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The conduction characteristics of SnF2 from room temperature (300 K) to 463 K have been investigated by using impedance spectroscopy. The temperature dependent conductivity plot shows a break in conductivity around 443 K corresponding to the ? ? ? phase transition temperature. The electrical properties of SnF2 are also investigated by extracting dielectric and modulus data from impedance values. The frequency dependent plots of M? and Z? show that the conductivity relaxation is non-Debye in nature. The activation energy responsible for relaxation has been calculated from the modulus spectra and is found to be almost the same as that from the temperature dependent dc conductivity data. The real part of conductivity and permittivity in addition to the modulus spectra of the present system show scaling behavior, which means ??(?), ??(?) and M?(?) isotherms successfully collapse to a single master curve indicating that the relaxation mechanism is temperature independent. Different scaling approaches have been applied to arrive at a correlation between the scaling parameters. � 2009 Elsevier B.V. All rights reserved.

Polycrystalline samples of BaSn1-xMnxO3 with x = 0, 0.01, 0.02, 0.03, 0.04 and 0.05 were prepared by solid state reaction method. Using the powder X-ray diffraction patterns, these samples were found to be free of secondary phases. The substitution of Mn for Sn is also evidenced by the gradual disappearance of the characteristic optical band gap absorption (at 3.1 eV) and disappearance of Raman modes (centered around 835�cm-1, 1157�cm-1 and 1473�cm-1) of the host BaSnO3 with increasing Mn-content. The field dependent magnetization data collected at 300 K show that the undoped BaSnO3 is diamagnetic; upon doping Mn, the diamagnetic character of BaSnO3 diminishes and the ferromagnetic character evolves gradually with increasing Mn-content. The presence of F-centers in the samples is witnessed by the electron spin resonance (ESR) spectrum and the first order Raman spectrum of BaSnO3. At room temperature, the electrical resistivity of Mn-doped BaSnO3 is of the order of 108�?�m. These results suggest that the ferromagnetism in these systems is due to F-center exchange interaction. The observed ferromagnetism in these samples is also supported by ESR spectra. � 2009 Elsevier Ltd. All rights reserved.

Al-based metal matrix composites consisting of pure Al reinforced with different amounts of mechanically alloyed Zr57Ti8Nb2.5Cu13.9Ni11.1Al7.5 glassy powder were produced by powder metallurgy, and their mechanical properties were investigated by room temperature compression tests. The samples were consolidated into highly dense bulk specimens at temperatures within the supercooled liquid region in order to take advantage of the viscous flow behavior of the glassy powder. Compression tests show that the addition of the glass reinforcement increases the strength of pure Al from 155 to 250 MPa, while retaining appreciable plastic deformation with a fracture strain ranging between 70% and 40%. The yield strength and the elastoplastic deformation of such composites containing a high volume fraction of glassy particles were accurately modeled using a shear lag model and a self-consistent effective medium approach. Finally, the fracture characteristics of the reinforcing particles were rationalized using a proposed fracture criterion. � 2009 Acta Materialia Inc.

Polycrystalline bulk samples of BaSn1-xFexO3, with x = 0.03, 0.04 and 0.05 were prepared by solid-state reaction method. These Fe-doped BaSnO3 systems exhibit ferromagnetism at room temperature with an average magnetic moment of 0.047, 0.038 and 0.025?B/Fe and Curie temperature of 510, 462 and 446 K, respectively. The observed magnetic properties are not attributed to any of the known impurity phases or clusters. The presence of ferromagnetic interaction at room temperature is supported by the ferromagnetic resonance (FMR) signals observed in the electron spin resonance spectra. The ferromagnetic order between Fe-ions is expected to be mediated by an electron trapped at the oxygen anion vacancy, called the F-centre exchange (FCE) interaction. � 2008 Elsevier B.V. All rights reserved.

Au and Au-Pt alloy nanoparticles are prepared and patterned at room temperature within the PMMA polymer matrix by the action of 254 nm UV light or X-rays. The polymer matrix enables us to entangle the kinetics of the photochemical reduction from the nucleation and growth processes, when monitored by UV-vis spectroscopy. Accordingly, increase of the temperature to 50 degrees C of the reaction medium increases the nucleation and growth rates of the nanoparticle formation by more than one order of magnitude, due to enhanced diffusion and nucleation at the higher temperature, but has no effect on the photochemical reduction process. Presence of Pt ions also increases the same rate, but by a factor two only. Similar photochemical reduction and particle growth take also place within the PMMA matrix, when these metal ions are subjected to prolonged exposure to X-rays, as evidenced by XPS analysis. Both angle-resolved and charge-contrast measurements using XPS reveal that the resultant Au and Pt species are in close proximity to each other, indicating the Au-Pt alloy formation to be the most likely case. (C) 2008 Elsevier Ltd. All rights reserved.

