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This paper studies the mechanical properties of the 2-D tri-axial braided composite. A volume element is established, so that the classical laminate plate theory and the series-parallel model can be adopted to study a bi-directional stress--strain response. Failure criteria are given and the failure strength is determined. The finite element simulation is used to verify the reliability of the present theoretical model. [ABSTRACT FROM AUTHOR]

The present paper is aimed at providing an updated review of prediction methods for the aerodynamic noise of ducted rotor–stator stages. Indeed, ducted rotating-blade technologies are in continuous evolution and are increasingly used for aeronautical propulsion units, power generation and air conditioning systems. Different needs are faced from the early design stage to the final definition of a machine. Fast-running, approximate analytical approaches and high-fidelity numerical simulations are considered the best-suited tools for each, respectively. Recent advances are discussed, with emphasis on their pros and cons. [ABSTRACT FROM AUTHOR]

The paper deals with the dynamics of a resistance spot welding system. At the core of this system is a transformer, which is powered on the primary side by a pulse-width modulated inverter and has a full-wave output rectifier on the secondary side that provides a direct welding current. The entire system is nonlinear, due to magnetic hysteresis and electronics. The electronics prevent the current from flowing in all parts of the welding transformer at separate time intervals during the voltage supply period; therefore, not all the parameters affect the dynamic of currents and voltages all the time so the system is also time-variant. To design a high-performance welding system and to predict the maximum possible welding current at a specific load, it is necessary to know the welding and primary currents. The leakage inductances of the system can reduce the maximum welding current significantly at higher frequencies and the same load. There are several methods to determine these currents, each with its drawbacks. Measurements are time-consuming, using professional software is expensive and requires time to learn and free open-source software has many limitations and does not guarantee the correctness of the results. The article presents a new, fourth option—a theoretical derivation of analytical expressions that facilitate straightforward and rapid calculation of the welding and primary currents of the resistance spot welding system with symmetrical secondary branches. The derivation of the mathematical expressions is based on the equivalent circuits that describe the system in different operating states. The results of the numerical simulations confirmed the derived expressions completely. [ABSTRACT FROM AUTHOR]

The diffuse field sound absorption coefficient (SAC) of a sound absorber can be obtained from an average over the incidence angles of the oblique incidence plane wave SAC. The plane wave SAC can be derived from the plane wave complex-valued reflection coefficient defined as the ratio of the reflected sound pressure at a given point on the material surface to the incident sound pressure at the same point. In practice, the material is excited by a monopole, and the reflection coefficient becomes a local quantity which is a function of the source height and the radial distance from the source. This local reflection coefficient obtained at various points on the material surface is commonly used to approximate the oblique incidence plane wave reflection coefficient. The error in estimating the diffuse field SAC introduced by this approximation has not been explored in the literature. This paper investigates this error as a function of the material extent, thickness, and source height using an analytical approach to calculate the local reflection coefficient. The calculation is based on Allard's model which describes the sound propagation above an infinite lateral extent porous material backed by a rigid wall and excited by a monopole. Using finite element simulations as a reference, the analytical model is shown to provide a good approximation of the diffuse field sound absorption performance of sufficiently large material areas. The diffuse field SAC calculated from plane wave reflection coefficients and local reflection coefficient are compared. The limitations inherent in deriving diffuse field SACs from local reflection measurements obtained with a monopole are highlighted. [ABSTRACT FROM AUTHOR]

Limited access to large-scale data is a key obstacle to building machine learning (ML) applications in practice, partly due to a reluctance of information exchange among data owners out of privacy and data security concerns. To address this "information silo" problem, federated learning (FL) techniques have been proposed to enable decentralized model training via an orchestrating central server and have received increasing attention in several industries (including healthcare and finance). Despite its superior privacy protection property, adoption of FL is limited by a lack of systematic understanding of its underlying economics. In this paper, we take an analytical approach to answer two questions: (1) when do data owners prefer to form a FL partnership over building ML models by themselves and (2) how can different contractual mechanisms be used to promote repeated contributions to FL (the cooperative outcome that benefits all participants). We formulate an iterated prisoner's dilemma (IPD) model that accounts for unique FL characteristics, including the specification of the payoff matrix and the involvement of a central server to sanction noncooperation. We find that partnership formation requires participants to be not too forward-looking in temporal preferences, which is contrary to the conventional wisdom in IPD. Furthermore, to promote repeated contributions, it is insufficient to only rely on penalties imposed by the central server or by participants for noncooperation, but a combination of both is enough. Our work advances theoretical understanding of the economics of FL and provides prescriptive insights that can inform FL participant selection and contract design. This paper was accepted by D. J. Wu, information systems. Funding: This work was partially supported by Cisco Research. Supplemental Material: The online appendices are available at https://doi.org/10.1287/mnsc.2023.00611. [ABSTRACT FROM AUTHOR]

