Insect habitat management in pasture systems

Two important habitat management strategies in pasture systems involve controlled burning and effective grazing manipulation schemes to maintain native climax grassland vegetation These climax grasslands have historically suffered less insect pest pressure than imported systems However, these types of grasslands are difficult to reestablish after relatively severe disruption by man Also, the proper diversity and stability is difficult to capture in developing imported systems. Imported pastures can exhibit substantial yields per land unit but are often composed of vegetation that rapidly mines nutrients stored by the native vegetation, and often need considerable inputs of fossil fuel, manufactured fertilizers and pesticides, because they are or become very susceptible to pestiferous insects. Habitat manipulation efforts can be effective in regulating forage pest populations below economic levels in imported pasture systems Such efforts include: 1) land use (coupled with plant diversity, grazing, and harvest manipulations), 2) sanitation (including controlled burning), 3) planting dates and harvest times (including grazing manipulations), 4) tillage methods, 5) fertilization, 6) trap crops, 7) water management, and 8) fire management for insect pest suppression and augmentation of natural enemies.     

谈森林防火中的计划火烧

计划火烧是预防森林火灾的一种有效手段,成本低,效果显著。本文详细阐述了计划火烧的意义和作用、计划火烧前的准备工作,并提出了计划火烧的注意事项及实际操作要领。     

Determination of turbulent burning velocities of dust air mixtures with the open tube method

Correlating turbulent burning velocity to turbulence intensity and basic flame parameters-like laminar burning velocity for dust air mixtures is not only a scientific challenge but also of practical importance for the modelling of dust flame propagation in industrial facilities and choice of adequate safety strategy. The open tube method has been implemented to measure laminar and turbulent burning velocities at laboratory scale for turbulence intensities in the range of a few m/s. Special care has been given to the experimental technique so that a direct access to the desired parameters was possible minimising interpretation difficulties. In particular, the flame is propagating freely, the flame velocity is directly accessible by visualisation and the turbulence intensity is measured at the flame front during flame propagation with special aerodynamic probes. In the present paper, those achievements are briefly recalled. In addition, a complete set of experiments for diametrically opposed dusts, starch and aluminium, has been performed and is presented hereafter. The experimental data, measured for potato dust air mixtures seem to be in accordance with the Bray Gülder model in the range of 1.5 m/s<u′<3.5 m/s. For a further confirmation, the measurement range has been extended to lower levels of turbulence of u′<1.5 m/s. This could be achieved by changing the mode of preparation of the dust air mixture. In former tests, the particles have been injected into the tube from a pressurised dust reservoir; for the lower turbulence range, the particles have been inserted into the tube from above by means of a sieve–riddler system, and the turbulence generated from the pressurised gas reservoir as before. For higher levels of turbulence, aluminium air mixtures have been investigated using the particle injection mode with pressurised dust reservoir. Due to high burning rates much higher flame speeds than for potato dusts of up to 23 m/s have been obtained.     

酒精在常见可燃地面材料燃烧痕迹特征规律研究

易燃液体燃烧痕迹识别对助燃剂放火火灾调查至关重要。选用丙纶地毯和PVC地板革作为纤维和塑料地板的代表,以工业酒精作为易挥发助燃剂的代表,研究酒精用量、灭火方式等对燃烧痕迹形成及痕迹稳定性的影响。通过与未加载酒精的痕迹对比,发现丙纶地毯因热稳定性较差,燃烧后往往能形成烧坑或烧洞,其燃烧轮廓以典型的灰化形式存在,加载酒精的部位熔融严重,与地面紧紧粘连在一起;PVC地板革因为表面光滑,酒精在其表面不断流淌,燃烧后会留下清晰的轮廓,类似于细线状的印痕,而地板革本身基本不会燃烧。燃烧熄灭的方式也会对其炭化程度、燃烧图痕、残余形状产生影响。     

Health risks of residential wood heat

The resurgence in the use of wood in the United States for residential heating has been accompanied by a dramatic increase in deaths and injuries from residential fires. Toxic materials present in woodsmoke also appear to present a significant public health hazard. As a result of these factors, production of residential wood heat can be up to two orders of magnitude more hazardous than generation of an equivalent amount of electric energy at a coal-fired power plant. Proper care in installation and operation of wood stoves, as well as technological innovations that control wood-stove emissions, can greatly reduce the health and safety hazards of residential heating with wood.     

