• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.2
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• pp.102-106
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• 2007

While the effort has been made in recycling the FRP (Fiber Reinforced Plastic) used for the medium-to-small size ships, researchers try to find out the methods more favorable for the environments and more value-added. In respect to the fact that the FRP consists of two types of layers, roving and mat, differentiated by the 2-dimensional structure, our group was able to separate the layers of FRP instead of grinding it. The roving cloth was cut to the long glass fibers (about 50 mm long; calling it 'F-fiber' afterwards). F-fiber showed increasing tensile strength and chemical-resistance possibly due to the remained resin (about 25% by weight). In this experiment fiber-reinforced mortars are made of the F-fiber as a recycling method of FRP. The mortar containing 2% (v/v) F-fiber results in 34.6% increment of bending strength from the standard after 28 day curing. The resulting strength is similar to that of the mortar with imported polyvinyl fiber P-54. These results imply that F-fiber can be applied to the 'fiber reinforced mortar' and furthermore may be a substitute for the imported fibers.

• Science of Emotion and Sensibility
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• v.13 no.2
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• pp.327-336
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• 2010

The purposes of this study are to evaluate mechanical properties and sensibility of tencel jacquard fabrics treated with ginkgo biloba extract and silicon softener, and to contribute to the research and development of the bedclothes made of the tencel jacquard fabrics. Mechanical properties and objective fabric hand evaluation were measured by using KES-FB system. Subjective sensibilities such as sensory, touch, and purchasing preference were estimated by using blind field test. The tensile properties such as EM, WT, and RT of tencel jacquard fabrics treated with ginkgo biloba extract and silicon softener showed increase. Bending properties and shear properties were decreased, but compression properties were increased compared to untreated fabric. With ginkgo biloba extract and silicon softener treatment, thickness and weight were increased. Therefore, tencel jacquard fabrics became more stretchable, softer, and bulkier than untreated fabrics. Consequently, THV of tencel jacquard fabrics treated with ginkgo biloba extract and silicon softener were increased. When fabrics were treated sequentially with ginkgo biloba extract and silicon softener, fabrics were estimated softer, more flexible, and bulkier than untreated fabrics. Also, tencel jacquard fabrics treated with ginkgo biloba extract and silicon softener were estimated to have good touch and preference.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.1
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• pp.97-106
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• 2011

Purpose: This review article was written to theoretically compare the depressing force (pressure, adhesion) to the cornea between when the spherical lenses were being tightly and flat fitted. Methods: Mathematical equations and their numerical solution programs (model) were formulated to calculate the depressing (adhesion) force to the cornea by both the tightly and flat fitted contact lenses. Based on this proposed model the effects of parameters characterizing a contact lens such as BCs, diameters, edge shape and corneal shape (ratio of long and short corneal axis, p) on the depressing force to the cornea were predicted/analyzed in both tightly and flat fitting regimes. Results: Corneal adhesion increased as the corneal p-value increased. Adhesion increase caused by the increased p-value was much larger in flat fitted case than in tight fitted one. Corneal adhesion reduced abruptly as the BC increased in flat fitting regimes while the adhesion rise was insignificant in tight fitting ones. Reduction in corneal adhesion due to lens-size increase was predicted to be insignificant in both tight and flat fitting regimes. Both the lens edge shape (edge angle) and thickness were relevant only in tight fitting regime. Corneal adhesion increased as the increased with tight-fitted lenses. As the thickness of tight fitted lenses increased, corneal adhesion inversely decreased. Conclusions: The two most significantly affecting the depressing force to cornea were found to be the degree of corneal bending toward the periphery and the BCs of lenses.

• Wind and Structures
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• v.23 no.6
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• pp.559-575
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• 2016

In order to investigate the influence of different blade positions on aerodynamic load and wind loads and load-effects of large scale wind turbine tower under the halt state, we take a certain 3 MW large scale horizontal axis three-blade wind turbine as the example for analysis. First of all, numerical simulation was conducted for wind turbine flow field and aerodynamic characteristics under different halt states (8 calculating conditions in total) based on LES (large eddy simulation) method. The influence of different halt states on the average and fluctuating wind pressure coefficients of turbine tower surface, total lift force and resistance coefficient, circular flow and wake flow characteristics was compared and analysed. Then on this basis, the time-domain analysis of wind loads and load-effects was performed for the wind turbine tower structure under different halt states by making use of the finite element method. The main conclusions of this paper are as follows: The halt positions of wind blade could have a big impact on tower circular flow and aerodynamic distribution, in which Condition 5 is the most unfavourable while Condition 1 is the most beneficial condition. The wind loads and load-effects of disturbed region of tower is obviously affected by different halt positions of wind blades, especially the large fluctuating displacement mean square deviation at both windward and leeward sides, among which the maximum response occurs in $350^{\circ}$ to the tower top under Condition 8; the maximum bending moment of tower bottom occurs in $330^{\circ}$ under Condition 2. The extreme displacement of blade top all exceeds 2.5 m under Condition 5, and the maximum value of windward displacement response for the tip of Blade 3 under Condition 8 could reach 3.35 m. All these results indicate that the influence of halt positions of different blades should be taken into consideration carefully when making wind-resistance design for large scale wind turbine tower.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.6
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• pp.571-583
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• 2013

The use of Thin Spray-on Liner (TSL) as an alternative to shotcrete has drastically increased since 1990s when it was first developed and introduced to mines. In this study, tensile strength test, bond strength test, compression test with specimens coated by TSL, and two kinds of bending tests proposed by EFNARC (2008) were performed with two kinds of TSLs with different material compositions in order to evaluate their support capacities. As a result, both TSLs were shown to be satisfactory for the minimum performance requirements for a structural rock support suggested by EFNARC (2008) and tensile strength of a TSL was shown to increase as its content of polymer was higher. In contrast, its bond strength was shown to increase proportional to the content of a cementitious component especially at the early age.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.3
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• pp.551-565
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• 2017