Handoff mechanisms are very important in fifth-generation (5G) mobile networks because of the cellular architecture employed to maximize spectrum utilization. Together with call admission control (CAC) mechanisms, they enable better optimization of bandwidth use. The primary objective of the research presented in this article is to analyze traffic levels, aiming to optimize traffic management and handling. This article considers the two most popular CAC mechanisms: the resource reservation mechanism and the threshold mechanism. It presents an analytical approach to occupancy distribution and blocking probability calculation in 5G mobile networks, incorporating connection handoff and CAC mechanisms for managing multiple traffic streams generated by multi-service sources. Due to the fact that the developed analytical model is an approximate model, its accuracy was also examined. For this purpose, the results of analytical calculations of the blocking probability in a group of 5G cells are compared with the simulation data. This paper is an extended version of our paper published in 17th ConTEL 2023. [ABSTRACT FROM AUTHOR]

The central components influencing future grid stability in the future are inverters and their controllers. This paper delves into the pivotal role of inverters and their controllers in shaping the future stability of grids. Focusing on grid-supporting inverters, the study utilizes a microgrid test setup to explore their impact on overall grid stability. Employing impedance-based stability analysis with the Nyquist criterion, the paper introduces variations in internal inverter parameters and external grid parameters using pole-zero map considerations. The inverter's control structure, resembling standard generators with droop control, facilitates the application of grid operators' knowledge to inverter control. Mathematical insights into stability principles are provided, highlighting the influence of poles related to the phase-locked loop and the strategic placement of additional poles for enhanced stability. Furthermore, the paper evaluates the effects of rotating inertia, revealing that a 50% increase in system inertia can stabilize unstable microgrid behavior, enabling grid-supporting inverters to actively contribute to grid reliability. [ABSTRACT FROM AUTHOR]

In this paper, the functionality of Mobile Wireless Sensor Networks (MWSNs) is analytically modeled and evaluated using Stochastic Reward Nets (SRNs). In MWSNs, mobile nodes can move around to collect data from the environment and send them to the sink. These nodes use a limited battery as the power source which can be charged according to environmental conditions. If the battery does not have enough power, the mobile node is disabled and, therefore, it cannot move around to collect/send data. The data collected by the nodes will expire if they are not received by the sink in a timely manner. In order to avoid data expiration, mobile nodes can send their data to other nodes around themselves, but this also increases the power consumption because of further communication. Furthermore, moving faster in the environment, the power consumption of the nodes increases. Therefore, environmental and movement conditions as well as communication between nodes can have a major impact on the functionality of the MWSNs. These challenges are considered in the paper and the proposed models analyze the impact of different conditions on the functionality of MWSNs. The results obtained from the comparison of different scenarios demonstrate that the environmental and movement conditions have a greater impact on system functionality than the communication conditions. [ABSTRACT FROM AUTHOR]

Damping through friction tends to be one of the most efficient methods to suppress damage to structures from earthquakes. Realizing robust structures is therefore highly dependent on designing for the dynamic forces of friction-damped structures and exploring their reliability against natural disasters. This paper presents a simplified matrix analysis algorithm for multi-story friction-damped buildings. The behavior of friction-damped systems has analyzed more accurately by modeling the master-slave degree of freedom of the joints. First, the formulation of the problem is discussed, and a condensed general equation is derived. Then, an end-to-end solution is proposed to find the responses of structures. The displacement response of each story has been carried out in both condensed and non-condensed general equations, and the results clearly show the accuracy of the proposed method. The numerical analysis and the results of the simulation of various friction-damped structures depicts the proposed approach consists with the commercial finite element method and is applicable for the analysis various types of structures. It is noted that the acceleration and displacement responses of the structures investigated under the proposed method and the traditional finite element method are so consistent that only a 1.5% difference is observed. Moreover, as a result of the proper allocation of degrees of freedom during the analysis, this method yields a reduction in computational costs especially in large buildings. [ABSTRACT FROM AUTHOR]

Analytical modeling presents symmetries and aesthetic-mathematical characteristics which are not catchable in numerical computation for science and technology; nanoscience plays a significant role in unification attempts, considering also models including holistic aspects of reality. In this paper we present new discovered results about the complete analytical quantum-relativistic form of the mean square deviation of position R 2 (t) related to a recently introduced Drude–Lorentz-like model (DS model), already performed at classical, quantum and relativistic level. The function R 2 (t) gives precise information about the distance crossed by carriers (electrons, ions, etc.) inside a nanostructure, considering both quantum effects and relativistic velocities. The model has a wide scale range of applicability; the nanoscale is considered in this paper, but it holds application from sub-pico-level to macro-level because of the existence of a gauge factor, making it applicable to every oscillating process in nature. Examples of application and suggestions supplement this paper, as well as interesting developments to be studied related to the model and to one of the basic elements of a current unified holistic approach based on vacuum energy. [ABSTRACT FROM AUTHOR]

