Modelling of wheels and rail discontinuities in dynamic wheel-rail contact analysis

A classification of wheel-rail contact is given. Difference is made between modelling of a running wheel with continuous single-point-contact, as is common practice in wheel-rail contact analysis, and a wheel with transient double- or multi-point-contact, which may occur for rail irregularities with curvatures larger than that of the wheel circumference. It is shown that application of the first model for these irregularities will strongly underestimate the contact forces as it does not describe occurring mechanisms correctly. Further, it is shown that in principle it is not possible to describe the second type of contact fully correct with a lumped wheel model. Both wheel models are formulated mathematically for some basic contact cases. Afterwards, results are applied to a linear track model. Analytical closed-form solutions are found in the frequency domain for arbitrary type of contact and numerically transformed to the time domain. Finally, the necessity is shown to avoid situations where transient multiple-point-contact may occur (like rail joints) in practice.     

水平岩层长大公路隧道建设动态管理

以重庆渝宜高速公路云万段庙梁特长隧道为例，对水平岩层长大公路隧道建设的动态管理进行分析与总结。通过建设过程中的工程地质调查、衬砌支护动态调整、支护参数优化论证及监控量测信息反馈等手段，在确保工程安全和功能的基础上，加快工程进度，降低工程造价，并为类似项目管理提供借鉴。     

胃动素受体在大鼠各脑区的分布

目的 检测胃动素受体在大鼠中枢各核团的分布,探索胃动素的中枢作用机制.方法 本实验以成年SD大鼠为研究对象,采用免疫组织化学方法检测大鼠脑胃动素受体分布.结果 大鼠中枢胃动素受体主要分布于神经细胞的胞膜上,而胞质及核膜未见明显阳性染色;胃动素受体在大鼠摄食、记忆相关脑区的分布为:海马CA1(4.02±1.27)、CA2(3.43±2.21)、CA3(6.10±4.03)、CA4(3.25±1.32),下丘脑腹内侧核(Vmh,2.52±1.37)、下丘脑外侧区(Lh,4.50±2.61),杏仁内侧核(Me,5.14±2.27)、杏仁基底内侧核(Bm,2.14±1.93)、杏仁基底外侧核前部(Bla,3.98±1.86)、杏仁基底外侧核后部(Blp,4.01±2.45)、杏仁中央核(Ce,1.22±1.33)、杏仁外侧核(La,2.43±1.78),海马CA3区为胃动素受体分布最多的部位.结论 中枢胃动素受体是一种细胞膜受体;胃动素是一种神经调节递质,其受体广泛分布于脑内多个核团;胃动素作用于中枢的胃动素受体,在记忆、情绪、食欲、进食等方面可能起着广泛的调节作用.     

Silicon dynamics in the Oder estuary, Baltic Sea

Studies on dissolved silicate (DSi) and biogenic silica (BSi) dynamics were carried out in the Oder estuary, Baltic Sea in 2000–2005. The Oder estuary proved to be an important component of the Oder River–Baltic Sea continuum where very intensive seasonal DSi uptake during spring and autumn, but also BSi regeneration during summer take place. Owing to the regeneration process annual DSi patterns in the river and the estuary distinctly differed; the annual patterns of DSi in the estuary showed two maxima and two minima in contrast to one maximum- and one minimum-pattern in the Oder River. DSi concentrations in the river and in the estuary were highest in winter (200–250 μmol dm^− 3) and lowest (often less than 1 μmol dm^− 3) in spring, concomitant with diatom growth; such low values are known to be limiting for new diatom growth. Secondary DSi summer peaks at the estuary exit exceeded 100 μmol dm^− 3, and these maxima were followed by autumn minima coinciding with the autumn diatom bloom. Seasonal peaks in BSi concentrations (ca. 100 μmol dm^− 3) occurred during the spring diatom bloom in the Oder River. Mass balance calculations of DSi and BSi showed that DSi + BSi import to the estuary over a two year period was 103.2 kt and that can be compared with the DSi export of 98.5 kt. The difference between these numbers gives room for ca. 2.5 kt BSi to be annually exported to the Baltic Sea. Sediment cores studies point to BSi annual accumulation on the level of 2.5 kt BSi. BSi import to the estuary is on the level of ca. 10.5 kt, thus ca. 5 kt of BSi is annually converted into the DSi, increasing the pool of DSi that leaves the system. BSi concentrations being ca. 2 times higher at the estuary entrance than at its exit remain in a good agreement with the DSi and BSi budgeting presented in the paper.     

