Characterization Of Internal Structure Research Articles

Comparative study of the microspot splitting characteristics of direct-current and pulsed cathodic vacuum arc

Ejection of macroparticles is an inherent and unavoidable characteristic of cold cathode arc discharges. The size of the cathode arc spot's melt pool is closely related to the emitted particle size, and existing studies mostly indicate that motion velocity of arc spots can be heightened primarily by magnetic fields, thereby reducing the ejection of macroparticles. However, scant consideration has been given to avoid the fundamental nature of arc spot current concentration discharge by exploring the phenomenon of arc spot splitting. In this paper, microspot splitting characteristics of direct current and pulsed cathodic vacuum arc were compared and analyzed to investigate the effect of pulsed discharges on the arc spot's internal structure, splitting, and kinematic characteristics. The results showed that pulsed arc discharges emit a dense, highly ionized plasma flow which impacts the relatively thin positive charge layer instantaneously during the peak pulsed period. This then produces a highly ionized plasma region, while also promoting an effect by which the arc spot is split into multiple microspots. Additionally, the degree of dispersion resulting from microspot splitting is positively correlated with the ratio of the plasma flow density to the concentration of the positive charge layer at the moment of microexplosion. Therefore, the microspot splitting effect of a second-order pulsed arc is weaker than that of a first-order pulsed arc. Moreover, the splitting characteristics indicated a trend toward the progressive splitting state of the direct current cathode arc. When the peak current of the single-order pulsed arc was increased from 100 to 400 A, the particle refinement effect on the surface of the CrN coating became much more evident compared to the effect of a 200 A arc in the direct current mode. And upon reaching a peak current of 500 A (and up to 600 A), the number of splits did not increase linearly due to the continuous increase in the discrete degree of microspot splitting and concurrent decrease in microspot stability. This resulted in relatively high individual microspot currents, while some relative macroparticles still appeared on the coating surface.

Cumulative deformation prediction and microstructure change of coarse-grained soil under cyclic loading

This research aims to reveal the macroscopic cumulative deformation development pattern and internal structural change characteristics of coarse-grained soils under moving vehicle loads. Dynamic triaxial tests are used to investigate the development of cumulative deformation of coarse-grained soils under various deviatoric stresses, moisture contents, and loading frequencies. Based on the results of indoor tests, a comprehensive prediction model for the cumulative deformation of coarse-grained soils was established. The cumulative deformation increases with the increasing deviatoric stress, moisture content, and loading frequency. As the deviatoric stress grows, the cumulative deformation rate increases correspondingly. The cumulative deformation prediction model for coarse-grained soils proposed in this study has high accuracy. Cyclic loading reduces the number of large pores, increases the number of smaller pores, and increases the proportion of micropores with increasing deviatoric stress and moisture content. The effect of loading frequency on the deformation of coarse-grained soils is relatively small but still not negligible. Cyclic dynamic loading can transform the long pores in coarse-grained soil subgrade filler into elliptical and circular pores. The increase in moisture content can increase the proportion of long pores in coarse-grained soil filler. This research can deliver a valuable reference for analyzing the cumulative deformation of coarse-grained soils subjected to cyclic loading.

How pore structure evolves in shale gas extraction: A new fractal model

The reservoir can be divided into four components with different properties: inorganic matrix, hydraulic fracture, natural fracture and kerogen according to the internal structure characteristics and the natural gas migration mode after hydraulic fracturing. Previous studies usually focus on the relationship between reservoir porosity and permeability, but ignore the influence of reservoir microstructure on gas production. The microstructure of different reservoir components can be described by corresponding fractal dimensions. The structure of fractures can be characterized by fractal dimension of fractures and the fractal dimension of pores can characterize the pore structure of inorganic matrix. Considering the complexity of mass transfer between components and structural deformation, in order to describe the evolution of reservoir microstructure and the influence of various factors on gas production, a fully coupled multi-scale fractal model is established. To verify that the model is reliable, the simulation results contrast with the conclusions of field tests. The effects of adsorption parameters, initial diffusion coefficient and compressibility coefficient on gas production and pore structure evolution were studied. The results show that:(1) when the adsorption constant decreases, the variation of the fractal dimension of pore structure becomes more obvious, and the shale reservoir's gas production and pore structure are most sensitive to the volume constant; (2) the deformation of pore structure increases with the increase of effective diffusion coefficient; (3) the change of compressibility of a single medium only has a major impact on the evolution of its own structure.

