• Korean Journal of Radiology
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• v.2 no.2
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• pp.68-74
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• 2001

Objective: To describe the brain CT and MR imaging findings of unusual acute encephalitis involving the thalamus. Materials and Methods: We retrospectively reviewed the medical records and CT and/or MR imaging findings of six patients with acute encephalitis involving the thalamus. CT (n=6) and MR imaging (n=6) were performed during the acute and/or convalescent stage of the illness. Results: Brain CT showed brain swelling (n=2), low attenuation of both thalami (n=1) or normal findings (n=3). Initial MR imaging indicated that in all patients the thalamus was involved either bilaterally (n=5) or unilaterally (n=1). Lesions were also present in the midbrain (n=5), medial temporal lobe (n=4), pons (n=3), both hippocampi (n=3) the insular cortex (n=2), medulla (n=2), lateral temporal lobe cortex (n=1), both cingulate gyri (n=1), both basal ganglia (n=1), and the left hemispheric cortex (n=1). Conclusion: These CT or MR imaging findings of acute encephalitis of unknown etiology were similar to a combination of those of Japanese encephalitis and herpes simplex encephalitis. In order to document the specific causative agents which lead to the appearance of these imaging features, further investigation is required.

• Korean Journal of Radiology
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• v.1 no.2
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• pp.91-97
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• 2000

Objective: To determine whether the time-intensity curves acquired by test and main dose contrast injections for MR angiography are similar. Materials and Methods: In 11 patients, repeated contrast-enhanced 2D-turbo-FLASH scans with 1-sec interval were obtained. Both test and main dose timeintensity curves were acquired from the abdominal aorta, and the parameters of time-intensity curves for the test and main boluses were compared. The parameters used were arterial and venous enhancement times, arterial peak enhancement time, arteriovenous circulation time, enhancement duration and enhancement expansion ratio. Results: Between the main and test boluses, arterial and venous enhancement times and arteriovenous circulation time showed statistically significant correlation (p < 0.01), with correlation coefficients of 0.95, 0.92 and 0.98 respectively. Although the enhancement duration was definitely greater than infusion time, reasonable measurement of the end enhancement point in the main bolus was impossible. Conclusion: Only arterial and venous enhancement times and arteriovenous circulation time of the main bolus could be predicted from the test-bolus results. The use of these reliable parameters would lead to improvements in the scan timing method for MR angiography.

• Smart Structures and Systems
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• v.33 no.3
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• pp.177-188
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• 2024

The fatigue-induced sequential failure of a structure having structural redundancy requires system-level analysis to account for stress redistribution. System reliability-based design optimization (SRBDO) for preventing fatigue-initiated structural failure is numerically costly owing to the inclusion of probabilistic constraints. This study incorporates the Branch-and-Bound method employing system reliability Bounds (termed the B³ method), a failure-path structural system reliability analysis approach, with a metaheuristic optimization algorithm, namely grey wolf optimization (GWO), to obtain the optimal design of structures under fatigue-induced system failure. To further improve the efficiency of this new optimization framework, an additional bounding rule is proposed in the context of SRBDO against fatigue using the B³ method. To demonstrate the proposed method, it is applied to complex problems, a multilayer Daniels system and a three-dimensional tripod jacket structure. The system failure probability of the optimal design is confirmed to be below the target threshold and verified using Monte Carlo simulation. At earlier stages of the optimization, a smaller number of limit-state function evaluation is required, which increases the efficiency. In addition, the proposed method can allocate limited materials throughout the structure optimally so that the optimally-designed structure has a relatively large number of failure paths with similar failure probability.

• Corrosion Science and Technology
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• v.23 no.1
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• pp.72-81
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• 2024

The Ti-6Al-4V alloy is widely used as an implant material due to its higher fatigue strength and strengthto-weight ratio compared to pure titanium, excellent corrosion resistance, and bone-like properties that promote osseointegration. For rapid osseointegration, the adhesion between the titanium surface and cellular biomolecules is crucial because adhesion, morphology, function, and proliferation are influenced by surface characteristics. Polymeric peptides and similar coating technologies have limited effectiveness, prompting a demand for alternative materials. There is growing interest in 2D nanomaterials, such as MoS₂, for good corrosion resistance and antibacterial, and bioactive properties. However, to coat MoS₂ thin films onto titanium, typically a low-temperature hydrothermal synthesis method is required, resulting in the synthesis of films with a toxic 1T@2H crystalline structure. In this study, through high-temperature annealing, we transformed them into a non-toxic 2H structure. The implant coating technique proposed in this study has good corrosion resistance and biocompatibility, and antibacterial properties.

• Progress in Superconductivity and Cryogenics
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• v.26 no.2
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• pp.19-23
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• 2024

3D printing has the advantage of being able to process various types of parts by layering materials. In addition to these advantages, 3D printing technology allows models to be processed quickly without any special work that can be used in different fields to produce workpieces for various purposes and shapes. This paper deals to not only increase the utilization of 3D printing technology, but also to revitalize 3D printing technology in applications that require similar cryogenic environments. The goal of this study is to identify the mechanical properties of polylactic acid and photopolymer resin processed by Fused Deposition Modeling (FDM) and Digital Light Processing (DLP) respectively. The entire process is meticulously examined, starting from getting the thermal contraction using an extensometer. A uniaxial tensile test is employed, which enables to obtain the mechanical properties of the samples at both room temperature (RT) and cryogenic temperature of 77 K. As the results, photopolymer resin exhibited higher tensile properties than polylactic acid at RT. However, at cryogenic temperatures (77 K), the photopolymer resin became brittle and failure occurred due to thermal contraction, while polylactic acid demonstrated superior tensile properties. Therefore, polylactic acid is more suitable for lower temperatures.

