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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.

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.

Appearance of transverse cracks in rotor systems mainly affects their stiffness content. The stability of such systems at steady-state running is usually analyzed by using the Floquet’s theory. Accordingly, the instability zones of rotational speeds are dominated by negative stiffness content in the whirl response in the vicinity of critical rotational speeds. Consequently, an effective stiffness measure is introduced here to analyze the effect of the crack and the unbalance force vector orientation on the intensity of negative potential and stiffness content in the whirl response. The effective stiffness expression is obtained from the direct integration of the equations of motion of the considered cracked rotor system. The proposed effective stiffness measure is applied for steady-state and transient operations using the Jeffcott rotor model with open and breathing crack models. The intensity of negative potential and stiffness content in the numerical and experimental whirl responses is found to be critically depending on the propagation level of the crack and the unbalance force vector orientation. Therefore, this can be proposed as a crack detection tool in cracked rotor systems that either exhibit recurrent passage through the critical rotational speeds or steady-state running.

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.

The non-linear partial differential (2+1) dimensional Breaking Soliton equation is studiedby using the direct integration and homotopy perturbation method. In this study, we use directintegration to obtain the known solution in the literature in practical and shortest way by assigningsome special values to the constants in the solutions of the (2+1) dimensional Breaking Solitonequation. We also obtain same type solution for (2+1) dimensional Breaking Soliton equation byusing the homotopy perturbation method with one iteration. Similarly, same type solutions can bedone different methods such as (G'/G)-expansion method.

The structural vibration of the main beam of a crane causes fatigue damage and discomfort to the driver. The swing of the payload has an effect on positioning precision, especially for a ladle crane, and this directly affects production safety. To study the influence of system parameters on the vibration of a crane’s main beam and the angle of the payload, a system consisting of the main beam, trolley, payload, and cabin was constructed. A rigid-flexible coupling dynamic model of a moving trolley with a hanging payload that moves on the flexible main beam with a concentrated cabin mass is established, and the direct integration method is used to solve the nonlinear differential equations of system vibration, which are obtained through Lagrange’s equation. Then, the time domain responses of the flexible main beam, payload angle, and cabin vibration are obtained. The influences of the trolley running speed, quality of the payload, and quality and position of the cabin on the vibration of the main beam and payload angle are analyzed. The results indicate that the amplitude of the main beam is directly proportional to the quality of the trolley, payload, and cab; the position of the cabin is closer to the mid-span; the amplitude of the main beam is larger; the structural damping has some influence on the vibration of the main beam; and the swing angle of the payload is related to the maximum running speed of the trolley, acceleration time, and length of the wire rope. In order to reduce the vibration of the main beam and cabin, the connection stiffness of the cabin should be ensured during installation.

The application of the sampling surfaces (SaS) method to the three-dimensional (3D) stress analysis of laminated composite plates is presented in a companion paper (Kulikov GM, Plotnikova SV. Strong sampling surfaces formulation for laminated composite plates. Compos Struct 2017;172:73–82). In this paper, we extend the strong SaS formulation to the 3D vibration analysis of laminated plates. The SaS formulation is based on choosing the arbitrary number of SaS parallel to the middle surface in order to introduce the displacements of these surfaces as basic plate unknowns. Such choice of unknowns with the use of the Lagrange polynomials in spatial approximations of displacements through the layer thicknesses leads to a robust laminated plate formulation. The feature of the proposed approach is that all SaS are located inside the layers at Chebyshev polynomial nodes. The use of outer surfaces and interfaces is avoided that makes it possible to minimize uniformly the error due to the Lagrange interpolation. Therefore, the strong SaS formulation based on direct integration of equations of motion of the elastic body can be applied efficiently for the 3D free and forced vibration analyses of laminated composite plates.

Local fatigue approaches, such as, the stress-life, strain-life or energetic approaches defines a framework to estimate the fatigue crack initiation from notches of structural details. Various engineering structures, such as, bridges, wind towers, among others, are subjected to cyclic dynamic loadings which may substantially reduce the strength of these structures. Nowadays, the structural systems tend to be more complex being necessary to find computationally efficient solutions to perform their fatigue analysis, accounting for dynamic actions corresponding to long complex loading events (e.g. diversity of trains crossing a bridge), mainly if local approaches are envisaged. Thus, this paper aims at presenting and validating a generalization of a methodology based on modal superposition technique, for fatigue damage parameters evaluation, which can be applied in fatigue analysis using local approaches. This technique was applied recently in the context of fatigue crack propagation based on fracture mechanics, although it can be extended to compute the history of local notch stresses and strains at notches. A very important conclusion is that the technique can be explored for the case of local confined plasticity at notches whenever the global elastic behaviour of the component prevails. Local submodelling can be explored with this technique to avoid the necessity of large computational models. Local models are only needed to be run under linear elastic conditions for the selected modal shapes of the structure, being the local time history of fatigue damage variable computed by modal superposition for each loading event. That time history may be further post-processed for elastoplastic conditions using Neuber or Glinka’s analyses. Comparisons with direct integration elastoplastic dynamic analysis confirmed the feasibility of the proposed approach.

