• Journal of the Korean Geosynthetics Society
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• v.21 no.1
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• pp.33-48
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• 2022

This paper presents illustrative examples of the application of advanced digital image correlation (DIC) technology in the geotechnical laboratory tests, such as shallow footing test, trapdoor test, retaining wall test, and wide width tensile test on geogrid. The theoretical background of the DIC technique is first introduced together with fundamental equations. Relevant reduced-scale model tests were then performed using standard sand while applying the DIC technique to capture the movement of target materials during tests. A number of different approaches were tried to obtain optimized images that allow efficient tracking of material speckles based on the DIC technique. In order to increase the trackability of soil particles, a mix of dyed and regular sand was used during the model tests while specially devised painted speckles were applied to the geogrid. A series of images taken during tests were automatically processed and analyzed using software named VIC-2D that automatically generates displacements and strains. The soil deformation field and associated failure patterns obtained from the DIC technique for each test were found to compare fairly well with the theoretical ones. Also shown is that the DIC technique can also general strains appropriate to the wide width tensile test on geogrid, It is demonstrated in this study that the advanced DIC technique can be effectively used in monitoring the deformation and strain field during a reduced-scale geotechnical model laboratory test.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.53-58
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• 2022

One of the most promising emerging technologies for the next generation of nonvolatile memory devices based on resistive switching (RS) is the resistive random-access memory mechanism. To date, RS effects have been found in many transition metal oxides. However, no clear evidence has been reported that ZnO-based resistive transition mechanisms could be associated with strong correlation effects. Here, we investigated N, F-co-doped ZnO (NFZO), which shows bipolar RS. Conducting micro spectroscopic studies on exposed surfaces helps tracking the behavioral change in systematic electronic structural changes during low and high resistance condition of the material. The significant difference in electronic conductivity was observed to attribute to the field-induced oxygen vacancy that causes the metal-insulator Mott transition on the surface. In this study, we showed the strong correlation effects that can be explored and incorporated in the field of multifunctional oxide electrons devices.

• Journal of Sensor Science and Technology
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• v.32 no.6
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• pp.352-356
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• 2023

The integration of bioelectronic devices with the skin is a promising strategy for personalized healthcare monitoring and diagnostics. On-skin bioelectrodes hold great potential for the real-time tracking of physiological parameters. However, persistent challenges of stability and reliability have instigated exploration beyond conventional noble metals. This study focuses on the ionic passivation and oxidation dynamics of copper-based on-skin thin-film bioelectrodes. Through parylene chemical vapor deposition, we harness a controlled thin film of parylene insulation to counter the intrinsic susceptibility of copper to oxidation in the ionic environment. The results represent the relationship among the parylene insulation thickness, copper oxidation, and electrode impedance over temporal intervals. Comparative analyses indicate that the short-term stability of the copper electrode is comparable to that of the gold electrode. Therefore, we propose a cost-effective strategy for fabricating copper-based on-skin bioelectrodes by introducing enhanced ionic stability within a discernible operational timeframe. This study enriches our understanding of on-skin bioelectronics and affordable material choices for practical use in wearable healthcare devices.

• Progress in Medical Physics
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• v.21 no.4
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• pp.311-322
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• 2010

In proton therapy, the analysis of secondary particles is important due to delivered dose outside the target volume and thus increased potential risk for the development of secondary cancer. The purpose of this study is to analyze the influence of secondary particles from proton beams on fluence and energy deposition in the presence of inhomogeneous material by using Geant4 simulation toolkit. The inhomogeneity was modeled with the condition that the adipose tissue, bone and lung equivalent slab with thickness of 2 cm were inserted at 30% (Plateau region) and 80% (Bragg peak region) dose points of maximum dose in Bragg curve. The energy of proton was varied with 100, 130, 160 and 190 MeV for energy dependency. The results for secondary particles were presented for the fluence and deposited energy of secondary particles at inhomogeneous condition. Our study demonstrates that the fluence of secondary particles is neither influenced insertion of inhomogeneties nor the energy of initial proton, while there is a little effect by material density. The deposited energy of secondary particles has a difference in the position placed inhomogeneous materials. In the Plateau region, deposited energy of secondary particles mostly depends on the density of inserted materials. Deposited energy in the Bragg region, in otherwise, is influenced by both density of inserted material and initial energy of proton beams. Our results suggest a possibility of prediction about the distribution of secondary particles within complex heterogeneity.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.11
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• pp.1081-1090
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• 2012

This study aims to track the longitudinal alteration pattern on the trabecular bone microarchitecture at tibial epiphysis induced by T-OA over time using in vivo micro computed tomography (${\mu}CT$). Ten SD rats were divided into control (n = 5) and T-OA (n = 5) groups. Anterior cruciate ligament transaction was performed for the T-OA group. The results showed that the alteration pattern on the trabecular bone microarchitecture at tibial epiphysis in the T.OA group was definitely different compared with that in the CON group from 0 to 8 weeks (approximately 4-16%, P > 0.05). In particular, a difference was observed in the bone formation and density distributions over time (from 0 or 4 to 8 weeks; approximately 5.15%, P < 0.05). An improved understanding of the alteration pattern on the trabecular bone microarchitecture at tibial epiphysis may assist in developing more targeted treatment interventions for T-OA.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.8
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• pp.334-341
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• 2020

The optimum solutions of the instability of the target velocity were studied to solve the case of the target velocity of the ship approaching at a speed of ◯◯knots and deviated by more than ± 10knots, while the surveillance radar rotating speed was varied, while the maximum search range of the radar was evaluated during the operational test & evaluation. The instability of the target velocity did not enable the radar to calculate the information of the target precisely and to degrade the probability of hit and the quality of the target management. The improvement to handle the deviation of the target velocity was optimally determined by using a fishbone diagram to find 9 reasons based on 4M1E, and the algorithm of the target management was identified as the crucial reason. In this study, the improvement was applied to the filter algorithm to stabilize the target velocity in the target tracking management SW by reviewing the current algorithm to find the velocity of the target and recognizing that the problem does not apply to different 𝜶, 𝞫 values when the antenna changed the rotating speed. The ability of the improvement to work was tested on board.

