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Developing efficient platinum (Pt)-based electrocatalysts is enormously significant for fuel cells. Herein, we report an integrated electrocatalyst of ultralow-Pt alloy encapsulated into nitrogen-doped nanocarbon architecture for efficient oxygen reduction reaction. This hybrid Pt-based catalyst achieves a mass activity of 3.46 A mgpt−1 at the potential of 0.9 V vs. RHE with a negligible stability decay after 10,000 cycles. More importantly, this half-cell activity can be expressed at full cell level with a high Pt utilization of 10.22 W mgPt−1cathode and remarkable durability after 30,000 cycles in single-cell. Experimental and theoretical investigations reveal that a highly strained Pt structure with an optimal Pt-O binding energy is induced by the incorporation of Co/Ni into Pt lattice, which would account for the improved reaction kinetics. The synergistic catalysis due to nitrogen-doped nanocarbon architecture and active Pt component is responsible for the enhanced catalytic activity. Meanwhile, the strong metal-support interaction and optimized hydrophilic properties of nanocarbon matrix facilitate efficient mass transport and water management. This work may provide significant insights in designing the low-Pt integrated electrocatalysts for fuel cells and beyond.

An investigation of dynamic behaviors of a sandwich plate containing an imperfect two dimensional functionally graded (2D-FG) core surrounded by two faces on a two-parameter elastic foundation and subjected to a moving load is carried out in this paper. The present sandwich solid is composed of a porous 2D-FG core covered by two homogenous layers. It is assumed that the middle layer has micro voids dispersed uniformly and unevenly through the layer thickness. The fundamental equations are governed within the framework of first-order-shear deformation theory by utilizing Hamilton’s principle, von-Karman geometrical nonlinearity and the principal of mixtures. Newmark direct integration procedure is implemented to transform the dynamic equations into a static form and then the kinetic dynamic relaxation numerical technique in conjunction with the finite difference discretization method are employed to solve the nonlinear partial differential governing equations. Finally, the effects of porosity fraction and scattering patterns, boundary constrains, the variation of materials’ grading indexes and elastic foundation constants on the transient performances of the plate are studied in detail.

Diamond has been forecasted as an excellent substrate material for acoustic devices and microelectromechanical systems owing to its exceptional mechanical and acoustic properties. The integration of piezoelectric thin films on diamond can realize devices operating in the GHz frequency range, which has great relevance in the 5G communication systems. The heterostructures, based on lead zirconate titanate (PZT) and diamond, could be highly promising for the aforesaid applications. However, the direct integration of PZT on diamond is problematic due to the formation of undesired pyrochlore phase and the mismatch in their thermal expansion coefficients. Thus, PZT/diamond heterostructures are often fabricated using a buffer layer. But the recent reports indicated that the direct integration of PZT on diamond is possible without any buffer layer, which is highly promising. This comprehensive review discusses various aspects, including the possibilities and challenges in the fabrication of PZT/diamond heterostructures.

To characterize the particle mass flow rate of gas–solid two-phase flow, a model of particle mass flow rate based on the comprehensive application of transferred current and induced current signals from an electrostatic sensor is proposed in this article. Compared with the characterization model of the particle mass flow rate using the transferred current signal or induced current signal separately, the proposed model can make full use of the characteristics of the two signals. The induced and transferred current signals are extracted from the electrostatic sensor based on the time-domain waveform characteristic method and the direct integration function method, respectively. According to the sensitivity of the time-domain characteristics of the transferred current signal (the radial motion of particles) and the macroscopic stability of the frequency-domain characteristics of the induced current signal (the axial motion of particles), the new signal characteristic value based on the two signals is used to establish a comprehensive signal characterization model (CSCM) of the particle mass flow rate. The coefficients in the model are fit using the Levenberg–Marquardt (LM) method. The experimental results show that the proposed model has higher accuracy and stability than the separate signal model under the experimental conditions in this article.

The direct integration of electrocatalysts with photovoltaic materials provides a strategy for photoelectrochemically powering chemical transformations and storing intermittent solar energy as fuel...

The development of advanced, human like tactile sensing capabilities is one of the key challenges for next generation robots or prosthetics. Tactile sensors arrays will need to exhibit the desired sensing capabilities, show robustness to external influences as well as good approaches for the integration of large amounts of sensors. We present a tactile sensor array technology, based on the fabrication of a flexible interconnection substrate containing directly integrated tactile sensors. This approach has several advantages: interconnection substrate technology is widely available making upscaling of sensor arrays easy to a large amount of sensors and/or large sensing areas, the direct integration of sensors allows for a simple and very compact approach to densely packed sensor arrays and the structured flexible substrate enables integration into complex, three-dimensional bodies. We present sensors with a size of 600 μm and arrays of up to 12 x 12 individually addressable sensors. The sensors have a wide measurement range; free membrane deformation results in a high sensitivity of 2.6 kPa⁻¹ respectively 2600 N⁻¹ for small applied pressures (0-0.6 kPa) whereas deforming polymer studs extend the measurement range for larger applied pressures (5-25 kPa) with a sensitivity of 0.022 kPa⁻¹ respectively 22 N⁻¹. A statistical study of six sensor arrays from three wafers showed repeatable performance of the fabricated structures and robustness tests proved the stable sensing conditions over 10'000 cycles., Journal of Microelectromechanical Systems, 30 (6), ISSN:1057-7157, ISSN:1941-0158

Conformal Loadbearing Antenna Structures (CLAS) take advantage of a combination of structural and electromagnetic functions. CLAS have been developed as an advanced replacement for conventional antennas (such as blades, wires and dishes) to improve the structural efficiency, as well as the electromagnetic and aerodynamic performance of a platform. The CLAS concept permits the direct integration of microwave radiating elements in the structural skin of a platform. Therefore, the antenna will be subjected to structural loading and will deform accordingly. The effects of these structural-induced deformations on the resonant frequency of the antenna will be reported in this paper. This paper will investigate the performance of a carbon veil patch antenna when it is subject to static in-plane. The work presented will include the effects of in-plane loading on the resonant behavior of the patch antenna when the carbon veil is fully bonded and when it is disbonded by the parent structure. This paper will also discuss the effects of substrate delamination on the RF response of the patch antenna. The RF characteristics of the antenna will be modelled using ANSYS High Frequency Structure Simulator (HFSS).

