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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Photon flux monitor for a mono-energetic gamma ray source

Mavrichi, Octavian 25 March 2010 (has links)
A novel photon flux monitor has been designed and tested for use at the Duke University High Intensity Gamma Source, where the photon beam produced is essentially mono-energetic but it is not tagged. Direct counting of the number of photons using a high-efficiency detector is not possible because of the high photon fluxes expected. Therefore, a direct counting detector with a low, accurately known efficiency was required.<p> The photon flux monitor based on a five scintillator paddle system detects recoil electrons and positrons from photoelectric, Compton and pair-production processes. It has been designed to be insensitive to gain and detector threshold changes and to be usable for photon energies above 5 MeV. It has been calibrated using direct counting with a NaI detector and its efficiency has been shown to be well predicted by a GEANT4 simulation.<p> Results of measurements, calibration and calculations required to characterize the 5-paddle photon flux monitor are presented. The photon flux monitor has met its design specifications of being able to determine the number of photons incident on it during the live time of a measurement to within a systematic error of 2%.<p> A paper based on the work for this thesis has been published in the Nuclear Instruments and Methods in Physics Research Journal.
92

The Studying about Major Factors of Manufacture in LED Backlight Module

Chen, Chun-Ho 17 June 2010 (has links)
In the LCD display products source section LED light display product is OK to replace the traditional CCFL light display products, especially in the NB computer and computer monitor are almost over two to three years CCFL products will be completely out of the market. The LCD itself does not glow and need another light source to support it. Backlight module can provide light source to LCD display product. In the early the light source of backlight module is CCFL. But LED light source is going to replace CCFL from 2007. Most of all new developments in the field of the NB computer backlight module changes light source from CCFL to LED. Even the computer monitor light source is starting to use LED too. The development technologies and production quality of the LED backlight module are significant challenges in LED backlight module factory. The purpose of this study was to identify development technologies and production technologies factors of bottlenecks, and finding a solution. And can provide some help to LED backlight module industry terms. This study selects ' 8D process ' to be analysis model. And collect 5 backlight module factories development experience and production status data. Hope these data through 8D analysis process can find the major related factors of development technologies and production technologies. In-depth research, look forward to finding out the production technologies relevant factors oppression ' technical specification ' production. This study is expected to be able to find some effect LED backlight module process yield factor, then apply the stratification out product issues and process issues, this study is intended for process issue do take an in-depth look at the problem and solution, but about product issue will be' design solutions ' way to describe. I believe this research can help LED backlight module industry to reduce production cost and improve the development speed.
93

The Relationship between Perceptions of Organization Politics and Career Planof HR¡GThe Moderating Effects of Self-Monitor and Political Skill

Tsai, Chia-ling 05 October 2009 (has links)
This purpose of the research is mainly at the investigation of the relationship between the perceptions of organization politics and career plan of HR. Moreover, we discuss that ¡§self-monitor¡¨ and ¡§political skill¡¨ had the moderating effect on the relationship between perceptions of organization politics and career plan of HR or not. The results give insights for theory building and give references for human resource development practice. We send out 199 questionnaires and get 175 returned ones. The return rate is 87.93%. The data respectively by methods and so on factor analysis, reliability analysis, ANOVA, t-test, correlation analysis, multiple linear regression and hierarchical regression analyzes. The result is indicated as below: ¤@¡BThe perceptions of organization politics and career plan of HR are portion related. ¤G¡BThe self-monitor does not have disturbance of effect the whole to the perceptions of organization politics and career plan of HR. ¤T¡BThe political skill does have portion disturbance of effect the whole to the perceptions of organization politics and career plan of HR.
94

A calibration neutron monitor for long-term cosmic ray modulation studies / H. Krüger

