Total Discharge Research Articles

Predicting individual patient and hospital-level discharge using machine learning

Abstract Background Accurately predicting hospital discharge events could help improve patient flow and the efficiency of healthcare delivery. However, using machine learning and diverse electronic health record (EHR) data for this task remains incompletely explored. Methods We used EHR data from February-2017 to January-2020 from Oxfordshire, UK to predict hospital discharges in the next 24 h. We fitted separate extreme gradient boosting models for elective and emergency admissions, trained on the first two years of data and tested on the final year of data. We examined individual-level and hospital-level model performance and evaluated the impact of training data size and recency, prediction time, and performance in subgroups. Results Our models achieve AUROCs of 0.87 and 0.86, AUPRCs of 0.66 and 0.64, and F1 scores of 0.61 and 0.59 for elective and emergency admissions, respectively. These models outperform a logistic regression model using the same features and are substantially better than a baseline logistic regression model with more limited features. Notably, the relative performance increase from adding additional features is greater than the increase from using a sophisticated model. Aggregating individual probabilities, daily total discharge estimates are accurate with mean absolute errors of 8.9% (elective) and 4.9% (emergency). The most informative predictors include antibiotic prescriptions, medications, and hospital capacity factors. Performance remains robust across patient subgroups and different training strategies, but is lower in patients with longer admissions and those who died in hospital. Conclusions Our findings highlight the potential of machine learning in optimising hospital patient flow and facilitating patient care and recovery.

Advancing water security in Africa with new high-resolution discharge data

VegDischarge v1, which covers over 64,000 river segments in Africa, is a natural river discharge dataset produced by coupled modeling; the agro-hydrologic VegET model and the mizuRoute routing model for the period 2001-2021. Using remote sensing data and hydrological modeling system, the 1-km runoff field simulated by VegET, was routed with mizuRoute. Performance metrics show strong model reliability, with R² of 0.5–0.9, NSE of 0.6–0.9, and KGE of 0.5–0.8 at the continental scale. The total average annual discharge for Africa is quantified at 3271.4 km³·year−1, with contributions to oceanic basins: 1000.0 km³·year−1 to the North Atlantic, primarily from the Senegal, Gambia, Volta, and Niger Rivers; 1327.2 km³·year−1 to the South Atlantic, largely from the Congo River; 214.7 km³·year−1 to the Mediterranean Sea, predominantly from the Nile River; and 729.4 km³·year−1 to the Indian Ocean, with inputs from rivers such as the Zambezi. The dataset is valuable for stakeholders and researchers to understand water availability, its temporal and spatial variations that affect water-related infrastructure planning, sustainable resource allocation, and the development of climate resilience strategies.

Discharge modes evolution characteristics of metal particle on the spacer surface in AC gas insulated switchgear

Abstract Flashover faults on gas insulated switchgear (GIS) insulators induced by metal particles occur frequently. Previous studies have obtained the characteristics of partial discharges (PDs) induced by metal particles on spacer surfaces, but these characteristics cannot explain the detection failure of ultra-high frequency (UHF) online monitoring. To enable further study of the PD characteristics induced by surface metal particles, the space electric field and a very-high-sensitivity pulse current (PC) measurement system were established. The electric field and PC characteristics of a PD induced by metal particle on the spacer surface of a 126 kV GIS were obtained. Two PD modes were found to be induced by surface metal particles. In addition to the typical pulse discharge (TP), there is a micro-discharge group (MG) mode with low apparent charge and long duration. The average apparent charge of the MG mode is approximately one-tenth of that of the TP at 0.4 pC. Its duration may extend to the millisecond level, causing significant distortion of the spatial electric field while hardly producing UHF signals. Moreover, increasing the applied voltage will increase the proportion of the MG within the total discharge, where this proportion can reach more than 90% before flashover, and the proportion of the discharge pulses that generates UHF signals is as low as 1%. The MG generation mechanism is analysed, the ion group stranded on the spacer surface by the TP changes the local electric field at the tip of the metal particle, which reduces the development length and apparent charge of the MG. Low apparent charge is cleared easily by the background electric field and thus the discharge interval is very short. This paper can provide an important basis for revealing the mechanism of GIS spacer surface discharge induced by metal particles and solving the effectiveness of PD monitoring devices.

