• Journal of The Korean Astronomical Society
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• v.28 no.1
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• pp.31-43
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• 1995

We present UBVRI CCD photometry of the Type Ie supernova SN 19941 in M51 which was discovered on April 2, 1994 (UT). UBVRI CCD photometry of SN 1994 I were obtained for the period of the first two months from April 4, 1994, using the Seoul National University Observatory 60 cm telescope. The light curves of SN 19941 show several interesting features: (a) SN 19941 reaches the maximum brightness at B-band on April 8.23 (B = 13.68 mag), at V-band on April 9.10 (V = 12.89 mag), and at I-band on April 10.32 (I = 12.48 mag); (b) The light curves around the maximum brightness are much narrower than those of other types of supernovae; (c) The light curves after the peak decline more steeply than those of other types of supernovae; and (d) The colors get redder from $(V-R){\approx}0.2 mag ((V - I){\approx} 0.3 mag, (B - V){\approx}0.7 mag)$ on April 4 to $(V-R){\approx}0.6 mag ((V-1){\approx}0.9 mag, (B-V){\approx}1.3 mag)$ on April 18. Afterwards (V - R) colors get bluer slightly $(by\~0.005 mag/day)$, while (V-I) colors stay almost constant around $(V-1){\approx}1.0 mag$. The color at the maximum brightness is (B-V)=0.9 mag, which is $\~1$mag redder than the mean color of typical Type la supernovae at the maximum brightness. The light curves of SN 1994I are similar to those of the Type Ie supernova SN 1962L in NGC 1073. Adopting the distance modulus of $(m-M)_0 = 29.2 mag$ and the reddening of E(B - V) = 0.45 mag [Iwamoto et al. 1994, preprint for ApJ], we derive absolute magnitudes at the maximum brightness of SN 1994I, Mv(max) = -17.7 mag and MB(max) = -17.4 mag. This result shows that SN 1994I was $\~2$mag fainter at the maximum brightness compared with typical Type Ia supernovae. A narrower peak and faster decline after the maximum in the light curve of SN 1994I compared with other types of supernovae indicate that the progenitor of SN 1994I might be a lower mass star compared with those of other types of supernovae.

• Journal of the Korean Geotechnical Society
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• v.27 no.7
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• pp.47-57
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• 2011

The p-y curve has been used to design pile foundations subjected to lateral loading. Although the p-y curve has a large influence on the pile lateral behavior, p-y curves have not been clearly suggested. In this study, the p-y curve of clay was evaluated for drilled shafts in marine deposits by using 3-dimensional numerical analyses. First, the optimization study was performed to properly determine boundary extent, mesh size, and interface stiffness. The numerical modeling in the study was verified by comparing the calculated and the pile loading test results. Then, the p-y curves of single and group piles were evaluated from the parametric study. The selected parameters were pile diameter, pile Young's modulus and pile head fixed condition for a single pile, and pile spacing for group piles. Finally, the p-multiplier was evaluated by comparing the p-y curves of a single pile and group piles. As a result, the p-multiplier at pile spacing of 3D was 0.83, 0.67 and 0.78 for the front, middle, and back row piles, respectively, and showed values similar to those of O'Neill and Reese (1999). For the pile group with pile spacing larger than 60, the group effect can be ignorable.

• Korean Journal of Crystallography
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• v.4 no.1
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• pp.36-41
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• 1993

Small angle X-ray scattering was used to study on the oxopolymers of sols derived from BaTiethoxide. The growths of the oxopolymers in tools obtained with NH40H as catalyst and catalystfree sol are similar. Their radii of gyration are 1.66-2.08nm. They exhibit a mass fractal behavior with a dimension of 1.6, which is almost inde pendent with amount of NH40H addition. Sols catalyzed with CHSCOOH have greater radii of gyration of 3.24-4.OOnm. Their scattering curves are similar in the intermediate Q region, showing a mass fractal dimension of 1.8. The oxopolymers of the tools from the base and the neutral hydrolysis conditions may have a short chain structure.

