Depth Distribution Research Articles

Dyakonov surface waves in a thin interfacial waveguide formed by negatively anisotropic dielectrics.

Dyakonov surface waves (DSWs) are electromagnetic surface waves that exist at the interface of two dissimilar materials, with at least one material being anisotropic. Although there are various types of these waves, they all exist in anisotropic materials with positive anisotropy. The requirement for positive anisotropy limits the choice of materials that can support these waves. In this study, we present a type of Dyakonov surface wave that occurs at the interface of negatively anisotropic materials. Specifically, we demonstrate their existence in a system consisting of two negatively anisotropic slabs confined between two perfect electric conductor (PEC) walls. By assuming a small distance between the walls, we derive analytical expressions for the propagation constant, penetration depth, and field distribution of these surface waves. We numerically demonstrate that these surface waves can also exist in structures beyond the approximations used to develop the theoretical framework. The existence of Dyakonov surface waves in negative crystals broadens the range of materials suitable for their practical implementation.

Calibration-free deep optics for depth estimation with precise simulation

Monocular depth estimation is an important computer vision task widely explored in fields such as autonomous driving, robotics, and more. Recently, deep optics approaches that optimize diffractive optical elements (DOEs) with differentiable frameworks have improved depth estimation performance. However, they only consider on-axis point spread functions (PSFs) and are highly dependent on system calibration. We propose a precise end-to-end paradigm combining ray tracing and angular spectrum diffraction. With this approach, we jointly trained a DOE and a reconstruction network for depth estimation and image restoration. Compared with conventional deep optics approaches, we accurately simulate both on-axis and off-axis PSFs, eliminating the need for calibration. We have validated the high similarity between captured PSFs and simulated ones at 19.4∘ field-of-view (FOV). Our optimized phase mask and network achieve state-of-the-art performance among semantic-based monocular depth estimation and existing deep optics methods. During real-world experiments, our prototype camera shows depth distributions similar to the Intel D455 infrared structured light camera.

Effect of impact-corrosion coupling damage on fatigue properties of 2198-T8 aluminum-lithium alloy

The peeling of aircraft surface paint due to foreign object impact can expose the aluminum–lithium alloy substrate to atmospheric corrosion, resulting in the fatigue performance being affected by the combined effect of impact damage and corrosion damage. In this work, the effects of impact damage and corrosion damage on the fatigue life of 2198-T8 aluminum–lithium alloy sheet were investigated. The strain field distribution of specimens with coupled impact and corrosion damage under cyclic loading was analyzed by Digital Image Correlation (DIC) technique, and the coupling relationship between impact and corrosion damage was analyzed based on the crack propagation path and fracture morphology. The results show that surface corrosion pits depth distribution of impact dents follows the same trend as residual stress distribution. For the coupling damage of the hemispherical punch, the coupled effect between impact damage and corrosion damage is most evident at low impact energy. At higher impact energies, the impact damage dominates the coupling damage. As the salt spray corrosion time increases, the fatigue life decrease rate gradually slows with increasing impact energy, and the impact damage has a greater effect on the fatigue life in the early corrosion stage. Compared to the salt spray corrosion environment at 35 °C, the fatigue life of the specimen at 25 °C increased by a maximum of 50.48 % as the impact energy increased from 10 J to 25 J.

Void swelling in pure iron after sequential self-ion-irradiation at different energies: Effect of injected interstitials and additional damage in regions containing pre-existing voids

The use of ion irradiation to add displacement dose onto previously neutron-irradiated material is becoming popular, especially since ion irradiation precedes on neutron-typical microstructures and microchemical distributions that would not be produced with ion irradiation alone. One issue to be addressed in these “neutron-preconditioned” specimens concerns the consequences of ion-injected interstitials on preexisting neutron-produced voids, especially since voids have been observed to disappear over a significant portion of the ion range in some recent preconditioning experiments. This situation can be explored using innovative ion simulation, thereby avoiding working with radioactive material.Two self-ion irradiation series of pure single-crystal iron were performed at 475 °C. The first series used 5 MeV Fe2+, reaching 50, 100 and 150 peak dpa, producing voids to ∼2 µm depth. The second series used 2.5 MeV Fe2+ to introduce additional 50 peak dpa onto each of the three first-step specimens with the ion range reaching ∼1.2 µm. Importantly, 1.2 × 10−3 peak dpa/s was used for both ions to minimize the influence of dpa rate. The major objective was to measure the influence of injected interstitials from the 2.5 MeV Fe2+ irradiation on previously existing voids. Another objective was to observe the behavior of voids exposed to additional dose and time, focusing not only on injected interstitials, but also on the effects of coalescence, ripening, and aging.There were significant changes in depth distribution of swelling following the second irradiation, especially void density. Whereas injected interstitials are well-known to suppress void nucleation at the end of ion range, it was shown in this study that injected interstitials are important in another manner, reducing growth of previously existing voids, producing a ‘notch” in both the swelling vs. depth profile and void size profile. At depths where the injected atoms for both ion energies are not significant, swelling proceeds at ∼0.2 %/dpa.

