• Structural Engineering and Mechanics
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• v.75 no.3
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• pp.401-414
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• 2020

Unlike the existing truss models for shear and torsion analysis, in this study, the torsional capacities of reinforced concrete (RC) members were estimated by introducing multi-potential capacity criteria that considered the aggregate interlock, concrete crushing, and spalling of concrete cover. The smeared truss model based on the fixed-angle theory was utilized to obtain the torsional behavior of reinforced concrete member, and the multi-potential capacity criteria were then applied to draw the capacity of the member. In addition, to avoid any iterative calculation in the existing torsional behavior model, a simple strength model was suggested that considers key variables, such as the effective thickness of torsional member, principal stress angle, and strain effect that reduces the resistance of concrete due to large longitudinal tensile strain. The proposed multi-potential capacity concept and the simple strength model were verified by comparing with test results collected from the literature. The study found that the multi-potential capacity could estimate in a rational manner not only the torsional strength but also the failure mode of RC members subjected to torsional moment, by reflecting the reinforcing index in both transverse and longitudinal directions, as well as the sectional and material properties of RC members.

• Journal of Digital Convergence
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• v.15 no.11
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• pp.221-229
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• 2017

The purpose of this study is to find out ways to enhance corporate value by using more efficient use of non-reflux Income which is commonly considered in existing corporate income tax refund and newly introduced investment and mutual aid promotion tax. Specifically, we analyzed the effect of income tax return income and income tax return on wages and fixed - asset investments, which are commonly considered in the two tax systems, on firm value. As a result of the analysis, it was confirmed that short-term internal reserves and income reflux activities had a negative impact on firm value, and long-term internal reserves and income reflux return had positive effects on firm value. It is recommended not to formulate uniform criteria such as the ratio of income refund activity to the contents of tax, but to apply the tax refund to the internal taxation system and the taxable income source.

• Advances in aircraft and spacecraft science
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• v.4 no.1
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• pp.37-52
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• 2017

Gas turbines operating in dusty or sandy environment polluted with micron-sized solid particles are highly prone to blade surface erosion damage in compressor stages and molten sand attack in the hot-sections of turbine stages. Commercial/Military fixed-wing aircraft engines and helicopter engines often have to operate over sandy terrains in the middle eastern countries or in volcanic zones; on the other hand gas turbines in marine applications are subjected to salt spray, while the coal-burning industrial power generation turbines are subjected to fly-ash. The presence of solid particles in the working fluid medium has an adverse effect on the durability of these engines as well as performance. Typical turbine blade damages include blade coating wear, sand glazing, Calcia-Magnesia-Alumina-Silicate (CMAS) attack, oxidation, plugged cooling holes, all of which can cause rapid performance deterioration including loss of aircraft. The focus of this research work is to simulate particle-surface kinetic interaction on typical turbomachinery material targets using non-linear dynamic impact analysis. The objective of this research is to understand the interfacial kinetic behaviors that can provide insights into the physics of particle interactions and to enable leap ahead technologies in material choices and to develop sand-phobic thermal barrier coatings for turbine blades. This paper outlines the research efforts at the U.S Army Research Laboratory to come up with novel turbine blade multifunctional protective coatings that are sand-phobic, sand impact wear resistant, as well as have very low thermal conductivity for improved performance of future gas turbine engines. The research scope includes development of protective coatings for both nickel-based super alloys and ceramic matrix composites.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.357-366
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• 1986

The flow characteristics of two-dimensional turbulent offset jet which is discharged parallel to a solid wall has been studied experimentally and numerically. In the experiment, 3-hole pitot tube and 2 channel constant temperature hot-wire anemometer are used to measure local mean velocity, turbulence intensity and Reynolds stress while scannivalve is used to measure the wall pressure distribution. It is confirmed experimentally that local mean velocity is closely related to wall pressure distribution. It is also verified that for large Reynolds numbers and fixed step height there exists a similarity in the distribution of wall pressure coefficient. The maximum values of turbulence intensity occur in the top and bottom mixing layers and the magnitude of Reynolds stress becomes large in the lower mixing layer than in the top mixing layer due to the effect of streamline curvature and entrainment. In the numerical analysis, standard k-.epsilon. model based on eddy viscosity model and Leschziner and Rodi model based on algebraic stress model are adopted. The numerical analyses predict shorter reattachment lengths than the experiment, and this difference is judged to be due mainly to the problem of turbulence model constants and numerical algorithm. This also causes the inconsistency between the two results for other turbulence quantities in the recirculation region and impingement region, which constitutes a subject of a continued future study.

