Photo-enhanced chemical vapor deposition (CVD) technique is investigated here for low temperature deposition of carbon nanotubes (CNTs) and hexagonal diamond. Most current deposition methods require high substrate temperature. Photo-enhanced CVD utilizes light energy to dissociate carbon containing precursor molecules and hence has a potential for low temperature deposition. CCl4, having a high absorption coefficient compared to other commonly employed hydrocarbons in the UV emission spectrum from a Xe arc lamp, is selected as a carbon precursor in this work. Extensive experimentation conducted by varying Al/Ni/Al catalyst layer thicknesses on SiO2 coated Si substrates, substrate annealing temperature in the range 350 - 450 ¡ÆC for 25 min, and chamber pressure in the range 0.22 - 10 Torr in ammonia ambient, yielded suitable catalyst layers of thicknesses 3/2/3, 5/1/5 and 5/3/5 nm and annealing pressure of 10 Torr. For photo-enhanced CVD deposition, experiments are conducted with various Ar/CCl4 flow ratio in 1.5 - 19 range, total chamber pressure in 3 - 10 Torr range, and substrate temperatures in 350 - 450 ¡ÆC range. Optimal condition for CNT deposition in this work is found to be 30 min at 400 ¡ÆC at 5 Torr total pressure with Ar/CCl4 ratio of 9 with 5/1/5 nm thick catalyst annealed at 400 ¡ÆC. Raman spectroscopy indicates MWCNT growth and I-V measurements yield sheet resistivity of 22 k§Ù/sq. The densest hexagonal diamond deposition is obtained at 450 ¡ÆC, 3 hr deposition time, at 10 Torr with Ar/CCl4 ratio of 2.3 with 5/3/5 nm thick catalyst annealed at 450 ¡ÆC. Lesser dense hexagonal diamond platelets are obtained at 450 ¡ÆC, 3 hr deposition time, at 10 Torr with Ar/CCl4 ratio of 2.3 with 3/2/3 nm thick catalyst annealed at 450 ¡ÆC. Based on the physical structures observed at various stages of growth in SEM images, a model is proposed for nucleation and subsequent growth of hexagonal diamond platelets with graphene layer playing role both during nucleation and during platelet growth. Raman spectroscopy and XPS results confirm the deposition material to be hexagonal diamond. The grown material is characterized with UV-Vis spectroscopy for optical and with a nanoindenter for electrical and mechanical properties.

Ubiquitous computing requires integration of physical space with digital information. This presents the challenges of integrating electronics, physical space, software and the interaction tools which can effectively communicate with the audience. Many research groups have embraced different techniques depending on location, context, space, and availability of necessary skills to make the world around us as an interface to the digital world. Encouraged by early successes and fostered by project undertaken by tangible visualization group. We introduce an architecture of Blades and Tiles for the development and realization of interactive wall surfaces. It provides an inexpensive, open-ended platform for constructing large-scale tangible and embedded interfaces. In this paper, we propose tiles built using inexpensive pegboards and a gateway for each of these tiles to provide access to digital information. The paper describes the architecture using a corridor fa\c{c}ade application. The corridor fa\c{c}ade uses full-spectrum LEDs, physical labels and stencils, and capacitive touch sensors to provide mediated representation, monitoring and querying of physical and digital content. Example contents include the physical and online status of people and the activity and dynamics of online research content repositories. Several complementary devices such as Microsoft PixelSense and smartdevices can support additional user interaction with the system. This enables interested people in synergistic physical environments to observe, explore, understand, and engage in ongoing activities and relationships. This paper describes the hardware architecture and software libraries employed and how they are used in our research center hallway and academic semester projects.

This dissertation is divided into two parts. In the first part we consider the problem of feedback stabilization of nonlinear systems described by state-space models. This approach is inherited from the methodology of sector bounded or passive nonlinearities, and influenced by the concept of absolute and quadratic stability. It aims not only to regionally stabilize the nonlinear dynamics asymptotically but also to maximize the estimated region of quadratic attraction and to ensure nominal performance at each equilibrium. In close connection to gain scheduling and switching control, a path of equilibria is programmed based on the assumption of centered-epsilon-cover which leads to a sequence of linear controllers that regionally stabilize the desired equilibrium asymptotically. In the second part we tackle the problem of control for fluid flows described by the incompressible Navier-Stokes equation. We are particularly interested in film cooling for gas turbine engines which we model with the jet in cross-flow problem setup. In order to obtain a model amenable to the controller design presented in the first part, the well-known Proper Orthogonal Decomposition (POD)/Galerkin projection is employed to obtain a nonlinear state-space system called the reduced order model (ROM). We are able to stabilize the ROM to an equilibrium point via our design method and we also present direct numerical simulation (DNS) results for the system under state feedback control.

