• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.9
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• pp.1010-1019
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• 2016

The K-user multiple-input single-output broadcast channel is considered under per-antenna power constraints, i. e., each transmit antenna must satisfy its own power constraints. A low complexity zeroforcing(ZF) precoder is proposed when the number of transmit antennas M is greater than K. The proposed precoder design significantly reduces computational complexity for the precoder construction while attaining the sum spectral efficiency close to that achievable by the optimal ZF precoder.

• Journal of Information Processing Systems
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• v.14 no.4
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• pp.1049-1061
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• 2018

As mobile devices such as smartphones and tablet PCs become more popular, users are becoming accustomed to consuming a massive amount of multimedia content every day without time or space limitations. From the industry, the need for user satisfaction investigation has consequently emerged. Conventional methods to investigate user satisfaction usually employ user feedback surveys or interviews, which are considered manual, subjective, and inefficient. Therefore, the authors focus on a more objective method of investigating users' brainwaves to measure how much they enjoy their content. Particularly for multimedia content, it is natural that users will be immersed in the played content if they are satisfied with it. In this paper, the authors propose a method of using a portable and dry electroencephalogram (EEG) sensor device to overcome the limitations of the existing conventional methods and to further advance existing EEG-based studies. The proposed method uses a portable EEG sensor device that has a small, dry (i.e., not wet or adhesive), and simple sensor using a single channel, because the authors assume mobile device environments where users consider the features of portability and usability to be important. This paper presents how to measure attention, gauge and compute a score of user's content immersion level after addressing some technical details related to adopting the portable EEG sensor device. Lastly, via an experiment, the authors verified a meaningful correlation between the computed scores and the actual user satisfaction scores.

• KIPS Transactions on Computer and Communication Systems
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• v.7 no.9
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• pp.227-234
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• 2018

Guaranteeing the end-to-end delay deadline is an important issue for quality of service (QoS) of delay sensitive systems, such as real-time system, networked control system (NCS), and cyber-physical system (CPS). Most routing algorithms typically use the mean end-to-end delay as a performance metric and select a routing path that minimizes it to improve average performance. However, minimum mean delay is an insufficient routing metric to reflect the characteristics of the unpredictable wireless channel condition because it only represents average value. In this paper, we proposes a deadline-aware routing algorithm that maximizes the probability of packet arrival within a pre-specified deadline for CPS by considering the delay distribution rather than the mean delay. The proposed routing algorithm constructs the end-to-end delay distribution in a given network topology under the assumption of the single hop delay follows an exponential distribution. The simulation results show that the proposed routing algorithm can enhance QoS and improve networked control performance in CPS by providing a routing path which maximizes the probability of meeting the deadline.

• The Transactions of the Korea Information Processing Society
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• v.7 no.2
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• pp.542-551
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• 2000

In this paper, a novel technique is presented for automatic brain region segmentation in single channel MR image data sets for 3D visualization and analysis. The method detects brain contours in 2D and 3D processing of four steps. The first and the second make a head mask and an initial brain mask by automatic thresholding using a curve fitting technique. The stage 3 reconstructs 3D volume of the initial brain mask by cubic interpolation and generates an intermediate brain mask using morphological operation and labeling of connected components. In the final step, the brain mask is refined by automatic thresholding using curve fitting. This algorithm is useful for fully automatic brain region segmentation of T1-weighted, T2-weighted, PD-weighted, SPGR MRI data sets without considering slice direction and covering a whole volume of a brain. In the experiments, the algorithm was applied to 20 sets of MR images and showed over 0.97 in comparison with manual drawing in similarity index.

• Journal of Sensor Science and Technology
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• v.29 no.3
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• pp.172-179
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• 2020

We studied an integrated-optic biosensor configuration that operates at a wavelength of 0.63 ㎛ based on the evanescent-wave and two horizontal mode power coupling of Si₃N₄ rib-optical waveguides formed on a Si/SiO₂/Si₃N₄/SiO₂ multilayer thin films. The sensor consists of a single-mode input waveguide, followed by a two-mode section which acts as the sensing region, and a Y-branch output for separating the two output waveguides. The coupling between the two propagating modes in the sensing region produces a periodically repeated optical power exchanges along the propagation. A light power was steered from one output channel to the other due to the change in the cladding layer (bio-material) refractive index, which affected the effective refractive index (phase-shift) of two modes through evanescent-wave. Waveguide analyses based on the rib optical waveguide dimensions were performed using various numerical computational software. Sensitivity values of 12~23 and 65~165 au/RIU, respectively for the width and length of 4 ㎛, and 3841.46 and 26250 ㎛ of the two-mode region corresponding to the refractive index range 1.36~1.43 and 1.398~1.41, respectively, were obtained.

