• Journal of the Korean Institute of Gas
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• 제16권3호
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• pp.65-70
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• 2012

Experimental investigations were carried out to examine the explosion characteristics by different sizes in the wall surface shape of a water gel barrier in an explosion chamber, 1,600 mm in length with a square cross-section of $100{\times}100\;mm^2$. The sizes in the wall surface shape were varied by using water gel barriers with a cross-section of $100{\times}200\;mm^2$ and its were varied in the bottom of the chamber away 300, 700 and 1,100 mm, respectively from the closed end of the chamber. The flame propagation images were photographed with a high speed camera and the pressure was recorded using a pressure transducer and a data acquisition system. It was found that as the size of the wall surface shape increased, the flame propagation process and the time taken to reach the maximum pressure were found to be faster. As a result, both the flame speed and the explosion overpressure increased as the size of the wall surface shape increased.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• 제13권4호
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• pp.152-159
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• 1999

This paper describes the rmtion characteristics of a particle in GIS under AC voltage. To measure the motion characteristics of the particle, a model gas chamber and parallel plain electrodes were designed and manufactured lift-off voltages of wire and spherical particles on the electrode were calculated and rreasured, and electric charge was calculated. By using a high speed carrera, the rmtion characteristics of various particles with aw}ied voltages, such as motion pattern, lift-off time, lift-off height, were analyzed 1be lift-off voltages were greatly affected by diarreters of wire and spherical particles. At voltage around lift-off voltage, the stand-up particle in vertical state rmved up and down between electrodes and the height of the lift-off particle was low. At voltage around breakdown voltage, the particle repeated vertical rotation a few times while they were being lifted off, and then, they were floating between the electrodes.trodes.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제32권1C호
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• pp.23-33
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• 2007

Video compression is essential technique for fast and efficient transmission of a large amount of video data maintaining high quality. Also, motion estimation and motion compensation is most important technique for efficient video compression. A proposed method is improved diamond search method which uses split diamond pattern and rotated diamond pattern. In particular, the proposed method shows superb result when it is used for the sequence with a direction of camera moving. Moreover when it is used for the sequence with little motion, complexity is reduced considerably by using fewer search points. Also, by varying the number of initial search points, the propose method can provide several options in terms of duality or speed. Simulation results shows that the proposed method sustains better visual quality compared with diamond search method and HEXBS even by using fewer search points. Besides, compared with existing methods, it is able to conduct a motion estimation more efficiently by changing the number of search points adaptively according to motion of video data.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제36권6호
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• pp.600-607
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• 2008

Reliable wireless transmission of data generated by the flight critical subsystems or mission equipments of the unmanned aerial system is critical for mission success. As the UAS system becomes more sophisticated, its dependency on a reliable high rate radio communication system also increases. This requirement is applied not only during the operation phase but also in the early development test phase. This paper introduces a practical cost-effective communication system for a UAS. The downlink module combines analog NTSC video signal with onboard data, and send them using 2.4 GHz carrier wave. The uplink system has less a severe requirement on the bandwidth, and thus uses 430 MHz signal. This paper also presents a sample packet structure which can be adopted for many UAS of similar class.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 한국해양정보통신학회 2006년도 춘계종합학술대회
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• pp.809-812
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• 2006

This paper describes about the vision system, which was developed for the recognition of material management characters in the slab processing line. The material management characters, which are marked at the surface of a slab, are recognized by real time processing before slab moves to the next hot strip line. The vision system for the character recognition include that CCD camera system which acquire slab image, image transmission system which transmit captured image to the long distance, I/O devices for the interface with peripheral control system. We have installed vision system to the slab processing line and tested. Through the testing, we have checked durability, reliability and recognition rate of our system. In the results, we have confirmed that our system have good performance and higher recognition ability.

• Journal of KIISE:Computing Practices and Letters
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• 제13권4호
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• pp.213-225
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• 2007

Flash memory is widely used as a storage device for potable equipments such as digital cameras, MP3 players and cellular phones because of its characteristics such as its large volume and nonvolatile feature, low power consumption, and good performance. However, a block in flash memories should be erased to write because of its hardware characteristic which is called as erase-before-write architecture. The erase operation is much slower than read or write operations. FTL is used to overcome this problem. We compared the performance of the existing FTL algorithms on Windows-based OS. We have developed a tool called FTL APAT in order to gather I/O patterns of the disk and analyze the performance of the FTL algorithms. It is the log buffer scheme with full associative sector translation(FAST) that the performance is best.

