2D bitmapping approach for identification and quantitation of common base flavor adulterants using surface acoustic wave arrays and artificial neural network data analysis

Arrays of polymer-coated surface acoustic wave microsensors are used in conjunction with a variety of signal-processing algorithms known as artificial neural networks (ANN). This format of data analysis has the capability to characterize complex mixtures of volatile and semi-volatile organic compounds commonly found in base flavors. The approach described, which minimizes the number of training sets while retaining the robustness of an ANN, utilizes a 2D bitmap matrix. The matrix is obtained by converting the time domain kinetics of sensor response into a bitmap. The high data throughput of this approach enables quantitation on the order of ppm of common base flavor adulterants.     

Nonlinear shallow-water solutions using the weak temperature gradient approximation

A form of the weak temperature gradient (WTG) approximation, in which the temperature tendency and advection terms are neglected in the temperature equation so that the equation reduces to a diagnostic balance between heating and vertical motion, is applied to a two-dimensional nonlinear shallow-water model with the heating (mass source) parameterized as a Newtonian relaxation on the temperature (layer thickness) towards a prescribed function of latitude and longitude, containing an isolated maximum or minimum, as in the classic linear Gill problem. In this model, temperature variations are retained in the Newtonian heating term, so that it is not a pure WTG system. It contains no free unbalanced modes, but reduces to the Gill model in the steady linear limit, so that steady solutions may be thought of as containing components corresponding to unbalanced modes in the same sense as the latter. The equations are solved numerically and are compared with full shallow-water solutions in which the WTG approximation is not made. Several external parameters are varied, including the strength, location, sign, and horizontal scale of the mass source, the Rayleigh friction coefficient, and the time scale for the relaxation on the mass field. Indices of the Walker and Hadley circulations are examined as functions of these external parameters. Differences between the WTG solutions and those from the full shallow-water system are small over most of the parameter regime studied, which includes time-dependent as well as steady solutions.     

Scheduling projects with stochastic activity duration to maximize expected net present value

Although uncertainty is rife in many project management contexts, little is known about adaptively optimizing project schedules. We formulate the problem of adaptively optimizing the expected present value of a project’s cash flow, and we show that it is practical to perform the optimization. The formulation includes randomness in activity durations, costs, and revenues, so the optimization leads to a recursion with a large state space even if the durations are exponentially distributed. We present an algorithm that partially exercises the “curse of dimensionality” as computational results demonstrate. Most of the paper is restricted to exponentially distributed task durations, but we sketch the adaptation of the algorithm to approximate any probability distribution of task duration.     

Anisotropy of the ultrasonic backscatter of myocardial tissue: II. Measurements in vivo

The purpose of this investigation was to determine the angular dependence of the backscatter from canine myocardial tissue in vivo and to compare it with the variation of backscatter over the cardiac cycle that has been recognized and reported previously. The backscatter was measured from regions of left ventricular wall in canine hearts in which the fibers of the muscle lay parallel to the surface of the heart and were oriented predominantly in a circumferential fashion. Because of technical considerations, the angle of insonification was varied systematically through two cycles in which the angle relative to the muscle fiber axes ranged from 60 degrees-120 degrees. Backscatter was maximum at angles of interrogation perpendicular to the myocardial fibers and minimum at those most acute (60 degrees) relative to the orientation of the fibers. The previously observed variation of integrated backscatter over the heart cycle was evident at each angle of interrogation. At end systole, the average maximum-to-minimum angular variation of integrated backscatter as 5.0 +/- 0.4 dB. At end diastole, the average maximum-to-minimum angular variation was 3.2 +/- 0.4 dB. Thus, even though angular dependence of the backscatter from tissues with directionally oriented structures is substantial, the anisotropy does not account for cardiac-cycle-dependent variation of backscatter. Accordingly, the angular dependence should be incorporated in approaches to quantitative tissue characterization with ultrasound.