Density Contours Research Articles

First principles investigations of linear and nonlinear optical, radiation shielding and thermoelectric properties of the non-centrosymmetric Ba-based chalcogenides Ba2In2X5 (X=S, Te)

We explore the structural, elastic, optoelectronic, Radiation Shielding, and thermoelectric properties of Ba2In2X5 (X = S, Te) using first-principles computations and semi-classical Boltzmann Transport equations. These materials are classified as semiconductors exhibiting band gaps of 2.0 eV and 3.0 eV for both investigated NLO compounds that have more significant direct band gaps of superior optical birefringence and second-order NLO coefficients. The bonding properties have been investigated by analyzing the electron charge density (ECD) contour of the (1 0 1) crystallographic plane. It is clear from the reflectivity spectra that both compounds have a high degree of reflectivity, which could make them useful as UV and visible light shields. From 0 to 14.0 eV, the approximated reflectivity values, R (ω), are displayed against the incident photon energy. Therefore, the reflectivity is around 30 % before E ≈ 12.0 eV and 40 % reflection at ∼13.0 eV. Phase matching is possible for both compounds detected, as shown by the birefringence computations. Furthermore, the radiation shielding properties of Ba2In2S5 and Ba2In2Te5 have been evaluated using Phy-X software, demonstrating their potential effectiveness in medical and nuclear energy applications. The thermoelectric properties display N-type nature at low temperatures when the Seebeck coefficient changes from N to P-type at higher temperature ranges. These compounds have remarkable optical and thermal properties, rendering them highly attractive materials for thermoelectric and optoelectronic devices.

Dependence of clay–water contact angle on surface charge and ambient temperature: A study from molecular dynamics perspective

The clay-water contact angle emerges as a pivotal parameter essential for elucidating various engineering challenges. Its variability is closely linked to surface charge and ambient temperature, thereby exerting significant influence on soil’s hydraulic properties. However, current research on the joint effects of ambient temperature and surface charge on clay’s contact angle is incomplete, lacking insights from molecular dynamics perspective. Focusing on Young’s contact angle, this study has established diverse montmorillonite-water systems under varying surface charge conditions (cation exchange capacity = 0, 27.60, 54.84, 108.38, and 134.73 meq/100 g) and ambient temperatures (277, 293, 313, 353, 393, and 433 K) through the molecular dynamics (MD) method. The liquid phase boundary is determined by extracting density contour plots and a unified conical curve is introduced to quantitatively analyze the contact angle calculated by MD simulations. This approach led to the development of a nonlinear equation for estimating contact angle variations under different surface charges and ambient temperatures. Finally, the proposed equation is validated against literature data, demonstrating a strong correlation with experimental findings. It exhibits remarkable accuracy in predicting the variations of contact angles induced by ambient temperature under various surface charge conditions. These findings offer valuable insights and practical equation for designing clay impermeable layers in engineering applications.

One‐Step Local Acceleration Process of Ultra‐Relativistic Electrons in the Center of the Outer Radiation Belt: Observations

AbstractUltra‐relativistic (>3 MeV) electrons are considered as a novel, separate population in the Earth's radiation belts since their loss and acceleration features are distinct from relativistic (∼MeV) electrons. The dominant acceleration mechanism of ultra‐relativistic electrons remains a subject of ongoing debate. Some studies suggest that the acceleration mechanism of ultra‐relativistic electrons is energy‐dependent: local acceleration dominants the enhancement of ∼3–5 MeV electrons while two‐step acceleration process leading by radial diffusion effects for ∼7 MeV electrons. However, a recent study (https://doi.org/10.1126/sciadv.abc0380) theoretically demonstrated that local acceleration could accelerate electrons up to >7 MeV directly under the extreme plasma depletion. In this study, we report four enhancement events of ultra‐relativistic electrons that occurred in September and October 2017. Analysis of phase space density (PSD) radial profiles and contours demonstrate that local acceleration plays the dominant role in the enhancements of ∼7 MeV electrons in mid‐September and mid‐October, supported by persistently growing peaks in electron PSD. While enhancements of ultra‐relativistic electrons in other two events still show energy‐dependent phenomenon, our results provide the observation evidence that one‐step local acceleration process can lead to the enhancement of ∼7 MeV electrons in some events. We suggest that the acceleration process of ultra‐relativistic electrons may be subject to the efficiency of local acceleration.

