822 resultados para Flow-performance relationship
Resumo:
The importance of education and experience to the successful performance of new firms is well recognized both by management practitioners and academics. Yet empirical research to support the significance of this relationship is inconclusive. This paper discusses theories describing the relationship between education and experience and firm performance. It also analyses and classifies the differing measures of performance, education and experience, and compares the results of multiple studies undertaken between 1977 and 2000. Possible reasons for conflicting results are identified, such as lack of sound theoretical bases that relate education and experience to performance, varying definitions of the key variables and the diversity of measures used. Finally, a framework is developed that incorporates variables that interact with experience and education to influence new venture performance.
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This study examined the relationship between ear preference, personality, and performance ratings on 203 telesales staff. Social desirability scores were a significant predictor of two relatively independent sets of supervisor ratings (actual performance and developmental potential) in interaction with ear preference. It was found that the social desirability scale was a significant positive predictor for staff preferring a right ear headset, but a negative predictor for staff preferring a left ear headset. These results were interpreted in terms of different strategies used to achieve successful sales.
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We have utilised the combination of sensitivity and specificity afforded by coupling high-performance liquid chromatography (HPLC) to a tandem mass spectrometer (MS-MS) to produce an assay which is suitable for assaying glutathione (GSH) concentrations in liver tissue. The sensitivity suggests it may also be suitable for extrahepatic tissues, The method has been validated for GSH using mouse liver samples and also allows the assay of GSSG. The stability of GSH under conditions relevant to the assay has been determined. A 20-mul amount of a diluted methanol extract of tissue is injected with detection limits of 0.2 pmol for GSH and 2 pmol for GSSG. The HPLC uses an Altima C-18 (150X4.6 mm, 5 mum) column at 35 degreesC. Chromatography utilises a linear gradient from 0 to 10% methanol in 0.1% formic acid over 5 min, with a final isocratic stage holding at 10% methanol for 5 min. Total flow rate is 0.8 ml/min. The transition from the M+H ion (308.1 m/z for GSH, and 613.3 m/z for GSSG) to the 162.0 m/z (GSH) and 355.3 m/z (GSSG) fragments are monitored. (C) 2001 Elsevier Science B.V. All rights reserved.
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An experimental study has been carried out for the gas-liquid two-phase flow in a packed bed simulating conditions of the gas and liquid flows in the lower part of blast furnace. The localised liquid flow phenomenon in presence of gas cross flow, which usually occurs around the cohesive zone and raceway in blast furnace, was investigated in detail. Such liquid flow is characterised in terms of liquid shift distance or liquid shift angle that can effectively be measured by the experiments involved in the current study. It is found that liquid shift angle does not significantly increase or decrease with different packing depth. This finding supports the hypothesis of the force balance model where a vectorial relationship among acting forces, i.e. gas drag force, gravitational force and solid-liquid friction force, and liquid shift angle does exist. Liquid shift angle is inversely proportional to particle size and liquid density, and proportional to square of gas superficial velocity, but is almost independent on liquid flowrate and liquid viscosity. The gas-liquid drag coefficient, an important aspect for quantifying the interaction between gas and liquid flows, was conceptually modified based on the discrete feature of liquid flow through a packed bed and evaluated by the combined theoretical and experimental investigation. Experimental measurements suggest that the gas-liquid drag coefficient is approximately a constant (C-DG(')=5.4+/-1.0) and is independent on liquid properties, gas velocity and packing structure. The result shows a good agreement with previous experimental data and prediction of the existing liquid flow model.
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This paper proposes an integrated methodology for modelling froth zone performance in batch and continuously operated laboratory flotation cells. The methodology is based on a semi-empirical approach which relates the overall flotation rate constant to the froth depth (FD) in the flotation cell; from this relationship, a froth zone recovery (R,) can be extracted. Froth zone recovery, in turn, may be related to the froth retention time (FRT), defined as the ratio of froth volume to the volumetric flow rate of concentrate from the cell. An expansion of this relationship to account for particles recovered both by true flotation and entrainment provides a simple model that may be used to predict the froth performance in continuous tests from the results of laboratory batch experiments. Crown Copyright (C) 2002 Published by Elsevier Science B.V. All rights reserved.
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This article examines whether the emotions of frustration and optimism mediate, fully or partially, the relationship between leadership style and subordinate performance in the context of structural equation modeling. The findings show that transformational leadership has a significant direct influence on frustration and optimism, with the negative influence of frustration having a stronger effect on performance than the positive influence of optimism. Frustration and optimism are found to have a direct influence on performance, and the emotions, frustration and optimism, fully mediate the relationship between transformational leadership and performance. Thus, the effect of transformational leadership style on performance is significant, but indirect. (C) 2002 Elsevier Science Inc. All rights reserved.
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The performance of the Oxford University Gun Tunnel has been estimated using a quasi-one-dimensional simulation of the facility gas dynamics. The modelling of the actual facility area variations so as to adequately simulate both shock reflection and flow discharge processes has been considered in some detail. Test gas stagnation pressure and temperature histories are compared with measurements at two different operating conditions - one with nitrogen and the other with carbon dioxide as the test gas. It is demonstrated that both the simulated pressures and temperatures are typically within 3% of the experimental measurements.
