• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.379-386
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• 2001

Piled raft foundations are usually used to reduce total and differential settlements of superstructures. In the piled raft foundations, the raft is often on its own able to provide adequate bearing capacity and only few widely spaced piles are added to the foundation to keep settlements be1ow a certain limit. In this paper, experimental studies on the load sharing ratio between piles and raft are carried out. Also, for evaluating the application of optimum design technique using a genetic algorithm, optimal locations of files are compared with the results of laboratory model tests. from tile results of laboratory model tests, there are found that the load sharing ratio between files and raft is depended on the number of piles and stiffness of raft, and the optimal locations of piles became concentrated on the middle of rafts. From these results of laboratory model tests, the optimum technique using a genetic algorithm is acknowledged to the application in the piled raft.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.415-422
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• 1999

This paper describes a new optimum design approach for piled raft foundations using the genetic algorithm. The objective function considered is the cost-based total weight of raft and piles. The genetic algorithm is a search or optimization technique based on nature selection. Successive generation evolves more fit individuals on the basis of the Darwinism survival of the fittest. In formulating the genetic algorithm-based optimum design procedure, the analysis of piled raft foundations is peformed based on the 'hybrid'approach developed by Clancy(1993), and also the simple genetic algorithm proposed by the Goldberg(1989) is used. To evaluate a validity of the optimum design procedure proposed based on the genetic algorithm, comparisons regarding optimal pile placement for minimizing differential settlements by Kim et at.(1999) are made. In addition using proposed design procedure, design examples are presented.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.2
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• pp.267-277
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• 2017

One of fundamental problems in developing robust distributed services is how to achieve distributed consensus agreeing some data values that should be shared among participants in a distributed service. As one of algorithms for distributed consensus, Raft is known as a simple and understandable algorithm by decomposing the distributed consensus problem into three subproblems(leader election, log replication and safety). But, the algorithm dose not mention any types of dynamic configuration of participant peers such as adding new peers to a consensus group or deleting peers from the group. In this paper, we present a new consensus algorithm named Raft-D, which supports the dynamic configuration of participant peers by extending the Raft algorithm. For this, Raft-D manages the additional information maintained by participant nodes, and provides a technique to check the connection status of the nodes belonging to the consensus group. Based on the technique, Raft-D defines conditions and states to deal with adding new peers to the consensus group or deleting peers from the group. Based on those conditions and states, Raft-D performs the dynamic configuration process for a consensus group through the log update mechanism of the Raft algorithm.

• Journal of the Korean Geotechnical Society
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• v.16 no.3
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• pp.47-55
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• 2000

본 연구에서는, 유전자 알고리즘을 이용한 piled raft 기초의 최적설계 기법을 제시하였다. 최적설계에 사용한 목적함수는 구조물의 사용한계에 해당하는 부등침하량과 piled raft 기초의 시고비용 차원에서의 말뚝과 raft의 총 중량으로 하였다. 유전자 알고리즘은 다읜의 적자생존의 법칙을 따르는 자연진화 법칙을 바탕으로 한 최적화 기법이다. 본 연구에서는 piled raft 기초의 해석방법으로 Clancy(1993)가 제시한 "hybrid" 해석방법을 사용하였으며, 유전자 알고리즘기법은 Goldberg(1989)가 제시한 단순 유전자 알고리즘(SGA)을 적용하였다. 또한 유전자 알고리즘을 이용한 최적설계기법의 유효성을 평가하기 위해 설계예제 및 매개변수변화연구를 통해 piled raft 기초시스템의 중요 설계인자들에 대한 분석을 수행하였다. 매개변수변화연구로부터 말뚝의 길이와 raft의 두께가 증가할수록 piled raft 기초시스템의 전체 중량은 일정한 값에 점차적으로 수렴하였으며, 지반의 강정, raft의 두께 말뚝의 길이 및 강성이 증가할수록 말뚝의 최적위치는 raft의 중앙에 집중되는 경향으로 나타났다.경향으로 나타났다.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.11
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• pp.453-462
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• 2017

OpenDaylight is an SDN (Software Defined Networking) open source framework, which is popular in network fields recently. This paper analyzes the performance of a controller cluster architecture by focusing on distributed datastore and Raft leader election algorithm. In addition, we propose an enhanced version of Raft algorithm in order to improve the performance of distributed datastore by distributing shard leaders over controller cluster. This paper compares the conventional Raft algorithm with the proposed version of the Raft algorithm. Moreover, we compare the performance of distributed datastore according to shard roles such as leader and follower. Experimental results show that Shard leaders provide better performance than followers and Shard updating requests need to be distributed over multiple controllers. So, by using proposed version of Raft algorithm, controller performance can be improved. The details of the experiment results are cleary described.

