Lassonde School of Engineering

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Open Access
IG-JADE-PKSlib: An Agent-Based Framework for Advanced Web Service Composition and Provisioning
(Jul-04) Martínez, Erick; Lespérance, Yves
In this paper we describe an agent-based infrastructure and toolkit to develop inter-operable, intelligent, multiagent systems for Web service composition (WSC) and provisioning. Our toolkit is realized through an interface library (IG-JADE-PKSlib) that combines state of the art agent-based and planning technologies (i.e., the IndiGolog model-based agent programming language, the JADE agent platform, and the PKS planning system). We show that each of these tools has its strengths and weaknesses, but combined together, they provide a very powerful toolkit. We argue that this infrastructure is particularly well suited for developing next generation Web services (WS) applications.
Open Access
Web Service Composition as a Planning Task: Experiments using Knowledge-Based Planning
(Jun-04) Martínez, Erick; Lespérance, Yves
Motivated by the problem of automated Web service composition (WSC), in this paper, we present some empirical evidence to validate the effectiveness of using knowledge-based planning techniques for solving WSC problems. In our experiments we utilize the PKS (Planning with Knowledge and Sensing) planning system which is derived from a generalization of STRIPS. In PKS, the agent’s (incomplete) knowledge is represented by a set of databases and actions are modelled as revisions to the agent’s knowledge state rather than the state of the world. We argue that, despite the intrinsic limited expressiveness of this approach, typical WSC problems can be specified and solved at the knowledge level. We show that this approach scales relatively well under changing conditions (e.g. user constraints). Finally, we discuss implementation issues and propose some architectural guidelines within the context of an agent-oriented framework for inter-operable, intelligent, multi-agent systems for WSC and provisioning.
Open Access
Feasibility of 20 km free-standing inflatable space tower
(British Interplanetary Society, May-10) Seth, R.K.; Quine, Brendan; Zhu, Z.H.
This paper describes the theory and analysis for the construction of a thin walled inflatable space tower of 20 km vertical extent in an equatorial location on Earth using gas pressure. The suborbital tower of 20 km height would provide an ideal surface mounting point where the geosynchronous orbital space tether could be attached without experiencing the atmospheric turbulence and weathering in the lower atmosphere. Kevlar is chosen as an example material in most of the computations due to its compatibility in the space environment. The Euler beam theory is employed to the inflatable cylindrical beam structure. The critical wrinkling moment of the inflated beam and the lateral wind load moments are taken into account as the key factors for design guidelines. A comparison between single inflatable cylindrical beam and inflatable multiple-beam structures is also presented in order to consider the problems involving control, repair and stability of the inflated space tower. For enhancing load bearing capacity of the tower and for availability of more surface area at the top, the non-tapered inflatable structure design is chosen for the basic analysis, however further analysis can be performed with tapered structures.
Open Access
Software Verification Tools
(© P. H. Roosen-Runge, 1999, 2003, 2007, 2008) Roosen-Runge, Peter
This text explores the problem of verifying software in terms of a set of simple tools which can be used to symbolically evaluate and prove properties of pieces of programs, represented either abstractly in functional terms, or by actual text. The tools can be thought of as roughly analogous to spelling and style checkers in word-processing; they reduce the labor of finding errors and provide some semi-automated aids to making corrections.
Open Access
A free-standing space elevator structure: a practical alternative to the space tether
(Elsevier, 2009-04-19) Quine, Brendan; Seth, R. K.; Zhu, Z. H.
Space tethers have been investigated widely as a means to provide easy access to space. However, the design and construction of such a device presents significant unsolved technological challenges. We propose an alternative approach to the construction of a space elevator that utilizes a free-standing core structure to provide access to near space regions and to reduce the cost of space launch. The structure is comprised of pneumatically inflated sections that are actively controlled and stabilized to balance external disturbances and support the structure. Such an approach avoids problems associated with a space tether including material strength constraints, the need for in-space construction, the fabrication of a cable at least 50,000 km in length, and the ageing and meteorite-damage effects associated with a thin tether or cable in Low Earth Orbit. An example structure constructed at 5 km altitude and extending to 20 km above sea level is described. The stability and control of the structure, methods for construction and its utility for space launch and other applications are discussed.
