• Title, Summary, Keyword: 대칭성

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Synthesis and Determination of Optical Purity of C2-Symmetric Pyrrolidine Amides as Chiral Auxiliaries (키랄 보조제로서의 C2-대칭성 피롤리딘 아미드의 합성과 광학 순도 결정)

  • Moon, Hong-sik;Koh, Dongsoo
    • Applied Chemistry for Engineering
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    • v.9 no.6
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    • pp.914-919
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    • 1998
  • Optically pure $C_2-Symmetric$ pyrrolidine amides (8) were synthesized from readily available 1,2:5,6-di-O-isopropylidene-D-mannitol (1). Cyclization of dimesylated hexitol (4) with benzyl amine gave an inseparable mixture of $C_2-Symmetric$ pyrrolidine amine derivative (5) as a major product, concurring with its cis isomer (6) as a minor product. The pyrrolidine amines (5,6) were converted to separable pyrrolidine amides (8,9) via free amine (7). Optical purity of desired $C_2-Symmetric$ pyrrolidine amide (8a) was determined with its Mosher derivatives (13,14) by their $^1H$ and $^{19}F$ NMR spectra.

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A Simulation Study of Atomic Resolution TEM images for Two Dimensional Single Layer and Bilayer Graphene Crystal (2차원적인 단층 및 복층 그래핀 결정에 대한 원자분해 투과전자현미경 영상 시뮬레이션 연구)

  • Kim, Hwang-Su
    • Applied Microscopy
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    • v.40 no.1
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    • pp.21-28
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    • 2010
  • In a simulation study of atomic resolution transmission electron microscope images of single layer and bilayer graphene, it is demonstrated that the conventional Bloch wave formulations can be used when high-order Laue zone reflections are properly taken into account in the theory. The simulated images for bilayer graphene show 3-fold rotational lattice symmetry rather than the 6-fold one under certain conditions. This result can be understood as revealed the 3-fold rotational lattice symmetry of bilayer graphene in three dimensions along [0001]. For single layer graphene the observed phase images showing 3-fold rotational lattice symmetry were particularly noted. This phenomenon has been explained by an assumption of the re-configuration of electron density on the surface of graphene. And the matching images have been obtained as simulated with up to the second order Laue zone reflections only, reflecting the re-configuration of electrons on the surface.

Multiple Symmetric Lipomatosis (다발성 대칭성 지방종증 -1례 보고-)

  • Lee, Jo-Han;Hong, Jong-Myeon;An, Jae-Ho
    • Journal of Chest Surgery
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    • v.29 no.2
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    • pp.244-247
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    • 1996
  • Multiple symmetric lipomatosis is a rare disease characterized by progressive growth of subcutaneous fat masses which are located symmetrically at neck, shoulders, chest, abdomen and groin. Recent surveys revealed a high incidence of combined somatic and autonomic neuropathy. The exact cause of the disease is not known. We have experienced one case of multiple symmetric lipomatosis with mediastinal involvement with symptomatic compression of trachea. The patient was a 55-year-male, complaining of dyspnea and slowly enlarging multiple symmetric masses at the neck, shoulders, chest, abdomen, flank and groin over a period of 10 years. He had a habit of excessive alcohol intake for many years. The fatty masses in the neck and the upper mediastinum including peritracheal region were excised through transverse cervical incision. But, because of the incomplete excision of peritracheal fatty tissue, we performed reoperation for the relief of residual tracheal compression at the 15th postoperative day. Two days later emergent tracheostomy was performed due to postoperative pneumomediastinum and subcutaneous emphysema. He could discharge with permanant tracheostomy.

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선형모형에서 오차의 대칭성에 대한 검정과 회귀계수의 추정에 관한 연구

  • 김순옥
    • Communications for Statistical Applications and Methods
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    • v.2 no.1
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    • pp.13-21
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    • 1995
  • 선형모형에서 오차가 대칭인 분포를 따르는지 또는 한쪽으로 치우친(skewed distribution)분포를 따르는지 검정하는 문제를 다루었다. 또 이러한 검정과정을 분석의 예비단계로 하는 회귀계수의 추정방법에 대해서 연구하고, 모의실험을 통해서 회귀계수 추정법들의 효율을 비교하였다.

