Dissertations / Theses on the topic 'Timekeeping'

Circadian rhythms are self-sustained endogenous biological oscillations with a period of approximately 24 hours. These rhythms are observed widely across kingdoms and at all levels of biological scale. Recent work has shown there to be circadian variation in metabolism, both at the organismal and cellular level. It has also been posited that rhythmic production of metabolites might be essential for maintenance of circadian rhythmicity within cells, even in the absence of nascent transcription. The first portion of this thesis investigates the contribution of primary carbohydrate metabolism to cellular timekeeping, with particular emphasis on the pentose phosphate pathway. I also describe and validate a new 13C labelling technique for accurate determination of the relative flux through early primary metabolic pathways. This is accompanied by the development and optimisation of a microfluidic system for long-term perfused tissue culture, which allows for longitudinal study of metabolic flux within the same population of cells with simultaneous recording of clock gene activity. This perfused system provides several advantages over static tissue culture. The second portion considers the effects of the metabolic hormone insulin on circadian rhythmicity, both at the level of the cell and of the whole organism. It shows that administration of insulin is sufficient to shift the phase of circadian gene expression and elicits induction of clock protein PER2. Strikingly, manipulation of insulin signalling is sufficient to determine all the essential parameters of the cellular clock (phase, period and amplitude) in a dose-dependent but glucose independent fashion. Using pharmacological and genetic approaches, a molecular explanation for this effect is determined. This data suggests that insulin is a primary determinant of rhythms in peripheral tissues and is most likely a major signal for circadian entrainment to feeding in mammals, for which I now propose a mechanistic basis.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 103-112).
Solid-state quantum systems have emerged as promising sensing platforms. In particular, the spin properties of nitrogen vacancy (NV) color centers in diamond make them outstanding sensors of magnetic fields, electric fields, and temperature under ambient conditions. This thesis focuses on spin-based sensing using multimode diamond waveguide structures to efficiently use large ensembles of NV centers (> 10¹⁰). Temperature-stabilized precision magnetometry, thermometry, and electrometry are discussed. In addition, the precision characterization of the NV ground state structure under a transverse magnetic field and the use of NV-diamond for spin-based clocks are reported.
by Hannah Clevenson.
Ph. D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 165-173).
Light pulse atom interferometry (LPAI) is a powerful technique for precision measurements of inertial forces and time. Laboratory LPAI systems currently achieve state-ofthe- art acceleration sensitivity and establish the international atomic time standard. However, the realization of practical LPAI in dynamic environments (e.g., rapidly accelerating or rotating platforms) has been limited in part by atom optics-the analogues to optical beamsplitters and mirrors. Atom optics in traditional LPAIs are composed of resonant laser pulses that are susceptible to variations in optical detuning and intensity expected in sensors designed for dynamic environments. This thesis investigates atom optics that use frequency- and intensity-modulated laser pulses to suppress sensitivity to these inhomogeneities. For atomic timekeeping applications, a Ramsey LPAI sequence based on stimulated Raman transitions and frequency-swept adiabatic rapid passage (ARP) was developed. Raman ARP drives coherent transfer in an effective two-level atomic system by sweeping the Raman detuning through the two-photon resonance. In experiments with ¹³³Cs atoms, Raman ARP reduced the sensitivity of Ramsey sequences to differential AC Stark shifts by about two orders of magnitude, relative to standard Raman transitions. Raman ARP also preserved fringe contrast despite substantial intensity inhomogeneity. The fractional frequency uncertainty of the ARP Ramsey sequence was limited by second-order Zeeman shifts to ~3.5 x 10-¹² after about 2500 s of averaging. For accelerometry applications, Raman ARP provided efficient, large momentum transfer (LMT) atom optics in an acceleration-sensitive LPAI. These atom optics produced momentum splittings of up to 30 photon recoil momenta between interfering wavepackets-the largest to date for Raman atom optics. This splitting, in principle, enables up to a factor-of-15 improvement in sensitivity over the nominal interferometer. By forgoing cooling methods that reduce atom number, this LMT method reduces the measurement uncertainty due to atom shot-noise and enables large area atom interferometry at higher data-rates. These features could prove useful for fielded inertial sensors based on atom interferometry.
by Krish Kotru.
Ph. D.

