Size Sorting Research Articles

Asteroid regolith strength: Role of grain size and surface properties

Most of the small asteroids with sizes below a few km are believed to be rubble piles. In order to study the strength of such bodies, we have performed bulk measurements on simulant granular material, varying the grain size and surface properties in ambient conditions. The samples were prepared from a high-fidelity asteroid soil simulant and subjected to compression and shear stresses. We measured the material angle of repose, Young Modulus, its angle of internal friction, bulk cohesion, and tensile strength. Grain sizes were varied from 0.1 to 10 ​mm. Grain surface properties (friction and cohesive forces) were modified by adding a surface frost layer. We find that, in shear, larger grains increase the strength in confined samples, representative of regolith subsurface layers on asteroids, while they decrease strength in unconfined samples, representative of surface regolith. In compression, confined samples become weaker with increasing grain size, while unconfined samples are barely sensitive to it. We also find that increasing surface friction and intergrain cohesion increases the strength in all the samples. We measure bulk cohesion values between ∼400 and 600 ​Pa, internal friction between 25 and 45°, and tensile strengths between 600 and 900 ​Pa. The measured angles of repose varied between ∼25 and 45° in an opposite trend to the internal friction. We compare these values to spacecraft data and numerical simulations and discuss implications of our findings for rubble-pile composition and disintegration behavior. We find that grain size sorting with depth, depletion of fines at the surface, or presence of water ice in the core can provide a mechanism for regular surface shedding event on small asteroids. • We performed mechanical strength measurements on high-fidelity CI asteroid simulant. • Larger grains weaken samples in compression but strengthen it in shear. • Surface frosting on grains strengthens the samples in both compression and shear. • Measured compression and tensile strengths are in agreement with in-situ measurements at Ryugu and Bennu. • We propose potential mechanisms for regular surface shedding event on rubble-pile asteroids.

Projeto e implementação de uma máquina sequencial de classificação por tamanho de frutas

ABSTRACT This study aimed to develop a simple and easy to construct fruits size sorting machine. The sorting machine was designed to sort oranges, apples, and yellow plums in small, medium, large, and extra-large size groups based on physical and mechanical properties including axial dimensions, arithmetic mean diameter, sphericity, mass, volume, projected area, and frictional characteristics (coefficient of static friction) against two structural surfaces of the sorting machine (galvanized iron and rubber). The maximum sorting efficiency of the machine was 98% at 20 rpm for plums. Whereas the minimum fruit sorting efficiency of the machine at 25 rpm was 76% for apple fruits. The sorting efficiency of the machine increased with increasing sphericity ratio of fruits. The sorting machine productivity was 280, 250, and 212 kg h-1 for sorting oranges, apples, and plums, respectively. It is recommended that the machine should be operated at three slope angles of the sorting unit 20º, 15º, and 10º for oranges, apples, and plums, respectively. These angles correspond to the coefficient of static friction of the tested fruit.

Unique Radar Observations of Large Raindrops in Tropical Warm Rain during PISTON

Abstract Isolated warm-rain cells are an important feature over the tropical oceans. Although warm rain is typically associated with relatively small raindrops, large raindrops (>4.5 mm in diameter) have been observed in some cases. Previous studies have examined warm rain cells with large drops on a case-study basis, but they have yet to be investigated in a broader, statistical sense. During the recent Propagation of Intraseasonal Oscillations (PISTON) field campaign, a C-band polarimetric radar routinely measured extreme values of differential reflectivity in small, isolated convection, indicating the presence of large drops. Using an objective feature identification and tracking algorithm, this study offers new insights to the structure and frequency of cells containing large drops. Cells with high differential reflectivity (>3.5 dB) were present in 24% of all radar scans. The cells were typically small (8-km2 mean area), short lived (usually <10 min), and shallow (3.7-km mean height). High differential reflectivity was more often found on the upwind side of the cells, suggesting a size sorting mechanism was operating establishing a low concentration of large drops on the upwind side. Differential reflectivity also tended to increase at lower altitudes, which is hypothesized to be due to continued drop growth and increasing temperature (increasing the dielectric constant of water). Rapid vertical cross-section radar scans, as well as transects made by a Learjet aircraft with onboard particle probes, are also used to analyze these cells, and support the conclusions drawn from statistical analysis.

