• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1162-1165
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• 2003

Contouring errors are important especially for high speed and precision machining. Since the contouring errors of a machine tool affect the error of a machined part directly, it is necessary to find the contouring errors by some relevant tests. In this study, contouring errors are obtained by performing circular tests with a grid plate. Various error sources are diagnosed by a least square method.

• Proceedings of the Korean Statistical Society Conference
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• 2005.05a
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• pp.95-100
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• 2005

In this paper a class of multifactor designs for estimating the slope of second order response surface regression models with correlated errors is considered. General conditions for second order slope rotatability over all directions and also with respect to the maximum directional variance in case of k=2 have been derived assuming errors have a general correlated error structure. And we consider the measures for evaluating slope rotatability with correlated errors similar to in case of uncorrelated error structures.

• Design & Manufacturing
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• v.17 no.4
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• pp.24-32
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• 2023

In this study, we introduce research aimed at minimizing machining errors without compromising productivity by compensating for the machining errors caused by tool deformation. Our approach experimentally establishes the direct correlation between cutting depth and machining error, and creates predictive models using mathematical functions. This method allows for the prediction of compensated cutting depths to obtain the desired cutting profiles, thereby maximizing the compensation of machining errors in the cutting process.

• Proceedings of the KSPS conference
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• 1996.10a
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• pp.275-276
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• 1996

Koreans learning Mandarin Chinese are faced with serious pronunciation errors in vowels, consonants and tones, etc. Most of these pronunciation errors are found to be due the transference of the native Korean phonetic habits. Following are some of the most common pronunciation errors encountered by Koreans learning Chinese.

• East Asian mathematical journal
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• v.31 no.3
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• pp.379-382
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• 2015

The purpose of this note is to study the estimation of errors of the implicit Mann iterative process with random errors.

• Journal of Power Electronics
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• v.14 no.1
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• pp.82-91
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• 2014

This paper proposes a compensation algorithm for the analog rotor position errors caused by nonideal sinusoidal encoder output signals including offset and gain errors. In order to achieve a much higher resolution, position sensors such as resolvers or incremental encoders can be replaced by sinusoidal encoders. In practice, however, the periodic ripples related to the analog rotor position are generated by the offset and gain errors between the sine and cosine output signals of sinusoidal encoders. In this paper, the effects of offset and gain errors are easily analyzed by applying the concept of a rotating coordinate system based on the dq transformation method. The synchronous d-axis signal component is used directly to detect the amplitude of the offset and gain errors for the proposed compensator. As a result, the offset and gain errors can be well corrected by three integrators located on the synchronous d-axis component. In addition, the proposed algorithm does not require any additional hardware and can be easily implemented by a simple integral operation. The effectiveness of the proposed algorithm is verified through several experimental results.

• English Language & Literature Teaching
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• v.13 no.1
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• pp.47-66
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• 2007

Error analysis plays an important role because understanding the types of errors can give a better opportunity for both teachers and learners to recognize the nature of errors and ways of preventing them. This study looks into errors in the medical research abstracts written by 26 Koreans and also examines hedging expressions since hedging can be a necessary tactic in which the validity and objectivity of their claims is conveyed. The hedging expressions of these research abstracts are to be compared with those of Hyland (1996)'s study done on ENL academic writers of cell and molecular biology. The results of the study reveal that wrong word choice was the most commonly occurred errors, followed by prepositions, articles, adding and missing words. Many of these errors, except articles, seemed to derive from the native language interference. There were also run-on sentences, subject & verb agreement, tense, word order and minor errors. As for hedging, ESL medical writers seemed to use very limited hedging expressions and inappropriately strong modals. It is recommended to take variations of hedges using epistemic adverbials and adjectives to present their claims in a more valid and polite way. Limited verb choice was also noted. As for preventing or minimizing similar future errors, collocation practices in ESP focused on commonly used medical related words and expressions can be effective.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.5
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• pp.139-148
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• 2002

Motion errors of linear motion guideway are analyzed theoretically in this paper. For the analysis, an new algorithm predicting motion errors of bearing and guideway is proposed using the Hertz's elastic deformation theory. Accuracy averaging effect can be calculated quantitatively by analyzing relationship between motion errors of guideway and spatial frequency of rail form error. Influences of design parameters on the motion errors including the number of balls, preload, ball diameter, bearing length and the number of bearings are analyzed. As it is difficult to measure the rail form error, experimental results are compared with results analyzed by the equivalent analysis method which evaluate the motion errors of guideway using the measured errors of bearing. From the experimental results, it is confirmed that the proposed analysis method it effective lo analyze the motion errors of linear motion bearing and guideway.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.5
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• pp.1-6
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• 2011

Machine tool errors have to be characterized and predicted to improve machine tool accuracy. Therefore, it is very important to assess errors in machine tools. Volumetric error analysis has been developed by many researchers. This paper presents a useful technique for analyzing the volumetric errors in machine tools using the ball bar. The volumetric error model is proposed in specific vertical machining center and the program is developed for generating NC code, acquiring the ball bar data, and analyzing the volumetric errors. The developed system assesses the volumetric errors such as positional, straightness, squareness, and back lash. Also this system analyzes the dynamic performance such as servo gain mismatch. The radial data acquired by ball bar on 3D space is used for analyzing these errors. It is convenient to test the volumetric errors on 3D space because all errors are calculated at once. The developed system has been tested using an actual vertical machining center.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.9
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• pp.702-708
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• 2002

The spectrum of impulse response signal from an impulse hammer testing is widely used to obtain frequency response function(FRF). However the FRFs obtained from impact hammer testing have not only leakage errors but also finite record length errors when the record length for the signal processing is not sufficiently long. The errors cannot be removed with the conventional signal analyzer which treats the signals as if they are always steady and periodic. Since the response signals generated by the impact hammer are transient and have damping, they are undoubtedly non-periodic. It is inevitable that the signals be acquired for limited recording time, which causes the errors. This paper makes clear the relation between the errors of FRF and the length of recording time. A new method is suggested to reduce the errors of FRF in this paper. Several numerical examples for 1-dof model are carried out to show the property of the errors and the validity of the proposed method.