• Electronics and Telecommunications Trends
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• v.21 no.3 s.99
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• pp.36-47
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• 2006

이동통신 시스템은 점차 고품질 및 고속의 멀티미디어 서비스를 제공하는 방향으로 가고 있다. 3GPP에서는 기존의 WCDMA 기반의 3세대 이동통신 시스템의 기술적 한계를 극복하기 위해 2004년 말에 3rd Generation Long Term Evolution(3G LTE) Plan을 발표하고, 2006년 6월까지 Technical Report 규격을 작성완료하고 2007년 6월까지 Technical Standard 작성완료를 목표로 2005년 초부터 규격 작업을 수행하고 있다. 본 고에서는 3G LTE 물리계층 및 MAC 계층의 기술 표준화 동향을 살펴본다.

• 정보화사회
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• s.188
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• pp.18-25
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• 2007

삼성전자가 주최하는'삼성 4G포럼'이 지난 8월 27일과 28일 이틀 간 서울 신라호텔에서 개최됐다. 삼성 4G포럼은 2005년 모바일 와이맥스(와이브로) 기술을 세계 최초로 선보였고, 지난해에는 세계 유수의 경쟁업체들을 크게 앞서는 4G 기술을 선보임으로써 차세대 통신기술의 발전상을 꿰뚫어볼 수 있는 행사로 자리를 잡고 있다. 올해 행사에서는 삼성전자가 주도하는 모바일 와이맥스뿐만 아니라, 3GPP LTE(Long Term Evolution), 3GPP2 UMB(Ultra Mobile Broadband) 등 ITU가 4G의 유력 후보 기술로 꼽은 3대 통신기술이 한자리에서 소개되고 기술개발 및 표준화 동향을 공유하는 자리가 마련돼 더욱 눈길을 끌었다. 4세대 이동통신, 즉'4G'란 이동 중 100Mbps, 정지 상태에서는 1Gbps급 속도를 제공하는 무선 통신기술로, 지난 2005년 10월 ITU(국제전기통신연합)이'IMT-어드밴스트(advanced)'를 공식 명칭으로 결정한 바 있다. 하지만 현재의 3G와는 완전히 다른 새로운 세대의 통신 기술이라는 점을 강조하기 위해 여전히 4G라는 용어가 널리 쓰이고 있다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2021.06a
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• pp.260-263
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• 2021

3GPP (3rd generation partnership project)는 5G 요구 조건을 충족시키기 위해 release 16 에서 FeMBMS (further evolved MBMS)를 LTE 기반 5G MBMS 로 개선하였다. 이어서, 현재 개발 중인 release 17 에서 NR 기반의 디지털 방송을 위한 NR MBS (multimedia broadcast services)가 논의되고 있다. 본 논문에서는 LTE (long term evolution) 기반 5G MBMS (fifth generation multimedia broadcast & multicast services)와 5G NR (fifth generation new radio)의 PBCH (physical broadcast channel) 에 대한 송수신기 구조를 설명하고, 성능을 평가한다. 본 논문에서는 가산 백색 가우시안 잡음(additive white Gaussian noise: AWGN) 및 고정 환경 하에서 LTE 기반 5G MBMS 와 5G NR 에 대한 PBCH 의 성능을 비교한다.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.37.1-37.1
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• 2013

We present our study of analyzing the photometric properties of the globular cluster (GC) system which resides in the extended halo of the central bright Coma cluster galaxy NGC 4874. The core of the Coma cluster of galaxies (Abell 1656) was observed with both the HST Advanced Camera for Surveys (ACS) in the F475W (g475) and F814W (I814) and Wide Field Camera 3 IR Channel (WFC3/IR) in the F160W (H160) filters. The data analysis procedure and GC candidate selection criteria are briefly described. We investigate the interesting "tilt" features in color-magnitude diagrams for this GC system and their link to the nonlinear color-metallicity relation for GCs. The NGC 4874's GC system exhibits a bimodal distribution in the optical g475-I814 color and much more than half the GCs fall in the red side at g475-I814 ~ 1.1. This bimodality is weakened in the optical-IR I814-H160 color; the quantitative analysis on the features of both color distributions using the Gaussian Mixture Modeling code proves the bimodalities are different. Both colors, thus, cannot linearly reflect the bimodality of an underlying metallicity, supporting the suggestion that observed bimodalities in extragalactic GC colors are the metallicity-to-color projection effect.

• BMB Reports
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• v.40 no.3
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• pp.419-425
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• 2007

In vitro directed evolution through DNA shuffling is a powerful molecular tool for creation of new biological phenotypes. E. coli $\beta$-galactosidase and $\beta$-glucuronidase are widely used, and their biological function, catalytic mechanism, and molecular structures are well characterized. We applied an in vitro directed evolution strategy through DNA shuffling and obtained five mutants named YG6764, YG6768, YG6769, YG6770 and YG6771 after two rounds of DNA shuffling and screening, which exhibited more $\beta$-glucuronidase activity than wild-type $\beta$-galactosidase. These variants had mutations at fourteen nucleic acid sites, resulting in changes in ten amino acids: S193N, T266A, Q267R, V411A, D448G, G466A, L527I, M543I, Q626R and Q951R. We expressed and purified those mutant proteins. Compared to the wild-type protein, five mutant proteins exhibited high $\beta$-glucuronidase activity. The comparison of molecular models of the mutated and wildtype enzymes revealed the relationship between protein function and structural modification.

