The Rewari meteorite

1979 ◽  
Vol 43 (327) ◽  
pp. 423-427
Author(s):  
S. P. Das Gupta ◽  
P. R. Sen Gupta ◽  
N. R. Sen Gupta ◽  
D. R. Das Gupta ◽  
A. Dube
Keyword(s):  
Chemical Analysis ◽  
Coarse Grained ◽  
Alteration Zone ◽  
Fragment Composition ◽  
Coarse Texture ◽  
The Matrix ◽  
Wet Chemical ◽  
High Degree ◽  
Lower Oxidation ◽  
Cut Surface

SummaryThe meteorite was an oriented polyhedron, which broke up into at least two parts after entry into the Earth's atmosphere. It has undergone some degree of terrestrial weathering. A cut surface of the meteorite shows light-grey interior with sporadic rusty-brown patches and a distinct brown alteration zone close to the fusion crust. Weathering has resulted in preferential replacement of NiFe by limonite, and veining of minerals by goethite.Rewari is an equilibrated chondrite with rare ghosts of chondrules and at least one lithic fragment. Composition of olivine, as indicated by microprobe analysis is Fa23, which agrees well with bulk wet chemical analysis; that indicated by d130 is Fa18–20. From the outer surface inwards, four petrographic zones can be distinguished in the meteorite: a skin, about 0.01 mm thick, a troilite-poor zone slightly thicker than the skin, a troilite-rich ‘soaking zone’, about 0.5–0.6 mm thick, and a relatively coarse-grained interior. These are described in detail.The interior of the meteorite is composed of relatively coarse-grained crystalline silicates with disseminated metallic minerals including plessitic and zoned inter-growths of kamacite and taenite. The matrix shows a high degree of integration with the chondrules. The coarse texture and zonation of taenite may be the result of protracted heat treatment responsible for recrystallization. The constituent grains show considerable shock effects such as fracturing, comminution, veins of shock-melted pseudotachylite, pressure twinning, and undulose extinction. Chemical composition (mean of two wet chemical analysis) of the meteorite is: metallic Fe 7.475, Ni 0.975, Co 0.045; as sulphide Fe 3.200, Ni 0.090, Co < 0.01; SiO2 38.060, TiO2 0.10, Al2O3 2.34, Fe2O3 0.175, Cr2O3 0.485, FeO 13.950, MnO 0.210, NiO trace, CaO 1.875, MgO 26.265, Na2O 0.89, K2O 0.115, P2O5 0.285, H2O− 0.295, H2O+ 0.81, CO2 trace, S (total) 1.890, C (total) 0.19 per cent. The chemistry, mineralogy, and texture show that the Rewari meteorite is an L6 chondrite. Compared to average L-group chondrite it has a higher content of MgO and lower of SiO2, a little lower oxidation state, and tends to be enriched in siderophilic elements.

Microstructural Design of Si3N4 Based Ceramics

1992 ◽  
Vol 287 ◽  
Author(s):  
M.J. Hoffmann ◽  
G. Petzow
Keyword(s):  
Mechanical Properties ◽  
Aspect Ratio ◽  
Microstructural Analysis ◽  
Coarse Grained ◽  
Boundary Phase ◽  
Microstructural Development ◽  
High Temperature Strength ◽  
Secondary Phases ◽  
The Matrix ◽  
High Degree

ABSTRACTParameters controlling the size and aspect ratio of elongated Si3N4 grains are discussed, based on the assumption that only pre-existing β-Si3N4 particles of the starting powder grow. Powder mixtures of α-rich and β-rich Si3N4 were prepared In order to study the microstructural development. The resulting microstructures were analyzed by quantitative microstructural analysis determining the distribution of the length and aspect ratio of the Si3N4 grains. Subsequently, the Influence of the sintering conditions on grain growth was analyzed In relation to mechanical properties. A high Weibull modulus and the non-catastrophic failure during thermal shock of coarse-grained materials Is attributed to an R-curve behaviour. Finally, the influence of sintering additives on the mechanical properties was studied. The Importance of phase relationships between the matrix and the grain boundary phase Is discussed for Si3N4 with Yb2O3 additives. It Is demonstrated that the oxygen content of Si3N4 powder must been taken Into account In order to devitrify defined secondary phases and to achieve a high degree of crystallization. A reduction in the amount of additives does not necessarily Improve the properties as high temperature strength and creep data Indicate.

Perancangan aplikasi multi criteria decision making dalam penerimaan beasiswa kepada dosen studi lanjut STMIK Balikpapan menggunakan metode SAW

2018 ◽  
Vol 1 (1) ◽  
pp. 35-42
Author(s):  
Muslimin B ◽  
Sumardi Sumardi
Keyword(s):  
Decision Making ◽  
Learning Process ◽  
Teaching And Learning ◽  
Teaching Assistants ◽  
Multi Criteria Decision Making ◽  
Scholarship Recipients ◽  
The Matrix ◽  
Application Decision ◽  
High Degree ◽  
New Student

 Interests and number of STMIK Balikpapan new student enrollments are increasing every year. The balance of the ratio of lecturers to students is one of the most important components in improving the quality and teaching and learning process of a university. Avoiding shortages in the number of lecturers can be realized by providing scholarship programs to alumni and teaching assistants. This study aims to build a multi criteria decision making application that can assist the Head of HRD in the process of receiving scholarships to advanced and effective study lecturers. The multi criteria decision making application developed in this study uses the SAW method. The implementation of the SAW method includes the process of evaluating the weighting of criteria, evaluating alternative weights, the matrix process, the results of decision making preferences, resulting in the weighting and ranking of each alternative candidate for the scholarship recipient. The results of the evaluation of multi-criteria application decision making in the study are expected to produce modeling with a high degree of accuracy. The results of the analysis carried out can provide alternative recommendations for prospective scholarship recipients to advanced study lecturers in STMIK Balikpapan.

