A new phase for screening redundant broadcast nodes in source-independent broadcasting protocols

Following the distributed approach, source-independent broadcasting protocols select a subset of nodes in a network as broadcasting nodes to cover the entire network. The selection of broadcasting nodes is performed prior to actual message transmission. These broadcasting nodes collectively form a connected dominating set or CDS. Aiming at finding a minimum CDS, existing source-independent broadcasting protocols consist of two phases. In this paper, we propose to add a third phase to eliminate unnecessary nodes in a CDS while ensuring all remaining nodes are still connected. We call it the redundant node screening phase. This paper shows that this new phase is a very important element that has been ignored by existing source-independent broadcasting protocols. When applying the new phase on existing broadcasting protocols, the savings in terms of number of nodes in the CDS could be as high as 21% in a 1000m x 1000m network of 20 nodes. © 2011 IEEE.published_or_final_versionThe 2011 IEEE International Conference on Communications (ICC 2011), Kyoto, Japan, 5-9 June 2011. In Proceedings of the IEEE ICC, 2011, p. 1-

Self-pruning broadcasting for mobile ad hoc networks

The IEEE Global Telecommunications Conference (GLOBECOM 2009), Honolulu, HI., 30 November-4 December 2009, p. 1-6Broadcasting is a process of delivering a message to all nodes in a network. While it is important to ensure that all nodes get a copy of the broadcast message, minimizing the number of sending nodes is equally important especially in resource-constrained wireless networks. Existing broadcasting protocols based on self-pruning are ineffective in achieving these objectives. Therefore this paper proposes two protocols based on simple timer mechanisms to prioritize broadcasting of messages such that node with most uncovered neighbors rebroadcast first. Additionally a timer suppression mechanism is proposed to further enhance the effectiveness of the broadcasting protocol. Compared with an existing protocol, extensive simulation experiments confirm that the proposed protocols achieve better performance.published_or_final_versio

Enhanced termination condition for deterministic broadcasting protocols in mobile ad hoc networks

Deterministic approach to broadcasting in Mobile Ad Hoc Networks (MANETs) is effective in reducing redundant broadcasting. In this approach, a transmitting node selects a subset of its immediate or 1-hop neighbors to rebroadcast the message such that all its 2-hop neighbors will receive the message, or being covered. In order to reduce redundant broadcasting, the set of 1-hop neighbors to be covered should be reduced as much as possible. Another important aspect that affects the effectiveness of a deterministic broadcasting protocol is the termination condition that inhibits a node from transmitting a particular message unnecessarily. However, existing termination conditions are not optimized. We propose a new covered/uncovered termination condition where each node is assigned with covered/uncovered status. In this paper, we show that our covered/uncovered termination condition ensures full network coverage, does not incur any control message overhead, and yet requires the least number of rebroadcasting nodes. When we apply the termination condition to some existing deterministic broadcasting protocols, the saving in the number of broadcasting nodes can be as significant as 45% when there are 100 nodes randomly distributed in an area of 1000 x 1000 m2. ©2010 IEEE.published_or_final_versionThe 72nd IEEE Vehicular Technology Conference (VTC 2010-Fall), Ottawa, ON., 6-9 September 2010. In Proceedings of the IEEE-VTS Vehicular Technology Conference, 2010, p. 1-

Variable power broadcasting based on local information for source-dependent broadcasting protocols

A typical broadcasting protocol for wireless network usually involves fixed transmission power that covers, for example an area within 250 meters (m). However, it is often unnecessary to broadcast using fixed power because a node that needs to be covered may just be 100m away. By reducing the transmission power enough to cover this node, energy expenditure would be reduced, thus, prolonging the lifetime of battery-powered wireless networks such as Mobile Ad Hoc Networks (MANETs) and Wireless Sensor Networks (WSNs). Existing source-dependent broadcasting protocols do not have any mechanisms for adjusting the transmission power of nodes. Therefore, this paper proposes some effective mechanisms based on local neighborhood knowledge, while ensuring the overall network is still covered. Results of extensive simulations confirm the effectiveness of the proposed protocols in reducing energy consumption. © 2011 IEEE.published_or_final_versionThe 2011 IEEE Wireless Communications and Networking Conference (WCNC), Cancun, Mexico, 28-31 March 2011. In Proceedings of IEEE WCNC, 2011, p. 796-80

Enhanced variable power broadcasting based on local information in mobile ad hoc networks

