• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.8
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• pp.91-100
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• 2004

A Green's function approach is adopted for analyzing the thermoelastic deformations and stresses of a plate made of functionally graded materials(FGMs). The solution to the 3-dimensional unsteady temperature is obtained by using the laminate theory. The fundamental equations for thermoelastic problems are derived in terms of out-plane deformation and in-plane force, separately. The thermoelastic deformation and the stress distributions due to the bending and in-plane forces are analyzed by using a Green's function based on the Galerkin method. The eigenfunctions of the Galerkin Green's function for the thermoelastic deformation and the stress distributions are approximated in terms of a series of admissible functions that satisfy the homogeneous boundary conditions of the rectangular plate. Numerical analysis for a simply supported plate is carried out and effects of material properties on unsteady thermoclastic behaviors are discussed.

• Clean Technology
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• v.17 no.1
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• pp.25-30
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• 2011

This study presents a fabrication method of cell-chip using aqueous solution based surface modification. The applications of cell-chip have potential for fundamental study of genetics, cell biology as well as cancer diagnostics and treatment. Conventional methods for fabrication of cell-chip have been limited in economic loss and environmental pollution because of the use of harsh organic solvent, complex process of silicon technology, and expensive equipment. In order to fabricate cell chip, we have proposed simple and eco-friendly process combined polyelectrolyte multilayer coating with microcontact printing. For the proof of concept, the cell chip can be applied to analyze the different expression of cell surface glycans and derivatives between cancer and normal cells. Our proposed method is useful technique for the application of novel cancer diagnostics and basic medical engineering.

• Journal of Environmental Health Sciences
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• v.26 no.3
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• pp.32-37
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• 2000

Nowadays, a new word called SBS(sick building syndrome) has been come into existence. At the point of time when an interest about indoor air pollution and, according to this, countermeasure plan are internationally. Moreover institutional countermeasure should be attended at national level since indoor air quality in public places where many people gather is directly connected with national health. Especially indoor pollution of indoor stadia where all sorts of sports are held can give rise to every kinds of respiratory ailments to players as well as audiences. So it is presented as a main factor that indoor space of stadia is crowded with players and audiences compared with other kinds of indoor space. Therefore, in this research to analyze pollution degree of indoor circumstance for gymnasium and exercising room of folk wrestling. basketball, judo, wrestling, hapkido, swordsmanship and boxing making indoor gymnasium and exercising room an object, when 7 items were measures such as thermocircumstance(temperature, relative humidity, air current, intensity of illumination), dust, carbon monoxide, and carbon dioxide being based on the indoor environmental standard of the first clause of Article 45 of public utilization service which is showed at public hygiene of the Ministry of Health and Social Affairs, it was showed that indoor temperature, relative humidity, air current and intensity of illumination were over standard amount at the most of folk wrestling gymnasium and exercising room. Indoor density of carbon monoxide was preserved to the extent of standard amount (10ppm) at all gymnasiums but carbon dioxide was not in excess of standard amount(1,000 ppm) at most of gymnasiums. Indoor density of dust induced from respiration exceeded the standard amount (150 $\mu\textrm{g}$/㎥) at all gymnasiums of the folk wrestling. Since the folk wrestling players and participants feel physical subjective symptom seriously, in other words the degree of indoor air pollution at gymnasiums and exercising rooms of the folk wrestling is very high, fundamental solution and countermeasure plan should be presented.

• Korea-Australia Rheology Journal
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• v.14 no.1
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• pp.33-45
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• 2002

