Thermal Profile Measurements Research Articles

Transcutaneous Pulsed RF Energy Transfer Mitigates Tissue Heating in High Power Demand Implanted Device Applications: In Vivo and In Silico Models Results.

This article presents the development of a power loss emulation (PLE) system device to study and find ways of mitigating skin tissue heating effects in transcutaneous energy transmission systems (TETS) for existing and next generation left ventricular assist devices (LVADs). Skin thermal profile measurements were made using the PLE system prototype and also separately with a TETS in a porcine model. Subsequent data analysis and separate computer modelling studies permit understanding of the contribution of tissue blood perfusion towards cooling of the subcutaneous tissue around the electromagnetic coupling area. A 2-channel PLE system prototype and a 2-channel TETS prototype were implemented for this study. The heating effects resulting from power transmission inefficiency were investigated under varying conditions of power delivery levels for an implanted device. In the part of the study using the PLE setup, the implanted heating element was placed subcutaneously 6–8 mm below the body surface of in vivo porcine model skin. Two operating modes of transmission coupling power losses were emulated: (a) conventional continuous transmission, and (b) using our proposed pulsed transmission waveform protocols. Experimental skin tissue thermal profiles were studied for various levels of LVAD power. The heating coefficient was estimated from the porcine model measurements (an in vivo living model and a euthanised cadaver model without blood circulation at the end of the experiment). An in silico model to support data interpretation provided reliable experimental and numerical methods for effective wireless transdermal LVAD energization advanced solutions. In the separate second part of the study conducted with a separate set of pigs, a two-channel inductively coupled RF driving system implemented wireless power transfer (WPT) to a resistive LVAD model (50 Ω) to explore continuous versus pulsed RF transmission modes. The RF-transmission pulse duration ranged from 30 ms to 480 ms, and the idle time (no-transmission) from 5 s to 120 s. The results revealed that blood perfusion plays an important cooling role in reducing thermal tissue damage from TETS applications. In addition, the results analysis of the in vivo, cadaver (R1Sp2) model, and in silico studies confirmed that the tissue heating effect was significantly lower in the living model versus the cadaver model due to the presence of blood perfusion cooling effects.

Studies on thermal profile measurement and fire detection in a power supply cable of a synchrotron radiation source by Raman optical fiber distributed temperature sensor system

The paper presents the work on development and application of Raman optical fiber distributed temperature sensor (ROFDTS). ROFDTS has been used for monitoring the temperature profile and detecting the progress of unforeseen fire events anywhere in a 160 m long power supply cable (current 760 A, DC) of dipole magnets in the Indus-2 synchrotron radiation source (SRS). Indus-2 is a national facility and is being operated in round the clock mode. The sensing fiber could survive in the harsh environment of Indus-2 SRS that consists of bremsstrahlung radiation of 6.7 Rad/h, high magnetic field of 1.5 T and radio frequency (RF) field of 1.27 MV at 505.812 MHz. The fire detecting capability of ROFDTS was first tested on the mock test setup in the laboratory by artificially creating the four hot zones. Each hot zone has the width of 1.0 m in the sensing fiber at the spatial locations of 26 m, 48 m, 70 m and 92 m respectively. An audio-visual alarm was generated when the temperature of the hot zones exceeded the set temperature limit of 50 °C within 30 s of the start of the fire. Finally, ROFDTS system was deployed to measure the temperature profile of power supply cable during ‘no operation’, ‘injection’ of the electron beam current (109 mA with the energy of electrons @ 550 MeV) and at ‘normal operation’ of the electron beam current (145 mA with the energy of electrons @ 2.5 GeV) in Indus-2 SRS. The peak temperature of power cable reached from 26 °C to 44 °C from ‘no operation’ to during the ‘normal operation’ condition of the Indus-2 SRS.

