• Women's Health Nursing
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• v.19 no.1
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• pp.36-47
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• 2013

Purpose: This study was to explore subjectivity on childbearing in high school students. Methods: A Q-methodology which provides a method of analyzing the subjectivity of each type was used. Forty-three high school students classified 40 selected Q-statements into 9 points standard. The obtained data were analyzed by using the pc-QUANL program. Results: High school students' subjectivity on childbearing were analyzed into two types: Type 1 turned out to be 'FOLS (family oriented life style)' and Type 2 'CINK (couple important no kid)'. Conclusion: In order to resolve such problems as low birth rate and the advanced age of the population, effective youth and adult programs, policy and institution are required. The current demographic, economic and other factors such as personal values and policies may lower birth rate. In particular, youths' need for children and birth rate tend to be lower. There are positive and negative patterns in high school students' subjectivity on childbearing. Thus, national and social efforts are needed to change negative factors into positive ones. In order to maintain positive subjectivity on childbearing in high school students, it is necessary to apply family-centered educational programs and to implement birth-friendly and realistic programs for promoting child birth.

• Transactions of Materials Processing
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• v.18 no.3
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• pp.236-244
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• 2009

In response to growing environmental and collision-safety concerns, the automotive industry has gradually used high-strength and ultla-high-strength steels to reduce the weight of automobiles. In order to overcome inherent process disadvantages of these materials such as poor formability and high springback at room temperature, hot forming has recently been developed and adopted to produce some important structural parts in automobiles. This method enables manufacturing of components with complex geometric shapes with minimal springback. In addition, a quenching process may enhance the material strength by more than two times. This paper investigates mechanical and forming characteristics of high-strength boron-alloyed steel with hot forming, in terms of hardness, microstructure, residual stress, and springback. In order to compare with experimental results, a finite element analysis of hot forming process coupled with phase transformation and heat transfer was carried out using DEFORM-3D V6.1 and also, to predict high temperature mechanical properties and flow curves for different phases, a material properties modeler, JMatPro was used.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.226-234
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• 2009

The purpose of this study was to investigate the melting phenomenon of filler wire in detail and to obtain the precise temperature distribution of filler wire during GTA welding under the ultra-high welding speed condition in order to develop the ultra-high-speed GTA welding process with the pulse-heated hot-wire system by using three kinds of materials. The melting phenomenon of filler wire was observed using a high-speed camera and the temperature distribution of filler wire was measured using a radiation thermometer. From the above result, the adequate welding conditions of each material to make the GTA welding process with the ultra-high welding speed could be obtained. The ultra-high-speed GTA welding process needed the adequate wire current in order to obtain the adequate temperature distribution and the adequate melting position of filler wire. Moreover, the temperature distributions of three kinds of filler wire could be estimated by using the proposed simple estimation method.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.275-278
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• 2005

INCONEL 718, nickel based superalloy, has good formability, high strength, excellent corrosion resistance and mechanical properties at high temperature. Owing to theses attractive properties, it finds use in applications such as combustion system, turbine engines and nuclear reactors. In such applications, components are typically required to be tolerant of high stress impact loading. This may cause material degradation and lead to catastrophic failure during service operation. In order to design optimal structural parts made of INCONEL 718, accurate understanding of material's mechanical properties, dynamic behavior and fracture characteristic as a function of strain rates are required. This paper concerned with the dynamic material properties of the INCONEL 718 for the various strain rates. The dynamic response of the INCONEL 718 at intermediate strain rate is obtained from the high speed tensile test machine test and at the high strain rate is from the split Hopkinson pressure bar test. Based on the experimental results, the effects of strain rate on dynamic flow stress, work hardening characteristics, strain rate sensitivity and elongation to the failure are evaluated. Experimental results from both quasi-static and high strain rate up to the 5000/sec are interpolated in order to construct the Johnson-Cook model as the constitutive relation that should be applied to simulate and design the structural parts made of INCONEL 718.

