Gallium nitride (GaN) power devices are an emerging technology that have only recently become available commercially. This new technology enables the design of converters at higher frequencies and ...efficiencies than those achievable with conventional Si devices. This paper reviews the characteristics and commercial status of both vertical and lateral GaN power devices, providing the background necessary to understand the significance of these recent developments. In addition, the challenges encountered in GaN-based converter design are considered, such as the consequences of faster switching on gate driver design and board layout. Other issues include the unique reverse conduction behavior, dynamic R ds,on , breakdown mechanisms, thermal design, device availability, and reliability qualification. This review will help prepare the reader to effectively design GaN-based converters, as these devices become increasingly available on a commercial scale.
•The paper reviews recent image plant segmentation-based methods (from 2008–2015).•We highlight the advantages and disadvantages for colour index-based methods.•The advantages and disadvantages of ...threshold-based approaches are discussed.•The advantages and disadvantages of learning-based approaches are also summarised.•The challenges and limitations of current segmentation approaches are highlighted.•Some specific algorithms that may be suit particular conditions are suggested.
In this review, we present a comprehensive and critical survey on image-based plant segmentation techniques. In this context, “segmentation” refers to the process of classifying an image into plant and non-plant pixels. Good performance in this process is crucial for further analysis of the plant such as plant classification (i.e. identifying the plant as either crop or weed), and effective action based on this analysis, e.g. precision application of herbicides in smart agriculture applications.
The survey briefly discusses pre-processing of images, before focusing on segmentation. The segmentation stage involves the segmentation of plant against the background (identifying plant from a background of soil and other residues). Three primary plant extraction algorithms, namely, (i) colour index-based segmentation, (ii) threshold-based segmentation, (iii) learning-based segmentation are discussed. Based on its prevalence in the literature, this review focuses in particular on colour index-based approaches. Therefore, a detailed discussion of the segmentation performance of colour index-based approaches is presented, based on studies from the literature conducted in the recent past, particularly from 2008 to 2015. Finally, we identify the challenges and some opportunities for future developments in this space.
The corticothalamic system is organized to play a key role in synchronizing the activities of thalamic and cortical neurons. Its synapses dominate the inputs to relay cells and to the GABAergic cells ...of the reticular nucleus; its organization in focused and diffuse projections promotes both coherent activity of relay neurons and the spread of activity across the cortex and thalamus. The capacity of relay neurons to operate in voltage‐dependent tonic or burst mode permits corticothalamic inputs to directly excite the relay cells or indirectly inhibit them via the reticular nucleus. This enables the corticothalamic projection to synchronize high‐ or low‐frequency oscillatory activity, respectively, in the thalamo–corticothalamic network. Differences in the subunit composition of AMPA receptors at synapses formed by branches of the same corticothalamic axon in the reticular nucleus and dorsal thalamus are an important element in the capacity of the cortex to synchronize low‐frequency oscillations in the network. Intrinsic voltage‐gated calcium channels of different kinds expressed in the relay neurons form a substrate for corticothalamic interactions with the relay cells that promote high‐ or low‐frequency oscillations. Focused corticothalamic axons arising from layer VI cortical cells and diffuse corticothalamic axons arising from layer V cortical cells, in conjunction with the core and matrix cells of the dorsal thalamus, form a substrate for synchronization of widespread populations of cortical and thalamic cells during high‐frequency oscillations that underlie discrete conscious events.
Operating Room Fires Jones, Teresa S; Black, Ian H; Robinson, Thomas N ...
Anesthesiology (Philadelphia),
2019-March, 2019-03-00, 2019-03-01, 20190301, Letnik:
130, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Operating room fires are rare but devastating events. Guidelines are available for the prevention and management of surgical fires; however, these recommendations are based on expert opinion and case ...series. The three components of an operating room fire are present in virtually all surgical proceduresan oxidizer (oxygen, nitrous oxide), an ignition source (i.e., laser, “Bovie”), and a fuel. This review analyzes each fire ingredient to determine the optimal clinical strategy to reduce the risk of fire. Surgical checklists, team training, and the specific management of an operating room fire are also reviewed.
