83 results about "Acoustic attenuation" patented technology

The invention relates to a fruit maturity nondestructive intelligent detection method and system based on high-frequency dynamic excitation and acoustic vibration signal analysis. The method comprises the following steps: controlling an excitation device to apply high-frequency transient mechanical excitation to a fruit; synchronously collecting a vibration response signal on the surface of the fruit and an internal sound wave signal; extracting dynamic feature vectors including formant characteristics, sound wave attenuation coefficients and time domain attenuation constants from the sound vibration signals; inputting the feature vector into a time sequence convolutional network model to obtain a final maturity grade and a judgment confidence coefficient; and starting an active learning mechanism for a low-confidence sample, and continuously optimizing the model through manual annotation and incremental learning. By detecting the internal physical characteristics of the fruits, the defects that the traditional visual and tactile methods are interfered by surface states and the internal maturity is difficult to judge are overcome, and rapid, lossless and high-precision intelligent detection of the maturity of the fruits with self-evolution capability is realized.

This disclosure provides a wedge and design method for a multipath acoustic attenuation phased array ultrasonic testing probe. The wedge includes a wedge body, multiple silencing grooves, and a damping block. The extension direction, spacing, and depth of each silencing groove are configured such that at least a portion of the reflected transverse wave generated at the detection surface can be guided to an attenuation interface formed by the groove wall of the silencing groove and the damping block. Furthermore, the reflected longitudinal wave generated at the detection surface undergoes at least six interface reflections within the wedge body before returning to the probe direction. The acoustic characteristics of the damping block are configured to absorb the reflected transverse wave. The reflected transverse wave is attenuated at the attenuation interface through a combination of scattering by the silencing groove and absorption by the damping block. After at least six interface reflections, the acoustic component of the reflected longitudinal wave returning to the probe direction forms a 180° phase difference with the incident longitudinal wave emitted by the probe, thus being attenuated through phase interference.

The invention relates to a method for influence of dislocation dipole defects in an aluminum matrix on acoustic parameters, belongs to the technical field of discrete solution, and provides a novel molecular dynamics simulation method for researching ultrasonic sound velocity, sound attenuation and acoustic nonlinear parameter change on the basis of two dislocation dipole structures. The method specifically comprises the following steps: controlling the type and the number of dislocation dipoles in an aluminum matrix, carrying out atomic scale acoustic simulation on dislocation dipole models of different types and numbers by adopting a phase inversion technology, extracting sound velocity by adopting a cross correlation method, extracting sound attenuation by adopting a Hilbert transformation method and extracting acoustic nonlinear parameters by adopting an FFT method aiming at four-phase signals; and precise extraction of acoustic parameters is realized. And determining the contribution of the dislocation defect to the acoustic parameters based on the relationship fitting of the three acoustic parameters and the dislocation defect, thereby realizing the prediction from the acoustic parameters to defect characteristics.

The invention discloses an ultrasonic sound attenuation display method and ultrasonic equipment, and the method comprises the steps: displaying an interface used for selecting a sound attenuation scanning mode, scanning a target tissue based on a first sound attenuation scanning mode in response to a first selection instruction, and obtaining a multi-frame sound attenuation result of a first target region of the target tissue; displaying a multi-frame sound attenuation statistical index of the first target area according to the multi-frame sound attenuation result of the first target area; under the condition that the multi-frame sound attenuation statistical index of the first target area does not meet a first index condition, first abnormity prompting is carried out; in response to the second selection instruction, scanning the target tissue based on a second sound attenuation scanning mode to obtain a single-frame sound attenuation result of a second target area of the target tissue; displaying a single-frame sound attenuation statistical index of the second target area according to the single-frame sound attenuation result of the second target area; and under the condition that the single-frame sound attenuation statistical index of the second target area does not meet a second index condition, carrying out second abnormity prompting.

