Memory metal actuator

A mechanical actuator can be constructed by employing a plurality of memory metal actuator elements in parallel to control the amount of actuating force. In order to facilitate direct control by digital control signals provided by a computer or the like, the actuating elements may vary in stiffness according to a binary relationship. The cooling or reset time of the actuator elements can be reduced by employing Peltier junction cooling assemblies in the actuator

On chip thermoelectric microcoolers

The present work reports the fabrication and characterization of a planar Peltier microcooler on a flexible substrate. The microcooler was fabricated on flexible Kapton© polyimide substrate, 12 µm in thickness, using Bi2Te3 and Sb2Te3 thermoelectric elements deposited by thermal co-evaporation. The cold area of the device is cooled using four pairs of thermoelectric elements, connected in series with aluminum/nickel contacts. Flexible substrates add uncommon mechanical properties to the composite filmsubstrate and enable their integration with many novel types of electronic devices. Films were deposited by coevaporation of Bismuth and Tellurium or Antimony and Tellurium to obtain Bi2Te3 or Sb2Te3 compounds, respectively. The performance of Peltier microcooler is analyzed by infrared image microscopy, on still-air and under vacuum conditions, and the temperature difference between the cold side and the hot side of the device is recorded and it’s comparable with literature available for Peltier microcoolers on rigid substrates.Agencia de Inovação (MPYROM) and Portuguese Foundation for Science and Technology (SFRH/BD/18142/2004)

Control of the deposition ratio of Bi2Te3 and Sb2Te3 in a vacuum evaporator for fabrication of Peltier elements

This article reports the main problem and the corresponding solution of the co-evaporation of Bi2Te3 and Sb2Te3 films for the fabrication of Peltier elements. This main problem consists in the control of the deposition rates of the two elements: Bi or Sb and Te, which have very different vapor pressures. The control of the deposition ratio was achieved by means of a PID controller, which permitted the fabrication of thin-film Peltier elements that produce a temperature gradient in the order of 2C between their hot and cold junctions, when measured at free air conditions.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/18142/2004.Agencia de Inovação (MPYROM)

Configurable DC current leads, with Peltier elements

There is interest in decreasing the thermal load to the cryogenic environment from the current leads. The cryogenic load is challenging both at the design current, as well as at part load operation, when the current is reduced or zero. In this paper we explore the combination of a Peltier elements and a novel concept of configurable current lead. The use of Peltier element reduces the cryogenic load by about 25%. The configurable concept is based on the use of multiple heat exchangers that allows the optimization of current leads when operating at various currents. When used together, Peltier/configurable current lead allows the reduction of the cryogenic load by a factor of 4 in low current/idle conditions. We also explore the transient operation of the current leads, as well as overload capacity.

IMC customer-based perception: strategic antecedents and consequences on post-purchase customer behaviour

Last decades Integrated Marketing Communications (IMC) have been mainly analysed from a managerial perspective, overlooking the customer opinion. Thus, this research studies IMC customer-based perception, its strategic antecedents and consequences on post-purchase customer behaviour (satisfaction, word-of-mouth recommendations, and repurchase intention), from a multi-country perspective. The structural equation modelling and multi-group analysis are based on the customers´ survey data in Belarus and Spain. The results suggest that technology orientation positively affects IMC, and, customer orientation does not. IMC positively affects customer satisfaction, which in turn positively impacts on WOM and repurchase intention. WOM does not influence on repurchase intention. IMC directly affects WOM and repurchase intention in Spain and does not in Belarus, which is the significant country difference

Sub-Hz line width diode lasers by stabilization to vibrationally and thermally compensated ULE Fabry-Perot cavities

We achieved a 0.5 Hz optical beat note line width with ~ 0.1 Hz/s frequency drift at 972 nm between two external cavity diode lasers independently stabilized to two vertically mounted Fabry-Perot (FP) reference cavities. Vertical FP reference cavities are suspended in mid-plane such that the influence of vertical vibrations to the mirror separation is significantly suppressed. This makes the setup virtually immune for vertical vibrations that are more difficult to isolate than the horizontal vibrations. To compensate for thermal drifts the FP spacers are made from Ultra-Low-Expansion (ULE) glass which possesses a zero linear expansion coefficient. A new design using Peltier elements in vacuum allows operation at an optimal temperature where the quadratic temperature expansion of the ULE could be eliminated as well. The measured linear drift of such ULE FP cavity of 63 mHz/s was due to material aging and the residual frequency fluctuations were less than 40 Hz during 16 hours of measurement. Some part of the temperature-caused drift is attributed to the thermal expansion of the mirror coatings. High-frequency thermal fluctuations that cause vibrations of the mirror surfaces limit the stability of a well designed reference cavity. By comparing two similar laser systems we obtain an Allan instability of 2*10-15 between 0.1 and 10 s averaging time, which is close to the theoretical thermal noise limit.Comment: submitted to Applied Physics

Thermodynamics of Thermoelectric Phenomena and Applications

Fifty years ago, the optimization of thermoelectric devices was analyzed by considering the relation between optimal performances and local entropy production. Entropy is produced by the irreversible processes in thermoelectric devices. If these processes could be eliminated, entropy production would be reduced to zero, and the limiting Carnot efficiency or coefficient of performance would be obtained. In the present review, we start with some fundamental thermodynamic considerations relevant for thermoelectrics. Based on a historical overview, we reconsider the interrelation between optimal performances and local entropy production by using the compatibility approach together with the thermodynamic arguments. Using the relative current density and the thermoelectric potential, we show that minimum entropy production can be obtained when the thermoelectric potential is a specific, optimal value

Longitudinal spin Seebeck coefficient: heat flux vs. temperature difference method

The determination of the longitudinal spin Seebeck effect (LSSE) coefficient is currently plagued by a large uncertainty due to the poor reproducibility of the experimental conditions used in its measurement. In this work we present a detailed analysis of two different methods used for the determination of the LSSE coefficient. We have performed LSSE experiments in different laboratories, by using different setups and employing both the temperature difference method and the heat flux method. We found that the lack of reproducibility can be mainly attributed to the thermal contact resistance between the sample and the thermal baths which generate the temperature gradient. Due to the variation of the thermal resistance, we found that the scaling of the LSSE voltage to the heat flux through the sample rather than to the temperature difference across the sample greatly reduces the uncertainty. The characteristics of a single YIG/Pt LSSE device obtained with two different setups was $(1.143\pm0.007)\cdot 10^{-7}$ Vm/W and $(1.101\pm0.015)\cdot 10^{-7}$ Vm/W with the heat flux method and $(2.313\pm0.017)\cdot 10^{-7}$ V/K and $(4.956\pm0.005)\cdot 10^{-7}$ V/K with the temperature difference method. This shows that systematic errors can be considerably reduced with the heat flux method.Comment: PDFLaTeX, 10 pages, 6 figure