10,321 research outputs found
Adaptive finite element approximation for a class of parameter estimation problems
No full textKunisch, Karl; Chang, Y.Z.; Liu, W.B.; Yan, N.N.; Li, R. (2010) Adaptive finite element approximation for a class of parameter estimation problems. Journal of Computational Mathematics, Bd. 28, S. 1-31
Using performance assessment in secondary school mathematics: an empirical study in a Singapore classroom
No full textThis article reports an exploratory study on using performance assessment in mathematics instruction in a high-performing secondary school in Singapore. An intact mathematics class participated in the study, and received chapter-based performance tasks as intervention during regular mathematics lessons for about one and a half school years. The performance tasks used included authentic and/or open-ended tasks. The students’ academic achievements and attitudes in mathematics were compared with a comparison class that did not receive the intervention. Both quantitative and qualitative data were collected, mainly through questionnaire surveys, performance task tests, conventional school exams, and interviews with students and teachers. The results suggest that the students receiving the intervention performed significantly better than their counterparts in solving conventional exam problems, and in general they also showed more positive changes in attitudes towards mathematics and mathematics learning. The students from the experimental class also expressed positive views about the benefits of using performance tasks in promoting their ability in higher order thinking, though no statistically significant difference was detected between the two classes of students in solving unconventional tasks before and after intervention. Overall, the results appear to support teachers’ using contextualised problems in real life situations and open-ended investigations in students’ learning of mathematic
Why hedge? Extent, nature, and determinants of derivative usage in U.S. municipalities
No full textUsing a hand-collected dataset of over 300 observations of large U.S. cities and counties, this paper investigates the extent, nature and determinants of derivatives usage in the municipal sector.Over half of our sample entities engage in derivative transactions and a vast majority of these transactions are intended to manage interest rate risk. Swaps, by far, are the most popular derivative instrument. In terms of the determinants of derivative usage,we find that the propensity to use derivatives as well as the extent of derivative usage is higher for municipalities that are larger and more financially constrained. We do not find growth to be related to municipal derivative usage. Contrary to suggestions made in the popular press, we fail to find managerial opportunism to be a significant factor in municipal derivative usage. We also find that more sophisticated managers of large municipalities and less sophisticated managers of small municipalities are more likely to engage in derivative transactions.Peer reviewe
A study on the reliability of consecutive k-Out-of-n: G systems based on Copula
No full textThe computation of reliability characteristics of a system that consists of dependent components is sometimes difficult especially when the type of dependence is not known. This article introduces the copula method to calculate the reliability of dependent consecutive k-out-of-n: G systems. The components in these systems are dependent on each other and the dependency may be either linear or nonlinear. The copula is a popular tool for modeling the dependence structure of data. It contains the information about the dependency structure of a vector of random variables and can capture nonlinear dependence. Based on the copula theory, the article analyzes the consecutive k-out-of-n: G systems and gets the reliability indexes. Finally, some numerical examples are presented to illustrate the results obtained in this article.Peer reviewe
Capital asset accounting policies under GASB Statement No. 34: Characteristics, antecedents, and implications
No full textIn this paper, we study the evolution of state and local governments’ capital asset accounting policies from the adoption of GASB Statement No. 34 through the fiscal year ending in 2016. We document substantial cross-sectional and time-series variation in the capitalization thresholds and estimated useful lives pertaining to major classes of capital assets, including buildings, equipment, improvements, and infrastructure assets. Diversity in capital asset accounting policies potentially diminishes the comparability of capital asset accounting information across governments and over time. We also discuss matters related to the implementation and ongoing use of the modified approach for reporting infrastructure assets. Our findings are useful to the GASB as well as to users of government financial reports.Peer reviewe
On the market timing and feedback effect of hedging: evidence from U.S. oil and gas producers
No full textPeer reviewe
The effect of four-wave mixing in fibers on optical frequency-division multiplexed systems
No full textThe optical nonlinearity in a single-mode fiber imposes a fundamental limitation on the capacity of optical frequency-division multiplexed (OFDM) systems. In particular, four-wave mixing (FWM) crosstalk may severely degrade the system performance when the fiber input powers are large and/or the channel spacing is too small. Theoretical and experimental results of the effects of FWM in OFDM systems are presented The theoretical results demonstrate the dependence of FWM on various systems parameters. Also included is an analysis of FWM in both unidirectional and bidirectional transmission systems. The receiver sensitivity degradation from FWM crosstalk was measured in a 16-channel coherent system. A sensitivity penalty of 0.4 dB resulted when a signal power of -3 dBm/channel was transmitted through 12 km of dispersion-shifted fiber
Fibre four-wave mixing induced by optical amplification in a 16 channel coherent system
No full textIn optical frequency division multiplexed systems, the nonlinear interaction between signal channels may set the ultimate limit on the allowable channel spacing, total number of channels, and maximum power per channel. The four-wave mixing (FWM) crosstalk in semiconductor amplifiers has been shown to cause a sensitivity degradation when the channel spacing is a few hundred megahertz. In contrast, when fiber amplifiers are used, nonlinear interactions have been considered negligible because of the long fluorescence time constant. However, we recently found that for a fiber amplifier with a saturation power in the 5-10-mW range, the transmission fiber following the amplifier can cause FWM crosstalk. Fiber FWM may also be observed without an amplifier if a wavelength selective coupler is used to combine the laser outputs with no splitting loss
Fibre four-wave mixing in multi-channel coherent systems
No full textThe crosstalk degradation due to four-wave mixing (FWM) in fiber is studied in a 155Mb/s, 16 channel coherent system with the signal powers amplified by an erbium-doped fiber amplifier. When a total power of +8.4dBm (0.46mW/channel) is launched into the fiber, the crosstalk degradation is 0.4dB. A theoretical study indicates the EWM dependence on fiber chromatic dispersion, the total number of channels, and the signal power levels and polarization states
Signaling under threats: evidence of voluntary disclosure in corporate control contests
No full textWe investigate voluntary disclosure strategies in contested takeovers and the associated economic consequences. Using a difference-in-differences research design and propensity score matching, we find that relative to friendly takeovers, target management in contested takeovers provides more earnings guidance and conveys more good news during the takeover. Moreover, voluntary disclosure helps contested targets negotiate a better offer and the results are stronger for targets with more information asymmetry. Collectively, targets adopt voluntary disclosure and alter their strategies under the threat of contested takeover to enhance their bargaining power. Voluntary disclosure by contested targets serves as a negotiation tactic that potentially benefits target shareholders.Peer reviewe
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