Measuring the flow properties of small powder samples using an avalanche tester

The feasibility of using a small-scale avalanche tester to measure the flow properties of pharmaceutical lactose powders was examined. The modes of behaviour observed in larger systems were displayed and showed a clear distinction between angular, free-flowing particles and more spherical particles of similar flow characteristics. Angular Lactohale LH100 particles showed slumping behaviour at a rotational frequency of 0.33Hz which disappeared at higher frequencies. Spherical lactose powder with a similar flow function to LH100 only showed rolling behaviour under the same conditions, as did more cohesive powders LH200 and LH300. Further investigation of the LH100 data using Fast Fourier analysis showed that the slumping frequency was 1/10th of the rotational frequency.

Le Passé simple est-il toujours en course? Enquête sur la position du PS dans le peloton des temps du reportage cycliste

Cellard (1979) avait avancé que le reportage sportif constituait un bastion du passé simple (PS). Cette affirmation, non étayée par une étude de corpus, semblait trouver un écho dans les études de la presse écrite des années 80-90 (Herzog 1981, Engel 1990). Toutefois, des études récentes consacrées exclusivement au reportage sportif remettent en cause cette prétendue suprématie dans les comptes rendus de la finale de la Coupe du Monde 2002 offerts par la presse francophone (Engel & Labeau 2003) même si des variations régionales (plus grande proportion de PS en périphérie qu’au centre parisien - Labeau 2002) et diachroniques (déclin du PS depuis 1950 – Labeau 2003) semblent se manifester. La présente étude se propose de poursuivre et de raffiner l’analyse de l’emploi du PS dans le compte rendu sportif en sollicitant de nouvelles variables. D’abord, le choix du corpus permettra d’approfondir des hypothèses évoquées dans les articles ci-dessous. Notre corpus sera constitué de la couverture du Tour d’Italie 2004 dans L’Equipe et La Dernière Heure / Les Sports. Le cyclisme se distingue du football par plusieurs aspects, parmi lesquels on peut noter sa linéarité : une course cycliste n’est pas un match joué dans un espace clos, délimité, mais consiste à effectuer un parcours linéaire aussi vite que possible. Cette linéarité pourrait s’avérer favorable au PS (Vetters 2003, Bres 2003). Contrairement aux événements sportifs étudiés précédemment, le Tour d’Italie ne bénéficie pas d’une couverture télévisuelle importante en France, un facteur susceptible d’influencer le compte rendu écrit (Labeau 2003) ; contrairement à ce qui se passe pour les finales de Coupe du Monde, le journaliste ne peut assumer que le lecteur connaît déjà les résultats de l’épreuve. Le corpus étudié ici se veut aussi plus complet : on travaillera sur l’ensemble des articles, en version papier, consacrés au Giro plutôt que sur une sélection d’articles en ligne. Cette prise en compte pourrait mettre en lumière des variations de genre. Un autre intérêt du présent corpus est qu’il illustre les pratiques de la presse sportive plutôt que celles des pages sportives des quotidiens « généralistes » : L’Equipe est l’hebdomadaire français de référence et la DH offre la couverture la plus complète en Belgique francophone. La comparaison des deux publications nous permettra donc de tester d’éventuelles variations régionales. Ainsi, par un corpus spécifiquement sportif et élargi, nous contribuerons à évaluer plus exactement la position réelle du PS dans la presse sportive contemporaine.

Interactions at the head-tape interface of a linear tape system

Many of the recent improvements in the capacity of data cartridge systems have been achieved through the use of narrower tracks, higher linear densities and continuous servo tracking with multi-channel heads. These changes have produced new tribological problems at the head/tape interface. It is crucial that the tribology of such systems is understood and this will continue since increasing storage capacities and faster transfer rates are constantly being sought. Chemical changes in the surface of single and dual layer MP tape have been correlated to signal performance. An accelerated tape tester, consisting of a custom made cycler ("loop tester"), was used to ascertain if results could be produced that were representative of a real tape drive system. A second set of experiments used a modified tape drive (Georgens cycler), which allowed the effects of the tape transport system on the tape surface to be studied. To isolate any effects on the tape surface due to the head/tape interface, read/write heads were not fitted to the cycler. Two further sets of experiments were conducted which included a head in the tape path. This allowed the effects of the head/tape interface on the physical and chemical properties of the head and tape surfaces to be investigated. It was during the final set of experiments that the effect on the head/tape interface, of an energised MR element, was investigated. The effect of operating each cycler at extreme relative humidity and temperature was investigated through the use of an environmental chamber. Extensive use was made of surface specific analytical techniques such as XPS, AFM, AES, and SEM to study the physical and chemical changes that occur at the head/tape interface. Results showed that cycling improved the signal performance of all the tapes tested. The data cartridge drive belt had an effect on the chemical properties of the tape surface on which it was in contact. Also binder degradation occurred for each tape and appeared to be greater at higher humidity. Lubricant was generally seen to migrate to the tape surface with cycling. Any surface changes likely to affect signal output occurred at the head surface rather than the tape.

