Isotopically labelled water - A valuable tracer to track initiation and progress of bud dormancy in temperate trees

<p>Leaf-out of deciduous trees is regulated by a set of environmental factors such as cool temperatures during winter-dormancy (chilling), warm spring temperatures (forcing), and daylength (photoperiod), with complex interactions between these factors. Teasing apart these different factors in situ is challenging as no visible changes occurs during the dormancy phase. Manipulating these factors in climate chamber experiments may overcome this issue but may not reflect how they truly interact in natural conditions. Previous researches suggested that bud meristems are disconnected from the xylem flow during endodormancy and that the connection become progressively restored once exposed to a certain duration of chilling. Here we developed a new method using isotopically labelled water (D<sub>2</sub>O) to quantify the amount of water that can reach buds during the whole dormancy till budburst for 5 different species (<em>Acer pseudoplatanus</em>, <em>Carpinus betulus</em>, <em>Fagus sylvatica</em>, <em>Quercus petraea</em>, <em>Tilia cordata</em>).</p><p>In detail, we harvested twig cuttings from leaf fall to budburst (~every two weeks, 12 times) of these species from two different sites (about 5°C of difference) and placed them into labelled water during 24 h at constant light and 20°C. Buds were then cut and water content extracted to quantify δD. Thus, tracing back the water flow into the buds by the amount of D<sub>2</sub>O taken up. In parallel a subset of twigs was left in the room at 20°C to assess the time to budburst as a proxy for dormancy depth. Analyses of the data are ongoing and preliminary results show progressive increase of water uptake after induction of winter dormancy until budburst as chilling duration increased. Further, we also found distinct differences between species whereas <em>Carpinus betulus</em> showed the highest and <em>Tilia cordata </em>the lowest label uptake during winter dormancy. Furthermore, individuals growing at higher elevation took up less label indicating a stronger dormancy at lower winter temperatures. In summary, we think that our method seems a valuable tool to track quantitative changes in dormancy depth of temperate species especially, in combination with investigations on the molecular level such as sugars or hormones during winter-dormancy.</p>

A Track Initiation Algorithm Using Residual Threshold for Shore-Based Radar in Heavy Clutter Environments

There is a large error in the actual radar trajectory tracking process. Track initiation is the primary problem in trajectory tracking and the first step in target tracking. The current track initiation algorithms are greatly affected by heavy clutter environments, so it is necessary to propose an algorithm to solve the problem of low track initiation efficiency. This paper presents a track initiation algorithm using a residual threshold in heavy clutter environments. The falling probability of measured value and decision threshold are used to determine the correlation window. The angle limiting condition is added to establish the track association, and the residual threshold is used to further eliminate the false tracks. The initial track experiment with the trajectory data in the sea near Rizhao Port shows that the algorithm is superior to the traditional logic method and Kalman filter method in track quality. The experiment uses the AIS buffer zone to calculate track initiation probability and uses the multi-region AIS trajectory data for verification. The experimental result shows that track initiation probability with the proposed algorithm in this paper can reach 92.31%.

Tracking multiple maneuvering targets hidden in the DBZ based on the MM-PHD filter

<p><a></a><a></a><a>For a ground moving target indication (GMTI) radar, the presence of </a><a></a><a></a><a></a><a>Doppler blind zone (DBZ)</a> results in many short tracks with frequent label switching, which seriously deteriorates the tracking performance. When the DBZ masking is coupled with targets maneuvering, tracking multiple maneuvering targets hidden in the DBZ becomes very challenging, which is reflected in the fact that there is no public research on this issue. To overcome this complicated problem, we propose a practical and fully functional GMTI multi-maneuvering-target tracker based on the multiple model probability hypothesis density (MM-PHD) filter. Unlike the standard MM-PHD filter, the proposed tracker utilizes the Doppler information and incorporates the minimum detectable velocity (MDV) to suppress the DBZ masking. Furthermore, to cope with the problems of the fixed initiation and no label output of the standard MM-PHD filter, the resulting MM-PHD filter with the Doppler and MDV information is augmented with measurement-driven adaptive track initiation and track label propagation, which are necessary for a practical tracker and also required for evaluating the overall GMTI tracking performance. Finally, numerical examples show that the proposed tracker outperforms significantly the existing ones, thus verifying its effectiveness.</p> <p> </p>

Tracking multiple maneuvering targets hidden in the DBZ based on the MM-PHD filter

<p><a></a><a></a><a>For a ground moving target indication (GMTI) radar, the presence of </a><a></a><a></a><a></a><a>Doppler blind zone (DBZ)</a> results in many short tracks with frequent label switching, which seriously deteriorates the tracking performance. When the DBZ masking is coupled with targets maneuvering, tracking multiple maneuvering targets hidden in the DBZ becomes very challenging, which is reflected in the fact that there is no public research on this issue. To overcome this complicated problem, we propose a practical and fully functional GMTI multi-maneuvering-target tracker based on the multiple model probability hypothesis density (MM-PHD) filter. Unlike the standard MM-PHD filter, the proposed tracker utilizes the Doppler information and incorporates the minimum detectable velocity (MDV) to suppress the DBZ masking. Furthermore, to cope with the problems of the fixed initiation and no label output of the standard MM-PHD filter, the resulting MM-PHD filter with the Doppler and MDV information is augmented with measurement-driven adaptive track initiation and track label propagation, which are necessary for a practical tracker and also required for evaluating the overall GMTI tracking performance. Finally, numerical examples show that the proposed tracker outperforms significantly the existing ones, thus verifying its effectiveness.</p> <p> </p>