21,597 research outputs found
Recent developments in CID imaging
Readout of CID imaging arrays was first performed by injecting and detecting the signal charge from each sensing site in sequence. A new readout method, termed parallel injection, has been developed in which the functions of signal charge detection and injection have been separated. The level of signal charge at each sensing site is detected during a line scan, and during the line retrace interval, all charge in the selected line is injected. The parallel injection technique is well adapted to TV scan formats in that the signal is read out at high speed, line by line. A 244 line by 248 element TV compatible imager, employing this technique and including an on chip preamplifier, has been constructed and operation demonstrated
A guided search non-dominated sorting genetic algorithm for the multi-objective university course timetabling problem
Copyright @ Springer-Verlag Berlin Heidelberg 2011.The university course timetabling problem is a typical combinatorial optimization problem. This paper tackles the multi-objective university course timetabling problem (MOUCTP) and proposes a guided search non-dominated sorting genetic algorithm to solve the MOUCTP. The proposed algorithm integrates a guided search technique, which uses a memory to store useful information extracted from previous good solutions to guide the generation of new solutions, and two local search schemes to enhance its performance for the MOUCTP. The experimental results based on a set of test problems show that the proposed algorithm is efficient for solving the MOUCTP
Tracking human face features in thermal images for respiration monitoring
A method has been developed to track a region related to respiration process in thermal images. The respiration region of interest (ROI) consisted of the skin area around the tip of the nose. The method was then used as part of a non-contact respiration rate monitoring that determined the skin temperature changes caused by respiration. The ROI was located by the first determining the relevant salient features of the human face physiology. These features were the warmest and coldest facial points. The tracking method was tested on thermal video images containing no head movements, small random and regular head movements. The method proved valuable for tracking the ROI in all these head movement types. It was also possible to use this tracking method to monitor respiration rate involving a number of head movement types. Currently, more investigations are underway to improve the tracking method so that it can track the ROI in cases larger head movements
Comparison of numerical methods for the calculation of cold atom collisions
Three different numerical techniques for solving a coupled channel
Schroedinger equation are compared. This benchmark equation, which describes
the collision between two ultracold atoms, consists of two channels, each
containing the same diagonal Lennard-Jones potential, one of positive and the
other of negative energy. The coupling potential is of an exponential form. The
methods are i) a recently developed spectral type integral equation method
based on Chebyshev expansions, ii) a finite element expansion, and iii) a
combination of an improved Numerov finite difference method and a Gordon
method. The computing time and the accuracy of the resulting phase shift is
found to be comparable for methods i) and ii), achieving an accuracy of ten
significant figures with a double precision calculation. Method iii) achieves
seven significant figures. The scattering length and effective range are also
obtained.Comment: 22 pages, 3 figures, submitted to J. Comput. Phys. documentstyle
[thmsa,sw20aip]{article} in .te
Average and worst-case specifications of precipitating auroral electron environment
The precipitation electrons in the auroral environment are highly variable in their energy and intensity in both space and time. As such they are a source of potential hazard to the operation of the Space Shuttle and other large spacecraft operating in polar orbit. In order to assess these hazards both the average and extreme states of the precipitating electrons must be determined. Work aimed at such a specification is presented. First results of a global study of the average characteristics are presented. In this study the high latitude region was divided into spatial elements in magnetic local time and corrected geomagnetic latitude. The average electron spectrum was then determined in each spatial element for seven different levels of activity as measured by K sub p using an extremely large data set of auroral observations. Second a case study of an extreme auroral electron environment is presented, in which the electrons are accelerated through field aligned potential as high as 30,000 volts and in which the spacecraft is seen to charge negatively to a potential approaching .5 kilovolts
A Component Based Heuristic Search Method with Evolutionary Eliminations
Nurse rostering is a complex scheduling problem that affects hospital
personnel on a daily basis all over the world. This paper presents a new
component-based approach with evolutionary eliminations, for a nurse scheduling
problem arising at a major UK hospital. The main idea behind this technique is
to decompose a schedule into its components (i.e. the allocated shift pattern
of each nurse), and then to implement two evolutionary elimination strategies
mimicking natural selection and natural mutation process on these components
respectively to iteratively deliver better schedules. The worthiness of all
components in the schedule has to be continuously demonstrated in order for
them to remain there. This demonstration employs an evaluation function which
evaluates how well each component contributes towards the final objective. Two
elimination steps are then applied: the first elimination eliminates a number
of components that are deemed not worthy to stay in the current schedule; the
second elimination may also throw out, with a low level of probability, some
worthy components. The eliminated components are replenished with new ones
using a set of constructive heuristics using local optimality criteria.
Computational results using 52 data instances demonstrate the applicability of
the proposed approach in solving real-world problems.Comment: 27 pages, 4 figure
Accommodation to hyperpolarization of human axons assessed in the frequency domain
Human axonsin vivowere subjected to subthreshold currents with a threshold-"ZAP" profile (Impedance [ Z: ] A: mplitude P: rofile) to allow the use of frequency domain techniques to determine the propensity for resonant behavior, and to clarify the relative contributions of different ion channels to their low-frequency responsiveness. Twenty-four studies were performed on the motor and sensory axons in 6 subjects. The response to oscillatory currents was tested between 'DC' and 16 Hz. A resonant peak at ~2 to 2.5 Hz was found in the response of hyperpolarized axons, but there was only a small broad response in axons at resting membrane potential (RMP). A mathematical model of axonal excitability developed using DC pulses provided a good fit to the frequency response for human axons, and indicated that the hyperpolarization-activated currentIh, and the slow potassium currentIKsare principally responsible for the resonance. However the results indicate that if axons are hyperpolarized more than -60% of resting threshold, the only conductances that are appreciably active areIhand the leak conductance - i.e., that the activity of these conductances can be studiedin vivovirtually in isolation at hyperpolarized membrane potentials. Given that the leak conductance dampens resonance it is suggested that the -60% hyperpolarization used here is optimal forIh As expected differences between the frequency responses of motor and sensory axons were present and best explained by reduced GKs, up-modulation ofIhand increased persistent Na(+)current,INaP(due to depolarization of RMP) in sensory axons
First and second simulator evaluations of advanced integrated display and control systems
Advanced integrated visual and control systems simulator evaluations for post-Apollo manned spacecraf
R-matrix Floquet theory for laser-assisted electron-atom scattering
A new version of the R-matrix Floquet theory for laser-assisted electron-atom
scattering is presented. The theory is non-perturbative and applicable to a
non-relativistic many-electron atom or ion in a homogeneous linearly polarized
field. It is based on the use of channel functions built from field-dressed
target states, which greatly simplifies the general formalism.Comment: 18 pages, LaTeX2e, submitted to J.Phys.
An evaluation of the spatial resolution of soil moisture information
Rainfall-amount patterns in the central regions of the U.S. were assessed. The spatial scales of surface features and their corresponding microwave responses in the mid western U.S. were investigated. The usefulness for U.S. government agencies of soil moisture information at scales of 10 km and 1 km. was ascertained. From an investigation of 494 storms, it was found that the rainfall resulting from the passage of most types of storms produces patterns which can be resolved on a 10 km scale. The land features causing the greatest problem in the sensing of soil moisture over large agricultural areas with a radiometer are bodies of water. Over the mid-western portions of the U.S., water occupies less than 2% of the total area, the consequently, the water bodies will not have a significant impact on the mapping of soil moisture. Over most of the areas, measurements at a 10-km resolution would adequately define the distribution of soil moisture. Crop yield models and hydrological models would give improved results if soil moisture information at scales of 10 km was available
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