A comprehensive approach to model and use context for adapting applications in pervasive environments

With an increasing diversity of pervasive computing devices integrated in our surroundings and an increasing mobility of users, it will be important for computer systems and applications to be context-aware. Lots of works have already been done in this direction on how to capture context data and how to carry it to the application. Among the remaining challenges are to create the intelligence to analyze the context information and deduce the meaning out of it, and to integrate it into adaptable applications. Our work focuses on these challenges by defining generic context storage and processing model and by studying its impact on the application core. We propose a reusable context ontology model that is based on two levels: a generic level and a domain specific level. We propose a generic adaptation framework to guarantee adaptation of applications to the context in a pervasive computing environment. We also introduce a comprehensive adaptation approach that involves content adaptation and presentation adaptation inline with the adaptation of the core services of applications. Our case study shows that the context model and the application adaptation strategies provide promising service architecture.     

Characterization of luminescent and thermal properties of long afterglow SrAlxOy:Eu2+,Dy3+ phosphor synthesized by combustion method

Europium and dysprosium codoped strontium aluminate green phosphor was synthesized by combustion method using urea as reducer and fuel. The morphology, particle size, and structure of the products were characterized by scanning electron microscopy, X‐ray diffraction, and transmission electron microscopy, while the characteristic luminescence properties were investigated using excitation and emission spectra. Polymer‐phosphor composites were made and thermally characterized by means of differential scanning calorimetry and thermogravimetric analysis. Phosphor nanocrystallites with high brightness were obtained without significantly changing the structure of the aluminate host. The average crystallite sizes, calculated from the Scherrer equation ranged between 34 ± 7 and 43 ± 7 nm. Emissions arising from transitions between the 5d and 4f orbital gaps of Eu²⁺ are manifested in the broadband excitation and emission spectra with major peaks at 360 and 515 nm, respectively. The decay curves and half‐life times show a clear trend in the influence of the phosphor in the improvement of the initial brightness and the afterglow times, which are ascribed to the presence of shallow and deep traps. Thermal results indicate that the phosphor nanoparticles acted as nucleating agents and improved the overall crystallinity in the LDPE/phosphor system. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Synthesis and characterization of CaAlxOy:Eu2+ phosphors prepared using solution-combustion method

Europium-doped calcium aluminate (CaAl_xO_y:Eu²⁺) phosphors were obtained at low temperatures (500 °C) by the solution - combustion of corresponding metal nitrate-urea solution mixtures. The particle size and morphology and the structural and luminescent properties of the as-synthesized phosphors were examined by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), Auger spectroscopy, transmission electron spectroscopy (TEM) and photoluminescence (PL). It was found that the Ca:Al molar ratios showed greatly influence not only on the particle size and morphology, but also on their PL spectra and structure. With the Ca: Al molar ratios increasing from 6:100 to 26:100, the structure of as-synthesized phosphor changed from CaAl₁₂O₁₉ to monoclinic CaAl₂O₄ and the dominant emitting light from red to blue, implying that the oxidation state of doped europium ions changed from trivalent to divalent due to the structure variation of host lattice. A blue phosphor with almost pure phase can be easily prepared by solution combustion method with suitable Ca:Al molar ratio.     

Synthesis and luminescence in sol–gel auto-combustion-synthesized $$\hbox {CaSnO}_{3}{:}\hbox {Eu}^{3+}$$ phosphor

Undoped and Eu-doped \(\hbox {CaSnO}_{3}\) nanopowders were prepared by a facile sol–gel auto-combustion method calcined at \(800{^{\circ }}\hbox {C}\) for 1 h. The samples are found to be well-crystallized pure orthorhombic \(\hbox {CaSnO}_{3}\) structure. Photoluminescence (PL) measurements indicated that the undoped sample exhibits a broad blue emission at about 420–440 nm, which can be recognized from an intrinsic centre or centres in \(\hbox {CaSnO}_{3}\). Eu-doped \(\hbox {CaSnO}_{3}\) showed broad blue emission centred about 434 nm, a weak peak at 465 nm and a sharp intense yellow emission line at 592 nm. The emission situated at 592 nm was assigned to the f–f transition of \(^{5}\hbox {D}_{0}\rightarrow ^{7}\hbox {F}_{1}\) in \(\hbox {Eu}^{3+}\) ions. The afterglow emission and PL decay results in Eu-doped \(\hbox {CaSnO}_{3}\) phosphor, which revealed that there are at least two different traps in this phosphor. From the obtained results, \(\hbox {Eu}^{3+}\)-doped \(\hbox {CaSnO}_{3}\) phosphor could be proposed as a potential white luminescent optical material.     

Effects of storage methods, storage time and different agro-ecological zones on chemical components of stored sorghum grain in Hararghe, Ethiopia

Sorghum grain stored in traditional underground pits was sampled from seven districts of Hararghe, eastern Ethiopia, representing lowland, intermediate and highland zones, from February to August 2001, and was analysed at the International Livestock Research Institute (ILRI) for changes in chemical composition over time. Samples were also taken from a replicated aboveground bin and pit storage experiment at Alemaya University campus at 2-month intervals from March 2000 to August 2001 and analysed in a similar manner. The effect of geographic location on chemical composition was significant, but there were differences in the sorghum varieties grown. The organic matter (OM) content of grain samples from pits in the lowlands was lower than those from the highlands. The crude protein (CP) and OM contents of samples from the seven districts did not change in 7–9 storage months. The OM content decreased and the CP slightly increased over time in samples from soil pits without any lining material on Alemaya University campus. The OM content decreased from 97.8 to 91.6%; and CP increased from 10.1 to 11.2% in these samples over a 17-month period. Soluble carbohydrate (SCHO) content significantly decreased over time in samples from the districts (from 2.4 to 1.2% by 7 months) and in samples from soil pits on campus (from 2.4 to 1.9% after 7 months and to 0.97% after 17 months). There was no significant change in the organic matter, CP and SCHO contents in samples taken from the cemented aboveground bin, cement- and dung-lined pits at the Alemaya campus, all of which were lined with polythene sheeting. From these data, we conclude that the combination of storage methods, storage period, geographic location and/or sorghum variety affected grain quality. Grain storage in traditional underground pits for long periods does lead to grain deterioration. The use of improved grain storage structures maintains the grain quality and nutritional value of sorghum for a reasonably long period.     

