Reliable detection of traffic congestion provides pertinent information for improving safety and comfort by alerting the driver to crowded roads or providing useful information for rapid decision-making. This paper addresses the problem of road traffic congestion estimation and detection from a statistical approach. First, a piecewise switched linear traffic model (PWSL)-based observer is introduced. The proposed hybrid observer (HO) estimates the unmeasured traffic density, thus reducing the cost of implementing and maintenance sensors and measurements devices. Here, the observer gains of each mode are obtained by solving a set of linear matrix inequalities. Second, a novel method for efficiently monitoring traffic congestion is proposed by combining the proposed HO with a generalized likelihood ratio (GLR) test. Also, an exponentially-weighted moving average (EWMA) filter is applied to the residual data to reduce high-frequency noise. Thus, as the EWMA filter, aggregates all of the information from past and actual samples in the decision rule, it extends the congestion detection abilities of the GLR test to the detection of incipient changes. This study shows that a better performance is achieved when GLR is applied to filtered data than to unfiltered data. The effectiveness of the proposed approach is verified on traffic data from the four-lane State Route 60 (SR-60) and the three lanes Interstate 210 (I-210) in California freeways. Results show the efficacy of the proposed HO-based EWMA-GLR method to monitor traffic congestions. Also, the proposed approach is compared to that of the conventional Shewhart and EWMA approaches and found better performance.

3D organic–inorganic hybrid halide perovskites have attracted great interest due to their impressive optoelectronic properties. Recently, the emergence of 2D layered hybrid perovskites, with their excellent and tunable optoelectronic behavior, has encouraged researchers to develop the next generation of optoelectronics based on these 2D materials. However, device fabrication methods of scalable patterning on both types of hybrid perovskites are still lacking as these materials are readily damaged by the organic solvents in standard lithographic processes. We conceived the orthogonal processing and patterning method: Chlorobenzene and hexane, which are orthogonal to hybrid perovskites, are utilized in modified electron beam lithography (EBL) processes to fabricate perovskite-based devices without compromising their electronic or optical characteristics. As a proof-of-concept, we used the orthogonal EBL technique to fabricate a 2D layered single-crystal (C6H5C2H4NH3)2PbI4 photodetector featuring nanoscale patterned electrodes and superior photodetection ability with responsivity of 5.4 mA/W and detectivity of 1.07 × 1013 cm Hz1/2/W. Such orthogonal processing and patterning methods are believed to fully enable the high-resolution, high-throughput fabrication of complex perovskite-based electronics in the near future.

Alkane cross-metathesis of light and heavy paraffins is a compelling way to upgrade two low cost streams into more valuable products, in only one step and using a single catalyst. Herein, we report the cross-metathesis reaction between light and heavy paraffins that occurs under mild conditions on a well-defined catalyst precursor [(≡SiO)W(Me)5] treated under hydrogen at 150 °C. Experiments with isotopic labeled alkanes (13C 1-propane + n decane or n-propane + C10D22) allow us to unambiguously prove the occurrence of the cross-metathesis reaction and to elucidate the plausible reaction mechanism. In order to optimize the percent cross-metathesis between propane and n-decane, we varied several parameters; in particular, the influence of the C3/C10 ratio was found to be the most important one due to the difference in the reactivity of the two components in the alkane mixtures.

Palladium (Pd) nanogap hydrogen gas (H2) sensors based on the large volume expansion of β phase palladium hydride (β-PdH) are highly promising, owing to their fast and accurate sensing capability at room temperature in air. However, such sensors do not work well at H2 concentrations below 1%. At such low H2 concentrations, Pd exists as α-PdH, which has a slow and insufficient volume expansion and cannot completely close nanogaps. Furthermore, the lattice strains induced from the phase transition (α-PdH → β-PdH) behavior degrade the stable and repeatable long-term sensing capability. Here, these issues are resolved by fabricating an array of periodically aligned alloyed palladium–gold nanoribbons (PdAu NRB) with uniform 15 nm nanogaps. The PdAu NRB sensor enables highly stable and ultrafast H2 sensing at the full detection range of H2 concentrations from 0.005% to 10% along with the excellent limit of detection (≈0.0027%), which is sufficiently maintained even after seven months of storage in ambient atmosphere. These breakthrough results will pave the way for developing a practical high-performance H2 sensor chip in the future hydrogen era.

One of the greatest challenges in a photovoltaic solar power generation is to keep the designed photovoltaic systems working with the desired operating efficiency. Towards this goal, fault detection in photovoltaic plants is essential to guarantee their reliability, safety, and to maximize operating profitability and avoid expensive maintenance. In this context, a model-based anomaly detection approach is proposed for monitoring the DC side of photovoltaic systems and temporary shading. First, a model based on the one-diode model is constructed to mimic the characteristics of the monitored photovoltaic array. Then, a one-class Support Vector Machine (1SVM) procedure is applied to residuals from the simulation model for fault detection. The choice of 1SVM approach to quantify the dissimilarity between normal and abnormal features is motivated by its good capability to handle nonlinear features and do not make assumptions on the underlying data distribution. Experimental results over real data from a 9.54 kWp grid-connected plant in Algiers, show the superior detection efficiency of the proposed approach compared with other binary clustering schemes (i.e., K-means, Birch, mean-shift, expectation–maximization, and agglomerative clustering).

