Detection Probability Function Research Articles

Frequency Diversity Gain of a Wideband Radar Signal

Wideband radar has high-range directional resolution, which can effectively reduce the fluctuation of echo and improve the detection probability of a target under the same detection probability requirement. In this paper, a unified wideband radar χ2 distribution target model with more practical significance is innovatively established, on which the probability density function and detection probability function of Swerling 0, Swerling II and Swerling IV targets are analyzed, respectively. A generalized “frequency diversity gain” of wideband radar is proposed and defined based on the contradiction between suppression of fluctuation and accumulation loss, which represents the ratio of Signal-to-Noise Ratio (SNR) gain between broadband signal and reference bandwidth signal under the same condition (when the reference bandwidth is used, the radar target has only one range unit), and the mathematical relation equation of the target detection performance and signal bandwidth (equivalent to the number of distinguishable range elements of the target) is given. A Monte Carlo simulation experiment is designed. Based on the target model established in this paper, the optimal number of target range units corresponding to different detection probability requirements is obtained, which verifies the correctness of the concept proposed in this paper.

Target characteristics and correlation detection probability calculation method in photoelectric detection screen testing system

AbstractThe changed environment factors will affect the capture rate of target and the detection performance in photoelectric detection screen testing system, to improve the detection performance of system, it is very necessary to establish the target optical characteristic model and correlation detection probability calculation model. Based on the detection principle of unit photoelectric detection screen and the spatial geometric relation of four photoelectric detection screens testing system, this article establishes a new target radiation characteristics calculation model by using target's radiation luminance and radiation energy, gives the output signal expression function, derived the detection probability function by signal to noise ratio (SNR) and false alarm probability. Through calculation analysis, the results show that the detection probability of four photoelectric detection screens testing system is related to the target optical characteristic, the output photoelectric current and SNR of photoelectric detection receiving sensor can describe target detection performance. According to the experiments testing, the proposed calculation model can effectively evaluate the performance of photoelectric detection screen testing system.

Cooperative multi-agent search using Bayesian approach with connectivity maintenance

PurposeThis paper aims to present a distributed Bayesian approach with connectivity maintenance to manage a multi-agent network search for a target on a two-dimensional plane.Design/methodology/approachThe Bayesian framework is used to compute the local probability density functions (PDFs) of the target and obtain the global PDF with the consensus algorithm. An inverse power iteration algorithm is introduced to estimate the algebraic connectivity λ2 of the network. Based on the estimated λ2, the authors design a potential field for the connectivity maintenance. Then, based on the detection probability function, the authors design a potential field for the search target. The authors combine the two potential fields and design a distributed gradient-based control for the agents.FindingsThe inverse power iteration algorithm can distributed estimate the algebraic connectivity by the agents. The agents can efficient search the target with connectivity maintenance with the designed distributed gradient-based search algorithm.Originality/valuePrevious study has paid little attention to the multi-agent search problem with connectivity maintenance. Our algorithm guarantees that the strongly connected graph of the multi-agent communication topology is always established while performing the distributed target search problem.

Core Emergence in a Massive Infrared Dark Cloud: A Comparison between Mid-IR Extinction and 1.3 mm Emission

Abstract Stars are born from dense cores in molecular clouds. Observationally, it is crucial to capture the formation of cores in order to understand the necessary conditions and rate of the star formation process. The Atacama Large Millimeter/submillimeter Array (ALMA) is extremely powerful for identifying dense gas structures, including cores, at millimeter wavelengths via their dust continuum emission. Here, we use ALMA to carry out a survey of dense gas and cores in the central region of the massive (∼105 M ⊙) infrared dark cloud (IRDC) G28.37+0.07. The observation consists of a mosaic of 86 pointings of the 12 m array and produces an unprecedented view of the densest structures of this IRDC. In this first Letter about this data set, we focus on a comparison between the 1.3 mm continuum emission and a mid-infrared (MIR) extinction map of the IRDC. This allows estimation of the “dense gas” detection probability function (DPF), i.e., as a function of the local mass surface density, Σ, for various choices of thresholds of millimeter continuum emission to define “dense gas.” We then estimate the dense gas mass fraction, f dg, in the central region of the IRDC and, via extrapolation with the DPF and the known Σ probability distribution function, to the larger-scale surrounding regions, finding values of about 5% to 15% for the fiducial choice of threshold. We argue that this observed dense gas is a good tracer of the protostellar core population and, in this context, estimate a star formation efficiency per free-fall time in the central IRDC region of ϵ ff ∼ 10%, with approximately a factor of two systematic uncertainties.

