Instantaneous Discharge Research Articles

$\Delta V-\Delta I$ Plane-Based Line Faults Detection and Classification in DC Microgrid

The high fault current rise due to instantaneous capacitor discharge necessitates quick line fault detection in DC microgrids. Hence, this paper proposes a communication-less <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Delta V-\Delta I$</tex-math></inline-formula> plane-based line faults detection and classification scheme in a Low-Voltage (LV) DC microgrid using local parameters. Simultaneous threshold violations of difference of successive line current and bus voltage samples, with sum of squared currents and disagreement of instantaneous line current to its average echo, aid the scheme to identify forward and backward faults and categorize Pole-to-Ground (PG) and Pole-to-Pole (PP) faults. The proposed scheme is time-efficient as it quickly detects and classifies the worst possible close-in and line-end PG and PP High Resistance Faults (HRFs) within 0.72 ms. The proposed method's feasibility is validated in Real-Time Digital Simulator (RTDS), Numerical Relay Development Environment (NRDE), and microcontroller-based hardware in loop setup. Comparison with previous techniques and tests on two LV DC microgrids indicate that the thresholds in the proposed scheme can aid in quick fault (even line-end HRFs) detection. Also, the proposed scheme is robust to grid-connected and islanded modes of operation, ring and radial configurations, noise, and non-fault events, like load switching, varying power output of sources, and AC side and internal converter faults.

მინიმალური ხარჯების შედარებითი ანალიზი ეკოლოგიური ხარჯის განსაზღვრისათვის მდ. ალაზნის (შაქრიანი); მტკვრისა (ხერთვისი) და ფარავნის (ხერთვისი) მაგალითზე

Minimal runoff plays a crucial role in designing industrial and domestic water supply, to determine minimal discharge of water in rivers observation data of winter and summer-autumn seasons are used. There are selected the stations of rivers which have the longest observed data series. These rivers are Alazani (H/S shakriani), river Mtkvari (H/S Khertvisi), river Paravani (H/S Khertvisi). As a result of actual observed data of minimum discharges were allocated to the research rivers, such as: · 30-day minimum discharge (non-calendar year) · Instantaneous minimum discharge · Minimum discharge taken from daily average data. Nowadays, in Georgia there is no legal basis and corresponding normative-technical documentation for determining the normative values of discharge of water discharged for ecological purposes which of course is the cause of numerous problems in terms of conservation and use of water resources. Therefore, it is crucially important to take into consideration the complex relationship between minimum and environmental flows.

Study of Potential Development of Rainfed Land in Maluka Baulin Swamp Irrigation Area

Agricultural land in South Borneo has high rice productivity. The supporting factors for rice productivity are irrigation areas, one of which is the Maluka Baulin Swamp Irrigation Area (DIR). It is located in Kurau, Tanah Laut Regency. It has an area of 421 ha (Decree of the Minister PUPR of the Republic Indonesia) now to 286 ha (land function and administrative other villages) with use as agricultural land. It so far has a low average rice production and cropping index of one crop in one year. The purpose of this study was to analyze the availability and demand of water well as the provision of irrigation water based on the water balance for the development of cropping patterns and schedules. This study collects primary and secondary data. Preliminary data are location survey, instantaneous discharge, and questionnaire. Secondary data are climatological data, maps of land types, and data on the discharge Tabanio-Bajuin River. The water requirement is obtained from the calculation of land preparation and consumptive use of water for plants. Water availability is obtained by analyzing rainfall, calculating evapotranspiration, calibrating F.J. Mock Model discharge, and calculating mainstay discharge. The temporary result obtained the water balance is land area is obtained with cropping pattern and schedule that increases to paddy-paddy-palawija, which was previously only paddy-paddy. Then, agricultural production, especially rice and secondary crops, will directly grow.

