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This article proposes model-based homogeneity (MBH) to extend compressed sensing (CS) for landmine-detection ground penetrating radar (GPR). Conventional CS methods have difficulty in distinguishing landmines from clutter, since it principally pays attention to signal magnitude. In contrast, our method visualizes landmines based on homogeneity of high-dimensional scattering features in a spatial model. It realizes both the exclusion of clutter and the reduction of measurement points. Experiments demonstrate that the total measurement and processing time are reduced to one-twentieth of a conventional dense measurement case. We also investigate the influence of model size and number of landmines on the performance. The proposed method is capable of visualizing any objects having respective shapes by configuring corresponding models. [ABSTRACT FROM AUTHOR]

We propose an approach for uncovering characteristic response paths of a population from an individual-level multivariate time series data set. The approach is based on a model that accommodates a set of arbitrary distributions for endogenous variables and interstep intervals and variables. The model enables reliable estimation of individual-level parameters by uncovering and statistically pooling clusters of similar individuals. We show that using such a model one can distribute the response of an outcome variable to an impulse over all possible preceding activity sequences. When a few such sequences explain most of the response, they describe the population's characteristic response paths from the impulse to the outcome. We apply the proposed approach to a customer touchpoint data set from a large multichannel specialty retailer. This application uncovers six customer segments, each with unique characteristic paths to purchase. These paths provide insights into the behavior of customers and the optimal over-time communication strategy for different customer segments. Summary of Contribution: Uncovering users' paths through physical and virtual spaces has been of considerable interest in the computing and operations research domain. The existing research suggests a demand for visualizing the primary paths of agents through geographic, online, and activity spaces. Thus far, most of the research have developed approaches that are unique to specific domains providing insight into the domain in the process. There is a need for a general statistically robust approach that can be applied to a broad range of domains to uncover variable sequences that lead to outcomes of interest. We propose a computational approach to uncover characteristic response paths of a population from an individual-level multivariate time series data set. The approach is based on a statistical model that accommodates arbitrary and mixed set of distributions for the endogenous variables, accommodates intersession intervals and variables, and reliably estimates individuals' parameters through statistical pooling by uncovering clusters of similar members. These features make the proposed model suitable for a large variety of real-world datasets. We show that using such a model one can extract characteristic paths over possible activity sequences starting from an impulse leading up to a target variable of interest. [ABSTRACT FROM AUTHOR]

Electric vehicles (EVs) have garnered significant attention as a vital driver of economic growth and environmental sustainability. Nevertheless, ensuring the safety of high-energy batteries is now a top priority that cannot be overlooked during large-scale applications. This paper proposes an innovative active protection and cooling integrated battery module using smart materials, magneto-sensitive shear thickening fluid (MSTF), which is specifically designed to address safety threats posed by lithium-ion batteries (LIBs) exposed to harsh mechanical and environmental conditions. The theoretical framework introduces a novel approach for harnessing the smoothed-particle hydrodynamics (SPH) methodology that incorporates the intricate interplay of non-Newtonian fluid behavior, capturing the fluid-structure coupling inherent to the MSTF. This approach is further advanced by adopting an enhanced Herschel-Bulkley (H-B) model to encapsulate the intricate rheology of the MSTF under the influence of the magnetorheological effect (MRE) and shear thickening (ST) behavior. Numerical simulation results show that in the case of cooling, the MSTF is an effective cooling medium for rapidly reducing the temperature. In terms of mechanical abuse, the MSTF solidifies through actively applying the magnetic field during mechanical compression and impact within the battery module, resulting in 66% and 61.7% reductions in the maximum stress within the battery jellyroll, and 31.1% and 23% reductions in the reaction force, respectively. This mechanism effectively lowers the risk of short-circuit failure. The groundbreaking concepts unveiled in this paper for active protection battery modules are anticipated to be a valuable technological breakthrough in the areas of EV safety and lightweight/integrated design. [ABSTRACT FROM AUTHOR]

