Wireless power transfer (WPT) has attracted much attention in recent years. In an underwater WPT system, the eddy current loss tends to be non-negligible as the frequency or the coil current ...increases. Thus, it is crucial to analyze the eddy current loss in an underwater WPT system. The analytical model of the eddy current loss of a coreless WPT system in the seawater is established with Maxwell's equations. The expressions of the electric field intensity and the eddy current loss are derived. The eddy current loss is analyzed in different circumstances to illustrate the impacts of related factors. For a WPT system in the air, there is an optimum resonant frequency, for a higher frequency leads to a larger induced voltage, but will result in larger coil losses simultaneously. However, the optimum resonant frequency will be shifted because of the eddy current loss in the seawater. Then, the optimum operating frequency is obtained based on the analytical model. It is found that the optimum operating frequency is supposed to be larger than the resonant frequency to achieve the maximum dc-dc efficiency in the seawater. An underwater WPT prototype was built and the experimental results verified the theoretical analysis.
•Dental implant anchorage was investigated by experiments, analytical and FE models.•Diameter increased normalized insertion torque and contact for tapered implant.•However, diameter did not affect ...these measures for parallel-walled implants.•Tapered design distributed PU foam stress further away from the thread.•This study demonstrated PU foam compression during insertion for tapered implants.
Anchorage, evaluated by the maximum insertion torque (IT), refers to mechanical engagement between dental implant and host bone at the time of insertion without external loads. Sufficient anchorage has been highly recommended in the clinic. In several studies, the effects of implant diameter and taper body design under external loading have been evaluated after insertion; however, there are few studies, in which their effects on stress distribution during insertion have been investigated to understand establishment of anchorage. Therefore, the objective of this study was to investigate the effects of dental implant diameter and tapered body design on anchorage combining experiments, analytical modeling, and finite element analysis (FEA). Two implant designs (parallel-walled and tapered) with two implant diameters were inserted into rigid polyurethane (PU) foam with corresponding straight drill protocols. The IT was fit to the analytical model (R2 = 0.88–1.0). The insertion process was modeled using explicit FEA. For parallel-walled implants, normalized IT and final FEA contact ratio were not related to the implant diameter while the implant diameter affected normalized IT (R2 = 0.90, p < 0.05, β1 = 0.20 and β2 = 0.93, standardized regression coefficients for implant diameter and taper body design) and final FEA contact ratio of tapered implants. The taper design distributed the PU foam stress further away from the thread compared to parallel-walled implants, which demonstrated compression in PU foam established by the tapered body during insertion.
Cyber-physical system (CPS) is a new trend in the Internet-of-Things related research works, where physical systems act as the sensors to collect real-world information and communicate them to the ...computation modules (i.e. cyber layer), which further analyze and notify the findings to the corresponding physical systems through a feedback loop. Contemporary researchers recommend integrating cloud technologies in the CPS cyber layer to ensure the scalability of storage, computation, and cross domain communication capabilities. Though there exist a few descriptive models of the cloud-based CPS architecture, it is important to analytically describe the key CPS properties: computation, control, and communication. In this paper, we present a digital twin architecture reference model for the cloud-based CPS, C2PS, where we analytically describe the key properties of the C2PS. The model helps in identifying various degrees of basic and hybrid computation-interaction modes in this paradigm. We have designed C2PS smart interaction controller using a Bayesian belief network, so that the system dynamically considers current contexts. The composition of fuzzy rule base with the Bayes network further enables the system with reconfiguration capability. We also describe analytically, how C2PS subsystem communications can generate even more complex system-of-systems. Later, we present a telematics-based prototype driving assistance application for the vehicular domain of C2PS, VCPS, to demonstrate the efficacy of the architecture reference model.
Building efficient embedded deep learning systems requires a tight co-design between DNN algorithms, hardware, and algorithm-to-hardware mapping, a.k.a. dataflow. However, owing to the large joint ...design space, finding an optimal solution through physical implementation becomes infeasible. To tackle this problem, several design space exploration (DSE) frameworks have emerged recently, yet they either suffer from long runtimes or a limited exploration space. This article introduces ZigZag, a rapid DSE framework for DNN accelerator architecture and mapping. ZigZag extends the common DSE with uneven mapping opportunities and smart mapping search strategies. Uneven mapping decouples operands (W/I/O), memory hierarchy, and mappings (temporal/spatial), opening up a whole new space for DSE, and thus better design points are found by ZigZag compared to other SotAs. For this, ZigZag uses an enhanced nested-for-loop format as a uniform representation to integrate algorithm, accelerator, and algorithm-to-accelerator mapping. ZigZag consists of three key components: 1) an analytical energy-performance-area Hardware Cost Estimator, 2) two Mapping Search Engines that support spatial and temporal even/uneven mapping search, and 3) an Architecture Generator that auto-explores the wide memory hierarchy design space. Benchmarking experiments against published works, in-house accelerator, and existing DSE frameworks, together with three case studies, show the reliability and capability of ZigZag. Up to 64 percent more energy-efficient solutions are found compared to other SotAs, due to ZigZag's uneven mapping capabilities.