Vertical asymmetric metal-semiconductor-metal photodiode based on β-Ga2O3 thin films fabricated via solution process for arc discharge detection

Arc discharge detection is a preeminent strategy for diagnosing aging of high-power electric equipment. Therefore, the timely detection of arc discharge can prevent immense disasters, such as massive fire accidents. Ultraviolet C (UVC) photodetectors (PD) are effective devices for optical arc discharge detection because of their solar blindness, which enables noise-free and highly selective arc discharge detection. In this study, we developed a solution-processed β-Ga2O3-based vertical asymmetric metal-semiconductor-metal (MSM) UVC PD as a high-performance and inexpensive UVC detector. The high bandgap of photoactive β-Ga2O3 (4.7–5.1 eV) enables selective UVC detection. The Schottky barrier heights at two different metal-semiconductor junctions (PEDOT:PSS/β-Ga2O3 and ITO/β-Ga2O3) were systematically modulated by varying the β-Ga2O3 film annealing temperature and thickness, which enabled fast photoresponse and self-powered operation, as demonstrated by various optical and electrical analyses. The optimized device exhibited a fast photoresponse (rise/fall time of 67/53 ms) and high responsivity (41 mA W−1) and detectivity (1.5×1011 Jones) in self-powered mode. The instantaneous arc discharge was successfully detected using the β-Ga2O3 based vertical MSM PD, demonstrating its feasibility for arc discharge detection. Thus, this study provides new insights into inexpensive self-powered PDs that can be implemented for the facile and prompt monitoring of aging electric equipment and prevention of potential fire accidents.

Kualitas dan Kuantitas Ketersediaan Sumber Air Minum Sungai Cikaduen Kecamatan Taktakan Provinsi Banten

The provision of drinking water is one of the basic needs and socio-economic rights of the community that must be fulfilled by the Government. The rapid development of housing in Taktakan Sub-district, the main and supporting infrastructure needs to be properly prepared. One infrastructure that is prioritised is the drinking water supply system. The research used the observation method to see the condition of the Cikaduen River, and laboratory tests to analyse raw water sources with physical, chemical, and microbiological parameters. This research was conducted from December 2021-March 2022. The purpose of this research is to prepare a drinking water supply system planning in Taktakan District. Based on the results of laboratory tests, physical parameters such as temperature, TDS, and TSS all meet the Class I Water Quality Standards PP 22 of 2021, while for chemical parameters some parameters exceed the quality standard threshold such as BOD5, COD, DO, Fluoride, Copper. Microbiology meets the Water Quality Standard. The instantaneous discharge of Cikaduen River is 518 l/s. From the results of hydrological analysis, it is known that the availability of water to serve the population in Taktakan is 60 ltr/s. Based on the availability of water from the results of the analysis using FJ Mock, the Cikaduen River is suitable to be used as a source of raw water.

Allergen-free extracts from birch, ragweed, and hazel pollen activate human and guinea-pig submucous and spinal sensory neurons.

Non-allergenic, low molecular weight components of pollen grains are suspected to trigger changes in gut functions, sometimes leading to inflammatory conditions. Based on extensive neuroimmune communication in the gut wall, we investigated the effects of aqueous pollen extracts (APE) on enteric and spinal sensory neurons. Using Ca2+ and fast potentiometric imaging, we recorded the responses of guinea-pig and human submucous and guinea-pig dorsal root ganglion (DRG) neurons to microejection of low (<3 kDa) and high (≥3 kDa) molecular weight APEs of birch, ragweed, and hazel. Histamine was determined pharmacologically and by mass spectrometry (LC-MS/MS). Birch APE<3kDa evoked strong [Ca+2 ]i signals in the vast majority of guinea-pig DRG neurons, and in guinea-pig and human enteric neurons. The effect of birch APE≥3kDa was much weaker. Fast neuroimaging in human enteric neurons revealed an instantaneous spike discharge after microejection of birch, ragweed, and hazel APE<3kDa [median (interquartile range) at 7.0 Hz (6.2/9.8), 5.7 Hz (4.4/7.1), and 8.4 Hz (4.3/12.5), respectively]. The percentage of responding neurons per ganglion were similar [birch 40.0% (33.3/100.0), ragweed 50.8% (34.4/85.6), and hazel 83.3% (57.1/100.0)]. A mixture of histamine receptor (H1-H3) blockers significantly reduced nerve activation evoked by birch and ragweed APEs<3kDa , but was ineffective on hazel. Histamine concentrations in ragweed, birch and hazel APE's < 3 kDa were 0.764, 0.047, and 0.013 μM, respectively. Allergen-free APEs from birch, ragweed, and hazel evoked strong nerve activation. Altered nerve-immune signaling as a result of severe pollen exposure could be a pathophysiological feature of allergic and non-allergic gut inflammation.

