Estimating the effect of water fog and nitrogen dilution upon the burning velocity of hydrogen deflagrations from experimental test data

Both very fine water mist fogs and oxygen depletion (via nitrogen dilution) have been suggested as possible methods of mitigating the overpressure rise should a hydrogen-air deflagration occur. A study has therefore been made to investigate the potential mitigating effect of very fine water mist fogs and oxygen reduction on the propagation of general hydrogen-oxygen-nitrogen flames. To do this a mathematical model was fitted to and used to estimate the burning velocity from a large number of pressure-time test data sets. These were obtained using a cylindrical explosion rig for both unmitigated and mitigated hydrogen-air deflagrations with nitrogen diluted (oxygen depleted) atmospheres and water fogs present. The experimental data examined covers both lean and rich hydrogen mixtures and a range of nitrogen dilution levels and water fog densities. The results suggest that the combination of high density water fog and nitrogen dilution can be extremely effective in reducing the estimated burning velocity especially for hydrogen rich H₂–O₂–N₂ mixtures with equivalence ratio >1 – even at relatively modest dilution levels where the oxygen index is reduced to 16%.     

Modeling effectiveness of agricultural BMPs to reduce sediment load and organophosphate pesticides in surface runoff

Quantifying effectiveness of agricultural BMPs at the watershed scale is a challenging issue, requiring robust algorithms to simulate not only the agricultural production system but also pollutant transport and fate. This research addresses the challenge to simulate performances of BMPs in reducing organophosphates (OPs) runoff at the watershed scale. The SWAT model is calibrated and validated following a sensitivity analysis combining Latin Hypercube sampling and One-factor-At-a-Time simulation. The calibrated model is then applied in the Orestimba Creek Watershed to simulate BMPs including buffer strips, sediment ponds, vegetated ditches, use reduction, and their combinations. BMP simulation suggested that sediment ponds trap 54-85% of sediment from field runoff, but less than 10% of dissolved diazinon and chlorpyrifos. Use reduction can reduce pesticide load in a close-to-linear fashion. Effectiveness of vegetated ditches and buffers depends on their physical dimension and vegetation cover. Combining individual BMPs provides enhanced mitigation effects. The combination of vegetated ditches, buffer strips and use reduction decreases diazinon and chlorpyrifos load by over 94%. This study has suggested that the SWAT model reasonably predicts BMP effectiveness at the watershed scale. Results will assist decision making in implementing BMPs to reduce pesticide loads in surface runoff.     

Development of a Structure for Blast Wave Mitigation

The internal structure of a blast containment container has been developed and examined by experiments involving the explosion of a high explosive. A steel pipe was selected as an effective structure for blast mitigation, because it dramatically reduces the blast wave in the radial direction near the explosion source. To also reduce the blast wave in the axial direction, two types of model structures consisting of a steel pipe as the main part were examined by both high‐speed photography and pressure measurements of the blast waves. A 0.34‐scale internal structure was constructed by combining these structures. To induce a powerful mitigation effect, the internal structure was filled with a shock‐absorbing material. The peak pressures of C4 explosions in free air were obtained on the basis of the published blast wave data for TNT explosions in free air using an equivalent weight of 1.37. The peak pressures of the blast waves from the structures for all cases were compared with the blast wave data for C4 explosions in free air to estimate the blast mitigation effect. As a result it was estimated that the internal structure not only eliminates the blast pressure in the radial direction but also reduces the blast wave in the axial direction by 36 %. By combining the effects of the internal structure and the shock‐absorbing material, the structure can reduce the peak pressure by 75 %.     

Impact of freezing and thawing on the quality of meat: review

This comprehensive review describes the effects of freezing and thawing on the physical quality parameters of meat. The formation of ice crystals during freezing damages the ultrastructure and concentrates the solutes in the meat which, in turn, leads to alterations in the biochemical reactions that occur at the cellular level and influence the physical quality parameters of the meat. The quality parameters that were evaluated are moisture loss, protein denaturation, lipid and protein oxidation, colour, pH, shear force and microbial spoilage. Additionally mechanisms employed to mitigate the effects of freezing and thawing were also reviewed. These include the use of novel methods of freezing and thawing, ante and post mortem antifreeze protein inclusion and vitamin E supplementation, brine injection and modified atmospheric packaging.     

