Impact of the arterial input function on microvascularization parameter measurements using dynamic contrast-enhanced ultrasonography

AIM: To evaluate the sources of variation influencing the microvascularization parameters measured by dynamic contrast-enhanced ultrasonography (DCE-US). METHODS: Firstly, we evaluated, in vitro , the impact of the manual repositioning of the ultrasound probe and the variations in flow rates. Experiments were conducted using a custom-made phantom setup simulating a tumor and its associated arterial input. Secondly, we evaluated, in vivo , the impact of multiple contrast agent injections and of examination day, as well as the influence of the size of region of interest (ROI) associated with the arterial input function (AIF). Experiments were conducted on xenografted B16F10 female nude mice. For all of the experiments, an ultrasound scanner along with a linear transducer was used to perform pulse inversion imaging based on linear raw data throughout the experiments. Semi-quantitative and quantitative analyses were performed using two signal-processing methods. RESULTS:In vitro , no microvascularization parameters, whether semi-quantitative or quantitative, were significantly correlated (P values from 0.059 to 0.860) with the repositioning of the probe. In addition, all semiquantitative microvascularization parameters were correlated with the flow variation while only one quantitative parameter, the tumor blood flow, exhibited P value lower than 0.05 (P = 0.004). In vivo , multiple contrast agent injections had no significant impact (P values from 0.060 to 0.885) on microvascularization parameters. In addition, it was demonstrated that semi-quantitative microvascularization parameters were correlated with the tumor growth while among the quantitative parameters, only the tissue blood flow exhibited P value lower than 0.05 (P = 0.015). Based on these results, it was demonstrated that the ROI size of the AIF had significant influence on microvascularization parameters: in the context of larger arterial ROI (from 1.17 ± 0.6 mm 3 to 3.65 ± 0.3 mm 3 ), tumor blood flow and tumor blood volume were correlated with the tumor growth, exhibiting P values lower than 0.001. CONCLUSION: AIF selection is an essential aspect of the deconvolution process to validate the quantitative DCE-US method.

Input function and simulated distributions of tritium in the North Pacific

An ocean general circulation model (OGCM) of the North Pacific with a southern open boundary condition is used to simulate the distribution and transport of tritium in the North Pacific. First, the observed tritium in precipitation dataset of GNIP/ISOHIS is chosen, and used to develop an input function of tritium for the model domain from 1951 to 1997 in terms of the triangulation for interpolation. Then, the input function is used as an upper flux for the tritium model. The OGCM with tritium is integrated for 47 years with the initial condition of zero tritium concentrations. Compared with the observations from GEOSECS and WOCE, the model generates a meridional gradient of surface tritium concentrations and the high tritium concentrations in the subsurface layer, which is consistent with that indicated in the observations. The simulated time series of total tritium fluxes from the atmosphere to the ocean shows a spike in 1963. The total inventory of tritium in the ocean changes slowly with time after 1975. Tritium enters the higher-latitude region, and then is mainly transported by the subsurface process towards the equatorial region, which is well simulated in the model. However, the difference mainly occurs at 30°N–40°N, which can be seen also in the simulation of CFCs. This difference may partly originate from the insufficient description of physical processes in the OGCM. Nevertheless, some uncertainties exist in the development of the tritium input function, which can also influence the simulated results.

A METHOD FOR CALCULATING TRANSIENT FUNCTIONS OF EQUIVALENT DETERMINISTIC INPUT

In the present paper the analytical formulas for calculating the equivalent deterministic transients for multivariable cross correlated random processes are developed.The formulas permit the determination of the Root-mean-square of the responses of a linear time-invariant system to stationary multiple random inputs in the time domain.The method is applicable in the study of flight of airplanes in atmospheric turbulence and is also useful for general engineering applications of stochastc processes control.

