Defining the Diurnal Pattern of Snowmelt Using a Beta Distribution Function

Snow is an important component of the hydrologic cycle for many regions worldwide. In addition to vital water resources, snowmelt can be important for forest ecosystem dynamics and flood risk. However, standard design events in the United States lack a design snowmelt event, including only precipitation events, though snowmelt has been shown to be larger than rainfall. In this article, we present a method using hourly snow water equivalent data to develop and test a function for representing the diurnal pattern of snowmelt. A two‐parameter beta distribution function is modified for the purposes of this study and found to fit the pattern of snowmelt well with a root mean squared error of 0.008. Soil moisture sensors were additionally utilized to assess the timing of the snowmelt water outflow from the base of the snowpack that supports the shape of the function, but suggests that the timing of losses recorded on snow pillows lag as much as 3 h. Further testing of the function showed the shape of the function to be accurate. The methods developed and tested in this paper can be applied for design purposes comparing snowmelt and rainfall events or to improve hydrological models investigating processes such as streamflow or groundwater recharge.     

微生物絮凝剂M-C11处理高岭土悬浊液的响应曲面优化

采用响应曲面法对微生物絮凝剂M-C11处理高岭土悬浊液的过程参数进行优化,选取中心复合实验设计(CCD),以p H、M-C11投加量和Ca Cl2投加量等因素为自变量,以处理后的高岭土悬浊液絮凝率(Fr)为响应值,并借助扫描电镜对絮凝剂的作用机理进行初步探讨。结果表明,微生物絮凝剂M-C11可显著改善高岭土悬浊液的絮凝性能,且选取的3种单因素水平均可影响絮凝剂活性。经多元回归拟合分析,在M-C11投加量为2.56 m L,Ca Cl2投加量为0.37 g/L的最优条件下,微生物絮凝活性实验值可达92.37%,接近模型预测值(92.30%)。Ca Cl2投加量对絮凝效果的影响高于M-C11投加量(PCa Cl2相似文献   

Adsorption of chlorpyrifos,penconazole and metalaxyl from aqueous solution by modified clays

Sorption of three pesticides (chlorpyrifos, metalaxyl and penconazole) has been measured on a commercial clay montmorillonite and on the same mineral modified with either of two cationic-surfactant micelles. Both micelle–clay complexes, commercial names Cloisite 20A and Cloisite 30B, showed a good capacity to sorb all three pesticides from water, whereas their sorption on the natural montmorillonite was not described by an isotherm. Modelling sorption on both micelle–clay complexes showed that the Freundlich sorption constant (K _F) was higher for chlorpyrifos on Cloisite 20A (K _F = 7.76) than on Cloisite 30B (K _F = 5.91), whereas the sorption of metalaxyl was stronger on Cloisite 30B (K _F = 1.07) than on Cloisite 20A (K _F = 0.57). Moreover the micelle–clay complex Cloisite 20A also showed a good affinity for penconazole, the maximum quantity adsorbed (q _m) of 6.33 mg g^?1 being 45% more than that on Cloisite 30B. Single-batch adsorption of each pesticide onto both micelle–clay complexes was studied using the Freundlich isotherm for chlorpyrifos and metalaxyl and the Langmuir isotherm for penconazole. The Cloisite 20A micelle–clay complex was predicted to require 23% less adsorbent to treat certain volumes of wastewater containing 30 mg L^?1 chlorpyrifos, 43% more to treat metalaxyl similarly and 57% less to treat penconazole compared with Cloisite 30B.     

一种基于预测法的电磁兼容设计方法

文章以数模混合电路设计实践为基础,介绍了一种基于预测法的电磁兼容设计方法。先以电磁兼容测试理论为基础介绍数模混合电路设计中的电磁兼容方法,在以此方法建立电磁兼容设计模型,并通数模混合电路实践来检验和改进设计模型。     

Ionic liquids as lubricants or lubrication additives: An ecotoxicity and biodegradability assessment

This paper reports on the (eco)toxicity and biodegradability of ionic liquids considered for application as lubricants or lubrication additives. Ammonium- and pyrrolidinium-based cations combined with methylsulphate, methylsulphonate and/or (CF₃SO₂)₂N⁻ anions were investigated in tests to determine their aquatic toxicity using water fleas Daphnia magna, green algae Selenastrum capricornutum and marine bacteria (Vibrio fischeri). Additional test systems with an isolated enzyme (acetylcholinesterase) and isolated leukaemia cells from rats (IPC-81) were used to assess the biological activity of the ionic liquids. These compounds generally exhibit low acute toxicity and biological activity. Their biodegradability was screened according to OECD test procedures 301 B and 301 F. For choline and methoxy-choline ionic liquids ready biodegradability was observed within 5 or 10 d, respectively. Some of the compounds selected have a considerable potential to contribute to the development of more sustainable products and processes.     