Η παρούσα διδακτορική διατριβή αποτελεί συμβολή στην ανάπτυξη εξελιγμένων θεωριών δοκού για την ανάλυση ραβδωτών φορέων. Οι εξελιγμένες θεωρίες δοκού που αναπτύχθηκαν λαμβάνουν υπόψη φαινόμενα γενικευμένης στρέβλωσης (διατμητική υστέρηση λόγω κάμψης και στρέψης), διαστρέβλωσης (παραμόρφωση διατομής – distortion), ενώ πραγματοποιείται και γεωμετρικά μη γραμμική δυναμική ανάλυση δοκών σταθερής ή μεταβλητής διατομής, λαμβάνοντας υπόψη φαινόμενα ανώτερης τάξης όπως η περιστροφική και στρεβλωτική αδράνεια, η μη γραμμικότητα εξωτερικής φόρτισης, οι όροι Wagner και η βράχυνση λόγω στρέψης. Οι εν λόγω καινοτόμες θεωρίες συνδυάζουν την αυξημένη ακρίβεια με τα εγγενή πλεονεκτήματα των στοιχείων δοκού, οδηγώντας στην ανάπτυξη εξελιγμένων υπολογιστικών εργαλείων για την ανάλυση ραβδωτών φορέων.Η γενικευμένη στρέβλωση λαμβάνεται υπόψη, με την εισαγωγή ανεξάρτητων παραμέτρων, που εκφράζουν την «ένταση» της στρέβλωσης στο μήκος της δοκού. Οι παράμετροι αυτές πολλαπλασιάζουν αντίστοιχες συναρτήσεις στρέβλωσης, που προκύπτουν από ισάριθμα διδιάστατα προβλήματα συνοριακών τιμών στο χωρίο της διατομής. Στην παρούσα διατριβή αντιμετωπίζεται το πρόβλημα παραβίασης της συνοριακής συνθήκης μηδενισμού της διατμητικής τάσης στην παράπλευρη επιφάνεια της δοκού (ισορροπία σε επίπεδο υλικού σημείου) από τις τάσεις που προκύπτουν από το υιοθετούμενο πεδίο μετατοπίσεων. Προτείνεται διαδικασία «διόρθωσης» του τασικού πεδίου με χρήση της εξίσωσης διαμήκους τοπικής ισορροπίας. Μέσω της διόρθωσης αυτής βελτιώνεται η ακρίβεια των παραγόμενων αποτελεσμάτων χωρίς αύξηση των κινηματικών αγνώστων και διατηρείται κατά το μέγιστο δυνατό βαθμό η απλότητα της διατύπωσης.Όσον αφορά στη διαστρέβλωση (distortion), παράγεται κατάλληλη βάση συναρτήσεων διαστρέβλωσης/στρέβλωσης μέσω επαναληπτικού σχήματος ισορροπίας στο χωρίο της διατομής. Το σχήμα αυτό παράγεται χρησιμοποιώντας τις εξισώσεις τοπικής ισορροπίας της θεωρίας ελαστικότητας. Η προσέγγιση αυτή παρουσιάζει πλεονεκτήματα έναντι των αντίστοιχων προσεγγίσεων της διεθνούς βιβλιογραφίας που βασίζονται στην Ανάλυση Ιδιομορφών (ανεξάρτητος προσδιορισμός αξονικών, καμπτικών, στρεπτικών μορφών διαστρέβλωσης/στρέβλωσης). Συνεπώς, διατυπώνεται θεωρία δοκού με το μικρότερο δυνατό αγνώστων παραμέτρων διαστρέβλωσης που αντιπροσωπεύουν εξίσου όλους τους μηχανισμούς αντίστασης.Στη συνέχεια οι ως άνω θεωρίες ενσωματώνονται στη μητρωική ανάλυση ραβδωτών φορέων. Παράγονται καινοτόμα τρισδιάστατα στοιχεία δοκού τυχούσας διατομής που περιλαμβάνουν διατμητικές παραμορφώσεις, γενικευμένη στρέβλωση (μητρώο στιβαρότητας 20×20) και διαστρέβλωση (μητρώο στιβαρότητας 32×32) μαζί με τα αντίστοιχα διανύσματα ισοδύναμης επικόμβιας φόρτισης. Τα εν λόγω στοιχεία δοκού ενσωματώνονται σε υπολογιστικό εργαλείο που βασίζεται στoν αλγόριθμο της Μεθόδου Άμεσης Στιβαρότητας (ΜΑΣ, Direct Stiffness Method – DSM) διαμορφώνοντας εξελιγμένο υπολογιστικό εργαλείο για την ανάλυση πλαισιωτών φορέων. Προκειμένου να αρθεί η αδυναμία μετασχηματισμού των επικόμβιων Βαθμών Ελευθερίας (ΒΕ) ανώτερης τάξης σε μέλη συνδεδεμένα υπό γωνία, αναπτύσσεται μεθοδολογία μετασχηματισμού που λαμβάνει υπόψη τις συνθήκες μετάδοσης διαστρέβλωσης/στρέβλωσης στους κόμβους του πλαισίου.Παρουσιάζεται επίσης γενική μεθοδολογία για τη γεωμετρικά μη γραμμική δυναμική ανάλυση δοκών σταθερής και μεταβλητής διατομής. Όσον αφορά στις πρισματικές δοκούς, εξετάζεται η πλέον γενική περίπτωση διατομής, ενώ όσον αφορά στην περίπτωση μεταβλητής διατομής, εξετάζεται η συνήθης περίπτωση της διπλά συμμετρικής διατομής με ομαλό νόμο μεταβολής. Η δοκός υπόκειται σε τυχούσα εξωτερική χρονικά μεταβαλλόμενη φόρτιση, συνοριακές και αρχικές συνθήκες και αναπτύσσει μετρίως μεγάλες μετατοπίσεις και στρεπτικές στροφές. Το μη γραμμικό φαινόμενο της αλλαγής μοχλοβραχίονα του εξωτερικού φορτίου, η επιρροή της περιστροφικής και στρεβλωτικής αδράνειας, των συντελεστών Wagner, καθώς και του φαινομένου βράχυνσης λόγω στρέψης λαμβάνονται υπόψη.Στην παρούσα διατριβή, τα προβλήματα συνοριακών και αρχικών τιμών επιλύονται αριθμητικά χρησιμοποιώντας τη Μέθοδο Συνοριακών Στοιχείων (ΜΣΣ, Boundary Element Method – BEM) και τη Μέθοδο Αναλογικής Εξίσωσης (ΜΑΕ, Analog Equation Method – AEM), η οποία αποτελεί εξέλιξη της BEM. Η AEM αντιμετωπίζει τις εγγενείς αδυναμίες της BEM και προσφέρεται για την επίλυση μεγάλου εύρους προβλημάτων μηχανικής που ορίζονται από χρονικά εξαρτώμενες ή/και μη γραμμικές διαφορικές εξισώσεις ή εξισώσεις με μεταβλητούς συντελεστές.Βάσει των διαδικασιών που αναπτύσσονται, μελετώνται αντιπροσωπευτικά αριθμητικά παραδείγματα. Η ακρίβεια και αξιοπιστία των προτεινόμενων μεθόδων επιβεβαιώνονται με υπάρχουσες αναλυτικές και αριθμητικές λύσεις, πειραματικά αποτελέσματα καθώς και με προσομοιώματα στερεών πεπερασμένων στοιχείων και πεπερασμένων στοιχείων κελύφους.