X-ray: Discovering DRAM Internal Structure and Error Characteristics by Issuing Memory Commands

X-ray: Discovering DRAM Internal Structure and Error Characteristics by Issuing Memory Commands

Structuring concrete boundary objects for project-to-project learning: a state-of-practice review

PurposeEffective project learning can prevent projects from repeating the same mistakes; however, knowledge codification is required for project-to-project learning to be up-scaled across the temporal, geographical and organisational barriers that constrain personalised learning. This paper explores the state of practice for the structuring of codified project learnings as concrete boundary objects with the capacity to enable externalised project-to-project learning across complex boundaries. Cross-domain reconceptualisation is proposed to enable further research and support the future development of standardised recommendations for boundary objects that can enable project-to-project learning at scale.Design/methodology/approachAn integrative literature review method has been applied, considering knowledge, project learning and boundary object scholarship as state-of-practice sources.FindingsIt is found that the extensive body of boundary object literature developed over the last three decades has not yet examined the internal structural characteristics of concrete boundary objects for project-to-project learning and boundary-spanning capacity. Through a synthesis of the dispersed structural characteristic recommendations that have been made across examined domains, a reconceptualised schema of 30 discrete characteristics associated with boundary-spanning capacity for project-to-project learning is proposed to support further investigation.Originality/valueThis review makes a novel contribution as a first cross-domain examination of the internal structural characteristics of concrete boundary objects for project-to-project learning. The authors provide directions for future research through the reconceptualisation of a novel schema and the identification of important and previously unidentified research gaps.

Energy security performance evaluation revisited: From the perspective of the energy supply chain

The previous research on energy security performance (ESP) has often treated the energy security system as a “black box,” meaning that it has not explored the internal composition structure of the system or the linking relationships of the energy supply chain. This study proposes a comprehensive evaluation framework and a comparative study of ESP evaluation in 32 OECD countries over 20 years, dividing the energy system into four processes. A dynamic network Data Envelopment Analysis (DNDEA) model is used to analyze the energy system's overall performance and each process's performance, considering their internal structure and dynamic characteristics. The ESP results show that half of the 32 OECD countries had perfect efficiency scores, while the other half had scores ranging from 0.0222 to 0.74. The study also found more progress in the second half of the 20-year period. In terms of the four individual processes, the total primary energy supply (TPES) and total final energy consumption (TFEC) processes had consistently high scores, while the secondary energy resources (SER) process had room for improvement. Based on a cross-check of the various ESP results over the past 20 years, as well as the ESP in the most recent decade, seven countries (Austria, Canada, Finland, South Korea, Luxembourg, Norway, and Switzerland) were identified as benchmarks for their strong performance, and the study examined the indicators underlying their success. The study also identifies areas for improvement in underperforming countries and determines future directions for improvement.

CFD-DEM analysis of internal packing structure and pressure characteristics in compressible filter cakes using a novel elastic–plastic contact model

Cake-forming filtration is a proven method for separating particles from suspensions. Most filtration models are based on the simplification of incompressible and homogeneous cake structures. However, most filter cakes are in fact unevenly compressed by e.g. the high transmembrane pressures, leading to dense structures with high flow resistance at the filtration membrane. Experimental investigations of these inhomogeneous cakes are challenging due to mostly invasive procedures after filtration has already taken place. In contrast, numerical methods can provide extensive information about fluid flow, particle separation and cake formation during filtration. However, this requires that both elastic and plastic particle deformation and forces are modeled correctly. To achieve this, the present study implemented a novel elastic–plastic DEM model that only requires measurable material parameters and therefore does not need any fitting. Subsequently, previously measured material parameters for elastic–plastic cellulose-lactose pellets (MCC) were used to investigate the packing density, fluid pressure levels and contact forces inside compressible filter cakes using CFD-DEM coupling. A comparison with incompressible and elastically compressible filter cakes showed a significant difference in the filtration behavior. Due to plastic deformation, a strong increase of the packing density when nearing the filtration membrane was found, leading to higher flow resistance for the filtration process. For cyclic filtration events, only the plastically deformed cake showed reduced height recovery in a relaxed state.