Beyond the post-industrial city Ferm, Jessica; Jones, Edward
Urban Studies,
11/2017, Letnik:
54, Številka:
14
Journal Article, Book Review
Recenzirano
Odprti dostop
This paper examines the challenges that planners face if industry is to survive and thrive in a growing ‘post-industrial’ city. It examines London, where the difference between the value of land for ...residential and industrial use, and the pressure to address the housing crisis, is leading to the rapid loss of industrial land and premises. The paper first explores the role of industry in a highvalue city such as London, arguing that trends in manufacturing in advanced economies are increasing the benefit for firms of an urban location, whilst at the same time, cities continue to need industry if they are to be economically and socially resilient, sustainable and vibrant. The paper then explores current approaches to planning for industry in London, identifying impacts of a policy framework that anticipates and plans for its decline. Finally, it focuses on the question of how to plan for a productive and inclusive city: we explore the arguments in favour of integrating industry into the urban fabric as well as the benefits of separating land uses and retaining employment land designations, and reveal how urbanists are divided. We argue that if London is to continue to prosper, and meet the needs of all Londoners, then we need to strategically and proactively plan for industry in the city, to experiment with innovative ways of integrating it with other city uses, whilst protecting land for industry, where required. We put forward a critical research agenda to effectively meet this challenge in the future.
本文考察了在一个蓬勃发展的“ 后工业” 城市，工业要想生存和繁荣，规划者面临着何种难题。 在伦敦，居住用地与工业用地之间价值的差异，以及应对住房危机的压力，正在导致工业用地 和工业设施快速消亡，本文对此做了考察。文章首先探讨了工业在伦敦这样的高价值城市中的 作用，认为发达经济中的制造业发展趋势使城区企业更加获益；同时，城市要想在经济层面和 社会层面保持弹力、可持续力和活力，就依然需要工业。然后，本文探讨了目前在伦敦规划工 业的几种方式，指明了一种预期并规划工业衰落的政策框架带来的影响。最后，文章重点讨论 如何规划一个富有生产力和包容度的城市：我们探讨了支持将工业整合入城市肌理的观点，以 及区分土地用途和保留使用权土地称号的益处，并揭示了城市研宄学者如何分立阵营。我们认 为，如果伦敦想要继续繁荣，并满足所有伦敦人的需求，那我们就需要以战略性的方式主动规 划城市中的工业，尝试用创新的方式将其与其他城市用途整合，同时在需要的时候保护工业用 地。我们提出了一项关键的研宄计划，以求在未来迎接这一挑战。
The double pulse test (DPT) is a widely accepted method to evaluate the dynamic behavior of power devices. Considering the high switching-speed capability of wide band-gap devices, the test results ...are very sensitive to the alignment of voltage and current (V-I) measurements. Also, because of the shoot-through current induced by C dv/dt (i.e., cross-talk), the switching losses of the nonoperating switch device in a phase-leg must be considered in addition to the operating device. This paper summarizes the key issues of the DPT, including components and layout design, measurement considerations, grounding effects, and data processing. Additionally, a practical method is proposed for phase-leg switching loss evaluation by calculating the difference between the input energy supplied by a dc capacitor and the output energy stored in a load inductor. Based on a phase-leg power module built with 1200-V/50-A SiC MOSFETs, the test results show that this method can accurately evaluate the switching loss of both the upper and lower switches by detecting only one switching current and voltage, and it is immune to V-I timing misalignment errors.
