A fundamental problem that confronts peer-to-peer applications is to efficiently locate the node that stores a particular data item. This paper presents Chord, a distributed lookup protocol that addresses this problem. Chord provides support for just one operation: given a key, it maps the key onto a node. Data location can be easily implemented on top of Chord by associating a key with each data item, and storing the key/data item pair at the node to which the key maps. Chord adapts efficiently as nodes join and leave the system, and can answer queries even if the system is continuously changing. Results from theoretical analysis, simulations, and experiments show that Chord is scalable, with communication cost and the state maintained by each node scaling logarithmically with the number of Chord nodes.

Chord: A scalable peer-to-peer lookup service for internet applications

This paper presents the design and evaluation of Pastry, a scalable, distributed object location and routing substrate for wide-area peer-to-peer ap- plications. Pastry performs application-level routing and object location in a po- tentially very large overlay network of nodes connected via the Internet. It can be used to support a variety of peer-to-peer applications, including global data storage, data sharing, group communication and naming. Each node in the Pastry network has a unique identifier (nodeId). When presented with a message and a key, a Pastry node efficiently routes the message to the node with a nodeId that is numerically closest to the key, among all currently live Pastry nodes. Each Pastry node keeps track of its immediate neighbors in the nodeId space, and notifies applications of new node arrivals, node failures and recoveries. Pastry takes into account network locality; it seeks to minimize the distance messages travel, according to a to scalar proximity metric like the number of IP routing hops. Pastry is completely decentralized, scalable, and self-organizing; it automatically adapts to the arrival, departure and failure of nodes. Experimental results obtained with a prototype implementation on an emulated network of up to 100,000 nodes confirm Pastry's scalability and efficiency, its ability to self-organize and adapt to node failures, and its good network locality properties.

/pdf/pastry-scalable-decentralized-object-location-and-routing-1u2equbbbp.pdf

Pastry: Scalable, Decentralized Object Location, and Routing for Large-Scale Peer-to-Peer Systems

Hash tables - which map "keys" onto "values" - are an essential building block in modern software systems. We believe a similar functionality would be equally valuable to large distributed systems. In this paper, we introduce the concept of a Content-Addressable Network (CAN) as a distributed infrastructure that provides hash table-like functionality on Internet-like scales. The CAN is scalable, fault-tolerant and completely self-organizing, and we demonstrate its scalability, robustness and low-latency properties through simulation.

https://www.cs.sjtu.edu.cn/~gchen/course/acn/Reading/CAN.pdf

A scalable content-addressable network

A review of the geologic history of the Himalayan-Tibetan orogen suggests that at least 1400 km of north-south shortening has been absorbed by the orogen since the onset of the Indo-Asian collision at about 70 Ma. Significant crustal shortening, which leads to eventual construction of the Cenozoic Tibetan plateau, began more or less synchronously in the Eocene (50–40 Ma) in the Tethyan Himalaya in the south, and in the Kunlun Shan and the Qilian Shan some 1000–1400 km in the north. The Paleozoic and Mesozoic tectonic histories in the Himalayan-Tibetan orogen exerted a strong control over the Cenozoic strain history and strain distribution. The presence of widespread Triassic flysch complex in the Songpan-Ganzi-Hoh Xil and the Qiangtang terranes can be spatially correlated with Cenozoic volcanism and thrusting in central Tibet. The marked difference in seismic properties of the crust and the upper mantle between southern and central Tibet is a manifestation of both Mesozoic and Cenozoic tectonics. The form...

Geologic Evolution of the Himalayan-Tibetan Orogen

Reliability at massive scale is one of the biggest challenges we face at Amazon.com, one of the largest e-commerce operations in the world; even the slightest outage has significant financial consequences and impacts customer trust. The Amazon.com platform, which provides services for many web sites worldwide, is implemented on top of an infrastructure of tens of thousands of servers and network components located in many datacenters around the world. At this scale, small and large components fail continuously and the way persistent state is managed in the face of these failures drives the reliability and scalability of the software systems.This paper presents the design and implementation of Dynamo, a highly available key-value storage system that some of Amazon's core services use to provide an "always-on" experience. To achieve this level of availability, Dynamo sacrifices consistency under certain failure scenarios. It makes extensive use of object versioning and application-assisted conflict resolution in a manner that provides a novel interface for developers to use.