After long-term service in deep ocean, pipelines are usually suffered from corrosions, which may greatly influence the Vortex-Induced Vibration (VIV) behavior of pipes. Thus, we investigate the VIV of defective pipelines. The geometric nonlinearity due to large deformation of pipes and nonlinearity in vortex-induced force are simulated. This nonlinear vibration system is simulated with finite element method and solved by direct integration method with incremental algorithm. Two kinds of defects, corrosion pits and volumetric flaws, and their effects of depth and range on VIV responses are investigated. A new finite element is developed to simulate corrosion pits. Defects are found to aggravate VIV displacement response only if environmental flow rate is less than resonance flow rate. As the defect depth grows, the stress responses increase, however, the increase of the defect range reduces the stress response at corroded part. The volumetric flaws affect VIV response stronger than the corrosion pits.

Microfabrication, electrical characterisation, and mathematical modelling of a non-spiral planar microcoil useful for wireless power transfer applications in biomedical devices are presented in this work. The fabrication method using the existing very-large-scale integration manufacturing process requires a single mask level, and a single metal level without any via enables direct integration with a complementary metal oxide semiconductor sensing circuitry. An analytical model of magnetic field distribution in a non-spiral microcoil is developed for the first time in this work, which satisfies the form of a Bessel function of the first kind. An electrical model of the non-spiral planar microcoil is also developed and compared with experimental results. Experimental results are in good agreement with the theoretical model. Based on the experimental results, using optimised coil geometry, a wireless power transfer link suitable for biomedical wireless power transfer applications is studied. The maximum possible value of coupling factor of the wireless link is found to be 60% for a small separation between the coil and the magnet whereas the minimum value of coupling factor is found to be below 10% for large separations. It is found that introducing Neodymium magnetic shield layer at the receiving coil enhances the coupling factor significantly.

High-density, point-of-load (PoL) power conversion and power delivery are required to continue scaling electronic systems with increased functionality, more bandwidth, and smaller sizes. To meet the demands of these highly complex and miniaturized electronic systems, new 3-D integration schemes of advanced passive and active components are needed to enable the next-generation power distribution networks (PDNs). In addition, shorter interconnect lengths are required to provide low losses and better transient response in switch-based power conversion systems. Tantalum capacitors have the potential to provide some of the highest volumetric densities of any current capacitor technology, but are generally bulky components with low frequency stability, limiting their use in future 3-D power systems. In this paper, a process for the embedding and integration of ultrathin, high-density tantalum capacitors with improved frequency stability is demonstrated. The 5-V capacitors show a density of $1~\mu \text{F}$ /mm2 at 1 MHz with only a 100- $\mu \text{m}$ thickness, and are shown to be capable of direct integration on silicon for short interconnect length of $ . The electrical performance of the capacitors is tested after integration and shows that they retain high capacitance density and low equivalent series resistance (ESR), while also providing low leakage currents. The combination of low loss, high volumetric density, and 3-D integration capability make the capacitors an ideal candidate for next-generation power modules.

The authors present an accurate solution to the task of elastic axial compression (tension) of the multilayered cylindrical beam with axial orthotropic layers surrounding a central core. The description of the geometry and structural framework of the beam requires the employment of the circular cylindrical system of coordinates where the mechanical characteristics of its inhomogeneous materials serve as the functions of the only variable. The task is solved via direct integration of the entire system of equations of the theory of elasticity within the selected system of coordinates upon the condition of rigid contact at the interfaces of the layers. The analytical relations for all the components of the features of the stress-strain state are obtained, their application is illustrated by the results of the solution to the test task of compression of the four-layered beam with the isotropic core.

A finite element model for predicting the nonlinear aeroelastic behavior of composite panels undergoing intralaminar and translaminar progressive damage in supersonic flow is presented. The classical plate theory in conjunction with the von Karman nonlinear strains is used for structural modeling, and the linear piston theory is used to model the aerodynamic loads . Progressive damage is modeled by a smeared cracking formulation in which stress-based, continuum damage mechanics and fracture mechanics approaches are combined. No modal reduction is performed and an iterative form of the Newmark method is used for the numerical direct integration in time of the nonlinear equations. Simulations considering different lay-ups are conducted, in which the influence of progressive damage on the aeroelastic behavior of the panels is investigated, and damage extent and failure mechanisms are assessed. The results obtained in the analyses consist in important insights concerning the flutter-induced damage in composite panels.

