• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.38 no.9
• /
• pp.862-868
• /
• 2010

Development of a small scale aircraft has been carried out for the BASA(Bilateral Aviation Safety Agreement) program in Korea. This aircraft adopted all the composite structures for environmental friendly by low fuel consumption due to its lightness behavior. However the composite structure has s disadvantage which is very weak against impact due to foreign object damages. Therefore the aim of this study is focusing on the damage evaluation and repair techniques of the aircraft composite structure. The damages of composite laminates including the carbon/epoxy UD laminate and the carbon/epoxy fabric face sheets-honeycomb core sandwich laminate were simulated by a drop weight type impact test equipment and the damaged specimen were repaired using the external patch repair method after removing damaged area. The compressive strength test and analysis results after repairing the impact damaged specimens were compared with the compressive strength test and analysis results of undamaged specimens and impact damaged specimens. Finally, the strength recovery capability by repairing were investigated.

• Journal of Dairy Science and Biotechnology
• /
• v.33 no.4
• /
• pp.271-275
• /
• 2015

Colloidal semiconductor CdSe-ZnS core-shell nanocrystal quantum dot (Qdot) are luminescent inorganic fluorophores that show potential to overcome some of the functional limitations encountered with organic dyes in fluorescence labeling applications. Salmonella Enteritidis has emerged as a major cause of human salmonellosis worldwide since the 1980s. A rapid, specific, and sensitive method for the detection of Salmonella Enteritidis was developed using Qdot as a fluorescence marker coupled with immunomagnetic separation. Magnetic beads coated with anti-Salmonella Enteritidis antibodies were employed to selectively capture the target bacteria, and biotin-conjugated anti-Salmonella antibodies were added to form sandwich immune complexes. After magnetic separation, the immune complexes were labeled with Qdot via biotin-streptavidin conjugation, and fluorescence measurement was carried out using a fluorescence measurement system. The detection limit of the Qdot method was a Salmonella Enteritidis concentration of $10^3$ colony-forming units (CFU)/mL, whereas the conventional fluorescein isothiocyanate-based method required over $10^5CFU/mL$. The total detection time was within 2 h. In addition to the potential for general nanotechnology development, these results suggest a new rapid detection method of various pathogenic bacteria from a complex food matrix.

• Steel and Composite Structures
• /
• v.29 no.1
• /
• pp.77-90
• /
• 2018

This paper presents a combined numerical, experimental, and theoretical study on the behavior of the concrete-filled double circular steel tubular (CFDT) stub columns under axial compressive loading. Four groups of stub column specimens were tested in this study to find out the effects of the concrete strength, steel ratio and diameter ratio on the mechanical behavior of CFDT stub columns. Nonlinear finite element (FE) models were also established to study the stresses of different components in the CFDT stub columns. The change of axial and transverse stresses in the internal and external steel tubes, as well as the change of axial stress in the concrete sandwich and concrete core, respectively, was thoroughly investigated for different CFDT stub columns with the same steel ratio. The influence of inner-to-outer diameter ratio and steel ratio on the ultimate bearing capacity of CFDT stub columns was identified, and a reasonable section configuration with proper inner-to-outer diameter ratio and steel ratio was proposed. Furthermore, a practical formula for predicting the ultimate bearing capacity was proposed based on the ultimate equilibrium principle. The predicted results showed satisfactory agreement with both experimental and numerical results, indicating that the proposed formula is applicable for design purposes.

• Journal of Korean Society of Steel Construction
• /
• v.24 no.3
• /
• pp.349-360
• /
• 2012

This paper describes a detailed assessment of the structural safety, serviceability, capacity rating and long-term performance of a glass fiber-reinforced polymer (GFRP) slab bridge superstructure. This first all-GFRP slab bridge was installed in Korea on May 2002. The GFRP slab bridge is a simply supported, its length is 10.0 m, and is designed to carry two-lane traffic and has an overall width of 8.0m. The GFRP slab bridge is a sandwich structure with a corrugated core, fabricated by hand lay-up process with E-glass fibers and vinyl ester resins. The assessment of long-term performance for the GFRP slab bridge in 2004, 2011 includes a field load testing identical to that performed in 2002. The assessment indicates that the GFRP slab bridge has no structural problems and is structurally performing well in-service as expected. The assessment may provide a baseline data for the capacity ratings assessment of the GFRP slab bridge and also serve as part of a long-term performance of all-GFRP bridge superstructure.

• Composites Research
• /
• v.29 no.4
• /
• pp.203-208
• /
• 2016

Metal and polymer sandwich composites, which are made of sheet metal sheath and polymer or fiber reinforced plastic core, have been reconsidered as an alternative to sheet metal due to their lightness and multifunctional properties such as damping and sound-proof properties. For the successful applications of these composites, the delamination prediction based on the adhesion strength is important element. In this study, the numerical simulation of the delamination behavior of polymeric adhesive tapes with metallic surfaces was performed using cohesive zone elements and finite element software. The traction-separation law of the cohesive zone element was defined using the fracture energy derived from peel mechanics and experimental results from peel test and implemented in finite element software. The peel test of the polymeric adhesive film against steel surface was simulated and compared with experiments, demonstrating reasonable agreement between simulation and experiment.

