• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.2
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• pp.115-124
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• 2015

A methodology is proposed to estimate a trajectory of a flying target and its velocity using the time and frequency analysis of the acoustic signal. The measurement of sound emitted from a flying acoustic source with a microphone above a ground shall receive both direct and ground-reflected sound waves. For certain frequency contents, the destructive interference happens in received signal waveform reflected path lengths are in multiple integers of direct path length. This phenomenon is referred to as the acoustical mirror effect and it can be observed in a spectrogram plot. The spectrogram of acoustic measurement for a flying vehicle measurement shows several orders of destructive interference curves. The first or second order of curve is used to find the best approximate path by using nonlinear least-square method. Simulated acoustic signal is generated for the condition of known geometric of a sensor and a source in flight. The estimation based on cepstrogram analysis provides more accurate estimate than spectrogram.

• Journal of Korean Society for Atmospheric Environment
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• v.33 no.4
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• pp.393-402
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• 2017

In this study, greenhouse gas (GHG) reductions from bioenergy (biogas, biomass) have been estimated in Korea, 2015. This study for construction of reduction inventories as direct and indirect reduction sources was derived from IPCC 2006 guidelines for national greenhouse gas inventories, guidelines for local government greenhouse inventories published in 2016, also purchased electricity and steam indirect emission factors obtained from KPX, GIR respectively. As a result, the annual GHG reductions were estimated as $1,860,000tonCO_{2eq}$ accounting for 76.8% of direct reduction (scope 1) and 23.2% of indirect reduction (scope 2). Estimation of individual greenhouse gases (GHGs) from biogas appeared that $CO_2$, $CH_4$, $N_2O$ were $90,000tonCO_2$ (5.5%), $55,000tonCH_4$ (94.5%), $0.3tonN_2O$ (0.004%), respectively. In addition, biomass was $250,000tonCO_2$ (107%), $-300tonCH_4$ (-3.2%), $-33tonN_2O$ (-3.9%). For understanding the values of estimation method levels, field data (this study) appeared to be approximately 85.47% compared to installed capacity. In details, biogas and biomass resulting from field data showed to be 76%, 74% compared to installed capacity, respectively. In the comparison of this study and CDM project with GHG reduction unit per year installed capacity, this study showed as 42% level versus CDM project. Scenario analysis of GHG reductions potential from bioenergy was analyzed that generation efficiency, availability and cumulative distribution were significantly effective on reducing GHG.

• Journal of the Korean Data and Information Science Society
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• v.28 no.1
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• pp.207-215
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• 2017

In this paper we study pooling effects in Bayesian testing procedures of independence for contingency tables from small areas. In small area estimation setup, we typically use a hierarchical Bayesian model for borrowing strength across small areas. This techniques of borrowing strength in small area estimation is used to construct a Bayes test of independence for contingency tables from small areas. In specific, we consider the methods of direct or indirect pooling in multinomial models through Dirichlet priors. We use the Bayes factor (or equivalently the ratio of the marginal likelihoods) to construct the Bayes test, and the marginal density is obtained by integrating the joint density function over all parameters. The Bayes test is computed by performing a Monte Carlo integration based on the method proposed by Nandram and Kim (2002).

• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.41-46
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• 2006

When new weapons are introduced, the target points estimation is one of the important objectives in the flight test as well as the safe separation. The prediction methods help to design the flight test schedule. However, the incremental aerodynamic coefficients in the aircraft flow field so-called BSE are difficult to predict. Generally, the semiempirical methods such as the grid methods, IFM and Flow TGP using database are used for estimation of BSE. However, these methods are quasi-steady methods using static aerodynamic loads. Nowadays the time-accurate CFD method is often used to predict the store separation event. In the current process, the incremental aerodynamic coefficients in BSE regime are calculated directly, and the elimination of delta coefficients is checked simultaneously. This stage can be used for the initial condition of Flow TGP with freestream database. Two dimensional supersonic and subsonic store separation problems have been simulated and incremental coefficients are calculated. The results show the time when the store gets out of BSE region.

• Proceedings of the KSR Conference
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• 2000.11a
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• pp.680-687
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• 2000

In this paper we present a new vector control scheme for induction motor. An exact knowledge of the rotor flux position is essential for a high-performance vector control. The position of the rotor flux is measured in the direct scheme or estimated in the indirect schemes. Since the estimation of the flux position requires a priori knowledge of the induction motor parameters, the indirect schemes are machine parameter dependent. The rotor resistance and stator resistance among the parameters change with temperature. Variations in the parameters of induction machine cause deterioration of both the steady state and dynamic operation of the induction motor drive. Several methods have been presented to minimize the consequences of parameter sensitivity in indirect scheme. In this paper new estimation scheme of rotor flux position is presented to eliminate sensitivity due to resistance change with temperature. Simulation results are used to verify the performance of the proposed vector control scheme.

