•There are significant satisfaction differences in bus traveling before and after COVID-19.•COVID-19 has severely affected satisfaction with bus traveling of low-income individuals.•Low-income ...individuals’ satisfaction with bus traveling is determined by socioeconomic attributes rather than traveling attributes after COVID-19.•Risk concern has a significant positive impact on risk perception, but risk concern and risk perception have only a minor impact on satisfaction before and after COVID-19.•There is a significant relationship between satisfaction levels and modes of traveling alone and traveling with companions by bus.
Although all cities in China have promulgated public transportation control measures to choke off the spread of COVID-19, it also has brought severe changes to low-income individuals’ bus traveling. However, the study focusing on satisfaction differences in bus traveling before and after COVID-19 is far under-researched, this paper therefore explored satisfaction differences among low-income individuals under socioeconomic attributes, traveling attributes, and psychological attributes by using the data consist of interviews addressed to 930 individuals in Taiyuan, China. Furthermore, the relationship between satisfaction levels and modes of traveling alone and traveling with companions by bus has also been deeply analyzed to reduce single-person driving problem. As a result, many exciting phenomena were discovered: the significant factors affecting low-income individuals’ satisfaction occur “shift” on a large scale after COVID-19; risk concern has a significant positive impact on risk perception, but risk concern and risk perception have only a minor impact on satisfaction before and after COVID-19; it was found that there is a significant relationship between satisfaction levels and modes of traveling alone and traveling with companions by bus. Understanding them can be a reference for improving the travel environment between low-income individuals.
Medium‐scale traveling ionospheric disturbances (MSTIDs) are one of the ionospheric plasma density structures and are observable through 630‐nm airglow images. Previous studies using airglow images ...at Tromsø (69.6°N, 19.2°E; magnetic latitude: 66.7°N), Norway, reported high‐latitude MSTIDs (here we call them as polar‐type MSTIDs) whose propagation direction changes associated with auroral brightening and magnetic field disturbances. However, there has been little statistical analysis on the connection of MSTIDs occurring at high and middle latitudes. In this study, we statistically analyzed the MSTIDs observed by an airglow imager at Nyrölä (62.3°N, 25.5°E; magnetic latitude: 59.4°N), Finland, which is located ∼7° south of Tromsø, corresponding to subauroral latitudes. The period analyzed was from 23 January 2017, to 30 September 2021. We found 11 cases of MSTIDs during this period. Eight cases were found to be the polar‐type MSTIDs whose motion changes associated with auroral brightening and magnetic field disturbances. We found that 9 cases of MSTID show the low‐latitude boundary at 61° ± 2°N for geographic latitude and 58° ± 2°N for magnetic latitude, indicating disconnection between high‐ and mid‐latitude MSTIDs. We also derived occurrence probability, velocity, wavelength, period, wave front direction, and propagation direction of these MSTIDs. The occurrence probability of MSTIDs at Nyrölä is 1.9%, which is much lower than those at high (Tromsoe, more than 50%) and middle (Japan, ∼30%) latitudes. We discuss these MSTID characteristics at subauroral latitudes based on possible difference of generation mechanisms of nighttime MSTIDs at high and middle latitudes.
Plain Language Summary
Medium‐scale traveling ionospheric disturbances (MSTIDs) are one of the ionospheric plasma density structures and are observable through 630‐nm airglow images. Previous studies using airglow images at Tromsø (69.6°N, 19.2°E; magnetic latitude: 66.7°N), Norway, reported high‐latitude MSTIDs (here we call them as polar‐type MSTIDs) whose propagation direction changes associated with auroral brightening and magnetic field disturbances. However, there has been little statistical analysis on the connection of MSTIDs occurring at high and middle latitudes. In this study, we analyzed 11 MSTID cases observed by an airglow imager at Nyrölä (62.3°N, 25.5°E; magnetic latitude: 59.4°N), Finland, which is located ∼7° south of Tromsø, corresponding to subauroral latitudes. We found that 9 cases of MSTID show the low‐latitude boundary at 61° ± 2°N for geographic latitude and 58° ± 2°N for magnetic latitude, indicating disconnection between high‐ and mid‐latitude MSTIDs. We also derived occurrence probability, velocity, wavelength, period, wave front direction, and propagation direction of these MSTIDs.
