VictorJuiz/thesis huggingface dataset:
In-situ calibration and direct de-embedding of RF integrated circuits and microwave structures using self-compensating techniques [electronic resource]

Characterization of on-wafer or system-on-chip RF devices and structures usually requires the use of an external calibration substrate followed by measurements and application of de-embedding techniques. While different de-embedding techniques have been published, none of them provides calibration and de-embedding in a single step. In this work an In-situ and self-compensating method that provides calibration and direct de-embedding is presented. This method relies on the integration of calibration and verification structures along with the device under test (DUT). Characterization or accurate modeling of a single standard allows reference-plane setting at the input/output ports of the DUT and direct measurement and de-embedding of the intrinsic DUT while embedded verification standards ensure validity of the calibration coefficients. Furthermore, the embedded verification structures can be used to implement an iterative method for determining the reactive element of the required single standard with nearly no constraints and the compactness of a self-contained test bench where the effects of any probing interface can be directly calibrated out in a single-step operation and without requiring separate measurement and/or modeling of each structure between the DUT and the probing point. Simulation and lab measurements ranging from the low MHz region up to V-band (67GHz) demonstrate that the new method is valid for direct extraction of DUT data without the need for separate calibration and de-embedding steps or external calibration substrates and with the advantage of being able to control the position of the reference plane by fulfilling very simple layout requirements. In addition, it also presents a direct method for detecting and possibly correcting the unavoidable probe displacement that affects most of the manual and automatic probe stations used for circuit and device characterization. This probe displacement detection technique treats mechanical shifts as deviations of a first set of complex solutions that would initially result in a fully balanced system. The only requirement for the implementation of this technique is the inclusion of a set of wideband coupled lines that allow direct sensing of the incident and reflected waves and a reference signal for phase and relative amplitude measurements. Moreover, this technique does not require any calibration process other than being able to store the initial state of the test system, an initial set of solutions and the actual solutions to the current state of the test system.

Keywords: Electrical Engineering
Advisor: Dutton Robert W. primary advisor. Thesis advisor
Howe Roger Thomas advisor. Thesis advisor
Wong S. advisor. Thesis advisor
An integrated impedance biosensor array [electronic resource]

Affinity biosensors are important tools for detecting DNA, proteins, cells, and other biomedical analytes. Although optical readout is prevalent, impedance readout is promising for many applications due to lower cost, reduced system size, and label-free operation. Impedance biosensors detect the binding of a target biomolecule to an immobilized probe by quantifying changes in the the electrode-electrolyte interface impedance. Impedance biosensors traditionally use bulky and expensive instruments to monitor the impedance of a single electrode. We describe miniaturized and inexpensive readout circuitry for an array of such sensors. By using a sensor array, multiple analytes can be simultaneously detected and limitations inherent to individual sensors can be mitigated. Reducing the size and cost of the measurement system enables new applications. We present a measurement system for a 6x6 array of impedance biosensors built from off-the-shelf components. Experimental results with DNA probe-target pairs confirm others' reports that changes in the interface impedance can signify binding. Other experiments with proteins demonstrate that changes in the nonlinearity of the I-V relationship can also indicate probe-target binding. We show that the impedance and the nonlinearity can be quantified simultaneously by superimposing a large-amplitude tone on the impedance-measurement tone and analyzing the resulting intermodulation tones. We conclude by describing an integrated array of measurement circuits implemented in 0.18 um CMOS. Each of the 36 measurement pixels contains an impedance-measuring circuit plus tone cancellation circuitry, which enables simultaneous nonlinearity measurement. To prevent the large-amplitude excitation from saturating the amplifier output, a per-pixel digital feedback loop injects an appropriate cancelling current at the amplifier input. Impedance changes of 0.2% can be detected using the integrated measurement circuit. Each pixel occupies 0.14 mm2 and consumes 1.9 mW.

Keywords: Electrical Engineering
Advisor: Lee Thomas primary advisor. Thesis advisor
Kenny Thomas William advisor. Thesis advisor
Pourmand Nader
Integrative modeling for genome-wide regulation of gene expression [electronic resource]