In this paper, a novel framework for the design of mixed (combined direct and indirect) integration for batch process systems is presented. The framework is based on the concept of pseudo-direct energy integration (PDEI) which reformulates indirect integration as direct integration using pseudo-process streams. Two algorithms are presented to achieve energy integration for batch processes operating cyclically (in a campaign mode). The first algorithm targets maximization of energy recovery and overcomes the limitations of some of the existing contributions for design of mixed integrated systems. The second algorithm provides a network reduction methodology to generate a cadre of integrated designs while exploring the trade off between capital (number of heat exchangers and storage units) and operating costs (utility consumption). The proposed framework is illustrated using a benchmark example of two hot and two cold streams. This article is protected by copyright. All rights reserved.

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). A series of PSR calculations is carried out using the direct integration (DI) and ISAT approaches, and validation of DI is performed through comparisons with previous experiments. Assessment of the accuracy of ISAT approach is conducted through direct comparisons with DI calculations. Moreover, accessed region of the composition space, sensitivity of ISAT calculations with respect to the absolute error tolerance values and speedup are analyzed for two different test cases, a hydrogen–air and an ethylene–air combustion case. In summary, the hydrogen–air case resulted in a speedup of 9.8 for 1 million of PSRs in series, whereas for the ethylene–air case it was 42 for 0.3 million PSRs.

Chemical engineering science 159, 84-92 (2017). doi:10.1016/j.ces.2016.05.038 special issue: "iCAMD – Integrating Computer-Aided Molecular Design into Product and Process Design / Edited by Claire Adjiman and André Bardow", Published by Elsevier Science, Amsterdam [u.a.]

A methodology for the construction of rational curves with rational arc length functions, by direct integration of hodographs, is developed. For a hodograph of the form r ′ ( ξ ) = ( u 2 ( ξ ) − v 2 ( ξ ) , 2 u ( ξ ) v ( ξ ) ) / w 2 ( ξ ) , where w ( ξ ) is a monic polynomial defined by prescribed simple roots, we identify conditions on the polynomials u ( ξ ) and v ( ξ ) which ensure that integration of r ′ ( ξ ) produces a rational curve with a rational arc length function s ( ξ ) . The method is illustrated by computed examples, and a generalization to spatial rational curves is also briefly discussed. The results are also compared to existing theory, based upon the dual form of rational Pythagorean-hodograph curves, and it is shown that direct integration produces simple low-degree curves which otherwise require a symbolic factorization to identify and cancel common factors among the curve homogeneous coordinates.

This paper presents a numerical dynamic analysis of a self-supporting transmission line (TL) latticed steel tower, for the purpose of compare the results with those obtained in an experimental dynamic analysis of a full-scale tower. The main objective of this work is to calibrate the structural damping ( c ) in the numerical model until the damping ratio ( ζ ) results the same that in the experimental analysis, since the damping is a fundamental parameter in numerical analysis, which can change significantly the response of the structure, especially in terms of dynamic amplification. It should be noted that in this type of structure is crucial perform a structural analysis most accurate possible, given the fact that in a TL are built hundreds of identical towers and the collapse of one can lead to a cascading failure. The dynamic characteristics, such as the frequencies and normal modes were evaluated in a modal analysis, using the ANSYS © program v. 15.0, and also through the direct numerical integration method, using an explicit approach (central finite differences). The experimental tower was tested using impulsive loads, which were reproduced in the numerical model to allow comparison with the experimental results. In the modal analysis were employed models commonly used in actual designs, that is, with space truss and space frame members. For the direct integration method, was used a program developed in FORTRAN, in which only space truss elements are allowed, necessitating the adoption of the fictitious bars to eliminate internal instabilities. The consideration of the damping in the direct integration method was taken in a simplest form, that is, proportional to the mass. Finally, the numerical values found were very close to the experimental response, setting the value of structural damping for use in such projects of this type of tower.

A sensitivity-based finite element model updating approach is presented to identify the local damages in axially functionally graded (AFG) beams. The local damage is simulated by a reduction in the elemental Young's modulus of the beam. In the forward analysis, free vibration analysis is conducted to obtain the natural frequency of the beam. Then forced vibration responses of the beam under external force are obtained from Newmark direct integration. In the inverse analysis, an objective function is established and a sensitivity-based finite element model updating approach is used to identify the local damages in the beam. Two numerical examples are investigated to illustrate the correctness and efficiency of the proposed method. Damage identification results from measured natural frequencies and the dynamic responses from different excitation forces are compared. The effects of measurement noise on the identification results are investigated. Studies in this paper indicate that the proposed method is efficient and robust for identifying damages in the axially functionally graded beams. Good identified results can be obtained from the short time histories of a few number of measurement points and the first several natural frequencies.