Optical assessment of vertical TFET based on heterojunction of GaSb-Si

This paper investigates the electrical and opto-sensing analysis of hetero stack vertical TFETs based on III/V group Gallium antimonide (GaSb)-Si at various wavelengths within the visible spectrum. Initially, the drain current, energy band diagram, and electron density contour plot are extracted in order to study the DC and electrical behavior of the device. Following that, their performance is evaluated by altering the source side thickness and observe the tunneling rate of device. Furthermore, the photo application of the device is noticed by computing the critical optical parameter such as sensitivity (Sn), noise factor, and efficient characteristics. Finally, a comparative table is included to set the benchmark and highlight the importance of hetero stack TFET. The device's maximum reported sensitivity is approximately 25.2 and responsivity (R) is 0.8 A/Watt at 320 nm wavelength. Additionally, we examined the effect of trap charges under light state at the gate-channel, isolator-channel, and source-channel interface respectively.

Numerical investigations of shock/boundary-layer interaction and control for Mach 2.5 flow in an axisymmetric inlet

The present work investigates the application of vortex generators for separation control in axisymmetric isolator flows. Reynolds-Averaged Navier-Stokes computations were performed to simulate a Mach 2.5 flow past a half-isolator geometry with a 20∘ axisymmteric compression ramp based on the experiments of Funderburk and Narayanaswamy at North Carolina State University. Single vortex generator and a vortex generator array placed upstream of the shock-induced separation region were investigated. Near wall streamlines, surface pressure contours and density contours on crosswise planes were compared with experiments for flow control using a single vortex generator. Results indicate that the present computations are able to capture the wake and shock structures, and also predict reduction in the streamwise extent of flow separation downstream of the device trailing edge. Finally, the effects of the shape/orientation (forward facing/backward facing) of a single vortex generator, and the design of an array of three vortex generators (with devices of similar and mixed orientations) on the flow separation were also investigated. Contours of near-surface streamwise velocity showed that device orientation had a strong effect on separation control, which is attributed to the differences in the primary streamwise vortices shed in the two cases. Further, the overall reduction in the footprint of separated flow was determined to be most with the use of an array of vortex generators with mixed orientations.

Mapping and Characterization of Local Structures of CsPbBr3.

Inorganic perovskite CsPbBr3 is a promising material for optoelectronic applications and high-energy radiation detection due to its excellent photophysical properties, high carrier mobility, large carrier diffusion length, and higher stability than organic perovskite materials. Understanding phase transitions at the atomic level is crucial for optimizing its applications. Here, we employ experimental characterizations and molecular dynamics simulations to study the phase transitions in CsPbBr3 as a function of temperature. The simulation results are compared with the experimental results, which include X-ray diffraction (XRD). Our simulations provide new insights into the electronic structure and dynamic behavior of the Cs, Pb, and Br atoms as a function of temperature. We observe distinct phase transitions from monoclinic to cubic and analyze the associated changes in the local environment through atomic density contour maps. Our analysis of the atomic density distributions of the Pb, Br, and Cs atoms provides information about the crystal symmetry as a function of temperature. The tilt and rotation angles of [PbBr6] octahedra are increasing with the temperature increase and are found nonzero above 410 K when the structure is cubic, exhibiting the presence of dynamic tilting. Overall, our findings shed light on the thermal stability and structural dynamics of CsPbBr3, contribute to the fundamental understanding of its phase behavior, and provide a crucial pivot for guiding the design of next-generation optoelectronic and radiation detection devices.

Constitutive description of distortional hardening in a TWIP steel: Addressing differential hardening under nonlinear strain paths

The present study aims to describe the in-plane differential hardening behaviour of the twinning induced plasticity sheet metal TWIP980 under various stress states, including uniaxial tension, plane strain tension, and pure shear, particularly focusing on non-proportional loading conditions. The true stress–strain curves for each stress states were inversely obtained from their corresponding load–displacement curves and modeled using a differential hardening model that can accommodate all three stress states simultaneously on plastic work (density) contours. For non-proportional loading tests, oversize specimens were initially stretched under uniaxial tension up to a 10% pre-strain along the rolling, diagonal, and transverse directions, respectively. Subsequently, the three stress states were applied to subsize specimens cut from the deformed oversize specimens along the rolling direction. To describe the hardening behaviours during non-proportional loading, a homogeneous anisotropic hardening model was adopted and calibrated using two-step uniaxial tension tests. Subsequently, the differential hardening model was successfully incorporated into the homogeneous anisotropic hardening model to describe both the differential hardening and the strain path change-induced hardening behaviours under the two-step loadings, i.e., uniaxial tension to pure shear and uniaxial tension to plane strain tension. Both experimental and simulation results underscore the necessity to consider differential hardening under non-proportional loading conditions.

