• 한국재료학회지
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• 제25권8호
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• pp.370-375
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• 2015

In this study, to confirm the effect of alloying elements on the phase transformation and conditions of the friction stir process, we processed two materials, SS400 and SM45C steels, by a friction stir process (FSP) under various conditions. We analyzed the mechanical properties and microstructure of the friction stir processed zone of SS400 and SM45C steels processed under 400RPM - 100mm/min conditions. We detected no macro (tunnel defect) or micro (void, micro crack) defects in the specimens. The grain refinement in the specimens occurred by dynamic recrystallization and stirring. The microstructure at the friction stir processed zone of the SS400 specimen consisted of an ${\alpha}$-phase. On the other hand, the microstructure at the friction stir processed zone of the SM45 specimen consisted of an ${\alpha}$-phase, $Fe_3C$ and martensite due to a high cooling rate and high carbon content. Furthermore, the hardness and impact absorption energy of the friction stir processed zone were higher than those of base metals. The hardness and impact absorption energy of FSPed SM45C were higher than that of FSPed SS400. Our results confirmed the effect of alloying elements on the phase transformation and mechanical properties of the friction stir processed zone.

• 한국해안해양공학회지
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• 제11권3호
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• pp.135-140
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• 1999

에너지 감쇠역으로 인한 파의 변형을 모의하기 위하여 타원형 수치모형을 구성하였다. 해석방정식은 에너지 감쇠항이 추가된 타원형 완경사 방정식을 사용하였다. 개방경계조건에는 포물형 가정을 도입하였고 이를 위해 수치기법으로는 GCGM을 사용하였다. 원형감쇠역에 대한 수치실험을 통하여 감쇠역 전부에서의 반사파의 생성, 감쇠효과에 의한 파고감소 등을 확인할 수 있었고 해석해와 잘 일치하였다. 사각형 감쇠역에 대한 실험을 통하여 감쇠계수의 크기에 따른 파고분포의 변화를 살펴보았고 감쇠역 주변에서는 회절효과에 의한 파고의 증가가 매우 완만히 진행됨을 확인하였다. 이러한 수치실험을 통하여 에너지 감쇠구조 또한 반복기법을 사용한 타원형 수치모형으로 잘 모의할 수 있음을 확인하였다.

• 한국광물학회지
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• 제29권2호
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• pp.73-78
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• 2016

점토 광물의 구조 내에 들어 있는 철의 산화수는 퇴적환경의 산화/환원 조건에 대한 정보를 제공하여 준다. 이러한 광물형성의 메커니즘을 밝히기 위해서는 고해상도를 가진 전자현미경을 이용한 나노 스케일 분석이 불가피하다. 투과전자현미경에 장착되어있는 전자에너지 손실분광 분석법(EELS)을 이용하여 정량적 철 산화수 분석을 논트로나이트 점토광물 구조 내 철의 환원으로 인한 K-논트로나이트의 형성의 예를 들어 설명하고자 한다. 철 산화/환원의 정량적 분석을 통하여 퇴적물의 위치에 따른 철 산화도 측정은 광물변화에 대한 연구를 용이하게 해준다. 따라서 본 논문은 전자에너지 손실분광의 분석방법 및 장점을 소개함을 목적으로 한다.

• 한국주조공학회지
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• 제32권1호
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• pp.32-37
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• 2012

In this study, microstructural evaluation was carried out on secondary hardening type ultrahigh strength steel, Fe-Co-Ni composition. This paper as a first part of whole research presented the microstructural behavior by cyclic heat treatment. The cyclic heat treatment method includes normalizing, stress relieving, solution treatment and aging. Especially, solution treatments performed triple times to get maximized solution hardening. Phase transformation and microstructure were observed by using optical microscope (OM), Electron back-scattered diffraction (EBSD) and X-ray stress analyzer. During the triple solution treatment, size of grain boundary was dramatically decreased by generating a packet from the martensite transformation of residual austenite in the inner part of grain, whereas the hardness increase was not significant.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.325-325
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• 2011

Very initial stage of oxidation process of Si (001) surface at room temperature (300 K) and high temperature (1200 K) was investigated using large scale molecular dynamics simulation. Reactive force field potential [1] was used for the simulation owing to its ability to handle charge variation as well as breaking and forming of bonds associated with the oxidation reaction. The results show that oxygen molecules adsorb dissociatively or otherwise leave the silicon surface. Initial position and orientation of oxygen molecule above the surface play important role in determining final state and time needed to dissociate. At 300 K, continuous transformation of ion $Si^+$ (or suboxide Si2O) to $Si2^+$ (SiO), $Si3^+$ (Si2O3) and finally to $Si4^+$ (SiO2) clearly observed. High temperature silicon surface provide heat energy that enable oxygen atom to penetrate into deeper silicon surface. The heat energy also retards adsorption process. As a result, transformation of ion $Si^+$ is impeded at 1200 K.

• Advances in aircraft and spacecraft science
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• 제3권3호
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• pp.271-298
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• 2016

In this paper, we study a problem of passive suppression of helicopter Ground Resonance (GR) using a single degree freedom Nonlinear Energy Sink (NES), GR is a dynamic instability involving the coupling of the blades motion in the rotational plane (i.e. the lag motion) and the helicopter fuselage motion. A reduced linear system reproducing GR instability is used. It is obtained using successively Coleman transformation and binormal transformation. The analysis of the steadystate responses of this model is performed when a NES is attached on the helicopter fuselage. The NES involves an essential cubic restoring force and a linear damping force. The analysis is achieved applying complexification-averaging method. The resulting slow-flow model is finally analyzed using multiple scale approach. Four steady-state responses corresponding to complete suppression, partial suppression through strongly modulated response, partial suppression through periodic response and no suppression of the GR are highlighted. An algorithm based on simple criterions is developed to predict these steady-state response regimes. Numerical simulations of the complete system confirm this analysis of the slow-flow dynamics. A parametric analysis of the influence of the NES damping coefficient and the rotor speed on the response regime is finally proposed.

