• 한국통신학회논문지
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• 제34권2A호
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• pp.85-90
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• 2009

In this paper, as an alternative to constant modulus algorithm based on MSE, maximization of the probability that equalizer output power is equal to the constant modulus of the transmitted symbols is introduced. The proposed algorithm using the gradient ascent method to the maximum probability criterion has superior convergence and steady-state MSE performance, and the error samples of the proposed algorithm exhibit more concentrated density functions in blind equalization environments. Simulation results indicate that the proposed training has a potential advantage versus MSE training for the constant modulus approach to blind equalization.

• Coupled systems mechanics
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• 제2권3호
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• pp.289-302
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• 2013

The piled raft is a geotechnical construction, consisting of the three elements-piles, raft and the soil, that is applied for the foundation of a tall buildings in an increasing number. The piled rafts nowadays are preferred as the foundation to reduce the overall and differential settlements; and also, provides an economical foundation option for circumstances where the performance of the raft alone does not satisfy the design requirements. The finite element analysis of the piled raft foundation is presented in this paper. The numerical procedure is programmed into finite element based software SAFE in order to conduct the parametric study wherein soil modulus and raft thickness is varied for constant pile diameter. The problems of piled raft for three different load patterns as considered in the available literature (Sawant et al. 2012) are analyzed here using SAFE. The results obtained for load pattern-I using SAFE are compared with those obtained by Sawant et al. (2012). The fair agreement is observed in the results which demonstrate the accuracy of the procedure employed in the present investigation. Further, substantial reduction in maximum deflections and moments are found in piled raft as compared to that in raft. The reduction in deflections is observed with increase in raft thickness and soil modulus. The decrease in maximum moments with increase in soil modulus is seen in raft whereas increase in maximum moments is seen in piled raft. The raft thickness and soil modulus affects the response of the type of the foundation considered in the present investigation.

• 한국통신학회논문지
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• 제36권12C호
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• pp.753-758
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• 2011

The constant modulus algorithm (CMA) widely used in blind equalization applications minimizes the averaged power of constant modulus error (CME) defined as the difference between an instant output power and a constant modulus. In this paper, a decision feedback version of the linear blind algorithm based on maximization of the zero-error probability for CME is proposed. The Gaussian kernel of the maximum zero-error criterion is analyzed to have the property to cut out excessive CMEs that may be induced from severely distorted channel characteristics. Decision feedback approach to the maximum zero-error criterion for CME is developed based on the characteristic that the Gaussian kernel suppresses the outliers and this prevents error propagation to some extent. Compared to the linear algorithm based on maximum zero-error probability for CME in the simulation of blind equalization environments, the proposed decision feedback version has superior performance enhancement particularly in cases of severe channel distortions.

• 대한수학회논문집
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• 제33권4호
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• pp.1303-1308
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• 2018

In this paper, we consider both maximum modulus and minimum modulus on a circle of some polynomials. These give rise to interesting examples that are about moduli of Chebyshev polynomials and certain sums of polynomials on a circle. Moreover, we obtain some root locations of difference quotients of Chebyshev polynomials.

• 마이크로전자및패키징학회지
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• 제21권4호
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• pp.125-131
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• 2014

웨어러블 패키징용 신축성 기판을 개발하기 위해 투명한 PDMS인 Sylgard 184와 검정색 PDMS인 Sylgard 170에 대해 base/curing agent 혼합비에 따른 탄성계수의 변화거동을 분석하였다. Sylgard 184와 Sylgard 170의 공칭응력-공칭변형률 곡선에서 구한 공칭탄성계수에 비해 진응력-진변형률 관계로부터 구한 진탄성계수가 2배 이상 높았으며, 진탄성계수와 공칭탄성계수의 차이는 PDMS의 강성도가 높아질수록 증가하였다. Sylgard 184에서는 base/curing agent의 혼합비가 10일 때 탄성계수의 최대값을 얻을 수 있었으며, 이때 공칭탄성계수는 1.74 MPa, 진탄성계수는 3.57 MPa이었다. Sylgard 170에서는 base/curing agent 혼합비가 2일 때 탄성계수가 최대가 되었으며, 이때 공칭탄성계수와 진탄성계수는 각기 1.51 MPa와 3.64 MPa이었다.

• Structural Engineering and Mechanics
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• 제78권3호
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• pp.281-296
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• 2021

This article analyzed the modulus degradation of concrete subjected to multi-level compressive cyclic loading. The evolution of secant elastic modulus is investigated based on measurements from top loading platen and LVDT in the middle part of concrete. The difference value of the two secant elastic moduli is reduced when close to failure and could be used as a fatigue failure precursor. The fatigue hardening is observed for concrete during cyclic loading. When the maximum stress is smaller the fatigue hardening is more obvious. The slight increase of maximum stress will lead to the "periodic hardening". The tangent elastic modulus shows a specific "bowknot" shape during cyclic loading, which can characterize the hysteresis of stress-strain and is influenced by the cyclic loading stresses. The deterioration of secant elastic modulus acts a similar role with respect to the P-wave speed during cyclic loading, can both characterize the degradation of the concrete properties.