Geochemical Characteristics and Environmental Implications of Surface Sediments from Different Types of Sand Dunes in the Dinggye Area, Southern Tibet.

Geochemical characteristics of aeolian sand are beneficial for understanding sand dune formation and evolution. Few studies in the Dinggye area, Southern Tibet, have focused on the geochemical characteristics of aeolian sand. Thus, we present new geochemical data that provide insights into the geochemical characteristics and environmental implications of aeolian sands in the Dinggye area. The results show that mobile dunes, climbing sand sheets, and nebkhas show heterogeneity in elemental concentrations and UCC-normalized distribution; MgO, TiO2, Ni, Pb, and Nb are higher in mobile dunes; SiO2, CaO, K2O, Na2O, P2O5, V, Cr, Co, Cu, Ba, and Ce are higher in climbing sand sheets; and Al2O3, Fe2O3, La, Zn, As, Sr, Y, Zr, Rb, and Ga are higher in nebkhas. Principal component analysis (PCA) and correlation analysis indicate that the main factor affecting elemental content is grain size sorting, followed by provenance, while chemical weathering and regional precipitation are less influential. The CIA and A-CN-K triangle indicate that the different dune types are at a lower chemical weathering stage, with plagioclase weathering and decomposition first. The combination of grain size characteristics, elemental ratios, multidimensional scale (MDS), PCA, and geomorphological conditions suggest that the flood plain and the lakeshore are the main sand sources of aeolian sands in the Dinggye area.

The influence of interparticle cohesion on rebounding slow impacts on rubble pile asteroids

The ballistic sorting effect has been proposed to be a driver behind the observed size sorting on the rubble pile asteroid Itokawa. This effect depends on the inelasticity of slow collisions with granular materials. The inelasticity of a collision with a granular material, in turn, depends on grain size. Here we argue that determining the inelasticity of such collisions in an asteroid-like environment is a nontrivial task. We show non-monotonic dependency of the coefficient of restitution (COR) on target particle size using experiments in microgravity. Employing numerical simulations, we explain these results with the growing influence of adhesion for smaller-sized particles. We conclude that there exists an optimum impactor to target particle size ratio for ballistic sorting.

Sedimentological, mineralogical and geochemical investigation of Chichaoua’s bassin depot system: potential origin and provenance

High Atlas Rivers are common along the Atlas Mountains of Morocco and result from the combined effectof river flow, winds, vegetation and other meteorological conditions. In this paper, we study the texturaland compositional parameters of fluvial deposits, from the Chichaoua catchment across the Seksaoua riverbanks, and their provenance. Morphologically, they are in the form of current active river, Paleozoic deposits.To study the provenance of the grains, we opted for laboratory analyses including grain size, mineralogy,micro textures and micro morphology. Sands from active deposits showed very fine to medium averagegrain size and moderate sorting, while those from fluvial deposits showed fine to very fine average grainsize and very low sorting. The deposits studied showed the dominance of grain forms ranging from angularto freshly angular. As far as mineralogy is concerned, calcite is predominant in the sands on the right bankof the river, whilequartz is more abundant in the deposits on the left bank. In the active streams on the leftbank, other carbonates were also detected in the bioclasts such as aragonite, dolomite and magnesian calcite,suggesting a fluvial origin. The siliciclastic grains of the studied stream generations are likely to be ofTriassic, Jurassic and Quaternary units origin crossed by the Seksaoua River. Indeed, the results revealedthe presence of minerals such as albite, plagioclase, microcline and illite which could come from Triassic asalts which is often associated with Jurassic evaporates associated with Jurassic evaporite rocks. This studyhas suggested the probable origin of the sands that form these deposits based on the detailed study of theirgrains, which has not been studied in previous research in the area. Furthermore, this research is particularlyrelevant as it is part of the current research trend related to the understanding of the evolution of Plio-Quaternary atlasic fluvial systems in the world and may be applicable to other fluvial systems in the mountainranges of Morocco in the future.

A Dual-Encoded Bead-Based Immunoassay with Tunable Detection Range for COVID-19 Serum Evaluation.