We devise automated workflows for the calculation of Helmholtz and Gibbs free energies and their temperature and pressure dependence and provide the corresponding computational tools. We employ nonequilibrium thermodynamics for evaluating the free energy of solid and liquid phases at a given temperature and reversible scaling for computing free energies over a wide range of temperatures, including the direct integration of $P\text{\ensuremath{-}}T$ coexistence lines. By changing the chemistry and the interatomic potential, alchemical and upscaling free energy calculations are possible. Several examples illustrate the accuracy and efficiency of our implementation.

International audience; Manufacturing of microsystems based on complex three-dimensional microstructures requires critical steps such as mass calibrations and integration process. However, such steps involve several manipulation steps which are not well controlled thus the fragile 3D microstructures could be damaged or destroyed. In this work, we have demonstrated an AFM based direct mass measurement and manufacturing of 3D helical microswimmer. The proposed method shows to be rapid, repeatable and minimally-destructive thanks to the precise force control and manipulation by AFM. The proposed micromanipulation steps consist of the pick-measure-integrate manipulation steps using van der Waals force-based attachment and the mass measurement by resonant frequency shift. For the testing structures, we fabricated the 6 different types of 3D helical microswimmers vertically fabricated on the conical shape microneedle supports for uniform surface metallization and facile detachment. With the mass measurement sensitivity of 25 Hz/pg and the direct integration to microfluidics, we successfully demonstrated the 3D propulsion and non-contact micromanipulation by 3D helical microswimmer in microfluidics.

In this paper, studies on a commercial parabolic trough solar collector (PTSC) using supercritical CO2 (s-CO2) as the heat transfer fluid (HTF) are presented. When compared to other HTFs, supercritical CO2 can operate at higher temperatures which is useful for power plants. The collector module used for this study is LS-2 module. The effect of mass flow rate and inlet temperature of the HTF on receiver wall temperature, thermal loss, heat transfer coefficient and thermal efficiency is analysed. CO2 is taken in supercritical state in order to facilitate the direct integration of the collector to high-temperature power cycles. It is found that higher mass flow rate results in lower wall temperature and higher heat transfer coefficient. At any particular mass flow rate, lower operating pressure results in higher wall temperature. Rise in HTF inlet temperature results in an increase in wall temperature and reduction in thermal efficiency of the collector. However, variation in operating pressure results in negligible change in wall temperature.

This article inspects the role of wall asymmetric heat fluxes and buoyant force on steady natural convection flow in a vertical microchannel with electrokinetic effect. The governing Poisson–Boltzmann, momentum and energy equations representing the electric potential, velocity profile and temperature distribution in the microchannel are obtained for the current investigation. Using the Debye–Huckel linearization, exact solutions for electric potential, velocity and temperature are found by method of undetermined coefficients and direct integration. In the course of graphical simulations, result shows that the skin-friction and mass flow rate in the microchannel would have been overestimated by approximately 37% and 30% respectively if the slip-condition at the microchannel walls for current investigation had not been taken into consideration regardless of the magnitude of buoyant force. In addition, the inclusion of buoyancy parameter acts as an enhancer on velocity profile and mass flow rate.

In this communication, we describe the direct integration of thin film SAW resonators on industrial metals. Two different structures were studied numerically and experimentally: Al/ZnO/Duralumin and Al/ZnO/Titanium. Resonators were manufactured on ZnO thin film directly deposited by RF magnetron sputtering on polished Duralumin and Titanium substrates. The presence of Rayleigh waves was demonstrated. The aim of these resonators is an application in the field of structural health monitoring.

In this study we look into the interference effect in multi-thread molecular junctions in between carbon-nanotube (CNT) electrodes of assorted edges. From the tube end into the tube bulk of selected CNTs, we investigate surface Green’s function and layer-by-layer local density of states (LDOS), and find that both the cross-cut and the angled-cut armchair CNTs exhibit 3-layer-cycled LDOS oscillations. Moreover, the angled-cut armchair CNTs, which possess a zigzag rim at the cut, exhibit not only the oscillations, but also edge state component that decays into the tube bulk. In the case of cross-cut zigzag CNTs, the LDOS shows no sign of oscillations, but prominent singularity feature due to edge states. With these cut CNTs as leads, we study the single-polyene and two-polyene molecular junctions via both ab initio and tight-binding model approaches. While the interference effect between transport channels is manifested through our results, we also differentiate the contributions towards transmission from the bulk states and the edge states, by understanding the difference in the Green’s functions obtained from direct integration method and iterative method, separately.

Three-dimensional (3D) printing is a next-generation free-form manufacturing technology for structural electronics. The realization of structural electronic devices necessitates the direct integration of electronic circuits into 3D objects. However, creating highly conductive, high-resolution patterns in 3D remains a major challenge. Here, we report on a metallic 3D printing method that incorporates electroless deposition (ELD) into the direct ink writing method. Our approach consists of two steps: (1) direct ink writing of catalyst microstructures with a functional catalyst ink containing Ag ions and (2) ELD of Cu onto the printed catalyst structures. High-quality, stable Cu 3D printing is achieved through the design of the Ag catalyst ink; hydroxypropyl cellulose is added as both a rheological modifier (printing) and dissolution inhibitor (ELD). As a result, various two-dimensional (2D) and 3D Cu micro circuitries with high conductivity (∼65% of bulk) can be directly integrated onto 3D plastic substrates without the need for high-temperature annealing. A hybrid strategy that combines ELD-assisted 3D printing and conventional fused deposition modeling enables full fabrication of structural electronic devices. This 3D printing strategy can be a low-cost and facile method for obtaining highly conductive metallic 2D and 3D microstructures in structural electronics.

An efficient technique for thermoelastic analysis of inhomogeneous anisotropic solids is suggested within the framework of three-dimensional formulation. By making use of the direct integration method, a system of governing equations is derived in order to solve three-dimensional problems of elasticity and thermoelasticity for transversely isotropic inhomogeneous solids with elastic and thermo-physical properties represented by differentiable functions of the variable in the direction that is transversal to the plane of isotropy. By implementing the relevant separation of variables, the obtained equations can be uncoupled and reduced to second-kind integral equations for individual stress-tensor components and the total stress, which represents the trace of the stress tensor. The latter equations can be attempted by any of the numerical, analyticalnumerical, or analytical means available for the solution of the second-kind integral equations. In order to construct the solutions in an explicit form, an advanced solution technique can be developed on the basis of the resolvent-kernel method implying the series representation by the recurring kernels, computed iteratively by the original kernel of an integral equation.

The aim of this study is to investigate the dynamic response of axially moving two-layer laminated plates on the Winkler and Pasternak foundations. The upper and lower layers are formed from a bidirectional functionally graded (FG) layer and a graphene platelet (GPL) reinforced porous layer, respectively. Henceforth, the combined layers will be referred to as a two-dimensional (2D) FG/GPL plate. Two types of porosity and three graphene dispersion patterns, each of which is distributed through the plate thickness, are investigated. The mechanical properties of the closed-cell layers are used to define the variation of Poisson’s ratio and the relationship between the porosity coefficients and the mass density. For the GPL reinforced layer, the effective Young’s modulus is derived with the Halpin-Tsai micro-system model, and the rule of mixtures is used to calculate the effective mass density and Poisson’s ratio. The material of the upper 2D-FG layer is graded in two directions, and its effective mechanical properties are also derived with the rule of mixtures. The dynamic governing equations are derived with a first-order shear deformation theory (FSDT) and the von K´arm´an nonlinear theory. A combination of the dynamic relaxation (DR) and Newmark’s direct integration methods is used to solve the governing equations in both time and space. A parametric study is carried out to explore the effects of the porosity coefficients, porosity and GPL distributions, material gradients, damping ratios, boundary conditions, and elastic foundation stiffnesses on the plate response. It is shown that both the distributions of the porosity and graphene nanofillers significantly affect the dynamic behaviors of the plates. It is also shown that the reduction in the dynamic deflection of the bilayer composite plates is maximized when the porosity and GPL distributions are symmetric.

It is still a challenging task to numerically solve flames using detailed chemical kinetics in multidimensional geometries of practical applications. To overcome this difficulty, many efforts have been done to develop chemical kinetics reducing techniques, such as ILDM, FPV, FPI, and FGM. Although these techniques are widely discussed in the literature, their implementation is not straightforward. In the present work, the FGM technique is implemented to solve a two-dimensional laminar premixed flame of $$\hbox {CH}_4/\hbox {air}$$ stabilized by heat losses to the burner rim. This configuration is explored to test the FGM prediction capabilities for some stable conditions, one of them close to the blow-off limit. Temperature, mass fraction of selected species, and the burning velocity variation along the flame surface are presented, and limitations of the technique were identified by comparing FGM results against the direct integration of the full set of conservation equation. In general, the FGM technique has shown a good quantitative agreement when compared with the direct integration.

A static and dynamic large deformation analysis of a tapered beam subjected to concentrated and distributed loads is presented in this paper by using a direct integration technique. The bending stiffness of the beam is coordinate dependent. The nonlinear differential equation is numerically solved using an iterative technique without an algebraic equation solver, thus the computational effort can be reduced. A concentrated mass fixed at the free end and suddenly released is studied, and the time-dependent displacements are presented. Comparison has been made with solutions obtained using Finite Element Analysis and excellent agreement is achieved.

This paper presents an improvement of a quadraxial feed designed for quadruple-ridged flared horn antennas. Selective laser melting (SLM) 3-D printing allows for complex structures to be realised as one unibody component. The integration of complex structures into the quadruple-ridged waveguide suppresses all higher order modes by more than 25 dB relative to the fundamental TE 11 mode, thereby achieving near pure-mode excitation over a 8.5:1 bandwidth. The impedance match is also significantly improved due to the relaxation of design constraints from previous manufacturing techniques. The quadraxial feed presented in this paper presents an ideal candidate for the integration with differential amplifiers and a quadruple-ridged flared horn for next generation radio astronomy reflector antennas.

Two-dimensional (2D) metal–semiconductor transition-metal dichalcogenide (TMDC) vertical heterostructures play a crucial role in device engineering and contact tuning fields, while their direct integration still challenging. Herein, a robust epitaxial growth method is designed to construct multiple lattice-matched 2D metal–semiconductor TMDC vertical stacks (VSe2/MX2, M: Mo, W; X: S, Se) by a two-step chemical vapor deposition method. Intriguingly, the metallic VSe2 preferred to nucleate and extend from the energy-favorable edge site of the semiconducting MX2 underlayer to form VSe2/MX2 vertical heterostructures. This growth behavior was also confirmed by density functional theory calculations of the initial adsorption of VSe2 adatoms. In particular, the formation of Schottky-diode or Ohmic contact-type band alignments was detected for the stacks between VSe2 and p-type WSe2 or n-type MoSe2, respectively. This work hereby provides insights into the direct integration, band-alignment engineering, and poten...

In this paper, the effect of green water impact on a flexible structure is studied based on three-step computational fluid dynamics (CFD)–boundary element method (BEM)–finite element method (FEM) approach. The impact due to shipping of water on the deck of the vessel is computed using commercial CFD software and used as an external force in coupled BEM-FEM solver. Other hydrodynamic forces such as radiation, diffraction, and Froude-Krylov forces acting on the structure are evaluated using 3D time domain panel method. To capture the structural responses such as bending moment and shear force, 1D finite element method is developed. Moreover, a direct integration scheme based on the Newmark–Beta method is employed to get the structural velocity, displacement, etc., at each time step. To check the effect of the green water impact on the structure, a rectangular barge without forward speed is taken for the analysis. The influence is studied in terms of bending moment, shear force, etc. Results show that the effect of green water impact on the bow region can be severe in extreme seas and lead to various structural damages. Similarly, it is also verified that vessel motion affects green water loading significantly and therefore one must consider its effect while designing a vessel.

