• Journal of Korean Society of Transportation
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• v.19 no.6
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• pp.131-142
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• 2001

Previous OD matrix estimation methods from link traffic counts have focused on the formulation of mathematical model and its solution algorithm. Thereby those methods have assumed that true or real OD is similar to the target OD and paid little attention to the properties of the change of OD structure. Although it is general situation that each OD pair increases or decreases due to significant land use and to large time variation between target OD with real OD, those methods have set unrealistic assumptions that target OD increases or decreases uniformly and that the OD structure does not change. Therefore those methods have showed poor performance of OD estimation in general situation. To cope with the problem. this paper suggests a new concept of OD matrix structure and shows the shortcomings of previous method′s dependancy on target OD matrix. We divide "OD trips" into "OD scale" and "OD structure". Where OD scale is a quantitative magnitude of OD trips and "OD structure" is ordinal OD scale. This paper use the same solution algorithm developed by Baek et al. (2000) for analysing the OD structure. Results of numerical examples show that the performance of the method is better than that of previous methods, while the previous methods have better performance in estimation only when OD trips increase or decrease. In addition to, if OD structure does not change, the results show that the error of estimation is low relatively regardless of the large difference of trips between target OD and real OD. This paper also shows that the model performance on OD structure and on OD trips is low as the number of origins that OD structure is changed increase. From the results we suggest that the change of OD structure can be more important information than the difference between target OD and real OD in OD estimation steps.

• Journal of Mechanical Science and Technology
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• v.18 no.6
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• pp.961-971
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• 2004

Methods for determination of the crack opening stress intensity factor ($K_{op}$) and for estimation of the effective stress intensity factor range ($\Delta{K}_{eff}$) are evaluated for crack growth test data of aluminum alloys. Three methods of determining $K_{op}$, visual measurement, ASTM offset compliance method, and the neural network method proposed by Kang and Song, and three methods of estimating $\Delta{K}_{eff}$, conventional, the 2/PIO and 2/PI methods proposed by Donald and Paris, are compared in a quantitative manner by using evaluation criteria. For all $K_{op}$ determination methods discussed, the 2/PI method of estimating $\Delta{K}_{eff}$ provides good results. The neural network method of determining $K_{op}$ provides good correlation of crack growth data. It is recommended to use 2/PI estimation with the neural $K_{op}$ determination method. The ASTM offset method used in conjunction with 2/PI estimation shows a possibility of successful application. It is desired to improve the ASTM method.

• Nuclear Engineering and Technology
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• v.52 no.9
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• pp.2119-2129
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• 2020

Flow-accelerated corrosion (FAC), liquid droplet impingement erosion (LDIE), cavitation and flashing can cause continuous wall-thinning in nuclear secondary pipes. In order to prevent pipe rupture events resulting from the wall-thinning, most NPPs (nuclear power plants) implement their management programs, which include periodic thickness inspection using UT (ultrasonic test). Meanwhile, it is well known in field experiences that the thickness measurement errors (or deviations) are often comparable with the amount of thickness reduction. Because of these errors, it is difficult to estimate wall-thinning exactly whether the significant thinning has occurred in the inspected components or not. In the previous study, the authors presented an approximate estimation procedure as the first step for thickness measurement deviations at each inspected component and the statistical & quantitative characteristics of the measurement deviations using plant experience data. In this study, statistical significance was quantified for the current methods used for wall-thinning determination. Also, the authors proposed new estimation procedures for determining local wall-thinning to overcome the weakness of the current methods, in which the proposed procedure is based on analysis of variance (ANOVA) method using subgrouping of measured thinning values at all measurement grids. The new procedures were also quantified for their statistical significance. As the results, it is confirmed that the new methods have better estimation confidence than the methods having used until now.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.493-496
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• 2010

In this paper, We introduces 3 types of methods for estimation of a moving vehicle's CO2 emissions. These estimation methods include method based on distance traveled, method according to the calculation method proposed by the IPCC and method using vehicle information & chemical reaction equations. we describe the operating principle of each estimation method and we have driven down the actual road about 5km path because we compare performance of 3 types of methods for estimation of a driving vehicle's CO2 emissions.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.806-811
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• 1994

Two kinds of static and dynamic state estimation methods are newly discussed for the problem of the measurement disturbance of environmental low-frequency noise in the presence of wind-induced noise. First, the probability characteristics of wind-induced noise are discussed in the form of probability distribution conditioned by wind speed, based on the simultaneous observation of the wind-induced noise and wind speed near a microphone. Next, especially form the viewpoint of simplicity for practical use, two kinds of static and dynamic state estimation methods are discussed. The static estimation method using the information on wind speed is fundamentally supported by the conservation principle of energy sum. The dynamic one is the method by using a recursive digital filter with the parameters successively renewed by the information on wind speed. This can be also simplified by using well-know Kalman filter under the assumption of the Gaussian distribution. The effectiveness of proposed two estimation methods are shown through experiments under a breezy condition in the open filed.

