• Journal of KIISE:Databases
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• v.31 no.3
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• pp.274-286
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• 2004

In mobile client-server environments, mobile clients usually are disconnected with their server because of high cost of wireless communication and keep their own local copies to provide efficient updating the cached map. The update of the server database leads to invalidation of the cached map in the client side. To solve the issues of invalidation of the cached map, it is not efficient to resend part of the updated server database to clients whenever the updating of the server database occurs. This paper proposes a log-based update propagation method to propagate the server's update into its relevant clients by using only update logs. Too many logs increasingly accumulate as the sever database is updated several times. The sequential search of the relevant log data for a specific client is time-consuming. Sending of unnecessary logs should be avoided for reducing the overhead of communication.'re solve these problems, we first define unnecessary logs and then suggest log reduction methods to avoid or cancel creating unnecessary logs. The update log index is used for quickly retrieving relevant logs.

• Membrane Journal
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• v.11 no.4
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• pp.170-178
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• 2001

PVC microfiltration membrane was prepared by phase immersion method and applied to membrane bioreactor (MBR) contained activated sludge. The hydrophilicity of membrane and the pore size increase with the amount of additive(PVP) ducting the preparation of membrane. Permeation characteristics and the membrane fouling behavior were investigated by varying the internal environment in MBR using the prepared membranes. When there is a sludge bulking in MBR caused by microorganism, membrane fouling was accumulated. The cake layer resistance, R$_{c}$, of membrane increased in the order of CP-0 > CP-1.0 > CP-1.5. Rc increased up to 3.5~7 fold where the sludge bulking occurred in MBR. CP-1.5 seems to be appropriated membrane on the basis of the surface characteristics and the flux. The average flux of all the test membrane was 12(${\pm}$2) L/$m^2$hr whereas the COD removal efficiency was 98.8%. The ratio of bulking sludge and the type and the size of microorganism in operating MBR accelerate the membrane fouling and flux decline. It is concluded that the characteristic of membrane filtration depends on the hydrophilicity of membrane, the internal environment of MBR reactor and the growth factor of sludge.

• Journal of Korea Multimedia Society
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• v.11 no.4
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• pp.434-442
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• 2008

The parallel beam SPECT acquires projection data by using parallel hole collimators in conjunction with photon detectors. Those projection data of the parallel beam SPECT are, however, contaminated by the distance dependent blurring because of the inaccuracy of the point response function of the collimator that is used to define the range of directions where photons can be detected. Thus an efficient aperture correction is required. In this paper we propose a distance dependent backprojection method to overcome the time limitation of iterative aperture correction methods and the performance limitation of Fourier-Distance Relation based method. The proposed method achieves aperture correction and fast image reconstruction by replacing the distance independent backprojection of the direct image reconstruction with the distance dependent one. We conducted several simulations to compare the performance of the proposed method with that of the conventional Fourier-Distance Relation based method. The simulation result shows that the proposed method outperforms the Fourier-Distance Relation based method in spatial resolution and robustness against noise.

• KIPS Transactions on Software and Data Engineering
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• v.3 no.2
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• pp.81-86
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• 2014

In this paper, we present an effective sound classification system for recognizing the real-time context of a smartphone user. Our system avoids unnecessary consumption of limited computational resource by filtering both silence and white noise out of input sound data in the pre-processing step. It also improves the classification performance on low energy-level sounds by amplifying them as pre-processing. Moreover, for efficient learning and application of HMM classification models, our system executes the dimension reduction and discretization on the feature vectors through k-means clustering. We collected a large amount of 8 different type sound data from daily life in a university research building and then conducted experiments using them. Through these experiments, our system showed high classification performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.11
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• pp.2047-2058
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• 2007

The business environment of enterprises could be difficult to obviate redundancy to filtrate data source occurred on data integrated to standard rules and meta-data and to produce integration of data and single viewer in geographical and spatial distributed environment. Specially, To can interchange various data from a heterogeneous system or various applications without types and forms and synchronize continually exactly integrated information#s is of paramount concern. Therefore data hub system based on SQL/XMDR message to overcome a problem of meaning interoperability occurred on exchanging or jointing between each legacy systems are proposed in this paper. This system use message mapping technique of query transform system to maintain data modified in real-time on cooperating data. It can consistently maintain data modified in realtime on exchanging or jointing data for cooperating legacy systems, it improve clarity and availability of data by providing a single interface on data retrieval.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.9
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• pp.14-19
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• 2019

