• The Journal of the Korea Contents Association
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• v.7 no.9
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• pp.212-219
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• 2007

This study were developed with the preventive structures of shore erosion using the seawater circulation system in wave dissipation block of the natural affinity. The shore protection structures were established to excellent by the hydraulic model experiment on reflectivity and stability and wave overtopping in comparison with existing other structures. These structures, in order to analyzes also as the shore protection and the erosion preventive, were examined with the field applications of performance and the capacity of prevention, respectively, from field construction of the pending positions. As the result, the structures were ensured with the applications and the efficiency as the shore protection structure of erosion preventive by certifying accumulated sediment deposits in the field measurement and monitoring.

• Imaging Science in Dentistry
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• v.50 no.4
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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.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.4 s.56
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• pp.101-106
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• 2009

In order to build an effective management system for structures and to propose national policy and vision for advance of safety and maintenance management, 'Fundamental Scheme of Safety and Maintenance Management for Structures' has been established and promoted. As developed countries adopt preventive maintenance management, which is preventive as well as aggressive repair/strengthening for structures, it is needed to introduce life-cycle analysis method for improvement of economical efficiency. Therefore, this paper presents not only analysis of domestic conditions and problems related to system for safety and maintenance management, policies and costs for structures but an improvement plan.

• International Journal of Reliability and Applications
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• v.9 no.1
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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.

• Journal of Applied Reliability
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• v.3 no.1
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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.

• Magazine of the Korea Concrete Institute
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• v.13 no.6
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• pp.52-57
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• 2001

• Journal of the Korean Society for Railway
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• v.10 no.2 s.39
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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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• v.15 no.3
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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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• v.21 no.6
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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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• v.19 no.10
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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.