• 한국지형학회지
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• 제23권3호
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• pp.27-39
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• 2016

This study statistically investigates relationships between physical properties of rocks and topography by measuring and analyzing section, topographical and measured parameters of 58 bedrock outcrops at areas covered by gneiss, schist, granite, andesite, sandstone and limestone in the Korean Peninsula. Multiple linear regression analysis suggests that the joint spacing, joint continuity, weathering grade and maximum joint width of rocks among the measured parameters are related to the topographical parameters with statistical significances. Therefore, this study suggests that rock properties such as joint spacing, joint continuity, weathering grade and maximum joint width seem to greatly influence topography, although various factors can affect topographical parameters.

• Korea-Australia Rheology Journal
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• 제20권4호
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• pp.221-226
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• 2008

The purpose of this study was to compare rheological properties of six dental interocclusal recording materials and to investigate the effect of temperature on the rheological properties during setting. Five polyvinylsiloxane materials and one polyether material were investigated in this study. The storage modulus (G') and the loss factor ($tan{\delta}$) were measured from 30s after mixing during setting, using the universal dynamic spectrometer. Viscoelastic properties were evaluated by means of G' and $tan{\delta}$ from 5 repeats at $21^{\circ}C$ and $33^{\circ}C$. Individual changes during setting were also evaluated. All data were statistically analyzed using one-way ANOVA and multiple comparison $Scheff{\acute{e}}$ test at the significance level of 0.05. The mean of G was checked at $t_{set}$ (the setting time provided from manufacturer) and $t_{300}$ (the end of experimental time) and the mean of $tan{\delta}$ was checked at to and $t_{set}$. Whereas the increase of the G' value showed generally exponential changes at $21^{\circ}C$, the change of the G' value at $33^{\circ}C$ displayed sigmoidal curves during setting. The change of loss factor $tan{\delta}$ during setting varied. Within the limitations of this study, dental interocclusal recording materials had different viscoelastic properties and most of the materials showed different fluidity at $21^{\circ}C$ and $33^{\circ}C$.

• Current Optics and Photonics
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• 제1권4호
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• pp.358-363
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• 2017

In this study, we present a detailed investigation of luminescence properties of a blue light-emitting diode using InGaN/GaN (indium component is 17.43%) multiple quantum wells as the active region grown on patterned sapphire substrate by low-pressure metal-organic chemical vapor deposition (MOCVD). High-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman scattering (RS) and photoluminescence (PL) measurements are employed to study the crystal quality, the threading dislocation density, surface morphology, residual strain existing in the active region and optical properties. We conclude that the crystalline quality and surface morphology can be greatly improved, the red-shift of peak wavelength is eliminated and the superior blue light LED can be obtained because the residual strain that existed in the active region can be relaxed when the LED is grown on patterned sapphire substrate (PSS). We discuss the mechanisms of growing on PSS to enhance the superior luminescence properties of blue light LED from the viewpoint of residual strain in the active region.

• 경영과정보연구
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• 제3권
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• pp.15-45
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• 1999

Processing techniques of remote sensed image data using computer have been recognized very necessary techniques to all social fields, such as, environmental observation, land cultivation, resource investigation, military trend grasp and agricultural product estimation, etc. Especially, accurate classification and analysis to remote sensed image da are important elements that can determine reliability of remote sensed image data processing systems, and many researches have been processed to improve these accuracy of classification and analysis. Traditionally, remote sensed image data processing systems have been processed 2 or 3 selected bands in multiple bands, in this time, their selection criterions are statistical separability or wavelength properties. But, it have be bring up the necessity of bands selection method by data distribution characteristics than traditional bands selection by wavelength properties or statistical separability. Because data sensing environments change from multispectral environments to hyperspectral environments. In this paper for efficient data classification in multispectral bands environment, a band feature extraction method using the Rough sets theory is proposed. First, we make a look up table from training data, and analyze the properties of experimental multispectral image data, then select the efficient band using indiscernibility relation of Rough set theory from analysis results. Proposed method is applied to LANDSAT TM data on 2 June 1992. From this, we show clustering trends that similar to traditional band selection results by wavelength properties, from this, we verify that can use the proposed method that centered on data properties to select the efficient bands, though data sensing environment change to hyperspectral band environments.

