Human respiration reflects abundant physiological information and could enable non‐invasive monitoring, providing information about various biological parameters such as respiration rate and depth. The rapidly growing field of humidity sensors bring forward the requirement for good performance. In this work, by virtue of good hydrophilicity and conductivity, a MXene/thermoplastic polyurethane (TPU) composite film is prepared by coating MXene nanosheets on chitosan‐modified TPU electrospun nanofibers via electrostatic interactions, for fabricating a humidity sensor. Based on the principle that the tunnel resistance changing with water molecules influences the distance of MXene nanosheets, the MXene/TPU humidity sensor exhibits fast response (12 s), wide humidity response range (11–94% RH), low hysteresis (<7% RH), and excellent repeatability. The humidity sensor can be assembled with a face mask for distinguishing different human respiration patterns and accurately monitoring respiratory signals during different physical activities, suggesting its promising applications in the fields of respiratory monitoring.
We have measured the magnetic hysteresis loops of an epitaxial YBa2Cu3O7−δ thin film using our recently developed device which can provide the field magnitude in the range of 0–1000 Oe and the field sweep rate up to 107 Oe/s. The shape of the hysteresis loop measured changes with the field-sweep rate up to the critical sweep rate; and over the critical sweep rate the ac magnetization reaches its real critical state where magnetization does not change even with a further increase in the field-sweep rate. The critical sweep rate is about 106 Oe/s at 77 K. With the hysteresis loops and Bean model, we have calculated the magnetization critical current density (Jcac) which is consistent with that obtained by I–V measurements. We have also studied flux motion and activation energy under the high sweep rate magnetic field. At temperature 77 K, the velocity of the flux motion is of the order 10 m/s and the pinning energy U0/k is about 339 K which is much smaller than the magnetization decay measurement.
A hysteresis loop tracer to measure the ac magnetization of high-Tc superconductors in the frequency range of 30 Hz–10 kHz is described, with driving field amplitudes up to 0.1 T. Due to the high frequency of the magnetic field, the hysteresis loops could be displayed on an oscilloscope and their details could be observed. The demagnetization factor, the stability, and the frequency characteristics of the tracer were tested. The ac magnetization of granular high-Tc superconductors was studied as a function of field amplitude and frequency.
Abstruct-Due to the roughness in the surface of the crystal sample, it is hard to use photolithography in the ptterning process of the BizSrzCaCuzOs+s intrinsic Josephson junction. In this paper, we report a simple technique for fabricating the BizSrzCaCuzOx+~ intrinsic Josephson junctions. In the patterning process, metal masks are used instead of photolithography and argon ion milling is applied to form a small mesa on the Bi,Sr,CaCu,Ox+s crystal surface. Real four-probe transport measurements are made on the Bi2SrzCaCuzOs+s intrinsic junctions and typical currentvoltage characteristics with multi-branch structure have been observed, from which the superconducting gap parameter can be extracted. Additionally, from the s t r a g hysteresis in the I-V characteristics, the capacitance CJ of the unit intrinsic Josephson junction can be estimated, which is in good agreement with that evaluated from the geometric parameters of the unit junction between the two copper oxide layers.
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