The sharing economy enables users to share idle resources through digital platforms between peers and is one of the effective methods to solve the problem of waste. In the sharing economy, most services are established on the

-to- relationship, which makes it crucial to find a way to enhance interaction between peers. In this paper, we proposed design guidelines to enhance trust between -to- and validated the design guidelines by using a case study.

抄録全体を表示

本稿では，近年注目を集めている-to-型分散システムを構築するための基盤技術，分散ハッシュテーブル(Distributed Hash Table; DHT)についての入門的な解説を行う．分散ハッシュテーブル技術は，システム全体を管理する中央サーバを持たないような-to-システム(pure -to-システム)において，効率的なオブジェクト発見の実現を可能にする．

抄録全体を表示

-to- (P2P) technology is not a new concept before it is popularly known through Napster [1], Gnutella [2] and other -to- projects. Because of its advantages on distributed file exchanging and cooperation between users, it attracts many attentions from academies and research groups. Meanwhile, mobile devices have a set of great innovations during recent 10 years. More additional functions have been embedded (e.g. memory size, camera). With its popularity, the request for searching and exchanging mobile content (e.g. java applications, picture etc.) is coming emergency. This paper introduces a solution to satisfy this requirement by realizing a mobile-oriented search system over current popular -to- techniques.

抄録全体を表示

Background: Individuals with severe mental disorders are increasingly using social media platforms to discuss their illnesses, seek advice, and support each other. This phenomenon is known as online

-to- support.

Objective: This study aimed to identify the characteristics of online

-to- support in Japan.

Methodology: Data were collected through semi-structured interviews and blog posts.

Results: Inductive thematic analysis revealed three themes: (1) expanding online networks of mutual support as self-organization progresses; (2) cultivating a positive self-identity for individuals with schizophrenia; and (3) taking steps toward social participation and inclusion.

Conclusion: Despite concerns regarding the risks of online communities, self-organized online

-to- support groups promote social participation rather than isolation. However, this result cannot be generalized to all online communities because its quality is influenced by peer support structures and environments. Self-organized online -to- support groups with a flexible and receptive organizational culture effectively promote social participation. Our results suggest that online interactions that foster positive self-identity may be a prelude to offline social affiliations. In this study, individuals living with schizophrenia who communicated online were provided with a foundation that enabled them to take steps toward engaging in offline social participation. However, a sustainable management system is required. Hence, peer partnership services, in which the service is provided by peers, but its operation is conducted in collaboration with professionals, should be considered.

抄録全体を表示

With an enhanced client computer performance and network bandwidth, content distribution services are receiving much attention. However client/server model and -to- model require vast cost for content distributions. These costs pose an impediment to broaden commercialization of content distribution services via the Internet. Content distribution cost consists of investment for server and network infrastructure which client/server model and -to- model require respectively. Thus, We focus on network infrastructure, especially in -to- content distribution networks which drastically increase traffic volume. The main feature of our proposal is utilization of inexpensive inter-ISP connections. This paper presents methods to constitute -to- content distribution networks that realizes lower cost content distribution and a reduction in the amount of inter-ISP traffic and its costs by considering the priority in usage of ISP interconnections in its distribution. Our proposal extends BitTorrent, which has been widely deployed by several content providers to reduce the load in congested servers and the distribution costs. Our performance evaluations show that our proposal achieves a reduction in network infrastructure costs and improved performance such as distribution time.

抄録全体を表示

A global stabilization method for the conversion characteristics of a bidirectional DC/DC converter and its application in

-to- energy transfer systems is described. -to- energy transfer is a control strategy in which the supply and load cooperate to transmit power, and it requires the global operation of the converter. According to the power relation, the bidirectional DC/DC converter has two equilibrium points. To realize global stability, a unique equilibrium point is achieved by eliminating the untargeted equilibrium point using the power relationship between the ports. Global stability is realized by setting feedback gains to converge globally to this equilibrium point. The experimental results demonstrate the global stability of the proposed method when applied to a stand-alone system and a -to- energy transfer system.

抄録全体を表示

This paper presents a novel -to- protocol to efficiently distribute virtual machine images in a datacenter. A primary idea of it is to improve the performance of -to- content delivery by employing deduplication to take advantage of similarity both among and within VM images in cloud datacenters. The efficacy of the proposed scheme is validated through an evaluation that demonstrates substantial performance gains.

