The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform
Hiroji Ohigashi - One of the best experts on this subject based on the ideXlab platform.
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Annealing effects on the Curie transition temperature and melting temperature of poly(vinylidene fluoride/trifluoroethylene) single crystalline films
Polymer, 2001Co-Authors: M.a. Barique, Hiroji OhigashiAbstract:Abstract The effect of Reannealing on the Curie transition temperature T C , melting point T m , and structures of single crystalline (SC) films of ferroelectric copolymer of poly(vinylidene fluoride/trifluoroethylene) (P(VDF/TrFE)) (75:25 mol%), which were prepared by uniaxial stretching of solvent cast films followed by crystallization/annealing at 140°C, was investigated using differential scanning calorimetry and X-ray diffraction. Accumulative Reannealing in the ferroelectric phase just below T C caused a large increase in T C by 17°C without distinctive change in T m , while prolonged Reannealing in the hexagonal phase caused an increase in T m by 5°C with a slight decrease in T C . From the X-ray diffraction study it is found that the Reannealing at a temperature below T C removes the gauche conformational defects existing in molecular chains, and that the Reannealing in the hexagonal phase for long periods leads to rearrangement of chain molecules through their sliding motion along the chain axis so as to eliminate crystal defects and to improve the preferential orientation distribution of the crystal axes perpendicular to the (110)/(200) planes in the film. The effects of such structural changes on T C and T m are explained on the basis of the Gibbs free energy-versus-temperature diagram.
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The possibility of formation of large ferroelectric domains in a copolymer of vinylidene fluoride and trifluoroethylene
Journal of Applied Physics, 1992Co-Authors: Nobuyuki Kagami, Hiroji OhigashiAbstract:Two Curie temperature Tc peaks in differential scanning calorimetry (DSC) are observed in a well‐crystallized, nonpoled film of a ferroelectric copolymer of vinylidene fluoride and trifluoroethylene [P(VDF‐TrFE)] when it is reannealed at temperatures near Tc. The DSC peak at higher Tc shifts to higher temperature with increasing Reannealing temperature, the phenomenon being very similar to that observed in thermally depolarized P(VDF‐TrFE) film. This result can be explained by the formation of large 60° or 180° domains during Reannealing. The free energy of the simple 180° domain model is used to discuss the temperature dependence of Tc on the domain width and thickness. It is concluded that large domains are generally formed in a P(VDF‐TrFE) film by Reannealing at temperatures near Tc irrespective of its macroscopic polarization.
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Formation of ferroelectric domains in a copolymer P(VDF–TrFE)
Journal of Applied Physics, 1992Co-Authors: Hiroji Ohigashi, Nobuyuki KagamiAbstract:The effects of Reannealing on the depolarization and phase transition behaviors of poled ferroelectric copolymer film of P(VDF–TrFE) (75/25) are studied by using differential scanning calorimetry (DSC) and piezoelectric resonance techniques from a viewpoint of formation of ferroelectric domains. It is found that the DSC peak at Curie point (Tc) splits into two peaks by Reannealing at temperatures around Tc, the broader one appearing at a lower temperature and the sharper one at a higher temperature TcH. As the annealing temperature increases, the peak at TcH shifts to the higher temperature side, and its peak intensity decreases less rapidly than the macroscopic polarization of the film. To explain these phenomena we propose that ferroelectric domains possibly composed of 60° and 180° domains are developed within lamellar single crystals during the Reannealing process at temperatures around Tc.
Wolfgang Knoll - One of the best experts on this subject based on the ideXlab platform.
