40 GHz polymer electro-optic modulators with coplanar waveguide (CPW) traveling-wave electrode were designed, fabricated and measured. Assuming the electro-optic coefficient γ33 of the core polymer is 30 pm/V, modula...
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40 GHz polymer electro-optic modulators with coplanar waveguide (CPW) traveling-wave electrode were designed, fabricated and measured. Assuming the electro-optic coefficient γ33 of the core polymer is 30 pm/V, modulators are designed with half-wave voltage of 12.9 V and bandwidth of 46.46 GHz. Modulators were fabricated using second-order nonlinear optical polymer BPAN-NT. The performance of the modulators at direct current (DC), low frequencies and microwave regions were tested. The DC half-wave voltages are 55.5 V at 1.31 μm and 83.3 V at 1.55 μm, corresponding to an in-device γ33 of 4.65 pm/V. The extinction ratio is 15 dB. In the frequency from 50 MHz to 40 GHz, the microwave attenuation coefficient of the electrode is 0.42 dB/(cm · GHz1/2), and the bandwidth is 42.70 GHz by theoretical calculation. Modulation index were measured by optical spectrum analyzer from 4 GHz to 17 GHz, and modulated optical signals were observed at 1.31 μm and 1.55 μm wavelengths.
We show that classical many-particle systems interacting with certain soft pair interactions in two dimensions exhibit novel low-temperature behaviors. Ground states span from disordered to crystalline. At some densit...
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We show that classical many-particle systems interacting with certain soft pair interactions in two dimensions exhibit novel low-temperature behaviors. Ground states span from disordered to crystalline. At some densities, a large fraction of normal-mode frequencies vanish. Lattice ground-state configurations have more vanishing frequencies than disordered ground states at the same density and exhibit vanishing shear moduli. For the melting transition from a crystal, the thermal expansion coefficient is negative. These unusual results are attributed to the topography of the energy landscape.
Based on electron-beam direct writing on the SiOx/Si substrates, favorable absorption sites for ferric cations (Fe3+ ions) were created on the surface oxide layer. This allowed Fe3+-assisted self-assembled arrays of s...
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Excitable cells can exhibit complex patterns of oscillations, such as spiking and bursting. In cardiac cells, pathological voltage oscillations, called early afterdepolarizations (EADs), have been widely observed unde...
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Excitable cells can exhibit complex patterns of oscillations, such as spiking and bursting. In cardiac cells, pathological voltage oscillations, called early afterdepolarizations (EADs), have been widely observed under disease conditions, yet their dynamical mechanisms remain unknown. Here, we show that EADs are caused by Hopf and homoclinic bifurcations. During period pacing, chaos always occurs at the transition from no EAD to EADs as the stimulation frequency decreases, providing a distinct explanation for the irregular EAD behavior frequently observed in experiments.
Rheological measurement has been an effective method to characterize the structure and properties for multiphase/multi-component polymers, owing to its sensitivity to the structure change of hetero- geneous systems. I...
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Rheological measurement has been an effective method to characterize the structure and properties for multiphase/multi-component polymers, owing to its sensitivity to the structure change of hetero- geneous systems. In this article, recent progress in the studies on the morphology/structure and rheological properties of heterogeneous systems is summarized, mainly reporting the findings of the authors and their collaborators, involving the correlation between the morphology and viscoelastic relaxation of LCST-type polymer blends, the microstructure and linear/nonlinear viscoelastic behavior of block copolymers, time scaling of shear-induced crystallization and rheological response of poly- olefins, and the relationship between the structure/properties and rheological behavior of filled polymer blends. It is suggested that a thorough understanding of the characteristic rheological response to the morphology/structure evolution of multiphase/multi-component polymers facilitates researchers’ op- timizing the morphology/structure and ultimate mechanical properties of polymer materials.
Solid scrolls are reversibly formed by self-assembly of rod-shaped molecules with laterally attached coil units, in contrast to the layered structures formed from self-assembly of planar molecules. As described by M. ...
