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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.
181

Spectral energy distribution fitting of the bulge and disk components of interacting galaxies

Palmer, Michael J. D. 23 August 2012 (has links)
We perform spectral energy distribution fitting to the total integrated light, bulge and disk components of ≈ 650,000 spectroscopically selected galaxies from the sloan digital sky survey data release 7. Using 4-band photometry (u, g, r, i) we derive physical properties for these components with particular emphasis placed on the star formation rates (SFR) and stellar masses. Using the total integrated fits as an indicator of the goodness of fit, we show that reliable estimates of the SFR can be recovered using a specific SFR (sSFR) cut of log(sSFR /yr) ≥ −10.45. We construct a close pairs sample and match isolated controls based on stellar mass, z and local density for galaxies that pass the sSFR cut. We develop a method to cross correlate the pair galaxies’ star formation rate posterior probability distribution functions (SFR PDFs) with the control SFR PDFs as a function of the pair galaxies projected separation, rp. We show that the SFR of the close pair galaxies is enhanced relative to the control sample. The SFR enhancement is at a level of ≈ 0.25 dex above that of the control at the closest separations and declines to a plateau at ≈ 0.15 dex for separations of 30 < rp < 60 kpc/h. Between 60 < rp < 80 kpc/h there appears to be a slight increase in the enhancement to a level ≈ 0.25 dex above the control. It is suggested that we observe this increase, where other studies have failed to, based on the updated photometry provided by Simard et al. (2011). From our total pair sample we also select a subsample of galaxies that are classified as active galactic nuclei (AGN). We note that at close separations the pair AGN galaxies have enhanced SFRs relative to their matched controls. The SFR enhancement is largest at the smallest separations, reaching a level of ≈ 0.3 dex above the control. The SFR enhancement for the AGN pairs becomes consistent with their controls at projected separations of 20 < rp < 80 kpc/h. We construct a bulge and disk pair sample that are required to pass the sSFR cut and match control bulges and disks, respectively, that also pass the sSFR cut. We cross correlate the bulge and disk pairs with their respective controls. We measure significant SFR enhancement in the bulge component of the interacting pairs. The SFR enhancement is highest at small separations, ≈ 0.4 dex, and steadily declines to ≈ 0.1 dex before turning around beyond rp > 50 kpc/h to again reach a level ≈ 0.4 dex above the control bulges. The disk SFR enhancement is relatively flat beyond rp > 30 kpc/h to a level ≈ 0.1 dex above the control and largely consistent with the control at close separations. The bulge and disk results suggest that the majority of induced star formation during an interaction is occurring in the bulge component, but that there is still slight SFR enhancement in the disk. We suggest that the upturn in the total and bulge SFR enhancement could potentially be caused by a delay between the interaction of the galaxy pairs and the onset of induced star formation. / Graduate
182

Procedural Skill Initiation, Chunks & Execution; Contributions of Offline Consolidation

Bhatia, Sanjeev Rai 02 October 2013 (has links)
It has been suggested that improvement in the performance of many motor sequence tasks such as playing musical instruments, operating complex machinery or tools, and/or performing a variety of athletic activities results from the learner’s ability to parse the movement into fundamental action primitives called motor chunks. Moreover, it has been suggested that the organization of motor chunks within a sequential behavior can be influenced by consolidation occurring outside the boundary of practice during which reorganization can occur leading to faster sequence production. The present study involved modest practice of a discrete sequence production task (DSPT) followed by subsequent assessment of performance of this task either immediately after the completion of practice or after a 24-hr delay. Of critical interest was the change in performance from the end of training to the test phase in three features of the sequence implementation namely sequence initiation, motor chunk transition, and element execution components. It was anticipated that motor chunk transition would be susceptible to significantly greater offline enhancement in the 24-hr delayed test case. Based on the extant literature it was also expected that sequence initiation and/or execution processes may also be sensitive to offline consolidation. No evidence emerged that supported the proposal that motor chunk transitions revealed additional gains following a longer interval between training and test. It is possible this effect was underestimated because of some imprecision in the manner in which motor chunk transitions were identified. There was clear evidence for offline gains for both sequence initiation and element execution processes. These data are difficult to interpret within the framework of a number of contemporary accounts of sequence production such as the dual-processor model in which sequence production is governed by a cognitive and motor processor.
183

