• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.2
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• pp.305-314
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• 2017

Most of the existing researches on systemwide optimization of generator maintenance scheduling do not consider the equivalent operating hours(EOHs) mainly due to the difficulties of calculating the EOHs of the CCGTs in the large scale system. In order to estimate the EOHs not only the operating hours but also the number of start-up/shutdown during the planning period should be estimated, which requires the mathematical model to incorporate the economic dispatch model and unit commitment model. The model is inherently modelled as a large scale mixed-integer nonlinear programming problem and the computation time increases exponentially and intractable as the system size grows. To make the problem tractable, this paper proposes an EOH calculation based on demand grouping by K-means clustering algorithm. Network congestion is also considered in order to improve the accuracy of EOH calculation. This proposed method is applied to the actual Korean electricity market and compared to other existing methods.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.5
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• pp.549-554
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• 2011

Recently, technical advances have been made in high efficiency gas turbine power plants. In domestic gas turbine facilities, the material properties of the blade and vane are degraded by the daily start-stop operations arising from the thermo mechanical cycle. We surveyed the time dependent degradation of the HP blade and vane to gather basic data for life assessment and damage analysis. The EOH(equivalent operating hours) of the blades were 23,686, 27,909, and 52,859 and the EOH of the vanes were 28,714 and 52,859, respectively. With increased operating hours, the shape of the primary ${\gamma}$' precipitate transformed from cubic to spherical, and its average size also increased. The leading edge area of the blades and the center of the vanes had the worst morphology, and this tendency agrees with the microhardness results. The thickness of the thermally grown oxide at the outer surface of the bond coat increased with increased operating hours.

• Plant Journal
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• v.9 no.4
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• pp.31-36
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• 2013

In order to extend a hot gas parts replacement cycle of a gas turbine, blade row 1 from low pressure turbine, which has a significant impact on the cycle, has been selected from stored set after one cycle use. Taking into account the status of the first stage moving blade in LP turbine operated more than 27,000 equivalent operating hours(EOH) and the replacement cycle in the same type of gas turbine, the replacement of the high temperature components installed on the GT, a study subject, can be extended from 24,000 to 27,000 EOH.

• Journal of the Korean Society for Library and Information Science
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• v.54 no.1
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• pp.115-143
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• 2020

This study conducted a survey on the current status and satisfaction of libraries participating in the opening hours support project in order to continue it to meet the purpose of improving information access and life welfare. To this end, a questionnaire and interview survey were conducted for those in charge of opening hours for each library, and the results are as follows. First, the opening hours support project is a project that needs a strategy that fits the characteristics of the region and the environment. Therefore, it is necessary to consider operating independently rather than relying on national support in the future through the preparation of regional-oriented operation plans. Second, it is necessary to establish a flexible operating model for opening hours that both employees and users can understand. Third, it is necessary to prepare an organizational operation plan that requires both duties and responsibilities along with the rights equivalent to existing regular employees. Fourth, in order for national public libraries in Korea to develop and implement a consistent policy for specific policies and projects, it is necessary to unify the separate public library operating system in the future. Fifth, it is necessary to prepare education and guidelines for the continuity and stable operation of the project, and to activate services other than labor costs, such as support for improving the space for the user's pleasant use.

• Journal of Korean Public Health Nursing
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• v.1 no.1
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• pp.45-61
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• 1987