All‐in‐One Sensing System for Online Vibration Monitoring via IR Wireless Communication as Driven by High‐Power TENG

AbstractAbnormal vibration is a direct response to the mechanical defects of electrical equipment, and requires reliable vibration sensing for health condition evaluation in the associated system. The triboelectric nanogenerator (TENG) triggered by random vibration to generate electrical energy/signal while giving feedback on the vibration state, paving a promising way towards self‐powered sensors. Here, an all‐in‐one sensing system configured with a vibration sensor demonstrates instantaneous discharge boosted TENG and IR wireless communication for vibration state online monitoring. The sandwich‐structured TENG combined with mechanical switches can release the co‐accumulated charges from dual triboelectric layers to yield giant instantaneous output power of 616 W, which is 106 times higher than that of the continuous discharge. Moreover, an IR LED as a transmitter driven by the TENG can form an all‐in‐one vibration sensor enabling wireless communication, where the sensor can be further integrated with repeaters and phones to establish a wireless vibration online monitoring system for vibration state visualization. This work presents a novel idea to implement high‐power TENG with IR communication integration for in situ vibration online monitoring. Such a strategy is potentially available for distributed sensor construction towards abnormal signal monitoring that reflects the operating state of equipment.

Performance Investigations of the Charging and Discharging Processes in a 3-Tank Thermal Energy Storage System

The paper presents a 3 tank thermal energy storage system. The system consists of cold oil reservoir, heat storage tank, and a residual drainage tank. Cold oil flows by gravity into a heating chamber and after being heated to the required temperature, a mechanical thermostat opens allowing the hot oil to flow into a heat storage tank. The storage tank was discharged through the cooking unit by boiling 0.5 litres of water. The used oil flowed by gravity to the drainage tank. The discharge flow rates of 0.5, 2.1, 2.8 and 6.5 g/s were considered. A charging efficiency of 51.3% and overall discharging efficiency range of 15.3 34.7% were achieved. Charging efficiency increased when the source was embedded in the storage tank. The instantaneous discharge power had a peak value for each flow rate. The adopted cooking unit had a thermal transfer efficiency range of 34.7 57.6%. A method for sizing oil based TES systems was proposed and illustrated based on the obtained discharge results.&#x0D; Keywords: 3-tank, sizing, discharging, efficiency, thermal energy

Spatial Analysis of Floods in Mazandaran Province and Strategies to Increase Resilience Using the Crisis Management Approach

Introduction: According to the flood records in Mazandaran province, this region is regarded as one of the flood-prone regions of the country, and due to the floods, it has suffered many casualties and financial losses. Therefore, this study aimed to investigate the settlements at risk of flooding as one of the main goals of this research. Methods: This descriptive-analytical study was conducted based on extensive and exploratory research approaches. The required data were collected from monthly discharge and the maximum instantaneous discharge in the stations of Mazandaran province along with the population statistics of the provincial cities, as well as the statistics of the Natural Resources and Watershed Management Organization concerning the floods. Accordingly, the statistics of hydrometric stations from 1971 to 2021 of Iran's water resources management main company, the population statistics of the province based on the census of 2015, and the statistics of floods that occurred from the beginning to 2021 have been used in this study. Flood return periods were obtained in the study stations in different statistical distributions using Hyfa software. Finally, Arc GIS software (version 10.3) was used to zone floods in Mazandaran province. Findings: Based on the results, about 1013 square kilometers of the province's surface accounting for 4.25% of its total area is located in the boundaries of large floods that have a return period of 50 to 100 years. Moreover, due to the high altitude, rainy-snowy events, and the significant amount of precipitation in Sarab (Dali Chai and Lar basins) and Payab, Haraz basin has a significant runoff rate discharge so that about 500 to 600 liters of water flow from this basin annually per square meter. Conclusion: According to the obtained results, strategies have been proposed to increase resilience against flood risk using different methods.

