• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4A
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• pp.360-370
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• 2010

In this paper, a distributed beamforming problem is considered in an amplify-and-forward (AF) wireless relay network consist of multiple source-destination pairs and relaying nodes. To exploit degree of freedom of the number of beamformers, in the first step, we proposed that the sources transmit their signals through orthogonal channels. During the second step, the relays transmit their received signals multiplied by complex weights to amplify and compensate for phase changes introduced by the backward channels through one common channel. The optimal beamforming vectors are obtained through minimization of the total relay transmit power while the signal-to-interference-plus-noise ratios (SINRs) at the destinations are above certain thresholds to meet a quality of services (QoSs) level. In the numerical example, it is shown that the proposed scheme needs less transmit power for moderate network data rates than other schemes, such as space division multiplexing or time-division multiplexing scheme.

• The Korean Journal of Food And Nutrition
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• v.17 no.1
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• pp.32-40
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• 2004

This Study was conducted to predict temperature profile of Jangjorim (boiled beef in soy sauce) food during retorting using the commercial NISA (Numerical Integrated Elements for System Analysis) program. NISA program is a good tool to simulate the temperature profile of a specific material based upon the finite element method. The cold point of Jangjorim food located not at the geometrical center but at 26.9 mm backward in y plane because specific heat of soy sauce was 20% higher than that of boiled beef. The effects of heat transfer coefficients on heat transfer during retorting process of Jangjorim were analyzed by response surface methodology (RSM). Independent variables were thermal conductivity of soy sauce, thermal conductivity of boiled beef, and convection heat transfer coefficient and dependent variables were temperature error and lethality error. Thermal conductivity of soy sauce was the most significant contributor among those (P<0.01).

• Journal of the Society of Naval Architects of Korea
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• v.29 no.1
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• pp.1-13
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• 1992

The objective of this study is to develop knowledge-based system for the preliminary design and midship section design of bulk carrier and to enhance the applicability of knowledge engineering in the field of Naval Architecture. First, expert system shell called E.1 is developed in C language. E.1 supports backward-chaining, automatic iteration procedure and reiterative inference mechanism for efficient application of knowledge-based system in structural design. Knowledge representation in E.1 includes IF-THEN rules, 'facts'and 'tables'. Second, knowledge bases for the principal particulars and midship section design are developed by experimental formula, design standard and experiential knowlege. Third, hybrid system combined this knowledge-based system with the optimization program of midship section is developed. Finally, the simplified design method utilizing the regression analysis of the optimum results of stiffened plate is developed for facilitating the design process. Using this knowledge-based system, the design process and results for Bulk carrier and stiffened plates are discussed. It is concluded that knowledge-based system is efficient for preliminary design and midship section design of the ship. It is expected that the performance of the CAD system would be enhanced if the better knowledge-base is accumulated in the E.1 tool.

• The Journal of the Acoustical Society of Korea
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• v.24 no.8
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• pp.441-446
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• 2005

This paper presents the changes of acoustic scattering pattern from a single cylinder and two identical cylinders in both theoretical calculations and experimental measurements. Bi-static scattering pattern by single cylinder and two parallel cylinders (length 2m, radius 30mm) was measured in $5m\times5m\times5m$ water tank using high frequency projector (120 kHz) and hydrophone. The results show similar agreement between experiment and theory. In case of single cylinder scattering. omni-directional pattern was observed in backward but there are fluctuations or target strength in forward. Interference between each cylinder's scattering fields produce fluctuations of target strength in all directions of two cylinders.

• Safety and Health at Work
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• v.5 no.2
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• pp.80-85
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• 2014

Background: Currently available questionnaires for evaluating the quality of worklife do not fully examine every factor related to worklife in all cultures. A tool in Thai is therefore needed for the direct evaluation of the quality of worklife. Our aim was to translate the Work-related Quality of Life Scale-2 (WRQLS-2) into Thai, to assess the validity and reliability of the Thai-translated version, and to examine the tool's accuracy vis-$\grave{a}$-vis nursing in Thailand. Methods: This was a descriptive correlation study. Forward and backward translations were performed to develop a Thai version of the WRQLS. Six nursing experts participated in assessing content validity and 374 registered nurses (RNs) participated in its testing. After a 2-week interval, 67 RNs were retested. Structural validity was examined using principal components analysis. The Cronbach's alpha values were calculated. The respective independent sample t test and intraclass correlation coefficient were used to analyze known-group validity and test-retest reliability. Multistate sampling was used to select 374 RNs from the In- and Outpatient Department of Srinagarind Hospital of the Khon Kaen University (Khon Kaen, Thailand). Results: The content validity index of the scale was 0.97. Principal components analysis resulted in a seven-factor model, which explains 59% of the total variance. The overall Cronbach's alpha value was 0.925, whereas the subscales ranged between 0.67 and 0.82. In the assessment results, the known-group validity was established for the difference between civil servants and university employees [F (7.982, 0.005) and t (3.351; p < 0.05)]. Civil servants apparently had a better quality worklife, compared to university employees. Good test-retest reliability was observed (r = 0.892, p < 0.05). Conclusion: The Thai version of a WRQLS appears to be well validated and practicable for determining the quality of the work-life among nurses in Thailand.

