Overwinter changes to near-surface bulk density, penetration resistance and infiltration rates in compacted soil

Previous studies at Yakima Training Center (YTC), in Washington State, suggest freeze-thaw (FT) cycles can ameliorate soil compacted by tracked military vehicles [J. Terramechanics 38 (2001) 133]. However, we know little about the short-term effects of soil freezing over a single winter. We measured bulk density (BD), soil penetration resistance (SPR), and steady-state runoff rates in soil newly tracked by an Abrams tank and in uncompacted soil, before and after a single winter at YTC. We similarly measured BD, SPR and saturated hydraulic conductivity (k_fs) in simulated tank tracks at another site near Lind Washington. Average BD was significantly greater in tank ruts at YTC and in simulated tracks at the Lind site than in uncompacted soil soon after tracking and did not change significantly during the winter of 1997–1998. Measurements of SPR were strongly influenced by soil moisture. When soil was moist or tracks were newly formed, SPR was significantly higher in tank ruts than in uncompacted soil from the surface to a depth of about 10–15 cm. The greatest average SPR in compacted soil was observed between 4 and 6 cm depth. We observed less difference in SPR between tank ruts and uncompacted soil near-surface at YTC as the time after trafficking increased. We observed highest SPR ratios (compacted rut:undisturbed) in fresh tracks near the surface, with lower ratios associated with increasing track age or soil depth, indicating that some recovery had occurred at YTC near-surface. However, we did not observe a similar over-winter change in SPR profiles at the Lind site. Rainfall simulator data from YTC showed higher steady-state runoff rates in tank ruts than over uncompacted soil both before and after winter. However, more time was required to reach steady-state flow in tank ruts and the proportion of runoff was slightly lower in May 1998 than in August 1997. At the Lind site, k_fs was lower in newly compacted soil than in one-year old compacted soil or uncompacted soil. Our data suggest that indices of water infiltration such as steady-state runoff rates or k_fs, are more sensitive indicators of soil recovery after compaction than are BD or SPR.     

硒蒸气浓度对制备CIGS薄膜的影响

采用“预制层硒化法”制备CuIn_1-xGa_xSe₂ (CIGS)薄膜. 基于自主设计的“双层管式硒化装置”, 通过控制硒蒸气浓度优化退火工艺, 研究硒蒸气浓度对薄膜光电性能的影响. 利用俄歇电子能谱(AES)和X射线衍射分析(XRD)等手段对不同硒浓度氛围下生成的CIGS薄膜的成分和物相进行表征, 并在AM1.5、1000 W·m^-2的标准光照条件下比较相应CIGS电池器件的输出性能. 实验结果表明: 饱和硒蒸气下退火得到的样品, 基底钼膜遭到严重腐蚀破坏, 失去背电极功能; 在低浓度硒气氛下退火不能有效消除CIGS薄膜的偏析和缺陷, 以致光电转换效率低; 而在无硒惰性氛围下退火的样品, 生成了物相均一化的CIGS薄膜, 由此制备的CIGS电池取得了8.5%的转换效率.     

The effect of a generalized nonlinear incidence rate on the stochastic SIS epidemic model

In this paper, we aim to analyze the classical SIS epidemic model with a generalized force of infection (including nonmonotonic cases), where the transmission rate is perturbed by white noise. Using Feller's test for explosions, we prove that the disease dies out with probability one without any restriction on the model parameters.     

基于面积灰关联相对贴近度模型的长三角制造业产业升级研究

借助“制造业高级化”产业升级理论, 从结构优度、价值链高度、环境保护程度三个维度构建制造业产业升级评价指标体系。根据TOPSIS思想, 以被评价对象数列和理想方案指标数列两相邻点间围成图形的面积来表征关联系数, 同时采用标准差修正G1组合赋权原理对指标赋权并进一步计算灰关联相对贴近度; 通过引入时间变量并赋予时间序列权重以实现对长三角制造业产业升级动态评价。研究结果显示:2010至2016年间, 上海市排名最高, 江苏省略高于浙江省, 安徽省最低; 安徽省是长三角制造业产业升级的短板。基于上述结论, 给出长三角制造业产业升级的政策建议。     

Qualitative analysis on an SIRS reaction–diffusion epidemic model with saturation infection mechanism

In this paper, we deal with an SIRS reaction–diffusion epidemic model with saturation infection mechanism. Based on the uniform boundedness of the parabolic system, we investigate the extinction and persistence of the infectious disease in terms of the basic reproduction number. To better investigate the effects of infection mechanism and individual diffusion, we further analyze the asymptotic profiles of the endemic equilibrium for small or large motility rate and large saturation rate. In particular it is shown that large saturation may cause the elimination of disease. Our study may provide some significant useful insight on disease control and prevention.     

Analysis of a Kind of Stochastic Dynamics Model with Nonlinear Function

In this paper, we establish stochastic differential equations on the basis of a nonlinear deterministic model and study the global dynamics. For the deterministic model, we show that the basic reproduction number $\Re _0$ determines whether there is an endemic outbreak or not: if $\Re _0< 1$, the disease dies out; while if $\Re _0> 1$, the disease persists. For the stochastic model, we provide analytic results regarding the stochastic boundedness, perturbation, permanence and extinction. Finally, some numerical examples are carried out to confirm the analytical results. One of the most interesting findings is that stochastic fluctuations introduced in our stochastic model can suppress disease outbreak, which can provide us some useful control strategies to regulate disease dynamics.     

Measurements of saturated basic and acidic rock electrical conductivities at lower crustal temperatures and high pressures

Abstract

Laboratory measurements of the electrical conductivity of brine saturated acidic and metabasic rocks were done at confining pressures up to 0.2 GPa, high pore pressures and temperatures of 900°C. Acidic rocks showed conductivities insufficient to explain the lower crustal high conductivity layer. Basic rocks, however, showed conductivities consistent with the high conductivity layer at those temperatures that the layer is thought to possess.     

A non-miquelian Laguerre plane satisfying a theorem of miquelian type

This note shows that a theorem of miquelian type known as (M2) holds in a certain non miquelian Laguerre plane of shear type as defined by Löwen and Pfüller[1].Dedicated to Professor H. Karzel on the occasion of his 70th birthday     

电子束相空间分布效应的三维计算

在386微机上建立了长脉冲单模的三维放大器数值模拟程序3DFEL,每个单程只需20分钟。模拟计算得出:(1)发射度对输出功率的影响几乎是指数式的。(2)电子相空间形状(相同发射度)对输出功率的重大影响主要表现为两方面:(a)不同相空间形状,等效能散度是不同的,(b)电子束包络和光场包络匹配关系。(3)非理想入射(偏入射和斜入射)超出一定范围之后将引起输出功率的指数下降。     

粤东柘林湾浮游植物与生态因子的灰关联-回归分析

应用灰关联方法对 2 0 0 1年 1 0月至 2 0 0 2年 7月柘林湾海域的海水采样结果进行数据分析 ,在磷酸盐、硅酸盐等 1 1项生态因子中找出影响浮游植物密度的关键因子 .根据这个结果 ,进一步建立了以这些关键因子为自变量的线性回归模型 ,模型最后的分析结果和灰关联分析的结果一致 ,即 Fe、水温、浊度是影响柘林湾浮游植物密度的关键因子 .