• 제목/요약/키워드: Periodic function

검색결과 435건 처리시간 0.027초

수직축 풍력터빈 성능향상을 위한 풍력타워 최적설계에 관한 연구 (Optimum Design of a Wind Power Tower to Augment Performance of Vertical Axis Wind Turbine)

  • 조수용;임채환;조종현
    • 한국항공우주학회지
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    • 제47권3호
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    • pp.177-186
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    • 2019
  • 풍력 타워는 수직형 풍력터빈의 성능을 향상시키기 위해 사용되어왔다. 하지만 올바르게 설계되지 않은 풍력 타워는 오히려 풍력터빈의 성능을 저하시킬 수 있다. 따라서 본 연구에서는 풍력 타워의 최적화 연구를 수행하였다. 이를 위하여 다음과 같이 6가지의 설계변수가 선택되었다. 즉, 가이드 벽의 외부 및 내부 반경, 스플리터의 적용 여부, 스플리터의 내부 반경, 가이드 벽의 개수 및 원주각도가 선정되었다. 최적화를 위한 목적함수는 풍력타워 내에 설치된 수직형 풍력터빈에서의 주기적인 평균 토크가 사용되었으며, 최적화 과정에서 지엽적인 최적화 결과를 피하기 위하여 실험계획법, 유전자알고리즘 및 인공신경망기법이 사용되었다. 인공신경망은 세대의 증가에 따라 지속적으로 향상하였으며, 수직 풍력터빈의 성능은 독립운전에 비하여 최적화된 풍력 타워 내에서 두 배 이상 향상되었다.

상악 전치부 임플란트의 비심미성 개선을 위한 임플란트 침수(submergence)를 동반한 치조제 증대술 (Pontic site development with an implant submergence technique for unaesthetic implant in the anterior maxilla)

  • 송유정;이주연
    • 구강회복응용과학지
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    • 제36권4호
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    • pp.289-295
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    • 2020
  • 비심미적인 임플란트유지형 보철물의 심미성 개선은 매우 어려운 문제이며 특히, 상악 전치부 임플란트와 관련되어 있는 경우는 더욱 그러하다. 본 증례는 상악전치부 임플란트의 주기적 배농과 비심미성을 주소로 보철과의사로부터 의뢰된 69세 남자 환자의 심미성 개선에 관한 보고이다. 임플란트는 다소 깊게 식립되어 긴 임상치관길이를 보였으며, 주변 연조직 양도 부족하였다. 임상 검사와 방사선검사 후, 깊게 식립된 임플란트의 제거 대신 예후가 불량한 인접 치아의 발치 후 임플란트를 추가 식립하여 임플란트 유지형 고정성보철물을 제작하고, 깊게 식립된 임플란트는 제거 대신 치조제 증대에 도움을 주기 위해 침수(submergence)시켜 치조제를 증대시키는 방식을 선택하였다. 적절한 진단이 동반된 임플란트 침수가 전치부의 임플란트 비심미성을 개선시킬 수 있는 또다른 대안이 될 수 있을 것이다.

Comparative Morphological Study on Parotid and Submandibular Salivary Glands in Ovariectomized Rats