Serological assay for coronavirus 2019 (COVID‐19) patients including asymptomatic cases can inform on disease progression and prognosis. A detection method taking into account multiplex, high sensitivity, and a wider detection range will help to identify and treat COVID‐19. Here we integrated color‐size dual‐encoded beads and rolling circle amplification (RCA) into a bead‐based fluorescence immunoassay implemented in a size sorting chip to achieve high‐throughput and sensitive detection. We used the assay for quantifying COVID‐19 antibodies against spike S1, nucleocapsid, the receptor binding domain antigens. It also detected inflammatory biomarkers including interleukin‐6, interleukin‐1β, procalcitonin, C‐reactive protein whose concentrations range from pg mL−1 to μg mL−1. Use of different size beads integrating with RCA results in a tunable detection range. The assay can be readily modified to simultaneously measure more COVID‐19 serological molecules differing by orders of magnitude.

A Dual‐Encoded Bead‐Based Immunoassay with Tunable Detection Range for COVID‐19 Serum Evaluation

AbstractSerological assay for coronavirus 2019 (COVID‐19) patients including asymptomatic cases can inform on disease progression and prognosis. A detection method taking into account multiplex, high sensitivity, and a wider detection range will help to identify and treat COVID‐19. Here we integrated color‐size dual‐encoded beads and rolling circle amplification (RCA) into a bead‐based fluorescence immunoassay implemented in a size sorting chip to achieve high‐throughput and sensitive detection. We used the assay for quantifying COVID‐19 antibodies against spike S1, nucleocapsid, the receptor binding domain antigens. It also detected inflammatory biomarkers including interleukin‐6, interleukin‐1β, procalcitonin, C‐reactive protein whose concentrations range from pg mL−1 to μg mL−1. Use of different size beads integrating with RCA results in a tunable detection range. The assay can be readily modified to simultaneously measure more COVID‐19 serological molecules differing by orders of magnitude.

Modelling the vertical grain size sorting process in aeolian sediment transport using the discrete element method

We present a model study of the aeolian saltation process where sediment samples are studied for the size selective transport processes. The discrete element method is used to simulate the sediment particles of different sizes, coupled with a fluid boundary layer model to capture the driving wind forces. Sediment samples with identical median grain size, but with systematically varying size distributions were simulated to investigate under various wind shear rates which sediment fractions are transported. The presented model results show - well in line with other research - that the median grain size is an appropriate sediment sample parameter to quantify the total rate of sediment transport. However, our results show that this does not determine what fractions of sediment are in transport. The larger the standard deviation in the sediment size distribution the smaller the median grain size becomes of the sediment that is in transport compared to the median grain size present at the bed.

Microphysical Piggybacking in the Weather Research and Forecasting Model

AbstractThis paper presents incorporation of the microphysical piggybacking into the Weather Research and Forecasting (WRF) model. Microphysical piggybacking is to run a single simulation applying two microphysical schemes, the first scheme driving the simulation and the second piggybacking this simulated flow. “Driving the simulation” means that the simulated microphysical processes, affect the cloud buoyancy and thus force the simulated flow. In contrast, the piggybacking variables are advected by the simulated flow and undergo microphysical transformation, but they do not affect the simulated flow (like in prescribed flow—kinematic—simulations). The two sets of variables (driver and piggybacker) include temperature, water vapor mixing ratio, and all microphysical variables. We provide details of implementing piggybacking into the WRF model, illustrate its applications, and demonstrate the benefits of this methodology in two idealized three‐dimensional cases: (a) a squall line case applying two microphysics schemes, the Thompson bulk microphysics scheme and the University of Pécs/NCAR bin (UPNB) scheme. The piggybacking simulations revealed that the microphysics‐dynamics interaction plays a more important role than the pure microphysical size sorting effect in the transition zone formation. (b) A case of daytime shallow‐to‐deep convective development over land. This case uses the UPNB scheme and contrasts convection developing in environments with either pristine or polluted cloud condensation nuclei (CCN). The piggybacking results indicated that the increase of cloud cover and decrease of supersaturation are mainly associated with the microphysical effect of increasing CCN while the change of precipitation on the ground is also influenced by microphysics‐dynamics interactions.

