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Feb 2009

Volume 80, Issue 2, Articles (02xxxx)

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Thermostat for high temperature and transient characterization of thin film thermoelectric materials

Rajeev Singh and Ali Shakouri

Rev. Sci. Instrum. 80, 025101 (2009); http://dx.doi.org/10.1063/1.3072603 (5 pages) | Cited 7 times

Online Publication Date: 5 February 2009

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We have designed and fabricated a vacuum-insulated thermostat capable of measuring the thermoelectric properties of thin films from room temperature to 850 K. High speed Seebeck voltage transients are resolved to 200 ns with 63 dB dynamic range in order to directly measure thermoelectric device figure of merit. In-plane Seebeck coefficient probes measure voltage and temperature difference at identical locations with low parasitic contributions. In-plane electrical conductivity measurement is accomplished at high speed to avoid possible Seebeck voltage effect on van der Pauw measurements.
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07.20.Ka High-temperature instrumentation; pyrometers
85.80.Fi Thermoelectric devices

Development of pressure cell for specific heat measurement at low temperature and high Magnetic field

T. Kawae, K. Yaita, Y. Yoshida, Y. Inagaki, M. Ohashi, G. Oomi, K. Matsubayashi, T. Matsumoto, and Y. Uwatoko

Rev. Sci. Instrum. 80, 025102 (2009); http://dx.doi.org/10.1063/1.3077146 (5 pages) | Cited 1 time

Online Publication Date: 5 February 2009

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We report the performance of Ag–Pd–Cu alloy as the material of a pressure cell to carry out specific heat measurements at low temperatures and high magnetic fields. The Ag–Pd–Cu alloy is advantageous to reduce the background due to the nuclear specific heat in the pressure cell growing at low temperatures and high magnetic fields. We prepared 70-20-10 alloy composed of 70 mass % of Ag, 20 mass % of Pd, and 10 mass % of Cu. The maximum hardness over 100 HRB (Rockwell-B scale) is achieved by the heat treatment. The magnetization and susceptibility results show that the alloy includes a small amount of magnetic ions, whose concentration is smaller than that in the Be–Cu alloy. We confirm that the specific heat of a piston cylinder cell made of the 70-20-10 alloy increases smoothly from 0.2 to 9 K and the nuclear specific heat decreases drastically in magnetic field compared to that expected in the Be–Cu alloy. The pressure value in the cell at low temperature increases almost linearly up to P = 0.4 GPa, which is nearly the limit of the inner piston made of the 70-20-10 alloy, with increasing of the load applied at room temperature.
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65.40.Ba Heat capacity
81.40.Gh Other heat and thermomechanical treatments
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp Friction, tribology, and hardness
75.30.Cr Saturation moments and magnetic susceptibilities
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Heat flux sensor calibration using noninteger system identification: Theory, experiment, and error analysis

Jean-Laurent Gardarein, Jean-Luc Battaglia, and Stefan Löhle

Rev. Sci. Instrum. 80, 025103 (2009); http://dx.doi.org/10.1063/1.3079328 (8 pages) | Cited 4 times

Online Publication Date: 12 February 2009

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This paper concerns the improvement of the calibration technique of null point calorimeters generally used in high enthalpy plasma flows. Based on the linearity assumption, this technique leads to calculate the impulse response that relates the heat flux at the tip of the sensor according to the temperature at the embedded thermocouple close to the heated surface. The noninteger system identification (NISI) procedure is applied. The NISI technique had been well described in previous study. The present work focuses on the accuracy of the identified system in terms of absorbed heat flux during the calibration experiment and of the estimated parameters in the model. The impulse response is thus calculated along with its associated standard deviation. Furthermore, this response is compared with that of the one-dimensional semi-infinite medium, which is classically used in practical applications. The asymptotic behavior of the identified system at the short times is analyzed for a better understanding of the noninteger identified system. Finally, the technique was applied to a new sensor geometry that has been developed particularly for high enthalpy plasma flows and it is shown that the method can be applied to any geometry suitable for a certain test configuration.
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07.20.Dt Thermometers
07.20.Fw Calorimeters
06.20.F- Units and standards
44.10.+i Heat conduction
02.30.Zz Inverse problems

Applied digital signal processing systems for vortex flowmeter with digital signal processing

Ke-Jun Xu, Zhi-Hai Zhu, Yang Zhou, Xiao-Fen Wang, San-Shan Liu, Yun-Zhi Huang, and Zhi-Yuan Chen

Rev. Sci. Instrum. 80, 025104 (2009); http://dx.doi.org/10.1063/1.3082044 (10 pages) | Cited 2 times

Online Publication Date: 20 February 2009

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The spectral analysis is combined with digital filter to process the vortex sensor signal for reducing the effect of disturbance at low frequency from pipe vibrations and increasing the turndown ratio. Using digital signal processing chip, two kinds of digital signal processing systems are developed to implement these algorithms. One is an integrative system, and the other is a separated system. A limiting amplifier is designed in the input analog condition circuit to adapt large amplitude variation of sensor signal. Some technique measures are taken to improve the accuracy of the output pulse, speed up the response time of the meter, and reduce the fluctuation of the output signal. The experimental results demonstrate the validity of the digital signal processing systems.
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47.80.-v Instrumentation and measurement methods in fluid dynamics
47.32.-y Vortex dynamics; rotating fluids
89.20.Kk Engineering

Signal extraction using ensemble empirical mode decomposition and sparsity in pipeline magnetic flux leakage nondestructive evaluation

Liang Chen, Xing Li, Xun-bo Li, and Zuo-ying Huang

Rev. Sci. Instrum. 80, 025105 (2009); http://dx.doi.org/10.1063/1.3082021 (6 pages) | Cited 1 time

Online Publication Date: 23 February 2009

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The commonly used and cost effective corrosion inspection tools for the evaluation of pipelines utilize the magnetic flux leakage (MFL) technique. The MFL signal is usually contaminated by various noise sources. In this paper, we propose that the pipeline flaw MFL signal is extracted using the ensemble empirical mode decomposition (EEMD) and the sparsity. At first, we introduce the EEMD method. The EEMD defines the true intrinsic mode function (IMF) components as the mean of an ensemble of trials, each consisting of the signal plus a white noise of finite amplitude. Moreover, sparsity selection restriction was defined. Then, The MFL signal is decomposed into several IMFs used for signal reconstruction. Some modes are selected to reconstruct a new signal considering their sparsity. Finally, the comparison is made with the empirical mode decomposition. At the same time, the comparison of the selection restriction between the sparsity and the energy is described. The results show that the EEMD and the sparsity is an efficient technology with the pipeline flaw extraction.
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89.20.Kk Engineering
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