• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.2
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• pp.183-193
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• 1995

Assuming that fishing nets are porous structures to suck water into their mouth and then filtrate water out of them, the flow resistance N of nets with wall area S under the velicity v was taken by $R=kSv^2$, and the coefficient k was derived as $$k=c\;Re^{-m}(\frac{S_n}{S_m})n(\frac{S_n}{S})$$ where $R_e$ is the Reynolds' number, $S_m$ the area of net mouth, $S_n$ the total area of net projected to the plane perpendicular to the water flow. Then, the propriety of the above equation and the values of c, m and n were investigated by the experimental results on plane nettings carried out hitherto. The value of c and m were fixed respectively by $240(kg\cdot sec^2/m^4)$ and 0.1 when the representative size on $R_e$ was taken by the ratio k of the volume of bars to the area of meshes, i. e., $$\lambda={\frac{\pi\;d^2}{21\;sin\;2\varphi}$$ where d is the diameter of bars, 21 the mesh size, and 2n the angle between two adjacent bars. The value of n was larger than 1.0 as 1.2 because the wakes occurring at the knots and bars increased the resistance by obstructing the filtration of water through the meshes. In case in which the influence of $R_e$ was negligible, the value of $cR_e\;^{-m}$ became a constant distinguished by the regions of the attack angle $ \theta$ of nettings to the water flow, i. e., 100$(kg\cdot sec^2/m^4)\;in\;45^{\circ}<\theta \leq90^{\circ}\;and\;100(S_m/S)^{0.6}\;(kg\cdot sec^2/m^4)\;in\;0^{\circ}<\theta \leq45^{\circ}$. Thus, the coefficient $k(kg\cdot sec^2/m^4)$ of plane nettings could be obtained by utilizing the above values with $S_m\;and\;S_n$ given respectively by $$S_m=S\;sin\theta$$ and $$S_n=\frac{d}{I}\;\cdot\;\frac{\sqrt{1-cos^2\varphi cos^2\theta}} {sin\varphi\;cos\varphi} \cdot S$$ But, on the occasion of $\theta=0^{\circ}$ k was decided by the roughness of netting surface and so expressed as $$k=9(\frac{d}{I\;cos\varphi})^{0.8}$$ In these results, however, the values of c and m were regarded to be not sufficiently exact because they were obtained from insufficient data and the actual nets had no use for k at $\theta=0^{\circ}$. Therefore, the exact expression of $k(kg\cdotsec^2/m^4)$, for actual nets could De made in the case of no influence of $R_e$ as follows; $$k=100(\frac{S_n}{S_m})^{1.2}\;(\frac{S_m}{S})\;.\;for\;45^{\circ}<\theta \leq90^{\circ}$$, $$k=100(\frac{S_n}{S_m})^{1.2}\;(\frac{S_m}{S})^{1.6}\;.\;for\;0^{\circ}<\theta \leq45^{\circ}$$

• Journal of the Korean Chemical Society
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• v.45 no.5
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• pp.429-435
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• 2001

The monomer N,N'-bis(2-pyrrol-1-yl-propyl)-4,4'-bipyridine(bpb) was electrochemically polymerized on the glassy carbon electrode surface, which was modified with 1:1 ratio of erichrome black T(EBT) and glutathione(GSSG) to give a type of GC/poly-bpb, EBT, GSSG electrode for depositing Zn(II). The diffusion coefficients of the incorporated ions were 2.43${\times}10^{-15}$ and 9.14${\times}10^{-15} cm^2s^{-1}$ before taking Zn(II) ions and after them respectively. The modified electrodes are stable at the electrode process. The polymerized poly-bpb of 2.83${\times}10^4gmol^{-1}$ can deposit 2.15${\times}10^4gmol^{-1}$ of Zn(II). The number of pumping ions involving in the redox procedure at 0.77 V was 81.7% of the captured 180 ions into the polymer matrix, which was 3 times larger than that of the electrode modified with EBT alone.

• Journal of the Korean Magnetics Society
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• v.6 no.1
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• pp.28-35
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• 1996

Dispersion behavior was investigated as functions of species and arrount of addtives, binders, abrasives, lubricants, etc.. Dispersibilityand other various properties were affected by the fuctional groups of binders. Friction coefficient and surface roughness of tape were changed with lubricants, therefore duratility of magnetic tape was varied. As a result of above investigations, we concluded that dispersion behavior of particles was very sensitive for obtaining maximum properties of metal particle tape.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.401-406
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• 2002

The purpose of this research was to obtain fatigue property of pavement concrete by flexural fatigue test. The size of specimen used in fatigue tests was 10$\times$10$\times$46cm. The specimens of pavement concrete were fabricated using the concrete at job site. The fatigue tests were performed by applying into a constant amplitude loading. The flexural fatigue tests were performed by stress levels of 90%, 80%, 70% and 60%, and stress ratio of 0.1. From this research, the S-N relationship, S-N-P relationship were derived and Weibull probability density functions was plotted using the distribution parameters.