L’imparfait dans la narration chez Simenon:une dérive aspectuelle?

Cette étude s’intéressera à deux questions majeures : 1. Dans quel cotexte trouve-t-on ce type d’IMP ? Quelles sont les marques syntaxiques, lexicales voire pragmatiques qui régissent cet emploi ? On passera en revue les critères répertoriés dans Labeau (à paraître) et on tentera de voir si d’autres peuvent être identifiés. 2. Comment la forme est-elle traduite en anglais ? Recourt-on principalement au simple past (Chuquet, 2000), ce qui suggèrerait peut-être une perfectivisation de la forme puisque l’IMP serait perçu équivalent à des formes perfectives ? D’autres équivalences sont-elles proposées ? Compte tenu de la fréquence présumée de l’IMP en contexte narratif dans les romans policiers de Simenon, notre corpus bilingue comprendra deux Maigret: L’Affaire Saint-Fiacre (SF) et Le chien jaune (CJ). Pour tester si cet emploi est restreint au genre policier, nous prendrons en compte deux autres romans du même auteur racontant une histoire d’adultère : Le train (LT) et La chambre bleue (CB).

Abrasion resistance of fibre reinforced concrete floors

This thesis focuses on the investigation of the abrasion resistance of fibre reinforced concrete floors at both the macro and micro levels. A literature review of the available literature concerning subjects allied to the current project is included. This highlights themes relevant to wear mechanisms and the factors influencing it: factors that affect the abrasion resistance of concrete and several test methods for assessing it; and the historical development of fibres and the properties of different fibre types and their influence on concrete. Three accelerated abrasion testers were compared and critically discussed for their suitability for assessing the abrasion resistance of concrete floors. Based on the experimental findings one accelerated abrasion apparatus was selected as more appropriate to be used for carrying out the main investigations. The laboratory programme that followed was undertaken to investigate the influence of various material and construction factors on abrasion resistance. These included mix variations (w/c ratio), fibre reinforcement, geometry, type and volume, curing method and superplasticizing agents. The results clearly show that these factors significantly affected abrasion resistance and several mechanisms were presumed to explain and better understand these observations. To verify and understand these mechanisms that are accountable for the breakdown of concrete slabs, the same concrete specimens that were used for the macro-study, were also subjected to microstructutural investigations using techniques such as Microhardness examination, Mercury intrusion porosimetry and Petrographic examination. It has been found that the abrasion resistance of concrete is primarily dependent on the microstructure and porosity of the concrete nearest to the surface. The feasibility of predicting the abrasion resistance of fibre reinforced concrete floors by indirect and non-destructive methods was investigated using five methods that have frequently been used for assessing the quality of concrete. They included the initial surface absorption test, the impact test, ball cratering, the scratch test and the base hardness test. The impact resistance (BRE screed tester) and scratch resistance (Base hardness tester) were found to be the most sensitive to factors affecting abrasion resistance and hence are considered to be the most appropriate testing techniques. In an attempt to develop an appropriate method for assessing the abrasion resistance of heavy-duty industrial concrete floors, it was found that the presence of curing/sealing compound on the concrete surface at the time of accelerated abrasion testing produces inappropriate results. A preliminary investigation in the direction of modifying the Aston accelerated abrasion tester has been carried out and a more aggressive head has been developed and is pending future research towards standardisation.

Quality control of pharmaceutical ingredients:developing a caking test for industry

Objectives - Powdered and granulated particulate materials make up most of the ingredients of pharmaceuticals and are often at risk of undergoing unwanted agglomeration, or caking, during transport or storage. This is particularly acute when bulk powders are exposed to extreme swings in temperature and relative humidity, which is now common as drugs are produced and administered in increasingly hostile climates and are stored for longer periods of time prior to use. This study explores the possibility of using a uniaxial unconfined compression test to compare the strength of caked agglomerates exposed to different temperatures and relative humidities. This is part of a longer-term study to construct a protocol to predict the caking tendency of a new bulk material from individual particle properties. The main challenge is to develop techniques that provide repeatable results yet are presented simply enough to be useful to a wide range of industries. Methods - Powdered sucrose, a major pharmaceutical ingredient, was poured into a split die and exposed to high and low relative humidity cycles at room temperature. The typical ranges were 20–30% for the lower value and 70–80% for the higher value. The outer die casing was then removed and the resultant agglomerate was subjected to an unconfined compression test using a plunger fitted to a Zwick compression tester. The force against displacement was logged so that the dynamics of failure as well as the failure load of the sample could be recorded. The experimental matrix included varying the number of cycles, the amount between the maximum and minimum relative humidity, the height and diameters of the samples, the number of cycles and the particle size. Results - Trends showed that the tensile strength of the agglomerates increased with the number of cycles and also with the more extreme swings in relative humidity. This agrees with previous work on alternative methods of measuring the tensile strength of sugar agglomerates formed from humidity cycling (Leaper et al 2003). Conclusions - The results show that at the very least the uniaxial tester is a good comparative tester to examine the caking tendency of powdered materials, with a simple arrangement and operation that are compatible with the requirements of industry. However, further work is required to continue to optimize the height/ diameter ratio during tests.

