1,085 research outputs found
Leptonic CP Violation and Wolfenstein Parametrization for Lepton Mixing
We investigate a general structure of lepton mixing matrix resulting from the
SU(3) gauge family model with an appropriate vacuum structure of SU(3)
symmetry breaking. It is shown that the lepton mixing matrix can be
parametrized by using the Wolfenstein parametrization method to characterize
its deviation from the tri-bimaximal mixing. A general analysis for the allowed
leptonic CP-violating phase and the leptonic Wolfenstein parameters
, , is carried out based on the observed lepton mixing
angles. We demonstrate how the leptonic CP violation correlates to the leptonic
Wolfenstein parameters. It is found that the phase is strongly
constrained and only a large or nearly maximal leptonic CP-violating phase
is favorable when . In
particular, when taking to be the Cabbibo angle \gl_e\simeq
\lambda \simeq 0.225, a sensible result for leptonic Wolfenstein parameters
and CP violation is obtained with , , \delta_{e}\sim
101.76\;^o, which is compatible with the one in quark sector. An interesting
correlation between leptons and quarks is observed, which indicates a possible
common origin of masses and mixing for the charged-leptons and quarks.Comment: 18 pages, 5 figures, sources of CP-violating phases are clarified,
references adde
Utopian fantasy
I design furniture and objects to express my utopian fantasy to people. I hope users can imagine the fantasy through the interaction with my furniture and objects. While people are interacting with my works, they become part of the fantasy. My works are the NPCs (nonplayer characters) of a game created by myself, called Utopian Fantasy.
My works are creature-istic, anthropomorphic, and always interactive. They are inspired by nature and everyday life. This series of works I created during my time at RISD express my appreciation for the underwater world and the Internet. My designs beg for interaction and play. Wander around one of my pieces for a couple of seconds, test it, play with it and through interaction my furniture will be happy to share with you everything they know. My furniture’s functional purpose emerges from play, while visually engaging people nearby. I love adding surprises into my pieces, giving them a sense of humor, a point of interaction and exchange.
I want people to say, “Oh, how joyful!”, when they interact with my work
Gauge Family Model and New Symmetry Breaking Scale From FCNC Processes
Based on the gauge family symmetry model which was proposed to
explain the observed mass and mixing pattern of neutrinos, we investigate the
symmetry breaking, the mixing pattern in quark and lepton sectors, and the
contribution of the new gauge bosons to some flavour changing neutral currents
(FCNC) processes at low energy. With the current data of the mass differences
in the neutral pseudo-scalar systems, we find that the
symmetry breaking scale can be as low as 300TeV and the mass of the
lightest gauge boson be about TeV. Other FCNC processes, such as the
lepton flavour number violation process
and the semi-leptonic rare decay , contain
contributions via the new gauge bosons exchanging. With the constrains got from
system, we estimate that the contribution of the new physics is
around , far below the current experimental bounds.Comment: 3figure
Holographic Dark Energy Characterized by the Total Comoving Horizon and Insights to Cosmological Constant and Coincidence Problem
The observed acceleration of the present universe is shown to be well
explained by the holographic dark energy characterized by the total comoving
horizon of the universe (HDE). It is of interest to notice that the very
large primordial part of the comoving horizon generated by the inflation of
early universe makes the HDE behave like a cosmological constant. As a
consequence, both the fine-tuning problem and the coincidence problem can
reasonably be understood with the inflationary universe and holographical
principle. We present a systematic analysis and obtain a consistent
cosmological constraint on the HDE model based on the recent cosmological
observations. It is found that the HDE model gives the best-fit result
() and the minimal
which is compatible with for the CDM model.Comment: 17 pages, 4 figures, two eqs. (26)(27) added for the consistent
approximate solution of dark energy in early universe, references added,
published version in PR
Development of Terahertz Quantum Well Photodetector at 3 THz
This thesis reports a new terahertz (=3.22 THz) quantum well photodetector (THz QWP) as well as comprehensive numerical models simulating device active region and different grating couplers including traditional diffraction metal grating and novel patch antenna structure.
