• 한국초전도ㆍ저온공학회논문지
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• 제22권4호
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• pp.24-30
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• 2020

The test results of the ITER toroidal field conductors demonstrated a decrease of the current sharing temperature (Tcs) with an increase in the number of electromagnetic cycles in general. This is associating with several factors. One of them is the superconducting Nb3Sn filaments cracking and another one is the redistribution of the relative deformation of the Nb3Sn strands under Lorentz forces. Despite these factors, some conductors have shown the absence or significantly less degradation of Tcs during electromagnetic cycling. This article considers another possible reason for a more stable conductors Tcs behavior, namely, the local compression of Nb3Sn wires in the cross section of a conductor. In this article presents the results of a quantitative analysis Nb3Sn superconducting filaments cracking of strands extracted from a conductor that has passed electromagnetic cycling and the model of a conductor compaction, as well as calculation results based on this model are presented also.

• 한국도로학회:학술대회논문집
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• 한국도로학회 2009년도 추계학술대회 논문집
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• pp.145-150
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• 2009

• Journal of the Korean Wood Science and Technology
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• 제45권6호
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• pp.872-882
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• 2017

The objective of this study was to evaluate the properties of bamboo oriented strand board (B-OSB) from andong (Gigantochloa psedoarundinacea) and betung (Dendrocalamus asper) with and without steam treatment. Strands were steam-treated at $126^{\circ}C$ for 1 h under 0.14 MPa pressure. The extractive content of bamboo strands before and after steam treatment were determined according to a standard (TAPPI T 204 om-88). Three-layer B-OSB with the core layer perpendicular to the surface and back layers were formed and binded with 8% of phenol formaldehyde (PF) resin with the addition of 1% of wax. The evaluation of physical and mechanical properties of the boards were conducted in accordance with the JIS A 5908:2003 standard. The results showed that steam treatment of bamboo strands significantly reduced the extractive content. Steam treatment tended to increase the dimensional stability and mechanical properties of B-OSB from andong and betung. The results showed that the dimensional stability and bending strength of B-OSB from betung was higher than those of andong. The internal bond strength of B-OSB from andong was higher than betung owing to a greater amount of extractives dissolved during the steam treatment.

• 콘크리트학회논문집
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• 제14권2호
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• pp.156-163
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• 2002

우리나라에서 교량이나 주차장 슬래브용으로 중공 슬래브를 활용한 예는 거의 없었다. 본 연구는 국내에서 생산중인 중공슬레브의 길이가 가장 큰 고성능 중공슬래브를 재설계하고, 그 적용성을 검토한 것이다. 이를 위해 최대 깊이 315 mm인 고성능 중공슬래브에 대하여 12.7 mm 슬래브 하부강선 10개와 상부강선을 4개를 배근한 중공슬래브 80mm 토핑콘크리트를 타설한 4개의 실험체에 휨실험을 실시하여, 차량 등을 위한 고하중에서의 활용성과 슬래브의 합성작용에 대한 검토를 병행하였다. 이 실험에서의 중공슬래브는 10 m-경간 슬래브에서 설계활하중 1,000 kgf/$m^2$를 고려할 때 강도설계에 적합한 연성적 휨파괴 거동을 보여주었다. 또한 슬래브와 토핑콘크리트의 합성거동을 위하여 사용한 직사각형 전단키와 원형 전단키는 모든 단부에서 순수 휨파괴까지 어떠한 미세 균열도 발생하지 않았으므로, 누 종류의 키는 전단키로 충분한 내력을 발휘한 것으로 판단된다.

• 한국의류산업학회지
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• 제13권6호
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• pp.856-865
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• 2011

