969 resultados para structural characteristics


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This study was concerned with the structure, functions and development, especially the performance, of some rural small firms associated with the Council for Small Industries in Rural Areas (C?SIRA) of England. Forty firms were used as the main basis of analysis. For some aspects of the investigation, however, data from another 54 firms, obtained indirectly through nine CoSIRA Organisers, were also used. For performance-analysis, the 40 firms were firstly ranked according to their growth and profitability rates which were calculated from their financial data. Then each of the variables hypothesised to be related to performance was tested to ascertain its relationship with performance, using the Spearman's Rank Correlation technique. The analysis indicated that each of the four factors .. the principal, the firm itself, its management, and the environment - had a bearing upon the performance of the firm. Within the first factor, the owner-manager's background and attitudes were found to be most important; in the second, the firm's size, age and scope of activities were also found to be correlated with performance; with respect to the third, it was revealed that firms which practised some forms of systems in planning, control and costing performed better than those which did not and, finally with respect to the fourth factor, it was found that some of the services provided by CoSIRA, especially credit finance, were facilitative to the firm's performance. Another significant facet of the firms highlighted by the study was their multifarious roles. These, meeting economic, psychological, sociological and political needs, were considered to be most useful to man and his society. Finally, the study has added light to the structural characteristics of the sampled firms, including various aspects of their development, orientation and organisation, as well as their various structural strengths and weakness. ' .

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This thesis reports a cross-national study carried out in England and India in an attempt to clarify the association of certain cultural and non-cultural characteristics with people's work-related attitudes and values, and with the structure of their work organizations. Three perspectives are considered to be relevant to the objectives of the study. The contingency perspective suggests that a 'fit' between an organization's context and its structural arrangements will be fundamentally necessary for achieving success and survival. The political economy perspective argues for the determining role of the social and economic structures within which the organization operates. The culturalist perspective looks to cultural attitudes and values of organizational members for an explanation for their organization's structure. The empirical investigation was carried out in three stages in each of the two countries involved by means of surveys of cultural attitudes, work-related attitudes and organizational structures and systems. The cultural surveys suggested that Indian and English people were different from one another with regard to fear of, and respect and obedience to, their seniors, ability to cope with ambiguity, honesty, independence, expression of emotions, fatalism, reserve, and care for others; they were similar with regard to tolerance, friendliness, attitude to change, attitude to law, self-control and self-confidence, and attitude to social differentiation. The second stage of the study, involving the employees of fourteen organizations, found that the English ones perceived themselves to have more power at work, expressed more tolerance for ambiguity, and had different expectations from their job than did the Indian equivalents. The two samples were similar with respect to commitment to their company and trust in their colleagues. The findings also suggested that employees' occupations, education and age had some influences on their work-related attitudes. The final stage of the research was a study of structures, control systems, and reward and punishment policies of the same fourteen organizations which were matched almost completely on their contextual factors across the two countries. English and Indian organizations were found to be similar in terms of centralization, specialization, chief executive's span of control, height and management control strategies. English organizations, however, were far more formalized, spent more time on consultation and their managers delegated authority lower down the hierarchy than Indian organizations. The major finding of the study was the multiple association that cultural, national and contingency factors had with the structural characteristics of the organizations and with the work-related attitudes of their members. On the basis of this finding, a multi-perspective model for understanding organizational structures and systems is proposed in which the contributions made by contingency, political economy and cultural perspectives are recognized and incorporated.

