Thermal Properties

Tungsten oxides are of interest as an oxidant for metals in metastable intermolecular composites (MICs), a reactive nanoscale powder useful for such applications as electric matches and gun primers. Smaller particles typically lead to fast reaction rates in this class of energetic material, and we have synthesized nanoscale WO3∙H2O using wet chemistry. Analysis by electron microscopy and small angle x-ray scattering revealed an approximately 100-nm-wide by7-nm-thick platelet morphology. X-ray diffraction verified the orthorhombic structure and composition of the hydrate. A MIC material was formulated using 44nm Al as the fuel. Performance was measured using a pressure cell where total enthalpy change and energy release rate was measured. This report includes the thermodynamic analysis of the pressure cell (calorimetry) that allows the determination of these metrics. Accuracy of the technique is discussed. Performance of the hydrate was found to significantly exceed that of MIC formu...

Lysimeters are often used in turfgrass and plant water-use studies; however, no detailed description exists for a lysimeter system of moderate volume allowing for rapid, direct measurement of evapotranspiration on a number of replicates. A lysimeter was developed using 250-mm diameter and 330-mm long polyvinvyl chloride piping resulting in a lysimeter volume of 15.5 L. These lysimeters were installed in the fi eld by constructing a plastic soil-retention sleeve that was placed in the soil. The sleeve was matched to the lysimeter diameter so that there was only a 6-mm air gap between the lysimeter and the sleeve. After turf had fi lled in around lysimeter edges, there was no detectable difference in measured soil temperatures between lysimeters and surrounding plots at the 15-cm depth; however, volumetric soil moisture content of lysimeters was ~3% higher than that of surrounding soil. The lysimeter was weighed in the fi eld by positioning a tripod hoist over the lysimeter. A load cell was installed in the hoist cable assembly so that when the lysimeter was lifted free of the soil-retention sleeve the weight of the lysimeter could be recorded. The system was shown to provide highly reproducible weight measurement data based on paired t-test analysis of repeated weighing data.

This paper addresses issues that are important to high quality flexographic printing of linerboard. The research includes a comparison of an objective measure of print quality to a subjective measure. The paper also identifies sheet properties that lead to improved print quality and the papermaking process variables that contribute to the development of those properties. An excellent correlation was obtained between subjective and objective measures of Print quality. Hence, simple, readily available, cost-effective image analysis software and hardware may be used. The work also shows that print mottle is the overriding factor influencing perceived print quality. By correlating sheet properties to print quality, a number of sheet physical properties that contribute to good printing were isolated. Those properties include L*a*b* color, Gurley air permeability, and to a lesser extent freeness and micro roughness. Additionally, it was observed that printing press clearance (loading) can have a major impact on print quality. By correlating sheet physical properties to papermaking process variables, it was determined that method of pressing, press impulse, calendering, and freeness impact these important sheet physical properties.

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

The specific heat of multiwalled titanium dioxide (anatase phase) nanotubes has been measured between 1.5 and 95K. Bulk anatase and rutile were also measured. The nanotube specific heat approaches that of bulk anatase at high temperatures. Below about 50K the nanotube specific heat begins to show large enhancements compared to bulk. Using an isotropic elastic continuum model, this can be understood qualitatively as a transition to low-dimensional behavior. Below about 3K there is a second transition and the nanotube specific heat becomes nearly constant, exceeding bulk anatase by an order of magnitude or more at 1.5K.

The Yb-content Li 6 Ln(BO 3) 3 (Ln: Gd, Y) solid solution has been investigated. Crystal growth has been successful for several compositions. A 22% molar content of ytterbium ions was determined by chemical analysis (ICP). Physical properties relevant to laser operation like mechanical hardness, thermal expansion and thermal conductivity were measured on single crystals. Optical measurements, including refractive index and low temperature spectroscopy, were also performed. Finally, the effect of the Y/Gd ratio is discussed.

The possibility of quantum computation using non-Abelian anyons has been considered for over a decade. However the question of how to obtain and process information about what errors have occurred in order to negate their effects has not yet been considered. This is in stark contrast with quantum computation proposals for Abelian anyons, for which decoding algorithms have been tailor-made for many topological error-correcting codes and error models. Here we address this issue by considering the properties of non-Abelian error correction in general. We also choose a specific anyon model and error model to probe the problem in more detail. The anyon model is the charge submodel of D(S3). This shares many properties with important models such as the Fibonacci anyons, making our method applicable in general. The error model is a straightforward generalization of those used in the case of Abelian anyons for initial benchmarking of error correction methods. It is found that error correction is possible under a threshold value of 7% for the total probability of an error on each physical spin. This is remarkably comparable with the thresholds for Abelian models.