• Architectural research
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• v.8 no.1
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• pp.77-84
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• 2006

In spite of enormous increase in data generation, its practical usage in the construction sector has not been prevalent enough compared to those of other industries. The author would explore the obstacles against efficient data application in the arena of expenditure forecasting, and suggest a forecasting method by applying Case-based Reasoning (CBR). The newly suggested method in the research, enables project managers to forecast monthly expenditures with less time and effort by retrieving and referring only projects of a similar nature, while filtering out irrelevant cases included in database. Among 99 projects collected, the cost data from 88 projects were processed to establish a new forecasting model. The remaining 10 projects were utilized for the validation of the model. From the comprehensive study, the choice of the numbers of referring projects was investigated in detail. It is concluded that selecting similar projects at 12~19 % out of the whole database will produce a more precise forecasting. The new forecasting model, which suggests the predicted values based on previous projects, is more than just a forecasting methodology; it provides a bridge that enables current data collection techniques to be used within the context of the accumulated information. This will eventually help all the participants in the construction industry to build up the knowledge derived from invaluable experience.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.4
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• pp.445-456
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• 2013

In this study, desalination by electrodialysis with ion exchange membranes was applied to synthetic waters with various ion concentrations and also for ground waters from coastal areas in Korea. Electrodialysis performance on the synthetic solutions showed the similar tendency in operation time and current curves, i.e., shorter operation time and higher maximum current with increasing applied voltages. The ED results of synthetic waters with different ion compositions, i.e., $Na_2SO_4$, $MgSO_4$, $CaSO_4$, at the similar conductivity condition, i.e., $1,250{\mu}s/cm$ revealed that effects of mono- and divalent ions on water quality and performance in electrodialysis were different. The divalent ions had less efficiency in the ED compared to monovalent sodium ions and also divalent calcium ions showed better performance than Mg ions. The electrodialysis on the ground waters produced high quality of drinking water. The groundwater from SungRoe however showed a buildup of membrane resistance. Organic matter concentrations and great portions of divalent ions in the groundwater were possible causes of the deteriorated performance.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.68.2-68.2
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• 2014

High Frequency Peakers (HFPs) are radio-loud Active Galactic Nuclei (AGN), which are regarded as being in the earliest evolutionary phase (102-103 years) of radio galaxies. They are expected to be small in size (< ~1 kpc) compared to their host galaxies (~a few 10s kpc), and have convex spectra, which are peaking at high radio frequency (> 5 GHz). Their size and spectral shape are the most obvious supporting evidence of extremely young ages. HFPs are therefore ideal targets to probe the earliest stage of radio sources. To date however, the young radio source classification has been relying mainly on the spectral shape which usually does not cover high enough frequencies where the true peak flux is located. Hence HFPs are often confused with blazars which may show a similar spectral shape and apparent compactness but are a somewhat evolved form of AGNs. Therefore, we have been challenging to identify HFPs among the sample of 19 candidates using the Korean VLBI Network (KVN) which enables us to extend the radio spectrum baseline up to 22 and 43 GHz. These are higher than the frequencies used in most previous studies of HFPs, allowing us to select genuine HFPs. By long-term monitoring of 18 epochs, we have also inspected the variability of the sample to select out blazars which are highly variable yet with a similar radio spectrum. In this work, we present the light curves and spectral properties of the HFP candidates. We discuss the results of our re-identification of HFPs.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.129-134
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• 2003

The importance of understanding the response of structural composites to impact and CAI cannot be overstated to develop analytical models for impact damage and CAI strength predictions. This paper presents experimental findings observed from quasi-static lateral load tests, low velocity impact tests, CAI strength and open hole compressive strength tests using 3mm thick composite plates ($[45/-45/0/90]_{3s}$ - IM7/8552). The conclusion is drawn that damage areas for both quasi-static lateral load and impact tests are similar and the curves of several drop weight impacts with varying energy levels (between 5.4 J and 18.7 J) fallow the static curve well. In addition, at a given energy the peak force is in good agreement between the static and impact cases. From the CAI strength and open hole compressive strength tests, it is identified that the failure behaviour of the specimens was very similar to that observed in laminated plates with open holes under compression loading. The residual strengths are in good agreement with the measured open hole compressive strengths, considering the impact damage site as an equivalent hole. The experimental findings suggest that simple analytical models for the prediction of impact damage area and CAI strength can be developed on the basis of the failure mechanism observed from the experimental tests.

