• Journal of Information Processing Systems
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• 제19권1호
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• pp.17-32
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• 2023

Centralized hierarchical routing protocols are often used to solve the problems of uneven energy consumption and short network life in wireless sensor networks (WSNs). Clustering and cluster head election have become the focuses of WSNs. In this paper, an energy balanced clustering routing algorithm optimized by sine cosine algorithm (SCA) is proposed. Firstly, optimal cluster head number per round is determined according to surviving node, and the candidate cluster head set is formed by selecting high-energy node. Secondly, a random population with a certain scale is constructed to represent a group of cluster head selection scheme, and fitness function is designed according to inter-cluster distance. Thirdly, the SCA algorithm is improved by using monotone decreasing convex function, and then a certain number of iterations are carried out to select a group of individuals with the minimum fitness function value. From simulation experiments, the process from the first death node to 80% only needs about 30 rounds. This improved algorithm balances the energy consumption among nodes and avoids premature death of some nodes. And it greatly improves the energy utilization and extends the effective life of the whole network.

• International Journal of Computer Science & Network Security
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• 제21권1호
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• pp.97-106
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• 2021

Social networking platforms have become a smart way for people to interact and meet on internet. It provides a way to keep in touch with friends, families, colleagues, business partners, and many more. Among the various social networking sites, Twitter is one of the fastest-growing sites where users can read the news, share ideas, discuss issues etc. Due to its vast popularity, the accounts of legitimate users are vulnerable to the large number of threats. Spam and Malware are some of the most affecting threats found on Twitter. Therefore, in order to enjoy seamless services it is required to secure Twitter against malicious users by fixing them in advance. Various researches have used many Machine Learning (ML) based approaches to detect spammers on Twitter. This research aims to devise a secure system based on Hybrid Similarity Cosine and Soft Cosine measured in combination with Genetic Algorithm (GA) and Artificial Neural Network (ANN) to secure Twitter network against spammers. The similarity among tweets is determined using Cosine with Soft Cosine which has been applied on the Twitter dataset. GA has been utilized to enhance training with minimum training error by selecting the best suitable features according to the designed fitness function. The tweets have been classified as spammer and non-spammer based on ANN structure along with the voting rule. The True Positive Rate (TPR), False Positive Rate (FPR) and Classification Accuracy are considered as the evaluation parameter to evaluate the performance of system designed in this research. The simulation results reveals that our proposed model outperform the existing state-of-arts.

• 한국통신학회논문지
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• 제34권10C호
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• pp.1001-1009
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• 2009

본 논문은 orthogonal frequency division multiplexing (OFDM) 통신에서 무선자원을 절약할 수 있는 효율적인 블라인드(blind) 주파수 옵셋 추정 방식을 제안한다. 제안된 방식은 OFDM 통신에서 cyclic prefix (CP)를 이용하여 시간차가 있는 2개의 OFDM 신호 블록을 얻고 이를 이용하여 블라인드 주파수 옵셋 추정을 위한 비용함수를 정의한다. 제안된 방식에서 비용함수는 3개의 독립적인 주파수 옵셋 위치에서 비용함수 값들을 이용하여 폐쇄형(closed form)의 코사인 함수로 나타낼 수 있음을 보인다. 이 코사인 함수를 이용하면 전체 주파수 옵셋 범위에 대한 탐색 없이 최저 비용함수 값을 쉽게 계산할 수 있기 때문에 주파수 옵셋 추정이 효율적이다. 폐쇄형 코사인 함수로부터 구한 주파수 옵셋은 정확도가 해상도에 제한 받지 않기 때문에 signal-to-noise ratio (SNR)이 증가할 수 록 추정 오차가 계속 줄거듦을 확인하였다. 컴퓨터 시뮬레이션 결과 제안된 방식은 기존의 오버샘플링(oversampling)기법이나 MUSIC 방식보다 평균제곱오차 (mean square error, MSE) 성능이 우수함을 보였다.

