• Korean Journal of Food Science and Technology
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• v.25 no.6
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• pp.643-648
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• 1993

A simple approximate model using equivalent time at a reference temperature ($t_{eq}$) was derived to predict quality changes caused by temperature fluctuations. The validity and effectiveness of this model have been assessed with experimental data of sucrose hydrolysis. Kinetic parameters of sucrose hydrolysis were estimated by one step method using equivalent time at a reference temperature with linearly increasing temperature profile. Sucrose hydrolysis was a first order reaction, and the activation energy was 25.84 kcal/mol. The extent of sucrose hydrolysis of liquid model system under accelerated test with sinusoidal temperature fluctuations were determined. The proposed model yielded accurate prediction with the correlation coefficient in the range of $0.92{\sim}0.99$.

• Archives of Pharmacal Research
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• v.29 no.12
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• pp.1164-1170
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• 2006

A triptolide-lysozyme (TP-LZM) conjugate was synthesized to achieve renal specific delivery and to reduce the side effects of triptolide. Triptolide was coupled to lysozyme through succinic via an ester bond with an average coupling degree of 1 mol triptolide per 1 mol lysozyme. The lysozyme can specifically accumulate in the proximal tubular cells of the kidney, making it a potential carrier for targeting drugs to the kidney. The structure of triptolide succinate (TPS) was confirmed by IR, $^{1}H-NMR$, MS and UV. The concentrations of triptolide in various samples were determined by reversed-phase high-performance liquid chromatography (HPLC). In this study, the physicochemical and stability profiles of TP-LZM under various conditions were investgated the stability and releasing profiles of triptolide-lysozyme (TP-LZM) under various conditions. In vitro release trails showed triptolide-lysozyme was relatively stable in plasma (less than 30% of free triptolide released) and could release triptolide quickly in lysosome (more than 80% of free triptolide released) at $37^{\circ}C$ for 24 h. In addition, the biological activities of the conjugate on normal rat kidney proximal tubular cells (NRK52E) were also tested. The conjugate can effectively reduce NO production in the medium of NRK52E induced by lipopolysaccharide (LPS) but with much lower toxicity. These studies suggest the possibility to promote curative effect and reduce its extra-renal toxicity of triptolide by TP-LZM conjugate.

• Biomolecules & Therapeutics
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• v.21 no.6
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• pp.442-446
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• 2013

Here in this study, we isolated 1,2,3,4,6-penta-O-galloyl-${\beta}$-D-glucose (PGG) from Curcuma longa L. and elucidated the lifespan-extending effect of PGG using Caenorhabditis elegans model system. In the present study, PGG demonstrated potent lifespan extension of worms under normal culture condition. Then, we determined the protective effects of PGG on the stress conditions such as thermal and oxidative stress. In the case of heat stress, PGG-treated worms exhibited enhanced survival rate, compared to control worms. In addition, PGG-fed worms lived longer than control worms under oxidative stress induced by paraquat. To verify the possible mechanism of PGG-mediated increased lifespan and stress resistance of worms, we investigated whether PGG might alter superoxide dismutase (SOD) activities and intracellular ROS levels. Our results showed that PGG was able to elevate SOD activities of worms and reduce intracellular ROS accumulation in a dose-dependent manner.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1293-1298
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• 2010

In most power plants, wall thinning in carbon-steel pipes due to flow-accelerated corrosion is one of the major aging phenomena, and it reduces the load-carrying capacity of the piping system. Various types of wall-thinning defects were manufactured in real-scale elbows, and monotonic in-plane bending tests were performed under internal pressure to evaluate the failure behavior of the elbows. In this paper, the behavior of elastic and plastic limit leads of locally thinned elbows in a real-scale failure test is presented. The loads determined on the basis of TES (twice elastic slope) were considered to be the limit loads of locally thinned elbows so that the integrity of the thinned elbows could be maintained, even when a small amount of plastic deformation might have occurred.