The effect of soil-structure interaction (SSI) on the dynamic responses of seismically isolated three-span continuous reinforced concrete (RC) bridge is investigated. Also, tuned mass damper(s) (TMD/s) is/are installed to control undesirable bearing displacement, even under the SSI effect. The TMDs are placed at the mid-span of the bridge and each tuned with a modal frequency, while controlling up to first few modes as desirable. The soil surrounding the foundation of pier is modeled by frequency independent coefficients. Dynamic analysis is carried out in time domain using direct integration method. In order to specify the effects of the SSI, the responses of the non-isolated, isolated, and controlled isolated bridge are compared. It is observed that the soil surrounding the pier has significant effects on the bearing displacement of the isolated RC bridges. In addition, it is observed that the seismic responses of isolated RC bridge reduced significantly with installation of the TMDs.

This paper deals with the problems investigating of parameters that influence the dynamic behaviour of the carrying structure of type H portal cranes with high carrying capacities excited by the motion of the crane and the load swing. The introduction of the paper presents the importance of the problem of the dynamics of structures. In accordance with the given problem, dynamic spatial models of the boom and portal of the crane were formed and solved. The main part of the paper presents a modal analysis and determines dynamic responses of the space structure with the application of the finite element method and direct integration. The influence of changes in speed and acceleration on the dynamic response of the structure was analysed. The influence of the change of boom rotation angle on the dynamic response of the structure was also analysed. The investigation results provide significant bases and conclusions for designing portal cranes and continuation of research in this field.

High-speed machining of thin-walled workpiece is widely used in aerospace industry. To optimize the machining parameters in milling operations, the related process stability is required to be predicted. Compared to the existing two-dimensional (2D) milling stability model, a more completed three-dimensional (3D) regenerative process stability prediction model of thin-walled workpiece is presented based on the newly developed dynamic model. The efficiency and accuracy of the regenerative milling stability can be improved in the presented 3D model. The analysis procedure of the stability of flexible dynamic milling is developed in details. The 3D stability lobes are calculated according to the full discretization method and direct integration scheme. To verify the accuracy of presented 3D stability model, the thin-walled workpiece milling sound pressure signal and surface quality are determined in experiments.

The prototype of mold oscillator that uses a non-sinusoidal generator was modified using Inverse dynamics and Multi-body dynamics. We maintained a basic structure of the mold oscillator including the motor, the gear, the leaf-spring and the caster. To reduce the coupling effect, the non-sinusoidal generator was replaced by a hollow cylinder that had non-sinusoidal surface. The system parameters were obtained from previous research [1], and a new design of the connecting rod between the cylinder and the leaf spring was analyzed by sensitivity analysis. A definition of the detailed system component including gear mesh, and non-sinusoidal surface, Lagrange's equation, Fourier series, and Cam profile synthesis was used to define an equation of motion. The response of oscillating system was derived by a direct integration method. The model was simulated according a specific assumption for each component, and a control system corresponding to real operation was applied. Dynamic responses are displacement, velocity and acceleration of each component. All responses from these simulations were analyzed in the time-frequency region by Fast Fourier transform. Using the model, sensitivity analysis about design variables was also executed about operating performance.

Usually, solar heat in combi systems is used via a buffer storage. In contrast to that, the solar collectors may be connected directly to the space heating circuit in order to store the heat in the building itself. Such a direct solar integration is investigated within system simulations for different layouts and heating elements. The simulations show significant reductions in the final energy demand as well as an increasing solar yield due to less thermal losses of the storage tank compared to the usual solution with one buffer storage. A prototype of one of the investigated heating concepts within a single family house proofs the functionality of the system concept and the high solar yield, particularly at low radiation levels. Since only a few manufacturers provide such system solutions with a direct solar integration, the results may have an important impact on the future development of combi systems.

Seismic qualification by test is widely used as a way to show the integrity and functionality of equipment that is related to the overall safety of nuclear power plants. Another means of seismic qualification is by direct integration analysis. Both approaches require a series of time histories as an input. However, in most cases, the possibility of using real earthquake data is limited. Thus, artificial time histories are widely used instead. In many cases, however, response spectra are given. Thus, most of the artificial time histories are generated from the given response spectra. Obtaining the response spectrum from a given time history is straightforward. However, the procedure for generating artificial time histories from a given response spectrum is difficult and complex to understand. Thus, this paper presents a simple time-domain method for generating a time history from a given response spectrum; the method was shown to satisfy conditions derived from nuclear regulatory guidance.