校园建筑安全与防灾减灾问题研究——以华南理工大学五山校区为例

基于当前防灾理念,以华南理工大学五山校园已落成的各主要建筑为研究对象,分析高校建筑主要灾害及隐患特征,总结了影响校园建筑安全问题的相关因素和最普遍的威胁类型。指出对已落成建筑物存在的安全隐患进行调查,并采取相应的防范措施,提高校园安全容量和防灾减灾能力,是城市防灾工作的重要组成部分。     

福州温泉生态城布局方案的情景分析法初探

城市用地布局总体框架由用地评价、情景归纳、情景模拟三个步骤组成。（1）进行用地适宜性评价;（2）分析影响土地使用规划的关键因素及其驱动力,在此基础上根据驱动力的状态分类归纳出若干情景方案;（3）进行情景模拟,在地理信息系统的支持下得到不同情景方案。在不同的发展阶段,模拟城市不同的发展情况,并提出响应各个情景的规划方案。该论文结合福州温泉生态城的实例讨论了这一方法的工作流程以及相应的技术支持。旨在探索一种实用的基于GIS的城市用地布局情景模拟与方案评价方法,为相关的研究提供一定的借鉴意义。     

A Shift Towards Landscape-Scale Approaches in Compensation - Suitable Mechanisms and Open Questions

ABSTRACT

Landscape-scale mitigation approaches reflect a shift from a project-by-project approach to more strategic planning by applying the mitigation hierarchy – avoidance, minimization, compensation – for impacts on natural resources on a larger scale. This paper discusses requirements for the implementation of landscape-scale mitigation approaches in general. It continues with a criteria-based analysis of compensation mechanism under the Endangered Species Act – conservation banks, in-lieu fees, and permittee-responsible mitigation – to determine which mechanism best meets these requirements. Findings show that, in theory, conservation banks are best-suited to implement landscape-scale compensation. However, evidence for claimed benefits of third-party mitigation and large-scale mitigation approaches is lacking. The article concludes by identifying a number of open questions in the field.     

Ecological compensation: an evaluation of regulatory compliance in New Zealand

Ecological compensation is an example of a trade-off whereby loss of natural values is remedied or offset by a corresponding compensatory action on the same site or elsewhere, determined through the process of Environmental Impact Assessment (EIA). Ecological compensation actions are often criticised for having low levels of compliance: meaning that they are achieved only partially or not at all, while development activity proceeds with much greater certainty. Our research investigated compliance with 245 conditions relating to ecological compensation across 81 case studies across New Zealand under the Resource Management Act 1991. Our results show that present tools and practice in New Zealand are not adequately securing the necessary benefits from ecological compensation requirements, with 35.2% of requirements not being achieved. Significant variation in non-compliance with ecological compensation occurs between different activities, applicant types and condition types, while critical variables within the planning process influence levels of compliance. Our research demonstrates the importance of understanding the nature of non-compliance and of providing a consistent and robust decision-making framework for the consideration of ecological compensation in practice.     

基于FIR模型的多径抑制方法研究

多径效应是卫星导航系统的主要误差源之一。在现有研究中,基于最大似然估计准则的方法被认为是最佳的多径抑制技术,但是当存在多路信号且路径数量未知时,其计算尤为复杂。本文提出了一种基于FIR模型的多径抑制方法,利用基准相关函数和最小均方误差准则对接收信号进行参数估计和多径信号对消。该方法具有实现简单,易于实时信号处理,计算量与多径路数无关等优点。仿真结果表明,其性能略优于基于最大似然估计准则的MEDLL（Multipath Estimating Delay Lock Loop）技术。      

Coal and energy security for India: Role of carbon dioxide (CO2) capture and storage (CCS)

Coal is the abundant domestic energy resource in India and is projected to remain so in future under a business-as-usual scenario. Using domestic coal mitigates national energy security risks. However coal use exacerbates global climate change. Under a strict climate change regime, coal use is projected to decline in future. However this would increase imports of energy sources like natural gas (NG) and nuclear and consequent energy security risks for India. The paper shows that carbon dioxide (CO₂) capture and storage (CCS) can mitigate CO₂ emissions from coal-based large point source (LPS) clusters and therefore would play a key role in mitigating both energy security risks for India and global climate change risks. This paper estimates future CO₂ emission projections from LPS in India, identifies the potential CO₂ storage types at aggregate level and matches the two into the future using Asia-Pacific Integrated Model (AIM/Local model) with a Geographical Information System (GIS) interface. The paper argues that clustering LPS that are close to potential storage sites could provide reasonable economic opportunities for CCS in future if storage sites of different types are further explored and found to have adequate capacity. The paper also indicates possible LPS locations to utilize CCS opportunities economically in future, especially since India is projected to add over 220,000 MW of thermal power generation capacity by 2030.