• Computers and Concrete
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• 제21권5호
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• pp.531-538
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• 2018

The slag through sieve #4 replaced the natural fine aggregate in different proportions (0-50%) to make ready-mixed soil and slag (RMSAS). The fresh properties studied, and the concrete specimens were produced to test the hardened properties at different ages. Results showed that the workability of RMSAS decreases when the replacement increases. The unit weight increases with the replacement. The setting time extends when the replacement decreases and shortens when the replacement increases. The compressive strength, ultrasonic pulse velocity and hammer rebound value increase with the replacement. However, the high-replacement results decrease because of the expansion factor at late age. Resistivity is close and less than $20k{\Omega}-cm$. After the industrial of steelmaking by-products are processed properly, they can be used in civil engineering, not only as a substitute for natural resources and to reduce costs, but also to provide environmental protection.

• Journal of Chest Surgery
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• 제22권6호
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• pp.951-959
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• 1989

Between September, 1972 and September, 1989, total 359 patients were operated for acquired heart disease at Department of Thoracic and Cardiovascular Surgery, Hanyang University Hospital. A consecutive series of 293 prosthetic valve replacement was also performed during this period. The results were summarized as follows; 1. There were 141 men and 218 women, whose ages ranged from 6 to 64 years, [mean 35.5 years] 2. Out of 293 cases, mitral valve replacement was 182 cases, aortic valve replacement was 39 cases and double valve replacement was70 cases. 3. Early post-operative death was 30 cases [Mortality; 8.4 %] and late death was 9 cases in the survivors. 4. Re-operation was 30 cases and operative mortality was 10%. 5. Mean post-operative interval was 76 months. [Ranged from 216 months to 2 months] 6. Among re-operation cases, primary prosthetic valve failure was 16 cases and paravalvular leakage was 2 cases. 7. Since January 1988, 79 cases of prosthetic valve replacement were performed and then 1 case was expired. [Mortality; 1.2 %]

• 품질경영학회지
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• 제19권2호
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• pp.117-124
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• 1991

In this paper, it is assumed that a system is composed of an essential unit and a nonessential unit. During the running of the system, an essential unit is replaced at periodic replacement time T or at nth failure of essential unit whichever occurs first. Nonessential unit is replaced at its failure and at the replacement of essential unit. This paper derive optimal replacement period which minmises the total expected cost for replacement. The unimodality of totoal maintenance cost function is proved under the assumption that hazard rate of each component is continuous and monotone increasing failure rate(IFR). Based on this condition, it is shown that the optimal replacement period is finite and unique.

• Journal of Chest Surgery
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• 제24권10호
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• pp.967-972
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• 1991

Between Feb. 1982 and July 1990, 173 patients [male: 89, female: 84] Who underwent heart valve replacement for acquired valvular heart disease on the Department of Thoracic and Cardiovascular Surgery, School of Medicine, Pusan National University, were reviewed for return to work after heart valve replacement. The replaced valve were mitral [128, 74.0%], aortic[10, 5.8%], mitral & aortic[35, 20.2%]. Two tricuspid valve replacement were excluded. Several important factors influencing the return to work were age, the employment status before surgery, the number of replaced valve, the pre - op NYHA functional class and cardiac function [ejection fraction]. These factors were closely related to the optimal time of heart valve replacement. It can be concluded that the rate of return to work and the quality of life would be improved if valve replacement were performed at an earlier stage of valvular heart disease.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.191-197
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• 2009

As a case study on determining the replacement interval for the CMB contactor, we analyzed a field failure data during 59 months and through the simulation reliability is analyzed. As a result of analyzing the reliability we estimated parameters and analyzed distribution characteristics. Ultimately using the estimated results and applying the Age Replacement Policy considered the cost information, CMB contactor's replacement interval is determined. Through the comparison, analysis between the replacement interval and manufacturing company's, the necessity of replacement interval that is reflected in our operation circumstances is examined.

