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1
Ellingson, William A., J. Scott Steckenrider et Thomas J. Meitzler. « Defect Detection in Ceramic Armor Using Phased Array Ultrasound ». Advances in Science and Technology 65 (octobre 2010) : 143–52. http://dx.doi.org/10.4028/www.scientific.net/ast.65.143.
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Monolithic ceramic tile is used as part of ceramic-composite armor. Rejection of individual tile that contain potential threat-defeat-reducing ―defects‖ must be accomplished in a fast and cost-effective manner. Water-immersion phased-array ultrasound using 10 MHz 128-element transducers sequenced at 32-elements has been demonstrated to quickly scan and detect 25-50 um known inclusion-type defects in individual 25 mm thick SiC tile. Further, use of similar phasedarray transducers and similar transducer-element activation sequences, has shown detection of intentional internal defects in tests of 40 cm square by 50 mm thick, multi-layered composite ceramic-armor specimens. Large changes in acoustic velocities of the various layered materials causes focusing issues of the ultrasonic wave. The use of various digital signal processing methods can be used to overcome some of these issues. The results show that use of phased array ultrasound can reliably be used for defect detection in either monolithic or composite ceramic-armor. The technology and various results are presented.
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Lavin, Lucianne. « The Windsor Ceramic Tradition in Southern New England ». North American Archaeologist 8, no 1 (juillet 1987) : 23–40. http://dx.doi.org/10.2190/w3lm-q1jy-5ywc-5myu.
Texte intégralRésumé :
Irving Rouse and Carlyle Smith originally reconstructed the sequences of the Windsor tradition in their studies of Connecticut and New York pottery assemblages. Since that time additional local ceramic assemblages have been described in the literature. There have been few attempts to test the validity of the Rouse/Smith sequence with this information, however. Utilizing these data and unpublished research from southern Connecticut, this article demonstrates that the Rouse/Smith construct remains a valid concept in Connecticut archaeology. The new data fit into the traditional system, elaborating and expanding the typology and sequences. The continuation of certain types and attribute classes from one stage into the next supports Rouse's and Smith's contention of great time depth for the Windsor tradition. It also suggests we should rethink our models of cultural history and cultural change.
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Pesonen, Petro, Markku Oinonen, Christian Carpelan et Päivi Onkamo. « Early Subneolithic Ceramic Sequences in Eastern Fennoscandia—A Bayesian Approach ». Radiocarbon 54, no 3-4 (2012) : 661–76. http://dx.doi.org/10.1017/s0033822200047330.
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In this contribution, we establish a radiocarbon-based chronology of early ceramic sequences in eastern Fennoscandia utilizing a Bayesian approach. The data consist of 56 individual 14C dates from charred or fermented food remains (charred crust, food residue) and birch bark tar used to seal cracks in vessels. We present the results of the models, discuss the chronological boundaries obtained, and compare the outcome with contemporary archaeological knowledge of the Subneolithic in eastern Fennoscandia. We also look at the role of charred crust δ13C values as indicators of reservoir effect present in the dates, perform some preliminary correction procedures for the dates, and discuss their effect on the chronologies.
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de Soto García, Isabel Sonsoles, María de los Reyes de Soto García, Blas Cabrera González et Rosario García Giménez. « Archaeometry and Analysis of Ceramic Materials from Ávila (Spain) : Late-Vetton Evidence ». Sustainability 13, no 11 (24 mai 2021) : 5910. http://dx.doi.org/10.3390/su13115910.
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From the archaeological excavations carried out during 2019/2020 in the walled Ávila city (Spain), numerous ceramic fragments of different chronologies have appeared that have allowed us to find settlement sequences in this city that place its beginnings before Romanization. The latest interventions allow us to know that the wall of Ávila has a Roman origin, and it was developed on an indigenous nucleus from the 1st century BC that received the Romanizing influence during the 1st century AD. In addition, it was possible to establish that the materials used for their preparation are consistent with the materials of the geological environment, which suggests a local origin. This paper presents the study of a set of ceramic samples using XRD, ICP/MS, SEM/EDX, and linescan analysis. A statistical analysis of the samples using the minor elements concentrations has suggested that even though the local origin, there were several production centers within painted ceramics that until now were always included as a single set. Finally, due to the importance of the “late-Vetton” or “late Iberic” ceramics (mid-1st century BC—middle of the 1st century AC) from the archaeological aspect, for the first time, these ceramics are studied in detail from chemical and mineralogical tests. It was discovered that these samples had been made in an oven that had not exceeded 800 °C due to the persistence of different phases after cooking.
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Callender, Rhonda L., et Andrew R. Barron. « Novel route to alumina and aluminate interlayer coatings for SiC, carbon, and Kevlart® fiber-reinforced ceramic matrix composites using carboxylate–alumoxane nanoparticles ». Journal of Materials Research 15, no 10 (octobre 2000) : 2228–37. http://dx.doi.org/10.1557/jmr.2000.0320.
Texte intégralRésumé :
SiC, carbon, and Kevlart® fibers were coated with carboxylate–alumoxane nanoparticles and their calcium-, lanthanum-, and yttrium-doped analogs; firing to 1400 °C formed uniform aluminate coatings. Optimum processing sequences were determined. Both carboxylate–alumoxane- and ceramic-coated fibers were examined by field emission scanning electron microscopy, microprobe analysis, and optical microscopy. Coatings produced were stable to thermal cycling under air at 1400 °C. Fiber-reinforced ceramic matrix composites were prepared and results from 3-point bend tests for carbon/Kevlar®-fabric-reinforced ceramic matrix composites (CMCs) and carbon-fiber-reinforced CMCs were determined. Flexure strength for carbon-fiber- and carbon/Kevlart®-fiber-reinforced alumina CMCs was determined.
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Ruiz-Hervias, Jesus, Axel Steuwer, Jonas Gurauskis, Thomas Buslaps et Carmen Baudín. « Residual Strain Profiles in Alumina-Zirconia Ceramic Composites ». Materials Science Forum 652 (mai 2010) : 57–62. http://dx.doi.org/10.4028/www.scientific.net/msf.652.57.
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Residual strain profiles were measured by synchrotron X-ray radiation in Al2O3/Y-stabilized ZrO2 (YSZ) ceramic laminates. Different stacking sequences were employed, including alternating layers containing 5 and 40 vol.% YSZ. Residual strains were found to be fairly constant within each layer; although they change at the interface between layers with different compositions. Different behaviour is observed for the strains along the in-plane and normal directions.
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Earle, Timothy, Attila Kreiter, Carla Klehm, Jeffrey Ferguson et Magdolna Vicze. « Bronze Age Ceramic Economy : The Benta Valley, Hungary ». European Journal of Archaeology 14, no 3 (2011) : 419–40. http://dx.doi.org/10.1179/146195711798356746.
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We describe the Bronze Age ceramic economy of the Benta Valley in Hungary. In the Bronze Age, long-distance trade in metals, metal objects, and other specialty items became central to expansive prestige goods exchange through Europe. Was that exchange in wealth, however, linked to broader developments of an integrated market system? The beginnings of market systems in prehistory are poorly understood. We suggest a means to investigate marketing by studying the changing ceramic economy of a region, rather than at a single site. Analysis of the ceramic inventory collected as part of the Benta Valley Project strongly suggests that, although ceramic production was quite sophisticated and probably specialized, exchange was highly localized (mostly within 10 km) and conducted through personalized community networks. Our ceramic study used three progressively finer-scaled analyses: inventorying ceramic forms and decoration to evaluate consumption patterns, petrographic analysis to describe manufacturing sequences, and instrumental neutron activation analysis (INAA) to describe exchange. We conclude that, based on present evidence, market systems had not developed in Hungary during the Bronze Age.
