• The Journal of Engineering Geology
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• v.27 no.3
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• pp.305-312
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• 2017

The most effective way to distinguish subsurface interfaces that produce various geophysical responses is through the integration of multiple geophysical methods, with each method detecting both a complementary and unique set of distinct physical properties relating to the subsurface. In this study, shallow seismic reflection (SSR) and ground penetrating radar (GPR) surveys were conducted at the Cheongju-Gadeok site of the Korea National Groundwater Monitoring Network to map the water table, which was measured at 12 m depth during the geophysical surveys. The water table proved to be a good target reflector in both datasets, as the abrupt transition from the overlying unsaturated weathered rock to the underlying saturated weathered rock yielded large acoustic impedance and dielectric constant contrasts. The two datasets were depth converted and integrated into a single section, with the SSR and GPR surveys conducted to ensure subsurface imaging at approximately the same wavelength. The GPR data provided detailed information on the upper ~15 m of the section, whereas the SSR data imaged structures at depths of 10-45 m. The integrated section thus captured the full depth coverage of the sandy clay, water table, weathered rock, soft rock, and hard rock structures, which correlated well with local drillcore and water table observations. Incorporation of these two geophysical datasets yielded a synthetic section that resembled a simplified aquifer model, with the best-fitting seismic velocity, dielectric constant, and porosity of the saturated weathered layer being $v_{seismic}=1000m/s$, ${\varepsilon}_r=16$, and ${\phi}=0.32$, respectively.

• Journal of Korean Neurosurgical Society
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• v.55 no.6
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• pp.370-374
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• 2014

To present a case of cauda equina syndrome (CES) caused by chronic inflammatory demyelinating polyneuropathy (CIDP) which seemed clinically similar to Charcot-Marie-Tooth disease type1 (CMT1). CIDP is an immune-mediated polyneuropathy, either progressive or relapsing-remitting. It is a non-hereditary disorder characterized by symmetrical motor and sensory deficits. Rarely, spinal nerve roots can be involved, leading to CES by hypertrophic cauda equina. A 34-year-old man presented with low back pain, radicular pain, bilateral lower-extremity weakness, urinary incontinence, and constipation. He had had musculoskeletal deformities, such as hammertoes and pes cavus, since age 10. Lumbar spine magnetic resonance imaging showed diffuse thickening of the cauda equina. Electrophysiological testing showed increased distal latency, conduction blocks, temporal dispersion, and severe nerve conduction velocity slowing (3 m/s). We were not able to find genetic mutations at the PMP 22, MPZ, PRX, and EGR2 genes. The pathologic findings of the sural nerve biopsy revealed thinly myelinated nerve fibers with Schwann cells proliferation. We performed a decompressive laminectomy, intravenous IgG (IV-IgG) and oral steroid. At 1 week after surgery, most of his symptoms showed marked improvements except foot deformities. There was no relapse or aggravation of disease for 3 years. We diagnosed the case as an early-onset CIDP with cauda equine syndrome, whose initial clinical findings were similar to those of CMT1, and successfully managed with decompressive laminectomy, IV-IgG and oral steroid.

• Journal of Veterinary Clinics
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• v.31 no.4
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• pp.325-328
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• 2014

A 8-month-old female Maltese dog was presented with a history of heart murmur. In physical examination, grade 4/6 systolic murmur heard at the left heart base. Electrocardiography showed sinus arrhythmia, right axis deviation, deep S wave and splintered QRS complex. Thoracic radiography revealed enlarged right side heart and bulging of the main pulmonary artery. Echocardiography showed mild hypertrophy of right ventricle, a supravalvular stenosis, marked post-stenotic dilation of the main pulmonary artery and a moderately increased pulmonary arterial velocity through the stenotic area (4.4 m/s, pressure gradient of 78.7 mmHg). The dog was diagnosed with supravalvular pulmonic stenosis based on the diagnostic imaging findings. Medical management using ${\beta}1$-blocker and ACE inhibitor was started in this dog and this is first case report described diagnostic characteristic features of supravalvular pulmonic stenosis in korea.

