• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.42 no.9
• /
• pp.745-751
• /
• 2014

For the multi-nozzle propulsion, the rupture pressure of nozzle closure has an effect on the initial strain rate of ignition. Moreover, the deviation of rupture pressure for each nozzle closure leads to side forces which can disturb the attitude control of rocket. When designed, it should be considered whether nozzle closures are ruptured equally and exactly in the intented pressure. In this paper, the rupture behavior is analyzed by analytical and experimental methods for plate and "+" notched nozzle closures. The rupture pressure and deviation for operating temperature, whether notched or not and notched directions are analyzed. This paper provides a comparison between rupture pressure prediction of finite elements method which tool is Abaqus/Explicit and results of the rupture test. Jonson-Cook shear failure model which corresponds to the damage initiation criterion were used in this simulation.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.9 no.6
• /
• pp.1-9
• /
• 2009

An analysis program to predict the behavior of a concrete filled steel tube column (CFT) was developed. It considered confining effect, material nonlinearity, strain hardening of steel, and initial axial load. With the developed program, axial load-bending moment interaction analyses, moment-lateral displacement relation analyses, and lateral load-lateral displacement relation analyses were performed. For the verification of the developed program, analysis results were compared with the test results from the other researches. The verified results showed that the developed program predicted the behavior of the CFT column with agreeable accuracy. And they showed that it is necessary to consider the confining effect for the reasonable analysis of the CFT column. A simple parametric study was performed and it chose the strength of unconfined concrete and the thickness of a steel tube as the major parameters affecting the behavior of the CFT column. The parametric analysis results showed that the CFT column had higher strength and smaller ductility by increasing the strength of concrete. But the CFT column showed higher strength and larger ductility by increasing the thickness of the steel tube.

• Food Science and Biotechnology
• /
• v.18 no.5
• /
• pp.1100-1108
• /
• 2009

Lactic acid bacteria (LAB) isolated from various fruits and vegetables were screened in order to determine appropriate fermentation starters for manufacturing functional fermented onion juice. From the initial screening test comprising more than 700 isolated LAB, 16 isolates were selected based on their acid production rate. Among the selected isolates, the fermentation broth of KC-007 exhibited the highest electron donating and nitrite scavenging activities, with values at pH 1.2 of 95.6 and 68.7%, respectively. From the overall results obtained in this study, we finally selected the bacterium KC-007 as a fermentation starter. This bacterium was identified and named as Pediococcus pentosaceus based on its morphological and physiological characteristics, carbon-utilization pattern (as assessed using an API 50CHL kit), and molecular genetic characteristics (as assessed using the nucleotide sequence of the 16S rRNA gene). The optimal temperature, pH, and starter inoculation concentration (v/v) required for growth of the isolated strain were $40^{\circ}C$, pH 4.0-6.0, and 2%(v/v), respectively.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.11 no.1
• /
• pp.72-79
• /
• 2006

Kojic acid production by Aspergillus flavus strain S44-1 using sucrose as a carbon source was carried out in a 250-mL shake flask and a 2-L stirred tank fermenter. For comparison, production of kojic acid using glucose, fructose and its mixture was also carried out. Kojic acid production in shake flask fermentation was 25.8 g/L using glucose as the sole carbon source, 23.6 g/L with sucrose, and 6.4 g/L from fructose. Reduced kojic acid production (13.5 g/L) was observed when a combination of glucose and fructose was used as a carbon source. The highest production of kojic acid (40.2 g/L) was obtained from 150 g/L sucrose in a 2 L fermenter, while the lowest kojic acid production (10.3 g/L) was seen in fermentation using fructose as the sole carbon source. The experimental data from batch fermentation and resuspended cell system was analysed in order to form the basis for a kinetic model of the process. An unstructured model based on logistic and Luedeking-Piret equations was found suitable to describe the growth, substrate consumption, and efficiency of kojic acid production by A. flavus in batch fermentation using sucrose. From this model, it was found that kojic acid production by A. flavus was not a growth-associated process. Fermentation without pH control (from an initial culture pH of 3.0) showed higher kojic acid production than single-phase pH-controlled fermentation (pH 2.5, 2.75, and 3.0).

• KSBB Journal
• /
• v.17 no.6
• /
• pp.555-559
• /
• 2002

Three different strains of Aureobasidium pullulans were grown in batch cultures to compare their abilities of enzyme production. It was found that specific enzyme activity was the highest with strain ATCC 9348 and the enzyme production was closely coupled to growth. Studies on morphology during the growth of A. pullulans revealed that mycelia cells were dominant at the initial stages of growth. However, yeast-like cells and chlamydospores were dominant in the latter stages of batch culture. The pattern of morphological changes during the growth period was not affected by pH. However, it appears that the ratio of intra- to extracellular enzyme activity tended to increase with fermentation time irrespective of the pH employed, suggesting that the secretion efficiency of intracellular enzyme to broth likely depends on cell morphology Using molasses as a cheap source of sucrose, enzymatic production of fructo-oligosaccharides as a feed additive with A. pullulans cells could be achieved successfully at 55$\^{C}$ and pH 5.5.

