The holy grail of pure Wissenschaft: University ideal and university reform in post World War II Germany

Pepin, Craig Kristian Duke University 2001 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

After 1945, German university professors drew on traditional university ideals of apolitical science and individual self-cultivation (<italic>Bildung </italic>) to deny the involvement of their scholarship, and the universities, with National Socialism. These traditional university values furnished both the cognitive categories and the discursive strategies through which professors constructed an exculpatory interpretation of the recent past. They based this exonerating narrative on a rigid conceptual separation between “political” Nazism and “objective” scholarship, and a focus on spiritual and cultural renewal. On an individual level, these discursive strategies allowed academics to claim that during the Nazi period they had focused purely on their research and remained separate from politics and Nazism. By “proving” the scholarly nature of their work, they could then escape punishment in the denazification courts. Professors also reemphasized the individual character of self-cultivation by claiming that individual spiritual renewal, an internal rededication to traditional university ideals, offered the best response to Nazism in the universities. Such a move displaced questions of university reform from an institutional to an individual level, and effectively blocked administrative or structural change. This in turn reinforced the traditional power of senior professors within the universities, ensuring their position as privileged interpreters of the past. The reassertion of traditional power relationships allowed professors to perpetuate this exculpatory narrative and marginalize those who offered competing, more negative interpretations of the universities' recent past. The first part of the dissertation establishes the context in which this discourse was articulated by examining the German philosophy of higher education in the Weimar and Nazi eras, the changes in higher education imposed by the Nazis, and the American approach to occupation and reeducation. The remainder uses both published and archival material to examine the arguments used by German academics in denazification court trials, administrative meetings, and public venues to defend themselves as individuals, and to defend the institutions of the German university.

New method of phase-space tomography and its application to electron beam dynamics in storage ring FEL

Chalut, Kevin Duke University 2005 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The maximum lasing power achievable in a storage ring FEL is limited by the induced energy spread of the electron beam participating in the lasing process. In order to facilitate high peak power in the optical cavity at the Duke/OK-4 storage ring FEL, we have used giant pulses, which are obtained by using gain modulation. The use of giant pulses has allowed the expansion of the operational range of the Duke FEL into the vacuum ultraviolet region via the production of harmonics of the fundamental FEL wavelength. Numerical simulations of the giant pulse process performed by the #uvfel code have predicted a phase-space refreshing process whereby the synchrotron motion of the electrons moves heated electrons away from the interaction region and brings fresh electrons to it. Experimental verification of this process is necessary in order to enrich our knowledge of the physics at the Duke SRFEL. The giant pulse process, and particularly phase-space refreshment, occurs on a very: fast time scale compared to one-half of a synchrotron period. For phase-space tomography, previously existing methods have traditionally needed close to one-half of a synchrotron period's worth of projections in order to perform an accurate reconstruction of the phase-space density of a particle beam. Therefore, it was necessary to create a new method of phase-space tomography that would meet the needs brought about by the giant pulse process. The method we created for this purpose is called SVD-Based Tomography. A dual-sweep streak camera provides a set of equidistant linear projections of the electron beam, which we use for the purposes of phase-space reconstruction using SVD-Based Tomography. SVD-Based Tomography provides excellent reconstructions of the phase-space density of the electron beam during the giant pulse process using a very limited number of projections (as few as two, which is the minimum number of projections required for non-degeneracy). This algorithm is also promising for use in other medical and industrial applications, as it provides numerous upgrades over previously existing methods of tomographic reconstruction.

Characteristics of the duke/ok-4 storage ring FEL and gamma ray source

박성희 Duke University 2000 해외박사

The Duke/OK-4 storage ring is a dedicated device for driving a short wavelength Free Electron Laser (FEL). In addition, Compton scattering of the laser light from the circulating electron beam produces a semi-monochromatic γ-ray source. The dynamics of such a system including accelerator physics, FEL physics, and Compton backscattering is complex and requires special study. This dissertation is a detailed theoretical and experimental analysis of such a system. The main emphasis of the theory presented here is the self-consistent analysis of the system which incorporates three drastically different processes - the dynamics of an intense electron beam, the free electron laser, and the Compton backscattering. The interdependence of these three processes and the physics of this complex system is discussed in this work. The OK-4/Duke storage ring FEL is the only accelerator facility capable of routine lasing in the deep-UV range and able to generate intense γ-ray beams with energy tunable from 2 MeV to 55 MeV, with energy resolution between 0.5 % - 1 % and with flux up to ∼ 5 x 10^7. The flexibility of this γ-ray source is due to the recordbreaking performance of the OK-4/Duke storage ring FEL (lasing from 193.7 nm to 730 nm). Experimental studies determining the parameters of the electron beams, OK-4 FEL beams, and γ-ray beams compare favorably with the theoretical predictions. This study confirms that the electron energy spread induced by NFL lasing is currently the main factor limiting energy resolution. These results provide a solid foundation for futu e development of the system to obtain more reliable predictions of its performance. A number of useful "scaling laws" are also presented here. The results of this work have provided the basis for a number of applications of the OK-4 FFL beam and γ-ray beam that are underway or in the advance planning stage. Future plans include the development and design of a system capable of generating γ-ray beams with an energy resolution as low as 0.1 %. Future theoretical studies will determine the influence of γ-ray generation on the performance of improved storage ring FELs.

