Wall heat flux partitioning during subcooled forced flow film boiling of water on a vertical surface

Subcooled flow film boiling experiments were conducted on a vertical flat plate, 30.5 cm in height, and 3.175 cm wide with forced convective upflow of subcooled water at atmospheric pressure. Data have been obtained for mass fluxes ranging from 0 to 700 kg/m²s, inlet subcoolings ranging from 0 to 25 °C and wall superheats ranging from 200 to 400 °C. Correlations for wall heat transfer coefficient and wall heat flux partitioning were developed as part of this work. These correlations derive their support from simultaneous measurements of the wall heat flux, fluid temperature profiles, liquid side heat flux and interfacial wave behavior during steady state flow film boiling. A new correlation for the film collapse temperature was also deduced by considering the limiting case of heat flux to the subcooled liquid being equal to the wall heat flux. The premise of this deduction is that film collapse under subcooled conditions occurs when there is no net vapor generation. These correlations have also been compared with the data and correlations available in the literature.     

Self‐assembled honeycomb polyurethane nanofibers

Electrospinning uses a high voltage electric field to produce fine fibers. A new phenomenon of self‐assembly in the electrospinning of polyurethane nanofibers is observed. This report is the first known self‐assembling phenomenon in polyurethane electrospun nanofibers. Electrospun polyurethane nanofibers self‐assemble into unique honeycomb patterns on the collector surface. This novel observation opens up new and interesting opportunities for electrospun fibers in the areas of drug delivery devices, protective clothing, filters, and tissue scaffolds. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3121–3124, 2006     

Neueste Entwicklungen beim baulichen Brandschutz von Straßentunneln

In der jüngeren Vergangenheit hat sich gezeigt, dass Straßen tunnel durch größere Brände in erheblichem Umfang geschädigt werden können. In der Folge wurden verschiedene internationale Forschungsprojekte durchgeführt, um den baulichen Brandschutz von Straßentunneln weiterzuentwickeln. Aufbauend auf den internationalen Forschungsprojekten wurden vom BMVBS und der BASt drei nationale Forschungsprojekte zum baulichen Brandschutz von Straßentunneln initiiert. In diesen Projekten wurden vorhandene Temperatur‐Zeit‐Verläufe (sog. “Brandkurven”) für Straßentunnel, Brandver suche in Tunneln und reale Brände in Straßentunneln im Hinblick auf eine mögliche Anwendung zur Bemessung des baulichen Brandschutzes von Straßentunneln analysiert. Außerdem wurden die Temperatureindringung in die Tunnelinnenschale und die Tragfähigkeit von üblichen Tunnelquerschnitten infolge Brandeinwirkung numerisch ermittelt. Schließlich wurde anhand von Brandversuchen an großmaßstäblichen Probekörpern die Wirkung von PP‐Faserbeton auf das Abplatzverhalten von Innenschalenbeton untersucht. Über das Vorgehen und die Ergebnisse dieser Forschungsprojekte wird im Folgenden berichtet. Latest developments for structural fire protection of road tunnels. In the recent past it was shown that road tunnels can be damaged severely by large fires. For that reason several international research projects were carried out for further development of structural fire protection of road tunnels. Based on international research projects three national research projects were initiated by the Federal Ministry of Transport, Building and Urban Development (BMVBS) and the Federal Highway Research Institute (BASt). In the course of these projects existing temperature‐time‐progressions (so called ”fire curves”) for road tunnels, fire tests in tunnels and real fires in road tunnels were analyzed with regard to a possible application for the design of structural fire protection of road tunnels. Furthermore the temperature penetration in the tunnel lining and the load bearing capacity of usual tunnel sections were numerically examined under fire influence. Finally the influence of fiber‐modified concrete on the effect of explosive spalling was investigated by means of large scale fire tests on specimens made of concrete for tunnel lining. In the following procedures and results of the national research projects are described.     

