The downfall of mating: the effect of mate-carrying and flight muscle ratio on the escape ability of a pierid butterfly

In many species, the ability to evade predators is known to be periodically impaired by increased weight loads due to feeding and reproduction. Not only may extra weight reduce escape speed, but feeding and mating can also make the prey more noticeable to visually hunting predators. A number of butterfly species mate for hours, and if a mating couple is disturbed, one of the butterflies is responsible for flying, whereas its partner remains still. This study investigated the ability of male Pieris napi butterflies to fly while mating, with the prediction that mate carrying impairs flight ability compared to single flying males and that males with relatively high flight muscle ratios (FMR; male thorax mass/male + female body mass) will have better flight performance in copula. Our results clearly show that whereas single males always take off at steep angles and fly upwards, couples invariably have a negative take-off angle and rarely gain height. Moreover, landing height of the couples is positively associated with higher FMR. Hence, male flight ability when in copula is positively associated with a high relative thorax mass. Butterfly pairs may thus be at greater risk of predation as a consequence of their impaired flight ability, especially couples with critically low FMRs (<16%).     

Trans-Sahara migrants select flight altitudes to minimize energy costs rather than water loss

Meteorological conditions influence strongly the energy and water budget of birds. By adjusting their flights spatially and temporally with respect to these conditions, birds can reduce their energy expenditure and water loss considerably. By radar, we quantified songbird migration across the western Sahara in spring and autumn. There autumn migrants face the trade-off between (a) favorable winds combined with hot and dry air at low altitudes and (b) unfavorable winds combined with humid and cold air higher up. Thus, it can be tested whether birds may chose altitudes to minimize water loss instead of energy expenditure. We predicted optimal flight altitudes with respect to water loss and energy expenditure based on a physiological flight model when crossing the western Sahara and compared these model predictions spatially and temporally with measured songbird densities. The model aiming for minimal water consumption predicted a mean flight altitude of 3,400 m under autumn conditions. However, 64% of the nocturnal songbird migration flew at altitudes below 1,000 m above ground level profiting from tailwind. This preference for tailwind in autumn, despite the hot and dry air, emphasizes the importance of energy savings and diminishes the significance of possible water stress for the selection of flight altitude. Nevertheless, during daytime, high energy expenditure due to air turbulences and water loss due to warmer air and direct solar radiation prevent songbirds from prolonging their nocturnal flights regularly into the day. Birds crossing the Sahara save water by nocturnal flights and diurnal rests.     

地下弹药库爆炸产生的地面空气冲击波的估算与数据值模拟

对某地下弹药库爆炸冲击波传播过程进行了较详细的分析和数值模拟,得到了弹药爆炸时地面空气冲击波的等效经验计算公式。两种方法得到的不同距离的冲击波超压值基本一致。     

An assessment of how distance and diesel oxidation catalyst will impact thermal decomposition behaviors of particles

Decomposition mass loss and pyrolysis products analyses of particles sampled at various locations along the tailpipe of a Euro-IV diesel engine were performed using a thermogravimetry in conjunction with Fourier transformation infrared spectrometry-mass spectrum. Diesel particles were collected at the same location with and without diesel oxidation catalyst (DOC) mounted on the test engine separately. The three poles in thermal gravity-differential thermal gravity images suggested that the decomposition process of diesel particles could be divided into three stages which correspond to the decompositions of lower boiling substances, higher boiling substances and soot respectively. It is noticed that no matter whether DOC was mounted or not, the further the particles were sampled away from the engine block, the lower the peak temperatures and the heavier the mass losses within the first two stages, which indicated that the soluble organic fraction in the particle samples increased and therefore lowering the activation energy of thermal decomposition. Hydroxyl, ammonia, C_xH_y fragments, benzene, toluene, and phenol were found to be the primary products of particle decomposition, which didn't change with the location of particle sample point. The employment of DOC increased the activation energy for particle oxidation and resulted in a higher peak temperature and lower mass loss within the first-stage. Moreover, the CO stretching bands of aldehyde and ketone at 1771 cm^?1 was only detected without a DOC, while the NO₂ peak at 1634 cm^?1 was solely noticed with the presence of DOC. Compared to the first-stage pyrolysis products, more polycyclic aromatic hydrocarbons and less C_xH_y fragments were seen in the second-stage.     

分层水库温度梯度对扬水曝气原位控藻效果的影响

基于计算流体力学(CFD)方法,数值模拟了不同温度梯度条件下扬水曝气器外围流场及藻类浓度场,并与实际工程运行数据进行对比.当水深为80m、水面下30m内的温度梯度从0.17℃/m增加到0.73℃/m时,核心控藻区域的半径从100m增加到150m,控藻区域百分比从25.16%增大到28.60%,藻类完全混合的时间分别从16d增加到24d.在稳定条件下,藻类在补偿点以下的停留时间均大于48h,基本不受温度梯度的影响,藻类生长受抑制.藻类浓度模拟结果与实际工程运行结果吻合良好.推荐水库中扬水曝气器合理设计间距为250m.     

