Formation of uranium mononitride by the reaction of uranium dioxide with carbon in ammonia and a mixture of hydrogen and nitrogen: II. Reaction rates

Kinetics of the carbothermic synthesis of UN from UO₂ in an NH₃ stream and a mixed 75% H₂ + 25% N₂ stream were studied in the temperature range of 1400–1600°C by X-ray analysis and weight change measurement of the sample. The weight change was divided into two parts; i.e. weight loss due to carbothermic reduction of UO₂ and weight loss due to removal of carbon by hydrogen. The former followed the first-order rate equation −1n(1 − ₀) = k₀t, and the latter the rate equation of phase boundary reaction 1 − (1 − _c)^1/3 = k_ct. The apparent activation energy of the former was in the range of 320–380 kJ/mol. The value of the latter in an NH₃ stream was 175–185 kJ/mol, which was smaller than that in a mixed 75% H₂ + 25% N₂stream (285 kJ/mol). In this method, the rate of the removal of carbon by hydrogen determines that of the formation of high purity UN.     

Formation of uranium mononitride by the reaction of uranium dioxide with carbon in ammonia and a mixture of hydrogen and nitrogen— I synthesis of high purity UN

Formation of uranium mononitride by the reaction between UO₂ and C in an ammonia stream, a mixed 75%H₂-25%N₂ stream and a mixed 8%H₂-92%N₂ stream has been studied at 1400–1600°C. For the formation of high purity UN, there exists a minimum mixing ratio ($\text{C}\text{UO}{}_2$). It largely depends on the reaction atmosphere and temperature. The mixing ratio in the three atmospheres decreases in the following order: ammonia >75%H₂ + 25%N₂ > 8%H₂ + 92%N₂, and it decreases with increasing temperature. The total amount of impurities (carbon + oxygen) in the UN obtained is in the range of 500–1000 ppm. The time necessary for completion of the reaction in ammonia is shorter than in a mixed hydrogennitrogen.     

A design of magnetic shielding for a superconducting magnetically levitated train

For EDS-type magnetically levitated trains, magnetic shielding of stray fields produced by superconducting magnets is an important task. We seek the “optimal” thickness distribution (configuration) of magnetic material, which is the lightest and keeps the magnetic field at tolerable levels in the vehicle. In many cases, trial-and-error methods have been adopted for this purpose. In this paper, we propose a new method for preliminary design of the magnetic shielding. In this method, we simplify the magnetic shielding problem, assuming infinite permeability of the magnetic material, and calculate the magnetic flux going into or out of the shield surface. In this case, we can design an optimal magnetic shield (distribution and configuration of the magnetic material) and know the minimum weight of the magnetic shielding. We finally present an example of the magnetic shielding designed by this method and investigate its characteristics in a magnetically levitated train. © 1998 Scripta Technica, Electr Eng Jpn, 124(1): 42–54, 1998     

叶片附着物对直线翼垂直轴风力机性能影响的风洞试验

直线翼垂直轴风力机是一种升力型风力机,多被作为离网型风能利用装置。在寒冷地区的冬季,风力机叶片表面结冰、积雪以及附着其他物质会影响风力机的性能。文章介绍了采用粘土作为附着物模拟叶片表面前缘结冰的风洞试验,研究了叶表附着物对风力机的转速和输出功率性能的影响。     

Alleviation of lipopolysaccharide-induced acute liver injury in Propionibacterium acnes-primed IFN-gamma-deficient mice by a concomitant reduction of TNF-alpha, IL-12, and IL-18 production

The present study was designed to investigate the role of IFN-gamma in LPS-induced liver injury following priming with Propionibacterium acnes. At 1 week after priming BALB/c mice with P. acnes, a large number of macrophages (Mphi) and lymphocytes predominantly infiltrated the portal area, resulting in the intrahepatic formation of granulomas consisting of epithelioid and lymphoid cells. In comparison, in IFN-gamma gene-disrupted BALB/c mice (IFN-gamma knockout mice), the number of infiltrated Mphi was decreased, with a significant reduction in the number and size of granulomas. Subsequent elicitation with a low dose of LPS induced massive hepatic necrosis in wild-type BALB/c mice, with a marked increase in the serum levels of TNF-alpha, IL-12, and IL-18 and subsequently of alanine transferase. In contrast, IFN-gamma knockout mice developed scattered focal necrosis of the liver with significantly lower levels of serum alanine transferase as well as drastic decreases in TNF-alpha, IL-12, and IL-18 production. The administration of an anti-IFN-gamma neutralizing mAb at the eliciting phase significantly alleviated liver injury and reduced serum IL-12 and IL-18 levels. Thus, endogenously produced IFN-gamma is involved in the pathogenesis of this liver injury model by regulating Mphi infiltration and granuloma formation in the priming phase as well as cytokine production in the eliciting phase.     

基于烟线法的直线翼垂直轴风力机静态流场可视化试验

为探明直线翼垂直轴风力机自起动性能与风力机叶片迎风角度的关系,设计制作了一台具有3枚NACA0018翼型叶片的直线翼垂直轴风力机模型.通过风洞试验测试了直线翼垂直轴风力机在不同风速下自起动性与叶片迎风角度的关系;利用烟线法对风力机的静态流场进行了可视化试验,获得了不同叶片迎风角度下风力机周围流场的流迹线图像;分析了风力机自起动性与叶片翼型、叶片个数、叶片受力情况和周围流场的关系.