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An optical waveguide study on the nanopore formation in block copolymer/homopolymer thin films by selective solvent swelling,” unpublished
2015Co-Authors: Dong Ha Kim, Wonchul Joo, Juan Peng, Unyong Jeong, Craig J. Hawker, Jin Kon Kim, Thomas P. Russell, King Hang Aaron Lau, Wolfgang KnollAbstract:Thin films of mixtures of asymmetric poly(styrene-block-methyl methacrylate) (PS-b-PMMA) diblock copolymers and PMMA homopolymers with cylindrical PMMA microdomains oriented normal to the substrate surface were used to couple optical modes in the Kretschmann configuration, and their optical properties were investigated by optical waveguide spectroscopy (OWS). The nanopore formation in the block copolymer (BCP) waveguide layer via selective solvent swelling and subsequent Reannealing was monitored in terms of shifts in the coupling mode angles. The sequential swelling/Reannealing of the initial mixture film resulted in a number of discrete or partially interconnected pores instead of cylindrical pores with a high aspect ratio. The simultaneous processes occurring inside and on top of the BCP waveguide layer were discerned independently with high selectivity for p- and s-polarization
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An optical waveguide study on the nanopore formation in block copolymer/homopolymer thin films by selective solvent swelling
The journal of physical chemistry. B, 2006Co-Authors: Dong Ha Kim, Hang Aaron Lau, Wonchul Joo, Juan Peng, Unyong Jeong, Craig J. Hawker, Jin Kon Kim, Thomas P. Russell, Wolfgang KnollAbstract:Thin films of mixtures of asymmetric poly(styrene-block-methyl methacrylate) (PS-b-PMMA) diblock copolymers and PMMA homopolymers with cylindrical PMMA microdomains oriented normal to the substrate surface were used to couple optical modes in the Kretschmann configuration, and their optical properties were investigated by optical waveguide spectroscopy (OWS). The nanopore formation in the block copolymer (BCP) waveguide layer via selective solvent swelling and subsequent Reannealing was monitored in terms of shifts in the coupling mode angles. The sequential swelling/Reannealing of the initial mixture film resulted in a number of discrete or partially interconnected pores instead of cylindrical pores with a high aspect ratio. The simultaneous processes occurring inside and on top of the BCP waveguide layer were discerned independently with high selectivity for p- and s-polarization.
Hüseyin Göksu - One of the best experts on this subject based on the ideXlab platform.
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design of a broadband microwave amplifier using neural performance data sheets and very fast simulated Reannealing
International Symposium on Neural Networks, 2006Co-Authors: Yavuz Cengiz, Hüseyin Göksu, Filiz GüneşAbstract:In this work, the neural performance data sheets of the transistor are employed to determine the feasible design target space in the optimization of a microwave amplifier. The basic amplifier with a single transistor between the input and output matching circuits (IMC and OMC) is also worked out. Very Fast Simulated Reannealing (VFSR) is utilized in the multi – objective optimization process for the global minimum of the objective function which is expressed as a function only gain of a matching circuit, in the negative exponential form to ensure the rapid convergence.
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ISNN (2) - Design of a broadband microwave amplifier using neural performance data sheets and very fast simulated Reannealing
Advances in Neural Networks - ISNN 2006, 2006Co-Authors: Yavuz Cengiz, Hüseyin Göksu, Filiz GüneşAbstract:In this work, the neural performance data sheets of the transistor are employed to determine the feasible design target space in the optimization of a microwave amplifier. The basic amplifier with a single transistor between the input and output matching circuits (IMC and OMC) is also worked out. Very Fast Simulated Reannealing (VFSR) is utilized in the multi – objective optimization process for the global minimum of the objective function which is expressed as a function only gain of a matching circuit, in the negative exponential form to ensure the rapid convergence.
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solution of the inverse electromagnetic problem of spontaneous potential sp by very fast simulated Reannealing vfsr
International Conference on Natural Computation, 2005Co-Authors: Hüseyin Göksu, Mehmet Kaya, Ali KökceAbstract:Very Fast Simulated Reannealing (VFSR) is applied to the solution of an inverse electromagnetic problem. The problem is to model the distribution of dipole current sources in a finitely resistive infinite half space. Modelling is done using the observed electrical potential on the interface between the half space and the free space. This method is known as Spontaneous Potential (SP) and is widely used for geophysical prospecting. Object of the VFSR algorithm is a quadratic error function between measured and synthetic data. Method is tested on a field data.
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application of very fast simulated Reannealing vfsr to low power design
International Conference on Embedded Computer Systems: Architectures Modeling and Simulation, 2005Co-Authors: Ali Manzak, Hüseyin GöksuAbstract:This paper addresses the problem of optimal supply and threshold voltage selection with device sizing by minimizing power consumption and maximizing battery charge capacitance using Very Fast Simulated Reannealing (VFSR). We assume that multiple supply voltages and multiple threshold voltage devices are available at gate level. Minimizing power consumption does not necessarily maximize battery charge capacitance. This paper achieves this by implementing both objectives in the cost function.
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SAMOS - Application of very fast simulated Reannealing (VFSR) to low power design
Lecture Notes in Computer Science, 2005Co-Authors: Ali Manzak, Hüseyin GöksuAbstract:This paper addresses the problem of optimal supply and threshold voltage selection with device sizing by minimizing power consumption and maximizing battery charge capacitance using Very Fast Simulated Reannealing (VFSR). We assume that multiple supply voltages and multiple threshold voltage devices are available at gate level. Minimizing power consumption does not necessarily maximize battery charge capacitance. This paper achieves this by implementing both objectives in the cost function.
