A large enhancement of the maximum drift velocity of electrons in the channel of a field-effect heterotransistor

It is shown that the optical-phonon momentum quantization in a GaAs quantum well resulting from the introduction of an InAs quantum-dot barrier layer provides for the elimination of inelastic scattering of electrons by optical phonons and, thus, makes the acceleration of electrons above the saturation drift velocity possible. It is shown experimentally that the maximum drift velocity of electrons in high electric fields in AlGaAs/GaAs heterostructure with InAs quantum-dot barriers introduced into the GaAs quantum well exceeds the saturation drift velocity in bulk GaAs by as much as a factor of 10. Such a rise in the maximum drift velocity of electrons ensures increased maximum current density, transconductance, and cutoff frequency of the heterostructure field-effect transistor with quantum dots.     

Poly(lactic acid)-based biocomposites reinforced with kenaf fibers

Biodegradable thermoplastic-based composites reinforced with kenaf fibers were prepared and characterized. Poly(lactic acid) (PLA) was selected as polymeric matrix. To improve PLA/fibers adhesion, low amount of a proper reactive coupling agent, obtained by grafting maleic anhydride onto PLA, was added during matrix/fibers melt mixing. Compared with uncompatibilized composites, this compatibilization strategy induces a strong interfacial adhesion and a pronounced improvement of the mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Drying creep of concrete: constitutive model and new experiments separating its mechanisms

A new experimental method which allows the direct separation of the components of drying creep due to microcracking and stress-induced shrinkage is developed, demonstrated and validated. The basic idea is to compare the curvature creep of beams subjected to the same bending moment but very different axial forces. The results confirm that drying creep has two different sources: microcracking and stress-induced shrinkage. The latter increases continuously, whereas the former first increases and then decreases. The test results are fitted using a finite element model. The results validate the present model for drying creep. The microcracking is described by an established model, and the free (unrestrained) shrinkage of a material element is shown to depend approximately linearly on the humidity drop.     

Dilemmas in Measurement of Human Body Temperature

Abstract

Measurement of human body temperature seems rather trivial until we become parents or medical professionals. If we use different thermometers, which are used at different body sites, inevitably we come across to different measurement results. Then we ask ourselves which result is the right one. The answer is far from trivial because there are a few dilemmas in measurement of human body temperature. To none of these dilemmas exists a straight answer. The article describes dilemmas in measurement of human body temperature and thermometers used for its measurement. Presented are also calibration results of certain clinical radiation thermometers and their improvement in the past few years in terms of accuracy and uncertainty.     

Effects of controlled nucleation on freeze-drying lactose and mannitol aqueous solutions

The lyophilization of lactose and mannitol aqueous solutions was investigated with an emphasis on analyzing the effects of controlled nucleation, temperature of nucleation, and pore size distribution on the freeze-drying process. The experimental procedure involved the depressurization technique of controlled nucleation, in-vial temperature measurements as well as measurements of the chamber pressure, which allowed the analysis of the product batch, loaded in the laboratory lyophilizator. The average pore enlargement was 93 and 58% with the incorporation of the controlled nucleation step in the lyophilization of 6?wt% lactose and 6?wt% mannitol solutions, respectively. Consequently, the primary drying times were lowered from 450 to 500?min in both cases. The pore sizes were determined to be as important as the solid material itself in the scope of the sublimation rates. Namely, the average equivalent diameter of the pores was larger in the dried mannitol cake compared to the lactose cake. However, despite the higher porosity of the dried mannitol cake, the end of the sublimation in the primary drying step was observed approximately 500?min earlier during the lyophilization of the lactose solution with the same initial concentration as the mannitol solution in a comparable freeze-drying protocol. In addition, an increase in mannitol concentration from 3 to 12?wt% was found to substantially extend the time required for the sublimation phase of the lyophilization.     

Average-case improvements when integrating ML and KA

In this paper we develop a mathematical analysis, based on empirical measurements, of expected average improvements when integrating Machine Learning and Knowledge Acquisition systems in real-life domains. The analysis is based on the characteristics of component systems and combining techniques. Important characteristics include the accuracy of component systems, the degree to which component systems complement each other's weaknesses, and the ability of the combining mechanism to make good choices among competing component systems. Empirical measurements in a real-life application, in the Sendzimir rolling mill, have shown that integrating both approaches enables significant improvements. Improvements when combining systems in two oncological domains were smaller, yet positive again. Analytical average-case integrated models consisting of two systems are introduced. Conditions for improvements over the best, average and the worst system are established and the expected gains are analytically computed based on expected performances. Models strongly suggest that a reasonable integration of two systems offers significant improvements over the best single system in many or even most real-life domains.