Intercalation of lithium ions into the electrodes of lithium ion batteries is affected by the stress of active materials, leading to energy dissipation and stress dependent voltage hysteresis. A reaction-diffusion-stress coupling model is established to investigate the stress effects under galvanostatic and potentiostatic operations. It is found from simulations that the stress hysteresis contributes to the voltage hysteresis and leads to the energy dissipation. In addition, the stress induced voltage hysteresis is small in low rate galvanostatic operations but extraordinarily significant in high rate cases. In potentiostatic operations, the stresses and stress induced overpotentials increase to a peak value very soon after the operation commences and decays all the left time. Therefore, a combined charge-discharge operation is suggested, i.e., first the galvanostatic one and then the potentiostatic one. This combined operation can not only avoid the extreme stress during operations so as to prevent electrodes from failure but also reduce the voltage hysteresis and energy dissipation due to stress effects. [ABSTRACT FROM AUTHOR]

This article demonstrates the design of charging strategies for lithium ion batteries with considering the balance between diffusion induced stress and total charge time for two- and three-stage charge methods. For the two-stage galvanostatic-potentiostatic charge method the low mechanical stress can be achieved without increasing total charge time by switching the galvanostatic to the potentiostatic at the time moment when the lithium concentration at the surface of particles reaches the limit c ¯ surf = 0 . A three-stage method, which consists of an initial galvanostatic stage of high current, a galvanostatic stage of low current and a potentiostatic ending stage, is suggested. Employing the initial galvanostatic stage of high current is helpful not only in accelerating the charge process, but also in controlling the mechanical stress once the electrical current and time duration of the initial galvanostatic stage are properly designed. [ABSTRACT FROM AUTHOR]

The state of charge (SOC) or the depth of discharge (DOD) to and the time to delamination onset and the critical size for delamination, which are potentially important in lithium ion battery design for preventing the patterned thin film electrodes from delamination, are investigated. A theoretical approach based on the cohesive model is proposed to formulate the time to and the SOC (or DOD) to delamination onset, as well as the critical size for patterned disk-like electrodes. It is found that for negative electrode the delamination initiation is dominated by mode-II during cell charging and by mode-I during cell discharging. For positive electrode both delamination modes are theoretically possible during cell charging. When the electrochemical load factor i ¯ is very high, the mode-I delamination is possible and an optimal size of electrodes exists for a given maximum i ¯ . The SOC to mode-II delamination onset decreases significantly with increasing dimensionless radius, being independent of i ¯ . When the mode-II is the dominated mode the critical size for delamination exists, and a formula for the critical size for delamination has been deduced, which is proportional to interface ductility and inversely proportional to maximum volumetric strain. [ABSTRACT FROM AUTHOR]

Abstract: This paper proposes a strategy to reduce the diffusion induced stress and enhance the capacity of a layered electrode by allowing the plastic deformation of current collector. Based on analytical formulations of the stress in whole electrode, three types of elastoplastic behaviors of current collector, i.e. pure elastic deformation, plastic shakedown and cyclic plasticity, are identified. Criterions separating the three cases are proposed. It is found applying a thin current collector and allowing it to plastically yield in the charge/discharge cycles is beneficial not only to capacity as more space can be provided for active materials but also to electrochemical stability because the stress in active layer is significantly reduced. Structural design corresponding to plastic shakedown shows good balance between the said improvements and structural safety, whereas the case of cyclic plasticity further enhances the improvements. Therefore, structural designing scheme is provided for the former case according to the criterion of plastic shakedown but for the latter one based on the Coffin–Manson relation with expected cycle life. [Copyright &y& Elsevier]

In this article, we propose a unified geolocation framework to automatically determine where on the earth a web video was shot. We analyze different social, visual, and textual relationships from a real-world dataset and find four relationships with apparent geography clues that can be used for web video geolocation. Then, the geolocation process is formulated as an optimization problem that simultaneously takes the social, visual, and textual relationships into consideration. The optimization problem is solved by an iterative procedure, which can be interpreted as a propagation of the geography information among the web video social network. Extensive experiments on a real-world dataset clearly demonstrate the effectiveness of our proposed framework, with the geolocation accuracy higher than state-of-the-art approaches. [ABSTRACT FROM AUTHOR]

