• 한국콘텐츠학회논문지
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• 제7권9호
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• pp.212-219
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• 2007

본 연구에서는 자연 친화형의 해안을 보호하고 침식을 방지할 수 있는 해수유통 호안블록을 개발하였다. 개발한 호안블록 구조물은 반사율과 안정성 및 월파량에 대한 기존 구조물과 수리모형 비교실험을 통해 안정성과 우수성을 입증하였다. 또한 이를 현장에 시공하여 구조물서의 현장 적용성과 기능을 검토하기 위해 침식해안의 일부 구간에 본 구조물을 설치하고 해안 표사의 변화를 조사관찰한 결과, 많은 양의 모래가 퇴적되는 것을 확인함으로써 해안침식 방지용 호안 구조물로서의 기능과 적용성을 확보하였다.

• Imaging Science in Dentistry
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• 제50권4호
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• pp.281-290
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• 2020

Purpose: The objective of the present study was to evaluate the prevalence of dental implants positioning errors and their associations with adjacent structures and anatomical variations by means of cone-beam computed tomography (CBCT). Materials and Methods: CBCT images of 207 patients (584 dental implants) were evaluated by 2 oral radiologists. The distance between the implant and the adjacent teeth/implants was measured and classified as adequate (≥1.5 mm and ≥3 mm, respectively) or inadequate. The presence of thread exposure, cortical perforation, implant dehiscence, implant penetration into adjacent structures, and anatomical variations was also recorded. The incisor canal diameter and the depth of the concavity of the submandibular fossa were measured in order to evaluate their correlations with the frequency of implant penetration in these structures. Descriptive analyses, the Fisher exact test, and Spearman correlation analysis were performed (α=0.05). Results: The overall prevalence of positioning errors was 82.9%. The most common error was the inadequate distance between the implant and the adjacent teeth/implants. The presence of anatomical variations did not significantly influence the overall prevalence of errors (P>0.05). There was a positive correlation between the diameter of the incisor canal and the frequency of implant penetration in this structure (r=0.232, P<0.05). Conclusion: There was a high prevalence of dental implant positioning errors, and positioning errors were not associated with the presence of anatomical variations. Professionals should be aware of the space available for implant placement during the preoperative planning stage.

• 한국구조물진단유지관리공학회 논문집
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• 제13권4호통권56호
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• pp.101-106
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• 2009

현재 시설물의 안전 및 유지관리 선진화를 위한 국가 기본시책과 비전을 제시하고 시설물을 효율적으로 관리할 수 있는 체계를 마련하기 위하여 안전 및 유지관리 기본계획이 수립되어 추진하고 있는 실정이다. 이와 같이 선진국에서 수행하고 있는 시설물에 대하여 예방적이고 적극적인 보수 보강을 수행하는 예방적 유지관리전략을 우리나라에서도 적극적으로 도입하여 안전 및 유지관리체계를 마련하고 이를 수행하는 것이 필요할 것으로 판단된다. 또한 시설물의 안전 및 유지관리기술에 생애주기분석기법을 적극적으로 도입하여 경제성을 높일 수 있는 기반을 마련해야 하겠다. 따라서 본 논문에서는 시설물의 안전 및 유지 관리의 체계, 제도적 문제, 예산 등에 대한 현재 국내의 실태와 문제점에 대한 분석과 함께 개선방안을 제시하였다.

• International Journal of Reliability and Applications
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• 제9권1호
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• pp.113-122
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• 2008

In this paper, we consider a periodic preventive maintenance policy in which each preventive maintenance reduces the hazard rate of amount proportional to the failure intensity, which increases since the system started to operate. And the effect of preventive maintenance at each preventive maintenance epoch is different. The expected cost rate per unit time for the proposed model is obtained. We discuss the optimal number N of the periodic preventive maintenance and the optimal period x, which minimize the expected cost rate per unit time and obtain the optimal preventive maintenance schedule for given cost structures of the model. A numerical example is given for the purpose of illustrating our results when the failure time distribution is Weibull distribution.

• 한국신뢰성학회지:신뢰성응용연구
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• 제3권1호
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• pp.73-82
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• 2003

Reliability Centered Maintenance(RCM) was initially developed for the commercial aviation industry in the late 1960s and now is equally applicable to a variety of equipment other than aircraft. RCM is a method for establishing a preventive maintenance program which will efficiently and effectively allow the achivement of the the required safety and availability levels of equipment and structures. RCM provides for the use of a decision logic tree to identify applicable and effective preventive maintenance requirements for equipment and structures according to the safety, maintenance requirements for equipment and structures according to the safety, operational and economic consequences of identifiable failures, and the degradation mechanism, reponsible for the those failures. The end result of working through the decision logic is a judgement as to the necessity of performing a maintenance task. In this paper, we provide guiding principles based on IEC 60300-3-11 for RCM analysis methods and operational method of structure and equipment.

