Constituent Systems Research Articles

Multilevel Modeling of System of Systems

A system of systems (SoS) is a large-scale integrated system. In an SoS, many complex independent systems work collectively for a common mission. Modeling of SoS is challenging due to their large-scale and complexity of the constituent systems. In this paper, generic modeling of a class of SoS, namely mechatronic systems, is proposed based on bond graph modeling approach. Bond graph modeling enables to develop a unified model of SoS, which combines the behavioral and the organizational modeling approaches of SoS. The proposed approach for SoS modeling is applied to intelligent transportation system, where road traffic dynamic in a platoon of intelligent autonomous vehicles (IAVs) is considered for modeling. Finally, the developed bond graph model is simulated for a platoon of four IAVs forming SoS.

Networked control approach for distributed generation systems

Microgrid has emerged as an answer to growing demand for distributed generation &#x0028 DG &#x0029 in power systems. It contains several DG units including microalternator, photovoltaic system and wind generation. It turns out that sustained operation relies on the stability of these constituent systems. In this paper, a microgrid consisting of microalternator and photovoltaic system is modeled as a networked control system of systems &#x0028 SoS &#x0029 subjected to packet dropouts and delays. Next, an observer-based controller is designed to stabilize the system in presence of the aforementioned communication constraints and simulation results are provided to support the control design methodology.

A Novel “Resilience Viewpoint” to aid in Engineering Resilience in Systems of Systems (SoS)

AbstractDesigning evolutionary systems to meet stakeholder expectations on safety, reliability and overall resilience is of great importance in an age of interconnectivity and high dependency systems. With incidents and disruptions becoming more frequent in recent years, the requirement for systems to demonstrate high levels of resilience given the economic, political and temporal dimensions of complexity, resilience is of great significance today. Systemic resilience is of high importance at the global level. Therefore, the role of the system engineer and architect is becoming more demanding due to the need to consider requirements from a broader range of stakeholders and to implement them into early conceptual designs. The early modeling process of all systems is common ground for most engineering projects, creating an architecture to both understand a system and to design future iterations by applying model‐based processes has become the norm. With the concept of systems‐of‐systems (SoS) becoming common language across multiple engineering domains, model‐based systems engineering techniques are evolving hand‐in‐hand to provide a paradigm to better analyse current and future SoS. The intrinsic characteristics of the constituent systems that make up the SoS make the challenge of designing and maintaining the reliability and resilience of a systems extremely difficult. This paper proposes a novel viewpoint, within an architecture framework (based around DoDAF, MoDAF and UPDM) to aid systems architects explore and design resilient SoS. This is known as the Resilience Viewpoint. Much of the research in the area is focussed on critical infrastructure (CI), looking at telecommunication networks, electric grid, supply networks etc, and little has been done on a generalizable tool for SoS architecture analysis, especially using existing modeling languages. Here, the application of the ‘Resilience Viewpoint’ is demonstrated using a case study from an integrated water supply system of systems, to portray its potential analytical capabilities.

Manage all recruitment efforts through one comprehensive platform

With new graduate programs launching and a new enrollment management structure, officials at Yeshiva University needed a comprehensive constituent relationship management system to manage marketing and admissions functions. Element 451 enables them to manage all parts of the enrollment process using one platform.

ON THE USE OF PERSPECTIVE IN MANAGING COMPLEXITY

ABSTRACTMost research into complexity has not directly addressed the fundamental issue that the complexity of any particular matter has a significant subjective component in which the degree of complexity depends on available frames of reference. Yet, researchers can readily show that the perceived complexity of an entity under consideration can vary dramatically if they take different perspectives. This paper illustrates that it is relatively easy in any context to state that context in such a manner as to cause confusion by establishing a perspective that incorporates all dimensions simultaneously in a two‐dimensional view. Further, the article shows that it is equally possible in many cases (and certainly in design), by choosing an appropriate view, to reduce the complexity. Finally, the article shows the utility of such an approach when designing systems‐of‐systems (SoS), in which the establishment of the perspective of system centricity is essential for the specification and acquisition of the constituent systems of an SoS.

