• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.8-13
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• 1995

High strength ready-miced concrete with delivering time of about 90 minutes is successfully produced at ready-mixed concrete plant and placed columns and retaining walls of a tall building without any problems. The design strength of the concrete is 450 kgf/$\textrm{cm}^2$ and the required average compressive strength is 540 kgf/$\textrm{cm}^2$ according to ACI 363R-84 report with assumed coefficient of variation of 12% For the producing of good quality concrete, many laboratary and field tests are carried out. As the results of this study, the slump loss of high strength concrete is largely influenced by kinds of superplasticizer. The measured pump pressure of high strength concrete with slump of 22cm is higher than that of normal strength concrete with slump of 18cm by about 20~30% The measured average 28-day compressive strength of the concrete is 551 kgf/$\textrm{cm}^2$ and the coefficient of variation is 2.3%

• The Journal of the Korea Contents Association
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• v.5 no.2
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• pp.221-228
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• 2005

The paper proposes the improved error diffusion halftoning system to enhance the edges using the spatial perceptual characteristics of the human visual system. The proposed method computes a spatial variation(SV), which is the difference between a pixel luminance and the average of its $3{\times}3$ neighborhood pixels' luminances weighted according to the spatial positioning. Information of edge enhancement(IEE) Is computed using the SV and the local average luminance. The IEE is added to the quantizer's input pixel and feeds into the halftoning quantizer. The quantizer produces the halftone image having the enhanced edge. The performance of the proposed method is compared with conventional methods by measuring the edge correlation. The halftone images by using the proposed method show better quality due to the enhanced edge. And the detailed edge is preserved in the halftone images by using the proposed method.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.376-381
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• 1996

In this study, the quality contral of high strength reacy-mixed concrete with design compressive strength of 420 kgf/$\textrm{cm}^2$ placed at a tail building for a long period is statistically investigated. The amount of cast-in-place high strength concrete is by about $15000\textrm{m}^3$. The required average compressive striength is 500 kgf/$\textrm{cm}^2$ according to KS F 4009 with assumed coefficient of variation of 11%. Since there are many concrete members in this construction, fly ash is used to reduce the heat of hydration of concrete. As the results of this study, the average actual 28-day compressive strength is 498 kgf/$\textrm{cm}^2$ and the coefficient of variation is 6.7%. The placing speed is comparable to normal strength concrete, however, the pump pressure is higher than that of normal strength concrete.

• Journal of information and communication convergence engineering
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• v.14 no.4
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• pp.258-267
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• 2016

Three-dimensional integrated circuits (3D ICs) experience die-to-die variations in addition to the already challenging within-die variations. This adds an additional design complexity and makes variation estimation and full-chip optimization even more challenging. In this paper, we show that the industry standard on-chip variation (AOCV) tables cannot be applied directly to 3D paths that are spanning multiple dies. We develop a new machine learning-based model and methodology for an accurate variation estimation of logic paths in 3D designs. Our model makes use of key parameters extracted from existing GDSII 3D IC design and sign-off simulation database. Thus, it requires no runtime overhead when compared to AOCV analysis while achieving an average accuracy of 90% in variation evaluation. By using our model in a full-chip variation-aware 3D IC physical design flow, we obtain up to 16% improvement in critical path delay under variations, which is verified with detailed Monte Carlo simulations.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.29 no.2
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• pp.97-103
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• 2006

Recently, the control chart is developed for monitoring processes with normal short production runs by the coefficient of variation(CV) characteristic for a normal distribution. This control chart does not work well in non-normal short production runs. And most of industrial processes are known to follow the non-normal distribution. Therefore, the control chart is required to be developed for monitoring the processes with non-normal short production runs by the CV characteristics for a non-normal distribution. In this paper, we suggest the control chart for monitoring the processes with a gamma short runs by the CV characteristics for a gamma distribution. This control chart is denoted by the gamma CV control chart. Futhermore evaluated the performance of the gamma CV control chart by average run length(ARL).

