Statistical criteria for microcrack propagation in b.c.c. polycrystals

1973 ◽  
pp. 49-61 ◽  
Author(s):  
G. J. Dvorak
Keyword(s):  
Microcrack Propagation ◽  
Statistical Criteria

Statistical criteria of stellar population types

1966 ◽  
Vol 24 ◽  
pp. 101-110
Author(s):  
W. Iwanowska
Keyword(s):  
Stellar Population ◽  
Chemical Properties ◽  
Spectrophotometric Study ◽  
Physical And Chemical Properties ◽  
Population Type ◽  
The Galaxy ◽  
Distribution Parameters ◽  
Physical And Chemical ◽  
Statistical Criteria ◽  
And Chemical Properties

In connection with the spectrophotometric study of population-type characteristics of various kinds of stars, a statistical analysis of kinematical and distribution parameters of the same stars is performed at the Toruń Observatory. This has a twofold purpose: first, to provide a practical guide in selecting stars for observing programmes, second, to contribute to the understanding of relations existing between the physical and chemical properties of stars and their kinematics and distribution in the Galaxy.

Expert survey and analysis of the results

2019 ◽  
Vol 85 (7) ◽  
pp. 73-82
Author(s):  
Vladimir O. Tolcheev
Keyword(s):  
Data Analysis ◽  
Research University ◽  
Statistical Processing ◽  
Educational Process ◽  
Expert Survey ◽  
Educational Modules ◽  
Training Modules ◽  
Engineering Institute ◽  
Good Agreement ◽  
Statistical Criteria

The issues of organizing an expert survey and carrying out statistical processing and analysis of the results are considered. The experts are the fifth-year students undergoing training at the Department of Management and Informatics «Moscow Power Engineering Institute» of the National Research University. The goal of the survey is revealing the disciplines that are most useful for employment in their specialty. We discuss the special features of the survey and a concept of «work in the specialty», with due regard for statistical reliability of the results. Data of written questionnaire gained in 2018 were processed and analyzed using cluster analysis (construction of dendrograms and application of the K-means method) and non-parametric statistical criteria (Friedman and Mann – Whitney – Wilcoxon). Data processing is implemented in the program STATISTICA. The analysis is carried out to reveal significant differences between the educational courses and assess the degree of consistency of the respondents to divide them into clusters that unite the students with similar judgments. Data analysis revealed that experts’ estimates in 2018 are in fairly good agreement with the estimates of previous studies; among the respondents there are three coalitions corresponding to the training modules «Software», «Management Theory», «Data Analysis»; the overall consistency of students in the two groups is very low (and, on the contrary, high in the identified clusters); grades are homogeneous and do not depend on training groups (and employment – unemployment of the respondents). The obtained results allow us to address a number of important questions regarding the ways of improving the educational process, e.g., to optimize yearly course hours for different educational modules.

Some Simple Thoughts on Model Building for Developing Countries

1983 ◽  
Vol 22 (2) ◽  
pp. 63-71 ◽  
Author(s):  
Henk C. Bos
Keyword(s):  
Developing Countries ◽  
Empirical Research ◽  
Model Building ◽  
Past Experience ◽  
Policy Advice ◽  
Production Functions ◽  
Policy Makers ◽  
Statistical Criteria ◽  
Simple Models

The revival of interest in using models for developing countries for planning and policy advice makes it desirable to draw lessons from past experience. Simple models, focussed on specific issues, are to be preferred to large and comprehensive models. More empirical research is needed on supply and production functions for developing countries. Not statistical criteria but developmental considerations must determine the conclusions to be drawn from models. More explicit explanations of assumptions and modesty in presenting results of modelling work to policy makers are desirable.

scholarly journals Presenting a Semi-Automatic, Statistically-Based Approach to Assess the Sharpness Level of Optical Images from Natural Targets via the Edge Method. Case Study: The Landsat 8 OLI–L1T Data

2021 ◽  
Vol 13 (8) ◽  
pp. 1593
Author(s):  
Luca Cenci ◽  
Valerio Pampanoni ◽  
Giovanni Laneve ◽  
Carla Santella ◽  
Valentina Boccia
Keyword(s):  
Landsat 8 ◽  
Image Sharpness ◽  
Optical Images ◽  
Data Quality Assessment ◽  
Relevant Role ◽  
Edge Method ◽  
Selection Of ◽  
Statistical Criteria

