Despite the growing awareness of harmful algal blooms (HABs) in the United States and abroad, estimates of welfare losses due to their presence are missing from the literature. Using a mail survey of ...767 Ohio Lake Erie recreational angler respondents and a choice experiment, this study provides the first empirical quantification of the economic impacts of HABs on U.S. recreational anglers. Our results demonstrate a significant and substantial willingness to pay by anglers for reduction in HABs, beyond the benefits associated with conventional water quality measures such as catch rates and water clarity. For instance, we find that anglers are willing to pay $8 to $10 more per trip for one less mile of boating through HABs en route to a fishing site. This finding suggests that explicit measures of HABs need to be collected and considered when valuing water quality in nutrient-rich bodies of water. We evaluate the welfare improvements resulting from several nutrient reduction policies, and find that anglers are willing to pay on average $40 to $60 per trip for a policy that cuts upstream phosphorus loadings by 40%. The majority of welfare gains for anglers result from improving the non-catchable component of the fishing experience, notably water clarity and HAB reduction, as opposed to better chances of angler success.
A refractive index sensor based on metal-insulator-metal (MIM) waveguides coupled double rectangular cavities is proposed and investigated numerically using the finite element method (FEM). The ...transmission properties and refractive index sensitivity of various configurations of the sensor are systematically investigated. An asymmetric Fano resonance lineshape is observed in the transmission spectra of the sensor, which is induced by the interference between a broad resonance mode in one rectangular and a narrow one in the other. The effect of various structural parameters on the Fano resonance and the refractive index sensitivity of the system based on Fano resonance is investigated. The proposed plasmonic refractive index sensor shows a maximum sensitivity of 596 nm/RIU.
Background Google Flu Trends (GFT) claimed to generate real-time, valid predictions of population influenza-like illness (ILI) using search queries, heralding acclaim and replication across public ...health. However, recent studies have questioned the validity of GFT. Purpose To propose an alternative methodology that better realizes the potential of GFT, with collateral value for digital disease detection broadly. Methods Our alternative method automatically selects specific queries to monitor and autonomously updates the model each week as new information about CDC-reported ILI becomes available, as developed in 2013. Root mean squared errors (RMSEs) and Pearson correlations comparing predicted ILI (proportion of patient visits indicative of ILI) with subsequently observed ILI were used to judge model performance. Results During the height of the H1N1 pandemic (August 2 to December 22, 2009) and the 2012–2013 season (September 30, 2012, to April 12, 2013), GFT’s predictions had RMSEs of 0.023 and 0.022 (i.e., hypothetically, if GFT predicted 0.061 ILI one week, it is expected to err by 0.023) and correlations of r =0.916 and 0.927. Our alternative method had RMSEs of 0.006 and 0.009, and correlations of r =0.961 and 0.919 for the same periods. Critically, during these important periods, the alternative method yielded more accurate ILI predictions every week, and was typically more accurate during other influenza seasons. Conclusions GFT may be inaccurate, but improved methodologic underpinnings can yield accurate predictions. Applying similar methods elsewhere can improve digital disease detection, with broader transparency, improved accuracy, and real-world public health impacts.
A visible-light-induced charge transfer pathway and a molecular-level photocatalysis mechanism on Bi semimetal@defective BiOBr hierarchical microspheres were revealed by combined in situ DRIFTS and ...DFT calculation.
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•Bi semimetal@defective BiOBr hierarchical microspheres were constructed.•Bi semimetal@defective BiOBr exhibited highly enhanced photocatalysis.•The charge transfer pathway on Bi metal@defective BiOBr was unraveled.•The photocatalysis mechanism on Bi metal@defective BiOBr was revealed.•A combined theoretical and experimental method was developed.
Charge transfer pathway and catalysis mechanism are two major issues in a specific catalytic reaction process. To further probe these two aspects of photocatalytic NO oxidation to address the environmental problem, Bi metal@defective BiOBr hierarchical microspheres were fabricated and used as a visible light photocatalyst. The interfacial and surface properties of Bi metal@defective BiOBr were optimized to understand the SPR effect of Bi metal and the oxygen vacancies (OVs) formed in situ. It was found that the charge transfer pathway on Bi metal@defective BiOBr has been significantly changed from that on pristine BiOBr. The Bi semimetal could act both as a charge transfer bridge and as a hot electron donor. The OVs induced the formation of an intermediate level in the band structure of BiOBr and promote O2 activation and thus the generation of O2− species. Due to the synergistic effects of Bi metal and OVs, Bi metal@defective BiOBr demonstrated highly enhanced visible light photocatalytic performance for NO removal. The photocatalytic NO oxidation process has been monitored by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), which could reveal the reaction intermediate products accurately. On the basis of an investigation with in situ DRIFTS and the simulation of the electronic structure, a new photocatalysis mechanism involving Bi metal, OVs, and NO transformation was proposed. The perspectives on the charge transfer pathway and photocatalysis mechanism in the present work can be extended to other catalysts for tuning the interfacial properties and enhancing the photocatalytic performance to address environmental problems.
