• Investigative Magnetic Resonance Imaging
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• v.19 no.4
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• pp.231-236
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• 2015

A 17-year-old girl presented with complaints of headache and decreasing vision of one month's duration, without any history of fever, weight loss, or any evidence of an immuno-compromised state. Her neurological examination was normal, except for papilledema. Laboratory investigations were within normal limits, except for a slightly increased Erythrocyte Sedimentation Rate (ESR). Non-contrast computerized tomography of her head revealed complex mass in left frontal lobe with a concentric, slightly hyperdense, thickened wall, and moderate perilesional edema with mass effect. Differential diagnoses considered in this case were pilocytic astrocytoma, metastasis and abscess. Magnetic resonance imaging (MRI) obtained in 3.0 Tesla (3.0T) scanner revealed a lobulated outline cystic mass in the left frontal lobe with two concentric layers of T2 hypointense wall, with T2 hyperintensity between the concentric ring. Moderate perilesional edema and mass effect were seen. Post gadolinium study showed a markedly enhancing irregular wall with some enhancing nodular solid component. No restricted diffusion was seen in this mass in diffusion weighted imaging (DWI). Magnetic resonance spectroscopy (MRS) showed increased lactate and lipid peaks in the central part of this mass, although some areas at the wall and perilesional T2 hyperintensity showed an increased choline peak without significant decrease in N-acetylaspartate (NAA) level. Arterial spin labelling (ASL) and dynamic susceptibility contrast (DSC) enhanced perfusion study showed decrease in relative cerebral blood volume at this region. These features in MRI were suggestive of brain abscess. The patient underwent craniotomy with excision of a grayish nodular lesion. Abundant acid fast bacilli (AFB) in acid fast staining, and epithelioid cell granulomas, caseation necrosis and Langhans giant cells in histopathology, were conclusive of tubercular abscess. Tubercular brain abscess is a rare manifestation that simulates malignancy and cause diagnostic dilemma. MRI along with MRS and magnetic resonance perfusion studies, are powerful tools to differentiate lesions in such equivocal cases.

• Elastomers and Composites
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• v.36 no.2
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• pp.111-120
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• 2001

Mechanical properties and their adhesion behavior with zinc- and brass-plated steel cords of natural rubber/acrylonitrile-butadiene blend compounds were investigated as a function of blend ratio. The Mooney viscosity and stress relaxation time were found to be lowered with increasing NBR content. Tensile modulus generally increased with increasing NBR content. Tensile stress at break stayed constant up to about 40 phr and showed minimum at $50{\sim}60 phr$, and thereafter increased with increasing NBR content. Strain at break decreased linearly below 50 phr, and above the level it showed nearly constant value. Based on the abrupt drops in elastic modulus and tan ${\delta}$ peak, the glass transition temperature of NR and NBR were found to be -55 and $-10^{\circ}C$, respectively. In the case of NR/NBR blend compounds, two distinct transition points were observed and each transition position was not affected by NBR level indicating an incompatible nature of NR/NBR blend system. The pullout force and rubber coverage decreased to the level of about 40% to that of pure m compound, when the 50 phr of NR was replaced by NBR. However, the pure NBR compound showed the comparable adhesion performance with NR(${\sim}90%$). The sulfur concentration was found to become lower with the increased NBR content at the adhesion interface based on the Auger spectrometer results, representing a lack of adhesion layer formation, and this was explained for a possible cause of low adhesion performance with adding NBR.

