• Applied Chemistry for Engineering
• /
• v.21 no.4
• /
• pp.469-474
• /
• 2010

Wood has an essential drawback such as high combustion ability. The purpose of this paper is to examine the combustion properties of the quercus variabilis and zelkova serrata dried at room temperature. The cone calorimeter (ISO 5660-1) was used to determine the heat release rate (HRR) and fire smoke index, as well as CO/$CO_2$ production and smoke obscuration. The total heat release (THR), $140.2\;MJ/m^2$ of the quercus variabilis under an external $50\;kW/m^2$ was high in comparison with THR $85.7\;MJ/m^2$ for the zelkova serrata. Furthermore, the quercus variabilis has high total smoke production (TSP), $3.50\;m^2$ compared with TSP $0.65\;m^2$ of zelkova serrata. Thease results depend on the bulk density of tested wood species. In addition, the CO/$CO_2$ production ratio of zelkova serrata and quercus variabilis was measured as 0.053, 0.043, respectively. Also, zelkova serrata showed an increase of fire-resistance attributed to char formation compared with that of quercus variabilis.

• Publications of The Korean Astronomical Society
• /
• v.27 no.4
• /
• pp.265-270
• /
• 2012

Many observations have found evidence of the presence of a large number of heavily obscured Active Galactic Nuclei (AGNs). However, the nature of this population is only poorly understood because heavy obscuration by dust prevents one from finding them at optical wavelengths. Mid-infrared AGN searches can overcome this obstacle by penetrating through dust and by detecting direct emission from the dust torus. Thus, we can identify most of the AGN population, including type-2 and buried AGNs. Using the AKARI mid-infrared all-sky survey, we performed an AGN search in the nearby universe. Utilizing the 2MASS photometry, we selected mid-infrared-excess sources and carried out near-infrared spectroscopic observations in the AKARI Phase 3. During these follow-up observations, we have found three galaxies that show strong near-infrared red continuum from hot dust with a temperature of about 500 K, but do not show any AGN features in other wavelengths. The most suitable explanation of near-infrared continuum is the presence of central AGNs. Therefore, we conclude that they are AGNs obscured by dust. We performed X-ray observations of the two galaxies with SUZAKU. No detections in the 0.4-10 keV suggest that the column density may be much higher than $N_H=10^{23.5}cm^{-2}$. Comparing the masses of the host galaxies with those of the SDSS AGNs, we find that the host galaxies of the dusty AGNs discovered with AKARI are less massive populations than those of optically selected AGNs.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.36 no.5
• /
• pp.472-482
• /
• 2008

A modulation transfer function(MTF) tree is established to estimate the overall MTF of an observation satellite and to analyze the image performance. Basic MTF models relevant to each MTF tree component are represented as mathematical relationship between optics-structural dynamics, thermal deformation, attitude and dynamic characteristics of a satellite and the effects due to the space environment. The Basic MTF models consist of diffraction limited MTF with central obscuration, aberration, defocus, line-of-sight(LOS) jitter, linear motion, detector integration, and so forth. Performance estimation is demonstrated for a virtual earth-observation satellite in order to validate the constructed modeling method. The proposed models enable the system engineers to calculate the overall system MTF and to determine the crucial design parameters that affect the image performance in the conceptual design phase of an observation satellite.

• Journal of Korean Society of Forest Science
• /
• v.98 no.3
• /
• pp.319-323
• /
• 2009

One of the limitation of wood as building material is its flammability. The purpose of this paper is to examine the combustion properties of the pinus rigida and castanea savita which are grown in Korea and meet the desirable characteristics for use of construction materials. The cone calorimeter (ISO 5660-1) was used to determine the heat release rate (HRR) and fire smoke index, as well as CO and $CO_2$ production and smoke obscuration. The $HRR_{mean}$ of the castanea savita at $50kW/m^2$ was $160.7kW/m^2$ in comparison with $150.7kW/m^2$ for the pinus rigida. Castanea savita showed an increase of retardant properties attributed to char formation compared with that of pinus rigida. The castanea savita has high $CO_{peak}$ yield and high CO/$CO_2$ yield compared with that of pinus rigida.