A Proposed Patient Selection Algorithm for Total Joint Arthroplasty Same-Day Discharge from an Ambulatory Surgery Center

IntroductionIdentifying appropriate patients for same-day discharge total joint arthroplasty (TJA) is critical for maintaining optimal patient safety and outcomes. This study investigated patient outcomes after same-day discharge TJA at a single ambulatory surgery center (ASC) and proposes a TJA patient-selection algorithm based on findings and existing literature. MethodsA retrospective chart review of 660 patients was performed between July 2019 and October 2021 for all patients who underwent primary TJA in a single ASC. Successful same-day discharge (SDD), length of surgery (LOS), estimated blood loss (EBL), complications, and readmission events were recorded for each patient. There were 20 total complications in 331 primary total knee arthroplasties (TKAs) (6.0%) and 15 total complications in 329 primary total hip arthroplasties (THAs) (4.6%). ResultsThere was one direct admission to the hospital in TKA patients and four direct admissions in THA patients, making the successful SDD rate 99.7% in TKAs, 98.8% in THAs, and 99.2% overall. In the TKA cohort, body mass index (BMI) was associated with total complications (r = -0.15, P = 0.006), comorbidities with wound complications (P = 0.006), and EBL was with readmissions (r = 0.30, P < 0.001), revision surgery (r = 0.12, P = 0.04), and total complications (r = 0.16, P = 0.03). In the THA cohort, BMI was weakly associated with wound complications (r = -0.12, P = 0.02), EBL was with emergency department visits (r = 0.18, P = 0.002) and total complications (r = 0.14, P = 0.01). However, there was no direct association between any of the analyzed characteristics and direct admission. ConclusionIn our ASC cohort, patients had low rates of perioperative complications and hospital admissions, supporting the safety of same-day discharge TJA using our proposed evidence-based algorithm to guide patient selection for same-day discharge.

Impact of Summer Air Temperature on Water and Solute Transport on a Permafrost‐Affected Slope in West Greenland

AbstractIn Arctic landscapes, the active layer forms a near‐surface aquifer on top of the permafrost where water and nutrients are available for plants or subject to downslope transport. Warmer summer air temperatures can increase the thickness of the active layer and alter the partitioning of water into evapotranspiration and discharge by increasing the potential evapotranspiration, the depth to the water table, and changing the flow paths but the interacting processes are poorly understood. In this study, a numerical model for surface‐ and subsurface cryo‐hydrology is calibrated based on field observations from a discontinue permafrost area in West Greenland considered sensitive to future climate changes. The validated model is used to simulate the effect of three summers with contrasting temperature regimes to quantify the variations in the active layer thickness, the resulting changes in the water balance, and the implications on solute transport. We find that an increase of summer air temperature by1.6°C, under similar precipitation can increase the active layer thickness by 0.25 m, increase evapotranspiration by 5%, and reduce the total discharge compared to a colder summer by 9%. Differences in soil moisture and evapotranspiration between upslope and downslope were amplified in a warm summer. These hydrological differences impact solute transport which is 1.6 times faster in a cold summer. Surprisingly, we note that future warmer summer with increase in permafrost thaw may not necessary lead to an increase in discharge along a hill slope with underlying permafrost.

The Affect of Physical Parameters on Flood Potential in the Upstream River and the Musi Watershed of Kepahiang, Indonesia

Fllod often occur if the rainfall is high, the flood-affected areas are downstream areas around the Musi Watershed of Kepahiang. The purpose of the study was to find out the characteristics of the physical parameters that affect the potential for flooding in the upstream river and the Musi Watershed. The method used are in situ measurement and laboratory analysis. The results of research, the characteristics of the river's physical parameters after the rain, the river flow discharge is 14.50 m3/s, floating sediment discharge 1.13 kg/s, bottom sediment discharge 43 x 10-4 kg/s, and total sediment discharge 113 x 10-2 kg/s. While the condition is not raining, the river flow discharge is 5.37 m3/s, the floating sediment discharge is 0.30 kg/s, the bottom sediment discharge is 32 x 10-4 kg/s, and the total sediment discharge is 30 x 10-2 kg/s. The dominant sediment texture is sand, clay and silt with a grain size of 1.4 mm - 600 µm. The river bathymetry has a lower elevation at the confluence of the Gegasan River and Lanang River which causes the river currents to reverse, if there is an increase in rainfall it will cause flooding in the area around the river.

