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In recent times, origami-inspired deployable structures have received significant interest from the research community as a major area of research in the fields of science and technology. This paper deals with the geometry and the deformation behavior of deployable cones based on the four-fold line origami concept. First, a novel geometric design algorithm is presented to develop axially foldable conical structures based on generalized Miura-ori pattern, which is then utilized to investigate the influence of four design parameters on folding geometry. The foldability of thus obtained origami patterns is verified with the help of physical models. The geometric incompatibilities during the deployment are highlighted using a simple experiment, showing the unfolding sequence of a paper model. The deformations due to incompatibilities are analyzed by adopting the concept of pin-jointed truss modeling of the origami structures. A mathematical model of the deployment problem is formulated to capture the deployment deformations of the structure, on the basis of which an algorithm for deformation analyses is developed. One example is considered to characterize the deformation behavior of the conical origami structures as the design parameters of the folding pattern are varied. The analytical findings demonstrate that the fold line strains of the origami cone are very sensitive to the changes in three design parameters, number of origami units (m), fold angle (α 0), and angle θ 2 ; except the length ratio (l r 0). The variation in design parameters may induce bi-stability in the deployment path of the conical structure. The findings of the analytical investigation are verified numerically, demonstrating that the strain responses obtained from the numerical analyses are completely consistent with the analytical results. [ABSTRACT FROM AUTHOR]

This paper presents a quasistatic problem of an elastic body in frictional contact with a moving foundation. The model takes into account wear of the contact surface of the body caused by the friction. We recall existence and uniqueness results obtained in Sofonea et al. (2017). The main aim of this paper is to present a fully discrete scheme for numerical approximation together with an error estimation of a solution to this problem. Finally, computational simulations are performed to illustrate the mathematical model. [ABSTRACT FROM AUTHOR]

Highlights • The mathematical model of corrugated shells with special shapes is presented. • Effect of corrugation parameters on critical load is investigated. • Linear and nonlinear buckling analyses are conducted. • Critical load of corrugated shells is compared to smooth ones. • Specific range of corrugation parameters significantly increase the value of relative critical load. Abstract The problem of elastic stability of the shells with special shapes with corrugated middle surfaces under external pressure is debated in the presented paper. Solution of the problem is based on FEM study. Corrugated barrelled, pseudo-barrelled, and cylindrical shells of constant mass are considered. Geometrical modification of the middle surface geometry is based on sine wave along principal directions. Middle surface of the corrugated shells are described referring to differential geometry of surfaces by parametric functions in three-dimensional Euclidean space. Linear and nonlinear buckling analyses are conducted. Examples of buckling modes are presented, which differ significantly from those typical for shells of revolution with positive or zero Gaussian curvature. It is proven that corrugation may lead to serious increase or decrease of critical load for all types of presented shells. [ABSTRACT FROM AUTHOR]

The nef cone volume appeared first in work of Peyre in a number-theoretic context on Fano varieties, and was then studied by Derenthal and co-authors in a series of papers on del Pezzo surfaces. The idea was subsequently extended to also measure the Zariski chambers of del Pezzo surfaces. We start in this paper to explore the possibility to use this attractive concept to effectively measure the size of the nef cone on algebraic surfaces in general. This provides an interesting way of measuring in how big a space an ample line bundle can be moved without destroying its positivity. We give here complete results for simple abelian surfaces that admit a principal polarization and for products of elliptic curves. [ABSTRACT FROM AUTHOR]

This paper presents an analytical solution for the analysis of axially-loaded compressible floating piles embedded in a homogeneous elastic soil layer of finite thickness. The mathematical model is based on a Tajimi-type elastic continuum formulation, that allows deriving an accurate closed-form expression for the frictional stresses developing at the soil-pile interface. The pile and its underlying soil column are considered as one-dimensional axially deforming rods, and solution of their governing equations leads to closed-form expressions for pile and soil displacements and stresses. The proposed model provides results of similar accuracy to boundary integral solutions for the special case of floating piles in elastic half-space, and to numerical analyses for the general problem of floating piles embedded in a layer of finite thickness. As such, the model is used to prepare charts for the settlement analysis of floating piles in practice, based on a parametric analysis that unveils the sensitivity of the axial response of floating piles to the different problem parameters. [ABSTRACT FROM AUTHOR]

In order to make full use of the advantages of superheated steam (SHS), SHS injection in multi-point injection wells (MPIW) is proposed in this paper. Firstly, a mathematical model comprised of SHS flow model in inner tubing (IT) or long tubing (LT) and annulus, transient heat transfer model in oil layer is established. Secondly, type curves of SHS flow in MPIW is obtained by finite difference method on space and the iteration technique. Then, the effect of injection temperature on distributions of thermophysical properties of SHS in MPIW is discussed in detail. Results show that: (a) When the heat exchange between IT and annulus is taken into consideration. SHS temperature in IT has a decrease while SHS temperature in annulus has an increase. (b) With the help of MPIW, heating effect at both heel and toe points of the horizontal wellbores can be enhanced. (c) While the increase of SHS temperature certainly benefits the formation heating effect through the increase of both SHS temperature and superheat degree, the following decrease of SHS pressure in annulus will lead to the decrease of SHS absorption rate. This paper unravels some intrinsic flow characteristics of SHS in MPIW, which has a significant impact on the optimization of SHS injection parameters and analysis of heat transfer law in MPIW. [ABSTRACT FROM AUTHOR]

This paper describes Large Eddy Simulations of a turbulent premixed flame (the VOLVO rig) comparing Analytically Reduced Chemistry (ARC) with globally reduced chemistry for propane-air combustion, a dynamic Thickened Flame (TFLES) model with the usual non-dynamic TFLES model and a high-order Taylor Galerkin numerical scheme with a low-order Lax–Wendroff scheme. Comparisons with experimental data are presented for a stable case in terms of velocity and temperature fields. They show that going from two-step to ARC chemistry changes the flame stabilization zone. Compared to the usual non-dynamic TFLES model, the dynamic formulation allows to perform a parameter-free simulation. Finally, the order of accuracy of the numerical method is also found to play an important role. As a result, the high-order numerical method combined with the ARC chemistry and the dynamic TFLES model provides the best comparison with the experimental data. Since the VOLVO data base is used in various benchmarking exercises, this paper suggests that these three elements (precise chemistry description, dynamic parameter-free turbulent combustion model and high-order numerical methods) play important roles and must be considered carefully in any LES approach . [ABSTRACT FROM AUTHOR]

