Fe_(73.5)Cu₁Nb₃Si_(13.5)B_(9) 초미세 결정립 합금의 분말코아 특성

노태환,최혁열 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.6

The melt-spun Fe_(73.5)Cu₁Nb₃Si_(13.5)B_(9) ribbons so called Finemet alloy were annealed in the temperature range of 490 to 610℃ for 1 h and milled by using a planetary ball mill into the powders with the size of 250~850 sm. Then the powder cores were produced through the blending of the magnetic powders with the 5 wt% of ceramic insulator and cold compaction. Further the annealing responses of magnetic, electrical properties and microstructure were investigated. At the annealing temperature of 550℃, the microstructure was transformed from amorphous to crystalline a-Fe phase with the grain size of 10.7 nm, and the electrical resistivity of 117 μΩ-㎝ was obtained. At the same time, the effective permeability and quality factor reached 120 and 50, respectively, and the permeability persisted up to about 500 kHz. Moreover the core loss at the frequency of 50 kHz and the magnetic induction of 0.1 T was about 300 mW/cm³. These magnetic properties were comparable to the conventional powder core materials such as MPP(molybdenum permalloy powder), Sendust etc. However the dc bias characteristics represented by the permeability stability upon dc magnetic field superposition were found to be unsatisfactory. (Received February 16, 2004)

Relation between Disease Incidence of Bacterial Grain Rot of Rice and Weather Conditions

Noh,Tae-Hwan,Kim,Hyung-Moo,Song,Wan-Yeob,Lee,Du-ku,Kang,Mi-Hyung,Shim,Hyeong-Kwon 한국자원식물학회 2004 Plant Resources Vol.7 No.1

Bacterial grain rot of rice caused by Burkholderia glumae was examined between weather condition and disease incidence. From 1998 to 2000, average disease incidence was 3.0 % without difference in survey regions. However, it was related closely to amount of rainfall that disease incidence higher in 1998 and 2000 to 3.0 % and 3.6 % respectively than 2.3 in 1999 relatively small volum of rainfall season.

중성자 수송방정식의 확산 접근성 해석

盧泰完,高鳳煥 弘益大學校 科學技術硏究所 1997 科學技術硏究論文集 Vol.8 No.-

In some classes of radiative and neutron transport problems that include strongly diffusing media, it might be impractical to refine the mesh enough to enter the regime of thin mesh cells. This is because such media are too optically thick to realistically allow sufficient mesh refinement. Considering that the simplified even-parity neutron transport equation is an approximation to the Boltzmann and even-parity transport equation, it is advantageous if the method has the correct diffusion limit; in other words, it gives generally accurate results in diffusing regimes, even when mesh cells are not thin. Our asymptotic analyses have shown that the so-called thick diffusion limit is satisfied by the finite element even-parity and simplified even-parity transport equations.

부유대역 용융응고법으로 제조된 YBa_2Cu_3O_x 산화물초전도체의 미세구조와 전기적 특성

노태형,송정환,장규철,한이섭,김소정,구본급,김호기 대전산업대학교 반도체기술연구소 2000 半導體技術硏究所報 Vol.2 No.-

The YBa_2Cu_3O_x-20 wt% Y_2BaCuO_5 composition designed in YBCO system was synthesized by solid state reaction method. The optimum condition of hot zone temperature and growth rate in floating-zone melt were 1080 ℃ and 2.5 mm/hour, respectively. In samples growth as these condition, the low angel boundaries in grain direction and small amount of amorphous phase known as decreasing characteristics of superconducting materials between grain boundaries in microstructure are investigated by polarized light microscopy on the whole. The critical current density(Jc) at 77k of sample using powder fabricated with no CeO_2 and doped 5 wt%CeO_2 were 8,000 A/㎠(Jc : 561A) and 12,000 A/㎠(Jc: 826A) at 0 T by direct current transport method, respectively.