Lijiang flood characteristics and implication of karst storage through Muskingum flood routing via HEC-HMS, S. China

Abstract We analyzed the characteristics of main karstic/non-karst reaches of the Lijiang River to uncover the causes behind different flood behaviors by providing a better understanding of the flood formation. Having 63 years of rainfall-runoff data and applying the HEC-HMS model, geo/hydrological features were investigated. The available reservoir capacity of karts (ARCK) was included through soil moisture accounting loss data to assess its impact. In particular, the expected instantaneous peak discharge rates/times were found largely imbalanced with generated unit hydrographs. Moreover, significant gaps among the floods’ features for different subbasins in terms of required peak modifications (2–4 times larger for mid-upstream, respectively) were mainly associated with the unique karst structure and initial condition due to various ARCK in rainy/dry seasons. Besides, notable dissimilarities between the wedge/prism storage volumes and the hydrograph’s wave traveling/receding time were observed owing to the geomorphological conditions. Although the contribution rates of drivers in karst flood formation cannot be quantitively modeled, based on our results the ARCK emerged to play a substantial role on the forecasted results, comparatively. Our results suggest that since ARCK varies, taking it into account (as initial abstraction) results in a more reliable estimation. This was underpinned by the results in which the unmodified simulations had a qualified rate of 52% accuracy on average and increased to 67.5% after the ARCK inclusion. This work adds to the body of evidence illustrating that in karst hydrology, ignoring the situational circumstances in modeling might lead to inaccuracies in flood forecasting for such dynamic watersheds.

Analysis of the Charge Density Variation Caused by the Physical Properties of the Electrodes of Lithium-Ion Batteries

The detection and characterization of electrode performance is a key problem of lithium-ion batteries. The physical properties of the electrodes affect the charge density during the life of a battery. The charge density is difficult to monitor because of the complexity of the charge distribution. In this paper, a visualized fractional derivative order (FDO) is used to characterize the charge distribution and to reveal variations in the charge density associated with the physical properties of the electrode. Instantaneous discharge datasets collected at different aging stages of batteries are used to identify the FDO in the fractional derivative model. The results show that the FDO has a strong correspondence with the charge density. As the charge density decreases, the charge mobility gradually increases due to changes in the charge distribution. Moreover, this paper finds that the capacity recovery effect is closely related to the mutation of the charge density and uses the FDO to explain the charge accumulation at the sharp edges of the electrodes. The analysis of the charge density variation caused by the physical properties of the electrodes provides guidance for the detection of the electrode performance and the design of the electrode microstructure.

Higher Water Yield but No Evidence of Higher Flashiness in Tropical Montane Cloud Forest (TMCF) Headwater Streams

There have been conflicting findings on hydrological dynamics in tropical montane cloud forests (TMCFs)—attributed to differences in climate, altitude, topography, and vegetation. We contribute another observation-based comparison between a TMCF (8.53 ha; 1906 m.a.s.l.) and a tropical lowland rainforest (TLRF) (5.33 ha; 484 m.a.s.l.) catchment in equatorial Sabah, Malaysian Borneo. In each catchment, a 90° v-notch weir was established at the stream’s outlet and instrumented with a water-level datalogger that records data at 10-min intervals (converted to discharge). A nearby meteorological station records rainfall at the same 10-min intervals via a tipping bucket rain gauge connected to a datalogger. Over five years, 91 and 73 storm hydrographs from a TMCF and a TLRF, respectively, were extracted and compared. Various hydrograph metrices relating to discharge and flashiness were compared between the TMCF and TLRF while controlling for event rainfall, rainfall intensity, and antecedent moisture. Compared to the TLRF, storm-event runoff in the TMCF was up to 169% higher, reflecting the saturated conditions and tendency for direct runoff. Instantaneous peak discharge was also higher (up to 6.6x higher) in the TMCF. However, despite high moisture and steep topography, stream responsiveness towards rainfall input was lower in the TMCF, which we hypothesise was due to its wide and short catchment dimensions. Baseflow was significantly correlated with API20, API10, and API7. Overall, we found that the TMCF had higher runoff, but higher moisture condition alone may not be sufficient to govern flashiness.