Electro-acupuncture at Zusanli(ST 36) to improve lower extremity motor function in sensory disturbance patients with cerebral stroke A randomized controlled study of 240 cases

BACKGROUND： Studies have shown that sensory transduction is a way to introduce needle sensation. OBJECTIVE： To observe the influence of electro-acupuncture at the ＂Zusanll＂ （ST 36） point on lower extremity motor function in various sensory disturbance patients with cerebral stroke. DESIGN, TIME AND SETTING： A randomized, controlled, clinical study was performed at the Department of Neurological Rehabilitation, China Rehabilitation Research Centre from September 2006 to June 2008. PARTICIPANTS： Patients with first-time cerebral infarction or hemorrhage, or with a stroke history, but no neurodysfunction （single damage）, were selected for this study. The subjects were right-handed and disease state was stable. A total of 240 inpatients were randomly assigned to the following groups： electro-acupuncture （n = 124） and control （n = 116）. The two groups were further assigned into sub-groups： no sensory disturbance, superficial sensory disturbance, deep sensory disturbance, and deep and superficial sensory disturbance. METHODS： On the basis of routine limb function training, the acupoint Zusanliwas utilized in all patients from the electro-acupuncture group. Perpendicular acupuncture was 3.0-4.0 cm deep. An electric acupuncture instrument was connected when patients developed the needle sensation, deqi. A stimulation pattern consisting of distant and dense waves of 50 Hz was used to elicit slight dorsal foot extension. Acupuncture was administered 5 times per week, 30 minutes per session, for 6 weeks in total. MAIN OUTCOME MEASURES： FugI-Meyer assessment （FMA） was used to evaluate lower extremity motor function; Ver.1.0 gait analysis to estimate gait （step frequency, step speed, and step scope）; lower extremity Composite Spasticity Scale （CSS） to estimate muscle spastic degree. RESULTS： Following treatment, motor function improved in both groups. Compared with the control group, FMA score, step speed, step frequency, and step scope were increased in the electro-acupuncture group, but there was no difference in lower extremity CSS scores between the electro-acupuncture and the control groups （P 〉 0.05）. Compared with the control group, Zusanli （ST 36） electro-acupuncture improved motor function indices as follows： FMA score, step frequency, step speed, and step scope of patients with no sensory disturbance （P 〈 0.05-0.01）, step frequency of patients with superficial sensory disturbance （P 〈 0.05）, and step frequency and step speed of patients with deep sensory disturbance （P 〈 0.05）. CONCLUSION： Zusanfi （ST 36） electro-acupuncture effects on lower extremity motor function in stroke patients were improved with no muscle tone rise. Therefore, this form of treatment can be used in convalescent treatment, Moreover, effects were different according to various sensory disturbance types, which suggested that sensory input influenced acupuncture effects.

Robust Stability of Uncertain Takagi-Sugeno Fuzzy Systems with Time-varying Input-delay

This paper aims to design a controller to robustly stabilize uncertain Takagi-Sugeno fuzzy systems with time- varying input delay.Based on Lyapunov-Krasovskii functional approach,the sufficient conditions for robust stabilization of such systems are given in the form of linear matrix inequali- ties.The controller design does not have to require that the time-derivative of time-varying input delay be smaller than one. A numeric example is given to show that the proposed results are effective and less conservative.

Adaptive Control Based on Neural Networks for an Uncertain 2-DOF Helicopter System With Input Deadzone and Output Constraints

In this paper, a study of control for an uncertain2-degree of freedom(DOF) helicopter system is given. The2-DOF helicopter is subject to input deadzone and output constraints. In order to cope with system uncertainties and input deadzone, the neural network technique is introduced because of its capability in approximation. In order to update the weights of the neural network, an adaptive control method is utilized to improve the system adaptability. Furthermore, the integral barrier Lyapunov function(IBLF) is adopt in control design to guarantee the condition of output constraints and boundedness of the corresponding tracking errors. The Lyapunov direct method is applied in the control design to analyze system stability and convergence. Finally, numerical simulations are conducted to prove the feasibility and effectiveness of the proposed control based on the model of Quanser's 2-DOF helicopter.

