• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• v.9 no.1
• /
• pp.175-178
• /
• 2005

인터넷 상의 불특정 다수의 컴퓨팅 자원을 연계하여 오버레이 네트워크를 구성하여 새로운 컴퓨팅 인프라를 구성하려는 분산 해쉬 테이블 (Distributed Hash Table)방식의 Peer-to-Peer(P2P) 네트워크 관련 연구가 진행되고 있다. DHT 방식의 P2P네트워크는 자원의 복제 및 공유하여 컴퓨팅 시스템 전반에 걸친 신뢰성과 결함 감내 능력을 향상시키는 장점이 있는 반면에 하부 네트워크 정보를 무시하기 때문에 전체 시스템 구성 및 메시지 전송에 있어 실제적인 성능상의 문제점을 드러낸다. 이 논문에서는 하부 네트워크의 구성 정보를 이용하여 DHT 기반의 P2P 네트워크의 메시지 전송 방식의 효율을 높이는 방법을 소개한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• v.9 no.2
• /
• pp.150-152
• /
• 2005

인터넷 상의 컴퓨팅 자원을 오버레이 네트워크를 구성하여 새로운 컴퓨팅 인프라를 구성하려는 연구가 분산 해쉬 테이블 (Distributed Hash Table) 방식의 Peer-to-Peer(P2P) 네트워크로 실현되고 있다. DHT 방식의 P2P 네트워크는 자원의 복제 및 공유하여 컴퓨팅 시스템 전반에 걸친 신뢰성과 결함감내 능력을 향상시키고 Exactly Matching Query에 장점이 있는 반면에 다중키 질의, 계층 질의 및 구간 질의와 같은 복합 질의(Rich Query) 제원에 문제점을 드러낸다. 이 논문에서는 DHT 기반의 P2P 네트워크에서 Rich Query 를 지원하기 위한 방법을 소개한다.

• Proceedings of the KIEE Conference
• /
• 2001.07d
• /
• pp.2792-2794
• /
• 2001

인터넷은 정보의 바다로 표현할 만큼 방대하며, 이러한 넘치는 정보 속에서 사용자에게 필요한 정보들을 추출하여 사용자들의 효율성과 만족도를 높이는 것이 개인화 정책이고, 결과적으로 전자상거래 사이트에서의 판매의 증가를 이루기 위해 필요한 것이다. 따라서 개개인의 특성에 맞춘 개인화 서비스가 현재의 인터넷에서 제공하는 효율성을 뛰어넘을 수 있는 새로운 해결점으로 주목받고 있다. 본 논문에서는 기존의 협력 필터링(Collaborative filtering) 방법을 개선하여 사용자의 선호도(preference)를 결정하고, 이를 토대로 알맞은 아이템 추천 서비스를 사용자에게 제공하는 해쉬테이블 기반 협력 필터링 에이전트(Hash Table based Collaborative Filtering Agent)를 제안하고자 한다. 이를 통하여 기존의 사용자 또는 처음 방문한 사용자에게도 사이트를 방문하는데 만족도와 효율성을 높이도록 하는 것이 목표이다.

• Journal of KIISE:Databases
• /
• v.35 no.3
• /
• pp.199-207
• /
• 2008

The FP-tree(Frequency Pattern Tree) mining association rules algorithm was proposed to improve mining performance by reducing DB scan overhead dramatically, and it is recognized that the performance of it is better than that of any other algorithms based on different approaches. But the FP-tree algorithm needs a few more memory because it has to store all transactions including frequent itemsets of the DB. This paper implements a FP-tree algorithm on a general purpose UNK system and compares it with the DHP(Direct Hashing and Pruning) algorithm which uses hash tree and direct hash table from the point of memory usage and execution time. The results show surprisingly that the FP-tree algorithm is poor than the DHP algorithm in some cases even if the system memory is sufficient for the FP-tree. The characteristics of the test data are as follows. The site of DB is look, the number of total items is $1K{\sim}7K$, avenrage length of transactions is $5{\sim}10$, avergage size of maximal frequent itemsets is $2{\sim}12$(these are typical attributes of data for large-scale convenience stores).

• IEMEK Journal of Embedded Systems and Applications
• /
• v.12 no.6
• /
• pp.413-424
• /
• 2017

In this paper, we show shortcomings of separate chaining scheme by way of experiments with NAND flash memory and improve the performance with merge chaining scheme which is proposed in this paper. We explain this merge chaining scheme and explain how to improve the performance of search operation. Merge chaining scheme shows better performance at insert and search operation compare to separate chaining scheme.

