Distribution Curves Research Articles

Synthesis and characterization of a new multifunctional aliphatic poly(amic acid): An efficient polymeric adsorbent for removing the heavy metal ions

The heavy-metal ions in wastewater have attracted intense attention due to environmental issues, including their toxicity, bioaccumulation tendency, and persistency in nature. Despite other strategies for heavy metal removal from wastewater, adsorption is one of the most promising methods, owing to its simplicity and efficiency. To conserve the carboxyl and amine functional groups and prevent amidation reaction, a new aliphatic tertiary poly(amic acid) with linear and cyclic spacers was synthesized via the catalyst-free process. The ring opening of ethylenediaminetetraacetic acid dianhydride (EDTADA) by piperazine, a bifunctional cyclic secondary diamine, was conducted in a polar solvent (DMF) in a nitrogen atmosphere for 3 h. The characterization was conducted by FTIR and NMR, and their morphology and elemental composition were investigated by field emission scanning electron microscopy and energy dispersive X-ray (FESEM-EDX). As-synthesized aliphatic tertiary poly(amic acid) could be separated as a white powder with an O/N ratio of 0.93 ± 0.03 and morphology of woven fiber. The white powder showed an average molecular weight (M̅w) of ∼12,000 and a polydispersity index (PDI) of 1.52 ± 0.05. In addition, the poly(amic acid) TGA/DTA analysis showed a high thermal stability with stepwise degradation with the onset of 346 °C. The poly(amic acid) DSC profile displayed a high glass transition at 124 °C. The Brunauer–Emmett–Teller (BET) surface area and pore volume were determined to be 146.05 m2/g and 0.78 cm3/g. The poly(amic acid) contains the mesopores and macropores based on its pore size distribution curve. Regarding an acidic pH and abundance of functional groups, as-prepared tertiary poly(amic acid) was employed as a heterogeneous adsorbent of different types of heavy-metal ions, including Ag (I), Cr (III), and Cu (II). A removal efficiency > 90 % after 10 min for three heavy metal ions demonstrates a strong chelating capacity of as-prepared tertiary poly(amic acid). An adsorption capacity of > 50 mg per gram of poly(amice acid) was recorded for three heavy-metal ions with a pH of 3 or higher than 3. Poly(amic acid) exhibited good recyclability. This work exhibited the applicability of novel poly(amic acid) as an efficient adsorbent for the heavy metal ions removal from wastewater.

Galaxies with grains: unraveling dust evolution and extinction curves with hydrodynamical simulations

Dust in galaxies is an important tracer of galaxy properties and their evolution over time. The physical origin of the grain size distribution, the dust chemical composition, and, hence, the associated ultraviolet-to-optical extinctions in diverse galaxies remains elusive. To address this issue, we introduce a model for dust evolution in the RAMSES code for simulations of galaxies with a resolved multiphase interstellar medium. Dust is modelled as a fluid transported with the gas component, and is decomposed into two sizes, 5 nm and 0.1 μm, and two chemical compositions for carbonaceous and silicate grains. This dust model includes the growth of dust by accretion of elements from the gas phase and by the release of dust in stellar ejecta, the destruction by thermal sputtering, supernovae, and astration, and the exchange of dust mass between the two main populations of grain sizes by coagulation and shattering. Using a suite of isolated disc simulations with different masses and metallicities, the simulations can explore the role of these processes in shaping the key properties of dust in galaxies. The simulated Milky Way analogue reproduces the dust-to-metal mass ratio, depletion factors, size distribution and extinction curves of the Milky Way. Galaxies with lower metallicities reproduce the observed decrease in the dust-to-metal mass ratio with metallicity at around a few 0.1 Z⊙. This break in the dust-to-metal ratio corresponds to a galactic gas metallicity threshold that marks the transition from an ejecta-dominated to an accretion-dominated grain growth, and that is different for silicate and carbonaceous grains, with ≃0.1 Z⊙ and ≃0.5 Z⊙ respectively. This leads to more Magellanic Cloud-like extinction curves, i.e. with steeper slopes in the ultraviolet and a weaker bump feature at 2175 Å, in galaxies with lower masses and lower metallicities. Steeper slopes in these galaxies are caused by the combination of the higher efficiency of gas accretion by silicate relative to carbonaceous grains and by the low rates of coagulation that preserves the amount of small silicate grains. Weak bumps are due to the overall inefficient accretion growth of carbonaceous dust at low metallicity, whose growth is mostly supported by the release of large grains in SN ejecta. We also show that the formation of CO molecules is a key component to limit the ability of carbonaceous dust to grow, in particular in low-metallicity gas-rich galaxies.