High-throughput genomics has been increasingly generating the massive amount of genome-wide data. With proper modeling methodologies, we can expect to archive a more comprehensive understanding of the regulatory mechanisms of biological systems. This work presents integrative approaches for the modeling and analysis of gene regulatory systems. In mammals, gene expression regulation is combinatorial in nature, with diverse roles of regulators on target genes. Microarrays (such as Exon Arrays) and RNA-Seq can be used to quantify the whole spectrum of RNA transcripts. ChIP-Seq is being used for the identification of transcription factor (TF) binding sites and histone modification marks. RNA interference (RNAi), coupled with gene expression profiles, allow perturbations of gene regulatory systems. Our approaches extract useful information from those genome-wide measurements for effectively modeling the logic of gene expression regulation. We present a predictive model for the prediction of gene expression from ChIP-Seq signals, based on quantitative modeling of regulator-gene association strength, principal component analysis, and regression-based model selection. We demonstrate the combinatorial regulation of TFs, and their power for explaining genome-wide gene expression variation. We also illustrate the roles of covalent histone modification marks on predicting gene expression and their regulation by TFs. We present a dynamical model of gene expression profiling, and derive the perturbed behaviors of the ordinary differential equation (ODE) system. Based on that, we present a regularized multivariate regression method for inferring the gene regulatory network of a stable cell type. We model the sparsity and stability of the network by a regularization approach. We applied the approaches to both a simulation data set and the RNAi perturbation data in mouse embryonic stem cells.

Keywords: Biology.
Advisor: Petrov Dmitri Alex
Wong Wing Tak Jack Wong primary advisor. Thesis advisor
Feldman Marcus W. advisor. Thesis advisor
Interest rate modeling and a time series model for functional data [electronic resource]

In finance, an interest rate derivative is a financial instrument where the underlying asset is an interest rate at which payments are made based on a notional amount. A common approach to price interest rate derivatives is through the use of interest rate models. However, a drawback with this approach is that calibration of interest rate models does not involve the interest rate being modeled. Hence, calibrated models may not be good representations of interest rates and may not produce reliable derivative prices. To deal with the issue, we propose a time series modeling approach to analyze interest rates, specifically, the zero-coupon yield curves. In this approach, yield curves are modeled as functional data and we introduce models that are based on the well-known autoregressive model in time series analysis. The objective of this approach is to understand the dependency of the yield curves on historical data and to predict future yield curves before they are observed. The proposed models are illustrated and compared with the time series of US Treasury zero-coupon yield curves. We explore how individual models perform during different times in an economic cycle. We also propose a way to predict future caplet prices by combining yield curve prediction using functional time series models and historical implied volatilities of caplets. The time series approach that we propose are shown to work well against existing models such as the Hull-White model.

Keywords: Statistics
Advisor: Lai T. L. primary advisor. Thesis advisor
Switzer Paul advisor. Thesis advisor
Walther Guenther advisor. Thesis advisor
Interplay of attractive interactions and trap anisotropy in Bose-Einstein condensates [electronic resource]

We evaporatively cool attractively interacting bosonic 7Li in a quasi-one dimensional (quasi-1D) trap to well below the non-interacting particle condensation temperature for our trap but do not observe conventional Bose-Einstein condensation (BEC). Rather than the macroscopic occupation of a single quantum state, for our coldest clouds we observe densities far above the minimum required for quantum degeneracy and widths many times greater than the non-interacting and Gross-Pitaevskii (GP) predictions. We quantify the discrepancies, which together indicate the formation of clouds with multiply macroscopically occupied trap states. We hypothesize that the specific combination of a quasi-1D anisotropic trap and attractively interacting atoms might provide for many-body states that reside in manifolds of nearly degenerate states, which could inhibit conventional BEC. This idea is probed theoretically using the two-body interaction Hamiltonian to extend the single-mode many-body mean-field GP formalism to allow for atom scattering between two single-particle trap modes. We find that many odd-relative parity energy-adjacent single-particle state pairs exhibit sizable degenerate many-body eigenenergy fractions for atom numbers below the critical atom number at which attraction-induced collapse occurs. The sensitivity to state pair relative parity and our variational width analyses indicate, however, that one and two single-particle state models are ultimately insufficient for these systems. Mechanism-independent, such bright short coherence length matter-wave sources, analogous to superluminescent diodes, could prove useful in actualizing portable atom-based sensors.

Keywords: Applied Physics
Advisor: Kasevich Mark A. primary advisor. Thesis advisor
Goldhaber-Gordon David
Mabuchi Hideo advisor. Thesis advisor
Intracardiac ultrasound imaging using Capacitive Micromachined Ultrasonic Transducer (CMUT) arrays [electronic resource]

