• Journal of Biomedical Engineering Research
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• v.32 no.4
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• pp.305-311
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• 2011

For effective stimulation with tDCS, spatial focality of induced electrical field(EF) and current density(CD) is one of the important factors to be considered. Recently, there have been some studies to improve the spatial focality via different types of electrodes and their new configurations: some improvements using ring electrodes were reported over the conventional pad electrodes. However, most of these studies assumed isotropic conductivities in the head. In this work, we have investigated the effect of tissue anisotropy on the spatial focality of tDCS with the 4 + 1 ring electrode configuration via a 3-D high-resolution finite element(FE) head model with anisotropic conductivities in the skull and white matter. By examining the profiles of the induced EF from the head models with isotropic and anisotropic conductivities respectively, we found that the spatial focality of the induced EF significantly drops and get diffused due to tissue anisotropy. Our analysis suggests that it is critical to incorporate tissue anisotropy in the effective stimulation of the brain via tDCS.

• Journal of Welding and Joining
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• v.17 no.2
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• pp.61-65
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• 1999

Because of the need for packages which accommodate high pin count, high density and high speed device, PBGA(plastic ball grid array) package gets more spotlight. But the substrate material which is used for PBGA package is in nature susceptible to moisture penetration. The objective of the study is to find out the path of delamination in the stacked structure of substrate. To increase the adhesion between the cooper laminate and PSR(photo solder resist) which is the weakest part, experiments were performed by changing parameters of printing pre-treatment and post-treatment process. As a result of experiments, the factor effects on the adhesion between the cooper laminate and PSR is caused by all of the pre-treatment and post-treatment condition. A considerable change was observed depending on the amount of UV irradiation after thermal cure which is typical of printing post-treatment condition rather than pre-treatment condition.

• Journal of Welding and Joining
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• v.29 no.1
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• pp.99-106
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• 2011

Joint strength between a solder ball and a pad on a substrate is one of the major factors which have effects on electronic device reliability. The effort to improve solder joint strength via surface cleaning, heat treatment and solder composition change have been in progress. This paper will discuss the method of solder ball joint strength improvement using LF hydrogen radical cleaning treatment and focus on the effects of surface treatment condition on the solder ball shear strength and interfacial reactions. In the joint without radical cleaning, voids were observed at the interface. However, the specimens cleaned by hydrogen-radical didn't have voids at the interface regardless of cleaning time. The shear strength between the solder ball and the pad was increased over 120%(about 800gf) when compared to that without the radical treatment (680gf) under the same reflow condition. Especially, at the specimen treated for 5minutes, ball shear strength was considerably increased over 150%(1150gf). Through the observation of fracture surface and cross-section microstructure, the increase of joint strength resulted from the change of fracture mode, that is, from the solder ball fracture to IMC/Ni(P) interfacial fracture. The other cases like radical treated specimen for 1, 3, 7, 9min. showed IMC/solder interfacial fracture rather than fracture in the solder ball.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.9
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• pp.1133-1140
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• 2013

A computer model is a useful tool that provides solution via physical modeling instead of expensive testing. In reality, however, it often does not agree with the experimental data owing to simplifying assumption and unknown or uncertain input parameters. In this study, a Bayesian approach is proposed to calibrate the computer model in a probabilistic manner using the measured data. The elasto-plastic analysis of a pyrotechnically actuated device (PAD) is employed to demonstrate this approach, which is a component that delivers high power in remote environments by the combustion of a self-contained energy source. A simple mathematical model that quickly evaluates the performance is developed. Unknown input parameters are calibrated conditional on the experimental data using the Markov Chain Monte Carlo algorithm, which is a modern computational statistics method. Finally, the results are applied to determine the reliability of the PAD.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.36 no.2
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• pp.62-66
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• 2014

Osteoradionecrosis is one of the most serious complications of patients receiving radiation therapy. It is characterized by hypovascularity, hypocellularity, and hypoxia-inducing necrosis of bone and soft tissue following delayed healing. In this case, a 72-year-old man was referred to the Department of Oral and Maxillofacial Surgery complaining of trismus following extraction three months before first visit. He had a history of right tonsillectomy, radical neck dissection and radiotherapy performed due to right tonsillar cancer seven years prior. After the diagnosis of osteoradionecrosis on right mandibular body and angle, conservative antibiotic therapy was used first, but an orocutaneous fistula gradually formed, and extensive bony destruction and sequestrum were observed. Sequestrectomy, free particulated iliac bone and umbilical fat pad graft were performed via a submandibular approach under general anesthesia. Preoperative regular exams and delicate wound care led to secondary healing of the wound without vascularized free flap reconstruction.

• Journal of the Korean Society for Railway
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• v.19 no.4
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• pp.498-505
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• 2016

As a basic study to develop maintenance-effective optimal ballast track in preparation for upgrading a conventional line to a high speed railway, a full-scale test that combined the components of ballast track was conducted and the characteristic of track settlement was analyzed. As a result of the full-scale test, reduction in maintenance via an increase of the elasticity of only the pad was insignificant; however, the effect increased significantly with increasing of the weight of the sleeper or with increasing of the weight of the sleeper and the thickness of the ballast together with use of a pad with high resiliency. An optimal type of ballast track, in line with upgrading the speed of a conventional line, shall be developed through cost efficiency analysis considering the maintenance cost depending on the track settlement as well as the initial construction cost.