• Journal of the Korean Magnetics Society
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• v.9 no.5
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• pp.251-255
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• 1999

NiFe(60 $\AA$)/Co(0$\AA$$\leq$x$\AA$$\leq$15$\AA$)/Cu(60$\AA$)/Co(30$\AA$) spin valve thin films were prepared on 4$^{\circ}$ tilt-cut Si(111) substrates with a 50 $\AA$ thick Cu underlayer without applying any external magnetic field during the deposition, and the effects of inserted ultrathin Co layer on magnetic anisotropy and GMR properties of the NiFe(60 $\AA$)/Cu(60$\AA$)/Co(30$\AA$) spin valves were investigated. As the ultrathin Co layer was inserted into the NiFe/Cu interface of the spin valves, GMR ratio was increased from about 1.5% to 3.5%, and the easy axis of NiFe(60 $\AA$) layer was rotated by 90$^{\circ}$. Accordingly, it was aligned along the same direction with the easy axis of Co(30 $\AA$)layer. Therefore, squared R-H curves was obtained in the spin valves, which is favorable properties for the digital GMR devices such as MRAM. In order to investigate the change of magnetic anisotropy of NiFe layer of the spin valves in more details,XRD measurement was performed using NiFe(500 $\AA$) and NiFe(500 $\AA$)/Co(10 $\AA$) thin films on the same templates. Strong (220) NiFe peak was observed in both films regardless of the inserted Co layer, so it was thought that the variation of magnetic anisotropy of NiFe layer is from the interface effect, the change of interface from NiFe/Cu to NiFe/Co, rather than the volume effect such as the change of magnetocrystalline effect.

• Korean Journal of Clinical Laboratory Science
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• v.41 no.4
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• pp.145-152
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• 2009

Novel influenza A virus, subtype H1N1 of swine-lineage, has been transmitted rapidly to many regions of the world. Rapid detection of the virus is essential to instigate appropriate patient care and public health management and for disease surveillance. The aim of this study is to determine the prevalence of novel influenza A (H1N1) virus in Korea using reverse-transcription real time polymerase chain reaction (rRT-PCR). Novel H1N1 virus was detected in a total of 8,948 nasopharyngeal samples from patients with influenza-like illness throughout Korea from August to September 2009. RNA was extracted from $300{\mu}l$of sample using an RNA extraction kit (Zymo Research, CA, USA). In the present study, Genekam kit (Genekam, Duisburg, Germany) was used to detect novel H1N1 virus. Novel H1N1 virus was found in 1,130 samples from a total of 8,948 samples (12.6%). The highest frequency was found in 10- to 19-year-olds (M: 29.3% vs. F: 16.4%), followed by 20- to 29-year-olds (M: 17.9% vs. F: 15.4%), 40- to 49-year-olds (M: 6.5% vs. F: 8.1%), 50- to 59-year-olds (M: 6.0% vs. F: 5.5%), and 30- to 39-year-olds (M: 4.6% vs. F: 3.8%). The mean positive rate was higher in men than in women (M: 14.7% vs. F: 7.4%). Novel H1N1 virus showed the lowest prevalence in patients over 60 years old. The positive rate increased daily and showed a significant high peak in mid-September 2009. In 19 provinces of Korea, Cheonan (41.1%), Busan (37.3%), Gangneung (33.3%), Jinju (32.1%), Ulsan (24.6%), Deajeon (23.7%) areas showed high frequencies and other provinces were found less than 10% of novel H1N1 virus. Since reverse-transcription real time PCR assay is rapid, accurate, and convenient, it may assist public health laboratories in detecting novel H1N1 virus. Moreover, these data could be useful for the management of patients with influenza-like illness.

• Earthquakes and Structures
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• v.13 no.1
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• pp.59-66
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• 2017

