• 전력전자학회논문지
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• 제8권6호
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• pp.478-487
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• 2003

본 논문에서는 고압 대용량 전동기 구동용 멀티레벨 인버터의 종류 및 특징을 간략히 살펴보고, 특히 입출력 전력품질이 우수하고 전압별 시리즈화가 용이한 H-브릿지 멀티레벨 인버터의 구조적 특징 및 장점을 기술하였다. 연구 개발된 3,300V lMVA 용량의 Cascaded H-브릿지 멀티레벨 인버터의 구체적인 전력회로 구조 및 설계방법, 제어기 구성 그리고 PWM 기법을 제시하였다. 또한, 실용량의 시험을 통해 H-브릿지 멀티레벨 인버터는 출력 전압 Step이 여러 단계이고 dv/dt가 적으며 입력단 THD를 크게 낮출 수 있어 성능 면에서도 여타 방식보다 우수함을 입증하였다. 또한 생산적인 측면에서도 저압 소자를 사용하여 설계하므로 기존의 생산/시험 기술과 설비를 이용할 수 있어 매우 경제적이며 Power Cell 단위 결합 구조이므로 신뢰성 측면이나 보수/유지 측면에서도 유리하다는 결론을 얻었다.

• The Korean Journal of Pain
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• 제26권1호
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• pp.39-45
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• 2013

Background: Good postoperative pain control is an important part of adequate postoperative care. Patient-controlled epidural analgesia (PCEA) provided better postoperative analgesia compared to other conventional analgesic methods, but several risks have been observed as well. We therefore surveyed the efficacy and safety of PCEA in this retrospective observational study. Methods: We analyzed collected data on 2,276 elective surgical patients who received PCEA with ropivacaine and fentanyl. Patients were assessed by a PCA service team in the post-anesthesia care unit (PACU), at 1-6 h, 6-24 h, and 24-48 h postoperatively for adequate pain control. The presence of PCEA-related adverse events was also assessed. Results: Numerical pain score (median [interquartile range]) were 3 [1-4], 5 [4-7], 4 [3-5], and 3 [3-5] in the PACU, at 1-6 h, 6-24 h, and 24-48 h postoperatively. Median pain scores in patients underwent major abdominal or thoracic surgery were higher than other surgical procedure in the PACU, at 1-6 h after surgery. Nausea and vomiting (20%) and numbness and motor weakness (15%) were revealed as major PCEA-related adverse events during the postoperative 48 h period. There were 329 patients (14%) for whom PCEA was ceased within 48 h following surgery. Conclusions: Our data suggest that the use of PCEA provides proper analgesia in the postoperative 48 h period after a wide variety of surgical procedures and that is associated with few serious complications. However, more careful pain management and sustainable PCEA monitoring considering the type of surgical procedure undergone is needed in patients with PCEA.

• Clinical and Experimental Pediatrics
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• 제64권7호
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• pp.313-321
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• 2021

Here we describe the neurodevelopmental outcomes of very low birth weight (VLBW) infants (birth weight ≤1,500 g) at 3 years of age in the Neonatal Research Network of Japan (NRNJ) database in the past decade and review the methodological issues identified in follow-up studies. The follow-up protocol for children at 3 years of chronological age in the NRNJ consists of physical and comprehensive neurodevelopmental assessments in each participating center. Neurodevelopmental impairment (NDI)-moderate to severe neurological disability-is defined as cerebral palsy (CP) with a Gross Motor Function Classification System score ≥2, visual impairment such as uni- or bilateral blindness, hearing impairment requiring hearing amplification, or cognitive impairment with a developmental quotient (DQ) of Kyoto Scale of Psychological Development score <70 or judgment as delayed by pediatricians. We used death or NDI as an unfavorable outcome in all study subjects and NDI in survivors using number of assessed infants as the denominator. Follow-up data were collected from 49% of survivors in the database. Infants with follow-up data had lower birth weights and were of younger gestational age than those without follow-up data. Mortality rates of 40,728 VLBW infants born between 2003 and 2012 were 8.2% before discharge and 0.7% after discharge. The impairment rates in the assessed infants were 7.1% for CP, 1.8% for blindness, 0.9% for hearing impairment, 15.9% for a DQ <70, and 19.1% for NDI. The mortality or NDI rate in all study subjects, including infants without follow-up data, was 17.4%, while that in the subjects with outcome data was 32.5%. The NRNJ follow-up study results suggested that children born with a VLBW remained at high risk of NDI in early childhood. It is important to establish a network follow-up protocol and complete assessments with fewer dropouts to enable clarification of the outcomes of registered infants.

