Positive Periodic Solutions of Second-Order Differential Equations with Delays

The existence results of positive ω-periodic solutions are obtained for the second-order differential equation with delays −u″+a(t)=f(t,u(t−τ1),...,u(t−τn)), where a∈C(ℝ,(0,∞)) is a ω-periodic function, f:ℝ×[0,∞)n→[0,∞) is a continuous function, which is ω-periodic in t, and τ1,τ2,...,τn are positive constants. Our discussion is based on the fixed point index theory in cones

The Existence of Positive Solutions for Boundary Value Problem of Nonlinear Fractional Differential Equations

We consider the existence of positive solutions for the nonlinear fractional differential equations boundary value problem -D0+αu(t)=f(t,u(t)),   0<t<1,  u(0)=u'(0)=u'(1)=0, where 2<α≤3 is a real number, D0+α is the Riemann-Liouville fractional derivative of order α, and f is a given continuous function. Our analysis relies on the fixed point index theory in cones

Changes in Tropical Clouds and Atmospheric Circulation Associated with Rapid Adjustment Induced by Increased Atmospheric CO2 A Multiscale Modeling Framework Study

The radiative heating increase due to increased CO2 concentration is the primary source for the rapid adjustment of atmospheric circulation and clouds. In this study, we investigate the rapid adjustment resulting from doubling of CO2 and its physical mechanism using a multiscale modeling framework (MMF). The MMF includes an advanced higher-order turbulence closure in its cloud-resolving model component and simulates realistic shallow and deep cloud climatology and boundary layer turbulence. The rapid adjustment over the tropics is characterized by 1) reduced ascent and descent strengths over the ocean, 2) increased lower tropospheric stability (LTS) over the subsidence region, 3) shoaling of planetary boundary layers over the ocean, 4) increased deep convection over lands and shift of cloud coverage from the ocean to lands, and 5) reduced sensible (SH) and latent heat (LH) fluxes over the oceanic deep convective regions. Unlike conventional general circulation models and another MMF, a reduction in the global-mean shortwave cloud radiative cooling is not simulated, due to the increase in low clouds at lower altitudes over the ocean, resulting from reduced cloud-top entrainment due to strengthened inversion. Changes in regional circulation play a key role in cloud changes and shift of cloud coverage to lands. Weaker energy transport resulting from water vapor and cloud CO2 masking effects reduces the upward motion and convective clouds in the oceanic regions. The ocean-land transports are linked to the partitioning of surface SH and LH fluxes that increases humidity over lands and enhances deep convection over the tropical lands