Open Access
Micro-computed tomography analysis of tubular braided composites
(Elsevier, 2015-06-22) Melenka, Garrett W; Lepp, Eric; Cheung, Benjamin KO; Carey, Jason
Two dimensional (2D) tubular braided composites consist of textile fibers imbedded in a resin matrix. Braid geometry and void content will affect the mechanical behavior of the tubular braided composite samples. In this study, tubular braid samples were assessed using micro X-ray computed tomography (μCT) to evaluate sample porosity/void content and to identify the strand geometry of the reinforcing fibers. The process described in this manuscript can be used to assess the quality and consistency of the tubular braided composite manufacturing process.
Open Access
Hierarchical Signal Processing for Tractable Power Flow Management in Electric Grid Networks
(IEEE Transactions on Signal and Information Processing over Networks, 2018-07) srikantha, P.; Kundur, D.
Rapid advancements in smart grid technologies have brought about the proliferation of intelligent and actuating power system components such as distributed generation, storage, and smart appliance units. Capitalizing fully on the potential benefits of these systems for sustainable and economical power generation, management, and delivery is currently a significant challenge due to issues of scalability, intermittency, and heterogeneity of the associated networks. In particular, vertically integrated and centralized power system management is no longer tractable for optimally coordinating these diverse devices at large scale while also accounting for the underlying complex physical grid constraints. To address these challenges, we propose a hierarchical signal processing framework for optimal power flow management whereby the cyber-physical network relationships of the modern grid are leveraged to enable intelligent decision-making by individual devices based on local constraints and external information. Decentralized and distributed techniques based on convex optimization and game theoretic constructs are employed for information exchanges and decision-making at each tier of the proposed framework. It is shown via theoretical and simulation studies that our technique allows for the seamless integration of power components into the grid with low computational and communication overhead while maintaining optimal, sustainable, and feasible grid operations.
Open Access
Comparative study on the detection of early dental caries using thermo-photonic lock-in imaging and optical coherence tomography
(The Optical Society of America, OSA, 2018-09-01) Shokouhi, Elnaz B.; Razani, Marjan; Gupta, Ashish; Tabatabaei, Nima
Early detection of dental caries is known to be the key to the effectiveness of therapeutic and preventive approaches in dentistry. However, existing clinical detection techniques, such as radiographs, are not sufficiently sensitive to detect and monitor the progression of caries at early stages. As such, in recent years, several optics-based imaging modalities have been proposed for the early detection of caries. The majority of these techniques rely on the enhancement of light scattering in early carious lesions, while a few of them are based on the enhancement of light absorption at early caries sites. In this paper, we report on a systemic comparative study on the detection performances of optical coherence tomography (OCT) and thermophotonic lock-in imaging (TPLI) as representative early caries detection modalities based on light scattering and absorption, respectively. Through controlled demineralization studies on extracted human teeth and µCT validation experiments, several detection performance parameters of the two modalities such as detection threshold, sensitivity and specificity have been qualitatively analyzed and discussed. Our experiment results suggests that both modalities have sufficient sensitivity for the detection of well-developed early caries on occlusal and smooth surfaces; however, TPLI provides better sensitivity and detection threshold for detecting very early stages of caries formation, which is deemed to be critical for the effectiveness of therapeutic and preventive approaches in dentistry. Moreover, due to the more specific nature of the light absorption contrast mechanism over light scattering, TPLI exhibits better detection specificity, which results in less false positive readings and thus allows for the proper differentiation of early caries regions from the surrounding intact areas. The major shortcoming of TPLI is its inherent depth-integrated nature, prohibiting the production of depth-resolved/B-mode like images. The outcomes of this research justify the need for a light-absorption based imaging modality with the ability to produce tomographic and depth-resolved images, combining the key advantages of OCT and TPLI.