• Journal of Environmental Health Sciences
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• v.29 no.1
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• pp.67-73
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• 2003

This study was carried out to characterize the behavior and sources of particulate trace metal in Daegu city. TSP (Total Suspended Particulate matter) was collected by filters on High Volume Air Sampler from the four areal (reference, residential, commercial, industrial area). The moult were analyzed by AAS after preliminary treatment. The average centration trend of trace metals contained in TSP was shown as follows : Fe > Cu > Pb > Mn > Ni > Cr > Cd. The trace metals showed the highest concentration in the industrial area. This study showed the seasonal variation of trace metals. Fe and Mn showed high concentration in spring, whereas Cr, Ni, Cd and Pb showed high concentration in winter. Also this study showed the regional variation of trace metals. The order of the average concentration of trace metals was : industrial > commercial > residential > reference area. Using Mn as a reference element, the enrichment factor analysis were used for identifying the trace element contributors. The enrichment factors of Cr, Fe < 10 were considered to have a significant dust and soil source and termed nonenriched. Pb, Cd, Cu >>10 were enriched and had a significant fraction which was contributed by anthropogenic sources.

• Korean Journal of Pharmacognosy
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• v.17 no.2
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• pp.123-128
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• 1986

The determination of berberine in Berberis koreana was examined by the high performance liquid chromatography using ${\mu}-Bondapak$ $C_{18}$ column and $CH_3CN/phosphate$ buffer (pH 5.2) (60/40) as a mobile phase. The seasonal variations of berberine contents in Berberis koreana were as follows; 1) In roots, the average berberine content was 0.94% with the highest level of 1.32% in October. 2) In stems, their average berberine content was about 0.1% and in March, April, October and November, the contents were relatively high. 3) In leaves, however, the content was as low as 0.005%. According to the experimental results obtained, we found that Berberis koreana roots can serve as the useful natural plant resources for the berberine and October is the optimal season for the collection.

• Journal of the Korean Ceramic Society
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• v.56 no.1
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• pp.84-90
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• 2019

The varistor properties and stability against dc-accelerated stress of $V_2O_5-Mn_3O_4-Co_3O_4-Dy_2O_3-Nb_2O_5-Bi_2O_3$ (VMCDNB)-doped zinc oxide ceramics sintered at $850-925^{\circ}C$ were investigated. Increasing the sintering temperature increased the average grain size from 4.6 to 8.7 mm and decreased the density of the sintered pellet density from 5.54 to $5.42g/cm^3$. The breakdown field decreased from 5919 to 1465 V/cm because of the increase in the average grain size. Zinc oxide ceramics sintered at $875^{\circ}C$ showed the highest nonlinear coefficient (43.6) and the highest potential barrier height (0.96 eV). Zinc oxide ceramics sintered at $850^{\circ}C$ showed the highest stability: the variation rate of the breakdown field was -2.0% and the variation rate of the nonlinear coefficient was -23.3%, after application of the specified stress (applied voltage/temperature/time).

• Health Policy and Management
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• v.11 no.3
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• pp.121-150
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• 2001

This study was conducted to investigate provider's behavior change after releasing the information on the Cesarean section rate. Claims data filed at the National Health Insurance Corporation was used for this analysis and the focus of this study was the change of cesarean rate after the public disclosure of information. Average rates of the year 1999 and 2000 were compared, on the institutional basis, and range and coefficient of variation were estimated. For the last decade, Cesarean section rate has been increased dramatically. Clinical or demographic factors could not adequately explain the increase. Instead, nonclinical factors, such as financial incentive, physician's convenience, practice characteristics, etc., were more significant in explaining the increasing rate. Providers' behavior was significantly affected by the public release of information: after the release, average rate was decreased by 10.2%, and variations were also decreased. In particular, the extent of decrease was explained mainly by nonclinical factor rather than clinical ones. The results suggest that disseminating practice information to providers and consumers could contribute to reducing unnecessary medical service.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.380-385
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• 1998

This paper proposes a current control algorithm to reduce the torque ripple to commutation in unipolar PWM inverter-fed trapezoidal brushless dc motor drives. In this paper, we analyze the average voltage variation of the conducting phase due to commutation, and design a current controller to compensate for the average voltage variation. The proposed method predicts the duration of commutation to reduce the torque ripple due to over-compensation. Experimental results are presented that validate the proposed method.