• 한국과학교육학회지
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• 제34권5호
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• pp.437-447
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• 2014

Learning Progressions(학습진행과정, 이하 LP)은 "과학의 핵심 아이디어(core idea) 혹은 과학 활동(scientific practices) 이해 과정을 상대적으로 단순한 체계에서 전문가의 지식체계로 논리적이고, 순차적인 단계로 정교하게 설명한 틀"로서, 한 교과 내 및 다른 과학영역들(물리, 지구과학, 생물, 화학)과 연결하여 연계적 교육과정을 구성하는 이론적 기반을 제공한다. 학습은 개개인의 선지식, 선경험, 교과교육과정, 교육과정 등의 여러 요소에 영향을 받는 복잡한 이해 과정으로, LP 단계를 모든 학생들이 동일하게 이동하지 않는다. 학생과 학습환경의 특성에 따른 이동 가능한 학습경로의 서술을 위해서는 다양한 학생데이터의 수집과 분석이 필요하다. 이러한 과정을 통해서 가설의 LP는 과학적으로 증명된 LP로 규명되며. 비로소 교과과정 개발의 틀(framework)로 역할을 할 수 있다. 본 연구는 미시간 대학 연구팀이 개발한 "물질의 본성(nature of matter)" 주요 개념에서, 하위개념인 "물질의 입자성(particule nature of matter)과 입자적 표상(submicroscophic representation)"의 LP와 관련 평가지를 우리나라 과학교육과정과 연계, 수정하여 개발하였다. 수정된 평가지와 LP는 124명의 중고등학생의 LP 경로 특성을 분석하는데 사용되었다. 학생들의 입자적 개념과 표상의 이해도, 개념과 표상 이해도 연관성을 중점으로 분석하여 관련 과학교육과정과 현장 수업의 문제점과 시사점을 도출하였다. 본 연구결과를 종합해 보면, 높은 레벨 문항의 정답을 고른 빈도수는 낮은 레벨 문항을 모두 정답으로 고른 경우에 높았으며 이는 학생들이 본 연구팀이 개발한 LP 경로로 이해과정을 정교화시킴을 알 수 있다. 하지만, 대부분의 학생들, 특히 고등학생들은 초등학교 수준의 거시적 물질의 본성 개념 LP 단계에 머물고 있으며, 중학교 수준인 미시적 표상 LP 단계에 있다. 입자적 개념과 표상 이해 실패의 주요 원인은 1) 과학적 모델의 본질, 2) 관련 선지식, 3) 미립자 표상의 이해부족으로 정리된다. 본 연구결과는 물질의 입자성과 관련된 개념, 과학활동(특히 모델링)을 증진시키고 개개인 특성에 맞는 맞춤형 학습환경 제공을 위한 학습, 교수, 평가자료 개발에 기여하는 바가 크다. 더 나아가 '물질의 본성'에 대한 LP연구와 과학적 소양 증진에 긍정적 역할을 할 것으로 기대한다.

• Journal of the Korean Physical Society
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• 제73권10호
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• pp.1596-1602
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• 2018

We suggest that the dark matter in the universe has quantum entanglement if the dark matter is a Bose-Einstein condensation of ultra-light scalar particles. In this theory, any two regions of a galaxy are quantum entangled due to the quantum nature of the condensate. We calculate the entanglement entropy of a typical galactic halo, which turns out to be at least O(ln(M/m)), where M is the mass of the halo and m is the mass of a dark matter particle. The entanglement can be inferred from the rotation curves of the galaxy or the interference patterns of the dark matter density.

• 한국초등과학교육학회지:초등과학교육
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• 제37권1호
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• pp.39-53
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• 2018

The purpose of this study was to investigate the conceptual structure of subjects related to matter having pre-service elementary school teachers by applying semantic network analysis (SNA). The analyzed concepts in the subjects of matter were 6 words such as 'atom', 'molecule', 'ion', 'electron', 'matter' and 'particle'. The results of SNA of the concepts are as follows : 1. In the semantic network of 'atom', words having a high betweenness centrality were linked with the words based on both the scientific context and the everyday context. 2. The network of 'molecule' was analyzed to be more organized than the network of the 'atom'. 3. In the network of 'ion', the group of words of the scientific context was distinguished from the group of words of the everyday context. 4. The network of 'electron' was analyzed to be more oriented on electricity and magnetism in the field of physics. 5. In the network of 'matter', the words related to compounds were linked with knowledge of history of science. 6. The network of 'particle' was not structured with words based on particulate nature of matter.