Continually improving and affordable wastewater management provides opportunities for both
pollution reduction and clean water supply augmentation, while simultaneously promoting
sustainable ...development and supporting the transition to a circular economy. This study aims to
provide the first comprehensive and consistent global outlook on the state of domestic and
manufacturing wastewater production, collection, treatment and reuse. We use a data-driven approach,
collating, cross-examining and standardising country-level wastewater data from online data
resources. Where unavailable, data are estimated using multiple linear regression. Country-level
wastewater data are subsequently downscaled and validated at 5 arcmin
(∼10 km) resolution. This study estimates global wastewater production at 359.4×109 m3 yr−1, of which 63 % (225.6×109 m3 yr−1) is
collected and 52 % (188.1×109 m3 yr−1) is treated. By extension, we
estimate that 48 % of global wastewater production is released to the environment untreated,
which is substantially lower than previous estimates of ∼80 %. An estimated 40.7×109 m3 yr−1 of treated wastewater is intentionally reused. Substantial
differences in per capita wastewater production, collection and treatment are observed across
different geographic regions and by level of economic development. For example, just over 16 %
of the global population in high-income countries produces 41 % of global wastewater. Treated-wastewater reuse is particularly substantial in the Middle East and North Africa (15 %) and
western Europe (16 %), while comprising just 5.8 % and 5.7 % of the global population,
respectively. Our database serves as a reference for understanding the global wastewater status
and for identifying hotspots where untreated wastewater is released to the environment, which are
found particularly in South and Southeast Asia. Importantly, our results also serve as a baseline
for evaluating progress towards many policy goals that are both directly and indirectly connected
to wastewater management. Our spatially explicit results available at 5 arcmin
resolution are well suited for supporting more detailed hydrological analyses such as water
quality modelling and large-scale water resource assessments and can be accessed at
https://doi.org/10.1594/PANGAEA.918731 (Jones
et al., 2020).
Water scarcity threatens people in various regions, and has predominantly been studied from a water quantity perspective only. Here we show that global water scarcity is driven by both water quantity ...and water quality issues, and quantify expansions in clean water technologies (i.e. desalination and treated wastewater reuse) to 'reduce the number of people suffering from water scarcity' as urgently required by UN's Sustainable Development Goal 6. Including water quality (i.e. water temperature, salinity, organic pollution and nutrients) contributes to an increase in percentage of world's population currently suffering from severe water scarcity from an annual average of 30% (22%-35% monthly range; water quantity only) to 40% (31%-46%; both water quantity and quality). Water quality impacts are in particular high in severe water scarcity regions, such as in eastern China and India. In these regions, excessive sectoral water withdrawals do not only contribute to water scarcity from a water quantity perspective, but polluted return flows degrade water quality, exacerbating water scarcity. We show that expanding desalination (from 2.9 to 13.6 billion m3 month−1) and treated wastewater uses (from 1.6 to 4.0 billion m3 month−1) can strongly reduce water scarcity levels and the number of people affected, especially in Asia, although the side effects (e.g. brine, energy demand, economic costs) must be considered. The presented results have potential for follow-up integrated analyses accounting for technical and economic constraints of expanding desalination and treated wastewater reuse across the world.
Rising water demands and diminishing water supplies are exacerbating water scarcity in most world regions. Conventional approaches relying on rainfall and river runoff in water scarce areas are no ...longer sufficient to meet human demands. Unconventional water resources, such as desalinated water, are expected to play a key role in narrowing the water demand-supply gap. Our synthesis of desalination data suggests that there are 15,906 operational desalination plants producing around 95 million m3/day of desalinated water for human use, of which 48% is produced in the Middle East and North Africa region. A major challenge associated with desalination technologies is the production of a typically hypersaline concentrate (termed ‘brine’) discharge that requires disposal, which is both costly and associated with negative environmental impacts. Our estimates reveal brine production to be around 142 million m3/day, approximately 50% greater than previous quantifications. Brine production in Saudi Arabia, UAE, Kuwait and Qatar accounts for 55% of the total global share. Improved brine management strategies are required to limit the negative environmental impacts and reduce the economic cost of disposal, thereby stimulating further developments in desalination facilities to safeguard water supplies for current and future generations.
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•Unconventional water resources are key to support SDG 6 achievement.•Desalinated water production is 95.37 million m3/day.•Brine production and energy consumption are key barriers to desalination expansion.•Brine production is 141.5 million m3/day, 50% greater than previous estimates.•Innovation and developments in brine management and disposal options are required.
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