Camouflage Effect Research Articles

Covet underwater acoustic communication based on spread spectrum orthogonal frequency division multiplexing (OFDM)

A covert underwater acoustic communication (UAC) method is realized with a dolphin whistle as the information carrier. The proposed method jointly utilizes the spread spectrum and orthogonal frequency division multiplexing (OFDM) techniques. The original dolphin whistle is represented as the complex baseband OFDM transmitted signal and the phase of its discrete Fourier transform (DFT) coefficients are modulated by a spread spectrum code to carry information. The audio quality and waveform similarity are used as two covert effect criterion. In simulations, the influences of the code length and modulation parameters are investigated. It is verified that the communication performance and camouflage effect are a pair of contradictions. Therefore, the best compromise formula should be chosen according to the actual demands.

Numerical Simulation Analysis of Temperature Field of Airport Concrete Pavement

In this paper, through the analysis of the structure of airport concrete pavement surface, thermal properties, thermal properties, air parameters, solar radiation, atmosphere long wave radiation, obvious heat exchange and latent heat exchange of background and other factors, this paper build one dimension ground temperature field model. Then, we find finite element method solution of the model by ANSYS, get the temperature contours of the airport road surface, so as to provide theoretical support for the airport equipment of infrared stealth design, camouflage to guide the practice of airport equipment, camouflage effectiveness evaluation.

Stereoscopic Segmentation Cues Improve Visual Timing Performance in Spatiotemporally Cluttered Environments.

Recently, Cass and Van der Burg demonstrated that temporal order judgment (TOJ) precision could be profoundly impaired by the mere presence of dynamic visual clutter elsewhere in the visual field. This study examines whether presenting target and distractor objects in different depth planes might ameliorate this remote temporal camouflage (RTC) effect. TOJ thresholds were measured under static and dynamic (flickering) distractor conditions. In Experiment 1, targets were presented at zero, crossed, or uncrossed disparity, with distractors fixed at zero disparity. Thresholds were significantly elevated under dynamic compared with static contextual conditions, replicating the RTC effect. Crossed but not uncrossed disparity targets improved performance in dynamic distractor contexts, which otherwise produce substantial RTC. In Experiment 2, the assignment of disparity was reversed: targets fixed at zero disparity; distractors crossed, uncrossed, or zero. Under these conditions, thresholds improved significantly in the nonzero distractor disparity conditions. These results indicate that presenting target and distractor objects in different planes can significantly improve TOJ performance in dynamic conditions. In Experiment 3, targets were each presented with a different sign of disparity (e.g., one crossed and the other uncrossed), with no resulting performance benefits. Results suggest that disparity can be used to alleviate the performance-diminishing effects of RTC, but only if both targets constitute a single and unique disparity-defined surface.

Adaptive camouflage: what can be learned from the wetting behaviour of the tropical flat bugs Dysodius lunatus and Dysodiusmagnus.

ABSTRACTThe neotropical flat bug species Dysodius lunatus and Dysodius magnus show a fascinating camouflage principle, as their appearance renders the animal hardly visible on the bark of trees. However, when getting wet due to rain, bark changes its colour and gets darker. In order to keep the camouflage effect, it seems that some Dysodius species benefit from their ability to hold a water film on their cuticle and therefore change their optical properties when also wetted by water. This camouflage behaviour requires the insect to have a hydrophilic surface and passive surface structures which facilitate the liquid spreading. Here we show morphological and chemical characterisations of the surface, especially the cuticular waxes of D. magnus. Scanning electron microscopy revealed that the animal is covered with pillar-like microstructures which, in combination with a surprising chemical hydrophilicity of the cuticle waxes, render the bug almost superhydrophilic: water spreads immediately across the surface. We could theoretically model this behaviour assuming the effect of hemi-wicking (a state in which a droplet sits on a rough surface, partwise imbibing the structure around). Additionally the principle was abstracted and a laser-patterned polymer surface, mimicking the structure and contact angle of Dysodius wax, shows exactly the behaviour of the natural role model – immediate spreading of water and the formation of a thin continuous water film changing optical properties of the surface.

Conservation implications of anthropogenic impacts on visual communication and camouflage.

