青藏铁路透壁通风管通风路基模型试验及初始温度场特征

通风路基作为一种积极主动保护冻土路基的冷却调控技术能有效的抬升多年冻土上限, 保护冻土路基的稳定性. 目前实体试验工程通风路基一般采用路基内预埋实体混凝土管或PVC管, 管壁不能透风, 管壁与土体间主要通过热传导进行换热. 一种管壁开孔、可以透风的新型通风管--"透壁通风管"既能以管内空气间的对流带走管内热量; 因其管壁透风, 低温的冷空气可以透过管壁的大孔眼穿透到通风管周围的介质中, 直接与其进行热交换, 从而改善传统通风管换热模式. 为探索透壁通风管在青藏铁路路基中的实际温控效果而进行了青藏铁路透壁通风管路基现场试验, 试验路基短期监测资料的分析结果显示, 透壁通风管对青藏铁路路基具有良好的冷却能力, 可在一定程度上抬升冻土上限; 透壁通风管路基经填土级配优化重组后更能充分发挥其路基冷却效果     

建筑物对城市通风自净能力影响的数值试验

应用城市气候数值模式，分别计算了三栋6层住宅楼和一栋20层住宅楼两类建筑形式影响下的风场，以及在此风场中街道汽车尾气的浓度分布。计算结果表明在总建筑面积基本相同的情况下，高层建筑周围环境的通风自净能力要优于多层建筑。     

DT-1型独头巷道高效通风系统的开发研究

介绍了一种独头巷道高效通风系统的组成、构造特点及其在坑道内的使用情况。     

Analysis of mine ventilation networks using nonlinear programming techniques

Summary Solving ventilation networks of natural air splitting is a classical problem in mine ventilation. A common approach to this problem is to formulate it based on Kirchhoff's voltage and current laws and obtain the solution by an iterative technique known as the Hardy Cross method. In this paper, it is shown that the problem can be formulated and analysed as an unconstrained optimization (minimization) problem. The computational experience with the method of conjugate gradients is also discussed.     

Rhizosphere: A new frontier for soil biogeochemistry

A range of key biological functions of plant roots such as uptake, respiration and exudation can considerably alter biogeochemical parameters of the soil in the vicinity of the roots, i.e., the rhizosphere: concentrations of nutrients, toxic elements (e.g., aluminium) and pollutants, concentrations of complexing or chelating compounds, pH and redox potential, partial pressures of gases such as O₂ and CO₂, etc. Such parameters can also be directly influenced by the activities of soil microorganisms that are known to be stimulated by root exudation in the rhizosphere. Changes of biogeochemical parameters of the soil solution occurring in the rhizosphere influence a whole range of reactions at the soil solid/soil solution interface. Higher plants thereby play a key role in (i) the weathering of soil minerals, (ii) soil formation processes (pedogenesis) and (iii) the biogeochemistry of elements that are either beneficial or toxic to themselves and other soil biota.     

Effects of Pinus sylvestris var. mongolica afforestation on soil phosphorus status of the Keerqin Sandy Lands in China

Few studies have considered the effects of afforestation on soil phosphorus (P) status in semiarid regions such as the Keerqin Sandy Lands in China, though plantations have been widely established on P-deficient sandy soils to control wind-induced desertification. Phosphorus fractions and acid phosphomonoesterase (AP) activities were compared in the rhizosphere and bulk soils (0–5 and 5–20 cm) under Mongolian pine (Pinus sylvestris L. var. mongolica Litv.) plantations of different ages (15, 22, and 30 years old) and in bulk soils under grasslands to understand soil P behavior with Mongolian pine plantation development and to find out major factors controlling soil P cycling. Stand age and rhizosphere processes had similar effects on the soil P fractions. Labile inorganic P and phosphate absorbed on aluminum and iron oxides were not affected by stand age and rhizosphere processes. Rhizosphere effects of Mongolian pine accelerated the mineralization of organic P by increasing microbial and AP activities. Soil P properties in bulk and rhizosphere soils changed similarly with plantation development. In the first 15 years after afforestation, total organic P, calcium phosphate, labile organic P, microbial biomass P (MBP) concentrations, and AP activities were reduced sharply. About 73% of the reduction in total P came from mineralization of organic P and 24% came from solubilization of calcium phosphate. From 15 to 22 years onward, soil total organic P and calcium phosphate decreased gradually and labile organic P, MBP, and AP activities increased greatly, whereas total inorganic P remained constant. The results suggest that soil P pool was depleted with Mongolian pine plantation development, especially in the early stage. As the dominant form of soil P, organic P was the main source of available P and associated biological processes controlled soil P cycling under Mongolian pine plantations. To ensure sustainability of pine plantations, it is imperative that soil fertility is conserved by adding fertilizer, thinning, and protecting litterfall.     

