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In this study, we have examined ceramic matrix composites with silicon carbide fibers in a melt-infiltrated silicon carbide matrix (SiC/SiC). We subjected samples to tensile loads while collecting micro X-ray computed tomography images. The results showed the expected crack slowing mechanisms and lower resistance to crack propagation where the fibers ran parallel and perpendicular to the applied load respectively. Cracking was shown to initiate not only from the surface but also from silicon inclusions. Post heat-treated samples showed longer fiber pull-out than the pristine samples, which was incompatible with previously proposed mechanisms. Evidence for oxidation was identified and new mechanisms based on oxidation or an oxidation assisted boron nitride phase transformation was therefore proposed to explain the long pull-out. The role of oxidation emphasizes the necessity of applying oxidation resistant coatings on SiC/SiC.
Ceramic matrix composites (CMCs) are structural materials, which have useful properties that combine high strength at high temperatures with moderate toughness. Carbon fibers within a matrix of carbon and silicon carbide, called C/C–SiC, are a particular class of CMC noted for their high oxidation resistance. Here we use a combination of four-point bending and X-ray radiography, to study the mechanical failure of C/C-SiC CMCs. Correlating X-ray radiographic and load/displacement curve data reveals that the fiber bundles act to slow down crack propagation during four-point bending tests. We attribute this to the fact that strain energy is expended in breaking these fibers and in pulling fiber bundles out of the surrounding matrix material. In addition, we find that the local distribution and concentration of SiC plays an important role in reducing the toughness of the material.
The Kingdom of Dahomey has a bad reputation. When the debate concerning the slave trade broke out in Europe during the late eighteenth century, Dahomey was defined as the classic example of either a pariah state dedicated to the capture and sale of people to European slavers, or of a state so addicted to violence that sale of its victims was an act of mercy. Yet there is always another side to this story, and that is of a Dahomey forced by one motive or another into the slave trade. One of the earliest writers on Dahomey’s history, Robert Adams, whose work was published in 1735, argued that Dahomey opposed the slave trade but that foreign pressure compelled the kingdom to participate in it. Two influential books about Dahomey, however, written by Europeans who claimed to be eyewitnesses, one by Robert Norris in 1789 and the other by Archibald Dalzel in 1793, both published in the thick of the debate, presented Dahomey in a different light, and indeed challenged factual data from Adams’s book, to reinforce the close association between Dahomey and the slave trade (Adams and Norris 1789; Dalzel 1793).
When abolitionists won the day, and the British decided that they needed to end the slave trade, Dahomey was widely regarded as an uncooperative holdout. Reports of untrammeled slave dealing and defiance of international pressure to stop enslaving people joined continued reports of Dahomey’s violence against its neighbors and practice of human sacrifice. Ultimately these claims against Dahomey and its rulers justified the colonial occupation of the kingdom by France at the end of the nineteenth century.
The formation of the Holy Congregation for the Propagation of the Faith in 1622 as a part of the Papacy's attempt to centralize control over overseas missions in Roman hands led to the formation of one of the most important archival deposits in Europe for documentation pertaining to Africa in the seventeenth and eighteenth centuries, the Archivio “De Propaganda Fide” in Rome. This Roman-directed missionary organization sent its priests to every corner of the globe, relying especially for its African enterprises on Italian clergy of the Capuchin order. In connection with research on the history of the kingdom of Kongo in the seventeenth and eighteenth centuries, I have worked extensively with materials frcm both the archives of the “Propaganda Fide” and various deposits of the Capuchin order, including a personal visit to the “Propaganda Fide” in January 1978.
The Archivio “De Propaganda Fide” is located in Rome at Piazza di Spagna, 48, and when I visited it, it was open only four hours a day from 9:00 a.m. until 1:00 p.m. every day except Sunday and holidays. Aside from the short hours, however, the archive is a pleasant place to work. The staff is friendly and helpful and the reading room well-lighted and well-appointed. In addition, the material is extremely well indexed and easy to use, so that the researcher who knows the system will have no difficulty in locating relevant material with a minimum of leafing and surveying. Fr. Lowrie J. Daly, has described the organization of the collection.
