abstract: An investigation of phase noise in amplifier and voltage-controller oscillator (VCO) circuits was conducted to show that active direct-current (DC) bias techniques exhibit lower phase noise performance than traditional resistive DC bias techniques. Low-frequency high-gain amplifiers like those found in audio applications exhibit much better 1/f phase noise performance and can be used to bias amplifier or VCO circuits that work at much higher frequencies to reduce the phase modulation caused by higher frequency devices. An improvement in single-side-band (SSB) phase noise of 15 dB at offset frequencies less than 50 KHz was simulated and measured. Residual phase noise of an actively biased amplifier also exhibited significant noise improvements when compared to an equivalent resistive biased amplifier. / Dissertation/Thesis / M.S. Electrical Engineering 2010

abstract: Current research has identified a specific type of visual experience that leads to faster cortical processing. Specifically, performance on perceptual learning of a directional-motion leads to faster cortical processing. This is important on two levels; first, cortical processing is positively correlated with cognitive functions and inversely related to age, frontal lobe lesions, and some cognitive disorders. Second, temporal processing has been shown to be relatively stable over time. In order to expand on this line of research, we examined the effects of a different, but relevant visual experience (i.e., implied motion) on cortical processing. Previous fMRI studies have indicated that static images that imply motion activate area V5 or middle temporal/medial superior temporal complex (MT/MST+) of the visual cortex, the same brain region that is activated in response to real motion. Therefore, we hypothesized that visual experience of implied motion may parallel the positive relationship between real directional-motion and cortical processing. Seven subjects participated in a visual task of implied motion for 4 days, and a pre- and post-test of cortical processing. The results indicated that performance on implied motion is systematically different from performance on a dot motion task. Despite individual differences in performance, overall cortical processing increased from day 1 to day 4. / Dissertation/Thesis / M.S. Psychology 2014

In current mammography practice, radiologists typically view mammograms in a symmetric, side-by-side, configuration in the belief that abnormalities will be made salient because they break the perceived symmetry. The literature on the use of symmetry as an aid to signal detection is limited and this thesis has taken a psychophysical approach to investigate the radiologist’s task of detecting a small mass (a blob) in paired mammogram backgrounds. Initial experiments used Gaussian white noise and synthetic mammogram backgrounds to test observer performance for the radiologist’s task using symmetric (side-by-side) displays and animated (the two images of a pair alternated sequentially in the same location) displays. The use of animated displays was then tested using real mammogram backgrounds in the subsequent experiments. The results showed that side-by-side presentation of paired images does not provide any benefit for the detection of a blob, whereas, alternated presentation enabled the observer to use the correlation present between the paired images to improve detection performance. The effect of alternation was not evident when applied to the task of detecting a small mass in real mammogram pairs and subsequent investigation suggested that the loss of effect resulted from the lack of scale invariance of real images. This meant that, regardless of the level of global correlation between two images, the localised correlation, at a region size reflecting the visual angle subtended by the fovea, was much lower. Thus, decorrelation by the visual system was ineffective and performance for the detection of a blob in the paired images was also ineffective. This thesis suggests that, whilst animated displays can be a powerful tool for the identification of differences between paired images, the underpinning mechanism of decorrelation makes them unsuited for mammograms where scale invariance means that correlation at local levels is a fraction of the global correlation level.

In a fascinating article in The Journal of Ethics, Eleonore Stump contends that while the flicker of freedom defense is the best available strategy for defending the principle of alternative possibilities against the threat posed to that principle by the Frankfurt cases, the defense is ultimately unsuccessful. In this article I identify a number of difficulties with Stump’s criticism of the flicker strategy. Along the way, I also clarify various nuances of the strategy that often get overlooked, and I highlight the advantages of one version of it in particular.

Frankfurt cases are supposed to provide us with counterexamples to the principle of alternative possibilities. Among the most well known responses to these cases is what John Fischer has dubbed the flicker of freedom strategy. Here we revisit a version of this strategy, which we refer to as the fine-grained response. Although a number of philosophers, including some who are otherwise unsympathetic to Frankfurt’s argument, have dismissed the fine grained response, we believe there is a good deal to be said on its behalf. We argue, in particular, that reflection on certain cases involving omissions undermines the main objections to the response and also provides the groundwork for an argument in support of it.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第19473号 / 理博第4133号 / 新制||理||1594(附属図書館) / 32509 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)講師 市川 正敏, 教授 佐々 真一, 教授 山本 潤 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

