• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.11 no.4
• /
• pp.14-21
• /
• 2015

Korean government plans to establish large-scale horticulture facility complexes using reclaimed land in order to improve the national competitiveness of agriculture at the government level. One of the most significant problems arising from the establishment of those large-scale horticulture facilities is that these facilities still largely depend on a fossil fuel and they require 24 h a day heating during the winter season in order to provide the necessary breeding conditions for greenhouse crops. These facilities show large energy consumption due to the use of coverings with large heat transmission coefficients such as vinyl and glass during heating in the winter season. This study investigated the applicability of waste heat from power plant for large-scale horticulture facilities by evaluating the waste heat water temperature, heat loss and energy saving performance as a function of distance between power plant and greenhouse. As a result, utilizing power plant waste heat can reduce the energy consumption by around 85% compared to the conventional gas boiler, regardless of the distance between power plant and greenhouse.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.24 no.10A
• /
• pp.1471-1479
• /
• 1999

This paper presents an adaptive beamforming algorithm for an MC-CDMA system with an adaptive array antenna. By employing an antenna array at the receiver of an MC-CDMA system, the performance of an MC-CDMA system, which is known to be effective for high data rate transmission due to its robustness to multipath fading and its simplicity for using a simple one-tap equalizer, is shown to be significantly improved. The proposed algorithm for adaptive beanforming in an MC-CDMA system is derived by (1) calculating the error signals between the pilot symbols of desired user and the received pilot signals in frequency domain, (2) transforming the frequency-domain error signals into time-domain error signals, (3) updating the filter coefficients of the adaptive beamformer in the direction of minimizing the MSE. Convergence behavior and performance improvement of the proposed approach are demonstrated through computer simulation by applying it to the conventional MC-CDMA system.

• Proceedings of the KOSOMBE Conference
• /
• v.1995 no.05
• /
• pp.235-238
• /
• 1995

In this paper, we propose an effective coding method of the angiography by using the scalable structure in the frequency domain for MPACS(Medical Picture Archiving and Communication System). We employed the subband decomposition method and MPEG-2 system which is the international standard coding method of the general moving picture. After the subband decomposition is applied to split an input image into 4 bands in the spatial frequency domain, the motion compensated DPCM coding method of MPEG-2 is carried out for each subband. As a result, an easily controllable coding Structure is accomplished by composing the compound hit stream for each subband group. Follows are the simulation results of the proposed sheme for the angiography. A scalable structure which can be easily controlled for a loss of transmission or the band limit can be accomplisbed in the MPEG-2 stucture by the subband decomposition minimizing the side information. And by reducing the search area of the motion vector between -4 and 3, the processing speed of a codec is enhanced by more than two times without a loss of the picture quality compare with the conventional DCT coefficients decompositon method. And the processing speed is considerably improved in the case of the parallel construction of each subband in the hardware.

• Journal of Korean Public Health Nursing
• /
• v.13 no.1
• /
• pp.63-76
• /
• 1999

The purpose of this study was to provide the basic data for developing a program for effective health education about AIDS (Acquired Immunodeficiency Syndrome) by investigating the knowledge and attitudes of middle and high school students about AIDS. The subjects were 476 middle school students and 658 high school students from Seoul and Kang Won province. The data were collected from November 19 to December 18. 1996. using a 56-item questionnaire. and analyzed by SAS program for t-test. x2-test. and pearson correlation coefficients. The results were as follows : 1. High school students had more knowledge than middle school students about AIDS. 2. Male. students from Seoul. and students who had drinking experience and smoking experience among middle school students. and male. students from Seoul. and students of non-coeducation among high school students were more knowledgeable about AIDS. 3. Misconceptions about the transmission of AIDS through non-intimate contact were especially common among middle school students. And a high proportion of middle and high school students knew very little about the symptoms of AIDS. 4. High school students had more positive attitudes toward AIDS than middle school students. 5. Students from Seoul and students who had smoking experience among middle school students. and students from Seoul and non-coeducation and students who had substance use experience among high school students were more positive attitudes about AIDS. 6. Most of the middle and high school students agreed that there is a need for AIDS education. 7. Middle and high school students reported that had learned about AIDS mostly from TV. Since students in the middle-school age group are especially at risk for developing AIDS­related behaviors. this study findings suggest that it is crucial to develop school-based AIDS education programs that help students acquire the knowledge and attitudes to adopt and maintain behaviors that reduce the risk of HIV (Human Immunodeficiency Virus) infection and other related health problems.

