نتائج البحث

1

Terahertz Ultralow-Voltage Gyrotron With Upstream Output

المؤلفون: Shi Pan, Chao-Hai Du, Li Luo, Pu-Kun Liu, Mingguang Huang

المصدر: IEEE Transactions on Plasma Science. 48:1195-1201

الوصف: A medium-power broadband-tuning terahertz (THz) gyrotron operating at low voltages is especially attractive for applications in biomedicine. This article tends to elaborate on the challenges related to startup oscillation and ohmic loss suppression of an extremely low-voltage THz gyrotron. High interaction efficiency is achievable by applying long transit time of electrons to compensate the unfavorable decline of the beam-wave coupling strength for low-energy electron beams. A cavity structure which favors backward-wave interaction is proposed to extend the frequency tuning range. The theoretical study predicts that the optimal cavity contributes to the robust frequency tunability at low voltages. The results indicate that a continuous tuning range of 10.7 GHz around the 330-GHz band with output power higher than 1 W can be expected by utilizing a 0.3 kV, 0.5 A helical electron beam.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::bf1e1539d449b3c7379adcecb39e172dTest
https://doi.org/10.1109/tps.2020.2979224Test

2

Theoretical Study of a ${W}$ -Band-Covering Frequency-Tunable Gyrotron

المؤلفون: Zi-Chao Gao, Fan-Hong Li, Kevin Ronald, Adrian W. Cross, Pu-Kun Liu, Chao-Hai Du, Shi Pan, Lei Zhang

المصدر: IEEE Transactions on Electron Devices. 67:659-666

مصطلحات موضوعية: Physics, Range (particle radiation), Multi-mode optical fiber, business.industry, TK, Fusion plasma, Radiation, Electronic, Optical and Magnetic Materials, law.invention, W band, Physics::Plasma Physics, law, Gyrotron, Optoelectronics, Electrical and Electronic Engineering, business

الوصف: The gyrotron has already demonstrated the capability of generating high-power coherent electromagnetic (EM) radiation at high frequencies and finds application in fusion plasma heating and magnetic resonance spectroscopy. In this article, we propose a ${W}$ -band gyrotron, which uses a so-called multimode switching scheme to realize ultrabroadband frequency tuning capability, nearly covering about 70% of the ${W}$ -band (75–110 GHz) range. The tuning strategy used to suppress mode competition and stabilize gun parameters in such an open-cavity multimode switching gyrotron is presented. Theoretical study shows that the multimode switching gyrotron can generate a frequency tuning range much wider than a conventional step-tuning gyrotron or a single-mode tuning gyrotron. In addition, another technology that uses a slot-assisted circuit to select only axis-symmetrical TE operating modes is presented. Using such a circuit, a tuning range of about 25 GHz in the ${W}$ -band is obtainable. The proposed multimode switching gyrotron is a promising ultrabroadband source for millimeter-wave and terahertz-wave applications.

وصف الملف: application/pdf

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::d065e4fc060414add258effc275d293dTest
https://doi.org/10.1109/ted.2019.2957040Test

3

Bnip3 regulates airway smooth muscle cell focal adhesion and proliferation

المؤلفون: Reynold A. Panettieri, Sushrut D. Shah, Shi Pan, Deepak A. Deshpande

المصدر: Am J Physiol Lung Cell Mol Physiol

مصطلحات موضوعية: 0301 basic medicine, Pulmonary and Respiratory Medicine, Physiology, Airway hyperresponsiveness, Muscle, Smooth, Vascular, Focal adhesion, 03 medical and health sciences, 0302 clinical medicine, Cell Movement, Proto-Oncogene Proteins, Physiology (medical), Cell Adhesion, medicine, Humans, Airway smooth muscle cell, Cells, Cultured, Cell Proliferation, Asthma, Focal Adhesions, business.industry, Membrane Proteins, Cell Biology, Airway smooth muscle, respiratory system, musculoskeletal system, medicine.disease, Mitochondria, respiratory tract diseases, Cell biology, 030104 developmental biology, 030220 oncology & carcinogenesis, Airway Remodeling, business, Airway, Research Article, Signal Transduction

