The concept of urban communication bred in the new media era takes short video platforms as the vehicle for emerging Internet-famous cities. The internal relationship between the communication ...strategy and development orientation of urban communication and the image practice and performance space of short videos is worth studying. Taking Chongqing and Xi’an as the research objects, this paper explores the operation mode and communication concept of urban space in the new media era from the perspectives of communication origin, user participation, and in-depth communication. The research shows that the advent of mobile short-video platforms offers a new vehicle and channel for the communication and reconstruction of urban space and enriches the audience’s cognition of city images.
Falling is among the most damaging event elderly people may experience. With the ever-growing aging population, there is an urgent need for the development of fall detection systems. Thanks to the ...rapid development of sensor networks and the Internet of Things (IoT), human-computer interaction using sensor fusion has been regarded as an effective method to address the problem of fall detection. In this paper, we provide a literature survey of work conducted on elderly fall detection using sensor networks and IoT. Although there are various existing studies which focus on the fall detection with individual sensors, such as wearable ones and depth cameras, the performance of these systems are still not satisfying as they suffer mostly from high false alarms. Literature shows that fusing the signals of different sensors could result in higher accuracy and lower false alarms, while improving the robustness of such systems. We approach this survey from different perspectives, including data collection, data transmission, sensor fusion, data analysis, security, and privacy. We also review the benchmark data sets available that have been used to quantify the performance of the proposed methods. The survey is meant to provide researchers in the field of elderly fall detection using sensor networks with a summary of progress achieved up to date and to identify areas where further effort would be beneficial.
Rising‐tone chorus waves have already been successfully produced in a mirror magnetic field with the use of one‐ and two‐dimensional particle‐in‐cell (PIC) simulations. However, in reality, the ...background magnetic field in the inner Earth's magnetosphere is a dipole magnetic field, unlike symmetric mirror fields. In this paper, with the two‐dimensional (2‐D) general curvilinear PIC (gcPIC) code, we investigate the generation of rising‐tone chorus waves in the dipole magnetic field configuration. The plasma consists of three components: immobile ions, cold background, and hot electrons. In order to save computational resource, the topology of the magnetic field is roughly equal to that at L = 0.6 RE, although the plasma parameters corresponding to those at L = 6 RE (RE is the Earth's radius) are used. Whistler mode waves are first excited around the magnetic equator by the hot electrons with a temperature anisotropy. The excited whistler mode waves propagate almost parallel and antiparallel to the background magnetic field in their source region, which is limited at ∣λ ∣ ≤ 3° (where λ is the magnetic latitude). When the waves leave from the source region and propagate toward high latitudes, both their amplitude and wave normal angle become larger. However, the group velocity of the waves is directed toward high latitudes almost along the magnetic field. During such a process, the waves have a frequency chirping, as shown by a rising tone in the frequency‐time spectrogram. To our best knowledge, it is for the first time that rising‐tone chorus are generated in a dipole magnetic field with a PIC simulation.
Key Points
The rising‐tone chorus waves are generated in a dipole magnetic field with a 2‐D gcPIC simulation for the first time
Whistler waves are excited around the magnetic equator and propagate almost along the background magnetic field
When whistler waves propagate toward high latitudes, their wave normal angles increase with the growth of the latitude
Oxidative stress leads to intestinal epithelial cells damage, which induces tight junction injury and systemic endogenous stress syndrome. The evidence suggests that SIRT1/PGC-1α pathway is closely ...associated with oxidative damage. However, the mechanism in protecting intestinal epithelial cells against oxidative stress dependant on autopahgy/mitophagy remains to be elucidated. In the current study, we investigated the functional role of SIRT1/PGC-1α pathway on regulation of autopahgy/mitophagy and tight junction protein expression underlying the oxidative dysfunction in porcine intestinal epithelial cells (IPEC-1). Results demonstrated that H2O2 exposure caused high accumulation of ROS, with a decrease of mitochondrial membrane potential and an inhibition of the tight junction molecules in IPEC-1 cells. Also, COX IV mRNA expression and SIRT1/PGC-1α pathway were suppressed. Autophagy and PINK1/Parkin dependant-mitophagy were activated following H2O2 treatment. Further research indicated that activation of SIRT1/PGC-1α pathway caused by specific activator SRT 1720 resulted in elevating autophagy/mitophagy related markers and SIRT1 inhibitor EX 527 reversed these effects. Additionally, SIRT1 activation significantly suppressed the ROS generation, leading to increase mitochondrial membrane potential and COX IV expression. Most importantly, the expression of tight junction molecules contributing to maintain intestinal barrier integrity was significantly up-regulated. Collectively, these findings indicated that autophagy/mitophagy elevation caused by SIRT1/PGC-1α pathway activation might be a protective mechanism to increase tight junction integrity against oxidative stress-mediated ROS production in IPEC-1 cells.
