广东省伴生放射性矿资源利用过程辐射水平调查

为加强伴生放射性矿物资源开发利过程中放射性环境管理 ,防治放射性污染 ,对广东省几个大型伴生矿(包括稀土矿、钽铌矿和铅锌矿 )资源利用 (开采、冶炼、加工 )过程中天然放射性核素的污染现状进行了调查。调查结果表明 :稀土矿中独居石 ,天然放射性核素含量最高 ,2 3 8U、2 3 2 Th、2 2 6Ra的含量分别为 3.5 1× 1 0 4、1 .74× 1 0 5、4 .8×1 0 4Bq/kg,其冶炼废渣中核素的含量分别为 5 .1 0× 1 0 5、6 .38× 1 0 6、1 .5 2× 1 0 6Bq/kg。稀土选冶厂周围陆地环境 γ射线的空气吸收剂量率比一般地区的高。     

无保护间隔的OFDM信道自适应均衡的一种新算法

近年来作为一种特殊的多载波调制方式——正交频分复用(OFDM)已得到越来越多的人的关注.对于传统的OFDM系统来说,如果循环前缀的长度大于信道的时延扩散值,则可以通过简单的频域均衡来解调OFDM信号.可是循环前缀的使用却降低了系统的传输效率,如果能压缩甚至去掉循环前缀,而保持系统性能不变,则是很有意义的,为此本文给出了一种新的均衡结构,利用循环迭代手段以减少甚至去掉循环前缀,最后通过计算机模拟,证实了这种结构的有效性.     

SMT测试技术

主要介绍了当前用于检测组装后PCB的缺陷和故障的一些常见测试技术 ,并对未来的发展趋势进行了初步探讨     

Oracle9i数据库安全管理机制剖析

数据库安全和数据安全机制是数据库开发设计者目前必须考虑的问题之一。Oracle9i数据库管理系统在数据库安全方面为数据库管理员和应用开发者提供了很好的安全机制。文章从不同侧面和角度讨论Oracle9i数据库系统的安全管理机制，为实施更安全更灵活的数据库安全策略提出了全方位的技术思路。     

宝钢研制的全氢罩式炉控制系统分析

对宝钢研制的全氢罩式炉计算机控制系统的逻辑结构、工作原理及硬件配置进行了分析.该系统与引进的系统相比,在通讯方式、程序结构、操作分析、报警和开放性等方面都有所改进.     

综合孔径微波辐射计二阶量化数字相关器研究

微波辐射计作为一种无源遥感器,在遥感技术领域有着巨大的应用前景.传统的微波辐射计的空间分辨率受到天线孔径的限制.综合孔径微波辐射计利用了干涉测量原理和复相关技术,是一种可以有效地提高空间分辨率的新型辐射计.本文针对综合孔径微波辐射计的数字相关器进行了深入研究,分析论证了二阶量化数字相关器的工作机理,并对采用该种相关器的系统的信噪比进行了分析.初步的试验验证结果证明了该方案的有效性.     

Improvement of RCA transistor using RTA annealing after theformation of interfacial oxide

A polysilicon emitter RCA transistor (an ultra-thin interfacial oxide layer exists between polysilicon and silicon emitter) is presented which can operate at 77 K for the first time. An ultra-thin (1.5 nm) interfacial oxide layer is grown deliberately between polysilicon and silicon emitter using RCA oxidation and excellent device stability is obtained after rapid thermal annealing (RTA) treatment in nitrogen atmosphere. The RCA transistor exhibits good electrical performance at very low temperature for an emitter area of 3 × 8 μm². The maximum toggle frequency of a 1:2 static divider is 1.2 GHz and 732 MHz at 300 K and 77 K, respectively     

Effect of Tongmai Decoction on expression of NF-κB in ox-LDL injured endothelial cells

Objective Study on the effect of NF-κB in ox-LDL injured HUVEC-304 and the intervention with the serum of Tongmai Decoction. Methods Tongmai Decoction herbage-contained serum was made by the serum pharmacology methods, then the HUVEC-304 cells were divided into 5 groups and incubated for 24 h: 1) normal group;2) fetal calf serum group; 3) ox-LDL group; 4) simvastatin group; 5) Tongmai Decoction group. RT-PCR was used to determine the mRNA of NF-κB in the cells, Western Blot Assay was used to determine the protein content of NF-κB in the cells. Results 1) Compared with the cells in normal group and serum control group , the endothelial cells in ox-LDL group are seriously injured, while those in Tongmai Decoction group grow better; 2) Compared with the cells in normal group and fetal calf serum group, the expressions of NF-κB gene and protein are up-regulated in ox-LDL group(P＜0.05, P＜0.01); 3) Compared with the cells in ox-LDL group, the expression of NF-κB gene and protein in Tongmai Decoction group are significantly down-regulated, there is no difference between Tongmai Decoction group and simvastatin group(P＞0.05). Conclusion Tongmai Decoction can protect the injured endothelial cells, up-regulate the expressions of NF-κB gene and protein content.     

Single-longitudinal-mode fiber ring laser employing an equivalent phase-shifted fiber Bragg grating

A novel single-longitudinal-mode (SLM) fiber ring laser that incorporates an equivalent phase-shifted fiber Bragg grating acting as an ultra-narrow bandpass filter in the laser cavity is proposed. The equivalent phase-shifted fiber Bragg grating has an ultra-narrow transmission bandwidth which ensures an SLM lasing. Stable SLM operation without mode hopping is demonstrated.     

巨型结构的抗震分析

采用ANSYS有限元程序对巨型框架结构、巨型框架隔震结构进行了抗震动力时程分析,讨论了两种结构在多条地震波作用下的动力位移及内力等地震响应,其计算结果对于确保巨型框架结构的抗震安全性具有较大的意义,对巨型框架结构的抗震设计有较大的参考价值。