This paper addresses a multi-stage inventory model that allows different order quantities among the selected suppliers to obtain the optimal solutions. To achieve the objective of the study, the single-objective and multi-objective methods are adopted for suitable real-world applications. With respect to a single-objective method, this paper aims to minimize the total ordering costs, holding costs, and purchasing costs, subject to the price, quality, and capacity. With respect to a multi-objective method, it focuses on cost minimization, as well as quality and capacity maximization. The proposed model not only considers the allocation of different order quantities among the selected suppliers, but also incorporates the multi-stage inventory problem. Furthermore, a numerical example is provided to illustrate the usefulness of the proposed model and a comparative understanding of various methods. In addition, a simulation test is performed to effectively validate the proposed model which outperforms the previous works. Finally, a sensitivity analysis is carried out to investigate the impact of supply chain cost. [ABSTRACT FROM AUTHOR]

Pressure cartridge type separation devices which are widely used in fairing, stage separations of space launch systems, and many other aerospace fields generate much lower pyroshock and produce no high-speed debris compared to frangible explosive separation devices. However, because the operation is completed in a few milliseconds and the releasing mechanism is complicated, their separation behavior is difficult to experimentally identify. This paper presents a mathematical model to simulate the separation behaviors for a split-type separation bolt, one of the pressure cartridge type separation devices. The mathematical model includes a combustion model, buckling resisting model, split behavior model related to static and dynamic friction, O-ring friction model, contact force model, and slip angle model. Each composing models are obtained by mathematical formulation or numerical analysis. An efficient contact model is constructed by using virtual penetration model appropriately for complex contact phenomenon. To validate the established model, separation experiments were performed; the results are then compared with the mathematical model. Present study show that complex mechanical behaviors coupled with combustion of solid propellant charge can be efficiently simulated by the mathematical model. • Established a mathematical model for a low-shock separation device using pressure cartridge. • Analyzed complicated separation behavior of the low-shock separation device. • Simulation results were well compared with separation experimental results. [ABSTRACT FROM AUTHOR]

Numerical back analysis based on incomplete in situ stress measurements is widely used to estimate the three-dimensional (3D) in situ stress fields of large deep underground caverns. However, the variable collinearity caused by complex geological environments has rarely been considered. This paper proposes a numerical back analysis method for 3D in situ stress fields based on stepwise regression (BSSR). In BSSR, the collinearity between independent variables is associated with the surface topography, and insignificant variables caused by variable collinearity are eliminated through stepwise regression. BSSR was applied to the underground powerhouse of a hydropower station for validation, and the results showed that it can reliably estimate the 3D in situ stress field despite the complex geological environments. Multidimensional mathematical models of in situ stress fields were established with the improved predictive ability and clear physical meaning, which can quantify the contributions of six geological actions and three stress sources. The findings of this study can help with understanding the formation mechanism of in situ stress fields for large, deep underground caverns in complex geological environments and provide a useful reference for optimizing excavation schemes and support designs. [ABSTRACT FROM AUTHOR]

A biofilm is usually defined as a layer of bacterial cells anchored to a surface. These cells are embedded into a polymer matrix that keeps them attached to each other and to a solid surface. Among a large variety of biofilms, in this paper we consider batch cultures. The mathematical model is formulated in terms of a quasilinear system of diffusion- reaction equations for biomass and nutrients concentrations, which exhibits possible degeneracy and singularities in the nonlinear diffusion coefficient. In the present paper, we propose a set of efficient numerical methods that speeds up the solution of the model. Mainly, Crank-Nicolson finite differences techniques for discretisation are combined with a Newton algorithm for the nonlinearities. Moreover, some numerical examples show the expected behaviour of the biomass and nutrients concentrations and also clearly illustrate some theoretically proved qualitative properties related to exponential decays or convergence to a critical biomass concentration depending on the values of the model parameters. [ABSTRACT FROM AUTHOR]

In this paper, we consider the Kirchhoff type problem with radial potentials and locally L i p s c h i t z functional and there is no subcritical growth and no Ambrosetti–Rabinowitz type condition. This is in contrast with some recent papers concerning similar problems. [ABSTRACT FROM AUTHOR]

Crowd induced dynamic loading in large structures, such as gymnasiums or stadiums, is usually modelled as a series of harmonic loads which are defined in terms of their Fourier coefficients. Different values of these Fourier coefficients that were obtained from full scale measurements can be found in codes. Recently, an alternative has been proposed, based on random generation of load time histories that take into account phase lags among individuals inside the crowd. This paper presents the results of some studies carried out in order to compare the existing load models used to simulate periodic jumpings and develop a new load model. Generally the testing is performed on platforms or structures that can be considered rigid because their natural frequencies are higher than the excitation frequencies associated with crowd loading. But in this paper, to validate these load models test have been performed on a structure designed to be a gymnasium, which has natural frequencies within that range. Test results have been compared with predictions based on the load modelling alternatives with quite good agreement. A calibrated finite element model of the structure has been used for this purpose. The new model provides a clear improvement in the energy contained within higher frequencies. [ABSTRACT FROM AUTHOR]