In this study, the possibility of using marine life for cosmetic materials was assessed by establishing a fermentation process of seaweed, such as Ecklonia cava, Enteromorpha prolifera, Chondria crassicaulis, Eiseniabicyclis, Codium fragile, Seaweed furcata, Gloiopeltis tenax, Grateloupia elliptica, Undaria pinnatifida, and Saccharina japonica. Lactobacillus sakei isolated from Kimchi was used for effective fermentation and whole milk powder was used as an additive. 2.0 % of crushed seaweed and 1.0 % of whole milk powder were added and afterwards, 1.0 % Lactobacillus sakei was added after cooling to $40^{\circ}C$. After cooling and filtering the fermented product, butylene glycol, glycerine, and 1,2-hexandiol, which have the effect of a preservative, were added to mix and complete the final product. Among the ten kinds of seaweeds, the process was found to be highly effective in the fermentation of Ecklonia cava, Codium fragile, Undaria pinnatifida, and Saccharina japonica. The amount of fermentable substances in cosmetics was determined and the safety of the raw material was verified using the HET-CAM (The Hen's egg test-Chorioallantoic membrane) test.

• Journal of the Korean Society of Radiology
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• v.14 no.7
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• pp.931-936
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• 2020

This study was conducted to observe the changes in radiation exposure dose and image quality of pediatric patients according to the presence and size of the gonadal shield when using the AEC system. X-ray equipment was used to measure the radiation exposure dose in the abdominal and gonads of the pediatric phantom when no shielding body was used and when three different sizes of shielding body were used, and SNR and CNR were measured through the obtained images. As a result of the study, the radiation exposure dose to the gonads decreased in proportion to the size of the radiation shield, but the radiation exposure dose to the abdomen was rather increased, and the image quality did not change. It is recommended to use a shield with a size optimized for the age, weight, and body size of the pediatric patient so as not to be overexposed by the increased radiation due to the radiation shield due to the use of the AEC System. For this purpose, information about the pediatric patient with the nurse It is believed that exchange is necessary.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.3
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• pp.77-85
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• 2002

A Research of binary random sequence generator that uses a linear shift register had been studied since the 1970s. These generators were used in stream cipher. In general, the binary random sequence generator consists of linear shift registers that generate sequences of maximum period and a nonlinear filter function or a nonlinear combination function to generate a sequence of high linear complexity. Therefore, To generate a sequence that have long period as well as high linear complexity becomes an important factor to estimate safety of stream cipher. Usually, the maximum period of the sequence generated by a linear feedback shift register with L resistors is less than or equal to $2^L$-1. In this paper, we propose new binary random sequence generator that consist of L registers and 2 sub-characteristic polynomials. According to an initial state vector, the least period of the sequence generated by the proposed generator is equal to or ions than it of the sequence created by the general linear feedback shift register, and its linear complexity is increased too.

• KIPS Transactions on Software and Data Engineering
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• v.11 no.4
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• pp.157-162
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• 2022

Today, most data is stored in a database (DB). In the DB environment, the users requests the DB to find the data they wants. Similarity Query has predicate that explained by a similarity. However, in the process of processing the similarity query, it is difficult to use an index that can reduce the range of processed records, so the cost of calculating the similarity for all records in the table is high each time. To solve this problem, this paper defines a lightweight similarity function. The lightweight similarity function has lower data filtering accuracy than the similarity function, but consumes less cost than the similarity function. We present a method for reducing similarity query processing cost by using the lightweight similarity function features. Then, Chebyshev distance is presented as a lightweight similarity function to the Euclidean distance function, and the processing cost of a query using the existing similarity function and a query using the lightweight similarity function is compared. And through experiments, it is confirmed that the similarity query processing cost is reduced when Chebyshev distance is applied as a lightweight similarity function for Euclidean similarity.

• Membrane Journal
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• v.32 no.6
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• pp.390-400
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• 2022

Nanofiltration (NF) membranes are more popular than reverse osmosis (RO) membranes as they can be operated at much lower pressures for applications in treatment of wastewater from industries like food processing and pharmaceutical as well as municipal sewage water. The separation mechanism in case of NF membranes is based on solution diffusion as well as sieving, for which the crosslinking density of the thin film of the composite membrane is less then RO membrane. Unlike ceramic membranes, membrane fouling is one of the chronic problems that occur during the nanofiltration process in polymeric membranes. Membrane cleaning is done to get rid of reversible as well as irreversible fouling by treatment with sodium hypochlorite. Compared to polymeric membranes, ceramic membranes show higher stability against these agents. In this review different types of ceramic membrane applied wastewater treatment by NF process are discussed.