Thermal conductivity of the improper ferroic Tb 2 (MoO 4) 3 was measured in the range 0.3 K-100 K by the method of the stationary heat flow. An additional maximum in thermal conductivity observed at 0.45 K is due to the anomaly of specific heat corresponding to the antiferromagnetic phase transition.

A low-cost, black nickel solar absorber coating, to be used in thermal solar collectors on nanostructured highly thermal conductor copper, was analyzed using the thermoanalytical flash method at 293 K and Cernuschi's two-layer models, to identify the thermal properties of the blackening layers and the energy losses connecting different parameters such as the chemical composition, diffusivity, conductivity, and emittance. The Cernuschi's modelling presents a good approximation of the experimental results. The black nickel layer has low thermal losses, an estimated specific heat of 390 J/(kg K), a thermal conductivity of 105.1 W/(m K) and a thermal diffusivity of 39.4 Â 10 26 m 2 /s. The black nickel layer has low optical losses and an emittance of 0.09 (293 K), but its thermal stability ends at 473 K, indicating that black nickel above 473 K is not stable and a structure change may occur. Chemical analysis shows that nanostructured black nickel is a cermet mainly composed of two metallic nickel atoms for each nickel and zinc sulphide, i.e. 2 Ni 0 : NiS: ZnS.

White dent corn was nixtamalized in a Ca(OH) 2 [1.2% (w/v)] solution, at a 1:3 corn/water ratio, at 70, 80, 90 and 100°C for 1 h, with and without mechanical agitation. After cooking the nixtamalized grains were steeped for 48 h. During cooking, kinetics of soluble and suspended solids and total sugar were determined, while that in the grain was determined the pericarp removed. During steeping, water and calcium absorption kinetics were determined in grains and apparent diffusion coefficients were calculated using Fick's second law. Changes in thermal properties were determined. Cooking temperature and agitation had significant effects on the chemical and physical properties of grains and nejayote. Soluble and suspended solids and total sugar in nejayote showed a linear trend over time for different temperatures, while pericarp removal during both cooking and steeping reached over 90%. Cooking temperature had a significant effect on water and calcium absorption in grains. Calcium and water diffusion were described adequately using Fick's model. Water and calcium diffusion coefficients values were 2.07-3.52 Â 10 À10 m 2 s À1 and of 0.332-1.43 Â 10 À10 m 2 s À1 , respectively. Gelatinization temperature and enthalpy were significantly influenced by the temperature and time of the cooking.

This work is the first attempt to prepare microporous polytetrafluoroethylene (PTFE) fibrous layers embedded with aerogels/phase change materials. For preparation of this layer, the needle-less electrospray technology of water dispersion of individual components is used. Microstructure characteristics, including surface morphology and particle size distribution, and various properties of the prepared materials were investigated and explained. Transport performance of the fibrous layers embedded with aerogels/phase change materials, such as the transmission of heat, air, and water vapor was evaluated and discussed in details. It was found that the electro-sprayed materials composed by spherical particles with rough surface had compact disordered stacking structure. Aerogels and phase change materials (PCMs) play different roles in determining structural parameters and transport properties of the materials. Those parameters and properties could be flexibly adjusted by optimizing the spinning parameters, changing the content or proportion of the fillers to meet specific requirements.

Fused filament fabrication (FFF) is an additive manufacturing technique that is used to produce prototypes and a gradually more important processing route to obtain final products. Due to the layer‐by‐layer deposition mechanism involved, bonding between adjacent layers is controlled by the thermal energy of the material being printed, which strongly depends on the temperature development of the filaments during the deposition sequence. This study reports experimental measurements of filament temperature during deposition. These temperature profiles were compared to the predictions made by a previously developed model. The two sets of data showed good agreement, particularly concerning the occurrence of reheating peaks when new filaments are deposited onto previously deposited ones. The developed experimental technique is shown to demonstrate its sensitivity to changing operating conditions, namely platform temperature and deposition velocity. The data generated can be valuable to pr...

