@conference {
	title = {HybridSim: A Modeling and Co-simulation Toolchain for Cyber-Physical Systems},
	author = {Wang, Baobing., Baras, John S.},
	year = {2013},
	month = {10/2013},
	abstract = {Cyber-physical systems (CPS) involve communication networks, computation algorithms, control systems and physical systems. Many CPS, such as Smart Buildings, are subject to very expensive deployment costs and complex network interactions. Thus comprehensive modeling and simulation of such systems are crucial to ensure that they function as intended before deployment. Given the multi-domain nature of CPS, it is more appropriate to use a heterogeneous simulation environment to study system dynamics. In this paper, we design and implement an integrated modeling and co-simulation toolchain, called HybridSim, for the design and simulation of CPS. Firstly, HybridSim can transform and import existing system components from multi-domains into SysML, which enables systems engineers to design CPS with only these imported SysML blocks. Secondly, HybridSim can generate Functional Mock-up Units (FMUs) and configuration scripts directly from SysML designs. Finally, HybridSim can co-simulate these FMUs according to the Functional Mock-up Interface standard to synchronize their corresponding simulators and exchange information between them. We demonstrate the convenience and efficiency of HybridSim using a comprehensive hydronic heating system model for Smart Buildings as the case study to investigate the impact of packet loss and sampling rate introduced by the communication network.},
	address = {Delft, Netherlands},
	booktitle = {Proceedings of 17th IEEE/ACM International Symposium on Distributed Simulation and Real Time Applications},
	pages = {pp. 33-40}
}
@conference {
	title = {Storage-centric Sensor Networks for Smart Buildings},
	author = {Wang, Baobing., Baras, John S.},
	year = {2013},
	month = {04/2013},
	abstract = {In my thesis, I propose a model-based systems design framework, called WSNDesign, to facilitate the design and implementation of wireless sensor networks (WSNs). WSNDesign provides a hierarchy of model libraries to model various behaviors and structures of WSNs in the context of Smart Buildings, and introduces a system design flow to compose both continuous-time and event-triggered modules to develop applications with support for performance evaluation. In order to handle various sensor data efficiently, WSNDesign provides a distributed database system, called HybridDB, for data collection and retrieval. HybridDB enables sensors to store large-scale datasets in situ on local NAND ash using a novel resource-aware data storage system, and can process typical queries inWSNs extremely efficiently. In addition, HybridDB supports incremental -approximate querying that enables clients to retrieve a just-sufficient set of sensor data by issuing refinement and zoom-in sub-queries to search events and analyze sensor data efficiently. HybridDB can always return an approximate dataset with guaranteed L1-norm error bound.},
	address = {Philadelphia, PA},
	booktitle = {12th ACM/IEEE Conference on Information Processing in Sensor Networks IPSN 2013}
}
@conference {
	title = {Interactive Tree Decomposition Tool for Reducing System Analysis Complexity},
	author = {Yang, Shahan., Wang, Baobing., Baras, John S.},
	year = {2013},
	month = {03/2013},
	abstract = {We present a graphical tool for the calculation of treewidth, a metric on the parametric structure of a system that is intimately tied to the complexity of system analysis. For many graphically describable systems, such as systems of parametric equations, as in a SysML Parametric diagram, or Bayesian networks or even mind maps and writing term papers, analysis of the system is exponential in treewidth and linear in system size. A tool facilitating comprehensive analysis can serve to bring competitive advantage to a systems engineering workflow by reducing costly unanticipated behaviors. Furthermore, a byproduct of computing treewidth is a framework for enumerating computationally compatible distributed algorithms. In this paper, we pose this NP-complete problem from the perspective of finding satisficing solutions, exposing choices that can influence the complexity of the resulting system to the designer. A designer can contribute two important things to the structure of the system: a visual intuition about the relationships between the underlying objects and the ability to change the relationships themselves at design time to reduce analysis complexity. Having a visual tool that provides instant feedback will help designers achieve an intuitive grasp of the relationship between design decisions and system complexity. As complexity is the root of almost every systems engineering problem, and also something not easily understood, incorporating complexity analysis into a design process should improve resulting system designs. The tool uses a randomized, anytime algorithm for interactive optimization of treewidth. It presents a sequence of choices to a designer and incrementally lowers an upper bound on system treewidth over time. This algorithm is novel, as few algorithms are targeted at interactivity with a human user. We present a number of simple examples for using the tool. We show how our tool helps to decompose some example systems, including a quadrotor optimization, a sensor network optimization, a Bayesian network, and a mind map.},
	address = {Atlanta, GA},
	booktitle = {Conference on Systems Engineering Research (CSER{\textquoteright}13),},
	pages = {pp. 138-147}
}
@conference {
	title = {HybridStore: An Efficient DataManagement System for Hybrid Flash-based Sensor Devices},
	author = {Wang, Baobing., Baras, John S.},
	year = {2013},
	month = {02/2013},
	abstract = {In this paper, we propose HybridStore, a novel efficient resourceaware data management system for flash-based sensor devices to store and query sensor data streams. HybridStore has three key features. Firstly, it takes advantage of the on-board random-accessible NOR flash in current sensor platforms to guarantee that all NAND pages used by it are fully occupied and written in a purely sequential fashion, and expensive in-place updates and out-of-place writes to an existing NAND page are completely avoided. Thus, both raw NAND flash chips and FTL-equipped (Flash Translation Layer) flash packages can be supported efficiently. Secondly, HybridStore can process typical joint queries involving both time windows and key value ranges as selection predicate extremely efficiently, even on large-scale datasets. It organizes a data stream into segments and exploits a novel index structure that consists of the inter-segment skip list, and the in-segment β-Tree and Bloom filter of each segment. Finally, HybridStore can trivially support time-based data aging without any extra overhead because no garbage collection mechanism is needed. Our implementation and evaluation with a large-scale real-world dataset in TinyOS reveals that HybridStore can achieve remarkable performance at a small cost of constructing the index.},
	address = {Ghent, Belgium},
	booktitle = {10th European Conference on Wireless Sensor Networks},
	pages = {pp. 50-66}
}