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Deformation microstructures in two batches of commercially pure copper (A and B) of allnost similar composition have been studied after rolling reductions from 5% to 95%. X- ray diffraction, optical metallography, scanning electron microscopy in the back-scattered mode, transmission and scanning electron microscopy have been used to examine the deformation microstructure. At low strains (~10 %) the deformation is accommodated by uniform octahedral slip. Microbands that occur as sheet like features usually on the {111} slip planes are formed after 10% reduction. The misorientations between rnicrobonds ond the matrix are usually small (1 - 2° ) and the dislocations within the bands suggest that a single slip system has been operative. The number of microbands increases with strain, they start to cluster and rotate after 60% reduction and, after 90 %, they become almost perfectly aligned with the rolling direction. There were no detectable differences in deformation microstructure between the two materials up to a deformation level of 60% but subsequently, copper B started to develop shear bands which became very profuse by 90% reduction. By contrast, copper A at this stage of deformation developed a smooth laminated structure. This difference in the deformation microstructures has been attributed to traces of unknown impurity in D which inhibit recovery of work hardening. The preferred orientations of both were typical of deformed copper although the presence of shear bands was associated wth a slightly weaker texture. The effects of rolling temperature and grain size on deformation microstructure were also investigated. It was concluded that lowering the rolling temperature or increasing the initial grain size encourages the material to develop shear bands after heavy deformation. Recovery and recrystallization have been studied in both materials during annealing. During recrystallization the growth of new grains showed quite different characteristics in the two cases. Where shear bands were present these acted as nucleation sites and produced a wide spread of recrystallized grain orientations. The resulting annealing textures were very weak. In the absence of shear bands, nucleation occurs by a remarkably long range bulging process which creates the cube orientation and an intensely sharp annealing texture. Cube oriented regions occur in long bands of highly elongated and well recovered cells which contain long range cumulative micorientations. They are transition bands with structural characteristics ideally suited for nucleation of recrystallization. Shear banding inhibits the cube texture both by creating alternative nuclei and by destroying the microstructural features necessary for cube nucleation.

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Refractive index and structural characteristics of optical polymers are strongly influenced by the thermal history of the material. Polymer optical fibres (POF) are drawn under tension, resulting in axial orientation of the polymer molecular chains due to their susceptibility to align in the fibre direction. This change in orientation from the drawing process results in residual strain in the fibre and also affects the transparency and birefringence of the material (1-3). PMMA POF has failure strain as high as over 100%. POF has to be drawn under low tension to achieve this value. The drawing tension affects the magnitude of molecular alignment along the fibre axis, thus affecting the failure strain. The higher the tension the lower the failure stain will be. However, the properties of fibre drawn under high tension can approach that of fibre drawn under low tension by means of an annealing process. Annealing the fibre can generally optimise the performance of POF while keeping most advantages intact. Annealing procedures can reduce index difference throughout the bulk and also reduce residual stress that may cause fracture or distortion. POF can be annealed at temperatures approaching the glass transition temperature (Tg) of the polymer to produce FBG with a permanent blue Bragg wave-length shift at room temperature. At this elevated temperature segmental motion in the structure results in a lower viscosity. The material softens and the molecular chains relax from the axial orientation causing shrinking of the fibre. The large attenuation of typically 1dB/cm in the 1550nm spectral region of PMMA POF has limited FBG lengths to less than 10cm. The more expensive fluorinated polymers with lower absorption have had no success as FBG waveguides. Bragg grating have been inscribed onto various POF in the 800nm spectral region using a 30mW continuous wave 325nm helium cadmium laser, with a much reduced attenuation coefficient of 10dB/m (5). Fabricating multiplexed FBGs in the 800nm spectral region in TOPAS and PMMA POF consistently has lead to fabrication of multiplexed FBG in the 700nm spectral region by a method of prolonged annealing. The Bragg wavelength shift of gratings fabricated in PMMA fibre at 833nm and 867nm was monitored whilst the POF was thermally annealed at 80°C. Permanent shifts exceeding 80nm into the 700nm spectral region was attained by both gratings on the fibre. The large permanent shift creates the possibility of multiplexed Bragg sensors operating over a broad range. -------------------------------------------------------------------------------------------------------------------- 1. Pellerin C, Prud'homme RE, Pézolet M. Effect of thermal history on the molecular orientation in polystyrene/poly (vinyl methyl ether) blends. Polymer. 2003;44(11):3291-7. 2. Dvoránek L, Machová L, Šorm M, Pelzbauer Z, Švantner J, Kubánek V. Effects of drawing conditions on the properties of optical fibers made from polystyrene and poly (methyl methacrylate). Die Angewandte Makromolekulare Chemie. 1990;174(1):25-39. 3. Dugas J, Pierrejean I, Farenc J, Peichot JP. Birefringence and internal stress in polystyrene optical fibers. Applied optics. 1994;33(16):3545-8. 4. Jiang C, Kuzyk MG, Ding JL, Johns WE, Welker DJ. Fabrication and mechanical behavior of dye-doped polymer optical fiber. Journal of applied physics. 2002;92(1):4-12. 5. Johnson IP, Webb DJ, Kalli K, Yuan W, Stefani A, Nielsen K, et al., editors. Polymer PCF Bragg grating sensors based on poly (methyl methacrylate) and TOPAS cyclic olefin copolymer2011: SPIE.