This work reports on the optical response and morphological changes of gold nanoparticles ͑NPs͒ induced by laser irradiation with single nanosecond laser pulses of different fluences and wavelengths. The as-grown specimens consist of irregularly shaped NPs ͑10-13 nm in average dimensions͒ produced by pulsed laser deposition on a substrate. They exhibit a broad optical absorption band related to the surface plasmon resonance ͑SPR͒ peaking in the range of 634-685 nm. After irradiation with fluences above a threshold value, a blueshift, a decrease of the overall absorption, and a narrowing of the SPR band are observed. The SPR peak wavelength and amplitude after irradiation at increasing fluences reach an approximately constant value, irrespective of the irradiation wavelength. This value is consistent with a homogeneous distribution of spherical gold NPs with a mean diameter close to the average initial dimensions as determined by transmission electron microscopy. The results demonstrate that the conversion of irregularly shaped NPs into spherical NPs with reduced dimension dispersion is a thermally driven process and occurs within a fluence interval defined by the melting threshold of all NPs and the ablation threshold. Whereas the useful fluence interval is controlled by the effective fluence absorbed, that is dependent on the laser wavelength and thermal properties of the substrate, the final shape and dimensions of the NPs are independent of the irradiation wavelength provided the fluence is within this useful interval.

We investigated the thermal properties of several imidazolium salts using DSC and TGA/SDTA data. Many of these salts are liquids at sub-ambient temperatures. These ionic liquids form glasses at low temperatures and have minimal vapor pressure up to their thermal decomposition temperature (>4008C). Thermal decomposition is endothermic with the inorganic anions and exothermic with the organic anions investigated. Halide anions drastically reduce the thermal stability of these salts (<3008C). We have observed that aluminium catalyzes the decomposition of the salts containing the inorganic¯uoride anions. The imidazolium cations are thermally more stable than the tetraalkyl ammonium cations.

We investigated the thermal properties of several imidazolium salts using DSC and TGA/SDTA data. Many of these salts are liquids at sub-ambient temperatures. These ionic liquids form glasses at low temperatures and have minimal vapor pressure up to their thermal decomposition temperature (>4008C). Thermal decomposition is endothermic with the inorganic anions and exothermic with the organic anions investigated. Halide anions drastically reduce the thermal stability of these salts (<3008C). We have observed that aluminium catalyzes the decomposition of the salts containing the inorganic¯uoride anions. The imidazolium cations are thermally more stable than the tetraalkyl ammonium cations.

Poly(-caprolactone) (PCL) nanocomposites with hybrid clay-supported carbon nanotubes (Clay-CNT) in concentrations 0.5, 1.0 and 2.5 wt% were prepared by melt mixing. Mechanical, structural and thermal properties of the nanocomposites were studied. All nanocomposites exhibited similar stress-strain patterns to those of neat PCL but, with increasing nanofiller content yield point and Young's Modulus values increased, despite the absence of chemical interactions between PCL and Clay-CNT. It was also found that the crystallinity of the nanocomposites is the same as for neat PCL, but the nanofiller acts as nucleating agent which promotes the crystallization and also allows it to occur at higher temperatures. Thermal stability is instead negatively influenced by the nanofiller, since Clay-CNT catalyzes the decomposition of PCL at lower temperature. The monomer-caprolactone is the main decomposition product resulting from intramolecular esterification while cis-elimination at ester bonds (␤-hydrogen bond scission) is favored at higher temperatures.

The work is aimed to propose a methodology for creating an equivalent of composite materials used for construction of small aircraft. Such equivalent should enable to create numerical models of small aircraft in the simulation of precertication EMC tests for aircraft resistance against the lightning. Eliminating situations threatening the aircraft and passengers in the initial steps of the design will allow savings in production costs and contribute to the safety of air transport. In order to nd the equivalent of composite materials, global optimization methods will be used

The building sector has been showing great interest in incorporating technologically advanced materials with lightweight, ecofriendly, high strength, and stiffness properties in flooring, roofing, and partition walls, etc. In addition to the mechanical properties, these materials should have good thermal properties as well. In response to these requirements, an attempt has been made to study the thermal behavior of green composite sandwich made of flax and agglomerated cork. Composite sandwiches were fabricated by using flax as skin reinforcement and agglomerated cork as core with different densities as 240, 280, and 340 kg m-3 using vacuum bagging method. Glass was also used as skin reinforcement for manufacturing composite sandwiches for comparison purpose. Experiments were conducted to predict thermal properties, viz. thermal conductivity, thermal expansion, flammability, and thermal stability. The experimental results show that the lowest thermal conductivity of 0.03 W m-1 K-1 was observed in flax-based composite sandwich having core density of 240 kg m-3 ; the lowest thermal expansion of 29.2 9 10-5°C-1 was observed in glass-based composite sandwich having core density of 340 kg m-3 ; the highest value of time to ignition was 12 s, and minimum propagation rate was 0.25 mm s-1 in flax-based composite sandwich having core density of 340 kg m-3 ; The highest initial degradation temperature was 362°C for glass-based skin and 263°C for cork having density of 240 kg m-3 .

