Removal of Heavy Metals by Two Free Floating Aquatic Macrophytes

A concentration-dependent decrease in biomass, protein, RNA, DNA, and nutrient (NO3- and PO43-) uptake of Lemna minor and Azolla pinnata by Cr, Ni, and Zn was detected. Cr was found to exert maximum toxicity followed by Ni and Zn. Metal uptake was dependent on time and concentration of metal in the external rnedium. Both the macrophytes, however, showed preference for Zn followed by Ni and Cr. The uptake kinetics also revealed a low Vmax and high Km for Cr. L. minor was more effcient in accumulating Zn and Cr than A. pinnata in Ni. Compared to immobilized algae and bacterial capsules the test macrophytes showed a greater efficiency for metal removal

Spatial Operator Algebra for Free-floating Space Robot Modeling and Simulation

As the dynamic equations of space robots are highly nonlinear,strongly coupled and nonholonomic constrained,the efficiency of current dynamic modeling algorithms is difficult to meet the requirements of real-time simulation.This paper combines an efficient spatial operator algebra（SOA） algorithm for base fixed robots with the conservation of linear and angular momentum theory to establish dynamic equations for the free-floating space robot,and analyzes the influence to the base body＇s position and posture when the manipulator is capturing a target.The recursive Newton-Euler kinematic equations on screw form for the space robot are derived,and the techniques of the sequential filtering and smoothing methods in optimal estimation theory are used to derive an innovation factorization and inverse of the generalized mass matrix which immediately achieve high computational efficiency.The high efficient SOA algorithm is spatially recursive and has a simple math expression and a clear physical understanding,and its computational complexity grows only linearly with the number of degrees of freedom.Finally,a space robot with three degrees of freedom manipulator is simulated in Matematica 6.0.Compared with ADAMS,the simulation reveals that the SOA algorithm is much more efficient to solve the forward and inverse dynamic problems.As a result,the requirements of real-time simulation for dynamics of free-floating space robot are solved and a new analytic modeling system is established for free-floating space robot.

Impact dynamics analysis of free-floating space manipulator capturing satellite on orbit and robust adaptive compound control algorithm design for suppressing motion

The impact dynamics, impact effect, and post-impact unstable motion sup- pression of free-floating space manipulator capturing a satellite on orbit are analyzed. Firstly, the dynamics equation of free-floating space manipulator is derived using the sec- ond Lagrangian equation. Combining the momentum conservation principle, the impact dynamics and effect between the space manipulator end-effector and satellite of the cap- ture process are analyzed with the momentum impulse method. Focusing on the unstable motion of space manipulator due to the above impact effect, a robust adaptive compound control algorithm is designed to suppress the above unstable motion. There is no need to control the free-floating base position to save the jet fuel. Finally, the simulation is proposed to show the impact effect and verify the validity of the control algorithm.

THE ROBUST CONTROL SCHEME FOR FREE-FLOATING SPACE MANIPULATOR TO TRACK THE DESIRED TRAJECTORY IN JOINTSPACE

The control of a free-floating space manipulator system isdiscussed. With the augmentation approach, the nonlinearparameterization problem of the dynamic equations of the spacemanipulator system is overcome. Based on the results, the robustcontrol scheme for free-floating space manipulator with uncer- tainpayload parameters to track the desired trajectory in jointspace isproposed, and the global convergence of the tracking is verified byusing the Lyapunov method.

Numerical and Experimental Investigation of Interactions Between Free-Surface Waves and A Floating Breakwater with Cylindrical-Dual/Rectangular-Single Pontoon

This paper investigates the hydrodynamic performance of a cylindrical-dual or rectangular-single pontoon floating breakwater using the numerical method and experimental study. The numerical simulation work is based on the multi-physics computational fluid dynamics(CFD) code and an innovative full-structured dynamic grid method applied to update the three-degree-of-freedom(3-DOF) rigid structure motions. As a time-marching scheme, the trapezoid analogue integral method is used to update the time integration combined with remeshing at each time step.The application of full-structured mesh elements can prevent grids distortion or deformation caused by large-scale movement and improve the stability of calculation. In movable regions, each moving zone is specified with particular motion modes(sway, heave and roll). A series of experimental studies are carried out to validate the performance of the floating body and verify the accuracy of the proposed numerical model. The results are systematically assessed in terms of wave coefficients, mooring line forces, velocity streamlines and the 3-DOF motions of the floating breakwater. When compared with the wave coefficient solutions, excellent agreements are achieved between the computed and experimental data, except in the vicinity of resonant frequency. The velocity streamlines and wave profile movement in the fluid field can also be reproduced using this numerical model.

