城市燃气管网的地震紧急处置系统研究

燃气管网的地震破坏有时会导致火灾、爆炸等严重的次生灾害。城市中的燃气管网系统若能具备地震紧急处置功能,在地震来临时及时采取自动关闭燃气供应阀门等紧急处置措施,可以避免或减少此类次生灾害的发生。介绍了普遍用于燃气管网日常调度管理的SCADA系统的组成与工作原理,探讨了在SCADA系统中加入地震紧急处置功能的可行性,并基于ArcGIS地理软件,通过VBA二次开发编制了燃气管网的地震紧急处置模拟程序,为燃气管网地震紧急处置系统的实现提供了一定依据。     

福建省热带气旋暴雨型地质灾害特征分析

福建是受热带气旋影响较严重的省份,又是一个多山的省份,每年都有因热带气旋暴雨诱发滑坡等地质灾害造成巨大人员伤亡和经济损失的事例发生.通过分析福建省1990～2006年热带气旋暴雨诱发的地质灾害个例,发现热带气旋暴雨型地质灾害的规模和强度均比雨季暴雨诱发的地质灾害大;它的发生与热带气旋路径、过程雨量和当日雨量关系密切,地质灾害主要发生在强降水后的48 h内;热带气旋登陆前后,若有偏东急流、西南季风、冷空气、暖式切变等系统共同作用,对暴雨具有增幅作用,极易引发地质灾害.     

Spatial sampling and the environment: some issues and directions

In this paper we summarize research issues for spatial environmental sampling stemming from a NISS/USEPA workshop held on 21-22 September 1994 at Chapel Hill, NC.     

内蒙古典型草原土壤不同剖面深度CO_2通量格局及其驱动因子

土壤CO2的释放能够显著增加大气牛CO2的浓度,增强温室效应,从而对全球气候和环境变化产生重要影响.但是,不同的土壤层对CO2通量的贡献量有很大的差异.文章通过挖坑法结合红外气体分析法研究了内蒙古草原典犁针茅(Stipa krylovii)群落和羊草(Leymus chinensis)群落不同剖面深度土壤CO2通量格局以及影响CO2通量的驱动因素.结果表明,表层土壤移走后,土壤CO2通量的变化可分为瞬时、短期、长期三种格局.新剖面上最初的0～21 min内释放的CO2通量最均大于初始土壤表层CO2通量,而且两者比值随土壤深度增加而增大,也随土壤CO2生产能力增强而增大.2～4 d后,新剖面CO2通量持续下降至低于初始土壤表层CO2通量的水平.形成短期稳定状态.更长时间后,新剖面则逐渐表现出与初始土壤剖面表层相近的CO2通量特征.我们认为,(1)在新剖面形成时的CO2通量瞬时和短期格局主要受土壤中存留的原始CO2的浓度及其扩散过程控制,(2)长期格局则由资源水平和环境条件共同决定的土壤CO2生产能力主导.文章进一步揭示了建立包含垂直分层的SOC分解和CO2扩散过程的生态系统模型的必要性.     

Observations on the function of the glands of the foot of the pediveliger of Ostrea edulis during settlement

The use during settlement of secretions of the 9 different types of gland in the foot of the pediveliger of Ostrea edulis L. was examined experimentally. During settlement, there is a progressive decrease in the crawling speed of the larva and a strengthening of its bond with the substratum. Both changes are related to (a) a change from ciliary to muscular pedal locomotion; (b) the increasing acidity and viscosity of the mucoid secretions used; (c) the secretion of a byssus thread by the glands of the byssus duet; (d) changes in the form and composition of this byssus. At the termination of settlement, the entire contents of 2 types of gland are discharged. Their secretions give rise to the cement which permanently fixes the larva to the substratum. The 9 types of gland are utilised sequentially in a manner closely related to the 6 phases recognised in settlement behaviour.     

