17,277 research outputs found
Tracking Data-Flow with Open Closure Types
Type systems hide data that is captured by function closures in function
types. In most cases this is a beneficial design that favors simplicity and
compositionality. However, some applications require explicit information about
the data that is captured in closures. This paper introduces open closure
types, that is, function types that are decorated with type contexts. They are
used to track data-flow from the environment into the function closure. A
simply-typed lambda calculus is used to study the properties of the type theory
of open closure types. A distinctive feature of this type theory is that an
open closure type of a function can vary in different type contexts. To present
an application of the type theory, it is shown that a type derivation
establishes a simple non-interference property in the sense of information-flow
theory. A publicly available prototype implementation of the system can be used
to experiment with type derivations for example programs.Comment: Logic for Programming Artificial Intelligence and Reasoning (2013
Ultracold molecules: new probes on the variation of fundamental constants
Ultracold molecules offer brand new opportunities to probe the variation of
fundamental constants with unprecedented sensitivity. This paper summarizes
theoretical background and current constraints on the variation of fine
structure constant and electron-to-proton mass ratio, as well as proposals and
experimental efforts to measure the variations based on ultracold molecules. In
particular, we describe two novel spectroscopic schemes on ultracold molecules
which have greatly enhanced sensitivity to fundamental constants: resonant
scattering near Feshbach resonances and spectroscopy on close-lying energy
levels of ultracold molecules
Efficient fault diagnosis of helicopter gearboxes
Application of a diagnostic system to a helicopter gearbox is presented. The diagnostic system is a nonparametric pattern classifier that uses a multi-valued influence matrix (MVIM) as its diagnostic model and benefits from a fast learning algorithm that enables it to estimate its diagnostic model from a small number of measurement-fault data. To test this diagnostic system, vibration measurements were collected from a helicopter gearbox test stand during accelerated fatigue tests and at various fault instances. The diagnostic results indicate that the MVIM system can accurately detect and diagnose various gearbox faults so long as they are included in training
Bulk and integrated acousto-optic spectrometers for radio astronomy
The development of sensitive heterodyne receivers (front end) in the centimeter and millimeter range, and the construction of sensitive RF spectrometers (back end) enable the spectral lines of interstellar molecules to be detected and identified. A technique was developed which combines acoustic bending of a collimated coherent light beam by a Bragg cell followed by detection by a sensitive array of photodetectors (thus forming an RF acousto-optic spectrometer (AOS). An AOS has wide bandwidth, large number of channels, and high resolution, and is compact, lightweight, and energy efficient. The thrust of receiver development is towards high frequency heterodyne systems, particularly in the millimeter, submillimeter, far infrared, and 10 micron spectral ranges
Acousto-optic spectrometer for radio astronomy
A prototype acousto-optic spectrometer which uses a discrete bulk acoustic wave Itek Bragg cell, 5 mW Helium Neon laser, and a 1024 element Reticon charge coupled photodiode array is described. The analog signals from the photodiode array are digitized, added, and stored in a very high speed custom built multiplexer board which allows synchronous detection of weak signals to be performed. The experiment is controlled and the data are displayed and stored with an LSI-2 microcomputer system with dual floppy discs. The performance of the prototype acousto-optic spectrometer obtained from initial tests is reported
Fault detection of helicopter gearboxes using the multi-valued influence matrix method
In this paper we investigate the effectiveness of a pattern classifying fault detection system that is designed to cope with the variability of fault signatures inherent in helicopter gearboxes. For detection, the measurements are monitored on-line and flagged upon the detection of abnormalities, so that they can be attributed to a faulty or normal case. As such, the detection system is composed of two components, a quantization matrix to flag the measurements, and a multi-valued influence matrix (MVIM) that represents the behavior of measurements during normal operation and at fault instances. Both the quantization matrix and influence matrix are tuned during a training session so as to minimize the error in detection. To demonstrate the effectiveness of this detection system, it was applied to vibration measurements collected from a helicopter gearbox during normal operation and at various fault instances. The results indicate that the MVIM method provides excellent results when the full range of faults effects on the measurements are included in the training set
Women Fighting Poverty in Cameroon: A Legal Perspective!
Poverty in Sub Saharan Africa has many causes, which range from the impact of the Structural Adjustment Programs, the huge foreign debt and policies that encourage mismanagement of state resources. This growing poverty and underdevelopment has attracted the attention of the international community to pursue programs aimed at attaining the UN Millennium Development Goals, foreign debt relief and increased development aid. During the introduction of policies that brought about economic hardship, African women were not consulted and their voices were not heard. Yet it is these women who feel most of the impact of these policies. During the period of the economic crisis, women did not remain silent in the face of the growing poverty. As a response, they organized themselves into groups for financial and self-help purposes. These organized women’s groups if legally and financially empowered will contribute a great deal in the fight against poverty in Cameroon. Micro financing is an important tool common in these groups, but it must be supported by the provision of basic resources and infrastructure. Women make up more than75% of subsistence farmers and are mostly found in the informal sector, their contribution helps to sustain the economy greatly, but it is still insufficient to make any significant improvement in their living standards. The inhibition stems from traditional and cultures practices that hinder women from claiming equal ownership and equal representation in decision-making settings. Hence, a good economic regulatory framework by any government fighting poverty should incorporate the economic and legal empowerment of women and target mostly rural women and their basic needs
Enhancement of variation of fundamental constants in ultracold atom and molecule systems near Feshbach resonances
Scattering length, which can be measured in Bose-Einstein condensate and
Feshbach molecule experiments, is extremely sensitive to the variation of
fundamental constants, in particular, the electron-to-proton mass ratio
(m_e/m_p or m_e/Lambda_{QCD}, where Lambda_{QCD} is the QCD scale). Based on
single- and two-channel scattering model, we show how the variation of the mass
ratio propagates to the scattering length. Our results suggest that variation
of m_e/m_p on the level of 10^{-11}~10^{-14} can be detected near a narrow
magnetic or an optical Feshbach resonance by monitoring the scattering length
on the 1% level. Derived formulae may also be used to estimate the isotopic
shift of the scattering length
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