• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1335-1340
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• 2007

The media transport systems, such as printers, copy machines, facsimiles, ATMs, cameras, etc. have been widely used and being developed rapidly. In the development of those sheet-handling machineries, it is important to predict the static and dynamic behavior of the sheet with a high degree of reliability because the sheets are fed and stacked at such a high speed. Flexible media are very thin, light and flexible, so they behave in geometric nonlinearity with large displacement and large rotation but small strain. In the flexible media analysis, aerodynamic effect from the surrounding air must be included because any small force can make large deformation. In this paper, surrounding air was modeled by incompressible Navier-Stokes flow and an arbitrary Lagranigan-Eulerian(ALE) finite element method with automatic mesh-updating technique was formulated for large domain changes. In the numerical simulations, the results with consideration of the air fast decayed and converged into static results while the results without considering air oscillated continuously.

• International Journal of Highway Engineering
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• v.7 no.1 s.23
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• pp.39-47
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• 2005

Fiber reinforced soils have recently implemented to fills and base layers of highways and railroads, and deformation behaviors of reinforced soils in turn should be investigated. The paper evaluated deformation characteristics of fiber reinforced sands and their effectiveness of reinforcement using resonant column tests. The specimens were prepared by varying gradation and mixing polypropylene staple fibers of 0.3% fiber content. Maximum shear moduli of reinforced sands were increased by up to 30% with increasing uniformity coefficient. Shear moduli of well-graded reinforced sands were larger than those of poorly-graded ones regardless of confining pressure in the whole range of shearing strain and reinforcement was, in turn, more effective with higher uniformity coefficient.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.690-693
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• 2005

In this paper, probabilistic distribution of fatigue life of chassis component is determined statistically by applying the design of experiments and the Pearson system. To construct $p-\varepsilon-N$ curve, the case that fatigue data are random variables is attempted. Probabilistic density function(p.d.f) for fatigue life is obtained by design of experiment and using this p.d.f fatigue reliability about any aimed fatigue life can be calculated. Lower control arm and rear torsion bar of chassis component are selected as examples for analysis. Component load histories, which are obtained by multi-body dynamic simulation for Belsian load history, are used. Finite element analysis are performed using commercial software MSC Nastran and fatigue analysis are performed using FE Fatigue. When strain-life curve itself is random variable, probability density function of fatigue life has very little difference from log-normal distribution. And the case of fatigue data are random variables, probability density functions are approximated to Beta distribution. Each p.d.f is verified by Monte-Carlo simulation.

• Korean Journal of Microbiology
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• v.47 no.2
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• pp.174-178
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• 2011

In Escherichia coli, DcuS/R two-component system controls fumarate import and utilization related gene expression. To understand the dynamic response of the bacterium DcuS/R two-component system with respect to fumarate concentrations, DcuS/R induced dctA promoter was integrated with GFP reporter protein. Expression monitoring study using recombinant strain showed that dctA promoter was upregulated with 1 mM of fumarate in M9 minimal medium.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.2
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• pp.161-167
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• 1983

In this study the phenomenon of cutting stress which arises on cutting tools and work pieces in cutting process is investigated by rake angle of cutting tools and feed for this measurement, P$_{s}$-1 (high modulus, photolastic Inc.) was used as a cutting tool, P$_{s}$-3 (medium modulus, photolastic Inc.) was used as work piece and reduction apparatus was attached to the head stock, and orthogonal cutting was adapted as a cutting method and transparent glass was used to block the strain in the orientation of thickness. The followings are the results of this study. (1) Photoelastic experimental equipments have made it possible to make dynamic measurement and analyze stress distribution in cutting tool and work piece surface which has hitherto been conducted only in static measurement and analyzing method. (2) The maximum stress arising at tools and work pieces in cutting process is on the tool edge tip, and the maximum stress arising on the tip of cutting tools is equal to that on the contacting area of work pieces in values. (3) The distributions of maximum shear stress on certain parts of the cutting tools and work pieces are as follows; for cutting tools, .alpha.=12.deg., .alpha.=0.deg., .alpha.=-12.deg. in order, and for work pieces, .alpha.=-12.deg., .alpha.=0.deg., .alpha.=12.deg. in opposite order.der.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.136-141
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• 2007

This paper introduces an artificial neuron which is a nano composite continuous sensor. The continuous nano sensor is fabricated as a thin and narrow polymer film sensor that is made of carbon nanotubes composites with a PMMA or a silicone matrix. The sensor can be embedded onto a structure like a neuron in a human body and it can detect deteriorations of the structure. The electrochemical impedance and dynamic strain response of the neuron change due to deterioration of the structure where the sensor is located. A network of the long nano sensor can form a structural neural system to provide large area coverage and an assurance of the operational health of a structure without the need for actuators and complex wave propagation analyses that are used with other methods. The artificial neuron is expected to effectively detect damage in large complex structures including composite helicopter blades and composite aircraft and vehicles.