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Strontium has been substituted for calcium in the glass series (SiO2)49.46(Na2O)26.38(P2O5)1.07(CaO)23.08x(SrO)x (where x = 0, 11.54, 23.08) to elucidate their underlying atomic-scale structural characteristics as a basis for understanding features related to the bioactivity. These bioactive glasses have been investigated using isomorphic neutron and X-ray diffraction, Sr K-edge EXAFS and solid state 17O, 23Na, 29Si, 31P and 43Ca magic-angle-spinning (MAS) NMR. An effective isomorphic substitution first-order difference function has been applied to the neutron diffraction data, confirming that Ca and Sr behave in a similar manner within the glass network, with residual differences attributed to solely the variation in ionic radius between the two species. The diffraction data provides the first direct experimental evidence of split Ca–O nearest-neighbour correlations in these melt quench bioactive glasses, together with an analogous splitting of the Sr–O correlations; the correlations are attributed to the metal ions correlated either to bridging or to non-bridging oxygen atoms. Triple quantum (3Q) 43Ca MAS NMR corroborates the split Ca–O correlations. Successful simplification of the 2 < r (A) < 3 region via the difference method has also revealed two distinct Na environments. These environments are attributed to sodium correlated either to bridging or to nonbridging oxygen atoms. Complementary multinuclear MAS NMR, Sr K-edge EXAFS and X-ray diffraction data supports the structural model presented. The structural sites present will be intimately related to their release properties in physiological fluids such as plasma and saliva, and hence the bioactivity of the material. Detailed structural knowledge is therefore a prerequisite for optimising material design.

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Self-similar optical pulses (or “similaritons”) of parabolic intensity profile can be found as asymptotic solutions of the nonlinear Schr¨odinger equation in a gain medium such as a fiber amplifier or laser resonator. These solutions represent a wide-ranging significance example of dissipative nonlinear structures in optics. Here, we address some issues related to the formation and evolution of parabolic pulses in a fiber gain medium by means of semi-analytic approaches. In particular, the effect of the third-order dispersion on the structure of the asymptotic solution is examined. Our analysis is based on the resolution of ordinary differential equations, which enable us to describe the main properties of the pulse propagation and structural characteristics observable through direct numerical simulations of the basic partial differential equation model with sufficient accuracy.

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Refractive index and structural characteristics of optical polymers are strongly influenced by the thermal history of the material. Polymer optical fibres (POF) are drawn under tension, resulting in axial orientation of the polymer molecular chains due to their susceptibility to align in the fibre direction. This change in orientation from the drawing process results in residual strain in the fibre and also affects the transparency and birefringence of the material (1-3). PMMA POF has failure strain as high as over 100%. POF has to be drawn under low tension to achieve this value. The drawing tension affects the magnitude of molecular alignment along the fibre axis, thus affecting the failure strain. The higher the tension the lower the failure stain will be. However, the properties of fibre drawn under high tension can approach that of fibre drawn under low tension by means of an annealing process. Annealing the fibre can generally optimise the performance of POF while keeping most advantages intact. Annealing procedures can reduce index difference throughout the bulk and also reduce residual stress that may cause fracture or distortion. POF can be annealed at temperatures approaching the glass transition temperature (Tg) of the polymer to produce FBG with a permanent blue Bragg wave-length shift at room temperature. At this elevated temperature segmental motion in the structure results in a lower viscosity. The material softens and the molecular chains relax from the axial orientation causing shrinking of the fibre. The large attenuation of typically 1dB/cm in the 1550nm spectral region of PMMA POF has limited FBG lengths to less than 10cm. The more expensive fluorinated polymers with lower absorption have had no success as FBG waveguides. Bragg grating have been inscribed onto various POF in the 800nm spectral region using a 30mW continuous wave 325nm helium cadmium laser, with a much reduced attenuation coefficient of 10dB/m (5). Fabricating multiplexed FBGs in the 800nm spectral region in TOPAS and PMMA POF consistently has lead to fabrication of multiplexed FBG in the 700nm spectral region by a method of prolonged annealing. The Bragg wavelength shift of gratings fabricated in PMMA fibre at 833nm and 867nm was monitored whilst the POF was thermally annealed at 80°C. Permanent shifts exceeding 80nm into the 700nm spectral region was attained by both gratings on the fibre. The large permanent shift creates the possibility of multiplexed Bragg sensors operating over a broad range. -------------------------------------------------------------------------------------------------------------------- 1. Pellerin C, Prud'homme RE, Pézolet M. Effect of thermal history on the molecular orientation in polystyrene/poly (vinyl methyl ether) blends. Polymer. 2003;44(11):3291-7. 2. Dvoránek L, Machová L, Šorm M, Pelzbauer Z, Švantner J, Kubánek V. Effects of drawing conditions on the properties of optical fibers made from polystyrene and poly (methyl methacrylate). Die Angewandte Makromolekulare Chemie. 1990;174(1):25-39. 3. Dugas J, Pierrejean I, Farenc J, Peichot JP. Birefringence and internal stress in polystyrene optical fibers. Applied optics. 1994;33(16):3545-8. 4. Jiang C, Kuzyk MG, Ding JL, Johns WE, Welker DJ. Fabrication and mechanical behavior of dye-doped polymer optical fiber. Journal of applied physics. 2002;92(1):4-12. 5. Johnson IP, Webb DJ, Kalli K, Yuan W, Stefani A, Nielsen K, et al., editors. Polymer PCF Bragg grating sensors based on poly (methyl methacrylate) and TOPAS cyclic olefin copolymer2011: SPIE.

