Nanomechanical resonators (NMRs), as the quantum mechanical sensing probers, have played the important roles for various high-precision quantum measurements. Differing from the previous emission ...spectral probes (i.e., the NMR modified the atomic emission), in this paper we propose an alternative approach, i.e., by probing the scattering spectra of the quantum mechanical prober coupled to the driving microwaves, to characterize the physical features of the NMR embedded in a rf-SQUID based superconducting qubit. It is shown that, from the observed specifical frequency points in the spectra, i.e., either the dips or the peaks, the vibrational features (i.e., they are classical vibration or quantum mechanical one) and the physical parameters (typically such as the vibrational frequency and displacements) of the NMR can be determined effectively. The proposal is feasible with the current technique and should be useful to design the desired NMRs for various quantum metrological applications.
To investigate critical frequency bands and channels, this paper introduces deep belief networks (DBNs) to constructing EEG-based emotion recognition models for three emotions: positive, neutral and ...negative. We develop an EEG dataset acquired from 15 subjects. Each subject performs the experiments twice at the interval of a few days. DBNs are trained with differential entropy features extracted from multichannel EEG data. We examine the weights of the trained DBNs and investigate the critical frequency bands and channels. Four different profiles of 4, 6, 9, and 12 channels are selected. The recognition accuracies of these four profiles are relatively stable with the best accuracy of 86.65%, which is even better than that of the original 62 channels. The critical frequency bands and channels determined by using the weights of trained DBNs are consistent with the existing observations. In addition, our experiment results show that neural signatures associated with different emotions do exist and they share commonality across sessions and individuals. We compare the performance of deep models with shallow models. The average accuracies of DBN, SVM, LR, and KNN are 86.08%, 83.99%, 82.70%, and 72.60%, respectively.
This paper proposes a method to predict fluctuations in the prices of cryptocurrencies, which are increasingly used for online transactions worldwide. Little research has been conducted on predicting ...fluctuations in the price and number of transactions of a variety of cryptocurrencies. Moreover, the few methods proposed to predict fluctuation in currency prices are inefficient because they fail to take into account the differences in attributes between real currencies and cryptocurrencies. This paper analyzes user comments in online cryptocurrency communities to predict fluctuations in the prices of cryptocurrencies and the number of transactions. By focusing on three cryptocurrencies, each with a large market size and user base, this paper attempts to predict such fluctuations by using a simple and efficient method.
Propagation delay based cyclic interference alignment design is proposed for general X channels with two transmitters and <inline-formula> <tex-math notation="LaTeX">K </tex-math></inline-formula> ...receivers. From the basic case with <inline-formula> <tex-math notation="LaTeX">K=3 </tex-math></inline-formula> to the general case with arbitrary <inline-formula> <tex-math notation="LaTeX">K </tex-math></inline-formula>, the transmit polynomial and the PD feature of the channels are given. The corresponding receive polynomials are deduced, which show that perfect cyclic IA has been performed in <inline-formula> <tex-math notation="LaTeX">K+1 </tex-math></inline-formula> time-slots to obtain the optimal degrees of freedom <inline-formula> <tex-math notation="LaTeX">{2K}/{(K+1)} </tex-math></inline-formula>. Furthermore, the feasibility analysis of node placement in the Euclidean space is provided, which demonstrates the wide application scope from underwater acoustic to terrestrial radio communications.
Fixed frequency beam-scanning leaky-wave antennas have been a focus of attention for many scholars in recent years, and numerous related results have been obtained. However, these antennas suffer ...from several issues such as small beam-scanning range, low gain, and unsatisfactory impedance matching. To address these problems, this paper proposes a microstrip line (ML) antenna unit based on liquid crystal (LC) materials etched Complementary Split Ring Resonator (CSRR). In a first-of-its-kind approach, the substrate integrated waveguide (SIW) structure and the ML transmission structure are combined to present the SIW-ML transmission structure. The antenna operates in the Ka-band with excellent resonance characteristics at 34.7 GHz, and the S11 parameters are below - 13 dB in the frequency range of 30-40 GHz, indicating outstanding impedance matching. By arranging 56 antenna units, a periodic leaky-wave antenna is created, enabling fixed-frequency beam-scanning at 34.7 GHz. Experimental results show that the antenna can achieve scanning of angles between - 53° and + 60° with a gain of up to 12.63 dB. Once single-beam scanning is achieved, a method combining LC and discrete amplitude weighting technique, as well as multi-beam theory, is proposed for multi-beam study. Experimental results reveal that the designed 56-unit beam-scanning antenna can effectively realize beam scanning in two directions.