  • Jeong, Moon-Jin;Lee, Myoung-Hwa;Lim, Do-Seon;Jeong, Myeongju;Jeong, Soon-Jeong
    • 치위생과학회지
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    • 제22권2호
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    • pp.83-89
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    • 2022
  • Background: Estrogen deficiency affects the structure and function of the salivary glands in women, leading to a decrease in salivary secretion and a change in the composition of saliva. Previous studies on changes in the salivary glands that cause estrogen deficiency have reported only partial results for the parotid and submandibular glands, and there are few comparative morphological studies of histological changes between the parotid and submandibular glands in ovariectomized rats (OVX) leading to estrogen deficiency. This study aimed to analyze the histopathological and histochemical changes in the parotid and submandibular salivary glands causing estrogen deficiency by using OVX, and to discuss the mechanism on these changes. Methods: The parotid and submandibular glands from sacrificed control and OVX groups were fixed with cold 4% paraformaldehyde in phosphate buffer (pH 7.2). The tissues were dehydrated using a series of graded ethyl alcohol and embedded in paraffin. For histopathological analysis, sections cut to a thickness of 6 to 7 ㎛ were stained with hematoxylin and eosin (H&E). For histochemical analysis, Periodic acid-Schiff (PAS), Alcian blue (AB, pH 2.5), and PAS+AB (pH 2.5 and pH 1) staining was performed. Results: Histopathological analysis of OVX tissue showed that the parotid and submandibular salivary glands were broadly and clearly separated and divided into lobes. In OVX, acinar and ductal cells with condensed polymorphic or pyknotic nucleus, which are presumed to be characteristic of apoptotic cells, and degenerated cells with lipid deposition in cytoplasmic granules and ruptured membranes were increased. Histochemical analysis of OVX, confirmed an increase in the number and acidification of acinar secretory granules. Conclusion: Histopathological and histochemical changes and the effects of estrogen deficiency are more evident in the submandibular salivary gland than in the parotid gland.

머신러닝을 이용한 선제적 VNF Live Migration (Proactive Virtual Network Function Live Migration using Machine Learning)

  • 정세연;유재형;홍원기
    • KNOM Review
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    • 제24권1호
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    • pp.1-12
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    • 2021
  • VM (Virtual Machine) live migration은 VM에서 동작하는 서비스의 downtime을 최소화하면서 해당 VM을 다른 서버 노드로 이전시키는 서버 가상화 기술이다. 클라우드 데이터센터에서는 로드밸런싱, 특정 위치 서버로의 consolidation 통한 전력 소비 감소, 서버 유지보수(maintenance) 작업 중에도 사용자에게 무중단 서비스를 제공하기 위한 목적 등으로 VM live migration 기술이 활발히 사용되고 있다. 또한 고장 및 장애 상황이 예측되거나 그 징후가 탐지되는 경우, 예방 및 완화 수단으로 활용될 수 있다. 본 논문에서 우리는 두 가지 선제적(proactive) VNF live migration 방법을 제안하며, 첫 번째 방법은 서버 로드밸런싱에 VNF live migration 기법을 사용하며 두 번째 방법은 고장 예측에 기반하여 고장 회피 목적으로 VNF live migration을 사용한다. 선제적 migration을 위한 예측에 머신러닝(기계학습)을 활용하며 실험을 통해 그 실효성을 검증한다. 특히 두 번째 방법에 대해 vEPC (Virtual Evolved Packet Core)의 고장 상황을 case study한 결과를 제시한다.

Ensemble-based deep learning for autonomous bridge component and damage segmentation leveraging Nested Reg-UNet

  • Abhishek Subedi;Wen Tang;Tarutal Ghosh Mondal;Rih-Teng Wu;Mohammad R. Jahanshahi
    • Smart Structures and Systems
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    • 제31권4호
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    • pp.335-349
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    • 2023
  • Bridges constantly undergo deterioration and damage, the most common ones being concrete damage and exposed rebar. Periodic inspection of bridges to identify damages can aid in their quick remediation. Likewise, identifying components can provide context for damage assessment and help gauge a bridge's state of interaction with its surroundings. Current inspection techniques rely on manual site visits, which can be time-consuming and costly. More recently, robotic inspection assisted by autonomous data analytics based on Computer Vision (CV) and Artificial Intelligence (AI) has been viewed as a suitable alternative to manual inspection because of its efficiency and accuracy. To aid research in this avenue, this study performs a comparative assessment of different architectures, loss functions, and ensembling strategies for the autonomous segmentation of bridge components and damages. The experiments lead to several interesting discoveries. Nested Reg-UNet architecture is found to outperform five other state-of-the-art architectures in both damage and component segmentation tasks. The architecture is built by combining a Nested UNet style dense configuration with a pretrained RegNet encoder. In terms of the mean Intersection over Union (mIoU) metric, the Nested Reg-UNet architecture provides an improvement of 2.86% on the damage segmentation task and 1.66% on the component segmentation task compared to the state-of-the-art UNet architecture. Furthermore, it is demonstrated that incorporating the Lovasz-Softmax loss function to counter class imbalance can boost performance by 3.44% in the component segmentation task over the most employed alternative, weighted Cross Entropy (wCE). Finally, weighted softmax ensembling is found to be quite effective when used synchronously with the Nested Reg-UNet architecture by providing mIoU improvement of 0.74% in the component segmentation task and 1.14% in the damage segmentation task over a single-architecture baseline. Overall, the best mIoU of 92.50% for the component segmentation task and 84.19% for the damage segmentation task validate the feasibility of these techniques for autonomous bridge component and damage segmentation using RGB images.