The first part of this study analyses and discusses astronomical timekeeping methods used in the New Kingdom. Diagonal star clocks are examined first, looking at classification of sources, decan lists, and the updating of the tables over time. The date list in the Osireion at Abydos is discussed, and issues concerning its place in the history of astronomical timekeeping are raised. The final stellar timekeeping method, the Ramesside star clock, is then examined. The conventional interpretation of the observational method behind the tables is challenged by a new theory, and a system of analysing the tables is introduced. The conclusions of the previous sections are then gathered together in a discussion of the development of stellar timekeeping methods. The small instruments known as shadow clocks, and their later relatives the sloping sundials, are also examined. The established hypothesis that the shadow clock was completed by the addition of a crossbar is challenged and refuted. The second part of this study is based on New Kingdom representations of the sky. Two major texts and several celestial diagrams are discussed in detail, beginning with the Book of Nut, which describes the motions of the sun and stars. New translations of the vignette and dramatic text are presented and discussed. Portions of the Book of the Day describing the behaviour of the sun and circumpolar group of stars are analysed. Finally, celestial diagrams dating from the New Kingdom are described. Their composition and significance is discussed and the conceptual framework behind the diagrams is recreated. By introducing new theories and analysis methods, and using a modem but sympathetic approach to the original sources, this study attempts to update and extend our knowledge of these areas of ancient astronomy.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 83-85).
Current state-of-the-art atomic clocks span the range from large accurate fountain clocks such as the NIST-F2 to relatively small inaccurate chip scale clocks. Small clocks with higher accuracy could greatly expand the range of applications for precision timekeeping, and enable cheaper implementation of existing applications. This type of clock may be realized by use of optical Raman interferometry based on pulsed interrogation of cold atoms. However, this method suffers from serious systematic error sources, e.g., AC Stark shift and Zeeman shift, which alter the atomic resonance frequency. A new method based on adiabatic rapid passage (ARP) has been recently demonstrated at Draper which has significantly reduced phase sensitivity to differential AC Stark shift. It is found that compared to standard Raman, use of ARP enhances timekeeping stability by a factor of three with stability of 2 x 10⁻¹² at 100 seconds. Increasing data rate may also improve short term stability. With all of the above improvements, ARP enhances short term fractional stability to 7 x 10⁻¹² at one second.
by Nancy Y. Wu.
S.M.

The suprachiasmatic nucleus (SCN) of the hypothalamus is the master mammalian pacemaker, co-ordinating the multitude of cell-autonomous circadian oscillators across the body to ensure internal synchrony, as well as maintaining an adaptive phase relationship with the light-dark cycle via projections from the retina. Intercellular communication between SCN clock neurons synchronises their oscillations, resulting in coherent output signals to the periphery. Vasoactive intestinal peptide (VIP), a neuropeptide expressed in the retinorecipient ventrolateral region of the SCN, is vital to this circuit-level co-ordination by signalling to its cognate VPAC2 receptor. In addition, VIP is important for the integration of light input into the SCN oscillation. The aims of the work presented in this thesis were to determine the roles of the VIP and VPAC2 cells in controlling circadian rhythmicity, and to elucidate the mechanisms of VIP signalling that underpin these roles. The first two experimental chapters utilise intersectional genetics and viral transduction to address separable roles for the VIP and VPAC2 cell populations. By diphtheria toxin-mediated cell ablation, or by adjusting cell-autonomous periodicity or rhythmicity specifically in these cell populations, I have identified that the VPAC2 cells are important for period setting and rhythmicity of both the SCN ex vivo and mouse behaviour in vivo, while the VIP cells play a vital role in behavioural rhythmicity and phase coherence across the SCN. The next two chapters use application of VIP to SCN slices to address mechanisms of phase-resetting through pharmacological manipulation and microarray analysis. I find that VIP has long lasting effects on all major circadian parameters of the SCN slice oscillation at both the cellular and circuit levels, and that it achieves this through a diversity of molecular pathways, in particular through cAMP/Ca2+ response elements within gene promoters. The final chapter focuses primarily on DUSP4, a negative regulator of the MAP kinase pathway that I have demonstrated to be upregulated by VIP. Here I demonstrate that DUSP4 affects the steady-state period of SCN slices, as well as influences phase shifting characteristics of both slices and mice. To conclude, the work presented here furthers our knowledge of neuropeptidergic communication in mammalian pacemaking. I have undertaken extensive characterisation of the molecular mechanisms through which the VIP neuropeptide influences SCN oscillators, and I have determined differential roles for the VIP and VPAC2 neurons in circadian timekeeping.

