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31.
在利用平面相控阵超声换能器对圆柱类构件检测时,受曲界面结构引起的入射波和回波时延的影响,扫描声束的波阵面产生弯曲,在利用传统迭代遍历算法计算延迟时间时效率低,无法发挥相控阵换能器检测优势。针对上述问题,建立了一种基于圆柱类构件特征和耦合介质特性的超声相控阵扫描成像的聚焦模型。该模型基于换能器、耦合介质、圆柱类构件材料特性和几何关系以及声线模型和折射定律,建立了耦合介质及被检构件的声速、曲面曲率半径、阵列与曲面间的距离等关联的延迟时间聚焦控制模型。利用该模型计算出的延时时间,对各阵元发射时间进行控制,从而实现扫描声束的聚焦。该文以液体和有机玻璃制介质楔块为例,对圆柱钢曲面的相控阵声束聚焦进行了仿真实验,结果表明该文方法计算效率显著提升,同时声束可以在预设位置实现聚焦,验证了该模型在计算效率上的优势与有效性。 相似文献
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A decorated lattice is suggested and the Ising model on it with three kinds
of interactions K1,
K2, and
K3 is studied. Using an equivalent transformation, the square decorated Ising lattice is transformed into a regular square Ising lattice with nearest-neighbor, next-nearest-neighbor, and four-spin interactions, and the critical fixed point is found at
K1=0.5769,
K2=-0.0671, and
K3=0.3428, which determines the critical temperature of the system. It is also found that this system and
the regular square Ising lattice, and the eight-vertex model belong to the
same universality class. 相似文献
34.
ZHANG Shu-zi ZHANG Hai-hong ZHANG Wa SHI He-liang YU Xiang-hui KONG Wei LI Wei 《高等学校化学研究》2008,24(4):505-510
Two eukaryotic vectors expressing 9 tandem repeats of human MUCI(VNTR), VR1012-VNTR, and pEGFP-VNTR, were constructed by cloning VNTR gene into VR1012 and pEGFP, respectively. VNTR stably expressing murine Lewis lung carcinoma(LLC) cell line(VNTR^+ LLC) was established by Lipofectamine-mediated transfection of pEGFP-VNTR into LLC cells. The EGFP expression was observed under a fluorescent microscope and VNTR expression in VNTR^+ LLC cells was confirmed by means of Western blotting. A syngenic graft tumor model was generated by subcutaneous injection of VNTR^+ LLC cells into C57/BL6 mice and tumor size increased rapidly with time and in a cell qumber dependent manner. VNTR mRNA expression in the tumor formed was confirmed by RT-PCR. After the third immunization mice were challenged subcutaneously with 5×10^5 VNTR^+ LLC cells, a significant reduction of subcutaneous tumor growth was observed in the groups immunized with VNTR plasmid DNA compared with that in the groups immunized with the vector DNA alone. Thus, the suppression of subcutaneous tumor was antigen-specific. This model is useful for the development of tumor vaccines targeting MUCI VNTRs. 相似文献
35.
Hai-hong ZHANG Xi-zhen ZHANG Dong-hai ZHAO He-liang SHI Yong-hui YU Yong-ge WU Xiang-hui YU Wei KONG 《高等学校化学研究》2008,24(6):767-770
Survivin, a novel member of inhibitor of apoptosis(IAP) protein family, is aberrantly expressed in cancer but undetectable in normal, differentiated adult tissues. The cancer-specific expression of survivin, coupled with its importance in inhibiting cell death and in regulating cell division makes it a useful diagnostic marker of cancer and a potential target for cancer treatment. Survivin cDNA amplified from the total RNA of 293 cells through RT-PCR was cloned into prokaryotic expression vector pRSET-B. The recombinant plasmid pRSET-B-Surv was expressed in E.coli BL21, and the relative molecule mass(Mr) of expressed fusion protein was approximately 21000. The recombinant protein was purified through Ni^2+ affinity chromatography column and characterized by SDS-PAGE and Western blot. The purified recombinant protein was then injected into rabbits, and antisurvivin polyclonal antibody with a high titer was obtained. 相似文献
36.
37.
近红外光谱技术快速鉴别地沟油与食用植物油的研究 总被引:1,自引:0,他引:1
地沟油检测是我国食品安全最为关注的话题之一,它给人们的生活健康带来了极大的危害。国内现有的检测手段也仅停留在定性检测水平上,只能确定地沟油的有无,还难以进行定量检测。本实验利用近红外光谱技术与光纤传感技术相结合的新方法对勾兑混合油中地沟油的含量进行了定量分析。将煎炸老油与九三大豆油按照一定的体积比进行勾兑,共计50个样本,采集其近红外透射光谱,分别采用偏最小二乘法(PLS)和BP人工神经网络建立了煎炸老油含量的定量分析模型,校正集决定系数分别为0.908和0.934,验证集决定系数分别为0.961和0.952,均方估计残差(RMSEC)为0.184和0.136,预测均方根误差(RMSEP)都为0.111 6,符合应用要求,同时还结合主成分分析法(PCA)对煎炸老油与食用植物油进行了鉴别,识别准确率为100%。实验研究证明近红外光谱技术不仅可以准确快速的定性分析地沟油, 还能定量的检测地沟油的含量,在油脂的检测方面具有很大的应用前景。 相似文献
38.
39.
Stereodynamics of the He + D2^+ → HeD^+ + D Reaction on the PALMIERI Surface 总被引:1,自引:0,他引:1 下载免费PDF全文
Using the quasi-classical trajectory method, the product rotational polarization of the ion-molecule reaction He^+D2^+ has been calculated at different collision energies on the PALMIERI potential energy surface [Palmieri et al. Mol. Phys. 98 (2000) 1835]. The distribution angle between k and j′, P(Or), the distribution of the dihedral angle P(Фr), and the angular distribution of product rotational vectors in the form of polar plots in θr and Фr are calculated. In addition, four polarization-dependent differential cross sections are also presented in the center-of-mass frame, respectively. The results indicate that the rotational polarization of the product HeD^+ presents different characters for different collision energies. These discrepancies may be ascribed to the different collision energies and constructions of the potential energy surface. 相似文献
40.
High-Frequency Einstein-Podolsky-Rosen Entanglement via Atomic Memory Effects in Four-Wave Mixing 下载免费PDF全文
Atomic memory effects occur when the atomic relaxation times are comparable to or much longer than the cavlty relaxation times. We show that by using the memory effects, it is possible to obtain high-frequency Einstein- Podolsky-tlosen entanglement between a pair of Stokes and anti-Stokes fields in a four-wave mixing system. The physical origin is traced to the dynamical Stark splittings of dressed states due to the parametrically amplified fields. This mechanism provides an alternative and efficient way for sideband entanglement. 相似文献