Anthropogenic environmental impacts can disrupt the sensory environment of animals and affect important processes from mate choice to predator avoidance. Currently, these effects are best understood for auditory and chemosensory modalities, and recent reviews highlight their importance for conservation. We examined how anthropogenic changes to the visual environment (ambient light, transmission, and backgrounds) affect visual communication and camouflage and considered the implications of these effects for conservation. Human changes to the visual environment can increase predation risk by affecting camouflage effectiveness, lead to maladaptive patterns of mate choice, and disrupt mutualistic interactions between pollinators and plants. Implications for conservation are particularly evident for disrupted camouflage due to its tight links with survival. The conservation importance of impaired visual communication is less documented. The effects of anthropogenic changes on visual communication and camouflage may be severe when they affect critical processes such as pollination or species recognition. However, when impaired mate choice does not lead to hybridization, the conservation consequences are less clear. We suggest that the demographic effects of human impacts on visual communication and camouflage will be particularly strong when human-induced modifications to the visual environment are evolutionarily novel (i.e., very different from natural variation); affected species and populations have low levels of intraspecific (genotypic and phenotypic) variation and behavioral, sensory, or physiological plasticity; and the processes affected are directly related to survival (camouflage), species recognition, or number of offspring produced, rather than offspring quality or attractiveness. Our findings suggest that anthropogenic effects on the visual environment may be of similar importance relative to conservation as anthropogenic effects on other sensory modalities.

Edge enhancement improves disruptive camouflage by emphasising false edges and creating pictorial relief.

Disruptive colouration is a visual camouflage composed of false edges and boundaries. Many disruptively camouflaged animals feature enhanced edges; light patches are surrounded by a lighter outline and/or a dark patches are surrounded by a darker outline. This camouflage is particularly common in amphibians, reptiles and lepidopterans. We explored the role that this pattern has in creating effective camouflage. In a visual search task utilising an ultra-large display area mimicking search tasks that might be found in nature, edge enhanced disruptive camouflage increases crypsis, even on substrates that do not provide an obvious visual match. Specifically, edge enhanced camouflage is effective on backgrounds both with and without shadows; i.e. this is not solely due to background matching of the dark edge enhancement element with the shadows. Furthermore, when the dark component of the edge enhancement is omitted the camouflage still provided better crypsis than control patterns without edge enhancement. This kind of edge enhancement improved camouflage on all background types. Lastly, we show that edge enhancement can create a perception of multiple surfaces. We conclude that edge enhancement increases the effectiveness of disruptive camouflage through mechanisms that may include the improved disruption of the object outline by implying pictorial relief.

Nest covering in plovers: How modifying the visual environment influences egg camouflage.

Camouflage is one of the most widespread antipredator defences, and its mechanistic basis has attracted considerable interest in recent years. The effectiveness of camouflage depends on the interaction between an animal's appearance and its background. Concealment can therefore be improved by changes to an animal's own appearance, by behaviorally selecting an optimal background, or by modifying the background to better match the animal's own appearance. Research to date has largely focussed on the first of these mechanisms, whereas there has been little work on the second and almost none on the third. Even though a number of animal species may potentially modify their environment to improve individual‐specific camouflage, this has rarely if ever been quantitatively investigated, or its adaptive value tested. Kittlitz's plovers (Charadrius pecuarius) use material (stones and vegetation) to cover their nests when predators approach, providing concealment that is independent of the inflexible appearance of the adult or eggs, and that can be adjusted to suit the local surrounding background. We used digital imaging and predator vision modeling to investigate the camouflage properties of covered nests, and whether their camouflage affected their survival. The plovers' nest‐covering materials were consistent with a trade‐off between selecting materials that matched the color of the eggs, while resulting in poorer nest pattern and contrast matching to the nest surroundings. Alternatively, the systematic use of materials with high‐contrast and small‐pattern grain sizes could reflect a deliberate disruptive coloration strategy, whereby high‐contrast material breaks up the telltale outline of the clutch. No camouflage variables predicted nest survival. Our study highlights the potential for camouflage to be enhanced by background modification. This provides a flexible system for modifying an animal's conspicuousness, to which the main limitation may be the available materials rather than the animal's appearance.

