This paper presents a case study for multi-variable and multimodal design optimisation of a doubly fed induction generator (DFIG) based on surrogate-model optimisation algorithm. The DFIG's winding of stator and r...
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ISBN:
(纸本)9781510825666
This paper presents a case study for multi-variable and multimodal design optimisation of a doubly fed induction generator (DFIG) based on surrogate-model optimisation algorithm. The DFIG's winding of stator and rotor are optimised to obtain higher efficiency for rewinding purposes. First, a Latin hypercube design is selected as the design of experiments to obtain sampling points. Then, the surrogate model is constructed using Kriging Model (KRG) method based on the Latin hypercube design. Finally, the particle swarm optimisation algorithm is applied in conjunction with the finite element method to achieve the machine design optimisation.
In this paper, the power allocation problem for Orthogonal frequency division multiplexing (OFDM)-based relay cognitive radio systems is investigated. An optimization power allocation algorithm is developed. In the al...
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ISBN:
(纸本)9781467384155
In this paper, the power allocation problem for Orthogonal frequency division multiplexing (OFDM)-based relay cognitive radio systems is investigated. An optimization power allocation algorithm is developed. In the algorithm, objective function is studied and simplified. The channel capacity of secondary users is maximized while keeping the total interference introduced to primary user less than a given threshold with a specified power. Compared to the optimal algorithm and the average power allocation algorithm, the proposed algorithm is close to the optimal algorithm and has a better performance than average power allocation algorithm, and has low complexity.
This study presents a new design of a planar transformer for dielectric barrier discharge (DBD). The requirements for such designs are mainly a high voltage ratio, a high voltage value at the secondary side, a specifi...
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This study presents a new design of a planar transformer for dielectric barrier discharge (DBD). The requirements for such designs are mainly a high voltage ratio, a high voltage value at the secondary side, a specific shape for industrial applications (planar shape in this case), a low volume and a high dv/dt value at the secondary side for capacitive loads. So as to propose an efficient design tool to power electronics designers, the authors propose a virtual prototyping methodology based on an optimisation algorithm and a finite element simulation software. Towards this case study, power electronics designers can use this methodology (bi-objective optimisation algorithm) to treat new designs and especially for very innovative power converters for DBD reactors. The first objective is to pre-size the planar transformer (geometrical variables). Virtual solutions are proposed on a Pareto front: the power designer can chose the best one according to specific contexts (cost, shape, volume, efficiency etc.). In a second step, the authors propose experimental results and highlight the voltage probes modelling that must be taken into account in the case of very fast transient waveforms especially for capacitive loads such as DBD reactors.
Small cell networks enhance spectrum efficiency by handling the indoor traffic of mobile networks on a frequency-reuse operation. Since most of the current mobile traffic happen in indoor, the authors introduce a prio...
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Small cell networks enhance spectrum efficiency by handling the indoor traffic of mobile networks on a frequency-reuse operation. Since most of the current mobile traffic happen in indoor, the authors introduce a prioritisation shift by imposing a limitation on the outage generated by the outdoor mobile system to the indoor small cells. The prioritisation shift consists of setting an outage probability threshold limitation on the macrocell system which is classically considered as a primary system. In this study, they consider downlink spectrum sharing between a system consisting of small cells and a macrocell with relays. The relays constitute a distributed-space-time block code (STBC) relaying for the outdoor system terminals. New closed-form expressions are derived to validate the proposed bit error rate (BER) function used in their optimisation algorithm considering STBC with unequal branch SNR. They propose a joint transmit antenna selection and power allocation which minimises the proposed BER. The proposed optimisation yields a dynamic selection of the relays with power control pertaining to the outdoor mobile terminal performance. The simulation results show that their proposal exhibits a better BER compared with the conventional Alamouti STBC with equal power allocation.
The approximation of a high-dimensional vector by a small combination of column vectors selected from a fixed matrix has been actively debated in several different disciplines. In this paper, a sampling approach based...
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ISBN:
(纸本)9781509018918
The approximation of a high-dimensional vector by a small combination of column vectors selected from a fixed matrix has been actively debated in several different disciplines. In this paper, a sampling approach based on the Monte Carlo method is presented as an efficient solver for such problems. Especially, the use of simulated annealing (SA), a metaheuristic optimization algorithm, for determining degrees of freedom (the number of used columns) by cross validation is focused on and tested. Test on a synthetic model indicates that our SA-based approach can find a nearly optimal solution for the approximation problem and, when combined with the CV framework, it can optimize the generalization ability. Its utility is also confirmed by application to a real-world supernova data set.
