Crystal structure of (Ba1−x Lax) [Mg(1 + x)/3Nb(2−x)/3]O3 ceramics

The crystal structure of (Ba_1–x La _x )[Mg_{(1 + x)/3}Nb_(2–x)/3]O₃ (BLMN) ceramics with 0 x 1 was investigated using X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). When the La content, x, was above 0.1, the 1:2 ordered hexagonal structure found in Ba(Mg_1/3Nb_2/3)O₃ (BMN) was transformed into the 1:1 ordered cubic structure. The 1:1 ordered cubic structure was maintained up to x = 0.7. When x exceeded 0.7, however, BLMN exhibited a 1:1 ordered monoclinic structure, rather than a 1:1 ordered cubic structure. La(Mg_2/3Nb_1/3)O₃ (LMN) has a 1:1 ordered monoclinic P2₁/n structure with a = 5.6004 Å, b = 5.6414 Å, c = 7.9346 Å, and = 89.9819°. The monoclinic LMN has the in-phase and the anti-phase tilt of oxygen octahedra. The anti-parallel shift of A-site cations was also found in LMN.     

Phantom studies of Cd, Hg and Cl by prompt gamma neutron activation analysis using a Pu-Be neutron source

Prompt gamma neutron activation analysis is a means of non-invasive monitoring for occupational exposure to toxic heavy metals such as Cd and Hg. Preliminary kidney detection limits from previous phantom studies at McMaster were 13.6 ± 0.2 ppm for Cd (125 mL phantom) and 315 ± 24 ppm for Hg (125 mL phantom) using the ²³⁸Pu-Be neutron source and 0.88 ± 0.01 ppm for Cd (125 mL phantom) and 16.91 ± 0.05 ppm for Hg (30 mL phantom) using the thermal neutron beam port at the McMaster Nuclear Reactor. The detection limits vary greatly between the two methods due to differences in experimental set-up, neutron energy spectra and a difference in dose by more than a factor of 100. The Hg detection limit from preliminary data is much higher than expected for both neutron source types. In order to explain the apparent detection limit discrepancy, measurements of Hg and Cd phantoms were performed using the ²³⁸Pu-Be neutron source. The results were compared to phantom measurements of Cl, a well-known neutron activation element.     

A Nonconventional Approach to Patterned Nanoarrays of DNA Strands for Template‐Assisted Assembly of Polyfluorene Nanowires

DNA molecules have been widely recognized as promising building blocks for constructing functional nanostructures with two main features, that is, self‐assembly and rich chemical functionality. The intrinsic feature size of DNA makes it attractive for creating versatile nanostructures. Moreover, the ease of access to tune the surface of DNA by chemical functionalization offers numerous opportunities for many applications. Herein, a simple yet robust strategy is developed to yield the self‐assembly of DNA by exploiting controlled evaporative assembly of DNA solution in a unique confined geometry. Intriguingly, depending on the concentration of DNA solution, highly aligned nanostructured fibrillar‐like arrays and well‐positioned concentric ring‐like superstructures composed of DNAs are formed. Subsequently, the ring‐like negatively charged DNA superstructures are employed as template to produce conductive organic nanowires on a silicon substrate by complexing with a positively charged conjugated polyelectrolyte poly[9,9‐bis(6′‐N,N,N‐trimethylammoniumhexyl)fluorene dibromide] (PF2) through the strong electrostatic interaction. Finally, a monolithic integration of aligned arrays of DNA‐templated PF2 nanowires to yield two DNA/PF2‐based devices is demonstrated. It is envisioned that this strategy can be readily extended to pattern other biomolecules and may render a broad range of potential applications from the nucleotide sequence and hybridization as recognition events to transducing elements in chemical sensors.     

Multi-exemplar inhomogeneous texture synthesis

This paper presents a new framework for the semi-automatic synthesis of an inhomogeneous texture from a theoretically infinite number of input exemplars. Our algorithm generates a result with natural multiway transitions, maintaining a reasonable synthesis time to keep interactivity. We introduce intermediate textures between multiple exemplars, called ‘transition textures’ which enable our algorithm to produce smooth transitions between input exemplar patches. We also propose ‘image index correction’ to achieve a synthesis speed that is independent of the number of input exemplars by smart placement of transition-texture samples. Our algorithm is semiautomatic, spatially deterministic and well suited to acceleration via parallel processors. Also, our algorithm can easily control the synthesis result to design a texture visual with user interactions.     

Evaluation of the Fracture Strength for Silicon Carbide Layers in the Tri-Isotropic-Coated Fuel Particle

A program to develop new methods to measure the fracture strength of the chemical vapor deposition SiC coatings in nuclear fuel particles has been carried out. Internal pressurization and crush test techniques were developed and applied to prototype-sized tubular and hemispherical shell specimens. The fracture strength measured from each test method applying the Weibull two-parameter distribution, and Weibull parameters were measured. It was shown that data generated with each test technique were independent of the test technique applied. This implies that the developed test methods are reliable and provide reasonable strength data. For the same material, fracture strength varied with the specimen geometry and loading configuration. These size and loading configuration effects on the fracture strength are explained with the concept of effective surface.     