The interfacial debonding between the active layer and the current collector has been recognized as a critical mechanism for battery fading, and thus has attracted great efforts focused on the related analyses. However, much still remains to be studied regarding practical methods for suppressing electrode debonding, especially from the perspective of mechanics. In this paper, a pre-strain strategy of current collectors to alleviate electrode debonding is proposed. An analytical model for a symmetric electrode with a deformable and limited-thickness current collector is developed to analyze the debonding behavior involving both a pre-strain of the current collector and an eigen-strain of the active layers. The results reveal that the well-designed pre-strain can significantly delay the debonding onset (by up to 100%) and considerably reduce the debonding size. The critical values of the pre-strain are identified, and the pre-strain design principles are also provided. Based on these findings, this work sheds light on the mechanical design to suppress electrode degradation. [ABSTRACT FROM AUTHOR]

Abstract: A semi-analytical method based on the cohesive model has been developed to investigate the progressive growth of interface delamination in an axisymmetric thin film electrode driven by diffusion-induced stresses under the assumption that the electrode remains elastic during the Li-ion diffusion process. The evolutions of the cohesive zone and debonding zone with respect to charging time have been predicted. The cohesive zone propagates in an accelerating manner and the debonding zone advances in a slowing down manner. The key parameters that control the interfacial stresses and delamination have been identified from the obtained governing equations. And according to the discussions on the key parameters, design insights into the geometry, charging velocity and material properties of the electrode have been provided. [Copyright &y& Elsevier]

Abstract This article sheds light on advantages of fast charging methods with time-varying current. Analytical solutions of concentration and stress for charging processes with general time-varying currents are derived. A fast charging protocol for a multistage constant current of gradually decreasing value is first evaluated. A properly designed multistage constant-current method is able to simultaneously suppress stress overflow and accelerate charging, but stress undulation induced by sharp switching between stages is inevitable. A charging scheme with a nonlinear exponential current is then investigated. The applied current varies continuously and smoothly with time so stress undulation is avoided. Suggestions for the design of an exponential current method are proposed to achieve the best charging acceleration without sacrificing charging capacity or increasing risk of mechanical failures. A well-designed exponential-current method is superior to a multistage constant-current method in accelerating charging speed. [ABSTRACT FROM AUTHOR]

Due to the complex mesostructure and components of composite active layers in lithium-ion battery (LIB) electrodes, coupled with the concentration-dependent material properties and eigenstrains, efficiently estimating the effective modulus of the active layers remains a great challenge. In this work, the classic Mori–Tanaka method is found to be unable to estimate the modulus of the active layer. By realizing the importance of the mesostructure feature, a rod-rod model is proposed. The resulting modulus is expressed analytically. It is shown that the rod-rod model can accurately estimate the modulus evolution of the active layer if the material properties of the components and the evolution of volume fractions are known in advance. Moreover, a simplified rod-rod model is also developed to reduce the complexity of the proposed method. By knowing the volume fractions at two arbitrary states of charge and subsequently determining two constants, the simplified model can estimate the modulus efficiently. Considering both its accuracy and its simplicity, the simplified rod-rod model is the most suitable for the estimation. Thus, the methods developed in this work provide a new perspective for analyzing the material properties of composite active layers in LIB electrodes. [ABSTRACT FROM AUTHOR]

Bilayer electrode, composed of a current collector layer and an active material layer, has great potential in applications of in-situ electrochemical experiments due to the bending upon lithiation. This paper establishes an elastoplastic theory for the lithiation induced deformation of bilayer electrode with consideration of the plastic yield of current collector. It is found that the plastic yield of current collector reduces the restriction of current collector to an active layer, and therefore, enhances in-plane stretching while lowers down the rate of electrode bending. Key parameters that influence the elastoplastic deformation are identified. It is found that the smaller thickness ratio and lower elastic modulus ratio of current collector to an active layer would lead to an earlier plastic yield of the current collector, the larger in-plane strain, and the smaller bending curvature, due to balance between the current collector and the active layer. The smaller yield stress and plastic modulus of current collector have similar impacts on the electrode deformation. [ABSTRACT FROM AUTHOR]

