Estimates of Southern Ocean primary production—constraints from predator carbon demand and nutrient drawdown

In view of the wide range of estimates for the total primary production for the Southern Ocean south of the Subantarctic Front—current estimates range from 1.2 to 3.5 Gtonne C year⁻¹—we have examined two indirect methods for assessing primary production. First, we have estimated the primary production needed to sustain the carbon requirements of the endotherm top predators in the ecosystem. Estimation of the carbon requirements for crabeater seals of about 7 Mtonne C year⁻¹ is extrapolated to a value for all endotherm predators of 15–30 Mtonne C year⁻¹. Current data indicate that 70–80% of the diet of this suite of predators is zooplankton (predominantly the euphausiid krill), making for highly efficient transfer from primary production to top predators. Our best estimate of Southern Ocean primary production by this method is of the order of 1.7 Gtonne C year⁻¹, or an averaged areal primary production of about 30–40 g C m⁻² year⁻¹. Our second approach is to estimate primary production from the drawdown of inorganic nutrients, based on the limited suite of studies from which an annual nutrient deficit can be calculated. Again, this indicates annual primary production of the order of 1.5 Gtonne. Although both methods have inherent uncertainties, taken together they provide a relatively robust constraint on annual primary production. For both methods to underestimate primary production by the 1–1.5 Gtonne C implied by the higher current estimates, carbon export from the Southern Ocean pelagic ecosystem would need to be much higher than is normally found in other oceans.     

An Experimental Study of a Prototype Active Anti-Roll Suspension System

Active roll control is known to offer substantial improvements in ride and handling performance over the most sophisticated passive suspension systems. However although many different active suspension systems have been discussed and analysed through simulation little information regarding experimental performance data from a prototype active roll control system has been published. This study focuses on the design, development, commissioning and experimental evaluation of a roll control suspension based on active anti-roll bar actuation. In tests, the prototype vehicle demonstrated excellent steady state and dynamic roll cancellation within the lateral acceleration range of 0.5g. Subjective assessments of the system confirmed the benefits of a level ride together with the added benefit accrued from the elimination of roll dynamics.     

声波测试法在铁路路基测试中的应用

通过采用声波测试法对既有线铁路路基进行测试,并结合现场地质调查及便携式可变能动力触探测试结果,对铁路路基承载力状况做出快速评价,为既有线路路基检测提供一种快速有效的测试方法。     

Material transport from the nearshore to the basinal environment in the southern Baltic Sea: I. Processes and mass estimates

Processes involved in erosion, transport and deposition of cohesive materials are studied in a transect from shallow (16 m) to deep (47 m) water of the SW Baltic Sea. The wave- and current-induced energy input to the seabed in shallow water is high with strong variability and suspended matter concentrations may double within a few hours. Primary settling fluxes (from sedimentation traps) are less than 10 g m⁻² day⁻¹, whereas resuspension fluxes (evaluated from sedimentation flux gradients) are 15–20 times higher and the residence time for suspended matter in the water column is 1–2 days. Settling velocities of aggregates are on average six times higher than for individual particles resulting in an enhanced downward transport of organic matter. Wave-induced resuspension (four to six times per month) takes place with higher shear stresses on the bottom than current-induced resuspension (three to five times per month). The short residence time in the water column and the frequent resuspension events provide a fast operating benthic–pelagic coupling. Due to the high-energy input, the shallow water areas are nondepositional on time scales longer than 1–2 weeks. The sediment is sand partly covered by a thin fluff layer during low-energy periods. The presence of the fluff layer keeps the resuspension threshold very low (<0.023 N m⁻²) throughout the year. Evaluated from 3-D sediment transport modeling, transport from shallow to deep water is episodic. The net main directions are towards the Arkona Basin (5.5×10⁵ t per year) and the Bornholm Basin (3.7×10⁵ t per year). Energy input to the bottom in deep water is low and takes place much less frequently. Wave-induced resuspension occurs on average once per month. Residence time of particles (based on radioactive isotopes) in the water column is half a year and the sediment accumulation rate is 2.2 mm year⁻¹ in the Arkona Basin.     