Abstract We study in this paper the accuracy and stability of partially and fully implicit schemes for phase field modeling. Through theoretical and numerical analysis of Allen–Cahn and Cahn–Hilliard models, we investigate the potential problems of using partially implicit schemes, demonstrate the importance of using fully implicit schemes and discuss the limitation of energy stability that are often used to evaluate the quality of a numerical scheme for phase-field modeling. In particular, we make the following observations: 1. a convex splitting scheme (CSS in short) can be equivalent to some fully implicit scheme (FIS in short) with a much different time scaling and thus it may lack numerical accuracy; 2. most implicit schemes are energy-stable if the time-step size is sufficiently small; 3. a traditionally known conditionally energy-stable scheme still possesses an unconditionally energy-stable physical solution; 4. an unconditionally energy-stable scheme is not necessarily better than a conditionally energy-stable scheme when the time step size is not small enough; 5. a first-order FIS for the Allen–Cahn model can be devised so that the maximum principle will be valid on the discrete level and hence the discrete phase variable satisfies | u h (x) | ≤ 1 for all x and, furthermore, the linearized discretized system can be effectively preconditioned by discrete Poisson operators. [ABSTRACT FROM AUTHOR]

Highlights • 1-D freezing behavior assessment of ice-rich sandy soil considering the phase change of water. • Numerical simulation model shows reliable prediction results for 1-D freezing test. • Freezing behavior of ice-rich sandy soil are dependent on various geotechnical properties. • The larger the porosity of the specimen, the greater the increase in the time for fully frozen. • Height of specimen has the greatest impact on the time for fully frozen. Abstract This paper evaluates a methodology that enables one-dimensional freezing to make a homogeneous frozen soil specimen. Numerical analyses that simulate one-dimensional freezing are conducted, considering the phase change of pore water. After evaluating the applicability of the numerical analysis model, the effects of geotechnical characteristics on the freezing behavior of ice-rich sandy soil are evaluated through parametric studies. In addition, a nonlinear regression model is proposed that can predict the time required for complete freezing of saturated soil. According to the results from nonlinear regression analysis, the model demonstrates reliable accuracy (R2 = 0.998) in predicting the amount of time required for complete freezing, even with data from testing datasets not used in the developing stage. [ABSTRACT FROM AUTHOR]

Highlights • The Constructal law is applied to thermochemical energy storage design. • Equipartition of imperfections leads to several layers of reacting salt. • The best design meets overall performance and compactness objectives. Abstract This paper documents an analytical and numerical study of thermochemical energy storage in an open reactor. The analysis of the pressure losses and temperature distributions allows to predict what the geometrical features of the reactor should be. A numerical model simulating the thermochemical process is then presented and validated. In accord with the Constructal design methodology, the module configuration is morphed following the trends obtained in the analytical part, to head for better overall performances. The results show that the ratio between the heat produced by the chemical reaction within the entire module and the overall pumping power necessary to blow the fluid through the module increases as the imperfections reach equipartition. In terms of module configuration, this means (i) an increase in the number of salt layers and (ii) aspect ratios moving the module volume towards more compactness. [ABSTRACT FROM AUTHOR]

Highlights • A novel spacetime meshless method for solving the backward heat conduction problem. • Numerical approximation using the Trefftz basis function of the heat equation. • Collocating the boundary points in the spacetime coordinate system in the Trefftz method. • Highly accurate numerical solutions can be obtained comparing to that from conventional time-marching scheme. • Boundary data on the inaccessible boundary can be recovered even the partial data on the final time boundary are absent. Abstract This paper presents a novel space–time meshless method for solving the backward heat conduction problem (BHCP). A numerical approximation is obtained using the Trefftz basis function of the heat equation. The Trefftz method, which differs from conventional collocation methods based on a set of unstructured points in space, is used in this study to collocate boundary points in the space–time coordinate system such that the initial and boundary conditions can both be treated as boundary conditions on the space–time domain boundary. Because the solution in time on the boundary of the domain is unknown, the BHCP can be transformed into an inverse boundary value problem. The numerical solution is obtained by superpositioning the Trefftz base functions that automatically satisfy the governing equation. The validity of the proposed method is established for several test problems, including the one-dimensional BHCP and two-dimensional BHCP. The accuracy of the proposed method is compared with that of a conventional time-marching scheme based on the finite difference method. The results demonstrate that highly accurate numerical solutions can be obtained and errors may not accumulate over the entire time domain. Moreover, the boundary data on the inaccessible boundary can be recovered even when the partial data on the final time boundary are absent. [ABSTRACT FROM AUTHOR]

Highlights • The damper has an excellent hysteretic energy dissipation capacity. • The damper exhibits a stable post-visible-rupture behavior. • The damper can be promptly repaired after a major earthquake. • The repaired damper behaved as the original one. • The model predicts acceptable results for yield and ultimate strengths of the damper. Abstract This research focused on a new type of seismic damper consisting of replaceable U-shaped steel plates. To investigate behavior of the damper, seven specimens were tested. The test parameters varied in these specimens included geometries and materials of the U-shaped steel plates and the loading protocols. Test results show that the specimens exhibited stable hysteretic behaviors and satisfactory energy dissipating capacities. In addition, this research provided clear evidence that the damper is robust and tolerant to the ruptures in the U-shaped steel plates. Some specimens continued to dissipate significant amounts of hysteretic energy even after formation of the visible ruptures in the U-shaped steel plates. Moreover, this research demonstrated that the damper repaired through replacement of the U-shaped steel plates following a severe earthquake remained satisfactory in a subsequent earthquake. Further, this paper presents the equations for estimating yield strength and ultimate strength of the damper. It was found that the derived equations provide reasonable predictions and can be used for future design. [ABSTRACT FROM AUTHOR]

