Computation of the Modes of Elliptic Waveguides with a Curvilinear 2D Frequency-Domain Finite-Difference Approach

A scalar Frequency-Domain Finite-Difference approach to the mode computation of elliptic waveguides is presented. The use of an elliptic cylindrical grid allows us to take exactly into account the curved boundary of the structure and a single mesh has been used both for TE and TM modes. As a consequence, a high accuracy is obtained with a reduced computational burden, since the resulting matrix is highly sparse

A free from local minima algorithm for training regressive MLP neural networks

In this article an innovative method for training regressive MLP networks is presented, which is not subject to local minima. The Error-Back-Propagation algorithm, proposed by William-Hinton-Rummelhart, has had the merit of favouring the development of machine learning techniques, which has permeated every branch of research and technology since the mid-1980s. This extraordinary success is largely due to the black-box approach, but this same factor was also seen as a limitation, as soon more challenging problems were approached. One of the most critical aspects of the training algorithms was that of local minima of the loss function, typically the mean squared error of the output on the training set. In fact, as the most popular training algorithms are driven by the derivatives of the loss function, there is no possibility to evaluate if a reached minimum is local or global. The algorithm presented in this paper avoids the problem of local minima, as the training is based on the properties of the distribution of the training set, or better on its image internal to the neural network. The performance of the algorithm is shown for a well-known benchmark.Comment: 9 pages, 4 figures, theoretical wor

A Free From Local Minima Algorithm for Training Regressive MLP Neural Networks

In this article an innovative method for training regressive MLP networks is presented, which is not subject to local minima. The Error-Back-Propagation algorithm, proposed by William-Hinton-Rummelhart, has had the merit of favoring the development of machine learning techniques, which has permeated every branch of research and technology since the mid-1980s. This extraordinary success is largely due to the black-box approach, but this same factor was also seen as a limitation, as soon more challenging problems were approached. One of the most critical aspects of the training algorithms was that of local minima of the loss function, typically the mean squared error of the output on the training set. In fact, as the most popular training algorithms are driven by the derivatives of the loss function, there is no possibility to evaluate if a reached minimum is local or global. The algorithm presented in this paper avoids the problem of local minima, as the training is based on the properties of the distribution of the training set, or better on its image internal to the neural network. The performance of the algorithm is shown for a well-known benchmark

Design of a Low-Cost Microstrip Directional Coupler with High Coupling for a Motion Detection Sensor

A coupled-line coupler based on the asymmetric cascade connection of two coupled line sections is used to achieve a high coupling factor using low-cost material and technology in the X frequency band, and its performance is compared with a standard quarter-wave, coupled-line coupler, showing an increase in the coupling factor of about 3 dB. The proposed coupler can be effectively used in a Doppler motion detection sensor, due to its strong coupling and relatively high isolation. The coupler is designed through a simple, yet rigorous, equivalent circuital model. Then,anoptimizationprocedurewasperformedusingthecommercialsoftwareAnsysHFSSinorder to compensate for losses and second order effects. A prototype of the designed coupler was realized, and the measured data show very good agreement with simulations

A Static Hybrid Renewable Energy System for Off-Grid Supply

The electrification of the rural areas of the planet has become one of the greatest challenges for sustainability. In fact, it would be the key to guaranteeing development for the poorest areas of the planet from which most of the raw material for the food market derives. The paradigm of centralized production is not applicable in these territories, because the distribution network would involve unjustifiable costs. For this reason, many studies have been carried out to ensure that the energy supply (specifically electricity) for off-grid utilities is maintained, in order to guarantee energy autonomy while reducing dependence on specialist assistance for the management of the system. In this work, a hybrid system (HRES) is proposed that combines the exploitation of solar radiation, wind power, and biomass using static devices, in order to improve the system’s availability and limit the cost of operation and maintenance. The aim of the study is to define promising lines of research, which can improve the sustainability of renewable harvesting systems to supply off-grids users

Is there an association between leukoaraiosis volume and diabetes?

