Comparison between seismic analysis of twisting and regular 52-story towers considering soil-structure interaction

A dynamic analysis of both twisting and regular towers is carried out to determine the results of considering soil-structure interaction(SSI)on high-rise buildings.In addition,the difference between the seismic performance of using twisting towers over regular ones is investigated.The twisting tower is a simulation of the Evolution Tower(Moscow).The towers’skeletons consist of RC elements and rest on a reinforced concrete piled-raft foundation.The soil model is considered as multi-layered with the same soil properties as the zone chosen for the analysis(New Mansoura City,Egypt).The only difference between both towers is their shape in elevation.The whole system is modelled and analyzed in a single step as one full 3D model,which is known as the direct approach in SSI.All analyses are carried out using finite-element software(Midas GTS NX).Dynamic output responses due to three records of seismic loads are proposed and presented in some graphs.Based on the results,it is concluded that SSI has a considerable effect on the dynamic response of tall buildings mainly because of the foundation flexibility,as it leads to lengthening the vibration period,increasing the story drift and the base shear for both cases.

双层自适应快速super twisting控制算法

为提高super twising算法的收敛速度,解决现有算法存在的增益过估计问题,提出了两种自适应增益快速super twisting算法.分别通过快速终端滑模趋近律和增加线性项加快收敛速度.利用基于等效控制的双层自适应律调节增益,保证滑模存在条件的成立,同时使增益尽量的小.采用Lyapunov方法证明了新算法具有更优良的收敛特性,根据有界实引理和Schur补定理分别给出了两种算法的参数整定策略.仿真算例表明,在相同控制参数下,新算法的能耗与原算法接近,并具有更快的收敛速度和更强的鲁棒性.

改进Twisting算法的相对位姿耦合控制

为实现对非合作目标航天器进行在轨服务,将Twisting算法与线性补偿项相结合,设计相对位置与姿态耦合的二阶滑模控制器.以航天器对接端口间耦合相对运动模型为基础,设计两种滑模平面的改进Twisting控制器.选取严格李雅普诺夫函数,证明所设计的改进Twisting控制器对有界干扰具有有限时间收敛的特性,并估计出收敛时间的上界.设计数学仿真,将其与标准Twisting算法进行对比,验证所设计的二阶滑模控制器对模型不确定性及有界干扰具有较强的鲁棒性,并能够有效抑制执行机构的震颤.

Development of Air Vehicle with Active Flapping and Twisting of Wing

This paper addresses mechanisms for active flapping and twisting of robotic wings and assesses flying effectiveness as a function of twist angle. Unlike the flapping motion of bird wings, insects generally make a twisting motion at the root of their wings while flapping, which makes it possible for them to hover in midair. This work includes the development of a Voice Coil Motor （VCM） because a flapping-wing air vehicle should be assembled with a compact actuator to decrease size and weight. A linkage mechanism is proposed to transform the linear motion of the VCM into the flapping and twisting motions of wings. The assembled flapping-wing air vehicle, whose weight is 2.86 g, produces an average positive vertical force proportional to the twist angle. The force saturates because the twist angle is mechanically limited. This work demonstrates the possibility of developing a flapping-wing air vehicle that can hover in midair using a mechanism that actively twists the roots of wings during flapping.

Aerodynamic mechanism of forces generated by twisting model-wing in bat flapping flight

The aerodynamic mechanism of the bat wing membrane Mong the lateral border of its body is studied. The twist-morphing that alters the angle of attack （AOA） along the span-wise direction is observed widely during bat flapping flight. An assumption is made that the linearly distributed AOA is along the span-wise direction. The plate with the aspect ratio of 3 is used to model a bat wing. A three-dimensional （3D） unsteady panel method is used to predict the aerodynamic forces generated by the flapping plate with leading edge separation. It is found that, relative to the rigid wing flapping, twisting motion can increase the averaged lift by as much as 25% and produce thrust instead of drag. Furthermore, the aerodynamic forces （lift/drag） generated by a twisting plate-wing are similar to those of a pitching rigid-wing, meaning that the twisting in bat flight has the same function as the supination/pronation motion in insect flight.

Quantum Fisher information and spin squeezing in one-axis twisting model

We investigate the dependence of the average parameter estimation precision （APEP）, which is defined by the quantum Fisher information, on the polar angle of the initial coherent spin state ｜θ0,φ0〉 in a one-axis twisting model. Jin et al. [New J. Phys. 11 （2009） 073049] found that the spin squeezing sensitively depends on the polar angle θ0 of the initial coherent spin state. We show explicitly that the APEP is robust to the initial polar angle θ0 in the vicinity of π/2 and a near- Heisenberg limit 2IN in quantum single-parameter estimation may still be achieved for states created with the nonlinear evolution of the nonideal coherent spin states θ0- π/2. Based on this model, we also consider the effects of the collective dephasing on spin squeezing and the APEE

Twisting theory for weak Hopf algebras

The main aim of this paper is to study the twisting theory of weak Hopf algebras and give an equivalence between the （braided） monoidal categories of weak Hopf bimodules over the original and the twisted weak Hopf algebra to generalize the result from Oeckl （2000）.

