Converter-fed subsea motor drives

A subsea adjustable-speed motor fed via a long cable in the range of several tens of kilometers between the converter and the motor are analyzed by simulations. Due to resonance, one critical frequency range occurs where significant generation of harmonics from the inverter should be avoided. A voltage source inverter is more feasible than a current source inverter since it is easier to modify the output waveform in order to avoid resonance problems. The resistive voltage drop in the long cable reduces the air-gap torque of the motor, particularly at low frequencies. This causes a problem for the start-up of the motor due to stiction torque. A start-up strategy is envisaged which is a compromise between voltage boost, inverter current, and transformer core dimensions. In normal operation mode the inverter voltage is proportional to the frequency. An open speed loop is used which keeps the system stable for potential load variations. The results from a 1-MW full-scale system test are summarised     

Minimizing the uncertainties associated with the measurement of thermal properties by the Transient thermo-reflectance method

An approach for optimizing the transient thermo-reflectance (TTR) measurement of thermal properties is presented. The influence of the most important parameters of the system on the accuracy of the TTR measurements is investigated. An overall performance criterion is defined based on the responsivity of a given system and the thermoreflectance coefficient of the sample under test. It is shown that in order to obtain the smallest measurement uncertainty one should use a metallic absorption layer with the highest possible thermoreflectance coefficient and then compute the optimum thickness of that layer by maximizing the responsivity of the TTR system. The responsivity represents the sensitivity of the TTR method to the measurement of the thermal properties of a sample and relates the overall uncertainty of a TTR measurement to the uncertainties associated with the TTR apparatus.     

In vitro efficacy of antimicrobial-coated bladder catheters in inhibiting bacterial migration along catheter surface

Most cases of catheter-related urinary tract infection are probably caused by organisms that migrate from the urethral meatus-catheter interface along the external surface of the catheter into the bladder. To examine the ability of bladder catheters coated with minocycline and rifampin to inhibit bacterial migration along the external surface of the catheter, a novel in vitro bladder model was used. Compared with uncoated catheters, antimicrobial-coated bladder catheters significantly impeded the migration of Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Enterococcus faecalis, and Candida albicans (bacteriuria developed at a mean of 2-5 days vs. 9-34 days, respectively, after bacterial contamination of the catheter). Although production of zones of inhibition by coated catheters may provide some protection against infection, there was no correlation between the size of zones of inhibition and level of efficacy in inhibiting bacterial migration in vitro. Examination of the clinical efficacy of these antimicrobial-coated bladder catheters is prudent.     

Robust multi-objective optimization for water distribution system design using a meta-metaheuristic

The design of an urban water distribution system (WDS) is a challenging problem involving multiple objectives. The goal of robust multi-objective optimization for WDS design is to find the set of solutions which embodies an acceptable trade-off between system cost and reliability, so that the ideal solution may be selected for a given budget. In addition to satisfying consumer needs, a system must be built to accommodate multiple demand loading conditions, withstand component failures and allow surplus capacity for growth. In a developmental setting, WDS robustness becomes even more crucial, owing to the limited availability of resources, especially for maintenance. Recent optimization studies have achieved success using multi-objective evolutionary algorithms, such as the Non-dominated Sorting Genetic Algorithm II (NSGA-II). However, the multi-objective design of a large WDS within a reasonable timeframe remains a formidable problem, owing to the extremely high computational complexity of the problem. In this paper, a meta-algorithm called AMALGAM is applied for the first time to WDS design. AMALGAM uses multiple metaheuristics simultaneously in an attempt to improve optimization performance. Additionally, a Jumping-gene Genetic Algorithm (NSGA-II-JG) is also applied for the first time to WDS design. These two algorithms were tested against some other metaheuristics (including NSGA-II and a new greedy algorithm) with respect to a number of benchmark systems documented in the literature, and AMALGAM demonstrated the best performance overall, while NSGA-II-JG fared worse than the ordinary NSGA-II. Large cost savings and reliability improvements are demonstrated for a real WDS developmental case study in South Africa.     

A ubiquitous smart home for elderly

One major challenge to successful aging is the capability to preserve health, or from another perspective to avoid disease. Unfortunately, a large percentage of the elderly people are living with chronic diseases or disabilities. Home care technologies and other emerging technologies have the potential to play a major role in home-based health care approach. The advent of sensor technology, in addition to telecom industry has made this possible. The main goal of the presented research in this paper is to develop a cost-effective user-friendly telehealth system to serve the elderly and disabled people in the community. The research also aims at utilizing the state-of-the-art advances in medical instrumentation technology to establish a continuous communication link between patients and caregivers and allow physicians to offer help when needed. Hence, we are presenting here an integrated user-friendly model of a smart home which provides telemedicine for elderly at home. The general problem addressed in this paper is that of offering a smart environment which monitors the elderly continuously as he moves around at home, and sends an emergency call for help in case of an occurrence of an accident or a severe health problem. The paper focuses on implementation details and practical considerations of integrating the diverse technologies into a working system.     

SHOOTING METHOD FOR BIFURCATION ANALYSIS OF BOUNDARY VALUE PROBLEMS†

The applications of the shooting method to the bifurcation analysis of boundary value problems are discussed. A new technique for computing the double-zero singularity or the origin of the Hopf bifurcation based on this method is developed. A classical problem from chemical reaction engineering, multiple steady-states and oscillations foi reaction-diffusion in a catalyst slab, is examined to illustrate these techniques and applications.     

Vertebral hemangioma symptomatic during pregnancy. A case report and review of the literature

A simple four-tube arteries-microvessels-veins system which simulates a more realistic loading for human circulation was built using transmission line network. Hemodynamic data from literature are used in the fluid-circuit analogy, and the flow leakage and viscoelastic properties of the blood vessels have been considered. The effect of veins on the input impedance spectrum was found to be negligibly small above 0.5 Hz. The predicted input impedance spectra agree reasonably well with the published measurements both in shape and magnitude. Parametric analysis shows that the changes of vascular properties in the lower body affect the first minimum, and the changes in the upper body influence the second minimum. The blood flow in and out of kidney and liver dominates the aortic impedance from 0 to 5 Hz. Decreasing capacitance (i.e., increasing arterial stiffness due to aging), reducing the lumen area, or decreasing the length of blood vessels result in an increase in the impedance modulus, and the first minimum shift to a higher frequency which agree well with experiments. In the current model, the pressure, flow waveform, and local impedance can be predicted at any location along the circulatory tree. The characteristic of arterial pulse propagation resembles published measurements.     

Computational methods for the tubular chemical reactor

The numerical methods that have been successfully applied to the tubular reactor are here reviewed. After demonstrating the essential stiffness of the equations, the Newton-Raphson iteration and collocation methods are described for the steady state. For the calculation of transients the collocation methods can be usefully supplemented by quasilinearization.