Large nonlinear rotor-bearing system is an important structure in rotating machinery, such as NC machine. Due to the mass imbalance of the system, vibrations induced by centrifugal forces inevitably exist in rotating machinery. So, nonlinear dynamic response of a complex rotor-bearing system was dealt with in this paper. The system considered was modeled using the finite element method and has 124 DOFs (degrees of freedom). A linear reduction method was used and a reduced-order dynamic model of the system with two DOFs had been obtained. Harmonic balance method was applied to the reduced-order dynamic model of the system and an approximate analytical expression of the solution for nonlinear dynamic response of the system at steady state was derived. The analytical solution obtained from the reduced-order dynamic model of the system was compared with the numerical one obtained from the direct integration of the equations of motion of the original system.

A direct integration scheme based on the trapezoidal integration method associated with Romberg's acceleration algorithm is proposed to calculate numerically with the desired accuracy, direct exchange areas (DEAs) within an axisymmetric enclosure confining non-isothermal and inhomogeneous non-grey gaseous combustion products with soot. A three-dimensional integral needs to be evaluated, but axisymmetry and reciprocity of DEAs bring a notable processing time reduction. The integration process poses difficulties pertinent to singular DEAs of self-irradiance. Evaluating self-irradiance of gas volume zones is the concern of this investigation, in which we introduce a new concept that we call the optical exchange gap (OEG). It has been established that the OEG width associated with a volume zone, optimized with extreme care to meet Erkku's data, decreases with the radial position and radial optical thickness. A correlation, deduced to derive the OEG width for a given situation, has been shown to be more efficient, simple and accurate than a proper center-to-center distance technique. The effectiveness of the developed procedure was demonstrated by comparison of model predictions, using the zonal method in conjunction with the weighted-sum of grey gases (WSGG) model, with highly accurate reference data and by carrying out an error analysis.

Summary Study of collapse-resisting properties of structures has attracted widespread attention because of frequently occurring earthquakes and extreme events (e.g. blast) around the world. The developments in computational methods have enabled researchers to numerically simulate the collapse of structures under different kinds of loadings and provide reliable assessments of the collapse performance of structures. The dynamic nature of structural collapse requires a direct integration algorithm to solve the equations of motion of the numerical simulation model. A major concern in such simulations is the computational efficiency, which stems from the need to use a small time step size in both implicit algorithm and explicit algorithm. In this paper, modeling techniques to simulate typical failure mechanisms in reinforced concrete frame structures combined with the application of the recently developed explicit, unconditionally stable, parametrically dissipative KR-α integration method to investigate collapse simulation are presented. A fiber beam-column element is used to model the frame members, where the material nonlinearities, especially material softening, are simulated by a plastic damage model combined with a failure criterion. Numerical examples are presented to illustrate the proposed collapse simulation technique. The results indicate that the proposed technique provides an accurate result and has exceptional computational efficiency. Copyright © 2015 John Wiley & Sons, Ltd.

Dynamic modeling of beveloid gears is less developed than that of conventional involute gears with parallel axis because of their complicated mesh mechanism and 3-dimensional dynamic coupling. For evaluating the dynamic characteristics of a marine gearbox with crossed beveloid gears more realistically, a systematic dynamic modeling approach was proposed based on the lumped parameter and the finite element method. Considering the time-varying mesh stiffness excitation, time-varying loaded translational transmission error excitation, sliding friction excitation and backlash nonlinearity, a coupled gear–shaft–bearing–housing dynamic model for a marine gearbox with crossed beveloid gears was developed based on the proposed modeling method. Then, numerical integrations applying the explicit Runge–Kutta formula and the implicit direct integration were used to solve the nonlinear dynamic model. The dynamic transmission error, dynamic mesh force, and dynamic equivalent shaft-bearing supporting force were obtained as well as the dynamic response of the housing. Finally, a test rig was established for the marine gearbox with crossed beveloid gears and vibration tests were performed to investigate the dynamic responses. Through analyzing the responses in time domain and frequency domain, the experimental results compared well with the theoretical dynamic results.

A fully automated optimization process is provided for the design of ducted propellers under open water conditions, including 3D geometry modeling, meshing, optimization algorithm and CFD analysis techniques. The developed process allows the direct integration of a RANSE solver in the design stage. A practical ducted propeller design case study is carried out for validation. Numerical simulations and open water tests are fulfilled and proved that the optimum ducted propeller improves hydrodynamic performance as predicted.

The dynamic response topology optimization problems are usually computationally expensive, so it is necessary to employ the model reduction methods to reduce computational cost. This work will investigate the effectiveness of the mode displacement method(MDM) and mode acceleration method(MAM) for time-domain response problems within the framework of density-based topology optimization. Three objective functions, the mean dynamic compliance, mean strain energy and mean squared displacement are considered. It is found that, in general cases, MDM is not suitable for time-domain response topology optimization problems due to its low accuracy of approximation, while MAM works well for problems of a wide range, and when there are many time steps, the MAM based topology optimization approach is more efficient than the direct integration based approach. So for practical applications, when the problem needs many time steps, the MAM based approach is preferred and otherwise, the direct integration based approach is suggested.

