• Journal of Korea Foundry Society
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• v.37 no.5
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• pp.148-156
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• 2017

The effects of minor additives on the casting properties of AC4A aluminum alloys were investigated. Measurements of the cooling curve and microstructure observations were conducted to analyze the effects of Ti-B and Sr minor elements during the solidification process. A fine grain size and an increase in the crystallization temperature for the ${\alpha}-Al$ solution were evident after the addition of 0.1wt% Al-5%Ti-1%B additive. The modification effect of the eutectic $Mg_2Si$ phase with the addition of 0.05% Al-10%Sr additive was prominent. A fine eutectic $Mg_2Si$ phase and a decrease in the growth temperature of the eutectic $Mg_2Si$ phase were evident. Fluidity, shrinkage and solidification-cracking tests were conducted to evaluate the castability of the alloy. The combined addition of Al-5%Ti-1%B and Al-10%Sr additives showed the maximum filling length owing to the effect of the fine ${\alpha}-Al$ grains. The macro-shrinkage ratio increased, while the micro-shrinkage ratio decreased with the combined addition of Al-5%Ti-1%B and Al-10%Sr additives. The macro-shrinkage ratio was nearly identical, while the micro-shrinkage ratio increased with the addition of the Al-10%Sr additive. The tendency of the occurrence of solidification cracking decreased owing to the effect of the fine ${\alpha}-Al$ grains and the modification of the $Mg_2Si$ phase with the combined addition of Al-5%Ti-1%B and Al-10%Sr additives.

• Carbon letters
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• v.3 no.4
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• pp.219-225
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• 2002

The two-step surface modifications of activated carbon was carried out to improve the adsorption capacity of toxic heavy metal ions in liquid phase. Physical and chemical properties of the as-received activated carbon (AC) and two kinds of surface-modified activated carbons ($1^{st}AC$ and $2^{nd}AC$) were evaluated through the BET analysis, surface acidity, and oxides measurements. Specific surface area and pore volume did not significantly change, but surface oxide-group remarkably increased by the surface modification. Equilibrium and batch adsorptions of the various metals, such as Pb, Cd, and Cr, using AC, $1^{st}AC$, and $2^{nd}AC$ were performed at initial pH 5. The adsorption capacity and rate of $2^{nd}AC$ were higher than those of AC and $1^{st}AC$. The carboxylic/sodium carboxylate complex groups were developed from the two-step surface modification of activated carbon, which strongly affected the adsorption of metal ions.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.6
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• pp.147-155
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• 1998

Conventional time-scale modification methods have the problem that as the modification rate gets higher the time-scale modified speech signal becomes less intelligible, because they ignore the effect of articulation rate on speech characteristics. In this paper, we propose a variable time-scale modification method based on the knowledge that the timing information of transient portions of a speech signal plays an important role in speech perception. After identifying steady protions only. The result of subjective preference test indicates that the proposed method produces performance superior to that of the conventional SOLA method.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.6
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• pp.453-463
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• 2002

Prognostic meteorological model, MM5V3 (Mesoscale Model 5 Version 3) was used to assess the effects of the land-use modifications on spatial variations of temperature and wind fields in Busan during the selected period of summer season in 2000. We first examined sensitivity analysis for temperature between MM5V3 predictions and meteorological data observed at 4 AWS (Automatic Weather System) stations in Busan, which exhibited low structural and accurate errors (Mean Bias Error, MBE: 0.73, Root Mean Square Error, RMSE: 1.18 on maximum). The second part of this paper, MMSV3 simulations for the modification of land-use was performed with 1 km resolution in target domain, 46$\times$46 $\textrm{km}^2$ area around city of Busan. It was found that modification result from change of surface land-use in central urban area altered spatial distributions of temperature and wind. In particular, heat island core moved slightly to the seaward at 1300 LST. This results may imply that modification of surface land-use leads to change the thermal environments; in addition, it has a significant effect on local wind circulations and dispersions of air pollutants.

• Carbon letters
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• v.16 no.2
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• pp.93-100
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• 2015

Surface modified carbon felts were utilized as an electrode for the removal of inorganic ions from seawater. The surfaces of the carbon felts were chemically modified by alkaline and acidic solutions, respectively. The potassium hydroxide (KOH) modified carbon felt exhibited high Brunauer-Emmett-Teller (BET) surface areas and large pore volume, and oxygen-containing functional groups were increased during KOH chemical modification. However, the BET surface area significantly decreased by nitric acid ($HNO_3$) chemical modification due to severe chemical dissolution of the pore structure. The capability of electrosorption by an electrical double-layer and the efficiency of capacitive deionization (CDI) thus showed the greatest enhancement by chemical KOH modification due to the appropriate increase of carboxyl and hydroxyl functional groups and the enlargement of the specific surface area.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.2
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• pp.45-49
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• 2008

This paper investigated the accuracy of the current design formulae for the elastic buckling strength of web-tapered I-beams in AISC-LRFD specification. The basic concept is to replace a tapered beam by an equivalent prismatic beam with a different length, but with a cross section identical to that of the smaller end of the tapered beam. The modification factor, B, is used to account for the stress gradient within the unbraced length and the lateral restraining effects offered by the adjacent segments. The modification factor(B) suggested in AISC-LRFD specification was compared with the finite element method(FEM) results. This paper presented a redefined method to calculate the modification factor(B).

