L∞准则约束下的高质量灰度指纹图像压缩算法

为克服基于传统 L2 准则的有损图像压缩算法难以准确控制每一像素值的误差范围 ,因而可能丢失指纹图像特殊细节的缺点 ,提出了一个在 L∞ 准则严格约束下针对灰度指纹图像的高质量图像压缩算法。该算法以当前性能最优的无损图像压缩算法 CAL IC为基础 ,结合了根据指纹局部纹线走向所设计的分类线性预测器 ,并提出了准无损模式下根据量化器对熵编码器自适应调节的方案。对一组真实灰度指纹图像的实验结果表明 ,与 CAL IC算法相比 ,新算法在同样的最大误差下 ,平均比特率降低了 8% ,同时峰值信噪比(PSNR)提高了 1.2 d B。新算法在最大误差不超过± 3个灰度级的情况下 ,实现了 5∶ 1左右的压缩比 ,且比当前 L2 准则下性能最优的压缩算法之一 SPIHT明显具有更高的均方信噪比。     

A force feedback master finger in exoskeleton type

In order to eliminate the drawbacks of conventional force feedback gloves,a new type of master finger has been developed.By utilizing three"four-bar mechanism joint"in series and wire coupling mechanism,the master finger transmission ratio is kept exactly 1:1.4:1 in the whole movement range and it can make active motions in both extension and flexion directions.Additionally,to assttre faster data transmission and near zero delay in the master-slave operation,a digital signal processing/field programmable gate array(DSP/FPGA-FPGA)structure with 200μs cycle time is designed.The operating modes of the master finger can be contact or non-contact,which depends on the motion states of a slave finger,free motion or constrained motion.The position control employed in non-contact mode ensures unconstrained motion and the force control adopted in contact mode guarantees natural contact sensation.To evaluate the performances of the master finger,an experiment between the master finger and a DLR/HIT dexterous finger is conducted.The results demonstrate that this new type master finger can augment telepresence.     

GTPase activating proteins: structural and functional insights 18 years after discovery

The conversion of guanosine triphosphate (GTP) to guanosine diphosphate (GDP) and inorganic phosphate (P_i) by guanine nucleotide binding proteins (GNBPs) is a fundamental process in living cells and represents an important timer in intracellular signalling and transport processes. While the rate of GNBP-mediated GTP hydrolysis is intrinsically slow, direct interaction with GTPase activating proteins (GAPs) accelerates the reaction by up to five orders of magnitude in vitro. Eighteen years after the discovery of the first GAP, biochemical and structural research has been accumulating evidence that GAPs employ a much wider spectrum of chemical mechanisms than had originally been assumed, in order to regulate the chemical players on the catalytic protein-protein interaction stage. Received 25 March 2005; received after revision 31 August 2005; accepted 6 September 2005     

聚甲基苯基硅烷的合成及非线性光学性能的研究

苯锂与甲基三氯硅烷反应制得了甲基苯基二氯硅烷，氮气保护下，在甲苯号金属钾反应生成了聚甲基苯基硅烷，用元素分析，ＩＲ，ＵＶ，＾１Ｈ－ＮＭＲ和ＧＰＣ作了表征，并测定了它的非线性谐波极化率Ｘ＾（３）的值为５．８＊１０＾－１２ｅｓｕ。     

Origin and evolution of new exons in the rodent zinc finger protein 39 gene

The origin of new structures and functions is an important process in evolution. In the past decades, we have obtained some preliminary knowledge of the origin and evolution of new genes. However, as the basic unit of genes, the origin and evolution of exons remain unclear. Because young exons retain the footprints of origination, they can be good materials for studying origin and evolution of new exons. In this paper, we report two young exons in a zinc finger protein gene of rodents. Since they are unique sequences in mouse and rat genome and no homologous sequences were found in the orthologous genes of human and pig, the young exons might originate after the divergence of primates and rodents through exonization of intronic sequences. Strong positive selection was detected in the new exons between mouse and rat, suggesting that these exons have undergone significant functional divergence after the separation of the two species. On the other hand, population genetics data of mouse demonstrate that the new exons have been subject to functional constraint, indicating an important function of the new exons in mouse. Functional analyses suggest that these new exons encode a nuclear localization signal peptide, which may mediate new ways of nuclear protein transport. To our knowledge, this is the first example of the origin and evolution of young exons.     

P钥原型及抗击ShortVector破译算法研究

在ＰＤＸ有限机公司密码体制研究的基础上，论述Ｐ的型Ｐ的各种函数形式，Ｐｎ转化Ｐｎ环指过程，并分析ＳＶ算法攻击Ｐｎ问题，指出Ｐ体制所具抗击各种破译算法的优越性。     

关于非饱和渗透理论中的几项基本问题的剖析

从基质吸力和水分特征曲线、非饱和渗透系数、非均匀流渗透机理、非饱和带中水气二相渗流四个方面评述了国内外有关非饱和渗透理论的研究成果,探讨了目前存在的问题和研究方向,并介绍了一种自研制的间接测量非饱和砂土基质吸力的方法.     

大鼠小脑特异基因Zic的克隆、序列分析和初步表达

EST（AW055732）片段是SD大鼠脑内一特异表达基因cDNA的3‘-端片段,与小鼠和人的Zic基因同源。基于小鼠及人的Zic基因的同源序列,设计引物用PCR方法从SD大鼠中克隆得到该基因的编码区序列（rZic)。该基因编码一锌指蛋白,其锌指结构域与线虫的tra-1基因,果蝇的ci^D基因。人的Gli癌基因和果蝇的opa基因的锌指结构域高度同源,用RT－PCR方法分析了rZic基因在大鼠脑区分布状况。结果表明,rZic基因在小脑中高表达。将该rZic基因克隆至带有6个组氨酸的表达载体pET-32a( )中,用IPTG诱导rZic融合蛋白在大肠杆菌BL21菌株中表达,诱导后重组蛋白质占菌体总蛋白的20．8％。     

基于小波去噪和直方图模板均衡化的手指静脉图像增强

提出一种手指静脉图像增强算法. 该算法包括去噪、 对比度增强和二值化. 在去噪部分, 根据小波变换后各频带的不同特点, 结合手指静脉的特点, 分别设计了不同的去噪策略; 在增强部分, 设计了一种新的方法, 称为灰度直方图模板均衡化方法, 较好地增强了静脉和背景的对比度; 在二值化部分, 采用了OTSU方法. 实验表明, 该算法能有效的增强图像的对比度, 改善图像的质量.