• 천문학회지
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• 제37권5호
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• pp.387-392
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• 2004

X-ray observations of galaxy clusters have played an important role in cosmology, especially in determining the cosmological density parameter and the fluctuation amplitude. While they represent the bright side of the universe together with the other probes including the cosmic microwave background and the Type Ia supernovae, the resulting information clearly indicates that the universe is dominated by dark components. Even most of cosmic baryons turns out to be dark. In order to elucidate the nature of dark baryons, we propose a dedicated soft-X-ray mission, DIOS (Diffuse Intergalactic Oxygen Surveyor). Recent numerical simulations suggest that approximately 30 to 50 percent of total baryons at z = 0 take the form of the warm-hot intergalactic medium (WHIM) with $10^5K < T < 10^7K $which has evaded the direct detection so far. The unprecedented energy resolution (${\~} 2eV$) of the XSA (X-ray Spectrometer Array) on-board DIGS enables us to identify WHIM with gas temperature $T = 10^6 {\~} 10^7K$ and overdensity $\delta$ = 10 ${\~}$ 100 located at z < 0.3 through emission lines of OVII and OVIII. In addition, WHIMs surrounding nearby clusters are detectable with a typical exposure time of a day, and thus constitute realistic and promising targets for DIOS.

• Radiation Oncology Journal
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• 제13권1호
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• pp.87-94
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• 1995

Since March 1992, total 200 patients who visited our hospital as functional or organic lesions of central nervous system were treated by gamma knife stereotactic radiosurgery for 27 months. Thirty-nine patients of total cases was diagnosed as cerebral arteriovenous malformation. The rate of magnification on X-ray film was reduced by cutting fixation adaptor from 1.0 to below 1.45 times. In order to treat the deep- and lateral-seated cerebral arteriovenous malformation, we slightly modified the angiographic indicator, the commercial Leksell system, by cutting each inner sides about 5mm, We performed the more distinction of the scales by adapting 0.5mm or 1mm copper filter to angiographic indicator. The center point of indicator(X=100mm, Y=100mm, Z=100mm) is corrected by adjusting scales of X-, Y-, Z-axis to each inner 100 and outer 100 point within 1-2mm by repeated exposure of X-ray on films in trial-and-errors. We have developed the 'GKANGIO' programed as the Fortran-77 in Microvax - 3100, which can save treatment planning time and perform accurate pretreatment planning using the theoretical target metrix center. The theoretical description of the simplified method is presented for the reduction of experimental and numerical errors in treatment planning of radiosurgery.

• 한국전자파학회논문지
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• 제21권6호
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• pp.553-563
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• 2010

본 논문에서는 UWB 대역에서 최적 임펄스 신호 전송을 위한 테이퍼 슬롯 안테나(Tapered Slot Antenna: TSA) 설계에 대해 연구하였다. UWB 대역에서 동작하는 TSA는 end-fire 특성을 갖는 광대역 안테나로, 펄스 전송을 위한 IR-UWB(Impulse Radio Ultra-Wide Band) 시스템에 적합하다. 지향성 특성을 갖는 테이퍼 슬롯 안테나는 UWB 대역에서 손실이 적고, 임펄스 전송시 최소 에러를 가져야 한다. 전송되는 펄스 왜곡을 최소로 하기 위해 테이퍼 슬롯 안테나 급전부를 구성하는 광대역 임피던스 변환기와 microstrip/slotline 천이부 설계에 대해 연구하였으며, 설계된 테이퍼 슬롯 안테나에 대한 펄스 충실도는 전자기파에 대한 시간 영역 분석이 가능한 CST를 이용한 FDTD(Finite-Difference Time-Domain) 시뮬레이션과 펄스 상관식 유도를 통해 계산하였으며, 제작된 안테나에 대해 두 안테나를 0.5 미터 이격시킨 두 안테나 사이에서 약 93.89 % 정도의 양호한 결과를 얻을 수 있었다. 또한 chirp Z-변환 알고리즘을 유도를 통해, 나노초 이하의 펄스 신호에 대해 zoom-in 기능을 부여함으로써 펄스 신호에 대한 왜곡, 지연 및 분산 특성 등의 분석이 가능하다.