The photocatalytic performance of the star photocatalyst g-C3N4 was restricted by the low efficiency because of the fast charge recombination. The present work developed a facile in situ method to ...construct g-C3N4/g-C3N4 metal-free isotype heterojunction with molecular composite precursors with the aim to greatly promote the charge separation. Considering the fact that g-C3N4 samples prepared from urea and thiourea separately have different band structure, the molecular composite precursors of urea and thiourea were treated simultaneously under the same thermal conditions, in situ creating a novel layered g-C3N4/g-C3N4 metal-free heterojunction (g-g CN heterojunction). This synthesis method is facile, economic, and environmentally benign using easily available earth-abundant green precursors. The confirmation of isotype g-g CN heterojunction was based on XRD, HRTEM, valence band XPS, ns-level PL, photocurrent, and EIS measurement. Upon visible-light irradiation, the photogenerated electrons transfer from g-C3N4 (thiourea) to g-C3N4 (urea) driven by the conduction band offset of 0.10 eV, whereas the photogenerated holes transfer from g-C3N4 (urea) to g-C3N4 (thiourea) driven by the valence band offset of 0.40 eV. The potential difference between the two g-C3N4 components in the heterojunction is the main driving force for efficient charge separation and transfer. For the removal of NO in air, the g-g CN heterojunction exhibited significantly enhanced visible light photocatalytic activity over g-C3N4 alone and physical mixture of g-C3N4 samples. The enhanced photocatalytic performance of g-g CN isotype heterojunction can be directly ascribed to efficient charge separation and transfer across the heterojunction interface as well as prolonged lifetime of charge carriers. This work demonstrated that rational design and construction of isotype heterojunction could open up a new avenue for the development of new efficient visible-light photocatalysts.
•Realizing a faster convergence time without relying on the initial system values.•Improving estimates accuracy of uncertainties and avoiding the learning explosion.•Avoid excessive samplings of ...control signal without degrading system behaviors.
In this paper, a fuzzy rule-based neural appointed-time control scheme for uncertain nonlinear systems with aperiodic samplings is proposed. To guarantee tracking properties with preassigned convergence time and remove the high dependency on accurate initial states of system, we construct an improved prescribed performance control (IPPC) scheme on the basis of a hyperbolic cosecant performance function with a finite-time behavior. In light of the unavailability of partial states and uncertainties, by combining a fuzzy wavelet neural network (FWNN) with a state observer, a FWNN-based state observer is developed, which can simultaneously approximate unavailable system states and unknown lumped disturbances with a remarkable accuracy. In addition, aimed at eliminating the problem of parameter updating explosion caused by overlarge learning dimensions, a minimum-learning-parameter (MLP) technique is embedded in the FWNN-based state observer, where the norm of weight matrix is employed for online adaptive updating. Furthermore, an event-triggered control scheme with relative thresholds is synthesized within the framework of dynamic surface control (DSC), which can allow for aperiodic samplings to save communication and actuating resources. Meanwhile, a Nussbaum type function is introduced to solve the issue of unknown control coefficients. The significant features of our work are twofold: (1) Appointed-time tracking performances with much fewer sampling times are assured. (2) An enhanced robustness against uncertainties is achieved with a lower computational complexity and the requirement of full-state measurements is relaxed. Finally, two simulation examples are performed to validate the effectiveness and advantages of the proposed control scheme.
•Two constitutive equations of homogenized AA7005 were established.•The predictability of the two constitutive descriptions is satisfactory.•The constitutive equation with strain compensation shows ...higher accuracy.•Reliable simulation results were obtained using the developed constitutive equation.
