• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2862-2867
• /
• 2008

High-temperature components of gas turbine operated for certain period of time can be reused by being repaired or rejuvenated. In case of the gas turbine combustion liners, the biggest and the most important one in the high-temperature components, come in a repair shop after operated for 8,000 or 12,000 hours according to the model and go through the repair and rejuvenation in order to be reused. A stated combustion liner is the first channel which has the combustion gas reached a nozzle from a fuel nozzle. Materials and coating properties of old and new model combustion liners were investigated. To repair these components after the visual inspection, the coatings of combustion liners were removed and then FPI(Fluorescent Penetrant Inspection), a kind of the NDI(Non-Destructive Inspection), was conducted. Damage patterns and the number of the damaged components were classified and analyzed based on data provided from the visual inspection over a long period of time. Focusing on the difference between old model and new model combustion liners, we analyzed the damage distribution and changes and consequently concluded that new model combustion liner would increase repair rate.

• Structural Engineering and Mechanics
• /
• v.17 no.3_4
• /
• pp.483-492
• /
• 2004

This paper presents an efficient algorithm for the estimation of damage location and severity in bridge structures using Probabilistic Neural Network (PNN). Generally, the Back Propagation Neural Network (BPNN)-based damage detection methods need a lot of training patterns for neural network learning process and the optimum architecture of a BPNN is selected by trial and error. In this paper, the PNN instead of the conventional BPNN is used as a pattern classifier. The modal properties of damaged structure are somewhat different from those of undamaged one. The basic idea of proposed algorithm is that the PNN classifies a test pattern which consists of the modal characteristics from damaged structure, how close it is to each training pattern which is composed of the modal characteristics from various structural damage cases. In this algorithm, two PNNs are sequentially used. The first PNN estimates the damage location using mode shape and the results of the first PNN are put into the second PNN for the damage severity estimation using natural frequency. The proposed damage assessment algorithm using the PNN is applied to a cable-stayed bridge to verify its applicability.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.16 no.3
• /
• pp.229-236
• /
• 2003

Artificial neural network has been used for damage assessment by many researchers, but there are still some barriers that must be overcome to improve its accuracy and efficiency. The major problems associated with the conventional artificial neural network, especially the Back Propagation Neural Network(BPNN), are on the need of many training patterns and on the ambiguous relationship between neural network architecture and the convergence of solution. Therefore, the number of hidden layers and nodes in one hidden layer would be determined by trial and error. Also, it takes a lot of time to prepare many training patterns and to determine the optimum architecture of neural network. To overcome these drawbacks, the PNN can be used as a pattern classifier. In this paper, the PNN is used numerically to detect damage in a plate girder railway bridge. Also, the comparison between mode shapes and natural frequencies of the structure is investigated to select the appropriate training pattern for the damage detection in the railway bridge.

• Fire Science and Engineering
• /
• v.25 no.6
• /
• pp.21-26
• /
• 2011

The purpose of this paper is to present the damage patterns of cellular phone (SCH_W830) batteries according to energy sources and have them utilized as data for the settlement of disputes between manufactures and consumers. The reliability was secured by maintaining the ambient temperature and humidity at $22{\pm}2^{\circ}C$ and 40~60 %, respectively. The voltage of the battery used for the tests was measured to be 4.18V between positive pole (+) and negative pole (-)(1), and 4.19 V between positive pole (+) and negative pole (-)(2). This study applied the Korean Industrial Standard (KS) to the flammability test of cellular phones due to a general flame applied to them and found that no damage occurred to the built-in battery even though the flame was applied to the cases of cellular phones for 30 seconds. From the results of immersing the cellular phones in the saline solution (NaCl, 0.9 %) for 180 seconds, it was found that there was a trace of carbonization and melting due to the heat caused by leaking current. It can be seen that when the cellular phones were heated for 70 seconds using a microwave oven (MWO), the areas containing the metal holder, recharging connector, antenna, etc., were melted and discolored and that other areas showed no particular problems. That is, while the external carbonization of cellular phones, built-in metals and dielectric materials, and damage and deformation of the battery terminal block, etc., occurred differently depending on the types of energy sources, the voltage showed comparatively constant characteristics. Therefore, it is thought to be possible to attribute the cause of damage to the battery by performing analysis taking into consideration comprehensively the characteristics of the flame spread pattern as well as the melting and deformation of metals.

