• Composites Research
• /
• v.13 no.1
• /
• pp.89-97
• /
• 2000

Fatigue damage detection and vibration sensing for a laminated composites and impact location detection for a steel beam have been carried out using optical fiber sensor. Intensity based optical fiber sensor is constructed by placing two cleaved fiber end in a hollow glass tube, and multiple reflection within the cavity is considered. Fatigue signals are measured by embedded optical fiber, surface mounted optical fiber sensor and strain gage simultaneously. For vibration sensing, optical fiber sensor is mounted on the carbon fiber composite beam and its response to free vibration and forced vibration is investigated. In impact location detection, two optical fiber sensors are used and the information obtained from two sensors is arrival time delay of vibration caused by impact. Impact location can be calculated from this time delay. The obtained results show that the intensity based optical fiber sensor provide reliable data during long-term fatigue loading, unlike strain gage which deteriorate during the early part of the fatigue test. Optical fiber sensor signals coincide with gap sensor in vibration sensing. The precise locations of impact can be detected within 4.1% error limit.

• Polymer(Korea)
• /
• v.39 no.2
• /
• pp.346-352
• /
• 2015

Polyalphaolefin (PAO) is a synthetic lubricant that is superior to mineral-based lubricants in the terms of physical and chemical characteristics such as low pour point, high viscosity index (VI), and thermal and oxidation stability. Several kinds of PAOs have been synthesized by using 1-pentene, 1-hexene, 1-octene, or 1-dodecene as monomer with three kinds of aluminum-based Lewis acid catalysts via cationic polymerization. The control of the catalytic performance and physical properties of PAO such like molecular weight, kinematic viscosity, pour point, and viscosity index was done by changing polymerization parameters. The alkyl aluminum halide-based catalysts show better catalytic activity than that of the conventional $AlCl_3$ catalyst. The microstructure of PAO was investigated by means of TOF-MS (time of flightmass spectroscopy) analysis in order to elucidate the correlation between the performances of the lubricant (VI, pour point) and the molecular structure of PAO. The VI of PAO increases with increases in the carbon number of ${\alpha}$-olefin. In other words, the performances of PAO as a lubricant strongly depended on the branch length of PAO.

• The Korean Journal of Mycology
• /
• v.26 no.1 s.84
• /
• pp.51-55
• /
• 1998

After bottle culture of Pleurotus ostreatus, sawdust was taken out from the bottle and accumulated in the middle of March, and then composted. As the result, Y value was decreased rapidly 30 days after composting, and it was decreased slowly after 30 days. It is considered that 118 days is required for composting, however, it is possible to use for casing material after at least 48 days composting. The pH and total nitrogen content of sawdust based on composting period had tendency to increase as composting was processed. Total carbon and C/N rate had tendency to decrease as time went on. Based on the rate of 10, 30 and 50%, each sawdust was added to clay loam used as casing material for culturing A. bisporrus. Among various treatments, the mycelial growth of A. bisporus was more favorable in the treatment of 30% sawdust than in the single treatment of clay loam. Based on the date necessary for primodium formation of A. bisporus, the primodium formation in the treatment of 30% sawdust was reduced to about 5 days as compared with that of any other treatments When 30% sawdust was added to clay loam used as casing material for culturing A. bisporus, the yield of its fruiting body was increased to 28%.

• Smart Structures and Systems
• /
• v.8 no.3
• /
• pp.303-320
• /
• 2011

Comparing to active damage monitoring, impact localization on composite by using time reversal focusing method has several difficulties. First, the transfer function of the actuator-sensor path is difficult to be obtained because of the limitation that no impact experiment is permitted to perform on the real structure and the difficulty to model it because the performance of real aircraft composite is much more complicated comparing to metal structure. Second, the position of impact is unknown and can not be controlled as the excitation signal used in the active monitoring. This makes it not applicable to compare the difference between the excitation and the focused signal. Another difficulty is that impact signal is frequency broadband, giving rise to the difficulty to process virtual synthesis because of the highly dispersion nature of frequency broadband Lamb wave in plate-like structure. Aiming at developing a practical method for on-line localization of impact on aircraft composite structure which can take advantage of time reversal focusing and does not rely on the transfer function, a PZT sensor array based phase synthesis time reversal impact imaging method is proposed. The complex Shannon wavelet transform is presented to extract the frequency narrow-band signals from the impact responded signals of PZT sensors. A phase synthesis process of the frequency narrow-band signals is implemented to search the time reversal focusing position on the structure which represents the impact position. Evaluation experiments on a carbon fiber composite structure show that the proposed method realizes the impact imaging and localization with an error less than 1.5 cm. Discussion of the influence of velocity errors and measurement noise is also given in detail.

• Journal of Digital Convergence
• /
• v.15 no.11
• /
• pp.231-243
• /
• 2017

This paper provides a review of the electrical sensing biosensors and examine research cases of biosensors based on clothing and textiels. A biosensor which can measure bio-signals is a device that senses the physical and chemical characteristics of biological materials by using biological sensing materials. Therefore, wellness wear that is closely integrated with the user's real life will play an important role in achieving U-Health. The biosensors' unique feature which can be differentiated from the existing sensors is it's using of selective reactions and binding of biological substances. The electrical sensing biosensors are very small in size due to the processing of electrical signals, which can be used to create ubiquitous. Therefore, it is necessary to study electrical sensing biosensors that are easy to miniaturize to develop wellness wear. This paper describes the electrical sensing biosensor (an electrochemical method nanowire/carbon nanotube FET method) in detail. Finally, the future direction of biosensors to be applied to wellness wear is suggested.