Controllable Modulation of Trapped Carriers in Mechano/Thermo Dual‐Responsive Particles for Advanced Stress‐Encoded Information Storage

AbstractMechanoluminescence (ML) is a fascinating phenomenon with diverse applications in pressure sensing, damage detection, and stress distribution visualization. However, most ML materials exhibit instantaneous photon emission that requires real‐time recording with a photodetector, and thereby circumscribing their applicability predominantly to real‐time stress‐sensing scenarios. In this work, a novel method is introduced for non‐real‐time stress sensing utilizing Li0.1Na0.9NbO3:Pr3+ phosphor, which allows for the retrieval of pressure location and intensity even 20 days after the event. The influence of heat and pressure on the trap depth distribution is analyzed using thermoluminescence (TL) and ML measurements, and it is proved that both heat and pressure release the captured electrons in the same traps. Leveraging the intricate competition between mechanical and thermal detrapping processes, stress information can be accessed through TL imaging. Furthermore, an algorithm is proposed based on this phenomenon to authenticate the stress information. This research not only advances the fundamental understanding of ML phenomena but also introduces a novel approach for applications such as mechano‐history indicators, security papers, and advanced data storage systems.

Distribution and ecology of shallow-water black corals across a depth gradient on Galápagos rocky reefs

AbstractAntipathes galapagensis is a prevalent habitat-forming black coral in subtidal ecosystems of the Galápagos Marine Reserve (GMR). Despite their ecological importance and status as a CITES-regulated order, little is known about their depth distribution, population structure and ecology in the GMR. Surveys were conducted in 2021 and 2022 at 9 sites in the central Galápagos Archipelago to investigate how black coral densities, occupancy, size, habitat utilization, and epizoan overgrowth varied between 2.0 and 20.0 m depth. The shallowest black corals occurred at 3.4 m depth, one of the shallowest occurrences of an Antipathes spp. in the world. Coral density increased with depth, with a maximum density of 5.2 colonies per m2 observed across the depth range surveyed. Occupancy modeling also yielded curves with increasing probabilities of black coral presence with depth at all sites. Colony height increased with depth at 8 out of 9 sites and was positively correlated with coral density at 6 of 9 sites. Overall, 47% of colonies surveyed occupied cryptic habitats and 53% were attached to exposed substrate, but black coral habitat usage patterns varied with depth at 5 of 9 sites. At these sites, colonies on shallower transects (5.0, 10.0 m depth) more frequently displayed cryptic habitat usage while colonies along the deeper transects (15.0, 20.0 m) were more often exposed. In general, coral density, probability of occupancy, height, and exposed habitat utilization increased with depth, while the average degree of overgrowth and number of epibiont taxa were unrelated to depth. Five hypotheses regarding factors potentially limiting the shallow (upper) depth distribution of A. galapagensis—ranging from negative impacts of the physical environment to high predation on exposed substrates—are presented for future testing. These results provide a comprehensive ecological characterization of Galápagos black coral populations that can be used to assess the impact of future environmental change and applied to management decisions for this key marine foundation species in the GMR.