This paper describes results obtained from scientific work and experiments performed on Livingston and Deception Islands. Located in the South Shetland Archipelago, these islands have been some of the most sensitive regions over the last 50 years with respect to climate change with a Mean Annual Air Temperature (MAAT) close to-2 ºC. Three Circumpolar Active Layer Monitoring (CALM) sites were installed to record the thermal regime and the behaviour of the active layer in different places with similar climate, but with different soil composition, porosity, and water content. The study's ultimate aim is to document the influence of climate change on permafrost degradation. Preliminary results, obtained in 2006, on maximum active-layer thickness (around 40 cm in the CALM of Deception Island), active layer temperature evolution, snow thickness, and air temperatures permit early characterization of energy exchange mechanisms between the ground and the atmosphere in the CALMS sites.

Composite materials containing amorphous iron embedded in poly(methylacrylate) or poly(methylmethacrylate) and amorphous cobalt embedded in poly(methylacrylate) were formed using a sonochemical method. The physical and thermal properties of the composite materials were probed. A significant difference in the solubility of the iron-poly(methylacrylate) and cobalt-poly(methylacrylate) in various solvents was observed. This difference is accounted for by the stronger interaction existing between the cobalt and the surrounding polymer. For iron-poly(methylacrylate) this interaction is weakened due to the formation of an iron complex.

Pyrope garnet grains found in Cretaceous and Quaternary alluvial sediments in the El Kseibat area (Algeria) suggest the presence of kimberlites along the NE margin of the West African Craton. The garnets have been studied using major-and trace-element chemistry ...

The polymorphism of rac-5,6-diisobutyryloxy-2-methylamino-1,2,3,4-tetrahydro-naphthalene hydrochloride (CHF 1035) was investigated. Three different crystal forms (Form I, Form II, and Form III) were obtained by recrystallization procedures from common organic solvents. The polymorphs were characterized by Raman and carbon-13 nuclear magnetic resonance (13 C NMR) spectroscopy, in solution and in solid state (cross polarization-magic angle spinning), powder X-ray diffractometry, and thermal methods (differential scanning calorimetry, hot stage microscopy, and thermogravimetry). Moreover, the diffraction patterns of Form I, collected at controlled temperatures, gave evidence of the presence of two reversible structural rearrangements at $60 and $75 8C. These structural variations were con®rmed by the results obtained by differential scanning calorimetry and hot stage microscopy techniques. The analysis of the Raman spectra allowed the identi®cation of peculiar absorption bands for each polymorph. Form III was the stable crystal form at room temperature as determined by the basis of slurry conversion method.

Solutions for safer, more durable
infrastructure are required in light of increasing
traffic and severe weather in Iraq. The most
significant road conservation and maintenance
challenges are the pavement's low resistance to
dynamic loads and short service life. As a result, vast
sums of money are spent annually to enhance the
road service capacities in Iraq. Thermoplastic
electrometric polymers for bitumen modification
create long-lasting, cost-effective roadways. This
study aims to determine how the mechanical
properties of neat asphalt binder change when
styrene butadiene styrene (SBS) is added as a
modifier. The current research investigates adding
three percentages of SBS (3, 5, and 7% of the weight
of bitumen). Both neat and polymer-modified
bitumen (PMB) were subjected to a series of
physical laboratory and Superpave tests, including a
dynamic shear rheometer tester (DSR) and a
storage stability test. In addition, a chemical
analysis test was conducted to identify any change
in the neat binder chemical composition due to the
addition of SBS polymer. The results indicated that
5% of SBS polymer was the optimum addition
percentage to the local asphalt in Iraq. Additionally,
it reduced the susceptibility of bitumen to
temperature changes and enhanced its
characteristics in all laboratory tests. The obtained
PMB significantly improved rutting and fatigue
factors compared to the neat asphalt binder. Based
on the DSR tester and the storage stability test, the
ratio of 5% SBS met the requirements of class PG76
10, used in the central and southern governorates of
Iraq. Using SBS polymer on the surface course in
Iraq reduces road damage due to the scorching
summer sun, reduces the likelihood of rutting and
fatigue cracking, and works well in hot regions,
resulting in roads that last longer, provide
comfortable riding, and require less maintenance.

