IMEKO Event Proceedings

Page 787 of 855 Results 7861 - 7870 of 8545

Nieves Medina
THERMAL EXPANSION COEFFICIENT OF WATER FOR VOLUMETRIC CALIBRATION

This paper describes an accurate determination for the water thermal expansion coefficient starting from CIPM water density equation. This thermal expansion coefficient, as it is determined, is to be used in the volume determination according to the volumetric method.

Jacek Gogól
THERMAL ISSUES IN MACHINE TOOLS AND COORDINATE MEASURING MACHINE SIMILARITIES AND DIFFERENCES.

Thermal issues are relatively well developed and described in machine tools and their development is quite rapid in recent decades. This is related to increased awareness of the impact of thermal conditions on the accuracy and efficiency of their work and the increased requirements of users (up to 75% of the overall geometrical errors of machined workpieces can be induced by the effects of temperatures). There is a large stock of published research and case studies aimed at compensation and reduction of thermal error of machine tools.
Branch of coordinate measuring machine (CMM) is strongly associated with the machine tool industry. There are a lot of convergence in approach to this theme in both subject groups. Both in the construction of machine tools and measuring machines as the key point of interest is the influence of various physical phenomena on the behavior of the executive point, in the case of measuring machines is the end of the measuring head, in the case of machine tools is a tool centre point (TCP). Considerable amount of research on the effects of thermal phenomena in the case of machine tools is carried out without taking into account the cutting forces, which also conforms research approach in both concerned areas. An important difference, however, is the fact that the compensation of thermal deformation in machine tools must be made immediately during work, if we want to improve the geometric parameters of the workpiece, which involves the introduction of some actuators, or correction of the trajectory in real time. While the result of work of the measurement machine are stored data that can be corrected or processed after the process of measuring and correction does not make any material actuator. Order of magnitude of precision in the case of machine tools and CMM is also different.
Thermal phenomena associated with measuring machines are relatively well developed in the case of steady thermal state, and the uniform temperature gradient. Mathematical models are described, compensation systems have been developed. There are imeko_proceedings concerned with selected aspects of the measuring machine work, or selected components that generate heat inside or outside of the machine structure. However problem of modeling of the whole machine and studies of thermal effects, and timevarying or locally occurring phenomenon ,based on numerical methods is relatively poorly studied. This probably results from the fact that both numerical methods and hardware have developed enough to address this issue only in recent decades. Important here is the economic aspect (the cost of computing hardware and software), and the performance parameters, which allow the calculation of the real-time close to the real-time or made in acceptable period of time post factum.

Francisco Santos, Rafael Cantalice, Raimundo Freire, Will Almeida, Elmar Melcher
THERMAL MICROSENSOR FOR APPLICATION IN RADIOMETER

In this paper presents two microsensors structures compatible with microelectronic technologies that are analyzed for application in radiometers. The first structure is formed by one resistor that is made by doping a monocrystalline silicon substrate with boron. The second is a polysilicon resistor doped with phosphorous, over a silicon dioxide (SiO2). The analysis is made by mathematical modeling of these devices, numeric simulation and graphics to obtain the better thermal-electrical characteristic of microsensor material. We choose the best microsensor structure with the increase performance of the system and with time decrease of sensor thermal response in relation the conventional manufacture for application in incident solar radiation measurement.

P. Cova, N. Delmonte, F. Giuliani, M. Citterio, S. Latorre, A. Lanza, M. Lazzaroni
Thermal modeling and characterization of power converters for LHC power supplies

Power supplies for LHC experiments require DC-DC power converters able to work in very hostile environment. The APOLLO collaboration, funded by the Italian Istituto Nazionale di Fisica Nucleare (INFN), aims to study dedicated topologies and to design, build and test demonstrators, developing the needed technology for the industrialization phase.
Besides the presence of radiation and magnetic fields, thermal specifications are particularly stringent in the working environment. In order to have the wanted features in terms of reliability and availability during the experimental activity, these power electronics circuits must be cooled by specifically designed water heat sinks, and an accurate thermal design is mandatory in order to guarantee safe and reliable operation.
In this paper thermal characterization is used for tuning a coupled thermo-fluid-dynamic 3D numerical model, for both the water heat sink and the whole system. Based on this model an optimized water heat sink was designed and fabricated. Thermal characterization of the power converter demonstrator in different operating conditions shows good agreement with simulation results.

