• Journal of the Korean Geotechnical Society
• /
• v.24 no.8
• /
• pp.125-135
• /
• 2008

Rigid-soft particle mixtures, which consist of sand and rubber, are investigated for the understanding of the stress-deformation and elastic moduli. Specimens are prepared with various size ratio sr between sand and rubber particles, and different volumetric sand fraction sf. Small strain shear waves are measured under $K_o$-loading condition incorporated with the stress-deformation test by using oedometer cell with bender elements. The stress-deformation and small strain shear wave characteristics of rigid-soft particle mixtures show the transition from a rigid particle behavior regime to a soft particle behavior regime under fixed size ratio. A sudden rise of $\Lambda$ factor and the maximum value of the $\zeta$ exponent in $G_{max}=\;{\Lambda}({\sigma}'_{o}/kPa)^{\zeta}$ are observed at $sf\;{\approx}\;0.4{\sim}0.6$ regardless of the size ratio sf. Transition mixture shows high sensitivity to confining stress. The volume fraction for the minimum porosity may depend on the applied stress level in the rigid-soft particle mixtures because the soft rubber particles easily distort under load. In this experimental study, the size ratio and volumetric sand fraction are the important factors which determine the behavior of rigid and soft particle mixtures.

• The Journal of the Convergence on Culture Technology
• /
• v.9 no.5
• /
• pp.19-25
• /
• 2023

This study was conducted to confirm the level of stress and infection prevention behavior of nursing college freshman during the COVID-19 pandemic. 119 nursing college freshmen who took remote classes because face-to-face classes were not possible due to the COVID-19 pandemic. The collected data were analyzed by descriptive statistics, Independent t-test, one-way ANOVA, and Pearson's correlation coefficient using SPSS WIN/PC 26.0 statistics program. As a result of this study, the sensitivity to stress was significantly higher when the attitude towards college life was passive (F=5.92, p=.004), and when people perceived themselves as healthy, their stress was significantly lower (t=-2.22, p=.029). In addition, those who responded that they were very uncomfortable due to activity restrictions due to COVID-19 had a significantly higher level of infection prevention behavior than those who responded that they did not feel any discomfort (F=3.51, p=.018). In a pandemic environment such as COVID-19, efforts to promote a positive attitude and awareness of health conditions are needed to reduce the stress of college freshmen and increase infection prevention behavior.

• Korean Journal of Remote Sensing
• /
• v.39 no.6_1
• /
• pp.1225-1234
• /
• 2023

The intensity of crop water stress caused by moisture deficit is affected by growth and heat conditions. For more accurate detection of crop water stress state using remote sensing techniques, it is necessary to select vegetation indices sensitive to crop response and to understand their changes considering not only soil moisture deficit but also heat conditions. In this study, we measured the MERIS terrestrial chlorophyll index (MTCI) and chlorophyll/carotenoid index (CCI) under drought and heat wave conditions. The MTCI, sensitive to chlorophyll concentration, sensitively decreased on non-irrigation conditions and the degree was larger with heat waves. On the other hand, the CCI, correlated with photosynthesis efficiency, showed less sensitivity to water deficit but had decreased significantly with heat waves. After re-irrigation, the MTCI was increased than before damage and CCI became more sensitive to heat stress. These results are expected to contribute to evaluating the intensity of crop water stress through remote sensing techniques.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.20 no.1
• /
• pp.75-82
• /
• 2007

This paper addresses a method for shape optimization of a continuous elastic body considering stability, i.e., buckling behavior. The sensitivity formula for critical load is analytically derived and expressed in terms of shape variation, based on the continuum formulation of the stability problem. Unlike the conventional finite difference method (FDM), this method is efficient in that only a couple of analyses are required regardless of the number of design parameters. Commercial software such as ANSYS can be employed since the method requires only the result of the analysis in computation of the sensitivity. Though the buckling problem is more efficiently solved by structural elements such as a beam and shell, elastic solids have been chosen for the buckling analysis because solid elements can generally be used for any kind of structure whether it is thick or thin. Sensitivity is then computed by using the mathematical package MATLAB with the initial stress and buckling analysis of ANSYS. Several problems we chosen in order to illustrate the efficiency of the presented method. They are applied to the shape optimization problems to minimize weight under allowed critical loads and to maximize critical loads under same volume.