点火因素对于重大井喷事故的影响分析

本文主要分析了高含硫气井点火时间的影响.首先分析国内某重大高含硫井喷事故的调查结果[1],其次采用大涡模拟方法对井喷气体扩散进行模拟,并将计算结果与现场实际调查结果进行对比.通过计算不同点火时间在事故中造成的灾难后果,得出点火时间对于灾难的影响.通过计算不同的气象条件下的扩散距离,提出15min的点火时间标准.     

高强预腐蚀铝合金单轴拉-拉疲劳断口定量分析

目的通过断口定量分析获得7A09铝合金的疲劳裂纹扩展规律,为7A09铝合金结构的寿命评估提供依据。方法使用EXCO溶液对试验件进行预腐蚀,利用疲劳拉伸机进行疲劳加载直至断裂,使用扫描电镜对疲劳断口进行定量化分析。结果疲劳裂纹在试件的腐蚀坑处萌生,从自由界面附近向纵深发展导致试件的断裂。通过断口分析和Paris公式确定了裂纹的萌生寿命和扩展寿命。结论腐蚀之后的试件裂纹萌生寿命占总寿命的比例下降,当裂纹扩展程度较大之后,受腐蚀影响减轻,得出裂纹扩展速率和应力强度因子的关系。     

TiO2薄膜光催化效果的强化

采用溶胶-凝胶法制备TiO2溶胶,将其涂覆在普通钠钙玻璃上,以TiO2对甲基橙的光分解率探讨TiO2薄膜最佳光催化性能.结果表明,当PEG400的加入量为7%时,TiO2薄膜的光催化性能最强;用锐钛型TiO2粉末二次引发的溶胶提拉制成的薄膜对甲基橙的光催化分解效果有很大的提高;经滴加操作后薄膜的光催化性能有明显改善;各个影响因素最好的组合效果为滴加操作 锐钛型粉体引发 H2SO4超强酸化 La3 掺杂.     

基于指标模糊权和协调性下的地下水水质评价模型构建及应用

在地下水质量标准中,各指标权重的选择与权重的内涵存在着不确定性;同一指标的分级界点值差异显著,近似地呈现几何级数变化。基于以上这两种情况,构建基于指标模糊权和协调性下的地下水水质评价模型。应用层次分析法和专家调查9标度法确定指标的相对权重,结合贝塔系数计算出指标的模糊权重。对评价标准及待评价地下水水质监测值进行对数变换,采用距离测度法来构造隶属函数,并对其进行求余,按最大隶属原则来评判地下水质量等级。应用此模型对徐州市的重要水源地——张集地下水水质进行评价。结果表明:研究区的20个采样点水质为Ⅱ、Ⅲ级的占90%,符合饮用水的要求。与投影寻踪法的评价结果基本一致。     

Predicting Water Quality Impaired Stream Segments using Landscape-Scale Data and a Regional Geostatistical Model: A Case Study in Maryland

In the United States, probability-based water quality surveys are typically used to meet the requirements of Section 305(b) of the Clean Water Act. The survey design allows an inference to be generated concerning regional stream condition, but it cannot be used to identify water quality impaired stream segments. Therefore, a rapid and cost-efficient method is needed to locate potentially impaired stream segments throughout large areas. We fit a set of geostatistical models to 312 samples of dissolved organic carbon (DOC) collected in 1996 for the Maryland Biological Stream Survey using coarse-scale watershed characteristics. The models were developed using two distance measures, straight-line distance (SLD) and weighted asymmetric hydrologic distance (WAHD). We used the Corrected Spatial Akaike Information Criterion and the mean square prediction error to compare models. The SLD models predicted more variability in DOC than models based on WAHD for every autocovariance model except the spherical model. The SLD model based on the Mariah autocovariance model showed the best fit (r² = 0.72). DOC demonstrated a positive relationship with the watershed attributes percent water, percent wetlands, and mean minimum temperature, but was negatively correlated to percent felsic rock type. We used universal kriging to generate predictions and prediction variances for 3083 stream segments throughout Maryland. The model predicted that 90.2% of stream kilometers had DOC values less than 5 mg/l, 6.7% were between 5 and 8 mg/l, and 3.1% of streams produced values greater than 8 mg/l. The geostatistical model generated more accurate DOC predictions than previous models, but did not fit the data equally well throughout the state. Consequently, it may be necessary to develop more than one geostatistical model to predict stream DOC throughout Maryland. Our methodology is an improvement over previous methods because additional field sampling is not necessary, inferences about regional stream condition can be made, and it can be used to locate potentially impaired stream segments. Further, the model results can be displayed visually, which allows results to be presented to a wide variety of audiences easily.