Entrainment-enhanced neural oscillator for rhythmic motion control

We propose a new neural oscillator model to attain rhythmic movements of robotic arms that features enhanced entrainment property. It is known that neural oscillator networks could produce rhythmic commands efficiently and robustly under the changing task environment. However, when a quasi-periodic or non-periodic signal is inputted into the neural oscillator, even the most widely used Matsuoka’s neural oscillator (MNO) may not be entrained to the signal. Therefore, most existing neural oscillator models are only applicable to a particular situation, and if they are coupled to the joints of robotic arms, they may not be capable of achieving human-like rhythmic movement. In this paper, we perform simulations of rotating a crank by a two-link planar arm whose joints are coupled to the proposed entrainment-enhanced neural oscillator (EENO). Specifically, we demonstrate the excellence of EENO and compare it with that of MNO by optimizing their parameters based on simulated annealing (SA). In addition, we show an impressive capability of self-adaptation of EENO that enables the planar arm to make adaptive changes from a circular motion into an elliptical motion. To the authors’ knowledge, this study seems to be the first attempt to enable the oscillator-coupled robotic arm to track a desired trajectory interacting with the environment.     

Dynamic frequency and voltage scaling for a multiple-clock-domain microprocessor

Multiple clock domains is one solution to the increasing problem of propagating the clock signal across increasingly larger and faster chips. The ability to independently scale frequency and voltage in each domain creates a powerful means of reducing power dissipation. A multiple clock domain (MCD) microarchitecture, which uses a globally asynchronous, locally synchronous (GALS) clocking style, permits future aggressive frequency increases, maintains a synchronous design methodology, and exploits the trend of making functional blocks more autonomous. In MCD, each processor domain is internally synchronous, but domains operate asynchronously with respect to one another. Designers still apply existing synchronous design techniques to each domain, but global clock skew is no longer a constraint. Moreover, domains can have independent voltage and frequency control, enabling dynamic voltage scaling at the domain level.     

Kernel duration and modulation gain in a coupled oscillator model and their implications on the progression of seizures

The coupled oscillator model has previously been used for the simulation of neuronal activities in in?vitro rat hippocampal slice seizure data and the evaluation of seizure suppression algorithms. Each model unit can be described as either an oscillator which can generate action potential spike trains without inputs, or a threshold-based unit. With the change of only one parameter, each unit can either be an oscillator or a threshold-based spiking unit. This would eliminate the need of a new set of equations for each type of unit. Previous analysis has suggested that long kernel duration and imbalance of inhibitory feedback can cause the system to intermittently transition into and out of ictal activities. The state transitions of seizure-like events were investigated here; specifically, how the system excitability may change when the system underwent transitions in the preictal and postictal processes. Analysis showed that the area of the excitation kernel is positively correlated with the mean firing rate of ictal activity. The kernel duration is also correlated to the amount of ictal activity. The transition into ictal involved the escape from the saddle point foci in the state space trajectory identified using Newton's method.     

Application of the modified frequency formulation to a nonlinear oscillator

He’s frequency formulation is used to obtain the relationship between the frequency and amplitude of a nonlinear oscillator. The general approach is to choose two linear oscillators; in this paper, however, one linear oscillator and the Duffing oscillator are chosen as trial equations. The solution procedure is of utter simplicity, while the result is of high accuracy.     

A feedback oscillator model for circulatory autoregulation

Circulatory autregulation is the phenomenon whereby an isolated organ can maintain a constant or almost-constant blood flow rate over a range of perfusion pressures. A mathematical model is developed, based on work reported in the physiological literature, and tuned to show that autoregulation can be accomplished by pressure-induced oscillations in arteriolar radius. Various features known lo be exhibited by skeletal muscle and by stretch receptors are incorporated in the model of smooth muscle surrounding the arterioles.     

