bluuebunny/crossref_metadata_2025 huggingface dataset:
A Probabilistic LCF Model for Turbo Charger Compressor of a Jet Engine
Authors: Saadi Mohamed
Published: December 2014

We present a probabilistic low cycle fatigue (LCF) Model for turbo charger compressor of a jet engine. This compressor is made of casted aluminum alloy (C355). This model has been implemented using the finite element method in R Language [4]. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling and design optimization of textiles via homogenization
Authors: Shiryaev Vladimir , Orlik Julia
Published: December 2014

This article deals with optimization of large structures of linear elastic material with contact modeled by Robin‐type boundary conditions. Homogenization is used to represent the structures as homogenous elastic bodies and is essential for formulation of the optimization problems, where optimization of the effective properties is considered. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analytical approximations for the solution of chance constrained optimization problems
Authors: Klöppel Michael , Geletu Abebe , Hoffmann Armin , Li Pu , Wensch Jörg
Published: December 2014

Uncertain influences are inherent in many practical processes, stemming for instance from measurement errors in process optimization or missing knowledge about the future behavior of a given system, e.g., the financial markets. Therefore, it is desirable to explicitly consider uncertainties when optimizing such processes. One possible approach for this task is the usage of chance constrained optimization (CCOPT), which allows that the constraints are only held with a certain probability level. This enables the user to make a compromised decision between reliability and profitability. Solving CCOPT problems usually consists of two steps. First, transforming the chance constraints into deterministic ones and then solving the transformed problem with a standard NLP solver. Depending on the underlying process, several approaches exist for the transformation. Here, we investigate the usage of so called analytical approximations (AAs). In general, AA approaches do not lead to an exact deterministic representation of CCOPT problems. Nonetheless, it can be shown that a solution obtained by AA is always feasible for the original problem. Furthermore, the corresponding optimization problem generated by AA is computationally more tractable than the original formulation, making these approaches interesting for larger scale processes. We propose a new AA method and present a comparison with existing AA approaches, considering efficiency and suitability. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On regularization in parameter‐free shape optimization
Authors: Riehl Stefan , Friederich Jan , Steinmann Paul
Published: December 2014

This contribution is concerned with a parameter‐free approach to computational shape optimization of mechanically‐loaded structures. Thereby the term ’parameter‐free’ refers to approaches in shape optimization in which the design variables are not derived from an existing CAD‐parametrization of the model geometry but rather from its finite element discretization. One of the major challenges in using this type of approach is the avoidance of oscillating boundaries in the optimal design trials. This difficulty is mainly attributed to a lack of smoothness of the objective sensitivities and the relatively high number of design variables within the parameter‐free regime. To compensate for these deficiencies, Azegami introduced the concept of the so‐called traction method, in which the actual design update is deduced from the deformation of a fictitious continuum that is loaded in proportion to the negative shape gradient. We investigate a discrete variant of the traction method, in which the design sensitivities are computed with respect to variations of the design nodes for a given finite element mesh rather than on the abstract level by means of the speed method. Moreover, the design update process is accompanied by adaptive mesh refinement based on discrete material residual forces. Therein, we consider radaptive node relocation as well as hadaptive mesh refinement. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Manufacturing constraints in parameter–free shape optimization
Authors: Schmitt Oliver , Friederich Jan , Steinmann Paul
Published: December 2014

Structural shape optimization has become an important tool for engineers when it comes to improving components with respect to a given goal function. During this process the designer has to ensure that the optimized part stays manufacturable. Depending on the manufacturing process several requirements could be relevant such as demolding or different kinds of symmetry. This work introduces two approaches on how to handle manufacturing constraints in parameter‐free shape optimization. In the so–called explicit approach equality and inequality equations are formulated using the coordinates of the FE‐nodes. These equations can be used to extend the optimization problem. Since the number of the additional constraint equations may be very large we apply aggregation formulations, e.g. the Kreisselmeier‐Steinhauser function, if necessary. In the second approach, the so–called implicit method, the set of design nodes is split in two groups called optimization nodes and dependent nodes. The optimization nodes are now handled as design nodes but the dependent nodes are coupled to the optimization nodes in such a way that the manufacturing constraint is fulfilled. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A hybrid approach to optimization of trajectories in micro manufacturing
Authors: Bauma Elisabeth , Schuster Thomas
Published: December 2014

A new approach for solving optimal control problem with state constraints is introduced. Therein a combination of direct and indirect methods enables the determination of numerical solutions of the problem. As a motivating task the trajectory optimization of a novel feed unit is investigated. As the mechanism contains compliances, small disturbances have to be taken into consideration, this is done by introducing a penalty term to the objective function. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A time transformation technique for Switched Systems Optimal Control Problems with fixed sequence of phases
Authors: Palagachev Konstantin , Gerdts Matthias
Published: December 2014

