Capture Distance Research Articles

Verifying the Effectiveness of New Face Spoofing DB with Capture Angle and Distance

Face recognition is a representative biometric that can be easily used; however, spoofing attacks threaten the security of face biometric systems by generating fake faces. Thus, it is not advisable to only consider sophisticated spoofing cases, such as three-dimensional masks, because they require additional equipment, thereby increasing the implementation cost. To prevent easy face spoofing attacks through print and display, the two-dimensional (2D) image analysis method using existing face recognition systems is reasonable. Therefore, we proposed a new database called the “pattern recognition-face spoofing advancement database” that can be used to prevent such attacks based on 2D image analysis. To the best of our knowledge, this is the first face spoofing database that considers the changes in both the angle and distance. Therefore, it can be used to train various positional relationships between a face and camera. We conducted various experiments to verify the efficiency of this database. The spoofing detection accuracy of our database using ResNet-18 was found to be 96.75%. The experimental results for various scenarios demonstrated that the spoof detection performances were better for images with pinch angle, near distance images, and replay attacks than those for front images, far distance images, and print attacks, respectively. In the cross-database verification result, the performance when tested with other databases (DBs) after training with our DB was better than the opposite. The results of cross-device verification in terms of camera type showed negligible difference; thus, it was concluded that the type of image sensor does not affect the detection accuracy. Consequently, it was confirmed that the proposed DB that considers various distances, capture angles, lighting conditions, and backgrounds can be used as a training DB to detect spoofing attacks in general face recognition systems.

A Self-Assembly Portable Mobile Mapping System for Archeological Reconstruction Based on VSLAM-Photogrammetric Algorithm

Three Dimensional (3D) models are widely used in clinical applications, geosciences, cultural heritage preservation, and engineering; this, together with new emerging needs such as building information modeling (BIM) develop new data capture techniques and devices with a low cost and reduced learning curve that allow for non-specialized users to employ it. This paper presents a simple, self-assembly device for 3D point clouds data capture with an estimated base price under €2500; furthermore, a workflow for the calculations is described that includes a Visual SLAM-photogrammetric threaded algorithm that has been implemented in C++. Another purpose of this work is to validate the proposed system in BIM working environments. To achieve it, in outdoor tests, several 3D point clouds were obtained and the coordinates of 40 points were obtained by means of this device, with data capture distances ranging between 5 to 20 m. Subsequently, those were compared to the coordinates of the same targets measured by a total station. The Euclidean average distance errors and root mean square errors (RMSEs) ranging between 12–46 mm and 8–33 mm respectively, depending on the data capture distance (5–20 m). Furthermore, the proposed system was compared with a commonly used photogrammetric methodology based on Agisoft Metashape software. The results obtained demonstrate that the proposed system satisfies (in each case) the tolerances of ‘level 1’ (51 mm) and ‘level 2’ (13 mm) for point cloud acquisition in urban design and historic documentation, according to the BIM Guide for 3D Imaging (U.S. General Services).

Analyte capture in an array of functionalized droplets for a regenerable biosensor.

We describe in this work an advanced microfluidic chip for the capture of bioanalyte on the surface of droplets arranged in a dense array. We show the procedure for generating, functionalizing, and arranging the droplets inside the device for capturing a specific bioanalyte. Then, we demonstrate the capacity of the array to capture analyte from a cross-flowing liquid, using a biotin/streptavidin model. The paper also proposes to use the droplets array, after integration with acoustic detection, as a regenerable detection interface for bioanalyte sensing. We model the arrangement of droplet in dense array and show that they present a larger effective capture surface and shorter capture distance than standard flat surface biosensor of the same footprint. As the droplets can be easily evacuated and replaced inside the device analysis chamber, the proposed biosensor would allow biointerface regeneration and chain measurement without dismounting the device.

Spatial and Seasonal Distribution of Holochilus sciureus with Schistosoma mansoni Infection in an Endemic Area for Schistosomiasis in Brazil.

