Compensation of Induction Hetaing load edge effect by space control

Purpose - The purpose of this paper is to present a calculation optimization method that is able to achieve the best induced power profile (and subsequent temperature distribution) in a disk or billet workpiece processed by induction heating. Design/methodology/approach - A volume integral method, also known as the mutually coupled circuits method, is implemented in MatLab (R) environment to solve axial-symmetrical induction systems. It is completed with an optimization procedure based on Nelder-Mead simplex algorithm, with the goal of obtaining a specified distribution of the induced power in the load. In this way, it is possible to predict current amplitudes for implementing the so-called "zone controlled induction heating" (ZCIH) process. Findings - Some examples of calculation results are given, both for disc and billet loads. By the excitation of the inductor coils with a set of currents of appropriate amplitude and phase values, it is possible to achieve an optimized profile of induced power distributions. Originality/value - This paper validates a method to predict currents and phases in a load-inductor ZCIH system, confirming the possibility of obtaining specified induced power density distributions, according to the process requirements, e.g. for compensation of the load edge-effec

Prospective randomized study on bilateral above-knee femoropopliteal revascularization: polytetrafluoroethylene versus reversed saphenous vein.

ABSTRACT. Objective: Some controversy exists as to whether polytetrafluoroethylene (PTFE) is equivalent to reversed saphenous vein (SV) as bypass graft material for the above-knee (AK) femoropopliteal revascularization. The purpose of this study was to compare the 5-year patency rate of reversed SV and PTFE grafts in claudicant patients who underwent bilateral AK femoropopliteal revascularizations. Methods: Between January 1994 and December 1997, 51 patients (102 limbs) with bilateral disabling claudication due to superficial femoral artery occlusion were treated with SV AK femoropopliteal bypass on one limb and with PTFE AK femoropopliteal bypass on the other. They were randomly selected for sequential surgical treatment involving either SV/PTFE or PTFE/SV. Kaplan-Meier analysis was used to estimate the patency rates and various factors were analyzed to ascertain any association with revascularization failure. Results: There was no perioperative (30-day) limb loss or perioperative death. There were 5 late deaths (late survival rate: 90%). The mean follow-up was 59 months. In the SV group, 3 bypasses failed, requiring a reoperation in only one patient; in the PTFE group 8 bypasses failed leading to 5 reoperations. There was no statistically significant difference in primary “assisted” patency rate for the two grafts: 100%, 98% and 94% for SV bypasses and 96%, 84% and 84% for PTFE grafts (p = .09), after 1, 3 and 5 years, respectively. Conclusions: The overall results of this randomized study show that SV and PTFE grafts have statistically comparable patency rates when used in the AK location in claudicant patients. The use of SV does lead to fewer occlusions and reoperations, however

Recycling Construction and Demolition Residues in Clay Bricks

In recent years, the management of construction and demolition residues (CDRs) has become a major challenge for the construction industry due to the increasing volume of waste produced and its associated environmental impact. The aim of this article is to assess the effect of fine-grained fractions (<0.125 mm–0.6–0.125 mm) of construction and demolition residues, obtained by industrial sorting in a CDR processing plant in Rovigo (Italy), on the technological behavior and technical performance of clay bricks. Simulating the brickmaking process on a laboratory scale, it was appraised whether the CDR additions determined any change in the main properties of both fired and unfired bricks, taking a CDR-free brick body as a reference. The results indicated that the use of CDR is technologically feasible. It is possible to obtain, through proper crushing and sorting operations, grain-sized fractions with quite homogenous chemical and mineralogical composition. The residues did affect the compositional properties, porosity and water absorption of the clay bricks. Nevertheless, the characterization of the residual-added semi-finished and fired products highlighted their good technological and mechanical properties, which allowed them to provide performances similar to those of standard bricks manufactured with raw natural materials

Cellular and synaptic alterations in the aging brain.

The morphological and functional impairments observed in the aging brain are discussed in the framework of theoretical concepts, such as the existence of different modalities of intercellular communication and of specific trophic features in the central nervous system. The relevance of changes at the cellular level (disappearance of neuronal cell bodies and proliferation of astroglial cells) and at the synaptic level (alterations in neurotransmitter and receptor levels) is discussed. Two, non-mutually exclusive hypotheses are advanced to explain the frequent absence of correlation between neuropathological findings and functional deficits in aged patients. According to the first, the physiological reshaping of brain circuits during aging may lead to "wrong" readjustments of neural networks (e.g. due to less effective endogenous and exogenous orienting signals) causing minor morphological alterations but marked functional deficits. The second hypothesis maintains that the absence of correlation between neuropathological and functional deficits is due to the impairment of restricted neuronal populations ("pacemaker and command neurons") which play a special role in the hierarchical organization of neuronal networks. These neurons (inter alia, peptidergic neurons) may also be involved in volume transmission (diffusion of electrical and chemical signals in the extracellular fluid to reach distant targets). Moreover, the relevance of glial cells, not only as regulators of the extracellular medium but also on the basis of their trophic links with neurons, is considered. Finally, the interplay between trophic factors and therapeutical experience for the maintenance and/or recovery of an impaired function in elderly patients is discussed