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.87-91
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• 2017

Polycyclic aromatic hydrocarbons (PAHs) are considered to be carriers of the unidentified infrared bands, which are ubiquitously observed in the Universe. PAHs are mainly formed around evolved carbon-rich stars and injected into interstellar space. Planetary nebulae (PNe), a late stage of low- and intermediate stellar mass evolution, are suitable objects to investigate the formation and evolution of PAHs. The shortest PAH feature is located in $3.3{\mu}m$, which is important to examine the excitation and size distribution of PAHs. While the number of samples had been limited before, the high sensitivity of AKARI /IRC has drastically increased the number of samples. We obtained the $2-5{\mu}m$ spectra of Galactic PNe with AKARI /IRC and compiled a near-infrared spectral catalog, containing 73 PNe. We investigate the detection rate and the evolution of the PAH features. The characteristics of the catalog are illustrated and the origin of the evolution of the PAH features is discussed.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.67.3-68
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• 2016

We present evidence of the bar driven secular evolution on disks from z~0.8 to z~0.01. Using $3.6{\mu}m$ images of nearby galaxies from the Spitzer Survey of Stellar Structure in Galaxies (S4G) and images from the Cosmological Evolution Survey (COSMOS), we find that barred galaxies show a light deficit in the disk surrounding the bar within the bar radius. We quantify this light deficit and find that galaxies with a stronger bar (longer, higher Bar/T) show a more pronounced light deficit. We examine snapshots from N-body simulations and confirm that as a barred galaxy evolves, the bar becomes longer and the light deficit becomes more pronounced. Theoretical studies have predicted that bars evolve by capturing nearby disk stars and employing them to make the bar more elongated and stronger. Therefore the light deficit in the disk is likely produced by bars, and thus bars play a major role in shaping their host galaxies, redistributing not only the gaseous but also the stellar mass within galaxies, with important consequences to their subsequent evolution.

• Ocean Systems Engineering
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• v.2 no.3
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• pp.189-203
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• 2012

New experiments focusing on the evolution characteristics of nonlinear wave trains were conducted in a large wave flume. A series of wave trains with added sidebands, varying initial steepness, perturbed amplitudes and frequencies, were physically generated in a long wave flume. The experimental results show that the increasing wave steepness, increases the speed of sidebands growth. To study the frequency and phase modulation, the Morlet wavelet transform is adopted to extract the instantaneous frequency of wave trains and the phase functions of each wave component. From the instantaneous frequency, there are local frequency downshifts, even an effective frequency downshift was not observed. The frequency modulation increases with an increase in amplitude modulation, and abrupt changes of instantaneous frequencies occur at the peak modulation. The wrapped phase functions show that in the early stage of the modulation, the phase of the upper sideband first diverges from that of the carrier waves. However, at the later stage, the discrepancy phase from the carrier wave transformed to the lower sideband. The phase deviations appear in the front of the envelope's peaks. Furthermore, the evolution of the instantaneous frequency exhibits an approximate recurrence-type for the experiment with large imposed sidebands, even when the corresponding recurrence is not observed in the Fourier spectrum.

• Journal of Astronomy and Space Sciences
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• v.34 no.3
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• pp.183-197
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• 2017

We present simulations of the optical-band images of high-redshift galaxies utilizing 845 near-ultraviolet (NUV) images of nearby galaxies obtained through the Galaxy Evolution Explorer (GALEX). We compute the concentration (C), asymmetry (A), Gini (G), and $M_{20}$ parameters of the GALEX NUV/Sloan Digital Sky Survey r-band images at z ~ 0 and their artificially redshifted optical images at z = 0.9 and 1.6 in order to quantify the morphology of galaxies at local and high redshifts. The morphological properties of nearby galaxies in the NUV are presented using a combination of morphological parameters, in which early-type galaxies are well separated from late-type galaxies in the $G-M_{20}$, $C-M_{20}$, A-C, and $A-M_{20}$ planes. Based on the distribution of galaxies in the A-C and $G-M_{20}$ planes, we examine the morphological K-correction (i.e., cosmological distance effect and bandshift effect). The cosmological distance effect on the quantitative morphological parameters is found to be significant for early-type galaxies, while late-type galaxies are more greatly affected by the bandshift effect. Knowledge of the morphological K-correction will set the foundation for forthcoming studies on understanding the quantitative assessment of galaxy evolution.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10C
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• pp.764-777
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• 2008

In 4G environments, which is the next generation technology for mobile network, it is forecasted that the wireless Internet using a mobile devices such as a mobile phone, PDA will increase because of expansion of Internet and integration of heterogeneous networks. Therefore, we need a Digital ID management technology that can prevent illegal uses and manage private information efficiently in wired and wireless environments. In this paper, we analyze various Digital ID management technologies, and then define requirements of user-centric Digital ID management technology. In addition, we newly propose the authentication mechanism for mobile applications in LTE/SAE network. Finally, we propose the mobile Digital ID Wallet mechanism suitable for 4G environments.