• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.11
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• pp.1060-1067
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• 2004

To apply an analysis method of life cycle cost when assessing economics of equipment system, we should basically set up preconditions such as useful life, price escalation rate, interest rate, etc. as well as consider a calculation algorism of source energy and heat source system, which is a complex process for life cycle costing. For this reason, equipment designers tend to plan heat source systems, without a thorough investigation on economics of alternative systems at the pre-design phase. In this process, architectural designers should adopt a proper heat source system, which is one of the most important factors for planning an appropriate architectural design, through a discussion with equipment designers in a short time. In order to offer an evaluation method for equipment designers to analyze economics of an alternative heat source system easily at the pre-design phase, this research would define the simplified economics, evaluation method through analysis of existing papers for economics evaluation, and examine validity through comparison of simplified method values ($LCC_{EC}$) and life cycle costing values ($LCC_{15}$) for six alternative heat source systems.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1631-1637
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• 2018

Electric utilities has been considered the necessity to introduce asset management of electric power facilities in order to reduce maintenance cost of existing facilities and to maximize profit. This paper aims to provide data that can helpful to make profitable decision in terms of power transformers which have a significant part in the power system. Therefore, this study is modeling input cost for power transformer during its entire life and also the life cycle cost (LCC) technique is applied. In particular, the variation of transformer state related with maintenance and the variation of the EUAC curve based on cost and effect of maintenance is examined. In this study, the trend of the equivalent uniform annual cost (EUAC) according to maintenance cycle and cost of equipment is analyzed. In line with that, sensitivity analysis influenced by the changes of other cost factors was performed.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.459-465
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• 2007

This study was conducted to calculate the LCC of a apartment complex with a type of heating system, district heating and cogeneration system. For the purpose of analyzing LCC according to size of apartment complex, 500, 1,500 and 4,000 houses of model apartment selected. This research performs design of heating system and the life cycle cost analysis including an initial cost, energy cost, maintenance and operation cost, replacement cost and renovation cost during the project period(15years). According to the calculated results, 1) Initial cost of cogeneration system with 500, 1500 and 4000 houses is higher than district heating system each of 20%, 13%, 12%. 2) In case of cogeneration system, the payback period by electric generation is 5.21, 4.92 and 4.47 years and saving cost was calculated 29 billion won, 94 billion won and 262 billion won after payback period. 3) Cogeneration system LCC was 1.12, 1.07 and 1.06 times larger than district system with the size of apartment complex. According to the case of this study district heating system is more efficient than cogeneration system in terms of the reduction of LCC. 4) Gas Engine Co-generation System is more efficient than other systems because it can collect progressive part from electric charge progressive stage system. However, the efficiency is decreasing because of raising of fuel bills(LNG) and lowering of power rate for house use. Especially the engine is foreign-made so the cost of maintenance and repair is high and the technical expert is short. 5) District heating is also affected by fuel bills so we should improve energy efficiency through recovering of waste heat(incineration heat, etc.). Also, we should supply district cooling on the pattern of heat using of let the temperature high in winter and low in summer.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.10
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• pp.544-551
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• 2015

This study was conducted to determine the LCC of apartment complexes with district heating and a cogeneration system. For the purpose of analyzing LCC according to the size of the apartment complex, 500, 1,500, and 4,000-unit model apartments were selected. Analysis was performed on the design of the heating system and the life cycle cost including total construction cost, maintenance and operation cost for the duration of the project period (15 years). According to the calculated results, 1) The initial cost of the cogeneration system for 500, 1,500, and 4,000-unit apartments is higher than that of the district heating system by 20%, 13%, and 12%, respectively. 2) In the case of the cogeneration system, the payback period by electric generation was found to be 5.21, 4.92 and 4.47 years, and saving cost was calculated to be 29 billion won, 94 billion won and 262 billion won after the payback period for 500, 1,500, and 4,000-unit apartments, respectively. 3) The LCC values of the cogeneration system were 1.12, 1.07 and 1.06 times larger than those of the district system according to the size of the apartment complex. In this study, the district heating system was found to be more efficient than the cogeneration system in terms of LCC reduction. 4) District heating is affected by fuel bills, so energy efficiency should be improved through recovering waste heat (incineration heat, etc.). Also, district cooling should be provided according to heat use to keep the temperature high in winter and low in summer.

• Korean Journal of Construction Engineering and Management
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• v.9 no.4
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• pp.57-65
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• 2008

As the society is being developed, the desire about life quality is also growing. Even though the process of waterproof work has very close relation with these life quality, we always focus on management after problem than the precaution of problem. So this process has the highest rate of mengel. We develop LCC analysis model considering the precaution and try to show the necessity of the precaution by comparing and analyzing every alternative proposal during LCC. By studying of the previous work and the result of questionnaire, we deduce the problem of waterproof work in construction area. By discussion with an expert in this process and research, we make solutions about precaution and set the cost items in every alternative proposal about these solutions. We understand the effect of each elements through sensitive analysis of the cost items, and find the economically best suited solution.

