• Broadcasting and Media Magazine
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• v.24 no.3
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• pp.10-23
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• 2019

5G 서비스가 공식적으로 시작되었다. 아직까지 서비스 개시 초기 단계이다 보니 서비스 제공 지역(coverage)이 제한되어 있다거나 통신품질이 안정적이지 않다는 등의 이슈가 존재하기는 하지만, 이러한 문제들은 시간이 지나면 충분히 해결될 수 있을 것으로 기대된다. 따라서, 지금 우리에게 중요한 것은 5G가 제공하는 특성을 제대로 이해하고 이를 활용한 서비스들을 차근차근 준비함으로써 새로운 기회를 준비하는 것이라고 생각한다. 그런 이유로 이 글에서는 5G 서비스의 주요 구현 기술들에 대해 소개하고 이해를 도움으로써 방송 및 미디어 사업자를 포함한 다양한 산업분야의 서비스 사업자들이 5G 특성을 제대로 활용한 서비스를 준비할 수 있도록 하고자 한다. 그렇다고 해서 5G 서비스를 가능하게 하는 다양한 기술들을 모두 소개할 수는 없으므로, 고속, 저지연, 대용량 특성과 이들을 효과적으로 사용할 수 있도록 하는 네트워크 슬라이싱과 관련된 기술들을 중심으로 소개하고자 한다. 또한, 5G 서비스가 제공하는 특성들로 인한 비즈니스 모델의 변화에 대해서도 함께 생각해 보고자 한다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.1
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• pp.70-81
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• 2024

In this study, Tridimensional Hybrid Isolation System(THIS) was proposed as a vibration isolator for traffic loads, combining vertical and horizontal isolation systems. Its efficacy in improving serviceability for vertical vibration was analytically evaluated. Firstly, for the analysis, the major vibration modes of the existing apartment were identified through eigenvalue analysis for the system and pulse response analysis for the bedroom slab using commercial structural analysis software. Subsequently, a 16-story model with horizontal, vertical and rotational degrees of freedom for each slab was numerically organized to represent the achieved modes. The dynamic analysis for the measured acceleration from an adjacent ground to high-speed railway was performed by state-space equations with the stiffness and damping ratio of THIS as variables. The result indicated that as the vertical period ratio increased, the threshold period ratio where the slab response started to be suppressed varied. Specifically, when the period ratio is greater than or equal to 5, the acceleration levels of all slabs decreased to approximately 70% or less compared to the non-isolated condition. On the other hand, it was ascertained that the influence of damping ratios on the response control of THIS is inconsequential in the analysis. Finally, the improvement in vertical vibration performance of THIS was evaluated according to design guidelines for floor vibration of AIJ, SCI and AISC. It was confirmed that, after the application of THIS, the residential performance criteria were met, whereas the non-isolated structure failed to satisfy them.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.10C
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• pp.1017-1026
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• 2005

In burst OFDM system, the frame synchronization should be performed first for the acquisition of received frame and the estimation of the correct FFT-window position. The conventional frame synchronization algorithms using design features of the preamble symbol, the repetition pattern of the OFDM symbol by pilot sub-carrier allocation rule and Cyclic Prefix(CP), has difficulty in the detection of precise frame timing because its correlation characteristics would increase and decrease gradually. Also, the algorithm based on the correlation between the reference signal and the received signal has performance degradation due to frequency offset. Therefore, we adopt a differential correlation method that is robust to frequency offset and has the clear peak value at the correct frame timing for frame synchronization. However, performance improvement is essential for differential correlation methods, since it usually shows multiple peak values due to the repetition pattern. In this paper, we propose an enhanced frame synchronization algorithm based on the differential correlation method that shows a clear single peak value by using differential correlation between samples of identical repeating pattern. We also introduce a normalization scheme which normalizes the result of differential correlation with signal power to reduce the frame timing error in the high speed mobile channel environments.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.169.1-169.1
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• 2015