교정치료 중 광범위한 치경부 탈회를 보이는 치아의 직접 레진 비니어 수복에 관한 증례 (Direct resin veneer restoration for cervical decalcification during orthodontic treatment)

  • 허유경;장훈상;황윤찬;황인남;오원만;이빈나
    • 구강회복응용과학지
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    • 제38권1호
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    • pp.52-59
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    • 2022
  • 고정성 교정치료 중 치아의 협면의 치경부 탈회가 종종 발생한다. 이번 증례보고에서는 교정치료 중 발생한 치아의 치경부 탈회를 직접 레진 비니어 수복을 통해 치료한 2가지 증례를 보고하고자 한다. 우식이 없는 초기 병변은 주기적인 불소도포, 식이조절, 구강위생 개선을 통해 재광화될 수 있으나 점차 진행됨에 따라 적절한 수복치료가 필요하며 병소 발생 후의 치료보다 예방에 중점을 두는 것이 더욱 바람직하다.

야전운용제원을 이용한 5.56 mm 소총 신뢰도 분석 (Reliability Analysis Using Field-Data of 5.56 mm Rifle)

  • 신태성;서현수;이호준;최시영;길현준
    • 한국산학기술학회논문지
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    • 제21권6호
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    • pp.584-591
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    • 2020
  • 무기체계에 있어서 신뢰도는 중요한 요소이다. 신뢰도가 낮으면 무기체계가 제대로 기능하지 못할 가능성이 높으며, 이는 우리군의 전투력 약화로 직결된다. 본 논문에서는 현재 우리 군이 개인화기로 사용하는 5.56 mm 소총의 구조를 총열, 윗총몸, 노리쇠집, 가스활대, 복좌용수철 및 밀대, 아랫총몸, 개머리 총 7개의 조립체로 분류하고, 소총이 정상작동하기 위한 8대 기능에 대하여 설명하였다. 또한 소총의 신뢰도의 개념을 고장 간 평균사격발수(MRBF: Mean Round Between Failure, 이하 MRBF)로 정의하고, 수리가능 시스템에 대한 신뢰도 분석 이론으로서 포아송 과정 모형과 이 모형에 대한 추세를 검정하기 위한 방법으로 TTT(Total Time on Test, 이하 TTT) 도시방법에 대하여 설명하였다. 다음으로 소총의 고장을 주기성 교환품목을 제외한 부품의 교환으로 정의하여 획득한 야전운용제원을 정제하였으며, 정제된 야전운용제원을 MINITAB 프로그램에 입력하여 신뢰도를 분석하였다. 그 결과 소총의 신뢰도는 251.73발로 분석되었으며, 소총의 조립체별 신뢰도 분석을 통해 개선이 필요한 조립체로 총열, 아랫총몸, 개머리 조립체를 식별하였고, 개선이 필요한 세부 부품 10가지를 식별하였다. 마지막으로 현재 획득 가능한 야전운용제원을 이용한 신뢰도 분석의 한계점에 대하여 고찰하였다.

