563 research outputs found

    Relationship between higher education level and GDP per capita of different American States

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    Education has long been considered a vital factor that determines a person’s income level. This paper aims to explore if this effect still exists after being magnified to a state-wide scale, and, if it still does, the extent to which this effect can be observed. The percentage of the population aged 25 or older that are bachelor’s degree holders, by state, is used as a measure of the education level of a state, and this paper attempts to find the relationship between this value and GDP per capita of a state. Furthermore, this paper takes other variables into account, which are unemployment and urban population, to better model the effect of education on GDP per capita

    Transparent and conductive polysiloxanes/ PEDOT:PSS nanocomposite thin films with a “water-impermeable” property to significantly enhance stability of organic–inorganic hybrid solar cells

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    We demonstrated for the first time that optically transparent and conductive polysiloxanes/PEDOT:PSS nanocomposite thin films were produced at 85oC by mixing a sol-gel modified polysiloxanes with the aqueous PEDOT:PSS solution. Polysiloxanes/PEDOT:PSS nanocomposite thin films were deposited by conventional solution-processed spin- or spray-coating methods, presenting superior water- and scratch- resistance. ~100 Ω/□ sheet resistance with ~ 80% transmittance was obtained and was further reduced to 25 Ω/□ by adding 90 nm±20 nm Ag nanowires in the solution. The p-type polysiloxanes/PEDOT:PSS nanocomposite thin films were then applied on n-type c-Si wafers to fabricate organic-inorganic Schottky hybrid photovoltaic devices, demonstrating the similar performance in power conversion efficiency as PEDOT:PSS. However, To the best of our knowledge our high conductive polysiloxanes/PEDOT:PSS nanocomposite c-Si hybrid photovoltaic devices presented the best stability among this type of devices under the ambient environment. Performance of our photovoltaic devices kept no degradation even if the devices were immersed in water without encapsulation for protection

    On the density and multiplicity of solutions to the fractional Nirenberg problem

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    This paper is devoted to establishing some results on the density and multiplicity of solutions to the fractional Nirenberg problem which is equivalent to studying the conformally invariant equation Pσ(v)=Kvn+2σn2σP_\sigma(v)=K v^{\frac{n+2\sigma}{n-2\sigma}} on the standard unit sphere (Sn,g0)(\mathbb{S}^n,g_0) with σ(0,1)\sigma\in (0,1) and n2n\geq 2, where PσP_\sigma is the intertwining operator of order 2σ2\sigma and KK is the prescribed curvature function. More specifically, by using the variational gluing method, refined analysis of bubbling behavior, extension formula, as well as the blow up analysis arguments, we obtain the existence of infinitely many multi-bump solutions. In particular, we show the smooth curvature functions of metrics conformal to g0g_0 are dense in the C0C^{0} topology. Moreover, the related fractional Laplacian equations (Δ)σu=K(x)un+2σn2σ(-\Delta)^{\sigma} u=K(x) u^{\frac{n+2\sigma}{n-2\sigma}} in Rn\mathbb{R}^n, with K(x)K(x) being asymptotically periodic in one of the variables, are also studied and infinitely many solutions are obtained under natural flatness assumptions

    A Meta-Analysis of Enteral Nutrition and Total Parenteral Nutrition in Patients with Acute Pancreatitis

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    Objective. To analyze the effect of total parenteral nutrition (TPN) and enteral nutrition (EN) in patients with acute pancreatitis. Methods. Randomized controlled trials of TPN and EN in patients with acute pancreatitis were searched in NCBI and CBM databases and The Cochrane Controlled Trials Register. Six studies were enrolled into the analysis, and the details about the trial designs, characters of the subjects, results of the studies were reviewed by two independent authors and analyzed by STATA 11.0 software. Results. Compared with TPN, EN was associated with a significantly lower incidence of pancreatic infection complications (RR = 0.556, 95% CI 0.436∼0.709, P = .000), MOF (RR = 0.395, 95% CI 0.272∼0.573, P = .003), surgical interventions (RR = 0.556, 95% CI 0.436∼0.709, P = .000), and mortality (RR = 0.426, 95% CI 0.238∼0.764, P = .167). There was no statistic significance in non-pancreatitis-related complications (RR = 0.853, 95% CI 0.490∼1.483, P = .017). However, EN had a significantly higher incidence of non-infection-related complications (RR = 2.697, 95% CI 1.947∼3.735, P = .994). Conclusion. EN could be the preferred nutrition feeding method in patients with acute pancreatitis

    A Novel Diffusion-based Empirical Mode Decomposition Algorithm for Signal and Image Analysis

