The Experts below are selected from a list of 180 Experts worldwide ranked by ideXlab platform
Li Zhao - One of the best experts on this subject based on the ideXlab platform.
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Does the wavelength dependent photoisomerization process of the p-coumaric acid come out from the electronic state dependent pathways?
PERGAMON-ELSEVIER SCIENCE LTD, 2019Co-Authors: Li Zhao, Liu Jianyong, Zhou PanwangAbstract:Similar to the anion photoactive yellow protein (PYP) chromophore, the neutral form of the PYP chromophore was also found to exhibit a the wavelength-dependent photoisomerization quantum yield. The isomerization quantum yield increases with the increasing excitation energy on the S-1 state, while decreases when being excited to the S-2 state. Does this wavelength dependent product yield come out from the specific reaction pathways of the S-1 and S-2 states? This would mean that, the relaxation pathway of the S-2 state is distinct from that of the S-1 state and does not involve twisting motion. Does it break Kasha's rule by exhibiting a direct transition from the S-2 state to the ground state? The underlying mechanism needs further in. In this article, we employed the on-the-fly dynamics simulations and static electronic structure calculations to reveal the deactivation mechanism of the neutral form of the PYP chromophore. Our results indicated that the C=C twisting motion dominates the S-1 state decay process. In contrast, for the decay process of the S-2 state, an ultrafast transition from the S-2 to the S-1 state through a planar conical intersection is observed, and the excess energy activates a new reaction channel to the ground state characterized by a puckering distortion of the ring. This pathway competes with the photoisomerization channel. No direct transition from S-2 to S-0 is observed, hence Kasha's rule is valid for this process. Our calcualtions can provide a reasonable explanation of the wavelength-dependent isomerization quantum yield of neutral PYP chromophore, and we hope it can provide theoretical foundations for comparing the effect of protonation state on the dynamcal behaviors of PYP chromophore. (C) 2018 Elsevier B.V. All rights reserved
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the photoinduced isomerization mechanism of the 2 1 methylimino methyl 6 chlorophenol smac nonadiabatic surface hopping dynamics simulations
Journal of Chemical Physics, 2018Co-Authors: Li Zhao, Jianyong Liu, Panwang ZhouAbstract:The photophysical properties of the Schiff base family are crucial for their applications such as molecular switches and molecular memories. However, it was found that the photophysical behavior is not uniform for all Schiff base molecules, which shows a significant substituent dependent property. In this article, we studied the photoisomerization mechanism of one Schiff base chlorosubstituted derivative 2-(1-(methylimino)methyl)-6-chlorophenol by employing geometrical optimization, energy profiles scanning, and on-the-fly dynamical simulations. Three types of minimum energy conical intersections were located on the S1/S0 crossing seam, with two characterized by twisting motion of the C=N bond and one featured with the excited state intramolecular proton transfer process and then twisting motion around the C=C bond [excited-state intramolecular proton transfer process (ESIPT)-then-twisting]. By a combination of the dynamics simulation results with the energy profiles scanned along with the ESIPT coordinate, it was found that the photophysical property of the targeted molecule is different from that of most Schiff base members, which prefer to decay by a twisting motion around the C=N bridge bond rather than the ESIPT-then-twisting channel. The minor ESIPT channel is probably governed by a tunneling mechanism. The proposed deactivation mechanism can provide a reasonable explanation for the observations in the experiment and would provide fundamental indications for further design of new and efficient photochromic products.
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non adiabatic dynamics investigation of the radiationless decay mechanism of trans urocanic acid in the s2 state
Journal of Chemical Physics, 2016Co-Authors: Li Zhao, Panwang Zhou, Guangjiu ZhaoAbstract:The trans-urocanic acid, a UV chromophore in the epidermis of human skin, was found to exhibit a wavelength dependent isomerization property. The isomerization quantum yield to cis-urocanic is greatest when being excited to the S1 state, whereas exciting the molecule to the S2 state causes almost no isomerization. The comparative photochemical behavior of the trans-urocanic on the S1 and S2 states continues to be the subject of intense research effort. This study is concerned with the unique photo-behavior of this interesting molecule on the S2 state. Combining the on-the-fly surface hopping dynamics simulations and static electronic structure calculations, three decay channels were observed following excitation to the S2 state. An overwhelming majority of the molecules decay to the S1 state through a planar or pucker characterized minimum energy conical intersection (MECI), and then decay to the ground state along a relaxation coordinate driven by a pucker deformation of the ring. A very small fraction of molecules decay to the S1 state by a MECI characterized by a twisting motion around the CC double bond, which continues to drive the molecule to deactivate to the ground state. The latter channel is related with the photoisomerization process, whereas the former one will only generate the original trans-form products. The present work provides a novel S2 state decay mechanism of this molecule, which offers useful information to explain the wavelength dependent isomerization behavior.
