• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.427-733
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• 2003

Adiabatic shear bands have been observed in the serrated chip during high strain rate metal cutting process of medium carbon steel and titanium alloy. The recent microscopic observations have shown that dynamic recrystallization occurs in the narrow adiabatic shear bands. However the conventional flow stress models such as the Zerilli-Armstrong model and the Johnson-Cook model, in general, do not predict the occurrence of dynamic recrystallization (DRX) in the shear bands and the thermal softening effects accompanied by DRX. In the present study, a strain hardening and thermal softening model is proposed to predict the adiabatic shear localized chip formation. The finite element analysis (FEA) with this proposed flow stress model shows that the temperature of the shear band during cutting process rises above 0.5T$\sub$m/. The simulation shows that temperature rises to initiate dynamic recrystallization, dynamic recrystallization lowers the flow stress, and that adiabatic shear localized band and the serrated chip are formed. FEA is also used to predict and compare chip formations of two flow stress models in orthogonal metal cutting with AISI 1045. The predictions of the FEA agreed well with the experimental measurements.

• Journal of The Korean Association For Science Education
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• v.23 no.4
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• pp.419-429
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• 2003

The developments of science education until the middle of the 20th century were often driven by personal ideas and achievements of some influential individual scientists (e.g. T. H. Huxley, H. E. Armstrong. L. Hogben, J. Conant). while that of the 2nd half of the 20th century can be characterized as collective efforts through various research grou ps of science educators (e.g. PSSC, HPP, Nuffield, SATIS). In this respect, John Tyndall(1820-1894), a physicist of the Victorian England best known as Tyndall's Effect, can be considered as one of the great scientists who made a big influence on science teaching and the popularization of science before science secured its place in school curricula. Tyndall worked as a research scientist at the Royal Institution of London, where various lectures and demonstrations of physical sciences were regularly performed for general public, and he was particularly famous for his fascinating physics demonstrations. In this study, we summarize his activities and achievements as a teacher as well as a popularizer of physics, illustrate some of his famous demonstrations and his ideas concerning physics teaching and discuss their implications to today's physics education.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1990.10a
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• pp.157-162
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• 1990

기계의 정밀도 향상을 위하여는 기계에 대한 보다 정확한 해석을 요구한다. 그러나 실제 기계 시스템은 마찰, Backlash, Saturation등과 같은 비서형 특 성을 가지고 있어 시스템의 해석 및 제어가 어렵게 된다. 특히, 축, 링크, 기 어, 풀리, 베어링등의 기계요소에서는 마찰로 인해 정밀도가 크게 덜어지고 있어, 마찰에 의한 동특성 및 제어는 많은 연구자들에 의해 관심의 대상이 되어 왔다. 마찰력을 고려한 기계시스템의 운동은 정지상태 근처에서 마찰력 의 변화가 심한 비선형 동특성을 보이고 있어 그 해석에 어려움을 겪고 있 다. 실제 마찰이 저속에서 고급 비선형임에도 불구하고 가장 널리 사용되는 형태의 모델로서 쿨통 마찰을 고려한 운동방정식 조차 비선형성으로 인하여 해석에 어려움이 따르고 있다. 마찰은 오랜동안 연구되어 오면서 Fig.1, Fig2 와 같이 등가선형점성 감쇠, 쿨통마찰, 정적마찰로 모델화되거나 이들의 조 합으로 나타내었다[1-5]. 마찰력은 시간영역에서도 연구되어 Walrath[7]는 Fig.3-a의 속도가 역전되는 지점에서 마찰토오크가 .+-.Tf를 공유하는 문제 를 고려하기 위해, Fig.3-b와 같이 동적마찰모델을 사용하였다. 최근의 연구 로서 Armstrong[7]은 마찰의 위치의존성을 고려한 정확한 마찰모델을 설정 하여 개루프제어에 적용, 좋은 제어특성을 확인하였고, Canudas[8]는 저속영 역에서 overcompensation시 limit cycle과 gain의 관계를 해석하였다.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.3
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• pp.795-798
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• 2012