Prescribed Performance Control of One-DOF Link Manipulator With Uncertainties and Input Saturation Constraint

In this paper, we mainly address the position control problem for one-degree of freedom(DOF) link manipulator despite uncertainties and the input saturation via the backstepping technique, active disturbance rejection control(ADRC) as well as predefined tracking performance functions. The extended state observer(ESO) is employed to compensate uncertain dynamics and disturbances, and it does not rely on the accurate model of systems. The tracking differentiator(TD) is utilized to substitute the derivative of the virtual control signals, and the explosion of complexity caused by repeated differentiations of nonlinear functions is removed. The auxiliary system is used to deal with the control input limitation, and the tracking accuracy and speed are improved by predefined tracking performance functions.With the help of the input-to-state stability(ISS) and Lyapunov stability theories, it is proven that the tracking error can be gradually converged into arbitrarily small neighborhood of the origin, and the tracking error is adjusted by suitable choice of control parameters. The simulation results are presented for the verification of the theoretical claims.

Robust Adaptive Control for Robotic Systems With Input Time-Varying Delay Using Hamiltonian Method

This paper addresses the problem of robust adaptive control for robotic systems with model uncertainty and input time-varying delay. The Hamiltonian method is applied to develop the stabilization results of the robotic systems. Firstly, with the idea of shaping potential energy and the pre-feedback skill, the n degree-of-freedom(DOF) uncertain robotic systems are realized as an augmented dissipative Hamiltonian formulation with delay.Secondly, based on the obtained Hamiltonian system formulation and by using of the Lyapunov-Krasovskii(L-K) functional method, an adaptive controller is designed to show that the robotic systems can be asymptotically stabilized depending on the input delay. Meanwhile, some sufficient conditions are spelt out to guarantee the rationality and validity of the proposed control law. Finally, study of an illustrative example with simulations shows that the controller obtained in this paper works very well in handling uncertainties and input delay in the robotic systems.

Complex Function Approximation Based on Multi-ANN Approach

This paper presents a multi-ANN approximation approach to approximate complex non-linear function. Comparing with single-ANN methods the proposed approach improves and increases the approximation and generalization ability, and adaptability greatly in learning processes of networks. The simulation results have been shown that the method can be applied to the modeling and identification of complex dynamic control systems.

服务投入质量与制造业功能升级

通过将功能升级定义为产业生产重心向非制造性高端生产环节转移,本文使用多国制造业子行业面板数据研究了服务投入质量对制造业功能升级的影响。研究结果显示,服务投入质量提高能够有效促进制造业功能升级,尤其是能够有效促进制造业生产重心向管理和研发功能倾斜。异质性研究表明,相较于国外服务投入,国内服务投入质量提高对功能升级的影响更显著,高技能制造业受到服务投入质量提高的促进效果更好。机制分析表明,创新和技术溢出效应是服务投入质量影响功能升级的可能渠道。本文为制造业投入服务质量与功能升级的关系提供了跨国视角的研究,为价值链重构背景下破解西方国家功能锁定等问题提供了相应的实证借鉴。

Extended ambiguity function for bistatic MIMO radar

This paper derives the extended ambiguity function for a bistatic multiple-input multiple-output （MIMO） radar system, which includes the whole radar system parameters： geometric sensor configuration, waveforms, range, range rate, target scattering and noise characteristics. Recent research indicates the potential pa- rameter estimate performance of bistatic MIMO radars. And this ambiguity function can be used to analyze the parameter estimate performance for the relationship with the Cramer-Rao bounds of the estimated parameters. Finally, some examples are given to demonstrate the good parameter estimate performance of the bistatic MIMO radar, using the quasi-orthogonal waveforms based on Lorenz chaotic systems.

