• Journal of Mechanical Science and Technology
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• v.15 no.9
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• pp.1281-1291
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• 2001

The hereditary integral form of a quasi-linear viscoelastic law has been employed. Four new concepts have been employed: 1. a reduced relaxation function with a non-linear exponential function of time, 2. an inverse method to determine the scale factor of the elastic response, 3. an instant elastic recovery strain during unloading, and 4. the results of a constitutive model for cyclic tests may be a function of the Heavyside class. These concepts have been supported by agreement between measured and predicted responses of soft connective tissue to three types of multiple cyclic tests which include rest periods of no extension and alternations between different strain levels. Such agreement has not been attained in the previous studies. Chun and Hubbard (2001) is our companion experimental analysis paper.

• Journal of Korea Foundry Society
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• v.22 no.1
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• pp.11-16
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• 2002

Hot deformation behavior of GCD-50 cast iron has been investigated by employing the compressive test. Phenomenological deformation behaviors, which were modeled based on the dynamic materials model and the kinetic model, have been correlated with the microstructural change taken place during compression. Microstructural investigation revealed that the adiabatic shear band caused by the locallized deformation was taken place in low temperature and high strain rate. On the other hand, the wavy and curved grain boundaries, which repersent the occurrence of dynamic microstructure change such as dynamic recovery and dynamic recrystallization, were observed in high temperature and low strain rate. Deformation model based on hyperbolic sine law has also been suggested.

• Microbiology and Biotechnology Letters
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• v.19 no.5
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• pp.439-443
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• 1991

A strain of Streptomyces sp. isolated from soil was found to produce extra-cellular $\beta$-lactamase associated partially to the cell growth. The $\beta$-lactamase was purified from the culture supernatant through anmonium sulfate fractionation, ion-exchange chromatographies and gel filtration. The final purification fold and recovery yield were 57 and 6.2%, respectively. Molecular weight of the $\beta$-lactamase was estimated to be about 67, 000 by SDS-polyacrylamide gel electrophoresis. The optimal reaction condition was at pH 7-8 and at 35-$45^{\circ}C$. The $K_m$ and $V_{max}$ values of the enzyme for penicillin G were estimated to he 3 mM and $3\times 10^3$ $\mu\textrm{M}$/min/mg protein, respectively. The purified $\beta$-lactamase was classified to the class A enzyme hydrolyzing only penicillin.

• Journal of the Korean Society of Safety
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• v.29 no.4
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• pp.28-33
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• 2014

Recently, the actuator worked by the driving recovery-force of the thermo elastic martensitic transformation of shape memory alloys(SMA) has been studied. This paper presents a study on the fatigue life of shape memory alloy (SMA) actuators undergoing thermally induced martensitic phase transformation under various stress levels. shape memory recoverable stress and strain of Ti-44.5at.%Ni-8at.%Cu alloys were by means of constant temperature tensile tests. Differential scanning calorimetry (DSC) was employed in order to investigate the transformation characteristics of the alloy before the tests. the results were summarized as follows. The martensite inducing stress incerased with the increasing of the Cu-contents. The fatigue life decreased with the increasing of the test load and the Cu-content. The data acquired will be very useful during the design process of an SMA NiTiCu element as a functional part of an actuator.

• Korean Journal of Materials Research
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• v.15 no.4
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• pp.240-245
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• 2005

An oxygen free copper was severely deformed by accumulative roll-bonding (ARB) process for improvement of its mechanical properties. Two copper sheets 1 m thick, 30 mm wide and 300 m long are first degreased and wire-brushed for sound bonding. The sheets are then stacked to each other, and roll-bonded by about $50\%$ reduction rolling without lubrication at ambient temperature. The bonded sheet is then cut to the two pieces of same dimensions and the same procedure was repeated to the sheets up to eight cycles $(\varepsilon-6.4)$. TEM observation revealed that ultrafine grains were developed after the third cycle, and their size was slightly increased at higher cycles. Tensile strength of the copper increased with the strain at low strain levels, but it hardly increased from 3 cycles $(\varepsilon>2.4)$ due to occurrence of dynamic recovery, even if the imposed strain increased.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.2
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• pp.461-472
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• 1996