The performance of wave energy converters and other offshore renewable energy platforms, non-linear effects is frequently assessed in time domain, especially when the nonlinear forces from the large amplitude motions, mooring forces, power take-off or the energy conversion control system are considered. One popular approach in the time-domain analysis is the so-called hybrid frequency–time domain analyses, in which the radiation forces must be calculated through a convolution integral of the motion history and the impulse response function. The direct integration of the convolution is not only time-consuming and inconvenient when a real time control is used, but also needs a storage and renewal of a certain history of motions. To this end, some approximation methods have been developed for calculating the memory effect, and these methods inevitably introduce additional equations into the dynamic system. In this paper, a new method is proposed for calculating the memory effect by extending the conventional Prony׳s function method so that the memory effect calculation can be carried out simply in a recursive manner. As a result of the recursive calculation, only one previous step of the values is needed, which can be renewed automatically in each time step calculation.

This paper introduces Romberg-Richardson\'s method as one of the numerical integration tools for computation of stress intensity factor in a pre-cracked specimen subjected to a complex stress field across the crack faces. Also, the computation of stress intensity factor for various stress fields using existing three methods: average stress over interval method, piecewise linear stress method, piecewise quadratic method are modified by using Richardson extrapolation method. The direct integration method is used as reference for constant and linear stress distribution across the crack faces while Gauss-Chebyshev method is used as reference for nonlinear distribution of stress across the crack faces in order to obtain the stress intensity factor. It is found that modified methods (average stress over intervals-Richardson method, piecewise linear stress-Richardson method, piecewise quadratic-Richardson method) yield more accurate results after a few numbers of iterations than those obtained using these methods in their original form. Romberg-Richardson\'s method is proven to be more efficient and accurate than Gauss-Chebyshev method for complex stress field.

Total site heat integration (TSHI) provides more opportunities for energy saving in industry clusters. Some design methods including direct integration using process streams and indirect integration using intermediate-fluid circuits, i.e. , steam, dowtherms and hot water, have been proposed during last few decades. Indirect heat integration is preferred when the heat sources and sinks are separated in independent plants with rather long distance. This improves energy efficiency by adaption of intermediate fluid circle which acts as a utility provider for plants in a symbiotic network. However, there are some significant factors ignored in conventional TSHI, i.e. the investment of pipeline, cost of pumping and heat loss. These factors simultaneously determine the possibility and performance of heat integration. This work presents a new methodology for indirect heat integration in low temperature range using hot water circuit as intermediate-fluid medium. The new methodology enables the targeting of indirect heat integration across plants considering the factors mentioned earlier. An MINLP model with economic objective is established and solved. The optimization results give the mass flow rate of intermediate-fluid, diameter of pipeline, the temperature of the circuits and the matches of heat exchanger networks (HENS) automatically. Finally, the application of this proposed methodology is illustrated with a case study.

This paper presents the methodology and challenges experienced in the microfabrication, packaging, and integration of a fixed-fixed folded spring piezoelectric energy harvester. A variety of challenges were overcome in the fabrication of the energy harvesters, such as the diagnosis and rectification of sol-gel PZT film quality and adhesion issues. A packaging and integration methodology was developed to allow for the characterizing the harvesters under a base vibration. The conditioning circuitry developed allowed for a complete energy harvesting system, consisting a harvester, a voltage doubler, a voltage regulator and a NiMH battery. A feasibility study was undertaken with the designed conditioning circuitry to determine the effect of the input parameters on the overall performance of the circuit. It was found that the maximum efficiency does not correlate to the maximum charging current supplied to the battery. The efficiency and charging current must be balanced to achieve a high output and a reasonable output current. The development of the complete energy harvesting system allows for the direct integration of the energy harvesting technology into existing power management schemes for wireless sensing.

The paper studies the efficiency of seismic isolation system in the form of rubber-metal bearings with different height buildings at multicomponent seismic impact. As an example, seismically insulated monolithic reinforced concrete 5-, 9-and 16-storey buildings are considered. The solution of the problem is obtained by a direct integration of the motion equations for an explicit scheme in the software package LS-DYNA. The calculation is performed considering nonlinear nature of rubber bearings. The analysis of the effectiveness of buildings with seismic insulation and without it is performed.

The article deals with a multi-storey monolithic concrete building calculation on the earthquake. The problem is solved in the time domain by a direct dynamic method. Direct integration of motion equations is carried out on an explicit scheme. This technique allows us to solve the problem in a nonlinear dynamic formulation considering geometric and physical nonlinearities. The paper presents and analyzes the main results of the calculation.