The occurrence of wild rodents in the Schistosoma mansoni life cycle may increase the transmission of schistosomiasis and understanding the spatial and seasonal distribution of the natural infection of these reservoirs is essential for the development of more effective control strategies. In this study, Holochilus sciureus rodents were captured from the flooded fields of São Bento city (an endemic area for schistosomiasis in Northeast Brazil), during the dry and rainy seasons. All these sites were georeferenced and the prevalence of S. mansoni was verified by the presence of adult worms in the mesenteric branches and livers of each animal. It was demonstrated that almost half of the animals collected were naturally infected with S. mansoni (45.45%) and this infection was not related to the distance from urban areas. Furthermore, the temperature, precipitation, sex, and weight did not interfere with the H. sciureus infection rates. Interestingly, we found, for the first time, the natural infection of H. sciureus in another endemic city of S. mansoni in Northeast Brazil. Therefore, the H. sciureus rodent shows a high natural infection rate for S. mansoni in the flooded fields of São Bento, regardless of the weather station, capture distance, and biological aspects. Additionally, we have demonstrated that H. sciureus naturally parasitized with S. mansoni may inhabit a much more extensive area that is currently described in the literature.

Measuring, Modeling, and Predicting the Magnetic Assembly Rate of 2D-Staggered Janus Particle Chains.

The assembly of magnetic Janus particles in a quasi-two-dimensional environment with a dipole moment shifted from the center and oriented perpendicular to the Janus cap height is studied with optical microscopy and found to adhere to a general model accounting for the particle dipole strength, the particle Brownian dynamics, the initial concentration, and, most importantly, the magnetic dipole shift. The particle aggregates are treated as diffusing spherocylinders with length and width dependent on the magnetic dipole shift. Aggregation occurs irreversibly once particle aggregates enter within a distance at which Brownian and dipole forces are equal, defined as the capture distance. The capture distance model is expressed as a general Smoluchowski coagulation rate kernel for chains of an arbitrary length, dipole strength, and dipole shift, allowing for aggregation rate predictions for related systems.

Simulating precursor steps for fibril formation in methylcellulose solutions

We use coarse-grained molecular dynamics simulations to study the precursor steps for fibril formation in methylcellulose solutions. Simulations of ring stacking between two collapsed methylcellulose chains demonstrate the existence of a capture radius that is much larger than that predicted by polymer diffusion alone. When two rings are in very close proximity, they stack together to form a fibril precursor. Simulations of stacks of such rings suggest that this structure is metastable. In contrast, chains that are within the capture radius but not in close proximity, as well as for systems containing both ringlike and relaxed chains, fibril-like structures form via a distinctly different mechanism. Irrespective of their initial arrangement, the chains undergo two specific conformational changes: (i) a part of either a ring or a randomly coiled chain splays out and (ii) the splayed chain subsequently engulfs a nearby chain if it is within a certain capture distance. The latter results are consistent with recent experimental measurements of fibril formation by short methylcellulose chains, which suggests the formation of a twisted bundle.

A Novel Parallel Convolutional Network Architecture for Depth-Dependent Object Recognition

This article presents the evaluation of a novel parallel convolutional neural network, oriented to recognize objects at different distances, in order to find a solution to the problem of variability in the value of confidence with which an object is recognized, by varying the distance of capture of the image with respect to the object. In order to test its performance, two additional convolutional neural network architectures are implemented, a conventional one with multiple branches of identification in parallel and a Directed Acyclic Graph convolutional network with the same parameters as the proposed one, which differ in the training database used and the structure of the network's output. This problem is identified when trying to develop assistive robotic systems that should recognize a particular object in a group of objects in order to be taken by an end effector capable of changing trajectories, avoiding possible collisions in human-machine work environments. Here, four different tools must be recognized at four distances (20, 40, 60 and 80 cm), where the conventional CNN obtain the lowest accuracy (80.6%), while, in comparison between the DAG and the parallel CNN, although their performances have been close, the proposed architecture has obtained better results, with 93% average accuracy. It is concluded that this network is able to function in environments with dynamic reference positions of the objects, allowing being implemented in mobile agents that require relocating an object and establishing a new path given an obstacle to evade.

