1,792 research outputs found
Investigation of temporal variations of winds
Nighttime observations of upper atmospheric wind data to determine physical properties of atmospher
Observations of chemical releases from high flying aircraft
Barium and lithium vapors were released from sounding rockets in the thermosphere and observed from aboard the NASA Convair 990 at an altitude of 40,000 ft. The purpose of the releases was to (1) check out observational and operational procedures associated with the large high altitude barium release from a Scout rocket (BIC); (2) develop an all-weather technique for observing chemical releases; (3) evaluate methods of observing daytime releases, and (4) investigate the possibilities of observations from a manned satellite. The initial analysis indicates that the previous limitations on the usage of the vapor release method have been removed by the use of the aircraft and innovative photographic techniques. Methods of analysis and applications to the investigation of the thermosphere are discussed
Investigation of the time variation of sporadic-E layers Final report
Analysis of wind and electron density profiles of E-region obtained from Nike-Apache rockets launched 22 Feb. 196
Numerical evaluation of the incomplete airy functions and their application to high frequency scattering and diffraction
The incomplete Airy integrals serve as canonical functions for the uniform ray optical solutions to several high frequency scattering and diffraction problems that involve a class of integrals characterized by two stationary points that are arbitrarily close to one another or to an integration endpoint. Integrals of such analytical properties describe transition region phenomena associated with composite shadow boundaries. An efficient and accurate method for computing the incomplete Airy functions would make the solutions to such problems useful for engineering purposes. Here, a convergent series solution form for the incomplete Airy functions is derived. Asymptotic expansions involving several terms were also developed and serve as large argument approximations. The combination of the series solution form with the asymptotic formulae provides for an efficient and accurate computation of the incomplete Airy functions. Validation of accuracy is accomplished using direct numerical integration data
Optimal Bond Trading with Personal Taxes: Implications for Bond Prices and Estimated Tax Brackets and Yield Curves
The assumption that bondholders follow either a buy-and-hold or a continuous realization trading policy, rather than the optimal trading policy,is at variance with reality and, as we demonstrate, may seriously bias the estimation of the yield curve and the implied tax bracket of the marginal investor. Tax considerations which govern a bondholder's optimal trading policy include the following: realization of capital losses, short term if possible; deferment of the realization of capital gains, especially if they are short term; changing the holding period status from long term to short term by sale of the bond and repurchase, so that future capital losses may be realized short term; and raising the basis through sale of the bond and repurchase in order to deduct from ordinary income the amortized premium. Because of the interaction of these factors, no simple characterization of the optimal trading policy is possible. We can say, however, that it differs substantially from the buy-and-hold policy irrespective of whether the bondholder is a bank, a bond dealer, or an individual. We obtain these strong results even when we allow for transactions costs and explicitly consider numerous IRS regulations designed to curtail tax avoidance.
Study of the dynamics and ionization of the upper atmosphere Final report
Wind effects on nighttime E region ionization layer distributio
KAPow: A System Identification Approach to Online Per-Module Power Estimation in FPGA Designs
In a modern FPGA system-on-chip design, it is often insufficient to simply assess the total power consumption of the entire circuit by design-time estimation or runtime power rail measurement. Instead, to make better runtime decisions, it is desirable to understand the power consumed by each individual module in the system. In this work, we combine boardlevel power measurements with register-level activity counting to build an online model that produces a breakdown of power consumption within the design. Online model refinement avoids the need for a time-consuming characterisation stage and also allows the model to track long-term changes to operating conditions. Our flow is named KAPow, a (loose) acronym for ‘K’ounting Activity for Power estimation, which we show to be accurate, with per-module power estimates as close to ±5mW of true measurements, and to have low overheads. We also demonstrate an application example in which a permodule power breakdown can be used to determine an efficient mapping of tasks to modules and reduce system-wide power consumption by over 8%
Identification of influence within the social media
Social media is expected to have a growing impact on the corporate reputation of organizations. Various social media actors referred to as social media influencers can have a particular impact on corporate reputation. It is important for organizations to identify these actors and understand how to interact with them in order to safeguard the organizational reputation. In this study, based on extensive literature review and a Delphi study, we constructed a model for the identification of the social media influencers; the ‘social media corporate reputation influencers model’. The Delphi study shows that the model is suitable for the identification of social media influencers by identifying the main indicators for determining and predicting the influence within the social media. Based on the Delphi study amongst social media marketing professionals, we conclude that social media has an impact on corporate reputations
Higher Education Marketing: A Study on the Impact of Social Media on Study Selection and University Choice.
The importance of the Internet as commercial platform is by now universally recognized, and businesses increasingly adopt online marketing channels at the cost of traditional ones. The social media, being second generation (Web 2.0) internet applications, allow interaction, one-to-one communication, customer engagement, and user generated content. The interest of higher education institutions in social media as part of the marketing toolkit is increasing, but little is known about the potential of these channels in higher education marketing strategies. Even less is known about the role of social media as influencers of future students in the choice of study and university. This article presents the results of a study identifying the role and importance of social media on the choice of future students for a study and university in comparison with the traditional university marketing channels in the Netherlands. The study identifies and describes three market segments among future students based on their use of the social medi
Delay-Bounded Routing for Shadow Registers
The on-chip timing behaviour of synchronous circuits can be quantified at run-time by adding shadow registers, which allow designers to sample the most critical paths of a circuit at a different point in time than the user register would normally. In order to sample these paths precisely, the path skew between the user and the shadow register must be tightly controlled and consistent across all paths that are shadowed. Unlike a custom IC, FPGAs contain prefabricated resources from which composing an arbitrary routing delay is not trivial. This paper presents a method for inserting shadow registers with a minimum skew bound, whilst also reducing the maximum skew. To preserve circuit timing, we apply this to FPGA circuits post place-and-route, using only the spare resources left behind. We find that our techniques can achieve an average STA reported delay bound of ±200ps on a Xilinx device despite incomplete timing information, and achieve <1ps accuracy against our own delay model
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