• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.3
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• pp.187-194
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• 2020

In this study, computational analyses are carried out to investigate the interference flows and the aerodynamic characteristics of a hit-to-kill intercepter due to lateral jets at medium altitude. In addition, the analyses are performed for air and multi-species gas used in the side jet. The results indicate that the position of the barrel shock are shifted upstream and the structure of the shock wave are changed for the multi-species jet when compared to the air jet. As a result, the high pressure region with multi-species jet moves forward and the pitching moment is higher under the same flow condition. Moreover, the inclusion of high temperature effects makes drastic changes in pressure distribution. The jet width is much bigger, and the jet diffuses over wider range in medium altitude than in low altitude, because of the low density of the freestream.

• Asian-Australasian Journal of Animal Sciences
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• v.29 no.1
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• pp.62-72
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• 2016

This study investigated the dynamics associated with prolonged ensiling and aerobic deterioration of whole crop corn (WCC) silages and total mixed ration (TMR) silages containing WCC (C-TMR silages) to clarify the differences that account for the enhanced aerobic stability of TMR silages. Laboratory-scale barrel silos were randomly opened after 7, 14, 28, and 56 d of ensiling and were subjected to analyses of fermentation quality, microbial and temperature dynamics during aerobic exposure. WCC and C-TMR silages were both well preserved and microorganisms were inhibited with prolonged ensiling, including lactic acid bacteria. Yeast were inhibited to below the detection limit of 500 cfu/g fresh matter within 28 d of ensiling. Aerobic stability of both silages was enhanced with prolonged ensiling, whereas C-TMR silages were more aerobically stable than WCC silages for the same ensiling period. Besides the high moisture content, the weak aerobic stability of WCC silage is likely attributable to the higher lactic acid content and yeast count, which result from the high water-soluble carbohydrates content in WCC. After silo opening, yeast were the first to propagate and the increase in yeast levels is greater than that of other microorganisms in silages before deterioration. Besides, increased levels of aerobic bacteria were also detected before heating of WCC silages. The temperature dynamics also indicated that yeast are closely associated with the onset of the aerobic deterioration of C-TMR silage, whereas for WCC silages, besides yeast, aerobic bacteria also function in the aerobic deterioration. Therefore, the inclusion of WCC might contribute to the survival of yeast during ensiling but not influence the role of yeast in deterioration of C-TMR silages.

• Korean Journal of Food Science and Technology
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• v.20 no.3
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• pp.303-309
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• 1988

The heat generation at the start-up period of an autogeneous single screw extruder was determined with various feed materials, die structure and operational conditions. The highest heat generation rate was observed with defatted soybean meal, while the lowest value was obtained with rice flour, and wheat and barley flour showed the intermediate rate. As the moisture content of the flour decreased and the screw speed increased, the electric power requirement and heat generation rate increased. The temperature at compression section increased with the decrease in the particle size. The same effect was also observed as breaker plate was installed. The optimum operation was established as the temperature profile was maintained in decreasing order of metering section, die and compression section.

• Korean Journal of Human Ecology
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• v.5 no.1
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• pp.62-70
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• 2002

The objective of this study was to evaluate the effects of processing parameters of co-rotating twin screw extruder and dry methods on the level of resistant starch (RS) and the properties of extrudate prepared from normal maize starch. The processing parameters were used 90, 110, 130$^{\circ}C$ in temperature, 25.0~30.0% in moisture content, 150, 200, 250 rpm in screw speed and hot and cool air drying and drying after refrigerating in drying methods. The barrel temperature and drying methods had affected the level of resistant starch of extrudate. RS levels of extrudates were ranged from 2.4 to 15.5% by AOAC method. The extrudates, extruded at 110$^{\circ}C$ and then stored at 4$^{\circ}C$, showed the highest level of RS level (15.5%). Water absorption index increased with increasing moisture content and peak temperatures and viscosities of extudates decreased compare to that of raw starch from 94$^{\circ}C$ to 50~65$^{\circ}C$ and from 220 to 46~98 RVU, respectively. Extudates treated in 90$^{\circ}C$ and 110$^{\circ}C$ showed strong peak at $2{\theta}=6.7{\sim}17.0^{\circ}$ by X-ray diffractometry and had ~150$^{\circ}C$ endotherm like as that of RS3 starch by differential scanning calorimetry. In case of 130$^{\circ}C$, extrudates showed strong peak at $2{\theta}=20.0^{\circ}$ and had 106$^{\circ}C$ endotherm.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.5
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• pp.783-787
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• 1999

