• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.1 s.256
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• pp.113-120
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• 2007

Design optimization of layered plates bonding process is conducted by considering uncertainties in a manufacturing process, in order to reduce the crack failure arising due to the residual stress at the surface of the adherent which is caused by different thermal expansion coefficients. Robust optimization is peformed to minimize the mean as well as its variance of the residual stress, while constraining the distortion as well as the instantaneous maximum stress under the allowable reliability limits. In this optimization, the dimension reduction (DR) method is employed to quantify the reliability such as mean and variance of the layered plate bonding. It is expected that the DR method benefits the optimization from the perspectives of efficiency, accuracy, and simplicity. The obtained robust optimal solution is verified by the Monte Carlo simulation.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.646-647
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• 2006

Nano-sized WC particles in WC/Co composite powders were synthesized by mechanochemical method. The raw powders$(WO_3,\;Co_3O_4,\;VC,\;Cr_3C_2$ and graphite) were mixed by planetary milling for 30 hours. The compositions were WC-10 and -20 wt% Co added VC and $Cr_3C_2$. The direct reduction and carburization of the mixed powders were carried at $900\;^{\circ}C$ for 1 to 3 hours under flowing Ar gas. The mean size of WC particles in WC/Co composite powders was about 16 nm. The resultant powders were compacted and sintered at $1300{\sim}1360\;^{\circ}C$ for 0.5 hour. After sintering the mean size of WC particles was about 50 nm.

• Journal of the Korea Society for Simulation
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• v.14 no.3
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• pp.129-136
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• 2005

We develop a variance reduction technique applicable in one simulation experiment whose purpose is to estimate the parameters of a first order linear model. This method utilizes the control variates obtained during the course of simulation run under Schruben and Margolin's method (S-M method). The performance of this method is shown to be similar in estimating the main effects, and to be superior to S-M method in estimating the overall mean response in a given model. We consider that a proposed method may yield a better result than S-M method if selected control variates are highly correlated with the response at each design point.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.3
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• pp.342-350
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• 2014

An active stimulating device, such as a fluttering net or canvas attached to the end of a cod end generating a shaking motion, could help to encourage the escape of juvenile fish positioned passively near the net. Field fishing trials using a shrimp beam trawl were carried out to examine the effect on the reduction of juvenile fish or other discard catch by generating a shaking movement of the cod end using an unbiased cap-like round canvas. The mean period of the shaking motion with the round canvas was ~14 s, and the mean amplitude was 0.4 m as measured by peak event analysis and the global wavelet method. The bycatch of juvenile fish in 14 trials decreased by ~30% and by ~25% using a steady cod end for the total bycatch using a shaking cod end in the shrimp beam trawl, while the marketing catch was similar between steady and shaking cod ends. There was no difference in the body size of the shrimp or fish and species composition between the steady and shaking cod ends. Above results demonstrate a new method for bycatch reduction using an active stimulating device, although more detailed studies are needed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.240-241
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• 2009

The method of the reduction of the duct noise can be classified by the method of passive control and the method of active control. However, the passive control method has a demerit to reduce the effect of noise reduction at low frequency (below 500Hz) range and to be limited by a space. Whereas, the active control method can overcome the demerit of passive control method. The algorithm of active control is mostly used the Least-Mean-Square (LMS) algorithm because the LMS algorithm can easily obtain the complex transfer function in real-time. Especially, When the Filtered-X LMS (FXLMS) algorithm is applied to an ANC system.

• Communications for Statistical Applications and Methods
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• v.13 no.1
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• pp.19-27
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• 2006

Outliers in survey are a perennial problem for applied survey statisticians to estimate the total or mean of population. The influence of outliers is more increasing as they have large weights in survey sampling. Many techniques have been studied to lower the impact of outliers on sample survey estimates. Outliers can be downweighted by winsorization or reducing the weight of outliers. The weight reduction is more reasonable than replacing one outlier by one value of non-outliers, because it has at least one unit. In this paper, we suggest the square root transformation of weight as the weight reduction method. We show this method is efficient with real data, and it's also easy to apply in practical affairs.

