806 resultados para Logarithm spiral
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A vantagem competitiva e o desempenho organizacional são conceitos administrativos estreitamente ligados à competitividade das empresas e sua permanência no mercado a longo prazo. Para que alcancem tal objetivo, de acordo com os fundamentos da RBV, as capacidades organizacionais dessas empresas devem ser dinâmicas, o que significa estar à frente das mudanças ambientais, mantendo, criando e desenvolvendo novas capacidades. Um dos caminhos para que isso se realize é a aposta na sua capitalização, que pode ocorrer com a captação de recursos de terceiros ou recursos próprios, com maior ou menor grau de risco. A captação de recursos com capital de terceiros acontece, principalmente, via instituições financeiras e factorings. A captação por meio de capital próprio pode ocorrer por retenção de lucros ou pelo underwriting. A emissão feita via mercado primário configura a oferta pública inicial de ações ou Initial Public Offering (IPO). No Brasil, a escolha dos fundos de Private Equity e Venture Capital, segmentos do mercado financeiro que consistem fundamentalmente em aporte temporário de capital, vem crescendo consideravelmente nos últimos anos. Contudo, existem poucas pesquisas a respeito da utilização e do desempenho financeiro que esses fundos trazem para as empresas. O presente estudo procura averiguar se as empresas que estavam listadas na BOVESPA no período de 2002 a 2008 e que receberam recursos via Private Equity e Venture Capital com IPO desenvolveram desempenho financeiro superior às que receberam ou não outros tipos de financiamento no mesmo período. Foram selecionados dados secundários como: balanços patrimoniais, demonstração de resultados e valores das ações, utilizando-se da base de dados da Economática. Tomando o logaritmo do Q de Tobin como variável dependente e log_Ativo, Debt to Equity, ROA, crescimento de vendas, crescimento de investimentos, crescimento investimento Fama e CrescInv_endividamento como variáveis de controle, foram aplicados testes estatísticos, comparando a média dos índices, seguidos de análise por setor econômico, subsetor e segmento. Os resultados encontrados apontam que as empresas que receberam recursos via Private Equity e Venture Capital com IPO, tornaram-se diferentes das demais empresas que estavam listadas na BOVESPA naquele período. O presente trabalho busca, dessa forma, contribuir para o enriquecimento de conhecimento acadêmico acerca do tema.(AU)
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Esta pesquisa propõe-se a tematizar a religião no pensamento de Paul Ricoeur. Correlaciona filosofia e teologia e tem na nomeação de Deus o primeiro pro-blema. Ao analisar os limites do assunto, a hipótese da tese sustenta que a inter-secção das áreas é produtiva e que um trabalho original de pensamento pode vir deste cruzamento. A tese sugere o termo da dobra da religião, tendo em vista a apropriação da tarefa do reconhecimento do si na ontologia quebrada. O desdo-bramento das aporias, pela filosofia reflexiva, articula a ontologia do possível nas categorias existenciais do autor, sobretudo em termos da linguagem religio-sa, da esperança e da aporia da graça. A pesquisa é feita com base no método fenomenológico e hermenêutico, dividido em quatro etapas: num primeiro mo-mento, introduz-se a relação da filosofia com a teologia e o teônimo como a primeira dobra da religião. No segundo capítulo, aborda-se a importância tempo-ralidade e a narratividade na mito-poética. O terceiro capítulo versa sobre a in-terpretação metafórica da religião na ontologia do possível. O quarto e último capítulo apresenta a dobra existencial cujo movimento se dá como um espiral fi-losófico na própria vida de Ricoeur. A pesquisa é concluída no horizonte do ser humano capaz e o reconhecimento de si mediado pela dobra da religião. Espera-se que o resultado seja uma reflexão que permita uma melhor compreensão da filosofia de Ricoeur, bem como que sirva de referencial e fundamento para fu-turos estudos acerca da filosofia da religião.