Adaptive Neural Observer-Based Nonsingular Super-Twisting Terminal Sliding-Mode Controller Design for a Class of Hovercraft Nonlinear Systems

Designing a controller to stabilize maneuvering hovercrafts is an important challenge in amphibious vehicles.Hovercrafts are implemented in several applications,such as military missions,transportation,and scientific tasks.Thus.to improve their performance,it is crucial to control the system and compensate uncertainties and disruptions.In this paper,both classic and intelligent approaches are combined to design an observer-based controller.The system is assumed to be both controllable and observable.An adaptive neural network observer with guaranteed stability is derived for the nonlinear dynamics of a hovercraft,which is controlled via a nonsingular super-twisting terminal sliding-mode method.The main merits of the proposed method are as follows:(1) the Lyapunov stability of the overall closed-loop system,(2) the convergence of the tracking and observer errors to zero,(3) the robustness against uncertainties and disturbances,and(4) the reduction of the chattering phenomena.The simulation results validate the excellent performance of the derived method.

The effect of waist twisting on walking speed of an amphibious salamander like robot

Amphibious salamanders often swing their waist to coordinate quadruped walking in order to improve their crawling speed. A robot with a swing waist joint, like an amphibious salamander, is used to mimic this locomotion.A control method is designed to allow the robot to maintain the rotational speed of its legs continuous and avoid impact between its legs and the ground. An analytical expression is established between the amplitude of the waist joint and the step length. Further, an optimization amplitude is obtained corresponding to the maximum stride. The simulation results based on automatic dynamic analysis of mechanical systems（ADAMS） and physical experiments verify the rationality and validity of this expression.

Helical twisting properties of new chiral dopants with double (S)-1,2-propanediol units for nematic liquid crystals

A novel series of chiral dopants synthesized from(S)-1,2-propanediol and mesogenic carboxylic acids were characterized by FT-IR,~1H NMR,elemental analysis and their helical twisting properties were investigated by doping the chiral dopants into a nematic liquid crystal host(SLC-1717).The results show that,the helical pitch of N~*-LC mixture exhibited a terminal alkyl chain length dependence and the molecular twisting power β also exhibited a temperature dependence(increasing β with increasing temperature).

Synthesis and helical twisting property of polymerizable chiral dopant with temperature-dependent solubility in liquid crystal

In this study, right-handed dicinnamate isosorbide was synthesized via the esterification reaction betweefi optically active isosorbide and cinnamate. The chiral dopant was characterized by FT-IR, ^1H NMR, elemental analysis, SEM, UV absorption spectrum. After dissolving in a nematic liquid crystal mixture, the chiral dopant exhibited a temperature-dependent solubility in the chiral nematic liquid crystal mixture. Meanwhile, a relatively high value of helical twisting power of the polymerizable chiral dopant was determined. The results show that the chiral dopant has great potential in achieving a polymer stabilized chiral nematic liquid crystal film with a broad-band selective reflection. C 2009 Huai Yang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Influence of terminal alkyl chain length on helical twisting property of chiral 1,2-propanediol derivatives

In this study, a novel series of chiral 1,2-propanediol derivatives with different terminal alkyl chain length were synthesized and characterized by FT-IR, ^1H NMR and DSC. After doped into a nematic liquid crystal host, all the chiral dopants induced chiral nematic liquid crystals exhibiting a helix inversion with temperature variation. The results indicate that terminal alkyl chain length has a prominent influence on helical twisting property of the chiral dopants. With increasing the terminal alkyl chain length, the molecular twisting power increases, the helix inversion temperatures varies slightly while the phase transition temperature decreases. An odd-even effect may exist in the molecular twisting power of the chirai dopants.

Twisting Sliding Mode Control of an Electrostatic MEMS Micromirror for a Laser Scanning System

In this paper,we present a twisting control scheme with proportional-integral-derivative(PID)sliding surface for a two-axis electrostatic torsional micromirror,and the utilization of the proposed scheme in a laser scanning system.The experimental results of set-point regulation verify that the proposed scheme provides enhanced transient response and positioning performance as compared to traditional sliding mode control.To evaluate the tracking performance of the closed-loop system,triangular waves with different frequencies are used as desired traces.With the proposed scheme the experimental results verified that the closed-loop controlled micromirror follows the given triangular trajectories precisely.A micromirror-based laser scanning system is developed to obtain images.When compared with open-loop control,the experimental results demonstrated that the proposed scheme is able to reduce the distortion of the raster scan,and improve the imaging performance in the presence of cross-coupling effect.

