19 resultados para The Index

em Aston University Research Archive


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Purpose – This study seeks to provide valuable new insight into the timeliness of corporate internet reporting (TCIR) by a sample of Irish-listed companies. Design/methodology/approach – The authors apply an updated version of Abdelsalam et al. TCIR index to assess the timeliness of corporate internet reporting. The index encompasses 13 criteria that are used to measure the TCIR for a sample of Irish-listed companies. In addition, the authors assess the timeliness of posting companies’ annual and interim reports to their web sites. Furthermore, the study examines the influence of board independence and ownership structure on the TCIR behaviour. Board composition is measured by the percentage of independent directors, chairman’s dual role and average tenure of directors. Ownership structure is represented by managerial ownership and blockholder ownership. Findings – It is found that Irish-listed companies, on average, satisfy only 46 per cent of the timeliness criteria assessed by the timeliness index. After controlling for size, audit fees and firm performance, evidence that TCIR is positively associated with board of director’s independence and chief executive officer (CEO) ownership is provided. Furthermore, it is found that large companies are faster in posting their annual reports to their web sites. The findings suggest that board composition and ownership structure influence a firm’s TCIR behaviour, presumably in response to the information asymmetry between management and investors and the resulting agency costs. Practical implications – The findings highlight the need for improvement in TCIR by Irish-listed companies in many areas, especially in regard to the regular updates of information provided on their web sites. Originality/value – This study represents one of the first comprehensive examinations of the important dimension of the TCIR in Irish-listed companies.

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Long-period fibre gratings (LPGs) have previously been used to detect quantities such as temperature, strain and refractive index (RI). The responsivity to surrounding refractive index means that, potentially, LPGs could be realised as optical biosensors for applications in biochemical and biomedical application areas. We report here to our best knowledge the first investigation on refractive index sensing properties of LPGs with sol-gel derived titanium and silicon oxide coatings. It is revealed that the RI sensitivity of an LPG is affected by both the thickness and the index value of the coating; the coating with higher index and thickness will enhance the LPG RI sensitivity significantly. The surrounding refractive index induced LPG resonance shift has been evaluated over the LPGs’ most sensitive RI region from 1.42 to 1.44. We have identified that, in this region, the uncoated LPG has an RI sensitivity of (-673.0±0.4)nm/uri (unit of refractive index) while the LPG coated with titanium oxide exhibits a sensitivity as high as (-1067.15±0.04)nm/uri.

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During 1999 and 2000 a large number of articles appeared in the financial press which argued that the concentration of the FTSE 100 had increased. Many of these reports suggested that stock market volatility in the UK had risen, because the concentration of its stock markets had increased. This study undertakes a comprehensive measurement of stock market concentration using the FTSE 100 index. We find that during 1999, 2000 and 2001 stock market concentration was noticeably higher than at any other time since the index was introduced. When we measure the volatility of the FTSE 100 index we do not find an association between concentration and its volatility. When we examine the variances and covariance’s of the FTSE 100 constituents we find that security volatility appears to be positively related to concentration changes but concentration and the size of security covariances appear to be negatively related. We simulate the variance of four versions of the FTSE 100 index; in each version of the index the weighting structure reflects either an equally weighted index, or one with levels of low, intermediate or high concentration. We find that moving from low to high concentration has very little impact on the volatility of the index. To complete the study we estimate the minimum variance portfolio for the FTSE 100, we then compare concentration levels of this index to those formed on the basis of market weighting. We find that realised FTSE index weightings are higher than for the minimum variance index.

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The fabrication and characterization of long-period gratings (LPGs) in fiber tapers is presented alongside supporting theory. The devices possess a high sensitivity to the index of aqueous solutions due to an observed spectral bifurcation effect, yielding a limiting index resolution of ±8.5×10-5 for solutions with an index in the range 1.330-1.335.

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This paper develops a productivity index applicable when producers are cost minimisers and input prices are known. The index is inspired by the Malmquist index as extended to productivity measurement. The index developed here is defined in terms of input cost rather than input quantity distance functions. Hence, productivity change is decomposed into overall efficiency and cost technical change. Furthermore, overall efficiency change is decomposed into technical and allocative efficiency change and cost technical change into a part capturing shifts of input quantities and shifts of relative input prices. These decompositions provide a clearer picture of the root sources of productivity change. They are illustrated here in a sample of hospitals; results are computed using non-parametric mathematical programming. © 2003 Elsevier B.V. All rights reserved.