• Composites Research
• /
• v.12 no.4
• /
• pp.42-54
• /
• 1999

FMLC(Fiber-Metal Laminate Composites) is a new structural material combining thin metal laminate with adhesive fiber prepreg, it nearly include all the advantage of metallic materials, for example: good plasticity, impact resistance, processibility, light weight and excellent fatigue properties. This research studied the optimum design of the FMLC subject to various loading conditions using genetic algorithm. The finite element method based on the shear deformation theory was used for the analysis of FMLC. Tasi-Hill failure criterion and Miser yield criterion were taken as fitness functions of the fiber prepreg and the metal laminate, respectively. The design variables were fiber orientation angles. In genetic algorithm, the tournament selection and the uniform crossover method were used. The elitist model was also used to be effective evolution strategy and the creeping random search method was adopted in order to approach a solution with high accuracy. Optimization results were given for various loading conditions and compared with CFRP(Carbon Fiber Reinforced Plastic). The results show that the FMLC is more excellent than the CFRP in point and uniform loading conditions and it is more stable to unexpected loading because the deviation of failure index is smaller than that of CFRP.

• Food Science and Preservation
• /
• v.13 no.3
• /
• pp.363-368
• /
• 2006

This study was performed to develop flavor materials from Elsholtzia ciliata Hylander with analyzing functionality and aroma profile and to optimize supercritical fluid extraction method and optimum condition. The qualities of water extracts such as total yield total phenolic compound electron donation ability, estragole and L-carvone, were affected by extraction pressure than time. The response variables had significant with pressure than with time and the established polynomial model was suitable(P>0.05) model by Lack-of-Fit analysis. The optimum extraction conditions which were limited of maximum value for dependent variables under experimental conditions based on central composite design were 238 bar and 42 min.

• Proceeding of Spring/Autumn Annual Conference of KHA
• /
• 2009.04a
• /
• pp.222-225
• /
• 2009

The apartment housing in Korea has been rapidly constructed by adapting the most suitable construction methods as like wall structure, wet and united construction. But most of short-lived equipments usually filled in the structure which has longer life, and it causes not only to make difficult coping with the deterioration of equipments but also to let buildings remained deteriorate themselves. The buildings can be remodelled to slow down the terms of deterioration or reconstructed to give a new life of themselves, although the disposal of wastes or the lack of natural resources still be problems and unsolved that can occurred in pulling down and reconstructing the buildings. Furthermore, it is the time to need keeping with worldwide trends and movements as like sustainability or 'green growth' movements based on low carbon emissions. The researches for Long-Life Housing apartments which has durability and variation have been advanced up to now. Long-Life Housing apartments can separate their structures from equipments and interior or exterior materials of buildings. Therefore equipments or materials of buildings can be easily repaired and replaced with new ones, even if they are deteriorated themselves. Also, the construction process of Long-Life Housing apartments can be independent from the matter of proprietary rights, terms of durability, decision rights and so on. 'The law of Possession and Management of Collective Building' and the 'Regulation of Management of Collective Building' established by each local governments are already legislated for declaring the rights of using and ownership, responsibilities of each parts of apartment buildings. These laws and regulations classify the ownership of each parts of apartment buildings, and divide the ownership with public possession and exclusive possession. Therefore, this study will conduct comparative analysis between 'The law of Possession and Management of Collective Building' and 'the Regulation of Management of Collective Building' and find problems which can be occurred in future construction of Long-Life Housing apartments. It will be helpful to revise laws and regulations.

• KIEAE Journal
• /
• v.14 no.1
• /
• pp.113-120
• /
• 2014

The Green growth has been demanded in all industrial sectors due to environmental destruction and exhaustion of natural resources. Buildings have consumed 1/3 of the total energy and 40% of natural resources and have accounted for 50% of $CO_2$ emissions and 30-50% of waste materials. In 1991, BREEAM(Building Research Establishment Environmental Assessment Method) of the British BRE(Building Research Establishment) had begun reduction of $CO_2$ emissions and energy saving movements, in which all the countries around the world have participated. The Republic of Korea has taken part in this trend by declaring a "National Vision in the Green Growth" in 2008 and implementing regulations on "Low Carbon, Green Growth" in 2010. G-SEED(Green Standard for Energy and Environmental Design) based on GBCS(Green Building Certification System) has been actively promoted for its application. This study has limited its scope to G-SEED office buildings. It has conducted surveys of problems and assessment items of the G-SEED identified in the preceding study by the AHP(Analytic hierarchy process) method. The purpose of this study is to conduct a comparison analysis of problems and ranking of evaluation items recognized in the survey and to be presented as reference materials for G-SEED system improvements at its next amendments.

• Composites Research
• /
• v.25 no.5
• /
• pp.136-140
• /
• 2012

This paper describes the bone healing process of fractured long bones such as a tibia applied by composite IM rods using finite element analysis. To simulated tissue differentiation process mechano-regulation theory with a deviatoric strain was implemented and a user's subroutine programmed by a Python code for an iterative calculation was used. To broadly find the appropriate rod modulus for healing bone fractures, composite IM rods were analyzed considering the stacking sequence. To compare mechanical stimulation at fracture gap, two kinds of initial loading conditions were applied. As a result, it was found that the initial loading condition was the most sensitive factor for the healing performance. In case a composite IM rod made of a plain weave carbon fiber/epoxy (WSN3k) had a stacking sequence of $[{\pm}45]_{nT}$, the healing efficiency was the most effective under a initial load of 10%BW.