Two-layer formation-containment fault-tolerant control of fixed-wing UAV swarm for dynamic target tracking

This paper tackles the formation-containment control problem of fixed-wing unmanned aerial vehicle(UAV)swarm with model uncertainties for dynamic target tracking in three-dimensional space in the faulty case of UAVs’actuator and sensor.The fixed-wing UAV swarm under consideration is organized as a“multi-leader-multi-follower”structure,in which only several leaders can obtain the dynamic target information while others only receive the neighbors’information through the communication network.To simultaneously realize the formation,containment,and dynamic target tracking,a two-layer control framework is adopted to decouple the problem into two subproblems:reference trajectory generation and trajectory tracking.In the upper layer,a distributed finite-time estimator(DFTE)is proposed to generate each UAV’s reference trajectory in accordance with the control objective.Subsequently,a distributed composite robust fault-tolerant trajectory tracking controller is developed in the lower layer,where a novel adaptive extended super-twisting(AESTW)algorithm with a finite-time extended state observer(FTESO)is involved in solving the robust trajectory tracking control problem under model uncertainties,actuator,and sensor faults.The proposed controller simultaneously guarantees rapidness and enhances the system’s robustness with fewer chattering effects.Finally,corresponding simulations are carried out to demonstrate the effectiveness and competitiveness of the proposed two-layer fault-tolerant cooperative control scheme.

Reinforcement effects of ground treatment with dynamic compaction replacement in cold and saline soil regions

The mechanical property of saline soils varies with moisture and climate in the cold and salt lake region of Qinghai-Tibet Plateau, which influences project construction. In order to improve foundation reinforcement effect of the QarharvaTrolmud Highway, Qinghai Province, China, dynamic compaction replacement （DCR） composite foundation was applied in saline soils. A field experiment was conducted in this area, where strength and working mechanism of pier-soil and deformation modulus of the composite foundation was analyzed after reinforcement. This paper presents methods for determining the coefficient on the bearing capacity evaluation and deformation modulus of composite foundation with DC1L Reinforcement case of DCR is highly effective in saline soils of the salt lake regions, which helps the mi-tion of water and salt in saline soils.

Intelligent Dynamic Aging Approaches in Web Proxy Cache Replacement

One of commonly used approach to enhance the Web performance is Web proxy caching technique. In Web proxy caching, Least-Frequently-Used-Dynamic-Aging (LFU-DA) is one of the common proxy cache replacement methods, which is widely used in Web proxy cache management. LFU-DA accomplishes a superior byte hit ratio compared to other Web proxy cache replacement algorithms. However, LFU-DA may suffer in hit ratio measure. Therefore, in this paper, LFU-DA is enhanced using popular supervised machine learning techniques such as a support vector machine (SVM), a naive Bayes classifier (NB) and a decision tree (C4.5). SVM, NB and C4.5 are trained from Web proxy logs files and then intelligently incorporated with LFU-DA to form Intelligent Dynamic- Aging (DA) approaches. The simulation results revealed that the proposed intelligent Dynamic- Aging approaches considerably improved the performances in terms of hit and byte hit ratio of the conventional LFU-DA on a range of real datasets.

A Two-layer Framework for Mitigating the Con-gestion of Urban Power Grids Based on Flexible Topology with Dynamic Thermal Rating

The urban power grid(UPG)combines transmission and distribution networks.Past studies on UPG congestion mitigation have primarily focused on relieving local congestion while ignoring large-scale energy transfer with safety margins and load balancing.This situation is expected to worsen with the proliferation of renewable energy and electric vehicles.In this paper,a two-layer congestion mitigation framework is proposed,one which considers the congestion of the UPG with flexible topologies.In the upper-layer,the particle swarm optimization algorithm is employed to optimize the power supply distribution(PSD)of substation transformers.This is known as the upper-layer PSD.The lower-layer model recalculates the new PSD,known as the lower-layer PSD,based on the topology candidates.A candidate topology is at an optimum when the Euclidean distance mismatch between the upper-and lower-layer PSDs is the smallest.This optimum topology is tested by standard power flow to ascertain its feasibility.The optimum transitioning sequence between the initial and optimum topologies is also determined by the two-layer framework to minimize voltage deviation and line overloading of the UPG considering dynamic thermal rating.The proposed framework is tested on a 56-node test system.Results show that the proposed framework can significantly reduce congestion,maintain safety margins,and determine the optimum transitioning sequence.

