3-D Reconstruction and Visualization of Laser-Scanned Trees by Weighted Locally Optimal Projection and Accurate Modeling Method

This paper presents a method to reconstruct 3-D models of trees from terrestrial laser scan(TLS)point clouds.This method uses the weighted locally optimal projection(WLOP)and the AdTree method to reconstruct detailed 3-D tree models.To improve its representation accuracy,the WLOP algorithm is introduced to consolidate the point cloud.Its reconstruction accuracy is tested using a dataset of ten trees,and the one-sided Hausdorff distances between the input point clouds and the resulting 3-D models are measured.The experimental results show that the optimal projection modeling method has an average one-sided Hausdorff distance(mean)lower by 30.74%and 6.43%compared with AdTree and AdQSM methods,respectively.Furthermore,it has an average one-sided Hausdorff distance(RMS)lower by 29.95%and 12.28%compared with AdTree and AdQSM methods.Results show that the 3-D model generated fits closely to the input point cloud data and ensures a high geometrical accuracy.

Finite element and experimental analysis of pinion bracket-assembly of three gorges project ship lift

The pinion bracket-assembly(PBA) is a major part of three gorges project(TGP) ship lift drive system. The static strength,fatigue strength and stress distribution of hinge pin of PBA were analyzed by ANSYS, and the structure of PBA was optimized. The results show that after the optimization, the maximum comprehensive stress is 259.59 MPa, the maximum fatigue cumulative damage of weld joints is 0.94 and the maximum vertical deformation of hinge pin is 0.14 mm. The elastic deformation, hydropneumatic spring cylinder(HSC) load response and the vibration characteristics of PBA were studied by the bearing test when PBA bore the load caused by different water level errors. The results indicate that when the water level of ship chamber ranges from 3.4 m to 3.6 m,the vertical elastic deformation of the pinion shaft is between-8.58 and 10.50 mm. When upward outage-load(1580 k N) is imposed by the test-rack, the vertical elastic deformation of the pinion shaft is 13.42 and 14.07 mm and HSC load response is 795.80-800.80 k N. In the process of imposing load on the pinion by the test-rack, the maximum vibration amplitude and acceleration of PBA internal components are 0.37° and 2.67 rad/s2, respectively; the maximum impact on the pin caused by vibration is 19.89 k N; the pinion shaft vertical displacement and HSC load response do not fluctuate. There is a great difference between the frequency of meshing force of the pinion and the rack(1.06 Hz) and first-order natural frequency of PBA(8.41 Hz), thus PBA will not resonate.From all above, PBA meets the static strength and fatigue strength requirements. The vibration of PBA internal components has no effect on the vertical displacement of the pinion shaft, HSC load response and smooth operation of PBA. There is a liner relationship in the ratio of 2:1 between the thrust imposed by the test-rack and HSC load, thus HSC can limit the load imposed on the pinion.

Assessment of macrobenthic community function and ecological quality after reclamation in the Changjiang(Yangtze)River Estuary wetland

An ecological optimization project(semi-closed reclamation project)was implemented to control the invasion of Spartina alterniflora,and optimize the habitat of the Chongming Dongtan wetland,in the Changjiang(Yangtze)River Estuary.After project implementation,a macrobenthic ecological survey was conducted in a natural tidal flat and a semi-closed reclamation restoration area within the Chongming Dongtan wetland from 2019 to 2020.Compared with historical data before reclamation,findings showed that the groups,numbers,and species diversity of the macrobenthos increased significantly,and the ecological optimization project resulted in good ecological benefits.In addition,compared to the natural tidal flat,the number of collected macrobenthic phyla,and the macrobenthic density and biomass were significantly lower in the restoration area.Furthermore,the biodiversity index and functional redundancy of natural tidal flats were generally higher,indicating that the community composition and function of natural tidal flats were relatively more stable.Even though the species composition differed between a number of restoration areas and natural tidal flats,there was no difference in functional diversity,indicating that the effect of restoring ecological functions in restoration areas was optimal.Among them,the biodiversity and functional redundancy of Site S2 were significantly reduced,and the ecosystem function was extremely unstable.Habitat heterogeneity,vegetation community and decreasing salinity were the main factors that affected the ecological functions of macrobenthos.The ecological quality was also evaluated;the Transects N3 and N4 showed good quality.The overall ecological quality of the restoration area was generally high,but that of Site S2 was poor and that of Site S2E was merely good,which was mainly due to modifications of the ecological function of macrobenthos.It is suggested that reeds mowing and freshwater species release should be adopted in restoration areas to improve the community function and the environmental disturbance resistance of the macrobenthos.

A comparative survey of SSVEP recognition algorithms based on template matching of training trials

Purpose-Steady-state visual evoked potential(SSVEP)has been widely used in the application of electroencephalogram(EEG)based non-invasive brain computer interface(BCI)due to its characteristics of high accuracy and information transfer rate(ITR).To recognize the SSVEP components in collected EEG trials,a lot of recognition algorithms based on template matching of training trials have been proposed and applied in recent years.In this paper,a comparative survey of SSVEP recognition algorithms based on template matching of training trails has been done.Design/methodology/approach-To survey and compare the recently proposed recognition algorithms for SSVEP,this paper regarded the conventional canonical correlated analysis(CCA)as the baseline,and selected individual template CCA(ITCCA),multi-set CCA(MsetCCA),task related component analysis(TRCA),latent common source extraction(LCSE)and a sum of squared correlation(SSCOR)for comparison.Findings-For the horizontal comparative of the six surveyed recognition algorithms,this paper adopted the“Tsinghua JFPM-SSVEP”data set and compared the average recognition performance on such data set.The comparative contents including:recognition accuracy,ITR,correlated coefficient and R-square values under different time duration of the SSVEP stimulus presentation.Based on the optimal time duration of stimulus presentation,the author has also compared the efficiency of the six compared algorithms.To measure the influence of different parameters,the number of training trials,the number of electrodes and the usage of filter bank preprocessing were compared in the ablation study.Originality/value-Based on the comparative results,this paper analyzed the advantages and disadvantages of the six compared SSVEP recognition algorithms by considering application scenes,realtime and computational complexity.Finally,the author gives the algorithms selection range for the recognition of real-world online SSVEP-BCI.

Curvature-aware simplification for point-sampled geometry

We propose a novel curvature-aware simplification technique for point-sampled geometry based on the locally optimal projection(LOP) operator.Our algorithm includes two new developments.First,a weight term related to surface variation at each point is introduced to the classic LOP operator.It produces output points with a spatially adaptive distribution.Second,for speeding up the convergence of our method,an initialization process is proposed based on geometry-aware stochastic sampling.Owing to the initialization,the relaxation process achieves a faster convergence rate than those initialized by uniform sampling.Our simplification method possesses a number of distinguishing features.In particular,it provides resilience to noise and outliers,and an intuitively controllable distribution of simplification.Finally,we show the results of our approach with publicly available point cloud data,and compare the results with those obtained using previous methods.Our method outperforms these methods on raw scanned data.

Multi-stage Rolling Optimization Model of Project Portfolio Configuration Under Phased Strategy Scenarios

The paper proposes a projected management method to organize,select and rolling configure the projects for multiple strategic stages. We illustrate the definitions of project portfolio rolling benefits,gain of resources and risk accumulation according to the correspondence between project life cycle and phased strategy scenarios. A heuristic-genetic algorithm has been designed to optimize the configuration model at the same time.The rolling configuration model and optimization algorithm are proved effectively by testing the case study of Y enterprise through the Matlab simulation.