Multiple-target tracking with adaptive sampling intervals for phased-array radar

A novel adaptive sampling interval algorithm for multitarget tracking is presented. This algorithm which is based on interacting multiple models incorporates the grey relational grade （GRG） into the particle swarm optimization （PSO）. Firstly, the desired tracking accuracy is set for each target. Secondly, sampling intervals are selected as particles, and then the advantage of the GRG is taken as the measurement function for resource management. Meanwhile, the fitness value of the PSO is used to measure the difference between desired tracking accuracy and estimated tracking accuracy. Finally, it is suggested that the radar should track the target whose prediction value of the next sampling interval is the smallest. Simulations show that the proposed method improves both the tracking accuracy and tracking efficiency of the phased-array radar.

Physiological and Biochemical Mechanisms of Exogenous Calcium Chloride on Alleviating Salt Stress in Two Tartary Buckwheat(Fagopyrum tataricum)Varieties Differing in Salinity Tolerance

Salt stress is one of the most serious abiotic stresses limiting plant growth and development.Calcium as an essential nutrient element and important signaling molecule plays an important role in ameliorating the adverse effect of salinity on plants.This study aimed to investigate the impact of exogenous calcium on improving salt tolerance in Tartary buckwheat cultivars,cv.Xinong9920(salt-tolerant)and cv.Xinong9909(salt-sensitive).Four-week-old Tartary buckwheat seedlings under 100 mM NaCl stress were treated with and without exogenous calcium chloride(CaCl_(2)),Ca^(2+)chelator ethylene glycol tetraacetic acid(EGTA)and Ca^(2+)-channel blocker lanthanum chloride(LaCl_(3))for 10 days.Then,some important physiological and biochemical indexes were determined.The results showed that salt stress significantly reduced seedling growth,decreased photosynthetic pigments,inhibited antioxidants and antioxidant enzyme activities.However,it increased the reactive oxygen species(ROS)levels in the two Tartary buckwheat cultivars.Exogenous 10 mM CaCl_(2)application on salt-stressed Tartary buckwheat seedlings obviously mitigated the negative effects of NaCl stress and partially restored seedlings growth.Ca^(2+)-treated salt-stressed seedlings diplayed a suppressed accumulation of ROS,increased the contents of total chlorophyll,soluble protein,proline and antioxidants,and elevated the activities of antioxidant enzymes compared with salt stress alone.On the contrary,the addition of 0.5 mM LaCl_(3)and 5 mM EGTA on salt-stressed Tartary buckwheat seedlings exhibited the opposite effects to those with CaCl_(2)treatment.These results indicate that exogenous Ca^(2+)can enhance salt stress tolerance and Ca^(2+)supplementation may be an effective practice to cultivate Tartary buckwheat in saline soils.

Unveiling exceptional sinterability of ultrafine a-Al2O_(3) nanopowders

Scalable pressureless sintering of nanocrystalline alumina(Al2O_(3))ceramics is a challenging problem with great scientific and technological interest.This challenge was addressed in our recent works utilizing ultrafine a-Al2O_(3) nanopowders with exceptional sinterability combined with two-step sintering technique.Here the sintering mechanism and kinetic parameters(grain boundary diffusivity and its activation energy)were analyzed from constant heating-rate sintering experiments by three different sintering models and compared with existing sintering data in the literature.We found that the lowtemperature sintering of 4.7 nm a-Al2O_(3) nanopowders can be well explained by conventional sintering mechanism via grain boundary diffusion,with reasonable activation energy of 4e5 eV that is smaller than that of coarse Al2O_(3) powders and enhanced diffusivity.However,unphysically small activation energy could be obtained if an inappropriate model was used.Lastly,successful two-step sintering was demonstrated under different heating rates.Our work illustrates that the exceptional sinterability of ultrafine a-Al2O_(3) nanopowders are most likely contributed by small size(short diffusion distance),large surface area(large sintering driving force)and good dispersity rather than new sintering mechanism,and highlights the importance of fast firing and the non-equilibrium nature for the low-temperature sintering of such nanopowders.

Grain size refinement of additive manufactured Ce-TZP ceramics by coupled two-step pre-sintering and HIP

Ceria-stabilized tetragonal zirconia polycrystal(Ce-TZP)has exceptional fracture toughness and flaw tolerance due to facile t‒m phase transformation toughening.However,its wider-range applications are limited by its relatively low strength due to its large grain size and low transformation stress,which results in yield-like failure.Here,we combined additive manufacturing(AM),pressureless two-step sintering,and hot isostatic pressing(HIP),and addressed the challenging grain size refinement problem in Ce-TZPs.We successfully produced dense ultrafine-grained Ce-TZP ceramics with an average grain size below 500 nm,a three-point bending strength above 800 MPa,and a single-edge-notch-beam fracture toughness in the range of 11‒12 MPa·m^(1/2).The critical roles of processing design,mixed Ce valences,and under-vs.over-stabilization of tetragonal polymorphs were noted.Our work offers insights and strategies for the future development of stronger and tougher Ce-TZP ceramics that can compete with tetragonal yttria-stabilized zirconia in various applications,including additive manufacturing.