This paper intends to examine how Fringe, which is in an inseparable relationship with modern fashion, has been changed and what characteristics it is expressed to have in fashion on the basis of its formative property expressed in modern fashion. In order to empirically analyze Fringe, this paper analyzed a total of 346 Fringe of every type that were generally found in the worldis four biggest collections, from 2006S/S to 2011S/S. This paper found some methods Fringe is made, which are: using a snagged fabric or knit as it is; intentionally snagging or tearing a fabric to make the effect of being snagged; knotting the tail or the edge of clothes, and then, macram$\grave{E}$; and cutting leather or suede, which canit be snagged easily, and making Fringe strands. Fringe strands which are made in the above ways are made into a band and then, attached, or Fringe strands, a feathers, a comb, or beads are attached one by one. Or a tassel is independently or consecutively applied to clothes or ornaments, which are expressed in the form of fringes. Threads, strings, leather, suede, metals, plastics, raffia, horsehair, paper, beads, pearls, crystals, or felt were used for rich texture or unique visual effects. Colors of various brightness and chromas were used in consideration of materials. Through the effects of sameness, similarity, contrast, harmony and gradation with colors of clothes, emphasis or unified harmony was expressed. The expressive characteristics of Fringe, which were found in the modern fashion through those formative characteristics, were organic rhythmical beauty, handicraft decorative beauty, and folksy natural beauty.

• 환경생물
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• 제20권4호
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• pp.386-390
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• 2002

소나무 구과의 열개현상을 비교형태학적 형질을 통해 관찰하였다. 어린 구과에서는 조직의 분화가 완전하게 일어나지 않았지만 각 기관으로 분화되는 과정임을 알 수 있었다. 성숙한 구과와 동일 크기의 녹색 구과에서 유관속다발과 보강조직의 수축률은 각각 1.0∼l.5%와 14.0∼l6.0%였다 실편의 종단부는 유조직과 보강세포로만 구성되어 있었고, 중앙부는 종단부와 기부 두께가 비슷하였다. 기부는 실편과 실편 받침이 있어 더욱 두꺼웠으며, 유관속다발보다 보강조직이 2배 이상 두껍게 나타났다. 결론적으로 구과가 완전 성숙하여 건조됨에 따라, 종단부는 보강조직으로만 구성되어있어 조직내 수축만 일어나고 중앙부는 두 조직간 두께가 비슷해 밖으로 휘지 않는다. 그러나 실편내 기부에서 배축면에 위치한 보강조직이 두껍고, 유관속다발보다 보강조직에서 수축률이 훨씬 크므로 실편의 기부가 밖으로 펴지게 되어 구과는 열개된다.

• Bulletin of the Korean Chemical Society
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• 제23권8호
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• pp.1106-1109
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• 2002

Studies on subtle spacer ligand effects of AgCF3SO3 with 3,3'-Py2X (X = O vs S) have been carried out. The reaction of AgCF3SO3 with 3,3'-Py2O and 3,3'-Py2S produces [Ag(CF3SO3)(3,3'-Py2O)] and [Ag(3,3'-Py2S)] (CF3SO3), respectively. Crystallographic characterization of [Ag(CF3SO3)(3,3'-Py2O)] (monoclinic P1, a =8.405(2) $\AA$, b = 10.714(2) $\AA$, c = 18.031(2) $\AA$, $\alpha=$ 77.36(2), $\beta=107.83(2)^{\circ}$, $\gamma=$ 66.92(2), V = 1438.0(5) $\AA3$ , Z =2,R = 0.0486) reveals that the skeletal structure is an anion-bridged double-strand. The double-strands are packed like a plywood. The framework of [Ag(3,3'-Py2S)](CF3SO3) (orthorhombic Pcab, a = 17.330(2) $\AA$, b = 8.640(1) $\AA$, c = 19.933(6) $\AA$, V = 2985(1) $\AA3$ , Z =8, R = 0.0437) is a sinusoidal single-strand. The formation of each coordination polymer appears to be primarily associated with the donating ability and the confor ma-tional energy barrier of the spacer ligands. Thermal analyses indicate that [Ag(CF3SO3)(3,3'-Py2O)] and [Ag(3,3'-Py2S)](CF3SO3) are stable up to 250 $^{\circ}C$ and 210 $^{\circ}C$, respectively. For the anion exchangeability, the nature of the spacer ligand is more significant factor than the distance of silver(Ⅰ)···triflate.

