Rate Of Depletion Research Articles

Structural and Chemical Evolutions of Li/Electrolyte Interfaces in Li-Metal Batteries: Tracing Compositional Changes of Electrolytes under Practical Conditions.

Despite the promises in high-energy-density batteries, Li-metal anodes (LMAs) have suffered from extensive electrolyte decomposition and unlimited volume expansion owing to thick, porous layer buildup during cycling. It mainly originates from a ceaseless reiteration of the formation and collapse of solid-electrolyte interphase (SEI). This study reveals the structural and chemical evolutions of the reacted Li layer after different cycles and investigates its detrimental effects on the cycling stability under practical conditions. Instead of the immediately deactivated top surface of the reacted Li layer, the chemical nature underneath the reacted Li layer can be an important indicator of the electrolyte compositional changes. It is found that cycling of LMAs with a lean electrolyte (≈3gAh-1 ) causes fast depletion of salt anions, leading to the dynamic evolution of the reacted Li layer structure and composition. Increasing the salt-solvent complex while reducing the non-solvating diluent retards the rate of depletion in a localized high-concentration electrolyte, thereby demonstrating prolonged cycling of Li||NMC622 cells without compromising the Li Coulombic efficiencies and high-voltage stability.

Influence of Internal Grinding Wheel using Aluminium Oxide with Boron Nitride and its Relation to Dressing and Surface Roughness

Performance of grinding wheel depends on different factors from dressing operations to wheel topography. This will directly show effect on grinding force, surface quality and wheel durability. During grinding, an improved wheel should reduce the number of passes as well as the dressing time (wheel gets loading) to increase the production rate and minimize the total cycle time to complete the parts. This paper presents several process parameters to obtain the improved surface roughness and round tolerance such as coarse dress depth of cut 30 microns for the first pass, fine dressing depth of cut 20 microns for the second pass and a dressing speed and feed rate of 0.5m/min respectively. The experiments with the optimal dressing parameters have been considered to check the wheel durability and its performance. The parameters investigated were wheel life, surface roughness and round tolerance from the experiments with different cutting variables like depth of cut, speed, feed rate and percentage of wheel depletion. For this purpose, a single point diamond dresser with four different test samples using Aluminium Oxide (Al2O3) with Boron Nitride (BN) for internal grinding wheels were chosen for the experiment.

Effect of Porous Catalyst Support on Plasma-Assisted Catalysis for Ammonia Synthesis.

We report on the effect of catalyst support particle porosity on the conversion of NH3 synthesis from N2 and H2 in a coaxial dielectric barrier discharge (DBD) plasma reactor. The discharge was created using an AC applied voltage with the reactor at room temperature and near atmospheric pressure (550 Torr). Two different particles of almost equal diameter (∼1.5 mm)─porous silica (SiO2) ceramic beads (average pore size: 8 nm) and smooth, nonporous soda lime glass beads─were compared in the DBD reactor. As the pore size in the SiO2 particles was smaller than the Debye length, penetration of the plasma into the pores of the particles was unlikely; however, reactive species generated in the plasma outside the particles could diffuse into the pores. The N2 conversion and energy yield of NH3 increased with applied voltage for both particle types, and these values were consistently higher when using the SiO2 beads. Discharge and plasma properties were estimated from Lissajous plots and using calculations with the BOLSIG+ software. The effect of these two different catalyst supports on the physical properties of the discharge was negligible. High resolution optical emission spectra revealed that the concentrations of N2+, atomic N, and atomic H (Hα, Hβ) in the plasma discharge were lower with the porous SiO2 beads than with the glass beads at every applied voltage tested. This indicates that these active species participate in heterogeneous reactions at support particle surfaces and that the larger surface area presented by the porous particles led to higher rates of depletion of these intermediates and a higher rate of ammonia synthesis.

