Personalized trip recommendation for tourists based on user interests,points of interest visit durations and visit recency

Tour recommendation and itinerary planning are challenging tasks for tourists, due to their need to select points of interest (POI) to visit in unfamiliar cities and to select POIs that align with their interest preferences and trip constraints. We propose an algorithm called PersTour for recommending personalized tours using POI popularity and user interest preferences, which are automatically derived from real-life travel sequences based on geo-tagged photographs. Our tour recommendation problem is modeled using a formulation of the Orienteering problem and considers user trip constraints such as time limits and the need to start and end at specific POIs. In our work, we also reflect levels of user interest based on visit durations and demonstrate how POI visit duration can be personalized using this time-based user interest. Furthermore, we demonstrate how PersTour can be further enhanced by: (i) a weighted updating of user interests based on the recency of their POI visits and (ii) an automatic weighting between POI popularity and user interests based on the tourist’s activity level. Using a Flickr dataset of ten cities, our experiments show the effectiveness of PersTour against various collaborative filtering and greedy-based baselines, in terms of tour popularity, interest, recall, precision and F\(_1\)-score. In particular, our results show the merits of using time-based user interest and personalized POI visit durations, compared to the current practice of using frequency-based user interest and average visit durations.     

New criteria for stochastic suppression and stabilization of hybrid functional differential systems

This paper establishes new criteria for stochastic suppression and stabilization of hybrid functional differential systems with general 1‐sided polynomial growth condition. For an unstable nonlinear hybrid functional differential system with general 1‐sided polynomial growth condition, 2 independent Brownian noise processes are used to perturb the system into the stochastic hybrid differential system. Theoretical analysis shows that one of the nonlinear diffusion terms may suppress the explosive solution of deterministic system, and the other one can make the perturbed hybrid system almost surely stable with general decay rate.     

Effects of Fluorinated Diluents in Localized High-Concentration Electrolytes for Lithium–Oxygen Batteries

A stable electrolyte is critical for practical application of lithium–oxygen batteries (LOBs). Although the ionic conductivity and electrochemical stability of the electrolytes have been extensively investigated before, their oxygen solubility, viscosity, volatility, and the stability against singlet oxygen (¹O₂) still need to be comprehensively investigated to provide a full picture of the electrolytes, especially for an open system such as LOBs. Herein, a systematic investigation is reported on the localized high-concentration electrolytes (LHCEs) using different fluorinated diluents in comparison with those of conventional electrolytes. The physical properties and activation energies for reactions with singlet oxygen (¹O₂) of these electrolytes are calculated by density functional theory. The electrochemical performances of LOBs using these electrolytes are compared. This study reveals that the correlation between the stability of the electrolytes and their physical and electrochemical properties depends strongly on the diluents in LHCEs. Therefore, it shines light on the rational design of new electrolytes for LOBs.     

Digital Laser Micropainting for Reprogrammable Optoelectronic Applications

Structural coloration is closely related to the progress of innovative optoelectronic applications, but the absence of direct, on-demand, and rewritable coloration schemes has impeded advances in the relevant area, particularly including the development of customized, reprogrammable optoelectronic devices. To overcome these limitations, a digital laser micropainting technique, based on controlled thin-film interference, is proposed through direct growth of the absorbing metal oxide layer on a metallic reflector in the solution environment via a laser. A continuous-wave laser simultaneously performs two functions—a photothermal reaction for site-selective metal oxide layer growth and in situ real-time monitoring of its thickness—while the reflection spectrum is tuned in a broad visible spectrum according to the laser fluence. The scalability and controllability of the proposed scheme is verified by laser-printed painting, while altering the thickness via supplementary irradiation of the identical laser in the homogeneous and heterogeneous solutions facilitates the modification of the original coloration. Finally, the proof-of-concept bolometer device verifies that specific wavelength-dependent photoresponsivity can be assigned, erased, and reassigned by the successive application of the proposed digital laser micropainting technique, which substantiates its potential to offer a new route for reprogrammable optoelectronic applications.     

Atomically Smooth Graphene-Based Hybrid Template for the Epitaxial Growth of Organic Semiconductor Crystals

Atomically thin 2D materials are good templates to grow organic semiconductor thin films with desirable features. However, the 2D materials typically exhibit surface roughness and spatial charge inhomogeneity due to nonuniform doping, which can affect the uniform assembly of organic thin films on the 2D materials. A hybrid template is presented for preparation of highly crystalline small-molecule organic semiconductor thin film that is fabricated by transferring graphene onto a highly ordered self-assembled monolayer. This hybrid graphene template has low surface roughness and spatially uniform doping, and it yields highly crystalline fullerene thin films with grain sizes >300 nm, which is the largest reported grain size for C₆₀ thin films on 2D materials. A graphene/fullerene/pentacene phototransistor fabricated directly on the hybrid template has five times higher photoresponsivity than a phototransistor fabricated on a conventional graphene template supported by a SiO₂ wafer.     

Nanowire-Based Soft Wearable Human–Machine Interfaces for Future Virtual and Augmented Reality Applications

A virtual world has now become a reality as augmented reality (AR) and virtual reality (VR) technology become commercially available. Similar to how humans interact with the physical world, AR and VR systems rely on human–machine interface (HMI) sensors to interact with the virtual world. Currently, this is achieved via state of-the-art wearable visual and auditory tools that are rigid, bulky, and burdensome, thereby causing discomfort during practical application. To this end, a skin sensory interface has the potential to serve as the next-generation AR/VR technology because skin-like wearable sensors have advantages in that they can be ultrathin, ultra-soft, conformal, and imperceptible, which provides the ultimate comfort and immersive experience for users. In this progress report, nanowire-based soft wearable HMI sensors including acoustic, strain, pressure sensors, and physiological sensors are reviewed that may be adopted as skin sensory inputs in future AR/VR systems. Further, nanowire-based soft contact lenses, haptic force, and thermal and vibration actuators are covered as potential means of feedback for future AR/VR systems. Considering the possible effects of the virtual world on human health, skin-like wearable artery pulses, glucose, and lactate sensors are also described, which may enable imperceptible health monitoring during future AR/VR practices.     

