11,750 research outputs found
Benchmarking and optimisation of Simulink code using Real-Time Workshop and Embedded Coder for inverter and microgrid control applications
When creating software for a new power systems control or protection device, the use of auto-generated C code via MATLAB Simulink Real-Time Workshop and Embedded Coder toolboxes can be a sensible alternative to hand written C code. This approach offers the benefits of a simulation environment, platform independence and robust code. This paper briefly summarises recent experiences with this coding process including the pros and cons of such an approach. Extensive benchmarking activities are presented, together with descriptions of simple (but non-obvious) optimisations made as a result of the benchmarking. Examples include replacement of certain Simulink blocks with seemingly more complex blocks which execute faster. "S functions" are also designed for certain key algorithms. These must be fully "in-lined" to obtain the best speed performance. Together, these optimisations can lead to an increase in execution speed of more than 1.4x in a large piece of auto-generated C code. An example is presented, which carries out Fourier analysis of 3 signals at a common (variable) frequency. The overall speed improvement relative to the baseline is 2.3x, of which more than 1.4x is due to non-obvious improvements resulting from benchmarking activities. Such execution speed improvements allow higher frame rates or larger algorithms within inverters, drives, protection and control applications
Increasing security of supply by the use of a local power controller during large system disturbances
This paper describes intelligent ways in which distributed generation and local loads can be controlled during large system disturbances, using Local Power Controllers. When distributed generation is available, and a system disturbance is detected early enough, the generation can be dispatched, and its output power can be matched as closely as possible to local microgrid demand levels. Priority-based load shedding can be implemented to aid this process. In this state, the local microgrid supports the wider network by relieving the wider network of the micro-grid load. Should grid performance degrade further, the local microgrid can separate itself from the network and maintain power to the most important local loads, re-synchronising to the grid only after more normal performance is regained. Such an intelligent system would be a suitable for hospitals, data centres, or any other industrial facility where there are critical loads. The paper demonstrates the actions of such Local Power Controllers using laboratory experiments at the 10kVA scale
Romantic Partnerships and the Dispersion of Social Ties: A Network Analysis of Relationship Status on Facebook
A crucial task in the analysis of on-line social-networking systems is to
identify important people --- those linked by strong social ties --- within an
individual's network neighborhood. Here we investigate this question for a
particular category of strong ties, those involving spouses or romantic
partners. We organize our analysis around a basic question: given all the
connections among a person's friends, can you recognize his or her romantic
partner from the network structure alone? Using data from a large sample of
Facebook users, we find that this task can be accomplished with high accuracy,
but doing so requires the development of a new measure of tie strength that we
term `dispersion' --- the extent to which two people's mutual friends are not
themselves well-connected. The results offer methods for identifying types of
structurally significant people in on-line applications, and suggest a
potential expansion of existing theories of tie strength.Comment: Proc. 17th ACM Conference on Computer Supported Cooperative Work and
Social Computing (CSCW), 201
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Characteristics of the surface soil ecosystem: Linkage to understanding soil dynamic functions
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Optimizing Pulsar Timing Arrays to Maximize Gravitational Wave Single Source Detection: a First Cut
Pulsar Timing Arrays (PTAs) use high accuracy timing of a collection of low
timing noise pulsars to search for gravitational waves in the microhertz to
nanohertz frequency band. The sensitivity of such a PTA depends on (a) the
direction of the gravitational wave source, (b) the timing accuracy of the
pulsars in the array and (c) how the available observing time is allocated
among those pulsars. Here, we present a simple way to calculate the sensitivity
of the PTA as a function of direction of a single GW source, based only on the
location and root-mean-square residual of the pulsars in the array. We use this
calculation to suggest future strategies for the current North American
Nanohertz Observatory for Gravitational Waves (NANOGrav) PTA in its goal of
detecting single GW sources. We also investigate the affects of an additional
pulsar on the array sensitivity, with the goal of suggesting where PTA pulsar
searches might be best directed. We demonstrate that, in the case of single GW
sources, if we are interested in maximizing the volume of space to which PTAs
are sensitive, there exists a slight advantage to finding a new pulsar near
where the array is already most sensitive. Further, the study suggests that
more observing time should be dedicated to the already low noise pulsars in
order to have the greatest positive effect on the PTA sensitivity. We have made
a web-based sensitivity mapping tool available at http://gwastro.psu.edu/ptasm.Comment: 14 pages, 3 figures, accepted by Ap
The Heider balance - a continuous approach
The Heider balance (HB) is investigated in a fully connected graph of
nodes. The links are described by a real symmetric array r(i,j), i,j=1,...,N.