• Clinics in Shoulder and Elbow
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• v.24 no.4
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• pp.239-244
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• 2021

Background: Radial neck fracture in children is rare. This study attempted to evaluate the outcome of surgically treated patients and any associated complications. Methods: This study evaluated 23 children under 15 years of age with radial neck fracture who were treated with open reduction between 2006 and 2016 to determine their range of motion, postoperative complications, and radiographic outcomes. The results were assessed clinically using the Mayo clinic elbow performance score. Results: The mean follow-up duration for patients was 34.6 months. The average postoperative angulation was 3.6°. Hypoesthesia was reported in only 9% of patients, and none of the patients complained of postoperative pain. The postoperative X-ray results were excellent in 60% and good in 40%. No radiographic complications were identified. The elbow score was excellent in 87% and good in 13% (mean score, 96.74). There was a statistical relationship between range of motion limitations and age, degree of fracture, initial displacement, and surgical pin removal time. Conclusions: Although most patients accept the closed reduction method as a primary treatment, the present study suggests that an open-reduction approach has been associated with optimal therapeutic outcomes for patients in whom closed reduction was not satisfactory or indicated.

• Journal of the Korean Society of Industry Convergence
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• v.8 no.4
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• pp.221-226
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• 2005

This paper presents a hybrid method for recognizing the faces by using zero mean and principal component analysis. Zero mean is applied to reduce the 1st order statistics to data nonlinearities. PCA is also used to derive an orthonormal basis which directly leads to dimensionality reduction, and possibly to feature extraction of face image. The proposed method has been applied to the problems for recognizing the 20 face images(10 persons * 2 scenes) of 324*243 pixels from Yale face database. The 3 distances such as city-block, Euclidean, negative angle are used as measures when match the probe images to the nearest gallery images. The experimental results show that the proposed method has a superior recognition performances(speed, rate). The negative angle has been relatively achieved more an accurate similarity than city-block or Euclidean.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.57-60
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• 2003

We have proposed the adaptive noise reduction algorithm using the MDFT. The algorithm proposed use the linear prediction coefficients of the AR method based on Sign algorithm that is the modified LMS instead of the least mean square(LMS). The signals with a random noise tracking performance are examined through computer simulations and confirmed that the high speed adaptive noise reduction processing system is realized with rapid convergence.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.17 no.4
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• pp.261-271
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• 2007

To provide necessary information for future environmental monitoring of storage batteries in Korea, authors analyzed environmental monitoring dataset of air lead concentration of 12 storage battery industries measured during 1989-2006. We calculated geometric mean and standard deviation with minimum and maximum value of each year dataset. Air lead concentration data were analyzed according to year of measurement, type of grid manufacturing method (grid casting type or expander type), size of industries and type of operation (casting, lead powder & pasting, assembly and others). The geometric mean and standard deviation of all lead industries for overall 18 years were $72{\mu}g/m^3$ and 3.65 with minimum of $6{\mu}g/m^3$ and maximum of $7,956{\mu}g/m^3$. The geometric mean air lead concentrations of years between 1989-1999 were above the Korean PEL($50{\mu}g/m^3$), whereas those of years after year 2000 were below the Korean PEL showing 50% of it. The geometric mean concentration of air lead was significantly lower in expander method battery industries than that of grid method battery industries and was lower in large sized battery industries than small & medium sized ones throughout the whole 18 years period. The distributions of over PEL($50{\mu}g/m^3$) were decreased by the years of environmental monitoring and those were lower in expander method battery industries than grid method battery industries. The significant reduction of mean air lead concentration during last 10 years may be induced partly due to more active environmental engineering control and new introduction of new operation in grid method battery industries, but may be also influenced by non-engineering method such as reduction of operation hours or reduction of exposure time during actual environmental measurement by industrial hygienist which is not concrete evidence, but just circumstantial evidence.