Paper Formulation Research Articles

Investigation of wave propagation in piezoelectric helical waveguides with the spectral finite element method

The dispersion behaviors of wave propagation in waveguides of piezoelectric helical structures are investigated. By using the tensor analysis in the helical curve coordinate, the general strain-displacement relationship of piezoelectric helix is firstly considered. This paper's formulation is based on the spectral finite element which just requires the discretization of the cross-section with high-order spectral elements. The eigenvalue matrix of the dispersion relationship between wavenumbers and frequencies is obtained. Numerical examples on PZT5A and Ba2NaNb5O15 helical waveguides of a wide range of lay angles are presented. The effects of the piezoelectric on the dispersive properties and the variation tendency of dispersion curves on helix angles are shown. The mechanism of mode separation in piezoelectric helical waveguides is further analyzed through studying waves structures of the flexural modes.

Automated Spatiotemporal Analysis of Fibrils and Coronal Rain Using the Rolling Hough Transform

A technique is presented that automates the direction characterization of curvilinear features in multidimensional solar imaging data sets. It is an extension of the Rolling Hough Transform (RHT) technique presented by Clark, Peek, and Putman (Astrophys. J. 789, 82, 2014), and it excels at rapid quantification of spatial and spatiotemporal feature orientation even for low signal to noise applications. It operates on a pixel-by-pixel basis within a data set and reliably quantifies orientation even for locations not centered on a feature ridge, which is used here to derive a quasi-continuous map of the chromospheric fine structure projection angle. For time-series analysis, a procedure is developed that uses a hierarchical application of the RHT to automatically derive apparent motion of coronal rain observed off-limb. Essential to the success of this technique is this paper's formulation for the RHT error analysis as it provides a means to properly filter results.

Managing the impact of high market growth and learning on knowledge worker productivity and service quality

Many high technology firms in the information technology, engineering, and internet content industries experience exponential growth but are also dependent on knowledge workers requiring extensive periods of training or apprenticeship. Under these conditions productivity management becomes a critical yet dynamically complex issue. This paper uses control theory techniques to dynamically solve this staffing problem at a strategic level. The novelty of this paper's formulation of the staffing problem lies in the use of time-discounting in combination with a special cost structure. The resulting optimal policy reflects the influence of both capacity shortfall and salary penalties. Under most real-world conditions, it will drive capacity and employment levels asymptotically towards a constant fractional shortfall. An illustration is presented using enterprise requirement planning (ERP) project implementers. One important managerial implication is that the interaction of extensive training requirements with market growth can cause firms to under-perform by delivering low levels of service at a high cost. Further this underperformance will escalate with increases in either market growth or training requirements. Finally, the paper puts this research into a framework with the experience curve and technology supply chain literatures to outline possible directions for future research.

Optimal Replication of Options with Transactions Costs and Trading Restrictions

This paper analyzes the strategy that minimizes the initial cost of replicating a contingent claim in a market with transactions costs and trading constraints. The linear programming and two-stage backward recursive models developed are applicable to the replication of convex as well as nonconvex payoffs and to a portfolio of options with different maturities. The paper's formulation conveniently accounts for fixed and variable transactions costs, lot size constraints, and position limits on trading. The article shows that in the presence of trading frictions, it is no longer optimal to revise one's portfolio in each period. At the optimum, cash flows in excess of the desired ones may be generated. The optimal policy trades off the curvature of the payoff that is generated against the terminal slack.

The Method of Lines Applied to a Finline/Strip Configuration on an Anisotropic Substrate

The method of lines (MOL), a numerical scheme for the solution of partial differential equations that recently has been adapted to the full-wave dispersive characterization of planar wavegnide structures, is modified to treat cases having uniaziatiy anisotropic dielectric regions. Anisotropy is present in commonly used substrate materials and typically leads to significant modeling error if neglected. The modus operandi of the method of lines is the discretization of spatial variables into a set of lines. Consequently, partial differential equations are reduced to ordinary kinds possessing simple, closed-form solutions. Being simple from the onset, the analysis effects an easily implemented method of good and controllable accuracy. The paper's formulation is exercised upon an interesting form of finline, one with both a fin and an isolated strip opposite one another on a uniazial substrate. Computations providing dispersive effective permittivities and impedances highlight the errors incurred in neglecting anisotropy.

THE RELATIONSHIP BETWEEN YIELD, RISK, AND RETURN OF CORPORATE BONDS

A COMMON STATISTIC for a bond is its market yield or internal rate of return. Numerous articles have been written utilizing the internal rate of return to examine the price volatility of bonds [9], [14], [21]. However, all these studies have two factors in common. One, they are nonstochastic and two, they involve Macaulay's duration. This paper, by introducing uncertainty, derives the general relationship between the expected return on a bond and its market yield. The derivation is for risky corporate as well as for default free government bonds. The relationship is nonlinear and involves an expression which is an approximation to the duration of a bond. As a corollary to the above methodology, an alternate expression for the systematic risk of a bond is discovered. The expression involves only the market yield and the approximation to a bond's duration. This corollary generalizes the previous work of Boquist, Racette, and Schalarbaum [6] in two respects. First, this paper's formulation is for any type of a bond, while Boquist, et al. examined only default free securities. Second, the single period capital asset pricing model (CAPM) is replaced by its intertemporal counterpart as formulated by Merton [15]. An outline for the paper is as follows. Section I derives the relationship between a bond's market yield and expected return. Section II examines the systematic risk of a bond, while Section III concludes the paper.