• 전기전자학회논문지
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• 제23권1호
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• pp.254-260
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• 2019

본 논문에서는 양방향 dc-to-dc 컨버터의 고장원인, 고장영향, 고장 결과를 파악하기 위한 failure mode and effect analysis(FMEA)와 양방향 컨버터의 위험도를 고려한 fault-tree analysis(FTA)를 통해 고장률을 예측한다. 전기차의 구동전압을 효율적으로 상승시키기 위해 인버터 앞단에 부착되는 양방향 컨버터는 배터리 전력을 dc-link 커패시터로 방전시키는 승압모드와 회생전력을 배터리로 충전시키는 강압모드를 가진다. 양방향 컨버터의 동작 특성을 고려한 FMEA 결과를 바탕으로 컨버터의 위험도를 고려한 고장나무를 설계한다. 전기차 MCU용에 맞는 설계 파라메타를 설정하고 출력전압 리플과 인덕터 전류 리플에 따른 커패시터와 인덕터의 부품 고장률을 분석한다. 또한 동작 온도에 따른 주요부품의 고장률을 MIL-HDBK-217F를 이용하여 구한다. 마지막으로 부품 고장률을 고장나무의 기본 사상의 고장률로 반영하여 컨버터 고장률과 평균고장시간을 예측한다.

• 한국기계가공학회지
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• 제18권3호
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• pp.33-40
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• 2019

FDM 3D printers have become widespread, and investment in the 3D printer industry is increasing. Therefore, many 3D printers are released and the functions of products are emphasized. However, to lower unit prices, open-type 3D printers are sold in kit form, and their performance is very low. If the 3D printer has many heat sources and is sealed, there is the possibility that the main accessories (the main board, power supply, and motor) will be damaged by trapped heat. At the same time, if the ambient temperature is low due to the properties of the material, the output quality deteriorates. In this study, we analyzed the temperature rise of the main accessories and the quality of the output by the heat bed when a chamber was added to an open-type 3D printer. We also compared the quality of the output due to the air flow with the temperature rise of the main accessories. Moreover, we found the optimal value. As a result of the quality analysis, it was finally confirmed that the case with the chamber at $95^{\circ}C$ was the best for the printing condition. In addition, in the absence of the chamber, the bending of the specimen was found to be large, and in the case of the chamber, the degree of bending was slightly decreased by 0.05 mm.

• Neonatal Medicine
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• 제25권4호
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• pp.178-185
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• 2018

Purpose: We aim to assess the Bayley Scales of Infant and Toddler Development, third edition (Bayley-III), Adaptive Behavior (AB) and Social-Emotional (SE) scales at 18 to 24 months of corrected age (CA) to examine their associations with school-age cognitive and behavioral outcomes in children born preterm. Methods: Eighty-eight infants born with a very low birth weight (<1,500 g) or a gestational age of less than 32 weeks who were admitted to the neonatal intensive care unit from 2008 to 2009 were included. Of the 88 children who completed school-age tests at 6 to 8 years of age, 37 were assessed using the Bayley-III, including the AB and SE scales, at 18 to 24 months of CA. Correlation, cross-tabulation, and receiver operating characteristic analyses were performed to assess the longitudinal associations. Results: A significant association was observed between communication scores on the Bayley-III AB scale at 18 to 24 months of CA and the Korean version of the Wechsler Intelligence Scale for Children (K-WISC) full-scale intelligence quotient (FSIQ) at school age (r=0.531). The total behavior problem scores of the Korean version of the Child Behavior Checklist (K-CBCL) at school age were significantly negatively related to the Bayley-III SE and AB scales but not to the cognitive, language, or motor scales. Conclusion: Our findings encourage AB and SE assessments during the toddler stage and have important implications for the early identification of children in need of intervention and the establishment of guidelines for follow-up with high-risk infants.

• 한국항공우주학회지
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• 제50권10호
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• pp.691-699
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• 2022

본 논문에서는 대형 메쉬 안테나 개발을 위한 모듈식 전개형 반사판 및 붐 구조의 전개 시 요구되는 구동력 및 전개 특성을 분석하고자 한다. 단위 전개 구조를 이용하여 모듈식 전개형 반사판 링과 붐 구조의 수납/전개된 형상을 분석하였다. Kane's 방정식을 이용하여 전개 구조물의 다물체 동역학 방정식을 유도하고 PUTD(Pseudo Upper Triangular Decomposition) 방법을 적용하여 구속조건 문제를 해결하였다. 다물체 동역학 시뮬레이션을 통해 설계된 모듈식 전개 반사판 링 그리고 붐 구조의 동적 특성을 살펴보고자 한다.

• 한국가스학회지
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• 제26권2호
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• pp.9-13
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• 2022

벨트나 체인을 이용한 감속기는 간단한 장치이긴 하지만 공간을 많이 차지하여 공간상의 제약이 있기 때문에 전동휠체어 구동부에는 부적합하다. 하지만 유성기어형태의 감속기는 동일 축에서 감속이 이루어지기 때문에 부피를 작게 할 수 있어 공간의 제약이 벨트나 체인형태의 감속기보다 덜하다. 따라서 본 연구에서는 수·전동전환이 가능한 휠체어의 구동부에 대한 연구를 통하여 유성기어형태를 이용한 감속기로 큰 추진력을 얻을 수 있는 구동부를 개발하였다. 그에 따라 감속기에 적용되는 유성기어의 치형을 Kisssoft 프로그램을 이용하여 설계를 진행하였다. 또한 기존 휠체어 바퀴에 적용 가능하도록 구동부의 설계를 진행하였고, 구동부의 수·전동 전환원리 및 작동원리에 대한 메커니즘의 최적화를 진행하였다. 연구내용을 토대로 하나의 선기어와 2개의 유성기어, 하나의 링기어를 갖는 유성기어 형태의 휠체어 감속기 구동부의 최종 설계 및 제작을 진행하였다.

