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You searched for +publisher:"Georgia Tech" +contributor:("Zhou, Guotong"). Showing records 1 – 3 of 3 total matches.

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1. Yu, Zhenhua. Optical wireless communications with optical power and dynamic range constraints.

Degree: PhD, Electrical and Computer Engineering, 2014, Georgia Tech

Along with the rapidly increasing demand for wireless data while more and more crowded radio frequency (RF) spectrum, optical wireless communications (OWC) become a promising candidate to complement conventional RF communications, especially for indoor short and medium range data transmissions. Orthogonal frequency division multiplexing (OFDM) is considered for OWC due to its ability to boost data rates. However, the average emitted optical power and dynamic range of driving signals of LEDs are two major constraints in OWC. OFDM waveforms exhibits high upper and lower peak-to-average power ratios (PAPRs), which make OFDM signals optical power inefficient and easy to violate the dynamic range of LEDs, resulting clipping and nonlinear distortions. In this dissertation, we analyze and design optical power and dynamic range constrained OWC systems, for which OFDM is our major subject. We first derive distributions of upper PAPR and lower PAPR of OWC-OFDM signals. Then we analyze the clipped OFDM signals in term of error vector magnitude (EVM), signal-to-distortion ratio (SDR), and achievable data rates under both optical power and dynamic range constraints. The next part of this dissertation is the OFDM system design for visible light communications (VLC) considering illumination requirement. We investigate the illumination-to-communication efficiency (ICE) in VLC-OFDM, and design the brightness control and flickering mitigation schemes for VLC-OFDM. In the end, to reduce the complexity of driving circuits of LEDs , we propose using delta-sigma modulators in VLC-OFDM systems to convert continuous magnitude OFDM symbols into two-level LED driver signals without loss of the communication theory advantages of OFDM. Advisors/Committee Members: Zhou, Guotong (advisor), Chang, Gee-Kung (committee member), Ma, Xiaoli (committee member), Barry, John R. (committee member), Baxley, Robert J. (committee member), Tuell, Grady (committee member).

Subjects/Keywords: Optical wireless communications (OWC); Visible light communications (VLC); Orthogonal frequency division multiplexing (OFDM); Optical power; Dynamic range; Peak-to-average power ratio (PAPR); Wireless communication systems; Optical communications; Orthogonal frequency division multiplexing

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APA (6th Edition):

Yu, Z. (2014). Optical wireless communications with optical power and dynamic range constraints. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/51784

Chicago Manual of Style (16th Edition):

Yu, Zhenhua. “Optical wireless communications with optical power and dynamic range constraints.” 2014. Doctoral Dissertation, Georgia Tech. Accessed November 15, 2019. http://hdl.handle.net/1853/51784.

MLA Handbook (7th Edition):

Yu, Zhenhua. “Optical wireless communications with optical power and dynamic range constraints.” 2014. Web. 15 Nov 2019.

Vancouver:

Yu Z. Optical wireless communications with optical power and dynamic range constraints. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2019 Nov 15]. Available from: http://hdl.handle.net/1853/51784.

Council of Science Editors:

Yu Z. Optical wireless communications with optical power and dynamic range constraints. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/51784

2. Oh, Ji Hun. Contrast-enhanced magnetic resonance liver image registration, segmentation, and feature analysis for liver disease diagnosis.

Degree: PhD, Electrical and Computer Engineering, 2012, Georgia Tech

The global objectives of this research are to develop a liver-specific magnetic resonance (MR) image registration and segmentation algorithms and to find highly correlated MR imaging features that help automatically score the severity of chronic liver disease (CLD). For a concise analysis of liver disease, time sequences of 3-D MR images should be preprocessed through an image registration to compensate for the patient motion, respiration, or tissue motion. To register contrast-enhanced MR image volume sequences, we propose a novel version of the demons algorithm that is based on a bi-directional local correlation coefficient (Bi-LCC) scheme. This scheme improves the speed at which a convergent sequence approaches to the optimum state and achieves the higher accuracy. Furthermore, the simple and parallelizable hierarchy of the Bi-LCC demons can be implemented on a graphics processing unit (GPU) using OpenCL. To automate segmentation of the liver parenchyma regions, an edge function-scaled region-based active contour (ESRAC), which hybridizes gradient and regional statistical information, with approximate partitions of the liver was proposed. Next, a significant purpose in grading liver disease is to assess the level of remaining liver function and to estimate regional liver function. On motion-corrected and segmented liver parenchyma regions, for quantitative analysis of the hepatic extraction of liver-specific MRI contrast agent, liver signal intensity change is evaluated from hepatobiliary phases (3-20 minutes), and parenchymal texture features are deduced from the equilibrium (3 minutes) phase. To build a classifier using texture features, a set of training input and output values, which is estimated by experts as a score of malignancy, trains the supervised learning algorithm using a multivariate normal distribution model and a maximum a posterior (MAP) decision rule. We validate the classifier by assessing the prediction accuracy with a set of testing data. Advisors/Committee Members: Hu, Xiaoping (Committee Chair), Yezzi, Anthony (Committee Co-Chair), Butera, Robert (Committee Member), Martin, Diego (Committee Member), Vela, Patricio (Committee Member), Zhou, Guotong (Committee Member).