• Development and Reproduction
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• v.21 no.4
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• pp.379-389
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• 2017

Connexin (Cx) involves in the regulation of various physiological functions of tissue by forming a channel, a gap junction which allows direct cell-cell communication, between adjacent cells. The effect of a single subcutaneous treatment of estradiol benzoate (EB) or flutamide (Flu) at the weaning age on the expression of Cx isoforms in the adult caput epididymis was evaluated in this research. Using quantitative real-time PCR analysis, a low-dose of EB [$0.015{\mu}g/kg$ body weight (BW)] caused significant decreases of Cx30.3, Cx32, Cx40, Cx43, and Cx45 mRNA levels and no change of Cx26, Cx31, Cx31.1, Cx37 transcript levels. The treatment of a high-dose EB ($1.5{\mu}g/kg\;BW$) resulted in reduced expression of Cx30.3, Cx31, Cx43, and Cx45 but increased expression of Cx37 and Cx40. Expression of all Cx isoforms examined, except Cx31, was significantly increased by the treatment of a low-dose Flu ($500{\mu}g/kg\;BW$). However, the treatment of a high-dose Flu (5 mg/kg BW) led significant expressional suppression of Cx30.3, Cx31, Cx31.1, Cx32, Cx40, Cx43, and Cx45 but an increase of Cx37 transcript level. With the comparison of previous findings, the expression of Cx isoforms in the adult epididymis after the exposure to EB or Flu is likely differentially regulated in regional-specific and/or exposed postnatal age-specific manner.

• The KIPS Transactions:PartC
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• v.19C no.1
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• pp.39-46
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• 2012

In this paper, we propose a key distribution scheme for flexible chipset pairing conditional access system. Chipset pairing conditional access system is the implementation of CA (Conditional Access) module by using both embedded secure chip in a Set-Top Box(STB) and smartcard, and the secure chip embedded in a STB forms a secure channel between the smartcard and the STB. In short, it is the system that a smartcard outputs encrypted CW (Control Word) to the STB, and the STB decrypts an encrypted CW by using the embedded secure chip. The drawback of this chipset pairing conditional access system is that one smartcard is able to be used for only one specified STB since it is the system using the STB bound to a smartcard. However, the key distribution scheme proposed in this paper overcomes a drawback of current chipset pairing conditional access system by using Chinese Remainder Theorem(CRT). To be specific, with this scheme, one smartcard can be used for multiple, not single, STBs, and applied to current chipset pairing without great changes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10C
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• pp.923-929
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• 2003

Turbo processing have been known as methods close to Shannon limit in the aspect of wireless multi-input multi-output (MIMO) communications similarly to wireless single antenna communication. The iterative processing can maximize the mutual effect of coding and interference cancellation, but LDPC coding has not been used for turbo processing because of the inherent decoding process delay. This paper suggests a LDPC coded MIMO system with turbo parallel space-time (Turbo-PAST) processing for high-speed wireless communications and proposes a average soft-output syndrome (ASS) check scheme at low signal to noise ratio (SNR) for the Turbo-PAST system to decide the reliability of decoded frame. Simulation results show that the suggested system outperforms conventional system and the proposed ASS scheme effectively reduces the amount of turbo processing iterations without performance degradation from the point of average number of iterations.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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• pp.84-87
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• 2005

본 논문에서는 p-type 고분자 물질인 P3HT (Poly-3-hexylthiophene)를 잉크젯 프린팅 방식으로 활성화층을 적층함으로써 Organic thin film transistor를 제작하여 이에 대한 특성을 연구하였다. Piezoelectric 방식의 잉크젯 프린팅을 이용하여 P3HT single drop jetting 시 두께 $150{\sim}200{\AA}$, 직경 약 70 ~ 80 um정도의 drop profile을 얻을 수 있었다. P3HT의 solvent로서 Chlorobenzene을 사용하여 농도 약 0.5 wt.%의 Ink-jet용 ink를 제작하여 이를 Channel Width 37, 236 um 크기의 Au 전극 위에 jetting 하여 각각의 특성을 측정하였다. 상기 실험은 상온의 외부환경에서 실시되었으며 실험 결과 최대 ${\mu}=1{\times}10^{-2}\;cm^2/Vsec$, $I_{on}/I_{off}=10^3{\sim}10^4$ 정도로서 off current가 높은 편이나 이동도 측면에서는 다른 방법의 박막 증착 실험결과와 비교할 때 동등 수준의 결과를 얻을 수 있었다.

• Nuclear Engineering and Technology
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• v.52 no.1
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• pp.19-26
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• 2020

Small nuclear reactor features higher power capacity, longer operation life than conventional power sources. It could be an ideal alternative of existing power source applied for special equipment for terrestrial or underwater missions. In this paper, a 25kWe heat pipe cooled reactor power source applied for multiple use is preliminary designed. Based on the design, a thermal-hydraulic analysis code for heat pipe cooled reactor is developed to analyze steady and transient performance of the designed nuclear reactor. For reactor design, UN fuel with 65% enrichment and potassium heat pipes are adopted in the reactor core. Tungsten and LiH are adopted as radiation shield on both sides of the reactor core. The reactor is controlled by 6 control drums with B₄C neutron absorbers. Thermoelectric generator (TEG) converts fission heat into electricity. Cooling water removes waste heat out of the reactor. The thermal-hydraulic characteristics of heat pipes are simulated using thermal resistance network method. Thermal parameters of steady and transient conditions, such as the temperature distribution of every key components are obtained. Then the postulated reactor accidents for heat pipe cooled reactor, including power variation, single heat pipe failure and cooling channel blockage, are analyzed and evaluated. Results show that all the designed parameters satisfy the safety requirements. This work could provide reference to the design and application of the heat pipe cooled nuclear power source.