Subsystem Solutions Research Articles

An Analytic Solution for 2D Heat Conduction Problems with Space–Time-Dependent Dirichlet Boundary Conditions and Heat Sources

This study proposes a closed-form solution for the two-dimensional (2D) transient heat conduction in a rectangular cross-section of an infinite bar with space–time-dependent Dirichlet boundary conditions and heat sources. The main purpose of this study is to eliminate the limitations of the previous study and add heat sources to the heat conduction system. The restriction of the previous study is that the values of the boundary conditions and initial conditions at the four corners of the rectangular region should be zero. First, the boundary value problem of 2D heat conduction system is transformed into a dimensionless form. Second, the dimensionless temperature function is transformed so that the temperatures at the four endpoints of the boundary of the rectangular region become zero. Dividing the system into two one-dimensional (1D) subsystems and solving them by combining the proposed shifting function method with the eigenfunction expansion theorem, the complete solution in series form is obtained through the superposition of the subsystem solutions. Three examples are studied to illustrate the efficiency and reliability of the method. For convenience, the space–time-dependent functions used in the examples are considered separable in the space–time domain. The linear, parabolic, and sine functions are chosen as the space-dependent functions, and the sine, cosine, and exponential functions are chosen as the time-dependent functions. The solutions in the literature are used to verify the correctness of the solutions derived using the proposed method, and the results are completely consistent. The parameter influence of the time-dependent function of the boundary conditions and heat sources on the temperature variation is also investigated. The time-dependent function includes exponential type and harmonic type. For the exponential time-dependent function, a smaller decay constant of the time-dependent function leads to a greater temperature drop. For the harmonic time-dependent function, a higher frequency of the time-dependent function leads to a more frequent fluctuation of the temperature change.

Analysis and evaluation of steady-state and non-steady-state preserving operator splitting schemes for reaction-diffusion(-advection) problems

Reaction-diffusion(-advection) problems are well-known in chemical engineering and computational fluid dynamics. A common feature of these systems is a linear (or non-stiff) transport sub-system and a non-linear (or stiff), highly coupled chemistry sub-system. The expected numerical effort often prohibits a fully coupled solution of the system. Therefore, the system is split into a transport and a reaction sub-system, and each sub-system is solved using specialized solvers. Operator splitting schemes are required to reconstruct the solution of the initial system from the sub-system solutions. Steady-state preserving splitting schemes are particularly essential for steady-state calculations since local time stepping (LTS) or other methods based on fictional time rely on large time steps to be efficient. This work formally analyzes common splitting schemes for reaction-diffusion problems by stability analysis and checking the steady-state preservation of a representative linear scalar problem. Balanced and Simpler Balanced splitting are the only steady-state conservative schemes analyzed. Three new steady-state preserving splitting schemes are proposed based on the findings of the formal analysis. To achieve steady-state preservation, the new schemes use splitting constants based on either the mixing derivative or the chemistry derivative. The formal analysis is accompanied by a dimensionless perfectly stirred reactor (PSR) case and a hydrogen combustion case, both known to be challenging for operator splitting schemes. The test case results are in line with the theoretical results but indicate that the scalar linear analysis is nonviable to capture the full effects of the chemical sub-system. The Simpler and the newly proposed Consistent Staggered splitting schemes give significantly better results than the remaining ones while being second-order and first-order accurate, respectively. If temporal accuracy is irrelevant, e.g., for steady-state solvers, the proposed Consistent Adaptive splitting scheme is promising since it preserves the steady-state solution first-order time accurate with less function evaluations.

Computing control invariant sets of cascade nonlinear systems: Decomposition and distributed computing

In this work, we present a distributed framework based on the graph algorithm for computing control invariant set for nonlinear cascade systems. The proposed algorithm exploits the structure of the interconnections within a process network. First, the overall system is decomposed into several subsystems with overlapping states. Second, the control invariant set for the subsystems are computed in a distributed manner. Finally, an approximation of the control invariant set for the overall system is reconstructed from the subsystem solutions and validated. We demonstrate the efficacy and convergence of the proposed method to the centralized graph-based algorithm using several numerical examples including a six dimensional continuous stirred tank reactor system.

