Resistance Law Research Articles

Calculated Waveform and Peculiarity of Radiated Electric Field due to Collision ESD Between Metallic Spheres With Charging Voltages Below 1000 V Using Spark Resistance Law

ABSTRACTCollision ESD between charged metallic objects below 1000 V causes electromagnetic interference in electronic equipment and devices. This interference is being observed to intensify at lower charging voltages. The phenomenon was first identified by Masmitsu Honda, but its underlying mechanism remains unclear even today. Originally, the charging voltage and spark length of collision ESD are unknown due to measurement difficulties, making it extremely challenging to establish the relationship between the radiated electric field strength and the spark property in such cases. In this study, to clarify the above mentioned electromagnetic phenomenon in collision ESD, a method of calculating the radiated electric field along with a spark length estimated from the measurement strength of radiated field peak is presented using the spark resistance law developed by Rompe and Weizel. The validity is confirmed by our previous measurement data on radiated electric field due to the collision ESD between charged spherical electrodes with a diameter of 30 mm at charging voltages from 300 to 600 V, employing an optical field probe with a wideband up to 10 GHz. The estimated spark length is verified by comparing it with the spark lengths based on an empirical Paschen's formula between fixed electrodes and the discharge data from past literature on metal electrodes, revealing the peculiarity effect of the radiated electric field strength caused by “constant breakdown potential gradient” that occurs at charging voltages below 1000 V.

Study on the influence of section shape of underground roadway on ventilation resistance

ABSTRACT Among the parameters that affect the ventilation capacity of an underground mine, the cross-sectional shape of the roadway plays a significant role. When the required airflow is constant, the roadways with different shapes but the same area evidently overcome the different wind resistance. In order to investigate the influence of roadway cross-sectional shape on airflow resistance, this study carried out experimental and Simulation Research on the influence of different cross-section shape and size changes on ventilation resistance. And the Relative Shape Factor (RSF) is established to quantitatively evaluate the influence of cross-section shape on ventilation resistance. Firstly, focusing on the four common types of cross-sectional in the roadway, including circular, rectangular, trapezoidal, and arched, the experimental platform of airflow resistance of the pipe is built, and the effect of the changes of cross-sectional shape on the ventilation resistance is studied. Furthermore, the law of airflow resistance with different scale changes under the same section shape is studied by numerical simulation. Subsequently, the scale-independent coefficient RSF is established through theoretical derivation to characterize the degree to which the section shape deviates from the circle. The further it deviates from the circular shape, the larger the RSF, indicating a greater impact of the cross-section shape on airflow resistance. Comparing the theoretical with the simulation results, the RSF errors of the rectangular, trapezoidal, and arched shapes are 7.3%, 4.01%, and 2.05%, respectively, indicating that the RSF can accurately describe the influence of the cross-section on ventilation resistance. Finally, the range of RSF for common roadway dimensions is summarized, the trapezoidal is 1.131 to 1.187, the arch-shaped is 1.0 to 1.160, and the rectangular is 1.128 to 1.152. The proposed RSF in this paper is intuitive and effective, which provides a reference for the engineering application and a new insight for the selection of the minimum ventilation resistance cross-section of roadway.

Atomistic Insights into the Ionic Response and Mechanism of Antifouling Zwitterionic Polymer Brushes.

Zwitterionic polymer brushes are not a practical choice since their ionic response mechanisms are unclear, despite their great potential for surface antifouling modification. Therefore, atomic force microscopy and molecular dynamics simulations investigated the ionic response of the surface electrical properties, hydration properties, and protein adhesion of three types of zwitterionic brushes. The surface of PMPC (poly(2-methacryloyloxyethyl phosphorylcholine)) and PSBMA (poly(sulfobetaine methacrylate)) zwitterionic polymer brushes in salt solution exhibits a significant accumulation of cations, which results in a positive shift in the surface potential. In contrast, the surface of PSBMA polymer brushes demonstrates no notable change in potential. Furthermore, divalent Ca2+ enhances protein adhesion to polymer brushes by Ca2+ bridges. Conversely, monovalent Na+ diminishes the number of salt bridges between PSBMA and PCBMA (poly(carboxybetaine methacrylate)) zwitterionic polymer brushes and proteins via a competitive adsorption mechanism, thereby reducing protein adhesion. A summary of polymer brush material selection and design concepts in a salt solution environment is provided based on the salt response law of protein adhesion resistance of various zwitterionic materials. This work closes a research gap on the response mechanism of zwitterionic polymer brushes' antifouling performance in a salt solution environment, significantly advancing the practical use of these brushes.

