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Date 21-24 Nov. 2005

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Displaying Results 1 - 25 of 520
  • Bayes Method of Power Quality Disturbance Classification

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1461 KB) |  | HTML iconHTML  

    With the proliferation of nonlinear loads, power quality problems have been paid more attention to. In order to mitigate the influence, various power quality disturbances must be classified before an appropriate action can be taken. Wavelet packet is developed on wavelet transform, which can provide more plenteous time-frequency information. This paper selects energy and entropy of terminal nodes through wavelet packet decomposition as feature vector respectively, using Bayes classifier to classify the disturbances, which are simulated and analyzed. The simulation results indicate that the entropy acted as feature vector has higher recognition accurate ratio. View full abstract»

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  • Compression of Power Quality Disturbance Data Based on Energy Threshold and Adaptive Arithmetic Encoding

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1083 KB) |  | HTML iconHTML  

    Recently, power quality issues have captured more attention. It is necessary to monitor power quality in order to analyze and evaluate it. The monitors will record huge data during disturbance. It is inconvenient for data storage and transmission. Compression of power quality disturbance data will save storage space efficiently and accelerate transmission speed. This paper proposes energy threshold method based on wavelet transform, and then integrates adaptive arithmetic encoding to compress disturbance data. The compression ratio is improved and performance is better. Four typical power quality disturbances including voltage sag, swell, interruption and transient impulse are used to test the proposed method, the validity is verified by simulation results. View full abstract»

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  • A Novel Resource Advertisement and Discovery Mdel for Ubiquitous Computing Environments using Mobile Agents

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4381 KB) |  | HTML iconHTML  

    Ubiquitous computing as a new branch in the field of distributed computing has received wide contribution from different researchers. In this novel computing model, vast range of computational and communication resources along with other types of services are gathered under a single system image based on certain predefined criteria. Ubiquitous computing and software mobile agents are both pursuing the aim of creating a collaborative problem solving environment. While the ultimate goals followed in each technology differs from the conceptual view but they both share many ideas that can be mutually exchanged. As the two fields advance they amusingly congregate. The convergence allows faster progress since many shared concepts have been to a great extent solved in the other field. In the pervasive computing environment a balanced distribution of available resources among different tasks is an important task. Devising efficient resource discovery and advertisement algorithms is therefore of much importance. In this article we aim to provide two algorithms for this problem using mobile agents. The proposed resource discovery algorithms use two different hierarchical and flat approaches. The simulations show a good performance for both of the proposed models; however the hierarchical algorithm shows better results based on some of the introduced factors. View full abstract»

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  • An Effective Hotspot Cell Management Scheme Using Adaptive Handover Time in 4G Mobile Networks

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB) |  | HTML iconHTML  

    We propose a hotspot cell management scheme using adaptive handover time in 4G mobile networks. 4G networks are expected to support various multimedia services over IP network and satisfy high spectral efficiency requirement with overcoming time and frequency selective fading due to the high speed of users. In cellular systems including 4G networks, hotspot cells can be occurred when available wireless resources at some location are not enough to sustain the needs of users. The hotspot cell can potentially lead to blocked and dropped calls and cause degradation of the service quality. In the meanwhile, a band of users enjoying multimedia services can move around in a 4G mobile network, which may generate heavy flows of traffic load in the network. This situation can generate the hotspot cell which has a short length of life at most a few minutes. In this paper, we propose a handover-based scheme which can effectively manage hotspot cells in 4G mobile networks. The proposed scheme adopts hard handoff mechanism and dynamically controls the time point of handover based on the amount of load of the current serving cell and the target cell. Adaptation of handover time according to the amount of load effectively and flexibly can manage the hotspot cell. And, through our hotspot cell management scheme, acceptable service quality can be supported as users maintain graceful connections with the network. In the simulation results, we find that our scheme makes smaller number of hotspot cells and supports higher service quality than compared schemes. View full abstract»

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  • A Simplified Sphere Decoding Algorithm for MIMO Transmission System

