• 한국응용과학기술학회지
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• 제14권3호
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• pp.39-46
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• 1997

Ultraviolet spectrophotometric investigation has been carried out on the rate constants for 1,3-dipolar cycloaddition of 4-substituted-3-phenyloxadiazole derivatives with dipolarophiles such as phenyl acetylene, propiolic acid methyl ester and dimethylacetylene dicarboxylate. From there, the rate constants for 1,3-dipolar cycloaddition were determined at 80, 100 and $120^{\circ}C$, and the reaction rates were increased with increasing temperature. From these rate constants, the values of the thermodynamic activation parameters were obtained. Some thermodynamic activation parameters such as $E_{\alpha}$, ${\Delta}H^{\ast}$, ${\Delta}S^{\ast}$ and ${\Delta}G^{\ast}$ from Arrhenius equation were also calculated for the electrophilic 1,3-dipolar cycloaddition of 3-phenyloxadiazole derivatives with dipolarophiles. In order to the proposal the mechanism and reactivity of 1,3-dipolar cycloaddition reaction, the effect of substituents having various kinds of electron withdrawing or releasing groups were examinated. Considering the effect of substituents, an electron withdrawing group attached at the 4-carbon position in 3-phenyloxadiazole derivatives decreases the reaction rate because of the lack of electron density in 3-phenyloxadiazole ring.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제10권4호
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• pp.199-206
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• 2003

Let N be a right near-ring. N is said to be strongly reduced if, for $a\inN$, $a^2 \in N_{c}$ implies $a\;\in\;N_{c}$, or equivalently, for $a\inN$ and any positive integer n, $a^{n} \in N_{c}$ implies $a\;\in\;N_{c}$, where $N_{c}$ denotes the constant part of N. We will show that strong reducedness is equivalent to condition (ⅱ) of Reddy and Murty's property $(^{\ast})$ (cf. [Reddy & Murty: On strongly regular near-rings. Proc. Edinburgh Math. Soc. (2) 27 (1984), no. 1, 61-64]), and that condition (ⅰ) of Reddy and Murty's property $(^{\ast})$ follows from strong reducedness. Also, we will investigate some characterizations of strongly reduced near-rings and their properties. Using strong reducedness, we characterize left strongly regular near-rings and ($P_{0}$)-near-rings.

• 천문학논총
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• 제30권2호
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• pp.517-519
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• 2015

A large-scale neutral hydrogen ($H\small{I}$) ring serendipitously found in the Leo I galaxy group is 200 kpc in diameter with $M_{H\small{I}}{\sim}1.67{\times}10^9M_{\odot}$, unique in size in the Local Universe. It is still under debate where this $H\small{I}$ ring originated - whether it has formed out of the gas remaining after the formation of a galaxy group (primordial origin) or been stripped during galaxy-galaxy interactions (tidal origin). We are investigating the optical and $H\small{I}$ gas properties of the dwarf galaxies located within the gas ring in order to probe its formation mechanism. In this work, we present the photometric properties of the dwarfs inside the ring using the CFHT MegaCam $u^{\ast}$, $g^{\prime}$, $r^{\prime}$ and $i^{\prime}$-band data. We discuss the origin of the gas ring based on the stellar age and metal abundance of dwarf galaxies contained within it.

• Kyungpook Mathematical Journal
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• 제61권1호
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• pp.23-32
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• 2021

Let D be an integral domain with quotient field K, X an indeterminate over D, ∗ a star operation on D, and Cl∗ (D) be the ∗-class group of D. The ∗w-operation on D is a star operation defined by I∗w = {x ∈ K | xJ ⊆ I for a nonzero finitely generated ideal J of D with J∗ = D}. In this paper, we study two star operations {∗} and [∗] on D[X] defined by A{∗} = ∩P∈∗w-Max(D) ADP [X] and A[∗] = (∩P∈∗w-Max(D) AD[X]P[X]) ∩ AK[X]. Among other things, we show that Cl∗(D) ≅ Cl[∗](D[X]) if and only if D is integrally closed.