Assessment of the Al-Bi-Mg system and extrapolation to the Al-Bi-Mg-Sn quaternary system

The phase equilibria in the Al-Bi-Mg-Sn quaternary system have been studied using the CALPHAD (CALculation of PHAse Diagram) method. One of the four ternary systems constituting the quarternary system, the Al-Bi-Mg system, is re-assessed by means of the CALPHAD technique and Thermo-Calc software package, in consideration of the associate model for the liquid phase instead of the Modified Quasi-chemical Model used in the literature report. While for the other three ternary systems, the Al-Bi-Sn, the Al-Mg-Sn and the Bi-Mg-Sn systems, the thermodynamic parameters are mainly adopted from the literature reported optimization results with a little modification to the Al-Bi-Sn and the Al-Mg-Sn systems for the compatibility of all the constituent binary systems. The assessment results of the Al-Bi-Mg ternary system are in good agreement with the available experimental phase relations, including the liquidus surface projection and the vertical sections. The thermodynamic database of the Al-Bi-Mg-Sn quaternary system was developed without the consideration of the quaternary interactions and the quaternary compounds. With this newly developed thermodynamic database, the phase equilibria and the solidification processes of the ternary and the quarternary systems are calculated and analyzed.

Energy-efficient HVAC management using cooperative, self-trained, control agents: A real-life German building case study

A variety of novel, recyclable and reusable, construction materials has already been studied within literature during the past years, aiming at improving the overall energy efficiency ranking of the building envelope. However, several studies show that a delicate control of indoor climating elements can lead to a significant performance improvement by exploiting the building’s savings potential via smart adaptive HVAC regulation to exogenous uncertain disturbances (e.g. weather, occupancy). Building Optimization and Control (BOC) systems can be categorized into two different groups: centralized (requiring high data transmission rates at a central node from every corner of the overall system) and decentralized1The terms “decentralized”, “distributed” and “agent-based” are considered to have similar meanings herein.1 (assuming an intercommunication among neighboring constituent systems). Moreover, both approaches can be further divided into two subcategories, respectively: model-assisted (usually introducing modeling oversimplifications) and model-free (typically presenting poor stability and very slow convergence rates). This paper presents the application of a novel, decentralized, agent-based, model-free BOC methodology (abbreviated as L4GPCAO) to a modern non-residential building (E.ON. Energy Research Center’s main building), equipped with controllable HVAC systems and renewable energy sources by utilizing the existing Building Management System (BES). The building testbed is located inside the RWTH Aachen University campus in Aachen, Germany. A combined rule criterion composed of the non-renewable energy consumption (NREC) and the thermal comfort index – aligned to international comfort standards – was adopted in all cases presented herein. Besides the limited availability of the specified building testbed, real-life experiments demonstrated operational effectiveness of the proposed approach in BOC applications with complex, emerging dynamics arising from the building’s occupancy and thermal characteristics. L4GPCAO outperformed the control strategy that was designed by the planers and system provider, in a conventional manner, requiring no more than five test days.

The performance of delay compensation in real-time dynamic substructuring

Real-time dynamic substructuring (RTDS) is a state-of-the-art experimental technique for evaluating the dynamic performance of a structural system subjected to time-varying loads in civil engineering. The accuracy and stability of RTDS is affected by the natural dynamics of the constituent transfer system. Of various control strategies, and due to the merits of simple implementation and low computational cost, delay-compensation methods have become most pervasive. In this paper, the performance of delay compensation based methods for RTDS is assessed in terms of accuracy and stability. Three commonly-used delay compensation schemes are considered, two of which are time variant and one time invariant. Stability is assessed analytically, numerically, and experimentally. Accuracy is assessed numerically and experimentally. To provide a suitable test for the delay compensation control schemes, a shaking table is adopted as the RTDS transfer system. It is demonstrated numerically, analytically, and experimentally that when applied to transfer systems such as these, delay compensation can work to the detriment of test accuracy and test stability. Adequate performance of delay compensated, shaking-table based RTDS is confined to a narrow low frequency bandwidth, which severely restricts the range of potential application.

A Contract Negotiation Model for Constituent Systems in the Acquisition of Acknowledged System of Systems

In the acquisition of acknowledged system of systems (SoSs), the SoS manager attempts to reach a coalition agreement with each of selected constituent systems. When the systems have self-interests that are incompatible with the SoS’s goal, contract negotiation is a way of resolving conflicts. Complexity of the acknowledged SoS acquisition makes the negotiation a hard decision process for constituent systems. To the SoS manager, the negotiation with consistent systems is difficult too, considering that the behavior and strategies of constituent systems in negotiation impact the ability and timeliness of a group to agree on an SoS architecture, and so the overall mission effectiveness of the SoS. Motivated by these, this paper develops a contract negotiation model for constituent systems in the acknowledged SoS acquisition. The model consists of: 1) a protocol for negotiating multiple interdependent issues of multiple items over multiple stages and 2) a decision framework of constituent systems. The model is not only a decision support for constituent systems but also a tool with which the SoS manager can better understand constituent systems.

