Speed of Sound in Pure Water at Temperatures between 274 and 394 K and at Pressures up to 90 MPa

A newly designed experimental apparatus has been used to measure the speed of sound u in high-purity water on nine isotherms between 274 and 394 K and at pressures up to 90 MPa. The measurement technique is based on a traditional double-reflector pulse-echo method with a single piezoceramic transducer placed at unequal distances from two stainless steel reflectors. The transit times of an acoustic pulse are measured at a high sampling rate by a digital oscilloscope. The distances between the transducer and the reflectors were obtained at ambient temperature and pressure by direct measurements with a coordinate measuring machine. The speeds of sound are subject to an overall estimated uncertainty of 0.05 %. The acoustic data were combined with available values of density ρ and isobaric heat capacity c_p along one isobar at atmospheric pressure to calculate the same quantities over the whole temperature and pressure range by means of a numerical integration technique. These results were compared with those calculated from the IAPWS-95 formulation with corresponding relative deviations which are within 0.1%. Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22–27, 2003, Boulder, Colorado, U.S.A.     

Spectral and directional emittance of alumina at 823 K

Spectral–directional emittance measurements of aluminum oxide (99.5% pure), in air, were performed at 823 K using an apparatus comprised of a Fourier Transform Infrared (FTIR) spectrometer, a blackbody radiating cavity (hohlraum), and a sample holder which allows directional measurements. The data cover a wide spectral range between 2 and 25 μm, and a directional range from a surface normal to a 72° polar angle. The aluminum oxide sample used in the experiment had a nominal surface roughness of 1 μm determined by a profilometer. Directional emittance shows no departure from dielectric behavior.     

Fire Risks and Prevention Strategies for Architecture at Historic Sites

This paper mainly discusses the features of China's architecture at historic sites with regard to fire protection, the causes of fire since 1949, reviewing their weaknesses in fire protection, and exploring modern technologies for fire prevention that are applicable to ancient buildings. We put forward suggestions to improve fire prevention and management: eliminating potential problems of fire, improving fire protection and establishing a better fire security system, which is especially important to protect ancient buildings.     

Phase behavior and thermal conductivity of urea at pressures up to 1 GPa and at temperatures in the range 50–370 K

The thermal conductivity of the solid phases I and III of urea was measured at temperatures in the range 50–370 K for pressures up to 1 GPa. Phase III, previously detected only at pressures above 0.5 GPa, was observed here at low pressures ( <0.07 GPa) below about 230 K. Extrapolation of the I–III phase line indicates that phase III might be obtained at 218 K at atmospheric pressure and, consequently, that urea might exhibit two solid phases at atmospheric pressure. The temperature dependence of the thermal conductivity of both phase I and phase III could be described by the Debye model for thermal conductivity assuming phonon scattering by three phonon umklapp processes only. Despite a volume decrease at the I III transition, the thermal conductivity decreased by about 20%. Normally, thermal conductivity increases at a phase transition at which volume decreases. This rather unusual behavior of urea might be due to an increase in the nearest-neighbor distance at the I III transition.     

Steel and nickel alloys at high temperatures: Part D of ‘The requirements for and limitations of materials at high temperatures’

The range of steels considered includes corrosion resistant ferritic and austenitic steels and low alloy, martensitic 12% Cr and austenitic steels for higher strength applications. Nickel superalloys are discussed under the gas turbine applications for which they were largely developed. Nickel alloys for corrosion resistant applications are discussed and a short section on the refractory materials Mo, Nb, Tn and W is included.     

Mechanical and thermal stresses at shot particles during fatigue of Kaowool aluminum composites at 20°C

During fatigue of Kaowool fiber reinforced aluminum composites at 20°C, cracks are initiated at hollow Kaowool particles. The stress concentrations associated with these particles arise from two sources: (i) residual stresses due to differential thermal contraction of the Kaowool and aluminum and (ii) the applied cyclic fatigue stress. These stresses are calculated from a finite element model which incorporates plasticity of the aluminum matrix. In general, the mechanical stresses are considerably larger than the thermal stresses. The total stress, in both the aluminum matrix and the Kaowool particle, increases with decreasing particle wall thickness and the proximity of the particle to the surface. In general, the stress concentrations in the aluminum matrix are more critical than those in the Kaowool particles, and are predicted to exceed locally the yield strength of 339 aluminum for all values of wall thickness. The particles observed experimentally at the fatigue fracture origins are thin walled and close to the surface, in quantitative agreement with the predictions of the finite element model.     

Wetting and reaction of molten La with poly- and mono-crystalline MgO at 1323 K

Wetting of poly- and mono-crystalline MgO substrates by molten La was investigated at 1323 K in a high vacuum using a modified sessile drop method. The wettability seems to depend mildly on the substrate orientation but strongly on the surface roughness. The initial contact angles on the smooth (100), (110), and (111) surfaces are 63° ± 1°, 69° ± 1°, and 69° ± 1°, respectively, while on the rough polycrystalline surfaces they are much larger (104° ± 3°). The wetting behavior is dictated by the disruption of the oxide film covering the La surface, the extent of the interfacial reaction and the evolution of the reaction product. A thick layer of La₂O₃ phase formed at the interface and then enwrapped the liquid surface, leading to the recession and warping of the triple line and finally the deterioration in the wettability. On the other hand, magnesium was displaced by the reaction and its evaporation provided additional impetus for the movement of the triple line. Due to different reaction intensities, the wetting behavior of La on the different orientations of the MgO surfaces also showed some discrepancies.     