Well hydraulics in wedge-shaped aquifer: Unsteady Darcian flow model revisited by lagging theory

Pumping events are often conducted in the alluvial fan due to its considerable amount of water; If pumping events occur in the nearby vicinity of the streams, it will inevitably influence the complex microbial ecosystems in both the river and the aquifer, induce the issue of water rights permits, and affect the development of the water resource management. Therefore, it becomes necessary to accurately predict groundwater flow as a result of pumping in the wedge-shaped aquifer. In this paper, we propose an analytical solution to describe the drawdown distribution and the stream depletion rate (SDR) due to pumping in a wedge-shaped aquifer, which represents the shape of the alluvial fan bounded by two streams. Moreover, we adopt the lagging theory into the model by introducing two lagging parameters in Darcy’s law to allow the water flow and the hydraulic gradient to occur at different times. This measure facilitates the reflection of the inertial force because of a higher pumping rate and the microstructural interaction resulting from the water transfer between the primary pores and secondary pores (e.g., dead-end pores and very-small pores). It leads to the predicted result being closer to reality when these effects are profound. We found that the drawdown and SDR curves will behave like waves when the flux lagging dominates. The SDR value can be over unit due to the additional recharge driven by inertial force; the drawdown and SDR acts more like an unconfined or dual-porosity flow if storage lagging governs the system. Moreover, lagging parameters have the largest effect on drawdown and SDR when the times are close to the corresponding values of lagging parameters. The case of wedge-shaped domain bounded by two impervious barriers is considered to further explore the boundary effects on aquifer response to pumping.

An analytical and meshless model for 3D transient flow in a confined aquifer with nonuniform thickness: Application to stream depletion due to groundwater extraction

This study proposes an analytical and meshless model for three-dimensional transient flow induced by multiple wells in a stream-confined aquifer system with arbitrary nonuniform aquifer thickness. The model involves allocating external image wells near the aquifer boundary. The aquifer drawdown is defined as Theis’ solution plus a simple series expanded by complementary error functions reflecting the boundary effects of the stream and impervious stratum. The solution for stream depletion rate (SDR) can be derived based on the drawdown solution. Results suggest the Dupuit assumption of no vertical flow is valid to estimate SDRs affected by the landward exponentially decreasing thickness. The SDR induced by multiple wells is the same as that by a single well if the total well discharge rate and stream-well distances in the multiple well case are identical to those in the single well case. The present solution outperforms a finite difference solution in computational efficiency.

Assessment of Best Performing Top 10 Economies Based on OECD Green Growth Indicators: Using AHP, TOPSIS and Regression

Abstract: Rapid economic growth is often accompanied by environmental depletion. Recent years have witnessed green growth as a renowned efficient approach to tracking the progress towards sustainable development. Green growth is imperative with the current energy depletion rate and environmental crisis. Green indicators and statistics can measure environmentally sustainable development; thus, they evaluate green growth and support its integration into policy. This study uses MCDM (Multi-criteria decision-making) techniques and OECD indicators for the world’s top 10 economies to evaluate their green growth. This research aims to rank the top 10 economies according to green growth. The top-ranked best-performing country will be further analyzed to assess its renewable energy production.

Modeling Potential Lymphocyte-Sparing Effect of Involved-Field Radiotherapy in Rectal Cancer

<h3>Purpose/Objective(s)</h3> Radiation-induced lymphopenia (RIL) is associated with worse disease-free and overall survival in solid tumors including rectal cancer, as well as lower response rates to checkpoint inhibitors. Large elective nodal volumes, as are utilized in whole-pelvis radiotherapy (WPRT) for rectal cancer, are associated with high RIL risk, while involved-field radiotherapy (IFRT) reduces planning target volume (PTV) size, potentially sparing circulating lymphocytes. In rectal cancer, effective use of IFRT may be facilitated by advances in imaging and high response rates to doublet/triplet chemotherapy regimens such as FOLFOX and FOLFIRINOX. We investigated the potential for IFRT to spare circulating lymphocytes in rectal cancer patients by comparing predicted absolute lymphocyte count (ALC) depletion rates associated with WPRT vs. IFRT. <h3>Materials/Methods</h3> Seventy-five rectal cancer patients who underwent chemoradiotherapy (CRT) were selected. Two different CTVs were contoured in all patients, CTV_(WP) containing traditional at-risk RTOG nodal volumes and CTV_(IF) incorporating primary tumor with a 1-2cm margin, entire mesorectum including a 1cm anterior margin, and any grossly enlarged lymph nodes with a 1cm margin. Two different PTVs, PTV_(WP) & PTV_(IF), were generated using a 0.8-cm isotropic expansion. Wilcoxon signed-rank test was used to compare the two different PTV volumes. Median PTV volume from each data set was used to compute the probability of ALC depletion resulting from PTV_(WP) & PTV_(IF). The equation used to calculate the ALC decay constant k_ALC was: k_ALC = 0.058 + (0.056 * PTV volume/total blood volume) * (dose per fraction)². The computed k_ALC was then used to calculate predicted end-treatment ALC for each field design. Predicted rate of CTCAE v5.0 Grade 3-4 lymphopenia was also computed for these cohorts. <h3>Results</h3> Of the 75 patients, 45 had node positive disease, and 6 patients had pelvic sidewall lymph node/s. 59 patients had T3 disease. Median PTV volume was 1330 cc (IQR: 1200,1534) for PTV_(WP) and 802 cc (IQR: 697,969.8) for PTV_(IF) (ΔPTV 41%, p<0.0001). In summary, PTV_(IF) was 41% smaller than the PTV_(WP). Assuming a baseline ALC of 1800 cells/μL, the predicted median ALC at the end of RT was 360.2cells/μL for PTV_(WP), and 483.0cells/μL for PTV_(IF)(p<0.0001). Grade 3 lymphopenia was predicted in all patients in the PTV_(WP) cohort, whereas it was predicted for only 60% if PTV_(IF) were to be used. <h3>Conclusion</h3> In rectal cancer patients undergoing neoadjuvant CRT, involved-field RT results in a significantly lower median PTV volume when compared to whole-pelvis RT (ΔPTV 41%). This in turn led to improved predicted lymphocyte-sparing and 40% absolute reduction in the risk of predicted grade 3 lymphopenia. These results will be validated in a larger cohort and will help design a prospective study investigating lymphocyte-sparing radiotherapy for rectal cancer patients.

