Time-Domain Analysis of Body Freedom Flutter Based on 6DOF Equation

The reduced weight and improved efficiency of modern aeronautical structures result in a decreasing separation of frequency ranges of rigid and elastic modes.Particularly,a high-aspect-ratio flexible flying wing is prone to body freedomflutter(BFF),which is a result of coupling of the rigid body short-periodmodewith 1st wing bendingmode.Accurate prediction of the BFF characteristics is helpful to reflect the attitude changes of the vehicle intuitively and design the active flutter suppression control law.Instead of using the rigid body mode,this work simulates the rigid bodymotion of the model by using the six-degree-of-freedom(6DOF)equation.A dynamicmesh generation strategy particularly suitable for BFF simulation of free flying aircraft is developed.An accurate Computational Fluid Dynamics/Computational Structural Dynamics/six-degree-of-freedom equation(CFD/CSD/6DOF)-based BFF prediction method is proposed.Firstly,the time-domain CFD/CSD method is used to calculate the static equilibrium state of the model.Based on this state,the CFD/CSD/6DOF equation is solved in time domain to evaluate the structural response of themodel.Then combinedwith the variable stiffnessmethod,the critical flutter point of the model is obtained.This method is applied to the BFF calculation of a flyingwing model.The calculation results of the BFF characteristics of the model agree well with those fromthe modalmethod andNastran software.Finally,the method is used to analyze the influence factors of BFF.The analysis results show that the flutter speed can be improved by either releasing plunge constraint or moving the center ofmass forward or increasing the pitch inertia.

Triad-displaced ULAs configuration for non-circular sources with larger continuous virtual aperture and enhanced degrees of freedom

Non-uniform linear array(NULA)configurations are well renowned due to their structural ability for providing increased degrees of freedom(DOF)and wider array aperture than uniform linear arrays(ULAs).These characteristics play a significant role in improving the direction-of-arrival(DOA)estimation accuracy.However,most of the existing NULA geometries are primarily applicable to circular sources(CSs),while they limitedly improve the DOF and continuous virtual aperture for noncircular sources(NCSs).Toward this purpose,we present a triaddisplaced ULAs(Tdis-ULAs)configuration for NCS.The TdisULAs structure generally consists of three ULAs,which are appropriately placed.The proposed antenna array approach fully exploits the non-circular characteristics of the sources.Given the same number of elements,the Tdis-ULAs design achieves more DOF and larger hole-free co-array aperture than its sparse array competitors.Advantageously,the number of uniform DOF,optimal distribution of elements among the ULAs,and precise element positions are uniquely determined by the closed-form expressions.Moreover,the proposed array also produces a filled resulting co-array.Numerical simulations are conducted to show the performance advantages of the proposed Tdis-ULAs configuration over its counterpart designs.

Degree of Freedom Analysis for Holographic MIMO Based on a Mutual-Coupling-Compliant Channel Model

Degree of freedom(DOF)is a key indicator for spatial multiplexing layers of a wireless channel.Traditionally,the channel of a multiple-input multiple-output(MIMO)half-wavelength dipole array has a DOF that equals the antenna number.However,recent studies suggest that the DOF could be less than the antenna number when strong mutual coupling is considered.We utilize a mutual-coupling-compliant channel model to investigate the DOF of the holographic MIMO(HMIMO)channel and give a upper bound of the DOF with strong mutual coupling.Our numerical simulations demonstrate that a dense array can support more DOF per unit aperture as compared with a half-wavelength MIMO system.

Subharmonic response of single-degree-of-freedom linear vibroimpact system to narrow-band random excitation

The subharmonic response of a single-degree-of-freedom linear vibroimpact oscillator with a one-sided barrier to the narrow-band random excitation is investigated.The analysis is based on a special Zhuravlev transformation,which reduces the system to the one without impacts or velocity jumps,and thereby permits the applications of asymptotic averaging over the period for slowly varying the inphase and quadrature responses.The averaged stochastic equations are exactly solved by the method of moments for the mean square response amplitude for the case of zero offset.A perturbation-based moment closure scheme is proposed for the case of nonzero offset.The effects of damping,detuning,and bandwidth and magnitudes of the random excitations are analyzed.The theoretical analyses are verified by the numerical results.The theoretical analyses and numerical simulations show that the peak amplitudes can be strongly reduced at the large detunings.