Open Access
Thermoelectric Nanocomposite Foams Using Non-Conducting Polymers with Hybrid 1D and 2D Nanofillers
(MDPI, 2018-09-18) Aghelinejad, Mohammadmehdi; Leung, Siu Ning
A facile processing strategy to fabricate thermoelectric (TE) polymer nanocomposite foams with non-conducting polymers is reported in this study. Multilayered networks of graphene nanoplatelets (GnPs) and multi-walled carbon nanotubes (MWCNTs) are deposited on macroporous polyvinylidene fluoride (PVDF) foam templates using a layer-by-layer (LBL) assembly technique. The open cellular structures of foam templates provide a platform to form segregated 3D networks consisting of one-dimensional (1D) and/or two-dimensional (2D) carbon nanoparticles. Hybrid nanostructures of GnP and MWCNT networks synergistically enhance the material system’s electrical conductivity. Furthermore, the polymer foam substrates possess high porosity to provide ultra-low thermal conductivity without compromising the electrical conductivity of the TE nanocomposites. With an extremely low GnP loading (i.e., ~1.5 vol.%), the macroporous PVDF nanocomposites exhibit a thermoelectric figure-of-merit of ~10−3. To the best of our knowledge, this ZT value is the highest value reported for organic TE materials using non-conducting polymers and MWCNT/GnP nanofillers. The proposed technique represents an industrially viable approach to fabricate organic TE materials with enhanced energy conversion efficiencies. The current study demonstrates the potential to develop light-weight, low-cost, and flexible TE materials for green energy generation.
Open Access
Decentralized Topology Reconfiguration in Multiphase Distribution Networks
(IEEE Transactions on Signal and Information Processing over Networks, 2019-02) Srikantha, P.; Liu, J.
The cyber-physical nature of the modern power grid allows active power entities to exchange information signals with one another to make intelligent local actuation decisions. Exacting effective coordination amongst these cyber-enabled entities by way of strategic signal exchanges is essential for accommodating highly fluctuating power components (e.g., renewables, electric vehicles, etc.) that are becoming prevalent in today's electric grid. As such, in this paper, we present a novel decentralized topology reconfiguration algorithm for the distribution network (DN) that allows the system to adapt in real time to unexpected perturbations and/or congestions to restore balance in loads across the feeder and improve the DN voltage profile. For this, individual agents residing in DN buses iteratively exchange signals with neighbouring nodes to infer the current state (e.g., power balance and voltage) of the system and utilize this information to make local line switching decisions. Strong convergence properties and optimality conditions of the proposed algorithm are established via theoretical studies evoking potential games and discrete concavity. Comparative simulation studies conducted on realistic DNs showcase the practical properties of the proposed algorithm.
Open Access
Three-Dimensional High-Fidelity Dynamic Modeling of Tether Transportation System with Multiple Climbers
(American Institute of Aeronautics and Astronautics, 2019-03-04) Zhu, Zheng H.; Li, Gangqiang; Shi, Gefei
This paper studies the dynamics of a tether transportation system by the nodal position finite element method in the framework of an arbitrary Lagrangian–Eulerian description. Material coordinate is introduced as a state variable that is decoupled with the position coordinate. The movement of climbers is represented by moving nodes associated with the material coordinates. It is integrated into the finite element method by a variable-length tether together with a process of dividing and merging elements. The dynamic behavior of the tether transportation system with multiple climbers is studied. The results show that the elastic-flexible tether model is able to capture the high-frequency oscillation of the tether transportation system. The oscillation could have an adverse effect on the safe operation of the tether transportation system, especially in causing fatigue failure of the tether, and must be considered.