Key Points
We statistically analyzed medium‐scale traveling ionospheric disturbances (MSTIDs) observed at subauroral latitudes at Nyrölä, Finland
Most MSTIDs are the polar‐type MSTIDs whose motion changes associated with auroral brightening and/or magnetic field disturbances
The low‐latitude boundary of these MSTIDs was at ∼61°N latitude, indicating disconnection between high‐ and mid‐latitude MSTIDs
This article reports a slow-wave structure (SWS) working at 1 THz which can be fabricated through nano-computer numerical control (nano-CNC) technology for the first time. First, a 1 THz deformed ...quasi sine waveguide (D-QSWG) SWS has been designed and simulated in this article. To reduce the metal loss of input and output waveguide, a coupler which transit the waveguide to over mode rectangular waveguide has been designed. The simulation result shows that input and output waveguides with this coupler have lower metal loss than that of WR1 rectangular waveguide. To fabricate the designed D-QSWG SWS, tungsten steel endmills have been used. The fabricated SWS has the surface roughness around 58-74 nm, the corresponding effective conductivity is around <inline-formula> <tex-math notation="LaTeX">2\times 10^{{7}} </tex-math></inline-formula>-1.85 <inline-formula> <tex-math notation="LaTeX">\times 10^{{7}} </tex-math></inline-formula> S/m. And the cold test results show that the insertion loss of the fabricated model is less than 30 dB while the reflection loss is less than −15 dB in the frequency range of 0.998-1.016 THz, which has a good consistency with the simulated results. The beam-wave interaction simulation results based on the cold test results show that the designed D-QSWG traveling wave tube (TWT) has the output power of 300 mW, and the 3 dB bandwidth is around 3 GHz.
The explosive eruption of the Hunga-Tonga volcano in the southwest Pacific at 0415UT on 15 January 2022 triggered gigantic atmospheric disturbances with surface air pressure waves propagating around ...the globe in Lamb mode. In space, concentric traveling ionosphere disturbances (CTIDs) are also observed as a manifestation of air pressure waves in New Zealand ∼0500UT and Australia ∼0630UT. As soon as the air pressure waves reached central Australia ∼0800UT, conjugate CTIDs appeared almost simultaneously in the northern hemispheres through interhemispheric coupling, much earlier than the arrival of the surface air pressure waves to Japan after 1100UT. Combining observations over Australia and Japan between 0800 and 1000UT, both direct and conjugate CTIDs show similar horizontal phase velocities of 320–390 m/s, matching with the dispersion relation of Lamb mode. The arrival of atmospheric Lamb wave to Japan later created in situ CTIDs showing the same Lamb mode characteristics as the earlier conjugate CTIDs.
Traveling wave parametric amplifiers (TWPAs) play a prominent role in modern superconducting quantum computing efforts. They are valued for their relatively high power handling capability, bandwidth, ...and simple operation. However, the core mechanism for producing gain in these systems is based on very long nonlinear transmission lines that can be difficult to engineer for ideal behavior and require additional bulky passive components to adequately isolate quantum circuits. In this article, we describe our attempt to distill the core principle of traveling wave amplifier operation and discuss prospects for extending this approach to building much smaller discrete circuits that possess some of the advantageous properties of TWPAs, specifically directional gain with a simple pumping scheme.
In this article, the design and experiment of a high continuous-wave (CW) power Ku-band gyrotron traveling-wave tube (gyro-TWT) are described. The hot experiment results indicate that the TE11 mode ...gyro-TWT, driven by a 50 kV-4.5 A electron beam, can produce a maximum CW output power of 49 kW, with an efficiency of 21.8% at 16 GHz. The saturated bandwidth is 2 GHz, and more than 30-kW CW output power is achieved from 15 to 17 GHz. However, the outgassing is observed in the low-frequency range, which limits the enhancement of CW output power. Then, the simulation is performed and indicates that the attenuated power distribution and heat dissipation on the dielectric-loaded circuit (DLC) are dependent on the frequency, attenuation of lossy ceramic, and input power. Also, the maximum temperature of lossy ceramic at 15 and 15.5 GHz is too high for stable operation. A nonuniform DLC is utilized to dissipate power dispersedly. The simulation results show that the maximum power loss on a single lossy ceramic is reduced by 77.9% and 48.9% at 15 and 15.5 GHz, respectively. It indicates that the nonuniform DLC could adjust the dissipation power on the lossy ceramics via the attenuation profile varying with frequency and effectively enhance the power capacity of dielectric-loaded gyro-TWT.
