• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.4
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• pp.694-699
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• 2011

A closed-form technique is presented for estimating a single source location from a set of noisy time delay measurements between distributed sensors. The localization formula is derived from nonlinear least squares minimization over the unknowns of target range and bearing in polar coordinates. Computer simulation results are provided for the purpose of performance analysis. Constrained least squares minimization method with prior source location information is also discussed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.10
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• pp.1874-1881
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• 2010

A recursive linear stochastic error compensation algorithm is newly proposed for target localization in sensor network which provides range difference of arrival(RDOA) measurements. Target localization with RDOA is a well-known nonlinear estimation problem. Since it can not solve with a closed-form solution, the numerical methods sensitive to initial guess are often used before. As an alternative solution, a pseudo-linear estimation scheme has been used but the auto-correlation of measurement noise still causes unacceptable estimation errors under low SNR conditions. To overcome these problems, a stochastic error compensation method is applied for the target localization problem under the assumption that a priori stochastic information of RDOA measurement noise is available. Apart from the existing methods, the proposed linear target localization scheme can recursively compute the target position estimate which converges to true position in probability. In addition, it is remarked that the suggested algorithm has a structural reconciliation with the existing one such as linear correction least squares(LCLS) estimator. Through the computer simulations, it is demonstrated that the proposed method shows better performance than the LCLS method and guarantees fast and reliable convergence characteristic compared to the nonlinear method.

• Communications of the Korean Mathematical Society
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• v.11 no.4
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• pp.1147-1157
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• 1996

Nonlinear ill-posed problems arise in many application including parameter estimation and inverse scattering. We introduce a least squares regularization method to solve nonlinear ill-posed problems with constraints robustly and efficiently. The regularization method uses Trust-Region approach to handle the constraints on variables. The Generalized Cross Validation is used to choose the regularization parameter in computational tests. Numerical results are given to exhibit faster convergence of the method over other methods.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.2
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• pp.54-60
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• 1984

In this paper, the modified Hunt's constrained least squares estimation method for image restoration is studied with the parameter ${\alpha}$ which represents the effect of inverse filter, And it is akown that high frequency components in the restored image obtained by the proposed method are emphasized by optimizing the constraining factor ${\gamma}$, depending upon ${\alpha}$.

• Journal of the Korean Geophysical Society
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• v.6 no.1
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• pp.1-11
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• 2003

There are numerous adjustment techniques that deal with the adjustment of geodetic networks but the least squares adjustment is the most common one. During the network adjustment procedure two techniques can be used, the free network adjustment technique and the constrained network adjustment technique. In order to determine the optimum technique for adjusting the geodetic networks, which used for the geodynamical purposes, data from two different geodetic networks "Sinai geodetic network, Egypt, and HGN network, South Korea" had been examined. The used networks had a different configuration and located in different areas with different seismic activity. The results show that both techniques have a high accuracy and no remarkable differences in terms of RMS. On the contrary, the resulted coordinates shows that the constrained network adjustment technique not only cause a remarkable distortion in the station final coordinates but also if the fixed points that define the datum parameters are changed different solutions for the coordinates will be determined. This distortion affect not only in the determination of point displacement but also in the estimation of the deformation parameters, which play a significant role in the geodynamical interpretation of results. Comparing the results which obtained from both techniques with the widely known geodynamical models of the area reviles that the free network adjustment technique results are clearly match with these models, while those obtained from the constrained technique didn’t match at all. By considering the results it seams to be that the free network adjustment technique is the optimum technique, which can be used for the geodetic network adjustment.

• International Journal of Concrete Structures and Materials
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• v.8 no.3
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• pp.213-228
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• 2014

Alkali-activated binder (AAB) is recently being considered as a sustainable alternative to portland cement (PC) due to its low carbon dioxide emission and diversion of industrial wastes and by-products such as fly ash and slag from landfills. In order to comprehend the behavior of AAB, detailed knowledge on relations between microstructure and mechanical properties are important. To address the issue, a new approach to characterize hardened pastes of AAB containing fly ash as well as those containing fly ash and slag was adopted using scanning electron microscopy (SEM) and energy dispersive X-ray spectra microanalyses. The volume stoichiometries of the alkali activation reactions were used to estimate the quantities of the sodium aluminosilicate (N-A-S-H) and calcium silicate hydrate (CSH) produced by these reactions. The 3D plots of Si/Al, Na/Al and Ca/Si atom ratios given by the microanalyses were compared with the estimated quantities of CSH(S) to successfully determine the unique chemical compositions of the N-A-S-H and CSH(S) for ten different AAB at three different curing temperatures using a constrained nonlinear least squares optimization formulation by general algebraic modeling system. The results show that the theoretical and experimental quantities of N-A-S-H and CSH(S) were in close agreement with each other. The $R^2$ values were 0.99 for both alkali-activated fly ash and alkali-activated slag binders.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.2
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• pp.131-142
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• 2015

In order to support the development of a cost-effective river bathymetric system, this research has focused on modeling GPS observables, which are obtained by array of five single-frequency receivers (i.e., two references and three rovers) to estimate the high accurate kinematic position, and the surveying vessel altitude. Also, by applying all GPS measurements as multiple-baselines with constraining rover baselines, we derived the socalled ‘kinematic network model.’ From the model, the integer-constrained least-squares (LS) for position estimation and the implicit LS for attitude determination were implemented, while a series of simulation tests with respect to the baseline lengths around 2km performed to demonstrate its accuracy analysis. The on-the-fly (OTF) ambiguity resolution tests revealed that ninety-nine percents of time-to-fix-first ambiguity (TTFF) can be decided in less than two seconds, when the positioning accuracy of ambiguity-fixed solutions was assessed as the greater than or equal to one and two centimeters in horizontal and vertical, respectively. Comparing to the GPS-derived attitudes, the achievable accuracy gradually descended in sequence of yaw, pitch and roll due to the antenna geometric configuration. Furthermore, the RMSE values for the baseline lengths of three to six meters were within ±1′for yaw, and less than ±10′and ±20′for pitch and roll, respectively, but those of between six to fifteen meters were less than ±1′for yaw, ±5′for pitch, and ±10′for roll.