• Structural Engineering and Mechanics
• /
• 제74권3호
• /
• pp.381-394
• /
• 2020

The structural performance of cold-formed steel (CFS) built-up battened columns were numerically investigated in this paper. The built-up column sections were formed by connecting two-lipped channels back-to-back, with a regular spacing of battens plates, and have been investigated in the current study. Finite element models were validated with the test results reported by the authors in the companion paper. Using the validated models, the parametric study was extended, covering a wider range of overall slenderness to assess the accuracy of the current design rules in predicting the design strengths of the CFS built-up battened columns. The parameters viz., overall slenderness, different geometries, plate slenderness (b/t ratio) and yield stress were considered for this study. In total, a total of 228 finite element models were analyzed and the results obtained were compared with current design strength predicted by Effective Width Method of AISI Specifications (AISI S100:2016) and European specifications (EN1993-1-3:2006). The parametric study results indicated that the current design rules are limited in predicting the accuracy of the design strengths of CFS built-up battened columns. Therefore, a design equation was proposed for the AISI and EC3 specifications to predict the reliable design strength of the CFS Built-up battened columns and was also verified by the reliability analysis.

• Journal of Communications and Networks
• /
• 제5권1호
• /
• pp.1-6
• /
• 2003

In this paper, we extend the derivation of the iterative soft-output Viterbi algorithm (SOVA) for partial response (PR) channels, and modify its decoding process such that it works consistently for arbitrary high code rates, e.g., rate 64/65. We show that the modified SOVA always outperforms the conventional SOVA that appears in the literature with a significant difference for high code rates. It also offers a significant cut down in the trace-back computations. We further examine its performance for parallel and serial concatenated codes on a precoded Class IC partial response (PR4) channel. Code rates of the form $\frac{k_0}{k_0+1}$($k_0$ = 4, 8, and 64) are considered. Our simulations indicate that the loss suffered by the modified SOVA, relative to the APP algorithm, is consistent for all code rates and is at most 1.2 dB for parallel concatenations and at most 1.6 dB for serial concatenations at $P_b$ = $10^{-5}$.

• Journal of the Optical Society of Korea
• /
• 제14권4호
• /
• pp.388-394
• /
• 2010

In this paper the object recognition performance of a photon counting integral imaging system is quantitatively compared with that of a conventional gray scale imaging system. For 3D imaging of objects with a small number of photons, the elemental image set of a 3D scene is obtained using the integral imaging set up. We assume that the elemental image detection follows a Poisson distribution. Computational geometrical ray back propagation algorithm and parametric maximum likelihood estimator are applied to the photon counting elemental image set in order to reconstruct the original 3D scene. To evaluate the photon counting object recognition performance, the normalized correlation peaks between the reconstructed 3D scenes are calculated for the varied and fixed total number of photons in the reconstructed sectional image changing the total number of image channels in the integral imaging system. It is quantitatively illustrated that the recognition performance of the photon counting integral imaging system can be similar to that of a conventional gray scale imaging system as the number of image viewing channels in the photon counting integral imaging (PCII) system is increased up to the threshold point. Also, we present experiments to find the threshold point on the total number of image channels in the PCII system which can guarantee a comparable recognition performance with a gray scale imaging system. To the best of our knowledge, this is the first report on comparisons of object recognition performance with 3D photon counting & gray scale images.

• 수산해양기술연구
• /
• 제28권2호
• /
• pp.117-131
• /
• 1992

A studies on the pattern of sea water circulation was carried out by using drogue experiments, tidal current measurement and hydrographic data in Kamak Bay which has two channels. At the flood, the water inflowed from the northern narrow channel flows mostly to the southward then the westward because Daekyung-island located at the flow path, at the same time the water from the southern channel of bay directed strongly to the north with a spine centered at around Gunnaeri. And these waters converged at the area between eng-Island and Deakyung-Island in the bigining of the flow, and placed at less southern part than the area at the late. The water of the north west inner bay having concave bottom topography inflows to Najin inlet with a spin of anti-clockwise. At the ebb, those waters in the bay turn back to two channels respectively, but most of waters directed to the southern channel of the bay. The directions of residual current of two channels are the southward mainly, and the current of inner area are influenced by the prevailing wind. The north-west inner bay which has the weak tidal current less than 10 cm/sec shows a similar upwelling by off-shore wind in winter, and the stratification in summer, respectively.

• 한국위성정보통신학회논문지
• /
• 제12권1호
• /
• pp.34-37
• /
• 2017

본 논문은 I/Q 채널을 다 이용하여 표적의 후퇴와 접근을 감지하는 연속파 레이다의 신호처리에 대하여 분석한다. 표적이 레이다로부터 접근 혹은 후퇴할 때 Quadrature 신호의 위상이 달라지는 것을 이용하여 물체의 후퇴와 접근을 감지하며, 상용 MMIC칩과 MCU를 이용하여 모듈을 구현하고, MMIC로부터 나온 수신데이터를 분석하여 검증하였다. 또한 사람을 대상으로 접근, 후퇴하는 동작에 대한 신호처리를 MCU를 사용하여 확인하였다. 사용한 주파수는 24.125GHz이며, 송신기 출력전력은 7.2 dBm이다. 실제 구현한 레이다로 최대 검출가능거리는 약 12m를 달성하였다.

