Modeling the interaction between TCP and Rate Adaptation

In this paper, we model and investigate the interaction between the TCP protocol and rate adaptation at intermediate routers. Rate adaptation aims at saving energy by controlling the offered capacity of links and adapting it to the amount of traffic. However, when TCP is used at the transport layer, the control loop of rate adaptation and one of the TCP congestion control mechanism might interact and disturb each other, compromising throughput and Quality of Service (QoS). Our investigation is lead through mathematical modeling consisting in depicting the behavior of TCP and of rate adaption through a set of Delay Differential Equations (DDEs). The model is validated against simulation results and it is shown to be accurate. The results of the sensitivity analysis of the system performance to control parameters show that rate adaptation can be effective but a careful parameter setting is needed to avoid undesired disruptive interaction among controllers at different levels, that impair QoS

Weight-control strategy for programmable CNN chips

This paper describes a hybrid weight-control strategy for the VLSI realization of programmable CNNs, based on automatic adaptation of analog control signals to levels specified by digital words. This approach merges the advantages of digital and analog programmability, achieving low areas and reduced number of control lines, simplifying the control and storage of the weight values, and eliminating their dependency on global process-parameter variations

Joint Adaptive Distributed Rate and Power Control for Wireless Networks

A novel adaptive distributed rate and power control (ADRPC) protocol is introduced for wireless networks. The proposed controller contrasts from others by providing nonlinear compensation to the problem of transmission power and bit-rate adaptation. The protocol provides control of both signal-to-interference ratio (SIR) and quality-of-service (QoS) support to bit-rate adaptation. Bit-rate adaptation is performed by local estimation of congestion levels, rendering little packet overhead, using Lyapunov based adaptive control methods. Performance of the proposed control scheme is shown through analytical proof and simulation examples

The “broken escalator” phenomenon: Vestibular dizziness interferes with locomotor adaptation

BACKGROUND: Although vestibular lesions degrade postural control we do not know the relative contributions of the magnitude of the vestibular loss and subjective vestibular symptoms to locomotor adaptation. OBJECTIVE: To study how dizzy symptoms interfere with adaptive locomotor learning. METHODS: We examined patients with contrasting peripheral vestibular deficits, vestibular neuritis in the chronic stable phase (n = 20) and strongly symptomatic unilateral Meniere’s disease (n = 15), compared to age-matched healthy controls (n = 15). We measured locomotor adaptive learning using the “broken escalator” aftereffect, simulated on a motorised moving sled. RESULTS: Patients with Meniere’s disease had an enhanced “broken escalator” postural aftereffect. More generally, the size of the locomotor aftereffect was related to how symptomatic patients were across both groups. Contrastingly, the degree of peripheral vestibular loss was not correlated with symptom load or locomotor aftereffect size. During the MOVING trials, both patient groups had larger levels of instability (trunk sway) and reduced adaptation than normal controls. CONCLUSION: Dizziness symptoms influence locomotor adaptation and its subsequent expression through motor aftereffects. Given that the unsteadiness experienced during the “broken escalator” paradigm is internally driven, the enhanced aftereffect found represents a new type of self-generated postural challenge for vestibular/unsteady patients

Brain computer interface based robotic rehabilitation with online modification of task speed

We present a systematic approach that enables online modification/adaptation of robot assisted rehabilitation exercises by continuously monitoring intention levels of patients utilizing an electroencephalogram (EEG) based Brain-Computer Interface (BCI). In particular, we use Linear Discriminant Analysis (LDA) to classify event-related synchronization (ERS) and desynchronization (ERD) patterns associated with motor imagery; however, instead of providing a binary classification output, we utilize posterior probabilities extracted from LDA classifier as the continuous-valued outputs to control a rehabilitation robot. Passive velocity field control (PVFC) is used as the underlying robot controller to map instantaneous levels of motor imagery during the movement to the speed of contour following tasks. In other words, PVFC changes the speed of contour following tasks with respect to intention levels of motor imagery. PVFC also allows decoupling of the task and the speed of the task from each other, and ensures coupled stability of the overall robot patient system. The proposed framework is implemented on AssistOn-Mobile - a series elastic actuator based on a holonomic mobile platform, and feasibility studies with healthy volunteers have been conducted test effectiveness of the proposed approach. Giving patients online control over the speed of the task, the proposed approach ensures active involvement of patients throughout exercise routines and has the potential to increase the efficacy of robot assisted therapies

Vascular changes in the rat brain during chronic hypoxia in the presence and absence of hypercapnia.

