大型薄壳制件真空辅助树脂传递模塑工艺充模方案仿真分析及优化

针对大型树脂基复合材料制件不适于用实验试错法进行充模方案设计的问题,在分析树脂流动规律的基础上将大型薄壳件的求解区域分解,仿真分析了不同充模方案下树脂在纤维中的流动行为和模腔内压力变化,提出在制件填充面积等分处设置流道的方法,选择和优化大型薄壳制件的充模方案。结果表明:①对于不便进行实验试错法进行真空辅助树脂传递模塑(VARTM)工艺充模方案设计的大型薄壳制件,可以采用数值模拟的方式,以达西定律、能量守恒定律等为计算依据,求解压力场和速度场,对比不同仿真方案的充模时间等数据合理安排注胶方式方法,指导VARTM工艺制备大型复合材料制件合理安排注胶方式,提高生产率、减少因树脂浸润不均匀产生的缺陷。②对于大型薄壳类制件,忽略厚度方向尺寸,影响充模时间的主要因素为流道长度和树脂流动距离。选取尽可能长的注胶流道,合理设置流道位置以减少树脂流动的距离;长流道可以增加树脂瞬时注入量、提高较长时间的压力差;而树脂流程越长,树脂前锋处压力损失越大,流速越慢。③试验提出了制件填充面积等分处设置流道的方法。将大型薄壳工艺制件充模面积等分,注胶流道布置在垂直于制件长度方向的面积等分线上,可缩短充模时间并减少制件两端的树脂富集现象。对于较狭长部分可再次进行面积等分设置流道,以免造成树脂流程过长压力流失过多;而对于较宽阔部分不宜设置过多流道以免树脂前锋稳定前互相接触造成制件充模不均匀。     

基于显著性增强和迁移学习的鱼类识别研究

针对水下鱼类无法快速准确识别的难点,提出一种具有图像主体自动增强功能的鱼类迁移学习方法。该方法将鱼类RGB图像转换至Lab颜色空间后,利用中央周边算子计算得到整个输入图像的显著性值,进而提供鱼类目标的潜在区域,并结合GrabCut算法获取鱼类分割图像,最终将融合分割图的原始图像送入优化后的残差网络中进行训练。通过对23种鱼类进行识别试验,结果显示,固定ImageNet数据集上ResNet-50预训练模型的conv1层和conv2层参数,微调高层参数的方法能够取得最好的识别效果,且在公开的Fish4Knowledge数据集上,该模型取得了最高的识别准确率,平均识别精度达到99.63%。与其他卷积神经网络方法的对比结果显示,本方法在Fish4Knowledge和Fish30Image数据集上的识别精度和时间性能均具有较大优势,其中识别准确率至少提升4.98%。多个数据集上的试验验证了模型的有效性。     

藏东南18种杜鹃属植物花粉形态的比较

利用电子显微镜，对藏东南18种杜鹃属植物花粉的形态特征进行观察与分析，以期为分类鉴定提供孢粉学依据。18种杜鹃属植物分属于杜鹃亚属、常绿杜鹃亚属、糙叶杜鹃亚属。结果表明，供试花粉均为四合体花粉，四合体直径以大萼杜鹃最大，林芝杜鹃最小。单粒花粉球形或近球形，为3孔沟，黄杯杜鹃萌发孔的长宽值最高，为17.38 μm×3.32 μm，而林芝杜鹃萌发孔的长宽值最低。花粉外壁由大小、形状不一的颗粒组成，其中黄毛雪山杜鹃和白毛杜鹃的颗粒形状较为特殊，为长颗粒状。综合认为，花粉形态特征不宜作为分类鉴定的主要依据，但仍具有积极的参考价值。     

Quantifying key model parameters for wheat leaf gas exchange under different environmental conditions

The maximum carboxylation rate of Rubisco(V_(cmax)) and maximum rate of electron transport(J_(max)) for the biochemical photosynthetic model, and the slope(m) of the Ball-Berry stomatal conductance model influence gas exchange estimates between plants and the atmosphere. However, there is limited data on the variation of these three parameters for annual crops under different environmental conditions. Gas exchange measurements of light and CO_2 response curves on leaves of winter wheat and spring wheat were conducted during the wheat growing season under different environmental conditions. There were no significant differences for V_(cmax), J_(max) or m between the two wheat types. The seasonal variation of V_(cmax), J_(max) and m for spring wheat was not pronounced, except a rapid decrease for V_(cmax) and J_(max) at the end of growing season. V_(cmax) and J_(max) show no significant changes during soil drying until light saturated stomatal conductance(gssat) was smaller than 0.15 mol m~(–2) s~(–1). Meanwhile, there was a significant difference in m during two different water supply conditions separated by gssat at 0.15 mol m~(–2) s~(–1). Furthermore, the misestimation of V_(cmax) and J_(max) had great impacts on the net photosynthesis rate simulation, whereas, the underestimation of m resulted in underestimated stomatal conductance and transpiration rate and an overestimation of water use efficiency. Our work demonstrates that the impact of severe environmental conditions and specific growing stages on the variation of key model parameters should be taken into account for simulating gas exchange between plants and the atmosphere. Meanwhile, modification of m and V_(cmax)(and J_(max)) successively based on water stress severity might be adopted to simulate gas exchange between plants and the atmosphere under drought.     