• Geomechanics and Engineering
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• 제7권3호
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• pp.297-316
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• 2014

This paper presents a detailed study focused on investigating the effects of silt content on the static and dynamic properties of sand-silt mixtures. Specimens with a low-plastic silt content of 0, 15, 30 and 50% by weight were tested in static triaxial, cyclic triaxial, and resonant columns in addition to consolidation tests to determine such parameters as compression index, internal friction angle, cohesion, cyclic stress ratio, maximum shear modulus, normalized shear modulus and damping ratio. The test procedures were performed on specimens of three cases: constant void ratio index, e = 0.582; same peak deviator stress of 290 kPa; and constant relative density, $D_r$ = 30%. The test results obtained for both the constant-void-ratio-index and constant-relative-density specimens showed that as silt content increased, the internal friction angle, cyclic stress ratio and maximum shear modulus decreased, but cohesion increased. In testing of the same deviator stress specimens, both cohesion and internal friction angle were insignificantly altered with the increase in silt content. In addition, as silt content increased, the maximum shear modulus increased. The cyclic stress ratio first decreased as silt content increased to reach the threshold silt content and increased thereafter with further increases in silt content. Furthermore, the damping ratio was investigated based on different silt contents in three types of specimens.

• 한국도로학회논문집
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• 제10권3호
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• pp.11-18
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• 2008

최근 국내외에서 역학적-경험적 설계법의 개발 및 이의 활용을 위한 각종 연구가 매우 활발하게 진행중에 있다. 미국의 경우 AASHTO 2002 설계법, 우리나라의 경우 한국형 도로포장설계법의 개발이 진행 중에 있고, 개발되는 설계법에 도로포장재료의 역학적 물성치 평가가 상당히 중요한 역할을 하도록 구성되어 있다. 따라서 설계법에 이용될 국내 아스팔트 혼합물의 재료물성의 평가가 매우 시급한 실정이다. 설계법에 이용되는 재료 물성을 평가하는 방법 중 최근에 많이 적용되는 방법이 동탄성계수 실험이다. 동탄성계수는 다양한 온도조건, 하중, 속도를 이용하여 다양한 교통조건을 반영할 수 있다. 사용된 골재의 입도, 아스팔트 바인더에 따라서 변화하며, 특히 아스팔트 혼합물의 점탄성적인 특성을 잘 묘사할 수 있는 물성치 평가방법이라고 할 수 있다. 본 연구에서는 아스팔트 혼합물에 사용되는 골재의 공칭최대치수 및 입도분포와 동탄성계수와의 상관관계를 규명하는 것이다. 국내의 실험장비 조건을 고려할 때, 시편의 직경 및 높이는 100mm 및 150mm를 이용하는 것이 바람직하다. 또한, 골재의 공칭최대치수가 커짐에 따라 동탄성계수가 증가하는 경향을 나타내었다.

• Geomechanics and Engineering
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• 제37권5호
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• pp.443-452
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• 2024

The use of sand-tire chip mixtures in construction industry is a sustainable and environmentally friendly approach that addresses both waste tire disposal and soil improvement needs. However, the addition of tire chip particles to natural soils decreases maximum shear modulus (G_max), but increases compressibility, which can be potential drawbacks. This study examines the effect of overconsolidation stress history on the maximum shear modulus (G_max) of rigid-soft mixtures with varying size ratios (SR) and tire chip contents (TC) by measuring the wave velocity through a 1-D compression test during loading and unloading. The results demonstrate that the G_max of tested mixtures in the normally consolidated state increased with increasing SR and decreasing TC. However, the tested mixtures with a smaller SR exhibited a greater increase in G_max during unloading because of the active pore-filling behavior of the smaller rubber particles and the consequent increased connectivity between sand particles. The SR-dependent impact of the overconsolidation stress history on G_max was verified using the ratio between the swelling and compression indices. Most importantly, this study reveals that the excessive settlement and lower G_max of rigid-soft mixtures can be overcome by introducing an overconsolidated state in sand-tire chip mixtures with low TC.

• 동력기계공학회지
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• 제10권4호
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• pp.99-104
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• 2006

Young's modulus of composite has been predicted by Eshelby's equivalent inclusion method modified with Mori-Tanaka's mean field theory, where short fibers of aspect ratio distribution are assumed to be aligned. Young's modulus of the composite is predicted with the smallest class interval for simulating the actual distribution of fiber aspect ratio, which is compared with that computed using different class intervals. Young's modulus of the composite predicted with mean aspect ratio or the largest class interval is overestimated by the maximum 10%. As the class interval of short fibers for predicting Young's modulus decreases, the predicted results show good agreements with those obtained using the actual distribution of fiber aspect ratio. It can be finally concluded from the study that if and only if the class interval of short fiber normalized by the maximum aspect ratio is smaller than 0.1, the predicted results are consistent with those obtained using the actual distribution of aspect ratio.