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•H2O2 exposure triggered intestinal injury, autophagy/mitophagy activation.•H2O2 exposure suppressed SIRT1/PGC-1α pathway.•SIRT1/PGC-1α pathway activation enhanced autophagy and mitophagy.•SIRT1/PGC-1α pathway activation ameliorated oxidative damage in intestinal epithelial cells.
Mineral image segmentation is widely used in mining, sorting, exploration, composition analysis, and other production works. The burgeoning field of deep learning provides preferred solutions for ...mineral image segmentation. We present a review of recent literature in this direction, covering the module components, encoder-decoders architecture, representative networks, mineral image datasets, performance metrics, and state-of-the-art models. In the application performance survey, the review contents include mineral type, image type, image resolution, image data quantity, architecture selection, and encoder network construction, as well as summarizes the advantages of deep learning-based mineral image segmentation methods. We conducted small-scale experiments for the current mainstream architectures and visualize the segmentation results for performance comparison. We also investigated the application challenges and bottlenecks of deep learning-based methods, propose several innovative directions, and discuss promising future applications.
•Review and analysis of deep learning-based mineral image segmentation.•Survey of mineral image datasets, commonly-used models, and optimization strategies.•Visualization of the segmentation performance of current mainstream models.•Discussion of the application changes and innovations in mineral image segmentation.•Outlook of application potentials of deep learning in mineral production fields.
Based on the predictions of global 3D hybrid simulations, we present a new transport/acceleration path for escaped O+ ions in the upstream solar wind region resulting from the impact of a particular ...IMF tangential discontinuity (TD) with negative (positive) IMF Bz on the discontinuity's anti‐sunward (sunward) side. For O+ ions escaping to the duskside magnetosheath and with gyro‐radii larger than the TD thickness, when they encounter the TD, they can first go sunward into the upstream solar wind. They then gyrate clockwise to the pre‐noon side and get accelerated within the solar wind region and circulate back to the dawnside magnetosphere. These ions may be accelerated to well within the ring current energy range depending on the solar wind electric field strength. This new transport/acceleration path can bring some of the escaped ions into the inner magnetosphere, thus providing a new mechanism for generating an O+ ring current population.
Plain Language Summary
O+ ions in the magnetosphere only come from the Earth's ionosphere. For O+ ions escaping the magnetosphere, scientists have been treating them as being lost. Using simulations that can describe the O+ ion's kinetic dynamics, we find that, due to the impact of a particular solar wind structure, some escaped O+ ions can circulate back to the magnetosphere via a transport path in the upstream solar wind region and some of them can even enter the inner magnetosphere. Additionally, they are also energized by solar wind electric field and thus can contribute to the ring current population. Therefore, this study shows a new journey of escaped O+ ions.
Key Points
First global 3D hybrid simulations to investigate the fate of O+ ions after escaping the dayside magnetosphere
New transport/acceleration path for escaped O+ ions in upstream solar wind region after impact of an IMF tangential discontinuity
New transport/acceleration path brings some of escaped O+ ions back to the inner magnetosphere, contributing to O+ ring current pressure
Bursts of electron butterfly distributions at 10s keV correlated with chorus waves are frequently observed in the Earth's magnetosphere. Strictly ducted (parallel) upper‐band chorus waves are ...proposed to cause them by nonlinear cyclotron trapping. However, chorus waves in these events are probably nonducted or not strictly ducted. In this study, test‐particle simulations are conducted to investigate electron scattering driven by ducted (quasi‐parallel) and nonducted upper‐band chorus waves. Simulation results show butterfly distributions of 10s keV electrons can be created by both ducted and nonducted upper‐band chorus waves in seconds. Ducted upper‐band chorus waves cause these butterfly distributions mainly by accelerating electrons due to cyclotron phase trapping. However, nonducted waves tend to decelerate electrons to form these butterfly distributions via cyclotron phase bunching. Our study provides new insights into the formation mechanisms of electron butterfly distributions and demonstrates the importance of nonlinear interactions in the Earth's magnetosphere.