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The chromium chalcogenide spinels, MCr2X4 (M = Zn, Cd, Hg; X = O, S, Se), have been the subject of considerable interest in recent years. In each case the crystal structure is that of a normal spinel with the chromium ions exclusively occupying the octahedral (B) sites, so that when diamagnetic ions are located at the tetrahedral (A) sites the only magnetic interactions present are those between B-site ions. Despite such apparently simple circumstances a rich variety of magnetic behaviour is exhibited. For the oxides the ground state spin configurations are antiferromagnetic whilst for the selenides ferromagnetic interactions dominate and several authors have drawn attention to the fact that the nature of the dominant interaction is a function of the nearest neighbour chromium - chromium separation. However, at least two of the compounds exhibit spiral structures and it has been proved difficult to account for the various spin configurations within a unified theory of the magnetic interactions involved. More recently, the possibility of formulating a simplified interpretation of the magnetic interactions has been provided by the discovery that the crystal struture of spinels does not always conform to the centrosymmetrical symmetry Fd3m that has been conventionally assumed. The deviation from this symmetry is associated with small < 111> displacements of the octahedrally coordinated metal ions and the structures so obtained are more correctly referred to the non-centrosymmetrical space group F43m. In the present study, therefore, extensive X-ray diffraction data have been collected from four chromium chalcogenide specimens and used to refine the corresponding structural parameters assuming F43m symmetry and also with conventional symmetry. The diffracted intensities from three of the compounds concerned cannot be satisfactorily accounted for on the basis of conventional symmetry and new locations have been found for the chromium ions in these cases. It is shown, however, that these displacements in chromium positions only partially resolve the difficulties in interpreting the magnetic behaviour. A re-examination of the magnetic data from different authors indicates much greater uncertainty in their measurements than they had claimed. By taking this into consideration it is shown that a unified theory of magnetic behaviour for the chromium chalcogenide spinels is a real possibility.
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Following a scene-setting introduction are detailed reviews of the relevant scientific principles, thermal analysis as a research tool and the development of the zinc-aluminium family of alloys. A recently introduced simultaneous thermal analyser, the STA 1500, its use for differential thermal analysis (DTA) being central to the investigation, is described, together with the sources of support information, chemical analysis, scanning electron microscopy, ingot cooling curves and fluidity spiral castings. The compositions of alloys tested were from the binary zinc-aluminium system, the ternary zinc-aluminium-silicon system at 30%, 50% and 70% aluminium levels, binary and ternary alloys with additions of copper and magnesium to simulate commercial alloys and five widely used commercial alloys. Each alloy was shotted to provide the smaller, 100mg, representative sample required for DTA. The STA 1500 was characterised and calibrated with commercially pure zinc, and an experimental procedure established for the determination of DTA heating curves at 10°C per minute and cooling curves at 2°C per minute. Phase change temperatures were taken from DTA traces, most importantly, liquidus from a cooling curve and solidus from both heating and cooling curves. The accepted zinc-aluminium binary phase diagram was endorsed with the added detail that the eutectic is at 5.2% aluminium rather than 5.0%. The ternary eutectic trough was found to run through the points, 70% Al, 7.1% Si, 545°C; 50% Al, 3.9% Si, 520°C; 30% Al, 1.4% Si, 482°C. The dendrite arm spacing in samples after DTA increased with increasing aluminium content from 130m at 30% to 220m at 70%. The smallest dendrite arm spacing of 60m was in the 30% aluminium 2% silicon alloy. A 1kg ingot of the 10% aluminium binary alloy, insulated with Kaowool, solidified at the same 2°C per minute rate as the DTA samples. A similar sized sand casting was solidified at 3°C per minute and a chill casting at 27°C per minute. During metallographic examination the following features were observed: heavily cored phase which decomposed into ' and '' on cooling; needles of the intermetallic phase FeAl4; copper containing ternary eutectic and copper rich T phase.