Effects of directionality, signal intensity, and short-wavelength components on iridescent warning signal efficacy

Many bright colors function as visual signals and are produced by structural mechanisms that result in their being iridescent. Iridescent colors differ from other types of animal coloration in that they vary in both hue and intensity, as the angle of viewing and illumination change relative to the color surface. Iridescent colors can serve as warning signals by deterring predation on distasteful animals. Due to their directional and mirror-like reflection, iridescent signals have the potential to (1) vary in appearance with each approach; (2) create a flashing signal; (3) under the right conditions, be more intense than diffusely reflecting signals; (4) display different hues with different positioning of the sun, predator, and prey; and (5) display angle-dependent camouflage, which could all influence warning signal effectiveness. Here, we examine how signal intensity, short-wavelength hue, and variation in appearance affect the response of domestic chickens (Gallus gallus domesticus) to warning signals. Variation did not affect their response. Higher intensity signals were more effective in terms of predator avoidance than were lower intensity, and blue-violet signals were more effective than were blue and blue-green. This could influence the effectiveness of an iridescent warning signal in nature if the prey displays more intense, blue-violet coloration. With the properties we tested, we found no cost to having warning colors that are iridescent and that there may be benefits in the ability to change hue and display a more intense signal. We suggest future research to examine the effects of iridescent flashing and angle-dependent camouflage on warning signal effectiveness. Iridescent colors have only been recently shown to function as warning signals, but we know very little about how they function to deter predation. Here, we show that birds are more likely to change their behavior in response to higher intensity and blue-violet signals compared to low intensity and blue and blue-green signals. The intensity results are consistent with previous experiments, but the role of short-wavelength hue on warning signal effectiveness has never been tested before. Variation due to the shifting appearance of an iridescent signal did not influence the response to the warning signal, consistent with studies in long-wavelength signals. We found no cost to displaying an iridescent signal and potentially an adaptive benefit as iridescent warning signals have the potential to be brighter and display a different hue based on the arrangement of light source, signaler, and receiver.

Articulation and Concordance: A Dialogue on Civil–Military Relations in Fiji

Articulation and Concordance: A Dialogue on Civil–Military Relations in Fiji

Microhabitat choice in island lizards enhances camouflage against avian predators.

Camouflage can often be enhanced by genetic adaptation to different local environments. However, it is less clear how individual behaviour improves camouflage effectiveness. We investigated whether individual Aegean wall lizards (Podarcis erhardii) inhabiting different islands rest on backgrounds that improve camouflage against avian predators. In free-ranging lizards, we found that dorsal regions were better matched against chosen backgrounds than against other backgrounds on the same island. This suggests that P. erhardii make background choices that heighten individual-specific concealment. In achromatic camouflage, this effect was more evident in females and was less distinct in an island population with lower predation risk. This suggests that behavioural enhancement of camouflage may be more important in females than in sexually competing males and related to predation risk. However, in an arena experiment, lizards did not choose the background that improved camouflage, most likely due to the artificial conditions. Overall, our results provide evidence that behavioural preferences for substrates can enhance individual camouflage of lizards in natural microhabitats, and that such adaptations may be sexually dimorphic and dependent on local environments. This research emphasizes the importance of considering links between ecology, behaviour, and appearance in studies of intraspecific colour variation and local adaptation.

Optical Digital Imitation Painting Design Based on Self-Adaptive Image Feature

Based on the study of existing digital imitation camouflage technology, we propose a kind of optical digital imitation camouflage design algorithm which is based on the characteristic of self-adaptive image. Picking main color feature of the background by using K-means clustering algorithm, counting the shape characteristics of each main color spots by separating layers, we generated digital camouflage pattern automatically by segmenting the background region characteristics and fill the background color image according to the statistics expected value. The simulation results show that, the digital camouflage generated automatically is blend well with the background .It keeps the background color and shape features, so has good camouflage effect. This algorithm can also provide the basic algorithm foundation for digital deformation camouflage.