抄録全体を表示

-to- overlay networks can easily achieve a large-scale content sharing system on the Internet. Although unstructured -to- networks are suitable for finding entire partial-match content, flooding-based search is an inefficient way to obtain target content. When the shared content is semantically specified by a great number of attributes, it is difficult to derive the semantic similarity of peers beforehand. This means that content search methods relying on interest-based locality are more advantageous than those based on the semantic similarity of peers. Existing search methods that exploit interest-based locality organize multiple peer groups, in each of which peers with common interests are densely connected using short-cut links. However, content searches among multiple peer groups are still inefficient when the number of incident links at each peer is limited due to the capacity of the peer. This paper proposes a novel content search method that exploits interest-based locality. The proposed method can organize an efficient -to- network similar to the semantic small-world random graph, which can be organized by the existing methods based on the semantic similarity of peers. In the proposed method, topology transformation based on local link replacement maintains the numbers of incident links at all the peers. Simulation results confirm that the proposed method can achieve a significantly higher ratio of obtainable partial-match content than existing methods that organize peer groups.

抄録全体を表示

Recently, many kinds of content are being circulated within a great many service-specific overlay networks. When the content is not extremely delay-sensitive, content circulation between wireless terminals can be realized without additional resources by using off-peak periods in wireless access links. In such content circulation, -to- content multicast is a promising approach to reduce the load on the centralized server. However, to minimize battery drain, each wireless terminal can only forward content to a restricted number of neighboring terminals once it has received the content. This paper proposes an efficient forwarding scheme for -to- content multicast between the wireless terminals intermittently connected with the backhaul network. In the proposed scheme, a restricted number of terminals with an earlier start time of off-peak periods are selected to forward the content when the number of forwarding hops from the source terminal is less than or equal to a predetermined threshold. In contrast, a restricted number of terminals are selected randomly when the number of forwarding hops exceeds the threshold. This paper clarifies that the proposed hybrid forwarding scheme can multicast the content to many terminals within an arbitrarily restricted period. A guideline to determine the optimum threshold for switching the terminal selection method in the proposed hybrid scheme is derived from simulation results.

抄録全体を表示

本研究では、既存の問題点を改善した新たなナレッジマネジメントシステムを提案することを目的とする。その際、-to-型アーキテクチャを採用する。-to-型システムは、1999年に音楽ファイル交換用アプリケーション「ナプスター(Napster)」が登場以来、注目を集めており、従来のクライアント·サーバ型システムに比べ、ネットワーク負荷や処理能力の分散の面や、人と人との結びつき直接的で強いなどの利点がある。-to-型システムはサーバーの存在の有無によって、ハイブリッド型とピュア型に分類されるが、ナレッジマネジメントシステムの特徴を考えると、サーバーによる知識の管理が求められる。本システムでは、日常業務で生産される書類を情報マイニング技術を用いて管理することで、人が潜在的に持つ知識の分野·方向性をサーバーにより管理するハイブリッド型システムを提案する。

抄録全体を表示

We present the concept of folksonomical -to- (P2P) file sharing networks that allow participants (peers) to freely assign structured search tags to files. These networks are similar to folksonomies in the present Web from the point of view that users assign search tags to information distributed over a network. As a concrete example, we consider an unstructured P2P network using vectorized Kansei (human sensitivity) information as structured search tags for file search. Vectorized Kansei information as search tags indicates what participants feel about their files and is assigned by the participant to each of their files. A search query also has the same form of search tags and indicates what participants want to feel about files that they will eventually obtain. A method that enables file search using vectorized Kansei information is the Kansei query-forwarding method, which probabilistically propagates a search query to peers that are likely to hold more files having search tags that are similar to the query. The similarity between the search query and the search tags is measured in terms of their dot product. The simulation experiments examine if the Kansei query-forwarding method can provide equal search performance for all peers in a network in which only the Kansei information and the tendency with respect to file collection are different among all of the peers. The simulation results show that the Kansei query forwarding method and a random-walk-based query forwarding method, for comparison, work effectively in different situations and are complementary. Furthermore, the Kansei query forwarding method is shown, through simulations, to be superior to or equal to the random-walk based one in terms of search speed.

抄録全体を表示

-to- (P2P) technology has gained popularity as a way to enhance system performance. Nodes in a P2P network work together by providing network resources to one another. In this study, we examine the use of P2P technology for video streaming and develop a distributed incentive mechanism to prevent free-riding. Our proposed solution combines WebTorrent and the Solana blockchain and can be accessed through a web browser. To incentivize uploads, some of the received video chunks are encrypted using AES. Smart contracts on the blockchain are used for third-party verification of uploads and for managing access to the video content. Experimental results on a test network showed that our system can encrypt and decrypt chunks in about 1/40th the time it takes using WebRTC, without affecting the quality of video streaming. Smart contracts were also found to quickly verify uploads in about 860 milliseconds. The paper also explores how to effectively reward virtual points for uploads.

