Derivation and verification of an aerosol dynamics expression for the below-cloud scavenging process using the moment method

An aerosol dynamics equation for the below-cloud scavenging process considering phoretic and electric charging effects in addition to the conventional mechanisms (the Brownian diffusion, interception, and impaction) is developed by using the moment method. Then, the dynamics of particle size distribution by the below-cloud scavenging process is calculated by using the developed equation and verified with the measurement data. The calculated particle size distribution changes are quite small compared to the measured changes. The calculated removal rate is smaller by 10^?2–10^?3 than the measured data when only the conventional mechanisms are considered. With the extended mechanisms, the scavenging coefficient increases upto 20 times, mainly for the particle size range of 0.1 μm<d_p<3.0 μm. However, the difference between the calculated and measured scavenging coefficient is still large, especially, for d_p<0.1 μm. Other possible scavenging mechanisms that might affect the below-cloud scavenging process such as coagulation and condensational growth of hygroscopic particles, turbulence, and updraft into cloud are discussed. It is recommended that further studies on wet scavenging process are needed.     

Mechanistic insight into gold nanorod transformation in nanoscale confinement of ZIF-8

Core-shell hybrid nanomaterials have shown new properties and functions that are not attainable by their single counterparts.Nanoscale confinement effect by porous inorganic shells in the hybrid nanostructures plays an important role for chemical transformation of the core nanoparticles.However,metal-organic frameworks(MOFs)have been rarely applied for understanding mechanical insight into such nanoscale phenomena in confinement,although MOFs would provide a variety of properties for the confining environment than other inorganic shells such as silica and zeolite.Here,we examine chemical transformation of a gold nanorod core enclosed by a zeolitic imidazolate framework(ZIF)through chemical etching and regrowth,followed by quantitative analysis in the core dimension and curvature.We find the nanorod core shows template-effective behavior in its morphological transformation.In the etching event,the nanorod core is spherically carved from its tips.The regrowth on the spherically etched core inside the ZIF gives rise toformation of a raspberry-like branched nanostructure in contrast to the growth of an octahedral shape in bulk condition.We attribute the shell-directed regrowth to void space generated at the interfaces between the etched core and the ZIF shell,intercrystalline gaps in mult-domain ZIF shells,and local structural deformation from the acidic reaction conditions.     

Biomimetic Chitin–Silk Hybrids: An Optically Transparent Structural Platform for Wearable Devices and Advanced Electronics

The cuticles of insects and marine crustaceans are fascinating models for man‐made advanced functional composites. The excellent mechanical properties of these biological structures rest on the exquisite self‐assembly of natural ingredients, such as biominerals, polysaccharides, and proteins. Among them, the two commonly found building blocks in the model biocomposites are chitin nanofibers and silk‐like proteins with β‐sheet structure. Despite being wholly organic, the chitinous protein complex plays a key role for the biocomposites by contributing to the overall mechanical robustness and structural integrity. Moreover, the chitinous protein complex alone without biominerals is optically transparent (e.g., dragonfly wings), thereby making it a brilliant model material system for engineering applications where optical transparency is essentially required. Here, inspired by the chitinous protein complex of arthropods cuticles, an optically transparent biomimetic composite that hybridizes chitin nanofibers and silk fibroin (β‐sheet) is introduced, and its potential as a biocompatible structural platform for emerging wearable devices (e.g., smart contact lenses) and advanced displays (e.g., transparent plastic cover window) is demonstrated.     

pH-sensitive photocatalytic activities of TiO2/poly(vinyl alcohol)/poly(acrylic acid) composite hydrogels

The pH-sensitive photocatalytic system was prepared by embedding TiO₂ into poly(vinyl alcohol)/poly(acrylic acid) hydrogel. Two different type TiO₂/hydrogel composites, such as matrix and nanofiber, were prepared to investigate the morphological effects on the photocatalytic activity. TiO₂ was distributed uniformly in the composite hydrogel and kept the original anatase structure without any structural change. The photocatalytic activity of TiO₂ was evaluated based on the efficiency of photobleaching of dye. The photobleaching of dye was improved greatly as the pH was changed into basic condition and the larger surface area of hydrogel was available for TiO₂ by using nanofiber supports.     

Magnetic instability of giant magnetoresistance spin-valves due to electromigration-induced inter-diffusion

Electromigration-induced magnetic failures in NiFe/(Co)/Cu/(Co)/NiFe spin-valve (SV) multilayers have been investigated. Electrically stressed NiFe/Cu/NiFe SV multilayers showed a dramatic reduction of magnetic moment up to 41%, and a shift of interlayer coupling characteristics, while no obvious magnetic degradation was observed in the NiFe/Co/Cu/Co/NiFe SV multilayers. It was experimentally confirmed that the magnetic degradation of the NiFe/Cu/NiFe SV multilayers is primarily due to the formation of Ni-Cu intermixing caused by the electromigration-induced Cu spacer inter-diffusion. Furthermore, it was demonstrated that an ultra thin Co diffusion barrier at the NiFe/Cu interface is promisingly effective to improve the magnetic stability of NiFe/(Co)/Cu/(Co)/NiFe SV multilayers against electromigration.     

Forecasting demand for low earth orbit mobile satellite service in Korea

Forecasting a new service diffusion process is critical in designing marketing strategies and analyzing the costs and benefits for service providers. It is very difficult, however, in cases that data are not available. We suggest the combination of analogy and survey to forecast the demand for Low Earth Orbit (LEO) mobile satellite service in Korea. First, we analyze the diffusion of existing mobile phone service, which is similar to LEO service. The diffusion parameters for mobile phone service are then used in a model for LEO service. A survey was made on two hundred fifty‐five subscribers of existing mobile phone service in Korea. We estimate the potential market size of LEO service by applying the logit model to the survey data. Then, we forecast the annual demand for LEO service in Korea from 1998 to 2005. We also derive the price elasticity of market potential of LEO service. This revised version was published online in August 2006 with corrections to the Cover Date.     

Reduction of musical noise in spectral subtraction method usingsubframe phase randomisation

A subframe phase randomisation method is proposed and applied to the enhanced speech with spectral subtraction method to reduce musical noise in the nonvoicing region. The musical noise in the spectral subtraction method is largely due to narrowband tonal components appearing somewhat periodically in the spectrogram of unvoiced and silence regions. Thus, each synthesis frame in a nonvoicing region is divided into several subframes to broaden the narrowband spectrum, and then phases of silence and unvoiced regions are randomised to disrupt the tonal spectrum structure     

Reduction of segregation during casting of 100Cr6 bearing steel by cerium inoculation

In order to reduce the segregation of alloying elements during casting of 100Cr6 high carbon chromium bearing steel, cerium was added to form dispersoids that act as inoculants to facilitate the formation not of columnar but of equiaxed grains. The influence of adding cerium alone to 100Cr6 steel on the degree of segregation and the resulting as-cast microstructure have been investigated. By adding cerium, the equiaxed grains became finer and the segregation diminished considerably. As a result, the rolling contact fatigue life of the steel was improved markedly. Among dispersoids, CeO₂ is supposed to play a more important role in refining as-cast structures because the observed number of CeO₂ was much larger than that of CeS and the size of the former was quite similar to that reported to be effective as inoculants. Consequently, the addition of cerium is proposed as the solution to one of the biggest subjects with regard to 100Cr6 steel, the reduction of segregation during casting.