• 한국수학교육학회지시리즈A:수학교육
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• 제58권1호
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• pp.121-138
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• 2019

The purpose of this study was to analyze the trends of domestic research on mathematics teacher education in terms of the period, topics, methods, subjects, and mathematics content strands. For this purpose, a total of 220 research articles dealing with mathematics teacher education were analyzed, which have been published since 2000 by the Korean Society of Mathematics Education in the three journals: (a) The Mathematical Education; (b) Education of Primary School Mathematics; and (c) Communications of Mathematical Education. Regarding the period when the research was conducted, the number of articles on mathematics teacher education has been rapidly increased since the late 2000s. Regarding the topics, research on teacher orientation has been the most frequent topic and the studies dealing with professional development for teachers, teaching practices, or teacher knowledge tend to be popular. Regarding methods, survey and case study have been most frequently employed in studying mathematics teacher education. Regarding subjects, the main participants were in-service teachers, pre-service teachers, elementary school teachers, and secondary school teachers, respectively, who were in charge of a regular class. Finally, regarding mathematics content strands, previous studies on mathematics teacher education were not specific to mathematics content strands. Given these results, this paper closes with important implications for future research directions on mathematics teacher education in Korea.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.961-965
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• 1998

The rapid development of small-scale (1-10 MJ) Superconducting Magnetic Energy Storage Systems (SMES) can be explained by real perspective of practical implementation of these devices in electro power nets. However the serious problem of all high mechanically stressed superconducting coils-problem of training and degradation (decreasing) of operating current still exists. Moreover for SMES systems this problems is more dangerous because of pulsed origin of mechanical stresses-one of the major sources of local heat disturbances in superconducting coils. We investigated acoustic emission (AE) phenomenon on model and 0.5 MJ SMES coils taking into account close correlation of AE and local heat disturbances. Two-coils 0.5 MJ SMES system was developed, manufactured and tested at Russian Research Center in the frames of cooperation with Korean Electrical Engineering Company (KEPCO) [1]. The two-coil SMES operates with the stored energy transmitted between coils in the course of a single cycle with 2 seconds energy transfer time. Maximum operating current 1.55 kA corresponds to 0.5 MF in each coil. The Nb-Ti-based conductor was designed and used for SMES manufacturing. It represents transposed cable made of Nb-Ti strands in copper matrix, several cooper strands and several stainless steel strands. The coils are wound onto fiberglass cylindrical bobbins. To make AE event information more useful a real time instrumentation system was used. Two main measured and computer processed AE parameters were considered: the energy of AE events (E) and the accumulated energy of AE events (E ). Influence of current value in 0.5 MJ coils on E and E was studied. The sensors were installed onto the bobbin and the external surface of magnets. Three levels of initial current were examined: 600A, 1000A, 2450 A. An extraordinary strong dependence of the current level on E and E was observed. The specific features of AE from model coils, operated in sinusoidal vibration current changing mode were investigated. Three current frequency modes were examined: 0.012 Hz, 0.03 Hz and 0.12 Hz. In all modes maximum amplitude 1200 A was realized.

• Computers and Concrete
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• 제31권4호
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• pp.349-358
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• 2023

This paper describes an in-depth analysis on flexural strength of a girder-deck system experiencing a strand debonding damage with various strengthening systems, based on finite element software ABAQUS. A detailed finite element analysis (FEA) model was developed and verified against the relevant experimental data performed by other researchers. The proposed analytical model showed a good agreement with experimental data. Based on the verified FE model, over a hundred girder-deck systems were investigated with the consideration of following variables: 1) debonding level, 2) span-to-depth ratio (L/d), 3) strengthening type, 4) strengthening material thickness. Based on the data above, a new detailed analytical model was developed and proposed for estimating residual flexural strength of the strand-debonding damaged girder-deck system with strengthening systems. It was demonstrated that both finite element model and analysis model could be used to predict flexural behaviors for debonding damaged prestressed girder-deck systems. Since the strands are debonding from surrounding concrete over a certain zone over the length of the beam, the increase of strain in strands can be linked with a ratio ψ, which is L_p/c. The analytical model was proposed and developed regarding the ratio ψ. By conducting procedure of calculating ψ, the ψ value varies from 9.3 to 70.1. Multiple nonlinear regression analysis was performed in Software IBM SPSS Statistics 27.0.1 to derive equation of ψ. ψ equation was curved to be an exponential function, and the independent variable (X) is a linear function in terms of three variables of debonding level (λ), span length (L), and amount of strengthening material (A_s). The coefficient of determinate (R²) for curve fitting in nonlinear regression analysis is 0.8768. The developed analytical model was compared to the ultimate capacities computed by FEA model.