稳键性水印实现机理探析

水印技术作为信息隐藏和知识产权保护的手段,正得到广泛的应用。为了保证隐藏信息的的安全性,需要对水印的稳键性进行研究。从水印嵌入模型和隐藏机理出发,研究稳键性水印的实现技术。对空域和变换域水印的嵌入算法进行比较,得到了具有良好稳键性的水印嵌入方案。在变换域中嵌入的信号可以分布到空域的所有像素上,与数据压缩标准兼容,对某些图像处理的稳键性更强。

线性回归模型中估计与检验的稳健性

本文讨论线性回归模型中回归系数的最小二乘估计和似然比检验统计量的稳健性,分别给出了充要条件,充分条件和必要条件;并给出这些结果在两阶段抽样回归模型中的应用。

论资产减值准备的计提

新的《企业会计制度》有关资产减值准备的规定是中国会计准则和会计制度制定过程中的一大进步 ,充分体现了会计的稳健原则 ,对于处于蓬勃发展的中国证券市场中的上市公司和面临重大改制任务的国企而言 ,有着不可估量的积极作用。但新的制度有效实施还需要一系列配套措施。

Gas Phase Conformations of Tetrapeptide Glycine-Phenylalanine- Glycine-Glycine

Systematic search of the potential energy surface of tetrapeptide glycine-phenylalanine- glycine-glycine （GFGG） in gas phase is conducted by a combination of PM3, HF and BHandHLYP methods. The conformational search method is described in detail. The relative electronic energies, zero point vibrational energies, dipole moments, rotational constants, vertical ionization energies and the temperature dependent conformational distributions for a number of important conformers are obtained. The structural characteristics of these conformers are analyzed and it is found that the entropic effect is a dominating factor in determining the relative stabilities of the conformers. The measurements of dipole moments and some characteristic IR mode are shown to be effective approaches to verify the theoreti- cal prediction. The structures of the low energy GFGG conformers are also analyzed in their connection with the secondary structures of proteins. Similarity between the local structures of low energy GFGG conformers and the α-helix is discussed and many β- and γ-turn local structures in GFGG conformers are found.

Superposed disturbance mechanism of sequential overlying strata collapse for gob-side entry retaining and corresponding control strategies

Gob-area roof rupture movement is a key disturbance factor for gob-side entry retaining.The characteristics of gob-area sequential roof collapse of overlying strata and superposed disturbance mechanism for gob-side entry retaining are obtained via physical simulation and theoretical analysis,in which the scope of disturbed strata is enlarged from main roof to fracture zone.The experiment reveals that as a working face advances,roof strata sequentially collapse from bottom to top and produce multiple disturbances to gob-side entry retaining.Key strata among the overlying strata control each collapse.Main roof subsidence is divided into three stages:flexure subsidence prior to rupture,rotational subsidence during rupture and compressive subsidence after rupture.The amounts of deformation evident in each of the three stages are 15%,55%and 30%,respectively.After the master stratum collapses,main roof subsidence approaches its maximum value.The final span of the key stratum determines the moment and cycling of gob-side entry retaining disturbances.Main roof subsidence influences the load on the filling wall.The sequential roof collapse of overlying strata results in fluctuations in the gob-side entry retaining deformation.Calculation formulae for the final span of the key stratum and the filling wall load are obtained via theoretical analysis.A control method for the stability of the gob-side entry retaining’s surrounding rock is proposed,which includes 3 measures:a“dual-layer”proactive anchorage support,roadside filling with dynamic strength matching and auxiliary support during disturbance.Finally,the gob-side entry retaining of the Xiaoqing mine E1403 working face is presented as an engineering case capable of verifying the validity of the research conclusions.

Density Functional Theory Study for Adsorption of Oxygen and Water Molecules on 6H-SiC(0001) Surface

6H-SiC is an important semiconductor material. The 6H-SiC wafer is always exposed to a high-humidity environment and the effect from the absorbed water molecule and some relative adsorbates is not negligible. Here, the oxygen and water molecules absorbed on the 6H-SiC(0001) surface and the dissociation process were studied with density functional theory. On the 6H-SiC(0001) surface, absorbed O2 is spontaneously dissociated into O*, which is absorbed on a hollow site, and further transforms the 6H-SiC(0001) surface into SiO2. The absorbed H2O is spontaneously broken into OH*and H*, which are both absorbed on the top of the Si atom, and OH* is further reversibly transformed into O* and H*. The H* could saturate the dangling Si bond and change the absorption type of O*, which could stabilize the 6H-SiC(0001) surface and prevent it from transforming into SiO2.

Comparative features of colorectal and gastric cancers with microsatellite instability in Chinese patients

Objective:The purpose of this study was to determine the unique and universal features of microsatellite instability-high(MSI-H) colorectal cancer(CRC) and MSI-H gastric cancer(GC) in the Chinese population.Methods:A new panel of mononucleotide MSI markers,BAT25,BAT26,NR21,NR24,and MONO-27,was used to define MSI status in 303 CRC and 288 GC subjects.Clinicopathological features of both types of MSI-H tumors were analyzed.Methylation analysis in the hMLH1 promoter region by methylation specific polymerase chain reaction(PCR) and mutation detection of hMSH2/hMLH1 genes by denaturing high-performance liquid chromatography(DHPLC) were carried out simultaneously.Results:MSI-H CRCs and MSI-H GCs account for 11.9% and 8.0% of unselected sporadic CRCs and GCs,respectively.MSI-H CRCs are strongly characterized by early onset,right-side location,low differentiation,mucinous tumor,less infiltration,less lymphatic metastasis,and more often familial tumor.MSI-H GCs only showed site preference for the antrum and less lymphatic metastasis.Genetic and epigenetic analyses were positive in 6/36 MSI-H CRCs and 0/23 MSI-H GCs with pathological mutation in major mismatch repair genes,and in 7/36 MSI-H CRCs and 18/23 MSI-H GCs with methylated hMLH1 promoter(P<0.01),respectively.Conclusions:Although there are many differences in the genetic basis and clinicopathological features between MSI-H CRC and MSI-H GC,when compared with their microsatellite stable(MSS) counterparts,site preference and lymphatic metastasis are features common to both types of MSI-H tumors.

Theoretical prediction on a special bridging metal–Xe–metal bond with remarkable stability in Re_2Cp_2(PF_3)_4Xe

The bridging Re-Xe-Re bond with a remarkable stability is firstly predicted. The average binding energies for Re-Xe bond in RezCpz（PF3）4Xe with bridging Xe are calculated to be higher than that in ReCp（CO）2Xe, ReCp（CO）（PF3）Xe and ReCp（PF3）2Xe with terminal Xe. The interaction between two ReCp（PF3）2 fragments provides an additional contribution for the stability of bridging Re-Xe-Re bond. Besides, the RezCp2（PF3）4Xe isomers with bridging Xe are also stable in energy than the isomers with bridging PF3. As the terminal Re-Xe bond was found to exist in experiments, the more stable bridging Re-Xe-Re bond might be existent under similar or even milder condition.