•We present a framework for operational modal analysis.•The framework can handle both time domain and frequency domain.•The method can handle common signal processing tasks.•We develop two robust ...methods for removing harmonics in time data.
In operational modal analysis (OMA), correlation functions, sometimes referred to as covariance functions, are commonly used for modal parameter extraction. Other techniques for parameter estimation use spectral density estimates. There are several known techniques for computing spectral density and correlation functions. The most common technique for spectral density estimates, is Welch’s method. A more infrequently used technique, however, is based on computing the discrete Fourier transform (DFT) of the entire signals, and multiplying these DFTs into auto and cross-periodograms. To produce a correlation function, the inverse Fourier transform of the periodogram is used. To produce spectral density estimates, the periodogram may be smoothed. In the present paper this method of computing the spectral and correlation functions is investigated, and compared to other methods of spectral and correlation estimation. It is shown that the method has several advantages not only for estimation of spectra and correlation functions, but also because filtering, integration and differentiation, removal of harmonics, and compensation for non-ideal sensor characteristics are functions that can readily be encompassed in this technique, with high performance, at a minimum of computational cost. Furthermore, two methods to remove harmonics in spectral densities as well as in correlation functions, are developed in the paper. The first method, frequency domain editing (FDE), removes one or more stable harmonics, where variations of the frequency are small. The other method, order domain deletion (ODD), works in cases where the frequency of the harmonic, or harmonics, varies, and where the instantaneous frequency as a function of time is known, for example by processing a tacho signal. Based on the several advantages with using long DFTs as the estimation method for spectra and correlation functions, it is recommended as the standard framework for signal processing in OMA applications.
We present astrochemical photodissociation region models in which cosmic-ray (CR) attenuation has been fully coupled to the chemical evolution of the gas. We model the astrochemical impact of CRs, ...including those accelerated by protostellar accretion shocks, on molecular clouds hosting protoclusters. Our models with embedded protostars reproduce observed ionization rates. We study the imprint of CR attenuation on ions for models with different surface CR spectra and different star formation efficiencies. We find that abundances, particularly ions, are sensitive to the treatment of CRs. We show the column densities of ions are underpredicted by the "classic" treatment of CRs by an order of magnitude. We also test two common chemistry approximations used to infer ionization rates. We conclude that the approximation based on the abundance underpredicts the ionization rate, except in regions where the CRs dominate the chemistry. Our models suggest the chemistry in dense gas will be significantly impacted by the increased ionization rates, leading to a reduction in molecules such as NH3 and causing H2-rich gas to become C ii bright.
Context.
Observations of the emission of the carbon cycle species (C, C
+
, CO) are commonly used to diagnose gas properties in the interstellar medium, but they are significantly sensitive to the ...cosmic-ray ionization rate. The carbon-cycle chemistry is known to be quite sensitive to the cosmic-ray ionization rate,
ζ
, controlled by the flux of low-energy cosmic rays which get attenuated through molecular clouds. However, astrochemical models commonly assume a constant cosmic-ray ionization rate in the clouds.
Aims.
We investigate the effect of cosmic-ray attenuation on the emission of carbon cycle species from molecular clouds, in particular the CII 158 μm, CI 609 μm, and CO (
J
= 1–0) 115.27 GHz lines.
Methods.
We used a post-processed chemical model of diffuse and dense simulated molecular clouds and quantified the variation in both column densities and velocity-integrated line emission of the carbon cycle with different cosmic-ray ionization rate models.
Results.
We find that the abundances and column densities of carbon cycle species are significantly impacted by the chosen cosmic-ray ionization rate model: no single constant ionization rate can reproduce the abundances modeled with an attenuated cosmic-ray model. Further, we show that constant ionization rate models fail to simultaneously reproduce the integrated emission of the lines we consider, and their deviations from a physically derived cosmic-ray attenuation model is too complex to be simply corrected. We demonstrate that the two clouds we modeled exhibit a similar average
A
V,eff
–
n
H
relationship, resulting in an average relation between the cosmic-ray ionization rate and density
ζ
(
n
H
).
Conclusions.
