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Achieving optimal camouflage in an aquatic environment necessitates the ability to modulate transmittance in response to the surrounding obscurity and potential threats. This adaptation involves a dynamic transition from transparency to a deep-blue color, especially in low-light or dark situations. Such a strategy promotes a seamless assimilation with the surroundings, enabling the absorption of searchlights and, subsequently, diminishing the risk of detection by predators. Therefore, the presence of sophisticated mechanisms that facilitates stable and efficient control of transmittance is imperative, enabling smooth transition between transparent and deep-blue hues within the aquatic environment. This study presents nature-inspired programmable camouflage system that integrates an electrochromic display as the primary transmittance change element and a wireless base module for power and data transmission. Such technology offers a robust and flexible construction, ensuring stable operation as demonstrated through mechanical-fatigue experiments and quantitative simulation. A custom circuit and a power-control software package enable active control of multiple electrochromic displays while submerged in water. [ABSTRACT FROM AUTHOR]

Foveated rendering (FR) technology is designed to improve the efficiency of graphical rendering processes. In rendering, individualized approaches can help to balance users’ experiences of visual quality and saving computational resource. However, previous studies have not rigorously examined it related with the FR techniques. To address this issue, we developed an individualized FR (IFR) method using different central vision sizes and peripheral vision resolutions across individuals in virtual reality. In three user studies with 88 participants who were divided into groups designated as “large central area (LCA)” and “small central area (SCA),” the effects of IFR were compared with those of using the full-resolution condition and the average FR condition. The results indicate that the LCA group experienced higher visual quality under the IFR and full-resolution conditions than under the average FR condition. In contrast, the SCA group exhibited comparable levels of dependent measures between the IFR and average FR conditions, but both were lower than those of the full-resolution condition. We also evaluated the computational benefits of the proposed IFR method, and the results demonstrated the effectiveness of our approach in saving resources across the two groups. Although lower-bound adjustments may be required for some users, our overall results suggest that IFR is a malleable technology for enhancing rendering efficiency in virtual reality. [ABSTRACT FROM AUTHOR]

Real-time monitoring of suspended particulate matter (PM) has become essential in daily life due to the adverse effects of long-term exposure to PMs on human health and ecosystems. However, conventional techniques for measuring micro-scale particulates commonly require expensive instruments. In this study, a smartphone-based device is developed for real-time monitoring of suspended PMs by integrating a smartphone-based digital holographic microscopy (S-DHM) and deep learning algorithms. The proposed S-DHM-based PM monitoring device is composed of affordable commercial optical components and a smartphone. Overall procedures including digital image processing, deep learning training, and correction process are optimized to minimize the prediction error and computational cost. The proposed device can rapidly measure the mass concentrations of coarse and fine PMs from holographic speckle patterns of suspended polydisperse PMs in water with measurement errors of 22.8 ± 18.1% and 13.5 ± 9.8%, respectively. With further advances in data acquisition and deep learning training, this study would contribute to the development of hand-held devices for monitoring polydisperse non-spherical pollutants suspended in various media. [ABSTRACT FROM AUTHOR]

This study investigated the deteriorations of precast prestressed concrete (PSC) ties that were used for 15 years in high-speed railways in Korea and its damaging mechanism. The collected PSC ties with longitudinal cracks on sides and map cracks on surfaces exhibited strength degradation. The deteriorations were likely related to alkali-silica reaction (ASR) and delayed ettringite formation (DEF) together, given that the presence of massive ettringite crystals and the decomposition of ASR gel were found from microstructural analyses. Although there were no typical reactive siliceous aggregates for ASR in this study, ASR cracks were generated in the PSC ties. This is because the aggregates in the PSC ties with cracks were potentially reactive, and its high alkali-silica reactivity was likely attributable to the presence of microcrystalline quartz, supplying reactive SiO2 to trigger ASR. Furthermore, the alkali content in aggregates was associated with the deterioration of the PSC ties. The alkali-bearing minerals in aggregates (i.e., alkali feldspars) likely supplied enough alkalis for ASR. Besides, micas in aggregates could promote ASR due to their porous structure, which helps easy water ingress. [ABSTRACT FROM AUTHOR]

The Pacific Island countries have a substantial socio-economic dependency on fisheries. Skipjack tuna is one of the most important species in the Western Central Pacific (WCP) and its catches in this region exhibit a spatio-temporal variability influenced by ocean conditions, mainly the El Niño-Southern Oscillation (ENSO). This study investigates the relationship between skipjack tuna catch amounts and environmental variables in the equatorial Pacific during 1990–2014, and evaluates the potential predictability of the catches based on their statistical relationship. A series of regressed and reconstructed spatial patterns of upper-ocean temperature, salinity, currents and precipitation represent ENSO-like variability, and their principal component time series are used to estimate the predictability of skipjack tuna catches in the Federated States of Micronesia (FSM). ENSO-like variability depicted from 100 m temperature and 5 m salinity in the equatorial Pacific exhibit a significant predictability for the annual catch amount in the FSM for several years with a training period of > 20 years. This suggests that the subsurface temperature or near surface salinity can be a better predictor of ecosystem variability than widely used sea surface temperature. Applications of this result to other species could have broad implications for the fishery industry in the WCP. [ABSTRACT FROM AUTHOR]

Aharonov–Bohm conductance oscillations emerge as a result of gapless surface states in topological insulator nanowires. This quantum interference accompanies a change in the number of transverse one-dimensional modes in transport, and the density of states of such nanowires is also expected to show Aharonov–Bohm oscillations. Here, we demonstrate a novel characterization of topological phase in Bi2Se3 nanowire via nanomechanical resonance measurements. The nanowire is configured as an electromechanical resonator such that its mechanical vibration is associated with its quantum capacitance. In this way, the number of one-dimensional transverse modes is reflected in the resonant frequency, thereby revealing Aharonov–Bohm oscillations. Simultaneous measurements of DC conductance and mechanical resonant frequency shifts show the expected oscillations, and our model based on the gapless Dirac fermion with impurity scattering explains the observed quantum oscillations successfully. Our results suggest that the nanomechanical technique would be applicable to a variety of Dirac materials. The density of states (DOS) of a topological insulator nanowire is expected to show Aharonov-Bohm (AB) oscillations, but they are never observed so far. Here, Kim et al. reveal AB oscillations in the DOS of a Bi2Se3 nanowire via nanomechanical resonance measurements. [ABSTRACT FROM AUTHOR]

Precise doping-profile engineering in van der Waals heterostructures is a key element to promote optimal device performance in various electrical and optical applications with two-dimensional layered materials. Here, we report tungsten diselenide- (WSe2) based pure vertical diodes with atomically defined p-, i- and n-channel regions. Externally modulated p- and n-doped layers are respectively formed on the bottom and the top facets of WSe2 single crystals by direct evaporations of high and low work-function metals platinum and gadolinium, thus forming atomically sharp p-i-n heterojunctions in the homogeneous WSe2 layers. As the number of layers increases, charge transport through the vertical WSe2 p-i-n heterojunctions is characterized by a series of quantum tunneling events; direct tunneling, Fowler-Nordheim tunneling, and Schottky emission tunneling. With optimally selected WSe2 thickness, our vertical heterojunctions show superb diode characteristics of an unprecedentedly high current density and low turn-on voltages while maintaining good current rectification. Vertical charge transport through homogeneous WSe2 layers can be effectively tuned by the layer number and contacting metals deposited. Here, the authors report WSe2 vertical diodes with superior device performance characteristics based on variable WSe2 thickness and gadolinium and platinum contact metals. [ABSTRACT FROM AUTHOR]