Plain Language Summary
The pitch angle distributions (PADs) of energetic electrons in the Earth's outer radiation belt are often modified by wave‐particle interactions. In recent years, the bursts of butterfly PADs of 10s keV electrons correlated with upper‐band chorus waves are frequently observed. By assuming these chorus waves are strictly ducted (parallel) along the geomagnetic field, previous test‐particle simulations suggest nonlinear cyclotron trapping is mainly responsible for the bursts of these butterfly PADs. In this study, test‐particle simulations in combination with two‐dimensional (2‐D) electron magnetohydrodynamics simulations are carried out to investigate how ducted (quasi‐parallel) and nonducted upper‐band chorus waves modify the electron PADs. Simulation results show that ducted chorus waves cause the bursts of butterfly PADs of 10s keV electrons by cyclotron phase trapping, consistent with previous simulation studies on strictly ducted chorus waves. However, nonducted chorus waves cause those by cyclotron phase bunching. Our study provides new insights into the formation mechanisms of the electron butterfly distributions.
Key Points
Simulations show butterfly pitch angle distributions (PADs) of tens of keV electrons are formed by ducted and nonducted upper‐band chorus waves in seconds
Ducted upper‐band chorus waves tend to accelerate electrons to form butterfly PADs of tens of keV electrons via phase trapping
Nonducted upper‐band chorus waves tend to decelerate electrons to form butterfly PADs of tens of keV electrons via phase bunching
Recently, the generation of rising‐tone chorus has been implemented with one‐dimensional (1‐D) particle‐in‐cell (PIC) simulations in an inhomogeneous background magnetic field, where both the ...propagation of waves and motion of electrons are simply forced to be parallel to the background magnetic field. In this paper, we have developed a two‐dimensional (2‐D) general curvilinear PIC simulation code and successfully reproduced rising‐tone chorus waves excited from an anisotropic electron distribution in a 2‐D mirror field. Our simulation results show that whistler waves are mainly generated around the magnetic equator and continuously gain growth during their propagation toward higher‐latitude regions. The rising‐tone chorus waves are observed off the magnetic equator, which propagate quasi‐parallel to the background magnetic field with the wave normal angle smaller than 25°. Due to the propagating effect, the wave normal angle of chorus waves is increasing during their propagation toward higher‐latitude regions along an enough curved field line. The chirping rate of chorus waves is found to be larger along a field line with a smaller curvature.
Key Points
A 2‐D general curvilinear PIC simulation code is developed
Rising‐tone chorus waves are successfully reproduced in the simulations
The wave normal angle of chorus waves is increasing during their propagation toward higher‐latitude regions along a curved field line
Whistler‐mode waves are electromagnetic waves pervasively observed in the Earth's and other planetary magnetospheres. They are considered to be mainly responsible for producing the hazardous ...radiation and diffuse aurora, which heavily relies on their properties. Density irregularities, frequently observed in the Earth's magnetospheres, are found to change largely the properties of whistler‐mode waves. Here we report, using Van Allen Probes measurements, whistler‐mode waves strongly modulated by two different density enhancements. With particle‐in‐cell simulations, we propose wave trapping caused by field‐aligned density irregularities (ducts) may account for this phenomenon. Simulation results show that whistler‐mode waves can be trapped inside the enhanced density ducts. These trapped waves remain quasi‐parallel and usually get much larger amplitudes than those unducted whistler waves during propagation away from the magnetic equator, and tend to focus at a spatially narrow channel, consistent with observations. Our results imply density irregularities may be significant to modulate radiation‐belt electrons.
Key Points
Particle‐in‐cell (PIC) simulations demonstrate whistler‐mode waves can be trapped inside the enhanced density ducts which can interpret satellite observations
These trapped waves remain quasi‐parallel and get much larger amplitudes during propagation toward high latitudes
These trapped waves focus at a spatially narrow channel inside the enhanced density ducts
With the increasing popularity of mobile applications, people enjoy browsing online tourism information on social media. This information may cause psychological resonance, which in turn stimulates ...travel intentions. This study examined the relationship between online travel information quality (OTIQ), resonance, and conative destination image. A partial least squares structural equation model was used to analyze the survey data of 426 users who recently used social media to browse online tourism information. The results show that four dimensions of OTIQ (value-added, relevancy, completeness, and design) affect cognitive resonance, and three dimensions of OTIQ (interestingness, design, and amount of information) affect emotional resonance. Both cognitive resonance and emotional resonance directly affect the conative destination image. This study contributes to online tourism marketing research by identifying the factors of OTIQ that rise tourists' resonance. It also contributes to destination image research by extending the application of resonance theory and examining the role of cognitive resonance and emotional resonance in forming a conative destination image. Understanding how QTIQ builds a destination image can help destinations improve the quality of online tourism information to attract potential tourists. This study also provides recommendations to destination marketers to formulate appropriate marketing strategies in the age of innovative technology.
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