A disaster scene simulation system in 3D for oil transmission stations: Design and implementation

The disaster scene in three-dimensional (3D) plays a crucial role in disaster emergency management and risk communication of oil transmission stations. However, existing research for the disaster scene mainly focuses on reproducing the disaster environment and rarely predicts the damage state of the disaster-affected object. This paper proposes an object-oriented modeling method that utilizes a multilevel decomposition pattern for disaster scenes. This method combines earthquake vulnerability assessment with 3D visualization technology to predict and characterize the damage state of critical infrastructure in oil transmission stations. To enhance earthquake risk perception, a simulation system is designed and developed, which allows for the construction of virtual scenes and quick simulation of disaster scenes in 3D. The case application shows that the system improves the 3D modeling efficiency of disaster scenes and enhances public awareness of earthquake risks. The simulation system can provide technical support for seismic mitigation planning and emergency management decision-making at oil transmission stations and has good application prospects.     

基于WRF-CMAQ评估秸秆禁烧对区域空气质量的影响

基于本地化的秸秆露天焚烧主要大气污染物排放清单,采用空气质量模式WRF-CMAQ,定量评估秸秆禁烧管控对东北地区空气质量的影响.结果显示,2013~2020年东北地区秸秆露天焚烧污染物排放总量整体呈现先增加再降低的趋势,每年的秸秆焚烧集中期为春耕前（3月和4月）和秋收后（10月和11月）.2017年秸秆焚烧集中期内,秸秆露天焚烧对东北三省的CO和PM_2.5浓度的贡献率分别为24.01%和39.98%,农作秸秆露天焚烧是造成东北地区空气质量下降的重要因素;相同气象条件下,2019年秸秆焚烧集中期,秸秆焚烧对东北三省大气中CO和PM_2.5浓度的贡献率较2017年同期分别下降了9.58%和13.95%,表明2019年的秸秆禁烧政策有效改善了东北地区的空气质量.同时,若东北三省均实施吉林省2019年的秸秆禁烧管控政策,则东北地区的空气质量将会进一步改善.本研究结果可为区域大气污染联防联控政策的制定提供科技支撑.     

浙江2001—2016年露天生物质燃烧排放污染物时空格局

生物质露天燃烧排放烟气颗粒物对大气环境、生态系统和人类健康有重要影响. 该研究基于MODIS - MCD64A1数据提取2001—2016年浙江省森林、灌丛、草地火灾面积和作物秸秆火点数据,结合植被类型、生物质密度和燃烧效率,运用排放因子法,估算16年间浙江区域露天生物质燃烧排放污染物总量. 结果表明,2001—2016年浙江区域露天生物质燃烧总量为58.78 mt,其中乔木、灌木、草本、水稻、小麦、玉米、豆类和油菜燃烧总量分别为202.18 kt、10.43 kt、300.10 t、46.66 mt、1.94 mt、2.45 mt、3.45 mt和4.06 mt. 森林和秸秆火次数分别为1783次和23257次,森林火灾多集中在浙江南部区域,秸秆火多集中在浙江北部区域. 森林和草地火灾次数主要集中在3月和10月,作物秸秆火点主要集中在5、7和8月份,占全年75%以上. 各污染物CO₂、CO、NO_x、VOCs、PM_2.5、TC、OC和EC排放总量分别为667.20、26.40、1.13、4.92、5.12、2.85、2.59和0.23 mt. 该研究揭示了浙江地区生物质露天燃烧排放污染物的时空变化,为深入揭示生物质燃烧对区域环境影响提供数据支持.     

插板对正庚烷油池火燃烧行为的影响研究

海上石油泄漏常规的处理方法是原位燃烧,加速其燃烧并使其燃尽是降低其对生态环境影响的重要措施之一。以正庚烷为燃料,在油池内插入竖直铝板,研究不同高度铝板对池火燃烧行为的影响。结果表明,插板对池火燃烧速率以及火焰高度具有明显的增强作用,随着板的高度的增加,增强作用先增大后减小,当H_p/D(板高与油池直径之比)为3.5时,增强作用最大。火焰高度、板的温度、热通量以及燃烧速率的变化趋势一致,它们的临界点均在H_p/D=3.5附近。插板后燃烧速率增大主要是因为插板自身的热传导导致了燃料的核态沸腾,使燃料接受的热反馈增大,从而加快了燃料的蒸发,增大了燃烧速率。     

氢气添加对乙醇/空气预混火焰燃烧特性影响的数值模拟研究

通过对不同混合比率的乙醇/氢气/空气燃烧特性进行数值模拟,研究氢气添加量对点火延迟时间、层流燃烧速度、火焰厚度、化学反应滞留时间及组分分布情况的影响。研究发现一定程度上氢气添加量的增加能够缩短混合气体的点火延迟时间,并且氢气对点火延迟时间的影响随着温度的升高而逐渐减小。随着混合比率的增大,层流燃烧速度增大,并且在混合比率大于0.4时显著增大。火焰厚度及化学反应滞留时间随氢气增加而逐渐减小。此外,进一步分析组分分布情况得知氢气添加使火焰中H*、O*、OH*自由基摩尔分数峰值增大,并且H+O+OH摩尔分数峰值与层流燃烧速度存在线性关系。