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This paper develops two new indices for measuring productivity in multi-input multi-output situations. One index enables the measure of productivity change of a unit over time while the second index makes it possible to compare two units on productivity at the same or different points in time. Productivity in a single input single output context is defined as the ratio of output to input. In multi-input multi-output contexts this ratio is not defined. Instead, one of the methods traditionally used is the Malmquist Index of productivity change over time. This is computed by reference to the distances of the input-output bundles of a production unit at two different points in time from the efficient boundaries corresponding to those two points in time. The indices developed in this paper depart form the use of two different reference boundaries and instead they use a single reference boundary which in a sense is the most efficient boundary observed over two or more successive time periods. We discuss the assumptions which make possible the definition of such a single reference boundary and proceed to develop the two Malmquist-type indices for measuring productivity. One key advantage of using a single reference boundary is that the resulting index values are circular. That is it is possible to use the index values of successive time periods to derive an index value of productivity change over a time period of any length covered by successive index values or vice versa. Further, the use of a single reference boundary makes it possible to construct an index for comparing the productivities of two units either at the same or at two different points in time. This was not possible with the traditional Malmquist Index. We decompose both new indices into components which isolate production unit from industry or comparator unit effects. The components themselves like the indices developed are also circular. The components of the indices drill down to reveal more clearly the performance of each unit over time relative either to itself or to other units. The indices developed and their components are aimed at managers of production units to enable them to diagnose the performance of their units with a view to guiding them to improved performance.

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In this paper we develop an index and an indicator of productivity change that can be used with negative data. For that purpose the range directional model (RDM), a particular case of the directional distance function, is used for computing efficiency in the presence of negative data. We use RDM efficiency measures to arrive at a Malmquist-type index, which can reflect productivity change, and we use RDM inefficiency measures to arrive at a Luenberger productivity indicator, and relate the two. The productivity index and indicator are developed relative to a fixed meta-technology and so they are referred to as a meta-Malmquist index and meta-Luenberger indicator. We also address the fact that VRS technologies are used for computing the productivity index and indicator (a requirement under negative data), which raises issues relating to the interpretability of the index. We illustrate how the meta-Malmquist index can be used, not only for comparing the performance of a unit in two time periods, but also for comparing the performance of two different units at the same or different time periods. The proposed approach is then applied to a sample of bank branches where negative data were involved. The paper shows how the approach yields information from a variety of perspectives on performance which management can use.

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A numerical model of a long period grating in photonic crystal fibre fabricated by an electric arc is proposed that allows for the spectral characterisation of the grating. In the combination with the suggested model of the photonic crystal and the experimentally recorded grating growth it is used to find the index change induced by the electric arc.

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Long-period fibre gratings (LPGs) have previously been used to detect quantities such as temperature, strain, and refractive index (RI). We report here, to the best of our knowledge, the first investigation on refractive index sensing properties of LPGs with sol–gel derived titanium and silicon oxide coatings. It is revealed that the RI sensitivity of an LPG is affected by both the thickness and the index value of the coating; a coating with higher index and thickness will enhance the LPG RI sensitivity significantly. The surrounding refractive index induced LPG resonance shift has been evaluated over the LPGs' most sensitive RI region from 1.42 to 1.44. We have identified that, in this region, the uncoated LPG has an RI sensitivity of (-673.0 ± 0.4) nm/uri (unit of refractive index) while the LPG coated with titanium oxide exhibits a sensitivity as high as (-1067.15 ± 0.04) nm/uri. The experimental results also reveal that, even in the RI insensitive region around 1.33, there still is a marked enhancement in RI sensitivity of the sol–gel coated LPG compared to the uncoated one. This is potentially significant as coated LPGs may be extended to low RI gas and semi-liquidized based sensing applications.

