907891
Segank: A Distributed Mobile Storage System
This paper presents a distributed mobile storage system designed for storage elements connected by a network of non-uniform quality. Flexible data placement is crucial, and it leads to challenges for locating data and keeping it consistent. Our system employs a location- and topology-sensitive multicast-like solution for locating data, lazy peer-to-peer propagation of invalidation information for ensuring consistency, and a distributed snapshot mechanism for supporting sharing. The combination of these mechanisms allows a user to make the most of what a non-uniform network has to offer in terms of gaining fast access to fresh data, without incurring the foreground penalty of keeping distributed elements on a weak network consistent.
6622555
A quantitative analysis of cache policies for scalable network file systems
Current network file system protocols rely heavily on a central server to coordinate file activity among client workstations. This central server can become a bottleneck that limits scalability for environments with large numbers of clients. In central server systems such as NFS and AFS, all client writes, cache misses, and coherence messages are handled by the server. To keep up with this workload, expensive server machines are needed, configured with high-performance CPUs, memory systems, and I/O channels. Since the server stores all data, it must be physically capable of connecting to many disks. This reliance on a central server also makes current systems inappropriate for wide area network use where the network bandwidth to the server may be limited.
In this paper, we investigate the quantitative performance effect of moving as many of the server responsibilities as possible to client workstations to reduce the need for high-performance server machines. We have devised a cache protocol in which all data reside on clients and all data transfers proceed directly from client to client. The server is used only to coordinate these data transfers. This protocol is being incorporated as part of our experimental file system, xFS. We present results from a trace-driven simulation study of the protocol using traces from a 237 client NFS installation. We find that the xFS protocol reduces server load by more than a factor of six compared to AFS without significantly affecting response time or file availability.
5165465
Adaptive control for packet video
Describes a portable and robust software mechanism for adaptive frame rate control for real time packet video transfer and viewing in workstation environments. No special hardware or system support is assumed. It includes (1) a responsive feedback system for dynamic presentation layer rate control in response to network load, (2) a simple and effective transport layer flow control scheme built upon an unreliable network protocol, and (3) data structures and scheduling support for integrating the rate and flow control mechanisms. The authors demonstrate that excellent jitter control is achieved by gracefully trading image resolution, and loss rates can be drastically reduced by appropriate flow control.<<ETX>>
1078044
PersonalRAID: Mobile Storage for Distributed and Disconnected Computers
This paper presents the design and implementation of a mobile storage system called a Personal-RAID. PersonalRAID manages a number of disconnected storage devices. At the heart of a Personal-RAID system is a mobile storage device that transparently propagates data to ensure eventual consistency. Using this mobile device, a PersonalRAID provides the abstraction of a single coherent storage name space that is available everywhere, and it ensures reliability by maintaining data redundancy on a number of storage devices. One central aspect of the PersonalRAID design is that the entire storage system consists solely of a collection of storage logs; the log-structured design not only provides an efficient means for update propagation, but also allows efficient direct I/O accesses to the logs without incurring unnecessary log replay delays. The PersonalRAID prototype demonstrates that the system provides the desired transparency and reliability functionalities without imposing any serious performance penalty on a mobile storage user.
8876890
Overlay mesh construction using interleaved spanning trees
In this paper we evaluate a method of using interleaved spanning trees to compose a resilient, high performance overlay mesh. Though spanning trees of arbitrary type could be used to construct an overlay mesh, we focus on a distributed algorithm that computes k minimum spanning trees on an arbitrary graph. The principal motivation behind this strategy is to provide applications with a k-redundant, high quality mesh suitable for demanding applications like A/V broadcast, video conferencing, data collection, multi-path routing, and file mirroring/transfer. We elaborate details of k-MST, pointing out advantages and potential problem points of the protocol, and then analyze its performance using a variety of metrics with simulation as well as a functional PlanetLab implementation.
208003557
Serverless network file systems
We propose a new paradigm for network file system design: serverless network file systems. While traditional network file systems rely on a central server machine, a serverless system utilizes workstations cooperating as peers to provide all file system services. Any machine in the system can store, cache, or control any block of data. Our approach uses this location independence, in combination with fast local area networks, to provide better performance and scalability than traditional file systems. Furthermore, because any machine in the system can assume the responsibilities of a failed component, our serverless design also provides high availability via redundatn data storage. To demonstrate our approach, we have implemented a prototype serverless network file system called xFS. Preliminary performance measurements suggest that our architecture achieves its goal of scalability. For instance, in a 32-node xFS system with 32 active clients, each client receives nearly as much read or write throughput as it would see if it were the only active client.
141843
Noise-induced cooperative behavior in a multicell system
MOTIVATION
All cell components exhibit intracellular noise on account of random births and deaths of individual molecules, and extracellular noise because of environment perturbations. Gene regulation in particular, is an inherently noisy process with transcriptional control, alternative splicing, translation, diffusion and chemical modification reactions, all of which involve stochastic fluctuations. Such stochastic noises may not only affect the dynamics of the entire system but may also be exploited by living organisms to actively facilitate certain functions, such as cooperative behavior and communication.


