• 제목/요약/키워드: Self diffusion

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Analysis of Image Distortion on Magnetic Resonance Diffusion Weighted Imaging

  • Cho, Ah Rang;Lee, Hae Kag;Yoo, Heung Joon;Park, Cheol-Soo
    • Journal of Magnetics
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    • 제20권4호
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    • pp.381-386
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    • 2015
  • The purpose of this study is to improve diagnostic efficiency of clinical study by setting up guidelines for more precise examination with a comparative analysis of signal intensity and image distortion depending on the location of X axial of object when performing magnetic resonance diffusion weighted imaging (MR DWI) examination. We arranged the self-produced phantom with a 45 mm of interval from the core of 44 regent bottles that have a 16 mm of external diameter and 55 mm of height, and were placed in 4 rows and 11 columns in an acrylic box. We also filled up water and margarine to portrait the fat. We used 3T Skyra and 18 Channel Body array coil. We also obtained the coronal image with the direction of RL (right to left) by using scan slice thinkness 3 mm, slice gap: 0mm, field of view (FOV): $450{\times}450mm^2$, repetition time (TR): 5000 ms, echo time (TE): 73/118 ms, Matrix: $126{\times}126$, slice number: 15, scan time: 9 min 45sec, number of excitations (NEX): 3, phase encoding as a diffusion-weighted imaging parameter. In order to scan, we set b-value to $0s/mm^2$, $400s/mm^2$, and $1,400s/mm^2$, and obtained T2 fat saturation image. Then we did a comparative analysis on the differences between image distortion and signal intensity depending on the location of X axial based on iso-center of patient's table. We used "Image J" as a comparative analysis programme, and used SPSS v18.0 as a statistic programme. There was not much difference between image distortion and signal intensity on fat and water from T2 fat saturation image. But, the average value depends on the location of X axial was statistically significant (p < 0.05). From DWI image, when b-value was 0 and 400, there was no significant difference up to $2^{nd}$ columns right to left from the core of patient's table, however, there was a decline in signal intensity and image distortion from the $3^{rd}$ columns and they started to decrease rapidly at the $4^{th}$ columns. When b-value was 1,400, there was not much difference between the $1^{st}$ row right to left from the core of patient's table, however, image distortion started to appear from the $2^{nd}$ columns with no change in signal intensity, the signal was getting decreased from the $3^{rd}$ columns, and both signal intensity and image distortion started to get decreased rapidly. At this moment, the reagent bottles from outside out of 11 reagent bottles were not verified from the image, and only 9 reagent bottles were verified. However, it was not possible to verify anything from the $5^{th}$ columns. But, the average value depends on the location of X axial was statistically significant. On T2 FS image, there was a significant decline in image distortion and signal intensity over 180mm from the core of patient's table. On diffusion-weighted image, there was a significant decline in image distortion and signal intensity over 90 mm, and they became unverifiable over 180 mm. Therefore, we should make an image that has a diagnostic value from examinations that are hard to locate patient's position.

Growth Mechanism and Crystal Ordering of Spherulitic Patterns in a Belousov-Zhabotinsky Type Reaction System

  • Yadav, Narendra;Majhi, S.S.;Srivastava, P.K.
    • Bulletin of the Korean Chemical Society
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    • 제33권10호
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    • pp.3397-3406
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    • 2012
  • Three types of spherulitic morphologies have been investigated in dual substrate mode of Belousov-Zhabotinsky (BZ) type reaction system. Prior to growth of spherulites, three distinct patterning behaviors have been observed sequentially during the reaction process. Initial and the early-phase of reaction showed the emergence of concentric ring-like wave patterns. A colloidal-state of reaction consists of numerous fine solid particles, which forms primarily some nucleation centers of dendritic characters. The nucleation centers were found to grow in sizes and shapes with the progress of reaction. It leads to growth of dendritic-like spherulitic crystal patterns. The resultant spherulites showed transitions in their morphologies, including sea-weeds and rhythmic spherulitic crystal patterns, by the effects substituted organic substrate and in the higher concentration of bromate-initiator respectively. The branching mechanism and crystal ordering of spherulitic textures were studied with help of optical microscope (OPM) and scanning electron microscope (SEM). Characteristics of crystal phases were also evaluated using X-ray diffraction (XRD) and differential thermal analysis (DTA). Results indicated that the compositions of reactants and crystal orderings were interrelated with morphological transitions of spherulites as illustrated and described.