We conclude by providing a number of implementation recommendations for cosmic rays in astrochemical models, but emphasize the necessity for column-dependent cosmic-ray ionization rate prescriptions.
In EDLCs the energy is stored in the double layer formed by the ions of the electrolyte. Hence, during charge–discharge the ion concentration changes and therefore also the electrolyte should be ...considered as active material. In the past it has been shown that the performance of EDLCs based on non-aqueous electrolytes is mainly limited by ion concentration of the electrolytes. Taking this point into account, we considered the influence of the salt concentration on the theoretical and practical energy of high voltage EDLCs containing innovative electrolytes with the aim to understand the advantages and the limits related to their use.
•Importance of salt concentration for the development of high energy supercapacitors.•High voltage PC-based electrolytes feature promising properties.•Ionic liquids-based EDLCs display limited power at room temperature.
Aim
To evaluate the clinical benefits and cost‐effectiveness of the sensor‐augmented pump compared with self–monitoring of plasma glucose plus continuous subcutaneous insulin infusion in people with ...Type 1 diabetes.
Methods
The CORE Diabetes Model was used to simulate disease progression in a cohort of people with baseline characteristics taken from a published meta‐analysis. Direct and indirect costs for 2010–2011 were calculated from a societal payer perspective, with cost‐effectiveness calculated over the patient's lifetime. Discount rates of 3% per annum were applied to the costs and the clinical outcomes.
Results
Use of the sensor‐augmented pump was associated with an increase in mean discounted, quality–adjusted life expectancy of 0.76 quality–adjusted life years compared with continuous subcutaneous insulin infusion (13.05 ± 0.12 quality–adjusted life years vs 12.29 ± 0.12 quality–adjusted life years, respectively). Undiscounted life expectancy increased by 1.03 years for the sensor‐augmented pump compared with continuous subcutaneous insulin infusion. In addition, the onset of complications was delayed (by a mean of 1.15 years) with use of the sensor‐augmented pump. This analysis resulted in an incremental cost–effectiveness ratio of 367,571 SEK per quality–adjusted life year gained with the sensor‐augmented pump. The additional treatment costs related to the use of the sensor‐augmented pump were partially offset by the savings attributable to the reduction in diabetes‐related complications and the lower frequency of self‐monitoring of plasma glucose.
Conclusions
Analysis using the CORE Diabetes Model showed that improvements in glycaemic control associated with sensor‐augmented pump use led to a reduced incidence of diabetes‐related complications and a longer life expectancy. Use of the sensor‐augmented pump was associated with an incremental cost–effectiveness ratio of 367,571 SEK per quality–adjusted life year gained, which is likely to represent good value for money in the treatment of Type 1 diabetes in Sweden.
What's new?
This study builds on a recent meta‐analysis to provide further insights into the clinical and safety aspects of real‐time continuous glucose monitoring.
Simulations of disease progression show how these aspects translate into long‐term patient benefits and healthcare costs.
Simulations indicate that continuous glucose monitoring leads to later onset and reduced incidence of acute and long‐term diabetes‐related complications.
The findings may have an important influence on informing treatment choices with respect to providing value both for patients and healthcare payers.
We use the gas-grain chemistry code uclchem to explore the impact of cosmic-ray feedback on the chemistry of circumstellar disks. We model the attenuation and energy losses of the cosmic rays as they ...propagate outward from the star and also consider ionization due to stellar radiation and radionuclides. For accretion rates typical of young stars of M yr−1, we show that cosmic rays accelerated by the stellar accretion shock produce an ionization rate at the disk surface ζ 10−15 s−1, at least an order of magnitude higher than the ionization rate associated with the Galactic cosmic-ray background. The incident cosmic-ray flux enhances the disk ionization at intermediate to high surface densities ( > 10 g cm−2), particularly within 10 au of the star. We find that the dominant ions are C+, S+, and Mg+ in the disk surface layers, while the ion dominates at surface densities above 1.0 g cm−2. We predict the radii and column densities at which the magnetorotational instability (MRI) is active in T Tauri disks and show that ionization by cosmic-ray feedback extends the MRI-active region toward the disk midplane. However, the MRI is only active at the midplane of a minimum-mass solar nebula disk if cosmic rays propagate diffusively (ζ ∝ r−1) away from the star. The relationship between accretion, which accelerates cosmic rays, the dense accretion columns, which attenuate cosmic rays, and the MRI, which facilitates accretion, creates a cosmic-ray feedback loop that mediates accretion and may produce variable luminosity.