• 대한간호학회지
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• 제27권4호
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• pp.831-842
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• 1997

The purpose of the study was to test the reliability and validity of the Korean version of Task Self-Efficacy Scale for activities of dally living (ADL). The Task Self-Efficacy Scale was developed by Roberts(1996) for low-intensity exercise study with older people to predict their performance of ADL. The scale was translated and back translated by bilingual persons, and then was modified to resolve variations in the translations. The Korean version of Self-Efficacy Scale for ADL was then administered to 193 elderly people including 95 hospitalized patients and 98 outpatients or healthy people. Face to face interview was used to fill out the structured questionnaire, and each interview took approximately 30 minutes. The subjects for the study were 80 women and 112 men with an age range of 65 to 95 years(M=71 years) of whom 82.6% classified themselves as moderate or quite active Most subjects(80.2%) had an education level of elementary school or less. The Self-Efficacy Scale for ADL is measured on a 0 to 10 VAS, assessing three areas of ADL : self care activities, household tasks, and motor tasks. The higher the score is, the higher person's confidence in performing ADL. Psychometric testing revealed that the scale was found to be internally consistent, showing a Cronbach's alpha of .97 The scale was significantly correlated with subjects' level of activity and subjective assessment of their health status. Moderate correlation with health-related hardiness scale also supported the validity. Factor analysis was performed to confirm whether the scale represents the three sub-areas as suggested in the literature. The results of the factor analysis led to a three factor solution according to Kaiser's criterion, but the items were not strongly and cleanly loaded for the third factor. This can be explained in that, among the three sub-ADL areas of the self-efficacy scale, the areas of self care activities and household tasks seem to have similar levels of difficulty in performance with not enough differences for the self-efficacy scale to distinguish between the two areas. Therefore, one factor solution was suggested since ADL can be seen as a unit of activities at similar level of difficulty in performance. One factor solution explained 68.1% of variance of the 19-item scale and all items were correlated over .6 with the factor, showing that the selected factor solution fits the model. The results indicated that the Korean version of Task Self-Efficacy Scale for ADL was reliable and valid in producing useful information to evaluate the effects of various interventions toward promoting health and quality of life for elderly people.

• Journal of Oral Medicine and Pain
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• 제26권3호
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• pp.261-276
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• 2001

본 연구는 구강안면동통 중에서 빈번히 나타나는 근육성 동통의 주 원인인 저작근의 과활성으로 유발된 근육의 피로 시에 운동단위전위, 압력통각역치, 근전도 power spectrum의 변화 양상과 이들 척도간의 연관성을 조사하기 위해 시행되었다. 두개하악장애의 병력 및 현증이 없고 정상적인 구치부 교합관계를 가진 평균연령 25.8세인 36명의 정상 성인(남자 26명, 여자 10명)을 대상으로 교근과 전측두근의 지속적인 등길이 수축 전후의 압력통각역치 및 운동단위전위를 측정하였고 인내시간까지의 근수축 동안 근전도 power spectrum을 분석하여 다음과 같은 결론을 얻었다. 1. 지속적인 등길이 수축 후 교근과 전측두근의 압력통각역치는 수축 전에 비해 유의하게 감소하였다. 2. 압력통각역치는 수축 전과 수축 후 모두에서 전측두근이 교근보다 유의하게 높게 나타났으며, 전체적으로 남성이 여성보다 높게 나타나는 양상을 보였으나 성별간의 차이는 전측두근의 수축 후 압력통각역치에서만 통계적으로 유의하게 나타났다. 3. 지속적인 등길이 수축말기의 중간주파수는 수축초기에 비하여 유의하게 감소하였고, 전측두근의 수축초기 중간주파수와 수축말기 중간주파수 모두 교근보다 유의하게 높게 나타났다. 4. 교근은 지속적인 등길이 수축 전에 비하여 수축 후의 운동단위전위의 지속시간,진폭, 면적, 상의 4가지 척도에서 유의한 증가를 보였고 전측두근은 진폭을 제외한 나머지 3가지 척도, 즉 지속시간, 면적, 상의 유의한 증가를 보였다. 5. 교근과 전측두근의 지속적인 등길이 수축 전의 압력통각역치와 운동단위전위 척도 사이에는 통계적으로 유의한 상관관계가 없었고 교근에서는 수축 후의 압력통각역치와 운동단위전위의 지속시간, 진폭, 면적, 상 사이에 유의한 상관관계가 존재하였다. 위의 실험결과를 통해 근육피로 검사에 압력통각역치, 근전도 power spectrum 검사 외에 근육수축의 기능적 최소 단위인 운동단위전위의 분석 또한 유용할 수 있고 추후 만성으로 진행된 근막동통환자와 정상 대조군간의 운동단위 수준에서의 비교연구와 근피로에 더욱 민감한 운동단위전위의 다른 척도에 대한 개발과 연구가 필요하다고 사료된다.