• Journal of the korean Society of Automotive Engineers
• /
• v.13 no.2
• /
• pp.103-111
• /
• 1991

To determine the effects of microstructure on the fatigue crack propagation behavior in SM45C steel, experimental investigations have been carried out with the specimens of different grain sizes and different spacings between the Fe$_{3}$C particles. Fatigue and tensile tests were conducted and the quantitative analysis of the relations between the threshold stress intensity range and grain size, interparticle spacing and yield stress were carried out. Some of the conclusions obtained are as follows; (1) .DELTA.K$_{th}$ was observed to increase with grain size and the spacing between the Fe3C particles. (2) In both pearlite and spheroidite microstructures, .DELTA.K$_{th}$ was increased when yield stress was decreased.sed.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2003.07a
• /
• pp.656-660
• /
• 2003

We studied the crystallization behavior of LP-CVD a-Si film using UV pulsed laser. With increase in the shot number of irradiation by fixing its energy density, poly-Si film having a large grain size of $0.5 {\mu}m$ was obtained. By analyzing the crystallized Si films using optical analysis such as Raman spectroscopy or AFM technique etc., conspicuous correlation between the grain size and the resultant film properties such as the stress or the roughness has been found. With the increase in the energy density or the shots number of laser, remarkable grain growth occurred following to the roughness formation corresponding to the increase in the tensile stress.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1999.03b
• /
• pp.249-252
• /
• 1999

A numerical analysis was perfomed to predict flow curves and dynamic recrystallization behaviors of Al-5%Mg alloy on the basis of results of hot compression tests. The hot compression tests were carried out in the ranges of 350-50$0^{\circ}C$ and 5$\times${{{{ {10 }^{-3 } }}}}~3$\times${{{{ {10 }^{0 } }}}}/sec to obtain the Zener-Hollmon parameter. In the modelling equation the effects os strain hardening and dynamic recrystallization were taken into consideration. A model for predicting the evolution of microstructure in Al-5%Mg alloy during thermomechanical processing was developed in terms of dynamic recrystallization phenomena, The microstructure model was combined with finite element modeling(FEM) to predict microstructure development Model predictions showed good agreement with microstructures obtained in compression tests.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.25 no.5
• /
• pp.301-310
• /
• 2013

For analyzing sand grain size, a specialized high-priced instrument has been used, such as sieve shaker, video camera, laser particle size analyzer, and microscope. Among these, the sieve shaker is commonly used because it is not only cheaper than others but also provides reasonable accuracy. However, it takes a long time and makes lots of dust and noise. In this study, a cheaper and easier method which can replace the sieve shaker is proposed. By using a commercial flat-bed scanner and a darkroom box, the sand size distribution can be analyzed. The darkroom box makes sand images clear and protects the glass of the scanner from being scratched. Comparison between the present method and sieve analysis shows that the present method not only has an accuracy comparable to the sieve analysis but also can save time and effort.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.23 no.4
• /
• pp.304-312
• /
• 2011

Grain size analysis was conducted for a total of 402 surface sediments collected from 67 sites along three (upper, middle, and lower) transects corresponding to the high-, mid-, and low-intertidal zone of beach on the Sinjado, Nakdong River estuary in Nov. 2005 and May 2006. Sinja-do beach sediments showed uni-modal grain size distributions, in which the mode of $3.0{\phi}$ was dominant in 2005 whereas the mode of $2.5{\phi}$ in 2006. This coarsening trend was more remarkable in the western side of beach as well as in the mid- and low-intertidal zone. In this study, we focused on investigating characteristics of sediment size changes on the basis of transect data that differ in tidal elevation. For this purpose, a statistical test was applied for transect by transect comparison of grain size parameters such as mean, sorting, and skewness. Mean values between middle and lower transect, sorting values between upper and lower transect, and skewness values over the beach reflected statistically significant temporal changes. Also, mean and skewness parameters showed an inverse relationship which was more stronger in 2006 than in 2005. Temporal changes in Sinja-do beach sediments resulted in decrease of mean and sorting values but increase of skewness values, intensifying the inverse relationship between mean and skewness parameters.

