Data compression and regression based on local principal curves.

Frequently the predictor space of a multivariate regression problem of the type y = m(x_1, …, x_p ) + ε is intrinsically one-dimensional, or at least of far lower dimension than p. Usual modeling attempts such as the additive model y = m_1(x_1) + … + m_p (x_p ) + ε, which try to reduce the complexity of the regression problem by making additional structural assumptions, are then inefficient as they ignore the inherent structure of the predictor space and involve complicated model and variable selection stages. In a fundamentally different approach, one may consider first approximating the predictor space by a (usually nonlinear) curve passing through it, and then regressing the response only against the one-dimensional projections onto this curve. This entails the reduction from a p- to a one-dimensional regression problem. As a tool for the compression of the predictor space we apply local principal curves. Taking things on from the results presented in Einbeck et al. (Classification – The Ubiquitous Challenge. Springer, Heidelberg, 2005, pp. 256–263), we show how local principal curves can be parametrized and how the projections are obtained. The regression step can then be carried out using any nonparametric smoother. We illustrate the technique using data from the physical sciences

Solution to the twin image problem in holography

While the invention of holography by Dennis Gabor truly constitutes an ingenious concept, it has ever since been troubled by the so called twin image problem limiting the information that can be obtained from a holographic record. Due to symmetry reasons there are always two images appearing in the reconstruction process. Thus, the reconstructed object is obscured by its unwanted out of focus twin image. Especially for emission electron as well as for x- and gamma-ray holography, where the source-object distances are small, the reconstructed images of atoms are very close to their twin images from which they can hardly be distinguished. In some particular instances only, experimental efforts could remove the twin images. More recently, numerical methods to diminish the effect of the twin image have been proposed but are limited to purely absorbing objects failing to account for phase shifts caused by the object. Here we show a universal method to reconstruct a hologram completely free of twin images disturbance while no assumptions about the object need to be imposed. Both, amplitude and true phase distributions are retrieved without distortion

Geological and Botanical Features of Sand Beach Systems in Maine and Their Relevance to the Critical Areas Program of the State Planning Office

Geological and Botanical Features of Sand Beach Systems in Maine and Their Relevance to the Critical Areas Program of the State Planning Office by Bruce W. Nelson and L. Kenneth Fink, Jr. A Report Prepared for the Maine Critical Areas Program, State Planning Office, Augusta, Maine 04330 - Planning Report Number 54 (14 March 1978). Contents: Abstract / Foreword / Acknowledgements / Geology, Distribution, and Geomorphology of Maine\u27s Coastal Sandy Beaches and Dune Systems / Methods of Locating Sandy Beaches and Dunes / General Consideration in Developing Criteria for Inclusion in the List of Significant Coastal Sandy Beaches and Dunes / Geological Criteria for Significance / Botanical Criteria for Significance / General Information on Coastal Sandy Dune Plant Species and Associations / Partial List of Maine\u27s Berm and Dune Plants / Description of Significant Maine Sandy Beaches / General Evaluation of Sandy Beaches for Inclusion on the Register of Critical Areas / Recommendations / Bibliographyhttps://digitalcommons.usm.maine.edu/me_collection/1083/thumbnail.jp

Exact time-reversal focusing of acoustic and quantum excitations in open cavities: The perfect inverse filter

The time-reversal mirror (TRM) prescribes the reverse playback of a signal to focalize an acoustic excitation as a Loschmidt echo. In the quantum domain, the perfect inverse filter (PIF) processes this signal to ensure an exact reversion provided that the excitation originated outside the cavity delimited by the transducers. We show that PIF takes a simple form when the initial excitation is created inside this cavity. This also applies to the acoustical case, where it corrects the TRM and improves the design of an acoustic bazooka. We solve an open chaotic cavity modeling a quantum bazooka and a simple model for a Helmholtz resonator, showing that the PIF becomes decisive to compensate the group velocities involved in a highly localized excitation and to achieve subwavelength resolution.Comment: 6 pages, 2 figure

