Deflection and frequency monitoring of the Forth Road Bridge, Scotland, by GPS

Permission is granted by ICE Publishing to print one copy for personal use. Any other use of these PDF files is subject to reprint fees. Copyright © 2012 Thomas Telford Ltd.The use of carrier phase kinematic GPS (global positioning system) has evolved into a reliable technique to measure both the three-dimensional magnitudes and frequencies of movements of structures. Techniques have been developed that tackle errors caused by multipath, tropospheric delay and issues relating to satellite geometry. GPS-derived movements compare well with data from both design predictions and structural models. Results from field trials carried out on the Forth Road Bridge are presented. This paper brings together key results that outline the procedure as well as a series of new data that indicate other potential applications. GPS data were collected continuously over a period of 46 h at a minimum rate of 10 Hz. During the trials wind speed, wind direction, relative humidity and temperature were also recorded. Frequently there was very heavy traffic flow, and at one point a special load (a 100-t lorry) passed over simultaneously to the heavy daytime flow of traffic. Data from a planned load trial during a brief bridge closure are reported and compared with the limited results available from a finite element model. Measured vibration frequencies are also computed from GPS data and compared with those given in the literature. In addition, results indicating the change in structural characteristics are also presented – in particular changes of mass associated with changes in traffic loading are observed. The results show the performance of GPS as it has developed in recent years, and that it can now reliably be used as a significant part of structural health monitoring schemes, giving both the magnitude of quasi-static deflections in known time periods and hence the frequency of dynamic movements of structures.Forth Estuary Transport Authorit

How well do conventional stock market indicators predict stock market movements?: Working paper series--03-02

The P/E ratios and the dividend yield of the S&P 500 are analyzed in relation to subsequent stock returns and are show to explain less than 20% of the variation in returns. Some analysts suggest that these indicators should be examined in relation to interest rates. Interest rates are shown not to improve the explanatory power of the indicators. Unfortunately, the conventional indicators studied here are not very helpful and may have caused some investors to miss out on substantial returns

The IPO market: Do investors and analysts who follow IPOs learn? Working paper series--02-26

5370 IPOs are examined between 1975 and 1996 for evidence of trends in investor and analyst behavior over time. Following Ritter (1991) and Loughran and Ritter (1995), wealth relatives are calculated and aftermarket performance is examined each year over the sample period. IPOs followed by analysts, and reported on IBES within one year of the offer date, have consistently outperformed IPOs not followed by analysts. Historically, however, all firms typically underperform the market in years two and three following the IPO. This underperformance appears to change in the years following 1990 when IPOs followed by analysts outperform an industry control in each of the first three years following the IPO. This suggests analysts may be learning over time. Investors, however, do not appear to be learning. In spite of years of evidence showing that the returns of IPOs underperform the market in the years following the offering, no change in investor behavior is shown in recent years

Application of p-Multigrid to Discontinuous Galerkin Formulations of the Poisson Equation

We investigate p-multigrid as a solution method for several different discontinuous Galerkin (DG) formulations of the Poisson equation. Different combinations of relaxation schemes and basis sets have been combined with the DG formulations to find the best performing combination. The damping factors of the schemes have been determined using Fourier analysis for both one and two-dimensional problems. One important finding is that when using DG formulations, the standard approach of forming the coarse p matrices separately for each level of multigrid is often unstable. To ensure stability the coarse p matrices must be constructed from the fine grid matrices using algebraic multigrid techniques. Of the relaxation schemes, we find that the combination of Jacobi relaxation with the spectral element basis is fairly effective. The results using this combination are p sensitive in both one and two dimensions, but reasonable convergence rates can still be achieved for moderate values of p and isotropic meshes. A competitive alternative is a block Gauss-Seidel relaxation. This actually out performs a more expensive line relaxation when the mesh is isotropic. When the mesh becomes highly anisotropic, the implicit line method and the Gauss-Seidel implicit line method are the only effective schemes. Adding the Gauss-Seidel terms to the implicit line method gives a significant improvement over the line relaxation method

The president's social security plan: How much would you pay to participate? Working paper series--05-07

President Bush is in favor of using private retirement accounts to partially replace the current pay-as-you-go social security program. We use a simple life-cycle model to analyze whether or not private accounts would benefit workers. "Cash equivalents" are calculated under different assumptions to see how much a worker would be willing to pay to participate in the private account program. In most circumstances, workers would benefit from the private account program. Only when market rates of return are very low or a person expects to live for a very long time does the current pay-as-you-go system give a greater present value to a worker

How well do conventional stock market indicators predict stock market movements? Working paper series--03-02

5370 IPOs are examined between 1975 and 1996 for evidence of trends in investor and analyst behavior over time. Following Ritter (1991) and Loughran and Ritter (1995), wealth relatives are calculated and aftermarket performance is examined each year over the sample period. IPOs followed by analysts, and reported on IBES within one year of the offer date, have consistently outperformed IPOs not followed by analysts. Historically, however, all firms typically underperform the market in years two and three following the IPO. This underperformance appears to change in the years following 1990 when IPOs followed by analysts outperform an industry control in each of the first three years following the IPO. This suggests analysts may be learning over time. Investors, however, do not appear to be learning. In spite of years of evidence showing that the returns of IPOs underperform the market in the years following the offering, no change in investor behavior is shown in recent years

High-order harmonic generation from polyatomic molecules including nuclear motion and a nuclear modes analysis

We present a generic approach for treating the effect of nuclear motion in the high-order harmonic generation from polyatomic molecules. Our procedure relies on a separation of nuclear and electron dynamics where we account for the electronic part using the Lewenstein model and nuclear motion enters as a nuclear correlation function. We express the nuclear correlation function in terms of Franck-Condon factors which allows us to decompose nuclear motion into modes and identify the modes that are dominant in the high-order harmonic generation process. We show results for the isotopes CH$_4$ and CD$_4$ and thereby provide direct theoretical support for a recent experiment [Baker {\it et al.}, Science {\bf 312}, 424 (2006)] that uses high-order harmonic generation to probe the ultra-fast structural nuclear rearrangement of ionized methane.Comment: 6 pages, 6 figure

Refining our understanding of beta through quantile regressions: Working paper series--10-07

The Capital Asset Pricing Model (CAPM) has been a key theory since the 1960's. One of its main contributions is to attempt to identify how the risk of a particular stock is related to the risk of the overall stock market using the risk measure, beta. If the relationship between an individual stock's returns and the returns of the market exhibit heteroskedasticity, then the estimates of beta for different quantiles of the relationship can be quite different. The behavioral ideas first proposed by Kahneman and Tversky (1979), which they called prospect theory, postulate that i) people exhibit "loss-aversion" in a gain frame, and, ii) people exhibit "risk-seeking" in a loss frame. If this is true people could prefer lower beta stocks after they have experienced a gain and higher beta stocks after they have experienced a loss. Stocks that exhibit converging heteroskedasticty (9.8% of our sample) should be preferred by investors and stocks that exhibit diverging heteroskedasticity (19.8% of our sample) should not be preferred. Investors may be able to benefit by choosing portfolios that are more closely aligned with their preferences