• 대한기계학회논문집B
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• 제22권1호
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• pp.131-138
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• 1998

Conventional yaw functions are compared with actual response of a hot wire to various yaw angles, and a new function is proposed, which can be applied at large yaw angles and low velocities. To compare the accuracy of the new yaw function with those of the conventional ones, measurements are made for the jet flow at the nozzle exit and at .chi./D=15 with an X hot-wire probe. In the potential core, the flow angles reduced by the present function, ideal angle method and full velocity-angle method are shown to be more accurate than those reduced by the cosine function and Hinze's formula. No matter which yaw functions are used, the profiles of mean velocity and turbulence intensity show little discrepancy at .chi./D=15. However, there is a significant difference between the probability density functions obtained by the present function, ideal angle method and full velocity-angle method and those obtained by the cosine function and Hinze's formula.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.9-13
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• 1997

This parer is a study on the inverse dynamics of a one-link flexible robot arm which is controlled by translational base motion. The system is composed of a flexible arm, a base for driving arm, a DC servomotor, and a computer. The arm base is moved so that the arm tip follows a desired function. The governing equations are based on the Bernoullie-Euler beam theory and solved by applying the Laplace transform method and then the numerical inversion method. Moter voltage is obtained by simulation for tip trajectory functions i. e. Bang-Bang, Cosine and Gauss Function. And, the tip motion is measured while simulation results are applying. Then the results are investigated to select most proper input and to compare their chateristics. Experimental results show the Cosine function is most proper with respect to low maximum voltage and steady state error.

• Kyungpook Mathematical Journal
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• 제60권4호
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• pp.781-795
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• 2020

In this paper, we obtain an analytical solution for an unsolved definite integral RC (m, n) from a 1915 paper of Srinivasa Ramanujan. We obtain our solution using the hypergeometric approach and an infinite series decomposition identity. Also, we give some generalizations of Ramanujan's integral RC (m, n) defined in terms of the ordinary hypergeometric function 2F3 with suitable convergence conditions. Moreover as applications of our result we obtain nine new infinite summation formulas associated with the hypergeometric functions 0F1, 1F2 and 2F3.

• 정보처리학회논문지B
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• 제8B권5호
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• pp.565-572
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• 2001

위치와 주파수 불확실성 곱이 작은 해석함수는 영상처리와 압축에 많은 장점이 있다. 지금까지의 불확실성원리에 기초하여 이 값을 계산하였으나, 이러한 측정은 최대 응답주파수가 0 이 아닌 인간시각필터에서 적절한 주파수 불확실성의 측정방법이 될 수 없다. 최대 응답을 갖는 주파수에 대한 주파수 불확실성을 계산하는 새로운 측정방법을 이용하여 결합유효폭을 유도하고자 한다. 결합변수가 커지면 많은 함수들의 결합유효폭이 0.5로 수렴하는 해석 결과를 얻었으며, 고려 대상 중에서 Gabor cosine 함수가 우수한 성능을 보였다.

• 정보처리학회논문지B
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• 제11B권3호
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• pp.303-308
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• 2004

Gabor 코사인과 사인 변환은 영상주파수 성분을 국부적으로 표현하므로 영상과 비디오 압축 알고리즘에 사용될 수 있다. 압축과 복원에 사용되는 순방향과 역방향 행렬 변환식의 계산 복잡도는 O($N^3$)이다. 이 논문에서는 기저함수들의 길이를 절단하여, 희소기저행렬을 생성하고, 영상압축과 복원에 적용하여 실시간 처리에 용이하게 변환 계산량을 감소시키고자 한다. 기저함수 길이가 감소함에 따라서, 기저함수 에너지에 미치는 절단의 영향을 조사하고 다른 여러 측정량의 변화를 살펴본다. 실험 결과로부터 약 1% 이하의 성능저하로 11배의 곱하기/더하기 수를 감소시킬 수 있음을 보았다.

• 농촌계획
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• 제23권2호
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• pp.67-74
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• 2017

Migration is defined as the movement of people between residential places, and represents interactions between regions. Changes in migration involve changes in both the number of migrants toward/from regions and migration patterns across regions. However, most migration studies have focused only on the change in migrants, while no empirical study captures changes in migration patterns. In this paper, I present a function using the cosine similarity to measure changes in migration patterns, and apply it to 2001-2016 migration data of Korea. The results show that the migration patterns of Korea shifted in 2007, resulting in two distinct clusters. Local areas experienced various migration pattern changes despite few changes in the number of migrants.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.107-108
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• 2007

In this paper, a cosine-modulated filter bank with a modified synthesis part is proposed for arbitrary scaling of images, whereby down/up-sampling kernels based on a compactly supported sampling function (CSSF) are utilized. Also, an optimized adaptive interpolation technique is incorporated into the filter bank structure to compensate for quality degradation arising in scaled images. Finally, simulation results verify that high quality images with arbitrary sizes can be obtained by applying the proposed approach.