To achieve higher throughputs in cellular networks, 3GPP proposes to use unlicensed frequency bands and develops technologies — the latest one is NR-U — allowing a cellular base station to transmit in unlicensed bands, which are already occupied by Wi-Fi networks. To enable fair channel sharing between two technologies, the base station uses a sort of CSMA/CA with binary exponential backoff similar to Wi-Fi. However, the base station can start data transmission only at strictly periodic time moments. Many papers propose sending a reservation signal between the end of the backoff procedure and such a moment to prevent nearby devices from accessing the channel. However, this approach significantly reduces Wi-Fi performance. The paper proposes a novel method CR-LBT of transmitting a reservation signal that greatly decreases channel resource waste caused by collisions and improves channel resource sharing fairness. With developed analytical models and simulations, it is shown that CR-LBT may simultaneously increase the throughput of both NR-U and Wi-Fi networks. The effect is more noticeable for the Wi-Fi network, the throughput of which may rise three times compared with the traditional method of sending the reservation signal. Finally, the influence of various factors on CR-LBT performance is studied. [ABSTRACT FROM AUTHOR]

The increasing bandwidth requirement of new wireless applications has lead to standardization of the millimeter wave spectrum for high-speed wireless communication. The millimeter wave spectrum is part of 5G and covers frequencies between 30 and 300 GHz that correspond to wavelengths ranging from 10 to 1 mm. Although millimeter wave is often considered as a communication medium, it has also proved to be an excellent ‘sensor’, thanks to its narrow beams, operation across a wide bandwidth, and interaction with atmospheric constituents. In this paper, which is to the best of our knowledge the first review that completely covers millimeter wave sensing application pipelines, we provide a comprehensive overview and analysis of different basic application pipeline building blocks, including hardware, algorithms, analytical models, and model evaluation techniques. The review also provides a taxonomy that highlights different millimeter wave sensing application domains. By performing a thorough analysis, complying with the systematic literature review methodology and reviewing 165 papers, we not only extend previous investigations focused only on communication aspects of the millimeter wave technology and using millimeter wave technology for active imaging, but also highlight scientific and technological challenges and trends, and provide a future perspective for applications of millimeter wave as a sensing technology. [ABSTRACT FROM AUTHOR]

Laser powder bed fusion (LPBF) is widely used in metal additive manufacturing to create geometrically complex parts, where heat transfer and its affected temperature distribution significantly influence the parts' materials' microstructure and the resulting materials' properties. Among all the microstructure representations, crystallographic orientations play a paramount role in determining the mechanical properties of materials. This paper first developed a physics-based analytical model to predict the 3D temperature distribution in PBF considering heat transfer boundary conditions; heat input using point-moving heat source solutions; and heat loss due to heat conduction, convection, and radiation. The superposition principle obtained temperature distributions based on linear heat sources and linear heat loss solutions. Then, the temperature distribution was used to analytically obtain the texture grown on a substrate with random grain orientations considering columnar-to-equiaxed transition (CET). Thus, the link between process parameters and texture was established through CET models and physical rules. Ti-6Al-4V was selected to demonstrate the capability of the analytical model in a single-phase situation. By applying advanced thermal models, the accuracy of the texture prediction was evaluated based on a comparison of experimental data from the literature and past analytical model results. Hence, this work not only provides a method of the fast analytical simulation of texture prediction in the single-phase mode for metallic materials but also paves the road for subsequent studies on microstructure-affected or texture-affected materials' properties for both academic research and industrial applications. The prediction of single-phase material texture has never been achieved before, and the scalability has been expanded. [ABSTRACT FROM AUTHOR]

Variable flux reluctance machines (VFRMs) are increasingly attracting research interest due to their magnetless and robust brushless structure. Under the modulation effect of the airgap permeance, the VFRM operates with a series of field harmonics, distinguishing it from conventional AC synchronous machines. This paper deals with the analysis and preliminary design of the VFRM from the perspective of multiple working airgap field harmonics. Firstly, the spatial and temporal order of the working field harmonics are defined. The systematic winding theory, including the unified star of slots and winding factor calculation method, is established to consider all these working harmonics. Then, an average torque model is built and simplified. The key role of 1st-order rotor permeance, 1st- and 3rd-order polarized stator permeance is deduced. The relationship between key parameters and average torque is computed, providing a guideline for the preliminary design of the VFRM. [ABSTRACT FROM AUTHOR]

Coreless fault current limiter with variable series reactor is an emerging technology for limiting the amplitude and shortening the fault duration in the power network with simple and reversible operation. The device includes two coaxial, coreless reactors with axial mobility to vary and increase the effective inductance of the network during the short circuit fault. The reactors are automatically returned back to their initial position after the fault is cleared, with minimal net inductance. This paper aims to analytically describe the electromagnetic theory and validate the functionality of the device. For this purpose, the resistance and inductance of the device are first computed at normal condition via the basic theory of engineering electromagnetics. Next, the respective electromechanical performance characteristics such as force, positional displacement of the reactors, and the effective inductance are calculated at the faulty condition. For verification purposes, analytical results are compared against the finite element model. [ABSTRACT FROM AUTHOR]