Geo-engineered buffer capacity of two-layered absorbing system under the impact of rock avalanches based on Discrete Element Method

Many rock avalanches were triggered by the Wenchuan earthquake on May 12, 2008 in southwest China. Protection galleries covered with a single soil layer are usually used to protect against rockfall. Since one-layer protection galleries do not have sufficient buffer capacity, a two-layered absorbing system has been designed. This study aims to find whether an expanded poly-styrol （EPS） cushion, which is used in the soil-covered protection galleries for shock absorption, could be positioned under dynamic loadings. The dynamic impacts of the two-layered absorbing system under the conditions of rock avalanches are numerically simulated through a 2D discrete dement method. By selecting reasonable parameters, a series of numerical experiments were conducted to find the best combination for the two- layered absorbing system. The values of the EPS layer area as a percentage of the total area were set as 0% （Sl）, 22~ （S2）, and 70% （$3）. 22~ of the area of the EPS layer was found to be a reasonable value, and experiments were conducted to find the best position of the EPS layer in the two-layered absorbing system. The numerical results yield useful conclusions regarding the interaction between the impacting avalanches and the two-layered absorbing system. The soil layer can absorb the shock energy effectively and S2 （0.4-m thick EPS cushion covered with soil layer） is the most efficient combination, which can reduce the impact force, compared with the other combinations.

A Reward Functional to Solve the Replacement Problem

The replacement problem can be modeled as a finite, irreducible, homogeneous Markov Chain. In our proposal the problem was modeled using a Markov decision process and then, the instance was optimized using dynamic programming. We proposed a new functional that includes a reward functional, that can be more helpful in processing industries because it considerate instances like incomes, maintenance costs, fixed costs to replace equipment, purchase price and salvage values;and this functional can be solved with dynamic programming and used to make effective decisions. Two theorems are proved related with this new functional. A numerical example is presented in order to demonstrate the utility of this proposal.

Effect of transcatheter aortic valve replacement on bicuspid coronary hemodynamics:A numerical study

To investigate the effects of transcatheter heart valve(THV)poses and bicuspid aortic valve(BAV)subtypes on coronary hemodynamics after transcatheter aortic valve replacement(TAVR).The computational models for BAV included left-right fusion(LR),non-coronary-left fusion(LN)and non-coronary-right fusion(RN).THV deployment height is defined as the distance below the aortic annulus of the lowest point of the stent,H_(1)=2mm,H_(2)=5mm and H_(3)=8mm,Orientations include O_(1)(one commissure is aligned with the raphe)and O_(2)(one commissure is aligned with the axis of non-fused leaflet symmetry).The maximum flow velocity(Vmax),mean wall shear stress(mWSS)and coronary perfusion pressure(CPP)of coronary were obtained by computational fluid dynamics(CFD)simulation.The CPP was 59%in left coronary and 82%in right coronary higher than that before deployment.At O_(1),the CPP of the LN left coronary and the RN right coronary was 74%and 79%higher than that before deployment.At O_(2),the CPP of the LN right coronary and the RN left coronary was 83%and 82%higher than that before deployment.When the THV deployment height is less than 2​mm,Vmax and CPP of coronary arteries do not return to healthy TAV levels or changed weakly.The overlap of the THV commissure with the coronary ostium makes the coronary CPP so large that it exceeds the level of a healthy TAV.

基于IDA方法的带可替换耗能梁段偏心支撑钢框架结构影响系数研究

为研究带可替换双槽钢型剪切耗能梁段偏心支撑钢框架中耗能梁段的截面尺寸、梁段长度、加劲肋个数以及结构层数对于结构影响系数R和位移放大系数C_(d)的影响,通过OpenSees有限元软件对18个不同参数的模型进行增量动力时程分析(IDA),得到各模型的结构影响系数和位移放大系数.结果表明:通过合理设计耗能梁段的构造参数,能够提高带可替换双槽钢型剪切耗能梁段防屈曲偏心支撑钢框架的抗震能力以及变形能力,给出R和C_(d)的建议值,为偏心支撑钢框架结构影响系数的研究提供参考.

LNG-FSRU储罐氮气置换动态模拟及方案优化研究

浮式储存及再气化装置(FSRU)的储罐氮气置换是投产运行前最重要的环节之一。因FSRU需对多个储罐进行氮气置换,常规置换方案氮气消耗量大,为减少资源浪费,基于氮气重复利用工艺,提出了串联置换优化方案,给出串联置换的工艺流程,利用HYSYS动态模拟技术建立FSRU多储罐氮气置换模型并进行验证,对同时置换方案、单罐置换方案和四种串联置换方案进行动态模拟。研究结果表明:串联置换方案可降低罐内初始氧气体积分数,经方案比选得出串联置换方案一为最经济方案,此方案用气量为286 t,置换时间为95 h,相比于同时置换和单罐置换的氮气用量分别可节省35%和31%,可为FSRU多储罐氮气置换方案的制定提供参考。

