ENTROPY DUALS

The convex nature of Jaynes's maximum entropy formalism implies the existence of mathematical duals. The paper derives two dual forms of entropy using classical Lagrange saddle-point conditions and posynomial geometric programming. The dual forms are shown to be equivalent under transformation. Insights into the nature of entropic processes are explored and possible interpretations of the dual entropies are given. Finally it is shown that the calculation of least biased probabilities underlying random statistical data can be done very easily using standard library subroutines for unconstrained nonlinear programming to solve the dual problem.     

Opto-thermal measurements for the non-invasive, non-occlusive monitoring of in vivo skin condition

Opto-thermal transient radiometry (OTTER) is a non-invasive measurement technique, well suited for in vivo skin research. Its excitation and detection wavelengths can be selected to give a high sensitivity to stratum corneum hydration. This is demonstrated with measurements of hydration changes resulting from occlusion with a neoprene cover and with a topical application of an occlusive preparation. In the former case, the hydration was found to recover to normal levels upon exposure to atmospheric conditions in a characteristic time of 15 min. In the latter case, a topical application of petroleum jelly was found to lead to a doubling of stratum corneum hydration over 2h. This ability to measure hydration changes in the presence of topical hydrating agents is thought to be a particularly valuable property of the OTTER technique. With a different choice of excitation and detection wavelengths, OTTER can be used to measure skin thickness, from the surface down to the vascular bed. This technique was used to measure a skin thickness map of the ventral surface of the forearm of a volunteer, showing distinct thickening near the wrist and ulna. Another use of this technique is the study of changes in subcutaneous blood distribution associated with erythema. As a demonstration of this, blood distribution changes brought about by the topical application of a salicylate/nicotinate preparation were studied. The main finding is that the subcutaneous blood spreads towards the surface, with the mean depth decreasing from 63 μm to 55μm.     

CONTINUED FRACTIONS: YET ANOTHER TOOL TO OVERCOME THE CURSE OF DIMENSIONALITY

We provide a rapid prediction method, in which a larger number of antecedents is accounted for than is currently considered. To this end, we encode the successive (possibly rescaled) values of a time series, as the partial quotients of a continued fraction, resulting in a number from the unit interval. The accuracy of a rule-based system utilizing this coding is investigated to some extent. Qualitative criteria for the applicability of the algorithm are formulated.     

The effective resolution element of Landsat Thematic Mapper

Abstract

As part of the U.K.'s contribution to NASA's Landsat [mage Data Quality Analysis (LIDQA) programme the system performance of the Thematic Mapper (TM) scanner has been studied by the determination of the Effective Resolution Element (ERE), a measure of its spatial resolution. Two methods have been used, the first by a simulation of the TM's spatial responses in an analytical model and the second by measurements of water bodies on a selected Landsat-5 TM scene. Bands 1-4 of the Thematic Mappers of both Landsat-4 and Landsal-5 have an effective resolution element by the former method of 52 m. This compares with a value of 122 m for band 4, near-infrared, of the Multispectral Scanner (MSS) by the same method. An image-derived value, by the latter method, for band 4 of the Landsat-5 TM scene is approximately 75 m. This increase in the ERE over the sensor-only value is attributed to additional factors within the imagery such as the pixel sampling of the scene, ground segment processing and the contribution of atmospheric effects. The image-derived measure of the ERE will give a useful indication of the size of targets that can be recorded to a given radiometric accuracy and can thus determine the type of informational classes that may be utilized from present methods of automated classifications of remotely-sensed data.     

Ten implementations of ptychography

Ptychography is an increasingly popular phase retrieval imaging technique, able to routinely deliver quantitative phase images with extended field of view at diffraction limited resolution. Different variants of this technique, like Bragg ptychography and Fourier ptychography, have also been developed and applied to various fields. Here we experimentally demonstrate 10 ways to implement the conventional real space transmission ptychography, and compare their properties to provide a guide to choosing the optimal setup for a specific application.     

Impact of Undergraduate Research Experience in Engineering

A survey of alumni from the College of Engineering at the University of Delaware was conducted to assess the impact of the undergraduate research experience. Students who had participated in undergraduate research were matched with a comparable group of alumni who had no research experience. Alumni were unaware that their responses would be used to assess the impact of undergraduate research. Respondents who had participated in research indicated that this experience was “very” or “extremely” important, with a greater perceived benefit for students who had participated in research for a longer time. Alumni with research experience were more likely to pursue graduate degrees, and they reported greater enhancement of important cognitive and personal skills. In addition, respondents who had been involved in research were much more likely to have reported that they had a faculty member play an important role in their career choice.     

AN OPTIMIZATION METHOD TO DESIGN HYDRAULIC NETWORKS

Nonlinear programming is applied to the solution of hydraulic network problems. The significant differences between the proposed optimization method and other conventional methods are that this method can solve problems with mixed unknowns (e.g. pipe sizes, discharges and pressures), it can optimize solutions involving unknowns defined by inequalities (e.g. specifled minimum discharge and pressure values), it can handle network control problems such as required valve adjustments or in-line booster pump needs, and it may solve problems of networks with continuous discharge distribution along the pipes.