Dolphin: Real-Time Hidden Acoustic Signal Capture with Smartphones

Dual-channel screen-camera communication has been proposed to enable simultaneous screen viewing and hidden screen-camera communication. However, it strictly requires a well-controlled camera-screen alignment and an obstacle-free access. In this paper, we propose Dolphin, a novel real-time acoustics-based dual-channel communication system. Leveraging masking effects of human auditory system and readily available audio signals, Dolphin enables real-time unobtrusive speaker-microphone data communication without affecting the primary audio-hearing experience of human users. Compared with screen-camera communication, Dolphin supports non-line-of-sight transmissions and more flexible speaker-microphone alignments. Dolphin can also automatically adapt the data rate to various channel conditions. We further develop a secure data broadcasting scheme on Dolphin, where only designated privileged users can recover the embedded information in the acoustic signals. Our Dolphin prototype, built using COTS (Commercial Off-The-Shelf) smartphones, realizes (potentially secure) real-time hidden information communication, supports up to 8-meter signal capture distance and $\pm 90^{\circ }$ listening angle, and achieves an average goodput of 240 bps at 2 m.

Evacuation simulation considering action of guard in artificial attack**Project supported by the National Key Research and Development Program of China (Grant No. 2017YFC0804900) and the National Natural Science Foundation of China (Grant Nos. 71790613 and 51534008).

To investigate the evacuation behaviors of pedestrians considering the action of guards and to develop an effective evacuation strategy in an artificial attack, an extended floor field model is proposed. In this model, the artificial attacker’s assault on pedestrians, the death of pedestrians, and the guard’s capture are involved simultaneously. An alternative evacuation strategy which can largely reduce the number of casualties is developed and the effects of several key parameters such as the deterrence radius and capture distance on evacuation dynamics are studied. The results show that congestion near the exit has dual effects. More specifically, the guard can catch all attackers in a short time because the artificial attackers have a more concentrated distribution, but more casualties can occur because it is hard for pedestrians to escape the assault due to congestion. In contrast, when pedestrians have more preference of approaching the guard, although the guard will take more time to capture the attackers resulting from the dispersion of the attackers, the death toll will decrease. One of the reasons is the dispersal of the crowd, and the decrease in congestion is beneficial for escape. The other is that the attackers will be caught before launching the attack on the people who are around the guard, in other words, the guard protects a large number of pedestrians from being killed. Moreover, increasing capture distance of the guard can effectively reduce the casualties and the catch time. As the deterrence radius reflecting the tendency of escaping from the guard for attackers rises, it becomes more difficult for the guard to catch the attackers and more casualties are caused. However, when the deterrence radius reaches a certain level, the number of deaths is reduced because the attackers prefer to stay as far away as possible from the guard rather than occupy a position where they could assault more people.

Communication: Adiabatic quantum trajectory capture for cold and ultra-cold chemical reactions.

The Langevin capture model is often used to describe barrierless reactive collisions. At very low temperatures, quantum effects may alter this simple capture image and dramatically affect the reaction probability. In this paper, we use the trajectory-ensemble reformulation of quantum mechanics, as recently proposed by one of the authors (Poirier) to compute adiabatic-channel capture probabilities and cross-sections for the highly exothermic reaction Li + CaH(v = 0, j = 0) → LiH + Ca, at low and ultra-low temperatures. Each captured quantum trajectory takes full account of tunneling and quantum reflection along the radial collision coordinate. Our approach is found to be very fast and accurate, down to extremely low temperatures. Moreover, it provides an intuitive and practical procedure for determining the capture distance (i.e., where the capture probability is evaluated), which would otherwise be arbitrary.