Strategies for optimal fertiliser management of vegetable crops in Europe

In Europe a number of procedures are used to assist growers and advisors to determine optimal N fertiliser recommendations. The implementation of European Union (EU) legislation is encouraging the adoption of fertiliser recommendation schemes. The most widely used schemes are those based on soil testing or on the use of indices that estimate the soil nitrogen supply. Soil testing approaches that are in use, particularly in NW Europe are the Nmin, KNS and N-Expert systems; the latter is operated as a computer-based decision support system (DSS). The comprehensive RB209 Fertiliser Manual of England and Wales uses soil N supply indices, but soil analysis can also be used. Nitrogen balance calculations are widely used throughout Europe and form part of the KNS and N-Expert systems, and a number of other DSSs. The N balance considers the various soil N sources and treats mineral N fertiliser as a supplemental N source. The EU-Rotate_N simulation model is a comprehensive and versatile tool, developed for diverse European conditions, that is useful for scenario analysis simulations to stakeholders. Various DSS have been developed in different European countries, with different levels of complexity. There are a number of different DSS that calculate N fertiliser recommendations for particular cropping systems; some DSS calculate the requirements for other nutrients, and some also do so for irrigation which is particularly useful where fertigation is used. Sap analysis has been shown to be sensitive to crop nutrient status, for N and some other nutrients; currently, there is renewed interest in sap analysis. Proximal optical sensors are a promising approach for N management

Power train for three-stage potassium test turbine. Volume 1 - Final design

Final design for power train for three stage potassium test turbin

Logistics Reduction Technologies for Exploration Missions

Human exploration missions under study are limited by the launch mass capacity of existing and planned launch vehicles. The logistical mass of crew items is typically considered separate from the vehicle structure, habitat outfitting, and life support systems. Although mass is typically the focus of exploration missions, due to its strong impact on launch vehicle and habitable volume for the crew, logistics volume also needs to be considered. NASA's Advanced Exploration Systems (AES) Logistics Reduction and Repurposing (LRR) Project is developing six logistics technologies guided by a systems engineering cradle-to-grave approach to enable after-use crew items to augment vehicle systems. Specifically, AES LRR is investigating the direct reduction of clothing mass, the repurposing of logistical packaging, the use of autonomous logistics management technologies, the processing of spent crew items to benefit radiation shielding and water recovery, and the conversion of trash to propulsion gases. Reduction of mass has a corresponding and significant impact to logistical volume. The reduction of logistical volume can reduce the overall pressurized vehicle mass directly, or indirectly benefit the mission by allowing for an increase in habitable volume during the mission. The systematic implementation of these types of technologies will increase launch mass efficiency by enabling items to be used for secondary purposes and improve the habitability of the vehicle as mission durations increase. Early studies have shown that the use of advanced logistics technologies can save approximately 20 m(sup 3) of volume during transit alone for a six-person Mars conjunction class mission

Logistics Reduction Technologies for Exploration Missions

Human exploration missions under study are very limited by the launch mass capacity of existing and planned vehicles. The logistical mass of crew items is typically considered separate from the vehicle structure, habitat outfitting, and life support systems. Consequently, crew item logistical mass is typically competing with vehicle systems for mass allocation. NASA's Advanced Exploration Systems (AES) Logistics Reduction and Repurposing (LRR) Project is developing five logistics technologies guided by a systems engineering cradletograve approach to enable used crew items to augment vehicle systems. Specifically, AES LRR is investigating the direct reduction of clothing mass, the repurposing of logistical packaging, the use of autonomous logistics management technologies, the processing of spent crew items to benefit radiation shielding and water recovery, and the conversion of trash to propulsion gases. The systematic implementation of these types of technologies will increase launch mass efficiency by enabling items to be used for secondary purposes and improve the habitability of the vehicle as the mission duration increases. This paper provides a description and the challenges of the five technologies under development and the estimated overall mission benefits of each technology