Although the extruded profiles of 7005 aluminum alloy have been widely used in the components of high speed train, automobile and aircrafts, the plastic deformation behavior of homogenized 7005 aluminum alloy at evaluated temperature has not been fully clarified. In this study, the isothermal hot compression tests of homogenized 7005 aluminum alloy at the deformation temperatures ranging from 623K to 823K and with the strain rates ranging from 0.001s−1 to 10s−1 were conducted for constitutive analysis. It was found that the flow stress increased with decreasing deformation temperatures and increasing strain rates. Two Arrhenius-typed constitutive equations without and with the compensation of strain were developed based on the true stress–strain curves. Although both constitutive equations show their excellent predictability on the flow stress, the one considering the influence of strain has higher accuracy. Furthermore, the extrusion experiment and corresponding finite element simulation using the developed constitutive equation with strain compensation were carried out. The simulated results confirmed that the material flow behavior of the 7005 aluminum alloy during extrusion process was well predicted.
We propose a flexible wireless pressure sensor, which uses a graphene/polydimethylsiloxane (GR/PDMS) sponge as the dielectric layer. The sponge is sandwiched between two surfaces of a folded flexible ...printed circuit with patterned Cu as the antenna and electrode. By adjusting graphene and NH
HCO
concentrations, a composite with 20% concentration of NH
HCO
and 2% concentration of graphene as the dielectric layer is obtained, which exhibits high sensitivity (2.2 MHz/kPa), wide operating range (0-500 kPa), rapid response time (~7 ms), low detection limit (5 Pa), and good stability, recoverability, and repeatability. In addition, the sensor is sensitive to finger bending and facial muscle movements for smile and frown, that are transmitted using wireless electromagnetic coupling; therefore, it has potential for a wide range of applications such as intelligent robots, bionic-electronic skin and wearable electronic devices.
The obtained cluster 1 at% Au@In2O3 gas sensor exhibits highly sensitive and low detection of limit for CO detection.
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•Regulated cluster In2O3 nanostructures were fabricated by ...adjusting reactant amount.•Compared with large size In2O3 nanocubes and monodispersed cubic nanoparticles, cluster In2O3 nanostructures exhibits higher response to CO.•Introducing of Au nanoparticles into cluster In2O3 nanostructures further improve the sensing performance toward CO.•The CO concentration dependence of 1 at% Au@In2O3 cluster sensor implied that 0.5 ppb CO could be detected under 20% relative humidity.
Cubic indium oxide (In2O3) of different sizes, In2O3 nanocube clusters, and In2O3 nanocube clusters embedded Au nanoparticles were obtained using solvothermal method. Compared with the large size or monodispersed In2O3 nanocubes, In2O3 nanocube clusters shows a higher response to carbon monoxide (CO), due to increased surface area and pore structures. Moreover, In2O3 nanocube clusters with an Au nanoparticle core (Au@In2O3) leads to a further increase of response to CO. Our results also show that 1 at% Au@In2O3 system presents the best sensing properties with response of 42.1–100 ppm CO, response/recovery speed of 2/2 s and ultra-low limit detection. The CO concentration dependence of the sensor response implies that ∼0.5 ppb and ∼28 ppb could be detected with a response value of 1.4 under 20 % and 93 % relative humidity, respectively. This increase in sensing response is due to the fact that Au nanoparticles can enhance the receptor function of the semiconductor gas sensor. Remarkably, Au@In2O3 system unifies three key factors of a semiconductor gas sensor, i.e., high specific surface area, high porosity, and noble metal loading.
•Electron transfer was demonstrated by Raman spectroscopy in situ.•Multilayer RGO and WS2 composites formed large area of p-n heterojunction.•The humidity sensor shows excellent sensitivity and fast ...response/recovery time.
High-performance multifunctional sensors that are powered wirelessly could find applications in athlete training, health monitoring, and human-machine interactions. In this paper, a humidity sensor based on a reduced graphene oxide (RGO) and tungsten disulfide (WS2) heterojunction is proposed. The sensor exhibits high performance in regard to humidity sensing. The wireless humidity sensor has a fast response time (0.56 s) and recovery time (2.26 s), which can be attributed to the heterojunction and the synergistic effect. The sensor also has a wide working range between 5%RH to 95 %RH. The flexible humidity sensor can be used to monitor the skin humidity and evaluate the metabolism of the human body. Moreover, in situ Raman spectrum was used to prove the electron transfer between the water molecule and RGO-WS2 (RGWS) at different humidity. Thus, this work could have broad applications in various fields such as personal health, physical training, and psychological state monitoring.
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