• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.6
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• pp.782-793
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• 2018

A small-scale horizontal axis hydrokinetic turbine is designed, manufactured and studied both experimentally and numerically in this study. The turbine is expected to work in most of China's sea areas where the ocean current velocity is low and to supply electricity for remote islands. To improve the efficiency of the turbine at low flow velocities, a magnetic coupling is used for the non-contacting transmission of the rotor torque. A prototype is manufactured and tested in a towing tank. The experimental results show that the turbine is characterized by a cut-in velocity of 0.25 m/s and a maximum power coefficient of 0.33, proving the feasibility of using magnetic couplings to reduce the resistive torque in the transmission parts. Three dimensional Computational Fluid Dynamics (CFD) simulations, which are based on the Reynolds Averaged Navier-Stokes (RANS) equations, are then performed to evaluate the performance of the rotor both at transient and steady state.

• Journal of the Korean Society of Safety
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• v.17 no.4
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• pp.94-100
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• 2002

As the use of automatic handling equipment for sensitive semiconductor devices is rapidly increased, manufacturers of electronic components and equipments need to be more alert to the problem of electrostatic discharges(ESD). In order to analyze damage characteristics of semiconductor device damaged by ESD, this study adopts a new charged-device model(CDM), field-induced charged model(FCDM) simulator that is suitable for rapid, routine testing of semiconductor devices and provides a fast and inexpensive test that faithfully represents ESD hazards in plants. High voltage applied to the device under test is raised by the field of non-contacting electrodes in the FCDM simulator, which avoids premature device stressing and permits a faster test cycle. Discharge current and time are measured and calculated. The characteristics of electrostatic attenuation of domestic semiconductor devices are investigated to evaluate the ESD phenomena in the semiconductors. Also, the field charging mechanism, the device thresholds and failure modes are investigated and analyzed. The damaged devices obtained in the simulator are analyzed and evaluated by SEM. The results obtained in this paper can be used to prevent semiconductor devices form ESD hazards and be a foundation of research area and industry relevant to ESD phenomena.

• Journal of Mechanical Science and Technology
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• v.19 no.7
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• pp.1478-1487
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• 2005

A small mixed-type turbine with a diameter of 19.9 mm has been substituted for a rotational part of pencil-type air tool. Usually, a vane-type rotor is applied to the rotational part of the air tool. However, the vane-type rotor has some problems, such as friction, abrasion, and necessity of accurate assembly etc.,. These problems make the life time of the vane-type air tool short, but air tools operated by mixed-type turbines are free of friction and abrasion because the turbine rotor dose not contact with the casing. Moreover, it is assembled easily because of no axis offset. These characteristics are merits for using air tools, but loss of power is inevitable on a non-contacting type rotor due to flow loss, tip clearance loss, and profile loss etc.,. In this study, four different rotors are tested, and their characteristics are investigated by measuring the specific output power. Additionally, optimum nozzle location against the rotor is studied. Output powers are obtained through measured pressure, temperature, torque, rotational speed, and flow rate. The experimental results obtained with four different rotors show that the rotor blade shape greatly influences to the performance, and the optimum nozzle location exists near the mid span of the rotor.

• Smart Structures and Systems
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• v.24 no.5
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• pp.607-616
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• 2019

The video deflectometer based on digital image correlation is a non-contacting optical measurement method which has become a useful tool for characterization of the vertical deflections of large structures. In this study, a novel imaging model has been established which considers the variations of pitch angles in the full image. The new model allows deflection measurement at a wide working distance with high accuracy. A monocular video deflectometer has been accordingly developed with an inclination sensor, which facilitates dynamic determination of the orientations and rotation of the optical axis of the camera. This layout has advantages over the video deflectometers based on theodolites with respect to convenience. Experiments have been presented to show the accuracy of the new imaging model and the performance of the monocular video deflectometer in outdoor applications. Finally, this equipment has been applied to the measurement of the vertical deflection of Yingwuzhou Yangtze River Bridge in real time at a distance of hundreds of meters. The results show good agreement with the embedded GPS outputs.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.1
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• pp.67-76
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• 1998