Development of Sichuan Brocade with Imitating Embroidery Effect Based on Free-Floats Interlacing Weave

Owing to the diversity of consumer’s demand, the traditional Sichuan brocade products have to be innovated in order to survive in a competitive environment. Since the construction of traditional Sichuan brocade was composed of basic-weave, the surface of the fabric shows a regular interweaving planar texture and is difficult to represent a three-dimensional effect. Inspired by embroidery handcraft, this paper attempts to achieve the embroidery-like effect on the fabric through the jacquard process. Based on the multi-backed structure of traditional Sichuan brocade, we adopted the zoned-combination design mode and added extra free-floats interlacing weave in the area where we want to show the embroidered effect and arranged the interlacing points by referring to the feature of the pattern. As a result, designed Sichuan brocades by this method are capable of displaying embroidered effect with high realism and three-dimensionality. This approach improves the artistic effect of the traditional Sichuan brocade and provides a technical reference for further texture design of jacquard fabrics.

Singular perturbation composite control of a free-floating flexible dual-arm space robot

The Free-floating Flexible Dual-arm Space Robot is a highly nonlinear and coupled dynamics system. In this paper, the dynamic model is derived of a Free-floating Flexible Dual-arm Space Robot holding a rigid payload. Furthermore, according to the singular perturbation method, the system is separated into a slow subsystem representing rigid body motion of the robot and a fast subsystem representing the flexible link dynamics. For the slow subsystem, based on the second method of Lyapunov, using simple quantitative bounds on the model uncertainties, a robust tracking controller design is used during the trajectory tracking phase. The optimal control method is designed in the fast subsystem to guarantee the exponential stability. With the combination of the two above, the system can track the expected trajectory accurately, even though with uncertainty in model parameters, and its flexible vibration gets suppressed, too. Finally, some simulation tests have been conducted to verify the effectiveness of the proposed methods.

Motion planning for redundant prismatic-jointed manipulators in the free-floating mode

This paper investigates the motion planning of redundant free-floating manipulators with seven prismatic joints. On the earth, prismatic-jointed manipulators could only position their end-effectors in a desired way. However, in space, the end-effectors of free-floating manipulators can achieve both the desired orientation and desired position due to the dynamical coupling between manipulator and satellite movement, which is formally expressed by linear and angular momentum conservation laws. In this study, a tractable algorithm particle swarm optimization combined with differential evolution （PSODE） is provided to deal with the motion planning of redundant free-floating prismatic-jointed manipulators, which could avoid the pseudo inverse of the Jacobian matrix. The polynomial functions, as argument in sine functions are used to specify the joint paths. The co- efficients of the polynomials are optimized to achieve the desired end-effector orientation and position, and simulta- neously minimize the unit-mass-kinetic energy using the redundancy. Relevant simulations prove that this method pro- vides satisfactory smooth paths for redundant free-floating prismatic-jointed manipulators. This study could help to recognize the advantages of redundant prismatic-jointed space manipulators.

