• Journal of the Korea Concrete Institute
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• v.21 no.3
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• pp.377-386
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• 2009

A reference diffusion coefficient model from ACI life-365 is drawn from test results by NT build 443. This test method gives a time-averaged diffusion coefficient during immersion period, thus the ACI model uses the time-averaged diffusion coefficient as a reference value. ACI model needs to be revised, considering the difference between the time-average value and reference value at specified time. In this study, firstly the analytic solutions of diffusion equation are derived considering the initiation time and period of exposure to chloride, and secondly the time-averaged diffusion coefficient from NT build 443 is converted into the diffusion coefficient at reference time. From this study, the reference diffusion coefficient of ACI model should be modified to be about 10% larger values than those of present ACI model. For convenient design of service life, previous relationship between the chloride diffusion coefficient from NT build 443 and that from NT build 492 is also modified. To compare the chloride diffusion coefficients of ACI and JCI models, the reference chloride diffusion coefficient with respect to the JCI model is drawn in the similar form of ACI model's, and service life prediction by ACI life-365 method is confirmed to give a conservative result.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.2
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• pp.16-27
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• 2011

Embryo is a very early stage of the development of multicellular organism such as animals and plants. It is an important research target for studying ontogeny because the fundamental body system of multicellular organism is determined during an embryo state. Researchers in the developmental biology have a large volume of embryo image databases for studying embryos and they frequently search for an embryo image efficiently from those databases. Thus, it is crucial to organize databases for their efficient search. Hierarchical clustering methods have been widely used for database organization. However, most of previous algorithms tend to produce a highly skewed tree as a result of clustering because they do not simultaneously consider both the size of a cluster and the number of objects within the cluster. The skewed tree requires much time to be traversed in users' search process. In this paper, we propose a method that effectively organizes a large volume of embryo image data in a balanced tree structure. We first represent embryo image data as a similarity-based graph. Next, we identify clusters by performing a graph partitioning algorithm repeatedly. We check constantly the size of a cluster and the number of objects, and partition clusters whose size is too large or whose number of objects is too high, which prevents clusters from growing too large or having too many objects. We show the superiority of the proposed method by extensive experiments. Moreover, we implement the visualization tool to help users quickly and easily navigate the embryo image database.

• Korean Journal of Microbiology
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• v.49 no.4
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• pp.360-368
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• 2013

Recently interactive water fountains are gaining popularity in making public facilities in South Korea. The total number of interactive fountains is rapidly growing at the rate of >50% annually. In this study, we performed quantitative microbial risk assessment to estimate infection risks in children by Legionella spp. while playing in interactive fountains. The exposure dose for a given concentration of Legionella in water was calculated using water-aerosol partition rate of Legionella, exposure duration, inhalation rate, and deposit rate of aerosols in the lungs following inhalation. The dose was converted to infection risk by using the dose-response function developed for L. pneumophila. High weight and/or old children, i.e., 12-year children, running around in fountains were the highest risk group by showing >0.05 infection probability for fountain waters containing ${\geq}10^4$ CFU/L Legionella. The result supported the current guideline by Korea Centers for Disease Control and Prevention, which permits use of water with < $10^3$ CFU/L Legionella cells for all purposes. However, the results still warrant further evaluation of the guideline to accommodate risks for children because the dose-response relationship in the model was developed for healthy adults. Further risk assessment studies need to be conducted by employing dose-response model for children who generally carries weaker immune system than adults.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.6
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• pp.57-65
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• 2010

In this paper, we present a universal steganalysis scheme. The proposed method extract features of two types. First feature set is extracted from histogram characteristic of the wavelet subbands. Second feature set is determined by statistical moments of wavelet characteristic functions. 3-level wavelet decomposition is performed for stego image and cover image using the Haar wavelet basis. We extract one features from 9 high frequency subbands of 12 subbands. The number of second features is 39. We use total 48 features for steganalysis. Multi layer perceptron(MLP) is applied as classifier to distinguish between cover images and stego images. To evaluate the proposed steganalysis method, we use the CorelDraw image database. We test the performance of our proposed steganalysis method over LSB method, spread spectrum data hiding method, blind spread spectrum data hiding method and F5 data hiding method. The proposed method outperforms the previous methods in sensitivity, specificity, error rate and area under ROC curve, etc.

• Journal of Digital Convergence
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• v.15 no.11
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• pp.261-269
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• 2017

The purpose of this paper is to provide a search system using a method of accessing the web in real time without using a database server in order to guarantee the up-to-date information in a single network, rather than using a plurality of bots connected by a wide area network Design. The method of the research is to design and analyze the system which can search the person and keyword quickly and accurately in crepe system. In the crepe server, when the user registers information, the body tag matching conversion process stores all the information as it is, since various styles are applied to each user, such as a font, a font size, and a color. The crepe server does not cause a problem of body tag matching. However, when executing the crepe retrieval system, the style and characteristics of users can not be formalized. This problem can be solved by using the html_img_parser function and the Go language html parser package. By applying queues and multiple threads to a general-purpose web crawler, rather than a web crawler design that targets a specific site, it is possible to utilize a multiplier that quickly and efficiently searches and collects various web sites in various applications.