RESULTS
We have provided a general model and an analytic tool to examine the cooperative behavior of a multicell system with both intracellular and extracellular stochastic fluctuations. A multicell system with a synthetic gene network is adopted to demonstrate the effects of noises and coupling on collective dynamics. These results establish not only a theoretical foundation but also a quantitative basis for understanding essential roles of noises on cooperative dynamics, such as synchronization and communication among cells.
18780724
Synchronizing a multicellular system by external input: an artificial control strategy
MOTIVATION
Although there are significant advances on elucidating the collective behaviors on biological organisms in recent years, the essential mechanisms by which the collective rhythms arise remain to be fully understood, and further how to synchronize multicellular networks by artificial control strategy has not yet been well explored.


RESULTS
A control strategy is developed to synchronize gene regulatory networks in a multicellular system when spontaneous synchronization cannot be achieved. We first construct an impulsive control system to model the process of periodically injecting coupling substances with constant or random impulsive control amounts into the common extracellular medium, and further study its effects on the dynamics of individual cells. We derive the threshold of synchronization induced by the periodic substance input. Therefore, we can synchronize the multicellular network to a specific collective behavior by changing the frequency and amplitude of the periodic stimuli. Moreover, a two-stage scheme is proposed to facilitate the synchronization in this paper. We show that the presence of the external input may also initiate different dynamics. The multicellular network of coupled repressilators is used to show the effectiveness of the proposed method. The results not only provide a perspective to understand the interactions between external stimuli and intrinsic physiological rhythms, but also may lead to development of realistic artificial control strategy and medical therapy.


AVAILABILITY



CONTACT
aihara@sat.t.u-tokyo.ac.jp.
5002092
How to Train a Classifier Based on the Huge Face Database?
The development of web and digital camera nowadays has made it easier to collect more than hundreds of thousands of examples. How to train a face detector based on the collected enormous face database? This paper presents a manifold-based method to subsample. That is, we learn the manifold from the collected face database and then subsample training set by the estimated geodesic distance which is calculated during the manifold learning. Using the subsampled training set based on the manifold, we train an AdaBoost-based face detector. The trained detector is tested on the MIT+CMU frontal face test set. The experimental results show that the proposed method is effective and efficient to train a classifier confronted with the huge database.
35854986
News Headline Generation based on Linguistic Methods
7961359
LexTrim: A Lexical Cohesion Based Approach to Parse-and-Trim Style Headline Generation
In this paper we compare two parse-and-trim style headline generation systems. The Topiary system uses a statistical learning approach to finding topic labels for headlines, while our approach, the LexTrim system, identifies key summary words by analysing the lexical cohesion structure of a text. The performance of these systems is evaluated using the ROUGE evaluation suite on the DUC 2004 news stories collection.