Studies on Thermal Profile Measurement and Fire Detection in a Power Supply Cable of a Synchrotron Radiation Source by Raman Optical Fiber Distributed Temperature Sensor System

Studies on Thermal Profile Measurement and Fire Detection in a Power Supply Cable of a Synchrotron Radiation Source by Raman Optical Fiber Distributed Temperature Sensor System

Early Age Thermal Measurements of Soil-Cement Mixtures for Quality Control during Paving

Abstract Cementitiously stabilized soil (i.e., soil-cement) is popular among some state departments of transportation (DOTs) for subbase and base pavement layers, particularly, states with limited supplies of quality aggregates. When constructed properly, soil-cement has proven to be a well-performing and economically beneficial product for multiple DOTs; however, there is still a growing need to better characterize soil-cement properties in the laboratory and especially during construction. This need could partly be met with thermal profile measurements of hydrating soil-cement mixtures. The overall purpose of this article is to investigate the potential use of thermal measurements as a quality control tool for compacted soil-cement mixtures used in pavement layers. A compaction device, referred to as the Plastic Mold (PM) device, was central to the approach presented in this article to perform thermal measurement and unconfined compressive strength (UCS) testing on the same specimen. Based on data presented in this article, thermal profile measurements of soil-cement mixtures are feasible and have some merit as a quality control tool. Variability analysis under laboratory conditions showed measured thermal profile results were less variable or equally as variable as UCS measurements. Under field conditions, thermal profile testing was observed to be sensitive to initial material temperature, thermal device insulation, and surrounding environment temperatures. Implementation of thermal measurements into soil-cement quality control seems to be best suited as supporting information only for cases in which UCS measured by the PM device needs more explanation.

Investigation of DNA‐Binding Activities of Zinc(II) and Cobalt(II) Phthalocyanine Compounds with 3,4,5‐Trimethoxybenzyloxy Substituents

AbstractIn this study, DNA‐binding activities of previously synthesized tetrakis(3,4,5‐trimethoxybenzyloxy)‐substituted Zn(II) and Co(II) phthalocyanines (Pc4 and Pc5) have been chosen for the study. The interaction of synthesized tetrakis(3,4,5‐trimethoxybenzyloxy)‐substituted Zn(II) and Co(II) phthalocyanine compounds with CT‐DNA was investigated by using UV/Vis titrimetric method, fluorescence spectroscopy, cyclic voltammetry, thermal denaturation profile, gel electrophoresis and viscosty measurement in a Tris‐HCI buffer at pH 7.0. The results indicated that tetrakis(3,4,5‐trimethoxybenzyloxy)‐substituted Zn(II) and Co(II) phthalocyanines (Pc4 and Pc5) can interact with CT‐DNA via intercalation binding mode.

A Novel Soft Sensor for Real-Time Monitoring of the Die Melt Temperature Profile in Polymer Extrusion

Polymer extrusion is the most fundamental technique for processing polymeric materials, and its importance is increasing due to the rapid growth of worldwide demand for polymeric materials. However, the process thermal monitoring is experiencing several problems resulting in poor process diagnostics and control. Most of the existing process thermal monitoring methods in industry only provide point/bulk measurements, which are less detailed and low in accuracy. Physical thermal profile measurements across the melt flow may not be industrially compatible due to their complexity, access requirements, invasiveness, etc. Therefore, inferential thermal profile monitoring techniques are invaluable for obtaining detailed, accurate, and industrially compatible measurements and, hence, to achieve improved process control. In this paper, a novel soft sensor strategy is proposed to predict the real-time temperature profile across the die melt flow in polymer extrusion for the first time in industry or research. It is capable of determining the melt temperature at a number of die radial positions only based on six readily measurable process parameters. A comparison between the simulation results of the novel melt temperature profile prediction soft sensor and the experimental measurements showed that the soft sensor can predict the real-time melt temperature profile of the die melt flow with good accuracy. Therefore, this will offer a promising solution for making real-time melt temperature profile measurements noninvasively in polymer extrusion, and also, it should be applicable to other polymer processes only with a few modifications. Moreover, this technique should facilitate in developing an advanced process thermal control strategy.

Average Power Handling Capability of Microstrip Passive Circuits Considering Metal Housing and Environment Conditions

In this paper, the average power handling capability (APHC) of microstrip passive circuits considering the metal housing and environment conditions is investigated in detail. A systematic method is proposed for the computation of the APHC of microstrip circuits in open and enclosed metal housing configurations, typically used in microwave components. The method also yields an estimate of the maximum temperature in a microstrip circuit for a given input power. Closed-form equations accounting for external conditions, such as convection or radiation heat transfer are given to evaluate the APHC. For validation, two microstrip bandstop filters centered at 10 GHz are analyzed following the proposed model, and the results are compared with those simulated showing a good agreement. In addition, both circuits are fabricated and characterized. Thermal profile measurements are provided, confirming the predicted results. The effect of the topology layout and the electromagnetic performance on the APHC are also discussed.

