• Journal of the Korean Society for Railway
• /
• v.20 no.4
• /
• pp.491-499
• /
• 2017

Railway turnout systems are one of the most important systems in a railway and abnormal turnout systems can cause serious accidents. To detect an abnormal state of a turnout, turnout clearance detectors are widely used. These devices consider a failure of a turnout clearance detectors to be a failure of the turnout system, that could hinder train operations. Analysis of turnout clearance detector failures is very important to ensure normal train operation. We categorized failures of detectors into four groups to identify failure characteristics of the 140 detectors, which are composed of main line detectors (A), side tracks (B), detectors that are in operation more than 80 times a day (C) and detectors that are in operation fewer than 10 times per day. Failures of detectors have mainly been caused in the control part, in the cables and sensors; failures are classified into four groups (A, B, C and D). We have tried to find failure density distributions for each type of failures, inferring the parameter distributions a priori. Finally, using the Bayesian inference we proposed a maintenance time for control parts through the mean time of the detector, life and the life expectancy.

• Nuclear Engineering and Technology
• /
• v.54 no.2
• /
• pp.617-626
• /
• 2022

To effectively monitor the variety of distributions of neutron flux, fuel power or temperatures in the reactor core, usually the ex-core and in-core neutron detectors are employed. The thermocouples for temperature measurement are installed in the coolant inlet or outlet of the respective fuel assemblies. It is necessary to reconstruct the measurement information of the whole reactor position. However, the reading of different types of detector in the core reflects different aspects of the 3D power distribution. The feasibility of reconstruction the core three-dimension power distribution by using different combinations of in-core, ex-core and thermocouples detectors is analyzed in this paper to synthesize the useful information of various detectors. A comparison of multilayer perceptron (MLP) network and radial basis function (RBF) network is performed. RBF results are more extreme precision but also more sensitivity to detector failure and uncertainty, compare to MLP networks. This is because that localized neural network could offer conservative regression in RBF. Adding random disturbance in training dataset is helpful to reduce the influence of detector failure and uncertainty. Some convolution neural networks seem to be helpful to get more accurate results by use more spatial layout information, though relative researches are still under way.

• The Journal of the Korea Contents Association
• /
• v.8 no.2
• /
• pp.9-17
• /
• 2008

Tn this paper, we design and analyze an election algorithm, based on the Bully algorithm, in synchronous distributed systems. We show that the Bully algorithm, when using Failure Detector, is more effectively implemented than the classic Bully algorithm for synchronous distributed systems.

• Journal of Korean Society of Transportation
• /
• v.12 no.4
• /
• pp.35-52
• /
• 1994

In order to operate the computerized traffic signal system, it requires the detectors which ensure the exact detections of actual traffic data (e.g., traffic volume, occupancy and velocity of vehicles). The octagonal detectors are used currently in Korea. However, the maintenance of the detectors has many problems with the road repairs and the constructions on the pavement, and failure due to the disconnection of the wires. Serious delay due to the long installation time of loops also causes the traffic disturbances. The low sensitivities and splash-over effect can sometimes create error data after installation of the octagonal loops. The mai purpose of this study is to evaluate the feasibility of domestic use of the round (circular) inductive loops which developed recently in U.S.A. It was found that the round loops are comparable to the existing octagonal loops. In addition, the use of the high quality of materials in the round loop system can reduce the current problems and weakpoints of the octagonal loops. The installation cost of the round loop was found out as economic as the octagonal loop. The installation time of the round loop system can be reduced with the specially equipped loop truck, and wide/deep slots without sharp corners can extend the durability without serious stress of loop head wires. In conclusion, the round loop is superior to the octagonal type in overall points. It is recommended that the localization of the materials and equipments of round loop system is required to carry out the extensive local installations. Also, several contractors to meet the nationwide demand should be arranged to gurantee the proper maintenance and operation of the systems.