Constraints on the timing of magmatism and rare-metal mineralization in the Fangzheng Rb deposit, Altai, NW China: Implications for the spatiotemporal controls on rare-metal mineralization

Amazonite granites are potential Rb resources given the abundance of Rb-bearing minerals they contain. The Altai Orogen, located in the southwestern portion of the Central Asian Orogenic Belt, is the world's most famous rare-metal metallogenic belt, containing numerous Li–Be–Nb–Ta–Cs deposits (e.g., the Koktokay No. 3 pegmatite deposit). The Fangzheng deposit, however, is the only known independent Rb deposit in this belt, with a proven Rb2O reserve of ∼12,940 tons at an average grade of 0.07%. The deposit is hosted by the Jiangjunshan pluton, which is composed largely of two-mica alkali feldspar granite and lesser amazonite granite on the peripheries, with amazonite pegmatite veins cutting the pluton and its wall-rocks. Although the pluton has been dated using various geochronological techniques, the magmatic and the rare-metal mineralization ages remain ambiguous given the complexity in zircon genesis and evolution, and their high Th and U contents. In this contribution, U–Pb geochronology of zircon, monazite, cassiterite, and columbite-group minerals, as well as their trace-element characteristics, are utilized to constrain the timing and evolution of magmatism and mineralization in the Fangzheng Rb deposit. Based on morphological and geochemical features, and cathodoluminescence images, zircon grains from different lithofacies are classified into three types — magmatic zircon, hydrothermally overprinted magmatic zircon, and hydrothermal zircon. The first two types of zircon grains are characterized by low Th/U ratios (0.22–4.00, with an average of 0.84) and ΣLREE contents (8.66–466, with an average of 90.6), indicative of a magmatic origin, whereas the third type is characterized by high Th/U ratios (0.22–7.26, with an average of 2.26) and ΣLREE contents (1154–4944 ppm, with an average of 2905 ppm), indicative of a hydrothermal origin. The magmatic and hydrothermally overprinted magmatic zircon grains from the two-mica alkali feldspar granite and amazonite granite yield U–Pb ages of 272.7±1.4 Ma and 272.5±1.7 Ma, respectively. Therefore, the earliest age of magmatism of the Jiangjunshan pluton is approximately 272 Ma (early–middle Permian). Based on the internal structure and geochemical characteristics of accessory minerals (monazite, cassiterite, and columbite-group minerals) selected from the ore bodies (amazonite granite and amazonite pegmatite), it is suggested that they crystallized during the magmatic–hydrothermal transition. The U–Pb ages of hydrothermal zircons (253.2±17.0 Ma), monazite (254.4±0.9 Ma), and columbite-group minerals (254.9±1.4 Ma) from the amazonite granite, as well as the U–Pb ages of monazite (253.3±0.7 Ma), cassiterite (250.4±1.4 Ma), and columbite-group minerals (254.5±0.8 Ma) from the amazonite pegmatite indicate that the age of rare-metal mineralization in the Fangzheng deposit is approximately 255–250 Ma (i.e., close to Permian/Triassic boundary). Combined with previous geochronological results and interpretations of tectonic evolution, it is evident that i) the middle Permian to Late Triassic is an important period of granitic magmatism and related rare-metal mineralization in the Chinese Altai, and ii) the rare-metal deposits formed in an intracontinental extensional setting after the tectonic transition from subduction to extension.

