2,328 research outputs found
Computational alternatives to obtain time optimal jet engine control
Two computational methods to determine an open loop time optimal control sequence for a simple single spool turbojet engine are described by a set of nonlinear differential equations. Both methods are modifications of widely accepted algorithms which can solve fixed time unconstrained optimal control problems with a free right end. Constrained problems to be considered have fixed right ends and free time. Dynamic programming is defined on a standard problem and it yields a successive approximation solution to the time optimal problem of interest. A feedback control law is obtained and it is then used to determine the corresponding open loop control sequence. The Fletcher-Reeves conjugate gradient method has been selected for adaptation to solve a nonlinear optimal control problem with state variable and control constraints
Millisecond single-molecule localization microscopy combined with convolution analysis and automated image segmentation to determine protein concentrations in complexly structured, functional cells, one cell at a time
We present a single-molecule tool called the CoPro (Concentration of
Proteins) method that uses millisecond imaging with convolution analysis,
automated image segmentation and super-resolution localization microscopy to
generate robust estimates for protein concentration in different compartments
of single living cells, validated using realistic simulations of complex
multiple compartment cell types. We demonstrates its utility experimentally on
model Escherichia coli bacteria and Saccharomyces cerevisiae budding yeast
cells, and use it to address the biological question of how signals are
transduced in cells. Cells in all domains of life dynamically sense their
environment through signal transduction mechanisms, many involving gene
regulation. The glucose sensing mechanism of S. cerevisiae is a model system
for studying gene regulatory signal transduction. It uses the multi-copy
expression inhibitor of the GAL gene family, Mig1, to repress unwanted genes in
the presence of elevated extracellular glucose concentrations. We fluorescently
labelled Mig1 molecules with green fluorescent protein (GFP) via chromosomal
integration at physiological expression levels in living S. cerevisiae cells,
in addition to the RNA polymerase protein Nrd1 with the fluorescent protein
reporter mCherry. Using CoPro we make quantitative estimates of Mig1 and Nrd1
protein concentrations in the cytoplasm and nucleus compartments on a
cell-by-cell basis under physiological conditions. These estimates indicate a
4-fold shift towards higher values in concentration of diffusive Mig1 in the
nucleus if the external glucose concentration is raised, whereas equivalent
levels in the cytoplasm shift to smaller values with a relative change an order
of magnitude smaller. This compares with Nrd1 which is not involved directly in
glucose sensing, which is almost exclusively localized in the nucleus under
high and..
The emergence of magnetic flux through a partially ionised solar atmosphere
We present results from 2.5D numerical simulations of the emergence of magnetic flux from the upper convection zone through the photosphere and chromosphere into the corona. Certain regions of the solar atmosphere are at sufficiently low temperatures to be only partially ionised, in particular the lower chromosphere. This leads to Cowling resistivities orders of magnitude larger than the Coulomb values, and thus to anisotropic dissipation in Ohm’s law. This also leads to localised low magnetic Reynolds numbers (R m < 1). We find that the rates of emergence of magnetic field are greatly increased by the partially ionised regions of the model atmosphere, and the resultant magnetic field is more diffuse. More importantly, the only currents associated with the magnetic field to emerge into the corona are aligned with the field, and thus the newly formed coronal field is force-free
Alternatives for Jet Engine Control
Approaches are developed as alternatives to current design methods which rely heavily on linear quadratic and Riccati equation methods. The main alternatives are discussed in two broad categories, local multivariable frequency domain methods and global nonlinear optimal methods
Ergonomic standards for pedestrian areas for disabled people: literature review and consultations
As part of the project for the Transport and Road Research
Laboratory concerned with the development of design guidance for
pedestrian areas and footways to satisfy the needs of disabled
and elderly people, a thorough examination of the literature was
required. In addition the literature search was to be
complemented by a wide-ranging series of discussions with local
authorities, organisations representing the interests of elderly
and disabled people, and other interested agencies. This Working
Paper sets out the findings of this exercise.
The objective of the literature review and the consultations was
to identify the key impediments for elderly and disabled people
when using pedestrian areas and footways. The current guidelines
and standards relating to footways, pedestrianised areas and
access to buildings were to be identified and their adequacy
commented upon, as were the conflicts such recommendations raise
between various groups of disabled people and with able-bodied
people. The consultations were intended to provide greater
insights into what the literature highlighted, and to suggest
possible solutions.
The literature review produced over 400 key references and a list
of 35 impediments. A more detailed examination of the literature
and the consultations reduced this list to six key impediments
namely: parking; public transport waiting areas; movement
distances; surface conditions; ramps, and information provision.
The type and scale of problem created by the above impediments
for various groups of disabled and elderly people are discussed,
together with their measurement and assessment. The type and
adequacy of existing design standards and guidance relating to
these impediments are also outlined
Ergonomic Standards for Pedestrian Areas for Disabled People: Methodology and Sample Identification
This project is a TRRL research contract, the aim of which is to
produce guidance on the design of pedestrian areas and footways
for elderly and disabled people. The first part of the project
was a literature review and consultation exercise, the objective
of which was to identify key impediments for investigation. The
second part of the project involved the detailed survey work on
the key impediments. This Working Paper reports upon the
development of the second part of the project and, in particular,
upon the identification of the sample of disabled people to be
used in the detailed interview and observation work.
The sample identification involved contacting some 3000 disabled
people listed in official disability registers, and 250 ablebodied
people via on-street interviews. From the disabled sample
approximately 500 people were interviewed in order to find out
more about their disability and to assess the usefulness of a
preliminary disability categorisation system; their activity
rate; problems they experience in using pedestrian areas and
footways; and their willingness to take part in further stages of
the study.
From the interviews, a sample of people in each of the revised
categories, together with samples of the elderly and the ablebodied,
were selected for an observation phase in which those
involved were observed completing a movement distance exercise,
and using different types of pedestrian facility, in central
Leeds
Economic Standards for Pedestrian Areas for Disabled People: Results from Observation Work
1.1.1 The Institute for Transport Studies was invited by the
Transport and Road Research Laboratory to submit a research
proposal, with costs, aimed at establishing suitable "Ergonomic
Standards for Pedestrian Areas for Disabled People". The project
commenced on 1st July, 1986 and was split into two parts, with
part one involving four months' work over the period to 31st
December, 1986 and part two finishing on 30th April, 1988.
1.1.2
The -objectives of the study laid down in the design
brief by the Transport and Road Research Laboratory were:
a) To produce a guide to good practice for the design and
maintenance of footways and pedestrianised areas;
b) To provide, where possible, recommended standards for design
and maintenance.
The good practice guide and the recommended standards were to be
primarily aimed at disabled people and the elderly, but the
requirements of the able-bodied were also to be considered, as
were conflicts between the needs of different groups of user.
The economic implications of implementation and maintenance were
also to be detailed.
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