• Journal of The Geomorphological Association of Korea
• /
• v.24 no.4
• /
• pp.27-41
• /
• 2017

In this study, geomorphological and geological research has been carried out to estimate the possibility of ancient port location near Hwaseong Dangseong. Geomorphological characteristics around Eunsupo were analyzed through comparison of past and present topographic maps and field survey. Grain size, age dating, and geochemical analysis on surface sediments and borehole sediments were performed. Through the geomorphological characteristics analysis, it was interpreted that Eunsupo area was submerged in seawater especially at high tide in the past, and that ships could approach to the inside of the area through the tidal channel which were developed in the area. It is also assumed that ships were anchored at a low elevation point in the area. The paleo-environmental change in the area was analyzed based on the classification of sedimentary environment using grain size distribution of surface and borehole sediments and geochemical analysis. It was confirmed that the geomorphological interpretation for the possibility of ancient port location coincided well with the paleo-environmental change interpreted through sediment analysis. This study is a basic study for estimating ancient port location, and it is expected that more accurate paleo-environmental changes will be restored through detailed geomorphological survey and additional borehole analysis in the future research.

• Korean Journal of Agricultural Science
• /
• v.38 no.2
• /
• pp.393-404
• /
• 2011

The international grain price shows dramatic change, which results in the price change of Korean processed food. Recently, Korean government and consumers started discussing about the effects of change of international grain price on the processed food. However, few studies have analyzed this effects. The goal of this paper is to analyze the effects of price change of international grain, especially wheat, soybean, and sugarcane, on the processed food price in Korea. As the results of analysis, three findings are presented: First, the size and timelag of the effects of change of international grain price on the processed food price is different due to products, Second, there is the possibility that processed food price in Korea will increase, Third, Korean government has some methods to manage the price change of processed food, even though government cannot totally control the price.

• Korean Journal of Materials Research
• /
• v.29 no.4
• /
• pp.264-270
• /
• 2019

As a case study on aspect ratio behavior, Kaolin, zeolite, $TiO_2$, pozzolan and diatomaceous earth minerals are investigated using wet milling with 0.3 pai media. The grinding process using small media of 0.3 pai is suitable for current work processing applications. Primary particles with average particle size distribution D50, ${\sim}6{\mu}m$ are shifted to submicron size, D50 ${\sim}0.6{\mu}m$, after grinding. Grinding of particles is characterized by various size parameters such as sphericity as geometric shape, equivalent diameter, and average particle size distribution. Herein, we systematically provide an overview of factors affecting the primary particle size reduction. Energy consumption for grinding is determined using classical grinding laws, including Rittinger's and Kick's laws. Submicron size is obtained at maximum frictional shear stress. Alterations in properties of wettability, heat resistance, thermal conductivity, and adhesion increase with increasing particle surface area. In the comparison of the aspect ratio of the submicron powder, the air heat conductivity and the total heat release amount increase 68 % and 2 times, respectively.

• The Journal of Advanced Prosthodontics
• /
• v.8 no.3
• /
• pp.181-186
• /
• 2016

PURPOSE. The opacity of zirconia is an esthetic disadvantage that hinders achieving natural and shade-matched restorations. The aim of this study was to evaluate the translucency of non-colored and colored framework zirconia and monolithic zirconia. MATERIALS AND METHODS. The three groups tested were: non-colored framework zirconia, colored framework zirconia with the A3 shade according to Vita Classic Scale, and monolithic zirconia (n=5). The specimens were fabricated in the dimensions of $15{\times}12{\times}0.5mm$. A spectrophotometer was used to measure the contrast ratio, which is indicative of translucency. Three measurements were made to obtain the contrast ratios of the materials over a white background ($L^*w$) and a black background ($L^*b$). The data were analyzed using the one-way analysis of variance and Tukey HSD tests. One specimen from each group was chosen for scanning electron microscope analysis. The determined areas of the SEM images were divided by the number of grains in order to calculate the mean grain size. RESULTS. Statistically significant differences were observed among all groups (P<.05). Non-colored zirconia had the highest translucency with a contrast ratio of 0.75, while monolithic zirconia had the lowest translucency with a contrast ratio of 0.8. The mean grain sizes of the non-colored, colored, and monolithic zirconia were 233, 256, and 361 nm, respectively. CONCLUSION. The translucency of the zirconia was affected by the coloring procedure and the grain size. Although monolithic zirconia may not be the best esthetic material for the anterior region, it may serve as an alternative in the posterior region for the bilayered zirconia restorations.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.11a
• /
• pp.207-210
• /
• 2008

We developed an integrated design system for a solid rocket motors. We can do a conceptual design of a solid rocket motor easily and quickly with this system. It consists of four modules, or, size design, structure design, grain design and performance analysis module. Size design module determines the lengths and diameters of some major parts, which results in fixing the whole size of a motor. Structure design module has many master models, which enables a designer can do a conceptual design of almost parts of motor structures. Grain design module can design a solid fuel according to the result of structure design. Finally performance analysis module verifies the proposed design with the output from grain design module.