FLOCKING OF A THERMODYNAMIC CUCKER-SMALE MODEL WITH LOCAL VELOCITY INTERACTIONS

In this paper, we study the flocking behavior of a thermodynamic Cucker–Smale model with local velocity interactions. Using the spectral gap of a connected stochastic matrix, together with an elaborate estimate on perturbations of a linearized system, we provide a sufficient framework in terms of initial data and model parameters to guarantee flocking. Moreover, it is shown that the system achieves a consensus at an exponential rate.

Leveraging on Flock Dynamics and Farmers’ Production Constraints in Designing Flock Health Program for Accelerated Goat Production

Compliance with appropriate flock health program is vital for preventing introduction and minimizing impact of diseases in goat farms. Unfortunately, most goat farms in Uganda, especially in the Albertine Graben Zone lack flock health program. The associated frequent outbreaks slow down effort aimed at commercializing goat production. In this study, we documented flock dynamics, identified and prioritized pressing challenges experienced by goat farms during the year 2022 and generated appropriate flock health program and packaged it for dissemination to farmers. Materials and Methods: Using a cross-sectional design, semi-structured questionnaire, data were collected and analyzed with MS Excel 2013. The data included: location and socio-demographics of household, farming system, flock dynamics, housing, feeding system, health management, challenges encountered by goat farm and suggested solutions. Results: Beginning January 2022 to December 2022, the number of goats reared in all the 45 sample farms increased from 2128 to 2220 goats. Results showed that 884 kids were produced and 88 breeding goats were introduced into the farms. Three hundred ninety-nine goats died due to mainly diseases and 435 goats got withdrawn through nondeath. The average farm level and overall mortality rate were 21 goats per 1000 goatmonths and 15 goats per 1000 goatmonths respectively. The most pressing challenges encountered by sample farms were death of goats especially due to diseases, poor access to veterinary extension services, high cost of inputs and feed scarcity. Solutions suggested by sample farms were improved access to veterinary services, improved housing, enhanced vaccination of goats against diseases, and enhanced grazing land management and feed conservation, all of which were incorporated into the flock health program. Conclusion and Recommendations: An appropriate flock health program was generated based on flock dynamics and production constraints which reveal high mortality and limited access to veterinary services respectively. Actors are recommended to promote adoption and adherence to the flock health program so as to increase goat production and access to wider market.

具有虚拟领导的Flocking聚类算法

该文提出一种改进的带虚拟领导的Flocking模型,并基于此模型开发了一种数据聚类算法。在此算法中,数据集中的数据点被考虑为可以在空间中移动的Agent,并且根据改进的模型,生成有权无向图。然后从数据集中选定一组虚拟领导,每个数据点与其中γ个虚拟领导建立连接。所有与这个数据点有连接的邻居,都通过一个势函数产生场,对这个数据点进行作用,此数据点将沿着所有场矢量叠加的方向移动一段距离。算法中,虚拟领导的加入有效减少了数据点,特别是邻居较少的数据点向某个中心收敛的时间。在所有数据点不断受到作用而移动的过程中,同类的数据点就会逐渐地聚集到一起,而不同类的数据点则相互远离,最后自动形成聚类。此算法的实验结果表明,数据点能合理有效地被聚类,并且算法具有较快的收敛速度,同时,与其他算法对比也验证了此算法的有效性。

基于加权准邻域和多虚拟领航者的Flocking算法

为解决Flocking模型中势函数没有考虑角度信息的问题,建立了基于加权准邻域势函数以及多虚拟领航的Flocking运动模型。首先,考虑运动的方向性,不同角度的邻居对智能体的影响不同,根据邻域角度信息设计基于加权势函数的控制器。然后,对单虚拟领航者的群智能体运动和两组群智能体受各自领航者引导混杂后又分离的运动过程进行了仿真。最后,通过误差分析证明所建立的Flocking运动模型符合群智能体的运动规律。

一种基于混合智能体系统的Flocking算法

对由多个具有二次积分动态、通信半径不同的智能体组成的混合群体跟随领航者取得flocking运动进行研究。针对不同智能体的通信半径存在个体差异这一现象,提出一种分散控制算法。该控制策略能够保证混合智能群体跟踪一个速度固定的虚拟领航者,形成紧凑、无碰撞的队列且各智能体的速度最终收敛于领航者的速度。最后给出了算法可行性的理论分析,并针对20个具有不同通信半径的智能体跟随一个速度固定的虚拟领航者的情形给出了计算机仿真,验证了算法的可行性。

基于flocking的多智能体群集与避障算法研究与仿真

多智能体运动规划问题逐渐成为智能体中研究的热点问题。多智能体运动规划主要包括路径规划、编队控制和避障避碰三种控制行为。主要介绍了基于分布式flocking的群集控制模式,实现了多智能体系统的集结与共识,使多智能体在运动过程中保持一致性,并为系统提供冗余性和结构的灵活性;同时对多智能体的避障控制和目标点控制开展了进一步的研究,解决群集避障问题,在复杂环境下成功抵达任务目标区域;最后通过仿真验证了该算法的合理性和有效性。

