Chien Hong Lin

Mechanical reinforcement of epoxy with self-assembled synthetic clay in smectic order.

Epoxy films containing self-assembled 2D colloidal α-zirconium phosphate nanoplatelets (ZrP) in smectic order were prepared using a simple, energy-efficient fabrication process suitable to industrial processing. The ZrP nanoplatelets form a chiral smectic mesophase with simultaneous lamellar order and helical arrangements in epoxy. The epoxy nanocomposite films are transparent and flexible and exhibit exceptionally high tensile modulus and strength. The findings have broad implications for development of multifunctional materials for engineering applications.

Micromechanical models for the effective time-dependent and nonlinear electromechanical responses of piezoelectric composites

This study introduces micromechanical models for analyzing the overall electromechanical responses of piezoelectric composites comprising polarized piezoelectric ceramics and polymeric constituents. The polarized piezoelectric ceramics can experience nonlinear electromechanical responses due to an application of large electric fields, while the polymer exhibits viscoelastic response. Thus, the piezoelectric composites can experience significant time-dependent and nonlinear electromechanical coupling behaviors. Two micromechanical models are considered: the Mori–Tanaka and unit-cell models. Linearized micromechanical relations are first defined for obtaining the overall responses of the piezoelectric composites followed by iterative schemes in order to correct errors from linearizing the nonlinear responses. Numerical results are presented for two composite systems, that is, piezoelectric unidirectional fiber with circular/square cross section and spherical/cubic particle inhomogeneities embedded in a polymeric matrix. The linear electromechanical responses from the two micromechanical models are compared with the experimental data available in the literature. Parametric studies are performed in order to examine the effect of inhomogeneity geometry and compositions and prescribed boundary conditions on the overall time-dependent and nonlinear electromechanical responses of the composites.

A Multi-scale Formulation for Predicting Non-linear Thermo-electro-mechanical Response in Heterogeneous Bodies

This study presents a multi-scale formulation for analyzing coupled heat conduction and thermo-electro-mechanical deformation in heterogeneous bodies, namely active composites. The studied active composite comprises ferroelectric inclusions dispersed in polymer matrix. The multi-scale framework is derived based on an integrated simplified micromechanical and finite element model. A non-linear thermo-electro-elastic constitutive model of materials undergoing large electric driving fields and small strains is used for the polarized ferroelectric inclusions. An integration algorithm with predictor and corrector schemes is developed to obtain approximate solutions of field variables: temperature, displacement, strain, stress, electric field, and electric displacement. The multi-scale model is capable of determining field variables at multiple length scales which is important when non-linear behaviors in the constituents of heterogeneous bodies are considered. We examine the effect of mismatches in the properties of the constituents in an active composite on the overall field coupling responses in the composite. We also compare the field coupling responses in an active composite to those of a homogeneous body, i.e., lead zirconate titanate (PZT). We finally present a simulation of controlling deformation in a smart cantilever beam using the multiscale framework.

The effect of microstructural morphologies on the effective electromechanical properties of piezoelectric particle composites

This study introduces a micromechanical model that incorporates detailed microstructures for analyzing the effective electro-mechanical properties, such as piezoelectric and permittivity constants as well as elastic moduli, of piezoelectric particle reinforced composites. The studied composites consist of polarized spherical piezoelectric particles dispersed into a continuous and elastic polymeric matrix. A micromechanical model generated using three-dimensional (3D) continuum elements within a finite element (FE) framework. For each volume fraction (VF) of particles, realization with different particle sizes and arrangements were generated in order to represent microstructures of a particle composite. We examined the effects of microstructural morphologies, such as particle sizes and distributions, and particle volume fractions on the overall effective electro-mechanical properties of the active composites. The overall electro-mechanical properties determined from the present micromechanical model were compared to those generated using the Mori-Tanaka, self-consistent, and simplified unit-cell micromechanical models.Copyright

Verifying expressed transcript variants by detecting and assembling stretches of consecutive exons

We herein describe an integrated system for the high-throughput analysis of splicing events and the identification of transcript variants. The system resolves individual splicing events and elucidates transcript variants via a pipeline that combines aspects such as bioinformatic analysis, high-throughput transcript variant amplification, and high-resolution capillary electrophoresis. For the 14 369 human genes known to have transcript variants, minimal primer sets were designed to amplify all transcript variants and examine all splicing events; these have been archived in the ASprimerDB database, which is newly described herein. A high-throughput thermocycler, dubbed GenTank, was developed to simultaneously perform thousands of PCR amplifications. Following the resolution of the various amplicons by capillary gel electrophoresis, two new computer programs, AmpliconViewer and VariantAssembler, may be used to analyze the splicing events, assemble the consecutive exons embodied by the PCR amplicons, and distinguish expressed versus putative transcript variants. This novel system not only facilitates the validation of putative transcript variants and the detection of novel transcript variants, it also semi-quantitatively measures the transcript variant expression levels of each gene. To demonstrate the system’s capability, we used it to resolve transcript variants yielded by single and multiple splicing events, and to decipher the exon connectivity of long transcripts.