• Journal of the Korean Ceramic Society
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• v.41 no.6
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• pp.430-434
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• 2004

The values of fracture energy and mechanical flexural strength of Fiber Reinforced Cement (FRC) with polypropylene (PP) fiber modified by Ion Assisted Reaction (JAR), by which functional groups were grafted on the surface of PP fiber, was improved about 2 times as those of fracture energy and flexural strength of cement reinforced by untreated PP fiber. PP fiber was irradiated in O$_2$ environment by Ar$\^$+/ ion. The contact angle of PP treated by IAR decreased largely when compared with untreated PP. From this result, we expected that surface energy and interfacial adhesion force of treated PP fiber increased. The strain hardening occurred in the strain-stress curve of FRC including PP treated by IAR when compared with that of FRC with untreated PP. These enhanced mechanical properties might be due to strong interaction between hydrophilic group on modified PP fiber and hydroxyl group in cement matrix. This hydrophilic group on surface modified PP fiber was confirmed by XPS analysis. We clearly observed hydration products that were fixed at modified PP fiber due to the strong adhesion force of interface in cement reinforced modified PP by SEM (Scanning Electron Microscopy) study.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.3
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• pp.218-224
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• 2005

Surface modification of glutaraldehyde fixed bovine pericardium (GFBP) was success­fully carried out with hyaluronic acid (HA) derivatives. At first, HA was chemically modified with adipic dihydrazide (ADH) to introduce hydrazide functional group into the carboxyl group of HA backbone. Then, GFBP was surface modified by grafting HA-ADH to the free aldehyde groups on the tissue and the subsequent HA-ADH hydrogel coating. HA-ADH hydrogels could be prepared through selective crosslinking at low pH between hydrazide groups of HA-ADH and crosslinkers containing succinimmidyl moieties with minimized protein denaturation. When HA­ADH hydrogels were prepared at low pH of 4.8 in the presence of erythropoietin (EPO) as a model protein, EPO release was continued up to $85\%$ of total amount of loaded EPO for 4 days. To the contrary, only $30\%$ of EPO was released from HA-ADH hydrogels prepared at pH=7.4, which might be due to the denaturation of EPO during the crosslinking reaction. Because the carboxyl groups on the glucuronic acid residues are recognition sites for HA degradation by hyaluronidase, the HA-ADH hydrogels degraded more slowly than HA hydrogels prepared by the crosslinking reaction of divinyl sulfone with hydroxyl groups of HA. Following a two-week subcutaneous implantation in osteopontin-null mice, clinically significant levels of calcification were observed for the positive controls without any surface modification. However, the calcification of surface modified GFBP with HA-ADH and HA-ADH hydrogels was drastically reduced by more than $85\%$ of the positive controls. The anti-calcification effect of HA surface modification was also confirmed by microscopic analysis of explanted tissue after staining with Alizarin Red S for calcium, which followed the trend as observed with calcium quantification.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.1
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• pp.42-49
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• 2016

This study was analyed V-bending in order to analyze the spring-back phenomenon in the roll forming process. The material of forming sheet used in the roll forming process is high tension steel and the product name of sheet material is POSTEN 60. The most important variable is the number of roll passes (3-Pass, 4-Pass, 5-Pass, 6-Pass and 10-Pass) and other roll forming process variables were fixed. To determine the characteristics of the tension and compression, the forming sheet was analyzed by dividing the layer (Upper and Bottom) in the thickness direction from the center line. The results of FEM simulation analysis was derived to von-mises stress equivalent strain, and the spring-back value was calculated according to the final forming shape. The more number of the roll pass, von-mises stress and equivalent strain value of forming sheet were lowed. Also, spring-back values tended to decrease. The results of this study can be utilized for prediction and trend of spring-back value in the roll forming process applied to high tension steel sheet. So, development time and cost of the roll forming process is expected to be reduced.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.12
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• pp.866-873
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• 2015