With the advance of data acquisition techniques, massive solid geometries are being collected routinely in scientific tasks, these complex and unstructured data need to be effectively correlated for various processing and analysis. Volumetric mapping solves bijective low-distortion correspondence between/among 3D geometric data, and can serve as an important preprocessing step in many tasks in compute-aided design and analysis, industrial manufacturing, medical image analysis, to name a few. This dissertation studied two important volumetric mapping problems: the mapping of heterogeneous volumes (with nonuniform inner structures/layers) and the mapping of sequential dynamic volumes. To effectively handle heterogeneous volumes, first, we studied the feature-aligned harmonic volumetric mapping. Compared to previous harmonic mapping, it supports the point, curve, and iso-surface alignment, which are important low-dimensional structures in heterogeneous volumetric data. Second, we proposed a biharmonic model for volumetric mapping. Unlike the conventional harmonic volumetric mapping that only supports positional continuity on the boundary, this new model allows us to have higher order continuity $C^1$ along the boundary surface. This suggests a potential model to solve the volumetric mapping of complex and big geometries through divide-and-conquer. We also studied the medical applications of our volumetric mapping in lung tumor respiratory motion modeling. We were building an effective digital platform for lung tumor radiotherapy based on effective volumetric CT/MRI image matching and analysis. We developed and integrated in this platform a set of geometric/image processing techniques including advanced image segmentation, finite element meshing, volumetric registration and interpolation. The lung organ/tumor and surrounding tissues are treated as a heterogeneous region and a dynamic 4D registration framework is developed for lung tumor motion modeling and tracking. Compared to the previous 3D pairwise registration, our new 4D parameterization model leads to a significantly improved registration accuracy. The constructed deforming model can hence approximate the deformation of the tissues and tumor.

In recent years, the accident rate related to traffic is high. Analyzing the crash data and extracting useful information from it can help in taking respective measures to decrease this rate or prevent the crash from happening. Related research has been done in the past which involved proposing various measures and algorithms to obtain interesting crash patterns from the crash records. The main problem is that large numbers of patterns were produced and vast number of these patterns would be obvious or not interesting. A deeper analysis of the data is required in order to get the interesting patterns. In order to overcome this situation, we have proposed a new approach to detect the most associated sequential patterns in the crash data. We also make use of the technique, Association Rule Mining to mine interesting traffic accident patterns from the crash records. The main goal of this research is to detect the most associated sequential patterns (MASP) and mine patterns within the data sets generated by MASP using a modified FP-growth approach in regular association rule mining. We have designed and implemented data structures for efficient implementation of algorithms. The results extracted can be further queried for pattern analysis to get a deeper understanding. Efficient memory management is one of the main objectives during the implementation of the algorithms. Linked list based tree structures have been used for searching the patterns. The results obtained seemed to be very promising and the detected MASPs contained most of the attributes which gave a deeper insight into the crash data and the patterns were found to be very interesting. A prototype application is developed in C# .NET.

Fault observability as well as fault location algorithms in distributed power system are studied in this thesis. The importance of finding the fault location in a distribution system with the purpose of increasing reliability and decreasing the maintenance time and cost is discussed. Then, different existing fault location algorithms and approaches in the literature are introduced and compared. Subsequently, a new strategy to achieve fault observability of power systems while aiming minimum required number of Phasor Measurement Units (PMUs) in the network is proposed. The method exploits the nodal voltage and mesh current analyses where the impedance and admittance matrices of the network and its dual circuit are developed and utilized for fault location. The criterion of determining the number and the places of PMUs is that the fault location and impedance can be obtained in a unique manner without multi estimation. In addition, the method considers faults along the lines as opposed to the faults only on system buses available in the literature. The proposed approach provides an economical solution to decrease measurement costs for large power networks, distributed generation networks, and micro grids. Simulation results for IEEE 7-bus, 14-bus, and 30-bus systems verify the effectiveness of the proposed approach.

