• Korean Journal of Applied Biomechanics
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• v.31 no.3
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• pp.183-188
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• 2021

Objective: The purpose of this study was to develop a stretchable joint motion sensor that is based on silver nano-particle. Through this sensor, it can be utilized as an equipment for rehabilitation and analyze joint movement. Method: In this study, precursor solution was created, after that, nozel printer (Musashi, Image master 350PC) was used to print on a circuit board. Sourcemeter (Keithley, Keithley-2450) was used in order to evaluate changes of electric resistance as the sensor stretches. In addition, the sensor was attached on center of a knee joint to 2 male adults, and performed knee flexion-extension in order to evaluate accurate analysis; 3 infrared cameras (100 Hz, Motion Master 100, Visol Inc., Korea) were also used to analyze three dimensional movement. Descriptive statistics were suggested for comparing each accuracy of measurement variables of joint motions with the sensor and 3D motions. Results: The change of electric resistance of the sensor indicated multiple of 30 times from initial value in 50% of elongation and the value of electric resistance were distinctively classified by following 10%, 20%, 30%, 40% of elongation respectively. Through using the sensor and 3D camera to analyze movement variable, it showed a resistance of 99% in a knee joint extension, whereas, it indicated about 80% in flexion phase. Conclusion: In this research, the stretchable joint motion sensor was created based on silver nanoparticle that has high conductivity. If the sensor stretches, the distance between nanoparticles recede which lead gradual disconnection of an electric circuit and to have increment of electric resistance. Through evaluating angle of knee joints with observation of sensor's electric resistance, it showed similar a result and propensity from 3D motion analysis. However, unstable electric resistance of the stretchable sensor was observed when it stretches to maximum length, or went through numerous joint movements. Therefore, the sensor need complement that requires stability when it comes to measuring motions in any condition.

• Journal of The Korean Society of Agricultural Engineers
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• v.66 no.4
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• pp.27-39
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• 2024

Soil texture is determined by the proportions of sand, silt, and clay within the soil, which influence characteristics such as porosity, water retention capacity, electrical conductivity (EC), and pH. Traditional classification of soil texture requires significant sample preparation including oven drying to remove organic matter and moisture, a process that is both time-consuming and costly. This study aims to explore an alternative method by developing an AI model capable of predicting soil texture from images of pre-sorted soil samples using computer vision and deep learning technologies. Soil samples collected from agricultural fields were pre-processed using sieve analysis and the images of each sample were acquired in a controlled studio environment using a smartphone camera. Color distribution ratios based on RGB values of the images were analyzed using the OpenCV library in Python. A convolutional neural network (CNN) model, built on PyTorch, was enhanced using Digital Image Processing (DIP) techniques and then trained across nine distinct conditions to evaluate its robustness and accuracy. The model has achieved an accuracy of over 80% in classifying the images of pre-sorted soil samples, as validated by the components of the confusion matrix and measurements of the F1 score, demonstrating its potential to replace traditional experimental methods for soil texture classification. By utilizing an easily accessible tool, significant time and cost savings can be expected compared to traditional methods.

• Economic and Environmental Geology
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• v.43 no.4
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• pp.371-379
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• 2010

Fresh water injection test in a fractured bedrock aquifer was applied as an efficient approach to lower saline concentrations in the saltwater-freshwater transition zone formed by seawater intrusion in a coastal area. The methodology and effectiveness of fresh water injection for hydraulically controlling seawater intrusion is overwhelmingly site dependent, and there is an urgent need to characterize the permeable fractures or unconsolidated porous formations which can allow for seawater flow and transport. Considering aquifer characteristics, injection and monitoring boreholes were optimally designed and completed to inject fresh water through sand layer and fractured bedrock, respectively. We devised and used the injection system using double packer for easy field operation and maintenance. Overall fracture distribution was systematically identified from borehole image logs, and the section of fresh water injection was decided from injection test and monitoring. With fresh water injection, the fluid electrical conductivity of the monitoring well started to be lowered by the inflow of fresh water at the specific depth. And this inflow leaded to the replacement of the fluid in the upper parts of the borehole with fresh water. Furthermore, the injection effect lasted more than several months, which means that fresh water injection may contribute to the mitigation of seawater intrusion in a coastal area.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.749-753
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• 2012

In present work, anode support for micro-tubular SOFC was fabricated with outer diameter of 3 mm and characterized with microstructure, mechanical properties and gas permeability. The microstructure of surface and cross section of a porous anode support were analyzed by using SEM (Scanning Electron Microscope) image. The gas permeability and the mechanical strength of anode support was measured and analysed by using differential pressure at the flow rates of 50, 100, 150 cc/min. and using universal testing machine respectively. The unit cell composed of NiO-YSZ, YSZ, YSZ-LSM/LSM/LSCF was fabricated and operated with reaction temperature and fuel flow rate and showed maximum power density of $1095mW/cm^2$ on the condition of $800^{\circ}C$. The performance of single cell for micro-tubular SOFC increased with the increasing the reaction temperature due to the decrement of ohmic resistance of cell by the increment of the ionic conductivity of electrolyte through the evaluation of electrochemical impedance analysis for single cell with reaction temperature.

