• Journal of Advanced Marine Engineering and Technology
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• v.39 no.2
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• pp.187-194
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• 2015

Accurate relative location estimation is a key requirement in indoor localization systems based on wireless sensor networks (WSNs). However, although these systems have applied not only various optimization algorithms but also fusion with sensors to achieve high accuracy in position determination, they are difficult to provide accurate relative azimuth and locations to users because of cumulative errors in inertial sensors with time and the influence of external magnetic fields. This paper based on ultra-wideband positioning system, which is relatively suitable for indoor localization compared to other wireless communications, presents an indoor localization system for estimating relative azimuth and location of location-unaware nodes, referred to as target nodes without applying any algorithms with complex variable and constraints to achieve high accuracy. In the proposed method, the target nodes comprising three mobile nodes estimate the relative distance and azimuth from two reference nodes that can be installed by users. In addition, in the process of estimating the relative localization information acquired from the reference nodes, positioning errors are minimized through a novel modified rounding estimation technique in which Kalman filter is applied without any time consumption algorithms. Experimental results show the feasibility and validity of the proposed system.

• International Journal of Ocean System Engineering
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• v.1 no.1
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• pp.52-59
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• 2011

A prototype radar display unit was implemented using inexpensive off-the-shelf components, including a nonlinear estimation algorithm for the target tracking in a clutter environment. Two custom designed boards; an analog signal processing board and a DSP board, can be plugged into an expansion slot of a personal computer (PC) to form a maritime radar display unit. Our system provided all the functionality specified in the International Maritime Organization (IMO) resolution A422(XI). The analog signal processing board was used for A/D conversion as well as rain and sea clutter suppression. The main functions of the DSP board were scan conversion and video overlay operations. A host PC was used to run the tracking algorithm of targets in clutter, using the discrete-time Bayes optimal (nonlinear, and non-Gaussian) estimation method, and the graphic user interface (GUI) software for Automatic Radar Plotting Aid (ARPA). The proposed tracking method recursively found the entire probability density function of the target position and velocity by converting into linear convolution operations.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.10
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• pp.811-816
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• 2012

The effect of co-sputtering condition on the structural properties of $Mg_xZn_{1-x}O$ thin films grown by RF magnetron co-sputtering system was investigated for manufacturing ZnO/MgZnO structure LED. $Mg_xZn_{1-x}O$ thin films were grown with ZnO and MgO target varying RF power. Structural properties were investigated by X-ray diffraction (XRD) and Energy dispersive spectroscopy (EDS). The ZnO thin films have sufficient crystallinity on the high RF power. As RF power of ZnO target increased, the contents of MgO in the $Mg_xZn_{1-x}O$ film decreased. LED was manufactured using ZnO/MgZnO multi-layer on p-GaN/$Al_2O_3$ substrate. Threshold voltage of multi-layer LED was appeared at 8 V, and it was luminesced at wave length of 550 nm.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.606-615
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• 2009

Estimating the reasonable construction-cost according to the construction phase in public construction is an important element for securing and executing a national budget efficiently. As a general rule, the predetermined cost of construction is estimated at the end of the design of the target structure. Therefore, it seems to be a considerably difficult problem to estimate the approximate cost of construction, only with its basic information of the bridge in the design planning phase and the early design stage where we can not have specific detailed-section of the target structure. In this paper, we present the calculation of construction-cost in the planning phase based on the analysis of factors affecting the cost of construction conducted in the previous study. Beside, to estimate the cost of construction in early design phase, we would like to present the calculation of construction-cost in the early design phase by executing the analysis of data collected from 61 steel box bridges. It was found from the result of study that the estimated cost of construction gained by the calculation of construction-cost in this paper reduces the error between the real cost of construction and that by the existing method of using.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.8
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• pp.661-669
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• 2017

This paper describes an MMTI(Maritime Moving Target Indicator) for periscope detection in airborne radar. Firstly, we analyze the characteristics of sea clutter, sea targets. Secondly, we study the differences between GMTI(Ground Moving Target Indicator) and MMTI. This paper proposes an optimal MMTI operating environment and method. We also suggest a signal processing algorithm using STAP(Space-Time Adaptive Processing) for detecting small RCS target moving low speed. The detection probability for moving target with MDV(Minimum Detectable Velocity) is simulated under various RCS and multi-channel system. Finally, we analyze the major performance for range, velocity and azimuth accuracy.

