Strike 3000: Standing Electric Trike

In the past decade there has been much research conducted on maintaining a healthy lifestyle, even in sedentary activities. It is clear to see this trend in the rising popularity of standing desks, ergonomic mice and keyboards, and the plethora of applications that remind the user not to stay inactive for too long. Ken Howes suggests that this revolution be brought to the world of motor vehicles with his proposed concept of the Strike 3000: an electric-powered three-wheeled vehicle that keeps the operator in a standing position while still maintaining all of the functionality and reliability of a standard automobile. To accomplish this goal, the members of Team 4 conducted thorough technical research into existing patents, competitive designs, and literature concerned with the essentials in designing a vehicle. With the information that was gathered, Team 4 then began to generate design concepts for every component of the vehicle including the chassis, steering, braking, suspension, etc. Together the team generated over one-hundred and fifty concepts. The team also conducted a Quality Function Deployment comparison to create a visual representation of how each component of the vehicle will help meet the wants of the sponsor as well as a comparison between the Strike 3000 and other competitive products. This gave the team a better understanding of what components were important to focus on and which could be sacrificed in order to improve the most essential parts. After the foundation work of the design was completed, Team 4 and Ken Howes collaborated to design a chassis to the aesthetic standards of Mr. Howes’ proposed design while making necessary revisions to keep the design technically acceptable. At the start of the second semester, Team 4 had sent out a final design and engineering drawing to a local welder for construction of the chassis. They ordered all the parts to be implemented into the vehicle. When the chassis arrived they began assembling the vehicle in the Kirk Machine Shop so that custom parts, such as suspension mounts and tie rods could be welded and modifications to the chassis could be made accordingly. The team was able to finish the construction with a lot of help from Nick Ladyga, a member of the team who lead the build effort. The motor was not able to be installed by the time of the Design Showcase but with technical documentation and guidance the team will be able to help Mr. Howes complete the vehicle in a short amount of time

A Review of Tunable Wavelength Selectivity of Metamaterials in Near-Field and Far-Field Radiative Thermal Transport

Radiative thermal transport of metamaterials has begun to play a significant role in thermal science and has great engineering applications. When the key features of structures become comparable to the thermal wavelength at a particular temperature, a narrowband or wideband of wavelengths can be created or shifted in both the emission and reflection spectrum of nanoscale metamaterials. Due to the near-field effect, the phenomena of radiative wavelength selectivity become significant. These effects show strong promise for applications in thermophotovoltaic energy harvesting, nanoscale biosensing, and increased energy efficiency through radiative cooling in the near future. This review paper summarizes the recent progress and outlook of both near-field and far-field radiative heat transfer, different design structures of metamaterials, applications of unique thermal and optical properties, and focuses especially on exploration of the tunable radiative wavelength selectivity of nano-metamaterials

A Structural Model for Octagonal Quasicrystals Derived from Octagonal Symmetry Elements Arising in β\beta-Mn Crystallization of a Simple Monatomic Liquid

While performing molecular dynamics simulations of a simple monatomic liquid, we observed the crystallization of a material displaying octagonal symmetry in its simulated diffraction pattern. Inspection of the atomic arrangements in the crystallization product reveals large grains of the beta-Mn structure aligned along a common 4-fold axis, with 45 degree rotations between neighboring grains. These 45 degree rotations can be traced to the intercession of a second crystalline structure fused epitaxially to the beta-Mn domain surfaces, whose primitive cell has lattice parameters a = b = c = a_{beta-Mn}, alpha = beta = 90 degrees, and gamma = 45 degrees. This secondary phase adopts a structure which appears to have no known counterpart in the experimental literature, but can be simply derived from the Cr_3Si and Al_3Zr_4 structure types. We used these observations as the basis for an atomistic structural model for octagonal quasicrystals, in which the beta-Mn and the secondary phase structure unit cells serve as square and rhombic tiles (in projection), respectively. Its diffraction pattern down the octagonal axis resembles those experimentally measured. The model is unique in being consistent with high-resolution electron microscopy images showing square and rhombic units with edge-lengths equal to that of the beta-Mn unit cell. Energy minimization of this configuration, using the same pair potential as above, results in an alternative octagonal quasiperiodic structure with the same tiling but a different atomic decoration and diffraction pattern.Comment: 25 pages, 10 figure

π+\pi^+ photoproduction on the proton for photon energies from 0.725 to 2.875 GeV

Differential cross sections for the reaction $\gamma p \to n \pi^+$ have been measured with the CEBAF Large Acceptance Spectrometer (CLAS) and a tagged photon beam with energies from 0.725 to 2.875 GeV. Where available, the results obtained here compare well with previously published results for the reaction. Agreement with the SAID and MAID analyses is found below 1 GeV. The present set of cross sections has been incorporated into the SAID database, and exploratory fits have been made up to 2.7 GeV. Resonance couplings have been extracted and compared to previous determinations. With the addition of these cross sections to the world data set, significant changes have occurred in the high-energy behavior of the SAID cross-section predictions and amplitudes.Comment: 18 pages, 10 figure

Photodisintegration of 4^4He into p+t

The two-body photodisintegration of $^4$He into a proton and a triton has been studied using the CEBAF Large-Acceptance Spectrometer (CLAS) at Jefferson Laboratory. Real photons produced with the Hall-B bremsstrahlung-tagging system in the energy range from 0.35 to 1.55 GeV were incident on a liquid $^4$He target. This is the first measurement of the photodisintegration of $^4$He above 0.4 GeV. The differential cross sections for the $\gamma$$^4$He$\to pt$ reaction have been measured as a function of photon-beam energy and proton-scattering angle, and are compared with the latest model calculations by J.-M. Laget. At 0.6-1.2 GeV, our data are in good agreement only with the calculations that include three-body mechanisms, thus confirming their importance. These results reinforce the conclusion of our previous study of the three-body breakup of $^3$He that demonstrated the great importance of three-body mechanisms in the energy region 0.5-0.8 GeV .Comment: 13 pages submitted in one tgz file containing 2 tex file and 22 postscrip figure

Exclusive Photoproduction of the Cascade (Xi) Hyperons

We report on the first measurement of exclusive Xi-(1321) hyperon photoproduction in gamma p --> K+ K+ Xi- for 3.2 < E(gamma) < 3.9 GeV. The final state is identified by the missing mass in p(gamma,K+ K+)X measured with the CLAS detector at Jefferson Laboratory. We have detected a significant number of the ground-state Xi-(1321)1/2+, and have estimated the total cross section for its production. We have also observed the first excited state Xi-(1530)3/2+. Photoproduction provides a copious source of Xi's. We discuss the possibilities of a search for the recently proposed Xi5-- and Xi5+ pentaquarks.Comment: submitted to Phys. Rev.

First measurement of target and double spin asymmetries for polarized e- polarized p --> e p pi0 in the nucleon resonance region above the Delta(1232)

The exclusive channel polarized proton(polarized e,e prime p)pi0 was studied in the first and second nucleon resonance regions in the Q2 range from 0.187 to 0.770 GeV2 at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). Longitudinal target and beam-target asymmetries were extracted over a large range of center-of-mass angles of the pi0 and compared to the unitary isobar model MAID, the dynamic model by Sato and Lee, and the dynamic model DMT. A strong sensitivity to individual models was observed, in particular for the target asymmetry and in the higher invariant mass region. This data set, once included in the global fits of the above models, is expected to place strong constraints on the electrocoupling amplitudes A_{1/2} and S_{1/2} for the Roper resonance N(1400)P11, and the N(1535)S11 and N(1520)D13 states.Comment: 13 pages, 13 figure

Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects