• 한국정밀공학회지
• /
• 제21권8호
• /
• pp.34-42
• /
• 2004

A new polishing technique for three dimensional micro/meso-scale parts is suggested using a micro quill and a magnetic chain structure. The principle of this method is to polish the target surface with the collected magnetic brushes at a micro tool by the non-uniform magnetic field generated around the tool. In a typical magnetic abrasive finishing process magnetic particles and abrasive particles are unbonded each other. But, to finish the three dimensional small parts bonded magnetic abrasive have to be used. Bonded magnetic abrasives are made from direct bonding, and their polishing characteristics are also examined. Alumina, silicon carbide and diamond micro powders are used as abrasives. Base metal matrix is carbonyl iron powder. It is found that bonded magnetic abrasives are superior to unbonded one by experiment. finally, the polished surface roughness is evaluated by atomic force microscope.

• 한국자기공명학회논문지
• /
• 제19권3호
• /
• pp.149-155
• /
• 2015

Acyl carrier protein is related with fatty acid biosynthesis in which specific enzymes are involved. Especially, acyl carrier protein (ACP) is the key component in the growing of fatty acid chain. ACP is the small, very acidic protein that covalently binds various intermediates of fatty acyl chain. Acylation of ACP is mediated by holo-acyl carrier protein synthase (ACPS), which transfers the 4'PP-moiety of CoA to the 36th residue Ser of apo ACP. Acyl carrier protein P (ACPP) is one of ACPs from Helicobacter plyori. The NMR structure of ACPP consists of four helices, which were reported previously. Here we show how acylation of ACPP can affect the overall structure of ACPP and figured out the contact surface of ACPP to acyl chain attached during expression of ACPP in E. coli. Based on the chemical shift perturbation data, the acylation of ACCP seems to affect the conformation of the long loop connecting helix I and helix II as well as the second short loop connecting helix II and helix III. The significant chemical shift change of Ile 54 upon acylation supports the contact of acyl chain and the second loop.

• 한국자기학회지
• /
• 제19권3호
• /
• pp.81-84
• /
• 2009

상관효과 U가 전자구조와 자성에 미치는 영향을 검토하기 위하여 대표적 자성물질인 철의 덩어리, 단층 및 사슬 구조에 대해 연구하였다. 이를 위하여 U = 3 eV로 택하여, 총 퍼텐셜 보강 평면파동 에너지 띠 방법을 이용하여 LDA+U 및 GGA+U 근사 하에 전자구조 계산을 수행하였다. 비교를 위하여 LDA 및 GGA를 이용한 계산도 수행하였다. 그 결과 U의 효과를 포함시켰을 때 덩어리 철의 경우 자기모멘트가 $0.3{\mu}_B$ 증가하여 실험값이나 LDA 및 GGA 계산에 비해 과다하게 계산되는 것으로 나타났으나, 단층이나 사슬의 경우는 그렇게 큰 차이를 보이지 않았다. 이로부터 전자구조 계산 시대상 계에 따라 U의 효과를 적절히 고려하여야 함을 알았다.

• 한국자기학회지
• /
• 제19권5호
• /
• pp.157-160
• /
• 2009

Ge 원자로 구성된 1차원 체인형태의 나노클러스터에 자성전이금속 Cr 및 Mn 원자를 치환 하였을 때 자성전이금속 원자사이의 자기적 상호작용을 제1원리의 범밀도함수법을 이용하여 계산하였다. 그 결과 Ge 원자와 전이금속 원자는 반강자성적인 상호작용을 하고 있으며, Ge-Ge원자 또한 반강자성 경향을 나타내었다. 이러한 자기 교환상호작용은 Ge 원자 여러 원자 층을 자화시켜 일어나고 있으며, 그 크기도 작지 않았다. 또한 자기 교환상호작용은 Ge 원자 수에 크게 의존하였다.

• 한국자기학회지
• /
• 제15권4호
• /
• pp.217-220
• /
• 2005

제일원리적 에너지 띠 계산 방법인 전 전자 총 퍼텐셜 선형보강평면파동(all-electron full-potential linearized augmented plane ave) 방법에 일반기울기근사(generalized gradient approximation)를 채용하여 Ag(001) 표면 위에 [110] 방향으로 놓인 Fe 선의 전자구조와 자성을 이론적으로 연구하였다. Fe 선의 원자당 자기모멘트는 $3.02\;{\mu}_B$로 Cu(001) 위에 놓인 Fe[110] 선의 값($2.99\;{\mu}_B$) 보다 약간 컸다. Fe 선의 자기모멘트가 상당히 증가한 것은 이웃한 결합수가 줄어들고 그 결과로 Fe-d 전자상태의 띠폭이 줄어들어 국소화 되고 스핀분리가 증가하였기 때문이다. Fe-d 전자상태의 띠 폭은 약 1.6eV였으며 스핀분리는 약 3.2 eV였다.

• 한국자기공명학회:학술대회논문집
• /
• 한국자기공명학회 1999년도 하계총회 및 제15회 자기공명 학술발표회
• /
• pp.13-13
• /
• 1999

• Bulletin of the Korean Chemical Society
• /
• 제17권1호
• /
• pp.43-45
• /
• 1996

Structural and electronic properties of an alkali metal fulleride, Rb1C60, was studied. In spite of the chain structure with shortdistance between balls along the crystallographic a-direction, the electronic structure calculation study with the X-ray defined crystal structure shows that Rb1C60 is a three-dimensional metal at room temperature. This result is different from the magnetic experiments in which the compound was found to behave as a quasi-one-dimensional metal. Partial Fermi surface nesting is supposed to be the reason for the metal-insulator transition found in Rb1C60 at ∼50 K.

• Bulletin of the Korean Chemical Society
• /
• 제27권10호
• /
• pp.1587-1592
• /
• 2006

We report the preparation, structure and magnetic properties of a new pillared complex, copper(II) hydroxy-1,4-butanedisulfonate, $Cu_2(OH)_3(O_3SC_4H_8SO_3)_{1/2}$. The titled compound was obtained by anion exchange, using copper hydroxyl nitrate $(Cu_2(OH)_3NO_3)$ as the starting material. According to the XRD data, this compound exhibits a pillared layered structure with organic layers tilted between the copper hydroxide layers with a tilt angle of $21.8^{\circ}$. FTIR spectroscopy confirms total exchange of nitrate by the sulfonate and indicates that the sulfonate functions are linked to the copper(II) ions with each aliphatic chain bridging the adjacent hydroxide layers. According to the dc and ac magnetic measurements, the title compound is a metamagnet consisting of spin-canted antiferromagnetic layers, with a Neel temperature of 11.8 K.

• 한국자기공명학회논문지
• /
• 제14권2호
• /
• pp.127-133
• /
• 2010

Redox-dependent conformational change of human 8-kDa Dynein light chain (LC8) plays important role in regulating NF-${\kappa}B$ signaling pathway. In this study we characterized the structural states of the oxidized and reduced forms of LC8 by using NMR spectroscopy. The $^1H-^{15}N$ 2D HSQC spectra of oxidized LC8 indicated that no significant change in tertiary structure of LC8 occurred upon oxidation. The chemical shift perturbations of LC8 upon oxidation suggest a redox-dependent quaternary structural change.

• Bulletin of the Korean Chemical Society
• /
• 제33권1호
• /
• pp.95-99
• /
• 2012

Two novel copper(II) complexes, [Cu(dmamhp)$(H_2O)_2(SO_4)]_n$ (1) and [Cu(dmamhp)$(NO_3)_2(H_2O)]{\cdot}H_2O$ (2) [dmamhp = 2-dimethylaminomethyl-3-hydroxypyridine] have been synthesized and structurally characterized by single crystal X-ray diffraction analysis. Compound 1 displays a double one-dimensional chains structure, in which each chain is constituted with the distorted octahedral copper(II) complex bridged through bidentate sulfate ligands resulting in a coordination polymer. The bifurcated hydrogen bonds and $\pi-\pi$ interactions play important roles in the formation of the double chains structure. On the other hand, compound 2 adopts a distorted square pyramidal geometry around copper(II) ion and exists as a discrete monomer. There are intermolecular bifurcated hydrogen bonds and $\pi-\pi$ stacking interactions between the monomeric units. The magnetic properties revealed that the paramagnetic behaviors are dominantly manifested and there are no intermolecular magnetic interactions in both compound 1 and 2.