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB) |  | HTML iconHTML  

    In sphere decoding the choice of sphere radius is crucial to excellent performance. In Chan-Lee sphere decoding - based algorithm, the problem of choosing initial radius has been solved by making the radius sufficiently large, thus increasing the size of the search region. In this paper we present maximum likelihood decoding using simplified sphere decoder as apposed to the original sphere decoder for the detection of cubic structure quadrature amplitude modulation symbols. This simple algorithm based on Chan-Lee sphere decoder allows the search for closest lattice point in a reduced complexity manner compared to original sphere decoder for multiple input multiple output system with perfect channel state information at the receiver. Results show symbol error rate has stabilized even at very low initial value of the square radius. View full abstract»

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  • A Full Rate Concatenated Space-Frequency and Space-Time OFDM over Naftali Fading Channels

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (185 KB) |  | HTML iconHTML  

    In this paper we investigate 2 transmit and 1 receive (2Tx:1Rx) space-frequency orthogonal frequency division multiplexing (SF-OFDM) and space-time OFDM (ST-OFDM) concatenated with convolutional channel coding as a redundancy method to combat channel impairments. We built our SF and ST-OFDM on top of our coded OFDM (COFDM) with coding rate of 1/4 and constraint length of 10. We simulate our concatenated SF-OFDM and ST-OFDM over a multipath fading channel using Naftali 802.11 channel model under different delay spreads in relation to outdoor environment. Concatenated SF- OFDM performs slightly better than ST-OFDM at delay spread of 2.0 microseconds, but both are almost comparable at all other delay spreads. These two schemes outperforms other schemes such as single antenna coded OFDM and Alamouti's Space-Time Block Code (STBC) under these conditions by as much as 10 dB at BER of 104. View full abstract»

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  • A Hybrid Admission Control Scheme for Wireless Networks

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (219 KB) |  | HTML iconHTML  

    Threshold access sharing (TAS) is a policy based call admission control (CAC) scheme in wireless IP networks. It has been shown to adapt well to the limited wireless resources. However, its handling of handoff calls is missing. In this paper, we proposed a hybrid scheme which combines an improved TAS scheme with a simplified rate-based borrowing scheme, aiming to improve its performance both on new call blocking and handoff call dropping probability. Our analysis and simulation have shown that the new scheme has met the expectation and its complexity is comparable to TAS. View full abstract»

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  • Cognitive Emotion in Speech Interactive Games

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB) |  | HTML iconHTML  

    This paper falls into the category of human computer interaction. Here the focus lies in injecting emotions into the non-player characters (NPC) in reaction to the emotion of the player in computer games. The idea of injecting emotion into games has been a popular topic for discussion in the games industry today. The paper reviews the emotional side of games from both the game side and the human player side, considering speech style and content, facial expressions and gestures. The emotional content is encapsulated within an XML and an associated finite state automaton. View full abstract»

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  • Trust Models and Security Considerations in Multicast Listener Discovery Protocol version 2 (MLDv2)

    Page(s): 1 - 8
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB) |  | HTML iconHTML  

    Multicast listener discovery (MLD) protocols are employed by IPv6 routers and hosts for group management. Routers use MLD to discover the presence of multicast listeners -nodes that wish to receive multicast packets- on their directly attached links, and to discover which multicast addresses are of interest to those neighbouring nodes. Existing MLDv2 protocol specification discusses the effects of on-link forgery of MLD packets but does not provide any protection from on-link attacks. By taking advantage of or abusing MLD messages, bogus devices can cause incorrect multicast records and disruption to multicast or unicast packet delivery. In this paper we identify and analyse the various trust models for MLD protocols, their workings and their interaction with link-layer and multicast proxy devices. We also provide security and threat analysis for each model. View full abstract»

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  • A New Cellular Search Algorithm for Motion Estimation