• Journal of Korean Neurosurgical Society
• /
• v.42 no.1
• /
• pp.16-19
• /
• 2007

Objective : This report describes the clinical study of the surgical method of lateral third infraclavicular implantation of vagal nerve stimulation (VNS) generator through the axillary wrinkle incision. Methods : In a retrospective study, the data for 20 patients with medically intractable epilepsy treated by this approach were examined. The mean age was 31.4 years (range : 14-50), and the mean follow-up period was 12.15 months (range : 4-21 months). The male to female ratio was 2.3 : 1. The subcutaneous pocket for the generator was located in the lateral third infraclavicular area through the axillary wrinkle. Our method was a modification of the standard VNS generator implantation in the mid-infraclavicular pocket through anterior axillary incision. Results : There were the excellent or good cosmetic satisfaction in 95% of the cases and fair in 5%. The generator was located outside the lung field in 15%, periphery of the lung field in 45%, and crossed over the lung field in 40%. Discomfort from shoulder motion occurred transiently in 35% of cases. Other complications were minimal. Conclusion : These results demonstrate that the lateral third infraclavicular apporach will offers cosmetic benefits and reduction of obscuration of the lung field without serious complications. Thus, this technique provides an attractive alternative among the surgical techniques for the vagal nerve stimulation.

• Fire Science and Engineering
• /
• v.31 no.2
• /
• pp.44-51
• /
• 2017

Accurate predictions of the activation time for smoke detectors using a fire simulation is are required to ensure the reliability of the RSET (Required Safe Egress Time) calculation in the process of PBD (Performance-Based Design). The objective of this study was to enhance the accuracy of input parameters for the numerical models of smoke detector based on the FDS. To this end, a Fire Detector Evaluator (FDE) developed in previous studies was improved. The uniformities of flow and smoke inside the FDE were improved and accurate measurements of the obscuration per meter (OPM) related to detector operation were also performed through a decrease in the forward scattering of smoke particles. The input parameters using the improved FDE showed a significant difference from the previous FDE quantitatively. In particular, a larger difference was found in a photoelectric detector compared to an ionization detector. Considering that the operating conditions of smoke detectors are affected by the detector type, combustibles, smoke particulars, and color, the database (DB) on the input parameters for various detectors and combustibles should be built to improve the reliability of PBD in future studies.

• Proceedings of the KSRS Conference
• /
• 1998.09a
• /
• pp.313-318
• /
• 1998

Electro-Optical Camera(EOC) is the main payload of Korea Multi-Purpose SATellite(KOMPSAT) with the mission of cartography to build up a digital map of Korean territory including Digital Terrain Elevation Map(DTEM). This instrument which comprises EOC Sensor Assembly and EOC Electronics Assembly produces the panchromatic images of 6.6 m GSD with a swath wider than 17 km by push-broom scanning and spacecraft body pointing in a visible range of wavelength, 510 ~ 730 nm. The high resolution panchromatic image is to be collected for 2 minutes during 98 minutes of orbit cycle covering about 800 km along ground track, over the mission lifetime of 3 years with the functions of programmable rain/offset and on-board image data storage. The image of 8 bit digitization, which is collected by a full reflective type F8.3 triplet without obscuration, is to be transmitted to Ground Station at a rate less than 25 Mbps. EOC was elaborated to have the performance which meets or surpasses its requirements of design phase. The spectral response the modulation transfer function, and the uniformity of all the 2592 pixel of CCD of EOC are illustrated as they were measured for the convenience of end-user. The spectral response was measured with respect to each gain setup of EOC and this is expected to give the capability of generating more accurate panchromatic image to the EOC data users. The modulation transfer function of EOC was measured as greater than 16% at Nyquist frequency over the entire field of view which exceeds its requirement of larger than 10%, The uniformity that shows the relative response of each pixel of CCD was measured at every pixel of the Focal Plane Array of EOC and is illustrated for the data processing.