Chaotic synchronisation for coupled neural networks based on T-S fuzzy theory

Chaotic synchronisation problems for fuzzy neural networks with hybrid coupling are investigated in this paper. A novel concept that can make use of more relaxed variables by employing the new type of augmented matrices with Kronecker product operation is proposed. The proposed method can handle multitude of Kronecker product operation in Lyapunov-Krasovskii functional, and introduce more arbitrary matrices to reduce the conservatism. Since the expression based on linear matrix inequality is used, the synchronisation criteria can be easily checked in practice. Numerical simulation examples are provided to verify the effectiveness and the applicability of the proposed method.     

Chirp scaling algorithm for bi-static SAR using a precise range model

Among the currently available chirp scaling algorithms for bi-static SAR, some compromise with approximation in the range model, while some others use the equivalent method by first changing bi-static SAR into mono-static SAR then apply chirp scaling algorithm of mono-static SAR. Consequently, as the squint angles get large, the performance of focusing will deteriorate significantly. This paper, however, abandons those traditional solutions to the bi-static imaging problems and introduces a novel method, based on the space model of bi-static platforms. First, a precise range model is established. Then, a new chirp scaling algorithm for bi-static SAR using the precise range model is advanced. It is theoretically proven that this is an analytic solution of the bi-static chirp scaling algorithm. Images can be focused accurately even with large squint angles. At last simulations with large squint angles are made to verify the validity of the algorithm. Supported by the National Basic Research Program of China     

A scaling model for electrowetting-on-dielectric microfluidic actuators

A hydrodynamic scaling model of droplet actuation in an electrowetting-on-dielectric (EWD) actuator is presented that takes into account the effects of contact angle hysteresis, drag from the filler fluid, drag from the solid walls, and change in the actuation force while a droplet traverses a neighboring electrode. Based on this model, the threshold voltage, V _T, for droplet actuation is estimated as a function of the filler medium of a scaled device. It is shown that scaling models of droplet splitting and liquid dispensing all show a similar scaling dependence on [t/ε_r(d/L)]^1/2, where t is insulator thickness and d/L is the aspect ratio of the device. It is also determined that reliable operation of a EWD actuator is possible as long as the device is operated within the limits of the Lippmann–Young equation. The upper limit on applied voltage, V _sat, corresponds to contact-angle saturation. The minimum 3-electrode splitting voltages as a function of aspect ratio d/L < 1 for an oil medium are less than V _sat. However, for an air medium the minimum voltage for 3-electrode droplet splitting exceeds V _sat for d/L ≥ 0.4. EWD actuators were fabricated to operate with droplets down to 35pl. Reasonable scaling results were achieved.

一种频率稳定的低功耗振荡器电路设计

设计了一种频率稳定的低功耗张弛振荡器电路。采用恒流源对电容两端同时充电和放电,然后将电容两端电压送入后级比较器进行判决,使得输出频率只与恒流源电流、电容以及比较器比较窗口相关。该电路采用GSMC 0.18μm CMOS工艺,在5 V电源电压以及室温条件下仿真,输出频率为123.6 kHz,平均电流消耗为2.67μA;在2 V～5.5 V电源电压和-40℃-+85℃的温度变化范围内,输出频率精度在-6.5%-1.3%范围内。     

Beyond synchronization: String instability in coupled harmonic oscillator systems

In this paper, we consider the problem of disturbance response and error amplification for a simple system of coupled harmonic oscillators. We first suppose that identical oscillators are connected in a string in which each oscillator attempts to track its predecessor by using the same control law that depends on the relative position information from its immediate predecessor. Such an oscillator string is called a homogeneous oscillator string with predecessor‐following architecture. Motivated by terminology from the problem of vehicle platooning, we say that the synchronized oscillator system is string unstable if the effect of a disturbance to the lead oscillator is amplified as it propagates along the string. With the use of a new Bode‐like integral relation that must be satisfied by the complementary sensitivity function, we provide sufficient conditions for string instability. The sufficient conditions show that any string of oscillators that satisfies certain time domain performance specifications and bandwidth limitations must necessarily be string unstable. We further introduce a concept of time headway for the oscillator system and extend our analysis of string instability to consider the heterogeneous oscillator string and a more general communication range. Copyright © 2014 John Wiley & Sons, Ltd.     

