• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.407-407
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• 2002

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1199-1204
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• 2003

The 3D simulations of the shielding concrete and the Rotary Specimen Rack(RSR) in the Korea Research Reactor-1&2(KRR-1&2) were carried out in present work. Four main dismantling processes, which are the removal of the RSR, reactor core region, beam tube, and thermal column and activated concrete, were selected for the graphic simulation by the consideration of the activation, worker training, work difficulty and so on. On the basis of these, we constructed their 3D CAD models and then drawn and reviewed their dismantling processes. In this study, the 3D simulation results of the shielding concrete and the RSR among main components are also presented and discussed.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.5 no.1
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• pp.23-28
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• 1972

The following results were obtained from the experiment on the oyster spatfall, Crassostrea gigas by means of the rack method in YonghoBay, on the southern coast of Korea, from June to August in 1962 and 1963. 1. The Outside of shells as a collector showed better result than inside in numbers of attached oyster spats. 2. The horizontal type of the rack was more efficient for spatfall than the typical type of the rack. 3. The mode variance, in shell height, were shown as 21-25mm and 26-30mm, and the variance of range was 13.0-53.0mm for 77 days. 4. The optimum spat-fall season was from August 17 to 19 and 24 to 27, and spat of the oyster were attached in number of 7 per collector each day. 5. The optimum exposure time in spatfall was 4 hours. 6, The average water temperature and specific gravity, during the spawning season, was $25.98^{\circ}C$ and 0.1871, respectively.

• Fisheries and Aquatic Sciences
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• v.21 no.4
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• pp.9.1-9.7
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• 2018

To establish a comprehensive management strategy, as part of the optimization of cultural practice for an oyster rack culture system, we used a numerical model to estimate the primary production in the waters on the eastern coast of Wando island, South Korea. The estimated primary production ranged from 17.12 to $1052.55mgC\;m^{-2}day^{-1}$ ($204.22{\pm}224.75mgC\;m^{-2}day^{-1}$ in average). Except for the times of peak phytoplankton blooms, the estimated primary production (PP) was consistently under $200mgC\;m^{-2}day^{-1}$, which is more similar to the value of PP measured off the western coast of South Korea than the southern coast. No clear relationship was observed between nitrogen content and rainfall with the exception of heavy rainfall events, indicating that precipitation might not be the main source of nutrients in these waters. No clear influence was observed from Doam tidal discharge, located 24 km north from these waters due to main tide comes in this area from the channel between Gunwe-myeon in Wando island and Pukpyeong-myeon in Haenam-gun. Because of the shallow water depth and strong tidal current, resuspension of sediments, which causes an input of nitrogen into the system, could be easily caused by even mild wind and the infrequent passing of ships. Microscopic examination of the phytoplankton composition showed additional contribution of benthic species such as Paralia sulcata into the waters, which increase the productivity of oyster farms in the waters. The availability of nitrate and phosphate for primary production was temporarily limited throughout most of the spring and autumn blooming season.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.05a
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• pp.307-307
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• 2002

• Structural Monitoring and Maintenance
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• v.1 no.3
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• pp.249-271
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• 2014