Design against fatigue requires thorough understanding of the underlying fatigue mechanisms and factors influencing them. The objective of the present work is to study the effect of nanoclay addition on the temperature rise and modulus drop during cyclic loading in polyamide-6 and polyamide-6 base nanocomposite. Isocyclic stress strain curves were used to understand the deformation characteristics of test materials. Polyamide-6 samples exhibited necking and continuous temperature rise until fracture at high stress levels investigated. Addition of nanoclay improved the modulus retention compared to pristine polymers. Nanocomposite samples sustained more than 105 cycles at all stress levels investigated. The performance improvement due to the addition of nanoclay is attributed to decrease in the cyclic strain amplitude at a given stress level which results in reduced hysteresis heating compared to polyamide-6. � 2008 Elsevier Ltd. All rights reserved.

Potassium p-nitrophenolate dihydrate, a potential semiorganic nonlinear optical material, has been synthesized and grown by slow evaporation technique at room temperature. Single crystal X-ray analysis presents an unprecedented bonding between ions in the crystal with acentric structure. In the new structural investigation, p-nitrophenolate instead of producing bond between phenolic O- and K+, it seems to put nitro group in bonding with the metal ion. Optical absorption shows excellent transmission in the entire visible and near-infrared region. Room temperature photocurrent, transport properties are carried out in order to enhance the application for second harmonic generation and opto-electronic devices. Dielectric constant is found to be independent at higher frequencies. The crystal possesses prominent positive photoconduction in the presence of photoactive centers formed with trap energy level. The nonlinear optical activity is confirmed by Kurtz powder test. � 2008 Elsevier Ltd. All rights reserved.

Dry sliding wear behavior of 8090Al alloy and its composites reinforced with 8, 12 and 18 vol% SiC particles was studied in as-extruded and peak-aged conditions using a pin-on-disc machine. Tests were done at room temperature in air under loads of 10, 20 and 50 N at a constant sliding speed of 1 m s-1. The unreinforced alloy and composites show mild wear upto 20 N. Transition from mild to severe wear takes place beyond 20 N. Composites exhibit better wear resistance compared to the unreinforced alloy in as-extruded condition. Effect of heat treatment (artificial ageing) on wear behavior has also been studied. The unreinforced alloy exhibits better wear resistance at all the three loads used here in peak-aged condition compared to the as-extruded condition. Composites on the other hand, show better wear resistance upto 20 N, however, they show lower wear resistance in peak-aged condition compared to as-extruded condition beyond 20 N. This can be attributed to higher surface and subsurface deformation in peak-aged condition at higher load. � 2008 Elsevier B.V. All rights reserved.

The electrochromic and photocatalytic properties of vanadium-doped tungsten trioxide thin films prepared at room temperature (300 K) by the electron beam evaporation technique are reported in this paper. The vanadium to tungsten ratio (V/W) in these films are 0.003, 0.019, 0.029 and 0.047. The optical band gap of the vanadium-doped tungsten oxide (WO3) thin film initially increases from 3.16 to 3.28 eV for V/W ratio 0.003 then decreases to 3.15 eV for V/W ratio 0.047. These vanadium-doped films switch between neutral gray and transparent states. The coloration efficiency (CE) decreases from 82 cm2 C-1 (pure WO3) to 27 cm2 C-1 for the film containing V/W ratio 0.047. The photocatalytic activity has enhanced with vanadium doping and maximum activity of 15% (percentage change in optical density of methylene blue due to photo degradation) has been observed for the film containing V/W ratio of 0.019. The Kelvin probe measurements show that the work function of pure WO3 films is 4.07 eV and vanadium doping initially increases the work function to 4.19 eV for V/W ratio 0.019 and then decreases it to 3.97 eV for film with V/W ratio 0.047. � 2008 Elsevier B.V. All rights reserved.

A series of meso-tetraarylporphyrins bearing electron-donor or electron-withdrawing substituents at the meso-phenyl groups were examined for antipodal ?-pyrrole tetrabromination using different brominating agents. Porphyrins bearing electron-donor substituents undergo bromination at moderate temperatures with N-bromosuccinimide as the brominating agent while the electron-deficient porphyrins require Hq. Br2 at room temperature. The brominated porphyrins were isolated in moderate to very good yields. Synthesized compounds were characterized by electronic absorption, 1HNMR, and mass spectroscopic methods. Regioselectivity of an electron-deficient porphyrin, 2,3,12,13-tetrabromo-5,10,15,20-tetrakis(4- methoxycarbonylphenyl)porphyrin was examined by single-crystal X-ray structure analysis and showed antipodal ?-pyrrole bromo substitution. � 2008 The Chemical Society of Japan.