Thesis: S.M., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 49-51).
This thesis presents an investigation into the development of a series of devices that alter our relationship to time. The intention behind each of these devices is to help people become more aware of the temporality that is at the core of our being. Time pressure comes from the networks of timekeeping that surround us. It's not just our clocks and watches. Time is synchronized across devices, cities, and continents. Networked time regulates our lives today more than ever before. Modern timekeeping has shaped our culture into one that squeezes productivity out of even the most inconceivably small time increments. Time was once kept at a distance. Church towers and grandfather clocks marked time in space. As technology advanced, timekeeping has shifted inwards and closer to our bodies. Time is embedded in watches, phones, and every digital electronic device that surrounds us. Today, fewer people wear watches and keep time for themselves. We've outsourced our sense of time to systems that we don't understand. Our phones and computers display time accurately without intervention or maintenance, making watches seem redundant. Those who are less aware of time are surrendering to an unfamiliar force. They invite environmental pressures to pull their sense of time away from an innate internal awareness towards a grossly distorted sense that views time as a commodity. Modern timekeeping might help with efficiency, but we are busier today than ever before. While we've shaped our temporal perception through the increasing precision of standardized time, human psychology remains connected to time, but not congruent to the physics of it. If we can become more aware of our relationships to time, we can manage our expectations and counteract temporal illusions, misperceptions, and distortions. The devices presented here call for a more mindful approach to timekeeping. Rather than pushing time into the periphery, I hope to empower people to make time their own. We can challenge the temporal pressures of our environment, culture, technology, and state of mind through an alternative relationship to time.
by Che-Wei Wang.
S.M.

Thesis (MTech (Business Information Systems))--Cape Peninsula University of Technology, 2019
The trend of using mobile devices for timekeeping in South African businesses appears to be novel, and certainly little canvassed in the academic literature. The general potential of using online tools and mobile applications for business is enormous (Columbus, 2015; Sajić et al., 2018), but informed opinion on the use of mobile devices specifically for timekeeping is hard to find (Mohandes, 2017). The purpose of this study is therefore to explore how can small businesses in Cape Town manage timekeeping on employees using mobile devices efficiently and effectively. A case study research methodology within the interpretive paradigm was employed to conduct interviews with owners and manages of small business in Cape Town. On the other hand, qualitative research findings were analysed within literature concepts. The findings showed that small businesses use three ways of timekeeping: fully automated, manual and mixed method. The findings also showed that mobile devices have great potential to address the weaknesses of current as-is model such as manual mistakes, data accessibility. Mobile devices can improve the process of timekeeping using cloud computing that allows the user to access data anywhere, at any time. Analysis of the “as is” model revealed the disadvantages of manual timekeeping, such as manual mistakes and inaccuracy in the payroll. This manner of timekeeping is nevertheless understandable, given the small numbers of employees and strong bonds of trust within such companies. The proposed “to be” model displays the advantages of automated timekeeping, such as the ease of accessing data, transparency, and the increased accuracy of business processes, including the payroll. This model makes use of cloud computing and creates an automated data flow within the organisation. Furthermore, the applications once installed does not need any physical development, which makes mobile timekeeping easy to use. Finally, the portability of mobile devices makes the process of collecting time and attendance data possible from anywhere, without stationary terminals. The study recommends the replacement of clock card terminals with mobile devices. The study also revealed that small businesses need to pay more attention to ICT tools such as cloud computing, Near Field Communication (NFC) and mobile technologies.