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Non-adiabatic dynamics investigation of the radiationless decay mechanism of trans-urocanic acid in the S-2 state
AMER INST PHYSICS, 2016Co-Authors: Li Zhao, Zhou Pan-wang, Zhao Guang-jiuAbstract:The trans-urocanic acid, a UV chromophore in the epidermis of human skin, was found to exhibit a wavelength dependent isomerization property. The isomerization quantum yield to cis-urocanic is greatest when being excited to the S-1 state, whereas exciting the molecule to the S-2 state causes almost no isomerization. The comparative photochemical behavior of the trans-urocanic on the S-1 and S-2 states continues to be the subject of intense research effort. This study is concerned with the unique photo-behavior of this interesting molecule on the S-2 state. Combining the on-the-fly surface hopping dynamics simulations and static electronic structure calculations, three decay channels were observed following excitation to the S-2 state. An overwhelming majority of the molecules decay to the S-1 state through a planar or pucker characterized minimum energy conical intersection (MECI), and then decay to the ground state along a relaxation coordinate driven by a pucker deformation of the ring. A very small fraction of molecules decay to the S-1 state by a MECI characterized by a twisting motion around the CC double bond, which continues to drive the molecule to deactivate to the ground state. The latter channel is related with the photoisomerization process, whereas the former one will only generate the original trans-form products. The present work provides a novel S-2 state decay mechanism of this molecule, which offers useful information to explain the wavelength dependent isomerization behavior. Published by AIP Publishing
Zhongjing Ren - One of the best experts on this subject based on the ideXlab platform.
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microstructure and twisting ability of an adjusted antisymmetric angle ply laminate
Applied Physics Letters, 2019Co-Authors: Zhongjing Ren, Jing Yan, Yong Shi, Quan PanAbstract:This letter describes an adjusted antisymmetric angle ply laminate that is able to twist as a result of temperature-dependent deformation. A theoretical explanation for this twisting ability is presented and the adjusted architecture of the proposed laminate is described. The effects of fiber and matrix volume fractions, laminate angle, total laminate thickness, and temperature range on the torsion of the laminate are analyzed. A sample of the proposed microlaminate is produced by a microfabrication process and tested as the temperature is increased from room temperature to 80 °C. Microscopy images reveal that the microlaminate twists by more than 180° within a length of 200 μm. The proposed material and its twisting ability show great potential for application in microrobotic actuators.This letter describes an adjusted antisymmetric angle ply laminate that is able to twist as a result of temperature-dependent deformation. A theoretical explanation for this twisting ability is presented and the adjusted architecture of the proposed laminate is described. The effects of fiber and matrix volume fractions, laminate angle, total laminate thickness, and temperature range on the torsion of the laminate are analyzed. A sample of the proposed microlaminate is produced by a microfabrication process and tested as the temperature is increased from room temperature to 80 °C. Microscopy images reveal that the microlaminate twists by more than 180° within a length of 200 μm. The proposed material and its twisting ability show great potential for application in microrobotic actuators.
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microstructure and twisting ability of an adjusted antisymmetric angle ply laminate
Applied Physics Letters, 2019Co-Authors: Zhongjing Ren, Jing Yan, Yong Shi, Quan PanAbstract:This letter describes an adjusted antisymmetric angle ply laminate that is able to twist as a result of temperature-dependent deformation. A theoretical explanation for this twisting ability is presented and the adjusted architecture of the proposed laminate is described. The effects of fiber and matrix volume fractions, laminate angle, total laminate thickness, and temperature range on the torsion of the laminate are analyzed. A sample of the proposed microlaminate is produced by a microfabrication process and tested as the temperature is increased from room temperature to 80 °C. Microscopy images reveal that the microlaminate twists by more than 180° within a length of 200 μm. The proposed material and its twisting ability show great potential for application in microrobotic actuators.