One of the most durable myths of the history of central Africa is that of the early subversion and domination of the kingdom of Kongo by the Portuguese in the sixteenth century. Its original statement was made by James Duffy in 1959 and was amplified by Basil Davidson two years later. According to this argument the Portuguese had found a well-developed kingdom of Kongo when they reached the mouth of the Zaire River in 1483, and had entered into an alliance with the ruler. The alliance, first made with king Nzinga a Nkuwu (baptized as João I in 1491) and strengthened and continued with his son Mvemba a Nzinga (better known under his baptized name of Afonso I, 1506-1543) involved a partnership in which Portuguese settled in Kongo and provided technological and military assistance to Kongo in exchange for trade, mostly in slaves. As a result of this exchange Kongo adopted Christianity, and for a time the two kings addressed each other as “Brother.” But the alliance, despite its good beginning, was rapidly upset by the greed of the Portuguese settlers, who saw the situation merely as an opening for quick riches through the slave trade. As a result the higher aims of the Portuguese court were subverted--first because the Portuguese, with a higher level of development, were able to benefit from their position more than Kongo; secondly because Lisbon was unable to control its settlers in Kongo or São Tomé. In the end there was a massive involvement of Portuguese in Kongolese affairs and a breakdown of authority in Kongo.
Historians of Nigeria have been curious for many years about the relationship between the various states of the southern zone since the sixteenth century. The fact that the area has produced a rich art, has a fairly elaborate set of traditional histories, and has been the subject of some systematic archeological work means that the modern scholar has somewhat more to go on in reconstructing the region's history than just the fairly sparse and disappointing contemporary texts that came out of the early Portuguese contacts and subsequent European trade and navigation. But contemporary documentation for southern Nigeria remains much weaker than that for other African areas, such as the central African zone, Gold Coast, or the western Atlantic coast.
Nevertheless, documents have raised problems in understanding the history of the area that cannot be fully solved by recourse to the other sources of information, in spite of the comparative richness of non-documentary sources. One of these documentary problems is the issue of the Ife-Benin relationship as documentated in archeology, contemporary texts, and art history. The problems raised by the relationship between these two southern Nigerian cities ultimately reflects on a much larger set of questions concerning the relationship of all the early states south of the Niger, at a period quite near the origin of the state system that would predominate the rest of the pre-colonial period.
The very full description of west central Africa given in Giovanni Antonio Cavazzi da Montecuccolo's book, Istorica Descrizione de’ tre regni Congo, Matamba ed Angola, first published in 1687, has long been one of the most important sources for the reconstruction of the social, political, economic, and religious history of these three Central African states in the seventeenth century. This is true even though it has long been known that Cavazzi was not an eyewitness to all that he described, especially in the kingdom of Kongo, which he visited only briefly after finishing the draft of the book. Therefore, the recent discovery of a new, unknown manuscript version of Cavazzi's work among the family papers of Dr. Carlo Araldi of Modena is very useful, for it helps us to understand the sources that Cavazzi used to write the portions of his work on Kongo, the one area of west central Africa of which he had no first hand knowledge.
Since the Istorica Descrizione was published several years after Cavazzi's death by another Capuchin, Fr. Fortunato Alamandini, who noted in his own introduction that he had edited the final version from a confused mass of documents and notes, the new manuscript initially raised the hope that fuller versions of Cavazzi's original source material might be contained in it. I therefore examined the portions of the manuscript pertaining to Kongo with high hopes that the document would contain masses of fresh eye-witness source materials that Fr. Alamandidi had weeded out to make Istorica Descriizione a publishable work.
This article examines the way in which Christianity and Kongo religion merged to produce a syncretic result. After showing that the Kongo church grew up under the supervision and direction of Kongo authorities rather than missionaries, it will track how local educational systems and linguistic transformations accommodated the differences between the two religious traditions. In Kongo, many activities associated with the traditional religion were attacked as witchcraft without assigning any part of the traditional religion to this category. It also addresses how Kongo religious thinkers sidestepped questions of the fate of the dead and the virginity of Mary when harmonizing them would be too difficult.
This book grew out of my desire to see Americans, living on both continents, develop a new understanding of their past and their heritage, one that was multicentered, complex, and interactional. While my thinking was initially directed in particular toward North America, I also realized that other countries in the Americas, especially as I witnessed in my experience in the English-speaking Caribbean and Brazil, shared in their own ways variants of the collective memory I hoped to change. As Maurice Halbwachs originally envisioned it, our collective memory is our sense of ourselves as having a memory that extends beyond our personal recollections and includes the memory of the whole of society. Others, notably Pierre Nora, who have expanded the concept, have noted the role that national symbols, cherished historical events, monuments, and, for my purposes above all, the curriculum of schools have in shaping the collective memory.