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Solid scrolls are reversibly formed by self-assembly of rod-shaped molecules with laterally attached coil units, in contrast to the layered structures formed from self-assembly of planar molecules. As described by M. Lee and co-workers in their Communication on page 1664 ff., the core structure of the scrolls, which are either filled cylinders or hollow tubes, can be controlled by variation of the length of the coil unit. The cover picture shows aligned tubular scrolls displaying well-defined in-plane ordering of the rod segments.
Thin films of low-polydispersity, high-molecular-weight polymers poly(2-methoxy-5(2'-ethylhexyloxy)1,4-phenylene vinylene) MEH-PPV, a derivative of polymer poly(phenylenevinylene) (PPV), were investigated. It was ...
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Thin films of low-polydispersity, high-molecular-weight polymers poly(2-methoxy-5(2'-ethylhexyloxy)1,4-phenylene vinylene) MEH-PPV, a derivative of polymer poly(phenylenevinylene) (PPV), were investigated. It was proposed that the primary reason for the anisotropy in measured mobility values is the solvent-dependent high-electron-density layer lying along the interface. The observed anisotropy indicate that the differences in mobilities measured in FET and diode configurations are due to a structural or morphological anisotropy induced by the spin-coating process. The results also show that lamella formation process is kinetically suppressed in spin-coated films, which were thinner and thus dried faster. The low-frequency modulation indicate an additional structure within the spin-coated films with a thickness of approximately 5nm.
The hydrophobicity of the poly(l-lactide) (PLLA) surface was modified by incorporating hydroxyapatite (HAp) nanocrystalline particles during the electrospinning process for the engineered scaffold applications. The HA...
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Recent advances in rheometer design and rheology theory have led to an abundance of information, both experimental and theoretical. In response to this wonderful opportunity, many of the world's leading rheologist...
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ISBN:
(纸本)9781605603209
Recent advances in rheometer design and rheology theory have led to an abundance of information, both experimental and theoretical. In response to this wonderful opportunity, many of the world's leading rheologists have begun to share expert software codes with a global community of materials researchers and practitioners. This has led to the creation of a virtual environment for rheology (called "Rheo-Hub") in which students, researchers and practitioners analyze experimental data comprehensively, compare experiments with theory, directly explore theories by varying parameters in a wide parameter space, and derive results in the form of graphs, which are ideal for conducting quantitative comparisons and searching for dominant patterns. Explorations may be repeated in different ways (different expert codes may lead to alternative answers for the same research question) and viewed from different graphical viewpoints. Such easy access to advanced rheology is important, as it allows us to efficiently harness the large, rapidly growing technical knowledge base in rheology for the purpose of research and industrial innovation. Currently, hub technology for rheology is used in over 70 laboratories throughout the world, both industrially and academically. The technology is described in recent papers on cyber infrastructure by Winter and Mours (2006) and Winter (2007).
We have shown that any pair potential function v(r) possessing a Fourier transform V(k) that is positive and has compact support at some finite wave number K yields classical disordered ground states for a broad densi...
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We have shown that any pair potential function v(r) possessing a Fourier transform V(k) that is positive and has compact support at some finite wave number K yields classical disordered ground states for a broad density range [R. D. Batten, F. H. Stillinger, and S. Torquato, J. Appl. Phys. 104, 033504 (2008)]. By tuning a constraint parameter χ (defined in the text), the ground states can traverse varying degrees of local order from fully disordered to crystalline ground states. Here, we show that in two dimensions, the “k-space overlap potential,” where V(k) is proportional to the intersection area between two disks of diameter K whose centers are separated by k, yields anomalous low-temperature behavior, which we attribute to the topography of the underlying energy landscape. At T=0, for the range of densities considered, we show that there is continuous energy degeneracy among Bravais-lattice configurations. The shear elastic constant of ground-state Bravais-lattice configurations vanishes. In the harmonic regime, a significant fraction of the normal modes for both amorphous and Bravais-lattice ground states have vanishing frequencies, indicating the lack of an internal restoring force. Using molecular-dynamics simulations, we observe negative thermal-expansion behavior at low temperatures, where upon heating at constant pressure, the system goes through a density maximum. For all temperatures, isothermal compression reduces the local structure of the system unlike typical single-component systems.
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