On upsampling, downsampling, and rational sampling rate filterbanks

Solutions to the problem of design of rational sampling rate filter banks in one dimension has previosly been proposed. The ability to interchange the operations of upsampling, downsampling, and filtering plays an important role in these solutions. The present paper develops a complete theory for the analysis of arbitrary combinations of upsamplers, downsamplers and filters in multiple dimensions. Although some of the simpler results are well known, the more difficult results concerning swapping upsamplers and downsamplers and variations thereof are new. As an application of this theory, the authors obtain algebraic reductions of the general multidimensional rational sampling rate problem to a multidimensional uniform filter bank problem. However, issues concerning the design of the filters themselves are not addressed. In multiple dimensions, upsampling and downsampling operators are determined by integer matrices (as opposed to scalars in one dimension), and the noncommutativity of matrices makes the problem considerably more difficult. Cascades of upsamplers and downsamplers in one dimension are easy to analyze. The new results for the analysis of multidimensional upsampling and downsampling operators are derived using the Aryabhatta/Bezout identity over integer matrices as a fundamental tool. A number of new results in the theory of integer matrices that a relevant to the filter bank problem are also developed. Special cases of some of the results pertaining to the commutativity of upsamplers/downsamplers have been obtained in parallel by several authors     

Analysis of dielectric guides by transverse magnetic field finiteelement penalty method

The main purpose of this paper is to use the finite element method using a penalty function formulation to solve the vector wave equation with transverse H-field formulation together with the boundary operator. We impose continuity conditions on the boundary interfaces for both E _z and H_z components. We apply this technique to obtain the propagation constant for a three-layer ridge structure and a multiple quantum well ridge guide as examples, and a comparison with previously published results shows excellent agreement     

Miniaturization of a patch antenna using circular reactive impedance substrate

In this article, to construct a reactive impedance substrate, unit ring is designed and proposed with radial and concentric mode analysis. A cylindrical substrate backed with a PEC plane and circular metallic elements on the top is used for achieving reactive surface impedance behavior. In this aspect, three unit rings structure with different ring elements are designed and simulated to realize the reflection phase characteristics. Afterwards, a probe‐fed circular patch antenna is miniaturized by stacking the three‐ring circular reactive impedance surface. The fundamental resonance frequency of the proposed antenna is reduced by about 30% with an improvement in impedance bandwidth by 121.6%. An improved front‐to‐back ratio as well as an acceptable co‐pol and cross‐pol isolation is exhibited in both E‐plane and H‐plane at the resonance frequency. In addition of miniaturization, dual band behavior has also been observed in the proposed design. Both resonance phenomena have been explained by circuit model representation and surface current distribution analysis. Improved radiation efficiency at 81.5% has been measured for the proposed antenna configuration.     

Solvent‐free cyanoethylation of selected alcohols using amberlyst A‐21 polymer resin

Solvent‐free cyanoethylation of selected alcohols with acrylonitrile (AN) using a weakly basic polymer resin, Amberlyst A‐21 (AA‐21) was studied at 75°C. The conversion of primary alcohols, 1‐octadecanol, hexane‐1,6‐diol, pentaerythritol, but‐2‐yne‐1,4‐diol, N‐methyldiethanolamine, triethanolamine and diethanolamine is higher than secondary alcohols, isopropanol and glycerol in the presence of polymer resin. Of various alcohols, but‐2‐yne‐1,4‐diol gave the product in high conversion (87%) in cyanoethylation with a polymer resin/AN weight ratio of 0.04. The polymer resin showed recycling ability only in two cycles to produce cyanoethylated product from diethanolamine. In case of 1‐octadecanol, hexane‐1,6‐diol, and N‐methyldiethanolamine with AN under similar conditions, no recycling ability was observed. Thermally treated polymer resin at 75°C afforded the product in lower conversion (55%) whereas the same product was obtained in 69% when fresh polymer resin was used in cyanoethylation of 1‐octadecanol. No catalytic effect was observed for polymer resin treated at 100°C. Fourier transform infrared (FTIR) spectra showed CN stretching at 2248 cm^?1 for the polymer resin collected after the reaction which was caused by the AN binding on polymer resin during the reaction. As per thermogravimetric curves, 5% weight loss was observed at 201°C for recovered resin and at 161°C for polymer resin treated at 100°C. Scanning electron microscope images confirmed the AN binding on polymer beads after catalytic activity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Rapid Reduction of U(VI) on Activated Platinum Wire Gauze Electrode for the Primary Coulometric Determination of Uranium