Particle Dynamics Study on Influencing Factors of Ice Slurry Flow Characteristics in District Cooling Systems

In district cooling systems, substituting the conventional cooling medium with ice slurry represents an ideal approach to achieve economical operation. During pipeline transportation, ice slurry exhibits heterogeneous flow characteristics distinct from those of pure fluids. Consequently, investigating the flow field characteristics of non-homogeneous ice slurry, quantitatively analyzing the rheological variations and flow resistance laws due to the uneven distribution of ice particles, and standardizing the comprehension and depiction of flow patterns within ice slurry pipes hold significant theoretical importance and practical value. This study analyzes the heterogeneous isothermal flow characteristics of ice slurry in a straight pipe by employing particle dynamics and the Euler–Euler dual-fluid model. Taking into account the impact of ice particles’ non-uniform distribution on the rheological properties of ice slurry, a particle concentration diffusion equation is incorporated to develop an isothermal flow resistance model for ice slurry. The flow behavior of ice slurry with initial average ice particle fractions (IPFs) ranging from 0% to 20% in DN20 horizontal straight and elbow pipes is examined. The findings reveal that the degree of heterogeneous flow in ice slurry is inversely proportional to the initial velocity and directly proportional to the initial concentration of ice particles. When the flow velocity is close to 0.5 m/s, the flow resistance of ice particles exhibits a linear positive correlation with changes in flow velocity, whereas the flow resistance of the fluid-carrying phase displays a linear negative correlation. As the flow rate increases to 1 m/s, the contribution of each phase to the total flow resistance becomes independent of the initial velocity parameter. Additionally, the drag fraction of the ice particle phase is positively associated with the initial concentration of ice particles. Furthermore, the phenomenon of “secondary flow” arises when ice slurry flows through an elbow, enhancing the mixing of ice particles with the carrier fluid. The extent of this mixing intensifies with a decrease in the turning radius and an increase in the initial velocity.

Modeling and Analysis of Resistance-Sensing Characteristics for Two-Way Shape Memory Alloy-Based Deep-Sea Actuators

Deep-sea actuators based on shape memory alloys (SMAs) are an emerging frontier field of multidisciplinary crossover, and the resistive sensing characteristics are the basis for the drive control of SMA deep-sea actuators. The resistance and resistivity of SMAs are complex and highly dependent on temperature and stress, and there is no complete description of SMAs for extreme environments of high pressure, low temperature, and high salinity in the deep sea. In this study, the logistic function is introduced to improve the kinetic equation of phase transition, and the macromechanical model, the law of resistance, and the resistivity mixing rule are integrated to model and analyze the resistive self-awareness characteristics of two-way shape memory alloy deep-sea actuators. The complex coupling relationships among resistance, strain, stress, resistivity, and temperature under constant load conditions are investigated, and the validity of the resistance-sensing model is verified by the water bath cycling test. The results show that the predicted values of the model agree well with the measured values. The self-perceived relationship between the resistance and deformation of the two-way shape memory alloy can be effectively expressed, which provides theoretical model support for the design of memory alloy deep sea actuators and sensorless drive control.

