Maximum Detection Distance Research Articles

On-line experiments on rapid detection of radionuclides based on sequential Bayesian analysis

A rapid detection method based on sequential Bayesian analysis provides a new perspective on national security in preventing the smuggling and illegal transportation of nuclear materials. In this paper, a sequential Bayesian analysis system, which mainly consists of a LaBr3(Ce) scintillator detector, a pulse analyzer based on a field-programmable gate array technique, and a sequential Bayesian analysis processor, is developed to directly validate the feasibility of sequential Bayesian analysis. The detection ability of 60Co, 137Cs, 133Ba, and 152Eu for a specific radioactivity is studied and quantified using the maximum detection distance and the equivalent minimum detection activity.

Efficacy of Portable PIT Detectors for Tracking Long‐Term Movement of Colorado River Cutthroat Trout in a Small Montane Stream

AbstractWe evaluated the efficacy of portable PIT detectors for tracking long‐term fish movement in an open stream environment. In June and October of 2012, we PIT‐tagged a total of 190 Colorado River Cutthroat Trout Oncorhynchus clarkii pleuriticus (CRCT) in a 1.7‐km segment of a small, montane stream. In the summers of 2012–2013 (15 total occasions), we relocated PIT‐tagged trout using portable PIT detectors. The maximum detection distance of 23‐mm PIT tags ranged from 6 to 56 cm and varied with detector, detection plane, and tag orientation. Of the CRCT tagged, 38% were never detected and 43% were detected on two or more occasions. Mean detection efficiencies of PIT‐tagged trout were 34% and 45% in 2012 and 2013, respectively, and were generally lower than in evaluations of closed systems and less mobile fishes. We observed a smaller range of CRCT than has been observed by others using radiotelemetry, a difference that could be explained by the spatial and temporal limitations of portable PIT detection we encountered. We conclude that portable PIT detector surveys have value but also drawbacks for tracking the movement of relatively mobile fishes in montane streams.Received September 27, 2014; accepted January 21, 2015

Offshore Activity of Bats Along the Mid-Atlantic Coast

Abstract Bat mortality caused by terrestrial wind-power plants has been documented and offshore wind-power developments may have similar effects. Determining which bat species occur offshore, how far they range from shore, and predictors of high activity may be helpful to developers and wildlife managers. We studied bat activity off the mid-Atlantic coast, using ultrasonic detectors mounted on ships in spring and fall 2009 and 2010. We investigated the association between nightly bat activity and weather variables, including wind speed, air temperature, and barometric pressure. Echolocation passes of bats totaled 166; maximum detection distance from shore was 21.9 km, and mean distance was 8.4 km. Most passes were identified as Lasiurnis borealis (Eastern Red Bats), representing 78% of bats identified to species or species group. Bat activity decreased as wind speed increased, but activity did not differ with distance from shore. Offshore wind projects proposed for locations beyond the maximum detection d...

A novel self-powered wireless temperature sensor based on thermoelectric generators

A novel self-powered wireless temperature sensor has been designed and presented for solving the power supply problem of temperature sensors. This sensor can autonomously measure temperature under positive temperature fluctuation situations. The self-powered characteristic, realized by using four thermoelectric generators, enables the sensor to operate without any batteries or other power sources. In order to obtain these features, attentions are not only focused on the method to combine signal sensing and power generating together, but also on the method to improve measurement accuracy. Experimental results confirm that this novel sensor has excellent measurement accuracy. The measured performance is consistent with the calculated characteristics. For typical application, this self-powered temperature sensor can detect fire before it develops to flashover state. And the maximum detection distance grows with the growth of burning rate. All the results indicate this innovative sensor is a promising self-powered device which can be used to measure temperature value in positive temperature fluctuation situations.

Planar Spiral Coil Design for a Pulsed Induction Metal Detector to Improve the Sensitivities

In a pulsed induction metal detector system, the sensitivity variation for detectable minimum metal target and the maximum detection distance are investigated as the winding geometry of the search coil is varied. A number of planar square spiral mono coils with various fill ratios and wire spacing-to-width ratios are comparatively analyzed based on a numerical simulation. Five representative coils are fabricated and applied to a pulsed induction metal detector system as a search coil. It is demonstrated that a search coil with a larger fill ratio has a high size sensitivity for a minimum metal target at close distances, which may be missed by coils with smaller fill ratios. A search coil with a smaller wire spacing-to-width ratio is shown to have a high depth sensitivity for maximum detection distances.

