• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.1
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• pp.54-61
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• 2009

This paper proposes the 2nd-order SDSDM (Space Dithered Sigma-Delta Modulation) for performance improvement of a buck converter. The PWM (Pulse Width Modulation) has a drawback in that power spectrum tends to be concentrated around the switching frequency. The resulting harmonic spikes cause a EMI(Electromagnetic Interference) and switching loss in semiconductor, etc. The 1st-order SDSDM scheme is a kind of DSDM for reducing these harmonic spikes. In this scheme, a switching frequency is spread through random dither generator placed on input part. In experimental result, the proposed 2nd-order SDSDM is confirmed by applying to a buck converter.

• 보존과학연구
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• s.19
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• pp.23-34
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• 1998

Bokam-ri site was excavated from July 1996 to September 1998 and archaeologically assumed to be grouped with tombs of Mahan period. Among these groups, Tomb No. 3 had built up with stone chamber and found one pair of gilted footware near the jar coffin. This footware was severely corroded and cracked so transfered it gently with soil. Radiography film of this footware showed spike decorations on the bottom and fish-shapped ornament. Gilted footware was consolidated with soil using Paraloid B72 10%~15%solution and cleaned using small tools and microscope. SV427 and HV427 as epoxy resin and Araldite(rapid type) used for joining and restoring. The fore part of gilted footware was connected with nails and folded “L” shape to introduce the bottom material. Tortoise-shell design and flower ornaments appeared on the surface and fish-shaped ornaments, spikes and spangles on the bottom. It was found that 7 spikes and 5 fish-shaped ornaments remained well. Especially, Fish-shaped ornaments were firstly found in the gilted footware and appraised archaeologically important materials.

• Natural Product Sciences
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• v.13 no.4
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• pp.359-364
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• 2007

Three known ${\alpha}$-amyrin triterpenoids, ursolic acid (1), $2{\alpha},3{\alpha}$-dihydro xyurs-12-ene-28-oic acid (2) and euscaphic acid (3), and ${\beta}$-amyrin triterpenoid, $3{\beta}$-hydroxyolean-5,12-diene (4), and ${\alpha}$-spinasterol (5) have been isolated from the fractionated n-butanol extracts of the spikes of Prunella vulgaris var. lilacina, guided by DNA topoisomerases I and II inhibitory activities and cytotoxic activity against human cancer cells. Their structures were elucidated on the basis of spectroscopic and chemical methods. Compound 4 exhibited significant cytotoxic activity against human colon adenoblastoma (HT-29), and 5 showed DNA topoisomerase I and II inhibitions.

• Journal of Power Electronics
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• v.19 no.4
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• pp.894-906
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• 2019

In this paper, a DC-DC converter is proposed based on the Cuk converter. The proposed converter has high efficiency and it can be used in multilevel DC-DC converters. A reduction of the inductors size in comparison to Cuk converter and a reduction in the inductors resistance negative effects on efficiency are the important points of the proposed converter. Its voltage ripple is reduced when compared to other converters. Its output voltage has a high quality and does not contain spikes. A theoretical analysis demonstrates the positive points of the proposed converter. The design and analysis of the converter are done in continues conduction mode (CCM). Experiments confirm the obtained theoretical equations. The proposed converter voltage gain is similar to that of a conventional Boost converter. As a result, they are compared. The comparison illustrates the advantages of the proposed converter and its higher quality. Furthermore, a prototype of the proposed converter and its combination with a 2x multiplier are built in the lab. Experimental results validate the analysis. In addition, they are in good agreements with each other.