The paper deals with a new robust PID controller design method based on integrating requirements on transient performance into the popular frequency-domain Ziegler-Nichols design approach. The developed method provides support to the designer by converting identified ultimate plant parameters into PID controller parameters using variable weights that depend on expected maximum overshoot η max and settling time t s of the closed-loop step response. An extension of this method is proposed which enables to design PID controller guaranteeing robust stability and nominal performance for the uncertain plant modeled using unstructured uncertainty. Fulfillment of performance specification is guaranteed for the nominal model as well as for the worst-case one. The main advantage of the proposed method is a direct integration of performance requirements in the design procedure. Effectiveness of the proposed robust PID design method is verified by simulations and experiments on the real plant.

The use of high-performance materials in bridges is leading to structures that are more susceptible to wind- and traffic-induced vibrations due to the reduction in the weight and the increment of the slenderness in the deck. Bridges can experience considerable vibration due to both moving vehicles and wind actions that affect the comfort of the bridge users and the driving safety. This work explored the driving safety and comfort in a very slender arch bridge under turbulent wind and vehicle actions, as well as the comfort of pedestrians. A fully coupled wind–vehicle–bridge interaction model based on the direct integration of the system of dynamics was developed. In this model, the turbulent crosswind is represented by means of aerodynamic forces acting on the vehicle and the bridge. The vehicle is modeled as a multibody system that interacts with the bridge by means of moving contacts that also simulate road-surface irregularities. A user element is presented with generality and implemented using a general-purpose finite-element software package to incorporate the aeroelastic components of the wind forces, which allows modeling and solving of the wind–vehicle–bridge interaction in the time domain without the need for using the modal superposition technique. An extensive computational analysis program is performed on the basis of a wide range of turbulent crosswind speeds. The results show that bridge vibration is significantly affected by the crosswind in terms of peak acceleration and frequency content when the crosswind intensity is significant. The crosswind has more effect on the ride comfort of the vehicle in the lateral direction and, consequently, on its safety in terms of overturning accidents.

This paper presents a mechanotransduction model designed to convert the multi-axial mechanical loads at the fingertip-contact interface into neural-spike trains, the MultiAxial Stress Mechanotransduction (MASM) model. Seeking a comprehensive solution and more direct integration with sensor systems in tactile applications, the model accounts for the conversion of multi-axial (pressure and shear) stresses at the fingertip-contact interface into spike trains with artificial slow adapting (SA) and rapidly adapting (RA) afferents type I (SAI, RAI) and II (SAII, RAII). These have been modelled based on the properties of those in human fingertips. To illustrate how the model works, artificial data mimicking typical stress stimuli profiles used to evaluate the response of biological afferents were fed to the model and results examined. Subsequently, the suitability of the model for real tactile applications was preliminary tested by inputting to the model real life, measured pressure and shear data in a fingertip ‘press-push-lift’ action. The response of the modelled afferents was analyzed and qualitatively compared to typical responses of biological units. Initial results show that it is possible to codify the mechanical contact tactile information measured by multi-axial sensor systems in a bio-inspired fashion, reproducing relevant features similar to those produced by biological mechanoreceptors.

A highly efficient and accurate I-HPDIM algorithm is proposed.An absolute-response-oriented scheme of PEM is derived.A scheme in modelling tridirectional non-uniform nonstationary spatial motions is presented.The proposed stochastic analysis scheme is implemented in general FE platform.The proposed analysis scheme is demonstrated in bridge seismic pounding analysis. This paper proposes an improved high precision direct integration method (I-HPDIM) and an absolute-response-oriented scheme of pseudo-excitation method (PEM) for nonstationary stochastic seismic analysis of large structures under tridirectional nonuniformly modulated spatial ground motions. The proposed approaches resolve the bottle-neck problem of conventional HPDIM and significantly improve computational efficiency of both PEM and HPDIM, making the proposed nonstationary stochastic analysis scheme more attractive for engineering purposes. Hence, it has been implemented in general finite element platforms, having powerful and versatile modelling and analysis capabilities, for stochastic seismic analysis of large and complex structures under tridirectional nonstationary spatial seismic motions.

Various types of flexure hinges have been introduced and implemented in a variety of fields due to their superior performances. The Castigliano’s second theorem, the Euler-Bernoulli beam theory based direct integration method and the unit-load method have been employed to analytically describe the elastic behavior of flexure hinges. However, all these methods require prior-knowledge of the beam theory and need to execute laborious integration operations for each term of the compliance matrix, thus highly decreasing the modeling efficiency and blocking practical applications of the modeling methods. In this paper, a novel finite beam based matrix modeling (FBMM) method is proposed to numerically obtain compliance matrices of flexure hinges with various shapes. The main concept of the method is to treat flexure hinges as serial connections of finite micro-beams, and the shearing and torsion effects of the hinges are especially considered to enhance the modeling accuracy. By means of matrix calculations, complete compliance matrices of flexure hinges can be derived effectively in one calculation process. A large number of numerical calculations are conducted for various types of flexure hinges with different shapes, and the results are compared with the ones obtained by conventional modeling methods. It demonstrates that the proposed modeling method is not only efficient but also accurate, and it is a more universal and more robust tool for describing elastic behavior of flexure hinges.