Earthquake Barcode from a Single-Degree-of-Freedom System

Earthquake is a violent and irregular ground motion that can severely damage structures. In this paper we subject a single-degree-of-freedom system, consisting of spring and damper, to an earthquake excitation, and meanwhile investigate the response behavior from a novel theory about the dynamical system, by viewing the time-varying signum function of It can reflect the characteristic property of each earthquake through and the second component of f, where is a time-sampling record of the acceleration of a ground motion. The barcode is formed by plotting with respect to time. We analyze the complex jumping behavior in a barcode and an essential property of a high percentage occupation of the first set of dis-connectivity in the barcode from four strong earthquake records: 1940 El Centro earthquake, 1989 Loma earthquake, and two records of 1999 Chi-Chi earthquake. Through the comparisons of four earthquakes, we can observe that strong earthquake leads to large percentage of the first set of dis-connectivity.

Trimming the Degrees of Freedom via a K^(+) Flux Rectifier for Safe and Long‑Life Potassium‑Ion Batteries

High degrees of freedom(DOF)for K^(+)movement in the electrolytes is desirable,because the resulting high ionic conductivity helps improve potassium-ion batteries,yet requiring support from highly free and flammable organic solvent molecules,seriously affecting battery safety.Here,we develop a K^(+)flux rectifier to trim K ion’s DOF to 1 and improve electrochemical properties.Although the ionic conductivity is compromised in the K^(+)flux rectifier,the overall electrochemical performance of PIBs was improved.An oxidation stability improvement from 4.0 to 5.9 V was realized,and the formation of dendrites and the dissolution of organic cathodes were inhibited.Consequently,the K||K cells continuously cycled over 3,700 h;K||Cu cells operated stably over 800 cycles with the Coulombic efficiency exceeding 99%;and K||graphite cells exhibited high-capacity retention over 74.7%after 1,500 cycles.Moreover,the 3,4,9,10-perylenetetracarboxylic diimide organic cathodes operated for more than 2,100 cycles and reached year-scale-cycling time.We fabricated a 2.18 Ah pouch cell with no significant capacity fading observed after 100 cycles.

Freedom EVO全自动酶联免疫前处理仪故障分析

全自动酶联免疫前处理是一种高自动化酶免诊断分析仪,用于检验科各类样品的液体处理工作。仪器在正常保养的情况下,由于标本量巨大、项目繁多,运行过程中不可避免地会出现故障。以Freedom EVO全自动酶联免疫前处理为例,分析总结使用过程中出现的常见故障及解决方法,以尽快解决故障,提高检验质量和工作效率,确保设备长期有效的运行,供操作及维护人员参考。

The Kinematics Performance of Self-Propelled Full Freedom Filament in Wakes of Flow around Cylinder

In vortex streets, the kinematics performance of self-propelled full freedom filament is closely related to the length and the position of filaments in the flow field. In this paper, the changes of passive propulsion velocity and pressure of full-degree-of-freedom filaments after cylindrical wake were analyzed by 15 sets of experiments when the length and position of filaments were changed. The results show that the propulsive velocity of the filament, it approximately increases first and then decreases with the filament length increasing, and the further away from the center of the cylinder, the smaller the propulsive velocity of the filament. In addition, the longer the filament length and the further it is from the center of the cylinder, the lower the pressure around the filament. Experiments show that filaments without energy input can obtain energy from the surrounding flow field to maintain self-propelled motion. Studying the influence of length and position on the kinematics of filaments is helpful to provide a reference for revealing the hydrodynamic mechanism on passive propulsion process and developing low resistance energy harvesting device in swimming fish movement.