System for Measuring the Burst Point Time Base on APD

Aiming at the burst point time measuring device cannot timely show the burst point time measurement situation, a new measuring system was designed. The pulse signal when the ammo was outing of the muzzle and exploding was detected by APD, the light pulse was converted to voltage pulse through an amplifying circuit. The timing display module was designed, the timing circuit got the voltage pulse and timing, and then the burst point time would show on LCD. All the photoelectric detector module was fixed with the special mechanical properties. The system could increase the maximum detection distance effectively, improve its detecting precision, and display the burst point time immediately. With the simulation experiment, the system had no failing to get the burst point time, and owned a stable performance. This design can provide a reference for the optimization and improvement of the burst point time measuring device.

Acoustic detection probability of bottlenose dolphins, Tursiops truncatus, with static acoustic dataloggers in Cardigan Bay, Wales

Acoustic dataloggers are used for monitoring the occurrence of cetaceans and can aid in fulfilling statutory monitoring requirements of protected species. Although useful for long-term monitoring, their spatial coverage is restricted, and for many devices the effective detection distance is not specified. A generalized additive mixed model (GAMM) was used to investigate the effects of (1) distance from datalogger, (2) animal behavior (feeding and traveling), and (3) group size on the detection probability of bottlenose dolphins (Tursiops truncatus) with autonomous dataloggers (C-PODs) validated with visual observations. The average probability of acoustic detection for minutes with a sighting was 0.59 and the maximum detection distance ranged from 1343-1779 m. Minutes with feeding activity had higher acoustic detection rates and longer average effective detection radius (EDR) than traveling ones. The detection probability for single dolphins was significantly higher than for groups, indicating that their acoustic behavior may differ from those of larger groups in the area, making them more detectable. The C-POD is effective at detecting dolphin presence but the effects of behavior and group size on detectability create challenges for estimating density from detections as higher detection rate of feeding dolphins could yield erroneously high density estimates in feeding areas.

Off-line experiments on radionuclide detection based on the sequential Bayesian approach

The sequential Bayesian approach proposed by Candy et al. for radioactive materials detection has aroused increasing interest in radiation detection research and is potentially a useful tool for prevention of the transportation of radioactive materials by terrorists. In our previous work, the performance of the sequential Bayesian approach was studied numerically through a simulation experiment platform. In this paper, a sequential Bayesian processor incorporating a LaBr3(Ce) detector, and using the energy, decay rate and emission probability of the radionuclide, is fully developed. Off-line experiments for the performance of the sequential Bayesian approach in radionuclide detection are developed by placing 60Co, 137Cs, 133Ba and 152Eu at various distances from the front face of the LaBr3(Ce) detector. The off-line experiment results agree well with the results of previous numerical experiments. The maximum detection distance is introduced to evaluate the processor′s ability to detect radionuclides with a specific level of activity.

Multimodal signals increase active space of communication by wolf spiders in a complex litter environment

Multimodal signals may compensate for environmental constraints on communication, as signals in different modalities vary in efficacy. We examined the influence of complex microhabitats on transmission of vibratory and visual signals of courting male Schizocosa ocreata wolf spiders (Araneae: Lycosidae) with laser Doppler vibrometry (LDV) and behavioral observations in lab and field. We measured maximum potential detection distance of visual and vibratory signals by females in laboratory mesocosms, recorded vibration signal attenuation on different substrates, and estimated transmission distances for male vibration signals in the field. We also determined effective line-of-sight visual detection distances in the field with laser distance measures. Together, these data were used to estimate the potential and effective active space of multimodal signals. LDV measures show leaves are highly conductive substrates for wolf spider vibratory signals compared to others (soil, wood, rock). For both visual and vibratory modes, lab estimates of maximum potential distance for signal transmission and detection (behavior studies) exceeded estimates of effective active space (signal attenuation, “vanishing point,” and “line-of-sight” measures). Field estimates of transmission distance for signal modes overlap, such that in close range (<20 cm), vibratory signals are more likely to be detected, while farther away, visual signals are more likely to be seen. These findings thus support current hypotheses regarding how multimodal communication might extend the range of overall signal active space or compensate for environmental constraints.