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    In the area of signal analysis and processing, the Fourier transform and wavelet transform are widely applied. Empirical Mode Decomposition(EMD) was proposed as an alternative frequency analysis tool. Although shown to be effective when analyzing non-stationary signals, the algorithmic nature of EMD makes the theoretical analysis and formulation difficult. Futhermore, it has some limitations that affect its performance. In this thesis, we introduce some methods to extend or modify EMD, in an effort to provide a rigorous mathematical basis for it, and to overcome its shortcomings. We propose a novel diffusion-based EMD algorithm that replaces the interpolation process by a diffusion equation, and directly construct the mean curve (surface) of a signal (image). We show that the new method simplifies the mathematical analysis, and provides a solid theory that interprets the EMD mechanism. In addition, we apply the new method to the 1D and 2D signal analysis showing its possible applications in audio and image signal processing. Finally, numerical experiments for synthetic and real signals (both 1D and 2D) are presented. Simulation results demonstrate that our new algorithm can overcome some of the shortcomings of EMD, and require much less computation time

    Kerr Solitons and Brillouin Lasers in Optical Microresonators

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    Optical resonators are capable of storing electromagnetic energies in the visible and infrared band. The light intensity is greatly enhanced within the resonator, which makes them suitable as a platform for nonlinear optics studies. Here, using silica microresonators as platforms, we explore the fundamental nonlinear dynamics of light induced by Kerr nonlinearity and Brillouin scattering. The first half of the thesis analyzes optical solitons as a result of Kerr nonlinearity, including its universal scaling, its dynamics in the presence of laser feedback, the analytical properties of its relativistic counterpart, as well as its applications as a wavelength reference. The second half of the thesis focuses on stimulated Brillouin lasers and their linewidth performance, demonstrating new performance levels of the Brillouin laser and two correction factors to its linewidth that have been established for semiconductor lasers.</p

    Sol-gel studies of the Yb2O3-Al2O3 system and alumina garnets with ytterbium.

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    Sol-gel science and techniques have mainly been used to synthesize inorganic oxides. Thousands of inorganic oxides or mixed oxides have been manufactured by the sol-gel method. They can take the form of thin films, powders, monolithic, and fibres. Many sol-gel oxides systems have been studied. One of the most important systems is the Y[2]O[3]-AI[2]O[3] system which has been studied for many years by sol-gel methods. In this system, there are several phases which have widespread uses in industry such as Y[3]AI[5]O[5], YAIO[3], and Y[4]AI[2]O[9]. For example, Nd doped Y[3]AI[5]O[5] is presently the most widely used solid-state laser material. Yb doped YAG is one of the most promising laser active materials and is more suitable for diode pumping than the traditional Nd-doped YAG. In fact, the rare earth aluminium garnet family is one of the most active areas of activities in recent years because of their optical, mechanical, and thermodynamical properties.In this thesis, the production and properties of the sol-gel Yb[2]O[3]-Al[2]O[3] system are studied using sol-gel science and techniques. Ytterbium is a rare earth element in the lanthanide series and belongs to the same group as yttrium in the periodic table and hence, the oxides that they form often have very similar properties and applications in industry. The research focuses on the sol-gel synthesis, sol-gel processing, crystallisation, and structures of alumina garnets in the Yb[2]O[3]-Al[2]O[3] system. The thermal behaviour of the sol-gel Yb[2]O[3]-Al[2]O[3] system was studied by DTA and TG. The crystallisation characteristics were investigated in the pure Yb[2]O[3]-Al[2]O[3] system. The effects of the crystallisation were also studied after other elements were doped in this system. Thin films, thick coatings, and nanosize powders of the pure and doped alumina garnets were produced by the sol-gel method. Their morphologies and structures were studied and consideration was given to their potential uses in industry.In this thesis, novel Mo doped YbAG garnets were synthesised for the first time by the sol-gel technique. Their application depends on the existing state of Mo (VI) cations in the YbAG matrix. Laser materials, Yb doped YbAG garnets, were successfully produced for the first time using the sol-gel method and their structural changes have been studied. The host crystal structures deform after doping with various concentrations of Yb[3+]. However, this deformation does not show a linear relationship with the doped Yb[3+] concentration, which could, in part, explain why around 20 atomic % doped Yb:YAG generally exhibits good properties in laser or scintillator applications

    Towards milli-Hertz laser frequency noise on a chip

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    Narrow-linewidth lasers are important to many applications spanning precision metrology to sensing systems. Their miniaturization in the form of on-chip lasers is receiving increasing attention. Here, a noise level that is consistent with a fundamental frequency noise of 9 mHz⋅Hz/Hz linewidth (60 mHz linewidth) is measured in a Brillouin laser. The results leverage ultra-high-Q silica-on-silicon resonators and point towards a new performance target for chip-based laser platforms
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