Laser‐Annealed SiO2/Si1−xGex Scaffolds for Nanoscaled Devices, Synergy of Experiment, and Computation

Laser‐Annealed SiO₂/Si_1−<i>x</i>Ge_<i>x</i> Scaffolds for Nanoscaled Devices, Synergy of Experiment, and Computation

On the rise and fall of galactic ionizing output at the end of reionization

ABSTRACT Quasar absorption spectra measurements suggest that reionization proceeded rapidly, ended late at z ∼ 5.5, and was followed by a flat ionizing background evolution. Simulations that reproduce this behaviour often rely on a fine-tuned galaxy ionizing emissivity, which peaks at z ∼ 6–7 and drops a factor of 1.5–2.5 by z ∼ 5. This is puzzling since the abundance of galaxies is observed to grow monotonically during this period. Explanations for this include effects such as dust obscuration of ionizing photon escape and feedback from photoheating of the IGM. We explore the possibility that this drop in emissivity is instead an artefact of one or more modelling deficiencies in reionization simulations. These include possibly incorrect assumptions about the ionizing spectrum and/or inaccurate modelling of IGM clumping. Our results suggest that the need for a drop could be alleviated if simulations are underestimating the IGM opacity from massive, star-forming haloes. Other potential modelling issues either have a small effect or require a steeper drop when remedied. We construct an illustrative model in which the emissivity is nearly flat at reionization’s end, evolving only ∼0.05 dex at 5 &amp;lt; z &amp;lt; 7. More realistic scenarios, however, require a ∼0.1–0.3 dex drop. We also study the evolution of the Ly α effective optical depth distribution and compare to recent measurements. We find that models that feature a hard ionizing spectrum and/or are driven by faint, low-bias sources most easily reproduce the mean transmission and optical depth distribution of the forest simultaneously.

On individual leaf depths of trees

We explore a generating function trick which allows us to keep track of infinitely many statistics using finitely many variables, by recording their individual distributions rather than their joint distributions. Building on previous work of Panholzer and Prodinger, we apply this method to study the depth distributions of individual nodes or leaves in rooted binary trees, plane trees, noncrossing trees, and increasing trees; the height distributions of individual vertices and individual steps in Dyck paths; and the number of diagonals separating two fixed sides of a convex polygon in a triangulation or dissection. We obtain both exact and asymptotic results, which sometimes refine known formulas or provide combinatorial proofs of results from the probability literature.

Estimating snow depth based on dual polarimetric radar index from Sentinel-1 GRD data: A case study in the Scandinavian Mountains

The sensitivity of synthetic aperture radar (SAR) polarization information to snow depth changes provides new opportunities for regional snow depth retrieval in mountains with thick snow cover. However, interference from soil signals can affect the accurate quantification of snow volume scattering signals. The aim of this study was to develop a dual-polarimetric radar snow depth estimation (DpRSE) methodological framework that utilizes Sentinel-1 data for snow depth retrieval in the Scandinavian Mountains. This framework is based on the dual-polarimetric radar vegetation index (DpRVIc), which enhances the snow volume scattering signal and reduces soil interference by integrating soil purity and a conditioning factor to fully exploit the advantages of polarimetric SAR information. The results revealed a strong correlation between the DpRVIc and snow depth, and the DpRVIc significantly outperformed the other polarimetric radar indices. The multitemporal retrieval results clearly reflect the heterogeneity of the snow depth distribution. This method is applicable to areas without tree cover. Meanwhile, the shrub-filled regions also affect the snow depth retrieval accuracy. Under the same environmental conditions and using the same validation dataset, a comparison between the DpRSE method and the cross-polarization ratio method was conducted. The results indicated that the DpRSE method surpasses similar existing methods in terms of snow depth retrieval accuracy. Specifically, the coefficient of determination (R2) for the DpRSE method reached 0.66, which represents a 26.9 % improvement over that of the cross-polarization ratio method. Moreover, the mean absolute error (MAE) decreased by 20 %. This study offers a novel perspective on SAR snow depth retrieval utilizing polarization information.

Suppression of thermal diffusion of vacancies across p + -n junction structures in diamond. Application to SnV centers by ion implantation