Molecular basis of thermal stability in truncated (2/2) hemoglobins

BackgroundUnderstanding the molecular mechanism through which proteins are functional at extreme high and low temperatures is one of the key issues in structural biology. To investigate this phenomenon, we have focused on two instructive truncated hemoglobins from Thermobifida fusca (Tf-trHbO) and Mycobacterium tuberculosis (Mt-trHbO); although the two proteins are structurally nearly identical, only the former is stable at high temperatures. MethodsWe used molecular dynamics simulations at different temperatures as well as thermal melting profile measurements of both wild type proteins and two mutants designed to interchange the amino acid residue, either Pro or Gly, at E3 position. ResultsThe results show that the presence of a Pro at the E3 position is able to increase (by 8°) or decrease (by 4°) the melting temperature of Mt-trHbO and Tf-trHbO, respectively. We observed that the ProE3 alters the structure of the CD loop, making it more flexible. ConclusionsThis gain in flexibility allows the protein to concentrate its fluctuations in this single loop and avoid unfolding. The alternate conformations of the CD loop also favor the formation of more salt-bridge interactions, together augmenting the protein's thermostability. General significanceThese results indicate a clear structural and dynamical role of a key residue for thermal stability in truncated hemoglobins.

A design protocol for tailoring ice-templated scaffold structure

In this paper, we show, for the first time, the key link between scaffold architecture and latent heat evolution during the production of porous biomedical collagen structures using freeze-drying. Collagen scaffolds are used widely in the biomedical industry for the repair and reconstruction of skeletal tissues and organs. Freeze-drying of collagen slurries is a standard industrial process, and, until now, the literature has sought to characterize the influence of set processing parameters including the freezing protocol and weight percentage of collagen. However, we are able to demonstrate, by monitoring the local thermal events within the slurry during solidification, that nucleation, growth and annealing processes can be controlled, and therefore we are able to control the resulting scaffold architecture. Based on our correlation of thermal profile measurements with scaffold architecture, we hypothesize that there is a link between the fundamental freezing of ice and the structure of scaffolds, which suggests that this concept is applicable not only for collagen but also for ceramics and pharmaceuticals. We present a design protocol of strategies for tailoring the ice-templated scaffold structure.

Heat dissipation performance of a high-brightness LED package assembly using high-thermal conductivity filler

This paper presents a thermal analysis and experimental validation of natural convective heat transfer of a high-brightness light-emitting diode (LED) package assembly. The substrate materials used in the LED package assembly were filled and doped using boron nitride (BN) filler. The thermal conductivity of the BN-filled substrate was measured. The temperature distribution and heat flow of the LED package were assessed by thermal profile measurement using an infrared (IR) camera and thermocouples. In addition, the heat transfer process of the LED package assembly in natural convection was also simulated using the computational fluid dynamics method. The optical performance of the LED package was monitored and investigated with various filler contents. The heat conduction mechanism in the substrate was analyzed. IR thermogram showed that the BN-doped substrate could effectively lower the surface temperature of the LED package by 21.5°C compared with the traditional FR4 substrate. According to the IESNA LM 80 lifetime testing method, reduction in LED temperature can prolong the LED's lifetime by 19,000h. The optical performance of the LED package assembly was also found to be improved significantly in lighting power by 10%. As a result, the overall heat dissipation capability of the LED package to the surrounding is enhanced, which improves the LED's efficacy.

Thermal investigation of a high brightness LED array package assembly for various placement algorithms

This paper presents a thermal management analysis and experimental validation of natural convective heat transfer of a high brightness LED array package assembly in various placement algorithms. The operating conditions include thermal conductivity of the PCB, heat sink design, and LED placement design in a system module. The temperature distribution and heat flow of the LED array package are assessed by thermal profile measurement using an IR camera and thermocouples. In addition, the heat transfer process of the LED array package assembly in natural convection is also simulated using the computational fluid dynamics (CFD) method. The optical performance of the LED array is monitored and investigated in accordance with the environmental variations. The thermal distribution of a commercial high-brightness LED array product using the developed placement method is compared to that of the original design. The change in radiant flux, LED efficacy, and uniformity of illuminance is compared. The results suggest that the new placement method for a LED array can lower the individual LED surface temperature by more than 10%. As a result, the overall heat dissipating capability of the LED array to the surrounding and hence LED efficacy is improved.