DFT insight on stability, optoelectronic, and thermoelectric features of Na3XO (X = Cu, Ag) anti‐perovskites: Promising materials for sustainable energy applications

AbstractThe structural stability, elastic, optoelectronic, and thermoelectric characteristics of anti‐perovskites Na3XO (X = Cu, Ag) have been studied using density functional theory (DFT). The computed formation energy suggests these materials' potential synthesis and thermal stability. The structural and elastic properties of Na3CuO and Na3AgO anti‐perovskite compounds were analyzed using the Perdew–Burke–Ernzerhof (GGA‐PBE) generalized gradient potential approximation. The electronic and thermoelectric properties are calculated using the TB‐mBJ approximation. The materials are identified as direct narrow band gap semiconductors with band gaps of 0.65 and 0.43 eV. The analysis of two‐dimensional charge density contours indicates that Na3CuO and Na3AgO have a mixed bonding character, as validated by the investigation of electron charge density. We analyzed the optical properties of Na3CuO and Na3AgO, including dielectric function, refractive index, absorbance, optical reflectivity, and energy loss, using photon energy up to 6 eV. The investigated thermoelectric characteristics demonstrate figure of merit (ZT) values of 0.58 and 0.56 at room temperature. Consequently, the analyzed anti‐perovskites might address waste heat management requirements and sustainable energy solutions.

Atomically substitution engineering of europium-based dichalcogenides for enhancing tailored properties and superior applications

Transition-metal chalcogenides can be used as photoconductors and in optoelectronic devices. Research on the electronic properties of KBaSbSe3 has established that the parental compound possesses an indirect band gap of 2.0 eV. By europium doping, the material’s band structure experienced a transformation, resulting in a direct semiconducting behavior. This change was observed in spin-up and spin-down polarizations, with a bandgap of 1.5 eV. An analysis of the electron charge density (ECD) contour of the (101) crystallographic plane has been conducted to examine the bonding characteristics. Based on the reflectivity spectra, it is evident that both compounds exhibit a significant level of reflectivity, making them potentially suitable for shielding against visible and UV radiation. The calculations of birefringence demonstrate the ability to achieve phase matching for both observed compounds. Calculations were performed using Boltzmann transport theory to determine the Seebeck coefficient, Hall coefficient, electrical and thermal conductivities, and figure of merit. The compound KBaSbSe3 exhibits N-type at low temperatures and P-type due to a change in the Seebeck coefficient. Both compounds have excellent optical and thermal responses, making them promising materials for optoelectronic and thermoelectric devices.

Improving the accuracy of halo mass based statistics for fast approximate N-body simulations

ABSTRACT Approximate N-body methods, such as fastpm and cola, have been successful in modelling halo and galaxy clustering statistics, but their low resolution on small scales is a limitation for applications that require high precision. Full N-body simulations can provide better accuracy but are too computationally expensive for a quick exploration of cosmological parameters. This paper presents a method for correcting distinct haloes identified in fast N-body simulations, so that various halo statistics improve to a percent level accuracy. The scheme seeks to find empirical corrections to halo properties such that the virial mass is the same as that of a corresponding halo in a full N-body simulation. The modified outer density contour of the corrected halo is determined on the basis of the fastpm settings and the number of particles inside the halo. This method only changes some parameters of the halo finder, and does not require any extra CPU-cost. We demonstrate that the adjusted halo catalogues of fastpm simulations significantly improve the precision of halo mass-based statistics from redshifts $z=0.0$ to 1.0, and that our calibration can be applied to different cosmologies without needing to be recalibrated.

Glioblastoma disrupts cortical network activity at multiple spatial and temporal scales.