Adequate mathematical description of magnetization curves is indispensable in engineering. The accuracy of the description has a significant impact on the design of electric machines and devices. The aim of this paper was to analyze the capability of Bézier curves systematically, to describe the nonlinear static magnetic properties of non-oriented electrical steels, and to compare this approach versus the established mathematical descriptions. First, analytic functions versus measurements were analyzed. The Bézier curves were then compared systematically with the most adequate analytic functions. Next, the most suitable orders of Bézier curves were determined for the approximation of nonlinear magnetic properties, where the influence of the range of the input measurement dataset on the approximation process was analyzed. Last, the extrapolation capabilities of the Bézier curves and analytic functions were evaluated. The general conclusion is that Bézier curves have adequate flexibility and significant potential for the approximation and extrapolation of nonlinear properties of non-oriented electrical steels. [ABSTRACT FROM AUTHOR]

Named-Data Networking (NDN) over Low Power and Lossy Networks (LLNs), employing IEEE 802.15.4 communication technology, is projected to provide native support for mobility and efficient content delivery for the emerging Internet of Things (IoT). While many interest forwarding strategies have been proposed for NDNs over LLNs, most existing studies have relied on software simulations to evaluate their performance due to the lack of analytical modeling tools. This paper introduces the first analytical model for estimating the Interest Satisfaction Ratio (ISR) in NDN over LLNs, which is a crucial metric for assessing the effectiveness of interest forwarding strategies. We develop the analytical model specifically for the broadcast forwarding strategy, which has been extensively studied due to its simplicity and ease of implementation. Simulation results confirm that the proposed model predicts the ISR with reasonable accuracy. The model is then used to elucidate the strong interaction between the CSMA/CA parameters of the IEEE 802.15.4 standard and the achieved ISR. [ABSTRACT FROM AUTHOR]

The resource of shear resistance provided by the dowel mechanism of rebar in reinforced concrete (RC) structures can significantly affected by the simultaneous presence of axial loading. This occurs for example of plastic hinges of seismic resistant structures. In fact, at load reversals in cycles of large deformation demand, rebars are subjected to combined axial and shear loading, particularly in those section where the shear transfer via aggregate interlocking is jeopardized by the opening of the crack throughout the entire section depth. Thus, a reliable assessment of the shear capacity of dowels under combined shear and axial load is required to check the element shear resistance. The paper describes the results of a specific experimental campaign on rebar dowels subjected to shear loading in presence of different levels of axial load. Both smooth and ribbed rebar dowels were investigated. A marked reduction of the dowel shear strength and stiffness in presence of increasing axial loading was experimentally observed, only partially compensated by the kinking effect. The latter was found to characterize the entire resource of dowel capacity when the axial load was close to the rebar yielding strength. The paper proposes an analytical model, adapted from others available in the literature, to predict the dowel shear-displacement response accounting for the applied axial load. The model helps the understanding of the dowel response, is suitable for hand calculation and can easily assist the dowel design. The experimental response was quite well captured for smooth dowels, while the prediction was less accurate for ribbed ones. Future refinements may address the local damage induce by the rebar pull-out, typical of ribbed rebars, which is neglected in present form of the model. [ABSTRACT FROM AUTHOR]

This paper exhibits a detailed explanation of an analytical band to band tunneling current model with gate misalignment effect for an ultrathin n type Asymmetric DG TFET considering fringing effect on the non gate overlapping channel region formed due to left side shifting of back gate. Model includes leakage current around the channel-drain interface, has a great impact in sub-threshold region and verified under front gate voltage with gate length scaled to 20 nm for different back gate shifts and various back gate voltages with Silicon Dioxide (SiO2) as gate insulator. It also exhibits a good concurrence with the device simulator in representing drain voltage dependent tunneling current characteristics with different front gate voltages. We authenticate our model throughout several simulations comparing device simulator ISE TCAD results and exhibits an excellent correlation. [ABSTRACT FROM AUTHOR]

An analytical approach for performance prediction of saturated brushed permanent magnet direct current (DC) motors is proposed in this paper. In case of a heavy saturation in the stator back core of electrical machines, some flux completes its path through the surrounding air, and the conventional equivalent circuit cannot be used anymore. This issue has not been addressed in the literature. The importance of considering the effect of the flux penetrating the surrounding air is shown in this paper using finite element simulations and experimental results, and an analytical approach is proposed to consider this effect on magnet operating point determination and performance prediction of saturated brushed permanent magnet DC motors. An analytical method is also presented to determine the boundary radius of the surrounding air for obtaining accurate results in finite element (FE) solutions and analytical calculations. An analytical approach based on Carter's coefficient is also proposed to calculate the effective length of the magnet when the length of the magnet and rotor length are not the same. The accuracy of the proposed analytical model is illustrated using finite element simulations and experimental results. With this accuracy, this analytical model is very suitable to be used for reliable and quick mathematical design optimization. [ABSTRACT FROM AUTHOR]