Gas Exchange Rates of Texas Persimmon (Diospyros texana) in Central Texas Woodlands

Diospyros texana (Texas persimmon) is a secondary species in most Juniperus ashei/Quercus fusiformis woodlands in central Texas. It has high density, but plants are mostly in the community understory. Light response curves at ambient and elevated levels of CO2 and temperature were measured for D. texana. The Anet (photosynthetic rate) increased significantly as both light level and CO2 levels increased but not temperature. The Amax (maximum photosynthetic rate) of D. texana in full sun at elevated levels of CO2 was increased for all treatments. Stomatal conductance increased with levels of CO2 but only if the interaction was removed from the model. Intercellular levels of CO2 increased with both temperature and CO2 treatments as did water use efficiency (WUE). Furthermore, light saturation (Lsat) increased with CO2 treatments and light compensation (Lcp) increased with temperature. The dark respiration (Rd) increased with both temperature and CO2 treatments. Markov population models suggested D. texana populations would remain ecologically similar in the future. However, sub-canopy light levels and herbivory should be considered when examining population projections. For example, Juniperus ashei juveniles are not recruited into any canopy unless there are high light levels. Herbivory reduces the success of Quercus juveniles from reaching the canopy. These factors do not seem to be a problem for D. texana juveniles which would allow them to reach the canopy without need of a high light gap and are not prevented by herbivory. Thus, Juniperus/Quercus woodlands will change in the future to woodlands with D. texana a more common species.

When to start renal replacement therapy in acute kidney injury: What are we waiting for?

Acute kidney injury remains a serious condition with a high mortality risk. In the absence of any new drugs, renal replacement therapy (RRT) is the most important treatment option. Randomized controlled trials have concluded that in critically ill patients without an emergency indication for RRT, a watchful waiting strategy is safe;however, further delays in RRT did not seem to confer any benefit, rather was associated with potential harm. During this process, balancing the risks of complications due to an unnecessary intervention with the risk of not correcting a potentially life-threatening complication remains a challenge. Dynamic renal function assessment, especially dynamic assessment of renal demand-capacity matching, combined with renal biomarkers such as neutrophil gelatinase-associated lipocalin and furosemide stress test, is helpful to identify which patients and when the patients may benefit from RRT.

基于分布式缓存的科技文献信息动态检索系统设计

为便于科研人员研究科技发展前沿动态,设计基于分布式缓存的科技文献信息动态检索系统,为用户匹配最佳检索结果。用户层将用户检索需求传输至处理层数据采集模块,该模块采集数据信息后经网络层通信模块将信息传输至数据层科技文献信息数据库中存储;数据层分布式存储模块采用分布式缓存方法将以往的检索记录信息分别存储至热数据库及冷数据库中;利用网络层传输科技文献信息数据库内的检索需求信息至处理层检索处理模块,通过科技文献信息动态检索方法处理接收到的检索信息,将处理后信息与数据层分布式存储模块内的关联数据进行排序重组,获取检索结果,并通过用户层展示检索结果。结果表明,该系统可有效且准确地为用户检索其所需的科技文献信息,检索MAP值为0.95以上,系统具备较快的读写速度与较强的数据传输能力。

动态心电图监测在经导管主动脉瓣置换术患者中的研究进展

经导管主动脉瓣置换术(transcatheter aortic valve replacement,TAVR)已经改变了严重主动脉瓣狭窄患者的治疗方法。然而,传导干扰的发生并没有随着时间的推移而显著减少,并且仍然是该治疗的主要并发症。此外,新发心房颤动是住院期间最常见的快速性心律失常,与更差的临床结果相关。然而,对于围手术期TAVR后心律失常事件的发生率和临床影响知之甚少。动态心电图(ambulatory electrocardiogram,AECG)监测最近已成为解决TAVR前后心律失常(缓慢性心律失常和快速性心律失常)复杂问题的工具。本综述概述了AECG监测在TAVR环境中的临床现状、临床意义以及发展前景,为主动脉瓣狭窄的治疗带来了新的时代。

软土地基强夯置换加固工艺及其效果分析

软土地基强夯置换加固工艺及其效果分析对于确保建筑物和基础设施的安全性、经济性和可持续性都具有重要性。为此,以某沿海石化基地为研究背景,利用现场试验从单击夯击能、垫层厚度、单墩影响范围、夯锤直径、夯锤重量和夯锤落距等参数对置换深度的影响展开了研究。结果表明,强夯置换软土地基在软土层厚度较小时,效果为最佳,施工中夯点间距应大于3 m,最佳夯距为3~6 m,夯锤面积与置深度呈负相关,在施工过程中建议采用小锤多夯进行置换加固,建议在施工过程中采用重锤小落距的组合进行置换,效果最佳。