The invention provides an ultrasonic plane wave multi-mode cooperative imaging method and system, and the method comprises the steps: controlling an ultrasonic probe to execute shear wave elastic imaging and sound attenuation imaging of which the mechanical index is equal to or greater than a first threshold value based on a multi-level voltage control scheme; and executing super-resolution imaging with the mechanical index smaller than or equal to a second threshold value after the super-resolution imaging is completed. The method comprises the following steps: acquiring a sound attenuation coefficient graph generated in a sound attenuation imaging process, and respectively acquiring a first super-resolution graph without contrast agent perfusion, a second super-resolution graph with contrast agent perfusion and a tissue elasticity graph generated in a shear wave elasticity imaging process based on an ultrafast plane wave technology; performing post-processing on the collected first super-resolution graph to generate a probability density graph of the tissue structure, and performing post-processing on the collected second super-resolution graph to generate a microbubble tracking speed graph; and carrying out cooperative imaging on the tissue elasticity map, the sound attenuation coefficient map, the probability density map and the velocity map. The imaging comprehensiveness and accuracy are improved, and early lesion diagnosis is facilitated.

An ultrasonic diagnostic imaging system and method produce attenuation coefficient maps of a region of interest in an ultrasound image. In order to detect the presence of elevation aperture blockage, the system estimates attenuation coefficients by two different methods. The estimates produced by the two different methods are combined to produce a metric, which is evaluated as a function of depth. If the metric satisfies one or more criteria of measurement bias, elevation aperture blockage is identified and an alert of the blockage is produced for the user.

Propulsion assembly for an aircraft, comprising a turbomachine (1), an attachment strut (40) and a structural element (10) carrying the turbomachine (1) by the attachment strut (40), the turbomachine having at least one rotating part (30) rotating about an axis of rotation (A), the rotating part (30) being arranged upstream of the structural element (10) and of the attachment strut (40) so that the air jet exiting from the rotating part (30) impacts the structural element (10) and the attachment strut (40) in the wake thereof, the leading edge of the structural element (10) and / or of the attachment strut (40) locally comprising at least one acoustic attenuation device (50, 60, 70, 80) arranged at least partially in the wake of the rotating part (30), the acoustic attenuation device being a partial modification of the structure and / or of the profile of the leading edge (11).

Acoustic attenuation assembly for a motor vehicle brake pedal assembly and a vehicle comprising such an assembly. The invention relates to an acoustic attenuation assembly for a vehicle brake pedal assembly (7), comprising: - an apron (9) behind which a passenger compartment is arranged and in front of which an engine compartment is arranged, - a brake pedal assembly (7), comprising a bracket (21) adapted to support a brake pedal actuated from said passenger compartment, fixed to said apron (9) and extending into said passenger compartment, - a brake amplifier (15), comprising an actuating rod (19) for a hydraulic control of a braking system passing through a cutout (23) made in said apron (9) and extending into a cavity (25) of said bracket.According to the invention, the assembly includes an acoustic attenuation device (27) radially connecting said clevis (21) and said actuating rod (19), comprising an acoustic attenuation material suitable for attenuating sound waves passing through it. Figure 3.

The invention relates to the technical field of medical image processing, in particular to a kidney ultrasonic image-based fibrosis quantitative evaluation method and system, and the method comprises the steps: obtaining an ultrasonic image, carrying out the standardization processing, and estimating a system response correction function and an optical flow field; selecting a key frame based on an optical flow field, performing registration and constructing pose map optimization, fusing a envelope to establish mapping between a cortical conformal coordinate system and a key frame pixel, and generating a cortical region probability field and a boundary uncertainty field; calculating a sound attenuation coefficient and a scattering statistical parameter in the sliding analysis window, correcting the sound attenuation coefficient and the scattering statistical parameter, projecting the sound attenuation coefficient and the scattering statistical parameter to a conformal coordinate system, carrying out Wasserstein gravity center fusion according to probability and uncertainty weighting, detecting the effective thickness of the cortex, and carrying out consensus optimization to obtain a fibrosis fraction field and a consensus residual field; and generating a non-consistency total score, outputting a confidence interval and a confidence level through conformal prediction calibration, and generating a fallback recalculation or re-collection instruction if necessary. The cross-view, cross-time and cross-equipment consistency is improved, and the closed-loop quality control capability is achieved.

The application is a method for the influence of dislocation dipole defects in aluminum matrix on acoustic parameters, belonging to the technical field of discrete solution, and provides a new molecular dynamics simulation method for researching the changes of ultrasonic velocity, acoustic attenuation and acoustic nonlinear parameters based on two dislocation dipole structures, specifically, the types and quantities of dislocation dipoles in the aluminum matrix are controlled, the atomic scale acoustic simulation is carried out on the dislocation dipole models of different types and quantities by using the phase inversion technology, the cross correlation method is used to extract the sound velocity, the Hilbert transform method is used to extract the sound attenuation, and the FFT method is used to extract the acoustic nonlinear parameters for the four-phase signals, so as to realize the precise extraction of acoustic parameters. Based on the fitting relationship between the three acoustic parameters and the dislocation defects, the contribution of the dislocation defects to the acoustic parameters is determined, and the prediction from the acoustic parameters to the defect characteristics is realized.

