Too much,too soon? Two Swedish case studies of short-term deadwood recruitment in riparian buffers

Forested riparian buffers are retained along streams during forest harvest to maintain a number of ecological functions. In this paper, we examine how recently established riparian buffers along northern Swedish streams provide deadwood, a key objective for riparian buffer management in Sweden. We used observational and experimental data to show that the investigated buffers provided large volumes of deadwood to streams and riparian zones shortly after their establishment, likely jeopardizing continued recruitment over the long term. Deadwood volume decreased with increasing buffer width, and the narrowest buffers tended to blow down completely. Wider buffers (~ 15 m) provided similar volumes of deadwood as narrow buffers due to blowdowns but were, overall, more resistant to wind-felling. It is clear from our study, that wider buffers are currently a safer strategy for riparian management that aims to sustain provision of deadwood and other ecological objectives continuously on the long term.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-022-01793-1.     

Computational fluid dynamics simulations of hydrogen releases and vented deflagrations in large enclosures

This paper presents model predictions obtained with the CFD tool FLACS for hydrogen releases and vented deflagrations in containers and larger enclosures. The paper consists of two parts. The first part compares experimental results and model predictions for two test cases: experiments performed by Gexcon in 20-foot ISO containers (volume 33 m³) as part of the HySEA project and experiments conducted by SRI International and Sandia National Laboratories in a scaled warehouse geometry (volume 45.4 m³). The second part explores the use of the model system validated in the first part to accidental releases of hydrogen from forklift trucks inside a full-scale warehouse geometry (32 400 m³). The results demonstrate the importance of using realistic and reasonably accurate geometry models of the systems under consideration when performing CFD-based risk assessment studies. The discussion highlights the significant inherent uncertainty associated with quantitative risk assessments for vented hydrogen deflagrations in complex geometries. The suggestions for further work include a pragmatic approach for developing empirical correlations for pressure loads from vented hydrogen deflagrations in industrial warehouses with hydrogen-powered forklift trucks.     

论库区贫困与库区发展：以山东大中型水库区为例

水库区是水库水面与周边陆地的区域复合体。本文以山东大中型水库区为例，在调查研究的基础上，探讨了库区贫困的根源及库区脱贫的出路，并提出了库区发展的战略构想。     

扭—压复合加载变形基础的研究

扭—压复合加载成形工艺是一种有效地利用工件与工具间摩擦的有害作用,达到减小变形力、改善工件组织性能的新方法。本文介绍了实现扭—压变形的实验装置,并对工艺因素对扭—压复合加载变形的影响作了阐述。     

Public Perception as a Barrier to Introducing Wood in Rivers for Restoration Purposes

Reintroduction of wood in rivers for restoration purposes is now recognized in a positive way by scientists. Nevertheless, the perception of wood in riverscapes is strongly affected by the socio-cultural environment. This cultural influence might explain why wood reintroduction is accepted and promoted in some regions of the world but not in others, despite the demonstrated ecological benefits. From an extensive student perception survey, we show that most of the groups from nine countries in the world considered riverscapes with wood to be less aesthetic, more dangerous, and needing more improvement than riverscapes without wood. By contrast, this way of thinking was not observed in Germany, Sweden, and Oregon (USA), where the first instances of wood reintroduction occurred.     

Large Woody Debris and Land Management in California’s Hardwood-Dominated Watersheds

Although large woody debris (LWD) has been studied extensively in conifer-dominated watersheds, relatively little is known about LWD in hardwood-dominated watersheds. Field surveys of 32 hardwood-dominated stream reaches in northern coastal California revealed that levels of LWD varied with land ownership and that living trees strongly influenced debris jam formation. Almost half of the channel-spanning debris jams, which stored the most wood and were most likely to form a pool, were formed behind a key piece that was still living. These living key pieces might provide greater longevity and stability than would otherwise be expected from hardwood LWD. Compared to streams on private land, streams on public land had significantly greater LWD loading and debris-jam frequency. Land management practices that remove wood from streams might be contributing to the degradation of salmonid habitat in Californias hardwood-dominated watersheds.     

气瓶水压试验合格标准实验研究

水压试验是气瓶检验的主要项目,将容积残余变形率超过１０％ 作为气瓶报废的标准沿用至今。笔者通过实验,分析了气瓶水压试验现行评定标准存在的问题,并对采用容积弹性变形作为评定指标进行了探讨,以期为制订更合理的水压试验标准提供有益的启示。     

吹吸罩在大型酸洗槽上的应用研究

大型酸洗槽的酸雾收集处理是很多企业污染治理的难题,不仅造成环境污染,而且直接威胁操作人员的健康,为解决此问题,我们利用吹风射流作用将有害物质输送到排风罩口附近并被排走的原理,通过研究吹吸气流的合理设计和计算方法,研制和设计了应用于大型酸洗槽的酸雾收集处理吹吸罩装置,实现了在减少抽风量,降低动力消耗基础上,有效提高酸雾收集效率,并且便于操作,应用前景广阔。     

Analysis of the velocity field in a large rectangular channel with lateral shockwave

In this work the authors describe the main characteristics of the velocity field of hydraulic jumps in a very large channel where lateral shockwaves occur. Experiments were carried out at the Coastal Engineering Laboratory of the Water Engineering and Chemistry Department of the Technical University of Bari (Italy). Extensive flow velocity measurements were investigated in order to have a clearer understanding of both hydraulic jump development and lateral shockwave formation in a very large channel. Eight experiments were performed in a 4m wide rectangular channel; the experiments differed in the inlet Froude number F ₀ and the jump type. Seven tests were carried out with undular jumps and one with a roller jump. The flow velocity and the flow free surface measurements were taken using a two-dimensional Acoustic Doppler Velocimeter (ADV) and an ultrasonic profiler, respectively. The experimental results can be summarized as follow: (i) the formation of well developed lateral shockwaves similar to those of oblique jumps were observed; (ii) the comparison of the experimental and theoretical data shows that the classic shockwave theory is sufficiently confirmed in the analyzed range of Reynolds number, taking into account the experimental errors and the difference between the theoretical and experimental assumptions; (iii) the transversal flow velocity profiles in the recirculating zone show a good agreement with the numerical simulations presented in literature in the case of a separated turbulent boundary layer over a flat plate. This conclusion enables us to confirm the hypothesis that the lateral shockwaves in the channel are the result of a boundary layer which, as observed, forms on the channel sidewalls.