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Caffeine's effect on the visual system was investigated. Twelve male and twelve female subjects (aged 18 - 25 years) were measured for Critical Flicker Frequency (CFF) thresholds at 15 levels of retinal illuminance (-1.0 to 3.0 log trolands) in each of four caffeine dosage conditions (0, 200mg, 400mg, 600mg). Variables of interest included dosage, gender, left and right eye differences, and time after ingestion. Significant results were found for dosage (p=.000), gender (p=.001), and eye differences (p=.000). Interactions were found for gender and dosage (p=.000), and gender and eye differences (p=.043). Implications of these findings are discussed in terms of caffeine's effect on the Central Nervous System (CNS) and corresponding effects on the visual system. It is concluded that ingestion of caffeine causes increased sensitivity of the visual system as displayed through lower Critical Flicker Frequency thresholds. / Master of Science

This study evaluated the usefulness of a psychophysical model as part of a new ANSI/HFES 100 standard for CRT flicker. A graph based flicker prediction method developed from Farrell, 1987 was evaluated. The Farrell model is based on phosphor persistence, screen luminance, display size, and viewing distance. The graph based method assumes a worse case scenario (i.e. a white display screen shown on a display with P4 phosphor). While the Farrell model requires photometric measurements to be taken using special equipment, the graph based method require a knowledge of the display size, viewing distance, screen luminance, and refresh rate. Ten participants viewed different display sizes from different eccentricities under different levels of illumination and luminance. In each condition the display's refresh rate was manipulated using the Method of Limits to determine the critical flicker frequency (CFF). An Analysis of Variance was used to detirmine significant effects on CFF. CFF increased with increasing luminance and display size. Adequate illumination significantly increased CFF. A viewing eccentricity of 30 degrees (measured horizontally from the center of the screen) produced the highest CFF values. Under the conditions of 30 degrees eccentricity and 250 to 500 lux illumination, observed 50% CFF threshold values exceeded the 90% CFF threshold values predicted by the graph based method. This study demonstates that when tested under the same conditions it was developed under, the Farrell method successfully predicts flicker perception; however, when tested under conditions representative of real world working conditions, the Farrell model fails to predict flicker perception. New parameters for the model are suggested.<INPUT TYPE="hidden" NAME="abstract" VALUE="This study evaluated the usefulness of a psychophysical model as part of a new ANSI/HFES 100 standard for CRT flicker. A graph based flicker prediction method developed from Farrell, 1987 was evaluated. The Farrell model is based on phosphor persistence, screen luminance, display size, and viewing distance. The graph based method assumes a worse case scenario (i.e. a white display screen shown on a display with P4 phosphor). While the Farrell model requires photometric measurements to be taken using special equipment, the graph based method require a knowledge of the display size, viewing distance, screen luminance, and refresh rate. Ten participants viewed different display sizes from different eccentricities under different levels of illumination and luminance. In each condition the display's refresh rate was manipulated using the Method of Limits to determine the critical flicker frequency (CFF). An Analysis of Variance was used to detirmine significant effects on CFF. CFF increased with increasing luminance and display size. Adequate illumination significantly increased CFF. A viewing eccentricity of 30 degrees (measured horizontally from the center of the screen) produced the highest CFF values. Under the conditions of 30 degrees eccentricity and 250 to 500 lux illumination, observed 50% CFF threshold values exceeded the 90% CFF threshold values predicted by the graph based method. This study demonstates that when tested under the same conditions it was developed under, the Farrell method successfully predicts flicker perception; however, when tested under conditions representative of real world working conditions, the Farrell model fails to predict flicker perception. New parameters for the model are suggested." / Master of Science

As computer usage has become more widespread, the number of complaints of visual discomfort and eye strain among computer operators has also increased. The temporal flicker of display screens can be a significant source of this visual discomfort. The purpose of this research was to determine how illuminance, luminance, screen test pattern, and viewing angle affect the perception of flicker in a CRT, especially in relation to the flicker evaluation method in the ANSI/HFS 100-1988 standard. Twenty participants viewed a CRT at different viewing angles, under different levels of illuminance and luminance, and with different screen test patterns. Two of the conditions matched conditions specified in the ANSIIHFS 100-1988 standard, while the remaining conditions represented additional levels of illuminance, luminance, and a different screen test pattern. For each condition, the display's refresh rate was manipulated in ascending and descending trials to determine the critical flicker frequency (CFF); the threshold point at which flicker was first noticeable (or not noticeable). An Analysis of Variance and post-hoc Newman-Keuls analyses were calculated to determine the significant effects on the CFF. The CFF values were higher with the higher illuminance and luminance values, and with the white screen viewed in the periphery. When compared with conditions specified in the ANSI/HFS 100-1988 standard, the additional levels of illuminance, luminance, and screen test pattern examined in this study are more representative of actual usage conditions and resulted in higher CFF values. Based on these results, it is concluded that the flicker evaluation procedure in the ANSIIHFS 100-1988 standard does not ensure flicker-free CRT viewing under typical office environment conditions. An alternative flicker evaluation procedure is proposed. / Master of Science