• Applied Biological Chemistry
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• 제39권2호
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• pp.140-146
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• 1996

Imidacloprid와 일련의 새로운 1-(6-chloro-3-pyridylmethy)-3-N-nitroimidazolidin-2-ylideneamine 유도체들을 합성하고 imidazolidine고리의 3-N-치환기(R) 변화에 따른 구조와 벼멸구(Nilaparvata lugens) 및 복숭아 혹 진딧물(Myzus persicae)에 대한 선택적인 살충활성 관계(SAR)를 검토한 바, 벼멸구에는 STERIMOL 파라미터인 B1상수$({\AA})$보다 소수성$({\pi})$, 그리고 복숭아 혹 진딧물에는 입체상수(Es)보다 극성 치환기상수$({\sigma}^{ast})$ 큰 변수로 작용하였다. 벼멸구의 경우에는 ${\pi}$상수의 적정값이 0.52이고 복숭아 혹 진딧물의 경우에는 $\sigma^{\ast}$상수의 적정값이 1.17로 이들 값에 가까운 값을 갖는 치환체일수록 큰 살충활성이 예상되었다. 두 경우, 모두 공통적으로 methyl 및 benzenesulfonyl-치환체(7 및 8)와 같은 센 전자끌게들은 살충활성에 기여하지 않았다. 그러나, 비치환(H)체(1)인 imidacloprid는 가장 큰 살충활성을 나타내었으며 H의 ${\pi}$상수와 ${\sigma}^{\ast}$상수가 이들 두 상수의 적정값에 미치지 못하지만, 양호한 살충활성을 나타낸 까닭은 2-N-nitro group의 산소원자와 3-imid group의 수소원자 사이에 형성된 분자내 회합(H-결합)에 기인함을 알았다. 그리고 pH 6.0 이하의 산성 수용액에서는 대단히 큰 잔류성을 나타내었으며 $45^{\circ}C$의 pH 7.0에서$(K_{obs};5{\times}10^8sec.^{-1})$ 반감기(t1/2)는 대략 6개월이었다.

• 분석과학
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• 제24권3호
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• pp.173-182
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• 2011

약물(Prostanozol)을 복용한 여성을 대상으로 한 뇨시료 중에 함유된 Prostanozol 및 그 대사체들을 검출하기 위해 LC/ESI/MS와 GC/TOF-MS를 이용하여 효과적으로 분리 및 검출하였고, LC/ESI/MS의 질량스펙트럼으로부터는 각각의 분자량을 추정하였으며 GC/TOF-MS로는 이들을 확인하였다. M1은 Prostanozol의 17번 탄소가 케톤기로 치환된 17-keto-Prostanozol, M2는 M1에서 pyrazole nucleus 와 Aring에 한 개의 히드록시기가 치환된 hydroxy-17-keto-Prostanozol, M3는 B-ring 또는 C-ring에 한 개의 히드록시기가 치환된 hydroxy-17-keto-Prostanozol, M4는 한 개의 히드록시기가 D-ring에 치환된 hydroxy-17-keto-Prostsnozol로 확인되었으며 M5는 17번 탄소 위치에 히드록시기를 갖고 B-ring 또는 C-ring에서 하나의 히드록시기가 치환된 hydroxy-17-hydroxy-Prostanozol로 추정되며 M6은 17번 탄소 위치에 케톤기를 갖고 pyrazole nucleus 혹은 A-ring에 하나의 히드록시기를 또한 B-ring 또는 C-ring에 또 하나의 히드록시기가 치환된 dihydroxy-17-keto-Prostanozol, M7은 M6와 같이 17번 탄소에 케톤기를 갖으며 pyrazole nucleus 혹은 A-ring에 하나의 히드록시기를, 또한 D-ring에 또 하나의 히드록시기를 가진 dihydroxy-17-keto-Prostanozol로 확인되었다. 마지막으로 M8은 pyrazole nucleus 혹은 A-ring에 하나의 히드록시기를 갖고 그 외의 ring에 또 다른 히드록시기가 치환된 dihydroxy-17-hydroxy-Prostanozol임을 확인할 수 있었다. 이중 M5, M7, 그리고 M8은 지금까지 밝혀지지 않았던 새로운 대사체였다. 체내에서의 포합반응 여부를 확인한 결과 Prostanozol과 8종의 모든 대사체가 글루쿠론산 포합체를 형성하였고, 8종의 대사체 중 일부는 포합체를 형성하지 않고도 배출되며 특히 M6과 M7은 황산 포합체로도 배설되는 것을 확인할 수 있었다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 제26회 KOSCO SYMPOSIUM 논문집
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• pp.159-165
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• 2003