Self-consistent compensated microfield model for a strongly coupled plasma

A compensated microfield model of plasma nonideality is proposed as an improvement of the traditional microfield models. In this model, a double contribution of a microfield to the truncation of statistical sums removed. The new method of truncation of the statistical sums of atoms or ions is compared with the results of experiments and computations performed by well-known Debye-type and other models. It is shown that only the microfield model correctly describes experiments. Ionization of Li and Hg atoms is calculated. The effect of metallization of plasma—an abrupt increase of ionization from zero to a single ionization at low temperatures and nearly normal densities—is qualitatively described. The results of calculation of Hg vapor ionization qualitatively agree with known experimental results on the measurement of electric conductivity of this vapor.     

Universal scaling functions of a dissipative Manna model

This study uses a losing probability f to measure the magnitude of the bulk dissipation of a dissipative Manna model where P(s;r,L,f), the probability distribution of toppling size s, on a L×(L/r) square lattice is calculated. This approach assumes that the bulk dissipation corresponds to a characteristic length ξ. The finding ξ∼f−ν leads to P(s;r,L,f)=s−τH(s/D[L/Ar],[L/Ar]fν) where H is a two-variable universal scaling function, τ, D, and ν are exponents, and Ar is a nonuniversal metric factor determined by the calculation of moment.     

双头垄断市场中广告模型的混沌动态特性

提出了一个二维离散动态广告模型,描述了两强垄断的市场中,由广告竞争引起市场份额的动态变化.在一定的参数下,对称的动态模型在二维相空间中将发生混沌同步,采用横向Lyapunov指数判定了模型的同步稳定性.定义了使模型具有经济意义的可行集,通过理论分析和数值仿真相结合的方法得到可行集的边界.通过对模型的同胚变换可得到:如果对角线上的混沌吸引子在垂直于对角线方向上局部稳定,那么它在可行集的范围内也全局稳定.     

Energy measurement,modeling, and prediction for processors with frequency scaling

The energy consumption is an important aspect of today’s processors and a large variety of research approaches deal with reducing the energy consumption for specific application codes on different platforms under certain constraints. These research approaches are based on energy information acquired by very different means, such as hardware settings with power-meters, software methods with hardware counters available for more recent CPUs, or simulations based on theoretical models. In this article, all of these energy acquisition methods are investigated and compared. As application programs, we consider the SPEC CPU2006 integer and floating-point benchmark collections, which represent a large variety of applications from different areas. The investigations are done for single multicore CPUs with the goal to get more insight into their energy consumption behavior. An experimental evaluation is performed on three recent processor types with dynamic voltage–frequency scaling. The article compares the measured energy and the energy provided by hardware counters with the energy predicted by simulation models. The comparison shows that the simulation models are able to capture the energy consumption quite accurately.     

Bi-level model reduction for coupled problems

In this work a methodology is proposed for the optimization of coupled problems, and applied to a 3D flexible wing. First, a computational fluid dynamics code coupled with a structural model is run to obtain the pressures and displacements for different wing geometries controlled by the design variables. Secondly, the data are reduced by Proper Orthogonal Decomposition (POD), allowing to expand any field as a linear combination of specific modes; finally, a surrogate model based on Moving Least Squares (MLS) is built to express the POD coefficients directly as functions of the design variables. After the validation of this bi-level model reduction strategy, the approximate models are used for the multidisciplinary optimization of the wing. The proposed method leads to a reduction of the weight by 6.6%, and the verification of the solution with the accurate numerical solvers confirms that the solution is feasible.     

A symmetric coupled line equivalent circuit model for asymmetric coupled lines

A new equivalent circuit model is proposed for an asymmetric coupled line based on a symmetric coupled line. The proposed equivalent circuit consists of a symmetric coupled line and two ideal transformers to represent an asymmetric coupled line and can be easily incorporated into the existing microwave and RF circuit simulators. This makes it easier to model and simulate the asymmetric coupled line circuits in terms of simple symmetric coupled lines. Using the proposed equivalent circuit model, it is shown that an asymmetric coupled line coupler is electrically equivalent to a symmetric coupled line coupler with transformed port impedances and the relation between the two couplers is investigated through the established equivalence. The validity of the proposed model is confirmed through the analysis of the directional couplers and the impedance transformers involving the asymmetric coupled lines. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:277–282, 2016.     

