This paper applied the modified Fourier series method to investigate the sound-vibration characteristics by establishing a composite laminated thin sector plate-cavity coupled model for the first ...time based on the classical plate theory (CPT) and Rayleigh-Ritz energy technique. The coupled system consists of an annular sector or circular sector plate backed by an acoustic cavity filled with air or water. Ignoring the influence of boundary conditions, displacements admissible functions of laminated sector plate and sound pressure admissible functions of cavity can be set up as a Fourier series superposition, whose composition are the superposition of Fourier cosine series and supplementary functions. The addition of these supplementary polynomials can effectively eliminate the discontinuity or jump phenomenon on the boundary. The correctness of the established analytical model has been validated by being compared with the results achieved by the finite element method (FEM). On this basis, the coupling mechanism of the weakly coupled system and the strongly coupled system are discussed in detail. In addition, some new results and discussions are given, including the cavity depth, plate thickness, anisotropic degree, varying boundary conditions and so on, which could provide reference for future research.
The main challenges hindering the practical application of seawater electrolysis are the substantial energy input for sluggish oxygen evolution reaction (OER) and anode corrosion by chlorine ...oxidation reaction (COR). Here we report a simple but reliable strategy of coupling seawater electrolysis with formaldehyde oxidation reaction (FOR) to achieve energy-saving and COR-free dual hydrogen production. For the anode FOR, the onset potential is cut to near -0.2 V vs. the reversible hydrogen electrode (RHE) much lower than the theoretical potential of OER (1.23 V vs. RHE), and the Faradaic efficiencies of both hydrogen and high-value formate products achieve nearly 100 %. In a two-electrode electrolyzer at 100 mA cm−2, the cell voltage of our integrated system is 1.75 V lower than that of the conventional seawater electrolysis, leading to a 66 % reduction in electricity consumption. Moreover, benefiting from the ultra-low reaction potential, the harmful COR is fundamentally avoided. This work opens up a new way to efficiently and stably convert sea resources into hydrogen fuel while also achieving chemical upgrades.
Coupling seawater electrolysis with formaldehyde oxidation reaction (FOR) was a simple but reliable strategy to achieve energy-saving and COR-free dual hydrogen production. With Cu/CF/O as the catalyst, this coupled strategy offers a notable economic advantage by reducing 66 % energy consumption for hydrogen production at 100 mA cm−2 and meanwhile enables upgrading formaldehyde to valuable formate products. Display omitted
Fire is a common tool for land conversion and management associated with oil palm production. Fires can cause biodiversity and carbon losses, emit pollutants that deteriorate air quality and harm ...human health, and damage property. The Roundtable on Sustainable Palm Oil (RSPO) prohibits the use of fire on certified concessions. However, efforts to suppress fires are more difficult during El Niño conditions and on peatlands. In this paper, we address the following questions for oil palm concessions developed prior to 2012 in Sumatra and Kalimantan, the leading producers of oil palm both within Indonesia and globally: (1) for the period 2012-2015, did RSPO-certified concessions have a lower density of fire detections, fire ignitions, or 'escaped' fires compared with those concessions that are not certified? and (2) did this pattern change with increasing likelihood of fires in concessions located on peatland and in dry years? These questions are particularly critical in fuel-rich peatlands, of which approximately 46% of the area was designated as oil palm concession as of 2010. We conducted propensity scoring to balance covariate distributions between certified and non-certified concessions, and we compare the density of fires in certified and non-certified concessions using Kolmogorov-Smirnov tests based on moderate resolution imaging spectroradiometer Active Fire Detections from 2012-2015 clustered into unique fire events. We find that fire activity is significantly lower on RSPO certified concessions than non-RSPO certified concessions when the likelihood of fire is low (i.e., on non-peatlands in wetter years), but not when the likelihood of fire is high (i.e., on non-peatlands in dry years or on peatlands). Our results provide evidence that RSPO has the potential to reduce fires, though it is currently only effective when fire likelihood is relatively low. These results imply that, in order for this mechanism to reduce fire, additional strategies will be needed to control fires in oil palm plantations in dry years and on peatlands.
This paper is devoted to exploring the fractional incompressible Navier–Stokes system coupled with a fractional reaction–diffusion equation involving multivalued boundary conditions and weakly ...continuous operators. Under suitable conditions, the solvability of the coupled system is established by the Rothe method, a surjectivity result for multivalued mappings, and a fixed point argument for a fractional reaction–diffusion equation.
We develop backstepping state feedback control to stabilize a moving shockwave in a freeway segment under bilateral boundary actuations of traffic flow. A moving shockwave, consisting of light ...traffic upstream of the shockwave and heavy traffic downstream, is usually caused by changes of local road situations. The density discontinuity travels upstream and drivers caught in the shockwave experience transitions from free to congested traffic. Boundary control design in this article brings the shockwave front to a static setpoint position, hindering the upstream propagation of traffic congestion. The traffic dynamics are described with Lighthil-Whitham-Richard model, leading to a system of two first-order hyperbolic partial differential equations (PDEs). Each represents the traffic density of a spatial domain segregated by the moving interface. By Rankine-Hugoniot condition, the interface position is driven by flux discontinuity and thus governed by an ordinary differential equation (ODE) dependent on the PDE states. The control objective is to stabilize both the PDE states of traffic density and the ODE state of moving shock position to setpoint values. Using delay representation and backstepping method, we design predictor feedback controllers to cooperatively compensate state-dependent input delays to the ODE. From Lyapunov stability analysis, we show local stability of the closed-loop system in <inline-formula><tex-math notation="LaTeX">H^1</tex-math></inline-formula> norm with an arbitrarily fast convergence rate. The stabilization result is demonstrated by a numerical simulation and the total travel time of the open-loop system is reduced by <inline-formula><tex-math notation="LaTeX">12 \%</tex-math></inline-formula> in the closed loop.