Friction materials for brake linings and clutches have severe performance requirements. The principal function of such frictional elements is to convert kinetic energy to heat, and then either to absorb or to dissipate heat. In order to achieve these objectives, the coefficient of friction must be as high as possible, independent of variations in operating conditions, and the necessary energy conversion must be accomplished with a minimum of wear on the contacting parts. In this study, Al powder, Al bronze powder and Mo powder used in general for automobile brake was sprayed on automobile brake disc to restrain rust and to maintain friction performance. Dynamo and corrosion tests have been carried out. It is concluded that the sprayed disc with Al bronze powder has the most improved frictional performance and anti-corrosive characteristics. The main results obtained can be summarized as follows; 1. From the corrosion current density test for gray cast iron and sprayed disc with powders of Al, Al bronze and Mo, it was cleared that the spray treatment with Al bronze powder showed the most superior anti-corrosive characteristics than other powders. 2. By anode polarization toward the noble direction from corrosion potential, corrosion current density with sprayed brake disc by Al-bronze powder was the lowest. 3. Mean frictional coefficients obtained from dynamo test are as follows : the sprayed disc with Al(99.99%) powder was 0.190 ; the sprayed disc with Al-bronze powder was 0.312 ; the sprayed disc with Mo powder was 0.257 ; the non-sprayed disc of gray cast iron was 0.331. In the case of the sprayed disc Al-bronze powder showed the most excellent frictional characteristics . 4. Amount of burnish quantity obtained from burnish test by dynamometer is as follows : the sprayed disc with Al-powder was 1.079 mm : the sprayed disc with Al-bronze powder was 0.155 mm : the sprayed disc with Mo powder was 0.253 mm : the non-sprayed disc of gray cast iron was 0.241 mm. Al-bronze powder also showed the most excellent burnish characteristics.

• Journal of the Korean Institute of Gas
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• v.5 no.1
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• pp.60-72
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• 2001

This paper presents the user-interactive productivity analysis model based on material balance as well as deliverability equations equipped with EOS model to perform a productivity analysis for Gorae V structure, Donghae-1 gas field. This model is designed to be able to analyse the productivity in the case of reservoir contacting with the aquifer. Also, in order to investigate the effect of condensation on productions, condensation phenomenon is considered as an apparent skin effect in the computation of bottomhole pressure from average reservoir pressure. By utilizing the developed model, we investigate the productivity analysis for B2 layer of Garae V structure with the various production cases in volumetric and non­volumetric reservoirs that contact with aquifer. From the results in the case of 5500 MMSCF/year of production and reservoir-aquifer contacting angle 270$^{\circ}C$ with aquifer size of 10 times greater than reservoir, B2 layer could maintain peak production rate even after 8.5 years of production by considering the bottomhole pressure which is estimated above the operating pressure of 1298 psia. It is also found that condensate will be formed after 1100 days of production and existed throughout the reservoir at 1270 days. Note that the computed reservoir pressure of B2 layer is maintained sufficiently high enough for production due to the water influx into the reservoir, and skin effect caused by condensation is not significant.

• Korean Journal of Acupuncture
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• v.21 no.3
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• pp.21-38
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• 2004