A switched systems optimal control problem regarding a quadcopter trajectory optimization is considered. Introducing a particular time transformation, the problem is reformulated as an optimal control problem, whose solution can be found by the SQP algorithm. A numerical example concludes the paper. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An LDLT factorization based ADI algorithm for solving large‐scale differential matrix equations
Authors: Lang Norman , Mena Hermann , Saak Jens
Published: December 2014

Large‐scale differential matrix equations appear in many applications like optimal control of partial differential equations, balanced truncation model order reduction of linear time varying systems etc. Here, we will focus on matrix Riccati differential equations (RDE). Solving such matrix valued ordinary differential equations (ODE) is a highly storage and time consuming process. Therefore, it is necessary to develop efficient solution strategies minimizing both. We present an LDLT factorization based ADI method for solving algebraic Lyapunov equations (ALE) arising in the innermost iteration during the application of Rosenbrock ODE solvers to RDEs. We show that the LDLT‐type decomposition avoids complex arithmetic, as well as cancellation effects arising from indefinite right hand sides of the ALEs appearing in the classic ZZT based approach. Additionally, a certain number of linear system solves can be saved within the ADI algorithm by reducing the number of column blocks in the right hand sides while the full accuracy of the standard low‐rank ADI is preserved. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical solution of singular Lur'e equations
Authors: Reis Timo , Rendel Olaf
Published: December 2014

We consider a generalization of Lur’e equations for differential‐algebraic systems. We aim to numerically solve these equations. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A geometrical numerical linear algebra approach to residual‐enhanced parametric model reduction
Authors: Zimmermann Ralf
Published: December 2014

The most prominent approaches to model reduction share the general principle, that a given large‐scale system is projected onto a suitable subspace spanned by a low‐dimensional basis. The projection basis essentially determines the approximation quality of the resulting reduced order system. Nonlinear parametric dependencies may be taken into account by applying interpolation techniques on matrix manifolds for computing projection bases and/or reduced systems at arbitrary parameter conditions, see [1] for a recent survey. In this short note, an original approach to enhance the prediction capabilities of the interpolated reduced‐order projection bases for parametrized linear systems is proposed. To this end, a suitable residual‐based goal function is introduced, which measures the approximation quality of a given projection subspace. As this function is invariant under changes of basis, it is to be considered as a mapping on the Grassmann‐Manifold Gr(n, p) of p‐dimensional subspaces of ℝn. As such, it may be optimized using the conjugate gradient method specifically adapted to the manifold structure of the Grassmannian Gr(n, p), [2,3]. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wavelet compression of integral operators arising from boudary‐domain integral method
Authors: Ravnik Jure , Škerget Leopold
Published: December 2014

The boundary‐domain integral method uses Green's functions to write integral representations of partial differential equations. Since Green's functions are non‐local, the systems of linear equations arising from the discretization of integral representations are fully populated. Several algorithms have been proposed, which yield a data‐sparse approximation of these systems, such as the fast multipole method, adaptive cross approximation and among others, wavelet compression.

In the framework of solving the Navier‐Stokes equations in velocity‐vorticity form one may utilize the boundary‐domain integral method for the solution of the kinematics equation to calculate the boundary vorticity values. Since the kinematics equation is a Poisson type equation, usually its integral representation is written with the Green's function for the Laplace operator. In this work, we introduce a false time into the equation and parabolize its nature. Thus, a time‐dependent Green's function may be used. This provides a new parameter, the time step, which can be set to control the Green's function. The time‐dependent Green's function is a global function, but by carefully choosing the time step, its behaviour is almost local. This makes it a good candidate for wavelet compression, yielding much better compression ratios at a given accuracy than when using the Green's function for the Laplace operator. However, as false time is introduced, several time steps must be solved in order to reach a converged solution. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Estimates of modeling errors for linear elliptic problems
Authors: Samrowski Tatiana S.
Published: December 2014

We derive new estimates of modeling errors for linear elliptic boundary value problems with periodic coefficients solved by homogenization method. Our approach is based on the concept of functional a posteriori error estimation. The estimates are obtained for the energy norm and use solely the global flux of the non‐oscillatory solution of the homogenized model and solution of a boundary value problem on the cell of periodicity. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Higher order Galerkin methods in time for free surface flows
Authors: Weller Stephan
Published: December 2014

In many engineering applications, free surface or two‐phase flows are discretized in time with an explicit decoupling of geometry and fluid flow. Such a strategy leads to a capillary CFL condition of the form
$\Delta t \le \sqrt{\rm{We}}\,h^{3/2}$
[3]. For the case of surface tension dominated flows (i.e. high Weber number We) this can dictate infeasibly small time steps.

