• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.4
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• pp.342-348
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• 2003

Ultrasonic backscattering profiles of the Zr plates(with a thickness of 1.32mm) with/without Be-Zr alloy layer(with a thickness of $100{\mu}m$) were measured at various incidence positions to evaluate the characteristics of Be diffusion layer. Four principal subprofiles were observed in the backward ultrasound radiated from leaky Lamb waves. The angles and the intensities of the subprofile peaks decreased by the stiffening effect of Be layer. Generation and change of the subprofiles were explained by the acoustical property, collective group velocity and leaky factor difference of the plates under consideration. Backward radiation subprofiles turned out to be an useful method for evaluating thin diffusion layers on plates.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.5
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• pp.837-844
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• 2017

The weir to regulate water level in a tide generation tank is above and below carried by two electric cylinders which are mounted on right and left of weir itself. In this case, a movement difference between right and left cylinder causes unbalance of weir and friction between weir and guide. And then, the weir will not be sent to target point. In this study, a synchronous control system is developed to take accurate and quick equilibrium of the weir. The control system based on cross coupled structure consists of two I-PD controllers and a lead compensator. Each of the I-PD controllers is designed in order that the electric cylinder may exactly follow the reference signal without overshoot and input saturation. And the lead compensator is designed to achieve stable and accurate synchronization. Finally, the simulation result shows that the designed synchronous control system is effective for elimination of synchronous error.

• Journal of Korean Society on Water Environment
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• v.28 no.1
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• pp.38-49
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• 2012

In this study, we analyze statistical characteristics of influent water quality in Daejeon waste water treatment plant and apply a stochastic model for data generation. In the analysis, the influent water quality data from year 2003 to 2008, except for year 2006, are used. Among water quality variables, we find strong correlations between BOD and T-N; T-N and T-P; BOD and T-P; $COD_{Mn}$ and T-P; and BOD and $COD_{Mn}$. We also find that different water quality variables follow different theoretical probability distribution functions, which also depends on whether the seasonal cycle is removed. Finally, we generate the influent water quality data using the multi-season 1st Markov model (Thomas-Fiering model). With model parameters calibrated for the period 2003~2005, the generated data for 2007~2008 are well compared with observed data showing good agreement in general. BOD and T-N are underestimated by the stochastic model. This is mainly due to the statistical difference in observed data itself between two periods of 2003~2005 and 2007~2008. Therefore, we expect the stochastic model can be applied with more confidence in the case that the data follows stationary pattern.

• Fashion & Textile Research Journal
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• v.14 no.2
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• pp.251-260
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• 2012

Nowadays, global wedding dress companies are interested in the Chinese wedding market because of expectations in consumption patterns of the post 80's generation. Therefore, wedding behavior, selection criteria for wedding dresses, and favored image by segmented groups targeting 20's to 30's Chinese women were studied to help the Korean wedding dress industry to establish their business in China. The survey was conducted in Shanghai city and three neighboring cities-Wuxi, Zhengziang, and Hangzhou-, and the primary data were analyzed using the SPSS program. As results, Chinese women thought that the wedding ceremony should be elegant and dignified, and they wanted to choose their favorite style rather than a recommended style. The criteria of selection were classified into four factors. Overall image and well fitting with their face and body were the most important factors in the selection of wedding dress. The most favored image was unique/novel image. Several favored images for their wedding dress were significantly different by occasion (ceremony day and photo shoot day) and education level. People of higher education level preferred more luxurious and classic image during the ceremony, and a classic and gorgeous image on the photo shoot day. A white dress and a colored dress for weddings were favored more than the Chinese traditional dress on both occasions. There was also a significant difference between general consumers and the wedding business employees in the quantity of wanted wedding dress.

• 한국해양학회지
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• v.12 no.1
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• pp.33-40
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• 1977

British Hydraulics research Station's Sparse Scheme was suggested for the solution of two dimensional finite difference tidal equations. 2D-numerical tidal model formed with 4.8km rectangular cells was set up to find out the barrage effects on tidal ranges of some possible areas for tidal power generation in Korea. The comparisons were made hetween spring tidal ranges with and without barrages at the entrance of Asan Bay, Garorim bay, Cheonsu bay and near Incheon Bay. Because of the coarseness of the grid, the model results could not represent the values of changes precisely. However the results show that the tidal amplitude near Incheon Bay increased by about 40cm by setting a barrage and about 50cm increase near the entrance of Asan Bay, respectively. But there were only a few centimeter changes in other areas.

