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Torsional analysis of a single-bent leaf flexure
Nghia Huu Nguyen,임병덕,이동연 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.1
We present a torsion analysis of single-bent leaf flexure that is partially restrained, subject to a torsional load. The theoretical equations for the torsional angle are derived using Castigliano’s theorem. These equations consider the partially restrained warping, and are verified using finite element analysis (FEA). A sensitivity analysis over the length, width, and thickness is performed and verified via FEA. The results show that the errors between the theory result and the FEA result are lower than 6%. This indicates that the proposed theoretical torsional analysis with partially restrained warping is sufficiently accurate.
Effect on TENG Performance by Phase Control of TiOx Nanoparticles
Nghia Dinh Huynh,박현우,정권범,최덕현 한국복합재료학회 2018 Composites research Vol.31 No.6
One of the critical parameters to improve the output power for triboelectric nanogenerators (TENGs) is the surface charge density. In this work, we modify the tribo-material of TENG by introducing the TiOx embedded Polydimethylsiloxane (PDMS) in anatase and rutile phase. The effect of dielectric constant and electronic structure of the TiOx on the capacitance of TENG and the output power as well are discussed. The surface charge density is increased as the control of the dielectric constant in difference weight percent of TiOx and PDMS. As the results of that, the 5% TiOx rutile phase and 7% TiOx anatase phase embedded PDMS exhibit the highest TENG output. The peak value of voltage/current obtained from TiOx rutile and anatase phase are ~180 V/8.2 μA and 211.6 V/8.7 μA, respectively, at the external force of 5 N and working frequency of 5 Hz, which gives over 12-fold and 15-fold power enhancement compared with the TENG based on the pristine PDMS film. This study provides a better understanding for TENG performance enhancement from the materials view.
Nghia, Nguyen Van,Oh, Jihun,Jung, Jaehoon,Lee, Min Hyung American Chemical Society 2017 Organometallics Vol.36 No.14
<P>Heteroleptic tris-cyclometalated Ir(III) complexes bearing an <I>o</I>-carborane at the 4- or 5-position in the phenyl ring of the ppy ligand (<I>closo</I>-<B>1</B> and -<B>2</B>) were prepared and characterized. The X-ray crystal structure of <I>closo</I>-<B>1</B> reveals the <I>fac</I> arrangement of the three C<SUP>∧</SUP>N chelates around the Ir atom. Treatment of <I>closo</I> complexes with fluoride anions led to selective deboronation of the <I>closo</I>-carborane cage, producing the corresponding <I>nido</I>-carborane-substituted complexes (<I>nido</I>-<B>1</B> and <B>-2</B>). Whereas <I>closo</I>-<B>1</B> and -<B>2</B> were almost nonemissive in THF, <I>nido</I>-<B>1</B> and -<B>2</B> were highly phosphorescent (Φ<SUB>PL</SUB> = 0.94–0.95). Theoretical studies suggested that, while the emission quenching in <I>closo</I>-<B>1</B> can be ascribed to the substantial involvement of <I>o</I>-carborane in the <SUP>3</SUP>MLCT excited state, the intraligand charge transfer (<SUP>3</SUP>ILCT) state from the <I>nido</I>-carborane to pyridyl moieties is responsible for the efficient phosphorescence in <I>nido</I>-<B>1</B>. The addition of fluoride to the buffered THF/H<SUB>2</SUB>O solution (1/1, v/v, pH 7) of <I>closo</I>-<B>1</B> and -<B>2</B> under mild heating led to strong emission intensity, allowing the turn-on phosphorescence detection of fluoride in aqueous medium at the ppb level.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/orgnd7/2017/orgnd7.2017.36.issue-14/acs.organomet.7b00139/production/images/medium/om-2017-00139w_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/om7b00139'>ACS Electronic Supporting Info</A></P>
Warping stresses of a rectangular single leaf flexure under torsion
Nghia Huu Nguyen,Ji-Soo Kim,이동연 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.59 No.3
We describe a stress analysis of a single leaf flexure under torsion in which the warping effect is considered. The theoretical equations for the warping normal stress (xx) and shear stresses (xz and xy) are derived by applying the warping function of a rectangular cross-sectional beam and the twist angle equation that includes the warping torsion. The results are compared with those of the non-warping case and are verified using finite element analysis (FEA). A sensitivity analysis over the length, width, and thickness is performed and verified via FEA. The results show that the errors between the theory of warping stress results and the FEA results are lower than 4%. This indicates that the proposed theoretical stress analysis with warping is accurate in the torsion analysis of a single leaf flexure.
Peer Effects on Corporate Cash Holdings: Evidence from Vietnam
Nghia Huu Nguyen,Wei-Hsien Li 한국재무학회 2022 財務硏究 Vol.35 No.2
This research examines corporate cash holdings in Vietnam, an emerging market, and finds reverse peer effects on them - that is, a firm’s level of cash holdings negatively relates to those of its peers. We also note the reverse peer effects are stronger for firms facing less competition and with low intangibility. Because the Vietnam market has noticeably lower competition and investment in innovation than in developed economics like the U.S., our evidence supports the role of competition and innovation investment in driving cash holdings’ peer effects and complements the literature that mostly focuses on developed economies. Our findings are consistent with the notion that some firms strategically accumulate cash to drive their competitors’ cash level lower when they are in less competitive industries or when they have lower innovation investments. Thus, the existing competition or innovation environment is crucial when modeling the cash holding behavior among industry peers. However, our tests on the preemptive motive for peer effects on cash holdings are inconclusive. Lastly, our results also support heterogeneity across countries in peer mimicking behavior and contributes to the cash holdings literature for the Vietnam market.
TRANSCENDENT VALUES OF UNIVERSAL HUMAN RIGHTS
( Nghia Van Hoang ) 고려대학교 법학연구원 2015 Korea University Law Review Vol.18 No.-
What are universal human rights? Why has the universality of human rights been challenged by all forms of particularity and relativism, especially cultural relativism and Asian values for over the last twenty years? Do non-Western cultures, such as Oriental, Latin American and African ones, accept or reject universal human rights enshrined in the Universal Declaration of Human Rights? Those questions need to be addressed thoroughly from both theoretical and practical perspectives. Thus, the ultimate goal of this paper is to explore the sustainable and solid values of universal human rights in the UDHR as not only a highest aspiration, but also a common heritage of their cultures, religions, and traditions of thoughts. By utilizing literature review, legal and comparative methods, the paper points out that as a global language of our world of diverse cultures and ideologies, the universal human rights are the foundation of peace, security, tolerance, and human development. At the same time, the paper urges that all forms of claiming the so-called cultural relativism, such as Asian-values model, could undermine and challenge the legitimacy of universal human rights in non-Western societies including Asian nations. The paper is to revisit the appreciation of universal human rights embraced from the human beings’ transcendent values, such as dignity, tolerance, humanity, and freedoms that are embedded in all cultures.