The application provides an ultrasonic attenuation compensation method and device and electronic equipment, for each point of interest in an ultrasonic image, a sound channel is determined according to a plurality of ultrasonic transmitting elements arranged on an ultrasonic probe; for each sound channel, target data of each pixel point on the sound channel is obtained from the ultrasonic image; and according to the target data, an ultrasonic attenuation value for the point of interest is calculated to compensate ultrasonic energy emitted to the point of interest. According to the method, the sound channel is determined according to each point of interest in the ultrasonic image in combination with the ultrasonic transmitting elements, and then the ultrasonic attenuation value for the point of interest is determined according to the target data such as the gray value and TGC value of each pixel point on the sound channel. Since the target data of different pixel points can reflect the heterogeneity of the acoustic impedance of different individuals, the accuracy of the obtained ultrasonic attenuation value can be improved, and the accuracy of the compensation of the ultrasonic energy is improved.

This invention provides an indoor air quality monitoring device and sensor collaborative control system, relating to the field of indoor environmental monitoring technology. It addresses the problems of response lag, temperature drift accumulation, and decreased alarm reachability that occur during long-term operation of air monitoring devices. By treating structural influences as a first-type input and unifying their parameterization, the device achieves feedforward identification and closed-loop suppression of sample degradation, filter material contamination and misalignment, internal thermal drift, and acoustic attenuation. The sampling confirmation window is adaptively adjusted to reduce false alarms; channel-level temperature drift compensation and power derating are prioritized and executed collaboratively for steady-state temperature control; the alert link maintains subjective loudness consistency based on equivalent gain; and the baseline is refreshed after maintenance to maintain long-term consistency. Thus, without altering the mechanical form, the device significantly improves monitoring accuracy, stability, and alarm reachability, highlighting the value of structure-aware driven device-level design.

This invention relates to the field of marine engineering and structural health monitoring technology, specifically a three-dimensional identification method for overburden fissures in submarine tunnels. When there are no fissures in the propagation path between the acoustic signal transmitter and receiver, the received signal is stable; however, when fissures exist in the path, the received signal will show significant attenuation or a sharp drop. This invention achieves online, rapid, and accurate detection of overburden fissures in submarine tunnels through a multi-source spatial superposition identification algorithm based on acoustic attenuation characteristics. Utilizing the principle of multi-path superposition, it can eliminate single-path measurement errors and improve positioning accuracy. The system has a high degree of automation, can quickly acquire and process signals, and meets the online monitoring needs during construction. The equipment is flexible in installation; the transmitter only needs to be placed outside the overburden layer, reducing modifications to the internal structure of the tunnel.

An EMI shielding and acoustic attenuation door frame and door system, including: a door connected to a door frame with a hinge, the door including a bottom portion having a plate, a door gasket, a door sponge, and conductive tape for grounding the door; the door frame including: a jamb section including: a jamb main frame; a jamb back frame; wherein the jamb main frame and back frame being adjustable along the wall; a layered jamb gasket at least partially in between the door frame and the jamb main frame; a flanged magnetic jamb gasket fixed to an acoustical retainer with a fastener; wherein the door is grounded when the door is in a closed position against the door frame; a sill section including: a spreader bar having at least one sill gasket covered by a threshold, the spreader bar and at least one sill gasket contacting a floor shielding.

The invention provides a DAS water content identification method based on shaft axial acoustic attenuation characteristics. The method comprises the following steps: acquiring DAS acoustic time-domain signals of a plurality of axial positions of a shaft by using a distributed optical fiber; performing preprocessing and frequency domain transformation on the time domain signal to obtain an acoustic frequency spectrum distributed along the axial direction of the shaft; according to the law that the acoustic spectrum amplitude changes along with the position, calculating an acoustic space attenuation feature alpha (f) by adopting least square fitting based on the distance; constructing an attenuation spectrum based on the spatial attenuation characteristics, and extracting attenuation characteristic parameters related to the moisture content from the attenuation spectrum; constructing a training set and establishing a support vector machine (SVM) moisture content identification model based on a radial basis function (RBF); and inputting the actual attenuation characteristic parameters into the trained SVM model to obtain the predicted moisture content. The invention further discloses a water content identification system for executing the method and a storage medium, and the system and the storage medium are suitable for identifying the water content of the oil well shaft fluid.