The relationship between plastic deformation and crystal grain change in warm forging processes of SM10C carbon steel is studied. If the carbon steel is deformed at warm forging temperature(about recrystallization range), material properties are changed due to microstructural chanre of the crystal grain and cementite of the internal part. Some experimental values are investigated in terms of the elliptic degree of cementite, the grain size of cementite and ferrite grain size. When plastic deformation proceeds, the elliptic degree of cementite becomes larger and the grain size of cementite particle becomes small. In addition, the size of ferrite grain becomes fines by recrystallization. The elliptic degree of cementite has a considerable effect on formability. The distribution of effective strain in the forging was calculated by the rigid visco-plastic FEM analysis. The effective strain distribution obtained from the FEM simulation is compared with the experimental result, At the level of effective strain 0.3, dynamic recovery and dynamic recrystallization begin and at the level of over 2.5, the organization of material has better internal structure that is suitable for the following cold forming.

• Journal of Microbiology and Biotechnology
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• v.24 no.4
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• pp.475-482
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• 2014

The metabolic pathway of eugenol degradation by thermophilic Geobacillus sp. AY 946034 strain was analyzed based on the lack of data about eugenol degradation by thermophiles. TLC, GC-MS, and biotransformation with resting cells showed that eugenol was oxidized through coniferyl alcohol, and ferulic and vanillic acids to protocatechuic acid before the aromatic ring was cleaved. The cell-free extract of Geobacillus sp. AY 946034 strain grown on eugenol showed a high activity of eugenol hydroxylase, feruloyl-CoA synthetase, vanillate-O-demethylase, and protocatechuate 3,4-dioxygenase. The key enzyme, protocatechuate 3,4-dioxygenase, which plays a crucial role in the degradation of various aromatic compounds, was purified 135-fold to homogeneity with a 34% overall recovery from Geobacillus sp. AY 946034. The relative molecular mass of the native enzyme was about $450{\pm}10$ kDa and was composed of the non-identical subunits. The pH and temperature optima for enzyme activity were 8 and $60^{\circ}C$, respectively. The half-life of protocatechuate 3,4-dioxygenase at the optimum temperature was 50 min.

• Journal of Microbiology
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• v.39 no.3
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• pp.240-243
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• 2001

The effect of cryoprotectants and suspending solutions on the preservation of marine heterotophic bacteria was investigated. Six halotolerant and four halophilic bacterial isolates suspended in either distilled water or artificial seawater were preserved in glycerol and dimethylsulfoxide at -70$\^{C}$, respectively. After one year of preservation, the recovery rates on the appropriate agar plates were estimated. The survival rate was found to be dependent on the strain tested, regardless of the preservation conditions tested.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.10a
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• pp.53-56
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• 1997

The multistage precision forming process for aperture of electronic guns consists mainly of drawing and swaging operations. The multistage forming sequence is analyzed in view of production industry, and based on the industrial investigation. The processes are simulated by the finite element code MARC. The elastic recovery, strain and stress distribution, and the die forces are summarized.

• KSBB Journal
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• v.8 no.1
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• pp.1-9
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• 1993

The acetone-butanol fermentation by C. acetobutylicum has gained increasing attention for the following reasons. First, the finite supply of petrochemical resources, combined with increasing concern over global environmental effects and the unstable nature of the price of petroleum has renewed interest in the development of fermentation technology that allows utilzation of biomass wastes for the production of alcohol. Second, it serves as excellent model system for understading the regulation and molecular biology of tightly regulated complex primary metabolism, and for applications of metabolic engineering. In this review various aspects of acetone-butanol fermentation by C. acetobutylicm including strain and fermentation characteristics, enzyme regulation, and solvent formation mechanism, and product recovery and summarized.