• Journal of Music and Human Behavior
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• v.13 no.1
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• pp.1-18
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• 2016

This study examined the correlation between the rhythm reproduction performance and cognitive function of school-aged children. A total of 59 third grade elementary students participated in this study. An iPad-based rhythm reproduction task, the Digit Span Test (DST), the Children's Color Trails Test (CCTT), and a self-paced tapping task via a MIDI keyboard were conducted for each participant. The results demonstrated that scores at each stage of the iPad-based rhythm reproduction test showed different patterns of correlation with cognitive function test scores. This result suggests that accuracy of a simple rhythm task is correlated to speed of self-paced tapping (second). Also cognitive function may affect rhythm grouping ability. Results of this analysis for each of 20 rhythm items showed that there was a common rhythm characteristics that correlated with executive function, working memory or self-paced tapping speed. These results indicate that rhythm ability is related to, and predictive of, the level of cognitive functioning in elementary school students and can be used as an useful parameter when examining cognitive function of school-aged children in multifaceted dimensions.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.523-523
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• 2012

As the wafer geometric requirements continuously complicated and minutes in tens of nanometers, the expectation of real-time add-on sensors for in-situ plasma process monitoring is rapidly increasing. Various industry applications, utilizing plasma impedance monitor (PIM) and optical emission spectroscopy (OES), on etch end point detection, etch chemistry investigation, health monitoring, fault detection and classification, and advanced process control are good examples. However, process monitoring in semiconductor manufacturing industry requires non-invasiveness. The hypothesis behind the optical monitoring of plasma induced ion current is for the monitoring of plasma induced charging damage in non-invasive optical way. In plasma dielectric via etching, the bombardment of reactive ions on exposed conductor patterns may induce electrical current. Induced electrical charge can further flow down to device level, and accumulated charges in the consecutive plasma processes during back-end metallization can create plasma induced charging damage to shift the threshold voltage of device. As a preliminary research for the hypothesis, we performed two phases experiment to measure the plasma induced current in etch environmental condition. We fabricated electrical test circuits to convert induced current to flickering frequency of LED output, and the flickering frequency was measured by high speed optical plasma monitoring system (OPMS) in 10 kHz. Current-frequency calibration was done in offline by applying stepwise current increase while LED flickering was measured. Once the performance of the test circuits was evaluated, a metal pad for collecting ion bombardment during plasma etch condition was placed inside etch chamber, and the LED output frequency was measured in real-time. It was successful to acquire high speed optical emission data acquisition in 10 kHz. Offline measurement with the test circuitry was satisfactory, and we are continuously investigating the potential of real-time in-situ plasma induce current measurement via OPMS.

• International Journal of Knowledge Content Development & Technology
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• v.7 no.3
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• pp.67-86
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• 2017

The emergence of smart devices such as smartphones (e.g., iPhone) and tablets (e.g., iPad) may enhance e-learning by increasing communication and collaborative learning outside the classroom. These devices also facilitate the use of online technologies such as Facebook. However, the adaptation of Learning Management System (LMS) services to mobile devices took longer than social networks or online tools such as Facebook and Twitter have already been long used via smartphone. The main purposes of this study are to explore students' skill levels of LMS (Moodle) and their knowledge of online tools or technologies and then examine if there is a correlation between smartphone use and using of online tools and Moodle in learning. The study conducted among 173 students in the Department of Information Studies (DIS) in Oman, using online survey. The study found that most students demonstrated high levels of accessing course/subject materials and regularly engaging with studies of using LMSs. YouTube, Wikipedia and Facebook were clearly recorded as the most popular sites among students while LinkedIn and Academia.edu were two online tools that had never been heard of by over half of the 142 participants. Emailing and searching are recorded the most popular online learning activities among students. The study concluded that students prefer to use smartphone for accessing these tools rather than using it to access LMSs, while a positive correlation was found between the use of these tools and smartphones, but there was no correlation between smartphones and using LMSs.

• Imaging Science in Dentistry
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• v.54 no.1
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• pp.115-120
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• 2024

Components derived from an infected lesion within the bone can spread through various passages in the mandible, particularly via the mental foramen. Radiologically, the spread of infection is typically nonspecific and challenging to characterize; however, multislice computed tomography (MSCT) can effectively detect pathological changes in soft tissues and the bone marrow space. This report describes the case of a 55-year-old woman who experienced mental nerve paresthesia due to a periapical infection of the right mandibular second premolar. MSCT imaging revealed increased attenuation around the periapical lesion extending into the mandibular canal and loss of the juxta-mental foraminal fat pad. Following endodontic treatment of the tooth suspected to be the source of the infection, the patient's symptoms resolved, and the previous MSCT imaging findings were no longer present. Increased bone marrow attenuation and obliteration of the fat plane in the buccal aspect of the mental foramen may serve as radiologic indicators of inflammation spreading from the bone marrow space.