To study the effects of different extrusion conditions of barley on growth performance, nutrient digestibility and nutrient excretion in feces, a total of 150 growing pigs ($Landrace{\times}Duroc{\times}Large$ White; average 24.4 kg body weight) were allotted to five treatments, in a completely randomized block design. The experimental diets were based on corn-soybean and 30% of barley was included in each diet; barley was the only extruded ingredient. The treatments were 1) no extrusion (Control); 2) extrusion at $100^{\circ}C$ without preconditioning (ENLT); 3) extrusion at $150^{\circ}C$ without preconditioning (ENHT); 4) extrusion at $100^{\circ}C$ with preconditioning (ECLT); 5) extrusion at $150^{\circ}C$ with preconditioning (ECHT). Temperature in the barrel was controlled within ${\pm}5^{\circ}C$ by feed rate with the addition of water at the rate of $3{\ell}\;per\;min$. in the extruder for each treatment. For the 6 week experimental period, extrusion of barley improved the average daily gain (ADG) and digestibilities of dry matter, crude protein and gross energy in growing pigs. As compared to control, significant improvements in ADG (p<0.05) were shown in the groups of feeding extruded barley at high temperature (ENHT and ECHT). There were also significant differences in the digestibilities of DM, CP and P between extrusion temperatures. Barley extruded at high temperature gave better digestibilities of DM, CP and GE than barley extruded at low temperature. Extruded barley diet groups showed significantly (p<0.05) lower excretions of DM, nitrogen (N) and P per kg gain as compared to the ground barley group. DM, N and P excretion per kg gain were also significantly lower in pigs fed barley extruded at $150^{\circ}C$ than at $100^{\circ}C$. In conclusion, extrusion considerably improved the nutritive value of barley and it appeared that temperature is the most important variable.

• Journal of Ginseng Research
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• v.29 no.2
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• pp.107-112
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• 2005

The objective of this study was to determine effects of the die temperature(100 and $120^{\circ}C$) and screw speed(200 and 300 rpm) on the characteristics of extruded raw ginseng such as crude saponin, ginsenosides, maltol and the color of powder. Crude saponin content increased after extrusion-cooking. Ginsenoside $Rg_1\;and\;Rg_2$ that contained in red ginseng increased from 0.2275 mg/g to 0.2835 mg/g$(Rg_l)$ and 0.1164 mg/g to 0.2230 mg/g$(Rg_2)$ with the increase in die temperature from 100 to $120^{\circ}C$, which increased with the decrease in screw speed from 300 to 200 rpm. Maltol, specific component in red ginseng was detected in extruded ginseng. Total sugar content was not changed by extrusion process, however reducing sugar decreased with the increase in die temperature from 100 to $120^{\circ}C$. In conclusion extrusion process can be applied to red ginseng manufacturing by controling extrusion process variables such as extrusion temperature and screw speed.

• Korean Journal of Food Science and Technology
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• v.27 no.3
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• pp.404-413
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• 1995

System parameters (extrusion temperature, extrusion pressure, specific mechanical energy, mean residence time) were analysed on three different screw configurations during twin-screw extrusion of wheat bran. Experiments were conducted over a screw speed of $280{\sim}380\;rpm$, feed rate of $22{\sim}38\;kg/hr$ and moisture content of $17{\sim}33%$ using screws assembled with 3, 4, and 5 reverse screw elements (RSE) adjacent to the heating zone of the barrel. Extrusion temperature increased with increasing RSE but it decreased with increasing feed rate and moisture content. Decreasing the filling ratio of the screw resulted in a lower extrusion pressure, and increasing the length of the RSE gave similar results due to the higher temperature and lower viscosity of melted dough. It was also observed that increasing the feed rate and decreasing moisture content resulted in the reduced extrusion pressure. Specific mechanical energy (SME) decreased when the feed rate and moisture content increased, and SME increased when using RSE posses from 3 to 5. Screw configuration posses with 4 RSE yielded the longest RT, and the smaller the die hole, the higher the RT. In contrast, RT decreased when the feed rate increased. With increasing moisture content RT for 3 RSE increased, but that for 4 and 5 RSE decreased.