The Prisoner of“Freedom”:Cultural Displacement of Santosh in Naipaul’s In a Free State

In a Free State is a post-colonial novel written by Naipaul.“One out of Many”is one of the stories in this novel to explore the freedom of the culturally rootless.The protagonist,Santosh,lives under the collision between the Indian culture and American culture.In the“crevice”of two different cultures,he is deeply involved in the tumultuous and painful process of cultural displacement.His behaviors in cultural displacement can be divided into three stages.Firstly,he has experienced a“cultural shock”after his arrival in Washington,D.C.as a new comer.Secondly,after being fully exposed to the host culture and American style,he has experienced assimilation and absorption to be like an American.Finally when he escapes from his employer and chooses his own way of living,he finds that he is not free at all because he is confronted with an awkward cultural dilemma:he can neither return to his past life;nor can he aspire to a better future.The anxiety about the dislocation causes misery for his fate.As a result,he becomes a prisoner in an unfamiliar culture,and his“freedom”can only be a rootless“freedom”.

The Conflict and Balance Between Intellectual Property Rights and Public Freedom of Information in the“Anti-circumvention Clause”

There is a long-standing conflict between intellectual property rights and public freedom of information.The continuous development of the“anti-circumvention clause”has caused the conflict to intensify.As a basic human right,freedom of information is being gradually eroded by the expansion of intellectual property rights.The existing research mainly carries on the right balance from the negative protection path,but the positive protection path is more advantageous to realizing the public freedom of information and alleviates the conflict between the two kinds of rights.In practice,there are some problems in the application of the anti-circumvention clause,such as the legality of the aim,the division of the protected part,and the determination of the circumvention.This is mainly due to the lack of restrictions on technical measures,the failure to distinguish between“copyright protection”and“contact control”,and the offside and absence of administrative bodies in practice.We should protect public freedom of information by distinguishing the two measures of copyright protection and contact control and the two torts of access and use,increasing the restrictive conditions for the use of technical protection measures,and changing the functions of administrative supervision agencies.

基于改进麻雀优化PID的波浪补偿控制方法

随着海上风电“十四五”规划的不断推动,在深远海域对兆瓦级大功率海上风机的需求量随之增加,其规模也在不断扩大。但是,在吊运、安装等海上工作过程中,复杂海浪对船舶产生的持续影响导致风机安装的精度和效率大幅下降,甚至会对人员安全以及财产造成重大损失。在深远海域复杂海况下对工程船舶进行有效的波浪补偿,可提供稳定的作业环境以保证精准高效地完成各项工作,因此,本文提出了一种基于改进麻雀优化PID的波浪补偿控制方法并将其应用于Stewart补偿平台。首先,建立波浪补偿平台动力学以及运动学反解模型,并设计正解模型迭代求解算法。随后,使用PID进行波浪补偿控制,并通过麻雀搜索算法优化参数。接着,采用Circle混沌映射对其进行初始化分布,以解决初始化不均匀的问题;并采用动态自适应加权、柯西突变以及反向学习以提升算法全局寻优能力。最后,生成4~6级海况下的某工程船运动数据作为系统输入,利用MATLAB和Simulink软件平台搭建模型进行补偿控制验证,并在Stewart硬件平台上做补偿试验。结果表明,改进麻雀搜索算法具有较快的收敛速度、较高的精度和更好的寻优能力,优化后的PID控制方法更适合用于复杂海况下波浪补偿平台的控制优化,可为大功率海上风机安装的补偿平台控制系统设计提供参考。

宪法视野下的婚检制度变革与完善——基于《民法典》第1053条告知义务的履行

《民法典》第1053条对禁婚疾病传统作出重大调整,成为新时代背景下婚检制度设计的重要法律依据。在婚姻宪法保护框架下,“婚姻自由—私人告知—自愿婚检”的传统思路忽略了比“婚姻自由保护”更为根本的“婚姻传统功能保护”。婚姻的公共性及解决相关司法实践难题的客观需要,使得婚检融入履行环节成为可能。从《宪法》到《民法典》再到《婚姻登记条例》,民法典时代婚检制度设计应沿循“婚姻保护—法定告知—弱强制婚检”设计思路,采取“程序强制+形式审查”模式,即当事人于婚前相互告知专业健康检查结论,婚姻登记机关仅要求当事人填写知晓声明并进行必要口头提示而不对告知内容及其真实性进行实质审查。