抄録全体を表示

Today's Multi-player Online Games (MOGs) are challenged by infrastructure requirements because of their server-centric nature. -to- overlay networks are an interesting alternative if they can implement the set of functions that are traditionally performed by centric game servers. In this paper, we propose a Zoned Federation Model (ZFM) to adapt MOGs to -to- overlay networks. We also introduce the concept of zone and zone owner to MOGs. A zone is some part of the whole game world, and a zone owner is a game sever of a specific zone. According to the demands of the game program, each node actively changes its role to a zone owner. By dividing the whole game world into several zones, workloads of the centric game server can be distributed to a federation of zones. In order to reduce response latency overhead on data exchanges between a zone owner and its clients, we limit the use of a Distributed Hash Table(DHT) to the rendezvous point of each zone; actual data exchanges are carried out through direct TCP connection between a zone owner and its members. We also use the DHT as backup storage media to cope with the resignation of a zone owner. We have implemented this zoned federation model as a middle layer between the game program and the DHT, and we evaluate our implementation with a prototypical multi-player game. Evaluation results indicate that our approach enables game creators to design scalable MOGs on the -to- environment with a short response latency which is acceptable for MOGs.

抄録全体を表示

Today's Multi-player Online Games (MOGs) are challenged by infrastructure requirements because of their server-centric nature. -to- overlay networks are an interesting alternative if they can implement the set of functions that are traditionally performed by centric game servers. In this paper, we propose a Zoned Federation Model (ZFM) to adapt MOGs to -to- overlay networks. We also introduce the concept of zone and zone owner to MOGs. A zone is some part of the whole game world, and a zone owner is a game sever of a specific zone. According to the demands of the game program, each node actively changes its role to a zone owner. By dividing the whole game world into several zones, workloads of the centric game server can be distributed to a federation of zones. In order to reduce response latency overhead on data exchanges between a zone owner and its clients, we limit the use of a Distributed Hash Table(DHT) to the rendezvous point of each zone; actual data exchanges are carried out through direct TCP connection between a zone owner and its members. We also use the DHT as backup storage media to cope with the resignation of a zone owner. We have implemented this zoned federation model as a middle layer between the game program and the DHT, and we evaluate our implementation with a prototypical multi-player game. Evaluation results indicate that our approach enables game creators to design scalable MOGs on the -to- environment with a short response latency which is acceptable for MOGs.

抄録全体を表示

Establishing -to- (P2P) live streaming for mobile ad hoc network (MANET) requires an efficient scheme to deliver the real-time data in the infrastructure-less disaster environment. However, P2P membership management is difficult in the dynamic mobility and resource limited MANET. In this paper, we present a cross-layer design for P2P-MANET which integrates P2P DHT-based routing protocol and IPv6 routing protocol. Therefore, the proposed scheme can manage and recover the P2P overlay as well as selecting efficient routing path to multicast video streaming. The simulation results demonstrate that the proposed scheme performs relatively better than the layered approach or the off-the-shelf design in terms of the playback continuity and signaling overhead.

抄録全体を表示

P2P (-to-) file sharing systems have been in operation for years. However, recent studies show that many peers in P2P networks are free-riders, who download files but are unwilling to share. This paper proposes a randomized search algorithm that considers the potential of a peer for information exchange and controlled query forwarding in the search process. Based on churn situations, the simulation results in this study demonstrate that the proposed algorithm can reduce network traffic and search latency while searching for files in the system.

抄録全体を表示

We study the use of network coding to speed up content distribution in -to- (P2P) networks. Our goal is to get the underlying reason for network coding's improved performance in P2P content distribution and to optimize resource consumption of network coding. We observe analytically and experimentally that in pure P2P networks, a considerable amount of data is sent multiple times from one peer to another when there are multiple paths connecting those two particular peers. Network coding, on the other hand, when applied at upstream peers, eliminates information duplication on paths to downstream peers, which results in more efficient content distribution. Based on that insight, we propose a network coder placement algorithm which achieves comparable distribution time as network coding, yet substantially reduces the number of encoders compared to a pure network coding solution in which all peers have to encode. Our placement method puts encoders at critical network positions to eliminate information duplication the most, thus, effectively shortens distribution time with just a portion of encoders.

抄録全体を表示

In P2P content distribution systems, there are many cases in which the content can be classified into hierarchically organized categories. In this paper, we propose a hybrid overlay network design suitable for such content called Pastry/NSHCC (Pastry for Non-Strictly Hierarchically Categorized Content). The semantic information of classification hierarchies of the content can be utilized regardless of whether they are in a strict tree structure or not. By doing so, the search scope can be restrained to any granularity, and the number of query messages also decreases while maintaining keyword searching availability. Through simulation, we showed that the proposed method provides better performance and lower overhead than unstructured overlays exploiting the same semantic information.

抄録全体を表示