Analytical Calculation of the No-Load Magnetic Field of a Hybrid Excitation Generator

Hybrid excitation generators combine the advantages of electric excitation motors and permanent magnet generators. Focusing on a permanent magnet generator as the object of study, an auxiliary excitation winding is introduced for voltage regulation. The main magnetic field is established by the permanent magnet, and the auxiliary excitation winding provides the magnetic potential required to regulate the air-gap magnetic field. While improving the voltage regulation performance of permanent magnet generators, it also reduces the loss of excitation windings in electrically excited generators. Based on a hybrid excitation generator with dual excitation windings, in the following article, we present a hybrid excitation generator equivalent to a full permanent magnet motor with the minimum output voltage, and an accurate subdomain model of the full permanent magnet motor is established considering the influence of slot opening. By establishing a matrix, the distribution curve of air-gap magnetic density was solved and ultimately verified using finite element analysis. The results of the present study lay a solid foundation for solving the air-gap magnetic density distribution of various parts of the hybrid excitation generator and studying its performance in the future.

Simplified Calculation of the Inertia Moment of the Cross Section of the Console under Loading

Introduction. Published studies on the rigidity of consoles under load focus on the issues of their deformation and destruction. Calculations of the inertia moment, fundamentally important characteristic of the strength of the rod, are described. However, the problem of significant time consumption for such calculations has not been solved. The presented study meets the lack. The objective of the work is to describe a new rapid method for analytical calculation of the shear stress distribution in the section of the console corresponding to the action of an external applied force. For the first time, tangential stresses are considered, and examples of calculating the inertia moment for two non-standard sections of the console are given in this context.Materials and Methods. To develop a new method, the console was presented as a pack of plates oriented parallel to the vector of external force. The source calculations were based on the scheme of a console beam with a dedicated plate. The deformation of the rod elements was modeled taking into account the effect of a uniform shear stress field in the plate section. To validate the simplified calculation of the inertia moment of the sections, schemes of a square, ellipse, triangle, hexagon, six-pointed star, and a figured cross were used. Analytical and mathematical research methods were applied, specifically, the Huygens–Steiner theorem.Results. A rapid valid method for calculating the inertia moment of the cross section of the console under loading has been developed. Its difference is the rejection of calculations for each section, taking into account the shape and other features. For any shape of the section, the beam is represented as a bundle of infinitely thin plates, their inertia moments are integrated, and a well-known solution for deflection of a thin plate is used. The method allows us to unambiguously show the distribution of tangential stresses at the end of the console, providing a given deflection, and tangential stresses are used for such solutions for the first time. Their profiles are obtained depending on the direction of the external applied force. Formulas for the inertia moments of complex sections — a six-pointed star and a figured cross — are derived for the first time. Each section is correlated with the stress distribution curve and its maximum value. This data is visualized in the form of diagrams. It is found that the inertia moment and the rigidity of the console do not change when the external applied force is rotated by 30° for a star-shaped section and by 45° for a square and a figured cross. In general, the tangent field depends on the geometry and on the orientation of the section relative to the external applied force.Discussion and Conclusion. The proposed simplified approach to calculating the inertia moment of the cross sections of the consoles makes it possible to uniquely determine the field of tangential stresses at the end, which provides the appropriate value of the external applied force for the given deflection. Engineers and mechanics can use the results of the presented work in the calculations and modeling of deformation of rod structural elements.