Highlights • Analytical and numerical study results of Y-type self-centering eccentrically braced frame (SCEBF-Y) are presented. • Post-gap opening stiffness of SCEBF-Y depend on PT cable properties. • Finite element model of the SCEBF-Y is verified with analytical and experimental test data. • Post-gap-opening stiffness and equivalent yield strength of SCEBF-Y is adjustable. Abstract This paper presents the results from both analytical and numerical study of a Y-type self-centering eccentrically braced frame (SCEBF-Y) subjected to earthquake loading. In this study, a three-story SCEBF-Y frame building has been designed along with a three-story conventional D-type eccentrically braced frame (EBF-D) for a site located in Los Angeles, California. The analytical results reveal that initial stiffness and post-gap opening stiffness of SCEBF-Y depend on brace section properties and PT strand properties respectively. The finite element model of the SCEBF-Y frame has been verified with analytical results as well as experimental test data from a similar one-story one-bay D-type self-centering eccentrically braced frame specimen. The study results demonstrate that SCEBF-Y frame can be designed to the same strength and stiffness as conventional EBFs while it can re-center itself after design basis earthquake (DBE). In the SCEBF-Y system, replaceable energy dissipation devices termed RHD devices are installed to dissipate seismic energy, and the primary structural members are intended to remain elastic under the DBE earthquakes. The nonlinear time history analysis results for the prototype SCEBF-Y buildings show that not only the SCEBF-Y building has negligible residual drift, but also it has its major damage confined to replaceable energy dissipation devices. In the parametric study, three different levels of PT strands' initial stress along with different PT cable length has been considered and the parametric study suggests that by properly choosing cable length and cable's initial post-tensioning stress level, key structural system properties such as the post-gap-opening stiffness and the equivalent yield strength of SCEBF-Y can be adjusted accordingly. [ABSTRACT FROM AUTHOR]

Highlights • Partially bonded (PB)-FREBs can retain the same advantages of unbonded-FREBs. • No relative slip occurs under low-rate lateral displacements in a PB-bearing. • The influence of static rotations on the hysteresis loops of PB-FREBs has been investigated. • A new copolymer employed in the bearings, and its response was examined experimentally. • The PB-application of FREBs as seismic isolators/bridge bearings is feasible. Abstract There are two classical types of application for fiber reinforced elastomeric bearings (FREB), namely, "bonded (B)" and "unbonded (UB)" applications. Although the UB-application results in improved seismic isolation efficiency due to rollover deformations, UB-FREB are not capable of transferring tensile forces, and may experience slip under certain loading conditions. As such, a new application type called Partially Bonded (PB) has been introduced to overcome these two limitations. A PB-FREB is achieved by partially bonding the top and bottom surfaces of the bearing to its contact supports. This paper presents the results of a comparative experimental study between UB-FREB and PB-FREB. Heat accelerated deterioration tests based on Arrhenius law was also conducted on the PB-FREB. Additionally, the low-temperature horizontal response of the PB-FREB was investigated. Results show that the displacement characteristics and damping values, long-term performance, and low-temperature response of the PB-FREB investigated in this study comply with current standard requirements. [ABSTRACT FROM AUTHOR]

Highlights • A comprehensive and discussion of the pros and cons of the different approaches to deal with frame conditions in behavioral verification of UML/OCL models. • A description of conceptual ideas how to integrate frame conditions given by modifies only statements into a symbolic formulation as well as a precise SMT-LIB realization. • An evaluation of the actual implementation including a comparison with other approaches. Abstract Validation and verification of UML/OCL models is a crucial task in the design of complex software/hardware systems. The behavior in those models is expressed in terms of operations with pre- and postconditions. These, however, are often not precise enough to describe what may or may not be modified in a transition between two system states. This frame problem is commonly addressed by providing additional constraints in terms of so-called frame conditions and has already been considered in different research areas in the last decades—except for UML/OCL where corresponding approaches have been investigated only recently. Among these, the so-called modifies only statements constitute a very promising concept which is complementary to all other approaches. More precisely, instead of allowing arbitrary modifications in principle and prohibiting certain undesired behavior, the statements explicitly describe what is allowed to change. However, this approach to frame conditions has not been considered so far in any of the numerous approaches for the automatic validation and verification of the behavior in UML/OCL models that have been proposed in the last years. Most of these approaches rely on a symbolic formulation of all possible system states and transitions between them. Therefore, in this paper we explain how modifies only statements can be integrated into an existing symbolic formulation. Based on this, we evaluate the applicability of the presented concept and compare it to previous implementations of frame conditions. [ABSTRACT FROM AUTHOR]

Highlights • Exo-parametric ("inside-out") model is used to calculate estimates of profitability, capital cost and "risk" for a conceptual chemical process design. • Inner model [four equations (one non-linear)] yields exact results from design outputs (process income and capital invested, i.e., P BT and TCI). • Complexity of DCF calculations is built into outer model structure. Values of the coefficients are generated from the outer model using a VBA macro coupled to an Excel spreadsheet. Abstract In a 2013 paper (Mellichamp, 2013), the author developed an internally-consistent discounted cash flow (DCF) model that represents the key financial outputs of a conceptual chemical process design using just four variables: • Total investment , TI (capital required to construct and operate a project for N Total years), • ROI BT and NPV proj (the traditional annual and long-term (NPV) profitabilities), and • NPV % [a new metric whose reciprocal, (NPV %)−1, directly expresses short-term project risk]. A traditional spreadsheet relating these four dependent long- and short-term financial metrics to a project's two independent design variables, P BT and FC , is functionally dependent on the many process design parameters (tax rate, discount factor, etc.) and highly complicated, involving non-linear (mostly geometric) relationships. Surprisingly, an exact linear-in-the-parameters "inner model" including the usual nonlinear relation for ROI BT is obtained by collapsing the original large-scale financial model (the complicated spreadsheet) using these four dependent variables, if the coefficients are functions of fixed design parameters , as when held constant in design. The power/utility to understand several key features of a project's design financial characteristics are revealed via the "inner model" through this reversal of the usual modeling hierarchy. The "outer model" coefficients incorporate the highly non-linear DCF functionalities. The new form is referred to as "exo-parametric" or an "inside-out" model. [ABSTRACT FROM AUTHOR]

Highlights • Utilizes data variety in subspace identification and control of batch processes. • The modeling approach is able to use data variety for batches of unequal lengths. • A novel model predictive control (MPC) with explicit model validity constraints, and the ability to specify target PSD is proposed. • The approach is demonstrated on batch crystallization process. Abstract This manuscript illustrates the use of big data for modeling and control of batch processes. A modeling and control framework is presented that utilizes data variety (temperature or concentration measurements along with size distribution) to achieve newer control objectives. For an illustrative crystallization process, an approach is proposed consisting of a subspace state-space model augmented with a linear quality model, able to model and predict, and therefore control the particle size distribution (PSD). The identified model is deployed in a linear model predictive control (MPC) with explicit model validity constraints. The paper presents two formulations: a) one that minimizes the volume of fines in the product by leveraging the variety of measurements and b) the other that directly controls the shape of the particle size distribution in the product. The former case is compared to traditional control practice while the latter's superior ability to achieve desired PSD shape is demonstrated. [ABSTRACT FROM AUTHOR]