• 한국세라믹학회지
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• 제51권2호
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• pp.127-131
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• 2014

Precipitated calcium carbonate(PCC) inorganic fillers for plastic offera higher replacement ratio with improved mechanical properties than any other inorganic fillers. Due to its secure economic feasibility, its fields of application areexpanding. For optimized PCC grain size and polymer replacement ratio, it is good to maintain at least $0.035{\mu}m$ grains and keep double the grain size of distance between particles, depending on the molecular weight and volume replacement rate of the polymer. PCC has unique characteristics, ie, with smaller grain size, dispersibility decreases, and if grain size is not homogenous, polymer cracking occurs. The maximum replacement ratio of PCC is approximately 30%, but in the range of 10 - 15% it produces the highest mechanical strength. When mixed with a biodegradable plastic like starch, it also improves initial environmental degradability.

• 한국신뢰성학회지:신뢰성응용연구
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• 제1권1호
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• pp.35-46
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• 2001

Replacement policy of a degradation system is investigated by incorporating the loss function. Loss function is defined by the deviation of the value of quality characteristic from its target value, which determines the loss cost. Cost function is comprised of the inspection cost, replacement cost and loss cost. Two cost minimization problems are formulated : 1)determination of an optimal inspection period given the state for the replacement and 2)determination of an optimal state for replacement under fixed inspection period. Simulation analysis is performed to observe the variation of total cost with respect to the variation of the parameters of loss function and inspection cost, respectively As a result, parameters of loss function are seen to be the most sensitive to the total cost. On the contrary, inspection cost is observed to be insensitive. This study can be applied to the replacement policy of a degradation system which has to produce the quality critical product.

• 산업경영시스템학회지
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• 제10권16호
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• pp.75-80
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• 1987

This paper is deals with the preventive replacement for the equipment which fails only when the total amount of damage reaches a prespecified failure level. Most of replacement model use time as their decision variable, but it is not appropriate for the cases in which failures dependent on their cumulative damage levels. In this paper, a new type preventive replacement model is introduced in which an equipment is replaced before failure when the cumulative damage reaches a certain level or replaced on failure, whichever occures first. The optimal replacement damage levels which minimize total expected cost are obtained by the Dynamic programming Method when the number of use of the equipment is finite. A numerical example is also presented. The optimal preventive replacement policy when the equipment will be used for a finite time span is also discussed.

• Journal of Chest Surgery
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• 제33권2호
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• pp.160-166
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• 2000

Background: The purpose of this study is to evaluate and analyze the surgical results in patients undergoing operations for multiple for multiple valvular heart diseases. Material and method: From April 1982 to June 1997 multiple valve replacement was performed in 150 patients mitral and aortic valve replacement were done in 135 patients mitral and tricuspid valve replacements in 10 patients triple replacements in 4 patients and aortic and tricuspid valve replacement in 1 patient. Of the valves implanted 157 were St. Jude 104 Duromedics 20 Carpenter-Edwards 6 Bjork-Shiley 6 Ionescu-Shiley and 2 Medtronics. Result: The hospital mortality rate was 10.7% (16/150) and the late mortality rate was 7.2% (8/134) The mortality rate was high in early operative period but decreased with time. The causes of death were low cardiac output in 9 sudden death in 3 congestive heart failure in 3 bleeding in 2 cerebral thrombosis in 1 leukemia in 1 multiorgan failure in 1 and so on . The actuarial survival rate excluding operative death was 83.1% at 15 years. Conclusion: With a follow-up now extending to 15 years the multiple valve replacement continues to be reliable procedure with relatively low mortality and morbidity.

• 국제학술발표논문집
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• The 4th International Conference on Construction Engineering and Project Management Organized by the University of New South Wales
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• pp.376-381
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• 2011

In Korea Water Resources Corporation (K-Water) has seen four problems rising in four aspects of property management of approximately 1,300 buildings scattered through put to country. To solve these, ground data for repair and replacement works to be conducted for prevention will be prepared and building maintenance system (hereinafter referred to as PBMS) intended to record related repair and replacement work histories and calculate LCC of the related these items will be developed. PBMS, a web-based system, will be developed for users' convenience and data monitoring in real time. To sum up, PBMS are expected to maximize efficiency in four aspects including the establishment of repair and replacement work plans for prevention, history management, DB for predicting future work to be occurred and enable the determination of priorities by being developing into facility condition assessment systems through the results of analysis of repair and replacement histories and LCC.