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McClure, Sarah B., Emil Podrug, Andrew M. T. Moore, Brendan J. Culleton et Douglas J. Kennett. « AMS 14C Chronology and Ceramic Sequences of Early Farmers in the Eastern Adriatic ». Radiocarbon 56, no 3 (2014) : 1019–38. http://dx.doi.org/10.2458/56.17918.
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The eastern Adriatic is a key area for understanding the mechanisms and effects of the spread of agriculture. This article presents an accelerator mass spectrometry (AMS) radiocarbon chronology for the introduction and subsequent development of farming villages on the eastern shore of the Adriatic (∼6000–1700 cal BC) and evaluates this in comparison with the established pottery chronology based on stylistic data from Pokrovnik (Drniš) on the Dalmatian coast of Croatia. Models for the spread of agriculture rely heavily on changing pottery styles to define cultural groups and trace geographic relationships. Based on AMS 14C dates presented here, Impressed Wares first appear in central Dalmatia by 6000 cal BC and persist until 5300 cal BC, well into what is generally termed the Middle Neolithic. Similarly, a typical Middle Neolithic ware, figulina, appeared earlier than anticipated. These findings stand in contrast to cave and rockshelter assemblages in the eastern Adriatic, but mirror assemblages from farming villages on the Italian Adriatic coast. This study argues that the similarities in ceramic assemblage composition and change through time may have less to do with direct contacts between areas, but more with the nature of ceramic production and consumption at village sites in general. These data shed light on the limitations of regional ceramic chronologies in the eastern Adriatic and highlight the necessity for systematic expansion of 14C chronologies to address the social, economic, and ecological relevance of early farming in the Adriatic for the spread of agriculture in Europe and the Mediterranean.
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Niemczycki, Mary Ann Palmer. « The Genesee Connection : The Origins of Iroquois Culture in West-Central New York ». North American Archaeologist 7, no 1 (juillet 1986) : 15–44. http://dx.doi.org/10.2190/gp1m-x2xd-1wf6-ej77.
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The Genesee Valley has long been recognized as a center of Iroquois development, but the connection between Owasco sites in the Genesee and Iroquois sequences in the adjacent regions has never been adequately demonstrated. Attempts to identify transitional Owasco-Iroquois sites in this region have been hampered by the use of diagnostic criteria based on data from eastern New York. This article examines ceramic patterns in the Genesee and establishes a regional cultural sequence based on ceramic criteria which have local diagnostic significance. This sequence reveals the transition from Owasco to Iroquois culture begins in the Genesee with a sudden influx of Ontario Iroquois ceramic traits from the west ca. 1250 A.D. This Owasco-Ontario Iroquois connection in the Genesee negates certain assumptions regarding Iroquois origins and alters our current concept of in situ development.
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Smyth, Michael P. « Before the Florescence ». Ancient Mesoamerica 9, no 1 (1998) : 137–50. http://dx.doi.org/10.1017/s0956536100001905.
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AbstractThe period preceding the Terminal Classic florescence in the Puuc region of Yucatan, Mexico has not received adequate research attention. Recent comprehensive site survey and excavation at Chac II (Chac) are exploring Puuc origins and have begun to redress the lack of chronological understanding regarding the region by independently linking architectural styles to ceramic sequences via a program of absolute dating. Results to date suggest that Chac was a significant Early Classic center (a.d.300–600) that also experienced a major Late Classic (a.d.600–800) occupation. Multiple lines of chronological evidence, including buildings with a mix of early architectural styles and associated pre-Cehpech and Cehpech ceramics (a.d.800–1000) within sealed architectural and stratigraphic contexts, suggest a period of architectural transition and the antecedents of Cehpech ceramics dating to the sixth century. These new chronological data and associated evidence for foreign contacts perhaps reaching to central Mexico argue for the assignment of a Middle Classic period (a.d.500–700) to the region, with broad evolutionary implications for Puuc origins and pan-Mesoamerican contacts.
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Yin, Lei, H. X. Peng, S. Dhara, L. Yang et B. Su. « Improvement of Microstructural Controllability of Cellular Ceramic for Multifunctional Composites ». Advanced Materials Research 47-50 (juin 2008) : 944–47. http://dx.doi.org/10.4028/www.scientific.net/amr.47-50.944.
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By modifying the sequences in preparation of aqueous ceramic slurries, starch was successfully employed to improve the microstructural controllability of alumina foams fabricated through protein coagulation casting technique. Open porosity was increased and the uniform distribution of microstructures was improved by the dual functions of starch as pore former and wet foam stabilizer. The viscosity of slurry was affected by the increasing amount of starch additive due to the total solid loading increase and the water uptake of starch. A well controlled pore structure will benefit multifunctional applications of these porous foams.
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Çevik, Özlem, et Osman Vuruşkan. « Ulucak Höyük ». Documenta Praehistorica 47 (1 décembre 2020) : 96–109. http://dx.doi.org/10.4312/dp.47.6.
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It has been increasingly clear that pottery was adopted as a continuous technology during the first quarter of the 7th millennium BC in a wide region, from Upper Mesopotamia through Central Anatolia and the Lakes District region. However, the absence of pottery in the basal level at Ulucak Höyük shows the presence of a pre-ceramic sequence in western Anatolia, before c. 6600/6500 cal BC. This article discusses the earliest pottery assemblage from Ulucak (6600/6500–6200 cal BC) and compares it with the later ceramic sequences at the site. Ultimately, the functional and typological developmental sequence of Neolithic pottery at Ulucak Höyük and its temporo-spatial relations with other Neolithic sites in Anatolia will be assessed.
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Dykeman, Douglas D., Ronald H. Towner et James K. Feathers. « Correspondence in Tree-Ring and Thermoluminescence Dating : A Protohistoric Navajo Pilot Study ». American Antiquity 67, no 1 (janvier 2002) : 145–64. http://dx.doi.org/10.2307/2694883.
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Dating of early Navajo residence and special use sites, ca. A.D. 1500-1775, has been hampered by a lack of datable materials and poor precision in radiocarbon results. Methods described in this paper use materials ubiquitous at early Navajo sites in northwestern New Mexico and employ a dual strategy involving tree-ring dating of nonarchitectural wood and thermoluminescence assay of ceramics and burned rock. Comparison of samples obtained from a number of sites near the Morris Site 1 pueblito indicates remarkable correspondence between tree-ring and thermoluminescence results. These techniques are argued to have considerable reliability for relatively recent cultural manifestations such as these early Navajo sites. Thermoluminescence in particular may be useful in protohistoric contexts where tree-ring dating is unavailable. The thermoluminescence technique has the added benefit of directly dating pottery sherds, which can be useful for developing ceramic cross-dating sequences.
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Mendisco, F., M. H. Pemonge, E. Leblay, T. Romon, G. Richard, P. Courtaud et M. F. Deguilloux. « Where are the Caribs ? Ancient DNA from ceramic period human remains in the Lesser Antilles ». Philosophical Transactions of the Royal Society B : Biological Sciences 370, no 1660 (19 janvier 2015) : 20130388. http://dx.doi.org/10.1098/rstb.2013.0388.