A semantic model for actions and events in ambient intelligence

Event ma nagement and response generation are two essential aspects of systems for ambient intelligence. This work proposes handling these issues through the use of a semantic model for ambient intelligence which, under the umbrella of a philosophical and common-sense optic, describes what actions and events are, how they are connected, and how computational systems should think about their meaning. This model entails an approach with which to both reason about and model context events and generate behavioral responses to those events, when necessary. The model supports this ad hoc response generation by automatically composing services when those which are available do not meet the expected functionality (without requesting user intervention). An evaluation methodology is presented and illustrated with a case scenario, in which synthetic data has been generated to emulate events and analyze the system response. The evaluation of the system response is carried out on the basis of a vector of attributes.     

High performance dynamic voltage/frequency scaling algorithm for real-time dynamic load management

Modern cyber-physical systems assume a complex and dynamic interaction between the real world and the computing system in real-time. In this context, changes in the physical environment trigger changes in the computational load to execute. On the other hand, task migration services offered by networked control systems require also management of dynamic real-time computing load in nodes. In such systems it would be difficult, if not impossible, to analyse off-line all the possible combinations of processor loads. For this reason, it is worthwhile attempting to define new flexible architectures that enable computing systems to adapt to potential changes in the environment.We assume a system composed by three main components: the first one is responsible of the management of the requests arisen when new tasks require to be executed. This management component asks to the second component about the resources available to accept the new tasks. The second component performs a feasibility analysis to determine if the new tasks can be accepted coping with its real-time constraints. A new processor speed is also computed. A third component monitors the execution of tasks applying a fixed priority scheduling policy and additionally controlling the frequency of the processor.This paper focus on the second component providing a “correct” (a task never is accepted if it is not schedulable) and “near-exact” (a task is rarely rejected if it is schedulable) algorithm that can be applicable in practice because its low/medium and predictable computational cost. The algorithm analyses task admission in terms of processor frequency scaling. The paper presents the details of a novel algorithm to analyse tasks admission and processor frequency assignment. Additionally, we perform several simulations to evaluate the comparative performance of the proposed approach. This evaluation is made in terms of energy consumption, task rejection ratios, and real computing costs. The results of simulations show that from the cost, execution predictability, and task acceptance points of view, the proposed algorithm mostly outperforms other constant voltage scaling algorithms.     

VMDFS: virtual machine dynamic frequency scaling framework in cloud computing

Development of modern techniques, such as virtualization, underlies new solutions to the problem of reducing energy consumption in cloud computing. However, for the infrastructure as a service providers, it would be a difficult process to guarantee energy saving. Analysis of the workload of applications shows that the average utilization of virtual machines has many fluctuations; therefore, deciding about how to control such fluctuations in virtual machines plays a significant role in improving the energy consumption of datacenters. In this study, an adaptable model called virtual machine dynamic frequency system (VMDFS) has been developed whose its innovation is monitoring the average fluctuations of workloads to vary the CPU frequency of virtual machines at runtime, dynamically. In this model, enhanced exponential moving average method is used to predict workload fluctuations, and then after calculating a smoothing coefficient for the utilization fluctuations, the coefficient is used to control the CPU frequency (or computing power) of virtual machines. The proposed model was compared with several base line approaches such as DVFS using real datasets from CoMon project (PlanetLab). The results of experiments on VMDFS show that besides the reduced service-level agreement violation by up to 43.22%, the overall energy consumption is reduced by 40.16%. In addition, the overall runtime before a host shutdown increased by 17.44% in average, while the runtime before a virtual machine migration increased by 7.2%. This also shows an overall decrease in the number of migrations.