Calculated Waveform and Peculiarity of Radiated Electric Field due to Collision ESD between Metallic Spheres with Charging Voltages below 1000 V Using Spark Resistance Law

Calculated Waveform and Peculiarity of Radiated Electric Field due to Collision ESD between Metallic Spheres with Charging Voltages below 1000 V Using Spark Resistance Law

Chaotic dynamic analysis of electrical contact resistance measured in sliding current-carrying friction

This work explores the dynamic laws of electrical contact resistance (ECR) signals measured in the sliding current-carrying friction tests based on chaos theory. It is found that ECR time series have a chaotic nature, strongly verified by the positive largest Lyapunov exponent λ1. The chaos may originate from the combined friction effects on short and long timescales. Phase space analysis indicates that the ECR phase trajectory adheres to the “convergence–stability” evolution law over time, which pertains closely to energy dissipation. Hence, the chaotic attractor exists during current-carrying friction. Strikingly, wear surfaces confirm that the ECR phase trajectory evolution process corresponds to the stages of “formation–keeping” of the chaotic attractor, and also agrees with the electrical wear stages of “running-in–steady-state”. Further, the chaos quantifier variation is consistent with the phase space analysis results to identify wear transition quantitatively.

Assessing a transitional and turbulent overland flow resistance law for surfaces with different roughness

The control and management of soil erosion phenomena caused by rainfall and runoff is a significant issue in sloping landscapes, especially if they are scarcely or not vegetated. The study of the relationship between soil roughness and flow resistance is a fundamental step in improving the knowledge of erosion processes. In this study, the suitability of a theoretically deduced flow resistance law, based on a power-velocity profile, was assessed by transitional and turbulent overland flow data obtained in laboratory and available in the literature. These measurements were obtained in a sloping (slope in the range 1–40 %) rectangular flume, testing the effects of six different roughness conditions. At first, for each investigated roughness condition, the available measurements were used to calibrate and test the equation relating the Γ function of the velocity distribution, the flow Froude number, and the channel slope. For all the investigated conditions, this analysis allowed for demonstrating that the flow resistance law gives a reliable estimate of the Darcy–Weisbach friction factor, with errors ≤±5 % for 89.8–100 % of the examined cases with reference to the considered roughness condition. Then, using coefficients b (1.05) and c (0.562) of the Γ function available in the literature, the roughness effect was exclusively attributed to the a coefficient. In this case, the friction factor values calculated by the flow resistance law, with b = 1.05 and c = 0.562 and the a values corresponding to the different roughness conditions, are characterized by errors ≤±5% for 70.4–100 % of the cases. Finally, the power relationships between the calibrated a, b, and c coefficients of the Γ function, and Manning’s n values, corresponding to the roughness of the investigated surfaces, pointed out that the a coefficient is the most affected by the roughness conditions, as the exponent of Manning’s assumes the highest value. The significance of this research is due to the fact that a relevant issue in modeling overland flow is to define the resistance coefficient for variable roughness, especially the vegetated ones.

Research on Numerical Pile Testing Methods and Parameter Selection for Large-Diameter Steel Pipe Piles at Sea

Numerical test research and inverse analysis research on large-diameter steel pipe piles are particularly important for optimizing design parameters. Based on the field pile test results completed at an offshore wind farm in Jiangsu Province (including compression static load test, pull-out test, and horizontal load test), the actual geological conditions and loading process of the site were simulated, and numerical pile tests were systematically conducted. Sensitivity analysis of some key parameters was carried out, parameter value methods were proposed, and on this basis, the deformation failure modes of the foundation under different loading conditions, the mechanism and distribution law of pile side friction resistance under compression and pull-out conditions, and the relationship between foundation resistance and pile displacement under horizontal loading conditions (p-y curve) were studied.