Impacts of C60-Ionic Liquids (ILs) Interactions and IL Alkyl Chain Length on C60 Dispersion Behavior: Insights at the Molecular Level

  • Wang, Zhuang;Tang, Lili;Wang, Degao
    • Bulletin of the Korean Chemical Society
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    • 제35권9호
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    • pp.2679-2683
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    • 2014
  • Mechanisms underlying the impacts of interactions between carbon nanoparticles (CNPs) and ionic liquids (ILs) on the physicochemical behavior of CNPs need to be more full worked out. This manuscript describes a theoretical investigation at multiple levels on the interactions of fullerene $C_{60}$ with 21 imidazolium-based ILs of varying alkyl side chain lengths and anionic types and their impacts on $C_{60}$ dispersion behavior. Results show that ${\pi}$-cation interaction contributed to mechanism of the $C_{60}$-IL interaction more than ${\pi}$-anion interaction. The calculated interaction energy ($E_{INT}$) indicates that $C_{60}$ can form stable complex with each IL molecule. Moreover, the direction of charge transfer occurred from IL to $C_{60}$ during the $C_{60}$-IL interaction. Quantitative models were developed to evaluate the self-diffusion coefficient of $C_{60}$ ($D_{fullerene}$) in bulk ILs. Three interpretative molecular descriptors (heat of formation, $E_{INT}$, and charge) that describe the $C_{60}$-IL interactions and the alkyl side chain length were found to be determinants affecting $D_{fullerene}$.

필터와 레죠네이터 응용을 위한 $La_3Ga_5SiO_{14}$ 의 결정화학 및 성장 (Crystal chemistry and growth of$La_3Ga_5SiO_{14}$ for the applications of filter and resonator)

  • 정일형;주경;심광보;오근호
    • 한국결정성장학회지
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    • 제9권1호
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    • pp.74-79
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    • 1999
  • Langasite($La_3Ga_5SiO_14$)는 acoustic 특성에서 quartz, $LiTaO_3$$LiNbO_3$에 비교되는 새로운 압전재료이다. 본 연구에서는 새로운 Langasite 계열의 물질을 공기 중에서 고상반응법에 의해 합성하였고, 합성공정에서의 주요 확산종 을 조사하였다. 이때 합성된 물질의 소결체를 제조하여 각각의 유전적 성질을 비교평가하였다. 또한, Langasite 단결정 을 자체제작한 Czochralski 시스댐을 사용하여 성장시키는데 성공하였고, 성장된 결정의 물성을 평가하였다

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Impacts of Social Media (Facebook) on Human Communication and Relationships: A View on Behavioral Change and Social Unity

  • Joo, Tang-Mui;Teng, Chan-Eang
    • International Journal of Knowledge Content Development & Technology
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    • 제7권4호
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    • pp.27-50
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    • 2017
  • The impact of social networking is varied from good to bad. Online activities have also been categorized into pros and cons of social networking, either as reported as hiding Internet activities among teenagers or killing loneliness among elderly. In terms of relationships, there have been argument over its closeness and quality of an online relationship in Internet settings. Looking at the contradiction in an innovative interaction between classic community communication and social media, there is an unknown scent of the future struggling and challenging both human communication and relationships in the presence of digital culture. This research uses Diffusion of Innovation to study the wide and continuous spread of digital culture in human communication; and, Media Dependency in learning and structuring the cognitive, affective and behavioral effects of social media on each person uses the media in different ways. This research will be using online survey to gain opinions from a social network site as an update of views and reflection of self-awareness to all levels of people. Social media like Facebook (FB) is perceived as a good tool of communication that it is able to bring closeness among the family members. The results show that social media like FB brings positive impact towards family members; it would help to build a better and harmonic society; and, relationships among family members and communication shall be improved and enhanced to the level of a united society.

2024 Al 합금의 고온 정상크리이프 중의 내부응력의 탄성 및 회복에 관한 연구 (Internal Stress, Anelasticity and Recovery in Steady State Creep of 2024 Al Alloy at High Temperature)

  • 박경동;오세욱;강상훈
    • 대한기계학회논문집
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    • 제10권3호
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    • pp.292-297
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    • 1986
  • 본 연구에서는 2024 Al 합금에 대하여 260-380.deg. C의 온도 범위 및 2~5kgf/ m $m^{2}$의 부과응력 범위에서 실시한 고온 정상 크리이프 변형 중의 내부응력 .sigma. $_{i}$,의탄성 변형 .epsilon.$_{A}$ 및 회복율 r의 측정 실험을 통하여 이들 상호간의 관계 를 살펴 보고자 한다.다.다.

Float 공법을 고려한 Plasma Display Panel용 기판유리 용융체의 특성 (Melt Properties of Plasma Display Panel Substrate Glasses Based on Float Process)

  • 김기동;정우만;정현수;권성구;최세영
    • 한국세라믹학회지
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    • 제43권7호
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    • pp.433-438
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    • 2006
  • In order to examine the working condition of melts in tin bath of float process it was investigated Sn diffusion behavior and solidification rate of melts for alkali-alkaline earth-silica PDP substrate glasses such as commercial CaO rich CS-77 glass, commercial $Al_2O_3$ rich PD-200 glass and self developed $SiO_2$ rich T-series (T-2, T-4, T-6) glasses. In the case of Sn depth and concentration created in glass surface by ion exchange between Sn and alkali, T-series showed lower value than CS-77, especially T-2 is more excellent than PD-200. The solidification rate of melts expressed by cooling time between $log{\eta}=4\;and\;7.6dPa{\cdot}s$ was low for T-series comparing with CS-77 and PD-200. Therefore, it was concluded that T-series is desirable considering forming condition in the tin bath of the float process.