• Structural Monitoring and Maintenance
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• v.11 no.1
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• pp.41-55
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• 2024

This study aims to determine the characteristics of concrete as identified by Rebound Hammer and Ultrasonic Pulse Velocity (UPV) tests, focusing particularly on their efficacy in estimating compressive strength of concrete material. The study involved three concrete samples designed to achieve a target strength of 29 MPa, comprising normal concrete, instant concrete, and concrete with additives. These were cast into cube specimens measuring 150×150×150 mm. Compressive strength values were determined through both destructive and non-destructive testing on the cubic specimens. As a result, the non-destructive methods yielded varying outcomes for each correlation approach, influenced by the differing constituent materials in the tested concretes. However, normal concrete consistently showed the most reliable correlation, followed by concrete with additives, and lastly, instant concrete. The study found that combining Rebound Hammer and UPV tests enhances the prediction accuracy of compressive strength of concrete. This synergy was quantified through multivariate regression, considering UPV, rebound number, and actual compressive strength. The findings also suggest a more significant influence of the Rebound Hammer measurements on predicting compressive strength for BN and BA, whereas UPV and RN had a similar impact on predicting BI compressive strength.

• Journal of Radiation Industry
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• v.18 no.1
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• pp.9-14
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• 2024

In order to thoroughly verify the denuclearization of the Korean Peninsula, it is urgent to develop technology capabilities to monitor, detect, collect, analyze, interpret, and evaluate nuclear activities using nuclear materials and secure nuclear transparency. The IAEA is actively using seal technology to maximize the efficiency of safety measures, and currently uses metal cap, paper, COBRA, and EOSS as seal devices. Unlike facilities that comply with safety measures requirements, such as domestic nuclear facilities, facilities subject to denuclearization are likely to have various risk environments that make it difficult to apply safety measures, and there is a high possibility that continuity of knowledge (COK) such as damage, malfunction, and power loss will not be maintained. This study aims to develop a real-time active seal device that can be applied in such special situations to enable immediate response in the event of a similar situation. To this end, the main functions of the real-time seal device were derived and applied, and a commercialized seal device and operation software. The real-time seal technology developed through this study can be applied to all nuclear facilities in South Korea, especially used as storage equipment for dry cask storage facilities of heavy water reactor's after fuel, and it is believed that unnecessary radiation exposure by inspectors can be minimized.

• Smart Structures and Systems
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• v.34 no.2
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• pp.87-96
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• 2024

Smart materials, such as magnetorheological (MR) fluid, have received considerable research attention in recent years due to their unique capabilities. MR fluid, which possesses a magnetic field controllable viscosity, has been extensively studied for vehicular applications with the aim of synthesizing optimal MR fluids, designing optimal MR dampers, and developing control strategies. However, a comprehensive study that primarily focuses on developing a cost-effective semi-active suspension system for a commercial vehicle in a developing nation is still lacking. This study addresses this gap by synthesizing an in-house MR fluid and studying its rheological properties. Subsequently, a novel single-sensor-based controller is developed and closed-loop simulations are conducted on a quarter-car semi-active model. Finally, the overall semi-active quarter-car suspension system is experimentally tested using a suspension test rig. The performance of the proposed system in terms of ride comfort and road holding is evaluated and is compared with simple control strategies. The dynamic range of the developed semi-active MR damper is found to be around 2.3, indicating a significant MR effect. The results suggest an intermediate response using the proposed acceleration-driven controller (ADV) at lower frequencies and similar performance to that of the skyhook controller at higher frequencies. The cost-effective methodology proposed in this study is effective and can be adapted for other semi-active engineering applications.

• Food Science of Animal Resources
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• v.44 no.5
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• pp.1156-1166
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• 2024

Texture is a major challenge in addressing the need to find sustainable meat alternatives, as consumers desire alternative meat to have a sensory profile like meat. In this study, the fabrication of imitated muscle fiber (IMF) is performed by introducing different kinds of protein sources, with an effective bottom-up technique- wet spinning. Herein, the protein sources (pea protein isolate, wheat protein, and myofibrillar paste) were combined with sodium alginate to stimulate the bonding with the coagulation solution for fabrication. It has been found that the fabrication of IMF is possible using all the protein sources, however, due to the difference in protein structure, a significant difference was observed in quality characteristics compared to conventional meat. Additionally, combination of wheat protein and pea protein isolate has given similar values as conventional meat in terms of some of the texture profiles and Warner-Bratzler shear force. In general, the optimization of protein sources for wet spinning can provides a novel way for the production of edible fiber of alternative meat.

• Journal of the Korean Society for Heat Treatment
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• v.37 no.5
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• pp.221-227
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• 2024

The damping capacities in the strain-amplitude dependent and strain-amplitude independent regions were comparatively investigated for pure Mg and Mg-X%Al solid solutions (X : 1, 2 at%) to clarify the role of Al solute in the damping properties of Mg-Al binary solid solution. In order to rule out the effect of grain size on damping capacity, grain sizes of the samples were adjusted to an almost similar level by changing the heat-treatment or solution treatment times at 683 K (12 h, 24 h and 32 h for pure Mg, Mg-1%Al and Mg-2%Al alloys, respectively). The damping capacities of the heat-treated pure Mg and Mg-X%Al solid solutions exhibited a decreasing tendency with an increase in Al concentration both in the strain-amplitude dependent and strain-amplitude independent regions. The observed damping trends depending on strain-amplitude were analyzed and discussed in association with decreasing length between weak pinning points (Al solutes) in Granato-Lücke model.