442 research outputs found

    Responsivity and noise equivalent power of a single cold-electron bolometer

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    We have developed a single-pixel capacitively coupled Cold-Electron Bolometer (CEB) and characterized it in the current-biased regime. The most attractive feature of the CEB is effective electron self-cooling of the absorber, which leads to a lower bolometer noise and higher dynamic range. The bolometer responsivity was measured by determining the voltage response to an applied power through the absorber from a heating current, modulated at frequencies from 35 Hz to 2 kHz. The optimum responsivity of 1.5 7 10 V/W was measured at a modulation frequency of 35 Hz. The noise equivalent power (NEP) was subsequently obtained from the estimated bolometer noise voltage with respect to the measured bolometer responsivity. The NEP of better 2 7 10 W/Hz was obtained for modulation frequencies greater than 100 Hz. The background power and the bolometer time constant were also estimated from the experimental results. The photon-noise-limited operation of CEB will dominate for a signal power of 10 fW and higher at frequency 80 GHz and higher. 10 ‚ąí18 1/

    ATTITUDE FORMATION, USE OF LIBRARY RESOURCES, AND PERCEIVED ACADEMIC PERFORMANCE OF STUDENTS IN PRIVATE UNIVERSITIES IN IBADAN

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    ABSTRACT The research delved into the attitude of postgraduate students when it comes to research and studying and the use of library resources. The study reveals that some postgraduate students are cumbered with many thoughts and think of the best way to ensure they balance their academic needs and family needs. The researcher talked about time management at some point to encourage postgraduate students to schedule their time appropriately to maximize research and family time. The researcher made some conclusions and recommendations at the end of the research

    Affective issues in learning technologies: emotional responses to technology and technology's role in supporting socio-emotional skills

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    This paper focuses on some of the author's research studies over the past thirty years and places these in a wider context to reflect on research into affective issues in learning technologies over this period, and to consider whether and how the issues uncovered by research have changed as technologies have developed over time. Three issues are given particular attention: firstly the reasons for learners' use or lack of use of technologies for their learning; secondly adult learners' attitudes towards using technology for learning and thirdly how technology might support socio-emotional development and expression in children. The discussion of these issues is framed by two of the author's research projects. For the first two issues this is an early study of students' perceptions and attitudes towards using computers for tutorial learning in 1980. The factors that influenced the students' use of the computer tutorials are discussed (including access, assessment and anxiety about using computers) and also the extent to which some of these factors persist for many learners using (or not using) technologies today. The discussion of the third issue draws on a series of studies conducted in the 1990s to investigate whether educational technology could support children and young people's emotional expression and communication and development of socio-emotional skills. Finally the paper considers how these kinds of issues have been taken forward and how they are represented in contemporary research and suggests that trust is an important factor in using learning technologies

    Effective Electron Microrefrigeration by SIN Tunnel Junctions with Advanced Geometry of Electrodes and Normal Metal Traps

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    We demonstrate effective electron cooling of the normal metal strip by superconductor-insulator-normal metal (SIN) tunnel junctions. The improvement was achieved by two methods: first by using an advanced geometry of the superconducting electrodes for more effective removal of the quasiparticles; and second, by adding a normal metal trap just near the cooling junctions. With simple cross geometry and without normal metal traps, the decrease in electron temperature is 56 mK. With the advanced geometry of the superconducting electrodes, the decrease in electron temperature is 129 mK. With the addition of the normal metal traps, the decrease in electron temperature is 197 mK

    Ti-TiO2-Al normal metal-insulator-superconductor tunnel junctions fabricated in direct-write technology

