• Industrial Engineering and Management Systems
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• v.14 no.1
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• pp.44-57
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• 2015

In recent years, for the purpose of solving the problem regarding environment protection and resource saving, certain measures and policies have been promoted to establish a reverse supply chains (RSCs) with material flows from collection of used products to reuse the recycled parts in production of products. It is necessary to analyze behaviors of RSC members to determine the optimal operation. This paper discusses a RSC with a retailer and a manufacturer and verifies the behavior strategies of RSC members which may change over time in response to changes parameters related to the recycling promotion activity in RSC. A retailer takes two behaviors: cooperation/non-cooperation in recycling promotion activity. A manufacturer takes two behaviors: monitoring/non-monitoring of behaviors of the retailer. Evolutionary game theory combining the evolutionary theory of Darwin with game theory is adopted to clarify analytically evolutionary outcomes driven by a change in each behavior of RSC members over time. The evolutionary stable strategies (ESSs) for RSC members' behaviors are derived by using the replicator dynamics. The analysis numerically demonstrates how parameters of the recycling promotion activity: (i) sale promotion cost, (ii) monitoring cost, (iii) compensation and (iv) penalty cost affect the judgment of ESSs of behaviors of RSC members.

• Journal of Korean Academy of Nursing
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• v.40 no.3
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• pp.349-358
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• 2010

Purpose: The purpose of this study was to estimate nursing costs and to establish appropriate nursing fees for long-term care services for community elders. Methods: Seven nurses participated in data collection related to visiting time by nurses for 1,100 elders. Data on material costs and management costs were collected from 5 visiting nursing agencies. The nursing costs were classified into 3 groups based on the nurse's visit time under the current reimbursement system of long-term care insurance. Results: The average nursing cost per minute was 246 won. The material costs were 3,214 won, management costs, 10,707 won, transportation costs, 7,605 won, and capital costs, 5,635 won per visit. As a result, the average cost of nursing services per visit by classification of nursing time were 41,036 won (care time <30 min), 46,005 won (care time 30-59 min), and 57,321 won (care time over 60 min). Conclusion: The results of the study indicate that the fees for nurse visits currently being charged for long-term care insurance should be increased. Also these results will contribute to baseline data for establishing appropriate nursing fees for long-term care services to maintain quality nursing and management in visiting nursing agencies.

• Particle and aerosol research
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• v.18 no.4
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• pp.109-127
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• 2022

Recently, low-cost particulate matter (PM) sensors have been widely used in monitoring mass concentration. Maintaining the accuracy of the sensors is important and requires rigorous performance evaluation and calibration. In this study, two commercial low-cost PM sensors(LCS), Plantower PMS3003 and Plantower PMS7003, were evaluated in the laboratory and field with a reference-grade PM monitor (GRIMM 11-D). Laboratory evaluation was conducted with single/mixed particles of PSL (Poly Styrene Latex) in an acrylic chamber at 20℃ and relative humidity of 20%. Field evaluation was conducted inside a building of Yonsei University (Shinchon) from February 12 to March 31, 2022. In both evaluations, LCS measured values became different from reference measured values when the relative humidity was high or the outdoor air PM10/PM2.5 ratio was high. Based on the field evaluation, the LCS measured values were corrected through four different regression analysis models. As a result, the multivariate polynomial regression analysis model showed highest matching with the reference PM monitor (PM2.5 >0.9, PM10 >0.85). In this model, the PM10/PM2.5 ratio and relative humidity were chosen as independent variables.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.202-203
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• 2020

Unlike price calculation by cost accounting, which categorizes costs into material costs, labor costs, and miscellaneous expenses to determine the construction budget price, construction cost calculation based on Construction Standard Unit Prices utilizes unit prices extracted from market prices of items from projects already completed to estimate costs of similar construction projects. Although unit price information is collected through construction site surveys to revise these construction standard unit prices every year, but due to the limitations of the site survey method, it is difficult to quickly implement the rapid changes in the construction methods and market prices. As such, an important issue that arose was the identification of work items whose prices need urgent revision. This study conducted research on factors that need to be considered when developing online survey system for monitoring construction site market prices. This study is expected to enhance convenience for users, and provide an efficient data collection and management system for administrators.

