On limb radiance calculations and convergence of relaxation type retrieval algorithms

Several approaches to the solution of the radiative transfer equation assume either Curtis-Godson average or linear change of the source function across grid segments. When such solutions are used for calculating limb radiances, the peak radiance response to the source function perturbation at tangent point i is displaced down to the tangent point i+1. This effect is explained through a geometric argument. Temperature profile retrievals performed by applying the ratio of signals at level i+1 for correcting temperature at level i demonstrate dramatic convergence acceleration of the iterative relaxation scheme.     

Properties of rubbery polymers for the recovery of hydrogen sulfide from gasification gases

Polydimethyl siloxane (PDMS) and two polyether‐polyamide copolymers (trade name Pebax) were evaluated for their ability to transport and separate gasification gases. Specifically, the permeabilities of hydrogen, carbon monoxide, carbon dioxide, and hydrogen sulfide were evaluated at temperatures up to 200°C. The permeabilities of all gases were approximately ten times faster through the PDMS than the Pebax materials. The permeabilities through all materials at all temperatures evaluated were H₂S > CO₂ > H₂ > CO. As the temperature increased, the permeabilities of all gases increased through the Pebax. Conversely, for PDMS, hydrogen and carbon monoxide permeabilites increased with temperature while those of H₂S and CO₂ decreased. The H₂S/H₂ selectivities ranges from 1.2 (PDMS at 200°C) to 10.3 (Pebax 2533 at 35°C). The activation energies for permeation of these polymer/penetrant pairs are reported. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2436–2444, 2002     

The “cold‐solutioning” phenomenon in cellulose triacetate–acetone mixtures

Direct mixing of cellulose triacetate (CTA) in acetone at room temperature produces only an opaque swollen gel at all concentrations. However, cycling the mixture between room temperature and ?78 ± 3°C results in a stable solution at room temperature, if the concentration is less than 6% (w/w). This process has been called “cold‐solutioning.” Such a process also produces a clear solution at concentrations between 6% (w/w) and 10% (w/w); however, in time, the solution separates slowly into at least two phases, a clear liquid and an opaque gel phase. At concentrations above 10% (w/w) and below 20% (w/w), the system exhibits two phases. A completely opaque swollen gel forms at concentrations of 20% (w/w) and above. The above‐described cold‐solutioning phenomena are shown to be the coupled kinetic and thermodynamic consequences of (1) the large thermal stresses that would result from thawing a swollen mixture of CTA and acetone, arising from the large differences in their thermal expansion coefficients; and (2) the “bimodal” composition of the cellulose derivative. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1697–1707, 2003     

Effect of vapor phase ethylenediamine crosslinking of matrimid on alcohol vapor sorption and diffusion

This work examines the sorption, diffusion, and polymer relaxation behavior for water and C1‐C7 alcohol vapors at 30 °C in ethylenediamine vapor‐phase crosslinked Matrimid. Ethylenediamine is sufficiently volatile that crosslinking can occur by exposing the polymeric film to saturated vapor, in contrast to more conventional means of dissolving the crosslinker in a solvent and immersing the polymeric film in the solution. The vapor‐phase exposure method avoids the use of additional solvent and undesired solvent‐induced swelling. Sorption isotherms demonstrate that water and C1‐C5 alcohols do not appreciably differ for unmodified and crosslinked Matrimid; however, an approximate 90% reduction in sorption was determined for hexanol and heptanol. A minor impact on diffusion coefficients for water, methanol, and ethanol was observed, while those of propanol and butanol were reduced over an order of magnitude. Relaxation kinetics were similarly unchanged for water and C1‐C3 alcohols, while being significantly reduced for butanol and higher alcohols. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44771.     

Prediction of Speech Quality Based on Resilient Backpropagation Artificial Neural Network

The paper presents a system for monitoring and assessment the speech quality in the IP telephony infrastructures using modular probes. The probes are placed at key nodes in the network where aggregating packet loss data. The system dynamically measures speech quality and results are collected on a central server. For data analysis we applied four-state Markov model for modeling the impact of network impairments on speech quality, afterwards, the resilient back propagation (Rprop) algorithm was used to train a neural network. Information about the speech quality are displayed in the form of automatically generated graphs and tables. The proposed solution has been tested with selected codecs and further generalizes the already presented concepts of the speech quality estimation in the IP environment.

     

Chemical stability of polyimide membranes at temperatures near Tg

The success of polymeric membranes for use in high temperature gas separation applications relies, in part, on the chemical stability of these materials in separation environment. This paper details experimental evaluation of the stability of the membranes prepared using a polyimide as the selective separating layer when exposed to butane/butene/hydrogen mixtures at temperatures near the glass transition temperature of the polymer, 310°C. Further, the effects of small concentrations of sulfur and ammonia compounds in the feed mixture were investigated, as was the influence of a simulated air leak. The gas transport rates and selectivities were unchanged when testing in the hydrocarbon/hydrogen environment for over 30 days. Further, no changes in transport properties were observed when hydrogen sulfide or ammonia was added to the feed mixture. However, degradation due to oxygen exposure was observed. The chemical stability of the polyimide layer appears to be sufficient to be utilized for the separation of high temperature petrochemical streams. © 1995 John Wiley & Sons, Inc.     

