3D laser simultaneous localization and mapping (SLAM) technology is one of the most efficient methods to capture spatial information. However, the low-precision of 3D laser SLAM point cloud limits ...its application in many fields. In order to improve the precision of 3D laser SLAM point cloud, we presented an offline coarse-to-fine precision optimization algorithm. The point clouds are first segmented and registered at the local level. Then, a pose graph of point cloud segments is constructed using feature similarity and global registration. At last, all segments are aligned and merged into the final optimized result. In addition, a cycle based error edge elimination method is utilized to guarantee the consistency of the pose graph. The experimental results demonstrated that our algorithm achieved good performance both in our test datasets and the Cartographer public dataset. Compared with the reference data obtained by terrestrial laser scanning (TLS), the average point-to-point distance root mean square errors (RMSE) of point clouds generated by Google’s Cartographer and LOAM laser SLAM algorithms are reduced by 47.3% and 53.4% respectively after optimization in our datasets. And the average plane-to-plane distances of them are reduced by 50.9% and 52.1% respectively.
The present study envisaged the effects of leaching solution on the mechanical properties of stope surrounding rock in in situ blasting leaching of sandstone type uranium deposit. Experiments were ...performed using uniaxial compression tests and SEM observation of sandstone samples after soaking in the H
2
SO
4
solution with pH 1, 2, 3 and 4 for 5, 10, 20, 30 and 40 days. The results showed that at pH 1, the solution levels increased slowly and steadily all the time, and for other pH solutions the levels increased rapidly in the first 5 days with a slow subsequent increase. The pH 2 solution showed reddish brown coloration in varying degrees, since it provided good conditions for Fe(OH)
3
precipitation. It is suggested that the pH value of leaching solution should be controlled within 1.5–2.0 during the regular leaching period of ore pile, and then adjusted to 2.0–2.5 after the leaching process based on the forming conditions and uranium-adsorbing characteristic of the Fe(OH)
3
colloid. Furthermore, with the increase in the solution pH, the mass change rate of the sandstone sample decreased. The uniaxial compressive strength and elasticity modulus of sandstone samples decreased with an increase in the soaking time and a decrease in the pH. After soaking in acid solution (pH < 4) for 40 days, the uniaxial compressive strength of sandstone decreased by about 50%, which needs to be considered in the design of pillar size. Compared to the samples in the natural state, the failure sound of sandstone treated with acidic solution weakened, accompanied by more debris and cracks, and the failure mode changed from brittle to less brittle. SEM analysis showed that, at the same soaking time, the stronger acid corrosion resulted in a looser surface structure and the larger diameter of the corrosion pore in the sandstone sample. After soaking in the same solution, there was no significant difference in the surface structure and pore diameter of the sandstone sample with an increase of soaking time.
The rendering of urban 3D scenes involves a large number of models. In order to render scenes more efficiently, the main solution is to build a level of detail model (LOD). This may have the problem ...of building fragmentation, while relying on building a level of detail model (LOD) alone cannot meet the accuracy and fluency of large‐scale scene visualisation. Effective and reasonable data organisation has important research significance for the authors to achieve accurate and fast rendering of scenes. Therefore, the authors propose a large‐scale city model data organisation method considering building distribution to solve the above problems. This method first classifies the buildings in the scene at macro‐, meso‐ and microscales and records the classification using R‐trees. Then an adaptive quadtree is used to construct the data index of the city model. Finally, the data organisation of the large‐scale 3D city model is achieved by using the information of each node of the R‐tree as a constraint and combining with the adaptive quadtree. The results show that the method not only ensures the integrity of the user's area of interest but also can improve the efficiency of 3D scene construction.
The rendering of urban 3D scenes involves a large number of models. In order to render scenes more efficiently, the main solution is to build LODs. This may have the problem of building fragmentation, while relying on LOD alone cannot meet the accuracy and fluency of large‐scale scene visualisation. Effective and reasonable data organisation has important research significance for the authors to achieve accurate and fast rendering of scenes.
The rendering of urban 3D scenes involves a large number of models, where the computer performance becomes a limitation. Arbitrarily putting all the models in a folder for storage significantly ...reduces the data processing efficiency when the models are called. There are also issues of storage redundancy and semantic fragmentation at the storage boundary. We propose a 3D scene management method based on an adaptive quadtree and scene graph (AQT-SG) that can solve the above problems. According to the spatial distribution characteristics of 3D scene data, this method adopts an adaptive quadtree for organizing complex 3D city scenes at the macro and meso scales, traversing the quadtree from bottom to top and calculating the geometric error at each level and in the middle. The node generates level of detail, builds a flexible multiscale 3D tile model, and uses scene graphs for the microscale organization and management of 3D scenes. We verified the proposed method with park data from a smart park management system. Large-scale complex 3D scene visualization and a comparison of the results of storage redundancy experiments verified that the data organization efficiency was optimized and the visual experience was improved by this method.
The current study attempts to investigate the role of anterior cervical discectomy and fusion (ACDF) in alleviating symptoms in patients with cervical vertigo associated with cervical instability.
...The patients of cervical instability with vertigo and dizziness who underwent ACDF between January 2011 and December 2019 were followed-up for more than two years. Demographic data (age, sex, follow up period and levels of instable cervical segments) were assessed; Symptoms of vertigo and dizziness before and after surgery were assessed by the 15-item version of the Vertigo Symptom Scale (VSS) and the 25-item Dizziness Handicap Inventory (DHI). The severity and frequency of other symptoms like neck and occipital pain, gastrointestinal discomfort, nausea, vomiting, tinnitus, palpitations, headache, diplopia and blurring of vision before and after surgery were also assessed.
