Revisiting the size selective performance of EPA's high-volume total suspended particulate matter (Hi-Vol TSP) sampler

Under the National Ambient Air Quality Standard (NAAQS) for airborne lead, measurements are conducted by means of a high-volume total suspended particulate matter (Hi-Vol TSP) sampler. In the decade between 1973 and 1983, there were 12 publications that explored the sampling characteristics and effectiveness of the Hi-Vol TSP, yet there persists uncertainty regarding its performance. This article presents an overview of the existing literature on the performance of the Hi-Vol TSP, and identifies the reported sampler effectiveness with respect to four factors: particle size (reported effectiveness of 7%–100%), wind speed (?36% to 100%), sampler orientation (7%–100%), and operational state (107%–140%). Effectiveness of the Hi-Vol TSP was evaluated with a solid, polydisperse aerosol in a controlled wind tunnel setting. Isokinetic samplers were deployed alongside the Hi-Vol TSP to investigate three wind speeds (2, 8, and 24 km h^?1), three sampler orientations (0°, 45°, 90°), and two operational states (on, off) for aerosols with aerodynamic diameters from 5 to 35 µm. Results indicate that particle diameter was the largest determining factor of effectiveness followed by wind speed. Orientation of the sampler did not have a significant effect at 2 and 8 km h^?1 but did at 24 km h^?1. In a passive state, the Hi-Vol TSP was collected between 1% and 7% of available aerosol depending on particle size and wind speed. Results of this research do not invalidate results of previous studies but rather contribute to our overall understanding of the Hi-Vol TSP's size-selective performance. While results generally agreed with previous studies, the Hi-Vol TSP was found to exhibit less dependence on these four factors than previously reported.

© 2017 American Association for Aerosol Research     

基于Park变换的单相光伏并网控制研究

近年来,LCL滤波器由于体积小、滤波效果好等优点在光伏并网系统中获得了广泛应用。采用并网电流、电容电流双闭环控制能够有效抑制LCL滤波器振荡,提高并网系统稳定性,但传统PI控制无法实现对交流并网电流的无静差跟踪。因此,提出了一种基于Park变换的双电流闭环控制策略,它能够大大提高并网功率因数,减小入网电流的总谐波失真(THD)。该方法首先通过构造虚拟正交电流分量,将单相并网电流虚拟为α-β坐标系下两相正交电流,然后基于Park变换,在旋转坐标系下进行PI控制,从而实现无静差控制。最后,通过Matlab仿真验证了这种控制策略的正确性和有效性。     

Heaven on Earth

‘By 2050 we will have probed the universe even further, peeling back time as we strive for some sense of creation and meaning.’ The world's first neurologist in space, Roberta L Bondar , who conducted international experiments on space mission STS 42 and has subsequently undertaken neurological research with NASA, urges us to look up and into space, which is set to remain a rich area of exploration, scientific investigation and wonder, with the discovery of new planets, light, patterns and materials on the not-so-distant horizon.     

Empowering Communities Through Design

Francesca Galeazzi is an architectural engineer who leads the sustainability team at Arup Associates in Shanghai. Here she looks back with hindsight from 2050, reflecting on how rapid urbanisation in China, which started in the 1990s, played out over the next half-century. She describes how the initial highly centralised, mass urbanisation programmes gave way to a more local and community-based, participatory approach to decision-making and planning, foreshadowed by some key legislation around land ownership and design for community-based planning models in the early 2010s.     

In the Pursuit of Pleasure: The Not so Fleeting Life of the Pavilion and its Ilk

Author and architecture critic for the London Evening Standard, Robert Bevan reflects on the enduring appeal of the temporary structure, speaking ‘to a latent desire for freedom and movement’ as a hangover of our nomadic past in a sedentary ‘civilised’ society. He highlights the type's historical apex in Henry VIII's palatial pop-up on the Field of the Cloth of Gold, questioning the purpose and purposelessness of more recent examples.     

Castles and Pavilions: Creating New Hybrid Places of Exchange

Tom Holbrook , Director at architecture and urban design practice 5th Studio, describes two projects in the south of England that respond spatially to the needs of ‘the knowledge economy’. The first is the River Lea Park, to the east of London, which promotes open connectivity between people in a post- industrial landscape; and the second is the Creative Exchange in St Neots, Cambridgeshire, a building designed to accommodate local enterprise. Both are designed to redirect social and economic activities, supporting creative swarming, and establishing what Stafford Beer has coined as ‘platforms for change’.     

The Stuttgart Region's Landscape Park – an efficient concept for the development of open spaces – an integrated approach to an attractive and resilient metropolitan landscape

This article focuses on the Stuttgart Region's Landscape Park concept, which is an instrument for the balanced development of open spaces within a densely populated region. The Stuttgart Region covers 5 counties and 179 independent municipalities over an area of 3650 square kilometres in the southwestern part of Germany. The competences of the Verband Region Stuttgart cover not only (mandatory) regional planning and spatial development, but also the construction and operation of the regional railway system, economic development and marketing.

In this context, the Landscape Park has been introduced to enhance the ecological quality and recreational value of open spaces. By now, it has become a successful instrument which helps local institutions to develop green infrastructure as an important locational factor.     

城市文化创意园区研究--以台北华山1914文化创意园区为例

文化创意园区是文化创意产业在空间上出现群聚,产业之间连接而形成的结果。不可忽略的是,文化创意园区的形成与后工业时代都市产业结构的改变是有关的,其与都市的发展是息息相关的。延续中西方文献对都市中闲置空间再利用的研究成果,结合文化产业的创新与文化园区的设置,引导出台湾文化产业与文化园区的设置,并以华山1914为例,分析台北市与设置文化园区的利害关系。台湾设置文化创意园区、对台湾的后工业时期经济的发展、产业结构的转型,产业能量的提升、城市营销高附加价值的创造有很大的正面影响。     

极简主义景观对当代风景园林建设的启示——以伯纳特公园为例

伯纳特公园注重景观的功能性,因地制宜的创造景观,在景观设计中,敢于创新,将4个景观层次统一在一个单纯的秩序之中;对光进行特殊设计,注重景观意境的营造：通过对伯纳特公园的设计手法和设计思想的分析,总结了极简主义景观对当今风景园林建设的启示。