• Journal of Aerospace System Engineering
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• v.10 no.1
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• pp.8-14
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• 2016

The optimal estimation of a bearing only target tracking problem be achieved through the solution of the Fokker-Planck equation and the Bayesian update. Recently, a nonlinear filtering algorithm using a direct quadrature method of moments in which the associated Fokker-Planck equation can be propagated efficiently and accurately was proposed. Although this approach has demonstrated its promising in the field of nonlinear filtering in several examples, the "degeneracy" phenomenon, similar to that which exists in a typical particle filter, occasionally appears because only the weights are updated in the modified Bayesian rule in this algorithm. Therefore, in this paper to enhance the performance, a more stable measurement update process based upon the update equation in the Extended Kalman filters and a more accurate initialization and re-sampling strategy for weight and abscissas are proposed. Simulations are used to show the effectiveness of the proposed filter and the obtained results are promising.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.9 s.186
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• pp.76-83
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• 2006

Machining accuracy is closely related with tool deflection induced by cutting forces. In this research, cutting forces and tool deflection in end milling are expressed as a closed form of tool rotational angle and cutting conditions. The discrete cutting fores caused by periodic tool entry and exit are represented as a continuous function using the Fourier series expansion. Tool deflection is predicted by direct integration of the distributed loads on cutting edges. Cutting conditions, tool geometry, run-outs and the stiffness of tool clamping part are considered together far cutting forces and tool deflection estimation. Compared with numerical methods, the presented method has advantages in prediction time reduction and the effects of feeding and run-outs on cutting forces and tool deflection can be analyzed quantitatively. This research can be effectively used in real time machining error estimation and cutting condition selection for error minimization since the form accuracy is easily predicted from tool deflection curve.

• Journal of Communications and Networks
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• v.18 no.1
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• pp.8-18
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• 2016

In this paper, we propose a number of blind equalization approaches for time-varying andmulti-path channels. The approaches employ cost reference particle filter (CRPF) as the symbol estimator, and additionally employ either least mean squares algorithm, recursive least squares algorithm, or $H{\infty}$ filter (HF) as a channel estimator such that they are jointly employed for the strategy of "Rao-Blackwellization," or equally called "mixture filtering." The novel feature of the proposed approaches is that the blind equalization is performed based on direct channel estimation with unknown noise statistics of the received signals and channel state system while the channel is not directly estimated in the conventional method, and the noise information if known in similar Kalman mixture filtering approach. Simulation results show that the proposed approaches estimate the transmitted symbols and time-varying channel very effectively, and outperform the previously proposed approach which requires the noise information in its application.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.781-785
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• 2005

Cutting forces and tool deflection in end milling are represented as the closed form of tool rotational angle and cutting conditions. The discrete cutting forces caused by tool entry and exit are continued using the Fourier series expansion. Tool deflection is predicted by direct integration of the distributed loads on cutting edges. Cutting conditions, tool geometry, run-outs and the stiffness of tool clamping pan are considered for cutting forces and tool deflection estimation. Compared to numerical methods, the presented method has advantages in short prediction time and the effects of feeding and run-outs on cutting forces and tool deflection can be analyzed quantitatively. This research can be effectively used in real time machining error estimation and cutting condition selection for error minimization since the ferm accuracy is easily predicted by tool deflect ion curve.

• Communications for Statistical Applications and Methods
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• v.26 no.2
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• pp.175-189
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• 2019

The problem of the estimation of quantitative sensitive variable using the item sum technique (IST) on successive occasions has been discussed. IST difference, IST regression, and IST general class of estimators have been proposed to estimate quantitative sensitive variable at the current occasion in two occasion successive sampling. The proposed new estimators have been elaborated under Trappmann et al. (Journal of Survey Statistics and Methodology, 2, 58-77, 2014) as well as Perri et al. (Biometrical Journal, 60, 155-173, 2018) allocation designs to allocate long list and short list samples of IST. The properties of all proposed estimators have been derived including optimum replacement policy. The proposed estimators have been mutually compared under the above mentioned allocation designs. The comparison has also been conducted with a direct method. Numerical applications through empirical as well as simplistic simulation has been used to show how the illustrated IST on successive occasions may venture in practical situations.