Krüger, Helena January 2006 (has links)
The propagation of high-energy cosmic rays is influenced by the time-varying heliospheric magnetic field embedded in the solar wind, and by the geomagnetic field. To penetrate through this geomagnetic field, they must have a rigidity that exceeds the geomagnetic cutoff rigidity for a given position on the earth. In the atmosphere, the primary cosmic rays interact with atmospheric nuclei, to form a cascade of secondary particles. Neutron monitors record these secondary cosmic rays, mainly the neutrons, with energies about a decade higher than detected by most spacecraft. Since neutron monitors are integral detectors, each with its own detection efficiency, energy spectra cannot readily be derived from their observations. One way to circumvent this is by conducting latitudinal surveys with mobile neutron monitors. Another way is to use the worldwide stationary neutron monitor network, but then the counting rates of these monitors must be normalised sufficiently accurate against one another. For this reason two portable calibration neutron monitors were built at the Potchefstroom campus of the North-West University and completed in 2002. To achieve sufficient calibration accuracy, several properties of the calibrator are investigated in this work. Effects such as atmospheric pressure variations, diurnal variations, short-term scintillations, and multiplicity, contribute to the fluctuations of the counting rate of a neutron monitor. Due to these effects, the coefficient of variation of the calibrator is determined to be -40% larger than the Poisson deviation. The energy response of the calibrator over the cutoff rigidity interval from the poles to the equator is investigated, with the result that it is almost 4% larger than that of a standard 3NM64 neutron monitor. It is also determined that not only the calibrator, but also the stationary NM64 and IGY neutron monitors, have fairly large instrumental temperature sensitivity, which must be accounted for in calibration procedures. Furthermore, the calibrator has a large sensitivity to the type of surface beneath it, influencing its counting rate by as much as 5%. This investigation is incomplete and requires further experimentation before the calibration of the stationary neutron monitors can start. When calibrations of a significant number of the worldwide neutron monitors are done, their intensity spectra as derived from differential response functions, will provide experimental data for modulation studies at rigidities above 1 GV. / Thesis (Ph.D. (Physics))--North-West University, Potchefstroom Campus, 2006.
95

Real-time beam-profile monitor for a medical cyclotron

Hoehr, C., Hendriks, C., Uittenbosch, T., Cameron, D., Kellog, S., Gray, D., Buckley, K., Verzilov, V., Schaffer, P. 19 May 2015 (has links) (PDF)
Introduction Measuring the beam profile on a medical cyclo-tron in real time can aid in improved tuning of the cyclotron and give important information for a smooth operation. Typically the beam profile is measured by an autoradiography technique or even by a scintillator that can be viewed in real time [1, 2]. Another method is to use collimators in front of the target to assess the beam center-ing [3]. All these methods have potential draw-backs including; an inability to monitor the beam in real time for the radiograph, exhibiting a non-linear correlation in signal response to the power deposited for a scintillator, and not providing a 2-dimensional profile of the complete beam for collimators. Our goal was to design a realtime, linear, 2-dimensional beam-profile monitor that is able to withstand the high power of a PET cyclotron. Material and Methods The beam-profile monitor (PM) is designed for the TR13, a 13MeV negative hydrogen-ion cyclotron at TRIUMF. The design follows the concept of a ‘harp’ monitor, widely used at TRIUMF for tuning proton and radioactive ion beams, and is installed on the extraction port without separation from the tank vacuum. The TR13 monitor is designed to withstand a 13 MeV proton beam with a beam current of up to 25 µA, has an active area of 10 by 10 mm and does not affect the 10-7 torr tank vacuum. The device consists of a water-cooled Faraday cup made out of aluminium for low activation and two orthogonal rows of eight tungsten electrodes each mounted on a water-cooled support frame. Electrodes are spaced 1 mm apart from each other, see FIG. 1. The electrodes are electrically isolated from each other and each has a current pickup soldered to it. The material and the shape of the electrodes are optimized to withstand the deposited power of the proton beam. A voltage of -90 V is applied to the electrodes to repel secondary electrons and prevent crosstalk between neighbouring electrodes. The electrode current is amplified using a custom current amplifier, and read by an ADC. From there, the current data is displayed on a PC. This allows one to observe changes of the beam profile in real time. The electronics are designed to read out all sixteen channels in parallel, or, if only a limited number of ADC channels are available, to cycle through the different channels. In our current setup all sixteen channels are read out simultaneously. Results and Conclusion The beam-profile monitor provides a real-time representation of the proton beam, see FIG. 2. The data can also be recorded and analyzed at a later time. The linearity of the monitor has been measured up to 30 µA of proton beam current [4]. With the use of the monitor, it was possible to increase the output of the ion source into the target by 50% in comparison to the standard tune.
96