Self-excited noise generation from laminar flames in thin annular jets of methane/air premixture has been investigated experimentally. Various flames were observed in this flow configuration, including conical shape flames, ring shape flames, steady crown shape flames, and oscillating crown shape flames. Self-excited noise with the total sound pressure level of about 70dB was generated from the oscillating crown shape flames for the equivalence ratio larger than 0.95. Sound pressure and $CH^{\ast}$ chemiluminescence were measured by using a microphone and a photomultiplier tube. The frequency of generated noise was measured as functions of equivalence ratio and premixture velocity. A frequency doubling phenomena have also been observed. The measured $CH^{\ast}$ chemiluminescence data were analyzed from which the corresponding sound pressure has been calculated. By comparing the data with those of measured ones, the noise source can be attributed to the flame front fluctuation near the edge of the oscillating crown-shape flames. The flame stability regime was influenced sensitively to the supplying air through the inner tube.

• 대한화학회지
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• 제42권4호
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• pp.391-397
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• 1998

퓨란 고리를 포함하는 bis-furan lexitropsin에서, DNA minor groove의 염기쌍과 결합하는 중요 부분인 퓨란의 기하학적 구조를 반경험적 방법(MNDO)과 ab initio(Hartree-Fock) 방법으로 최적화 시켰다. 최적화된 구조에 대해 6-31G와 $6-31G^{\ast}$ basis set을 사용하여 전자적 구조와 양성자 친화도를 구하였다. 아울러 퓨란의 양성자 친화도에 미치는 치환기 효과를 알아보기 위해 전자를 주는 기와 전자를 끄는 기를 갖는 여러 치환 퓨란에 대해 양성자 친화도를 조사하였다. 그 결과 전자를 주는 기는 퓨란의 양성자 친화도를 증가시키는 반면 전자를 끄는 기는 양성자 친화도를 감소시켰으며, 이 결과 치환 퓨란의 산소 원자의 atomic charge와 전자밀도로 설명할 수 있었다

• 천문학회보
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• 제44권1호
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• pp.59.1-59.1
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• 2019

Immediate vicinity of a supermassive black hole (SMBH) is an important place to test general relativity in strong gravity regime. Also, this is a place where mass accretion and jet formation actively occurs at the centers of active galaxies. Theoretical studies predict presence of bright ring-like emission encircling an accreting SMBH with a diameter of about 5 Schwarzschild radii, and a flux depression at the center (i.e., BH shadow). Direct imaging of the BH shadow is accordingly of great importance in modern astrophysics. However, the angular sizes of the horizon-scale structures are desperately small (e.g., ~40-50 microarcseconds (uas) diameter for the nearest best candidates). This poses serious challenges to observe them directly. Event Horizon Telescope (EHT) is a global network of sensitive radio telescopes operating at 230 GHz (1.3 mm), providing ultra-high angular resolution of 20 uas by cutting-edge very long baseline interferometry techniques. With this resolution, EHT aims to directly image the nearest SMBHs; M87 and the galactic center Sgr $A{\ast}$ (~40-50 uas diameters). In Spring 2017, the EHT collaboration conducted a global campaign of EHT and multiwavelength observations of M87 and Sgr $A{\ast}$, with addition of the phased ALMA to the 1.3mm VLBI array. In this talk, I review results from past mm-VLBI and EHT observations, provide updates on the results from the 2017 campaign, and future perspectives.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.226-226
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• 2006

Ethylene was polymerized with a catalyst having sterically hindered pentamethylcyclopentadienyl ligand, $Cp^{\ast}_{2}ZrCl_{2}/MAO$, and the polymerization mixture were treated with dry oxygen (oxidative workup) to produce hydroxyl-terminated polyethylenes (PE-OH). Polyethylene-block-Poly (${\Box}-caprolactone$) was synthesized from PE-OH and ${\cdot}\^{A}-caprolactone$A by using stannous octoate as a catalyst for ring opening polymerization of ${\cdot}\^{A}-caprolactone$. Polyethylene-block-Poly(methyl methacrylate) was obtained by transforming the hydroxyl-terminated polyethylenes to macroinitiators for atom transfer radical polymerization (ATRP) and by reacting them with MMA.