• Korean Journal of Adult Nursing
• /
• v.17 no.5
• /
• pp.719-731
• /
• 2005

Purpose: This research was conducted to explore the experience of middle-aged women parting with their children and to develop a grounded theory. Method: The participants were 11 women in their 50's who had experienced parting with their children due to schooling, military service and marriage. The grounded theory methodology based on symbolic interactionism was used. Results: 106 concepts, 30 subcategories and 14 categories were derived from the analysis through processes of open coding, axial coding and selective coding. The central phenomenon was 'happy but sad' and the core category was a process of 'independence that is sorrowful yet delightful'. Four types were identified; the independent-type; submissive -type; family-reliant-type ; and fragile-type; based on the attachment to the child, state of mind, satisfaction of the situation, family support system and self-achievement. Conclusion: This research identified that the modern Korean middle-aged women who are considered to be the 'sandwich generation' since they have experienced a turbulent history and the change from a confucian parent-child lifestyle to a couple-oriented one, moved away from an attitude dependent on children in parting with them and started preparing for an independent late life. Based on the results, the verification research is advised on the variables that affect the experience of parting with children.

• Composites Research
• /
• v.17 no.3
• /
• pp.15-22
• /
• 2004

Acoustic load generated by rocket propulsion system is one of major dynamic loads during lift-off phase so that it causes the structural failure and electronic malfunction of payloads. Acoustic loads can be greatly reduced by an appropriate acoustical design of nose faring structures. This paper deals with the acoustical design of the nose fairing structure for launch vehicle. It is well known that a honeycomb sandwich structure is a poor sound insulator because of its high specific stiffness. In this paper, the sound transmission characteristics of four kinds of honeycomb structures for noise fairing were investigated by means of numerical and experimental ways. In order to estimate transmission loss, infinite plate theory by Moore and Lyon and statistical energy analysis (SEA) method were used. The predicted results showed a good agreement with measured ones. These enabled us to determine a proper core material for nose fairing, which shows good sound insulation performance per weight.

• Journal of the Society of Naval Architects of Korea
• /
• v.35 no.1
• /
• pp.88-97
• /
• 1998

Large aluminium extrusions can be used in rolling stocks and high speed vessels to reduce weight and labor cost. As sandwich plates with corrugated core have enough strength in transverse and longitudinal direction, welding lines to connect members are reduced and transverse members to strength longitudinal members are not required. However, for proper design of aluminium extrusion plates, understanding of structural behaviors of the exclusions are necessary. In this paper, at first, detailed finite element analysis is carried out to understand structural behavior. And then, simple theoretical formulas for design purpose are proposed using the orthotropic plate theory. Shear stresses resulting from end twisting which is characteristics of deep aluminium extrusion plates can also be calculated by the simple theoretical formula. Comparison with the results by detailed finite element analysis shows good accuracy of the proposed simple formulas. The simple formulas can be useful in repetitive analysis in the initial design stage.

• Molecules and Cells
• /
• v.39 no.6
• /
• pp.495-500
• /
• 2016

We have solved the crystal structure of a predicted fructose-specific enzyme $IIB^{fruc}$ from Escherichia coli ($EcEIIB^{fruc}$) involved in the phosphoenolpyruvate-carbohydrate phosphotransferase system transferring carbohydrates across the cytoplasmic membrane. $EcEIIB^{fruc}$ belongs to a sequence family with more than 5,000 sequence homologues with 25-99% amino-acid sequence identity. It reveals a conventional Rossmann-like ${\alpha}-{\beta}-{\alpha}$ sandwich fold with a unique ${\beta}$-sheet topology. Its C-terminus is longer than its closest relatives and forms an additional ${\beta}$-strand whereas the shorter C-terminus is random coil in the relatives. Interestingly, its core structure is similar to that of enzyme $IIB^{cellobiose}$ from E. coli ($EcIIB^{cel}$) transferring a phosphate moiety. In the active site of the closest $EcEIIB^{fruc}$ homologues, a unique motif CXXGXAHT comprising a P-loop like architecture including a histidine residue is found. The conserved cysteine on this loop may be deprotonated to act as a nucleophile similar to that of $EcIIB^{cel}$. The conserved histidine residue is presumed to bind the negatively charged phosphate. Therefore, we propose that the catalytic mechanism of $EcEIIB^{fruc}$ is similar to that of $EcIIB^{cel}$ transferring phosphoryl moiety to a specific carbohydrate.

• Journal of Sensor Science and Technology
• /
• v.24 no.6
• /
• pp.379-384
• /
• 2015

An infrared image sensor is a core device in a thermal imaging system. The fabrication method of a focal plane array (FPA) is a key technology for a high resolution infrared image sensor. Each pixels in the FPA have $Si_3N_4/SiO_2$ membranes including legs to deposit bolometric materials and electrodes on Si readout circuits (ROIC). Instead of polyimide used to form a sacrificial layer, the feasibility of an amorphous silicon (${\alpha}-Si$) was verified experimentally in a $8{\times}8$ micro-bolometer array with a $50{\mu}m$ pitch. The elimination of the polyimide sacrificial layer hardened by a following plasma assisted deposition process is sometimes far from perfect, and thus requires longer plasma ashing times leading to the deformation of the membrane and leg. Since the amorphous Si could be removed in $XeF_2$ gas at room temperature, however, the fabricated micro-bolomertic structure was not damaged seriously. A radio frequency (RF) sputtered nickel oxide film was grown on a $Si_3N_4/SiO_2$ membrane fabricated using a low stress silicon nitride (LSSiN) technology with a LPCVD system. The deformation of the membrane was effectively reduced by a combining the ${\alpha}-Si$ and LSSiN process for a nickel oxide micro-bolometer.