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The identity and history of the indigenous groups who occupied the Lesser Antilles during the ceramic periods remain highly controversial. Although recent archaeological evidence has challenged hypotheses concerning the organization of human groups in this region, more biological data are needed to fully inform the discussion. Our study provides, to our knowledge, the first palaeogenetic data for Late Ceramic groups of the Guadeloupe archipelago, yielding crucial information concerning the identities of these groups. Despite the generally poor DNA preservation in the tested remains, we were able to retrieve Hypervariable Region 1 sequences from 11 individuals and mitochondrial single-nucleotide polymorphisms from 13 individuals. These novel data provide interesting preliminary results in favour of a common origin for all Saladoid Caribbean communities, i.e. the first ceramic groups of the region, as well as for a local continuity between the Saladoid and post-Saladoid groups. A combination of the genetic data obtained and several pieces of cultural evidence allows us to propose that two different groups inhabited the Guadeloupe archipelago during the Late Ceramic period, with the possible occupation of the La Désirade and Marie-Galante islands by groups affiliated with the Taíno communities. The working hypotheses proposed here appear consistent with recent archaeological evidence.
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Lavin, Lucianne. « Pottery Classification and Cultural Models in Southern New England Prehistory ». North American Archaeologist 7, no 1 (juillet 1986) : 1–14. http://dx.doi.org/10.2190/b0xl-xl3a-xvd0-n4ke.
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Pottery is a major component of many prehistoric sites in northeastern North America. In southern New England, it appears to be the primary means by which archaeologists may establish finely delineated regional cultural sequences. Yet there are few comprehensive pottery studies from the region. Major reasons include controversies over the appropriate classification system and the utility of limited contextual materials. Recent research in Connecticut indicates that a combination of attribute analysis and typology provides maximum information in the reconstruction of cultural histories and processes, facilitates inter-site comparisons, and eliminates the need for re-analysis of collections. Application of the attribute/type method provides data that support and expand the Windsor ceramic sequences formulated by Rouse (1947) and Smith (1950) and suggests a gradual transition in material cultural change rather than the model of abrupt, periodic replacements that has often been used to explain cultural sequences and change in the Northeast.
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Longbiao, Li. « Thermomechanical fatigue damage evolution of fiber-reinforced ceramic–matrix composites under multiple loading sequences ». Advances in Mechanical Engineering 11, no 5 (mai 2019) : 168781401984859. http://dx.doi.org/10.1177/1687814019848599.
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Ball, Joseph W. « Rethinking the Becán Ceramic Sequence-Disjunctions, Continuities, Segmentation, and Chronology ». Latin American Antiquity 25, no 4 (décembre 2014) : 427–48. http://dx.doi.org/10.7183/1045-6635.25.4.427.
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One of the benchmark ceramic chronologies for the Central Maya Lowlands—that of Becán, Campeche—was critically flawed in its inception. Its flaws resultedfrom a perceived need to parallel the established Uaxactún bellwether and a failure to recognize that the typological and modal content of the sequence of assemblages defined was not continuous but disjunctive in character. In fact, this sequence reflected a broken continuum of discrete segments separated by a major break representing an actual occupational and historical gap in the site history of Becán. This paper reexamines the premises of the original Becán sequence, reassesses its structure and chronology, and offers a new alternative for its replacement and future fieldtesting. Reassessments of individual types and groups and their relationships and established chronologies, joined with a fresh consideration of Bejuco-phase depositional circumstances and stratigraphies, suggest that the political failure of Becán and the consequent abandonment of the center may have occurred as early as A.D. 730-750. The resulting gap in the occupational and ceramic sequences of the site lasted into the early ninth century. The suggested changes have significant ramifications not only for the chronologies of the site and the surrounding Río Bec region, but also for their cultural, architectural, and political histories.
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Kriba, Ilhem, et A. Djebaili. « The Interaction between Particles and a Plasma Beam in the Thermal Projection Process ». Advanced Materials Research 83-86 (décembre 2009) : 801–9. http://dx.doi.org/10.4028/www.scientific.net/amr.83-86.801.
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Plasma spray processes have been widely used to produce high performance coatings of a wide range of Materials (metallic, non-metallic, ceramics), offering protection from, eg. wear, extreme temperature, chemical attack and environmental corrosion. To obtain good quality coatings, spray parameters must be carefully selected. Due to the large variety in process parameters, it is difficult to optimize the process for each specific coating and substrate combinations. Furthermore modelling the spray process allows a better understanding of the process sequences during thermal spraying. Good agreement of the virtual spraying process with the real coating formation is achieved by modelling the particular process steps. The simulation of coating formation to estimate the process parameters is an important tool to develop new coating structures with defined properties. In this work, the process of plasma sprayed coating has been analyzed by numerical simulation. Commercial code is used to predict the plasma jet characteristics, plasma –particle interaction, and coating formation. Using this model we can obtain coating microstructure and characteristics which form a foundation for further improvement of an advanced ceramic coating build up model.
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AJADI, Michael Olaniyi. « Eclecticism Style in Ceramic Art Practices of Ife Art School ». Journal of Education and Practice 5, no 2 (2 août 2021) : 45–58. http://dx.doi.org/10.47941/jep.630.
Texte intégralRésumé :
Purpose: The study discusses Ife ceramic wares in tandem with the historical approach of the decorative patterns. It equally determines the origin of each style and how it moved and spread across the phases. The sequences of creative impulse and stylistic trends of ceramic practices in the art school from inception have not received scholarly attention in terms of the examination of the approaches towards the conceptions. The specific objective is to investigate the inception of eclecticism in the art school and circumstances behind the conceptions in order to reveal the contextual definitions of used designs and factors influence the innovation.
Methodology: Descriptive and analytical approaches were used to trace decorative trends of each phase and the integration of the various motifs and styles of the previous phases in the new phases that sprung up. Samples of ceramic wares in the art school exhibition brochures, galleries and ceramic studios were collected for analysis and photographs were also taken for evidence.
Findings: In concept, the praxis reveals traditional ideology at inception and desegregation of different themes, ideas, and styles in the recent phase of the practice. The practices are eclectic inclined as of late with reflection of traditional ideology, contemporary issues and customs of Western societies. Notwithstanding, the ceramic art tradition of the art school is aesthetically inclined both in principle and practice.
Unique contribution to theory, policy and practice: No doubt, the sculptural creativeness of Ife wares has preserved cultural heritage for public awareness. This is largely evident in the proliferation of her ingenious adaptation of indigenous deco-stylistic techniques with Western influence that portrayed Nigerian traditional culture by themes, forms and styles in concepts and renditions.
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Bamford, Matthieu, et Jean Christophe Batsale. « Analytical Singular Value Decomposition of infrared image sequences : microcrack detection on ceramic composites under mechanical stresses ». Comptes Rendus Mécanique 336, no 5 (mai 2008) : 440–47. http://dx.doi.org/10.1016/j.crme.2007.12.003.
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Li, Longbiao. « Modeling of fatigue hysteresis behavior in carbon fiber-reinforced ceramic–matrix composites under multiple loading stress levels ». Journal of Composite Materials 51, no 7 (28 juillet 2016) : 971–83. http://dx.doi.org/10.1177/0021998316657863.
