한국, 미국, 영국, 싱가포르의 과학 교육과정 비교 - 에너지 개념을 중심으로 -

윤혜경 ( Hye-gyoung Yoon ),정용욱 ( Yong Wook Cheong ) 한국과학교육학회 2017 한국과학교육학회지 Vol.37 No.5

에너지는 매우 복합적인 과학개념으로 많은 국가의 과학 교육과정에서 핵심을 이루는 개념이지만, 교수 학습 과정에서 많은 어려움을 야기하는 개념이기도 하다. 본 연구는 한국, 미국, 영국, 싱가포르의 교육과정을 비교분석하여 향후 교육과정 개정 시 고려해야 하는 에너지 교육과정의 쟁점들을 추출하고자 하였다. 이를 위해 한국의 2015 개정교육과정, 미국의 차세대 과학교육표준(NGSS, Next Generation Science Standards), 영국의 과학 교육과정(National curriculum in England: Science programmes of study), 싱가포르의 과학 교육과정(Science syllabus)에서 에너지를 명시적으로 포함하는 성취기준들을 추출하여, 여섯 가지 개념 요소(에너지 형태, 에너지 자원, 에너지 전달, 에너지 전환, 에너지 보존, 에너지 산일)에 따라 분류하고 비교 하였다. 에너지 관련 성취기준이 학교 급별, 학문 영역별, 에너지 개념 요소별로 어떻게 분포하는지 빈도 분석을 실시하였고, 에너지 개념 요소별로 내용 분석을 병행하였다. 그 결과 모든 나라의 교육과정 모두에서 에너지 개념의 중요성을 확인할 수 있었지만, 세부적으로는 강조하고 있는 개념 요소와 개념 요소별 내용에 있어서 상당한 차이를 발견하였다. 그 중 다른 나라와 대비되는 한국 교육과정의 가장 큰 특징은 에너지 개념 요소 중 에너지의 형태와 관련된 성취기준의 빈도가 가장 높다는 점, 특정 물리량에 대응하지 않는 체 포괄적인 의미로 사용되는 에너지 형태를 포함하고 있다는 점, 에너지 전달에 비해 좀 더 어려운 개념 요소인 에너지 전환을 강조하고 있는 점, 에너지 보존의 경우 역학적 상황에만 국한하여 성취기준이 제시되고 있는 점, 에너지 개념과 관련하여 ‘계’를 도입하지 않고 있는 점 등을 들 수 있다. 이러한 차이가 야기하는 교육과정 개편 상의 쟁점들에 대해서 논의하였다. Energy as a powerful and unifying concept to understand natural world has been regarded as one of the key concepts of the science curricula in many countries. However, concerning learning and teaching of energy, various difficulties have been reported widely. This study aimed at analyzing and comparing science curricula of Korea, the U.S., England, and Singapore regarding energy to identify the potential issues for energy curriculum in the future. 2015 revised Korean science curriculum, Next Generation Science Standards of the U.S., Science programmes of study of England, and the Science syllabus of Singapore were compared based on six basic elements of the concept of energy: energy form, energy resource, energy transfer, energy transformation, energy conservation, and energy dissipation. Achievement criteria that include energy were extracted from all curricula and categorized into the six elements. The frequency and distribution of the six elements in the four curricula were compared in terms of school levels and disciplinary areas. Contents of six energy elements were also compared. Though all curricula emphasized energy as a key science concept, we found many differences in the degree of emphasis of basic ideas and specific contents and approaches. Korean curriculum is characterized by 1) high frequency concerning energy form among the elements of the concept of energy, 2) introducing energy forms of unclear meaning, which are not linked with other physical quantities, 3) emphasis on energy conversion in comparison of energy transfer, 4) focusing on mechanical energy conservation instead of more general energy conservation, and 5) absence of the concept of ‘system’ concerning energy. Issues for energy curriculum development were discussed.

Energy Dissipation Characteristics Modelling for Hot Extrusion Forming of Aluminum-Alloy Components

Hongcheng Li,Yuanjie Wu,Huajun Cao,Feng Lu,Congbo Li 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.6

