• Journal of Energy Engineering
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• v.18 no.2
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• pp.101-107
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• 2009

The combustion characteristics of a single droplet of diesel and bio-diesel have been investigated experimentally with varying droplet size, ambient temperature and compound ratio in a high temperature chamber. The fuels used were diesel with bio-diesel contents varied from 0% to 100%. Each experiment has been performed from 970K to 1070K by 50K intervals. Imaging with a high-speed digital camera was adopted to measure the ignition delay and flame life-time, as well as to observe micro-explosion behavior. The increase of droplet size and decrease of furnace temperature cause an increase of the ignition delay time. As the bio-diesel content decreases, the ignition delay increases and the micro-explosion behavior is strengthened. It is also confirmed that the full combustion time decreases as the micro-explosion occurred.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.258-258
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• 2014

Spark discharge in water generates shockwaves which have been utilized to generate mechanical actuation for potential use in pumping application. Discharge pulses of several microseconds generate shockwaves and vapor bubbles which subsequently displace the water for a period of milliseconds. Through the use of a sealed discharge chamber and metal bellow spring, the fluid motion can be used create an oscillating linear actuator. Continuous actuation of the bellow has been demonstrated through the use of high frequency spark discharge. Discharge in water forms a region of high electric field around the electrode tip which leads to the creation of a thermal plasma channel. This process produces fast thermal expansion, vapor and bubble generation, and a subsequent shockwave in the water which creates physical displacement of the water [1]. Previous work was been conducted to utilize the shockwave effect of spark discharge in water for the inactivation of bacteria, removal of mineral fouling, and the formation of sheet metal [2-4]. Pulses ranging from 25 to 40 kV and 600 to 900 A are generated inside of the chamber and the bellow motion is captured using a slow motion video camera. The maximum displacements measured are from 0.7 to 1.2 mm and show that there is a correlation between discharge energy input to the water and the displacement that is generated. Subsequent oscillations of the bellow are created by the spring force of the bellow and vapor in the chamber. Using microsecond shutter speed ICCD imaging, the development of the discharge bubble and spark can be observed and measured.

• Journal of Energy Engineering
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• v.16 no.3
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• pp.113-119
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• 2007

The auto-ignition characteristics and combustion behaviors of one-dimensional array of water-in-fuel droplets suspended in a high temperature chamber have been investigated experimentally with various droplet spacing and number of droplets. The fuels used were pure n-decane and emulsified n-decane with water contents varied from 10% to 30%. All experiments have been performed at 920 K under the atmospheric pressure. The number of droplets in an array were fixed as 3 or 5 and its spacing was varied from 3 mm to 7 mm by 1mm interval. The imaging technique with a high-speed camera has been adopted to measure the ignition delay and flame life time. The micro-explosion behaviors were also observed. As the droplet array sparing increased, the ignition delay also increased regardless of water contents. However, the life time of droplet array decreased as the droplet spacing increased. The full combustion time in array of 3 droplets was found to be longer than that for 5 droplets case due to the longer ignition delay.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.356-359
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• 2017

According to the plan of operation of the Ministry of Education, IWB (Interactive White Board) was distributed to one or two classrooms per school. Therefore, instead of the overhead projector (OHP) and the screen, the visual presenter and the IWB replaced the role. However, the development speed of the imaging device and the display device could not keep up, and the utilization was often lowered. In this study, we study to obtain a high resolution image using the camera of smartphone. It uses WiGig(Wireless Gigabit) technology to transmit the acquired high-resolution images to IWB or large-screen TV without delay in wireless communication. In addition, while the smartphone camera is equipped with a lens of a wide field of view(FOV), the microscope lens can be used to magnify and magnify a specific portion of a smartphone 400 times. As s result of this study it will be used as active material for real-time 400 times magnification in education and research field.

