MAXIMIZING SELECTIVITY OF LIQUID-LIQUID REACTION SYSTEMS. CONTROL OF THE DISPERSION PROCESS

Currently available information on droplet coalescence and break-up rates in turbulent flows in mixing vessels can be used to control drop sizes in dispersed phase equipment. The effect of drop size distributions on the selectivity and productivity in multi-reaction systems is examined in this paper.

The reaction system features the primary desired product (C) as resulting from reaction (in the bulk phase) between a reactant (A) in the drop phase and a second reactant (B) in the bulk phase. An adverse reaction is also envisaged which consumes (C) by further reaction with (B) to form a waste product. While small drops promote conversion because of large interfacial area, larger drops promote selectivity because of the facility of the product to re-enter the drop phase avoiding further reaction (to form waste) in the bulk phase. The effect of the bivariate distribution of drop size and reactant (A) concentration in the feed to a continuous stirred tank reactor on the selectivity and productivity of (C) is investigated within the framework of film theory while neglecting drop dynamics such as coalescence and break-up.

The results show the selectivity can be substantially improved by controlling drop size and distribution of the reactants among the differently sized droplets. Contrary to conventional wisdom which emphasizes creation of interfacial area by promoting very small droplets, it emerges that optimal distributions of drop size and reactant concentration which maximize productivity of the desired product exist. The practical implications are discussed.     

Influence of metal ion concentration in the glycol mediated synthesis of Gd2O3:Eu nanophosphor

The solvothermal synthesis of highly luminescent and homogeneous Gd₂O₃:Eu³⁺ nanophosphor using diethylene glycol as medium, followed by controlled combustion with citric acid as fuel is reported. The influence of concentrations of carboxylic acid and metal cations on the structure, morphology and luminescence properties are investigated in detail. The microscopic investigations indicate the nanocrystalline nature and the strong influence of cation concentration on the size, shape and agglomeration of the particles. It is found that increase in concentration of metal cations lead to the reduction in agglomeration of nanophosphors. The large value of intensity parameter Ω_2, suggested that Eu³⁺ ions reside in a more asymmetric environment, resulted in intense emission due to ⁵D₀–⁷F₂ electric dipole transition. Emission decay analysis of the samples exhibited one exponential nature. The samples prepared under optimum conditions showed a quantum efficiency of 78.63% and a moderately high life time of 1.217 ms.     

Synthesis and optical properties of azobenzene side chain polymers derived from the bifunctional fumaric acid and itaconic acid

Three type polymers containing the same azobenzene side chain group with different backbone structures, poly(DMAz6Fm), poly(DMAz6It) and poly(MAz6Ac) derived respectively from fumaric acid, itaconic acid and acrylic acid, were synthesized. The dependence of photo-response properties on the polymeric architecture was investigated for the solutions and films. By irradiation of the linearly polarized light (436 nm), uniaxial orientations of the thin films were induced and anisotropic properties were investigated by measurements of the order parameters and birefringence values.     

The Effects of Touch Button Size on Touchscreen Operability

The present study investigated the effects of touch button size on touchscreen operability and compared these effects between young adult and elderly participants. A total of 21 young adults （aged 22.3 ± 1.5 years） and 20 elderly adults （aged 68.1 ±4.9 years） were recruited and asked to press square number buttons （from 0 to 9） on an experimental touchscreen with their right index finger. The buttons＇ size changed during the experiment with six conditions （6, 8, 10, 12, 14 and 16 mm）. It was found that a decrease of the button size to l0 mm or below tended to increase the operation time and error rate, whereas it decreased the subjective overall operability of the touchscreen. Such effects were greater in the elderly adults than in the young adults. In addition, the reaction positions on the buttons were found to be close to the right side of them, which led the fingertip to approach the right outline of the buttons. These findings suggest that the use of small touch buttons should be minimised on touchscreens, especially for elderly users.     