Spring water resources in the Tatra Mountains

The Tatra Mountains stand out as the wettest and most water-rich region in Poland. Despite this, limited studies addressed this issue, and current knowledge largely relies on data obtained in the mid-20th century, with a substantial lack of current estimates. This study aims to fill this gap by evaluating the contemporary water resources of springs in the Tatra Mountains. The study bases on the most recent hydrological mapping of 1,018 springs. The spring resources were evaluated using parameters such as the number of springs, specific runoff, and crenological index, analysed across different physiographic regions, tectonic units, and altitudinal zones. Our studies showed that the highest number of springs occurs in the Western Tatras (66%) between 1000 and 1400 m a.s.l., especially within the Sub-Tatric unit. Springs with discharges ranging from 0.1–1.0 dm3∙s−1 constitute approximately 70% of all springs but they contribute to only 8.1% of spring water resources. Total spring discharge amounted to 2726 dm3∙s−1 and was higher in the Western Tatras (1982.5 dm3∙s−1 than in the High Tatras (743.5 dm3∙s−1 . The specific runoff amounted to 12.9 dm3∙s−1 m−2 with the highest total runoff at altitudes occupied by the most abundant karst springs (1000–1100 m a.s.l.). The crenological index amounted to 4.8 springs∙km−2 and was higher in the Western Tatras (6.5 springs∙km−2) than in the High Tatras (4.9 springs∙kmup−2) . The analysis revealed that the only five largest karst springs, constituting a mere 0.5% of all springs, account for 65% of spring water resources in the Tatras.

Modelling of Steady-State Seepage of an Embankment Dam Using Teaching-Learning Based Optimization Algorithm

The goal of the this study is to investigate the applicability of the teaching-learning based optimization (TLBO) algorithm for modeling seepage in embankment dams. The input parameters selected for the models to be built are the values of permeability (ks), van Genuchten's suitability parameters α and n, whose effect on seepage has been investigated over the years due to their uncertainties. The validity of the TLBO was compared with that of conventional regression analysis (CRA) methods. Both methods were utilized with different regression forms. The parameters chosen as input are modeled as random variables with a log-normal distribution, and total discharge (Q) was obtained. Four statistical indices, that is, root mean square error, mean absolute error, average relative error and coefficient of determination, were used to evaluate the performance of the models. The equations obtained using TLBO algorithms can predict the total discharge in embankment dams better than CRA. In addition, the reliability of TLBO has been demonstrated by conducting analyses using the outputs of CRA as a benchmark.

Modelling lateral meltwater flow and superimposed ice formation atop Greenland's near-surface ice slabs

Abstract At high elevations on the Greenland ice sheet meltwater percolates and refreezes in place, and hence does not contribute to mass loss. However, meltwater generation and associated surface runoff is occurring from increasingly higher altitudes, causing changes in firn stratigraphy that have led to the presence of near-surface ice slabs. These ice slabs force meltwater to flow laterally instead of percolating downwards. Here we present a simple, physics-based quasi-2-D model to simulate lateral meltwater runoff and superimposed ice (SI) formation on top of ice slabs. Using an Eulerian Darcy flow scheme, the model calculates how far meltwater can travel within a melt season and when it appears at the snow surface. Results show that lateral flow is a highly efficient runoff mechanism, as lateral outflow exceeds locally generated meltwater in all model gridcells, with total meltwater discharge sometimes reaching more than 30 times the average amount of in situ generated melt. SI formation, an important process in the formation and thickening of the ice slabs, can retain up to 40% of the available meltwater, and generally delays the appearance of visible runoff. Validating the model against field- or remote-sensing data remains challenging, but the results presented here are a first step towards a more comprehensive understanding and description of the hydrological system in the accumulation zone of the southwestern Greenland ice sheet.

