• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.658-665
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• 2013

While the chirp signal is extensively used in radar and sonar systems for target decision in wireless communication systems, it has not been widely used for positioning in indoor environments. Recently, the IEEE 802.15.4a standard has adopted the chirp spread spectrum (CSS) as an underlying technique for low-power and low-complexity precise localization. Chirp signal based ranging solutions have been established and deployed but their ranging performance has not been analyzed in multipath environments. This paper presents a ranging performance analysis of a chirp signal and suggests a method to suppress multipath error by using a type of non-linear chirp signal. Multipath ranging performance is evaluated using a conventional linear chirp signal and the proposed non-linear chirp signal. We verify the feasibility of both methods using two-ray multipath model simulation. Our results demonstrate that the proposed non-linear chirp signal can successfully suppress the multipath error.

• Journal of Power System Engineering
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• v.17 no.5
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• pp.100-111
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• 2013

Indoor real-time positioning for multiple targets is required to realize human-robot symbiosis. This study firstly presents positioning accuracy on an autonomous mobile robot controlled by 3-D coordinates that is obtained by a real-time indoor positioning system with spread spectrum (SS) ultrasonic signals communicated by code-division multiple access. Although many positioning systems have been investigated, the positioning system with the SS ultrasonic signals can measure identified multiple 3-D positions in every 70 ms with noise tolerance and error within 100 mm. This system is also robust to occlusion and environmental changes. However, thus far, the positioning errors in an autonomous mobile robot, controlled by these systems using the SS ultrasonic signals, have not been evaluated as an experimental study. Therefore, a positioning experiment for trajectory control is conducted using an autonomous mobile robot and our positioning system. The effectiveness of this positioning method for robot self-localization is shown, from this experiment, because the average control error between the target position and the robot's position at 29 mm is obtained.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.438-440
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• 2005

At present, characteristic of high color reproduction for LCD TV is needed in Display market according to start mass production of LCD TV. Therefore development target for LCD is focused on improvement of color reproduction. The improving methods of high color reproduction are alteration of color Filter or Red, Green, Blue phosphor alteration of CCFL. But decrease of luminance and panel transmittance is caused by alteration of Color Filter. Accordingly, we completed LCD with high color reproduction by the most suitable emission spectrum of CCFL phosphor at panel with conventional color filter. In this experiment, we knew that LCD applied to CCFL with high color rendering characteristic had color reproduction range of 81% compared with NTSC in CIE color coordinate. According to increase of intensity peak and alteration of Red, Green, Blue phosphor spectrum, we made LCD with high color reproduction characteristic. In conclusion we achieved improvement of color reproduction ratio by alteration of CCFL phosphor without changing color filter.

• BMB Reports
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• v.52 no.7
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• pp.424-433
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• 2019

Autism spectrum disorder (ASD) is a complex neurodevelopmental monogenic disorder with a strong genetic influence. Idiopathic autism could be defined as a type of autism that does not have a specific causative agent. Among signalling cascades, mTOR signalling pathway plays a pivotal role not only in cell cycle, but also in protein synthesis and regulation of brain homeostasis in ASD patients. The present review highlights, underlying mechanism of mTOR and its role in altered signalling cascades as a triggering factor in the onset of idiopathic autism. Further, this review discusses how distorted mTOR signalling pathway stimulates truncated translation in neuronal cells and leads to downregulation of protein synthesis at dendritic spines of the brain. This review concludes by suggesting downstream regulators such as p70S6K, eIF4B, eIF4E of mTOR signalling pathway as promising therapeutic targets for idiopathic autistic individuals.