Stable Flocking Motion of Mobile Agents Following a Leader in Fixed and Switching Networks

Multiple mobile agents with double integrator dynamics, following a leader to achieve a flocking motion formation, are studied in this paper. A class of local control laws for a group of mobile agents is proposed. From a theoretical proof, the following conclusions are reached： （i） agents globally align their velocity vectors with a leader, （ii） they converge their velocities to the leaders velocity, （iii） collisions among interconnected agents are avoided, and （iv） agent＇s artificial potential functions are minimized. We model the interaction and/or communication relationship between agents by algebraic graph theory. Stability analysis is achieved by using classical Lyapunov theory in a fixed network topology, and differential inclusions and nonsmooth analysis in a switching network topology respectively. Simulation examples are provided.

群机器人Flocking行为研究综述

主要回顾了群机器人自组织flocking行为的研究。首先,介绍群机器人学的含义及关键特征;然后,指出flocking行为在生物学上及机器人学上的意义,之后对目前的研究现状进行介绍。最后,按照以下的三个分类对群机器人flocking行为进行总结:行为控制,硬件设备及交流策略。

一种带有变速虚拟领航者的flocking算法

对由多个具有不同通信半径的智能体组成的混合群体跟随领航者取得flocking运动进行研究。针对不同智能体的通信半径存在个体差异这一现象,提出一种分散控制算法。该控制策略能够保证混合智能群体跟踪一个速度变化的虚拟领航者,形成flocking运动。在最后给出计算机仿真。

The effects of food abundance and disturbance on foraging flock patterns of the wintering Hooded Crane(Grus monacha)

Background:Food abundance and availability affect flock patterns of foraging birds.Cost and risk tradeoffs are especially critical for flocks of wintering waterbirds foraging in lake wetlands.Waterbirds losing suitable habitats face insufficient food supplies and high levels of disturbance,affecting their foraging activities.Our objective was to study the effects of food abundance and disturbances on flock size and the structure of Hooded Crane flocks wintering at Shengjin Lake and,as well,to understand the response of wintering waterbirds to habitat degradation for future management decisions and protection of the population.Methods:We investigated food abundance,disturbances and flock foraging activities of the wintering Hooded Crane in several foraging habitats of Shengjin Lake from November 2013 to April 2014.Flock size and structure were observed by scan sampling.Data on food abundance and disturbances were collected by sampling.Flock size and structure were compared among three wintering stages.The relationship between food resources,disturbances and flock size were illustrated using a generalized linear model.Results:In the early and middle wintering periods,the Hooded Crane used paddy fields as its major foraging habitat,where the number of foraging birds and flocks were the highest.During the late period,the cranes took to meadows as their major foraging habitat.The variation among foraging flock was mainly embodied in the size of the flocks,while the age composition of these flocks did not change perceptibly.Family flocks were notably different from flock groups in size and age composition.The results of a generalized linear model showed that the food abundance had a marked effect on foraging flock size and age composition,while disturbances had a significant effect only on flock size.From our analysis,it appeared that the combined effect of the two variables was significant on the size of the foraging flock,but had less impact on age composition.Conclusions:Food abundance and disturbances affected the flock size of the Hooded Crane.With abundant food and high disturbances,flock sizes increased owing to cooperation in foraging.To avoid competition and maximize foraging benefits,flock size reduces with an abundance of food but low disturbance.By trading off risks and costs,the cranes showed flexible flock distributions and a variety of foraging strategies to maximize benefits and to improve their fitness.

Multiagent flocking with formation in a constrained environment

We consider the problem of controlling a group of mobile agents to form a designated formation while flocking within a constrained environment. We first propose a potential field based method to drive the agents to move in connection with their neighbors, and regulate their relative positions to achieve the specific formation. The communication topology is preserved during the motion. We then extend the method to flocking with environmental constraints. Stability properties are analyzed to guarantee that all agents eventually form the desired formation while flocking, and flock safely without collision with the environment boundary. We verify our algorithm through simulations on a group of agents performing maximum coverage flocking and traveling through an unknown constrained environment.

关于flocking的综述

本文着重介绍了群及其聚结规则,由雷诺兹启发提出的控制规律确保所有个体的前进方向和速度以渐近线趋向于相同值,并且避免个体间的相互碰撞。阐述了国内外研究的历史和现状,以及对未来发展的预测。本文在总结国内外flocking研究发展的基础上,预测其在航空等方面发展的前途,为我们在新的领域中研究flocking提供了可能。

EXISTENCE AND UNIQUENESS OF ENTROPY SOLUTION TO PRESSURELESS EULER SYSTEM WITH A FLOCKING DISSIPATION

We study the existence and uniqueness problem for the nonhomogeneous pressureless Euler system with the initial density being a Radon measure. Our uniqueness result is obtained in the same space as the existence theorem. Besides, by counterexample we prove that Huang-Wang’s energy condition is also necessary for our nonhomogeneous system.