Recent results obtained for the port-pom model and the constitutive equations with time-strain separability are examined. The time-strain separability in viscoelastic systems Is not a rule derived from fundamental principles but merely a hypothesis based on experimental phenomena, stress relaxation at long times. The violation of separability in the short-time response just after a step strain is also well understood (Archer, 1999). In constitutive modeling, time-strain separability has been extensively employed because of its theoretical simplicity and practical convenience. Here we present a simple analysis that verifies this hypothesis inevitably incurs mathematical inconsistency in the viewpoint of stability. Employing an asymptotic analysis, we show that both differential and integral constitutive equations based on time-strain separability are either Hadamard-type unstable or dissipative unstable. The conclusion drawn in this study is shown to be applicable to the Doi-Edwards model (with independent alignment approximation). Hence, the Hadamardtype instability of the Doi-Edwards model results from the time-strain separability in its formulation, and its remedy may lie in the transition mechanism from Rouse to reptational relaxation supposed by Doi and Edwards. Recently in order to describe the complex rheological behavior of polymer melts with long side branches like low density polyethylene, new constitutive equations called the port-pom equations have been derived in the integral/differential form and also in the simplifled differential type by McLeish and carson on the basis of the reptation dynamics with simplifled branch structure taken into account. In this study mathematical stability analysis under short and high frequency wave disturbances has been performed for these constitutive equations. It is proved that the differential model is globally Hadamard stable, and the integral model seems stable, as long as the orientation tensor remains positive definite or the smooth strain history in the flow is previously given. However cautious attention has to be paid when one employs the simplified version of the constitutive equations without arm withdrawal, since neglecting the arm withdrawal immediately yields Hadamard instability. In the flow regime of creep shear flow where the applied constant shear stress exceeds the maximum achievable value in the steady flow curves, the constitutive equations exhibit severe instability that the solution possesses strong discontinuity at the moment of change of chain dynamics mechanisms.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1950-1956
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• 1997

An engineering goal in vibration and noise professionals is to develope quiet machines at the preliminary design stage, and various numerical techniques such as FEM, SEA or BEM are one of the schemes toward the goal. In this paper, the research has been focused on the sensitivity effect of mesh sizes for FEM application so that the optimum size of the mesh that leads to engineering solution within acceptable computing time could be generated. In order to evaluate the mesh size effect, three important parameters have been examined : natural frequencies, number of modes and driving point mobility. First, several lower modes including the fundamental frequency of a 2-D plate structure have been calculated as mesh size changes. Since theoretical values of natural frequencies for a simple structure are known, the deviation between the numerical and theoretical values is obtained as a function of mesh size. The result shows that the error is no longer decreased if the mesh size becomes a quarter wavelength or smaller than that. Second, the mesh size effect is also investigated for the number of modes. For the frequency band up to 1.4 kHz, the structure should have 38 modes in total. As the mesh size reaches to the quarter wavelength, the total count in modes approaches to the same values. Third, a mobility function at the driving point is compared between SEA and FEM result. In SEA application, the mobility function is determined by the modal density and the mass of the structure. It is independent of excitation frequencies. When the mobility function is calculated from a wavelength to one-tenth of it, the mobility becomes constant if the mesh becomes a quarter wavelength or smaller. We can conclude that dynamic parameters, such as eigenvalues, mode count, and mobility function, can be correctly estimated, while saving the computing burden, if a quarter wavelength (.lambda./4) mesh is used. Therefore, (.lambda./4) mesh is recommended in structural vibration analysis.

• Archives of design research
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• v.15 no.4
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• pp.149-156
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• 2002

The success of a product is only possible on the basis of user preference for products and the user preference for products is greatly influenced by the design. Designers have to understand user preference and convert it into the combination of specified design attribute, and after that they should design products which have the image that they want to get. Then the product will be sure to be a hit. Therefore, on the point of view of design, it is necessary to find oui definitely the consumer preference frame : the relationship among design preference - design images - design attribute. This study will give you guidelines on which designers can select and design some more objective and reliable design factors, finding out the relation of cause and effect by which they can know what kind of product designs their consumers like and how the popular image which that products offer is composed of. Therefore, in this study, after we developed the consumer response framework which is proposed by Bloch(1995) : distinct relationship model among preference - design image adjective - design factors, we analyzed the relationship among preference-design image adjective - design factors through the empirical researches. And then we give the way of design.

• Journal of Korean Ophthalmic Optics Society
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• v.4 no.2
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• pp.1-16
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• 1999

Differential equations and its numerical solution program using Turbo-C were formulated to describe the radical distribution and average displacement amplitude of vibrating dehydrated contact lens(HEMA) driven by sinusoidal or rectangular pressure. The natural resonant frequency of the lens diaphram(thickness 0.08mm, diameter 14mm, curvature radius 8mm) was measured to be 5730 Hz from the extrapolation of frequency vs addedmass to the diaphram curve. The Young's modulus of the lens was measured to be $4{\times}10^9$ Pa with altering the original shape. The effect of parameters such as thickness, effective radius, damping coeff., amplitude of driving pressure on the vibration characteristics was illustrated by the computer simulation of the derived program. When the frequency of driving pressure coincides with the integral multiple of fundamental resonance frequency of the lens the wave pattern changes from arc to bell-shape along the radial position of the diaphram. If this happens to the contact lens on the cornea in vivo, it might create the feel of pull of the lens due to the increased rise of central part of the lens.