As an alternative we suggest a Galerkin method in time based on the discontinuous Galerkin method of first order (dG(1)). For this choice, an energy estimate can be proved [7], so unconditional stability of the method is given. While for ODEs or parabolic PDEs the method is of third order at the discrete points in time tn [4], in the case of free surface flows second order convergence can still be achieved.

Numerical examples using the Arbitrary Lagrangian Eulerian (ALE) method for both capillary one‐phase and two‐phase flow demonstrate this convergence order. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling and Simulation of the Transport of Protein Foams
Authors: Gladbach Katharina , Delgado Antonio , Rauh Cornelia
Published: December 2014

The behaviour of foams at rest, but particularly during fluid mechanical transport is not sufficiently investigated yet. The present article deals with protein foams as they have a great importance in food production. In the first part, the foaming process of a highly viscous liquid due to gaseous materials dispersed under pressure in the liquid and mass transport of volatile components dissolved in the liquid is considered. The aim is to calculate the foam volume and the concentration of the dissolved, volatile components as a function of the material and process parameters. In the second part, material equations for bubble suspensions with gas volume fractions ϕ ≤ 0.6 and small bubble deformations (i.e. NCa ≪ 1) are presented. The basics form two constitutive laws which are used for describing a steady shear flow. If the rates of work of the two models are compared, material equations for the shear viscosity and the normal stress differences can be derived. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectral Bounds on the Solution of Linear Time‐Periodic Systems
Authors: Benner Peter , Denißen Jonas
Published: December 2014

Linear time‐periodic systems arise whenever a nonlinear system is linearized about a periodic trajectory. Stability of the solution may be proven by rigorous bounds on the solution. The key idea of this paper is to derive Chebyshev projection bounds on the original system by solving an approximated system. Depending on the smoothness of the original function, we formulate two upper bounds. The theoretical results are illustrated and compared to trigonometric spline bounds by means of two examples which include an anisotropic rotor‐bearing system. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sensitivities for topological graph changes in finite element meshes and application to adaptive refinement
Authors: Friederich Jan , Leugering Günter , Steinmann Paul
Published: December 2014

We propose a novel approach to adaptivity in FEM based on local sensitivities for topological mesh changes. To this end, we consider refinement as a continuous operation on the edge graph of the finite element discretization, for instance by splitting nodes along edges and expanding edges to elements. Thereby, we introduce the concept of a topological mesh derivative for a given objective function that depends on the discrete solution of the underlying PDE. These sensitivities may in turn be used as refinement indicators within an adaptive algorithm. For their calculation, we rely on the first‐order asymptotic expansion of the Galerkin solution with respect to the topological mesh change. As a proof of concept, we consider the total potential energy of a linear symmetric second‐order elliptic PDE, minimization of which is known to decrease the approximation error in the energy norm. In this case, our approach yields local sensitivities that are closely related to the reduction of the energy error upon refinement and may therefore be used as refinement indicators in an adaptive algorithm. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal Control of an Elastic Tyre‐Damper System with Road Contact
Authors: Kimmerle Sven‐Joachim , Moritz Roman
Published: December 2014

We study an elastic tyre with a wheel rim that is suspended at the chassis of a car by means of a spring‐damper element. This quarter car model may be controlled by varying the damping constant of the electrorheological damper. Our mathematical model yields a coupled ODE‐PDE problem with a free boundary at the tyre‐road contact. In this study we approximate the tyre by the Hertz contact stress formula. The resulting optimal control problem with control constraints is solved numerically. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pole placement by dynamic output feedback of minimal order
Authors: Franke Matthias , Röbenack Klaus
Published: December 2014

In the present contribution, an approach for calculating a dynamic output feedback of minimal order is presented. The feedback is of minimal order in the sense that the controller state has lowest possible dimension among all controllers placing the poles of the closed loop system as desired. The main idea is to extend the system under consideration succesively by independent integrators until a static compensator can be computed. This is also discussed on a computational example. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamical Modeling and Flatness Based Control of a Belt Drive System
Authors: Jörgl Matthias , Gattringer Hubert
Published: December 2014

Belt driven systems are part of many industrial applications, like computerized numerical control (CNC) machines in particular cutting machines and 3D‐printers. In this paper the dynamical modeling and a flatness based controller design for belt driven systems are proposed. Due to the special kinematics, the stiffness of the belt is nonlinear, leading to nonlinear equations of motion. By neglecting some minor dynamical effects, the resulting system simplifies to a differentially flat one. This allows to calculate nominal feed‐forward control torques by using the flat output of the system. To stabilize the error dynamics, an additional PD control law is introduced. The proposed method is compared with a controller, where elastic deflections for the feed forward part are neglected and elastic deformations are compensated by modifying the desired trajectories in a model‐based manner. The tracking performance of both methods is evaluated in certain simulations and experiments. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling, simulation and adaptive process control of biotechnological processes in decentralized anaerobic treatment of domestic wastewater
Authors: Vega‐De Lille Marisela , Groß Frauke , Delgado Antonio
Published: December 2014