This thesis presents a study of the bias-induced threshold voltage metastability phenomenon of the hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs). An application of gate bias stress shifts the threshold voltage of a TFT. After the bias stress is removed, the threshold voltage eventually returns to its original value. The underlying physical mechanisms for the shift in threshold voltage during the application of the bias and after the removal of the bias stress are investigated. <br /><br /> The creation of extra defect states in the band gap of a-Si:H close to the gate dielectric interface, and the charge trapping in the silicon nitride (SiN) gate dielectric are the most commonly considered instability mechanisms of threshold voltage. In the first part of this work, the defect state creation mechanism is reviewed and the kinetics of the charge trapping in the SiN is modelled assuming a simplified mono-energetic and a more realistic Gaussian distribution of the SiN traps. The charge trapping in the mono-energetic SiN traps was approximated by a logarithmic function of time. However, the charge trapping with a Gaussian distribution of SiN traps results in a more complex behavior. <br /><br /> The change in the threshold voltage of a TFT after the gate bias has been removed is referred to threshold voltage relaxation, and it is investigated in the second part of this work. A study of the threshold voltage relaxation sheds more light on the metastability mechanisms of a-Si:H TFTs. Possible mechanisms considered for the relaxation of threshold voltage are the annealing of the extra defect states and the charge de-trapping from the SiN gate dielectric. The kinetics of the charge de-trapping from a mono-energetic and a Gaussian distribution of the SiN traps are analytically modelled. It is shown that the defect state annealing mechanisms cannot explain the observed threshold voltage relaxation, but a study of the kinetics of charge de-trapping helps to bring about a very good agreement with the experimentally obtained results. Using the experimentally measured threshold voltage relaxation results, a Gaussian distribution of gap states is extracted for the SiN. This explains the threshold voltage relaxation of TFT after the bias stress with voltages as high as 50V is removed. <br /><br /> Finally, the results obtained from the threshold voltage relaxation make it possible to calculate the total charge trapped in the SiN and to quantitatively distinguish between the charge trapping mechanism and the defect state creation mechanisms. In conclusion, for the TFTs used in this thesis, the charge trapping in the SiN gate dielectric is shown to be the dominant threshold voltage metastability mechanism caused in short bias stress times.

Non-linear programming has been extensively used in wireless telecommunication systems design. An important criterion in optimization is the minimization of mean square error. This thesis examines two applications: peak to average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems and wireless airtime traffic estimation. These two applications are both of interests to wireless service providers. PAPR reduction is implemented in the handheld devices and low complexity is a major objective. On the other hand, exact traffic prediction can save a huge cost for wireless service providers by better resource management through off-line operations. <br /><br /> High PAPR is one of the major disadvantages of OFDM system which is resulted from large envelope fluctuation of the signal. Our proposed technique to reduce the PAPR is based on constellation shaping that starts with a larger constellation of points, and then the points with higher energy are removed. The constellation shaping algorithm is combined with peak reduction, with extra flexibilities defined to reduce the signal peak. This method, called MMSE-Threshold, has a significant improvement in PAPR reduction with low computational complexity. <br /><br /> The peak reduction formulated into a quadratic minimization problem is subsequently optimized by the semidefinite programming algorithm, and the simulation results show that the PAPR of semidefinite programming algorithm (SDPA) has noticeable improvement over MMSE-Threshold while SDPA has higher complexity. Results are also presented for the PAPR minimization by applying optimization techniques such as hill climbing and simulated annealing. The simulation results indicate that for a small number of sub-carriers, both hill climbing and simulated annealing result in a significant improvement in PAPR reduction, while their degree of complexity can be very large. <br /><br /> The second application of non-linear optimization is in airtime data traffic estimation. This is a crucial problem in many organizations and plays a significant role in resource management of the company. Even a small improvement in the data prediction can save a huge cost for the organization. Our proposed method is based on the definition of extra parameters for the basic structural model. In the proposed technique, a novel search method that combines the maximum likelihood estimation with mean absolute percentage error of the estimated data is presented. Simulated results indicate a substantial improvement in the proposed technique over that of the basic structural model and seasonal autoregressive integrated moving average (SARIMA) package. In addition, this model is capable of updating the parameters when new data become available.