Dynamic modelling of die melt temperature profile in polymer extrusion: Effects of process settings, screw geometry and material

Extrusion is one of the major methods for processing polymeric materials and the thermal homogeneity of the process output is a major concern for manufacture of high quality extruded products. Therefore, accurate process thermal monitoring and control are important for product quality control. However, most industrial extruders use single point thermocouples for the temperature monitoring/control although their measurements are highly affected by the barrel metal wall temperature. Currently, no industrially established thermal profile measurement technique is available. Furthermore, it has been shown that the melt temperature changes considerably with the die radial position and hence point/bulk measurements are not sufficient for monitoring and control of the temperature across the melt flow. The majority of process thermal control methods are based on linear models which are not capable of dealing with process nonlinearities. In this work, the die melt temperature profile of a single screw extruder was monitored by a thermocouple mesh technique. The data obtained was used to develop a novel approach of modelling the extruder die melt temperature profile under dynamic conditions (i.e. for predicting the die melt temperature profile in real-time). These newly proposed models were in good agreement with the measured unseen data. They were then used to explore the effects of process settings, material and screw geometry on the die melt temperature profile. The results showed that the process thermal homogeneity was affected in a complex manner by changing the process settings, screw geometry and material.

Analysis of Electromagnetic Fields Induced in Operation of a Wireless Fully Passive Backscattering Neurorecording Microsystem in Emulated Human Head Tissue

This paper reports on a fully passive microsystem that wirelessly records and transmits neuropotentials exclusively by means of electromagnetic backscattering techniques, affording substantially simpler circuitry and potentially safer and more reliable approach for implantable wireless neurorecording. A fundamental practical barrier for wireless brain-implantable microsystems includes heat dissipation by on-chip circuitry, which may cause permanent brain damage. Hence, measurement of thermal profiles of surrounding tissue induced by operation of wireless implants is imperative in assessing the safety of these devices. Evaluation of specific absorption rate (SAR) is especially relevant for wireless electromagnetic transmission schemes operating at microwave frequencies and directly relates to the heat generated within biological tissue media. In this study, computational and empirical methods are used to measure SAR within a human-head-equivalent phantom during operation of the embedded fully passive wireless neurorecording microsystem. The maximum average SAR, coinciding with the worst case scenario, measured within 1 g of brain tissue is $ , complying with the U.S. FCC threshold (1.6 W/kg).

A review and evaluation of melt temperature sensors for polymer extrusion

Melt temperature is one of the key variables in polymer extrusion which determines process thermal stability and hence melt quality. Therefore, melt temperature is commonly measured in polymer processing and point/bulk melt temperature measurement methods are widely used in the present industry. Some thermal profile measurement methods have also been attempted in research. This study presents a review of melt temperature measurements in polymer extrusion in research and industry, and describes the results of an experimental evaluation carried out to explore the performance of five melt temperature measurement techniques. In addition, an investigation was carried out on the fully developed melt temperature profile of a cylindrical rod die. Moreover, the existing challenges and possible future applications for extrusion thermal monitoring are discussed. The results confirmed that melt temperature varied significantly at different radial locations within the die. Point/bulk melt temperature measurements were found to provide relatively limited information on process thermal quality close to the die wall. Hence, information provided by these sensors is less representative of actual thermal conditions as they are unable to capture thermal information from the whole melt flow cross-section. Therefore, the importance of the development of industrially compatible thermal profile measurement techniques is emphasised.

In situ Silicon-Wafer Surface-Temperature Measurements Utilizing Polarized Light

An overview is presented on the activity with industrial partners to solve problems at the production sites in the semiconductor industry. Based on a survey on temperature needs and techniques in the semiconductor device fabrication industry, two target processes with the most pressing demands for in situ temperature measurements were selected: plasma etching and flash lamp annealing (FLA). A novel approach for emissivity compensated radiation thermometry was applied to sub-millisecond response measurement for FLA. The approach has features that make it suitable for in situ applications. Results of thermal profile measurements conducted on a FLA chamber are described.