Strength and Fractal Characteristics of Artificial Frozen–Thawed Sandy Soft Soil

In regions with sandy soft soil strata, the subway foundation commonly undergoes freeze–thaw cycles during construction. This study focuses on analyzing the microstructural and fractal characteristics of frozen–thawed sandy soft soil to improve our understanding of its strength behavior and stability. Pore size distribution curves before and after freeze–thaw cycles were examined using nuclear magnetic resonance technology. Additionally, fractal theory was applied to illustrate the soil’s fractal properties. The strength properties of frozen remolded clay under varying freezing temperatures and sand contents were investigated through uniaxial compression tests, indicating that soil strength is significantly influenced by fractal dimensions. The findings suggest that lower freezing temperatures lead to a more dispersed soil skeleton, resulting in a higher fractal dimension for the frozen–thawed soil. Likewise, an increase in sand content enlarges the soil pores and the fractal dimension of the frozen–thawed soil. Furthermore, an increase in fractal dimension caused by freezing temperatures results in increased soil strength, while an increase in fractal dimension due to changes in sand content leads to a decrease in soil strength.

Association of oropharyngeal colostrum administration with decreased inflammatory indices in premature newborns weighing less than 1500 g.

The administration of colostrum through its absorption at the oropharyngeal level stimulates the mucosa-associated lymphoid tissue, providing a local immunological protection barrier. The study aimed to investigate the association of oropharyngeal colostrum administration with the reduction of inflammatory indices. This was an observational, ambispective, analytical study of newborns < 32 weeks of gestation at risk of sepsis. Oropharyngeal colostrum was administered at 0.2 mL every 4 h for 5 days. Inflammatory indices were analyzed. Statistical analysis included frequencies, percentages, mean and Standard deviation, contingency coefficient, and Kolmogorov-Smirnov test for the distribution curve of the numerical data. There were 50 patients, 33 (66%) female and 17 (34%) male, with a median gestational age of 30-31 weeks (95% confidence interval [CI]). Nineteen patients had sepsis. A lower positivity rate in C-reactive protein was found, with a median of 0.5-0.6 (95% CI) at 5 days of colostrum administration versus 0.5-1.1 (95% CI) as the initial C-reactive protein. Analysis with χ2 yielded a p = 0.13, and the contingency coefficient showed a p = 0.196, indicating an association. Oropharyngeal colostrum administration was associated with a lower C-reactive protein positivity rate and clinical improvement in premature newborns at risk of sepsis.

Experimental study on the flexural behaviors of ECC-reinforced masonry beams with GFRP mesh

This study aims to investigate the flexural behaviors of ECC-reinforced masonry beams with GFRP mesh under various interface treatment methods. Eleven sets of ECC-reinforced masonry beams with GFRP mesh were fabricated and subjected to a four-point bending test. The effects of the fibre volume fraction and thickness of ECC, interface treatment methods, GFRP mesh strength and layers on the flexural behavior of masonry beams were investigated and analyzed, including the failure mode, crack distribution, flexural strength, and load-deflection curves. The test results revealed that a transition in the failure mode of masonry beams from brittle failure to interfacial stripping failure or ductile failure after reinforcement. Increasing the number of GFRP mesh layers, the fibre volume fraction and thickness of ECC improved the flexural performance of the masonry beams, while increasing the GFRP mesh strength had the opposite effect. Among the variables, the interface treatment method exerted the greatest influence on the flexural performance of the masonry beams. The masonry beams treated with a bolt interface exhibited the best flexural performance, with flexural toughness and ultimate deflection increasing by 1.69 times and 0.32 times, respectively. Furthermore, the flexural performance of the masonry beams reinforced with a 15 mm thick ECC and single-layer GFRP mesh demonstrated similar reinforcement effects to the masonry beams reinforced with a 20 mm thick ECC, while reducing costs by 23 %. Based on the existing codes governing the calculation method of flexural strength and considering the influence of various factors, a calculation model for the flexural strength of ECC-reinforced masonry beams with GFRP mesh was established.

Unraveling microstructural evolution in air-entrained mortar and paste: Insights from MIP and micro-CT tomography amid cyclic freezing-thawing damage