Effects of the Cascade Discharge on Hollow Plasma Properties by Using Snowplow Model Simulation

The cascade discharge of the hollow plasma device is modeled using the snowplow model. In the model, one or three condenser banks discharge between the two electrodes, with a different time delay. The results were achieved with and without the hollow plasma’s multidischarge cascade. The cascade discharge aims to increase the plasma’s energy to keep the discharge current from breaking down and to keep the plasma column compressed for an extended period. Both the cascade and the single discharges affect the pinching time. The calculated induced magnetic field increases progressively until it reaches the pinch point, and then it decreases, at which point the total discharge current reaches a low value. The magnetic field distribution was calculated as a function of the plasma radius, both with and without the cascade discharge. The model demonstrates that, both with and without a cascade discharge, the magnetic field distribution is low at the tube’s exterior wall and increases toward the axis, reaching a maximum value of 138 kG in the case of a cascade discharge and 42.5 kG with a single discharge. A delay unit resembling the one found in a hollow plasma device is utilized to manually manage the electric circuit discharge simulation.

Revealing the flashover mechanism of EP/GF composite insulation under DC combined harmonic voltage

Abstract In ultra-high voltage converter stations, the phenomenon of flashover along the outer insulation of dry hollow reactors made of epoxy/glass fiber composites poses a potential threat to the stability of the power system. To enhance its flashover performance under varying complex conditions, it is necessary to conduct in-depth research on the flashover mechanism of this material under different voltage forms. This study conducted tests on the flashover voltage, surface space charge distribution, and partial discharge parameters under varying AC-DC ratios and AC frequencies, and exploring their relationships. The results show that the DC content in the AC-DC ratio decreases, the flashover voltage decreases, the apparent total discharge of partial discharges increases, and the maximum surface space charge density decreases. The main influencing factor is the increase in the number of seed charges involved in gas ionization. Increasing the AC frequency, the flashover voltage decreases, the apparent total discharge increases significantly, and the surface charge density remains basically unchanged. The main reason is that the change in the number of alternating cycles further increases the number of seed charges. This study reveals the flashover mechanism of epoxy/glass fiber composites under different voltage forms, which provides theoretical support for subsequent material modification.&amp;#xD;

Co-analysis of total suspended particles and discharge reveals the dynamic of mercury input into glacier meltwater runoff in the northern Tibetan Plateau

Climate warming has accelerated glacier melting, releasing legacy pollutants such as mercury (Hg) into aquatic ecosystems. While the relationship between Hg in glacier meltwater runoff, total suspended particles (TSP), and runoff discharges has been established, the underlying inter-relationships and governing factors remain poorly understood. To address this knowledge gap, we conducted a continuous fixed-point sampling at Laohugou No. 12 Glacier in the northern Tibetan Plateau from June to September 2019 spanning the entire glacier ablation season. Our study analyzed the variations of Hg partition in the meltwater runoff and conducted a comprehensive co-analysis of Hg with TSP and discharge to uncover the dominant factors of Hg input into meltwater runoff. The concentration of total Hg (THg) in the meltwater runoff ranged from 0.7 to 112.6 ng/L, with an average concentration of 26.6 ± 25.1 ng/L. Particulate Hg (PHg) was found to be the predominant partition, while dissolved Hg (DHg) exhibited a notable increase in June and September. THg concentration significantly correlated with TSP concentration (r = 0.94, P < 0.01), exceeding the correlation with discharge (r = 0.76, P < 0.01) during the entire ablation period. However, further examination during varying hydrological periods revealed differing associations among Hg speciation concentrations, TSP concentration, and discharge. During the rising limb of the hydrograph, THg (r = 0.86, P < 0.01) and PHg concentrations (r = 0.87, P < 0.01) exhibited a significant correlation with TSP concentration, primarily driven by TSP, implying that Hg availability determines the Hg input into meltwater runoff. Conversely, during the recession limb of the hydrograph, THg concentration was primarily influenced by discharge (r = 0.85, P < 0.01). PHg (r = 0.84, P < 0.01) and TSP (r = 0.97, P < 0.01) concentrations were strongly influenced by discharge, indicating that hydraulic action is the dominant factor affecting Hg input. Our study elucidated the impact of glacier hydrological processes on Hg transport, revealing the dominant factors of Hg input during different hydrological periods. This contributes to a deeper understanding of Hg input into meltwater runoff and improves predictions of Hg export through glacier melt in high mountain regions.

