First experimental proof of a clear and strong dependence of the standard phase scintillation index (σφ) derived using Global Positioning System measurements on the ionospheric plasma flow around the ...noon sector of polar ionosphere is presented. σφ shows a strong linear dependence on the plasma drift speed measured by the Super Dual Auroral Radar Network radars, whereas the amplitude scintillation index (S4) does not. This observed dependence can be explained as a consequence of Fresnel frequency dependence of the relative drift and the used constant cutoff frequency (0.1 Hz) to detrend the data for obtaining standard σφ. The lack of dependence of S4 on the drift speed possibly eliminates the plasma instability mechanism(s) involved as a cause of the dependence. These observations further confirm that the standard phase scintillation index is much more sensitive to plasma flow; therefore, utmost care must be taken when identifying phase scintillation (diffractive phase variations) from refractive (deterministic) phase variations, especially in the polar region where the ionospheric plasma drift is much larger than in equatorial and midlatitude regions.
Key Points
A clear strong linear dependence of phase scintillation index on the plasma drift speed around noon sector of the polar ionosphere is presented
Observed dependence can be very possibly explained by the dependence of the shifted Fresnel frequency from the relative drift
Amplifies the importance of using dynamic cutoff frequency in detrending the phase of GPS signal in the polar region
Lung cancer is the most common cancer in China. Previous studies have indicated that lung cancer incidence exhibits remarkable spatial heterogeneity, and lung cancer is related to outdoor air ...pollution. However, the non-linear spatial association between outdoor air pollution and lung cancer incidence in China remains unclear.
In this study, the relationships between the lung cancer incidence of males and females from 207 counties in China in 2013 with annual concentrations of PM2.5, PM10, SO
, NO
, CO and O
were analysed. GeoDetector q statistic was used for examining the non-linear spatial association between outdoor air pollution and incidence of lung cancer.
An apparent spatial and population gender heterogeneity was found in the spatial association between outdoor air pollution and lung cancer incidence. Among the six selected pollutants, SO
has the greatest influence on lung cancer (q = 0.154 in females) in north China. In the south, each selected pollutant has a significant impact on males or females, and the mean q value in the south is 0.181, which is bigger than that in the north (q = 0.154). In addition, the pollutants have evident non-linear interaction effects on lung cancer. In north China, the interaction between SO
and PM2.5 is the dominant interaction, with q values of 0.207 in males and 0.334 in females. In the south, the dominant interactive factors are between SO
and O
in males and between SO
and CO in females, with q values of 0.45, 0.232 respectively. Smoking is a substantial contributor to lung cancer among men, either in South or North China, with q value of 0.143 and 0.129 respectively, and the interaction between smoking and air pollutants increases this risk.
This study implies that the influence of SO
and PM2.5 on lung cancer should be focused on in north China, and in the south, the impact of O
and CO as well as their interaction with SO
need to be paid more attention. Smoking, particularly in men, remains a significant risk factor for lung cancer in both North and South China.
Abstract
This paper presents the burst pressure design of the cargo tank used in the University of Stavanger (UiS) Subsea Freight-Glider (USFG). The USFG is an innovative large underwater cargo ...glider drone that is 50 m long and has a DWT of 1500 ton. It uses variable-buoyancy propulsion instead of traditional propellers for movement. This is an extremely efficient propulsion method and allows the USFG to achieve an average energy consumption of less than 10 kW. Structural weight is a premium as the USFG is required to be neutrally buoyant in water. Therefore, the design of the cargo tank which is the largest component in the USFG needs to be optimal for minimal structural weight. One approach used in design optimisation is to utilise design codes and/or methods that are more precise and therefore allow for lower safety margins. This approach will be investigated in this paper for the burst pressure design of the cargo tank. The different parts of ASME BPVC codes will be compared. The sensitivity of the codes to changes in design parameters is also investigated. Lastly, some comments on the use of reliability methods to further optimise the design are also presented.
