基于改进CGHT的光学遥感图像舰船尾迹检测

根据遥感图像舰船目标检测的实时性要求,提出了一种应用改进CGHT算法检测舰船尾迹的方法.通过加入舰船船体的检测结果,改进CGHT算法中种子点的选取方式,以改善尾迹检测的计算复杂度,并将检测重点侧重于舰船船体附近区域,避免尾迹检测的盲目性.实验表明,该算法显著减少了尾迹检测的运行时间,降低了伪尾迹引起的虚警,提高了尾迹定位的准确性.     

Effects of Ca on the distribution, structure and morphology of aluminum species in polyaluminum chloride

The flocculation efficiency of polyaluminum chloride (PAC) is closely related to the distribution and structure of its AI species, and Al13 is the optimal species in PAC for flocculation. A series of PAC containing Ca was prepared by adding Ca before and after the basifying reaction. The effects of Ca on the Al species were studied by ^27Al nuclear magnetic resonance (NMR) and atomic force microscope (AFM) techniques. The experimental results show that the introduction of Ca increases the content of Alm and Al13 in PAC and decreases their chemical shifts in NMR spectra due to the electric repulsion between the positive Ca species and AI species and the formation of AI-O-Ca complexes.With the rise of Ca/AI molar ratio, the AI species in PAC tend to scatter. It is observed that the formerly branch-aggregated clusters are tending to form granule-aggregated ones whose diameter gets smaller and smaller, and the floccule aggregates are formed at a higher Ca/Al molar ratio. The introduction of Ca to PAC, which increases the Al13 content, is certainly to enhance the flocculation efficiency of PAC in water treatment.     

巨厚砾岩下开采地表沉陷预计模型的改进

为了探究巨厚砾岩下开采的地表沉陷规律,结合关键层理论,通过数值模拟从垂直应力、塑性区、垂直位移3个方面分析覆岩内部稳定性及造成地表倾向下沉曲线偏态的原因,基于概率积分法,建立改进的地表沉陷预计模型。结果表明:关键层初次破断距为291 m,周期破断距为281 m;悬力臂是造成下沉曲线偏态的主要原因;相对于经典的概率积分沉陷预计模型,改进的地表沉陷预计模型相对误差减小114%。可见在巨厚砾岩层下开采地表沉陷预计中,改进的地表沉降预计模型具有较高的准确度和适用性。     

Assignment of the μ4-O5 atom in catalytic center for water oxidation in photosystem II

The detailed structure of catalytic center of water oxidation, Mn4Ca-cluster, in photosystem ⅡI (PSII) has been reported recently. However, due to the radiation damage induced by X-ray and the complexity of the Mn4Ca-cluster, the assignment of the μ4-O5 atom coordinated by three Mn and one Ca2+ ions is still lack of essential evidences. In this article, we synthesized one Mn complex containing two μ4-O atoms. It is found that the lengths of all μ4-O-Mn bonds in this Mn complex are in the range of 1.89-2.10 , which are significantly shorter than 2.40-2.61 distance of μ4-O5-Mn bonds in Mn4Ca-cluster observed in the crystal structure of PSII. In addition, DFT calculations have been carried out on the Mn4Ca-cluster. It is found that the O atom of μ4-O or μ4-OH always trends to deviate from the center position of four metal ions, resulting in unequal bond lengths of four μ4-4-M (M=Mn or Ca), which is obviously different with larger and nearly equal distances between μ4-O and four metal ions observed in the crystal structure. Based on these results, we suggest that the μ4-atom in Mn4Ca-cluster of PSII is unlikely to be a μ4-O, μ4-OH or μ4-OH2 , and its assignment is still an open question.     

整体叶盘结构模态特性分析及应力分布规律

为了研究整体叶盘结构的模态特性及应力分布规律,基于有限元分析方法建立了整体叶盘结构有限元仿真模型,对自由状态及离心力载荷下的整体叶盘进行模态及振动特性分析;并探究实心与空心整体叶盘的应力分布差异及不同叶片间隙的整体叶盘应力分布规律。为了验证仿真结果的准确性,基于多点激励单点响应方法开展了整体叶盘结构模型的模态试验,并在多功能转子实验台上开展不同转速下应力测试试验。结果表明,该结构模态频率的仿真结果与试验测试结果误差在4%以内,验证了所建立的有限元仿真模型的正确性;应力测试试验验证了其不同转速下的应力分布规律;离心力载荷对整体叶盘二节径振动下固有频率影响最为显著;空心叶盘较实心叶盘应力集中现象更为突出,且叶片根部应力值会随着叶片间隙的增大而有明显提高。     

探地雷达技术在白蚁巢穴探测中的应用

白蚁是危害堤坝安全运行的重要隐患之一,如何准确的找到白蚁蚁巢并对蚁巢进行回填加固,是当今水利工作者的一个难题。本文简要的探讨了探地雷达技术在堤坝蚁巢探测中的原理,通过在白龟山水库堤坝中的应用,将理论与实际相结合,证实了探地雷达技术在蚁巢探测中的可行性。     

北京怀沙-怀九河种子植物区系分析

对怀沙-怀九河种子植物区系进行了初步分析,该区共有种子植物67科177属264种,以禾本科(Gramineae)、菊科(Compositae)等为优势科;以蓼属(Polygonum)、眼子菜属(Potamogeton)、鬼针草属(Bidens)等为优势属,但属的组成较为分散,寡种属和单种属占总属数的97.18%,表明该区植物成分较为复杂,物种多样性指数较高.从分布区类型看,科以热带成分占优势(51.28%);属的分布区类型可划分为14类,以北温带分布属为主,占27.27%,泛热带成分比例也较高,占21.21%,总体上温带成分(71.21%)高于热带成分(28.79%).表明该区植物区系地理成分复杂,具有一定的过渡性,分布区类型多样.特有植物匮乏.列为国家首批保护的珍稀濒危植物3种.     

浅谈工程项目施工管理

工程项目施工管理通过项目队伍建设,把科学的基本原理应用到项目管理中,实现管理目标,提高施工管理水平。     

基于遗传算法的三维空间柱面拟合

从二维平面曲线的定义出发,进而扩展至三维空间柱面的定义.提出采用遗传算法拟合得出空间柱面的参数,将空间柱面唯一确定.以空间圆柱面为例,说明采用遗传算法进行空间柱面拟合的原理以及方法.以空间曲面的表达参数作为需辨识的参数值,并且对相关的参数值加以约束,基于最小二乘原理建立优化目标函数,采用遗传算法进行进化寻优.实例研究表明本文方法的有效性与拟合精度优势.     

人类终极能源梦——太阳光分解水制氢研究进展

 利用太阳光分解水制备氢气,从太阳照射能量中直接获得大功率的动力能源,被认为是人类能源的终极梦想.本文介绍了太阳光催化分解水制氢的原理,阐述了光解水对光催化材料的热力学和动力学要求.重点从新型光催化材料研发、共催化复合体系构筑、纳米形貌调控、器件化设计等4个方面综述了近年来国内外光解水制氢关键材料和技术的研究进展.结合实际应用,对制氢体系中牺牲剂应用、模拟自然光合作用、光解海水、光催化剂稳定性等方面的研究进行了分析.展望了未来太阳光催化分解水制氢技术的发展方向.