The mitochondrial sodium/calcium exchanger NCLX (Slc8b1) in B lymphocytes

Antigen receptor stimulation triggers cytosolic Ca2+ signals, which activate transcriptional and metabolic programs critical for immune function. B-cell receptor (BCR) engagement causes rapid cytosolic Ca2+ rise through the ubiquitous store-operated calcium entry (SOCE) pathway. Slc8b1, which encodes the mitochondrial Na+/Ca2+ exchanger (NCLX), extrudes Ca2+ out of the mitochondria and maintains optimal SOCE activity. Inhibition of NCLX in DT40 and A20 B lymphocyte lines was recently shown to impair cytosolic Ca2+ transients in response to antigen-receptor stimulation, however the downstream functional consequences of this impairment remain unclear. Here, we generated Slc8b1 knockout A20 B-cell lines using CRISPR/Cas9 technology and B-cell specific Slc8b1 knockout mice. Surprisingly, while loss of Slc8b1 in B lymphocytes led to reduction in SOCE, it had a marginal effect on mitochondrial Ca2+ extrusion, suggesting that NCLX is not the major mitochondrial Ca2+ extrusion mechanism in B cells. Furthermore, endoplasmic reticulum (ER) Ca2+ content and rates of ER depletion and refilling remained unaltered in Slc8b1 knockout B cells. Slc8b1 deficiency increased mitochondrial production of oxidants, reduced mitochondrial bioenergetics and altered mitochondrial ultrastructure. B-cell specific Slc8b1 knockout mice showed reduced germinal center B cell responses following foreign antigen and pathogen driven immune responses. Our studies provide novel insights into the function of Slc8b1 in germinal center B cells and its contribution to B-cell signaling and effector function.

Prospects of Application of Ultramicroelectrode Ensembles for Voltammetric Determination of Compounds with Close Standard Electrode Potentials and Different Diffusion Coefficients

The spherical diffusion that occurs when using ultramicroelectrodes (i.e., electrodes with a characteristic size of 1–10 µm) contributes to a higher mass transfer rate. This leads to equalization of the depletion rates of the near-electrode layer due to the electrochemical reaction and to the supply of the product from the solution depth. This is the reason why, for ultramicroelectrodes, a limiting size of the spherical layer exists in which the concentration gradient is localized (diffusion layer). Thus, a stationary mass transfer mode is achieved, which is expressed in the sigmoidal CV curve’s shape. In ultramicroelectrode arrays, when the diffusion hemispheres are separated, a steady-state diffusion is realized. However, with a decrease in the interelectrode distance, which leads to the diffusion spheres intersection, a mixed regime arises, which is not fully time-independent. The resulting voltammogram’s shape change can serve as an analytical signal in the study of substances with differing diffusion coefficients, since the diffusion layer growth rate and, consequently, the area of intersection of neighboring spheres, depends on it. This work shows the applicability of voltammetry using ensembles of ultramicroelectrodes operating in the transient mode for the analysis of mixtures of electrochemically active compounds with close electrode reaction parameters, such as exchange currents and electrode potential. Ferrocenemethanol esters are used as an example. The applicability of cyclic voltammetry on the UME array for analysis of mixtures was illustrated by means of finite element modelling. The reliability of the modelling results was experimentally proved for ferrocenemethanol esters with glycine and triglycine.