Investigating the Energy Dissipation Mechanism of Piano Key Weir: An Integrated Approach Using Physical and Numerical Modeling

The enormous energy carried by discharged water poses a serious threat to the Piano Key Weir (PKW) and its downstream hydraulic structures. However, previous research on energy dissipation in PKWs has mainly focused downstream effects, and the research methods have been largely limited to physical model experiments. To deeply investigate the discharge capacity and hydraulic characteristics of PKW, this study established a PKW model with universally applicable geometric parameters. By combining physical model experiments and numerical simulations, the flow pattern of the PKW, the discharge at the overflow edges, and the variation in the energy dissipation were revealed for different water heads. The results showed that the discharge of the side wall constitutes the majority of the total discharge at low water heads, resulting in a relatively high overall discharge efficiency. As the water head increases, the proportion of discharge from the inlet and outlet keys increases, while the proportion from the side wall decreases. This change results in less discharge from the side wall and a consequent reduction in the overall discharge efficiency. The PKW exhibits superior energy dissipation efficiency under low water heads. However, this efficiency exhibits an inverse relationship with an increasing water head. The overall energy dissipation efficiency can reach 40% to 70%. Additionally, the collision of the water flows inside the outlet chamber and the mixing of the overflow jet play a primary role in energy dissipation. The findings of this study have significant implications for hydraulic engineering construction and PKW operational safety.

Electrochemical Activation Inducing Rocksalt-to-Spinel Transformation for Prolonged Service Life of LiMn2O4 Cathodes.

LiMn2O4 spinel is emerging as a promising cathode material for lithium-ion batteries, largely due to its open framework that facilitates Li+ diffusion and excellent rate performance. However, the charge-discharge cycling of the LiMn2O4 cathode leads to severe structural degradation and rapid capacity decay. Here, an electrochemical activation strategy is introduced, employing a facile galvano-potentiostatic charging operation, to restore the lost capacity of LiMn2O4 cathode without damaging the battery configuration. With an electrochemical activation strategy, the cycle life of the LiMn2O4 cathode is extended from an initial 1500 to an impressive 14 000 cycles at a 5C rate with Li metal as the anode, while increasing the total discharge energy by ten times. Remarkably, the electrochemical activation enhances the diffusion kinetics of Li+, with the diffusion coefficient experiencing a 37.2% increase. Further investigation reveals that this improvement in capacity and diffusion kinetics results from a transformation of the redox-inert LiMnO2 rocksalt layer on the surface of degraded cathodes back into active spinel. This transformation is confirmed through electron microscopy and corroborated by density functional theory simulations. Moreover, the viability of this electrochemical activation strategy has been demonstrated in pouch cell configurations with Li metal as the anode, underscoring its potential for broader application.

Patterns and outcomes of Emergency Pediatric Unit admissions in Usmanu Danfodiyo University Teaching Hospital in Sokoto State, Nigeria: a five-year review

Children are susceptible to illnesses that often require urgent medical attention, with attendant high mortality rates, especially in resource-constrained settings. Periodic audits in tertiary care facilities can guide preventive and therapeutic policies. The aim was to determine the admissions pattern and outcome over five years in the Emergency Paediatric Unit (EPU) of Usmanu Danfodiyo University Teaching Hospital (UDUTH), Sokoto, a major tertiary facility in North Western Nigeria. This was a retrospective study between January 2017 and December 2021. The admission records of children aged &gt;1 month to 15 years were retrieved, relevant information extracted, and entered into a study proforma. Data was analyzed using SPSS version 23. There were 6088 admissions. Under-fives constituted 4448 (73.1%), and males were 3558 (58.4%). The median age was 24.0 months (Interquartile Range, IQR, 12, 60). Top admissions were severe malaria (1100; 18.1%), acute diarrhoeal disease (631; 10.4%), Sickle Cell Disease (SCD) (624; 10.2%), pneumonia (547;9.0%), Severe Acute Malnutrition (SAM) (438;7.2%), febrile convulsions (421;6.9%), pharyngotonsillitis (402;6.6%) and sepsis (398;6.5%). Total discharges were 2483 (40.8%), 2635 (43.3%) were transferred, and mortalities were 679 (11.2%). Case fatality rates of the top admissions were sepsis (19.6%), SAM (19.4%), severe malaria (13.7%), pneumonia (10.6%), febrile convulsions (5.0%), acute diarrhoeal disease (4.9%), pharyngotonsillitis (2.5%) and SCD (2.1%). SCD was the most common non-infectious morbidity and responsible for most re-admissions. Malaria was the top cause of mortality in all age groups except infancy, where sepsis and pneumonia predominated. In conclusion, malaria and other infectious diseases accounted for most admissions. Non-communicable diseases, like SCD, also constitute significant morbidity. Hence, policymakers need to scale up targeted preventive measures.