This Study was an attempt to estimate the optimum numbers of Operating Room Nursing Manpower by measuring the amount of service hours required by the patients in Operating Room in relation to the service amount actually provided by the nurses. The major concern of this study was placed on the measurement of Nursing Service Requirements by using the Operating Room (O. R) Patient Acuity System recently developed by M. M. Hart to classify the O. R. patients into four groups according to the degree of the complexity of operative procedure and some other elements which increase nursing activities in respect of patient care; Acuity IV group is the one requires nursing services most, on the other hand Acuity I requires least. nu sing The objectives of this study were as follows; 1. To analyze functions of the nursing personnel in O. R. by time unit and to estimate the average time a nurse can activate for productive functions. 2. To measure the actual amount of nursing times provided by nurses to the surgical patients. 3. To develop a patient classification system in order to measure the amount of Nursing services required by the patients. 4. To calculate an appropriate number of nursing manpower to meet the needs of the patients. In order to conduct the research both selected nurses and patients in 'S' University Hospital were Studied by utilizing the O. R. Patient Acuity System as well as the Classification Chart developed by Association of Operating Room Nurses (A. O. R. N) as a means of classifying functions of O. R. nurses. That is; Functions of the 10 selected O. R. nurses observed during the period of June 30 to July 4, 1986, whereas the amount of nursing services required by or provided to the 974 patients who had received surgeries during the period of June 9 to July 4, 1986. The results of this study were as follows; 1) The actual working hours per a nurse averaged 6.7 hours a day. 2) Each nurse's daily routine schedule consists of $71.4\%$ for Technical Functions, $16.1\%$ for Nonprodective Functions, $6.6\%$ for Assessment and Evaluation, $3.9\%$ for Overseeing and Supervision and the rest $2.0\%$ for Patient Preparation respectively. 3) Preoperative waiting time per a patient was 24.1 minutes on the average; for the first case was 10.7 minutes, whereas for the following cases was 32.0 minutes. 4) Total Operation time for the 974 patients during the period of observation for this study amounted to 2759.6 hours, weekly hour was equivalent to 689.9 hours, Whereas daily operation time averaged 130 hours. Meanwhile the average operation time per patient was 2.8 hours ; for the case of Acuity IV was 5.6 hours, 5. 1 hours for the case of Acuity III, 2.3 hours for Acuity II and 1.1 hours for Acuity I. 5) According to the O. R. Patient Acuity System, $64.5\%$ of the whole patients belonged to Acuity II, $23.7\%$ to Acuity III, 11. $3\%$ to Acuity IV and $0.7\%$ to Acuity I respectively. 6) Required amount of nursing times based on the preoperative waiting time and operation time was 7167.8 person hours, which showed that $5.5\%$ of them needed for preoperative nursing care, whereas the rest $94.5\%$ for intraoperative nursing care. In terms of the O. R. Patient Acuity System, $49.7\%$ of total nursing service requirements was needed for Acuity II patients, $27.4\%$ for Acuity III patients, $17.2\%$ for Acuity IV patients and $0.2\%$ for Acuity I patients. 7) The rate of the nursing services provided against the required nursing times was about $81.4\%$ on the average; some departments, like those of Plastic Surgery, Otolaryngology and Ophthalmology whose patients mostly belonged to Acuity II recorded hegher provision rate than average, whereas other departments of Thoracic Surgery. Neurosurgery and Orthopedic Surgery whose patients belonged to Acuity III and Acuity IV as well as Acuity II recorded lower provision rate than average. 8) Subsequently, required numbers of nursing manpower was 10.7 nurses additionally. Based on the above findings the following recommendations will be made; 1) this study recommends, develops. and adopts an accurate and realistic O. R. Patient Acuity System which can help measure the nursing service requirements objectively to elicit the rationales of allocation of nursing personnels. 2) this study proposes storongly place nurses who take the role of preoperative nursing care exclusively for the waiting patients in O. R. and shortening their waiting time by close communication between the designated O. R. and the ward.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1909-1915
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• 2010

The material properties of gas turbine components change during the daily start/stop thermal cycle because of exposure to the hot combustion gas. Recently, single-crystal Ni-based superalloys have been used to manufacture many hot-gas components for gas turbines. However, the user needs to depend on the manufacturer for maintenance issues because of the lack of data required for predicting blade life and material degradation. In this study, we investigate the time-dependent degradation of first-stage blades at various operating facilities to collect the basic data for life assessment and damage analysis. The blade material is a single-crystal Ni-based superalloy, CMSX-4, and the EOH (equivalent operating hours) are 25,000 and 52,000, respectively. We prepared the test specimen directly from used blades and carried out mechanical tests and microstructural observations.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.2
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• pp.273-278
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• 2016

In order to evaluate the lifespan of high-temperature parts with thermal barrier coating in gas turbines used for power generation, this study was performed on an 80 MW-class gas turbine exceeding 24 k equivalent operating hours. Degradation characteristics were evaluated by analyzing the YSZ (Yttria Stabilized Zirconia) top coat, which serves as the thermal barrier coating layer, the NiCrAlY bond coat, and interface layers. Microstructural analysis of the top, middle, and bottom sections showed that Thermal Growth Oxide (TGO) growth, Cr precipitate growth within the bond coat layer, and formation of diffusion layer occur actively in high-temperature sections. These microstructural changes were consistent with damaged areas of the thermal barrier coating layer observed at the surface of the used blade. The distribution of Cr precipitates within the bond coat layer, in addition to the thickness of TGO, is regarded as a key indicator in the evaluation of degradation characteristics.

