Non-Linear Response of Tethers Subjected to Parametric Excitation in Submerged Floating Tunnels

For the study of the non-linear response of inclined tethers subjected to parametric excitation in submerged floating tunnels, a theoretical model for coupled tube-tether vibration is developed. Upon the assumption that the static equilibri- um position of the tether is a quadratic parabola, the governing differential equations of the tether motion are derived by use of the Hamihon principle. An approximate numerical solution is obtained by use of Galerkin method and Runge-kutta method. The results show that, when the static equilibrium position of the tether is assumed to be. a quadratic parabola, the tether sag effect on its vibration may be reflected; the tether sag results in the asymmetry of tether vibration amplitude ; for the reduction of the tether amplitude, the buoyant unit weight of the tether should approach to zero as far as possible during the design.

Anti-Disturbance Control for Tethered Aircraft System With Deferred Output Constraints

In this paper,we investigate the peaking issue of extended state observers and the anti-disturbance control problem of tethered aircraft systems subject to the unstable flight of the main aircraft,airflow disturbances and deferred output constraints.Independent of exact initial values,a modified extended state observer is constructed from a shifting function such that not only the peaking issue inherently in the observer is circumvented completely but also the accurate estimation of the lumped disturbance is guaranteed.Meanwhile,to deal with deferred output constraints,an improved output constrained controller is employed by integrating the shifting function into the barrier Lyapunov function.Then,by combining the modified observer and the improved controller,an anti-disturbance control scheme is presented,which ensures that the outputs with any bounded initial conditions satisfy the constraints after a pre-specified finite time,and the tethered aircraft tracks the desired trajectory accurately.Finally,both a theoretical proof and simulation results verify the effectiveness of the proposed control scheme.

基于TCP流RTT测量的Tethering行为检测架构

Tethering行为是一种移动设备通过自身传输介质共享其互联网连接服务的行为,其不仅对移动互联网造成运营压力和收益影响,还对移动互联网隐藏其内部网络结构,造成网络安全隐患。由于Tethering存在诸多混淆和规避方法,现有Tethering行为检测技术难以有效检测。鉴于此,分析了移动互联网通信基站中,Tethering行为终端在数据流量的处理、转发等特征,以及移动互联网用户流量中传输控制协议(TCP)流往返时延(RTT)的相关特性,提出一种基于TCP流RTT测量的Tethering检测架构,构建了所提架构的测试网络环境。实验结果表明:所提架构在检测Tethering行为中具有有效性,实现了利用无监督学习和被动监测网络流量对移动互联网中Tethering行为的有效检测,对Tethering行为检测的准确率达到97.50%。

Effect of lengthening alkyl spacer on hydroformylation performance of tethered-phosphine modified Rh/SiO_2 catalyst

Rh/SiO2 catalysts with tethered-phosphines with different alkyl spacer lengths have been prepared,tested and characterized.Lengthening the alkyl spacer of the tethered-phosphine improved the flexibility of tethered-phospine,promoted the formation of active species and enhanced the activity of hydroformylation over other tethered-phosphine modified Rh/SiO2 catalysts.

脊髓拴系综合征手术治疗的研究现状

脊髓拴系综合征（tethered cord syndrome,TCS）是由遗传、发育或后天因素等导致的脊髓和神经被非弹性结构固定,在生长发育或运动过程中脊髓和神经在一定的牵拉力下血供发生变化,造成其氧化代谢功能受损,并由此产生一系列以畸形和神经功能障碍为代表的临床综合征[1-3]。TCS不仅存在脊髓圆锥的牵拉损伤,也存在神经和神经根的牵拉损伤[4、5],

脊髓栓系的诊断及合并脊柱侧凸的手术治疗进展

脊髓栓系综合征(tethered spinal cord syndrome,TCS)是由各种先天因素和后天因素导致脊髓或圆锥受拉,脊髓缺血、缺氧,受到损伤发生病理改变而出现的一系列神经功能损伤的症状和畸形的综合征。1953年在临床上首次报道,1981年由Yamada命名[1]。脊髓栓系出现临床症状的不多,因此早期脊髓栓系的诊断并不多。随着影像技术,特别是MR技术的发展,一些隐匿的脊髓栓系被人们发现的越来越多。

Boundary Layer Characteristics and Numerical Simulation Analysis of Winter Dense Fog in Nanjing

Based on the boundary layer data of winter dense fog in 2007 from Nanjing University of Information Science & Technology,the profile characteristics of temperature,wind direction,wind speed and humidity in a dense fog weather on December 13-14 in 2007 were analyzed,as well as their evolution laws in the formation and dispersion of fog,and the boundary layer characteristics of winter dense fog in Nanjing were revealed,while the development of fog was simulated by means of mesoscale numerical model.The results showed that the formation and dispersion of fog was greatly affected by inversion and humidity in the surface layer,and the wind direction in the surface layer also had effect on the formation and dispersion of advection fog.Mesoscale numerical model could preferably simulate the evolution of temperature,humidity,vertical speed in the development of fog,and the simulation of water vapor content in the fog could forecast the formation and dispersion of fog.