• Journal of KIISE:Computing Practices and Letters
• /
• v.16 no.11
• /
• pp.1031-1040
• /
• 2010

Hash join is one of the core algorithms in databases management systems. If a hash join cannot complete in one-pass because the available memory is insufficient (i.e., hash table overflow), however, it may incur a few sequential writes and excessive random reads. With harddisk as the tempoary storage for hash joins, the I/O time would be dominated by slow random reads in its probing phase. Meanwhile, flash memory based SSDs (flash SSDs) are becoming popular, and we will witness in the foreseeable future that flash SSDs replace harddisks in enterprise databases. In contrast to harddisk, flash SSD without any mechanical component has fast latency in random reads, and thus it can boost hash join performance. In this paper, we investigate several important and practical issues when flash SSD is used as tempoary storage for hash join. First, we reveal the va patterns of hash join in detail and explain why flash SSD can outperform harddisk by more than an order of magnitude. Second, we present and analyze the impact of cluster size (i.e., va unit in hash join) on performance. Finally, we emperically demonstrate that, while a commerical query optimizer is error-prone in predicting the execution time with harddisk as temporary storage, it can precisely estimate the execution time with flash SSD. In summary, we show that, when used as temporary storage for hash join, flash SSD will provide more reliable cost estimation as well as fast performance.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.10 no.9
• /
• pp.4307-4325
• /
• 2016

With the aim of solving the problems of long processing times, high memory consumption and low event throughput in the current processing approaches in out-of-order RFID event streams, an efficient complex event processing method based on INFA-HTS (Improved Nondeterministic Finite Automaton-Hash Table Structure) is presented in this paper. The contribution of this paper lies in the fact that we use INFA and HTS to successfully realize the detection of complex events for out-of-order RFID event streams. Specifically, in our scheme, to detect the disorder of out-of-order event streams, we expand the traditional NFA model into a new INFA model to capture the related RFID primitive events from the out-of-order event stream. To high-efficiently manage the large intermediate capturing results, we use the HTS to store and process them. As a result, these problems in the existing methods can be effectively solved by our scheme. The simulation results of our experiments show that our proposed method in this paper outperforms some of the current general processing approaches used to process out-of-order RFID event streams.

• Journal of KIISE
• /
• v.41 no.10
• /
• pp.774-784
• /
• 2014

Studies of fault-injection into state machine diagram have been studied for generating robustness test cases. Conventional studies have, however, tended to inject too many faults into diagrams because they only have considered structural aspects of diagrams. In this paper, we propose a method that aims to reduce the number of injected fault without a decrease in effectivenss of robustness test. A proposed method is demonstrated using a microwave oven sate machine diagram and evaluated using a hash table state machine diagram. The result of the evaluation shows that the number of injected faults is decreased by 43% and the number of test cases is decreased by 63% without a decrease in effectiveness of hash table robustness test.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.8 no.3
• /
• pp.71-82
• /
• 2009

As a solution to spectrum under-utilization problem, Cognitive radio (CR) introduces a dynamic spectrum access technology. In the area, one of the most important problems is how secondary users (SUs) should choose between the available channels, which means how to achieve load balancing between channels. We consider spectrum load balancing problem for CR system in frequency domain and especially in time domain. Our objective is to balance the load among the channels and balance the occupied time length of slots for a fixed channel dynamically in order to obtain a user-optimal solution. In frequency domain, we refer to Dynamic Noncooperative Scheme with Communication (DNCOOPC) used in distributed system and a distributed Dynamic Spectrum Load Balancing algorithm (DSLB) is formed based on DNCOOPC. In time domain, Spectrum Load Balancing method with QoS support is proposed based on Dynamic Feed Back theory and Hash Table (SLBDH). The performance of DSLB and SLBDH are evaluated. In frequency domain, DSLB is more efficient compared with existing Compare_And_Balance (CAB) algorithm and gets more throughput compared with Spectrum Load Balancing (SLB) algorithm. Also, DSLB is a fair scheme for all devices. In time domain, SLBDH is an efficient and precise solution compared with Spectrum Load Smoothing (SLS) method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2002.11a
• /
• pp.592-596
• /
• 2002

Can speak that DTD is meta data that define meaning of expressed data on XML document. Therefore, In case DTD information is damaged this information to base security of XML document dangerous. Not that attach digital signature on XML document at send-receive process of XML document in this research, proposed method to attach digital signature to DTD. As reading DTD file to end first, do parsing, and store abstracted element or attribute entitys in hash table. Read hash table and achieve message digest if parsing is ended. Compose and create digital signature with individual key after achievement. When sign digital, problem that create entirely other digest cost because do not examine about order that change at message digest process is happened. This solved by method to create DTD's digital signature using DOM that can embody tree structure for standard structure and document.