Behavioral aspects of sperm competition in cuttlefish, Sepia officinalis (Sepioidea: Cephalopoda)

Sexual selection studies in cephalopods indicate that sperm competition is a central feature of their mating systems, yet this has not been studied experimentally in any detail. In 1998 we staged 20 matings of the cuttlefish, Sepia officinalis L., in the laboratory. Males rapidly initiated mating in the “head-to-head” position, with no apparent courtship. Mating lasted an average of 10 min (range 7 to 14 min). For the first 6 min (on average 63% of the mating duration), the male flushed strong jets of water directly at the female's buccal membrane, which sometimes resulted in the expulsion of parts of spermatangia placed there in recent matings. Then, in a single discrete movement that lasted an average of only 14 s, the male's modified fourth left arm – the hectocotylus – wrapped around a single large bundle of spermatophores (ca. 150 to 300) and transferred them to the female's buccal membrane. For the remainder of the mating (average 3 min, range 1.5 to 5.0 min), the hectocotylus repeatedly broke the spermatophores open, and manipulated them, so that sperm were released and many spermatangia were attached along the ventral buccal membrane, near the paired seminal receptacles. Approximately 140 spermatangia were attached in rows 3 to 5 deep around the ventral buccal membrane in a single mating; the rest were usually discarded during mating. Histology revealed that each of the seminal receptacles consists of a series of sperm storage bulbs connected by a central duct, which leads to a single pore at the surface of the buccal membrane. Baseline data on sperm motility were obtained, but the mechanism by which sperm enter the seminal receptacle remains unknown. Females seemed to initiate termination of mating, then males guarded their mates temporarily. These results, combined with other recent laboratory experiments, provide evidence that sperm competition may be a major feature of the mating system of S. officinalis. Received: 4 January 1999 / Accepted: 18 May 1999     

Modeling porosity reductions caused by mineral fouling in continuous-wall permeable reactive barriers

A study was conducted to assess key factors to include when modeling porosity reductions caused by mineral fouling in permeable reactive barriers (PRBs) containing granular zero valent iron. The public domain codes MODFLOW and RT3D were used and a geochemical algorithm was developed for RT3D to simulate geochemical reactions occurring in PRBs. Results of simulations conducted with the model show that the largest porosity reductions occur between the entrance and mid-plane of the PRB as a result of precipitation of carbonate minerals and that smaller porosity reductions occur between the mid-plane and exit face due to precipitation of ferrous hydroxide. These findings are consistent with field and laboratory observations, as well as modeling predictions made by others. Parametric studies were conducted to identify the most important variables to include in a model evaluating porosity reduction. These studies showed that three minerals (CaCO3, FeCO3, and Fe(OH)2 (am)) account for more than 99% of the porosity reductions that were predicted. The porosity reduction is sensitive to influent concentrations of HCO3-, Ca2+, CO3(2-), and dissolved oxygen, the anaerobic iron corrosion rate, and the rates of CaCO3 and FeCO3 formation. The predictions also show that porosity reductions in PRBs can be spatially variable and mineral forming ions penetrate deeper into the PRB as a result of flow heterogeneities, which reflects the balance between the rate of mass transport and geochemical reaction rates. Level of aquifer heterogeneity and the contrast in hydraulic conductivity between the aquifer and PRB are the most important hydraulic variables affecting porosity reduction. Spatial continuity of aquifer hydraulic conductivity is less significant.     

化学溶胀法分离废弃线路板中金属与基板

废弃线路板的粉碎和所含金属组分的高效解离是后续分选回收的前提条件。本研究分别使用乙二胺等10种溶剂浸泡废弃线路板,比较对线路板中铜箔与基板间剥离强度的影响,从而筛选出4种有代表性的溶剂,即溶剂D、溶剂F、丙酮和水, 比较废弃线路板经化学溶胀后的单体解离度和获得一定粒径分布的颗粒所需的破碎时间。研究结果表明,化学溶胀后破碎能大幅提高金属的单体解离度,浸泡效果的优良排序为：溶剂D>溶剂F>丙酮>水;浸泡时间越长,浸泡温度越高,对剥离强度的降低越有利;使用溶剂D在150℃、3 h或140℃、5 h的工艺下浸泡废弃线路板,可以使铜箔与基板自动脱落。研究结果为后续的分选提供了便利的条件。     

Ammonia emission from grassland and livestock production systems in the UK

Emissions of ammonia were measured from livestock excreta and fertilisers applied to grass swards, from grazed paddocks, from decomposing grass herbage and from an animal house containing dairy cows. Emissions from urine, dung, slurry and fertilisers were determined using a system of wind tunnels with each tunnel covering an area of 1 m(2). Emissions from grazed swards were determined using a micrometeorological mass balance method. From the results of these measurements, together with other published information, an inventory for ammonia emissions has been calculated for grassland and livestock production systems over the UK as a whole. It is estimated that emissions from grassland and cattle and sheep production amount to about 230 kt NH(3)-N annually, while emissions from pig and poultry production amount to about 40 kt and 80 kt NH(3)-N, respectively.