Control in anaerobic wastewater treatment plants is difficult to achieve but necessary due to a high sensitivity to disturbances and process complexity. With the help of different mathematical tools, control strategies can be developed. Particularly, a well‐defined mathematical model can be highly effective for design, assessment and optimization of treatment plants. However, applications directly in the control system of a treatment plant are hard to achieve due to model complexity and usually require specialized software and the engagement of experts in the subject. The objective of the present study was the development of less empirical methods for assessment and control of a decentralized anaerobic plant for the treatment of domestic wastewater. A lab‐scale plant, which consisted of a two‐stage anaerobic digestion process followed by an anaerobic ammonium oxidation (ANAMMOX) reactor for nitrogen removal, was used as object of study. Ordinary differential equation models were implemented to simulate the processes that took place in the treatment plant. With the help of the implemented models, control tools were developed. These tools include a standalone application for monitoring of the two‐stage anaerobic digestion process and an ammonium estimator for the ANAMMOX reactor by means of artificial neural networks (ANNs). The procedures followed aimed to reduce the amount of experimental work required so they can be easily transferred from laboratory to full‐scale conditions. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variational approach to modeling and control of dynamic systems with distributed parameters
Authors: Kostin Georgy
Published: December 2014

Controlled motions of a thin elastic rod are studied. A variational statement of the initial‐boundary value problem is given based on the integral formulation of constitutive relations. An approach relying on the Ritz method and finite element technique is proposed to design the boundary control that moves the rod with certain accuracy to a given final state and minimizes the mean energy. The results of numerical simulation and the estimates of solution quality are presented and discussed. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Feedback control for parabolic systems with in‐domain actuation
Authors: Wang Siqian , Woittennek Frank , Knüppel Torsten
Published: December 2014

State feedback design for linear parabolic systems with in‐domain actuation and general Robin boundary conditions is considered. To this end the system is shown to be state equivalent to a boundary controlled system. By means of the backstepping transformation the latter system is shown to be feedback equivalent to a stable parabolic equation. Within the contribution previous results concerning such systems are supplemented by numerical simulation studies. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Normal form observers for hyperbolic distributed parameter systems with spatially varying coefficients
Authors: Woittennek Frank
Published: December 2014

Observer design for 1D linear distributed parameter systems of hyperbolic type with boundary measurement is discussed. The approach is based on the observer canonical form introduced on the basis of a functional‐differential equation (f.d.e.) equivalent to the original posed boundary value problem. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Constraint handling in optimization‐based control of a heat‐up problem using a transformation approach
Authors: Utz Tilman , Rhein Sönke , Graichen Knut
Published: December 2014

An approach is presented for optimization‐based control of a class of boundary‐controlled parabolic partial differential equations, which are subject to state and input constraints. In order to avoid the potential numerical complexity of constrained optimization, suitably chosen asymptotic saturation functions are used to reformulate the original problem in new coordinates. The resulting unconstrained problem can then be solved with methods of unconstrained optimization, which is interesting for use in model predictive control schemes. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear MPC: the Impact of Sampling on Closed Loop Stability
Authors: Worthmann Karl , Reble Marcus , Grüne Lars , Allgöwer Frank
Published: December 2014

In this paper we consider model predictive control (MPC) schemes without stabilizing terminal constraints and/or costs for continuous time systems. While the estimates on the required prediction horizon length such that asymptotic stability of the MPC closed loop is guaranteed yield, in general, satisfactory results their applicability is limited due to the fact that the respective proofs assume that the input function can be switched arbitrarily often on compact time intervals. We present a technique which allows to determine a suitable discretization accuracy such that the obtained performance bound is preserved while the control signal is only switched at the sampling instants of the corresponding sampled data system. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Hybrid Systems Framework for Motion Planning with Motion Primitives of Mechanical Systems
Authors: Flaßkamp Kathrin , Hage‐Packhäuser Sebastian , Ober‐Blöbaum Sina
Published: December 2014

Motion planning with motion primitives is a solution concept for the optimal control of mechanical systems based on a quantization of the search space. In this contribution, we write the resulting system as a hybrid automaton and discuss the arising structures. In this context, we focus on the exploitation of symmetries. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐Gain Scheduling of the Proportional‐Integral‐Observer
Authors: Bakhshande Fateme , Söffker Dirk
Published: December 2014