Highlights • Independent variable transformation in surrogate models through introduction of self-optimizing variables. • Self-optimizing variables allow the mapping of regions we are interested in and avoid uninteresting regions. • The response surface is simplified and close to the optimal response surface. • The variable transformation can result in a reduction of independent variables. • Application to a three-bed ammonia reactor with B-splines as basis function results in a simpler response surface and variable reduction. Abstract This paper presents the application of self-optimizing concepts for more efficient generation of steady-state surrogate models. Surrogate model generation generally has problems with a large number of independent variables resulting in a large sampling space. If the surrogate model is to be used for optimization, utilizing self-optimizing variables allows to map a close-to-optimal response surface, which reduces the model complexity. In particular, the mapped surface becomes much "flatter", allowing for a simpler representation, for example, a linear map or neglecting the dependency of certain variables completely. The proposed method is studied using an ammonia reactor which for some disturbances shows limit-cycle behaviour and/or reactor extinction. Using self-optimizing variables, it is possible to reduce the number of manipulated variables by three and map a response surface close to the optimal response surface. With the original variables, the response surface would include also regions in which the reactor is extinct. [ABSTRACT FROM AUTHOR]

Abstract This paper investigates the stable orbital transfer of a climber in a partial space elevator system in circular orbits. The elevator includes a main satellite, an end body, and a climber, which are connected by two straight, inextensible, massless and variable length tethers. Derived from system dynamics, two closed-loop velocity control strategies are proposed to regulate the tethers' deploying and retrieving speeds directly to control the Coriolis forces acting on the climber and the end body directly. The stable region of the control strategies is analyzed, and the effectiveness of the proposed strategies is demonstrated by numerical simulation. Simulation results show that the newly proposed strategies effectively minimize the libration of a partial space elevator system during the orbital transfer of the climber and the system states successfully approach to the desired equilibrium by the end of the orbital transfer. Furthermore, the proposed deployment/retrieval control strategies can be converted to tension control laws easily. Highlights • Studied stable orbital transfer of a partial space elevator in circular orbits. • Developed velocity control strategies to suppress libration of elevator. • Controlled velocities by regulating tether deployment and retrieval rates. [ABSTRACT FROM AUTHOR]

Plant-wide oscillation detection is an important task in the maintenance of large-scale industrial control systems, owing to the fact that in an interactive multi-loop environment oscillation generated in one loop may propagate to the different parts of the plant. In such a scenario, it is required that different loops oscillating due to a common cause and hence similar frequency may be grouped together. In this paper an adaptive method for plant-wide oscillation detection based on multivariate empirical mode decomposition (MEMD) along with a grouping algorithm is proposed. The method can identify multiple oscillation groups among different variables as well as variables with random noise only. The proposed method is also applicable to both non-linear and non-stationary time series where the techniques based on the conventional Fourier analysis are prone to errors. Within each group that oscillate due to a common cause, the method can also indicate the location of the probable root cause of oscillations. The efficacy of the proposed method is established with the help of both simulation and industrial case studies. [ABSTRACT FROM AUTHOR]

This paper presents an improved scheme for the state-of-health (SOH) estimation, applicable to battery management system (BMS) of electric vehicles. The original scheme requires the prior information for the estimation, which is the prior SOH identified from the last charging. This limit implies that if a battery or its BMS is replaced, the prior SOH stored within the BMS no longer matches with the actual SOH, resulting in a critical error. To avoid this potential but critical pitfall, we newly devise an improved SOH estimation scheme. The original scheme is revised by adopting the fixed-point iteration method into its parameter estimation. By removing dependencies on the prior information, the revised scheme can function regardless of such replacements. The revised scheme is experimentally validated and demonstrated that even without the prior information, it can satisfy the requirement of the SOH estimation (within 3%) thanks to its improved design. [ABSTRACT FROM AUTHOR]

The paper is mainly concerned with the oscillations of numerical solutions by the linear θ − methods for a kind of linear delay differential equations with positive and negative coefficients. Some conditions under which the numerical solutions are oscillatory are obtained and it is proved that oscillations of the analytical solutions are preserved by the numerical solutions under mild conditions. Numerical experiments are given to demonstrate our results. [ABSTRACT FROM AUTHOR]

The paper presents two Direct Numerical Simulations of bubble swarms in a vertical turbulent channel flow and is intended as a complement to the companion paper, Santarelli and Fröhlich (2015). Both swarms addressed here are composed of spherical bubbles in contaminated fluid with a void fraction of 2.14%, as for the reference case in the companion paper. The first simulation reported is done for a monodisperse swarm of larger bubbles while in the second case a bidisperse swarm is considered. The influence of the bubble size and of the bidispersity is investigated by means of flow visualizations and quantitative statistical analysis. Due to the higher Reynolds number, the behavior of the larger bubbles differs from the one of the small bubbles and this impacts the turbulence of the carrier phase. The results show that for the parameter range considered both swarms induce elongated flow structures in the streamwise direction and that the liquid turbulence is enhanced by the bubbles, as quantified by the budget of the turbulence kinetic energy. In both cases the tendency of bubbles to align horizontally is confirmed while the analysis of mixed pairs in the bidisperse swarm allows elucidating the complex interaction of bubbles of different size. [ABSTRACT FROM AUTHOR]