This work reports on defect engineering related to optical centers in diamond by ion implantation. In particular, we demonstrate that thermal diffusion of vacancies to a few micrometers in depth can be effectively suppressed provided these are electrically charged and located within the depletion region of an abrupt p+ -n junction. The observed effect is complementary to the observations in the previous study (Favaro et al 2017 Nat. Commun. 8 15409) showing that charging of implantation-induced vacancies at such junction structures in diamond inhibits the formation of vacancy complexes in proximity to the targeted optical centers. In the present work we first generate vacancies near the surface of a low nitrogen doped CVD diamond substrate by He and C ion implantation before these are diffused by annealing at 1200∘C into the bulk. In the next step the depth distribution of NV centers generated by trapping of these vacancies is analyzed on a micron scale. For precise tuning of the implantation conditions we derived data on the boron and nitrogen doping by step etching of planar p+ resistors and p+ -n- p+ diode structures combined with electrical characterization and modeling. In the next step, tin-vacancy (SnV) centers were produced by 40 keV Sn implantation across the same junction structures at optimized conditions. In this way we observe an enhancement of the SnV yield and noticeable suppression of NV centers by diffusion and trapping of vacancies along the tracks of tin ions. Such ‘subsidiary’ NVs could significantly affect the emission of SnV and potentially other centers in the same spectral range.

Analysis of thermal-hydraulic comprehensive performance of composite corrugated tubes composed of simple droplet-shaped corrugations

Corrugation parameter design seeks to maximize the thermal-hydraulic comprehensive performance (THCP) of corrugated tubes as much as possible. Among them, composite corrugations composed of simple corrugations are proposed to strengthen the THCP of corrugated pipes. However, the rule and mechanism regarding the impact of composite corrugations on the THCP of corrugated tubes, particularly when those composite corrugations are composed of simple asymmetric corrugations, are not well understood. Therefore, in this work, the effect of composite corrugations consisting of two simple droplet-shaped corrugations on THCP is assessed numerically, where the first composite corrugation is concave-convex (CTCC1) and the second composite corrugation is concave-concave (CTCC2). In addition, the effect of traditional corrugation (CTSC) on THCP is also examined to further highlight the advantages of composite corrugation in enhancing the THCP of corrugated tubes. The results of the study indicated a 49 %, 55 %, and 61 % increase in THCP at a Reynolds number (Re) of 5000 for CTSC, CTCC1, and CTCC2, respectively, compared to a smooth tube, indicating that the combination of composite corrugations in CTCC2 is superior to that in CTCC1. In addition, a smaller corrugation width on the upstream side of CTCC2 is more conducive to enhancing THCP. Furthermore, it should be ensured that the corrugation depth on the upstream side of CTCC2 is not greater than the depth on the downstream side to achieve better THCP. The work confirms the advantages of composite corrugations over traditional corrugations in enhancing THCP and guides the selection of composite corrugation combination forms and the design of composite corrugation width and depth distribution.

Development and Evaluation of Flood Early Warning System for the Small Streams

As the frequency of local extreme rainfall increases due to climate change, frequent flood damage is occurring in small stream watersheds. Casualties in these small-streams can only be significantly reduced through non-structural measures, such as the development of flood early warning systems. Howeve owever, the development and evaluation of flood early warning systems have been limited due to a lack of measurement data in small streams. Recently, the National Disaster Management Institute operated five test beds for small streams across the country. A dditionally, the Ministry of Interior and Safety, along with local governments, established a smart measurement and management system for approximately 10% of all small streams, totaling 2,200, by 2027, making it possible to secure measurement data in small streams. Considering onsidering the flow characteristics of small streams, an optimization system is developed using the rainfall-discharge nomograph and rating curve rather than a numerical-based method that requires considerable calculation time. To evaluate the developed system, the discharge and depth data measured at the time of a flood accident on August 16, 2021, are compared on a one-to-one basis with the prediction results. The prediction results show that the measured discharge and depth distribution of the five small streams over time were accurately reproduced. Based on these results, the developed rainfall-discharge nomograph and rating curve are expected to serve as effective tools to support flood early warning systems.

From snow accumulation to snow depth distributions by quantifying meteoric ice fractions in the Weddell Sea

Abstract. Year-round snow cover is a characteristic of the entire Antarctic sea ice cover, which has significant implications for the energy and mass budgets of sea ice, e.g., by preventing surface melt in summer and enhancing sea ice growth through extensive snow ice formation. However, substantial observational gaps in the seasonal cycle of Antarctic sea ice and its snow cover limit the understanding of important processes in the ice-covered Southern Ocean. They also introduce large uncertainties in satellite remote sensing applications and climate studies. Here we present results from 10 years of autonomous snow observations from Snow Buoys in the Weddell Sea. To distinguish between actual snow depth and potential snow ice thickness within the accumulated snowpack, a one-dimensional thermodynamic sea ice model is applied along the drift trajectories of the buoys. The results show that potential snow ice formation, with an average maximum thickness of 35 cm, was detected along 41 % of the total track length of the analyzed Snow Buoy tracks, which corresponds to about one-quarter of the snow accumulation. In addition, we simulate the evolution of internal snow properties along the drift trajectories with the more complex SNOWPACK model, which results in superimposed ice thicknesses between 0 and 14 cm on top of the snow ice layer. These estimates will provide an important reference dataset for both snow depth and meteoric ice rates in the Southern Ocean.