Influence of GaSe deposition temperature on the structural properties and in-depth compositional features of two-step grown Cu(In,Ga)Se2 thin films

In this study, Cu(In,Ga)Se₂ thin films were prepared by a classical two-stage growth process, which involved the selenization of thermally evaporated InSe/Cu/GaSe precursors. During the precursor-formation step the InSe and Cu were always deposited at 200 °C, while the GaSe layers were deposited at temperatures between 200 °C and 400 °C. The respective precursors were simultaneously selenized under identical conditions in elemental Se vapor. In cases where the GaSe layers were deposited at low temperatures around 200 °C, X-ray fluorescence (XRF) analysis revealed a large variation in element concentration with sample depth after selenization. In correspondence, X-ray diffraction (XRD) studies revealed the presence of separate CuInSe₂ and CuGaSe₂ phases in these specific samples. Optimum structural properties were obtained when the GaSe films were deposited at 300 °C, followed by selenization. In general, these films were uniform and dense and XRD studies revealed single-phase Cu(In,Ga)Se₂ material. Even more importantly, XRF analysis revealed a remarkable improvement in in-depth compositional uniformity when the GaSe films were deposited at or above 300 °C. An increase in GaSe deposition temperature to 400 °C, however, resulted in a deterioration in the structural features of the Cu(In,Ga)Se₂ thin films. In contradiction with other reports, these results indicated that the in-depth composition uniformity and especially the Ga diffusion profile in two-step grown Cu(In,Ga)Se₂ thin films can be controlled. The crucial factor influencing the depth profile of these films is the GaSe deposition temperature during the precursor formation step.     

Impregnation and Characterization of High Performance Extraction Columns for Separation of Metal Ions

Impregnation behaviors of reverse-phase silica materials and C18-silica HPLC columns were studied using di-(2-ethylhexyl)phosphoric acid (HDEHP) as a model extractant. Initially, the adsorption efficiency of the ligand on different types of bulk particles was investigated using various concentration of HDEHP in different composition of methanol/water mixtures based on a batch technique. Subsequently, impregnation of HPLC columns was performed using the dynamic flow-through technique. The experimental data fitted well to the Langmuir model and the adsorption isotherms from the flow-through experiment were used to prepare extraction columns of different ligand densities. Finally, the impregnated columns were characterized and validated through HPLC separation of the lanthanides.     

Direct observation of the spin-dependent Peltier effect

The Peltier coefficient describes the amount of heat that is carried by an electrical current when it passes through a material. When two materials with different Peltier coefficients are placed in contact with one another, the Peltier effect causes a net flow of heat either towards or away from the interface between them. Spintronics describes the transport of electric charge and spin angular momentum by separate spin-up and spin-down channels in a device. The observation that spin-up and spin-down charge transport channels are able to transport heat independently of each other has raised the possibility that spin currents could be used to heat or cool the interface between materials with different spin-dependent Peltier coefficients. Here, we report the direct observation of the heating and cooling of such an interface by a spin current. We demonstrate this spin-dependent Peltier effect in a spin-valve pillar structure that consists of two ferromagnetic layers separated by a non-ferromagnetic metal. Using a three-dimensional finite-element model, we extract spin-dependent Peltier coefficients in the range -0.9 to -1.3 mV for permalloy. The magnetic control of heat flow could prove useful for the cooling of nanoscale electronic components or devices.     

Identification of Host Blends that Attract the African Invasive Fruit Fly,Bactrocera invadens

Bactrocera invadens, an invasive fruit fly species in the Afro-tropical region belonging to the Bactrocera dorsalis complex, causes considerable damage to fruit production and productivity. We sought to find attractants from hosts of B. invadens that could serve as baits in traps for monitoring and management of this pest. The attractiveness of volatiles from four different fruit species (mango, guava, banana and orange) at two stages of ripeness (ripe or unripe) was tested in an olfactometer assay. All fruits were attractive against a clean air control. Using hexane extracts of volatile collections of fruits, we demonstrated that male flies preferred the volatiles of ripe guava and orange over unripe fruit extracts. There was a slight difference in preference between females and males; females preferred orange to guava and mango, whereas males preferred mango and guava to orange. Gas chromatography/electroantennographic detection (GC/EAD) and GC/mass spectrometry (GC/MS) were used to identify compounds to which B. invadens antennae were sensitive. GC/EAD recordings from distal and medio-central parts of the fly antenna showed responses to a number of compounds from each fruit species, with esters dominating the responses. Synthetic blends were made for each fruit species using the shared antennally active compounds in ratios found in the extracts. In the olfactometer, B. invadens was most attracted to the banana and orange blends, followed by the mango and guava blends. The synthetic banana blend was as attractive as the volatile collection of banana, although both were less attractive than the fruit. The results demonstrate that composing attractive blends from GC/EAD-active constituents shared by host fruits can be effective for formulating attractive synthetic host mimics for generalist fruit fly species, such as B. invadens.