Evaluation of E-sail parameters on central spacecraft attitude stability using a high-fidelity rigid–flexible coupling model

This study examines the impact of electric solar wind sail(E-sail)parameters on the attitude stability of E-sail’s central spacecraft by using a comprehensive rigid–flexible coupling dynamic model.In this model,the nodal position finite element method is used to model the elastic deformation of the tethers through interconnected two-node tensile elements.The attitude dynamics of the central spacecraft is described using a natural coordinate formulation.The rigid–flexible coupling between the central spacecraft and its flexible tethers is established using Lagrange multipliers.Our research reveals the significant influences of parameters such as tether numbers,tether’s electric potential,and solar wind velocity on attitude stability.Specifically,solar wind fluctuations and the distribution of electric potential on the main tethers considerably affect the attitude stability of the spacecraft.For consistent management,the angular velocities of the spacecraft must remain at target values.Moreover,the attitude stability of a spacecraft has a pronounced dependence on the geometrical configuration of the E-sail,with axisymmetric E-sails proving to be more stable.

Recent Advances in Space-Deployable Structures in China

Deployable space structure technology is an approach used in building spacecraft,especially when realizing deployment and folding functions.Once in orbit,the structures are released from the fairing,deployed,and positioned.With the development of communication,remote-sensing,and navigation satellites,space-deployable structures have become cutting-edge research topics in space science and technology.This paper summarizes the current research status and development trend of spacedeployable structures in China,including large space mesh antennas,space solar arrays,and deployable structures and mechanisms for deep-space exploration.Critical technologies of space-deployable structures are addressed from the perspectives of deployable mechanisms,cable-membrane form-finding,dynamic analysis,reliable environmental adaptability analysis,and validation.Finally,future technology developments and trends are elucidated in the fields of mesh antennas,solar arrays,deployable mechanisms,and on-orbit adjustment,assembly,and construction.

Prognostic value and nomograms of proximal margin distance in gastric cancer with radical distal gastrectomy

Objective:The proximal margin(PM)distance for distal gastrectomy(DG)of gastric cancer(GC)remains controversial.This study investigated the prognostic value of PM distance for survival outcomes,and aimed to combine clinicopathologic variables associated with survival outcomes after DG with different PM distance for GC into a prediction nomogram.Methods:Patients who underwent radical DG from June 2004 to June 2014 at Department of General Surgery,Nanfang Hospital,Southern Medical University were included.The first endpoints of the prognostic value of PM distance(assessed in 0.5 cm increments)for disease-free survival(DFS)and overall survival(OS)were assessed.Multivariate analysis by Cox proportional hazards regression was performed using the training set,and the nomogram was constructed,patients were chronologically assigned to the training set for dates from June 1,2004 to January 30,2012(n=493)and to the validation set from February 1,2012 to June 30,2014(n=211).Results:Among 704 patients with p TNM stage I,p TNM stage II,T1-2,T3-4,N0,differentiated type,tumor size≤5.0 cm,a PM of(2.1-5.0)cm vs.PM≤2.0 cm showed a statistically significant difference in DFS and OS,while a PM>5.0 cm was not associated with any further improvement in DFS and OS vs.a PM of 2.1-5.0 cm.In patients with p TNM stage III,N1,N2-3,undifferentiated type,tumor size>5.0 cm,the PM distance was not significantly correlated with DFS and OS between patients with a PM of(2.1-5.0)cm and a PM≤2 cm,or between patients with a PM>5.0 cm and a PM of(2.1-5.0)cm,so there were no significant differences across the three PM groups.In the training set,the C-indexes of DFS and OS,were 0.721 and 0.735,respectively,and in the validation set,the C-indexes of DFS and OS,were 0.752 and 0.751,respectively.Conclusions:It is necessary to obtain not less than 2.0 cm of PM distance in early-stage disease,while PM distance was not associated with long-term survival in later and more aggressive stages of disease because more advanced GC is a systemic disease.Different types of patients should be considered for removal of an individualized PM distance intra-operatively.We developed a universally applicable prediction model for accurately determining the 1-year,3-year and 5-year DFS and OS of GC patients according to their preoperative clinicopathologic characteristics and PM distance.