• International Journal of High-Rise Buildings
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• v.8 no.4
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• pp.303-311
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• 2019

The effectiveness of aerodynamic modification to reduce wind loadings has been widely reported. However, most of previous studies have been investigated dynamic forces and pressure distributions on tall buildings with various unconventional configurations. This study was investigated dynamic characteristics and aerodynamic instability of super-tall buildings with unconventional configurations through extensive aeroelastic model experiments. Seventeen types of supertall building models were considered such as basic and corner modification with corner cut, chamfered, oblique opening, tapered, inversely tapered, bulged, helical with twist angles of $90^{\circ}$, $180^{\circ}$, $270^{\circ}$, $360^{\circ}$ and composite with $360^{\circ}$ helical & corner cut, 4-tapered & $360^{\circ}$ helical & corner cut, setback & corner cut, setback & $45^{\circ}$ rotate. As a result, aerodynamic characteristics of helical models with single modification are superior to those of other models with single modification. However, effect of twist angle for helical model is negligible. Further, the 4-tapered & $360^{\circ}$helical & corner cut model is most effective in reducing the along- and across-wind fluctuating displacement responses in all of experimental models.

• Safety and Health at Work
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• v.12 no.3
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• pp.346-350
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• 2021

Background: The high sensitivity of individuals toward safety information in production activities, that is, attentional bias toward safety (ABS), can positively predict safe behaviors. It has become a hot topic in current organizational safety behavior research. However, there is no literature on its modification method. Methods: Based on the modified dot-probe task, we designed a modification training method of ABS. The training method required subjects to respond to the location of detection points that presented after safety stimulus and neutral stimulus pictures. Subjects' attentional bias values of safety and neutral pictures were measured during the experiment. Twenty-one students were selected and divided into a control group and training group to gain comparable results. Results: A novel training method was developed in this study to promote the efficacy of safety stimulus by activating ABS of the subjects. Moreover, repeated trainings and preacquired relative knowledge can enhance this effect. Conclusion: This study develops an experimental approach to evaluate the effectiveness of safety education and safety training, and also provides a new research idea for accident prevention.

• Bulletin of the Korean Chemical Society
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• v.8 no.4
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• pp.280-285
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• 1987

FMN-dependent glycolate oxidase from spinach is inactivated by diethyl pyrocarbonate at pH 7.0. Inactivation of both apo- and holoenzyme by diethyl pyrocarbonate follows pseudo-first-order kinetics and first order with respect to the reagent. A series of difference spectra of inactivated and native enzymes show a single peak at 240 nm, indicating the modification of histidyl residues. No decrease in absorbance at around 280 nm due to formation of O-carbethoxytyrosine is observed. The rate of inactivation is dependent on pH, and the data for pH dependent rates implicate the involvement of a group with a pKa of 6.9. The activity lost by treatment with diethyl pyrocarbonate could be almost fully restored by incubation with 0.75M hydroxylamine. The reactivation by hydroxylamine and the pH dependence of inactivation are also consistent with that the inactivation is due to modification of histidyl residues. Although coenzyme FMN is without protective effect, the substrate glycolate, the product glyoxylate, and two competitive inhibitors, oxalate and oxalacetate, provide marked protection against the inactivation of the holoenzyme. These results suggest that the inactivation of the oxidase by diethyl pyrocarbonate occurs by modification of essential histidyl residue(s) at the active site.

• Korean Journal of Health Education and Promotion
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• v.3 no.1
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• pp.83-98
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• 2001

Although periodic health examination has been one of the most common practices of preventive medicine, its effect on modification of risk behavior has been seldom assessed. Thus, this study attempted to demonstrate the influence of a health examination on modification of cardiovascular disease related health risk behaviors such as smoking, physical inactivity, and obesity. Data of 893 adults were derived from two types of a popular and highly acclaimed health examination program. With a conceptual model constructed using Persuasive Communication variables, McNemar tests examined Source-Outcome association, hypothesizing that different health examination programs would yield different levels of behavior change in smoking, physical inactivity, and obesity. No significant behavior change was found in any of the two health examination programs. Instead, previously established Receiver-Outcome relationship was reconfirmed by logistic regression modeling where gender was the most prominent predictor of all three behaviors. Men were more likely to be current smokers (OR=0.029), exercisers (OR=2.629), and obese (OR=0.237). The importance of followups after health examination is highly stressed as well as that of gender-specific health education strategies. This study recommends applying the social-ecological approaches in health examination, which emphasizes the support and collaboration at individual, family, organizations, community, and policy level to improve health. Long term and qualitative evaluation of health examination may provide more foundation for increasing the effectiveness of health education and communication in health examinations.