• Journal of Environmental Health Sciences
• /
• v.45 no.6
• /
• pp.622-629
• /
• 2019

Objectives: The occurrence of norovirus food poisoning in South Korea has been reported since 2003. This study was performed to investigate the characteristics of norovirus food poisoning outbreaks in Korea from 2006 to 2015 and to analyze the relationship between these outbreaks and climate factors. Methods: Data on norovirus food poisoning outbreaks were obtained from the Korea Ministry of Food and Drug Safety. Data on climate factors were obtained from the Korea Meteorological Administration. Frequency analysis and Pearson's correlation analysis were adopted for this study. Results: During the study period, norovirus was the greatest contributing factor of food poisoning outbreaks. Approximately half of the outbreaks of norovirus food poisoning occurred in winter. Average temperature, highest and lowest temperatures, precipitation, number of days with rainfall, and humidity all had a significant negative correlation with monthly number of outbreaks of norovirus food poisoning (p<0.05). Among these, the lowest and average temperature showed higher correlation coefficients. However, the sum of the outbreaks in spring and autumn was similar to that of winter, and more than one-third occurred in group meal-service settings, including school lunches. This was strongly assumed as the use of norovirus-contaminated groundwater for preparation of meals in some settings. Conclusion: The cold and dry of the winter season in Korea may assist the transmission of norovirus. Also, the use of groundwater in group meal service is suspected of inducing a larger scale of norovirus food poisoning. Both health authorities and community-based prevention and control measures are required to respond to these complex etiological outbreaks.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.9
• /
• pp.892-899
• /
• 2013

This paper discusses difficulties in precise measurements of the scattering parameters in (sub-)millimeter-wave range and tips for more accurate measurements, and provides measurement examples in the G-band(140~220 GHz). First, one investigates the differences in operating principles of scattering parameters measurement systems used in microwave and (sub-)millimeter-wave ranges and describes tips for better operation of the (sub-)millimeter-wave scattering parameters measurement system. In addition, one describes tips for better transmission properties and connection repeatability of waveguides and a precise measurement method for devices with small reflection coefficients.

• Journal of Digital Convergence
• /
• v.12 no.3
• /
• pp.249-254
• /
• 2014

Wireless LAN system is evolving toward high-speed data transmission and more accurate channel estimation is necessarily required to improve communication performance. The PLCP preamble field in IEEE 802.11 based wireless MODEM consists of ten short symbols and two long symbols and is used for synchronization and channel estimation. The existing least square (LS) channel estimation is based on only two long training symbols. After estimating channel response separately by using each long training symbol, the final channel estimation is obtained by the average of each estimation. In this paper, a new channel estimation algorithm is presented to improve the performance of the existing LS channel estimation algorithm. From the fact that the short training symbol consists of 12 non-zero subcarriers, it gives us a clue of being able to additionally estimate at least one fourth of channel coefficients. The new LS algorithm performs channel estimation based on both two long training symbols and a short training symbol. The proposed LS algorithm shows a little bit performance improvement over the existing LS estimation and it will be able to be applied to the IEEE 802.11p WAVE system.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.3A
• /
• pp.240-248
• /
• 2006

In this paper, we consider an OFDM receiver algorithm design for IEEE 802.11a/p system, which targeting large coverage area while keeping the transmission format unchanged. Particularly, taking into account the inter-symbol interference(ISI) and inter-carrier interference(ICI) that can be induced with large RMS delay spread, we employ channel shortening time-domain equalizer(TEQ) and evaluate the receiver performance in terms of SINR and packet error rate(PER). The preamble defined in IEEE802.11a/p is used to estimated the initial equalizer tap coefficients. Primary purpose of the paper is to give an answer to the question, though partially, whether or not 16-QAM constellation can be used in none line of sight environment at the boundary of a large coverage area. To this end, we first analyze the required TEQ parameters for the target channel environment and then perform simulation for PER performance evaluation in a generic frequency selective fading channel with exponential power-delay profile.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.32 no.5
• /
• pp.509-517
• /
• 2012

In the present study, temperature and frequency dependences of ultrasonic properties such as attenuation coefficient and phase velocity was investigated for six kinds of commercial MC-Nylon polymer samples. The ultrasonic properties of the samples were measured by using a pulse transmission method in water over a broadband frequency range of 2 to 8 MHz. Water temperature was varied from 10 to $60^{\circ}C$ with the $10^{\circ}C$ interval. The attenuation coefficients of the samples increased with the frequency and the exponent n of frequency dependence ranged within 1.16 to 1.44, slightly deviating from the linear dependence (n=1). The phase velocities of the samples exhibited negative dispersion, i.e., decreasing velocity with increasing frequency, except for ivory sample at $60^{\circ}C$. The frequency-dependent phase velocities of the samples showed the decreasing tendency with increasing temperature.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.53 no.3
• /
• pp.21-28
• /
• 2016

We propose an adaptive scheme of a differential codebook for temporally correlated channels. And the codeword entries of the propose codebook are selected among the set of M-PSK constellations - the values of M proposed in this paper are 8, 16, or 32. Firstly, we analyze mathematically how the optimal spherical cap radius of the proposed codebook is tracked. Then, we explain the practical implementation of the proposed adaptive method. Practically, some candidate differential codebooks we propose in this paper can be switched according to the temporal correlation coefficients of wireless channels in the proposed scheme. Monte-Carlo simulations demonstrate that the achievable throughput performance employing the proposed codebook is always superior to those of the differential codebooks employing M-PSK constellations and non-adaptive differential codebooks with the same amount of feedback information.