• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.5
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• pp.477-484
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• 2020

Reservoir operation affects the sustainability of a water supply. However, the increase in the temporal and spatial variability of rainfall, attributed to climate change, has led to severe droughts and increased difficulty in maintaining a sustainable discharge at certain locations in a reservoir system operation. In this study, water yield was evaluated using reservoir simulation with varied water supply. Three reservoir system models were simulated for nine reservoirs in the Han River basin. The time-based reliability, volumetric reliability, and resiliency were used to evaluate the results. Each case was simulated by applying firm supply, deficit supply, and deficit supply with historical power release of the Hwacheon Reservoir. As a result of the simulation, all indexes were increased when the deficit supply was applied. In particular, the time-based reliability increased by more than 30%, and the supply reliability increased by about 4%. The result showed that the water supply of the entire water system could be increased when all reservoirs in the water system were operated to supply water and maintain sustainable discharge at the same downstream point. The deficit supply was an efficient reservoir operation method for responding to climate change, especially increased rainfall variability.

• Journal of Aerospace System Engineering
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• v.7 no.3
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• pp.7-14
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• 2013

Hypersonic vehicles over Mach 5 need active cooling or thermal management systems to resolve excessive heating problems on their fuselage and engines. Endothermic fuels are widely used these days not only for the energy source but also for a heat sink. Therefore, fuel supply systems of hypersonic vehicles should be mainly composed of adiabatic fuel storage tank, cooling systems for the airframe and engine/nozzle, and fuel supply/injection systems in high pressure, high temperature, and high fuel flow rate conditions. This paper describes a conceptual design process of a hypersonic fuel supply system in order for designing a layout of the system, and identifying components and their specification requirements.

• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.3
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• pp.46-56
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• 2001

The present study concerns the numerical simulation of a supply airflow control in a variable air volume (VAY) system. A stratified thermal model (multi-zone model) is suggested to predict a local thermal response of an air-conditioned space. The effects of various thermal parameters such as the cooling system capacity, the thermal mass of an air-conditioned space, the time delay of thermal effect, and the building envelope heat transmission are investigated. Further, the influence of control parameters such as the supply air temperature, the PI control factor and the thermostat location on a VAV system is quantitatively delineated. The results obtained show that the previous homogeneous lumped thermal model (single zone model) may overestimate the time taken to the set point temperature. It is also found that there exist the appropriate ranges of the control parameters for the optimal airflow control of the VAV system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2150-2156
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• 2007

According as level of industry develops day after day, electricity load system of industry requires high level control, effectiveness and high efficiency. Among supply and control unit of suitable power supply in these load characteristic, inverter systems of constant current regulate is used widely control of lighting and electric heating system. But, problems that power factor deterioration and fast response of control, efficiency, harmonics and etc are still remain. Therefore, in this paper proposed an inverter systems with constant current regulation and power factor correction (PFC) circuit for lighting and beaconing of aerodromes. The effectiveness of the proposed system confirmed through experimental results of 10[kW] power supply system.

• Journal of applied mathematics & informatics
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• v.9 no.1
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• pp.349-357
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• 2002

In this paper, we analyze queueing behaviors and investigate the possibilities of reducing and controlling shortages and oversupplies in the bidirectional queueing system which forms a negative queue by demand and a positive queue by supply. Interarrival times of units in the bidirectional queueing system investigated are exponetially distributed. Instant pairing off implies that queue can be either positive or negative, but not both at the same time. The results include a proof that sum of queue lengths is minimized if rates of demand and supply in each system are equal and optimum solutions for rates of supply which minimize the sum of queue lengths when rates of demand and sum of rates of supply are given. In addition, the relationship between the ordinary queueing system and the bidirectional queueing system is investigated.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.216-218
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• 2017

The imbalance at the 3-phase side at the railway power supply substation has been a well-known issue. Due to the difference in status of loads at each phase at any given moment, it is difficult to maintain the balance in the 2-phase side of the transformer. Consequently, the 3-phase side also presents a certain level of imbalance as well. A co-phase power supply was proposed as a solution. The real application of such system is gradually expanding, proving the effectiveness of the system. In this paper, the application of the single phase D-Q rotating frame theory was applied to the control of the co-phase power supply system. In addition, the power stack of the system was composed of MMC valves, which offers superior operational characteristics. The effectiveness of the system was verified with a real-time simulation, and the results are presented.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.54
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• pp.189-209
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• 2012

This Work intends to study on some issues of business and law in relation to Contract for Turnkey Base System. The continuing advance of export system of the plant with the importance for efficient and effective management emphasizes the need for business and legal approach to uniform international model contract. ICC Model Contract for Turnkey Supply of Industrial Plant by ICC covers a particular category of turnkey contract, i.e. contracts for the supply of a plant or production line to be erected within facilities which already exist or which are constructed by the purchaser. Furthermore, the application of the ICC Model Contract for Turnkey Supply of Industrial Plant leaves much to be desired from a business and legal point of view. Therefore, there would appear to be room for compromise between the supplier and purchaser in respect to make a contact for Turnkey supply of industrial plant.

• Industrial Engineering and Management Systems
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• v.12 no.2
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• pp.103-111
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• 2013

This paper discusses how to manage supply chain disruption risks from natural disasters or other low-likelihood-high-impact risk drivers. After the catastrophic earthquake in Eastern Japan and the severe flood in Thailand, most companies have been attempting to re-establish the business continuity plan to prevent their supply chain from disruption. However, the challenges for managers and individual risks are often interrelated, and thus, actions that mitigate one risk can end up being no contribution as a whole. In this paper, we describe a framework for assessing how much impact individual mitigation strategies have on the entire supply chain protection against disruption, using network reliability. We propose three categories of risk-mitigation approaches: Stabilization, Absorption, and Duplication. We analyze the situation under which each of these strategies is the best suitable. With a clear understanding of relations between these mitigation strategies and the entire supply chain risks, managers can select effective risk-reduction approaches to their supply chain.

• Journal of Advanced Information Technology and Convergence
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• v.9 no.2
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• pp.75-87
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• 2019

This paper presents a fully digital controlled power supply unit for the wireless controlled dimmable LED lighting system. The proposed power supply designed using a fly-back converter, which is directly controlled by a microprocessor. Although the proposed circuit does not sense the AC input current and has not AC input voltage feed-forward, it can achieve a high power factor. The proposed power supply directly regulates the output power for LED loads using the PWM and PFM control of the fly-back converter without additional regulator. For a wireless remote control function, the Zigbee modem is equipped in the proposed power supply. A prototype set-up has been built and tested. Through the experiment with a prototype set-up, the usefulness of the proposed power supply is verified.

• Journal of the Korea Institute of Building Construction
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• v.9 no.5
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• pp.87-93
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• 2009

A construction supply chain needs an integrated information system, as the general contractor and subcontractors must communicate regularly with one another and share a substantial amount of information in their cooperative work. In the construction industry, supply chain management is necessary in the management of a system, including business process improvement, participant-oriented management, and the supply chain. This research proposed a supporting system and developed the prototype focusing on materials that play an important role in the supply chain. Construction projects are managed mainly through schedule management. As such, supply chain management should be linked with schedule management. The research implemented a prototype of the supporting system for construction supply chain management. The prototype was implemented in Microsoft Project using VBA, including a simulation tool based on @Risk for Project.