An ultrasound probe includes an ultrasound transducer stack comprising one or more ultrasound transducers emitting an acoustic signal, and an acoustic window passing the acoustic signal. The acoustic window is composed of a butadiene-based compound. In one or more embodiments, the acoustic window is made of butadiene rubber. Butadiene rubber has acoustic characteristics that may be suitable for acoustic windows, as subsequently discussed. Specifically, the use of butadiene rubber may result in desirable acoustic attenuation, acoustic velocity and acoustic impedance.

A method employing the principle of mechanical reciprocity to image the relative acoustic attenuation called shear wave reciprocity imaging (SRI). SRI does not require the pre-stored sample signal for acoustic attenuation evaluation. In SRI, sequential marching pushes similar to acoustic radiation force impulse (ARFI) imaging are excited from an array transducer, and the reciprocal displacements are collected similarly to the plane wave single-track location method (p-STL).

This utility model relates to the field of ventilation and noise reduction technology, and discloses a silencing box, including a box body assembled from several silencing panels; an air inlet is provided on one side of the box body, and an air outlet is provided on the opposite side; wherein the air inlet and air outlet are at different heights; a partition component assembled from the silencing panels is disposed within the box body to divide the box body into a first silencing chamber and a second silencing chamber; the first silencing chamber is connected to the air inlet and air outlet; the second silencing chamber is also connected to the air inlet and air outlet; a flow guiding structure is disposed within at least one of the first and second silencing chambers; wherein the flow guiding structure is used to form a "Z"-shaped air duct within its respective silencing chamber to guide airflow. This utility model significantly improves broadband noise attenuation efficiency through the synergistic effect of the dual-chamber layout and the zigzag air duct, while the modular assembly structure facilitates maintenance and expansion, combining the advantages of high noise reduction performance and low maintenance costs.

The application provides an optimal installation method and system of an active control noise reduction sound barrier, and belongs to the technical field of noise control.The active control noise reduction sound barrier comprises a source noise reduction module and a sound barrier, the method blocks the propagation path of a noise sound field through the sound barrier to form a sound shadow area, and the noise sound field is a primary sound field; the primary sound field is gathered at the top of the sound barrier to form a new diffraction sound source; the active noise reduction module is arranged at the top of the sound barrier to emit anti-sound to reduce the diffraction sound emitted by the diffraction sound source, and the area of the sound shadow area is enlarged to form an interference area; the enlarged sound shadow area and the formed interference area are superposed to form a noise reduction area after the noise reduction effect is superposed. The application overcomes the shortcomings of limited noise reduction effect of a traditional passive noise reduction measure on low-frequency noise and the insufficient low-frequency noise attenuation capacity of limited geometric size, so that the overall noise reduction performance of the sound barrier is improved.

This invention belongs to the field of offshore natural gas hydrate reservoir development technology, and relates to a simulation test method for acoustic detection of fractures in hydraulic fracturing of natural gas hydrate reservoirs. This invention processes array full-wavelength logging data from a fracture-wellbore model of a hydrate reservoir to obtain a Stoneley wave signal. Then, through empirical mode decomposition and Hilbert-Huang transform, the cumulative Hilbert energy is constructed. The acoustic attenuation coefficient of the Stoneley wave signal and the reciprocal of the cumulative Hilbert energy are combined as the fracture sensitivity parameter to determine the predicted fracture height. Addressing the unique characteristics of the complex acoustic properties of natural gas hydrate reservoirs, this invention solves the problem of the difficulty in accurately characterizing the acoustic response of fractures in hydrate-bearing fracturing models using acoustic detection methods, providing guidance for the interpretation and detection of hydraulic fracturing fractures in offshore natural gas hydrate reservoirs.