Sector growth and symmetry of (F,OH) apatite from the Asio mine, Japan

1994 ◽  
Vol 58 (391) ◽  
pp. 307-314 ◽  
Author(s):  
Mizuhiko Akizuki ◽  
Hirotugu Nisidoh ◽  
Yasuhiro Kudoh ◽  
Tomohiro Watanabe ◽  
Kazuo Kurata
Keyword(s):  
Optical Properties ◽  
Crystal Growth ◽  
Electron Diffraction ◽  
Chemical Analysis ◽  
Growth Surface ◽  
Complete Disappearance ◽  
X Ray ◽  
Solid Crystal ◽  
Wet Chemical ◽  
Growth Features

AbstractA study of apatite crystals from the Asio mine, Japan, showed sectoral texture related to the growth of the crystal, and with optically biaxial properties within the sectors. Wet chemical analysis gave a composition Ca5(PO4)3(F0.64,OH0.38,Cl0.01)1.03 for the specimen.Additional diffraction spots were not observed in precession and oscillation X-ray photographs and electron diffraction photographs. Since the internal textures correlate with the surface growth features, it is suggested that the internal textures and the unusual optical properties were produced during nonequilibrium crystal growth. The fluorine/hydroxyl sites in hexagonal apatite are symmetrically equivalent in the solid crystal but, at a growth surface, this equivalence may be lost, resulting in a reduction of crystal symmetry. Heating of the apatite to about 850°C results in the almost complete disappearance of the optical anomalies due to disordering, which may be related to the loss of hydroxyl from the crystal.

Criteria for optimal operation of automobiles on alternative fuels

2021 ◽  
Vol 13 (1) ◽  
pp. 124-132
Author(s):  
Volodymyr Rudzinskyi ◽  
◽  
Bohdan Yemets ◽  
Serhii Melnychuk ◽  
Oleksandr Ryabchuk ◽  
...  
Keyword(s):  
Economic Efficiency ◽  
Alternative Fuels ◽  
Local Level ◽  
Optimal Operation ◽  
Expert Assessment ◽  
Depth Analysis ◽  
Analysis And Synthesis ◽  
The Matrix ◽  
Matrix Correlation ◽  
High Degree

The article deals with some criteria that substantiate the design and operational performance of automobiles running on alternative fuels; economic efficiency of operation of such vehicles, their ecological conformity; the level of complexity of the design of converted automobiles; labor intensity of their maintenance, repair, etc. ; traction-speed and other different, in comparison with the basic, properties of automobiles while working on alternative fuel (AF); energy consumption and (or) cost price of AF; efficiency of power plant and (or) car on AF; the degree of commissioning (mass production) and further prospects for the development of the design of such automobiles; state of support developed structures at the national (local) level. An expert assessment of the adopted criteria in the order of their importance is made. Along with the analysis of scores, which are presented in points, it is used the ranking method to study the results of the survey of experts. This allows applying the values of the established optimal criteria to justify the operation of vehicles during their work on the AF. The analysis of the matrix correlation shows that the numerical estimates set by the accepted criteria are characterized by a high degree of correlation, and experts are generally unanimous in assessing their importance. The most important criteria for the operation of automobiles on the AF are economic efficiency, traction and speed and other, different compared to the basic, the properties of automobiles while working on the AF. Other criteria are also quite important, the weights for them are much higher than 7%, and they also should be taken into account while conducting an in-depth analysis and synthesis of indicators of optimal operation of automobiles on the AF. In addition, it is important that the group of criteria that characterize only one type of automobile when working on the AF (for example, the degree of commissioning) experts gave only about 17% of the importance.

scholarly journals Mechanical Resonance Dispersion Revisited

2014 ◽  
Vol 1 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Haskell V. Hart
Keyword(s):  
Plastic Deformation ◽  
Shear Stress ◽  
Chemical Analysis ◽  
Normal Modes ◽  
Theoretical Explanation ◽  
Mechanical Resonance ◽  
Complex Shear ◽  
High Degree ◽  
Shear Compliance ◽  
Strain Responses

Mechanical resonance dispersion is the inelastic response of a solid to a periodic shear stress. Instead of the elastic Young's Modulus, the phenomenon is described by both a real J', and an imaginary J'' component of complex shear compliance, corresponding to in phase and out of phase strain responses, respectively. The experimental results are plots of J' and J'' vs. frequency, which are typically in the audiofrequency range of 10 - 5600 Hz. Resonances are observed as maxima in J'' and inversions in J' at frequencies corresponding to modes of plastic deformation, which are much lower frequencies (audiofrequency range) than elastic normal modes. The theoretical explanation of Edwin R. Fitzgerald involves particle waves and momentum transfer and leads to a particle-in-a-box frequency formula for these inelastic modes. Unfortunately, most of his and other published raw data were never analyzed by this model. The purpose of this article is to apply this formula to previously uninterpreted resonance dispersion curves and to address some of the earlier criticism of Fitzgerald's work. Results of these calculations support the Fitzgerald Theory to a high degree, demonstrate the importance of impurities and chemical analysis, largely mollify previous criticisms, and suggest the possibility of a new particle wave mass spectroscopy at great distances.

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