We investigate the velocity distribution of dark matter in the disk of a galaxy like the Milky Way at the solar radius. Using N-body simulations with the total mass and z-component of angular momentum conserved, we calculate the response of a dissipationless dark matter galactic halo during the dissipational collapse of the baryonic matter in spiral galaxy formation. The initial distribution of dark matter and baryonic particles is assumed to be a homogeneous mixture based on a King model. The baryonic matter is assumed to contract, forming the final luminous components of the galaxy, namely the disk and, in some cases, a bulge and central point. Both slow and fast growth of the luminous components are considered. We find that the velocity distribution of dark matter particles in a reference frame rotating slowly about the galaxy center in the plane of the disk is similar to a Maxwellian, but it is somewhat boxier, being flatter at the peak and truncated in the tails of the distribution. We tabulate parameters for the best-fitting Maxwellian and modified-Maxwellian distributions. There is no significant difference between slow collapse and fast collapse for all these results. We were unable to detect any effect of disk formation on the z-dependence of the dark matter density distribution.
The effect of alloying mode and porosity on the axial tension-tension fatigue behavior of a P/M steel of nominal composition Fe-4w/o Ni-1.5w/o Cu-O.5w/o Mo-O.5w/o C has been evaluated. Alloying modes utilized were elemental powder mixing, partial alloying(distaloy) and prealloying by water atomization; in each case the carbon was introduced as graphite prior to sintering. Powder compacts were sintered(/30 min.) in 7Sv/o /25v/o to densities in the range 6.77-7.2 g/. The dependence of fatigue limit response on alloying mode and porosity was interpreted in terms of the constituent phases and the pore and fracture morphologies associated with the three alloying modes. For the same nominal composition, the three alloying modes resulted in different sintered microstructures. In the elemental mix alloy and the distaloy, the major constituent was coarse and fine pearlite, with regions of Ni-rich ferrite, Ni-rich martensite and Ni-rich areas. In contrast, the prealloy consisted primarily of martensite by with some Ni-rich areas. From an examination of the fracture surfaces following fatigue testing it was concluded that essentially all of the fracture surfaces exhibited dimpled rupture, characteristic of tensile overload. Thus, the extent of growth of any fatigue cracks prior to overload was small. The stress amplitude for the three alloying modes at 2x was used for the comparison of fatigue strengths. For load cycles <3x, the prealloy exhibited optimum fatigue response followed by the distaloy and elemental mix alloy, respectively. At load cycles >2x, similar fatigue limits were exhibited by the three alloys. It was concluded that fatigue cracks propagate primarily through pores, rather than through the constituent phases of the microstructure. A decrease in pore SIze improved the S-N behavior of the sintered steel.
버섯 재배지에 있어서 주요 해충인 Sciarid fly(Lycoriella sp.)의 생활사와 발육단계별 특성을 조사하였다. 버섯 파리는 팽이버섯(Flammulina velutipes) 균사를 먹이로 공급하고 , 555% 습도, 16L:8D 조건의 항온기에서 누대 사육하였다. 버섯 파리의 알은 직경 0.17 mm, 길이 0.27 mm의 타원형으로 알 기간은 평균 4일이었다. 1령으로부터 3령까지 유충의 체장은 각각 0.7, 1.5와 4.5 mm이었고, 평균 체중은 각각 1.9, 15.4와 9 93.6 이었다. 4령기 유충의 암컷과 수컷은 체장, 마디 크기 및 처1중에 의해 형태적 특정으로 뚜렷하게 구별 할 수 있었다. 4령유충 암컷의 평균 체장과 제중이 각각 5 mm와 162 이었고 수컷은 체장이 3.5 mm, 체중이 90 으로 조사 되었고, 유충 기간은 암컷이 13.5일, 수컷이 13일이였다. 번데기 기간의 암컷과 수컷의 체장은 각각 3.5와 2.7 mm로 나타났으며 평균 체중은 각각 136 과 65으로 암수간 차이가 현저하였다. 성충은 용화 이후 암컷이 5.5일, 수컷은 5일 경과한 후 우화하였고, 성충 기간은 암컷이 평균 5일 수컷은 7일이었다. 암컷의 체중은 수컷보다 2배 이상 높은 것으로 조사되었고, 교미 후 암컷은 130에서 150개의 알을 버섯 균사 위와 속에 산란하였다. 이상의 결과로, 버섯 파리 암컷과 수컷의 경과 일수는 각각 평균 29일 과 213일로 조사되었다.
Large field spectrographs are severely influenced by atmospheric refraction. LAMOST is a large field multi-object spectroscopy telescope with 5° field of view, f/5 focus ratio and 20m focal length. There will be 4000 fibers simultaneous on it's ∮1.75m focal plane. Here we discuss the atmospheric refraction effects on LAMOST in two hands. One is the effect of differential refraction across the field, another is the effect of atmospheric dispersion. According to the calculation, we find that: 1. The largest deviation from center within the field is 4.32" during a 1.5-hour integration at 80° declination. 2. The directions of deviation are complex, so the deviations can't be decreased by rotating the field. We also give out the atmospheric dispersions.