Dong Ha Kim - One of the best experts on this subject based on the ideXlab platform.
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An optical waveguide study on the nanopore formation in block copolymer/homopolymer thin films by selective solvent swelling,” unpublished
2015Co-Authors: Dong Ha Kim, Wonchul Joo, Juan Peng, Unyong Jeong, Craig J. Hawker, Jin Kon Kim, Thomas P. Russell, King Hang Aaron Lau, Wolfgang KnollAbstract:Thin films of mixtures of asymmetric poly(styrene-block-methyl methacrylate) (PS-b-PMMA) diblock copolymers and PMMA homopolymers with cylindrical PMMA microdomains oriented normal to the substrate surface were used to couple optical modes in the Kretschmann configuration, and their optical properties were investigated by optical waveguide spectroscopy (OWS). The nanopore formation in the block copolymer (BCP) waveguide layer via selective solvent swelling and subsequent Reannealing was monitored in terms of shifts in the coupling mode angles. The sequential swelling/Reannealing of the initial mixture film resulted in a number of discrete or partially interconnected pores instead of cylindrical pores with a high aspect ratio. The simultaneous processes occurring inside and on top of the BCP waveguide layer were discerned independently with high selectivity for p- and s-polarization
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An optical waveguide study on the nanopore formation in block copolymer/homopolymer thin films by selective solvent swelling
The journal of physical chemistry. B, 2006Co-Authors: Dong Ha Kim, Hang Aaron Lau, Wonchul Joo, Juan Peng, Unyong Jeong, Craig J. Hawker, Jin Kon Kim, Thomas P. Russell, Wolfgang KnollAbstract:Thin films of mixtures of asymmetric poly(styrene-block-methyl methacrylate) (PS-b-PMMA) diblock copolymers and PMMA homopolymers with cylindrical PMMA microdomains oriented normal to the substrate surface were used to couple optical modes in the Kretschmann configuration, and their optical properties were investigated by optical waveguide spectroscopy (OWS). The nanopore formation in the block copolymer (BCP) waveguide layer via selective solvent swelling and subsequent Reannealing was monitored in terms of shifts in the coupling mode angles. The sequential swelling/Reannealing of the initial mixture film resulted in a number of discrete or partially interconnected pores instead of cylindrical pores with a high aspect ratio. The simultaneous processes occurring inside and on top of the BCP waveguide layer were discerned independently with high selectivity for p- and s-polarization.
Nobuyuki Kagami - One of the best experts on this subject based on the ideXlab platform.
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The possibility of formation of large ferroelectric domains in a copolymer of vinylidene fluoride and trifluoroethylene
Journal of Applied Physics, 1992Co-Authors: Nobuyuki Kagami, Hiroji OhigashiAbstract:Two Curie temperature Tc peaks in differential scanning calorimetry (DSC) are observed in a well‐crystallized, nonpoled film of a ferroelectric copolymer of vinylidene fluoride and trifluoroethylene [P(VDF‐TrFE)] when it is reannealed at temperatures near Tc. The DSC peak at higher Tc shifts to higher temperature with increasing Reannealing temperature, the phenomenon being very similar to that observed in thermally depolarized P(VDF‐TrFE) film. This result can be explained by the formation of large 60° or 180° domains during Reannealing. The free energy of the simple 180° domain model is used to discuss the temperature dependence of Tc on the domain width and thickness. It is concluded that large domains are generally formed in a P(VDF‐TrFE) film by Reannealing at temperatures near Tc irrespective of its macroscopic polarization.
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Formation of ferroelectric domains in a copolymer P(VDF–TrFE)
Journal of Applied Physics, 1992Co-Authors: Hiroji Ohigashi, Nobuyuki KagamiAbstract:The effects of Reannealing on the depolarization and phase transition behaviors of poled ferroelectric copolymer film of P(VDF–TrFE) (75/25) are studied by using differential scanning calorimetry (DSC) and piezoelectric resonance techniques from a viewpoint of formation of ferroelectric domains. It is found that the DSC peak at Curie point (Tc) splits into two peaks by Reannealing at temperatures around Tc, the broader one appearing at a lower temperature and the sharper one at a higher temperature TcH. As the annealing temperature increases, the peak at TcH shifts to the higher temperature side, and its peak intensity decreases less rapidly than the macroscopic polarization of the film. To explain these phenomena we propose that ferroelectric domains possibly composed of 60° and 180° domains are developed within lamellar single crystals during the Reannealing process at temperatures around Tc.
