• The Journal of the Petrological Society of Korea
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• v.23 no.4
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• pp.351-366
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• 2014

We assumed the situation where an eruption column had been formed by the explosive Plinian eruption from Mt. Baekdu and that the collapse of eruption column had caused pyroclastic density currents to occur. Based on this assumption, we simulated by using a Titan2D model. To find out about the range of the impacts of pyroclastic density currents by volcanic eruption scenarios, we studied the distance for the range of the impacts by VEIs. To compare the results by each volcanic eruption scenario, we set the location of the vent on the 8-direction flank of the outer rim and on the center of the caldera, the internal friction angle of the pyroclastic density currents as $35^{\circ}$, the bed friction angle as $16^{\circ}$. We set the pile height of column collapse and the vent diameter with various VEIs. We properly assumed the height of the column collapse, the diameter of the vent, the initial rates of the column collapse and the simulation period, based on the VEIs, gravity and the volume of the collapsed volcanic ash. According to the comparative analysis of the simulation results based on the increase of the eruption, the higher VEI by the increase of eruption products, the farther the pyroclastic density currents disperse. To the northwest from the vent on the northeast slope of the outer rim of the caldera, the impact range was 3.3 km, 4.6 km, 13.2 km, 24.0 km, 50.2 km, 83.4 km or more from VEI=2 to VEI=7, respectively. Once the database has been fully constructed, it can be used as a very important material in terms of disaster prevention and emergency management, which aim to minimize human and material damages in the vicinity of Mt. Baekdu when its eruption causes the pyroclastic density currents to occur.

• Journal of Biomedical Engineering Research
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• v.21 no.4
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• pp.373-384
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• 2000

The goal of this paper is to develop a computational method to predict cancellous bone density distributions based upon continuum levels of volumetric strain. Volumetric strain is defined as the summation of normal strains, excluding shear strains, within an elastic range of loadings. Volumetric strain at a particular location in a cancellous structure changes with changes of the boundary conditions (prescribed displacements, tractions, and pressure). This change in the volumetric strain is postulated to predict the adaptive change in the bone apparent density. This bone remodeling theory based on volumetric strain is then used with the finite element method to compute the apparent density distribution for cancellous bone in both lumbar spine and proximal femur using an iterative algorithm, considering the dead zone of strain stimuli. The apparent density distribution of cancellous bone predicted by this method has the same pattern as experimental data reported in the literature (Wolff 1892, Keller et al. 1989, Cody et al. 1992). The resulting bone apparent density distributions predict Young's modulus and strength distributions throughout cancellous bone in agreement with the literature (Keller et al. 1989, Carter and Hayes 1977). The method was convergent and sensitive to changes in boundary conditions. Therefore, the computational algorithm of the present study appears to be a useful approach to predict the apparent density distribution of cancellous bone (i.e. a numerical approximation for Wolff's Law)

• Journal of the Korean Society for Marine Environment & Energy
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• v.7 no.3
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• pp.152-157
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• 2004

Wave energy distribution along the Korean coastal sea area was analysed based on the calculated wave data at KORDI. The wave data for the analysis is for the last 24 years (1979∼2002) and the model is HYPA and WAM using known wind field. The wave energy or wave power was evaluated based on the linear wave theory with a simple wave period assumption. The results shed some idea on the amount of usable wave energy and the sites of higher efficiency. It is fair to say that 3kw/m wave energy is easily observable and 10kw/m is frequently available depending on the season and location. The south west region of Jeju island is believed to have the highest overall wave energy density.

• Journal of Information Technology Services
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• v.22 no.2
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• pp.1-21
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• 2023

Due to the convergence and complexity of the 4th Industrial Revolution, the boundaries between industries have become unclear and ambiguous. Consequently, there is a lack of research on how firms engaged in this industry are changing their location behavior. Recently, some attempts to classify the industrial groups of the 4th Industrial Revolution and their detail occupations have been made, and this study adopts the classification of Lee and Jung (2020) of the Korea Institute for Industrial Economics & Trade. In this study, the 18 detailed industries commonly included in multiple industrial groups are defined as 'core industries' and are classified into manufacturing and service industries to explore the spatial patterns of firms' location. Specifically, this study aims to examine how the location behavior of firms in core industries of the 4th Industrial Revolution has changed from 2010 to 2019 in the Seoul metropolitan area, using the 「National Business Survey」 data. We employed two methods based on spatial auto-correlation: (i) spatial kernel density estimation analysis and (ii) local Moran's I_i analysis. The results indicate that the core industry firms form more distinct and larger clusters in 2019 based on the clusters formed in 2010. Specifically, manufacturing industry firms tended to concentrate in the southern region of Gyeonggi and parts of Seoul, while serivce industry firms were more concentrated in Seoul. These core industries play a critical role in industries and are closely related to the ICT industries, which generate high-added value and increase productivity in the front and rear industries. This study reveals that the agglomeration of these industries in specific regions is intensifying and may exacerbate regional inequality.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.2
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• pp.107-113
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• 2014

