• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.2005-2006
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• 2011

Due to the advantages of small sizes, more I/O ports, etc., Ball Grid Array (BGA) has been used in the production of printed circuit board (PCB). However, BGA voids can degrade the performance of the board and cause failure. To automatically detect the voids in X-ray image, a novel blob filter that makes use of the local image gradient magnitude is proposed in this paper. The utilization of the local image gradient magnitude makes the proposed filter invariant to the image brightness, void shape, void position, and component interference. Furthermore, different sizes of box filters are employed to analyze the image in multi-scale, and as a result, the proposed blob filter is robust to void size. Experimental results show that the proposed method can obtain void detection accuracy up to 96.104% while keep low false ratio.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.2
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• pp.69-80
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• 2017

In or To use, manage, and preserve sustainable water resources for the current and future generations amid the threat of abnormal climate, it is necessary to establish a smart water grid system, the next-generation intelligent water management system. In this study, sensors, which make use of the five senses to watch, listen, and detect machine vibration, bearing temperature, machine operation sounds, current, voltage, and other symptoms that cannot be verified when the irrigation facilities are running, are used to establish various decision-making criteria appropriate to on-site situations. Based on such criteria, the unmanned conditions in the facilities were verified and analyzed. Existing technologies require on-site workers to check any defects caused by overloading of machines, which is the biggest constraining factor in the application of an unmanned control system for irrigation facilities. The new technology proposed in this study, on the other hand, allows for the unmanned analysis of the existence of machine vibration. This controls the decision-making process of any defect based on the analysis results, and necessary measures are taken automatically, resulting in improved reliability of the unmanned automation.

• Earthquakes and Structures
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• v.10 no.5
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• pp.1089-1109
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• 2016

Modified two-surface model (M2SM) is one of the steel elasto-plastic hysteretic constitutive models that consider both analysis accuracy and efficiency. However, when M2SM is used for complex strain history, sometimes the results are irrational due to the limitation of stress-strain path judgment. In this paper, the defect of M2SM was re-modified by improving the judgment of stress-strain paths. The accuracy and applicability of the improved method were verified on both material and structural level. Based on this improvement, the nonlinear time-history analysis was carried out for a deck-through steel arch bridge with a 200 m-long span under the ground motions of Chi-Chi earthquake and Niigata earthquake. In the analysis, we compared the results obtained by hysteretic constitutive models of improved two-surface model (I2SM) presented in this paper, M2SM and the bilinear kinematic hardening model (BKHM). Results show that, although the analysis precision of displacement response of different steel hysteretic models differs little from each other, the stress-strain responses of the structure are affected by steel hysteretic models apparently. The difference between the stress-strain responses obtained by I2SM and M2SM cannot be neglected. In significantly damaged areas, BKHM gives smaller stress result and obviously different strain response compared with I2SM and M2SM, and tends to overestimate the effect of hysteretic energy dissipation. Moreover, at some position with severe damage, BKHM may underestimate the size of seismic damaged areas. Different steel hysteretic models also have influences on structural damage evaluation results based on deformation behavior and low cycle fatigue, and may lead to completely different judgment of failure, especially in severely damaged areas.

• Structural Engineering and Mechanics
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• v.74 no.6
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• pp.771-787
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• 2020

The paper provides an inside look into experimental measurements, followed by numerical simulations and their related uncertainties. The goal of the paper is to present findings related to blast loading and the handling of defects that are inherent in experiments. Very often it might seem that experiments are simplified reflections of real-life conditions. In most cases this is true, but there is a good reason for that. The more complex an experiment is, the larger the amount of uncertainties that can be expected. This especially applies when the blast loading of concrete is the subject of research. When simulations fail to reproduce the results of experimental measurements, it does not necessarily mean there is something wrong with the numerical model. The problem could be missing information. Put differently, the numerical simulation may lack information that seemed irrelevant with regard to the experiment. In the presented case, a reference simulation with a proven material model unexpectedly failed to replicate the results of an experiment where concrete slabs were exposed to blast loading. This resulted in a search for possible unknowns. When all of the uncertainties were examined, the missing information turned out to be the orientation of the charge to the concrete slab. Since the experiment was burdened with error, a sensitivity study had to take place so the influence of this factor could be better understood. The findings point to the fact that even the smallest defect during experiments must somehow be taken into account when designing numerical simulations. Otherwise, the simulations are not correlated to the experiments, but merely to some expectations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.142-145
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• 2015