Estimation of states and unknown inputs simultaneously can be done by Proportional‐Integral‐Observer (PIO). This observer is used in nonlinear and robust control. It has additional integral feedback loop in comparison with the usual Luenberger observer. Increasing the gain of this observer the performance would be increased, however due to this high gain the performance is influenced by measurement noise. Advanced PI‐Observer (API) algorithm is a method which is used for scheduling the optimal gain of PI‐Observer based on the cost function and by using a bank of PI‐Observer. In this contribution the proposed method obtains relative optimal gain by using a given cost function. Afterwards the absolute optimal gain is computed by changing the design parameters at each step based on the desired performance criteria. The absolute optimal gain is found instead of relative optimal gain in comparison with the API‐Observer. Simulation results estimating contact forces acting to a vibrating elastic beam based on indirect measurements illustrate the improvement of the proposed method. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
System Identification based on Model Synchronization
Authors: Koester Marius , Jehle Georg , Fidlin Alexander
Published: December 2014

Detailed knowledge about system parameters is required in many technical applications in order to model the system adequately. The question how to obtain parameter values and state maps of certain components thus is of significant importance in engineering applications. In this contribution, a novel approach to identifying system parameters and parameter‐free state maps of a simple nonlinear clutch actuation device is presented. To identify parameters, the Extended Kalman Filter (EKF) is used for synchronizing a system model with measurements of the system response to transient excitation. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Soft‐Computing Algorithm‐based Cognitive Observer for an Elastic Robotic Arm
Authors: Tamimi Hammam , Söffker Dirk
Published: December 2014

This paper proposes the use of Support Vector Machine (SVM) algorithm for modeling and states estimation of an elastic robotic arm. Due to the complexity of the elastic robotic arm, an accurate mathematical model and large number of sensors are needed to achieve accurate estimation. Initially, it is assumed that all system states are measurable for a short period of time. Additionally, the system output and input signals are being continuously measured. The modeling module builds two models, the internal model which will capture the dynamics of the elastic robotic arm and the data‐driven observer model which will estimate the system states. The internal model and data‐driven observer are obtained based on the experimental measurements using SVM algorithm in contrast to classical methods that uses the mathematical system model to drive an observer. The internal model is able to make multi‐steps ahead predictions of all system states; therefore it can be used to generate a suitable control strategy. Once the models are ready, the main sensors can be removed or turned off. The proposed modeling module will eliminate the need for mathematical modeling and reduces the number of permanent sensors needed. If the main sensors are removed completely, the hardware price can be radically reduced. The simulation result demonstrates the efficiency and high performance of the modeling module. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Solution of Large Scale Sparse Matrix Equations in Python
Authors: Baran Björn , Köhler Martin , Prasad Nitin , Saak Jens
Published: December 2014

The M.E.S.S. software suite for solving large scale matrix equations and related problems is the successor of the obsolete LyaPack MATLAB® toolbox. The software suite consists of a new MATLAB toolbox and a separate C library C‐M.E.S.S. which works independent from MATLAB. Due to the fact that many scientists use Python with NumPy and SciPy for their computations, we want to provide the key algorithms of M.E.S.S. there as well. In this paper, we describe and compare two possible approaches for the implementation, with special focus on their multicore performance. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sum factorization of the static condensed Helmholtz equation in a three‐dimensional spectral element discretization
Authors: Huismann Immo , Haupt Lars , Stiller Jörg , Fröhlich Jochen
Published: December 2014

We propose a factorization technique for the Helmholtz operator of a static condensed, three‐dimensional, cartesian spectral‐element discretization, that yields linear complexity in the number of degrees of freedom. We then compare its performance to a reference implementation of the conventional, unfactorized approach. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interpolation‐based nonlinear parametric MOR for gas pipelines
Authors: Lu Yi , Marheineke Nicole , Mohring Jan
Published: December 2014

This work deals with the model order reduction (MOR) of nonlinear, parametric systems of partial differential equations as they arise in gas pipeline modeling. We present an approach that is based on a linearization around parametric working points, linear modal reduction and interpolation. The choice of the working points as well as the interpolation strategy crucially determine the approximation quality. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Laplacians on quantum hypergraphs
Authors: Mugnolo Delio
Published: December 2014

We introduce quantum hypergraphs, in analogy with the theory of quantum graphs developed over the last 15 years by many authors. We emphasize some problems that arise when one tries to define a Laplacian on a hypergraph. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fluid Flow in Wedge Type Domains
Authors: Maier Siegfried , Saal Jürgen
Published: December 2014

Maximal regularity for the Stokes equations with perfect slip type boundary conditions on wedge domains is studied. The approach is based on operator theoretical methods, such as the operator sum method and ℋ∞‐calculus, and the reduced Stokes system. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Local moment problem
Authors: Adamyan Vadym , Tkachenko Igor
Published: December 2014