The emergence of glioblastoma in cortical tissue initiates early and persistent neural hyperexcitability with signs ranging from mild cognitive impairment to convulsive seizures. The influence of peritumoral synaptic density, expansion dynamics, and spatial contours of excess glutamate upon higher order neuronal network modularity is unknown. We combined cellular and widefield imaging of calcium and glutamate fluorescent reporters in two glioblastoma mouse models with distinct synaptic microenvironments and infiltration profiles. Functional metrics of neural ensembles are dysregulated during tumor invasion depending on the stage of malignant progression and tumor cell proximity. Neural activity is differentially modulated during periods of accelerated and inhibited tumor expansion. Abnormal glutamate accumulation precedes and outpaces the spatial extent of baseline neuronal calcium signaling, indicating these processes are uncoupled in tumor cortex. Distinctive excitability homeostasis patterns and functional connectivity of local and remote neuronal populations support the promise of precision genetic diagnosis and management of this devastating brain disease.

Modeling of tungsten impurity transport and distribution in EAST based on multi-fluid and kinetic Monte Carlo simulations

In recent years, the materials of plasma facing components, such as divertor target plates, domes, and outer walls of tokamaks, such as ASDEX Upgrade, WEST, JET, EAST, and ITER, have been changed from carbon to tungsten because of its lower erosion and tritium retention rates. Impurities are produced by interactions between the plasma and the first wall. This study provides an investigation to simulate the transport and distribution of tungsten impurities in the edge plasma on EAST. The 2D multi-fluid edge plasma transport code SOLPS-ITER and 2D kinetic Monte Carlo impurity transport code DIVIMP were used in the simulations. The multi-fluid model in SOLPS-ITER and the kinetic Monte Carlo model in DIVIMP were employed to treat tungsten impurity ions. The 2D density contour distributions in the computational region and the 1D density radial profiles at the inner and outer midplanes of tungsten impurity particles with ionization states (W0–W+74) and the total tungsten particles with all charge states were obtained. With the heating power 1.5 MW and the line-averaged plasma density 2 × 1019 m−3, the results from SOLPS-ITER and DIVIMP show that the maximum density of tungsten ion with single ionization state is about 1014 m−3 and the total density of tungsten impurities with all charge states is about 1015 m−3 at the core boundary. To the best of our knowledge, the simulation results from SOLPS-ITER and DIVIMP are compared for the first time to benchmark SOLPS-ITER with the multi-fluid mode and DIVIMP with the kinetic model for tungsten impurity transport. The density distributions of tungsten impurities with different ionization states from SOLPS-ITER and DIVIMP are highly similar, and good agreement can be found under similar conditions involved in the calculation. From the comparison benchmark between SOLPS-ITER and DIVIMP for tungsten impurity transport, it can be concluded that the impurity transport approximation used by DIVIMP is good.

Pressure‐Induced Effects on BaPbO3: A Prospectively Valuable Material for Piezoelectric Applications via DFT

AbstractEmploying density functional theory within the Wien2k code, first‐principle calculations are conducted to explore the impact of applied pressure up to 80 GPa on the structural, mechanical, thermal, and electronic characteristics of BaPbO3. Demonstrating metallic behavior with ductile attributes, BaPbO3 exhibits a decreasing anisotropic nature under escalating pressure. Evaluation of cubic elastic constants, optimization curves, and enthalpy of formation indicates the compound's mechanical and thermodynamic stability under high pressure conditions. Calculated values of C11 and C44 reflect heightened resistance to unidirectional compression and increased stiffness under pressure. These mechanical properties position BaPbO3 as a promising candidate for diverse industrial applications across varying pressure ranges, including utilization in piezoelectric materials (0–20 GPa) and high‐pressure sensors. Additionally, charge density contours suggest a combination of ionic (Ba─Pb) and covalent bonding (Pb─O) within the compound's constituent atoms. The material can exhibit potential applications as a piezoelectric sensor at 0–20 GPa, high‐pressure actuators ≈20 GPa, and as a high melting temperature resistive substrate for laser welding and cutting materials.

