• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.13-19
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• 2019

After the Fukushima nuclear accident, a new power supply using a lithium polymer battery has been proposed the first time in the world as the safety of the emergency battery facility has been required. It is required to have the safety of the rack system in which the battery device is installed in order to apply the proposed technology to the field. Therefore, the purpose of this study is to evaluate the seismic performance of string and rack frame for lithium-polymer battery devices developed for the first time in the world to satisfy 72 hours capacity. (1) The natural frequency of the unit rack system was 9 Hz, and the natural frequency before and after the earthquake load did not change. This means that the connection between members is secured against the design earthquake load. (2) he vibration reduction effect by string design was about 20%. (3) As a result of the seismic performance test under OBE and SSE conditions, the rack frame system was confirmed to be safe. Therefore, the proposed rack system can be applied to the nuclear power plant because the rack system has been verified structural safety to the required seismic forces.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.1
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• pp.44-51
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• 2009

A bonded warehouse is the warehouse located in bonded area. It functions not only as a general warehouse but also as a place for managing the work related to import and export bonded goods. As a general warehouse, it uses the rack system to store the goods and the folk lift truck to move the unitized goods. The operation of the storing system closely related to the efficiency of space uses in a warehouse and vehicle working. Thus, vehicle performance measured in distance units in the ware-house could be used as one of the key performance measure in warehouse system. This paper focuses on the operation efficiency of the bonded warehouse which uses rack system for the storing and the folk lift truck for moving goods. The method of load allocation for balancing the rack uses and vehicle operation for maximizing efficiency are the specific concerns in this paper. The simulation study is conducted to find a policy for efficient vehicle operation based on balanced rack utilization, and the favorable result for the system operation would lead the usable proposal in vehicle operation.

• Structural Engineering and Mechanics
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• v.64 no.5
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• pp.671-681
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• 2017

This study investigates the structural performance of 3D steel pipe rack suspended scaffolding systems. For the purpose, a standard full scale 3D steel pipe rack suspended scaffolding system considering two frames, two plane trusses, purlins and wooden floor is constructed in the laboratory. A developed load transmission system was placed in these experimental systems to distribute single loads to the center of a specific area in a step-by-step manner using a load jack. After each load increment, the displacements are measured by means of linear variable differential transducers placed in several critical points of the system. The tests are repeated for five different system conditions to determine the structural performance. The means of system conditions is the numbers of the tie bars which are used to connect plane trusses under level. Finite elements models of the 3D steel pipe rack suspended scaffolding systems considering different systems conditions are constituted using SAP2000 software to support the experimental tests and to use the models in future studies. Each of models including load transmission platform is analyzed under a single loading and the displacements are obtained. In addition, to calibrate the numerical models some uncertain parameters such as elasticity modulus of wooden floor and connection rigidity of purlins to plane trusses are assessed experimentally. The results of this work demonstrate that when increasing numbers of tie bars the displacement values are decreased. Also the results obtained from developed numerical models have harmony with those of experimental. In addition, the scaffolding system with two tie bars at the beginning and at the end of the plane truss has the optimum structural performance compared the results obtained for other scaffolding system conditions.

• 제어로봇시스템학회:학술대회논문집
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• 1999.10a
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• pp.198-201
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• 1999

An automated storage and retrieval machinery for high rack warehouse systems is developed in order to stack the various kinds of productions. However, according to increase in the rack height, the long lead time should be taken. In stacker crane systems, the variations of the lifting height and the load generate the vibration of lifting machine, and it makes a Position control to be difficult Therefore, the reduction of vibration will be important factor for saving the lead time and the damage of Productions. This paper deals with a position control of stacker crane in automated high rack warehouse system by using a gain-scheduled control algorithm via a LMI method, where the variations of elastic coefficient of the stacker crane's post are considered.

• ETRI Journal
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• v.33 no.4
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• pp.648-651
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• 2011

This letter presents a highly efficient rack-level DC power architecture combined with a node-level DC uninterruptible power supply (UPS). The proposed system can provide almost the equivalent power efficiency of a high-voltage DC data center without any change in the existing power infrastructure. The node-level DC UPS combined with a power distribution board provides high power efficiency as well as lower UPS installation costs. Implemented on a rack, the entire power system can be monitored through a network.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.5
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• pp.108-115
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• 2008

Recently, a demand of the digital dimmer system is increasing steadily, but domestic research is not sufficient to the expectation. In this paper, a digital dimmer equipment is developed and resented to compose a system. Digital dimmer system compose console and dimmer rack. Console controls of user interface and a total system, and dimmer rack controls brightness of lighting equipment by a way of phase angle control with each illumination level to get from console.

• Fire Science and Engineering
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• v.30 no.6
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• pp.84-91
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• 2016

In case of fire, vertically and intensively loaded rack warehouses are faced with a severe status due to the rapid increase in fires. In this regard, there have been trials to prevent fires from spreading by applying fire extinguishing systems, such as ESFR and In-Rack Sprinklers, vertical and horizontal barriers, etc.; however, it is difficult to calculate and design proper fire extinguishing systems caused by various composition conditions, such as the size and loading density of the rack, types of loading commodities, etc. Therefore, in this study, a standard rack was manufactured, incorporating a rack warehouse in Korea by site investigations, surveys, etc. In addition, a full scale fire test was executed to check the fire characteristics depending on the conditions of the ignition points. As a result, the extracted fire spread speed is expected to be utilized as a reference for performance comparisons of the fire extinguishing systems to be developed and applied in the future.

• Journal of Korean Institute of Industrial Engineers
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• v.30 no.4
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• pp.306-316
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• 2004

We present a closed form approximate analytical model to estimate the expected waiting times for the storage and retrieval requests of an automated storage/retrieval (AS/R) system, assuming that the storage/retrieval (S/R) machine idles either at the rack or at the input/output point. The expected waiting times (and the associated mean queue lengths) can play an important role to decide whether the performance of a stable AS/R system is actually acceptable, to determine buffer size (or length) of the input conveyor, and to compute the number of the rack openings which is required to hold the loads which are requested by processing machines but waiting in the rack to be retrieved by the SIR machine. This model can be effectively used in the early design stage of an AS/R system.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.24 no.66
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• pp.91-98
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• 2001

In this study, a heuristic for surface mounters is developed to find an efficient sequence on PCB and rack assignment by component grouping. As setting up 4 reels in a group, the distance of rack moving can be minimized. And then, a generalized model for N reels in a group is developed. It is found that the performance of this heuristic is better than other heuristics found in the literature. Throughout the simulation study, the suggested heuristic is performed about 8.2 ∼ 12% better than other heuristics.

• Fire Science and Engineering
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• v.33 no.5
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• pp.55-60
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• 2019

The occurrence of fire in rack-type warehouses may either lead to the warehouses getting entirely burned up or collapsing. This can be attrubuted to the high height of rack-type warehouses, in which combustibles are generally vertically stacked. These characteristics make it difficult to detect a fire early; because detectors are installed on the ceiling, these fires cannot be extinguished at an early stage. In this study, the flow of heat and smoke generated by a fire in a rack-type warehouse was analyzed using a fire dynamic simulator. Through this analysis, the optimal installation conditions of fire detectors for the early detection of fire in rack-type warehouses were confirmed. The analysis results confirmed that complex detection of heat and smoke is required for the early detection of fire in rack type warehouses. Furthermore, it was found that fixed temperature detectors are not suitable for these warehouses, resulting in the need to install heat-smoke hybrid detectors at every three rack levels.