Brittle sedimentary strata focus a multimodal depth distribution of seismicity during hydraulic fracturing in the Sichuan Basin, Southwest China

The number of background earthquakes (ML ≥ 0) in the southern Sichuan basin, southwest China, has increased thirtyfold as a result of hydraulic fracturing. Background events are originally deep (4–6 km) within the sedimentary section but build into a multimodal distribution both at depth and in the shallow stimulated reservoir (2–4 km) - representing a counterpoint to the usual triggering of seismicity on deep sub-reservoir basement faults. Surprisingly, the largest events (ML ≥ 3) evolve in the deep sedimentary strata (4–6 km) that are hydraulically isolated from the injection zone (2–4 km) by low permeability layers. We evaluate the friction-stability rheology of the strata within the full stratigraphic section to define the feasibility of nucleation within these shallow and deep strata. These show velocity-neutral to velocity-weakening behavior in the shallow reservoir transitioning to more strongly velocity-weakening with increase in both depth and temperature. Poroelastic stress calculations confirms that stress transfer, rather than transmitted fluid pressures, are capable of directly reactivating critically-stressed faults at depth, with fluid pressures the triggering source within the shallow reservoir.

Tree water uptake patterns across the globe.

Plant water uptake from the soil is a crucial element of the global hydrological cycle and essential for vegetation drought resilience. Yet, knowledge of how the distribution of water uptake depth (WUD) varies across species, climates, and seasons is scarce relative to our knowledge of aboveground plant functions. With a global literature review, we found that average WUD varied more among biomes than plant functional types (i.e. deciduous/evergreen broadleaves and conifers), illustrating the importance of the hydroclimate, especially precipitation seasonality, on WUD. By combining records of rooting depth with WUD, we observed a consistently deeper maximum rooting depth than WUD with the largest differences in arid regions - indicating that deep taproots act as lifelines while not contributing to the majority of water uptake. The most ubiquitous observation across the literature was that woody plants switch water sources to soil layers with the highest water availability within short timescales. Hence, seasonal shifts to deep soil layers occur across the globe when shallow soils are drying out, allowing continued transpiration and hydraulic safety. While there are still significant gaps in our understanding of WUD, the consistency across global ecosystems allows integration of existing knowledge into the next generation of vegetation process models.

Morphological and molecular characterization of cubios (Tropaeolum tuberosum Ruiz &amp; Pavón) collected in two municipalities in Boyaca - Colombia

In this study, we aimed to determine the extent of genetic variation among cubios (Tropaeolum tuberosum) in a diversity micro-center in the department of Boyacá, Colombia, with morphological and ISSR (Inter Simple Sequence Repeats) molecular markers. Twenty-five cubio morphotypes were collected across different farms within the municipalities of Belén and Ventaquemada in Boyacá and were sown for subsequent morphological and molecular characterizations. Tuber features were evaluated according to descriptors of the International Potato Center, namely predominant tuber surface color, secondary tuber surface color, secondary tuber surface color distribution, predominant tuber pulp color, secondary tuber pulp color, distribution of secondary tuber pulp color, tuber shape, and depth of tuber eyes. Molecular variation was assessed via eight ISSR primers. Morphological and molecular characterizations allowed us to identify 25 cubio morphotypes with significant genetic variation in the study area. This finding is likely attributed to mechanisms maintaining genetic variability, such as naturally occurring crosses between morphotypes modulated by environmental conditions and local agricultural practices, including seed exchange and a preference for given morphotypes.