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The fatigue hysteresis behavior in fiber-reinforced ceramic–matrix composites under multiple loading stress levels has been investigated. Based on the fatigue damage mechanism of fiber slipping relative to matrix in the interface debonded region upon unloading/reloading, the fatigue hysteresis loops models corresponding to different interface slip cases under multiple loading stress levels have been derived. The fatigue hysteresis loss energy and interface slip corresponding to single/multiple loading stress levels and different loading sequences have been investigated. The fatigue hysteresis loops of unidirectional SiC/CAS−II composite under multiple loading stress levels have been predicted.
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Anderson, Atholl, John Chappell, Geoffrey Clark et Sarah Phear. « Comparative Radiocarbon Dating of Lignite, Pottery, and Charcoal Samples from Babeldaob Island, Republic of Palau ». Radiocarbon 47, no 1 (2005) : 1–9. http://dx.doi.org/10.1017/s0033822200052139.
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It is difficult to construct archaeological chronologies for Babeldaob, the main island of Palau (western Micronesia), because the saprolitic clays of the dominant terraced-hill sites and associated ceramic sherds often contain old carbon that originated in lignites. This has implications, as well, for chronologies of sedimentary sequences. Comparative analysis of the dating problem using lignite, pottery, and charcoal samples indicates that, in fact, there are both old and young sources of potential contamination. It is concluded that radiocarbon samples from Babeldaob need to be tested for appropriate carbon content rather than relying solely upon material identification.
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Longbiao, Li. « Interfacial Debonding and Slipping of Carbon Fiber-Reinforced Ceramic-Matrix Composites Subjected to Different Fatigue Loading Sequences ». Journal of Aerospace Engineering 29, no 5 (septembre 2016) : 04016029. http://dx.doi.org/10.1061/(asce)as.1943-5525.0000618.
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Zeidler, James A., Caitlin E. Buck et Clifford D. Litton. « Integration of Archaeological Phase Information and Radiocarbon Results from the Jama River Valley, Ecuador : A Bayesian Approach ». Latin American Antiquity 9, no 2 (juin 1998) : 160–79. http://dx.doi.org/10.2307/971992.
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Archaeological syntheses of western Ecuadorian prehistory have been hampered by a lack of reliable absolute chronologies and detailed cultural sequences for many key areas, one of which is northern Manabí Province, known principally as the territory of the Jama-Coaque cultural tradition. This study presents a seven-phase cultural sequence for the Jama River valley of northern Manabí that spans over 3,600 calendar years. A statistical model relating the successive archaeological phases is established, based on prior knowledge of the stratigraphy and ceramic seriation from key archaeological sites throughout the valley. A Bayesian statistical approach is then employed to calibrate 37 radiocarbon determinations for the purpose of estimating calendar dates for the limits of these phases. Apart from its contribution to the prehistory of a poorly studied area, the analysis illustrates the value of a probabilistic Bayesian approach to radiocarbon calibration, especially when the determinations relate to archaeologically predefined phases. It also demonstrates the dangers of uncritically applying generalized periodization schemes to specific sequences of historical development and highlights the need for reassessing Ecuadorian chronology through more precise interregional correlations.
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McCafferty, Geoffrey G. « The Ceramics and Chronology of Cholula, Mexico ». Ancient Mesoamerica 7, no 2 (1996) : 299–323. http://dx.doi.org/10.1017/s0956536100001486.
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AbstractChronology is a fundamental prerequisite for problem-oriented, anthropologically relevant archaeology. It is also the shaky foundation that has hampered attempts to reconstruct the culture history of Cholula, Mexico. Cholula is among the oldest continuously occupied urban centers of the New World, yet it remains one of the most enigmatic. This paper evaluates previous cultural sequences for the site, and summarizes recent evidence to construct a chronology using absolute dates and ceramic assemblages from primary depositional contexts. This revised sequence features a clearer understanding of Middle Formative settlement and the definition of ritual and domestic contexts from the Classic period. In addition, there is now evidence for a gradual transition between Late Classic and Early Postclassic material culture; and for the evolution of the Postclassic polychrome tradition within a sequence of short, clearly defined phases.
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Myers, Todd, Parag Banerjee, Susmita Bose et Amit Bandyopadhyay. « Layered lead zirconate titanate and lanthanum-doped lead zirconate titanate ceramic thin films ». Journal of Materials Research 17, no 9 (septembre 2002) : 2379–85. http://dx.doi.org/10.1557/jmr.2002.0348.
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The physical layering of sol-gel-derived lead zirconate titanate (PZT) 52/48 and lanthanum-doped PZT (PLZT) 2/52/48 on platinized silicon substrates was investigated to determine if the ferroelectric properties and fatigue resistance could be influenced by different layering sequences. Monolithic thin films of PZT and PLZT were characterized to determine their ferroelectric properties. Sandwich structures of Pt/PZT/PLZT/PLZT/PZT/Au and Pt/PLZT/PZT/PZT/PLZT/Au and alternating structures of Pt/PZT/PLZT/PZT/PLZT/Au and Pt/PLZT/PZT/PLZT/PZT/Au were then fabricated and characterized. X-ray photoelectron spectroscopy depth profiles revealed that the layering sequence remained intact up to 700 °C for 45 min. It was found that the end layers in the multilayered films had a significant influence on the resulting hysteresis behavior and fatigue resistance. A direct correlation of ferroelectric properties and fatigue resistance can be made between the data obtained from the sandwiched structures and their end-layer monolithic thin film counterparts. Alternating structures also showed an improvement in the fatigue resistance while the polarization values remained between those for PZT and PLZT thin films.
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Easton, Donald, et Bernhard Weninger. « A possible new Bronze Age period at Troy ». Anatolian Studies 68 (2018) : 33–73. http://dx.doi.org/10.1017/s0066154618000029.
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AbstractStatistical analysis of Carl Blegen's pottery sequence using Correspondence Analysis (CA) suggests a gap of 100–200 years between his Troy III and IV periods. From the Manfred Korfmann excavations three stratigraphic sequences hitherto assigned to Troy IV and V appear to bridge it. This allocation is based on stratigraphic/architectural grounds and on the observable development in ceramic shapes and wares. Heinrich Schliemann's pottery sequence from 1870–1873 is also analysed by CA and found to compare well with Blegen's (with limited exceptions probably due to the larger scope of his excavations), but it does not exhibit the same gap. This suggests that during the ‘bridge’ period occupation shrank to the summit on the western end of the citadel mound. This ‘bridge’ period of seven or more building phases has a distinctive ceramic assemblage and may be called the Proto-IV period. It is broadly contemporary with Middle Helladic I, Beycesultan VIII–VI, Küllüoba II and the Tarsus Early Bronze to Middle Bronze transitional period. Careful re-evaluation of the radiocarbon evidence dates it to ca 2150–1990 cal. BC. Botanical and faunal evidence from the strata in question attests significantly drier climatic conditions which, together with the smaller size of the settlement, probably reflect the 4.2ka cal. BP climatic deterioration.
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Abel, Timothy J. « Rethinking the Iroquoian Occupation of Northern New York ». Canadian Journal of Archaeology 45, no 2 (2021) : 283–302. http://dx.doi.org/10.51270/45.2.283.
