저고도 표적추적을 위한 다중주파수 다중빔을 이용한 각도추정 방법

임재혁,이의혁,정대교,오선진 한국전자파학회 2025 한국전자파학회논문지 Vol.36 No.5

레이다를이용한저고도표적추적시, 해수면·지상과가까워다중경로간섭이크게발생하고, 이로인해모노펄스각도추정에 큰 오차가 생긴다. 본 논문에서는 이러한 문제를 해결하기 위하여 다중주파수(multi-frequency)와 다중빔(multi-beam)을 결합한 MFMB(multi-frequency multi-beam) 방법을 제안한다. 먼저, 주파수별 간섭 패턴이 서로 상쇄될 수있도록회기신호기반최적의주파수조합을도출한다. 이후, 각주파수에서생성된수신신호를합성하고다중빔을적용함으로써각도추정정확도를높일수있다. 시뮬레이션결과, 제안된MFMB 방법은모노펄스대비각도추정오차를크게 줄임을확인하였다. When tracking low-altitude targets using radar, significant multi-path interference occurs because of their proximity to the sea surface or ground, leading to substantial errors in the monopulse angle estimation. To address this issue, this study proposes the multi-frequency multi-beam (MFMB) technique that combines the multi-frequency and multi-beam approaches. First, an optimal frequency combination is derived using linear regression to ensure that the interference patterns at different frequencies cancel one another out. Subsequently, the received signals at each frequency are synthesized, and multi-beam processing is applied to enhance the angle estimation accuracy. The simulation results confirm that the proposed MFMB method significantly reduces angle estimation errors compared with monopulse techniques, thereby contributing to improved detection and tracking of low-altitude targets in maritime and complex terrain environments.

깊이 1200mm급 변단면보의 중간모멘트골조용 내진접합부 개발

정시화,알미아이유 로벨 원디므,박만우,주영규 대한건축학회 2019 大韓建築學會論文集 : 構造系 Vol.35 No.4

Deep beam has high section modules compared with shallow beam of the same weight. However, deep beam has low rotational capacity and high possibility of brittle failure so it is not possible to apply deep beams with a long span to intermediate moment frames, which should exhibit a ductility of 0.02rad of a story drift angle of steel moment frames. Accordingly, KBC and AISC limit the beam depth for intermediate and special moment frame to 750mm and 920mm respectively. The purpose of this paper is to improve the seismic performance of intermediate moment frame with 1200mm depth beam. In order to enhance vulnerability of plastic deformation capacity of deeper beam, Multi-Reduced Taper Beam(MRTB) shape that thickness of beam flange is reinforced and at the same time some part of the beam flange width is weakened are proposed. Based on concept of multiple plastic hinge, MRTB is intended to satisfy the rotation requirement for intermediate moment frame by dividing total story drift into each hinge and to prevent the collapse of the main members by inducing local buckling and fracture at the plastic hinge location far away from connection. The seismic performance of MRTB is evaluated by cyclic load test with conventional connections type WUF-W, RBS and Haunch. Some of the proposed MRTB connection satisfies connection requirements for intermediate moment frame and shows improved the seismic performance compared to conventional connections. 본 연구에서는 보 깊이 1200mm의 중간모멘트골조 접합부를 개발하여 기존 철골 중간모멘트골조의 회전 성능을 향상시키고자 하였다. 깊은 보가 가지는 취약한 소성변형능력을 향상시키고자 보의 휨거동에 기반한 MRTB 접합부를 제안하였고, 제안된 접합부들의 내진 성능은 기존 접합부들과 함께 반복가력실험을 수행하여 평가하였다. MRTB 접합부는 중간모멘트골조 요구 성능을 만족하며 기존 접합부들 보다 향상된 회전 성능을 나타내었고, MRTB 형상별 거동 특성 차이를 나타내었다.

다중빔 측면주사음탐기의 고해상도 영상 분석 및 성능평가

계중읍(Joongeup Kye),박재현(Jaehyun Park),최성록(Sungrok Choi),최완식(Wansik Choi),김아영(Ah-young Kim) 제어로봇시스템학회 2014 제어로봇시스템학회 각 지부별 자료집 Vol.2014 No.11

In this paper, we propose and present the implementation result of high-resolution sonar using multi-beam array processing. Single-beam side scan sonar is widely used to survey the seabed and generate precise underwater images. A multi-beam side scan sonar system is proposed to increase the along-track resolution in spite of a high towing speed. To process massive amounts of signal data of multi-beam side scan sonar, an effective signal processing algorithm based on the quadrature method was developed that can minimize the complicated calculations by selecting the optimum sampling interval. Through a sea trial, the efficiency and performance of the developed multi-beam processing algorithm is verified. The results of the sea trial show that the efficiency of the survey is at least twice faster than single beam side scan sonar without a decrease in the along-track resolution.

