• Communications of the Korean Mathematical Society
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• v.19 no.2
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• pp.307-319
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• 2004

In this paper, we establish some new oscillation criteria for the functional differential equations of the form $\frac{d}{dt}$$\frac{1}{a_{n-1}(t)}$$\frac{d}{dt}(\frac{1}{{a_{n-2}(t)}\frac{d}{dt}(...(\frac{1}{a_1(t)}\frac{d}{dt}x(t))...)))^\alpha$ + $\delta[f_1(t,s[g_1(t)],\frac{d}{dt}x[h_1(t)])$ + $f_2(t,x[g_2(t)],\frac{d}{dt}x[h_2(t)])]=0$ via comparing it with some other functional differential equations whose oscillatory behavior is known.

• Elastomers and Composites
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• v.56 no.2
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• pp.92-99
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• 2021

Microstructure-dependent changes in the crystalline properties of poly(ethylene-co-vinyl acetate) (EVA) was investigated using various EVAs at different VA contents via X-ray diffraction (XRD). The parameters analyzed herein were percentage crystallinity (X_c), interplanar crystal spacing (d_hkl), crystal stack size (D_hkl), and the number of crystal plane piles (N_hkl). The X_cs of [110] and [200] crystals were 21.0-4.1 and 6.7-1.4%, respectively, and they decreased by approximately 2.3 and 0.7% for every mol% of the VA content, respectively. The X_c ratios of the [110] and [200] crystals were approximately 3. The d₁₁₀s and d₂₀₀s values were 0.41-0.42 and 0.37-0.38 nm, respectively. The D₁₁₀s and D₂₀₀s values were 9.56 -21.92 and 7.00-16.42 nm, respectively. The d_hkls increased with an increase in the VA content, whereas the D_hkls decreased. The N₁₁₀s and N₂₀₀s were 22.7-51.3 and 18.3-43.2, respectively, and they decreased by increasing the VA content. EVA with the same VA content showed different crystalline properties as per the suppliers, and some EVAs deviated from the average trends. This could be explained by the difference in their microstructures such as the sizes and distribution uniformity of the ethylene sequences in EVA chains.

• Journal for History of Mathematics
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• v.24 no.4
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• pp.1-6
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• 2011

We investigate a method to find the least common multiples of numbers in the mathematics book GuIlJib(구일집(九一集), 1724) written by the greatest mathematician Hong Jung Ha(홍정하(洪正夏), 1684~?) in Chosun dynasty and then show his achievement on Number Theory. He first noticed that for the greatest common divisor d and the least common multiple l of two natural numbers a, b, l = $a\frac{b}{d}$ = $b\frac{a}{d}$ and $\frac{a}{d}$, $\frac{b}{d}$ are relatively prime and then obtained that for natural numbers $a_1,\;a_2,{\ldots},a_n$, their greatest common divisor D and least common multiple L, $\frac{ai}{D}$($1{\leq}i{\leq}n$) are relatively prime and there are relatively prime numbers $c_i(1{\leq}i{\leq}n)$ with L = $a_ic_i(1{\leq}i{\leq}n)$. The result is one of the most prominent mathematical results Number Theory in Chosun dynasty. The purpose of this paper is to show a process for Hong Jung Ha to capture and reveal a mathematical structure in the theory.

• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.4.2-4.2
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• 2008

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.3
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• pp.93-101
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• 2018

FDM is one of the popular 3D printing technologies because of an inexpensive extrusion machine and multi-material printing. FDM can use thermoplastics such as ABS and PLA. The 3D-printed ABS parts fabricated by FDM are attractive in the automotive industry because of their weight. A 10% reduction in weight can increase the fuel economy by approximately 7%. To use 3D-printed ABS parts as automotive parts, we should evaluate the 3D-printed parts in terms of automotive reliability. In this study, 3D-printed ABS samples were evaluated using Ono's rotary bending fatigue test. We obtained an S-N curve for the 3D-printed ABS specimen from the finite-element analysis. The S-N curve can be useful in early-stage design decisions for 3D-printed ABS parts.

• Honam Mathematical Journal
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• v.38 no.2
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• pp.243-257
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• 2016

If we let $L(2K;n):=\sum_{s=0}^{k-1}(^{2k}_{2s+1})\sum_{m=1}^{n-1}{\sigma}_{2k-2s-1,1}(m;2){\sigma}_{2s+1,1}(n-m;2)$ with $${\sigma}_{k,l}(n;2):=\sum\limits_{{d{\mid}n}\atop{d{\equiv}l(mod2)}}d^k$$, then we get the formula of L(2u; p)L(2v; p)L(2w; p).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4A
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• pp.224-231
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• 2003

In this in this thesis, we have proposed the Kor-231 which compared with Hata by dividing 4 classes and 8 details, which based on that the area subdivision which is defined by the City planning Regulation of Korea classified on its rate of building-to-land, floor area and distance between buliding and botanical coefficient. The experiments are carried out at the point of the RMS delay spread and the recerived power in the two kinds of geographical areas, LOS(Line of Sight) and N-LOS(Non Line of Sight). When the measured result is compared with Kor-231 model, we can catch the result that received power are 25.5dB and 14.5dB, the RMS delay spread are 101ns and 35ns and N-LOS received power are 4.1dB and 1.6dB. So we have certified that it is well due to the result analyzed into the difference of the RMS delay spread from 74ns to 200ns.

• The Journal of Korean Association of Computer Education
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• v.17 no.2
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• pp.115-124
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• 2014

Hypercube and star graph are widely known as interconnection network. The embedding of an interconnection network is a mapping of a network G into other network H. The possibility of embedding interconnection network G into H with a low cost, has an advantage of efficient algorithms usage in network H, which was developed in network G. In this paper, we provide an embedding algorithm between HCN and HON. HCN(n,n) can be embedded into HON($C_{n+1},C_{n+1}$) with dilation 3 and HON($C_d,C_d$) can be embedded into HCN(2d-1,2d-1) with dilation O(d). Also, star graph can be embedded to half pancake's value of dilation 11, expansion 1, and average dilation 8. Thus, the result means that various algorithms designed for HCN and Star graph can be efficiently executed on HON and half pancake, respectively.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.200.1-200
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• 2003

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.5
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• pp.1138-1144
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• 2013

Cross-correlation functions of maximal period sequences have been studied for decades. In this paper, we find the cross-correlation values of non-linear sequences $S_a^r(t)=Tr_1^m\{[Tr_m^n(a{\alpha}^t+{\alpha}^{dt})]^r\}$ having the maximal period $2^n-1$ for Niho type decimation $d=2^{m-2}(2^m+3)$, where n=2m. In particular, we call d Niho type decimation in case $d{\equiv}1(mod\;2^m-1)$. And we analyze the cross-correlation distributions of $S_a^r(t)$ when the phase shift ${\tau}=(2^m+1)k(0{\leq}k{\leq}2^m-2)$ and provide experiment results.