Life cycle strategies of epipelagic copepods in the Southern Ocean

Twelve epipelagic copepod species were reviewed to compare their adaptations to the short primary production season and low temperatures which characterise the Southern Ocean. The species show a spectrum of adaptations, but three broad life cycle strategies were defined: (1) herbivorous in summer, a short reproductive period and winter diapause at depth (Calanoides acutus and possibly Ctenocalanus citer); (2) predominantly omnivorous/detritivorous diet, an extended period of feeding, growth and reproduction and less reliance on diapause at depth (Metridia gerlachei, Calanus propinquus, Calanus simillimus, Oithona similis, Microcalanus pygmaeus, and possibly Oncaea curvata and Oithona frigida); (3) overwintering and feeding within sea ice as early nauplii or copepodids (Stephos longipes and Paralabidocera antarctica). The large species Rhincalanus gigas appears to be intermediate between strategies (1) and (2). Contrasting species from groups (1) and (2), namely C. acutus and O. similis, were selected for more detailed comparison. For C. acutus, maximum (probably food saturated) feeding and egg production rates are well below equivalent values for Calanus spp. at lower latitudes. Likewise, summer growth and moulting rates are slower, and the growth season of this herbivore is only 2–4 months. Therefore, both the low summer temperatures and short primary production season seem to dictate a long (1 year) life cycle for C. acutus. A collation of data on O. similis revealed that its abundance increases about tenfold from the Antarctic shelf northwards to the Polar Frontal Zone, where abundances are similar to those in temperate and tropical shelf seas. In contrast to C. acutus, O. similis appears to remain in the epipelagic and reproduce there year-round, although the food sources which sustain this are still uncertain.     

掺外加剂沥青砂浆的力学性能

应用压缩试验应力-应变数据, 分析了常规条件与冻融条件下, 70^#沥青砂浆、90^#沥青砂浆、橡胶沥青砂浆及其对应掺外加剂砂浆的应力响应规律、强度损失指数与影响砂浆力学性能的物理化学原因, 并基于能量转化原理与能量指标, 研究了压缩过程中沥青砂浆的破坏本质与力学耐久性能。分析结果表明: 在常规条件下, 加入外加剂KS的橡胶沥青砂浆、70^#沥青砂浆与90^#沥青砂浆的最大应力分别为1.345、1.218、1.186 MPa, 分别为对应未掺外加剂沥青砂浆最大应力的1.12、1.18、1.30倍, 加入外加剂沥青砂浆的能量释放系数增量分别为0.152、0.067、0.054 MPa^-1·J^-1, 分别为对应未掺外加剂沥青砂浆能量释放系数增量的68.8%、78.8%、41.9%, 因此, 加入外加剂提高了沥青砂浆的抗压强度, 改善了沥青砂浆的力学耐久性能; 在冻融条件下, 加入外加剂的橡胶沥青砂浆、70#沥青砂浆与90#沥青砂浆的最大应力分别为1.311、1.170、1.083 MPa, 分别为对应未掺外加剂沥青砂浆最大应力的1.22、1.11、1.06倍, 加入外加剂沥青砂浆的能量释放系数增量分别为0.221、0.070、0.073 MPa^-1·J^-1, 分别为对应未掺外加剂沥青砂浆能量释放系数增量的61.7%、72.9%、65.2%, 能量释放系数越小, 抗疲劳性能越好, 因此, 加入外加剂能够改善沥青砂浆的水稳定性, 减少冻融损伤, 确保冻融后沥青砂浆的力学耐久性能。     

Nutrient biogeochemical cycles in the Gulf of Riga: scaling up field studies with a mathematical model

A box model has been implemented to understand the large-scale biogeochemical cycles of nitrogen, phosphorus, and silicon in the Gulf of Riga. The large data sets collected within the international Gulf of Riga Project in 1993/1995 were used to validate the model. The comparison to data was useful in scaling up to the gulf-wide level and scrutinizing the conclusions based on short-term field surveys and experimental studies. The simulations indicate that the limiting role was passing from silicon to phosphorus to nitrogen over the seasons of organic production. However, on an annual scale, nutrient limitation was close to the “Redfield equilibrium”. Mass balance considerations, based on modeled coupled fluxes, disagree with the conclusions on low sediment denitrification and high phosphorus retention in the pelagic system, which were derived from isolated measurements.Nutrient budgets constructed with the model revealed the high buffer capacity of the Gulf of Riga. The nutrient residence times span a range from 6 years for N to 70 years for Si. The buffering arises from intensive internal recycling in the water body and by the bottom sediments. The budgets indicate that the Gulf retains about two-thirds of external nitrogen and silicon inputs, while phosphorus retention is only 10%.A slow response to external perturbations is demonstrated with numerical experiments run for 15 years under 50% reductions of terrestrial nutrient inputs. These experiments imply that the most effective is the N+P reduction scenario, which resulted in a 20% decrease of primary production after 12 years. A reduction of P resulted in only a 6% decrease of primary production; however, it yielded an 80% drop in the amount of nitrogen fixation.     