人工湿地构筑根孔作用下土壤物质分布状况

嘉兴市石臼漾湿地应用人工构筑根孔技术,以玉米秸秆和油菜秸秆按比例混合埋植于土壤亚表层,作为湿地的基质/填料。在湿地运行一年半后,按照正交设计表,以埋植秸秆的种类(S)、填埋的土壤层次(L)、距离秸秆外环的远近(D)和秸秆周围土壤的表观颜色(C)作为实验因素,对秸秆周围养分物质浓度、土壤酶活性以及铁含量进行采样分析。实验结果显示:玉米秸秆和油菜秸秆腐烂较充分,分别形成较发达的粗根孔和细根孔;根孔周围土壤呈中度还原状态;粗根孔具有较强的优先流效应,其周围土壤具有较高的养分物质含量和较低的Fe2+/Fe3+比。粗根孔周围土壤具有较高的磷酸酶活性,而细根孔周围具有较高的β-葡糖苷酶活性和脲酶活性。综合比较,人工湿地构建初期,径级较大秸秆腐烂后形成的粗根孔发挥着更高的水分传导效率和更强的物质截留效应。     

微波修复原油污染土壤的均匀设计实验

采用均匀设计实验方法,研究了微波修复原油污染土壤时原油去除率与微波能耗、含水率和含炭率等因素的关系,并应用MATLAB编程拟合出经验公式。结果分析表明:微波能耗在0～288 kJ范围内,污染土壤的原油去除率随微波能耗线性增加;在含水率为6%、含炭率为4%、微波能耗从0增加到288 kJ时,原油去除率从0%增加至92.3%;含炭率在0%～4%范围内原油去除率与含炭率成线性关系,在微波能耗为288 kJ、含水率为6%、含炭率从0%增加到4%时,原油去除率从12.3%增加至92.3%;原油去除率与含水率成二次曲线关系且开口向下,微波修复原油污染土壤的最佳含水率为6.6%。研究结果对微波修复原油污染土壤技术的优化提供了有价值的参考。     

响应曲面法优化复合絮凝剂的制备工艺

为了提高染料废水中COD和色度的去除效果,采用响应曲面法对聚硅酸类新型复合絮凝剂的制备工艺进行了优化实验研究。在单因素实验基础上采用Box-Behnken Design(BBD)实验设计方法,设计出了影响染料废水处理效果的3因素3水平共15组实验,其中n(Fe+Al):n(Si)的摩尔比为4～6,n(B+Mg):n(Si)的摩尔比为0.3～0.7,熟化时间为1～3 d。根据15组实验结果,以COD去除率和色度去除率为响应值分别建立了二次多项式响应曲面模型。模型优化结果显示,在n(Fe+Al):n(Si)摩尔比为5∶1,n(B+Mg):n(Si)为0.5∶1,熟化时间为2 d的条件下,制备得到的新型复合絮凝剂聚硅酸铝铁硼镁具有最佳的絮凝处理性能和脱色效果,能有效去除染料废水中的COD和色度,其中出水色度接近于0,COD的去除率达到87.65%,模型验证实验进一步验证了本文所建立的响应曲面法在复合絮凝剂制备工艺优化中的有效性。     

基于冷阴极触发管振动试验夹具的设计

介绍了一种基于冷阴极触发管性能检测及振动试验所需的夹具,从夹具材料的选取、结构设计和刚度要求进行了设计,分析了该夹具在制造过程中存在的关键问题及解决方法,并在振动试验中加以验证。     

产品的振动冲击响应设计

在抗振缓冲设计中,人们通常按标准、合同中的要求进行设计,本文认为要按产品受振动与冲击后的响应进行设计,及如何按振动与冲击后的响应进行设计。