Frequencies and modal shapes analysis of multi-point supported beam structures for a resonator sensitive component

Ruiqin Wu,Guofeng Xia,Wenhua Hu,Yibao Cai,Jianen Chen,Jingjing Feng 국제구조공학회 2024 Smart Structures and Systems, An International Jou Vol.34 No.6

Multi-supported beam structures are widely used in engineering applications, particularly as sensitive components in resonators. The intrinsic properties of these sensitive components significantly influence the performance of resonators. In this study, a dynamic theoretical model of a multi-point supported beam was established, considering the impact of the supported beams on the overall structure. The governing equations of motion of the multi-point supported beam structure were derived using the Hamiltonian principle. A theoretical method was proposed to calculate frequencies and global modal shapes of the multi-point supported beam structures. The theoretical results were validated through numerical simulations with specific parameters. The natural frequencies of a multi-point supported beam were also experimentally measured and compared with the simulation results. Our investigation into the effects of structural parameters on the frequency and global modal shapes demonstrated the effectiveness of the proposed method. The findings show that frequencies and modal shapes of the complex beam undergo regular changes as structural parameters vary. This study provides a theoretical foundation for improving the performance of beam resonators and serves as a guide for the parametric design of multi-point supported beam structures.

다중 에이전트 강화학습을 이용한 RC보 최적설계 기술개발

강주원,김현수 한국공간구조학회 2023 한국공간구조학회지 Vol.23 No.2

Reinforcement learning (RL) is widely applied to various engineering fields. Especially, RL has shown successful performance for control problems, such as vehicles, robotics, and active structural control system. However, little research on application of RL to optimal structural design has conducted to date. In this study, the possibility of application of RL to structural design of reinforced concrete (RC) beam was investigated. The example of RC beam structural design problem introduced in previous study was used for comparative study. Deep q-network (DQN) is a famous RL algorithm presenting good performance in the discrete action space and thus it was used in this study. The action of DQN agent is required to represent design variables of RC beam. However, the number of design variables of RC beam is too many to represent by the action of conventional DQN. To solve this problem, multi-agent DQN was used in this study. For more effective reinforcement learning process, DDQN (Double Q-Learning) that is an advanced version of a conventional DQN was employed. The multi-agent of DDQN was trained for optimal structural design of RC beam to satisfy American Concrete Institute (318) without any hand-labeled dataset. Five agents of DDQN provides actions for beam with, beam depth, main rebar size, number of main rebar, and shear stirrup size, respectively. Five agents of DDQN were trained for 10,000 episodes and the performance of the multi-agent of DDQN was evaluated with 100 test design cases. This study shows that the multi-agent DDQN algorithm can provide successfully structural design results of RC beam.

Continuum mechanics based beam elements for linear and nonlinear analyses of multi-layered composite beams with interlayer slips

Kim, Hyo-Jin,Yoon, Kyungho,Lee, Phill-Seung Elsevier 2020 Composite Structures Vol.235 No.-

<P><B>Abstract</B></P> <P>In this study, we present continuum mechanics based beam elements for linear and nonlinear analyses of multi-layered composite beams with interlayer slips. Nonlinear kinematics of multi-layered beams allowing interlayer slips and the finite element formulation for nonlinear incremental analysis are derived. An important feature of the proposed beam element is an advanced modeling capability that originates from individual modeling of each beam layer using cross-sectional elements and layer degrees of freedom, which are embedded in the beam formulation. Complicated layered beam geometries including arbitrary numbers of layers and interlayers, varying and composite cross-sections, and eccentricities can be easily modeled without additional interface elements or constraints. Further, the proposed beam finite element is successfully applicable for predicting geometric and material nonlinear behaviors of the multi-layered beams including nonlinear load-slip relations at interlayers. The superb performance and predictive capability of the proposed beam element are demonstrated through several representative numerical examples.</P>