Atrial fibrillation, the most common type of cardiac arrhythmia, now affects more than 2.2 million adults in the United States alone. Currently, electrophysiological interventions are performed under fluoroscopic guidance, which does not provide adequate soft-tissue resolution and exposes the patient and the operator to harmful ionizing radiation. Intracardiac echocardiography (ICE) provides real-time anatomical information that has proven valuable in reducing the fluoroscopy time and enhancing procedural success. This dissertation describes the design and implementation of two types of multi-functional, forward-looking ICE catheters developed using capacitive micromachined ultrasonic transducer (CMUT) technology: MicroLinear (ML) and Ring catheters. The ML catheter enables real-time, forward-looking 2D imaging using a 24-element, fine-pitch 1D CMUT phased array. The Ring catheter uses a 64-element, ring-shaped 2D CMUT array that enables real-time, forward-looking, volumetric imaging. Both of these catheters are equipped with custom-designed, front-end electronic circuits that are integrated with each transducer array at the catheter tip. The close integration of custom electronic circuits with the ML and Ring CMUT arrays improves the signal-to-noise ratio (SNR) in each case by 18 dB and 20dB, respectively. The integration process of the CMUT arrays with the electronics dice in the tight space available for full catheter construction shows 100% yield. The characterization of the fully-integrated CMUT arrays demonstrates excellent pulse-echo response with over 100% fractional bandwidth as well as surface transmit pressure levels in excess of 1 MPa (peak-to-peak). The first fully-functional 9F ML CMUT ICE catheter shows remarkable in vivo imaging performance using porcine animal models. A similar in vivo imaging experiment with the first fully-functional 12F Ring CMUT ICE catheter proves very promising. The volumetric imaging capability of the Ring ICE catheter and the versatility offered by its inner lumen make it an attractive interventional device. This dissertation also introduces a novel CMUT structure, called PCMUT. The preliminary simulation and experimental verification of the PCMUT structure show that it is possible to fabricate CMUTs that exhibit non-flexural piston-like plate motion with a significantly improved volume displacement and fill-factor.

Keywords: Electrical Engineering
Advisor: Khuri-Yakub Butrus T.
Howe Roger Thomas advisor. Thesis advisor
Murmann Boris advisor. Thesis advisor
Oralkan Ömer advisor. Thesis advisor
Investigating structure property relations in compound semiconductors using single nanowire devices [electronic resource]

Semiconductor nanowires are an important class of materials. They have been used in a huge number of applications in the information, energy and medical sciences, and they also offer unique opportunities to study the large number of fundamental physical processes whose basic mechanisms operate on the nanoscale. Great progress has been made in the synthesis of these nanowires and the fabrication necessary to integrate them into top-down architectures; however, fully accounting for structural heterogeneity and understanding processing induced structural changes in these materials remains a challenge. A new approach to investigating structure property relationships combining in-situ transmission electron microscope (TEM) techniques with single nanowire devices and test structures fabricated on electron transparent membranes will be presented, and example studies on several metal chalcogenide materials for use in nonvolatile memory and thin film photovoltaics will be discussed. Several emerging strategies for nonvolatile information storage rely on systems in which an active element can be reversibly actuated between two structural states which can then be electronically distinguished. Gaining fundamental understanding of these systems requires an understanding of these different structural states, how they give rise to the required electronic properties, as well as the dynamics of the reversible process used to actuate the active element. In order to reach the high integration densities required to compete with existing technologies, these active elements must be on the nanoscale. To probe the materials science of two such candidate systems, silver selenide for pulsed electrochemical cell memory and germanium telluride for phase change memory, nanowires were synthesized and single nanowire memory devices were fabricated on electron transparent 50 nm thick silicon nitride substrates for ex-situ and in-situ experiments in the TEM. Currently, the world record power conversion efficiency, 20%, for a thin film photovoltaic device is held by the complicated quaternary material copper indium gallium selenide (CIGS). This excellent performance is not yet clearly understood, but may arise in large part due to the unique nature of the internal boundaries in CIGS materials. In order to understand the complicated relationship between processing and interface structure in this material, extensive TEM studies were undertaken using a variety of single nanowire test structures and in-situ heating. The fundamental understanding obtained by these studies was leveraged both to synthesize high quality p-type copper indium selenide (CIS) nanowires, and also to fabricate for the first time a single nanowire CIS solar cell, an achievement which will serve as a powerful platform for fundamental investigation into this important materials system.

Keywords: Materials Science and Engineering
Advisor: Cui Yi
Brongersma Mark L. advisor. Thesis advisor
McIntyre Paul Cameron advisor. Thesis advisor
Investigating the nucleation, growth and energy levels of organic semiconductors for high performance plastic electronics [electronic resource]