A comparison tool has been developed by mapping the global GPS total electron content (TEC) and large coverage of ionospheric scintillations together on the geomagnetic latitude/magnetic local time ...coordinates. Using this tool, a comparison between large‐scale ionospheric irregularities and scintillations is pursued during a geomagnetic storm. Irregularities, such as storm enhanced density, middle‐latitude trough, and polar cap patches, are clearly identified from the TEC maps. At the edges of these irregularities, clear scintillations appeared but their behaviors were different. Phase scintillations (σφ) were almost always larger than amplitude scintillations (S4) at the edges of these irregularities, associated with bursty flows or flow reversals with large density gradients. An unexpected scintillation feature appeared inside the modeled auroral oval where S4 were much larger than σφ, most likely caused by particle precipitations around the exiting polar cap patches.
Key Points
A comparison tool has been developed by mapping global GPS TEC and large coverage of scintillations together on MLAT/MLT coordinates
σφ were larger than S4 at the edges of the irregularities associated with bursty flows or flow reversals with large density gradients
S4 were much larger than σφ in the auroral oval, most likely caused by particle precipitations around the exiting polar cap patches
Exploiting crossing symmetry, the hadron scale pion valence quark distribution function is used to predict the kindred elementary valence quark fragmentation function (FF). This function defines the ...kernel of a quark jet fragmentation equation, which is solved to obtain the full pion FFs. After evolution to a scale typical of FF fits to data, the results for quark FFs are seen to compare favourably with such fits. However, the gluon FF is markedly different. Notably, although FF evolution equations do not themselves guarantee momentum conservation, inclusion of a gluon FF which, for four quark flavours, distributes roughly 11% of the total light-front momentum fraction, is sufficient to restore momentum conservation under evolution. Overall, significant uncertainty is attached to FFs determined via fits to data; hence, the features of the predictions described herein could potentially provide useful guidance for future such studies.
The occurrence and intensity of the geomagnetic storms/activity in the weak solar cycle 24 (SC24) were studied mainly for low latitudes, with intensity being the maximum value of the activity. The ...impulsive strength of the activity giving its mean value during the main phase, which can better indicate the effect of the activity on utility systems, has not received much attention at any latitude. In this paper, we investigate the intensity and impulsive strength of the 179 and 85 clear geomagnetic activities (DstMin ≤ −50 nT) identified in the low, mid and high latitude indices (SymH, Kp, and AE) and corresponding solar wind velocity V, IMF Bz, and the product V × Bz in solar cycles 23–24 (1996–2019) for the first time. Compared to SC23, the total intensity and total impulsive strength in SC24 in all latitudes reduce by nearly equal amounts (∼60%) as the reduction in the number of activities (∼53%). The average intensity and average impulsive strength, however, reduce by nearly equal and largest amounts in low latitudes (∼23%), which is close to the reduction in the combination <−(V × Bz)MP > by ∼30%. At mid and high latitudes, the average intensity and average impulsive strength reduce by only small amounts (∼7.5%). Only the impulsive strength of the geomagnetic activity at low latitudes (IpsSymH) and the combination <−(V × Bz)MP> identify the two power outages happened in SC23. The correlation between IpsSymH and <−(V × Bz)MP> is also high (0.83) in SC23.
Plain Language Summary
The geomagnetic activity is known to depend directly on the solar activity that undergoes an 11‐year solar cycle. The last solar cycle 24 (SC24) was the weakest solar cycle in 100 years with a prior long‐deep solar minimum. The occurrence and intensity of the geomagnetic activity in SC24 have been known mainly for low latitudes. The impulsive strength of the activity, which can better indicate its effects on utility systems, has not received much attention at any latitude. In this paper, we investigate the intensity and impulsive strength of the 179 and 85 clear geomagnetic activities (DstMin ≤ −50 nT) identified in the low, mid and high latitude geomagnetic activity indices (SymH, Kp, and AE) and corresponding solar wind velocity V, north‐south component of the interplanetary magnetic field (IMF Bz), and the product (V × Bz) during the full period of the solar cycles 23 and 24 (1996–2019). The results reveal that the average intensity and average impulsive strength of the geomagnetic activity in SC24 compared to SC23 reduce by nearly equal and largest amounts in low latitudes (21% and 25%) and the reductions are small at mid (∼7.5%) and high (∼6.5%) latitudes.