Historic Spatial Patterns of Storm-Driven Compound Events in UK Estuaries

AbstractCompound estuarine flooding is driven by extreme sea-levels and river discharge occurring concurrently, or in close succession, and threatens low-lying coastal regions worldwide. We hypothesise that these drivers of flooding rarely occur independently and co-operate at sub-daily timescales. This research aimed to identify regions and individual estuaries within Britain susceptible to storm-driven compound events, using 27 tide gauges linked to 126 river gauges covering a 30-year record. Five methods were evaluated, based on daily mean, daily maximum, and instantaneous 15-min discharge data to identify extremes in the river records, with corresponding skew surges identified within a ‘storm window’ based on average hydrograph duration. The durations, relative timings, and overlap of these extreme events were also calculated. Dependence between extreme skew surge and river discharge in Britain displayed a clear east–west split, with gauges on the west coast showing stronger correlations up to 0.33. Interpreting dependence based on correlation alone can be misleading and should be considered alongside number of historic extreme events. The analyses identified 46 gauges, notably the Rivers Lune and Orchy, where there has been the greatest chance and most occurrences of river-sea extremes coinciding, and where these events readily overlapped one another. Our results were sensitive to the analysis method used. Most notably, daily mean discharge underestimated peaks in the record and did not accurately capture likelihood of compound events in 68% of estuaries. This has implications for future flood risk in Britain, whereby studies should capture sub-daily timescale and concurrent sea-fluvial climatology to support long-term flood management plans.

Research on the pressure and flow characteristics of seawater axial piston pump considering cavitation for reverse osmosis desalination system

Seawater axial piston pump (SWAPP) has been widely used as the power component in the seawater reverse osmosis (SWRO) desalination systems, whose flow quality could result in significant influences on the performance of RO membranes and SWRO system. This thesis proposed an efficient fully parameterized mathematical approach for the flow and pressure characteristics of SWAPP that is modeled by lumped parameter techniques considering gaseous and vaporous cavitation simultaneously. To address the complex structure of the port plate in SWAPP, especially silencing groove, an innovative model based on the Monte Carlo method was originally proposed, and In-depth comparison with piecewise functions validated the accuracy, efficient and convenient of Monte Carlo approach for calculating the flow area of SWAPP. Particularly, the influence of shaft rotational speed and inlet pressure on the instantaneous discharge flow and pressure of SWAPP was comparatively studied. In addition, a SWRO desalination system was constructed to evaluate the effect of discharge pressure of SWAPP on the RO concentrated brine pressure. The results indicate that the presented model can precisely capture the instantaneous discharge pressure and flow of SWAPP. Besides, increasing the shaft rotational speed and inlet pressure are reliable solutions to enhance the flow performance of SWRO system.

Up-conversion luminescence, temperature sensitive and energy storage performance of lead-free transparent Yb3+/Er3+ co-doped Ba2NaNb5O15 glass-ceramics