• Journal of Navigation and Port Research
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• v.41 no.5
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• pp.297-302
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• 2017

The tracking filter plays a key role in accurate estimation and prediction of maneuvering the vessel's position and velocity. Different methods are used for tracking. However, the most commonly used method is the Kalman filter and its modifications. The ${\alpha}-{\beta}-{\gamma}$ filter is one of the special cases of the general solution provided by the Kalman filter. It is a third order filter that computes the smoothed estimates of position, velocity, and acceleration for the nth observation, and predicts the next position and velocity. Although found to track a maneuvering target with good accuracy than the constant velocity ${\alpha}-{\beta}$ filter, the ${\alpha}-{\beta}-{\gamma}$ filter does not perform impressively under high maneuvers, such as when the target is undergoing changing accelerations. This study aims to track a highly maneuvering target experiencing jerky motions due to changing accelerations. The ${\alpha}-{\beta}-{\gamma}$ filter is extended to include the fourth state that is, constant jerk to correct the sudden change of acceleration to improve the filter's performance. Results obtained from simulations of the input model of the target dynamics under consideration indicate an improvement in performance of the jerky model, ${\alpha}-{\beta}-{\gamma}-{\eta}$ algorithm as compared to the constant acceleration model, ${\alpha}-{\beta}-{\gamma}$ in terms of error reduction and stability of the filter during target maneuver.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2017.11a
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• pp.145-147
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• 2017

Tracking filter plays a key role in accurate estimation and prediction of maneuvering vessel's dynamics. The third-order ${\alpha}-{\beta}-{\gamma}$ filter is one of the special cases of the general solution provided by the Kalman filter. Fading memory algorithm performs a better performance in numerous of ${\alpha}-{\beta}-{\gamma}$ filter algorithms. This study aims to optimize the fourth-order fading memory algorithm ${\alpha}-{\beta}-{\gamma}-{\eta}$ filter, which is extended form ${\alpha}-{\beta}-{\gamma}$ filter, to get much more accurate position of high dynamic target on the condition that the own ship is also high dynamic.

• Journal of Navigation and Port Research
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• v.28 no.2
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• pp.113-119
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• 2004

Ships' collision accident has often occurred in congested waterways or in harbour areas. To examine the cause of collision accident may be necessary to prevention against another similar one. We discuss the construction of ship-manoeuvring-simulator system used for reproducing ships' collision phenomenon The system consists of one simulator bridge for own ship and two control consoles for own ship and target ship. Own ship and target ship are linked each other, and are simultaneously manoeuvred in simulator bridge or at control console respectively. And a simulator experiment for reproducing ships' collision phenomenon and for examining the cause of accident is carried out. Through the present case study, we find out that the constructed simulator system is very useful for reproducing ships' collision phenomenon and for examining the cause of accident.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1981-1983
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• 1998

The principle of the MHD generation is based on Faraday's law of induction that a eletromotive force(u ${\times}$ B) is generated when the working gas of velocity u flows a channel in which magnetic field of strength(B) exists. In MHD power generation system, enthalpy of the working gas is converted to electric power directly through expansion in generator channel. It means that electric power can be generated without moving mechanical linkage such as turbine blades. There are two types in the MHD generator; linear type Faraday and disk type hall generator. Disk type hall generator is the main target of this paper. Isentropic efficiency and enthalpy extraction rate of disk type shock tube driven hall generator is discussed here.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.5
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• pp.562-568
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• 2008

In this study, the target FSICR class is 1A whose target thickness of the brash ice is 46 mm in model scale. Normally ice floes for brash ice do not exceed 2 m in full scale, so the model ice sheet was cut by about 10 cm by 10 cm using hand saws. Since the target thickness of brash ice is 46 mm, 46 mm ice sheet makes one layer brash ice. For 23 mm thickness ice sheet, two layers should be accumulated to reach 46mm brash ice thickness. For 15mm thickness ice sheet, three layers need to be accumulated as the same as those in 23 mm ice sheet. New methodology to produce a brash ice was proposed. The results showed that it would be important to use multi-layer rather than single layer possibly because of significant thrust deduction from the propeller-ice interaction in the present ice condition (FSICR 1A).