Al-Li-SiCp composites were fabricated by a simple and cost effective stir casting technique. A compound billet technique has been developed to overcome the problems encountered during hot extrusion of these composites. After successful fabrication hardness measurement and room temperature compressive test were carried out on 8090 Al and its composites reinforced with 8, 12 and 18 vol.% SiC particles in as extruded and peak aged conditions. The addition of SiC increases the hardness. 0.2% proof stress and compressive strength of Al-Li-8%SiC and Al-Li-12%SiC composites are higher than the unreinforced alloy. In case of the Al-Li-18%SiC composite, the 0.2% proof stress and compressive strength were higher than the unreinforced alloy but lower than those of Al-Li-8%SiC and Al-Li-12%SiC composites. This is attributed to clustering of particles and poor interfacial bonding. � 2008 Elsevier B.V. All rights reserved.

cited By 24; International audience; Supported molybdenum-sulfide nanoparticles are known catalysts for petroleum hydrodesulfurization as well as for electrochemical hydrogen evolution. In this study, we investigate molybdenum-sulfide nanoparticles supported on Au(1 1 1) using X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM), aiming to correlate spectroscopically determined chemical states with atomically resolved nanostructure. The results of this study allow us to conclude the following: (1) the XPS results from our model system are in good agreement with previously published results on supported MoS2 for industrial applications, validating in part the fidelity of the model system; (2) STM reveals that catalytically active, crystalline MoS2 nanoparticles exhibiting the well-known metallic edge state are only present after a post-deposition annealing step in the synthesis procedure, without which the particles exhibit amorphous shapes and incomplete sulfidation; and (3) the sulfided nanoparticles are found to be stable in air at room temperature. © 2009 Elsevier B.V. All rights reserved.

Key properties of organic coatings, such as mechanical strength and solvent resistance, are greatly influenced by the structure of the polymeric binder. In general, a 3-dimensional polymeric network gives the best properties and therefore most performance coatings have a 3-dimensional network structure. However, 3-dimensional networks cannot easily be repaired. Through molecular design in combination with different synthetic routes, a series of new building blocks has been prepared that render conventional coating types thermally remendable. Damage can be repaired through thermally reversible cross-linking of the coating through reversible bond scission within these specially designed building blocks. At room temperature, a fully cross-linked network is present, whereas at elevated temperatures the cross-link density becomes much lower and the system becomes mouldable or low viscous. This self-healing concept was proven by various techniques. Both the thermal reversibility window and the final coating properties can be tuned by careful design of the system. © 2008 Elsevier B.V. All rights reserved.

The effect of Mo substitution at Ti site of orthorhombic Sm5 Ge4 -type R2 Ti3 Ge4 compounds on the magnetic and electrical transport properties has been studied. The Tb2 Ti3-x Mox Ge4 (x=0.3,0.75) and Er2 Ti2.7 Mo0.3 Ge4 compounds have been synthesized and it is found that these compounds retain parent crystal structure at room temperature (space group Pnma, No. 62). Mo substitution decreases the antiferromagnetic ordering temperature (TN) of Tb2 Ti3 Ge4 compound from ?18 to ?13 and ?10 K, respectively, for x=0.3 and 0.75. The Er2 Ti2.7 Mo0.3 Ge4 compound shows a tendency to order at ?2 K, whereas the parent Er2 Ti3 Ge4 is magnetically ordered at 3 K. Magnetization versus field data of Tb2 Ti3-x Mox Ge4 (x=0.3,0.75) reveal soft ferromagnetic nature. The metamagnetic transition that is present in parent Tb2 Ti3 Ge4 is found to disappear with Mo substitution. Magnetization value reaches ?6.2 ?B / Tb3+ at 2 K in fields of 8 T, indicating incomplete ferromagnetic ordering with or without an antiferromagnetic component. Electrical resistivity of the Tb-based compounds has a linear variation with temperature from 300 to ?50 K and shows a prominent slope change at temperatures much above TN, supporting the presence of competing short range ferromagnetic interactions. � 2009 American Institute of Physics.

It has been shown that the annealing of cold-worked 03Kh14GNF steel is accompanied by several strengthening and softening processes that take place in different temperature intervals. Therefore, the temperature dependence of its hardness has a complicated form; i.e., it contains several maxima and minima. The following processes should be noted: recovery and recrystallization of δ ferrite, precipitation of M 2(CN) carbonitrides and M 23C6 carbides from the α martensite, their dissolution in the γ phase, the formation of austenite with different stability, polygonization of the α martensite, etc. Tempering for 30 h can produce the level of mechanical properties required according to technical specifications for two processing regimes. These regimes are the annealing at 680°C and at 600°C, but in the second case the high plasticity is probably caused by the formation of a highly stable austenite that is retained down to room temperature. However, the degree of plasticity of this γ phase at room and lower temperatures is unknown. After annealing at 660°C, the steel does not achieve the level of ultimate strength of 480 N/mm2, which is required by the technical specifications. However, since the relative elongation of 35% exceeds the required magnitude, the required level of mechanical properties can apparently be produced by a decrease in the duration of annealing to 20–25 h.