Evaluation of Brix Refractometry for the Estimation of Colostrum Quality in Jennies

Donkey placenta does not allow the passage of immunoglobulins; thus, foals are born hypogammaglobulinemic and an adequate intake of high-quality colostrum in the first 24 hours of life is crucial for the surviving. The study aims to assess the relation between colostrum immunoglobulin G (IgG) concentration evaluated by the single radial immunodiffusion (SRID) test and the Brix refractometer in donkeys to establish a cutoff value for high quality of colostrum based on Brix refractometry. Colostrum was collected at foaling, and at 6, 12, and 24 hours after foaling from the left and the right half of nine Amiata jennies. A total of 72 colostrum samples were analyzed. A Friedman test with a Dunn’s test for multiple comparisons was used for assessing the differences between the left and right half at each sampling time. No differences were found between the left and right halves; the average value was used to analyze the effect of sampling time on the IgG concentrations and Brix values. The relationship between colostrum IgG concentrations (SRID test) versus Brix value and Brix value versus time was analyzed using two different mixed linear models. A strong statistically significant relation has been found between IgG concentrations and Brix values (R² = 0.84). The relation between IgG concentrations and Brix refractometer showed a cutoff point of 17% Brix score for the identification of high-quality colostrum. The Brix value (%) decreased continuously from 16.29 by 0.29 × hour. Jennies’ and donkey foals’ management may be greatly improved using this simple and cheap device.     

复合式分离型热管在原油采出液余热回收中的应用

通过蒸汽辅助重力泄油(Steam Assisted Gravity Drainage,SAGD)技术开采稠油时,采出液温度较高,对其进行热回收的节能潜力较高,油田采用热管式换热器回收采出原油的余热,将其作为工业或生活用热具有研究价值。考虑到现场空间要求和工程设备模块化的特点,利用U形管壳式换热器、螺旋板式换热器作为分离型热虹吸热管蒸发段和冷凝段,并建立复合式分离型热管模型,分析其换热性能、循环压降、充液率及换热能力。采用新疆油田油水二次换热区的分离型热管系统验证该模型,结果表明:复合式分离型热管计算模型可行;复合式热管具备U形管壳式换热器、螺旋板式换热器的优点,换热性能强,系统换热能力可以满足实际要求,有较好的环境适应性。     

灰茶尺蠖触角感器的扫描电镜观察

使用扫描电子显微镜对灰茶尺蠖Ectropis grisescens成虫触角感器的种类、形态和分布进行了观察。结果表明:灰茶尺蠖触角上主要存在3种感器,分别为毛形感器(sensilla trichodea, ST)、刺形感器(sensilla chaetica, SC)和栓锥形感器(sensilla styloconica, SS)。感器的种类和分布在雌雄成虫触角上没有差异。     

印度谷螟成虫喙的感器及分布

为了很好地理解印度谷螟成虫取食适应性,利用扫描电子显微镜观察其口器的超微形态及感器种类和分布。印度谷螟成虫口器与其他螟蛾口器相似,由小的上唇,左、右下颚的外颚叶嵌合形成的喙,3节的下唇须组成。口器感器主要分布于喙管上,共有4种感器:刺形感器、毛形感器、锥形感器和栓锥形感器。毛形感器数量最多,大量分布于整个喙管;栓锥形感器仅位于喙的端部;锥形感器分布于喙的外表面端部区域和食道内侧,纵向排列。雌雄虫间差异主要表现为,栓锥形感器雌虫较雄虫数量多,锥形感器在食道内雌虫多于雄虫。     

贫困地区基于农民专业合作社的土地流转模式及选择——以贵州、四川、甘肃三省为例

基于贵州、四川、甘肃三省贫困连片区的调研,采用问卷调查、关键人访谈和统计分析相结合的方法,总结出农户与农民专业合作社间土地流转模式主要有转包、转让、出租、入股、出租-入股5种,同时分析了每种模式的运作机制和利弊,并在此基础上为不同类型农户的土地流转模式选择提出建议。