Modern seismic codes rely on performance-based seismic design methodology which requires that the structures withstand inelastic deformation. Many studies have focused on the inelastic deformation ratio evaluation (ratio between the inelastic and elastic maximum lateral displacement demands) for various inelastic spectra. This paper investigates the inelastic response spectra through the ductility demand ${\mu}$, the yield strength reduction factor $R_y$, and the inelastic deformation ratio. They depend on the vibration period T, the post-to-preyield stiffness ratio ${\alpha}$, the peak ground acceleration (PGA), and the normalized yield strength coefficient ${\eta}$ (ratio of yield strength coefficient divided by the PGA). A new inelastic deformation ratio $C_{\eta}$ is defined; it is related to the capacity curve (pushover curve) through the coefficient (${\eta}$) and the ratio (${\alpha}$) that are used as control parameters. A set of 140 real ground motions is selected. The structures are bilinear inelastic single degree of freedom systems (SDOF). The sensitivity of the resulting inelastic deformation ratio mean values is discussed for different levels of normalized yield strength coefficient. The influence of vibration period T, post-to-preyield stiffness ratio ${\alpha}$, normalized yield strength coefficient ${\eta}$, earthquake magnitude, ruptures distance (i.e., to fault rupture) and site conditions is also investigated. A regression analysis leads to simplified expressions of this inelastic deformation ratio. These simplified equations estimate the inelastic deformation ratio for structures, which is a key parameter for design or evaluation. The results show that, for a given level of normalized yield strength coefficient, these inelastic displacement ratios become non sensitive to none of the rupture distance, the earthquake magnitude or the site class. Furthermore, they show that the post-to-preyield stiffness has a negligible effect on the inelastic deformation ratio if the normalized yield strength coefficient is greater than unity.

• Journal of the Korean Institute of Landscape Architecture
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• v.14 no.2
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• pp.81-90
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• 1986

The full grasp of recreation demand and factors affecting on recreation demand can be very important information for park planning and management. The object-tives of this study are to investigate factors affecting the fluctuation of urban park visitors and to analyze the relationship between these factors and the daily parti-cipations. The results were as follows; 1) The peak of monthly participations comes on May, April, August and October in order. And these months are specified as school picnic period and vacation of school children. 2) In correlation analysis, the variables such as ‘Day of a week(D)’, ‘Monthly mean temp.(T)’and ‘Monthly character(M)’have high correlations with ‘No. of visitors’in order. And it is better to categorize months by its charater(picnic period in school, vacation etc) than by seasons. 3) Candidate regression model were established, as for 1984 log U= 1.51 + 0.64D1 + 0.02T + 0.36W1 - 0.23M4 + 0.003SS + 0.24Ml($R^2$=0.5326) where, U=no. of daily visitors D1 = sunday.ho1iday(1), weekday(0) T=monthly mean temperature($^{\circ}C$) W1= weather (sunny.cloudy(1) , rainy (>5mm)(0)> M4=non vacations and non school picnic period(1) , if not (0) SS=monthly sunshining hours M1=summer vacation(1), if not(0) 4) The most important variable was ‘Day of a week’(sunday.holiday or not). And temperature, weather and monthly charcter(especially picnic period of school and vacation) were in turn, hence ‘Children's grand park’shows the use pattern of park.

• The Korean Journal of Quaternary Research
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• v.20 no.1 s.26
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• pp.9-27
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• 2006

The East Asian (China, Korea and Japan) summer monsoon precipitation and its variability are examined from the outputs of the 22 coupled climate models performing coordinated experiments leading to the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) following the multi-model ensemble (MME) technique. Results are based on averages of all the available models. The shape of the annual cycle with maximum during the summer monsoon period is simulated by the coupled climate models. However, models fail to simulate the minimum peak in July which is associated with northward shifts of the Meiyu-Changma-Baiu precipitation band. The MME precipitation pattern is able to capture the spatial distribution of rainfall associated with the location of the north Pacific subtropical high and the Meiyu-Changma-Baiu frontal zone. However precipitation over the east coast of China, Korea-Japan peninsular and the adjoining oceanic regions is underestimated. Future projections to the radiative forcing of doubled $CO_2$ scenario are examined. The MME reveals an increase in precipitation varying from 5 to 10 %, with an average of 7.8 % over the East Asian region at the time of $CO_2$ doubling. However the increases are statistically significant only over the Korea-Japan peninsula and the adjoining north China region. The increase in precipitation may be attributed to the projected intensification of the subtropical high, and thus the associated influx of moist air from the Pacific to inland. The projected changes in the amount of precipitation are directly proportional to the changes in the strength of the subtropical high. Further a possible increase in the length of the summer monsoon precipitation period from late spring through early autumn is suggested.