낮은 큐리온도를 가진 Fe-Ni-Zr 비정질 합금의 저온 구조완화와 자기적 특성

노태환 국립7개대학공동논문집간행위원회 2001 공업기술연구 Vol.1 No.-

The coercive force(H_c), ac permeability(μ_ac), and remanence(B_r) as a function of annealing temperature for metal-metal type (Fe_0.85Ni_0.15)_90Zr_10 amorphous alloy with low T_c(= 412 K) were measured, and temperature dependence of an enthalpy relaxation was examined. The increase in H_c and decrease in μ_ac and B_r were observed at the annealing temperature ranging from 425 to 550 K, where the low temperature enthalpy relaxation originated from Fe-Ni interactions occurred. Thus the degradation of soft magnetic properties was attributed to local-ranged Fe-Ni atom regroupings enhancing the structural heterogeneity and probably causing the non-uniform internal stresses.

Fe-(89-x)Hf-(x)B-(11) 비정질 합금의 자기적 특성

노태환 安東大學校 工業技術硏究所 2001 공업기술연구논문집 Vol.8 No.1

Fe_(89-x)Hf_(x)B_(11) (at%) 비정질 합금의 자기적 특성과 결정화 온도에 미치는 Hf의 영향을 조사하였다. Hf의 농도를 5~10at%의 범위에서 변화시킬 경우, 약 7at%의 조성 부근에서 가장 높은 실효투자율과 가장 낮은 보자력을 나타내고 동시에 최소의 고주파 자심손실이 얻어졌다. 그리고 Hf을 증가시키면 포화자기변형이 감소하여 연자성 및 교류자화 특성의 향상에 대한 원인을 제공하는 것으로 밝혀졌으며, 결정화온도가 증가하여 보다 높은 열적 안정성이 얻어지는 것으로 관찰되었다. 포화자속밀도는 Hf증가에 따라 감소하였으나 그 정도는 그리 크지 않았으며 Hf=7at%에서 대략 10kG의 값을 나타내었다. 결국 Hf이 7at% 정도 되는 조성에서 양호한 연자성과 적절한 자화의 크기를 가지면서 우수한 고주파 자심손실 특성이 함께 얻어짐을 알게 되었다. The effects of Hf on the magnetic properties and crystallization temperature of Fe_(89-x)Hf_(x)B_(11) (x=5~10)(at%) amorphous alloys were investigated. At the concentration of x=7, the highest effective permeability, lowest coercive force and high-frequency core loss were observed. Further, saturation magnetostriction decreased with increasing the Hf content, which was considered to give rise to improvement of the soft magnetic properties and a.c. magnetization characteristics. Moreover crystallization temperature increased with the Hf content, and then higher thermal stability resulted. The Hf decreased the saturation magnetization of the alloys, however the amount of decrease was not so large. The value of Bio of the alloy having 7at% Hf was about 10 kG. In consequence, good soft magnetic properties, moderate magnetization and excellent core-loss properties at high frequency were obtained in the alloy with optimum Hf content (x=7).

인산염 피막처리 분말을 사용한 철계 나노결정합금 분말코아의 자기적 특성에 미치는 인산농도의 영향

김영민,노태환 국립7개대학공동논문집간행위원회 2005 공업기술연구 Vol.5 No.-

Phosphate coating to the FeCuNbSiB nanocrystalline alloy powders for electrical insulation has been carried out in aqueous solutions with different phosphoric acid concentrations, and the surface-treated powders were cold-compressed into the powder cores. In the solutions with higher acid concentration, the more phosphatized surface was obtained. The powder cores using phosphate-coated powders in the solution with 2.0 wt% H₃PO₄ exhibited effective permeability of 95 up 500kHz and core loss of 380 mW/cm3 at 50kHz/0.1 T. The effective permeability and core loss had a tendency to decrease with increasing the acid concentration. These indicate that the formation of larger quantity of phosphates on the surface could provide more effective electrical insulation between magnetic nanocrystalline powders.

