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Three Stage Neural Networks for Direction of Arrival Estimation (도래각 추정을 위한 3단계 인공신경망 알고리듬)

  • Park, Sun-bae;Yoo, Do-sik
    • Journal of Advanced Navigation Technology
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    • v.24 no.1
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    • pp.47-52
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    • 2020
  • Direction of arrival (DoA) estimation is a scheme of estimating the directions of targets by analyzing signals generated or reflected from the targets and is used in various fields. Artificial neural networks (ANN) is a field of machine learning that mimics the neural network of living organisms. They show good performance in pattern recognition. Although researches has been using ANNs to estimate the DoAs, there are limitationsin dealing with variations of the signal-to-noise ratio (SNR) of the target signals. In this paper, we propose a three-stage ANN algorithm for DoA estimation. The proposed algorithm can minimize the performance reduction by applying the model trained in a single SNR environment to various environments through a 'noise reduction process'. Furthermore, the scheme reduces the difficulty in learning and maintains efficiency in estimation, by employing a process of DoA shift. We compare the performance of the proposed algorithm with Cramer-Rao bound (CRB) and the performances of existing subspace-based algorithms and show that the proposed scheme exhibits better performance than other schemes in some severe environments such as low SNR environments or situations in which targets are located very close to each other.

Numerical Analysis on Penetration Reduction of a WHA Penetrator by an Impact of Linear Explosively Formed Penetrator(LEFP) (선형폭발성형탄(LEFP) 충격에 의한 WHA 관통자의 관통성능 감소에 관한 수치해석 연구)

  • Joo, Jaehyun;Choi, Joonhong;Koo, ManHoi;Kim, Dongkyu
    • Journal of the Korea Institute of Military Science and Technology
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    • v.20 no.3
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    • pp.384-392
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    • 2017
  • A linear explosively formed penetrator(LEFP) is a modification of the explosively formed penetrator(EFP). An EFP is axisymmetric and has a dish-shaped liner while LEFP has a rectangular-shaped liner with curved cross section. Upon detonating LEFP forms laterally wide projectile like blade, leaving a long penetration hole on the target. On the other hand, a long-rod tungsten heavy alloy(WHA) penetrator is one of the major threats against most of the ground armored vehicles. In this paper, the feasibility of using an LEFP in protecting against a long-rod WHA penetrator by colliding LEFP into the threat was investigated through a set of numerical simulations. In this study, a scale-down WHA penetrator with length to diameter ratio(L/D) of 10.7 and 7.0 mm diameter was used to represent a long-rod WHA penetrator. LS-DYNA and Multi-Material ALE technique were employed for the simulation. For estimation of the protection effect by LEFP, residual penetration depths into RHA by the threat were compared according to various impact locations against the threat.

A Study on the Heat Release Analysis to Compensate the Error due to Assumption of Single Zone in Diesel Engine (디젤 기관 단일 영역 모델 열발생율 계산의 오차 보상에 관한 연구)

  • Ryu Seung-Hyup;Kim Ki-Doo;Yoon Wook-Hyeon;Ha Ji-Soo
    • Journal of Advanced Marine Engineering and Technology
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    • v.30 no.5
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    • pp.572-579
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    • 2006
  • Accurate heat release analysis based on the cylinder pressure trace is important for evaluating combustion process of diesel engines. However, traditional single-zone heat release models (SZM) have significant limitations due mainly to their simplified assumptions of uniform charge and homogeneity while neglecting local temperature distribution inside cylinder during combustion process. In this study, a heat release analysis based on single-zone model has been evaluated by comparison with computational simulation result using Fire-code, which is based on multidimensional model (MDM). The limitations of the single-zone assumption have been estimated, To overcome these limitations, an improved model that includes the effects of spatial non-uniformity has been applied. From this improved single-zone heat release model (Improved-SZM), two effective values of specific heat ratios, denoted by ${\gamma}_V$ and ${\gamma}_H$ in this study, have been introduced. These values are formulated as the function of charge temperature changing rate and overall equivalence ratio. Also, it is applied that each equation of ${\gamma}_V$ and ${\gamma}_H$ has respectively different slopes according to several meaningful periods during combustion progress. The heat release analysis results based on improved single-zone model gives a good agreement with FIRE-code results over the whole range of operating conditions of target engine, Hyundai HiMSEN H21/32.