Understanding the microstructure evolution during the cyclic freezing-thawing process is crucial to studying the deterioration mechanisms of concrete under cyclic freezing-thawing. In this study, air voids were entrained into cement mortar and paste by AEA and polymeric microspheres. Mercury intrusion porosimetry (MIP) and micro-CT techniques were integrated to investigate the microstructure of the specimens with various freezing-thawing cycles. After subjecting the Ref. and AEA mixed mortar to 100 and 200 freezing-thaw cycles, an increase in porosity and pore entrapment was observed from the MIP results, suggesting the occurrence of damage induced by cyclic freezing-thawing. Conversely, in the microspheres mixed mortar, the presence of surface adsorbed moisture led to an initial increase in porosity and pore entrapment after 100 freezing-thaw cycles, followed by a decrease after 200 cycles, indicating a healing effect. Micro-CT analysis revealed that while the AEA mixed specimens exhibited higher air content than the microspheres mixed specimens, the latter showed a greater number of voids, which ultimately enhanced their resistance to freezing-thawing. The micro-CT results unveiled that air bubbles tended to merge in AEA mixed specimens, adversely affecting their resistance to freezing-thawing. Conversely, the microsphere-incorporated specimens displayed smooth void distribution curves, indicating a well-distributed air void system that enhances their freezing-thawing resistance. This work suggests that microspheres can be a great candidate for air-entraining materials. Combining the MIP and micro-CT analysis can better understand the microstructure change of concrete with cyclic freezing-thawing.

A Sociological Try of Linear Regression with R to Recognize Customers Traits

In todays digital age, enterprises are faced with the emergence of vast amounts of data. Thus, it is critical for those who have a large number of users to understand the pouring data and to extract information for accurate decision making. This paper suggests an interdisciplinary way to explain the regression results of mass user enterprises database, including a normal distribution curve of behavior, an unexpected correlation between factors and a few models built for specific business stratagems. These regressions are performed on a database of a game publishing company called Talent Game where game makers launch their masterpieces. The sociological and psychological methodology adapts perfectly for companies like Talent Games (TG) that establishing on the value of mass data. Finally, a controversial issue is that distributions and slope levels are found out, but some correlations are slight, which is conceived statistically skewed, and negligible in communication and sociology. Therefore, theories of the masses and statistical diagrams are coordinately shown.

Impact of Lime Saturation Factor on Alite-Ye'Elimite Cement Synthesis and Hydration.

Alite(C3S)-Ye'elimite(C4A3$) cement is a high cementitious material that incorporates a precise proportion of ye'elimite into the ordinary Portland cement. The synthesis and hydration behavior of Alite-Ye'elimite clinker with different lime saturation factors were investigated. The clinkers were synthesized using a secondary thermal treatment process, and their compositions were characterized. The hydrated pastes were analyzed for their hydration products, pore structure, mechanical strength, and microstructure. The clinkers and hydration products were characterized using XRD, TG-DSC, SEM, and MIP analysis. The results showed that the Alite-Ye'elimite cement clinker with a lime saturation factor (KH) of 0.93, prepared through secondary heat treatment, contained 64.88% C3S and 2.06% C4A3$. At this composition, the Alite-Ye'elimite cement clinker demonstrated the highest 28-day strength. The addition of SO3 to the clinkers decreased the content of tricalcium aluminate (C3A) and the ratio of Alite/Belite (C3S/C2S), resulting in a preference for belite formation. The pore structure of the hydrated pastes was also investigated, revealing a distribution of pore sizes ranging from 0.01 to 10 μm, with two peaks on each differential distribution curve corresponding to micron and sub-micron pores. The pore volume decreased from 0.22 ± 0.03 to 0.15 ± 0.18 cm3 g-1, and the main peak of pore distribution shifted towards smaller sizes with increasing hydration time.

Pore structure characterization and reservoir quality prediction in deep and ultra-deep tight sandstones by integrating image and NMR logs