Entrainment and Transport of Well‐Sorted and Mixed Sediment Under Wave Motion

AbstractEntrainment and suspension of sediment particles with the size distribution similar to a range of natural sands were simulated with a focus on the vertical size sorting and transport dynamics in response to different wave conditions. The simulations were performed using a two‐phase Eulerian‐Lagrangian model by combining the LIGGGHTS discrete element method solver for sediment and SedFoam solver for the fluid phase. The model was first validated for a range of sand grain sizes from 0.21 to 0.97 mm having well‐sorted and mixed (bimodal) size distributions using laboratory oscillatory flow data. Three sediment bed configurations were studied under a wide range of velocity‐skewed waves with different wave intensity and skewness. It was found that the bimodal distribution having only 30% of coarse fraction and 70% of medium fraction responds similar to a well‐sorted coarse sand configuration. Sediment fluxes of the bimodal distribution were slightly higher than those of well‐sorted coarse sand because of the pronounced inverse grading in the bimodal distribution. Furthermore, for the bimodal distribution the medium fraction acted as a relatively smooth foundation underneath the coarse fraction which facilitated the mobilization of the coarser particles. Under high energy wave conditions, the smoothing feature was exacerbated and further caused the formation of plug flow where a thick layer of intense sediment flux was observed. Model results also showed that under high skewness waves, phase‐lag effect occurred in well‐sorted medium sand which caused lower net onshore sediment transport rates but the effect was significantly reduced for mixed sediments.

Grain Size and Sedimentary Sorting Characteristics of Atmospheric Dust in the Cele Oasis, Southern Margin of Taklimakan Desert

Grain size is a proxy indicator of airflow intensity and also provides a scientific basis for the prevention of dust hazards. However, the variations in grain size characteristics that occur during transport and deposition processes are seldom discussed. Here, atmospheric dust samples were collected before and after deposition in a sand–dust storm for grain size analysis. The results showed that the grain size distributions of the atmospheric dust were unimodal during transportation but always became bimodal after deposition. This indicates that the bimodal grain size distribution of the aeolian deposits was caused by sedimentary sorting. The coarse-grained component, which was between 20 and 200 μm, was mainly deposited during the sand–dust storm. Grain size may indicate the strength of the airflow field. The fine-grained component, which ranged in size from 0.4 to 20 μm, was mainly deposited after the sand–dust storm. This component can remain suspended in the atmosphere for a long period of time. Oasis shelterbelts can be used to reduce the fine-grained component of the dust aerosol through the interception of particles by foliage. The grain size variation found in this study from before to after sand–dust storm deposition deepens our understanding of the sediment sorting process.

Evaluation of modelled summertime convective storms using polarimetric radar observations

Abstract. Ensemble simulations with the Terrestrial Systems Modelling Platform (TSMP) covering northwestern Germany are evaluated for three summertime convective storms using polarimetric X-band radar measurements. Using a forward operator, the simulated microphysical processes have been evaluated in radar observation space. Observed differential reflectivity (ZDR) columns, which are proxies for updrafts, and multi-variate fingerprints for size sorting and aggregation processes are captured by the model, but co-located specific differential phase (KDP) columns in observations are not reproduced in the simulations. Also, the simulated ZDR columns, generated by only small-sized supercooled drops, show smaller absolute ZDR values and a reduced width compared to their observational counterparts, which points to deficiencies in the cloud microphysics scheme as well as the forward operator, which does not have explicit information of water content of ice hydrometeors. Above the melting layer, the simulated polarimetric variables also show weak variability, which can be at least partly explained by the reduced particle diversity in the model and the inability of the T-matrix method to reproduce the polarimetric signatures of snow and graupel; i.e. current forward operators need to be further developed to fully exploit radar data for model evaluation and improvement. Below the melting level, the model captures the observed increase in reflectivity, ZDR and specific differential phase (KDP) towards the ground. The contoured frequency altitude diagrams (CFADs) of the synthetic and observed polarimetric variables were also used to evaluate the model microphysical processes statistically. In general, CFADs of the cross-correlation coefficient (ρhv) were poorly simulated. CFADs of ZDR and KDP were similar but the model exhibits a relatively narrow distribution above the melting layer for both, and a bimodal distribution for ZDR below the melting layer, indicating either differences in the mechanism of precipitation formation or errors in forward operator which uses a functional form of drop size distribution. In general, the model was found to underestimate the convective area fraction, high reflectivities, and the width/magnitude of ZDR columns, all leading to an underestimation of the frequency distribution for high precipitation values.

