Core Parameters Research Articles

Dual-frequency excited combination resonance and global stability of an oscillating cylindrical bubble

Based on the multi-scale method and Lyapunov stability theory, the second-order analytical model of combination resonance under dual-frequency acoustic excitation of an oscillating cylindrical bubble is established. The nonlinear dynamic characteristics of the additive combination resonance and the subtractive combination resonance are explored by analyzing the frequency response curve and global stability. The primary findings are given as follows: (1) the combination resonance exhibits complex dynamic characteristics, which are manifested in the frequency response curve as multiple response peaks and unstable regions. (2) The response peak of the additive combination resonance consists of a single resonance peak on the left and a small-amplitude double peak on the right. The response amplitude is highly sensitive to changes in core parameters, and the changes at the top of the response peak are obvious. (3) The response peak of the subtractive combination resonance is composed of a large-amplitude double-peak resonance on the left and a small-amplitude single-peak resonance on the right. When the frequency is relatively high, three discontinuous unstable regions will appear in the frequency response curve.

3D Lattices of Core/Shell Ge/Mn Quantum Dots in an Alumina Matrix: Structure, Fabrication, and Photo-Electrical Properties

Materials consisting of quantum dots with a semiconductor-core, metal–shell structure often have exciting and tunable photo-electrical properties in a large range of values, and they are adjustable by core and shell structure parameters. Here, we investigated the influence of Mn-shell addition to Ge quantum dots formed in an alumina matrix by magnetron sputtering deposition. We show a well-achieved formation of the 3D regular lattices of Ge-core, Mn-rich shell quantum dots, which were achieved by self-assembled growth mode. Intermixing of Ge and Mn in the shell was observed. The optical, electrical, and photo-conversion properties were strongly affected by the addition of the Mn shell and its thickness. The shell induced changes in the optical gap of the materials and caused an increase in the material’s conductivity. The most significant changes occurred in the photo-electrical properties of the materials. Their quantum efficiency, i.e., the efficiency of the conversion of photon energy to the electrical current, was very strongly enhanced by the shell addition, though it depended on its thickness. The best results were obtained for the thinnest shell added to the Ge core, for which the maximal quantum efficiency was significantly enhanced by more than 100%. The effect was, evidently, the consequence of multiple exciton generation, which was enhanced by the shell addition. The obtained materials offer great potential for various applications in photo-sensitive devices.

Study on the equivalent model considering in-plane and out-of-plane mechanical properties for a curved sandwich structure with square honeycomb core

The curved honeycomb sandwich structure has larger surface area, effectively reducing the number of fasteners and parts of civil airplane fuselages, engine cowls, and ship’s hulls. Its equivalent model building can significantly shorten the simulation analysis time and improve the efficiency of optimal design and performance prediction, but the reliability and precision of the model are closely related to the calculation accuracy of equivalent elastic parameters. In the present study, an equivalent model considering the in-plane and out-of-plane mechanical properties of the core is developed for a curved square honeycomb sandwich structure. The in-plane and out-of-plane equivalent elastic parameters of the honeycomb core composed of hollow quadrangular frustum cells with symmetrical rectangular sides (i.e. square cell) are derived by analytical method, equivalent strain energy principle, and equivalent stiffness principle. And then combined with the sandwich panel theory, an equivalent model of the curved sandwich structure is established. The three-dimensional (3D) geometric models of planar honeycomb cores with hollow quadriprism cells are built by SolidWorks software, and the 3D printing is performed using Polylactic Acid (PLA) material. The three-point bending tests are conducted on the planar honeycomb sandwich structures with carbon fiber composite face sheets, and the test data are compared with the numerical results of this structure and its equivalent model. Based on ANSYS Workbench, the static analysis under bending and compression conditions, modal analysis, and harmonic response analysis are implemented on honeycomb sandwich structures with different bending degrees and their equivalent models. The results show that the load-displacement test curves of planar sandwich structures agree well with the finite element results of these structures and their equivalent models, and the equivalent models of curved sandwich structures accurately reflect the bending and vibration characteristics, fully verifying the feasibility of the presented equivalent model. This study provides important references and guidance for establishing the equivalent model of curved honeycomb sandwich structures.

