Search results for "MICROWAVE"
showing 10 items of 693 documents
Slinky inflation
2005
We present a new approach to quintessential inflation, in which both dark energy and inflation are explained by the evolution of a single scalar field. We start from a simple scalar potential with both oscillatory and exponential behavior. We employ the conventional reheating mechanism of new inflation, in which the scalar decays to light fermions with a decay width that is proportional to the scalar mass. Because our scalar mass is proportional to the Hubble rate, this gives adequate reheating at early times while shutting off at late times to preserve quintessence and satisfy nucleosynthesis constraints. We discuss a simple model which solves the horizon, flatness, and "why now" problems.…
Impact of general reionization scenarios on extraction of inflationary parameters
2010
Determination of whether the Harrison-Zel'dovich spectrum for primordial scalar perturbations is consistent with observations is sensitive to assumptions about the reionization scenario. In light of this result, we revisit constraints on inflationary models using more general reionization scenarios. While the bounds on the tensor-to-scalar ratio are largely unmodified, when different reionization schemes are addressed, hybrid models are back into the inflationary game. In the general reionization picture, we reconstruct both the shape and amplitude of the inflaton potential. We discuss how relaxing the simple reionization restriction affects the reconstruction of the potential through the c…
Primordial power spectrum features in phenomenological descriptions of inflation
2016
We extend an alternative, phenomenological approach to inflation by means of an equation of state and a sound speed, both of them functions of the number of $e$-folds and four phenomenological parameters. This approach captures a number of possible inflationary models, including those with non-canonical kinetic terms or scale-dependent non-gaussianities. We perform Markov Chain Monte Carlo analyses using the latest cosmological publicly available measurements, which include Cosmic Microwave Background (CMB) data from the Planck satellite. Within this parametrization, we discard scale invariance with a significance of about $10\sigma$, and the running of the spectral index is constrained as …
Microwave, High-Resolution Infrared, and Quantum Chemical Investigations of CHBrF2: Ground and v4 = 1 States
2011
A combined microwave, infrared, and computational investigation of CHBrF(2) is reported. For the vibrational ground state, measurements in the millimeter- and sub-millimeter-wave regions for CH(79)BrF(2) and CH(81)BrF(2) provided rotational and centrifugal-distortion constants up to the sextic terms as well as the hyperfine parameters (quadrupole-coupling and spin-rotation interaction constants) of the bromine nucleus. The determination of the latter was made possible by recording of spectra at sub-Doppler resolution, achieved by means of the Lamb-dip technique, and supporting the spectra analysis by high-level quantum chemical calculations at the coupled-cluster level. In this context, the…
Computationally Efficient Analysis of Microwave Injection-Locked Amplifiers
2011
In this paper, some preliminary results on a novel approach to the analysis of injection-locked amplifiers are presented. The proposed method is based on a behavioral block modeling of the circuit in the fundamental-frequency dynamical phasor domain. The first-order exact perturbation refined treatment developed provides, in the end, explicit equations describing the entrained oscillation amplitude and phase dynamics. A secondary simplification then can be adopted in case of low-level injection, to determine a closed form expression for the locking bandwidth, generalizing the well known Adler’s one. By virtue of its semi-analytical nature, the proposed approach turns out to be much more eff…
Analysis of Bias-Shift Effects in Free-Running and Injection-Locked Negative Resistance Oscillators
2012
In this paper, the interaction between DC and RF in quasi-sinusoidal free-running and injection-locked oscillators is addressed. To account for and illustrate in a user-friendly manner the bias-shift related effects stemming from such interaction, a frequency-domain method of analysis has been developed for a rather wide class of negative-resistance circuits. Grounding on a first-approximation exact perturbation-refined approach, it permits computationally efficient simulation of the oscillator behavior directly in terms of the DC and RF signals evolutions (dynamical complex envelopes). In fact, it allows the investigation of both steady-state and transient operation of the shifting-bias dr…
Pyrolysed cork-geopolymer composites: A novel and sustainable EMI shielding building material
2019
Abstract In this investigation, and for the first time, pyrolysed sustainable cork was used to produce waste-based geopolymer-cork composites with enhanced electromagnetic interference (EMI) shielding properties. The influence of the pyrolysed cork amount and the geopolymer porosity on the EMI shielding ability of the composites was studied. The maximum total shielding effectiveness (SET) values achieved by these novel building materials (−13.8 to −15.9 dB) are equal to any other reported geopolymer microwave (MW) absorbers over the X-band, despite containing much lower carbon content. In addition, our composites were produced using an industrial waste (biomass fly ash) as raw material and …
A Domino Ring‐Closure Followed by Retro‐Diels–Alder Reaction for the Preparation of Pyrimido[2,1‐ a ]isoindole Enantiomers
2016
A simple method was developed to prepare pyrimido[2,1-a]isoindole derivatives by using di-endo- and di-exo-ethyl 3-aminobicyclo[2.2.1]hept-5-ene-2-carboxylate enantiomers as chiral sources. The method is based on a domino ring-closure reaction of norbornene 2-aminohydroxamic acid followed by microwave-induced retro-Diels–Alder reaction. In the case of enantiomeric starting substances, the chirality is transferred from norbornene derivatives to pyrimido[2,1-a]isoindoles. The configurations of the synthesized compounds were determined by 1D and 2D NMR spectroscopy [based on 2D NOE cross-peaks and 3JH,H coupling constants] and X-ray crystallography.
Time Evolution of two distant SQUID rings irradiated with entangled electromagnetic field
2006
Two distant mesoscopic SQUID rings are irradiated with two mode microwaves produced by the same source. The time evolution of the system is studied. The two microwave modes are correlated. It is shown that the currents tunnelling through the Josephson junctions in the distant rings, are also correlated.
A geostatistical approach to map near-surface soil moisture through hyperspatial resolution thermal inertia.
2021
Thermal inertia has been applied to map soil water content exploiting remote sensing data in the short and long wave regions of the electromagnetic spectrum. Over the last years, optical and thermal cameras were sufficiently miniaturized to be loaded onboard of unmanned aerial systems (UASs), which provide unprecedented potentials to derive hyperspatial resolution thermal inertia for soil water content mapping. In this study, we apply a simplification of thermal inertia, the apparent thermal inertia (ATI), over pixels where underlying thermal inertia hypotheses are fulfilled (unshaded bare soil). Then, a kriging algorithm is used to spatialize the ATI to get a soil water content map. The pr…