Precision measurements of deuteron photodisintegration using linearly polarized photons of 14 and 16 MeV

Blackston, Matthew Duke University 2007 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

A precision measurement of the d( g&ar; ,n)p reaction was performed at the High Intensity gamma-ray Source (HIgammaS), which is located at the Duke Free Electron Laser Laboratory on the campus of Duke University. The gamma-ray beams were nearly 100% linearly polarized, allowing the angular distributions of both the analyzing power and unpolarized cross section to be measured at 14 and 16 MeV. The photons were incident on a heavy water target and the neutrons from the photodisintegration reaction were detected using the Blowfish detector array, which consists of 88 liquid scintillator detectors with large angular coverage. A transition matrix element (TME) analysis was performed on the data which allowed the amplitudes of the TMEs which contribute to the reaction at these energies to be extracted. This was done by invoking Watson's theorem, which fixes the relative TME phases using the n-p scattering phase shifts, leaving the TME amplitudes as free parameters in fits to the data. The results indicated very good agreement with a recent potential model calculation for the amplitudes of the three electric dipole (E1) p-waves, which account for over 90% of the cross section at these energies. The extracted TME amplitudes were then used to construct the observable which enters into the Gerasimov-Drell-Hearn (GDH) sum rule integrand. The results are the first experimental indication of a positive value of the GDH integrand in the region near photodisintegration threshold. A positive value at these energies has been shown by theory to be due to relativistic contributions.

Playing Church: Toward a Behavioral Theological Understanding of Church Growth

Evers-Hood, Kenneth Scott Duke University 2014 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Just as biological life becomes more interesting and diverse when the edges of ecosystems meet, intellectual life crackles with energy and possibility when leaders from different disciplines collaborate. The recent emergence of behavioral economics, a fusion of economic theory with psychological cognitive theory, represents the best of what can happen when different fields collide. Behavioral economists combine the sophisticated and nuanced anthropology articulated by cognitive theorists such as Nobel laureate Daniel Kahneman with classical economic theory to offer more realistic models and expanded explanatory power, giving particular insight into why humans do not always behave in ways that are purely rational and self interested. I show that theological reflection and pastoral leadership, specifically, have much to gain by undertaking a similar 'behavioral turn' and exploring the insights cognitive theory offers. By exploring the nature and history of the behavioral turn in economics and then showing the relevance to Christology and theological anthropology, I lay the groundwork for a 'behavioral theology'. Behavioral theology sheds light on the Chalcedonian full divinity and humanity of Christ and underscores the view of sin as hubris. Behavioral theology also encourages pastors to see themselves as choice architects responsible for making decisions that help busy and tired congregants be the people they desire to be. Finally, I will demonstrate the experimental spirit of behavioral theology in a study of one facet of ecclesial life: church numerical growth and decline, using an approach inspired by behavioral game theory. With the permission of Duke's Independent Review Board I observed sessions, local church governing bodies in the Presbyterian Church (U.S.A.), play two versions of a public goods game to determine whether the willingness and ability of leaders to cooperate, defect, reward, and punish one another correlates to a congregation's ability to sustain membership.

