• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.5
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• pp.421-428
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• 2016

The present work extends the recent variational formulation to more general time-dependent problems. Thus, based upon recent works of variational formulation in dynamics and pure heat diffusion in the context of the extended framework of Hamilton's principle, formulation for fully coupled thermoelasticity is developed first, then, with thermoelasticity-poroelasticity analogy, poroelasticity formulation is provided. For each case, energy conservation and energy dissipation properties are discussed in Fourier transform domain.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.1
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• pp.37-43
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• 2014

The extended framework of Hamilton's principle provides a new rigorous weak variational formalism for a broad range of initial boundary value problems in mathematical physics and mechanics in terms of mixed formulation. Based upon such framework, a new variational numerical method of linear elasticity is provided for the classical single-degree-of-freedom dynamical systems. For the undamped system, the algorithm is symplectic with respect to the time step. For the damped system, it is shown to be accurate with good convergence characteristics.

• Journal of Korean Association for Spatial Structures
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• v.14 no.1
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• pp.101-108
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• 2014

In order to overcome the key shortcoming of Hamilton's principle, recently, the extended framework of Hamilton's principle was developed. To investigate its potential in further applications especially for material non-linearity problems, the focus is initially on a classical single-degree-of-freedom elasto-viscoplastic model. More specifically, the extended framework is applied to the single-degree-of-freedom elasto-viscoplastic model, and a corresponding weak form is numerically implemented through a temporal finite element approach. The method provides a non-iterative algorithm along with unconditional stability with respect to the time step, while yielding whole information to investigate the further dynamics of the considered system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.71-81
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• 2008

This paper proposes a spectral element which can represent dynamic responses in high frequency domain such as Lamb waves on a thin plate. A two layer beam model under 2-D plane strain condition is introduced to simulate high-frequency dynamic responses induced by piezoelectric layer (PZT layer) bonded on a base plate. In the two layer beam model, a PZT layer is assumed to be rigidly bonded on a base beam. Mindlin-Herrmann and Timoshenko beam theories are employed to represent the first symmetric and anti-symmetric Lamb wave modes on a base plate, respectively. The Bernoulli beam theory and 1-D linear piezoelectricity are used to model the electro-mechanical behavior of a PZT layer. The equations of motions of a two layer beam model are derived through Hamilton's principle. The necessary boundary conditions associated with electro mechanical properties of a PZT layer are formulated in the context of dual functions of a PZT layer as an actuator and a sensor. General spectral shape functions of response field and the associated boundary conditions are formulated through equations of motions converted into frequency domain. A detailed spectrum element formulation for composing the dynamic stiffness matrix of a two layer beam model is presented as well. The validity of the proposed spectral element is demonstrated through comparison results with the conventional 2-D FEM and the previously developed spectral elements.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.11
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• pp.1157-1169
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• 2008

This paper presents spectral element formulation which approximates Lamb wave propagation by PZT transducers bonded on a thin plate. A two layer beam model under 2-D plane strain condition is introduced to simulate high-frequency dynamic responses induced by a piezoelectric (PZT) layer rigidly bonded on a base plate. Mindlin-Herrmann and Timoshenko beam theories are employed to represent the first symmetric and anti-symmetric Lamb wave modes on a base plate, respectively. The Euler-Bernoulli beam theory and 1-D linear piezoelectricity are used to model the electro-mechanical behavior of a PZT layer. The equations of motions of a two layer beam model are derived through Hamilton's principle. The necessary boundary conditions associated with the electro-mechanical properties of a PZT layer are formulated in the context of dual functions of a PZT layer as an actuator and a sensor. General spectral shape functions of response field and the associated boundary conditions are obtained through equations of motions converted into frequency domain. Detailed spectrum element formulation for composing the dynamic stiffness matrix of a two layer beam model is presented as well. The validity of the proposed spectral element is demonstrated through numerical examples.