Proizvodnja kompozitnih materijala, naročito prirodnih, je u sve većem porastu kao i njihova primjena u raznim granama industrije. U prvom dijelu završnog rada opisana je povijest nastanka kompozita te njihova svojstva i podjela s obzirom na vrstu matrica i ojačavala. Drugi dio završnog rada odnosi se isključivo na prirodne kompozite odnosno prirodne materijale ojačavala i matrica. Također, opisana je njihova proizvodnja, prednosti i nedostaci u usporedbi s konvecionalnim kompozitnim materijalima te njihova sve šira primjena.The production of composite materials, especially natural ones, is growing up and they have been used in different industries. The first part of the paper describes the history of composites and their properties. Furthermore it is described their division due to the type of matrices and reinforcements. The second part of the paper refers exclusively to natural composites, that is natural materials of reinforcements and matrices. Also, their production, advantage...

Thermal properties and crystalline structure of liquid crystalline (LC) poly(ethylene terephthalate-co-2(3)-chloro-1,4-phenylene terephthalate) [copoly(ET/ CPT)] were investigated using differential scanning calorimetry (DSC), thermogravimetry (TGA), limiting oxygen index (LOI) measurement, electron dispersive X-ray analysis (EDX), X-ray diffractometry, and infrared spectrometry (IR). The thermal transition temperatures of copoly(ET/CPT) were changed with the composition. Copoly(ET/ CPT) showed two thermal decomposition steps and the residues at 700°C and LOI values of copoly(ET/CPT) were almost proportional to its chlorine content. The activation energy of thermal decomposition of LC units was very low compared to that of poly(ethylene terephthalate)(PET) units. Crystal structure of copoly(ET/CPT) (20/80) was of triclinic system with the lattice constants of a ϭ 9.98 Å , b ϭ 8.78 Å , c ϭ 12.93 Å , ␣ ϭ 97.4°, ␤ ϭ 96.1°, and ␥ ϭ 90.8°, which is very close to that of poly(chloro-pphenylene terephthlate) (PCPT) with the lattice constants of a ϭ 9.51 Å , b ϭ 8.61 Å , c ϭ 12.73 Å , ␣ ϭ 96.8°, ␤ ϭ 95.4°, and ␥ ϭ 90.8°. When copoly(ET/CPT)(50/50) was annealed at 220°C in vacuum, crystallization induced sequential reordering (CISR) was not observed but the heat of fusion was slightly increased due to the increase of the trans isomer content in PET units.

Thermal properties and crystalline structure of liquid crystalline (LC) poly(ethylene terephthalate-co-2(3)-chloro-1,4-phenylene terephthalate) [copoly(ET/ CPT)] were investigated using differential scanning calorimetry (DSC), thermogravimetry (TGA), limiting oxygen index (LOI) measurement, electron dispersive X-ray analysis (EDX), X-ray diffractometry, and infrared spectrometry (IR). The thermal transition temperatures of copoly(ET/CPT) were changed with the composition. Copoly(ET/ CPT) showed two thermal decomposition steps and the residues at 700°C and LOI values of copoly(ET/CPT) were almost proportional to its chlorine content. The activation energy of thermal decomposition of LC units was very low compared to that of poly(ethylene terephthalate)(PET) units. Crystal structure of copoly(ET/CPT) (20/80) was of triclinic system with the lattice constants of a ϭ 9.98 Å , b ϭ 8.78 Å , c ϭ 12.93 Å , ␣ ϭ 97.4°, ␤ ϭ 96.1°, and ␥ ϭ 90.8°, which is very close to that of poly(chloro-pphenylene terephthlate) (PCPT) with the lattice constants of a ϭ 9.51 Å , b ϭ 8.61 Å , c ϭ 12.73 Å , ␣ ϭ 96.8°, ␤ ϭ 95.4°, and ␥ ϭ 90.8°. When copoly(ET/CPT)(50/50) was annealed at 220°C in vacuum, crystallization induced sequential reordering (CISR) was not observed but the heat of fusion was slightly increased due to the increase of the trans isomer content in PET units.

