The Experts below are selected from a list of 213 Experts worldwide ranked by ideXlab platform
T. Sander-thömmes - One of the best experts on this subject based on the ideXlab platform.
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SQUID measurements of remanent magnetisation in refillable 3He spin-filter cells (SFC)
Physica B-condensed Matter, 2007Co-Authors: V. Hutanu, A. Rupp, T. Sander-thömmesAbstract:Abstract A strong influence of external magnetic fields on the relaxation time constant T1 of glass cells serving as reservoirs for polarised 3He, observed for various alkali metal-coated cells made of different glass types, was initially associated with the presence of a large number of ferromagnetic clusters on the glass surface. Later experiments showed the presence of the so-called “T1 hysteresis” phenomenon with a similar distinctiveness also in uncoated cells made of pure synthetic quartz glass. It suggests that the origin of such a relaxation is a macroscopic magnetisation in the bulk of the cell. We present the results of a multi-SQUID system investigation on magnetised and non-magnetised quartz glass cells, Cs coated as well as bare wall, to be used as neutron spin filters at HMI Berlin. The presence of a macroscopic remanent magnetic moment in the cells after their exposition to external magnetic fields has been experimentally shown. More than 80% of the remanent magnetic moment of the magnetised cells was found to be concentrated in the region of the glass valves. SQUID measurements reveal the existence of some remanent magnetisation in all valve parts and also in the Vacuum Grease, but most magnetic are the plastic parts and the O-ring. Different valve and sealing types have been compared in order to find the less magnetisable one.
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SQUID measurements of remanent magnetisation in refillable 3He spin-filter cells (SFC)
Physica B: Condensed Matter, 2007Co-Authors: V. Hutanu, A. Rupp, T. Sander-thömmesAbstract:A strong influence of external magnetic fields on the relaxation time constant T1 of glass cells serving as 3He neutron spin filters, observed for different glass types in alkali metal coated cells, was initially associated with the presence of a large number of ferromagnetic clusters on the glass surface. Later experiments showed the presence of the so called T1 hysteresis phenomenon with a similar distinctiveness also in uncoated cells made of pure synthetic quartz glass. It suggests that the origin of such relaxation is a macroscopic magnetisation in the bulk material of the cell. We present the results of a multi SQUID system investigation on magnetised and non magnetised quartz glass cells, Cs coated as well as bare wall, to be used as neutron spin filters at HMI Berlin. The presence of a macroscopic remanent magnetic moment in the cells after their exposition to external magnetic fields has been experimentally shown. More than 80 of the remanent magnetic moment of the magnetised cells was found to be concentrated in the region around the glass valves. SQUID measurements reveal the existence of some remanent magnetisation in all valve parts and also in the Vacuum Grease, but most magnetic are the plastic parts and the O ring. Different valve and sealing types has been compared in order to find less magnetisable on
Shefali Dubey - One of the best experts on this subject based on the ideXlab platform.
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Field performance evaluation of a newly developed PM2.5 sampler at IIT Kanpur
Science of The Total Environment, 2011Co-Authors: Tarun Gupta, Jaiprakash, Shefali DubeyAbstract:Abstract In order to meet the challenges of growing air pollution for a developing nation and to measure the ambient fine particles (PM 2.5 , particles having aerodynamic diameter less than 2.5 μm) on routine basis an air sampler was designed, developed and evaluated in the field. The impactor removes particles greater than 2.5 μm from the air stream via impacting them onto a Vacuum Grease substrate and finer particles get eventually collected on a backup filter. Various impactor nozzles with conical geometry were designed based on the published theoretical design equations. A detail parametric investigation was carried out which resulted in the optimum impactor nozzle design. For this exercise, a novel dry aerosol generator was employed in addition to the well known time-of-flight instrument, APS (Aerodynamic Particle Sizer, Model 3021, TSI Inc.). The average particle losses for the impactor nozzle as well as the sampler body were below 10% and the overall pressure drop (including a backup 47 mm filter) through the PM 2.5 sampler was only 2 in. of H 2 O. This developed PM 2.5 sampler operates at a flow rate of 15 LPM. Field performance of this sampler was evaluated through co-located sampling with a high volume PM 2.5 reference sampler (HVS, GEM-BLI Model 2360, Tisch Environment Instrument) within the IIT Kanpur campus. The sampling period was 10 h long and it was carried out on six different days. The entire sets of filters were analyzed gravimetrically followed by their chemical analysis for elemental and anionic analyses. The particle mass, elemental, and anionic concentrations obtained with this newly developed PM 2.5 sampler as well as those from the reference HVS sampler showed moderate to good correlation.