Effects of varying rates of tallgrass prairie hay and wet corn gluten feed on productivity of lactating dairy cows

Productivity of lactating dairy cows fed diets with wet corn gluten feed (WCGF, Sweet Bran, Cargill Inc., Blair, NE) as the primary energy substrate and prairie hay as the primary source of physically effective neutral detergent fiber (peNDF) was assessed relative to a control diet. Forty-eight Holstein cows, 100 to 250 d in milk, were randomly assigned to 1 of 6 pens and pens were randomly assigned to treatment sequence in a replicated 3×3 Latin square. Treatments were a control diet with 18% alfalfa, 18% corn silage, 33% WCGF, and 15% forage NDF (CON); a diet with 20% tallgrass prairie hay, 46% WCGF, and 13% forage NDF (TPH20); and a diet with 14% tallgrass prairie hay, 56% WCGF, and 9% forage NDF (TPH14). Midway through period 2, TPH14 was discontinued due to the high prevalence of diarrhea among cows on that treatment. Data from period 2 for TPH14 pens were discarded, and the pens that had been assigned to TPH14 for period 3 were randomly assigned to the other 2 treatments. Pen-level data were analyzed using linear mixed models, including the random effects of period and pen and the fixed effect of treatment. For animal-level data, additional random effects were introduced to account for subsampling. No evidence for treatment effects was apparent on dry matter intake. Least squares mean milk yields were 36.2, 34.6, and 35.2 kg/d for CON, TPH20, and TPH14, respectively, and were not significantly different. Milk fat concentration was higher for CON and TPH20 than for TPH14, with means of 3.48, 3.41, and 2.82%, respectively. Fat yield was significantly greater for CON compared with TPH20 and TPH14. Milk urea nitrogen was greatest for TPH20 and TPH14 and least for CON, consistent with differences in dietary protein content. Efficiencies, expressed as energy-corrected milk divided by dry matter intake, were 1.47, 1.42, and 1.24 for CON, TPH20, and TPH14, respectively, and were not significantly different. These data indicate that TPH14 did not provide adequate peNDF to support normal rumen function in mid lactation dairy cows; instead, TPH20 may be a feasible diet for use on dairies where high-NDF grass hay and WCGF are available.     

Preparation of polymer–ceramic composite membranes with thin defect-free separating layers

Polymer—ceramic composite membranes with essentially defect-free separating layers have been prepared by a solution deposition technique. Rigid polymers were used for the selective organic layer. These included high molecular weight samples of 5,5′-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]bis-1,3-isobenzofuran-dione, isopropylidenedianiline (6FDA-IPDA), 5,5′-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]bis-1,3-isobenzofuran-dione, methylenedianiline (6FDA-MDA), tetramethylhexafluorobisphenol-A polycarbonate (TMHFPC), and tetramethylhexafluoropolysulfone (TMHFPSF). Attempts to prepare composite membranes from lower molecular weight samples of bisphenol-A polycarbonate (PC) and tetrabromohexafluorobisphenol-A polycarbonate (TBHFPC) were unsuccessful. The PC and TBHFPC composites exhibited a decrease in the measured gas flux after polymer deposition; however, the selectivities of the composites were considerably less than that of a dense film of the same materials. A microporous ceramic membrane prepared by Anotec Separations was used as the support layer. This ceramic membrane provided minimal resistance to gas flow. The selective composite membranes were found to have high gas fluxes and gas separating abilities essentially equivalent to that of a dense isotropic film. The estimated, effective skin layer thicknesses for these membranes are on the order of 1500 Å to 1.0 μm. The formation of these composites is believed to occur through a sieving process in which large swollen polymer chains are sieved out of solution by the ceramic support. Polymer solutions that had swollen coil diameters that were smaller than that of the ceramic membrane did not produce selective composite membranes, while those solutions with swollen coil diameter that were larger than that of the ceramic membrane produced defect-free polymer layers. © 1992 John Wiley & Sons, Inc.     

Fusion neutron detector for time-of-flight measurements in z-pinch and plasma focus experiments

We have developed and tested sensitive neutron detectors for neutron time-of-flight measurements in z-pinch and plasma focus experiments with neutron emission times in tens of nanoseconds and with neutron yields between 10(6) and 10(12) per one shot. The neutron detectors are composed of a BC-408 fast plastic scintillator and Hamamatsu H1949-51 photomultiplier tube (PMT). During the calibration procedure, a PMT delay was determined for various operating voltages. The temporal resolution of the neutron detector was measured for the most commonly used PMT voltage of 1.4 kV. At the PF-1000 plasma focus, a novel method of the acquisition of a pulse height distribution has been used. This pulse height analysis enabled to determine the single neutron sensitivity for various neutron energies and to calibrate the neutron detector for absolute neutron yields at about 2.45 MeV.     

Effect of copolymer composition on the solubility and diffusivity of water and methanol in a series of polyether amides

Sorption and diffusion of water and methanol in polydimethylsiloxane and a series of PEBAX™ copolymers (polyether block amide copolymers) were measured over a wide range of activities near room temperature. The goal was to identify a membrane material for separation of the hazardous air pollutant methanol from wet air streams in the pulp and paper industry. The PEBAX™ copolymer series used here allows a unique insight into transport of small molecules, because solubilities are virtually constant, while diffusion coefficients vary. This is due to the similar chemical structure, but different chain mobility of the homopolymers. The grade PEBAX™ 2533 is most promising for the separation process due to high solubility and diffusivity. The unwanted simultaneous highly selective separation of methanol and water from the targeted air/vapor streams will be addressed in future work. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1983–1993, 1997