• Journal of Science and Technology Studies
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• v.19 no.3
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• pp.1-49
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• 2019

First proposed by Paul Crutzen and Eugene Stoermer in 2000, the concept of the Anthropocene has had staggering repercussions in a variety of disciplines. In response to the Anthropocene narrative as a problematization of the eco-ontological emergency that humanity is confronted with in the 21st-century, I will deal with the following theoretical themes in this article. Firstly, I will analyze the central agendas underlying the Anthropocene discourse: the expansion of human agency into the planetary level and the possibility of unprecedented catastrophes in the near future. Secondly, I will propose to address the Anthropocene discourse as problem-assemblage. Thirdly, I will examine Clive Himilton and Dipesh Chakrabarty's theses in order to understand the shock that was brought to bear on the humanities and social sciences by the Anthropocene narrative. Fourthly, I will reinterpret the allegory of the angel appearing in Benjamin's Theses on the Philosophy of History to explore new possibilities of transformative becoming of the subjectivity, focusing on the concept of patiency. Finally, I will present the concept of reflexive catastrophism.

• Composites Research
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• v.13 no.5
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• pp.50-59
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• 2000

In this paper, two methods to suppress flutter of the composite panel are examined. First, in the active control method, a controller based on the linear optimal control theory is designed and control input voltage is applied on the actuators and a PZT is used as actuator. Second, a new technique, passive suppression scheme, is suggested for suppression of the nonlinear panel flutter. In the passive suppression scheme, a shunt circuit which consists of inductor-resistor is used to increase damping of the system and as a result the flutter can be attenuated. A passive damping technology, which is believed to be more robust suppression system in practical operation, requires very little or no electrical power and additional apparatuses such as sensor system and controller are not needed. To achieve the great actuating force/damping effect, the optimal shape and location of the actuators are determined by using genetic algorithms. The governing equations are derived by using extended Hamilton's principle. They are based on the nonlinear von Karman strain-displacement relationship for the panel structure and quasi-steady first-order piston theory for the supersonic airflow. The discretized finite element equations are obtained by using 4-node conforming plate element. A modal reduction is performed to the finite element equations in order to suppress the panel flutter effectively and nonlinear-coupled modal equations are obtained. Numerical suppression results, which are based on the reduced nonlinear modal equations, are presented in time domain by using Newmark nonlinear time integration method.

• Journal of the Korean Society of Clothing and Textiles
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• v.39 no.5
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• pp.641-655
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• 2015

This study examined the ideal image and fashion of Korean women in the 1970s from a socio-cultural context. This study used information on the 1970s politics, economy, and culture provided by "Chosun Ilbo" and "Yosungjungang" as well as their presentation of the ideal image and fashion for Korean women in the 1970s. The ideal image and fashion of women were considered from the viewpoint of Hamilton's Meta-theory. The ideal image of women in the 1970s is divided into two aspects. The image from the traditional Confucian perspective was prevalent and restricted the lives of women to housekeeping chores. On the contrary, women have increasingly participated in society vis-$\grave{a}$-vis education and employment opportunities to present a progressive image of women. These aspects coexisted during the turmoil of social change. Progressive women had money to buy clothes because they were economically independent. These women embraced styles that included mini, midi, maxi, and bell-bottom pants. Further, pants were developed into different styles such as pant suits. T-shirts and blue jeans as casual wear were very popular among the youth. At the end of the 1970s, the tailored look and the big look (which copied men's clothing) were in fashion. Masculine styles such as wide shoulders with pads and neckties strengthened gender equality. Other fashions were dominated by feminine styles described as beautiful, sweet, and elegant that reflected Korean society's tendency to regard women as sex objects. Clothing that exposed the body highlights this sexual objectification aspect. Women wore miniskirts, hot pants, and bikinis because they wanted to enhance their sex appeal, propagating the view of women as sex objects. In conclusion, all aspects of society and culture were closely interrelated with a fashion style that reflected the values of those aspects.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.7
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• pp.29-36
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• 2004

In this work, the effect of composite couplings on hub loads of a hingeless rotor in forward flight is investigated. The hingeless composite rotor blade is idealized as a laminated thin-walled box-beam. The nonclassical effects such as transverse shear, torsional warping are considered in the structural formulation. The nonlinear differential equations of motion are obtained by applying Hamilton's principle. The blade response and hub loads are calculated using a finite element formulation in space and time. The aerodynamic forces acting on the blade are calculated by quasi-steady strip theory. The theory includes the effects of reversed flow and compressibility. The magnitude of elastic couplings obtained by MSC/NASTRAN is compared with the classical pitch-flap $({\delta}3)$ or $pitch-lag({\alpha}1)$ coupling. It is found that the elastic couplings have a substantial effect on the behavior of $N_b/rev$ hub loads. Nearly 10 to 40% of hub loads is reduced by appropriately tailoring the fiber orientation angles in the laminae of the composite blade.