• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.1
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• pp.39-49
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• 2018

In the satellite operation phase, a ground station should continuously monitor the status of the satellite and sends out a tasking order, and a satellite should transmit data acquired in the space to the Earth. Therefore, the communication between the satellites and the ground stations is essential. However, a satellite and a ground station located in a specific region on Earth can be connected for a limited time because the satellite is continuously orbiting the Earth, and the communication between satellites and ground stations is only possible on a one-to-one basis. That is, one satellite can not communicate with plural ground stations, and one ground station can communicate with plural satellites concurrently. For such reasons, the efficiency of the communication schedule directly affects the utilization of the satellites. Thus, in this research, considering aforementioned unique situations of spacial communication, the mixed integer programming (MIP) model for the optimal communication planning between multiple satellites and multiple ground stations (MS-MG) is proposed. Furthermore, some numerical experiments are performed to verify and validate the mathematical model. The practical example for them is constructed based on the information of existing satellites and ground stations. The communicable time slots between them were obtained by STK (System Tool Kit), which is a well known professional software for space flight simulation. In the MIP model for the MS-MG problems, the objective function is also considered the minimization of communication cost, and ILOG CPLEX software searches the optimal schedule. Furthermore, it is confirmed that this study can be applied to the location selection of the ground stations.

• Journal of Society of Preventive Korean Medicine
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• v.16 no.2
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• pp.41-52
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• 2012

Objectives : This study aimed to analyze the trend of financial balance of Korean medicine clinics during 20 years, and to provide basic information for adjusting the fee schedule of Korean medicine procedures in national health insurance(NHI). Methods : We collected 6 financial analysis reports for Korean medicine clinics from the Association of Korean Oriental Medicine(AKOM). The data on incomes, costs and EBIT(earning before interests and taxes) of subject clinics were abstracted, and their long-term trends were evaluated. Results : The proportion of insurance income in total income increased from 23% to 56% during 20 years. Among 5 treatment groups, 'non-insurance medication' took up 65~67% of total incomes in 1997, but its proportion decreased to 42.4% in 2007. 'medical procedure, physical therapy and others' increased from 12.4% in 1987 to 29.2% in 2007. The labor cost was major part of total cost and its proportion maintained from 52% to 54%. Cost of 'non-insurance medication' was on the decline from 41% in 1996 to 31.6% in 2007. EBIT were -17.4 million won in 1996, and 18.4 million won in 2007. Conclusions : Financial balance of Korean medicine clinics improved until early 2000, but it became worse in 2007. Though deficits from NHI procedures has been covered up by profit from 'non-insurance medication', health insurance became a major source of income during last two decades.

• Korean Journal of Construction Engineering and Management
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• v.8 no.2
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• pp.155-163
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• 2007

Multiple parties-owners, engineering and construction contractors, and suppliers involve the delivery process of capital facility projects in the construction industry, and each party obtains or provides their workforce, material, equipment, or service tied into specific contracts. Considering that construction projects are based on the contracted relationship between the parties and that contract types are one of the significant factors determining project success. it is critical for project stakeholder to select appropriate contract types for successful deliveries of projects. With these considerations, this paper assesses impacts of different contract types on project cost, schedule, safety, change, or rework. Analyzing data from real construction projects, the differences in project performance between two contract types, Cost Reimbursable and Lump Sum are measured and statistically tested to investigate if the differences are significant. For this analysis, performance metrics developed by Benchmarking and Metrics program, the Construction Industry Institute are used.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.05a
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• pp.318-320
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• 2018

When a ship sails on sea, it may be influenced by the environmental disturbance such as wind, wave, sea surface temperature, etc. These affect on the ship's speed, fuel consumption, safety and operating performance. It is necessary to find the optimal weather route of a ship to avoid adverse weather conditions which can put the crews in serious danger or cause structural damage to the vessel, machinery, and equipment. This study introduced how to apply A* algorithm based on sea trial test data for determining the optimal ship routes. The path cost function was modelled as a function of minimum arrival time or minimum energy depending on the time of various environment conditions. The specially modelled path-cost function and the safety constraints were applied to the A* algorithm in order to find the optimal path of the ship. The comparison of ship performances estimated by real sea trial's path and estimated optimal route during the voyage of the ship was investigated. The result of this study can be used to create a schedule to ensure safe operation of the ship with short passage time or minimum energy. In addition, the result of this study can be integrated into an on-board decision supporting expert system and displayed in Electronic Chart Display and Information System (ECDIS) to provide all the useful information to ship master.

