• Journal of Communications and Networks
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• 제1권3호
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• pp.166-181
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• 1999

The object of this paper is to investigate the influence of antenna pattern on indoor radio channel characteristics. Different from previous works where this analysis was carried out at a fixed frequency using different antennas, in the present paper (where measurements were taken in a wide frequency range) the variation of the radiation pattern was caused by two factors: the change of the radiation pattern when the same antenna was used at different frequenicies and the use of different type of antennas. To carry out this analysis, frequency domain measurements of the indoor radio channel at 1 GHz, 5.5 GHz, 10 GHz and 18 GHz were collected. Measurements were taken using a network analyzer. Serveral re-alizations of the channel transfer function were obtained varying, for each measurement, the positon of the transmitter and keep-ing the receiver fixed. Estimate of the channel impulse response was obtained from the Inverse Fourier Transform (IFT) of the fre-quency response. The measurements were performed in an office enviroment with mostly metallic walls and inner separations. The obtained data were elaborated to obtain the power versus distance relationship, the Cummulative Distribution Functions(CDFs) of rms Delay Spread(DS) and of the 3 dB frequency correlation band-width. Finally, the 3 dB width of the frequency correlation func-tion has been empirically related to the inverse of the rms DS of the impulse response.

• 대한물리의학회지
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• 제13권4호
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• pp.139-148
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• 2018

PURPOSE: This study compared the effects of indoor and outdoor environmental changes on the activity of the major lower limb muscles and walking factors in people 40-50 years and those aged older than 70 years. METHODS: Ten middle-aged people in their forties (age:$44.2{\pm}2.7$, BMI:$21.8{\pm}1.8$) and 10 elderly aged more than 70 years (age:$76.4{\pm}5.9$, BMI:$22.2{\pm}1.9$) with a normal walking ability were included. The participants walked 100 m both indoors and outdoors at their own speed. Using a 3D motion analyzer and EMG, the walking speed, angle of the ankle and activity changes of the lower limb muscles were compared. RESULTS: Significant differences in walking speed and peak-plantar flexion angle were observed between the two groups (p<.05). The muscular activity of the gastrocnemius muscle (GCM) was significantly different outdoors in the swing phase between the two groups (p<.05). In the people aged in their forties, the muscular activity of the rectus femoris (RF) was significantly higher outdoors than indoors (p<.05). In the elderly, however, the muscular activity of the RF was lower outdoors than indoors (p<.05). When compared to those in there forties, the muscular activity of the outdoor RF significantly decreased in the elderly group (P<.05). The muscular activity of the biceps femoris (BF) in the elderly decreased significantly outdoors compared to indoors (p<.05). CONCLUSION: For the elderly, increasing the exposure to the new environments or focusing on the performance of repeated movements for gradual speed control and precise movements is required to maintain normal gaits and movements that are less affected by environmental changes.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 학술대회지
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• pp.810-813
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• 2004

In this paper, a background initialization for video surveillance proposed. The proposed algorithm is that the background images are sampled n frames during ${\Delta}t$ All Sampling frames are divided by $M{\times}N$ size block every frame. Average values of pixels for same location block of the sampling frames during ${\Delta}t$t are taken. then the maximum intensity $\alpha$ and the minimun intensity $\beta$ is obtained, respecticely. The intial by $M{\times}N$ size block, then average intensity $\eta$ of pixels for the block is obtained. If the average intensity $\eta$ is out of the initial range of the background image, it is decided the moving object image, and if the average intensity $\eta$ is included in the initial range of the background image. it is decided the background image. To examine the propriety of the proposed algorithm in this paper, the accuracy and robustness evaluation results for human and car in the indoor and outdoor enviroment. the error rate of the proposed method is less than the existing methods and the extraction rate of the proposed method is better than the existing methods.

