• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.11
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• pp.837-847
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• 2020

A velocity profile for flapping flight is optimized to increase the power efficiency of 20g weighted flapping wing micro air vehicle in hover. The experimental optimization of flapping velocity profile is carried out with a real sized flapper, and various velocity profiles are realized by non-circular gear. Kriging with noise is adopted as a meta model of the profile optimization to reflect the data noise by uncertainty. The optimization results confirm that the flapping efficiency (thrust-to-power ratio) is substantially improved (11.3%) through the elastic deformation that carries the angular kinetic energy from previous stroke.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.1
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• pp.106-113
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• 2013

One of feasible non-destructivity test methods for evaluation of concrete permeability is the measurement of surface resistivity. But the application to steel fiber-reinforced concrete has been limited because mis-evaluation could be caused by the steel fibers in concrete. In this study, the effect of fiber distribution on surface electrical resistivity of steel fiber-reinforced concrete was investigated through experimental program. Resistivity was measured three times on four surfaces in three rectangular and circular specimens with 0.5%, 1% and 1.5% steel fibers by volume and compared each other. The results obtained from circular specimens were consistent compared to those from rectangular specimens. And the results demonstrated that the effect of fiber distribution on surface resistivity was not significant compared to that of mixing ratio of steel fibers. In conclusion, this non-destructive testing method using measurement of surface resistivity could be used for SFRC within 0.5% steel fibers by volume.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3A
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• pp.139-148
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• 2012

Circular concrete-filled tubes (CFTs) are composite members, which consists of a steel tube and concrete infill. CFTs have been used as building columns and bridge piers due to several advantages such as their strength-to-size efficiency and facilitation of rapid construction. Extensive experimental studies about CFT have been conducted for past decades. However experimental results alone are not sufficient to support the engineering of these components. Complementary advanced numerical models are needed to simulate the behavior of CFT to extend the experimental research and develop predictive tools required for design and evaluation of structural systems. In this study, a finite element modeling technique for CFT was developed. The confinement effects, and behavior of CFT subjected various types of loading predicted by the proposed finite element model for CFT were verified by comparing with test results.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.413-416
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• 2005

Developement of computer and digitalizing of medical implement are being caused digitalizing of medical image. Medical Images are being managed more by PACS. In this situation comes out many problem about ownership, the right of properity of the medical images and notice wheather the data are modified. Digital watermarking can solve this problem. The proposed schemes have a two weak point that Non-blind method need a original image and Blind method use gaussian watermarking. In this paper, we propose a blind watermarking using binary image in order to easily recognize result of watermark This proposed scheme using wavelet transform and Circular Input method that input in medium-band of frequency domain.

• Clean Technology
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• v.30 no.3
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• pp.276-286
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• 2024

Since the Paris Agreement and the surge in global interest in climate change, the importance of measuring and managing national-level resource productivity has steadily grown. However, concerns about the reliability of productivity indicators persist due to inherent uncertainties. This study estimated the metal and non-metal resource productivities of 38 OECD countries through multiple regression analysis and conducted a comparative analysis of their ranking changes according to their current resource productivities. The study results revealed that the 38 OECD countries could be classified into four categories. First, countries with low overall resource productivities due to a high economic dependence on low-value metal resources by weight exhibited a substantial rise in their non-metal resource productivity rankings. Second, countries that have minimal metal industries in their national economies but generate high value-added from these sectors showed a notable increase in their metal resource productivity rankings. Third, countries with a low proportion of metal industry in their economies and low metal resource productivities experienced significant declines in their metal resource productivity rankings. Fourth, countries with a small disparity between their metal and non-metal resource productivities showed minimal changes in their rankings for both categories. These results highlight that changes in metal resource productivity rankings were more pronounced than those for non-metal resources, which implies that the influence of non-metal resources (biomass, fossil fuels, non-metallic minerals) dominates national-level resource productivity because their economic value is higher than metal resources. These findings suggest that it is necessary to manage the economic value of each resource type as distinct statistical data to provide a more nuanced understanding of national resource productivity.

• Smart Structures and Systems
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• v.19 no.2
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• pp.163-179
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• 2017

The axisymmetric buckling delamination of the Piezoelectric/Metal/Piezoelectric (PZT/Metal/PZT) sandwich circular plate with interface penny-shaped cracks is investigated. The case is considered where open-circuit conditions with respect to the electrical displacement on the upper and lower surfaces, and short-circuit conditions with respect to the electrical potential on the lateral surface of the face layers are satisfied. It is assumed that the edge surfaces of the cracks have an infinitesimal rotationally symmetric initial imperfection and the development of this imperfection with rotationally symmetric compressive forces acting on the lateral surface of the plate is studied by employing the exact geometrically non-linear field equations and relations of electro-elasticity for piezoelectric materials. The sought values are presented in the power series form with respect to the small parameter which characterizes the degree of the initial imperfection. The zeroth and first approximations are used for investigation of stability loss and buckling delamination problems. It is established that the equations and relations related to the first approximation coincide with the corresponding ones of the three-dimensional linearized theory of stability of electro-elasticity for piezoelectric materials. The quantities related to the zeroth approximation are determined analytically, however the quantities related to the first approximation are determined numerically by employing Finite Element Method (FEM). Numerical results on the critical radial stresses acting in the layers of the plate are presented and discussed. In particular, it is established that the piezoelectricity of the face layer material causes an increase (a decrease) in the values of the critical compressive stress acting in the face (core) layer.

• BMB Reports
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• v.53 no.2
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• pp.82-87
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• 2020

Circular RNAs (circRNAs), one kind of non-coding RNA, have been reported as critical regulators for modulating gene expression in cancer. In this study, microarray analysis was used to screen circRNA expression profiles of bladder cancer (BC) 5637 cells, T24 cells and normal control SV-HUC-1 cells. The data from the microarray showed that hsa_circ_0075828 (named circCASC15) was most highly expressed in 5637 and T24 cells. circCASC15 was highly expressed in BC tissues and cells. Overexpression of circCASC15 was closely associated with BC tumor stage and promoted cell proliferation significantly in vitro and in vivo. Mechanistically, circCASC15 could act as miR-1224-5p sponge to activate the expression of CREB1 to promote cell proliferation in BC. In short, circCASC15 promotes cell proliferation in BC, which might be a new molecular target for BC diagnosis and therapy.

• Transactions of Materials Processing
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• v.7 no.1
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• pp.81-93
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• 1998

Identification of forming limits of sheet metals is an important task to be done before the sheet metal forming processes. The information of the forming limit is indispensable for design of deformed shapes and related forming processes. This procedure becomes more important than ever as the auto-body becomes complicated and the number of auto-body parts is reduced for lower production cost. To identify the forming limit of sheet metals stretching with a hemispherical punch has gained popularity because of the convenient experimental procedure. The stretching experiment however has localized deformation or the shear band is originated from the non-unifrom deformation in the critical circum-stance instead of the absolute criterion. More accurate information of the forming limit therefore could be obtained by a more appropriate experiment to the real process. In this papaer an experiment program is devised to practivally identify the forming limits of sheet metals for auto-body parts. The experiment program contains not only stretching but deep-drawing Both forming experiments use the same hemispherical punch while they use different specimens. Deep-drawing experiments use speci-mens cut out in circular arc on both sides of circular blank to make it torn during the deep-drawing They also use speciments cut out straight in one side of a circular blank to make it deformed unevenly which causes local deformation during the deep-drawing. The experimental result demonstrates that the forming limit diagrams in the two cases show difference in their effective magnitude. The forming limit curve from deep-drawing is located lower than that from stretching. It is noted from the result that the deep-drawing process causes acceleration of localized deformation in comparison with the stretching process. From the experimental result the maximum value of forming limit could be pre-dicted for safe design.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.2
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• pp.105-112
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• 2011

The objective of this study is to predict the heat-transfer performance of a spirally coiled circular fin-tube evaporator in which either R134a or R600a was used; this heat-transfer performance was predicted by varying the mass flow rate, inlet air temperature, air flow rate, and tube thickness. Mean deviation for the analytical model from the measured data was ${\pm}8.3%$. Simulation results revealed that at a given mass flow rate, the heat-transfer rate of the evaporator using R600a was higher than that usingR134a because the enthalpy of the former is higher than that of the latter at the given conditions. The heat-transfer rate of both refrigerants increased with an increase in the air flow rate and inlet air temperature but decreased with an increase in the tube thickness.

• Hwankyungkyoyuk
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• v.13 no.2
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• pp.74-90
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• 2000

The environmental quality in Korea was significantly deteriorated though the past economic development period. Even though the government has spent huge sum of resources on the policies and projects to improve the environmental quality, it is much removed from what the people hope for. To solve the environmental problems effectively, pollutants generated at source should be kept as minimum as possible, and possible, and pollutants from source be controlled before leaving the sources, and most of all, environmental strategies and systems be established and enforced properly. So, it is not too much to say that nation's environmental quality is entirely dependent on the education and training of the environmental managers such as environmental employees for air, water, and noise discharge facilities, technicians at environmental plants, and environmental officers of central and local governments. Regimes for the improvement of the education and training for environmental managers are suggested into four categories-educational institute, circular of the study, training contents and trainees. Referring to the improvement of integrated institute, and to improvement on educational institute, it is necessary to investigate the feasibility of integrated institute, and to recommend the inclusion of the local colleges and universities, and environmental societies. For the improvement on training courses, it is necessary that the non-obligatory course be expanded, and the courses be developed in such a way to meet the needs from the field. As for the improvement on training contents. It is suggested that the practical training on size be strengthened, and also full time environmental specialist and integrated committee be required to develop the effective circular and selection of proper lectures. Finally, environmental education for high ranked officers of autonomies, and international courses for developing countries are suggested.