1,720,959 research outputs found
Unknown Deformations on the Facades of the Pyramid of Khafre at Giza Pyramid Complex in Egypt
No full textAbstractThe pyramids of Giza in Egypt are the architectural heritage of ancient civilizations and for many thousand years served as great examples of ancient design, planning and construction solutions. Their scale is grandiose and the attempts of ancient architects to find perfect forms to ensure the structure stands for eternity are admirable. The initial geometry of the structures, their form, proportions and symmetry, was adapted to construction material and technologies available at that time. However, during more than 4500 years these monuments were damaged and partly destroyed; some pyramids were razed to the ground due to construction faults and seismic activity. The second largest pyramid at Giza is the pyramid of Khafre. This monument was not reconstructed and rebuild, therefore it was chosen as an object of our study. During the time period of 2009 – 2012 the photographic documentation of the facades of this pyramid was performed, fixing the location of fractures, cracks and displacement of construction blocks. The location of major fractures and cracks was verified in situ in 2012 and confirmed the validity of the interpretations. Several types of fractures and cracks were identified. One of the types indicates the detachment of stone blocks from the massive crack. The other type refers to the long linear cracks and fracture areas traceable through the major part of the pyramid's facade, threatening the stability and integrity of the whole structure
Regional studies of flint characteristic properties abstract /
No full textTyt. z nagłówka.Art. jest abstr. referatu z konferencji.Bibliogr. s. 149.Searching of flint sources and localization of places where once the Stone Age people obtained this raw material for tool making is an important subject of research not only in archeology, but in broader sense when exploring the ancient civilizations lifestyle, human migrations and interaction between ancient archaeological cultures, as well as tracing cognitive development, that covers not just simple geological observations and orientation in space, but also the first notions of material properties and their determination. Flint and its formation conditions are not the focus of particular attention in traditional geological studies today, since most of relevant studies have been carried out (Rykart 1989, Sieveking & Hart 1986), and their quality is still very high. In turn, the knowledge level of detail required for the results interpretation in ancient cultures studies is insufficient. Diversity of analytical measurements and divisive results so far failed to give reliable and convincing answers, because natural variations of flint properties cover significantly wider range of values than those identified in relevant artefacts. As a result, the current approach allows to relatively reliably detect only the local flint sources; in other cases just a general evaluation is possiblie. In the research of flint samples of different geological ages from several Northern Europe countries, as well as flint tools, material of artifacts collection from excavations of the Institute of History of Latvia were studied. This flint is mainly derived from the Jurassic and Cretaceous sediments, less Carboniferous and Devonian rocks, but an unique and distinct group consists of samples that cover chert and chalcedony saturated rocks. Such formations are quite widely known and are found in tectonic fractures and crack spreading zones in almost all rocks exposed in earth's surface, regardless of their geological age. In this study, the focus was on research methodology that would allow to find an approach to a more reliable flint source localization. The accumulated experience indicates the importance of sample macroscopic analysis and evaluation, including notes about characteristic inclusions, structural heterogeneity, typical fractures. The latter is particularly important because it contains a direct reference to rock cryptocrystalline structure properties, and was a relevant indication for ancient man about the possibilities to use such material for making tools. Without evaluation of the heterogeneity, the more detailed results of chemical and physical analysis may characterize variations of values rather than characteristic properties. In next stage of the research, it is appropriate to evaluate the sample in ultraviolet light (calibrated wavelength 365, using additional emission filter (485-655 nm). In this UV light it is possible to assess heterogeneity and to identify areas for future research. It is appropriate to study the selected areas of the samples additionally under microscope with a magnification of approx. 50 times. This allows to describe samples microscopically and to obtain more detailed data on inclusions, cracks, layers changes, etc., which can be saved in digital image format for further analysis. Only after this assessment, it is optimal to make detailed chemical and chemical-physical examinations, as the data obtained will be safely comparable. By following such a procedure, it is possible to identify many characteristics which allow to distinguish flint samples from different sites. However, it should be noted that the research carried out is still regional and it will require several more years of study to collect data on naturally occurring flint compositions and to create a corresponding database. At the same time, it should be noted that flint tools characterising the Stone Age archaeological cultures are made from different quality source material. The found material at many sites has been obtained quite remotely and not necessarily such "distant" material is of higher quality than the known local material. Perhaps, there had been sort of reserves or stocks that were carried, taking