8,143 research outputs found
Microcomputer based controller for the Langley 0.3-meter Transonic Cryogenic Tunnel
Flow control of the Langley 0.3-meter Transonic Cryogenic Tunnel (TCT) is a multivariable nonlinear control problem. Globally stable control laws were generated to hold tunnel conditions in the presence of geometrical disturbances in the test section and precisely control the tunnel states for small and large set point changes. The control laws are mechanized as four inner control loops for tunnel pressure, temperature, fan speed, and liquid nitrogen supply pressure, and two outer loops for Mach number and Reynolds number. These integrated control laws have been mechanized on a 16-bit microcomputer working on DOS. This document details the model of the 0.3-m TCT, control laws, microcomputer realization, and its performance. The tunnel closed loop responses to small and large set point changes were presented. The controller incorporates safe thermal management of the tunnel cooldown based on thermal restrictions. The controller was shown to provide control of temperature to + or - 0.2K, pressure to + or - 0.07 psia, and Mach number to + or - 0.002 of a given set point during aerodynamic data acquisition in the presence of intrusive geometrical changes like flexwall movement, angle-of-attack changes, and drag rake traverse. The controller also provides a new feature of Reynolds number control. The controller provides a safe, reliable, and economical control of the 0.3-m TCT
A Doubly Nudged Elastic Band Method for Finding Transition States
A modification of the nudged elastic band (NEB) method is presented that
enables stable optimisations to be run using both the limited-memory
quasi-Newton (L-BFGS) and slow-response quenched velocity Verlet (SQVV)
minimisers. The performance of this new `doubly nudged' DNEB method is analysed
in conjunction with both minimisers and compared with previous NEB
formulations. We find that the fastest DNEB approach (DNEB/L-BFGS) can be
quicker by up to two orders of magnitude. Applications to permutational
rearrangements of the seven-atom Lennard-Jones cluster (LJ7) and highly
cooperative rearrangements of LJ38 and LJ75 are presented. We also outline an
updated algorithm for constructing complicated multi-step pathways using
successive DNEB runs.Comment: 13 pages, 8 figures, 2 table
It's about time: Analysing simplifying assumptions for modelling multi-step pathways in systems biology.
Thoughtful use of simplifying assumptions is crucial to make systems biology models tractable while still representative of the underlying biology. A useful simplification can elucidate the core dynamics of a system. A poorly chosen assumption can, however, either render a model too complicated for making conclusions or it can prevent an otherwise accurate model from describing experimentally observed dynamics. Here, we perform a computational investigation of sequential multi-step pathway models that contain fewer pathway steps than the system they are designed to emulate. We demonstrate when such models will fail to reproduce data and how detrimental truncation of a pathway leads to detectable signatures in model dynamics and its optimised parameters. An alternative assumption is suggested for simplifying such pathways. Rather than assuming a truncated number of pathway steps, we propose to use the assumption that the rates of information propagation along the pathway is homogeneous and, instead, letting the length of the pathway be a free parameter. We first focus on linear pathways that are sequential and have first-order kinetics, and we show how this assumption results in a three-parameter model that consistently outperforms its truncated rival and a delay differential equation alternative in recapitulating observed dynamics. We then show how the proposed assumption allows for similarly terse and effective models of non-linear pathways. Our results provide a foundation for well-informed decision making during model simplifications
Transforum system innovation towards sustainable food. A review
Innovations in the agri-food sector are needed to create a sustainable food supply. Sustainable food supply requires unexpectedly that densely populated regions remain food producers. A Dutch innovation program has aimed at showing the way forward through creating a number of practice and scientific projects. Generic lessons from the scientific projects in this program are likely to be of interest to agricultural innovation in other densely populated regions in the world. Based on the executed scientific projects, generic lessons across the whole innovation program are derived. We found that the agricultural sector requires evolutionary rather than revolutionary changes to reshaping institutions. Measuring sustainability is possible against benchmarks and requires stakeholder agreement on sustainability values. Results show the importance of multiple social views and multiple stakeholder involvement in agricultural innovation. Findings call for flexible goal rather than process-oriented management of innovation. Findings also emphasise the essential role of profit in anchoring sustainable development in business. The results agree with concepts of evolutionary innovation. We conclude that there is no single best solution to making the agri-food sector more sustainable densely populated areas, but that the combination of a range of solutions and approaches is likely to provide the best way forward
Multifingered robot hand robot operates using teleoperation
The purpose of research on anthropomorphic dextrous manipulation is to develop
anthropomorphic dextrous robot hand which approximates the versatility and
sensitivity of the human hand by teleoperation methods that will communicate in
master– slave manners. Glove operates as master part and multi-fingered hand as
slave. The communication medium between operator and multi-fingered hand is via
KC-21 Bluetooth wireless modules. Multi-fingered hand developed using 5 volt,
298:1 gear ratio micro metal dc motors which controlled using L293D motor drivers
and actuator controlled the movement of robot hand combined with dextrous human
ability by PIC18F4520 microcontroller. The slave components of 5 fingers designed
with 15 Degree of Freedom (DOF) by 3 DOF for each finger. Fingers design, by
modified IGUS 07-16-038-0 enclosed zipper lead E-Chain® Cable Carrier System,
used in order to shape mimic as human size. FLEX sensor, bend sensing resistance
used for both master and slave part and attached as feedback to the system, in order
to control position configuration. Finally, the intelligence, learning and experience
aspects of the human can be combined with the strength, endurance and speed of the
robot in order to generate proper output of this project
Recent Progress in Some Aircraft Technologies
The book describes the recent progress in some engine technologies and active flow control and morphing technologies and in topics related to aeroacoustics and aircraft controllers. Both the researchers and students should find the material useful in their work
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