THRESHOLD TIME SERIES MODELING OF TWO ICELANDIC RIVERFLOW SYSTEMS1

ABSTRACT: This paper reports our experience in building time series models which connect the flows in two Icelandic rivers with the meteorological variables of precipitation and temperature. Two rivers with different hydrological characteristics were studied. In areas where precipitation may be either in the form of rain or snow linear models are inadequate to describe the relationship between the river and the meteorological variables. The methodology of threshold models recently developed seems to be well suited for taking into account the sharp difference in the relationship according to whether it is freezing or not. The possibility of identifying an alternative threshold variable is also explored.     

Processing of copper converter slag for metals reclamation: Part II: mineralogical study.

Chemical and mineralogical characterizations of a copper converter slag, and its products obtained by curing with strong sulphuric acid and leaching with hot water, were carried out using ore microscopy, scanning electronic microscopy with energy dispersive spectrometry, wave-length dispersive X-ray fluorescence spectrometry, X-ray diffractometry and chemical phase analysis, which provided necessary information to develop a new process for treating such slag and further understanding of the chemical and mineralogical changes in the process.     

关于测高、测角受大气折射影响的讨论

大气折射对测量工作影响的研究,早已成为测量学的一个重要内容,但到目前为止尚未得到解决。本文将在已有的理论和实践基础上,仅就大气折射对测高和测角影响问题作一些探讨,并给出削弱该影响的实际作业方法。     

超声回弹综合法测强曲面五参数幂函数公式

提出了一种新的混凝土 f -v -R曲面五参数幂函数公式 ,它能够很好地描述混凝土的超声值v、回弹值Rm 和抗压强度值 f之间的关系 ,克服了传统的 f -v -R曲面公式拟合试验数据误差较大的缺点 ,在实际工作中 ,采用这种新提出的 f -v -R曲面公式 ,可以更准确地评价建筑结构的混凝土强度     

GEOSTATISTICAL ESTIMATION OF HORIZONTAL HYDRAULIC CONDUCTIVITY FOR THE KIRKWOOD‐COHANSEY AQUIFER1

ABSTRACT: The Kirkwood‐Cohansey aquifer has been identified as a critical source for meeting existing and expected water supply needs for southern New Jersey. Several contaminated sites exist in the region; their impact on the aquifer has to be evaluated using ground water flow and transport models. Ground water modeling depends on availability of measured hydrogeologic data (e.g., hydraulic conductivity, for parameterization of the modeling runs). However, field measurements of such critical data have inadequate spatial density, and their locations are often clustered. The goal of this study was to research, compile, and geocode existing data, then use geostatistics and advanced mapping methods to develop a map of horizontal hydraulic conductivity for the Kirkwood‐Cohansey aquifer. Spatial interpolation of horizontal hydraulic conductivity measurements was performed using the Bayesian Maximum Entropy (BME) Method implemented in the BMELib code library. This involved the integration of actual measurements with soft information on likely ranges of hydraulic conductivity at a given location to obtain estimate maps. The estimation error variance maps provide an insight into the uncertainty associated with the estimates, and indicate areas where more information on hydraulic conductivity is required.     

Biohydrogen production from starch in wastewater under thermophilic condition

Batch experiments were conducted to convert starch in wastewater into hydrogen at 55 degrees C at various wastewater pH (4.0-9.0) and starch concentrations (9.2-36.6 g/l). The maximum hydrogen yield of 92 ml/g of starch added (17% of the theoretical value) was found at wastewater pH 6.0, and the maximum specific hydrogen production rate of 365 ml/(g-VSS.d) was at wastewater pH 7.0. The methane-free biogas contained up to 60% of hydrogen. The mixed liquor was composed mostly of acetate (40.2-53.4%) and butyrate (26.0-40.9%). Phylogenetic analysis based on 16S rDNA sequences of the 72 clones developed from the sludge at pH 6.0 shows that 85.7% of the clones were closely affiliated with genus Thermoanaerobacterium in family Thermoanaerobacteriaceae; the remaining 14.3% were with an uncultured Saccharococcus sp. clone ETV-T2.     

Promoting sustainable agriculture development by improvingthe efficiency of chemical fertilizers and soil nutritions

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基于故障物理的集成控制器电路板可靠性预计

目的实现商用电动汽车集成控制器的可靠性预计与提升,采用应力仿真与故障物理相结合的方法对其关键电路板进行可靠性预计。方法针对集成控制器的数字样机,开展热、振动仿真应力分析,采用故障模式机理及影响分析(FMMEA)方法,分析电路板可能存在的故障模式和故障机理,确定潜在故障模式的故障物理模型。将应力分析结果作为故障物理模型的输入,进行基于故障物理的可靠性预计,寻找设计薄弱环节,并提出改进措施。结果找到了电路板的8个高温器件和热集中区域,振动仿真分析表明,电路板顶端与中心振动强度较大,可能引起疲劳失效,需要给予关注。通过FMMEA分析,得到电路板的主要故障模式为焊点开裂,主要受温度循环影响,造成热疲劳失效。最后采用Coffin-Mason模型,计算得到电路板的平均故障间隔时间为15869 h,找出了电路板的可靠性设计的薄弱环节。结论该方法基于故障物理,相对传统基于手册的可靠性预计方法精度更高,同时能够在产品研制阶段与性能设计并行,通过分析和改进产品设计,达到正向可靠性设计的目的,为新能源汽车领域电子产品的可靠性预计提供新的思路。     

絮凝天然碱碱泥的絮凝剂产生菌的筛选及最佳产絮条件研究

从生活污水中分离得到一株在强碱性条件下能絮凝天然碱碱泥的高效絮凝剂产生菌EWY1,并通过稳定性试验证明了其具有较好的稳定性,经鉴定为肠球菌属(Enterococcus)中的盲肠肠球菌(E.cecorum).通过单因素试验和正交试验确定了该菌产絮凝剂的最佳培养基为:麦芽糖15 g·L-1,KNO3 1.2 g·L-1,KH2PO4 0.5 g·L-1,MgSO4·7H2O 0.4 g·L-1,NaCl0.6 g·L-1,FeSO4·7H2O 0.008 g·L-1;该菌产絮凝剂的最佳培养条件为pH 7.0、温度30℃、摇床转速170 r·min-1.絮凝实验结果表明,用该菌产生的絮凝剂处理天然碱碱泥效果较好,絮凝率达到了89%.     

Windows95下的锻造CAD系统开发

从系统原理、数据管理、图形处理等几方面探讨了Windows95下的锻造CAD系统开发,并简单介绍了该系统的主要功能和特色。