A new conceptual model of the Travale (Italy) enhanced geothermal system: Insights from electromagnetic geothermometry

The paper presents an electromagnetic geothermometer-based two-dimensional temperature model for the Travale (Italy) enhanced geothermal system derived from magnetotelluric and temperature data. Joint analysis of the temperature and electrical resistivity models made feasible a new self-consistent conceptual model of this site, which agrees with available geological data and previous geophysical results. It explains the nature of seismic reflection horizons detected in 1978 and unusual seismicity distribution in depth which could not be properly addressed earlier without temperature predicting beyond boreholes. It is concluded that the heat source feeding this system may be a granitic intrusion located at a depth below 4 km, which corresponds to the isotherm of 600 °C. A sharp temperature gradient above this intrusion forms a contact thermo-metamorphic halo in the depth range of 3–4 km. Assessment of the released fluid volume fraction from the electrical resistivity model indicates that the general amount of thermo-metamorphic and magmatic fluids in the rock-dominated Travale geothermal system is negligible. It is concluded that meteoric waters are the main source of fluids penetrating along normal faults up to 3 km. Despite some supercritical fluids of thermo-metamorphic origin could circulate in the system below this depth, their amount is hardly sufficient for economically justified exploration drilling. The results of the study indicate that building the temperature model of the geothermal area is crucially important for the exploration of enhanced geothermal systems.

Resemblance of the global depth distribution of internal-tide generation and cold-water coral occurrences

Abstract. Internal tides are known to be an important source of mixing in the oceans, especially in the bottom boundary layer. The depth of internal-tide generation therefore seems important for benthic life and the formation of cold-water coral mounds, but internal-tide conversion is generally investigated in a depth-integrated sense. Using both idealized and realistic simulations on continental slopes, we found that the depth of internal-tide generation increases with increasing slope steepness and decreases with intensified shallow stratification. The depth of internal-tide generation also shows a typical latitudinal dependency related to Coriolis effects. Using a global database of cold-water corals, we found that, especially in Northern Hemisphere autumn and winter, the global depth pattern of internal-tide generation correlates (rautumn = 0.70, rwinter = 0.65, p &lt; 0.01) with that of cold-water corals: shallowest near the poles and deepest around the Equator, with a decrease in depth around 25° S and N, and shallower north of the Equator than south. We further found that cold-water corals are situated significantly more often on topography that is steeper than the internal-tide beam (i.e. where supercritical reflection of internal tides occurs) than would be expected from a random distribution: in our study, in 66.9 % of all cases, cold-water corals occurred on a topography that is supercritical to the M2 tide whereas globally only 9.4 % of all topography is supercritical. Our findings underline internal-tide generation and the occurrence of supercritical reflection of internal tides as globally important for cold-water coral growth. The energetic dynamics associated with internal-tide generation and the supercritical reflection of internal tides likely increase the food supply towards the reefs in food-limited winter months. With climate change, stratification is expected to increase. Based on our results, this would decrease the depth of internal-tide generation, possibly creating new suitable habitat for cold-water corals shallower on continental slopes.

Microstructure Evolution and Fretting Wear Mechanisms of Steels Undergoing Oscillatory Sliding Contact in Dry Atmosphere.

Variations in the microstructure and the dominant fretting wear mechanisms of carbon steel alloy in oscillatory sliding contact against stainless steel in a dry atmosphere were evaluated by various mechanical testing and microanalytical methods. These included scanning electron microscopy and energy dispersive spectrometry with corresponding elemental maps of the wear tracks, in conjunction with cross-sectional transmission electron microscopy of samples prepared by focused ion beam machining to assess subsurface and through-thickness changes in microstructure, all as a function of applied load and sliding time. Heavily dislocated layered microstructures were observed below the wear tracks to vary with both the load and sliding time. During the accumulation of fretting cycles, the subsurface microstructure evolved into stable dislocation cells with cell walls aligned parallel to the surface and the sliding direction. The thickness of the damaged subsurface region increased with the load, consistent with the depth distribution of the maximum shear stress. The primary surface oxide evolved as Fe2O3 and Fe3O4 with increasing sliding time, leading to the formation of a uniform oxide scale at the sliding surface. It is possible that the development of the dislocation cell structure in the subsurface also enhanced oxidation by pipe diffusion along dislocation cores. The results of this study reveal complex phase changes affecting the wear resistance of steels undergoing fretting wear, which involve a synergy between oxidative wear, crack initiation, and crack growth along dislocation cell walls due to the high strains accumulating under high loads and/or prolonged surface sliding.