Effects of the chirality and functionality of monomers on the holographic gratings formed in photosensitive films

Photosensitive holographic polymer films were fabricated. Instead of liquid crystals, a nonreactive high‐refractive‐index diphenyl sulfide was mixed with several monomers and an initiator for the preparation of the holographic grating films. To investigate the formation of periodic arrays of the photosensitive refractive‐index modulation films and the effects of the chirality and functionality of monomers on the diffraction efficiency, chiral monomeric (?)‐bornyl acrylate, (+)‐bornyl acrylate, and the racemate (±)‐bornyl acrylate were synthesized and copolymerized with various multifunctional monomers. A reasonable schematic of the photosensitive polymerization mechanism was proposed. The effects of the multifunctional monomers, initiator concentrations, and feed monomer concentrations on the diffraction efficiencies were investigated. The morphologies of the polymer matrices were studied with scanning electron microscopy. Pictures of real light diffraction patterns with 15 grating points were obtained. In comparison with those described in the literature, the diffraction efficiency obtained in this investigation was relatively high. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2246–2254, 2003     

Synthesis of photoisomeric azobenzene monomers and model compound effect on electric–optical properties in PDLC films

A series of azobenzene monomers and related model compounds with various side‐chain lengths were synthesized. The electrooptical properties of a polymer‐dispersed liquid crystal (PDLC) were verified by side‐chain methoxy azobenzene in various chain lengths (n = 3, 6, 11). The properties under various voltages were measured and the effect of extra voltage on the transmittance of PDLC was researched as well. The experiment demonstrated the validity of employing these side chain methoxy azobenzene materials in electrooptical devices. The azobenzene model compound showed better electric–optical and thermal–optical properties, having a higher contrast ratio (CR = 689) and a lower saturation voltage (4.7 V/μm). All the azobenzene molecules can be photoisomerized through UV light irradiation, following the mechanism of isomerization. The reversible photo and heat isomerization property was studied. The cis‐azobenzene that was transformed from the trans‐azobenzene irradiated by UV light can decrease the clearing point of the liquid crystal phase. We used this unique characteristic to record image patterns and it worked successfully. We synthesized the azobenzene monomers can stabilize the PDLC and their relative model compounds with various alkyl chain lengths even got better electric–optical effects. We found that azobenzene monomer shows different behaviors in the electric–optical property from its relative model compound. The difference between the systems were explained using a proposed model. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 721–732, 2005     

Material Characterization of Photo-Fabrication Process

The characterization of photopolymerization for the rapid prototyping process has been studied using a laser stereolithography machine. The cross sections of the cured layers and lines were examined using an optical microscope. Perkin-Elmer differential scanning calorimeter (DSC)-7 was employed to investigate the degree of curing after laser scanning. It was observed that the profile of the cross section of a cured line and/or part determined by the laser exposure density is a function of laser power and scanning speed. DSC analysis shows the retained resin to be governed by laser exposure intensity and laser scanning pattern. By increasing the laser exposure or the overlapping area of two adjacent scanning lines, retained and uncured resin could be minimized. However, the efficiency of photopolymerization is lowered. The most efficient operating parameters for part building can be determined by a T factor.     

Absolute stability analysis for a class of Takagi–Sugeno fuzzy control systems

This article presents absolute stability conditions for a particular class of Takagi–Sugeno fuzzy control systems. Initially, a Takagi–Sugeno fuzzy control system is transformed into a multivariable Lur’e type system. A simple algorithm for checking the absolute stability of this system is then proposed. Since the key of the proposed algorithm is to solve algebraic Riccati equations, software packages such as MATLAB provides a simple means to check the conditions. The proposed approach does not limit the methods of fuzzification and defuzzification. This article presents several analytical examples to verify the simplicity and efficiency of the proposed approach.     

Micro-pillars enhanced all vanadium redox flow batteries and the effect of assembly torque on the electrochemical performance

A uniformly distributed electrolyte system based on enhanced micro-pillars flow field design is proposed for a vanadium redox flow battery (VRFB). The uniformity experiments show that the flow uniformity can be effectively increased and normalized velocity variation for any channel is measured to be less than 18 %, demonstrating the effectiveness of micro-pillars for enhanced flow field. Experimental validation is carried out experimentally and the effect of different assembly torque is also investigated for VRB cell electrochemical performance via polarization and cyclic voltammograms (CV) test. The results show that an optimal assembly torque (11 N-m) can yield a significant improvement of 68.5 % current density when compared with the case of 10 N-m. Furthermore, the CV results clearly indicate that the optimal assembly torque with enhanced micro-pillars design can result in the 37.3 % improvement of electrochemical surface area. Moreover, the contact pressure contours from the pressure-sensitive films are measured to check the influence on the configuration of VRFB unit cell.

     

Design parameterization and tool integration for CAD-based mechanism optimization

This paper presents an open and integrated tool environment that enables engineers to effectively search, in a CAD solid model form, for a mechanism design with optimal kinematic and dynamic performance. In order to demonstrate the feasibility of such an environment, design parameterization that supports capturing design intents in product solid models must be available, and advanced modeling, simulation, and optimization technologies implemented in engineering software tools must be incorporated. In this paper, the design parameterization capabilities developed previously have been applied to support design optimization of engineering products, including a High Mobility Multi-purpose Wheeled Vehicle (HMMWV). In the proposed environment, Pro/ENGINEER and SolidWorks are supported for product model representation, DADS (Dynamic Analysis and Design System) is employed for dynamic simulation of mechanical systems including ground vehicles, and DOT (Design Optimization Tool) is included for a batch mode design optimization. In addition to the commercial tools, a number of software modules have been implemented to support the integration; e.g., interface modules for data retrieval, and model update modules for updating CAD and simulation models in accordance with design changes. Note that in this research, the overall finite difference method has been adopted to support design sensitivity analysis.     

Child-rearing antecedents of intergenerational relations in young adulthood: A prospective study.

Data gathered from mothers on parenting and family climate when almost 1,000 children in the Dunedin, New Zealand, longitudinal study were 3, 5, 7, 9, 13, and 15 years of age were used to predict intergenerational relations between young adult children (age 26) and their middle-aged parents. Analyses focused on distinct developmental epochs revealed greater prediction from the middle-childhood and early-adolescent periods than from the early-childhood years; most indicated that more supportive family environments and child-rearing experiences in the family of origin forecasted more positive and less negative parent-child relationships (in terms of contact, closeness, conflict, reciprocal assistance) in young adulthood, though associations were modest in magnitude. Some evidence indicated that (modestly) deleterious effects on intergenerational relations of experiencing relatively unsupportive child-rearing environments in 1 but not 2 (of 3) developmental periods studied could be offset by relatively supportive family environments in the remaining developmental periods. (PsycINFO Database Record (c) 2010 APA, all rights reserved)