• Clinical and Experimental Pediatrics
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• v.50 no.9
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• pp.896-900
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• 2007

Purpose : The aim of this study was to investigate the speech problems in benign rolandic epilepsy (BRE) according to the seizure focus in EEG and semiology. Methods : Twenty three patients [right origin (13 patients) or left side (10 patients)] who met the BRE criteria by International League Against Epilepsy (ILAE) were prospectively enrolled. We excluded the patients who had abnormal MRI or showed both side spikes in EEG. Computerized Speech Lab was used to assess the speech characteristics of the patients. Results : The error pattern of laryngeal articulation in BRE was exclusively substitution of stop consonants, these errors showed more frequent in the left group (16.0% vs 25.5%). Voice onset time (VOT) of stop consonants and Total duration (TD) of word in both groups were prolonged than normal control group, especially in left group (P<0.05). The first formant of vowel /o/ and second formant of /e/ were significantly decreased in left group (P<0.05). The right group scored wider on pitch range ($192.9{\pm}54.0Hz$) and energy range in spontaneous speech ($14.2{\pm}6.4db$) than the left group ($233.3{\pm}12.5Hz$, $19.4{\pm}9.3db$, respectively, P>0.05). Duration of counting (5 to 9) in left group slower than right group ($8.6{\pm}1.7$ vs $7.9{\pm}1.8sec$). Conclusion : Our data suggested that interictal spikes and seizures in either centrotemporal sides, especially left side group, may induce speech problems. We recommend the logopedic and phoniatric evaluations of speech in BRE patients.

• Clinical and Experimental Pediatrics
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• v.46 no.9
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• pp.893-897
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• 2003

Purpose : Benign childhood epilepsy with centrotemporal spikes(BECT) is characterized by an excellent prognosis. Therefore, the necessity for the use of antiepileptic drugs is controversial. The object of this study is to know about the long-term follow-up of BECT, comparing daily treatment with antiepileptic drug(AED) versus no medication. Methods : We retrospectively studied 56 cases of BECTs, examined at Pediatric Neurology Clinic, Korea University Medical Center as reference study time, August 2002. Thirty-eight patients didn't have mediation(group I), while eighteen patients received one or two AED(group II). We evaluated demographics, clinical manifestations at diagnosis, EEG findings and clinical courses in groups I & II. Results : There was no significant differences of sex, age, seizure frequency, seizure type, seizure onset time, family history and EEG findings between group I & II. The reasons to start AED were : parents' anxiety(three cases), frequent seizure(12 cases) and daytime seizure(three cases). There was no evolution of status epilepticus and no difficulty in school performance. Conclusion : AED treatment was of no advantage and long-term prognosis was good regardless of treatment strategy. So it is advisable not to choose AED as the first line of therapy, provided that the patient himself/herself or the family understands the benign nature of BECT.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.156-163
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• 2020

The purpose of this study was to select the wheat varieties, among 8 domestic cultivates, that are suitable, for use as grain feed at paddy fields in the Honam region. The seeds of wheat were sown and harvested in Wanju County. Among the wheat varieties, "Jojoong" was the earliest for its heading date on April 15, and it showed the earliest day for the maturing date on May 24. The heading date of "Baegjong" was the same as that for "Keumkang" on April 18, and the maturing date was one day later than that for "Keumkang" on May 29. But there was no significant difference of heading and maturing dates among the 8 wheat varieties. The lowest number of spikes/㎡ was 513/㎡ of "Goso", and the highest number of spikes/㎡ was 974/㎡ of "Chongwoo". The spikes/㎡ and yield of "Baegjon" was 542kg/10a and it was the highest yielding variety among the 8 wheat varieties. The chemical compositions of DM (dry matter) and CP (crude protein) on rumen digestibility were not significantly different among the 8 wheat varieties. Furthermore, rumen digestibility of DM and CP, and the nutrients value were slightly higher than those of corn. The domestic 8 wheat varieties for grain feed, with their high nutrient qualities, could eventually replace imported grain feed and wheat grain feed. These 8 varieties are cost-effective feed and paddy field fodder for livestock farmers.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.5
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• pp.481-490
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• 1999

