Matching Items (6)

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Low-cost Image-assisted Inertial Navigation System for a Micro Air Vehicle

Description

The increasing civilian demand for autonomous aerial vehicle platforms in both hobby and professional markets has resulted in an abundance of inexpensive inertial navigation systems and hardware. Many of these

The increasing civilian demand for autonomous aerial vehicle platforms in both hobby and professional markets has resulted in an abundance of inexpensive inertial navigation systems and hardware. Many of these systems lack full autonomy, relying on the pilot's guidance with the assistance of inertial sensors for guidance. Autonomous systems depend heavily on the use of a global positioning satellite receiver which can be inhibited by satellite signal strength, low update rates and poor positioning accuracy. For precise navigation of a micro air vehicle in locations where GPS signals are unobtainable, such as indoors or throughout a dense urban environment, additional sensors must complement the inertial sensors to provide improved navigation state estimations without the use of a GPS. By creating a system that allows for the rapid development of experimental guidance, navigation and control algorithms on versatile, low-cost development platforms, improved navigation systems may be tested with relative ease and at reduced cost. Incorporating a downward-facing camera with this system may also be utilized to further improve vehicle autonomy in denied-GPS environments.

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Date Created
  • 2014-12

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Measurements and Simulations of Self-Heating in 40nm SOI MOSFETs

Description

Combining the rapid development of semiconductor technologies, miniaturization of integrated circuits (ICs), and scaling down the device size is trending towards faster, cheaper, and more reliable components for low-power integrated

Combining the rapid development of semiconductor technologies, miniaturization of integrated circuits (ICs), and scaling down the device size is trending towards faster, cheaper, and more reliable components for low-power integrated circuits. Most research and development relate to efficiency, structure, materials, and performance. However, the thermal problem is also created and becomes more critical with shrinking device dimensions and increased integration densities, such that it affects the device performance and leads to degradation and damage. At the nanometer scale, the self-heating effect (SHE) is one of the main factors to degrade devices. Therefore, tracking and quantifying the SHE is important for reliability and efficiency issues. In this dissertation, engineers design two identical and closely spaced 40nm gate length silicon-on-insulator (SOI) n-channel metal-oxide-semiconductor-field-effect transistors (NMOSFETs) that share a common source with the same active silicon region. One of the MOSFETs acts as a heater to heat-up the active region, while the other one is a thermometer to evaluate the SHE and local temperature changes. The thermometer provides a method to calibrate the numerical models of self-heating and track the heat flow. Moreover, it also involves a trap-rich SOI wafer technology, in which a trap-rich layer, with higher resistivity and lower thermal conductivity compared to conventional bulk silicon substrates. The trap-rich SOI substrates can reduce the cross-talk and minimize the power consumption to increase the system performance. In particular, it offers a solution to radio frequency integrated circuits (RFICs) which require fast switching and low leakage. In high power amplifier (PA) applications, Watt-level PAs operates at less than 50% efficiency because of temperature limitations. The author uses experimental measurements of the local temperature changes, combined with simulations to examine the heat flow and temperature distribution. The approach may be useful to build a self-test application, because it can quantify the temperature changes by putting one or multiple NMOSFET thermometers around a complementary metal-oxide-semiconductor (CMOS) power amplifier, while only adding minimum die area. It points to ways in which it can optimize the reliability of RFIC applications, which operate under high-temperature or high-power conditions to protect the device before it is overheated or damaged.

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Created

Date Created
  • 2020

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Compact modeling and simulation for digital circuit aging

Description

Negative bias temperature instability (NBTI) is a leading aging mechanism in modern digital and analog circuits. Recent NBTI data exhibits an excessive amount of randomness and fast recovery, which are

Negative bias temperature instability (NBTI) is a leading aging mechanism in modern digital and analog circuits. Recent NBTI data exhibits an excessive amount of randomness and fast recovery, which are difficult to be handled by conventional power-law model (tn). Such discrepancies further pose the challenge on long-term reliability prediction under statistical variations and Dynamic Voltage Scaling (DVS) in real circuit operation. To overcome these barriers, the modeling effort in this work (1) practically explains the aging statistics due to randomness in number of traps with log(t) model, accurately predicting the mean and variance shift; (2) proposes cycle-to-cycle model (from the first-principle of trapping) to handle aging under multiple supply voltages, predicting the non-monotonic behavior under DVS (3) presents a long-term model to estimate a tight upper bound of dynamic aging over multiple cycles, and (4) comprehensively validates the new set of aging models with 65nm statistical silicon data. Compared to previous models, the new set of aging models capture the aging variability and the essential role of the recovery phase under DVS, reducing unnecessary guard-banding during the design stage. With CMOS technology scaling, design for reliability has become an important step in the design cycle, and increased the need for efficient and accurate aging simulation methods during the design stage. NBTI induced delay shifts in logic paths are asymmetric in nature, as opposed to averaging effect due to recovery assumed in traditional aging analysis. Timing violations due to aging, in particular, are very sensitive to the standby operation regime of a digital circuit. In this report, by identifying the critical moments in circuit operation and considering the asymmetric aging effects, timing violations under NBTI effect are correctly predicted. The unique contributions of the simulation flow include: (1) accurate modeling of aging induced delay shift due to threshold voltage (Vth) shift using only the delay dependence on supply voltage from cell library; (2) simulation flow for asymmetric aging analysis is proposed and conducted at critical points in circuit operation; (3) setup and hold timing violations due to NBTI aging in logic and clock buffer are investigated in sequential circuits and (4) proposed framework is tested in VLSI applications such DDR memory circuits. This methodology is comprehensively demonstrated with ISCAS89 benchmark circuits using a 45nm Nangate standard cell library characterized using predictive technology models. Our proposed design margin assessment provides design insights and enables resilient techniques for mitigating digital circuit aging.