• Transactions of Materials Processing
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• v.14 no.6 s.78
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• pp.559-564
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• 2005

INCONEL 718, nickel based superalloy, has good formability, high strength, excellent corrosion resistance and mechanical properties at high temperature. Owing to theses attractive properties, it is utilized in applications such as combustion system, turbine engines and nuclear reactors. In such applications, components are typically required to be tolerant of high stress impact loading. This may cause material degradation and lead to catastrophic failure during service operation. Accurate understanding of material's mechanical properties with various strain rates is required in order to guarantee the reliability of structural parts made of INCONEL 718. This paper is concerned with the dynamic material properties of the INCONEL 718 at various strain rates. The dynamic response of the INCONEL 718 at the intermediate strain rate is obtained from the high speed tensile test and at the high strain rate is from the split Hopkinson pressure bar test. The effect of the strain rate on dynamic flow stress, work hardening characteristics, strain rate sensitivity and elongation to the failure is evaluated with the experimental results. Experimental results from both the quasi-static and the high strain rate up to 5000/sec are interpolated in order to construct the Johnson-Cook model as the constitutive relation that should be applied to simulate and design the structural parts made of rNCONEL 718.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.2
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• pp.13-20
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• 2019

This study was conducted in order to validate the nose shape factors of projectile in existing impact formulas for high-strength concrete in the event of collision with high-speed projectiles. In order to conduct the high-speed impact experiment, specified concrete strengths of 35, 100, and 120 MPa were prepared and tested in collision with both conical and hemispherical projectiles. The results showed that the measured penetration depth did not decrease linearly as concrete strength increased. Comparing the ratio penetration depth to the kinetic energy of the conical and hemispherical projectiles, the difference in the ratios for high strength concrete was observed to decline as concrete strength increased. However, in the modified NDRC and the Hughes formulas, the difference in the predicted penetration depth of the conical and hemispherical projectiles was constant despite increasing concrete strength. The modified NDRC and Hughes formulas should be improved upon so as to be applied to high strength concrete.

• Structural Engineering and Mechanics
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• v.77 no.5
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• pp.627-635
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• 2021

The speed of rail vehicles become higher and higher over two decades, and China has unveiled a prototype high-speed train in October 2020 that has been able to reach 400 km/h. At such high speeds, wheel-rail force items that had previously been ignored in common computational model should be reevaluated and reconsidered. Aiming at this problem, a new model for investigating the vehicle-bridge interaction at high moving speed is proposed. Comparing with the common model, the new model was more accurate and applicable, because it additionally considers the second-order pseudo-inertia forces effect and its modeling equilibrium position was based on the initial deformed curve of bridge, which could include the influences of temperature, pre-camber, shrinkage and creep deformation, and pier uneven settlement, etc. Taking 5 km/h as the speed interval, the dynamic responses of the classical vehicle-bridge system in the speed range of 5 km/h to 400 km/h are studied. The results show that ignoring the second-order pseudo-inertia force will underestimate the dynamic response of vehicle-bridge system and make the high-speed railway bridge structure design unsafe.

• ETRI Journal
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• v.27 no.5
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• pp.647-650
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• 2005

A new configuration to realize the most general n-th order voltage transfer function is proposed. It employs only one operational transresistance amplifier (OTRA) as the active element. In the synthesis of the transfer function, the RC:-RC decomposition technique is used. To the best of author's knowledge, this is the first topology to be used in the realization of n-th order transfer function employing single OTRA.

• IE interfaces
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• v.13 no.3
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• pp.396-404
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• 2000

For most order-based production, it is important to meet urgent orders from important customers while maintaining high on-time delivery rate for successful supply chain management. In this paper, we propose an approach and a structure of planning system to implement Capable-To-Promise which promises the delivery time to the received order. We suggest and compare a few alternative order receiving policies for CTP.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.5
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• pp.18-26
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• 1994

We express fundamental second-order and third- order harmonic distortions and intermodulation distortions in terms of the laser parameters. Compared to the Darcie `s result only limited to the high frequency (f >1GHz), these expression are quite valid in the entire modulation frequency region. It is found that the fundamental nonlinear distortions are strongly effected by the spontaneous emission to lasing mode as well as the gain compresion damping in the low frequency region.