• Journal of Wetlands Research
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• v.18 no.4
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• pp.404-412
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• 2016

This paper not only aims to establish a plan to acquire the water stage data in a constant and proper manner by using limited manpower and costs, but also establishes the fundamental technology for acquiring the water level observation data or the stage data. For this, this paper focuses on how to acquire the stage data, in a uniform manner, that can represent each basin by developing the technology for establishing the optimal observational network. For that, this paper identifies the current status of the stage gauge stations installed in the ChungJu dam including wetland basin mainly along the national rivers. Then, thus obtained factors are used to develop the representative unit hydrograph. After that, the data are converted into the probability density function. Then, the stations are calculated information transfer amount. As a last step, we establish the optimized stage gauge network by the location of the stage station and space impact that takes into account for the combinations of the number of the stations. In other words, we consider the combination of the stage gauge station with information transfer amount and spatial correlation analysis for estimation.

• The KIPS Transactions:PartB
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• v.17B no.1
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• pp.69-78
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• 2010

Spectral modeling synthesis (SMS) has been used as a powerful tool for musical sound modeling. This technique considers a sound as a combination of a deterministic plus a stochastic component. The deterministic component is represented by the series of sinusoids that are described by amplitude, frequency, and phase functions and the stochastic component is represented by a series of magnitude spectrum envelopes that functions as a time varying filter excited by white noise. These representations make it possible for a synthesized sound to attain all the perceptual characteristics of the original sound. However, sometimes considerable phase variations occur in the deterministic component by using the conventional SMS for the complex sound such as whale sounds when the partial frequencies in successive frames differ. This is because it utilizes the calculated phase to synthesize deterministic component of the sound. As a result, it does not provide a good spectrum matching between original and synthesized spectrum in higher frequency region. To overcome this problem, we propose a modified SMS that provides good spectrum matching of original and synthesized sound by calculating complex residual spectrum in frequency domain and utilizing original phase information to synthesize the deterministic component of the sound. Analysis and simulation results for synthesizing whale sounds suggest that the proposed method is comparable to the conventional SMS in both time and frequency domain. However, the proposed method outperforms the SMS in better spectrum matching.

• Progress in Medical Physics
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• v.5 no.1
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• pp.55-66
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• 1994

After proving home-made imaging pulse sequences including tailored RF pulse by phantom, susceptibility-contrast-enhanced MR venograms of cat brain were obtained using tailored RF gradient-echo(TRGE) method. Sagittal MR imaging of the cat brain obtained by TRGE technique shows several veins, for example, dorsal sagittal sinus, straight sinus, vein of corpus callosum and internal cerebral vein, etc., compared with cats anatomical figure. Tailored RF waveform was generated by PASCAL language in ASPECT 3000 computer(Switzland, Bruker). Rectangular-shaped slice profile with bi-linear ramp function as phase distribution in the slice, at which maximum value was 2$\pi$, was fourier transformed to make tailored RF pulse. Experimental MR imaging parameters were TR/TE=205/10 msec, slice thickness TH=7mm, maxtrix size=256$\times$256, in-plane resolution=0.62$\times$0.31mm$^2$, and field of view(FOV)=8cm for both conventional gradient-echo(GE) imaging and TRGE imaging techniques.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.11-22
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• 1987

A plane buoyant jet discharged vertically upward into a crossflow is analyzed by numerical solution of the governing equations of continuity, momentum and constituent transport. The turbulent transport is modelled by the Prandtl's mixing length theory. In the numerical solution procedure, the governing equations are transformed by stream function and vorticity transport, non-dimensionalyzed by discharge velocity, slot width, and parameters representing flow characteristics, and solved by Gauss-Seidel iteration method with successive underrelaxation. The numerical experiments were performed for the region of established flow of buoyant jet in the range of discharge densimetric Froude number of 4 to 32 and in the range of velocity ratio of 8 to 15, which is the ratio of discharge velocity to crossflow velocity. Variations of velocities and temperatures, flow patterns and vorticity patterns of receiving water due to buoyant jet were investigated. Also investigated are the effects of velocity ratio and discharge densimetric Froude number on the trajectories of buoyant jet. Computed are velocities, temperatures and local densimetric Froude numbers along the trajectory of the buoyant jet. Spreading rate and dispersion ratio were analyzed in terms of discharge densimetric Froude number, local densimetric Froude number and distance from the source along the jet trajectory. It was noted that the similarity law holds in both the profiles of velocity and temperatures across the jet trajectory and the integral type analysis of Gaussian distribution is applicable.

• Journal of Korea Multimedia Society
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• v.8 no.3
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• pp.313-321
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• 2005

Digital halftoning is a process to produce a binary image so that the original image and its binary counterpart appear similar when observed from a distance. Among digital halftoning methods, error diffusion is a procedure for generating high quality bilevel images from continuous-tone images but blurs the edge information in the bilevel images. To solve this problem, we propose the improved error diffusion using local spatial information of the original images. Based on the fact that the human vision perceives not a pixel but local mean of input image, we compute edge enhancement information(EEI) by appling the ratio of a pixel and its adjacent pixels to local mean. The weights applied to local means is computed using the ratio of local activity measure(LAM) to the difference between input pixels of 3$\times$3 blocks and theirs mean. LAM is the measure of luminance changes in local regions and is obtained by adding the square of the difference between input pixels of 3$\times$3 blocks and theirs mean. We add the value to a input pixel of quantizer to enhance edge. The performance of the proposed method is compared with conventional methods by measuring the edge correlation. The halftone images by using the proposed method show better quality due to the enhanced edge. And the detailed edge is preserved in the halftone images by using the proposed method. Also the proposed method improves the quality of halftone images because unpleasant patterns for human visual system are reduced.