This dissertation presents a novel satellite timekeeping system which does not require on-board atomic clocks as used by existing navigation satellite systems such as GPS, GLONASS or the planned GALILEO system. This concept is differentiated by the employment of a synchronization framework combined with lightweight steerable on-board clocks which act as transponders re-broadcasting the precise time remotely provided by the time synchronization network located on the ground. This allows the system to operate optimally when satellites are in direct contact with the ground station, making it suitable for a system like the Japanese Quasi-Zenith Satellite System, QZSS. Low satellite mass and low satellite manufacturing and launch cost are significant advantages of this novel system. Two possible implementations of the time synchronization network for QZSS are presented. Additionally, the problem of satellite communication interruption is analyzed and a solution is presented. Finally a positioning and timing quality analysis, aimed to provide understanding of the actual timing quality requirements for QZSS, is presented.

Ancient settlements in Oman are frequently found where crops can be cultivated with groundwater distributed to fields by gravity flow. These irrigation systems are called aflāj (s. falaj), and they are still pivotal to community life: in 1997 over 3000 such systems were still in use. The allocation of falaj water among farmers traditionally depended on the use of the sun and the stars to track the passage of time. This practice, and particularly the use of stars, is disappearing rapidly: the availability of watches since c. 1970 means that there is now little technical reason to use the stars. The study records fast disappearing information on the ethnography of agricultural communities in northern Oman and, in particular, on the use of stars. It aims to identify the stars used and record the methods of stargazing in sufficient detail that the systems could be replicated if all local knowledge were lost. It also aims to raise awareness and improve the understanding of the significance of the traditional use of the stars in irrigated agriculture. This aspect of the cultural heritage of the region has not been written about previously in such detail. The research questions concern how, where and why stars are still used. There are several documents on falaj building and organisation in Oman, but relatively little on telling the time, and much less on the stars than on the use of the sun. The available documents were reviewed, but the main source for this study is data collected in the field, interviewing falaj managers and stargazers and watching the stars with them. Field work was carried out in different seasons since the stars used vary through the year. International experts were consulted on various aspects of the work, including Daniel Varisco on folk astronomy and Paul Kunitzsch on star names. The study focuses on five settlements where stars are used to this day. These are Qarya Beni Subh (Qarya), close to the mountains near the town of Al Hamra in the Interior Region; Al Fath, Zahib, Sudayra and Barzaman near the towns of Mudaybi and Sinaw in the Eastern Region. Additional information was obtained from a few other places for comparison, and during the course of the research it was found that only about eight of three thousand active falaj communities still use stars for time keeping. The methods of stargazing are given in detail, together with the names of the stars in Oman and their international classification where possible. It was found that the number of stars, the stars used, and their names in Oman vary from place to place. The time that each star represents is more variable than expected from the difference in length of night during the year. The stars used for falaj purposes are compared with those used in the region for navigation and with the stations of the moon of the Islamic calendar, but no evidence of any link between them was identified. On the basis of the history of falaj systems in Oman, the star names and the stars used, at least two of which are from the pre-Islamic Bedu tradition, it is concluded that the system of stargazing for timing water dates from pre-Islamic times, before the introduction of the stations of the moon. The main reason for the continued use of stars by a few communities, even though wristwatches are now widely available, is thought to be adherence to tradition both for its own sake and to avoid disputes over the sharing of water. It is considered unlikely that this ancient practice will survive more than 10 or 20 years unless the younger generation takes an interest in learning, and putting into practice, the traditions of their forefathers.