Broadcasting in mobile ad hoc networks (MANETs) usually involve fixed transmission power that covers, for example an area within 250 meters. However, it is often unnecessary to broadcast using fixed power because a node that needs to be covered may just be 100 meters away. By reducing the transmission power enough to cover this node, energy expenditure would be reduced, thus, prolonging the lifetime of a battery-powered MANET. Existing works on variable power broadcasting based on local information are effective in achieving this objective. However, they are not optimized and can be improved by dynamically adjusting the transmission power based on where a broadcast message comes from. This paper proposes simple mechanisms based on local knowledge to adjust the transmission power dynamically and incorporates a timer suppression mechanism to further enhance the effectiveness of the protocols in reducing energy expenditure. Results of simulation studies confirm the effectiveness of the proposed enhancements. ©2010 IEEE.published_or_final_versionThe 2010 IEEE Wireless Communications and Networking Conference (WCNC), Sydney, Australia, 18-21 April 2010. In Proceedings of IEEE-WCNC, 2010, p. 1-

State-dependent distributed-delay model of orthogonal cutting

In this paper we present a model of turning operations with state-dependent distributed time delay. We apply the theory of regenerative machine tool chat- ter and describe the dynamics of the tool-workpiece sys- tem during cutting by delay-diferential equations. We model the cutting-force as the resultant of a force sys- tem distributed along the rake face of the tool, which results in a short distributed delay in the governing equation superimposed on the large regenerative de- lay. According to the literature on stress distribution along the rake face, the length of the chip-tool inter- face, where the distributed cutting-force system is act- ing, is function of the chip thickness, which depends on the vibrations of the tool-workpiece system due to the regenerative efect. Therefore, the additional short de- lay is state-dependent. It is shown that involving state- dependent delay in the model does not afect linear sta- bility properties, but does afect the nonlinear dynamics of the cutting process. Namely, the sense of the Hopf bi- furcation along the stability boundaries may turn from sub- to supercritical at certain spindle speed regions

Representation of cognitive reappraisal goals in frontal gamma oscillations

Recently, numerous efforts have been made to understand the neural mechanisms underlying cognitive regulation of emotion, such as cognitive reappraisal. Many studies have reported that cognitive control of emotion induces increases in neural activity of the control system, including the prefrontal cortex and the dorsal anterior cingulate cortex, and increases or decreases (depending upon the regulation goal) in neural activity of the appraisal system, including the amygdala and the insula. It has been hypothesized that information about regulation goals needs to be processed through interactions between the control and appraisal systems in order to support cognitive reappraisal. However, how this information is represented in the dynamics of cortical activity remains largely unknown. To address this, we investigated temporal changes in gamma band activity (35-55 Hz) in human electroencephalograms during a cognitive reappraisal task that was comprised of three reappraisal goals: To decease, maintain, or increase emotional responses modulated by affect-laden pictures. We examined how the characteristics of gamma oscillations, such as spectral power and large-scale phase synchronization, represented cognitive reappraisal goals. We found that left frontal gamma power decreased, was sustained, or increased when the participants suppressed, maintained, or amplified their emotions, respectively. This change in left frontal gamma power appeared during an interval of 1926 to 2453 ms after stimulus onset. We also found that the number of phase-synchronized pairs of gamma oscillations over the entire brain increased when participants regulated their emotions compared to when they maintained their emotions. These results suggest that left frontal gamma power may reflect cortical representation of emotional states modulated by cognitive reappraisal goals and gamma phase synchronization across whole brain regions may reflect emotional regulatory efforts to achieve these goals. Our study may provide the basis for an electroencephalogram-based neurofeedback system for the cognitive regulation of emotion.open0

Re-examination of the Controversial Coexistence of Traumatic Brain Injury and Posttraumatic Stress Disorder: Misdiagnosis and Self-Report Measures

The coexistence of traumatic brain injury (TBI) and posttraumatic stress disorder (PTSD) remains a controversial issue in the literature. To address this controversy, we focused primarily on the civilian-related literature of TBI and PTSD. Some investigators have argued that individuals who had been rendered unconscious or suffered amnesia due to a TBI are unable to develop PTSD because they would be unable to consciously experience the symptoms of fear, helplessness, and horror associated with the development of PTSD. Other investigators have reported that individuals who sustain TBI, regardless of its severity, can develop PTSD even in the context of prolonged unconsciousness. A careful review of the methodologies employed in these studies reveals that investigators who relied on clinical interviews of TBI patients to diagnose PTSD found little or no evidence of PTSD. In contrast, investigators who relied on PTSD questionnaires to diagnose PTSD found considerable evidence of PTSD. Further analysis revealed that many of the TBI patients who were initially diagnosed with PTSD according to self-report questionnaires did not meet the diagnostic criteria for PTSD upon completion of a clinical interview. In particular, patients with severe TBI were often misdiagnosed with PTSD. A number of investigators found that many of the severe TBI patients failed to follow the questionnaire instructions and erroneously endorsed PTSD symptoms because of their cognitive difficulties. Because PTSD questionnaires are not designed to discriminate between PTSD and TBI symptoms or determine whether a patient's responses are accurate or exaggerated, studies that rely on self-report questionnaires to evaluate PTSD in TBI patients are at risk of misdiagnosing PTSD. Further research should evaluate the degree to which misdiagnosis of PTSD occurs in individuals who have sustained mild TBI