• Geomechanics and Engineering
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• 제12권3호
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• pp.505-522
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• 2017

A fundamental study of drilled shafts-soil systems subjected to lateral cyclic loading in weathered soil was conducted using numerical analyses. The emphasis was on quantifying the soil resistance of laterally cyclic loaded pile using 3D finite element analysis. The appropriate parametric studies needed for verifying the cyclic p-y characteristic are presented in this paper. A framework for determining the cyclic lateral load transfer curve (p-y curves) on the basis of numerical analyses is proposed. Through comparisons with results of field load tests, the three-dimensional numerical methodology in the present study is in good agreement with the general trend observed by in situ measurements and thus, represents a realistic soil-pile interaction for laterally loaded piles in soil than that of existing p-y method. It can be said that a rigorous present analysis can overcome the limitations of existing cyclic p-y methods to some extent by considering the effect of realistic three-dimensional combination of pile-soil forces. The proposed cyclic p-y curve is shown to be capable of predicting the behavior of the drilled shafts in weathered soil.

• Geomechanics and Engineering
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• 제14권1호
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• pp.1-8
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• 2018

This paper presents an investigation of the liquefaction characteristics and particle crushing of isotropically consolidated silica sand specimens at a wide range of confining pressures varying from 0.1 MPa to 5 MPa during undrained cyclic shearing. Different failure patterns of silica sand specimens subjected to undrained cyclic loading were seen at low and high pressures. The sudden change points with regard to the increasing double amplitude of axial strain with cycle number were identified, regardless of confining pressure. A higher cyclic stress ratio caused the specimen to liquefy at a relatively smaller cycle number, conversely producing a larger relative breakage $B_r$. The rise in confining pressure also resulted in the increasing relative breakage. At a specific cyclic stress ratio, the relative breakage and plastic work increased with the rise in the cyclic loading. Less particle crushing and plastic work consumption was observed for tests terminated after one cyclic loading. Majority of the particle crushing was produced and majority of the plastic work was consumed after the specimen passed through the phase transformation point and until reaching the failure state. The large amount of particle crushing resulted from the high-level strain induced by particle transformation and rotation.

• Journal of Plant Biology
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• 제21권1_4호
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• pp.13-21
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• 1978

The effect of cyclic-AMP on the induction of acid phosphatase activity in barley aleurone layers was examined. Tannic acid was used as a inhibitor. Decursinol and coumarin were also used as a comparison. Maxiumu promotion of the enzyme activity was obtained with 10-5M cyclic-AMP, but this promotion was lower than that of 10-5M GAS induced enzyme activity in incubation medium. The inhibition rate in the addition of tannic acid was shown 17% and 63% at a ratio to GAs (by weight) of 10 : 1, and 58% and 94% at a ratio of 100 : 1 treated with GAs, and cyclic-AMP, respectively. The most potentiation of 10-6M GAS effect was induced by the additiion of suboptimal concentration (10-6M) of cyclic-AMP. Additional GAs and cyclic-AMP were shown the recovery of the enzyme activity inhibited by tannic acid. The combination with cyclic-AMP and theophylline enhanced the enzyme activity, too. Any other nucleotides tested except cyclic-AMP didn't show the action. There were no differences in acid phosphatase isozyme patterns by polyacrylamide disc electrophoresis, in conjunction with the different additions but the size of bands showed great differences. Especially, the 3rd band and the 5th band group were remarkable.

• Nuclear Engineering and Technology
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• 제48권6호
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• pp.1376-1386
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• 2016

This study investigated the loading rate effect on the fracture resistance under cyclic loading conditions to understand clearly the fracture behavior of piping materials under seismic conditions. J-R fracture toughness tests were conducted under monotonic and cyclic loading conditions at various displacement rates at room temperature and the operating temperature of nuclear power plants (i.e., $316^{\circ}C$). SA508 Gr.1a low-alloy steel and SA312 TP316 stainless steel piping materials were used for the tests. The fracture resistance under a reversible cyclic load was considerably lower than that under monotonic load regardless of test temperature, material, and loading rate. Under both cyclic and monotonic loading conditions, the fracture behavior of SA312 TP316 stainless steel was independent of the loading rate at both room temperature and $316^{\circ}C$. For SA508 Gr.1a lowalloy steel, the loading rate effect on the fracture behavior was appreciable at $316^{\circ}C$ under cyclic and monotonic loading conditions. However, the loading rate effect diminished when the cyclic load ratio of the load (R) was -1. Thus, it was recognized that the fracture behavior of piping materials, including seismic loading characteristics, can be evaluated when tested under a cyclic load of R = -1 at a quasistatic loading rate.