Enzymatic potato starch modification and structure-function analysis of six diverse GH77 4-alpha-glucanotransferases

4-α-glucanotransferase (EC 2.4.1.25) mediated glucan transfer in starch provides opportunities for production of clean label starch ingredients with unique gelling properties. 4-α-glucanotransferases can be found in glycoside hydrolase (GH) family GH13, GH57, and in the monospecific glycoside hydrolase family 77 (GH77). Here, pH-temperature optima, steady-state kinetics, potato starch modifying properties and structural folds are reported for six phylogenetically distinct GH77 members, representing four different domain architectures including a novel multi-domain 4-α-glucanotransferase from Lactococcus lactis. Four of the enzymes exhibited starch modifying activity leading to a gradual decrease of the amylose content, elongation of amylopectin chains, and enabled formation of firm starch gels. Unexpectedly, these diverse enzymes catalyzed similar changes in chain length distributions. However, the amylose depletion and amylopectin elongation rates spanned more than two orders of magnitude between the enzyme showing very different specific activities. Tt4αGT from Thermus thermophilus had highest temperature optimum (73 °C) and superior potato starch modifying efficacy compared to the other five enzymes.

Impact of Microbial Uptake on the Nutrient Plume around Marine Organic Particles: High-Resolution Numerical Analysis.

The interactions between marine bacteria and particulate matter play a pivotal role in the biogeochemical cycles of carbon and associated inorganic elements in the oceans. Eutrophic plumes typically form around nutrient-releasing particles and host intense bacterial activities. However, the potential of bacteria to reshape the nutrient plumes remains largely unexplored. We present a high-resolution numerical analysis for the impacts of nutrient uptake by free-living bacteria on the pattern of dissolution around slow-moving particles. At the single-particle level, the nutrient field is parameterized by the Péclet and Damköhler numbers (0 < Pe < 1000, 0 < Da < 10) that quantify the relative contribution of advection, diffusion and uptake to nutrient transport. In spite of reducing the extent of the nutrient plume in the wake of the particle, bacterial uptake enhances the rates of particle dissolution and nutrient depletion. These effects are amplified when the uptake timescale is shorter than the plume lifetime (Pe/Da < 100, Da > 0.0001), while otherwise they are suppressed by advection or diffusion. Our analysis suggests that the quenching of eutrophic plumes is significant for individual phytoplankton cells, as well as marine aggregates with sizes ranging from 0.1 mm to 10 mm and sinking velocities up to 40 m per day. This microscale process has a large potential impact on microbial growth dynamics and nutrient cycling in marine ecosystems.

Employing machine learning to quantify long-term climatological and regulatory impacts on groundwater availability in intensively irrigated regions

The steady overexploitation of the Ogallala Aquifer underlying the U.S. High Plains Region has put irrigated crop production at risk, particularly in the Southern and Central High Plains. To manage this issue properly, a data-driven modeling framework is developed and tested that is fast to employ and yet provides reliable long-term groundwater level (GWL) forecasts as a function of climatological and anthropogenic factors. The modeling framework uses the random forests (RF) technique in combination with ordinary kriging, and is tested in Finney County in southwest Kansas. The introduction of groundwater withdrawal potential as a new surrogate for pumping intensity enables the RF model to capture decline in groundwater depletion rate as the system progresses towards aquifer depletion and/or as a result of well retirement policies. The RF model is executed from 2017 to 2099 for 20 different downscaled global climate models (GCMs) for the two representative concentration pathways (RCP) scenarios of 4.5 and 8.5. The results show the aquifer will cease to support irrigated agriculture in most of the county by 2060 under status quo management and average climate conditions. Moreover, climate will likely shift the aquifer’s depletion time frame by 15 years or less in most of the study area. The long-term combined impact of well retirement plans and climate conditions on groundwater depletion trends imply well retirement policies do not lead to sustained groundwater savings. This study demonstrates the capacity of machine learning models to serve as a rapid assessment tool, informing policymakers about future groundwater availability in intensively irrigated regions and under different climate and management conditions.