RESEARCH ON INPUT IMPEDANCE OF DIPOLE ANTENNA IN GTEM CELL

The formula of input impedance of dipole antenna in Gigahertz Transverse ElectroM agnetic(GTEM) cell based on the dyadic Green's function is first obtained in this paper. The validation of the formula is verified by the results of theoretical derivation and simulation with well agreements. In comparison with the formula of input impedance in free space, the relationship between the change of input impedance with the length of antenna and the position of antenna in GTEM cell is obtained. In addition, some meaningful conclusions are presented, which not only can be referred by the further research of ElectroM agnetic Interference(EMI) measurements in GTEM cell, but also provide the theoretical basis for testing compensation and error analysis.

Tracking Control of Uncertain Nonlinear Systems With Unknown Constant Input Delay

A robust delay compensator has been developed for a class of uncertain nonlinear systems with an unknown constant input delay.The control law consists of feedback terms based on the integral of past control values and a novel filtered tracking error,capable of compensating for input delays.Suitable Lyapunov-Krasovskii functionals are used to prove global uniformly ultimately bounded(GUUB)tracking,provided certain sufficient gain conditions,dependent on the bound of the delay,are satisfied.Simulation results illustrate the performance and robustness of the controller for different values of input delay.

The Analysis of Global Input-to-state Stability for Piecewise Affine Systems with Time-delay

In this paper, global input-to-state stability （ISS） for discrete-time piecewise affine systems with time-delay are considered Piecewise quadratic ISS-Lyapunov functions are adopted. Both Lyapunov-Razumikhiu and Lyapunov-Krasovskii methods are used The theorems of Lyapunov-Razumikhin type and Lyapunov-Krasovskii type for piecewise affine systems with time-delay are shown respectively.

冻融季温带森林土壤真菌群落结构及功能类群对不同土壤有机碳输入的响应

根系与凋落物有机碳输入变化对土壤生物群落的影响研究是目前学术界关注的热点问题,但冻融季不同有机碳输入方式将对土壤真菌群落结构及功能类群产生何种影响尚不明确。土壤真菌群落是调节森林生态系统稳定性的重要因素,有助于维持生态系统生产力时间尺度的稳定性。为了探索冻融季温带森林土壤真菌群落对控制根系和凋落物有机碳输入方式的响应特征,通过在帽儿山生态站设置4种碳源输入控制处理植物残体添加去除(DIRT):去除凋落物仅根系输入处理、去除根系仅凋落物输入处理、无碳源输入处理和同时进行根系与凋落物输入处理,采用ITS rDNA高通量测序技术和FUNGuild功能预测平台,来分析控制根系和凋落物有机碳输入方式对温带森林土壤真菌群落结构和功能类群的影响。研究结果显示:(1)不同有机碳输入方式改变了土壤真菌类群的多度:与自然生长状态下有机碳输入方式相比,根系有机碳输入比凋落物有机碳输入对土壤真菌类群多度影响更明显,去除根系碳源输入处理使真菌群落中子囊菌门含量升高19.52%,担子菌门含量下降16.77%。(2)有机碳输入方式对土壤真菌群落功能类群产生影响:与自然生长状态下有机碳输入方式相比,去除根系碳源输入处理使群落内腐生营养型真菌、病原营养型真菌数量占比增加9.79%、1.22%;去除凋落物碳源输入处理下群落内腐生营养型、病原营养型真菌数量占比下降7.58%、0.85%。(3)有机碳输入方式对真菌群落结构的影响与土壤理化环境因子有关,微生物氮的含量是主导土壤真菌群落结构出现显著差异的关键因子。以上结果表明有机碳输入方式对土壤真菌群落结构及功能类群有重要调控作用,研究结果丰富了温带森林土壤微生物群落的研究内容,为研究土壤微生态环境的变化对生态系统过程的影响提供理论支持和参考依据,此外未来的研究应重点关注不同季节间凋落物和根系输入处理对土壤真菌群落的长期影响。