Impact of diabetes on prognosis of gastric cancer patients performed with gastrectomy

Objective: This study aimed to determine the impact of type 2 diabetes mellitus(T2 DM) on clinical outcomes of gastric cancer(GC) patients and explore whether metformin use and good glycemic control could reverse it.Methods: Clinicopathologic data of consecutive GC patients who underwent gastrectomy at Nanfang Hospital between October 2004 and December 2015 were included. Propensity score matching(PSM) was performed to balance the important factors of the disease status between non-T2 DM and T2 DM group. The last follow-up time was January 2019.Results: A total of 1,692 eligible patients(1,621 non-T2 DM vs. 71 T2 DM) were included. After PSM, nonT2 DM group(n=139) and T2 DM group(n=71) were more balanced in baseline variables. The 5-year cancerspecific survival(CSS) rate in T2 DM group(47.0%) was inferior to that in non-T2 DM group(58.0%), but did not reach statistical significance [hazard ratio(HR)=1.319, 95% confidence interval(95% CI): 0.868-2.005, P=0.192].While the 5-year progress-free survival(PFS) rate of T2 DM group(40.6%) is significantly worse than that in nonT2 DM group(56.3%)(HR=1.516, 95% CI: 1.004-2.290, P=0.045). Univariate and multivariate analyses showed that T2 DM was an independent risk factor for PFS but not for CSS. In T2 DM group, metformin use subgroup was associated with superior 5-year CSS and PFS in compared with non-metformin use subgroup, although the difference was not statistically significant(5-year CSS: 48.0% vs. 45.4%, HR=0.680, 95% CI: 0.352-1.313,P=0.246;5-year PFS: 43.5% vs. 35.7%, HR=0.763, 95% CI: 0.400-1.454, P=0.406). The 5-year CSS rate was47.5% in good glycemic control subgroup and 44.1% in poor glycemic control subgroup(HR=0.826, 95% CI:0.398-1.713, P=0.605). And both two subgroups yielded a similar 5-year PFS rate(42.2% vs. 36.3%, HR=0.908,95% CI: 0.441-1.871, P=0.792).Conclusions: DM promoted disease progress of GC after gastrectomy but had not yet led to the significant discrepancy of CSS. For GC patients with T2 DM, metformin use was associated with superior survival but without statistical significance, while better glycemic control could not improve the prognosis.

Trajectory Planning of High Precision Collaborative Robots

In order to satisfy the high efficiency and high precision of collaborative robots,this work presents a novel trajectory planning method.First,in Cartesian space,a novel velocity look-ahead control algorithm and a cubic polynomial are combined to construct the end-effector trajectory of robots.Then,the joint trajectories can be obtained through the inverse kinematics.In order to improve the smoothness and stability in joint space,the joint trajectories are further adjusted based on the velocity look-ahead control algorithm and quintic B-spline.Finally,the proposed trajectory planning method is tested on a 4-DOF serial collaborative robot.The experimental results indicate that the collaborative robot achieves the high efficiency and high precision,which validates the effectiveness of the proposed method.

氮杂环卡宾(NHC)/银(I)共催化合成2-氧代-2-芳乙基芳甲酸酯

在氮杂环卡宾(NHC)/银(I)的共催化下,以芳醛和(溴乙炔)苯及其衍生物为原料实现了2-氧代-2-芳乙基芳甲酸酯高效合成.该方法具有底物范围广、原料简单易得、操作简便等优点,为α-酰氧基羰基衍生物的简捷合成提供了新思路.

A combined experimental and computational study of NHC-catalyzed allylation of allenoate with MBH esters:new regiospecific and stereoselective access to 1,5-enyne

An NHC-catalyzed regiospecific allylation ofα-substituted allenoates with MBH carbonates derived from aryl aldehyde furnished highly functionalized 1,5-enynes bearing a quaternary carbon successfully.Combining with DFT calculations,the reaction mechanism of this conversion was proposed.This method has the advantages of high regioselectivity,good yields and mild reaction conditions.This transformation not only provided a new access to 1,5-enyne,but also enriched the chemistry of allenoates and NHC catalysis.