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    We present a novel Ti- based direct- write technology for fabricating Ti - TiO2 - Al tunnel junctions for bolometer and thermometry applications. The goal of our research is to develop simple and efficient technology for fabricating SIS tunnel junctions between Ti and Al with TiO2 as an insulating barrier. The key point of this technology is the deposition of a Ti film as a base electrode and deposition of an Al electrode after oxidation of the Ti. This approach allows one to realize any geometry of the tunnel junctions and of the absorber with no limitation related to the area of the junctions or the thickness of the absorber. In particular, a very thin and completely flat absorber can be created with no bending parts, which is not possible using the shadow evaporation technique or standard trilayer technology. Besides, the proposed new approach does not require one- cycle evaporation for deposition of tunnel junctions which gives us more freedom in the geometry of the counter- electrodes. The junctions are to be used for bolometer applications, such as the fabrication of microwave receivers for sensitive measurements in new generation telescopes, e. g. CLOVER and BOOMERANG projects including polarization cosmic microwave background radiation measurements, and the OLIMPO balloon telescope project which is dedicated to measuring the Sunyaev - Zeldovich effect in clusters of galaxies. A s the first step, SIN tunnel junctions have been fabricated and characterized

    Affective issues in learning technologies: emotional responses to technology and technology's role in supporting socio-emotional skills

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    This paper focuses on some of the author's research studies over the past thirty years and places these in a wider context to reflect on research into affective issues in learning technologies over this period, and to consider whether and how the issues uncovered by research have changed as technologies have developed over time. Three issues are given particular attention: firstly the reasons for learners' use or lack of use of technologies for their learning; secondly adult learners' attitudes towards using technology for learning and thirdly how technology might support socio-emotional development and expression in children. The discussion of these issues is framed by two of the author's research projects. For the first two issues this is an early study of students' perceptions and attitudes towards using computers for tutorial learning in 1980. The factors that influenced the students' use of the computer tutorials are discussed (including access, assessment and anxiety about using computers) and also the extent to which some of these factors persist for many learners using (or not using) technologies today. The discussion of the third issue draws on a series of studies conducted in the 1990s to investigate whether educational technology could support children and young people's emotional expression and communication and development of socio-emotional skills. Finally the paper considers how these kinds of issues have been taken forward and how they are represented in contemporary research and suggests that trust is an important factor in using learning technologies

    La Caldera de hundimiento de Vallehermoso Isla de La Gomera (Canarias).

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    Durante la realizaci√≥n del Proyecto MAGNA a escala 1:25.000 de la isla de La Gomera (Islas Canarias), se ha identificado una caldera de colapso en el √°rea de Vallehermoso (hojas 73-81 Agulo y 73-82 Hermigua). La caldera presenta una forma casi circular con un di√°metro de 2.4 Km aproximadamente. Su g√©nesis puede, en principio, ser atribuida a un brusco y repentino vaciado de una c√°mara magm√°tica s√°lica, dando lugar al hundimiento del techo. Este magma s√°lico es el responsable de la formaci√≥n traqui-fonol√≠tica (cone-sheets). La caldera est√° delimitada por fracturas escalonadas con desarrollo de importantes brechastect√≥nicas y rellenada por tobas y brechas pirocl√°sticas (¬Ņignimbr√≠ticas?) y por abundantes facies diferentes de debris-avalanche. Posteriormente al hundimiento, en las zonas de borde de la caldera, se han desarrollado intrusiones s√°licas con morfolog√≠a de pitones, domos, etc. Su novedad geol√≥gica dentro del marco de la isla de La Gomera, nos ha impulsado a redactar esta nota previa, que posteriormente, ser√° seguida de una publicaci√≥n m√°s detallada

    Cold-Electron Bolometer

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    On-Chip Cooling by Heating with Superconducting Tunnel Junctions

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    Heat management and refrigeration are key concepts for nanoscale devices operating at cryogenic temperatures. The design of an on-chip mesoscopic refrigerator that works thanks to the input heat is presented, thus realizing a solid state implementation of the concept of cooling by heating. The system consists of a circuit featuring a thermoelectric element based on a ferromagnetic insulator-superconductor tunnel junction (N-FI-S) and a series of two normal metal-superconductor tunnel junctions (SINIS). The N-FI-S element converts the incoming heat in a thermovoltage, which is applied to the SINIS, thereby yielding cooling. The cooler's performance is investigated as a function of the input heat current for different bath temperatures. We show that this system can efficiently employ the performance of SINIS refrigeration, with a substantial cooling of the normal metal island. Its scalability and simplicity in the design makes it a promising building block for low-temperature on-chip energy management applications.Comment: 7 pages, 6 figure
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