Distributed and Asynchronous Coordination of a Mixed-Integer Linear System via Surrogate Lagrangian Relaxation

With the emergence of the Internet of Things that allows communications and local computations and with the vision of Industry 4.0, a foreseeable transition is from centralized system planning and operation toward decentralization with interacting components and subsystems, e.g., self-optimizing factories. In this article, a new “price-based” decomposition and coordination methodology is developed to efficiently coordinate a system consisting of distributed subsystems such as machines and parts, which are described by mixed-integer linear programming (MILP) formulations, in an asynchronous way. The novel method is a dual approach, whereby the coordination is performed by updating Lagrangian multipliers based on economic principles of “supply and demand.” To ensure low communication requirements within the method, exchanges between the “coordinator” and subsystems are limited to “prices” (Lagrangian multipliers) broadcast by the coordinator and to subsystem solutions sent at the coordinator. Asynchronous coordination, however, may lead to convergence difficulties since the order in which subsystem solutions arrive at the coordinator is not predefined as a result of uncertainties in communication and solving times. Under realistic assumptions of finite communication and solve times, the convergence of our method is proven by innovatively extending the Lyapunov stability theory. Numerical testing of generalized assignment problems through simulation demonstrates that the method converges fast and provides near-optimal results, paving the way for self-optimizing factories in the future. Accompanying CPLEX codes and data are included. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —In view of a foreseeable transition toward self-optimizing factories whereby machines and parts have communication and computational capabilities, a novel “price-based” distributed and asynchronous method to coordinate a system consisting of distributed subsystems is developed. Under realistic assumptions of finite communication and solve times, method convergence is proven. Numerical testing of generalized assignment problems through simulation demonstrates that the method converges fast and provides near-optimal results, paving the way for self-optimizing factories in the future. Accompanying CPLEX codes and data are included.

THE INVESTIGATION AND EVALUATION MULTISERVICE NETWORK NGN/IMS FOR MULTIMEDIA TRAFFIC

The subject of the study is multiservice communication network using the concept NGN (Next Generation Network) based on the open network architecture IMS (Internet Protocol Multimedia Subsystem), supporting a wide range services. The basis of this architecture is the IMS core, consisting of a set of specialized modules responsible for various functions for customer service. The purpose of the article is to analyze the existing technical capabilities of the IMS multimedia messaging subsystem and perspective solutions for the functioning of the NGN/IMS network efficiency in providing multimedia service. As the efficiency of the system, the capacity NGN/IMS networks is selected using the signaling system and protocols NGN. The capacity NGN/IMS networks during the establishment of a multimedia session was analyzed and the functional architecture of the IMS multimedia messaging subsystem that determine the interaction NGN signaling systems an protocols was explored. Manage the presentation Triple Play services to subscribers and simultaneously modify the media stream within the session allows the protocol for the initialization of the SIP and Diameter sessions, which are the main IMS signaling protocol. One of the important requirements for the IMS subsystem is the maintenance QoS (Quality of Service). A mathematical model for estimating the quality of communication services using a system GI/G/1/N based on the theory diffusion approximation is proposed. The research presented in this paper is very important for the theory queuing systems, since the article proposes a method for investigating multiservice communication networks with non-Poisson incoming flow and effective results are obtained for NGN/IMS networks. On the basis of the model analytical expressions are obtained, which allow evaluating the performance indicators of the Triple Play service. The proposed mathematical model can be used to solve a wide range of practical problems, including the management multiservice traffic in the process its transmission in multiservice telecommunications networks, taking into account the quality of service classes. Thus, studies NGN/IMS network capacity indicators using SIP protocols are relevant.

