I. The crystal structure of a new dimer of triphenylfluorocyclobutadiene. II. A low temperature refinement of the cyanuric triazide structure

I. THE CRYSTAL STRUCTURE OF A NEW DIMER OF TRIPHENYLFLUOROCYCLOBUTADIENE

The crystal structure of thermal isomer of the “head-to-head” dimer of triphenylfluorocyclobutadiene was determined by the direct method. The Σ₂ relationship involving the low angle reflections with the largest E’s were found and solved for the signs by the symbolic method of Zachariasen. The structure was seen in the electron density map and the E-map, and was refined antisotropically by the method of least squares. The residual R was 0.065.

The structure is a gem-difluorohexaphenyldihydropentalene. All of the phenyl groups are planar as it is the cyclopentadiene ring of the dihydropentalene skeleton. Overcrowding at the position of the flourines causes some deviations from the normal bond angles in the cyclopentene ring.

The list of observed and calculated structure factors on pages 32-34 will not be legible on the microfilm. Photographic copies may be obtained from the California Institute of Technology.

II. A LOW TEMPERATURE REFINEMENT OF THE CYANURIC TRIAZIDE STRUCTURE

The structure of cyanuric triazide was refined anisotropically by the method of least squares. Three-dimensional intensity data, which has been collected photographically with MoK_α radiation at -110˚C, were used in the refinement. The residual R was reduced to 0.081.

The structure is completely planar, and there is no significant bond alternation in the cyanuric ring. The packing of the molecules causes the azide groups to deviate from linearity by 8 degrees.

Sputtering of the gallium-indium eutectic alloy in the liquid phase

We have measured sputtering yields and angular distributions of sputtered atoms from both the solid and liquid phases of gallium, indium, and the gallium-indium eutectic alloy. This was done by Rutherford backscattering analysis of graphite collector foils. The solid eutectic target shows a predominance of indium crystallites on its surface which have to be sputtered away before the composition of the sputtered atoms equals the bulk target composition. The size of the crystallites depends upon the conditions under which the alloy is frozen. The sputtering of the liquid eutectic alloy by 15 keV Ar⁺ results in a ratio of indium to gallium sputtering yields which is 28 times greater than would be expected from the target stoichiometry. Furthermore, the angular distribution of gallium is much more sharply peaked about the normal to the target surface than the indium distribution. When the incident Ar⁺ energy is increased to 25 keV, the gallium distribution broadens to the same shape as the indium distribution. With the exception of the sharp gallium distribution taken from the liquid eutectic at 15 keV, all angular distributions from liquid targets fit a cos² θ function. An ion-scattering-spectroscopy analysis of the liquid eutectic alloy reveals a surface layer of almost pure indium. A thermodynamic explanation for this highly segregated layer is discussed. The liquid eutectic alloy provides us with a unique target system which allows us to estimate the fraction of sputtered material which comes from the first monolayer of the surface.

Normal structures and automorphism groups of t-designs

Combinatorial configurations known as t-designs are studied. These are pairs ˂B, ∏˃, where each element of B is a k-subset of ∏, and each t-design occurs in exactly λ elements of B, for some fixed integers k and λ. A theory of internal structure of t-designs is developed, and it is shown that any t-design can be decomposed in a natural fashion into a sequence of “simple” subdesigns. The theory is quite similar to the analysis of a group with respect to its normal subgroups, quotient groups, and homomorphisms. The analogous concepts of normal subdesigns, quotient designs, and design homomorphisms are all defined and used.

This structure theory is then applied to the class of t-designs whose automorphism groups are transitive on sets of t points. It is shown that if G is a permutation group transitive on sets of t letters and ф is any set of letters, then images of ф under G form a t-design whose parameters may be calculated from the group G. Such groups are discussed, especially for the case t = 2, and the normal structure of such designs is considered. Theorem 2.2.12 gives necessary and sufficient conditions for a t-design to be simple, purely in terms of the automorphism group of the design. Some constructions are given.

Finally, 2-designs with k = 3 and λ = 2 are considered in detail. These designs are first considered in general, with examples illustrating some of the configurations which can arise. Then an attempt is made to classify all such designs with an automorphism group transitive on pairs of points. Many cases are eliminated of reduced to combinations of Steiner triple systems. In the remaining cases, the simple designs are determined to consist of one infinite class and one exceptional case.