• Journal of the Korean Society of Clothing and Textiles
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• v.38 no.3
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• pp.372-385
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• 2014

Lignin is an abundant natural polymer in the biosphere and second only to cellulose; however, it is under-utilized and considered a waste. In this study, lignin was fabricated into nanofibers via electrospinning. The critical parameters that affected the electrospinnability and morphology of the resulting fibers were examined with the aim to utilize lignin as a resource for a new textile material. Poly(vinyl alcohol) (PVA) was added as a carrier polymer to facilitate the fiber formation of lignin, and the electrospun fibers were deposited on polyester (PET) nonwoven substrate. Eleven lignin/PVA hybrid solutions with a different lignin to PVA mass ratio were prepared and then electrospun to find an optimum concentration. Lignin nano-fibers were electrospun under a variety of conditions such as various feed rates, needle gauges, electric voltage, and tip-to-collector distances in order to find an optimum spinning condition. We found that the optimum concentration for electrospinning was a 5wt% PVA precursor solution upon the addition of lignin with the mass ratio of PVA:lignin=1:5.6. The viscosity of the lignin/PVA hybrid solution was determined as an important parameter that affected the electrospinning process; in addition, the interrelation between the viscosity of hybrid solution and the electrospinnability was examined. The solution viscosity increased with lignin loading, but exhibited a shear thinning behavior beyond a certain concentration that resulted in needle clogging. A steep increase in viscosity was also noted when the electrospun system started to form fibers. Consequently, the viscosity range to produce bead-free lignin nanofibers was revealed. The energy dispersive X-ray analysis confirmed that lignin remained after being transformed into nanofibers. The results indicate the possibility of developing a new fiber material that utilizes biomass with resulting fibers that can be applied to various applications such as filtration to wound dressing.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.124-124
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• 2011

This study investigated the interaction of varied plasma power with ultralow-k toluene-tetraethoxysilane (TEOS) hybrid plasma polymer thin films, as well as changing electrical and mechanical properties. The hybrid thin films were deposited on silicon(100) substrates by plasma enhanced chemical vapor deposition (PECVD) system. Toluene and tetraethoxysilane were utilized as organic and inorganic precursors. In order to compare the electrical and the mechanical properties, we grew the hybrid thin films under various conditions such as rf power of plasma, bubbling ratio of TEOS to toluene, and post annealing temperature. The hybrid plasma polymer thin films were characterized by Fourier transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM), nanoindenter, I-V curves, and capacitance. Also, the hybrid thin films were analyzed by using ellipsometry. The refractive indices varied with the RF power, the bubbling ratio of TEOS to toluene, and the annealing temperature. To analyze their trends of electrical and mechanical properties, the thin films were grown under conditions of various rf powers. The IR spectra showed them to have completely different chemical functionalities from the liquid toluene and TEOS precursors. Also, The SiO peak intensity increased with increasing TEOS bubbling ratio, and the -OH and the CO peak intensities decreased with increasing annealing temperature. The AFM images showed changing of surface roughness that depended on different deposition rf powers. An nanoindenter was used to measure the hardness and Young' modulus and showed that both these values increased as the deposition RF power increased; these values also changed with the bubbling ratio of TEOS to toluene and with the annealing temperature. From the field emission scanning electron microscopy (FE-SEM) results, the thickness of the thin films was determined before and after the annealing, with the thickness shrinkage (%) being measured by using SEM cross-sectional images.

• Journal of Dairy Science and Biotechnology
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• v.26 no.2
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• pp.51-56
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• 2008