The Effectiveness NGN/IMS Networks in the Establishment of a Multimedia Session

The subject of the study is multiservice communication network using the concept NGN (Next Generation Network) based on the open network architecture IMS (Internet Protocol Multimedia Subsystem), supporting a wide range of services. The basis of this architecture is the IMS core, consisting of a set of specialized modules responsible for various functions for customer service. The purpose of the article is to analyze the existing technical capabilities of the IMS multimedia messaging subsystem and perspective solutions for the functioning of the NGN/IMS network efficiency in providing multimedia services. The effectiveness NGN/IMS networks during the establishment of a multimedia session was analyzed and the functional architecture of the IMS multimedia messaging subsystem that determine the interaction of NGN signaling systems an protocols was explored. One of the important requirements for the IMS subsystem is the maintenance QoS (Quality of Service). A mathematical model for estimating the quality of communication services using a system <i>GI</i>/<i>G</i>/1/<i>N_6H</i> based on the theory of diffusion approximation is proposed. On the basis of the model analytical expressions are obtained, which allow evaluating the performance indicators of the Triple Play service.

Stability of subsystem solutions in agent-based models

The fact that relatively simple entities, such as particles or neurons, or even ants or bees or humans, give rise to fascinatingly complex behaviour when interacting in large numbers is the hallmark of complex systems science. Agent-based models are frequently employed for modelling and obtaining a predictive understanding of complex systems. Since the sheer number of equations that describe the behaviour of an entire agent-based model often makes it impossible to solve such models exactly, Monte Carlo simulation methods must be used for the analysis. However, unlike pairwise interactions among particles that typically govern solid-state physics systems, interactions among agents that describe systems in biology, sociology or the humanities often involve group interactions, and they also involve a larger number of possible states even for the most simplified description of reality. This begets the question: when can we be certain that an observed simulation outcome of an agent-based model is actually stable and valid in the large system-size limit? The latter is key for the correct determination of phase transitions between different stable solutions, and for the understanding of the underlying microscopic processes that led to these phase transitions. We show that a satisfactory answer can only be obtained by means of a complete stability analysis of subsystem solutions. A subsystem solution can be formed by any subset of all possible agent states. The winner between two subsystem solutions can be determined by the average moving direction of the invasion front that separates them, yet it is crucial that the competing subsystem solutions are characterised by a proper composition and spatiotemporal structure before the competition starts. We use the spatial public goods game with diverse tolerance as an example, but the approach has relevance for a wide variety of agent-based models.

Second-Order Free-Riding on Antisocial Punishment Restores the Effectiveness of Prosocial Punishment

Economic experiments have shown that punishment can increase public goods game contributions over time. However, the effectiveness of punishment is challenged by second-order freeriding and antisocial punishment. The latter implies that non-cooperators punish cooperators, while the former implies unwillingness to shoulder the cost of punishment. Here we extend the theory of cooperation in the spatial public goods game by considering four competing strategies, which are traditional cooperators and defectors, as well as cooperators who punish defectors and defectors who punish cooperators. We show that if the synergistic effects are high enough to sustain cooperation based on network reciprocity alone, antisocial punishment does not deter public cooperation. Conversely, if synergistic effects are low and punishment is actively needed to sustain cooperation, antisocial punishment does act detrimental, but only if the cost-to-fine ratio is low. If the costs are relatively high, cooperation again dominates as a result of spatial pattern formation. Counterintuitively, defectors who do not punish cooperators, and are thus effectively second-order freeriding on antisocial punishment, form an active layer around punishing cooperators, which protects them against defectors that punish cooperators. A stable three-strategy phase that is sustained by the spontaneous emergence of cyclic dominance is also possible via the same route. The microscopic mechanism behind the reported evolutionary outcomes can be explained by the comparison of invasion rates that determine the stability of subsystem solutions. Our results reveal an unlikely evolutionary escape from adverse effects of antisocial punishment, and they provide a rationale for why second-order freeriding is not always an impediment to the evolutionary stability of punishment.