A large enhancement in the active area of a hollow cylindrical platinum wire gauze electrode was achieved by repetitive multilayer growth of oxide followed by its reduction. Growth of oxide was obtained by a combination of chemical and electrochemical treatments. Enhancement in the active area of the electrode was checked by determining the time taken for the quantitative reduction of U(VI) to U(IV) at a controlled potential of –0.150 V vs SCE in 1 M H₂SO₄. A six-fold decrease in the reduction time was observed, indicating a corresponding six-fold increase in the active area of the electrode. The enhanced activity of the electrode was found to decay on ageing. Determination of uranium was carried out by a successive addition technique using the activated platinum wire gauze electrode and carrying out the reduction U(VI) to U(IV) at a controlled potential of –0.150 V vs SCE. Precision and accuracy of better than ±0.2% were obtained at 5 to 10 mg levels of uranium. This demonstrates the applicability of a platinum electrode, instead of the conventionally used Hg electrode, for determination of uranium by primary coulometry.     

Amphiphilic ABA‐type triblock copolymers for the development of high‐performance poly(vinylidene fluoride)/poly(vinyl pyrrolidone) blend ultrafiltration membranes for oil separation

ABA‐type amphiphilic triblock copolymers (TBCs) were synthesized by a reversible addition fragmentation chain transfer (RAFT) process with a telechelic polystyrene macro‐RAFT agent and 4‐[n‐(acryloyloxy)alkyloxy]benzoic acid monomers. Ultrafiltration (UF) membranes were fabricated by a phase‐inversion process with blends of the TBC, poly(vinylidene fluoride) (PVDF), and poly(vinyl pyrrolidone) (PVP) in dimethylformamide. The UF‐fabricated membranes were characterized by scanning electron microscopy, atomic force microscopy, water contact angle measurement, thermogravimetric analysis, and differential scanning calorimetry. Pure water permeation, molecular weight cutoff values obtained by the permeation of different molecular weight polymers as probe solutes, bovine serum albumin (BSA) solution permeate flux, and oil–water emulsion filtration tests were used to evaluate the separation characteristics of the fabricated membranes. The tripolymer blend membranes exhibited a higher flux recovery ratio (FRR) after the membrane was washed with sodium lauryl sulfate (0.05 wt %) solution for a BSA solution (FRR = 88%) and oil–water emulsion (FRR = 95%) feeds when than the PVDF–PVP blend membrane (57 and 80% FRR values for the BSA solution and oil–water emulsion, respectively). The pendant carboxylic acid functional moieties in this ABA‐type TBC have potential advantages in the fabrication of high‐performance membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45132.     

Switching Futile para‐Quinone to Efficient Reactive Oxygen Species Generator: Ubiquitin‐Specific Protease‐2 Inhibition,Electrocatalysis, and Quantification

Understanding the correlation between structural features of small‐molecule drugs and their mode of action is a fascinating topic and crucial for the drug‐discovery process. However, in many cases, knowledge of the exact parameters that dictate the mode of action is still lacking. Following a large screening for ubiquitin specific protease 2 (USP2) inhibition, an effective para‐quinone‐based inhibitor with an unclear mode of action was identified. To gain a deeper understanding of the mechanism of inhibition, a set of para‐quinones were prepared and studied for USP2 inhibition, electrocatalysis, and reactive oxygen species (ROS) quantification. The excellent correlation obtained from the above‐mentioned studies disclosed a distinct pattern of “N?C=O?N” in the bicyclic para‐quinones to be a crucial factor for ROS generation, and demonstrated that minor changes in such a skeleton drastically altered the ROS‐generating ability. The knowledge acquired herein would serve as an important guideline for future medicinal chemistry optimization of related structures to select the preferred mode of action.