Horndal at Heathrow? Capacity creation through co-operation and system evolution

At Europe's most congested airports demand for take-off andlanding slots has exceeded the available supply for many years.Yet, in the face of persistent growth in air traffic activities,these airports have achieved remarkable increases in their capacitiesto handle flights, despite retaining the same basic infrastructures.This paper investigates this growth of capacity as a ‘problemcentred innovating system’, in which the roles of proceduralchange and co-operation between teams are highlighted. ‘Systemevolution’ is also observed, as over time new agents withdifferent knowledge bases have been brought into ‘thesystem’ to assist with the search for additional capacity.     

α-Tricalcium phosphate hydrolysis to hydroxyapatite at and near physiological temperature

The kinetics of hydroxyapatite (HAp) formation by direct hydrolysis of -tricalcium phosphate (-TCP) [-Ca₃(PO₄)₂] have been investigated. Transformation kinetics were examined for reactions at 37 °C, 45 °C and 56 °C by isothermal calorimetric analysis. Setting times and morphologies of the resultant HAp were found to be strongly dependent on reaction temperature. XRD analysis accompanied by FTIR confirmed that phase pure calcium-deficient hydroxyapatite (CDHAp) [Ca_10-x(HPO₄)_x(PO₄)_6-x(OH)_2-x] was formed. Complete reaction occurs within 18, 11, 6.5 h at 37, 45 and 56 °C, respectively. The extent of HAp formation differs for particulate slurries and pre-shaped forms of reactant -TCP. Formation of hydroxyapatite in pre-formed pellets was hindered due to limited water penetration, but enhanced with the presence of NaCl as a pore generator. Regardless of the precursor characteristics and temperature, HAp formation is characterized by an initial period of wetting of the -TCP precursor, an induction period and a growth period during which the bulk transformation to HAp occurs. The microstructures of the resultant HAp at all temperatures were generally similar and are characterized by the formation porous flake-like morphology. Microstructural coarsening was observed for the CDHAp formed above the physiological temperature. The hardening generated by the hydrolysis reaction was demonstrated using diametrical compression tests. The original tensile strength of 56% dense -TCP increased from 0.70±0.1 MPa to 9.36±0.4 MPa after hydrolysis to CDHAp at 37 °C, corresponding to a density of 70%. ©2000 Kluwer Academic Publishers     

Vibrational Coupling and Kapitza Resistance at a Solid–Liquid Interface

The rapid development and application of nanotechnologies have promoted an increasing interest in research on heat transfer across the solid/liquid interface. In this study, molecular dynamics simulations are carried out to elucidate the effect of vibrational coupling between the solid and the liquid phases on the Kapitza thermal resistance. This is accomplished by altering the atomic mass and interatomic interaction strength in the solid phase (thus, the vibrational properties), while keeping the solid–liquid interfacial interaction unchanged. In this way, the Kapitza resistance can be altered with a constant work of adhesion between the solid and the liquid phases. The simulation results show that the overlap degree between the vibrational density of states profiles of the interfacial liquid layer and the outermost solid layer, which measures the degree of interfacial vibrational coupling, increases with larger atomic mass and weaker inter-atomic interaction in the solid phase. An inverse relation exists between the Kapitza resistance and the overlap degree of the vibrational density of states profiles. It means that the Kapitza resistance decreases with better interfacial vibrational coupling. The simulations show that the Kapitza resistance is not only affected by the interfacial bonding strength but also the vibrational coupling between the solid and the liquid atoms. The interfaces with better thermal transport efficiency should be the ones with stronger interfacial interaction and preferable vibrational coupling between solid and liquid phases.     

Understanding bioenergy production and optimisation at the nanoscale – a review

ABSTRACT

Nanotechnology has an increasingly large impact on a wide range of biotechnological, pharmacological and pure technological applications. Its current use in bioenergy production from biomass is very limited. This paper examines the potential interrelationships between nanotechnology and bioenergy production through a comprehensive literature review and analysis of data from biomass characterisation studies. The aim of this review is to indicate how nanotechnology can be applied in biomass-to-bioenergy conversion. This study shows currently nanotechnology has been applied in the production of only two types of biomass, i.e. sludge and algae. Hence, interaction of nanomaterials with active sludge and algal cells were examined. Our extensive literature review indicates that anaerobic digestion process in sludge can potentially be enhanced by using magnetite nanoparticles, which gives higher methane yields. On the other hand, nanosilver reduces growth and causes adverse effects on the morphology of green algae. This process for bioenergy generation has already been successfully applied to sludge and algae biomass. Our study confirms that the process can also be used in the production of bioenergy from the other biomasses, such as agricultural wastes and industrial residues. Outcomes of this work will be an important tool for implementing nanotechnology in bioenergy research.     