Tuned Mass Damper (TMD) devices are one of the oldest vibration control means and are widely used in different engineering contexts. Despite the bulk of literature on various TMD-related issues, the effectiveness of TMDs in reducing the earthquake response of civil engineering structures is still debated. This paper deals with the optimum tuning of the free parameters of a passive TMD applied to sample frame structures subjected to selected seismic excitations. A tuning procedure consisting of a numerical Minimax optimization algorithm is implemented within MATLAB. The so-conceived TMD turns out to be optimum with respect to the specific seismic event, hence allowing for optimum reduction in primary seismic response. Both optimization process and seismic analysis are carried out in the time domain, through direct integration of the equations of motion. The method is tested on benchmark single-DOF and multi-DOF shear-type prototype structures from the literature by assuming first the Imperial Valley 1940 seismic input, as a sort of benchmark excitation, and then additional recent strong motion earthquakes. In essence, this paper shows that, in principle, with present reference to frame structures, the optimum tuning of TMD parameters at given seismic input is theoretically possible.

The aim of this paper is to study the ultimate bearing capacity of steel tubular transmission tower’s joint with annular plate based on the theoretical analysis. A simplified model of annular plate joints was performed to investigate the force distribution of the tube-gusset joints. To obtain the state of stress and ultimate bearing capacity, the annular plate with clamped boundary condition on the inner edges and subjected to diametric loading is employed in this study by the direct integration and thin plate energy principle theory. Experiment and finite element analysis are carried out and the results show that both are the similar.

This article suggests methods of calculations of buildings and structures responsible for specific effects on the basis of nonlinear dynamic methods. Example of calculations wide-span structures in the time domain by direct integration of equations of motion, taking into account the nonlinear nature of the structures.

This paper investigates the characteristics of riding comfort of double-deck bridges under multi-lane moving vehicles based on a framework for spatial dynamic analysis of double-deck bridges carrying both road vehicles and monorail trains taking into account road surface roughness and both vertical and lateral track irregularities. The bridge is modelled by finite elements with proper boundary conditions. And the road vehicle is modelled as a mass-spring-damper system with 7 degrees of freedom (DOFs) while that of the monorail train has 15 DOFs. Then holistic bridge-vehicle interaction system was assembled using a fully computerized approach and solved by direct integration method. The riding characteristics of an authentic long-span bridge carrying both road vehicles and monorail trains are investigated in details as per ISO 2631.

This paper presents an effective numerical approach for welding process parameter optimization to minimize weld-induced distortion in structures. A numerical optimization framework based on coupled Genetic Algorithm (GA) and Finite Element Analysis (FEA) is developed and implemented for a low and a high fidelity model. Classical weakly coupled thermo-mechanical analysis with thermo-elasto-plastic assumptions is carried out for distortion prediction of numerical models. The search for optimum process parameters is executed by direct integration of numerical models and GA-based optimization technique. The developed framework automatically inserts the process parameters into the simulation models, executes the FE-based welding simulations and evaluates the required simulation output data for iterative evolutionary optimization. The optimization results show that the proposed approach can contribute substantially to enhance final welded product quality while facilitating and accelerating the product design and development.

Cooling tower is analyzed as an assembly of layered nonlinear shell elements. Geometric representation of the shell is enabled through layered nonlinear shell elements to define the different layers of reinforcements and concrete by considering the material nonlinearity of each layer for the cooling tower shell. Modal analysis using Ritz vector analysis and nonlinear time history analysis by direct integration method have been carried out to study the effects of the inclination of the supporting columns of the cooling tower shell on its dynamic characteristics. The cooling tower is supported by I-type columns and ᴧ-type columns supports having the different inclination angles. Relevant comparisons of the dynamic response of the structural system at the base level (at the junction of the column and shell), throat level and at the top of the tower have been made. Dynamic response of the cooling tower is found to be significantly sensitive to the change of the inclination of the supporting columns. It is also found that the stiffness of the structure system increases with increase in inclination angle of the supporting columns, resulting in decrease of the period of the structural system. The participation of the stiffness of the tower in structural response of the cooling tower is fund to be dependent of the change in the inclination angle and even in the types of the supporting columns.