• Polymer(Korea)
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• v.39 no.1
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• pp.88-98
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• 2015

4-Amino-N-hexadecylbenzamide-graphene sheets (AHB-GSs), used in the preparation of the polyimide (PI) nanocomposite films, were synthesized by mixing a dispersion of graphite oxide with a solution of the ammonium salt of AHB. The atomic force microscope image of functionalized-GS on mica and a profile plot revealed the average thickness of AHB-GS to be ~3.21 nm. PI films were synthesized by reacting 4,4'-biphthalic anhydride and bis(4-aminophenyl) sulfide. PI nanocomposite films containing various contents of AHB-GS over the range of 0-10 wt% were synthesized using the solution intercalation method. The PI nanocomposite films under different thermal imidization temperatures, 250 and $350^{\circ}C$, were examined. The graphenes, for the most part, were well dispersed in the polymer matrix despite some agglomeration. However, micrometer-scale particles were not detected. The average thickness of the particles was <10 nm, as revealed from the transmission electron microscope images. Only a small amount of AHB-GS was required to improve the gas barrier, and electrical conductivity. In contrast, the glass transition and initial decomposition temperatures of the PI hybrid films continued to decrease with increasing content of AHB-GS up to 10 wt%. In general, the properties of the PI hybrid films heat treated at $350^{\circ}C$ were better than those of films heat treated at $250^{\circ}C$.

• Geophysics and Geophysical Exploration
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• v.20 no.1
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• pp.33-42
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• 2017

Recently, the grounded electrical-source airborne transient electromagnetic (GREATEM) system with high power source was introduced to achieve deeper investigation depth and to overcome high noise level. Although the GREATEM is a transient electromagnetic system using a long grounded wire as the transmitter, GREATEM data have been interpreted with 1D earth models because 2D or 3D modeling and inversion of vast airborne data are complicated and expensive to calculate. Generally, 1D inversion is subsequently applied to every survey point and combining 1D images together forms the stitched conductivity-depth image. However, the stitched models often result in abrupt variations in neighboring models. To overcome this problem, laterally constrained inversion (LCI) has been developed in inversion of ATEM data, which can yield layered sections with lateral smooth transitions. In this study, we analysed the GREATEM data through 1D numerical modeling for a curved grounded wire source. Furthermore, we developed a laterally constrained inversion scheme for continuous GREATEM data based on a layered earth model. All 1D data sets and models are inverted as one system, producing layered sections with lateral smooth transitions. Applying the developed LCI technique to the GREATEM data, it was confirmed that the laterally constrained inversion can provide laterally smooth model sections that reflect the layering of the survey area effectively.

• Geophysics and Geophysical Exploration
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• v.11 no.1
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• pp.68-77
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• 2008

We have developed an inversion algorithm for loop-loop electromagnetic (EM) data, based on the localised non-linear or extended Born approximation to the solution of the 2.5D integral equation describing an EM scattering problem. Source and receiver configuration may be horizontal co-planar (HCP) or vertical co-planar (VCP). Both multi-frequency and multi-separation data can be incorporated. Our inversion code runs on a PC platform without heavy computational load. For the sake of stable and high-resolution performance of the inversion, we implemented an algorithm determining an optimum spatially varying Lagrangian multiplier as a function of sensitivity distribution, through parameter resolution matrix and Backus-Gilbert spread function analysis. Considering that the different source-receiver orientation characteristics cause inconsistent sensitivities to the resistivity structure in simultaneous inversion of HCP and VCP data, which affects the stability and resolution of the inversion result, we adapted a weighting scheme based on the variances of misfits between the measured and calculated datasets. The accuracy of the modelling code that we have developed has been proven over the frequency, conductivity, and geometric ranges typically used in a loop-loop EM system through comparison with 2.5D finite-element modelling results. We first applied the inversion to synthetic data, from a model with resistive as well as conductive inhomogeneities embedded in a homogeneous half-space, to validate its performance. Applying the inversion to field data and comparing the result with that of dc resistivity data, we conclude that the newly developed algorithm provides a reasonable image of the subsurface.