Temporal Coding of Volumetric Imagery

Llull, Patrick Ryan Duke University 2016 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

'Image volumes' refer to realizations of images in other dimensions such as time, spectrum, and focus. Recent advances in scientific, medical, and consumer applications demand improvements in image volume capture. Though image volume acquisition continues to advance, it maintains the same sampling mechanisms that have been used for decades; every voxel must be scanned and is presumed independent of its neighbors. Under these conditions, improving performance comes at the cost of increased system complexity, data rates, and power consumption. This dissertation explores systems and methods capable of efficiently improving sensitivity and performance for image volume cameras, and specifically proposes several sampling strategies that utilize temporal coding to improve imaging system performance and enhance our awareness for a variety of dynamic applications. Video cameras and camcorders sample the video volume (x,y,t) at fixed intervals to gain understanding of the volume's temporal evolution. Conventionally, one must reduce the spatial resolution to increase the framerate of such cameras. Using temporal coding via physical translation of an optical element known as a coded aperture, the compressive temporal imaging (CACTI) camera emonstrates a method which which to embed the temporal dimension of the video volume into spatial (x,y) measurements, thereby greatly improving temporal resolution with minimal loss of spatial resolution. This technique, which is among a family of compressive sampling strategies developed at Duke University, temporally codes the exposure readout functions at the pixel level. Since video cameras nominally integrate the remaining image volume dimensions (e.g. spectrum and focus) at capture time, spectral (x,y,t,lambda) and focal (x,y,t,z) image volumes are traditionally captured via sequential changes to the spectral and focal state of the system, respectively. The CACTI camera's ability to embed video volumes into images leads to exploration of other information within that video; namely, focal and spectral information. The next part of the thesis demonstrates derivative works of CACTI: compressive extended depth of field and compressive spectral-temporal imaging. These works successfully show the technique's extension of temporal coding to improve sensing performance in these other dimensions. Geometrical optics-related tradeoffs, such as the classic challenges of wide-field-of-view and high resolution photography, have motivated the development of mulitscale camera arrays. The advent of such designs less than a decade ago heralds a new era of research- and engineering-related challenges. One significant challenge is that of managing the focal volume (x,y,z ) over wide fields of view and resolutions. The fourth chapter shows advances on focus and image quality assessment for a class of multiscale gigapixel cameras developed at Duke. Along the same line of work, we have explored methods for dynamic and adaptive addressing of focus via point spread function engineering. We demonstrate another form of temporal coding in the form of physical translation of the image plane from its nominal focal position. We demonstrate this technique's capability to generate arbitrary point spread functions.

Multi Stage Heavy Quark Transport in Ultra-Relativistic Heavy-Ion Collisions

Fan, Wenkai ProQuest Dissertations & Theses Duke University 2022 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The quark-gluon plasma (QGP) is one of the most interesting forms of matter providing us with insight on quantum chromodynamics (QCD) and the early universe. It is believed that the heavy-ion collision experiments at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) have created the QGP medium by colliding two heavy nuclei at nearly the speed of light. Since the collision happens really fast, we can not observe the QGP directly. Instead, we look at the hundreds or even thousands of final hadrons coming out of the collision. In particular, jet and heavy flavor observables are excellent probes of the transport properties of such a medium. On the theoretical side, computational models are essential to make the connections between the final observables and the plasma. Previously studies have employed a comprehensive multistage modeling approach of both the probes and the medium.In this dissertation, heavy quarks are investigated as probes of the QGP. First, the framework that describes the evolution of both soft and hard particles during the collision are discussed, which include initial condition, hydrodynamical expansion, parton transport, hadronization, and hadronic rescattering. It has recently been organized into the Jet Energy-loss Tomography with a Statistically and Computationally Advanced Program Envelope (JETSCAPE) framework, which allows people to study heavy-ion collision in a more systematic manner.To study the energy loss of hard partons inside the QGP medium, the linear Boltzmann transport model (LBT) and the MATTER formalism are combined and have achieved a simultaneous description of both charged hadron, D meson, and inclusive jet observables. To further extract the transport coefficients, a Bayesian analysis is conducted which constrains the parameters in the transport models.

The Psychology of Loyalty and its Impact on Harm Perception

Tang, Simone ProQuest Dissertations & Theses Duke University 2018 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This dissertation examines how people's loyalty to their groups influences their perception of harm. Specifically, people who are loyal (vs. not loyal) to their ingroup perceive negative actions by an outgroup against their group as more harmful. Three studies provided support for this hypothesis. Students loyal to their university's basketball team perceived greater harm from its rival basketball team than those who were not (Studies 1 and 2). The effect held controlling for related group constructs, such as group identification (Studies 1 and 2), and related moral constructs, such as belief in a just world (Study 1). The association between loyalty and harm perception generalized to a country context by showing that Americans more loyal to the United States were more likely to perceive foreign tariffs as harmful (Study 3). Rather than differences in memory recall or general negative perceptions of the outgroup, this effect appeared to be due to loyalists exaggerating the perceived harm inflicted (Studies 2 and 3). Furthermore, as perceptions of harm increased, desire for punitive actions also increased (Study 3).

