THash: A Practical Network Optimization Scheme for DHT-based P2P Applications

International audienceP2P platforms have been criticized because of the heavy strain that they can inflict on costly inter-domain links of network operators. It is therefore mandatory to develop network optimization schemes for controlling the load generated by a P2P platform on an operator network. While many research efforts exist on centralized tracker-based systems, in recent years multiple DHT-based P2P platforms have been widely deployed and considered as commercial services due to their scalability and fault tolerance. Finding network optimization for DHT-based P2P applications has thereby potential large practical impacts. In this paper, we present THash, a simple scheme that implements a distributed and effective network optimization for DHT systems. THash uses standard DHT put/get semantics and utilizes a triple hash method to guide the DHT clients to choose their sharing peers in proper domains. We have implemented THash in a major commercial P2P system (PPLive), using the standard ALTO/P4P protocol as the network information source. We conducted experiments over this network in real operation and observed that compared with Native DHT, THash reduced respectively by 47.4% and 67.7% the inter-PID and inter-AS traffic, while reducing the average downloading time by 14.6% to 24.5%

Network Optimization for DHT-based Applications

International audienceP2P platforms have been criticized because of the heavy strain that some P2P services can inflict on costly inter-domain links of network operators. It is therefore necessary to develop network optimization schemes for controlling the load generated by P2P platforms on an operator network. Previous focus on network optimization has been mostly on centralized tracker-based systems. However, in recent years multiple DHT-based P2P networks are widely deployed due to their scalability and fault tolerance, and these networks have even been considered as platforms for commercial services..Thereby, finding network optimization for DHT-based P2P applications has potentially large practical impacts. In this paper, we present THash, a simple scheme to implement an effective distributed network optimization for DHT systems. THash is based on standard DHT put/get semantics and utilizes a triple hash method to guide the DHT clients sharing resources with peers in proper domains. We have implemented THash in a major P2P application (PPLive) by using the standard ALTO/P4P protocol as the network information source. We conducted realistic experiments over the network and observed that compared with Native DHT, THash only generated 45.5\% and 35.7\% of inter-PID and inter-AS traffic, and at the same time shortened the average downloading time by 13.8\% to 22.1\%

The nonequilibrium evolution near the phase boundary

We study the nonequilibrium evolution near the phase boundary of the 3D Ising model, and find that the average of relaxation time (RT) near the first-order phase transition line (1st-PTL) is significantly larger than that near the critical point (CP). As the system size increases, the average of RT near the 1st-PTL increases at a higher power compared to that near the CP. We further show that RT near the 1st-PTL is not only non-self-averaging, but actually self-diverging: relative variance of RT increases with system size. The presence of coexisting and metastable states results in a substantial increase in randomness near the 1st-PTL, making it difficult to achieve equilibrium.Comment: 6 pages, 3 figure

FACILE AND EFFECTIVE PHONONIC STRUCTURES FOR ULTRASOUND FOCUSING APPLICATION

ABSTRACT Ultrasound therapy is a highly popular non-invasive method to treat diseases. It is desired to increase the resolution of ultrasound therapy, providing more efficient therapeutic effect. In this study, a simple but effective phononic structure was designed to achieve higher resolution close to wavelength resolution of ultrasound focusing. The objective of this study is to design a unique phononic structure to focus acoustic wave into human body more deeply and precisely. It is known that overheating by high frequency ultrasound will cause a series of side effects including bone burns, soft tissue burns, swelling and bleeding problems. In addition, due to the limited propagation of recovered evanescent wave, the penetration depth of acoustic energy being focused by the acoustic metamaterials is often hindered. In this study, we will design a multilayer acoustic metamaterial which shows sub-wavelength focusing ability at relatively low frequencies. More importantly, our design will also extend the ability of penetration depth by manipulating the focusing length through optimization of the phononic structure

Autonomous analysis of infrared images for condition diagnosis of HV cable accessories

Infrared thermography has been used as a key means for the identification of overheating defects in power cable accessories. At present, analysis of thermal imaging pictures relies on human visual inspections, which is time-consuming and laborious and requires engineering expertise. In order to realize intelligent, autonomous recognition of infrared images taken from electrical equipment, previous studies reported preliminary work in preprocessing of infrared images and in the extraction of key feature parameters, which were then used to train neural networks. However, the key features required manual selection, and previous reports showed no practical implementations. In this contribution, an autonomous diagnosis method, which is based on the Faster RCNN network and the Mean-Shift algorithm, is proposed. Firstly, the Faster RCNN network is trained to implement the autonomous identification and positioning of the objects to be diagnosed in the infrared images. Then, the Mean-Shift algorithm is used for image segmentation to extract the area of overheating. Next, the parameters determining the temperature of the overheating parts of cable accessories are calculated, based on which the diagnosis are then made by following the relevant cable condition assessment criteria. Case studies are carried out in the paper, and results show that the cable accessories and their overheating regions can be located and assessed at different camera angles and under various background conditions via the autonomous processing and diagnosis methods proposed in the paper

The Role of Wild-Type p53 in Cisplatin-Induced Chk2 Phosphorylation and the Inhibition of Platinum Resistance with a Chk2 Inhibitor

The major obstacle in platinum chemotherapy is the repair of platinum-damaged DNA that results in increased resistance, reduced apoptosis, and finally treatment failure. Our research goal is to determine and block the mechanisms of platinum resistance. Our recent studies demonstrate that several kinases in the DNA-repair pathway are activated after cells are exposed to cisplatin. These include ATM, p53, and Chk2. The increased Chk2 phosphorylation is modulated by p53 in a wild-type p53 model. Overexpression of p53 by cDNA transfection in wt-p53 (but not p53 deficient) cells doubled the amount of Chk2 phosphorylation 48 hours after cisplatin treatment. p53 knockdown by specific siRNA greatly reduced Chk2 phosphorylation. We conclude that wild-type p53, in response to cisplatin stimulation, plays a role in the upstream regulation of Chk2 phosphorylation at Thr-68. Cells without normal p53 function survive via an alternative pathway in response to the exogenous influence of cisplatin. We strongly suggest that it is very important to include the p53 mutational status in any p53 involved studies due to the functional differentiation of wt p53 and p53 mutant. Inhibition of Chk2 pathway with a Chk2 inhibitor (C3742) increased cisplatin efficacy, especially those with defective p53. Our findings suggest that inhibition of platinum resistance can be achieved with a small-molecule inhibitor of Chk2, thus improving the therapeutic indices for platinum chemotherapy