Characterizing nitrogen deposited on urban road surfaces: Implication for stormwater runoff pollution control

Nitrogen (N) is one of the most important pollutants on urban road surfaces. Understanding the N deposition forms, load characteristics, and influential factors can help to provide management and control strategies for road stormwater runoff pollution. This study focuses on a highly urbanized area in Guangzhou, China, and presents the characteristics of both dissolved and particulate N deposition forms as well as their correlations with land-use types and traffic factors. In addition, an artificial neural network (ANN) based classification model is utilized to estimate N pollution hotspot area and total nitrogen (TN) flux from road to receiving water bodies. The results showed that N on urban road surfaces mainly existed in the form of particulate organic nitrogen. Land use types dominated by residential area (RA) and urban village (UV) have higher TN build-up loads. Geodetector analysis indicated that land use has a greater impact on nitrogen build-up loads than traffic factors. Through classification and estimation using the ANN model, RA, and UV were classified as hotspot areas, and the TN flux from roads in the study area was calculated to be 3.35 × 105 g. Furthermore, it was estimated that the annual TN flux from roads in Guangzhou accounts for 19 % of the city's total urban domestic discharge. These findings are expected to contribute to the pollution control of stormwater runoff from urban road surfaces and provide valuable guidance for enhancing the ecological health of urban water environments.

Distribution and seasonal variations of perfluoroalkyl substances (PFAS) in streams within the Changwon region

This study investigates the distribution and seasonal variations of Poly- and Perfluoroalkyl Substances (PFAS) concentrations in local streams within the Changwon area, aiming to quantify the total PFAS load entering Masan Bay. Using solid-phase extraction (SPE) cartridges for pretreatment, we analyzed 36 types of Perfluorinated carboxylic acids (PFCAs), Perfluorinated sulfonates (PFSAs), and precursor compounds via liquid chromatography-high resolution mass spectrometry (LC-HRMS). The study observed varying concentration levels across different streams, with notable detections of Perfluorohexanoic acid (PFHxA), Perfluorooctanoic acid (PFOA), Perfluorobutanesulfonic acid (PFBS), Perfluoropentanoic acid (PFPeA), and Perfluoroheptanoic acid (PFHpA) at quantifiable levels. Except for the Sogye Stream (SGC), PFCA-based compounds comprised over 50% of the total PFAS detected, predominantly featuring shorter-chain compounds with fewer than eight carbon atoms. Seasonal trends indicated that PFAS concentrations were lowest during the high rainfall period in summer and peaked in winter and spring. The Nam Stream (NC) contributed the highest PFAS inflow into Masan Bay, attributed to its elevated flow rates, while Sum B had high concentrations but lower emissions due to its limited flow. The total annual PFAS discharge was estimated at 1.9 kg. These findings highlight the urgent need for targeted management and comprehensive countermeasures to protect environmental health.