Prelithiation has been intensively investigated in high-capacity lithium-ion batteries (LIBs). However, the optimization of prelithiation degrees for long service life of LIBs still remains a challenge. The positive efffect of prelithiation on suppressing degradation of LIBs, besides directly pursuing the high first Coulomb efficiency which has been widely reported in the literature, is revealed and discussed based on an analytical model focusing on the interfacial delamination in electrodes. For full charge-discharge cycling, well-designed prelithiation can effectively suppress the delamination and reduce the debonding size by approximately 25%, compared with the case without prelithiation. For the strategy combining partial charge-discharge cycling and prelithiation, the largest reversible capacity without debonding can be significantly improved by approximately 100% with well-designed prelithiation. This work is expected to provide a prelithiation design principle and further improve the mechanical stability of LIB electrodes. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, structural configuration of layered Li-ion battery electrode plates is evaluated by analytically formulating the diffusion induced stress. Both symmetric electrode and asymmetric bilayer electrode are discussed. The thickness ratio and the modulus ratio of current collector to active plate are analytically identified to be the important influence parameters on the stress. Applying a material with smaller elastic modulus for current collector could reduce the peak stresses in both current collector and active plate. Increasing the thickness of current collector would reduce the stress in itself while promote the stress in active plate. Therefore, from mechanical viewpoint on designing an electrode, the material for current collector should be as soft and flexible as possible. And the thickness of current collector should be in an appropriate range. Basically, it should be as small as possible on the precondition that the mechanical strength is satisfied. Finally, effects of three charging conditions, i.e. uniform, galvanostatic, and potentiostatic, on the diffusion induced stress is discussed. It is found the maximum stresses for three cases are linear to the total amount of intercalated lithium ions. Based on the stresses, an optimized charging operation, i.e. first galvanostatic followed by potentiostatic, is suggested. [Copyright &y& Elsevier]

Volatile organic solids, such as cyclododecane or menthol, have been employed as temporary reinforcement material during archaeological excavations. They are usually applied as melts and reinforcement is achieved once the melts solidify. Such solidification process can induce internal stress on the artifacts, which can be a big concern, especially to those very precious and fragile ones. However, information about such stress is still extremely limited at present. This paper proposes an experimental method based on resistance strain gauge technique to monitor the deformation induced by solidification of menthol melt. Bending tests are performed on very thin glass slides. The solidification process of menthol melt is well characterized by the development of mechanical strains. Then, menthol melts are applied to three kinds of simulated samples, i.e. glass, sandstone and rice paper, to investigate the mechanical response of preserved bodies upon solidification. It is found that menthol melt will generate certain amount expansion or contraction of the objects upon solidification. The stresses induced, evaluated according to obtained strains, are generally quite small, indicating that application of menthol as reinforcement material is safe in mechanics for cultural relics. [ABSTRACT FROM AUTHOR]

[Display omitted] • This work designed Ni 35 Cu 15 Zr 15 Ti 35 MG ribbon as a dealloying precursor. • Flexible porous Cu x O/NiO photo-assisted hybrid electrode was synthesized. • The photoelectrode exhibits an intriguing multi-layered porous architecture. • The photoelectrode demonstrates the enhanced energy storage with light radiation. • The mechanism of photo-assisted charging supercapacitors was investigated. With the utilization of sustainable sunlight efficiently, it is of paramount important to develop a new type of electrode for boosting photo-assisted supercapacitor performance. Herein, this work originally designs the Ni 35 Cu 15 Zr 15 Ti 35 metallic glass (MG) ribbon as dealloying precursor. Benefiting from the different oxidation behavior of Ni and Cu metals during the dealloying and anodizing processes, a new type of multi-layered porous hybrid photoelectrode (namely Cu x O/np-NiCu@NiCuO/MG, x = 1, 2) that simultaneously achieve the flexible, hierarchical porous structure as well as the NiO/Cu 2 O heterojunction, are successfully synthesized. An intriguing multi-layered structure consists of the outermost photosensitive Cu x O nanowire layer formed by the anodizing technique, the nanoporous NiCu@NiCuO layer just beneath the nanowire layer via the dealloying as well as the glass central layer offering an excellent flexibility. In particular, 3D interconnected hierarchical porous structure is benefit to the penetration and utilization of visible light efficiently. The photoelectrode demonstrates a maximum specific capacitance of 1182.2 F cm−3 with light irradiation, which is 18% higher than that without light. This photo-assisting charging for the supercapacitor is ascribed to the combination of photosensitive Cu x O and pseudocapacitive NiO components. Moreover, the photoelectrode exhibits an excellent flexibility and the photocurrent response is basically unchanged after bending for 1000 times. The aqueous supercapacitor shows a maximum energy density of 44.9 mWh cm−3 under light. This work provides new insights into the development of next generation wearable photo-assisted supercapacitor. [ABSTRACT FROM AUTHOR]