Technical Appraisal Method of Circuit Breaker Material Evidence in Fire

Circuit breaker is an important electrical control on and off in the electrical line, which refers to the switch device that can close, load and break the current under normal loop conditions, and can close, load and break the current under abnormal loop conditions in the specified time. Circuit breakers are divided into high voltage circuit breakers and low voltage circuit breakers according to their range of use. Low voltage circuit breakers are common to molded case circuit breakers. Play a protective role in the safety of electrical lines and electrical appliances. When a fire occurs, the action of the circuit breaker plays a vital role in the occurrence and development of the fire. Therefore, the circuit breaker is an important material evidence in the investigation of the cause of electrical fire, and it will play an irreplaceable role in the investigation of the cause. In particular, the plastic case circuit breaker is the most commonly used type in life. The plastic case circuit breaker extracted from the fire scene, according to the appearance characteristics or internal structure characteristics, identify its working state in a period of time before and after the fire, and can judge the relationship between the physical evidence and the cause of fire.

New Insights into the Internal Structures and Geotechnical Rock Properties of the Giant San Andrés Landslide, El Hierro Island, Spain

The San Andrés landslide on El Hierro (Canary Islands) represents a rare opportunity to study an incipient volcanic island flank collapse with an extensive onshore part. The presented research improves the knowledge of the internal structure and rock characteristics of a mega-landslide before its complete failure. The investigation combines multiple geophysical measurement techniques (active and passive seismic) and remotely sensed, high spatial resolution surveys (unmanned aerial vehicle) with in situ and laboratory geotechnical descriptions to characterize the rock properties inside and outside the San Andrés landslide. The available geophysical and geological data have been integrated into 3D geomodels to enhance their visual interpretation. The onshore geophysical investigations helped detect the possible San Andrés landslide sliding surfaces at depths between 320 m and 420 m, with a rather planar geometry. They also revealed that rocks inside and outside of the landslide had similar properties, which suggests that the previous fast movements of the landslide did not affect the bulk properties of the displaced rocks as the failure chiefly occurred along the weakened sliding plane. Uniaxial strength tests on basalt rocks further indicate a high variability and spatial heterogeneity of the rock strength properties due to the different types of volcanic rocks and their texture. The new information on the rock properties and structural setting of the San Andrés landslide can now be used to develop realistic geotechnical slope models of the onshore part of the flank collapse that are possibly applicable for slope stability or deformation calculations. It will also help assess related hazards marked by a low occurrence probability and a high impact potential.

Artificial Intelligence and Economic Development: An Evolutionary Investigation and Systematic Review

In today’s environment of the rapid rise of artificial intelligence (AI), debate continues about whether it has beneficial effects on economic development. However, there is only a fragmented perception of what role and place AI technology actually plays in economic development (ED). In this paper, we pioneer the research by focusing our detective work and discussion on the intersection of AI and economic development. Specifically, we adopt a two-step methodology. At the first step, we analyze 2211 documents in the AI&ED field using the bibliometric tool Bibliometrix, presenting the internal structure and external characteristics of the field through different metrics and algorithms. In the second step, a qualitative content analysis of clusters calculated from the bibliographic coupling algorithm is conducted, detailing the content directions of recently distributed topics in the AI&ED field from different perspectives. The results of the bibliometric analysis suggest that the number of publications in the field has grown exponentially in recent years, and the most relevant source is the “Sustainability” journal. In addition, deep learning and data mining-related research are the key directions for the future. On the whole, scholars dedicated to the field have developed close cooperation and communication across the board. On the other hand, the content analysis demonstrates that most of the research is centered on the five facets of intelligent decision-making, social governance, labor and capital, Industry 4.0, and innovation. The results provide a forward-looking guide for scholars to grasp the current state and potential knowledge gaps in the AI&ED field.