The Riesz space structure of an Abelian W*-algebra

Let M be an Abelian W*-algebra of operators on a Hilbert space H. Let M₀ be the set of all linear, closed, densely defined transformations in H which commute with every unitary operator in the commutant M’ of M. A well known result of R. Pallu de Barriere states that if ɸ is a normal positive linear functional on M, then ɸ is of the form T → (Tx, x) for some x in H, where T is in M. An elementary proof of this result is given, using only those properties which are consequences of the fact that ReM is a Dedekind complete Riesz space with plenty of normal integrals. The techniques used lead to a natural construction of the class M₀, and an elementary proof is given of the fact that a positive self-adjoint transformation in M₀ has a unique positive square root in M₀. It is then shown that when the algebraic operations are suitably defined, then M₀ becomes a commutative algebra. If ReM₀ denotes the set of all self-adjoint elements of M₀, then it is proved that ReM₀ is Dedekind complete, universally complete Riesz spaces which contains ReM as an order dense ideal. A generalization of the result of R. Pallu de la Barriere is obtained for the Riesz space ReM₀ which characterizes the normal integrals on the order dense ideals of ReM₀. It is then shown that ReM₀ may be identified with the extended order dual of ReM, and that ReM₀ is perfect in the extended sense.

Some secondary questions related to the Riesz space ReM are also studied. In particular it is shown that ReM is a perfect Riesz space, and that every integral is normal under the assumption that every decomposition of the identity operator has non-measurable cardinal. The presence of atoms in ReM is examined briefly, and it is shown that ReM is finite dimensional if and only if every order bounded linear functional on ReM is a normal integral.

Effect of bismuth oxide on the thermal stability and Judd-Ofelt parameters of Er 3(+)/Yb3(+) co-doped aluminophosphate glasses

The Er3+/Yb3+ co-doped glasses with compositions of xBi(2)O(3)-(65-x)P2O5-4Yb(2)O(3)-11Al(2)O(3)-5BaO-15Na(2)O (where x = 0, 2.5, 5, 7.5 and 10 mol%) were prepared using the normal melt quench technique. The optical absorption spectra of the glasses were recorded in the wavelength range 300-1700 nm. The effect of Bi2O3 content on the thermal stability and absorption spectra of glasses was investigated. In addition, the Judd-Ofelt parameters and oscillator strengths were calculated by employing Judd-Ofelt theory. It was observed that the positions of the fundamental absorption edge and cut-off wavelength shifted towards red as the content of Bi2O3 increased. However, there were no red shifts found both in the peak wavelength and in the center of mass wavelength of all absorption bands with Bi2O3 content increasing. The results of Judd-Ofelt theory analysis showed that Judd-Ofelt parameters Omega(t), (t = 2, 4, 6) changed sharply when Bi2O3 concentration exceeded 5 mol%. The variation trends of experimental oscillator strength were similar with those of Judd-Ofelt parameters as function of Bi2O3 concentrations. Moreover, differential scanning calorimetry experiments showed that the increases of Bi2O3 content weakened the network structure and then lowered the thermal stability of the glasses. The spontaneous emission probability A(rad), branching ratio beta and the radiative lifetime tau(rad) were also calculated and analyzed. The stimulated emission cross-section of Er3+ was calculated according to the McCumber theory. It was found that the stimulated emission cross-section of Er3+ was monotonically increases with Bi2O3 content increasing. (C) 2006 Elsevier B.V. All rights reserved.

A-SCALA: an age-structured statistical catch-at-length analysis for assessing tuna stocks in the eastern tropical Pacific Ocean