• 한국통신학회논문지
• /
• 제34권10C호
• /
• pp.946-954
• /
• 2009

일반적인 RFID 시스템에서는 리더와 백 엔드 데이터베이스 사이의 통신 채널을 안전한 채널로 가정하고 있다. 하지만 응용 환경에 따라 리더와 데이터베이스 사이의 통신 채널이 리더와 태그 간의 통신 채널처럼 안전하지 않은 채널을 통하여 메시지를 송수신 하게 되는 경우가 얼마든지 존재한다. 본 논문에서는 데이터베이스, 리더 그리고 태그 간의 모든 통신 채널이 안전하지 않은 공개 채널임을 가정하여 공개 채널 기반의 안전한 RFID 상호인증 프로토콜을 제안한다. 제안한 프로토콜은 공개된 채널 상에 송수신되는 모든 통신 메시지의 인증과 무결성을 보장하기 위해 안전한 일방향 해쉬 함수를 사용하였다. 또한 상호인증 후 데이터베이스와 태그가 다음 세션을 위해 기존의 비밀키를 새로운 비밀키로 각각 갱신하도록 하여 전방향 안전성을 제공하도록 설계하였다.

• 멤브레인
• /
• 제18권4호
• /
• pp.325-335
• /
• 2008

본 연구에서는 관형보다 단위시간당 투과량이 월등히 많은 다채널 세라믹 분리막을 사용하였으며, 고도정수처리 혼성공정은 모듈 내부와 다채널 정밀여과막 외부 사의의 공간에 입상활성탄(GAC)을 충전하여 구성하였다. 정수 원수 중의 자연산 유기물(NOM)과 미세 무기 입자를 대체하기 위해, 휴믹산(humic acid)과 카올린(kaolin) 모사용액을 사용하였다. 유기물질의 영향을 살펴보기 위해 일정한 30mg/L의 카올린 농도에서 휴믹산(humic acid)의 농도를 $2{\sim}10\;mg/L$로 변화시켰다. 그 결과, 막오염의 저항($R_f$)과 투과선속(J)은 휴믹산의 농도에 따라 큰 영향을 받았다. 또한 역세척 주기(FT)의 영향을 살펴본 결과, 더 짧은 FT는 빈번한 역세척으로 막오염의 감소와 투과선속의 향상에 더 효과적이었다. 그러나 운전비용을 고려하면, 최적 FT조건은 8분이였다. 한편, 이 다채널 정밀여과막 및 GAC 혼성공정을 호소수에 적용한 결과, 평균 처리효율은 탁도 98.02%, $UV_{254}$ 흡괌도 75.64%, 총용존고형물(TDS) 7.18%, 화학적산소요구량 84.73%이었다.

• 한국군사과학기술학회지
• /
• 제10권2호
• /
• pp.90-99
• /
• 2007

We demonstrate an 80km-reach 64-channel DWDM-PON based on wavelength-locked F-P LDs by changing the position of the C-band BLS for upstream channels from the CO to the RN. It mitigates the necessity of the high power C-band BLS and its handling problems. It also reduces back scattering induced penalty. We obtained less than $10^{-6}$ PLRs in all 128channels through 80km SMF. We also demonstrate a 240km-reach DWDM-PON based on wavelength-locked F-P LDs by adding a bidirectional erbium-doped fiber amplifier(EDFA). We show packet-loss-free transmission in all 128channels at 125 Mb/s per channel over 240km SMF We report the detuning effect of arrayed waveguide gratings(AWGs) and crosstalk effect in the implemented system. We Propose an architecture of a next generation defense wire communication system with the demonstrated long-reach DWDM-PON.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
• /
• pp.89-91
• /
• 2004

In SCADA systems, an RTU is a device installed at a remote location that collects data, codes the data into a format that is transmittable and transmits the data back to a central station, or MTU. An RTU also collects information from the master device and implements processes that are directed by master device. RTUs are equipped with input channels for sensing or metering, output channels for control, indication or alarms and a communications port. In general, the data are transmitted via a wired communication infrastructure such as RS422 or RS485 between RTU and MTU. But, limited range of wired communication doesn't allow the system to cover remote areas over the limitation, and building a wired communication network is not easy in the circumstances. In this Paper, we design and implement a smart cost-effective Web-RTU that can communicate with MTU via Web. Web is of benefit to the Web-RTU, because it is not only free from the distance limitations, but also is built easily and cost-effectively wherever Internet resources are available. Additionally, Web can be easily applied to the SCADA system with the development of hardware and software for communications. The Web-RTU has a program memory, a data memory and a RAM inside, and uses Atmega128, low-cost 8 bit micro-processor with eight AI(Analog Input). It performs well enough to implement all existing roles of RTU.

• 대한기계학회논문집B
• /
• 제31권2호
• /
• pp.141-150
• /
• 2007

This paper presents a lumped model to predict crosstalk characteristics of thermally driven inkjet print heads. Using the lumped R-C model, heating characteristics of the head are predicted to be in agreement with IR temperature measurements. The inter-channel crosstalk is simulated using the lumped R-L network. The values of viscous flow resistance, R and flow inertance, L of connecting channels are adjusted to accord with the 3-D numerical simulation results of three adjacent jets. The crosstalk behaviors of a back shooter head as well as a top shooter head have been investigated. Predictions of the proposed lumped model on the meniscus oscillations are consistent with numerical simulation results. Comparison of the lumped model with experimental results identifies that abnormal two-drop ejection phenomena are related to the increased meniscus oscillations because of the more severe crosstalk effects at higher printing speeds. The degree of crosstalk has been quantified using cross-correlations between neighboring channels and a critical channel dimension for acceptable crosstalk has been proposed and validated with the numerical simulations. Our model can be used as a design tool for a better design of thermal inkjet print heads to minimize crosstalk effects.