1,337 research outputs found
Adoption of Astm A956-06 Leeb Hardness Testing Standard to Rock Engineering Applications
No full textThe Leeb dynamic hardness test was originally developed for metallic materials and is now widely used in rock engineering and engineering geology. This study aims to fundamentally investigate the application conditions of the Leeb hardness test in rock engineering because it is a high-precision, fast, nondestructive, and portable method. Therefore, four main limitations of the Leeb method mentioned in ASTM A956-06 have been further analyzed. The important challenges, including scale effect, temperature effect, surface roughness effect, and the effect of physical properties on the Leeb method, have been studied. For this purpose, 33 rock samples with a wide range of hardness and different geology origins were used. Based on the results, the minimum thickness of the block samples of 5 cm (or volume of 500 cm3) and the length-to-diameter ratio of 1.6 on core samples were suggested. Moreover, block samples were exposed to various temperatures, including −30, 0, 20, 50, 100, and 150 °C. The results indicated that with increasing the temperature, the Leeb hardness decreased, but the trend of the Leeb hardness variations is unnoticeable. The roughness analyses using a laser profilometer indicate that the Leeb hardness of rough samples can easily be determined with high reliability using the Leeb hardness of polished samples. Also, the Leeb hardness test for rough surfaces with JRC \u3c4 (classes 1 and 2) can be used properly and performed locally in classes 3 to 10. Finally, the statistical analyses showed that the density and porosity have reasonable effects on Leeb\u27s hardness
Design of an Electric Scooter Drivetrain
No full textThesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 33).Professor Steven Leeb teaches Power Electronics Lab, which teaches the fundamentals of power electronic systems and has students build their own motor controllers. As a fun way to test these student built motor controllers, Professor Leeb has been using large go-karts built specifically for the class. However, these go-karts are large, heavy, and difficult to maintain. Professor Leeb recently acquired a number of production stand-up electric scooters with the intention of replacing the aging gokarts. To enhance the educational value of the scooters, Professor Leeb wanted them heavily modified to allow students to explore the effect of gearing on electromechanical systems. Furthermore, the scooters were modified to incorporate a modular motor mounting system, allowing students to easily switch out different motor models, including brushed and BLDC motors. This thesis details the design and construction of the scooter transmission and motor mount.by Andrew T. Carlson.S.B
Application of Leeb Hardness Test in Prediction of Dynamic Elastic Constants of Sedimentary and Igneous Rocks
No full textThe Leeb hardness test is a non-destructive and portable technique that can be used both in the laboratory and in-field applications. The main purpose of this study is to predict the dynamic elastic constants of the igneous and sedimentary rocks using Leeb dynamic hardness testing. For this purpose, three vital topics have been investigated and analyzed. First, the relationships between ultrasonic wave velocities and dynamic elastic constants with the Leeb hardness were investigated. Thereafter, by determining the rock quality index (IQ) using microscopic studies and by analyzing the quality index-porosity plot, the variation of the Leeb hardness values was studied. Eventually, the longitudinal waveform in rock samples with different quality indexes and Leeb hardness were analyzed. To achieve these outputs, 33 samples of igneous and sedimentary rocks with a wide range of physical, mechanical, and textural features were collected and tested. The results of the analyses show that in both igneous and sedimentary rocks, the dynamic modulus of elasticity (Ed) has a significant correlation with the Leeb hardness. Generally, based on the microscopic studies, it was observed that the existence of the porosity in sedimentary rocks and intercrystalline and intracrystalline fissures in igneous rocks sharply reduce the Leeb hardness and thus lead to changes in the form of the longitudinal waves
Das EU-Investitionsschutzrecht im Wandel
No full textAnalysing European investment protection law, Matthias Leeb focuses on the resulting legal protection deficits for investors and provides concrete recommendations for dealing with them. In particular, he examines recent decisions of the ECJ on intra-EU investment protection agreements - Achmea, Komstroy, PL-Holdings and European Food SA, among others - and takes a critical look at them and their effects. Furthermore, the author addresses the EU's intended reform of investment protection in relation to third countries, taking into account current developments in the context of the Energy Charter Treaty (ECT).PublishedDas europäische Investitionsschutzrecht analysierend, rückt Matthias Leeb die sich daraus ergebenden Rechtsschutzdefizite für Investoren in den Fokus und gibt konkrete Handlungsempfehlungen für den Umgang mit diesen. Insbesondere untersucht er dafür aktuelle Entscheidungen des EuGH zu Intra-EU-Investitionsschutzabkommen – Achmea, Komstroy, PL-Holdings und European Food SA u. a. – und setzt sich kritisch mit diesen und deren Auswirkungen auseinander. Darüber hinaus geht der Autor auf die von der EU angestrebte Reform des Investitionsschutzes im Verhältnis zu Drittstaaten ein, wobei er die aktuellen Entwicklungen im Zusammenhang mit dem Energiecharta-Vertrag (ECT) berücksichtigt
Leeb Hardness Approach in the Determination of Strength after Accelerated Weathering Tests
No full textThis study aimed to investigate the usability of the Leeb hardness test in determining changes in strength as a result of atmospheric weathering in works of cultural heritage built with low-strength pyroclastic rocks. To this end, the effects of weathering processes on strength properties were investigated in two building stones commonly used in Ni & gbreve;de province located in the Cappadocia (Turkey) region, which contains the most important works of cultural heritage created using low-strength pyroclastic rocks. The index, strength, mineralogical, and petrographic properties of rocks were first investigated. Then, freeze-thaw (F-T) and salt crystallization (SC) tests, the weathering processes of which consisted of six periods, were performed on samples prepared in cubic form. After the F-T and SC processes, the macro change in the samples and changes in weight loss, uniaxial compressive strength (UCS), and Leeb hardness (HL) values were determined. Highly correlated linear relationships were obtained between the SC and F-T cycles of the samples and the UCS and HL values. The HL test was applied to samples for which the UCS test could not be applied due to the loss of sample integrity after the advancing cycles of the accelerated weathering tests. Linear relationships with high correlation were determined between the UCS and HL values obtained from the samples after the accelerated weathering test. This study revealed that the HL approach could be used as an alternative in modeling the strength parameters of the weathering processes of the structures of cultural heritage built using low-strength rocks
