• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.1
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• pp.144-149
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• 2012

The cutting characteristics of hardened aluminum alloy A17075-T6 were investigated during turning processing. Under variation conditions of cutting speed, depth of cut, and feed rate, the characteristics of cutting force, surface roughness, and machined texture were investigated. Surface roughness became worse in proportion to the increase of the feed rate. The thickness of material alteration layer which is derived from the effect of cutting force was the biggest when feed rate 0.148mm/rev. This research confirmed that the deformed layer is dominantly dependent on the variation of feed rate.

• Journal of the Korean Society for Railway
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• v.12 no.2
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• pp.285-290
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• 2009

This paper implemented a Speech Recognition System in order to recognize Commands of Ticketing Machine (314 station-names) at real-time using Continuous Hidden Markov Model. Used 39 MFCC at feature vectors and For the improvement of recognition rate composed 895 tied-state triphone models. System performance valuation result of the multi-speaker-dependent recognition rate and the multi-speaker-independent recognition rate is 99.24% and 98.02% respectively. In the noisy environment the recognition rate is 93.91%.

• Journal of Environmental Health Sciences
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• v.26 no.2
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• pp.91-96
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• 2000

We investigated characters of transdermal therapeutic system(TTS) and the skin permeability of that with applying drug delivery system(DDS). Natural gums were selected as material of TTS. The permeation of natural gums ointment containing drug in rat skin using diffusion cell model. Permeation properties of materials were investigated for water soluble drug such as riboflavin in vitro. We used glycerin, PEG 600 and oleic acid as enhancers. Since dermis has more hydration than the stratum corneum, skin permeation rate at steady state was highly influenced when glycerin was used in riboflavin. The permeation rate of content enhancer and drug was found to be faster than that of content riboflavin only. These results showed that skin permeation rate of drug across the composite was mainly dependent on the property of ointment base and drug. All the gum ointment tested showed good safety. Proper selection of the materials which resemble and enhance properties of the delivering drug was found to be important in controlling the skin permeation rate.

• Bulletin of the Korean Chemical Society
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• v.8 no.2
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• pp.79-83
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• 1987

The reduction of a series of 1-substituted benzyl-3-cyanoquinolinium ions (p-$cH_3$, H, p-Br, m-F, p-CN) by sodium borohydride has been investigated. In all cases the products from these reactions were found to be 1, 2-dihydroquinolines over 82% yields. Rates of reduction were measured in basic condition and in solvent system consisting of 4 parts of isopropyl alcohol and 1 part of water by volume. Second order rate constants were obtained for these reactions. When the ratio of [$OH^-$] to [$BH_4^-$] becomes large the observed rate constants ($K_{obs}$) decrease by a small factor. Reaction scheme and rate law are discussed. Bronsted ${\alpha}(=\frac{d\;In\;k}{d\;In\;K})$ obtained by using the value of equilibrium constant K, which was obtained previously, was not 0. Instead, a value of 0.36 was obtained which indicated that the reduction by borohydride was structure-dependent according to the Marcus formalism even though the reaction rate was close to the diffusion limit.

• Bulletin of the Korean Chemical Society
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• v.19 no.10
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• pp.1063-1068
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• 1998

The nature of F electronic excitation energy transfer to OH- vibrational levels in KCl crystals is the exchange interaction, although the transfer process exhibits three temporally distinguishable components depending on the distance between excited F center and OH-. The critical distance as well as rate of the major energy transfer process in randomly distributed samples increases rapidly as OH- librational motions become active with temperature rise. The excited state character introduced into the OH- ground electronic state by perturbation is essential for the exchange interaction. The perturbation is brought about by the expanded electron cloud of excited F center for OH- associated to F center, whereas by librations and lattice vibrations perpendicular to the bond axis for isolated OH- . F excitation quenching efficiency by OH- is dependent on the variation of the critical distance rather than the rate as the rate is much faster than the normal F bleach recovery rate.