Modified super twisting controller for servicing to uncontrolled spacecraft

A relative position and attitude coupled sliding mode controller is proposed by combining the standard super twisting （ST） control and basic linear algorithm for autonomous rendezvous and docking. It is schemed for on-orbit servicing to a tumbling non- cooperative target spacecraft subjected to external disturbances. A coupled dynamic model is established including both kinemati- cal and dynamic coupled effect of relative rotation on relative translation, which illustrates the relative movement between the docking port located in target spacecraft and another in service spacecraft. The modified super twisting （MST） control algorithm containing linear compensation items is schemed to manipulate the relative position and attitude synchronously. The correction provides more robustness and convergence velocity for dealing with linearly growing perturbations than the ST control algorithm. Moreover, the stability characteristic of closed-loop system is ana- lyzed by Lyapunov method. Numerical simulations are adopted to verify the analysis with the comparison between MST and ST control algorithms. Simulation results demonstrate that the pro- posed MST controller is characterized by high precision, strong robustness and fast convergence velocity to attenuate the linearly increasing perturbations.

Mechanical enhancement and weakening in Mo_(6)S_(6)nanowire by twisting

The torsional,bending and tensile mechanical properties of Mo_(6)S_(6)nanowire are examined by molecular dynamics(MD)simulations with a first-principles-based reactive force field(ReaxFF).It is found that Mo_(6)S_(6)nanowire shows unique mechanical properties such as high torsional and bending flexibility,high Young's modulus and strength,and negative Poisson's ratio.The Mo_(6)S_(6)nanowire can be strengthened or weakened via twisting,depending on the twist angle.The Mo_(6)S_(6)nanowire with a slight twist angle shows brittle failure,whereas it with a large twist angle exhibits ductile failure and necking behavior.Twisted Mo_(6)S_(6)nanowires show a crossover in the negative Poisson's ratio at critical strains,that is,Poisson's ratio first decreases but then increases,with a minimum value down to around-0.8 at the strain of 0.01 as the twist angle is 21.0°/nm.The negative Poisson's ratio and the crossover are explained by the bond transform that makes zero angles to the wire cross-section.

Observation and Research on the Twisting Characteristics of Flare Loop System

We analyze the evolution of Hβ monochromatic images and Hβ velocity fields of the flare loops system on June 4, 1991. It is the first time to demonstrate directly the dynamic process of the energy storage, transportation and release of the twisting magnetic fields in the flare process.

INVESTIGATION ON OVERCOMING WEFT DETWISTING AIR-INSERTION OF AIR-JET LOOM

A special tip of vortex twisting nozzle is designed and fastened at the exit out of the drafted reed space or shed. Compressed air is supplied by the tube near the last subnozzle, weft yarn is retwisted and twistloss can be totally compensated with slight excess of 0.74%.

Implement of the Production Monitoring and Control System for Coning,Drawing and Twisting's Workshop

To achieve the production information management of the coning,drawing and twisting's workshop,and promote a good and fast development of the textile enterprise,firstly,we analyze the information technology development status of the textile enterprise at home and abroad,study the weaknesses of the existing computer monitoring system,introduce the system design project,and propose a system network model based on client/server(C/S)mode.Secondly,a multi-agent production monitoring and control system is developed,and the communication of the single-port-multi-protocol and a multi-thread data collection technology are studied via the multi-thread and standard template library(STL)technologies.Thirdly,the system management functions,the structure design of the database,and the technical difficulties in the process of software design are also introduced.As proved in practice,the system satisfies the production management requirements of the workshop,and implements the network management of the production information.

Influence of Twisting Degree and Number of Cords on the Structure of Silk

Properties of the fibrous material which has oriented supermolecular formations are depended on such structural factors as morphology, inter position of structure elements, and their interaction. Influence of processing on changing original structure of fibrous material during mechanical processing that causes deformation at loading is determined by peculiarities of its structure. Reversible and irreversible changes of structural elements in fibrous material causes changing of volume and sorption properties and will essentially influence on its chemical finishing processes. Influence of twisting degree and number of silk cords on structure and physical mechanical properties. Changing of supermolecular structure of thread in the process of its forming by X-ray graphic, sorption and focused beam electronic microscopic methods was researched.

Twisting of the Spermatic Cord in an Elderly Subject at the Yaounde Central Hospital: About a Case

Introduction: Twisting of the spermatic cord is part of urological emergencies. It can occur at any age with a predilection for children and adolescents. There is no literature on spermatic cord torsion in octogenarians, probably due to its rarity. The majority of recent studies show spermatic cord torsion in patients under 55 years of age. This is why we present a case of spermatic cord torsion in an 80 years old subject. Case Presentation: We present a case of torsion of the spermatic cord in an 80-year-old subject. The diagnosis was made on anamnestic and clinical grounds. The patient presented with scrotal pain, unilateral, of sudden onset, violent intensity without urinary signs with an ascended testicle. The urine dipstick was unremarkable. Management was done surgically and as an emergency. The postoperative course was satisfactory. Conclusion: Spermatic cord torsion in octogenarians is exceptional and should be suspected in the first instance in the presence of any sudden onset, severe testicular pain without urinary signs with an ascended testicle and a negative urine dipstick.