昭和三一年における小選挙区制導入の断念 : 「独立の完成」挫折の一要因

昭和三一年における小選挙区制導入の断念 : 「独立の完成」挫折の一要因

Stimuli-SoS: a model-based approach to derive stimuli generators for simulations of systems-of-systems software architectures

BackgroundSystems-of-systems (SoS) are alliances of independent and interoperable software-intensive systems. SoS often support critical domains, being required to exhibit a reliable operation, specially because people’s safety relies on their services. In this direction, simulations enable the validation of different operational scenarios in a controlled environment, allowing a benchmarking of its response as well as revealing possible breaches that could lead to failures. However, simulations are traditionally manual, demanding a high level of human intervention, being costly and error-prone. A stimuli generator could aid in by continuously providing data to trigger a SoS simulation and maintaining its operation.MethodsWe established a model-based approach termed Stimuli-SoS to support the creation of stimuli generators to be used in SoS simulations. Stimuli-SoS uses software architecture descriptions for automating the creation of such generators. Specifically, this approach transforms SoSADL, a formal architectural description language for SoS, into dynamic models expressed in DEVS, a simulation formalism. We carried out a case study in which Stimuli-SoS was used to automatically produce stimuli generators for a simulation of a flood monitoring SoS.ResultsWe run simulations of a SoS architectural configuration with 69 constituent systems, i.e., 42 sensors, 9 crowdsourcing systems, and 18 drones. Stimuli generators were automatically generated for each type of constituent. These stimuli generators were capable of receiving the input data from the database and generating the expected stimuli for the constituents, allowing to simulate constituent systems interoperations into the flood monitoring SoS. Using Stimuli-SoS, we simulated 38 days of flood monitoring in little more than 6 h. Stimuli generators correctly forwarded data to the simulation, which was able to reproduce 29 flood alerts triggered by the SoS during a flooding event. In particular, Stimuli-SoS is almost 65 times more productive than a manual approach to producing data for the same type of simulation.ConclusionsOur approach succeeded in automatically deriving a functional stimuli generator that can reproduce environmental conditions for simulating a SoS. In particular, we presented new contributions regarding productivity and automation for the use of a model-based approach in SoS engineering.

Interfacial reactions between Ni and Bi2(Se0.1Te0.9)3 and its constituent material systems

Bi2(Se0.1Te0.9)3and Ni are the most commonly used N-type thermoelectric material and barrier layer in commercial thermoelectric modules. This study systematically examines the interfacial reactions between Ni and Bi2(Se0.1Te0.9)3and its constituent material systems. Results related to the interfacial reactions between Ni/Se and Ni/Bi2Se3 are not available in the literature, and are reported for the first time in this study. The reaction phases in the solid/solid Ni/Bi, Ni/Se, Ni/Bi2Te3 and Ni/Bi2(Se0.1Te0.9)3 couples are NiBi3, α-Ni3Se2 and Ni1-xSe, NiTe2 and (Bi2)m(Bi2Te3)n, and NiTe2 and (Bi2)m(Bi2Te3)n, respectively. The reaction phases in the solid/solid Ni/Te and Ni/Bi2Te3 couples evolve with reaction time. Respectively, they are NiTe2 and Bi-oversaturated Ni1-xSe phase in the early stage of reaction, and become Ni3Te2, NiTe0.775 and NiTe2, and NiBi3 and Ni1-xSe phases with longer reaction time. The Ni/Te reaction rate is slower compared with those of Ni/Bi and Bi/Se, yet the dominant reaction phase is the NiTe2 phase in both the Ni/Bi2Te3 and Ni/Bi2(Se0.1Te0.9)3 couples.

