• International Journal of Highway Engineering
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• v.20 no.2
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• pp.57-65
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• 2018

PURPOSES : The study aims to predict the service life of national highway asphalt pavements through deep learning methods by using maintenance history data of the National Highway Pavement Management System. METHODS : For the configuration of a deep learning network, this study used Tensorflow 1.5, an open source program which has excellent usability among deep learning frameworks. For the analysis, nine variables of cumulative annual average daily traffic, cumulative equivalent single axle loads, maintenance layer, surface, base, subbase, anti-frost layer, structural number of pavement, and region were selected as input data, while service life was chosen to construct the input layer and output layers as output data. Additionally, for scenario analysis, in this study, a model was formed with four different numbers of 1, 2, 4, and 8 hidden layers and a simulation analysis was performed according to the applicability of the over fitting resolution algorithm. RESULTS : The results of the analysis have shown that regardless of the number of hidden layers, when an over fitting resolution algorithm, such as dropout, is applied, the prediction capability is improved as the coefficient of determination ($R^2$) of the test data increases. Furthermore, the result of the sensitivity analysis of the applicability of region variables demonstrates that estimating service life requires sufficient consideration of regional characteristics as $R^2$ had a maximum of between 0.73 and 0.84, when regional variables where taken into consideration. CONCLUSIONS : As a result, this study proposes that it is possible to precisely predict the service life of national highway pavement sections with the consideration of traffic, pavement thickness, and regional factors and concludes that the use of the prediction of service life is fundamental data in decision making within pavement management systems.

• Journal of the Korean Society of Clothing and Textiles
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• v.34 no.11
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• pp.1889-1899
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• 2010

This study examines the preparation and characterization of Kenaf/Starch bio-composites used as filler and a matrix. Kenaf was cultivated in Chung-ju in Korea, and the Kenaf/Starch bio-composites were prepared under various conditions of kenaf fiber length (1-5 centimeters); the content of Kenaf fiber was 10%, 20%, 30%, and 40%, and the number of composite layers (one-four). Depending on the formation conditions of Kenaf/Starch composites, the physical properties such as tensile strength, elongation, and the young modulus of the Kenaf/Starch composites were measured. In addition, we measured the SEM cross-section images in order to investigate the interfacial adhesion properties of fractured surfaces. As a result, the tensile strength and elongation of the Kenaf/Starch composites were highest in the molding conditions of a hot press at $120^{\circ}C$, 3000PSI of pressure, and for 30 minute periods. The result of measuring the physical properties of the composites manufactured by varying the content of Kenaf fiber when the content of Kenaf fiber was 30% as well the physical properties of the Kenaf/Starch composite was found desirable. It was found that the physical properties improved with more overlapped layers in the composites manufactured by varying the number of overlapped layers. Through the measuring of the SEM cross-section images, we found that the interfacial adhesion state between the filler and matrix of Kenaf/Starch composite greatly affects the physical properties.

• Structural Engineering and Mechanics
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• v.90 no.4
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• pp.371-390
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• 2024

Investigating the impact of openings on the structural behavior of ferrocement I-beams with two distinct types of reinforcing metallic and non-metallic meshes is the primary goal of the current study. Up until failure, eight 250x200x2200 mm reinforced concrete I-beams were tested under flexural loadings. Depending on the kind of meshes used for reinforcement, the beams are split into two series. A control I-beam with no openings and three beams with one, two, and three openings, respectively, are found in each series. The two series are reinforced with three layers of welded steel meshes and two layers of tensar meshes, respectively, in order to maintain a constant reinforcement ratio. Structural parameters of investigated beams, including first crack, ultimate load, deflection, ductility index, energy absorption, strain characteristics, crack pattern, and failure mode were reported. The number of mesh layers, the volume fraction of reinforcement, and the kind of reinforcing materials are the primary factors that vary. This article presents the outcomes of a study that examined the experimental and numerical performance of ferrocement reinforced concrete I-beams with and without openings reinforced with welded steel mesh and tensar mesh separately. Utilizing ANSYS-16.0 software, nonlinear finite element analysis (NLFEA) was applied to illustrate how composite RC I-beams with openings behaved. In addition, a parametric study is conducted to explore the variables that can most significantly impact the mechanical behavior of the proposed model, such as the number of openings. The FE simulations produced an acceptable degree of experimental value estimation, as demonstrated by the obtained experimental and numerical results. It is also noteworthy to demonstrate that the strength gained by specimens without openings reinforced with tensar meshes was, on average, 22% less than that of specimens reinforced with welded steel meshes. For specimens with openings, this value is become on average 10%.