EMC Research Efforts in the IEEJ Technical Committee and State‐of‐the‐Art Case Studies on ESD Found in its Technical Papers

Electrostatic discharge (ESD) has been known to cause electromagnetic noise against electronic equipment and devices even before the technical concept of electromagnetic compatibility (EMC) was established 68 years ago in the United States and 48 years ago in Japan, while the ESD still continues to be studied as one of the most significant issues that should be solved in EMC areas. This is largely because the underlying nature of ESD has yet to be essentially elucidated from an EMC perspective. On the other hand, as an academic research organization on EMC in Japan, a Technical Committee named ‘EMCJ’ on ‘Environmental Electromagnetic Engineering’ was founded in 1976 in both the Institute of Electrical Engineers of Japan (IEEJ) and the Institute of Electronics and Communication Engineers or the present IEICE (Institute of Electronics, Information and Communication Engineers) to address EMC concerns. Since then, the EMCJ has been jointly conducting EMC research activities under the IEICE as the nominating body and the IEEJ as the associative body, whereas the EMCJ of IEEJ was dissolved in 1999 to form a new Technical Committee on EMC (TC‐EMC) in order to deal with EMC issues appropriate to the IEEJ. In this review, to mark the 25th anniversary of the IEEJ Technical Committee on EMC (TC‐EMC) in 2024, the EMC research efforts and activities that the TC‐EMC has conducted over the past 25 years from January 2000 to March 2024 are surveyed from 1272 technical papers presented at the technical meetings. Furthermore, among the ESD issues identified in these technical papers, the latest case studies utilizing ‘spark resistance laws’ that allow the analysis of the initial behavior of sparks, in which a spark is the essence of ESD and is the key to open the door to elucidate the phenomenon, particularly from an EMC perspective, are reviewed. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

New Insight into Electric Force in Metal and the Quadratic Electrical Resistivity Law of Metals at Low Temperatures

Considering that Einstein’s relation between the diffusion coefficient and the drift mobility of free randomly moving charge carriers in homogeneous materials including metals is always valid, it is shown that the effective electric force acting on free electrons in metal depends on the ratio between the kinetic free electron energy at the Fermi surface to the classical particle energy 3 kT/2. The electrical resistivity of elemental metals dependence on very low temperatures has the quadratic term, which has been explained by electron–electron scattering. In this paper, it is shown that the quadratic term of the electrical resistivity at low temperatures is caused by scattering of the free randomly moving electrons by electronic defects due to linear effective free electron scattering cross-section dependence on temperature, but not by electron–electron scattering.

A frictional soliton controls the resistance law of shear-thickening suspensions in pipes

Pipe flows are commonly found in nature and industry as an effective mean of transporting fluids. They are primarily characterized by their resistance law, which relates the mean flow rate to the driving pressure gradient. Since Poiseuille and Hagen, various flow regimes and fluid rheologies have been investigated, but the behavior of shear-thickening suspensions, which jam above a critical shear stress, remains poorly understood despite important applications (e.g., concrete or food processing). In this study, we build on recent advances in the physics of shear-thickening suspensions to address their flow through pipes and establish their resistance law. We find that for discontinuously shear-thickening suspensions (large particule volume fractions), the flow rate saturates at high driving stress. Local pressure and velocity measurements reveal that this saturation stems from the emergence of a frictional soliton: a unique, localized, superdissipative, and backpropagating flow structure coexisting with the laminar frictionless flow phase observed at low driving stress. We characterize the remarkably steep effective rheology of the frictional soliton and show that it sets the resistance law at the whole pipe scale. These findings offer an unusual perspective on low-Reynolds suspension flows through pipes, intriguingly reminiscent of the transition to turbulence for simple fluids. They also provide a predictive law for the transport of such suspensions in pipe systems, with implications for a wide range of applications.

Investigation of the resistance characteristics of the transverse groove for laminar flows

Transverse grooves are known to significantly affect drag reduction. However, additional investigation is required to understand the impact of groove geometry and flow velocity on resistance and flow characteristics. This study examines the impact of transverse grooves on laminar flow over a plate at various velocities. By conducting numerical simulations in three-dimensional domains, we analyze the evolution of resistance and flow characteristics over surfaces containing rectangular grooves perpendicular to the flow. The focus lies on understanding the interaction mechanisms between the evolution of the transverse groove resistance law and the flow characteristics of the external flow field of the groove. A detailed parametric study is conducted, considering a total of 32 groove size combinations, comprising 4 groove depths and 8 widths. The results demonstrate that transverse grooves in laminar flows can reduce total drag by up to 15.5% compared to a flat plate, while also causing a thousandfold increase in drag under specific operating conditions. These findings have practical implications for industries such as aerospace, automotive, and hydraulic systems to improve overall performance by reducing drag and enhancing fluid flow efficiency using transverse grooves in laminar flows.