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Radiographic Evaluation of Condyle Position at Maximum Intercuspal Position Using Cone-beam CT (Cone-beam CT를 이용한 최대교두간접촉위(MIP)에서 과두 위치에 대한 방사선적 평가)

  • Oh, Sang-Chun;Chee, Young-Deok
    • Journal of Dental Rehabilitation and Applied Science
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    • v.26 no.2
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    • pp.111-120
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    • 2010
  • Purpose: This investigation was designed to evaluate the condyle position and the symmetry of the both condyle heads at the maximum intercuspal position on the sagittal CT image of the temporomandibular joint. Materials and Methods: Cone-beam CT was used to assess 400 joints in 100 symptom and 100 symtom-free subject(100 male, 100 female). Three independent observers(dentists) determined the positions classified with Anterior Position(AP), Middle Position(MP), and Posterior Position(PP), and the symmetry of the both condyle. Results: According to gender, the mean percentages of AP, MP, and PP were 48.5, 28.5, and 23 in male group, and 34, 38, and 28 in female group. The symmetry of condylar heads was more common than asymmetry in the both of groups. In the respect of symptom or symptom-free, the mean percentages of AP, MP, and PP were 44.5, 34, and 21.5 in the symptom-free group, and 37, 33.5, and 29.5 in the symptom group. The symmetry of condylar heads was more common in the symptom-free group, but the asymmetry of condylar heads was more common in the symptom group. Conclusions: These data might serve as useful criteria for the clinical assessment of condyle position at the maximum intercuspal position optained by Cone-beam CT.

A Study on Economic Characteristics of Two-way Network Interconnection System (쌍방향 상호접속체계의 경제적 특성분석)

  • 김방룡
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.39-42
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    • 2003
  • The issues on the interconnection of telecommunications network are recently prevailed in the IT industry. In this study, we classify the network interconnection system into two categories: two way-same price model and two way-different price model. The purpose of this paper is to analyze economic characteristics of optimal settlement system according to each model. One of the most important policy implications we derive through this study is that symmetry between enterprises is required for policy maker or regulatory agency to set an efficient settlement system under two way-same price model, but that symmetry is not necessarily required under two way-sane price model.

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A Study on Economic Characteristics of Two-way Network Interconnection System (통신망 상호접속체계의 경제적 특성분석)

  • ;Pang-Ryong Kim
    • Proceedings of the Korea Technology Innovation Society Conference
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    • pp.41-53
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    • 2003
  • The issues on the interconnection of telecommunications network are recently prevailed in the IT industry. In this study, we classify the network interconnection system into two categories: two way-same price model and two way-different price model. The purpose of this paper is to analyze economic characteristics of optimal settlement system according to each model. One of the most important policy implications we derive through this study is that symmetry between enterprises is required for policy maker or regulatory agency to set an efficient settlement system under two way-same price model, but that symmetry is not necessarily required under two way-same price model.

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Affinity and Variety between Words in the Framework of Hypernetwork (하이퍼네트워크에서 본 단어간 긴밀성과 다양성)

  • Kim, Joon-Shik;Park, Chan-Hoon;Lee, Eun-Seok;Zhang, Byoung-Tak
    • Journal of KIISE:Computer Systems and Theory
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    • v.35 no.4
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    • pp.166-171
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    • 2008
  • We studied the variety and affinity between the successive words in the text document A number of groups were defined by the frequency of a following word in the whole text (corpus). In the previous studies, the Zipf's power law was explained by Chinese restaurant process and hub node was searched after by examining the edge number profile in scale free network. We have observed both a power law and a hub profile at the same time by studying the conditional frequency and degeneracy of a group. A symmetry between the affinity and the variety between words were found during the data analysis. And this phenomenon can be explained within a viewpoint of "exploitation and exploration." We also remark on a small symmetry breaking phenomenon in TIPSTER data.

Pre-processing Method for Face Recognition Robust to Lightness Variation; Facial Symmetry (조명 변화에 강건한 얼굴 인식의 전처리 기법; 얼굴의 대칭성)

  • Kwon Heak-Bong;Kim Young-Gil;Chang Un-Dong;Song Young-Jun
    • The Journal of the Korea Contents Association
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    • v.4 no.4
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    • pp.163-169
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    • 2004
  • In this paper. we propose a shaded recognition method using symmetric feature. When the existing PCA is applied to shaded face images, the recognition rate is decreased. To improve the recognition rate, we use facial symmetry. If the difference of light and shade is greater than a threshold value, we make a mirror image by replacing the dark side with the bright side symmetrically Then the mirror image is compared with a query image. We compare the performance of the proposed algorithm with the existing algorithms such as PCA, PCA without three eigenfaces and histogram equalization methods. The recognition rate of our method shows $98.889\%$ with the excellent result.

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