Experimental, numerical and optimization investigation of sandwich structures with 3D-printed sacrificial core under explosive loading

Sandwich panel structures are widely used in aerospace, marine, and automotive applications due to their high stiffness, high strength-to-weight ratio, good vibration damping, and thermal conductivity. The present study investigates the response of 3D printed polylactide acid (PLA) honeycomb structures when used as a crushable core with a protective metal coating in order to analyze the extent of damage and deformation of the center of the back sheet. This research is based on experimental testing and finite element simulation. The purpose of this study is to investigate the effect of three parameters of sandwich panel core, including filling density of the sacrificial core, 3D printer nozzle thickness, and the geometry of printed cells on the strength of sandwich panel under explosive loading. In this study, the effect of these three parameters is investigated at the same time, and finally, the optimal state of these three parameters that leads to the least displacement of the center of the back sheet is introduced. At first, a sandwich structure with a honeycomb core was made by a 3D printing machine, and the filling density of the core was 13 %. Then this set was subjected to explosive loading in open air with C4 explosive and the displacement of the center of the back sheet was measured. Further, considering the cost of experimental tests, the conditions of this test were simulated by the finite element code in LS-DYNA software, and the results of the displacement of the center of the back sheet were verified by experimental testing. In the following, Design-Expert software was used to check the three parameters of filling density, geometry of cells and thickness of the 3D printer nozzle at the same time. Finally, to verify the value obtained for the optimal state, the finite element simulation and experimental test were performed by placing the input parameters of the optimal state and the results were compared.

Deep Reinforcement Learning-Driven Jamming-Enhanced Secure Unmanned Aerial Vehicle Communications.

Despite its flexibility, unmanned aerial vehicle (UAV) communications are susceptible to eavesdropping due to the open nature of wireless channels and the broadcasting nature of wireless signals. This paper studies secure UAV communications and proposes a method to optimize the minimum secrecy rate of the system by using interference technology to enhance it. To this end, the system not only deploys multiple UAV base stations (BSs) to provide services to legitimate users but also assigns dedicated UAV jammers to send interference signals to active or potential eavesdroppers to disrupt their eavesdropping effectiveness. Based on this configuration, we formulate the optimization process of parameters such as the user association variables, UAV trajectory, and output power as a sequential decision-making problem and use the single-agent soft actor-critic (SAC) algorithm and twin delayed deep deterministic policy gradient (TD3) algorithm to achieve joint optimization of the core parameters. In addition, for specific scenarios, we also use the multi-agent soft actor-critic (MASAC) algorithm to solve the joint optimization problem mentioned above. The numerical results show that the normalized average secrecy rate of the MASAC algorithm increased by more than 6.6% and 14.2% compared with that of the SAC and TD3 algorithms, respectively.

A deeper investigation of membrane fouling in anaerobic membrane bioreactors for wastewater treatment: Influencing factors and fouling layer characteristics

Identifying the core parameters affecting membrane fouling and analyzing fouling layer characteristics are crucial for membrane fouling mitigation of anaerobic membrane bioreactors (AnMBRs). This study investigated the influence of various operating parameters on membrane fouling and the characteristics of different fouling layers. The ratio of flux to specific gas demand per unit of membrane area (SGD) was proposed as a key parameter for membrane fouling control and was applicable under various flux, SGD, and sludge concentration conditions. The membrane resistance and specific filtration resistance of foulants at high flux and sludge concentration reached 1.56 × 1012 m−1 and 3.56 × 1015 m−1/kg, respectively. Solid foulants accumulated on the membrane surface during rapid fouling stage. Protein-like pollutants accounted for a higher proportion (85%) of soluble foulants on the membrane surface. Humic acids were enriched on the cake/gel layer and the longitudinal enrichment process from the cake layer to the gel layer was uneven. Proteocatella (>45%) at the phylum level, Desulfovibrio (>3.1%), Syntrophobacter (>2.8%), and Treponema (>0.25%) at the genus level colonized in the gel layer and were the pioneers of membrane biofouling. Their enrichment on the membrane surface was primarily based on their own characteristics and was less sensitive to the operating conditions of AnMBRs. Therefore, this study provides a deeper understanding of membrane fouling formation process, which contributes to the long-term stable operation of AnMBR and scales up its engineering application.