Phenotypic sex in sea turtles is determined by nest incubation temperatures, with warmer temperatures producing females and cooler temperatures producing males. The common finding of highly skewed female-biased hatchling sex ratios in sea turtle populations could have serious repercussions for the long-term survival of these species and prompted us to examine the thermal profile of a relatively pristine hawksbill nesting beach in Guadeloupe, French West Indies. Data loggers placed at nest depth revealed that temperatures in the forested areas were significantly cooler than temperatures in the more open, deforested areas. Using these temperatures as a predictor of sex ratio, we were able to assess the relative contributions of the different beach zones to the primary sex ratio: significantly more males were likely to be produced in the forested areas. Coastal forests are therefore important maleproducing areas for the hawksbill sea turtle, and this has urgent conservation implications. On Guadeloupe, as on many Caribbean islands, deforestation rates are high and show few signs of slowing, as there is continual pressure to develop beachfront areas. The destruction of coastal forest could have serious consequences both in terms of local nesting behavior and of regional demography through the effects on population sex ratios. Human alterations to nesting habitat in other reptile taxa have been shown to modify the thermal properties of nest sites in ways that can disrupt their ecology by allowing parasite transmission, increasing vulnerability to climate change, or rendering existing habitat unsuitable.

Climate change is perhaps the most pressing and urgent environmental issue facing the world today. However our ability to predict and quantify the consequences of this change is severely limited by the paucity of in situ oceanographic measurements. Marine animals equipped with sophisticated oceanographic data loggers to study their behavior offer one solution to this problem because marine animals range widely across the world's ocean basins and visit remote and often inaccessible locations. However, unlike the information being collected from conventional oceanographic sensing equipment, which has been validated, the data collected from instruments deployed on marine animals over long periods has not. This is the first long-term study to validate in situ oceanographic data collected by animal oceanographers. We compared the ocean temperatures collected by leatherback turtles (Dermochelys coriacea) in the Atlantic Ocean with the ARGO network of ocean floats and could find no systematic errors that could be ascribed to sensor instability. Animal-borne sensors allowed water temperature to be monitored across a range of depths, over entire ocean basins, and, importantly, over long periods and so will play a key role in assessing global climate change through improved monitoring of global temperatures. This finding is especially pertinent given recent international calls for the development and implementation of a comprehensive Earth observation system (see http://iwgeo.ssc.nasa.gov/documents.asp?s=review) that includes the use of novel techniques for monitoring and understanding ocean and climate interactions to address strategic environmental and societal needs.

A comparative study has been made on the operating characteristics of gas-tungsten arc (GTA) welding for several types of electrodes. The work was carried out with a pure tungsten electrode and tungsten electrodes activated with a small quantity of the rare earth metal oxides, La203, Y203, CeO2, and with ZrO2, ThO2, and MgO. Their behaviors during arcing were analyzed and compared from the points of view of arc starting characteristics, electrode consumption, change in shape due to long-term operation, and incompleteness of insert gas shielding and electrode temperature. The results indicated that W-La203 electrodes have superior characteristics among those tested. Metallographic studies of the electrodes indicate that the superiority of operating characteristics strongly depends on the behavior of the rare earth metal oxides during arc burning. It is observed that the rare earth metal oxides form tungstate or oxytungstate during arc burning. These newly formed compounds have low melting points and migrate from the low temperature zones to the high temperature zones throughout the electrode tip, while ThO2 reacts with tungsten, forming pure Th. Also, the investigation demonstrates good stability of La203 during arc burning compared with the other oxides. Particular attention was also paid to the electrode temperature measurement and the important phenomena concerning the emissivity of a particular surface as one of the thermal properties. The investigation reveals the effects of temperature and oxide distribution on the spectral emissivity of the electrode in addition to the main different effect of oxides added to tungsten. Observations of the cathode tip microstructure during and after arc burning were made, and important phenomena concerning the formation of a tungsten "rim" at the periphery of the cathode area, which governs the durability of the electrode and the stability of the arc, are discussed theoretically and experimentally based on the temperature measurement of the tip and the oxidation of tungsten.

In order to estimate the impact of groundwater flow on performance of geothermal heat exchangers in ground source heat pump systems, an equation of conduction-advection is established for heat transfer in porous media, and an analytical transient solution is obtained for a line heat source in an infinite medium by means of the Green function analysis. An explicit expression has also been derived of the mean temperature on circles around the heat source. Dimensionless criteria that dictate the process are summarized, and influence of the groundwater advection on the heat transfer is discussed accordingly. Computations show that water advection in the porous medium may alter significantly the conductive temperature distribution, result in lower temperature rises and lead to a steady condition eventually. The hydraulic and thermal properties of soils and rocks influencing the advection heat transfer are briefly summarized. The analytical solution has provided a theoretical basis and practical tool for design and performance simulation of the ground heat exchangers.

