1,721,062 research outputs found
A Training Algorithm for Locally Recurrent Neural Networks Based on the Explicit Gradient of the Loss Function
Full text linkIn this paper, a new algorithm for the training of Locally Recurrent Neural Networks (LRNNs) is presented, which aims to reduce computational complexity and at the same time guarantee the stability of the network during the training. The main feature of the proposed algorithm is the capability to represent the gradient of the error in an explicit form. The algorithm builds on the interpretation of Fibonacci's sequence as the output of an IIR second-order filter, which makes it possible to use Binet's formula that allows the generic terms of the sequence to be calculated directly. Thanks to this approach, the gradient of the loss function during the training can be explicitly calculated, and it can be expressed in terms of the parameters, which control the stability of the neural network
Laparoscopic management of nonparasitic splenic cysts.
No full textNon-parasitic cysts are an infrequent disease of the spleen. Most likely congenital in their origin, epithelial splenic cysts require surgical treatment if enlarged or symptomatic. The aim of this study was to assess the impact of the laparoscopic technique in the management of splenomegaly due to cystic disease. From July 2001 to September 2002 4 patients underwent laparoscopic splenectomy in our department for symptomatic enlarged non-parasitic splenic cysts. Cystic lesions were evaluated by ultrasonography, CT scan and magnetic resonance of the abdomen. The choice of total laparoscopic splenectomy according to the "hanged spleen" procedure was conditioned by the technical difficulty of performing conservative treatment due to the site of the upper pole of the enlarged lesions, adherent to the diaphragm in 3 cases, and by the presence of multiple trabeculated splenic cysts in 1 case. Laparoscopy was always completed and all patients obtained relief of their symptoms. When conservative treatment such as partial splenectomy or decapsulation may jeopardize the good outcome of the operation, the management of nonparasitic splenic cysts can be successfully achieved by total laparoscopic splenectomy
Optimization of a power line communication system to manage electric vehicle charging stations in a smart grid
Full text linkIn this paper, a procedure is proposed to design a power line communication (PLC) system to perform the digital transmission in a distributed energy storage system consisting of fleets of electric cars. PLC uses existing power cables or wires as data communication multicarrier channels. For each vehicle, the information to be transmitted can be, for example: the models of the batteries, the level of the charge state, and the schedule of charging/discharging. Orthogonal frequency division multiplexing modulation (OFDM) is used for the bit loading, whose parameters are optimized to find the best compromise between the communication conflicting objectives of minimizing the signal power, maximizing the bit rate, and minimizing the bit error rate. The off-line design is modeled as a multi-objective optimization problem, whose solution supplies a set of Pareto optimal solutions. At the same time, as many charging stations share part of the transmission line, the optimization problem includes also the assignment of the sub-carriers to the single charging stations. Each connection between the control node and a charging station has its own frequency response and is affected by a noise spectrum. In this paper, a procedure is presented, called Chimera, which allows one to solve the multi-objective optimization problem with respect to a unique frequency response, representing the whole set of lines connecting each charging station with the central node. Among the provided Pareto solutions, the designer will make the final decision based on the control system requirements and/or the hardware constraints
Two geometries for alternate liquid metal MHD disk generator
No full textA quasi-static electric generator is presented and discussed. The quasi-static nature means that no solid moving part is envisaged, and the operating fluid remains contained within the device. More precisely, the generator is a liquid-metal MHD device activated by a pressure vibration that causes the liquid metal to oscillate in a DC magnetic field, giving rise to an electromotive force. Due to the high conductivity of the liquid metal, the induced electromotive force causes an alternating current circulating in the liquid metal. The liquid metal performs as a primary winding of a transformer, which is coupled with a secondary coil, wrapped in a way that it is co-axial with the liquid metal flow and connected to the electrical load. Alternate pressure can be provided by a wide range of processes, opening the possibility of using the proposed generator for harvesting energy from several renewable primary sources
Uso selettivo o routinario della colangiografia intraoperatoria durante colecistectomia laparoscopica.
No full textSimulink model of an iductive MHD generator
No full textThis paper deals with the study of the analytical model of an inductive MHD generator. In the proposed inductive generator the plasma is produced by means of a periodical non-equilibrium ionization, and an external electrical field segregates the charge carriers contained in the plasma, obtaining two electrically unbalanced flows. The time variation of the charge density makes the ions current time-dependent, allowing the power transmission by magnetic induction, rather than by electrical contact. In this work, a mono-dimensional Simulink model is described with the aim to perform a preliminary dimensioning of this generator. It is shown that the simulations are in good agreement with the expected behavior of the generator and the proposed generation system could be effective for industrial applications
Optimal Design of an Inductive MHD Electric Generator
Full text linkIn this paper, the problem of optimizing the design of an inductive Magneto-Hydro-Dynamic (MHD) electric generator is formalized as a multi-objective optimization problem where the conflicting objectives consist of maximizing the output power while minimizing the hydraulic losses and the mass of the apparatus. In the proposal, the working fluid is ionized with periodical pulsed discharges and the resulting neutral plasma is unbalanced by means of an intense DC electrical field. The gas is thus split into two charged streams, which induce an electromotive force into a magnetically coupled coil. The resulting generator layout does not require the use of superconducting coils and allows you to manage the issues related to the conductivity of the gas and the corrosion of the electrodes, which are typical limits of the MHD generators. A tailored multi-objective optimization algorithm, based on the Tabu Search meta-heuristics, has been implemented, which returns a set of Pareto optimal solutions from which it is possible to choose the optimal solution according to further applicative or performance constraints
Performance analysis of an inductive MHD generator
No full textIn this paper, an inductive MHD generator is proposed, which aims to overcome the typical drawbacks of the conventional MHD generators, such as the need to operate at high temperatures and have superconducting coils for the generation of the external magnetic field. The conceptual idea and the finite elements model are described
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