Ultra-high-precision time control system over any long time delay for laser pump and synchrotron x-ray probe experiment

An ultra-high-precision clock system for long time delay has been developed for picosecond time-resolved x-ray diffraction measurements using synchrotron radiation (SR) pulses and synchronized femtosecond laser pulses. The time delay control between pump laser pulse and the probe SR pulse was achieved by combining an in-phase quadrature modulator and a synchronous counter. This method allowed us to change the delay time by a nearly infinite amount while maintaining the precision of +/-8.40 ps. Time-resolved diffraction measurements using the delay control system were demonstrated for precise measurement of an acoustic velocity in a single crystal of gallium arsenide.     

Different feeding and gustatory responses to ecdysone and 20-hydroxyecdysone by larvae of the silkworm,Bombyx mori

The feeding and gustatory responses to ecdysone and 20-hydroxyecdysone were investigated in the silkworm,Bombyx mori. 20-Hydroxyecdysone reduced feeding response strongly in fourth- and fifth-instar larvae, whereas ecdysone had no effect on feeding response. 20-Hydroxyecdysone stimulated the R receptor, the receptor to feeding deterrents, to a great degree. By contrast, ecdysone was much less effective for stimulating the R receptor. These results indicate that ecdysone and 20-hydroxyecdysone have different effects on feeding response due to different interactions with mouthpart chemoreceptors.     

Micro Textures in Concentrated-Conformal-Contact Lubrication: Effect of Distribution Patterns

Micro-scale textures may be engineered into surfaces for lubrication performance improvement. It is expected that a carefully chosen texture helps retain lubricant and enhances the hydrodynamic effect at the interface. The concept of model-based virtual texturing enables textured surfaces to be generated and “tested” through numerical simulations. This paper reports virtual texturing and simulation of a group of textured surfaces in a lubricated concentrated contact. The focus of the study is on the selection of texture distribution patterns based on their lubrication performance. Patterns of fishbone, sinusoidal, triangular, and honeycomb distributions have been investigated. The effects of texture direction, orientation angle, feature continuity, and aspect ratio are also studied. The results indicate that, for the given material and geometry system under the given conditions in the present work, the textures generating the strongest hydrodynamic lifting are short grooves with a small aspect ratio and sinusoidal waves of a small wavelength/amplitude ratio propagating in the motion direction.     

Terahertz time domain attenuated total reflection spectroscopy with an integrated prism system

We demonstrated attenuated total reflection (ATR) spectroscopy with an integrated prism system that included a terahertz emitter, a terahertz receiver, and an ATR prism. The ATR prism had two internal off-axis parabolic mirrors for, respectively, collimating and focusing the terahertz waves. The Fresnel loss at each interface was reduced, and the total propagation efficiency was 3.36 times larger than when using a non-integrated prism system. The refractive index of water samples calculated from the experimental data showed good agreement with values reported in the literature.     

Experimental and simulation study of undesirable short-period deformation in piezoelectric deformable x-ray mirrors

To construct adaptive x-ray focusing optics whose optical parameters can be varied while performing wavefront correction, ultraprecise piezoelectric deformable mirrors have been developed. We computationally and experimentally investigated undesirable short-period deformation caused by piezoelectric actuators adhered to the substrate during mirror deformation. Based on the results of finite element method analysis, shape measurements, and the observation of x-ray reflection images, a guideline is developed for designing deformable mirrors that do not have short-period deformation errors.     

Residual oil cracking combined with hydrogen production by steam-iron reaction

A new residual oil upgrading process has been developed. Residual oils were cracked over an iron oxide catalyst with simultaneous generation of hydrogen. The newly-developed iron oxide catalyst containing CaO and Cr₂O₃ was found to be a good catalyst for this process because it exhibited stable activity in the steam-iron reaction in the laboratory experiment and also in a large scale pilot plant. Effects of these foreign oxides on redox cycles were investigated. The catalyst was designed so as to maintain the stoichiometric balance between the reduction of magnetite and the oxidation of wustite by adding CaO and Cr₂O₃.