A calibration neutron monitor for long-term cosmic ray modulation studies / H. Krüger

Krüger, Helena January 2006 (has links)
The propagation of high-energy cosmic rays is influenced by the time-varying heliospheric magnetic field embedded in the solar wind, and by the geomagnetic field. To penetrate through this geomagnetic field, they must have a rigidity that exceeds the geomagnetic cutoff rigidity for a given position on the earth. In the atmosphere, the primary cosmic rays interact with atmospheric nuclei, to form a cascade of secondary particles. Neutron monitors record these secondary cosmic rays, mainly the neutrons, with energies about a decade higher than detected by most spacecraft. Since neutron monitors are integral detectors, each with its own detection efficiency, energy spectra cannot readily be derived from their observations. One way to circumvent this is by conducting latitudinal surveys with mobile neutron monitors. Another way is to use the worldwide stationary neutron monitor network, but then the counting rates of these monitors must be normalised sufficiently accurate against one another. For this reason two portable calibration neutron monitors were built at the Potchefstroom campus of the North-West University and completed in 2002. To achieve sufficient calibration accuracy, several properties of the calibrator are investigated in this work. Effects such as atmospheric pressure variations, diurnal variations, short-term scintillations, and multiplicity, contribute to the fluctuations of the counting rate of a neutron monitor. Due to these effects, the coefficient of variation of the calibrator is determined to be -40% larger than the Poisson deviation. The energy response of the calibrator over the cutoff rigidity interval from the poles to the equator is investigated, with the result that it is almost 4% larger than that of a standard 3NM64 neutron monitor. It is also determined that not only the calibrator, but also the stationary NM64 and IGY neutron monitors, have fairly large instrumental temperature sensitivity, which must be accounted for in calibration procedures. Furthermore, the calibrator has a large sensitivity to the type of surface beneath it, influencing its counting rate by as much as 5%. This investigation is incomplete and requires further experimentation before the calibration of the stationary neutron monitors can start. When calibrations of a significant number of the worldwide neutron monitors are done, their intensity spectra as derived from differential response functions, will provide experimental data for modulation studies at rigidities above 1 GV. / Thesis (Ph.D. (Physics))--North-West University, Potchefstroom Campus, 2006.
97

A GPS-based method for pressure corrections to neutron monitor data / Izak G. Morkel

Morkel, Izak Gerhardus January 2008 (has links)
Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2008.
98

A GPS-based method for pressure corrections to neutron monitor data / Izak G. Morkel

Morkel, Izak Gerhardus January 2008 (has links)
Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2008.
99

Physical activity assessed by accelerometry in children

Nilsson, Andreas January 2008 (has links)
Physical activity (PA) is likely to constitute an important aspect of health-related behaviour in growing children. However, the knowledge on levels and patterns of PA in children is limited, due to the difficulty of precisely measuring this complex behaviour in normal daily living. Information on variables that significantly contributes to the variability in PA patterns is warranted as it may inform strategies for promoting physically active lifestyles in school-age youth. The overall purpose of the present studies was to increase the knowledge about the use of accelerometry when assessing PA in children, and examine sources of variability in objectively assessed PA behaviour in children. The study samples included 1954 nine- and 15-year-old children from four geographical locations in Europe (Norway, Denmark, Estonia and Portugal), and additionally 16 Swedish seven-year-old boys and girls. PA was assessed by the MTI accelerometer during free-living conditions, including both weekdays and weekend days. A part of the PA assessment was conducted using different time sampling intervals (epochs). Predictions of estimates of daily energy expenditure from accelerometer output were calculated using previously published equations. Potential correlates of PA behaviour were assessed by self-report. The main findings were; a) the epoch setting had a significant effect when interpreting time spent at higher intensities of PA in young children, b) predicted energy expenditure differed substantially between equations, c) between- and within-day differences in overall levels of PA, time spent at moderate-to-vigorous intensity physical activity and time spent sedentary differed between age, gender and geographical location, d) outdoor play and sports participation were differentially associated with objectively measured PA in 9- and 15-year-old children. It is concluded that the sporadic nature of children’s physical activity require very short epoch settings for detecting high intensity PA, and that different published equations for estimations of daily energy expenditure cannot be used interchangeably. The interpretations of average energy expenditure from available equations should be made with caution. Based on a large sample of children of different ages, weekend days and leisure time during weekdays seem appropriate targets when promoting PA in order to increase the proportion of children achieving current recommendations on health enhancing PA. Further, significant correlates of PA behaviour dependent on age group are presented, which should be considered when planning interventions for promoting PA in school-age youth.
100