Lithium Dissolution and SEI Formation on Lithium Metal Anodes: Electrolyte and Surface Effects

The lithium metal battery (LMB) rises as one of the most promising energy storage alternatives primarily due to the lithium metal’s high theoretical specific capacity (3860 mAh/g vs. 372 mAh/g for graphite) and high achievable operation voltage [1, 2]. However, and regardless of the coupling cathode electrode, one of the main challenges before the practical application of LMBs comes down to engineering electrolyte formulations compatible with lithium metal to eliminate dendrite formation and the uncontrolled loss of electrolyte and active lithium by forming a robust, ionic-conductive, and electron insulating, solid electrolyte interphase (SEI).Any improvement of the electrolyte/lithium metal interface passes through a thorough understanding of the reaction mechanisms behind the electrolyte degradation and the subsequence formation of the SEI. Characterizing this interface via experimental techniques is a challenge because of its delicate nature and simultaneous presence of liquid and solid phases. Here, we successfully narrowed this gap via computational modeling by using a recently introduced hybrid ab initio and reactive molecular dynamics (HAIR) scheme that uses in sequence the ab-initio molecular dynamics (AIMD) and the reactive force field (ReaxFF) methods to extend the time window achievable with the AIMD method alone. We performed a series of HAIR calculations with multiple electrolytes formulations on a lithium metal slab (Li(100)) with varying electrolyte/anode (E/A) ratios to evaluate the impact of the lithium salt concentration, type of solvent, presence of a diluent, and lithium thickness on the rate of electrolyte depletion, lithium dissolution, and SEI morphology. It is found that increasing salt concentration in a LiFSI/DMC electrolyte from 1 to 5 and then to 10 M yields significant changes in SEI morphology. The 1 M electrolyte led to DMC degradation into -O-CH3 with no significant LiO formation. In contrast, the 5 and 10 M formulations evolved into an SEI structure dominated by continuous and stratified LiO and LiF phases.Changes in the SEI morphology based on the E/A ratio for the 10 M LiFSI/DMC electrolyte revealed the existence of an intermediate E/A ratio leading to a more compact and more inorganic-rich SEI; the formed LiO phase density was higher than that in other ensembles representative of dry and flooded electrolyte operation conditions. Our third set of calculations focused on the effect of solvent chemistry. The 5 M LiFSI/DME electrolyte led to the formation of a LiO phase surrounded by some residual DME solvent; in this wetted SEI, the residual solvent provides diffusion channels for Li+ ions. Finally, we tested the impact of adding 1,1,2,2-tetrafluoroethylene 2,2,3,3-tetrafluoropropyl ether (TTE) as a diluent into the electrolyte using a 1.3 M LIFSI:DMC:TTE (1:1.2:3 molar ratio) formulation. The TTE diluent showed decomposition and helped grow a LiF-dominated SEI film with a lower LiO/LiF phase ratio than the equivalent 5.0 M LiFSI/DMC formulation with no electrolyte. These results form the basis for a deeper understanding of the SEI formation mechanisms and provide a design guideline for SEI films based on the lithium salt concentration, relative electrolyte/electrode content, and presence of a diluent.

SEI formation mechanisms and Li+ dissolution in lithium metal anodes: Impact of the electrolyte composition and the electrolyte-to-anode ratio

The lithium metal battery is one of today's most promising high-energy-density storage devices. Its full-scale implementation depends on solving operational and safety issues intrinsic to the Li metal high reactivity leading to uncontrolled electrolyte decomposition and uneven Li deposition. In this work, we study the spontaneous formation of the solid electrolyte interphase (SEI) upon contact of Li metal with the electrolyte and describe the heterogeneous SEI morphological features. Multiple electrolyte formulations based on lithium bis(fluorosulfonyl)imide (LiFSI), dimethoxyethane (DME), dimethyl carbonate (DMC), 1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) and bis(2,2,2-trifluoroethyl) ether (BTFE) are used. Findings include the description of the SEI evolution from dispersed LiO, LiS, LiN, and LiF clusters to a continuous and compact inorganic phase in which the LiO and LiF content depend on the presence of fluorine diluents. The role of the DME ether solvent helping the growth of a “wet-SEI” is compared to that of the highly unstable carbonate DMC, which decomposes into complex radical oligomers that might contribute to further electrolyte decomposition. The impact of the electrolyte-to-anode ratio on LiFSI decomposition is highlighted. Finally, we suggest the existence of a critical LiFSI concentration and electrolyte-to-anode ratio that could potentially balance the rate of electrolyte depletion and lithium consumption.

