• The Mathematical Education
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• v.62 no.4
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• pp.457-471
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• 2023

Measurement is an imperative content area of early elementary mathematics, but it is reported that students' understanding of units in measurement situations is insufficient despite its importance. Therefore, this study examined lower-grade elementary students' quantitative reasoning of units in length measurement by identifying the levels of reasoning of units. For this purpose, we collected and analyzed the responses of second-grade elementary school students who engaged in a set of length measurement tasks using an open number line in terms of unitizing, iterating, and partitioning. As a result of the study, we categorized students' quantitative reasoning of unit levels into four levels: Iterating unit one, Iterating a given unit, Relating units, and Transforming units. The most prevalent level was Relating units, which is the level of recognizing relationships between units to measure length. Each level was illustrated with distinct features and examples of unit reasoning. Based on the results of this study, a personalized plan to the level of unit reasoning of students is required, and the need for additional guidance or the use of customized interventions for students with incomplete unit reasoning skills is necessary.

• The Journal of the Korea Contents Association
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• v.12 no.11
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• pp.368-376
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• 2012

Government has strictly regulated the concentration of the media market because the number of broadcasters was traditionally limited and they had significant influence on public. However as the media market converges with Internet's open architecture, scarcity and pervasiveness are losing their roles in justifying media regulation. This article examines market convergence and its impact on market concentration, and criticizes the current concentration regulation. The study indicates that market performance are much governed by firm's competitive actions than market structure, and that vertical integration contributes to service innovations, and that horizontal concentration makes it difficult to measure due to its even-changing market definition. Therefore, the regulation for market concentration should shift its focus from firm's market share to broadcaster's unfair acts driving market inefficiency and hurting content diversity.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.9 s.339
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• pp.97-100
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• 2005

An orthogonal antenna is presented for reader application of radio frequency identification (RFID) at 433 MHz. Two 1x2 sub-arrays are orthogonally placed on a ground plane and two different feeding networks are applied to control horizontal and vertical radiation current flows for each sub-array, respectively. Inverted-F structures are used as radiation elements and can generate two linear polarizations by relative current distribution of radiators forming sub-arrays. Antenna gains are 2.7 and 0.4 dBi and isolation between two input ports is less than 25dB.

• Journal of the Korean earth science society
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• v.36 no.6
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• pp.533-542
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• 2015

The Gochang beach is located in the southwestern coast of Korea along the eastern part of the Yellow Sea, comprising the Donghori, Gwangseungri, and Myeongsasipri beaches from north to south. The Gochang beach is characterized by macro-tide, open-coast, linear shoreline, and sand substrates. This study has investigated annual and seasonal characteristics of surface topography variation and sediment accumulation rate in the Gochang beach. During the five seasons of winter (Feb.), spring (May), summer (Aug.), and fall (Nov.) in 2014 and winter (Feb.) in 2015, the topographic elevation of total 315 sites was measured along three survey lines. It consists of 21 sites at 30 m intervals in each transverse line perpendicular to the shoreline, respectively. Annual accumulation rate of the Gochang beach in 2014 was -0.081 m/yr, indicative of erosional condition. Annual accumulation rates of the comprising beaches represent -0.091m/yr of the Donghori, -0.051 m/yr of the Gwangseungri, and -0.10 m/yr of the Myeongsasipri.

• Journal of Advanced Navigation Technology
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• v.27 no.4
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• pp.463-468
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• 2023

In this paper, we proposed reconfigurable dual polarization patch array antenna that can select two polarizations(Vertical, RHCP) using defected ground structure and Pin diode. The proposed antenna was designed arranging a circular polarization patch antenna implemented with a square microstrip patch and two slots 3x3 at 25.8mm placed, a half-wavelength of 5.8 GHz. Conect the pin diode and the capacitor to the slot diagonally placed on the ground of each antennas, and select polarization using the open/short operating according to the application of DC voltage to the pin diode. As a result of the design, the gain of the antenna is 11.7 dBi at vertical polarization and 11.6 dBic at RHCP. The axial ratio is 20.3 dB at 1.8 dB vertical polarization at RHCP. Mutual Coupling is Maximum to -20.8 dB for vertical polarization and Maximum to -30.1 dB for RHCP.

• The Journal of Information Technology
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• v.2 no.2
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• pp.23-34
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• 1999

The computer industry has come to the generation of personal computer. The organization of the existing industry has the distinct boundary among companies in vertically integrated companies, produce whole assembled system, and compete in the part of hardware, operating system, and its related software based on theirselves design. Then according to keep the distinct monopolized architecture of industry, the enterprises only centralized on developing the monopolistic market and sharing the static market rather than competition and compatibility with other system. The horizontal distribution in small part industry is occurring, by the times of personal computer, and the companies of personal computer have coming into free competition with parts standardization and the open architecture of system. This paper suggests a reasonable model of industry under horizontal structure with analyzing the above phenomenon.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.84-87
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• 2009