Optimal configuration of a micro-earthquake network

Abstract. This study simulates automatic event detection and location performance of a micro-earthquake network centred around a future power plant site in Finland, Fennoscandian Shield. Simulation of the event location capability is based on a relationship derived between event magnitude and maximum detection distance. Azimuthal coverage and threshold magnitude are computed for different station configurations and the results are presented as contour maps. An optimal configuration of ten seismograph stations is proposed for further on-site survey. The network fulfils the preconditions of automatic event location capability down to ML 0.0 and azimuthal coverage better than 180° within 25 km radius from the study site. Annual number of earthquakes (ML ≥ 0.0) detected by the network is estimated to be 2 and 8 within 25 and 50 km radius from the power plant site.

Estimation of the acoustic range of bat echolocation for extended targets

Extended natural structures of the bat environment such as trees, meadows, and water surfaces were ensonified in distances from 1 to 20 m and the echoes recorded using a mobile ultrasonic sonar system. By compensating the atmospheric attenuation, the attenuation of the reflected echo caused by diffraction, energy absorption of the target, and two-way-geometric spreading was calculated for each distance. For each target type the attenuation of the compensated echo sound pressure level was fitted over distance using a linear function which yields simple laws of reflection loss and geometric spreading. By adding to this function again variable atmospheric attenuation, the overall attenuation of a signal reflected from these targets can be estimated for various conditions. Given the dynamic range of a sonar system, the acoustic maximum detection distance can thus be estimated. The results show that the maximum range is dominantly limited by atmospheric attenuation. Energy loss in the reflecting surface is more variable than geometric spreading loss and accounts for most of the differences between the ensonified targets. Depending on atmospheric conditions, echolocation frequency, and the dynamic range of the sonar system, the maximum range for extended backgrounds such as a forest edge can be as short as 2.4 m.

Using binomial distance-sampling models to estimate the effective detection radius of point-count surveys across boreal Canada

ABSTRACT. We used binomial distance-sampling models to estimate the effective detection radius (EDR) of point-count surveys across boreal Canada. We evaluated binomial models based on 0–50 m and >50 m distance categories for goodness-of-fit and sensitivities to variation in survey effort and habitats sampled. We also compared binomial EDRs to Partners in Flight's maximum detection distances (MDD) to determine differences in landbird population sizes derived from each. Binomial EDRs had a small positive bias (4%) averaged across 86 species and a large positive bias (30–82%) for two species when compared with EDRs estimated using multinomial distance sampling. Patterns in binomial EDRs were consistent with how bird songs attenuate in relation to their frequencies and transmission through different habitats. EDR varied 12% among habitats and increased 17% when birds were counted to an unlimited distance, compared with a limited distance of 100 m. The EDR did not vary with the duration of surveys, and densiti...

Orientation behavior in fish larvae: A missing piece to Hjort's critical period hypothesis

Larval reef fish possess considerable swimming and sensory abilities, which could enable navigation towards settlement habitat from the open ocean. Due to their small size and relatively low survival, tagging individual larvae is not a viable option, but numerical modeling studies have proven useful for understanding the role of orientation throughout ontogeny. Here we combined the theoretical framework of the biased correlated random walk model with a very high resolution three-dimensional coupled biophysical model to investigate the role of orientation behavior in fish larvae. Virtual larvae of the bicolor damselfish (Stegastes partitus) were released daily during their peak spawning period from two locations in the Florida Keys Reef Tract, a region of complex eddy fields bounded by the strong Florida Current. The larvae began orientation behavior either before or during flexion, and only larvae that were within a given maximum detection distance from the reef were allowed to orient. They were subjected to ontogenetic vertical migration, increased their swimming speed during ontogeny, and settled on reefs within a flexible window of 24 to 32 days of pelagic duration. Early orientation, as well as a large maximum detection distance, increased settlement, implying that the early use of large-scale cues increases survival. Orientation behavior also increased the number of larvae that settled near their home reef, providing evidence that orientation is a mechanism driving self-recruitment. This study demonstrates that despite the low swimming abilities of the earliest larval stages, orientation during this “critical period” would have remarkable demographic consequences.