A Geometric Transversals Approach to Sensor Motion Planning for Tracking Maneuvering Targets

This paper presents a geometric transversals approach for representing the probability of track detection as an analytic function of time and target motion parameters. By this approach, the optimization of the detection probability subject to sensor kinodynamic constraints can be formulated as an optimal control problem. Using the proposed detection probability function, the necessary conditions for optimality can be derived using calculus of variations, and solved numerically using a variational iteration method (VIM). The simulation results show that sensor state and control trajectories obtained by this approach bring about a significant increase in detection probability compared to existing strategies, and require a computation that is significantly reduced compared to direct methods.

Maximum Magnitude of Completeness in a Salt Mine

Abstract In this study, we analyze acoustic emission (AE) data recorded at the Morsleben salt mine, Germany, to assess the catalog completeness, which plays an important role in any seismicity analysis. We introduce the new concept of a magnitude completeness interval consisting of a maximum magnitude of completeness ( M c(max) ) in addition to the well‐known minimum magnitude of completeness. This is required to describe the completeness of the catalog, both for the smallest events (for which the detection performance may be low) and for the largest ones (which may be missed because of sensors saturation). We suggest a method to compute the maximum magnitude of completeness and calculate it for a spatial grid based on (1) the prior estimation of saturation magnitude at each sensor, (2) the correction of the detection probability function at each sensor, including a drop in the detection performance when it saturates, and (3) the combination of detection probabilities of all sensors to obtain the network detection performance. The method is tested using about 130,000 AE events recorded in a period of five weeks, with sources confined within a small depth interval, and an example of the spatial distribution of M c(max) is derived. The comparison between the spatial distribution of M c(max) and of the maximum possible magnitude ( M max ), which is here derived using a recently introduced Bayesian approach, indicates that M max exceeds M c(max) in some parts of the mine. This suggests that some large and important events may be missed in the catalog, which could lead to a bias in the hazard evaluation.

Bayesian search for low-mass planets around nearby M dwarfs – estimates for occurrence rate based on global detectability statistics

Due to their higher planet-star mass-ratios, M dwarfs are the easiest targets for detection of low-mass planets orbiting nearby stars using Doppler spectroscopy. Furthermore, because of their low masses and luminosities, Doppler measurements enable the detection of low-mass planets in their habitable zones that correspond to closer orbits than for Solar-type stars. We re-analyse literature UVES radial velocities of 41 nearby M dwarfs in a combination with new velocities obtained from publicly available spectra from the HARPS-ESO spectrograph of these stars in an attempt to constrain any low-amplitude Keplerian signals. We apply Bayesian signal detection criteria, together with posterior sampling techniques, in combination with noise models that take into account correlations in the data and obtain estimates for the number of planet candidates in the sample. More generally, we use the estimated detection probability function to calculate the occurrence rate of low-mass planets around nearby M dwarfs. We report eight new planet candidates in the sample (orbiting GJ 27.1, GJ 160.2, GJ 180, GJ 229, GJ 422, and GJ 682), including two new multiplanet systems, and confirm two previously known candidates in the GJ 433 system based on detections of Keplerian signals in the combined UVES and HARPS radial velocity data that cannot be explained by periodic and/or quasiperiodic phenomena related to stellar activities. Finally, we use the estimated detection probability function to calculate the occurrence rate of low-mass planets around nearby M dwarfs. According to our results, M dwarfs are hosts to an abundance of low-mass planets and the occurrence rate of planets less massive than 10 M$_{\oplus}$ is of the order of one planet per star, possibly even greater. ...

Combining data from 43 standardized surveys to estimate densities of female American black bears by spatially explicit capture–recapture

AbstractSpatially explicit capture–recapture (SECR) models are gaining popularity for estimating densities of mammalian carnivores. They use spatially explicit encounter histories of individual animals to estimate a detection probability function described by two parameters: magnitude (g0), and spatial scale (σ). Carnivores exhibit heterogeneous detection probabilities and home range sizes, and exist at low densities, so g0 and σ likely vary, but field surveys often yield inadequate data to detect and model the variation. We sampled American black bears (Ursus americanus) on 43 study areas in ON, Canada, 2006–2009. We detected 713 animals 1810 times; however, study area‐specific samples were sometimes small (6–34 individuals detected 13–93 times). We compared AICc values from SECR models fit to the complete data set to evaluate support for various forms of variation in g0 and σ, and to identify a parsimonious model for aggregating data among study areas to estimate detection parameters more precisely. Models that aggregated data within broad habitat classes and years were supported over those with study area‐specific g0 and σ (ΔAICc ≥ 30), and precision was enhanced. Several other forms of variation in g0 and σ, including individual heterogeneity, were also supported and affected density estimates. If study design cannot eliminate detection heterogeneity, it should ensure that samples are sufficient to detect and model it. Where this is not feasible, combing sparse data across multiple surveys could allow for improved inference.

