• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.5
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• pp.563-570
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• 2015

The existing research on the damage detection method for building structures has considered the damages from the excessive loadings such as the earthquake. However, the structural performance of building structures could be reduced due to the deterioration based on the chloride, carbonation during the long-term time. Thus, to effectively manage the healthiness of structures, the deterioration influences on the structures should be checked. In this study, the corrosion of rebars by the chloride is considered as the deterioration factor. To consider the structural performance reduction of the corroded rebars, the yield strength, cross-sectional area, rupture strain of rebars and the compressive strength of cover concrete based on the corrosion level are estimated. These properties of rebars and cover concrete are used for the procedure to evaluate the structural performance reduction of structural member level and the building level. The moment-curvature analysis is performed to evaluate the structural performance reduction of structural member level. Also, the eigenvalue analysis and the pushover analysis are performed to investigate the natural period and mode shape and the strength and deformation performance of buildings, respectively.

• Restorative Dentistry and Endodontics
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• v.29 no.3
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• pp.267-272
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• 2004

The purpose of this in vitro study was to evaluate the effect of surface defects and cross-sectional configuration of NiTi rotary files on the fatigue life under cyclic loading. Three NiTi rotary files ($K3^{TM},{\;}ProFile^{\circledR},{\;}and{\;}HERO{\;}642^{\circledR}$) with ＃30/.04 taper were evaluated. Each rotary file was divided into 2 subgroups : control (no surface defects) and experimental group (artificial surface defects), A total of six groups of each 10 were tested. The NiTi rotary files were rotated at 300rpm using the apparatus which simulated curved canal (40 degree of curvature) until they fracture. The number of cycles to fracture was calculated and the fractured surfaces were observed with a scanning electron microscope. The data were analyzed statistically. The results showed that experimental groups with surface defects had lower number of cycles to fracture than control group but there was only a statistical significance between control and experimental group in the $K3^{TM}$ (p<0.05), There was no strong correlation between the cross-sectional configuration area and fracture resistance under experimental conditions. Several of fractured files demonstrated characteristic patterns of brittle fracture consistent with the propagation of pre-existing cracks. This data indicate that surface defects of NiTi rotary files may significantly decrease fatigue life and it may be one possible factor for early fracture of NiTi rotary files in clinical practice.

• Economic and Environmental Geology
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• v.38 no.1
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• pp.33-43
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• 2005

The purpose of this study is to make and validate landslide susceptibility map using artificial neural network and GIS in Kangneung area. For this, topography, soil, forest, geology and land cover data sets were constructed as a spatial database in GIS. From the database, slope, aspect, curvature, water system, topographic type, soil texture, soil material, soil drainage, soil effective thickness, wood type, wood age, wood diameter, forest density, lithology, land cover, and lineament were used as the landslide occurrence factors. The weight of the each factor was calculated, and applied to make landslide susceptibility maps using artificial neural network. Then the maps were validated using rate curve method which can predict qualitatively the landslide occurrence. The landslide susceptibility map can be used to reduce associated hazards, and to plan land use and construction as basic data.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.8
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• pp.689-698
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• 2021

The development of modern warfare detection technology is increasingly threatening the survivability of aircraft. Among them, IR-seeking missiles greatly affect the survivability of aircraft and are a main factor that reduces the success rate of aircraft missions. In order to increase aircraft survivability, studies on shape-modifying nozzles with added curvature are being actively conducted. In this study, we selected a double serpentine nozzle among shape-modifying nozzles to increase aircraft survivability. We then investigated the effects of the location of the maximum area change rate of the nozzle. It was confirmed that the location of the change rate of area affects the thrust and exit temperature of the nozzle. In addition, it was shown that the thrust penalty was reduced as the position of the change rate of the maximum area was located at the rear of the nozzle.

• Annals of Rehabilitation Medicine
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• v.42 no.6
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• pp.863-871
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• 2018

Objective To evaluate the association between progression of curvature of scoliosis, and correction for functional component in patients with juvenile idiopathic scoliosis (JIS). Methods We retrospectively reviewed medical data of patients prescribed custom molded foot orthosis (FO) to correct inequality of RCSPA (resting calcaneal stance position angle), and chose 52 patients (26 females, 26 males) with Cobb angle ${\geq}10^{\circ}$ in radiology and uneven pelvic level at iliac crest by different RCSPA (${\geq}3^{\circ}$) as a factor of functional scoliosis. They had different hump angle ${\geq}5^{\circ}$ in forward bending test, for idiopathic scoliosis component. Their mean age and mean period of wearing FO were $79.5{\pm}10.6months$ and $18.6{\pm}0.70months$. Results Cobb angle was reduced from $22.03^{\circ}{\pm}4.39^{\circ}$ initially to $18.86^{\circ}{\pm}7.53^{\circ}$ after wearing FO. Pelvis height difference and RCSPA difference, were reduced from $1.07{\pm}0.25cm$ initially to $0.60{\pm}0.36$, and from $4.25^{\circ}{\pm}0.71^{\circ}$ initially to $1.71^{\circ}{\pm}0.75^{\circ}$ (p<0.01). Cobb angle improved most in 9 months. However, there was no significant improvement for those with more than $25^{\circ}$ of Cobb angle initially. Mean Cobb angle improved in all age groups, but patients less than 6 years had clinically significant improvement of more than $5^{\circ}$. Conclusion JIS can have functional components, which should be identified and managed. Foot orthosis is useful in correcting functional factors, in the case of pelvic inequality caused by different RCSPA, for patients with juvenile idiopathic scoliosis.

