• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.433-433
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• 2016

Carbon nanotubes (CNT) emitter has widely become an attractive mechanism that draws growing interests for cold cathode field emission. CNT yarns have demonstrated its potential as excellent field emitters. It was demonstrated that a small focal spot size was achieved by manipulating some electrical parameters, such as applied bias voltage at the mesh gate, and electrostatic focal lenses, geometrical parameters, such as axial distances of the anode, and the electrostatic focal lens from the cathode assembly, and the dimension of the opening of the electrostatic lens. Electrical-optics software was used to systematically investigate the behavior of the electron beam trajectory when the aforementioned variables were manipulated. The results of the experiment agree with the theoretical simulation results. Each variable has an individual effect on the electron beam focal spot size impinging on the target anode. An optimum condition of the parameters was obtained producing good quality of X-ray images. Also, MWCNT yarn was investigated for field emission characteristics and its contribution in the X-ray generation. The dry spinning method was used to fabricate MWCNT yarn from super MWCNTs, which was fabricated by MW-PECVD. The MWCNT yarn has a significant field emission capability in both diode and the triode X-ray generation structure compared to a MWCNT. The low-voltage-field emission of the MWCNT yarn can be attributed to the field enhancing effect of the yarn due to its shape and the contribution of the high-aspect-ratio nanotubes that protrude from the sides of the yarn. Observations of the use of filters on the development of X-ray images were also demonstrated. The amount of exposure time of the samples to the X-ray was also manipulated. The MWCNT yarn can be a good candidate for use in the low voltage field emission application of X-ray imaging.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.6
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• pp.814-819
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• 2011

An Oxy-fuel combustion has been studied in order to reduce exhaust emissions and fuel consumption. The flow and flame behaviors are analyzed with focal length variation in one-focussing oxygen burner introduced in this study. Oxygen is supplied into the center of the nozzle, methane fuel is into the outer nozzle of the center, and then oxygen is again supplied into the outer of the fuel nozzle. The test conditions are 5 focal lengths of 100mm to 500mm. The mixing behaviors and temperature distributions are analyzed. The result shows that the shorter the focal length is, the longer the mixing length becomes, and the flame width and length are the biggest in the case of 300mm.

• Childhood Kidney Diseases
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• v.5 no.1
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• pp.73-77
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• 2001

Acute lobar nephronia is a focal of acute bacterial nephritis, affecting one or more of the renal lobules. Nephronia is being diagnosed more frequently in accordance with the advancing imaging techniques of urinary tract. We report a case of acute nephronia in a 4 month old boy who presented persisting urinary tract infection after intial antibiotic treatment. Ultrasonography and computerized tomography showed round wedge-shaped, non-enhancing mass in right kidney. Gallium scan also revealed the lesion in the right kidney. This lesion resolved completely on one month follow up examinations. (J. Korean Soc Pediatr Nephrol 5 : 73- 7, 2001)

• Childhood Kidney Diseases
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• v.16 no.1
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• pp.21-31
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• 2012

Focal segmental glomerulosclerosis (FSGS) is the name of the primary glomerular disease as well as the terminology to describe the secondary phenomena of any other glomerular diseases. It is characterized by sclerosis, hyalinosis, foam cell infiltration, vacuolar change of podocytes, and halo formation in the glomerulus. Throughout the interstitium, lymphocytes infiltration, tubular atrophy and vascular changes are accompanied. Occasionally, IgM and/or C3 depositions are noted in the sclerotic areas. Electron microscopically, diffuse effacement of foot processes are seen in non-sclerotic area like minimal change disease. Podocyte injury patterns including vacuolar changes are frequently examined. Recently, Columbia group has suggested morphologic classification of FSGS and they demonstrated very good prognosis of tip lesion and poor prognosis of both collapsing and cellular types. However, the pathogenetic classification has been suggested by others; hyperfilteration, podocyte injury, genetic lesions etc. Further studies are necessary to understand and treat this disease.

• Biomolecules & Therapeutics
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• v.5 no.2
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• pp.133-149
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• 1997

4-week repeated dose toxicity of DA-5018, a new capsaicin analogue analgesic agent, was examined in 5D rats at dosage levels of 0,0.4,2, 10 and 50 mg/kg/day. DA-5018 was administered orally to 17 males and 17 females per group at doses of 0, 10 and 50 mg/kg and to 12 males and 12 females per group at doses of 0.4 and 2 mg/kg. After the administration period, 5 males and 5 females at the 0, 10 and 50 mg/kg were placed on withdrawal for 2 weeks. Treatment-related clinical signs were observed at 10 and 50 mg/kg. Clinical signs observed immediately after the administration of DA-5018 were grooming, sedation or depression, lacrimation, atacia, reddening of extremities and ears, ventral or lateral recumvincy, respiratory distress, cyanosis and convulsion. Delayed-type clinical signs including focal scabbing and depilation around nose were also observed 1 or 2 weeks after the start of administration of DA-5018. Only at the 50 mg/kg group, corneal opacities, reduced body weight gain (male) and death (male 6/17, female 3/17) were noted. In blood biochemical analysis, serum levels of glucose and triglyceride decreased at 10 and 50 mg/kg. In hematological examination, there were increases in the number of red blood cell, hemoglobin content and percent of hematocrit at 10 and 50 mg/kg. Pulmonary enlargement and hemorrhagic spot, focal scabbing and depilation around nose and corneal opacities were seen at the necropsy of the animals died during the dosing of DA-5018 50 mg/kg. Focal scabbing and depilation around nose were observed in the animals terminally necropsied at doses of 10 and 50 mg/kg. Histopathological examination revealed pulmonary hemorrhage, focal necrosis in the scabbed area, corneal necrosis, fibrosis and neovasculization in the stroma. At 0.4 and 2 mg/kg, there were no significant toxic changes attributable to the administration of DA-5018. In conclusion, target organs following to 4-week repeated dose of DA-5018 in the rat were determined to be lung, skin and eyes. Definite toxic dose and no-observed-adverse-effect-level (NOAEL) were estimated to be 50 and 2 mg/kg/day, respectively.