• Progress in Medical Physics
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• v.19 no.1
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• pp.42-48
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• 2008

Bio-implantable devices such as heart pacers, gastric pacers and drug-delivery systems require power for carrying out their intended functions. These devices are usually powered through a battery implanted with the system or are wired to an external power source. This paper describes an inductive power transmission link, which was developed for an implantable stimulator for direct stimulation of denervated muscles. The carrier frequency is around 1MHz, the transmitter coil has a diameter of 46mm, and the implant coil is 46mm. Data transmission to the implant with amplitude shift keying (ASK) and back to the transmitter with passive telemetry can be added without major design changes. We chose the range of coil spacing (2 to 30mm) to care for lateral misalignment, as it occurs in practical use. If the transmitter coil has a well defined and reliable position in respect to the implant, a smaller working range might be sufficient. Under these conditions the link can be operated in fixed frequency mode, and reaches even higher efficiencies of up to 37%. The link transmits a current of 50 mA over a distance range of 2-15 mm with an efficiency of more than 20% in tracking frequency. The efficiency of the link was optimized with different approaches. A class E transmitter was used to minimize losses of the power stage. The geometry and material of the transmitter coil was optimized for maximum coupling. Phase lock techniques were used to achieve frequency tracking, keeping the transmitter optimally tuned at different coupling conditions caused by coil distance variations.

• International Journal of Highway Engineering
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• v.5 no.2 s.16
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• pp.15-24
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• 2003

The performance of waterproofing system (WPS) is known to be a function of many complex interaction of material factors, design details, and the quality of construction, but it is mainly determined by the bond strength, which is measured by tensile adhesive strength (TAS) test. to the concrete bridge deck. In this research, eight waterproofing membranes were selected from commercial market and the tensile adhesive characteristics of the WPS on concrete bridge deck were investigated in view of various factor in asphalt pavement. The factors include type of asphalt mixture, pavement thickness, paving temperature and influence of wheel loading. TAS test of different asphalt pavement types showed that TAS of WPS under SMA (Stone Mastic Asphalt) pavement was greater than that under dense asphalt pavement. TAS of sheet membranes was improved as the compaction temperature of asphalt concrete increase, but TAS of liquid membranes were not. The influence of thickness of pavement val minimal with given laboratory test condition. TAS of sheet membranes after wheel tracking test were in the order of the sites under wheel path (UWP), before wheel tracking (BWT) and nearby wheel path (NWP). Since TAS of the same WPS of UWP was higher than TAS of BWT, wheel loading had function of pressing WPS resulting in higher adhesive strength. But liquid membranes were variable on types. The feature of detached interface after TAS test showed that sheet types were all detached in between deck concrete and WPS, and liquid types were detached in between asphalt pavement and WPS.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.489-495
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• 2016

In this study, the Warm-Mix Asphalt was prepared using a modified Sulfur Binder mixed with an additive of a polymer component in sulfur, which is an industrial by-product generated in the crude oil refining process. The dynamic stability and durability characteristics of the prepared Warm-Mix Asphalt was evaluated by the indirect tensile strength, the tensile strength ratio before and after water immersion and freezing-thawing, and the dynamic stability by wheel tracking test. The Warm-Mix Asphalt Mixtures using Modified Sulfur Binder has a tensile strength ratio before and after water immersion of 0.88, which is about 1.13 times that of the Warm-Mix formed modified Asphalt, and the tensile strength ration before and after freezing-thawing is also 0.82, thus, all tensile strength ratios satisfied the KS quality standard value of 0.75 or more. The indirect tensile strength was 1.6MPa which was twice the KS quality standard value of 0.8MPa, and about 1.24 times higher than that of normal heated asphalt 1.29MPa. In addition, the dynamic stability by the wheel tracking test was 14,075 times/mm, which was about 15 times higher than that of normal heated asphalt and about 3 times higher than that of the Warm-Mix formed modified Asphalt, showing excellent resistance to plastic deformation such as fatigue cracks.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.4
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• pp.339-343
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• 2011

This study is to examine the effect of freshwater influx on residence time to understand a long-term material transportation in enclosed bay. To predict the residence times of the coastal water in Masan bay, we were carried out the numerical simulations by using a EFDC model to simulate seawater circulation and particle tracking. The average residence times of Masan bay obtained from the particle release simulations under the condition to neglect a freshwater influx were estimated to be about 110 days in northern part of the bay to near Dotseom, 40 days in around Modo and 20 days in Budo to open sea. However, the average residence times under the condition consider with freshwater influx decreased about 81 days in both Region 1(northen Masan bay to near Dotseom) and Region II (Dotseom to Modo), but the Region III(Modo to Budo) and Region IV(Budo to open sea) incresed about 58 days and 17 days, respectively.