developed to apply a consistent high frequency impact load on the concrete plate, thereby increasing the reliability of the test procedure. The frequency and transient characteristics of the measured reflected waveforms were analyzed via fast Fourier transform and short time Fourier spectrum. It was shown that the shapes of Fourier spectra are very similar to one another, and therefore cannot be used to predict the presence of cavity. A new index, termed resonance duration, is defined to record the time of vibration exceeding a prescribed intensity. The results showed that the resonance duration is a more effective parameter for predicting the presence of a cavity. A value of the resonance period was proposed to estimate the presence of cavity. Further studies using various soil types and field tests are warranted to validate the proposed approach.

• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.377-383
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• 2007

In recent years the field application of high performance concrete has been increased to improve the quality and reliability of concrete structures. The mix design of the high performance concrete includes the 2 set-off mixture theory of mortar and coarse aggregate and that of paste and aggregate. The 2 set-off mixture theory of mortar and coarse aggregate has a problem of having to determine its value through repeated experiments in applying the rheological characteristics of mortar. The 2 set-off mixture theory of paste and aggregate has never been applied to high performance concrete since it doesn't take into account the relationship between optimum fine aggregate ratio and unit volume of powder nor does it consider the critical aggregate volume ratio. As the mixture theory of these high performance concretes, unlike that of general concrete, focuses on flowability and charge-ability, it does not consider intensity features in mix design also, the unit quantity of the materials used is determined by trial and error method in the same way as general concrete. This study is designed to reduce the frequency of trial and error by accurately calculating the optimum fine aggregate ratio, which makes it possible to minimize the aperture of aggregate in use by introducing the maximum density theory to the mix design of high performance concrete. Also, it is intended to propose a simple and reasonable mix design for high performance concrete meeting the requirements for both intensity and flowability. The mix design proposed in this study may reduce trial and error and conveniently produce high performance concrete which has self-chargeability by using more than the minimum unit volume of powder and optimum fine aggregate with minimum porosity.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.10-19
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• 2012

In this paper, we propose an Adaptive Modulation and Coding (AMC) scheme using relay protocols generally known as Relay Node (RN). The AMC scheme is used for improving the throughput and a reliability of a communication system, because of the nature of different modulation and coding schemes. We analyze the performance of relay protocols with the AMC scheme and observed that relay protocols with the AMC scheme is capable of providing better average throughput at a lower Signal to Noise Ratio (SNR) level as compared to the conventional scheme with no AMC. We perform Monte Carlo simulations with Long Term Evolution-Advanced (LTE-A) parameters to prove the performance comparison of adaptive Modulation and Coding Scheme (MCS) relay protocols with the non-adaptive MCS relay protocols. The simulation results of the proposed system with adaptive MCS prove that among the Amplify-and-Forward (AF), Decode-and-Forward (DF) and DeModulate-and-Forward (DMF), the DMF protocol performs best at a lower SNR value and also provides better average throughput.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.3
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• pp.6-13
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• 2000

Ultra-thin gate oxide was grown on nitrogen implanted silicon substrates. For nitrogen implantation, the energy was fixed at 25keV, but the dose was split into 5.0$\times$10$^{13}$ /c $m^{2}$ and 1.0$\times$10$^{14}$ /c $m^{2}$. The grown gate oxide thickness were 2nm, 3nm and 4nm. The oxidation time to grow 3nm was increased by 20% and 50% for the implanted wafers of 5.0$\times$10$^{13}$ /c $m^{2}$ and 1.0$\times$10$^{14}$ /c $m^{2}$ doses, respectively, when it was compared with control wafers which were not implanted by nitrogen. The value of charge-to-breakdown ( $Q_{BD}$ ) is decreased with increasing nitrogen doses. If an annealing process( $N_{2}$, 85$0^{\circ}C$, 60min.) is peformed after nitrogen implantation, $Q_{BD}$ is increased. It is indicated that nitrogen implantation damage affect gate oxide reliability and the damage can be removed by post-implantation annealing process.

• Journal of Broadcast Engineering
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• v.20 no.6
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• pp.901-911
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• 2015

Many studies tried to develop a 3D display based stereo test as a substitute for the conventional stereo test. Although many 3D monitor based stereo tests have various advantages over the conventional stereo tests with printed stimuli, they have a crucial limitation in manipulating disparity. The least value for disparity manipulation is one pixel, which is too big to screen the normal stereo acuity in pc environment with a short viewing distance. In this explorative study, a Gabor image was employed as a test stimulus, because its position can be manipulated by changing its phase information, which allows sub-pixel manipulation for disparity. Instead of employing the methods of the conventional stereo tests where measurement was made only once for each of a wide range of disparity values, 10 replications were administrated for each of 6 disparity levels. The results from the test using Gabor images were compared with those using random dot stimulus because the latter stimulus was exactly the same as that of the conventional stereo test. The correlation coefficient between two tests was found to be moderate. After one month later, the whole test was repeated in the same settings. The correlation coefficient between test and retest results from Gabor images was found to be as high as that from a random dot stimulus, implying high test-retest reliability. These results suggest that a Gabor stimulus could be used as a test stimulus for the valid and reliable stereo test, even in the limited condition, such as 3D environment with a short viewing distance and a condition for evaluating the stereo acuity very precisely.