Subjects/Keywords: Image segmentation; Image registration; Contrast-enhanced MRI; Feature analysis; Liver Diseases; Liver Diseases Diagnosis; Magnetic resonance imaging; Contrast-enhanced magnetic resonance imaging; Image processing Digital techniques

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Oh, J. H. (2012). Contrast-enhanced magnetic resonance liver image registration, segmentation, and feature analysis for liver disease diagnosis. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/45912

Chicago Manual of Style (16th Edition):

Oh, Ji Hun. “Contrast-enhanced magnetic resonance liver image registration, segmentation, and feature analysis for liver disease diagnosis.” 2012. Doctoral Dissertation, Georgia Tech. Accessed November 15, 2019. http://hdl.handle.net/1853/45912.

MLA Handbook (7th Edition):

Oh, Ji Hun. “Contrast-enhanced magnetic resonance liver image registration, segmentation, and feature analysis for liver disease diagnosis.” 2012. Web. 15 Nov 2019.

Vancouver:

Oh JH. Contrast-enhanced magnetic resonance liver image registration, segmentation, and feature analysis for liver disease diagnosis. [Internet] [Doctoral dissertation]. Georgia Tech; 2012. [cited 2019 Nov 15]. Available from: http://hdl.handle.net/1853/45912.

Council of Science Editors:

Oh JH. Contrast-enhanced magnetic resonance liver image registration, segmentation, and feature analysis for liver disease diagnosis. [Doctoral Dissertation]. Georgia Tech; 2012. Available from: http://hdl.handle.net/1853/45912


Georgia Tech

3. Hamilton, Benjamin Russell. Low-Overhead Opportunistic Routing for Wireless Ad Hoc and Sensor Networks in a Fading Environment.

Degree: MS, Electrical and Computer Engineering, 2007, Georgia Tech

The development of miniaturized radio and sensing technologies have enabled the deployment of large quantities of wireless sensors capable of forming multi-hop networks. Emerging applications of this technology such as surveillance and disaster monitoring have throughput and efficiency requirements not met by current routing algorithms. These requirements are also shared by ad-hoc networks. Early routing protocols for these wireless networks were based on algorithms designed for wired networks. Geographic routing (routing based on position), was proposed. These algorithms perform poorly since they do not account for the fading and interference effects of wireless channels. Recent protocols that have attempted to account for the wireless channel focus on single-hop situations and are not readily extensible to multi-hop networks. In this thesis we present a framework for routing based on a distributed routing decision and provide several example protocols. This framework provides a cross-layer design where the routing decision is decided through silent negotiation between candidate relays. We investigate the performance and parameters of this framework. We then present an example protocol using this framework which provides low-overhead opportunistic routing using cooperative diversity. This protocol uses the intrinsic characteristics of the wireless channel to achieve diversity while still maintaining relatively low overhead. An adaptation of the protocol for heterogeneous networks equipped with multiple antennas has also been discussed and evaluated through simulations. We also investigate another protocol based on this framework using the product of the instantaneous packet reception rate and the marginal progress towards the destination as a routing metric, offering enhanced throughput. Advisors/Committee Members: Ma, Xiaoli (Committee Chair), Zhou, Guotong (Committee Member), Anderson, David (Committee Member).

Subjects/Keywords: Sensor networks; Routing; Opportunistic; Sensor networks; Ad hoc networks (Computer networks); Wireless communication systems; Routing (Computer network management)

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Hamilton, B. R. (2007). Low-Overhead Opportunistic Routing for Wireless Ad Hoc and Sensor Networks in a Fading Environment. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/19749

Chicago Manual of Style (16th Edition):

Hamilton, Benjamin Russell. “Low-Overhead Opportunistic Routing for Wireless Ad Hoc and Sensor Networks in a Fading Environment.” 2007. Masters Thesis, Georgia Tech. Accessed November 15, 2019. http://hdl.handle.net/1853/19749.

MLA Handbook (7th Edition):

Hamilton, Benjamin Russell. “Low-Overhead Opportunistic Routing for Wireless Ad Hoc and Sensor Networks in a Fading Environment.” 2007. Web. 15 Nov 2019.

Vancouver:

Hamilton BR. Low-Overhead Opportunistic Routing for Wireless Ad Hoc and Sensor Networks in a Fading Environment. [Internet] [Masters thesis]. Georgia Tech; 2007. [cited 2019 Nov 15]. Available from: http://hdl.handle.net/1853/19749.

Council of Science Editors:

Hamilton BR. Low-Overhead Opportunistic Routing for Wireless Ad Hoc and Sensor Networks in a Fading Environment. [Masters Thesis]. Georgia Tech; 2007. Available from: http://hdl.handle.net/1853/19749

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