Objectives : Moxibustion has been become very useful tool to prevent and treat various diseases with acupuncture in oriental medicine. Expecially, moxibustion combining the heat stimulation and chemical stimulation of Artemisiae Argyi has a non-invasive characteristics comparing to the other therapeutic tools. However, because the moxibustion makes the patient's skin be burn by the combustible feature of moxibustion, most of people have been scared of being scald. Methods : In this study, we have developed new non-combustible moxibustion tools in collaboration with company (Hana Medical, co. and ICURE, co.) and tested the efficacy through effects of moxibustion of Cheon-chu $(ST_{25})$ on the abdominal thermography of health subject. The non-combustible moxibustion has main characteristics of controlled heating to inhibit being scald and heat stimulation lasting over 1 hrs. Also, to induce the chemical stimulation, the bottom contacting with skin was coated by the extract of artemisiae argyi. The volunteers who participating in this study had taken rest for 20 - 30 mins in room temperature $(23-25^{\circ}C)$ before the examination and informed them what to prohibit smoking, drinking and administration of drug for the previous day The thermography of abdomen including a below part of the chest was taken using Infra-Red Imaging System (IR 2000, MEDI-CORE Co., Korea) by time interval of 15 minutes. Results : The results showed that moxibustion of Cheon-chu $(ST_{25})$ had more potencies of changes on all the ROIs of abdominal thermography than those of control group. Also, it was observed that the quantities of thermal changes following moxibustion of Cheon-chu $(ST_{25})$ been increased significantly comparing that of control group at all the ROIs (region of interest). Observed the thermography classified by ROI, however, moxibustion of Cheon-chu $(ST_{25})$ could modulate ipsilateral specific areas concerning to the abdominal pathway of Stomach Meridian. Conclusion : These results suggest that new non-combustible moxibusion has some similarity as like as the conventional moxibustion and moxibustion of Cheon-chu $(ST_{25})$ may modulate thermal changes of abdominal areas.

• Journal of the Korean Geographical Society
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• v.39 no.1
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• pp.116-131
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• 2004

The purpose of this study is to inquiry spatial features of shipbuilding subcontract structures. These days, firms are trying to get their goals by wav of production system which is related to other firm. Shipbuilding subcontract structures which builds complex and grand plant show a different peculiarity according to spatial features having rules of business relations with contracting firms. First of all, internal subcontracting firms which takes part in the production process of contracting firm and shipbuilding cooperative complex firms which showing a peculiarity of spin-off firms are closely related with contracting firm. And firms in Changwon that have a specialized with machine industry and those of Busan that have made development in marine equipment industries traditionally are connected with subcontract relations because of a high level of specialization relatively. On the other hand, subcontracting firms which range from non-localized and provide standardized products are less connected with contracting firm. In order to develop of Korea' shipbuilding industry, first, close cooperative relation is important with subcontracting firms which concentrate internal and outside contacting firm. And, it is necessary to strengthen selective business relations with far distance firms which are specialized in technology.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.10
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• pp.927-933
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• 2011

This paper presents an optical sampling technique which can be used to overcome the limited bandwidth of a commercial electronic sampling oscilloscope for pulsed signal measurement. Employing an ultrafast laser with 0.1 ps pulse duration, 20 GHz electromagnetic pulses were generated through a fast photodiode. These pulses were transmitted through a microstrip line and sampled with an optically triggered electro-optic system. Two sampled 20 GHz pulses - measured independently over the transmission line with a non-contacting electro-optic method and conventional electronic one through a coaxial cable - were compared.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.1
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• pp.48-55
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• 2012

Pressure vessels in vehicle industries, power plants, and chemical industries are often affected by flaw and defect generated inside the pressure vessels due to production processes or being used. It is very important to detect such internal defects of pressure vessel because they sometimes bring out serious problems. In this paper, an optical defect detection method using digital shearography is used. This method has advantages that the inspection can be performed at a real time measurement and is less sensitive to environmental noise. Shearography is a laser-based technique for full-field, non-contacting measurement of surface deformation (displacement or strain). The ultimate goal of this paper is to detect flaws in pressure vessels and to measure the lengths of the flaws by using unwrapping, phase images which are only obtained by Phase map. Through this method, we could decrease post-processing (next processing). Real length of a pixel can be calculated by comparing minimum and maximum unwrapping images with shearing angle. Through measuring several specimen defects which have different lengths and depths of defect, it can be possible to interpret quantitatively by calculating gray level.