into account that not always it would be possible to find a suitable raw material. The choice of suitable raw material is the knowledge that was acquired very gradually, and therefore often rejects and mistakenly made tools can be found. However, although the knowledge about material properties was increasing, there was no tendency to use higher-quality flint raw material. Rather the opposite appears true - with more skills it was becoming increasingly possible to create higher quality tools from worse quality (less appropriate) materials. Additionally, it should be taken into account that in the historical course of time stone tools and their diversity was significantly changing, which required to search for a various quality raw materials. The overall tendency points to more pronounced symmetry of the tools, that are derived from cryptocrystalline flint types with small fractures, a material with very few inclusions and hidden cracks. The research results indicate that, following the proposed composition and properties, the investigation procedure (methodology) can identify characteristic and distinct features of flint samples, and they are indicative of to certain corresponding flint mining regions.Dostępny również w formie drukowanej.KEYWORDS: archeology, ancient civilization, human migration
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Sadarbība Latvijas zemes dzīļu resursu izpētei un to izmantošanas tehnoloģiju izstrādei – Valsts pētījumu programma „Zemes dzīles”
No full textRakstā ir aplūkota valsts pētījumu programmas projekta „Zemes dzīles“ mērķi un organizatoriskā struktūra, kas atspoguļo projekta mērķtiecīgu virzību un sadarbību Latvijas zemes dzīļu izpētei un to izmantošanas tehnoloģiju izstrādei. Apskatīti programmā ietverto dažādās zinātniskās institūcijās izveidoto pētnieku grupu zinātniskās pētniecības virzieni. Izcelta pētniecisko grupu sadarbība un tās attīstības iespējas jaunu tehnoloģiju un inovatīvu produktu izstrādē. Tāpat ir apskatīti arī citi prognozētie pētījumu zinātniskie rezultāti zemes dzīļu resursu un dabisko izejvielu izpētē
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Latvijas piekrastes zonas jutiguma indikatori un ieprieksejos gados ievakto datu apkopojums
No full textAvailable from Latvian Academic Library / LAL - Latvian Academic LibrarySIGLEMinistry of Environmental Protection and Regional Development of the Republic of Latvia, Riga (Latvia)LVLatvi
Modification of Illite Structure by Differential Treatment
No full textCommonly illite is described as a clay mica with a general composition of [KxAlx(Si4-xAlx)O10 (OH)2 (where 0.75<x<0.9). Structural illite belong to sheet silicates where structural units consist two Si-O tetrahedral sheets always joined with an octahedral Al-O sheet. One of more investigated processes to attain an increased compressive strength of clay minerals containing materials is by proper mix development with highly alkaline solution. Although for this preparation the mainly used is 1:1 layer lattice alumosilicates, i.e., geopolymers, it is also of interest 2:1 minerals such as 2:1 illite.
The aim of this study is to show how the chemical, mechanical and thermal treatment condition influenced the structure and some properties of treated illite, as well as impact of its on development of dense high–temperature ceramics.
MATERIALS and METHODS
In this study Quartenary limno-glacial clays from State importance meaning clay deposit, Apriki, are used. The mean SiO2/Al2O3 wt. ratio for clay is in range 3,20 -3,45.
Clay fraction, mainly illite, from Apriki clay were separated using sedimentation and chemical methods.
For characteristic not treated and treated illite as well as sintered ceramic samples there was used X-ray diffraction analysis, as well SEM- analysis. Differential thermal analysis was applied to characterize the phases change by thermal treatment of illite.
There were used four differentially treated illite samples:
ap 0- not treated, ap 1 – milled for 10h, ap 2 –treated with 3M NaOH, ap 3- treated with 6M NaOH and ap 4 – thermally treated at 580°C. Some ceramics properties were established in accordance with EN.
RESULTS and DISCUSSIONS
The XRD patterns showed that chemical, mechanical and thermal treatment impact on change of intensity of diffraction peaks of illite which could characterize that
the breakdown of illite structure is insignificant. The DTA analysis indicate significant changes of illite for the thermally treated sample. For other treated samples the DTA curves seem similar with a little shifted exo-effect to the lowest temperatures, Fig.1.
Fig.1.DTA - curves of differential treated illite: : ap 0- not treated, ap-1-milled for 24h, ap-2, 3 treated by 3M and 6M NaOH, ap-4 pre-thermal treated at 580°C for 1h.
Scanning electron micrographs of clay fraction powder before and after treatment show that thermal treatment yield homogenous illite powder mixture with particles having almost spherical shape. Significantly differs illite sample treated by 6M NaOH there is observed needle-shaped new crystalline phase formation –sodium aluminosilicate hydrate-Na(AlSiO4)6·H2O, which pervades illite.
Thermal treated illite was used for new compositions development with Al(OH)3. After sintering samples with 40 % Al(OH)3 additive there was found that compressive strength of ceramic samples reaches value 168 N/mm2.
CONCLUSIONS
It is shown that more effective is the thermal and chemical by 6M NaOH treatment. Thermal treatment yield to homogenous illite formation, chemical -by 6M NaOH lead to formation of a new crystalline phase –sodium aluminosilicate hydrate -Na(AlSiO4)6·H2O, which pervades illite.
After sintering samples of thermal teated illite sample with 40 % Al(OH)3 there was found that compressive strength of ceramics reaches value 168 N/mm2
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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