Depositional environments and diagenesis of north Gondwana Ediacaran clays (Zenifim and Elat Conglomerate Formations, Israel)

A thick sequence of arkosic sandstones and conglomerates, locally interbedded with volcanic rocks, was deposited in the piedmont region and within intramountain basins of the northern Arabian-Nubian Shield (ANS) during the late Neoproterozoic Ediacaran period. We have studied the geochemistry and clay mineralogy of these sediments in outcrops and drill cores along a ∼200 km long transect in southern Israel, in order to constrain their depositional environments and the diagenetic processes that have affected them. Whole rock trace element data for the Israeli Ediacaran sediments indicates magmatic island arc provenance, consistent with a source in the ANS. Major elements data indicate the importance of pedogenic processes in the source area and modification by grain size sorting during transport and deposition. In the southernmost part of the study area, clay assemblages of the Ediacaran formations include significant proportions of the mineral illite–smectite (I/S), including of randomly interlayered (R0) structure. In the central and northern parts of the study area, the entire Ediacaran section is dominated by illite, while the minor I/S found in this area is always ordered, and changes from R1- to R3-type structure with increasing depth. This transition from R1- to R3-type I/S seems to shallow towards the north. These trends of clay minerals composition along the Ediacaran strata reflect increased paleo-thermal gradient and/or burial depths toward the north, which is correlated with the formation of late Devonian – Carboniferous thermal structure over the Levant area. The pristine, I/S dominated clay assemblage found in the Ediacaran sediments of southernmost Israel is remarkable given these sediments' relatively old age and offers a unique opportunity to probe the Ediacaran climate in this region, which resided at low latitudes at that time. This I/S dominated, kaolinite lacking, clay assemblage, together with relatively low chemical index of alteration values found for the Ediacaran sediments of southern Israel, reflect limited chemical weathering of ANS basement rocks under relatively dry, potentially cool, climatic conditions. The persistence of such climatic conditions within the tropical belt is consistent with a series of late Ediacaran glaciation events, although negating a complete, prolonged 'Snowball Earth'-type global glaciation.

Nondestructive Dimension Sorting by Soft Robotic Grippers Integrated with Triboelectric Sensor.

In smart logistics, traditional manual sorting and sorting systems based on rigid manipulators limit the warehousing development and damage the goods. Here, a nondestructive sorting method based on bionic soft fingers is proposed. This method is implemented by the soft robotic gripper (SRG) for grasping of the breakable objects, the triboelectric sensor (TES) for size sorting of the objects, and the signal processing module. In the fabrication of SRG, the silicon rubber is prepared by controlling the material synthesis process, and its Young's modulus is 600.91 kPa, which is comparable to the Young's modulus of skin tissue. Also, the maximum input pressure of SRG is 71.4 kPa. The TES has a linear relationship between pulse number and sliding displacement, and its resolution is 3 mm. It induces pulse signal sequences to quantify the SRG bending state and thus realize the size sorting of objects. Additionally, a nondestructive sorting system based on TES and SRG has been developed for fruit sorting (e.g., apples, oranges), enabling nondestructive grasping and accurate sorting. Its sorting range is 70-120 mm, and the sorting accuracy rate is up to 95%. This work also provides a way for the application of SRG and triboelectric sensors in the sorting field.