Development Study of an Air Independent Fuel Cell System for an Autonomous Underwater Vehicle (AUV)

The paper is focused on the design concept of a fuel cell system for an autonomous underwater vehicle (AUV) developed within a common project of the German Navy research institute WTD 71, Fraunhofer ICT and the norwegian defense research institute “Forsvarets forskningsinstitutt (FFI)”. The presented work is therefore based on the boundary conditions for the system defined in this project. However, a more general approach is pursued by not only presenting the developed fuel cell system, but by defining a design strategy and applying it to the framework of the development in the project. For this, constraints and objectives which define the development will be defined as boundary conditions. Most of these boundary conditions also apply to the general development of air independent underwater systems and can therefore be used to outline similar systems. Based on the literature and the constraints, system and subsystem solutions for fuel cell systems are discussed to find the most suiting system for the AUV. The different system solutions are discussed on the basis of different objectives for the system design, namely space, runtime, stability and efficiency.

Competition of tolerant strategies in the spatial public goods game

Tolerance implies enduring trying circumstances with a fair and objective attitude. To determine whether evolutionary advantages might be stemming from diverse levels of tolerance in a population, we study a spatial public goods game, where in addition to cooperators, defectors, and loners, tolerant players are also present. Depending on the number of defectors within a group, a tolerant player can either cooperate in or abstain from a particular instance of the game. We show that the diversity of tolerance can give rise to synergistic effects, wherein players with a different threshold in terms of the tolerated number of defectors in a group compete most effectively against defection and default abstinence. Such synergistic associations can stabilise states of full cooperation where otherwise defection would dominate. We observe complex pattern formation that gives rise to an intricate phase diagram, where invisible yet stable strategy alliances require outmost care lest they are overlooked. Our results highlight the delicate importance of diversity and tolerance for the provisioning of public goods, and they reveal fascinating subtleties of the spatiotemporal dynamics that is due to the competition of subsystem solutions in structured populations.

Demonstration platform for collaborative design of space science missions

There are several problems during the demonstration process of collaborative design of space science missions,such as strong coupling between sub-system solutions,poor data consistency,difficulty in data modification,and associated relationship between data and demonstration process. In order to solve these problems,a multi-layer digital model for typical space missions was proposed. The demonstration process was graphically modeled,and the mapping between the process and data was established. The shared data pool was provided as the data collaboration mechanism for all users and all sub-system solutions. The message bus was adopted as the timely reminder to notify the changes of data. The design solution coupling matrix was used to describe the coupling relationship between sub-system solutions and to gain the system solution for the missions by the automatically merged method. The demonstration platform,as a distributed platform for the collaborative design of space science missions,uses the technology architecture of Eclipse RCP and Spring and integrates the middlewares of Hibernate and Activiti5. The platform can provide a unified portal and support multiuser,multi-mission,multi-solution and multi-version data management,and also support process monitor and data interactive collaboration. A space mission was used as an example to verify the efficacy of the platform.

Dynamic satellite system QoS architecture integrated with IP Multimedia Subsystem core network

SummaryConvergence is one of the most important challenges for Next Generation Networks (NGN). This includes service convergence as well as fixed‐mobile convergence. The integration of satellite telecommunication system into NGN is a key to increasing the coverage of future networks and opening satellite access networks to a wider range of terrestrial solutions. Digital Video Broadcast (DVB) Return Channel via Satellite system (DVB‐RCS) and its evolution (DVB‐RCS2) are widely used European standards that are specified for broadband satellite systems using dynamic capacity assignment and multifrequency TDMA. This paper introduces a new QoS architecture derived from terrestrial IP Multimedia Subsystem solutions to provide advanced end‐to‐end QoS support, and defines cross‐layer optimization paths suited to the satellite context and in particular using DVB standards. Copyright © 2014 John Wiley &amp; Sons, Ltd.

A methodology for vehicle and mission level comparison of More Electric Aircraft subsystem solutions: Application to the flight control actuation system