The dynamic growth of void in an infinite elastic-viscoplastic medium under thermal shock is analyzed theoretically. The technique of direct integration is presented to obtain the analytic solutions of stress and displacement. The initial purely elastic deformation before the viscoplastic deformation is considered. Especially, the nonlinear ODE for moving interface of the elastic and viscoplastic zone is derived from the interface conditions. The dynamic evolution of void growth is different from the static case, since the moving interface leads to the intrinsic nonlinearity. The numerical results indicate that the effect of viscosity has significant influence on void growth.

In this contribution, we present a system of adaptive vortex generators (VGs) enabling an on-demand optimization of the airflow for high angles of attack. The generated vortices enhance the boundary layer with kinetic energy and prevent flow separation. The maximum cruise efficiency is ensured as VGs are stowed. The system presented uses active hybrid composites, where the actuation is initiated by shape memory alloys (SMA). By the direct integration of SMA elements in flat fiber-reinforced polymer (FRP) parts, the components turn into active hybrid composites. A well-selected amount of SMA wire is integrated in a composite layup and allows small elements of about 25 × 30 mm2 and a thickness of only 1.8 mm to deflect up to 8 mm upwards into the airflow. These small active VG with a weight of 1.5 g each can easily be integrated in the wing structure, since only an electrical connection is required. This contribution will highlight the actuation performance of these elements under airflow in the laboratory, illustrate the required system architecture and will give a first look on results of flight tests with functional setup equipped on a glider for measuring the aerodynamic impact on the flight behavior.

This contribution discusses technology development for the realization of chip-to-chip interconnection based on flexible optical waveguides. Two approaches for optical coupling between waveguides and active devices are presented. Both approaches built on the planar polymeric optical multimode waveguides integrated on flexible substrates (PEN-foil). This waveguides structured using UV-photolithography and Ormocere-materials feature low optical attenuation below 0.05 dB/cm. The first approach for coupling between optical waveguides uses a bidirectional interruption-free waveguide coupler. The principle bases on directional core-core-coupling and allows for adjustable coupling ratio by tuning the overlap area. In addition, an asymmetric coupling behavior depending on the coupling direction due to a bending of one of the coupling waveguides is achieved. This coupling method shows supremacy for optical bus systems where tunable, asymmetric coupling ratios are desired. The second optical coupling approach for waveguide-to-chip coupling bases on out-of-plane optics. Direct integration of 45° micro-mirrors into polymer waveguides using dicing process is investigated. Two approaches for optoelectronic (OE) subassembly with flexible optical waveguides are considered one with flip-chip bonded and one with embedded OE-devices. Using optical characterization the influence of fabrication parameters on the optical performance of diced mirrors with insertion power loss measurement is derived and presented.

This paper presents an efficient computational implementation of the in situ adaptive tabulation (ISAT) approach (Pope, 1997) for combustion chemistry in a network of perfectly stirred reactors (PSRs) for the investigation of soot formation and growth. This study, for the first time, extends the thermochemical composition vector to contain the soot moments, using the method of moments with interpolative closure (MOMIC) as a soot model with six concentration moments. A series of PSR calculations is carried out using the direct integration (DI) and ISAT approaches. Assessment of the accuracy of ISAT approach is conducted through direct comparisons with DI calculations. Moreover, complimentary cumulative distribution function (CCDF), sensitivity of ISAT calculations with respect to the absolute error tolerance values and speedup are analyzed for two different test cases of ethylene-air using two different chemical kinetic mechanisms. A maximum speedup of 50 x was achieved for an error tolerance of 10(-4). (C) 2018 Elsevier Ltd. All rights reserved.

Inline phase-change switch (IPCS) devices were fabricated on top of an AlN heat spreading layer deposited on a thick SiO2 layer. The thick SiO2 emulates the inter-layer dielectric thermal properties that prevent direct integration of IPCS devices at the end of a back-end-of-line CMOS process. The AlN acts as a heat spreading layer, enabling the proper thermal quench rate despite the low thermal conductivity of the oxide underneath. Multiple AlN thicknesses were examined and shown to properly quench the device. Use of this heat spreading layer experimentally demonstrates a substrate agnostic monolithic integration scheme, where IPCS devices can be integrated at the end of any microfabrication process—regardless of the substrate or materials underneath. This is attractive for many CMOS applications, where wafer real-estate is expensive, or in III–V applications, where the wafer thermal properties are poor and vary among different technologies.

A new method for the site-selective synthesis of nanowires has been developed to enable material growth with defined morphology and, at the same time, different composition on the same chip surface. The chemical vapor deposition approach for the growth of these nanowire-based resistive devices using micromembranes can be easily modified and represents a simple, adjustable fabrication process for the direct integration of nanowire meshes in multifunctional devices. This proof-of-concept study includes the deposition of SnO2, WO3, and Ge nanowires on the same chip. The individual resistors exhibit adequate gas sensing responses toward changing gas concentrations of CO, NO2, and humidity diluted in synthetic air. The data have been processed by principal component analysis with cluster responses that can be easily separated, and thus, the devices described herein are in principle suitable for environmental monitoring.

Surface acoustic wave (SAW) sensors are very promising for structural health monitoring (SHM) applications as they have the advantages of being robust, passive (batteryless), remotely interrogated (wireless) and can even be packageless. This paper describes ultralow-profile SAW resonators that can be directly fabricated and integrated on metallic parts in industrial facilities. They are based on piezoelectric thin films (ZnO) which are directly sputtered on polished industrial titanium (Ti) and stainless steel. With this approach, no sensor glue-bonding to the target is needed, and measurement errors related to this step are avoided. Demonstrator devices have been studied numerically and experimentally. The structural properties of the ZnO thin films were characterized through x-ray diffraction and atomic force microscopy. A preferred orientation (002) was achieved with a roughness of 50 nm on the top surface. Resonators were microfabricated and their functional parameters (i.e. resonance frequency, quality factor and electromechanical coupling) were extracted through impedance measurements and fitted with a Butterworth-van Dyke model. By increasing applied temperatures (up to 450 °C) and the strain (up to 1800 μϵ), a linear decrease of the resonance frequency has been shown. A temperature coefficient of frequency of −46.4 ppm °C−1 and a good strain sensitivity (1.49 ppmμϵ−1) were obtained, thus making the structure promising as a high temperature and strain sensing element in industrial SHM applications.

