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It has been suggested that the presence of a limited area of damaged outer hair cells (OHCs) with intact inner hair cells, which may not be detected on the conventional audiogram, results in unbalanced neural activity between Type I and Type II fibers leading to tinnitus. In normal-hearing tinnitus patients, DPOAEs provided ambiguous data of OHC function when compared to non-tinnitus controls. Hearing loss in the extended high-frequency (EHF) region may decrease DPOAEs evoked at lower frequencies. Results of EHF audiometry in tinnitus patients are limited. The aim of the study was to evaluate DPOAEs and EHF thresholds in normal-hearing patients reporting unilateral tinnitus in left ear. Thus, each subject acted as their own control. Data were obtained for 26 subjects with bilateral hearing thresholds10, 12.5, 14, and 16 kHz. The DP-grams were measured in the 0.5-8 kHz range using 65/55-dB SPL primaries and f2/f1=1.2. The data analyses included DPOAEs with S/N>3 dB. Median audiometric data showed that thresholds in the left ears were significantly higher than those in the right ears at all four EHFs. Mean DPOAE levels of the left ears were lower than those of the right ears in the frequency range above 1 kHz. Additionally, a paired-comparison test of DPOAE levels of each patient’s right and left ear revealed significant differences at 6 and 8 kHz. The results indicate that: 1. OHC impairment in the most basal region reduces contribution to more apically generated DPOAEs; 2. OHC impairment in a limited area, which may be revealed by DPOAEs but not by conventional audiometry, can contribute to tinnitus generation; and 3. patients with unilateral tinnitus and normal hearing on the conventional audiogram are likely to demonstrate hearing loss in the EHF region.

No description available.

No description available.

As power electronic based controllers and loads become more prevalent in power systems, there is a growing concern about how the harmonics generated by these controllers and loads affect the power quality of the system. One widely used power electronic based load is the Variable Frequency Drive (VFDs) used to vary the speed of an induction motor; whereas a common example of a power electronic based controller used in power systems is the Static VAR Compensator (SVC) for improving a system’s power factor. In this thesis, the harmonic content and overall performance of a system including both a VFD and a SVC will be studied and analyzed. Specifically, the cases of no compensation, static capacitor compensation, and power electronic based static VAR compensation are examined. A small-scale model of a system for study was constructed in lab. Several cases were then performed and tested to simulate a system which contained both fixed and power electronic based harmonic generating loads. The performance of each case was determined by total harmonic current and voltage distortions, true power factor, and RMS current levels at different points in the system.

Lenses in virtual reality headsets make it possible to put displays close to users' eyes and they provide users with wider field of view. However, they also distort the displayed image. Providing we know the lens distortion properties, it is possible to compensate for the distortion by displaying an image that is distorted in the opposite way. This thesis focuses on measurement of the distortion for an arbitrarily complex lens, while also considering chromatic aberration. A system capable of measuring of the distortion using just a camera attached to the virtual reality headset is designed and implemented. It is based on pattern detection and comparison of relative positions of points on the display and their correspondences in the distorted image. The result is a 2D distortion map that can be used to transform images such that they appear undistorted to the virtual reality headset users.