The electron optical system (EOS) plays a vital role in vacuum electronic devices (VEDs). A 19.3-mA, 19.4-kV electron gun with a multistage focus electrode is designed, and the multistage focus ...electrode advantage is analyzed to generate a high-quality beam that meets the requirement of traveling-wave tubes (TWTs) operating higher than 0.6 THz. The tunnel and beam waist radii are 50 and <inline-formula> <tex-math notation="LaTeX">35~\mu \text{m} </tex-math></inline-formula>, respectively, and the current density in the waist reaches as high as 501 A/cm2. A novel dynamic-matched focusing magnetic field upswing from 0.35 to 0.5 T at the circuit tail, produced by an open-side asymmetrical magnetic focusing system, is proposed to balance the increasing divergence force of the rise of space charge focus. Two different asymmetrical magnet design methods are analyzed. Compared to the uniform magnet (UM) and inclined magnet (IM), the inclined dynamic-matched magnet (IDMM) performs optimally in beam transmission and output power, verified by particle-in-cell (PIC) simulation. The proposed dynamic-matched focusing magnetic field can benefit the performance of terahertz TWTs by improving the beam transmission rate and beam-wave interaction efficiency.
To further increase the average output power of the <inline-formula> <tex-math notation="LaTeX">{Q} </tex-math></inline-formula>-band gyrotron traveling wave tube (gyro-TWT), the power capacity and ...stability of the collector are investigated. In this article, the characteristics of the electron collection, the modeling of the cooling system, and the suppression of stray electrons are analyzed. The dissipated power is associated with the transverse energy of the electron beam. When the gyro-TWT operates at zero drive, the collector has a maximum dissipated power density of 2 kW/cm 2 for a high average power state. Thermal results indicate a maximum temperature of 381 °C on the collector with an optimized cooling system. By applying a transverse magnetic field, the stray electrons can be completely intercepted by the collector. The hot experiment results indicate that the gyro-TWT (45% duty cycle), driven by a 60-kV-9.82-A electron beam, can withstand a maximum beam power of 265 kW at zero drive. Then, a pulse power of 111 kW, with an average power of 50 kW and an efficiency of 18.8% at 47 GHz, is measured stably. The simulation and experimental results demonstrate the high-power capacity and high stability of the curved collector.
In this paper travelling waves with distributional profiles for the Camassa–Holm equation are studied. Using a product of distributions a new solution concept is introduced which extends the ...classical one. As a consequence, necessary and sufficient conditions for the propagation of a distributional profile are established and we present examples with discontinuous solutions, measures and even distributions that are not measures. One of these examples may be interpreted as a simple model for a “tsunami” in the setting of shallow water theory. We also prove that, under natural assumptions, profiles belonging to the Sobolev space
H
loc
1
(
R
)
usually considered in the classical weak formulation can be seen as particular cases of our distributional solution concept.
A Ka -band gyrotron traveling wave tube (gyro-TWT) with a single depressed collector (SDC) has been designed, and the SDC has been experimentally verified for the first time in the tube with a ...dielectric-loaded circuit. The effect of reflection electrons on the output power and the movement of electrons in gyro-TWT with an SDC are also analyzed in this article. The simulation results indicate that gyro-TWT driven by a 60-kV, 10-A electron beam can achieve about 230-kW maximum peak power and 150 kW recycled power with a 15-kV depressed collector. The overall efficiency of gyro-TWT increases from 38.3% to 51.1%. The hot experiment results show that the measured maximum peak power is 155.3 kW at 31 GHz, corresponding to an average power of 15.53 kW with a 10% duty factor and 140 kW pulsed recycle power with a 14-kV depressed collector. The overall efficiency is improved from 27.1% to 33.8% and increased by 24.7%. The saturated bandwidth is 4 GHz from 27.7 to 31.7 GHz.