术中直接电刺激在脊髓栓系综合征手术中的应用

脊髓栓系综合征（tethered cord syndrome,TCS）为各种因素导致脊髓圆锥受到牵拉而引起的神经功能障碍症候群[1]。近年来术中应用显微外科和体感诱发电位（somatosensory evoked potential,SEP）、运动诱发电位（motor evoked potential,MEP）等技术显著提高了患者预后,

Advances in dynamics and control of tethered satellite systems

The concept of tethered satellite system （TSS） promises to revolutionize many aspects of space exploration and exploitation. It provides not only numerous possible and valuable applications, but also challenging and interesting problems related to their dynamics, control, and physical implementation. Over the past decades, this exciting topic has attracted significant attention from many researchers and gained a vast number of analytical, numerical and experimental achievements with a focus on the two essential aspects of both dynamics and control. This review article presents the historic background and recent hot topics for the space tethers, and introduces the dynamics and control of TSSs in a progressive manner, from basic operating principles to the state-of-the-art achievements.

Review of deployment technology for tethered satellite systems

Tethered satellite systems（TSSs） have attracted significant attention due to their potential and valuable applications for scientific research. With the development of various launched on-orbit missions, the deployment of tethers is considered a crucial technology for operation of a TSS. Both past orbiting experiments and numerical results have shown that oscillations of the deployed tether due to the Coriolis force and environmental perturbations are inevitable and that the impact between the space tether and end-body at the end of the deployment process leads to complicated nonlinear phenomena. Hence, a set of suitable control methods plays a fundamental role in tether deployment. This review article summarizes previous work on aspects of the dynamics, control, and ground-based experiments of tether deployment. The relevant basic principles, analytical expressions, simulation cases, and experimental results are presented as well.

Measurement of single-fish target strength in the South China Sea

We measured the target strength （TS） of three commercial fish species： whitespotted spinefoot （Siganus canaliculatus）, black porgy （Acanthopagrus schlegelii）, and creek red bream （Lutjanus argentimaculatus）, in the South China Sea. The TS of caged or tethered fish （n=76 total） was measured using a Simrad EY60 portable scientific echosounder at 120 kHz. We evaluated the relationship between TS and total length （TL, cm） for the three species. This is the first attempt to use split-beam acoustics to measure single-fish TS in the South China Sea by Chinese researchers. Our results will improve the accuracy and precision of acoustic abundance estimates of commercially important species and fi.trther the development of underwater acoustic survey techniques in fisheries in the South China Sea.

Effects of Serum Calcium and Phosphorus under Different Feeding Conditions on Production Traits of Young Xinjiang Brown Bulls

[Objective] In the Xinjiang new era from October 2012 to February 2013, agricultural and animal husbandry Co. Ltd. feedlot Yining Tuogelake village used tethered and scattered feeding methods to conduct fattening young Xinjiang brown cattle experiment. [Method] The 16-month-old young Xinjiang brown bulls were se- lected totaling 68 heads, divided into scattered group and tethered group. Male claves were taken as test subjects from October to February of following year and body conformation linear evaluation were made, followed by measurement of body size indexes and Regular collection of Blood samples. [Result] In the two feeding ways, scattered group feeding improved the ADG of youth Xinjiang brown cattle bull calf （P〈0.01）, and the whole calf ADG 845.58g was significantly higher than that in tethered group at 619.11g, increasing by 36.58%; furthermore, scattered group in the December, January and February average daily weight gain was significantly higher compared with the tethered group at 13.61%, 32.32%, 53.47%, respectively. Scattered group feeding significantly increased the young calf serum phosphorus content （P〈0.01）, higher than the tethered group at 0.62%, 7.89%, 14.29% in February, December and January respectively. But the tethered feeding young cattle serum phosphorus content gradually declined. Of the two groups, male calf serum calcium content had little effects on the serum calcium with insignificant difference （P〉0.05）. Bulls by scattered feeding method was proved faster and better in the whole growth period, in terms of body height, body length, circumference, leg cir- cumference, rump length, waist high, sciatic wide, hip width basically in the contin- ued growth trend. [Conclusion] Scattered feeding can significantly improve the young Xinjiang brown cattle＇s daily gain, and accelerate the body height, heart girth and body length etc body growth. What＇s more, scattered feeding serum calcium and phosphorus content are significantly higher than tethered feeding.