Coping with selfish on-going behaviors

A rational and selfish environment may have an incentive to cheat the system it interacts with. Cheating the system amounts to reporting a stream of inputs that is different from the one corresponding to the real behavior of the environment. The system may cope with cheating by charging penalties to cheats it detects. In this paper, we formalize this setting by means of weighted automata and their resilience to selfish environments. Automata have proven to be a successful formalism for modeling the on-going interaction between a system and its environment. In particular, weighted finite automata (WFAs), which assign a cost to each input word, are useful in modeling an interaction that has a quantitative outcome. Consider a WFA A over the alphabet Σ. At each moment in time, the environment may cheat A by reporting a letter different from the one it actually generates. A penalty function η : Σ × Σ → R ⩾ 0 maps each possible false-report to a penalty, charged whenever the false-report is detected. A detection-probability function p : Σ × Σ → [ 0 , 1 ] gives the probability of detecting each false-report. We say that A is ( η , p ) -resilient to cheating if 〈 η , p 〉 ensures that the minimal expected cost of an input word is achieved with no cheating. Thus, a rational environment has no incentive to cheat A . We study the basic problems arising in the analysis of this setting. In particular, we consider the problem of deciding whether a given WFA A is ( η , p ) -resilient with respect to a given penalty function η and a detection-probability function p; and the problem of achieving resilience with minimum resources, namely, given A and η, finding the minimal (with respect to ∑ σ , σ ′ η ( σ , σ ′ ) ⋅ p ( σ , σ ′ ) ) detection-probability function p, such that A is ( η , p ) -resilient. While for general WFAs both problems are shown to be PSPACE-hard, we present polynomial-time algorithms for deterministic WFAs.

Assessing the viability of tiger subpopulations in a fragmented landscape

Summary Conservation managers require accurate and timely information on the occurrence, size and viability of populations, but this is often difficult for cryptic species living at low densities over large areas. This study aimed to provide such information for tigers in the 36 400‐km2 Kerinci Seblat (KS) region, Sumatra, by identifying and assessing subpopulation viability under different management strategies. Tiger occurrence was mapped within a geographical information system (GIS) using repeat detection–non‐detection surveys to incorporate a function of detection probability into a logistic regression model. The landscape variables that influenced tiger occupancy were then used to construct a spatially explicit habitat model to identify core areas. The number of tigers within each core area was estimated by calculating the area of different forest types and their respective tiger densities as determined through camera trapping. The viability of each subpopulation was then assessed under different management scenarios using a population viability analysis (PVA). Tiger occurrence was negatively correlated with distance to public roads. Four core tiger areas were identified, all predominantly located within KS National Park, estimated to support subpopulations of 21, 105, 16 and three adult tigers, respectively. PVA showed that the three larger subpopulations could be demographically viable if well protected. However, if poaching removed ≥ 3 tigers per year, then only the largest subpopulation would not reach extinction within 50 years. Connectivity to this large subpopulation would ensure survival of the smaller subpopulations, through providing a source of tigers to offset poaching losses. Synthesis and applications. Our key management recommendations for tigers in the Kerinci Seblat region of Sumatra stress the importance of maintaining connectivity between the smaller areas and the larger area, and minimizing poaching within these smaller areas. More widely, our research has shown the feasibility of using detection–non‐detection surveys combined with spatial modelling to provide timely information for conservation management.

Line Transect Estimates of Ungulate Populations in a Mediterranean Forest

We used line transect (distance) methodology to estimate the population density of fallow deer (Dama dama), roe deer (Capreolus capreolus), and wild boars (Sus scrofa) in a dense Mediterranean forest. Three different surveys ( 1 per year from 1995 to 1997) were analyzed. Density estimates, pooled among years, for fallow deer (9.9 deer/km 2 , %CV = 24) and roe deer (8.5 deer/km 2 , %CV = 21) were more precise than the estimate for wild boars (10.6 boars/km 2 , %CV = 55). Fallow deer density was significantly higher during 1997 than during 1995 or 1996. For wild boars, we found differences among years (1995: 23.6 boars/km 2 , %CV = 23; 1996: 10.9 boars/km 2 , %CV = 24; 1997: 3.9 boars/km 2 , %CV = 33). We attempted a confirmatory analysis using an independent survey method for fallow deer and total counts at supplementary feeding sites for wild boars. These comparisons showed that line transect estimates were negatively biased for fallow deer during 1996-1997 and for wild boars during 1997. For adults, the composition by sex from line transects was compared with information collected from fixed observation points. Differences in sex composition for fallow deer and wild boars were found when these 2 methods were compared. The structure of the roe deer population was similar when line transect information was compared with independent survey data. A spike in the detection probability function for wild boars may have been caused by the difficulty of detecting boars >20 m from the transect. The careful use of line transect sampling may prove useful for both research and management of fallow deer, roe deer, and wild boars.