Feasibility Study of Robotics-based Patient Immobilization Device for Real-time Motion Compensation

  • Chung, Hyekyun;Cho, Seungryong;Cho, Byungchul
    • Progress in Medical Physics
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    • v.27 no.3
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    • pp.117-124
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    • 2016
  • Intrafractional motion of patients, such as respiratory motion during radiation treatment, is an important issue in image-guided radiotherapy. The accuracy of the radiation treatment decreases as the motion range increases. We developed a control system for a robotic patient immobilization system that enables to reduce the range of tumor motion by compensating the tumor motion. Fusion technology, combining robotics and mechatronics, was developed and applied in this study. First, a small-sized prototype was established for use with an industrial miniature robot. The patient immobilization system consisted of an optical tracking system, a robotic couch, a robot controller, and a control program for managing the system components. A multi speed and position control mechanism with three degrees of freedom was designed. The parameters for operating the control system, such as the coordinate transformation parameters and calibration parameters, were measured and evaluated for a prototype device. After developing the control system using the prototype device, a feasibility test on a full-scale patient immobilization system was performed, using a large industrial robot and couch. The performances of both the prototype device and the realistic device were evaluated using a respiratory motion phantom, for several patterns of respiratory motion. For all patterns of motion, the root mean squared error of the corresponding detected motion trajectories were reduced by more than 40%. The proposed system improves the accuracy of the radiation dose delivered to the target and reduces the unwanted irradiation of normal tissue.

Double-layered Peer-to-Peer Systems in MobileAd-hoc Networks (모바일애드혹 네트워크에서의 2계층 피어-투-피어 시스템)

  • Kim, Ji-Hoon;Yang, Sung-Bong
    • The KIPS Transactions:PartC
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    • v.17C no.1
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    • pp.61-68
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    • 2010
  • As the mobile technology advances, file searching among the mobile device users becomes more important. In this paper, we propose the uniform grid, greedy, and MIS P2P systems that have double-layered topology to search files efficiently for mobile ad-hoc networks. In these systems, peers are classified into two groups, super-peers and sub-peers, and each super-peer manages its neighboring sub-peers. In the proposed systems, each super-peer maintains the appropriate information of its sub-peers so that when a peer requests a file, the request is sent to its super-peers and then to neighboring super-peers. Hence the proposed systems could avoid multi-broadcasting and reduce network overheads. The experimental results show that the proposed systems outperform a single-layered P2P system in terms of the average number of messages to find target files. Especially the MISsystem improves by reducing the average number of messages by 48.9% while maintaining the same search accuracy.

The Response Modification Factor of Inverted V-type Braced Steel Frames (역V형 가새골조의 반응수정계수)

  • Ahn, Hyung Joon;Jin, Song Mei
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.1
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    • pp.1-9
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    • 2013
  • In this study of Eccentric Braced Frames have identified the following target eccentricity on the length of the inelastic behavior of the reaction by calculating the correction factor by comparing it to the value suggested by the earthquake provided material for the rational design aims to There are. As a variable-length V-braced frame analysis model stations were set up. Eccentricity faults in the model according to the length stiffness ratio, the maximum amount of energy dissipation were analyzed base shear and multi-layered model of the reaction from the eccentricity correction factor calculated on the length of the building standards proposed by KBC 2009 in response eccentricity correction factor calculated from The length varies. does not have the same response modification factor was confirmed.

Combination therapy with cilostazol, aripiprazole, and donepezil protects neuronal cells from β-amyloid neurotoxicity through synergistically enhanced SIRT1 expression

  • Heo, Hye Jin;Park, So Youn;Lee, Yi Sle;Shin, Hwa Kyoung;Hong, Ki Whan;Kim, Chi Dae
    • The Korean Journal of Physiology and Pharmacology
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    • v.24 no.4
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    • pp.299-310
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    • 2020
  • Alzheimer's disease (AD) is a multi-faceted neurodegenerative disease. Thus, current therapeutic strategies require multitarget-drug combinations to treat or prevent the disease. At the present time, single drugs have proven to be inadequate in terms of addressing the multifactorial pathology of AD, and multitarget-directed drug design has not been successful. Based on these points of views, it is judged that combinatorial drug therapies that target several pathogenic factors may offer more attractive therapeutic options. Thus, we explored that the combination therapy with lower doses of cilostazol and aripiprazole with add-on donepezil (CAD) might have potential in the pathogenesis of AD. In the present study, we found the superior efficacies of donepezil add-on with combinatorial mixture of cilostazol plus aripiprazole in modulation of expression of AD-relevant genes: Aβ accumulation, GSK-3β, P300, acetylated tau, phosphorylated-tau levels, and activation of α-secretase/ADAM 10 through SIRT1 activation in the N2a Swe cells expressing human APP Swedish mutation (N2a Swe cells). We also assessed that CAD synergistically raised acetylcholine release and choline acetyltransferase (CHAT) expression that were declined by increased β-amyloid level in the activated N2a Swe cells. Consequently, CAD treatment synergistically increased neurite elongation and improved cell viability through activations of PI3K, BDNF, β-catenin and α7-nicotinic cholinergic receptors in neuronal cells in the presence of Aβ1-42. This work endorses the possibility for efficient treatment of AD by supporting the synergistic therapeutic potential of donepezil add-on therapy in combination with lower doses of cilostazol and aripiprazole.