Essays on the Economics of Higher Education: Investigating College Major Choice

Hopson, Amy Kathleen ProQuest Dissertations & Theses Duke University 2017 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This dissertation consists of two separate essays on major choice in higher education. In the first chapter, I investigate how differences in information affect students' major choices over time. Since college has such a short time horizon, the amount of information students have before coming in may play a big role in how well they are matched to their final major. They may also choose their initial major based on how uncertain they are about their match with that major, especially since they have the option to switch in future periods. This paper discusses students' search process in finding a major, and how information impacts behavior and ultimate outcomes. I set up a tiered structure where the student must first choose a field (either STEM or Non-STEM) and then choose a major within that field. This allows for matches within a particular field to be correlated, thus providing information on non-chosen majors within the same field. The student makes decisions based on the choices that will maximize her expected utility over her entire college career. Since her current choices and information set depend on past decisions, and since there are a finite number of periods, I can solve the dynamic decision problem using backwards recursion. Once I solve for the student's optimal decision path, I estimate the model using data from the Campus Life and Learning Survey from Duke University. The CLL data allows me to observe students' expected majors at multiple points throughout their college career. I attempt to find the model parameters that best match particular moments in the data. The first key type of moment involves overall switching patterns, that is, the probability of choosing a particular field in the initial period, and then the probabilities of later decisions conditional on the first choice. The second key type of moment I match captures which students are making which decisions. I look at how academic ability, as measured by SAT Math scores, and gender affect the choice probabilities in the data. I find that the STEM field has a much lower average match value than non-STEM, but a higher variance in matches. Thus, students are less certain about how well they might match with STEM. Students with higher math ability are more likely to choose STEM in the first period, but the sorting by ability greatly increases in the later period. It is costly to switch into STEM from non-STEM in the second period, while the reverse move is virtually costless. All of these results support the theoretical result that students will choose the field with more uncertainty in the early periods (given similar expected match values) because of the option to switch later if they get a bad match. This is especially true when the more uncertain field is also more costly to switch into in later periods, as in the case of STEM. In the second chapter, co-authored with Thomas Ahn, Peter Arcidiacono, and James Thomas, we estimate an equilibrium model of grading policies. On the supply side, professors offer courses with particular grading policies. Professors set both an intercept and a return to studying and ability in determining their grading policies. They make these decisions, attempting to maximize their own utility, but taking into account all other professors' grading policies. On the demand side, students respond by selecting a bundle of courses, then deciding how much to study in each class conditional on enrolling. We allow men and women to have different preferences over different departments, how much they like higher grades, and how costly it is to exert more effort in studying. Two decompositions are performed. First, we separate out how much of the differences in grading policies across fields is driven by differences in demand for courses in those fields and how much is due to differences in professor preferences across fields. Second, we separate out how much differences in female/male course taking across fields is driven by i) differences in cognitive skills, ii) differences in the valuation of grades, iii) differences in the cost of studying, and iv) differences in field preferences. We then use the structural parameters to evaluate restrictions on grading policies. Restrictions on grading policies that equalize grade distributions across classes result in higher (lower) grades in science (non-science) fields but more (less) work being required. As women are willing to study more than men, this restriction on grading policies results in more women pursuing the sciences and more men pursuing the non-sciences.

Invariants and Metrics for Multiparameter Persistent Homology

Thomas, Ashleigh Linnea ProQuest Dissertations & Theses Duke University 2019 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This dissertation is about building fundamental techniques for comparing data via a geometric and topological data analysis method called multiparameter persistent homology. The techniques used are largely algebraic. A new summary statistic, called the multirank function, is introduced as a measure of persistence output that detects relationships between important features of the data being analyzed. Also introduced is a technique for modifying existing metrics on the space of persistence outputs. Existing metrics can return infinite distances, which do not give as much information as a finite distance; the proposed modification gives fewer such situations. The final chapter of this dissertation details work in a long-term biology research project. Persistence is used to study the relationship between continuous morphological variation and rates of topologically abnormal morphologies in populations of fruit flies. Some preliminary computations showing proof of concept are included. Future plans involve using theoretical contributions from this dissertation for final analysis of the fly data. The distance modification is joint work with Ezra Miller and the biology application is joint with Surabhi Beriwal, Ezra Miller, and biologists at the Houle Lab at Florida State University.