• The Journal of Natural Sciences
• /
• v.8 no.1
• /
• pp.145-151
• /
• 1995

The stretching of synthetic fibers by hot dry process is very difficult, because these fibers have high glass transition temperature at above $150^{\circ}C$. But, we used a swell-wet stretching precess; the fibers are stretched in a swelling agent such as organic solvents at lower temperature. In this study, 100% acryl fibers were uniaxially stretched with free width at $70^{\circ}C$ by swell-wet process in organic solvents. The stretchability was estimated by stretching work. This work is concerned with stretching stress and strain, and initial modulus. We found that it is a good parameter for the estimatation of high strength to the acrylic fiber. The effects of stretching conditions on the molecular orientation for high strength and mechanical properties of PAN fibers were measured.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.17 no.4
• /
• pp.423-431
• /
• 2004

For the fracture mechanics analysis of cracks in welds of dissimilar steels, residual stress analysis and fracture analysis must be performed simultaneously. The standard definition of the J -integral leads to a path dependent value in the presence of a residual stress field. And unlike cracks in homogeneous materials, a bimaterial interface crack always induces both opening and shearing modes of stress in the vicinity of the crack tip. Therefore, it is necessary to develope a path independent J-integral definition for a crack in a residual stress field generated by welding of dissimilar steels. This paper addresses the modification of the Rice-J-integral to produce a path independent J -integral when residual stresses due to welding of dissimilar steels and external forces are present. The residual stress problem is treated as an initial strain problem and the J-integral proposed for this class of problems is used. And a program which can evaluate the J -integral for a crack in a weld of dissimialr steels is developed using proposed J integral definition.

• Mycobiology
• /
• v.29 no.3
• /
• pp.160-163
• /
• 2001

Sikhae is a Korean traditional beverage of saccharified rice. Its factory waste(SFW) is usually thrown away instead of being used. We developed a cheap substrate of SFW for use in liquid spawn that is known for its higher fruit body yields than grain spawn in sawdust cultivation. Mycelia of Lentinula edodes ASI 3046, which is regarded as the most suitable strain for sawdust cultivation, were cultured on six kinds of previous known media and SFW. As the seven kinds of media were applied, a Sikhae Factory Waste(SFW) was most excellent in growth. The dried mycelial weight in SFW was almost four times as much as that in the other media. In the flask culture, optimum culture conditions for the mycelial growth were obtained after 13 days of cultivation at media volume of 100 ml, 100 rpm, initial pH 4.5, and $25^{\circ}C$. The best mycelial growth was observed when $MgSO_4{\cdot}7H_2O$ and D-sucrose were added as a supplement in SFW. SWM must be a remarkable medium for L. edodes because of its simple preparation and low cost.

• Korean Journal of Food Science and Technology
• /
• v.24 no.5
• /
• pp.451-455
• /
• 1992

In the medium containing 7% rice powder, 0.15% $NH_4NO_3$ and 0.1% $MnSO_4$ with initial pH 6.0, the red pigment production by Monascus anka albidus was observed. The mycelium were cultured at $30^{\circ}C$ for 5 days with reciprocal shaking (130 rpm). As a carbon source, glutinous rice gave the highest production of pigment. Ammonium nitrate and $KH_2PO_4$ as a nitrogen source and phosphate source, respectively, stimulated best the production of the red pigment. The optimum C:N ratio was found to be 18:1. The production of the pigment by the strain was 2.6 mg/ml in a flask, but 1.8 mg/ml in 5l fermentor, respectively.

• Journal of Biomedical Engineering Research
• /
• v.17 no.1
• /
• pp.61-70
• /
• 1996

In cementless total hip arthroplasty(THA), an initial stability of the femoral component is mandatory to achieve bony inyowth and secondary long term fixation. Primary stability of the femoral component can be obtained by minimizing the magnitude of relative micromotions at bone stem interface. An accurate evaluation of interf'ace micromotion and stress/strain fields in the bone-implant system may be relevant for better understanding of clinical situations and improving THA design. Recently finite element method(FEM) was introduced in'orthopaedic research field due to its unique capacity to evaluate stress in structure of complex shape, loading and material behavior. The authors developed the 3-dimensional finite element model of proximal femur with $Multilock^{TM}$ stem of 1179 blick elements to analyse the micromotions and mechanical behaviors at the bone-stem inteface in early post-operative period for the load simulating single leg stance. The results indicates that the values of relative motion for this well fit stem were $150{\mu}m$ in maximum $82{\mu}m$ in minimum and the largest relative motion was developed in medial region of Proximal femur and in anterior-posterior direction. The motion in the proximal bone was much greater than in the distal bone and the stress pattern showed high stress concentration on the cortex near the tip of the stem. These findings indicate that the loading on the hip joint in the early postoperative situation before achieving bony ingrowth could produce large micromotion of $150{\mu}m$ and clinicaly non-cemented THA patient should not be allowed weight bearing strictly early in the postoperative period.