Ergonomic Task Analysis for Prioritization of Work-Related Musculoskeletal Disorders among Mango-Harvesting Farmers

This paper proposes a mixed ergonomic tool analysis algorithm to prioritize work-related musculoskeletal problems. This study is a cross-sectional study assessing the prevalence of work-related musculoskeletal disorders (WMSDs) with associated risk factors among 14 male mango-harvesting farmers (all right-handed) with the mean age of 52.28 ± 7.75 years. Four tasks following mango-harvesting processes were analyzed: (1) mango harvesting, (2) mango transporting, (3) mango size sorting, and (4) mango weighing and transporting to the truck. The perceived physical exertion while working on a mango-harvesting farm was based on the Borg CR-10 with a modified Standardized Nordic Questionnaire. Physical risk level due to awkward posture was evaluated by the Rapid Upper Limb Assessment (RULA), and risk due to whole-body posture in association with the level of WMSDs risk was evaluated by the Rapid Entire Body Assessment (REBA) score sheets. The subjective feelings of fatigue and posture analysis were normalized and combined using the theorem of power superposition to establish the fatigue effective index (FEI) for determining priorities to solve ergonomics-based task problems. This study indicated clearly that WMSDs are highly prevalent in mango-harvesting farmers, whereas the highest prevalence of WMSDs was reported in the right shoulder, right upper arm and lower back. The result provided the FEI of mango-harvesting farmers, ranked as follows: (1) size-sorting task, (2) weight-lifting task, (3) harvesting task, and (4) transporting task. The authors concluded that mango size sorting should be the first task to be improved to resolve the muscle fatigue problems among male mango-harvesting farmers.

Convective and Microphysical Characteristics of Extreme Precipitation Revealed by Multisource Observations Over the Pearl River Delta at Monsoon Coast

AbstractExtreme precipitation is an issue of worldwide concern, but its microphysics remain elusive. The convective and microphysical characteristics of extreme precipitation features (EPFs) in a monsoon coastal area (South China) are investigated mainly using 2‐year observations from a dual‐polarization radar and distrometers. The EPFs are accompanied by a broad range of convective intensity, and categorized into the “intense”, “moderate”, and “weak” convection accounting for 17.3%, 48.6% and 34.1% of the total population, respectively. The EPFs with weaker convection show weakened size sorting and less breakup of large raindrops, but a larger ratio of liquid water path to ice water path and more prominent coalescence warm‐rain process. All the three categories are dominated by the coalescence in the liquid‐phase processes, and have much more populous raindrops than the “continental” with a mean size larger than the “maritime” regime. These results improve our understanding of extreme precipitation from the microphysical perspective.

Investigation of particle manipulation mechanism and size sorting strategy in a double-layered microchannel.

Traditionally, comprehensive laboratorial experiments on newly proposed microfluidic devices are necessary for theoretical validation, technological design, methodological calibration and optimization. Multiple parameters and characteristics, such as the flow rate, particle size, microchannel dimensions, etc., should be studied by controlled trials, which could inevitably result in extensive experiments and a heavy burden on researchers. In this work, a novel numerical model was introduced to simulate particle migration within a complicated double-layered microchannel. Using the hybrid meshing method, the proposed model achieved a significant improvement in meshing quality, and remarkably reduced the required calculation resources at the same time. The robust, efficient and resource-saving numerical model was calibrated and validated with experimental results. Based on this model, 1) the mechanism of microparticle manipulation within the microchannel was revealed; 2) the primary reason for the microparticle focusing failure was investigated; and 3) the optimal microparticle sorting strategy at different flow rates was analyzed. In experiments, the obtained optimal strategy could approach a good sorting performance with a high recovery rate and high concentration ratio in a high-throughput manner. The proposed numerical model shows great potential in mechanism investigation and functional prediction for microfluidic technologies using unconventional designs.

Optimization Analysis of Mechanical Properties of Fly Ash‐Based Multicontent Gasification Slag Paste Filling Material