Experimental analysis to improve charge/discharge of thermal energy storage in phase change materials using helical coil and porous metal foam

The use of phase change materials (PCM) for latent heat thermal energy storage (LHTES) is a common method of storing thermal energy in buildings. Because the thermal conductivity of the PCMs is low, so the rate of their energy charge/discharge would be confined. To overcome this issue, a new design is proposed using helical coil to maximize the contact surface between the heat transfer fluid (HTF) and the PCM. Both sides of the helical coil are filled with PCM, while in the inner region, copper metal foams (porosity of 0.9 and density of 12 PPI) are utilized for heat transfer rate enhancement. Effects of various parameters, including the inlet HTF flow rate, its temperature, and use of porous media on thermal energy storage performance in charge and discharge processes are analyzed experimentally. Six thermocouples are placed inside the PCM in different regions and melting and solidification processes are recorded using a thermal imaging camera. Results are presented in terms of temperature variation in different regions, temperature contours, mean temperature response, Stefan number, the charge/discharge time, and the extracted power of discharge. The results reveal that using porous media can remarkably reduce the charge/discharge time up to 57 %, which is depended on the inlet working fluid temperature. The charging time reduction is higher when the inlet HTF temperature increases. When the flow rate of HTF is increased, the charging time can be slightly shortened, while this effect becomes dominant when using porous media. Use of porous media could also accelerate the discharge time, while a faster discharge rate was observed for lower HTF flow rates during discharging the stored energy. Also, a lower initial temperature of the inlet HTF provides faster depletion rate.

Adult Atlantic salmon (Salmo salar) delayed below dams rapidly deplete energy stores

Atlantic salmon ( Salmo salar) return to rivers in spring for an energetically costly upstream migration for spawning. These fish are often delayed in the lower river below dams, subjecting them to warmer waters than occur in upstream sections of river, that may increase metabolic costs. We sought to quantify the energetic cost of dam-mediated delays in migrating adults in the Penobscot and Kennebec rivers, ME. We radio-tagged fish at the lower most dams, released them downstream (18 and 14 km), and tracked their movements back upstream. We used a Distell Fish Fatmeter as a noninvasive measurement of full-body energy at tagging and then again after re-ascending the fish-way at the dams. We found that adults ( n = 99) experienced average delays of 16–23 days at dams, losing 11%–22% of initial fat reserves. Using linear regressions, we showed thermal experience as a strong predictor of fat loss. Delay time was also a contributing factor. Extensive delays at dams expose migrating Atlantic salmon to warmer temperatures and increase the depletion rate of energy reserves required for spawning and post-spawn survival.

Application of artificial bee colony programming techniques for predicting the compressive strength of recycled aggregate concrete

The use of recycled aggregate concrete (RAC) in the construction industry can help to prevent irreparable environmental damages and to mitigate the depletion rate of natural resources. However, the quality of the RAC should be investigated before its practical applications. Compressive strength of the RAC (fRAC′) is one of the most crucial design parameters, which is measured by time-consuming and cost-extensive experiments. One solution to restrict the number of experiments and achieve reliable fRAC′ estimation is through employing machine learning methods, Artificial Bee Colony Expression Programming (ABCEP) is a newly proposed automatic regression technique that is used in this study to predict the fRAC′. For comparison purposes, four extensions of artificial bee colony programming techniques (i.e., Artificial Bee Colony Programming (ABCP), quick Artificial Bee Colony Programming (qABCP), Quick semantic Artificial Bee Colony Programming (qsABCP), and Semantic Artificial Bee Colony Programming (sABCP)) were also served. To analyze the results, the average and best performances of all algorithms, regression analysis, execute run times, Wilcoxon signed-rank test, and the behavior of algorithms dealing with the local optima were investigated. The results show that the ABCEP method is the most effective technique, with the average root mean squared error of 10.36 MPa compared to 16.23 MPa, 10.82 MPa, 17.71 MPa, and 14.20 MPa for the developed ABCP-, qABCP-, qsABCP-, and sABCP-based models, respectively, in colony size of 30. In addition, the run time of this algorithm is remarkably less than the other algorithms.