In this work, a new type of Yb 3+ /Er 3+ co-doped lead-free glass-ceramics (GCs) containing Ba 2 NaNb 5 O 15 nanocrystals was synthesized via traditional melt-quenching and controlled crystallization. The research results illustrate that a transparency of GCs can reach 50% at wavelength of 600 nm and the up-conversion (UC) luminous performance of GCs has been improved obviously compared with precursor glass (PG). And the dual-mode temperature measurement was carried out by fluorescence intensity ratio technology. Using thermally/non-thermally coupled energy levels (TCELs/non-TCELs), the maximum absolute sensitivities of S a-max (TCELs) and S a-max (non-TCELs) are 0.65% K −1 and 0.68% K −1 , and the maximal relative sensitivities of S r-max (TCELs) and S r-max (non-TCELs) are 1.19% K −1 and 0.90% K −1 , respectively. Furthermore, the discharge energy density (W d ) of 1.53 J cm −3 and the instantaneous discharge power density of 370 MW cm −3 with ultra-fast discharge time of 7 ns are simultaneously achieved in the GCs. These findings reveal the potential applications of new lead-free transparent Yb 3+ /Er 3+ co-doped Ba 2 NaNb 5 O 15 GCs for optical temperature measurement and energy storage. • Multi-function RE-doped Ba 2 NaNb 5 O 15 transparent glass ceramics were first fabricated. • Realizing dual-mode Up-conversion optical thermometry in the glass ceramics. • The maximum S r-max and S a-max can reach 1.19% K −1 and 0.68% K −1 . • Achieving high W d of 1.53 J cm − 3 and high P d of 370 MW cm − 3 at 600 kV/cm.

Prediction of flood discharge and flood flow depth using a hydraulic model and flood marks on the trees in ungauged forested watersheds

It is difficult to estimate flood discharges and the flood zones as well as to design hydraulic structures in rivers without using hydrometric stations. Furthermore, using different models to determine the mentioned cases will be accompanied by errors. Therefore, flood marks on the trunks of trees located in the Babolrood riverbed were used to determine the peak discharge, flood flow depth, and flood zone in northern Iran. First, a hydraulic model for the study river was provided using topographic maps with a scale of 1: 1 000, HEC-GeoRAS extension (GIS), and HEC-RAS model. Then, the flood marks of past floods in the form of silt and clay sediments (deposits on the trees in the riverbed) were evaluated and the maximum flood flow depth was determined. Finally, the peak discharge of the past flood was estimated by the trial-and-error method to achieve the flood flow depth in the different river reaches. Then, the hydraulic model using the flow depth data was calibrated in the reaches, and, in the final step, based on the flood marks of other reaches, the model was validated. According to the results, the maximum instantaneous discharge rate of the study flood was 155 m&lt;sup&gt;3&lt;/sup&gt;·s&lt;sup&gt;–1&lt;/sup&gt; and the maximum flood flow depth was about 2 m. Furthermore, the results showed that the flood mark data in forest lands can be used as a tool for the calibration and validation of hydraulic models. The present methodology is an efficient method for determining the flood peak discharge, spatial variation of the flood depth, and flood zone in forest watersheds without hydrometric stations.

Instantaneous discharge characteristics and its methane ignition mechanism of coal mine rock damage.

The goaf is the main site of gas explosions in coal mines. A large number of accidents indicate that the occurrence of gas explosion in the goaf is related to the deformation and fracture of the goaf roof. An experimental system was constructed to study the instantaneous discharge characteristics and its ignition mechanism caused by rock damage. The research results reveal that different rocks produce avalanche-like dust clouds ejected outward during the fracture process, and the generation process takes an extremely short time. This dust cloud is not caused by rock fragments heated to incandescence because of friction. The electric sparks produced in the process of rock rupture and the appearance of instantaneous discharge are related not only to the quartz content of the rock, but also to the compressive strength of the rock. The piezoelectric effect of the rock becomes the key factor for the strength or the generation of an electric spark. The instantaneous discharge leaded to the collision of high-energy electrons released during the fracture process with air molecules, ionising, and breaking down the air. When the surrounding medium is gas air within the explosion limit, ionisation is formed and causes gas explosions.