In a social group, nodes represent group members and links represent relations
between them, positive (friendly) or negative (hostile). At the balanced state,
r(i,j)r(j,k)r(k,i)>0 for all the triads (i,j,k). As follows from the structure
theorem of Cartwright and Harary, at this state the group is divided into two
subgroups, with friendly internal relations and hostile relations between the
subgroups. Here the system dynamics is proposed to be determined by a set of
differential equations. The form of equations guarantees that once HB is
reached, it persists. Also, for N=3 the dynamics reproduces properly the
tendency of the system to the balanced state. The equations are solved
numerically. Initially, r(i,j) are random numbers distributed around zero with
a symmetric uniform distribution of unit width. Calculations up to N=500 show
that HB is always reached. Time to get the balanced state varies with the
system size N as N^{-1/2}. The spectrum of relations, initially narrow, gets
very wide near HB. This means that the relations are strongly polarized. In our
calculations, the relations are limited to a given range around zero. With this
limitation, our results can be helpful in an interpretation of somestatistical
data.Comment: 9 pages, 4 figures. Int. J. Mod. Phys. C (2005), in prin
Supersymmetric Galileons
Galileon theories are of considerable interest since they allow for stable
violations of the null energy condition. Since such violations could have
occurred during a high-energy regime in the history of our universe, we are
motivated to study supersymmetric extensions of these theories. This is carried
out in this paper, where we construct generic classes of N=1 supersymmetric
Galileon Lagrangians. They are shown to admit non-equivalent stress-energy
tensors and, hence, vacua manifesting differing conditions for violating the
null energy condition. The temporal and spatial fluctuations of all component
fields of the supermultiplet are analyzed and shown to be stable on a large
number of such backgrounds. In the process, we uncover a surprising connection
between conformal Galileon and ghost condensate theories, allowing for a deeper
understanding of both types of theories.Comment: 41 pages, v2: added a referenc
Integrated electrical and mechanical modelling of integrated-full-electric-propulsion systems
Integrated Full Electric Propulsion (IFEP) systems are the subject of much interest at present. Current research is focused on analysing and improving aspects of subsystem and system performance. However, there is a great need to look more widely at the `multi-physics' problem of characterising the dynamic interactions between the electrical and mechanical systems. This paper will discuss the changing nature of modelling and simulation to aid research into IFEP systems, outlining the alternative angle taken by the Advanced Marine Electrical Propulsion Systems (AMEPS) project to characterise and investigate electrical-mechanical system interactions. The paper will describe this approach and highlight the unique challenges associated with the problem, discussing the suitable methods that will be adopted to address these challenges. Finally, an overview of the present and future research opportunities facilitated via the AMEPS project will be presented
Emotional Strategies as Catalysts for Cooperation in Signed Networks
The evolution of unconditional cooperation is one of the fundamental problems
in science. A new solution is proposed to solve this puzzle. We treat this
issue with an evolutionary model in which agents play the Prisoner's Dilemma on
signed networks. The topology is allowed to co-evolve with relational signs as
well as with agent strategies. We introduce a strategy that is conditional on
the emotional content embedded in network signs. We show that this strategy
acts as a catalyst and creates favorable conditions for the spread of
unconditional cooperation. In line with the literature, we found evidence that
the evolution of cooperation most likely occurs in networks with relatively
high chances of rewiring and with low likelihood of strategy adoption. While a
low likelihood of rewiring enhances cooperation, a very high likelihood seems
to limit its diffusion. Furthermore, unlike in non-signed networks, cooperation
becomes more prevalent in denser topologies.Comment: 24 pages, Accepted for publication in Advances in Complex System
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