Improving the resolution of GRACE-based water storage estimates based on machine learning downscaling schemes

The applications of the Gravity Recovery and Climate Experiment (GRACE) on local scales are obstructed owing to the coarser spatial resolution of GRACE observations. Much attempts recently have been taken to improve the resolution of GRACE-based water storage estimates based on machine learning algorithms, focusing on new algorithm development. However, there are still two deficiencies in previous GRACE downscaling research, namely the selection of input variables and the scale of model construction. In this study, the partial least squares regression (PLSR) model firstly is employed to identify the representative predictors associated with GRACE observations. Then, the performance of two different downscaling schemes (namely pixel-scale and regional-scale models) are comprehensively investigated, based on a machine learning algorithm known as random forest, to enhance the resolution of GRACE-based water storage estimates to the grid resolution as small as 5 km. The downscaled results are validated against hydrological model simulations and a number of in-situ groundwater level measurements within one of most rapidly urbanized basin in China, Haihe River Basin. The PLSR model recognizes four variables (namely evapotranspiration, temperature, land surface temperature, and soil moisture) as the predominant factors, acting as the predictors of downscaling models. Starting with the GRACE observations, two kinds of pixel and regional downscaling schemes are developed. The downscaled results were consistent each other and with the original GRACE data at a broad scale with the correlation up to 0.98. It was found that there was 3.20 times deviation of the results from the model simulation in computation of groundwater depletion rates within plain areas. In-situ water level measurements highlight that the downscaling models are improved by 36.95 % and 23.25 % in correlation relative to the original GRACE data and the simulated groundwater storage anomalies, respectively. Generally, the pixel-scale model is slightly better than the regional-scale model with 69 % (171 out of 249 observation wells) of higher correlation and 53 % (131 out of 249 observation wells) of smaller root mean squared error. The high-resolution results presented in this study can lead to better understanding on regional water resources and provide quantitative information to water management considering irrigation water use and groundwater consumption.

Inferring decelerated land subsidence and groundwater storage dynamics in Tianjin–Langfang using Sentinel-1 InSAR

ABSTRACT To meet the growing demand for socioeconomic development, a large amount of groundwater is extracted from confined aquifers worldwide. The North China Plain has experienced considerable groundwater depletion and subsidence during the past six decades. In this study, we use Sentinel-1A/B SAR images from 2015 to 2020 to map the ground subsidence of the Tianjin–Langfang area. Three subsiding zones centered at Guangyang, Wuqing–Bazhou, and Jinghai are identified with maximum subsidence rates of 98.1, 121.8, and 104.7 mm/yr. Seasonal and long-term signals are separated from time series subsidence and hydraulic measurements using continuous wavelet transform to retrieve aquifer parameters. The long-term subsidence, which fits well with an exponential decaying model, remarkably slows down in our study area. The elastic skeletal storage coefficients range between 0.52×10−3 and 9.66×10−3. We then retrieve the spatial–temporal variations of total groundwater storage, recoverable groundwater storage, and irreversible groundwater storage. Groundwater storage depletion rates are apparently reducing, which benefits from the operation of the South-to-North Water Transfer Project and local groundwater management practices.

Spatio-temporal assessment of changing land surface temperature and depleting water in the Lake Chad area

Lake Chad is located at the south of the Sahara Desert in an arid region. The lake’s water resources are under severe pressure due to the basic needs of the growing population around the lake, global warming, and increasing irrigation demands. Numerous land cover change studies have measured the rate of depletion of the lake’s surface water. However, the contribution of the increasing high temperatures in the region which is also a compounding factor has received little attention. In this study, an assessment of the changes in surface water extent of Lake Chad from 1973-2017 was carried out through a land cover analysis. The potential influence of the rising land surface temperatures on the water losses was also studied. The extraction of the land cover was done using maximum likelihood classification. The results show that between 1973 and 1987, the lake lost 12,796.81km2 of its surface water area. This period coincided with a season of drought and dry seasons reported to have occurred in the lake’s area during the 1970s. Between 1987 and 2003, average temperature rise and change in surface water area was +1.54˚C and +962.71km2 respectively. Between 2003 and 2017, average temperature rise and change in surface water area was +3.69˚C and -25.17km2 respectively. These results provide further evidence of the alarming rate of water loss in the lake’s environment, and suggest a link between rising land surface temperatures and diminution of the lake’s water. The findings inform efforts directed at addressing the ecological problem facing the lake.