• 대한환경공학회지
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• 제36권1호
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• pp.13-19
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• 2014

청정한 물환경에 대한 기대가 높아지는 시대에서, 관리가 쉽지 않은 비점오염원에서 발생하는 오염부하량을 산정하여 합리적인 국토관리를 도모할 수 있는 기초자료를 제시하였다. 연구는 2개소의 밭경작지를 대상으로 하였으며 고구마와 벚나무를 재배하는 비점오염원으로 각각 3년 동안에 걸쳐 강우사상을 모니터링 하였다. 오염부하량에 영향을 미치는 가장 중요한 인자는 강우량으로 50 < rainfall (mm)의 강우사상에서는 100% 강우유출량이 발생하여 오염물질을 발생하였다. 그러나 30 < rainfall (mm) ${\leq}50^a$와 10 < rainfall (mm) ${\leq}30^b$에서는 강우유출수에 의한 오염부하에는 작물의 재배방법과 토양의 특성 등이 결정인자로 작용되어, 작물성장이 현저한 벚나무경작지에서 강우유출수 발생빈도는 a : 60%, b : 5%로 고구마경작지에서의 강우유출수 발생빈도보다 낮았으며, 이로 인해 오염부하량도 적었다. 반면, 고구마경작지에서의 강우유출수 발생빈도는 a : 80%, b : 15%로 나타났다.

• 전기전자학회논문지
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• 제22권1호
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• pp.127-135
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• 2018

본 논문에서는 MNR(Mu-negative) Metamaterial 단일 셀을 사용하여 700 MHz UHD 방송 대역과 2.45 GHz/5 GHz WiFi 대역에서 동작하는 삼중대역 폴디드 모노폴 안테나 설계에 관하여 연구하였다. MNG metamaterial 단일셀이 MZR(Mu zero resonator)에서 동작하도록 안테나 기판 뒷면에 커패시터를 형성하고, 스트립선로와 비아홀을 통해서 접지면과 연결하여 구현하였다. 이를 통해서 700 MHz대역에서 영차모드에서 공진하도록 공진점을 제어할 수 있고, 대역폭을 개선할 수 있다. 최종적으로 700 MHz UHD방송 대역과 2.45 GHz/5 GHz WiFi 대역에서 동작하는 안테나를 구현하였다. 설계 제작한 안테나의 크기는 $100{\times}100mm^2$이고, 실험 결과 첫 번째 공진점에서 10 dB 대역폭과 이득은 각각 309 MHz(41.2%), 5.298 dB이며, 두 번째 공진점에서 10 dB 대역폭과 이득은 각각 821.9 MHz(33.5%), 2.7840 dB이며, 세번째 공진점에서 10 dB 대역폭과 이득은 각각 1.1314 GHz(20.6%), 2.9484 dB의 결과를 확인하였다. 안테나의 공진주파수는 이론과 실험이 일치함을 확인하였다. 그리고 방사패턴은 대체적으로 전방향 특성을 가지고 있으며, 0.75 GHz와 2.45 GHz에서는 측면보다 전방향과 후방향으로 방사특성이 양호하며, 5.5 GHz에서는 다중로브를 갖는 방사패턴 특성을 확인하였다.

• 한국정밀공학회지
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• 제3권4호
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• pp.53-63
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• 1986

In this study, the stress distribution of rectangular bar under torsion, when warping of both ends is free or constrained, is investigated. Method of separation of variable and Fourier Series are used for the theoretical analysis, and 3dimensional photoelastic stress-freezing method for experimental analysis. The main results are as follows; 1) In the case of warping-constrained rectangular bar, the normal stresses are negligible because they are less then 0.5% of the shear stresses. The maximum normal stress is placed on the point of y=0.61 b when b/a=1 and it gradually moves to the corner y=b when the value of b/a is increased. 2) According to increase of the value of b/a, on the crossection, the maximum shear stress is placed on the middle point of the long side (x=${\pm}a$, y=0) when warping of both ends is free but the middle of the short side (x=0, y=${\pm} b$) when warping is constrained. The stress distribution is straight line when warping is constrained, namely, the stress distribution is proportional to the distance from the axis of centroid, but parabolic when warping is free. 3) The values of the combined stress of warping-constrained bar, if the influence of the loaded point is neglected, are generally smaller than those of warping-free.

• Smart Structures and Systems
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• 제13권4호
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• pp.547-565
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• 2014

This paper investigates the design of a perfect point load actuator based on flat triangular piezoelectric patches. Applying a difference of electric potential between the electrodes of a triangular patch leads to point loads at the tips and distributed moments along the edges of the electrodes. The previously derived analytical expressions of these forces show that they depend on two factors: the width over height (b/l) ratio of the triangle, and the ratio of the in-plane piezoelectric properties ($e_{31}/e_{32}$) of the active layer of the piezoelectric patch. In this paper, it is shown that by a proper choice of b/l and of the piezoelectric properties, the moments can be cancelled, so that if one side of the triangle is clamped, a perfect point load actuation can be achieved. This requires $e_{31}/e_{32}$ to be negative, which imposes the use of interdigitated electrodes instead of continuous ones. The design of two transducers with interdigitated electrodes for perfect point load actuation on a clamped plate is verified with finite element calculations. The first design is based on a full piezoelectric ceramic patch and shows superior actuation performance than the second design based on a piezocomposite patch with a volume fraction of fibres of 86%. The results show that both designs lead to perfect point load actuation while the use of an isotropic PZT patch with continuous electrodes gives significantly different results.