Abstract 3873: Understanding spatial organization of cellular plasticity in pancreatic ductal adenocarcinoma

Abstract Pancreatic ductal adenocarcinoma (PDAC) is notorious for poor survival rates, underscoring the urgency of understanding factors that drive tumor progression. A key player in this process is epithelial-mesenchymal transition (EMT), known for its role in enhancing cancer cell adaptability, resistance to treatment, and metastasis. Our study focuses on EMT within PDAC, using single-cell spatial transcriptomics to explore how the tumor microenvironment influences changes in cellular states. We introduce a novel method involving Gaussian mixture models (GMM) to categorize EMT stages in single-cell data and utilize deep learning for label transfer of these tumor cell states, including intermediate cell states, onto spatial transcriptomic data with limited gene panels and sparse count profiles. We find strong spatial autocorrelation of classical cells and a dispersion of basal cells alongside other cells at intermediate stages of the EMT spectrum. By leveraging the spatial proximity of clonally related cells, we confirm that cells transition along the EMT spectrum in a gradient and infer transition rates. We next leverage density gradients of tumor cells in different states to identify distinct neighborhoods with varying EMT subtype composition. We observe significant variations in cell density among different EMT states. A focus on cancer-associated fibroblasts (CAFs) and macrophages reveals differences in these cells across density contours. We also examine differential ligand-receptor interactions across cell state gradients to better understand the cellular interactions that drive EMT transitions and alter the tumor environment. By leveraging spatial transcriptomics, this research aims to provide new biological insights into PDAC intratumoral heterogeneity, potentially leading to the identification of novel therapeutic targets to disrupt treatment resistance. Citation Format: Izabella Zamora, Milan Parikh, Bidish K. Patel, Lynn Bi, Doron Haviv, Jingyi Cao, Carina Shiau, Martin Hemberg, William L. Hwang, Nir Hacohen, David T. Ting, Arnav Mehta. Understanding spatial organization of cellular plasticity in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3873.

Theoretical studies on phase stability, electronic, optical, mechanical and thermal properties of chalcopyrite semiconductors HgXN2 (X=Si, Ge and sn): A comprehensive DFT analysis

In this study, the ground state physical properties of Hg-based chalcopyrite semiconductors, HgXN2 (X = Si, Ge and Sn), are investigated using the density functional theory (DFT), which is based on full potential linearized augmented plane wave (FP-LAPW) method. The structural, electronic, optical, mechanical and thermal properties of the body-centered tetragonal (BTC) phase, HgXN2 (X = Si, Ge and Sn), have been calculated using the modified Becke-Johnson exchange-correlation potential (TB-mBJ). The obtained lattice parameters and volume are in good agreement with the values reported earlier, indicating that the results are reliable and reproducible. The phase stability of the titled compounds is elaborately studied and it is confirmed that all are thermodynamically, dynamically and mechanically stable. The electronic band structure demonstrated a direct band gap of 1.70 eV, 0.99 eV, and 0.94 eV for the HgXN2 (X = Si, Ge and Sn) compounds, respectively. Both HgGeN2 and HgSnN2 compounds have a notably lighter carrier effective mass, resulting in higher carrier mobility and conductivity than HgSiN2. The order of the mechanical hardness is as follows: HgSiN2> HgGeN2> HgSnN2. The studied materials are also anisotropic in mechanically and optically. All the title compounds exhibit ductile behavior. The charge density contour plots indicates the dominant covalent nature of the bonds in HgXN2 (X = Si, Ge and Sn). All these compounds have a high absorption coefficient and low optical reflectivity in the visible light range. Due to the favorable band gap and high absorption coefficient, these compounds could be suitable for optoelectronic or photovoltaic device applications. Moreover, the thermal expansion coefficient, thermal conductivity, melting point and fracture toughness behavior have been calculated, which also showed promise for thermal barrier coating (TBC) applications.

On the variability of the atomic oxygen density in the upper atmosphere under different solar activity and geomagnetic conditions and its impacts on satellite drag