• Journal of KIISE:Databases
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• v.33 no.2
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• pp.188-200
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• 2006

Once a continuous query, which is commonly used in sensor networks, is issued, the query is executed many times with a certain interval and the results of those query executions are collected to the base station. Since this comes many communication messages continuously, it is important to reduce communication cost for collecting data to the base station. In sensor networks, in-network processing reduces the number of message transmissions by partially aggregating results of an aggregate query in intermediate nodes, or merging the results in one message, resulting in reduction of communication cost. In this paper, we propose a routing tree for sensor nodes that qualify the given query predicate, called the query specific routing tree(QSRT). The idea of the QSRT is to maximize in-network processing opportunity. A QSRT is created seperately for each query during dissemination of the query. It is constructed in such a way that during the collection of query results partial aggregation and packet merging of intermediate results can be fully utilized. Our experimental results show that our proposed method can reduce message transmissions more than 18% compared to the existing one.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.6
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• pp.505-513
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• 2018

Main engine failures in ship operations can lead to a major damage in terms of the vessel itself and the financial cost. In this respect, monitoring of a vessel's main engine condition is crucial in ensuring the vessel's performance and reducing the maintenance cost. The collection of a huge amount of vessel operational data in the maritime industry has never been easier with the advent of advanced data collection technologies. Real-time monitoring of the condition of a vessel's main engine has a potential to create significant value in maritime industry. This study presents a case study on the establishment of upper control limit to detect vessel's main engine failures using multivariate control chart. The case study uses sample data of an ocean-going vessel operated by a major marine services company in Korea, collected in the period of 2016.05-2016.07. This study first reviews various main engine-related variables that are considered to affect the condition of the main engine, and then attempts to detect abnormalities and their patterns via multivariate control charts. This study is expected to help to enhance the vessel's availability and provide a basis for a condition-based maintenance that can support proactive management of vessel's main engine in the future.

• Journal of Korean Society of Forest Science
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• v.106 no.1
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• pp.54-62
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• 2017

This study was carried to develop the chip-harvester and to analysis the operation productivity and cost for effective collection and forwarding of forest biomass. Main target specification of chip-harvester is speed of 8km/h, maximum climbing capacity of $30^{\circ}$ and maximum load capability of 2000 kg. Body structure is articulate type to reduce turning radius. Driving equipment is six-wheel drive, and a rear wheel is tandem bogie type to increase grip force. As a result of the driving test about developed chip-harvester, driving speed was 6.9 km/hr and 8.1 km/hr in ${\pm}10%$ slope with loaded and 7.3 km/hr and 7.9 km/hr in ${\pm}10%$ slope without load. As a result of the operation productivity and cost, operation productivity of grinding and forwarding was approximately $10m^3$ per day, and operation cost was 393,126 won per day.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.3
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• pp.375-383
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• 2024

The size of the construction industry is increasing, and its impact on the entire national industry is also significant. However, construction cost increases, construction period delays, safety accidents, and quality problems occur during the construction process. This paper analyzed the construction cost, construction period, and change order performance for civil infrastructures for which post evaluation was performed. The analysis was conducted by dividing civil engineering facilities by type, construction nature, construction cost, contract nature, and delivery method. Planned and actual construction cost and period were compared during the planning, design, and construction process of civil engineering facilities. There is a possibility of input errors in project performance data, this paper proposes to the post-evaluation center should perform post-evaluation. Also, post-evaluation implementation guidelines for change orders should be revised. Additionally, further analysis of each facility was proposed through continuous data collection.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.2
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• pp.151-159
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• 2021

Cost information in the Korean construction industry is mainly controlled by the government agencies. However, there have been wild-spread speculations among participants on the adequacy of these unit prices and difference with the actual market condition. Korean public-led unit prices are developed using mainly a top-down approach by a few designated public institutions. Due to the rapid fluctuations in market prices and high-volume of information, it is impossible for a few public institutions to properly consider market conditions. However, there are almost none private cost reference while many are available in other countries to supplement the public cost references. Needs for private cost references have recognized, and this study can be seen as a pilot study to support them. This study attempts to identify the problem areas of Korean cost references and to provide guidance by benchmarking other countries. This study has confirmed the need of developing market-driven cost references by employing a bottom-up approach in which a large number of various construction participants are fostered to provide their own cost information and share with others. It is envisioned that this study provides foundations for further study on the development on-line construction market platform based on abundant and appropriate cost information.

• Journal of the Korean Dietetic Association
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• v.2 no.2
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• pp.158-167
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• 1996

Food waste left by patients in hospitals is an important indicator of the nutritional adequacy of the patients' diet and of their satisfaction with food. Food wasted by patients or staff in hospitals is one of the most serious problem in hospital foodservice systems. The purpose of this study was to evaluate the disposal practices of food waste in hospital foodservices for providing basic information for an efficient solid waste management. This approach was achieved using a variety of qualitative and quantitative information including general food waste practices and measurement of food waste left by patients and staff in 20 hospital foodservices. The average food wasted by patients and staff per day was 402.20kg and 206.98kg respectively, being total food waste of 578.08kg per day. The mean plate waste of a staff was 115.95g, which was much lower than that of a patient (221.03g). As means of food waste treatment, most hospitals(60%) are using animal feed, followed by means of collection by contracters(15%) and disposal of waste collection after condensing. An average monthly cost for disposing food waste was 915,000 won and average 138.58 minutes were spent to dispose food waste in hospital foodservices.