Objectives: The relation between white matter loss (WML) and diabetes is still debated. The aim of this study was to investigate the correlation between typical WML— and diabetesrelated magnetic resonance imaging (MRI) findings in a cohort of patients scheduled for carotid endarterectomy (CEA). Materials and methods: Ninety-three consecutive patients (mean age 71 ± 9 years; male 71) were included in a single-centre retrospective study. All the patients underwent MRI as baseline evaluation prior to CEA. A neuroradiologist blinded to the presence of risk factors calculated WML volume and number of lesions on FLAIR images using a semi-automated segmentation technique. Receiver operating characteristics analysis was performed to search for any association between WML volume and the number of WML lesions. The Mann—Whitney tests were used to determine significant WML differences between diabetic and non-diabetic patients. Logistic regression analysis was performed to evaluate the potential association of other variables. Results: The prevalence of diabetes was 20.4% (n = 19). WML volume and number of WML lesions were significantly associated with diabetes (P = 0.001). A statistically significant difference in WML volume was found between diabetic and non-diabetic patients (P < 0.0001). Only diabetes, among all the investigated variables (WML volume, CAD status, age, smoking status, gender, hypertension, hyperlipidemia, diabetes) was significantly associated with WML (P = 0.0001)

Syncope and Cannabis: hypervagotonia from chronic abuse? A case report and literature review

Background: Cannabis is the most consumed drug worldwide and number of users is increasing, particularly among youth. Moreover, cannabis potential therapeutic properties have renewed interest to make it available as a treatment for a variety of conditions. Albeit rarely, cannabis consumption has been associated with cardiovascular diseases such as arrhythmias, myocardial infarction (MI) and potentially sudden death. Case presentation: A 24-year-old woman presented to the emergency department sent by her cardiologist because of a recent finding of a 16 seconds asystole on the implantable loop recorder (ILR) she implanted 7 months before for recurrent syncopes. She declared that she is a heavy cannabis user (at least 5 cannabis-cigarette per day, not mixed up with tobacco, for no less than 12 years) and all syncopes occurred shortly after cannabis consumption. After a collective discussion with the heart team, syncope unit, electrophysiologists and toxicologist, we decided to implant a dual chamber pacemaker with a rate response algorithm due to the high risk of trauma of the syncopal episodes. 24 months follow-up period was uneventful. Conclusions: Cannabis cardiovascular effects are not well known and, although rare, among these we find ischemic episodes, tachyarrhythmias, symptomatic sinus bradycardia, sinus arrest, ventricular asystole and possibly death. Because of cannabis growing consumption both for medical and recreational purpose, cardiovascular diseases associated with cannabis use may become more and more frequent. In the light of the poor literature, we believe that cannabis may produce opposite adverse effects depending on the duration of the habit. Acute administration increases sympathetic tone and reduces parasympathetic tone; conversely, with chronic intake an opposite effect is observed: repetitive dosing decreases sympathetic activity and increases parasympathetic activity. Clinicians should be aware of the increased risk of cardiovascular complications associated with cannabis use and should investigate its consumption especially in young patients presenting with cardiac dysrhythmias

comment on shore et al association between hyperglycemia at admission during hospitalization for acute myocardial infarction and subsequent diabetes insights from the veterans administration cardiac care follow up clinical study diabetes care 2014 37 409 418

We read with great interest the recently published article by Shore et al. (1) that addresses the important issue of admission hyperglycemia during hospitalization for acute myocardial infarction (AMI). The authors measured the prevalence of admission hyperglycemia in a very large cohort of AMI patients without known diabetes and examined its association with new evidence of diabetes in the 6 months following hospitalization. Diagnostic codes for diabetes, outpatient prescriptions for glucose-lowering medications, and/or HbA1c ≥6.5% during or after the index hospitalization were used for

Optimal Design of an Inductive MHD Electric Generator

In 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

Multiphysics Analysis of a Thermo Acoustic MHD Inductive Generator

This paper fits in the multi-physics analysis of an innovative conceptual design of Magneto-Hydrodynamic (MHD) inductive generator, coupled with a Thermo-Acoustic (TA) resonator. The thermo-acoustic effect occurs when an intense gradient of temperature is present along the axial direction of a duct containing a gas. Such effect allows the heat to be statically converted into mechanical energy of vibration. If the gas is ionized and the charges of opposite sign are separated into two clouds, an alternate electric current is associated to the thermo-acoustic vibration. That current, in its turn, can induce an electromotive force into a magnetically coupled coil. In this way, a thermo-electric conversion is performed, without solid moving parts or matter transport. A FEM analysis has been performed to assess the suitability of the complete energy transformation chain. In particular, the possibility that the charge carriers are involved in the vibration motion is investigated. An acoustic analysis has been done, in a glass tube containing a ionized gas, in order to study the velocity profiles within the duct in presence of viscous and thermal effects. Then, a multiphysics simulation has been performed by using the same geometry, by coupling the acoustic module with the electrostatic module, and the particle tracing module, in order to study the behavior of the unbalanced charge carriers when they are subject to a vibration and to an electric force, for a given set of design parameters