In Situ Monitoring of the MBE Growth of AlSb by Spectroscopic Ellipsometry

  • 김준영;윤재진;이은혜;배민환;송진동;김영동
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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    • pp.342-343
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    • 2013
  • AlSb is a promising material for optical devices, particularly for high-frequency and nonlinear-optical applications. And AlSb offers significant potential for devices such as quantum-well lasers, laser diodes, and heterojunction bipolar transistors. In this work we study molecular beam epitaxy (MBE) growth of an unstrained AISb film on a GaAs substrate and identify the real-time monitoring capabilities of in situ spectroscopic ellipsometry (SE). The samples were fabricated on semi-insulating (0 0 1) GaAs substrates using MBE system. A rotating sample stage ensured uniform film growth. The substrate was first heated to $620^{\circ}C$ under As2 to remove surface oxides. A GaAs buffer layer approximately 200 nm- thick was then grown at $580^{\circ}C$. During the temperature changing process from $580^{\circ}C$ to $530^{\circ}C$, As2 flux is maintained with the shutter for Ga being closed and the reflection high-energy electron diffraction (RHEED) pattern remaining at ($2{\times}4$). Upon reaching the preset temperature of $530^{\circ}C$, As shutter was promptly closed with Sb shutter open, resulting in the change of RHEED pattern from ($2{\times}4$) to ($1{\times}3$). This was followed by the growth of AlSb while using a rotating-compensator SE with a charge-coupled-device (CCD) detector to obtain real-time SE spectra from 0.74 to 6.48 eV. Fig. 1 shows the real time measured SE spectra of AlSb on GaAs in growth process. In the Fig. 1 (a), a change of ellipsometric parameter ${\Delta}$ is observed. The ${\Delta}$ is the parameter which contains thickness information of the sample, and it changes in a periodic from 0 to 180o with growth. The significant change of ${\Delta}$ at~0.4 min means that the growth of AlSb on GaAs has been started. Fig. 1b shows the changes of dielectric function with time over the range 0.74~6.48 eV. These changes mean phase transition from pseudodielectric function of GaAs to AlSb at~0.44 min. Fig. 2 shows the observed RHEED patterns in the growth process. The observed RHEED pattern of GaAs is ($2{\times}4$), and the pattern changes into ($1{\times}3$) with starting the growth of AlSb. This means that the RHEED pattern is in agreement with the result of SE measurements. These data show the importance and sensitivity of SE for real-time monitoring for materials growth by MBE. We performed the real-time monitoring of AlSb growth by using SE measurements, and it is good agreement with the results of RHEED pattern. This fact proves the importance and the sensitivity of SE technique for the real-time monitoring of film growth by using ellipsometry. We believe that these results will be useful in a number of contexts including more accurate optical properties for high speed device engineering.

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경남지역 일부 산업간호사의 보건관리 업무 및 관련요인에 관한 연구 (A Study on Health Care Activities of Some Industrial Nurses and their Related Factors in Kyungnam Area)