Flow resistance law in channels with emergent rigid vegetation

AbstractFlow resistance estimate is a challenging topic for establishing flooding propensity of streams, designing river restoration works, and evaluating the use of soil bioengineering practices. In this paper, flume measurements with rigid cylinders set in two arrangements (aligned, staggered) were used to evaluate the effect of rigid emergent vegetation on flow resistance. A well‐known theoretical flow resistance equation was firstly reviewed. Then, it was calibrated and tested by measurements performed for these arrangements with six concentrations (0.53–11.62 stems dm−2). The analysis was conducted using three approaches: (i) distinguishing the experimental runs corresponding to different arrangements and stem concentrations; (ii) using only a scale factor representing the effect of the stem concentration; and (iii) joining all available data. The results demonstrated that the flow resistance equation gives an accurate estimate of the Darcy–Weisbach friction factor f, characterized, for the best approach among the tested ones, by errors less than or equal to ±5% for 95.9% of the examined cases for the aligned arrangement and for the staggered arrangement less than or equal to ±5% for 94.2% of the examined cases. For both arrangements, the measurements demonstrated that, for a given longitudinal distance between vegetation elements, flow resistance increases for decreasing values of the transverse distance and, for a given transverse distance, f decreases for increasing values of the longitudinal distance between elements. Finally, in the range of the investigated stem concentrations, the influence of the arrangement on flow resistance resulted negligible.

Exploration of high-temperature oxidation resistance laws in ultra-high temperature boride ceramics through data-driven approaches

This study employed machine learning that leverage historical experimental data to construct predictive models capable of estimating the oxidation resistance of ultra-high-temperature diboride. The support vector machine regression (SVR) model exhibited superior prediction metrics with R2 of 0.88. The Shapley-Additive-exPlanations and genetic algorithm symbolic regression models revealed that SiC content plays a crucial role in the antioxidant damage of UHT borides, and the results suggested that the critical addition amount of SiC in the ZrB2-SiC system is 13.8 vol%, and the optimal addition amount is 23.5 vol%. The trained SVR model promptly identified optimal formulas exhibiting exceptional oxidation resistance.

Effect of hydrothermal treatment on the corrosion resistance of CO2 gas-assisted MAO coatings

1Micro-arc oxidation (MAO) is an effective method for preparing highly corrosion-resistant coatings on metal surfaces, but the presence of a porous structure on the surface tends to limit further improvements in corrosion resistance. In this paper, we report a CO2 gas-assisted MAO method to prepare a ceramic coating on the surface of magnesium alloys and seal the pores using a hydrothermal reaction. By comparing the corrosion resistance of the coatings of the specimens in different electrolytes, the study reveals the mechanism of the influence of CO2 gas and hydrothermal post-treatment method on the initial structure of the coating, as well as the influence law of the corrosion resistance of different coatings. The results show that the coating prepared in NaOH + Na2SiO3 solution has the largest thickness and exhibits the most excellent corrosion resistance, which is at least one order of magnitude higher than that of several other groups of specimens.