• 대한화학회지
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• 제51권1호
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• pp.65-72
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• 2007

본 연구에서는 우리나라 7차 과학과 교육과정(화학 영역)에서 물질의 의미, 입자 개념, 물질의 상태등의 내용을 살펴보았다. 교육과정에서 ‘물질'이라는 용어를 명확하게 정의하지 않은 채 material, matter, substance 등 서로 다른 의미로 혼용하고 있어 학생들이 순물질 개념을 이해하는 데 어려움을 주고 있다. 물질의 입자성에 대해서는 9학년에서 원자 개념, 10학년에서 이온 개념을 도입하기 이전에, 7학년에서 물질의 기본 단위로 분자 개념을 도입한다. 학생들이 물질의 구조에 대해 통합적으로 일관성 있게 이해할 수 있도록 각 입자 개념의 제시 순서를 재고할 필요가 있다. 상태 변화에서는 물질 보존이나 가역성 등 주요 개념들을 교육 과정에서 명시하지 않고 있으며, 다양한 입자적 관점에서의 설명을 충분히 제공하지 못한 경향이 있었다. 물질 개념은 화학에서 기본이 되므로, 이를 명확히 가르칠 것을 유념해야 할 것이다. 교육과정 개선에 대한 시사점을 논의하였다.

• 한국의학물리학회지:의학물리
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• 제29권3호
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• pp.81-91
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• 2018

Particulate matter (PM) in dust causes serious pathological conditions, and it has been considered a critical health issue for many years. Respiratory disorders such as bronchitis, asthma, and chronic inflammation, are the most common illnesses due to PM that appears as dust. There is evidence that cardiovascular and neurological abnormalities are caused by PM. Although an extensive amount of work has been conducted on this topic, including studies on the nature of the particles, particle size measurements, particle distribution upon inhalation, the health effects of fine particles, disease prevention, diagnosis, and treatment, to this date, there is still a considerable lack of knowledge in these areas. Therefore, the identification of the key components that cause diseases owing to PM, and the specific diagnoses of the diseases, is important. This review will explore the current literature on the origin and nature of PM and their effects on human health. In addition, it will also highlight the approaches that have been adopted in order to diagnose the effects of PM using positron emission tomography (PET) or single-photon emission computerized tomography (SPECT).

• 한국초등과학교육학회지:초등과학교육
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• 제37권2호
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• pp.147-160
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• 2018

The purpose of this study is to compare the elementary science curriculum and textbooks of Korea, the United States, Japan, and Singapore to know how the contents on particulate concept of matter is introduced and expressed. In Korea, particulate concept of matter was adopted as a term for 'molecules' in the 3rd through 6th curriculum, and the term for 'particles' was adopted in the 2009 revised curriculum. In the United States, NGSS adopted the term 'particle' in fifth grade. Japan presented the concept of 'particle' as a core concept of matter in the commentary, and the expressions 'particles' were being introduced in the textbooks. But it did not cover particulate nature of matter at the elementary school level in Singapore. An analysis of elementary textbooks in Korea, the United States and Japan except Singapore showed particulate expressions in 'dissolution', 'state change of water', 'gas pressure and volume', 'combustion and extinguishment' units. Korean textbook was only being introduced in 'dissolution' and 'gas pressure and volume', but in the textbooks of Japan and the United States, water was expressed as particles in 'state change of water' unit. Discussion and implication on the introduction of particulate concept to elementary science curriculum and textbooks were suggested based on the results.

• Advances in environmental research
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• 제8권1호
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• pp.39-54
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• 2019

This paper presents comprehensive scientific details about mangrove soil in Gulf of Kachchh, Gujarat. A total of ten sites were studied during November, 2011 to December, 2014 in order to know the physico-chemical characteristics of mangrove soil. The results indicated that the soil in GoK had silty loam texture. Other physico-chemical parameters ranged as; pH: 7.39-7.61, Bulk Density: 0.30 g/㎤-0.54 g/㎤, Particle Density: 1.26 g/㎤-1.76 g/㎤, Organic Carbon: 0.70%-1.13%, Organic Matter: 1.01%-1.74% and Moisture Content: 33.45%-56.38%. The paper would be useful to the stakeholders, coastal managers and scientific communities to know the mangrove soil conditions of Gulf of Kachchh for management and planning for conservation of mangrove ecosystem.

