• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.810-813
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• 2003

Wide spread using of mobile and handy electronic apparatus is giving rise to a question on the harmfulness of health and causing troubles when electical and electronic equipments are in use. This paper reports on the experimental results obtained by using a pliable and structured specimen that has a long shape aperture, made of stainless steel fibers. Based on the TEM mode transfer structure that was designed and manufactured through HFSS, we measured electromagnetic shielding effectives, where the network analyzer was applied. We could draw a conclusion from this research that the metal fabric showed a good electromagnetic shielding effect, mainly by means of the good reflex loss at the fiber surface. Even though the material itself possesses a good absorption loss. the specimen revealed that structural factors. e.g.. the shape of the aperture. the size of the aperture, etc., can have a more influence on the shielding effect than the components of material have. A special notice is required for modeling and analyzing the electromagnetic characteristics of metal fabrics, because there exists a strong possibility that multiple reflection can happen on the surface of metal fibers. which can presume a model of fiber bundle and fabric structure.

• Journal of the Korean Society of Radiology
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• v.17 no.7
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• pp.1123-1131
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• 2023

This study aimed to present a method to effectively suppress metal artifacts caused by spinal fusion surgery during spinal MRI study. For this purpose, a phantom made of spinal surgery screws was created to reproduce the metal artifact. Then, images were acquired with 1.5T and 3.0T MRI to evaluate changes in metal artifacts according to magnetic field strength. In addition, metal artifacts were evaluated by increasing the receive bandwidth to 200, 400 and 800 Hz/PX. As a result, metal artifacts occurring in images obtained from the 1.5T MRI decreased by approximately 52.2% compared to images obtained from the 3.0T MRI, showing a significant difference (p<0.05). In particular, the signal loss and signal pile up areas were reduced by approximately 52.81% and 42.71%, respectively, showing a significant effect in suppressing metal artifacts. On the other hand, when images were acquired while increasing the receive bandwidth from 200 to 800 Hz/PX, there was no significant effect, with a decrease of up to 8.93% for the 1.5T MRI and up to 10.98% for the 3.0T MRI (p>0.05). As a result of this study, increasing the receive bandwidth reduced signal loss and reduced some metal artifacts, but did not have a significant effect because it did not suppress signal pile up. However, when the magnetic field strength was reduced from 3.0T to 1.5T, signal loss and signal pile up were greatly reduced, effectively improving the metal artifact. Therefore, in order to suppress metal artifacts caused by spinal fusion surgery, study using a low magnetic field MRI can be said to be the most effective method.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.2
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• pp.132-138
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• 2000

The effect of fluid flow on corrosion and erosion-corrosion of metal is a well-recognized phenomenon in pipelines and machinery equipment, and so on. Not only are fluid hydrodynamics important, but also the corrosiveness of the process or production stream affects the corrosion system. Recent research demonstrates that it is possible to erosion-corrosion(E/C) phenomena in terms of hydrodynamics, electrochemical corrosion kinetics and film growth/removal phenomena. Stress corrosion cracking behavior under cavitation erosion-corrosion of mild steel(SS41) was investigated of base metal and weldment under loaded stress. Main result obtained are as follows : 1) The cavitation erosion sensitivity of base metal affected weight loss is more susceptive than heat affected zone, 2) The corrosion sensitivity affected weight loss of welding heat cycle is less susceptive on stress corrosion under cavitation erosion-corrosion than stress corrosion.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.4
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• pp.637-643
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• 2006

The bench-scale chlorine exposure study was performed to investigate the effect of pretreatment by free chlorine and monochloramine ($NH_2Cl$) on the performance of RO membranes made of polyamide (PA). Feed monochloramination at 2mg/L did not cause significant productivity loss compared to free chlorine. However, metal coagulants reacted with monochloramine, the PA membrane suffered from a gradual loss of membrane integrity by chlorine oxidation, which was characterized as a decrease in salt rejection. Especially, RO membranes exposed to alum coagulants with monochloramine revealed the salt rejection lower than those exposed to iron coagulants. XPS membrane surface analysis demonstrated that the chlorine uptake on the membrane surface increased and carbon peaks were shifted significantly when exposed to alum coagulants with monochloramine.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.203-208
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• 2005

In this paper, an automated adaptive mesh generation scheme, based on an advancing-front-Delaunay method, is developed for finite element simulation of three dimensional bulk metal forming processes. During the simulation, the finite element mesh system is adaptively remeshed whenever the mesh is unacceptable. Several schemes are developed such as curvature compensation scheme to minimize volume loss, optimal smoothing scheme to improve element quality, etc. The presented approach is evaluated and applied to automatic forging simulation in order to demonstrate the effect of the developed schemes.

