Influence of different heat transfer models on therapeutic temperature prediction and heat-induced damage during magnetic hyperthermia.

Magnetic hyperthermia regulates the therapeutic temperature within a specific range to damage malignant cells after exposing the magnetic nanoparticles inside tumor tissue to an alternating magnetic field. The therapeutic temperature of living tissues can be generally predicted using Pennes' bio-heat equation after ignoring both the inhomogeneity of biological structure and the microstructural responses. Although various of the bio-heat transfer models proposed in literature fix these shortages, there is still a lack of a comprehensive report on investigating the discrepancy for different models when applied in the magnetic hyperthermia context. This study compares four different bio-heat equations in terms of the therapeutic temperature distribution and the heat-induced damage situation for a proposed geometric model, which is established based on computed tomography images of a tumor bearing mouse. The therapeutic temperature is also used as an index to evaluate the effect of two key relaxation times for the phase lag behavior on bio-heat transfer. Moreover, this work evaluates the effects of two blood perfusion rates on both the treatment temperature and the cumulative equivalent heating minutes at 43 °C. Numerical analysis results reveal that relaxation times for phase-lag behavior as well as the porosity for living tissues directly affect the therapeutic temperature variation and ultimately the thermal damage for the malignant tissue during magnetic hyperthermia. The dual-phase-lag equation can be converted into Pennes' equation and simple-phase-lag equation when relaxation times meet specific conditions during the process of heat transfer. In addition, different blood perfusion rates can result in an amplitude discrepancy for treatment temperature, but this parameter does not change the characteristics of thermal propagation during therapy.

Nondestructive inspection of metal specimen using tone-burst vibro-acoustography.

Even though the pulse-echo ultrasonic technique is commonly used for the assessment of metal structures, it has some inherent limitations. Vibro-acoustography (VA) is a relatively new ultrasonic technique which has demonstrated a great potential in revealing defects in objects, however it is traditionally used to analyze the integrity of specimens made of low-stiffness materials. This work presents the evaluation of the performance of VA technique for the inspection of a steel structure, which was manufactured with defects of known geometry on its inner surface. All the inspection process was done automatically, from the data acquisition to the image processing for characterizing the defects. Experimental results show that VA was able to identify and characterize even the smallest defects in the structure, with a diameter of 2 mm. In addition, the results show that VA was able to characterize the artificial defects in the steel structure with almost the same errors as the traditional pulse-echo method, which indicates a potential use of VA in the inspection of materials with high mechanical stiffness.

Unified dead-time compensation structure for SISO processes with multiple dead times.

This paper proposes a dead-time compensation structure for processes with multiple dead times. The controller is based on the filtered Smith predictor (FSP) dead-time compensator structure and it is able to control stable, integrating, and unstable processes with multiple input/output dead times. An equivalent model of the process is first computed in order to define the predictor structure. Using this equivalent model, the primary controller and the predictor filter are tuned to obtain an internally stable closed-loop system which also attempts some closed-loop specifications in terms of set-point tracking, disturbance rejection, and robustness. Some simulation case studies are used to illustrate the good properties of the proposed approach.

Estimation of pressure-particle velocity impedance measurement uncertainty using the Monte Carlo method.

The pressure-particle velocity (PU) impedance measurement technique is an experimental method used to measure the surface impedance and the absorption coefficient of acoustic samples in situ or under free-field conditions. In this paper, the measurement uncertainty of the the absorption coefficient determined using the PU technique is explored applying the Monte Carlo method. It is shown that because of the uncertainty, it is particularly difficult to measure samples with low absorption and that difficulties associated with the localization of the acoustic centers of the sound source and the PU sensor affect the quality of the measurement roughly to the same extent as the errors in the transfer function between pressure and particle velocity do.

Conception of a test bench to generate known and controlled conditions of refrigerant mass flow.

Refrigerant compressor performance tests play an important role in the evaluation of the energy characteristics of the compressor, enabling an increase in the quality, reliability, and efficiency of these products. Due to the nonexistence of a refrigerating capacity standard, it is common to use previously conditioned compressors for the intercomparison and evaluation of the temporal drift of compressor performance test panels. However, there are some limitations regarding the use of these specific compressors as standards. This study proposes the development of a refrigerating capacity standard which consists of a mass flow meter and a variable-capacity compressor, whose speed is set based on the mass flow rate measured by the meter. From the results obtained in the tests carried out on a bench specifically developed for this purpose, it was possible to validate the concept of a capacity standard.