Romeo Ciobanu, José Francisco Blanco Villalba, Thomas Schreiner, Bogdan Tamba
Thermal Simulation of Biological Tissues with Magnetite Microinsertions under Microwave Energy in Support of Chemo-Hyperthermal Delivery

This paper deals with the investigations of biological tissues with magnetite insertions through computer simulation and measurements in support of chemo-hyperthermal delivery. Modeling of microwave-thermal effects in tissues, under different clinical specifications, in relation with magnetic nanoassemblies features is taken into account to correlate the thermal effect of microwave with the thermal effect in the volume under irradiation. Simulation of the tissues was performed in CST Microwave Studio in the presence and absence of insertions. It has been observed that there is a very beneficial effect on the uniformity of the thermal effect in the tissue, in the presence of the inserts, due to the much better thermal conductivity of these materials beside the tissues.

T. Katsumata, K. Morita, A. Okabe, H. Aizawa, S. Komuro, T. Morikawa
THERMALLY EXCITED LUMINESCENCE FROM RARE-EARTH DOPED SiO2 FOR FIBER-OPTIC THERMOMETER

Thermally excited luminescence from rare-earth element doped SiO2 fibers were studied for the fiber-optic thermometer application in high temperature. Thermal radiation similar to the black body radiation was observed in visible light region from the SiO2 fibers doped with Y, La, Ce, Pr, Eu, Tb and Lu. Visible light radiation peaks due to f-f transitions of rare-earth ions were clearly observed in the Nd, Dy, Er, Ho, Tm and Yb doped SiO2 fibers. Intensity ratio of thermal radiation at different wavelength is suitable for the highly sensitive temperature measurement. The hybridization of fluorescent thermometry and thermal radiation thermometry is suggested to extend the temperature range and increase the temperature resolution.

T. Adjarov
THERMO COMPENSATED CONDUCTIVITY MEASURING CELL

The water analytic methods, based on the conductivity measurements are in the field of the physico-chemistry, called conductometrie. Its main task is the defining the material quality, but also quantity via soluble materials. One important element in this hardware is the conductivity measuring device and especially the conductivity cell.

J. Vogel, H.-J. Feige, J. Saupe, G. Grützner, J. Grimm
THERMO-MECHANICAL MATERIAL CHARACTERIZATION OF PHTOTORESISTS WITH HIGH ASPECT RATIO

MEMS made of photosensitive polymers offer new functionalities and applications in the micro world. Additionally to the new materials and advanced technologies the analysis of the thermo-mechanical material properties is required to ensure reliability and lifetime. Under this point of view, an uniaxial micro tensile measuring system has been developed to determine stress-strain-curves, Young’s modulus or Poisson’s ratio. The results will be shortly compared with those of Dynamic-Mechanical Analysis (DMA).

Krzysztof Konopka
Thermocouple Dynamic Errors Correction for Instantaneous Temperature Measurements in Induction Heating

The most commonly used thermometer to measure high temperatures in metallurgy is the thermocouple, but because of its long response time it can be used mainly for measuring time-averaged temperatures. Research on steel wire patenting using inductive heating required instantaneous temperature values. Pyrometers or thermographic cameras could be used, however they are generally expensive, and temperature measurements are not always reliable due to differing emissivities. In described case expensive infrared thermometers could be replaced by cheap thermocouple provided that dynamic errors were corrected. Correction algorithm would not increase the total cost of the measuring system as no additional hardware is required. Correction algorithm was implemented in LabVIEW. The time constant was determined experimentally. Experiments were carried out to examine improvement in response time of thermocouple with correction algorithm.

L. D’Acquisto, A. Normanno, G. Pitarresi, A. M. Siddiolo
THERMOELASTIC SIGNAL PROCESSING USING AN FFT LOCK-IN BASED ALGORITHM ON EXTENDED SAMPLED DATA

A fast infrared scanner is used to acquire the thermoelastic effect induced temperature changes along a line on the surface of cyclically loaded tensile samples. The raster scanning movement of the single detector allows the sampling of temperature versus time. This data are then post-processed by means of a lock-in algorithm coupled with 1D and 2D FFT analyses in order to filter out the thermoelastic signal from the noisy measured signal. A data extension algorithm is proposed which uses the information from different acquired frames to extend the data sampling window. The whole signal processing setup is evaluated on experimental data with successful results, proposing a potential tool for low cost Thermoelastic Stress Analysis.

Page 787 of 855 Results 7861 - 7870 of 8545