Convergence of the Malvinas Current branches near 44°S

Field measurements of the Malvinas Current (MC) velocity distribution were performed at the western slope of the Argentine Basin in the South Atlantic Ocean between 47° and 43°S including several sections across the current. The data were collected in January and March 2020 using a Shipborne Acoustic Current Doppler Profiler (SADCP) and allowed us to study circulation patterns in the upper 700 m of the ocean. The observations reveal substantial differences in the current structures at each location; the SADCP data suggest that two distinct current branches at 46°S converge downstream near 44°S making it difficult to distinguish the high-velocity cores farther north. A detailed comparison between the velocity structures indicates that the branches converge due to the change in the orientation and width of the continental slope, and is consistent with potential vorticity conservation. At the same time, satellite altimetry shows that the branches merge to a single high-velocity jet, suggesting that satellite altimetry does not reproduce all features of the MC internal structure and indicates the importance of further direct velocity observations in this region. Despite the above-mentioned limitations of altimetry, the satellite-derived geostrophic velocities suggest that the pathways of the MC high-velocity jets are quite stable. In addition, both satellite altimetry and direct measurements indicate that the branches tend to converge downstream near 44°S.

Utilizing Imaging Analysis to Determine the Internal Structure Characteristics of Asphalt Mixtures for Permeability and Moisture Damage Performance

Moisture is a significant problem in standard pavements, causing asphalt mixtures to deteriorate due to insufficient water permeability. This failure from moisture damage is often caused by precipitation accumulation or poor drainage, which allows water to weaken adhesion by seeping between the aggregates and the asphalt. The relationship between permeability and aggregate contact length is believed to be inverse. To effectively assess water permeability performance and moisture damage, an asphalt concrete design criterion was established using the Image Processing and Analysis System (IPAS) to determine aggregate contact lengths. The objective of this research was to use laboratory experiments in conjunction with IPAS to investigate air-void-controlled asphalt mixtures with various material properties and assess the correlation of water permeability with other factors. The results show that AC60/70, AC60/70+Carbon Black, and AC60/70+SBS combinations with coconut peat filler had the lowest permeability coefficient (k) among similar mixtures, with values of 0.056 × 10−5 cm/s, 0.010 × 10−5 cm/s, and 1.508 × 10−5 cm/s, respectively. Both the dense and porous gradations of the modified asphalt binder demonstrated positive linear relationships between TSR and permeability. This study found a strong linear relationship between TSR (tensile strength ratio) and k (permeability coefficient) in both dense and porous modified asphalt binder gradations, with R2 values of 0.79 and 0.74, respectively. Additionally, we found that the number of contact points and contact length in the skeleton strongly influenced the mixes’ permeability, with a linear trend of 0.93 for both indices.

Gravitational Deformation and Reactivation Mechanism of a Fault-Bounded Slope, Eastern Yanshan Mountains, China

The Nandongzi landslide occurred in the Yanshan region of North China. From 2017, the slope of the Nandongzi landslide has been significantly deformed after several excavations. Field investigations show that the Nandongzi landslide is a special toppling deposit that does not have basic toppling conditions. The toppling deformation mechanism of the slope has become a difficult issue for engineers, attracting the attention of scientists. Joint, surface, and borehole lithology surveys revealed the surface and internal structural characteristics of the slope. The structure of the soft and hard interbedded rock and the proximity of the fault are the dominant factors of slope toppling deformation. The slope toppling failure process can be divided into four stages: initial deformation, compression and bending, toppling and overlapping, and reactivation. In the first three stages, slope toppling deformation is triggered by the downcutting of the upstream gully, gravity, and differential weathering of soft and hard rocks, which promote the dumping deformation of the slope. In the final stage, engineering excavations triggered the reactivation of residual deposits. Monitoring data indicate that slope deformation is directly related to rainfall events. Flac 3D was used to simulate the slope failure process under natural and rainfall conditions after the two excavations. The results show that multiple excavations changed the surface and runoff conditions of the slope, which led to slope failure. Rainfall promoted deformation of the back edge of the landslide, which led to shear failure from the back edge to the front edge. Our results provide new and unique understanding into the spatiotemporal evolution and deformation mechanism of similar toppling-accumulation landslides around the study area.