Radar as a remote sensor of regions of supercooled cloud water

Massambani, Oswaldo. January 1982 (has links)
A new technique, named Vertical Profile Indicator (VPI), which uses the vertical structure of the reflectivity profile to delineate regions most likely to have supercooled liquid water content (SCLWC) within the precipitation field, was developed. When the aircraft flew in the "active regions" (as defined by the VPI technique) it was found that 90% of the time significant amounts of SCLWC were observed. / Using Doppler and "Quasi-Doppler" radar data, high convergence cores (> 3.0 x 10('-3) s('-1)) and updraft activity were observed to occur preferentially in the "active regions". During the 1981 winter-spring period of the Precipitation Enhancement Project in the Duero Basin of Spain percentages of "active regions" in relation to the whole precipitation field, and in relation to the total radar observation area, did not exceed 47% and 18% respectively. / The VPI technique provides information which may be used to direct research aircraft to cloud regions containing SCLWC to allow measurements of the time evolution of their microphysical state. These measurements would permit a better estimation of the residence time of the SCLWC and its removal rates. This is a key parameter for better understanding the microphysical properties of clouds and consequently the possibility of artificial modification of precipitation.
184

Public attitudes towards ethical issues raised by biotechnologies that may substantially extend human life.

Bradley Partridge Unknown Date (has links)
Demonstrations that ageing and life-span can be manipulated in model animal species have increased hopes that the length of the human life-span may also be dramatically extended. The possibility of human life-span extension has provoked debate amongst bioethicists. Proponents of life-extension cite the benefits of a longer and healthier life. Opponents argue that these technologies: violate human nature; may not necessarily increase the quality of life; and, they will lead to overpopulation and social strife that outweighs any benefits to individuals. Others see problems of equity and justice in access to any potential life-extension technologies. The attitudes of members of the public have largely been neglected in ethical and policy discussions of human life-extension. In the absence of empirical evidence on public attitudes, proponents and opponents have assumed either widespread public enthusiasm for life-extension or strong opposition because of concerns about its moral acceptability or its adverse social consequences. All agree that public attitudes could be a powerful facilitator or a major obstacle to the development of life-extending technologies. The goal of this thesis is to characterise public attitudes towards life-extension and describe factors that influence these views. It examines the following questions: (1) What is the prevalence of public support for (or opposition to) life-extension research? (2) How much interest is there among the public in using a technology that could increase life-span by slowing ageing? (3) What issues are important to members of the public in forming their attitudes? (4) What ethical issues, if any, do members of the public identify? (5) Are these ethical and moral issues the same ones expressed by ethicists and social scientists? (6) How do these ethical attitudes affect their overall interest in, or support for, life-extension? (7) How are attitudes towards life-extension related to demographic characteristics such as age, gender, education, and religious beliefs? Three empirical studies were designed using a mixed methodology to answer these questions. Study 1 (focus groups) and Study 2 (individual interviews) were qualitative investigations of public attitudes towards life-extension. The results of these two studies informed the design of Study 3 - a quantitative survey of attitudes towards life-extension via telephone interviews with 605 adult members of the Australian public. Participants in Study 3 were presented with a vignette outlining the prospect of a life-extension pharmaceutical that could increase life-span to 150 years by slowing the ageing process. They were then asked to express their level of agreement with a series of statements about ethical, social and personal implications of life-extension, and their overall support and interest in using such a technology. All three studies found mixed public attitudes towards the development and use of life-extension technologies. Participants in Studies 1 and 2 were concerned about whether life-extension would be accompanied by good quality of life. Studies 1 and 2 also suggested that participants were concerned about social and ethical issues that included: the potential impact on society; whether life-extension was “natural”; and whether access to life-extension technologies would be fair and equitable. Study 3 confirmed the diversity of public views identified in the qualitative phase. While 65% supported such research, only 35% said that they would use a life-extension technology if one became available. Men were more supportive of research and more disposed to use life-extension technologies than women. 58% of participants expressed ethical or moral concerns about life-extension technologies. When asked to weigh up the potential benefits and negatives that they identified as important, almost half (48%) said that life-extension technologies would do more harm than good to society, and 40% thought that taking a life-extension pharmaceutical would do them more harm than good personally. Study 3 also showed that valid scales could be constructed to assess the strength of concerns about social and ethical issues. These scales were: personal benefits/negatives; social benefits/negatives; and natural concerns. Higher levels of support for using and developing life-extension technologies were associated with higher levels of perceived personal and societal benefits from life-extension. Participants who had more ethical concerns, and perceived more personal and social negatives were less likely to support or express an interest in using life-extension technologies. Perceptions of personal and social benefits, and having concerns about the “naturalness” of life-extension were the best predictors of support or interest in using life-extension technologies. This thesis shows that public attitudes towards life-extension are more varied than some ethicists have assumed. While there are substantial minorities who were clearly “pro” or “con”, many members of the public are concerned about ethical and social issues. It would be unwise for researchers of life-extension not to take account of public attitudes and concerns if they hope to foster public support for their work.
185