• Tribology and Lubricants
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• v.39 no.3
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• pp.87-93
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• 2023

Nanofluids are dispersions of particles smaller than 100 nm (nanoparticles) in base fluids. They exhibit high thermal conductivity and are mainly applied in cooling applications. Nanolubricants use nanoparticles in base oils as lubricant additives, and have recently started gathering increased attention owing to their potential to improve the tribological and thermal performances of various machinery. Nanolubricants reduce friction and wear, mainly by the action of nanoparticles; however, only a few studies have considered the rheological properties of lubricants. In this study, we adopt a parallel slider bearing model that does not generate geometrical wedge effects, and conduct thermohydrodynamic (THD) analyses to evaluate the effect of higher thermal conductivity and viscosity, which are the main rheological properties of nanolubricants, on the lubrication performances. We use a commercial computational fluid dynamics code, FLUENT, to numerically analyze the continuity, Navier-Stokes, energy equations with temperature-viscosity-density relations, and thermal conductivity and viscosity models of the nanolubricant. The results show the temperature and pressure distributions, load-carrying capacity (LCC), and friction force for three film-temperature boundary conditions (FTBCs). The effects of the higher thermal conductivity and viscosity of the nanolubricant on the LCC and friction force differ significantly, according to the FTBC. The thermal conductivity increases with temperature, improving the cooling performance, reducing LCC, and slightly increasing the friction. The increase in viscosity increases both the LCC and friction. The analysis method in this study can be applied to develop nanolubricants that can improve the tribological and cooling performances of various equipment; however, additional research is required on this topic.

• Korean Journal of Radiology
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• v.21 no.6
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• pp.684-694
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• 2020

Objective: The purpose was to review the diagnostic performance of the length of tumor capsular contact (LCC) on magnetic resonance imaging (MRI) for detecting prostate cancer extraprostatic extension (EPE). Materials and Methods: PubMed and EMBASE databases were searched up to March 24, 2019. We included diagnostic accuracy studies that evaluated LCC on MRI for EPE detection using radical prostatectomy specimen histopathology as the reference standard. Quality of studies was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. Sensitivity and specificity were pooled and graphically presented using hierarchical summary receiver operating characteristic (HSROC) plots. Meta-regression and subgroup analyses were conducted to explore heterogeneity. Results: Thirteen articles with 2136 patients were included. Study quality was generally good. Summary sensitivity and specificity were 0.79 (95% confidence interval [CI] 0.73-0.83) and 0.67 (95% CI 0.60-0.74), respectively. Area under the HSROC was 0.81 (95% CI 0.77-0.84). Substantial heterogeneity was present among the included studies according to Cochran's Q-test (p < 0.01) and Higgins I² (62% and 86% for sensitivity and specificity, respectively). In terms of heterogeneity, measurement method (curvilinear vs. linear), prevalence of Gleason score ≥ 7, MRI readers' experience, and endorectal coils were significant factors (p ≤ 0.01), whereas method to determine the LCC threshold, cutoff value, magnet strength, and publication year were not (p = 0.14-0.93). Diagnostic test accuracy estimates were comparable across all assessed MRI sequences. Conclusion: Greater LCC on MRI is associated with a higher probability of prostate cancer EPE. Due to heterogeneity among the studies, further investigation is needed to establish the optimal cutoff value for each clinical setting.

• Journal of the Korea Institute of Building Construction
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• v.5 no.4 s.18
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• pp.91-98
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• 2005

This paper illustrates a comparative analysis on the economic efficiency of remodeling method that is one of major factors in totting more desirable standards and proposes to utilize LCC calculation techniques in generating a required budget for more effective quantity-based analysis that is both objective and effect. Rather than comparing only the initial lost of two different methods, it seems through to compare their entire life cycle cost that includes any repair and reconstruction/ remodeling expenses, thus generate overall quantitative analysis in objective perspective

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.56-57
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• 2014

As school facilities have been expanding quantity better than quality, efficient school facility management has been focused on from 2001 in domestic. Due to obsolescence of school facility, objective management and maintenance cost of school facility is very important. However LCC(Life cycle cost) analyst, owner, engineer, contractor and facility manager have a difficulty to obtain and facilitate the basic analyzed data required to analyze LCC of school facility and establish maintenance plan. Therefore this research presents muti-dimensional analysis method through data warehouse technique for supplying maintenance cost information of school facility that can trace and accumulate the scattered LCCing data in the perspective of life cycle of school facility.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.1299-1305
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• 2006

In this paper, the objective is an evaluation of economics using Life Cycle Cost(LCC) analysis for the ballasted track and the concrete track. However, since the absence of reliable data on maintenance activities, the degree of a reliability about the results of the LCC analysis is insufficient yet. In order to remedy the problems, we surveyed a professional research group for an approximate estimation which can be represented a degree of maintenance through a application of examples. Hereby we found that it is possible to expect the retrenchment of cost using preventive maintenance management. Moreover we proposed appropriate and economical restrictions between track structures.