In the present work, a Schiff base was obtained from reaction of 1-naphthylamine with salicylaldehyde and its polymer (poly(NIMP)) was synthesized via oxidative polycondensation. The characterizations of the synthesized Schiff base and poly(NIMP) were determined by 1 H NMR, 13 C NMR, FT-IR, GPC and TGA techniques. The film of synthesized poly(NIMP) was prepared. The film thickness was found to be 106 μm. The optical band gap (E g) values of the film were determined by UV-vis spectroscopy. Direct, indirect and forbidden indirect band gap (E gd , E gid and E gfid) values of the film were found as 1.698, 1.223 and 1.461 eV, respectively. Surface properties of the film were investigated by Atomic force microscope (AFM). In the AFM results, the average surface roughness and average square root roughness were obtained as 2.46 and 3.79 nm, respectively. A negative skewness value exhibited dominant valleys while the high kurtosis value exhibited spiky features.

A detailed x-ray scattering and high-resolution ac calorimetric study has been carried out near the smectic-A to chiral smectic-C phase transition of liquid-crystal compounds 4-͑2-methyl butyl͒ phenyl 4n-octylbiphenyl-4-carboxylate ͑CE8͒ and p-͑n-decyloxy͒ benzylidene-p-amino-͑2-methylbutyl͒ cinnamate ͑DOBAMBC͒ confined in hydrophilic and hydrophobic aerosil nanoparticle networks. The character of the transition, which is mean field near a tricritical point in bulk, is changed dramatically with an increase of aerosil-induced disorder. X-ray measurements revealed pretransitional behavior and compression of the smectic layers, phenomena that are strongly pronounced in high aerosil concentrations. A theoretical model that takes into account the interplay of relevant mechanisms is proposed to explain the observed phenomena. The effect of chirality on the interaction of liquid crystals with aerosils is discussed.

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

The thermal stability of organic-inorganic nano-composites prepared by a two-stage polymerization of urea-formaldehyde resin (UF) with furfuryl alcohol (FA) and TiO 2 before and after irradiation has been researched. The two resins of urea-formaldehyde-TiO 2 composites, named: UF/TiO 2 and UF/TiO 2 /FA, were synthesized. The thermal stability of obtained materials was studied by non-isothermal thermo-gravimetric analysis (TG), differential thermal gravimetry (DTG) and differential thermal analysis (DTA). UF hybrid composites have been irradiated (50 kGy) and after that their radiation stability was evaluated on the basis of thermal behavior. The free formaldehyde (HCOH) percentage in all prepared samples was determined. The minimum percentage values of free formaldehyde (0.04% and 0.03%) for UF/TiO 2 and UF/TiO 2 /FA, respectively, after irradiation dose of 50 kGy are detected. The shift of temperature values for selected mass losses (T 10 %) to a high temperature indicates the increase in thermal stability of samples based on UF resin modified with FA.

The goal of this work was to synthesize and characterize ternary rubber blends based on polyisoprene (natural rubber (NR)), polybutadiene rubber (BR), and styrene–butadiene rubber (SBR) (NR/BR/SBR = 25/25/50) reinforced with different loading silica (SiO2) nanoparticles (0–100 part per hundred parts of rubber (phr)). The specimens were subjected to thermooxidative aging at 100°C, for two times: at 72 and 168 h, respectively, and then mechanically stretched to fracture by tension with a Zwick 1425 (Zwick GmbH, Ulm, Germany) universal tensile testing machine. Rheological and mechanical properties were used as characterization of the ternary rubber blends. The reinforcing performance of the filler was investigated using rheometric, mechanical, and swelling measurements, thermogravimetric analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy with attenuated total reflectance. Hardness, tensile strength, elongation at break, and swelling degree were assessed...

The urban heat island (UHI) phenomenon is mainly caused by the differences in the thermal behaviour between urban and rural settlements that are associated with the thermal properties of urban materials, urban geometry, air pollution, and the anthropogenic heat released by the urban activities. The UHI has a serious impact on the energy consumption of buildings, increases smog production, while contributing to an increasing emission of pollutants from power plants, including sulfur dioxide, carbon monoxide, nitrous oxides and suspended particulates. This study presents the applicability of artificial neural networks (ANNs) and learning paradigms for UHI intensity prediction in Athens, Greece. The proposed model is tested using Elman, Feed-Forward and Cascade neural network architecture. The data of time, ambient temperature and global solar radiation are used to train and test the different models. The prediction accuracy is analyzed and evaluated.