Atomic oxygen (AO) is the most abundant species in the terrestrial thermosphere at altitudes of 180 to 700 km and plays a crucial role in numerous upper atmospheric processes. The drag encountered by a spacecraft is directly influenced by the background atmospheric density, making AO a notable contributor in this regard. The objective of this study is to analyze the variability of the density of AO in the near-Earth space environment under different solar activity conditions, as well as during severe space weather events. The analysis is primarily focused on the altitude range of 300 to 500 km in the Earth’s thermosphere across the globe, which is a crucial operating region for a large number of Low Earth Orbiting satellites. AO exerts significant drag on the Low Earth Orbit (LEO) satellites and reacts with the materials of the satellite body and in situ probes mounted therein, causing considerable degradation to both. Additionally, AO interferes with measurements made by optical instruments through phenomena such as ‘shuttle glow’. Analysis based on NRLMSIS 2.0 model revealed that the concentration of AO displays significant seasonal variations primarily due to the asymmetry in solar insolation. The highest concentration of AO was observed during the spring equinoctial month of the solar maximum year, while the lowest concentration was noted during the winter solstitial month of the solar minimum year. The enhancement seen in AO density contours show an asymmetry in the zonal direction at approximately 50∘ N in June and 50∘ S in December. Similarly, during geomagnetically disturbed days, the AO density shows enhancements along various longitudes, as indicated by the elongated contours. During geomagnetic storms, the heightened Joule heating in the polar region modifies the meridional circulation, which in turn affects the global distribution of AO density. Similarly, an analysis of thermospheric neutral winds obtained from the HWM93 model reveals that the zonal winds exhibit a strong westward acceleration over the region where AO density is enhanced. Furthermore, such an increase in AO density during geomagnetic storms has been found to cause orbital degradation ranging from a few tens of meters to a few hundred meters, depending on the strength and geo-effectiveness of the storms. This study emphasizes the critical contribution of AO density to satellite drag force, necessitating in situ measurements for an accurate estimation of the altitude decay of the spacecraft.

A proposed method for calculating the voltage and current distributions of grounded and isolated networks subjected to line‐to‐ground faults

AbstractOne crucial objective of this article is to present simplified and accurate approaches to study the current distribution and ground surface potential around the area surrounding an earthed and isolated system in case of a line‐to‐earth fault. The present study is done in the case of uniform and two‐layer soils. Suggested models for calculating the distribution of the earth's surface current density, step, and touch voltages in grounded and isolated systems are presented, discussed, and adapted. The contact and arc resistances of line to ground faulty conductors are considered. Rods and/or grounding grids usually do grounded systems. The impact of both step and touch potentials and current density are investigated in this article. The methods of the calculations are based on the electrical concepts, the charge simulation method, and the imaging procedure for the grounding system. The suggested method can be considered a novel and simple technique for calculating the current distributions of the ground surface during line to ground fault. The results agree with those obtained by others, with the advantage of the proposed algorithm for its ease of application and simplicity. 3‐D dimensions’ contours of the current density and the electric potential on the earth surface around the faulty point are presented in case of homogeneous and two layers’ soil. Finally, this article's novelty is to devise a method for calculating the step and touch potentials and current density around the point of contact of the conductor carrying the electric voltages in the event of faults occurring in the electrical network, whether the network is grounded or isolated. Such faults of electrical networks may cause human hazards.

The Relationship Between Green Finance, Sustainable Technological Innovation and Energy Efficiency

Sustainable technological innovation can promote this progress in finance. This optimization and upgrading of energy efficiency can provide a good energy environment for green development. The collaborative innovation of financial enterprises has brought such development to the tertiary industry, driving the upgrading of consumer demand, and thus promoting the development of green finance. At this same time, sustainable technological innovation will increase investment in environmental protection, reduce energy consumption, promote the reduction of carbon emissions in the financial industry, and accelerate the development of green finance. This paper uses the data envelopment analysis method to calculate the Marquis production efficiency index, examines the dynamic generation efficiency of intertemporal energy input and output, and calculates the energy efficiency of green finance. This article measures and deconstructs energy efficiency at the provincial level, and pays attention to its changes. The study depicted the efficiency distribution of 28 provinces in two stages of the survey period. By using random kernel estimation for two periods during the survey period, dynamic distribution three-dimensional maps and density contour maps of total factor energy productivity, energy utilization efficiency, and energy allocation efficiency growth rates were drawn for the two periods. The results show that the transfer probability group of energy efficiency and its decomposition terms mainly falls near the diagonal, indicating that TFP and its decomposition term growth rate have certain transferability. From 2005 to 2015, the energy utilization efficiency of the seven economic regions has been significantly improved, and the energy efficiency differences in different regions have gradually converged. The energy efficiency of the Yangtze River Delta and the Pearl River Delta is the highest and has been continuously improved, followed by the Beijing Delta, the central region, the northeast region and the southwest region are again in terms of energy efficiency. Compared with provinces with relatively poor industrial structures, provinces with better industrial structures do not have significant advantages in energy efficiency, while provinces with higher levels of technological innovation typically have relatively higher energy efficiency.

