• Journal of the Korea Institute of Military Science and Technology
• /
• v.21 no.1
• /
• pp.25-39
• /
• 2018

In this paper, an integrated analysis model for evaluating the underwater acoustic performance of the multilayered acoustic coatings containing visco-elastic composite layers with hollow glass microspheres is described. The model uses the effective medium theory considering the acoustic scattering and resonance effects of the inclusions. Also, the model incorporates the compressive deformation mechanism associated with hydrostatic pressure. The technique developed in this work was used as the acoustic layer design and performance analysis tools for the practical hull coatings and acoustic baffles in Korean next generation submarines.

• Steel and Composite Structures
• /
• v.17 no.4
• /
• pp.453-470
• /
• 2014

This article is the result of an investigation on the influence of a Pasternak elastic foundation on the stability of exponentially graded (EG) cylindrical shells under hydrostatic pressure, based on the first-order shear deformation theory (FOSDT) considering the shear stresses. The shear stresses shape function is distributed parabolic manner through the shell thickness. The governing equations of EG orthotropic cylindrical shells resting on the Pasternak elastic foundation on the basis of FOSDT are derived in the framework of Donnell-type shell theory. The novelty of present work is to achieve closed-form solutions for critical hydrostatic pressures of EG orthotropic cylindrical shells resting on Pasternak elastic foundation based on FOSDT. The expressions for critical hydrostatic pressures of EG orthotropic cylindrical shells with and without an elastic foundation based on CST are obtained, in special cases. Finally, the effects of Pasternak foundation, shear stresses, orthotropy and heterogeneity on critical hydrostatic pressures, based on FOSDT are investigated.

• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.1
• /
• pp.65-70
• /
• 2002

An analysis method for calculating motion accuarcy of double sides hydrostatic table is proposed in this paper. In this method, profiles of each rails are assumed as periodic function, therefore it is represented as the sum of spacial frequencies. Bearing clearance at any position rail is depended on the variation of linear, angular motion error of table and the form errors of both sides of a rail. Finite element method is applied to calculate pressure distributions in bearing clearance. In order to simplify the analyzing process, double sides table model is converted into equivalent single side table model. Results calculated by the proposed modeling method agree well with the results directly caculated by double sides modeling method, and also agree well with experimental results. From the theoretical and experimental analysis, it is verified that the proposed analysis method is very effective to analyze the motion accuracy of double sides hydrostatic table.

• Journal of Aerospace System Engineering
• /
• v.8 no.2
• /
• pp.7-13
• /
• 2014

In order to enable fail-safe operation the electro-hydrostatic actuators can be dualized. When a symmetrical actuator is combined in series with an asymmetrical actuator with single rod cylinder, the flow rates of their cylinders are unmatched. If their position controller has same configuration, one of their pumps can supply too much flow rate under particular load conditions, which should be bypassed into low pressure side e.g. by a relief valve. In this paper it is shown how the hydraulic circuit for the asymmetrically combined electro-hydrostatic actuator can be designed without sacrificing power consumption.

• Proceedings of the Korean Ceranic Society Conference
• /
• 2004.04b
• /
• pp.44.1-44.1
• /
• 2004

• YAKHAK HOEJI
• /
• v.57 no.5
• /
• pp.323-329
• /
• 2013

This study was designed to determine and compare the cognitive enhancing effect of various Codonopsis lanceolata extracts by steaming, fermentation and high hydrostatic pressure process. We prepared water extract of C. lanceolata, steamed C. lanceolata, steamed and fermented C. lanceolata and C.lanceolata by high hydrostatic pressure process and fermentation. Cognitive enhancing effect of extracts was evaluated in scopolamine-induced memory impairment mice using by passive avoidance test and Morris water maze tests. MTT assay was conducted to investigate neuroprotective effect on glutamate induced cell death in HT22 cells. Steamed and fermented C. lanceolata water extract decreased escape latency in Morris water maze test and increased the latency time of the passive avoidance test compared to other extracts. Furthermore, the steamed and fermented C. lanceolata water extract showed neuroprotective effect. These results suggest that steaming and fermentation process more improve cognitive enhancing effect of C. lanceolata than other process.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.3
• /
• pp.196-203
• /
• 2007