• Fire Science and Engineering
• /
• v.24 no.3
• /
• pp.86-92
• /
• 2010

One of the limitation of wood as building materials is its flammability. The purpose of this paper is to examine the combustion properties of the Pinus rigida and Castanea savita which are grown in Korea and meet the desirable characteristics for use of construction materials. The cone calorimeter (ISO 5660-1) was used to determine the heat release rate (HRR) and fire smoke index, as well as CO and $CO_2$ production and smoke obscuration. The $HRR_{mean}$ of the Castanea savita and Pinus rigida at $50\;kW/m^2$ of radiant heat flux was $70.4\;kW/m^2$ and $68.5\;kW/m^2$. Furthermore, the THR of Castanea sativata was 120.8 MJ/kg and it was higher than the THR of Pinus rigida ($81.9\;MJ/m^$). These results are depend on the bulk density of tested wood species. The Castanea savita has high $CO_{mean}$ yield and high CO/$CO_2$ yield compared with that of Pinus rigida.

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.1
• /
• pp.35.4-35.4
• /
• 2019

We have conducted a 22 GHz very long baseline interferometry (VLBI) survey of 281 local (z < 0.05) active galactic nuclei (AGNs) selected from the Swift Burst Alert Telescope (BAT) 70-month ultra hard X-ray (14-195 keV) catalog. The main goal is to investigate the relation between the strengths of black hole accretion and the parsec-scale nuclear jet, which is expected to tightly correlate but has not been observationally confirmed yet. The BAT AGN Spectroscopic Survey (BASS) provides the least biased AGN sample against obscuration including both Seyfert types, hence it makes an ideal parent sample for studying the nuclear jet properties of an overall AGN population. Using the Korean VLBI Network (KVN), the KVN and VERA Array (KaVA), and the Very Long Baseline Array (VLBA), we observed 281 objects with a 22 GHz flux > 30 mJy, detecting 11 targets (~4% of VLBI detection rate). This implies that the fraction of X-ray AGNs which are currently ejecting a strong nuclear jet is very small. Although our 11 sources span a wide range of pc-scale morphological types, from compact to complex, they lie on a tight linear relation between accretion luminosity and nuclear jet luminosity. Our finding may indicate that the power of nuclear jet is directly responsible for the amount of black hole accretion. We also have probed the fundamental plane of black hole activity in VLBI scale (e.g., few milli-arcsecond). The results from our high-frequency VLBI radio study support that the change of jet luminosity and size follows what is predicted by the AGN evolution scenario based on the Eddington ratio (ƛ$_{Edd}$) - column density ($N_H$) plane, proposed by a previous study.

• Journal of Astronomy and Space Sciences
• /
• v.18 no.1
• /
• pp.33-42
• /
• 2001

In the spectrum of the young bipolar planetary nebula M2-9 obtained from the 1.5m telescope at the Cerro Tololo Inter-American Observatory, we detected the He II feature at 6545 $\AA$ that are proposed to be formed via Raman scattering by atomic hydrogen. However, in the same spectrum, the He II emission lines at 6527 $\AA$ and 6560 $\AA$ are absent, which implies that the He II emission region is hidden from our line of sight and that the H I scattering region is pretty much extended not to be obscured entirely. We performed photoionization computations to estimate the physical size of the He II emission line region to be $10^{16}cm$, from which the location and dimension of the obscuring circumstellar region are inferred and the temperature of the central star must exceed $10^5K$. The angular size of the circumstellar region responsible for the obscuration of the He II emission region is ~1" with the assumption of the distance 01 kpc to M2-9, which is consistent with the recent image of M2-9 obtained with the Hubble Space Telescope.