A total of 92 patients underwent ACDF for cervical instability with vertigo and dizziness between January 2011 and December 2019, of which 79 patients were included in the final analysis. The number of instable levels had no correlation with VSS and DHI scores before surgery (
> 0.05), while patients with C3/4 instability suffering a severer vertigo than other levels. Both DHI and VSS scores were significantly reduced after ACDF and this was sustained within two years after surgery (
< 0.001). Although there was no statistical difference in the ratio of patients with vertigo relief, patients with one-level cervical instability demonstrated a more rapid recovery than patients with multi-level cervical instability (
= 0.048). Also, there was improvement in other symptoms such as neck and occipital pain, gastrointestinal discomfort, nausea, vomiting, tinnitus, palpitations, headache and blurring of vision after surgery.
Vertigo caused by C3/4 instability was severer than other levels such as C4/5 and C5/6. During 2 years' follow-up the significant relief of vertigo and dizziness was observed after anterior cervical surgery. Other accompanying symptoms except hypomnesia were also extenuated in follow-up period.
Adsorption isotherms of CH4 and CO2 on Qinshui Basin anthracite were obtained at the temperatures of 283 K, 303 K, and 323 K using the gravimetric method. The feasibility of the displacement of CH4 ...by injecting CO2 on this anthracite was verified by calculating the selectivity factor of CO2 over CH4 (αCO2/CH4), adsorption affinities, and thermodynamic properties of CH4 and CO2. Results show that the values of αCO2/CH4 are more than 4.0. Henry’s constant (KH) of CH4 is smaller than that of CO2, and CH4 has a weaker affinity with coal surface. As temperature improves, KH of CO2 and CH4 decrease. Gibbs free energy change (ΔG) and surface potential (Ω) of CO2 are more negative than those of CH4, indicating that CO2 adsorption on anthracite is more spontaneous and favorable. The absolute values of Ω and ΔG of CH4 and CO2 increase with pressure rises. Isosteric heat of adsorption (Qst) of CH4 is lower than that of CO2. With increasing loading, Qst and entropy loss (ΔS) of CH4 decrease, while Qst and ΔS of CO2 increase. The higher ΔS of CO2 reveals that the adsorbed CO2 molecules constitute a more stable rearrangement than CH4 molecules. High temperature reduces ΔS of CH4 and CO2.
Background Premenstrual dysphoric disorder (PMDD) is a heritable mood disorder that is triggered by gonadal steroids during the luteal phase in susceptible women. Methods We performed haplotype ...analyses of estrogen receptors alpha and beta (ESR1 and ESR2) in 91 women with prospectively confirmed PMDD and 56 control subjects to investigate possible sources of the genetic susceptibility to affective dysregulation induced by normal levels of gonadal steroids. We also examined associations with the valine (Val)158methionine (Met) single nucleotide polymorphism (SNP) of the gene for catechol-O-methyltransferase (COMT), an enzyme involved in estrogen metabolism and prefrontal cortical activation. Results Four SNPs in intron 4 of ESR1 showed significantly different genotype and allele distributions between patients and control subjects. Significant case-control differences were seen in sliding-window analyses of two-, three-, and four-marker haplotypes but only in those haplotypes containing SNPs in intron 4 that were positive in the single-locus analysis. No significant associations were observed with ESR2 or with the COMT Val158Met polymorphism, although the significant associations with ESR1 were observed only in those with the Val/Val genotype. Conclusions These are the first positive (albeit preliminary) genetic findings in this reproductive endocrine-related mood disorder and involve the receptor for a hormone that is pathogenically relevant.
In the study of 3D route scene construction, the expression of key targets needs to be highlighted. This is because compared with the 3D model, the abstract 3D symbols can reflect the number and ...spatial distribution characteristics of entities more intuitively. Therefore, this research proposes a symbolic 3D route scene representation method based on the importance of the object. The method takes the object importance evaluation model as the theoretical basis, calculates the spatial importance of the same type of objects according to the spatial characteristics of the geographical objects in the 3D route scene, and constructs the object importance evaluation model by combining semantic factors. The 3D symbols are then designed in a hierarchical manner on the basis of the results of the object importance evaluation and the CityGML standard. Finally, the LOD0-LOD4 symbolic 3D railway scene was constructed on the basis of a railroad data to realise the multi-scale expression of symbolic 3D route scene. Compared with the conventional loading method, the real-time frame rate of the scene was improved by 20 fps and was more stable. The scene loading speed was also improved by 5–10 s. The results show that the method can effectively improve the efficiency of the 3D route scene construction and the prominent expression effect of the key objects in the 3D route scene.
A healthy microenvironment of the intervertebral disc tissue is characterized by hypoxia owing to its sparse vascular distribution. Oxidative stress plays a pivotal role in the pathological ...development of intervertebral disc degeneration (IVDD). We found that the expression of prolyl endopeptidase (PREP) increased in degenerative nucleus pulposus (NP) tissues. The purpose of this study was to determine whether PREP is involved in oxidative-stress-induced IVDD. Tertbutyl hydroperoxide can inhibit the expression of PREP by activating the PI3K/AKT signaling pathway at low concentrations in NP cells. Knockdown of PREP protected NP cells from apoptosis induced by oxidative stress, whereas overexpression of PREP exacerbated the apoptosis of NP cells. We also investigated the connection between the PI3K/AKT signaling pathway and PREP and found that the activation of the PI3K/AKT signaling pathway downregulated the expression of PREP by inhibiting p53. As a crucial transcription factor, p53 binds to the PREP promoter region and promotes its transcription. Overexpression of PREP also impairs protein secretion in the extracellular matrix of NP cells. Furthermore, the in vivo knockout of PREP could attenuate puncture-induced IVDD. These findings suggested that the downregulation of PREP might maintain the viability of NP cells and attenuate IVDD under oxidative stress.
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