Cloud point behavior for poly(isodecyl methacrylate)+supercritical solvents+cosolvent and vapor-liquid behavior for CO<Subscript>2</Subscript>+isodecyl methacrylate systems at high pressure

Experimental cloud-point data of binary and ternary mixtures for poly(isodecyl methacrylate) [P(IDMA)] in supercritical carbon dioxide, dimethyl ether (DME), propane, propylene, butane and 1-butene have been studied experimentally using a high pressure variable volume view cell. These systems show the phase behavior at temperature of 308 K to 473 K and pressure up to 255 MPa. The cloud-point curves for the P(IDMA)+CO₂+isodecyl methacrylate (IDMA) are measured in changes of the pressure-temperature (P-T) slope, and with cosolvent concentrations of 0-60.1 wt%. Also, experimental data of phase behaviors for IDMA in supercritical carbon dioxide is obtained at temperature range of 313.2–393.2 K and pressure range of 5.8–22.03 MPa. The experimental results were modeled with the Peng-Robinson equation of state. The location of the P(IDMA)+CO₂ cloud-point curve shifts to lower temperatures and pressures when DME is added to P(IDMA)+CO₂ solution. The P(IDMA)+C₄ hydrocarbons cloud-point curves are ca. 16.0 MPa lower pressures than the P(IDMA)+C₃ hydrocarbons curves at constant temperature. This article is dedicated to Professor Chul Soo Lee in commemoration of his retirement from Department of Chemical and Biological Engineering of Korea University.     

Effect of various processing methods on the interfacial reactions in SiCp/2024 Al composites

SiC_p/2024 Al composites were prepared using various processing techniques, such as spray forming, powder metallurgical hot pressing, thixoforming, and compocasting. The interfacial characterizations of these composites were performed using scanning electron microscopy, Auger electron spectrometry, transmission electron microscopy, and X-ray diffraction on reaction products extracted using the electrochemical dissolution. The value of these combined techniques in elucidating the morphologies of the interfacial reaction products was also demonstrated. The influence that each fabrication process has on the extent of the interfacial reaction was studied. Adequate process parameters to fabricate SiC_p/Al alloy composites were proposed based on thermodynamic considerations.     

Improving inter-destination synchronization in hierarchical reliable multicast

In hierarchical reliable multicast schemes, the number of repair proxies and their locations influence inter-destination synchronization. The inter-destination synchronization in multicast environments means the adjustment of the output timing among destinations over the Internet. Improving the inter-destination synchronization is beneficial to collaborative applications such as multi-conference system and multi-playing online game. In this paper, we propose a scheme to find the optimal locations of repair proxies that can improve inter-destination synchronization maximally in heterogeneous network environments. The simulation results show that if repair proxies are placed by the proposed scheme, delivery delay fairness of inter-destination can be improved by 0.05 maximally. In addition, we perform t-Test on the simulation results in order to verify that our optimal placement improves synchronization.     

Free surface transition and momentum augmentation of liquid flow in Micro/Nano-scale channels with hydrophobic and hydrophilic surfaces

We propose a novel micro/nano-scale nozzle structure, featuring an interfacial line between the hydrophilic and the hydrophobic surfaces for a jetting system, such as an inkjet head or electrospray devices. This research will investigate the impact of the interfacial line on flow instability and momentum augmentation as the liquid meniscus moves across the line. The research methods used in this paper, in respect to micro-and nano-scale channels, are computational fluid dynamics (CFD) and non-equilibrium molecular dynamics (MD), respectively. With the growing interest in micro/nano electromechanical systems (MEMS/NEMS), many studies have been conducted to develop an advanced micro/nanofluidic system. However, until now, there have been few in-depth studies on passive flow control in micro and nano nozzles using the hydrophilic and hydrophobic surface characteristics. In this research, the sequential arrangement of hydrophilic and hydrophobic surfaces in the nozzle is presented along with an investigation into how flow instability and momentum augmentation are going to be applied to an efficient micro/nano jetting system. When a liquid meniscus arrives at the interfacial line between hydrophilic and hydrophobic surfaces, the meniscus shape changes from concave to convex and the fluid motion near the wall stops until the concave shape is fully converted. Because the momentum should be conserved, the lost momentum near the wall transfers to the center region, and therefore the liquid at the center region is accelerated as it crosses the line. If we use this nozzle structure and the augmentation of the momentum near the center, a tiny droplet can be easily generated. This paper was recommended for publication in revised form by Associate Editor Haecheon Choi Doyoung Byun received the B.S., M.S, and Ph.D. degrees in school of mechanical and aerospace engineering from the Korea Advanced Institute of Science and Technology (KAIST), Taejon, Korea, in 1994, 1996, and 2000, respectively. From 2000 to 2002, he was in the Korea Institute of Science and Technology Evaluation and Planning as a Senior Researcher. In 2003, he joined the faculty of the School of Mechanical and Aerospace Engineering, Konkuk University, Seoul, Korea. His current research topics are development of electrohydrodynamic inkjet head, microfluidic devices, and biomimetic robot systems. His research interests include microfluidics, MEMS, and biomimetics.     

On pattern classification of EMG signals for walking motions

We present a method to calssify electromyogram (EMG) signals which are utilized as control signals for a patient-responsive walker-supported system for paraplegics. Patterns of EMG signals for different walking motions are classified via adequate filtering, real EMG signal extraction, AR-modeling, and a modified self-organizing feature map (MSOFM). In particular, a data-reducing extraction algorithm is employed for real EMG signals. Moreover, MSOFM classifies and determines the results automatically using a fixed map. Finally, the experimental results are presented for validation.