Solvent-induced aggregation and its effect on the intrinsic emission properties of amine, hydroxy and carboxylate terminated, poly(amidoamine) (PAMAM) dendrimers have been investigated in glycerol, ethylene glycol, methanol, ethylene diamine and water. Altering the solvent medium induces remarkable changes in the intrinsic emission properties of the PAMAM dendrimers at identical concentration. Upon excitation at 370 nm, amine terminated PAMAM dendrimer exhibits an intense emission at 470 nm in glycerol, ethylene glycol as well as glycerol-water mixtures. Conversely, weak luminescence is observed for hydroxy and carboxylate terminated PAMAM dendrimers in the same solvent systems. When the solvent is changed to ethylene diamine, hydroxy terminated PAMAM exhibits intense blue emission at 425 nm. While the emission intensity is varied when the solvent milieu is changed, excited state lifetime values of PAMAM dendrimers remain independent of the solvent used. UV-visible absorption and dynamic light scattering (DLS) experiments confirm the formation of solvent-controlled dendrimer aggregates in the systems. Comparison of the fluorescence and DLS data reveals that the size distribution of the dendrimer aggregates in each solvent system is distinct, which control the intrinsic emission intensity from PAMAM dendrimers. The experimental results suggest that intrinsic emission intensity from PAMAM dendrimers can be regulated by proper selection of solvents at neutral conditions and room temperature. � 2008 Elsevier B.V. All rights reserved.

Key properties of organic coatings, such as mechanical strength and solvent resistance, are greatly influenced by the structure of the polymeric binder. In general, a 3-dimensional polymeric network gives the best properties and therefore most performance coatings have a 3-dimensional network structure. However, 3-dimensional networks cannot easily be repaired. Through molecular design in combination with different synthetic routes, a series of new building blocks has been prepared that render conventional coating types thermally remendable. Damage can be repaired through thermally reversible cross-linking of the coating through reversible bond scission within these specially designed building blocks. At room temperature, a fully cross-linked network is present, whereas at elevated temperatures the cross-link density becomes much lower and the system becomes mouldable or low viscous. This self-healing concept was proven by various techniques. Both the thermal reversibility window and the final coating properties can be tuned by careful design of the system. © 2008 Elsevier B.V. All rights reserved.

Thermopower measurements in a range of 300-650 K along with room temperature optical absorption and electrical resistivity studies were performed on indium oxide (IO) and indium tin oxide (ITO) thin films grown by reactive dc sputtering. The thermopower of as-grown and oxygen-annealed IO and ITO films measured in Ar ambient displayed characteristics attributable to oxygen loss. The observations were substantiated with optical absorption and electrical resistivity results. � 2009 IOP Publishing Ltd.

Mischmetal (Mm) nickel (Ni) alloys with different aluminium (Al) contents are tested for hydrogen storage characteristics under dynamic operating conditions. The compositions considered are MmNi5, MmNi4.7Al0.3, MmNi4.5Al0.5, MmNi4.2Al0.8 and MmNi4Al. Pressure concentration isotherms (PCI), plateau slopes and absorption rates are measured. Activation energies are calculated by fitting Arrhenius equation to the absorption data. As expected, the plateau pressure of MmNi5 decreased with increase in Al content. Apparent reaction enthalpy values (as distinct from enthalpy of formation calculated from static measurements), plateau slope, and activation energies increased, and absorption rate decreased with increase in Al content. The study confirms MmNi4.5Al0.5 as a preferred candidate for reversible hydrogen storage at room temperature with nominal supply pressure and fast kinetics. � 2008 Elsevier B.V. All rights reserved.

The effect of ambient and cryogenic temperature rolling on the microstructure, aging and wear behaviour of Al-4Cu-5TiB2 in situ composite was studied. The results indicate significant increase in aging kinetics and improvement in hardness and wear resistance of the cryo-rolled and room temperature rolled composite in comparison with as-cast composite. � 2009 Elsevier B.V. All rights reserved.

La 0.67 Ca 0.33 MnO 3 doped with different amounts of V, resulting in the series La 0.67 Ca 0.33 Mn 1− x V x O 3 [ x = 0.03, 0.06, 0.1, 0.15, 0.25, 0.5] was synthesized by conventional solid-state ceramics route. Heat treatment conditions during synthesis were optimized to have small changes in the Curie temperature ( T C ). The compounds with x > 0.06 were found to have the additional LaVO 4 phase. A quantitative analysis of the extra phase with increase in V doping was investigated by the Rietveld refinement of the X-ray diffraction patterns. Variation of magnetic and magnetocaloric properties at different temperatures and magnetic fields was studied. Magnetocaloric effect has been studied in terms of isothermal magnetic entropy change (Δ S M ). Magnetization was found to change drastically at around 275 K and the isothermal magnetic entropy change was found to peak in the temperature range 265–275 K. With increase in V content, Δ S M initially shows a considerable increase and then a decrease at higher V concentrations.