The higher-order gradient plasticity theory is successful in explaining the size effects encountered at the micron and submicron length scale. Due to the incorporation of spatial gradients of one or more internal variables in these theories and the associated non-classical boundary conditions, special types of elements in the finite element method maybe necessary. This makes the numerical implementation of this higher-order theory not straightforward. In this paper, a robust but straightforward numerical implementation of higher-order gradient-dependent plasticity theories is presented. The novelty of this paper is in (1) the application of the meshless methods, particularly the moving weighted least square method, combined with the finite element method for the numerical computation of plastic strain gradients, and (2) the numerical implementation of different types of higher-order microscopic boundary conditions at internal/external surfaces, interfaces, and moving elastic–plastic boundaries. The proposed numerical implementation algorithms can be easily adapted in the implementation of any form of higher-order gradient-dependent constitutive models. Examples of applying the current numerical approach is demonstrated for capturing mesh-objective shear band formation and size effect and boundary layer formation in thin films on elastic substrates and metal matrix composites with embedded elastic inclusions through the consideration of stiff, intermediate, and soft interfaces. [ABSTRACT FROM AUTHOR]

Entrainment of bottom material has a substantial influence on the dynamics of slope flows such as snow avalanches and debris flows, and should therefore be taken into account by mathematical models. An approach based on the assumption that the entrainment takes place when the bed shear stress is equal to the shear strength of the bottom material was proposed by Issler and Pastor Pérez (2011). In this paper, this approach is applied to model laminar flows of Bingham and Herschel–Bulkley fluids as well as turbulent flows with entrainment. Full (not depth-averaged) equations are used to calculate the flow parameters including the shear stress at the bottom, the velocity profile and the flow depth variation with time due to entrainment. The paper focuses on studying of qualitative features of motion with basal entrainment. Modeling of real flows from start to stop is not considered here. It is shown that in entraining flows moving down long constant slopes the flow velocity increases. The velocity profiles in laminar flows described by Bingham and Herschel–Bulkley models at large time become almost linear except in a relatively narrow layer near the upper flow surface and the entrainment rate tends to a constant value. This value depends on the coefficients describing the flow material properties, the shear strength of the bottom material, and the slope angle. Asymptotic formulae for the entrainment rate and the shear rate in the linear part of the velocity profile are derived analytically and confirmed by numerical calculations. [ABSTRACT FROM AUTHOR]

A graph G = ( V , E ) is word-representable if there exists a word w over the alphabet V such that letters x and y alternate in w if and only if x y is an edge in E . It is known (Kitaev and Pyatkin, 2008) that any word-representable graph G is k -word-representable for some k , that is, there exists a word w representing G such that each letter occurs exactly k times in w . The minimum such k is called G ’s representation number. A crown graph (also known as a cocktail party graph) H n , n is a graph obtained from the complete bipartite graph K n , n by removing a perfect matching. In this paper, we show that for n ≥ 5 , H n , n ’s representation number is ⌈ n ∕ 2 ⌉ . This result not only provides a complete solution to the open Problem 7.4.2 in Kitaev and Lozin (2015), but also gives a negative answer to the question raised in Problem 7.2.7 in Kitaev and Lozin (2015) on 3-word-representability of bipartite graphs. As a byproduct, we obtain a new example of a graph class with a high representation number. [ABSTRACT FROM AUTHOR]

Let Γ n be the symmetric group on { 1 , 2 , … , n } and S be the generating set of Γ n . The corresponding Cayley graph is denoted by Γ n ( S ) . If all elements of S are transpositions, a simple way to depict S is via a graph, called the transposition generating graph of S , denoted by A ( S ) (or say simply A ), where the vertex set of A is { 1 , 2 , … , n } , there is an edge in A between i and j if and only if the transposition ( i j ) ∈ S , and Γ n ( S ) is called a Cayley graph obtained from a transposition generating graph A . In this paper, by exploring and utilizing the structural properties of these Cayley graphs, we obtain that the pessimistic diagnosability of Γ n ( S ) is equal to 2 | E ( A ) | − 2 if A has no triangles or 2 | E ( A ) | − 3 if A has a triangle. As corollaries, the pessimistic diagnosability of many kinds of graphs such as Cayley graphs generated by unicyclic graphs, wheel graphs, complete graphs, and tree graphs is obtained. [ABSTRACT FROM AUTHOR]

In this paper, we introduce obnoxious effects into obnoxious facility location games on a line, where each agent i has a private location x i on a closed interval [ 0 , 1 ] and one facility will be built on a location y in the interval according to the bids of all the agents. In addition, there are two thresholds d 1 and d 2 in the utility function of each agent, where 0 ≤ d 1 ≤ d 2 ≤ 1 . Denote d ( y , x i ) = | y − x i | to be the distance between agent i and the facility on the location y . The utility function of agent i is 0 if d ( y , x i ) is at most d 1 ; 1 if d ( y , x i ) is at least d 2 ; otherwise a linear increasing function between 0 and 1. Each agent attempts to get the largest utility while the social welfare is to maximize the sum of all the agents' utilities. The classic obnoxious facility game [4,11] is a special case of our problem when d 1 = 0 and d 2 = 1 . In this work, we first study the hardness of approximate mechanism design on this generalized problem, which states that our problem cannot admit any deterministic strategy-proof mechanism with bounded approximation ratio if d 1 ≥ 1 2 . Then we limit the thresholds to some ranges, both deterministic and randomized strategy-proof mechanisms are studied, and the approximation ratios vary with the specific values of d 1 and d 2 . [ABSTRACT FROM AUTHOR]

In this paper, we would like to give an indirect possible way to reconstruct the shape of rotating body by temperature measurements. The mathematical model is governed by a heat conduction equation in which the parameter to determine is denoted by an unknown coefficient of first-order derivative. Firstly, the uniqueness of the solution is proved by using the maximum principle. Then, on the basis of optimal control framework, the inverse problem is transformed into an optimization problem. To ensure the well-posedness of the considered problem, we prove the existence and derive the necessary condition of the minimizer. By carefully analysing the necessary condition, we obtain the local uniqueness and stability on the basis of some a-priori estimates of forward problem. Finally, some numerical implements are performed to show the validity of the proposed method. [ABSTRACT FROM AUTHOR]