Plastic or organic electronics offer several advantages over conventional inorganic technologies. Firstly, the molecular structure of organic semiconductors and conductors can be tuned for various applications using synthetic chemistry. In addition organic thin films are flexible, and can be processed and patterned inexpensively. However, improving the thin film conductivity of organic semiconductors and conductors is necessary for widespread application and adoption. The overall goal of this thesis is to investigate and control organic small molecule growth at surfaces in order to improve the performance of organic electronic devices. In first part of the thesis, improving the charge carrier mobility of organic thin film transistors (OTFTs), the building block for plastic electronics, is discussed. The nucleation, stability and thin film growth of model organic semiconductors such as pentacene and C60 are described with focus on correlating thin film structure to charge carrier mobility. More specifically, pentacene nucleation and growth on the most common substrate for OTFTs, an octadecylsilane (OTS) monolayer modified silicon oxide surface, is investigated. The role of the density of the OTS was determined to be a critical device parameter that impacts organic semiconductor nucleation and growth, and the charge carrier mobility, as the OTS transitions from an amorphous monolayer into a crystalline one. Dense OTS monolayers were fabricated using the well known ultrathin film Langmuir Blodgett (LB) technique, as well as a new spin-coating technique developed in our lab. The crystalline OTS monolayer serves as an excellent template for promoting desirable organic semiconductor thin film growth leading to high performance transistors. Therefore a crystalline OTS dielectric surface modification layer, which greatly improves organic semiconductor performance, may be important for the future success of OTFTs and organic circuits. In the second part of the thesis, lessons learned from studying organic semiconductor nucleation and growth are applied to improving the conductivity of carbon nanotube (CNT) networks for transparent electrode applications. Selective growth of organic small molecules with low molecular orbital energies was used to greatly reduce the sheet resistance of CNT films by both decreasing junction resistances and stable doping of the semiconducting CNTs. The result is a material which has the highest value (in terms of transparency and sheet conductivity) of any carbon based transparent electrode.

Keywords: Chemical Engineering
Advisor: Bao Zhenan primary advisor. Thesis advisor
Frank C. W. advisor. Thesis advisor
Spakowitz Andrew James advisor. Thesis advisor
Investigation of a plasma deflagration gun and magnetohydrodynamic Rankine-Hugoniot model to support a unifying theory for electromagnetic plasma guns [electronic resource]

Electromagnetic Plasma Guns generally operate by pulsing a large current through a gas, thereby ionizing it, and then using the Lorentz force from the self-induced magnetic field to accelerate the generated plasma. In most cases, plasma gun operation is characterized by the formation of a current sheet which forms at the gun breech and is then accelerated downstream. Therefore, these devices are often described using a snowplow model, which describes the observed luminous front as a moving piston that has a certain sweeping efficiency associated with it. In plasma guns where the snowplow model does not apply, a complete set of magnetohydrodynamic (MHD) equations often has to be solved numerically. As an alternative to these approaches, this dissertation explores an underutilized concept that is based on an MHD extension of the Rankine-Hugoniot model from combustion theory. This approach treats the snowplow as an MHD detonation rather than as a piston and suggests that a plasma deflagration should also be possible. A plasma gun was then designed and constructed based on this concept and investigated through a series of experiments. It was determined that the constructed gun does operate in a plasma deflagration mode. In addition, the extent of the MHD Rankine-Hugoniot analogy to the combustion case and the breadth of its applicability to different types of plasma guns were briefly explored. Finally, an interesting effect was observed when operating in deflagration mode and at high energy. An intense, inductively amplified current loop forms near the exit plane of the gun. It is believed that this effect may also cast new light on the so-far unexplained origin of energetic ion beams emitted from Dense Plasma Focus devices.

Keywords: Mechanical Engineering
Advisor: Cappelli Mark A. (Mark Antony) primary advisor. Thesis advisor
Edwards C. F. (Christopher Francis) advisor. Thesis advisor
Gascon Nicolas
The investigation of online consumer reviews as intentional social actions [electronic resource]

Online reviews play an increasingly important role in consumers' purchase decisions. Such internet-enabled Word-of-Mouth communication offers society a tremendous potential to reduce information asymmetries and in this way, increase the efficiency of electronic and traditional markets (Dellarocas, 2005). Voluntary reporting, however, introduces the potential for reporting biases. In this dissertation, I argue that consumers' willingness to post a review on an online forum is conditioned on the social normative landscape of this public space. I conducted four exploratory investigations of the social dynamics involved in review posting behavior. Given the broadness of the research agenda, these studies focus on different aspects of the research question and, as a result, vary in their levels of analysis and methods. As evidence, I found that review posting behavior was motivated by social obligations and regulated by social norms. Furthermore, these social motives produced systematic biases in review valence distributions. The implications of these findings are clear: Biased distribution of online product reviews can lead to inefficiencies in consumer choice and erroneous conclusions about consumer product preferences.

Keywords: Business.
Advisor: Miller Dale T. primary advisor. Thesis advisor
Flynn Francis J. advisor. Thesis advisor
Mullen Elizabeth advisor. Thesis advisor