Ball milling was employed to produce Zr65Ag5Cu12.5Ni10Al7.5 glassy powder from pre-alloyed mixtures of crystalline intermetallic compounds. Differential scanning calorimetry (DSC) in isochronal as well as in isothermal modes was used to study the thermal stability and the crystallization kinetics of the glassy powder. The activation energy for crystallization was calculated using isothermal and isochronal DSC data as well as from viscosity measurements, which lead to values of the activation energy ranging between 298 and 314 kJ/mol. Johnson-Mehl-Avrami analysis shows that the transformation is a diffusion controlled three-dimensional process and the crystallization proceeds with increasing nucleation rate at annealing temperatures within the super-cooled liquid region. To test the effectiveness of the glassy powder as reinforcement in Al-based metal matrix composites, bulk specimens consisting of pure Al powder blended with 50 vol.% of Zr65Ag5Cu12.5Ni10Al7.5 glassy powder were synthesized by powder metallurgy. Room temperature compression tests reveal that the strength increases from 155 MPa for pure Al to 235 MPa for the composite with 50 vol.% of glass reinforcement. � 2009 Elsevier B.V. All rights reserved.

Ultrafine grained (ufg) and nanocrystalline (nc) materials are widely researched due to significant improvements in yield and fracture strength. However, achieving a reasonable ductility in these materials is still a challenge. Recent results have shown that the combination of high strength and ductility could be achieved in precipitation hardening alloys through severe plastic deformation followed by annealing/ageing treatments. In the present work, the solutionised plates of an Al-Mg-Si alloy (modified AA6061 alloy) were subjected to severe cold rolling at room and liquid nitrogen temperatures to a true strain ?1.6. The rolled sheets were aged to induce precipitation. The equilibrium second phase distribution for the above alloy was calculated using CALPHAD. The rolled and aged samples were analysed using differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), hardness and tensile tests. The stored energy obtained from DSC measurements was found to be independent of the rolling temperature. The volume fraction of S {1 2 3} ?6 3 4? orientation is predominant (?40%) in both the rolling conditions. The strength and ductility were simultaneously improved following ageing of the cryorolled (CR) and room temperature rolled (RT) samples. Transmission electron microscopy analysis revealed dislocation cell structures in the CR and RT conditions. Analysis of second phases revealed fine spherical Mn rich precipitates (most likely Al6Mn) following ageing. � 2009 Elsevier B.V. All rights reserved.

Spectroscopic techniques such as 29Si MAS-NMR, M�ssbauer, magnetic susceptibility, EPR and microwave variation EPR studies were used in order to study the location, coordination, oxidation state and stability of trivalent in FeMCM-41. 29Si MAS-NMR studies revealed that paramagnetic Fe(III) is present in the direct vicinity of [SiO4] tetrahedral and therefore results in broadening of spectral lines. Absence of side spinning bands are attributed to the uniform dispersion of FexOy within the matrix. Observed isomer shift value of

We studied film formation of composites of surfactant-free polystyrene (PS) nanoparticles and modified Na-activated bentonite (MLB), by steady state fluorescence (SSF) technique. The films were prepared from a mixture of pyrene (P)-labeled PS particles and MLB at various compositions at room temperature. These films were annealed at elevated temperatures above the glass transition ( T g ) temperature of polystyrene for 10 min. Scattered light ( I s ) and fluorescence intensities ( I P ) from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of the composite films was monitored by using photon transmission intensity, I tr . Atomic force microscopy (AFM) was used to detect the variation in physical structure of annealed composite films. The nanocomposite films exhibited a percolation threshold at 20 wt.% MLB content. Below this fraction two distinct film formation stages were observed which are known as void closure and interdiffusion and above this fraction no film formation was detected. At 0–20 wt.% MLB, minimum film formation, T 0 , void closure, T v and healing, T h temperatures were determined. Void closure and interdiffusion stages were modeled and related activation energies were determined. Void closure activation energies decreased as the percent of MLB increased, no variation was observed in backbone activation energies.

