• Journal of Communications and Networks
• /
• 제11권4호
• /
• pp.359-367
• /
• 2009

Trust-based solutions provide some form of payment to peers to encourage good behavior. The problem with trust management systems is that they require prior knowledge to work. In other words, peers are vulnerable to attack if they do not have knowledge or correct knowledge of other peers in a trust management system. Therefore, considering only trust is inadequate when a decision is made to identify the best set of peers to utilize. In order to solve the problem, we propose a distributed decision-making mechanism for wireless peer-to-peer (P2P) networks based on game theory and relevant trust mechanisms in which we incorporate the element of trust and risk into a single model. The main idea of our mechanism is to use utility function to express the relationship between benefits and costs of peers, and then make the decision based on expected utility as well as risk attitude in a fully distributed fashion. The unique feature of our mechanism is that it not only helps a peer to select its partners, but also mitigates vulnerabilities in trust-based mechanisms. Through analysis and experiments, we believe our approach is useful for peers to make the decision regarding who to interact with. In addition, it is also a good starting point for exploring tradeoffs among risk, trust and utility.

• Journal of Biosystems Engineering
• /
• 제43권4호
• /
• pp.263-272
• /
• 2018

Purpose: The load on the planet gear of a planetary gear set is uniformly distributed. However, manufacturing and assembly errors cause uneven load sharing in the planetary gear set. To solve this problem, most studies have suggested applying a floating sun gear to the planetary gear set. However, the effect of the floating ring gear and floating carrier has not been extensively studied. This study aimed to investigate the effect of the floating ring gear. Methods: Two models were developed; one was the fixed ring gear model, and the other was the floating ring gear model. In the fixed ring gear model, the clearance between the ring gear and the housing was $0{\mu}m$, and in the floating ring gear model, the clearance was from $10{\mu}m$ to $100{\mu}m$. The load sharing of the planetary gear set was evaluated by the load sharing factor. Results: Our study showed that with increase in clearance, the load sharing factor of the planetary gear set approached unity. In addition, when the clearance increased above a certain level by which a fully floating ring gear was achieved, the load sharing factor was not affected by the clearance. Conclusions: This indicates that the fully floating ring gear increased the power density of the planetary gearbox by uniformly dividing the load of the planetary gear set. For this reason, the size of the gearbox could be decreased by using a fully floating ring gear.

• 대한전기학회논문지:전력기술부문A
• /
• 제48권6호
• /
• pp.760-772
• /
• 1999

The CAN is a serial communication protocol for distributed real-time control and automation systems. Data generated from field devices in the distributed control of power plant are classified into three categories: real-time event data, real-time control data, non-real-time data. These data share a CAN medium. If the traffic of the CAN protocol is not efficiently controlled, performance requirements of the power plant system could not be satisfied. This paper proposes a bandwidth allocation algorithm that can be applicable to the CAN protocol. The bandwidth allocation algorithm not only satisfies the performance requirements of the real-time systems in the power plant but also fully utilizes the bandwidth of CAN. The bandwidth allocation algorithm introduced in this paper is validated using the integrated discrete-event/continuous-time simulation model which comprises the CAN network and distributed control system of power plant.

• 한국빅데이터학회지
• /
• 제4권2호
• /
• pp.73-83
• /
• 2019

4차 산업혁명의 기술 등장 이후 대규모 데이터 시대에서 새로운 가치 창출을 위한 데이터 정보 분석은 다양한 분야에서 시도되고 있다. 대용량 데이터를 빠르게 처리하는데 있어서 분산 데이터 처리는 이미 필수적이다. 하지만 아직 국방 분야에서 운용하고 있는 시뮬레이션들은 쌓여 있는 비정형 데이터를 활용할 수 있는 시스템이 미비하다. 이에 본 연구에서는 훈련간 발생하는 문제에 대응하기 위한 지휘결심에 가시화된 데이터를 제공하기 위해서 대대급 규모의 시뮬레이션 모델에 적용 가능한 분산 처리 플랫폼을 제안한다. 전략게임 데이터 50만개를 분석하는 과정으로, 데이터가 가지고 있는 여러 요인들 중 승리요인에 영향을 미치는 요소들을 분석할 수 있게 구현하였다. 결과적으로 상위 10%에 있는 팀들의 데이터를 분석하는 과정에서의 분산처리 사용한 결과를 측정 및 비교 하였다.

