title: Precision crystal frequency reference disciplined using mains power

authors: Dirks, Sam

subjects: Clocks

abstract: We describe a clock that keeps time and provides a reference frequency with better than 1PPM accuracy, through a quartz crystal automatically calibrated via the power line frequency. The long-term precision of line-frequency-based time is used to correct the crystal-based timekeeping system, a process referred to as disciplining. A microcontroller calibrates the internal reference dynamically with no user assistance. Precision is improved to better than 1ppm as measured against a rubidium standard. The precise signal is useful for calibrating frequencybased instrumentation or keeping time without periodic correction and costs much less than comparable alternatives. The algorithm can be implemented in any mains-powered device using a microcontroller, such as thermostats and lighting timers. The prototype clock uses a Nixie-tube display, requires no transformer, is housed a glass tube, and is offered as an opensource design.

text: Precision crystal frequency reference disciplined using mains power We describe a clock that keeps time and provides a reference frequency with better than 1PPM accuracy, through a quartz crystal automatically calibrated via the power line frequency. The long-term precision of line-frequency-based time is used to correct the crystal-based timekeeping system, a process referred to as disciplining. A microcontroller calibrates the internal reference dynamically with no user assistance. Precision is improved to better than 1ppm as measured against a rubidium standard. The precise signal is useful for calibrating frequencybased instrumentation or keeping time without periodic correction and costs much less than comparable alternatives. The algorithm can be implemented in any mains-powered device using a microcontroller, such as thermostats and lighting timers. The prototype clock uses a Nixie-tube display, requires no transformer, is housed a glass tube, and is offered as an opensource design.

year: 2016

title: The impact of background and context on car distance estimation

authors: Zhang, Fan

subjects: Distance Estimation

abstract: It is well established that people underestimate the distance to objects depicted in virtual environments and two-dimensional (2D) displays. The reasons for the underestimation are still not fully understood. It is becoming more common to use virtual environment displays for driver training and testing and so understanding the distortion of perceived space that occurs in these displays is vital. We need to know what aspects of the display cause the observer to misperceive the distance to objects in the simulated environments. The research reported in this thesis investigated how people estimate distance between themselves and a car in front of them, within a number of differing environmental contexts.  Four experiments were run using virtual environment displays of various kinds and a fifth experiment was run in a real-world setting.
It was found that distance underestimation when viewing 2D displays is very common, even when familiar objects such as cars are used as the targets. The experiments also verified that people have a greater underestimation of distance in a virtual environment compared to a real-world setting. A surprising and somewhat counterintuitive result was that people underestimate distance more when the scene depicts forward motion of the observer compared to a static view.  The research also identified a number of visual features in the display (e.g., texture information) and aspects of the display (e.g., field of view) that affected the perception of distance or that had no effect. The findings should help the designers of driver-training simulators and testing equipment to better understand the types of errors that can potentially occur when humans view two-dimensional virtual environment displays.

text: The impact of background and context on car distance estimation It is well established that people underestimate the distance to objects depicted in virtual environments and two-dimensional (2D) displays. The reasons for the underestimation are still not fully understood. It is becoming more common to use virtual environment displays for driver training and testing and so understanding the distortion of perceived space that occurs in these displays is vital. We need to know what aspects of the display cause the observer to misperceive the distance to objects in the simulated environments. The research reported in this thesis investigated how people estimate distance between themselves and a car in front of them, within a number of differing environmental contexts.  Four experiments were run using virtual environment displays of various kinds and a fifth experiment was run in a real-world setting.
It was found that distance underestimation when viewing 2D displays is very common, even when familiar objects such as cars are used as the targets. The experiments also verified that people have a greater underestimation of distance in a virtual environment compared to a real-world setting. A surprising and somewhat counterintuitive result was that people underestimate distance more when the scene depicts forward motion of the observer compared to a static view.  The research also identified a number of visual features in the display (e.g., texture information) and aspects of the display (e.g., field of view) that affected the perception of distance or that had no effect. The findings should help the designers of driver-training simulators and testing equipment to better understand the types of errors that can potentially occur when humans view two-dimensional virtual environment displays.

year: 2014

title: Breaking the browsing barrier for historic search of newspaper texts

authors: Keegan, Te Taka Adrian Gregory

subjects: computer science

abstract: Traditionally, to find information in a newspaper collection it has been necessary to painstakingly browse through the individual issues hoping that relevant words will catch your eye. Researchers of New Zealand’s encounter history received a boost when, in 1996, the Alexander Turnbull Library produced a collection on microfiche totaling almost 18,000 pages and covering a printing period from 1842 to 1933. While having all the newspapers in a single collection was a large step forward, browsing or searching for information in this microfiche collection was still time consuming.
By incorporating the collection into a digital library with an Internet interface, and by enabling full-text search, we have broken this browsing barrier. Making the information available this way is even more significant as the majority of the collection is written in the Māori language; we have created a Māori language resource that is sorely needed by education and research institutes, and one that provides quick and accurate access to the previously obscure source. The process involved in developing this unique digital library collection, the advantages of traditional newspaper stored in this medium, and the possibilities that we intend to investigate in the future, will be discussed in this paper.

text: Breaking the browsing barrier for historic search of newspaper texts Traditionally, to find information in a newspaper collection it has been necessary to painstakingly browse through the individual issues hoping that relevant words will catch your eye. Researchers of New Zealand’s encounter history received a boost when, in 1996, the Alexander Turnbull Library produced a collection on microfiche totaling almost 18,000 pages and covering a printing period from 1842 to 1933. While having all the newspapers in a single collection was a large step forward, browsing or searching for information in this microfiche collection was still time consuming.
By incorporating the collection into a digital library with an Internet interface, and by enabling full-text search, we have broken this browsing barrier. Making the information available this way is even more significant as the majority of the collection is written in the Māori language; we have created a Māori language resource that is sorely needed by education and research institutes, and one that provides quick and accurate access to the previously obscure source. The process involved in developing this unique digital library collection, the advantages of traditional newspaper stored in this medium, and the possibilities that we intend to investigate in the future, will be discussed in this paper.

year: 2001