최근 디스플레이 기술은 급속도로 발전해 가고 있다. 디스플레이 산업의 눈부신 성장에 발맞추어 초고화질, 초고선명, 고속 구동 및 대형화 등을 포함하는 최신 기술의 디스플레이 구동이 필요하다. 이러한 요구사항을 만족하기 위해서는 각 픽셀에 영상정보를 기입하는 충전시간을 급격히 감소시켜야 하고 따라서 픽셀 트랜지스터(TFT)의 이동도는 급격히 증가해야 한다. 따라서 차세대 디스플레이 실현을 위해서 고이동도 특성을 구현 할 수 있는 신물질의 개발이 매우 중요하다. 현재 산화물박막트랜지스터는 차세대 디스플레이 실현을 위해 가장 주목받고 있으며, 실제로 산화물박막 트랜지스터의 핵심소재인 In-Ga-Zn-O(a-IGZO) 산화물의 경우 국내외에서 디스플레이에 적용되어 생산이 시작되고있다. 그러나 a-IGZO 산화물의 경우 이동도가 $5-10cm^2V{\cdot}s$ 수준이어서 향후 개발 되어질 초고해상도/고속구동 디스플레이 실현(이동도 $50cm^2V{\cdot}s$)에는 한계가 있다. 따라서 본 연구에서는 이를 해결 할 수 있는 'post-IGZO' 개발을 위해 In2O3에 Ga2O3를 조성별로 고용시켜 박막의 구조적, 전기적, 광학적 특성 및 TFT를 제작하여 특성 연구를 진행하였다. 조성은 In2O3에 Ga2O3를 7.5%~15% 도핑 하였으며, Sputtering을 이용하여 indium gallium oxide(IGO) 박막을 제작하였다. 박막은 상온 및 $300^{\circ}C$에서 증착 하였으며 증착 된 IGO 박막은 Ga=12.5% 까지는 In2O3에 Ga이 모두 고용되어 cubic In2O3 poly crystalline을 나타내는 것을 확인하였으며 Ga=15%에서 Gallium 관련 2차상이 확인되었다. Ga양이 변화함에 따라 박막의 전기적 특성이 조절 가능하였으며 이를 이용하여 IGO 박막을 30 nm 두께로 증착 하여 IGO 박막을 channel layer로 사용하는 bottom gate structured TFTs를 제작 하였다. IGO TFTs는 Ga=10%에서 on/off ratio ${\sim}10^8$, 그리고 field-effect mobility $84.8cm^2/V{\cdot}S$를 나타내며 초고화질, 초고선명 차세대 디스플레이 적용 가능성을 보여 준다.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.12
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• pp.1237-1244
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• 2016

Vehicle classification system in domestic tollgates is usually to use treadle sensor for calculating wheel width and tread of the vehicle. Due to the impact that occurs when the wheels of the vehicle contact, treadle sensor requires high durability. Recently, KHC(Korea Highway Corporation) began operating high-speed lane for cargo truck. High-speed cargo truck generate more impact the design criteria of previous treadle. Therefore, an increase in the maintenance and management costs of the treadle damage is concerned. In this paper, we propose an algorithm to classify vehicles using non-contact treadle sensors for improving durability from physical impacts. This was based on the KHC's classification criteria and showed a classification accuracy of 99.5 % in one experiment with 1892 vehicles through Changwon tollgate in 1020 local road. Therefore, it shows that vehicle classification system using non-contact treadle sensor could be applied to domestic toll tollgates, effectively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.28-31
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• 2001

Recently, in order to satisfy the consumer's demand the life cycle and the lead-time of a product is to be shortened. It is thus important to reduce the time and cost in manufacturing trial products. Several techniques have been developed and successfully commercialized in the market RPM(Rapid Prototyping and Manufacturing). However, most commercial systems currently use resins or waxes as the raw materials. So, the limited mechanical strength for functional testing is regarded as an obstacle towards broader application of rapid prototyping techniques. To overcome this problems, high-speed machining technology is being investigated worldwide for rapid manufacturing and even for direct rapid tooling application. In this paper, some fundamental experiments and analyses are carried out to obtain the filling time, materials, method, and process parameters for HisRP process. HisRP is a combination process using high-speed machining technology with automatic filling. In filling process, Bi58-Sn alloy is chosen because of the properties of los-melting point, low coefficient of thermal expansion and enviromental friendship. Also the use of filling wire is of advantage in term of simple and flexible mechanism. Then the rapid manufacturing product, for example a skull, is machined for aluminum material by HisRP process with an automatic set-up device of 4-faces machining.

• Journal of Broadcast Engineering
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• v.19 no.3
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• pp.316-328
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• 2014

In this paper, we parallelize the popular feature detection algorithms, i.e. SIFT and SURF, and its application to fast panoramic image generation on the latest embedded GPU. Parallelized algorithms are implemented using recently developed OpenCL as the embedded GPGPU software platform. We compare the implementation efficiency and speed performance of conventional OpenGL Shading Language and OpenCL. Experimental result shows that implementation on OpenCL has comparable performance with GLSL. Compared with the performance on the embedded CPU in the same application processor, the embedded GPU runs 3~4 times faster. As an example of using feature extraction, panorama image synthesis is performed on embedded GPU by applying image matching using detected features.