List do Redakcji. Omówienie doniesienia: „An investigation of the ‘female camouflage effect’ in autism using a new computerized test showing sex/gender differences during ADOS-2”. IMFAR 2016, Baltimore, USA

List do Redakcji. Omówienie doniesienia: „An investigation of the ‘female camouflage effect’ in autism using a new computerized test showing sex/gender differences during ADOS-2”. IMFAR 2016, Baltimore, USA

Chitons’ apparent camouflage does not reduce predation by green crabs Carcinus maenas

ABSTRACTChitons are very common molluscs on European rocky shores. They are common prey of fish and crabs and often display several colour morphs within a given habitat. Predation is one of the potential mechanisms accounting for chiton colour polymorphism. The colour variation is considered to provide a camouflage protection through a match with the substratum surface typology. However, the effectiveness of chiton polymorphism as a predation defence requires further investigation. Previously we found a relationship between chiton colour morphs and substrate characteristics, with chitons most commonly found on substrates that were of similar colour to their shells. Here, we examined whether each morph displayed an active choice for matching the substratum. Next, we assessed if the predation success of the intertidal common crab Carcinus maenas varied significantly with the absence/presence of an apparent camouflage effect created between the chiton colour morph and the substratum type. The present study indicates that chiton colour morphs probably actively choose substratum types where they blend in. Carcinus maenas was able to prey on all Lepidochitona cinereus colour morphs, regardless of the substrate camouflage effect. Surprisingly, the predation frequency was higher on camouflaged chitons than on contrasting chitons. It was concluded that chiton camouflage is probably not a defence mechanism against predation by the crab C. maenas, and that chiton colour polymorphism is probably promoted by other, more visual predators.

Camouflage performance analysis and evaluation framework based on features fusion

The analysis and evaluation of camouflage performance is an important procedure in digital camouflage pattern design, as it helps to improve the design quality of camouflage patterns. In this paper, we propose a novel framework that uses the nonlinear fusion of multiple image features to quantitatively evaluate the degree to which the target and surrounding background differ with respect to background-related and internal features. In our framework, background-related features are first formulated as a measure of conspicuousness, which is calculated and quantized by the saliency detection method, whereas internal features refer to the interior saliency of camouflage textures, such as lines and other regular patterns. These two features are fused to evaluate the camouflage effect. A subjective evaluation is carried out as the baseline of our evaluation model. Experimental results show that our camouflage evaluation framework accords with the human visual perception mechanism, and is an effective method for evaluating camouflage pattern design.

Human Visual Search Performance for Camouflaged Targets

There is a paucity of published systematic research investigating object detection within the military context. Here, we establish baseline human detection performance for five standard military issued camouflage patterns. Stimuli were drawn from a database of 1242 calibrated images of a mixed deciduous woodland environment in Bristol, UK. Images within this database were taken during daylight hours, in summer and contained a PASGT helmet, systematically positioned within each scene. Subjects (20) discriminated between the two image types in a temporal 2AFC task (500ms presentation for each interval), with the detection scenario being the percentage of instances participants correctly detected the target. Cueing (cued/not-cued to target location), colour (colour/greyscale) and distance from the observer (3.5/5/7.5m) were manipulated, as was helmet camouflage pattern. A Generalized Linear Mixed Model revealed significant interactions between all variables on participant performance, with greater accuracy when stimuli were in colour, and the target location was cued. There was also a clear ranking of patterns in terms of effectiveness of camouflage. We also compare the results with a computational model based on low-level vision, and eye tracking data, with encouraging results. Our methodology provides a controlled means of assessing any camouflage in any environment, and the potential to implement a machine vision solution to assessment. In this instance, we show differences in the effectiveness of existing solutions to the problem of camouflage, concealment and deception (CCD) on the battlefield. Funded by QinetiQ as part of Materials and Structures Low Observable Materials Research Programme. Meeting abstract presented at VSS 2015. Language: en

The Optimal Camouflage Pattern Assessment and Design in all Conditions

As we all know, there are a large mount of camouflage patterns and complex terrains in the real world. Therefore, we classify the camouflage patterns and pick up five representative terrains firstly, After that, we establish five abstract models evaluating the low-efficiency of camouflage patterns and set corresponding indexes to establish the quantitative relationship between patterns and effect. Then, we acquire the consequence by programming in MATLAB. Furthermore, we use the fuzzy comprehensive evaluation to maintain the best camouflage pattern in a single terrain and obtain the use frequency of different type of camouflage patterns in different terrains, the optimal camouflage patterns are discovered and designed in all terrains. Finally, combining with the above results, we make an advertising sheet for a website highlighting to show our design and the best camouflage effect.