English: We describe an age-structured statistical catch-at-length analysis (A-SCALA) based on the MULTIFAN-CL model of Fournier et al. (1998). The analysis is applied independently to both the yellowfin and the bigeye tuna populations of the eastern Pacific Ocean (EPO). We model the populations from 1975 to 1999, based on quarterly time steps. Only a single stock for each species is assumed for each analysis, but multiple fisheries that are spatially separate are modeled to allow for spatial differences in catchability and selectivity. The analysis allows for error in the effort-fishing mortality relationship, temporal trends in catchability, temporal variation in recruitment, relationships between the environment and recruitment and between the environment and catchability, and differences in selectivity and catchability among fisheries. The model is fit to total catch data and proportional catch-at-length data conditioned on effort. The A-SCALA method is a statistical approach, and therefore recognizes that the data collected from the fishery do not perfectly represent the population. Also, there is uncertainty in our knowledge about the dynamics of the system and uncertainty about how the observed data relate to the real population. The use of likelihood functions allow us to model the uncertainty in the data collected from the population, and the inclusion of estimable process error allows us to model the uncertainties in the dynamics of the system. The statistical approach allows for the calculation of confidence intervals and the testing of hypotheses. We use a Bayesian version of the maximum likelihood framework that includes distributional constraints on temporal variation in recruitment, the effort-fishing mortality relationship, and catchability. Curvature penalties for selectivity parameters and penalties on extreme fishing mortality rates are also included in the objective function. The mode of the joint posterior distribution is used as an estimate of the model parameters. Confidence intervals are calculated using the normal approximation method. It should be noted that the estimation method includes constraints and priors and therefore the confidence intervals are different from traditionally calculated confidence intervals. Management reference points are calculated, and forward projections are carried out to provide advice for making management decisions for the yellowfin and bigeye populations. Spanish: Describimos un análisis estadístico de captura a talla estructurado por edad, A-SCALA (del inglés age-structured statistical catch-at-length analysis), basado en el modelo MULTIFAN- CL de Fournier et al. (1998). Se aplica el análisis independientemente a las poblaciones de atunes aleta amarilla y patudo del Océano Pacífico oriental (OPO). Modelamos las poblaciones de 1975 a 1999, en pasos trimestrales. Se supone solamente una sola población para cada especie para cada análisis, pero se modelan pesquerías múltiples espacialmente separadas para tomar en cuenta diferencias espaciales en la capturabilidad y selectividad. El análisis toma en cuenta error en la relación esfuerzo-mortalidad por pesca, tendencias temporales en la capturabilidad, variación temporal en el reclutamiento, relaciones entre el medio ambiente y el reclutamiento y entre el medio ambiente y la capturabilidad, y diferencias en selectividad y capturabilidad entre pesquerías. Se ajusta el modelo a datos de captura total y a datos de captura a talla proporcional condicionados sobre esfuerzo. El método A-SCALA es un enfoque estadístico, y reconoce por lo tanto que los datos obtenidos de la pesca no representan la población perfectamente. Además, hay incertidumbre en nuestros conocimientos de la dinámica del sistema e incertidumbre sobre la relación entre los datos observados y la población real. El uso de funciones de verosimilitud nos permite modelar la incertidumbre en los datos obtenidos de la población, y la inclusión de un error de proceso estimable nos permite modelar las incertidumbres en la dinámica del sistema. El enfoque estadístico permite calcular intervalos de confianza y comprobar hipótesis. Usamos una versión bayesiana del marco de verosimilitud máxima que incluye constreñimientos distribucionales sobre la variación temporal en el reclutamiento, la relación esfuerzo-mortalidad por pesca, y la capturabilidad. Se incluyen también en la función objetivo penalidades por curvatura para los parámetros de selectividad y penalidades por tasas extremas de mortalidad por pesca. Se usa la moda de la distribución posterior conjunta como estimación de los parámetros del modelo. Se calculan los intervalos de confianza usando el método de aproximación normal. Cabe destacar que el método de estimación incluye constreñimientos y distribuciones previas y por lo tanto los intervalos de confianza son diferentes de los intervalos de confianza calculados de forma tradicional. Se calculan puntos de referencia para el ordenamiento, y se realizan proyecciones a futuro para asesorar la toma de decisiones para el ordenamiento de las poblaciones de aleta amarilla y patudo.

Congregação da Escola Normal: da legitimidade outorgada à legitimidade (re) conquistada (1880-1910)