Nonlinear dynamics of flexible tethered satellite system subject to space environment

The paper studies the nonlinear dynamics of a flexible tethered satellite system subject to space environments, such as the J2 perturbation, the air drag force, the solar pressure, the heating effect, and the orbital eccentricity. The flexible tether is modeled as a series of lumped masses and viscoelastic dampers so that a finite multi- degree-of-freedom nonlinear system is obtained. The stability of equilibrium positions of the nonlinear system is then analyzed via a simplified two-degree-freedom model in an orbital reference frame. In-plane motions of the tethered satellite system are studied numerically, taking the space environments into account. A large number of numerical simulations show that the flexible tethered satellite system displays nonlinear dynamic characteristics, such as bifurcations, quasi-periodic oscillations, and chaotic motions.

Parametric Vibration of Submerged Floating Tunnel Tether Under Random Excitation

For the study of the parametric vibration response of submerged floating tunnel tether under random excitation, a nonlinear random parametric vibration equation of coupled tether and tube of submerged floating tunnel is set up. Subsequently, vibration response of tether in the tether-tube system is analyzed by Monte Carlo method. It may be concluded that when the tube is subjected to zero-mean Gaussian white noise random excitation, the displacement and velocity root mean square responses of tether reach the peak if the circular frequency of tube doubles that of tether; the displacement and velocity root mean square responses of tether increase as the random excitation root mean square increases; owing to the damping force of water, the displacement and velocity root mean square responses of tether decrease rapidly compared with tether in air; increasing the damping of the tether or tube reduces the displacement and velocity root mean square responses of tether; the large-amplitude vibration of tether may be avoided by locating dampers on the tether or tube.

Microsurgical efficacy in 326 children with tethered cord syndrome: a retrospective analysis

Tethered cord syndrome is a progressive disease with a typically insidious onset in infants and children, and which can lead to persistent progress of neurological deficits and a high rate of disability without timely intervention. The purpose of this study was to investigate the curative effect of microsurgery in children with different types of tethered cord syndrome. In this study, we analyzed 326 patients with tethered cord syndrome, aged from 2 months to 14 years old, who were followed for 3-36 months after microscopic surgery. Based on clinical manifestations and imaging findings, these patients were classified into five types： tight ilium terminale （53 cases）, lipomyelome- ningocele （55 cases）, lipomatous malformation （124 cases）, postoperative adhesions （56 cases）, and split cord malformation （38 cases）. All patients underwent microsurgery. Curative effects were measured before and 3 months after surgery by Spina Bifida Neurological Scale based on sensory and motor functions, reflexes, and bladder and bowel function. The results showed that Spina Bifida Neurological Scale scores improved in all five types after surgery. Overall effective rates in these patients were 75%. Effective rates were 91% in tight ilium terminale, 84% in lipomyelomeningocele, 65% in lipomatous malformation, 75% in postoperative adhesion, and 79% in split cord mal- formation. Binary logistic regression analysis revealed that types of tethered cord syndrome （lipoma-type or not） and symptom duration before surgery were independent influencing factors of surgical outcome. These results show that therapeutic effect is markedly different in patients with different types of tethered cord syndrome. Suitable clinical classification for tethered cord syndrome will be helpful in predicting prognosis and guiding treatment. This trial has been registered in the Chinese Clinical Trial Registry （registration number： ChiCTR1800016464）.

Seismic Response of Submerged Floating Tunnel Tether

A mathematical equation for vibration of submerged floating tunnel tether under the effects of earthquake and parametric excitation is presented. Multi-step Galerkin method is used to simplify this equation and the fourth-order Runge-Kuta integration method is used for numerical analysis. Finally, vibration response of submerged floating tunnel tether subjected to earthquake and parametric excitation is analyzed in a few numerical examples. The results show that the vibration response of tether varies with the seismic wave type; the steady maximum mid-span displacement of tether subjected to seismic wave keeps constant when parametric resonance takes place; the transient maximum mid-span displacement of tether is related to the peak value of input seismic wave acceleration.

