• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.272-277
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• 2007

Generally railway vehicle runs on the rail with endless interaction between wheel and rail. Irregularity of rail causes the periodic motion of the vehicle. In association with this motion, the design of vehicle would be carried out in order to avoid the resonance between car-body and bogie. It may be seen that the first vertical bending mode of car-body contributes considerably to the vertical ride comfort level. In this paper to know the effect of the car-body first vertical bending mode on vertical ride comfort, the mode has been considered with dynamic model. I-DEAS program was used to get the car-body first vertical bending mode and VAMPIRE program was used to analyze ride comfort index(Wz) with FE interface file.

• Journal of the Optical Society of Korea
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• 제16권3호
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• pp.191-195
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• 2012

Among the atmospheric effect of laser propagation, the variations of the radiation transmittance by water aerosol evaporation have quantitatively been investigated. When the aerosol was exposed by a 1.07 ${\mu}m$ cw fiber laser, the increased amount of the transmittance variation was a maximum of 19.1% and the volume concentration variation of aerosol was observed as an increasing of laser intensity. Also, significant irregularity of refractive index was not found in the heated area during the continuous laser heating.

• 대한소아치과학회지
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• 제41권3호
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• pp.207-217
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• 2014

본 연구는 제2대구치까지 구강 내에 맹출하여 비교적 안정된 교합을 이루기 시작한 영구치열기 청소년의 부정교합과 치아우식 유병률 사이의 연관성을 알아보고자 하였다. 전라북도 익산시 소재의 2개 중학교 학생 385명을 대상으로 시행한 구강검진을 통해 치아심미지수와 우식경험영구치지수를 조사하였다. 조사 대상 청소년의 치아심미지수는 평균 12.42점, 우식경험영구치지수는 평균 2.89개로 나타났다. 교정치료가 매우 필요하다고 판단되는 치아심미지수 36점 이상은 4명(1.03%)이었으며, 남학생이 여학생에 비해 상악 중절치의 정중이개와 하악 전치부 수평피개를 나타내는 비율이 유의하게 높았다(p < 0.05). 치아심미지수를 구성하는 10개 항목 중 7개 항목(결손치아 수, 전치부 악궁 총생도, 상악 전치부 최대 변위량, 하악 전치부 최대 변위량, 하악 전치부 수평피개량, 전치부 개방교합, 제1대구치의 전후방 관계)에서 각 항목의 정상 범주에 속하는 집단에 비해 정상 범주에서 벗어난 집단의 우식경험영구치 지수가 유의하게 높았다(p < 0.05). 명백한 부정교합의 존재가 인정되는 치아심미지수 26점을 기준으로, 26점 미만에 비해 26점 이상인 집단의 우식경험영구치지수가 높았으며(p < 0.01), 치아심미지수와 우식경험영구치지수 사이에 유의한 선형 상관관계가 나타났다(r = 0.584, p < 0.01). 이상의 결과로부터 청소년의 부정교합과 치아우식증 유병률 사이에 유의한 양의 상관관계가 존재함을 알 수 있었으며, 치아우식증과 높은 상관성을 보이는 특정 형태의 부정교합을 확인할 수 있었다.

• 대한치과교정학회지
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• 제35권5호
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• pp.381-387
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• 2005

본 연구의 목적은 교정치료 초기에 사용되는 스테인레스스틸, 다가닥철선. 초탄성 NiTi, 열활동성 NiTi재료로 이루어진 총 4가지 호선의 초기 치료효과를 비교하기 위하여 시행되었으며, 실험의 설계는 전향적 임상 실험(prospective randomized clinical trial)으로서 브라질 리오데자네이로 주립 치과대대학에 내원한 45명의 고정식 교정장치 환자를 대상으로 시행되었다. 각 호선의 재료는 환자의 치열에 무작위로 배당되었는데 스테인레스스틸은 20명, 다가닥철선은 22명, 초탄성 NiTi는 22명, 열활동성 NiTi는 20명에게 할당되었고. 8주 후에 모형을 다시 제작한 후 3차원 디지털영상 장비를 이용하여 모형의 치관에 설정된 해부학적 지표의 변화를 측정하였는데 치료전 및 치료후 치열불규칙지수(Dental Irregularity Index)의 차이로 초기 교정치료 효과를 비교하였다. 분산분석을 시행하여 불규칙지수의 변화를 살펴본 결과 호선의 재료에 따른 초기 치료 효과는 유의한 차이가 나타나지 않았다

• Journal of Astronomy and Space Sciences
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• 제34권4호
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• pp.245-250
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• 2017