الوصف: Increased airway smooth muscle (ASM) mass is a key contributor to airway narrowing and airway hyperresponsiveness in asthma. Besides conventional pathways and regulators of ASM proliferation, recent studies suggest that changes in mitochondrial morphology and function play a role in airway remodeling in asthma. In this study, we aimed at determining the role of mitochondrial Bcl-2 adenovirus E1B 19 kDa-interacting protein, Bnip3, in the regulation of ASM proliferation. Bnip3 is a member of the Bcl-2 family of proteins critical for mitochondrial health, mitophagy, and cell survival/death. We found that Bnip3 expression is upregulated in ASM cells from asthmatic donors compared with that in ASM cells from healthy donors and transient downregulation of Bnip3 expression in primary human ASM cells using an siRNA approach decreased cell adhesion, migration, and proliferation. Furthermore, Bnip3 downregulation altered the structure (electron density) and function (cellular ATP levels, membrane potential, and reacitve oxygen species generation) of mitochondria and decreased expression of cytoskeleton proteins vinculin, paxillin, and actinin. These findings suggest that Bnip3 via regulation of mitochondria functions and expression of adhesion proteins regulates ASM adhesion, migration, and proliferation. This study reveals a novel role for Bnip3 in ASM functions and establishes Bnip3 as a potential target in mitigating ASM remodeling in asthma.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::912ee10155dde6ff89b1c39aaf3afdd8Test
https://doi.org/10.1152/ajplung.00224.2019Test

4

Three Gaps for Quantisation in Learned Image Compression

المؤلفون: William J. Knottenbelt, Shi Pan, Chris Finlay, Chri Besenbruch

المساهمون: Innovate UK

المصدر: CVPR Workshops
New Trends in Image Restoration and Enhancement (NTIRE 2021) (CVPR Workshop)

مصطلحات موضوعية: Image coding, Artificial neural network, Computer science, business.industry, Differentiable function, Artificial intelligence, Lossy compression, business, Algorithm, Image compression, Lossy image compression, Visualization

الوصف: Learned lossy image compression has demonstrated impressive progress via end-to-end neural network training. However, this end-to-end training belies the fact that lossy compression is inherently not differentiable, due to the necessity of quantisation. To overcome this difficulty in training, researchers have used various approximations to the quantisation step. However, little work has studied the mechanism of quantisation approximation itself. We ad-dress this issue, identifying three gaps arising in the quantisation approximation problem. These gaps are visualised, and show the effect of applying different quantisation approximation methods. Following this analysis, we propose a Soft-STE quantisation approximation method, which closes these gaps and demonstrates better performance than other quantisation approaches on the Kodak dataset.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::b750d6f0a0516b66b4a5eec1e75bf311Test
https://doi.org/10.1109/cvprw53098.2021.00081Test

5

Terahertz Broadband Whispering-Gallery Mode Gyrotron Backward-Wave Oscillator

المؤلفون: Hui-Qi Bian, Chao-Hai Du, Shi Pan, Zi-Chao Gao, Pu-Kun Liu, Fan-Hong Li

المصدر: IEEE Transactions on Electron Devices. 66:2389-2395

مصطلحات موضوعية: 010302 applied physics, Physics, Field (physics), business.industry, Terahertz radiation, Mode (statistics), 01 natural sciences, Electronic, Optical and Magnetic Materials, law.invention, Optics, law, Gyrotron, 0103 physical sciences, Broadband, Backward-wave oscillator, Electrical and Electronic Engineering, Whispering-gallery wave, business, Effective frequency