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The mechanism of "Helical Interference" in milled slots is examined and a coherent theory for the geometry of such surfaces is presented. An examination of the relevant literature shows a fragmented approach to the problem owing to its normally destructive nature, so a complete analysis is developed for slots of constant lead, thus giving a united and exact theory for many different setting parameters and a range of cutter shapes. For the first time, a theory is developed to explain the "Interference Surface" generated in variable lead slots for cylindrical work and attention is drawn to other practical surfaces, such as cones, where variable leads are encountered. Although generally outside the scope of this work, an introductory analysis of these cases is considered in order to develop the cylindrical theory. Special emphasis is laid upon practical areas where the interference mechanism can be used constructively and its application as the rake face of a cutting tool is discussed. A theory of rake angle for such cutting tools is given for commonly used planes, and relative variations in calculated rake angle between planes is examined. Practical tests are conducted to validate both constant lead and variable lead theories and some design improvements to the conventional dividing head are suggested in order to manufacture variable lead workpieces, by use of a "superposed" rotation. A prototype machine is manufactured and its kinematic principle given for both linear and non-linearly varying superposed rotations. Practical workpieces of the former type are manufactured and compared with analytical predictions,while theoretical curves are generated for non-linear workpieces and then compared with those of linear geometry. Finally suggestions are made for the application of these principles to the manufacture of spiral bevel gears, using the "Interference Surface" along a cone as the tooth form.
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A study of information available on the settlement characteristics of backfill in restored opencast coal mining sites and other similar earthworks projects has been undertaken. In addition, the methods of opencast mining, compaction controls, monitoring and test methods have been reviewed. To consider and develop the methods of predicting the settlement of fill, three sites in the West Midlands have been examined; at each, the backfill had been placed in a controlled manner. In addition, use has been made of a finite element computer program to compare a simple two-dimensional linear elastic analysis with field observations of surface settlements in the vicinity of buried highwalls. On controlled backfill sites, settlement predictions have been accurately made, based on a linear relationship between settlement (expressed as a percentage of fill height) against logarithm of time. This `creep' settlement was found to be effectively complete within 18 months of restoration. A decrease of this percentage settlement was observed with increasing fill thickness; this is believed to be related to the speed with which the backfill is placed. A rising water table within the backfill is indicated to cause additional gradual settlement. A prediction method, based on settlement monitoring, has been developed and used to determine the pattern of settlement across highwalls and buried highwalls. The zone of appreciable differential settlement was found to be mainly limited to the highwall area, the magnitude was dictated by the highwall inclination. With a backfill cover of about 15 metres over a buried highwall the magnitude of differential settlement was negligible. Use has been made of the proposed settlement prediction method and monitoring to control the re-development of restored opencase sites. The specifications, tests and monitoring techniques developed in recent years have been used to aid this. Such techniques have been valuable in restoring land previously derelict due to past underground mining.
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We propose and analyze a flat-top pulse generator based on a fiber Bragg grating (FBG) in transmission. As is shown in the examples, a uniform period FBG properly designed can exhibit a spectral response in transmission close to sinc function (in amplitude and phase) in a certain bandwidth, because of the logarithm Hilbert transform relations, which can be used to reshape a Gaussian-like input pulse into a flat-top pulse.
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The objective of Total Productive Maintenance (TPM) is to maximise plant and equipment effectiveness, to create a sense of ownership for operators, and promote continuous improvement through small group activities involving production, engineering and maintenance personnel. This paper describes and analyses a case study of TPM implementation at a newspaper printing house in Singapore. However, rather than adopting more conventional implementation methods such as employing consultants or through a project using external training, a unique approach was adopted based on Action Research using a spiral of cycles of planning, acting observing and reflecting. An Action Research team of company personnel was specially formed to undertake the necessary fieldwork. The team subsequently assisted with administering the resulting action plan. The main sources of maintenance and operational data were from interviews with shop floor workers, participative observation and reviews conducted with members of the team. Content analysis using appropriate statistical techniques was used to test the significance of changes in performance between the start and completion of the TPM programme. The paper identifies the characteristics associated with the Action Research method when used to implement TPM and discusses the applicability of the approach in related industries and processes.