考虑自由液面影响的多凸体结构浮态计算方法

针对液舱内自由液面对浮态和稳性的影响,文中提出了一种新的多凸体组合结构浮态算法。该方法将浮体和液舱分解成多个四面体单元,通过分析每个四面体与水面/液面的相对位置关系来确定浮体的浮力和浮心以及液舱液体的重心。该方法还提出了一种改进的双重迭代法用来确定多凸体组合结构的浮态:内层迭代法模拟浮体的升沉运动,得到浮体外的水面方程和液舱内的液面方程;通过外层迭代法模拟浮体的旋转运动。两种迭代方法交替进行,直至浮体的重力作用线和浮力作用线之间的距离满足精度要求,同时重力等于浮力。自编程序对某半潜船和某半潜式海洋平台的多种典型工况进行了浮态计算,同时也考虑了自由液面影响。此外利用Maxsurf建模进行了对比分析,还利用AUTOCAD进行了精度验证。对照结果表明:该研究提出的算法可以考虑自由液面对浮态的影响,原理清晰,收敛性好;算法无论对传统的单凸体结构(例如单体船),还是多凸体结构(例如多体船、漂浮式海洋平台等)均更容易取得准确解,且计算效率更高;算法可以实现“搭积木”式的建模方式,多工况建模时可以极大地减小工作量;算法无需依赖国外第三方图形平台(比如AUTOCAD、CATIA),可为我国相关工业软件的国产化打下良好的基础。

圆球上浮运动特性数值仿真及试验研究

以圆球状浮体为对象,研究尺度、密度比(圆球密度与流体密度比值)对其上浮运动性能的影响。建立静水中圆球上浮运动数值模拟方法,通过与模型试验测试结果对比,验证数值方法的可靠性。通过验证的计算方法对不同尺度和密度比的圆球上浮运动过程进行分析,结果表明:圆球在稳定上浮阶段的阻力系数大致为常数1,不随圆球尺度和密度比变化产生较大变化;若2个圆球满足相似条件且尺度之比为λ,则它们的稳定速度之比和上浮总时间之比大致为λ0.5。本研究通过对圆球上浮运动的计算和分析,寻求不同尺度圆球上浮运动之间的相关性,可为其他结构物上浮运动性能的尺度相关性研究分析提供参考依据。

超声检查对骨折患者下肢深静脉漂浮血栓脱落的诊断意义

目的探讨超声检查对骨折患者下肢深静脉(DV)漂浮血栓脱落的诊断意义。方法收集127例下肢DV漂浮血栓并植入下腔静脉过滤器(IVCF)的患者超声资料及临床资料。超声资料包括血栓的回声、活动程度、长度、位置、侧别及彩色多普勒情况;临床资料包括性别、年龄、骨折部位、凝血酶时间(TT)、D-二聚体(D-D)、纤维蛋白原(FIB)。采用Logistic回归分析DV漂浮血栓患者发生血栓脱落的影响因素(P<0.05)。结果根据IVCF内有无脱落血栓将患者分为血栓脱落组51例,血栓未脱落组76例。血栓呈极低回声、血栓活动程度为漂浮或轻微漂浮是DV漂浮血栓脱落的独立危险因素。血栓呈极低回声的患者发生脱落的风险是血栓呈中等回声患者的4.182倍(95%CI:1.209~14.468,P=0.024),血栓活动程度为轻微漂浮或漂浮的患者血栓脱落的风险分别是血栓头端漂浮患者的4.979倍(95%CI:1.851~13.391,P=0.001)和11.373倍(95%CI:3.936~32.863,P<0.001)。结论超声指标血栓回声及血栓活动程度对外伤性骨折患者DV漂浮血栓脱落具有一定的诊断意义。

基于改进无模型自适应控制的漂浮式海上风机转矩-变桨协调控制策略研究

针对漂浮式海上风机建模困难、频繁变桨造成的严重疲劳损伤等问题,提出一种基于改进无模型自适应控制的转矩-变桨协调控制策略。该策略不依赖漂浮式海上风机的数学模型,通过集成迭代学习控制策略改进无模型自适应控制方法,设计发电机电磁转矩和桨距角作为控制变量的多输入多输出控制器进行协调控制,允许非零度桨距角下风机用做动能缓冲,在平滑输出功率的同时减少变桨动作量。为证明所提出控制策略的有效性,在多种风场景下,与增益调度PI控制等方法进行了对比实验。结果表明:所提出的控制策略使漂浮式海上风机在满足发电功率平稳性的同时减缓了漂浮平台的俯仰运动,可有效降低漂浮式海上风机的疲劳载荷。

