• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.1
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• pp.48-53
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• 2008

Twelve black seabreams (Acanthopagrus schlegeli) were tagged with acoustic transmitters and their movement and behavior patterns were tracked using acoustic telemetry from 12 December 2006 to 15 August 2007. Seven of the 12 fish stayed within 500 m of the release point for over a month. In the spring tide, the number of detected signals and swimming depth of tagged fish changed at 12-hour intervals with the ebb tide. The number of detected signals of tagged fish decreased dramatically with the passage of time and had decreased by over 80% in May 2007, compared with January 2007.

• Journal of Multimedia Information System
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• v.6 no.1
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• pp.37-42
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• 2019

Skyline queries are used in a variety of fields to make optimal decisions. However, as the volume of data and the dimension of the data increase, the number of skyline points increases with the amount of time it takes to discover them. Mainly, because the number of skylines is essential in many real-life applications, various studies have been proposed. However, previous researches have used the k-parameter methods such as top-k and k-means to discover representative skyline points (RSPs) from entire skyline point set, resulting in high query response time and reduced representativeness due to k dependency. To solve this problem, we propose a new Connected Component Clustering based Representative Skyline Query (3CRS) that can discover RSP quickly even in high-dimensional data through connected component clustering. 3CRS performs fast discovery and clustering of skylines through hash indexes and connected components and selects RSPs from each cluster. This paper proves the superiority of the proposed method by comparing it with representative skyline queries using k-means and DBSCAN with the real-world dataset.

• Journal of information and communication convergence engineering
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• v.19 no.1
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• pp.1-7
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• 2021

Reinforcement learning is an area of machine learning that studies how an intelligent agent takes actions in a given environment to maximize the cumulative reward. In this paper, we propose a new MAC protocol based on the Q-learning technique of reinforcement learning to improve the performance of the IEEE 802.11 wireless LAN CSMA/CA MAC protocol. Furthermore, the operation of each access point (AP) and station is proposed. The AP adjusts the value of the contention window (CW), which is the range for determining the backoff number of the station, according to the wireless traffic load. The station improves the performance by selecting an optimal backoff number with the lowest packet collision rate and the highest transmission success rate through Q-learning within the CW value transmitted from the AP. The result of the performance evaluation through computer simulations showed that the proposed scheme has a higher throughput than that of the existing CSMA/CA scheme.

• Journal of the Korean Mathematical Society
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• v.60 no.5
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• pp.1087-1107
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• 2023

Let E be an elliptic curve defined over ℚ of conductor N, c the Manin constant of E, and m the product of Tamagawa numbers of E at prime divisors of N. Let K be an imaginary quadratic field where all prime divisors of N split in K, P_K the Heegner point in E(K), and III(E/K) the Shafarevich-Tate group of E over K. Let 2u_K be the number of roots of unity contained in K. Gross and Zagier conjectured that if P_K has infinite order in E(K), then the integer c · m · u_K · |III(E/K)| $\frac{1}{2}$ is divisible by |E(ℚ)_tor|. In this paper, we prove that this conjecture is true if E(ℚ)_tor ≅ ℤ/2ℤ or ℤ/4ℤ except for two explicit families of curves. Further, we show these exceptions can be removed under Stein-Watkins conjecture.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.1
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• pp.58-63
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• 2020

This paper proposes the method for improving the localization accuracy of the mobile robot based on the stereo camera. To restore the position information from stereo images obtained by the stereo camera, the corresponding point which corresponds to one pixel on the left image should be found on the right image. For this, there is the general method to search for corresponding point by calculating the similarity of pixel with pixels on the epipolar line. However, there are some disadvantages because all pixels on the epipolar line should be calculated and the similarity is calculated by only pixel value like RGB color space. To make up for this weak point, this paper implements the method to search for the corresponding point simply by calculating the gap of x-coordinate when the feature points, which are extracted by feature extraction and matched by feature matching method, are a pair and located on the same y-coordinate on the left/right image. In addition, the proposed method tries to preserve the number of feature points as much as possible by finding the corresponding points through the conventional algorithm in case of unmatched features. Because the number of the feature points has effect on the accuracy of the localization. The position of the mobile robot is compensated based on 3-D coordinates of the features which are restored by the feature points and corresponding points. As experimental results, by the proposed method, the number of the feature points are increased for compensating the position and the position of the mobile robot can be compensated more than only feature extraction.

