Evaluation and extensions of the probabilistic multi-hypothesis tracking algorithm to cluttered environments

This research examines the probabilistic multi-hypothesis tracker (PHMT), a batch mode, empirical, Bayesian data association and tracking algorithm. Like a traditional multi-hypothesis tracker (MHT), track estimation is deferred until more conclusive data is gathered. However, unlike a traditional algorithm, PMHT does not attempt to enumerate all possible combinations of feasible data association links, but uses a probabilistic structure derived using expectation maximization. This study focuses on two issues: the behavior of the PMHT algorithm in clutter and algorithm initialization in clutter. We also compare performance between this algorithm and other algorithms, including a nearest neighbor tracker, a probabilistic data association filter (PDAF), and a traditional measurement oriented MHT algorithm.Naval Undersea Warfare CenterApproved for public release; distribution is unlimited

Reception of laser generated ultrasound from a CFRP plate by an air matched piezoelectric composite transducer

Laser generated ultrasound is being investigated [1,2] for testing structures made of both conventional metals and carbon fibre reinforced polymer (CFRP). Laser interferometers are widely used in such work to detect the normal surface motion caused by ultrasonic pulses. Interferometers offer non-contact, remote and high-fidelity detection, together with a potential to cover large areas rapidly by optical scanning. However their cost is high and only in testing large and/or expensive structures may the cost be justified. A lower cost alternative, but with some compromise on the virtues of an interferometer, would be to use an air transducer as a receiver

Controlling Restricted Random Testing: An Examination of the Exclusion Ratio Parameter

In Restricted Random Testing (RRT), the main control parameter is the Target Exclusion Ratio (R), the proportion of the input domain to be excluded from test case generation at each iteration. Empirical investigations have consistently indicated that best failure-finding performance is achieved when the value for the Target Exclusion Ratio is maximised, i.e. close to 100%. This paper explains an algorithm to calculate the Actual Exclusion Ratio for RRT, and applies the algorithm to several simulations, confirming that previous empirically determined values for the Maximum Target Exclusion Ratio do give Actual Exclusion Ratios close to 100%. Previously observed trends of improvement in failure-finding efficiency of RRT corresponding to increases in Target Exclusion Ratios are also identified for Actual Exclusion Ratios.published_or_final_versio

Narrow-Band Hybrid Pulsed Laser/EMAT System for Non-Contact Ultrasonic Inspection Using Angled Shear Waves

Conventional ultrasonic testing (UT) using angled shear waves to locate and size potentially critical cracks and flaws in power generation and refinery equipment has become a widely utilized industrial tool. Because this technique uses piezoelectric transducers it requires intimate surface contact and fluid couplants. Therefore, conventional UT has the important drawback that it is difficult to use on surfaces at elevated temperature and, as a result, may require costly plant shut downs to implement. The development of non-contact techniques for angled shear wave UT would represent a significant improvement in the ability to test hot vessels and pipes

Effects of Iron, Silicate, and Light on Dimethylsulfoniopropionate Production in the Australian Subantarctic Zone

Shipboard bottle incubation experiments were performed to investigate the effects of iron, light, and silicate on algal production of particulate dimethylsulfoniopropionate (DMSPp) in the Subantarctic Zone (SAZ) south of Tasmania during March 1998. Iron enrichment resulted in threefold to ninefold increases in DMSPp concentrations relative to control treatments, following 7 and 8-day incubation experiments. Additions of Fe and Si preferentially stimulated the growth of lightly-silicified pennate diatoms and siliceous haptophytes, respectively, to which we attribute the increased DMSPp production in the incubation bottles. Both of these algal groups were previously believed to be low DMSPp producers; however, our experimental data suggest that addition of iron and silicate to the low-silicate low-iron waters of the SAZ will result in increased production of DMSPp by lightly silicified diatoms and siliceous haptophytes, respectively. Increased irradiance enhanced DMSPp production in iron-amended treatments with both low (0.5 nM) and high (5 nM) concentrations of added iron. However, the role of light in stimulating DMSPp production was apparently of secondary importance compared to the effects of iron addition. The combination of high irradiance and high iron enrichment produced the highest DMSPp production in the experiments, suggesting that iron and light may have a synergistic effect in limiting algal DMSPp production in subantarctic waters

Comment on “The complex effects of ocean acidification on the prominent N2-fixing cyanobacterium Trichodesmium”

Author Posting. © The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Science 357 (2017): eaao0067, doi:10.1126/science.aao0067.Hong et al. (Reports, 5 May 2017, p. 527) suggested that previous studies of the biogeochemically significant marine cyanobacterium Trichodesmium showing increased growth and nitrogen fixation at projected future high CO2 levels suffered from ammonia or copper toxicity. They reported that these rates instead decrease at high CO2 when contamination is alleviated. We present and discuss results of multiple published studies refuting this toxicity hypothesis