Objective: This descriptive, cross sectional study was conducted to examine the effect of levels of self-efficacy on children's perceptions of pros and cons of smoking. Methodology: The sample was 233 fifth-grade students. Data were collected in September 2010 using the Socio-Demographic Data Collection Form, Self Efficacy Scale Child Form and Child Decision Balance Scale and analyzed via percentage calculations and t test with the SPSS 11.00 statistical package program. Results: Average age of the students participating in the research was $11.1{\pm}0.41$, 49.8 % (n: 116) being female and 50.2 % (n:117) male. The difference between the score averages of the pros of smoking perceptions of children with a high self-efficacy level and of those with a low self efficacy level (t=2.117, p=.042) and the difference between the score averages of the cons of smoking perceptions of children with a high self-efficacy level and of those with a low self-efficacy level (t=2.206, p=.035) were found to be statistically significant. Conclusions: Children's positive perceptions of smoking were low and negative perceptions high when their self efficacy levels were high. Conversely, children's positive perceptions of smoking were high when their self efficacy levels were low.

• Transactions of Materials Processing
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• v.12 no.4
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• pp.358-363
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• 2003

Adiabatic shear bands have been observed in the serrated chip during high strain rate metal cutting process of medium carbon steel and titanium alloy The recent microscopic observations have shown that dynamic recrystallization occurs in the narrow adiabatic shear bands. However the conventional flow stress models such as the Zerilli-Armstrong model and the Johnson-Cook model, in general, do not predict the occurrence of dynamic recrystallization (DRX) in the shear bands and the thermal softening effects accompanied by DRX. In the present study, a strain hardening and thermal softening model is proposed to predict the adiabatic shear localized chip formation. The finite element analysis (FEA) with this proposed flow stress model shows that the temperature of the shear band during cutting process rises above 0.5Τ$_{m}$. The simulation shows that temperature rises to initiate dynamic recrystallization, dynamic recrystallization lowers the flow stress, and that adiabatic shear localized band and the serrated chip are formed. FEA is also used to predict and compare chip formations of two flow stress models in orthogonal metal cutting with AISI 1045. The predictions of the FEA agreed well with the experimental measurements.s.

• Knee surgery & related research
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• v.30 no.4
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• pp.319-325
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• 2018

Purpose: Body mass index (BMI) is often used to predict surgical difficulty in patients receiving total knee arthroplasty (TKA); however, BMI neglects variation in the central versus peripheral distribution of adipose tissue. We sought to examine whether anthropometric factors, rather than BMI alone, may serve as a more effective indication of surgical difficulty in TKA. Materials and Methods: We prospectively enrolled 67 patients undergoing primary TKA. Correlation coefficients were used to evaluate the associations of tourniquet time, a surrogate of surgical difficulty, with BMI, pre- and intraoperative anthropometric measurements, and radiographic knee alignment. Similarly, Knee Injury and Osteoarthritis Outcome Score (KOOS) was compared to BMI. Results: Tourniquet time was significantly associated with preoperative inferior knee circumference (p=0.025) and ankle circumference (p=0.003) as well as the intraoperative depth of incision at the quadriceps (p=0.014). BMI was not significantly associated with tourniquet time or any of the radiographic parameters or KOOS scores. Conclusions: Inferior knee circumference, ankle circumference, and depth of incision at the quadriceps (measures of peripheral obesity) are likely better predictors of surgical difficulty than BMI. Further study of alternative surgical indicators should investigate patients that may be deterred from TKA for high BMI, despite relatively low peripheral obesity.

• Journal of English Language & Literature
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• v.64 no.1
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• pp.3-24
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• 2018