Μελέτη επίδρασης μεθόδων ενίσχυσης εικόνας στο χαρακτηρισμό αλλοιώσεων στη μαστογραφική απεικόνιση

Τσάκωνας, Ιωάννης 14 December 2009 (has links)
Στη παρούσα διπλωματική εργασία έχοντας σα βάση το γεγονός ότι η μαστογραφία αποτελεί την καλύτερη τεχνική έγκαιρης ανίχνευσης του καρκίνου του μαστού και ότι το μέγιστο όφελος της μαστογραφίας βρίσκεται στην πρώιμη ανίχνευση του καρκινώματος στα αρχικά στάδιά του, ασχοληθήκαμε με την ανάλυση και εφαρμογή μεθόδων ψηφιακής επεξεργασίας εικόνας, που εφαρμόζονται στη μαστογραφία. Ορίσαμε και αναλύσαμε τους διάφορους αλγόριθμους ενίσχυσης εικόνας, που στηρίζονται στην ενίσχυση αντίθεσης μέσω: (α) αύξησης των διαβαθμίσεων του γκρι σε συγκεκριμένες υπό περιοχές (π.χ. μέθοδος παραθύρου, εξίσωση ιστογράμματος) (μέθοδοι ενίσχυσης αντίθεσης) (β) αύξησης των διαφορών διαβάθμισης του γκρι της εικόνας, που αντιστοιχούν στην ενίσχυση της παρυφής της εικόνας, που συνήθως παρέχεται από φίλτρα που υλοποιούν τελεστές παραγώγου εικόνας (μέθοδοι ενίσχυσης αιχμών). Οι τεχνικές ενίσχυσης εικόνας που χρησιμοποιήσαμε στα πλαίσια της παρούσας Διπλωματικής Εργασίας είναι η Μέθοδος παραθύρου (Intesity Windowing), η Εξισορρόπηση Ιστογράμματος με ψαλίδισμα (Clipped Adaptive Histogram Equalization) και η Καταστολή θορύβου-Ενίσχυσης παρυφής με μέθοδο μετασχηματισμού κυματίου (Wavelet). Πριν την εφαρμογή των μεθόδων ενίσχυσης εικόνας στις μαστογραφικές εικόνες ήταν αναγκαία η δημιουργία ψηφιακών συνθετικών εικόνων οι οποίες μιμούνται τα παθολογικά ευρήματα και μέσω αυτών εξάγουμε τις βέλτιστες παραμέτρους που θα χρησιμοποιηθούν στις μεθόδους ενίσχυσης εικόνας. Αυτό το πετύχαμε κάνοντας χρήση των ποσοτικών δεικτών αξιολόγησης ποιότητας εικόνας. Οι δείκτες αυτοί στηρίχτηκαν σε μετρήσεις θορύβου και αντίθεσης για συγκεκριμένη περιοχή ενδιαφέροντος μαστογραφικής εικόνας και είναι ο Δείκτης Βελτίωσης Αντίθεσης (Contrast improvement index-CII), ο Δείκτης Ενίσχυσης Θορύβου (Noise amplification index- NAI) και ο λόγος CII/NAI (Contrast to noise ratio index -CNRI). Στη συνέχεια κάνοντας χρήση των βέλτιστων παραμέτρων ενίσχυσης εικόνας που βρήκαμε μέσω των ποσοτικών δεικτών, ενισχύσαμε το δείγμα των 105 μαστογραφικών εικόνων (περιοχής ενδιαφέροντος) και με τη βοήθεια ακτινολόγου προχωρήσαμε στο πειραματικό στάδιο της Διπλωματικής Εργασίας αξιολογώντας τις μαστογραφικές εικόνες με βάση το σύστημα BIRADS του ACR. Τελευταίο βήμα της μελέτης μας αποτέλεσε η διαγνωστική ακρίβεια του ακτινολόγου βασιζόμενη στη ROC καμπύλη. Υπολογίσαμε το εμβαδό κάτω από την καμπύλη ROC για κάθε μέθοδο ενίσχυσης