Changes in brain vascularity in adult rats during adaptation to chronic normobaric hypoxia with or without elevated CO(2) were morphometrically investigated. Immunohistochemistry with anti-rat endothelial cell antigen (RECA-1) antibody was carried out for the vascular analysis. After the rats were subjected to hypoxia for 2 to 8 weeks (wks)(10 percent O(2) in N(2)), the total area of blood vessels was measured in 6 brain regions. After 2 wks of hypoxia, the blood vessel area was found to be significantly increased in the frontal cortex, striatum, hippocampus, thalamus, cerebellum, and medulla oblongata, by 44% , 96% , 65% , 50% , 102% and 97% , respectively. The ratio of large vessels with an area &#62; 500 micro m(2) was also increased in all brain regions. Hypoxic adaptation in brain vascularity did not change during 8 wks of hypoxia, and the hypoxia-induced levels measured in the vasculature returned to control levels 2 wks after the termination of hypoxia in areas of the brain other than the cortex and thalamus. In addition, hypoxia-induced changes in terms of the total vascular area and vessel size distribution were significantly inhibited by the elevation in CO(2), whereas chronic hypercapnia without hypoxia had no effect on brain vascularity. These findings suggested that adaptations in brain vascularity in response to hypoxia are rapidly induced, and there are regional differences in the reversibility of such vascular changes. Carbon dioxide is a potent suppressor of hypoxia-induced vascular changes, and may play an important role in vascular remodeling during the process of adaptation to chronic hypoxia.</p

Activity-driven content adaptation for effective video summarisation

In this paper, we present a novel method for content adaptation and video summarization fully implemented in compressed-domain. Firstly, summarization of generic videos is modeled as the process of extracted human objects under various activities/events. Accordingly, frames are classified into five categories via fuzzy decision including shot changes (cut and gradual transitions), motion activities (camera motion and object motion) and others by using two inter-frame measurements. Secondly, human objects are detected using Haar-like features. With the detected human objects and attained frame categories, activity levels for each frame are determined to adapt with video contents. Continuous frames belonging to same category are grouped to form one activity entry as content of interest (COI) which will convert the original video into a series of activities. An overall adjustable quota is used to control the size of generated summarization for efficient streaming purpose. Upon this quota, the frames selected for summarization are determined by evenly sampling the accumulated activity levels for content adaptation. Quantitative evaluations have proved the effectiveness and efficiency of our proposed approach, which provides a more flexible and general solution for this topic as domain-specific tasks such as accurate recognition of objects can be avoided

Scheduling with Rate Adaptation under Incomplete Knowledge of Channel/Estimator Statistics

In time-varying wireless networks, the states of the communication channels are subject to random variations, and hence need to be estimated for efficient rate adaptation and scheduling. The estimation mechanism possesses inaccuracies that need to be tackled in a probabilistic framework. In this work, we study scheduling with rate adaptation in single-hop queueing networks under two levels of channel uncertainty: when the channel estimates are inaccurate but complete knowledge of the channel/estimator joint statistics is available at the scheduler; and when the knowledge of the joint statistics is incomplete. In the former case, we characterize the network stability region and show that a maximum-weight type scheduling policy is throughput-optimal. In the latter case, we propose a joint channel statistics learning - scheduling policy. With an associated trade-off in average packet delay and convergence time, the proposed policy has a stability region arbitrarily close to the stability region of the network under full knowledge of channel/estimator joint statistics.Comment: 48th Allerton Conference on Communication, Control, and Computing, Monticello, IL, Sept. 201

Stability Analysis and Stabilization Strategies for Linear Supply Chains

Due to delays in the adaptation of production or delivery rates, supply chains can be dynamically unstable with respect to perturbations in the consumption rate, which is known as "bull-whip effect". Here, we study several conceivable production strategies to stabilize supply chains, which is expressed by different specifications of the management function controlling the production speed in dependence of the stock levels. In particular, we will investigate, whether the reaction to stock levels of other producers or suppliers has a stabilizing effect. We will also demonstrate that the anticipation of future stock levels can stabilize the supply system, given the forecast horizon is long enough. To show this, we derive linear stability conditions and carry out simulations for different control strategies. The results indicate that the linear stability analysis is a helpful tool for the judgement of the stabilization effect, although unexpected deviations can occur in the non-linear regime. There are also signs of phase transitions and chaotic behavior, but this remains to be investigated more thoroughly in the future.Comment: For related work see http://www.helbing.or

How are practices made to vary? Managing practice adaptation in a multinational corporation

Research has shown that management practices are adapted and ‘made to fit’ the specific context into which they are adopted. Less attention has been paid to how organizations anticipate and purposefully influence the adaptation process. How do organizations manage the tension between allowing local adaptation of a management practice and retaining control over the practice? By studying the adaptation of a specialized quality management practice – ACE (Achieving Competitive Excellence) – in a multinational corporation in the aerospace industry, we examine how the organization manages the adaptation process at the corporate and subsidiary levels. We identified three strategies through which an organization balances the tension between standardization and variation – preserving the ‘core’ practice while allowing local adaptation at the subsidiary level: creating and certifying progressive achievement levels; setting discretionary and mandatory adaptation parameters; and differentially adapting to context-specific and systemic misfits. While previous studies have shown how and why practices vary as they diffuse, we show how practices may diffuse because they are engineered to vary for allowing a better fit with diverse contextual specificities