The physical models of MOS transistors used in the design of modern integrated circuits are accurate, which makes it possible to simulate their operation with the given degree of reliability, but they are highly complex. Therefore, less accurate but more compact analytical models of transistors and devices based on them are usually used. However, in the calculations and evaluation, the values of the parameters that make up the model equations might not be known in all cases sufficiently accurately. This paper presents a technique for the iterative refinement of parameter values in analytical models that describe devices based on integrated MOS transistors. Using the results of modeling carried out with Cadence EDA with the connection of a precise BSIM4 MOS transistor model, the possibility of the practical application of the proposed technique is shown using the example of a previously developed analytical model of a voltage multiplier. It is found that the use of the parameter refinement technique significantly reduces the errors of models of electronic devices based on integrated MOS transistors. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to study the free vibration of a Timoshenko–Ehrenfest single-walled carbon nanotube based on the nonlocal theory and taking surface effects into account. To model these effects on frequency response of nanotubes, we use Eringen's nonlocal elastic theory and surface elastic theory proposed by Gurtin and Murdoch to modify the governing equation. A modified version of Timoshenko nonlocal elasticity theory—known as the nonlocal truncated Timoshenko beam theory—is put forth to investigate the free vibration behavior of single-walled carbon nanotubes (SWCNTs). Using Hamilton's principle, the governing equations and the corresponding boundary conditions are derived. Finally, to check the accuracy and validity of the proposed method, some numerical examples are carried out. The impacts of the nonlocal coefficient, surface effects, and nanotube length on the free vibration of single-walled carbon nanotubes (SWCNTs) are evaluated, and the results are compared with those found in the literature. The findings indicate that the length of the nanotube, the nonlocal parameter, and the surface effect all play important roles and should not be disregarded in the vibrational analysis of nanotubes. Finally, the results show how effective and successful the current formulation is at explaining the behavior of nanobeams. [ABSTRACT FROM AUTHOR]

With the development of new technology and business innovation, firms are actively adjusting their channel choices. Some retailers operate a hybrid and special omnichannel structure referred to as New Retail promising to tightly integrate online and physical channels. In the meanwhile, some retailers such as Ross choose to only operate physical channels. In this paper, we provide insights into competing firms' retail-channel choices among online channel, physical channel, and omnichannel under the New Retail model. We find that firms' channel choices determine which channels compete directly with each other and hence the intensity of competition between firms. Firms' channel choices also give rise to three other effects-market expansion, consumer segmentation, and intrafirm cannibalization. The tradeoff among these effects along with the nature and intensity of competition determine the equilibrium channel structure in the market. The Internet and online channels have immensely transformed retailing, which has traditionally relied on brick-and-mortar and physical channels. In recent years, a hybrid and special omnichannel structure referred to as New Retail promising to tightly integrate online and physical channels has emerged within the industry; some industry experts tout New Retail as the future of retailing. For instance, in the New Retail model, retailers use physical stores not only as front ends for physical channel consumers but also as small local warehouses to serve online consumers. In this paper, we provide insights into competing firms' retail channel choices among online channel, physical channel, and omnichannel under the New Retail model. The online and physical channels could differ in terms of geographical market coverage, consumer shopping cost, and consumer valuation: An online channel can serve both city and remote (suburban) consumers, whereas a physical channel may only be able to serve city consumers, and consumers could have a lower shopping cost in the online channel than in the physical channel but a lower valuation for the online channel than for the physical channel. We find that an equilibrium in which at least one firm operates the omnichannel emerges only when consumers have a higher valuation for the physical channel. Moreover, neither firm would operate only the online channel in this case. In contrast, when consumers have a higher valuation for the online channel than the physical channel, neither firm is likely to operate the omnichannel. The market and channel characteristics have nonuniform and counterintuitive impacts on firms' profits under different equilibria. For instance, firms might not benefit from either increasing the differentiation between the channels within a firm or increasing the differentiation between channels across firms. Furthermore, an increase in the number of city consumers relative to suburban consumers can hurt the firm that serves only city consumers. The tradeoffs among interfirm competition, market expansion, consumer segmentation, and intrafirm cannibalization effects of firms' channel choices drive our findings. History: Giri Kumar Tayi, Senior Editor; Yifan Dou, Associate Editor. Supplemental Material: The online appendix is available at https://doi.org/10.1287/isre.2023.1198. [ABSTRACT FROM AUTHOR]

