Publications by authors named "Ke Jun Xu"

In the underdoped n-type cuprate NdCeCuO, long-range antiferromagnetic order reconstructs the Fermi surface, resulting in a putative antiferromagnetic metal with small Fermi pockets. Using angle-resolved photoemission spectroscopy, we observe an anomalous energy gap, an order of magnitude smaller than the antiferromagnetic gap, in a wide portion of the underdoped regime and smoothly connecting to the superconducting gap at optimal doping. After considering all the known ordering tendencies in tandem with the phase diagram, we hypothesize that the normal-state gap in the underdoped n-type cuprates originates from Cooper pairing.

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The effect of Lifshitz transition on thermodynamics and superconductivity in hole-doped cuprates has been heavily debated but remains an open question. In particular, an observed peak of electronic specific heat is proposed to originate from fluctuations of a putative quantum critical point (e.g.

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To use acoustic-emission technology to detect leaks inside valves, the necessary first step is to model the valve-internal-leakage acoustic-emission signal (VILAES) mathematically. A multi-variable classification model that relates the VILAES characteristics and the leakage rate under varying pressure is built by combining time-frequency domain characteristics and the random-forest method. A Butterworth bandpass filter is used to preprocess the VILAES from a liquid medium, and the best frequency band for filtering is determined as being 140 kHz-180 kHz.

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Article Synopsis
  • - Ultrasonic gas flow meters are effective for large-diameter pipelines but face challenges in accurately measuring gas flow due to signal stability issues and heavy computations that can slow down real-time performance.
  • - This study identifies stable peak points in the echo signal that can be utilized for calculating real-time flow rates more efficiently, leading to a proposed signal processing method that is simple and has strong anti-interference properties.
  • - The developed method, tested on a dual-core system, achieves high accuracy (1.0-level) across a wide range of gas flow rates (30 m/h to 1100 m/h), enhancing the reliability of real-time measurements.
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The resistance of a conventional insulator diverges as temperature approaches zero. The peculiar low-temperature resistivity saturation in the 4f Kondo insulator (KI) SmB has spurred proposals of a correlation-driven topological Kondo insulator (TKI) with exotic ground states. However, the scarcity of model TKI material families leaves difficulties in disentangling key ingredients from irrelevant details.

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In normal metals, macroscopic properties are understood using the concept of quasiparticles. In the cuprate high-temperature superconductors, the metallic state above the highest transition temperature is anomalous and is known as the "strange metal." We studied this state using angle-resolved photoemission spectroscopy.

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The steam generator (SG) is a heat exchange device between a sodium coolant and water in sodium-cooled fast reactors. Its transfer tubes are prone to leakage to result in sodium-water reaction, which will affect the operational safety of the entire nuclear reactor. To this end, a signal processing method is studied to detect the SG leakage using an electromagnetic vortex flowmeter (EVFM).

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Fermi surface (FS) topology is a fundamental property of metals and superconductors. In electron-doped cuprate Nd Ce CuO (NCCO), an unexpected FS reconstruction has been observed in optimal- and overdoped regime ( = 0.15-0.

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The echo signal of the ultrasonic gas flow-meter is difficult to locate, and the computation of signal processing methods proposed by others is extensive which affects the meter's real-time performance. Aiming at solving these problems the echo signal envelopes under different flow rates are analyzed. And three kinds of signal processing methods based on echo signal envelope fitting are proposed.

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Background: Echinococcosis is a parasitic zoonosis caused by Echinococcus larvae parasitism causing high mortality. The Tibetan Region of Sichuan Province is a high prevalence area for echinococcosis in China. Understanding the geographic distribution pattern is necessary for precise control and prevention.

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The ordinary electromagnetic flowmeter (EMF) utilizes the steady-state period of the excitation current for measuring the flow rate in order to ensure zero stability and measurement accuracy. In this paper, the transient process of EMF is studied to measure the flow rate so as to realize applications requiring ultra-low power consumption, for example, water meters. For this reason, the dynamic excitation current and signal voltage of the transient process are analyzed, and three kinds of transient measurement methods are proposed to determine the relationship between the processing results of the signal voltage and flow rates.

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The present study was designed to investigate laryngeal function responses to chemoreceptor activation after unilateral high-cervical spinal cord contusion in rats. Adult male Sprague-Dawley rats received laminectomy or unilateral contusion at the C2 spinal cord. Both respiratory airflow and subglottal pressure were measured in spontaneously breathing rats at three days, two weeks, or six weeks after spinal surgery.

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Aiming at reducing the estimation error of the sensor frequency response function (FRF) estimated by the commonly used window-based spectral estimation method, the error models of interpolation and transient errors are derived in the form of non-parameter models. Accordingly, window effects on the errors are analyzed and reveal that the commonly used hanning window leads to smaller interpolation error which can also be significantly eliminated by the cubic spline interpolation method when estimating the FRF from the step response data, and window with smaller front-end value can restrain more transient error. Thus, a new dual-cosine window with its non-zero discrete Fourier transform bins at -3, -1, 0, 1, and 3 is constructed for FRF estimation.

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Most of the ultrasonic gas flow-meters measure the gas flow rate by calculating the ultrasonic transmission time difference between the downstream and upstream. Ultrasonic energy attenuation occurs in the processes of the ultrasonic generation, conversion, transmission, and reception. Additionally, at the same time, the gas flow will also affect the ultrasonic propagation during the measurement, which results in the ultrasonic energy attenuation and the offset of ultrasonic propagation path.

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In Garze Tibetan autonomous prefecture in Sichuan province, China, 41 echinococciasis patients who had received surgical treatment were recruited in the study, and 82 health persons who had lived in Garze for at least 10 years were selected as controls. The serum levels of Zn, Se and Cu of the cases and controls were detected. The results showed that most echinococciasis cases were distributed in Shiqu county (17.

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Coriolis mass flowmeter (CMF) often suffers from two-phase flowrate which may cause flowtube stalling. To solve this problem, a digital drive method and a digital signal processing method of CMF is studied and implemented in this paper. A positive-negative step signal is used to initiate the flowtube oscillation without knowing the natural frequency of the flowtube.

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To obtain accurate results in dynamic measurements it is required that the sensors should have good dynamic performance. In practice, sensors have non-ideal dynamic characteristics due to their small damp ratios and low natural frequencies. In this case some dynamic error correction methods can be adopted for dealing with the sensor responses to eliminate the effect of their dynamic characteristics.

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A new case of visceral leishmaniasis (kala-azar) was reported by Changzhi CDC of Shanxi Province in September 2011. The case was investigated clinically and epidemiologically. The patient was a two-year-old boy who lived in Huangnian Town of Changzhi County in Shanxi Province.

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Some digital signal processing methods have been used to deal with the output signal of vortex flowmeter for extracting the flow rate frequency from the noisy output of vortex flow rate sensor and achieving the measurement of small flow rate. In applications, however, the power of noise is larger than that of flow rate sometimes. These strong disturbances are caused by pipe vibration mostly.

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Digital signal processing methods have been applied to vortex flowmeter for extracting the useful information from noisy output of the vortex flow sensor. But these approaches are unavailable when the power of the mechanical vibration noise is larger than that of the vortex flow signal. In order to solve this problem, an antistrong-disturbance signal processing method is proposed based on frequency features of the vortex flow signal and mechanical vibration noise for the vortex flowmeter with single sensor.

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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.

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