다중빔 음향측심기의 내수면 적용성 평가

정진우,조광희,홍승서 한국측량학회 2018 한국측량학회지 Vol.36 No.6

본 연구에서는 영산강의 죽산보에서 죽산교까지 길이 약 840m, 폭 약 230m, 넓이 약 0.16㎢를 대상으로 단빔 음 향측심기와 다중빔 음향측심기의 내수면 적용성을 분석하였다. 무인선에 단빔 음향측심기와 다중빔 음향측심기 를 장착하고 각각의 데이터를 획득한 다음 비정규삼각망(TIN: Triangular Irregular Network)을 생성하고 10m 간 격의 격자 수심을 추출하였다. 추출한 단빔 및 다중빔 음향측심기의 격자수심 총 5,024개의 데이터를 중첩 비교하 여 다음의 결론을 얻을 수 있었다. 첫째, 수심의 차이는 평균 0.0319m로서 전체적으로 큰 차이는 없었으나 표준편 차는 2.4095m로 크게 나타났다. 둘째, TIN으로 구현된 하상의 형태는 서로 유사하였으나, 다중빔의 하상면보다 높 거나 낮은 단빔의 하상면 구역들의 체적은 총 161,882㎥의 차이가 있었다. 셋째, 대상지역 전체를 다중빔으로 스캔 했을 때 단빔에 비해 운항 거리는 4,595.85m, 약 55% 정도 증가하였으며, 운항 시간은 59분, 약 47% 정도 증가하였 다. 넷째, 작업공정, 투입인원 및 소요비용에서는 같거나 큰 차이가 없었다. 운항 거리나 운항 시간과 같은 작업 효율 면에서 단빔을 장착했을 때보다 다중빔을 장착했을 때 효율이 약 0.5배 정도 낮은 것으로 판단되나, 하상변동 예측 과 같이 하상면의 정확한 데이터가 필요한 분야에서는 다중빔 음향측심기를 이용한 데이터 획득이 필요한 것으로 판단된다. In this study, the application of the single beam echosounder and multi beam echosounder was analyzed for the Youngsan river, from the Juksanbo to the Juksan bridge, length of 840m, width 230m and area 0.16㎢. A single beam echosounder and a multi beam echosounder are mounted on an USV (Unmanned Surface Vessel), and each data is acquired. Then, TIN (Triangular Irregular Network) is created and the grid depth of 10m intervals is extracted. The grid depth of the single beam echo sounder and the grid depth of the multi beam echo sounder were overlapped to compare the two data. As a result of analysis using 5,024 data, the mean depth difference was 0.0319m and the standard deviation was 2.4095m. The river bed shape was similar to each other. If the multi-beam echo sounder is regarded as the standard, the volume difference of the stream is 161,882㎥. With a multi-beam echo sounder installed, the operating distance increased by approximately 55% to 4595.85m, and the operating time increased by approximately 59% to approximately 47%.

선형 모멘트 하중을 받는 계단식 단면변화 I형보의 비탄성 횡-비틀림 좌굴강도산정을 위한 모멘트 구배계수 연구

박종섭,손지민 한국방재학회 2008 한국방재학회논문집 Vol.08 No.06

The cross-sections of continuous multi-span beams sometimes suddenly increase, or become stepped, at the interior supports of continuous beams to resist high negative moments. The three-dimensional finite-element program ABAQUS (2007) was used to analytically investigate the inelastic lateral-torsional buckling behavior of stepped beams subjected to linear moment gradient and resulted in the development of design equations. The ratios of the flange thickness, flange width, and stepped length of beam are considered for the analytical parameters. Two groups of 27 cases and 36 cases, respectively, were analyzed for doubly and singly stepped beams in the inelastic buckling range. The combined effects of residual stresses and geometrical imperfection on inelastic lateral-torsional buckling of beams are considered. First, the distributions of residual stress of the cross-section is same as shown in Pi and Trahair (1995), and the initial geometric imperfection of the beam is set by central displacement equal to 0.1% of the unbraced length of beam. The new proposed equations definitely improve current design methods for the inelastic lateral-torsional buckling problem and increase efficiency in building and bridge design. 일반적으로 연속경간을 가지는 강합성 I-형강 교량에 있어서 내부 지점 부근에서 상대적으로 큰 부모멘트가 발생하므로, 이에 경제적인 단면 활용을 위하여 변단면을 적용하여 휨강도를 증가시킨다. 본 연구에서는 기존 횡-비틀림 좌굴식에 관한 연구를 토대로 하여 비탄성 구간에 있는 계단식 I형보의 횡-비틀림 좌굴강도를 유한요소해석프로그램 ABAQUS(2007)를 이용하여 산정하고, 간편한 설계식을 제안하고 있다. 양단 및 일단 계단식 단면변화를 가지는 보에 대해서 고려하였으며, 플랜지 길이방향 비, 너비방향 비, 두께의 비로 계단식 I형보를 나타내었다. 해석에 사용된 단면매개변수는 각각 27가지 및 36가지 조합이며, 비탄성 횡-비틀림 거동을 고려하기위하여 잔류응력 및 초기결함을 고려한 비선형해석을 실시하였는데, Pi와 Trahair(1995)가 고려한 잔류응력의 형상과 국내 I형강 표준 치수 허용치에 근거하여 부재 길이의 0.1%를 초기제작오차로 고려하였다. 해석모델의 양쪽 끝단에는 모멘트하중을 재하하였다. 개발․제한된 식은 선형 모멘트 하중이 작용할 때 적용가능한 식으로 경제적이고 합리적인 설계에 적극 활용될 수 있을 것이며, 다양한 하중을 받는 계단식 단면 변화보의 비탄성 좌굴강도 연구에 활용될 수 있을 것이다.