Hill Instability Analysis of TLP Tether Subjected to Combined Platform Surge and Heave Motions

This paper presents the Hill instability analysis of Tension keg Platform （TLP） tether in deep sea. The 2-D nonlinear beanl model, which is undergoing coupled axial and transverse vibrations, is applied. The governing equations are reduced to nonlinear Hill equation by use of the Galerkin＇ s method and the modes superposition principle. The Hill instability charted up to large parameters is obtained. An important parameter M is defined and can be expressed as the functions of tether length, the platform surge and heave motion amplitudes. Some example studies are performed for various envirotnnental conditions. The results demonstrate that the nonlinear coupling between the axial and transverse vibrations has a significant effect on the response of structure. It needs to be considered for the accurate dynamic analysis of long TI2 tether subjected to the combined platfolna surge and heave motions.

Effects of magnetic field,porosity,and wall properties for anisotropically elastic multi-stenosis arteries on blood flow characteristics

A mathematical model for blood flow through an elastic artery with multistenosis under the effect of a magnetic field in a porous medium is presented. The considered arterial segment is simulated by an anisotropically elastic cylindrical tube filled with a viscous incompressible electrically conducting fluid representing blood. An artery with mild local narrowing in its lumen forming a stenosis is analyzed. The effects of arterial wall parameters represent viscoelastic stresses along the longitudinal and circumferential directions T t and T θ , respectively. The degree of anisotropy of the vessel wall γ, total mass of the vessel, and surrounding tissues M and contributions of the viscous and elastic constraints to the total tethering C and K respectively on resistance impedance, wall shear stress distribution, and radial and axial velocities are illustrated. Also, the effects of the stenosis shape m, the constant of permeability κ, the Hartmann number Ha and the maximum height of the stenosis size δ on the fluid flow characteristics are investigated. The results show that the flow is appreciably influenced by surrounding connective tissues of the arterial wall motion, and the degree of anisotropy of the vessel wall plays an important role in determining the material of the artery. Further, the wall shear stress distribution increases with increasing T t and γ while decreases with increasing T θ , M, C, and K. Transmission of the wall shear stress distribution and resistance impedance at the wall surface through a tethered tube are substantially lower than those through a free tube, while the shearing stress distribution at the stenosis throat has inverse characteristic through totally tethered and free tubes. The trapping bolus increases in size toward the line center of the tube as the permeability constant κ increases and decreases with the Hartmann number Ha increased. Finally, the trapping bolus appears, gradually in the case of non-symmetric stenosis, and disappears in the case of symmetric stenosis. The size of trapped bolus for the stream lines in a free isotropic tube （i.e., a tube initially unstressed） is smaller than those in a tethered tube.

Observation and modeling of vertical carbon dioxide distribution in a heavily polluted suburban environment

The vertical distribution of carbon dioxide(CO2)is important for the calibration and validation of transport models and remote sensing measurements.Due to the large mass and volume of traditional instruments as well as supporting systems,in-situ measurements of the CO2 vertical profile within the boundary layer are rare.This study used a miniaturized CO2 monitoring instrument based on a low-cost non-dispersive infrared(NDIR)sensor to measure the CO2 vertical profile and meteorological parameters of the lower troposphere(0–1000 m)in southwestern Shijiazhuang,Hebei Province,China.The sensors were onboard a tethered balloon with two processes:the ascending process and the descending process.The results showed that the overall trend of CO2 concentration decreased with height.Weather conditions and CO2 emission sources caused fluctuations in CO2 concentrations.The CO2 concentration varied from morning to afternoon due mainly to the faster spread of air mass during daytime,with strong convections and the accumulation of emissions at night.The low-cost sensor produced results consistent with the traditional gas chromatography method.The Weather Research and Forecasting model could not capture the CO2 profiles well due mainly to the bad performances in boundary layer height and the potential outdated fossil fuel emissions around the experimental site.This experiment is the first successful attempt to observe the CO2 vertical distribution in the lower troposphere by using lowcost NDIR sensors.The results help us to understand the vertical structure of CO2 in the boundary layer,and provide data for calibrating and validating transport models.

Numerical investigation of dynamical behavior of tethered rigid spheres in supersonic flow

The dynamical behavior of two tethered rigid spheres in a supersonic flow is numerically investigated. The tethered lengths and radius ratios of the two spheres are different. The two spheres, which are centroid axially aligned initially, are held stationary first, then released, and subsequently let fly freely in a supersonic flow. The mean qualities of the system and the qualities of the bigger sphere are considered and compared with the situations without the tether. In the separation process, six types of motion caused by the spheres, tether, and fluid interaction are found. The results show that the mean x-velocity of the system changes in a different manner for different radius ratios, and the x-velocity of the bigger sphere is uniformly reduced but through different mechanisms.