Effective population size of an indigenous Swiss cattle breed estimated from linkage disequilibrium
No full textEffective population size is an important parameter for the assessment of genetic diversity within a livestock population and its development over time. If pedigree information is not available, linkage disequilibrium (LD) analysis might offer an alternative perspective for the estimation of effective population size. In this study, 128 individuals of the Swiss Eringer breed were genotyped using the Illumina BovineSNP50 beadchip. We set bin size at 50 kb for LD analysis, assuming that LD for proximal single nucleotide polymorphism (SNP)-pairs reflects distant breeding history while LD from distal SNP-pairs would reflect near history. Recombination rates varied among different regions of the genome. The use of physical distances as an approximation of genetic distances (e.g. setting 1 Mb = 0.01 Morgan) led to an upward bias in LD-based estimates of effective population size for generations beyond 50, while estimates for recent history were unaffected. Correction for restricted sample size did not substantially affect these results. LD-based actual effective population size was estimated in the range of 87-149, whereas pedigree-based effective population size resulted in 321 individuals. For conservation purposes, requiring knowledge of recent history (<50 generations), approximation assuming constant recombination rate seemed adequate
Child maltreatment surveillance; uniform definitions for public health and recommended data elements
No full textThe purpose of the child maltreatment uniform definitions and recommended data elements is to present a definition of child maltreatment, its associated terms, and recommended data elements for voluntary use by individuals and organizations in the public health community. The definitions and data elements are intended to promote and improve consistency of child maltreatment surveillance for public health practices. It is designed to be used by state and local health department staff to assist in and provide a framework for the collection of public health surveillance data on child maltreatment. The definitions included in the document draw upon definitions that are currently in use in the literature and were adapted in collaboration with a panel of experts on child maltreatment and public health surveillance. The definitions and data elements are designed be flexible tools for developing an ongoing surveillance system. Agencies that use the document can modify data elements to fit their system. This document is the third in a series of Uniform Definitions and Recommended Data Elements which includes: Intimate Partner Violence Surveillance: Uniform Definitions and Recommended Data Elements and Sexual Violence Surveillance: Uniform Definitions and Recommended Data Elements.CDC-INFO Pub ID 999180Rebecca T. Leeb, Leonard J. Paulozzi, Cindi Melanson, Thomas R. Simon, Ileana Arias.999180Includes bibliographical references (p.131-135).Suggested citation: Leeb RT, Paulozzi L, Melanson C, Simon T, Arias I. Child Maltreatment Surveillance: Uniform Definitions for Public Health and Recommended Data Elements, Version 1.0. Atlanta (GA): Centers for Disease Control and Prevention, National Center for Injury Prevention and Control; 2008
Genomic structures and sequences of two closely linked genes (AMT, TCTA) on dog chromosome 20q15.1 -> q15.2
No full textAnalysis of genomic sequence from canine chromosome 20q15.1 --> q15.2 revealed the presence of two closely linked genes. The two genes represent the corresponding canine orthologs of human aminomethyltransferase (AMT) and the human T-cell leukemia translocation associated (TCTA) gene, Aminomethyltransferase or glycine cleavage system T-protein is an important enzyme in glycine metabolism. The reported canine AMT gene spans 5 kb and consists of nine exons. It encodes a protein of 403 amino acids with 88%, identity to human aminomethyltransferase. Human TCTA is located on 3p21 near the breakpoint of a t(1;3) translocation observed in some cancer cell lines. The 4-kb canine TCTA gene consists of three exons and probably represents a pseudogene. It is located adjacent to AMT and very close to DAG 1 and BSN, Copyright(C)2000S.KargerAG,Basel
Prkg2 splice site variant in dogo argentino dogs with disproportionate dwarfism
No full textDwarfism phenotypes occur in many species and may be caused by genetic or environmental factors. In this study, we investigated a family of nine Dogo Argentino dogs, in which two dogs were affected by disproportionate dwarfism. Radiographs of an affected dog revealed a decreased level of endochondral ossification in its growth plates, and a premature closure of the distal ulnar physes. The pedigree of the dogs presented evidence of monogenic autosomal recessive inheritance; combined linkage and homozygosity mapping assigned the most likely position of a potential genetic defect to 34 genome segments, totaling 125 Mb. The genome of an affected dog was sequenced and compared to 795 control genomes. The prioritization of private variants revealed a clear top candidate variant for the observed dwarfism. This variant, PRKG2:XM_022413533.1:c.1634+1G>T, affects the splice donor site and is therefore predicted to disrupt the function of the PKRG2 gene encoding protein, kinase cGMP-dependent type 2, a known regulator of chondrocyte differentiation. The genotypes of the PRKG2 variant were perfectly associated with the phenotype in the studied family of dogs. PRKG2 loss-of-function variants were previously reported to cause disproportionate dwarfism in humans, cattle, mice, and rats. Together with the comparative data from other species, our data strongly suggest PRKG2:c.1634+1G>T to be a candidate causative variant for the observed dwarfism phenotype in Dogo Argentino dogs
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