Liquidus Projection and Thermodynamic Modeling of a Sn-Ag-Zn System

Sn-Ag-Zn alloys are promising Pb-free solders. In this study, the Sn-Ag-Zn liquidus projection was determined, and the Sn-Ag-Zn thermodynamic modeling was developed. Various Sn-Ag-Zn alloys were prepared. Their as-cast microstructures and primary solidification phases were examined. The invariant reaction temperatures of the ternary Sn-Ag-Zn system were determined. The liquidus projection of the Sn-Ag-Zn ternary system was constructed. It was found that the Sn-Ag-Zn ternary system has eight primary solidification phases: e2-AgZn3, γ-Ag5Zn8, β-AgZn, ζ-Ag4Sn, (Ag), e1-Ag3Sn, β-(Sn) and (Zn) phases. There are eight ternary invariant reactions, and the liquid + (Ag) = β-AgZn + ζ-Ag4Sn reaction is of the highest temperature at 935.5 K. Thermodynamic modeling of the ternary Sn-Ag-Zn system was also carried out in this study based on the thermodynamic models of the three constituent binary systems and the experimentally determined liquidus projection. The liquidus projection and the isothermal sections are calculated. The calculated and experimentally determined liquidus projections are in good agreement.

SmartPowerchair: Characterization and Usability of a Pervasive System of Systems

A characterization of a pervasive system of systems (SoS) called the SmartPowerchair is presented, integrating pervasive technologies into a standard powered wheelchair (powerchair). The SmartPowerchair can be characterized as a SoS due to focusing on selection of the correct combination of independent and interoperable systems that are networked for a period of time to achieve the specific overall goal of enhancing the quality of life for people with disability. A high-level 2-D SoS model for the SmartPowerchair is developed to illustrate the different SoS lifecycle stages and levels. The results from a requirements elicitation study consisting of a survey targeting powerchair users were the input to a hierarchical task analysis defining the supported tasks of the SmartPowerchair. The system architecture of one constituent system (SmartATRS) is described as well as the results of a usability evaluation containing workload measurements. The establishment of the SmartAbility framework was the outcome of the evaluation results that concluded range of movement (ROM) was the determinant of suitable technologies for people with disability. The framework illustrates how a SoS approach can be applied to disability to recommend interaction mediums, technologies, and tasks depending on the disability, impairments, and ROM of the user. The approach, therefore, creates a “recommender system” by viewing disability type, impairments, ROM, interaction medium, technologies, and tasks as constituent systems that interact together in a SoS.

Electoral motives, constituency systems, ideologies, and a free trade agreement: The case of Japan joining the Trans-Pacific Partnership negotiations

This study examines the relationship between candidates and voters in the dispute over a free trade agreement. We theoretically show that candidates’ electoral promises about a free trade agreement are related to the economic interests of their districts, the types of constituency systems under which they compete with one another, and their ideologies. We empirically confirm the theoretical expectations, using as a case study the 2012 general election in Japan, where whether to join the Trans-Pacific Partnership (TPP) talks was one of the biggest issues. The TPP tends to be opposed by voters working in the agricultural sector and those living in districts with a larger amount of cultivated land, whereas it tends to be supported by college-educated voters and those living in districts with more export manufacturers. Accordingly, candidates tend to oppose (support) the TPP when their districts have a larger stake in agriculture (export manufacturers) and a smaller (larger) number of college-educated voters. Further, proportional representation candidates are more supportive of the TPP; likewise, candidates and voters who prefer a small government and who emphasize the Japan–United States relationship tend to support the TPP.

Thermal response construction in randomly packed solids with graph theoretic support vector regression

Material discontinuities and heterogeneities are very common in engineering systems. The thermal response of such systems to heating and cooling is strongly dependent upon the thermal resistance found at the interfaces. Due to difficulties in modeling thermal resistances between different solid objects of a constituent system or assembly, an alternative approach is proposed in this work. In this paper, the dynamic flow of heat through multiple solid objects within a system is predicted by a machine learning model that uses a graph theoretic diffusion kernel. To demonstrate this approach, a randomly packed assembly of cylindrical rods was selected to represent a network of solids where heat transfer rates are largely governed by contacts and/or gaps between the solids. This assembly of cylindrical rods represents a network of solids with unknown interconnecting thermal resistances. Each rod represents a node in the network. The cylindrical rods were assembled in a quartz tube with axis aligned parallel to each other and the tube. The assembly was heated to temperatures up to 1200K, and then cool-down experiments were conducted. An infra-red (IR) camera and IR transparent ports in the high temperature experimental facility were used to obtain time dependent, high-fidelity thermographic data for training and validation purposes. In particular, the temperature information from an ‘outer’ set of rods, i.e., directly cooled by contact with an external surface, was used for generating training data. This data was then used to train the models for predicting the thermal response of ‘inner’ rods of graphite, quartz and alumina materials. The network of ‘inner’ and ‘outer’ rods touching each other was used to construct a graph. A Support Vector Regression (SVR) model was trained using a diffusion kernel obtained from this graph’s Laplacian matrix. The regression models were used to predict the thermal response in different materials, sizes and networks. When trained with the optimal thermographic data, the RMS error magnitudes from these model predictions were consistently below 3%.