• Journal of the Korean Geosynthetics Society
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• v.9 no.4
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• pp.39-45
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• 2010

The effects of non-woven geotextiles on mechanical behavior of sand were investigated. A comprehensive series of triaxial compression tests were performed for these investigation on unreinforced and reinforced sand with geotextiles. The Joomunjin standard sand was used and non-woven geotextiles were included into sand specimen with three layers. The inclusion of non-woven geotextile reinforcement into sand increased the peak strength of sand significantly and the reinforced samples exhibited a greater axial strain at failure. Also the effect on number of reinforcement layers was studied and found as increasing the number of reinforcement layers resulting in more ductility by clogging developed in the shear band within the specimens. It was also found that the tendency of samples to dilate is restricted by non-woven geotextile inclusion. The effect of nunber of reinforcement layer increasing is just same to the effect of decreasing void ratio of sand in this case.

• Journal of the Korean Geotechnical Society
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• v.20 no.7
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• pp.107-117
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• 2004

A series of model tests were conducted to investigate how the number of reinforcement layers, stiffnesses, types of reinforcement material and buried depth of a flexible pipe can affect bearing capacity-settlement curve at a loose sand foundation. In the test results, whereas the type of failure in unreinforced sand was local shear, the type of failure, for model tests with more than 2 reinforcement layers in loose sand, was general shear: The number of the optimum reinforcement layers was found to be two: Stiffness and type of reinforcement were more important than the maximum tensile strength of reinforcement in improving bearing capacity. When the depth of buried pipe from the sand surface was less than the width of the footing, test results showed that both bearing capacity and ultimate bearing capacity of buried pipe in unreinforced sand significantly decreased, and the type of failure in the reinforced sand changed from general shear to local shear.

• Solar Energy
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• v.12 no.3
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• pp.37-46
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• 1992

An experimental study was carried out to investigate the performance of a latent heat storage system using paraffin wax as the phase change material. A thermosyphon was employed to transfer heat from the hot ethylene glycol flowing across the evaporator section of the thermosyphon into the wax. In order to increase the effective thermal conductivity of wax, layers of copper wire mesh were immersed in the wax. Experiments were run for volume ratios of 2%, 3%, and 4%, varying mass flow rate of ethylene glycol in each case. Some of the important results are as follows : (1) The wire mesh enhanced the conductive hea transfer and thus, helped even out the temperature distribution in the wax : (2) The increase of the number of layers of wire mesh increased the conduction. However, it also resulted in increasing the resistance to the convective motion of liquefied wax : and (3) There is an optimal number of layers of wire mesh, maximizing the performance of the storage system, which occurred at a volume ratio of $3{\sim}4%$ in the present study.

• International Journal of Highway Engineering
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• v.9 no.3
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• pp.135-143
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• 2007

The pavement system constructed by tieing a number of precast concrete slabs employing prestressing techniques is called the precast prestressed concrete pavement. The behavior of this type of pavement system under post-tensioning was analyzed using a finite element model. First, the optimal number of anchors was determined by investigating the distribution of compressive stresses in the pavement system due to post-tensioning. Then, the effects of the parameters such as the horizontal resistance of underlying layers, the pavement length, the slab thickness, and the bearing area of the anchorage on the distribution of compressive stresses were analyzed. The horizontal resistance of underlying layers induced the loss of compressive stresses, and the loss increased in the middle of the pavement. As the pavement length increased or the slab thickness decreased, the stress loss due to the horizontal resistance of underlying layers became larger. However, the bearing area of the anchorage where the compressive forces were applied did not much affect the distribution of compressive stresses.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.21 no.2
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• pp.165-179
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• 1991