This paper investigates the effect of the solidification conditions and silicon content on the mechanical properties of ductile iron and presents empirical models for predicting the tensile behavior based on the microstructural characterizations. Two ductile iron grades of GJS-500-7 and GJS-500-14 were cast with silicon content of 2.36 and 3.71%, respectively. The cast geometry consisted of six plates with different thicknesses that provided different cooling rates during the solidification. Microstructure analysis, tensile and hardness tests were performed on the as-cast material. Tensile behavior was characterized by the Ludwigson equation. The tensile fracture surfaces were analyzed to quantify the fraction of porosity. The results showed that graphite content, graphite nodule count, ferrite fraction and yield strength were increased by increasing the silicon content. A higher silicon content resulted in lower work hardening exponent and strength coefficient on the Ludwigson equation. The results for 0.2% offset yield and the Ludwigson equation parameters were modeled based on microstructural characteristics, with influence of silicon content as the main contributing factor. The models were implemented into a casting process simulation to enable prediction of microstructure-based tensile behavior. A good agreement was obtained between measured and simulated tensile behavior, validating the predictions of simulation in cast components with similar microstructural characteristics.

In this paper we report a novel method for preparing interpenetrating polymer hydrogels of agarose and polyacrylamide (PAAm) in three steps. The procedure consists in (i) formation of physical hydrogels of agarose, (ii) diffusion of acrylamide, N, N'-methylene-bis-acrylamide and potasium persulfate (the initiator) from aqueous solutions inside the gel of agarose, and (iii) cross-linking copolymerization reaction of the aforementioned reactants to produce PAAm chemical gels interpenetrated with the agarose physical gels. Viscoelasticity measurements and thermal analysis have been performed in order to follow the kinetics of copolymerization. The viscoelastic, swelling and thermal properties of the resulting hydrogels confirm the formation of an interpenetrated system. Further evidence of interpenetration is obtained from inspection with Atomic Force Microscopy .The improvement of the agarose and PAAm gel properties in the resulting interpenetrated hydrogel is analyzed in view of the results.

The effect of water stress (WS) at 8 and 15 days post anthesis (DPA) on the characteristics of starch and protein separated from C-306, HD-2329, PBW-175, PBW-343 and NI-5439 wheat varieties was studied. WS-induced changes in A-, Band C-type granules distribution were variety-and stage-dependent. A-type granules increased in response to WS at both stages in all varieties, the extent of increase being greater at 15 DPA. The proportion of B-type granules decreased in all the varieties, except C-306, in response to WS at 15 DPA. C-type granules also decreased in response to 15 DPA in all varieties, except HD-2329. The starch from wheat exposed to WS at 15 DPA showed lower amylose content, lipids content and pasting temperature, and higher peak viscosity, final viscosity and setback. DSC analysis of starches showed two endotherms (associated with the melting of crystallites and amylose-lipid [AML] complexes) during heating, and an exotherm (associated with reforming of AML) during cooling. Transition temperatures (T o , T p and T c) of AML dissociation and association were lower for starch from wheat exposed to WS, the effect being more at 15 DPA. The changes in pasting and thermal properties of starch caused by WS were observed to be related to lipids, amylose content and distribution of granules. The effect of WS on accumulation of different dimethyl formamide-soluble and insoluble proteins was significant and variety dependent.

Biodegradable polymers poly(D,L-lactide) PDLLA was synthesized by a ring-opening polymerization process of D,L-lactide. Maghnite-H + (Mag-H +), a montmorillonite sheet silicate clay exchanged with protons, was used as a non-toxic catalyst to induce the polymerization. Various techniques, including 1 H NMR, IR, DSC, GPC and viscosimetry, were used to elucidate structure and thermal properties of resulting polymer. Effect of Mag-H + /D,L-lactide weight ratio, temperature, solvent, and time reaction on the rate of polymerization and on average molecular weight of the resulting polymer, was studied. The polymerization rate increases with increasing of temperature and proportion of catalyst. A cationic mechanism was proposed. Mechanism studies showed that monomer inserted into the growing chains with the acylAoxygen bond scission rather than the break of alkylAoxygen bond.