• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.11-15
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• 2018

Torque tubes in High Temperature Superconducting (HTS) motor transfer torque from superconducting field winding rotor to the room temperature shaft. It should have minimum heat conduction property for minimizing the load on cryo-refrigerator. Generally, these torque tubes are made with stainless steel material because of high strength, very low outgassing and low thermal contraction properties at cryogenic temperatures and vacuum conditions. With recent developments in composite materials, these torque tubes could be made of composites such as Kevlar and S-Glass, which have the required properties like high strength and low thermal conductivity at cryogenic temperatures, but with a reduced weight. Development and testing of torque tubes made of these composites for HTS motor are taken up at Bharat Heavy Electricals Limited (BHEL), Hyderabad in collaboration with Central Institute of Plastics and Engineering Technology (CIPET), Chennai and Indian Institute of Technology (IIT), Kharagpur. As these materials are subjected to vacuum, it is important to measure their outgassing rates under vacuum conditions before manufacturing prototype torque tubes. The present study focusses on the outgassing characteristics of Kevlar and S-Glass, using an Outgassing Measurement System (OMS), developed at IIT Kharagpur. The OMS facility works under vacuum environment, in which the test samples are exposed to vacuum conditions over a sufficient period of time. The outgassing measurements for the composite samples were obtained using pressure-rise technique. These studies are useful to quantify the outgassing rate of composite materials under vacuum conditions and to suggest them for manufacturing composite torque tubes used in HTS motors.

• Progress in Superconductivity and Cryogenics
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• v.24 no.3
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• pp.62-67
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• 2022

Liquid hydrogen (LH₂) has a higher density than gaseous hydrogen, so it has high transport efficiency and can be stored at relatively low pressure. In order to use efficient bulk hydrogen in the industry, research for the LH₂ supply system is needed. In the high-pressure hydrogen station based on LH₂ currently being developed in Korea, a heat exchanger is used to heat up supercritical hydrogen at 700 bar and 60 K, which is pressurized by a cryogenic high-pressure pump, to gas hydrogen at 700 bar and 300 K. Accordingly, the heat exchanger used in the hydrogen station should consider the design of high-pressure tubes, miniaturization, and freezing prevention. A helical heat exchanger generates secondary flow due to the curvature characteristics of a curved tube and can be miniaturized compared to a straight one on the same heat transfer length. This paper evaluates the heat transfer performance through parametric study on the distance between coils, guide effect, and anti-icing design of helical heat exchanger. The helical heat exchanger has better heat transfer performance than the straight tube exchanger due to the influence of the secondary flow. When the distance between the coils is uniform, the heat transfer is enhanced. The guide between coils increases the heat transfer performance by increasing the heat transfer length of the shell side fluid. The freezing is observed around the inlet of distribution tube wall, and to solve this problem, an anti-icing structure and a modified operating condition are suggested.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.2
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• pp.54-63
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• 2022

Among the various industrial robots, palletizing robots have received particular attention because of their higher productivity in accordance with technological progress. When designing a palletizing robot, the main components, such as the servo motors and reducers, should be properly selected to ensure its performance. In this study, a practical method for selecting the motors and reducers of a robot was proposed by performing the dynamic analysis of rigid-flexible multibody systems using ANSYS and ADAMS. In the first step, the links and frames were selected based on the structural analysis results obtained from ANSYS. Subsequently, a modal neutral file (MNF) with information on the flexible body was generated from the links and frames using modal analysis through ANSYS and APDL commands. Through a dynamic analysis of the flexible bodies, the specifications of the major components were finally determined by considering the required torque and power. To verify the effectiveness of the proposed method, the analysis results were compared with those of a rigid-body model. The comparison showed that rigid-flexible multibody dynamic analysis is much more useful than rigid body analysis, particularly for movements heavily influenced by gravity.

• Journal of the Korea Institute of Building Construction
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• v.17 no.2
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• pp.191-197
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• 2017

The safety nature of construction industry differs from that of manufacturing sector. For instance, accident risk level dramatically varies at each phase of construction process. Korean Occupational and Health Safety Act has been regulated OHS expense and it contributed reducing accident risk and enhancing safety culture for many years. However, although current regulation guides to use OHS expense proportionate to construction progress, it still allows late use of the expense. This study was conducted for the purpose of presenting methods of estimating a step-by-step OHS expense rate required at each construction phase. In order to do provide proper OHS expense schedule, it analysed accident risk of each construction phase by sorting out 1439 cases of construction site fatality reports, and proposed a method of generating appropriate OHS expense scheme according to its construction work progress characteristics. Both linear and sigmoidal S-curve model were used for the analysis, and the latter generally requires earlier use of OHS expense. By comparing the estimated OHS expense use schedule with current criteria, more than 27%p early use of OHS expense is required for the prevention of accident.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.58-65
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• 2020

3D Models of offshore plant piping materials designed by 3D CAD systems are provided to the production processes in the form of 2D piping drawings and 2D piping installation drawings. In addition to the standard engineering information, the purchasing, procurement, manufacturing, installation, and inspection of raw materials are managed systematically in an integrated process control system. The existing integrated process management system can help reduce the processing time by managing the flow and progress of resources systematically, but it does not include 3D design model information. Hence, it is difficult to understand complicated pipe structures before installing the pipe. In addition, when design changes or immediate design modifications are required, it is difficult to find related data or exchange information quickly with each other. To solve this problem, an offshore plant-piping process-monitoring system was developed based on a 3D model. The 3D model-based piping monitoring system is based on Visual Studio 2017 C# and UNITY3D so that the piping-process work information can be linked to the 3D CAD model in real time. In addition, the 3D model could check the progress of the pipe installation process, such as block, size, and material, and the progress of functional inspection items, such as cleaning, hydraulic inspection, and pneumatic inspection.