Carbon nanotubes (CNTs) are nanomaterials that exhibit many remarkable electrical, mechanical and thermal properties, which can be exploited in various smart sensing applications by integrating them in standard CMOS processes. However, such integration technique is challenging since CMOS does not tolerate high temperatures required for local CNT synthesis. This work involves designing power efficient CMOS micro-heaters that can generate CNT growth temperature (~ 900 °C) in a post-CMOS CNT fabrication step, while maintaining CMOS compatible temperature (

An exact analytical solution to the three-dimensional elasticity problem for a transversely-isotropic composite layer is constructed by making use of the direct integration method along with the Fourier double-integral transform. The original problem is reduced to a system of governing partial-differential equations for separate stress-tensor components. The governing equations are accompanied with corresponding local and integral boundary conditions, obtained on the basis of the original local boundary conditions imposing the normal and shearing forces on the limiting planes of the layer. The numerical analysis of the obtained solution is presented for certain transversely-isotropic composite materials.

Vertical III-V nanowire (NW) is a promising channel material for high-speed switching devices in future integrated circuits because surrounding-gate structures have good electrostatic gate controllability while suppressing inherent large leakage current in III-V channels and outperform lateral switching devices in terms of power consumption while keeping good scalability. As for the integration of III-V NWs on Si, direct integration of vertical III-V NWs by selective-area growth has advantages for high -performance transistor applications because of position/size-uniformity and core-shell structure with modulation doping.

Transient (time-history) response of an optical fiber, vibrating in its resonance frequency, using thermo-mechanical actuation is studied in this paper. The optical fiber is modeled as a cantilever beam that is excited via expansion/contraction cycles, from internal heat generation in the actuator. To simulate this system, time-dependent heat conduction equation, under internal heat generation, is solved for the actuator system. The outcome is heat distribution and thermal expansion (actuation) in the actuator, as a function of time. Then, the full dynamic model is developed using a continuous beam equation, which represents the optical fiber; the beam formulation takes into account the hydrodynamic forces from the surrounding fluid medium. The latter equation is solved with respect to its boundary condition to attain the time-dependent dynamic response of the optical fiber. Laplace transformation and its numerical inverse via direct integration are used to tackle the time-dependency of the partial differential equations. The resultant thermal actuation is calculated, and recommendations to improve performance of actuator are presented. Analytical solution for dynamic model is validated against 3D Finite Element (FE). Then, the effect of surrounding medium on the performance of the system is evaluated.

We present a new and innovative approach for the direct integration of sensors into aluminum during casting to obtain strain and temperature data for the aluminum. This technology will enable a variety of new applications in sensing technology such as sensing car parts in the automotive industries (e.g., a suspension arm), innovative parts of an exoskeleton with integrated sensors for feedback information, or sensing structural components of vehicles. Furthermore, these sensors can result in more efficient quality assurance, are fully encapsulated against environmental influence, provide an ideal connection between sensor and metal matrix due to integration in the casting process, and enable engineers to place sensors directly at the place of interest without limitations. To reach the goal of integrating sensors in aluminum, we first focus on silicon-based sensors. We will show that sensor integration is possible, but the failure rate is high. This is analyzed by evaluating sensor data during casting. Due to the high difference in coefficiency of thermal expansion between aluminum and silicon, high thermal-induced compressive stress is generated in the silicon and is destroyed in the casting process during solidification cooling. This is why we convert in the second part of this paper to a new sensor concept, which is adapted to the conditions of the casting process. A sensor and its electrical connections are printed on aluminum sheets and integrated in aluminum in an industrial high-pressure casting process. As a result of these pre-tests, more than three-quarters of the devices survived the process of integration. Finally, we show that we obtain strain and temperature data from the cast part to develop smart components out of cast aluminum and to enable new sensing technologies.

Present investigation is concerned with the free vibration property of a beam with periodically variable cross-sections. For the special geometry characteristic, the beam was modelled as the combination of long equal-length uniform Euler-Bernoulli beam segments and short equal-length uniform Timoshenko beam segments alternately. By using continuity conditions, the hybrid beam unit (ETE-B) consisting of Euler-Bernoulli beam, Timoshenko beam and Euler-Bernoulli beam in sequence was developed. Classical boundary conditions of pinned-pinned, clamped-clamped and clamped-free were considered to obtain the natural frequencies. Numerical examples of the equal-length composite beam with 1, 2 and 3 ETE-B units were presented and compared with the equal-length and equal-cross-section Euler-Bernoulli beam, respectively. The work demonstrates that natural frequencies of the composite beam are larger than those of the Euler-Bernoulli beam, which in practice, is the interpretation that the inner-welded plate can strengthen a hollow beam. In this work, comparisons with the finite element calculation were presented to validate the ETE-B model.

The seamless combination of plasmonic structures with metal oxides and in particular with 2D materials has attracted significant recent interests. Here, a novel approach to grow molybdenum disulfide (MoS2) is presented: an optically active 2D material, directly onto plasmonic nanoscale gold disks via a surface diffusion delivery of Mo from within the nanostructure and a sulfidation process. X-ray photoelectron spectroscopy and Raman spectroscopy measurements demonstrate the existence and the reaction process of few layered MoS2. Delivery of Mo from within the nanostructure and direct growth of MoS2 has the potential to form better defined metal/MoS2 interfaces compared to exfoliation routes. This facile approach has the potential for application in photodetector or other devices.