• Journal of Korea Soil Environment Society
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• v.1 no.1
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• pp.67-79
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• 1996

Clay soils typically have low hydraulic conductivities in the presence of high polarity pore fluid, such as water. Low polarity fluids, such as hydrocarbon fuels and halogenated organic solvents, typically cannot migrate into clay pores because they cannot displace the pore water. Oxygenated additives in gasoline, such as alcohols and methyl-tert-butyl ether, are increasingly used to control air pollution emissions. These relatively polar and highly water-soluble compounds may facilitate displacement of pore water and enhance migration of fuels and solvents through clay-rich soil strata. In the reported research, the migration of gasoline-alcohol fuel mixtures (gasohol) through consolidated clay was examined. Prepared kaolinite clay samples were consolidated from slurry, and various combinations of gasoline, alcohol, and water were applied to the clays under 152 Pa gauge pressure. Movement of the fluids into the clay samples was monitored by measur ing displaced pore fluid and by magnetic resonance imaging of the samples. The structures of selected samples were examined using environmental scanning electron microscopy. Results of the research suggest that alcohol added to hydrocarbon fuels can enhance migration through some clays significantly. Gasoline did not migrate appreciably into water saturated clay, even after 14 days under pressure. The gasohol mixture migrated readily into the clay in only 20 minutes. Increased hydraulic conductivity of the clay in the presence of gasohol is hypothesized to be due to the collapse of the clays pore structure when ethanol is present, creating larger pores. Increasing pore diameter decreases the capillary pressure needed for the gasohol to replace water and allows gasohol to migrate through the clay.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.409-409
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• 2014

Recently hexagonal boron nitride (h-BN), III-V compound of boron and nitrogen with strong covalent $sp^2$ bond, is a 2 dimensional insulating material with a large direct band gap up to 6 eV. Its outstanding properties such as strong mechanical strength, high thermal conductivity, and chemical stability have been reported to be similar or superior to graphene. Because of these excellent properties, h-BN can potentially be used for variety of applications such as dielectric layer, deep UV optoelectronic device, and protective transparent substrate. Ultra flat and charge impurity-free surface of h-BN is also an ideal substrate to maintain electrical properties of 2 dimensional materials such as graphene. To synthesize a single or a few layered h-BN, chemical vapor deposition method (CVD) has been widely used by using an ammonia borane as a precursor. Ammonia borane decomposes into hydrogen (gas), monomeric aminoborane (solid), and borazine (gas) that is used for growing h-BN layer. However, very active monomeric aminoborane forms polymeric aminoborane nanoparticles that are white non-crystalline BN nanoparticles of 50~100 nm in diameter. The presence of these BN nanoparticles following the synthesis has been hampering the implementation of h-BN to various applications. Therefore, it is quite important to grow a clean and high quality h-BN layer free of BN particles without having to introduce complicated process steps. We have demonstrated a synthesis of a high quality h-BN monolayer free of BN nanoparticles in wafer-scale size of $7{\times}7cm^2$ by using CVD method incorporating a simple filter system. The measured results have shown that the filter can effectively remove BN nanoparticles by restricting them from reaching to Cu substrate. Layer thickness of about 0.48 nm measured by AFM, a Raman shift of $1,371{\sim}1,372cm^{-1}$ measured by micro Raman spectroscopy along with optical band gap of 6.06 eV estimated from UV-Vis Spectrophotometer confirm the formation of monolayer h-BN. Quantitative XPS analysis for the ratio of boron and nitrogen and CS-corrected HRTEM image of atomic resolution hexagonal lattices indicate a high quality stoichiometric h-BN. The method presented here provides a promising technique for the synthesis of high quality monolayer h-BN free of BN nanoparticles.

• The Journal of Engineering Geology
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• v.24 no.4
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• pp.525-534
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• 2014

Environmental problems typically occurring in abandoned mine lands (AML) include: contaminated and acidic surface water and groundwater; stockpiled waste rock and mill tailings; and ground subsidences due to mining operations. This study examines the effectiveness of various geophysical techniques for mapping potential hazard and contaminated zones. Four AML sites with sedimentation contamination problems, acid mine drainage (AMD) channels, ground subsidence, manmade liner leakage, and buried mine tailings, were selected to examine the applicability of various geophysical methods to the identification of the different types of mine hazards. Geophysical results were correlated to borehole data (core samples, well logs, tomographic profiles, etc.) and water sample data (pH, electrical conductivity (EC), and heavy metal contents). Zones of low electrical resistivity (ER) corresponded to areas contaminated by heavy metals, especially contamination by Cu, Pb, and Zn. The main pathways of AMD leachate were successfully mapped using ER methods (low anomaly peaks), self-potential (SP) curves (negative peaks), and ground penetrating radar (GPR) at shallow penetration depths. Mine cavities were well located based on composite interpretations of ER, seismic tomography, and well-log records; mine cavity locations were also observed in drill core data and using borehole image processing systems (BIPS). Damaged zones in buried manmade liners (used to block descending leachate) were precisely detected by ER mapping, and buried rock waste and tailings piles were characterized by low-velocity zones in seismic refraction data and high-resistivity zones in the ER data.