Structural complexity inherited from a microbial synthesis of glycolipids was translated into unique poly(sophorolipid) biomaterials. ROMP polymerization of natural diacetylated lactonic sophorolipids gave a high molecular weight polymer with asymmetric bola-amphiphilic repeating units. The poly(sophorolipid) chain alternates C18 oleic-like aliphatic segments (90% cis-configured double bonds) with bulky diacetylated disaccharide moieties. The solid-state properties were investigated by means of TGA, DSC, TMDSC, and variable-temperature X-ray diffraction. The poly(sophorolipid) is a solid at room temperature that undergoes the glass transition at 61 degrees C and melts at 123 degrees C. The crystal phase is associated with ordered packing of the aliphatic chain segments. The semicrystalline poly(sophorolipid) also displays a long-range order (d = 2.44 nm) involving sophorose groups that is found to persist after crystal phase melting (in high-T diffractograms) with a slightly shortened distance (2.27 nm). Upon annealing at 80 degrees C the poly(sophorolipid) recrystallizes and concomitantly the disaccharide units space out again at 2.44nm. An exothermal phenomenon that immediately follows melting and is revealed by TMDSC might be associated with the observed adjustment of sophorose units spacing in the melt. The peculiar structural organization of this novel biomaterial is discussed.

In this work, we have employed spectroscopic ellipsometry technique to study the optical properties of polymer/carbon nanotube (CN) composites as a function of nanotube concentration. Using a two-layer structural model based on Airy rigorous equations, the optical constants in various CN concentrations have been extracted. In the optical absorption spectra, we have observed a tuning of the excitonic transitions with the addition of single wall CN concentration. Based on theoretical calculations for the interaction of CNs with the surrounding effective media, the spectral evolution of the binding energy of optically active excitonic transitions with the addition of CNs suggests that the effective dielectric function of surrounding media decreases. Furthermore, using an oscillator Lorentz model, the absorption peaks, oscillator strengths and energy broadenings of the excitonic transitions have been extracted. © 2008 Elsevier B.V. All rights reserved. 17 7-10 1600 1603

The results of a study of the magnetic, NGR and other parameters of EuO:Fe composites, which really meet the requirements imposed on the use of them as spin injectors in the developed semiconductor spin-electronic structures capable of operating under normal conditions at room temperatures, are reported. The manifestation of superparamagnetism in these composites is established. Copyright © 2008 American Scientific Publishers. All rights reserved.

The objective of this research was to develop control solutions for building services systems and total building energy management methods as well as to demonstrate some new solutions in a real building. The main focus was in residential buildings but many of the results can also be applied to non-domestic buildings. The subtasks of the research dealt with intelligent systems in building energy management in general, control of air-conditioning, heating and lighting, building total energy management and demonstration of the results. Ten new control and energy management solutions were developed. In addition, other theoretical and experimental examinations as well as general inspections were made. First it was found out how learning and intelligent methods have been used in controlling building services and in building energy management. Also the usage of intelligent systems in tuning of controllers was studied. A fuzzy logic based automatic tuner for a PI controller of a heating coil was developed within the project. Effects of the properties of a fuzzy controller on the control result were examined using a simple system. It was found out that the membership functions need to cover the examined area widely enough. In the project, control of water circulated heating was examined. A method was developed that automatically forms a compensation curve between outdoor air temperature and either supply water temperature or supply water pressure. Simulations showed that the curve is found quickly and that average room temperatures stay close to the setpoint. The method developed is simple and it requires only little computation power and memory. If this method would be implemented into all suitable residential buildings in Finland, this would save about 830 GWh of heating energy, about 40 GWh of electrical energy and about 4 million € in maintenance costs annually. The return water of a radiator network can be used as a main energy source for heating coils of air-handling units when the supply air temperature setpoint is kept close to room temperature. In the project, an intelligent and learning room temperature control algorithm was developed for a constant air volume system and was developed further for a variable air volume system. The algorithm suits especially buildings/apartments that are used periodically. The operation of the algorithm was tested in simulations and in experimental tests in a real building. According to the simulations, up to a fifth of both the heating energy and the electricity consumption of fans can be saved in residential buildings during winter. The energy consumption decreases because by using the developed algorithm the room air temperature can be dropped from its normal value and the air flow rate can be reduced when there is nobody present. The temperature can again be raised to its normal level and the building ventilated before somebody returns to the building. The algorithm is able to adapt to the thermodynamics of the building and to learn the time required for the temperature increase. The occupant can prioritize maximum energy saving or comfort by using a control switch accordingly. The algorithm was tested in a low-energy building where the energy consumption is much lower than in a normal modern building. In a tight and well-insulated building the temperature changes are slow, hence the smaller savings. However, even in the lowenergy building the algorithm reduced the already low energy consumption. In addition, an implementation solution of the intelligent indoor control algorithm for a big office complex was made. Also the equivalent Java code was programmed. The optimisation of the energy management of a ventilation system during operation was examined using a mathematical optimisation method. Linear programming was applied in an air heated system for a comfort oriented as well as a cost oriented case. In the cost oriented case, the method clearly favoured heating by increasing the air flow. The method worked well. It was also studied how to implement an automated ventilation control method in a residential building with centralized exhaust ventilation or with separate supply and exhaust ventilation in each apartment. If the air flows in each room can be controlled with control dampers, the method enables the ventilation to be steered into the rooms where it is needed the most. Based on the study, a practically workable control solution was presented. Issues related to integrated control of artificial light and daylight were studied. In addition, a fuzzy logic based algorithm for integrated control of natural daylight and blinds combined was developed. Simulation results in different daylight conditions showed that the controller worked satisfactorily. A total energy management problem was discussed. The total energy management concept was dealt with using a case study. In addition, properties of an intelligent system integration were clarified. It is essential that the intelligent system integration means more than just an open data transfer. Depending on the case, energy savings of about 10.40% can be reached by using intelligent system integration. Using real measurements, factors affecting the total energy consumption of a residential building were examined to be used in a neural network or a fuzzy logic model predicting the energy need. A linear regression model was formed to predict the power consumption. Relatively good predictions for heating powers were easy to calculate even with a simple linear model. Reliable information on occupancy is needed in advanced control of building services systems. Hints can be received for example from occupancy sensors, by monitoring water or electricity consumption or carbon dioxide concentration, or by a combination of the previous. Security systems are likely to convey the most reliable information in this respect.