公序良俗在情人遗赠纠纷中的适用——基于私法与基本权利冲突理论的二元视角

遗赠是否违背公序良俗应以遗赠本身为审查对象,而不能以遗赠以外之事实为断。同时,情人遗赠行为是否违背公序良俗,尤应考察当事人一方遗赠的动机是否是将性奉献与经济上的对待给付联结起来,抑或是存在其他更值得尊重的动机。但在私法视角下,情人遗赠的效力,总是呈现出完全有效或完全无效的形态。而在基本权利冲突与权衡的视角下,各基本权利相互较量各自在具体个案中的分量,此种权衡和较量之结果体现在法律行为效力上,即既非完全有效亦非完全无效,而是在两者间存在多种可能性,因而更能适应个案中的具体情况,也更具灵活性。

基于双自由度转台的全向空间单目视觉室内定位测量方法

针对传统单目视觉测量系统测量视场有限的问题,本文提出一种基于双自由度旋转平台的全向空间单目视觉测量方法。首先,对双自由度旋转平台的转轴参数进行标定,用副相机拍摄固定在双自由度转台上的棋盘格标定板,提取棋盘格角点的位置坐标,并将其转化到同一相机坐标系下。利用PCA(主成分分析)平面拟合得到初始位置转轴参数中的方向向量,使用空间最小二乘圆拟合方法得到初始位置下转轴参数中的位置参数。然后,通过转台转动的角度以及罗德里格斯公式将不同位置下相机获取的数据进行坐标系统一,实现水平和竖直方向全向空间下的目标测量。最后,通过高精度激光测距仪验证了本方法的测量精度,并通过与双目视觉测量系统、wMPS测量系统进行比对实验,验证了本方法的全向空间测量能力。实验结果表明,本方法测量精度基本达到双目视觉测量系统水平,但测量范围远大于双目视觉测量,可以满足全向空间测量要求。

针对半月板损伤患者的运动学步态分析

目的:探讨应用Codamotion 2CX1三维动态关节运动捕捉系统分析不同程度半月板损伤患者运动学特征。方法:2020年12月至2022年6月收治的半月板损伤患者及招募的正常人共135例,男82例,女53例;年龄14~29岁;病程1~3个月。结合临床症状及MRI检查明确半月板损伤诊断,根据Stoller分级标准将半月板损伤分为4级:0级(正常)37例,Ⅰ级30例,Ⅱ级33例,Ⅲ级35例。采用Codamotion 2CX1三维动态关节运动捕捉系统对各组受试者进行行走测试,采集步行及运动学定量化指标,包括膝关节屈伸、内外旋、内外翻,并对其进行运动学进行分析。结果:在膝关节屈曲/伸直的分布中,4组患者膝关节最大屈曲、最小伸直及膝关节屈伸范围比较,差异有统计学意义(P<0.05);在膝关节内旋/外旋的分布中,4组患者膝关节内旋及膝关节旋转范围比较,差异有统计学意义(P<0.05);在膝关节内翻/外翻的分布中,4组患者膝关节外翻及膝关节翻转范围比较,差异有统计学意义(P<0.05);临床分期进展与膝关节伸直、外旋、内外翻及翻转活动范围呈正相关(P<0.05);与膝关节屈曲、内旋及屈伸、旋转活动范围呈现负相关(P<0.05);膝关节内旋、外旋角度可以作为半月板损伤临床分期的独立影响因素(P=0.006,0.019<0.05)。结论:半月板损伤患者膝关节运动发生了明显变化,且不同临床分期下,变化有一定差异,步态分析为半月板损伤的运动学分析提供了一个可靠的依据,有助于更好了解关节的运动学指标,同时提供了一个较为可靠的辅助诊疗方案,为后续医学研究提供了新方向。