• The Journal of the Korea Contents Association
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• v.10 no.2
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• pp.330-341
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• 2010

The purpose of this study is to have comparative analysis on the differences between metropolis and provincial city's electronic security system users' security needs satisfaction and life satisfaction. This study sampled total 400 users with using purposeful sampling after selecting specific metropolis and provincial cities as population. It was conducted on 4 realms-bank, jewelry store, convenience store and communication industry- with two times. First one was on June, 2008, it was conducted in Seoul, 5 areas divided based on Hangang, which are Gang-dong, Gang-seo, Gang-nam, Gang-buk, and civic center. We sampled 40 electronic security system users of each area which are 200 in sum. Second one was on January, 2009, with users in Cheonan and Asan, 200 was sampled in the same way with metropolis; 100 users of each city. The reliability of the questionnaire showed Cronbach's ${\alpha}$ value over .812. The results are as follows. First, there showed difference on physical security needs satisfaction of electronic security system users with the size of city. In other word, users in metropolis have higher environmental, psychological, and informational security needs satisfaction than users in provincial city. Second, there is also difference in life satisfaction. Namely, users in metropolis have higher security needs satisfaction than users in provincial city. Third, security needs satisfaction of electronic security system users by city size effects life satisfaction. That is, in case of users in metropolis, the more physical, environmental, and informational security needs satisfaction it shows, the more life satisfaction it showed.

• Fire Science and Engineering
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• v.34 no.1
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• pp.11-17
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• 2020

As performance-based design (PBD) has a direct impact on evacuation safety assessments, designing fire scenarios based on real fire tests is essential. To improve the reliability of the PBD for fire safety in multiplexes, information on fire behavior, such as heat release rate (HRR) and fire spread rate, are provided in this study by conducting a standard fabric flammability test. To this end, several chairs were arranged in a pattern that resembled a theater-style seating. The peak HRR and heating value per unit mass for each chair ranged from 415 kW to 988 kW and 15.2 MJ/kg to 23.8 MJ/kg, respectively. The heating values per unit mass of the new and old chairs were 23.6 MJ/kg and 16.7 MJ/kg, respectively. As the quantity of plastic and cushioning materials in the new chairs was more than that of the old ones, the new chairs were more vulnerable to fire hazards. Furthermore, when the chairs were arranged in a line, the fire spread rate was observed to be 0.39-0.42 m/min, regardless of the ignition location. Finally, a fire growth curve showing the peak HRR and fire spread rate was also demonstrated.

• Industry Promotion Research
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• v.2 no.1
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• pp.77-83
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• 2017

The purpose of this study is to analyze the effect of sustainability of festival in Gangwon province on satisfaction. A total of 243 questionnaires were analyzed for the tourists participating in the Gangwon - do area festival. Using SPSS Statistics 20, we conducted frequency analysis, factor analysis, reliability analysis, correlation analysis, regression analysis, and ANOVA (Variance Analysis of Variance among Respondents). The results of this study are as follows. First, the satisfaction of the local festival persistence in Gangwondo area festival was found to be higher when the service satisfaction, program satisfaction, and red general satisfaction were higher in the regional festival sustainability. And it was analyzed to have a statistically significant effect. Second, there was no statistically significant effect of participating motivation on the program festival. Third, the correlation between the persistence of local festivals and the satisfaction of the local specialties was higher in R = .812, and the t value was 21.569 (p = .000) Respectively. The purpose of this study was to examine the effect of personal factors on regional festival tourists' satisfaction with regional festival sustainability and participatory motivation for service satisfaction, program satisfaction, There is a significance of research.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.1
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• pp.83-90
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• 2017

In this paper, we evaluated the solderability of thin electroless nickel-electroless palladium-immersion gold (ENEPIG) plating layer for fine-pitch package applications. Firstly, the wetting behavior, interfacial reactions, and mechanical reliability of a Sn-3.0Ag-0.5Cu (SAC305) solder alloy on a thin ENEPIG coated substrate were evaluated. In the wetting test, maximum wetting force increased with increasing immersion time, and the wetting force remained a constant value after 5 s immersion time. In the initial soldering reaction, $(Cu,Ni)_6Sn_5$ intermetallic compound (IMC) and P-rich Ni layer formed at the SAC305/ENEPIG interface. After a prolonged reaction, the P-rich Ni layer was destroyed, and $(Cu,Ni)_3Sn$ IMC formed underneath the destroyed P-rich Ni layer. In the high-speed shear test, the percentage of brittle fracture increased with increasing shear speed.

• Korean Journal of Ichthyology
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• v.23 no.4
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• pp.269-277
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• 2011

Age and growth pattern of Pacific cod Gadus macrocephalus were determined using samples collected in Jinhae Bay in Korea during the spawning period from 2006 to 2009. The ages of 333 specimens were estimated using their otoliths. The reliability of scales as a means of age determination was analyzed by comparing the ages estimated from otoliths and scales of 96 specimens. The scales collected from the base of the second dorsal fin or from the caudal peduncle were proved to be suitable for age determination of Pacific cod. Monthly changes in the marginal index in otoliths decreased from December showing the lowest value in February. Ages ranged from 4 to 6 years for both females and males, and most of them were 6 years old. Relationships between the otolith radius (R) and total length (TL) were TL=10.4R+3.1 for males, and TL=11.5R+3.4 for females. The growth curves in total length ($L_t$, cm) were expressed as $L_t$=141.5 [1-exp{-0.089 (t+0.209)}] for males and $L_t$=127.5 [1-exp {-0.124 (t+0.077)}] for females.