Organization and Energy Transfer of Fused Aromatic Hydrocarbon Guests within Anion‐Confining Nanochannel MOFs

Noh, Tae Hwan,Lee, Haeri,Jang, Jaeseong,Jung, Ok‐,Sang WILEY‐VCH Verlag 2015 Angewandte Chemie Vol.127 No.32

<P><B>Abstract</B></P><P>The self‐assembly of Zn<SUP>II</SUP> ions with 1,3,5‐tris(isonicotinoyloxyethyl)cyanurate produces new topological (4<SUP>2</SUP>⋅12<SUP>4</SUP>)<SUB>3</SUB>(4<SUP>3</SUP>)<SUB>4</SUB> 2D metal–organic frameworks (MOFs) with anion‐confining cages. The eclipsed assembly of each 2D MOF by π–π stacking of cyanurate moieties (3.352(5) Å) forms 3D MOFs consisting of nanochannels (10.5 Å). Two of the three anions are confined in each peanut‐type cage, resulting in hydrophobicity of the nanochannels. The hydrophobic nanochannel effectively adsorbs a wide range of fused aromatic hydrocarbons (FAHs) as monomers or dimers, rendering it potentially highly useful as an energy‐transfer material.</P>

Recent Advances in Various Metal–Organic Channels for Photochemistry beyond Confined Spaces

Noh, Tae Hwan,Jung, Ok-Sang American Chemical Society 2016 Accounts of chemical research Vol.49 No.9

<P>Tailor-made molecular channel architectures are a hot issue in the fields of nanotechnology, molecular sieves, ion sensors, recognition, confined space reactors, and fluidic transport systems. Carbon nanotubes have been a particular focus, though they cannot easily be synthesized to predefined structures and sizes. Rational design and construction of molecular channel structures based on coordination chemistry has been recognized as a useful approach. Metalorganic channel (MOC) structures can be generated by utilizing, at least in principle, molecular self-assembly of metal ions as angular units with designed ligands as spacers. Recent developments in molecular channel chemistry include exciting advances in photochemical applications and supramolecular material functionality, in addition to general applications such as transport, diffusion and exchange, separation, gas storage, catalysis, and simple encapsulation. In order to carry out the diverse channel functionalities, a large number of studies have been conducted on the synthesis of robust and stable 3D coordination polymers, which show permanent porosity without any guest molecules within the channels, in that the robustness of the channel structures after removal of the solvate/guest molecules is of interest because the structural integrity of the extended structures must be maintained during the reactions. These compounds can be regarded as analogous to zeolites. This Account highlights advances in the construction, from metal cations and multidentate pyridyl ligands, of various MOCs and useful molecular materials as photoreaction platforms. We begin by discussing the fact that detailed proof-of-concept construction of various systematic MOC structures has been introduced mainly in terms of the metal ions as angular components and the pyridyl ligands as spacers. This approach leads to structural complexity of assembled MOC motifs such as metallamacrocycles, helical and cylindrical coordination polymers, vertical arrays of 1D coordination polymers, interweaving and eclipsed stacking of 2D coordination polymers, and typical 3D coordination polymers. Notwithstanding the diversity of their skeletal structures, confined spaces of the channels are suitable for the study of photochemical performances including radical trapping, photocyclopropanation, dye inclusion and energy transfer, and guest-to-host structural transmission. The key aspect of their utility is not only the preparation of photoresistant MOCs but also channel tuning for inclusion of photoactive guests. Guest molecules, which are compatible with the size, shape, and polarity of the channels, can be incorporated into the crystals, instead of simple organic solvents, thus giving rise to hostguest complexes in the solid state. Such MOC studies could facilitate the development of chemical sensors, new photocatalytic systems, and useful molecular photochemical reactors.</P>

Early detection of herbicide dose-response using spectral image analysis

Tae-Kyeong Noh,Tae-Young Lee,Sang-Hwan Park,Do-Soon Kim 한국잡초학회 2018 한국잡초학회 별책(학술대회 초록집) Vol.38 No.2