Air-to-air indirect evaporative cooling (IEC) systems are particular heat exchangers that use the latent heat of evaporation of water to cool down an air stream, without increasing its specific humidity, thus guaranteeing adequate thermohygrometric conditions in the refrigerated environment with low energy consumption. Dew-point indirect evaporative cooling (DIEC) systems are based on the IEC technology, but they recirculate a part of the air taken from the room to be refrigerated, in order to possibly achieve a lower air temperature. IEC and DIEC systems are becoming increasingly common these years, as they can ensure a good efficiency, minimizing the environmental impact of the air-conditioning system. Consequently, it has been necessary to develop models, both analytical and numerical, to quickly and accurately design this type of system and to predict their performance. This paper presents a review of the analytical and numerical models developed specifically for IEC and DIEC systems, highlighting their method, main innovations and advantages, and possible limitations. From this analysis, it emerged that analytical models have been developed since the late 1990s and only few of them are suitable for DIEC heat exchangers, while numerical models for both IEC and DIEC systems are gaining popularity in recent years. Almost all the analyzed models have been validated by comparison with numerical and/or experimental data, showing a maximum discrepancy within 10% in the majority of the cases. However, the validations were performed for a few specific cases, so in real applications it might be difficult to associate the model boundary conditions and the heat exchangers operating conditions, such as nozzles orientations, plates materials, water flow rates, and configurations. Another common limitation concerns the modeling of some properties, as wettability factor and air density, which might affect the accuracy of the results. [ABSTRACT FROM AUTHOR]

Propeller-crossing probability analysis is crucial for evaluating the impact resistance and foreign object exclusion capability of turboprop engines. However, due to the complex structure of the propeller and the uncertainties associated with the impact location as well as the flight attitude of the foreign object, developing a comprehensive model for analyzing the propeller-crossing process remains a significant challenge. This paper presents a novel simulation method that can obtain the probability of a foreign object successfully crossing the propeller using a high-fidelity structure model of the propeller and a comprehensive substituted model of the foreign object. To validate the performance of the proposed method, an analytical model is developed that takes into account the spatial structure constraints of the propeller and the foreign object. The proposed method is applied to calculating the probability of bird ingestion, and the results reveal that the increments in flight speed and aspect ratio of the bird have opposite effects on the propeller-crossing probability, and the values eventually converge to a constant value. [ABSTRACT FROM AUTHOR]

This paper presents an upset geometry sequence to determine the fracture forming limits in a wide variety of strain loading paths ranging from uniaxial compression to equibiaxial tension. The strains at fracture in principal strain space are obtained by combination of digital image correlation and experimental evolutions of the compression force versus time, and their representation in the effective strain versus stress triaxiality space is accomplished by means of a new analytical framework that uses the instantaneous slope of the strain loading paths. Modeling of the experimental strains at fracture by means of an uncoupled ductile fracture criterion built upon combination of the Cockcroft-Latham and McClintock criteria and fractography analysis using a scanning electron microscope allow understanding and characterizing the crack opening modes by shear and tension as well as the uncertainty region inside which mixed crack opening modes are observed. Results confirm that the overall philosophy and objectives underlying the new upset geometry sequence for determining the fracture forming limits in bulk forming resemble those of the Nakajima test that is commonly used in sheet forming. [ABSTRACT FROM AUTHOR]

In this paper, the air-gap flux density components in the eccentric surface-mounted phase modulation (SPM) machines are predicted analytically. In the provided model, the slotting effects of the armature are taken into account. In the modeling process, conformal transformations (CTs) are employed to obtain an equivalent concentric slotless machine for the eccentric slotted PM machine. To satisfy the condition of using CTs, i.e., having a Laplace equation, the PMs are replaced with an equivalent current sheet at the surface of the rotor. The approach of finding this current sheet is approved by the basis of the electromagnetic theory. One of the contributions of this paper is that the provided model is capable of modeling the eccentric SPM machines with any PM magnetization pattern by means of CTs. Substituting the predicted air-gap flux density components in the Maxwell stress tensor, the machine unbalanced magnetic force and its cogging torque are computed. Finally, the accuracy of the obtained results is evaluated by means of finite-element analysis. [ABSTRACT FROM PUBLISHER]

Factors such as insufficient heat dissipation and excessively high temperature can easily lead to demagnetization of the PMs in permanent-magnet (PM) motors. As a result, the magnetic field distribution of the motor will not be uniform, producing fault harmonics and lowering the operational performance of the motor. An essential stage in the diagnosis of faults and the monitoring of motor condition is the establishment of an accurate model of motors with demagnetization faults. In this paper, demagnetization faults are modeled by changing the Fourier coefficients in the Fourier expansion of the magnetization of PMs. This model can be used to determine the motor performance under various types of demagnetization, including radial air gap flux density, back electromotive force (EMF), and torque. On this basis, the corresponding relationship between the demagnetization degree and the fault signature is established, to provide a theoretical foundation for the subsequent demagnetization fault diagnosis. The finite element analysis (FEA) verifies the effectiveness and superiority of the proposed analytical model. The modeling method proposed in this paper can be applied to PM motors with PMs having different magnetization directions and shapes because it is based on the demagnetization region of PMs. [ABSTRACT FROM AUTHOR]

