51 research outputs found
Substrate noise analysis and techniques for mitigation in mixed-signal RF systems
Get PDFThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 151-158).Mixed-signal circuit design has historically been a challenge for several reasons. Parasitic interactions between analog and digital systems on a single die are one such challenge. Switching transients induced by digital circuits inject noise into the common substrate creating substrate noise. Analog circuits lack the large noise margins of digital circuits, thus making them susceptible to substrate voltage variations. This problem is exacerbated at higher frequencies as the effectiveness of standard isolation technique diminishes considerably. Historically, substrate noise was not a problem because each system was fabricated in its own package shielding it from such interactions. The work in this thesis spans all areas of substrate noise: generation, propagation, and reception. A set of guidelines in designing isolation structures was developed to assist designers in optimizing these structures for a particular application. Furthermore, the effect of substrate noise on two key components of the RF front end, the voltage controlled oscillator (VCO) and the low noise amplifier (LNA), was analyzed. Finally, a CAD tool (SNAT) was developed to efficiently simulate large digital designs to determine substrate noise performance.(cont.) Existing techniques have prohibitively long simulation times and are only suitable for final verification. Determination of substrate noise coupling during the design phase would be extremely beneficial to circuit designers who can incorporate the effect of the noise and re-design accordingly before fabrication. This would reduce the turn around time for circuits and prevent costly redesign. SNAT can be used at any stage of the design cycle to accurately predict (less than 12% error when compared to measurements) the substrate noise performance of any digital circuit with a large degree of computational efficiency.by Nisha Checka.Ph.D
Substrate noise analysis and experimental verification for the efficient noise prediction of a digital PLL
No full textCultural Preferences for Chaperone Use during Breast Examinations: A Preliminary Study.
No full textAbstract
Previous studies have demonstrated that use of chaperones by physicians occurs most consistently for pelvic and rectal exams than for breast examinations. Factors that may influence chaperone for breast examination include duration of doctor-patient relationship, gender of the examiner, and availability of an assistant. The purpose of this study is to characterize patient preferences, not previously reported, for chaperone use.A patient questionnaire was approved by the institutional IRB at NYU Langone Medical Center and Bellevue Hospital. It was translated into Chinese, Spanish, and Arabic. Responses were collected from 277 patients. Variables included age, marital status, highest level of education, income, family background, religion, primary language, and chaperone and examiner preferences. For the respondents who preferred a chaperone, education was categorized as some college or none, language was English or non-English-speaking, background was Caucasian or non-Caucasian, and religion was Christian or non-Christian. Descriptive analyses and Pearson's chi-square test was used to determine significance.Median age was 49 years, range 17-87 years. 28 (10%) respondents preferred to have a chaperone present. An equal proportion of respondents did not want a chaperone (N=95, 34%) or had no preference (N=95, 34%). An additional 19% (N=53) of patients indicated that they preferred to be asked about their wishes. 142 (52%) indicated that they preferred a female examiner, 2 (1%) preferred a male examiner, and 126 (46%) had no preference regarding the examiner's gender.Table 1. Respondent Characteristics (N=277)VariablesN (%)EDUCATION (N=256) Grade School10 (4%)High School44 (17%)College116 (45%)Graduate School86 (34%)FAMILY BACKGROUND (N = 251) Caucasian/European159 (64%)African-American18 (7%)Hispanic28 (11%)Middle-Eastern17 (7%)Asian28 (11%)Other1 (0%)RELIGION (N = 250) Christian137 (55%)Jewish, reform49 (20%)Jewish, orthodox16 (6%)Islam14 (5%)Buddhist5 (2%)Other22 (9%)LANGUAGE (N = 256) English198 (77%)Spanish15 (6%)Chinese9 (3%)Arabic12 (5%)Other22 (9%)CHAPERONE PREFERENCE (N = 277) Do not use95 (34%)Use28 (10%)No preference94 (34%)Like to be asked53 (19%)Unknown7 (3%)EXAMINER GENDER PREFERENCE (N = 273) Female142 (52%)Male2 (1%)No preference126 (46%)Unknown3 (1%) Of the 28 patients who did prefer a chaperone, there was a statistically significant difference, p=0.011, for family background that was non-Caucasian. There was no statistical finding for differences in education, religion, or language.Table 2. Characteristics of Respondents who Prefer a Chaperone (N = 28)VARIABLESP-VALUEEducation0.078Language0.409Family Background0.011*Religion0.161* Denotes Statistical SignificanceThe majority of women responding to our survey either did not want a chaperone present for a breast examination or had no preference. However, the majority of all respondents did prefer to have a female examiner. This may simply represent that these patients were comfortable with a woman performing the exam. Additional investigation will further evaluate possible cultural differences.
Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6080.</jats:p
Plan-view Trajectory Estimation with Dense Stereo Background Models
Get PDFIn a known environment, objects may be tracked in multiple views using a set of back-ground models. Stereo-based models can be illumination-invariant, but often have undefined values which inevitably lead to foreground classification errors. We derive dense stereo models for object tracking using long-term, extended dynamic-range imagery, and by detecting and interpolating uniform but unoccluded planar regions. Foreground points are detected quickly in new images using pruned disparity search. We adopt a 'late-segmentation' strategy, using an integrated plan-view density representation. Foreground points are segmented into object regions only when a trajectory is finally estimated, using a dynamic programming-based method. Object entry and exit are optimally determined and are not restricted to special spatial zones
Activity maps for location-aware computing
No full textLocation-based context is important for many applications. Previous systems offered only coarse room-level features or used manually specified room regions to determine fine-scale features. We propose a location context mechanism based on activity maps, which define regions of similar context based on. observations of 3-D patterns of location and motion in an environment. We describe an algorithm for obtaining activity maps using the spatio-temporal clustering of visual tracking data. We show how the recovered maps correspond to regions for common tasks in the environment and describe their use in some applications.</p
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