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Objective To evaluate the effect of periparturient disease accompanied by vulval discharge, and weaning-to-mating intervals, on sow fertility and litter size. Design Reproductive data were collected and analysed from 19 Hungarian swine herds over a 4 year period. Conception rates, farrowing rates and litter sizes of sows with periparturient disease accompanied by vulval discharge were used to evaluate the relationship between duration of vulval discharge and subsequent fertility and litter size. The possibility of interactions between weaning-to-mating intervals and duration of vulval discharges was investigated to determine if there was any effect on subsequent fertility and litter size. Results and conclusions Both parity 1 and parity 2 to 8 sows having had periparturient disease accompanied by vulval discharge in excess of 6 days duration had significantly (P < 0.001) lower subsequent fertility (conception, farrowing and adjusted farrowing rates) compared with sows of similar parity where the duration of vulval discharge was < 4 or 4 to 6 days. There was no difference in fertility rates between sows, in both parity categories, with vulval discharge for < 4 days compared with 4 to 6 days. A duration of vulval discharge in excess of 6 days in parity 1 sows significantly reduced litter size (total born and live-born) in subsequent farrowings, but not in parity 2 to 8 sows. There was no interaction between the duration of vulval discharge and post-weaning to mating intervals. However sows with weaning to mating intervals between 7 and 10 days had smaller (P < 0.001) subsequent litter sizes compared with 3 to 6 or 11 to 14 day intervals. It was concluded that the duration of vulval discharge in excess of 6 days was an indication of a severe persistent endometritis adversely affecting fertility of sows.
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The aim of this study was to further investigate the mechanism of suppression of natural killer (NK) cell cytotoxic activity In peripheral blood following strenuous exercise. Blood was collected for analysis of NK cell concentration, cytotoxic activity, CD2 surface expression and perforin gene expression from runners (RUN, n = 6) and resting controls (CONTROL, n = 4) pre-exercise, 0, 1.5, 5, and 24 h following a 60-min treadmill run at 80% of VO2 peak. Natural killer cytotoxic activity, measured using a whole blood chromium release assay, fluctuated minimally in the CONTROL group and increased by 63% and decreased by 43% 0 and 1.5 h post-exercise, respectively, in the RUN group (group x time, P < 0.001). Lytic index (cytotoxic activity per cell) did not change. Perforin mRNA, measured using quantitative real-time polymerase chain reaction (ORT-PCR) decreased from pre- to post-exercise and remained decreased through 24 h, The decrease from pre- to 0 In post-exercise was seen predominately in the RUN group and was inversely correlated r = - 0.95) to pre-exercise perform mRNA. The NK cell surface expression of CD2 (lymphocyte function-associated antigen-2) was determined using fluorescent antibodies and flow cytometry, There was no change in the proportion of NK cells expressing CD2 or CD2 density, We conclude that (1) numerical redistribution accounted for most of the change in NK cytotoxic activity following a strenuous run, (2) decrease in perforin gene expression during the run was inversely related to pre-exercise levels but did not parallel changes in cytotoxic activity, and (3) CD2 surface expression was not affected by exercise.
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At least 6% of primary school aged children present with DCD, where co-ordination is substantially below the normal range for the child’s age and intelligence. Motor skill difficulties negatively affect academic achievement, recreation and activities of daily living. Poor upper-limb co-ordination is a common difficulty for children with DCD. A possible cause of this problem is deviant muscle timing in proximal muscle groups, which results in poor postural and movement control. While studies have been published investigating postural control in response to external perturbations, detail about postural muscle activity during voluntary movement is limited even in children with normal motor development. No studies have investigated the relationship between muscle timing, resultant arm motion and upper-limb coordination deficits. Objectives: To investigate the relationship between functional difficulties with upper-limb motor skills and neuromuscular components of postural stability and coordination. Specifically, to investigate onset-timing of muscle activity, timing of arm movement, and resultant three-dimensional (3D) arm co-ordination during rapid, voluntary arm movement and to analyse differences arising due to the presence of DCD. This study is part of a larger research program investigating postural stability and control of upper limb movement in children. Design: A controlled, cross-sectional study of differences between children with and without DCD. Methods: This study included 50 children aged eight to 10 years (25 with DCD and 25 without DCD). Children participated in assessment of motor skills according to the Movement ABC Test and a laboratory study of rapid, voluntary arm movements. Parameters investigated included muscle activation timing of shoulder and trunk muscles (surface electromyography), arm movement timing (light sensor) and resultant 3D arm motion (Fastrak). Results: A MANOVA is being used to analyse between-group differences. Preliminary results indicate children with DCD demonstrate altered muscle timing during a rapid arm raise when compared with the control group of children. Conclusion: Differences in proximal muscle timing in children with DCD support the hypothesis that altered proximal muscle activity may contribute to poor proximal stability and consequently poor arm movement control. This has implications for clinical physiotherapy.