Correction of River Bathymetry Parameters Using the Stage–Discharge Rating Curve

AbstractRiver bathymetry is an important parameter for hydrodynamic modeling; however, it is associated with large bias because direct large‐scale measurements are impractical. Recent studies adjusted river bathymetry data based on assessment of the difference between modeled and observed water surface elevation (WSE); however, model uncertainties in river discharge can lead to unintended errors in correcting river bathymetry. In this study, we propose a simple but robust and rational correction method of river bathymetry using the bias between stage–discharge rating curves rather than WSE time series data. The rating curve represents the internal characteristics of the river section, and is not sensitive to the instantaneous simulated discharge errors. Our results showed that the corrected river bathymetry are robust to bias in runoff as they converged among experiments driven by noise‐corrupted or multimodel runoff forcing. Evaluation with the corrected river bathymetry against virtual truth demonstrated that the new method reduced 0.85–1.12 m of the absolute bias than the result from the conventional method. The deviation among the results reduced by more than 70% particularly in river sections with no backwater effects. Evaluation of the corrected river model output also showed the advantage of rating‐curve bias correction, as the simulated WSE is reasonably better only with better runoff and it does not conceal errors in runoff inputs. Given the difficulty of eliminating discharge errors and bias in runoff, a method for correcting river bathymetry that is free from discharge and runoff errors is important for improving hydrodynamic modeling.

Understanding the Combined Effects of Land Cover, Precipitation and Catchment Size on Nitrogen and Discharge—A Case Study of the Mississippi River Basin

Biological processes of rivers are strongly influenced by concentration and fluxes of nitrogen (N) levels. In order to restrain eutrophication, which is typically caused by urbanisation and agricultural expansion, nitrogen levels must be carefully controlled. Data from 2013 to 2017 were gathered from 26 sub-catchments in the Mississippi River basin to assess the effects that catchment size, land cover, and precipitation can have on the discharge and total nitrogen (TN) and how TN yields deviate from a generalised local trend. The findings indicated that land cover and precipitation had a determinative effect on area-weighted discharge (Qarea). More specifically, Qarea had significant positive (directly proportional) relationships with precipitation, forest, and urbanised land cover, and significant negative (inversely proportional) relationships with grassland/pasture and scrub/shrub land covers. Concurrently, the TN concentration significantly increased in the presence of agricultural land cover, but significantly decreased in forest land cover. The TN yield (TN concentration × Qarea) was largely determined by Qarea because the latter was observed to fluctuate more dramatically than concentration levels. Consequently, the TN yield exhibited the same relationships that Qarea had with precipitation and land covers. The TN yield changed significantly (p &lt; 0.05) and positively with instantaneous discharge across all sites. Nevertheless, the rate of TN yield variations with discharge displayed a significant (p &lt; 0.0001) negative (r2 = 0.80) relation with the catchment size. Ultimately, this study used discharge readings to facilitate the prediction of TN concentrations and yields across various catchment areas in the Mississippi River basin and provided a robust model for future research in this area.

Flow amplification from cascading landslide dam failures: Insights from flume experiments

The 2008 Wenchuan Earthquake triggered numerous co-seismic landslides, and formed many landslide dams. Debris flows or floods during intense rainfall can cause the sequential collapse of those landslide dams. There is an amplification effect of the cascading landslide dam failures, which increases the magnitudes of debris flows or floods. Runs of flume experiments with different initial conditions were conducted to study the scale amplification effect. Among them, a large-scale flume experiment was performed to reduce the size effect of the miniaturized physical experiments to some extent. Experimental data such as the flow discharge, pore pressures, and microseismic and acoustic signals were used to investigate the dam failure processes and to quantify the amplification scale. The experimental results show that channel gradients and dam-failure patterns have significantly influences on the amplification effect. The intrinsic mechanism of the amplification effect can be interpreted from the perspective of energy, which is a progressive storage of potential energy and subsequent rapid release of the energy. Steep channel gradients imply greater potential energy and lower stability of the landslide dam. The sudden dam collapse related to internal pore pressure evolution will lead to rapid release of the accumulated potential energy to downstream, and cause a maximum instantaneous dam-break discharge. Experimental results show that the peak dam-break discharge caused by sudden failure can be 2–3 times that of overtopping, which should be fully considered to avoid underestimating the scale of the potential catastrophe.