• Fire Science and Engineering
• /
• v.15 no.4
• /
• pp.34-40
• /
• 2001

The spontaneous ignition of hydroxypropyl methyl cellulose(HPMC) was investigated at constant ambient temperature in the oven and minimum ignition temperature of dust clouds with Godbret-Creenwald Furnace respectively, In the experiments of the vessel filled with sample. the larger the vessel was the lower the spontaneous ignition temperature and ambient temperature was calculated from the Frank-Kamenetskii thermal ignition theory. The minimum ignition temperature for the dust cloud state was found under 21% oxygen concentration. At the experiment with the change of oxygen concentration, HPMC was not ignite at 10% $O_2$and so the limiting oxygen concentration was obtained at 10%.

• Atmosphere
• /
• v.30 no.1
• /
• pp.75-89
• /
• 2020

Current in-situ airborne probes that measure the sizes of ice crystals smaller than 50 ㎛ are based on the concept that the measured intensity of light scattered by a particle in the forward and/or backward direction can be converted to particle size. The relationship between particle size and scattered light used in forward scattering probes is based on Mie theory, which assumes the refractive index of particle is known and all particles are spherical. Not only are small crystals not spherical, but also there are a wide variety of non-spherical shapes. Although it is well known that the scattering properties of non-spherical ice crystals differ from those of spherical shapes, the impacts of non-sphericity on derived in-situ particle size distributions are unknown. Thus, precise relationships between the intensity of scattered light and particle size and shape are required, as based on accurate calculations of scattering properties of ice crystals. In this study, single-scattering properties of ice crystals smaller than 50 ㎛ are calculated at a wavelength of 0.55 ㎛ using a numerically exact method (i.e., discrete dipole approximation). For these calculations, hexagonal ice crystals with varying aspect ratios are used to represent the shapes of natural small ice crystals to determine the errors caused by non-spherical ice crystals measured by forward scattering probes. It is shown that the calculated errors in sizing nonspherical ice crystals are at least 13% and 26% in forward (4~12°) and backward (168~176°) directions, respectively, and maximum errors are up to 120% and 132%.

• Korean Journal of Remote Sensing
• /
• v.22 no.1
• /
• pp.75-85
• /
• 2006

This paper has dealt with a data fusion for the problem of land-cover classification using multisensor imagery. Dempster-Shafer evidence theory has been employed to combine the information extracted from the multiple data of same site. The Dempster-Shafer's approach has two important advantages for remote sensing application: one is that it enables to consider a compound class which consists of several land-cover types and the other is that the incompleteness of each sensor data due to cloud-cover can be modeled for the fusion process. The image classification based on the Dempster-Shafer theory usually assumes that each sensor is represented by a single channel. The evidential approach to image classification, which utilizes a mass function obtained under the assumption of class-independent beta distribution, has been discussed for the multiple sets of mutichannel data acquired from different sensors. The proposed method has applied to the KOMPSAT-1 EOC panchromatic imagery and LANDSAT ETM+ data, which were acquired over Yongin/Nuengpyung area of Korean peninsula. The experiment has shown that it is greatly effective on the applications in which it is hard to find homogeneous regions represented by a single land-cover type in training process.

• Publications of The Korean Astronomical Society
• /
• v.20 no.1 s.24
• /
• pp.7-10
• /
• 2005

We have calculated 2448 interstellar cloud models to investigate the formation and destruction of high rotational level $H_2$ according to the combinations of five physical conditions: the input UV intensity, the $H_2$ column density, cloud temperature, total density, and the $H_2$ formation rate efficiency. The models include the populations of all the accessible states of $H_2$ with the rotational quantum number J < 16 as a function of depth through the model clouds, and assume that the abundance of $H_2$ is in a steady state governed primarily by the rate of formation on the grain surfaces and the rates of destruction by spontaneous fluorescent dissociation following absorption in the Lyman and Werner band systems. The high rotational levels J = 4 and J = 5 are both populated by direct formation into these levels of newly created molecules, and by pumping from J = 0 and J = 1, respectively The model results show that the high rotational level ratio N(4)/N(0) is proportional to the incident UV intensity, and is inversely proportional to the $H_2$ molecular fraction, as predicted in theory.

• Proceedings of the KSR Conference
• /
• 2006.11b
• /
• pp.990-1003
• /
• 2006

To cope with the change of railway safety environment and to prevent the catastrophic accident, the railway safety management system was established through the legislation of railway safety rules. And to audit and evaluate the accomplishment of railway safety rules by the railway operators, the Integrated Railway Safety Audit System(IRSAS) has been conducting. This study find out the strategy to stabilize the IRSAS by applying Theory of Constraints(TOC) Thinking Process. For meeting the IRSAS's goal of effective levelling up of railway safety, the two necessary conditions, 1)the secure of substantial safety through the IRSAS and 2)the execution of efficient IRSAS, should be fulfilled. Estimated undesirable effects(UDEs) from the IRSAS were identified, and 3 of them were selected for creating the requisite conflict clouds. Entities from these conflict clouds were synthesized into a core conflict cloud that foamed the base of Current Reality Tree. The strategic direction for change extracted from the conflict cloud is the reinforcement of IRSAS preparation system including the level up of operator's self audit, the deepening of preliminary survey, the establishment of complementing system of audit check list and the build up of auditor's specialization. These injection were logically validated via a Future Reality Tree and expected to be confirmed by further progressing of IRSAS.