• Geophysics and Geophysical Exploration
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• v.7 no.1
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• pp.7-13
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• 2004

In this paper, we demonstrate that Common Mid-Point (CMP) cross-correlation gathers of multi-channel and multi-shot surface waves give accurate phase-velocity curves, and enable us to reconstruct two-dimensional (2D) velocity structures with high resolution. Data acquisition for CMP cross-correlation analysis is similar to acquisition for a 2D seismic reflection survey. Data processing seems similar to Common Depth-Point (CDP) analysis of 2D seismic reflection survey data, but differs in that the cross-correlation of the original waveform is calculated before making CMP gathers. Data processing in CMP cross-correlation analysis consists of the following four steps: First, cross-correlations are calculated for every pair of traces in each shot gather. Second, correlation traces having a common mid-point are gathered, and those traces that have equal spacing are stacked in the time domain. The resultant cross-correlation gathers resemble shot gathers and are referred to as CMP cross-correlation gathers. Third, a multi-channel analysis is applied to the CMP cross-correlation gathers for calculating phase velocities of surface waves. Finally, a 2D S-wave velocity profile is reconstructed through non-linear least squares inversion. Analyses of waveform data from numerical modelling and field observations indicate that the new method could greatly improve the accuracy and resolution of subsurface S-velocity structure, compared with conventional surface-wave methods.

• Korean Journal of Bronchoesophagology
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• v.4 no.1
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• pp.64-72
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• 1998

This study aimed at observing the effect of diazepam on the contractility of trachealis muscle isolated from canine trachea, possible involvement of central or peripheral type benzodiazepine receptor, and the calcium related mechanism of action of diazepam. Trachealis muscle strips of 15 mm long were suspended in an isolated organ bath containing 1 ml of physiologic salt solution maintained at $37^{\circ}C$, and aerated with 95% $O_2$ /5% $CO_2$. Isometric myography was performed. Diazepam reduced the basal tone concentration dependently, and this inhibitory action was not affected by neither flumazenil, a central benzodiazepine receptor antagonist, nor PK11195, a peripheral benzodiazepine receptor antagonist. Pretreatment with diazepam showed the inhibitory effect on the concentration-response curves to agonists such as bethanechol, 5-hydroxytryptamine and histamine. Diazepam also caused concentration-related inhibition of contraction with potassium chloride 30 mM. The effect of diazepam on the basal tone and potassium chloride-induced contraction with calcium channel blockers were compared. Similar results were obtained in canine trachealis with verapamil, nifedipine and diltiazem. These results suggest that diazepam relax an airway muscle not via specific receptors but by a similar action as calcium channel blockers in canine trachealis muscle.

• Steel and Composite Structures
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• v.31 no.4
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• pp.409-417
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• 2019

The choice of individual material for industrial application is primarily based on knowledge of its behavior in similar applications and similar environmental conditions. Contemporary design implies knowledge of material behavior and knowledge in the area of structural analysis supported by large capacity computers. Bearing this in mind, this paper presents and analyzes the experimental results related to the mechanical properties of the material considered (30CrNiMo8/1.6580/AISI 4340) at different temperatures as well as its creep and fatigue behavior. All experimental tests were carried out as uniaxial tests. The test results related to the mechanical properties are presented in the form of engineering stress-strain diagrams. The results related to the creep behavior of the material are shown in the form of creep curves, while the fatigue of the material is shown in the form of stress - life (S - N) diagram. Based on these experimental results, the values of the following properties are determined: ultimate tensile strength (${\sigma}_{m,20}=696MPa$), yield strength (${\sigma}_{0.2,20}=355.5MPa$), modulus of elasticity ($E_{,20}=217GPa$) and fatigue limit (${\sigma}_{f,20,R=-1}=280.4MPa$). Results related to fatigue tests were obtained at room temperature and stress ratio R = -1.