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A long-term experiment was conducted to compare the effects of flowing and still water on growth, and the relationship between water flow and nutrients, in Aponogeton elongatus, a submerged aquatic macrophyte. A. elongatus plants were grown for 23 weeks with three levels of nutrition (0, 0.5 and 1g Osmocote Plus(R) fertiliser pot(-1)) in aquaria containing stirred or unstirred water. Fertilized plants grew much better than non-fertilized. The highest fertilizer level produced 29% wider leaves and 58% higher total dry weight in stirred water. Stirred water increased leaf area by 40% and tuber size by 81%, but only with the highest level of nutrition. These results suggest that this plant depends on its roots for mineral uptake, rather than from the open water, and the major limitation to growth in still water is the supply of dissolved inorganic carbon. It was the combined effects of nutrient availability and stirring that produced the strongest response in plant growth, morphology and composition. This study provides some explanation for the observations of others that these plants grow best in creeks or river systems with permanently flowing water.
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We investigated the burst swimming performance of five species of Antarctic fish at -1.0degreesC. The species studied belonged to the suborder, Notothenioidei, and from the families, Nototheniidae and Bathydraconidae. Swimming performance of the fish was assessed over the initial 300 ms of a startle response using surgically attached miniature accelerometers. Escape responses in all fish consisted of a C-type fast start; consisting of an initial pronounced bending of the body into a C-shape, followed by one or more complete tail-beats and an un-powered glide. We found significant differences in the swimming performance of the five species of fish examined, with average maximum swimming velocities (U-max) ranging from 0.91 to 1.39 m s(-1) and maximum accelerations (A(max)) ranging from 10.6 to 15.6 m s(-2). The cryopelagic species, Pagothenia borchgrevinki, produced the fastest escape response, reaching a U-max and A(max) of 1.39 m s(-1) and 15.6 m s(-2), respectively. We also compared the body shapes of each fish species with their measures of maximum burst performance. The dragonfish, Gymnodraco acuticeps, from the family Bathdraconidae, did not conform to the pattern observed for the other four fish species belonging to the family Nototheniidae. However, we found a negative relationship between buoyancy of the fish species and burst swimming performance. (C) 2002 Elsevier Science Ltd. All rights reserved.
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In many respects, Australian boards more closely approach normative best practice guidelines for corporate governance than boards in other Western countries. Do Australian firms then demonstrate a board demographic-organisational performance link that has not been found in other economies? We examine the relationships between board demographics and corporate performance in 348 of Australia's largest publicly listed companies and describe the attributes of these firms and their boards. We find that, after controlling for firm size, board size is positively correlated with firm value. We also find a positive relationship between the proportion of inside directors and the market-based measure of firm performance. We discuss the implications of these findings and compare our findings to prevailing research in the US and the UK.
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Pulp lifters, also known, as pan lifters are an integral part of the majority of autogenous (AG), semi-autogenous (SAG) and grate discharge ball mills. The performance of the pulp lifters in conjunction with grate design determines the ultimate flow capacity of these mills. Although the function of the pulp lifters is simply to transport the slurry passed through the discharge grate into the discharge trunnion, their performance depends on their design as well as that of the grate and operating conditions such as mill speed and charge level. However, little or no work has been reported on the performance of grate-pulp lifter assemblies and in particular the influence of pulp lifter design on slurry transport. Ideally, the discharge rate through a grate-pulp lifter assembly should be equal to the discharge rate through at a given mill hold-up. However, the results obtained have shown that conventional pulp lifter designs cause considerable restrictions to flow resulting in reduced flow capacity. In this second of a two-part series of papers the performance of conventional pulp lifters (radial and spiral designs) is described and is based on extensive test work carried out in a I m diameter pilot SAG mill. (C) 2003 Elsevier Science Ltd. All rights reserved.
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Discharge grates play an important role in determining the performance of autogenous, semi-autogenous and grate discharge ball mills. The flow capacity (grinding capacity) of these mills is strongly influenced by the discharge grate design-open area and position of apertures, as well as the performance of the pulp lifters. As mill sizes have progressively increased and closed-circuiting has become more popular the importance of grate and pulp lifter design has grown. Unfortunately very few studies have concentrated on this aspect of mill performance. To remedy this a series of laboratory and pilot-scale tests were undertaken to study both the performance of grates on their own and in conjunction with pulp lifters. In this first paper of a two-part series the results from the grate-only experiments are presented and discussed, whilst the performance of the grate-pulp-lifter system is covered in the second paper. The results from the grate-only experiments have shown that the build-up of slurry (hold-up) inside the mill starts from the shoulder of the charge, while the toe position of the slurry progressively moves towards the toe of the charge with increasing flowrate. Besides grate design (open area and position of apertures), charge volume and mill speed were also found to have a strong influence on mill hold-up and interact with grate design variables. (C) 2003 Elsevier Science Ltd. All rights reserved.