The application discloses a ship pipeline noise prediction method, which comprises the following steps: S1, determining all elements in a target pipeline; S2, calculating the regenerated noise sound power level L wi of each element i in the target pipeline wi , wherein i is the number of the element; S3, determining the sound power level of a noise source in the target pipeline; sequentially calculating the sound power level L wi‑out of the noise after passing through each element i from the noise source, so as to obtain the sound power level after passing through the pipeline outlet; S4, obtaining the sound pressure level L p at a measuring point according to the positions of the measuring point and the pipeline outlet in a room. The method of the application can be carried out at the initial stage of ship design without detailed design parameters, avoids complex pipeline modeling, and has a simple and clear prediction process, high efficiency and low cost.

This invention belongs to the field of marine geotechnical engineering technology and relates to an active learning optimization method for in-situ cone penetration test layout based on seismic reflection data. First, based on a physically driven deep learning model, using modules such as wavelet inversion, reflection coefficient inversion, and acoustic attenuation compensation, cone tip resistance is gradually predicted from seismic reflection data, achieving high-fidelity extrapolation from sparse one-dimensional in-situ test data to continuous multi-dimensional profiles. Second, the average seismic reflection amplitude is used to quantitatively evaluate stratigraphic complexity, prioritizing the deployment of initial test points at locations with high complexity. In the sequential sampling stage, a two-stage candidate point selection strategy is proposed: an early inter-layer reflection amplitude strategy is used to quickly discover hidden strata, and a prediction uncertainty strategy is used in the later stage to minimize global error. A joint termination criterion combining the moving average convergence criterion and the continuous no-improvement criterion is introduced, stopping sampling when the marginal information gain decreases, avoiding the cost waste or insufficient accuracy caused by empiricism.

The invention belongs to the technical field of medical materials, and particularly relates to a long-carbon-chain modified polyurethane elastomer ultrasonic body film material and a preparation method and application thereof.The ultrasonic body film material is prepared from 40-80 parts of long-carbon-chain modified polyurethane (methyl) acrylate, 19-60 parts of reactive diluent monomer and 0.1-5 parts of free radical photoinitiator, the raw materials are mixed to be uniform under the dark condition, and the long-carbon-chain modified polyurethane elastomer ultrasonic body film material is prepared. The prepared ultrasonic phantom material has acoustic characteristics such as sound velocity, sound attenuation coefficient and the like similar to those of human tissues, the requirement of an ultrasonic phantom on ultrasonic characteristics is met, a long carbon chain is introduced into a polyurethane cross-linked network, and the ultrasonic phantom material is prepared through photocuring molding. And the puncture resistance of the polyurethane elastomer can be effectively reduced through the low polarity and the plasticizing effect.

A sound-absorption body (100) for attenuating frequencies below 500Hz, having a sound-absorption surface (101) configured to be exposed in an environment (200) where acoustic emissions (50) to be attenuated are present. A plurality of through-openings (102) is formed in the sound-absorption surface (101 ), and a corresponding plurality of acoustic attenuation elements (110) are provided, each defining a blind acoustic attenuation path. The acoustic attenuation elements (110) extend from an opposite side of the sound-absorption surface (101 ) each starting from a through opening (102). Each blind acoustic attenuation element (110) extends along an axis (111) having a predetermined length, has a main diameter (112), comprises a plurality of annular partitions (113) having an internal hole (114) with a restricted diameter (115) less than or equal to 95% of the main diameter (112) and terminates with a closed end (116). The invention provides a sound-absorption body with low thickness, high absorption of low-frequency acoustic emissions and ease of manufacture. The restricted diameter (115) can be adjustable, and the axis (111) of the blind acoustic attenuation path can include an initial curve, so that the acoustic attenuation elements (110) are parallel to the sound-absorption surface (101 ).

The invention relates to the technical field of pipeline hot-melting joint defect detection, in particular to a phased array transduction detection device for pipeline hot-melting joint defects, which comprises a seat body with an adaptive surface on one side and an inclined surface on the other side, the adaptive surface is used for fitting with the outer wall of a pipeline, and the inclined surface is used for inclining relative to the cross section of the pipeline; and the phased array detection transducer is arranged on the inclined plane, so that the phased array detection transducer can incline towards the pipeline hot melting joint from one side of the pipeline hot melting joint. The invention further relates to a phased array transduction detection method for the pipeline hot melting joint defect, when a pipeline hot melting joint is detected, the phased array detection transducer obliquely faces the pipeline hot melting joint from one side, and the distance between a plurality of array elements of the curved surface array of the phased array detection transducer is adjusted for multi-position measurement. According to the scheme, defects in different positions and directions, especially defects perpendicular to a pipeline, can be detected, and the detection problem caused by sound attenuation and irregular convex edges in a conventional detection method is solved.