• 대한간호학회지
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• 제30권5호
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• pp.1145-1155
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• 2000

The purpose of this study is to explore the concept spirituality and to gain understanding of nursing intervention that may improve spiritual well-being. The concept analysis framework developed by Walker and Avant (1995) was used to clarify the concept. In the study, 'Harmonious interconnectedness', 'Transcendence', 'Integrative Energy' and 'Purpose and Meaning in Life' emerged as the critical attributes of spirituality. The first attribute, 'harmonious Inter- connectedness', has three categories including intrapersonal, (self), interpersonal (others/ nature) and transpersonal (the Supreme Being). The second attribute, 'Transcendence', is defined as the ability to extend one's own self beyond the limits of usual experiences and to achieve new perspectives. This attribute is demonstrated by 'coping with situations', to 'self-healing', and 'transformation'. The third attribute of spirituality is 'Integrative Energy', which integrates all dimensions and acts as a creative and dynamic force that keeps a person growing and changing. 'Integrative Energy is also defined as an inner resource that gives a sense of empowerment. Therefore the highly spiritual person demonstrate 'inner peace', 'growing', 'inner strength,' and 'well-being'. The fourth attribute 'Purpose and Meaning in Life' represents a sense of connectedness with one's inner values and with a greater purpose in life. It is demonstrated by 'hope' and 'a powerful life'. In this study, the antecedents of the spirituality represented as 'spirit' and its potential enablers were 'Introspection/reflection', 'Interconnectedness with all living things', and an 'Awareness of a Higher-Power'. The consequences of this concept may be described as 'physical, psychosocial, and spiritual well-being'. Empirical referents of this are 'purposeful life' 'self-worth' 'hope' 'love' 'service' 'forgiveness' 'trust/belief' 'inner peace' 'self-actualization' 'religious practices' 'transformation' 'inner strength' and 'coping'. In conclusion, spirituality can be defined based on these critical attributes. Spirituality is a dynamic, integrative energy based on a feeling of harmonious interconnection with self, others and a higher power. Through it, one is enabled to transcend and to live with meaning and purpose in life.

• Journal of Information Processing Systems
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• 제13권5호
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• pp.1372-1381
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• 2017

In this paper, a texture feature extraction method using local energy and local correlation of Gabor transformed images is proposed and applied to an image retrieval system. The Gabor wavelet is known to be similar to the response of the human visual system. The outputs of the Gabor transformation are robust to variants of object size and illumination. Due to such advantages, it has been actively studied in various fields such as image retrieval, classification, analysis, etc. In this paper, in order to fully exploit the superior aspects of Gabor wavelet, local energy and local correlation features are extracted from Gabor transformed images and then applied to an image retrieval system. Some experiments are conducted to compare the performance of the proposed method with those of the conventional Gabor method and the popular rotation-invariant uniform local binary pattern (RULBP) method in terms of precision vs recall. The Mahalanobis distance is used to measure the similarity between a query image and a database (DB) image. Experimental results for Corel DB and VisTex DB show that the proposed method is superior to the conventional Gabor method. The proposed method also yields precision and recall 6.58% and 3.66% higher on average in Corel DB, respectively, and 4.87% and 3.37% higher on average in VisTex DB, respectively, than the popular RULBP method.

• Steel and Composite Structures
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• 제22권3호
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• pp.589-611
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• 2016

The primary objectives of this research are to investigate the energy factor response of steel moment resisting frame (MRF) systems equipped with fuses subject to ground motions and to develop an energy-based evaluation approach for evaluating the damage-control behavior of the system. First, the energy factor of steel MRF systems with fuses below the resilience threshold is derived utilizing the energy balance equation considering bilinear oscillators with significant post-yielding stiffness ratio, and the effect of structural nonlinearity on the energy factor is investigated by conducting a parametric study covering a wide range of parameters. A practical transformation approach is also proposed to associate the energy factor of steel MRF systems with fuses with classic design spectra based on elasto-plastic systems. Then, the energy balance is extended to structural systems, and an energy-based procedure for damage-control evaluation is proposed and a damage-control index is also derived. The approach is then applied to two types of steel MRF systems with fuses to explore the applicability for quantifying the damage-control behavior. The rationality of the proposed approach and the accuracy for identifying the damage-control behavior are demonstrated by nonlinear static analyses and incremental dynamic analyses utilizing prototype structures.

• 전자통신동향분석
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• 제36권1호
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• pp.109-119
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• 2021

The Korean government recently announced a plan of the Carbon Neutral policy in addition to the Green New Deal of the Korean New Deal and the Renewable Energy 3020. The energy sector is entering the era of major transformation involving the expansion of decarbonization, decentralization, and digitalization. DNA-oriented ICT technology will be incorporated into the sector. Further, new energy industries and services are being realized via efficient and smart operation and by appropriately managing the energy-environment changes. Recently, ETRI presented a technology development map for 2035 comprising 12 new concepts in four major fields(personal, social, industrial and public) of national intelligence. This map includes the concept of "Energy Maestro" associated with the field of public intelligence for human sustainability. This paper briefly introduces this concept and ETRI's Energy-R&D status. Based on the domain knowledge and the experience acquired through the R&D, ETRI will lead to a new paradigm with respect to the creation of new energy services and industries via the incorporation of the new ICT technologies including AI and big-data into the energy sector.