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Technical Paper

Performance Characteristics of MOSFETs Operating at High Power

This paper demonstrates that the on-resistance of a power MOSFET decreases significantly when the operating temperature decreases. The decrease in on-resistance under cryogenic temperature allows the device to operate at a much higher power and current condition. Also, it is demonstrated that the MOSFET device can be effectively kept at cryogenic temperature by spray cooling with liquid nitrogen. Over 80 W of heat generated can be removed continuously with spray cooling.
Technical Paper

Statistical Process Control and Design of Experiment Process Improvement Methods for the Powertrain Laboratory

The application of Statistical Process Control and Design of Experiment methods in the research laboratory can lead to significant gains in the Powertrain development process. Empirical methods such as Design of Experiments, Regression, and Neural Network techniques can be applied to help researchers gain better understanding of the cause and effect relationships of emission, alternative fuel source, performance, fuel economy, and engine management system - calibration studies. The use of these empirical modeling techniques along with model based Genetic Algorithm, Gradient, or Constraint based solution search methods will help identify the “process settings” that improve fuel economy, improve performance, and reduce pollutants. Since empirical methods are fundamentally based on the acquired test data, it is vitally important that the laboratory measurements are repeatable, consistent, and void of sources of variance that have a significant effect on the acquired test data.
Technical Paper

The AAMA Traffic Noise Model - A Better Approach

Currently there are no community noise computer programs commonly in use in the United States dedicated to the modeling of interrupted flow. Constant speed programs (such as STAMINA 2.0) have been used with modified input to predict noise levels at intersections, but they cannot directly simulate traffic signal operation, actual deceleration and acceleration of vehicles, or queues of vehicles at signals. Noise prediction procedures for intersections can be improved by simulating actual intersection movements. The American Automobile Manufacturers Association has produced a model that not only models continuous flow (Constant Speed Traffic program - CST), but also allows modeling of interrupted flow (Variable Speed Traffic program - VST). This model has been updated to improve user friendliness and accuracy and is discussed in this paper.
Technical Paper

The Distributed Simulation of Intelligent Terrain Exploration

In this study we consider the coordinated exploration of an unfamiliar Martian landscape by a swarm of small autonomous rovers, called Swarmies, simulated in a distributed setting. With a sustainable program of return missions to and from Mars in mind, the goal of said exploration is to efficiently prospect the terrain for water meant to be gathered and then utilized in the production of rocket fuel. The rovers are tasked with relaying relevant data to a home base that is responsible for maintaining a mining schedule for an arbitrarily large group of rovers extracting water-rich regolith. For this reason, it is crucial that the participants maintain a wireless connection with one another and with the base throughout the entire process. We describe the architecture of our simulation which is composed of HLA-compliant components that are visualized via the Distributed Observer Network tool developed by NASA.
Technical Paper

The Effect of Operating Conditions at Idle in the S.I. Engine

A gasoline engine with an electronically controlled fuel injection system has substantially better fuel economy and lower emissions than a carburetted engine. In general, the stability of engine operation is improved with fuel injector, but the stability of engine operation at idle is not improved compared with a carburetted gasoline engine. In addition, the increase in time that an engine is at idle due to traffic congestion has an effect on the engine stability and vehicle reliability. Therefore, in this research, we will study the influence of fuel injection timing, spark timing, dwell angle, and air-fuel ratio on engine stability at idle.
Journal Article

The Semantic Web and Space Operations

In this paper, we introduce the use of ontologies to implement the information developed and organized by resource planning tools into standard project management documents covering integrated cost, resource modeling and analysis, and visualization. The basic upper ontology used for NASA Space Operations is explained and the results obtained are discussed. This ontology-centered approach is looking for tighter connections between software, hardware, and systems engineering.
Journal Article

Weapon Combat Effectiveness Analytics Using Big Data and Simulations: A Literature Review

The Weapon Combat Effectiveness (WCE) analytics is very expensive, time-consuming, and dangerous in the real world because we have to create data from the real operations with a lot of people and weapons in the actual environment. The Modeling and Simulation (M&S) of many techniques are used for overcoming these limitations. Although the era of big data has emerged and achieved a great deal of success in a variety of fields, most of WCE research using the Defense Modeling and Simulation (DM&S) techniques studied have considered a lot of assumptions and limited scenarios without the help of big data technologies. Furthermore, WCE analytics using previous methodologies cannot help but get the bias results. This paper reviews and combines the basic knowledge for the new WCE analytics methodology using big data and M&S to overcome these problems of bias. Then this paper reviews the general overview of WCE, DM&S, and big data.
Journal Article

ℒ1 Adaptive Flutter Suppression Control Strategy for Highly Flexible Structure

The aim of this work is to apply an innovative adaptive ℒ1 techniques to control flutter phenomena affecting highly flexible wings and to evaluate the efficiency of this control algorithm and architecture by performing the following tasks: i) adaptation and analysis of an existing simplified nonlinear plunging/pitching 2D aeroelastic model accounting for structural nonlinearities and a quasi-steady aerodynamics capable of describing flutter and post-flutter limit cycle oscillations, ii) implement the ℒ1 adaptive control on the developed aeroelastic system to perform initial control testing and evaluate the sensitivity to system parameters, and iii) perform model validation and calibration by comparing the performance of the proposed control strategy with an adaptive back-stepping algorithm. The effectiveness and robustness of the ℒ1 adaptive control in flutter and post-flutter suppression is demonstrated.