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Peptides are of great therapeutic potential as vaccines and drugs. Knowledge of physicochemical descriptors, including the partition coefficient P (commonly expressed in logarithm form: logP), is useful for screening out unsuitable molecules and also for the development of predictive Quantitative Structure-Activity Relationships (QSARs). In this paper we develop a new approach to the prediction of LogP values for peptides based on an empirical relationship between global molecular properties and measured physical properties. Our method was successful in terms of peptide prediction (total r2 = 0.641). The final model consisted of 5 physicochemical descriptors (molecular weight, number of single bonds, 2D-VDW volume, 2D-VSA hydrophobic and 2D-VSA polar). The approach is peptide specific and its predictive accuracy was high. Overall, 67% of the peptides were able to be predicted within +/-0.5 log units from the experimental values. Our method thus represents a novel prediction method with proven predictive ability.
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PURPOSE. To compare the objective accommodative amplitude and dynamics of eyes implanted with the one-compartment-unit (1CU; HumanOptics AG, Erlangen, Germany) accommodative intraocular lenses (IOLs) with that measured subjectively. METHODS. Twenty eyes with a 1CU accommodative IOL implanted were refracted and distance and near acuity measured with a logMAR (logarithm of the minimum angle of resolution) chart. The objective accommodative stimulus-response curve for static targets between 0.17 and 4.00 D accommodative demand was measured with the SRW-5000 (Shin-Nippon Commerce Inc., Tokyo, Japan) and PowerRefractor (PlusOptiX, Nürnberg, Germany) autorefractors. Continuous objective recording of dynamic accommodation was measured with the SRW-5000, with the subject viewing a target moving from 0 to 2.50 D at 0.3 Hz through a Badal lens system. Wavefront aberrometry measures (Zywave; Bausch & Lomb, Rochester, NY) were made through undilated pupils. Subjective amplitude of accommodation was measured with the RAF (Royal Air Force accommodation and vergence measurement) rule. RESULTS. Four months after implantation best-corrected acuity was -0.01 ± 0.16 logMAR at distance and 0.60 ± 0.09 logMAR at near. Objectively, the static amplitude of accommodation was 0.72 ± 0.38 D. The average dynamic amplitude of accommodation was 0.71 ± 0.47 D, with a lag behind the target of 0.50 ± 0.48 seconds. Aberrometry showed a decrease in power of the lens-eye combination from the center to the periphery in all subjects (on average, -0.38 ± 0.28 D/mm). Subjective amplitude of accommodation was 2.24 ± 0.42 D. Two years after 1CU implantation, refractive error and distance visual acuity remained relatively stable, but near visual acuity, and the subjective and objective amplitudes of accommodation decreased. CONCLUSIONS. The objective accommodating effects of the 1CU lens appear to be limited, although patients are able to track a moving target. Subjective and objective accommodation was reduced at the 2-year follow-up. The greater subjective amplitude of accommodation is likely to result from the eye's depth of focus of and the aspheric nature of the IOL. Copyright © Association for Research in Vision and Ophthalmology.
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Cell exclusion is the phenomenon whereby the hematocrit and viscosity of blood decrease in areas of high stress. While this is well known in naturally occurring Poiseuille flow in the human body, it has never previously been shown in Couette flow, which occurs in implantable devices including blood pumps. The high-shear stresses that occur in the gap between the boundaries in Couette flow are known to cause hemolysis in erythrocytes. We propose to mitigate this damage by initiating cell exclusion through the use of a spiral-groove bearing (SGB) that will provide escape routes by which the cells may separate themselves from the plasma and the high stresses in the gap. The force between two bearings (one being the SGB) in Couette flow was measured. Stained erythrocytes, along with silver spheres of similar diameter to erythrocytes, were visualized across a transparent SGB at various gap heights. A reduction in the force across the bearing for human blood, compared with fluids of comparable viscosity, was found. This indicates a reduction in the viscosity of the fluid across the bearing due to a lowered hematocrit because of cell exclusion. The corresponding images clearly show both cells and spheres being excluded from the gap by entering the grooves. This is the first time the phenomenon of cell exclusion has been shown in Couette flow. It not only furthers our understanding of how blood responds to different flows but could also lead to improvements in the future design of medical devices.
