• Transactions of the KSME C: Technology and Education
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• v.1 no.1
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• pp.99-105
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• 2013

In this paper, we carried out the basic design of 36 MTD natural gas BOG re-liquefaction system to recover the generated natural gas during performance test of LNG pump and natural gas compressor. The re-liquefaction process of natural gas is designed to have 1500 kg/h of liquefaction rate with reverse Brayton refrigeration cycle. With the designed process, the variation of liquefaction rate is calculated for various inlet conditions of feed gas. From results, the liquefaction rate is more sensitive for inlet temperature than gas composition. The specifications of equipments such as gas blower, natural gas compressor, cryogenic heat exchanger and nitrogen compander are determined on the basis of the designed process. The requirement of power consumption and cooling water are also determined through the basic design.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.3
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• pp.1255-1262
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• 2012

Look into the nuclear power plant of Wolsong currently, it is controlled in order to required operating pressure with PI controller. PI controller has a simple structure and satisfy design requirements to gain setting. However, It is difficult to control without changing the gain from produce changes in parameters such as loss of the valves and the pipes. To solve these problems, the dynamic change of the PI controller gain, or to compensate for the PI controller output is desirable to configure the controller. The aim of this research and development in the parameter variations can be controlled to a stable controller design which is reduced an error and a vibration. Proposed PI/NN control techniques is the PI controller and the neural network controller that combines a parallel and the neural network controller part is compensated output of the controller for changes in the parameters were designed to be robust. To directly evaluate the controller performance can be difficult to test in real processes to reflect the characteristics of the process. Therefore, we develope the simulator model using the real process data and simulation results when compared with the simulated process characteristics that showed changes in the parameters. As a result the PI/NN controller error and was confirmed to reduce vibrations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.6
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• pp.2458-2464
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• 2012

Recently, component materials for display are being developed into higher value-added industries which can strengthen national industrial competitiveness. However, a system for production of component materials for display is nearly depending on import, and its development level is inadequate. For this reason, localization of the embossing treatment system for production of the spacer tape and system improvement for increasing of productivity are needed. Therefore, in this paper, we propose rotary type embossing process system for spacer tape production for localization of system and increasing productivity. The system consists of unwinding, forming, cleaning, winding and testing parts. The mold of forming part is designed to rotary type. And we designed each part and made a prototype to test its performance. We measured embossing shapes, diameter and distance between each embossing and opposite embossing using three coordinate measuring machine. Also, we measured impurity level and the number of impurity particles of sample through the testing and cleaning part. Additionally, the productivity of spacer tape produced by the prototype is measured.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.11-18
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• 2013

Cement concrete pavement offers long-term service life and excellent applicability for heavy traffic. It is easier to purchase and more durable and economical than the asphalt pavement. However, it is difficult to repair and rehabilitate compared to the asphalt pavement when it comes to the maintenance problem. Since the crack is the main reason of the damage of concrete pavement, it is necessary to control the early and long-term crack in the concrete pavement. In this experimental study, the basic performance tests have been carried out to investigate the effect of hybrid fibers which were composed of micro fibers with small diameter and high aspect ratio and macro fibers with large diameter and low aspect ratio on the concrete pavement, in which lower water ratio and larger aggregates were used compared to the general concrete mixture. The test results showed that the flexural strength and toughness of concrete pavement mixture have been increased with the use of hybrid fibers in the concrete pavement mixture, even though they were less effective compared to the normal concrete mixture. It was found that the hybrid fibers were effective to control the early shrinkage of the concrete pavement which is one of the main reasons of the damage in the concrete pavement.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.3
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• pp.164-173
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• 2014

In underwater robotics, vision would be a key element for recognition in underwater environments. However, due to turbidity an underwater optical camera is rarely available. An underwater imaging sonar, as an alternative, delivers low quality sonar images which are not stable and accurate enough to find out natural objects by image processing. For this, artificial landmarks based on the characteristics of ultrasonic waves and their recognition method by a shape matrix transformation were proposed and were proven in Part 1. But, this is not working properly in undulating and dynamically noisy sea-bottom. To solve this, we propose a framework providing a selection phase of likelihood candidates, a selection phase for final candidates, recognition phase and tracking phase in sequence images, where a particle filter based selection mechanism to eliminate fake candidates and a mean shift based tracking algorithm are also proposed. All 4 steps are running in parallel and real-time processing. The proposed framework is flexible to add and to modify internal algorithms. A pool test and sea trial are carried out to prove the performance, and detail analysis of experimental results are done. Information is obtained from tracking phase such as relative distance, bearing will be expected to be used for control and navigation of underwater robots.

• Journal of the Korean Electrochemical Society
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• v.11 no.4
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• pp.256-261
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• 2008

In this study, Nafion membrane was modified to prevent methanol crossover by layer-by-layer self assembly using polyaniline (PANi) as a polycation and sulfonated poly(ether sulfone) (SPES) as a polyanion onto the Nafion surface. Since PANi and SPES possess thermal and chemical stability and rigid backbone, their layer-by-layer self-assembled films on the Nafion are expected to reduce methanol permeability and to increase mechanical stability. UV-Vis absorption spectroscopy verified a linear build-up of the multilayers of PANi and SPES. We found that the thickness per bilayer was about 10 nm by TEM measurement. Although modified Nafion membrane exhibited 15% decrease of proton conductivity, it reduceded 67% of methanol permeability compared to that of the pristine Nafion membrane, resulting in 2.5 times larger selectivity. At the performance test of the fuel cell using 5M methanol as a fuel, the modified Nafion membrane showed 2.4 times higher maximum power density at $30^{\circ}C$ and 1.4 times larger at $60^{\circ}C$ than the pristine Nafion.