Various numerical tools have been developed to predict the level of aeolian vibrations for a damped span of transmission-line conductors. In part I of this study, nonlinear time history models of two types of transmission-line dampers were developed. In this paper, a model for the complete conductor-damper system is presented. When combined with empirical equations for wind power input and conductor self-damping using the Energy Balance Principle, the direct integration time history model proposed allows the prediction of the vibration amplitudes expected on a damped span. The amplitudes predicted by the model compare well to experimental data sets available in the literature. Since the damper is modelled from its mechanical properties of geometry, mass, stiffness, and damping, the optimization of a conductor-damper system can be done easily with this model, without additional experimental tests. A sensitivity analysis is conducted to demonstrate the capabilities of the model.

Based on time precise integration method, an improved precise integration method, which called, is studied in the paper to solve the dynamic equation of , where v is an unknown n dimensions vector, Hv and f are respectively the linear homogeneous part and nonlinear part on the right end of equation. Then the calculation expressions of the method are given. The numerical example of nonlinear dynamic analysis of low pressure rotor of high parameter turbine shows that the proposed method is no need to solve the H-1 and the computational accuracy and efficiency can be ensured.

Nonlinear Dynamic analysis can be done by direct integration of the equations of motion by step by step procedures. Direct integration provides the most powerful and informative analysis for any given earthquake motion. A time dependent forcing function (earthquake accelerogram) is applied and the corresponding response-history of the structure during the earthquake is computed. That is, the moment and force diagrams at each of a series of prescribed intervals throughout the applied motion can be found. Computer programs have been written for both linear elastic and non-linear inelastic material behaviour using step-by-step integration procedures. One such program is ETAB in which three-dimensional non-linear analyses can be carried out taking as input the three orthogonal accelerogram components from a given earthquake, and applying them simultaneously to the structure.

A semi-analytical simulation of a rotor bearing system that consisted of a multi-segment continuous rotor and plain fluid film bearings with finite length is developed in this paper in order to investigate the system's response under the current proposal of simulation. The rotor is simulated using the continuous medium theory and the bearings with finite length follow a very recent analytical simulation that incorporates the analytical solution of the Reynolds equation for the plain, finite journal bearing. The boundary conditions combine the rotor's shearing force and the fluid film forces at the points where the bearings are located, which are expressed analytically with direct integration of the pressure distribution function. A case study of simulating a multi-segment shaft is used in order to compare the current simulation with corresponding simulations using continuous rotor mounted on linear bearings, or finite bearings numerically simulated using the finite difference method. The time response, the amplitude of the response and the phase during passage through resonance are evaluated for these three cases of bearing simulation using numerical procedures and the differences are notified and remarked.

This paper consists of two parts. In the first part a numerical model describing the thermo hydraulic behavior of district heating (DH) networks has been used to investigate the pressure and temperature profile within a solar assisted system. The network description is based on a graph-theoretical method and the Newton algorithm was used for solving the system of nonlinear equations. A direct integration without heat storage is implemented here for an existing network topology in South Germany. The simulation shows that critical differential pressure driven operation of the district pump is not realizable with a reasonable number of pressure transmitters. The volume flow driven control provides more stability but has to be optimized by means of pressure measurements. The second part of the paper presents the new test facility built for decentralized solar heat integration. It also gives an overview about the design topics that will be investigated during the next test period: component suitability for bidirectional heat exchange, station control, net metering and handling both solar and load sides.

The paper studies the efficiency of seismic isolation system in the form of lead rubber bearings with different height buildings at multicomponent seismic impact. As an example, seismically isolated monolithic ferro-concrete 5-, 9- and 16-storey buildings are considered. The solution of the problem is obtained by a direct integration of the motion equations for an explicit scheme in the software package LS-DYNA. The calculation is performed considering the nonlinear nature of lead rubber bearings. The analysis of the effectiveness of buildings with and without seismic isolation it is performed.

Spar floating platforms have been largely used for deepwater drilling, oil and natural gas production, and storage. In extreme weather conditions, such structures may exhibit a highly nonlinear dynamical behavior due to heave-pitch coupling. In this paper, a 2-DOF model is used to study the heave and pitch dynamical response in free and forced vibration. Special attention is given to the determination of the nonlinear vibration modes (NNMs). Nonsimilar and similar NNMs are obtained analytically by direct application of asymptotic and Galerkin-based methods. The results show important NNM features such as instability and multiplicity of modes. The NNMs are used to generate reduced order models consisting of SDOF nonlinear oscillators. This allows analytic parametric studies and the derivation of important features of the system such as its frequency-amplitude relations and resonance curves. The stability is analyzed by the Floquet theory. The analytical results show a good agreement with the numerical solution obtained by direct integration of the equation of motion. Instability analyses using bifurcation diagrams and Mathieu charts are carried out to understand the fundamental mechanism for the occurrence of unstable coupled heave-pitch resonant motions of floating structures in waves and to study the dependencies of the growth rate of unstable motions on physical parameters.