Flocking for swarm systems with fixed topology in a changing environment

This paper is mainly devoted to the flocking of a class of swarm with fixed topology in a changing environment. Firstly, the controller for each agent is proposed by employing the error terms between the state of the agent and the average state of its neighbors. Secondly, a sufficient condition for the swarm to achieve flocking is presented under assumptions that the gradient of the environment is bounded and the initial position graph is connected. Thirdly, as the environment is a plane, it is further proved that the velocity of each agent finally converges to the velocity of the swarm center although not one agent knows where the center of the group is. Finally, numerical examples are included to illustrate the obtained results.

Effect of sex,temperature,time and flock size on the diving behavior of the wintering Scaly-sided Merganser(Mergus squamatus)

Background: The foraging and diving behavior of waterfowl are affected by a number of important factors. Hence, learning more about these major factors is of great concern in order to protect endangered species. In this study, we verified the effect of sex, temperature, time and flock size on the diving behavior of the Scaly-sided Merganser(Mergus squamatus).Methods: The study was conducted by means of focal animal sampling in the Wuyuan section of the Poyang Lake watershed in Jiangxi Province, China from December 2015 to March 2016. We used one-way ANOVA and LSD tests to investigate the differences among these factors. Pearson correlations were used to test the relation between pause duration and the previous or subsequent dive duration. The relations between these factors and dive/pause duration are illustrated using Spearman correlations.Results: Mean dive duration and mean time on the pause of males were significantly higher than those of females. With an increase in temperature, dive duration significantly increased. Along with the passage of time of year and daytime, dive duration significantly increased, while dive duration decreased significantly with the increase in flock size.Conclusions: Sex, temperature, time and flock size have an effect on the diving behavior of the wintering Scalysided Merganser. The difference of diving behavior between males and females is related to differences in body mass. The difference of diving behavior among various temperatures and time periods may be related to a low minimum rate of oxygen consumption, while the difference among various flock sizes may be caused by rising intraspecific competition.

Pathology and molecular characterization of recent Leucocytozoon caulleryi cases in layer flocks

Leucocytozoonosis was found in three layer farms in chickens with suspected fatty liver or fatty liver hemorrhagic syndrome in Korea between 2009 and 2011.These layer chicken flocks showed both mortality and decreased egg production for one or two weeks when they were between 59 and 82 weeks old.At the necropsy,the most prominent gross lesions were found in the liver,which was enlarged,had a fragile texture,exhibited yellowish discolorations,and had various hemorrhagic lesions.Tissue reactions associated with megaloschizonts specific for Leucocytozoon caulleryi were prominent upon microscopic examination of the liver without significant lipidosis.In addition,the ovaries and uterus were the most affected organs for Leucocytozoon caulleryi multiplication,which led to decreased egg productions.Molecular studies with formalin-fixed,paraffin-embedded tissues were performed in search of a partial region of the cytochrome b gene for hemosporidian parasites.Based on these results,the causal agent was determined to be closely related to Leucocytozoon caulleryi reported in Japan and Malaysia.In this study,we describe recently re-occurring leucocytozoonosis in layer chickens,which required histopathology for disease diagnosis.To prevent outbreaks and maintain chicken health and egg production,layer chickens need to be monitored for symptoms of leucocytozoonosis.

Multi-Variable Flocking Control for Multi-Agent Systems via a Received Signal Strength Indicator

A novel flocking control approach is proposed for multi-agent systems by integrating the variables of velocities, motion directions, and positions of agents. A received signal strength indicator （RSSI） is applied as a variable to estimate the inter-distance between agents. A key parameter that contains the local information of agents is defined, and a multi-variable controller is proposed based on the parameter. For the position control of agents, the RSSI is introduced to substitute the distance as a control variable in the systems. The advantages of RSSI include that the relative distance between every two agents can be adjusted through the communication quality under different environments, and it can shun the shortage of the limit of sensors. Simulation studies demonstrate the effectiveness of the proposed control approach.

基于Flocking的车辆编队分布式控制

完成基于Flocking的车辆编队模型的分布式控制。首先建立基于Hebb规则的Flocking运动模型,其次引入路线和面积势能控制完成控制器设计,然后以直线运动为例仿真验证基于Flocking的车辆编队模型,最后进行误差分析。建立的Flocking运动模型可以实现车辆编队的分布式控制。

Latest evidence of the existence of the northern flock of the Chinese Crested Tern(Sterna bernsteini)

Three Chinese Crested Terns (Sterna bernsteini) were seen stopping at the Golden Coast of Rizhao (city), southern Shandong Province, China, on 6 September 2011. This is the third record of the bird appearing in northern

Flocking for Leader-Following Multi-Agent Systems with Time-Varying Delay

This paper investigates the flocking problem in multi-agent system with time-varying delay and a virtual leader. Each agent here is subject to nonlinear dynamics. For the system, the corresponding algorithm with time-varying delay is proposed. Under the assumption that the initial network is connected, it is proved that the distance between agents is in the desired distance. The theoretical deduction shows that the stable flocking motion is achieved.