Confining pressure is an essential factor to consider in geological disasters in geothermal reservoirs and deep geological formations. Assessing the confining pressure holds practical importance, ...particularly in mitigating high-risk disasters associated with resource production. This study focuses on the development of a theoretical model for the mechanical properties of drilled rocks, specifically considering the impact of elevated confining pressure during the drilling process. Digital drilling experiments with different confining pressures are carried out to investigate the effect of confining pressure on the drilling mechanical properties of rock. A new method for identifying confining pressure and strength parameters using digital drilling is proposed. A comparison between the predicted confining pressure and the measured confining pressure is conducted to verify the accuracy of the model. The results show that the cutting force and the normal thrust at the cutting point increase with an increase in confining pressure. The drilling parameters (the bit rake angle a, the contact friction angle θ, the friction angle of rock φ, the cohesion of rock c, the effective stress generated by the drill torque St, the effective stress generated by the thrust along the normal axis Sn.) also increase gradually as confining pressure increases. Digital drilling technology offers shorter testing cycles and lower costs in comparison to traditional confining pressure testing techniques such as stress relief and hydraulic fracturing. The predicted confining pressure is consistent with the actual value. In summary, the method of determining confining pressure based on digital drilling has practical engineering significance.
•The confinement is crucial on the drilling mechanical property of rock.•The theoretical model of drilling was established considering the crushed zone.•The confining pressure increases the cutting force at the cutting point.•The developed method is efficient for confinement prediction.
With high reliability and good cost-performance ratio, Si SJMOS and SiC SBD pair is often preferred in commercial single-phase PFC applications. Switching dynamics of Si SJMOS is different compared ...to 650<inline-formula><tex-math notation="LaTeX">\,</tex-math></inline-formula>V wide bandgap devices due to differences in device characteristics. This paper presents an improved analytical model to study the switching dynamics of Si SJMOS and SiC SBD pair. Unlike the existing literature on high-voltage Si MOSFETs, this paper considers the nonlinearities in channel current and internal capacitances of Si SJMOS, the nonlinear reverse-biased capacitance of SiC SBD, along with parasitic gate-drain capacitance arising due to PCB layout. As a result, the proposed analytical model presents a significant improvement over the existing models of high-voltage Si MOSFET in predicting switching loss, time, <inline-formula><tex-math notation="LaTeX">(dv/dt</tex-math></inline-formula>), <inline-formula><tex-math notation="LaTeX">(di/dt)</tex-math></inline-formula>, etc. Experimental and simulation results for three 650V Si SJMOS and SiC SBD pairs with different current ratings provide validation of the proposed analytical model.
•Global Interception Model (GIM) is a modified version of the sparse Gash model.•We developed linear regression models for global estimates of c and Sv parameters.•The new c and Sv models used remote ...sensing data and exhibited high performance.•GIM outperforms existing global products (PMLv2 and GLEAMv3.7a)
Accurate estimates of rainfall interception loss are crucial for modeling the water balance of forested areas. However, considerable regional variability exists in the interception process, and much uncertainty remains. This study enhances the estimation of rainfall interception loss at the global scale by integrating remote sensing products into the parameterization of Gash’s analytical model. We refer to this enhanced configuration as the Global Interception Model (GIM). High-resolution satellite imagery was used to derive vegetation indices and spectral reflectance, which were then employed in linear regression models to estimate canopy cover fraction (c) and vegetation water storage capacity (Sv). Their importance in ecological processes, and land and water resource management, makes the modeling of these parameters of particular interest. The other two parameters required to run the Gash model, namely the mean rainfall and evaporation rates under saturated canopy conditions, were obtained via the integration of MWSEP and ERA5-Land meteorological products. Modeling performance was evaluated using in situ measurements and gridded datasets. GIM estimates exhibited a superior performance statistic when compared to PMLv2 and GLEAMv3.7a. Our results demonstrate the high potential of this approach for improving the accuracy of rainfall interception loss estimates from local to global scales.
This paper presents a novel analytical model that significantly enhances the characterization of the magnetic field within the air-gap of slotted surface-mounted permanent magnet (SPM) motors. The ...model, based on complex relative permeance (CRP), not only improves accuracy but also accelerates the computation of the magnetic field in comparison to existing CRP models and traditional numerical methods. The model denoted as improved complex relative permeance (ICRP) model is derived from the governing equations for magnetic scalar potential functions across the various domains of the motor elements, diverging from traditional methodologies such as conformal mapping. The application of the ICRP model ensures the incorporation of precise boundary conditions reflective of the permanent magnet's geometry, its angular orientation, and magnetic polarity. It proves applicable across a spectrum of motor design aspects, including pole-slot combinations, the geometry of the slotted iron core, the rotational angle of the rotor, and other critical parameters such as the stator core slot opening angle, the pole-arc to pole-pitch ratio, and the air gap length in two dimensional (2D) spatial framework. The ICRP has been applied to the magnetic field analysis of three distinct motor designs, covering both slotless and slotted configurations, where it precisely assesses the effects of slotting through the relative permeance functions of the slotted core. The accuracy and computational efficiency of the ICRP are shown through comparative analyses with finite element analysis (FEA) and existing CRP models, focusing on scalar potential, relative permeance, and magnetic flux density within the air gap region. The results validate the model's superior capability, suggesting its utility in the design process of three different SPM motors.
In this paper, the end forces caused by the longitude end effects in linear permanent magnet synchronous machines (LPMSMs) are analyzed and minimized. First, the left/right-end forces are calculated ...based on an analytical model and the Maxwell stress tensor, in which the optimal integration surfaces are investigated. Then, based on the spectrum analysis of the left/right-end forces, two different methods are adopted to minimize the fundamental and high-order harmonics, respectively. The optimal length of the primary iron is obtained from the phase difference of the fundamental and a two-step iteration instead of the trial-and-error with the finite element method. Furthermore, step-skewed auxiliary irons are added to the primary end to eliminate the high-order harmonics. Third, to reduce the secondary end effect when the primary moves to the secondary end, a compensation method of adding mirror permanent magnet is proposed and good results are obtained. Finally, an LPMSM prototype is manufactured and experiments are conducted. The experimental results verify the theoretical study.
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