Development of Genetic Algorithm based 3D-PTV technique

A new 3D-PTV technique has been developed using GA (Genetic Algorithm). The measurement system consists of three CCD cameras, Ar-ion laser, an image grabber and a host computer. One-to-one correspondences are made by taking advantage of the combinatorial optimization of the genetic algorithm for the whole particles of the two images during the time interval of image frames. Two fitness functions are introduced in order to enhance the correspondences of the particles. One is based on the concept of continuum theory and the other one is based on the minimum error of threedimensional distance. Performance of the developed algorithm is tested using a set of virtual images constructed by the use of LES data set on an impinging jet. The developed 3D-PTV system is successfully applied to the measurement of flow characteristics of the wake of a circular cylinder.     

Effect of solvated ionic liquids on the ion conducting property of composite membranes for lithium ion batteries

We prepared the polyethylene oxide (PEO)-based composite membrane electrolytes which contained the specialized ionic liquids and the inorganic filler of Li₇La₃Zr₂O₁₂ (LLZO). Mixtures of ionic liquids and tetragonal inorganic fillers were used as additives to prepare composite electrolytes for an application of all solid-state lithium ion batteries (ASLBs). In order to improve the ionic conductivity of composite membranes, we studied the structural change and the electrochemical behaviors as a function of the amounts of solvated ionic liquids (ILs). The addition effect of solvated ILs showed the higher ionic conductivity such as 10^?4 S/cm at 55 °C by reducing the crystalline character of polymer based composite, resulting in the enhanced ion conducting property. The hybrid composite membranes were successfully made in flexible form, and have an excellent thermal and electrochemical stability. Finally, the electrochemical performance of the half-cell was evaluated, and it was confirmed that the ion-conducting characteristics were influenced and controlled by the effect of ILs.     

Effects of Thermal Radiation on a 3D Sisko Fluid over a Porous Medium Using Cattaneo-Christov Heat Flux Model

This paper investigates the three-dimensional flow of a Sisko fluid over a bidirectional stretching sheet, in a porous medium. By using the effect of Cattaneo-Christov heat flux model, heat transfer analysis is illustrated. Using similarity transformation the governing partial differential equations are transferred into a system of ordinary differential equations that are solved numerically by applying Nachtsheim-Swigert shooting iteration technique along with the 6-th order Runge-Kutta integration scheme. The effect of various physical parameters such as Sisko fluid, ratio parameter, thermal conductivity, porous medium, radiation parameter, Brownian motion, thermophoresis, Prandtl number, and Lewis number are graphically represented.     

Photoluminescence spectra of laser-synthesized Si/C/N ultrafine powders

Ultrafine Si/C/N ceramic powders were synthesized by a CO₂-laser-induced reaction between silane (SiH₄), ammonia (NH₃) and acetylene (C₂H₂). The powders were characterized by infrared (IR) reflection and photoluminescence (PL) spectroscopy. From the infrared reflection spectra of Si/C/N powders, we have identified the causes of the strong photoluminescence present in these powders. The photoluminescence spectra of Si/C/N powders originate from the presence of hydroxylated and amorphous silicon (a-SiO₂) formed at the porous surface of these powders. We have shown that different chemical bonding between Si, C and N atoms, the degree of crystallinity of ternary powders and their porosity strongly influence the processes at their surface, i.e. the formation of amorphous silicon and silanole. Received: 16 June 2000 / Accepted: 24 June 2000 / Published online: 9 November 2000     

Large eddy simulation on the unsteady aerodynamic response of a road vehicle in transient crosswinds

A large eddy simulation method based on a fully unstructured finite volume method was developed, and the unsteady aerodynamic response of a road vehicle subjected to transient crosswinds was investigated. First, the method was validated for a 1/20-scale wind-tunnel model in a static aerodynamic condition; this showed that the surface pressure distributions as well as the aerodynamic forces and moments were in good agreement with wind-tunnel data. Second, the method was applied to two transient crosswind situations: a sinusoidal perturbation representing the typical length scale of atmospheric turbulence and a stepwise crosswind velocity corresponding to wind gusts. Typical transient responses of the aerodynamic forces and moments such as phase shifting and undershooting or overshooting were observed, and their dependence on the frequency and amplitude of the input perturbation is discussed. Thus, the utility and validity of the large eddy simulation was demonstrated in the context that such transient aerodynamic forces are difficult to measure using a conventional wind tunnel.     