Aero-spike and aero-disk effects of on wave drag reduction of supersonic flow past over blunt body

PurposeThe purpose of this study is to explore the effects of aerospike and hemispherical aerodisks on flow characteristics and drag reduction in supersonic flow over a blunt body. Specifically, the study aims to analyze the impact of varying the length of the cylindrical rod in the aerospike (ranging from 0.5 to 2.0 times the diameter of the blunt body) and the diameter of the hemispherical disk (ranging from 0.25 to 0.75 times the blunt body diameter). CFD simulations were conducted at a supersonic Mach number of 2 and a Reynolds number of 2.79 × 106.Design/methodology/approachICEM CFD and ANSYS CFX solver were used to generate the three-dimensional flow along with its structures. The flow structure and drag coefficient were computed using Reynolds-averaged Navier–Stokes equation model. The drag reduction mechanism was also explained using the idea of dividing streamline and density contour. The performance of the aero spike length and the effect of aero disk size on the drag are investigated.FindingsThe separating shock is located in front of the blunt body, forming an effective conical shape that reduces the pressure drag acting on the blunt body. It was observed that extending the length of the spike beyond a specific critical point did not impact the flow field characteristics and had no further influence on the enhanced performance. The optimal combination of disk and spike length was determined, resulting in a substantial reduction in drag through the introduction of the aerospike and disk.Research limitations/implicationsTo predict the accurate results of drag and to reduce the simulation time, a hexa grid with finer mesh structure was adopted in the simulation.Practical implicationsThe blunt nose structures are primarily employed in the design of rockets, missiles, and re-entry capsules to withstand higher aerodynamic loads and aerodynamic heating.Originality/valueFor the optimized size of the aero spike, aero disk is also optimized to use the benefits of both.

Paleotectonic Stress and Present Geostress Fields and Their Implications for Coalbed Methane Exploitation: A Case Study from Dahebian Block, Liupanshui Coalfield, Guizhou, China

The macroscopic structural fractures (joints) and geostress distribution characteristics of coal reservoirs are important factors affecting the exploitation of coalbed methane (CBM). In this study, the joints in the sedimentary strata of the Dahebian block in Liupanshui area, Guizhou Province were investigated. Directional coal samples were collected for observation and statistical analysis of coal microfractures, the paleotectonic stress fields of the study area were reconstructed, and the tectonic evolution was elucidated. The geostress distribution characteristics of the target coal seam (coal seam No. 11, P3l) in the study area were analyzed using the finite element numerical simulation method. The results indicate that the structural evolution of the Dahebian syncline in the study area can be divided into two stages. The Late Jurassic–Early Cretaceous stage (Early Yanshanian) is the first stage. Affected by the sinistral strike slip of the Weining–Ziyun–Luodian (WZL) fault zone, the derived stress field in the study area exhibits maximum principal stress (σ1) in the NEE–SWW direction. The Late Cretaceous stage (Late Yanshanian) is the second stage. Affected by the dextral strike slip of the WZL fault zone, the derived stress field exhibits σ1 in the NNW–SSE direction. The folds and faults formed in the first stage were modified by the structural deformation in the second stage. The dominant strikes of joints in the sedimentary strata are found to be in the NW–NNW (300°–360°) and NE (30°–60°) directions, with dip angles mostly ranging from 60° to 90°. The dominant strikes of coal microfractures are in the NW (285°–304°) and NE (43°–53°) directions. The distribution of geostress in the study area is characterized by high levels of geostress in the syncline center, decreasing towards the surrounding periphery. The overall trend of the geostress contour line is similar to the shape of the syncline and is influenced by folds and faults. The σ1 of coal seam No. 11 is vertical stress. The prediction results show that the joint density of coal seam No. 11 in the block is 36–50 joints/m, and the shape of the joint density contour line is also affected by the axial direction of the Dahebian syncline and the surrounding faults. The variation in coal seam joint density and the control effect of geostress on joints opening or closing affects the permeability of coal reservoirs. The study results provide significant guidance for the exploitation of CBM.