• Earthquakes and Structures
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• v.16 no.4
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• pp.437-453
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• 2019

This study investigates a new optimal placement method for viscous dampers between structures in order to prevent pounding of adjacent structures with different dynamic characteristics under earthquake effects. A relative displacement spectrum is developed in two single degree of freedom system to reveal the critical period ratios for the most risky scenario of collision using El Centro earthquake record (NS). Three different types of viscous damper design, which are classical, stair and X-diagonal model, are considered to prevent pounding on two adjacent building models. The objective function is minimized under the upper and lower limits of the damping coefficient of the damper and a target modal damping ratio. A new algorithm including time history analyses and numerical optimization methods is proposed to find the optimal dampers placement. The proposed design method is tested on two 12-storey adjacent building models. The effects of the type of damper placement on structural models, the critical period ratios of adjacent structures, the permissible relative displacement limit, the mode behavior and the upper limit of damper are investigated in detail. The results of the analyzes show that the proposed method can be used as an effective means of finding the optimum amount and location of the dampers and eliminating the risk of pounding.

• Journal of Astronomy and Space Sciences
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• v.37 no.4
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• pp.219-228
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• 2020

A CubeSat platform has become a popular choice due to inexpensive commercial off-the-shelf (COTS) components and low launch cost. However, it requires more power-efficient and higher-data rate downlink capability for space applications related to remote sensing. In addition, the platform is limited by the size, weight and power (SWaP) constraints as well as the regulatory issue of licensing the radio frequency (RF) spectrum. The requirements and limitations have put optical communications on promising alternatives to RF communications for a CubeSat platform, owing to the power efficiency and high data rate as well as the license free spectrum. In this study, we analyzed the performance of optical downlink communications compatible with CubeSat platforms in terms of data rate, bit error rate (BER) and outage probability. Mathematical models of BER and outage probability were derived based on not only the log-normal model of atmospheric turbulence but also a transmitter with a finite extinction ratio. Given the fixed slot width, the optimal guard time and modulation orders were chosen to achieve the target data rate. And the two performance metrics, BER and outage data rate, were analyzed and discussed with respect to beam divergence angle, scintillation index and zenith angle.

• Journal of the Korean Vacuum Society
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• v.15 no.1
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• pp.103-109
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• 2006

A target for a high-brightness microfocus x-ray tube, which is based on carbon nanotubes (CNT) as electron source, is designed. The x-ray tube has the following specifications: brightness of $1\times10^{11}phs/s.mm^2. mrad^2$, spot size $\~5{\mu}m$, and average x-ray energy of $20\~40 keV$. In order to meet the specifications, the design parameters of the target, such as configuration, material, thickness of the target as well as the required beam current, were optimized using computer code MCNPX. The design parameters were determined from the calculation of both x-ray spectrum and intensity distribution for a transmission type configuration. For the thin transmission type target to withstand vacuum pressure and localized thermal loading, the structural stability and temperature distribution were also considered. The material of the target was selected as molybdenum(Mo) and the optimized thickness was $7.2{\mu}m$ to be backed by $150{\mu}m$ beryllium (Be). In addition, the calculations revealed that the maximum temperature of the transmission target can be maintained within the limits of stable operation.

• Korean Journal of Biological Psychiatry
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• v.19 no.4
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• pp.205-210
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• 2012

Objectives The purpose of this study was to investigate clinical profile, efficacy, and safety of long-term treatment with selective serotonin reuptake inhibitors (SSRIs) in Korean autism spectrum disorders (ASDs) patients. Methods Effectiveness was assessed through a retrospective review of self-reported target symptom improvement at the last follow-up visit. Changes in illness severity and improvement were measured using the Clinical Global Impression-Severity (CGI-S) of illness and Clinical Global Impression-Improvement (CGI-I) Scales. Tolerability was assessed through a review of the reason for discontinuation of SSRI and documented adverse events. Results A total of 21 ASDs patients (aged 9 to 19 years) treated with SSRI during July 2010 to July 2011 in department of child and adolescent psychiatry of Seoul National Hospital were identified. The mean duration of SSRI treatment was 47.9 (standard deviation = 36.9) months (range 0.7-114.5), and the mean fluoxetine equivalent dosage of SSRIs was $27.1{\pm}10.8$ mg. Nineteen (90.5%) patients were using concomitant medication. We found that SSRIs were prescribed for symptoms of agitation, stereotyped behavior, aggression, depression, impulsivity and self-injury in ASDs. Ten patients (47.6%) reported improvement in their target symptom after SSRI treatment based on CGI-I scores (CGI-I ${\leq}$ 2). The side effects were reported in 5 patients (23.8%) ; vomiting (n = 2, 9.5%), excessive mood elevation (n = 1, 4.8%), insomnia (n = 1, 4.8%), somnolence (n = 1, 4.8%) and decreased appetite (n = 1, 4.8%). Self-injurious behavior was reported in one patient (4.8%). Conclusions The results of this study suggest that SSRIs may be used effectively in children and adolescents diagnosed with ASDs. However, safety issues need to be considered carefully when choosing SSRIs for treatment. Future controlled trials are needed to confirm these findings.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.26 no.4
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• pp.273-278
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• 2015

