• Korean Chemical Engineering Research
• /
• v.55 no.3
• /
• pp.322-331
• /
• 2017

District heating was first introduced in Korea in 1985. As the service life of the underground thermal piping network has increased for more than 30 years, the maintenance of the underground thermal pipe has become an important issue. A variety of complex technologies are required for periodic inspection and operation management for the maintenance of the aged thermal piping network. Especially, it is required to develop a model that can be used for decision making in order to derive optimal maintenance and replacement point from the economic viewpoint in the field. In this study, the analysis was carried out based on the repair history and accident data at the operation of the thermal pipe network of five districts in the Korea District Heating Corporation. A failure probability model was developed by introducing statistical techniques of qualitative analysis and binomial logistic regression analysis. As a result of qualitative analysis of maintenance history and accident data, the most important cause of pipeline damage was construction erosion, corrosion of pipe and bad material accounted for about 82%. In the statistical model analysis, by setting the separation point of the classification to 0.25, the accuracy of the thermal pipe breakage and non-breakage classification improved to 73.5%. In order to establish the failure probability model, the fitness of the model was verified through the Hosmer and Lemeshow test, the independent test of the independent variables, and the Chi-Square test of the model. According to the results of analysis of the risk of thermal pipe network damage, the highest probability of failure was analyzed as the thermal pipeline constructed by the F construction company in the reducer pipe of less than 250mm, which is more than 10 years on the Seoul area motorway in winter. The results of this study can be used to prioritize maintenance, preventive inspection, and replacement of thermal piping systems. In addition, it will be possible to reduce the frequency of thermal pipeline damage and to use it more aggressively to manage thermal piping network by establishing and coping with accident prevention plan in advance such as inspection and maintenance.

• Journal of Information Processing Systems
• /
• v.12 no.1
• /
• pp.57-72
• /
• 2016

To provide effective communication in the wireless mesh network (WMN), several algorithms have been proposed. Since the possibilities of numerous failures always exist during communication, resiliency has been proven to be an important aspect for WMN to recover from these failures. In general, resiliency is the diligence of the reliability and availability in network. Several types of resiliency based routing algorithms have been proposed (i.e., Resilient Multicast, ROMER, etc.). Resilient Multicast establishes a two-node disjoint path and ROMER uses a credit-based approach to provide resiliency in the network. However, these proposed approaches have some disadvantages in terms of network throughput and network congestion. Previously, the buffer based routing (BBR) approach has been proposed to overcome these disadvantages. We proved earlier that BBR is more efficient in regards to w.r.t throughput, network performance, and reliability. In this paper, we consider the node/link failure issues and analogous performance of BBR. For these items we have proposed a resilient packet transmission (RPT) algorithm as a remedy for BBR during these types of failures. We also share the comparative performance analysis of previous approaches as compared to our proposed approach. Network throughput, network congestion, and resiliency against node/link failure are particular performance metrics that are examined over different sized WMNs.

• Journal of Distribution Science
• /
• v.17 no.5
• /
• pp.5-17
• /
• 2019

Purpose - This study aims to exploratorily analyze relationship among pressure on business failure, social safety net perception, and entrepreneurial intention targeting potential business founders - pre-entrepreneurs and re-entrepreneurs. Research design, data, and methodology - Out of 450 collected surveys, 386 were used for analysis. Among these, 216 were from pre-entrepreneurs and 170 were from re-entrepreneurs. Frequency analysis, reliability and validity analysis, and regression analysis were performed. Results - In analysis of pre-entrepreneur and re-entrepreneur's pressure on business failure and social safety net perception, objective environment perception - a subfactor of social safety net perception - had statistically significant difference between the two potential entrepreneur groups. Conclusions - We categorized potential entrepreneurs into pre-entrepreneurs and re-entrepreneurs. Also, the current study suggests importance of social safety net to vitalize food service business startup by validifying its mediating effect between pressure on business failure and attitude towards restaurant business establishment. This research also established groundwork for future studies on ways to improve entrepreneurial intention or startup business sustainability by deducing social safety net perception difference between pre-entrepreneurs and re-entrepreneurs. This study was able to analyze relationship between those two groups in terms of entrepreneurial intention and startup business sustainability.

• Journal of Korean Society of Transportation
• /
• v.17 no.3
• /
• pp.117-130
• /
• 1999

Earthquakes damage roadway bridges and structures, resulting in significant impacts on transportation system Performance and regional economy. Seismic risk analysis (SRA) procedures establish retrofit priorities for vulnerable highway bridges. SRA procedures use average daily traffic volumes to determine the relative importance of a bridge. This research develops a cost-effective transportation network analysis (TAN) procedure for evaluating numerous traffic flow analyses in terms of the additional system cost due to failure. An important feature of the TNA Procedure is the use of an associative memory (AM) approach in the artificial intelligence held. A simple seven-zone network is developed and used to evaluate the TNA procedure. A subset of link failure system states is randomly selected to simulate synthetic post-earthquake network flows. The performance of different AM model is evaluated. Results from numerous link-failure scenarios demonstrate the applicability of the AM models to traffic flow estimation.