• Bulletin of the Korean Chemical Society
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• v.17 no.7
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• pp.621-625
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• 1996

A variety of metal oxides were coated by sol-gel process from their metal alkoxides on the ribbons of Co-based and Fe-based amorphous alloys, and the effects of surface oxide coating on the magnetic properties of the alloy are investigated. The core loss is found to be reduced significantly by the oxide coating, the loss reduction becoming more prominent at higher frequencies. The shape of the hystersis loop is also dependent upon the kind of the coated metal oxide. The coatings of MgO, SiO2, MgO·SiO2 and MgO·Al2O3 induce tensile stress into the Fe-based ribbon whereas those of BaO, Al2O3, CaO·Al2O3, SrO·Al2O3 and BaO·Al2O3 induce compressive stress. These results may be explained by the modification of domain structures via magnetoelastic interactions with the shrinkage stress induced by the sol-gel coating.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.633-636
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• 1992

The need for more efficient transformer core materials, due to increased recognition by the loss reduction of electric utilities, has spurred the development of amorphous metal usage in transformer. The loss of amorphous core is one third to one fourth that of silicon steel at equivalent inductions 15KG and below. Thus, the substitution of amorphous metal for conventional silicon steel in a transformer core can reduce core loss by 75%. This paper describes the development trend, the manufacturing processes of amorphous core transformer and the characteristics of amorphous core transformer in comparison with those of silicon core transformer.

• Journal of IKEEE
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• v.23 no.2
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• pp.403-406
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• 2019

We propose a low-loss on-chip transformer using an auxiliary primary part (APP) for an output matching network for fully integrated CMOS power amplifiers. The APP is designed using a fifth metal layer while the primary and secondary parts are designed using a sixth metal layer with a width smaller than that of the primary and secondary parts of the transformer to minimize the substrate loss and the parasitic capacitance between the primary and secondary parts. By adapting the APP in the on-chip transformer, we obtain an improved maximum available gain value without the need for any additional chip area. The feasibility of the proposed APP structure is successfully verified.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.81-87
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• 2006

In this paper, the belt-pulley mechanical loss is investigated. A bondgraph model for the mechanical loss is developed from the viewpoint of the power flow by assuming that all power losses are attributed to the torque loss. The mechanical loss model consists of transient and steady state part. The coefficients of the power loss model are obtained from the experiments. It is found from the simulations and experiments that the steady state loss depends on the line pressure, input torque and rotational speed while the transient loss depends on the rotational speed, shift speed and the inertial torque.

• Journal of the Korean Wood Science and Technology
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• v.48 no.1
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• pp.50-60
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• 2020

Fungi are wood-decaying organisms, and this is an important trait that should be considered in wood utilization. When fungi attack wood, it decreases the quality of the wood. The use of metal screws has become an important part of woodworking. The ability of fungi to decay wood and damage metal screws that are embedded into wood is varied. In this study, eight fungal species were evaluated with respect to their ability to decay Parashorea smythiesii and P. tomentella wood. In addition, the effect of fungi on corroding metal screws was determined using the Kolle flask method. The evaluation showed that the fungal species Schizophyllum commune, Pycnoporus sanguineus, and Polyporus arcularius were highly capable of decaying Parashorea spp. woods. The greatest wood weight loss occurred with the heartwood of P. tomentella exposed to S. commune. Based on the classification of wood resistance against fungal attack, the two Parashorea spp. were classified as moderately resistant woods (class III). Schizophyllum commune was classified as highly capable of decaying wood that was embedded with metal screws and was highly capable of corroding metal screws placed in fungi-culture media. The greatest weight of rust powder formed because of screw corrosion was obtained from screw-embedded wood exposed to S. commune. Additionally, the most severe corrosion of metal screws that were embedded into woods was caused by the activities of P. arcularius. Moreover, the average weight loss of screw-embedded wood was greater than that of unscrewed wood.