Mesoscale wind field patterns play important roles in episodes of high particulate matter (PM2.5). Previous studies have reported the main synoptic meteorological features associated with high-PM2.5 ...days with two primary modes: long-range transport (LRT) and stagnation or local contribution (STL). However, due to the lack of more small-scale analyses spanning across multiple administrative regions, statistical quantification of representative mesoscale wind patterns with elevated PM2.5 episodes is needed to explore region-specific emissions reduction strategies in South Korea. This study applied k-means clustering to NCEP FNL reanalysis data from 2016 to 2020 to identify mesoscale wind field patterns associated with high-PM2.5 episodes across all 17 administrative regions of South Korea. Our statistical approach yielded region-specific wind fields for 17 individual administrative regions, and also empirically yielded a total of eight representative patterns, four patterns each for both LRT and STL modes, which were applicable across all regions. The eight patterns were consistent with most previous studies. In addition, we quantified the LTP and STL modes in all 17 regions, and showed that they were more prevalent in the western and southeastern administrative regions of South Korea, respectively. Our results serve as a reference for region-specific mitigation strategies in all administrative regions of South Korea, and will also be useful for analyzing relations between meteorology and high-PM2.5 episodes in the SIJAQ and ASIA-AQ studies.
•Mesoscale wind patterns for high PM2.5 episodes in South Korea are presented.•Mesoscale wind patterns well compared between local and transported patterns.•Dominant wind patterns correlated with geographical locations in Korea.•Patterns can be a reference for aircraft-based campaign studies over Korea.
We are concerned with the inverse scattering problem of recovering an inhomogeneous medium by the associated acoustic wave measurement. We prove that under certain assumptions, a single far-field ...pattern determines the values of a perturbation to the refractive index on the corners of its support. These assumptions are satisfied, for example, in the low acoustic frequency regime. As a consequence if the perturbation is piecewise constant with either a polyhedral nest geometry or a known polyhedral cell geometry, such as a pixel or voxel array, we establish the injectivity of the perturbation to far-field map given a fixed incident wave. This is the first unique determinancy result of its type in the literature, and all of the existing results essentially make use of infinitely many measurements.
The design of a proton exchange membrane (PEM) electrolyzer and various hardware options remain key research areas for green hydrogen production technology. We have proposed an approach to select ...optimum design factors, including a flow-path design for the PEM electrolyzer using a machine learning (ML) technique for the first time. Efficient multiple ML models employing k-nearest neighbors and decision tree regression approaches predict the optimal hydrogen-generating system design for the PEM electrolyzer cell. The proposed ML model was trained and validated using 1062 design data points. The model predicts 17 parameters of the electrolyzer assembly for five input parameters: the hydrogen production rate, electrode area, anode flow area, cathode flow area, and type of cell design (e.g., single or stack). The model shows an absolute mean square error of 0.31 when compared to the experimental results (e.g., potential), which indicates that the model has excellent reliability. Finally, this study presents that the ML model can predict the optimal design of a PEM electrolyzer for commercial-scale hydrogen production rates at 50–3000 mL/min. This research will contribute to reducing the cost and time required to develop future water electrolyzers for hydrogen production.
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•Machine learning models predicted optimal design parameters for PEM electrolyzers.•Optimal design and flow-field pattern were determined.•A commercial-scale PEM electrolyzer was designed.
This paper is concerned with the intrinsic geometric structures of conductive transmission eigenfunctions. The geometric properties of interior transmission eigenfunctions were first studied in ...Blåsten, E., Liu, H. (2017). On vanishing near corners of transmission eigenfunctions. J. Funct. Anal. 273(11):3616-3632. It is shown in two scenarios that the interior transmission eigenfunction must be locally vanishing near a corner of the domain with an interior angle less than π. We significantly extend and generalize those results in several aspects. First, we consider the conductive transmission eigenfunctions which include the interior transmission eigenfunctions as a special case. The geometric structures established for the conductive transmission eigenfunctions in this paper include the results in Blåsten, E., Liu, H. (2017). On vanishing near corners of transmission eigenfunctions. J. Funct. Anal. 273(11):3616-3632 as a special case. Second, the vanishing property of the conductive transmission eigenfunctions is established for any corner as long as its interior angle is not π when the conductive transmission eigenfunctions satisfy certain Herglotz functions approximation properties. That means, as long as the corner singularity is not degenerate, the vanishing property holds if the underlying conductive transmission eigenfunctions can be approximated by a sequence of Herglotz functions under mild approximation rates. Third, the regularity requirements on the interior transmission eigenfunctions in Blåsten, E., Liu, H. (2017). On vanishing near corners of transmission eigenfunctions. J. Funct. Anal. 273(11):3616-3632 are significantly relaxed in the present study for the conductive transmission eigenfunctions. In order to establish the geometric properties for the conductive transmission eigenfunctions, we develop technically new methods and the corresponding analysis is much more complicated than that in Blåsten, E., Liu, H. (2017). On vanishing near corners of transmission eigenfunctions. J. Funct. Anal. 273(11):3616-3632. Finally, as an interesting and practical application of the obtained geometric results, we establish a unique recovery result for the inverse problem associated with the transverse electromagnetic scattering by a single far-field measurement in simultaneously determining a polygonal conductive obstacle and its surface conductive parameter.
Abstract This paper addresses an inverse cavity scattering problem associated with the time-harmonic biharmonic wave equation in two dimensions. The objective is to determine the domain or shape of ...the cavity. The Green’s representations are demonstrated for the solution to the boundary value problem, and the one-to-one correspondence is confirmed between the Helmholtz component of biharmonic waves and the resulting far-field patterns. Two mixed reciprocity relations are deduced, linking the scattered field generated by plane waves to the far-field pattern produced by various types of point sources. Furthermore, the symmetry relations are explored for the scattered fields generated by point sources. Finally, we present two uniqueness results for the inverse problem by utilizing both far-field patterns and phaseless near-field data.
Cerebral fat embolism (CFE) is a rare but potentially fatal complication that can occur after long bone fractures. It represents one subcategory of fat embolisms (FE). Diagnosing CFE can be ...challenging due to its variable and nonspecific clinical manifestations. We report a case of CFE initially presenting with turbid urine, highlighting an often neglected sign.
A 69-year-old male was admitted after a traffic accident resulting in bilateral femoral fractures. Sixteen hours post-admission, grossly turbid urine was noted but received no special attention. Four hours later, he developed rapid deterioration of consciousness and respiratory distress. Neurological examination revealed increased upper limb muscle tone and absent voluntary movements of lower limbs. Brain MRI demonstrated a 'starfield pattern' of diffuse punctate lesions, pathognomonic for CFE. Urine microscopy confirmed abundant fat droplets. Supportive treatment and fracture fixation were performed. The patient regained consciousness after 3 months but had residual dysphasia and limb dyskinesia.
CFE can present with isolated lipiduria preceding overt neurological or respiratory manifestations. Heightened awareness of this subtle sign in high-risk patients is crucial for early diagnosis and intervention. Prompt urine screening and neuroimaging should be considered when gross lipiduria occurs after long bone fractures.
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