• Bulletin of the Korean Chemical Society
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• v.7 no.3
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• pp.241-245
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• 1986

The vibration-vibration energy exchange of $N_2(v=1)+O_2(v=0){\to}N_2(v=0)+O_2(v=1)$ has been investigated, in particular, at low temperatures. The energy exchange rate constants are calculated by use of the solution of the time-dependent Schrodinger equation with the interaction potential of the colliding molecule as a perturbation term. The predicted rate constants are significantly agree with a experimental values in the range of 295∼$90^{\circ}K$. The consideration of the VV-VT coupling decreases the predicted pure VV energy exchange value by a factor of ∼2. When the collision frequency correction is introduced, the VV-VT rate constant is consistent with the observed value in the liquid phase. The consideration of the population of the rotational energy level increases the VV-VT value significantly.

• Structural Engineering and Mechanics
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• v.80 no.5
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• pp.539-551
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• 2021

With the continuous increase of computational capacity, more and more complex nonlinear elastoplastic constitutive models were developed to study the mechanical behavior of elastoplastic materials. These constitutive models generally contain a large amount of physical and phenomenological parameters, which often require a large amount of computational costs to determine. In this paper, an inverse parameter determination method is proposed to identify the constitutive parameters of elastoplastic materials, with the consideration of both strain rate effect and temperature effect. To carry out an efficient design, a hybrid optimization algorithm that combines the genetic algorithm and the Nelder-Mead simplex algorithm is proposed and developed. The proposed inverse method was employed to determine the parameters for an elasto-viscoplastic constitutive model and Johnson-cook model, which demonstrates the capability of this method in considering strain rate and temperature effect, simultaneously. This hybrid optimization algorithm shows a better accuracy and efficiency than using a single algorithm. Finally, the predictability analysis using partial experimental data is completed to further demonstrate the feasibility of the proposed method.

• Korean Journal of Materials Research
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• v.26 no.5
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• pp.281-286
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• 2016

In the present study, the tensile properties and dynamic strain aging of an Fe-24.5Mn-4Cr-0.45C alloy were investigated in terms of strain rate. During tensile testing at room temperature, all the stress-strain curves exhibited serrated plastic flows related to dynamic strain aging, regardless of the strain rate. Serration appeared right after yield stress at lower strain rates, while it was hardly observed at high strain rates. On the other hand, strain-rate sensitivity, indicating a general relationship between flow stress and strain rate at constant strain and temperature, changed from positive to negative as the strain increased. The negative strain-rate sensitivity can be explained by the Portevin Le Chatelier effect, which is associated with dynamic strain aging and is dependent on the strain rate because it is very likely that the dynamic strain aging phenomenon in high-manganese steels is involved in the interaction between moving dislocations and point-defect complexes.

• Journal of environmental and Sanitary engineering
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• v.11 no.2
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• pp.27-31
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• 1996

2,4,6-Trinitrotoluene(TNT) was reduced into intermediate products by mixed culture incubated in anaerobic condition. To test the effects of extracellular material to electron transfer between sulfide and TNT, filtered medium of mixed culture was loaded in the test tubes with TNT and sulfide. The transformation rate was measured under four different conditions. The rate under microbial activity was the fastest among under different conditions. With sulfide or filtrate alone and TNT, the reactions were measured as the slowest reactions or no reactions occured, respectively. The reaction rate coefficient were calculated by linear regression and the first order kinetic was fitted best. Also, the plot of rate coefficients (K$_{f}$) showed linear relationships when at time zero TNT and sulfide concentration were 20 mg/1 and 6.0 mM, respectively. By extrapolation, reaction rate coefficient of 100% filtrate could be calculated as 0.0054/minute. However, reaction rate was affected by different concentration of sulfide, so it is a dependent of sulfide concentration. The results of this test showed TNT reduction rate can be limited more by microbial reaction than by mediation of filtrate or sulfide and filtrate alone.

• The Journal of Engineering Geology
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• v.20 no.3
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• pp.271-279
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• 2010

Time-dependent behavior similar to secondary deformation related to mineral dissolution is easily observed when performing a laboratory pressure experiment. In this research, to observe the dissolution of quartz found in bentonite used as buffer material for the geological disposal of high-level waste (HLW) under conditions of high pH, we calculated the diffusion of $OH^-$ ions and the behavior of quartz dissolution using the homogenization analysis method. The results reveal that the rate of quartz dissolution is proportional to the temperature and interlayer water thickness. In particular, in a high-pH environment, the reacted area (and therefore the dissolution rate) increases with decreasing interlayer water thickness.