الوصف: Conventional gyrotron backward-wave oscillators (gyro-BWOs) operate in a low-order mode, e.g., TE $_{0,1}$ mode. As the operating frequency extends to the terahertz (THz) band, the transverse size of low-order mode cavity shrinks, and the power capability is reduced, consequently. A solution to adopt an overmoded interaction cavity with a significantly enlarged index of the operating mode is valid on the condition that the challenging problem of mode competition can be controlled during the broadband frequency tuning. In this paper, a high-order whispering-gallery mode (WGM) THz gyro-BWO with a cathode-end output circuit is investigated. A segment-tapered circuit is applied to suppress the ${Q}$ factors of competing modes and to obtain a the competition-free stable start-oscillation scenario. The theoretical result predicts that the effective frequency tuning range continuously covers between 252.3 and 260 GHz when the ${B}$ -field is changed from 9.41 to 9.96 T. Our studies are beneficial to the development of high-performance sources for THz biomedical and material science applications.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::3fe7be2519785a5cf4bb8807409d843eTest
https://doi.org/10.1109/ted.2019.2903897Test

6

Mitochondrial regulation of airway smooth muscle functions in health and pulmonary diseases

المؤلفون: Deepak A. Deshpande, Shi Pan, Stanley Conaway

المصدر: Archives of Biochemistry and Biophysics. 663:109-119

الوصف: Mitochondria are important for airway smooth muscle physiology due to their diverse yet interconnected roles in calcium handling, redox regulation, and cellular bioenergetics. Increasing evidence indicates that mitochondria dysfunction is intimately associated with airway diseases such as asthma, IPF and COPD. In these pathological conditions, increased mitochondrial ROS, altered bioenergetics profiles, and calcium mishandling contribute collectively to changes in cellular signaling, gene expression, and ultimately changes in airway smooth muscle contractile/proliferative properties. Therefore, understanding the basic features of airway smooth muscle mitochondria and their functional contribution to airway biology and pathology are key to developing novel therapeutics for airway diseases. This review summarizes the recent findings of airway smooth muscle mitochondria focusing on calcium homeostasis and redox regulation, two key determinants of physiological and pathological functions of airway smooth muscle.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::27eab09f88b91378ab70b403ef92f948Test
https://doi.org/10.1016/j.abb.2019.01.002Test

7

Terahertz rectangular corrugated transmission line with Gaussian mode filtering for DNP‐NMR

المؤلفون: Shi Pan, Tie-Jun Huang, Hong Pu, Pu-Kun Liu, Chao-Hai Du

المصدر: IET Microwaves, Antennas & Propagation. 12:2080-2084

الوصف: Gyrotrons have been developed as terahertz wave sources in dynamic nuclear polarisation (DNP) system to increase the sensitivity of nuclear magnetic resonance (NMR) in the high-magnetic field regime. However, the transmission of the Gaussian beam from the gyrotron output window to the NMR system proves to be a critical challenge. In this study, a terahertz transmission system, composed of a rectangular corrugated waveguide and a back-to-back rectangular corrugated horn for Gaussian mode filtering, is proposed. The attenuation in the optimised 0.33 THz corrugated waveguide remains lower than 0.01 dB/m in a broad frequency range from 280 GHz to 450 GHz. Besides, the coupling coefficient from the electric field in the 0.33 THz mode-filtering horn to the fundamental HE11 mode in the rectangular corrugated waveguide is obtained nearly 99.5%. This terahertz transmission system is potential to be applied in DNP-NMR spectrometer based on continuous wave gyrotrons.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::8fee862d5c76b58731781608764841c6Test
https://doi.org/10.1049/iet-map.2018.5064Test

8

Electronic-Tuning Frequency Stabilization of a Terahertz Gyrotron Oscillator

المؤلفون: Zi-Chao Gao, Hui-Qi Bian, Shi Pan, Pu-Kun Liu, Chao-Hai Du

المصدر: IEEE Transactions on Electron Devices. 65:3466-3473

الوصف: Gyrotron oscillator, as one kind of efficient terahertz (THz) source, is developed with the capability of frequency and power tuning to meet diverse application demands. Due to system nonlinearity, it is quite difficult to achieve high frequency stabilization (FS) during power tuning without using external auxiliary components. This paper proposes an FS scheme with simultaneous power tuning in gyrotron backward-wave oscillator state. This is realized by compensating the detuning electron cyclotron frequency during the electronic tuning process. The required quasi-linear relationship between the electron-beam pitch factor and the accelerating voltage is numerically verified by using the SLAC EGUN code. The investigation focuses on a Watt-level open-cavity gyrotron oscillator. The tens-of-Watts-level output power can be tuned by over 40% at the FS point, and especially the self-adaptive FS reaches the accuracy of about 10-MHz level. The proposed scheme would be attractive for the high-stability THz-wave heating in material sciences and biomedicines.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::4ccb0eb515756f0af8c07ad53c7fe804Test
https://doi.org/10.1109/ted.2018.2839907Test

