• Earthquakes and Structures
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• 제12권6호
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• pp.619-628
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• 2017

The intent of this paper is to investigate the propagation of Love waves in a dry sandy medium sandwiched between fiber-reinforced layer and prestressed porous half-space. Separate displacement components have been deduced in order to characterize the dynamics of individual materials. Using suitable boundary conditions, the frequency equation has been derived by means of separation of variables which reveals the significant role of reinforcement parameters, sandiness, thickness of layers, porosity and prestress on the wave propagation. The phase velocity of the Love wave has been discussed in accordance with its typical cases. In both cases when fiber-reinforced and dry sandy media are absent, the derived equation of Love type wave coincides with the classical Love wave equation. Numerical computations have been performed in order to graphically illustrate the dependencies of different parameters on phase velocity of Love waves. It is observed that the phase velocity decreases with the increase of parameters pertaining to reinforcement and prestress. The results have certain potential applications in earthquake seismology and civil engineering.

• Geomechanics and Engineering
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• 제9권6호
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• pp.793-813
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• 2015

Characterization of discontinuous media is an endeavor that poses great challenge to engineers in practice. Since the inherent defects in cracked domains can substantially influence material resistance and govern its behavior, a lot of work is dedicated to efficiently model such effects. In order to overcome difficulties of material instability problems, one needs to comprehensively represent the geometry of cracks along with their impact on the mechanical properties of the intact material. In the present study, stress-strain results from laboratory experiments on Inada granite was used to derive crack tensor as a tool for the evaluation of fractured domain stability. It was found that the formulations proposed earlier could satisfactorily be employed to attain crack tensor via the invariants of which judgment on cracks population and induced anisotropy is possible. The earlier criteria based on crack tensor analyses were reviewed and compared to the results of the current study. It is concluded that the geometrical parameters calculated using mechanical properties could confidently be used to judge the anisotropy as well as strength of the cracked domain.

• Advances in nano research
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• 제12권5호
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• pp.489-499
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• 2022

Nanofluids have recently triggered a substantial scientific interest as cooling media. However, their stability is challenging for successful engagement in industrial applications. Different factors, including temperature, nanoparticles and base fluids characteristics, pH, ultrasonic power and frequency, agitation time, and surfactant type and concentration, determine the nanofluid stability regime. Indeed, it is often too complicated and even impossible to accurately find the conditions resulting in a stabilized nanofluid. Furthermore, there are no empirical, semi-empirical, and even intelligent scenarios for anticipating the stability of nanofluids. Therefore, this study introduces a straightforward and reliable intelligent classifier for discriminating among the stability regimes of alumina-water nanofluids based on the Zeta potential margins. In this regard, various intelligent classifiers (i.e., deep learning and multilayer perceptron neural network, decision tree, GoogleNet, and multi-output least squares support vector regression) have been designed, and their classification accuracy was compared. This comparison approved that the multilayer perceptron neural network (MLPNN) with the SoftMax activation function trained by the Bayesian regularization algorithm is the best classifier for the considered task. This intelligent classifier accurately detects the stability regimes of more than 90% of 345 different nanofluid samples. The overall classification accuracy and misclassification percent of 90.1% and 9.9% have been achieved by this model. This research is the first try toward anticipting the stability of water-alumin nanofluids from some easily measured independent variables.

• Steel and Composite Structures
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• 제44권6호
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• pp.817-828
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• 2022

In this study, considering dissipated energy in fracture process zone (FPZ), a novel criterion based on maximum strain energy release rate (SER) for orthotropic materials is presented. General case of in-plane loading for cracks along the fibers is assumed. According to the experimental observations, crack propagation is supposed along the fibers and the reinforcement isotropic solid (RIS) concept is employed as a superior model for orthotropic materials. SER in crack initiation and propagation phases is investigated. Elastic properties of FPZ are extracted as a function of undamaged matrix media and micro-crack density. This criterion meaningfully links between dissipated energy due to toughening mechanisms of FPZ and the macroscopic fracture by defining stress intensity factors of the damaged zone. These coefficients are used in equations of maximum SER criterion. The effect of crack initiation angle and the damaged zone is considered simultaneously in this criterion and mode II stress intensity factor is extracted in terms of stress intensity factors of damage zone and crack initiation angle. This criterion can evaluate the effects of FPZ on the fracture behavior of orthotropic material. Good agreement between extracted fracture limit curves (FLC's) and available experimental data proves the ability of the new proposed criterion.

• Structural Engineering and Mechanics
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• 제90권2호
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• pp.209-218
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• 2024

The present paper is focused on the study of the propagation of plane waves in thermoelastic media under a modified Green-Lindsay (MG-L) model having the influence of non-local and two temperature. The problem is formulated for the considered model in dimensionless form and is explained by using the reflection phenomenon. The plane wave solution of these equations indicates the existence of three waves namely Longitudinal waves (LD-Wave), Thermal waves (T-wave), and Shear waves (SV-wave) from a stress-free surface. The variation of amplitude ratios is computed analytically and depicted graphically against the angle of incidence to elaborate the impact of non-local, two temperature, and different theories of thermoelasticity. Some particular cases of interest are also deduced from the present investigation. The present study finds applications in a wide range of problems in engineering and sciences, control theory, vibration mechanics, and continuum mechanics.