舰船水下爆炸鞭状运动中的阻尼效应

舰船在水下爆炸气泡脉动压力作用下将产生鞭状运动冲击响应。为了掌握冲击响应的衰减规律,建立了舰船结构、设备、水舱内流体和外部流体等在振动和晃荡过程中的阻尼效应动力学模型,并编写程序对是否考虑上述阻尼效应的舰船鞭状运动响应进行了数值计算。研究结果表明,对于具有相对较大质量的内部设备和水舱的舰船来说,上述阻尼效应对舰船水下爆炸鞭状运动的衰减起到重要的作用,如不予以考虑有可能造成对舰船鞭状运动响应幅值的高估。     

Benthic sediment composition and nutrient cycling in an Intermittently Closed and Open Lake Lagoon

Surfical sediments within Corunna Lake, a moderate size Intermittently Closed and Open Lake Lagoon (ICOLL), were examined for solid phase nutrient concentrations (TN, TP, TOC,) and solute exchange rates between the sediment and water column (O₂, NO₃–N, NH₄–N, FRP, and N₂). The surfical sediments in Corunna Lake contained high concentrations of TN (5 mg/g dry mass), total phosphorus (0.6 mg/g dry mass), and TOC (~ 5% dry mass). The carbon stable isotope ratio (δ¹³C) and TOC:TN ratios (δ¹³C ~ ? 24, TOC:TN ~ 11–14) demonstrated that the composition of the organic matter in the sediment was a mixture derived primarily of degraded planktonic matter. The close association between TP and Fe concentrations highlighted the potential role Fe plays in mediating Filterable Reactive Phosphorus (FRP) concentrations in the water column of Corunna Lake. In situ benthic chamber incubations were used to measure benthic fluxes. Solute exchange rates between the sediment and water column in Corunna Lake were similar to other reported studies (O₂ = ? 469 to ? 1765 µmol m^? 2 h^? 1, NH₄–N = 0.1–63 µmol m^? 2 h^? 1, NO₂/NO₃–N = 0 µmol m^? 2 h^? 1, FRP = ? 4–1.6 µmol m^? 2 h^? 1and N₂ = 12–356 µmol m^? 2 h^? 1). As more carbon was deposited and mineralized the efficiency of the bacterial population to denitrify nitrogen in the sediment decreases. The linkage between land use and benthic biogeochemistry was also explored. A dairy farm exists in the middle catchment of Corunna Lake, and the receiving bay sediment consistently demonstrated the highest oxygen consumption rates in winter and spring (? 1408 µmol m^? 2 h^? 1 in winter, ? 1691 µmol m^? 2 h^? 1 in spring) and lowest denitrification efficiencies during summer (~ 3%). Nitrate/nitrite fluxes were not observed during any of the chamber incubations, with the concentrations of nitrate/nitrite being below detection limits (< 10 μg/L). Seasonal changes influenced the rates of solute exchange between the sediment and water column. Critical measures of solute exchange for NH₄–N and biogenic N₂ indicated that seasonal temperature changes play a significant role in mediating the reaction rates of sedimentary based biogeochemical processes. Measurable FRP fluxes were small but greater in the benthic sediments which received higher carbon inputs. Sediments have a high capacity to adsorb P which is released as sediment oxygen demand increases as a result of increases in labile carbon loads.     

MAN 40/45中速柴油机排气门杆损伤分析

分析了MAN40／45中速柴油机排气门杆常发生损伤的原因，认为是排气门及导套的结构与排气门的材质问题造成的。     

Estimation of the effects of aircraft noise on residential satisfaction

This study assesses the effects of aircraft noise on residential satisfaction, an important indicator of subjective well-being. A structural equation model is specified that estimates the relationships between objective variables, noise annoyance variables and residential satisfaction. Secondary data-analysis is used to estimate the model. The survey was conducted in 1996/1997 among the population living within a 25-km radius of Amsterdam Schiphol, the largest airport in the Netherlands. The effect of aircraft noise annoyance is found to be relatively small. In addition, the objective level of aircraft noise exposure is found to be a better predictor of residential satisfaction than its subjective counterpart. The most important determinants of residential satisfaction are found to be road traffic noise annoyance, age and neighbor noise annoyance.     

Scantling multi-objective optimisation of a LNG carrier

Numerous real-world problems related to ship design can be solved by various alternatives. However, the scantling design has conflicting objectives such as minimum production cost, minimum weight and maximum moment of inertia (stiffness). Therefore a multi-purpose solution had to be settled in order to meet all these requirements at once. Ship design is a complex endeavour requiring successful coordination of many different disciplines, both technical and non-technical. Basic design is the least defined stage of the ship design process and seeks to define the optimal amidships section structure. For that purpose, recent improvements have been made to a numerical tool in order to optimise the scantling of ship sections by considering production cost, weight and moment of inertia in the optimisation objective function. A multi-criteria optimisation of a LNG carrier is conducted in this paper to illustrate the analysis process. Pareto frontiers are obtained and results have been validated by the Bureau Veritas rules. The methodology presented in this paper has demonstrated its effectiveness in optimising scantling of ships at a very early design stage thanks to a management of critical problems usually studied at a later stage of the design.     

船员权益保障与培训教育应同举并重

从内用和外派两方面分析中国船员人才资源情况,对"船员权益保障与培训教育应同举并重"的维权思路进行解读,建议提高航海专业教育在国家教育体系的地位和资金投入比重,强化航海专业教育的专业特点,积极探索培养职业航海家的教育模式,加大对航海知识的普及与社会宣传,加强航海职业教育。