3C-SiC epitaxially grown on Si displays a large wealth of extended defects. In particular, single, double and triple stacking faults (SFs) are observed to coexist in several experiments. Overabundance of defects has so far limited the exploitation of 3C-SiC/Si for power electronics, in spite of its several ideal properties (mainly in terms of the wide gap, high breakdown fields and thermal properties) and the possibility of direct integration in the Si technology. Here we use a multiscale approach, based on both classical molecular dynamics (MD) simulations and first-principles calculations, for the in-depth investigation of the origin, nature and properties of most common 3C-SiC/Si(001) extended defects. Our MD simulations reveal a natural path for the formation of partial dislocation complexes terminating both double and triple SFs. The MD results are used as an input for superior DFT calculations, allowing us to better determine the core structure and to investigate electronic properties. It turns out that the partial dislocation complexes terminating double and triple SFs are responsible for the introduction of electronic states significantly filling the band gap. On the other hand, individual partial dislocations terminating single SFs only induce states very close to the gap edge. We conclude that partial dislocation complexes, in particular the most abundant triple ones, are killer defects in terms of favoring leakage currents. Suggestions coming from theory/simulations for devising a strategy to lower their occurrence are discussed.

A general approach to the analysis of thermoelastic response of solids exhibiting spatial or thermal variation in their material properties is addressed in this study. The approach is based on the idea of the direct integration method, which allows for the construction of analytical solutions to the relevant thermoelasticity problems in explicit functional form satisfying the thermal and force boundary conditions on the entire surface of a solid.

To determine the influence of temperature on the mechanical properties of crane metal structures, three Q355 alloy steel samples were processed and their elastic moduli were tested at different temperatures using a metal tension test bed. The constitutive equation for the elastic modulus of Q355 alloy steel at different temperatures was predicted using test data and a neural network algorithm. Based on crane structural characteristics and the principle of system dynamics, a coupling vibration model was established that included the crane flexible girder, cabin, trolley, crane, and temperature. System motion equations were established according to the Lagrange equation, and the approximate solution of nonlinear system vibration was solved by the direct integration method (the Newmark method). The dynamic characteristics of the main beam and cabin were analyzed at different temperatures, as well as safety during service. The results show that, with increasing temperature, the maximum midspan displacement of the main beam increases gradually, by 14.3%, 21.4%, and 57.1% at temperatures of 300°C, 400°C, and 600°C, respectively. The cabin vibration displacement increases with temperature, by up to 32.5% at 600°C, but the influence of temperature on cabin vibration acceleration is not obvious. It was concluded that the influence of temperature on the dynamic characteristics of the main beam must be considered during the design stage of cranes. The proposed model and analysis method provide a theoretical basis for the design of casting cranes according to temperature.

Based on Mindlin plate theory and finite element method (FEM), dynamic response analysis of sandwich composite plates with auxetic honeycomb core resting on the elastic foundation (EF) under moving oscillator load is investigated in this work. Moving oscillator load includes spring-elastickand damperc. The EF with two coefficients was modelled by Winkler and Pasternak. The system of equations of motion of the sandwich composite plate can be solved by Newmark’s direct integration method. The reliability of the present method is verified through comparison with the results other methods available in the literature. In addition, the effects of structural parameters, material properties, and moving oscillator loads to the dynamic response of the auxetic honeycomb plate are studied.

The paper deals with complex nonlinear time-dependent material models used in a structure exposed to fast dynamic loading. The finite element solution with the use of the explicit method for the direct integration of equations of motion is provided. Two material models suitable for description of nonlinear response of structure to dynamic loading were developed. These models are based on combination of visco-elastic behavior with the visco-plastic or visco-damage behavior. Behavior of these two models is compared. The behavior of the models under the impact loading is different and the paper shows the results.

Highly stretchable strain sensors, with embedded microchannels filled with conductive liquid, have been widely used in various applications in soft robotics for detecting different types of deformation modes, when attached to human or robot bodies. One of recent applications that draws an attention is direct integration of soft sensors with soft actuators for proprioceptive feedback. However, it is not easy to obtain a high resolution in curvature sensing when combined with bending actuators in which curvature is indirectly measured from strain sensing, since the placement of soft sensors are limited to the location where the strain sensitivity is relatively small. Therefore, we propose a new design of high gauge factor strain sensors using a multi-material structure. By alternately arranging low and high stiffness elastomers, the structure experiences amplified strain changes on each of the low-stiffness regions. The gauge factor was significantly increased as high as over three times of a conventional single material sensor. In this paper, the design and fabrication of the proposed sensor are described with an analytical model. The sensor was tested while integrated with a PneuNet bending actuator for curvature detection as an application.

Based on the concept of isoparametric mapping, a generic approach for investigating the bending and shear deformation in a non-prismatic elastic beam with corrugated steel webs (CSWs) was presented in this study. The strain field of an actual element (namely, the non-prismatic beam segments) is expressed as a function of the local coordinates in the parent element. Continually, the solution of the bending and shear deformation of the non-prismatic beam segment can be transformed into the integration of strain in the parent element under local coordinates. Since it is usually laborious to solve the displacement field by direct integration of strain in a non-prismatic beam segment using global coordinates. In addition, this study found that shear deformation cannot be ignored in the actual design of this type of structure because the thin-walled section has a small shear stiffness. In contrast, for a composite beam with CSWs, shear deformation occurs beyond bending deformation and becomes a major contributor of total deformation in some critical sections. Finally, experimental study of the mechanical properties of a non-prismatic beam with CSWs is conducted for the first time. The experimental results further demonstrate the validity of the proposed theoretical analysis methods.

The authors present an analytical solution for two-layered beam with interlayer slip. Timoshenko’s kinematic assumptions are used for both layers imposing the constraint of equal cross-sectional rotation. A linear constitutive equation between the horizontal slip and the interlaminar shear force is considered. The applied loads act in the plane of symmetry of composite beam and the material and geometrical properties do not depend on the axial coordinate. Analytical solution for the deflection, slip, cross-sectional rotation and internal forces are derived. The effect of the cross-sectional shear deformation to the deflection is analyzed. Closed form solutions are given for the stresses. A Rayleigh-Betti type reciprocity relation for composite shear deformable beam with interlayer slip is formulated, whose applications are illustrated by some examples.