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The paper has been presented at the 12th International Conference on Applications of Computer Algebra, Varna, Bulgaria, June, 2006
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Pre-eclampsia is a vascular disorder of pregnancy where anti-angiogenic factors, systemic inflammation and oxidative stress predominate, but none can claim to cause pre-eclampsia. This review provides an alternative to the 'two-stage model' of pre-eclampsia in which abnormal spiral arteries modification leads to placental hypoxia, oxidative stress and aberrant maternal systemic inflammation. Very high maternal soluble fms-like tyrosine kinase-1 (sFlt-1 also known as sVEGFR) and very low placenta growth factor (PlGF) are unique to pre-eclampsia; however, abnormal spiral arteries and excessive inflammation are also prevalent in other placental disorders. Metaphorically speaking, pregnancy can be viewed as a car with an accelerator and brakes, where inflammation, oxidative stress and an imbalance in the angiogenic milieu act as the 'accelerator'. The 'braking system' includes the protective pathways of haem oxygenase 1 (also referred as Hmox1 or HO-1) and cystathionine-γ-lyase (also known as CSE or Cth), which generate carbon monoxide (CO) and hydrogen sulphide (H2S) respectively. The failure in these pathways (brakes) results in the pregnancy going out of control and the system crashing. Put simply, pre-eclampsia is an accelerator-brake defect disorder. CO and H2S hold great promise because of their unique ability to suppress the anti-angiogenic factors sFlt-1 and soluble endoglin as well as to promote PlGF and endothelial NOS activity. The key to finding a cure lies in the identification of cheap, safe and effective drugs that induce the braking system to keep the pregnancy vehicle on track past the finishing line.
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One of the simplest ways to create nonlinear oscillations is the Hopf bifurcation. The spatiotemporal dynamics observed in an extended medium with diffusion (e.g., a chemical reaction) undergoing this bifurcation is governed by the complex Ginzburg-Landau equation, one of the best-studied generic models for pattern formation, where besides uniform oscillations, spiral waves, coherent structures and turbulence are found. The presence of time delay terms in this equation changes the pattern formation scenario, and different kind of travelling waves have been reported. In particular, we study the complex Ginzburg-Landau equation that contains local and global time-delay feedback terms. We focus our attention on plane wave solutions in this model. The first novel result is the derivation of the plane wave solution in the presence of time-delay feedback with global and local contributions. The second and more important result of this study consists of a linear stability analysis of plane waves in that model. Evaluation of the eigenvalue equation does not show stabilisation of plane waves for the parameters studied. We discuss these results and compare to results of other models.
New negative temperature coefficient thermistor ceramics in Mn-doped CaCu3-xMnxTi4O12 (0≤x≤1) system
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New negative temperature coefficient (NTC) ceramics based on CaCu 3-xMnxTi4O12 (0≤x≤1) compositions have been investigated. The grain size of the CaCu 3-xMnxTi4O12 samples decreases at first and then increases with increasing Mn content. The X-ray photoelectron spectroscopy analysis corroborates the presence of Mn3+ and Mn 4+ in Mn-doped samples, which results in a decrease in the activation energy. All the NTC thermistors prepared show a linear relationship between the natural logarithm of the resistivity and the reciprocal temperature, indicative of NTC characteristics. The Mn-doped CaCu3-xMnxTi 4O12 NTC thermistors provide various electrical properties, depending on Mn content. The values of ρ25, B constant and activation energy of the NTC thermistors are in the range of 2.22×106-3.22×108 Ω cm, 5488-8031 K, and 0.473-0.692 eV, respectively. © 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.