During a winter of storms in a small UK catchment, hydrology and water quality responses follow a clear rural-urban gradient

This paper presents the hydrological and water quality response from a series of extreme storm events that passed across the UK during the winter of 2013/2014, in an experimental catchment with a strong rural-urban gradient across four nested sub-catchment areas. The Ray catchment in the upper Thames basin, UK, was extensively monitored using in-situ, high-resolution (15 minute) flow and water quality instrumentation. Dissolved oxygen, ammonium, turbidity and specific conductivity are used to characterise the water quality dynamics. The impact of the Swindon sewage treatment works (SSTW) on water chemistry at the catchment outlet is considerable. Hydrological and water-quality response varies considerably during the events, with the rural catchments exhibiting a much slower hydrological response compared to urban areas. A simple hydrological model (TETIS) was developed to provide insight into water sources in nested subcatchments, highlighting the disparity of the hydrological dynamics across contrasting land-uses during events. The variation in stormwater runoff sources impacts water quality signals with urban sites contributing to dilution dynamics in ammonium, whereas the more rural site experiences a peak in ammonium during the same event. Dissolved oxygen concentrations vary on a rural-urban gradient and experience a notable sag at the Water Eaton outlet (4.4mg/l) during the events, that would have resulted in significant ecological harm had they occurred during the summer in warmer temperatures. The water-quality legacy of these storms in the wider context of the hydrological year is somewhat negligible, with markedly poorer water quality signals being observed during the summer months of 2014. Although ammonium concentrations during the events are elevated (above the ‘good’ status threshold under the WFD), higher values are observed during spring and summer months. The high flows actually appear to flush contaminants out of the Ray and its subcatchments, though the urban sites demonstrate a resupply dynamic during interim dry periods. Data suggest winter storms following dry spells in urban catchments cause some short-lived and spatially extensive deteriorations in water quality. More chronic effects, although prolonged, are only seen downstream of SSTW. These are indicative of capacity of infrastructure being reached, and from the data do not appear to be severe enough to cause ecological harm

Experimental Study of the Guided Wave Directivity Patterns of Thin Removable Magnetostrictive Patches

© 2020 by the authors. The characteristics of removable magnetostrictive thin patches are investigated for the generation of guided waves in plates. The directivity patterns of SH, S0 and A0 modes have been measured in a thin metallic plate for different combinations of static and dynamic magnetic field directions. This used different coil geometries such as racetrack and spiral coils to generate the dynamic magnetic field, as well as separate biasing static magnetic fields from permanent magnets. This arrangement generated signals via both Lorentz and magnetostrictive forces, and the resultant emitted guided waves were studied for different dynamic and static magnetic field directions and magnitudes. It is demonstrated that different guided wave modes can be produced by controlling these parameters.Marie Skłodowska Curie Training Network in Non-Destructive Testing and Structural Health Monitoring of Aircraft structure

Progressive genetic aberrations detected by comparative genomic hybridization in squamous cell cervical cancer

Genetic changes orchestrated by human papillomaviruses are the most important known factors in carcinogenesis of the uterine cervix. However, it is clear that additional genetic events are necessary for tumour progression. We have used comparative genomic hybridization to document non-random chromosomal gains and losses within a subset of 37 cervical carcinomas matched for clinical stage Ib, but with different lymph node status. There were significantly more chromosomal changes in the primary tumours when the lymph nodes were positive for metastases. The most frequent copy number alterations were loss of 3p, 11q, 6q and 10q and gain of 3q. The smallest areas of loss and gain on chromosome 3 were 3p14–22 and 3q24–26. The study identifies progressive DNA copy number changes associated with early-stage invasive cervical cancers with and without lymph node metastases, a factor of potential prognostic and therapeutic value. © 2000 Cancer Research Campaign http://www.bjcancer.co

How robust is the evidence for beneficial hydrological effects of urban tree planting?

Sustainable urban water management initiatives are increasingly required to combat rapid urbanisation and climate pressures. Initiatives include the role of tree planting for which there is need for strong evidence of benefits and drawbacks to support effective future planning. We report robustness of evidence from an assimilated database of urban hydrological impact studies which often had differing primary purposes. Consistent impacts were found at local level, with trees reducing runoff and infiltration. Despite the consistency of evidence, much is undermined by being somewhat lacking in robustness and scientific rigour. Many studies lack adequate controls, and models are often not strongly tested against observations. Moreover, evidence of impact at larger scales is lacking. Effects of tree characteristics were also investigated; such as maturity and species for which evidence is consistent and detailed, and arrangement for which there is less evidence. Realising the full potential of trees in urban water management decision-making would benefit from more-rigorous evidence