Investigar a forma como a Congregação da Escola Normal se legitimou no cenário político-educacional nos últimos anos do século XIX e nos primeiros anos do século XX é o objetivo de meu estudo. Surgida no Regulamento de criação da Escola Normal a Congregação, era composta pelos professores da instituição que ministravam aulas no curso de formação de professores para as escolas públicas primárias da cidade do Rio de Janeiro. Estes professores eram intelectuais de procedências diversas, com experiência educacional, que se reuniam em sessões, sob a presidência e convite do Diretor da Escola Normal. A legitimação da Congregação foi conquistada pelo Regulamento de 1880, outorgado pelo Governo Imperial e, face ao trabalho e experiência dos congregados à frente desta instituição durante todo um ano, foi-lhes conferido ainda mais poder político, pela elaboração de um novo Regulamento para a Escola Normal, criando-se, então, um grupo diferenciado formado no campo intelectual, pelo conhecimento da formação de professores primários. A Congregação foi extinta em 1888. (Re) conquistando a legitimidade foi criado o Regulamento de 1890, elaborado por Benjamin Constant Botelho de Magalhães, ex- congregado, ex- presidente da Congregação por cinco anos consecutivos e na República ocupando o cargo de Ministro da Instrução Pública, Correios e Telégrafos. Esta pesquisa foi instigada por alguns documentos, ainda não investigados, do Centro de Memória Institucional do Instituto Superior de Educação do Rio de Janeiro, que possibilitaram conhecer a ação política- educacional desses intelectuais da Congregação. Tais fontes, confrontadas com outras de várias instituições de guarda de memória, possibilitaram uma visão não só da ação dos congregados, como de sua rede de sociabilidade dentro e fora da Escola Normal, assim como sua procedência, as estratégias utilizadas como instrumento político e o papel de Benjamin Constant Botelho de Magalhães, líder mais antigo deste grupo. A intervenção política da Congregação, advinda do trabalho realizado na Escola Normal, possibilitou que criassem uma autoimagem de executores do processo civilizador em curso no final do Império e início da República. Os embates travados por este grupo mostram a defesa intransigente da legitimação e o uso de instrumentos próprios da intelectualidade para não perdê-la outra vez.

Dealing with the Effects of Sensor Displacement in Wearable Activity Recognition

Most wearable activity recognition systems assume a predefined sensor deployment that remains unchanged during runtime. However, this assumption does not reflect real-life conditions. During the normal use of such systems, users may place the sensors in a position different from the predefined sensor placement. Also, sensors may move from their original location to a different one, due to a loose attachment. Activity recognition systems trained on activity patterns characteristic of a given sensor deployment may likely fail due to sensor displacements. In this work, we innovatively explore the effects of sensor displacement induced by both the intentional misplacement of sensors and self-placement by the user. The effects of sensor displacement are analyzed for standard activity recognition techniques, as well as for an alternate robust sensor fusion method proposed in a previous work. While classical recognition models show little tolerance to sensor displacement, the proposed method is proven to have notable capabilities to assimilate the changes introduced in the sensor position due to self-placement and provides considerable improvements for large misplacements.

Conhecimentos pedagógicos como orientação para a "missão docente": a formação na Escola Normal de Niterói na Primeira República (1893-1915)

A dissertação analisa a política de formação docente oferecida pela Escola Normal de Niterói entre 1893 e 1915. O projeto de institucionalização da escolarização de professores representou momento de transformações significativas na profissão, então associada aos ideais de progresso e modernidade republicanos, com destaque para a circulação e apropriação de teorias pedagógicas. Buscou-se conhecer o lugar de tais teorias e dos saberes na formação institucional de professores, visando compreender, em que medida, as representações sobre a missão docente se fez presente nos discursos dos Presidentes de Estado no período. Com esse objetivo, analisamos as reformas de ensino e as frequentes inserções e retiradas de disciplinas escolares, em meio aos intensos debates na esfera governamental sobre o que ensinar ao povo e aos professores. Almejava-se um saber que fosse capaz de ampliar a visão do cidadão brasileiro, modificar seus hábitos e inseri-lo na modernidade, aspectos que condiziam com a construção de um espírito republicano. Para compreender o funcionamento e a contribuição dessa escola para a história da educação fluminense, analisamos a legislação educacional, os programas e as disciplinas, e também alguns exames de admissão e finais dos alunos. Foram utilizadas as mensagens dos presidentes do Estado (1892 a 1918), as leis que reformaram ou regulamentaram a instrução pública (1893, 1895, 1900, 1912 e 1915), em particular a Escola Normal de Niterói, os exames de admissão (1901 a 1908), os exames finais dos alunos (1897 a 1911) e um diário de Geografia (1915). Tais documentos foram analisados à luz de extensa historiografia sobre a formação docente e permitiram conhecer práticas escolares da instituição. As leis que modificaram os programas tentaram imprimir um caráter mais científico ao curso e muito se discutiu sobre a questão prática. Para tanto, as disciplinas tencionavam articular a teoria à experiência corroborando a aptidão do professor. A aprendizagem era verificada por meio de exames finais, que sucediam as sabatinas e as provas. Examinar era um dispositivo de poder que comparava e excluía e não apenas mensurava o conhecimento. Investigar a formação de professores nos levou a olhar as articulações históricas e as relações de forças que a constituíram. A pesquisa documental sugere a necessidade de ampliarmos a visão sobre a formação docente na Primeira República, tendo em vista que houve esforços em se organizar a instrução pública, sobretudo, no que concerne à Escola Normal de Niterói.