Open Access
A Novel Distributed and Stealthy Attack on Active Distribution Networks and a Mitigation Strategy
(IEEE Transactions on Industrial Informatics, 2019-05) Srikantha, Pirathayini; J. Liu; J. Samarabandu
Rapid advances in smart devices tremendously facilitate our day-to-day lives. However, these can be exploited remotely via existing cyber vulnerabilities to cause disruption at the physical infrastructure level. In this paper, we discover a novel distributed and stealthy attack that uses malicious actuation of a large number of small-scale loads residing within a distribution network (DN). This attack is capable of cumulatively violating the underlying operational system limits, leading to widespread and prolonged disruptions. A key element of this attack is the efficient use of attack resources, planned via Stackelberg games. To mitigate this type of an attack, we propose a countermeasure strategy which adaptively suppresses adverse effects of the attack when detected in a timely manner. The effectiveness of the proposed mitigation strategy is demonstrated via theoretical convergence studies, practical evaluations, and comparisons with the state-of-the-art strategies using realistic load flow and DN infrastructure models.
Open Access
Optimal Decentralized Microgrid Coordination via the Schur’s Complement and S-Procedure
(IEEE Transactions on Smart Grid, 2019-06) Srikantha, Pirathayini; M. Mallick
The evolving landscape of the electricity sector along with increasing environmental concerns necessitate modern power grids to be more efficient, sustainable, and adaptive. Microgrids are typically composed of distributed energy sources which have great potential for enabling energy independence, sustainability, and flexibility. However, practical difficulties that deter the widespread deployment of microgrids include the unpredictability of local generation sources (e.g., renewables) and the lack of inertia that is naturally present in systems containing bulk synchronous plants. In this paper, we propose a near real-time microgrid coordination algorithm that allows actuating components to adapt to changing system conditions. We account for the electrical dependencies and limits in microgrid systems by constructing voltage/current balance relations in the dq0 frame and applying strategic decompositions to invoke the Schur's complement and S-procedure that allow for zero duality gap. We highlight the convergence, feasibility, and scalability features of the proposed decentralized algorithm via theoretical and comparative practical simulation studies.
Open Access
Electro‐Thermal Subsurface Gas Generation and Transport: Model Validation and Implications
(American Geophysical Union, 2019-06-07) Molnar, Ian; Mumford, Kevin; Krol, Magdalena
Gas generation and flow in soil is relevant to applications such as the fate of leaking geologically sequestered carbon dioxide, natural releases of methane from peat and marine sediments, and numerous electro‐thermal remediation technologies for contaminated sites, such as electrical resistance heating. While traditional multiphase flow models generally perform poorly in describing unstable gas flow phenomena in soil, Macroscopic Invasion Percolation (MIP) models can reproduce key features of its behavior. When coupled with continuum heat and mass transport models, MIP has the potential to simulate complex subsurface scenarios. However, coupled MIP‐continuum models have not yet been validated against experimental data and lack key mechanisms required for electro‐thermal scenarios. Therefore, the purpose of this study was to (a) incorporate mechanisms required for steam generation and flow into an existing MIP‐continuum model (ET‐MIP), (b) validate ET‐MIP against an experimental lab‐scale electrical resistance heating study, and (c) investigate the sensitivity of water boiling and gas (steam) transport to key parameters. Water boiling plateaus (i.e., latent heat), heat recirculation within steam clusters, and steam collapse (i.e., condensation) mechanisms were added to ET‐MIP. ET‐MIP closely matched observed transient gas saturation distributions, measurements of electrical current, and temperature distributions. Heat recirculation and cluster collapse were identified as the key mechanisms required to describe gas flow dynamics using a MIP algorithm. Sensitivity analysis revealed that gas generation rates and transport distances, particularly through regions of cold water, are sensitive to the presence of dissolved gases.