• Korean Management Science Review
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• v.14 no.1
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• pp.131-149
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• 1997

Software cost estimation is an important both for buyers and sellers(developers). We reviewed domestic and foreign researches and practices on software cost estimation with function point method comprehensively, In this paper, we derived four promising alternative function point models. They are an IFPUG(International Function Point User Group)-based model(Model I), a shorthand model for client/sever software systems(Model II), a data-oricnted model for relatively large software projects(Model III), and a general- purpose function point model for non business application softwares as well as business applications(Model IV). Empirical data shows that Model I, II, and IV are very useful function point models. In particular, model II and IV look very useful models since they are concise and accurate. These models can be incorporated in a new improved guideline for software cost estimation. General opinion survey shows that Model I, II and IV are preferable. There are no significant differences in preference between buyers and sellers. The survey also shows that users think function point method is better than step(line of code)-oriented cost estimation methods in many ways including objectivity and estimation accuracy.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.3
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• pp.9-18
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• 2001

In this paper, we present the joint symbol detection and channel estimation for an orthogonal frequency division multiplexing (OFDM) system in fading channels. The proposed methods are based on decision-directed channel estimation (DDCE) method and their symbol detection is achieved by using Viterbi algorithm. This Viterbi decision-directed channel estimation (VDDCE) method tracks time-varying channels and detects a maximum likelihood symbol sequence. Recursive Viterbi decision-directed channel estimation (RVDDCE) method based on VDDCE method is proposed to shorten the detecting depth. In this method, channel estimate and Viterbi processing are recursively performed every interval of training symbol. Also, average chann'el estimation (ACE) technique to reduce the effect of additive white Gaussian noise (AWGN) is applied VDDCE method and RVDDCE method. These proposed methods arc demonstrated by computer simulation.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.10
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• pp.927-932
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• 2010

Estimation methods of motion intention from bio-signal present challenges in man machine interaction(MMI) to offer user's command to machine without control of any devices. Measurements of meaningful bio-signals that contain the motion intention and motion estimation methods from bio-signal are important issues for accurate and safe interaction. This paper proposes a novel motion estimation sensor based on a geometrical muscle changes, and a motion estimation method using the sensor. For estimation of the motion, we measure the circumference change of the muscle which is proportional to muscle activation level using a flexible piezoelectric cable (pMAS, piezo muscle activation sensor), designed in band type. The pMAS measures variations of the cable band that originate from circumference changes of muscle bundles. Moreover, we estimate the elbow motion by applying the sensor to upper limb with least square method. The proposed sensor and prediction method are simple to use so that they can be used to motion prediction device and methods in rehabilitation and sports fields.

• Journal of Soil and Groundwater Environment
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• v.8 no.2
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• pp.70-77
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• 2003

Theoretical estimation of overall stoichiometry for the microbial degradation of hazardous organic compounds is described. Half-reaction method based on microbial energetics was used in the theoretical estimation. In addition to the half-reaction method, other theoretical methods such as intermediate formation, oxygenation reaction, and estimation of the standard free energy of formation by group contribution theory were also applied. As a case study, the application of these methods was demonstrated for the estimation of microbial kinetics in the biodegradation of phenanthrene which was chosen as a model hazardous organic compound along with glucose and hexadecane. The cell yield, oxygen requirement, nitrogen requirement, and mineralization ratio could be estimated from the overall stoichiometry. It is believed that these theoretical estimation methods are useful tools for practical design and assessment of bioremediation of soil and groundwater contaminated with hazardous organic compounds.

• Journal for History of Mathematics
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• v.17 no.1
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• pp.97-108
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• 2004

There are so many methods in population estimation such as logistic estimation and compound interest estimation. If we have some pieces of information about population of one tribe, we can estimate progenitor chronology of that tribe used by inverse estimation. In this paper, we describe several theory of population estimation, and develop mathematical method for estimation progenitor chronology from prior general data and statistical estimation theory. Several examples are illustrated.