• Proceedings of the Korean Society of Computer Information Conference
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• 2018.01a
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• pp.9-10
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• 2018

SDN 환경에서 여러 컨트롤러의 동기화는 중요한 문제로 대두되었다. 모든 컨트롤러의 네트워크 상태가 동일한지 여부를 확인하려면 컨트롤러를 효율적으로 동기화하기 위한 합의과정이 필요하다. 하지만 합의 과정에서 일어나는 지도자 선출과정이 임의적이기 때문에 시스템 상에서 시간지연이 일어날 수 있다. 본 논문에서 제안하는 우선순위 기반 Raft 알고리즘은 동기화 프로세스를 제어하는 강력한 지도자를 선택하여 동기화로드에서 시간을 절약할 수 있다.

• Geomechanics and Engineering
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• v.5 no.6
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• pp.519-540
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• 2013

This paper presents an optimal design method for determining pile lengths of piled raft foundations. The foundation settlement is evaluated by taking into account the raft-pile-soil interaction. The analysis of settlement is simplified by using Steinbrenner's equation. Then the total pile length is minimized under the settlement constraint. An extended sequential linear programming technique combined with an adaptive step-length algorithm of pile lengths is used to solve the optimal design problem. The accuracy of the simplified settlement analysis method and the validity of the obtained optimal solution are investigated through the comparison with the actual measurement result in existing piled raft foundations.

• Journal of the Korea Society of Computer and Information
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• v.26 no.12
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• pp.99-104
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• 2021

Blockchain technology is a distributed ledger technology that shares the ledger between multiple nodes connected to a distributed network. The data managed through the existing central server is managed through the blockchain, and the transparency, accuracy, and integrity of the transaction data is increased, and the need for data management through the blockchain is increasing. In this paper, recognizing the need for trust-based data sharing between trust-based institutions in the financial industry, this paper describes the process of selecting leader nodes in Raft, a private blockchain consensus algorithm, as a way to increase data management efficiency through blockchain. A modified consensus algorithm is presented. The performance of the modified consensus algorithm and the general Raft consensus algorithm presented in this paper was compared and analyzed based on the transaction processing time, and it was confirmed that the efficiency of the consensus process was increased by applying the proposed consensus algorithm.

• Coupled systems mechanics
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• v.1 no.2
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• pp.115-131
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• 2012

Paper presents an improved solution algorithm based on Finite Element Method to analyse piled raft foundation. Piles are modelled as beam elements with soil springs. Finite element analysis of raft is based on the classical theory of thick plates resting on Winkler foundation that accounts for the transverse shear deformation of the plate. Four node, isoparametric rectangular elements with three degrees of freedom per node are considered in the development of finite element formulation. Independent bilinear shape functions are assumed for displacement and rotational degrees of freedom. Effect of raft thickness, soil modulus and load pattern on the response is considered. Significant improvement in the settlements and moments in the raft is observed.

• Structural Engineering and Mechanics
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• v.7 no.6
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• pp.533-550
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• 1999

Optimal design of raft-pile foundations is examined by combining finite element technique and the optimization approach. The piles and soil medium are modeled by three dimensional solid elements while the raft is modelled by shell elements. Drucker-Prager criterion is adopted for the soil medium while the raft and the piles are assumed to be linear elastic. For the optimization process, the approximate semi-analytical method is used for calculating constraint sensitivities and a constraint approximation method which is a combination of the extended Bi-point approximation and Lagrangian polynomial approximation is used for predicting the behaviour of the constraints. The objective function of the problem is the volume of materials of the foundation while the design variables are raft thickness, pile length and pile spacing. The generalized reduced gradient algorithm is chosen for solving the optimization process. It is demonstrated that the method proposed in this study is promising for obtaining optimal design of raft-pile foundations without carrying out a large number of analyses. The results are also compared with those obtained from the previous study in which linear analysis was carried out.