An energy cost allocation system records the energy consumption of a building and divides the overall energy costs between the flats. Because the indoor temperatures of rooms are usually not equal, static heat flows between flats cannot be avoided. Hence, in order to ensure fair energy costs per flat the system should be able to determine the static heat flows, preferably without utilising design data or in-situ measurements. This paper presents a new method for estimating static heat flows between neighbouring rooms. It also outlines the instrumentation and technical properties of the energy allocation system (EAS), needed in implementation. The approach is strictly technical, focusing only on heat transfer issues. Energy cost allocation is not considered. The approach is based on the proposed control techniques and the ARMAX-model describing dynamic behaviour of heating power. The model is created for each room/flat of a building. Parameter values are identified using real-time measurements collected from each room/flat and its environment. Only ordinary instrumentation is required. The tuning of parameters takes a few days using a fifteen-minute sampling time. A prerequisite for successful estimation is the overall control and the precise adjustment of the room temperatures at specified level. This is accomplished by the suggested set point control. All test runs are performed in a simulated office hotel using the TRNSYS simulation program. Realistic inner and outer heating loads, and their daily schedules and variations are included. The results are encouraging, but further research is needed, especially in a real building environment.

The objective of this research was to develop control solutions for building services systems and total building energy management methods as well as to demonstrate some new solutions in a real building. The main focus was in residential buildings but many of the results can also be applied to non-domestic buildings. The subtasks of the research dealt with intelligent systems in building energy management in general, control of air-conditioning, heating and lighting, building total energy management and demonstration of the results. Ten new control and energy management solutions were developed. In addition, other theoretical and experimental examinations as well as general inspections were made. First it was found out how learning and intelligent methods have been used in controlling building services and in building energy management. Also the usage of intelligent systems in tuning of controllers was studied. A fuzzy logic based automatic tuner for a PI controller of a heating coil was developed within the project. Effects of the properties of a fuzzy controller on the control result were examined using a simple system. It was found out that the membership functions need to cover the examined area widely enough. In the project, control of water circulated heating was examined. A method was developed that automatically forms a compensation curve between outdoor air temperature and either supply water temperature or supply water pressure. Simulations showed that the curve is found quickly and that average room temperatures stay close to the setpoint. The method developed is simple and it requires only little computation power and memory. If this method would be implemented into all suitable residential buildings in Finland, this would save about 830 GWh of heating energy, about 40 GWh of electrical energy and about 4 million € in maintenance costs annually. The return water of a radiator network can be used as a main energy source for heating coils of air-handling units when the supply air temperature setpoint is kept close to room temperature. In the project, an intelligent and learning room temperature control algorithm was developed for a constant air volume system and was developed further for a variable air volume system. The algorithm suits especially buildings/apartments that are used periodically. The operation of the algorithm was tested in simulations and in experimental tests in a real building. According to the simulations, up to a fifth of both the heating energy and the electricity consumption of fans can be saved in residential buildings during winter. The energy consumption decreases because by using the developed algorithm the room air temperature can be dropped from its normal value and the air flow rate can be reduced when there is nobody present. The temperature can again be raised to its normal level and the building ventilated before somebody returns to the building. The algorithm is able to adapt to the thermodynamics of the building and to learn the time required for the temperature increase. The occupant can prioritize maximum energy saving or comfort by using a control switch accordingly. The algorithm was tested in a low-energy building where the energy consumption is much lower than in a normal modern building. In a tight and well-insulated building the temperature changes are slow, hence the smaller savings. However, even in the lowenergy building the algorithm reduced the already low energy consumption. In addition, an implementation solution of the intelligent indoor control algorithm for a big office complex was made. Also the equivalent Java code was programmed. The optimisation of the energy management of a ventilation system during operation was examined using a mathematical optimisation method. Linear programming was applied in an air heated system for a comfort oriented as well as a cost oriented case. In the cost oriented case, the method clearly favoured heating by increasing the air flow. The method worked well. It was also studied how to implement an automated ventilation control method in a residential building with centralized exhaust ventilation or with separate supply and exhaust ventilation in each apartment. If the air flows in each room can be controlled with control dampers, the method enables the ventilation to be steered into the rooms where it is needed the most. Based on the study, a practically workable control solution was presented. Issues related to integrated control of artificial light and daylight were studied. In addition, a fuzzy logic based algorithm for integrated control of natural daylight and blinds combined was developed. Simulation results in different daylight conditions showed that the controller worked satisfactorily. A total energy management problem was discussed. The total energy management concept was dealt with using a case study. In addition, properties of an intelligent system integration were clarified. It is essential that the intelligent system integration means more than just an open data transfer. Depending on the case, energy savings of about 10.40% can be reached by using intelligent system integration. Using real measurements, factors affecting the total energy consumption of a residential building were examined to be used in a neural network or a fuzzy logic model predicting the energy need. A linear regression model was formed to predict the power consumption. Relatively good predictions for heating powers were easy to calculate even with a simple linear model. Reliable information on occupancy is needed in advanced control of building services systems. Hints can be received for example from occupancy sensors, by monitoring water or electricity consumption or carbon dioxide concentration, or by a combination of the previous. Security systems are likely to convey the most reliable information in this respect.