带干扰项的ARZ交通流模型的时滞控制与ISS稳定性

针对线性化之后的ARZ交通流模型,已有文献通常基于如下假设:一是系统的平衡态恰好等于自由流的速度,二是进入上游路段的交通量恰好等于交通需求的数学期望,三是边界反馈不考虑时滞因素的影响.该文抛开各类限制条件,结合时滞边界控制策略,建立了具有模型漂移项和边界扰动项的PDE-PDE无穷维耦合闭环系统.具体地,采用算子半群理论,将闭环系统改写为抽象发展方程的形式;结合线性系统解与控制算子的允许性理论,证明了闭环系统的适定性;构造加权ISS-Lyapunov函数,证明了闭环系统的输入-状态稳定性(ISS),得到了反馈参数的耗散性条件.通过数值仿真实验,进一步验证本文设计的时滞控制器的有效性与参数条件的可行性.

基于Nussbaum函数的板球系统输入受限控制研究

为了实现板球系统在控制输入约束下的高精度轨迹跟踪控制,在反步法(Backstepping)的基础上采用了基于Nussbaum函数的控制输入受限控制方法。首先建立带有伺服系统的板球系统一体化模型,设计带有约束条件的控制律,设计Nussbaum函数,结合反步法设计其自适应律,最后,利用Barbalat引理证明了闭环系统的稳定性。仿真结果表明,该方法在输入受限的情况下,具有一定的抗扰动能力,以及良好的轨迹跟踪控制性能。

一种新型宽带小型化低损耗LTCC滤波器

根据滤波器技术要求,从原理层面将滤波器电路与数学公式相结合。通过广义切比雪夫函数确定了传输零点的频率再通过输入导纳公式确定了产生传输零点的元件取值,进而得到滤波电路。同时,证明了传输零点的添加不会改变通带特性。基于低温共烧多层陶瓷三维封装的工艺特性,对电路进行建模与分析,优化了滤波器电磁特性,最终得到封装尺寸为1206(3.2 mm×1.6 mm)的两款带通滤波器。滤波器30 dB矩形度(BW30dB/BW1dB)在1.75以内。低损耗的滤波器插入损耗在1.2 dB以内。高抑制的滤波器在1.68f0~2.5f0频率范围内,带外抑制在40 dB以上。该滤波器满足了无线通信系统对滤波器小型化、低损耗的要求。

考虑输出约束及外部干扰的柔性航天器振动控制

针对具有输出约束及外部干扰的柔性航天器系统,提出一种直接关节力矩输入的振动控制方法。利用哈密顿原理,系统动力学特性由偏微分方程(PDE)和常微分方程(ODE)耦合组成的分布参数模型来描述。设计了非线性干扰观测器补偿外界干扰,并基于正切型障碍李雅普诺夫函数解决了航天器姿态角度误差和振动误差的多输出约束问题。利用扩展的拉塞尔不变集原理和半群理论证明了系统的渐近稳定性。不仅实现了姿态角的位置控制,还抑制了柔性航天器的弹性振动。通过对比仿真验证了所提方法的有效性。

基于输入饱和的欠驱动水面舰艇预定义时间跟踪控制

[目的]为解决欠驱动水面舰艇(USV)在模型不确定性、强耦合特性和控制器输入饱和情况下的轨迹跟踪问题,提出基于输入饱和的USV预定义时间跟踪控制方法。[方法]针对USV模型具有非零对角项和强耦合特性问题,引入坐标变换,将系统模型转变为斜对角形式;将预定义时间性能函数与障碍Lyapunov函数(BLF)结合,保证瞬态和稳态的跟踪性能;利用自组织神经网络(SSNN)降低未知外部环境扰动和复杂的连续未知非线性项以及输入饱和产生的影响,以保证控制系统的跟踪精度,并且在线调整优化SSNN的神经元数目,减少控制系统的计算负担。[结果]基于Lyapunov稳定性理论,证明了闭环系统在预定义时间内是有界稳定的,跟踪误差始终保持在约束范围内。[结论]仿真结果表明,所提控制策略是有效的,其具有良好的跟踪性能。