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB) |  | HTML iconHTML  

    Fast block-matching motion estimation algorithms for video compression are in real-time video conference applications. Three-step Search (TSS) and other fast search algorithms such as Diamond Search (DS), Cellular Search (CS), New Cross Diamond Search (NCDS), Fast Cellular Search (FCS) have been proposed to reduce the computation time instead of the full-search block-matching algorithm in video compression applications. To reduce more computational complexity and maintain the quality of compressed video, a novel algorithm based on the spirit of CS is proposed and named New Cellular Search (NCS). This proposed algorithm has two search patterns in horizontal and vertical directions with different switching strategy to reduce the computation time. The experimental results are shown that this proposed algorithm is superior to some fast search algorithms. View full abstract»

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  • Analysis of Conversational Game Pidgin Language

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (239 KB) |  | HTML iconHTML  

    In this paper we analyze a new language called game Pidgin language (GPL) for speech interactive computer games. We use two formulas namely entropy and perfect information of Information Theory to perform the analysis. We establish that GPL is an efficient language for communication in real time speech interactive systems. View full abstract»

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  • Three-Phase Capacitor-Clamped Active Power Filter for Harmonic and Reactive Power Compensation

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (358 KB) |  | HTML iconHTML  

    This paper presents an active power filter based on a capacitor-clamped topology to compensate harmonics and reactive power generated from the nonlinear loads. The balanced and sinusoidal line currents are drawn from the AC source under the balanced and unbalanced loads. The capacitor-clamped topology is used in the voltage source inverter to reduce the voltage stress of power semiconductors. A DC-link voltage controller, a hysteresis comparator and a neutral point voltage compensator are used in the control scheme to maintain a constant DC bus voltage of the inverter, track the compensated current and balance the neutral point voltage on DC side, respectively. The experimental results are provided to verify the effectiveness and validity of the proposed control scheme. View full abstract»

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  • A New Automatic Gait Recognition method based on the Perceptual Curve

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (434 KB) |  | HTML iconHTML  

    Recognizing people by their gait is an emerging biometrics. In this paper we proposed a new automatic gait recognition approach based on the perceptual curve, which can effectively preserve the temporal changes of the walker's silhouette shape consistency with human vision. Firstly, we detect the walking person in each frame of the monocular image sequences. Then we use inner boundary tracking algorithm to extract the walker's binary silhouettes and compute the PSD (perceptual shape descriptor) of the shapes. Next, accumulative PSD of each image sequence forms a perceptual curve as its gait signature. Finally, the STC (spatio-temporal correlation) similarity measure and two different simple classification methods (NN and KNN) are used to recognize different subjects. Experimental results on the UCSD database and CMU database demonstrate the feasibility of the proposed approach. View full abstract»

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  • Macroaction Synthesis for Agent System

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB) |  | HTML iconHTML  

    We present methods to synthesize macroactions for agent systems and the methods are combined with SOS algorithm that learns rules for agent's behavior using reinforcement learning and evolutionary computation. To acquire useful macroactions, our methods use some kinds of numerical values evaluated in performing SOS algorithm, e.g., fitness values of actions or the number of transitions between rules. New macroactions generated by our methods are fed back to SOS algorithm for learning rules. By repeating macroaction synthesis and learning rules alternately, rules for agent's behavior are acquired. The methods shown here have been implemented and some experimental results have been shown. View full abstract»

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  • Internet Protocol Television (IPTV)

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (7758 KB) |  | HTML iconHTML  

    This paper is intended to be an introduction into the issues involved with delivering IPTV over DSL. IPTV technology and available broadband bandwidths are evolving to the point where DSL providers can effectively enter the market of TV delivery to their customers. However, there are still issues concerning bandwidth, codec selection, QoS, and ROI. This paper will address each of these issues and discuss the major players involved in deploying this new technology. Though the paper will not go in-depth technically about how IPTV works, it will provide a good overview of IPTV architecture, how it will be delivered from the service provider's head-end equipment to the end-user (the consumer), and the differences between IPTV architecture and legacy cable TV (television) architecture. Most importantly, it will describe the importance of why moving to IPTV is a competitive "have-to" for service providers to survive. View full abstract»