• Journal for History of Mathematics
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• v.15 no.3
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• pp.1-16
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• 2002

The area between the arc and chord of a circle is called Hosichun whose figure looks like a bow and an arrow, and had been evaluated by the two formulas $\textit{H}_{n1}$=a(a＋y)/2 and $\textit{H}_{n2}$=3ay/4, where $\alpha$ is the length of the arrow and y the chord of the circle. By the inspection of the area of the Hosichun, some errors of the numeration table in Thurmans S. Peterson's CALCULUS were found easily, that is, the area of the Hosichun is smaller than its subarea in the same Hosichun and perhaps has been to be the worldwide and centurial invalid standard. From now on, the chain proofreadings of the errors will be necessary in our mathematical world. This paper is intended to introduce some such problems related to a circle and another Pythagorean Theorem which is the ratio of the side and diagonal of five and seven In a square.

• Journal of Ocean Engineering and Technology
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• v.20 no.5 s.72
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• pp.82-88
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• 2006

This assessment is concerned with the fatigue strength of the tendon porch found in TLP. Lorge-scale fatigue tests with models constructed at 30% the size of the real structures have been carried out to investigate the fatigue behavior of the API 2W Grade 50 steel recently produced by POSCO. The fatigue life for the present test models was obtained based on the concept of nominal stress. A comparison of the present test results with those obtained by a numerical approach based on the structural analysis results has showngood agreement. The present results were also compared with the design curves in DnV RP-C203.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.179-182
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• 2007

The compressive fatigue tests on the closed cell Al-Si-Ca alloy foams with two different thicknesses were performed using a load ratio of 0.1. The quasi-static and cyclic compressive behaviors were obtained respectively. The fatigue stress-life (S-N) curves were evaluated from the obtained cyclic compressive behaviors. S-N curves were presented for the onset of progressive shortening. It turned out that the fatigue strength showed higher value for the thicker foam and the onset of shortening of thinner foam took place earlier. The crushing was found to initiate in a single band which broadens gradually with additional fatigue cycles. Progressive shortening of the specimen took place due to a combination of low cycle fatigue failure and cyclic ratcheting.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.505-506
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• 2009

This paper is an investigation of the fatigue behaviors on the GFRP bar and GSP embedded method as repair and reinforced method. In the experiments, the stress ratio R is 0.1 and loading frequency is 1.5 Hz. As a result of fatigue test, the fatigue strengths of the GFRP bar and GSP reinforced beams were 58%, 52% of the static strength in S-N curve.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.3
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• pp.439-448
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• 1993

One of the main purposes of this paper is to propose a high resolution direction finding method performing particularly well under the circumstances such as correlated sensor noises, very closely spaced signal sources, and low signal-to-noise ratio(S/N), in array signal processing. Furthermore, the other is to demonstrate the superiority of the proposed method for each circumstance described above, in comparison with the methods previously developed.

• Journal of the Korean Home Economics Association
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• v.35 no.2
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• pp.111-122
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• 1997

This thesis researched for the conservation of a suit of armor, one glove, one belt, and on knife case that General Jung, Gong-chung had been worn in the early 17 th centuries. The armor was Doojung-kab for the battle. It was made of two kinds of fabrics, one of them was silk satin's outer fabrics, the other was quilt4d cotton's lining. as the armor was made of silk and cotton, it was treated by dry solvents and dry soap. In the dry cleaning method, used solvents were n-hexane, cyclohexane, benzene, and n-decane. the volume ratio of dry soap was 120: 1. The reaction temperature was 30℃, and reaction time was 10 to 30 minutes per one turn. The glove, belt and knife case were made with leather. They were dipped on the polyethyleneglycol 150 saturated solution during 24hours at 50℃ and then dried naturally. They were washed by toluene to remove the untreated pp.E.G. on the surfaces. It was sterilized by two gases of methylenebromide and ethyleneoxied. For the conservation, it was packed thoroughly by ？ polyethylene film sheet without air.