The icebreaking research vessel, ARAON had her second ice trial in the Arctic Sea from 16th July to 12th August 2010. During the voyage, the local ice loads acting on the bow of port side were measured from 14 strain gauges. The measurements were also carried out in ice waters with various ice concentration ratio as well as the icebreaking performance tests. In this study, the ice loads measured during the 'general' operation in ice waters were analyzed. As a first step, the relationship between the location of strain gauges and the ice loads were investigated, and then the possibility for observation of higher ice loads was estimated based on the probability density function. The relationship between the ship speed and the ice load was also investigated. 718 peak stresses data higher than 20 MPa obtained from strain gauges array attached in longitudinally and vertically was analyzed. In general, the ice load increases as the ship speed increases in the low ship speed range, and ice load decreases as the ship speed is greater than a certain speed.

• Journal of Korean Institute of Industrial Engineers
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• v.21 no.3
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• pp.371-385
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• 1995

The yield of semiconductor chips is dependent not only on the average defect density but also on the distribution of defects over a wafer. The distribution of defects leads to consider a cluster index. This paper briefly reviews the existing yield prediction models ad proposes a new cluster index, which utilizes the information about the defect location on a wafer in terms of the coefficient of variation. An extensive simulation is performed under a variety of defect distributions and a yield prediction model is derived through the regression analysis to relate the yield with the proposed cluster index and the average number of defects per chip. The performance of the proposed simulation-based yield prediction model is compared with that of the well-known negative binomial model.

• Communications for Statistical Applications and Methods
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• v.23 no.4
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• pp.321-334
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• 2016

In this paper, we propose power t distribution based on t distribution. We also study the properties of and inferences for power t model in order to solve the problem of real data showing both skewness and heavy tails. The comparison of skew t and power t distributions is based on density plots, skewness and kurtosis. Note that, at the given degree of freedom, the kurtosis's range of the power t model surpasses that of the skew t model at all times. We draw inferences for two parameters of the power t distribution and four parameters of the location-scale extension of power t distribution via maximum likelihood. The Fisher information matrix derived is nonsingular on the whole parametric space; in addition we obtain the profile log-likelihood functions on two parameters. The response plots for different sample sizes provide strong evidence for the estimators' existence and unicity. An application of the power t distribution suggests that the model can be very useful for real data.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.95-102
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• 2003

To define an analytical model for a structural system or to assess damage in the system, system identification(SI) methods have been developed and widely applied. The paper presents a method of determining optimal sensor location(OSL) based on the maximum likelihood approach, which is applicable to modal SI methods. To estimate unknown parameters reliably, it is necessary that the information provided by the experiment should be maximized. By applying the Cramer-Rao inequality, a Fisher information matrix in terms of the probability density function of measurements is obtained from a lower bound of the estimation error. The paper also proposes a scheme of determining of OSL on damaged structures by using maximum strain energy factor. Simulation studies have carried out to investigate the proposed OSL algorithm for both undamaged and damaged structures.

• Geomechanics and Engineering
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• v.21 no.3
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• pp.259-268
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• 2020

The synthetic rock mass (SRM) were used to investigate the influence of specimen size on the mechanical properties of jointed rock mass. The SRM were established based on parallel bond model (PBM) and smooth joint model (SJM) and the scaled rock specimens were sampled in two SRMs considering three sampling locations. The research results show that the smaller the initial fracture density is, the greater the uniaxial compressive strength (UCS), elastic modulus (E) is when compared with the same sampling location. The mechanical properties of rock specimens obtained by different sampling methods in different SRMs have different scale effects. The strength of rock specimens with more new cracks is not necessarily less than that of rock specimens with fewer new cracks and the failure of rock is caused by the formation of macro-fracture surface.

• Journal of KIISE:Databases
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• v.27 no.1
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• pp.53-63
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• 2000

The mobile computing service market is increasing rapidly due to the development of low-cost wireless network technology and the high-performance mobile computing devices. In recent years, several methods have been proposed to effectively deal with restrictions of the mobile computing environment such as limited bandwidth, frequent disconnection and short-lived batteries. Amongst those methods, much study is being done on the caching method - among the data transmitted from a mobile support station, it selects those that are likely to be accessed in the near future and stores them in the local cache of a mobile host. Existing cache replacement methods have some limitations in efficiency because they do not take into consideration the characteristics of user mobility and spatial attributes of geographical data. In this paper, we show that the value and the semantic of the data, which are stored in the cache of a mobile host, changes according to the movement of the mobile host. We argue it is because data that are geographically near are better suited to provide an answer to a users query in the mobile environment. Also, we define spatial location of geographical data has effect on, using the spatial attributes of data. Finally, we propose two new cache replacement methods that efficiently support user mobility and spatial attributes of data. One is based on the location of data and the other on the meaningful region of data. From the comparative analysis of the previous methods and that they improve the cache hit ratio. Also we show that performance varies according to data density using this, we argue different cache replacement methods are required for regions with varying density of data.