• Journal of Information Technology Services
• /
• v.21 no.6
• /
• pp.73-89
• /
• 2022

After COVID-19, the percentage of digital consumption has soared. Meanwhile, as the online platform market grows in size and digital commerce is activated, controversy over the "dark pattern" that induces consumers to do unintended things online continues. Dark patterns are deceptive design patterns that cause consumer rights and financial damage and can result in damaging fair market competition. As a result, the need to regulate dark patterns is raised not only by overseas regulators but also in Korea, and there are growing calls for strengthening consumer protection against dark patterns, with amendments to related laws being proposed by the National Assembly. On the other hand, there is no agreed definition of dark pattern from a normative point of view, and there is a concern that even legitimate advertising marketing activities of companies may be regulated, so a review of dark pattern regulatory measures is required. In this study, dark patterns were reviewed from a normative point of view and appropriate regulatory measures were analyzed. In particular, the problem of the dark pattern can be applied in a way that the market regulates and controls itself in consideration of the characteristics of the online platform. This study reviewed the possibility of self-regulation for dart patterns and proposed the role of each subject.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.22 no.7
• /
• pp.667-675
• /
• 2012

A damage estimation method for support structure of offshore wind turbine using modal parameters is presented for effective structural health monitoring. Natural frequencies and mode shapes for a support structure with monopile of an offshore wind turbine were calculated considering soil condition and added mass. A neural network was learned based on training patterns generated by the changes of natural frequency and mode shape due to various damages. Natural frequencies and mode shapes for 10 prospective damage cases were input to the trained neural network for damage estimation. The identified damage locations and severities agreed reasonably well with the accurate damages. Multi-damage cases could also be successfully estimated. Enhancement of estimation result using another parameters as input to neural network will be carried out by further study. Proposed method could be applied to other type of support structure of offshore wind turbine for structural health monitoring.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2006.11a
• /
• pp.489-492
• /
• 2006

In this study we collected and analyzed cases where typhoons damaged coastal structures in Korea in the past 6 years, and hydraulic model tests were conducted in 2D flume. 2 areas where damage was concentrated were selected from ports that had suffered damage. The selected area was Kyungsang-namdo, where there are a total of 26 national ports. Damage to these two areas was organized by wind direction of the typhoons and the direction of the entrance of the port, and destruction patterns were analyzed. 2D hydraulic model tests were conducted of Deabyeun port, one of the damaged areas. Results were as follows: 1. As a result of survey, ports that had entrances that were open to winddirection of typhoon (Anti-clockwise direction) tended to be damaged mare, whereas ports that blocked by island and ports that were not open to wind direction of typhoon were not damaged. 2. As a result of the tests, there was damage that occurred when using the section of designed section, whereas there was no damage when the TTP weight was increased.

• Computational Structural Engineering : An International Journal
• /
• v.3 no.1
• /
• pp.9-17
• /
• 2003

This paper aims at investigating the damage process of steel members leading to the failure under strong repeated loading, proposing the damage index using various factors related to the damage, and developing the analysis method for evaluating the damage state. Cantilever-type steel members were analyzed under uniaxial load and combined with a constant axial load, considering a horizontal displacement history. In analyzing the models, loading patterns and steel types (SS400, SM570, Posten80) were considered as main parameters. From the analysis results, the effects of parameter on the failures mode, the deformation capacity, the damage process are also discussed. Each failure process was compared as steel types. Consequently, the failure of steel members under strong repeated loading was determined by loading. Especially it was seen that the state of the failure is closely related to the local strain.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.5 no.4
• /
• pp.20-30
• /
• 2001

This study represents the Nondestructive Test about impact damage of composite materials made by different lay-up patterns and degrees. For this study, they were examined by the drop test on composite materials of two type lap-up patterns with fabric and unidirectional prepreg and examined nondestructive test of those. Nondestructive methods were X-ray test with $ZnI_2$ penetrant and Ultrasonic C-scan. The defect detectability of X-ray and Ultrasonic test was compared according to defect species. And the amounts of damage on impacted zone wert compared according to impact energy on two type test specimens. At results, Ultrasonic test was more effective to detect delamination and Penetrant X-ray test was more effective to detect matrix crack and fiber fracture. There were some differences in defect shapes and grades according to lay-up patterns and degrees, and the trend appeared that matrix crack, delamination, fiber fracture occured and increasing defects sizes according to increasing impact energy.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2001.04a
• /
• pp.190-195
• /
• 2001

In the present paper computational simulation of a concrete dam is performed to determine the effect of vertical ground motions on earthquake response of concrete dams. Cyclic and dynamic versions of the plastic-damage model proposed by Lee and Fenves are used to represent micro-crack development and crack opening/closing, which is important mechanism in nonlinear damage analysis of concrete structures subject to strong earthquake loading. The result shows that the vertical component of ground motion effects on final crack patterns and consequently, on displacement response.