Evangelos Hristoforou

Bio: Evangelos Hristoforou is an academic researcher from National Technical University of Athens. The author has contributed to research in topics: Amorphous solid & Magnetostriction. The author has an hindex of 27, co-authored 206 publications receiving 2577 citations. Previous affiliations of Evangelos Hristoforou include National University of Science and Technology & National Technical University.

Magnetostrictive delay lines: engineering theory and sensing applications

Abstract: A review of the engineering theory and the sensing element applications of the magnetostrictive delay line (MDL) technique is presented. The state of the art of magnetic materials and effects used in sensor design is overviewed and the operation of MDLs and their basic engineering properties are discussed. The resulting position, stress and field sensors based on this technique as well as their most significant applications are demonstrated. Finally, the industrialization process and the integration of the sensors with electronic circuitry as well as their evaluation with respect to the state of the art are discussed.

Barkhausen noise as a microstructure characterization tool

Abstract: Magnetic Barkhausen noise (mBN) is known to be related to magnetization reversal mechanisms and the underlying microstructure in magnetic materials. However, the quantitative evaluation of the material properties is hindered by the stochastic nature of the method combined with the lack of standardization. In this paper, the results of interlaboratory tests on the same series of samples are presented. Electrical steel samples have been prepared with controlled grain size (11–148 μm) and strain (0–29%) and have been characterized using the mBN technique as developed in three different laboratories. In spite of the different methodologies used, mBN is found to increase with strain and decrease with decreasing grain size, in all cases. Of special interest is the variation of the double-peaked BN envelope with the grain size, with one peak occurring in positive and the other in negative fields. The significance of the methodology used in the correct interpretation of the results for a given material is discussed.

Dewatering of microalgal cultures : a major bottleneck to algae-based fuels

Abstract: Microalgae dewatering is a major obstruction to industrial-scale processing of microalgae for biofuel prodn. The dil. nature of harvested microalgal cultures creates a huge operational cost during dewatering, thereby, rendering algae-based fuels less economically attractive. Currently there is no superior method of dewatering microalgae. A technique that may result in a greater algal biomass may have drawbacks such as a high capital cost or high energy consumption. The choice of which harvesting technique to apply will depend on the species of microalgae and the final product desired. Algal properties such as a large cell size and the capability of the microalgae to autoflocculate can simplify the dewatering process. This article reviews and addresses the various technologies currently used for dewatering microalgal cultures along with a comparative study of the performances of the different technologies.

High Performance Thermoelectric Materials: Progress and Their Applications

Abstract: Thermoelectric (TE) materials have the capability of converting heat into electricity, which can improve fuel efficiency, as well as providing robust alternative energy supply in multiple applications by collecting wasted heat, and therefore, assisting in finding new energy solutions. In order to construct high performance TE devices, superior TE materials have to be targeted via various strategies. The development of high performance TE devices can broaden the market of TE application and eventually boost the enthusiasm of TE material research. This review focuses on major novel strategies to achieve high-performance TE materials and their applications. Manipulating the carrier concentration and band structures of materials are effective in optimizing the electrical transport properties, while nanostructure engineering and defect engineering can greatly reduce the thermal conductivity approaching the amorphous limit. Currently, TE devices are utilized to generate power in remote missions, solar-thermal systems, implantable or/wearable devices, the automotive industry, and many other fields; they are also serving as temperature sensors and controllers or even gas sensors. The future tendency is to synergistically optimize and integrate all the effective factors to further improve the TE performance, so that highly efficient TE materials and devices can be more beneficial to daily lives.

Cantilever-like micromechanical sensors

Abstract: The field of cantilever-based sensing emerged in the mid-1990s and is today a well-known technology for label-free sensing which holds promise as a technique for cheap, portable, sensitive and highly parallel analysis systems. The research in sensor realization as well as sensor applications has increased significantly over the past 10 years. In this review we will present the basic modes of operation in cantilever-like micromechanical sensors and discuss optical and electrical means for signal transduction. The fundamental processes for realizing miniaturized cantilevers are described with focus on silicon- and polymer-based technologies. Examples of recent sensor applications are given covering such diverse fields as drug discovery, food diagnostics, material characterizations and explosives detection.