• ETRI Journal
• /
• v.28 no.5
• /
• pp.555-560
• /
• 2006

A PIN photodiode having a low dark current of 1.35 nA and a high external quantum efficiency of 95.3% fabricated for a passive optical network receiver. As the current was increased under a high voltage of 38 V and a temperature of $190^{\circ}C$, it was observed that there is a threshold current at 11 mA which induces a junction failure. Experimental data suggest that the junction failure occurs due to the crystal breaking at the end facet as a result of thermal heat or energetic carriers. This threshold behavior of junction failure is a valuable observation for the safe treatment of photodiodes. As long as the current is limited below the threshold currents, we have not observed failure events of our photodiodes.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.5
• /
• pp.2457-2464
• /
• 2013

In this paper, we design and analyze a mutual exclusion algorithm, based on the Token and Failure detector, in asynchronous distributed systems. A Failure Detector is an independent module that detects and reports crashes of other processes. There are some of advantages in rewriting the Token-based ME algorithm using a Failure Detector. We show that the Token-based ME algorithm, when using Failure Detector, is more effectively implemented than the classic Token-based ME algorithm for synchronous distributed systems.

• The Transactions of the Korea Information Processing Society
• /
• v.7 no.12
• /
• pp.3815-3820
• /
• 2000

This paper is about the minimum requirements to solve the Election problem in asynchronous distributed systems. The focus of the paper is to find out what failure detector is the weakest one to solve the Election problem. We first discuss the relationship between the Election problem and the Consensus problem in asynchronous distributed systems with unreliable failure detectors and show that the Election problem is harder than the Consensus problem. More precisely, the weakest failure detector that is needed to solve this problem is a Perfect Failure Detector. which is strictly stronger than the weakest failure detector that is needed to solve Consensus.

• Journal of the Korea Society of Computer and Information
• /
• v.8 no.4
• /
• pp.35-40
• /
• 2003

In this paper, I raise an issue regarding the relationships between the Election problem and the Consensus problem in asynchronous systems with unreliable failure detectors. First, I describe our system model, and then define Leader Election. After then, I show that the Election problem is harder to resolve than the Consensus problem. Each correct process eventually gets into the state in which it considers only one process to be a leader. Therefore a Perfect Failure Detector is the weakest failure detector which is sufficient to solve the Election. In order to show that the Election problem is harder to resolve than the Consensus problem, I utilize the Reduction protocol in this paper.

• International Journal of Contents
• /
• v.7 no.4
• /
• pp.30-34
• /
• 2011

A Leader is a Coordinator that supports a set of processes to cooperate a given task. This concept is used in several domains such as distributed systems, parallelism and cooperative support for cooperative work. In completely asynchronous systems, there is no solution for the election problem satisfying both of safety and liveness properties in asynchronous distributed systems. Therefore, to solve the election problem in those systems, one property should be weaker than the other property. If an election algorithm strengthens the safety property in sacrifice of liveness property, it would not nearly progress. But on the contrary, an election algorithm strengthening the liveness property in sacrifice of the safety property would have the high probability of violating the safety property. In this paper, we presents a safety strengthened Leader Election protocol with an unreliable failure detector and analyses it in terms of safety and liveness properties in asynchronous distributed systems.

• International Journal of Contents
• /
• v.1 no.1
• /
• pp.21-28
• /
• 2005

This paper is about the hardness of Leader Election problem in asynchronous distributed systems in which processes can crash but links are reliable. Recently, the hardness of a problem encountered in the systems is defined with respect to the difficulty to solve it despite failures: a problem is easy if it can be solved in presence of failures, otherwise it is hard [9]. It is shown in [9] that problems are classified as three classes: F (fault-tolerant), NF (Not fault-tolerant) and NFC (NF-completeness). Among those, the class NFC is the hardest problem to solve. It is also shown in [9] that the construction of Perfect Failure Detector (problem P) belongs to NFC. In this paper, we show that Leader Election is also one of NFC problems by using a general reduction protocol that reduces the Leader Election Problem to P. We use a formulation of the Leader Election problem as a prototype to show that it belongs to NFC.