Experimental Characterization of Internal Structure and Physical Properties of Unidirectional Ply‐Level Hybrid Carbon Composite Material

The complexities associated with the response of carbon fiber composites to different loading cases and methods of improving it without increasing their cost are still being researched. Herein, by an experimental approach, the ply‐level hybridization technique for tailoring the composite response is explored, and two different types of unidirectional prepregs with the same fiber type but different quality and prices are mixed. The purpose of this study is to analyze the influence of this type of hybridization on the structure and mechanical response of carbon fiber composites and to assess the compromise between manufacturing cost reduction and mechanical response. Hybridization is obtained in both layer thickness and material quality and reference materials are also manufactured. The properties of the unidirectional hybrid and nonhybrid composites are evaluated by density and fiber volume fraction measurements. The in‐plane mechanical properties are determined using quasistatic tensile tests, in 0° and 90° directions. No thickness effects are noticed on the stress–strain response under both longitudinal and transverse directions and hybrid composites exhibit an improved 0° failure stress.

Design and analysis of bridge microstructure under the condition of large-scale geographical environment

The design and analysis of bridge microstructure are two indispensable parts of bridge construction and maintenance and the two always complement each other throughout bridge's life cycle. Furthermore, bridge microstructure design and analysis under large-scale geographic environment are more complicated. In order to ensure bridges' safe construction and normal traffic under this environmental condition, it is necessary to find a suitable microstructure and use a scientific classification method to analyze it. Under large-scale geographic condition, the design and analysis of bridge microstructure should be planned from multiple steps after construction party puts forward bridge planning and construction goals. The stability of bridge engineering geology should give more consideration to the feedback mechanism of internal structural system characteristics for microstructure design and analysis, and must have a geographical viewpoint. Therefore, on the basis of summarizing and analyzing previous research works, this paper expounds the current research status and significance of large-scale geographic environment, elaborates the development background, current status and future challenges of bridge microstructure design and analysis, introduces the methods and principles of single-degree-of-freedom energy structure reaction and the dynamic microstructure characteristics, constructs bridge microstructure model, conducts bridge microstructure data analysis, performs bridge microstructure design under large-scale geographical environment condition, proposes the combined analysis of load effect, discusses the optimization analysis of structural topology, puts forward the bridge microstructure analysis under large-scale geographic environment condition, and finally carries out a simulation experiment and its result analysis. The study results show that when the large-scale geographic environment is divided into regular rectangular plots, the bridge microstructure can maintain its design cohesion, and the stretch and continuity of those plots and bridge convey a strong sense of structure. Microstructure parameters represent the stiffness caused by the average properties of cross-sectional materials of bridge microstructure. For a uniform classical continuous microstructure, the design can accurately describe bridge's bending resistance. The study results of this paper provide a reference for further researches on the design and analysis of bridge microstructures under the condition of large-scale geographic environment.

Study on the Decoupling and Interaction Effect between Industrial Structure Upgrading and Carbon Emissions under Dual Carbon Targets.

The issue of climate and environment has been paid more and more attention by countries all over the world, especially regarding carbon emissions. Many national policies and scholars' research contents have focused on this issue, which has become a hot topic in today's society. As the world's largest carbon emitter, it is vital for China to achieve green development, upgrade its industrial structure and explore the relationship between industrial structure upgrading and carbon emissions. To explore the decoupling and interactive effects of industrial structure upgrading and carbon emissions, this paper divides industrial structure upgrading into two aspects: rationalization of industrial structure and upgrading of industrial structure. Indicators related to industrial structure upgrading and carbon emissions are selected and the decoupling model of carbon emissions and industrial structure upgrading is constructed using panel data from 30 regions from 1997 to 2019. The core density function is used to analyze the decoupling distribution characteristics, and then the Gini coefficient decomposition method is used to analyze the carbon emissions decoupling index, revealing the regional differences and sources of carbon emissions decoupling index. Finally, spatial factors are included in the regression model to verify the spatial synergy effect of industrial structure upgrading on carbon emissions. The overall and local Moran indexes are used to reveal the spatial internal structure and agglomeration characteristics of industrial structure upgrading and carbon emissions, and, based on the research results, policy recommendations are put forward to promote sustainable and stable development of industrial structure upgrading in China. This provides a new perspective for understanding the relationship between industrial structure upgrading and carbon emissions and also provides a decision-making reference for promoting decoupling of industrial structure upgrading and carbon emissions under high-quality economic development and forcing low-carbon transformation of the industrial structure.