As a part of collaborative efforts to understand ionospheric irregularities, the Korea ionospheric scintillation sites (KISS) network has been built based on global positioning system (GPS) receivers with sampling rates higher than 1 Hz. We produce the rate of TEC index (ROTI) to represent GPS TEC fluctuations related to ionospheric irregularities. In the KISS network, two ground-based GPS sites at Kiruna (marker: KIRN; geographic: $67.9^{\circ}$ N, $21.4^{\circ}$ E; geomagnetic: $65.2^{\circ}$ N) and Chuuk (marker: CHUK; geographic: $7.5^{\circ}$ N, $151.9^{\circ}$ E; geomagnetic: $0.4^{\circ}$ N) were selected to evaluate the ROTI value for ionospheric irregularities during the occurrence of the 2015 St. Patrick's Day storm. The KIRN ROTI values in the aurora region appear to be generally much higher than the CHUK ROTI values in the EIA region. The CHUK ROTI values increased to ~0.5 TECU/min around UT=13:00 (LT=23:00) on March 16 in the quiet geomagnetic condition. On March 17, 2015, CHUK ROTI values more than 1.0 TECU/min were measured between UT=9:00 and 12:00 (LT=19:00 and 22:00) during the first main phase of the St. Patrick's Day storm. This may be due to ionospheric irregularities by increased pre-reversal enhancement (PRE) after sunset during the geomagnetic storm. Post-midnight, the CHUK ROTI showed two peaks of ~0.5 TECU/min and ~0.3 TECU/min near UT=15:00 (LT=01:00) and UT=18:00 (LT=04:00) at the second main phase. The KIRN site showed significant peaks of ROTI around geomagnetic latitude=$63.3^{\circ}$ N and MLT=15:40 on the same day. These can be explained by enhanced ionospheric irregularities in the auroral oval at the maximum of AE index

• Journal of Periodontal and Implant Science
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• 제51권3호
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• pp.163-178
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• 2021

Purpose: The aim of this study was to evaluate clinical factors affecting the longevity of fixed retainers and the influence of fixed retainers on periodontal health in periodontitis patients. Methods: In total, 52 patients with at least 2 years of follow-up after periodontal and orthodontic treatment were included in this study. After scaling and root planing, orthodontic treatment with fixed appliances or clear aligners was performed. Fixed retainers with twist-flex stainless steel wires were bonded to the palatal or lingual sides of anterior teeth. Changes in clinical parameters, including the plaque index, gingival index, calculus index (CI), probing pocket depth, and radiographic bone levels, were evaluated before bonding of fixed retainers and at a 12-month follow-up. Cumulative survival rates (CSRs) for retainer failure were evaluated according to sex, site, CI, stage of periodontitis, and the severity of the irregularity with the log-rank test and hazard ratios (HRs). Results: Twelve months after bonding of fixed retainers, improvements were observed in all clinical parameters except CI and radiographic bone gain. The overall CSR of the retainers with a CI <1 at the 12-month follow-up after bonding of fixed retainers was significantly higher than that of the retainers with a CI ≥1 at the 12-month follow-up (log-rank test; P<0.001). Patients with stage III (grade B or C) periodontitis had a higher multivariate HR for retainer failure (5.4; 95% confidence interval, 1.22-23.91; P=0.026) than patients with stage I (grade A or B) periodontitis. Conclusions: Although fixed retainers were bonded in periodontitis patients, periodontal health was well maintained if supportive periodontal treatment with repeated oral hygiene education was provided. Nonetheless, fixed retainer failure occurred more frequently in patients who had stage III (grade B or C) periodontitis or a CI ≥1 at 12-month follow-up after bonding of fixed retainers.

• 대한치과교정학회지
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• 제27권6호
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• pp.871-880
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• 1997