A continuum X is said to be semi-Kelley provided that for each subcontinuum K and for every two maximal limit continua M and L in K either M ⊂ L or L ⊂ M . In this paper we show that the property of being semi-Kelley is a sequentially strong Whitney-reversible property, with this result we obtain that the property of being semi-Kelley is a Whitney-reversible property, answering a question posed by A. Illanes in [2] . Moreover, we generalize the Charatonik's Theorem ( [4, p. 83, 4.5] ) and we prove a version of this theorem on n -fold Symmetric Product. [ABSTRACT FROM AUTHOR]

Given a continuum X , let F n ( X ) denote the hyperspace of nonempty subsets of X with at most n points. For n ≥ 2 , let S F n ( X ) = F n ( X ) / F 1 ( X ) be the quotient space. Given a mapping between continua f : X → Y , we consider the induced mappings f n : F n ( X ) → F n ( Y ) and S f n : S F n ( X ) → S F n ( Y ) . Given a class of mappings M , in this paper we consider relations between the statements f ∈ M , f n ∈ M and S f n ∈ M , and we answer some questions about these relations considering the following classes of mappings: almost monotone, atriodic, freely decomposable and joining. [ABSTRACT FROM AUTHOR]

In this paper every polyhedron is finite and every ANR is compact. Let P ≥ X 1 ≥ X 2 ≥ … , be a sequence, in which P is a polyhedron and ≥ are homotopy dominations. One may ask, if each sequence of this form contains only finitely many homotopy dominations that are not homotopy equivalences, or if there exists an integer l P (independent of the sequence) that each sequence contains only ≤ l P homotopy dominations that are not homotopy equivalences. Closely related open questions are: Does there exist a polyhedron P homotopy dominating an infinite sequence of polyhedra { P i } , where P i homotopy dominates P i + 1 but P i and P i + 1 have different homotopy types, for every i ∈ N ? (M. Moron) [30, Problem 1436] , and the famous problem of K. Borsuk (1967): Is it true that two A N R ′ s homotopy dominating each other have the same homotopy type? Here we prove that, if dim ⁡ P = 2 , then the answers to all these questions depend only on the properties of the fundamental group of P (for 1-dimensional polyhedra, the answers are obvious). Furthermore, if sequences in consideration contain only polyhedra, then, for the positive answer it suffices to answer positively the analog of our topological question for finitely presented groups (the fundamental groups) with retractions. Applying these results, we prove that for each polyhedron P with dim ⁡ P ≤ 2 and elementary amenable fundamental group G with cd G < ∞ , there is a bound l P on the lengths of all descending sequences P ≥ X 1 ≥ X 2 … of homotopy dominations that are not homotopy equivalences. The same holds if the fundamental group of P is a limit group. It means that such polyhedra P have finite depth. [ABSTRACT FROM AUTHOR]

This paper comprehensively studies the nonlinear vibration of functionally graded nano-beams resting on elastic foundation and subjected to uniform temperature rise. The small-size effect, playing an essential role in the dynamical behavior of nano-beams, is considered here applying the innovative stress driven nonlocal integral model due to Romano and Barretta. The governing partial differential equations are derived from the Bernoulli–Euler beam theory utilizing the von Karman strain–displacement relations. Using the Galerkin method, the governing equations are reduced to a nonlinear ordinary differential equation. The closed form analytical solution of the nonlinear natural frequency for four different boundary conditions is then established employing the Homotopy Analysis Method. The nonlinear natural frequencies, evaluated according to the stress-driven nonlocal integral model, are compared with those obtained by Eringen differential model. Finally, the effects of different parameters such as length, elastic foundation parameter, thermal loading and nonlocal characteristic parameter are investigated. The emergent results establish that when the nonlocal characteristic parameter increases, the nonlinear natural frequencies obtained by the stress-driven nonlocal integral model reveal a stiffness-hardening effect. On the other hand, Eringen's differential law reveals a stiffness-softening effect excepting the case of cantilever nano-beam. Also, increase in temperature and the elastic foundation parameter leads to increase in the nonlinear frequency ratios in Eringen differential model but decrease in the frequency ratios in the stress-driven nonlocal integral model. [ABSTRACT FROM AUTHOR]

This paper aims to present a model verification technique for general numerical computations of linear second-order systems. Strict upper and lower bounds on quantities of interest are eventually obtained. The model verification technique consists of two major steps. The first is the representation of the error in quantities of interest through an adjoint correction; the second is the application of the strict upper bound derived for the time-discretization error. Moreover, the bounds on quantities of interest are further improved through an optimization procedure. Academic examples are studied to verify the proposed bounds and to explore the potential application of these bounds to adaptive time-stepping. [ABSTRACT FROM AUTHOR]

This paper deals with the solvability of interval matrix equations in max-plus algebra. Max-plus algebra is the algebraic structure in which classical addition and multiplication are replaced by ⊕ and ⊗ , where a ⊕ b = max { a , b } and a ⊗ b = a + b . The notation A ⊗ X ⊗ C = B , where A , B , and C are given interval matrices, represents an interval max-plus matrix equation. We define three types of solvability of interval max-plus matrix equations, namely the strong universal , universal , and weak universal solvability. We derive the necessary and sufficient conditions which can be verified in polynomial times. [ABSTRACT FROM AUTHOR]

This paper presents studies carried out on physical models and numerical analyses aimed at determining the equivalent pure torsion second moment of area of built-up steel columns laced in a single plane, with the lacing located on the symmetry axis of the column cross-section. Such columns are used in overhead contact line supporting structures and in industrial halls. In order to determine the spatial stability critical loads for such columns one needs to know their pure torsion rigidity. The experimental research were carried out on single-span column models fork-restrained at their ends and subjected to a concentrated twisting moment applied at the mid-span. Among other things, the dependence between the torsion angle of the column’s mid-section and the twisting moment load was determined. A similar column model was studied numerically using the finite element method and the ABAQUS software. The experimental and numerical results and the results obtained by solving a proper differential equation for the non-uniform torsion of the column, formulated in terms of the Vlasov theory, were found to be in good agreement. Also the effect of the lacing of the column with a solid web with an equivalent thickness was analysed. In addition, extensive parametric analyses of similar columns, but with a wider range of cross-sections, subjected to pure torsion were carried out using the SOFiSTiK software. The aim was to devise practical formulas for calculating the equivalent pure torsion second moment of area on the basis of the cross-section. These relations ( I T ‾ ) together with sectorial second moment of area allow to calculate the critical load capacity of spatial stability (lateral and flexural–torsional buckling) of the considered columns. Practical conclusions have been drawn. [ABSTRACT FROM AUTHOR]