Separation Effects of Renewable Solvent Ethyl Lactate on the Vapor–Liquid Equilibria of the Methanol + Dimethyl Carbonate Azeotropic System

Ethyl lactate, which is an expected renewable solvent, was tested as an entrainer candidate for the separation of the binary methanol + dimethyl carbonate (DMC) azeotropic system by extractive distillation. Isobaric vapor–liquid equilibria (VLE) for two binary constituent systems, that is, methanol + DMC and DMC + ethyl lactate of the methanol + DMC + ethyl lactate ternary system, were determined by an ebulliometric method at pressures of (40.00 to 101.3) kPa. The experimental VLE data were fitted by the nonrandom two-liquid (NRTL) model. Predictions of the binary systems were also performed by the NIST-modified universal functional activity coefficient (UNIFAC) group contribution model. The separation effects of ethyl lactate were examined by two methods: residue curve map and relative volality α12 using the binary NRTL parameters. Both sets of calculated results indicated that ethyl lactate can be used as entrainer. Compared to other entrainers reported in the previous works, ethyl lactate would be a mo...

Modeling the Convergence of Collaborative Systems of Systems: A Quantitative Case Study

A system of systems SoSs provides functionality beyond that offered by its constituent systems. The functionality emerges over time, and there is a need to predict and affect the system's convergence toward the desired functionality. The convergence of a collaborative SoS is dependent on political, economic, societal, and technological PEST factors. In this paper, the authors propose a model for predicting and analyzing the convergence of SoSs. We use the United States smart grid, a collaborative SoS, to demonstrate the power of the developed model. The United States smart grid's convergence depends on factors such as energy policies, roadmaps, grants, cost recovery, consumer support, and sufficiency of technological solutions. We constructed a dynamic Bayesian network to predict the convergence and then assess the influence of each of the PEST factors. The output of the convergence model can be used to predict and communicate technical progress to stakeholders and to analyze and optimize the investment of resources to affect the PEST factors. Understanding the convergence of SoSs is important for making sound business and technology investment decisions. This approach of predicting and analyzing convergence should be extended to other SoSs.

Knowledge Based Decision Model for Architecting and Evolving Complex System‐of‐Systems

AbstractArchitecting complex System‐of‐System (SoS) has evinced keen interest recently, specifically towards factoring in the operational and managerial independence of the constituent systems, and the evolutionary and adaptive nature of SoS development. Architectural decisions have a significant bearing on the operational measures of success, referred to as Measures of Effectiveness (MOEs), of the SoS. There is inherent uncertainty while making an architectural decision for complex SoS due to the incomplete knowledge on the implications of the decision. The impact on the MOEs of the SoS may be realized only later in the development lifecycle, influencing the performance and the emergent behavior of the SoS. Further, when learning cycles on the architectural decisions are experienced, once the implication of decision is realized, there needs to be means for incorporating the feedback on the decisions taken, and to reflect back on the uncertainty associated with the decisions. This paper proposes a knowledge based decision model for architecting and evolving complex SoS, that takes into account the uncertainty associated with architectural decisions and the learning cycles and feedback loops experienced. It also enables augmenting the architectural knowledge base, both at a constituent system level as well as at the System‐of‐System level. The proposed model adopts a decision oriented view that enables factoring in uncertainty, learning cycles and feedback loops in architectural decisions. It facilitates exploring the implications of various SoS evolution scenarios on architectural decisions, while analyzing MOEs of the SoS in relation to the MOEs of the constituent systems.

Verification of Requirements: System of Systems Theory, Framework, Formalisms, Validity

AbstractBuilding on the success of systems verification, a new approach and method were developed to improve verification of requirements for system of systems. Following the formal logic (mereology) of Leśniewski, an integrative framework was structured on ontology‐based artifacts built from objects and processes within the problem domain. Meta‐structures of systems and system of systems artifacts were extracted to form a model of verification to a system of systems and its constituent systems.