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京都大学 / 新制・課程博士 / 博士(理学) / 甲第23705号 / 理博第4795号 / 新制||理||1686(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 嶺重 慎, 准教授 前田 啓一, 准教授 野上 大作 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Although emergency management is established for the purpose of addressing disasters and other major emergencies, I have found that it can be purposefully engineered to also be an assist leader to other agencies and entities during nonemergency periods because the key element of synchrony that enables emergency managers to be effective during an emergency can also be employed during nonemergency periods to assist other departments in a manner that not only delivers a direct benefit to the department but also enhances the emergency preparedness, mitigation, and resiliency efforts of the jurisdiction. Emergency managers can create this performance-enhancing synchrony using boundary spanning functions that bridge the divide that separates stakeholders. Emergency management practitioners are steadfast in their pursuit of methods and practices by which they can be more effective. The recent increase in the frequency and severity of natural disasters is only one example of the ever-growing demands placed upon these professionals. Compounding this development is the fact that the occurrences of natural disasters have outpaced research and theory development regarding how emergency management professionals should prepare for and respond to these events. This research study envisions, proposes, and outlines a framework in which emergency managers function in a broader capacity that could elevate their overall performance and importance to a higher plane than the one on which perhaps most currently operate. / Business Administration/Strategic Management

Astrophysical phenomena such as exploding primordial black holes (PBHs), gamma-ray bursts (GRBs), compact object mergers, and supernovae, are expected to produce a single pulse of electromagnetic radiation detectable at the low-frequency end of the radio spectrum. Detection of any of these pulses would be significant for the study of the objects themselves, their host environments, and the interstellar/intergalactic medium. Furthermore, a detection of a radio transient from an exploding PBH could be a signature of an extra spatial dimension, which would drastically alter our perception of spacetime. However, even upper limits on the existence of PBHs, from transient searches, would be important to discussions of cosmology. We describe a method to carry out an agnostic single-dispersed-pulse search, and apply it to data collected with the Eight-meter-wavelength Transient Array (ETA). ETA is a radio telescope dedicated to searching for transient pulses. It consists of 12 crossed-dipole antenna stands with Galactic-noise-limited performance from 29-47 MHz. There is a vast amount of data collected from an ETA observation. It is therefore greatly beneficial to use a computer cluster, which works in parallel on different parts of a data set, in order to carry out a single-pulse search quickly and efficiently. Each spectrogram in a data set needs to be analyzed individually, without reference to the rest, in order to utilize a computer cluster's capabilities. The data reduction software has been developed for single-dispersed-pulse searches, and is described in this thesis. The data reduction involves sweeping through the collected data with a dedispersion routine assuming a range of dispersion measures. The resulting time series are searched with multiple matched filters for signals above a signal-to-noise threshold. Applying the single pulse search to ~ 30 hours of ETA data did not yield a compelling detection of an astrophysical signal. However, from ≈ 5 hours of interference-free data we find an observational upper limit to the rate of exploding PBHs of r ≈ 4.8 × 10⁻⁷ pc⁻³ y⁻¹ for a PBH with a fireball Lorentz-factor f = 10^4.3. This limit is applicable to PBHs in the halo of the Galaxy to distances ≲ 2 kpc, and dispersion measures ≲ 80 pc cm⁻³ . We also find a source-agnostic rate limit ≲ 0.25 events y⁻¹ deg⁻² for pulses of duration < 3 s, and having apparent energy densities ≳ 2.6 × 10⁻²³ J m⁻² Hz⁻¹ at 38 MHz. / Ph. D.

Most thin-walled metallic structural members experience some extent of interactive buckling that corrodes the load carrying capacity. Current design methods predict the strength of thin-walled metallic structural members based on individual buckling limit-states and limited case of interactive buckling limit state. In order to develop design methods for most coupled buckling limit states, the interaction of buckling modes needs to be studied. This dissertation first introduces a generally applicable methodology for Generalized Beam Theory (GBT) elastic buckling analysis on members with holes, where the buckling modes of gross cross-section interact with those of net cross-section. The approach treats member with holes as a structural system consisting of prismatic sub-members. These sub-members are connected by enforcing nodal compatibility conditions for the GBT discretization points at the interfaces. To represent the shear lag effect and nonlinear normal stress distribution in the vicinity of a hole, GBT shear modes with nonlinear warping are included. Modifications are made to the GBT geometric stiffness because of the influence from shear lag effect caused by holes. In the following sections, the GBT formulation for a prismatic bar is reviewed and the GBT formulation for members with holes is introduced. Special aspects of analyzing members with holes are defined, namely the compatibility conditions to connect sub-members and the geometric stiffness for members with holes. Validation and three examples are provided. The second topic of this dissertation involves a buckling mode decomposition method of normalized displacement field, bending stresses and strain energy for thin-walled member displacement field (point clouds or finite element results) based on generalized beam theory (GBT). The method provides quantitative modal participation information regarding eigen-buckling displacement fields, stress components and elastic strain energy, that can be used to inform future design approaches. In the method, GBT modal amplitudes are retrieved at discrete cross-sections, and the modal amplitude field is reconstructed assuming it can be piece-wisely approximated by polynomials. The unit displacement field, stress components and strain energy are all retrieved by using reconstructed GBT modal amplitude field and GBT constitutive laws. Theory and examples are provided, and potential applications are discussed including cold-formed steel member design and post-disaster evaluation of thin-walled structural members. In the third part, post-buckling modal decomposition is made possible by development of a geometrically nonlinear GBT software. This tool can be used to assist understanding couple-buckling limit-states. Lastly, the load-deformation response considering any one GBT mode is derived analytically for fast computation and interpretation of structural post-buckling behavior. / Ph. D.