The work is devoted to the local moment problem, which consists in finding of non‐decreasing functions on the real axis having given first 2n + 1, n ≥ 0, power moments on the whole axis and also 2m + 1 first power moments on a certain finite axis interval. Considering the local moment problem as a combination of the Hausdorff and Hamburger truncated moment problems we obtain the conditions of its solvability and describe the class of its solutions with minimal number of growth points if the problem is solvable. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A note on causality in reflexive Banach spaces.
Authors: Waurick Marcus
Published: December 2014

In this short note we discuss the causality of linear closable operators in reflexive Banach spaces. We show that in general causality is not preserved under closure procedures. We shall give an alternative definition of causality for closable operators by means of a certain continuity poperty that carries over to the closure. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Operator splitting for dissipative delay equations
Authors: Bátkai András , Csomós Petra , Farkas Bálint
Published: December 2014

Operator splitting methods for a special class of nonlinear partial differential equations with delay are investigated. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Parabolic equations with mixed boundary conditions, degenerate diffusion and diffusion on interfaces
Authors: Disser Karoline
Published: December 2014

We provide a unified functional analytic framework and prove a well‐posedness result for linear scalar parabolic problems in a non‐smooth setting, including mixed boundary conditions and additional dynamics and possible diffusion on the boundary and on an enclosed interface. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Perron‐Frobenius type results for the block numerical range
Authors: Radl Agnes
Published: December 2014

We survey results for the block numerical range of positive operators and Perron polynomials. It turns out that many properties of the block numerical range resemble the spectral properties known from Perron‐Frobenius theory for matrices and its generalisations to bounded linear operators. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The parareal algorithm as a new approach for numerical integration of ODEs in real‐time simulations in automotive industry
Authors: Loderer Thomas , Heuveline Vincent , Lohner Rudolf
Published: December 2014

In the automotive industry, there is a growing demand for real‐time simulation of dynamic physical models. This work investigates the capability of the parareal algorithm to meet these requirements for those physical models that are described by a system of ODEs. For this purpose, it is investigated in numerical simulations how different choices for some of the degrees of freedom arising in the implementation of parareal affect the accuracy and run time of the numerical integration in case of a benchmark task. Furthermore, the stability of the parareal scheme is investigated theoretically in case that the coarse stage uses a simplified model. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamics of discrete screw dislocations via discrete gradient flow
Authors: De Luca Lucia
Published: December 2014

We present variational approaches (developed in [3,4,11]) to the study of statics and dynamics of screw dislocations in crystals.

We model the crystal as a cubic lattice and we give the asymptotic Γ‐convergence expansion of the elastic energy induced by a finite family of screw dislocations as the lattice spacing goes to zero. We show that the effective energy associated to the presence of a finite system of screw dislocations coincides with the renormalized energy, studied within the Ginzburg‐Landau framework and ruling the interactions between the dislocations. As a byproduct of this analysis, we show the existence of many metastable configurations of dislocations pinned by energy barries. Using the minimizing movement approach á la De Giorgi, we introduce a discrete‐in‐time variational dynamics, referred to as Discrete Gradient Flow, which allows to overcome these energy barriers. More precisely, we show that lettting first the lattice spacing and then the time step of minimizing movements tend to zero, dislocations move accordingly with the gradient flow of the renormalized energy. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computational studies of the effects of ortho‐ring and para‐ring activation on the kinetics of SNAr reactions of 1‐chloro‐2‐nitrobenzene and 1‐phenoxy‐2‐nitrobenzene with aniline
Authors: Oloba‐Whenu Oluwakemi A. , Isanbor Chukwuemeka
Published: December 2014

Computational studies are reported for reactions of 4‐substituted‐1‐chloro‐2,6‐dinitrobenzenes 1, 6‐substituted‐1‐chloro‐2,4‐dinitrobenzenes 2 and some of the corresponding 1‐phenoxy derivatives 3 and 4 with aniline in the gas phase. The effects of substituent groups in the calculated energy values for reactants 1–4, transition states structures, intermediates and products formed in the reactions between the compounds and anilines have been compared. Calculated bonds length and angles from optimized structures of the reactants were comparable with values reported for some of compounds 1–4 obtained by X‐ray crystal structures analysis. Generally, the decomposition of the Meisenheimer intermediate to the products requires more energy compared with the reactants except for when R = H. The order of stabilization of the intermediate was found to reflect the relative order of activation by substituents in the substrates. The 4‐substituted‐1‐chloro‐2,6‐dinitrobenzenes 1 and the phenoxy derivatives 3 were found to be more stable than their corresponding 6‐substituted analogues. This is an indication that the rate of nucleophilic attack at 1‐position will increase with increasing ring activation but may be reduced by steric repulsion at the reaction centre that increases in the order Cl < OPh. However, the steric hindrance to the steps involved in nucleophilic substitution by aniline is significantly increased when the substrates contain two ortho‐substituents. In most cases, the rate determining step is the decomposition of the σ‐adduct intermediate except with 1‐chloro‐2,6‐dinitrobenzenes 1 and 6‐substituted‐1‐chloro‐2,4‐dinitrobenzenes 2, either because of reduction in ring activation or the presence of bulky ortho‐substituents in the chloro compounds 1 and 2. Copyright © 2014 John Wiley & Sons, Ltd.
The Use of Cuff Weights for Aquatic Gait Training in People Post‐Stroke with Hemiparesis
Authors: Nishiyori Ryota , Lai Byron , Lee Do Kyeong , Vrongistinos Konstantinos , Jung Taeyou
Published: December 2014