• Journal of the Korean Society of Combustion
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• v.20 no.1
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• pp.6-14
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• 2015

Numerical study was conducted to clarify effects of added $H_2O$ for the downstream interaction between $H_2$-air and CO-air premixed flames in counterflow configuration. The reaction mechanism adopted was Davis model which had been known to be well in agreement with reliable experimental data. The results showed that both lean and rich flammable limits were reduced in increase of strain rate. The most discernible difference between the two with and without having $H_2O$ and/or $H_2$ addition into $H_2$-air and CO-air premixtures was two flammable islands for the former and one island for the latter at high strain flame conditions. Even a small amount of $H_2$, in which $H_2$-air premixed flame cannot be sustained by itself, participates in CO oxidation, thereby altering the CO-oxidation reaction path from the main reaction route $CO+O_2{\rightarrow}CO_2+O$ with a very long chemical time in CO-air flame to the OH-related reaction routes including $CO+OH{\rightarrow}CO_2+H$ with very short chemical times. This intrinsic nature alters flame stability maps appreciably. The results also showed that chemical effects of added $H_2O$ help lean flames at relatively low strain rate be sustained, and suppress the flame stabilization at high strain rates.

• 한국노년학
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• v.32 no.2
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• pp.541-557
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• 2012

This study aims to understand public perceptions of aging Korean society and related factors in the context of population aging and generational difference. Data are from 1,498 individuals older than 20 who were recruited through the quota sampling technique. Results indicated that the respondents reported less then three as the number of positive aspects of aging Korean society. Among the factors related to population aging, such as knowledge about aging, perceptions about family care, anxiety about later life, and perspectives about generational conflict, anxiety about later life was shown to be negatively associated with perception of aging Korean society across age groups. Respondents 65 and older showed more positive perception about aging Korean society and this association was conditioned by perspectives about generational conflict. Perspectives about generational conflict revealed positive associations with perception of aging Korean society among respondents aged 20-44 and 45-64, while no association was found among those 65 and older. Discussions focused on ways to alter perceptions of aging Korean society and needs for future research on this topic.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8853-8860
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• 2015

This study is to identify recognition of and preference for toy breeds between young and older generations by investigating their understating on pet dogs, difference in pet preference and reasons behind their choice of dog breeds, recognition and preference by toy breeds. A survey was conducted among 137 youths and 60 elderlies in medium/large cities and rural areas. Collected data was processed with ${\chi}^2$-test to see statistical significance. The result showed a significance of p<0.01 in recognition of pet/companion animals and toy breeds, and in pet dog preference and reasons of dog choice, along with p<0.05 in recognition and preference by toy breeds. Thus, this research to provide basic information requires to widely understand characteristics of toy breeds throughout generations due to widespread preference for such breeds and to continue research on change factors in their level of recognition and preference for the right choice when he/she decides to raise a toy dog.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.6
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• pp.1307-1312
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• 2015

As smart-phones become popular, mobile data traffic has been dramatically increasing and intensive researches on the next-generation mobile communication network is in progress to meet the increasing demand for mobile data traffic. In particular, heterogeneous network (HetNet) is attracting much interest because it can significantly enhance the network capacity by increasing the spatial reuse with macro and small cells. In the HetNet, we have several problems such as load imbalance and interference because of the difference in transmit power between macro and small cells and cell range expansion (CRE) can mitigate the problems. In this paper, we propose a new cell selection scheme with adaptive cell range expansion bias (CREB) for ultra dense HetNet and we analyze the performance of the proposed scheme in terms of average cell transmission rate through system-level simulations and compare it with those of other schemes.

• Tunnel and Underground Space
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• v.18 no.1
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• pp.1-9
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• 2008

Acoustic emission (AE) and Microseimsic (MS) activities are law-energy seismic events associated with a sudden inelastic deformation such as the sudden movement of existing fractures, the generation of new fractures or the propagation of fractures. These events rapidly increase before major failure and happen within a given rock volume and radiate detectable seismic waves. The main difference between AE and MS signals is that the seismic motion frequencies of AE signals are higher than those of MS signals. As the failure of geotechnical structures usually happens as a high velocity and small displacement, it is nat easy ta determine the precursor and initiation stress level of failure in displacement detection method. To overcame this problem, AE/MS techniques far detection of structure failure and damage have recently adapt in civil engineering. This study deal with the basic theory of AE/MS and state of arts in monitoring technique using AE/MS.