As precursors of cathode materials for lithium ion batteries, Ni1/3Co1/3Mn1/3(OH)2 powders are prepared in a continuously stirred tank reactor via a co-precipitation reaction between aqueous metal sulfates and NaOH in the presence of NH4OH in air or nitrogen ambient. Calcination of the precursors with Li2CO3 for 8 h at 1,000°C in air produces dense spherical cathode materials. The precursors and final powders are characterized by X-ray diffraction (XRD), scanning electron microscopy, particle size analysis, tap density measurement, and thermal gravimetric analysis. The precursor powders obtained in air or nitrogen ambient show XRD patterns identified as Ni1/3Co1/3Mn1/3(OH)2. Regardless of the atmosphere, the final powders exhibit the XRD patterns of LiNi1/3Co1/3Mn1/3O2 (NCM). The precursor powders obtained in air have larger particle size and lower tap density than those obtained in nitrogen ambient. NCM powders show similar tendencies in terms of particle size and tap density. Electrochemical characterization is performed after fabricating a coin cell using NCM as the cathode and Li metal as the anode. The NCM powders from the precursors obtained in air and those from the precursors obtained in nitrogen have similar initial charge/discharge capacities and cycle life. In conclusion, the powders co-precipitated in air can be utilized as precursor materials, replacing those synthesized in the presence of nitrogen injection, which is the usual industrial practice.

We present the latest results from the Mission Program NIRLT, the NIR spectroscopic observations of brown dwarfs using the IRC on board AKARI. The near-infrared spectra in the wavelength range between 2.5 and 5.0 μm is especially important to study the brown dwarf atmospheres because of the presence of non-blended bands of major molecules, including CH4 at 3.3 μm , CO2 at 4.2 μm , CO at 4.6 μm and H2O around 2.7 μm . Our observations were carried out in the grism-mode resulting in a spectral resolution of ~ 120. In total, 27 sources were observed and 18 good spectra were obtained. We investigate the behavior of three molecular absorption bands, CO, CH4 and CO2 , in brown dwarf spectra relative to their spectral types. We find that the CH4 band appears in the spectra of dwarfs later than L5 and CO band is seen in the spectra of all spectral types. CO2 is detected in the spectra of late-L and T type dwarfs.

In this paper we present an independent FORTRAN code for calculating LTE-plane-parallel model atmospheres. The transfer equation has been solved using Avrett and Loeser method. It is shown that, using an approximate non-gray temperature distribution together with the iteration factors method (Simonneau and Crivellari) for correcting the temperature distribution reduce the number of iteration required to achieve the condition of radiative equilibrium. Preliminary results for pure helium model atmospheres are presented.

본 연구에서는 에어러솔 대기 상태에서 국내 COMS 연구자들이 사용하는 세 개의 단파 복사전달모델에서 산출된 복사속 성분을 비교분석하였으며, 대기 복사 수지에서 에어러솔 역할도 분석하였다. 국내 모델들의 평가를 위하여, 15개 모델값을 평균한 Halthore et al.(2005) 결과를 기준값으로 사용하였다. 두 종류 에어러솔 농도(AOT=0.08, 0.24)에서 조사된 열대 또는 한대 대기의 에어러솔 강제력은 지표에서의 하향 일사 및 상향 산란, 대기 상부의 상향 산란, 그리고 대기 흡수도의 복사 성분들에 있어서 국외 연구에 비하여 국내 결과들에서 체계적으로 약하게 나타났다. 에어러솔 강제력은 지표에서의 하향 일사에 대하여 -10∼-40Wm-2 이었으며, 지표 및 대기 상부의 상향 산란의 경우에 상대적으로 큰 태양천정각과 고농도 에어러솔 상태에서 컸다. 두 종류 에어러솔 조건에서 지표에서의 하향 및 상향 산란값들은 대기 종류보다는 태양천정각에 더 민감하였다. 하향 산란은 상대적으로 작은 태양천정각과 고농도 에어러솔 조건에서 컸다. 에어러솔 농도 증가는 하향 산란 증가에도 불구하고 하향 직달 일사의 감소가 이를 초과함으로써 지표 냉각을 유도하는 것으로 조사되었다. 동일한 에어러솔 농도 및 태양천정각 조건에서 직달일사 소산은 열대 대기에서는 주로 수증기, 그리고 한대 대기에서는 수증기뿐만 아니라 오존에도 기인하는 것으로 조사되었다. 특히 열대 대기에서는 수증기의 역할이 오존에 비하여 3∼4배 컸다. 저농도 및 고농도 에어러솔 대기에서 대기 흡수도는 국내외 연구간에 ±10% 내에서 일치하였다.

The effect of individual gas constituents in a sintering atmosphere is examined to optimize the sintered properties of Iron-Carbon P/M components. The influence of sintered properties is reviewed as a function of hydrogen percentages and dew point in the sintering zone. Microstructures, porosity, pore morphology and dimensional changes are the subject of this review. The effects of CO containing atmospheres are compared against the non CO atmospheres in terms of hardness, carbon control and dimensional changes.

