Michigan Technological University

About: Michigan Technological University is a education organization based out in Houghton, Michigan, United States. It is known for research contribution in the topics: Population & Volcano. The organization has 8023 authors who have published 17422 publications receiving 481780 citations. The organization is also known as: MTU & Michigan Tech.

Observation of the Crab Nebula with the HAWC Gamma-Ray Observatory

Abstract: Author(s): Abeysekara, AU; Albert, A; Alfaro, R; Alvarez, C; Alvarez, JD; Arceo, R; Arteaga-Velazquez, JC; Solares, HAA; Barber, AS; Bautista-Elivar, N; Becerril, A; Belmont-Moreno, E; Benzvi, SY; Berley, D; Braun, J; Brisbois, C; Caballero-Mora, KS; Capistran, T; Carraminana, A; Casanova, S; Castillo, M; Cotti, U; Cotzomi, J; Leon, SCD; Fuente, EDL; Leon, CD; Deyoung, T; Dingus, BL; Duvernois, MA; Diaz-Velez, JC; Ellsworth, RW; Fiorino, DW; Fraija, N; Garcia-Gonzalez, JA; Gerhardt, M; Munoz, AG; Gonzalez, MM; Goodman, JA; Hampel-Arias, Z; Harding, JP; Hernandez, S; Hernandez-Almada, A; Hinton, J; Hui, CM; Huntemeyer, P; Iriarte, A; Jardin-Blicq, A; Joshi, V; Kaufmann, S; Kieda, D; Lara, A; Lauer, RJ; Lee, WH; Lennarz, D; Vargas, HL; Linnemann, JT; Longinotti, AL; Raya, GL; Luna-Garcia, R; Lopez-Coto, R; Malone, K; Marinelli, SS; Martinez, O; Martinez-Castellanos, I; Martinez-Castro, J; Martinez-Huerta, H; Matthews, JA; Miranda-Romagnoli, P; Moreno, E; Mostafa, M; Nellen, L; Newbold, M; Nisa, MU; Noriega-Papaqui, R; Pelayo, R; Pretz, J; Perez-Perez, EG; Ren, Z; Rho, CD; Riviere, C; Rosa-Gonzalez, D; Rosenberg, M; Ruiz-Velasco, E; Salazar, H; Greus, FS | Abstract: The Crab Nebula is the brightest TeV gamma-ray source in the sky and has been used for the past 25 years as a reference source in TeV astronomy, for calibration and verification of new TeV instruments. The High Altitude Water Cherenkov Observatory (HAWC), completed in early 2015, has been used to observe the Crab Nebula at high significance across nearly the full spectrum of energies to which HAWC is sensitive. HAWC is unique for its wide field of view, nearly 2 sr at any instant, and its high-energy reach, up to 100 TeV. HAWC's sensitivity improves with the gamma-ray energy. Above ∼1 TeV the sensitivity is driven by the best background rejection and angular resolution ever achieved for a wide-field ground array. We present a time-integrated analysis of the Crab using 507 live days of HAWC data from 2014 November to 2016 June. The spectrum of the Crab is fit to a function of the form φ(E)= φ0(E/E0)-α-β In(E/E0). The data is well fitted with values of α = 2.63 ±0.03, β = 0.15 ±0.03, and log10(φ0cm2s TeV)=-12.60±0.02 when E 0 is fixed at 7 TeV and the fit applies between 1 and 37 TeV. Study of the systematic errors in this HAWC measurement is discussed and estimated to be ±50% in the photon flux between 1 and 37 TeV. Confirmation of the Crab flux serves to establish the HAWC instrument's sensitivity for surveys of the sky. The HAWC all-sky survey will be the deepest survey of the northern sky ever conducted in the multi-TeV band.

Class E Power Amplifiers and Frequency Multipliers with finite DC-Feed Inductance

Abstract: Previous descriptions of class E amplifiers and frequency multipliers have required a radio frequency choke between the dc power supply and the active device "switch." In this paper, it is shown that class E operation may be maintained with the RF choke replaced by a smaller reactance. The analysis technique used is similar to that used by Raab in his description of class E amplifiers in that the equations describing circuit operation are obtained from Fourier series methods and the assumption of an infinite output network Q . The equations so obtained are used to determine (1) optimum operation (maximum power output capability at 100-percent efficiency) at any harmonic and (2) design equations that yield the requisite component values for optimum operation. The equations show that class E circuits may be configured to accommodate devices with arbitrary output capacitance and that class E amplifiers may be configured to provide greater power output capability than can be obtained using an RF choke design. Class E circuits with moderate values of output network Q were constructed and tested. The measured performance of these experimental circuits shows excellent agreement with the theoretical performance predicted by the equations.

Heterogeneous surface crystallization observed in undercooled water.

Abstract: We report laboratory observations of higher freezing temperatures when an ice-forming nucleus is near the surface of an undercooled water drop than when the nucleus is immersed in the drop. The nucleation rate at the water surface is a factor of 10(10) greater than in bulk water, thereby complementing and providing evidence for homogeneous surface crystallization, which has been hypothesized recently. Interpretation of the data via classical nucleation theory shows that the free energy of formation of a critical ice germ is decreased by a factor of approximately 2 when the substrate is near the air-water interface. Furthermore, the analysis suggests that the jump frequency of molecules from the liquid to the solid may be greatly enhanced at the interface.