Open Access
WINDII Observations and WACCM‐X Simulations of High‐Latitude Winds Under Different Solar Radio Flux and Geomagnetic Disturbance Conditions
(American Geophysical Union, 2019-07-04) Liu, Shushi; Shepherd, Gordon; Chen, Yongsheng; Shepherd, Marianna; Bhutia, Sangay
Thermospheric zonal winds at altitudes of 140 to 250 km are shown to reverse from eastward to strong westward between 100° and 200° in geographic longitude and 60°S to 70°S latitude in the Southern Hemisphere. The reversal also occurs at the same latitude in the Northern Hemisphere, but from 200° to 340° longitude. The phenomenon has been previously described as a “wind wall.” Observations by the Wind Imaging Interferometer (WINDII) on the National Aeronautics and Space Administration's Upper Atmosphere Research Satellite (UARS) and simulations by the Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM‐X) are utilized to explore the characteristics of what has been called a wind wall. In order to study the dependence on solar radio flux and geomagnetic activity, the relationships of the maximum zonal wind and F10.7 (the solar radio flux at 10.7 cm) and ap indices are investigated. The results show that WINDII observations and WACCM‐X simulations agree well in describing this wind signature. Moreover, the appearance of the wind wall is found to have a strong dependence on the solar radio flux and geomagnetic activity. In addition, WINDII winds have a stronger response to geomagnetic activity than WACCM‐X winds.
Restricted
The bifurcation of periodic orbits and equilibrium points in the linked restricted three-body problem with parameter ω
(AIP Publishing, 2019-10-08) Shan, Jinjun; Liang, Yuying; Xu, Ming; Lin, Mingpei
This paper is devoted to the bifurcation of periodic orbits and libration points in the linked restricted three-body problem (LR3BP). Inherited from the classic circular restricted three-body problem (CR3BP), it retains most of the dynamical structure of CR3BP, while its dynamical flow is dominated by angular velocity ω and Jacobi energy C. Thus, for the first time, the influence of the angular velocity in the three-body problem is discussed in this paper based on ω-motivated and C-motivated bifurcation. The existence and collision of equilibrium points in the LR3BP are investigated analytically. The dynamic bifurcation of the LR3BP under angular velocity variation is obtained based on three typical kinds of periodic orbits, i.e., planar and vertical Lyapunov orbits and Halo orbits. More bifurcation points are supplemented to Doedel's results in the CR3BP for a global sketch of bifurcation families. For the first time, a new bifurcation phenomenon is discovered that as ω approaches to 1.4, two period-doubling bifurcation points along the Halo family merge together. It suggests that the number and the topological type of bifurcation points themselves can be altered when the system parameter varies in LR3BP. Thus, it is named as “bifurcation of bifurcation” or “secondary bifurcation” in this paper. At selected values of ω, the phase space structures of equilibrium points L2 and L3 are revealed by Lie series method numerically, presenting the center manifolds on the Poincaré section and detecting three patterns of evolution for center manifolds in LR3BP. Holding the key to the origin of the universe, small bodies, e.g., asteroids are attracting more and more interest from academic and industrial fields. Current simulation on asteroid is implemented based on the regular spinning rate of an asteroid body. However, recently, the observation results on some asteroids show that their spinning velocity varies due to the solar radiation pressure, such as 2000 PH5, whose spinning velocity increases by (2.0 ± 0.2) × 10−4°/day2. The effect of the variable spinning velocity has not been fully understood. To cope with the orbital dynamics near a celestial object with varying angular velocity, a linked restricted three-body problem (LR3BP) is proposed in this paper given that the primary and the secondary are connected by a massless link. The bifurcations motivated by both angular velocity and Jacobi energy are detected to present the influence of the angular velocity. The expected results will provide new insights into orbital dynamics near asteroids, serving for future asteroid exploration mission. The LR3BP and the discovered bifurcation phenomena are important theoretical supplementation to the classic three-body problem theory.
