• Journal of Korea Water Resources Association
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• v.33 no.6
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• pp.711-723
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• 2000

Existing equations of bed load transport have large variations in their forms and adopt different variables so that it is very difficult to understand the characteristics of each equation. Different sets of measurement data have been employed for the development of various equations, and the comparison between them is completely dependent on the choice of the data for the verification. Several equations seem to have some defects in their basic assumptions. Various non-dimensional physical numbers directly associated with the mechanism of bed load transport are related with each other, and one of them is chosen for the unification of the form. Good ideas introduced in a certain equation are employed for the refinement of other equations. Then optimum values of empirical parameters have been determined by using the data collected by Brownlie(1981) and a new bed load equation has been developed, which is considered widely valid and relatively very accurate.curate.

• KIISE Transactions on Computing Practices
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• v.23 no.10
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• pp.605-610
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• 2017

In distributed environments, dynamic partitioning is needed to resolve the load on a particular server or the load caused by communication among servers. In heterogeneous environments, existing dynamic partitioning schemes can distribute the same load to a server with a low physical performance, which results in a delayed query response time. In this paper, we propose a dynamic partitioning scheme for large RDF data in heterogeneous environments. The proposed scheme calculates the query loads with its frequency and the number of vertices used in the query for load balancing. In addition, we calculate the server loads by considering the physical performance of the servers to allocate less of a load to the servers with a smaller physical performance in a heterogeneous environment. We perform dynamic partitioning to minimize the number of edge-cuts to reduce the traffic among servers. To show the superiority of the proposed scheme, we compare it with an existing dynamic partitioning scheme through a performance evaluation.

• The KIPS Transactions:PartA
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• v.10A no.6
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• pp.729-736
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• 2003

With the rapid growth of the Internet, popular Web sites are visited so frequently that these cannot be constructed with a single server or mirror site of high performance. The rapid increase of Internet uses and uses raised the problems of overweighted transmission traffic and difficult load balancing. To solve these, various schemes of server clustering have been surveyed. Especially, in order to fully utilize the performance of computer systems in a cluster, a good scheduling method that distributes user requests evenly to servers in required. In this paper, we propose a new method for reducing the service latency. In our method, each Web server in the cluster has different content. This helps to reduce the complexity of load balancing algorithm and the service latency The Web server that received a request from the load balancer responds to the client directly without passing through the load balancer. Simulation studies show that our method performs better than other traditional methods. In terms of response time, our method shows shorter latency than RR (Round Robin) and LC (Least Connection) by about 16%, 14% respectively.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.39 no.6
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• pp.1-10
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• 2002

According to the rapid evolution of internet, the number of internet users has greatly increased, so that the web servers are getting more important. If there are a great number of users trying to connect to a popular web server, the load of the web server will increase rapidly, so that failures may occur or web services may stop. An efficient load monitoring technique is required for the available web services and the performance management. The traditional techniques for load monitoring of web server using the client-server method have the problem that the server programs in client-server method must be pre-installed to all web servers. This paper implements web server load monitoring system using the mobile agent in order to overcome the problem of client-server computing. The system based on the mobile agent has no need to install the program in advance and it reduces the network traffic and the additional overheads in web servers.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.2
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• pp.107-120
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• 1987

This study is directed for the evolution of the rational approaches to the systematic evaluation of the load carrying capacity of bridges based on the practical and second moment reliability methods. A new approach for the evaluation of load carrying capacity of exsisting bridges is proposed in this study. The key idea behind this approach is in the fact that the load carrying capacity of an existing bridges under extreme traffic truck loadings may be measured by evaluating and classifying the reliability state of the bridge in terms of reliability index(${\beta}$). The rating formulas developed in this study are applied for the evaluation of load carrying capacity of the several actual deteriorated bridges inspected and tested for the capacity rating, and the results are compared with those calculated by using the current rating formulas. It may be concluded that the proposed rating formulas which is derived based on reliability methods, have to eventually replace the current rating formula when the basic statistical data for the resistance and load effects become available in the near future.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.183-193
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• 2008

The reliability analysis of simply-supported and continuous composite plate girder and box girder bridges under flexure was performed to provide a basic data for the development of LRFD c ode. The bridges were designed based on LRFD specification with newly proposed design live load which was developed by analyzing traffic statistics from highways and local roads. A performance function for flexural failure was expressed as a function of the flexural resistance of composite section and the design moments due to permanent load and live load. For the flexural resistance, the statistical parameters obtained by analyzing over 16,000 domestic structural steel samples were used. Several different values of bias factors for the live load moment from 1.0 to 1.2 were used. Due to the lack of available domestic measured data on the moment by permanent loads, the same statistical properties used in the calibration of ASHTO-LRFD were ap plied. The reliability indices for the composite girder bridges with various span lengths, different live load factors, and bias fact or for the live load were obtained by applying the Rackwitz-Fiessler technique.

• Journal of Advanced Navigation Technology
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• v.27 no.3
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• pp.255-261
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• 2023

A main purpose of this research was to analyze environmental factors to influence helicopter accidents contrary to the fact that the almost 80% of helicopter accidents happened due to pilots' human errors. There have been about 14 helicopter accidents in civil aviation sector last decade. It is noteworthy that nine of 14 accidents happened during the external sling load operation. Moreover, there is no law or regulation which could cover the helicopter external sling load operation or human external cargo in Korea. In this paper, it was analyzed the training and education regulations regarding helicopter external sling load operation or human external cargo in regulations of FAA and EASA, Based on analyzing and comparing the FAR part 133 and domestic aviation law (aviation safety act and flight safety regulations), it was found out the implication how to apply helicopter type rating for external sling load operation and human external cargo operation. To sum up, this paper expect central government should cooperate and amend aviation law which apply external sling load operation and external cargo to establish sound safety culture in Korea.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.873-876
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• 2002

This paper presents the effect of internal corrosion, external corrosion, material properties, operation condition, earthquake, traffic load and design thickness in pipeline on the failure prediction using a failure probability model. A nonlinear corrosion is used to represent the loss of pipe wall thickness with time. The effects of environmental, operational, and design random variables such as a pipe diameter, earthquake, fluid pressure, a corrosion rate, a material yield stress and a pipe thickness on the failure probability are systematically investigated using a failure probability model for the corrosion pipeline.

• The Transactions of the Korea Information Processing Society
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• v.6 no.11S
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• pp.3251-3259
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• 1999

In this paper, we present a new mechanism applying more strict priority than RIO mechanism proposed as a drop precedence policy of AF classes in differentiated services. In this mechanism, applying strict priority to drop precedence policy, we get better performance on priority level. Simulation results indicate that the proposed mechanism may provide more efficient and more strict priority transmissions as compared to RIO regardless of traffic load.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10c
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• pp.553-555
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• 2003

Mobile Ad hoc network에서 이동 노드들의 안정적이고 신뢰성이 높은 데이터 전송을 하기 위해서 multipath routing을 통하여 소스 목적지 노드간에 다중 경로를 구하고 기존의 라우팅 방법과 비교해 본다. 또한 다중 경로를 활용하는 방법과 경로구간의 링크 다운 시에 보다 빠른 복원을 할 수 있는 방법을 제시하고자 한다. 모바일 노드들의 이동성과 낮은 대역폭으로 인한 데이터 손실을 줄이는 방법으로 데이터 트래픽을 다중경로에 분산시키는 Traffic Load Balancing 방법과 데이터 전송 중에 발생하는 링크 다운 시에 새로운 경로를 찾는 메커니즘이 아닌 중간 경로에서 기존에 유효한 경로를 이용하는 Local recovery 방법을 소개하고자 한다.