We study the worst-case adaptive optimization problem with budget constraint that is useful for modeling various practical applications in artificial intelligence and machine learning. We investigate the near-optimali...
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ISBN:
(纸本)9781510838819
We study the worst-case adaptive optimization problem with budget constraint that is useful for modeling various practical applications in artificial intelligence and machine learning. We investigate the near-optimality of greedy algorithms for this problem with both modular and non-modular cost functions. In both cases, we prove that two simple greedy algorithms are not near-optimal but the best between them is near-optimal if the utility function satisfies pointwise submodularity and pointwise cost-sensitive submodularity respectively. This implies a combined algorithm that is near-optimal with respect to the optimal algorithm that uses half of the budget. We discuss applications of our theoretical results and also report experiments comparing the greedy algorithms on the active learning problem.
Sparse representations over redundant learned dictionaries have shown to produce high quality results in various image processing tasks. An important characteristic of a learned dictionary is the mutual coherence of d...
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ISBN:
(纸本)9781479999897
Sparse representations over redundant learned dictionaries have shown to produce high quality results in various image processing tasks. An important characteristic of a learned dictionary is the mutual coherence of dictionary that affects its generalization performance and the optimality of sparse codes generated from it. In this paper, we present a dictionary learning model equipped with coherence regularization. For this model, two novel dictionary optimization algorithms based on group-wise minimization of inter- and intra-coherence penalties are proposed. Experimental results demonstrate that the proposed algorithms improve the generalization properties and sparse approximation performance of the trained dictionary compared to several incoherent dictionary learning methods.
Storm identification and tracking based on weather radar data are essential to nowcasting and severe weather warning. A new two-dimensional storm identification method simultaneously seeking in two directions is propo...
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Storm identification and tracking based on weather radar data are essential to nowcasting and severe weather warning. A new two-dimensional storm identification method simultaneously seeking in two directions is proposed, and identification results are used to discuss storm tracking algorithms. Three modern optimization algorithms (simulated annealing algorithm, genetic algorithm and ant colony algorithm) are tested to match storms in successive time intervals. Preliminary results indicate that the simulated annealing algorithm and ant colony algorithm are effective and have intuitionally adjustable parameters, whereas the genetic algorithm is unsatisfaetorily constrained by the mode of genetic operations Experiments provide not only the feasibility and characteristics of storm tracking with modern optimization algorithms, but also references for studies and applications in relevant fields.
Synchronous machines are the most widely used form of generators in electrical power systems. Identifying the parameters of these generators in a non-invasive way is very challenging because of the inherent non-linear...
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Synchronous machines are the most widely used form of generators in electrical power systems. Identifying the parameters of these generators in a non-invasive way is very challenging because of the inherent non-linearity of power station performance. This study proposes a parameter identification method using a stochastic optimisation algorithm that is capable of identifying generator, exciter and turbine parameters using actual network data. An eighth order generator/turbine model is used in conjunction with the measured data to develop the objective function for optimisation. The effectiveness of the proposed method for the identification of turbo-generator parameters is demonstrated using data from a recorded network transient on a 178 MVA steam turbine generator connected to the UK's national grid.
We present Cyclades, a general framework for parallelizing stochastic optimization algorithms in a shared memory setting. Cyclades is asynchronous during model updates, and requires no memory locking mechanisms, simil...
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ISBN:
(纸本)9781510838819
We present Cyclades, a general framework for parallelizing stochastic optimization algorithms in a shared memory setting. Cyclades is asynchronous during model updates, and requires no memory locking mechanisms, similar to Hog-??wild!-type algorithms. Unlike HOGWILD!, Cyclades introduces no conflicts during parallel execution, and offers a black-box analysis for provable speedups across a large family of algorithms. Due to its inherent cache locality and conflict-??free nature, our multi-core implementation of Cyclades consistently outperforms Hogwild!-type algorithms on sufficiently sparse datasets, leading to up to 40% speedup gains compared to Hogwild!, and up to 5× gains over asynchronous implementations of variance reduction algorithms.
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