两种净全辐射测量方法的比较

净全辐射是研究地球热量收支状况的重要指标,我国目前使用的净全辐射表的测量准确度并不能满足需求。为了提高净全辐射测量的准确度,提出了利用四分量法测量净全辐射,在相同条件下对2种测量方法进行比对试验,通过比对实验数据的分析和研究,结果表明该方法有效的提高了净全辐射的精确度。     

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��The method of "running the drill pipe into the big diameter casing's interior" is suitable for the cementing of big diameter casing at the interval with many thief zoner By use of this method,the quantity of cement can be exactly eontroled,the quantity of the mud used for replacing the cement slurry is lesser,the time for cementing operation is shortened and the return velocity of mud and cement slurry in annular space can be effectively controled,thus,it can decrease the mud damage and exactly guarantee the quality of the cement plug and annular cement column. The equipment,operation and the usege result in field are briefly stated in this article.     

Ultra2 SCSI PCB设计中的阻抗匹配问题

在高速逻辑设计中,需要考虑避免出现振铃、串扰等传输线现象.就此,详细讨论了在Ultra2 SCSI单端和差分模式兼容下PCB的两种输出阻抗及其与连接电缆的阻抗匹配问题的解决方法,简单介绍了在这样的高速逻辑系统中,PCB设计通常要考虑的一些其它问题.     

液态模锻在防爆工具中的应用

叙述了液态模锻的工艺实质、应用范围及工艺参数。防爆工具液态模锻是一种行之有效的新技术,也在优质、高产及改善劳动条件等方面创造了新的途径。     

凝胶离心成型制备316L-TiC复合材料

将凝胶离心成型工艺应用于316L-TiC复合粉末的坯体成型,研究了固含量对316L-TiC复合粉末浆料流变性的影响以及引发剂的加入量对粉末浆料固化时间的影响,分析了凝胶离心成型工艺中离心转速与316L-TiC坯体的密度和强度的关系。结果表明：以油酸作分散剂,制备稳定且流动性好的浆料的最佳固含量为55％（体积分数）;引发剂的加入量为0．7％（占预混液的质量分数）,采用自行设计的离心成型机,选择最佳转速3000r／min,制备出的坯体密度高、无残留气孔,相对密度64．3％,强度26．3MPa。坯体经真空脱胶1380℃烧结保温1h制备出316L-TiC合金管,烧结体收缩均匀无变形,TiC颗粒呈均匀分布。     

The effect of the thermal exposure on microstructure of MP159 alloy

The effect of the thermal exposure at different temperatures on the microstructure is investigated for MP159 alloy by optical microscopy and transmission electron microscopy (TEM). Thermal exposure at 660°C is related to the aging induced hardening mechanism, thermal exposure at the neighborhood of 920°C is associated with static recrystallization behavior, and thermal exposure at a temperature range of 920 to 1070°C for a short time is investigated with a view toward obtaining the longest permissible thermal exposure time during which microstructural reconstitution of the cold deformed microstructure would not occur at the corresponding temperature, which would provide guidance for determining reasonable hot forging parameters of fasteners. The results indicate that both solution heat treated (ST) and cold worked (CW) MP159 alloy could be hardened by aging. This aging induced hardening is attributable to the precipitation of a very finely dispersed fcc ordered solid solution. The precipitating process is so rapid that the air cooling (AC) or water cooling (WC) process of the sample exposed to elevated temperature higher than normal aging temperature could produce an appreciable hardening effect. The recrystallization temperature of the alloy is as high as 920°C, such a high recrystallization temperature is attributed to deformation twins and a variety of alloying elements due to their inhibition to the nucleation and growth of recrystallization grains, other than to the hcp-phase which used to be believed to explain high recrystallization temperature in MP alloys in some literature.     

陷阱型双通带声表面波滤波器的设计

研究比较了几种陷阱型双通带声表面波滤波器的设计方法。实验表明,采用组合式均匀叉指换能器及变形多条耦合器元件可有效提高对陷阱频率的抑制。     

A statistical watermark detection technique without using originalimages for resolving rightful ownerships of digital images

Digital watermarking has been proposed as the means for copyright protection of multimedia data. Many of existing watermarking schemes focused on the robust means to mark an image invisibly without really addressing the ends of these schemes. This paper first discusses some scenarios in which many current watermarking schemes fail to resolve the rightful ownership of an image. The key problems are then identified, and some crucial requirements for a valid invisible watermark detection are discussed. In particular, we show that, for the particular application of resolving rightful ownership using invisible watermarks, it might be crucial to require that the original image not be directly involved in the watermark detection process. A general framework for validly detecting the invisible watermarks is then proposed. Some requirements on the claimed signature/watermarks to be used for detection are discussed to prevent the existence of any counterfeit scheme. The optimal detection strategy within the framework is derived. We show the effectiveness of this technique based on some visual-model-based watermark encoding schemes.     

用数值方法分析绝热毛细管的流量特性

根据均相流假设,用两相流基本方程建立了毛细管的数学模型,采用一种快速、有效的计算方法对绝热毛细管的流量特性进行数值模拟,并把计算结果与实验数据进行了对比分析。     

固液相变蓄能数学模型中有效导热系数的理论及实验研究

引入有效导热系数经验公式 ,将固液蓄能数学模型简化为仅用能量方程加以描述 ,运用热焓法求解能量方程 ,得到计算相变位置随时间变化曲线。并通过实验测得相变过程的实际温度场 ,得到实验相变位置随时间变化曲线。二者比较 ,证明了自然对流对固液相变换热的影响不可忽略 ,验证了该公式在Ra <10 1 0 ,Pr<10 5下的正确性。