I felt that our contemporary collective memory is often unidirectional, anchored in Europe and focused on a relatively few incidents and locations in the Americas. The locations and narratives vary from country to country; in Mexico more than many others, the indigenous heritage joins that of Europe, for example. My way to address, and hopefully to change, our collective memory is through Atlantic history. I see an Atlantic basin focus not as replacing the Western civilization approach to our heritage, but as augmenting and extending it. While Atlantic history as a subdiscipline has a fairly long and respectable lineage, its earliest manifestation was in fact simply to recognize that Europe and the Americas shared a common history. However, in the early 1990s, new conceptions of Atlantic history were emerging. The new Atlantic history deliberately decentered Europe and gave much more attention to non-European regions. Furthermore, Atlantic history’s new formulation has been struggling to move from using modern countries as a unit of analysis to look at regional or continental trends.
It is easy to forget in the age of motorized travel that before the middle of the nineteenth century, the easiest, fastest, and cheapest way to move cargo of any significant size and people in any numbers was by water. Only extraordinary effort with horses and draught animals could move goods faster, and then only at considerably more expense. This simple fact goes a long way to explaining why river and sea travel was so important, and why humans worked hard to master maritime and nautical technology.
Given this fact, it may seem extraordinary that the Atlantic Basin was the last large body of water to be mastered for navigation. The vast Pacific was being crossed by Polynesians in increasingly more elaborate watercraft from the time of Christ, following remarkable breakthroughs in oceanic navigation and watercraft construction. The Indian Ocean was crisscrossed with trading boats long before the Common Era began, as the Periplus of the Erythrean Sea, a guide to navigation of the first century, shows. Ancient navigators voyaged into the Mediterranean even before historical records marked their journeys, and Europe’s northern seas saw ports and trade long before the Romans conquered Gaul.
The formation of the Atlantic world was the result of Columbus’s voyages to America and subsequent discoveries in navigation that allowed European sailors, for the first time in history, to reach every other part of the world. It is not any surprise, then, that 1492, the date of Columbus’s crossing of the Atlantic, is a signal year in the history of the world, for the creation of the Atlantic world involved one of history’s great intercontinental migrations and the most massive cultural encounter and engagement that the world had seen up to that time. It is easy to give too much credit for this to European achievement, for a great deal of what happened was as much accident and happy circumstance as it was part of a deliberate plan. And although Europeans initiated the Atlantic navigations, others also benefited from or exploited the opportunities that the navigations created.
Europeans did not possess decisive advantages over any of the people they met, even though their sailing craft were indeed capable of nautical achievements that no other culture up to that time was able to perform. But although we focus on the Atlantic as a maritime highway that connected cultures, the real stuff of human interaction took place on land. There, often enough, sailing advantages were not much help.
The book that follows examines the cultural consequences of European navigation and settlement outside of Europe in three parts. The first part traces the backgrounds of the three continental landmasses whose populations were brought into contact by those navigations. The second section examines the primarily political and social implications of the contact and traces the origins of a variety of Atlantic societies. Only in the third part are specifically cultural issues addressed, in an attempt to see how new ways of eating, drinking, speaking, and worshipping developed in the newly created Atlantic world.
European possession of most of the Americas ended almost as abruptly as it had begun. While the Spanish had occupied vast tracts of American land in a little over a half-century between 1492 and 1550, even larger regions of the Americas won their independence in the half-century between 1775 and 1825. While there had been rebellions and disobedience in the earlier periods, there was nothing like the massive and successful resistance to rule from Europe that characterized the American revolutions.
These observations may make it appear that the American revolutions were fairly straightforward; in fact, the period was one of immense complexity. In many regions, the movement toward independence was as much an inter-American civil war as the ousting of an occupying power. Moreover, in many cases, the revolutions were social movements as well as political movements, and involved a complex dance between the revolutionaries who wanted a radical change in social order and the nationalists who wanted simply to rid American colonies of their overlords in Europe. Both sorts of movement were part of a pattern of a revolutionary age that began with the American Revolution in 1775 and extended to the end of the Spanish American Revolutions in 1825. In between there was the French Revolution and a powerful slave revolt and revolution in Haiti.