3,385 research outputs found
Solar power satellite rectenna design study: Directional receiving elements and parallel-series combining analysis
Rectenna conversion efficiencies (RF to dc) approximating 85 percent were demonstrated on a small scale, clearly indicating the feasibility and potential of efficiency of microwave power to dc. The overall cost estimates of the solar power satellite indicate that the baseline rectenna subsystem will be between 25 to 40 percent of the system cost. The directional receiving elements and element extensions were studied, along with power combining evaluation and evaluation extensions
Direct observation of the picosecond dynamics of I_2-Ar fragmentation
Picosecond real‐time observations of the dynamics of I_2–Ar fragmentation are reported. The state‐to‐state rates, k(ν^i,,ν^f,), are directly measured and related to the homogeneous broadening of the initial state, and to product state distributions in the exit channel. Comparisons with different theories of vibrational (and electronic) predissociation are made
Simultaneous fitting of X-ray and neutron diffuse scattering data
Conventional crystallographic refinement uses the Bragg-peak intensities and gives the single-site average crystal structure. Information about short-range order and local order is contained in the diffuse scattering that is distributed throughout reciprocal space. Models of the short-range order in materials can now be automatically refined. The complementarity of X-ray and neutron diffraction data, and the value of simultaneously refining a structural model against both types of data, has long been known. This paper presents the first refinement of a short-range-order model against comprehensive X-ray and neutron diffuse scattering data simultaneously. The sample is the organic molecular crystal benzil, C14H10O2 (for neutron work H is replaced by D). The technique gives new insights into local order in crystalline materials, including the dynamic correlation structure indicative of the dynamics of molecules in the crystalline state, and successfully overcomes limitations of using only the X-ray data set
Derivation of the Quantum Probability Rule without the Frequency Operator
We present an alternative frequencists' proof of the quantum probability rule
which does not make use of the frequency operator, with expectation that this
can circumvent the recent criticism against the previous proofs which use it.
We also argue that avoiding the frequency operator is not only for technical
merits for doing so but is closely related to what quantum mechanics is all
about from the viewpoint of many-world interpretation.Comment: 12 page
Commensurate to incommensurate magnetic phase transition in Honeycomb-lattice pyrovanadate Mn2V2O7
We have synthesized single crystalline sample of MnVO using
floating zone technique and investigated the ground state using magnetic
susceptibility, heat capacity and neutron diffraction. Our magnetic
susceptibility and heat capacity reveal two successive magnetic transitions at
19 K and 11.8 K indicating two distinct magnetically
ordered phases. The single crystal neutron diffraction study shows that in the
temperature () range 11.8 K 19 K the magnetic structure is
commensurate with propagation vector , while upon lowering
temperature below 11.8 K an incommensurate magnetic order emerges
with and the magnetic structure can be represented by
cycloidal modulation of the Mn spin in plane. We are reporting this
commensurate to incommensurate transition for the first time. We discuss the
role of the magnetic exchange interactions and spin-orbital coupling on the
stability of the observed magnetic phase transitions.Comment: 8 pages, 7 figure
Correlation functions of the One-Dimensional Random Field Ising Model at Zero Temperature
We consider the one-dimensional random field Ising model, where the spin-spin
coupling, , is ferromagnetic and the external field is chosen to be
with probability and with probability . At zero temperature, we
calculate an exact expression for the correlation length of the quenched
average of the correlation function in the case that is not an integer. The
result is a discontinuous function of . When , we also
place a bound on the correlation length of the quenched average of the
correlation function .Comment: 12 pages (Plain TeX with one PostScript figure appended at end), MIT
CTP #220
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