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Choi, Dukhyun,Lee, Keun Young,Jin, Mi-Jin,Ihn, Soo-Ghang,Yun, Sungyoung,Bulliard, Xavier,Choi, Woong,Lee, Sang Yoon,Kim, Sang-Woo,Choi, Jae-Young,Kim, Jong Min,Wang, Zhong Lin Royal Society of Chemistry 2011 ENERGY AND ENVIRONMENTAL SCIENCE Vol.4 No.11
<P>In this paper, we present a simple, low-cost and flexible hybrid cell that converts individually or simultaneously low-frequency mechanical energy and photon energy into electricity using piezoelectric zinc oxide (ZnO) in conjunction with organic solar cell design. Since the hybrid cell is designed by coupled piezoelectric and photoconductive properties of ZnO, this is a naturally hybrid architecture without crosstalk and an additional assembling process to create multi-type energy scavengers, thus differing from a simple integration of two different energy generators. It is demonstrated that the behavior of a piezoelectric output is controlled from alternating current (AC) type to direct current (DC)-like type by tailoring mechanical straining processes both in the dark and under light illumination. Based on such controllability of output modes, it is shown that the performance of the hybrid cell is synergistically enhanced by integrating the contribution made by a piezoelectric generator with a solar cell under a normal indoor level of illumination. Our approach clearly demonstrates the potential of the hybrid approach for scavenging multi-type energies whenever and wherever they are available. Furthermore, this work establishes the methodology to harvest solar energy and low-frequency mechanical energies such as body movements, making it possible to produce a promising multi-functional power generator that could be embedded in flexible architectures.</P> <P>Graphic Abstract</P><P>Naturally hybrid flexible energy generator that converts individually or simultaneously low-frequency mechanical energies and photon energy into electricity was developed. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1ee02080c'> </P>
Flowability and Strength Properties of High Flowing Self-Compacting Concrete Using for Tunnel Lining
Choi, Yun-Wang,Choi, Wook,Kim, Byoung-Kwon,Jung, Jea-Gwone Korea Concrete Institute 2008 International Journal of Concrete Structures and M Vol.2 No.2
So far, there has been no study of the concrete to strengthen in the lining of the tunnels, except for the study of the stability of subgrade and the tunnel construction technologies. In the existing concrete work for tunnel lining, lots of problems happen due to the partial compaction and the material segregation after casting concrete. Accordingly, the aim of this study is to improve economic efficiency and secure durability through the improvement of the construction performance and quality of the concrete for the tunnel lining among the civil structures. Therefore, the compactability and strength properties of the High Flowing Self-Compacting Lining Concrete (HSLC) are evaluated to develop the mixing proportion for design construction technology of HSLC that can overcome the inner cavity due to the reduced flowability and unfilled packing, which has been reported as the problem in the existing lining concrete. The result of the evaluation shows that the ternary mix meets the regulations better than the binary mix. Consequently, it has been judged applicable to the cement for tunnel lining.
Choi, Yun-Wang,Oh, Sung-Rok,Choi, Byung-Keol Hindawi Publishing Corporation 2017 Advances In Materials Science And Engineering Vol.2017 No.1
<P>We fabricated crack self-healing capsules using cement powder for mixing into cement composites and evaluated the properties of the capsule manufacturing process in this study. The manufacture of the self-healing capsules is divided into core production processing of granulating cement in powder form and a coating process for creating a wall on the surfaces of the granulated cement particles. The produced capsules contain unhardened cement and can be mixed directly with the cement composite materials because they are protected from moisture by the wall material. Therefore, the untreated cement is present in the form of a capsule within the cement composite, and hydration can be induced by moisture penetrating the crack surface in the event of cracking. In the process of granulating the cement, it is important to obtain a suitable consistency through the kneading agent and to maintain the moisture barrier performance of the wall material. We can utilize the results of this study as a basis for advanced self-healing capsule technology for cement composites.</P>
Choi, Yun-Wang,Oh, Sung-Rok,Kim, Cheol-Gyu,Lee, Jae-Heun Hindawi Limited 2018 Advances In Materials Science And Engineering Vol.2018 No.1
<P>The purpose of this study was to investigate the base material of the biological panel as one of the researches for developing the biological panel using (micro)organisms. In order to select the base material for the biological panel, the applicability of the magnesia-potassium-phosphate-foamed mortar composites material using the superabsorbent polymer was evaluated through the evaluation of basic quality and characteristics. Experiments were conducted to evaluate the fluidity, compressive strength, pH, roughness (porosity distribution), and moisture retention (absorbency) of the magnesia-phosphate-foamed mortar composites according to the additional amount of the superabsorbent polymer. Experimental results showed that the addition of a suitable superabsorbent polymer can provide good results in terms of compressive strength, workability, and moisturizing properties (absorbency). As a result, it can be used as a basic quality study data of the biological panel design.</P>