Mechanisms controlling lateral and vertical porewater migration of depleted uranium (DU) at two UK weapons testing sites

Uranium associations with colloidal and truly dissolved soil porewater components from two Ministry of Defence Firing Ranges in the UK were investigated. Porewater samples from 2-cm depth intervals for three soil cores from each of the Dundrennan and Eskmeals ranges were fractionated using centrifugal ultrafiltration (UF) and gel electrophoresis (GE). Soil porewaters from a transect running downslope from the Dundrennan firing area towards a stream (Dunrod Burn) were examined similarly. Uranium concentrations and isotopic composition were determined using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Multi-Collector-Inductively Coupled Plasma-Mass Spectrometry (MC-ICP-MS), respectively.The soils at Dundrennan were Fe- and Al-rich clay-loam soils whilst at Eskmeals, they were Fe- and Al-poor sandy soils; both, however, had similar organic matter contents due to the presence of a near-surface peaty layer at Eskmeals. These compositional features influenced the porewater composition and indeed the associations of U (and DU). In general, at Dundrennan, U was split between large (100 kDa-0.2 μm) and small (3-30 kDa) organic colloids whilst at Eskmeals, U was mainly in the small colloidal and truly dissolved fractions. Especially below 10 cm depth, association with large Fe/Al/organic colloids was considered to be a precursor to the removal of U from the Dundrennan porewaters to the solid phase. In contrast, the association of U with small organic colloids was largely responsible for inhibiting attenuation in the Eskmeals soils.Lateral migration of U (and DU) through near-surface Dundrennan soils will involve both large and small colloids but, at depth, transport of the smaller amounts of U remaining in the porewaters may involve large colloids only. For one of the Dundrennan cores the importance of redox-related processes for the re-mobilisation of DU was also indicated as Mn^IV reduction resulted in the release of both Mn^II and U^VI into the truly dissolved phase.     

An investigation of a heat pipe cooling system for use in turning on a lathe

A novel proposal is presented in this paper for reducing the thermal inaccuracy of turning on a lathe by removing the portion of the heat generated during the cutting process which is transferred to the carbide cutting insert by installing a heat pipe in the toolholder. The ability of the heat pipe to affect the temperature of the carbide cutting insert and the elongation of the toolholder is inferred from the response of thermocouples and strain gauges mounted on the toolholder to the heat generated during various cutting conditions. The results of the experimental investigation have proved the feasibility of the concept and recommendations have been made for continuing the research and improving the performance of the system.     

深层切割——加工花岗岩的一种新方法（下）

在第一阶段的实验中,确立了加工温度与工艺参数之间的一些基本关系。在接触区域,切割深度与温度之间存在着特定的关系。而在大量研究中,并没有建立温度与刀片圆周速度之间的明确关系。这些关系从图９可以看出。 为解释这种现象,必须研究刀具与工件接触区域的微观加工过程。每个晶粒的作用表面积在更高的切割速率下,随每一锯齿的每转材料去除速率Ｑｗ／ｎｓ值的减少而减少。切片厚度ｈｃ也同样如此。因此,随着刀片上的载荷的降低,温度也相应地降低。然而,温度没有降低到同样多的原因是,由于刀片在更高的圆周速度下臭有更高的旋转能…     

用CVDRESS和MONODRESS金刚石工具修整陶瓷砂轮（上）

详细地分析了利用CVDRESS和MONODRESS金刚石工龄修整陶瓷砂轮的过程,讨论了影响陶瓷砂轮修整质量的关键因素,强调了修整过程中金刚石保持锋利的切削刃的重要性。