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Recent Bayesian modeling of new high-precision AMS dates has caused a revision of the Iroquoian chronology of northern New York. The Iroquoian occupation is now estimated to date between AD 1425–1520, with no good evidence for developmental precursors in the region. The more than 50 village components in the region must now fit into almost half the temporal span as previously believed. All the settlement clusters now seem to have been contemporary and dual village settlement for some of the clusters now seems likely. For the ceramic seriation to remain true, one of the cluster sequences must be chronologically reversed, having significant implications for its culture history. Finally, while their dispersal from northern New York remains complex, it must be rethought considering the new chronology.
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Forsyth, Donald W. « The Ceramic Sequence at Nakbe, Guatemala ». Ancient Mesoamerica 4, no 1 (1993) : 31–53. http://dx.doi.org/10.1017/s0956536100000766.
Texte intégralRésumé :
AbstractThe site of Nakbe, located approximately 13 km southeast of El Mirador in the far northern part of the Peten, has been investigated by the RAINPEG Project, directed by Richard Hansen, for the last four field seasons. The ceramic sequence from Nakbe has provided us with a much broader view of cultural development in the north-central Peten. We have defined a series of preliminary ceramic complexes that span Middle Preclassic through Late Classic times.The earliest complex at Nakbe, called Ox, which belongs to the Mamom horizon, is one of the two best represented at the site, and definitely associated, late in the period, with large-scale architecture. The principal ceramic groups are the Juventud, Chunhinta, and Pital. The main forms are bowls or basins with flaring walls and direct or everted rims, short-necked jars, cuspidors or semicuspidors, and composite-silhouette bowls. Particularly notable, although rare, are the types Muxanal Red-on-Cream and Tierra Mojada Resist. The Ox Complex is characterized by a high frequency of decoration executed by penetration methods, especially incision and chamfering.The unslipped pottery pertains to the types Achiotes Unslipped and Palma Daub. The latter is marked by a red wash applied to the exterior neck of the jar, the major form in these types. Daub is a form of decoration limited to the Middle Preclassic in this area, as is the chamfering technique on the slipped pottery.The ceramic complexes most similar to Ox are located to the south of Nakbe at Uaxactun and Tikal. The high frequency of chamfering, daub, and other traits strongly link Nakbe to these southern sites during the Middle Preclassic, while sites to the north and southwest, such as Seibal, Altar de Sacrificios, and Becan exhibit more tenuous connections.The Kan Complex belongs to the Late Preclassic period, and is characterized by the Sierra, Polvero, Flor, and Sapote Ceramic Groups. Although associated with the large structures in the site center, Kan ceramics are less abundant than Ox ceramics in our samples. Kan pottery corresponds closely to that of El Mirador and is similar to other complexes of the Chicanel horizon. Particularly noteworthy are everted rims with circumferential grooves and lateral, labial, and medial flanges and ridges. The unslipped pottery of the Kan Complex consists almost exclusively of jars bearing exterior striation from the shoulder to the base.The closest ceramic ties to Kan pottery continues to be with the southern complexes, especially Uaxactun and Tikal. Moreover, the similarity to Seibal is greater during Chicanel times, while Belize appears to differentiate itself ceramically from the Peten during this time. Nevertheless, the Chicanel horizon is the period in which the maximum geographical extent of a ceramic sphere is reached.“Protoclassic” ceramics are rare, but the small amounts recovered at Nakbe are similar to those from El Mirador. The major type is Iberia Orange, found in small quantities in surface contexts. Characterized by hollow, mammiform supports, hooked rims, and orange slip, this Nakbe pottery seems to be more similar to pottery at Seibal than to other complexes with Protoclassic pottery.Early Classic pottery is virtually nonexistent in our excavations, suggesting an insignificant occupation during this period.Late Classic pottery (Uuc Complex) appears in significant quantities at Nakbe, mainly in the outskirts of the site. All of the types and modes defined at El Mirador are found at Nakbe, principally Tinaja Red, Chinja Impressed, Infierno Black, and Carmelita Incised, as well as the polychrome types. Moreover, Codex-style polychrome was also found at the site. As at El Mirador, the Uuc ceramics are not found in association with large-scale architecture, and it appears that Nakbe was not a major center at this time.The major occupations at Nakbe pertain to the Middle and Late Preclassic periods. The abundance of architecture, ceramics, and other classes of artifacts from the Ox Complex provides us with an opportunity to investigate a Middle Preclassic occupation in which there was a much more complex social organization, at least at Nakbe, than had previously been suspected.
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Spiridonova, Tatyana S., Aleksandra A. Savina, Evgeniy V. Kovtunets et Elena G. Khaikina. « New triple molybdate and tungstate Na<sub>5</sub>Rb<sub>7</sub>Sc<sub>2</sub>(<i>X</i>O<sub>4</sub>)<sub>9</sub> ; (<i>X</i> ; = Mo, W) ». Chimica Techno Acta 8, no 4 (16 décembre 2021) : 20218412. http://dx.doi.org/10.15826/chimtech.2021.8.4.12.
Texte intégralRésumé :
New compounds of the composition Na5Rb7Sc2(XO4)9 (X = Mo, W) were obtained via the ceramic technology. The sequences of chemical transformations occurring during the formation of these compounds were established, and their primary characterization was performed. Both Na5Rb7Sc2(XO4)9 (X = Mo, W) were found to melt incongruently at 857 K (X = Mo) and 889 K (X = W). They are isostructural to Ag5Rb7Sc2(XO4)9 (X = Mo, W), Na5Cs7Ln2(MoO4)9 (Ln = Tm, Yb, Lu) and crystallize in the trigonal crystal system (sp. gr. R32). The crystal structures were refined with the Rietveld method using the powder X-ray diffraction data. The thermal expansion of Na5Rb7Sc2(WO4)9 was studied by high-temperature powder X-ray diffraction; it was shown that this triple tungstate belongs to high thermal expansion materials.
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Sutton, Nicholas, Glenn Summerhayes et Anne Ford. « Regional Interaction Networks in Southern Papua New Guinea During the Late Holocene : Evidence from the Chemical Characterisation of Chert Artefacts ». Proceedings of the Prehistoric Society 81 (9 octobre 2015) : 343–59. http://dx.doi.org/10.1017/ppr.2015.14.
Texte intégralRésumé :
Over 40 years of archaeological investigations along the south coast of Papua New Guinea has identified a rapid succession of cultural changes during the late Holocene. The so-called ‘Papuan Hiccup’ (c. 1200–800 cal bp) is a poorly understood period of socio-economic upheaval along the coast, identified mainly from changes in archaeological ceramic styles and settlement patterns. During this period, the region-wide Early Papuan Pottery (EPP) tradition diverges into separate, localised ceramic sequences that have generic associations with local ethnographic wares. A correspondence between the timing of the Papuan Hiccup and a period of peak El Niño-Southern Oscillation (ENSO) activity implies a link between cultural and climate change. This paper explores this relationship further by examining changes in interaction networks along the south coast of Papua New Guinea, specifically focusing on chert artefacts. Chemical characterisation (portable X-Ray Fluorescence; pXRF) and technological analysis are used to map changes in lithic technology over time, including access to raw materials and technological organisation, at the site of Taurama, a prehistoric coastal village site that was occupied both prior to and after the Papuan Hiccup. Although the sample sizes are small and the interpretations necessarily circumscribed, it is argued that changes in the number of chert sources being exploited and in the intensity of core reduction at Taurama may be related to climate change in the region.