• 대한기계학회논문집B
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• 제23권6호
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• pp.753-760
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• 1999

Experiments were conducted to investigate the effect of the initial turbulent intensity on the flow and heat transfer characteristics for a two-dimensional impinging jet. A square rod was installed at the nozzle exit to increase initial turbulent intensity. A hot wire probe and thermochromic liquid crystal technique were used to measure the turbulent intensity and the surface temperature. All measurements were made over a range of nozzle-to-plate distance from 1 to 10 at Re=20,000. When the rod is not installed, the maximum stagnation point Nusselt number is occurred at H/B=9. A higher initial turbulent intensity enhanced the heat transfer on the surface. A correlation between stagnation point Nusselt number and turbulent intensity are presented.

• 대한수학회지
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• 제56권3호
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• pp.645-667
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• 2019

It has been little known when an Artinian point quotient has the strong Lefschetz property. In this paper, we find the Artinian point star configuration quotient having the strong Lefschetz property. We prove that if ${\mathbb{X}}$ is a star configuration in ${\mathbb{P}}^2$ of type s defined by forms (a-quadratic forms and (s - a)-linear forms) and ${\mathbb{Y}}$ is a star configuration in ${\mathbb{P}}^2$ of type t defined by forms (b-quadratic forms and (t - b)-linear forms) for $b=deg({\mathbb{X}})$ or $deg({\mathbb{X}})-1$, then the Artinian ring $R/(I{\mathbb_{X}}+I{\mathbb_{Y}})$ has the strong Lefschetz property. We also show that if ${\mathbb{X}}$ is a set of (n+ 1)-general points in ${\mathbb{P}}^n$, then the Artinian quotient A of a coordinate ring of ${\mathbb{X}}$ has the strong Lefschetz property.

• Journal of Welding and Joining
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• 제18권5호
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• pp.90-97
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• 2000

Effect of alloy elements on joinability of insert metal for liquid phase diffusion bonding of heat resistant alloys was investigated in this study. Also, optimum chemical composition of insert metal was explained using interpolation method. The insert metals utilized was commercial Ni-base amorphous foils and newly developed Ni-base filler metals with B, Si and Cr in this study. Melting point and critical interlayer width(CIW) decreased with increasing additional amount of B, Si and Cr, melting point lowering element of the insert metal. Optimized chemical composition of insert metals could be estimated by interpolation method. The optimum amount of B, Si, Cr addition into the insert metal were found to be about 3%, 4% and 3%, respectively. The measured characteristic values, melting point, microhardness in the bonded interlayer and CIW of the insert metals were the almost identical to ones of the calculated results by interpolation method.

• 전자공학회논문지A
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• 제33A권12호
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• pp.1-8
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• 1996

In this paper, we propose a hybrid blind equalizer with TEA and SG (stop & Go) algorithm with switching point a 0 dB of MSE value for improvement of convergence performance, where TEA is used initially to open the eye and then SG algorithm as rapid convergence is employed. The switching point is selected at the point of 0 dB MSE level because of settling the coefficients of blind equalier. As a result of computer simulatons for 8-PAM in the non-minimum phase channel, the proposed algorithm has better convergence speed as 3,500 ~ 4,500 iterations and has better MsE about 3 ~ 6 dB than those of original TEA. Also, computational cost of proposed algorithm is reduced as 5 ~ 16% than that of original TEA. and, the proposed algorithm has better convergence than SG algorithm as 8,500 ~ 17,500 iteratins but, the MSE is similar to original SG.

• 대한화학회지
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• 제14권4호
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• pp.287-296
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• 1970

The varation of potential and completeness of reaction in an oxidation-reduction titration of Red$_1$ ($a\;Ox_1+N_1e{\leftrightarrow}b\;Red_1)\;by\;Ox_2\;(C\;Ox_2+n_2e{\leftrightarrow}d\;Red_2)$ is analyzed on the basis of general expressions. It is shown that the reaction deficiency as well as the rate of variation of the potential with titration fraction change in proportion to the $[n_2(a-b)-n_1(c-d)]$ th power of the concentration of the reagents. In particular, at the equivalence point, the expression of the potential contains a concentration dependent term that is proportional to ac-bd. Thus, the equivalence-point potential varies with the concentration of the reagents unless ac=bd is satisfied. It is also shown that the sharpness of the potentiometric titration curve is shown to occur either prior to or after the equivalence point depending upon whether $n_1cn_2b$, the deviation being the same order of magnitude as the relative deficiency at the equivalence point.

• 대한치과기공학회지
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• 제39권1호
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• pp.25-33
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• 2017

Purpose: The aim of this study was to evaluate accuracy of glass fiber mesh complete denture of before and after curing. Methods: Edentulous model was selected as the master model. Ten study models were made by Type IV stone. Wax complete dentures were produced by the denture base and artificial teeth. CD and GD groups were measured six measurement distance before curing. The wax complete denture was investment after measurement is completed. Using a heat polymerization resin was injected resin. After injecting the resin it was curing. A complete denture was re-measured after curing. The measured data was verified by paired t-test. Results: Overall CD group was larger the value of the measured length. In the CD group, A-D point was larger. The smallest point was the B-D point. However, there was no statistically significant difference only C-D point(p>0.05). In the GD group, A-B point was larger. but B-D point was the smallest. A-D and B-C statistically points showed significant differences(p<0.05). Conclusion: Glass fiber mesh resin complete denture can be clinically applied to the edentulous patient.