This paper presents a unique study of Structural Health Monitoring (SHM) for the maintenance decision making about a real life movable bridge. The mechanical components of movable bridges are maintained on a scheduled basis. However, it is desired to have a condition-based maintenance by taking advantage of SHM. The main objective is to track the operation of a gearbox and a rack-pinion/open gear assembly, which are critical parts of bascule type movable bridges. Maintenance needs that may lead to major damage to these components needs to be identified and diagnosed timely since an early detection of faults may help avoid unexpected bridge closures or costly repairs. The fault prediction of the gearbox and rack-pinion/open gear is carried out using two types of Artificial Neural Networks (ANNs): 1) Multi-Layer Perceptron Neural Networks (MLP-NNs) and 2) Fuzzy Neural Networks (FNNs). Monitoring data is collected during regular opening and closing of the bridge as well as during artificially induced reversible damage conditions. Several statistical parameters are extracted from the time-domain vibration signals as characteristic features to be fed to the ANNs for constructing the MLP-NNs and FNNs independently. The required training and testing sets are obtained by processing the acceleration data for both damaged and undamaged condition of the aforementioned mechanical components. The performances of the developed ANNs are first evaluated using unseen test sets. Second, the selected networks are used for long-term condition evaluation of the rack-pinion/open gear of the movable bridge. It is shown that the vibration monitoring data with selected statistical parameters and particular network architectures give successful results to predict the undamaged and damaged condition of the bridge. It is also observed that the MLP-NNs performed better than the FNNs in the presented case. The successful results indicate that ANNs are promising tools for maintenance monitoring of movable bridge components and it is also shown that the ANN results can be employed in simple approach for day-to-day operation and maintenance of movable bridges.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.2
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• pp.52-59
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• 2008

The objective of this study is to develop an automatic object changer unit to improve processing problems existed in the conventional horizontal machining center. To achieve this goal, this study designed a horizontal transfer as the second project continued to the first project that designed a upward and downward traverse unit. A horizontal traverse unit shows a symmetric structure and consists of frame, which consists of four unit tools, motor and reducer, which are fixed at a frame, operation unit with pinions, first traverse unit, and second traverse unit. Constraint conditions based on the operation mechanism with these elements were configured and obtained following results after modeling a model for a traverse motor. In the kinematic expression of sliding motion with one degree of freedom, the sliding motion is constrained. Also, the rack 3 installed at a frame is used to configure possible kinematic constraint conditions of the rack 2 according to the rolling motion of the pinion 2 in the first traverse unit. In addition, the moment of inertia that is a type of kinetic energy in a converted horizontal traverse unit in the side of the reducer can be applied to introduce the moment of inertia of a converted horizontal traverse unit in the side of the reducer by using the sum of kinetic energy in the rack and pinion, which is a part of the horizontal traverse unit. Also, the equation of motion of the converted upward and downward traverse unit in the side of the motor using the equation of motion of the motor. Furthermore, the horizontal traverse unit predetermines the mass of the first and second traverse unit and applied load including the radius and reduction ratio of the pitch circle in the pinion 1 and applied load to the rack 2. Then, a proper motor can be determined using several parameters in the upward and downward traverse unit in order to verify such predetermined specifications. In future studies later this study, a simulation that verifies the results of the previous two stages of studies using a finite element method.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.05a
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• pp.91.1-91
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• 2001

• Journal of the Korean Operations Research and Management Science Society
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• v.13 no.1
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• pp.39-50
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• 1988

The warehousing of inventories is an enormous expense to industries worldwide, and yet there are few available that can be used to design rack storage systems while considering overall system costs. The primary objective of this paper is the development of an overall ware hous storage system costs model to aid a warehous planner in the design of automated warehouse systems. A simulation model and statistical estimation procedures are used to determine the maximum inventory levels accumulated in the receiving, storage, and shipping areas. The overall cost model is developed to determine the required total land, the initial investment fund, the number of pieces of handling equipment, and the storage rack configuration for the main storage area. A numerical example is then presented to demonstrate the application of the overall system cost model developed in this paper.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.1
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• pp.127-134
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• 2002

This study present a direct steering system using rack and pinion for ultra-small vehicles. The traditional small vehicles for special use had the limitation of space by reason of short wheel tread. These vehicles has adopted a indirect steering system or a center arm system for steering. The disadvantages of these system were deterioration of gear efficiency and increase of parts. For direct-linkage to both knuckles, steering system is made up of out-side tie rods, tie-rod ends, and gear box. Thus, the proposed system has a minimum number of parts. The experimental results show a maximum efficiency at minimum steering angle and a minimum clearance circle. These effects were accomplished by adopting a Ackerman-Jantaud theory.