The revolutionary concept of space-time coding introduced in the last decade has demonstrated that the deployment of multiple antennas at the transmitter allows for simultaneous increase in throughput and reliability because of the additional degrees of freedom offered by the spatial dimension of the wireless channel. However, the use of antenna arrays is not practical for deployment in some practical scenarios, e. g. , sensor networks, due to space and power limitations. <br /><br /> A new form of realizing transmit diversity has been recently introduced under the name of user cooperation or cooperative diversity. The basic idea behind cooperative diversity rests on the observation that in a wireless environment, the signal transmitted by the source node is overheard by other nodes, which can be defined as "partners" or "relays". The source and its partners can jointly process and transmit their information, creating a "virtual antenna array" and therefore emulating transmit diversity. <br /><br /> Most of the ongoing research efforts in cooperative diversity assume frequency flat channels with perfect channel knowledge. However, in practical scenarios, e. g. broadband wireless networks, these assumptions do not apply. Frequency-selective fading and imperfect channel knowledge should be considered as a more realistic channel model. The development of equalization and channel estimation algorithms play a crucial element in the design of digital receivers as their accuracy determine the overall performance. <br /><br /> This dissertation creates a framework for designing and analyzing various time and frequency domain equalization schemes, i. e. distributed time reversal (D-TR) STBC, distributed single carrier frequency domain (D-SC-FDE) STBC, and distributed orthogonal frequency division multiplexing (D-OFDM) STBC schemes, for broadband cooperative communication systems. Exploiting the orthogonally embedded in D-STBCs, we were able to maintain low-decoding complexity for all underlying schemes, thus, making them excellent candidates for practical scenarios, such as multi-media broadband communication systems. <br /><br /> Furthermore, we propose and analyze various non-coherent and channel estimation algorithms to improve the quality and reliability of wireless communication networks. Specifically, we derive a non-coherent decoding rule which can be implemented in practice by a Viterbi-type algorithm. We demonstrate through the derivation of a pairwise error probability expression that the proposed non-coherent detector guarantees full diversity. Although this decoding rule has been derived assuming quasi-static channels, its inherent channel tracking capability allows its deployment over time-varying channels with a promising performance as a sub-optimal solution. As a possible alternative to non-coherent detection, we also investigate the performance of mismatched-coherent receiver, i. e. , coherent detection with imperfect channel estimation. Our performance analysis demonstrates that the mismatched-coherent receiver is able to collect the full diversity as its non-coherent competitor over quasi-static channels. <br /><br /> Finally, we investigate and analyze the effect of multiple antennas deployment at the cooperating terminals assuming different relaying techniques. We derive pairwise error probability expressions quantifying analytically the impact of multiple antenna deployment at the source, relay and/or destination terminals on the diversity order for each of the relaying methods under consideration.

While the RF building blocks of narrowband system-on-chip designs have increasingly been created in CMOS during the past decade, researchers have started to look at the possibility of implementation of broadband transceivers in CMOS technology. High speed optical links with operating frequencies of up to 40 GHz and ultra wideband (UWB) wireless systems operating in 3 to 10 GHz frequency band are examples of these broadband applications. CMOS offers a low fabrication cost, and a higher level of integration compared with compound semiconductor technologies that currently claim broadband RFIC applications. <br /><br /> In this work, we focus on the design of broadband low-noise amplifiers: the fundamental building blocks of high data rate wireline and wireless telecommunication systems. A well established microwave engineering technique -distributed amplification- with a potential bandwidth up to the cut-off frequency of transistors is employed. However, the implementation of distributed amplifiers in CMOS imposes new challenges, such as gain attenuation because of substrate loss of on-chip inductors, a typical large die area, and a large noise-figure. These problems have been addressed in this dissertation as described below. <br /><br /> On-chip inductors, the essential components of the distributed amplifiers' gate and drain transmission lines, dissipate more and more power in silicon substrates as well as in metal lines as frequency increases, which in turn reduces the gain and deteriorates the input/output matching. Using active negative resistors implemented by a capacitively source degenerated configuration, we have fully compensated the loss of the transmission lines in order to achieve a flat gain of 10 dB over the entire DC-to-44 GHz bandwidth. <br /><br /> We have addressed another drawback of distributed amplifiers, large die area, by utilizing closely-placed RF transmission lines instead of spiral inductors. Because of a more compact implementation of transmission lines, the area of the distributed amplifiers is considerably reduced at the expense of extra design steps required for the modeling of the closely-placed RF transmission lines. A post-layout simulation method is developed to take into account the effect of inductive and capacitive coupling by incorporating a 3D EM simulator into the design process. A 9-dB 27-GHz distributed amplifier has been fabricated in an area as small as 0. 17 <em>mm</em>² using 180nm TSMC's CMOS process. <br /><br /> For wireless applications (UWB), a very low-noise figure is required for the broadband preamplifier. Conventional distributed amplifiers fail to provide a low noise figure mainly because of the noise injected by the terminating resistor of the gate transmission lines. We have replaced the terminating resistor with a frequency-dependent resistor which trades off the low frequency input matching of the distributed amplifier (not required for UWB) with a better noise performance. Our proposed design provides a gain of 12 dB with an average noise figure of 3. 4 dB over the entire 3-10 GHz band, advancing the state-of-the-art implementation of broadband LNAs.