In the framework of the Cost Action CERTBOND (Reliable roadmap for certification of bonded primary structures), a wide group of researchers from 27 European Countries have had the opportunity to work on the topic of certification of bonded joints for primary structural applications from different engineering sectors such as the aerospace, automotive, civil engineering, wind energy and marine sectors. Since virtual testing and optimization are basic tools in the certification process, one of the key objectives of CERTBOND is to critically review some of the available models and failure theories for adhesive joints. The present paper summarizes the outcome of this task. Nine different models/theories are described in detail. Specifically, reviewed are the Classical Analytical Methods, the Process Zone Methods, Linear Elastic Fracture Mechanics (LEFM), the Virtual Crack Closure Technique (VCCT), the Stress Singularity Approach, Finite Fracture Mechanics (FFM), the Cohesive Zone Method (CZM), the Progressive Damage Modeling method and the Probabilistic methods. Also, at the end of the paper, the modeling of temperature effects on adhesive joints have been addressed. For each model/theory, information on the methodology, the required input, the main results, the advantages and disadvantages and the applications are given. [ABSTRACT FROM AUTHOR]

Highlights: Analytically modeling the effect of eccentricity on flexible crankshaft and piston secondary motion; Analytically modeling the eccentricity of the crankshaft; Analytically modeling the absolute value of the dynamic displacement of the center of the crankshaft; Showing how sensitive the dynamic displacement in flexible crankshafts is to the changes in its independent variables; Double experimental validation of the analytical models based on the eccentricity of the crankshaft and based on fatigue analysis; A proposed approach of fatigue failure analysis for vehicular dynamic components; A proposed nanostructure of crankshafts for improved structural mechanics. In spite of the fact that the flexibility of the crankshaft of diesel engines exhibits notable nonlinearities, analytical modeling of such nonlinearities is not yet realized. The present study thus analytically models the effect of eccentricity on flexible crankshaft and piston secondary motion. The eccentricity of the crankshaft is modeled as the summation of the hydrodynamic eccentricity and the dynamic mass eccentricity of the crankshaft. The study also models the absolute value of the vibrational dynamic displacement of the center of the crankshaft. The paper proves that such dynamic displacement of the center of the crankshaft is sensitive to the changes in its independent variables. It was found that the most influential parameters on the dynamic displacement of the center of the crankshaft due to vibration are the natural frequency and the eccentricity of the crankshaft. The modeling of the dynamic displacement in a flexible crankshaft was validated using a case study based on the eccentricity of the crankshaft showing a relative error of 4%, which is less than the relative error in the CMEM and GT-Power. Furthermore, the analytical modeling of the dynamic displacement in the flexible crankshaft was validated using another case study based on fatigue analysis of the crankshaft showing a relative error of 9%, which is less than that the relative error in Newman's model of diesel engine fuel consumption and Lansky's model of diesel engine cylinders. The paper also presents a proposed approach of fatigue failure analysis for vehicular dynamic components and presents a proposed nanostructure of crankshafts for improving such fatigue performance. The developed models would help develop efficient diesel engines and help prolong their service life. [ABSTRACT FROM AUTHOR]

In this paper, we develop an accurate analytical electrostatic potential model for both the n-type and p-type double-gate heterostructure tunnel field-effect transistors (H-TFETs). We solve the Poisson’s equation in four distinct regions inside the device, the depletion regions of the source, channel, and drain, and the drift-diffusion region of the channel, where the mobile charge carriers should be taken into account. It is shown that the model predicts the electrostatic potential profile of the various heterostructure devices with different material systems in all regions of the device operation accurately. The potential model is used for developing a model for the tunneling distance at the given energy level. Due to the physical nature of the models, the influence of the transistor parameters on the electrostatic characteristics of H-TFETs with desired heterojunction materials may be easily pursued. We show that the model results accurately predict the numerical simulation results for different device parameters. [ABSTRACT FROM AUTHOR]

Accurate solar power forecasting plays a critical role in ensuring the reliable and economic operation of power grids. Most of existing literature directly uses available weather conditions as input features, which might ignore some key weather factors and the coupling among weather conditions. Therefore, a novel solar power forecasting approach is proposed in this paper by exploring key weather factors from photovoltaic (PV) analytical modeling. The proposed approach is composed of three engines: 1) analytical modeling of PV systems; 2) machine learning methods for mapping weather features with solar power; and 3) a deviation analysis for solar power forecast adjustment. In contrast to the existing research that directly uses available weather conditions, this paper explores the physical knowledge from PV models. Different irradiance components and PV cell temperatures are derived from PV analytical modeling. These weather features are used to reformulate the input of machine learning methods, which helps achieve a better forecasting performance. Moreover, based on the historical forecasting deviations, a compensation term is presented to adjust the solar power forecast. Case studies based on measured datasets from PV systems in Australia demonstrate that the forecasting performance can be highly improved by taking advantage of the key weather features derived from PV models. [ABSTRACT FROM AUTHOR]