Pore structure and fracture determine reservoir quality in deep and ultra-deep tight sandstones, however, the limited availability of core data makes it challenging to describe the complexity of pore-throat structure and characterize the wide range of fractures. To fill this gap, a comprehensive analysis was conducted to evaluate pore structure and fractures from multiple perspectives. Integration of core, thin sections, scanning electron microscopy (SEM), high pressure mercury injection (HPMI) and nuclear magnetic resonance (NMR) tests are used to evaluate pore structure and characterize fracture of deep and ultra-deep tight sandstones in the Cretaceous Bashijiqike Formation in the Kuqa Depression. Pore structure and reservoir quality types can be divided into dominantly three types according to characteristics of NMR transverse relaxation time (T2) distribution and HPMI curves. Correlation analysis among HPMI and NMR parameters with petrophysical parameters indicate that maximum pore throat size (rmax), logarithmic mean of T2 (T2gm), irreducible water saturation (Swi), and reservoir quality index (RQI) are the most sensitive parameters for pore structure characterization. The Type Ⅰ pore structure is composed of intergranular and intragranular pores, and NMR T2 spectrum shows the highest magnitude, with the calculated mobile fluid saturation content also being the highest. The Type II and III pore structures are composed of intergranular pores, intragranular dissolved pores and intercrystalline micropores in clay minerals. T2gm of Type II and III are smaller, with the calculated mobile fluid saturation content being the lower.The fracture features and parameters including fracture density, porosity, aperture, and length are analyzed using image logs and core. The pore structure characteristics are quantificationally and qualitatively analyzed by NMR logs. Integration of pore structure and fractures by image logs and NMR logs are used for prediction of high quality reservoir and hydrocarbon productivity. High hydrocarbon productivity is obtained in well intervals with abundant natural fractures, and favorable pore structure will also contribute to high matrix porosity. Therefore, NMR logs and image logs are crucial for evaluating reservoir quality and predicting productivity when calibrated with core and analysis data. The comprehensive analysis integrating core data with geophysical well logs provide important insights for reservoir quality prediction of deep and ultra-deep tight sandstones.

Kaleckian Models of Conflict Inflation, Distribution and Employment: A Comparative Analysis

ABSTRACT This paper conducts a systematic comparison of two main textbook variants within the Kaleckian tradition of post-Keynesian conflict inflation and distribution theory: the Blecker and Setterfield (2019) and Lavoie (1992; 2022) (BSL) model based on Dutt (1987), and the Hein (2023a) and Hein and Stockhammer (2011) (HS) model founded on Rowthorn (1977). Focusing on a basic closed economy framework sans government, we explore various iterations of each approach. Our analysis reveals that disparities chiefly centre around the treatment of price inflation expectations (‘indexation’) and the incorporation of bargaining power in wage- and price-inflation equations. BSL variants generally yield stable price Phillips curves, stable distribution and employment curves, and hence stable equilibria. Only the BSL-3 variant with complete indexation and complete pass-through generates shifting Phillips and employment curves, implying instability. It is thus similar to the HS-0 approach, which has bargaining power and complete indexation representing adaptive expectations in wage inflation and incomplete pass-through in price inflation. Introducing a workers’ wage share target directly into the wage-inflation equation, but keeping full indexation/adaptive expectations in wage inflation and incomplete pass-through in price inflation, allows for stable and even flat Phillips curves, stable distribution and employment curves, and hence stable equilibria in the HS approach.

Comparison of the Efficacy of Omalizumab and Mepolizumab in Non-Steroidal Anti-Inflammatory Drug-Exacerbated Respiratory Disease

Introduction: Non-steroidal anti-inflammatory drug-exacerbated respiratory disease (N-ERD) is heterogeneous in both phenotypes and endotypes. Due to insufficient head-to-head comparison studies, it is hard to decide which biological to initiate. This study aimed to compare the efficacy of omalizumab and mepolizumab which can be used in the treatment of patients with severe eosinophilic asthma diagnosed with N-ERD. Methods: The population of this observational, cross-sectional study comprised of N-ERD patients who received omalizumab or mepolizumab for at least 6 months for severe asthma. Outcomes included the asthma control test (ACT), and sino-nasal outcome test scores (SNOT-22), blood eosinophil counts at initiation of biological treatment (T0, baseline) and at the end of 6th months (T6). Adverse effects related to biological treatment and changes of oral corticosteroids dose was recorded. Results: The study included a total of 22 patients, of whom 11 received mepolizumab and 11 received omalizumab. The change in ACT, SNOT-22, eosinophil counts, and adverse effects related to biologicals were similar at T6 (p = 0.606, p = 0.168, p = 0.05, p = 0.053, respectively). However, when examining the SNOT-22 and ACT based on the cumulative distribution curve (SUCRA), mepolizumab (SUCRA value: 0.61, 0.72, respectively) demonstrated greater efficacy compared to omalizumab (SUCRA value: 0.19, 0.35, respectively). The oral corticosteroids discontinuation rate was similar between the two groups (p = 0.05). Conclusion: We found both omalizumab and mepolizumab to be effective in treatment; however, we determined that mepolizumab may have a potential superiority in efficacy.