Objectives : We retrospectively investigated the efficacy and tolerability of risperidone monotherapy in subjects with autism spectrum disorder (ASD). In addition, we did mixed effect model analysis of the effects of risperidone in patients with ASDs naturalistically treated in a routine clinical setting to determine whether the clinical effects were maintained and the side effects were tolerable. Methods : This retrospective study assessed children and adolescents with ASD, who were on risperidone monotherapy from July 2010 to July 2011 at the Child and Adolescent ASD Clinic at Seoul National Hospital. Outcome measures included the Clinical Global Impression-Severity of Illness (CGI-S) and the CGI-Improvement (CGI-I) scales along with other clinical indices: dosage, target symptoms, and side effects. Results : The mean dose of risperidone in 47 children and adolescents with ASD (40 males, 7 females; age range 5-19 years) who were on risperidone monotherapy was $1.6{\pm}0.8mg/day$, and the mean duration of the treatment period was $20.2{\pm}17.3months$. Aggressive behavior, stereotypic behavior, irritability, and self-injurious behavior were the most frequent target symptoms of risperidone. The most common side effects were weight gain followed by somnolence and extrapyramidal symptoms. In a mixed effects model analysis of CGI-I scores, the mean CGI-I score at the 1 month follow-up was significantly different from the mean CGI-I score of the 3-month follow-up (p=.046), and the CGI-I scores were equally maintained over 3 to 48 months [F(6, 28.9)=4.393, p=.003]. Of the 47 patients, 33 patients (70.2%) were identified as the response group, showing an end point CGI-I rating of 3 or under and having continued risperidone treatment for at least 6 months. The baseline CGI-S score showed significant association with clinical response to risperidone (p=.005), the mean baseline CGI-S was higher in the response group compared to the non-response group. Conclusion : In this study, clinical improvement of risperidone stabilized around 3 months and was equally maintained up to 48 months with tolerable side effects, supporting maintenance of risperidone treatment in children and adolescents with ASDs.

• Journal of Music and Human Behavior
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• v.14 no.2
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• pp.19-43
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• 2017

This study aimed to examine the effects of a reciprocal attention intervention on the joint attention behaviors of children with autism spectrum disorder (ASD) by comparing the music and nonmusic conditions. An alternating treatment design was applied as one of the single subject designs and the reciprocal attention intervention included music and nonmusic conditions implemented alternately within a session. The participants were four children between the ages 4 and 5 years and each participant who participated in 23 intervention sessions that followed the sequence of baseline (3 sessions), treatment (15 sessions), and follow-up (5 sessions). The music condition consisted of structured joint instrument playing, trials for attentional shift, and interactive instrument playing. The nonmusic condition consisted of joint toy play, trials for attentional shift, and turn taking-based play. The occurrence of target behaviors (i. e., joint attention behavior, eye gaze, and joint action) was analyzed across sessions. At pretest and posttest, the Early Social Communication Scale was administered. All participants showed increasing tendency in all target behaviors, but such occurrence was greater in the music condition than in the nonmusic condition. The findings support the use of a reciprocal attention intervention with musical stimuli to effectively improve joint attention in this population.