• The KIPS Transactions:PartA
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• 제16A권2호
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• pp.89-100
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• 2009

With the advance in digital technologies and the increasing prevalence of high quality multimedia contents, there is a growing user demand for multimedia devices, such as mobile phones, digital TV, PMP, digital camcoders, digital cameras. Such devices provide various services associated with multimedia file manipulation, including multimedia contents playback, multimedia file editing, etc. Conventional file systems exhibit a performance-related drawback that requires considerable amount of time and disk I/Os in order to store large-sized edited multimedia files. This paper proposes a fast, efficient writing technique for large-sized edited multimedia files by using data block sharing with adjustment of inode block pointers. Our experiments show that the proposed scheme not only improves write performance of the Ext3 file system on average by 16 times with various types of edited multimedia files, but also reduces consumed disk space dramatically through the data block sharing.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 한국자원리싸이클링학회 2005년도 춘계임시총회 및 제25회 학술발표대회
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• pp.57-61
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• 2005

In this study, the machine vision system for inspection using color recognition method have been designed and developed to automatically sort out a specified material such as Cu scraps or other non-ferrous metal scraps mixed in Fe scraps. The system consists of a CCD camera, light sources, a frame grabber, conveying devices and an air nozzled ejector, and is program-controlled by a image processing algorithm. The ejector is designed to be operated by an I/O interface communication with a hardware controller. The sorting examination results show that the efficiency of separating Cu scraps from the Fe scraps mixed with Cu scraps is around 90 % at the conveying speed of 15 m/min. and the system is proven to be excellent in terms of its efficiency. Therefore, it is expected that the system can be commercialized in shredder firms, if the high-speed automated sorting system will be realized.

• Korean Journal of Optics and Photonics
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• 제16권4호
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• pp.361-365
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• 2005

An absolute interferometer system with multiple point-sources is devised for tile 3-D measurement of rough surface profiles. The positions of the point sources are determined to be the system parameters that influence the measurement accuracy, so they are calibrated precisely prior to performing actual measurements. For the calibration, a CCD camera composed of a two-dimensional array of photo-detectors was used. Performing optimization of the cost function constructed with phase values measured at each pixel on the CCD camera, the position coordinates of each point source is precisely determined. Measurement results after calibration performed for the warpage inspection of chip scale packages (CSPs) demonstrate that the maximum discrepancy is 9.8 mm with a standard deviation o( 1.5 mm in comparison with the test results obtained by using a Form Taly Surf instrument.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.443-443
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• 2010

액체 표면을 전극으로 하는 플라즈마 방전은 생물학적 살균, 분해 처리 등에 필요한 UV 및 화학적 활성종의 생성에 유리하여 널리 활용되고 있다. 하지만 그 특성 등에 관한 연구는 액체막의 유동 및 기하학적 구조 상 진단의 제한으로 인하여 아직 미비한 상태이다. 전해질 내 방전은 전극 표면의 기포 막 에 인가되고 그 두께에 따라 변한다. 따라서 본 연구에서는 액상 전해질의 인가 전압 및 점성도를 독립적으로 조절하여 기포 막 크기와 인가 전력간의 관계와 이에 따른 전해질 내 플라즈마의 특성이 음극 글로우 방전임을 밝혔다. 실험에서는 전기 전도도 1.6-3.2 S/m의 NaCl 수용액 전해질에 양극성 전극을 삽입하고 350 kHz의 전압을 인가하여 플라즈마를 발생하였다. 인가된 전압은 230 - 280 V이며 전해질의 점성도는 젤라틴을 첨가하여 1E-4-1.1 kg/m${\times}$sec로 조절하였다. 기포 막의 두께 및 변화는 고속카메라를 통하여 관측하였으며 인가되는 전압 및 전류는 고전압 프로브와 전류 프로브를 통하여 관찰하였다. 기포 막은 전극표면에서 막 비등을 통하여 발생됨을 밝혔다. 인가 전력과 손실 열에너지간의 비율에 따라 기포막은 수축과 확장의 진동을 반복하였으며 전기 유체적 모델을 통하여 기포 막의 동적 거동에 따른 플라즈마에 인가된 전력의 변화를 정량적으로 분석할 수 있었다. 기포 막의 평균적인 두께는 인가 전압과 비례하여 약 $150\;{\mu}m$에서 $200\;{\mu}m$로 증가하였으며 진폭은 점성의 증가 시 약 $50\;{\mu}m$에서 $20\;{\mu}m$로 감소하였다. 순간적인 플라즈마 인가 전력은 평균적인 두께에 따른 평균적인 두께에 대해서는 15 - 20 W의 변화를 보였으나 진폭의 감소 시 17 - 70 W의 보다 큰 폭으로 증가하였다. 이를 통하여 점성도가 큰 조건에서 기포 막의 확장이 억제되어 방전이 유지됨을 알 수 있었다.