The lion and man game on polyhedral surfaces with obstacles

We study a geometric version of the cops and robbers game known as the lion and man game. In this game, a group of lions (the pursuers) try to capture a man (the evader). The players have equal speed. They can observe each other at all times. While the lion and man game is well-studied in planar domains such as polygons, very little is known about its properties in higher dimensions. In this paper, we study the game when played on the surface of a polyhedron with or without boundary, possibly in the presence of obstacles (i.e. forbidden regions). In particular, in the absence of obstacles, the surface has genus zero, and it can be homeomorphic to either a disk or a sphere. We assume that the input surface is triangulated. We show that three lions with non-zero capture distance δ can capture the man in O((Aδ2+Lδ+N)2δ2+(Aδ2+Lδ+N)D) steps where A is the area, L is the total edge length of the polyhedron, N is the number of triangular faces used in the representation of the polyhedron, and D is the length of the longest shortest path on the surface.

The effect of tides on the population of PN from interacting binaries

We have used the tidal equations of Zahn to determine the maximum orbital distance at which companions are brought into Roche lobe contact with their giant primary, when the primary expands during the giant phases. This is a key step when determining the rates of interaction between giants and their companions. Our stellar structure calculations are presented as maximum radii reached during the red and asymptotic giant branch (RGB and AGB, respectively) stages of evolution for masses between 0.8 and 4.0 Mo (Z=0.001 - 0.04) and compared with other models to gauge the uncertainty on radii deriving from details of these calculations. We find overall tidal capture distances that are typically 1-4 times the maximum radial extent of the giant star, where companions are in the mass range from 1 Jupiter mass to a mass slightly smaller than the mass of the primary. We find that only companions at initial orbital separations between ~320 and ~630 Ro will be typically captured into a Roche lobe-filling interaction or a common envelope on the AGB. Comparing these limits with the period distribution for binaries that will make PN, we deduce that in the standard scenario where all ~1-8 Mo stars make a PN, at most 2.5 per cent of all PN should have a post-common envelope central star binary, at odds with the observational lower limit of 15-20 per cent. The observed over-abundance of post-interaction central stars of PN cannot be easily explained considering the uncertainties. We examine a range of explanations for this discrepancy.

Three-dimensional kinetic Monte Carlo simulations of cubic transition metal nitride thin film growth

A three-dimensional kinetic Monte Carlo (KMC) model has been developed and used to simulate the microstructure and growth morphology of cubic transition metal nitride (TMN) thin films deposited by reactive magnetron sputtering. Results are presented for the case of stoichiometric TiN, chosen as a representative TMN prototype. The model is based on a NaCl-type rigid lattice and includes deposition and diffusion events for both N and Ti species. It is capable of reproducing voids and overhangs, as well as surface faceting. Simulations were carried out assuming a uniform flux of incoming particles approaching the surface at normal incidence. The ballistic deposition model is parametrized with an interaction parameter ${r}_{0}$ that mimics the capture distance at which incoming particles may stick on the surface, equivalently to a surface trapping mechanism. Two diffusion models are implemented, based on the different ways to compute the site-dependent activation energy for hopping atoms. The influence of temperature (300--500 K), deposition flux (0.1--100 monolayers/s), and interaction parameter ${r}_{0}$ (1.5--6.0 \AA{}) on the obtained growth morphology are presented. Microstructures ranging from highly porous, [001]-oriented straight columns with smooth top surface to rough columns emerging with different crystallographic facets are reproduced, depending on kinetic restrictions, deposited energy (seemingly captured by ${r}_{0})$, and shadowing effect. The development of facets is a direct consequence of the diffusion model which includes an intrinsic (minimum energy-based) diffusion anisotropy, although no crystallographic diffusion anisotropy was explicitly taken into account at this stage. The time-dependent morphological evolution is analyzed quantitatively to extract the growth exponent $\ensuremath{\beta}$ and roughness exponent $\ensuremath{\alpha}$, as indicators of kinetic roughening behavior. For dense TiN films, values of $\ensuremath{\alpha}\ensuremath{\approx}0.7$ and $\ensuremath{\beta}=0.24$ are obtained in good agreement with existing experimental data. At this stage a single lattice is considered but the KMC model will be extended further to address more complex mechanisms, such as anisotropic surface diffusion and grain boundary migration at the origin of the competitive columnar growth observed in polycrystalline TiN-based films.