Ionic liquids in supercapacitors Brandt, A.; Pohlmann, S.; Varzi, A. ...
MRS bulletin,
07/2013, Letnik:
38, Številka:
7
Journal Article
Recenzirano
Supercapacitors are nowadays considered to be one of the most important electrochemical storage devices. These devices display high power and extraordinary cycle life, and they are currently used in ...an increasing number of applications. However, in order to further increase the applications of supercapacitors, an increase in their energy capacity appears to be necessary. Moreover, the development of safe and environmentally friendly supercapacitors is also required. In this article, we illustrate the contributions ionic liquids (ILs) might play in the development of high energy and safe supercapacitors. First, the use of ILs as electrolytes in supercapacitors is considered, and the advantages as well as challenges related to the use of this kind of electrolyte are analyzed. Next, the interaction between ILs and electrode materials is taken into account, with particular attention paid to inactive components of supercapacitor electrodes. The introduction of natural cellulose as a binder is used as an example of the contribution ILs might provide to the development of environmentally friendly supercapacitors.
Vision loss after optic neuropathy is considered irreversible. Here, repetitive transorbital alternating current stimulation (rtACS) was applied in partially blind patients with the goal of ...activating their residual vision.
We conducted a multicenter, prospective, randomized, double-blind, sham-controlled trial in an ambulatory setting with daily application of rtACS (n = 45) or sham-stimulation (n = 37) for 50 min for a duration of 10 week days. A volunteer sample of patients with optic nerve damage (mean age 59.1 yrs) was recruited. The primary outcome measure for efficacy was super-threshold visual fields with 48 hrs after the last treatment day and at 2-months follow-up. Secondary outcome measures were near-threshold visual fields, reaction time, visual acuity, and resting-state EEGs to assess changes in brain physiology.
The rtACS-treated group had a mean improvement in visual field of 24.0% which was significantly greater than after sham-stimulation (2.5%). This improvement persisted for at least 2 months in terms of both within- and between-group comparisons. Secondary analyses revealed improvements of near-threshold visual fields in the central 5° and increased thresholds in static perimetry after rtACS and improved reaction times, but visual acuity did not change compared to shams. Visual field improvement induced by rtACS was associated with EEG power-spectra and coherence alterations in visual cortical networks which are interpreted as signs of neuromodulation. Current flow simulation indicates current in the frontal cortex, eye, and optic nerve and in the subcortical but not in the cortical regions.
rtACS treatment is a safe and effective means to partially restore vision after optic nerve damage probably by modulating brain plasticity. This class 1 evidence suggests that visual fields can be improved in a clinically meaningful way.
ClinicalTrials.gov NCT01280877.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The radioactive decay of aluminum-26 (26Al) is an important heating source in early planet formation. Since its discovery, there have been several mechanisms proposed to introduce 26Al into ...protoplanetary disks, primarily through contamination by external sources. We propose a local mechanism to enrich protostellar disks with 26Al through irradiation of the protostellar disk surface by cosmic rays accelerated in the protostellar accretion shock. We calculate the 26Al enrichment, 26Al/27Al , at the surface of the protostellar disk in the inner au throughout the evolution of low-mass stars, from M-dwarfs to proto-Suns. Assuming constant mass accretion rates, , we find that irradiation by MeV cosmic rays can provide significant enrichment on the disk surface if the cosmic rays are not completely coupled to the gas in the accretion flow. Importantly, we find that low accretion rates, M yr−1, are able to produce canonical amounts of 26Al, . These accretion rates are experienced at the transition from Class I- to Class II-type protostars, when it is assumed that calcium-aluminum-rich inclusions condense in the inner disk. We conclude that irradiation of the inner disk surface by cosmic-ray protons accelerated in accretion shocks at the protostellar surface may be an important mechanism to produce 26Al. Our models show protostellar cosmic rays may be a viable model to explain the enrichment of 26Al found in the solar system.
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