9

Development of a 1-THz 4th-harmonic gyrotron

المؤلفون: Zi-Wen Zhang, Lei Zhang, Si-Qi Li, Juan-Feng Zhu, Zi-Chao Gao, Fan-Hong Li, Shi Pan, Chao-Hai Du, Adrian W. Cross

مصطلحات موضوعية: Physics, business.industry, Superconducting magnet, Electromagnetic radiation, Magnetic field, law.invention, Harmonic analysis, Optics, law, Magnet, Gyrotron, Harmonic, business, QC, Electron gun

الوصف: A design of a 1-THz 4th Harmonic Gyrotron is proposed in this paper. Fourth harmonic interaction is adopted to lower the strength of the external magnet. The magnet can be as low as 10T. Such a low-intensity magnetic field can be easily proposed by a superconduct magnet, which make the generation of continuous waves at 1 THz possible. Seeing that the mode competition is extremely fierce, a large orbit gun is employed as the driven source. An 80-kV, 0.7-A electron beam is injected into the interaction circuit to excite the fourth-harmonic electromagnetic waves. According to the cold dispersive diagram, the TE4, 8 mode of the cylindrical waveguide is selected as the operating mode to further suppress the mode competition induced by the fundamental modes, the 2nd harmonic modes and the 3rd harmonic modes. It could be inferred based on the multi-mode time-domain theory that an output power of 1.15 kW can be achieved. The scheme diagram for the hot test is proposed. The LOG is chosen as the electron gun. Particular structure is employed for improving the output efficiency in the interaction circuit.

وصف الملف: application/pdf

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::3ff8e3a75c58f9cdd42967f8496759ecTest
https://strathprints.strath.ac.uk/76308/1/Li_etal_UCMMT_2020_Development_of_a_1_THz_4th_harmonic_gyrotron.pdfTest

10

A Directional Coupler with Corrugated Waveguide and Wire Array for 330 GHz DNP-NMR System

المؤلفون: Feng-Yuan Han, Zi-Chao Gao, Chao-Hai Du, Shi Pan, Xing-Chen Yang, Pu-Kun Liu

المصدر: 2020 International Conference on Microwave and Millimeter Wave Technology (ICMMT).

مصطلحات موضوعية: 010302 applied physics, Materials science, Spectrometer, business.industry, Port (circuit theory), 010402 general chemistry, 01 natural sciences, Electromagnetic radiation, 0104 chemical sciences, law.invention, Electric power transmission, Optics, Transmission line, law, 0103 physical sciences, Power dividers and directional couplers, business, Waveguide, Energy (signal processing)

الوصف: High power and frequency stability of electromagnetic wave input are required in the DNP-NMR system. It is necessary to monitor the electromagnetic wave energy in the transmission line in real-time to judge the magnitude and stability of the energy transmitted to the NMR spectrometer. However, the energy in the transmission system is too large to be directly measured in the transmission line. A part of the energy must be extracted to facilitate the measurement. We design a directional coupler by placing a wire array in the middle of the three-port circular corrugated waveguide for real-time extraction of transmitted energy. In the frequency range of 290 – 360 GHz, 0.05% energy can be stably coupled to port 3, so it is convenient for the energy detection. The S 11 parameter of the designed directional coupler can below −20dB from 290 to 360 GHz, and even −41dB at the operating frequency of 330 GHz.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::8720d4287b2b172eb72311dfd8c1a2f5Test
https://doi.org/10.1109/icmmt49418.2020.9386338Test

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