Key Points
The total intensity and total impulsive strength of the geomagnetic activity in solar cycle 24 compared to solar cycle 23 reduce ∼60% each in all latitudes
Reductions in the average intensity and impulsive strength are large ∼23% at low latitudes and nearly equal to that in <−(V × Bz)MP> by 30%
The correlation coefficient is also highest (0.86) between the low latitude impulsive strength and the combination <−(V × Bz)MP>
In this paper, a novel separation of variables is presented for solving the exact solutions for the free vibrations of thin orthotropic rectangular plates with all combinations of simply supported ...(S) and clamped (C) boundary conditions, and the correctness of the exact solutions are proved mathematically. The exact solutions for the three cases SSCC, SCCC, and CCCC are successfully obtained for the first time, although it was believed that they are unable to be obtained. The new exact solutions are further validated by extensive numerical comparisons with the solutions of FEM and those available in the literature.
Supposing there exists an effective charge which defines an evolution scheme for both unpolarised and polarised parton distribution functions (DFs) that is all-orders exact and using Ansätze for ...hadron-scale proton polarised valence quark DFs, constrained by flavour-separated axial charges and insights from perturbative quantum chromodynamics, predictions are delivered for all proton polarised DFs at the scale ζC2=3 GeV2. The pointwise behaviour of the predicted DFs and, consequently, their moments, compare favourably with results inferred from data. Notably, flavour-separated singlet polarised DFs are small. On the other hand, the polarised gluon DF, ΔG(x;ζC), is large and positive. Using our result, we predict ∫0.051dxΔG(x;ζC)=0.214(4) and that experimental measurements of the proton flavour-singlet axial charge should return a0E(ζC)=0.33(2).
The dependencies of global positioning system (GPS) scintillation indices on ionospheric plasma flow and the rate of change of total electron content (TEC) around the dawn sector for the first time ...of the polar ionosphere are investigated. The phase scintillation index (σφ) derived from GPS measurements of the Canadian High Arctic Ionospheric Network (CHAIN) shows linear dependencies on both the plasma drift speed measured by the SuperDARN radar and on the rate of change of TEC estimated from the GPS receivers of CHAIN. However, the amplitude scintillation index (S4) does not show any dependence on the plasma flow or the rate of change of TEC. These results further support Wang et al. (2018), https://doi.org/10.1002/2017JA024805 at the noon sector. The dependence of the phase scintillation index on the plasma flow further evidences that the standard phase scintillation index is dominated by refractive variations due to the use of a fixed cut‐off frequency of 0.1 Hz while detrending the phase observable. The dependence of the phase scintillation index on the rate of change of TEC consolidates the dominance of refractive variations inside.
Plain Language Summary
In decades, the standard scintillation indices are widely used to represent the strength of scintillations in the ionosphere, which were usually calculated from the sixth order Butterworth filter with a fixed cut‐off frequency of 0.1 Hz by the ground‐based Global Navigation Satellite System (GNSS) receiver automatically. At middle‐to‐low latitudes, the applications of these indices are working very well. However, over the polar ionosphere, the completely different scintillation phenomenon “Phase without Amplitude” occurred when confronting the hazard conditions. Then, in order to explaining this weird, many researchers have carried out a lot of valuable approaches, fundamentally challenging the direct adopt of standard phase scintillation index. Here, for the first time, we present an experimental evidence on the dawn sector to prove the clear positive dependence of phase scintillation index on the convection flow speed and also the TEC variations. It reminds us to be careful when using the standard phase scintillation index over the polar region, in particular with high‐speed flows.
Key Points
The dependencies of global positioning system scintillation indices on plasma flow and total electron content (TEC) variation were evaluated around the dawn sector of polar ionosphere
The phase scintillation index depends linearly only on the plasma flow speed and the rate of change of TEC
However, the amplitude scintillation index does not rely on the plasma flow and also the rate of change of TEC
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