This thesis describes the design, development and realization of a wireless electronic timer for use in firesport. Specification of the final product is built with regard to versatility, ease of use and low acquisition costs. Commercial products have been compared as inspiration for this work. Requirements of the timer are based on the rules of firesport disciplines, where the timer can be used. It consists of a base station that can be accompanied for additional elements used to starting, splits capturing and stopping. An independent communication module has been created to ensure wireless connection. Libraries for comfort work with the module, support for USB bus and reliable protocol for wireless transmission have been implemented.

This thesis deals with the design and realization of wireless electronic timer for fire sport. The first part of thesis provides an analysis of the given problems and all component parts of the system which are needed for time measurement in the fire sport. The principal aim of thesis was to create a wireless electronic timer for simultaneous measurement of up to four lanes. The designed measuring system is equipped with a large LED display to show the final time. Targets and starting pistols are wirelessly connected with the main unit of timer with using a communication platform IQRF. The whole device is structural designed to the handling was as simple as possible.

The main goal of this master‘s thesis was to create software solution suitable for measuring and results processing of regularity rally races and to create supplementary web application. The measuring application was created using integrated development environment Microsoft Visual Studio 2015 and c# programming language. For application to work correctly, it was necessary to create a database model, using MySQL relational database management system. The measuring application can work both with local and remote database server. Web application allows user to see various data including results of racing events or tournaments, data are being fetched from the MySQL database. There was an option to explore existing circuit racing software Vola Timing Circuit – Pro for inspiration.

The thesis seeks to reveal, through the use of numerous case studies, the timekeeping processes that helped to make New Zealand. Whilst the period under review covers primarily the period 1840 to 1868 there is also a discussion of the emergence of clock time in thirteenth century Britain and Europe and its development through to the late nineteenth century. This is because the settlers‟ apprehension of time and their use of clocks and watches had evolved over the preceding centuries. The importance of reliable time was recognised by the Church from the medieval period but as ownership of public and private clocks proliferated the decentralisation of clock time commenced. Clock time commanded the lives of people and imprinted itself through the inculcation of such notions as punctuality and productivity. Better clocks brought a new emphasis to workplace efficiency underpinning the belief that time was money and facilitated the efficient coordination of Land, Labour and Capital. The discovery of New Zealand required timekeeping at sea. The achievements of James Cook, underpinned by improved chronometers, facilitated the large-scale British colonisation of New Zealand and seldom brought respite from the rule of time. Once on land, the settlers looked to establish a temporal order similar to Britain. The challenge to establish and disseminate the „true‟ local time within communities led to the setting up of observatories and the use of public clocks, time ball stations, bells and guns to signal clock time. The myriad of local times was not a problem at first but once the telegraph began to link communities they hindered its optimal efficiency. This led to the introduction of „telegraph time‟ in early 1868, dual time systems in communities using the telegraph, and public debate. Whilst most provinces accepted the new clock time, Otago saw it as an affront to their community‟s autonomy and identity. The province challenged the imposition of telegraph time, instigated a Parliamentary debate, and argued for the introduction of a common New Zealand time. Parliament‟s 1868 decision was a triumph for convenience and economic rationality over tradition and local identity. New Zealand was the first country entirely to abandon local times and regulate its time in relation to Greenwich mean time.

This work deals with the design of universal wireless timer for fire sport disciplines. Fire sport is a group of more than 15 disciplines. There are different ways of time measurement for each discipline. Important part of this work is detailed research of individual disciplines and their requirements at time measurement system and it's accessories. Another part of this work deals with the specification of wireless timekeeping system, which involves suitable partitioning of time measurement system into wirelessly communication modules. The interface for connecting sensors and accessories is also specified. Designed system is suitable for racing and training purposes, it has short installation time. This work also deals with the design of electronics (power and digital circuits) for each module and also with building of prototype, which is tested using prepared scenarios. New findings are evaluated and lead to design of next generation of time measurement system.