• Geomechanics and Engineering
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• 제17권3호
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• pp.261-270
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• 2019

Because the estimation of the tensile strength is very important in any geotechnical project, many attempts have been made to determine. But the immediate determination of the tensile strength is usually difficult owing to well-shaped specimens, time-consuming, expensive and sometimes unreliable. In this study, engineering properties of several ultramafic rock samples were measured to assess the correlations between the Brazilian Tensile Strength (BTS) and degree of serpentinization, physical, dynamic and mechanical characteristics. For this purpose, a comprehensive laboratory testing program was conducted after collecting thirty-two peridotite and fifty-one serpentinite rock samples, taken from central Greece, in accordance with ASTM and ISRM standards. In addition, a representative number of them were subjected to petrographic studies and the obtained results were statistically described and analysed. Simple and multiple regression analyses were used to investigate the relationships between the Brazilian Tensile Strength and the other measured properties. Thus, empirical equations were developed and they showed that all of the properties are well correlated with Brazilian Tensile Strength. The curves with the $45^{\circ}$ line (y = x) were extracted for evaluating the validity degree of concluded empirical equations which approved approximately close relationships between Brazilian Tensile Strength and the measured properties.

• Smart Structures and Systems
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• 제30권2호
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• pp.183-193
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• 2022

Structural health monitoring and structural vibration control are multidisciplinary and frontier research directions of civil engineering. As intelligent materials that integrate sensing and actuation capabilities, shape memory alloys (SMAs) exhibit multiple excellent characteristics, such as shape memory effect, superelasticity, corrosion resistance, fatigue resistance, and high energy density. Moreover, SMAs possess excellent resistance sensing properties and large deformation ability. Superfine NiTi SMA wires have potential applications in structural health monitoring and micro-drive system. In this study, the mechanical properties and electrical resistance sensing characteristics of superfine NiTi SMA wires were experimentally investigated. The mechanical parameters such as residual strain, hysteretic energy, secant stiffness, and equivalent damping ratio were analyzed at different training strain amplitudes and numbers of loading-unloading cycles. The results demonstrate that the detwinning process shortened with increasing training amplitude, while austenitic mechanical properties were not affected. In addition, superfine SMA wires showed good strain-resistance linear correlation, and the loading rate had little effect on their mechanical properties and electrical resistance sensing characteristics. This study aims to provide an experimental basis for the application of superfine SMA wires in engineering.

• 한국토양비료학회지
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• 제45권6호
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• pp.920-924
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• 2012

This study was performed to estimate total contents of arsenic (As) by stepwise multiple-regression analysis using chemical properties and extractable contents of metal in paddy soil adjacent to abandoned mines. The soil was collected from paddies near abandoned mines. Soil pH, electrical conductively (EC), organic mater (OM), available phosphorus ($P_2O_5$), and exchangeable cations (Ca, K, Mg, Na) were measured. Total contents of As and extractable contents of metals were analyzed by ICP-OES. From stepwise analysis, it was showed that the contents of extractable As, available phosphorus, extractable Cu, exchangeable K, exchangeable Na, and organic mater significantly influenced the total contents of As in soil (p<0.001). The multiple linear regression models have been established as Log (Total-As) = 0.741 + 0.716 Log (extractable-As) - 0.734 Log (avail-$P_2O_5$) + 0.334 Log (extractable-Cu) + 0.186 Log (exchangeable-K) - 0.593 Log (exchangeable-Na) + 0.558 Log (OM). The estimated value in total contents of As was significantly correlated with the measured value in soil ($R^2$=0.84196, p<0.0001). This predictive model for estimating total As contents in paddy soil will be properly applied to the numerous datasets which were surveyed with extractable heavy metal contents based on Soil Environmental Conservation Act before 2010.