본 연구에서는 치열심미지수(DAI)의 10가지 교합적 요소와 악안면 형태와의 상호관계를 단변수와 다변수 통계처리 기법을 이용하여 조사하였다. 자료는 교정치료를 위해 내원한 영구치열을 가진 182명(남자 79명, 여자 103명)의 치료전 연구모형과 측모 두부규격방사선 사진으로부터 얻었다. 악안면 형태를 분석하기 위해서 DiPaolo의 사변형 분석 방법을 이용하였으며 치열심미지수의 10가지 교합적 요소는 Jenny, Cons 등에 의해 발표된 진단기준에 따라 각 항목을 측정하여 기록하였다. 또한 안모의 심미관계도 조사하여 다음과 같은 결론을 얻었다. 1. 치열심미지수의 구성요소중 결손치수, 절치부 총생도, 절치부 공극도, 정중이개량, 상악전치부 최대 변이량등 대부분의 구성요소가 악안면 형태와 상관관계를 보이지 않았다. 2. 치열심지지수의 구성요소중 상악전치부 수평피개량, 하악전치부 수평피개량, 전 후방 구치관계 등은 시상면적 악골관계를 나타내는 골격요소인 MdBL/MxDL, MdLL/MxLL, MdSL/MxSL들과 상관관계를 보였다. 3. 치열심미지수의 구성요소중 전치부 수직 개방교합량은 수직적 악골관계를 나타내는 ALFM/AUFH, MPA, SA등과 미약한 상관관계를 보였다. 4. 교합의 여러 측면을 기초로 한 치열심미지수는 악안면 형태와 무관하였다. 5. 교정치료 필요 유무의 선별 및 부정교합의 심도에 관한 포괄적인 평가에는 어느 특정 지수에 의존하기보다는 교합적 요소와 악안면 골격적 요소 모두에 기초를 두어야 할 것으로 사료된다.

• 대한치과교정학회지
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• 제20권1호
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• pp.183-195
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• 1990

The purposes of present study were to identify possible relationships between post-treatment changes and post-retention changes. The patient's models were composed of 58 samples, and were classified non-extraction group (30 samples) and extraction group (28 samples). For each sample the first models were taken prior to the start of treatment, the second models just after the end of treatment, and the third models two years after. The results were as follows: 1. In the cases of non-extraction group, increases were in intermolar width of maxilla, interbicuspid width of maxilla and arch perimeter of mandible during treatment period, but decreases were in the same measurements during post-retention period. 2. In the cases of extraction group, decreases were in intermolar width of mandible, interbicuspid widths of maxilla and mandible, arch length of mandible, arch perimeters of maxilla and mandible during treatment period. 3. Significant decreases were in the irregularity index of both extraction and non-extraction group during treatment period. 4. There were significant differences of arch dimensional changes in intermolar widths of maxilla and mandible, interbicuspid widths of maxilla and mandible, arch lengths of maxilla and mandible, arch perimeters of maxilla and mandible between non-extraction and extraction group.

• Earthquakes and Structures
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• 제11권3호
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• pp.421-443
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• 2016

When conducting seismic assessment of an asymmetric building, it is essential to carry out three-dimensional analysis considering all the possible directions of seismic input. For this purpose, the author proposed a simplified procedure is to predict the largest peak seismic response of an asymmetric building subjected to horizontal bidirectional ground motion acting in an arbitrary angle of incidence in previous study. This simplified procedure has been applied to torsionally stiff (TS) asymmetric buildings with regular elevation. However, the suitability of this procedure to estimate the peak response of an asymmetric building with vertical irregularity, such as an asymmetric building with setback, has not been assessed. In this article, the pushover-based simplified procedure is applied to estimate the peak response of asymmetric buildings with bidirectional setback. Nonlinear dynamic (time-history) analysis of two six-storey asymmetric buildings with bidirectional setback and designed according to strong-column weak beam concept is carried out considering various directions of seismic input, and the results compared with those estimated by the proposed method. The largest peak displacement estimated by the simplified method agrees well with the envelope of the dynamic analysis response. The suitability assessment of the simplified procedure to analysed building models is made as well based on pushover analysis results.

• 대한치과교정학회지
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• 제42권5호
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• pp.255-262
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• 2012

Objective: We aimed to compare the retention characteristics of Essix and Hawley retainers. Methods: Adolescents undergoing fixed appliance treatment at 2 centers were recruited for this study. Twenty-two patients (16 women and 6 men) wore Essix retainers (Essix group) while 20 (14 women and 6 men) wore Hawley retainers (Hawley group). The mean retention time was 1 year, and the mean follow-up recall time for both groups was 2 years. Two qualified dental examiners evaluated the blind patient data. Maxillary and mandibular dental casts and lateral cephalograms were analyzed at 4 stages: pretreatment (T1), post-treatment (T2), post-retention (T3), and follow-up (T4). Results: The results revealed that Essix appliances were more efficient in retaining the anterior teeth in the mandible during a 1-year retention period. The irregularity index increased in both arches in both groups after a 2-year post-retention period. The mandibular arch lengths increased during treatment and tended to return to their original value after retention in both groups; however, these changes were statistically significant only in the Hawley group. Cephalometric variables did not show any significant differences. Conclusions: The retention characteristics of both Essix and Hawley retainers are similar.