Development and evaluation of a boat-mounted RFID antenna for monitoring freshwater mussels

Development of radio frequency identification (RFID) technology and passive integrated transponder (PIT) tags has substantially increased the ability of researchers and managers to monitor populations of aquatic organisms. However, use of transportable RFID antenna systems (i.e., backpack- mounted) is currently limited to wadeable aquatic environments (,1.4 m water depth). We describe the design, construction, and evaluation of a boat-mounted RFID antenna to detect individually PIT-tagged benthic aquatic organisms (mussels). We evaluated the effects of tag orientation on detection distances in water with a 32-mm half-duplex PIT tag. Detection distances up to 50 cm from the antenna coils were obtained, but detection distance was dependent on tag orientation. We also evaluated detection distance of PIT tags beneath the sediment to simulate detection of burrowing mussels with 23- and 32-mm tags. In sand substrate, the maximum detection distance varied from 3.5 cm and 4.5 cm (vertical tag orientation) to 24.7 cm and 39.4 cm (45u tag orientation) for the 23- and 32-mm PIT tags, respectively. Our results suggest a 1.4-m total detection width for tagged mussels on the substrate surface by the boat-mounted antenna system regardless of tag orientation. However, burrowed mussels may require multiple passes to increase detection that would be influenced by depth, tag orientation, and tag size. Construction of the boat- mounted antenna was relatively low in cost (,500 USD) and had several advantages (less labor and time intensive, increased safety) over traditional mussel sampling techniques (diving, snorkeling) in nonwadeable habitats.

Performance testing of collision-avoidance system for power wheelchairs

The Drive-Safe System (DSS) is a collision-avoidance system for power wheelchairs designed to support people with mobility impairments who also have visual, upper-limb, or cognitive impairments. The DSS uses a distributed approach to provide an add-on, shared-control, navigation-assistance solution. In this project, the DSS was tested for engineering goals such as sensor coverage, maximum safe speed, maximum detection distance, and power consumption while the wheelchair was stationary or driven by an investigator. Results indicate that the DSS provided uniform, reliable sensor coverage around the wheelchair; detected obstacles as small as 3.2 mm at distances of at least 1.6 m; and attained a maximum safe speed of 4.2 km/h. The DSS can drive reliably as close as 15.2 cm from a wall, traverse doorways as narrow as 81.3 cm without interrupting forward movement, and reduce wheelchair battery life by only 3%. These results have implications for a practical system to support safe, independent mobility for veterans who acquire multiple disabilities during Active Duty or later in life. These tests indicate that a system utilizing relatively low cost ultrasound, infrared, and force sensors can effectively detect obstacles in the vicinity of a wheelchair.

Detection Distances of Selected Radio and Acoustic Tags in Minnesota Lakes and Rivers

AbstractIn freshwater, the optimal choice between radiotelemetry or acoustic telemetry has often been unclear because the combined effects of tag power, conductivity, tag depth, and antenna type on radio tag detection distances have not been quantified. To enable more informed decisions regarding the best telemetry methods to use at particular study sites, we measured maximum detection distances of an acoustic tag and two different 48–49‐MHz radio tags over a wide range of conductivities, depths, and acoustic conditions in Minnesota lakes and rivers. Radio tag detection distances increased with increasing tag power, decreased with increasing conductivity, and generally decreased with increasing depth. Detection distances measured with a Yagi antenna were typically about double those measured with a loop antenna. Maximum detection distances of the radio tags were predicted by the equation logeR = 13.69 − 0.005771·C − 0.006575·D + 0.1044·P + 0.7275·A − 0.001302·C·D − 0.00008208·C·P (where R = maximum detection distance, m; C = surface conductivity, μS/cm, at ambient temperature; D = tag depth, m; P = tag output power, dB relative to 1 mW; and A = antenna type [1 = Yagi, 0 = loop]). Acoustic detection distances were less variable overall than radio detection distances but still differed substantially between and within water bodies. We saw no consistent relationship between acoustic detection distance and tag depth, but detection distance was negatively affected by ambient noise. Our model indicates that a 48–49‐MHz radio tag can be detected with a boat‐mounted Yagi antenna at a depth of 50 m or more if conductivity is low enough, but the maximum detection depth decreases drastically as conductivity increases. The equation above can be used to predict whether detection distances of radio tags similar to the ones we tested will be adequate for a particular study.

Directed fluorescence sensor element for standoff detection of uranium in soil

A passive signal enhancement device for the standoff detection of uranium in soil was developed and tested. The device consists of a spherical ball lens half-coated with a polymer–silica gel composite. The nanoporous silica gel, when placed in contact with moist soil, absorbs water and dissolved uranyl ions and significantly enhances the fluorescence intensity of the uranyl. The ball lens focuses the UV excitation energy to the focal point of the lens located within the silica gel layer and directs the resulting fluorescence signal back towards the excitation source. Our results show that this ‘Directed Fluorescence’ (DF) device can be used to enhance the uranyl fluorescence signal intensity by more than 200 times. Consequently, the maximum standoff detection distance is increased by more than an order of magnitude.