In view of the difficult utilization of a large amount of coal‐based solid waste produced by coal electrification in the Ningdong mining area, especially the large storage and low utilization rate of gasified slag, combined with the advantages of high paste filling concentration, fast efficiency, and low construction cost, it is of great significance to study the appropriate proportion of fly ash‐based multicontent gasified slag paste filling material for green mining and large‐amount utilization of gasified slag. Based on the microstructure, composition, and particle size distribution of gasification slag, fly ash, broken coal gangue, furnace bottom slag, and desulfurization gypsum tested by XRD, SEM, and particle size sorting screen, the mass fraction (X1), gasification slag content (X2), m (c): m (FA) (X3). 29 groups of schemes are designed by four factors : mass fraction X1 refers to the proportion of solid in the filling paste, the amount of gasification slag in the solid X2 refers to the proportion of gasification slag in the solid, and m (c): m (FA) X3 refers to the proportion of fly ash and cement in the solid excluding gasification slag, coal gangue, desulfurization gypsum, and furnace bottom slag. The amount of desulfurization gypsum in the solid X4 refers to the proportion of desulfurization gypsum in the solid. The flow and strength characteristics of each group are analyzed. It is found that before proportioning, coal gangue of 2.5∼5 mm accounts for 80.8%, furnace bottom slag of less than 2.5 mm accounts for 56.5%, fly ash of 20∼80% μm accounts for 80%, and fly ash of 10∼20% μm accounts for 90%. XRD patterns reveal that the main components of four solid wastes and cement are SiO2 and Ca3SiO5, and the chemical composition of desulfurization gypsum is Ca(SO4)(H2O)2. The regularity of size change tends to be consistent, and the uniaxial compressive strength of 3 days later in group thirteenth exceeds 0.991 MPa. Combined with the flow characteristics, it is determined that there are 6 optimization groups in the inclined ladder area with the expansion of 200∼250 mm and the uniaxial compressive strength of 0.6∼1.4 MPa. The compressive strength increases with the increase of the mass fraction of single‐factor analysis. The response surface method of C shows that the significance of X1, X2, X3, and X4 decreases in turn. The central combination design is used to predict that the mix proportion of X1 is 84%, X2 is 15%, X3 is 1 : 5, and X4 is 7%, the content of coal gangue is 10%, and the content of furnace bottom slag is 5% which is the best. The supplementary experimental results show that σ3d is 1.35 MPa and the expansion is 200 mm. Combined with SEM, it is found that the microstructure before and after optimization is rich in hydration products and the internal structure is well cemented, which further explains σC. The above research provides important basic parameters for large‐scale disposal and green filling mining which is difficult to deal with a large amount of stockpiled gasification slag.

A closer look at sedimentation processes in two dam reservoirs

Dam reservoirs are complex depositional systems, which provide barriers to natural sediment transport along river courses. In addition, reservoir sedimentation causes serious problems in their operational management. Given the wide variability of reservoir bottom shapes, total volumes of stored water, river discharges, sediment loads and sediment textures, universal depositional models are difficult to achieve for dam reservoirs. This article focuses on the need to improve current understandings of sedimentation processes, and thorough spatial particle size distribution in dam reservoirs. To achieve this aim, sonar and ground penetrating radar surveys were combined with high-resolution stratigraphic data from 44 short sediment cores in two valley-type reservoirs, Seč and Křižanovice, part of a reservoir cascade in the Chrudimka River, which is a left-hand tributary of the Labe River (Czech Republic). Sonar survey was used to construct bathymetric maps and bottom reflection intensity images. The results showed topography inherited from pre-reservoir times and a good degree of correspondence between bottom reflection intensity and grain size. The sedimentation patterns exhibit distinct proximal-to-distal and transversal changes in sediment facies and grain size. Pre-reservoir and present morphologies have substantially shaped sediment accumulation. Spatial grain size sorting is a function of travel distance within reservoirs, which is conditioned by their bended and narrow geometry, as well as by reservoir management. Two stages of reservoir sedimentation are recognised. The initial stage was characterised by the filling of local depressions, which were overlain by the second stage, typified by continuous and horizontally deposited sediments. Relatively low sediment accumulation rates (from 0.2 to 1.06 cm/year) are the consequence of reservoir characteristics (capacity and associated accommodation space) and factors at a basin scale (low discharge, geology and land-use). Slow reduction of reservoir capacity was observed. The calculated trap efficiency is very high in the Seč Reservoir and much lower in the Křižanovice Reservoir. The main factor controlling trap efficiency is reservoir capacity and shape combined with low inflow. Ultimately, the trap efficiency change over time because of varying reservoir capacity due to seasonal water level fluctuation and varying hydrologic conditions. Due to the slow silting of the reservoir, the trap efficiency has decreased only slightly. Aside from general trends, some specific features exist for every reservoir based on local geometry and reservoir management strategy. This implies that an innovative approach combining map, sonar and geophysical surveys with core data is required to develop better facies models and to optimise sediment management strategies.