• Korean Journal of Construction Engineering and Management
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• v.9 no.3
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• pp.136-145
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• 2008

Occasionally an owner of public construction work pays financial costs in addition to progress payments. However, the overall scale of financial costs are not known. This research examines, based on a case study, the financial cost incurred in public construction works and the following issues: the overall scale of financial costs, the impact on financial costs on the owner, and the impact of timing on the overall sum of the financial costs. Annually, more than 2.3 trillion KRW are paid as progress payments for public construction work; yet, there is no research data showing the scale of financial costs thus incurred. The purpose of this research is to illustrate the scale of financial costs incurred due to progress payments for public construction works, and to suggest alternatives that would improve relevant regulations.

• The Journal of Society for e-Business Studies
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• v.24 no.3
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• pp.99-110
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• 2019

As the 4th industrial revolution progressing, manufacturers are trying to apply intelligent information technologies such as IoT(internet of things) and machine learning. In the semiconductor/LCD/tire manufacturing process, schedule plan that minimizes setup change and due date violation is very important in order to ensure efficient production. Therefore, in this paper, we suggest the deep learning based scheduling generation model minimizes setup change and due date violation in parallel machines. The proposed model learns patterns of minimizing setup change and due date violation depending on considered order using the amount of historical data. Therefore, the experiment results using three dataset depending on levels of the order list, the proposed model outperforms compared to priority rules.

• Journal of Korean Society for Quality Management
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• v.50 no.1
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• pp.153-167
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• 2022

Purpose: The purpose of this study is to guide the operation managers who plan daily production of large mass-processing facility that services multi-customers with multi-product, small-batch item characteristics by providing the practical best production quantity and the inventory allowed to build. Methods: Close observation of a subcontract paint-shop operator captured the daily decision process which was reflected in the subcontractor-unique mathematical model and the system dynamics simulation model. Multiple simulations were run to find the practical best production quantity and the maximum allowable stock level of inventory that did not undermine the profit from practical best daily production. Actual data and a few constant values were obtained from the firm under study. Results: While the inventory holding cost for the customer-owned material harms the total profit of the subcontractor, the running cost of the processing facility hinders production in small batches. This balances the maximum possible productions and results in practical best daily production which can be found through simulation runs with actual data. The maximum level of stocked inventory is deduced from the practical best daily production. Conclusion: To build a large volume that enables economy-of-scale production, operators should deal with multi-product small-batch items from multiple customers. When the planned schedule of the time and amount of material in-flow tend not to be reliable, operators can find it practical to execute level production across the planning horizon instead of adjusting to day-to-day in-flow fluctuations.

• Korea Journal of Hospital Management
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• v.2 no.1
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• pp.1-21
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• 1997