Burnout at Large Subcoolings and Near‐Critical Pressures of Toluene

The results of experimental investigation of a burnout of toluene at subcoolings t = 50–270°C at the tube inlet and pressures P/P _cr = 0.70–0.94 are given. The critical heat fluxes as functions of the mass velocity of the liquid and its subcooling to the saturation temperature are established. The results obtained are compared to the data for water.     

Probing Contact-Electrification-Induced Electron and Ion Transfers at a Liquid–Solid Interface

As a well-known phenomenon, contact electrification (CE) has been studied for decades. Although recent studies have proven that CE between two solids is primarily due to electron transfer, the mechanism for CE between liquid and solid remains controversial. The CE process between different liquids and polytetrafluoroethylene (PTFE) film is systematically studied to clarify the electrification mechanism of the solid–liquid interface. The CE between deionized water and PTFE can produce a surface charges density in the scale of 1 nC cm⁻², which is ten times higher than the calculation based on the pure ion-transfer model. Hence, electron transfer is likely the dominating effect for this liquid–solid electrification process. Meanwhile, as ion concentration increases, the ion adsorption on the PTFE hinders electron transfer and results in the suppression of the transferred charge amount. Furthermore, there is an obvious charge transfer between oil and PTFE, which further confirms the presence of electron transfer between liquid and solid, simply because there are no ions in oil droplets. It is demonstrated that electron transfer plays the dominant role during CE between liquids and solids, which directly impacts the traditional understanding of the formation of an electric double layer (EDL) at a liquid–solid interface in physical chemistry.     

Determination of the second-order susceptibility of ammonium dihydrogen phosphate and α-quartz at 633 and 1064 nm

The second-order susceptibility d(36) of ammonium dihydrogen phosphate (ADP) was determined from phase-matched second-harmonic generation (SHG) at two wavelengths. A cw single-mode He-Ne laser (λ= 633 nm) and a cw single-mode Nd:YAG laser (λ= 1064 nm) were used as fundamental beam sources. The results were d(36)(ADP, 633 nm) =(1.31 ± 0.05) ×10(-9) esu = 0.55 ± 0.02 pm/V and d(36)(ADP, 1064 nm) = (1.10 ± 0.06) × 10(-9) esu = 0.46 ± 0.03 pm/V. The d(11) values of α-quartz were determined relative to d(36)(ADP) to be d(11)(α-quartz, 633 nm) = (7.4 ± 0.3) × 10(-10) esu = 0.31 ± 0.01 pm/V and d(11)(α-quartz, 1064 nm) = (7.1 ± 0.3) × 10(-10) esu = 0.30 ± 0.01 pm/V by the use of the Maker fringe method. The Miller's delta ofADP and α-quartz is in good agreement at the two wavelengths.     

Development and Realization of Iron–Carbon Eutectic Fixed Point at NPLI

The concept of metal–carbon eutectic temperature fixed point has been introduced in 1999 and is extensively being investigated by thermometry researchers to cover the high-temperature range above copper fixed point. Metal–carbon eutectic fixed points also helped to provide direct traceability with reduced associated uncertainty in the high temperature range for thermometry and radiometry applications. In view of this, CSIR-National Physical Laboratory, India (NPLI) has developed iron–carbon (Fe–C, 1153 °C) eutectic fixed point cell in the graphite crucible and realized by using the noble metal thermocouples. The preparation parameters such as design and fabrication of a graphite crucible, Fe:C eutectic composition and filling procedure, furnace profile, melting and freezing plateau measurements, heat flux immersion, inhomogeneity, etc. have been optimized and presented in this paper. The measurement uncertainty of the Fe–C eutectic cell realized with Type-S thermocouple was estimated to be 3.04 μV (0.25 °C) at coverage factor k = 2.     

‘Swiping … and Daguerreotyping’: Photographing Golf at St Andrews

Abstract

When photography was invented, St Andrews was already a very old town, littered with the remains of a glorious and turbulent his tory: notably the skeletons of a once magnificent cathedral and a large Augustinian priory and a ruined castle, horne of the former bishops and archbishops. Zealous reformers had helped reduce these great symbols of medieval Scotland's archiepiscopal see, which were now picturesque ruins, ideal for recording in the new medium of photography. However, St Andrews in the nineteenth century was more than just ‘that Reformation bombsite’.1 This rather apt phrase was used recently by Les Murray in his poem, St Andrews University AD 2000, one of ten poems specially commissioned to mark the 250th anniversary of the birth of Robert Fergusson, poet, former St Andrews student and inspiration to Robert Burns. It had a small, sleepy university, with old college buildings nestling among the town's commercial and private properties. But also it had something else alive and stirring in the western end of the town — its famous 'Old' golf course. Around the time the first St Andrews photographs were being made, George Fullerton Carnegie penned the following lines in his Golfiana: Address to St Andrews: