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Aberdeen, MD, United States

Dawidowicz E.,CERDEC
SAE International Journal of Alternative Powertrains | Year: 2012

The effectiveness of elements comprising a hybrid electric power generating system was studied. The wind and photovoltaic renewable resources served as integral components of the hybrid systems configuration. A HMMWV towable trailer system provided an intermediary basis for formulation of methodology needed for optimization of power generation and energy storage capacity constrained by cost, size and weight of the system. The methodology employed in this paper is scalable from kilowatts to megawatts or from man portable systems to significantly larger systems which can be housed in 40 foot ISO containers. Copyright © 2012 SAE International. Source

Perera R.D.W.,CERDEC | Anand S.,Stevens Institute of Technology | Subbalakshmi K.P.,Stevens Institute of Technology | Chandramouli R.,Stevens Institute of Technology
Proceedings - IEEE Military Communications Conference MILCOM | Year: 2010

We study the temporal behavior of messages arriving in a social network. We specifically study the tweets and re-tweets sent to president Barack Obama on Twitter. We characterize the inter-arrival times between the tweets, the number of re-tweets and the spatial coordinates (latitude, longitude) of the users who sent the tweets. The modeling of the arrival process of tweets in Twitter can be applied to predict co-ordinated user behavior in social networks. While there is sufficient literature on social networks that present large volumes of collected data, the modeling and characterization of the data have been rarely discussed. The available data are usually very expensive and not comprehensive. Here, we develop a software architecture that uses a Twitter application program interface (API) to collect the tweets sent to specific users. We then extract the user ids and the exact time-stamps of the tweets. We use the collected data to characterize the inter-arrival times between tweets and the number of re-tweets. Our studies indicate that the arrival process of new tweets to a user can be modeled as a Poisson Process while the number of re-tweets follow a geometric distribution. Our data collection architecture is operating system (OS) independent. The results obtained in this research can be applied to study correlations between patterns of user behavior and their locations. ©2010 IEEE. Source

Xiao Z.,University of Maryland University College | Goldsman N.,University of Maryland University College | Dhar N.K.,CERDEC
International Conference on Simulation of Semiconductor Processes and Devices, SISPAD | Year: 2015

Germanium can be transformed from an indirect bandgap material to a direct bandgap material by applying strain. Unstrained Ge has an indirect bandgap of 0.66eV (at L point) and a direct bandgap of 0.8eV [1]. When strain is applied, the band structure of germanium will be altered. When the strain is tensile, both the indirect and the direct bandgaps tend to decrease. Under certain strains, the direct bandgap will be pushed even below the indirect bandgap, at which point, germanium becomes a direct bandgap material. The value of the bandgap when Ge transforms from an indirect to direct semiconductor upon the application of strain is named the Bandgap Transition Point (BTP), and the required strain is named STP (Strain at Transition Point). Previous research has been done on uniaxial and biaxial strained germanium on the conventional orientations. In this work, calculations are made on the effect of applying tensile stress in arbitrary orientations based on nonlocal empirical pseudopotential method (EPM) [2] [3]. We also use cubic spline interpolation of the atomic form factors [4] [5], as well as the rules for strain translation [6], to determine how the Indirect-Direct transformation phenomenon of germanium changes with respect to virtually any orientation of the crystal planes. In addition, we calculated the optimal orientation and the effect that departure from this optimal orientation has on the bandgap. © 2015 IEEE. Source

Manousakis K.,Ericsson AB | Gottlieb Y.,Ericsson AB | Chadha R.,Ericsson AB | Chiang C.J.,Ericsson AB | Moeltner K.,CERDEC
Proceedings - IEEE Military Communications Conference MILCOM | Year: 2011

In the tactical military context, the network exists to support a mission. Consequently, part of the process of mission planning is to define the required network performance in terms of measurable quantities (metrics). These metrics, such as required message delivery rates, maximum acceptable latencies, and acceptable-loss thresholds are used to design the network. This paper presents the TITAN (Tactical Information Technologies for Assured Networks) Network Management System (NMS), which uses these metrics to manage the network as well. The TITAN NMS generates maintenance policies from the stated mission goals and the generated network plan. The maintenance policies describe the metrics to be measured, the acceptable values of those metrics and the actions to take on various levels of the management hierarchy when values of the metrics are not acceptable. If the policy-defined actions do not restore the network performance to acceptable levels, the TITAN NMS dynamically replans the network to meet the mission needs. We describe the TITAN NMS system and its application to the problem of automating the management of future military tactical networks, along with scenarios illustrating the operation of the system. © 2011 IEEE. Source

Rittenbach T.,CERDEC | Kovarik Jr. V.J.,Harris Corporation | Krause-Aiguier R.,Harris Corporation | Stewart C.,Harris Corporation
Proceedings - IEEE Military Communications Conference MILCOM | Year: 2010

The Government Reference Architecture (GRA) was initiated in response to unique requirements of above 2 GHz Satellite Communications (SATCOM) systems not effectively addressed by the Software Communications Architecture (SCA). Fundamental objectives of the GRA effort were to, 1) develop a modular open systems architecture (MOSA) approach that promotes well-defined module decomposition and use of COTS, 2) define a reference model of the terminal architecture using standard modeling languages and tools, and 3) address system-level architecture aspects of the SATCOM domain not effectively specified by the SCA. A key objective was to maximize the use of available systems design tools and languages thereby decreasing the lead time required to initiate SATCOM projects. This paper presents benefits and drawbacks of COTS system design tools and languages for the SATCOM domain. The paper will also present the results of early prototypes developed to validate specific aspects of the GRA and the development tools output with analysis of specific areas of the validation prototype. ©2010 IEEE. Source

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