Performance and hydrodynamic study of a new multi‐stage solar photoreactor with immobilized ZnO for synthetic wastewater treatment

AbstractThis study aims to design a new multi‐stage photoreactor with immobilized ZnO and assess its performance in reducing textile wastewater toxicity using solar energy. The electric conductivity measurement is retained as a detection method to obtain the residence time distribution (RTD) function. The RTD is then used to characterize the hydrodynamic behavior of the photoreactor and to evaluate its deviation from the distribution curves of ideal reactors. Solar experiments are conducted to demonstrate the performance of this multistage reactor towards the degradation of a textile azo dye namely Solophenyl Red 3BL (SR 3BL). The influence of the flow rate and the SR 3BL initial concentration (CO) are considered. The variation of the flow rate slightly influences the SR 3BL photodegradation efficiency and it is inversely proportional to its concentration. The study of the reuse of the immobilized catalyst shows that the degradation efficiency of 98% is reached even after multiple photocatalytic cycles. The figure of merit collector area per order was in the range of 35 to 110 . This result provides useful information for scaling up and estimating energy efficiency of the reactor.

Fault diagnosis method for arrester in infrared images based on improved U-Net

Conducting target detection on arresters in practical settings is challenging due to complex backgrounds and occlusion by surrounding objects. This study proposes a method based on improved U-Net for segmenting arresters in infrared images, and achieves fault diagnosis by obtaining surface temperature of the arrester. Firstly, traditional standard convolution in the U-Net backbone is replaced with depthwise separable convolution, reducing computational complexity to about 11% of the original. Secondly, ECA is introduced in the skip connection section to enable cross-channel information exchange, improving segmentation accuracy by 3.21%. Thirdly, to reduce potential errors during the conversion of grayscale images into temperature maps, the data file storage format defined in DL/T 664 is adopted, ensuring the accuracy of the temperature matrix obtained for the arrester. Finally, three fault diagnosis methods based on the surface temperature distribution curve of the arrester were proposed, and the effectiveness of the methods was verified through experiments.

Quantitative Analysis of Influencing Factors on Changzhou Ship Lock Capacity

The Changzhou ship lock is approaching its capacity limit. In order to quantitatively analyze the influencing factors that restrict the capacity of the Changzhou ship lock, this study proposes an influencing factor analysis method based on principal component analysis (PCA). This method estimates the confidence interval of ship passing time by fitting a lognormal distribution curve, eliminates redundancy in navigability data by combining the hydrological data and cargo load data, and quantitatively analyzes the influencing factors of ship lock capacity under saturated operating conditions. The results show that the influencing factors of Changzhou ship lock capacity are classified according to their influence contribution rate as minimum water depth above the lock sill, operation direction, ship dimensions, draft, loading capacity, and actual load. The research results can provide a theoretical basis for improving the ship lock capacity and have application value for lock scheduling management.

A Review on Fluoroquinolones' Toxicity to Freshwater Organisms and a Risk Assessment.

Fluoroquinolones (FQs) have achieved significant success in both human and veterinary medicine. However, regulatory authorities have recommended limiting their use, firstly because they can have disabling side effects; secondly, because of the need to limit the spread of antibiotic resistance. This review addresses another concerning consequence of the excessive use of FQs: the freshwater environments contamination and the impact on non-target organisms. Here, an overview of the highest concentrations found in Europe, Asia, and the USA is provided, the sensitivity of various taxa is presented through a comparison of the lowest EC50s from about a hundred acute toxicity tests, and primary mechanisms of FQ toxicity are described. A risk assessment is conducted based on the estimation of the Predicted No Effect Concentration (PNEC). This is calculated traditionally and, in a more contemporary manner, by constructing a normalized Species Sensitivity Distribution curve. The lowest individual HC5 (6.52 µg L-1) was obtained for levofloxacin, followed by ciprofloxacin (7.51 µg L-1), sarafloxacin and clinafloxacin (12.23 µg L-1), and ofloxacin (17.12 µg L-1). By comparing the calculated PNEC with detected concentrations, it is evident that the risk cannot be denied: the potential impact of FQs on freshwater ecosystems is a further reason to minimize their use.