Telemetry of Anisoptera after emergence first results (Odonata)

Abstract The behaviour of Anisoptera during the period between emergence and the onset of sexual activity is poorly known, mainly because freshly emerged adults are hard to follow. In the present study the system RECCO® Transmitter/Receiver and custombuilt tags made from Schottky diodes and copper wire were used to monitor freshly emerged Anisoptera. The system had an average maximum detection distance of ca 85 m. Ten individuals of Libellula fulva were successfully tracked for up to five consecutive days. They almost exclusively utilized trees or shrubs as perches at heights ranging from 1.8 to ca 31 m. Open meadows or open river bank vegetation, which were present close to the release site, were never used for perching. Considering that human observers can reasonably detect adult anisopteran up to a height of 3 m, 92.5% of all registered perch sites were “out of reach”. The maximum distances covered on the first day averaged 37.7 m and 31.1 m for males and females, respectively. Two individuals, followe...

In the mating system of the bat Saccopteryx bilineata, bioacoustic constraints impede male eavesdropping on female echolocation calls for their surveillance

At night, bats utter loud echolocation calls at high repetition rates that may reveal the location and current behaviour of callers to eavesdropping bats. Given the strong attenuation of echolocation calls, we predicted that territorial males of a harem-polygynous species ought to forage at close distance to females to survey their movements by social eavesdropping. We estimated a maximum detection distance of 38 m for echolocation calls of Saccopteryx bilineata (Temminck, 1838) (Chiroptera; Emballonuridae) broadcasted within the forest under the sound transmission conditions of our study site and for an assumed signal detection threshold of 20 dB SPL (50 m for a threshold of 0 dB SPL). We then simultaneously radio-tracked the nocturnal movements of eight male–female pairs that each rested in the same harem territory during the day and measured the distances at which dyads foraged. Male–female pairs foraged at a median distance of 139 m. In the case of 90% of simultaneous bearings, males foraged at distances that prevented eavesdropping on 44 kHz echolocation calls (&gt;38 m; 87% of radio fixes &gt;50 m). Males and females of the same daytime territory roosted, on average, 226 ± 194 m apart from each other at night. Thus, males were most likely unaware of where females foraged as a result of the strong attenuation of female echolocation calls. In general, such acoustic constraints on social eavesdropping may promote extra-harem group paternities, female choice, and sperm competition in bats, and may therefore present an important selective force in the evolution of bat mating systems.

Detection probability of Golden-winged Warblers during point counts with and without playback recordings

ABSTRACT Use of point-count data to estimate population sizes of North American landbirds may be challenged by limitations on detection probability of particular species, thereby requiring correction factors to ensure accurate estimates. We estimated detection probability of Golden-winged Warblers (Vermivora chrysoptera) during 3-min point-count surveys conducted both with and without use of playback recordings in a mixed shrubland-forest habitat (clearcut area) and a 60-m wide electric transmission line right-of-way (ROW) in central Pennsylvania from 20 May to 17 June 2002–2003. In addition, we assessed the value of playback with respect to response rates of warblers and distance within which warblers approached the observer. Without playback, detection probability was approximately 23% in the clearcut area and 61% in the ROW. Use of playback resulted in 7% and 19% net increases in probability at the clearcut area and the ROW, respectively; proportional increase was approximately 30% for both habitats. Warblers responded to playback 68% of the time, but response rate was greater within 100 m (72%) than beyond (53%). Most responses (85%) included approach of the warbler toward the observer, and most individuals approached within 10 m. We conclude that 3-min point counts with playback do not yield detection probabilities sufficient to estimate population size of Golden-winged Warblers without use of correction factors. Furthermore, detection probability in mixed shrubland-forest habitats can be much lower than in linear habitats such as utility ROWs. Efforts to estimate population size of Golden-winged Warblers from data of the North American Breeding Bird Survey should recognize that habitat structure has much influence on detection probability as it relates to distance at which an observer can hear (or see) warblers. Accordingly, we recommend that such efforts incorporate a maximum detection distance of 100–150 m in mixed shrubland-forest habitats.