• Journal of applied mathematics & informatics
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• 제41권6호
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• pp.1409-1418
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• 2023

The Hurwitz-type Euler zeta function ζ_E(z, q) is defined by the series ${\zeta}_E(z,\,q)\,=\,\sum\limits_{n=0}^{\infty}{\frac{(-1)^n}{(n\,+\,q)^z}},$ for Re(z) > 0 and q ≠ 0, -1, -2, . . . , and it can be analytic continued to the whole complex plane. An asymptotic expansion for ζ^'_E(-m, q) has been proved based on the calculation of Hermite's integral representation for ζ_E(z, q).

• 지구물리와물리탐사
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• 제24권4호
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• pp.158-163
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• 2021

Cole-Cole 모델에 대한 주파수영역 유도분극 반응은 닫힌 형태의 간단한 수식으로 정의된다. 그러나 시간영역 유도분극 반응은 닫힌 형태로 표현되지 않아 Cole-Cole 모델이나 다른 완화모델에 대한 반응을 계산하는 것은 쉽지 않다. 이 논문에서는 Cole-Cole 모델에 대한 시간영역 유도분극 반응을 계산하는 세 가지 방법, 즉 급수 전개법, 선형 필터링법 및 푸리에 변환법을 비교 분석하였다. 수치 실험 결과 급수 전개법은 안정적인 결과를 제시하지 못할 뿐 아니라 수렴 속도가 느리다는 문제점이 있다. 선형 필터링법은 후기 시간에서 만족할 만한 정밀도를 보이지 못 하였다. 푸리에 변환법은 계산시간이 더 많이 걸린다는 단점이 있으나 다른 방법에 비하여 보다 안정적인 것으로 확인되었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권5호
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• pp.2588-2609
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• 2019

Speech homomorphic encryption has become one of the key components in secure speech storing in the public cloud computing. The major problem of speech homomorphic encryption is the huge data expansion of speech cipher-text. To address the issue, this paper presents a speech homomorphic encryption scheme with less data expansion, which is a probabilistic statistics and addition homomorphic cryptosystem. In the proposed scheme, the original digital speech with some random numbers selected is firstly grouped to form a series of speech matrix. Then, a proposed matrix encryption method is employed to encrypt that speech matrix. After that, mutual information in sample speech cipher-texts is reduced to limit the data expansion. Performance analysis and experimental results show that the proposed scheme is addition homomorphic, and it not only resists statistical analysis attacks but also eliminates some signal characteristics of original speech. In addition, comparing with Paillier homomorphic cryptosystem, the proposed scheme has less data expansion and lower computational complexity. Furthermore, the time consumption of the proposed scheme is almost the same on the smartphone and the PC. Thus, the proposed scheme is extremely suitable for secure speech storing in public cloud computing.

• 대한조선학회논문집
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• 제60권6호
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• pp.416-423
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• 2023

Recently, the design point of the propeller is gradually changing due to the demand for energy saving and environmental protection. Until recently, self-propulsion model tests were conducted using stock propellers and geometry information was provided to propeller designers, but the range of existing stock propellers did not keep up with the changing design points, and the range of series propellers required in the initial design was also insufficient. Future propeller performance requires high performance and eco-friendliness, and the need for expansion of series propellers has increased. In order to respond to future needs and provide a wide range of advantages in propeller design, KRISO manufactures about 100 series propellers and builds series data through a model tests. In this paper, the approach method for deriving the representative optimal shape to be applied to the 4-blade series propeller in the initial stage of series propeller development was summarized.

• East Asian mathematical journal
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• 제17권1호
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• pp.135-146
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• 2001

Several families of infinite series were summed recently by means of certain operators of fractional calculus(that is, calculus of derivatives and integrals of any real or complex order). In the present sequel to this recent work, it is shown that much more general classes of infinite sums can be evaluated without using fractional calculus. Some other related results are also considered.

• Structural Engineering and Mechanics
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• 제16권6호
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• pp.655-674
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• 2003

Investigated in this study are the natural vibration characteristics of the coaxial cylindrical shells coupled with a fluid. Theoretical method is developed to find the natural frequencies of the shell using the finite Fourier series expansion, and their results are compared with those of finite element method to verify the validation of the method developed. The effect of the fluid-filled annulus and the boundary conditions on the modal characteristics of the coaxial shells is investigated using a finite element modeling.

• Journal of applied mathematics & informatics
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• 제4권2호
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• pp.529-534
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• 1997

Even though the Shannon wavelet is a prototype of wavelets are assumed to have. By providing a sufficient condition to compute the size of Gibbs phe-nomenon for the Shannon wavelet series we can see the overshoot is propotional to the jump at discontinuity. By comparing it with that of the Fourier series we also that these two have exactly the same Gibbs constant.

• Journal of applied mathematics & informatics
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• 제8권2호
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• pp.429-437
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• 2001

In [1, 2], described a Chebyshev series method for the numerical solution of integral equations with three automatic algorithms for computing tow regularization parameters, C/sub f/ and r. Here we describe a Fourier series expansion method for a class singular integral equations with Hilbert kernel and constant coefficients with using a new automatic algorithm.

• 대한의용생체공학회:의공학회지
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• 제12권3호
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• pp.171-176
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• 1991

A solution for the course of the general deterministic epidemic model is obtained by elementary series expansion. This is valid over all times, and appears to hold accurate]y over a very wide range of population and threshould parameter values. This algorithm can be more efficient than either numerical or recursive procedures in terms of the number of operations required to evaluate a sequence of points along the course of the epidemic.

• The Journal of Asian Finance, Economics and Business
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• 제8권2호
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• pp.1263-1268
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• 2021

This study investigates how dramatic increase of university and college graduates affects labor market outcomes. Using a series of seven repeated cross sections of the Vietnam Household Living Standards Surveys, this paper analyzed the changes in the rate of returns to higher education attainment along with the increased supply of university and college graduates due to the higher education expansion throughout the 2002-2014 period. The study utilized a ratio of number of university and college students to the number of upper-secondary pupils within each province as an instrumental variable to calculate the effects of higher education expansion on the labor wage. The study found that, with the basic equations, the coefficients for higher education attainment are statistically significant and have positive values for the whole period. Our instrumental variables were found to be valid. For instrumental variable estimation, the return to higher education in IV earning equations was quite high. The findings of this study suggested that the expansion of the higher education system in Vietnam during 2002-2014 had positive effects on wages for those who increased their education attainment due to the reforms and there was a declining trend of the returns to higher education toward the end of the period.