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  • Intellectual Property - Challenges for the Future

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB) |  | HTML iconHTML  

    Intellectual property law is based on a balance between the interests and needs of the public and those of creators. When the legal systems that underpin intellectual property no longer maintain the correct balance or even worse, neglect it, then respect for those systems and intellectual property erodes. This paper discusses the current level of respect for intellectual property, and measures that could be employed to addresses problems with the current system, particularly for patents and copyright. View full abstract»

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  • Mobility Prediction with Direction Tracking on Dynamic Source Routing

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (134 KB) |  | HTML iconHTML  

    Mobility prediction is one the most efficient techniques used to calculate lifetime estimation of wireless links (link lifetime-LLT) for a more reliable path selection. To incorporate a mobility prediction model into ad hoc routing protocols, an updating scheme should be used to maintain prediction accuracy especially for those source initiated on-demand routing protocols where LLT values are continuously changing after the route discovery phase. In this paper, a light-weight direction tracking scheme is introduced to enhance performance of the mobility prediction based routing by reassuring the accuracy of LLT used for path selection process. The simulation results show an improvement in terms of average packet latency with minimum impact on number of control messages utilized. View full abstract»

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  • Ontology-Based Multimedia Presentation Generation

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB) |  | HTML iconHTML  

    Multimedia data are illusory entities for the machines. Their contents include interpretable data as well as binary representations. Understanding and accessing the content-driven information for multimedia objects allow us to design an efficient multimedia querying and retrieval system. In this paper, we propose a framework to represent the multimedia information and object roles in order to generate automatic multimedia presentations. The proposed architecture attempts to represent the semantic information and the relations amongst the multimedia objects in a disclosure domain. Thus, the system is domain dependent. The represented data associates with the presentation mechanisms to create an integrated presentation generation system. A multi-layer design defines the various levels of abstraction for the proposed framework. View full abstract»

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  • Low Cost Interdigital BST Varactors for Tunable Microwave Applications

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (394 KB) |  | HTML iconHTML  

    In this paper, a simple and inexpensive technique for the fabrication of barium strontium titanate (BST) varactors is presented. BST films were deposited using RF magnetron sputtering on platinum coated silicon substrates. The advantages of silicon include low cost and ease of integration with existing fabrication processes. The microstructural properties of the BST layer were examined with scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. Gold top layer electrodes were deposited using DC sputtering and patterned with a conventional photolithographic process. The S-parameters of the varactor were measured from 40 MHz to 20 GHz on a vector network analyser. From this data, the capacitance, tunability and Q-factor of the device were extracted. The BST-based varactors show potential for integration into electronically tunable microwave circuits. View full abstract»

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  • Digital Control of High DC Voltage Converter Based on Cockcroft Walton Voltage Multiplier Circuit

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB) |  | HTML iconHTML  

    A new method of controlling high DC voltage based on Cockcroft Walton voltage multiplier circuit by using digital controller is presented. The digital controller is developed using complex programmable logic devices (CPLD). The proposed system utilizes a single-phase AC as an input supply. The power switching devices in the controlled bridge are controlled by the multiple-pulse pulse width modulation (PWM) switching technique so as to minimize the low order harmonic present on the AC side of the converter system. A low pass filter is incorporated in the circuit to filter out unwanted harmonics and to give a sinusoidal AC current. A high frequency transformer with 1:1 ratio is incorporated in the design to provide galvanic isolation for better circuit performance and protection. The optimum operation of transformer core in four quadrant of B-H curve is also considered in the proposed converter topology. The laboratory model of the converter is developed and tested. The experimental result is compared with the simulation result. View full abstract»

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  • A New Approach for Harmonic Compensation Using Single- phase Hybrid Active Power Filter