自由漂浮机械臂奇异分析和避奇异轨迹规划

针对空间自由漂浮机械臂在任务工作空间进行轨迹规划时可能存在奇异的问题,首先对奇异点的主要影响因素进行了分析和证明,给出了奇异点的3个基本性质和一种奇异度量定义;然后基于鲁棒伪逆思想设计了一种光滑避奇异算法,并利用奇异值分解的手段给出了鲁棒伪逆法的避奇异机理,以及详细计算了避奇异时在关节工作空间和任务工作空间所引入的跟踪误差;最后,在此基础上提出了一种改进的鲁棒伪逆法,在实现奇异规避的同时,进一步减小了引入的跟踪误差。数值仿真验证了结论的正确性和设计方法的有效性。

改良呼吸管路冷凝水处理装置的设计与应用

目的探讨改良呼吸管路冷凝水处理装置的设计及应用效果。方法利用浮球式疏水阀“阻汽排水”的结构特点,改良呼吸机管路,于2023年8月选取我院神经外科ICU工作的12名护士,并选取2台呼吸机随机分为对照组和观察组,对照组使用普通呼吸机管路,观察组使用改良后呼吸机管路,比较48 h内2组设备冷凝水相关工作量、冷凝水处理质量督导情况及护士满意度。结果观察组收集冷凝水1050 mL,对照组收集冷凝水1035 mL,差异无统计学意义(P>0.05),冷凝水处理质量督导(超过50%容积情况、溅洒情况)有所改善。观察组护士在节约时间、减少工作量、提高护理安全3个维度满意度均高于对照组,差异有统计学意义(P<0.001)。结论改良呼吸管路冷凝水处理装置可有效降低护士处理冷凝水的工作负担,提高呼吸机冷凝水管理质量,提高护士的工作满意度。本设计也使机械通气患者呼吸管路的完全密闭成为可能,最大程度的降低了疾病传播风险及医务人员职业暴露的风险。

多浮筒全潜式海上风机整机拖航运动特性试验对比

[目的]基于搭载了DTU 10 MW风机的三四筒型全潜式浮式风机整机海上拖航过程,开展了物理模型试验,对比研究三浮筒型式和四浮筒型式的SFOWT在拖航过程中各自由度运动响应及拖缆力在不同工况下的变化规律。[方法]首先在静水中开展自由衰减试验,随后在规则波和不规则波浪环境中开展拖航过程试验,研究不同的拖缆点高度、波高以及周期对拖航过程的影响。[结果]结果表明:(1)对SFOWT的垂荡、横摇和纵摇自振周期进行分析,发现相同自由度下2种结构SFOWT的自振周期相差在5 s以内,三浮筒式SFOWT与四浮筒式SFOWT相比,三浮筒式SFOWT垂荡加速度更小,纵摇和横摇的自然周期更大;(2)随着波高的增加,SFOWT在各自由度上的响应以及拖缆力都在增大,规则波和不规则波工况下波高的增加对三浮筒型式SFOWT垂荡加速度、横摇角的影响更大,纵摇角以及拖缆力较小;(3)当波浪周期与SFOWT自身的固有周期相差较大时,随着波浪周期的增大,除垂荡加速度外SFOWT各自由度上的响应呈现减小的趋势;(4)当拖缆点高度与水线面齐平时,2种型式SFOWT的拖缆力幅值较其他两种工况最大分别减小11.1%和14.7%。[结论]四浮筒型式SFOWT的拖航运动性能更佳。在实际工程中,应当将拖缆点高度布置在结构自浮时水面线所在的位置,以减小拖航过程中的运动响应。

输入受限的漂浮基多柔性空间机器人轨迹跟踪的混合控制及振动主动抑制

空间机器人在实际运作中往往会遇到控制系统输入受限的情况,这将严重影响系统的控制品质。考虑输入受限的情况,对漂浮基多柔性空间机器人系统进行研究。通过对系统进行运动学和动力学分析,构建系统的动力学方程。采用奇异摄动方法,将刚柔耦合系统分为慢变子系统和快变子系统,并为各个子系统设计控制方法。最终提出由改进的鲁棒滑模模糊控制方法、速度差值反馈控制法和线性二次最优控制方法组成的混合控制方法。该控制方法能够主动减小空间机器人完成期望运动所需的力矩,使系统适应输入受限的工作条件;同时能够补偿系统的不确定参数和外部干扰,最终实现系统运动的精确控制和振动的主动抑制。仿真对比实验证明了在输入受限的情况下,所提出的混合控制方法的有效性和强适应性。