The postbuckling behavior and failure of composite cylinders subjected to external hydrostatic pressure are investigated by a finite element method and test. A nonlinear finite element program, ACOS, is used for the postbuckling progressive failure analysis of composite cylinders. A total of 5 carbon/epoxy composite cylinders were fabricated and tested to verify the finite element results. For comparison, analyses by MSC/NASTRAN and MSC/MARC are additionally conducted. Among the softwares, the finite element program, ACOS, predicts the buckling loads the best with about 11 to 26% deviation from experimental results except for one specimen. While the finite element analysis shows global buckling modes with 4 waves in hoop direction, in the experiments the local buckling appears first and results in the final failure without global buckling.

• Food Science of Animal Resources
• /
• v.36 no.2
• /
• pp.283-288
• /
• 2016

The objective of this study was to investigate the microbial count of duck meat and duck meat products commercially available in Korea. High hydrostatic pressure (HHP) treatment was applied at 0.1, 300, 400, and 500 MPa for 5 min to enhance the microbiological safety of duck meats. The levels of total aerobic bacteria were in the ranges of 3.53-6.19 and 3.62-6.85 Log CFU/g in raw and smoked duck products, respectively. By DNA sequence analysis, we identified microorganisms responsible for spoilage, with the most common species in the raw and smoked duck products being Aeromonas spp. or Pseudomonas spp. and Leuconostoc mesenteroides, respectively. HHP treatment significantly reduced the levels of total aerobic bacteria in raw and smoked duck products. This study demonstrates that HHP treatment may be used to effectively improve the safety of raw and smoked duck meat products.

• Journal of Ginseng Research
• /
• v.44 no.1
• /
• pp.154-160
• /
• 2020

Background: Korean ginseng (Panax ginseng Meyer) powder is in rising demand because powder forms of foods are convenient to handle and are highly preservable. However, ginseng powder (GP) manufactured using the conventional process of air drying and dry milling suffers nutrient destruction and a lack of microbiological safety. The objective of this study was to prepare GP using a novel process comprised of UV-TiO₂ photocatalysis (UVTP) as a prewashing step, wet grinding, high hydrostatic pressure (HHP), and freeze-drying treatments. Methods: The effects of UVTP and HHP treatments on the microbial population, ginsenoside concentration, and physiological characteristics of GP were evaluated. Results: When UVTP for 10 min and HHP at 600 MPa for 5 min were combined, initial 4.95 log CFU/g-fw counts of total aerobes in fresh ginseng were reduced to lower than the detection limit. The levels of 7 major ginsenosides in UVTP-HHP-treated GP were significantly higher than in untreated control samples. Stronger inhibitory effects against inflammatory mediator production and antioxidant activity were observed in UVTP-HHP-treated GP than in untreated samples. There were also no significant differences in CIELAB color values of UVTP-HHP-treated GP compared with untreated control samples. Conclusion: Combined processing of UVTP and HHP increased ginsenoside levels and enhanced the microbiological safety and physiological activity of GP.

• Food Science of Animal Resources
• /
• v.29 no.3
• /
• pp.317-324
• /
• 2009

In order to reduce the increased hardness of beef bulgogi due to hydrostatic pressure (HP), kiwifruit (Actinidia chinensis) was applied. To understand the changes of shear force in beef bulgogi with kiwifruit induced by HP, changes in chemical properties of myofibril (Mf) with 10% kiwifruit induced by HP were investigated. From the SDS-PAGE patterns of Mf with 10% kiwifruit, there was an observed increase in the degradation of myosin heavy chain (MHC) by HP (300-500 MPa) to that by 0.1 MPa. This result indicates that HP may enhance enzyme action from a kiwifruit for the degradation of MHC, and the similar phenomenon occurred in the beef bulgogi with kiwifruit induced by HP. The shear force of beef bulgogi without a kiwifruit induced by 400 and 500 MPa significantly increased compared to that by 0.1 MPa (p<0.05). However, in the beef bulgogi with 10% or 20% kiwifruit, the shear force induced by 400 or 500 MPa was similar or slightly lower than that by 0.1 MPa. Consequently, adding kiwifruit to bulgogi could reduce the hardness of HP-induced beef bulgogi due to the enzyme action in the kiwifruit accelerated by HP.