• 한국경영과학회지
• /
• 제19권3호
• /
• pp.1-14
• /
• 1994

In this paper, an analytical model of the message delay in the DQDB (Distributed Queue Dual Bus) network is investigated. The DQDB network has been adopted as a subnetwork for the IEEE 802 MAN (Metropolitan Area Network) standard. The DQDB network consists of two high speed undirectional buses and a series of stations attached to both of the buses. Massages arriving at each station consists of severla packets according to its size. This system is approximated into " $B^{[x]}$/G/1 with exceptional first service queueing " by defining the concept of service time on a packet. The service time for a packet is defined as the time from the instant the packet arrives at the transmission buffer until the time the packet is fully transmitted. By using the BASTA property and the average work in the system, the mean message delay time is obtained.age work in the system, the mean message delay time is obtained.d.

• 한국정보기술학회 영문논문지
• /
• 제10권2호
• /
• pp.73-81
• /
• 2020

The number of mobile devices roaming into a ubiquitous city (u-city) continues to rise as wireless systems have been widely deployed. The number of mobile devices also varies with time, and they tend to frequently change their locations. In addition, the available wireless access networks may belong to different domains, administrations, management, and internet service providers (ISPs). A fusion of overlapping heterogeneous wireless access networks (e.g., WiMax, Wi-Fi, LTE, etc.) serves the u-city in order to reach different coverage. In this context, technical challenges arise in mobility management for heterogeneous networks to realize their potential coverage and capacity benefits. This paper deals with the analysis of a decentralized mobility management support for u-City wireless network infrastructure. This scheme takes advantage of the features of the fully-distributed model of networked-based mobility management protocol to alleviate and realize the ubiquitous requirements of a u-City.

• 보건교육건강증진학회지
• /
• 제19권4호
• /
• pp.61-76
• /
• 2002

The purpose of this study is to identify differences in processes of change, decision making, and self-efficacy by exercise behavioral stages and determine variables significantly affecting the older people's participation in exercises. The subjects of this study included 299 people aged 65 or over who were residents of G and S districts in Busan Metropolitan City. They were selected through purposive quota sampling at colleges and centers for old people and homes in order that they could be evenly distributed over stages of pre-contemplation, contemplation, preparation, action and maintenance. Data were analyzed using descriptive, ANOVA, Logistic Regression. Variables that discriminate between participants and non-participants in exercise include self-reevaluation, reinforcing management, cons and self-efficacy. Thus if variables that discriminate between participant and non-participation in exercise such as self-reevaluation, reinforcing management, cons and self-efficacy are fully considered in designing nursing interventions for inducing old people to become exercise participants, it would provide guidelines for nursing intervention programs as appropriate for the people's exercise stages. The purpose of this study is to identify differences in processes of change, decision making, and self-efficacy by exercise behavioral stages and determine variables significantly affecting the older people's participation in exercises. The subjects of this study included 299 people aged 65 or over who were residents of G and S districts in Busan Metropolitan City. They were selected through purposive quota sampling at colleges and centers for old people and homes in order that they could be evenly distributed over stages of pre-contemplation, contemplation, preparation, action and maintenance. Data were analyzed using descriptive, ANOVA, Logistic Regression. Variables that discriminate between participants and non-participants in exercise include self-reevaluation, reinforcing management, cons and self-efficacy. Thus if variables that discriminate between participation and non-participation in exercise such as self-reevaluation, reinforcing management, cons and self-efficacy are fully considered in designing nursing interventions for inducing old people to become exercise participants, it would provide guidelines for nursing intervention programs as appropriate for the people's exercise stages.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제11권11호
• /
• pp.5338-5359
• /
• 2017