Using central composite design, we have designed optimization of the manufacturing of processed butter. And response surface analysis by least-square regression was used Statistical Analysis System(SAS). Central composite design can be achieved by response surface techniques that allow flexibility in modeling and analysis. Response surface methodology(RSM) was used to optimize hardness(%) using as independent variables; the content of butter($X_1$), ranging from 50 to 90(%), the content of soybean oil($X_2$), from 0 to 20(%), and the hydrogenated soybean oil($X_3$) from 0 to 4(%). The results on the regression coefficients calculated for overrun by response surface by least-square regression(RSREG) were followed. It was considered that the linear regression was significant(p<0.01). As for the processed butter, the regression model equation for the hardness(Y, %) to the change of an independent variable could be predicted as follow: $Y=60.88-8.92X_2-{29.3X_2}^2$. The optimal for the manufacturing of processed butter were determined at the content of butter of 88.22%, soybean oil of 6.71% and hydrogenated soybean oil of 2.36%, respectively. Optimum compositions were resulted in hardness of 65.78 N. Finally the reference sample(Butter in the morning, Seoul Dairy Co-op.) and processed butter manufacturing under the optimal conditions were compared with spreadability test. The spreadability scores result from reference sample and butter under optimal conditions was not found a significant difference.

• Journal of Hydrogen and New Energy
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• v.13 no.2
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• pp.110-118
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• 2002

The hydrogen storage vessel having a good heat conductivity along with a simple structure and a low cost for these alloys was designed and manufactured, and then its characteristic properties were studied in this study. The various parts in hydrogen storage vessel consisted of copper pipes and stainless steel of 250 mesh reached the setting temperature after 4~5 minutes, which indicated that storage vessel had a good heat conductivity that was required in application. And also the storage vessel had a good property of hydrogen transport considering that the reaction time between hydrogen and rare-earth metal alloys in storage vessel was found to be within 10 min at $18^{\circ}C$ under 10 atmospheric pressure. It showed that the average capacity of discharged hydrogen volume was found to be $120{\ell}$ for $MmNi_{4.5}Mn_{0.5}$ under discharging conditions of $40^{\circ}C{\sim}80^{\circ}C$ at a constant flow rate of $5{\ell}$/min. It was found that the optimum discharging temperature for obtaining an appropriate pressure of 3atm was determined to be $60^{\circ}C$ for $MmNi_{4.5}Mn_{0.5}$ hydrogen storage alloy.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.56 no.2
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• pp.172-182
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• 2020

In order to offer specific information needed to assist in operation of a ship with same type rudder through evaluating the maneuverability of training ship A-Ra with flapped rudder, sea trials based full scale for turning test, zig-zag test with rudder angle 10° and 20°, and spiral test at service condition were carried out on starboard and port sides around Jeju Island according to the standards of maneuverability of IMO. As a result, the angular velocity of port turn was higher than that of starboard turn. Therefore, the size of turning circle was longer on the starboard side. In addition, variation of the transfer due to various factors was more stable than those of the others. In the Z-test results, the mean of 1st and 2nd overshoot angles were 9.8°, 6.3° and 15.3°, 9.2° respectively when the port and starboard was 10°; the 1st overshoot angle were 18°, 13.7° when using 20°. Her maneuverability index T' and K' can be easily determined by using a computer with the data obtained from Z-test where K' and T' are dimensionless constants representing turning ability and responsiveness to the helm, respectively. In the Z-test under flap rudder angle 10°, the obtained K' value covered the range of 2.37-2.87 and T' was 1.74-3.45. Under the flap rudder angle 20°, K' and T' value showed 1.43-1.63, 1.0-1.73, respectively. In the spiral test, the loop width was unstable at +0.3° and -0.5°-0.9° around the midship of flap rudder. As a result, course stability was comparatively good. From the sea trial results, training ship ARA met the present criterion in the standards of maneuverability of IMO.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.9
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• pp.1057-1063
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• 2007

To analyze the performance of mobile communication systems, the exact information of the carrier-to-interference ratio is important. Under the presence of an interferer in a cell, the carrier-to-interference ratio of the receiver is determined by the ratio between the informer-receiver distance$(d_0)$ and the receiver-interferer distance$(d_1)$. In this paper, we derive the carrier-to-interference distribution based on $d_0/d_1$ values using the geometric relation among the informer, interferer and receiver, and confirm its exactness using the simulation result. We also apply the derivation result to a system with the adjacent channel interference, and analyze the outage probability.