46,714 research outputs found
Nonlinear Hall Effects in Strained Twisted Bilayer WSe
Recently, it has been pointed out that the twisting of bilayer WSe would
generate topologically non-trivial flat bands near the Fermi energy. In this
work, we show that twisted bilayer WSe (tWSe) with uniaxial strain
exhibits a large nonlinear Hall (NLH) response due to the non-trivial Berry
curvatures of the flat bands. Moreover, the NLH effect is greatly enhanced near
the topological phase transition point which can be tuned by a vertical
displacement field. Importantly, the nonlinear Hall signal changes sign across
the topological phase transition point and provides a way to identify the
topological phase transition and probe the topological properties of the flat
bands. The strong enhancement and high tunability of the NLH effect near the
topological phase transition point renders tWSe and related moire materials
new platforms for rectification and second harmonic generations.Comment: 5 pages, 3 figures. Comments are welcom
Nucleon Sigma Term and In-medium Quark Condensate in the Modified Quark-Meson Coupling Model
We evaluate the nucleon sigma term and in-medium quark condensate in the
modified quark-meson coupling model which features a density-dependent bag
constant. We obtain a nucleon sigma term consistent with its empirical value,
which requires a significant reduction of the bag constant in the nuclear
medium similar to those found in the previous works. The resulting in-medium
quark condensate at low densities agrees well with the model independent linear
order result. At higher densities, the magnitude of the in-medium quark
condensate tends to increase, indicating no tendency toward chiral symmetry
restoration.Comment: 9 pages, modified version to be publishe
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Research on VCSEL interference analysis and elimination method
Laser methane gas sensors have been increasingly accepted in coal mine safety monitoring. Most laser spectroscopic methane gas sensors are based in BFB lasers at around 1650nm. However, they suffer from high power consumption and high cost due to temperature control is required for laser diode operation at constant temperature. VCSEL lasers have offered low operation current and low power consumption when operating at non-TEC mode. However, it is found that the interference noise is critical for laser methane detection. This paper report typical results of the laser diode ripple characterization method and methods of noise reduction methods are discussed
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Coal mine low power laser methane detection and alarm instrument
At present, the portable carrier catalytic methane detection and alarm instrument for coal mine generally has many problems, such as high power consumption, short standby time, low detection accuracy, few parameters and single function, which can not meet the rapid development needs of mine safety. In this paper, a low power portable laser methane detection and alarm instrument based on tunable laser absorption spectroscopy (TDLAS) is designed. The instrument can detect methane concentration, ambient temperature and ambient pressure at the same time. It has the functions of sound and light alarm, historical data storage and query, and integrates Wi-Fi to realize data wireless transmission. The instrument can work continuously for 36 hours, and the response time is less than 15 seconds. It has the function of self-diagnosis. The overall performance of the instrument has been greatly improved compared with the traditional mine methane portable instrument. A mobile methane alarm Internet of things(IOT) system for coal mine based on portable instrument has been developed, which realizes real-time upload of data and cloud analysis, makes the traditional mine gas monitoring and control system powerfully supplemented, greatly improves the detection level of coal mine gas, and has broad application prospects
NuSTAR observations and broadband spectral energy distribution modeling of the millisecond pulsar binary PSR J1023+0038
We report the first hard X-ray (3-79 keV) observations of the millisecond
pulsar (MSP) binary PSR J1023+0038 using NuSTAR. This system has been shown
transiting between a low-mass X-ray binary (LMXB) state and a rotation-powered
MSP state. The NuSTAR observations were taken in both LMXB state and
rotation-powered state. The source is clearly seen in both states up to ~79
keV. During the LMXB state, the 3-79 keV flux is about a factor of 10 higher
that in the rotation-powered state. The hard X-rays show clear orbital
modulation during the X-ray faint rotation-powered state but the X-ray orbital
period is not detected in the X-ray bright LMXB state. In addition, the X-ray
spectrum changes from a flat power-law spectrum during the rotation-powered
state to a steeper power-law spectrum in the LMXB state. We suggest that the
hard X-rays are due to the intra-binary shock from the interaction between the
pulsar wind and the injected material from the low-mass companion star. During
the rotation-powered MSP state, the X-ray orbital modulation is due to Doppler
boosting of the shocked pulsar wind. At the LMXB state, the evaporating matter
of the accretion disk due to the gamma-ray irradiation from the pulsar stops
almost all the pulsar wind, resulting the disappearance of the X-ray orbital
modulation.Comment: 8 pages, 6 figures; accepted for publication in Ap
Some recent progress on quark pairings in dense quark and nuclear matter
We give a brief overview on some recent progress in quark pairings in dense
quark/nuclear matter mostly developed in the past five years. We focus on
following aspects in particular: the BCS-BEC crossover in the CSC phase, the
baryon formation and dissociation in dense quark/nuclear matter, the
Ginzburg-Landau theory for three-flavor dense matter with (1) anomaly,
and the collective and Nambu-Goldstone modes for the spin-one CSC.Comment: RevTex 4, 25 pages, 9 figures, presented for the KITPC (Kavli
Institute for Theoretical Physics China) program "AdS/CFT and Novel
Approaches to Hadron and Heavy Ion Physics' in Oct. 11- Dec. 3, 201
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Application and research of wireless laser methane sensor in drainage pipeline monitoring
Laser methane sensor has been widely promoted and successfully applied in coal mines as a new and effective technology building on the approach of laser-based absorption detection. Compared with the traditional catalytic methane sensor, the laser methane sensor discussed offers the important advantages of a long calibration period, high detection precision, the absence of zero drift and low power consumption, all of which are significant advantages for use in coal mining applications. By compensating for the temperature and pressure of the gases present, the accuracy of the methane sensor is evident across a wide range of temperatures and pressures, making it suitable for gas detection, including methane, in pipelines as well. The wireless laser approach which is incorporated into the methane sensor allows wireless transmission and data uploading to a cloud server through NB-IoT. This tackles the problem in gas pipeline monitoring of the length of many pipelines and thus the wide distribution of the sensors, avoiding complicated wiring and thus high associated cost. Further, remote data management can then be achieved, all of which greatly improves the flexibility and security of the management of the pipeline and the data generated
How does reputation win trust? A customer-based mediation analysis
This study investigates the relationship between customer-based corporate reputation (CBR) and customer trust, in particular, the mediating role of customer perceived risk in this relationship. We propose and test a model comprising of four components: cognitive CBR, affective CBR, customer perceived risk, and customer trust using a sample of 156 customers from the fast-food services industry in Pakistan. The results suggest that the cognitive and affective dimensions of CBR behave differently in developing customer trust. Affective CBR has a direct positive relationship with customer trust; whereas, customer perceived risk and affective CBR mediate the relationship between cognitive CBR and customer trust. Implications for future researchers and practicetioners are proposed based on the study results
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