• Journal of Gastric Cancer
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• v.18 no.4
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• pp.339-347
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• 2018

Purpose: To evaluate the status of number 3b lymph node (LN) station in patients with adenocarcinoma of the esophagogastric junction (AEG) and to investigate the optimal indications for radical proximal gastrectomy (PG) for AEG. Materials and Methods: Data of 51 patients with clinically advanced Siewert types II and III AEG who underwent total gastrectomy (TG) between April 2010 and July 2017 were reviewed. The proportion of metastatic LNs at each LN station was examined. Number 3 LN station was separately classified into number 3a and number 3b. The risk factors for number 3b LN metastasis and the clinicopathological features of number 3b-positive AEG patients were investigated. Results: The incidences of LN metastasis were the highest in number 1 (47.1%), followed by number 2 (23.5%), number 3a (39.2%), and number 7 (23.5%) LN stations. LN metastasis in number 3b LN station was detected in 4 patients (7.8%). A gastric invasion length of more than 40 mm was a significant risk factor for number 3b LN metastasis. All 4 patients with number 3b-positive AEG had advanced cancer with a gastric invasion length of more than 40 mm. The 5-year survival rate of patients with a gastric invasion length of more than 40 mm was 50.0%. Conclusions: Radical PG may be indicated for patients with AEG with gastric invasion length of less than 40 mm.

• Structural Engineering and Mechanics
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• v.82 no.1
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• pp.121-131
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• 2022

The main goal of this study is to prepare a program for analyzing High Strength Steel Fibrous Reinforced Concrete (HSSFRC) slabs and predict the response and strength of the slab instead of preparing a prototype and testing it in the laboratory. For this purpose, new equations are proposed to represent the material properties of High Strength Steel Fibrous Reinforced Concrete. The proposed equations obtained from performing regression analysis on many experimental results using statistical programs. The finite element method is adopted for non-linear analysis of the slabs. The eight-node "Serendipity element" (3 DoF) is chosen to represent the concrete. The layered approach is adopted for concrete elements and the steel reinforcement is represented by a smeared layer. The compression properties of the concrete are modeled by a work hardening plasticity approach and the yield condition is determined depending on the first two stress invariants. A tensile strength criterion is adopted in order to estimate the cracks propagation. many experimental results for testing slabs are compared with the numerical results of the present study and a good agreement is achieved regarding load-deflection curves and crack pattern. The response of the load deflection curve is slightly stiff at the beginning because the creep effect is not considered in this study and for assuming perfect bond between the steel reinforcement and the concrete, however, a great agreement is achieved between the ultimate load from the present study and experimental results. For the models of the tension stiffening and cracked shear modulus, the value of Bg and Bt (Where Bg and Bt are the curvature factor for the cracked shear modulus and tension stiffening models respectively) equal to 0.005 give good results compared with experimental result.

• Journal of the Korean Association of Geographic Information Studies
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• v.15 no.2
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• pp.86-102
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• 2012

For predictive flooded area susceptibility mapping, this study applied and verified probability model and the frequency ratio using a geographic information system (GIS) and frequency raio. Flooded areas were identified in the study area of field surveys, For predictive flooded area susceptibility mapping, this study applied and verified probability model and the frequency ratio using a geographic information system (GIS) and frequency raio. Flooded areas were identified in the study area of field surveys, and maps of the topography, geology, landcover and green infrastructure were constructed for a spatial database. The factors that influence flooded areas occurrence, such as slope gradient, slope, aspect and curvature of topography and distance from darinage, were calculated from the topographic database. Lithology and distance from fault were extracted and calculated from the geology database. The frequency ratio coefficient is overlaid for flooded areas susceptibility mapping as each factor's ratings. Then the flooded areas susceptibility map was verified and compared using the existing flooded areas. As the verification results, the frequency ratio model showed 82% in prediction accuracy. The method can be used to reduce hazards associated with flooded areas and to plan land use.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.1
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• pp.35-40
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• 2018

Nd:YAG laser was used to carbonize polyimide films to produce carbon films. This is a simple manufacturing process to fabricate low cost sensors. By applying this method, we studied characteristics of flexible and low-cost piezoresistive. Previously, many studies focused on carbonization of polyimide using $CO_2$ laser with wavelength of $10.6{\mu}m$. In this paper, carbonization (carbonization process) was performed on polyimide films using an Nd:YAG laser with a wavelength of $1.064{\mu}m$. In order to increase the resolution, we optimized the laser conditions of the power density ($W/cm^2$) and the beam scan rate. In previous studies using $CO_2$ laser, the minimum line width was $140{\sim}220{\mu}m$ but in this study, carbon line width was reduced to $35{\sim}40{\mu}m$. The initial sheet resistance of the carbon sensor was $100{\sim}300{\Omega}/{\square}$. The resistance decreased by 30% under stretched with a curvature radius of 21 R. The calculated gauge factor was 56.6. This work offers a simple, highly flexible, and low-cost process to fabricate piezoresistive sensors.

• Journal of Korean Society of Steel Construction
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• v.30 no.1
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• pp.1-12
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• 2018

A curved member should resist bending and torsional moments simultaneously even though the primary load is usually supposed to be gravitational load. The torsional moment causes complicate stress state and also can result in early yielding of material to reduce member strength. According to analysis results, the strength of a curved member that has 45 degrees of subtended angle could decrease more than 50% compare to straight girder. Nevertheless, there have been very few of researches related with ultimate strength of curved girders. In this study, various kinds of stiffness about bending, pure torsion and warping were considered with a number of models in order to verify the main factor that affects ultimate behavior of curved girder. Lateral and rotational displacement of curved member were introduced as lateral-torsional-vertical behavior and bending-torsional moment interaction curve was derived. Finally, a strength equation for ultimate moment of horizontally curved steel I-girders subjected to equal end moments based on the interaction curves. The equation could take account of the effect of curvature, unbraced length and sectional properties.