The current study analyzes the potential of an environmentally benign integration of a parabolic trough solar collector (PTSC) with a heat-intensive multi-effect evaporator (MEE) used in pulp and paper industry. Actual plant data was used to simulate the MEE and estimate the steam economy (SE) and steam consumption (SC), which are used to judge the performance of PTSC-MEE system. Four distinct alternatives for the integration are investigated with Self-adaptive Differential Evolution (SaDE) utilized for optimization. Initially, a normal PTSC with four different model configurations of MEE, basic or with energy reduction schemes (ERSs) are tested and found that SE is slightly increased for each. Next, a geometrically optimized/combinatorial optimized PTSC with basic MEE is examined, a rise of ∼3.4% in SE is noted for both, with current integration outperforming one out of three ERSs. Subsequently, geometrical plus combinatorial optimized PTSC with basic MEE is inspected, increase in SE reached 7.59% and two of the three ERSs outperformed. Economic analysis is conducted to estimate the steam saving with different PTSC-MEE systems and corresponding payback periods. The possibility of decarbonization with the various integration possibilities is also explored by evaluating the fuel savings and related CO 2 savings. • Integration of PTSC with an MEE used in pulp and paper industry is investigated. • The fusion of PTSC with MEE is studied with various possibilities. • Self-adaptive Differential Evolution (SaDE) is used for various optimizations. • The steam savings and payback times are estimated for various PTSC-MEE systems. • Decarbonization is studied by analyzing fuel savings and CO 2 reductions. [ABSTRACT FROM AUTHOR]

The ZL205A aluminum alloy is mostly used in automobiles, aircraft, aerospace, and other mechanical components, but now, it focuses on the study of its casting performance, and there is still a lack of research on its cutting performance. In this paper, the milling ZL205A aluminum alloy was milled for testing and simulation analysis. The milling test showed that the impact of the axial cutting depth, radial cutting depth, feed, and cutting speed on the milling force was successively reduced. A thermodynamic analysis model is proposed to evaluate the cutting force and tool design in milling. The model considers the front angle and friction angle of the tool, in which the friction angle is adjusted by the friction coefficient, the variable is the cutting parameter, the constant is fitted through the milling experiment, and the effectiveness of the model is verified to predict the milling force. The pre-grinding test was carried out before the experiment, and the stability of the test was proved by observing the macroscopic shape of the chip and the wear of the cutting edge. The model comprehensively considers the tool angle and quickly calculates the minimum load on the milling cutter based on the optimal geometric parameters, which can be used to optimize the milling cutter structure and provide a theoretical basis for the preparation of ZL205A aluminum alloy mechanical components. [ABSTRACT FROM AUTHOR]

After the closure of an underground mine, tunnels commonly become flooded and can be potentially exploited for its geothermal resource. Developing new methods for quantifying the energy content of this reservoir with a complex geometry is important to assess the economic value of its heat resource. The objective of this paper is to provide a first-order assessment of the geothermal potential of an underground mine using the Con Mine near Yellowknife, Northwest Territories, Canada, as an example. Field data allowed the development of an improved analytical approach to evaluate the geothermal potential of the Con Mine based on a thermal power budget. The sources considered in the thermal power budget are the thermal inertia of the water in the mine and the surrounding host rock, and the water that infiltrates the mine from nearby lakes. Analytical calculations are based on the finite linear heat source equation, considering cooled or heated water in the mine tunnels as heat sources or sinks. The geometry of the underground mine is consequently simplified to a linear heat source of equivalent length and fixed radius. The Thiem equation is used to calculate the water seeping into the mine. Results obtained with this approach and considering the operation of a geothermal heat pump system indicate a total energy of 17,520 MWh y−1 and 8234 MWh y−1 that can be delivered to buildings for heating and cooling purposes, respectively. This new approach provides an improvement to the volumetric method commonly used to assess geothermal resources. [ABSTRACT FROM AUTHOR]

In recent years, the doubly fed induction generator (DFIG)-based wind power generation and high-voltage direct-current (HVDC) transmission are widely utilized in practice. The stability issues of sending AC grid, which is composed of line-commutated converter (LCC)-based HVDC and DFIG system, is worthy of attention. Commutation is an important factor in the impedance model of LCC-HVDC rectifier, due to the nonnegligible leakage inductance of transformer. However, it was overlooked in previous studies because there are many difficulties in modeling commutation overlap characteristic. In this paper, the spectral models of voltage and current mapping functions are proposed by 3-D Fourier series method, in which the commutation overlap angle is considered. Then, based on the concept of harmonic linearization, an analytical model that describes the commutation process is established and validated by simulations. The mechanism that the commutation overlap characteristic affects the impedance model of LCC-HVDC is investigated, and the simplified modeling method in different frequency bands is studied. The stability of sending AC grid is analyzed applying the Generalized Nyquist Criterion (GNC). The results of stability analysis show that the effect of commutation overlap cannot be ignored. The simulation results confirm the correctness of the obtained conclusion. [ABSTRACT FROM AUTHOR]