• 콘크리트학회지
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• 제13권6호
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• pp.52-57
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• 2001

• 한국철도학회논문집
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• 제10권2호
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• pp.167-178
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• 2007

In general, it is known that the concrete ballast track is possible to reduce a cost of maintenance activities cause of maintenance free by restrictive maintenance in application of track ballast structures. However, if deteriorations and fracture mechanism of a material are considered, proper maintenance activities and repairing are continually required. For the problems, we evaluated an economical efficiency of the gravel ballast and the concrete ballast on a proper level of maintenance activities. As the method based on history path is difficult to obtain sufficient reliabilities cause of an absence of real data for maintenance activities, we chose the delphi survey method by professional group, and we obtained the appropriate index and profiles for maintenance activities. As a result, we founded that effects for cost reduction can be expected by preventive maintenance management, and we proposed economical restrictions and life cycle cost for track ballast structures in a life cycle.

• Smart Structures and Systems
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• 제15권3호
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• pp.609-625
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• 2015

Management of infrastructure stock is essential in sustainability of society, and its analysis and optimization are studied in the light of control system modeling in this paper. At the first part of the paper, cost of stock management is analyzed based on macroscopic statistics on infrastructure stock and economical growth. Stock management burden relative to economy is observed to become larger at low economic growth periods in developed economies. Then, control system modeling of stock management is introduced and by augmenting maintenance actions as control input, dynamic behavior of stock is simulated and compared with existing time history statistics. Assuming steady state conditions, applicability of the model to cross sectional data is also demonstrated. The proposed model is enhanced so that both preventive and corrective maintenance can be included as system inputs, i.e., feedforward and feedback control inputs. Optimal management strategy to achieve specified deteriorated stock level with minimal cost, expressed in terms of preventive and corrective maintenance actions, is derived based on estimated parameter values for corrosion of steel bridges. Relative cost effectiveness of preventive maintenance is shown when target deteriorated stock level is lower.

• Journal of Dental Anesthesia and Pain Medicine
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• 제21권6호
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• pp.547-556
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• 2021

Background: This study aimed to determine the efficacy of Physics Forceps in pediatric dental extractions. Methods: This was a double-blind, randomized controlled trial with a parallel-arm design and identical allocation ratio (1:1). Children (n=104) were randomly divided into two groups for extraction of mandibular primary teeth (group I: Physics Forceps; group II: conventional forceps). The outcome variables assessed in the study were the time taken for extraction, pre- and postoperative anxiety (using RMS pictorial scale), incidence of fractured teeth, and postoperative pain on the first and third days (using the Wong-Baker faces pain scale). Results: A significant reduction (P < 0.001) in intraoperative time, anxiety, and incidence of tooth fracture was confined to group I. The pain significantly reduced from the first to the third postoperative day in both groups, but the mean reduction in RMS scores in the physics forceps group was far better than that in the conventional forceps group. Conclusion: Physics Forceps aid in extraction of primary teeth with minimal trauma to supporting structures, as well as reducing anxiety in the pediatric population.

• Journal of Microbiology and Biotechnology
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• 제19권10호
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• pp.1176-1183
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• 2009

Lactobacillus crispatus (L. crispatus) ZJ001 is highly adhesive to epithelial cells and expresses S-layer proteins. In this study, S-S-layer layer genes were sequenced and expressed in E. coli to characterize the function of proteins with this particular strain. L. crispatus ZJ001 harbored two S-layer genes slpA and slpB, and only slpA gene was expressed in the bacterium, as revealed by RT-PCR and immunoassays. The mature SlpA showed 47% amino acid sequence identity to SlpB. The SlpA and SlpB of L. crispatus ZJ001 were highly homologous at the C-terminal region to other Lactobacillus S-layer proteins, but were substantially variable at N-terminal and middle regions. Electron microscopic analysis indicated that His-slpA expressed in E. coli was able to form a sheet-like structure similar to the natural S-layer, but His-slpB formed as disc-like structures. In the cell binding experiments, HeLa cells were able to bind to both recombinant His-slpA and His-slpB proteins to the extent similar to the natural S-layer. The cell binding domains remain mostly in the N-terminal regions in SlpA and SlpB, as shown by high binding of truncated peptides SlpA2-228 and SlpB2-249. Our results indicated that SlpA was active and high binding to HeLa cells, and that the slpA gene could be targeted to display foreign proteins on the bacterial surface of ZJ001 as a potential mucosal vaccine vector.