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Created

Date Created
  • 2012

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Modeling, simulation and analysis for software-as-service in cloud

Description

Software-as-a-Service (SaaS) has received significant attention in recent years as major computer companies such as Google, Microsoft, Amazon, and Salesforce are adopting this new approach to develop software and systems.

Software-as-a-Service (SaaS) has received significant attention in recent years as major computer companies such as Google, Microsoft, Amazon, and Salesforce are adopting this new approach to develop software and systems. Cloud computing is a computing infrastructure to enable rapid delivery of computing resources as a utility in a dynamic, scalable, and virtualized manner. Computer Simulations are widely utilized to analyze the behaviors of software and test them before fully implementations. Simulation can further benefit SaaS application in a cost-effective way taking the advantages of cloud such as customizability, configurability and multi-tendency.

This research introduces Modeling, Simulation and Analysis for Software-as-Service in Cloud. The researches cover the following topics: service modeling, policy specification, code generation, dynamic simulation, timing, event and log analysis. Moreover, the framework integrates current advantages of cloud: configurability, Multi-Tenancy, scalability and recoverability.

The following chapters are provided in the architecture:

Multi-Tenancy Simulation Software-as-a-Service.

Policy Specification for MTA simulation environment.

Model Driven PaaS Based SaaS modeling.

Dynamic analysis and dynamic calibration for timing analysis.

Event-driven Service-Oriented Simulation Framework.

LTBD: A Triage Solution for SaaS.

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Created

Date Created
  • 2015

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Design, modeling and simulation of nanoscale optoelectronic devices: semiconductor nano-lasers and plasmonic waveguides

Description

This thesis summarizes the research work carried out on design, modeling and simulation of semiconductor nanophotonic devices. The research includes design of nanowire (NW) lasers, modeling of active plasmonic waveguides,

This thesis summarizes the research work carried out on design, modeling and simulation of semiconductor nanophotonic devices. The research includes design of nanowire (NW) lasers, modeling of active plasmonic waveguides, design of plasmonic nano-lasers, and design of all-semiconductor plasmonic systems. For the NW part, a comparative study of electrical injection in the longitudinal p-i-n and coaxial p-n core-shell NWs was performed. It is found that high density carriers can be efficiently injected into and confined in the core-shell structure. The required bias voltage and doping concentrations in the core-shell structure are smaller than those in the longitudinal p-i-n structure. A new device structure with core-shell configuration at the p and n contact regions for electrically driven single NW laser was proposed. Through a comprehensive design trade-off between threshold gain and threshold voltage, room temperature lasing has been proved in the laser with low threshold current and large output efficiency. For the plasmonic part, the propagation of surface plasmon polariton (SPP) in a metal-semiconductor-metal structure where semiconductor is highly excited to have an optical gain was investigated. It is shown that near the resonance the SPP mode experiences an unexpected giant modal gain that is 1000 times of the material gain in the semiconductor and the corresponding confinement factor is as high as 105. The physical origin of the giant modal gain is the slowing down of the average energy propagation in the structure. Secondly, SPP modes lasing in a metal-insulator-semiconductor multi-layer structure was investigated. It is shown that the lasing threshold can be reduced by structural optimization. A specific design example was optimized using AlGaAs/GaAs/AlGaAs single quantum well sandwiched between silver layers. This cavity has a physical volume of 1.5×10-4 λ03 which is the smallest nanolaser reported so far. Finally, the all-semiconductor based plasmonics was studied. It is found that InAs is superior to other common semiconductors for plasmonic application in mid-infrared range. A plasmonic system made of InAs, GaSb and AlSb layers, consisting of a plasmonic source, waveguide and detector was proposed. This on-chip integrated system is realizable in a single epitaxial growth process.

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Created

Date Created
  • 2012

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Dispatch strategy development for grid-tied household energy systems

Description

The prevalence of renewable generation will increase in the next several decades and offset conventional generation more and more. Yet this increase is not coming without challenges. Solar, wind, and

The prevalence of renewable generation will increase in the next several decades and offset conventional generation more and more. Yet this increase is not coming without challenges. Solar, wind, and even some water resources are intermittent and unpredictable, and thereby create scheduling challenges due to their inherent “uncontrolled” nature. To effectively manage these distributed renewable assets, new control algorithms must be developed for applications including energy management, bridge power, and system stability. This can be completed through a centralized control center though efforts are being made to parallel the control architecture with the organization of the renewable assets themselves—namely, distributed controls. Building energy management systems are being employed to control localized energy generation, storage, and use to reduce disruption on the net utility load. One such example is VOLTTRONTM, an agent-based platform for building energy control in real time. In this thesis, algorithms developed in VOLTTRON simulate a home energy management system that consists of a solar PV array, a lithium-ion battery bank, and the grid. Dispatch strategies are implemented to reduce energy charges from overall consumption ($/kWh) and demand charges ($/kW). Dispatch strategies for implementing storage devices are tuned on a month-to-month basis to provide a meaningful economic advantage under simulated scenarios to explore algorithm sensitivity to changing external factors. VOLTTRON agents provide automated real-time optimization of dispatch strategies to efficiently manage energy supply and demand, lower consumer costs associated with energy usage, and reduce load on the utility grid.

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Created

Date Created
  • 2015