Nonlinear electro-thermo-mechanical dynamic behavior of complexly curved GPL-reinforced panels with auxetic core

This research aims to study the nonlinear electro-thermo-mechanical dynamic responses of cylindrical, sine, and parabolic graphene platelets reinforced panels with auxetic cores and piezoelectric layers. By applying the higher-order shear deformation theory, viscoelastic foundation model, approximate technique for stress function, Rayleigh dissipation function, and energy method, the governing formulations are established. The natural frequency is determined explicitly, and the Runge-Kutta method is used to acquire the time amplitude responses of panels numerically. The noticeable effects of piezoelectrical layers, auxetic core, and GPL parameters on the mechanical and thermal dynamic buckling and vibration responses are recognized from the numerical investigations.

On the Generalization of an Attention-based GRU Model for Shield Attitude and Position Prediction

Abstract Misalignment between the shield machine and tunnel design axis during tunneling can result in several issues. Shield attitude parameters are crucial for ensuring stable tunneling and reducing the risk of accidents in shield projects. This study investigates a method for predicting EPB shield attitudes using various algorithms. A reliable model for predicting shield attitudes was constructed by a Gated Recurrent Unit (GRU) and attention mechanism that can prioritize core parameters with higher weights. The Pearson correlation coefficient method was conducted to analyze input parameters in order to enhance prediction efficiency. The test results indicate that the proposed GRU-Attention based method achieves satisfactory predictions, with an average R2 value of 0.85. Additional data is extracted to validate the generalization of the trained model. Finally, the factors influencing the model’s generalization were analyzed to provide experience for further development of cross-engineering predictive models.

Modeling and Simulation of Wide-Frequency Characteristics of Electromagnetic Standard Voltage Transformer

To achieve the broadband applicability of standard voltage transformers in “dual high” power systems, an equivalent circuit model of the standard voltage transformer is first established. Using the complex magnetic permeability method and utilizing existing core parameters, the excitation impedance values are obtained. Next, based on the equivalent circuit model, the no-load error function of the standard voltage transformer is analyzed, and through simulation, the no-load error response curve of the standard voltage transformer in the frequency range of 20 Hz to 3000 Hz is derived. The simulation results indicate that within the 20 Hz to 700 Hz range, both the no-load ratio error and the no-load angular error meet the accuracy requirements, with the ratio error within ±0.05% and the angular error within 2′. Additionally, the derivation of the error transfer function demonstrates the correlation between the no-load error values and the number of turns and cross-sectional area of the standard voltage transformer. Simulation results, obtained by increasing and decreasing the number of turns and cross-sectional area by 10%, provide valuable insights for the error compensation and structural design of standard voltage transformers.

Algorithm for extracting the normal cross-section parameters of multiple ball screw shaft ball tracks based on an optical micrometer measurement system

Abstract The accurate and efficient measurement of the normal cross-section parameters of multiple ball screw shaft spiral ball tracks are pivotal for ensuring quality control in ball track machining. Given the intricate nature of the ball screw shaft spiral ball track, balancing the accuracy and efficiency of the normal cross-section parameters measurement is a significant challenge. In this study, we present a method to calculate two core parameters, arc radius and contact angle. The method consists of four parts: the automatic axial cross-section separation method, the arc symmetric extraction method, the spiral transformation method, and the parameter algorithm based on the weighted least squares method. The experimental and simulation results validated the effectiveness of our method. Compared with the traditional axial measurement and transformation (AMT) method, our algorithm reduced the errors in arc radius and contact angle by up to 13.9 µm and 4.77°, respectively, and improved the accuracy by up to 78.34% and 85.04%. Compared with the traditional AMT methods and directly normal measurement method, the measurement time of our algorithm was reduced by up to 1565 s and 3475 s, respectively, and the efficiency was improved by up to 71.01% and 84.51%, respectively.