Longitudinal Tire Dynamics

This article begins with a brief review of the traditional concept of lateral relaxation length. The review illustrates that this concept yields a useful approximation which can be used with semi-empirical tire models which assume lateral forces are a function of steady-state slip angles. The article then presents an analogous derivation for longitudinal slip. Like its lateral counterpart, the derivation yields an approximation for transient longitudinal slip which can be used with tire models which assume longitudinal forces are a function of steady-state longitudinal slip. It is shown that, like the relaxation-length-based lateral slip angle, this formulation for longitudinal slip yields the ability to compute shear forces at the tire/road interface for either high or low speed applications, a necessary feature of simulations which support human in the loop driving simulation. Like traditional kinematically-based longitudinal slip, the transient formulation presented here is coupled with the wheel spin equation, and it shares the characteristic that it is very stiff compared to the equations of vehicle motion. This characteristic is a challenge impeding the real-time calculations required for driving simulation. The paper shows that local linearization of the wheel spin equations coupled with analytical solutions of the transient longitudinal slip formulation provide the basis for both insight into the longitudinal dynamics of the tire and for integrating the model in real-time.     

Cost assessment for abyssal seafloor waste isolation

We develop an integrated model for estimating the internal cost of abyssal seafloor waste isolation. The model captures the major economic, engineering, geographic and social factors that influence the management cost for sewage sludge and municipal incinerator ash. Considering five representative metropolitan areas and five proposed abyssal study sites, we apply this model to produce cost estimates for four deep-ocean waste delivery system concepts. The results show that the unit cost depends primarily on regional waste volume, the marine delivery system and transportation distance. Based on available data, the abyssal ocean option may be competitive with present land-based disposal costs in New York City. The option is less competitive in other metropolitan areas.     

宋丽关系与密州板桥镇

关于宋朝与高丽王朝的关系史,很多学者已作了大量的研究,但多是集中在两个国家总体上的政治经济文化交流,从地方史角度出发的不多,即使有也大多是对两浙地区比如明州(今浙江宁波)和杭州等地的宋丽关系史的考察,研究山东胶州地区中韩关系的则很少.对于山东胶州的问题也有人研究,李晓先生曾在<海交史研究>(1985年第1期)上发表过<山东胶州港兴衰问题初探>,介绍了胶州港在北宋前、宋金元初及明清两代的兴衰过程,不过,重点是在港口历史沿革,不在宋丽关系.所以本文拟以胶州(即宋朝历史上的密州板桥镇)为中心对宋丽关系作一初步探索,以就正于诸位前辈.     

转臂式轴箱定位装置等效刚度计算与分析

文章从能量守恒定律出发，结合转臂式轴箱定位装置的结构特点，通过分析其受力状况和运动几何关系，在充分合理简化的基础上，推导出通用的转臂式轴箱定位装置的垂向、纵向和横向等效刚度计算公式，并对我国典型动车组的转臂式轴箱等效定位刚度进行了计算。     

Benefits and challenges of controlling a LED AFS (adaptive front-lighting system) using fuzzy logic

The vehicular illumination system has undergone considerable technological advances in recent decades such as the use of a Light Emitting Diode (LED) Adaptive Front-lighting System (AFS), which represents an industry breakthrough in lighting technology and is rapidly becoming one of the most important innovative technologies around the world in the lighting community. This paper presents AFS control alternatives using fuzzy logic (types 1 and 2) to determine its operating parameters taking into consideration the road conditions in the state of São Paulo (Brazil). Fuzzy logic is a well-known extension of the conventional (Boolean) logic that enables the treatment of uncertainty present in the information through the definition of intermediary membership values between the “completely true” and the “completely false”. This technique or modeling strategy is particularly important when a multi-parameter decision must be taken or the decisions are based on the human knowledge. The results show the potential of the methodology proposed and its suitability for light control providing safer nighttime driving.     

计算机联锁模拟培训系统

主要介绍了计算机联锁培训系统平台的研制开发。系统依靠计算机技术、控制技术、网络技术，完全模拟计算机联锁设备的显示界面与操作方法，做到与现实设备操作一致，使操作人员如同亲临现场，从而达到使电务工作者能进行培训、演练和开发的目的。