• Journal of radiological science and technology
• /
• v.32 no.2
• /
• pp.153-160
• /
• 2009

In this study, we investigated utility of ultrasonography for urinary tract infections of infants. The results of the research is as follows : 1. The number of infants under one year old was 100 out of 122 infants who were diagnosed as a unitary infection. The ratio of males to females was 1.7 : 1. Seventy-seven infants who underwent three kinds of radiologic examinations such as kidney sonography (51%), $^{99m}TC$ DMSA-scan (42%), and VCUG (22%). 2. In comparison of correlation between kidney sonography and VCUG, the sensitivity of kidney sonography was 82% while the specificity of kidney sonography was 58%. In comparison of correlation between kidney sonography and $^{99m}TC$ DMSA-scan, the sensitivity of kidney sonography was 66% while the specificity of kidney sonography was 67%. 3. Utility of kidney sonography showed the highest efficiency when we considered pain, discomfort, a sense of shame, psychological stress when infants may undergo at the examination, side-effect of a contrast agent after the examination, and complication of exposure to radiation.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.28 no.5
• /
• pp.441-449
• /
• 2015

In this paper we perform a linearized buckling analysis using the Kirchhoff plate theory and the von Karman nonlinear strain-displacement relation. Design sensitivity analysis(DSA) expressions for plane elasticity and buckling problems are derived with respect to Young's modulus and thickness. Using the design sensitivity, we can formulate the topology optimization method for minimizing the compliance and maximizing eigenvalues. We develop a topology optimization method applicable to plate buckling problems using the prestress for buckling analysis. Since the prestress is needed to assemble the stress matrix for buckling problem using the von Karman nonlinear strain, we introduced out-of-plane motion. The design variables are parameterized into normalized bulk material densities. The objective functions are the minimum compliance and the maximum eigenvalues and the constraint is the allowable volume. Through several numerical examples, the developed DSA method is verified to yield very accurate sensitivity results compared with the finite difference ones and the topology optimization yields physically meaningful results.

• Computers and Concrete
• /
• v.8 no.2
• /
• pp.229-241
• /
• 2011

In this work, cement paste samples with 1% (by cement mass) of a conductive carbon fiber admixture have been studied under uniaxial compression. Three different arrangements were used to measure the resistivity of the samples. According to the results obtained, the resistance should be measured using the four wire method in order to obtain good sensitivity and repeatability. The effect of the load value and the load rate on the fractional change of the volume resistivity has been determined. It has been observed that the gage factor (fractional change in resistance respect to strain) increases when the maximum load is increased, and the loading rate does not affect significantly this parameter. The effect of the sample ambient humidity on the material piezoresistivity has also been studied, showing that the response of the composite is highly affected by this parameter.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.1
• /
• pp.164-172
• /
• 1997

Two parameter technique that uses far-field stress and displacement distributions was applied to composite laminates in order to calculate mode II energy release rate, $G_{II}$ . The $G_{II}$ calculated by two parameter technique was compared with that calculated from the crack closure method to inspect the effectiveness of two parameter technique. Sensitivity study of two parameter technique to the crack extension size was also performed. The results showed that both methods produced comparable $G_{II}$ results. In particular, it was found that although the crack closure method was affected by the crack extension size, the two parameter technique was less affected by the crack extension size.

• 제어로봇시스템학회:학술대회논문집
• /
• 2003.10a
• /
• pp.1945-1950
• /
• 2003

Conceived to acquire personal information for an electronic medical record, the clinical interview contains probing questions. The number and type of inquiries are assumed to fulfill medical protocols, and therefore are deemed essential for treatment - but the rate can and should be controlled. High rates of inquiry merely intimidate the patient and affect replies. The purpose of this paper is to mathematically formulate permissible rates of clinical interviews held during telehomecare virtual visits and designed to avoid patient anxiety. Mental stress is derived as a function of the weight of importance assigned by the patient, virtual visit duration, and the rate of questioning in the direction of greater sensitivity. Two operations are of interest: Collecting and recording information by the provider, and maintaining synchrony of questions and answers by the patient. The Lorentz transformation yields the patient’s view of the operational rates. Conservation of information momentum is postulated and applied before and after replies are recorded. It is shown that the weight of importance designated by the patient to collecting and recording personal information is driven by a singularity that depends on the rate of questioning. The findings should serve as a guideline in interviewer training programs.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.354.1-354.1
• /
• 2016

Nanoporous gold (NPG) is a very promising material in various fields such as sensor, actuator, and catalysis because of its high surface to volume ratio and conducting nature. In this study, we fabricated a NPG based amperometric sensor on a glass substrate by means of co-sputtering of Au and Si. During the sputtering process, we found the optimum conditions for heat treatment to reduce the residual stress and to improve adhesion between NPG films and the glass substrate. Subsequently, Si was selectively etched from Au-Si alloy by KOH solution, which forms nanoporous structures. Scanning electron microscopy (SEM) and auger electron spectroscopy (AES) were used to estimate the structure of NPG films and their composition. By employing appropriate heat treatments, we could make very stable NPG films. We tested the performance of NPG sensor with aniline molecules, which shows high sensitivity for sensing low concentration of aniline.