ξεχωριστά αλλά και για τις αρχικές μαστογραφικές εικόνες στις οποίες είχαμε τις εκτιμήσεις από δύο ακτινολόγους. / In the present postgraduate thesis, we studied the application of image enhancement methods in X-ray mammography, the best technique for detection of breast cancer in early stages. We defined and analyzed the various algorithms of mammographic image enhancement, which are based in contrast enhancement: (a) Increasing the differences in grey level values in specific regions (Intensity Windowing, Histogram Equalization), called contrast enhancement methods. (b) Increasing the gradation of the differences of grey level values of regions that correspond in edge enhancement, provided by filters such applying first or second order derivatives, called edge enhancement methods). Three image enhancement methods were used in the present study, Manual Intensity Windowing (MIW), the Contrast-Limited Adaptive Histogram Equalization (CLAHE) and a dual-stage (denoising and enhancement) Adaptive Wavelet-based Enhancement method (WAVELET). Before applying the three image enhancement methods in mammographic images (regions of interests, ROIs), it was necessary to determine the optimal values of parameters that will be used in image enhancement methods. Digital synthetic images simulating pathological findings, such as microcalcification clusters, were developed for the determination of optimal values of parameters for CLAHE and WAVELET of the image enhancement methods. This was achieved by using quantitative metrics for image quality evaluation. These metrics were based on measurements of noise and contrast for a specific ROI in mammographic images containing the simulated microcalcification clusters. These metrics are: Contrast Improvement Index (CII), Noise Amplification Index (NAI) and the Contrast-to-Noise Ratio Index (CNRI). For the two image enhancement methods (CLAHE and WAVELET) the optimal values of parameters were used, while for MIW a radiologist manually determined the values of parameters (centre and level of windowing) for enhancing the sample of 105 mammographic images (ROIs) containing microcalcification clusters. Evaluation of the three image enhancement methods was performed based on BI-RADS of ACR for patient management determined by one radiologist. Last step of our study was to estimate the diagnostic accuracy of radiologist based on ROC analysis. We calculate the area under ROC curve for each enhancement method, as well as for the initial mammographic images (original).
186