Adaptive body patterning, three-dimensional skin morphology and camouflage measures of the slender filefish Monacanthus tuckeri on a Caribbean coral reef.

The slender filefish is a master of adaptive camouflage and can change its appearance within 1-3 seconds. Videos and photographs of this animal's cryptic body patterning and behavior were collected in situ under natural light on a Caribbean coral reef. We present an ethogram of body patterning components that includes large- and small-scale spots, stripes and bars that confer a variety of cryptic patterns amidst a range of complex backgrounds. Field images were analyzed to investigate two aspects of camouflage effectiveness: (i) the degree of color resemblance between animals and their nearby visual stimuli and (ii) the visibility of each fish's actual body outline versus its illusory outline. Most animals more closely matched the color of nearby visual stimuli than that of the surrounding background. Three-dimensional dermal flaps complement the melanophore skin patterns by enhancing the complexity of the fish's physical skin texture to disguise its actual body shape, and the morphology of these structures was studied. The results suggest that the body patterns, skin texture, postures and swimming orientations putatively hinder both the detection and recognition of the fish by potential visual predators. Overall, the rapid speed of change of multiple patterns, color blending with nearby backgrounds, and the physically complicated edge produced by dermal flaps effectively camouflage this animal among soft corals and macroalgae in the Caribbean Sea.

Preliminary Research on One Multiband Smoke Material Preparation

Precision guided weapons (PGWs) have valuable application in field warfare. In order to interfere with Laser, Thermal Infrared (TIR) and Television guidance, this paper intends to research and develop a smoke-generating material that is capable of shielding visible lights, TIR and Millimeter Wave (MMW), based on the attenuation characteristic of expandable graphite to IR and MMW. The formulation is studied by orthogonal design, camouflage effect is verified by experiment, and the material with multiband interfering capacity is preliminarily prepared.

Herbivore diet breadth mediates the cascading effects of carnivores in food webs.

Predicting the impact of carnivores on plants has challenged community and food web ecologists for decades. At the same time, the role of predators in the evolution of herbivore dietary specialization has been an unresolved issue in evolutionary ecology. Here, we integrate these perspectives by testing the role of herbivore diet breadth as a predictor of top-down effects of avian predators on herbivores and plants in a forest food web. Using experimental bird exclosures to study a complex community of trees, caterpillars, and birds, we found a robust positive association between caterpillar diet breadth (phylodiversity of host plants used) and the strength of bird predation across 41 caterpillar and eight tree species. Dietary specialization was associated with increased enemy-free space for both camouflaged (n = 33) and warningly signaled (n = 8) caterpillar species. Furthermore, dietary specialization was associated with increased crypsis (camouflaged species only) and more stereotyped resting poses (camouflaged and warningly signaled species), but was unrelated to caterpillar body size. These dynamics in turn cascaded down to plants: a metaanalysis (n = 15 tree species) showed the beneficial effect of birds on trees (i.e., reduced leaf damage) decreased with the proportion of dietary specialist taxa composing a tree species' herbivore fauna. We conclude that herbivore diet breadth is a key functional trait underlying the trophic effects of carnivores on both herbivores and plants.

Application Research of Slow-Release Fertilizer in Plant Camouflage

Plant camouflage is one of the camouflage methods, which is conducted by using of planting and collecting plant and changing color of plant to conceal targets. It can be used to camouflage relatively big permanent fixed targets in peace time and also to camouflage relatively big permanent fixed targets in peace time and also to camouflage relatively small fixed or moving targets. However, in recent years, with the natural disasters occurring alternately, plant camouflage can be destroyed easily, and it is difficult to rebuild in a short time. To improve the effect of plant camouflage, more fertilizers are required, which may become an environmental hazard, unless adequate technical and socioeconomic impacts are addressed. A multifunctional slow-release nitrogen fertilizer has been developed to improve fertilizer use efficiency and reduce environmental pollution. In this paper, a series of slow-release formulations of nitrogen fertilizer were developed on the basis of natural attapulgite clay, ethylcellulose film, and sodium carboxymethylcellulose/hydroxylethylcellulose hydrogel. The structural of the product were examined. The slow-release profiles of ammonium chloride, ammonium sulfate, and urea as nitrogen fertilizer substrates were determined in soil.