This paper focuses on numerical modeling of the responses of Ballina test embankment by an improved EVP-SANICLAY constitutive model with a novel rotational hardening (RH) law. The modified RH law guarantees the uniqueness of the critical state line, prevents excessive rotation of yield surface and is particularly simple that makes it very useful for practical applications. To consider strain-rate dependency of the soil behavior, Perzyna’s overstress theory is employed. Using the newly released data at Ballina test embankment site, the values of model parameters and state variables are calibrated and evaluated for Class C predictions, and their differences with the previously determined parameter values for Class A predictions are highlighted and discussed. The elasto-viscoplastic anisotropic constitutive model is implemented in PLAXIS software to carry out the simulations of the case study embankment. The numerical modeling results, in terms of time-dependent variations of deformations and pore water pressures, both during and after the embankment construction, are compared with the physical measurements at the test site. The results of Class C analyses show that the model is capable of capturing the temporal changes in surface settlement and lateral deformations with good accuracy, with the latter being particularly challenging when modeling the behavior of soft clays. Simulation of pore water pressure variations however proved more difficult. To highlight the advantages of the proposed EVP-SANICLAY model, the simulations are also compared with those using the classical Mohr-Coulomb and modified Cam-clay models, and the results are presented and discussed in detail. [ABSTRACT FROM AUTHOR]

This paper is concerned with the asymptotic spreading of a predator–prey system, which formulates that the predator invades the habitat of the prey. By constructing auxiliary equation, we obtain the speed of asymptotic spreading of the predator. [ABSTRACT FROM AUTHOR]

Accuracy identification of geometric errors of rotary axis is important for error compensation of the multi-axis machine tool. However, it is not easy because of the influence of setup error of measurement instrument, and there exists angular errors and displacement errors need to be identified simultaneously. In this paper, a decoupled method based on double ball bar is proposed to identify the geometric errors of rotary axis including both position independent geometric error (PIGE) and position dependent geometric error (PDGE). A formulation for ball bar measurement is derived from kinematic analysis to reveal the relationship between sensitivity direction and setup position of ball bar. The angular errors and displacement errors can be identified separately when choosing the appropriate setup position and direction of ball bar. It can effectively reduce the interaction influence between them and improve the accuracy. To identify the 4 PIGEs, a method by averaging the measured results of ball bar to compute the eccentricity and slant of rotary axis is proposed. And, the PDGEs are leaved to mainly describe the oscillation of geometric errors of rotary axis. It is useful to correct the deviation error resulting from setup error of ball bar. For the identification of 6 PDGEs, by means of adjusting setup position and direction of ball bar, they can be identified one by one along the sensitivity direction of ball bar. Furthermore, in order to reduce the influence of setup error of ball bar, the sensitivity analysis is performed to obtain the sensitivity of measured results of ball bar with respect to setup error. According to the sensitivity characteristics of setup error, a method is presented to correct the PDGEs. Finally, several numerical simulations and experiments are conducted to verify the theoretical model and the proposed identification method. The results from the simulations and experiments demonstrate that the method can identify the geometric errors of rotary axis effectively and accurately. [ABSTRACT FROM AUTHOR]

Separation of the effects of initial horizontal stress and relative density on cone tip resistance in sandy soils has been a complicated issue for many years. In order to overcome this problem, a numerical modeling of CPT which has been verified by calibration chamber tests, has been used in this paper to achieve a reliable analytical solution. The analytical solution has resulted in two relationships for sleeve friction and cone tip resistance in terms of the initial conditions of sandy soil. Based on the presented solution, the initial horizontal stress and relative density can be determined according to CPT measurements. [ABSTRACT FROM AUTHOR]

Using the Euler scheme to simulate the stochastic differential equations (SDEs) models in finance often gives rise to the problem that the exact solution is positive while the numerical solution is not. Recently, we find that this problem existed in the jump–diffusion models as well. Hence, this paper aims to construct a numerical method preserving positivity for jump–diffusion option pricing models. We generalize the balanced implicit method (BIM) to the jump–diffusion models, which already turned out to be efficient for preserving positivity in SDE models. Then the positivity of BIM for jump–diffusion models is proved under some conditions. Finally, a numerical example is simulated to verify the positivity and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

The paper presents a set of newly developed exact analytical solutions for triple- equal-span arrangements of panels with fully profiled faces in flexure. Their derivation was based on a set of general fundamental equations retrieved from the governing differential equations for sandwich beams. Specifically designed tests of single- and triple-span fully profiled panels with steel faces (outer fully profiled and inner lightly profiled) and polyisocyanurate cores were conducted to investigate the response with regards to stiffness and initial failure, which are critical for serviceability limit states. Good agreement between test and theory was demonstrated, with safe results in all cases. The new design method permits the elimination of a significant amount of conservatism compared to current methods. [ABSTRACT FROM AUTHOR]

This paper introduces the principle of Ingested Debris Monitoring System in aero-engine and establishes a mathematical model of its core component, the ring-like probe; this paper simulates foreign object's movement based on the established model and performs numerical analysis of the induced charge pulse waveform. Pulse amplitude and pulse width are used as the two pulse features of pulse waveform. Numerical analysis gets the relationship between pulse features and foreign object's charge amount, velocity and radial position. A new method for estimating foreign object's radial position and charge amount has been proposed based on the conclusion of numerical analysis. Both the correctness of numerical analysis and the new estimating method has been verified in the oil calibration test rig. All the relative errors are within 10%. Further experiments with high velocity condition are carried out in an air-gun test rig. The occurrence time, radial position, charge amount, velocity and material category of foreign object can all be obtained, which has important significance to the safety of aero-engines. [ABSTRACT FROM AUTHOR]