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Marsh, Erik J., Andrew P. Roddick, Maria C. Bruno, Scott C. Smith, John W. Janusek et Christine A. Hastorf. « Temporal Inflection Points in Decorated Pottery : A Bayesian Refinement of the Late Formative Chronology in the Southern Lake Titicaca Basin, Bolivia ». Latin American Antiquity 30, no 4 (décembre 2019) : 798–817. http://dx.doi.org/10.1017/laq.2019.73.
Texte intégralRésumé :
The Late Formative period immediately precedes the emergence of Tiwanaku, one of the earliest South American states, yet it is one of the most poorly understood periods in the southern Lake Titicaca Basin (Bolivia). In this article, we refine the ceramic chronology of this period with large sets of dates from eight sites, focusing on temporal inflection points in decorated ceramic styles. These points, estimated here by Bayesian models, index specific moments of change: (1) cal AD 120 (60–170, 95% probability): the first deposition of Kalasasaya red-rimmed and zonally incised styles; (2) cal AD 240 (190–340, 95% probability): a tentative estimate of the final deposition of Kalasasaya zonally incised vessels; (3) cal AD 420 (380–470, 95% probability): the final deposition of Kalasasaya red-rimmed vessels; and (4) cal AD 590 (500–660, 95% probability): the first deposition of Tiwanaku Redwares. These four modeled boundaries anchor an updated Late Formative chronology, which includes the Initial Late Formative phase, a newly identified decorative hiatus between the Middle and Late Formative periods. The models place Qeya and transitional vessels between inflection points 3 and 4 based on regionally consistent stratigraphic sequences. This more precise chronology will enable researchers to explore the trajectories of other contemporary shifts during this crucial period in Lake Titicaca Basin's prehistory.
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Hedjazi, Lotfi, Sofiane Belhabib, Angélina D’Orlando et Sofiane Guessasma. « Breaking Material Symmetry to Control Mechanical Performance in 3D Printed Objects ». Symmetry 15, no 1 (22 décembre 2022) : 28. http://dx.doi.org/10.3390/sym15010028.
Texte intégralRésumé :
Additive manufacturing is a modern manufacturing technology allowing the material structuring at a fine scale. This structuring affects the performance of printed parts. In this study, the quantification of the material arrangement in 3D printed ceramic on the mechanical performance is tackled. The experimental layout considers two main printing parameters, namely, part orientation and printing angle, where 12 different printing configurations are studied. These configurations differ in terms of filament arrangement in the building direction, and within the plane of construction. Material characterisation is undertaken through tensile testing, which are performed for vertical, lateral and longitudinal orientations, and combined with a printing angle of 0°, 15°, 30°, and 45°. In addition, Scanning Electron Microscopy is considered to study how the material symmetry affects the fractured patterns. This analysis is completed with optical imaging and is used to monitor the deformation sequences up to the rupture point. The experimental results show a wide variety of deformation mechanisms that are triggered by the studied printing configurations. This study concludes on the interpretation of the observed trends in terms of mechanical load transfer, which is related to the lack of material connectivity, and the relative orientation of the filaments with respect to the loading directions. This study also concludes on the possibility to tune the tensile performance of 3D printed ceramic material by adjusting both the part orientation and the printing angle.
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Longbiao, Li. « Thermomechanical fatigue damage development of continuous carbon fiber-reinforced ceramic-matrix composites subjected to different loading sequences and phase angles ». Journal of the Australian Ceramic Society 55, no 2 (1 septembre 2018) : 443–68. http://dx.doi.org/10.1007/s41779-018-0252-x.
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Ilie, Sorin, Adrian Miuţescu, Mircea Stoianovici et Gabriela Mitran. « Recovery of Precious Metals from Catalytic Converters of Automobiles by Hydrometallurgical Solid-Liquid Extraction Processes ». Advanced Materials Research 837 (novembre 2013) : 105–9. http://dx.doi.org/10.4028/www.scientific.net/amr.837.105.
Texte intégralRésumé :
Today, among the basic requirements to be fulfilled by an automobile, those relating to environmental protection and recyclability are of great importance. This paper aims to present a new technological solution to recover rare metals - Platinum, Palladium and Rhodium - from automotive used catalysts, based on hydrometallurgical method of solid-liquid extraction. Following the theoretical and experimental researches, were established the technological sequences which must be carried for recovering precious metals from used automotive catalysts, in the pilot phase. The proposed technology has been applied for a quantity of 10 kg of used automotive catalysts of ceramic monolithic type, at the end of the recovery process and selective separation, resulting the following recovery efficiencies: 95 % for Platinum, 95 % for Palladium and 92 % for Rhodium. Finally, there were highlighted the main advantages of hydrometallurgical processes: versatility, economicity, high efficiencies and relatively low costs.
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Cassari, Leonardo, Martina Todesco, Annj Zamuner, Saima Jalil Imran, Martina Casarin, Deborah Sandrin, Joaquin Ródenas-Rochina et al. « Covalently Grafted Peptides to Decellularized Pericardium : Modulation of Surface Density ». International Journal of Molecular Sciences 24, no 3 (2 février 2023) : 2932. http://dx.doi.org/10.3390/ijms24032932.
Texte intégralRésumé :
The covalent functionalization of synthetic peptides allows the modification of different biomaterials (metallic, polymeric, and ceramic), which are enriched with biologically active sequences to guide cell behavior. Recently, this strategy has also been applied to decellularized biological matrices. In this study, the covalent anchorage of a synthetic peptide (REDV) to a pericardial matrix decellularized via Schiff base is realized starting from concentrated peptide solutions (10−4 M and 10−3 M). The use of a labeled peptide demonstrated that as the concentration of the working solution increased, the surface density of the anchored peptide increased as well. These data are essential to pinpointing the concentration window in which the peptide promotes the desired cellular activity. The matrices were extensively characterized by Water Contact Angle (WCA) analysis, Differential Scanning Calorimetry (DSC) analysis, geometric feature evaluation, biomechanical tests, and preliminary in vitro bioassays.
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Marsh, Erik J. « A Bayesian Re-Assessment of the Earliest Radiocarbon Dates from Tiwanaku, Bolivia ». Radiocarbon 54, no 2 (2012) : 203–18. http://dx.doi.org/10.2458/azu_js_rc.v54i2.15826.
Texte intégralRésumé :
The development of sociopolitical complexity at Tiwanaku around AD 500 was one of the major episodes of social change in the history of the Lake Titicaca Basin. It was the result of poorly understood processes that took place at a series of ceremonial centers in the preceding centuries. The history of Tiwanaku during this time is especially unclear, because the only radiocarbon dates are from excavations whose details were never completely published. Despite this, there is consensus that Tiwanaku was founded around 300 BC. A re-evaluation of the archaeological context of each of these dates shows many of them to be unreliable. Two Bayesian models from independent excavations agree that Tiwanaku was in fact founded centuries later, most likely around AD 110 (50-170, 1σ). This has important implications for widely used monolith and ceramic sequences, as well as understanding the rise of Tiwanaku and other archaic states.
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Marsh, Erik J. « A Bayesian Re-Assessment of the Earliest Radiocarbon Dates from Tiwanaku, Bolivia ». Radiocarbon 54, no 02 (2012) : 203–18. http://dx.doi.org/10.1017/s0033822200046932.
