• International Journal of Aeronautical and Space Sciences
• /
• 제15권2호
• /
• pp.163-172
• /
• 2014

This paper proposes a novel guidance law based on the block backstepping sliding mode control and extended state observer (ESO), which also takes into account the autopilot dynamic characteristics of the near space interceptor (NSI), and the impact angle constraint of attacking the maneuvering target. Based on the backstepping control approach, the target maneuvers and the parameter uncertainties of the autopilot are regarded as disturbances of the outer loop and inner loop, respectively. Then, the ESO is constructed to estimate the target acceleration and the inner loop disturbance, and the block backstepping sliding model guidance law is employed, based on the estimated disturbance value. Furthermore, in order to avoid the "explosion of complexity" problem, first-order low-pass filters are also introduced, to obtain differentiations of the virtual control variables. The stability of the closed-loop guidance system is also proven, based on the Lyapunov theory. Finally, simulation results demonstrate that the proposed guidance law can not only overcome the influence of the autopilot dynamic delay and target maneuvers, but also obtain a small miss distance.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2002년도 하계종합학술대회 논문집(4)
• /
• pp.199-202
• /
• 2002

This paper introduces the near field shading beamformer using widely known Chebyshev and Hanning window in the field of digital signal processing. The proposed shading beamformer improves the estimation of range as well as azimuth angle of targe residing in near field. A series of sensor weighting values are calculated from the FFT operation of given shading functions in time domain. This paper verifies the performance of the focused beamformer having the proposed shading sensor weights which are used to detect the range of target. Throughout computer simulations this paper exploits the performance improvement of the proposed shading beamformer as varying the frequency band of the received radiated signal along the non-uniform array.

• Radiation Oncology Journal
• /
• 제33권3호
• /
• pp.226-232
• /
• 2015

Purpose: Toxicity of mucosa is one of the major concerns of radiotherapy (RT), when a target tumor is located near a mucosal lined organ. Energy of photon RT is transferred primarily by secondary electrons. If these secondary electrons could be removed in an internal cavity of mucosal lined organ, the mucosa will be spared without compromising the target tumor dose. The purpose of this study was to present a RT dose reduction in near target inner-surface (NTIS) of internal cavity, using Lorentz force of magnetic field. Materials and Methods: Tissue equivalent phantoms, composed with a cylinder shaped internal cavity, and adjacent a target tumor part, were developed. The phantoms were irradiated using 6 MV photon beam, with or without 0.3 T of perpendicular magnetic field. Two experimental models were developed: single beam model (SBM) to analyze central axis dose distributions and multiple beam model (MBM) to simulate a clinical case of prostate cancer with rectum. RT dose of NTIS of internal cavity and target tumor area (TTA) were measured. Results: With magnetic field applied, bending effect of dose distribution was visualized. The depth dose distribution of SBM showed 28.1% dose reduction of NTIS and little difference in dose of TTA with magnetic field. In MBM, cross-sectional dose of NTIS was reduced by 33.1% with magnetic field, while TTA dose were the same, irrespective of magnetic field. Conclusion: RT dose of mucosal lined organ, located near treatment target, could be modulated by perpendicular magnetic field.

• 감성과학
• /
• 제21권2호
• /
• pp.73-88
• /
• 2018

본 연구는 손과 가까운 시각 정보의 처리적 특성이 과제전환에 미치는 영향을 살펴보기 위해 수행되었다. 최근 연구들은 손과 가깝게 제시된 정보에 대한 인지통제가 향상됨을 보고하고 있다. 이러한 인지통제 향상효과를 손 근접성과 주의의 관계를 통해 규명하고자 두 번의 실험을 실시하였다. 그 결과 과제전환 수행에서 단서와 목표자극의 감각양상에 따라 손 근접성의 효과가 달라짐을 관찰할 수 있었다. 첫 번째 실험에서 손에 근접한 자극에 대한 전환비용의 감소가 관찰되었다. 선행 연구들에서 전환비용의 감소원인으로 지목되었던 특징결합 문제를 제외시켰을 경우에도 동일한 결과가 관찰되었다. 즉, 손 근접성이 전환비용을 감소시켰음을 검증할 수 있었다. 두 번째 실험에서는 손 근접성과 감각양상의 상호작용이 전환비용에 미치는 영향을 살펴보기 위해 수행되었다. 과제전환에서 목표자극은 시각으로 단서는 시각 또는 청각으로 제시하였고, 단서의 준비성 효과를 관찰하기 위해 단서-목표자극 간격을 조변하였다. 연구 결과 손에 근접한 시각 단서는 과제 준비 시간을 단축시켜 전환비용을 감소시켰으나, 청각 단서의 경우 손에 근접할 때 오히려 과제 준비 시간이 더 오래 걸렸다. 시각 단서의 결과는 손에 근접한 시각 정보에 대한 신속한 주의정향으로 인한 이득으로 설명될 수 있다. 반면에 청각 단서에서 나타난 손실은 청각 단서와 시각 자극 간의 감각 간 전환이 손 근접성의 주의 범위 고정 효과로 인해 방해된 결과로 해석될 수 있다. 마지막으로 손 근접성의 주의효과로 인해 달라지는 전환비용에 대해 논의하였다.