大面积盐渍土地基处理措施

盐渍土广泛分布于在西北干旱地区,随着我国基础建设的需求越来越高,盐渍土的盐溶、盐胀、腐蚀等不良工程特性有时严重影响工程的安全性及建设成本。换填法和强夯法处理盐渍土的盐溶、盐胀、腐蚀等不良工程特性效果显著,以兰州中川国际机场三期扩建工程的盐渍土地基做研究对象,通过实验数据证明该处理措施效果良好,满足机场基础设计要求。

柱锤强夯加固深厚填土层的分析与研究

随着我国建筑行业的不断发展,建筑用地的地质条件也愈发复杂多变。为了平整场地而采取的高挖低填措施往往带来高昂的地基处理费用,且处理效果较难评估。通过在深厚回填土层进行柱锤强夯配合多重原土置换的处理工艺,并采取平板载荷试验、标准贯入试验等检测手段对处理前后的地基土层进行分析与评价,结果表明该工艺能显著提高大厚度回填土层的物理力学参数,为类似的工程项目提供参考依据。

强夯置换对软土基坑边坡开挖稳定性的影响研究

强夯置换作为一种地基处理方法,主要用于提高地基承载力,减小沉降,而将其作为基坑支护的相关研究却鲜有报道。通过一系列室内模型试验探讨了不同强夯置换率、基坑边坡坡率条件下,强夯置换后软土基坑在开挖过程中的变形位移规律。通过构建墩土合并计算、墩土分开计算、墩土耦合3种有限元数值模型,对室内模型试验结果进行了对比验证。结果表明:水平位移向四周呈辐射式递减,室内模型试验与数值模拟的水平位移变化趋势一致且吻合度较高;坡体稳定系数随置换率的增加而不断上升;在墩与土之间加入界面单元提高了墩土之间的相互作用,可以有效提高数值模拟的准确性。

瑞士球全程核心动态训练对TKA患者功能恢复的影响

目的探讨瑞士球全程核心动态训练在全膝关节置换术(TKA)患者功能恢复中的应用效果。方法选取2020年1月至2023年7月应急总医院收治的200例TKA患者,按照随机数字法分为对照组和观察组,对照组采用常规护理康复方案,观察组在此基础上采取瑞士球全程核心动态训练康复方案,每组各100例。采用修订版面部表情疼痛量表(FPS-R)评分、美国特种外科医院(HSS)评分、膝关节活动范围(ROM)、Berg平衡量表(BBS)评分、腘绳肌/股四头肌肌力比值(H/Q)、屈肌群和伸肌群峰力矩(PT)、恐动症评估简表(TSK-11)评分以及术后并发症发生率评估两组患者疗效差异。结果两组术后2、4、8、12、24 h FPS-R评分比较,差异并不明显(P>0.05);出院时和出院1、3个月两组患者膝关节HSS评分、ROM及BBS评分均较术前改善,且观察组优于对照组(P<0.05);观察组术后3个月H/Q及屈肌群、伸肌群PT均高于对照组,出院时TSK-11评分低于对照组(P<0.05);观察组锻炼依从性高于对照组(P<0.05);两组术后并发症发生率比较,差异无统计学意义(P>0.05)。结论将瑞士球核心动态训练用于TKA患者围术期康复训练全过程,在不增加患者疼痛感受的情况下,有利于增强术后及出院后膝关节功能,提高平衡功能和核心肌力,降低恐动水平。

机载灭火系统管网设计综述

作为飞机防火系统的重要组成部分,机载灭火系统管网因其恶劣的工作环境、短时间内实现全淹没灭火的高性能要求以及尽可能小的装置重量而成为飞机火灾工程领域的重难点研究对象。为设计出高效的机载灭火系统管网,对机载灭火系统管网的结构、机制及输运动态进行了详尽分析,对影响灭火剂输运释放的设计要素与优化方法进行了分类综述,并总结了优化设计机载灭火系统管网的关键要点,指出将计算流体力学(CFD)与实验相结合的方式,是当前兼具可靠性与经济性的主流设计方法,为机载灭火系统管网未来的设计趋势与深入研究提供一定的参考。

加油站软土地基处理方案的比选及应用

软土地质承载力低,在此类地质建设加油站,容易导致建筑物地基产生不均匀沉降和变形,路面沉降开裂,稳定性不满足规范要求,严重影响加油站建设及运营安全。文章结合具体项目案例,对比分析桩基础和强夯置换法两种软土地质处理方案,并以强夯置换法作为软土地质的处理方法,采用竖向抗压静载试验、平板载荷试验等试验手段对处理后的地基进行检测,结果表明强夯置换法可以提高加油站软土的承载性能,处理后的地质能够满足设计要求。