• Journal of Environmental Health Sciences
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• v.7 no.1
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• pp.51-57
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• 1981

This Study was carried out to investigate yeast and mold contamination in fermented milk products produced by 9 different domestic manufacturers from October 20. to December 5. 1980 The results obtained in the study were as follows 1) pH values of the products were ranged from pH 3.14 to pH 4.20 and average of sour milk drinks was pH $3.66\pm 0.19$ and fermented milks pH $3.74\pm 0.11$. Therefore the difference of pH average among sour milk drinks and fermented milks was statistically significant. (p<0.01) 2) In case of yeast contamination, yeast was found on all the four producted at the same date. From this result, it seemed that yeast contamination occured during the manufacturing progress. 3) Degree of contamination by the indicator organisms was E. coli positive, 3.7%: over 1,000 yeasts/ml, 14.8% over 10 molds/ml, 0.9%. 4) In the range of over 1,000 yeasts/ml, degree of contamination by yeast was 8.4% in fermented milk and 16.7% in sour milk drink. 5) Yeasts in product C increased to the spoilage number within 5 days and in H increased within 10 days at 5C. At 15$\circ$C, yeast increased to the spoilage number within 15 days in product A.D. 6) It seems that the yeast number of initial contamination should be important than the increase rate as criteria on the fermented Milk products.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.7
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• pp.1166-1173
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• 1997

Due to progress in manufacturing techniques, the performance of the harmonic drive has been improved but not sufficiently. One of the important problems which the current harmonic drive has is that while there is the potential for having a wider tooth contact area, the total number of teeth engaged simultaneously is still small. This is mainly due to the involute tooth profile. Hence, in this study, the cycloid-type tooth profile is developed to improve this problem. This paper represents the design methodology and performance evaluation f the cycloid-type harmonic drive. Cycloide tooth profile was derived by analyzing geometry of the tooth engagement and the contact mechanisms of the tooth which were examined and analyzed by load analysis. The stress due to elastic deformation of a flexspline was also obtained by approximate formula and computer analysis. Finally, the cycloid-type harmonic drive with 1:100 speed ratio was manufactured and the performance of the harmonic drive was evaluated.

• Progress in Superconductivity and Cryogenics
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• v.18 no.3
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• pp.21-24
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• 2016

Recently, production technique and property of the High-Temperature Superconductor (HTS) tape have been improved. Thus, the study on applying an HTS magnet to the high magnetic field application is rapidly increased. A Nuclear Magnetic Resonance (NMR) spectrometer requires high magnitude and homogeneous of central magnetic field. However, the HTS magnet has fabrication errors because shape of HTS is tape and HTS magnet is manufactured by winding HTS tape to the bobbin. The fabrication errors are winding error, bobbin diameter error, spacer thickness error and so on. The winding error occurs when HTS tape is departed from the arranged position on the bobbin. The bobbin diameter and spacer thickness error occur since the diameter of bobbin and spacer are inaccurate. These errors lead magnitude and homogeneity of central magnetic field to be different from its ideal design. The purpose of this paper is to investigate the effect of winding error, bobbin diameter error and spacer thickness error on the central field and field homogeneity of HTS magnet using the virtual NMR signals in MATLAB simulation.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.363-367
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• 2009

Recently, the manufacturing of micro-cavity by means of laser surface texturing (LST) technique and low friction study by the LST have been in great progress. Most of current works have been dealing with the effect of cavity on friction and wear. The main objective of the present study was to investigate numerically two-dimensional lubrication characteristics of micro-dimple shapes fabricated on solid surfaces, and this study utilized the commercial CFD code (Fluent V.6.3). For the evaluation, preliminary simulation was conducted and numerical predictions were compared with the analytic solution obtained from the Reynolds's equation. Mainly, the present study investigated the influence of dimple depth, pattern shapes, and film thickness on lubrication characteristics related to the reduction of friction. It is found that the existence of micro-dimpled surface makes it possible to substantially reduce the friction forces exerted on the surfaces. In particular, substantial decrease in shear stresses was observed as the lubricant film thickness decreases. For instance, in the case of the film thickness of 0.01 mm, the estimated shear stress decreases up to about 40%. It indicates that the film thickness would be important factor in designing the micro-dimpled surfaces. Furthermore, it was observed that such a optimum dimple depth would be present because the dimple depth larger than the optimum value did no longer affect the reduction in shear stresses.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.9 s.174
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• pp.107-114
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• 2005

With the recent progress in flexible manufacturing systems (FMS) in industry, increasing attention has been given to Automatic Guided Vehicle (AGV) systems. An AGV is a self-powered unit for transporting materials between stations without needing to be controlled by an operator. Such a system has several sensors to recognize the external state, and it is designed to travel between stations automatically without external assistance. To manage each device automatically in real time it requires a distributed controller with a main computer as the host, as well as a number of micro-controllers. In this study, an AGV system with dual motor drive was constructed. A Pentium 4 personal computer was set up as the main host for the distributed control, and this communicated with other micro-controllers in the management of the motor. The speed of each motor was also controlled by a micro-controller.