Magnetic, magnetoresistive, and magnetocaloric properties of a novel double perovskite oxide, namely, LaCaMnCo O6 have been studied. Polycrystalline sample of LaCaMnCo O6 has been synthesized by sol-gel technique. It has cubic crystal structure (space group Fm 3- m) at room temperature. The temperature variation in magnetization reveals a steep increase in magnetization around 168 K (TC). The magnetization does not even saturate at 5 K and a magnetic moment of 0.7 ?B f.u. is obtained at 5 K in an applied field of 50 kOe. The electrical resistivity measurement indicates that the material is semiconducting-like in the temperature range of ?300-50 K and below ?50 K the sample becomes insulating. A maximum magnetoresistance (MR) of about 8% is found at 200 K in an applied field of 7 T and MR has a negative sign. The magnetocaloric effect is calculated from the magnetization versus temperature data and a maximum magnetic entropy change of 3.1 Jkg K for a field change of 11 kOe is obtained near TC. Thus a moderate magnetocaloric effect is achieved in rather low magnetic fields. � 2009 American Institute of Physics.

Indium nitride films have been grown using modified activated reactive evaporation (MARE). The films were grown on glass and silicon substrates at room temperatures, i.e. without any intentional substrate heating. In this technique, the substrates were kept on the cathode instead of the grounded electrode and hence subjected to low energy nitrogen ion bombardment leading to highly c-axis oriented films. The photoluminescence (PL) and Raman spectrum shows significant improvement in the quality of the films compared with conventional activated reactive evaporation. The band gap measured from the room temperature PL was found to be 1.9 eV. Very high growth rates can be achieved in the MARE growth technique. The modification in the activated reactive evaporation technique may have a large impact on the growth of various compounds such as metal oxides. � 2008 IOP Publishing Ltd.

An energy cost allocation system records the energy consumption of a building and divides the overall energy costs between the flats. Because the indoor temperatures of rooms are usually not equal, static heat flows between flats cannot be avoided. Hence, in order to ensure fair energy costs per flat the system should be able to determine the static heat flows, preferably without utilising design data or in-situ measurements. This paper presents a new method for estimating static heat flows between neighbouring rooms. It also outlines the instrumentation and technical properties of the energy allocation system (EAS), needed in implementation. The approach is strictly technical, focusing only on heat transfer issues. Energy cost allocation is not considered. The approach is based on the proposed control techniques and the ARMAX-model describing dynamic behaviour of heating power. The model is created for each room/flat of a building. Parameter values are identified using real-time measurements collected from each room/flat and its environment. Only ordinary instrumentation is required. The tuning of parameters takes a few days using a fifteen-minute sampling time. A prerequisite for successful estimation is the overall control and the precise adjustment of the room temperatures at specified level. This is accomplished by the suggested set point control. All test runs are performed in a simulated office hotel using the TRNSYS simulation program. Realistic inner and outer heating loads, and their daily schedules and variations are included. The results are encouraging, but further research is needed, especially in a real building environment.