The economic impact in the U.S. hotel industry after the terrorist attacks on September 11, 2001

Includes bibliographical references

Signals of New Gauge Bosons in Gauged Two Higgs Doublet Model

Recently a gauged two Higgs doublet model, in which the two Higgs doublets are embedded into the fundamental representation of an extra local $SU(2)_H$ group, is constructed. Both the new gauge bosons $Z^\prime$ and $W^{\prime (p,m)}$ are electrically neutral. While $Z^\prime$ can be singly produced at colliders, $W^{\prime (p,m)}$, which is heavier, must be pair produced. We explore the constraints of $Z^\prime$ using the current Drell-Yan type data from the Large Hadron Collider. Anticipating optimistically that $Z^\prime$ can be discovered via the clean Drell-Yan type signals at high luminosity upgrade of the collider, we explore the detectability of extra heavy fermions in the model via the two leptons/jets plus missing transverse energy signals from the exotic decay modes of $Z^\prime$. For the $W^{\prime (p,m)}$ pair production in a future 100 TeV proton-proton collider, we demonstrate certain kinematical distributions for the two/four leptons plus missing energy signals have distinguishable features from the Standard Model background. In addition, comparisons of these kinematical distributions between the gauged two Higgs doublet model and the littlest Higgs model with T-parity, the latter of which can give rise to the same signals with competitive if not larger cross sections, are also presented.Comment: 39 pages, 23 figures, 7 tables and two new appendixes, to appear in EPJ

Understanding the interactions between vibrational modes and excited state relaxation in garnet structured phosphors

This thesis concerns investigations of the local structural environments andvibrational dynamics of the three garnet type oxide phosphors Ce3+-dopedY3Al5O12 (YAG:Ce3+), Ca3Sc2Si3O12 (CSS:Ce3+), and Sr3Y2Ge3O12(SYG:Ce3+), which show promising optical properties as luminescent materialsused in solid state white lighting technologies. The study focuses on acomprehensive analysis of the nature of the long-range vibrations (phonons)in terms of local atomic and molecular motions of the garnet structure, as wellas their dependence on the nature of the garnet chemical composition, Ce3+concentration and temperature. The aim is to understand how these materialsproperties aect key optical properties, such as the intensity and wavelength(color) of the emitted light. The investigations have been conductedby using a combination of Raman, infrared, luminescence, and neutron spectroscopies,together with mode-selective vibrational excitation experiments,and are further supported by theoretical and semi-empirical analyses andcomputer modeling based on density functional theory.The results show that increasing the Ce3+ concentration and/or temperaturecause(s) a red-shifting eect on the emission color due to an increasedcrystal eld acting on the Ce3+ ions in YAG:Ce3+. This is primarily attributedto the thermal excitation of certain high-frequency phonon modesthat induce dynamical tetragonal distortions of the local CeO8 moieties. Areversal (blue-)shift of the emission color observed at higher temperatures is,however, the result of counteracting thermal lattice expansion which turnsthe local coordination of CeO8 into a more cubic symmetry. Specically, it isfound that the upward-shift of the frequencies of certain vibrational modesin YAG:Ce3+ through decreasing the Ce3+ concentration or cosubstitution ofsmaller and/or lighter atoms on the Y sites increases the thermal stability ofthe emission intensity. This higher thermal stability of the emission intensityis attributed to a less activation of modes that give rise to nonradiative relaxationof electrons in the excited states via electron{phonon coupling and/orenergy migration processes. For SYG:Ce3+, the emission intensity is foundto decrease strongly with increasing temperature, as a result of thermal ionizationby promoting the electrons of Ce3+ ions into the conduction band ofthe host, followed by charge trapping at defects. CSS:Ce3+ exhibits excellentthermal stability up to very high temperatures, 860 K

Detecting Slow Wave Sleep Using a Single EEG Signal Channel

Background: In addition to the cost and complexity of processing multiple signal channels, manual sleep staging is also tedious, time consuming, and error-prone. The aim of this paper is to propose an automatic slow wave sleep (SWS) detection method that uses only one channel of the electroencephalography (EEG) signal. New Method: The proposed approach distinguishes itself from previous automatic sleep staging methods by using three specially designed feature groups. The first feature group characterizes the waveform pattern of the EEG signal. The remaining two feature groups are developed to resolve the difficulties caused by interpersonal EEG signal differences. Results and comparison with existing methods: The proposed approach was tested with 1,003 subjects, and the SWS detection results show kappa coefficient at 0.66, an accuracy level of 0.973, a sensitivity score of 0.644 and a positive predictive value of 0.709. By excluding sleep apnea patients and persons whose age is older than 55, the SWS detection results improved to kappa coefficient, 0.76; accuracy, 0.963; sensitivity, 0.758; and positive predictive value, 0.812. Conclusions: With newly developed signal features, this study proposed and tested a single-channel EEG-based SWS detection method. The effectiveness of the proposed approach was demonstrated by applying it to detect the SWS of 1003 subjects. Our test results show that a low SWS ratio and sleep apnea can degrade the performance of SWS detection. The results also show that a large and accurately staged sleep dataset is of great importance when developing automatic sleep staging methods

A model explaining neutrino masses and the DAMPE cosmic ray electron excess

We propose a flavored $U(1)_{e\mu}$ neutrino mass and dark matter~(DM) model to explain the recent DArk Matter Particle Explorer (DAMPE) data, which feature an excess on the cosmic ray electron plus positron flux around 1.4 TeV. Only the first two lepton generations of the Standard Model are charged under the new $U(1)_{e\mu}$ gauge symmetry. A vector-like fermion $\psi$, which is our DM candidate, annihilates into $e^{\pm}$ and $\mu^{\pm}$ via the new gauge boson $Z'$ exchange and accounts for the DAMPE excess. We have found that the data favors a $\psi$ mass around 1.5~TeV and a $Z'$ mass around 2.6~TeV, which can potentially be probed by the next generation lepton colliders and DM direct detection experiments.Comment: 7 pages, 3 figures. V2: version accepted by Physics Letters

Variable selection based on entropic criterion and its application to the debris-flow triggering

We propose a new data analyzing scheme, the method of minimum entropy analysis (MEA), in this paper. New MEA provides a quantitative criterion to select relevant variables for modeling the physical system interested. Such method can be easily extended to various geophysical/geological data analysis, where many relevant or irrelevant available measurements may obscure the understanding of the highly complicated physical system like the triggering of debris-flows. After demonstrating and testing the MEA method, we apply this method to a dataset of debris-flow occurrences in Taiwan and successfully find out three relevant variables, i.e. the hydrological form factor, numbers and areas of landslides, to the triggering of observed debris-flow events due to the 1996 Typhoon Herb.Comment: 9 pages and 4 table