• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.6
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• pp.564-568
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• 2010

When ultrasound propagates to a crack, transmitted and reflected waves are generated. These waves have useful information for the detection of the crack lying in a structure. When a crack is under residual stress, crack surfaces will contact each other and a closed crack is formed. For closed cracks, the fundamental component of the reflected and transmitted waves will be weak, and as such it is not easy to detect them. In this case, higher harmonic components will be useful. In this paper, nonlinear characteristic of a closed crack is modeled by a continuum material having a tensile-compressive unsymmetry, and the amplitude of the second harmonic wave was obtained by spectrum analysis. Variation of the second harmonic component depending on the nonlinearity of the inclusion was investigated. Two-dimensional plane strain model is considered, and finite element software ABAQUS/Explicit is used.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.2
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• pp.173-182
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• 1996

An analytical model has been developed to predict the elastic properties of a filled resin reinforced by chopped fibers, a three-phase composite such as a filled sheet molding compound(SMC). In the model the matrix material and fillers form an effective matrix. The effective matrix is then considered to be reinforced with long fibers lying in the sheet plane but randomly oriented in the plane. Expressions for the resulting transversely isotropic composite properties are explicitly presented. Using this model, the Young's and shear moduli are calculated for the SMC sample with filler weight fraction of 35% and fiber content of 30%. The same properties are also determined experimentally. The agreement between the calculated and measured elastic moduli is found to be very good for the in-plane properties. However, the out-of-plane properties show a large difference because the effect of voids is not taken into account in the model.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.7
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• pp.1324-1330
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• 2007

In this paper, we propose pattern recognition algorithm for activities of daily living by adopting extreme learning machine based on single layer feedforward networks(SLFNs) to the signal from bidirectional accelerometer. For activity classification, 20 persons are participated and we acquire 6, types of signals at standing, walking, running, sitting, lying, and falling. Then, we design input vector using reduced model for ELM input. In ELM classification results, we can find accuracy change by increasing the number of hidden neurons. As a result, we find the accuracy is increased by increasing the number of hidden neuron. ELM is able to classify more than 80 % accuracy for experimental data set when the number of hidden is more than 20.

• Bulletin of the Korean Mathematical Society
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• v.47 no.6
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• pp.1163-1170
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• 2010

We study finite type curve in $R^3$(-3) which lies in a cylinder $N^2$(c). Baikousis and Blair proved that a Legendre curve in $R^3$(-3) of constant curvature lies in cylinder $N^2$(c) and is a 1-type curve, conversely, a 1-type Legendre curve is of constant curvature. In this paper, we will prove that a 1-type curve lying in a cylinder $N^2$(c) has a constant curvature. Furthermore we will prove that a curve in $R^3$(-3) which lies in a cylinder $N^2$(c) is finite type if and only if the curve is 1-type.

• Advances in environmental research
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• v.4 no.3
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• pp.183-196
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• 2015

Migration of leachate generated through embankment of construction waste soil (CWS) in low-lying areas was studied through physical and chemical analysis. A leachate solution containing soluble cations from CWS was found to have a pH above 9.0. To determine the distribution coefficients in the alkali solution, column and migration tests were conducted in the laboratory. The physical and chemical properties of CWS satisfied environmental soil criteria; however, the pH was high. The effective diffusion coefficients for CWS ions fell within the range of $0.725-3.3{\times}10^{-6}cm^2/s$. Properties of pore water and the amount of undissolved gas in pore water influenced advection-diffusion behavior. Contaminants migrating from CWS exhibited time-dependent concentration profiles and an advective component of transport. Thus, the transport equations for CWS contaminant concentrations satisfied the differential equations in accordance with Fick's 2nd law. Therefore, the migration of the contaminant plume when the landfilling CWS reaches water table can be predicted based on pH using the effective diffusion coefficient determined in a laboratory test.

• Structural Engineering and Mechanics
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• v.68 no.1
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• pp.131-157
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• 2018

In this study, Eringen nonlocal elasticity theory in conjunction with surface elasticity theory is employed to study nonlinear free vibration behavior of FG nano-plate lying on elastic foundation, on the base of Reddy's plate theory. The material distribution is assumed as a power-law function and effective material properties are modeled using Mori-Tanaka homogenization scheme. Hamilton's principle is implemented to derive the governing equations which solved using DQ method. Finally, the effects of different factors on natural frequencies of the nano-plate under hygrothermal situation and various boundary conditions are studied.

• Environmental Engineering Research
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• v.11 no.2
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• pp.106-125
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• 2006

Cesium and strontium are two important fission products and the removal/speciation of these two cations with several inorganic/bio-materials is an interesting topic to discuss. It is to be noted that inorganic materials are found to be fairly effective and efficient in the removal/speciation of these cations. Moreover, these solids are to be found promising as they show fairly good radiation and temperature stability. Hence, they play an important role in the radioactive waste management studies. However, various studies reveal that in addition to inorganic materials various biosorbents can also be employed in the removal/speciation of these ions. But the radiation and temperature stability of these bio-sorbents and dead biomasses are still the topic lying among the researchers to be investigated.

• The Korean Journal of Pharmacology
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• v.9 no.2
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• pp.9-16
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• 1973

It is said that the chinese medicine, Ginseng root has some effects on the central nervous system . Ginseng saponin was prepared from Ginseng methanol extract and its effect on general behavioral activity was studied in rats. Each experimental group was composed of 8 rats. The behavioral activity of rats was observed in terms of 7 components i.e. sleeping, lying, grooming, rearing, walking, eating and drinking. In each group, total duration of behavior-observation was 2 hours, which were devided into four 30 min-intervals. The behavior-observation was done 10 times for each interval, so total number of observation was 40 times throughout 2 hours. Ginseng sapoain showed central nervous system stimulant action in reduced sleeping component and in increased activity components. From the results of this study, it is suggested that Ginseng saponin inhibits the extrapyramidal action of chlorpromazine.

• Journal of Biomedical Engineering Research
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• v.38 no.5
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• pp.264-270
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• 2017

A Doppler radar sensor was applied to detect respirations and heartbeats of persons who were lying on a bed. This study is preliminary study aiming at non-contact and non-intrusive respiration and heart rate monitoring during sleep in daily life. For the experiments, 10GHz Doppler radar with patch-type antenna was used and installed on the upper right and the distance between the body and the antenna was 1 m. The results show that each signal of respiration and heartbeat is observed in each frequency band however the frequency band and the waveform vary according to the subjects and the posture. The results show that the heartbeats can be detected with the peak detection in some frequency band. This study shows the feasibility of applying the Doppler radar to detection of heartbeat and respiration during sleep and further studies about heartbeat detection algorithm are required.

• Kyungpook Mathematical Journal
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• v.57 no.2
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• pp.187-191
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• 2017

Let R be a domain with quotient field K and prime subring A. Then R is integral over each of its subrings having quotient field K if and only if (A, R) is a survival pair. This shows the redundancy of a condition involving going-down pairs in a earlier characterization of such rings. In characteristic 0, the domains being characterized are the rings R that are isomorphic to subrings of the ring of all algebraic integers. In positive (prime) characteristic, the domains R being characterized are of two kinds: either R = K is an algebraic field extension of A or precisely one valuation domain of K does not contain R.