• 분석과학
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• 제24권6호
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• pp.435-442
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• 2011

폴리 브롬화 디페닐 에테르류(PBDEs)는 난연제의 한 종류로서 인체와 생태계에 영향을 미치는 잠재적인 독성물질이며 최근 들어 관심의 대상이 되고 있는 화학물질이다. 유럽연합을 비롯하여 많은 국가들은 전기전자제품에 이 물질의 사용을 제한하고 있다. 이와 관련된 시험소인정을 지원하기 위해 고충격 폴리스티렌(HIPS) 중 PBDE류 측정을 위한 숙련도시험을 ISO/IEC 17043을 기초로 하여 수행하였다. 고충격 폴리스티렌에 포함된 4종의 PBDE류(PBDE-154, 183, 206, 209)를 측정 대상 물질로 하여 숙련도시험이 수행되었다. 10 g의 펠렛형 고충격 폴리스티렌 시료를 35개 참가실험실들에게 배포하였고 실험실들의 능력을 평가하기 위해 z-score를 사용하였다. 숙련도 시험의 결과 및 참가 실험실 평가결과를 기술하였다.

• Journal of Preventive Medicine and Public Health
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• 제43권2호
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• pp.174-184
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• 2010

Objectives: This study shows the issues that should be considered when applying standardized rates using Community Health Survey(CHS) data. Methods: We analyzed 2008 CHS data. In order to obtain the reliability of standardized rates, we calculated z-score and rank correlation coefficients between direct standardized rate and indirect standardized rate for 31 major indices. Especially, we assessed the change of correlations according to population composition (age and sex), and characteristics of the index. We used Mantel-Haenszel chi-square to quantify the difference of population composition. Results: Among 31 major indices, 29 indices' z-score and rank correlation coefficients were over 0.9. However, regions with larger differences in population composition showed lower reliability. Low reliability was also observed for the indices specific to subgroups with small denominator such as 'permanent lesion from stroke', and the index with large regional variations in age-related differences such as 'obtaining health examinations'. Conclusions: Standardized rates may have low reliability, if comparison is made between areas with extremely large differences in population composition, or for indicies with large regional variations in age-related differences. Therefore, the special features of standardized rates should be considered when health state are compared among areas.

• 대한치과보철학회지
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• 제21권1호
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• pp.59-66
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• 1983

Distal extension partial dentures are supported by both the relatively rigid teeth and the resilient mucosa. So impression techniques of residual alveolar ridge in case of distal extension partial denture have particular importance in order to broad distribution of the masticatory force. McLean recognized the need for recording the tissues supporting distal extension partial denture base in functional form to equalize the resilient and non-resilient support, and this was called functional impression. Many investigators proposed various techniques of the functional impression for a distal extension partial denture, but only a little studies were performed about displacement of soft tissue under distal extension partial denture base. The purpose of this study is to investigate the amount of vertical displacement of the soft tissue under distal extension partial denture base by different functional impression techniques. Impression techniques used were Z.O.P. Impression, Selective Tissue Placement Impression, Functional Relining Impression. Measurement of the vertical displacement of soft tissue were made with Depth Gauge and Measuring Platform. A Anatomic Impression was used as a control. The results were tested statistically using 3 way ANOVA and Scheffe test. The followings were the results obtained from this study. 1. The greatest amount of soft tissue displacement was observed in the center of the retromolar pad. 2. No significant differences were found between the crest of alveolar ridge and the buccal shelf area. 3. The greatest soft tissue displacement was observed in Functional Relining Impression using Iowa wax, and the least displacement was observed in Selective Tissue Placement Impression using murcaptan rubber base. 4. No significant differences were found between finger pressure and biting pressure in Z.O.P. Impression, but greater displacement was observed by biting pressure than finger pressure in Functional Reling Impression.

