Richard R. Simonds

Combined forced and free convection for laminar flow in horizontal tubes with uniform heat flux

Abstract This study considers the effects of free convection on laminar flow of water in horizontal circular tubes having essentially constant heat flux at the tube wall. A visual and quantitative study was performed utilizing electrically heated glass tubing. These data were combined with other data and correlations to obtain a general picture of the influence of free convection on the Nusselt number. The final correlation curves given in Fig. 11 are provisionally recommended for obtaining heat-transfer coefficients in practical situations. With reasonable heating rates, the heat-transfer coefficients can be three to four times the values predicted by traditional constant property solutions.

Testing for Nonstationarity of Market Risk: An Exact Test and Power Considerations

This paper reexamines the issue of common stock market risk stationarity by applying a newly available exact test for random-walk regression coefficients. For each eight-year subperiod tested in the 1951–1974 interval, betas for individual New York Stock Exchange-listed stocks appeared to be nonstationary. The statistical powers of the exact test and of locally most powerful tests are compared to the power of the test employed previously by Sunder. These power considerations are cited to explain the differences between test results obtained here and those reported by Sunder.

Mutual fund strategies for IRA investors

Z K ual may place in an Individual Retirement Account (IRA) in any one year is restricted by law, investors who use the IRA to achieve the maximum incremental benefit must select assets with great care. The purpose of this article is to evaluate the benefit of using an IRA to tax shelter common stock mutual funds, many of which aim to achieve substantial capital appreciation. Since all money withdrawn from an IRA is subject to taxation at ordinary rates, IRA capital gains do not receive favorable tax treatment. Capital gains are ultimately taxed at exactly the same rate as dividends and interest income. Therefore, the question arises as to whether or not it is wise to tax shelter through an IRA a stock mutual fund investment. The answer, as we shall see, depends primarily on the distribution of the fund’s return between current dividends, realized capital gains, and unrealized capital gains. A secondary consideration is whether or not a 10% IRA early withdrawal penalty is likely to be incurred. Based on the results presented here, I establish a strategy for employing stock mutual funds in IRAs. z

An Empirical Examination of the Predictive Performance of an Econometric Model with Random Coefficients

This paper compares the forecasting performance of a small quarterly econometric model under two different assumptions: (1) the structural coefficients are constants and (2) the structural coefficients follow a first-order Markov process over time (the Kalman filter model). Several univariate time series models (random walk, exponential smoothing, Box-Jenkins ARIMA models) are also considered in order to provide yardsticks for the comparison.