VISUOMENĖS VAISTINĖS PACIENTŲ INFORMAVIMUI SKIRTAME MONITORIUJE ESANČIOS REKLAMOS IR INFORMACIJOS ĮTAKA VAISTŲ PASIRINKIMUI / THE ADVERTISEMENT AND INFORMATION IN THE MONITOR DEDICATED FOR INFORMING OF PATIENTS IN PUBLIC PHARMACIES AND INFLUENCE TO THE CHOICE OF DRUGS

Petrošiūtė, Monika 18 June 2014 (has links)
Tyrimo tikslas Ištirti paciento informavimui skirto monitoriaus įtaką vaistų pasirinkimui. Tyrimo uždaviniai Atlikti vaistinės pacientų stebėjimą ir išsiaiškinti dažniausiai naudojamus informacinius šaltinius apie vaistus; Nustatyti, ar skiriasi pacientų, kurie naudojasi/nesinaudoja, monitoriaus teikiama informacija apsilankymo vaistinėje ir vaistų vartojimo dažnis, vaistų pirkimo bei pasirinkimo būdai; Įvertinti, ar pacientai pastebi reklamas monitoriuose; Išanalizuoti priežastis, lemančias kokį informacijos turinį pacientas pastebėjo monitoriuje; Apibendrinti gautus rezultatus ir pateikti rekomendacijas. Tyrimo metodai Teorinis analizės metodas - apžvelgtos ir aprašytos mokslinės publikacijos ir tyrimai, susiję su analizuojama tema. Empirinis analizės metodas - pasirinktas stebėjimo metodas. Statistiniai analizės metodai - atlikta naudojant SPSS 17.0, Microsoft Office Excel programas. Tyrimo dalyviai Pacientai, perkantys receptinius/nereceptinius/kompensuojamuosius vaistus. Tyrimo rezultatai 2011 m. Lietuvoje ieškodami informacijos apie vaistus internetu naudojosi 41 proc. pacientų, 2014 m. šis skaičius išaugo iki 69 proc. 2009 m. duomenimis 57 proc. JAV gyventojų naudojosi internetu ieškodami informacijos apie vaistus. Lietuvoje 85 proc. populiariausias informacijos šaltinis apie vaistus yra vaistininko konsultacija. Moterys labiau pastebi maisto papildų reklamas ir vaistinės (tinklo) pavadinimą, vyrai – vaistų reklamas ir taip pat vaistinės (tinklo) pavadinimą... [toliau žr. visą tekstą] / The aim To investigate the influence of monitor for patient on drug choice. Objectives of the study To analyze the various countries experience of information to patients in pharmacies regulation of Lithuania on the patient information for the monitor; Perform data collection in pharmacies and the monitor on drug choice; Identify where the information contained in the monitor does/does not influence the choice of drugs; The findings of the survey results to compare with each other for patients looked at the monitor/not looked at the monitor; Summarize the results and make recommendations. The methods Theoretical analysis method - an overview and description of scientific publications and studies related to the topic under consideration. Empirical analysis method - a prospective observational study. Statistical analysis methods - was performed using SPSS 17.0, Microsoft Office Excel applications. The study participants Patients who buy prescription/non-prescription/reimbursable drugs. The results In 2011. in Lithuania patients looking for information about medications 41% used internet, in 2014 this number increased to 69%. In 2009 – 57% of patients in USA used the internet to search for information about drugs, in Lithuania it was 85%. Most popular source of information on drugs is a medical consultation. Women becoming aware of food supplements and pharmacy commercial adverts (pharmacy network) brand name, for men – pharmacy commercials and as well as pharmacies... [to full text]

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