Outstanding Low-Temperature Performance of Structure-Controlled Graphene Anode Based on Surface-Controlled Charge Storage Mechanism

The energy and power performance of lithium (Li)-ion batteries is significantly reduced at low-temperature conditions, which is mainly due to the slow diffusion of Li-ions in graphite anode. Here, it is demonstrated that the effective utilization of the surface-controlled charge storage mechanism through the transition from layered graphite to 3D crumpled graphene (CG) dramatically improves the Li-ion charge storage kinetics and structural stability at low-temperature conditions. The structure-controlled CG anode prepared via a one-step aerosol drying process shows a remarkable rate-capability by delivering ≈206 mAh g^–1 at a high current density of 10 A g^–1 at room temperature. At an extremely low temperature of −40 °C, CG anode still exhibits a high capacity of ≈154 mAh g^–1 at 0.01 A g^–1 with excellent rate-capability and cycling stability. A combination of electrochemical studies and density functional theory (DFT) reveals that the superior performance of CG anode stems from the dominant surface-controlled charge storage mechanism at various defect sites. This study establishes the effective utilization of the surface-controlled charge storage mechanism through structure-controlled graphene as a promising strategy to improve the charge storage kinetics and stability under low-temperature conditions.     

Biomass-Derived P,N Self-Doped Hard Carbon as Bifunctional Oxygen Electrocatalyst and Anode Material for Seawater Batteries

Owing to the demand for low-cost batteries with safety, Na-seawater batteries (SWBs) have received considerable attention as a new energy storage system (ESS). In SWB, it is necessary to use an advanced oxygen evolution/reduction reaction (OER/ORR) catalyst for high energy efficiency (EE) in the cathode and a good sodium storage material for a highly reversible capacity in the anode part. In this study, nanostructured and N and P dual-doped hard carbon is fabricated by simply carbonizing abundant biomass, pine pollen. The oxygen electrocatalytic performance of pine pollen carbon (PPC) for a cathode is confirmed by a seawater half-cell test, which exhibits the lowest overpotential reported among Pt/C (20 wt%) and commercial hard carbon (HC) electrodes. The sodium-storage performance of PPC as an anode active material is tested using a coin-type Na half-cell, which exhibits a higher reversible capacity than that of the HC electrode. To reduce the manufacturing cost, this SWB, comprising both PPC electrodes at the anode and cathode, are fabricated and shown an EE of 74% and a coulombic efficiency (CE) of 98%. This study proposes a low-cost and safe ESS system by utilizing seawater as catholyte, bifunctional (OER/ORR, sodiation/desodiation) electrode configuration, and abundantly available biomass carbon.     

Multi-Fidelity High-Throughput Optimization of Electrical Conductivity in P3HT-CNT Composites

Combining high-throughput experiments with machine learning accelerates materials and process optimization toward user-specified target properties. In this study, a rapid machine learning-driven automated flow mixing setup with a high-throughput drop-casting system is introduced for thin film preparation, followed by fast characterization of proxy optical and target electrical properties that completes one cycle of learning with 160 unique samples in a single day, a > 10 ×  improvement relative to quantified, manual-controlled baseline. Regio-regular poly-3-hexylthiophene is combined with various types of carbon nanotubes, to identify the optimum composition and synthesis conditions to realize electrical conductivities as high as state-of-the-art 1000 S cm⁻¹. The results are subsequently verified and explained using offline high-fidelity experiments. Graph-based model selection strategies with classical regression that optimize among multi-fidelity noisy input-output measurements are introduced. These strategies present a robust machine-learning driven high-throughput experimental scheme that can be effectively applied to understand, optimize, and design new materials and composites.     

Self-Assembled Perovskite Nanoislands on CH3NH3PbI3 Cuboid Single Crystals by Energetic Surface Engineering

Organometal perovskite single crystals have been recognized as a promising platform for high-performance optoelectronic devices, featuring high crystallinity and stability. However, a high trap density and structural nonuniformity at the surface have been major barriers to the progress of single crystal-based optoelectronic devices. Here, the formation of a unique nanoisland structure is reported at the surface of the facet-controlled cuboid MAPbI₃ (MA = CH₃NH₃⁺) single crystals through a cation interdiffusion process enabled by energetically vaporized CsI. The interdiffusion of mobile ions between the bulk and the surface is triggered by thermally activated CsI vapor, which reconstructs the surface that is rich in MA and CsI with reduced dangling bonds. Simultaneously, an array of Cs-Pb-rich nanoislands is constructed on the surface of the MAPbI₃ single crystals. This newly reconstructed nanoisland surface enhances the light absorbance over 50% and increases the charge carrier mobility from 56 to 93 cm² V⁻¹ s⁻¹. As confirmed by Kelvin probe force microscopy, the nanoislands form a gradient band bending that prevents recombination of excess carriers, and thus, enhances lateral carrier transport properties. This unique engineering of the single crystal surface provides a pathway towards developing high-quality perovskite single-crystal surface for optoelectronic applications.