Quantitative Analysis about the Spatial Heterogeneity of Water Conservation Services Function Using a Space–Time Cube Constructed Based on Ecosystem and Soil Types

Precisely delineating the spatiotemporal heterogeneity of water conservation services function (WCF) holds paramount importance for watershed management. However, the existing assessment techniques exhibit common limitations, such as utilizing only multi-year average values for spatial changes and relying solely on the spatial average values for temporal changes. Moreover, traditional research does not encompass all WCF values at each time step and spatial grid, hindering quantitative analysis of spatial heterogeneity in WCF. This study addresses these limitations by utilizing an improved water balance model based on ecosystem type and soil type (ESM-WBM) and employing the EFAST and Sobol’ method for parameter sensitivity analysis. Furthermore, a space–time cube of WCF, constructed using remote-sensing data, is further explored by Emerging Hot Spot Analysis for the expression of WCF spatial heterogeneity. Additionally, this study investigates the impact of two core parameters: neighborhood distance and spatial relationship conceptualization type. The results reveal that (1) the ESM-WBM model demonstrates high sensitivity toward ecosystem types and soil data, facilitating the accurate assessment of the impacts of ecosystem and soil pattern alterations on WCF; (2) the EHSA categorizes WCF into 17 patterns, which in turn allows for adjustments to ecological compensation policies in related areas based on each pattern; and (3) neighborhood distance and the type of spatial relationships conceptualization significantly impacts the results of EHSA. In conclusion, this study offers references for analyzing the spatial heterogeneity of WCF, providing a theoretical foundation for regional water resource management and ecological restoration policies with tailored strategies.

Effects of Injected Current Streams on MHD Equilibrium Reconstruction of Local Helicity Injection Plasmas in a Spherical Tokamak

Open field line currents are intrinsic to DC helicity injection plasma startup and pose a challenge for inferring the plasma equilibrium with standard reconstruction analysis. Local helicity injection (LHI) is a type of DC helicity injection which uses small, modular current sources to drive force-free current along helical field lines to produce tokamak plasmas. MHD modeling and magnetic measurements during LHI indicate the injected current streams remain coherent as helical structures on the outboard edge of a core toroidal plasma that is tokamak-like in a toroidally averaged sense. To extract core plasma equilibrium properties, external magnetic diagnostics corrected for contributions from the injected current streams are fitted by a standard Grad-Shafranov equilibrium code. An iterative approach for estimating and subtracting the stream contributions from the diagnostic signals is described and applied to a model equilibrium database to reduce systematic errors introduced by the streams. Convergence is usually attained with 2 to 4 iterations, with derived equilibrium parameters matching the prescribed axisymmetric core values to within estimated experimental uncertainties. Accurate recovery of core parameters occurs when the ratio of the net toroidal windup current from the streams to the core plasma current is less than 0.2, which is typically satisfied in most experiments.

Meshing pair geometry of the intersecting-axis internally geared screw compressor

The Intersecting-Axis Internally Geared Screw Compressor (IISC) is an emerging advanced positive displacement machine showing the potential to greatly broaden the application of screw compressor technology. The core component of the IISC is an internally geared meshing pair with the intersecting-axis gearing, while its design methodology has not been disclosed yet. To fill the gap, this paper established the geometry model for the meshing pair and discussed the influence of its core parameters on geometric performance. First, the generation model of meshing pairs was presented, and the complete parameters set of meshing pairs was defined. The established model was verified by a meshing pair manufactured by 3D printing and CNC techniques. Next, the geometric analysis model of IISCs was established such as working volume and leakage channels, which was verified by commercial 3D software. Using the analysis model, the mesh pair parameters (rotor profile, cone angle, wrap angle, and L/D ratio) were discussed to reveal the design methodology of IISCs. Finally, the variable-pitch technology was discussed, and a novel variable-pitch method was proposed to further enhance the performance of IISCs. This paper could effectively guide the design of IISCs to further promote the development of the screw compressor technology.

