选区激光熔化316L不锈钢多孔过滤零件的组织性能研究

【目的】揭示选区激光熔化316L不锈钢粉末成型多孔过滤零件的成型规律和机理。【方法】试验设计孔洞尺寸为1 mm的圆形、正方形多孔316L不锈钢过滤零件,采用选区激光熔化方法进行成型,选用光学显微镜、扫描电子显微镜、X射线衍射等手段对其组织特征和性能进行分析检测,采用显微硬度计测量其显微硬度。【结果】获得了无气孔、裂纹、偏析等缺陷,且致密度达到95%的成型组织。组织内部主要由垂直于界面呈现外延生长的树枝晶组成,所得组织分层均匀,各层间呈冶金结合,定向凝固特征明显。【结论】多孔过滤零件成型件由奥氏体组成,显微硬度为:258~294 HV0.3。采用选区激光熔化方法可以成型孔洞尺寸较小的过滤零件。     

磴口县地下水空间异质性分析及其对景观格局变化的响应

应用地统计学和地理信息系统方法,分析内蒙古自治区巴彦淖尔市磴口县地下水埋深对景观格局演变的响应。首先,通过半变异函数模型分析了磴口县地下水埋深的空间异质性特征,进而利用克里金插值对研究区2008、2016年的地下水埋深空间分布进行了拟合;其次,基于磴口县2008年与2016年的景观格局分布数据,研究了其景观格局演变特点;最后利用GIS叠加分析手段,将地下水埋深变化与景观格局演变数据进行耦合,分析了地下水埋深对景观格局演变的响应机制。研究结果如下：①空间上,磴口县地下水埋深大体遵循由东北向西南逐渐加深的趋势,研究时段内其空间异质性呈上升趋势,空间异质性中的随机扰动增强。②县域主要景观类型为林地,其次为沙地、裸地与水体,研究时段内建筑用地与水体增加明显,耕地与沙地略有减少。③景观格局演变对地下水埋深有较明显的影响,建筑用地的扩张使其加深,地表灌溉系统的不断完善使其上升。总体来看,磴口县地下水资源利用效率有较明显的提高。     

Endogenous development of Hemolivia mauritanica (Apicomplexa: Adeleina: Haemogregarinidae) in the marginated tortoise Testudo marginata (Reptilia: Testudinidae): evidence from experimental infection

Six young tortoises Testudo marginata Schoepff, 1792 were experimentally infected with Hemolivia mauritanica (Sergent et Sergent, 1904). The prepatent period ranged from 6 to 8 weeks. Young, smaller, club-like forms (6-9 x 3-6 Am) of gametocytes appeared in the peripheral blood first, whereas mature, elongated, cylindrical forms (9-12 x 5-7 Am) were detected after 1-2 weeks and predominated during later patency. Three of the infected tortoises were euthanized and dissected to study the endogenous stages. Meronts occurred in the cells of the reticulo-endothelial system and in the erythrocytes; these were observed mostly in parenchymatous organs. Mature forms measured 14.2 x 9.3 microm and contained 7-12 merozoites. Cysts with two (exceptionally one) cystozoites were also found predominantly in parenchymatous organs and measured 14.8 x 7.9 microm. Pathological changes attributable to Hemolivia were mild and limited to liver and kidneys. The role of individual developmental stages of haemogregarines is discussed with respect to evolution of heteroxenous life cycle and long-term persistence of parasites in their intermediate hosts.     

An assessment of methacrifos as a grain protectant and its efficacy against oryzaephilus surinamensis L., Tribolium castaneum herbst,Sitophilus granarius L., Sitophilus oryzae L., Acarus siro L., Glycyphagus destructor schrank and Tyrophagus longior gervais

A trial was carried out to investigate the efficacy of methacrifos against susceptible and multi-resistant strains of four species of insect and three species of mite. Methacrifos was applied to two separate 20-tonne loads of English wheat which were then stored under ambient conditions for 24 weeks. The efficacy of methacrifos was assessed using established bioassay techniques which showed complete control for 24 weeks of all susceptible insects except S. oryzae, where there were survivors at week 24. Methacrifos also gave 100% mortality of resistant O. surinamensis for 24 weeks. There was >95% mortality for 16 weeks of resistant strains of T. castaneum and of resistant S. granarius and S. oryzae for 20 weeks. After S. granarius and S. oryzae were removed, the grain was incubated for 10 weeks. Subsequent F₁ emergence was considerably less from the treatments than from the controls. Methacrifos produced 100% mortality for T. longior for 24 weeks, but control of G. destructor fluctuated and was <100% at week 24. There were survivors of A. siro from week 4.     

Book reviews

Marilyn Holly is an Associate Professor of Philosophy at the University of Florida. Her special interests include political philosophy, ethics and ecology, Jungian thought, and Native American spirituality in its relation to the environment. She is currently at work on a monograph-length piece on the latter topic. She has taught an undergraduate course in ethics and ecology, and plans to do so again. The following essay emerged from her search for a suitable text for such a course.     

自然降雨条件下农田地表产流及氮磷流失规律研究

基于淮北平原自然降雨条件下2个连续汛期观测的降雨-径流试验数据,分析不同试验处理下农田地表产流规律和氮磷浓度及其构成,探讨地表径流氮磷浓度和流失量的时间变化过程及其分布差异。结果表明,当地农田地表径流氮磷浓度构成分别以颗粒态氮和可溶性磷为主,而可溶性氮中又以溶解性有机氮为主,且硝态氮是农田地表径流无机氮流失的主要成分。汛初7月不同土地利用方式下农田地表径流量及铵态氮、硝态氮、可溶性氮磷和颗粒态氮磷的浓度及流失量间的差异相对较小,但8月期间的差异却明显增加,低秆高密度作物种植模式下的相应流失量最低。在淮北平原夏季种植黄豆、棉花等矮秆高密度作物,可起到有效减少地表径流氮磷流失量的作用,减缓因农业非点源污染对地表水体富营养化产生的潜在威胁。     

松嫩平原耕作黑土Cu、Pb、Zn的污染现状分析

黑土区是中国重要的商品粮生产基地之一,对于中国的粮食安全和国民经济的稳定起着举足轻重的作用。此文以松嫩耕作黑土土壤为研究对象,对呼兰、绥化、海伦、依安与嫩江5个调查区的土壤中Cu、Pb、Zn的污染现状进行研究,揭示耕作黑土的健康状况,为黑土生态系统的科学管理提供理论依据。采用内梅罗综合污染指数法及TOPSIS法进行环境质量综合评价。结果表明：土壤Cu、Pb、Zn的污染程度,由东南至西北未表现出明显的分布规律。呼兰、依安土壤Cu、Pb、Zn的污染程度低于绥化、海伦和嫩江;大部分样地土壤Cu、Pb、Zn污染程度具有随剖面深度的增加而增加的特点,仅有绥化土壤10~20 cm土层污染程度小于0~10 cm土层。Cu、Pb、Zn各元素之间没有呈现显著的相关性,表明3种元素来源是不同的。两种方法的评价结果基本一致,研究区域黑土环境质量良好。     

紫花苜蓿太阳能干燥系统干燥箱的结构设计

紫花苜蓿是世界范围内种植量最广的牧草之一,低温干燥是常用的贮存方法,可有效保存苜蓿当中的营养成分。太阳能干燥箱可以为苜蓿提供干燥环境,保证干燥温度。为此,设计了一种立式箱式结构干燥箱,并对其工作原理、制作方式、内外部的结构形式及保温材料进行了相应的研究。