Particle capture modeling for an axial magnetic filter with a bounded non-Newtonian flow field

Capturing fine magnetic particles in axial magnetic filter from non-Newtonian suspension was examined theoretically. A trajectory model was formed for the movement of the particle in bounded flow field magnetic filter that has advantages for various theoretical modeling and practical applications as presented in the literature [1–8]. The effects of the non-Newtonian properties of the suspension on the particle capture distance were evaluated. Since the magnetized ferromagnetic wire was outside the cylindrical tube in which the suspensions flow, the velocity profile within the tube was determined according to the power law rheological model. The conditions to use the approximation expression for the flow profile in the tube were determined by considering the energy dissipation. Analytical solutions for the particle trajectory equation were obtained under above-mentioned conditions. Based on these results, the effects of the non-Newtonian properties of the carrier suspension on the movement trajectory of the particle and the capture cross-section were scrutinized.

Removal of cadmium(II) from wastewater with gas-assisted magnetic separation

In this study, a method combined low-field magnetic separation (MS) with flotation, named as gas-assisted magnetic separation (GAMS), was applied for the removal of cadmium from wastewater. With bubbles’ assistance, the speed of magnetic separation can be greatly improved and the limitation of magnetic force on the capture distance can be overcome. Thus, GAMS is much more efficient and easily scalable than MS. In this work, ethanediamine-modified magnetic poly-(glycidyl methacrylate) microspheres (EMPs) were synthesized as the adsorbent for cadmium. And GAMS was used to separate the EMPs and Cd-loaded EMPs. The effects of pH, gas flow rate, concentration of Cd-loaded EMPs, loading volume, and ionic strength on GAMS were investigated. The results indicated that the EMPs and Cd-loaded EMPs could be rapidly and remotely removed from the solution with GAMS. And the separation time decreased with the increase of gas flow rate and NaCl concentration, but grew with the rise of pH value, loading volume, and concentration of the EMPs. This work showed the great potential of GAMS in the area of water treatment.

Flight movement and spatial distribution of immunomarked thrips in onion, potato, and tomato

The objective of this work was to evaluate the spatial distribution of thrips in different crops, and the correlation between meterological parameters and the flight movements of this pest, using immunomarking. The experiment was conducted in cultivated areas, with tomato (Solanum lycopersicum), potato (Solanum tuberosum), and onion (Allium cepa); and non-cultivated areas, with weedy plants. The areas with tomato (100 days), potato (20 days), and weeds were sprayed with casein, albumin, and soy milk, respectively, to mark adult thrips; however, the areas with onion (50 days) and tomato (10 days) were not sprayed. Thrips were captured with georeferenced blue sticky traps, transferred into tubes, and identified by treatment area with the Elisa test. The dependence between the samples and the capture distance was determined using geostatistics. Meteorlogical parameters were correlated with thrips density in each area. The three protein types used for immunomarking were detected in different proportions in the thrips. There was a correlation between casein-marked thrips and wind speed. The thrips flew a maximum distance of 3.5 km and dispersed from the older (tomato) to the younger crops (potato). The immunomarking method is efficient to mark large quantities of thrips.

Comparing permeability of matrix cover types for the marsh rice rat (Oryzomys palustris)