A spray-applied waterproofing membrane which consists of polymers has a relatively higher constructability and adhesion than the conventional sheet-type waterproofing materials. Additionally, the spray-applied waterproofing membrane generally shows a waterproofing ability as a composite structure with shotcrete or concrete lining. Because its purpose is waterproofing at the structure, structural effects were not well reported than waterproofing abilities. In this study, structural effects of the membrane-attached concrete lining were evaluated using 3-point bending test by the numerical method. From the analysis, a load-displacement behavior of the concrete lining and fracturing energy after yielding were compared with various conditions. Consequently, concrete lining with spray-applied waterproofing membrane shows higher flexural strength and fracturing energy than the single-layer concrete lining.

• Journal of Conservation Science
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• v.28 no.3
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• pp.265-276
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• 2012

Physicochemical properties of HBA epoxy resins were controlled by varying hardener mixture and reactive diluent to improve applicability for stone conservation. The epoxy risen comprises hydrogenated Bisphenol-A based epoxide (HBA), fast curing agent (FH), slow curing agent poly(propyleneglycol)bis(2- aminopropylether) (SH) and difunctional polyglycidyl epoxide (DPE). Talc was used as an inorganic additive. The changes in viscosity and temperature during curing reactions depending on the composition of the epoxy resins were investigated. Additionally, bending, tensile and adhesive strengths were measured to identify the effective mechanical strength in stone conservation. Finally various compositions of epoxy resin/inorganic additives were developed for stone conservation by controlling cure kinetics and mechanical properties.

• Journal of Conservation Science
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• v.35 no.5
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• pp.518-527
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• 2019

This investion studies the manufacturing techniques of chimi(ridge-end roof tiles based on the) fragments excavated from the Wonju Beopcheonsa temple site(Historic site No. 466) and aids in the conservation of the fragments. The results of the investigation are categorized into the production of the body parts, the wing and the feather attachment, the production of the decorative parts, the scratches in the upper and lower part, the perforations connecting the upper and lower parts, and the formative features(bending phenomenon). The procedures in the conservation treatment of the chimi was performed in a sequential order beginning with a preliminary examination, followed by the removal of foreign substances, coating, joining and restoration, and color retouching. A three-dimensional scanning data was employed to restore the missing parts after adhesion to determine the location, size, and angle of the original shape. The restored chimi measures 118 cm in height and weighs 121 kg, which makes it the fifth largest in size among any chimi(including restored) in Korea. We expect that the pointed feathers will make the chimi from the Beopcheonsa temple site a rare reference as no specimens with these features have been found in Korea until now.

• Journal of Biosystems Engineering
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• v.33 no.4
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• pp.224-229
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• 2008

This study was aimed to minimize the impact force and vibration transmitted to the transporting materials from the trailer and wheel shaft by installing the leaf spring suspension device at the space between the wheel shaft and frame of power tiller trailer. The developed trailer equipped with leaf spring suspension device was compared to the existing trailer without suspension device, in order to identify the vibration absorption effect of the leaf spring. The results of this study could be summarized as follows; (1) The length and the maximum bending amount of the leaf spring were designed as 1,000 mm and 42 mm, respectively, considering the possible space for installing at below the trailer. When 4 leaf springs were installed on both wheel shafts, the allowable maximum load was identified as 9,418 N. (2) The average vibration accelerations for the frequency less than 20 Hz, where the severe transporting loss could be represented, were $0.017\;m/s^2$ and $0.133\;m/s^2$ for the developed and the existing trailer, respectively, showing the vibration absorption effect of about 87%. And the average vibration accelerations on the driver's seat for the frequency less than 20 Hz were $0.01\;m/s^2$ and $0.20\;m/s^2$ for the developed and the existing trailer, respectively, which showed the similar vibration absorption effect. (3) The change of the average vibration accelerations for the frequency from 20 Hz to 80 Hz showed the similar tendency with the result for the frequency less than 20 Hz, but the effect for developed trailer was reduced slightly. And the effect of vibration absorption for the above 80 Hz was reduced highly. However, by installing the leaf spring suspension device at the trailer, the low frequency below 40 Hz, which could affect on transporting loss severely, could be reduced highly. (4) The maximum vibration acceleration for the frequency less than 20 Hz were $0.027\;m/s^2$ and $1.267\;m/s^2$ for the developed and the existing trailer, respectively. And the change of maximum acceleration between 20 Hz and 120 Hz was showed similar tendency with the result for the frequency less than 20 Hz, but the width of change was reduced highly.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.611-617
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• 2018

The application of health monitoring, including a fault detection technique, is needed to secure the structural safety of large structures. A 2-step crack identification method for detecting the crack location and size of the beam structure is presented. First, a crack occurrence region was estimated using the modified Laplacian operator for the strain mode shape obtained from the distributed local strain data. The crack location and size were then identified based on the natural frequencies obtained from the acceleration data and the neural network technique for the pre-estimated crack occurrence region. The natural frequencies of a cracked beam were calculated based on an equivalent bending stiffness induced by the energy method, and used to generate the training patterns of the neural network. An experimental study was carried out on an aluminum cantilever beam to verify the present method for crack identification. Cracks were produced on the beam, and free vibration tests were performed. A crack occurrence region was estimated using the modified Laplacian operator for the strain mode shape, and the crack location and size were assessed using the natural frequencies and neural network technique. The identified crack occurrence region agrees well with the exact one, and the accuracy of the estimation results for the crack location and size could be enhanced considerably for 3 damage cases. The presented method could be applied effectively to the structural health monitoring of large structures.