• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.9-14
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• 2001

A new model utilizing a transfer function is introduced in the present paper for analizing motion errors of hydrostatic tables. Relationship between film reaction force in a single hydrostatic pad and form error of a guide rail is derived at various spacial frequencies by finite element analysis, and it is expressed as a transfer function. This transfer function clarifies so called averaging effect of the oil film quantitively. For example, it is found that the amplitide of the film reaction force is reduced as the spacial frequency increases or relative width of the pocket is reduced. Motion errors of a multiple pad table is estimated from transfer function, geometric relationship between each pads and form errors of a guide rail, which is named as Transfer Function Method. Calculated motion errors by TFM show good agreement with motion errors calculated by Multi Pad Method, which is considered entire table as an analysis object. From the results, it is confirmed that the proposed TFM is very effective to analyze the motion errors of hydrostatic tables.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.40-46
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• 2003

Synchronizing errors between the spindle motor and the z-axis motor directly influences the cutting characteristics and the thread quality in tapping, because the tapping process is accomplished by synchronizing the movement of the z-axis with the revolutionary spindle motion. Generally synchronizing errors are decided by tile parameters of the servo system and commanded velocity. The excessive synchronizing errors which are induced by the parameter mismatch and high cutting velocity can cause tap breakage due to the abrupt increase of cutting torque or damage the thread accuracy by overcutting the already cut threads. In this paper, the influences of the synchronizing errors on the tapping characteristics in the ultra high-speed tapping will be described and a minimum level of synchronizing errors necessary to maintain the quality of the cut thread will be presented.

• Proceedings of the KSPS conference
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• 2007.05a
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• pp.99-101
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• 2007

This study analyzes Korean middle school students' pronunciation errors of stop-liquid sequences in English. The results showed two typical errors: the insertion of a vowel between a stop and a liquid and the substitution of a liquid with a flap or vice versa. Those pronunciation errors seem to occur since English and Korean have different syllable structures and different types of liquids. A teaching material, which emphasizes no vowel insertion for a proper pronunciation of the consonant clusters, was designed to reduce Korean students' pronunciation errors. Errors were reduced substantially after a 50-minute class with the newly designed material.

• English Language & Literature Teaching
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• v.12 no.2
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• pp.19-40
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• 2006

This paper deals with a part-specific analysis of grammatical errors in the production of the English passive in writing. The purpose of the study is dual: to explore common error types in forming the passive; and to provide plausible sources of the errors, with special attention to the role of the native language. To this end, this study obtained a large amount of data from Korean EFL university students using an essay writing task. The results show that in forming the passive sentence, errors were made in various ways and that the most common problem was the formation of the be-auxiliary, in particular, the proper use of tense and S-V agreement. Another important finding was that the global errors found in this study were not necessarily those with the greatest frequency. Also corroborated was the general claim that many factors work together to account for errors. In many cases, interlingual and intralingual factors were shown to interact with each other to explain the passive errors made by Korean students. On the basis of the results, suggestions are made for effective and well-formed use of the passive sentence.

• Journal of Korean Society for Quality Management
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• v.25 no.1
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• pp.69-79
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• 1997

We consider the semiparametric linear errors-in-variables model: yi=(${\alpha}+{\beta}ui+{\varepsilon}i$, xi=ui＋${\varepsilon}i$ i=1, …, n where (xi, yi) stands for an observation vector, (ui) denotes a set of incidental nuisance parameters, (${\alpha}$ , ${\beta}$) is a vector of regression parameters and (${\varepsilon}i$, ${\delta}i$) are mutually uncorrelated measurement errors with zero mean and finite variances but otherwise unknown distributions. On the basis of a simple small-sample low-noise a, pp.oximation, we propose a new method of comparing the mean squared errors(MSE) of the various competing estimators of the true regression parameters ((${\alpha}$ , ${\beta}$). Then we show that a class of estimators including the classical least squares estimator and the maximum likelihood estimator are consistent and first-order efficient within the class of all regular consistent estimators irrespective of type of measurement errors.

• Knowledge Management Research
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• v.13 no.2
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• pp.37-52
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• 2012

A spreadsheet is a office automation software which has been widely used in almost all areas in business. A spreadsheet is used for calculation, data analysis, model building and so on. As a result, spreadsheet is a very important tool for generating knowlege in a firm. Errors in a spreadsheet model can cause a serious financial damage in a corporation. However in Korea few researches for reducing errors have been performed. Neither serious efforts to reduce errors have been executed by corporations. In this research we provided summarized the results from a survey for spreadsheet usage, summarized researches on errors in spreadsheet up to now, and suggested a rules and structured development method for reducing errors in a spreadsheet. Errors in spreadsheets are prevalent. To solve this serious problem, we need much more attention on this problem in research area. Corporations must put more efforts on setting policies and rules. And also we need the government's concern and support.

• 한국항공운항학회:학술대회논문집
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• 2006.11a
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• pp.61-65
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• 2006

The flight deck crew are under the operational time pressure in the cockpit. The crew tend to make errors when they face the threats of operational time pressure because they are in a rush. The flight deck crew can reduce threats and errors which existing within the airlines by using threat and error management when the crew know these threats and errors. The airlines can implement meaningful safety management system by analyzing into the useful information for to identify the hazard and manage the risk to reduce these threats and errors since aircrafts accidents can be fatal.With the threats and errors that were found regard to operational time pressures, company may implements safety change process to improve the safety systematically and the crew can manage the threats and errors more effectively.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.37 no.3
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• pp.141-145
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• 1988

This paper reports a new and simple posteriori error estimate method for adaptive finite element mesh genration especially for the magnetic field problems. To estimate local errors, we consider the interelement boundary conditions. Elements which violate much the conditions are considered to have great errors. Magnetic flux density errors are considered as a basis for refinement. This estimator is tested on two dimensional proplems with singular points. The estimated errors are always under estimated but in same order as exact errors, and this algorithm is much simpler and more convenient than other methods. The adaptive mesh gives much better rate of convergence in global errors than the uniform mesh.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.17-18
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• 2006

In this paper, we propose a robust detection scheme of OSTBCs with channel estimation errors over time-selective fading channels. Channel estimation errors are inevitable over time-selective fading channels and even small channel estimation errors dramatically degrade the performance of space-time block coding schemes. Therefore, it is desired to investigate the effect of channel estimation errors on the performance of the proposed detection scheme compared with the existing detection scheme. The proposed detection scheme minimizes noise enhancement and impact of channel estimation errors which occur in an existing detection scheme. It is shown by simulations that the proposed detection scheme performs better than the existing detection scheme over time-selective fading channels.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.417-422
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• 2002

One of the major limitations of productivity and quality in metal cutting is the machining accuracy of machine tools. The machining accuracy is affected by geometric errors, thermally-induced errors, and the deterioration of the machine tools. Geometric and thermal errors of machine tools should be measured and compensated to manufacture high quality products. In metal cutting, the machining accuracy is more affected by thermal errors than by geometric errors. In this study, the compensation device and temperature-based algorithm have been implemented on the machining center in order to compensate thermal error of machine tools under the real-time. The thermal errors are predicted using the neural network and multi-regression modeling methods. In order to compensate thermal characteristics under several operating conditions, experiments performed with five gap sensors and manufactured compensation device on the horizontal machining center.