Quan Pan - One of the best experts on this subject based on the ideXlab platform.
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microstructure and twisting ability of an adjusted antisymmetric angle ply laminate
Applied Physics Letters, 2019Co-Authors: Zhongjing Ren, Jing Yan, Yong Shi, Quan PanAbstract:This letter describes an adjusted antisymmetric angle ply laminate that is able to twist as a result of temperature-dependent deformation. A theoretical explanation for this twisting ability is presented and the adjusted architecture of the proposed laminate is described. The effects of fiber and matrix volume fractions, laminate angle, total laminate thickness, and temperature range on the torsion of the laminate are analyzed. A sample of the proposed microlaminate is produced by a microfabrication process and tested as the temperature is increased from room temperature to 80 °C. Microscopy images reveal that the microlaminate twists by more than 180° within a length of 200 μm. The proposed material and its twisting ability show great potential for application in microrobotic actuators.This letter describes an adjusted antisymmetric angle ply laminate that is able to twist as a result of temperature-dependent deformation. A theoretical explanation for this twisting ability is presented and the adjusted architecture of the proposed laminate is described. The effects of fiber and matrix volume fractions, laminate angle, total laminate thickness, and temperature range on the torsion of the laminate are analyzed. A sample of the proposed microlaminate is produced by a microfabrication process and tested as the temperature is increased from room temperature to 80 °C. Microscopy images reveal that the microlaminate twists by more than 180° within a length of 200 μm. The proposed material and its twisting ability show great potential for application in microrobotic actuators.
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microstructure and twisting ability of an adjusted antisymmetric angle ply laminate
Applied Physics Letters, 2019Co-Authors: Zhongjing Ren, Jing Yan, Yong Shi, Quan PanAbstract:This letter describes an adjusted antisymmetric angle ply laminate that is able to twist as a result of temperature-dependent deformation. A theoretical explanation for this twisting ability is presented and the adjusted architecture of the proposed laminate is described. The effects of fiber and matrix volume fractions, laminate angle, total laminate thickness, and temperature range on the torsion of the laminate are analyzed. A sample of the proposed microlaminate is produced by a microfabrication process and tested as the temperature is increased from room temperature to 80 °C. Microscopy images reveal that the microlaminate twists by more than 180° within a length of 200 μm. The proposed material and its twisting ability show great potential for application in microrobotic actuators.
Sérgio Frascino Müller De Almeida - One of the best experts on this subject based on the ideXlab platform.
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effect of bending twisting coupling on the compression and shear buckling strength of infinitely long plates
Composite Structures, 2018Co-Authors: C B York, Sérgio Frascino Müller De AlmeidaAbstract:This article describes the development of closed form polynomial equations for compression and shear buckling to assess the effect of Bending-Twisting coupling on infinitely long laminated plates with simply supported edges. The equations are used to generate contour maps, representing non-dimensional buckling factors, which are superimposed on the lamination parameter design spaces for laminates with standard ply orientations. The contour maps are applicable to two recently developed databases containing symmetric and non-symmetric laminates with either Bending-Twisting or Extension-Shearing Bending-Twisting coupling. The contour maps provide new insights into buckling performance improvements that are non-intuitive and facilitate comparison between hypothetical and practical designs. The databases are illustrated through point clouds of lamination parameter coordinates, which demonstrate the effect of applying common design heuristics, including ply angle, ply percentage and ply contiguity constraints.
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Tapered laminate designs for new non-crimp fabric architectures
Composites Part A: Applied Science and Manufacturing, 2017Co-Authors: Christopher York, Sérgio Frascino Müller De AlmeidaAbstract:Non-Crimp Fabric (NCF) materials are now available in a range of areal weights and layer architectures, including 0/45, 0/−45, 45/−45 and 0/90, which correspond to the standard ply orientations employed in traditional UD material lay-ups. The benefit of NCF material is generally associated with increased deposition rate, but this advantage may be offset by reduced design freedoms when a specific form of mechanical coupling behaviour is required, layer terminations must be introduced and/or thermal warping distortion eliminated. This article investigates the extent to which new NCF architectures can be tailored to achieve warp free tapered laminates with mechanical Extension-Shearing Bending-Twisting coupling, by single axis (longitudinal) deposition of all ply angles; thus avoiding ply discontinuities that may be introduce in large component manufacture. Lamination parameter design spaces are used to demonstrate the extent of the feasible solutions both before and after applying a laminate tapering scheme.