To investigate the changes in the responses of vestibular neurons with time during vestibular compensation, the resting activity and dynamic responses of type I and II neurons in the medial vestibular nuclei to sinusoidal angular acceleration were recorded following unilateral labyrinthectomy (ULX) in Sprague-Dawley rats. The unitary extracellular neuronal activity was recorded from the bilateral medial vestibular nuclei with stainless steel microelectrodes of $3{\sim}5\;M{\Omega}$ before ULX, and 6, 24, 48, 72 hours, and 1 week after ULX under pentobarbital sodium anesthesia (30 mg/kg, i.p.). Gain (spikes/s/deg/s) and phase (in degrees) were determined from the neuronal activity induced by sinusoidal head rotation with 0.05, 0.1, 0.2, and 0.4 Hz. The mean resting activity before ULX was $16.7{\pm}8.6$ spikes/s in type I neurons $(n=67,\;M{\pm}SD)$ and $14.5{\pm}8.4$ spikes/s in type II neurons (n=43). The activities of ipsilateral type I and contralateral type II neurons to the lesion side decreased markedly till 24 hr post-op, and a significant difference between ipsilateral and contralateral type I neurons sustained till 24 hr post-op. The gain at 4 different frequencies of sinusoidal rotation was depressed in all neurons till 6 or 24 hr post-op and then increased with time. The rate of decrease in gain was more prominent in ipsilateral type I and contralateral type II neurons immediately after ULX. Although the gain of those neurons increased gradually after 24 hours, it remained below normal levels. The phase was significantly advanced in all neurons following ULX. These results suggest that a depression of activities in ipsilateral type I and contralateral type II neurons is closely related with the occurrence of vestibular symptoms and restoration of activities in those neurons ameliorates the vestibular symptoms.

• Journal of Biomedical Engineering Research
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• v.25 no.5
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• pp.361-367
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• 2004

The axial compressive strength, relative 3-D stability and osteoconductive shape design of an intervertebral fusion cage are important biomechanical factors for successful intervertebral fusion. Changes in the stress distribution of the vertebral end plate and in cage stability due to changes in the spike shape of a newly contrived box-shaped fusion cage are investigated. In this investigation, the initial contact of the cage's spikes with the end plate and the penetration of the cage's spikes into the end plate are considered. The finite element analysis is conducted to study the effects of the cage's spike height, tip width and angle on the stress distribution of the vertebral end plate, and the micromigration of the cage in the A-P direction. The stress distribution in the end plate is examined when a normal load of 1700N is applied to the vertebra after inserting 2 cages. The micromigration of the cage is examined when a pull out load of l00N is applied in the A-P direction. The analysis results reveal that the spike tip width significantly influences the stress concentration in the end plate, but the spike height and angle do not significantly influence the stress distribution in the end plate touching the cage's spikes. In addition, the analysis results show that the micromigration of the cage can be reduced by adjusting the spike angle and spike arrangement in the A-P direction. This study proposes the optimal shape of an intervertebral fusion cage, which promotes bone fusion, reduces the stress concentration in a vertebral end plate, and increases mechanical stability.

• Korean Journal of Environmental Biology
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• v.32 no.1
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• pp.49-57
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• 2014

Orb-web spiders can be considered as an effective bio-indicative animal to monitor the ecological air pollution of certain habitat since they have limited shifting ability during their life spans. In this study we revealed the fine structural characteristics of booklung in the orb-web spider Nephila clavata, and its bio-indicative significance in the monitoring environmental asbestos exposure. The high resolution scanning electron microscopy results suggest that the cuticular spikes near the atrium could be act as an effective filtering structure for dust materials. Furthermore, inner cuticular spikes which protruded across the air sacs, have the functions not only sustaining appropriate respiratory volume of each air sac but also help to enhance respiratory capacity by maximizing the gross surface area for gas exchange. Interestingly, in spite of short exposure, the asbestose fibrils were effectively captured on the surface of the atrial cuticular spikes. Furthermore, histologic damages were observed due to penetration of asbestos fibrils through air sacs and fixed on the hemolymph space. In addition, although accumulated mass of hemocytes were observed near the fibrils, there were no asbestos bodies or coagulated hemocytes were found on the surface of the fibrils, This could be mainly due to the short exposure period towards asbestos. Briefly, these results indicate the spider's booklung could be valuable tool in the detection ecological air pollutants.