• 대한조선학회논문집
• /
• 제47권2호
• /
• pp.196-209
• /
• 2010

For the analysis of Acoustic Target Strength(TS) that indicates the scattered acoustic intensity from the underwater vehicles, an analysis program that is applicable to scatterers insonified by spherical wave source in near field is developed. In this program, the Physical Optics(PO) method is embedded as a base component. To increase the accuracy of the program, multiple bounce effects based on Geometrical Optics(GO) method are applied. To implement multiple bounce effects, GO method is used together with PO method. In detail, GO method has a concern in the evaluation of the effective area, and PO method is involved in the calculation of Acoustic Target Strength for the final effective area that is evaluated by GO method. For the embodiment of near field spherical wave source originated multiple bounce effects, image source concept is implemented additively to the existing multiple bounce algorithm which assumes plane wave insonification. Various types of models are tested to evaluate the reliability of the developed program and finally, a submarine is analyzed as an arbitrary scatterer.

• The Korean Journal of Legal Medicine
• /
• 제42권4호
• /
• pp.146-152
• /
• 2018

We investigated the neural correlates of accurate eyewitness memory retrieval using functional near-infrared spectroscopy. We analyzed oxygenated hemoglobin ($HbO_2$) concentration in the prefrontal cortex during eyewitness memory retrieval task and examined regional $HbO_2$ differences between observed objects (target) and unobserved objects (lure). We found that target objects elicited increased activation in the bilateral ventrolateral prefrontal cortex, which is known for monitoring retrieval processing via bottom-up attentional processing. Our results suggest bottom-up attentional mechanisms could be different during accurate eyewitness memory retrieval. These findings indicate that investigating retrieval mechanisms using functional near-infrared spectroscopy might be useful for establishing an accurate eyewitness recognition model.

• Coupled systems mechanics
• /
• 제12권2호
• /
• pp.167-181
• /
• 2023

The determination of the blast protection level and the corresponding minimum load-bearing capacity for a laminated glass (LG) window is of crucial importance for safety and security design purposes. In this paper, the focus is given to the window response under near-field blast loading, i.e., where relatively small explosives would be activated close to the target, representative of attack scenarios using small commercial drones. In general, the assessment of the load-bearing capacity of a window is based on complex and expensive experiments, which can be conducted for a small number of configurations. On the other hand, nowadays, validated numerical simulations tools based on the Finite Element Method (FEM) are available to partially substitute the physical tests for the assessment of the performance of various LG systems, especially for the far-field blast loading. However, very little literature is available on the LG window performance under near-field blast loads, which differs from far-field situations in two points: i) the duration of the load is very short, since the blast wavelength tends to increase with the distance and ii) the load distribution is not uniform over the window surface, as opposed to the almost plane wave configuration for far-field configurations. Therefore, the current study focuses on the performance assessment and structural behaviour of LG windows under near-field blasts. Typical behavioural trends are investigated, by taking into account possible relevant damage mechanisms in the LG window components, while size effects for target LG windows are also addressed under a multitude of blast loading configurations.

• Steel and Composite Structures
• /
• 제32권1호
• /
• pp.91-110
• /
• 2019

In the present study, the effects of six different ground motion scaling methods on inelastic response of nonlinear steel moment frames (SMFs) are studied. The frames were designed using energy-based PBPD approach with the design concept using pre-selected target drift and yield mechanism as performance limit state. Two target spectrums are considered: maximum credible earthquake spectrum (MCE) and design response spectrum (DRS). In order to investigate the effects of ground motion scaling methods on the response of the structures, totally 3216 nonlinear models including three frames with 4, 8 and 16 stories are designed using PBPD approach and then they are subjected to ensembles of ground motions including 42 far-fault and 90 near-fault pulse-type records which were scaled using the six different scaling methods in accordance to the two aforementioned target spectrums. The distributions of maximum inter-story drift over the height of the structures are computed and compared. Finally, the efficiency and reliability of each ground motion scaling method to estimate the maximum nonlinear inter-story drift of special steel moment frames designed by energy-based PBPD approach are statistically investigated, and the most suitable scaling methods with the lowest dispersion for two groups of earthquake ground motions are introduced.

• 전자공학회논문지 IE
• /
• 제46권4호
• /
• pp.42-48
• /
• 2009

본 논문에서는 전송 대역폭에 따라 손실을 최소화하며 적응적으로 압축률을 조절하는 준무손실 영상 부호화 알고리즘을 제안한다. 제안하는 방법은 슬라이스 부호화 간격으로 부호화된 비트량과 목표 부호화 비트량을 이용하여 적응적으로 허용 오류 범위를 변경한다. 실험 결과, 제안하는 방법은 기존 알고리즘들에 비하여 효과적으로 전송 대역폭에 맞추어 압축률을 조절할 뿐만 아니라 화질 또한 향상됨을 알 수 있다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 춘계학술대회논문집
• /
• pp.1165-1169
• /
• 2003

This paper presents an approach to optimally design the air-bearing surface (ABS) of the optical flying head for near-field recording technology (NFR). NFR is an optical recording technology using very small beam spot size by overcoming the limit of beam diffraction. One of the most Important problems in NFR is a head disk interface (HDI) issue over the recording band during the operation. A multi-criteria optimization problem is formulated to enhance the flying performances over the entire recording band during the steady state. The optimal solution of the slider, whose target flying height is 50 nm, is automatically obtained. The flying height during the steady state operation becomes closer to the target values than those fur the initial one. The pitch and roll angles are also kept within suitable ranges over the recording band. Especially, all of the air-bearing stiffness are drastically increased by the optimized geometry of the air bearing surface.