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Self-similar optical pulses (or “similaritons”) of parabolic intensity profile can be found as asymptotic solutions of the nonlinear Schr¨odinger equation in a gain medium such as a fiber amplifier or laser resonator. These solutions represent a wide-ranging significance example of dissipative nonlinear structures in optics. Here, we address some issues related to the formation and evolution of parabolic pulses in a fiber gain medium by means of semi-analytic approaches. In particular, the effect of the third-order dispersion on the structure of the asymptotic solution is examined. Our analysis is based on the resolution of ordinary differential equations, which enable us to describe the main properties of the pulse propagation and structural characteristics observable through direct numerical simulations of the basic partial differential equation model with sufficient accuracy.

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Metallocene ethylene-1-octene copolymers having different densities and comonomer content ranging from 11 to 36 wt% (m-LLDPE), and a Ziegler copolymer (z-LLDPE) containing the same level of short-chain branching (SCB) corresponding to one of the m-LLDPE polymers, were subjected to extrusion. The effects of temperature (210-285 °C) and multi-pass extrusions (up to five passes) on the rheological and structural characteristics of these polymers were investigated using melt index and capillary rheometry, along with spectroscopic characterisation of the evolution of various products by FTIR, C-NMR and colour measurements. The aim is to develop a better understanding of the effects of processing variables on the structure and thermal degradation of these polymers. Results from rheology show that both extrusion temperature and the amount of comonomer have a significant influence on the polymer melt thermo-oxidative behaviour. At low to intermediate processing temperatures, all m-LLDPE polymers exhibited similar behaviour with crosslinking reactions dominating their thermal oxidation. By contrast, at higher processing temperatures, the behaviour of the metallocene polymers changed depending on the level of comonomer content: higher SCB gave rise to predominantly chain scission reactions whereas polymers with lower level of SCB continued to be dominated by crosslinking. This temperature dependence was attributed to changes in the different evolution of carbonyl and unsaturated compounds including vinyl, vinylidene and trans-vinylene. © 2007 Elsevier Ltd. All rights reserved.

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We study numerically depressed-cladding, buried waveguides that can be formed in a lithium niobate crystal by femtosecond laser writing. We demonstrate that the guiding properties can be controlled by the waveguide structural characteristics.

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Applied problems of functional homonymy resolution for Russian language are investigated in the work. The results obtained while using the method of functional homonymy resolution based on contextual rules are presented. Structural characteristics of minimal contextual rules for different types of functional homonymy are researched. Particular attention is paid to studying the control structure of the rules, which allows for the homonymy resolution accuracy not less than 95%. The contextual rules constructed have been realized in the system of technical text analysis.

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2000 Mathematics Subject Classification: 16R50, 16R10.