• International Journal of Aeronautical and Space Sciences
• /
• v.16 no.4
• /
• pp.510-519
• /
• 2015

Concerning the issue of high-dimensions, hybrid uncertainties of randomness and intervals including implicit and highly nonlinear limit state function, reliability analysis based on the hybrid uncertainty reliability mode combining with back propagation neural network (HU-BP neural network) is proposed in this paper. Random variables and interval variables are as input layer of the neural network, after the training and approximation of the neural network, the response variables are obtained through the output layer. Reliability index is calculated by solving the optimization model of the most probable point (MPP) searching in the limit state band. Two numerical cases are used to demonstrate the method proposed in this paper, and finally the method is employed to solving an engineering problem of the aerospace friction plate. For this high nonlinear, small failure probability problem with interval variables, this method could achieve a good analysis result.

• The KIPS Transactions:PartC
• /
• v.10C no.5
• /
• pp.603-610
• /
• 2003

On the optical network, it is important to build restoration scheme capable to network survivability in preparation of potential failure on communication route. This paper analyze the existing schemes on restoration of failure on the optical network, and propose deferred commit scheme to improve resource utilization and management efficiency. Also, the transfer flow of messages needed for transferring restoration signal are presented in a concrete way and delay time required by shared mesh restoration scheme is explained in a substantial way. Simulation-based comparative analysis of various schemes is performed.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.4B
• /
• pp.306-315
• /
• 2003

On the optical network, it is important to build restoration scheme capable to network survivability in preparation of potential failure on communication route. This analyze the existing schemes on restoration of failure on the optical network, and propose deferred commit scheme to improve resource utilization signal management efficiency. Also, the transfer flow of messages needed for transferring restoration signal are presented in a concrete way and delay time required by shared mesh restoration scheme is explained in a substantial way. Simulation-based comparative analysis of various scheme is performed.

• International Journal of Contents
• /
• v.5 no.4
• /
• pp.88-93
• /
• 2009

It is important for communication networks to possess the capability to overcome failures and provide survivable services. We address modeling and analysis of performability affected by both performance and availability of system components for a token ring network under failure and repair conditions. Stochastic reward nets (SRN) is an extension of stochastic Petri nets and provides compact modeling facilities for system analysis. In this paper, hierarchical SRN modeling techniques are used to overcome state largeness problem. The upper level model is used to compute availability and the lower level model captures the performance. And Normalized Throughput Loss (NTL) is obtained for the composite ring network for each node failures occurrence as a performability measure. One of the key contributions of this paper constitutes the Petri nets modeling techniques instead of complicate numerical analysis of Markov chains and easy way of performability analysis for a token ring network under SRN reward concepts.

• Geomechanics and Engineering
• /
• v.30 no.3
• /
• pp.281-291
• /
• 2022

Complex rock masses include various joint planes, bedding planes and other weak structural planes. The existence of these structural planes affects the mechanical properties, deformation rules and failure modes of jointed rock masses. To study the influence of the parameters of a nonpersistent joint network on the mechanical properties and failure modes of jointed rock masses, synthetic rock mass (SRM) technology based on discrete elements is introduced. The results show that as the size of the joints in the rock mass increases, the compressive strength and the discreteness of the rock mass first increase and then decrease. Among them, the joints that are characterized by "small but many" joints and "large and clustered" joints have the most significant impact on the strength of the rock mass. With the increase in joint density in the rock mass, the compressive strength of rock mass decreases monotonically, but the rate of decrease gradually decreases. With the increase in the joint dip angle in rock mass, the strength of the rock mass first decreases and then increases, forming a U-shaped change rule. In the analysis of the failure mode and deformation of a jointed rock mass, the type of plastic zone formed after rock mass failure is closely related to the macroscopic displacement deformation of the rock mass and the parameters of the joints, which generally shows that the location and density of the joints greatly affect the failure mode and displacement degree of the jointed rock mass. The instability mechanism of jointed surrounding rock is revealed.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.27 no.4C
• /
• pp.316-325
• /
• 2002

This paper investigates the restoration schemes which are applied to the MPLS domain upon a network failure. We define the following three restoration service models by combining the various restoration schemes: "FIS-based protection service" (FIS: failure indication signal), "inversion traffic protection service" and "1+1 protection service". After a qualitative analysis of the performance in them, we have analyzed it on quantitative basis by the simulation. According to the simulation results, "1+1 protection service" guarantees the fastest and most lossless restoration service among them; however, it results in consuming considerable bandwidth and producing an amount of control traffic, which means poor network utilization. On the other hand, "FIS-based protection service" spends less bandwidth and generates less control traffic, which means better network utilization, but produces poor restoration service. "Inversion traffic protection service" provides the medium restoration service and utilization between "1+1 protection service" and "FIS-based protection service."