海底隧道穿岛通风竖井地震作用下动力分析

通风竖井对隧道内的通风换气、车辆动力效应调整以及防灾救援起到至关重要的作用,是长大型隧道的重要组成部分。由于受到周围岩土的约束,海底隧道穿岛通风竖井结构的稳定性往往优于水中自立式竖井。但在地震动作用下,受周围岩土的约束及土体变形的影响,隧道通风竖井的地震响应将与普通井筒及井筒式基础存在明显差异。基于大型有限元分析软件ABAQUS建立海底隧道穿岛通风竖井结构的数值模型,考虑周围岩土及底部隧道对竖井的约束,利用时程分析法计算竖井在垂直于隧道轴向的水平地震作用下的动力响应,得出了竖井内力及位移沿深度的分布特点,通过考虑不同类型的岩土材料得到了竖井结构动力响应随场地剪切波速的变化规律。     

Response of drip water temperature to climate variability: a case study in Xiaoyan Cave,southwest China

Detailed monitoring of surface atmospheric and subterranean microclimatic conditions has provided a new opportunity to interpret drip water temperature changes associated with climate variability. High-resolution multi-index monitoring was conducted in Xiaoyan Cave, Guilin, southwest China, for a period of four years (2011–2014) to identify the processes that control drip water temperature. The results show that variations in drip water temperature are mainly coupled to changes in the cave air temperature unless large drip discharge occurs. The controls on cave air temperature depend on the ventilation modes that eventually affect drip water. The multiple thermal mechanisms are winter ventilation, heat conduction in summer and water flow-induced convection derived from subsurface water percolation into the cave due to fast preferential flow during heavy rain events. Drip water response to extreme temperature anomalies is shown to be sensitive to outside climate.     

基于风廓线雷达的北京春季一次“先霾后沙”空气污染过程分析

利用NCEP再分析资料、逐小时污染物浓度数据、风廓线雷达及地面常规观测资料,对北京2018年3月26—29日一次“先霾后沙”的空气污染过程进行了分析。结果表明：霾污染期间PM_2.5峰值浓度为242 μg·m^-3,PM_2.5/PM₁₀值为0.86。受蒙古气旋影响,PM₁₀浓度出现爆发性增长,增长速率达到912 μg·m^-3·h^-1,PM_2.5/PM₁₀值下降至0.11。霾主要影响时段边界层内以西南风为主,平均通风量为15 907 m²·s^-1,大气边界层以稳定的弱上升或下沉运动为主;而沙尘影响时段平均通风量为9 226 m²·s^-1,沙尘天气爆发前边界层明显的下沉运动先于地面污染物浓度的变化。基于后向轨迹模式和潜在源贡献分析方法PSCF计算结果,霾影响时段河北中南部、山西中部等地对北京PM_2.5贡献较多;而沙尘影响时段,北京地区的PM₁₀主要来源于内蒙古中部和辽宁西部。     

Ventilation of the North Pacific Ocean: Water exchange between subtropical and tropical gyres

INTRODUCTIONIntheearly 1 980 s,ventilationtheoryemergedtopredictthehorizontalandverticalstructureofthethermocline.Thereweretwodifferentviewsonthestratifiedoceans.Thefirsttheory (RhinesandYoung,1 982 ,hereafterRY ;YoungandRhines,1 982 )proposedanunventilatedmodelinwhichonlytheuppermostlayerisexposedtothesurfaceandisforcedbythewindstress.Thesecondtheory (Luytenetal.,1 983 ,hereafterLPS)offeredaventilatedmodelwhichisclosertotheclassicalthermoclinetheoriesthanthatofthefirstone (e.g .,Nee…