• Current Research on Agriculture and Life Sciences
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• 제23권
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• pp.53-60
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• 2005

본 연구는 경주남산의 산림토양의 이화학적 특성을 분석하여 산림의 다목적이용과 남산의 산림보호 관리에 도움을 주고자 실시하였다. 조사지는 각 층위별로 토양성분을 분석하였고, 그 결과는 다음과 같다. 남산 산림토양의 물리적 특성은 토심이 31.4cm 이고 유효토심은 20.0cm 였으며 유기물층의 깊이는 5.9cm였다. 계곡부를 제외한 다른 조사지의 토성은 사질 양토이었다. 전체 토양 pH는 평균 4.76으로 우리나라 산림토양의 평균보다 낮게 나타났으며 유효인산의 함량은 평균 3.64로 유효인산의 함량이 매우 적은 것으로 나타났다. 치환성양이온($Ca^{2+}$, $Mg^{2+}$, $K^+$, $Na^+$)의 함량은 우리나라 산림토양의 함량과 보다 낮은 수치를 나타내었으며 특히 $Ca^{2+}$함량은 우리나라 산림토양의 평균 $2.44cmol_c/kg$보다 낮은 함량인 $1.04cmol_c/kg$를 나타내었다.

• 한국지반공학회논문집
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• 제30권4호
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• pp.101-106
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• 2014

관입시험은 한정된 범위에서 1차원적 정보를 얻을 수 있으나, N치는 다양한 지반설계정수와 실험적으로 연관되어 있다. 탄성파를 이용한 비파괴 검사는 역산 과정을 통해 비용 및 시간에 효율적으로 2차원 및 3차원 물성에 대한 지도를 얻을 수 있으며, N치와 탄성파 속도는 간극비, 포화도, 유효응력 등에 의해 좌우된다. 따라서 N치와 탄성파 속도간의 경험적 관계들이 제안되어 왔다. 본 연구는 다양한 간극비와 포화도를 갖는 주문진사에 대해 정지토압조건에서 탄성파를 실험적으로 측정하였다. 그 결과 하중 조건이 간극비 및 포화도에 비하여 가장 영향을 주는 요소로 나타났으며, 간극비와 포화도는 응력-속도 관계의 경향에 영향을 주었다. 각 영향인자간의 관계를 다중회귀분석을 통해 상관식으로 나타내었다.

• Yonsei Medical Journal
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• 제59권9호
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• pp.1115-1122
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• 2018

Purpose: To investigate biomechanical properties of the cornea using a dynamic Scheimpflug analyzer according to age. Materials and Methods: In this prospective, cross-sectional, observational study, participants underwent ophthalmic investigations including corneal biomechanical properties, keratometric values, intraocular pressure (IOP), and manifest refraction spherical equivalent (MRSE). We determined the relationship of biomechanical parameters and ocular/systemic variables (participant's age, MRSE, IOP, and mean keratometric values) by piecewise regression analysis, association of biomechanical parameters with variables by Spearman's correlation and stepwise multiple regression analyses, and reference intervals (RI) by the bootstrap method. Results: This study included 217 eyes of 118 participants (20-81 years of age). Piecewise regression analysis between Corvis-central corneal thickness (CCT) and participant's age revealed that the optimal cut-off value of age was 45 years. No clear breakpoints were detected between the corneal biomechanical parameters and MRSE, IOP, and mean keratometric values. Corneal velocity, deformation amplitude, radius, maximal concave power, Corvis-CCT, and Corvis-IOP exhibited correlations with IOP, regardless of age (all ages, 20-44 years, and over 44 years). With smaller deformation amplitude and corneal velocity as well as increased CorvisIOP and Corvis-CCT, IOP became significantly increased. We provided the results of determination of confidence interval from RI data using bootstrap method in three separate age groups (all ages, 20-44 years, and over 44 years). Conclusion: We demonstrated multiple corneal biomechanical parameters according to age, and reported that the corneal biomechanical parameters are influenced by IOP.