Background and Purpose

This study aimed to examine how spatiotemporal and kinematic gait variables are influenced by the application of a cuff weight during aquatic walking in people post‐stroke. The secondary purpose was to compare the differences in gait responses between the placements of cuff weights on the proximal (knee weight) and distal end (ankle weight) of the shank.

Methods

Twenty‐one participants post‐stroke with hemiparesis aged 66.3 ± 11.3 years participated in a cross‐sectional comparative study. Participants completed two aquatic walking trials at their self‐selected maximum walking speed across an 8‐m walkway under each of the three conditions: 1) walking with a knee weight; 2) walking with an ankle weight; and 3) walking with no weight. Cuff weights were worn on the paretic leg of each participant. Gait speed, cadence, step width and joint kinematics of the hip, knee and ankle joints were recorded by a customized three‐dimensional underwater motion analysis system.

Results

Mean aquatic walking speeds significantly increased with the use of cuff weights when compared to walking with no weight. Changes in gait variables were found in the non‐paretic leg with the addition of weight, while no significant changes were found in the paretic leg.

Conclusion

The results suggest that the use of additional weight can be helpful if the goal of gait training is to improve walking speed of people post‐stroke during pool floor walking. However, it is interesting to note that changes in gait variables were not found in the paretic limb where favourable responses were expected to occur. Copyright © 2014 John Wiley & Sons, Ltd.
Certificateless online/offline signcryption scheme
Authors: Li Jiguo , Zhao Jingjing , Zhang Yichen
Published: December 2014

Signcryption is a highly efficient approach to achieve simultaneously confidentiality and authentication of message, which is more feasible than the simple combination of encryption and signature. The online/offline cryptography can further enhance the efficiency of signcryption system process without affecting its security. At present, most online/offline signcryptions focus on the ID‐based setting. However, the key escrow problem is inherent in ID‐based cryptography, which is regarded as the main barrier to affect the implementation of system. In this paper, we propose a brand new certificateless online/offline signcryption scheme. We prove the security of our scheme under q‐mBDHI, CDH and q‐CAA assumptions in the random oracle model. The proposed scheme overcomes the key escrow problem in the ID‐based setting. Copyright © 2014 John Wiley & Sons, Ltd.
Improvement of the mechanical properties of paper by starch coatings modified with sepiolite nanoparticles
Authors: Janković‐Častvan Ivona , Lazarević Slavica , Stojanović Dušica , Živković Predrag , Petrović Rada , Janaćković Đorđe
Published: December 2014

The modern and rapidly developing paper and board industry requires more efficient agents for the surface of paper in order to improve the mechanical properties. The starch coating used for the reinforcement of schrenz (110 g/m2) contained ultrasonicated nanoparticles of the mineral sepiolite. The viscosity of starch dispersions modified with different concentration of sepiolite was followed at the temperature of the coating on schrenz. The values of the breaking length, bursting strength and CMT‐strength of the paper reinforced with modified starch were increased by up to 20%. The viscoelastic properties as storage modulus were increased, too. Scanning electron microscopy of the samples showed deagglomeration and homogeneity of the sepiolite nanoparticles.
Shear strength of deep beams: a mathematical model and design formula
Authors: Kassem Wael
Published: December 2014

This paper presents a proposal for estimating the shear capacity of reinforced concrete deep beams. The proposed model is based on the fixed‐angle softened truss model and utilizes a newly proposed formula for the effective transverse compressive stress acting on the beam web. The proposed formula is developed using a stepwise multiple linear regression analysis of the reported shear capacity values of 445 experimental deep beams. The validity of the mathematical model is examined by comparing its response with the experimental results as well as the predictions of other formulas available in the literature, and it results in the one best fitting the measured shear strengths. The mathematical model leads to an explicit single closed‐form expression for computing the shear strength of deep beams. The proposed expression is dimensionless and contains four variables that express the horizontal and vertical reinforcement ratios, the concrete strength and the shear span‐to‐depth ratio. On the basis of the results of this paper, a design formula is proposed with predictions that are more consistent and also more reliable than those of the ACI Code and the Eurocode.
Global optimization for the OPF problem via two‐degree SDP method
Authors: Tian Junyang , Wei Hua
Published: December 2014

