A correlation model to compute the incidence angle modifier and to estimate its effect on collectible solar radiation

Radiation transmittance and absorptance of materials vary according to the angle of incidence of the incoming solar radiation. Therefore, the efficiency of most solar converters (thermal or photovoltaic) at a given radiation amount is a function of the sun's position through the angle of incidence. This problem is accounted for by the Incidence Angle Modifier, which is considered in this paper. An analytic expression for the incidence angle modifier, based on meteorological data or on geographic and geometric parameters, has been developed; this expression includes the effect of beam and diffuse radiation as well as the global influence. A comparison between measured data and computed from our model has given a very good correlation, the results being within a ±3% of difference for horizontal and tilted planes, and within ±17% for vertical surfaces, on average. The method also computes the collectible solar energy within a 5% error for thresholds up to 300 W m⁻². The method has been validated for more than 30 locations of south and west Europe.     

Mass-sensitive detection of gas-phase volatile organics using disk microresonators

The detection of volatile organic compounds (VOCs) in the gas phase by mass-sensitive disk microresonators is reported. The disk resonators were fabricated using a CMOS-compatible silicon micromachining process and subsequently placed in an amplifying feedback loop to sustain oscillation. Sensing of benzene, toluene, and xylene was conducted after applying controlled coatings of an analyte-absorbing polymer. An analytical model of the resonator's chemical sensing performance was developed and verified by the experimental data. Limits of detection for the analytes tested were obtained, modeled, and compared to values obtained from other mass-sensitive resonant gas sensors.     

Infrared hollow waveguide sensors for simultaneous gas phase detection of benzene, toluene, and xylenes in field environments

Simultaneous and molecularly selective parts-per-billion detection of benzene, toluene, and xylenes (BTX) using a thermal desorption (TD)-FTIR hollow waveguide (HWG) trace gas sensor is demonstrated here for the first time combining laboratory calibration with real-world sample analysis in field. A calibration range of 100-1000 ppb analyte/N(2) was developed and applied for predicting the concentration of blinded environmental air samples within the same concentration range, and demonstrate close agreement with the validation method used here, GC-FID. The analyte concentration prediction capability of the TD-FTIR-HWG trace gas sensor also compares well with the industrial standard and other experimental techniques including GC-PID, ultrafast GC-FID, and GC-DMS, which were simultaneously operated in the field. With the advent of a quantum cascade laser with emission frequencies specifically tailored to efficiently overlap benzene absorption as the most relevant analyte, the overall sensor footprint could be considerably reduced to ultimately yield hand-held trace gas sensors facilitating direct and real-time detection of BTX in air down to low ppb levels.     

High-throughput, accurate mass metabolome profiling of cellular extracts by flow injection-time-of-flight mass spectrometry

Direct injection of samples on high-resolving mass spectrometers is an effective way to maximize analytical throughput and yet allow analyte discrimination in complex samples by mass-to-charge ratio. We present a platform of flow injection electrospray-time-of-flight mass spectrometry to profile small molecules in >1400 biological extracts per day at native mass resolution. We comprehensively benchmark the performance with more than 5000 injections of chemically defined standards and Escherichia coli cellular extracts obtained from miniscale cultivations. For at least 90% of tested compounds, we attain a linear response over 3 decades of concentration, interday coefficient of variation of <20%, and a mass accuracy of <0.001 amu. In polar Escherichia coli fractions, we reproducibly detected >1500 distinct ions in each mode. The accurate mass and correlation analysis enabled one to assign with good confidence 400-800 ions to electrospray derivatives of metabolites listed in the genome-wide reconstruction of Escherichia coli metabolism. Hence, we attain a coverage of about one-quarter of the total number of compounds listed in the reconstruction. Finally, we present an exemplary screen with Escherichia coli deletion mutants to show the exquisite capacity of the platform to identify lesions in primary metabolism at high throughputs.     

Ring-type plasmon resonance in metallic nanoshells

A simple, approximate theoretical model of surface plasmon resonance in two-dimensional metal nanoshells is developed. The model is based on the concept of short-range surface plasmons propagating around closed circular metal nanotubes. In this model, the plasmon resonance in a metal nanotube is treated as a propagating, self-interfering plasmonic wave, in a ring-type resonance, at plasmonic wavelengths matching an integer fraction of the nanotube's effective circumference. The model is validated by detailed computer simulations based on the finite-difference time-domain method and is shown to be in full agreement with the widely used plasmon hybridization model, which is based on the quasi-static approximation.     

Direct and indirect effects of perceived price on perceived value of mobile phones

Nowadays many leading companies understand that creating outstanding customer value is necessary to achieving sustainable market success. The main problem discussed in this article is the examination of factors affecting perceived value, emphasizing the relationship between perceived price and perceived value. Based on literature and their own findings, the authors designed a model of relationships between researched factors. This model was tested using structural equation modeling. The results reflected that statistically significant relationships exists and that perceived price has direct as well as indirect efects on perceived product value.     

Stochastic model of self-regulation decision making exemplified by decisions concerning hypoglycemia.

The following sequence—internal condition → symptom perception → appraisal → decision—models various symptom-based self-regulation processes. A formal mathematical model describes the first three steps by continuous variables and the decisions at the fourth step by binary variables. The stochastic transitions between the sequential steps are quantified by transition probabilities. The model is illustrated by blood glucose level estimation and detection and treatment of hypoglycemia in 78 patients with insulin-dependent diabetes mellitus. These patients made 50 to 70 data collection trials over 3 to 4 weeks recording perceived symptoms, cognitive-motor performance, subjective estimates of blood glucose, decisions about treatment of hypoglycemia, and driving. A statistical estimation of the model's parameters demonstrates the utility of this approach for understanding the awareness, detection, and treatment of hypoglycemia as a process of symptom-based decision making. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sigma Phase in Tungsten-Rhenium Alloys. I

In developing tungsten alloys for service both above the recrystallization temperature and below room temperature the main task is to make an alloy, which in addition to having a low ductile to brittle transition temperature in the recrystallized condition can readily be manufactured into various configurations.

Tungsten-rhenium alloys have been found to be useful for such applications, since they have a combination of high strength and good ductility. The best ductility is reached in alloys with a rhenium content close to the solubility limit in tungsten. During manufacturing of such alloys the forming properties are adversely affected by the precipitation of the intermetallic compound W₂Re₃ (σ-phase).

The purpose of this work is to clarify the influence of sigma phase on the formability and product quality after high temperature densification and thermomechanical treatment (TMT) of powder metallurgy manufactured W-25%Re alloys using different processing parameters. The study consists of two parts. Part I deals with theoretical and practical aspects on the formation of sigma phase particles and their influence on metal flow and product quality. Different ways of interpreting the W-Re phase are discussed and the characteristics of the σ-phase are presented. Practical recommendations to control the negative influence of the σ-phase are also given. A more complete understanding of the effect of various processing parameters will be the subject of Part II of this paper.