• 한국인쇄학회:학술대회논문집
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• 한국인쇄학회 2007년도 추계 학술논문 발표회
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• pp.29-43
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• 2007

Web offset newspaper prints is the most widely used printing process in domestic printing industry, but there are no industry-wide specifications for press control to assure consistent quality across newspaper printing plants. As newspaper printing becomes more of a commodity and less of an art, it is necessary to develop the print quality specification standard suitable for Korea web offset newspaper printing field. There are a few commonly employed printing standards such as, SNAP(Specification for Non-Heatset Publication) of the US, IFRA(INCA-FIEJ Research Association), J-color (Japan printing machinery association). And there exists KS for domestic standards, however, since it has been directly imported from ISO standards, there are discrepancies in printing materials and media. This paper aims to examine the color reproduction quality of domestic web offset newspaper prints by comparing with foreign standards. Printing experiments on this study have been performed at one of the domestic newspaper printing companies. The color reproduction properties of the web offset newspaper prints are measured by means of densitometry and colorimetry. These measures are evaluated comapratively with the international standards by means of analyzing, the major factors that determine the color reproduction quality of web offset newspapar prints.

• 한국인쇄학회지
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• 제25권1호
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• pp.27-41
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• 2007

Web offset newspaper prints is the most widely used printing process in domestic printing industry, but there are no industry-wide specifications for press control to assure consistent quality across newspaper printing plants. As newspaper printing becomes more of a commodity and less of an art, it is necessary to develop the print quality specification standard suitable for Korea web offset newspaper printing field. There are a few commonly employed printing standards such as, SNAP (Specification for Non-Heatset Publication) of the US, IFRA(INCA-FIEJ Research Association), J-color (Japan printing machinery association). And there exists KS for domestic standards, however, since it has been directly imported from ISO standards, there are discrepancies in printing materials and media. This paper aims to examine the color reproduction quality of domestic web offset newspaper prints by comparing with foreign standards. Printing experiments on this study have been performed at one of the domestic newspaper printing companies. The color reproduction properties of the web offset newspaper prints are measured by means of densitometry and colorimetry. These measures are evaluated comapratively with the international standards by means of analyzing, the major factors that determine the color reproduction quality of web offset newspaper prints.

• Structural Engineering and Mechanics
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• 제34권4호
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• pp.449-474
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• 2010

A smart hollow cylinder consisting of a host functionally graded elastic core layer and two surface homogeneous piezoelectric layers is presented in this paper. The bonding between the layers can be perfect or imperfect, depending on the parameters taken in the general linear spring-layer interface model. The effect of such weak interfaces on free vibration and steady-state response is then investigated. Piezoelectric layers at inner and outer surfaces are polarized axially or radially and act as a sensor and an actuator respectively. For a simply supported condition, the state equations with non-constant coefficients are obtained directly from the formulations of elasticity/piezoelasticity. An approximate laminated model is then introduced for the sake of solving the state equations conveniently. It is further assumed that the hollow cylinder is embedded in an elastic medium and is simultaneously filled with compressible fluid. The interaction between the structure and its surrounding media is taken into account. Numerical examples are finally given with discussions on the effect of some related parameters.

• 한국콘텐츠학회논문지
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• 제18권5호
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• pp.95-104
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• 2018

이 연구는 모바일 기기 이용 변화와 관련하여 뉴스 소비자 집단의 뉴스에 대한 인식을 분석하고 실제 수용자들이 원하는 뉴스 콘텐츠는 어떤 것인지를 알아보았다. 모바일 시대 수용자들은 뉴스 제작자들이 수용자들과의 커뮤니케이션을 통해 뉴스콘텐츠를 제작하기 원했으며 수용자들의 수준을 지나치게 낮게 생각하는 것에 대해 부정적인 태도를 취했다. 그리고 모바일 환경에 맞는 새로운 뉴스형식과 서비스를 선호하였다. 그러면서도 표피적이거나 선정적인 뉴스보다 해설기사나 탐사보도 같은 언론 본연의 임무를 수행하는 뉴스콘텐츠를 요구하였다. 따라서 각 언론사는 뉴스 생산과 전달에 있어 수용자의 입장을 고려하고 모바일 매체를 더 적극적으로 활용해야 함을 확인할 수 있었다.

• 한국환경교육학회지:환경교육
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• 제21권1호
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• pp.45-56
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• 2008

This study is to consider the fundamental perceptions of pre-service elementary school teachers to natural environments. The recognition items of questionnaire for those environments include ones of water, atmospheric, soil, biologic and oceanic environments constituting of the earth system. From the results of the study, they affirmatively recognized biologic environment, but they showed highly negative recognitions to others. In other side, it is considered that their recognitions to natural environments were probably transferred by the things which involve press media, curricula and real lives. On the basis of the study results, systematic teaching-learning for natural environments is essential because the encouragement of eco-friendly attitude, one of main goal for environmental education, is budded from basic understandings to natural environments. Affirmatively environmental worldviews for elementary school students are important for reasons why teacher's quality and practice will is fundamental, and then teacher could change the views of the students for environmental education. So, preparing balanced attitudes, right concepts and connection to applicable knowledges for natural environments, pre-service elementary school teachers in environmental education must be pointed to organized education between human and natural environment.