• Journal of the Korean Society of Safety
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• v.29 no.5
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• pp.15-21
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• 2014

The aim of this work is conduct the study on light weight and structural performance improvement of the composite wind power blade. GFRP (Glass Fiber Reinforced Plastic) pre-empted by CFRP(Carbon Fiber Reinforced Plastic), the major material of wind power blade, was identified the superiority of mechanical performance through the tensile and fatigue test. SENT(Single Edge Notched Tension) specimen fracture test was conducted on the specimen that laminated together 2 ply CFRP with 4 ply GFRP through DIC(Digital Image Correlation) analysis. The SENT specimen thickness and $a_0/W$ ratio is 1.45 mm and 0.2, respectively. The fracture test accomplished with displacement control with 0.1 mm/min at the room temperature. The experimental apparatus used for the fracture test consisted of a 50kN universal dynamic tester and CCD camera connected to a personal computer (PC), which was used to record images of the specimen surface. Following data acquisition, the images and load-displacements were transferred to the PC, on which the DIC software was implement. The experiment and DIC analysis results show that CFRP/GFRP laminated composite exhibits improvement of the strength, compared with that of the existing blade material. This study shows the result that the strength of CFRP rotor blade of wind turbine satisfies through the experimental and DIC method.

• Computers and Concrete
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• v.7 no.4
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• pp.317-329
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• 2010

The paper describes localization of deformation in a bar under tensile loading. The material of the bar is considered as non-linear viscous elastic and the bar consists of two symmetric halves. It is assumed that the model represents behavior of the quasi-brittle viscous material under uniaxial tension with different loading rates. Besides that, the bar could represent uniaxial stress-strain law on a single plane of a microplane material model. Non-linear material property is taken from the microplane material model and it is coupled with the viscous damper producing non-linear Maxwell material model. Mathematically, the problem is described with a system of two partial differential equations with a non-linear algebraic constraint. In order to obtain solution, the system of differential algebraic equations is transformed into a system of three partial differential equations. System is subjected to loadings of different rate and it is shown that localization occurs only for high loading rates. Mathematically, in such a case two solutions are possible: one without the localization (unstable) and one with the localization (stable one). Furthermore, mass is added to the bar and in that case the problem is described with a system of four differential equations. It is demonstrated that for high enough loading rates, it is the added mass that dominates the response, in contrast to the viscous and elastic material parameters that dominated in the case without mass. This is demonstrated by several numerical examples.

• Structural Engineering and Mechanics
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• v.63 no.4
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• pp.521-536
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• 2017

Reinforced concrete core-wall structures with buckling-restrained brace outriggers are interesting systems which have the ability to absorb and dissipate energy during strong earthquakes. Outriggers can change the energy demand in a tall building. In this paper, the energy demand was studied by using the nonlinear time history analysis for the mentioned systems. First, the structures were designed according to the prescriptive codes. In the dynamic analysis, three approaches for the core-wall were investigated: single plastic hinge (SPH), three plastic hinge (TPH) and extended plastic hinge (EPH). For SPH approach, only one plastic hinge is allowed at the core-wall base. For TPH approach, three plastic hinges are allowed, one at the base and two others at the upper levels. For EPH approach, the plasticity can extend anywhere in the wall. The kinetic, elastic strain, inelastic and damping energy demand subjected to forward directivity near-fault and ordinary far-fault earthquakes were studied. In SPH approach for all near-fault and far-fault events, on average, more than 65 percent of inelastic energy is absorbed by buckling-restrained braces in outrigger. While in TPH and EPH approaches, outrigger contribution to inelastic energy demand is reduced. The contribution of outrigger to inelastic energy absorption for the TPH and EPH approaches does not differ significantly. The values are approximately 25 and 30 percent, respectively.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.2
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• pp.73-84
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• 2004

In general, static firing test is conducted before flight in order to obtain data such as thrust. pressure, temperature and strain, which show the characteristics of rocket motors. But the measured thrust of the obtained data is especially distorted by the effects of dynamic characteristics of thrust stand so that it is difficult for us to determine the exact value of peak thrust and rising time etc., which represent the performance of rocket motor. This paper, therefore. verified the causes of distortion of measured thrust, and proposed the theoretical method to estimate the true thrust from the distorted thrust. And also the proposed method was applied to virtual thrust stand using computer simulation, and showed good result. As a result of that, the proposed method was proven to be valid and applicable to estimate distorted thrust.