This letter proposes a two‐degree semidefinite programming (SDP) method for achieving the global optimum of the optimal power flow (OPF) problem. The method extends the variables to four degrees, and formulates an SDP problem with a two‐degree extended matrix. It satisfies the rank‐1 condition. Experimental results show that this method is more reliable for reaching the OPF's global optimum than existing SDP methods. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Fundamental characteristics of a MEMS‐diaphragm actuator using a thermal expansion drive composed of a conductive polymer
Authors: Imai Satomitsu , Adachi Koji
Published: December 2014

Performance of a MEMS actuator using a thermal expansion drive of a conductive polymer (CP) is investigated by applying electricity to it. The actuator consists of a thin polymer diaphragm (5 mm diameter) and a thin CP (ion‐doped polythiophene) layer coated on the diaphragm surface. Polyimide (10 μm thickness) and PET (110 μm thickness) sheets were chosen as the diaphragm materials. The diaphragm is deflected by the thermal expansion of the CP by applying electricity to it. Merits of using the CP instead of metal are realizing flexible actuators and the applicability to a low‐heat‐resistant material diaphragm. The relationship between thickness of the CP layer (10–50 μm thickness) and electrical resistance (30–600 Ω) and the relationship between the input voltage (1–8 V) and the generated diaphragm displacement (several tens of micrometers) were investigated experimentally. These relationships were compared with those in the case of using the thermal expansion of a vapor‐deposited aluminum layer (0.1 μm thickness). The results of the investigation indicate that the diaphragm based on CP can produce the required displacement. In the case the CP‐layer‐based thermal expansion, however, larger input voltage than in the case of the aluminum‐layer‐based thermal expansion is needed to obtain the same displacement amplitudes. Therefore, the main problem concerning use of the CP‐based diaphragm is considered to be enhancing the electrical conductance of the CP layer. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Tough on Drugs: Law and Order Dominance and the Neglect of Public Health in U.S. Drug Policy
Authors: Neill Katharine A.
Published: December 2014

Since the War on Drugs began, U.S. drug policy has been dominated by a law and order policy model. The emphasis on incarceration and punishment as responses to drug use has resulted in the neglect of public health concerns related to drug addiction. In this paper I trace the development of drug policy in the United States and argue that the social construction of drug offenders as a deviant population has led to the dominance of the law and order approach to drugs. While other scholars have argued that perceptions of drug users affect drug policy, this analysis focuses specifically on the creation and consequences of social constructions for modern drug policy within the policy design framework. By analyzing current trends this paper identifies a way forward for drug policy reform and calls for the adoption of a public health approach to drug use.
Single‐molecule bioelectronics
Authors: Rosenstein Jacob K. , Lemay Serge G. , Shepard Kenneth L.
Published: December 2014

Experimental techniques that interface single biomolecules directly with microelectronic systems are increasingly being used in a wide range of powerful applications, from fundamental studies of biomolecules to ultra‐sensitive assays. In this study, we review several technologies that can perform electronic measurements of single molecules in solution: ion channels, nanopore sensors, carbon nanotube field‐effect transistors, electron tunneling gaps, and redox cycling. We discuss the shared features among these techniques that enable them to resolve individual molecules, and discuss their limitations. Recordings from each of these methods all rely on similar electronic instrumentation, and we discuss the relevant circuit implementations and potential for scaling these single‐molecule bioelectronic interfaces to high‐throughput arrayed sensing platforms. WIREs Nanomed Nanobiotechnol 2015, 7:475–493. doi: 10.1002/wnan.1323

This article is categorized under:

Diagnostic Tools > Biosensing
4‐H Healthy Living programs with impact: A national environmental scan
Authors: Downey Laura H. , Peterson Donna J. , LeMenestrel Suzanne , Leatherman JoAnne , Lang James
Published: December 2014

The 4‐H youth development program of the nation's 109 land‐grant universities and the Cooperative Extension System is one of the largest youth development organization in the United States serving approximately six million youth. The 4‐H Healthy Living initiative began in 2008 to promote achievement of optimal physical, social, and emotional well‐being for youth and families. In 2013, the National 4‐H Council sought to identify 4‐H Healthy Living programs in the domains of healthy eating and physical activity that adhered to the national 4‐H Healthy Living mission and were ready for comprehensive outcome evaluation or replication at a national level. This chapter shares findings from an environmental scan of 4‐H programs and (a) identifies programs with evidence of promoting a healthy diet and physical activity, (b) describes program impacts related to healthy diet and physical activity, and (c) clarifies select program characteristics associated with reported healthy eating and/or physical activity outcomes. The RE‐AIM evaluation framework is introduced as an effective approach to assessing program impact for 4‐H Healthy Living and similar out‐of‐school time programs.