To facilitate efficient communications (i.e., minimum power consumption and maximum information throughput) in vehicle cavities, it is necessary to fully understand the underlying physics of the ...propagation process. This can be characterized as a statistical model of the channel impulse response, which we derive from a general starting point. The impulse response model is useful in its own right for ultrawideband pulse radio communications, channel simulations, and time-of-arrival positioning systems, and it also allows us to verify the generally accepted property that the energy retained in the cavity exponentially decays with time after an impulse input. This property can be characterized as a cavity Formula Omitted-factor, and we investigate methods of Formula Omitted-factor estimation in vehicle cavities, using only a limited amount of data, such as would typically be available to a deployed in-vehicle wireless network. We find that the most reliable approach utilizes an inverse-discrete-Fourier-transform-based method, which finds the maximum-likelihood instantaneous Formula Omitted-factor, given measured data across various spatial links and frequency channels.
Abstract
Solar flares are explosions on the Sun. They happen when energy stored in magnetic fields around solar active regions (ARs) is suddenly released. Solar flares and accompanied coronal mass ...ejections are sources of space weather, which negatively affects a variety of technologies at or near Earth, ranging from blocking high-frequency radio waves used for radio communication to degrading power grid operations. Monitoring and providing early and accurate prediction of solar flares is therefore crucial for preparedness and disaster risk management. In this article, we present a transformer-based framework, named SolarFlareNet, for predicting whether an AR would produce a
$$\gamma$$
γ
-class flare within the next 24 to 72 h. We consider three
$$\gamma$$
γ
classes, namely the
$$\ge$$
≥
M5.0 class, the
$$\ge$$
≥
M class and the
$$\ge$$
≥
C class, and build three transformers separately, each corresponding to a
$$\gamma$$
γ
class. Each transformer is used to make predictions of its corresponding
$$\gamma$$
γ
-class flares. The crux of our approach is to model data samples in an AR as time series and to use transformers to capture the temporal dynamics of the data samples. Each data sample consists of magnetic parameters taken from Space-weather HMI Active Region Patches (SHARP) and related data products. We survey flare events that occurred from May 2010 to December 2022 using the Geostationary Operational Environmental Satellite X-ray flare catalogs provided by the National Centers for Environmental Information (NCEI), and build a database of flares with identified ARs in the NCEI flare catalogs. This flare database is used to construct labels of the data samples suitable for machine learning. We further extend the deterministic approach to a calibration-based probabilistic forecasting method. The SolarFlareNet system is fully operational and is capable of making near real-time predictions of solar flares on the Web.
Abstract
Paper reports the main results of a systematic study on longitudinal train dynamics (LTD) of long freight trains, equipped with radio communication. The simulation results have been used to ...prepare an experimental test campaign to test the Distributed Power System (DPS) technology. The simulations refer to up/down and level track and they compare the LTD of trains with and without DPS, for different train operations and radio link conditions. The DPS technology is proved (by simulations and test) to be a very effective way to increase the efficiency of future freight trains.
Optical frequency combs act as rulers in the frequency domain and have opened new avenues in many fields such as fundamental time metrology, spectroscopy and frequency synthesis. In particular, ...spectroscopy by means of optical frequency combs has surpassed the precision and speed of Fourier spectrometers. Such a spectroscopy technique is especially relevant for the mid-infrared range, where the fundamental rotational-vibrational bands of most light molecules are found. Most mid-infrared comb sources are based on down-conversion of near-infrared, mode-locked, ultrafast lasers using nonlinear crystals. Their use in frequency comb spectroscopy applications has resulted in an unequalled combination of spectral coverage, resolution and sensitivity. Another means of comb generation is pumping an ultrahigh-quality factor microresonator with a continuous-wave laser. However, these combs depend on a chain of optical components, which limits their use. Therefore, to widen the spectroscopic applications of such mid-infrared combs, a more direct and compact generation scheme, using electrical injection, is preferable. Here we present a compact, broadband, semiconductor frequency comb generator that operates in the mid-infrared. We demonstrate that the modes of a continuous-wave, free-running, broadband quantum cascade laser are phase-locked. Combining mode proliferation based on four-wave mixing with gain provided by the quantum cascade laser leads to a phase relation similar to that of a frequency-modulated laser. The comb centre carrier wavelength is 7 micrometres. We identify a narrow drive current range with intermode beat linewidths narrower than 10 hertz. We find comb bandwidths of 4.4 per cent with an intermode stability of less than or equal to 200 hertz. The intermode beat can be varied over a frequency range of 65 kilohertz by radio-frequency injection. The large gain bandwidth and independent control over the carrier frequency offset and the mode spacing open the way to broadband, compact, all-solid-state mid-infrared spectrometers.
The incoherent orbital angular momentum (OAM) radio waves can be used to transmit different information on the same frequency and have a great potential in wireless communication system. However, it ...needs a large aperture size to receive and demultiplex the orthogonal OAM waves due to the amplitude null in the beam centre and the beam divergence. An improved receiving scheme named partial aperture sampling receiving (PASR) is proposed to solve this problem. The theoretical analysis of PASR is first presented and simulations of OAM radio communication link are carried on to evaluate the performance of PASR. The effects of some non-ideal receiver conditions, e.g. radial deviation and angular deviation on the PASR scheme and the superiority of PASR are explored. These simulated results will give a helpful guide on the manipulation of practical OAM-based wireless communication systems.
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