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Field performance evaluation of a newly developed PM2.5 sampler at IIT Kanpur
Science of The Total Environment, 2011Co-Authors: Tarun Gupta, Shefali DubeyAbstract:In order to meet the challenges of growing air pollution for a developing nation and to measure the ambient fine particles (PM2.5, particles having aerodynamic diameter less than 2.5??m) on routine basis an air sampler was designed, developed and evaluated in the field. The impactor removes particles greater than 2.5??m from the air stream via impacting them onto a Vacuum Grease substrate and finer particles get eventually collected on a backup filter. Various impactor nozzles with conical geometry were designed based on the published theoretical design equations. A detail parametric investigation was carried out which resulted in the optimum impactor nozzle design. For this exercise, a novel dry aerosol generator was employed in addition to the well known time-of-flight instrument, APS (Aerodynamic Particle Sizer, Model 3021, TSI Inc.). The average particle losses for the impactor nozzle as well as the sampler body were below 10% and the overall pressure drop (including a backup 47mm filter) through the PM2.5 sampler was only 2in. of H2O. This developed PM2.5 sampler operates at a flow rate of 15LPM. Field performance of this sampler was evaluated through co-located sampling with a high volume PM2.5 reference sampler (HVS, GEM-BLI Model 2360, Tisch Environment Instrument) within the IIT Kanpur campus. The sampling period was 10h long and it was carried out on six different days. The entire sets of filters were analyzed gravimetrically followed by their chemical analysis for elemental and anionic analyses. The particle mass, elemental, and anionic concentrations obtained with this newly developed PM2.5 sampler as well as those from the reference HVS sampler showed moderate to good correlation. ?? 2011 Elsevier B.V.
Qun Li - One of the best experts on this subject based on the ideXlab platform.
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Effects of acoustic reflection on the performance of a cladding-etched all-fiber acoustooptic variable optical attenuator
IEEE Photonics Technology Letters, 2004Co-Authors: A.a. Au, Qun LiAbstract:We analyzed the effects of acoustic reflection on the performance of an acoustooptic variable optical attenuator on a cladding-etched single-mode fiber. It is shown that the acoustic reflection will generate time-dependent modulation on the output optical signal and reduce the maximum achievable attenuation of the device. By employing a tapered fiber structure and using Vacuum Grease as the acoustic absorber, we showed that the acoustic reflectance can be reduced by two orders and the maximum attenuation of the device is increased from -10 to -29 dB.
Xing Zhang - One of the best experts on this subject based on the ideXlab platform.
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Experimental Investigation of the Thermal Impedance of Interstitial Material at a Junction
International Journal of Thermophysics, 2010Co-Authors: Jianli Wang, Ming Gu, Bai Song, Xing ZhangAbstract:Using a quasi-steady-state T-type probe, experimental evidence of the different behavior of the thermal impedance of a junction with different interstitial material (interposer) was presented. In the T-type probe, a short hot wire serves both as a heater and a thermometer, which is subjected to an alternating current, and a thermally infinite long test wire is attached to the midpoint of the hot wire with an interposer. The thermal impedance of the interposer was introduced, which was taken to be the product of the steady-state thermal resistance and a complex ratio function. A complete expression for the thermal impedance of the interposer was derived, and the effects of the radiation heat loss as well as the deviation of the contact junction position were theoretically estimated. A microscale Pt wire with two interposers was measured, including solidified platinum black and Apiezon N Vacuum Grease. Experimental results showed that the platinum black contact with high thermal effusivity served as a negative thermal impedance, while a positive thermal impedance was observed for the Apiezon N contact. The obtained thermal impedance of the Apiezon N contact could be equivalent to its thermal resistance, which was verified by measuring the thermal conductivity of a Cu wire using the steady-state T-type probe.