Stories are important instruments for configuring our cognitive and social worlds, but they do not necessarily make us more caring or less aggressive and self-involved. The ability to tell and follow a story requires cognitive capacities that are basic to the neurobiology of mental functioning, and so it would stand to reason that our experiences with stories would draw on and re-shape patterns of interaction that extend beyond the immediate experience of reading or listening to a narrative. Our intuitive, bodily-based ability to understand the actions of other people is fundamental to social relations, including the circuit between the representation of a configured action emplotted in a narrative and the reader's or listener's activity of following the story as we assimilate its patterns into the figures that shape our worlds. The activity of following a narrative can have a variety of beneficial or potentially noxious social consequences, either promoting the shared intentionality that neurobiologically oriented cultural anthropologists identify as a unique human capacity supporting culturally productive collaboration, or habitualizing and thereby naturalizing particular patterns of perception into rigid ideological constructs. The doubling of "me" and "not-me" in narrative acts of identification may promote the "we-intentionality" that makes socially beneficial cooperation possible, or it can set off mimetic conflict and various contagion effects. Neuroscience cannot predict what the social consequences of narrative will be, but it can identify the brain- and body-based processes through which (for better or worse) stories exercise social power.

• East Asian Economic Review
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• v.26 no.1
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• pp.3-25
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• 2022

East Asia's Regional Comprehensive Economic Partnership (RCEP) came into force in 2022 as the world's largest free trade agreement. RCEP was concluded, signed and brought into force in the face of major international uncertainty and is a significant boost to the global trading system. RCEP brings Australia, China, Japan, South Korea and New Zealand into the same agreement with the ten member ASEAN group at its centre. It keeps markets open and updates trade and investment rules in East Asia, a major centre of global economic activity, at a time of rising protectionism when the WTO itself is under threat. The agreement builds on ASEAN's free trade agreements and strengthens ASEAN centrality. One of the pillars of RCEP is an economic cooperation agenda which has its antecedents in ASEAN's approach to bringing along its least developed members and builds on the experience of capacity building in APEC and technical cooperation under the ASEAN Australia-New Zealand Free Trade Agreement. There is an opportunity to create a framework that facilitates deeper economic cooperation that involves experience-sharing, extending RCEP's rules and membership at the same time as strengthening political cooperation. The paper suggests some areas that might be best suited to cooperation - that is confidence and trust building instead of or before negotiation - and discusses how non-members may be engaged and the membership expanded. Options such as multilateralising provisions and becoming a platform for policy convergence and coordinating unilateral reforms are canvassed.

• International Journal of High-Rise Buildings
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• v.12 no.2
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• pp.107-120
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• 2023

Tall buildings are frequently decried as unsustainable due to their excessive energy usage. Early skyscrapers used natural light and ventilation to facilitate human comfort and applied organic materials such as stone, glass, wood, concrete, and terra cotta for cladding and finishes. With the advent of fluorescent lighting, modern heating, ventilation, air-conditioning (HVAC) systems, and thermally sealed curtain walls, tall office buildings no longer had to rely on natural light and ventilation to provide comfort. Energy efficiency was not a significant factor when the operational costs of buildings were relatively inexpensive. However, today's skyscrapers must become more energy-efficient and sustainable due to energy crises and climate change. This paper highlights vital energy-efficient design principles and demonstrates with illustrative case studies how they are applied to tall buildings in various parts of the world. It shows how sustainable environmental systems do not act alone but are integrated with advanced curtain wall systems, sky gardens, and atria, among others, to regulate and sustain thermal comfort and conserve energy.

• Transactions of Materials Processing
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• v.33 no.1
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• pp.18-35
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• 2024

In the present work, the evolution rules for the internal variables including continuum damage factors are obtained using the thermodynamic framework, which are in turn facilitated to derive the elastic-plastic constitutive relation for the particulate composites. Using the Mori-Tanaka scheme, the homogenization on state and internal variables such as back-stress and damage factors is carried out to procure the rate independent plasticity relations. Moreover, the degradation of mechanical properties of constituents is depicted by the distinctive damages such that the phase and interfacial damages are treated individually accordingly, whereas the kinematic hardening is depicted by combining the Armstrong-Frederick and Phillips' back-stress evolutions. On the other hand, the present constitutive relation for each phase is expressed in terms of the respective damage-free effective quantities, then, followed by transformation into the damage affected overall nominal relations using the aforementioned homogenization concentration factors. An emphasis is placed on the qualitative analyses for strain localization by observing the perturbation growth instead of the conventional bifurcation analyses. It turns out that the proposed constitutive model offers a wide range of strain localization behavior depending on the evolution of various internal variable descriptions.