The hot extrusion forming process is widely used to process aluminum-alloy components in both the automobile and aircraft manufacturing industries. Since it involves pushing the material through the die at increased temperature, it is very energy-intensive despite requiring less blank material allowance. During hot extrusion forming, the multi-stage dynamic conversion of electricity, mechanical energy, and hydraulic energy to heat results in high energy dissipation. In order to improve the power and energy conversion efficiency of hot extrusion forming process, it is necessary to identify the energy dissipation characteristics. The transfer and conversion paths of the electrical, mechanical, and hydraulic energy from the motor to the hydraulic cylinder were firstly depicted based on the motion cycle of the extruder. A bond graph-based energy dissipation model was then proposed for dynamically identifying the energy-saving potentials. The energy dissipation model integrated the power bond graph sub-model of energy conversion elements such as motor, pump, hydraulic valve group, and hydraulic cylinder. These power bond graph sub-models were separately developed to find the energy dissipation state equations of energy conversion elements. An experiment was carried out using data obtained from the energy management system to validate the bond graph-based energy dissipation model. The results have shown that the power and energy conversion efficiency of hot extrusion forming is primarily controlled by the parameters such as extrusion velocity and extrusion force. Both the higher extrusion velocity and lower extrusion force will reduce the power and energy conversion efficiency. An optimal combination of extrusion velocity and pressure can achieve the lowest energy consumption per unit product.

내진 설계를 위한 에너지 소산량 산정법의 활용

임혜정,박홍근,엄태성 한국지진공학회 2003 한국지진공학회논문집 Vol.7 No.6

기존의 비선형 정적 및 동적 해석에서는 철근콘크리트 구조물의 에너지 소산능력을 정확히 고려하지 못하고 있다. 최근 연구에서는 휨지배 철근콘크리트 부재의 에너지 소산능력을 정확히 평가할 수 있는 식이 개발되었으며, 본 연구에서는 이 평가방법을 이용하여 에너지 소산능력을 정확히 고려할 수 있는 비선형 정적 및 동적 해석 방법을 개발하였다. 비선형 정적 해석을 위하여 에너지 스펙트럼 곡선을 개발하고 이를 적용하여 능력스펙트럼법을 개선하였으며, 또한 비선형 동적 해석을 위하여 철근콘크리트 부재의 단순화된 에너지 기초 주기거동모델을 개발하였다. 제안된 모델은 부재의 강성에 기초한 기존의 주기거동모델과는 달리 완전한 주기거동 발생시 소산되는 에너지를 정확하게 반영할 수 있다. 본 연구에서는 제안된 방법에 따라 비선형 정적 및 동적 해석법의 절차를 정립하였으며 이를 적용한 컴퓨터 해석 프로그램을 개발하였다. 제안된 해석 방법은 부재의 단면형태, 철근비, 배근형태 등 설계 변수에 따른 에너지 소산능력을 정확하게 고려하고 지진발생시 에너지 소산능력이 구조물의 성능에 미치는 효과를 반영할 수 있다. Traditional nonlinear static and dynamic analyses do not accurately estimate the energy dissipation capacity of reinforced concrete structure. Recently, simple equations which can accurately calculate the energy dissipation capacity of flexure-dominated RC members, were developed in the companion study. In the present study, nonlinear static and dynamic analytical methods improved using the energy-evaluation method were developed. For nonlinear static analysis, the Capacity Spectrum Method was improved by using the energy-spectrum curve newly developed. For nonlinear dynamic analysis, a simplified energy-based cyclic model of reinforced concrete member was developed. Unlike the existing cyclic models which are the stiffness-based models, the proposed cyclic model can accurately estimate the energy dissipating during complete load-cycles. The procedure of the proposed methods was established and the computer program incorporating the analytical method was developed. The proposed analytical methods can estimate accurately the energy dissipation capacity varying with the design parameters such as shape of cross-section, reinforcement ratio and arrangement, and can address the effect of the energy dissipation capacity on the structural performance under earthquake load.

Parametric study on energy demands for steel special concentrically braced frames

Selçuk Doğru,Bora Akşar,Bülent Akbaş,Jay Shen 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.24 No.2

Structures are designed in such a way that they behave in a nonlinear manner when subject to strong ground motions. Energy concepts have been widely used to evaluate the structural performance for the last few decades. Energy based design can be expressed as the balance of energy input and the energy dissipation capacity of the structure. New research is needed for multi degree of freedom systems (MDOFs)-real structures- within the framework of the energy based design methodology. In this paper, energy parameters are evaluated for low-, medium- and high-rise steel special concentrically braced frames (SCBFs) in terms of total energy input and hysteretic energy. Nonlinear dynamic time history analyses are carried out to assess the variation of energy terms along the height of the frames. A seismic energy demand spectrum is developed and hysteretic energy distributions within the frames are presented.

Study of the Energy Dissipation over the Type-A Piano Key Weir

Deepak Singh,Munendra Kumar 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.4

This study assesses the effects of geometrical variations, i.e., relative width ratio, magnification ratio, and cyclic variation, on the Piano Key Weir energy dissipation performance. In order to assess this, 12 type-A PKW models were tested by conducting an experimental investigation. The analysisincludes results from 280 tests and comprehensive findings of the fluid domain. The results demonstrated that the configuration of the PKWs has a greater influence on energy dissipation. The present study’s findings show that the type-A PKW dissipates energy more efficiently than nonlinear or standard weirs. The energy loss over the PKW decreases as the magnification and relative width ratios increase, although the energy dissipation increases with key cycle numbers. Furthermore, the sensitivity analysis of the weir was examined by making steps at outlet key floors and found that the energy dissipation has been increased by 6.67% at low heads while reduced by 1.59% at higher heads. In addition, the author proposed two empirical projection equations for the optimal relative residual energy configuration downstream of the PKW. The proposed equations are the function of headwater ratio, relative width ratio, and magnification ratio. The results of this investigation are in perfect correlation with earlier studies.