This study was performed to understand the irradiation effects on the mandibular condyle and mandibular growth in developing white rats. Forty eight white male rats of the Sprague-Dawley strain aged 4 weeks, were devided into two groups; control group and experimental group. A single target dose of l0Gy of radiation was given to the mandibular condylar area and the observations of the photo analysis, radiologic, histopathologic and immunohistochemical study revealed as follows; 1. Animals killed one week after irradiation showed lesser increase in body weights, no difference in photo analysis and decreased thickness of cartilagenous layers of the condyle than the control group. 2. Two weeks after irradiation the weight increases were almost same in both irradiated and control groups and in photo analysis, the distance from Mental Foramen to Incisal tip (Mf-It) was longer than the controls. Repair processes were taken place in irradiated group, but the cartilagenous layers were thinner than the controls. 3. By the third week after exposure further repair was seen in the trabeculae and the distance from Condylion to Mandibular plane (Cd-Cd') was longer than the controls and the weight increases were almost same as the controls. 4. At 4 weeks after irradiation the cells of proliferating zone repaired to almost normal findings, but the cartilagenous cell layers were still thinner than the control animals. In photo analysis, the distances from Menton to Anterior Notch (Me-An), from First Molar to Mandibular plane (Fm-Fm') were shorter and the weight increases were lesser than the controls. 5. In the S-100 antibody, the positive cells were increased in number, but decreased reactivities were seen at the proliferating zone of the irradiated groups. In the Monoclonal Anti-Proteoglycan antibody and Type Ⅰ collagen antibody, the irradiated groups showed little decreased number of positive cells and in the Type Ⅱ collagen antibody, the differences between irradiated and control groups were undetectable in immunohistochemical study.

• Applied Microscopy
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• v.20 no.1
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• pp.105-119
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• 1990

In order to know the morphological characteristics and changes according to the developmental stage, the comparative observations have been studied by light and electron microscope on the midgut(gastric caecum, stomach) of the grasshopper(Oxya sinuosa Mistshenko). The results obtained are summarized as follow : In light microscopic level, the cuboidal shaped cells of the gastric caecum in the 5th instar nymph are differentiated the columnar epithelium in the adult. A number of pigment granules are appeared in the gastric caecum of the 5th instar nymph, however the pigment granules were absent in the adult. Indistinct or undifferentiated folds of the epithelial layer were appeared in the 5th instar nymph, whereas the well-developed folds were appeared the gastric caecum in the adult. The well-developed muscular layers are seen in the 5th instar numph, however in the adult the muscular layers are appeared thin or a few layers. In electron microscopic level, in the midgut epithelium, a number of well-developed rER, a few lipid droplets, multi vesicular bodies, small vesicles and glycogen granules were found. Two types of the pigment granules in the gastric caecum of the 5th instar nymph were appeared, whereas the whorl-membrane, a few secretory granules and one type of the gastro-entero-endocrine cell were found in the adult midgut. The light and dark cells could be distinguished in the stomach epithelim of the 5th instar nymph.

• Imaging Science in Dentistry
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• v.32 no.1
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• pp.11-18
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• 2002

Purpose: To evaluate cultured human artificial skin as an experimental model for studying radiation effects in vitro. Materials and Methods: The skin was constructed by culturing keratinocytes over collagen lattice which made by culturing fibroblasts. Two groups were irradiated to gamma rays at single dose of 25 Gy with or without 3.5% of DMSO. Ultrastructures were investigated by electron microscopy after irradiation. The number of epidermal layers and expression of cytokeratin (CK) 14 & 10 were also seem by light microscopy. Results: At 2 days after irradiation in experimental group without DMSO, necrotic cells were rarely found in the spinosal layer and undercornified cells were visible in the homey layer. Similar findings were also found in experimental group with DMSO but in mild form. The number of epidermal layers in experimental group without DMSO were significantly fewer than other group. CK 14 expressed in all the layer excluding homey layer but CK 10 expressed over 3∼4 basal layers. Such patterns of CK expression were similar to all groups. It is suggested that structures of the keratinocytes and epidermal formation could be disturbed by irradiation in artificial skin and that DMSO can protect these damages. Conclusion : Therefore this work could be used as an organotypic experimental model in vitro using human cells for studying radiation effect in skin. Furthermore structural findings provided in this study could be used as useful basic data in further study using this model.