• Journal of Biosystems Engineering
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• v.34 no.2
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• pp.127-132
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• 2009

In the working population, muscle fatigue and musculoskeletal discomfort are common, which, in the case of insufficient recovery may lead to musculoskeletal pain. Workers suffering from musculoskeletal pains need to be rehabilitated for recovery. Isokinetic testing has been used in physical strengthening, rehabilitation and post-operative orthopedic surgery. Frequency analysis of electromyography (EMG) signals using the mean frequency (MNF) has been widely used to characterize muscle fatigue. During isokinetic contractions, EMG signals present strong nonstationarities. Hilbert-Haung transform (HHT) and autoregressive (AR) model have been known more suitable than Fourier or wavelet transform for nonstationary signals. Moreover, several analyses have been performed within each active phase during isokinetic contractions. Thus, the aims of this study were i) to determine which one was better suitable for the analysis of MNF between HHT and AR model during repetitive maximum isokinetic extensions and ii) to investigate whether the analysis could be repeated for sequential fixed epoch lengths. Seven healthy volunteers (five males and two females) performed isokinetic knee extensions at $60^{\circ}/s$ and $240^{\circ}/s$ until 50% of the maximum peak torque was reached. Surface EMG signals were recorded from the rectus femoris of the right thigh. An algorithm detecting the onset and offset of EMG signals was applied to extract each active phase of the muscle. Following the results, slopes from the least-square error linear regression of MNF values showed that muscle fatigue of all subjects occurred. The AR model is better suited than HHT for estimating MNF from nonstationary EMG signals during isokinetic knee extensions. Moreover, the linear regression can be extracted from MNF values calculated by sequential fixed epoch lengths (p> 0.0I).

• Polymer(Korea)
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• v.29 no.5
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• pp.457-462
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• 2005

Polyurethane foams (PUFs) were prepared from polymeric 4,4'-diphenylmethane diisocyanate (PMDI), mixed polyol with OH value of 480, silicone surfactant, three catalysts, and hydrofluorocarbon(HFC) as blowing agent. Balance (PC-8), gelling (33LV), and trimerization (TMR-2) catalysts were used. The effect of the catalysts on the physical properties of PUF with increase of isocyanate (NCO) index and aging time was investigated. The cell size of the PUF with PC-8 and 33LV slightly increased with an increase in NCO index from 100 to 170 but compressive strength did not change significantly. In case of trimerization catalyst, the compressive strength of PUF increased from 8.75 to 1$10.5 kg_f/cm^2$ and the cell size decreased with an increase in NCO index. The compressive strength of the PUF with 33LV increased from 9.21 to $10.15 kg_f/cm^2$ with an increase in aging time. However, there was no detectable change in the compressive strength of PUF with TMR-2. A possible interpretation of the results includes an additional cross-link reaction of non-reacted MDI and FTIR spectrum illustrated the change of NCO peak.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.78-78
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• 2000