Abstract Partial lithiation strategies for silicon composite electrodes are experimentally investigated in this article. Two types of partial lithiation, i.e. voltage- and capacity-control strategies, are presented. Capacity loss and irreversibility of silicon electrodes are significantly suppressed by either partial lithiation strategy without any complicated modifications or treatments. The capacity of partially lithiated silicon electrodes is even higher than that of fully lithiated one after certain cycles. The images of scanning electron microscope suggest that the mechanical damage generated in partially lithiated electrodes is less than that in fully lithiated one. Furthermore, after dozens of cycles with partial lithiation, capacity decay also slows down in subsequent full charge-discharge cycles. The presented experimental results suggest that the partial lithiation strategy relieves the coupled mechanical-electrochemical degradation and is a promising approach for the long-term use of silicon composite electrodes. [ABSTRACT FROM AUTHOR]

A fully coupling model for the diffusion induced finite elastoplastic bending of bilayer electrodes in lithium-ion batteries is proposed. The effect of the mechanical stress on the lithium diffusion is accounted for by the mechanical part of the chemical potential derived from the Gibbs free energy along with the logarithmic stress and strain. Eight dimensionless parameters, governing the stress-assisted diffusion and the diffusion induced elastoplastic bending, are identified. It is found that the finite plasticity starting from the interface of the bilayer increases the chemical potential gradient and thereby facilitates the lithium diffusion. The full plastic flow makes the abnormal lithium concentration distribution possible, i.e., the concentration at the lithium inlet can be lower than the concentration at the interface (downstream). The increase in the thickness of the active layer during charging is much larger than the eigen-stretch due to lithiation, and this excess thickening is found to be caused by the lithiation induced plastic yield. [ABSTRACT FROM AUTHOR]

This paper discovers and reveals a phenomenon of feigned death induced by partial delithiation in silicon composite electrodes. Unexpected extremely rapid capacity fading occurs in the initial dozens of the cycles with low upper cut-off voltages. By looking into the irreversibility, the crack, the elemental analysis and the thickness/weight of the electrode, it suggests that the rapid capacity fading is not induced by degradation. Additionally, by providing a reboot with full delithiation, the capacity can be recovered completely, which confirms the integrity of the electrode. This novel type of capacity fading is named by "feigned death" to distinguish it from the "true death" caused by degradation. It is further confirmed that the feigned death is caused by the asymmetric phase transformation between crystalline and amorphous phases in silicon electrodes. When the depth of lithiation is high enough to generate the c-Li 3.75 Si phase but the depth of delithiation is too low to eliminate the generated crystalline phase, the feigned death is triggered. The findings of this work provide an in-depth understanding of the electrochemical performance of Si-based electrodes. • The impact of partial delithiation on cycling performances of silicon electrodes is revealed. • Feigned death of silicon electrodes is discovered. • Feigned death is caused by the asymmetric phase transformation of lithiated silicon. [ABSTRACT FROM AUTHOR]

An analytical model of mechanical contact problems in composite electrodes of lithium-ion batteries is developed in this article. Two typical types of mechanical contact, namely contact between particles and contact between particle and current collector, are investigated. Key parameters that affect the contact problem are identified from the analytical solution. High uniformity of the particle size is found to be critical to the electrode. Furthermore, a soft current collector could significantly reduce the contact stress and hence is also suggested. It is figured out that contact stress is comparable to or even higher than the diffusion-induced stress under free-expansion state, even if the mechanical constraint in electrodes is weak. To highlight the significance of contact stress, an electrochemical cycling verification experiment which involves a charging pause is conducted. Both analytical and experimental results indicate that the mechanical contact plays a crucial role in the evaluation of mechanical stability of lithium-ion battery electrodes. • Analytical solutions of PP and PC contact are established. • The contact stress can be higher than the diffusion-induced stress. • The stress within the active particle is mainly induced by mechanical contacts. [ABSTRACT FROM AUTHOR]