/pdf/dynamo-amazon-s-highly-available-key-value-store-2ozfk43ou4.pdf

Dynamo: amazon's highly available key-value store

The language model design and implementation issue is researched in this paper. Different from previous research, we want to emphasize the importance of n-gram models based on words in the study of language model. We build up a word based language model using the toolkit of SRILM and implement it for contextual language processing on Chinese documents. A modified Absolute Discount smoothing algorithm is proposed to reduce the perplexity of the language model. The word based language model improves the performance of post-processing of online handwritten character recognition system compared with the character based language model, but it also increases computation and storage cost greatly. Besides quantizing the model data non-uniformly, we design a new tree storage structure to compress the model size, which leads to an increase in searching efficiency as well. We illustrate the set of approaches on a test corpus of recognition results of online handwritten Chinese characters, and propose a modified confidence measure for recognition candidate characters to get their accurate posterior probabilities while reducing the complexity. The weighted combination of linguistic knowledge and candidate confidence information proves successful in this paper and can be further developed to achieve improvements in recognition accuracy.

/pdf/a-word-language-model-based-contextual-language-processing-3853gy0lmd.pdf

A word language model based contextual language processing on Chinese character recognition

We represented herein a synthetic endeavor to the epoxy-lactone moiety that is commonly present in the C/D ring of highly oxygenated triterpene. Two strategies were applied to the synthesis based on the ursolic acid, namely, the Br+-promoted cyclization isomerization for late-stage epoxidation and the one-step SeO2-promoted oxidative cyclization. Finally, the desired epoxy-lactone moiety could be readily prepared on gram-scale in one step using our modified SeO2/TBHP/AcOH oxidative system.

Construction of the Epoxy-lactone Moiety on C/D Ring of Highly Oxygenated Triterpenes Through a Modified SeO2-promoted Oxidative Cyclization

본 발명은 상향링크 데이터 전송 방법 및 장치를 개시한다 상기 방법은, 단말 장치에게 할당되는 M개의 전송 영역을 결정하고, M개의 전송 영역을 지시하기 위해 사용되는 제1 정보를 생성하는 단계 - 여기서 M은 양의 정수이고, 전송 영역은 통신 시스템에 의해 특정되는 시간 범위 및 주파수 범위를 포함하는 무선 인터페이스 시간-주파수 자원을 나타냄 -; M개의 전송 영역의 각 전송 영역에 대해, 전송 블록 크기를 지시하기 위해 사용되는 제2 정보를 결정하는 단계; 및 단말 장치가 제1 정보 및 제2 정보를 포함하는 지시 메시지에 따라 상향링크 데이터를 전송할 수 있도록, 지시 메시지를 단말 장치에게 송신하는 단계를 포함한다 본 발명의 실시예에서 제공되는 상향링크 데이터 전송 방법 및 장치에 의하여, 네트워크 장치는 전송 블록 크기에 따라 전송 영역 상의 상향링크 데이터를 복호할 수 있어서, 처리 지연이 감소될 수 있다

상향링크 데이터 전송 방법 및 장치

Provided are a method and device for releasing a resource capable of regulating action of a terminal, such that the terminal and a network apparatus agree on action or understanding upon release of a resource configuration, thereby facilitating normal communication. The method comprises: a network apparatus generating first downlink control information (DCI) and sending the first DCI to a terminal, and the terminal receiving the first downlink control information (DCI) from the network apparatus; the terminal determining whether the first DCI meets a release condition; and if it is determined that the first DCI meets the release condition, the terminal releasing one or more resource configurations on a bandwidth part (BWP) in an active state.

Method and device for releasing resource

Existing image matching is mostly limited to homologous images, but there are few researches on heterogeneous image matching such as UAV images and satellite remote sensing images. Aiming at the slow speed and low accuracy of traditional image matching methods when matching small-scale UAV images with satellite remote sensing images, a secondary matching method based on image edge features is proposed. The gradient information calculates the normalized cross-correlation formula to obtain the first matching result, and then obtains the optimal matching result through the shape context algorithm. Experimental results show that this method can well overcome the influence of factors such as illumination, low resolution, rotation, etc., and match UAV images and remote sensing images in a short time. The average precision and recall of the algorithm can reach 67.75% and 64.66%. Compared with the traditional SURF algorithm, it has faster matching speed and better matching accuracy.

Yan Chen

Papers

A word language model based contextual language processing on Chinese character recognition

Construction of the Epoxy-lactone Moiety on C/D Ring of Highly Oxygenated Triterpenes Through a Modified SeO2-promoted Oxidative Cyclization

상향링크 데이터 전송 방법 및 장치

Method and device for releasing resource

Secondary Matching Algorithm: a New Heterogeneous Image Matching Algorithm for the UAV Image and Satellite Remote Sensing Image