Research on Urban Road Network Evaluation Based on Fractal Analysis

The structure of the urban road network affects the mode of urban development and the position of urban social and economic activities, families, and employment centers. Therefore, it is necessary to consider the supply inequality of urban road network and its impact on urban development so as to form a sustainable and fair urban development model in cities. Based on the fractal analysis, this paper seeks the evaluation index of urban road network layout and internal structure characteristics to guide the optimization and adjustment of the urban road network, which is of great significance for guiding urban land use, effectively utilizing geospatial space, and promoting sustainable urban development, and attempts to apply the fractal analysis concept to evaluate the urban road network in Harbin, China. It is found that there is a good relationship between the length of the urban road network and the build-up area. Therefore, fractal analysis is used to reasonably determine the spatial demand of incremental road networks, considering the impact of road network increase on development mode. This paper argues that fractal analysis is an auspicious tool for the evaluation of urban road networks, including solving the problem of supply inequality in urban road networks, which is very suitable for the gradual construction of road networks in urban situations, especially in the development environment of road networks with scarce resources.

Utilization of excavated soil and sewage sludge for green lightweight aggregate and evaluation of its influence on concrete properties

Green lightweight aggregate produced by excavated soil and sewage sludge (LWA-ES), which can be served as value-added materials, has remarkable practical utility to tackle the urban waste stockpile and survival environment pollution. This study explored the effect of particle size and replacement level of LWA-ES on the concrete performance. The surface morphology, internal structure and physical characteristic of LWA-ES and the microstructure of LWA-ES concrete were evaluated by stereo microscope, digital image analyser and SEM-EDS. LWA-ES with coarse particle size exhibited less irregular shape, rough surface texture and loose structure, while LWA-ES with fine particle size possessed elongated shape, smooth surface texture and dense structure, thus improved its physical characteristic. Microstructure analysis revealed that the enhancement on the boundary of LWA-ES and the mechanical interlocking of ITZ between LWA-ES and cement matrix was notable. Due to the pozzolanic reactivity supplied from the LWA-ES, the Ca/Si ratio in the vicinity of LWA-ES was diminished progressively. Incorporation of LWA-ES with higher replacement and coarse particle size into concrete yielded a degradation in the dry density, strength, water absorption and porosity. However, it had more favourable effect on the resistance against thermal conductivity than LWA-ES with lower replacement and fine particle size. Overall, due to the apparent discrepancy in the LWA-ES features, lightweight concrete with hierarchical pore structure was more beneficial in thermal insulation after well-designed replacement and particle size, but its strength decreased.

Effect of effuser throat diameter on the internal flow structure and energy characteristics of the jet pump

The jet pump is one of the most popular types of fluid machinery in agriculture, industry and environmental engineering and many other fields. However, its internal flow structure is complex, showing obvious unsteady characteristics. The effect of throat diameter size on jet pump performance and energy property was investigated in this study based on numerical calculation and test verification, in order to improve the performance and internal flow field stability of jet pump. Five models with different throat diameters were obtained by adjusting the assembly structure and simulated by the computational fluid dynamics software to solve the Navier–Stokes equations for three-dimensional steady flow. The accuracy of numerical methods was verified by comparison with the experimental results. The compact jet pump performance under different throat diameters was then compared and analysed. The backflow at effuser outlet of different throat diameters causes the changes of vortex structure inside the injector rear chamber. The vortex diffuses downstream to the impeller inlet, making the flow structure of the impeller inlet show obvious circumferential inhomogeneity. This forms different vortex structures at different impeller flow channels, changing the distribution of entropy production within the impeller, ultimately leading to a decrease of pump efficiency. Therefore, this study found that selecting a reasonable throat diameter of the injector can improve the performance of the jet pump impeller, and thus improve the overall efficiency of the system. For the research object in this paper, the recommended range of throat diameter of injector is 16 mm–17 mm. This finding could provide useful insights for the improvement of the hydraulic performance and operational stability of compact jet pumps.