Ενίσχυση ήχων κάτω από περιβάλλον θορύβου

Αθανασίου, Γεωργία 08 July 2011 (has links)
Στόχος της συγγραφής αυτής της διπλωματικής εργασίας είναι η μελέτη των διαδικασιών μέσω των οποίων πραγματοποιείται η ενίσχυση ήχου κάτω από περιβάλλον θορύβου. Γίνεται εισαγωγή στις βασικές έννοιες του speech enhancement και ανάλυση των τεχνικών αποθορυβοποίησης. Επίσης γίνεται μελέτη των αρχών και μεθόδων αξιολόγησης Αναβαθμισμένων Ενθόρυβων Σημάτων. Όλα αυτά ολοκληρώνονται από τον αντίστοιχο κώδικα στο Matlab. / The main goal of this project is the study of the premium techniques of speech enhancement and explore the way that they are evaluated.
187

Performance improvement for stochastic systems using state estimation

Zhou, Yuyang January 2018 (has links)
Recent developments in the practice control field have heightened the need for performance enhancement. The designed controller should not only guarantee the variables to follow their set point values, but also ought to focus on the performance of systems like quality, efficiency, etc. Hence, with the fact that the inevitable noises are widely existing during industry processes, the randomness of the tracking errors can be considered as a critical performance to improve further. In addition, due to the fact that some controllers for industrial processes cannot be changed once the parameters are designed, it is crucial to design a control algorithm to minimise the randomness of tracking error without changing the existing closed-loop control. In order to achieve the above objectives, a class of novel algorithms are proposed in this thesis for different types of systems with unmeasurable states. Without changing the existing closed-loop proportional integral(PI) controller, the compensative controller is extra added to reduce the randomness of tracking error. That means the PI controller can always guarantee the basic tracking property while the designed compensative signal can be removed any time without affecting the normal operation. Instead of just using the output information as PI controller, the compensative controller is designed to minimise the randomness of tracking error using estimated states information. Since most system states are unmeasurable, proper filters are employed to estimate the system states. Based on the stochastic system control theory, the criterion to characterise the system randomness are valid to different systems. Therefore a brief review about the basic concepts of stochastic system control contained in this thesis. More specifically, there are overshoot minimisation for linear deterministic systems, minimum variance control for linear Gaussian stochastic systems, and minimum entropy control for non-linear and non-Gaussian stochastic systems. Furthermore, the stability analysis of each system is discussed in mean-square sense. To illustrate the effectiveness of presented control methods, the simulation results are given. Finally, the works of this thesis are summarised and the future work towards to the limitations existed in the proposed algorithms are listed.
188

Enhancement, Commodification, and Human Flourishing

January 2012 (has links)
abstract: At present, the ideological bias in the human enhancement debate holds that opponents to human enhancement are primarily techno-conservatives who, lacking any reasonable, systematic account of why we ought to be so opposed, simply resort to a sort of fear-mongering and anti-meliorism. This dissertation means to counteract said bias by offering just such an account. Offered herein is a heuristic explanation of how, given a thorough understanding of enhancement both as a technology and as an attitude, we can predict a likely future of rampant commodification and dehumanization of man, and a veritable assault on human flourishing. / Dissertation/Thesis / Ph.D. Philosophy 2012
189

Self-esteem, motivation, and self-enhancement presentation on WeChat

Qiu, Xiao 23 March 2018 (has links)
The purpose of the present study was to analyze whether self-esteem stability moderated the association between self-esteem level and the forms of self-enhancement strategies. Previous research has found that self-esteem level can predict the forms of self-enhancement, whereas the advances in the conceptualization of self-esteem recommend that the self-esteem stability is another essential variable in terms of analyzing the relationship between self-esteem and self-enhancement. Depending on the relevant researches on use and gratification theory, which indicate that people use social media for self-enhancement and fulfilling their inner needs. This research focused on examining the forms of individual’s self-enhance on WeChat Circle of Friends (COF) and how it influenced by the interaction between self-esteem level and self-esteem stability by analyzing 305 participants in China. The results of the study show that both self-esteem level and stability was positively correlated with direct self-enhancement, but negatively correlated with indirect self-enhancement. Furthermore, the findings also show that self-esteem stability moderated the association between self-esteem level and direct self-enhancement such that individuals with stable high self-esteem reported higher levels of frequency in direct self-enhancement. However, the findings also revealed the self-esteem stability failed to moderate the association between self-esteem level and indirect self-enhancement presentation. These results suggest that self-esteem level and self-esteem stability will interact to impact the forms of self-enhancement. The importance of considering both stability and level of self-esteem in analyses of self-enhancement presentation on social media is discussed.
190

Putting on a Show or Showing My True Self? When and Why Consumers Signal Accurate versus Enhanced Self-View Information

January 2016 (has links)
abstract: This research investigates the conditions under which people use consumption choices to signal accurate versus enhanced information about themselves to others. Across five studies, I demonstrate that activating a self-verification, as opposed to self-enhancement, motive leads consumers to choose products that signal accurate information about a self-view, even when this view is negative. I replicate this finding across several self-view domains, including physical attractiveness, power, and global self-esteem. However, I find that this effect is attenuated when consumers have a high fear of negative social evaluation. My findings suggest that this type of consumption, in which choice is driven by the desire to be seen accurately (vs. positively), can explain abundant real-world behavior; contradicting the notion that consumers choose products primarily for self-enhancement. / Dissertation/Thesis / Doctoral Dissertation Business Administration 2016

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