The transverse vibration of the deploying beam from rigid hub was analyzed by simulation and experiment. The linear governing equation of the deploying beam was obtained using the Euler-Bernoulli beam theory. To discretize the governing equation, the Galerkin method was used. After transforming the governing equation into the weak form, the weak form was discretized. The discretized equation was expressed by the matrix-vector form, and then the Newmark method was applied to simulate. To consider the damping effect of the beam, we conducted the modal test with various beam length. The mass proportional damping was selected by the relation of the first and second damping ratio. The proportional damping coefficient was calculated using the acquired natural frequency and damping ratio through the modal test. The experiment was set up to measure the transverse vibration of the deploying beam. The fixed beam at the carriage of the linear actuator was moved by moving the carriage. The transverse vibration of the deploying beam was observed by the Eulerian description near the hub. The deploying or retraction motion of the beam had the constant velocity and the velocity profile with acceleration and deceleration. We compared the transverse vibration results by the simulation and experiment. The observed response by the Eulerian description were analyzed.

• Research in Community and Public Health Nursing
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• v.14 no.2
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• pp.351-361
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• 2003

Purpose: The purposes of this study were to understand the types of coping strategies that family caregivers experience during the process of caring demented elderly: to grasp the coping strategies used for resolving this problem: and to develop a substantive theory by analyzing the coping types of the family caregivers of demented elderly. Method: The methodology of data collection and analysis used in this study was grounded theory proposed by Strauss and Corbin (1990). The data was collected through in-depth interviews with participants using open-ended and descriptive questions about their coping experiences. All data were were audio-taped and transcribed. The data were collected from February, 2000 to February, 2001. The participants of this study were 17 women. Results: Caregiver's coping types varied according to 'family's support', 'the condition of caregiver's health', 'the relationship with dementia elderly', 'family perception of dementia', 'fixed idea of traditional female role' and 'economic state'. In this study, five types of coping strategies were emerged: active role allotment tyle, meaning grant tyle, devotion tyle, duty defense type, and pessimism type. Among these, those who belong to the types of active role allotment, meaning grant, and devotion, including caregiver's good health were found to adapt themselves to caregiver roles. Conclusion: The results of this study may be helpful for developing effective and individualized nursing strategies suitable for individual caregivers coping types. It is suggested to practice nursing mediation and to analyze the changes in nursing effect and family members' adaptation based on coping types of the well-adapted caregivers as we as on their affirmative coping strategy.

• Journal of Korean Elementary Science Education
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• v.34 no.3
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• pp.265-275
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• 2015

The purpose of this study was to develop forensic science program for the improvement of scientific creative problem-solving abilities in gifted elementary-school students. A program that consists of six sessions (18 hours) is developed in accordance with the CPS model, which has been already proven effective for the improvement of creative problem-solving abilities. This program was applied to sixth-grade 18 gifted students in an elementary school in Gyeonggi province. Examinations of scientific creative problem-solving abilities were performed before and after applying the program in order to determine its effect on gifted elementary students. A qualitative analysis of students' activity sheets, peer assessment and teacher's class journal was made in order to examine the process of improvement of students' scientific creative problem-solving abilities. The results of this study are as follows: First, forensic science program to enhance the scientific creative problem-solving abilities of gifted students was developed. Second, forensic science program is significantly effective in the improvement of scientific creative problem-solving abilities of gifted children of elementary school (p<.05). Third, in early stage of the class, a student, who showed the highest range of change in pre and post tests, revealed the trend of responding in a short answer type. In the late stage of the class, he revealed the capability of producing various creative ideas promptly. On the other hand, students belonging to the upper group of both pre and post test revealed the improvement of divergent thinking skills such as fluency, flexibility, and originality. Fourth, after class, the students responded that the forensic science program developed in this study intrigued the interests and curiosities, and helped them break away from fixed ideas.