数字时代的“表达”:算法推荐的信息干预及其法治化因应

算法正位于生活的中心,算法推荐服务所带来的隐性信息干预隐含着侵蚀表达自由的风险。数字时代“表达”的结构已发生更迭,保护“表达”所依赖的信息基础尤为重要。算法推荐领域保护“表达”的二阶规范渊源分别为契约与立法,契约责任面临有限的意思自治与公法属性权利让渡的悖论,走向“算法治理”的立法规制则面临执行的困境。宪法基本权利第三人效力及我国社会主义性质宪法“合作的基本权利”结构为宪法基本权利条款的介入提供了法理依据。宪法为划定政府、平台责任边界提供根本依据,宪法基本权利条款的新内涵能够指导规则体系的生成及运行,有利于形成统一的法秩序。将算法推荐规则纳入合宪性审查、备案审查的制度体系内,能够实现平台权力与国家权力的衔接统合。

稳定分析中滑动面构造方法分析

滑动面的构造方法是边坡稳定分析的关键课题之一。任意滑动面的构造比较复杂,基于Logistic函数积分等基函数构造的曲线可以代替传统的折线形滑动面,改善滑动面的光滑性,也有利于减少其自由度。对基于基函数的滑动面构造方法进行梳理,将其划分为基于连续函数叠加的构造方法和基于积分运算的构造方法。重点对Logistic函数及其积分的性质进行分析,得到了不同参数对曲线形态的影响规律,从而缩小了相关参数的取值范围,为减小滑动面自由度提供了依据。在此基础上也给出了一种确定给定滑动面参数初值的方法。针对两个边坡算例的计算表明,所提出的方法能够满足边坡稳定分析的要求。

基于定位法线的工件最少定位点布局规划方法

以建立满足工序需求的工件定位点数量最少的定位布局为目标,以定位法线为介质,基于定位法线的工件定位的几何定理,推论出工件自由度与定位法线关系,获得自由度约束模型的定位法线信息;建立工件自由度数学模型,运用逻辑减运算法则建立工件各类型自由度之间关系,获得自由度模型的规划方案;根据规划方案中的定位法线信息,得出定位点初始布局。利用典型实例详细介绍了基于定位法线进行工件定位点布局规划的应用过程。该方法仅需自由度信息,规划过程简便,适用于各类工件,尤其是复杂工件的初步定位方案设计。

赋能还是制约:智能技术如何影响学生学习自由的实现

学习自由是学生在学习过程中自主性、能动性与自为性的重要体现,是促进学生创新发展的重要条件。在智能环境中,智能技术既能为学生提供丰富的学习资源和空间自由,也可能以技术意向性和算法黑箱规训和制约学生学习的自由。如何构建智能技术影响学生学习自由实现的分析框架,成为探析两者辨证关系的关键所在。具体而言,应围绕数据、算力、算法、技术伦理等智能技术要素,权利学习自由、自我实现学习自由两类学习自由,以及隐私与表达、机会与选择、发现与认知、整合与创新、情感与价值塑造5个学习自由层次来构建分析框架,以厘清智能技术要素与不同层次学习自由之间的复杂关系。显然,智能技术的不同要素会从不同层面影响和干预学生的学习权利自由和自我实现自由,限制其身心自然成长和创造性学习与发展。为更好地利用智能技术推动学生学习自由的实现,教育管理部门应以负责任创新治理理念为引导,明确技术作用限度及超越方法;教师应强化与智能技术的高效协同,实现从“技术追新”向“育人创新”的转变;学生应明确在人机协同中的主体作用,推动实现高学习自由度—高创造性学习;信息化行业应面向学生发展规律设计智能学习产品,促进自由开放学习的发生。

半无限介质多自由度频响函数离散时间有理近似的稳定参数识别

离散时间有理近似函数是将半无限土频响函数转化为时域模型的重要工具,离散时间有理近似函数和时域模型具有相同的稳定性和精度。目前关于离散时间有理近似函数的研究只针对于单自由度系统。该文基于线性控制理论,给出了多自由度有理近似系统的稳定条件。将稳定性条件与遗传-序列二次算法相结合,开发了多自由度频响函数参数辨识方法,保证了多自由度系统的稳定性和精度。不同维度的多自由度有理近似系统的数值仿真验证了该文方法可以保证多自由度有理近似系统的稳定性和精度。