A hybrid approach combining UD and GA-CV-SVM to evaluate shear performance in high asphalt concrete core

The shear effect on high asphalt concrete core is significant. However, studies on the reliability of 100-meter-scale cores against shear damage remain limited. A key challenge in this research field is establishing the control criteria for the core and improving the computational efficiency of implicit limit state function (LSF). Additionally, the impact of material parameter uncertainty on the shear failure reliability of the core during the dam construction and impoundment stages remains unclear. To address this, a safety evaluation method based on time discretization was proposed, combining uniform design (UD), K-fold cross-validation (K-CV), and genetic algorithm (GA) to optimize the support vector machines (SVM). The core parameters of 52 asphalt concrete-core rockfill dams (ACCRDs) were analyzed, with the statistical values of the basic variables considered in determining the reliability index. The theoretical derivation of the critical shear failure safety index established a stability formula to assess the safety state of the dam core. The significance parameters were identified, and the sample points were generated at each stage using UD, and the Support Vector Regression (SVR) was applied to reconstruct the LSF, and reliability was calculated through the checking point method.

Enhancing green housing diffusion through density bonuses: An analysis using the Use-Purchase-Supply model

Green housing plays a crucial role in advancing sustainable land use and urban development. The evident paradox of the sluggish diffusion of cost-effective green housing has garnered growing attention. This study introduces a Use-Purchase-Supply (U-P-S) model to unveil the "black box" of this paradox and develops a simulation model to quantify the diffusion dynamics of green housing based on the classic "epidemic model". Using China as a case for simulation, the model identifies key drivers, with a specific focus on the impact of density bonuses. The results reveal that lower-rated green housing can proliferate independently, whereas higher-rated green housing development hinges on policy instruments for market traction. Density bonuses demonstrate to be as potent as the reduction of green incremental costs, which is the paramount driver of green housing diffusion. Furthermore, this study extends its insights globally by contrasting core parameters across countries. The U-P-S model enhances the theoretical lens of "how to diffuse sustainability" and functions as a "policy laboratory" for simulating and evaluating the effects of various policy measures on green housing diffusion.

The direction of core solidification in asteroids: Implications for dynamo generation

Paleomagnetic studies of meteorites over the past two decades have revealed that the cores of multiple meteorite parent bodies, including those of certain chondritic groups, generated dynamo fields as they crystallised. However, uncertainties in the direction and mode of core solidification in asteroid-sized bodies have meant using the timings and durations of these fields to constrain parent body properties, such as size, is challenging. Here, we use updated equations of state and liquidus relationships for Fe-FeS liquids at low pressures to calculate the locations at which solids form in these cores. We perform these calculations for core-mantle boundary (CMB) pressures from 0–2 GPa, and Fe-FeS liquid concentrations on the iron-rich side of the eutectic, as well as two values of iron thermal expansivity that cover the measured uncertainties in this parameter, and adiabatic and conductive cooling of these cores. We predict inward core crystallisation from the CMB in asteroids due to their low < 0.5 GPa pressures regardless of the uncertainties in other key core parameters. However, due to low internal pressures in these cores, remelting of any iron snow, as proposed to generate Ganymede’s present-day field, may be unlikely as the cores are approximately isothermal. Therefore a different mode of inward core solidification is possibly required to explain compositionally-driven dynamo action in asteroids. Additionally, we identify possible regimes at higher > 0.6 − 2 GPa pressures in which crystallisation can occur concurrently at the CMB and the centre.

Context‐driven implementation strategies: Exploring three approaches to implement a lean capability framework within a global production company

AbstractThis paper explores global implementation of capability building projects as part of an corporate lean programme. The aim is to identify the core parameters in global implementation of complex knowledge in various contexts within the corporation. The empirical research investigates the global implementation of a lean capability project in three regional clusters within a large pharmaceutical multinational production company. The findings indicate that contextual situations in regional clusters, for example, maturity levels, national culture, and previous experiences, influence the design of the implementation approaches embedding knowledge management principles in various ways. Three types of implementation approaches (horizontal, parallel, and delegated) are identified, which highlights the strategically different pathways to realise new frameworks for knowledge management. This study shows how adjustments to contextual situations influence the implementation process and identifies various hallenges with various approaches that may hinder the execution of lean strategy. This paper puts forward five identified implementation parameters that could guide future research and knowledge management practitioners in opex, HR, and learning and development functions.