With the rapid development of digital multimedia and internet techniques in the last few years, more and more digital images are being distributed to an ever-growing number of people for sharing, studying, or other purposes. Sharing images digitally is fast and cost-efficient thus highly desirable. However, most of those digital products are exposed without any protection. Thus, without authorization, such information can be easily transferred, copied, and tampered with by using digital multimedia editing software. Watermarking is a popular resolution to the strong need of copyright protection of digital multimedia. In the image forensics scenario, a digital watermark can be used as a tool to discriminate whether original content is tampered with or not. It is embedded on digital images as an invisible message and is used to demonstrate the proof by the owner. In this thesis, we propose a novel localized geometric-distortion resilient digital watermarking scheme to embed two invisible messages to images. Our proposed scheme utilizes two complementary watermarking techniques, namely, local circular region (LCR)-based techniques and block discrete cosine transform (DCT)-based techniques, to hide two pseudo-random binary sequences in two kinds of regions and extract these two sequences from their individual embedding regions. To this end, we use the histogram and mean statistically independent of the pixel position to embed one watermark in the LCRs, whose centers are the scale invariant feature transform (SIFT) feature points themselves that are robust against various affine transformations and common image processing attacks. This watermarking technique combines the advantages of SIFT feature point extraction, local histogram computing, and blind watermark embedding and extraction in the spatial domain to resist geometric distortions. We also use Watson’s DCT-based visual model to embed the other watermark in several rich textured 80×80 regions not covered by any embedding LCR. This watermarking technique combines the advantages of Harris feature point extraction, triangle tessellation and matching, the human visual system (HVS), the spread spectrum-based blind watermark embedding and extraction. The proposed technique then uses these combined features in a DCT domain to resist common image processing attacks and to reduce the watermark synchronization problem at the same time. These two techniques complement each other and therefore can resist geometric and common image processing attacks robustly. Our proposed watermarking approach is a robust watermarking technique that is capable of resisting geometric attacks, i.e., affine transformation (rotation, scaling, and translation) attacks and other common image processing (e.g., JPEG compression and filtering operations) attacks. It demonstrates more robustness and better performance as compared with some peer systems in the literature.

The goal of this dissertation is to investigate the impact of presentation formats on nonprofessional investors’ impressions of firm performance in the context of digital annual reports. The dissertation implements a three-essay approach. Essay 1 examines whether the effect of positive/negative financial performance news on nonprofessional investors’ impressions of management and firm performance depends on whether the graphical display of that news is vivid or pallid. Conducting a 2 x 2 between-participants experiment with 470 participants from Amazon Mechanical Turk (M-Turk), I find that when the news is positive, presenting graphs vividly allows nonprofessional investors to have a more positive impression of management and firm performance. In contrast, when the news is negative, presenting graphs vividly has little effect on nonprofessional investors’ impressions. The essay informs regulators and practice by demonstrating that vivid graphical website disclosures can significantly affect the behavior of nonprofessional investors when the financial performance news is positive, but the effect is minimal when the news is negative. The essay also contributes to the financial disclosure literature by demonstrating the impact of graphical vividness in presenting financial performance information. Essay 2 conducts a 2 x 2 between-participants experiment with 565 participants from M-Turk. I investigate whether varying the user interactivity and graphical vividness of the presentation of non-financial good news counteracts bad news presented in the audited financial data. I find a positive effect of user interactivity when the graphical presentation of non-financial information is vivid but not when it is pallid. In mediation analyses, I find unexpected results in that user engagement negatively mediates the effects of user interactivity on nonprofessional investors’ perceptions of firm performance and investment-related judgments and decisions. Subsequent analyses indicate that user interactivity alone reduces nonprofessional investors’ satisfaction with digital annual reports, but the joint effect of user interactivity and graphical vividness overcomes this negative effect. These results have implications for designers of digital annual reports, investor groups consuming this information, and regulators concerned about the need for assurance on the (unregulated) non-financial disclosures in annual reports. Essay 3 studies whether using hyperlinks that connect summarized financial graphs with detailed financial statement information reduces the effect of graphical distortions on nonprofessional investors’ perceptions of firm performance. Using 385 participants from M-Turk, I find that while distorted graphs do bias nonprofessional investors’ perceptions of firm performance, the provision and use of hyperlinks to the underlying source information eliminate those effects (i.e., debias). Using the dual-process theory of cognitive processing (Kahneman and Frederick 2002; Evans 2006, 2008), I find that hyperlinks enhance the overriding effect of System 2 processing (i.e., analytical processing) on System 1 processing (i.e., intuitive processing) and indirectly reduce the decision-biasing effect of distorted graphs on nonprofessional investors’ perceptions. The study contributes to standard setting as well as financial reporting practice by providing empirical evidence that the SEC’s policy guidance on implementing hyperlinks has benefits to nonprofessional investors. Second, it contributes to both the literature on distorted graphs and hyperlinks by suggesting hyperlinking to source data as a technique to mitigate the effects of graphical distortions. The findings of the three essays have implications for the designers of digital annual reports, investor groups consuming this information, and regulators concerned about the need to standardize the presentation formats in digital annual reports and potentially require auditor oversight of graphical displays of both financial and non-financial data in these reports.