Matrix land cover types differ in permeability to animals moving between habitat patches, and animals may actually move faster across less-suitable areas. Marsh rice rats are wetland specialists whose dispersal crosses upland matrix. Our objectives were to (1) compare matrix permeability for the marsh rice rat among upland cover types, (2) compare permeability within versus outside perceptual range of the wetland, and (3) explore intrinsic and extrinsic features influencing matrix use and permeability. We quantified permeability of grassland, crop field, and forest to the marsh rice rat during 2011–2012, by marking rats in wetlands and estimating the slope of capture rate versus distance (0–95 m) into the matrix. We also compared permeability within (0–15 m) and beyond the perceptual range of rice rats, and tested whether age, sex, time, water depth, rice rat abundance, and vegetation density influenced matrix use and permeability. Permeability was greater for soybean fields than grassland or forest but did not appear to differ within versus beyond rice rats’ perceptual range. Matrix capture rates were higher early in the study and in times and locations with thick ground vegetation and high rice rat abundance in the wetlands. Rice rats captured in the matrix were younger than those in wetland patches. Our findings expand known matrix use by marsh rice rats, and support permeability being high in matrix types dissimilar to suitable habitat. Studying individual movements will help identify mechanisms underlying enhanced permeability in crop fields.

Oligo-Miocene mafic intrusions of the San Juan Volcanic Field, southwestern Colorado, and their relationship to voluminous, caldera-forming magmas

The trigger(s) of ignimbrite flare-ups in continental environments and their connection to “high power” mantle-melting events are the subject of ongoing debate, often hampered by the relative scarcity of mantle-derived basalts compared to voluminous amounts of intermediate and silicic lavas, intrusions, and welded-tuffs. This study focused on locating and analyzing mafic magmas in the San Juan Mountains of Colorado, the largest erosional remnant of the Oligocene Southern Rocky Mountain ignimbrite flare-up. The “flare-up in” the San Juan Volcanic Field (SJVF) has several potential explanations including: crustal anatexis or MASH processes from either an asthenospheric “high power” melting event triggered by rifting and/or lithospheric delamination or a lithospheric mantle “high power” event caused by exposure of Farallon metasomatism to the underlying asthenosphere. The required volumes of crustal melt (a column 34–45km tall over an area of 10,000km2) and crustal heterogeneity disqualify anatexis as a source of the SJVF. Basalt and basaltic andesite magmas of the SJVF have εNd (−6 to −8) and 87Sr/86Sr (0.705–0.706), high Ba concentrations (750–1500ppm) with low Rb/Zr (0.25–0.5) compatible with a lithospheric basalt MASH model. An OIB-like basalt source would require nearly twice the crustal assimilation (50%+) and MASH zone thickness (∼17km) to produce the isotopic ratios of intermediate to silicic SJVF rocks and could not produce their elevated Ba concentrations. The location of the SJVF may be controlled by its maximum distance of magma capture and lateral transport or by the underlying lithospheric mantle.

Rapid and large‐scale separation of magnetic nanoparticles by low‐field permanent magnet with gas assistance

SignificanceBubbles can be used to greatly improve the speed of magnetic separation (MS) and overcome the limitation of magnetic force on the capture distance, making low‐field MS highly efficient and easily scalable. This novel method leads to the development of a medium‐free continuous gas‐assisted magnetic separator on small pilot scale using low‐field permanent magnet. This separator is demonstrated highly efficient for recovery of proteins‐loaded magnetic nanoparticles from large volume biosuspension. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3101–3106, 2014

Experimental Investigation on the Flow Characteristics of an Exhaust Hood Assisted by a Jet

An air curtain generated by a jet is used to enhance an exhaust hood’s capture ability in many research studies on local ventilation systems. This paper focuses on experimental methods to investigate the flow characteristics formed by an exhaust hood associated with a jet. The basic flow characteristics of this kind of exhaust hood are obtained by smoke visualization as a jet forms an air curtain, and the flow field is a combination of three parts: the jet flow region, the exhaust flow region and the vortex flow region. The conditions for forming an air curtain are determined. The air curtain generated by a jet can decrease the decay of the exhaust centreline velocity Vx, therefore enhancing the efficient capture distance. Increasing the exhaust flow rate has higher efficiency than increasing the supply air velocity to enhance the control effect. A regression formula to determine the required supply velocity is obtained if the capture distance and the capture velocity for different contaminants are known. Furthermore, it is found that installing vertical guard-plates between the inlet and the outlet can effectively enhance the capture ability of the hood.