As part of the More Electric Initiative, there is a significant interest in designing energy-optimized More Electric Aircraft, where electric power meets all non-propulsive power requirements. To achieve this goal, the aircraft subsystems must be analyzed much earlier than in the traditional design process. This means that the designer must be able to compare competing subsystem solutions with only limited knowledge regarding aircraft geometry and other design characteristics. The methodology presented in this work allows such tradeoffs to be performed and is driven by subsystem requirements definition, component modeling and simulation, identification of critical or constraining flight conditions, and evaluation of competing architectures at the vehicle and mission level. The methodology is applied to the flight control actuation system, where electric control surface actuators are likely to replace conventional centralized hydraulics in future More Electric Aircraft. While the potential benefits of electric actuation are generally accepted, there is considerable debate regarding the most suitable electric actuator – electrohydrostatic or electromechanical. These two actuator types form the basis of the competing solutions analyzed in this work, which focuses on a small narrowbody aircraft such as the Boeing 737-800. The competing architectures are compared at both the vehicle and mission levels, using as metrics subsystem weight and mission fuel burn, respectively. As shown in this work, the use of this methodology aids the decision-making process by allowing the designer to rapidly evaluate the significance of any performance advantage between the competing solutions.

Fast quadratic programming approach for large scale reactive power optimization

A fast quadratic programming approach has been developed to control the reactive power (VAR) generation in dispatching centers. The main objective of VAR control is to minimize the transmission losses taking into consideration the voltage constraints at each node of the network. The developed approach utilizes the decomposition of whole system into smaller subsystems and coordination of different subsystem solutions to obtain the optimal VAR control in the large scale systems. The smallest practical size of the decomposed subsystems is the one-generator-bus subsystem. The fast and non-iterative VAR optimization of the decomposed subsystems is obtained based on considering only one active constraint at a time by solving the quadratic programming sub-problems. The numerical test results of IEEE-118 and 200 buses power system have indicated that the speed and accuracy of the proposed approach are adequate for real-time applications on large-scale systems. This approach is also applicable for large system deviations from its normal conditions and needs small memory size.

Provisioning in complex networks

IP Multimedia Subsystem (IMS) solutions emphasize services including all-Internet Protocol (IP) voice, data, video, multimedia, and other user-centric services. IMS applications allow network convergence among wireline, wireless, and packet networks and interaction of services in disparate, multivendor, multitechnology networks. This increased level of sophistication leads to increased operational complexity and underscores the need for a unified provisioning system to minimize the overhead of managing network data. This paper outlines a scalable, distributed, provisioning framework for disparate data networks. It examines the current approaches to provisioning and their shortcomings in dealing with disparate data. At a fundamental level, it views provisioning as two distinct problems of data management and process modeling. It depicts a unifying framework, by separating data management from the application that provisions the data, leading to data-model independence. It shows that unified provisioning requires the support of many distinct technologies including federated data management, software component framework, distributed computing framework, and formalisms for describing behavior. © 2007 Alcatel-Lucent.

CMOS-Compatible Through Silicon Vias for 3D Process Integration

ABSTRACTAs the limits of traditional CMOS scaling are approached, process integration has become increasingly difficult and resulting in a diminished rate of performance improvement over time. Consequently, the search for new two- and three- dimensional sub-system solutions has been pursued. One such solution is a silicon carrier-based System-on-Package (SOP) that enables high-density interconnection of heterogeneous die beyond current first level packaging densities. Silicon carrier packaging contains through silicon vias (TSV), fine pitch Cu wiring and high-density solder pads/joins, all of which are compatible with traditional semiconductor methods and tools. These same technology elements, especially the through silicon via process, also enable three dimensional stacking and integration. An approach to fabricating electrical through-vias in silicon is described, featuring annular-shaped vias instead of the more conventional cylindrical via. This difference enables large-area, uniform arrays to be produced with high yield as it is simpler to integrate into a conventional CMOS back-end-of-line (BEOL) process flow. Furthermore, the CTE-matched silicon core provides improved mechanical stability and the dimensions of the annular via allows for metallization by various means including copper electroplating or CVD tungsten deposition. An annular metal conductor process flow will be described. Through-via resistance measurements of 50, 90, and 150μm deep tungsten-filled annular vias will be compared. Two silicon carrier test vehicle designs, containing more than 2,200 and 9,600 electrical through-vias, respectively, were built to determine process yield and uniformity of via resistance. Through silicon via resistances range from 15-40 mΩ, and yields in excess of 99.99% have been demonstrated.