• Journal of the Optical Society of Korea
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• v.12 no.3
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• pp.200-204
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• 2008

Coherent tunable terahertz generation was demonstrated in periodically poled stoichiometric lithium tantalate crystal via difference frequency generation of femtosecond laser pulses. Simultaneous forward and backward terahertz radiations were obtained around 1.35 and 0.63 THz, respectively at low temperature. By cooling the crystal to reduce losses caused by phonon absorptions, the generated THz bandwidth was as narrow as 23GHz at the center frequency of 0.63 THz. The measurement result of temperature-dependent showed gradual intensity increase of the generated terahertz pulse and red shift of the center frequency as the temperature decrease from 291 to 143 K, but insignificant reduction of the spectral bandwidth. Furthermore, the stoichiometric crystal was very suitable for the suppression of THz loss at low temperature compared to the congruent $LiNbO_3$ crystal.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1138-1146
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• 1990

A knowledge-based expert system has been developed implementing the ambiguous process of conceptual design of flywheels in earlier design stage to assist the selection of proper flywheel types and dimensions. Knowledge for the flywheel design consists of the rules for conventional as well as super flywheels and other informations required for the design process. Those knowledges were extracted from literatures and some experts in the field. With these knowledges, an integrated knowledge based expert system was developed to help users with informations and facilities to design flywheels interactively using a commercial package of knowledge-based system called INSIGHT2 of backward chaining and proprietary package of forward chaining written in LISP language. The developed system consists of the knowledge base part and calculation park : the first one consists of main module and user level modules and the other one is to assist in analyzing the stress distribution in the flywheels and deciding the flywheel dimensions and specifications for various types of flywheels using proper data bases and graphic facilities. With this flywheel design software, several examples were tried generating acceptable design results.

• Journal of the Korean Home Economics Association
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• v.23 no.3
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• pp.27-38
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• 1985

In KOREA, the history of weaving is so long even in prinitive, there are the traces of fabric emmision using Spindle already in the Neolithic age. And coming up to the period of Three States, becoming active of cultivation of fibers, it can be known the variety of kinds and the production of fine products by improvement of new method of weaving using weaving machine. In the period of shilla state, there is a record of making the fine fabrics with 28 bracts. But wearing of silks fabrics was limitted for only the nobility and common people were wearing native thick hemp clothes. Also in the period of Korea state, they were wearing the hemp clothes by cultivation of hemp. The good quality products were worn by the King or the nobility and women in KOREA made their best with whole efforts to pay to the authorities with woven products of hemp clothes, so in the 14th year of King Chung- Ryul, King prohibited the presentation of fine hemp clothes by his order. By the end of KOREA state, before the production, common people was mainly wearing the hemp clothes. Coming up to the Kingdom of Chosun the sericulture was promoted by establishment of the sericulture encouraging low. Therefore the working hours of women were highly increased. The products of Song-do, Chin-ju for cotton clothes, those of Han-san-the same now as in old times-for ramie clothes, those of Han-Kyung province and An-dong for hemp fabrics were estimated as the best qualities. And the hemp clothes of Kang-won province is not so fine but is very useful and famous for mourning clothes and summer clothes for the farmer. It is true that our history of weaving was begun with hemp as a continous and precious friend of common people during all the historical periods-even though for a while it went backward because of chinese silks.

• Atmosphere
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• v.29 no.5
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• pp.525-535
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• 2019

Vertical distributions of aerosol mass concentrations over Seoul and Gangneung from January to February 2015 were investigated using aerosol Mie-scattering lidars. Vertical mass concentration of aerosol was calculated from the lidar data using KALION's algorithm and quantitatively compared with ground PM₁₀ concentration to obtain objectivity of data. The backward trajectories calculated using HYSPLIT (version 4) were clustered into 5 traces for Seoul and 6 traces for Gangneung, and the observed aerosol vertical mass distribution was analyzed for individual trajectories. Result from the analysis shows that, aerosol concentrations with in the planetary boundary layer were highest when airflows into the measurement points originated in the Shandong Peninsula or the Inner Mongolia. In addition, the difference of aerosol mass concentrations in the two regions below 1 km was about twice as large as that in the long range transport from the Shandong Peninsula compared to the local emission. This result shows that the air quality over Korea related to particulate matters are affected more by aerosol emissions in the upstream source regions and the associated transboundary transports than local emissions. This study also suggests that the use of local aerosol observations is critical for accurate simulations of aerosol-cloud interactions.

• Journal of Korean Ophthalmic Optics Society
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• v.5 no.2
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• pp.119-125
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• 2000

We analyzed to calculate optical capacity after we chose established 2 component zoom copier lens system in this research. As the lens system is zoom lens system of finite object point, it has moving area limited not like to use generally camera zoom lens of infinite object point because it moves between object and image plane. The magnification of optical system can obtain -1.41~-0.64 i.e., extended or shortened image as transverse magnification, and it acquires f/12 and about $20^{\circ}$ field of view. Although this 2 component zoom copier lens system will be down resolution and dark compared with f/2.8 acquired at camera lens, it will be possibile to be able to make large aperture and it can acquire more better correct aberration with the addition of auxiliary group forward or backward.