Ka 대역 위성 출력 전력 제어 기술 연구

신동환(Dong-hwan Shin),윤소현(So-hyeun Yun),문성모(Seong-mo Moon),이홍열(Hong-yeol Lee),엄만석(Man-seok Eom),염인복(In-bok Yom) 한국통신학회 2012 韓國通信學會論文誌 Vol.37 No.11B

Ka 대역 위성통신 시스템에서 강우 감쇠 보상을 위해서는 위성 탑재체에서 강우 지역의 출력 전력을 높일 수 있는 시스템이 요구된다. Ka 대역 출력 전력 제어 기술은 위성 탑재체에서 하향 링크(19.8 ~ 22.2 ㎓)의 출력전력 조정을 가능하게 한다. 본 논문에서는 다중 빔 안테나와 다중 입출력 증폭기를 이용한 Ka 대역 위성 출력전력 제어 기술에 대하여 소개한다. 한반도 상에 8개의 빔을 형성하기 위해 배열 급전 소자와 반사판으로 구성된 다중 빔 안테나가 설계되었다. 빔 당 목표 EIRP는 59 ㏈W 이상이며, 강우 감쇠 보상을 위한 전력 제어 기능은 강우 지역에 비 강우 지역 대비 최대 6 ㏈의 EIRP 상승이 가능하도록 설계하였다. 다중 입출력 증폭기는 다중 빔안테나와 함께 구성될 때 위성 출력 전력 제어를 위해 효과적으로 사용될 수 있다. 4x4 다중 입출력 증폭기가 기술 검증을 위해 제작되었으며 Ka 대역 위성 송신 주파수 대역에서 24 ㏈ 이상의 격리도 성능을 나타낸다. For Ka-band satellite communication system, a new flexible payload technologies which can compensate rain attenuation have to be developed. The Ka-band satellite output power control technology enables to adjust downlink output power of satellite payload in Ka-band (19.8 ~ 22.2 ㎓). In this paper, we introduce multi-beam antenna with multi-port amplifiers for Ka-band flexible output power allocation system. We have designed multi-beam antenna with array-fed reflector to form 8 beams on the Korean Peninsula. The target EIRP per beam is more than 59 ㏈W. The system is designed to present 6 ㏈ boost beams for rainfall areas. Individual beams were optimized by the excited amplitude and phase of feed elements of the feed cluster. The multi-port amplifier(MPA) is one of effective approaches for flexible power allocation in combination with multi-beam antenna. In case of using MPA in multi-beam system, the inter-port isolation characteristic of MPA is important parameter to avoid interference among the output ports. In this paper, we propose a new MPA structure that consists of two 4x4 Buttler matrixes and phase/amplitude controllable power amplifier modules.

MDCT 장치의 z-축 기하학적 선량효율에 관한 연구

김유현(You-Hyun Kim),김문찬(Moon-Chan Kim) 대한방사선과학회(구 대한방사선기술학회) 2006 방사선기술과학 Vol.29 No.3