Development of self-centring energy-dissipative rocking columns equipped with SMA tension braces

Yan-Wen Li,Michael C.H. Yam,Ping Zhang,Ke Ke,Yan-Bo Wang 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.82 No.5

Energy-dissipative rocking (EDR) columns are a class of seismic mitigation device capable of dissipating seismic energy and preventing weak-story failure of moment resisting frames (MRFs). An EDR consists of two hinge-supported steel columns interconnected by steel dampers along its height. Under earthquakes, the input seismic energy can be dissipated by plastic energy of the steel dampers in the EDR column. However, the unrecoverable plastic deformation of steel dampers generally results in residual drifts in the structural system. This paper presents a proof-of-concept study on an innovative device, namely self-centring energy-dissipative rocking (SC-EDR) column, aiming at enabling self-centring capability of the EDR column by installing a set of shape memory alloy (SMA) tension braces. The working mechanism of the SC-EDR column is presented in detail, and the feasibility of the new device is carefully examined via experimental and numerical studies considering the parameters of the SMA bar diameter and the steel damper plate thickness. The seismic responses including load carrying capacities, stress distributions, base rocking behaviour, source of residual deformation, and energy dissipation are discussed in detail. A rational combination of the steel damper and the SMA tension braces can achieve excellent energy dissipation and self-centring performance.

Effect of the sagittal ankle angle at initial contact on energy dissipation in the lower extremity joints during a single-leg landing

Lee, Jinkyu,Song, Yongnam,Shin, Choongsoo S. Elsevier 2018 GAIT AND POSTURE Vol.62 No.-

<P><B>Abstract</B></P> <P><B>Background</B></P> <P>During landing, the ankle angle at initial contact (IC) exhibits relatively wide individual variation compared to the knee and hip angles. However, little is known about the effect of different IC ankle angles on energy dissipation.</P> <P><B>Research question</B></P> <P>The purpose of this study was to investigate the relationship between individual ankle angles at IC and energy dissipation in the lower extremity joints.</P> <P><B>Methods</B></P> <P>Twenty-seven adults performed single-leg landings from a 0.3-m height. Kinetics and kinematics of the lower extremity joints were measured. The relationship between ankle angles at IC and negative work, range of motion, the time to peak ground reaction force, and peak loading rate were analyzed.</P> <P><B>Results</B></P> <P>The ankle angle at IC was positively correlated with ankle negative work (r = 0.80, R<SUP>2</SUP> = 0.64, <I>p <</I> 0.001) and the contribution of the ankle to total (ankle, knee and hip joint) negative work (r = 0.84, R<SUP>2</SUP> = 0.70, p < 0.001), but the ankle angle was negatively correlated with hip negative work (r = −0.46, R<SUP>2</SUP> = 0.21, <I>p</I> = 0.01) and the contribution of the hip to total negative work (r = −0.61, R<SUP>2</SUP> = 0.37, <I>p <</I> 0.001). The knee negative work and the contribution of the knee to total negative work were not correlated with the ankle angle at IC. The ankle angle at IC was positively correlated with total negative work (r = 0.50, R<SUP>2</SUP> = 0.25, <I>p < </I>0.01) and negatively correlated with the peak loading rate (r = −0.76, R<SUP>2</SUP> = 0.57, <I>p </I>< 0.001).</P> <P><B>Significance</B></P> <P>These results indicated that landing mechanics changed as the ankle angle at IC increased, such that the ankle energy dissipation increased and redistributed the energy dissipation in the ankle and hip joints. Further, these results suggest that increased ankle energy dissipation with a higher IC plantar flexion angle may be a potential landing technique for reducing the risk of injury to the anterior cruciate ligament and hip musculature.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ankle angle at initial contact (IC) alter energy dissipation of lower limb joints. </LI> <LI> Higher plantar flexion at IC increases ankle energy dissipation during landing. </LI> <LI> Higher plantar flexion at IC decreases hip energy dissipation during landing. </LI> <LI> Higher plantar flexion at IC decreases peak loading (GRF) rates. </LI> <LI> Higher plantar flexion at IC may reduce injury risk to the ACL and hip musculature. </LI> </UL> </P>

