Over the last several decades, many concrete tunnels have been constructed on roads, highways, and railways. For safety in concrete tunnels, periodic inspections have been conducted using nondestructive testing technologies and techniques. However, non-destructive test cannot replace the visual inspection due to their slow and complicated procedures. For this reason, they have been limited to precision inspections. The visual means also need time and there may be subjective in the measured crack data. Here, this study proposes inspection system for fast measuring cracks in tunnel lining and providing objective crack data for safety assessment. The system consists of both image data acquisition system and analysis system. The acquisition system takes images with CCD line-scan cameras. The analysis system extracts crack information from the acquired images using image processing. Measured crack information is crack thickness, length, and orientation. To improve the accuracy of crack recognition, the geometric properties and patterns of cracks in concrete structure should be applied to image processing. This proposed system was verified through a series of experiments in both laboratory and field environment -subway tunnel.
Reliability estimation methods using attribute data are widely used in reliability evaluation of various systems such as nuclear energy plants, food and drug, and space launch vehicles. This paper shows sensitivity analysis and comparison results of reliability estimation methods including a parametric estimation method in open literature with respect to both sample size and sampling points of time. And ways to improve accuracy of each reliability estimation method were proposed from the sensitivity analysis results.
This paper proposes a way to predict electrical lifetime of a relay using Accelerated Life Testings (ALTs). The relay of interest mounting on printed circuit boards is usually under an inrush current stress. The inrush current is generated and accelerated through controlling a lamp switching device in the ALT. We find that the dominant failure mechanism under high levels of inrush current would be contact welding in the contact surface of the relay and the contact welding process is accelerated according to increase in inrush current. The electrical lifetime model based on Inverse Power Law in term of inrush current is proposed, and parameters characterizing relay's lifetime distribution are statistically estimated using ALTA 6 PRO software.
It is necessary to both analyze root-cause of non-conformance of effective illumination time to the specification, and estimate the storage lifetime for 81 mm illuminating projectile stockpiled over 10 years. In this paper, aging mechanism of magnesium flare material due to long-term storage was supposed, and two-stage tests, pre-test and main test based on accelerated degradation tests were performed. Field storage environment of moistureproof was set up, and illumination times in the accelerated degradation tests for temperatures 60 and 70 ℃ were measured.Then, storage reliability of the projectile was estimated through analyzing the measured data and applying distribution-based degradation models to the data. The B 10 life by which 10 % of a population of the projectiles will have failed at storage temperature of 25 ℃ was estimated about 7 years.
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