Hydrogen gas production from cellulose was investigated using an integrated hydrogen production process consisting of a dark fermentation reactor and microbial fuel cells (MFCs) as power sources for ...a microbial electrolysis cell (MEC). Two MFCs (each 25mL) connected in series to an MEC (72mL) produced a maximum of 0.43V using fermentation effluent as a feed, achieving a hydrogen production rate from the MEC of 0.48m3 H2/m3/d (based on the MEC volume), and a yield of 33.2mmol H2/g COD removed in the MEC. The overall hydrogen production for the integrated system (fermentation, MFC and MEC) was increased by 41% compared with fermentation alone to 14.3mmol H2/g cellulose, with a total hydrogen production rate of 0.24m3 H2/m3/d and an overall energy recovery efficiency of 23% (based on cellulose removed) without the need for any external electrical energy input.
In the dynamic analysis of railway lines, both lateral and vertical track irregularities should be considered. In addition, uncertainties in the bridge structure and train load will have different ...effects on the train-bridge coupled system (TBCS). This paper presents a three-dimensional model of the TBCS to study the influence of various sources of randomness on the response of the TBCS. The Karhunen-Loéve expansion is combined with the point estimate method (KLE-PEM) to calculate the statistical moment of the system response with high accuracy and efficiency. Furthermore, applicability of KLE-PEM method is discussed and the influence of different combinations of sources of randomness on the train and bridge responses under different speeds is analyzed according to the maximum range of probability values. Random track irregularities are found to have a much greater influence on the train response than uncertain parameters, whereas uncertain parameters have the greatest influence on the displacement of the bridge.
In this paper, we study the existence of normalized solutions to the following nonlinear Schrödinger systems with critical exponential ...growth:{−Δu+λ1u=f1(u)+βr1|u|r1−2u|v|r2,inR2,−Δv+λ2v=f2(v)+βr2|u|r1|v|r2−2v,inR2,∫R2u2dx=a2and∫R2v2dx=b2,u,v∈H1(R2), where 0<a,b<1,β>0,r1,r2>1 and r1+r2∈(4,+∞), f1,f2∈C(R,R) have critical exponential growth in the sense of Trudinger-Moser inequality. λ1,λ2∈R will arise as Lagrange multipliers. Under some suitable assumptions on f1,f2, we prove the existence of positive normalized ground state solutions for the problem when β>0 is sufficiently large via variational method. Our results improve and extend the previous results.
•Propose direct coupled PVEH-UFHs for remote areas.•Validation of the TRNSYS simulation model for direct coupled PVEHs.•Propose an evaluation method for the performance of direct coupled ...PVEH-UFHs.•SA identified the key factors affect the performance of direct coupled PVEH-UFHs.•THAR and payback time of direct coupled PVEH-UFHs were evaluated.
Limited access to grids and the unavailability of traditional energy sources present significant challenges to effective heating in remote rural. This paper proposes a direct coupled photovoltaic electric heater underfloor heating system with phase change materials (direct coupled PVEH-UFHs), which eliminates the reliance on the power grid or conventional energy sources for heating in remote areas. The model of the direct coupled photovoltaic electric heating system (direct coupled PVEHs) and the building model with PCM floor were created and the accuracy of the direct coupled PVEHs model was verified experimentally. The study proposes using the total heating achievement rate (THAR) as the evaluation index and identifies the critical parameters affecting the system performance through sensitivity analysis. The results indicate that the photovoltaic capacity factor (PVCF), PCMs thickness and melting temperature are the key parameters affecting the heating performance of the system. The recommended 1.4 PVCF and PCM melting temperature of 294 K. The minimum payback time for system configuration that achieves 90 % THAR is 16.2 years. In summary, this paper proposes a design method and evaluation criteria for direct coupled PVEH-UFHs suitable for energy-efficient heating in remote areas.
Today many vehicle manufacturers are interested in an inductive power transfer system design with a secondary side that is simple and low in cost, weight, and size. To achieve this, a more ...sophisticated primary side design is required to ensure interoperability with various magnetic topologies. Simple secondary pads such as the circular pad and double-D pad (DDP) (similar to the flat solenoid) can only couple either the perpendicular or parallel component of flux entering the surface of the pad respectively. This paper investigates using various known multiple coil pad designs as the primary that can be switched between various excitation modes during operation, without making tuning or other expensive adjustments. The primary pads considered here include; the DDP, the double-D quadrature pad (DDQP) and the bipolar pad (BPP). Results show that the mutually coupled structure of the DDP primary makes it a poor choice for interoperability, whereas the DDQP and BPP are able to achieve good results because of the decoupled coil structures inherent in their design. The DDQP has improved leakage characteristics while the BPP shows better interoperability characteristics with improved material usage efficiency and is easy to drive because of its identical coil structures.
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