This thesis describes the outcome of study to investigate methods of broadband matching to photonic devices such as lasers and high speed detectors. The thesis is divided into two areas of interest relating to the design of broadband fiber optic links. The first area is the application of numerical methods and commensurate line methods to the design of compact equalisers which allow an improved transducer power gain over a wide band. It is shown that physically small equalisers can yield an improvement of 4 dB over a 2 GHz bandwidth. The second area considered is the distortion inherent in a laser diode. Detailed measurements of the second order and intermodulation products are given. A small signal perturbation analysis is presented which helps to explain the observed distortion products. The results of numerical simulation of the distortion using a state variable implementation of the full rate equations and related first, second and intermodulation equations is presented and possible methods of reducing the distortion are explored. It is shown that in principle the distortion could be reduced by pre-generating the distortion and adding an inverted form of the distortion to the transmitted signal. The distortion can then be corrected in the fiber and simulation studies suggest that an improvement of 13 dB optical or 26 dB electrical may be possible.

Dans cette thèse, nous étudions les trois sujets suivants sur les systèmes de multiples entrées multiples sorties (MIMO) avec retour limité: Distorsion bout-à-bout: La première partie de la thèse présente l'impact conjoint des les nombres d'antenne, le ratio de bande passante de la source au canal, la corrélation spatiale et diversité dans le temps sur l'espérance de la distorsion optimale bout-à-bout dans les MIMO systèmes sans panne. En particulier, repose sur l'expression analytique pour tout les ratios du signal au bruit (SNR), l'expression asymptotique de l'espérance de la distorsion optimal bout-à-bout au SNR élevé est dérivé, composé de l'exposant de distorsion optimale et le facteur de distorsion optimale. Les résultats des simulations montrent que, à un SNR élevé pratique, l'analyse sur les impacts de l'exposant de distorsion optimale et le facteur de distorsion optimale explique le comportement de la distorsion optimale bout-à-bout. Les résultats présentés dans cette partie pourraient être les objectifs de performance pour les systèmes qui transmettent les sources analogique et en outre les directives sur la conception du système. Retour analogique du canal: Dans la seconde partie de cette thèse, nous proposons d'appliquer le codage bloc d'espace-temps orthogonal (OSTBC) sur retour analogique linéaire du canal. Considérant l'information du canal MIMO est une sorte de source vectorielle analogique, par rapport au retour du canal quantifié, le retour analogique linéaire a les avantages comme sans panne, l'adaptation automatique au canal et peu complexe. Il est prouvé que la méthode de transmission analogique linéaire OSTBC peutatteindre le borne de filtre adapté (MFB) sur SNR reçu. Par rapport en méthode analogique linéaire du codage bloc d'espace-temps circulant, la méthode linéaire analogique OSTBC obtient de meilleurs résultats à l'égard de SNR reçu et erreur quadratique moyenne (MSE) ; Par rapport en méthode de la quantification vectorielle aléatoire, les résultats des simulations montrent que sous une contrainte stricte de latence, leur performances sont proches à l'égard de l'erreur moyenne au sens et la méthode linéaire analogique OSTBC exécute encore mieux à l'égard erreur quadratique moyenne. Nous étudions également l'incidence de appliquer le retour linéaire analogique OSTBC au beamforming en liaison descendante pour multiutilisateurs MIMO et nous montrons que le retour linéaire analogique OSTBC peut rendre l'approche du système des performances optimales dans un temps de latence court. Multiplexage par couche: Dans la troisime partie de cette thèse, en considérant les systèmes avec des blocs courts, une nouvelle stratégie de multi-plexage par couches est proposée d'adapter un canal incertain par le codage couche-temps Walsh, l'annuleur d'interférence successif et HARQ signalisation. Comme l'illustrent les résultats de la simulation, en raison de ses performances proches mais beaucoup moins complexe, cette stratégie serait un bon substitut µa la stratégie de modulation QAM adaptive qui est largement utilise.