Exhaust Gas Recirculation (EGR) is a frequently used technique to reduce the production of NOx. The effect of EGR on the early flame evolution, two-stage ignition process and spray flame structures for n-heptane spray flames are investigated using large eddy simulation. The two-stage ignition process is identified based on the formation of key species and early heat release process. Results demonstrate that a longer ignition delay (ID) and flame lift-off length (LOL) under lower oxygen concentration conditions could increase the mixing time for fuel and air. However, the first-stage ignition still initiates in fuel-richer regions for the cases with higher EGR rates due to the lack of oxygen. In contrast, compared to the case with the same initial oxygen content but at a higher gas temperature of 1000 K, the first-stage ignition moves to stoichiometric mixture fraction regions at 900 K. The combustion mode analysis based on hydroxyl and formaldehyde is conducted to distinguish between the low- and high-temperature combustion regions. Most importantly, to study the stabilization mechanism, the chemical explosive mode analysis (CEMA) is conducted based on analysis on the local flow time scale and the chemical time scale. During the early stage of ignition, a balance between reaction and mixing implies that cool flame propagates from the ignition spots through the entire flow field. And during the quasi-steady state, autoignition plays a dominant role.

We present a leaf-inspired biomimetic omnidirectional photon management scheme for ultrathin flexible graphene silicon Schottky junction solar cell. An all-dielectric approach comprising lossless spheroidal silica and titania nanoparticle bilayers is used for mimicking the two essential light trapping mechanisms of a leaf - focusing and waveguiding, and scattering. The ratio of the nanoparticle diameters of the two optically tuned layers plays a crucial role in confining the incident light through whispering gallery modes and subsequent forward scattering into the substrate via strong leaky channels. The scheme does not employ any nanostructuring of the silicon substrate, thereby preventing the optical gain from being offset by recombination losses, completely decoupling the optical and electrical performances of the device. The light-trapping scheme shows ultralow broadband reflection of only 10.3% and causes a 30% increase in efficiency compared to a bare graphene/silicon solar cell. An efficiency of ~9% is obtained for solar cell with 20 µm thick n-silicon absorber and doped bilayer graphene, resulting in highest (1.89) watt/gram utilization of silicon among all graphene/silicon solar cells. The light-trapping nanoparticle-embellished solar cell retains its characteristics for >10 bending cycles for a bend radius as low as 3 mm, demonstrating its flexibility, durability and reliability.

Reduced invertebrate abundance and diversity are common responses to metals contamination in mining-impacted streams. The resulting changes in community composition may have implications for metals accumulation and transfer through the food web. We investigated how changes in invertebrate community composition (abundance, species richness, and food web complexity) influence metals bioaccumulation and exposure risk to upper trophic levels along a contamination gradient in the upper Blackfoot River Basin, Montana. Invertebrate species richness exhibited the strongest decline with increasing sediment metals concentrations, driven by the loss of metals-sensitive taxa. These changes in invertebrate community composition resulted in a decline in the proportion of invertebrates in the scraper functional feeding group, likely influencing dietary metals exposure to the invertebrate community. Additionally, invertebrates with a strong propensity-to-drift increased with sediment contamination, potentially facilitating metals transfer to fish and higher trophic levels through predation. Using invertebrate exposure values (invertebrate abundance × metals concentrations), we found that moderately contaminated sites in our study area produced both the highest invertebrate exposure values and the highest fish tissue metals concentrations. Considering both changes in invertebrate community composition and metal concentrations is an important step towards understanding and evaluating potential toxic effects to upper trophic levels in mining-impacted streams.

Processing metal–organic frameworks (MOFs) as films with controllable thickness on a substrate is increasingly crucial for many applications to realize function integration and performance optimization. Herein, we report a facile cathodic deposition process that enables the large-area preparation of uniform films of zeolitic imidazolate frameworks (ZIF-8, ZIF-71, and ZIF-67) with highly tunable thickness ranging from approximately 24 nm to hundreds of nanometers. Importantly, this oxygen-reduction-triggered cathodic deposition does not lead to the plating of reduced metals (Zn and Co). It is also operable cost-effectively in the absence of supporting electrolyte and facilitates the construction of well-defined sub-micrometer-sized heterogeneous structures within ZIF films.

A transmission + reflection wave-equation traveltime and waveform inversion method is presented that inverts the seismic data for the anisotropic parameters in a vertical transverse isotropic medium. The simultaneous inversion of anisotropic parameters v and ε is initially performed using transmission wave-equation traveltime inversion method. Transmission wave-equation traveltime only provides the low-intermediate wavenumbers for the shallow part of the anisotropic model; in contrast, reflection wave-equation traveltime estimates the anisotropic parameters in the deeper section of the model. By incorporating a layer-stripping method with reflection wave-equation traveltime, the ambiguity between the background-velocity model and the depths of reflectors can be greatly mitigated. In the final step, multi-scale full-waveform inversion is performed to recover the high-wavenumber component of the model. We use a synthetic model to illustrate the local minima problem of full-waveform inversion and how transmission and reflection wave-equation traveltime can mitigate this problem. We demonstrate the efficacy of our new method using field data from the Gulf of Mexico.