The audio device includes a first receiver 501 that receives audio data of a sound source of a scene including acoustic environments divided by an acoustic attenuation boundary. A second receiver 501 receives metadata including a reverberation parameter set indicating a level of reverberation resulting from the audio source in the acoustic environment and an energy transfer parameter indicating energy attenuation between the acoustic environments. For a listening acoustic environment, a selector 513 selects a first one of the reverberation parameter sets in response to parameter values ​​of the first one of the reverberation parameter sets and the energy transfer parameter indicating the acoustic environments of the first one of the reverberation parameter sets and attenuation from the listening acoustic environment. A reverberator of a plurality of reverberators 509, 511 generates a reverberated audio signal based on the first reverberation parameter set, and a renderer 507 renders an audio signal for the listening acoustic environment including a component derived from the reverberant audio signal.

The invention particularly relates to an underwater sediment sound attenuation calculation method based on multi-point sound pressure level measurement and a Biot-Stoll correction model. In order to solve the problems that in an existing submarine sediment sound attenuation modeling method, the deviation between a theoretical prediction result and actually-measured data is large, and a multi-frequency-point correction mechanism is lacked, the Biot-Stoll porous medium theory serves as the physical basis, multi-point actually-measured sound pressure level data are combined, frequency-related multiplication coefficient correction empirical factors are introduced, and the modeling method for the sound attenuation of the submarine sediment is obtained. Therefore, the difference between a theoretical result and actual measurement observation is effectively compensated, and a sound attenuation expression which better conforms to actual sediment acoustic characteristics is obtained. Moreover, the method integrates the advantages of theoretical modeling and actually measured data correction, has the characteristics of high modeling precision, strong adaptability, excellent frequency resolution capability and the like, and can be widely applied to the underwater acoustic engineering fields such as seabed sound propagation simulation, sediment acoustic parameter inversion, acoustic fuze system performance evaluation and the like.

The invention provides a mass concrete crack attenuation velocity field modeling method and device, electronic equipment and a storage medium, and belongs to the technical field of geophysics, and the method comprises the steps: building a sound wave velocity field based on a target size; the sound wave velocity value of the sound wave velocity field is the sound wave velocity value corresponding to the cement paste; randomly putting aggregate into the sound wave velocity field to obtain an aggregate modeling velocity field; adding a reinforcing steel bar structure in the aggregate modeling velocity field, and carrying out wave velocity assignment on the reinforcing steel bar structure to obtain a reinforcing steel bar modeling velocity field; adding a crack structure in the steel bar modeling velocity field, and carrying out wave velocity assignment on the crack structure to obtain a crack modeling velocity field; performing attenuation coefficient calculation on the crack modeling velocity field based on a sound wave attenuation formula to obtain an attenuation coefficient field; according to the method, the attenuation coefficient field and the sound wave velocity field containing aggregate, steel bars and crack structures are established, and the propagation path and attenuation response of sound waves in a complex medium are accurately reflected.

An electronic device, method and computer program product provide recommending wearable audio output devices (e.g., earphones, headsets) for audio output that are appropriate for the ambient sound context and sound quality of the audio output. A controller of the electronic device monitors the context, associates a respective air leakage value and a respective ambient sound attenuation value associated with each wearable audio output device. In response to use of a wearable audio output device exceeding a duration threshold, the controller identifies and presents a recommendation to switch to a candidate wearable audio output device to mitigate a risk level while successfully presenting the audio output for the context.

The present description relates to an ultrasound probe (400) extending in a longitudinal direction (Z), the ultrasound probe comprising an acoustic attenuation structure (420) extending in the longitudinal direction, and an acoustic component (210) positioned on a first face (420A) of the acoustic attenuation structure and comprising an array of ultrasonic transducers; the acoustic attenuation structure comprising: - a stack (221) of at least one acoustic attenuation layer made of a material suitable for attenuating the ultrasonic waves, the stack extending along a plane comprising the longitudinal direction; and - a mechanical reinforcement structure (422) in the stack; the mechanical reinforcement structure comprising at least one first metal element (423A) associated with at least one second metal element (423B), the at least one first and at least one second metal elements extending in two different directions from the plane of the stack.