최근의 나선형 CT와 MDCT는 기존의 고식적 CT보다 X-선 조사시의 겹침 현상과 영상 재구성에 있어서의 보간삽입처리로 인해 보다 높은 선량을 환자에게 주게 되었다. MDCT와 나선형 CT장치가 보다 많은 의학적 정보를 제공하는 것에도 불구하고 환자가 받는 방사선 노출은 기존의 고식적 CT검사에 비해 2~4배 정도로 증가되고 있는 실정이므로, 그 잠재적 위험성을 아무리 강조해도 지나침이 없다. CT장치에서의 보다 많은 X-선에 관련된 자료들, 특히 선량효율적 디자인이나 X-선 조절 소프트웨어에 대한 자료들이 필요하다. 왜냐하면 CT장치의 디자인 요소는 임상적 진단에 있어서 환자선량을 성공적으로 줄일 수 있는 중요한 요소이기 때문이다. 이에 본 연구에서는 최근 급격히 확산되어 사용되고 있는 여러 단계의 MDCT의 z-축 선량효율을 측정하여 SDCT와 비교하였다. 그리고 MDCT에서 스캔 시 채택하는 focal spot size와 beam collimation, 검출기 조합 등을 비롯한 파라메터들의 변화에 따른 z-축 선량효율을 파악하여 다음과 같은 결과를 얻었다. 1. SDCT가 z-축 기하학적 선량효율이 가장 높았고, 4 슬라이스 MDCT가 가장 낮았다. MDCT 중에서는 small beam collimation 적용 시 64 MDCT가 기하학적 선량효율이 가장 높았고 16, 8, 4 슬라이스 MDCT 순이었으며, large beam collimation 적용 시에는 small focal spot에서는 8 MDCT가, large focal spot에서는 16 MDCT가 가장 높았다. 2. MDCT의 경우 large focal spot에 비해 small focal spot의 z-축 기하학적 선량효율이 최저 0.67%에서 최대 13.62%의 범위에서 높았다. 3. MDCT의 경우 small beam collimation에 비해 large beam collimation의 z-축 기하학적 선량효율이 3.13~51.52%의 범위에서 높았다. 4. 동일한 focal spot size와 beam collimation을 채택한 상태에서 detector combination 차이에 따른 z-축 기하학적 선량효율은 4 슬라이스 MDCT의 모든 경우와 8 슬라이스 MDCT의 large beam collimation에서 일정하였다. 하지만 8 슬라이스 MDCT의 small beam collimation과 16 슬라이스 MDCT에서는 z-축 기하학적 선량효율이 차이를 보였으며 변화의 일률성은 없었다. 5. 동일한 스캔 파라메터를 적용시 나선형 스캔과 고식적 스캔 모드의 z-축 기하학적 선량효율은 동일하였으며, pitch를 변화시키거나 영상재구성 시 슬라이스 두께와 간격을 변화시켜도 z-축 기하학적 선량효율은 변화가 없었다. 결론적으로, CT검사 시 환자가 받는 X-선 피폭선량을 줄이기 위해 연구자는 CT장치의 선량효율에 대해 각별히 주의하여야 하며, Z-축 선량효율성을 높이는 동시에 최적의 임상적 정보를 보존할 수 있는 스캔 파라메터를 선택하여야 한다 With the recent prevalence of helical CT and multi-slice CT, which deliver higher radiation dose than conventional CT due to overbeaming effect in X-ray exposure and interpolation technique in image reconstruction. Although multi-detector and helical CT scanner provide a variety of opportunities for patient dose reduction, the potential risk for high radiation levels in CT examination can"t be overemphasized in spite of acquiring more diagnostic information. So much more concerns is necessary about dose characteristics of CT scanner, especially dose efficient design as well as dose modulation software, because dose efficiency built into the scanner"s design is probably the most important aspect of successful low dose clinical performance. This study was conducted to evaluate z-axis geometric dose efficiency in single detector CT and each level multi-detector CT, as well as to compare z-axis dose efficiency with change of technical scan parameters such as focal spot size of tube, beam collimation, detector combination, scan mode, pitch size, slice width and interval. The results obtained were as follows ; 1. SDCT was most highest and 4 MDCT was most lowest in z-axis geometric dose efficiency among SDCT, 4, 8, 16, 64 slice MDCT made by GE manufacture. 2. Small focal spot was 0.67-13.62% higher than large focal spot in z-axis geometric dose efficiency at MDCT. 3. Large beam collimation was 3.13-51.52% higher than small beam collimation in z-axis geometric dose efficiency at MDCT. 4. Z-axis geometric dose efficiency was same at 4 slice MDCT in all condition and 8 slice MDCT of large beam collimation with change of detector combination, but was changed irregularly at 8 slice MDCT of small beam collimation and 16 slice MDCT in all condition with change of detector combination. 5. There was no significant difference for z-axis geometric dose efficiency between conventional scan and helical scan, and with change of pitch factor, as well as change of slice width or interval for image reconstruction. As a conclusion, for reduction of patient radiation dose delivered from CT examination we are particularly concerned with dose efficiency of equipment and have to select proper scanning parameters which increase z-axis geometric dose efficiency within the range of preserving optimum clinical information in MDCT examination.