A comparison of compacting and caking behaviour of carbonate-based washing powders

Two types of sodium carbonate powder produced by spray drying (SD) and dry neutralisation (DN) were studied for their compaction properties using a uniaxial compression tester. Dry neutralised sodium carbonate showed a greater resistance to compression and also produced a weaker compact when compressed to 100kPa. Differential Scanning Calorimetry (DSC) showed that both types of powder were predominantly amorphous in nature. Moisture sorption measurements showed that both powders behaved in a similar way below 50% RH. However, dry neutralised sodium carbonate had a high moisture affinity above this RH. On examining the particle structures using Scanning Electron Microscopy (SEM), the most likely explanation for the increased tendency of spray dried sodium carbonate to form strong compacts was the hollow particle structure.

A comparison of compacting and caking behavior of carbonate-based washing powders

Two types of sodium carbonate powder produced by spray drying (SD) and dry neutralization (DN) were studied for their compaction properties using a uniaxial compression tester. A comparison was also made with Persil washing powder. Dry neutralized sodium carbonate showed greater resistance to compression and also produced a weaker compact when compressed to 100 kPa. Spray-dried sodium carbonate had an absence of fine particles but compacted easily. Differential scanning calorimetry (DSC) showed that both types of powder were predominantly amorphous in nature. Moisture sorption measurements showed that both powders behaved in a similar way below 50% relative humidity (RH). However, dry neutralized sodium carbonate had a high moisture affinity above this RH. Particle structures were also examined using scanning electron microscopy, showing the heterogeneous interior of the spray-dried particles. © 2013 Copyright Taylor and Francis Group, LLC.

Properties of ultra fast deposited diamond-like hydrogenated carbon films

Hydrogenated amorphous carbon films with diamond like structures have been formed on different substrates at very low energies and temperatures by a plasma enhanced chemical vapor deposition process employing acetylene as the precursor gas. The plasma source was of a cascaded arc type with Ar as carrier gas. The films were grown at very high deposition rates. Deposition on Si, glass and plastic substrates has been studied and the films characterized in terms of sp3 content, roughness, hardness, adhesion and optical properties. Deposition rates up to 20 nm/s have been achieved at substrate temperatures below 100°C. The typical sp3 content of 60-75% in the films was determined by X-ray generated Auger electron spectroscopy. Hardness, reduced modulus and adhesion were measured using a MicroMaterials Nano Test Indenter/Scratch tester. Hardness was found to vary from 4 to 13 GPa depending on deposition conditions. Adhesion was significantly influenced by the substrate temperature and in situ DC cleaning. Hydrogen content in the film was measured by a combination of the Fourier transform infrared and Rutherford backscattering techniques. Advantages of these films are: low ion energy and deposition temperature, very high deposition rates, low capital cost of the equipment and the possibility of film properties being tailored according to the desired application.

Measurements of stress-optic coefficient and Young's modulus in PMMA fibers drawn under different conditions

We have systematically measured the differential stress-optic coefficient, ΔC, and Young's modulus, E, in a number of PMMA fibers drawn with different stress, ranging from 2 up to 27 MPa. Effect of temperature annealing on those parameters was also investigated. ΔC was determined in transverse illumination by measuring the dependence of birefringence on additional axial stress applied to the fiber. Our results show that ΔC in PMMA fibers has a negative sign and ranges from -4.5 to -1.5×10-12 Pa -1 depending on the drawing stress. Increase of the drawing stress results in greater initial fiber birefringence and lower ΔC. The dependence of ΔC and initial birefringence upon drawing stress is nonlinear and gradually saturates for higher drawing stress. Moreover, we find that ΔC is linearly proportional to initial fiber birefringence and that annealing the fiber has no impact on the slope of this dependence. On the other hand, no clear dependence was observed between the fiber drawing stress and the Young's modulus of the fibers as measured using microscopic digital image correlation with the fibers tensioned using an Instron tension tester. © 2010 SPIE.