• International Journal of High-Rise Buildings
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• v.1 no.1
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• pp.15-19
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• 2012

Occupant footfalls are often the most critical source of floor vibration on upper floors of buildings. Floor motions can degrade the performance of imaging equipment, disrupt sensitive research equipment, and cause discomfort for the occupants. It is essential that low-vibration environments be provided for functionality of sensitive spaces on floors above grade. This requires a sufficiently stiff and massive floor structure that effectively resists the forces exerted from user traffic. Over the past 25 years, generic vibration limits have been developed, which provide frequency dependent sensitivities for wide classes of equipment, and are used extensively in lab design for healthcare and research facilities. The same basis for these curves can be used to quantify acceptable limits of vibration for human comfort, depending on the intended occupancy of the space. When available, manufacturer's vibration criteria for sensitive equipment are expressed in units of acceleration, velocity or displacement and can be specified as zero-to-peak, peak-to-peak, or root-mean-square (rms) with varying frequency ranges and resolutions. Several approaches to prediction of floor vibrations are currently applied in practice. Each method is traceable to fundamental structural dynamics, differing only in the level of complexity assumed for the system response, and the required information for use as model inputs. Three commonly used models are described, as well as key features they possess that make them attractive to use for various applications. A case study is presented of a tall building which has fitness areas on two of the upper floors. The analysis predicted that the motions experienced would be within the given criteria, but showed that if the floor had been more flexible, the potential exists for a locked-in resonance response which could have been felt over large portions of the building.

• Proceedings of the Korean Geotechical Society Conference
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• 2007.09a
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• pp.623-634
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• 2007

The aim of this research is development and verification of resistivity seismic dilatometer (RSDMT) system. The resistivity module for obtaining resistivity-depth plot and seismic module for obtaining wave velocity-depth plot are attached to the conventional flat dilatometer testing equipment. To enhance reliability and repeatability of seismic part in RSDMT, automatic testing system including automatic surface source, PC based data acquisition system and operating program were developed. To obtain real resistivity value of soil, geometric factor for the array of electrodes in RSDMT was derived empirically. The verification studies for the developed RSDMT system were performed at the southeast side of Korea where soil improvement work is planned. SPT, CPT, geophysical subsurface imaging techniques and some laboratory tests were performed for the comparisons. As one penetration of RSDMT, various soil parameters could be obtained. The results of field test showed good repeatability and reliability in every part. From these studies, developed RSDMT system was checked and the effectiveness of this system was verified in light of proper evaluation of geotechnical characteristics of soft soil.

• Pediatric Infection and Vaccine
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• v.23 no.3
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• pp.236-239
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• 2016

$Guillain-Barr{\acute{e}}$ syndrome (GBS) is caused by antecedent infectious diseases in approximately two-thirds of cases. GBS is considered an autoimmune response. Among reported preceding infections, influenza virus is relatively rare. Several reports have identified antibodies related to GBS pathogenesis. However, no case report has described the detection of influenza virus in the cerebrospinal fluid (CSF) of a patient with GBS by polymerase chain reaction (PCR). Here we report the case of a 6-year-old girl who was diagnosed with influenza A 1 week prior and was treated with oseltamivir, after which she visited our hospital for headache and bilateral leg weakness that had persisted for 1 day. We diagnosed her with GBS based on physical and neurologic examination findings, CSF analysis, nerve conduction velocity test results, spinal magnetic resonance imaging, and detection of influenza A virus in her CSF by PCR. She was treated with intravenous immunoglobulin and her symptoms slowly improved. This case report suggests that GBS may be caused by influenza virus through penetration of the CSF.

• Journal of The Korean Astronomical Society
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• v.41 no.5
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• pp.121-137
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• 2008

We present optical and near-infrared imaging and long-slit spectroscopy for the blue compact dwarf galaxy (BCD) Mrk 49 in the Virgo Cluster. The surface brightness distribution analysis shows that Mrk 49 consists of an off-centered blue bright compact core of r = 10" and a red faint outer exponential envelope. The $H_{\alpha}$ image and color difference suggest that these two components have different stellar populations: a high surface brightness population of massive young stars and an underlying low surface brightness population of older stars. The redder near-infrared colors of the inner most region suggest that the near-infrared flux of Mrk 49 originates from evolved massive stars associated with the current star-forming activity. The total apparent magnitude is $B_T\;=\;14.32$ mag and the mean effective surface brightness is ${\mu}_{eff}(B)\;=\;21.56$ mag $arcsec^{-2}$. Long-slit spectroscopy shows that Mrk 49 rotates apparently as a solid body within r = 10" in a plane at position angle 55 degrees with an amplitude of about $20\;km\;sec^{-1}$. The measured radial velocity of Mrk 49 was derived as $1,535\;km\;sec^{-1}$; and the total mass of stars and gases is in the range of 3 to $6\;{\times}\;10^9\;M_{\odot}$. The mass-to-light ratios for the central region of Mrk 49 in I and B band are estimated 1.0 and 0.5, respectively. The upper limit of the dark matter to visible matter ratio seems to be < 5. The oxygen abundance is $12\;+\;\log(O/H)\;=\;8.21\;{\pm}\; 0.1$ which is about one quarter of the solar value while the relative helium abundance appears to be similar to that of the sun.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.41.1-41.1
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• 2010