Open Access
Flexural testing of cellulose fiber braided composites using three dimensional digital image correlation
(Elsevier, 2019-10-15) Unlusoy, Can; Melenka, Garrett W.
Braided composites consist of woven fibers embedded within a matrix material. Braided structures are commonly produced using conventional materials such as carbon, glass and aramid fibers. However, natural fibers and bio-based resins may also be utilized with this manufacturing process. In this work, the flexural properties of tubular braid structures produced using bio-based materials was investigated. Braid samples were assessed using a contact free three dimensional digital image correlation (3D DIC) technique to assess the strain fields that occur in the samples due to applied flexural loads. Additionally, the bio-based structures were evaluated using micro-computed tomography (µCT) to assess the cross-sectional geometry and void content of the produced samples.
Open Access
Flight Dynamics and Control Strategy of Electric Solar Wind Sails
(American Institute of Aeronautics and Astronautics, 2019-11-27) Zhu, Zheng H.; Li, Gangqiang; Du, Chonggang
This paper studies the flight dynamics and control strategy for electric solar wind sails based on the nodal position finite element method, where the coupling effects between tether dynamics and the electrical field are considered. A modified throttling control strategy is proposed to control the attitude of electric sails by modulating individual tether voltage synchronously with the spinning motion of the sails. The effects of four critical physical parameters (tether numbers, tether length, sail spin rate, and mass of remote units) are investigated. The results show that the effect of the relative velocity of the solar wind has a significant effect on the spin rate of the sail in attitude maneuvering, which in turn affects the attitude dynamics and orbit motion of the sail. Numerical results show that the proposed control strategy work successfully stabilizes the spin rate of sail when the new type sail is adopted.
Open Access
Advanced Measurement Techniques for Braided Composite Structures: A Review of Current and Upcoming Trends
(Sage, 2020-04-15) Melenka, Garrett
Braiding is an advanced textile manufacturing method that is used to produce two dimensional (2D) and three dimensional (3D) components. Unlike a laminated structures braids have interlaced yarns that forms a continuity between layers. This structure allows for improved impact resistance, damage tolerance and improved through-thickness reinforcement. Despite the numerous advantages of braided composites, braids also have shortcomings. Their highly complex fiber architecture presents challenges in the availability and choice of the strain measuring and characterization techniques. Advanced measurement methods such as optical strain measurement, micro-computed tomography, and in-situ strain measurement are required. Optical strain measurement methods such as digital image correlation and high speed imaging are necessary to accurately measure the complex deformation and failure that braided composites exhibit. X-ray based micro-computed tomography measurements can provide detailed geometric and morphologic information for braided structures which is necessary for accurately predicting the mechanical properties of braided structures. Finally, in-situ strain measurement methods will provide detailed information on the internal deformation and strain that exists within braided structures. In-situ sensors will also allow for in-service health monitoring of braided structures. This paper provides a detailed review of the aforementioned sensing technologies and their relation to the measurement of braided composite structures.
Open Access
Hidden Convexities in Decentralized Coordination for the Distribution Networks
(IEEE Transactions on Power Systems, 2020-05) Srikantha, Pirathayini; M. Mallick
The modern power grid is undergoing unprecedented levels of transformations due to the rising prevalence of diverse power entities, cyber-enablement of grid components and energy deregulations. In this paper, we focus on distribution networks (DNs) to enable the seamless plug-and-play coordination of actuating cyber-enabled power entities for cost-effective and feasible system operations. The proposed distributed algorithm empowers individual cyber-physical agents residing in active power nodes with the ability to iteratively compute local actuation setpoints by exchanging information with neighbouring entities. The main contribution of this work is the identification of hidden convexities in the original non-convex optimal power flow (OPF) formulation for the DN via strategic decomposition and strong duality principles. These eliminate the need for OPF relaxations/approximations. Strong convergence and feasibility results are presented via theoretical analysis and practical simulation studies conducted on realistic systems.