Line transect sampling from a curving path.

Cutting straight line transects through dense forest is time consuming and expensive when large areas need to be surveyed for rare or highly clustered species. We argue that existing paths or game trails may be suitable as transects for line transect sampling even though they will not, in general, run straight. Formulas and software currently used to estimate local density using perpendicular distance data can be used with closest approach distances measured from curving transects. Suitable paths or trails are those for which the minimum radius of curvature is rarely less than the width of the shoulder in the detection probability function. The use of existing paths carries the risk of bias resulting from unrepresentative sampling of available habitats, and this must be weighed against the increase in coverage available.

Efficacy of Northern Goshawk Broadcast Surveys in Washington State

Statewide surveys conducted for northern goshawks (Accipiter gentilis) by the Washington Department of Fish and Wildhfe (WDFW) in the early 1990s had relatively low detection rates throughout the state and different rates of detection between easte n (1 bird/55 kn and western Washington (1 bird/174 km To investigate the possibility that survey methods or regional habitat characteristics affected detection rates, we tested broadeast calls at 40 nest stands known to be occupied by nesting northern goshawks. During 439 station visits and 210 trials, we recorded 109 detections, 68% of which were vocalizations. Northern goshawks at 37 of the 40 (93%) occupied territories re detected at least once, including 4 occupied sites that failed. Detectability was eater at successful nests Juvenile northern goshawks were more responsive than adults, which increased detection rates at successful nests by 37% during the postfledging period and accounted for 87% of responses. Logistic regression modeling identified distance of the surveyon to the nest as the only factor correlated with detection rates (P < 0.001). Probability of detecting northern goshawks at occupied stands increased as nests were approached from 400 m (0.20), 250 m (0.25), and 100 in (0.42). Binomial expansion of detection probabilities at a single nest visit found broadcasting to attain ≥90% detections required 5 visits at 100 m, 8 at 250 m, and 10 at 400 m. Because analysis of detection rates by area did not show an effect of vegetation screening, slope, or topography, differences in the relative abundance of northern goshawks from earlier surveys reflect true variation in abundance, differences in nest success, or some combination of both. Results lend more justification for use of broadcast calling for northern goshawk in Pacific Northwest torests and provide a hypothetical model for estimating survey costs as a function of detection probability, trial frequency, and station spacing.

CHEREN, the Cherenkov counting efficiency

A program is presented that computes the Cherenkov counting efficiency for β-particle-emitting nuclides counted in commercial liquid-scintillation spectrometers. The detection probability function for the Cherenkov light is derived experimentally for standards of 36C1 and 32P, and integrated over the energy interval between the Cherenkov threshold and the end-point of the β-particle distribution. We emphasize the importance of the shape factor forms in the computation of the counting efficiency.

Line Transect Sampling with Unknown Probability of Detection along the Transect

SUMMARY A model is given for line transect sampling for the purpose of estimating animal population density which makes no assumption about the value of the detection probability along the transect or about the form of the detection probability function other than continuity. In addition, animals are permitted to be available, or not, according to a process that is independent of the sampling process. The model requires sampling at two effort levels, either by varying the speed of the observers and/or their number. The unconditional maximum likelihood estimate does not exist, whereas the maximum likelihood estimate, given the total numbers detected at each effort level, exists but does very poorly. A generalization of a moment-like estimator given by Cooke (1985, Report of the International Whaling Commission 35, 319-323) is proposed instead. Asymptotic and small-sample behavior is examined. The estimator is also applied to a field experiment.

The relative importance of contrast and motion in visual detection.

The relative roles of contrast and motion in the detection of targets were investigated using a television display of an artificial target inserted in several different backgrounds of varying complexity. Independent effects of both contrast and motion on the detectability of targets were found. The magnitude of these effects can be accounted for in the detection probability function by modifying the exponent with a linear contrast term and a second-power velocity term. At target speeds greater than about 5 deg/sec, the detection probability began to level off, probably due to interference of the boundaries of the display. Single-fixation experiments confirmed a larger detection field for moving targets than for static, but also demonstrated a gradual increase in the fixation time required to detect a target as a function of its distance from the fixation point.

Optimum Distribution of Effort: An Extension of the Koopman Basic Theory

The fundamental problem of search theory is to allocate a given amount of search effort in such a way as to maximize the over-all probability of discovering an object located in a given space. The problem has already been solved under the assumption that the probability of detecting the object is a negative exponential function of the search effort density, this assumption seems to be fairly realistic in many military applications, but has definite drawbacks in others. In this paper a method is provided for solving the problem in the general case, where no assumption is made concerning the form of the detection probability function. A theorem is derived that gives a general relation governing the optimal solution.