Numerical simulation of thermal boundary layer profile measurement

Heat transfer rates from a surface can be determined from the slope of the temperature profile measured with a thermocouple wire traversing within a boundary layer. However, accuracy of such measurement can suffer due to flow distortion and conduction through the thermocouple wire. The present numerical study consists of two parts—a 2D simulation of flow distortion due to a cylinder in cross flow near a solid wall and a 3D simulation defined as a fin problem to calculate the thermal profile measurement error due to conduction through the thermocouple wires. Results show that the measured temperature is lower than the true temperature resulting in a 5% under-prediction of local heat transfer coefficient. A parametric study shows that low thermal conductivity thermocouple (E type) with a small wire diameter (76 micron) is desirable to reduce the measurement error in local Nusselt number.

Local Temperature Profile Measurement in Microchannels Using Temperature Sensitive Leuco-Dye Microbeads

Microfluidics has shown the ability to reproduce many of the techniques used in chemistry and biology, achieving faster and inexpensive results with smaller samples. As part of this effort towards miniaturization, the heating and cooling of samples has become an important step in many devices, especially for nucleic acid analysis. Measuring temperature profiles inside microchannels is required to verify the performance of such devices. Here we introduce a new technique to measure thermal profiles in microchannels: leuco-dye temperature sensitive microbeads, which permits fast, simple and inexpensive measurement of thermal profiles based on color, which enable its use to quickly assess temperature profiles to verify device performance, or as an educational tool for visualizing microscale heat transfer. Using the technique, we present visualization of thermal profiles and measurement of color transition lengths in microfluidic devices and compare the results with theoretical and numerical models with good a...

Thermal performance of high brightness LED array package on PCB

This paper presents a thermal analysis and experimental validation of natural convective air cooling of a high brightness 3 × 3 LED array package on a printed circuit board (PCB) during operation from 0 to 180° inclinations. Temperature distribution and heat flow of the LED package are assessed by thermal profile measurement using an IR camera and thermocouples. In addition, a design study on the thermal performance of the packaging structure is also performed. The analysis results reveal that the effect of position and inclination plays an important role in the heat dissipation of the LED package. The heat transfer process of the LED PCB package in natural convection is also modelled and simulated using computational fluid dynamics (CFD) method. The proposed thermal analytical study provides a detailed understanding of the thermal response of an open or enclosed LED array PCB unit under various operating conditions. The results provide criteria for setting up a LED array system and for adopting design features that would be beneficial to effective thermal management.

Effect of transparency within a semiconductor on emissivity mapping for thermal profile measurements of a semiconductor device

The paper reports on infra-red (IR) measurements made on silicon and gallium arsenide substrates which are transparent to IR radiation. The work showed that the measured emissivity is dependent on the wafer back-face technology, for example, a gold heat-sink or epoxy attachment. The work also indicated that the measured emissivity for the thermal mapping of a device is a function of the emitted radiation from the front, back face and layer interfaces, as well as internally reflected radiation and will be dependent on the thickness of the semiconductor wafer. Experimental work has shown that the two-temperature emissivity correction method will give a very accurate value of the total surface emissivity received from the sample.

Measurement of autoclave thermal profiles during high pressure steam de-waxing of investment shells Part 1 - Vessel profiles

Investment casting research is being carried out by the University of Birmingham, sponsored by EPSRC and a consortium of industrial companies. The programme is aimed at developing a fundamental understanding of the process, with a view to routinely producing sound, net shape castings. A key stage within the investment process is that involving the removal of wax from the unfired ceramic shell. This important process is carried out within the confines of a sealed pressure vessel, more commonly referred to as a Boilerclave*, with external pressure gauges as the only indication of what is actually happening inside the cavity. To metaphorically 'see' inside the vessel would allow the factors controlling de-wax to be characterised and controlled. This paper contains results obtained at The University of Birmingham using a specially instrumented steam autoclave that allows visual data capture, thermal and steam pressure profiles within the chamber, and thermal instrumentation of waxes and shells to be obtained. Results of thermal and pressure profiles inside the vessel body are presented and implications of these results upon the mechanism of wax removal and the effect upon ceramic shells are discussed.