The slow evolution of global magnetic fields and other dynamical processes in atmospheres of CP magnetic stars lead to the development of induced electric currents in all conductive atmospheric layers. The Lorentz force, which results from the interaction between a magnetic field and the induced currents, may modify the atmospheric structure and provide insight into the formation and evolution of stellar magnetic fields. This modification of the pressure-temperature structure influences the formation of absorption spectral features producing characteristic rotational variability of some spectral lines, especially the Balmer lines (Valyavin et al., 2004 and references therein). In order to study these theoretical predictions we began systematic spectroscopic survey of Balmer line variability in spectra of brightest CP magnetic stars. Here we present the first results of the program. A0p star ⊝ Aur revealed significant variability of the Balmer profiles during the star's rotation. Character of this variablity corresponds to that classified by Kroll (1989) as a result of an impact of significant Lorentz force. From the obtained data we estimate that amplitudes of the variation at Hα, Hβ, Hɤ and Hδ profiles reach up to 2.4%during full rotation cycle of the star. Using computation of our model atmospheres (Valyavin et al., 2004) we interpret these data within the framework of the simplest model of the evolution of global magnetic fields in chemically peculiar stars. Assuming that the field is represented by a dipole, we estimate the characteristic e.m.f. induced by the field decay electric current (and the Lorentz force as the result) on the order of E ~ 10 -11 cgs units, which may indicate very fast (< < 1010 years) evolution rate of the field. This result strongly contradicts the theoretical point of view that global stellar magnetic fields of CP stars are fossil and their the characteristic decay time of about 1010 yr. Alternatively, we briefly discuss concurring effects (like the ambipolar diffusion) which may also lead to significant atmospheric currents producing the observable Lorentz force.

리튬이온이차전지의 부극재로 사용되는 탄소재인 비정질 탄소(needle cokes)에 B2O3를 첨가하여 공기중의 질소 분위기와 Ar 분위기에서 고온으로 흑연화 열처리를 하였을 때의 표면미세구조의 변화와 제 2상의 분포를 투과전자현미경으로 분석하였다. 또한 전지용량, 전지효율과 같은 전지성능이 탄소재의 표면미세구조와 관련되어 있음을 고찰하였다.

The dependencies of the chemical element abundances in stellar atmospheres with respect to solar abundances on the second ionization potentials of the same elements were investigated using the published stellar abundance patterns for 1,149 G and K giants in the Local Region of the Galaxy. The correlations between the relative abundances of chemical elements and their second ionization potentials were calculated for groups of stars with effective temperatures between 3,764 and 7,725 K. Correlations were identified for chemical elements with second ionization potentials of 12.5 eV to 20 eV and for elements with second ionization potentials higher than 20 eV. For the first group of elements, the correlation coefficients were positive for stars with effective temperatures lower than 5,300 K and negative for stars with effective temperatures from 5,300 K to 7,725 K. The results of this study and the comparison with earlier results for hotter stars confirm the variations in these correlations with the effective temperature. A possible explanation for the observed effects is the accretion of hydrogen and helium atoms from the interstellar medium.

To broaden the understanding of classical Cepheid structure, evolution and atmospheres, we have extended our continuing secret lives of Cepheids program by obtaining XMM/Chandra X-ray observations, and Hubble space telescope (HST) / cosmic origins spectrograph (COS) FUV-UV spectra of the bright, nearby Cepheids Polaris, δ Cep and β Dor. Previous studies made with the international ultraviolet explorer (IUE) showed a limited number of UV emission lines in Cepheids. The well-known problem presented by scattered light contamination in IUE spectra for bright stars, along with the excellent sensitivity & resolution combination offered by HST/COS, motivated this study, and the spectra obtained were much more rich and complex than we had ever anticipated. Numerous emission lines, indicating 104 K up to ~3 × 105 K plasmas, have been observed, showing Cepheids to have complex, dynamic outer atmospheres that also vary with the photospheric pulsation period. The FUV line emissions peak in the phase range φ ≈ 0.8-1.0 and vary by factors as large as 10×. A more complete picture of Cepheid outer atmospheres is accomplished when the HST/COS results are combined with X-ray observations that we have obtained of the same stars with XMM-Newton & Chandra. The Cepheids detected to date have X-ray luminosities of log LX ≈ 28.5-29.1 ergs/sec, and plasma temperatures in the 2–8 × 106 K range. Given the phase-timing of the enhanced emissions, the most plausible explanation is the formation of a pulsation-induced shocks that excite (and heat) the atmospheric plasmas surrounding the photosphere. A pulsation-driven α2 equivalent dynamo mechanism is also a viable and interesting alternative. However, the tight phase-space of enhanced emission (peaking near 0.8-1.0 φ) favor the shock heating mechanism hypothesis.