基于视觉心理学的SFS流形算法研究

通过视觉方法获取形状在科学研究及工程实践中有着重要作用,灰度图像是最容易获取的视觉信息之一。目前由灰度重构的形状(SFS,shape from shading)受到了广泛的关注,但现有的算法稳定性差、效率低,一直阻碍着SFS方法的推广应用。受近期的视觉心理学研究成果的启发,针对SFS问题,从局部分析入手,即:在图像上,在每一灰度极值点附近,根据灰度单调变化的情况,形成一个椭圆形邻域,对应着表面凹凸区;在每一椭圆域上,形状可用抛物面逼近,其参数可由局部辐射度约束求解;整个图像被椭圆形邻域覆盖,这些覆盖可构成一个二维流形;借助于流形上单位分解函数,各局部抛物面粘合在一起,形成光滑的整体形状;总体形状在整幅图像的灰度约束下再进行全局优化,可得到最终的重构结果。给出了初步算例,算法的稳定性和效率均有大幅度提高。     

KMnO4引发魔芋粉-丙烯腈的接枝共聚反应

以KMnO4为引发剂进行魔芋粉与丙烯腈的接枝共聚反应。研究了魔芋粉预氧化时间、引发剂浓度、单体浓度、酸度、反应时间、反应温度和反应物加料方式等聚合条件对接枝效率的影响，并对接枝机理作了探讨。     

自由基引发马来酸二丁酯熔融接枝低密度聚乙烯的研究

用马来酸二丁酯(DBM)为接枝单体,过氧化二枯基(DCPO)为引发剂,对低密度聚乙烯(LDPE)进行了熔融接枝功能化。样品的红外光谱表明接枝反应确已发生。通过对样品中酯基的皂化水解测定产物的接枝率,对产物进行萃取,用凝胶量间接表征产物的交联程度;用溶液的特性粘度从侧面显示样品的支化或降解情况。实验结果表明,产物的接枝率和凝胶量可以通过选择反应条件(温度、时间及反应混合物的组成)来控制;过量的DCPO是引起交联产生凝胶的主要原因;向体系中添加DMF可阻止交联反应的发生,但产物的接枝率也有所下降,以自由基机理对上述结果进行了讨论。     

壳多糖与丙烯酸丁酯的乳液接枝共聚研究

以十二烷基苯磺酸钠为乳化剂，过硫酸钾－亚硫酸氢钠为引发剂，研究了壳多糖与丙烯酸丁醋的乳液共聚合，结果表明当［Ｋ２Ｓ２Ｏ８］＝［ＮａＨＳＯ３］＝２．５７×１０－３ｍｏｌ·１－１，［ＢＡ］＝０．６８ｍｏｌ．１－１，［Ｃｈｉｔｏｓａｎ］＝１９．２ｇ·ｌ－１，在７０℃下反应５小时，共聚反应的接技率和接枝效率均较高．用红外光谱，差热分析，Ｘ射线衍射，扫描电镜对接技共聚物进行了表征，此外测试了共聚物胶乳成膜的机械性能，表明用丙烯酸丁酯对壳多糖进行接枝改性，可提高壳多糖的韧性，扩大其应用范围．     

氯化聚乙烯对甲基丙烯酸甲酯／苯乙烯共聚动力学的影响

将甲基丙烯酸甲酯（ＭＭＡ）／苯乙烯（Ｓ）在氯化聚乙烯（ＣＰＥ）存在下进行悬浮溶胀接枝共聚，考察了ＣＰＥ对ＭＭＡ／Ｓ共聚动力学行为的影响．ＣＰＥ提高了聚合体系的粘度，使自动加速提前，扩散因素增加，对共聚有阻滞作用．ＣＰＥ是链转移剂，使ＭＭＡ／Ｓ共聚物分子量降低．ＣＰＥ对ＭＭＡ的吸附渗透优于对Ｓ的吸附，造成接技部分与非接技部分组成的差异．ＣＰＥ含量、溶胀时间、转化率、硫酸用量对共聚组成均有影响。     