다결정 실리콘-게르마늄 (poly-SiGe)은 태양전지 개발에 있어서 중요한 물질이다. 우리는 소량의 Ge(x=0.05)으로부터 다량의 Ge(x=0.67)을 함유한 수소화된 비정질 실리콘-게르마늄 (a-SiGe:H) 박막의 고상결정화 과정을 ESR (electron spin resonance)방법으로 조사해보았다. 먼저 PECVD 방법으로 Corning 1737 glass 위에 a-Si1-xGex:H 박막을 증착시켰다. 증착가스는 SiH4, GeH4 가스를 썼으며, 기판온도는 20$0^{\circ}C$, r.f. 전력은 3W, 증착시 가스압력은 0.6 Torr 정도이었다. 증착된 a-SiGe:H 박막은 $600^{\circ}C$ N2 분위기에서 다시 가열되어 고상결정화 되었고, 결정화 정도는 XRD (111) peak의 세기로부터 구해졌다. ESR 측정은 상온 x-band 영역에서 수행되었다. 측정된 ESR스팩트럼은 두 개의 Gaussian 함수로써 Si dangling-bond와 Ge dangling-bond 신호로 분리되었다. 가열 초기의 a-SiGe:H 박막 결함들의 스핀밀도의 증가는 수소 이탈에 기인하고, 또 고상결정화 과정에서 결정화된 정도와 Ge-db 스핀밀도의 변화는 서로 깊은 상관관계가 있음을 알 수 있었다. 특히 Ge 함유량이 큰 박막 (x=0.21, 0.67)에서 뿐만 아니라 소량의 Ge이 함유된 박막(x=0.05)에서도 Ge dangling-bond가 Si dangliong-bond 보다 고상결정화 과정에서 더 중요한 역할을 한다는 것을 알수 있었다. 또한 초기 열처리시 Si-H, Ge-H 결합에서 H의 이탈로 인하여 나타나는 Si-dangling bond, Ge-dangling bond 스핀밀도의 최대 증가 시간은 x 값에 의존하였는데 이러한 결과는 x값에 의존하는 Si-H, Ge-H 해리에너리지로 설명되어 질 수 있다. 층의 두께가 500 미만인 커패시터의 경우에 TiN과 Si3N4 의 계면에서 형성되는 슬릿형 공동(slit-like void)에 의해 커패시터의 유전특성이 파괴된다는 사실을 알게 되었으며, 이러한 슬릿형 공동은 제조 공정 중 재료에 따른 열팽창 계수와 탄성 계수 등의 차이에 의해 형성된 잔류응력 상태가 유전막을 기준으로 압축응력에서 인장 응력으로 바뀌는 분포에 기인하였다는 사실을 확인하였다.SiO2 막을 약화시켜 절연막의 두께가 두꺼워졌음에도 기존의 SiO2 절연막의 절연 파괴 전압 및 누설 전류오 비교되는 특성을 가졌다. 이중막을 구성하고 있는 안티퓨즈의 ON-저항이 단일막과 비교해 비슷한 것을 볼 수 잇는데, 그 이유는 TiO2에 포함된 Ti가 필라멘트에 포함되어 있어 필라멘트의 저항을 감소시켰기 때문으로 사료된다. 결국 이중막을 구성시 ON-저항 증가에 의한 속도 저하 요인은 없다고 할 수 있다. 5V의 절연파괴 시간을 측정한느 TDDB 테스트 결과 1.1$\times$103 year로 기대수치인 수십 년보다 높아 제안된 안티퓨즈의 신뢰성을 확보 할 수 있었다. 제안된 안티퓨즈의 이중 절연막의 두께는 250 이고 프로그래밍 전압은 9.0V이고, 약 65$\Omega$의 on 저항을 얻을수 있었다.보았다.다.다양한 기능을 가진 신소재 제조에 있다. 또한 경제적인 측면에서도 고부가 가치의 제품 개발에 따른 새로운 수요 창출과 수익률 향상, 기존의 기능성 안료를 나노(nano)화하여 나노 입자를 제조, 기존의 기능성 안료에 대한 비용 절감 효과등을 유도 할 수 있다. 역시 기술적인 측면에서도 특수소재 개발에 있어 최적의 나노 입자 제어기술 개발 및 나노입자를 기능성 소재로 사용하여 새로운 제품의 제조와 고압 기상 분사기술의 최적화에 의한 기능성 나노 입자 제조 기술을 확립하고 2차 오염 발생원인 유기계 항균제를 무기계 항균제로 대체할 수 있다. 이와 더불