Estimating velocity distribution and flood discharge at river bridges using entropy theory – insights from computational fluid dynamics flow fields

Abstract. Estimating the flow velocity and discharge in rivers is of particular interest for monitoring, modeling, and research purposes. Instruments for measuring water level and surface velocity are generally mounted on bridge decks, and this poses a challenge because the bridge structure, with piers and abutments, can perturb the flow field. The current research aims to investigate the applicability of entropy theory to estimate the velocity distribution and the discharge in the vicinity of river bridges. For this purpose, a computational fluid dynamics (CFD) model is used to obtain three-dimensional flow fields along a stretch of the Paglia River (central Italy), where a historical multi-arch bridge strongly affects flood flows. The input data for the entropy model include the cross-sectional bathymetry and the surface velocity provided by the numerical simulations. A total of 12 samples, including three different flow conditions at four cross-sections, one upstream and three downstream of the bridge, are considered. It is found that the entropy model can be reliably applied upstream of the bridge, also when forced with a single (i.e., the maximum) value of the surface velocity, with errors on total discharge below 13 % in the considered case. By contrast, downstream of the bridge, the wakes generated by the bridge piers strongly affect the velocity distribution, both in the spanwise and in the vertical directions and for very long distances. Here, notwithstanding the complex and multimodal spanwise distribution of flow velocity, the entropy model estimates the discharge with error lower than 8 % if forced with the river-wide distribution of the surface velocity. The present study has important implications for the optimal positioning of sensors and suggests the potential of using CFD modeling and entropy theory jointly to foster greater knowledge of river systems.

Ultra-low frequency discharge instability of a barium tungsten hollow cathode at lower self-sustaining margin

Development of low-orbiting constellations stimulated the demand for low-power Hall thrusters, as well as their accompanying low-current hollow cathodes. In this paper, such cathodes were tested on quite low currents to search their self-sustaining limit, and were found to exhibit an ultra-low frequency instability at lower current limit. The instability would grow fast when the cathode current was below 0.3A, and oscillate on 0.1Hz to a few Hz with a visibly blinking plume. At the same time, the emitter temperature was fluctuating with a 15 °C peak-to-peak amplitude. The instability was confirmed to originate from the cathode interior, as a result of depleted plasma heating. Then the thermionic cathode had to rely mainly on neutral gas to heat the emitter. Because thermionic emission was in exponential relation with emitter temperature, the temperature fluctuation was then amplified to cause larger fluctuation in total current as well as in total discharge power, which led to deeper fluctuation in temperature. Regarding the heating of both neutral gas and emitter, an instability model showed that multiple unnoticed factors could determine the onset of instability, including the thermal inertia of neutral gas and emitter, the heat transfer from discharging plasma to neutral gas, the heat loss of cathode and the response time of power supply. As a result of this instability, the plume ion energy was elevated from <50eV to 30∼120eV due to the fluctuating density on cathode exit and fluctuating discharge voltage. It was estimated that the increased ion energy could accelerate the keeper erosion by 4∼22 times.

Drainage water management, woodchip bioreactor, and saturated riparian buffer as stacked conservation practices for improving crop yields and water quality

Stacking edge-of-field practices may improve nutrient removal from crops. To examine the effects of stacking edge-of-field conservation practices, a woodchip bioreactor (WBR) and saturated riparian buffer (SRB) were installed in series by intercepting tile flow from a field having a drainage water management system. Nutrient monitoring from 5 years evaluated nutrient export annually and based on the precipitation intensity. Drainage water was monitored for total suspended solids (TSS), nitrate-N, total-P, total-N, and ortho-P at the inlet and outlet of WBR and control structure of SRB. Nutrient export reductions of WBR and SRB were determined for precipitation events that were categorized as low <12.7 mm, mid 12.7–25.4 mm, high 25.4–50.8 mm, and very high >50.8 mm. Over the five seasons, nitrate-N export was reduced 88 % at the WBR outlet and 78 % at SRB outlet when used in a stacked series configuration. The efficacy of edge-of-field practices was affected by the intensity of precipitation events. The low and mid-intensity precipitation events generated 67 % of the total discharge from the subsurface drainage system which accounted for 74 % of the influent nitrate-N. During low and mid-intensity precipitation events, discharge was reduced by 58–65 %, nitrate-N was reduced by 49–88 % and total-P was reduced by 65–73 % by using stacked practice of WBR and SRB. During high and very high-intensity precipitation events only nitrate-N export was reduced by 61–66 %. This indicates that when designing stacked edge-of-the-field practices the cumulative effect of the practices and their performance during different precipitation events should be taken into account when managing conservation practice-based cropping systems.