임상간호사의 근거기반실무 실행 구조모형 (Structural Model of Evidence-Based Practice Implementation among Clinical Nurses)

  • 박현영;장금성
    • 대한간호학회지
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    • 제46권5호
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    • pp.697-709
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    • 2016
  • Purpose: This study was conducted to develop and test a structural model of evidence-based practice (EBP) implementation among clinical nurses. The model was based on Melnyk and Fineout-Overholt's Advancing Research and Clinical Practice through Close Collaboration model and Rogers' Diffusion of Innovations theory. Methods: Participants were 410 nurses recruited from ten different tertiary hospitals in Korea. A structured self-report questionnaire was used to assess EBP knowledge/skills, EBP beliefs, EBP attitudes, organizational culture & readiness for EBP, dimensions of a learning organization and organizational innovativeness. Collected data were analyzed using SPSS/WINdows 20.0 and AMOS 20.0 program. Results: The modified research model provided a reasonable fit to the data. Clinical nurses' EBP knowledge/skills, EBP beliefs, and the organizational culture & readiness for EBP had statistically significant positive effects on the implementation of EBP. The impact of EBP attitudes was not significant. The dimensions of the learning organization and organizational innovativeness showed statistically significant negative effects on EBP implementation. These variables explained 32.8% of the variance of EBP implementation among clinical nurses. Conclusion: The findings suggest that not only individual nurses' knowledge/skills of and beliefs about EBP but organizational EBP culture should be strengthened to promote clinical nurses' EBP implementation.

YBCO coated conductor with a single buffer layer of Yttrium Oxide

  • Park, Chan;Dongqi Shi;Kyujeong Song;Rokkil Ko;Park, Soojeong;Yoo, Sang-Im
    • 한국초전도ㆍ저온공학회논문지
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    • 제5권3호
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    • pp.20-22
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    • 2003
  • Y$_2$O$_3$ films were pulsed laser deposited on cube textured Ni and Ni-W substrates to be used as a single buffer layer of YBCO coated conductor. Initial deposition of $Y_2$O$_3$ films was performed in a reducing atmosphere, and subsequent deposition was done in the base pressure of the chamber and oxygen atmosphere. The $Y_2$O$_3$ films have a strong cube texture (The full width at half maximum of the ø-scan of $Y_2$O$_3$ was 8.4 which was the same as that of metal substrate) and smooth crack-free microstructure. The biaxially textured YBCO films (The full width at half maximum of the ø-scan was 10.2) pulsed laser deposited on the $Y_2$O$_3$/metal exhibited Tc(R=0) of 86.5K and Jc of 0.7 MA/cm2 at 77K in self field, representing that the $Y_2$O$_3$ single buffer layer is an efficient diffusion barrier of Ni and thus very promising for the achievement of high-Jc YBCO coated conductor.

Improvement in LED structure for enhanced light-emission

  • Park, Seong-Ju
    • 한국재료학회:학술대회논문집
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    • 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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    • pp.21-21
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    • 2003
  • To increase the light-emission efficiency of LED, we increased the internal and external quantum efficiency by suppressing the defect formation in the quantum well and by increasing the light extraction efficiency in LED, respectively. First, the internal quantum efficiency was improved by investigating the effect of a low temperature (LT) grown p-GaN layer on the In$\sub$0.25/GaN/GaN MQW in green LED. The properties of p-GaN was optimized at a low growth temperature of 900oC. A green LED using the optimized LT p-type GaN clearly showed the elimination of blue-shift which is originated by the MQW damage due to the high temperature growth process. This result was attributed to the suppression of indium inter-diffusion in MQW layer as evidenced by XRD and HR-TEM analysis. Secondly, we improved the light-extraction efficiency of LED. In spite of high internal quantum efficiency of GaN-based LED, the external quantum efficiency is still low due to the total internal reflection of the light at the semiconductor-air interface. To improve the probability of escaping the photons outside from the LED structure, we fabricated nano-sized cavities on a p-GaN surface utilizing Pt self-assembled metal clusters as an etch mask. Electroluminescence measurement showed that the relative optical output power was increased up to 80% compared to that of LED without nano-sized cavities. I-V measurement also showed that the electrical performance was improved. The enhanced LED performance was attributed to the enhancement of light escaping probability and the decrease of resistance due to the increase in contact area.

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