Thesis (MPA)--Stellenbosch University, 2011.
ENGLISH ABSTRACT: Human beings are constantly confronted with change because their current situation is continually being questioned. In order to change the way humans behave, it is necessary to change the mindset of those who will be influenced by new ideas. Stellenbosch Municipality faces a dilemma because the current management of its employee attendance is having a negative impact on its daily operations – service delivery is becoming an increasingly serious concern because the inability to manage employees’ daily attendance results in inefficient and ineffective rendering of services to citizens. This research addresses the question of whether the change from a manual attendance register to a biometric time and attendance system would more effectively ensure the availability of Municipal employees to improve basic service delivery. Moreover, the dilemma Stellenbosch Municipality faces concerns the monitoring of employees on a daily basis, including the availability of an attendance register for audit purposes. A questionnaire was used to examine the situation and obtain responses from employees who make use of both the manual attendance register and the biometric time and attendance device. It was established that the use of the manual attendance register caused certain problems, although it has served a monitoring purpose for more than 30 years. At the time of answering the questionnaire, some respondents requested the implementation of an electronic system with real-time capability to remove any doubt concerning the confirmation of employee attendance. The feedback from the questionnaire confirms: - the unreliability of a human-dependent employee attendance register; - that delivery of basic services can only be done on condition of the availability of employees who report for duty; and - that the use of the manual attendance system creates unrecoverable losses. The inability of employees to maintain their manual attendance registers led to the recommendation that: - a mechanised system needs to be implemented to reduce administration procedures and to secure compliance and an unqualified audit.
AFRIKAANSE OPSOMMING: Mense word voortdurend met verandering gekonfronteer omdat hul huidige situasie gedurig bevraagteken word. Ten einde die manier waarop mense optree te verander, is dit nodig om die geestesingesteldheid van diegene wat deur nuwe idees beïnvloed sal word te verander. Die Munisipaliteit Stellenbosch staan voor ’n dilemma omdat die huidige bestuur van sy werknemerbywoning ’n negatiewe uitwerking op sy daaglikse werksaamhede het – dienslewering word ’n al ernstiger saak weens die onvermoë om werknemers se daaglikse bywoningsresultate by onbekwame en ondoeltreffende lewering van dienste aan dorpsbewoners te bestuur. Hierdie navorsing ondersoek die vraagstuk of die omskakeling van ’n bywoningsregister per hand na ’n biometriese tyd- en bywoningstelsel die beskikbaarheid van munisipale werknemers meer effektief sal verseker om basiese dienslewering te verbeter. Hierbenewens het die dilemma van die Munisipaliteit Stellenbosch te doen met die daaglikse monitering van werknemers, waaronder die beskikbaarheid van ’n bywoningsregister vir ouditeringsdoeleindes. ’n Vraelys is gebruik om die situasie te ondersoek en reaksies te verkry van werknemers wat van die bywoningsregister per hand sowel as die biometriese tyd- en bywoningsinstrument gebruik maak. Daar is vasgestel dat die bywoningsregister per hand sekere probleme veroorsaak het, hoewel dit langer as 30 jaar ’n moniteringsdoel gedien het. Met die beantwoording van die vraelys het party respondente die implementering van ’n elektroniese stelsel met intydse vermoë versoek om enige twyfel omtrent die bevestiging van werknemerbywoning te verwyder. Die terugvoering van die vraelys bevestig: - die onbetroubaarheid van ’n menslik afhanklike werknemerbywoningsregister; - dat lewering van basiese dienste slegs kan plaasvind op voorwaarde van die beskikbaarheid van werknemers wat vir diens aanmeld; en - dat die gebruik van die bywoningstelsel per hand onverhaalbare verliese skep. Die onvermoë van werknemers om hul bywoningsregisters per hand by te hou het gelei tot die aanbeveling dat: - ’n gemeganiseerde stelsel geïmplementeer moet word om administratiewe prosedures te verminder; en om ’n ongekwalifiseerde ouditering te verseker.