In-band full-duplex (IBFD) wireless communication supports symmetric dual transmission between two nodes and asymmetric dual transmission among three nodes, which allows improved throughput for distributed IBFD wireless networks. However, inter-node interference (INI) can affect desired packet reception in the downlink of three-node topology. The current Half-duplex (HD) medium access control (MAC) mechanism RTS/CTS is unable to establish an asymmetric dual link and consequently to suppress INI. In this paper, we propose a medium access control mechanism for use in distributed IBFD wireless networks, FD-DMAC (Full-Duplex Distributed MAC). In this approach, communication nodes only require single channel access to establish symmetric or asymmetric dual link, and we fully consider the two transmission modes of asymmetric dual link. Through FD-DMAC medium access, the neighbors of communication nodes can clearly know network transmission status, which will provide other opportunities of asymmetric IBFD dual communication and solve hidden node problem. Additionally, we leverage FD-DMAC to transmit received power information. This approach can assist communication nodes to adjust transmit powers and suppress INI. Finally, we give a theoretical analysis of network performance using a discrete-time Markov model. The numerical results show that FD-DMAC achieves a significant improvement over RTS/CTS in terms of throughput and delay.

• International Journal of Computer Science & Network Security
• /
• 제24권1호
• /
• pp.140-150
• /
• 2024

Database-as-a-Service is one of the prime services provided by Cloud Computing. It provides data storage and management services to individuals, enterprises and organizations on pay and uses basis. In which any enterprise or organization can outsource its databases to the Cloud Service Provider (CSP) and query the data whenever and wherever required through any devices connected to the internet. The advantage of this service is that enterprises or organizations can reduce the cost of establishing and maintaining infrastructure locally. However, there exist some database security, privacychallenges and query performance issues to access data, to overcome these issues, in our recent research, developed a database security model using a deterministic encryption scheme, which improved query execution performance and database security level.As this model is implemented using a deterministic encryption scheme, it may suffer from chosen plain text attack, to overcome this issue. In this paper, we proposed a new model for cloud database security using nondeterministic encryption, order preserving encryption, homomorphic encryptionand database distribution schemes, andour proposed model supports execution of queries with equality check, range condition and aggregate operations on encrypted cloud database without decryption. This model is more secure with optimal query execution performance.

• 한국지능시스템학회논문지
• /
• 제27권1호
• /
• pp.7-14
• /
• 2017

이론적으로 분산 비동기 통신 환경에서 공통믿음 또는 공통지식의 형성은 불가능하다고 받아들여져 왔으나, 서로 신뢰하는 에이전트 그룹에서는 비동기 통신을 사용하더라도 데드라인이 있는 명제들은 공통믿음이 될 수 있고 이를 바탕으로 한 추론이 가능함을 보여준다. 일반적으로 멀티에이전트 환경에서 공통믿음의 형성은 통신의 문제로 접근하며 통신 시간의 제약이 없는 시스템 상에서는 공통믿음이 형성되지 않는다는 공통믿음 역설 문제를 느슨한 정밀도를 적용하고 필요한 요구조건을 완화시켜 공통믿음을 형성 할 수 있음을 카카오톡 채팅방 모델을 통해 확인한다. 또한 카카오톡 채팅방 모델의 각 에이전트에 추론 기능을 구현하여 생성된 공통믿음을 알고 있는지에 관한 질의를 통해 공통믿음임을 확인하는 추론 기능을 실험하였다. 분산 멀티에이전트 환경에서 공통믿음의 표현과 추론을 메타논리 프로그래밍으로 형식화하였으며, 카카오톡 채팅방 모델을 통해 비동기 통신을 사용하는 분산 에이전트 그룹이 공통믿음을 형성할 수 있음을 실험적으로 보였다.