丙烯酸酯类与亚麻纤维接枝共聚反应的研究

Abou-Zeid等人曾报道以Fe(~2+)-H_2O_2体系引发丙烯腈等单体与黄麻纤维的接枝共聚反应,Misra等人报道了以S_2O_8_2-TU为引发体系,甲基丙烯酸甲酯与黄麻纤维的接枝共聚,最近,我们报道了以Ce(Ⅳ)引发甲基丙烯酸甲酯、丙烯酸乙酯(EA)分别与苧麻及亚麻纤维的接枝共聚。亚麻纤维与丙烯酸酯类单体接枝改性后,仲长率有所提高,加强了结合力,改善了成纱品质,因此引起人们的重视。本文以过硫酸钾-硫脲(KPS-TU)为引发体系,研究丙烯酸甲酯(MA)、EA及丙烯酸丁酯(BA)与亚麻纤维的接枝共聚反应规律,用IR、SEM、X射     

STUDY ON THE PROPERTIES OF BLEND OF NATURAL RUBBER LATEX/METHYL METHACRYLATE GRAFTED RUBBER LATEX BY GAMMA RADIATION

Natural rubber latex(NRL)and methyl methacrylate(MMA)grafted rubber latex were blended in different ratios and irradiated at various absorbed doses by gamma rays from Co-60 source at room temperature.The tensile properties, swelling ratio and permanent set were measured.The maximum tensile strength and modulus at 500% elongation were obtained at an absorbed dose of 8 kGy.Modulus increases from 6.99 MPa to 9.87 MPa for an increase in proportion of MMA grafted rubber from 40% to 60% in the blend at similar absorbed dose.Elongation at break and swelling ratio decrease with increasing absorbed dose as well as the MMA grafted rubber content in the blends.The decreasing trend of permanent set is high up to 5 kGy absorbed dose,and beyond that dose,it becomes almost flat.     

由两个同型部件和一个修理设备组成的系统的主算子的谱

文章研究了由两个同型部件和一个修理设备组成的系统的主算子在左半复平面中的谱.在一定的条件下,该系统的主算子在左半复平面中的任何带形区域至多有有限多个特征值,且这些特征值的几何重数为1.该模型的主算子的共轭算子在左半复平面中的任何带形区域至多有有限多个特征值,且这些特征值的几何重数为1.0是该系统的主算子及其共轭算子的严...     

一类无限群中局部幂零性的判定准则

设G是任意群,群G的Frattini子群nat(G)定义为G的所有极大子群的交.类似地,群G的另外两个特征子群nFrat(G)及R(G)分别定义为群G的所有极大正规子群及群G的所有正规的极大子群的交.本文通过对nat(G),nnat(G)及R(G)的相互包含关系的研究,得到CF-群或中心由多重循环群的扩张群中局部幂零性的一个判定准则.同时也讨论了在某些群类中若干种广义幂零性的等价性.     

Codimension two bifurcation of a vibro-bounce system

A three-degree-of-freedom vibro-bounce system is considered. The disturbed map of period one single-impact motion is derived analytically. A center manifold theorem technique is applied to reduce the Poincaré map to a three-dimensional one, and the normal form map associated with Hopf-flip bifurcation is obtained. Dynamical behavior of the system, near the point of codimension two bifurcation, is investigated by using qualitative analysis and numerical simulation. It is found that near the point of Hopf-flip bifurcation there exists not only Hopf bifurcation of period one single-impact motion, but also Hopf bifurcation of period two double-impact motion. The results from simulation show that there exists an interesting torus doubling bifurcation near the codimension two bifurcation. The torus doubling bifurcation makes the quasi-periodic attractor associated with period one single-impact motion transform to the other quasi-periodic attractor represented by two attracting closed circles. The torus bifurcation is qualitatively different from the typical torus doubling bifurcation occurring in the vibro-impact systems. Different routes from period one single-impact motion to chaos are observed by numerical simulation.The project supported by the National Natural Science Foundation of China (10172042, 50475109) and the Natural Science Foundation of Gansu Province Government of China (ZS-031-A25-007-Z (key item))