IGRINS (the Immersion GRating Infrared Spectrograph) is a high resolution infrared spectrograph which is being developed by a collaboration of the University of Texas, the Korea Astronomy and Space Science Institute, and Kyung Hee University. The wavelength calibration unit of IGRINS will be situated between the telescope flange and IGRINS dewar. It will include Th-Ar hallow cathode lamp, optical elements, and gas absorption cell for the case that requires precise calibration (e.g., radial velocity observation). The system will also use a tungsten halogen lamp in an integrating sphere as a blackbody source for the flat-field imaging. IGRINS will be placed initially on the McDonald 2.7m Harlan J. Smith telescope and later on 4-8m class telescopes. We present an overview of the plan for the wavelength calibration sources and of the development process for the optical and mechanical design of the IGRINS calibration system.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.29.1-29.1
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• 2017

I present new near-infrared (NIR) photometry of globular cluster (GC) systems associated to a cD galaxy NGC 4874 in the core of the Coma cluster and 16 early-type galaxies in the Fornax and Virgo clusters of galaxies using the Infrared Channel of the Wide Field Camera 3 (WFC3/IR) on board the Hubble Space Telescope (HST). Combining these high-resolution NIR data with new HST Advanced Camera for Surveys (ACS) optical photometry for NGC 4874 and existing ACS GC catalogs from the ACS Fornax and Virgo Cluster Surveys, I have examined for the first time the GC systems in a statistically significant optical/NIR sample of galaxies spanning a wide range of luminosities and colors. A primary goal of this study is to explore empirically whether the distributions of purely optical and hybrid optical - NIR color indices for extragalactic GCs have different forms and whether the relations between these color indices are nonlinear, indicating that they behave differently with underlying metallicity. I find that some GC systems of large galaxies in our sample show color bimodalities that differ between the optical and optical - NIR colors, in the sense that they have disparate ratios of "blue" and "red" peak GCs, as well as differing ratios in their color dispersions. Consistent with these results, I find empirically that the dependence of hybrid optical-NIR color on purely optical color is nonlinear, with an inflection at intermediate metallicities. These findings underscore the importance of understanding the nature of galaxy-to-galaxy variations in the GC color distributions and color-color relations, as well as the exact forms of the color-metallicity transformations, in interpreting the observational data on GC color bimodality. Our ACS data for NGC 4874 shows that its GC system exhibits a very strong blue tilt, implying a very steep mass-metallicity scaling, and the centroid of this GC system is offset by $4{\pm}1kpc$ from the luminosity center of NGC 4874, in the direction of NGC 4872. Finally, I discuss the asymmetrical GC distribution around a dwarf elliptical galaxy in Coma that has a very high relative velocity with respect to the cluster mean at small clustercentric radius.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.2
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• pp.102-106
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• 2016

An experimental study on the flow characteristics under various laminar coflow diffusion flames was conducted with a particular focus on the buoyancy force exerted from gaseous hydrocarbon fuels. Methane ($CH_4$), ethylene ($C_2H_4$), and n-butane ($C_4H_{10}$) were used as the fuels. A coflow burner and the Schlieren imaging technique were used to observe the flow field of each fuel near the nozzle exit as well as the flow characteristics in the flames. The results show that a vortex with a density heavier than air appeared in n-butane near the nozzle exit with a strong negative buoyancy on the fuel steam. As the Reynolds number increased through the control of the fuel velocity of the n-butane flame, the vortices were greater and the vortex tips were moved up from the nozzle exit. In addition, the heated nozzle affected the flow fields of the fuel steam near the nozzle exit.