Developing reliable methodologies of data quality assessment is of paramount importance for maximizing the exploitation of Earth observation (EO) products. Among the different factors influencing EO optical image quality, sharpness has a relevant role. When implementing on-orbit approaches of sharpness assessment, such as the edge method, a crucial step that strongly affects the final results is the selection of suitable edges to use for the analysis. Within this context, this paper aims at proposing a semi-automatic, statistically-based edge method (SaSbEM) that exploits edges extracted from natural targets easily and largely available on Earth: agricultural fields. For each image that is analyzed, SaSbEM detects numerous suitable edges (e.g., dozens-hundreds) characterized by specific geometrical and statistical criteria. This guarantees the repeatability and reliability of the analysis. Then, it implements a standard edge method to assess the sharpness level of each edge. Finally, it performs a statistical analysis of the results to have a robust characterization of the image sharpness level and its uncertainty. The method was validated by using Landsat 8 L1T products. Results proved that: SaSbEM is capable of performing a reliable and repeatable sharpness assessment; Landsat 8 L1T data are characterized by very good sharpness performance.

scholarly journals Investigation of Microcrack Propagation and Energy Evolution in Brittle Rocks Based on the Voronoi Model

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2108
Author(s):  
Guanlin Liu ◽  
Youliang Chen ◽  
Xi Du ◽  
Peng Xiao ◽  
Shaoming Liao ◽  
...  
Keyword(s):  
Uniaxial Compression ◽  
Damage Evolution ◽  
Rock Sample ◽  
Rock Fracture ◽  
Damage Threshold ◽  
Crack Development ◽  
Energy Evolution ◽  
Shear Cracks ◽  
Compression Tests ◽  
Microcrack Propagation

The cracking of rock mass under compression is the main factor causing structural failure. Therefore, it is very crucial to establish a rock damage evolution model to investigate the crack development process and reveal the failure and instability mechanism of rock under load. In this study, four different strength types of rock samples from hard to weak were selected, and the Voronoi method was used to perform and analyze uniaxial compression tests and the fracture process. The change characteristics of the number, angle, and length of cracks in the process of rock failure and instability were obtained. Three laws of crack development, damage evolution, and energy evolution were analyzed. The main conclusions are as follows. (1) The rock’s initial damage is mainly caused by tensile cracks, and the rapid growth of shear cracks after exceeding the damage threshold indicates that the rock is about to be a failure. The development of micro-cracks is mainly concentrated on the diagonal of the rock sample and gradually expands to the middle along the two ends of the diagonal. (2) The identification point of failure precursor information in Acoustic Emission (AE) can effectively provide a safety warning for the development of rock fracture. (3) The uniaxial compression damage constitutive equation of the rock sample with the crack length as the parameter is established, which can better reflect the damage evolution characteristics of the rock sample. (4) Tensile crack requires low energy consumption and energy dispersion is not concentrated. The damage is not apparent. Shear cracks are concentrated and consume a large amount of energy, resulting in strong damage and making it easy to form macro-cracks.

scholarly journals Defining and Characterising Clusters in Palaeolithic Sites: a Review of Methods and Constraints

2021 ◽  
Author(s):  
Laura Sánchez-Romero ◽  
Alfonso Benito-Calvo ◽  
Joseba Rios-Garaizar
Keyword(s):  
Distribution Patterns ◽  
Horizontal Distribution ◽  
Spatial Studies ◽  
Innovative Methods ◽  
General Terms ◽  
Fabric Analysis ◽  
Gis Tools ◽  
Definition Of ◽  
Intentional Activities ◽  
Statistical Criteria

AbstractSpatial analysis studies in Palaeolithic archaeology arise as indispensable research tools for understanding archaeopalaeontological sites. In general terms, spatial studies have been specialised in the description of the distribution of materials and in the definition of accumulation areas, with the aim of distinguishing intentional activities or studying postdepositional processes. In recent decades, the development of GIS tools has enabled huge strides forward in the field of spatial archaeology research, such as spatial inferential statistics. These tools are particularly useful in the identification and location of clustering from statistical criteria, facilitating the subsequent analysis of accumulations through other archaeological, taphonomic and spatial techniques, such as fabric analysis or directional distribution. The cluster analysis, and its contextualisation considering all the archaeological and stratigraphical variables, allows the inference of some of the processes and factors that could have taken part in the accumulation of materials, as well as assessing how this affected the composition and preservation of the archaeological assemblage. The present article reviews the more traditional and innovative methods for studying horizontal distribution patterns and the objective definition of clusters, highlighting the parameters, uses and limitations of these techniques. We present an application of these methods to different Palaeolithic sites, going through different scenarios, such as location (open-air vs. cave), context, scale (large vs. small area), excavation methodology and spatial record methods.