Texte intégralRésumé :
The development of sociopolitical complexity at Tiwanaku around AD 500 was one of the major episodes of social change in the history of the Lake Titicaca Basin. It was the result of poorly understood processes that took place at a series of ceremonial centers in the preceding centuries. The history of Tiwanaku during this time is especially unclear, because the only radiocarbon dates are from excavations whose details were never completely published. Despite this, there is consensus that Tiwanaku was founded around 300 BC. A re-evaluation of the archaeological context of each of these dates shows many of them to be unreliable. Two Bayesian models from independent excavations agree that Tiwanaku was in fact founded centuries later, most likely around AD 110 (50-170, 1σ). This has important implications for widely used monolith and ceramic sequences, as well as understanding the rise of Tiwanaku and other archaic states.
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Piec, Marek, Leszek Adam Dobrzański, Krzysztof Labisz, Ewa Jonda et Andrzej Klimpel. « Laser Alloying with WC Ceramic Powder in Hot Work Tool Steel Using a High Power Diode Laser (HPDL) ». Advanced Materials Research 15-17 (février 2006) : 193–98. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.193.
Texte intégralRésumé :
Investigations include alloying the X38CrMoV5-3 hot-work tool steel surface layer with the tungsten carbide, using the high power diode laser (HPDL). The tungsten carbide ceramic particles of the medium grain size according to FSSS = 50 /m were introduced using the rotor conveyer to improve the properties of the surface layer. The powder feed rate was set at the steady level of 8.64g/min. Remelting and alloying were carried out several times in the laser power range of 1.2 – 2.3 kW in the remelting/alloying, alloying/remelting sequences. The structural mechanism was determined of gradient layer development, effect was studied of alloying parameters, gas protection method, and powder feed rate on its mechanical properties, and especially on its hardness, abrasive wear resistance, and roughness. Structure changes were revealed consisting, in particular, in its refining, and also hardness and microhardness changes in comparizon to the nonremelted steel. Examination results obtained with the EDX microanalysis, surface and linear analysis of the chemical composition, as well as the X-ray qualitative phase analysis are presented.
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Yao, Xiaogang, Yi Zhang, Haishen Ren, Haiyi Peng, Tianyi Xie, Mingzhao Dang et Huixing Lin. « Investigation on the reaction sequences and properties of β-eucryptite ceramic fabricated by a novel solid state reaction route from hydroxides ». Journal of the European Ceramic Society 39, no 4 (avril 2019) : 1564–68. http://dx.doi.org/10.1016/j.jeurceramsoc.2018.11.014.
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Schechter, Martin. « The Use of Cerami Sequences in Critical Point Theory ». Abstract and Applied Analysis 2007 (2007) : 1–28. http://dx.doi.org/10.1155/2007/58948.
Texte intégralRésumé :
The concept of linking was developed to produce Palais-Smale (PS) sequencesG(uk)→a,G'(uk)→0forC1functionalsGthat separate linking sets. These sequences produce critical points if they have convergent subsequences (i.e., ifGsatisfies the PS condition). In the past, we have shown that PS sequences can be obtained even when linking does not exist. We now show that such situations produce more useful sequences. They not only produce PS sequences, but also Cerami sequences satisfyingG(uk)→a,(1+||uk||)G'(uk)→ 0as well. A Cerami sequence can produce a critical point even when a PS sequence does not. In this situation, it is no longer necessary to show thatGsatisfies the PS condition, but only that it satisfies the easier Cerami condition (i.e., that Cerami sequences have convergent subsequences). We provide examples and applications. We also give generalizations to situations when the separating criterion is violated.
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Perrin, Thomas, Tiphaine Dachy, Esther López-Montalvo, Claire Manen et Grégor Marchand. « What relations between North Africa and Europe in the early holocene ? » Tabona : Revista de Prehistoria y Arqueología 22 (2022) : 261–81. http://dx.doi.org/10.25145/j.tabona.2022.22.13.
Texte intégralRésumé :
Between the 8th and 5th millennium BCE, human societies in the Western Mediterranean underwent several major changes. One of them took place during the 7th millennium with a profound change in material production, especially in their stone industries. It resulted in a fundamental change in production patterns, operating sequences and technical procedures. The precise origin of these changes is currently unknown, but it is possible that they initially occurred in North Africa before spreading rapidly along the shores of the Mediterranean and reaching Western Europe. This south-to-north expansion could reflect population shifts, at least in the early stages of the expansion of these new technical processes. However, possible contacts between Africa and Europe are not limited to this technical sphere, and exchanges can also be documented in both ceramic productions and graphic expressions. Several recent research programmes have brought new data to these hypotheses, the main results of which are presented here.
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Siklósi, Zsuzsanna, et Márton Szilágyi. « CULTURE, PERIOD OR STYLE ? RECONSIDERATION OF EARLY AND MIDDLE COPPER AGE CHRONOLOGY OF THE GREAT HUNGARIAN PLAIN ». Radiocarbon 63, no 2 (21 janvier 2021) : 585–646. http://dx.doi.org/10.1017/rdc.2020.115.
Texte intégralRésumé :
ABSTRACTThe main goal of our research project was to date the Early and Middle Copper Age (4500/4450–3800 cal BC) of the Great Hungarian Plain more precisely. In our project, we took samples for accelerator mass spectrometry (AMS) dating from both settlement features and burials, and the data were analyzed using Bayesian modeling. We examined the Early and Middle Copper Age finds of the Great Hungarian Plain on several levels (site, microregional, and regional levels) using a bottom-up approach. The AMS measurements were supplemented by statistics-based pottery analysis in order to make our understanding of the relationship between the Tiszapolgár and Bodrogkeresztúr cultures more detailed. As a result, we can see a significant, 130 (68.2%) 230 years overlap between the two types of find assemblages, which contradicts to the earlier accepted chronological sequences created by the traditional culture-historical approach. According to the stylistic analyzes, the two ceramic styles are not clearly distinguishable.
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Taladoire, Eric, Sara Dzul, Philippe Nondédéo et Mélanie Forné. « CHRONOLOGY OF THE RÍO BEC SETTLEMENT AND ARCHITECTURE ». Ancient Mesoamerica 24, no 2 (2013) : 353–72. http://dx.doi.org/10.1017/s0956536113000254.
Texte intégralRésumé :
AbstractChronology is a crucial issue given the specific settlement patterns of the Río Bec region located on the northern fringe of the Maya central lowlands. Fine-resolution chronology of the local residential occupation in its many spatial and temporal forms is one of the main proxies available to reconstruct social organization and dynamics, in the absence of a nucleated center with the typical Maya political monuments usually investigated. Variability can be traced in residential morphologies and evolution that must be dated. The scope of the paper aims to describe the construction of the Río Bec chronology in its multiple dimensions, based on a diversity of methods from ceramic Type-Variety classification up to seriation of building sequences defining the evolution of the famous Río Bec architectural style. Epigraphic evidence exists, albeit limited and ambiguous. The general sequence of occupation for the targeted micro-region stretches from the Middle Preclassic to the end of the Terminal Classic period.
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Choi, S. R., et J. P. Gyekenyesi. « Slow Crack Growth Analysis of Advanced Structural Ceramics Under Combined Loading Conditions : Damage Assessment in Life Prediction Testing ». Journal of Engineering for Gas Turbines and Power 123, no 2 (1 octobre 2000) : 277–87. http://dx.doi.org/10.1115/1.1365160.