Study of the variation law of the airflow resistance and related physical parameters of the pile throughout compost process with cattle manure

Composting is widely adopted in livestock waste management, and the ventilation system control is essential for composting efficiency. For ventilation system, the airflow resistance is a major factor influencing the ventilation intensity and oxygen supply capacity. This study explored the variation law of airflow resistance, bulk density, specific gravity, particle size and total pressure throughout composting with cattle manure. The airflow resistance was calculated with Ergun equation, and contribution coefficients of different components were analyzed with principal component analysis (PCA). Results showed that the viscous airflow resistance was dominant throughout cattle manure composting. The average airflow resistance was 0.146 Pa/m, and resistance of pile at lower layer was higher than that at the upper layer by 18.1 %. For contribution coefficient affecting airflow resistance, the ranks were bulk density, average particle size and specific gravity. During composting process, the average airflow resistance decreased by 40.1 % and the total pressure reduced by 3.47 %. All parameters had the greatest variation at thermophilic phase, which accounted for more than 60 % of the total variation amplitude. Meanwhile, less than 10 % of the total pressure was used to overcome the airflow resistance. Therefore, reducing bulk density of pile should be considered preferentially to decrease the airflow resistance. During cattle manure composting process, the total pressure of ventilation system ought to be adjusted with the aerobic reaction to a lower level, especially at thermophilic phase with the most rapid descent rate. This study can provide support for reducing the energy consumption required for ventilation of composting.

Comparative Study Assessing the Relative Contributions of Ship Resistance Factors Based on Data Analysis

Ship resistance has a very important value in the determination of ship power and the design of emission standards. In this paper, a ship resistance model with different displacement, speed, and attachment under the condition of a fixed scale ratio is tested by means of experimental research, which is used to analyze the change law of ship resistance under the condition of a single factor. The coupling effects of multiple factors on the actual ship power are studied after the establishment of a mathematical relationship between the actual ship power and resistance on the basis of the response surface method. The research results show that: (1) there is an obvious positive correlation between ship resistance and speed, which matches the change law of the exponential equation. Compared with ship appendages, displacement and speed have the greatest influence on resistance. (2) According to the correlation analysis, the maximum correlation coefficient between ship speed/resistance and power is 0.99, and the correlation coefficients between displacement/resistance and power are 0.93 and 0.88, respectively. However, the correlation coefficients between ship appendages and resistance and power are only 0.23 and 0.14, respectively. (3) The actual ship power and speed, displacement, and appendages form a quadratic polynomial relationship. The multi-factor interaction analysis results show that speed and displacement have the greatest influence on the actual ship power. The research results have a certain guiding significance for ship design.

An improved method for sand wave morphology discrimination in rivers by combining a flow resistance law and support vector machines

A parameterized expression for sand wave morphology in rivers is established using a flow resistance law while accounting for sediment incipient velocity. A distinct relation is drawn between the proposed characteristic parameters and the sand wave morphology based on flume data. Support vector machines (SVMs) are then used to separate the boundaries of the sand wave morphology due to the high classification accuracy of SVMs. The boundary line data from each sand wave morphology is extracted and fitted to establish a discriminant standard, which is then successfully validated using experimental and quantifiable data. Also, based on the foregoing methodoly, it is further discovered that the short-term significant fluctuation of sand wave morphology is closely correlated with significant channel changes in rivers with a high width-depth ratio, using Yellow River Estuary as an example.

Wide flow model for converging gravity currents and the effects of the flow resistance model on the propagation

We are investigating flows in the viscous-buoyancy balance regime in a converging channel with a cross section described by a power function y∼xkzr, where x and y are the streamwise and spanwise horizontal coordinates, respectively, and z is the vertical coordinate. We are interested in the different results depending on whether we use a simplified model of the flow resistance law, which varies depending on whether the height of the current is much greater/smaller than the channel width or a somewhat more general model described by the Darcy–Weisbach equation in which the flow resistance law depends on the shape of the cross section through the Fanning friction factor. The simplified models, one of which developed here is original and new, allow a self-similar solution of the second kind, unlike the general model. The general model, to the best of our knowledge applied for the first time to a generic cross section described by a power function, requires numerical integration. However, a comparison of the front propagation of the gravity current according to the different models, performed by numerical integration of the differential problem, shows that the current assumes a self-similar arrangement as a good approximation for the general model. For some channel geometries, the three models give a very similar result, which results in a difficult attribution to a specific model based on experiments. The effects of anisotropy in the vertical direction of the channel cross section are also highlighted by both the numerical and self-similar solutions.