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An ordered macroporous host (mac-SiO2) has been used to prevent aggregation of layered photocatalysts based on carbon nitride. Using typical carbon nitride synthesis conditions, cyanamide was condensed at 550 °C in the presence and absence of mac-SiO2. Condensation in the absence of mac-SiO2 results in materials with structural characteristics consistent with the carbon nitride, melon, accompanied by ca. 2 wt% carbonization. For mac-SiO2 supported materials, condensation occurs with greater carbonization (ca. 6 wt%). On addition of 3 wt% Pt cocatalyst photocatalytic hydrogen production under visible light is found to be up to 10 times greater for the supported composites. Time-resolved photoluminescence spectroscopy shows that excited state relaxation is more rapid for the mac-SiO2 supported materials suggesting faster electron-hole recombination and that supported carbon nitride does not exhibit improved charge separation. CO2 temperature programmed desorption indicates that enhanced photoactivity of supported carbon nitride is attributable to an increased surface area compared to bulk carbon nitride and an increase in the concentration of weakly basic catalytic sites, consistent with carbon nitride oligomers.

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This research is based on the premises that teams can be designed to optimize its performance, and appropriate team coordination is a significant factor to team outcome performance. Contingency theory argues that the effectiveness of a team depends on the right fit of the team design factors to the particular job at hand. Therefore, organizations need computational tools capable of predict the performance of different configurations of teams. This research created an agent-based model of teams called the Team Coordination Model (TCM). The TCM estimates the coordination load and performance of a team, based on its composition, coordination mechanisms, and job’s structural characteristics. The TCM can be used to determine the team’s design characteristics that most likely lead the team to achieve optimal performance. The TCM is implemented as an agent-based discrete-event simulation application built using JAVA and Cybele Pro agent architecture. The model implements the effect of individual team design factors on team processes, but the resulting performance emerges from the behavior of the agents. These team member agents use decision making, and explicit and implicit mechanisms to coordinate the job. The model validation included the comparison of the TCM’s results with statistics from a real team and with the results predicted by the team performance literature. An illustrative 26-1 fractional factorial experimental design demonstrates the application of the simulation model to the design of a team. The results from the ANOVA analysis have been used to recommend the combination of levels of the experimental factors that optimize the completion time for a team that runs sailboats races. This research main contribution to the team modeling literature is a model capable of simulating teams working on complex job environments. The TCM implements a stochastic job structure model capable of capturing some of the complexity not capture by current models. In a stochastic job structure, the tasks required to complete the job change during the team execution of the job. This research proposed three new types of dependencies between tasks required to model a job as a stochastic structure. These dependencies are conditional sequential, single-conditional sequential, and the merge dependencies.

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The Comprehensive Everglades Restoration Plan (CERP) attempts to restore hydrology in the Northern and Southern Estuaries of Florida. Reefs of the Eastern oyster Crassostrea virginica are a dominant feature of the estuaries along the Southwest Florida coast. Oysters are benthic, sessile, filter-feeding organisms that provide ecosystem services by filtering the water column and providing food, shelter and habitat for associated organisms. As such, the species is an excellent sentinel organism for examining the impacts of restoration on estuarine ecosystems. The implementation of CERP attempts to improve: the hydrology and spatial and structural characteristics of oyster reefs, the recruitment and survivorship of C. virginica, and the reef-associated communities of organisms. This project links biological responses and environmental conditions relative to hydrological changes as a means of assessing positive or negative trends in oyster responses and population trends. Using oyster responses, we have developed a communication tool (i.e., Stoplight Report Card) based on CERP performance measures that can distinguish between responses to restoration and natural patterns. The Stoplight Report Card system is a communication tool that uses Monitoring and Assessment Program (MAP) performance measures to grade an estuary's response to changes brought about by anthropogenic input or restoration activities. The Stoplight Report Card consists of both a suitability index score for each organism metric as well as a trend score (− decreasing trend, +/− no change in trend, and + increasing trend). Based on these two measures, a component score (e.g., living density) is calculated by averaging the suitability index score and the trend score. The final index score is obtained by taking the geometric score of each component, which is then translated into a stoplight color for success (green), caution (yellow), or failure (red). Based on the data available for oyster populations and the responses of oysters in the Caloosahatchee Estuary, the system is currently at stage “caution.” This communication tool instantly conveys the status of the indicator and the suitability, while trend curves provide information on progress towards reaching a target. Furthermore, the tool has the advantage of being able to be applied regionally, by species, and collectively, in concert with other species, system-wide.