A system of partial differential equations modeling the competition for two complementary resources in flowing habitats

This paper examines a system of reaction-diffusion equations arising from a flowing water habitat. In this habitat, one or two microorganisms grow while consuming two growth-limiting, complementary (essential) resources. For the single population model, the existence and uniqueness of a positive steady-state solution is proved. Furthermore, the unique positive solution is globally attracting for the system with regard to nontrivial nonnegative initial values. Mathematical analysis for the two competing populations is carried out. More precisely, the long-time behavior is determined by using the monotone dynamical system theory when the semi-trivial solutions are both unstable. It is also shown that coexistence solutions exist by using the fixed point index theory when the semi-trivial solutions are both (asymptotically) stable.     

水泥砂浆石在准一维应变下的动态力学性能研究

以改进的SHPB被动围压试验方法 ,研究了水泥砂浆石在准一维应变下的动态力学响应。分析讨论了试验结果与围压套筒材料性质、几何尺寸等的关系。得到了水泥砂浆石的动态泊松比、动态杨氏模量、动态压缩强度。分析了试验中的摩擦力效应及其对围压下轴向应力应变关系的影响 ,完成了对材料弹性常数的修正。     

地塞米松衍生物的合成及其抗肿瘤活性研究

地塞米松(dexamethasone)为人工合成的肾上皮质激素类药物,具有抗炎、应激保护[1],增强化疗药物诱导肿瘤细胞凋亡[2],促进细胞分化[3]等药理作用.     

普通话常规重音分布规则的研究

采用心理统计方法对中等规模语料库进行分析，探讨句法、韵律及其声学相关物之间的关系，根据汉语口语常规重音分布的规律，研究普通话常规重音分布规则及其在实际话语中应用的先后次序，最终建立适用于汉语文语转换系统的常规重音分布规则系统。     

氢、氧终端掺硼金刚石薄膜的电子结构

利用氢微波等离子体溅射和浓酸中沸煮方法分别制备了氢、氧终端掺硼金刚石薄膜.借助X射线光电子能谱及接触角检测对两种终端薄膜表面进行了分析，通过扫描探针显微镜研究了针尖和样品间的扫描隧道谱.结果表明，氢终端掺硼金刚石表面能带向上弯曲，在高于价带顶位置存在浅受主能级；氧终端表面能带向下弯曲，带隙较宽，带隙中不存在表面态.对两种终端金刚石薄膜的导电机理进行了讨论.     

Formation of epitaxial Tl_2Ba_2Ca_2Cu_3O_(10) superconducting films by dc-magnetron sputtering and triple post-annealing method

For obtaining pure phase T12Ba2Ca2Cu3O10 （T1-2223） films with good superconducting properties, the growth technique is improved by dc magnetron sputtering and a triple post-annealing process. The triple post-annealing process comprises annealing twice in argon and once in oxygen at different temperatures. In the first low-temperature annealing phase in argon, T12Ba2CaCu2O8 （T1-2212） is obtained to effectively minimize evaporation in the next step. With the increase of temperature in the second annealing stage in argon, the previously prepared T1-2212 inter-phase is converted into T1-2223 phase. An additional annealing in oxygen is also adopted to improve the properties of T1-2223 films, each containing an optimal oxygen content value. The results of X-ray diffraction （XRD） θ-2θ scans, 09 scans and rotational φ scans show that each of the T1-2223 films has a high phase purity and an epitaxial structure. Smooth films are observed by scanning electron microscopy （SEM）. The critical temperatures Tc of the films are measured to be about 120 K and the critical current densities Jc can reach 4.0 MA/cm2 at 77 K at self field.     

Steady-state solutions of a reaction–diffusion system arising from intraguild predation and internal storage

Intraguild predation is added to a mathematical model of competition between two species for a single nutrient with internal storage in the unstirred chemostat. At first, we established the sharp a priori estimates for nonnegative solutions of the system, which assure that all of nonnegative solutions belong to a special cone. The selection of this special cone enables us to apply the topological fixed point theorems in cones to establish the existence of positive solutions. Secondly, existence for positive steady state solutions of intraguild prey and intraguild predator is established in terms of the principal eigenvalues of associated nonlinear eigenvalue problems by means of the degree theory in the special cone. It turns out that positive steady state solutions exist when the associated principal eigenvalues are both negative or both positive.     

不同密度氢吸附金刚石(100)表面的微观结构

利用基于广义梯度近似的密度泛函理论,计算了金刚石(100)表面不同氢吸附密度的平衡态几何结构和态密度.结果表明对于2×1构型,在平行和垂直表面两个方向上发生弛豫,而1×1构型仅在垂直表面方向上发生弛豫.另外,清洁2×1,2×1 ∶0.5H和1×1 ∶1.5H表面,带隙中存在空表面态;而对于1×1 ∶2H和2×1 ∶H两种表面结构,空表面态上移进入导带,带隙中不存在表面态.结合电荷密度分布,探讨了金刚石(100)不同构型和氢吸附密度表面的表面态诱发机理. 关键词： 氢吸附 金刚石 弛豫 表面态     

新试剂N-苯基-N′-(氨基对苯磺酸钠)硫脲的合成及其测定微量铂(Ⅳ)的研究和应用

介绍了新试剂N 苯基 N′ (氨基对苯磺酸钠 )硫脲 (PPT)的合成 ,研究了其与铂的显色条件 ,在pH为 3.4～ 4 .2的HOAc NaOAc缓冲体系中 ,在溴化十六烷基三甲胺 (CTMAB)存在下 ,Pt(Ⅳ )与PPT形成组成比 1∶3的绿色水溶性络合物 ,其最大吸收峰位于 778.4nm ,表观摩尔吸光系数ε778.4=2 .95× 10 4 L·mol- 1·cm- 1,铂含量在 0～ 10 0 μg/ 2 5ml范围内服从比耳定律。此法线性范围宽 ,选择性好 ,4 0余种离子不干扰测定 ,用于矿石与催化剂中铂的分析 ,结果满意