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Measuring the Thermal Contact Resistance of a Junction by T Type Probe Method
ASME 2009 Second International Conference on Micro Nanoscale Heat and Mass Transfer Volume 2, 2009Co-Authors: Jianli Wang, Ming Gu, Xing ZhangAbstract:Using a T type probe, the effect of the interstitial material (interposer) on the thermal contact resistance of a junction has been estimated by measuring an individual carbon fiber with different interposers, including the solidified metallic powder, lubricant Grease, and dry contact as a comparison. For the metallic powder, the thermal contact conductance was obtained to be 3.0 M W m−2 K−1 by changing the fiber length when the same contact between the fiber and the hot wire was maintained. However, this method can only be applicable to the solidified contact, and the stability of the operating temperature is a must in each length measurement. To estimate the thermal contact resistance of the lubricant Apiezon N Grease, even a dry contact, an improved T type probe was employed, by applying an alternative current to the hot wire. This method was verified by measuring the same type of carbon fiber in the frequency range of 0.1 to 1Hz based on a Labview-based virtual lock-in measurement system. The same value of the thermal effusivity of the test fiber was obtained with different interposers, and the thermal contact conductances for the dry contact and high Vacuum Grease were found to be 0.10 M W m−2 K−1 and 0.26 M W m−2 K−1 , respectively.© 2009 ASME
V. Hutanu - One of the best experts on this subject based on the ideXlab platform.
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SQUID measurements of remanent magnetisation in refillable 3He spin-filter cells (SFC)
Physica B-condensed Matter, 2007Co-Authors: V. Hutanu, A. Rupp, T. Sander-thömmesAbstract:Abstract A strong influence of external magnetic fields on the relaxation time constant T1 of glass cells serving as reservoirs for polarised 3He, observed for various alkali metal-coated cells made of different glass types, was initially associated with the presence of a large number of ferromagnetic clusters on the glass surface. Later experiments showed the presence of the so-called “T1 hysteresis” phenomenon with a similar distinctiveness also in uncoated cells made of pure synthetic quartz glass. It suggests that the origin of such a relaxation is a macroscopic magnetisation in the bulk of the cell. We present the results of a multi-SQUID system investigation on magnetised and non-magnetised quartz glass cells, Cs coated as well as bare wall, to be used as neutron spin filters at HMI Berlin. The presence of a macroscopic remanent magnetic moment in the cells after their exposition to external magnetic fields has been experimentally shown. More than 80% of the remanent magnetic moment of the magnetised cells was found to be concentrated in the region of the glass valves. SQUID measurements reveal the existence of some remanent magnetisation in all valve parts and also in the Vacuum Grease, but most magnetic are the plastic parts and the O-ring. Different valve and sealing types have been compared in order to find the less magnetisable one.
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SQUID measurements of remanent magnetisation in refillable 3He spin-filter cells (SFC)
Physica B: Condensed Matter, 2007Co-Authors: V. Hutanu, A. Rupp, T. Sander-thömmesAbstract:A strong influence of external magnetic fields on the relaxation time constant T1 of glass cells serving as 3He neutron spin filters, observed for different glass types in alkali metal coated cells, was initially associated with the presence of a large number of ferromagnetic clusters on the glass surface. Later experiments showed the presence of the so called T1 hysteresis phenomenon with a similar distinctiveness also in uncoated cells made of pure synthetic quartz glass. It suggests that the origin of such relaxation is a macroscopic magnetisation in the bulk material of the cell. We present the results of a multi SQUID system investigation on magnetised and non magnetised quartz glass cells, Cs coated as well as bare wall, to be used as neutron spin filters at HMI Berlin. The presence of a macroscopic remanent magnetic moment in the cells after their exposition to external magnetic fields has been experimentally shown. More than 80 of the remanent magnetic moment of the magnetised cells was found to be concentrated in the region around the glass valves. SQUID measurements reveal the existence of some remanent magnetisation in all valve parts and also in the Vacuum Grease, but most magnetic are the plastic parts and the O ring. Different valve and sealing types has been compared in order to find less magnetisable on