An evaluation of the survival of Atlantic salmon (Salmo salar L.)fry stocked in eight streams in the North West of England.

Eight streams from the North West of England were stocked with Atlantic salmon (Salmo salar L.) fed fry at densities ranging from 1 to 4/m2 over a period of up to three years to evaluate survival to the end of the first an d second growing periods and hence assess the value of stocking as a management practice. Survival to the end of the first growin g period (mean duration of 108 days) was found to vary between 7.8 and 41.3% with a mean of 22% and CV of 0.44. Survival from the end of the first growing period to the end of the second growing period (mean duration of 384 days) ranged from 19.9 to 34.1% with a mean of 26.3% and CV of 0.21. Survival was found to be positively related to 0+ trout density (P < 0.05) and negatively related to altitude (P < 0.05). A comparison of the raw survival data (non standardised with respect to duration of experiments) with that from other studies in relation to stocking densities revealed a negative relationship between fry survival and stocking density (P < 0.05). Densities in excess of 5/m2 tended to result in lower levels of survival. Post stocking fry dispersal patterns were examined for the 1991 data. On average 86.7% of the number of fry surviving remained within the stocked zone by the end of the first growing period. With the exception of one stream there was little in the way of dispersal beyond the stocked zone. The dispersal pattern approximated to the normal distribution (P < 0.05). It was estimated that stocking can result in a net gain of fish to a river system compared with natural productivity, however the numerical significance of this gain and its cost effectiveness need to be determined on a river specific basis.

Effect of Neonatal Asphyxia on the Impairment of the Auditory Pathway by Recording Auditory Brainstem Responses in Newborn Piglets: A New Experimentation Model to Study the Perinatal Hypoxic-Ischemic Damage on the Auditory Syste

Introduction Hypoxia-ischemia (HI) is a major perinatal problem that results in severe damage to the brain impairing the normal development of the auditory system. The purpose of the present study is to study the effect of perinatal asphyxia on the auditory pathway by recording auditory brain responses in a novel animal experimentation model in newborn piglets. Method Hypoxia-ischemia was induced to 1.3 day-old piglets by clamping 30 minutes both carotid arteries by vascular occluders and lowering the fraction of inspired oxygen. We compared the Auditory Brain Responses (ABRs) of newborn piglets exposed to acute hypoxia/ischemia (n = 6) and a control group with no such exposure (n = 10). ABRs were recorded for both ears before the start of the experiment (baseline), after 30 minutes of HI injury, and every 30 minutes during 6 h after the HI injury. Results Auditory brain responses were altered during the hypoxic-ischemic insult but recovered 30-60 minutes later. Hypoxia/ischemia seemed to induce auditory functional damage by increasing I-V latencies and decreasing wave I, III and V amplitudes, although differences were not significant. Conclusion The described experimental model of hypoxia-ischemia in newborn piglets may be useful for studying the effect of perinatal asphyxia on the impairment of the auditory pathway.

A Escola Normal de Juiz de Fora: crises e permanências (1881-1911)

A motivação apresentada nesta dissertação alimentou-se pela instabilidade evidenciada no processo de criação e na tentativa de consolidação da Escola Normal de Juiz de Fora. Sendo alvo de constantes críticas e debates, o papel da escola normal, assim como sua permanência, motivou propostas, reformas e manifestações, que envolveram não só o poder político, mas também a sociedade. Tais apontamentos foram observados tanto em periódicos da cidade, como o Jornal do Commercio e o Correio de Minas, quanto em documentos encontrados no Arquivo Público Mineiro, como relatórios de inspetores e correspondências de professores.Algumas das publicações presentes nesses periódicos expressaram e, de certa forma, mobilizaram a população a tomar atitudes contra a supressão da mesma, através de abaixo-assinados e representações enviadas ao governo do estado, muitas vezes enaltecendo não só a escola normal, mas principalmente a cidade de Juiz de Fora, considerada a principal da Zona da Mata mineira. Assim, foram mapeadas as discussões sobre a instituição, levantando questões sobre o posicionamento dos diferentes atores sociais acerca da instituição que, mesmo após sua supressão, não deixou de ser alvo de debates. Ainda, teceu-se algumas reflexões acerca da Reforma do Ensino Primário e Normal de João Pinheiro (1906), no que se refere ao ensino normal, mais especificamente no contexto juizforano. Para tanto, foram abordadas questões sobre a preferência da mulher para o magistério,o papel do professor e os institutos equiparados à Escola Normal Modelo de Belo Horizonte. Esse estudo concluiu que as determinações políticas não são produzidas apenas pelos discursos e decisões dos governantes, mas também são influenciáveis e podem ser modificadas por pressões de outros grupos sociais. Tais grupos sociais são formados por indivíduos com ideias e objetivos semelhantes, fazendo parte de um lugar e de uma posição social que os permitam circular e se manifestar em espaços que atinjam proporções significativas, como é o caso da imprensa.