云南高海拔地区沥青混合料的水稳定性初探

通过对选定的三种沥青混合料级配类型,进行粘附性试验和冻融劈裂试验的研究,以确定适合云南高海拔地区的沥青混合料级配,结果证实AC-13,AC-20,ATB-25都有较高的水稳定性,为实际工程应用提供参考。     

电动汽车维护周期现状及确定方法探究

本文分别分析了6个电动乘用车车型和商用车车型的维护周期,得到纯电动乘用车(小客车)的平均维护周期间隔为1.2万公里或8个月,纯电动商用车平均维护里程区间为6000~51000km;分析了5种国内动力电池品牌的维护周期设置,动力电池企业给出的维护周期多数按照三级间隔划分,其平均间隔为1个月、4个月和10个月。总结了现行维护周期制定优化方法,并结合传统燃油汽车维护周期优化数学模型,探索性提出了适用于电动汽车维护周期的优化改进路径。研究结论对指导道路运输经营者科学制定维护周期、开展车辆维护工作具有参考意义。     

Life cycle of Epischura baicalensis Sars (Copepoda, Calanoida) in Lake Baikal

Epischura baicalensis Sars is a dominant pelagic species of Lake Baikal zooplankton. This is endemic to Lake Baikal and inhabits the entire water column. It produces two generations per year: the winter–spring and the summer. These copepods develop under different ecological conditions and vary in the duration of life stages, reproduction time, maturation of sex products and adult males and females lifespan. The total life period of the animals from each generation is one year. One female can produce 10 egg sacks every 10–20 days during its life time. The ratio of males and females is 1:1. One of the most essential features of the ecology of E. baicalensis is the alteration of its mass inhabited areas during a year, as well as in day time. This is due to the need for various conditions for gonad maturation, reproduction, nourishing and protection from being consumed by planktivors.     

干湿循环作用下炭质泥岩溶蚀孔隙度的化学计量方法

为建立干湿循环作用下炭质泥岩溶蚀孔隙度的化学计量方法,对干湿循环作用后的炭质泥岩试样进行X射线衍射试验,测试干湿循环作用下炭质泥岩的矿物成份演变;同时,采用电感耦合等离子发射光谱测试技术,研究干湿循环作用下炭质泥岩浸泡溶液的离子浓度变化规律;基于离子守恒定律,推断干湿循环作用下炭质泥岩矿物发生的化学反应;在此基础上,建立浸泡溶液离子浓度与炭质泥岩矿物反应量的定量关系,并计算炭质泥岩各矿物反应的体积;基于唯象理论,提出以反应物与生成物的体积差为溶蚀孔隙体积增量,构建炭质泥岩溶蚀孔隙度的化学计量方法;最后,利用比重瓶法和核磁共振法对炭质泥岩溶蚀孔隙度的计算结果进行验证。结果表明：干湿循环作用下炭质泥岩的方解石、钾长石和钠长石含量减小,高岭石含量增加;随干湿循环次数增加,浸泡溶液中Ca²⁺、K⁺、Na⁺、Fe²⁺和Al³⁺离子浓度均增加,其中Ca²⁺离子浓度增长速率是其他阳离子的数十倍;经化学分析发现,方解石溶蚀和长石水解生成高岭石是干湿循环作用下炭质泥岩孔隙演...     

均衡二分图中含有大圈的2-因子的度和条件

设G=(V1,V2;E)是一个二分图,满|V1|=|V2|=n sk 1足,其中s 4,k 1是两个正整数.定义G中不相邻两点的最小度和为σ2(G)=min{dG(u) dG(v)∶u,v∈V(G),uv E(G)}.在这篇文章中,我们证明了如果σ2(G)2「(1-1s)n﹁ 2,则G有一个2-因子包含k个长至少为2s的点不交的圈     

细粒硫酸盐渍土盐胀特性试验研究

选取典型细粒硫酸盐渍土,进行反复冻融循环条件下的试验研究,分析了典型细粒硫酸盐渍土的盐胀规律。试验结果表明:低液限黏土硫酸盐渍土的前5次冻融循环过程中盐胀具有较好累加性,随着冻融循环次数的增加,盐胀量增长速度逐渐降低;含砂低液限黏土硫酸盐渍土的盐胀过程可以被分为3个阶段。