• Journal of Korea Multimedia Society
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• v.6 no.1
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• pp.28-39
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• 2003

This paper is an overview of research contributions by the authors to the use of compression techniques to handle high resolution, multi-spectral images. Originally developed in the remote sensing context, the same techniques are here applied to food and medical images. The objective is to point out the potential of this kind of processing in different contexts such as remote sensing, food monitoring, and medical imaging and to stimulate new research exploitations. Compression is based on the simple assumption that it is possible to find out a relationship between pixels close one each other in multi-spectral images it translates to the possibility to say that there is a certain degree of correlation within pixels belonging to the same band in a close neighbourhood. Once found a correlation based on certain coefficient on one band, the coefficients of this relationship are, in turn, quite probably, similar to the ones calculated in one of the other bands. Based upon this second observation, an algorithm was developed, able to reduce the number of bit/pixel from 16 to 4 in satellite remote sensed multi-spectral images. A comparison is carried out between different methods about their speed and compression ratio. As reference it was taken the behaviour of three common algorithms, LZW (Lempel-Ziv-Welch), Huffman and RLE (Run Length Encoding), as they are used in common graphic format such as GIF, JPEG and PCX. The Presented methods have similar results in both speed and compression ratio to the commonly used programs and are to be preferred when the decompression must be carried out on line, inside a main program or when there is the need of a custom made compression algorithm.

• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.103-105
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• 2003

After fifteen years of development, Magnetic Resonance (MR) technology for human imaging and spectroscopy is reaching a refined state with FDA approved 3T clinical products from Siemens, GE, and Philips. Broker has cleared CE approval with a 4T system. Varian supports a 4T system platform as well. Shielded magnets are standard at 3T from GE, Oxford, Magnex, and IGC. A shielded 4T whole body magnet is available from Oxford. Stronger switched gradients and dynamic shim coils, desired at any field, areespecially useful at higher static magnetic fields B0. In addition to the higher currents required for higher resolution slice or volume selection afforded by higher SNR, whole body gradient coils will be driven at increasing slew rates to meet the needs of new cardiac applications and other requirements. For example 3T and 4T systems are now being equipped with 2kV, 500A gradient coils and amplifiers capable of generating 4G/cm in 200msec, over a 67+/-cm bore diameter. High field EPI applications require oscillation rates at 1 kHz and higher. To achieve a benchmark 0.2 ppm shim over a 30cm sphere in a high field magnet, at least four stages of shimming need to be considered. 1) A good high field magnet will be built to a homogeneity spec. falling in the range of 100 to 150 ppm over this 30cm spherical "sweet spot" 2) Most modern high field magnets will also have superconducting shim coils capable of finding 1.5 ppm by their adjustment during system installation. 3) Passive ferro-magnetic shimming combined with 4) active, high order room temperature shim coils (as many as five orders are now being recommended) will accomplish 0.2 ppm over the 30cm sphere, and 0.1 ppm over a human brain in even the highest field magnets for human studies. Safety concerns for strong, fast gradients at any B0 field include acoustic noise and peripheral nerve stimulation. One or more of the mechanical decoupling methods may lead to quieter gradients. Patient positioning relative to asymmetric or short gradient coils may limit peripheral nerve stimulation at higher slew rates. Gradient designs combining a short coil for local speed and strength with a longer coil for coverage are being developed for 3T systems. Local gradients give another approach to maximizing performance over a limited region while keeping within the physiologically imposed dB0/dt performance limits.

• Korean Journal of Optics and Photonics
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• v.19 no.5
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• pp.376-380
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• 2008

This paper presents the Projection Moire method using a line scan camera. The high resolution feature of a line scan camera makes it possible to scan an image quickly, thus enabling a much quicker 3D profile. This method uses a high resolution line scan camera making it possible to scan an image at high speed simultaneously measuring the 3D profile of a large FOV. When using a high resolution scan camera, a full FOV is scanned, thus requiring just one movement of a projection grating. As a result, the number of grating movements is reduced drastically. The end result is a faster and more accurate 3D measurement. Moving the grating too quickly causes vibration in the imaging system, which will normally be required to apply a stitching technique when using an area scan camera. However the technique is not required when using a line scan camera. Compared with the previous techniques, it has the advantages of simple hardware without moving mechanical parts - single exposure for obtaining three-dimensional information. A method using a high resolution line scan camera can be used in mass production to measure the bump height of wafers or the bump height of package substrates.

