EFFECT OF GRAIN REFINING ON PRIMARYαPHASE IN SEMI-SOLID A356 ALLOY PREPARED BY LOW SUPERHEAT POURING AND SLIGHT ELECTROMAGNETIC STIRRING

The semi-solid slurry of A356 alloy, which is grain-refined by Al-Ti-B master alloy, is prepared by low superheat pouring and slight electromagnetic stirring. The effects of grain refining on the morphology and the grain size of the primary α phase in the slurry manufactured are researched. The results indicate that the slurry with particle-like and rosette-like primary α phases can be prepared by low superheat pouring and slight electromagnetic stirring from liquid A356 alloy grain-refined, in which the pouring temperature can be suitably raised. Compared with the A356 samples without grain refining, the grain size and particle morphology of primary α phase as well as the distribution of the grain with particle-like or rosette-like along radial in the ingot in A356 are markedly improved by grain refining.

急性胰腺炎中胃裸区和左肾上腺受累的腹部CT特点及预后价值

显示急性胰腺炎（AP）中胃裸区受累（GBAI）和左肾上腺受累（LAGI）的cT表现，并评价其预后价值。回顾性分析了2003年1月至2006年12月间的116例AP病人的cT表现。34例GBAI病人（29.3％）显示胃裸区模糊、条带状高密度或积液，18例LAGI病人（15．5％）显示左肾上腺变形和密度减低。伴有GBAI和LAGI的AP病人的平均住院期长于不伴GBAI与LAGI的病人（P〈0．001）。GBAI预测并发症的敏感度和特异度分别为43．3％和89．8％，预测死亡率的敏感度和特异度分别为83．3％和73．6％。

A NEW ARRAY STRUCTURE FOR ESTIMATING 2-D DIRECTION-OF-ARRIVAL:Y-SHAPED ARRAY

This paper presents a new array structure for estimating two-dimensional (2-D) direction-of-arrivals (DOAs). The structure is called Y-shaped array, which has 10% better accuracy potential than the newly-developed L-shaped array. A great merit is its ability to estimate 2-D DOAs whichever directions the arriving signals come from, compared with L-shaped array whose performance depends on DOAs. Simulation results are given to demonstrate the performance of the new array.

Phosphorus Dynamics in Two Poultry-Litter Amended Soils of Mississippi Under Three Management Systems

An experiment arranged in a randomized complete block design with three replications was conducted on a Lexington soil (fine-silty,mixed,active,thermic,Ultic Hapludalfs) and a Loring soil (fine-silty,mixed,active,thermic,Oxyaquic Fragiudalfs) in Mississippi from September 1997 to September 2000 on 18 runoff plots under natural rainfall condition to study the phosphorus (P) dynamics in poultry litter amended soils under three management systems combining tillage and planting date treatments to identify effective management practices in southern U.S.A.The management systems in the study were:1) tillage in the fall prior to litter application followed by a delayed planting of fall forages (CT-DP);2) tillage followed by immediate planting of the fall forage with subsequent litter application (CT-IP);and 3) no-till with planting prior to litter application (NT-IP).The results indicated that there was significant increase in soil P after 3 years of poultry litter application for both Lexington and Loring soils (P < 0.05).Based on P budget analysis,the majority of P from poultry litter application (> 90%),was accumulated in both soils.In Loring soil,soluble P mass in the runoff was significantly higher from NT-IP than from CT-DP and CT-IP over the entire study period (P < 0.01).For both soils,there were no significant differences in sediment P mass between management systems.For Loring soil,CT-DP and CT-IP were effective management practices to mitigate negative effects due to poultry litter application.

Wide Absorption Spectrum Measuring Methods by DFB-LDs in Water Vapor Detection System

由分布式的反馈激光二极管(DFB-LDs ) 的宽吸收光谱的二测量方法在检测水蒸汽吸收线被介绍。一个人是扫描方法的分部，并且由当前的调整由温度调整和快光谱调节速度调节范围利用宽光谱。明确地，这个方法被划分一个目标认识到光谱区域进对应于 DFB-LD 的特定的温度的几节，为百由当前的调整扫描每节预定，并且平均数据提起信号到噪音比率( SNR )，然后联合所有节得到整个系列。10 ppmv 的精确性被这个方法与 10 厘米的路径长度在水蒸汽的测量获得了。另外一个是适合方法的数据，基于吸收线形状功能；吸收线能被与部分测量数据适合描述。恰当的吸收线与测量数据被适合很好，并且关联系数(R 平方) 的平方是不亚于 0.99。