• Journal of Bio-Environment Control
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• v.23 no.2
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• pp.123-130
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• 2014

Oriental melon (Cucumis melo var. makuwa) should be cultivated on the soil and be harvested. It is difficult to find because it is covered with leaves, and furthermore, it is very hard to grip it due to its climbing stems. This study developed and tested oriental melon harvesting robots such as an end-effector, manipulator and identification device. The end effector is divided into a gripper for harvest and a cutter for stems. In addition, it was designed to control the gripping and cutting forces so that the gripper could move four fingers at the same time and the cutter could move back and forth. The manipulator was designed to realize a 4-axis manipulator structure to combine orthogonal coordinate-type and shuttle-type manipulators with L-R type model to rotate based on the central axis. With regard to the identification device, oriental melon was identified using the primary identification global view camera device and secondary identification local view camera device and selected in the prediction of the sugar content or maturity. As a result of the performance test using this device, the average harvest time was 18.2 sec/ea, average pick-up rate was 91.4%, average damage rate was 8.2% and average sorting rate was 72.6%.

• Korean Journal of Optics and Photonics
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• v.5 no.3
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• pp.423-430
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• 1994

We designed and fabricated the single mode fiber pigtailed DFB-LD module for 2.5 Gbps optical communication system. In the design of the DFB-LD module, we made the module divided into two parts of inner sub-module and outer 14-pin butterfly package and cylindrical shaped sub-module contain quasi confocal 2 lens system including optical isolator and electrical connection between these parts via hybrid substrate of bias T circuit. Laser welding was used to assemble the sub-module which requires accurate fixing between optical elements. The fabricated DFB-LD module showed optical coupling efficiency of 20% and - 3 dB small signal response of more than 2.6 GHz. We confirmed mechanical reliability of the module by temperature cycle test where the tested module exhibit optical power fluctuation of less than 10%. Finally we evaluated the performance of the fabricated DFB-LD module as light source of 2.5 Gbps optical communication system, sensitivity of - 30.2 dBm was obtained through 47 km optical fiber transmission under the criterion of $1\times10^{-10}$ BER and transmission penalties were 1.5 dB caused by extinction ratio and 1.0 dB caused by chromatic dispersion of normal single mode fiber. fiber.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.9
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• pp.854-864
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• 2016

The use of small drone platform has become a popular topic in these days but its application for SAR operation has been little known due to the burden of the payload implementation. Drone platforms are distinguished from the conventional UAV system by the increased vulnerability to the turbulences, control-errors and poor motion stability. Consequently, sophisticated motion compensation may be required to guarantee the successful acquisition of high quality SAR imagery. Extremely limited power and mass budgets may prevent the use of additional hardwares for motion compensation and the difficulty of SAR focusing is further aggravated. In this paper, we have carried out a feasibility study of mico-SAR drone operation. We present the image acquisition results from the preliminary flight tests and a quality assessment is followed on the experimental SAR images. The in-flight motion errors derived from the unique drone movements are investigated and attempts have been made to compensate for the geometrical and phase errors caused by motions against the nominal trajectory. Finally, the successful operation of drone SAR system is validated through the focussed SAR images taken over test sites.

• Archives of Plastic Surgery
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• v.36 no.4
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• pp.380-384
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• 2009

Purpose: Autologous vessels remain the gold standard for vascular grafts in microanastomoses. However, they are sometimes unavailable and have a limited long - term patency. Synthetic vessels have high success rates in large - diameter reconstructions but failed when used as small - diameter grafts due to graft occlusion. It has been proved that endothelial cell seeding improves prosthesis performance and long - term patency. Among polyurethane, PET and ePTFE, polyurethane has the best affinity to endothelial cells and mechanical properties closest to human vessels. We examined the ability of endothelial cells to attach to a polyurethane graft manufactured by the electrospinning method. Methods: Endothelial cells, which were cultured from porcine internal jugular veins, were attached to polyurethane grafts with an internal diameter of 3 mm. The same cells were attached to allogeneic decellularized porcine internal carotid artery grafts as controls. Both of the 10 mm - long grafts were exposed to endothelial cells in a well for 1 hour. Each well contained $2{\times}10^5$ endothelial cells. The graft materials were rotated through 90 degrees every 15 minutes in order to minimize the effect of gravity. The extent of cell attachment was examined with the MTT assay. Results: The MTT assay showed good incorporation of endothelial cells into both grafts. For the evaluation of affinity, the number of attached cells was counted at 10 fields of microscopic examination with ${\times}40$ magnification. Endothelial cells adhered more to polyurethane grafts (mean, $127.4{\pm}6.2cells$) compared to porcine artery grafts (mean $45.8{\pm}5.1cells$)(p<0.05,Mann - Whitney test). Conclusion: In this study, we attached porcine endothelial cells to polyurethane grafts, manufactured by electrospinning. The grafts exhibited a better affinity to endothelial cells than allogeneic decellularized porcine internal carotid artery grafts. It is suggested that the time required for endothelial cells to attach to decellulized artery grafts may be longer than that which is required for attachment to polyurethane grafts.