• Economic and Environmental Geology
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• v.39 no.4 s.179
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• pp.507-524
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• 2006

3-D seismic tomographic inversion is applied to investigation on velocity structure in and near Korean Peninsula. Firstly, it is applied to the region in southeastern Korean Peninsula. According to the results low-velocity zone seems to be clearly appeared in the so called Gyeongsang sedimentary basin and high-velocity zone is shown at the section of 7.5 km depth it implies the inclusion of plutonic rocks at the sedimentary basin. At the depth about $20{\sim}30$ km existence of low-velocity zone seems to be related with the development of Yangsan fault system. Secondly it is applied to the region not only in Korean Peninsula but also East Sea using data from both Korean Peninsula and Japan Islands. Accorging to the results, subduction zone starting from eastern part of Japan seems to be extended to the region beneath the East Sea.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.10
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• pp.1279-1289
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• 2013

In recent times, turbomolecular pumps (TMPs) have been used frequently to generate and maintain high and clean vacuum. Because of the high-speed rotation of the rotor, its structural safety should be treated as the first design concern. This paper presents the structural analysis and optimization of rotor blades of a TMP. To increase the numerical efficiency in the finite element modeling and analysis, the P-method provided in Pro/ENGINEER was used for simulation. The structural responses for several types of rotor blades were investigated, and the effects of the blade angle, blade length, and round size are thoroughly studied for each type of TMP blade. In addition, structural optimization to reduce and even the maximum stress at each stage of the TMP by changing the size of rounds between the blade and the hub was performed very successfully by using the P-method.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.89-89
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• 2011

반도체 공정 등에서 $10^{-6}{\sim}10^{-8}$ mbar의 고진공 환경을 제공하기 위하여 사용되는 고진공 터보분자펌프 (Turbomolecular Pump, TMP)는 다층의 회전깃을 갖는 로터를 회전시켜 분자를 배출시키는 방식을 사용하는 진공펌프이다. 또한 최근에는 디스플레이 및 반도체 공정에서 높은 진공도뿐만 아니라, 높은 배기속도를 요구하는 추세에 따라, 터보 펌프와 드래그 펌프부분을 동시에 가지고 있어 상대적으로 작동 진공도 영역이 넓은 복합 분자펌프(Compound Turbomolecular Pump, CMP)의 활용도가 넓어지고 있다. 이러한 분자펌프가 장시간의 고속회전에 적합하도록 비접촉 방식인 자기부상 방식의 적용이 최근 거의 표준화 되어 있다. 자기베어링 시스템은 전자기력을 이용하여 자성체인 회전축을 부상지지 함으로써 비접촉 고속 회전이 가능하여 윤활이 용이하지 않은 진공 환경 등 가혹한 환경에 적합하며, 터보분자펌프는 자기베어링이 가장 널리 사용되고 있는 분야이기도 하다. 자기베어링 시스템의 설계는 크게 하드웨어와 소프트웨어로 나누어질 수 있는데, 하드웨어의 경우 전체 로터 시스템의 특성을 고려하여 설계되어야 하며, 주로 자기베어링 코어와 코일, 변위센서 및 전력 증폭 시스템 등의 기전적인 요소들이 이루어져 있다. 하드웨어 설계와 함께 제어시스템의 설계도 매우 중요하며, 이는 자기베어링 시스템이 불안정한 특성을 갖는 개루프계를 갖고 있으므로 안정화를 위한 능동제어 시스템이 필수적이며 진동제어 등 여러 가지 기능이 요구되기 때문이다. 본 논문에서는 이러한 자기부상형 고진공 복합분자펌프의 제어를 위한 선형제어시스템의 구성을 실제 시스템의 적용을 통하여 설명하였다. 각 제어기는 DSP 를 이용한 디지털 제어시스템으로 구성되었으며, 2,500 l/s 급의 복합 분자펌프 시작품에 적용하여 25,000 rpm 까지의 기본 성능시험을 수행하였으며, 발열 특성의 개선을 위한 비선형 제어기의 설계 사례에 대한 시뮬레이션 결과를 나타내었다.