• 한국과학교육학회지
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• 제20권3호
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• pp.432-442
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• 2000

초등학교 자연 교과서와 중학교 8종 과학 교과서에서 다루어지는 '전류'와 '전지'에 관련된 내용을 분석한 결과, 교과서 진술이나 교육과정 구성에서 현재까지 이루어진 학습자의 오개념 연구 결과와 관련지을 수 있는 문제점이 많이 발견되었다. 이 단원의 내용은 물리학과 화학 분야에서 모두 다루고 있는데, 특히 물리학 분야에서는 입자 관점의 부족으로 인해, 그리고 화학 영역에서는 에너지 관점의 부족으로 인해 전체적인 개념 획득이 어렵도록 내용이 구성되어 있었다. 물리와 화학에서 제시하는 개념의 시각 차이뿐 아니라, 같은 학문 안에서도 단원에 따라 다른 시각을 제시하는 경우가 많았다. 이러한 문제를 해결하기 위해서 현대적 입자와 에너지 관점으로 통합하여 전류와 전지 단원의 교육과정과 교과서의 진술 방식을 재구성할 필요가 있다. 이를 통해 학문간의 괴리를 줄이고 조화를 이루기 위한 노력이 매우 필요하다.

• 천문학회지
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• 제36권3호
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• pp.89-95
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• 2003

Observations of dark matter dominated dwarf and low surface brightness disk galaxies favor density profiles with a flat-density core, while cold dark matter (CDM) N-body simulations form halos with central cusps, instead. This apparent discrepancy has motivated a re-examination of the microscopic nature of the dark matter in order to explain the observed halo profiles, including the suggestion that CDM has a non-gravitational self-interaction. We study the formation and evolution of self-interacting dark matter (SIDM) halos. We find analytical, fully cosmological similarity solutions for their dynamics, which take proper account of the collisional interaction of SIDM particles, based on a fluid approximation derived from the Boltzmann equation. The SIDM particles scatter each other elastically, which results in an effective thermal conductivity that heats the halo core and flattens its density profile. These similarity solutions are relevant to galactic and cluster halo formation in the CDM model. We assume that the local density maximum which serves as the progenitor of the halo has an initial mass profile ${\delta}M / M {\propto} M^{-{\epsilon}$, as in the familiar secondary infall model. If $\epsilon$ = 1/6, SIDM halos will evolve self-similarly, with a cold, supersonic infall which is terminated by a strong accretion shock. Different solutions arise for different values of the dimensionless collisionality parameter, $Q {\equiv}{\sigma}p_br_s$, where $\sigma$ is the SIDM particle scattering cross section per unit mass, $p_b$ is the cosmic mean density, and $r_s$ is the shock radius. For all these solutions, a flat-density, isothermal core is present which grows in size as a fixed fraction of $r_s$. We find two different regimes for these solutions: 1) for $Q < Q_{th}({\simeq} 7.35{\times} 10^{-4}$), the core density decreases and core size increases as Q increases; 2) for $Q > Q_{th}$, the core density increases and core size decreases as Q increases. Our similarity solutions are in good agreement with previous results of N-body simulation of SIDM halos, which correspond to the low-Q regime, for which SIDM halo profiles match the observed galactic rotation curves if $Q {\~} [8.4 {\times}10^{-4} - 4.9 {\times} 10^{-2}]Q_{th}$, or ${\sigma}{\~} [0.56 - 5.6] cm^2g{-1}$. These similarity solutions also show that, as $Q {\to}{\infty}$, the central density acquires a singular profile, in agreement with some earlier simulation results which approximated the effects of SIDM collisionality by considering an ordinary fluid without conductivity, i.e. the limit of mean free path ${\lambda}_{mfp}{\to} 0$. The intermediate regime where $Q {\~} [18.6 - 231]Q_{th}$ or ${\sigma}{\~} [1.2{\times}10^4 - 2.7{\times}10^4] cm^2g{-1}$, for which we find flat-density cores comparable to those of the low-Q solutions preferred to make SIDM halos match halo observations, has not previously been identified. Further study of this regime is warranted.

• Journal of Forest and Environmental Science
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• 제36권2호
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• pp.133-142
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• 2020

Soil physical and chemical properties at three layers such as top (0-10 cm), middle (10-20 cm) and bottom (20-30 cm) layers under three different vegetation types were studied. Soil samples were collected from Acacia forest, vegetable and fallow lands of Chittagong university campus, Chittagong, Bangladesh. Results showed that sand was the dominant soil particle followed by clay and silt fractions in all soil depths under different vegetation types. Soils of fallow land showed the highest values of bulk density while forest soils had the lowest values at three depths. Acacia forest soil having lowest values of dispersion ratio (DR) is less vulnerable while fallow soil with highest DR values is more vulnerable to soil erosion. The lower pH value at all soil layers in three ecosystems represented that soils under study are acidic in nature. Contents of organic matter, total nitrogen, exchangeable cations (Ca²⁺, Mg²⁺, K⁺ and Na⁺) and cation exchange capacity (CEC) were observed higher in Acacia forest soils compared to vegetable and fallow soils. Only soils of vegetable land had higher level of available phosphorus in three layers than that of other two land covers. The study also revealed that different soil properties were observed in three different vegetation types might be due to variation in vegetation and agronomic practices.