Characterization of a Mexican halloysitic clay and behavior in dry pressing

A Mexican clay, intended to be used as refractory raw material, was identified. Problems encountered in the characterization of halloysitic clays are discussed and emphasis is made on the use of the electron microscope (scanning or transmission type) as a definite evidence of the existence of halloysite due to its unique morphology within the kaolinite group of clay minerals. Beneficiation of this particular clay was carried out on a small scale hydrocyclone equipment and the results are discussed. In an attempt to increase the green density in dry pressing of this halloysitic clay, mixtures with grog were prepared using different additives, grinding and low temperature preheating treatment. The effect of these variables upon green density is given and discussed. It is believed that an increase in the dry pressing density will be reflected in better after burning properties of bricks made out of clays. Pressure levels in the dry pressing experiments were made in a range similar to an industrial power press production --Abstract, page ii

Censure et réécriture de l'histoire du roi Zar'a Ya'eqob (1434-1468) : analyse des deux versions de la "chronique" d'un souverain éthiopien

The text known as "the chronicle of Zar'a Ya'eqob" is composed by two different versions, written by two authors who lived during the reign of the king. The second text is a rewriting of the first version, probably because this version was considered as not enough laudatory. This article try to analyse how the two versions where written, by whom, for what and how in the 16th century these texts were associated to form one texte, the "chronicle" known to us.Le texte que l'on connait sous le nom de "chronique de Zar'a Ya'eqob" est composé de deux versions différentes, écrites par deux auteurs contemporains du roi éthiopien. Le second texte est une réécriture de la première version, sans doute jugée trop peu élogieuse. Cet article propose d'analyser comment les deux versions ont été écrites, par qui, pour quoi et comment au XVIe siècle très vraisemblablement elles ont été associées pour ne plus former qu'un seul texte

On the dispersive nature of the power dissipated into a lossy half-space close to a radiating source

International audienceIn this paper, we study how the power dissipated into a lossy medium excited by a nearby antenna is affected by drifts in the electrical parameters of the lossy medium. The statistical distribution of the sensitivity of the dissipated power is determined by means of a spectral analysis of the transmission of electromagnetic energy from air into the lossy half-space. A clear link is drawn between the reactive content of the field excited by the source and the dispersiveness of the sensitivity. The case of a stratified structure is also addressed, by defining a modification factor representing the alteration of the transmissivity and of its sensitivity when a buffer layer is introduced. All of the results provided point out that, in general, the sensitivity of the total amount of power dissipated into the half-space cannot be predicted independently from a precise knowledge of the source characteristics, unless under a paraxial propagation approximation or in a far-field configuration

Analysis of SAR on flat phantom for different multi-antenna mobile terminals

Evaluation of Specific Absorption Rate (SAR) for multiple antenna systems is becoming important, with the upcoming deployment of LTE-Advanced. In this work, the influence of different antenna locations and antenna types was investigated for stand-alone SAR and simultaneous SAR, to provide some guidelines for antenna design in multi-antenna handsets. For simultaneous SAR, different phase shifts between antenna ports were considered and the averaged SAR was used as a metrics for comparison. The SAR performances were evaluated in simulation for the body worn scenario, and different placements of the mobile handset, i.e., with either the screen or back side closer to the body, were studied

Istvan Bejczy: La lettre du Prêtre Jean, une utopie médiévale

  Review  

La passe d’Aheyyā Fağğ (XVe-XVIe siècle) : Itinéraires, places fortes et contrôle du territoire éthiopien

Circuler sur les hauts plateaux éthiopiens nécessite d’emprunter des voies particulières, passes, gués, qui ne s’improvisent pas. La maîtrise de ces voies d’accès assurait une grande partie de la défense de certaines régions du royaume chrétien d’Éthiopie, mais aussi le contrôle économique sur ce qui entrait et sortait de ces régions. L’une de ces passes, voie d’accès difficilement contournable pour se rendre du Choa à l’Amḥārā, appelée de manière très imagée « la mort des ânes » (Aheyyā Fağğ) illustre parfaitement ce rôle de verrou défensif et économique. Empruntée au début du XVIe siècle par un voyageur portugais qui en décrit très bien les accès, elle reste aujourd’hui une voie difficile mais directe pour rejoindre le grand marché que représente la capitale Addis-Abeba. C’est l’histoire de cette passe au XVe et au début du XVIe siècle, quand elle devient un accès incontournable pour rejoindre la cour royale éthiopienne qui fait l’objet de cette contribution.The Aheyyā Fağğ pass (15th-16th centuries): routes, strongholds and control of Ethiopian territoryTo travel in the Ethiopian Highlands it is necessary to follow special tracks, passes and fords which cannot be improvised. Mastery of these passageways was closely tied to the defence of some parts of the Christian kingdom of Ethiopia and allowed for economic control over what went in and came out of these areas. One of these passes – tellingly named “Donkeys’ Death” (Aheyyā Fağğ) – was practically unavoidable when travelling to Amḥārā from Shoa and perfectly illustrates how it served as a defensive and economic lock. Used in the early sixteenth century by a Portuguese traveller who described its access in good detail, it is still today a difficult but direct way to reach the large market potential of the capital, Addis Ababa. This article examines the history of the pass in the 15th and early 16th centuries, when it became an unavoidable route to access the Ethiopian royal court

Paolo Marrassini: “Vita”, “omelia”, “miracoli” del santo Gabra Manfas Qeddus

Review  

Tombes et cimetières éthiopiens : des rois, des saints, des anonymes

L’histoire des tombes et cimetières éthiopiens, dans la longue durée, en est encore à ses balbutiements. Si les tombes des saints et des rois nous sont un peu mieux connus grâce à des textes témoignant à la fois des enjeux entourant les sépultures de ces personnages hors du commun et des soins apportés à leur inhumation, en revanche, les cimetières ordinaires échappent encore largement à l’enquête, en grande partie parce que le commun des mortels est inhumé dans l’anonymat et dans un grand dépouillement. C’est donc par quelques observations contemporaines que débute cet article afin de saisir ce qu’est aujourd’hui un cimetière dans l’Éthiopie chrétienne et mieux appréhender le caractère exceptionnel d’autres formes de sépultures. Puis, grâce aux textes, nous remonterons aux xive et xve siècles pour suivre la création d’un cimetière monastique, et parallèlement, le développement de nécropoles royales, qui permettent de souligner comment les rites réservés aux saints et ceux réservés aux rois se sont parfois inspiré les uns des autres pour mettre en place des rituels d’exception.The history of the Ethiopian graves and cimeteries is still very poorly studied. The tombs of the saints and kings are better known to us thanks to texts testifying the stakes about the burial of these figures out of the ordinary and the care taken concerning their inhumation. On the contrary, the ordinary cimeteries defy the enquiry because ordinary people is buried anonymously and in a great poverty. It is the reason why this article begins with some contemporary observations in order to better understand what is today a cimetery in the Christian Ethiopia and the exceptional aspect of other forms of burial. Then, with the historical texts, we will explore the 14th and 15th Centuries to follow the erection of a monastic cimetery and the developement in parallel of royal necropolis. These two informations allow us to underline how the rites for the saints and for the kings have inspired one another to give birth to exceptional rituals