연결보의 이력단계별 에너지 소산계수의 변화에 관한 연구

유석형 대한건축학회 2023 대한건축학회논문집 Vol.39 No.11

철근콘크리트 부재는 이력거동 시 핀칭과 강성 및 강도 저하로 인한 에너지소산을 경험하므로, 비선형 시간이력해석 시 재료 및 부재의 이력거동 특성을 적절히 고려해야 한다. 에너지소산계수는 소산에너지와 이상화된 탄소성 거동에너지의 비율로 구하며, 이력거동이 진행됨에 따라 감소할 것으로 예상된다. 그러나 지침서(AIK-B-2021-001)에서는 각 부재별로 단일한 에너지 소산 계수를 제안하고 있다. 본 연구에서는 기존 실험 결과와 Perform 3D의 Shear Hinge Displacement Type 요소를 이용한 비선형 시간이력해석을 통해 연결보의 에너지소산계수의 변화를 관찰하였다. 이상화된 탄소성 에너지를 구하기 위해 이력 거동 모델을 정립하였다. 결론적으로, 이력단계가 진행됨에 따라 에너지소산계수는 감소하는 것으로 관찰되었으며, 이를 정량화하였다. Reinforced concrete members undergo energy dissipation as they experience pinching and a reduction in both stiffness and strength duringhysteretic behavior. Thus, it is crucial to adequately account for the hysteretic behavior characteristics of materials and members in nonlineartime history analysis. The energy dissipation coefficient, which measures how energy is lost during cyclic behavior, is expected to decreaseas the behavior progresses. However, current guidelines referred to as AIK-B-2021-001 suggest a single energy dissipation factor for eachmember. In this study, changes were observed in the energy dissipation coefficient of coupling beams based on existing experimental resultsand nonlinear time history analysis using the Shear Hinge Displacement Type element of Perform 3D. A model was established for thehysteretic behavior to determine the idealized elastoplastic energy. In conclusion, it was found that the energy dissipation coefficient decreasedas the hysteretic behavior advanced, and this change was quantified.

Application of Energy Dissipation Technology in High-Rise Buildings

Hu, Da-Zhu,Zhang, Xiao-Xuan,Li, Guo-Qiang,Sun, Fei-Fei,Jin, Hua-Jian Council on Tall Building and Urban Habitat Korea 2021 International journal of high-rise buildings Vol.10 No.2

The principle of energy dissipation technology is to dissipate or absorb the seismic energy input through the deformation or velocity change of dampers installed in the main structure of high-rise buildings, so as to reduce the seismic response of the buildings. With the development of energy dissipation technology, recognized as an effective and new measurement for reducing seismic effects, its application in high-rise buildings has become more and more popular. The appropriate energy dissipation devices suitable for high-rise buildings are introduced in this paper. The effectiveness of energy-dissipation technology for reducing the seismic response of high-rise buildings with various structural forms is demonstrated with a number of actual examples of high-rise buildings equipped with various energy dissipation devices.

Dissipation of energy in steel frames with PR connections

Reyes-Salazar, Alfredo,Haldar, Achintya Techno-Press 2000 Structural Engineering and Mechanics, An Int'l Jou Vol.9 No.3

The major sources of energy dissipation in steel frames with partially restrained (PR) connections are evaluated. Available experimental results are used to verify the mathematical model used in this study. The verified model is then used to quantify the energy dissipation in PR connections due to hysteretic behavior, due to viscous damping and at plastic hinges if they are formed. Observations are made for two load conditions: a sinusoidal load applied at the top of the frame, and a sinusoidal ground acceleration applied at the base of the frame representing a seismic loading condition. This analytical study confirms the general behavior, observed during experimental investigations, that PR connections reduce the overall stiffness of frames, but add a major source of energy dissipation. As the connections become stiffer, the contribution of PR connections in dissipating energy becomes less significant. A connection with a T ratio (representing its stiffness) of at least 0.9 should not be considered as fully restrained as is commonly assumed, since the energy dissipation characteristics are different. The flexibility of PR connections alters the fundamental frequency of the frame. Depending on the situation, it may bring the frame closer to or further from the resonance condition. If the frame approaches the resonance condition, the effect of damping is expected to be very important. However, if the frame moves away from the resonance condition, the energy dissipation at the PR connections is expected to be significant with an increase in the deformation of the frame, particularly for low damping values. For low damping values, the dissipation of energy at plastic hinges is comparable to that due to viscous damping, and increases as the frame approaches failure. For the range of parameters considered in this study, the energy dissipations at the PR connections and at the plastic hinges are of the same order of magnitude. The study quantitatively confirms the general observations made in experimental investigations for steel frames with PR connections; however, proper consideration of the stiffness of PR connections and other dynamic properties is essential in predicting the dynamic behavior.