Recent Advances in Linear Polarization‐Sensitive Photodetectors Based on Perovskites with Different Molecular Dimensions

AbstractThe function of photodetectors is to convert optical signals into current or voltage output. Polarization‐sensitive perovskite photodetectors have attracted significant interest because of their potential applications in imaging and remote sensing technologies. This study provides an overview of the advancements in research on halide perovskite photodetectors, particularly focusing on their capability for linear polarization‐sensitive detection. First, there is a brief description of the background and strengths of linear polarization‐sensitive photodetectors. Then, the core parameters of linear polarization‐sensitive photodetectors are introduced briefly. Third, according to the classification of active layer materials, linear polarization‐sensitive photodetectors are divided into 3D perovskites and low‐dimensional perovskites. The research on linear polarization‐sensitive perovskite detectors are reviewed. Finally, the developments and challenges faced by linear polarization‐sensitive perovskite photodetectors are analyzed.

Assessment of nominal and off-nominal parameters of a soluble boron free small modular reactor design

Boric acid is traditionally used for reactivity control in pressurised water reactors. However, it increases the rate at which reactor components corrode. This leads to increased operational radioactive waste produced through neutron-activation of corrosion fragments. During reactor operation, radioactive corrosion product deposits, or so-called crud, accumulate on fuel cladding in regions of high burnup. Boron compounds have been detected in such deposits, and they cause axial-offset anomaly, i.e. deviation in axial power prediction. Accumulation of boron-laden deposits can reduce plant efficiency to about 70 % over time. This work presents the design process and analysis of nominal and off-nominal parameters of a soluble boron-free small modular reactor core. The design, and analyses were carried out using CASMO4e, CMSLINK, and SIMULATE3 codes. In addition, a borated variant of the target boron-free core was designed and used as reference. Equilibrium cycles were achieved for both the reference and the boron-free core. The limiting FΔH during the transition to equilibrium was found to be 1.754 and 1.651 for the reference and boron-free cores. The equilibrium FΔH were found to be 1.624 and 1.57 compared to the design limit of 1.7. The hot zero power MTC for the boron-free core at beginning of cycle was found to be –22.67 pcm/K compared to −3.64 pcm/K for the reference. The removal of boric acid made the MTC coefficients more negative and the FΔH lower compared to the reference. The boron-free core had enough rod-worth for power and isothermal defect counteraction and reactor shut down.

Integrating the deep learning and multi-objective genetic algorithm to the reloading pattern optimization of HPR1000 reactor core

The deep learning and multi-objective genetic algorithm were employed to optimize the fuel reloading pattern for HPR1000, a state-of-the-art nuclear power reactor designed and operated in China, also known as Hualong-1. In this study, the deep-learning algorithm was applied to establish the rapid evaluator for fuel-reloading patterns, for which the random samples between fuel-reloading patterns and corresponding key core parameters were generated by our home-developed nuclear-design code, named Bamboo-C. The advanced machine-learning platform TensorFlow was utilized for the deep-learning model. Then, the multi-objective genetic algorithm was applied to search the optimal fuel-reloading patterns, combined with the rapid evaluator to evaluate the key core parameters in a very short time. The DAKOTA toolkit was employed for optimization using a multi-objective genetic algorithm, for which the cycle length and power-peak factors were selected as the target parameters to establish the fitness function. For verification and application, the above method has been applied to the fuel-reloading optimization for Cycle 2 of HPR1000 operated in China. The optimization pattern results in an extension of the cycle length by about 21 EFPD (Effective Full Power Day), keeping all the key safety parameters satisfying corresponding safety criteria.