症状性颈动脉漂浮血栓的血管内治疗探索

目的探索症状性颈动脉漂浮血栓(carotid free-floating thrombus,CFFT)血管内治疗的临床疗效与安全性。方法回顾性纳入2008年8月—2022年11月在西安交通大学第二附属医院神经内科住院诊断为症状性CFFT,并行颈动脉支架置入术的患者,分析CFFT患者临床表现、危险因素、病变部位、颈动脉支架器材、手术方式及临床效果。结果共纳入6例CFFT导致急性脑梗死的患者,其中女性4例(66.7%),发病年龄中位数63.5(48.0~68.7)岁。术前NIHSS评分中位数3.0(0~3.5)分,mRS评分中位数2.0(1.0~3.0)分。6例患者中,血栓位于右侧颈总动脉中远段1例,左侧颈内动脉C1段1例,右侧颈内动脉C1段4例,2例患者合并颈动脉原位重度狭窄。患者均接受了远端保护装置下的支架置入术,2例合并原位狭窄者支架置入前进行了球囊预扩张。5例患者置入了Wallstent闭环支架,1例患者置入了Precise开环支架。所有患者术中均未发生血栓脱落、远端大血管闭塞事件。1例(16.7%)患者术后12 h因支架内血栓发生脑水肿及病情加重。所有患者术后7 d NIHSS评分中位数减至1.0(0~3.0)分,术后90 d mRS评分中位数为1.0(0~2.0)分。结论颈动脉支架置入术可能是治疗症状性CFFT的一种可行的安全有效的方法。

小鼠脑切片漂浮染色方法研究

为了提高小鼠脑组织学研究效率,解决传统石蜡切片和冰冻切片样品准备时间长、步骤复杂等问题,提出了振动切片结合漂浮染色快速进行小鼠脑组织切片形态学研究的方法。该方法通过小鼠心脏灌注后,获取脑组织,利用琼脂糖快速包埋固定;通过振动切片方法,40微米厚度连续获取脑组织切片,结合漂浮染色观测特征区域神经元形态;最后通过体视学方法,快速统计估算神经元数量。实验结果表明,振动切片联合漂浮染色可快速进行小鼠脑组织学研究,并具有较高的稳定性和可重复性。

考虑需求可拆分的共享单车调度优化研究

研究考虑需求可拆分的共享单车调度优化问题为可拆分单商品取送货TSP问题,考虑一辆调度车,允许调度车多次访问各站点,每次满足站点的部分需求,即允许对站点的需求进行拆分。首先,考虑到调度车容量限制,统筹安排调度车行驶路径和调度车在每个站点的取车量、送车量,使得企业的运营成本达到最优。其次,提出了一种改进的变邻域搜索算法求解上述问题,使算法在陷入局部最优解时改变邻域结构,扩大搜索范围,以此提升算法跳出局部最优解的能力,加快收敛速度。最后,用数值实验验证了算法的有效性。研究结论拓展了可拆分单商品取送货问题的相关理论,并为共享单车企业的实际运营提供决策支持。

基于Bi-LSTM网络的自由漂浮空间机械臂控制

自由漂浮空间机械臂轨迹跟踪控制受模型不确定性和外部扰动影响。针对该问题,提出了基于神经网络估计的自适应滑模控制策略.对模型不确定问题,采用双向长短期记忆神经网络(Bi-LSTM)对空间机械臂模型不确定性进行估计,其中神经网络的估计方式为离线学习方式.采用自适应滑模控制解决网络估计中的误差和外部扰动影响.通过Lyapunov方法证明系统的稳定性,数值仿真验证控制策略的有效性.结果表明所提出的新型控制器能够实现低增益下控制性能的有效提升.