The impact of inverted density gradients on density profiles measured by reflectometry: an experimental and numerical investigation at ASDEX Upgrade

The high-field side high-density (HFSHD) region at ASDEX Upgrade (AUG) is a well-documented phenomenon leading to a dense plasma in the inner divertor region that expands upwards to the midplane, resulting in poloidally asymmetric scrape-off layer density profiles. This work investigates, via simulation and experiment, whether the HFSHD at the midplane leads to hollow density profiles at the high-field side. Using the frequency-modulated continuous-wave O-mode reflectometer at AUG, experimental evidence has been found of reflection patterns compatible with a hollow density profile that are reproduced by 1D full-wave simulations. Furthermore, this work assesses the uncertainties in the density profile reconstruction as a consequence of the inverted gradient, showing that the presence of an HFSHD may lead to an overestimation of the density in the confined region.

A Deep Neural Network Method for Arterial Blood Flow Profile Reconstruction

Arterial stenosis will reduce the blood flow to various organs or tissues, causing cardiovascular diseases. Although there are mature diagnostic techniques in clinical practice, they are not suitable for early cardiovascular disease prediction and monitoring due to their high cost and complex operation. In this paper, we studied the electromagnetic effect of arterial blood flow and proposed a method based on the deep neural network for arterial blood flow profile reconstruction. The potential difference and weight matrix are used as inputs to the method, and its output is an estimate of the internal blood flow velocity distribution for arterial blood flow profile reconstruction. Firstly, the weight matrix is input into the convolutional auto-encode (CAE) network to extract its features. Then, the weight matrix features and potential difference are combined to obtain the features of the blood velocity distribution. Finally, the velocity features are reconstructed into blood flow velocity distribution by a convolution neural network (CNN). All data sets are obtained from a model of the carotid artery with different rates of stenosis in a uniform magnetic field by COMSOL. The results show that the average root mean square error of the reconstruction results obtained by the proposed method is 0.0333, and the average correlation coefficient is 0.9721, which is better than the corresponding indicators of the Tikhonov, back propagation (BP) and CNN methods. The simulation results show that the proposed method can achieve high accuracy in blood flow profile reconstruction and is of great significance for the early diagnosis of arterial stenosis and other vessel diseases.

Assessing Low-Cost Terrestrial Laser Scanners for Deriving Forest Structure Parameters

The increasingly affordable price point of terrestrial laser scanners has led to a democratization of instrument availability, but the most common low-cost instruments have yet to be compared in terms of the consistency to measure forest structural attributes. Here, we compared two low-cost terrestrial laser scanners (TLS): the Leica BLK360 and the Faro Focus 120 3D. We evaluate the instruments in terms of point cloud quality, forest inventory estimates, tree-model reconstruction, and foliage profile reconstruction. Our direct comparison of the point clouds showed reduced noise in filtered Leica data. Tree diameter and height were consistent across instruments (4.4% and 1.4% error, respectively). Volumetric tree models were less consistent across instruments, with ~29% bias, depending on model reconstruction quality. In the process of comparing foliage profiles, we conducted a sensitivity analysis of factors affecting foliage profile estimates, showing a minimal effect from instrument maximum range (for forests less than ~50 m in height) and surprisingly little impact from degraded scan resolution. Filtered unstructured TLS point clouds must be artificially re-gridded to provide accurate foliage profiles. The factors evaluated in this comparison point towards necessary considerations for future low-cost laser scanner development and application in detecting forest structural parameters.

Chasing sand: evolution of the surface and subsurface drainage of the Sinkhole Plain, Central Kentucky Karst, USA

<p>This work extends the established geochronology of the Mammoth Cave region, Kentucky, USA, spatially and temporally, to infer evolution of the karst landscape and to consider the shifting drainage basins of the Barren River and the Green River in relation to regional drainage rearrangements. Previous studies have focused on the Mammoth Cave System and used cosmogenic radionuclide dating to link the incision history of the Green River and the Cave as far back as 3.25 Ma. We posit that prior to the wide-spread karstification that produced Mammoth Cave, drainage consisted of a purely fluvial stream network flow on the youngest clastic rocks. When this caprock was breached, carbonate dissolution ensued and the system transitioned to fluviokarst. Relict large trunk passages that originated at that time can be found in features such as Prewitts Knob, Bald Knob, and Huckleberry Knob. We intend to use sediments and speleothems collected from Crystal Onyx Cave in Prewitts Knob to constrain the age of this stage of karst development and to provide an estimate of the long-term erosion rate of the Sinkhole Plain surrounding the knob. These relict trunks were also used for cave stream profile reconstruction in combination with the east-west trending uvalas and sets of steep, deep sinkholes. We interpret that paleodrainage as having been west-flowing into the Barren River which then served as regional base level. Thus, we infer that as the rivers incised, this drainage was pirated to the north and began flowing to the Green River. The system then evolved into a more mature karst, large conduits near the surface collapsed, and dissected the landscape into isolated depressions. The collapsed limestone formed red soil and the sandstone produced angular clasts scattered throughout that soil. The retreating Chester Cuesta, marking the boundary between the Sinkhole Plain and the sandstone-capped Chester Upland, eroded most rapidly where limestone was exposed to the surface and more slowly where it was sandstone-capped leaving abandoned isolated cave trunk passage segments in remnant knobs. The results of this work have implications for understanding timescales of the evolution of karst systems in unconfined carbonate sequences as well as the interaction of karst areas with the transience in drainage networks.</p>