• Journal of environmental and Sanitary engineering
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• v.16 no.2
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• pp.63-70
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• 2001

This study was initiated to evaluate and resolve the potential problems caused as the MSWI(Municipal Solid Waste Incinerator) fly ash were stabilized and solidified into the cement. The physical and chemical properties of fly ashes (K and M) used in this study were fixed according to the operating conditions of the incineration plant. The compressible strength of the solidified matrix used in this study were measured at 7, 28, and 56 curing days, respectively, to evaluate the stability of the solidified matrix, which were further analyzed by XRD and SEM. The experimental results obtained in this study showed that the relatively long hours of curing periods were needed to solidify the fly ash. The solidified matrix containing K ash had the high and excellent compressible strength of $200{\;}kg/\textrm{cm}^2$, after 56 curing days, but was not good enough in appearance. The analytical data by SEM confirmed that the alkaline Na and K, which are highly dissolved in water, were included in the fly ash and evenly distributed into the exterior surface of the solidified matrix. Whereas, the solidified matrix containing M ash never showed such a compressible strength as shown in the K ash due to the severe fracture, even as early as 7 curing days. Based on its XRD analysis, it appeared that both $C_2S$ and $C_3S$ highly related to the compressible strength were not crystallyzed into the solidified matrix. However, the compressible strength of the solidified and cemented M ash was remarkably improved by 100 times, after the alkalinity was washed out, which indicated that it is equivalent to 30 to 40g per one kg of fly ash.

• Archives of Plastic Surgery
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• v.46 no.4
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• pp.336-343
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• 2019

Background Sternal rigid plate fixation (RPF) has been adopted in recent years in high-risk cases to reduce complications associated with steel wire cerclage, the traditional approach to sternal closure. While sternal RPF has been associated with lower complication rates than wire cerclage, it has its own complication profile that requires evaluation, necessitating a critical examination from a national perspective. This study will report the outcomes and associated risk factors of sternal RPF using a national database. Methods Patients undergoing sternal RPF from 2005 to 2016 in the American College of Surgeons-National Surgical Quality Improvement Program were identified. Demographics, perioperative information, and complication rates were reviewed. Logistic regression analysis was performed to identify risk factors for postoperative complications. Results There were 381 patient cases of RPF identified. The most common complications included bleeding (28.9%), mechanical ventilation >48 hours (16.5%), and reoperation/readmission (15.2%). Top risk factors for complications included dyspnea (odds ratio [OR], 2.672; P<0.001), nonelective procedure (OR, 2.164; P=0.010), congestive heart failure (OR, 2.152; P=0.048), open wound (OR, 1.977; P=0.024), and operating time (OR, 1.005; P<0.001). Conclusions Sternal RPF is associated with increased rates of three primary complications: blood loss requiring transfusion, ventilation >48 hours, and reoperation/readmission, each of which affected over 15% of the study population. Smokers remain at an increased risk for surgical site infection and sternal dehiscence despite RPF's purported benefit to minimize these outcomes. Complications of primary versus delayed sternal RPF are roughly equivalent, but individual patients may perform better with one versus the other based on identified risk factors.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.12
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• pp.1275-1280
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• 2015

A large-sized exciter that vibrates a two-ton component is required to simulate the field operating conditions of a counterweight of an excavator. However, it is difficult for a small-medium sized company to obtain a large exciter for the life test of a counterweight which is an equivalent counterbalancing weight that balances a load. Therefore, in this study, we developed life test equipment for evaluating the reliability of construction machinery weighing about two tons. It simulates the field operating conditions using rotational vibrators consisting of electric motors. A failure analysis of the counterweight was also performed for the major components. Field data acquired from various sites were applied to the life test design of the counterweight. Finally, a zero-failure qualification test based on the accelerated life test was designed, and there was no failure during the test, which guarantees a life of $B_5$ 10,000 hours.