• Current Research on Agriculture and Life Sciences
• /
• v.5
• /
• pp.134-142
• /
• 1987

The purpose of this study is to establish more rational and practical planning theory for amusementpark. It analyze and considerate the fluctuation of the people who come and use a Tong-Ch'on amusementpark. The results drawn from this research work are as follows ; There are considerable correlation between use fluctuation and some factors. The factors are season (spring, summer, autumn) as a time, temperature, cloud amount, duration of sunshine, weather (rainy day) as a climate and date (weekday, holiday) as a social system. The important variables are temperature, cloud amount, duration of sunshine and date (week day, holiday) to estimate the user of amusementpark. I can reduce the following two types of regression models. 1.${\log}_eY1=6.9114+0.1135TEM+0.00002_eSUM-0.4068WI+0.4316W3$ ($R^2=0.94$) 2. ${\log}_eY2=7.2069+0.1177TEM-0.0990CLO+0.488W3$ ($R^2=0.95$) Y ; Number of User TEM ; Temperature CLO ; Amount of cloud SUN ; Duration of Sunshine WI ; Weekday W3 ; Holiday Those model is inorder to estimate the user for management of Tong-Ch'on amusementpark and use on the computation of facility size for reconstruction. Besides the amusementpark, city park and outdoor recreation area could estimate of user throuth this method. But, I am not sure about the regression models because I didn't apply the regression models to the other amusementpark, city park or outdoor recreation area. Therefore, I think that this problem needs to study in the future.

• Elastomers and Composites
• /
• v.37 no.4
• /
• pp.211-216
• /
• 2002

The polymer-polymer interaction parameter, x 23t, of the styrene-butadiene polymer (SBR) and ethylene-propylene-diene terpolymer (EPDM) was investigated by observing the phase behavior of the ternary system of SBR/EPDM/solvent. The solvent used in this study was benzene acting as a good solvent for SBR but as a poor solvent for EPDM. Ternary solutions with various concentrations and mixing ratios of the two component polymers were separated into two phases by temperature change The cloud point curves (CPC) showed that the differerence of solvent affinities toward each polymer and the repulsive interaction between two polymers considerably affect the shape of CPC near 15℃. In the temperature range of 5℃ ~ 25℃, incompatible behaviours arised from both the difference of mixing ratios and concentration were clearly observed. Also the phase separation temperature greatly influenced on the composition of each separated phase. The calculated x 23t values from Flory-Huggins theory were in the range of 0.6301 ~ 1.0775, which suggest that the SBR/EPDM systems are incompatible.

• Journal of Digital Contents Society
• /
• v.19 no.6
• /
• pp.1151-1160
• /
• 2018

The study has been derived through the empirical analysis so as to find the usage behavior of cloud-based common collaboration platform. Independent variables of the cloud-based platform have been selected as flexibility, reliability, versatility, security and interaction, which have been selected by utilizing UTAUT theory. After selecting the use intent as a parameter, usage behavior was been finally selected as a dependent variable. The firm type was used as a control variable. We used AMOS 23.0 and SPSS 23.0 statistical programs for the hypothesis test and distributed the questionnaires to users using the cloud-based common collaboration platform. Then, a total of 180 copies from distributed questionnaires were used for the analysis. The results showed that reliability, security and interaction had a positive effect on intention to use. On the other hand, flexibility and versatility did not affect intention to use positively. Finally, it was verified that the intention to use had a positive effect on the use behavior. At last, it showed that there is a moderation effect according to the type of company.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.6
• /
• pp.2356-2363
• /
• 2015

Localization of lightning strike point (LSP) in the forest is modeled to mitigate the forest fire damage. Though forest fire ignited by lightning rarely happens, its damage on the forest is grievousness. Therefore, predicting accurate location of LSP becomes crucial in order to control the forest fire. In this paper, we proposed a new hybrid localization algorithm by combining the received signal strength (RSS) and the received signal strength ratio (RSSR) to improve the accuracy by mitigating the environmental effect of lightning strike location in the forest. The proposed hybrid algorithm employs antenna theory (AT) model of cloud-to-ground (CG) return stroke lightning channel to forecast the location of the lightning strike. The obtained results show that the proposed hybrid algorithm achieves better location accuracy compared to the existing RSS method for predicting the lightning strike location considering additive white Gaussian noise (AWGN) environment.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.14 no.6
• /
• pp.2634-2648
• /
• 2020

In this paper, an adaptive sparse singular value decomposition (ASSVD) algorithm is proposed to estimate the signal matrix when only one data matrix is observed and there is high dimensional white noise, in which we assume that the signal matrix is low-rank and has sparse singular vectors, i.e. it is a simultaneously low-rank and sparse matrix. It is a structured matrix since the non-zero entries are confined on some small blocks. The proposed algorithm estimates the singular values and vectors separable by exploring the structure of singular vectors, in which the recent developments in Random Matrix Theory known as anisotropic Marchenko-Pastur law are used. And then we prove that when the signal is strong in the sense that the signal to noise ratio is above some threshold, our estimator is consistent and outperforms over many state-of-the-art algorithms. Moreover, our estimator is adaptive to the data set and does not require the variance of the noise to be known or estimated. Numerical simulations indicate that ASSVD still works well when the signal matrix is not very sparse.