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Effect of Design Heuristics on the Compression and Shear Buckling Performance of Infinitely Long Plates With Bending-Twisting Coupling
2017Co-Authors: York, Christopher Bronn, Sérgio Frascino Müller De AlmeidaAbstract:This article investigates the effect of design heuristics, including ply percentages and ply contiguity constraints, on the compression and shear buckling performance of Bending-Twisting coupled infinitely long laminated plates with simply supported edges. The buckling solutions are presented as contour maps, representing non-dimensional buckling factors, which are superimposed on the lamination parameter design spaces for laminates with standard ply orientations. The applicability of the results extends beyond the current certification envelope, comprising symmetric laminate configurations. Indeed, the contour maps are applicable to two recently developed databases containing non-symmetric and symmetric laminates with either Bending-Twisting or Extension-Shearing Bending-Twisting coupling. The contour maps provide insights into buckling performance improvements that are non-intuitive and facilitate comparison between hypothetical and practical designs. The databases are illustrated through point clouds of lamination parameter coordinates, which demonstrate the effect of applying design heuristics
Sunghoon Ahn - One of the best experts on this subject based on the ideXlab platform.
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design and analysis of a smart soft composite structure for various modes of actuation
Composites Part B-engineering, 2016Co-Authors: Sunghyuk Song, Hyeok Lee, Jonggu Lee, Jangyeob Lee, Maenghyo Cho, Sunghoon AhnAbstract:Abstract This article describes a novel design for a smart soft composite structure, capable of four actuating modes, with three different types of scaffold structures, and two shape memory alloy wires embedded above and below the scaffold structures. Each component is combined with polydimethylsiloxane (PDMS) so it has the advantage of a soft morphing motion. Actuating modes, consisting of symmetric, anti-symmetric, asymmetric, and torsional motion, and the associated end edge displacement and twisting angle, were measured according to different ply combinations, which were symmetric, anti-symmetric, and asymmetric. The 60-mm actuator is capable of end edge displacement up to 67 mm and twisting up to 85° in a bend-twist coupled motion. In the torsion-only motion, without bending, 108.4° deformation was achieved. Next, a finite element method (FEM) model, based on the Lagoudas shape memory alloy (SMA) model, is presented to predict the actuating performance of the actuator according to the scaffold stacking sequence. Using the FEM model, end edge displacement and twisting angle are compared with experimental data in the four modes of actuation. The actuating trajectory expected from the FEM model is compared with the experimental data.
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a turtle like swimming robot using a smart soft composite ssc structure
Smart Materials and Structures, 2013Co-Authors: Hyungjung Kim, Sunghyuk Song, Sunghoon AhnAbstract:This paper describes the development of a biomimetic swimming robot based on the locomotion of a marine turtle. To realize the smooth, soft flapping motions of this type of turtle, a novel actuator was also developed, using a smart soft composite (SSC) structure that can generate bending and twisting motions in a simple, lightweight structure. The SSC structure is a composite consisting of an active component to generate the actuation force, a passive component to determine the twisting angle of the structure, and a matrix to combine the components. The motion of such a structure can be designed by specifying the angle between a filament of the scaffold structure and a shape-memory alloy (SMA) wire. The bending and twisting motion of the SSC structure is explained in terms of classical laminate theory, and cross-ply and angled-ply structures were fabricated to evaluate its motion. Finally, the turtle-like motion of a swimming robot was realized by employing a specially designed SSC structure. To mimic the posterior positive twisting angle of a turtle?s flipper during the upstroke, the SMA wire on the upper side was offset, and a positive ply-angled scaffold was used. Likewise, for the anterior negative twisting angle of the flipper during the downstroke, an offset SMA wire on the lower side and a positive ply-angled scaffold were also required. The fabricated flipper?s length is 64.3?mm and it realizes 55?mm bending and 24??twisting. The resulting robot achieved a swimming speed of 22.5?mm?s?1.