In order to analyze the shifts in the volume and profits of Computed Tomography(CT) and Magnetic Resonance Imaging(MRI) utilization for a year before and after the implementation of insurance coverage for CT, this study has been undertaken examining CT and MRI cost data from 'Y' University Hospital situated in Seoul, Korea. Following are the results of this study: 1. The medical insurance payment for CT, implemented on January 1, 1996, increased CT utilization from January 1996 to April 1996 due to low insurance premiums: however, from May 1996 the number of CT cases significantly decreased as a result of strengthened medical cost reviews and the new 'Detailed standards for approval of CT' announced near the end of April 1996 by the insurer. 2. Since the implementation of insurance coverage for CT, CT fee reduction rates for reimbursements by the insurer to the hospital were 50% and 40% for January and February, respectively, and 31% and 15% for March and April. A significant point in the lowering of the reduction rate was reached in May at 11%; furthermore, since June the reduction rate fell below the average reduction rate for reimbursements for all procedures. If the 'Detailed standards for approval of CT' had been announced before the implementation of insurance coverage for CT, CT utilization would not have been so high due to the need to meet those 'standards'. In addition, loss of hospital profits resulting from the reduction for reimbursements would not have occurred. 3. The shifts in MRI utilization showed that there was no particular change with the beginning of insurance coverage for CT, and the introduction of the 'Detailed standards for approval of CT' made MRI utilization increase because MRI is free of restrictions imposed by the insurer. 4. The relationship between CT utilization and MRI utilization showed that they were supplementary to each other before insurance coverage for CT, but that CT was substituted for MRI because of strengthened medical cost reviews after t~e beginning of insurance coverage for CT. 5. The shifts in volume by patient characteristics showed that the number of inappropriate case patients, according to the insurer's "Standards for approval", decreased more than the number of appropriate case patients after the introduction of insurance coverage for CT. Therefore, the health insurance fee schemes for CT have influenced patient care. 6. The shifts in profits from CT utilization showed a net profit decrease of 31.6%. In order to match the pre-coverage profit level, 5,471 more cases would need to be seen and productivity would need to be increased by 32.7%. This profit decrease resulted from a decrease of CT utilization and low reimbursements. With insurance coverage, net profits from CT were 24.4%, and a margin of safety ratio was 39.6%. Because of the net profits and margin of safety ratio, CT utilization fees for insured appropriate cases could not be considered inappropriate. 7. The shifts in profits from MRI utilization before and after the introduction of CT coverage showed that in order to match pre-CT coverage profit levels, 2,011 more cases would need to be seen and productivity would need to be increased by 9.2%. The reasons for needing to increase the number of cases and productivity result from cost burdens created by adding new MRI units. But with CT coverage already begun, MRI utilization increased. Combined with a minor increase in the MRI fee schedule, MRI utilization showed a net profit increase of 18.5%. Net profits of 62.8% and a 'margin of safety ratio' of 43.1% for MRI utilization showed that the hospital relied on this non-covered procedure for profits. 8. The shifts in profits from CT and MRI utilization showed the net profits from CT decreased by 2.33billion Won while the net profits from MRI increased by 815.7million Won. Overall, these two together showed a net profit decrease of 1.51billion Won. The shifts in utilization showed a functional substitutionary relationship, but the shifts in profits did not show a substitutionary relationship. From these results, We can conclude that if insurance is to be expanded to include previously uncovered procedures using expensive medical equipment, detailed standards should be prepared in advance. The decrease in profits from the shifts in coverage and changes in fees is a difficult burden that should be shared, not carried by the hospital alone. Also, a new or improved fee schedule system should include revised standards between items listed and the appropriateness of the fee schedule should constantly be ensured. This study focused on one university hospital in Seoul and is therefore limited in general applicability. But it is valuable for considering current issues and problems, such as the influence of CT coverage on hospital management. Future studies will hopefully expand the scope of the issues considered here.

• Korean Journal of Construction Engineering and Management
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• v.13 no.1
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• pp.118-128
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• 2012

As the bearing wall structure, which has been widely applied to domestic apartment buildings since the 1980s, cause many problems during remodeling of buildings, the government encourages constructors to adopt flat plate or rahmen structure through legal incentives. In line with such a trend, the green frame, an eco-friendly rahmen structure that has removed the shortcomings of previous structures, was developed to enhance structural safety, constructability, and eco-friendliness. The construction of green frame can reduce the labor cost and facilitate the composition of iron bars to reduce rebar loss through calculating the quality and establishing the bar bending schedule automatically on the precast concrete member data collected over the design phase. Therefore, the purpose of this study is to develop the algorithm to automate the calculation of iron bar volume for the green frame designed on composite precast concrete members. Automated algorithm to calculate concrete structural design information and design information. Practices through the application site should prove efficacy. The database established by the developed algorithm will automate the establishment of iron bar processing map and bar cutting list and the calculation of optimal composition and order volume to minimize the rebar loss. This will also reduce the expenses on management staff and overall construction cost through the minimization of rebar loss.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6D
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• pp.623-629
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• 2010

Recently, the Shield TBM (Tunnel Boring Machine) construction method is used gradually to increase at the Tunnel Constructin site. However the design and application of the Shield TBM were carried out without sufficient investigation of the ground conditions in the construction site. Due to insufficient understanding to the corresponding equipment is frequently occurring unexpected construction cost and extension of a construction period. The most suitable alternative construction method was determined by analyzing tunneling rate, duration, construction cost of shield machine and tunneling data of alternative method. The result of the case study is suggested as follows. First, the accurate soil exploration on the construction site should be preceded to prevent from tunneling stoppage and schedule delay. Second, the most suitable selection of the shield machine to the ground conditions of the construction site should be executed based on the investigation. Third, the best alternative method for boring of hard rock section is 'hard rock blasting after open cut and cover method'.