Among all the terahertz detectors, terahertz quantum well photodetector (THz QWP), has proved its fast optical response speed and remarkable sensitivity and shown great potential for applications in security, bio-medical technology and space communication. However, due to high requirements in experiment condition and growth quality, THz QWPs absorbed at 3 THz or lower have not been much developed yet. Furthermore, THz QWP working around 3 THz can be combined with one of the strongest terahertz emitters, terahertz quantum cascade laser (THz QCL), for ultrafast spectroscopy and imaging applications. Recently, THz QWPs integrated with different grating couplers have been explored and are now intensively investigated to improve device temperature performance.
In that regard, we aim to improve the simulation model and develop a new THz QWP absorbing at 3 THz. Moreover, numerical COMSOL models are built to analyze optical properties of traditional diffraction metal grating coupler and novel patch antenna coupler in this work. According to measured current density-voltage (j-V) profiles and absorption spectrum, the proposed THz QWP with a new active region design has its background-limited infrared performance (BLIP) temperature at 10 K and manages to achieve terahertz range absorption at lower frequency around 3 THz. Results show a peak responsivity of 1.9 A/W, a peak detectivity of 4.63×1010 cmHz1/2/W and an absorption range from 94.5 cm-1 (2.83 THz) to 142.7 cm-1 (4.25 THz). To our knowledge, this THz QWP has the lowest peak absorption frequency (3.22 THz) and it is the second one that works near 3 THz. Measured j-V profiles show a size-dependent shifting, indicating the existence of sidewall leakage currents, and the comparison between simulation and measurement results of j-V profiles reveals the consistency, especially at higher temperature. In addition, simulation results on 1D metal grating coupler and patch antenna coupler are demonstrated and they strongly agree with the experiment data from literatures as well as general rules of thumb
Timing and Congestion Driven Algorithms for FPGA Placement
Placement is one of the most important steps in physical design for VLSI circuits. For field programmable gate arrays (FPGAs), the placement step determines the location of each logic block. I present novel timing and congestion driven placement algorithms for FPGAs with minimal runtime overhead. By predicting the post-routing timing-critical edges and estimating congestion accurately, this algorithm is able to simultaneously reduce the critical path delay and the minimum number of routing tracks. The core of the algorithm consists of a criticality-history record of connection edges and a congestion map. This approach is applied to the 20 largest Microelectronics Center of North Carolina (MCNC) benchmark circuits. Experimental results show that compared with the state-of-the-art FPGA place and route package, the Versatile Place and Route (VPR) suite, this algorithm yields an average of 8.1% reduction (maximum 30.5%) in the critical path delay and 5% reduction in channel width. Meanwhile, the average runtime of the algorithm is only 2.3X as of VPR
Bioimaging with photonic crystal enhanced microscopy
The work presented in this dissertation addresses the optimization and application
of a newly developed imaging modality, named photonic crystal enhanced microscopy (PCEM) for label-free detection of the surface attached biological samples. Photonic crystal, supporting guided-mode resonances and providing local optical modes, can enhance the light-matter interaction on its surface and thus used for label-free detection
and biosensing. One dimensional photonic crystal surfaces are designed and utilized as a biosensor, and further integrated with an ordinary bright-field microscope. To demonstrate the validity of the photonic crystal biosensor, a three-dimensional modeling is developed and evaluated with finite-difference time-domain (FDTD) algorithm to
predict and visualize the electromagnetic field redistribution upon the device surface.
Applications of the photonic crystal enhanced microscopy are carried out for live cell imaging, nanoparticle detection and protein-protein binding detection. First, labelfree detection for live cell with PCEM imaging system is performed. Three different cellular phenomena are involved in this study, including cell adhesion, cell migration and stem cell differentiation. A novel imaging analysis software is developed to dynamically track the cell plasma membrane evolution. This traction software reveals mass
redistribution with high resolution during cell migration which is previously difficult to
evaluate quantitatively. Furthermore, both dielectric and metallic nanoparticles are examined and proved to be detectable as label-free detection using PCEM imaging system. Another novel imaging analysis software is developed to automatically count the number of nanoparticles attached on the sensor surface within the imaging field of view. Finally, a newly developed detection modality for protein-protein binding is demonstrated through PCEM imaging system using nanoparticle as tags. This new
detection modality can avoid the photobleach problem and may also hold the potential to detect ultra-low concentrations of protein in the future.
In summary, photonic crystal biosensor and its associated imaging system with microscopy developed in this work show great promise to the label-free biosensing and bioimaging. Future work will extend the application of PCEM to broader research and
application fields served as the next generation sensing modalities
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