• Journal of Korean Neurosurgical Society
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• v.30 no.1
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• pp.12-19
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• 2001

Objective : Albumin is a very useful drug for the improving of cerebral blood volume and the oncotic effect in cerebral ischemia or cerebral vasospasm. The purpose of this study was to examine the morphological and neurological effect of albumin therapy on reperfusion injury following transient focal cerebral ischemia. Materials and Methods : 18 Male Sprague-Dawley rats weighing 270-320g were used. The ischemia model was produced by 2-hour period of transient middle cerebral artery occlusion with a poly-L-lysin coated intraluminal suture. The agent(20% human serum albumin[HSA]) or control solution(NaCl 0.9%) was administered intravenously at a dosage of 1% of body weight immediate after reperfusion following a 2-hour period occlusion. Neurological function was evaluated by the postural reflex and the forlimb placing test during occlusion(at 60 min) and daily for 3 days thereafter. The brain was perfusion-fixed, and infarct volumes and brain edema were measured. Results : The HSA significantly improved the neurological score in treated group. The rats of albumin treatment group showed significantly reduced total infarct volume(by 34%) and brain edema(by 81%) compared with salinetreated rats. Conclusion : HSA showed a substantial effect on the transient focal cerebral ischemia and reperfusion injury model. These results may indicate its usefulness in treating reperfusion injury patients after thrombolysis treatment for the thrombo-embolic major cerebral artery occlusions.

• The Korean Journal of Nuclear Medicine
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• v.26 no.1
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• pp.26-32
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• 1992

Minimal deterioration of cerebral perfusion or microanatomical changes were undetectable on conventional Brain CT or MRI. So evaluation of focal functional changes of the brain parenchyme is essential in chronic head injury patients, who did not show focal anatomical changes on these radiological studies. However, the patients who had longstanding neurologic sequelae following head injury, there had been no available imaging modalities for evaluating these patients precisely. Therefore we tried to detect the focal functional changes on the brain parenchyme using $^{99m}Tc-HMPAO$ Brain SPECT on the patients of chronic head injuries. Twenty three patients who had suffered from headache, memory dysfunction, personality change and insomnia lasting more than six months fellowing head injury were included in our cases, which showed no anatomical abnormalities on Brain CT or MRI. At first they underwent psychological test whether the symptoms were organic or not. Also we were able to evaluate the cerebral perfusion changes with $^{99m}Tc-HMPAO$ Brain SPECT in 22 patients among the 23, which five patients were focal and 17 patients were nonfocally diffuse perfusion changes. Thus we can predict the perfusion changes such as local vascular deterioration or functional defects using $^{99m}Tc-HMPAO$ Brain SPECT in the patients who had suffered from post-traumatic sequelae, which changes were undetectable on Brain CT or MRI.

• Childhood Kidney Diseases
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• v.9 no.2
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• pp.237-244
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• 2005

Membranoproliferative glomerulonephritis (MPGN) is a progressive primary glomerulonephritis characterized by mesangial proliferation with increased mesangial matrix, subendothelial immune deposits, mesangial interposition and a double contour feature of the glomerular basement membrane. The glomerular involvement in MPGN is usually diffuse, however, cases of focal or segmental MPGN have been reported by several authors. We report a case of focal segmental MPGN with prolonged hypocomplementemia for ,3 years in a 5 years old girl. (J Korean Soc Pediatr Nephrol 2005;9:237-244)

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.2
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• pp.77-83
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• 2003

To investigate the influence of the variation of conic coefficient of the front surface on the RMS SD(Root Mean Square Spot Diameter) in a back focal plane, we use programs which are Cove V and LOSA 2.0. We consider a spectacle lens with back vertex power of -4.00D, diameter of 70 mm, the front surface powers which are 2.00D, 4.00D, 6.00D, and 8.00D, and the indices which are $n_d$=1.498, 1.523, 1.586, and 1.660, respectively. The RMS SD in the back focal plane and the thickness of an aspherical tens having the optimized conic constant are smaller than those of a spherical lens. The RMS SD in the back focal plane decreases as the front surface power decreases. From these results, we determine the optimized conic constant to improve the optical image quality and decrease RMS SD in the back focal plane.

• Journal of Broadcast Engineering
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• v.14 no.3
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• pp.299-310
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• 2009

In this paper, we proposed a new method to correct the zoom lens distortion for the video sequence captured by the zoom lens. First, we defined the nonlinear zoom lens distortion model which is represented by the focal length and the lens distortion using the characteristic that lens distortion parameters are nonlinearly and monotonically changed while the focal length is increased. Then, we chose some sample images from the video sequence and estimated a focal length and a lens distortion parameter for each sample image. Using these estimated parameters, we were able to optimize the zoom lens distortion model. Once the zoom lens distortion model was obtained, lens distortion parameters of other images were able to be computed as their focal lengths were input. The proposed method has been made experiments with many real images and videos. As a result, accurate distortion parameters were estimated from the zoom lens distortion model and distorted images were well corrected without any visual artifacts.