• Korean Journal of Veterinary Research
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• v.29 no.1
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• pp.1-6
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• 1989

The number and distribution of the retinal ganglion cells in the 2 years old Korean native cattle was determined from whole fiat mounted preparation stained with methylene blue and thionin. The results were summarized as follows. 1. The total number of retinal ganglion cells was estimated to be 3,085,200 in the bovine retina ranging from $2,214mm^2$ in total area. 2. Visual streak was recognized at the area 2.5mm superior to the optic disc and ganglion cell density drops off rapidly to the directions superior to and inferior to the visual streak. 3. Area centralis ($6,800cells/mm^2$) was located at the area 10mm temporally from the point of 3mm superior to the optic disc. 4. The number of ${\alpha}-type$ ganglion cells (above $15{\mu}$) was 57,000 in the bovine retina and ${\alpha}-type$ ganglion cells constituted 18.5% of the total cells. 5. The relative frequency of ${\alpha}-type$ ganglion cells was higher in the peripheral regions than in the visual streak, especially higher in the superior-temporal quadrant than in other region of the bovine retina.

• Particle and aerosol research
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• v.17 no.4
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• pp.81-89
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• 2021

Understanding particle-laden flow around cylindrical bodies is essential for the better design of various applications such as filters. In this study, laminar flows around two tandem cylinders and the motions of particles in the flow are numerically investigated at low Reynolds numbers. We aim to reveal the effects of the spacing between cylinders, Reynolds number and particle Stokes number on the characteristics of particle trajectories. When the cylinders are placed close, the unsteady flow inside the inter-cylinder gap at Re = 100 shows a considerable modification. However, the steady recirculation flow in the wake at Re = 10 and 40 shows an insignificant change. The change in the flow structure leads to the variation of particle dispersion pattern, particularly of small Stokes number particles. However, the dispersion of particles with a large Stokes number is hardly affected by the flow structure. As a result, few particles are observed in the cylinder gap regardless of the cylinder spacing and the Reynolds number. The deposition efficiency of the upstream cylinder shows no difference from that of a single cylinder, increasing as the Stokes number increases. However, the deposition on the downstream cylinder is found only at Re = 100 with large spacing. At this time, the deposition efficiency is generally small compared to that of an upstream cylinder, and the deposition location is also changed with no deposited particles near the stagnation point.

• Journal of The Korean Association of Information Education
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• v.2 no.1
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• pp.35-51
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• 1998

Software reliability growth model is one of the evaluation methods, software quality which quantitatively calculates the software reliability based on the number of errors detected. For correct and precise evaluation of reliability of certain software, the reliability model, which is considered to fit dose to real data should be selected as well. In this paper, the optimal model for specific test data was selected one of among five software reliability growth models based on NHPP(Non Homogeneous Poission Process), and in result reliability estimating scales(total expected number of errors, error detection rate, expected number of errors remaining in the software, reliability etc) could obtained. According to reliability estimating scales obtained, Software development and predicting optimal release point and finally in conducting systematic project management.

• Journal of Applied Reliability
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• v.17 no.1
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• pp.11-21
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• 2017

Purpose: The occurrence ranks of failure modes can come from the real failure but the severity ranks of failure modes require a highly subjective point of view of users. The severity ranks have to find more objective and scientific values. Methods: We found the optimal values by using the correlation analysis between failure mode effects and the criticality number like RPN (Risk Priority Number) in RCM. Result: This paper shows the result that verified whether the weighted values on each failure effect in criticality number calculation is suitable to the actual failures or not. To get the verification, it used the 5 year data and correlation analysis. Based on the analyzed result, We proposed the more suitable values. Conclusion: This correlation analysis approach can provide guidance of RCM analysis across many industries and situations.

• Journal of the Korea Safety Management & Science
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• v.15 no.2
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• pp.31-38
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• 2013

As people make efforts on accident prevention, the number of accidents has decreased over the years, however the number of fatal major industry accidents has rather increased, which resulted in the increase of the number of deaths in total. Under these conditions, there is an attempt to introduce and perform the safety vocational education system as a means for preventing major industry accidents. Therefore, in this paper, we analyse vocational education of manufacturing industry from the safety's point of view and suggest the efficient techniques measuring and managing each safety management. Proposed techniques show that the specification on safety determines weight through the managers of firms and each process is suggested by using SN ratio.