본 논문에서는 최근 초고층 건축물에 많이 활용되어지는 기둥-가새 시스템인 다이아그리드 시스템을 활용하여 중저층 건축물에 적용가능성을 평가하였다. 본 시스템은 튜브구조의 형태로 횡력에 대한 저항력이 우수하며 중력하중과 황하중을 기초와 지반에 안전하게 하중을 전달한다. 다이아그리드는 경사기둥과 보를 반복적으로 삼각형 형태로 배치되어 중력하중을 받을 경우 수직부재는 압축력을 보는 인장력을 받게 된다. 경사기둥과 보를 연결하는 접합부는 H-형강으로 설계 시 제작이 복잡하고 외관이 좋지 않다. 하지만 원형강관을 사용 할 경우 복합하지 않은 형태로 설계가 가능하고 외관이 우수하기 때문에 외부에 노출이 가능해진다. 또한 원형강관은 개방형 단면 부재에 비해 압축좌굴과 비틀림에 대한 성능 등이 우수하여 구조적인 성능이 우수하다. 원형강관을 이용하여 다이아그리드 시스템이 고층 건축물 뿐만 아니라 중저층 건축물에도 적용 타당성을 검토하였으며 원형강관 접합부 설계는 한계상태설계법이 사용 된 KBC2008(안)을 이용하여 설계하였다.

• Korean Journal of Computational Design and Engineering
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• v.16 no.2
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• pp.156-164
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• 2011

The automation technology is able to enhance the business process more rapidly and effective. Open BIM technology which supports automation technology of building overcomes the limitations of two dimensions drawings system. The purpose of this study is on the development of open BIM based modules for creating and verifying the core model for super-tall building in the schematic design phase. The module is expected to create cases of core models automatically and it is expected to verify the requirement of building model. This module is anticipated to utilize for creating the core model rapidly in order to create the alternative plan and to make the model accurate by its verification.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.05
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• pp.108-110
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• 1996

Open MRI is a new concept in clinical application of the MRI such as interventional study. Receiving RF coils used in the open MRI must have open structures to insure convenient manipulations fur the patient. In this paper, we presented experimental study fur open head coil suitable to 0.3 Tesla vertical field MRI system with its experimental results.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2003.04a
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• pp.139-139
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• 2003

원예작물은 수확 후 여러 가지 요인에 의해 품질이 저하되어 상품성을 잃게되는데, 특히 수확 후 품온상승에 의해 호흡작용이 왕성해져 품질변화를 촉진하게 된다. 그러므로 수확 후 품온을 가능한 한 빠르게 낮추어 신선도를 유지하기 위한 예냉, 저온저장, 저온수송기술등 저온유통시스템을 활용하는 것이 매우 필요하다. 저온유통시스템을 효과적으로 활용하기 위해서는 냉기의 순환이 원활하여 냉각효율이 좋고 파손의 위험과 물류비용을 줄일 수 있는 포장상자의 구조에 대한 연구가 필요하다. 포도, 방울토마토, 참외의 소비형태는 핵가족화와 더불어 신선 고품질의 농산물을 소량 구매하는 소비패턴으로 변화하면서 저온유통 및 소포장을 위한 포장형태의 개선이 요구되고 있다. 따라서 예냉.저온유통에 적합한 포장상자를 개발하기 위하여 연구소, 농협중앙회, 상자제작회사, 포장디자인 업체, 산지농협 작목반이 개발협의체를 구성하여 참외, 포도, 방울토마토의 저온유통용 골판지 상자를 개발하여 압축강도 및 냉각시험을 실시하여 소비지에 시범 보급하였다. 1. 참외 포장상자는 3kg용 상부 개방형 골판지상자로써 손잡이를 부착하고, 포장상자 상부에 덮개용 필름을 부착하였다. 제작된 상자의 압축강도는 저온유통 후 에도 안전압축강도 이상인 343kgf의 압축강도를 나타냈고, 냉각효율도 기존상자에 비하여 높게 나타났다. 또한 개발된 상자를 사용하여 시중에 출하할 경우 기존 5kg 상자에 비하여 8%이상의 부가가치를 높일 수 있었다. 2. 포도 포장상자는 소비자 기호도를 충족하고 다층적재시 손상을 방지하기 위하여 내용물을 1단 적재하고 상자를 개방형으로 하여 덮개용 필름을 부착하므로써 소비자가 내용물을 확인할 수 있도록 하고, 상자의 압축강도는 소비지까지 유통이 완료된 후 에도 수직압축강도가 400kgf이상으로 안전압축강도 보다 높아 저온에서 안전하게 유통할 수 있었다. 또한 개발된 상자를 사용하여 시중에 출하할 경우 기존 5kg 상자에 비하여 2kg상자는 21%, 4kg상자는 12%이상의 부가가치를 높일 수 있었음. 3. 방울토마토 포장상자는 외포장 상자를 4kg용 상부 개방형 골판지상자를 사용하고, 내포장상자는 500g용 PET용기를 사용하여 1상자에 8개의 내포장상자가 적재될 수 있도록 제작하였다. 제작된 외포장상자의 압축강도는 저온유통후에도 320kgf으로 안전압축강도보다 높게 나타났고, 파랫트 적재효율도 96%이상으로 나타나 물류의 효율성을 높일 수 있었다. 개발된 상자를 사용하여 시중에 출하할 경우 기존 산물형태의 4kg용 상자에 비하여 500g 내포장상자에 출하할 경우 20%이상의 부가가치를 높일 수 있었다.