Multiple aggregation prediction algorithm applied to traffic accident counts (다중 결합 예측 알고리즘을 이용한 교통사고 발생건수 예측)

  • Bae, Doorham;Seong, Byeongchan
    • The Korean Journal of Applied Statistics
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    • v.32 no.6
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    • pp.851-865
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    • 2019
  • Discovering various features from one time series is complicated. In this paper, we introduce a multi aggregation prediction algorithm (MAPA) that uses the concepts of temporal aggregation and combining forecasts to find multiple patterns from one time series and increase forecasting accuracy. Temporal aggregation produces multiple time series and each series has separate properties. We use exponential smoothing methods in the next step to extract various features of time series components in order to forecast time series components for each series. In the final step, we blend predictions of the same kind of components and forecast the target series by the summation of blended predictions. As an empirical example, we forecast traffic accident counts using MAPA and observe that MAPA performance is superior to conventional methods.

Effect of the substrate temperature on the properties of transparent conductive IZTO films prepared by pulsed DC magnetron sputtering

  • Ko, Yoon-Duk;Kim, Joo-Yeob;Joung, Hong-Chan;Son, Dong-Jin;Choi, Byung-Hyun;Kim, Young-Sung
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.08a
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    • pp.167-167
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    • 2010
  • Indium tin oxide (ITO) has been widely used as transparent conductive oxides (TCOs) for transparent electrodes of various optoelectronic devices, such as liquid crystal displays (LCD) and organic light emitting diodes (OLED). However, indium has become increasingly expensive and rare because of its limited resources. In addition, ITO thin films have some problems for OLED and flexible displays, such as imperfect work function, chemical instability, and high deposition temperature. Therefore, multi-component TCO materials have been reported as anode materials. Among the various materials, IZTO thin films have been gained much attention as anode materials due to their high work function, good conductivity, high transparency and low deposition temperature. IZTO thin films with a thickness of 200nm were deposited on Corning glass substrate at different substrate temperature by pulsed DC magnetron sputtering with a sintered ceramic target of IZTO (In2O3 70 wt%, ZnO 15 wt%, SnO2 15 wt%). We investigated the electrical, optical, structural properties of IZTO thin films. As the substrate temperature is increased, the electrical properties of IZTO are improved. All IZTO thin films have good optical properties, which showed an average of transmittance over 80%. These IZTO thin films were used to fabricate organic light emitting diodes (OLEDs) as anode and the device performances studied. As a result, IZTO has utility value of TCO electrode although it reduced indium and we expect it is possible for the IZTO to apply to flexible display due to the low processing temperature.

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Computation Algorithm for Launch Acceptability Region of Air-to-Surface Missiles (공대지 유도탄의 발사유효범위(LAR) 산출 알고리듬)

  • Park, Sang-Sup;Hong, Ju-Hyeon;Ryoo, Chang-Kyung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.43 no.10
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    • pp.910-919
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    • 2015
  • A weapon control algorithm equipped on a fighter is closely related to the mission accomplishment and fighter survivability during the engagement. In the case of a air-to-surface missile, the weapon control algorithm typically provides a pilot the target shoot-down possible region known as launch acceptability region(LAR) in the multi function display(MFD). LAR is produced by the range table(RT) through computation of an engagement range. In this paper, the operation system of AGM-84 and AGM-88 air-to-surface missiles is introduced. And the engagement range computation and LAR algorithm based on the real-time pseudo 6-DOF simulation are proposed. In order to verify the performance of the algorithm, numerical engagement simulations of air-to-surface missiles to produce LAR have been done.