Presentation is the form of communication to draw out audience's behaviors in a limited time. The importance of presentation is emphasized over time. So speaker uses various remote toola. Therefor, in this paper, the remote control system for presentation using mobile network was proposed. The existing remote control applications has error on network connection, and are difficult to use without description for use. This system was designed and implemented to compensate the defect of the existing system. The system we have will connect PC and smartphones through socket to communication with TCP, which is connection-oriented transport service. It is made for users to select the files from the list of sent files and operate the process of presentation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.7
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• pp.380-388
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• 2014

Transmission methods for terrestrial UHDTV broadcasting have been actively studied in order to provide enhanced broadcasting service in many countries. Most of the countries are considering multi-carrier transmission methods based on OFDM and some of them have performed UHDTV experimental broadcasting by using the DVB-T2 standard with the adoption of an improved data compression technique. However, since single carrier transmission methods, which are known to be susceptible to multi-path fading, could remedy this defect by using the SC-FDE method where a frequency domain equalizer is utilized in the receiver, they may achieve a similar transmission performance with multi-carrier transmission methods. In consideration of these circumstances, we compare the transmission performances of two-type methods to provide a decision criterion on a suitable transmission method for UHDTV broadcasting.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.7
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• pp.23-31
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• 2008

Experiment results are presented for gate oxide degradation under the constant voltage stress conditions using MOSFETs with 3-nm-thick gate oxides that are treated by deuterium gas. Two kinds of methods, annealing and implantation, are suggested for the effective deuterium incorporation. Annealing process was rather difficult to control the concentration of deuterium. Because the excess deuterium in gate oxide could be a precursor for the wear-out of gate oxide film, we found annealing process did not show improved characteristics in device reliability, compared to conventional process. However, deuterium implantation at the back-end process was effective method for the deuterated gate oxide. Device parameter variations as well as the gate leakage current depend on the deuterium concentration and are improved by low-energy deuterium implantation, compared to those of conventional process. Especially, we found that PMOSFET experienced the high voltage stress shows a giant isotope effect. This is likely because the reaction between "hot" hole and deuterium is involved in the generation of oxide trap.

• Composites Research
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• v.31 no.5
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• pp.251-259
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• 2018

In this paper, statistical volume element modeling method was developed for multi-scale progressive failure analysis of fiber reinforced composite materials. Big-size statistical volume elements (BSVEs) was considered to minimize the size effect in the micro-scale, by including as many fibers as possible. For that purpose, a mesh cutting method is suggested and adapted into the fiber model generator that creates finite element domain rapidly. The fiber defect model was also developed based on the experimental distribution of the fiber strength. The size effects from the local load sharing (LLS) are evaluated by increasing the fiber inclusion in the micro-scale model. Finally, continuum damage mechanics (CDM) model to the fiber direction was extracted from numerical analysis on BSVEs. And it was compared with strength prediction from typical representative volume element (RVE) model.

• Fire Science and Engineering
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• v.33 no.3
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• pp.121-127
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• 2019

This study examined a fire accident caused by a defect in the vehicle ABS module. A large number of vehicles using the same manufacturer's ABS module in recent fire events showed a tendency to combust due to the same faults. As previously stated in the ABS module which shows the electrical breakdown between the power lines supplied to the constant power source by the battery. The electrical breakdown of the ABS module was caused by defects of the ABS module itself that were influenced by of the external flame. These results highlight the need to determine if there is a deficiency of the ABS module in the investigation of the cause of a fire in a vehicle which is produced by the same manufacturer.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.4
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• pp.12-19
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• 2016

The monitoring system in railway is under study to forecast any derailment and accident by defect of train. Because the monitoring system is composed of wireless sensor network based on ZigBee-communication between inside and outside of train, the study for wireless channel analysis is required. Especially, if multipath delay profile exist in the channel, the equalizer and channel estimator can be required for preventing receiver performance degradation. Therefore, we analyzed the wireless channel in train environment using measured data and, proposed the channel estimation method through the characterisitic of chip code, under the consideration of the channel characteristics in train. To show the performance of proposed method, we demonstrate the performance by mean square error(MSE), computational complexity and bit error rate(BER).