• 한국환경보건학회지
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• 제30권5호
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• pp.469-480
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• 2004

The radon concentrations were measured to survey distribution of radon concentrations in Seoul subway stations. The radon concentrations in air and water were measured at seventeen subway stations(Mapo, Chungjongno, Sodaemun, Kwanghwamun, Chongno3ga, Ulchiro4ga, Tangdaemun, Sangildong on Line 5;Nowon, Chunggye, Hagye, Kongnung, Taenung, Mokkol, Chunghwa, Sangbong, Myomok on Line 7) using the $RAdtrak^{TM}$ radon gas detector, Pylon AB-5 continuous passive radon detector and liquid scintillation counting method from January to May 1999. The major results obtained from this study were as follows: The long-term mean concentrations of radon were $61.8\;Bq/m^3$ in office, $78.9\;Bq/m^3$ in platform, $38.2\;Bq/m^3$ in concourse and $20.1\;Bq/m^3$ in outdoor, respectively. These levels were less than the action level ($148\;Bq/m^3$) of the U.S. EPA. The highest level of short-term mean concentrations was $116.55\;Bq/m^3$ at Chongno3ga station on the 5th line subway stations, while the lowest mean concentration was $19.55\;Bq/m^3$ at Mokkol station on the 7th line subway stations. The highest concentration of radon in the road water and storing underground water in the subway stations was $234.7\;KBq/m^3\;and\;155.5\;KBq/m^3$ in Sodaemun subway station, respectively. The results suggest that radon concentration in subway stations seems to be affected by ventilation and radon concentratin in underground water in the subway stations.

• 접착 및 계면
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• 제8권1호
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• pp.1-7
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• 2007

본 연구에서는 자동차 실내에서 발생되는 VOCs 성분 및 농도를 분석하기 위해 승용차와 RV차에 대해서 각각 15일, 30일, 45일, 60일 경과한 차량을 대상으로 시험하였다. 그 결과 TVOC는 승용차와 RV차 모두 기준치보다 2~8배 상회하였으며 승용차보다는 RV차량이 더 많이 검출되었다. 특히 톨루엔의 경우 30일 경과 후부터 급격히 감소되었으며 60일 경과 후에도 기준치보다 높게 검출되었다. 크실렌의 경우 45일 경과 후 기준치 이하로 검출됨을 확인하였다. 본 연구결과를 볼 때 자동차 내장부품의 무용제화 및 수성화 대체기술 개발이 시급함을 알 수 있었다. 아직 국제표준화 되어 있지 않은 VOCs의 시험방법표준화를 통하여 성분, 농도, 인체유해성을 충분히 분석하여 대체함으로써 친환경 자동차 생산에 기여할 수 있을 것으로 사료된다.

• 교육시설 논문지
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• 제21권4호
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• pp.21-30
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• 2014

In general, teachers' perceptions on the physical environment of elementary school are related on the quality of education and school life. But, we don't have study what teachers think of their enviroment of school. This study analyzed elementary school teachers' satisfaction with overall physical environment and their assessment of spaces with specific functions in order to understand teachers' perception of the physical environment of elementary schools. A survey questionnaire was administered to 982 homeroom teachers working at 67 elementary schools located in Seoul and Busan. Teachers' satisfaction with physical environment of school and their assessment were analyzed comparatively according to the teachers' personal attributes and school conditions. 1) Most of the surveyed teachers were satisfied with overall physical environment of the school, and assessed high the substantiality of functional spaces indoor and outdoor. By sub-factor, however, their satisfaction with work environment was lower than that with education and living environment. 2) The teachers perceived that the optimal number of classes was 30~36, and this is probably because they were relatively accustomed to large scale schools. 3) As might be expected, negative assessments were more frequent among teachers working at a large-scale school, an old school, or a school with small outdoor spaces. The results of this study show that, though partially different according to region, gender, teaching experience and school condition, teachers' satisfaction with school environment was relatively high. This suggests that elementary school teachers perceive their current school environment positively. Because they are accustomed to traditional education methods that have been maintained.