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Recent cognitive research indicates that the human brain possesses special abilities for processing information relating to outdoor scenes. Simulated outdoor scenes are presented as an effective method of displaying higher dimensional data in an efficient and comprehensible manner. We demonstrate novel methods of using outdoor objects and scenes to display multidimensional content in a way that that is intuitive for humans to understand, and to exploit various cues commonly found in scenes from the natural world to communicate the values of multiple variables.

Auditory graphsdisplays that represent graphical, quantitative information with soundhave the potential to make graphical representations of data more accessible to blind students and researchers as well as sighted people. No research to date, however, has systematically addressed the attributes of data that contribute to the complexity (the ease or difficulty of comprehension) of auditory graphs. A pair of studies examined the role of both data density (i.e., the number of discrete data points presented per second) and the number of trend reversals for both point estimation and trend identification tasks with auditory graphs. For the point estimation task, results showed main effects of both variables, with a larger effect attributable to performance decrements for graphs with more trend reversals. For the trend identification task, a large main effect was again observed for trend reversals, but an interaction suggested that the effect of the number of trend reversals was different across lower data densities (i.e., as density increased from 1 to 2 data points per second). Results are discussed in terms of data sonification applications and rhythmic theories of auditory pattern perception.

This study aims to investigate the effects of event type (concepts represented by the graph) in graph comprehension with three graph types (line, bar, area) and two graph designs (linear, round) by means of two different task types (trend assessment, discrete comparison). A novel round graph type was designed for that purpose. Five hypotheses were investigated: H1: Graph type affects comparison strategies / H2: Event type affects comparison strategies / H3: Graph design affects comparison strategies / H4: Graph design and event type interact / H5: Task type affects comparison strategies. As a method to collect data on subjects&#039 / graph perception and comprehension, behavioral (recollected values, word preferences in the description task) and eye-tracking data (scan paths, gaze length, number of fixation, fixation duration and number of transitions) were collected. As an outcome of this thesis, while the event type and the task type seemed to affect the graph comprehension, the effect of graph type, the graph design and interaction between graph design and event type were partially observed. These results point out that although round and linear graph designs are informationally equivalent, the round graphs are computationally better suited than linear graphs for the interpretation of cyclic concepts. However, grasping trend information for the linear events and making discrete comparisons were achieved with the same effort in both graph designs. This result is not trivial at all, given the fact that participants were not familiar with the round graph design and were confronted with them in this experiment for the first time.

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The objective of this research is to explore high-speed analog-to-digital converters (ADCs) using silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) for wireless digital receiver applications. The stringent requirements of ADCs for the high-performance next-generation wireless digital receiver include (1) low power, (2) low cost, (3) wide input signal bandwidth, (4) high sampling rate, and (5) medium to high resolution. The proposed research achieves the objective by implementing high-performance ADC's key building blocks and integrating these building blocks into a complete sigma-delta analog-to-digital modulator that satisfies the demanding specifications of next-generation wireless digital receiver applications. The scope of this research is divided into two main parts: (1) high-performance key building blocks of the ADC, and (2) high-speed sigma-delta analog-to-digital modulator. The research on ADC's building blocks includes the design of two high-speed track-and-hold amplifiers (THA) and two wide-bandwidth comparators operating at the sampling rate > 10 GS/sec with satisfying resolution. The research on high-speed sigma-delta analog-to-digital modulator includes the design and experimental characterization of a high-speed second-order low-pass sigma-delta modulator, which can operate with a sampling rate up to 20 GS/sec and with a medium resolution. The research is envisioned to demonstrate that the SiGe HBT technology is an ideal platform for the design of high-speed ADCs.

The research concerns presented in this dissertation addresses aspects of students’ interaction with commonly occurring graphical artefacts in teaching and learning environments. In particular, focus is on how the students make sense of these artefacts in relation to subject specific tools and forms of expression. The dissertation comprises of four studies guided by a semiotics cultural- historical perspective to cognition. The first study which is largely quantitative, analyses the percentage scores from students’ responses to selected items from OECD PISA surveys for items containing graphical elements. The second and the third studies in keeping with a more sociocultural perspective to learning as point of departure, examine the students’ collaborative interaction around tasks containing graphical elements. The fourth study explores the nature of students’ solutions from the Swedish national test in mathematics based on a tools and forms of expression sensitive empirically derived construct of Identification contra Critical-analytical approach to graphicacy. The main outcomes of these studies can be summarised as follows: first there is justification for re-examining the predominant characterisation of students’ interaction with graphical artefacts. Secondly, while it is not uncommon for students to take a more visual-perceptive and intuitive approach to graphicacy, results from task items interactions indicate that a Critical-analytical approach seems to be more reliable and capable of yielding desirable outcomes. The outcomes of these studies call for vigilance on the type of tasks used in relation to graphicacy and how these can be used to foster students’ Critical-analytical disposition.