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (254 KB) |  | HTML iconHTML  

    This paper presents a new approach for harmonic control, and its practical implementation for a single-phase hybrid active power filter. It is a combination of a series active power filter and a shunt passive filter. The shunt passive filter is connected in parallel with a load and suppresses the harmonic current produced by the load, whereas the active filter connected in series to a source acts as a harmonic isolator between the source and load. For active filter control, sinusoidal pulse width modulation (SPWM) is developed and the modulation index is selected by calculating the DC bus voltage of the active filter. The PSpicereg, Matlab/Simulinkreg and MAX PLUS IIreg softwares are used for simulation and hardware implementation. ALTERAreg FLEX 10K controller and some peripheral circuits are used. Simulation and experimental results show that the proposed active power filter topology is capable of compensating the load current and voltage harmonic up-to the limit specified by IEC. View full abstract»

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  • Fast MPLS Network Optimisation using Machine Learning

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB) |  | HTML iconHTML  

    This paper presents the application of a machine learning technique (neural networks) to the problem of optimising the traffic flows (label switched path placement) within telecommunications networks using multi-protocol label switching (MPLS). It is shown here that the machine learning technique achieves very fast computation of accurate solutions to the problem of placing label switched paths in order to maximise the performance of the network. Results are presented which compare the accuracy of the neural network solutions with the optimal solutions produced by the standard mixed integer linear programming technique, and the time taken to produce the solutions. As well, network simulation results are presented which show the improvement in network performance, in terms of packet loss, that can be achieved when using such a technique. View full abstract»

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  • A Game Theoretic Framework for Call Admission Control in CDMA Mobile Multimedia Systems with Traffic Asymmetry between Uplink and Downlink

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB) |  | HTML iconHTML  

    In code-division multiple-access (CDMA) mobile multimedia systems, call admission control (CAC) is essential to prevent overloading and ensure quality of service (QoS) requirement for each traffic class. While efficiency is an important performance issue in the mobile networks with multimedia services, the concept of fairness among services should also be considered. Game theory can provide an appropriate framework for formulating such fair and efficient CAC problem. In this paper, a selection method for fair-efficient threshold parameters of the CAC scheme in CDMA mobile multimedia systems with traffic asymmetry based on the framework of game theory is proposed. The proposed scheme provides fairness and efficiency in terms of uplink and downlink signal-to-interference ratio (SIR) for the 2 classes of traffic, and also guarantees the priority of class 0 calls over class 1 calls. Class 0 calls and class 1 calls are viewed as two players of a game. For the cooperative game, the arbitration schemes for the interpersonal comparisons of utility and the bargaining problem are investigated. In the aspect of the social welfare (total utility), the numerical results indicate that the Nash solution of the bargaining problem outperforms the equilibrium point of the noncooperative game and the solution of the interpersonal comparisons of utility due to its much higher total utility. View full abstract»

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  • Series active power filter for current harmonic and load voltage compensation

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB) |  | HTML iconHTML  

    A multi-function of series active power filter is presented to achieve current harmonic and load voltage regulation. Under the normal utility voltage condition, the series inverter is controlled to achieve current harmonic suppression so that the total harmonic distortion is reduced. If the abnormal utility voltage is detected at the load side, the series inverter is operated as a controlled voltage source to protect the sensitive loads against the voltage disturbances due to short-term abnormal voltage conditions. The reduced switch-count inverter is used in the single-phase system to compensate voltage disturbance for low power applications. The front-end diode rectifier is used to supply the necessary active power under the voltage sag condition. The adopted topology and control strategy are evaluated through several simulation studies. View full abstract»

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  • The 802.11 Technology Gap - Case Studies in Crime

    Page(s): 1 - 7
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (8885 KB) |  | HTML iconHTML  

    Much has been written discussing the security vulnerabilities with 802.11 based networks, and what constitutes legal and illegal activity within the area. However, there is little academic literature available discussing whether this technology is being exploited for criminal purposes, and if it is, for what purposes. This paper investigates all public prosecutions where the accused have misused 802.11 wireless networks and the consequent outcomes. From this, it can be observed how similar crimes are being investigated, and possible future crimes may be examined. View full abstract»

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