The effect of porosity on the thermal conductivity of nuclear graphite

During service in a high-temperature reactor, graphite will be oxidized by impurities such as water vapour present in the helium coolant. Oxidation will affect the thermal conductivity of the graphite and hence the fuel temperature. This report describes experiments on the effect of oxidation at 1000°C by water vapour of a semi-isotropic moulded graphite. The value of thermal conductivity at room temperature decreases with increasing weight loss, but not linearly, the decreases being most rapid at low weight losses. The percentage change in thermal conductivity is approximately linear with the increase in open porosity.     

Effect of the ethylene content of poly(ethylene-co-vinyl alcohol) on the formation of microporous membranes via thermally induced phase separation

Porous poly(ethylene-co-vinyl alcohol) (EVOH) membranes were prepared via thermally induced phase separation. The effect of the EVOH ethylene content on the membrane morphology and solute rejection property was investigated. For EVOHs with ethylene contents of 27–44 mol %, polymer crystallization (solid–liquid phase separation) occurred, and the membrane morphology was the particulate structure. However, the liquid–liquid phase separation occurred before crystallization for EVOH with a 60 mol % ethylene content. Cellular pores were formed in this membrane. For the particulate membranes, higher solute rejection and lower water permeance were obtained for EVOH with a lower ethylene content. The membrane formed by the liquid–liquid phase separation showed a sharper solute rejection change with a change in the solute radius than the particulate membranes did. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2583–2589, 2001     

Nondestructive determination of water and protein in surimi by near-infrared spectroscopy

Nondestructive near-infrared spectroscopy (NIRS) between 400 and 1100 nm regions was employed directly on surimi using a surface interactance fibre optic accessory, to investigate the potential of NIRS as a fast method to determine water and protein contents. The reason why NIRS is well suited when assessing the presence of water or protein is due to the specificity of O–H and N–H bindings. At 980 nm only one broad peak in the original spectra can be seen due to the absorption of water since it contained nearly 80% of surimi. Predictive equations were developed using partial least squares (PLS) regression where excellent predictions for protein and water are noticed. Regression coefficients are higher than 0.98, errors are small and RPD value for protein is well over 8 and that for water is very close to it which can be used for any analytical purpose.     

Hybrid White Light Emitting Diode Based on Silicon Nanocrystals

A novel design of white light emitting diodes (WLEDs) emerges to meet the growing global demand for resource sustainability while preserving health and environment. To achieve this goal, a facile method is developed for the chemical synthesis of a luminescent silicon nanocrystal (ncSi) with a large Stokes shift between absorption and emission. The WLED is prepared by a simple spin‐coating method, and contains a hybrid‐bilayer of the ncSi and luminescent polymer in its device active region. Interestingly, a well‐controlled ultrathin ncSi layer on the polymer makes possible to recombine electrons and holes in both layers, respectively. Combining red and blue‐green lights, emitted from the ncSi and the polymer layers, respectively, produces the emission of white electroluminescence. Herein, a hybrid‐WLED with a sufficiently low turn‐on voltage (3.5 V), produced by taking advantages of the large Stokes shift inherent in ncSi, is demonstrated.     

Effect of the addition of the surfactant Tetronic 1307 on poly(ether sulfone) porous hollow-fiber membrane formation

Poly(ether sulfone) (PES) hollow-fiber membrane was prepared via a nonsolvent-induced phase-separation method, and the effect of the addition of the surfactant Tetronic 1307 on the membrane performance and characteristics was investigated. The phase diagram of the PES/N-methyl-2-pyrrolidone (NMP)/water system was clarified. When the polymer solution involved Tetronic 1307, the amount of water required to induce the phase separation decreased, which indicated that Tetronic 1307 was one kind of nonsolvent. The kinetics of phase separation for the PES/NMP/Tetronic 1307 system were studied by light-scattering measurements. With the addition of Tetronic 1307, delayed phase separation was observed, and the structure growth rate decreased. Scanning electron microscopy images for all of the membranes showed the formation of fingerlike macrovoids through the cross section. Membrane surface morphologies were measured by atomic force microscopy. The obtained results indicated that membrane with 7 wt % Tetronic 1307 had higher roughness parameters than original membrane without the addition of surfactant. Ultrafiltration experiment results showed that the addition of Tetronic 1307 brought about an increase in water permeability and decreased the rejection of dextran with a molecular weight of about 10,000. The contact angles of water on the membrane outer surface decreased with the addition of Tetronic 1307. This mean the membrane surface became more hydrophilic. Thus, the addition of Tetronic 1307 was useful for improving the water permeability and for obtaining a hydrophilic membrane surface. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Development of a digital real‐time simulator for power electronics systems

A digital real‐time simulator for power electronics systems has been developed using MATLAB^TM/SIMULINK^TM. This paper describes the modeling and calculation accuracy of static synchronous compensator (STATCOM) models. Since the simulator operates in a large time step of 50 µs, compensation processing is implemented with the STATCOM model to improve the simulation accuracy. The calculation result of the real‐time STATCOM model is the same as that of non‐real‐time PSCAD^TM/EMTDC^TM. Stable operation of the newly developed simulator was successfully confirmed when connected to a commercial real‐time digital simulator (RTDS^TM). © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(4): 41–49, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10321     

DEPOSITION OF AEROSOL PARTICLES ON A SURFACE COMPOSED OF DIFFERENT TYPES OF MATERIALS

Experimental and theoretical studies have been conducted on the deposition of aerosol particles on a surface composed of different types of materials (copper-polyethylene and copper-nickel). Deposition of charged particles is affected by localized electrostatic fields created by the contact potential difference between the different types of materials. The particles charged with positive polarity deposit mainly on the polyethylene or the nickel surfaces, which are negatively charged. The deposition profile has been also controlled by varying the thickness of gold layers deposited on nickel surface.     

Effect of blade rotation on particle classification performance of hydro-cyclones

The effects of top blade rotation of hydro-cyclones on particle classification performance were examined experimentally and via a simulation study.It was noticed that the cut size of a hydro-cyclone decreases as the rotational speed of the top plate increases. Compared to the standard case without rotation, the accuracy of classification with top plate rotation increases under the wide range of operational conditions.Newly proposed type-D cyclones with a special blade indicated the smallest cut size with a high accuracy of classification. The increase of classification accuracy is due to the production of outward radial flow near the top plate and this result was simulated by a CFD calculation.The computer simulation also agreed qualitatively with the experimental data.