• Journal of Microbiology and Biotechnology
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• v.27 no.4
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• pp.775-784
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• 2017

A neutral xylanase (CcXyn) was identified from Coprinus cinereus. It has a single GH10 catalytic domain with a basic amino acid-rich extension (PVRRK) at the C-terminus. In this study, the wild-type (CcXyn) and C-terminus-truncated xylanase ($CcXyn-{\Delta}5C$) were heterologously expressed in Pichia pastoris and their characteristics were comparatively analyzed with aims to examine the effect of this extension on the enzyme function. The circular dichorism analysis indicated that both enzymes in general had a similar structure, but $CcXyn-{\Delta}5C$ contained less ${\alpha}-helices$ (42.9%) and more random coil contents (35.5%) than CcXyn (47.0% and 32.8%, respectively). Both enzymes had the same pH (7.0) and temperature ($45^{\circ}C$) optima, and similar substrate specificity on different xylans. They all hydrolyzed beechwood xylan primarily to xylobiose and xylotriose. The amounts of xylobiose and xylotriose accounted for 91.5% and 92.2% (w/w) of total xylooligosaccharides (XOS) generated from beechwood by CcXyn and $CcXyn-{\Delta}5C$, respectively. However, truncation of the C-terminal 5-amino-acids extension significantly improved the thermostability, SDS resistance, and pH stability at pH 6.0-9.0. Furthermore, $CcXyn-{\Delta}5C$ exhibited a much lower $K_m$ value than CcXyn (0.27 mg/ml vs 0.83 mg/ml), and therefore, the catalytic efficiency of $CcXyn-{\Delta}5C$ was 2.4-times higher than that of CcXyn. These properties make $CcXyn-{\Delta}5C$ a good model for the structure-function study of $({\alpha}/{\beta})_8$-barrel-folded enzymes and a promising candidate for various applications, especially in the detergent industry and XOS production.

• The Korean Journal of Food And Nutrition
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• v.25 no.4
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• pp.850-854
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• 2012

This study is carried out in order to develop food materials for the promotion of rice consumption. In this study, we researched the physicochemical properties of extruded rice flour (ER) and gelatinization popped rice flour (GPR) by the extrusion process and by the popped method with milled rice and brown rice. The extrusion process used a couple of screw extruders. The extrusion parameter was kept constant at a feed moisture content of 25%, barrel temperature of $120^{\circ}C$ and screw speed of 400 rpm. GPR was prepared by batch popping machine after gelatinization of rice. In order to evaluate the physicochemical properties of ER and GPR, as well as the gelatinization rate, water soluble index (WSI), water adsorption index (WAI), DPPH radical scavenging activity and total dietary fiber content, the color value was carried out. The gelatinization rate was similar to 71.1~73.8%. Further, the results of WSI and WAI were increased at ER and GPR compared to the raw materials; ER was also higher than GPR. DPPH radical scavenging activity and total dietary fiber content showed a tendency to reduce after extrution and popping. As a result of the color value, the L value of ER decreased more than the raw materials, whereas GPR increased at a and b values.

• Korean Journal of Food Science and Technology
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• v.29 no.1
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• pp.72-76
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• 1997

The effect of the energy supplied in extrusion on the starch gelatinization was analyzed. The energy needed for extrusion is generated by motor and heater. The motor energy is transformed into a thermal energy by heat dissipation and a mechanical energy, and the heater energy is of a thermal energy. At the low barrel temperature $({\leq}80^{\circ}C)$, it was found out there are two kinds of thermal energy by heat dissipation: one by a powder friction of corn grit with low moisture contents and the other by a viscous dissipation of corn grit with high moisture contents. The dissipated thermal energy by the powder friction was more effective on the starch gelatinization than that by the viscous dissipation. The effect of the mechanical energy was also analyzed in terms of a relative mechanical energy. The gelatinization of corn grit with high moisture contents $({\geq}33%)$ largely depended on the change in the relative mechanical energy, whereas that with low moisture contents $({\leq}30%)$ hardly depended on it.