Growth, mortality and yield-per-recruit of the poor cod, Trisopterus minutus capelanus, from the Strait of Sicily

Length-based methods (LBMs) were used to study the growth of Trisopterus minutus capelanus in the Strait of Sicily (Messina Strait). A total of 16,304 'merluzzetto' or poor cod collected by experimental trawling off the southern coast of Sicily during spring, summer, autumn 1986 and winter 1987 were measured in order to estimate the length structure of the population. Length-frequency distribution were analyzed and normal components were discriminated. Von Bertalanffy growth parameters were derived from the mean length of the normal components. The growth parameters obtained by weighted non-linear regression were: K=0.462 (yr super(1)), L sub( infinity )=222.3 (TL,mm) and t sub(o)=-0.679 yr. The resulting growth performance index ( Phi ') was 4.36, a value slightly lower than those derived for Western Mediterranean (mean Phi '=4.45) and Adriatic ( Phi '=4.58) populations and slightly higher than that derived for Hellenic waters ( Phi '=4.27). On the basis of the von Bertalanffy parameters estimated, an array of age-specific instantaneous natural mortality rate (M sub(t)=0.5-1.1) and an average value of total natural mortality rate (Z=2.1 yr super(1)) were estimated and used in the Thompson and Bell yield per recruit (Y/R) analysis in order to evaluate the status of the fishery and forecast the effects of changes in the fishing pattern. Results indicate that this resource is overexploited and that Y/R could be increased by postponing the age at first capture from 0.5 to 1.0 yr. Even a slight reduction in fishing mortality could improve the performance of the fishery. At the present level of exploitation, and assuming a constant recruitment, the spawning stock biomass per recruit (SPR) is well below the conservative threshold of 30% of the pristine or unexploited SPR.

Normal e patológico: leituras contemporâneas

O objetivo do trabalho é investigar as teses conceituais contemporâneas sobre o normal e o patológico em medicina. Após a célebre tese de Georges Canguilhem sobre o tema e sobretudo a partir da década de 1970, a filosofia da medicina anglo-saxônica ofereceu importantes contribuições para o debate. Analisamos principalmente as teses de Christopher Boorse e Lennart Nordenfelt, autores que compartilham com Canguilhem a convicção de que a análise filosófica pode contribuir para o esclarecimento dos conceitos médicos. O primeiro é apontado na literatura como naturalista e o segundo como normativista, polarização apresentada na literatura anglo-saxônica contemporânea que reflete o debate sobre a descrição da saúde e da doença como fenômenos naturais ou como estados determinados por valores antropomórficos. Vemos que, para distinguir o normal do patológico, os autores contemporâneos naturalistas fazem uso dos critérios de função biológica e tipo biológico e os autores normativistas falam em função social e tipos ideais. Problematizamos estes conceitos usando o referencial da filosofia da biologia e dos estudos da deficiência, respectivamente, e notamos que as definições propostas pelos filósofos da medicina merecem ser refinadas.

Sensitivity of wear rates in the micro-scale abrasion test to test conditions and material hardness

Micro-scale abrasion (ball cratering) tests were performed with different combinations of ball and bulk specimen materials, under different test conditions, such as load and abrasive slurry concentration. Wear modes were classified into two types: with rolling particle motion and with grooving particle motion. Wear rates observed with rolling particle motion were relatively insensitive to test conditions, whereas with grooving motion they varied much more. It is suggested that rolling abrasion is therefore a more appropriate mode if reproducible test results are desired. The motion of the abrasive particles can be reliably predicted from the knowledge of hardnesses and elastic properties of the ball and the specimen, and from the normal load and the abrasive slurry concentration. General trends in wear resistance measured in the micro-scale abrasion test with rolling particle motion are similar to those reported in tests with fixed abrasives with sliding particle motion, although the variation in wear resistance with hardness is significantly smaller. © 2004 Published by Elsevier B.V.