Advanced components and sub-system solutions for 40 Gb/s transmission

With the commissioning of the latest 10-Gb/s systems, vendors are now in the process of developing architectures for their next-generation products. 40-Gb/s components and subsystems are currently in development to address the necessities of these next-generation systems. The top three challenges associated with 40-Gb/s transmission are optical signal-to-noise ratio, dispersion, and high-speed components. In order to realize 40-Gb/s transmission, new component and subsystem developments are crucial. This paper reviews the latest transmission technologies and dispersion compensation techniques developed to fulfill 40-Gb/s transmission system requirements.

Electrothermal CAD of power devices and circuits with fully physical time-dependent compact thermal modeling of complex nonlinear 3-d systems

An original, fully analytical, spectral domain decomposition approach is presented for the time-dependent thermal modeling of complex nonlinear (3-D) electronic systems, from metallized power FETs and MMICs, through MCMs, up to circuit board level. This solution method offers a powerful alternative to conventional numerical thermal simulation techniques, and is constructed to be compatible with explicitly coupled electrothermal device and circuit simulation on CAD timescales. In contrast to semianalytical, frequency space, Fourier solutions involving DFT-FFT, the method presented here is based on explicit, fully analytical, double Fourier series expressions for thermal subsystem solutions in Laplace transform s-space (complex frequency space). It is presented in the form of analytically exact thermal impedance matrix expressions for thermal subsystems. These include double Fourier series solutions for rectangular multilayers, which are an order of magnitude faster to evaluate than existing semi-analytical Fourier solutions based on DFT-FFT. They also include double Fourier series solutions for the case of arbitrarily distributed volume heat sources and sinks, constructed without the use of Green's function techniques, and for rectangular volumes with prescribed fluxes on all faces, removing the adiabatic sidewall boundary condition. This combination allows treatment of arbitrarily inhomogeneous complex geometries, and provides a description of thermal material nonlinearities as well as inclusion of position varying and non linear surface fluxes. It provides a fully physical, and near exact, generalized multiport network parameter description of nonlinear, distributed thermal subsystems, in both the time and frequency domains. In contrast to existing circuit level approaches, it requires no explicit lumped element, RC-network approximation or nodal reduction, for fully coupled, electrothermal CAD. This thermal impedance matrix approach immediately gives rise to minimal boundary condition independent compact models for thermal systems. Implementation of the time-dependent thermal model as N-port netlist elements within a microwave circuit simulation engine, Transim (NCSU), is described. Electrothermal transient, single-tone, two-tone, and multitone harmonic balance simulations are presented for a MESFET amplifier. This thermal model is validated experimentally by thermal imaging of a passive grid array representative of one form of spatial power combining architecture.

Rule-based approach for real-time reactive power control in interconnected power systems

This paper presents two rule-based modules for voltage profile improvement and power loss minimization of interconnected power systems. The first module is used to alleviate voltage limit violations based on the voltage sensitivities to the most effective voltage control devices in the network. The second module deals with power loss minimization by optimal adjustment of voltage control buses. In this module, the large-scale system is decomposed to small subsystems, and the solution of these subsystems is coordinated to minimize the overall network losses. The subsystem solutions are very fast and robust. The proposed modules minimize the actions taken and are suitable for real-time applications. The required rules are developed using turbo-Prolog and integrated with the network simulation programs. The performance of the developed modules is evaluated on a real power system and the obtained results are presented in the paper.

PARALLEL STATE ESTIMATION WITH CONFIDENCE LIMIT ANALYSIS

This paper describes the parallelisation of a state estimator with confidence limit analysis. State estimation involves the optimal fitting of an overdetermined set of measurements to the corresponding values calculated from the mathematical model of the system. The inaccuracies associated with measurements lead to discrepancies within the state estimate. Consequently for the state estimation algorithm to be of practical use it needs to quantify the effect of these discrepancies in the form of state confidence limits [2], However, the quasi-quadratic numerical complexity of the state estimation algorithms suggests a need for parallel implementation of the probabilistic state estimation, so that the real-time performance may be maintained also for large-scale systems. The algorithm is based on the idea of ‘tearing’ the original system into subsystems and then coordination of the resulting subsystem solutions. The algorithm has been tested in the context of water distribution systems state estimation.