Effectiveness of Treatment for Dissociative Identity Disorder

1998 ◽  
Vol 83 (2) ◽  
pp. 483-490 ◽  
Author(s):  
Russell A. Powell ◽  
Andrew J. Howell
Keyword(s):  
Dissociative Identity Disorder ◽  
Initial Assessment ◽  
Systematic Research ◽  
Millon Clinical Multiaxial Inventory ◽  
Effect Of Treatment ◽  
Severe Pathology ◽  
Differential Responsiveness ◽  
Rule Out ◽  
Statistical Criteria

In a recent study by Ellason and Ross, patients with Dissociative Identity Disorder reported a decrease in symptoms on the Millon Clinical Multiaxial Inventory–II over a 2-yr. follow-up period. Patients judged to have achieved integration of their personalities rated themselves as more substantially improved on the Millon–II than did patients judged not to have achieved integration. Ellason and Ross suggested that this improvement reflected the influence of treatment; however, for several reasons, their findings are open to alternative interpretations. First, in the absence of proper control conditions, one cannot rule out the contribution of other factors to the over-all improvement of patients such as regression of symptoms toward the mean following the initial assessment. Second, patients' self-reported improvement was less substantial when data were reanalyzed using more appropriate statistical criteria. Third, the greater improvement observed among integrated patients relative to nonintegrated patients may reflect influences other than differential responsiveness to treatment, such as less severe pathology prior to treatment. More systematic research is needed to clarify the effect of treatment on Dissociative Identity Disorder.

scholarly journals Dependence of the Threshold Stress of Microcrack Propagation on the Stress Ratio

1988 ◽  
Vol 31 (4) ◽  
pp. 768-773
Author(s):  
Seiichiro KITAOKA ◽  
Jian-Qiao CHEN ◽  
Masaichiro SEIKA
Keyword(s):  
Threshold Stress ◽  
Stress Ratio ◽  
Microcrack Propagation

scholarly journals Rapid Consolidation of WC-ZrSiO4 Hard Materials by Spark Plasma Sintering: Microstructure, Densification, and Mechanical Properties

2021 ◽  
Author(s):  
Jeong-Han Lee ◽  
Ik-Hyun Oh ◽  
Ju-Hun Kim ◽  
Sung-Kil Hong ◽  
Hyun-Kuk Park
Keyword(s):  
Mechanical Properties ◽  
Spark Plasma Sintering ◽  
Lattice Distortion ◽  
Hard Materials ◽  
Plasma Sintering ◽  
Microcrack Propagation ◽  
Spark Plasma ◽  
Crack Tips ◽  
Ductile Component ◽  
Constant Heating

Abstract Densely consolidated WC-based hard materials with 5–20 vol% ZrSiO4 was fabricated by spark plasma sintering at 1400 ℃ at a constant heating rate of 70 ℃/min−1. To achieve mechanical alloying of WC-ZrSiO4, planetary ball milling was carried out for 12 h, during which the brittle-brittle components (WC-ZrSiO4) became fragmented and their particles became refined. It was observed that certain, specific, non-isothermal sintering kinetics, such as apparent activation energy, sintering exponents, and densification strain, affected the densification behavior. The evolution of phase structure from powder to compact was found to be related the lattice distortion and micro-strain in the basal planes of WC. By examining the mechanical properties of the samples, it was that the added zircon content leads to enhanced fracture toughness (12.9 MPa m1/2) owing to the presence of WC-ZrSiO4 in the cemented carbide. In fact, the microcrack propagation of the fracture passed through zircon from a transgranular to a ductile component (fcc) where the crack tips could be absorbed. Graphic Abstract

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