  • 김영숙
    • 한국직업건강간호학회지
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    • 제4권호
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    • pp.48-57
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    • 1995
  • The purpose of this study was to assess the performance of the role and function of some industrial nurses and to characterize the factors affecting the performance of their activities. Thus the results could be used to suggest the direction in the performance of industrials nurses' activities effectively. During a period from January 10 to March 31, 1994, the data were collected from 87 industrial nurses, who were working as health managers in the plants, in Ulsan city and the vicinity in Kyungnam province, using a structured questionnaire. The results were as follows : 1. The general characteristics of industrial nurses in this study were 82.8% being 30 years old or less, 60.9%, being not married, and 93.1% having eduction levels above junior college. 2. With respect to general work conditions, 94.3% were working in a separate room provided for health care division, 40.2% working under the safety and health department, and 98.9% working as common-level staffs. And 60.9% were working less than 44 hours a week, 70.1% had work experiences less than 5 years, and 50.6% had annual incomes ranging 10 to 14 million wons. 3. As work conditions related to health care activities, 49.4% performed the activities not related to health care as always or occasionally, and 87.4% answered that occupational physicians were appointed in their plant and among them, however, only 6.9% worked on full-time basis and 52.8% perform little activities as occupational physicians. For a decision related to health care activity, 69.0% discussed the problems with the supervisors, and 19.5% made decisions by themselves. 4. As for attitude and perception to their activities as health managers, 66.7% moderately recognized the importance of health manager in the workplace, with 63.2% being satisfied their wages and treatment from the company, 57.5% being satisfied with their job positions and 51.7% having positive attitudes as being health managers. 5. The degree of performance at least in one of health related activities were very high in activities such as general medical care(100%), general health examination(98.0%) and specific health examination(100%), and relatively high in health education(72%), new employee health examination(60.9%), document handling(79.3%) and activity for work environment(70.1%). However, the performance rate was very low in preparing protective equipment (20.8%). 6. The levels of activities related to health care were significantly high when making decisions by themselves, when occupational physicians not being full-time, and when satisfying their job positions, and, on the other hand, significantly decreased as work hours increased. 7. In addition to some kinds of periodic education asked by all of the nurses, 89.7% wanted a specialized licensing system for industrial nurse, and 97.4% wanted to apply for the license test. As a conclusion, it is suggested that industrial nurses should be given more authority and placed in more self-controlled system to perform health care and other activities more efficiently, and the role and function of the occupational physician should be clearly distinguished from that of the industrial nurse as a health manager to avoid an unnecessary overlapping.

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수면무호흡증과 수면변수가 인지기능에 미치는 영향과 우울증의 매개효과 (The Effects of Sleep Apnea and Variables on Cognitive Function and the Mediating Effect of Depression)

  • 박경원;김형욱;최말례;김병조;김태형;송옥선;은헌정
    • 수면정신생리
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    • 제24권2호
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    • pp.86-96
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    • 2017
  • 목 적 : 본 연구는 폐쇄성 수면무호흡증 환자에서 수면무호흡지수, 수면관련척도, 기분관련척도, 그리고 인지기능간의 연관성을 보고자 하였다. 방 법 : 폐쇄성 수면무호흡증후군을 보이는 105명의 환자를 선정하였다. 수면무호흡지수로 RDI, AHI가 사용되었고, 수면관련척도로는 PSG에서 측정되는 TST, Duration N1, Duration N2, Duration N3, Duration R, Arousal Index, PLM Index, Snoring Index, Mean SpO2, Minimum SpO2와 설문지로 측정되는 PSQI, ESS, SIS (snoring index by scale)를 사용하였으며 기분관련척도로는 BDI, 인지기능관련 척도로는 Moca-K, MMSE-K, CDR을 사용하였다. 이를 이용하여 수면무호흡증 환자에서 수면무호흡지수, 수면 및 기분관련척도와 인지기능간의 상관관계를 분석하였으며 수면무호흡증 환자에서 보이는 인지기능장애의 기전을 밝히고자 우울증의 매개효과를 분석하였다. 결 과 : Duration N1가 증가할수록 그리고 TST가 감소할수록 MOCA-K에 부적 인과관계를 나타내었다(p < 0.01). BDI와 Supine RDI가 증가할수록 MOCA-K에 부적 인과관계를 보였다(p < 0.01). PSQI가 증가할수록(p < 0.001) 그리고 MMSE-K가 감소할수록(p < 0.01) 또한 SIS가 증가할수록(p < 0.01) BDI에 정적 인과관계를 보였다. 폐쇄성수면무호흡증 환자에서 나이가 MOCA-K에 미치는 영향에 BDI가 부분 매개하는 것으로 확인되었다. 결 론 : 수면무호흡증 환자에서 Duration N1, TST, BDI, Supine RDI가 인지기능과 연관성이 있었으며, 특히 BDI로 측정되는 우울증상이 수면무호흡증 환자의 인지기능저하에 부분적으로 매개 하였다.