Pore Structure and Heterogeneity Characteristics of Coal-Bearing Marine–Continental Transitional Shales from the Longtan Formation in the South Sichuan Basin, China

Marine–continental transitional shale has become a new field for shale gas exploration and development in recent years. Its reservoir characteristics analysis lags significantly behind that of marine shale, which restricts the theoretical research on the accumulation of marine–continental transitional shale and the progress of exploration and development. The shale pore system is complex and has strong heterogeneity, which restricts the fine evaluation and optimization of the reservoir. Based on nitrogen adsorption–desorption experiments, the morphology and structural characteristics of coal-bearing shale pores were analyzed, and then the micro-pore structure heterogeneity was quantitatively characterized based on fractal theory and nitrogen adsorption–desorption data, and the relationship between pore structure parameters and their influence on fractal characteristics were discussed. The hysteresis loop of nitrogen desorption isotherm mainly belongs to type B, indicating ink bottle, flat plate, and slit are the main pore shapes. The pore size distribution curves are left unimodal or multimodal, with the main peak around 4 nm and 20–60 nm. Smaller pores develop a larger specific surface area, resulting in a high value of fractal dimension (2.564 to 2.677). The rougher the pore surface and the larger the specific surface area provide an adequate adsorption site for shale gas adsorption and aggregation. Thus, fractal characteristics conduced to understand the pore structure, heterogeneity, and gas-bearing property of coal-bearing shale.

Fragmentation behavior of diamond particles with different particle size and ratio under high pressure compaction

The fragmentation behavior of mixed diamond particles with different grain sizes under high pressure is important to guide the design of raw material diamond powder ratios and obtain high performance polycrystalline diamond compact (PDC). In this study, five different grain size diamond powders commonly used for the preparation of PDCs were selected, and the single and mixed diamond particles were cold pressed at 7.7 GPa for 60s. The particle size variations of diamond powders with different principal particle sizes and ratios after cold pressing were analyzed by a laser particle size scanner, and the crushing behavior was observed by scanning electron microscopy. The results showed that the larger the initial grain size, the more significant the degree of fragmentation under high pressure. The crushing morphology of fine-grained diamond showed that the majority of grains were locally fractured at the edge, and the peak of the grain size distribution curve was shifted to the left after high pressure. In comparison, the coarse-grained diamond produced a large number of cracks and fractures along the weak grain boundaries under high pressure, which generated a large number of fine grains, and multiple secondary peaks in the particle size distribution curve. The addition of fine-grained diamond as filler particles to coarse-grained diamond could inhibit the crushing phenomenon to some extent. As the proportion of filler particles increased, the crushing of coarse-grained diamond was inhibited more significantly. When the proportion of filler particles was 30 wt%, the crushing under high pressure was greatly limited, especially when the size difference between filler particles and main particles was large. The results of the cold pressing experiments provided preliminary evidence that 30 wt% of filler particles were too high, and that a better ratio should be between 10 wt% and 20 wt%.

Experimental approach and analysis of the effectiveness of a tubular helical flow flocculator for water supply in developing communities

The main objective of this study was to evaluate the impact of the length and retention time of a tubular helical flow flocculator (THFF) on the elimination of turbidity and color from raw water, to obtain quality treated water for consumption in areas rural. For this, a large-scale field experimental system was used, the THFF was built with 4-inch diameter polyethylene hose and coupled to a sedimentation and filtration process. For the different experimental tests, aluminum sulfate was chosen as the coagulant. To find the optimal dose of coagulant, jar tests were previously carried out. For the tests the length of the THFF was varied (50 m and 75 m), flow rates of 0.25, 0.5, 0.75, 1 and 2 L/s and turbidity ranges of <10, 10–20, 21–50, 51–100 and > 100 NTU of raw water were tested. An evaluation of the hydraulic behavior of the THFF was carried out through an analysis of the temporal distribution curve of the concentration of a tracer, applying the Wolf-Resnick model. The average results revealed a haze and color removal efficiency of 98.07 % and 98.50 %, respectively. The residence time and velocity gradient exhibited variations in a range of 2.25–35.0 min and 3.64 to 56.94 s−1, respectively. It was evident that the operation and effectiveness of THFF are directly influenced by the turbidity of the raw water, the residence time and the velocity gradient. These findings indicate that THFF could play a valuable role as a flocculation unit in a purification system, mainly the existence of a plug-type flow was observed. The findings indicate that THFF, complemented by settling and filtration processes, could be a valuable tool for implementation in rural areas.