Texte intégralRésumé :
Slow crack growth analysis was performed with three different loading histories including constant stress-rate/constant stress-rate testing (Case I loading), constant stress/constant stress-rate testing (Case II loading), and cyclic stress/constant stress-rate testing (Case III loading). Strength degradation due to slow crack growth and/or damage accumulation was determined numerically as a function of percentage of interruption time between the two loading sequences for a given loading history. The numerical solutions were examined with the experimental data determined at elevated temperatures using four different advanced ceramic materials, two silicon nitrides, one silicon carbide and one alumina for the Case I loading history, and alumina for the Case II loading history. The numerical solutions were in reasonable agreement with the experimental data, indicating that notwithstanding some degree of creep deformation presented for some test materials slow crack growth was a governing mechanism associated with failure for all the test materials.
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Gai, Pratibha L. « In-situ Electron Microscopy in catalysis research ». Proceedings, annual meeting, Electron Microscopy Society of America 48, no 4 (août 1990) : 228–29. http://dx.doi.org/10.1017/s0424820100174278.
Texte intégralRésumé :
The dynamic nature of surfaces and interfaces in catalytic oxides, and in metal particle catalysts on oxide supports, is of fundamental importance in heterogeneous catalysis. In-situ electron microscopy with a controlled environment has been used, together with other EM-based techniques, to obtain a better understanding of disorder under reaction conditions in these non-stoichiometric materials. It is important to recognize that the structure of the solid surface under reaction conditions may differ from that occurring under static conditions or in different atmospheres, including the usual EM high vacuum specimen environment.Powders of co-precipitated silica supported copper-ruthenium are used in ethane hydrogenolysis; whilst Cu on alumina is used in methanol related catalysis and some power cells. The performance, sintering, metal-ceramic adhesion and fracture depend on the interface structures. They are controlled by chemical and other materials properties under working conditions Fig.1a and c show in-situ EM reaction sequences of Cu with amorphous alumina at ∼200°C in H2 and CO Fig.1c and d show the subsequent reaction of the particles in oxygen.
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Dobrzański, Leszek Adam, Marek Piec, Zuzanka Trojanová, Józef Lelątko et Andrzej Klimpel. « Structure and Properties of Gradient Layers Using High Power Diode Laser ». Materials Science Forum 530-531 (novembre 2006) : 269–74. http://dx.doi.org/10.4028/www.scientific.net/msf.530-531.269.
Texte intégralRésumé :
Investigations include alloying the X38CrMoV5-3 hot-work tool steel surface layer with the tungsten carbide, using the high power diode laser (HPDL). The tungsten carbide ceramic particles of the medium grain size according to FSSS = 50 Bm were introduced using the rotor conveyer to improve the properties of the surface layer. The powder feed rate was set at the steady level of 8.64g/min. Remelting and alloying were carried out several times in the laser power range of 1.2 – 2.3 kW in the remelting/alloying, alloying/remelting sequences. The structural mechanism was determined of gradient layer development, effect was studied of alloying parameters, gas protection method, and powder feed rate on its mechanical properties, and especially on its hardness, abrasive wear resistance, and roughness. Structure changes were revealed consisting, in particular, in its refining, and also hardness and microhardness changes in comparison to the non-remelted steel. Examination results obtained with the EDX microanalysis, surface and linear analyses of the chemical composition, as well as the X-ray qualitative phase analysis are presented.
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Lesure, Richard G. « Refining an Early Formative Ceramic Sequence From the Chiapas Coast of Mexico ». Ancient Mesoamerica 9, no 1 (1998) : 67–81. http://dx.doi.org/10.1017/s0956536100001851.
Texte intégralRésumé :
AbstractAnalysis of Early Formative ceramics from the site of Paso de la Amada, on the coast of Chiapas, Mexico, yields a refined sequence for the period 1400–1000b.c.A simple key has been developed to classify midden assemblages. Its utility for creating chronologically sensitive groupings is confirmed by multidimensional scaling of 32 units. The refined ceramic sequence provides a basis for investigating short-term sociopolitical dynamics during the Early Formative period.
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Mebrahitom Asmelash, G., et Othman Mamat. « Pressureless Sintering and Characterization of Al2O3-SiO2-ZrO2 Composite ». Defect and Diffusion Forum 329 (juillet 2012) : 113–28. http://dx.doi.org/10.4028/www.scientific.net/ddf.329.113.
Texte intégralRésumé :
An Oxide Ceramic-Based Composite in the Al2o3-Sio2-Zro2(ASZ) System Was Developed and Investigated Using a Pressureless Sintering Route. the Effect of the Content of each Component and Sintering Temperature upon the Microstructure, Density, Hardness and Strength Was Studied. X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) Were Used to Investigate the Phase Transformation Sequences of the ASZ Composite System. the Flexural Strength Was Measured Using Three-Point Bending Method on a Universal Testing Machine, while the Indentation Fracture (IF) Method Was Used to Determine the Fracture Toughness of the Composite. the Results Showed that, with Varying Zro2Content, Keeping the Silica Content Constant and the Alumina as a Matrix, Densification Tends to Decrease as the Content of Zirconia Increases from 20 Wt. % of the Composition. X-Ray Diffraction Peaks Indicated Fully Developed Alumina, Mullite and Zirconia Phases due to Solid-Phase Reaction and Liquid-Phase Sintering of the System. the Experimental Results Also Revealed that, for a Sintering Temperature of 1500°C, the Hardness Value Ranged from 12 Gpa to 14 Gpa and the Flexural Strength Was 420±31MPa.The Fracture Toughness (KIc) Was Also Reported to Be between 4.5 and 5.1 Mpa.m1/2, for Samples Sintered at a Temperature of 14500C.
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Guo, Manli, Zhidong Zhang, Jiyuan Lu, Di Wang, Yimin Yan, Shen Zhang, Xin Yu et al. « Differences in Supragingival Microbiome in Patients with and without Full-Crown Prostheses ». Dentistry Journal 10, no 8 (15 août 2022) : 152. http://dx.doi.org/10.3390/dj10080152.
Texte intégralRésumé :
Objectives: To characterize the microflora profile of supragingival biofilm in patients with and without full-crown prostheses. Methods: Plaque samples of full-crown prostheses and teeth in patients with porcelain-fused-to-metal crowns, all-ceramic crowns, and no prostheses were collected (three patients per group), using 16S rRNA high-throughput sequencing technology to conduct DNA sequencing on the samples and using Qiime, R, and PICRUSt2 software to perform bioinformatics analyses and functional analyses on sequencing data. Results: In total, 110,209 valid sequences were obtained in the experiment, corresponding to 11 phyla and 120 genera. The predominant species shared by the three groups were phyla Actinobacteria, Bacteroidetes, Firmicutes, Fusobacteria, and Proteobacteria and genera Rothia, Porphyromonas, Prevotella, Streptococcus, Veillonella, Leptotrichia, Neisseria, Citrobacter, and Pseudomonas. The species-difference analysis showed that genus Hameophilus significantly increased after the patient wore the dental prosthesis. Compared with the no-prosthesis samples, the functional analysis showed that cell motility increased in the samples from full-crown prostheses, while replication and repair, and translation decreased. Conclusions: This study reveals the changes in the oral microbial community of patients with full-crown prostheses, which could provide insights regarding the safety of materials for long-term use in the oral cavity.