Aspect ratio effects on natural convection in a water-saturated porous cavity near its density maximum

In this study, two-dimensional steady-state solutions of buoyancy-driven convection in a water-saturated porous cavity is conducted numerically for a range of different aspect ratios. The left vertical wall is considered into a partially heating location. The Brinkman–Forchheimer extended Darcy model is used to investigate the average heat transfer rate. The governing equations are solved using a finite volume method. The results obtained for various values of parameters are presented graphically in the form of streamlines, isotherms and velocity at mid-plane of the cavity. In addition, numerical results for the average Nusselt number are presented for various parametric conditions.     

Microelectrofluidic bench using UV-curable rigid polymer fabricated by rapid and low-temperature process

We present a rapid and low-temperature polymer fabrication method based on the direct patterning by UV light. Compared to the conventional polymer micromolding method for polydimethylsiloxane (PDMS) and cyclic olefin copolymers (COC), the present method has advantages of rapid fabrication in low-temperature environment. We used an AEO3000, UV-curable low-stress hyper-branched polymer (HBP), as a polymer material. The AEO3000 layer was selectively exposed to UV light by a photomask at room temperature for 3 min. Using the present method, we designed the rigid substrate for the microelectrofluidic bench. The measured electrical and fluidic interconnection characteristics in the bench were 0.75 ± 0.44 Ω and 8.3 kPa (at the flow rate of 100 μl/min), respectively. Both electric and fluidic characteristics were equivalent or lower than the sum of individual devices. We also successfully verified the bio-sample analysis through the interconnected devices on the microelectrofluidic bench using yeast cell samples. The proposed method offers fast and bio-compatible process applicable to biomedical micro total analysis systems.     

Characterization of traditional Korean lacquers using surface analytical techniques

Traditional Korean lacquer films, such as Otchil and Hwangchil, are natural paints extracted from Rhus vernicifera and Dendropanax morbifera trees that grow in the eastern part and on the west and south coast of the Korean Peninsula, respectively. Rhus lacquer has a black color, and Hwangchil has a transparent gold color and a rich camphoric perfume (benzoin). These lacquers have been used since ancient times. In this study, analytical techniques, such as Fourier transform infrared (FT‐IR) spectroscopy, X‐ray photoelectron spectroscopy (XPS), and time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS), were used to study the traditional Rhus lacquer and Hwangchil films, avoiding time‐consuming and destructive extraction procedures. To compare the Rhus and Hwangchil lacquers, reference lacquer films were prepared using Rhus and Dendropanax saps. These films were then analyzed using FT‐IR, XPS, and TOF‐SIMS. After establishing the methodology using the reference lacquer films, surface analytical techniques were applied to two different plates painted by an artist. The results suggest that FT‐IR, XPS, and TOF‐SIMS are simple and complementary analytical techniques for the discrimination of old lacquer films. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigation of Asian lacquer films using ToF‐SIMS and complementary analytical techniques

Lacquer has been used in Asian countries for thousands of years as a natural coating material owing to its durable, adhesive, decorative, and protective properties. Protection and restoration of lacquer‐coated cultural remains has become an important subject, and identification of the lacquer types in old lacquer‐wares has also become very important for conservation and restoration research. This paper provides identification of several molecular species of vegetal‐source Asian lacquers with the aim of providing a methodology for application in the field of cultural heritage. Several chemical markers of the vegetal species in Asian lacquers were identified using a methodology consistent with the sampling restrictions required for cultural‐heritage objects. Surface analytical methods such as time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS), X‐ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy were used to characterize Korean, Chinese, and Vietnamese lacquers; avoiding time‐consuming and destructive extraction processes. These ToF‐SIMS results provided the structural characterization of a series of catechol derivatives. The ToF‐SIMS spectra of Rhus vernicifera from Korea and China, and Rhus succedanea from Vietnam indicated a series of urushiol and laccol repeat units, respectively, in the mass range of m/z 0–1800. Because of its sensitivity, specificity, and speed of analysis, the ToF‐SIMS technique can be used to investigate cultural lacquer‐coated treasures as well as to discriminate among different Asian lacquer coatings or binding mediums for the conservation or restoration of lacquer‐ware. Copyright © 2016 John Wiley & Sons, Ltd.     

Rapid synthesis and consolidation of nanostructured 2MgAl2O4–MgAl2Ti3O10 composite and its mechanical properties

Rapid sintering of nanostructured 2MgAl₂O₄–MgAl₂Ti₃O₁₀ composite in a pulsed current activated sintering process was investigated. The advantage of this process is that it enables very rapid densification to near theoretical density and prevents grain growth in nanostructured materials. Highly dense nanostructured 2MgAl₂O₄–MgAl₂Ti₃O₁₀ composite was produced by simultaneous application of 80 MPa pressure and a pulsed current of 2,800 A for 2 min. The sintering behavior, grain size, and mechanical properties of the 2MgAl₂O₄–MgAl₂Ti₃O₁₀ composite were investigated.