• Earthquakes and Structures
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• v.14 no.4
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• pp.313-322
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• 2018

The present study is dedicated to investigate the SH body-as well as Love-waves propagation effects in porous media with uncertain porosity and permeability. A unified formulation of the governing equations for one-dimensional (1-D) wave propagation in anisotropic porous layered media is presented deterministically. The uncertainties around the above two cited parameters are taken into account by random fields with the help of Monte Carlo Simulations (MCS). Random samples of the porosity and the permeability are generated according to the normal and lognormal distribution functions, respectively, with a mean value and a coefficient of variation for each one of the two parameters. After performing several thousands of samples, the mathematical expectation (mean) of the solution of the wave propagation equations in terms of amplification functions for SH waves and in terms of dispersion equation for Love-waves are obtained. The limits of the Love wave velocity in a porous soil layer overlaying a homogeneous half-space are obtained where it is found that random variations of porosity change the zeros of the wave equation. Also, the increase of uncertainties in the porosity (high coefficient of variation) decreases the mean amplification function amplitudes and shifts the fundamental frequencies. However, no effects are observed on both Love wave dispersion and amplification function for random variations of permeability. Lastly, the present approach is applied to a case study in the Adapazari town basin so that to estimate ground motion accelerations lacked in the fast-growing during the main shock of the damaging 1999 Kocaeli earthquake.

• The Journal of the Korea Contents Association
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• v.7 no.4
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• pp.250-258
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• 2007

Typography is the combination of language of formative art. It is indeed the core means of human communication through understanding of language and formative values. Studies began on introduction of various techniques to overcome the phenomenon of the 'reaction of language', which appears as an impediment in delivery and sharing of information as the most fundamental roles. Successively, mobile printing types more readable and effective in delivering of meanings have been developed, thus widely distributed for general use. However, although such printing types might be easily used in image and digital media, such as in computer monitors, screens and mobile phone LCDs, etc., it is in fact difficult to use these printing types in printed surfaces, the traditional medium of information delivery, or in sign systems frequently encountered in our surrounding environment. As a solution for this, it is intended to create an effect of communication closer to dynamic typography expression by approaching visual message delivery system from the essence and substance of the color application, which corresponds to the visual spatial expression effect, the core element of expression in dynamic typography to possess significantly more powerful effect in terms of both message delivery capacity and readability than the conventional means of static typography.

• The Korean Journal of Physiology and Pharmacology
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• v.9 no.2
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• pp.69-75
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• 2005

TRPM7, a cation channel protein permeable to various metal ions such as $Mg^{2+}$, is ubiquitously expressed in variety of cells including lymphocytes. The activity of TRPM7 is tightly regulated by intracellular $Mg^{2+}$, thus named $Mg^{2+}$-inhibited cation (MIC) current, and its expression is known to be critical for the viability and proliferation of B lymphocytes. In this study, the level of MIC current was compared between immature (WEHI-231) and mature (Bal-17) B lymphocytes. In both cell types, an intracellular dialysis with $Mg^{2+}$-free solution (140 mM CsCl) induced an outwardly-rectifying MIC current. The peak amplitude of MIC current and the permeability to divalent cation ($Mn^{2+}$) were several fold higher in Bal-17 than WEHI-231. Also, the level of mRNAs for TRPM7, a molecular correspondence of the MIC channel, was significantly higher in Bal-17 cells. The amplitude of MIC was further increased, and the relation between current and voltage became linear under divalent cation-free conditions, demonstrating typical properties of the TRPM7. The stimulation of B cell receptors (BCR) by ligation with antibodies did not change the amplitude of MIC current. Also, increase of extracellular $[Mg^{2+}]_c$ to enhance the $Mg^{2+}$ influx did not affect the BCR ligation-induced death of WEHI-231 cells. Although the level of TRPM7 was not directly related with the cell death of immature B cells, the remarkable difference of TRPM7 might indicate a fundamental change in the permeability to divalent cations during the development of B cells.