• 한국정보통신학회논문지
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• 제2권4호
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• pp.643-652
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• 1998

이동통신용 중계안테나는 현재 약 -20 dB의 후방부엽이 존재한다. 이는 인접한 안테나에 전파감쇠 및 장애를 일으키고 있어 후방부엽을 억제시키는 것이 절실히 요구되고 있다. 본 논문에서는 기존의 Back Plate 구조를 새롭게 변형하여 후방부엽의 발생을 억압시키고, -30 dB이하의 Null Point의 각도를 넓히고자 한다. 새로운 구조의 Back Plate는 리플렉터안테나의 원리를 이용하여 ㄷ자 형태로 만들었다. Back Plate구조의 설계를 위해 범용 소프트웨어 툴인 NEC Win Pro를 사용하였다. 각 파라미터에 대한 계산으로부터 $\pm180^\circ$에서 -48.48 dB 의 후방부엽을 갖는 중계국안테나를 설계하였으며, 또한 다이폴의 길이, 다이폴 사이의 간격 및 Back Plate 크기 등의 조정으로부터 -30 dB이하에서 64$^{\circ}$의 Null Point 각도를 가지는 안테나를 설계하였다.

• Tribology and Lubricants
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• 제21권6호
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• pp.268-271
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• 2005

In this study, the wear characteristics of five different dental composite resins cured by conventional halogen light and LED light sources were investigated. Five different dental composite resins of Surefil, Z100, Dyract AP, Fuji II LC and Compoglass were worn against a zirconia ceramic ball using a pin-on-disk type wear tester with 15N contact force in a reciprocal sliding motion of sliding distance of 10mm/cycle at 1Hz under the room temperature dry condition. The wear variations of dental composite resins were linearly increased as the number of cycles increased. It was observed that the wear resistances of these specimens were in the order of Dyract AP > Surefil > Compoglass > Z100 > Fuji II LC. On the morphological observations by SEM, the large crack formation on the sliding track of Fuji II LC specimen was the greatest among all resin composites. Dyract AP showed less wear with few surface damage. There is no significant difference in wear performance between conventional halogen light curing and light emitting diodes curing sources. It indicates that a light emitting diodes (LED) source can replace a halogen light source as curing unit for composite resin restorations.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2004년도 학술대회지
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• pp.350-354
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• 2004

In this study, the wear characteristics of five different dental composite resins cured by conventional halogen light and LED light sources were investigated. Five different dental composite resins of Surefil, Z100, Dyract AP, Fuji II LC and Compoglass were worn against a zirconia ceramic ball using a pin-on-disk type wear tester with 15 N contact force in a reciprocal sliding motion of sliding distance of 10 mm/cycle at 1Hz under the room temperature dry condition. The wear variations of dental composite resins were linearly increased as the number of cycles increased. It was observed that the wear resistances of these specimens were in the order of Dyract AP > Surefil > Compoglass > Z100 > Fuji II LC. On the morphological observations by SEM, the large crack formation on the sliding track of Fuji ?LC specimen was the greatest among all resin composites. Dyract AP showed less wear with few surface damage. There is no significant difference in wear performance between conventional halogen light curing and light emitting diodes curing sources. It indicates that a light emitting diodes (LED) source can replace a halogen light source as curing unit for composite resin restorations.

• 대한지역사회영양학회지
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• 제17권3호
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• pp.271-279
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• 2012

The prevalence of atopic dermatitis (AD) has increased recently all over the world. Several studies worldwide reported growth retardation associated with AD, but few studies were reported in Korea. Therefore, the objective of this study was to identity the differences in growth and nutrient intakes between Korean children with and without AD. The participants were 71 AD children and age, gender-matched 81 control children aged 10 to 36 months. Demographic information was gathered by questionnaires. Height and weight were measured at clinic and health centers. Height and weight for age, and weight for height were converted as deviation in Z scores using World Health Organization Standard. A 24 hour dietary recall method was performed to estimate nutrient intakes. A higher percentage of AD children had insufficient energy and intakes of calcium, phosphorus, iron, zinc and vitamin B2, defined as intakes lower than 75% of the Dietary Reference Intakes for Korean, compared to the control group (P < 0.001, P < 0.001, P = 0.003, P = 0.001, P = 0.014, P = 0.001, respectively). The percentages of children with height and weight for age Z score below than-1 (stunted) were significantly higher in the AD group (P < 0.001 and P < 0.001, respectively). Multiple food restriction, defined as ${\geq}$ 3 food elimination, was associated with insufficient energy and intakes of calcium, phosphorus, iron, zinc, vitamins A and B2. In conclusion, children with AD need regular nutrient assessment and education about alternative food choices to avoid r food elimination in order to prevent growth retardation or inadequate nutrient intakes. Further longitudinal studies for growth and nutrient intakes should be performed to understand the patterns of growth in children with AD.