• Imaging Science in Dentistry
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• v.36 no.1
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• pp.49-54
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• 2006

Purpose : To evaluate accuracy and reliability of program to measure facial soft tissue thickness using 3D computed tomographic images by comparing with direct measurement. Materials and Methods : One cadaver was scanned with a Helical CT with 3 mm slice thickness and 3 mm/sec table speed. The acquired data was reconstructed with 1.5 mm reconstruction interval and the images were transferred to a personal computer. The facial soft tissue thickness were measured using a program developed newly in 3D image. For direct measurement, the cadaver was cut with a bone cutter and then a ruler was placed above the cut side. The procedure was followed by taking pictures of the facial soft tissues with a high-resolution digital camera. Then the measurements were done in the photographic images and repeated for ten times. A repeated measure analysis of variance was adopted to compare and analyze the measurements resulting from the two different methods. Comparison according to the areas was analyzed by Mann-Whitney test. Results : There were no statistically significant differences between the direct measurements and those using the 3D images (p>0.05). There were statistical differences in the measurements on 17 points but all the points except 2 points showed a mean difference of 0.5 mm or less. Conclusion : The developed software program to measure the facial soft tissue thickness using 3D images was so accurate that it allows to measure facial soft tissues thickness more easily in forensic science and anthropology.

• Journal of Sensor Science and Technology
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• v.7 no.2
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• pp.124-130
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• 1998

High-speed 3D vision systems are essential for autonomous robot or vehicle control applications. In our study, a stereo vision process has been developed. It consists of three steps : extraction of edges in right and left images, matching corresponding edges and calculation of the 3D map. This process is implemented in a VME 150/40 Imaging Technology vision system. It is a modular system composed by a display, an acquisition, a four Mbytes image frame memory, and three computational cards. Programmable accelerator computational modules are running at 40 MHz and are based on TMS320C31 DSP with a $64{\times}32$ bit instruction cache and two $1024{\times}32$ bit internal RAMs. Each is equipped with 512 Kbytes static RAM, 4 Mbytes image memory, 1 Mbytes flash EEPROM and a serial port. Data transfers and communications between modules are provided by three 8 bit global video bus, and three local configurable pipeline 8 bit video bus. The VME bus is dedicated to system management. Tasks between DSPs are distributed as follows: two DSPs are used to edges detection, one for the right image and the other for the left one. The last processor computes the matching process and the 3D calculation. With $512{\times}512$ pixels images, this sensor generates dense 3D maps at a rate of about 1 Hz depending of the scene complexity. Results can surely be improved by using a special suited multiprocessors cards.

• Korean Journal of Psychosomatic Medicine
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• v.26 no.2
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• pp.194-200
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• 2018

Objectives : The significance of leukoaraiosis on brain magnetic resonance imaging (MRI) is uncertain, but it is often seen with vascular risk factors or in the context of cognitive impairment. We aimed to investigate the effect of leukoaraiosis on the severity and course of delirium. Methods : Periventricular hyperintensity and deep white matter hyperintensity on brain MRI were rated in 42 patients with delirium by semiquantative visual rating scale. Correlations between their grades and the scores of Korean version of Delirium Rating Scale-Revised-98 (K-DRS-R-98) were analyzed, and the interaction effects between the groups according to the levels of leukoaraiosis and two evaluation points were also analyzed. Results : The grade of deep white matter hyperintensity in the occipital lobe was positively correlated with the scores on the total, severity items, cognitive items, and non-cognitive items of K-DRS-R-98. The cognitive items scores of K-DRS-R-98 in the low grade group of periventricular hyperintensity showed significantly steeper decrease than the high grade group. Conclusions : A difference in severity or recovery speed of delirium according to the level of leukoaraiosis may result from disruption in brain functional connectivity. Our results have a clinical implication in that the severity and course of delirium can be possibly predicted using the level of leukoaraiosis.