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A set of long period grating devices have been fabricated in photosensitive single mode fibre coated with a series of copper rings (period of 380μm, 50% duty cycle and length of 4cm). The long period gratings were inscribed with a uniform UV-laser exposure across the entire length of the copper ring patterned coating. The devices ranged in copper thickness from 0.5μm to 1.5μm. In addition, a control long period grating was fabricated in the same type of fibre with the same period for comparison. The refractive index and temperature spectral sensitivity of these devices were investigated and it was found that the index and temperature sensitivity is a function of the thickness of the copper rings, as supported by theoretical modelling. Furthermore, the index sensitivity of these devices in the 1.333 index region is greater than the control long period grating. The patterned 0.5μm coated long period grating gave a sensitivity of Δλ/Δn = -74 nm leading to a resolution of 1.4×10-3 compared to the control which had a sensitivity of Δλ/Δn = -32 nm with a resolution of 3.2×10-3 in the index region of 1.320 to 1.380 (aqueous solution regime). This demonstrates a two fold increase in the sensitivity. This novel fibre long period grating device shows potential for increasing the resolution of measurements of the index of aqueous solutions.

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The fabrication and characterization of long-period gratings (LPGs) in fiber tapers is presented alongside supporting theory. The devices possess a high sensitivity to the index of aqueous solutions due to an observed spectral bifurcation effect, yielding a limiting index resolution of ±8.5 × 10-5 for solutions with an index in the range 1.330-1.335. © 2006 IEEE.

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A numerical model of a long period grating in photonic crystal fibre fabricated by an electric arc is proposed that allows for the spectral characterisation of the grating. In the combination with the suggested model of the photonic crystal and the experimentally recorded grating growth it is used to find the index change induced by the electric arc. © Springer Science+Business Media B.V. 2007.

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Long-period fibre gratings (LPGs) have previously been used to detect quantities such as temperature, strain and refractive index (RI). The responsivity to surrounding refractive index means that, potentially, LPGs could be realised as optical biosensors for applications in biochemical and biomedical application areas. We report here to our best knowledge the first investigation on refractive index sensing properties of LPGs with sol-gel derived titanium and silicon oxide coatings. It is revealed that the RI sensitivity of an LPG is affected by both the thickness and the index value of the coating; the coating with higher index and thickness will enhance the LPG RI sensitivity significantly. The surrounding refractive index induced LPG resonance shift has been evaluated over the LPGs’ most sensitive RI region from 1.42 to 1.44. We have identified that, in this region, the uncoated LPG has an RI sensitivity of (-673.0±0.4)nm/uri (unit of refractive index) while the LPG coated with titanium oxide exhibits a sensitivity as high as (-1067.15±0.04)nm/uri.

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Purpose – This study seeks to provide valuable new insight into the timeliness of corporate internet reporting (TCIR) by a sample of Irish-listed companies. Design/methodology/approach – The authors apply an updated version of Abdelsalam et al. TCIR index to assess the timeliness of corporate internet reporting. The index encompasses 13 criteria that are used to measure the TCIR for a sample of Irish-listed companies. In addition, the authors assess the timeliness of posting companies’ annual and interim reports to their web sites. Furthermore, the study examines the influence of board independence and ownership structure on the TCIR behaviour. Board composition is measured by the percentage of independent directors, chairman’s dual role and average tenure of directors. Ownership structure is represented by managerial ownership and blockholder ownership. Findings – It is found that Irish-listed companies, on average, satisfy only 46 per cent of the timeliness criteria assessed by the timeliness index. After controlling for size, audit fees and firm performance, evidence that TCIR is positively associated with board of director’s independence and chief executive officer (CEO) ownership is provided. Furthermore, it is found that large companies are faster in posting their annual reports to their web sites. The findings suggest that board composition and ownership structure influence a firm’s TCIR behaviour, presumably in response to the information asymmetry between management and investors and the resulting agency costs. Practical implications – The findings highlight the need for improvement in TCIR by Irish-listed companies in many areas, especially in regard to the regular updates of information provided on their web sites. Originality/value – This study represents one of the first comprehensive examinations of the important dimension of the TCIR in Irish-listed companies.

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The fabrication and characterisation of Long Period Gratings in fibre tapers is presented alongside supporting theory. The devices possess a high sensitivity to the index of aqueous solutions due to an observed spectral bifurcation effect.