• 한국지반공학회논문집
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• 제27권3호
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• pp.63-73
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• 2011

반복수평하중을 받는 말뚝의 거동은 반복하중의 크기와 재하횟수 뿐만 아니라 반복하중의 재하방법(한방향 또는 양방향 재하)에도 영향을 받는다. 본 연구에서는 반복수평하중의 재하방법이 모래지반에 타입된 항타말뚝의 거동에 미치는 영향을 조사하기 위해서 가압토조를 이용한 모형말뚝재하시험을 수행하였다. 실험결과에 따르면 반복수평하중을 한방향으로 받는 말뚝의 누적 영구수평변위는 최초 재하방향과 같은 방향으로 발생하지만, 반복하중을 양방향으로 받는 말뚝의 영구수평변위는 최초 재하방향과 반대 방향으로 발생하였다. 그리고 이와 같은 반복하중의 재하방법에 따른 말뚝 영구수평변위의 변화로 인해 한방향 반복재하는 말뚝의 반복극한수평지지력을 감소시키고 양방향 반복 재하는 말뚝의 반복극한수평지지력을 증가시켰으며, 수평하중의 반복재하횟수가 많아질수록 하중의 재하방법에 따른 말뚝의 반복극한수평지지력 차이는 더욱 확대되었다. 또한 반복수평하중의 재하방법에 따른 말뚝 주변지반의 다짐도 차이로 인해 수평하중이 반복재하되는 동안 말뚝에 발생하는 최대 휨모멘트는 반복하중이 양방향보다 한방향으로 재하되는 경우에 더 크게 나타났다. 그러나 극한상태에서 말뚝에 발생한 최대 휨모멘트는 반복하중이 한방향보다 양방향으로 재하된 경우에 그리고 반복재하를 받은 경우보다 그렇지 않은 경우에 더 큰 것으로 조사되었다.

• 한국통신학회논문지
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• 제25권5B호
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• pp.859-870
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• 2000

본 논문에서는 OFDM(Orthogonal Frequency Division Multiplexing) 시스템에서 사용되는 보호구간을 하드웨어로 효율적으로 구현할 수 있는 기법을 제안하고, OFDM기반의 25 Mbps 무선 ATM 모뎀에 적용하여 ASIC칩을 설계한다. OFDM 시스템에서는 가장 긴 delay spread 보다 긴 cyclic prefix를 삽입하여 채널의 선형 컨볼루션을 이산 Fourier 영역에서 circular 컨볼루션으로 변형함으로써 부채널간의 직교성을 유지하고, OFDM 블록내의 심볼간 간섭은 방지한다. 그러나 OFDM 시스템에서 이러한 cyclic prefix를 사용하기 위해서는 원래 샘플을 저장하고 각 블록의 시작 위치에 cyclic prefix를 붙이기 위한 추가적인 하드웨어가 송신단에서 요구된다. 본 논문에서는 cyclic suffix를 사용한 새로운 기법을 제안하고, 제안된 기법이 기존의 cyclic prefix 기법에 비하여 매우 적은 하드웨어로 동일한 성능을 갖게 됨을 확인한다. 마지막으로 제안된 기법을 OFDM기반의 25 Mbps 무선 ATM 모뎀의 ASIC칩 설계에 적용하여 그 성능을 확인한다.

• 한국지반공학회논문집
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• 제31권11호
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• pp.15-23
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• 2015

반복단순전단시험기를 사용하여 조밀한 해양실트질 모래의 비배수 파괴거동에 대한 평균전단응력과 반복전단응력의 영향을 평가하였다. 시험결과는 평균전단응력비가 0인 경우는 비교적 좌우 대칭형태의 반복전단변형률이 주된 변형모드였으며 영구전단변형률은 상대적으로 작게 발생하였다. 평균전단응력비가 0이상인 경우는 반복횟수가 증가함에 따라 주로 한 방향으로 영구전단변형률이 증가하고 반복전단변형률은 거의 변화가 없었다. 평균전단응력비는 응력-변형률 거동에 상당한 영향을 보였으나, 파괴에 필요한 반복하중횟수 등에 대한 영향이 반복전단응력비에 비해 상대적으로 적었다. 본 논문에서 제안한 응력기반 파괴기준은 해양구조물 설계 시 기초 하부 지반의 반복전단강도를 평가하는 데 효과적으로 사용될 수 있다.

• 한국지진공학회논문집
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• 제21권3호
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• pp.145-152
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• 2017

The objective of this study is to propose a simple and accurate analytical model for HSS braces. For this purpose, a physical theory model is adopted. Rectangular hollow section steel (HSS) braces are considered in this study. To accurately simulate the cyclic behavior of braces using the physical theory model, empirical equations calculating constituent parameters are implemented on the analytical model, which were proposed in the companion paper. The constituent parameters are cyclic brace growth, cyclic buckling load, and the incidence of local buckling and fracture. The analytical model proposed in this study was verified by comparing actual and simulated cyclic curves of brace specimens. It is observed that the proposed model accurately simulates the cyclic behavior of the braces throughout whole response range.

• Journal of applied mathematics & informatics
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• 제31권3_4호
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• pp.337-342
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• 2013

In this paper, we study a special class of linear codes, called skew cyclic codes, over the ring $R=F_p+vF_p$, where $p$ is a prime number and $v^2=v$. We investigate the structural properties of skew polynomial ring $R[x,{\theta}]$ and the set $R[x,{\theta}]/(x^n-1)$. Our results show that these codes are equivalent to either cyclic codes or quasi-cyclic codes. Based on this fact, we give the enumeration of distinct skew cyclic codes over R.

• Journal of applied mathematics & informatics
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• 제36권5_6호
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• pp.359-368
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• 2018

In this paper, we investigate quasi-cyclic codes over the ring $R={\mathbb{F}}_2+v{\mathbb{F}}_2$, where $v^2=v$. We investigate the structure of generators for one-generator quasi-cyclic codes over R and their minimal spanning sets. Moreover, we find the rank and a lower bound on minimum distances of free quasi-cyclic codes over R. Further, we find a relationship between cyclic codes over a different ring and quasi-cyclic codes of index 2 over R.