Impact of Water Blending on Calcium Carbonate Equilibrium in Water Distribution Systems

A set of equations describing calcium carbonate equilibrium in water was applied to water mixtures found in an existing water supply system. A theoretical model was used to calculate the total alkalinity and pH resulting from the mixing of two waters of different origin. The accuracy of the results was tested experimentally. The experimental results confirmed the theoretical calculations with acceptable accuracy. Two different sources of possible errors in the Langelier saturation index computations were investigated and compared graphically. The first source resulted from possible inaccuracy of data, assumed to be equal to the standard errors of laboratory measurements. The second was caused by neglecting the inorganic complexes of calcium and magnesium in calculations.     

Effect of Nitrification and GAC Filtration on Copper and Lead Leaching in Home Plumbing Systems

Nitrification and granular activated carbon (GAC) filtration impact leaching of lead/copper to potable water under typical home plumbing configurations. GAC filters removed the disinfectant and caused rapid establishment of nitrification in chloraminated systems. The potential adverse consequences of whole house GAC filters deserve increased scrutiny in chloraminated systems. The lower pH values from nitrification and other microbes during overnight stagnation in pipes can markedly increase (up to 800%) lead and copper contamination of water.     

稀土元素对Ca在细胞中分布影响机制的探讨

本文采用HPLC与ICP-AES联用及HPLC与ICP-MS联用的方法研究了细胞质膜上稀土元素与Ca的化学形态,同时还研究了土壤施加混合稀土对生物膜上Ca分布的影响.研究结果表明,稀土元素和Ca竞争膜磷脂上的结合位点,从而影响了膜上的Ca2+转运机制,导致了Ca在细胞中分布的改变.     

Effect of Slag Basicity on Phase Equilibria and Selenium and Tellurium Distribution in Magnesia-Saturated Calcium Iron Silicate Slags

New measurements have been made on the phase equilibria of magnesia-saturated CaO-FeO_x-SiO₂ slags at 1573 K (1300 °C) and an oxygen partial pressure of 10⁻⁹ atm. The thermodynamic behavior of selenium (Se) and tellurium (Te) in the slag and the stability of oxide mineral phases within the slag were examined as a function of slag composition. The measured equilibrium distribution of Se and Te between the slag and the copper showed nonlinear dependence on the slag basicity, reaching maxima at CaO/(CaO + SiO₂) ratios of about 0.2 and 1 and a minimum at a ratio of about 0.5. The solubility of the copper oxide in the bulk slag also passed through a minimum value at a ratio of about 0.5. Results from drop-quench experiments confirmed the stability of various oxide solid solution phases at 1573 K (1300 °C) that had virtually no solubility for Se and Te. The deduced capacity of the liquid slag for Se was found to be independent of basicity in relatively basic slags, and decreased sharply as SiO₂ replaced CaO in relatively acidic slags.     

Valve Distribution and Impact Analysis in Water Distribution Systems

In water distribution systems, valves play a crucial role in system reliability and security by providing a shutoff function when it is necessary to isolate subsystems. In this paper failure of shutoff valves to close is considered. The failure impact is quantified in terms of the expanding subnetwork and the increased number of customers out of service. To evaluate a system-wide valve failure impact, three methods are suggested: segment–valve matrix, decision tree analysis, and simulation. The segment–valve matrix shows the propagation of failure through the network as valves fail to close. The decision tree enumerates all possible valve failure combinations and corresponding event probabilities. Because the complete enumeration can be unwieldy, simulation procedures are offered that approximate the enumeration results closely. The details of the methods are illustrated with the aid of an example.     

关于铅锌原矿Pb、Zn品位分布状况的研究

铅锌矿所采出原矿的Pb、Zn品位在出矿随机取样分析时所得到的检测结果的统计分布状况同时也反映了矿产资源在一定的地质条件下所生成的地质原矿金属品位的分布.根据统计资料对原矿的Pb、Zn品位分布状况进行研究,目的就是找出其分布规律,以建立其分布的概率密度函数,结合探矿时矿体的资料科学地计算出原矿Pb、Zn品位分布区间的概率.以便更准确地推断矿产资料储有量.     

铅钙合金浇铸生产线设备的研制

铅钙合金浇铸生产线是为国内某大型冶炼企业研制的生产设备 ,介绍该设备组成、工作原理及特点。铅钙合金浇铸生产线自动化程度高 ,减轻了工人的劳动强度 ,改善的工作环境 ,具有良好的社会效益和经济效益。     

亚硫酸钙脱硫法在铅烧结烟气脱硫中的应用

冶炼厂铅烧结烟气中 SO2 浓度高 ,波动大 ,用亚硫酸钙脱硫法和 XP型板式吸收塔脱硫 ,其平均脱硫率达 95 %左右 ,每吨 SO2 脱硫成本 371元。以电石渣作脱硫剂副产石膏销往水泥厂 ,有一定经济效益。该工艺较好地解决了设备结垢的问题。     

Modeling Discoloration in Potable Water Distribution Systems

Discoloration of potable water supplied to customer taps is one of the biggest causes of water quality related customer complaints. At present, understanding of the fundamental processes that cause discoloration is limited and the modeling of events unfeasible. This paper describes the development, verification, and validation of a novel cohesive transport modeling approach to simulate discoloration within distribution systems. The model is based on the principal that strength characteristics of fine particulate material accumulated at the pipe walls are conditioned by the shear stress of the usual daily hydraulics. Discoloration occurs when the flow through the systems changes, exceeding the peak daily value. Fieldwork results from two sites are presented in detail: Site 1 demonstrates model application including sensitivity and parameter dependence, while data from Site 2 is used to investigate the hypothesis that daily hydraulic forces condition the material layers within the pipes. Model simulations are also presented for a selection of other field sites to demonstrate the wider applicability of the model.     

The Effect of Calcium Fluoride on Slag Viscosity

The effect of CaF₂ on the viscosity of high-basicity Al₂O₃-CaO-MgO-SiO₂ (-CaF₂) slags for secondary steelmaking was studied using a Brookfield digital viscometer. The addition of approximately 3 mass pct CaF₂ could decrease the liquidus temperature substantially in the case of high CaO containing slags, leading to good flowability of the slag at the temperature of the ladle treatment. The addition of CaF₂ had the strongest effect on the viscosity of liquid slag with high SiO₂ content.     

Competent Genetic-Evolutionary Optimization of Water Distribution Systems

A genetic algorithm has been applied to the optimal design and rehabilitation of a water distribution system. Many of the previous applications have been limited to small water distribution systems, where the computer time used for solving the problem has been relatively small. In order to apply genetic and evolutionary optimization technique to a large-scale water distribution system, this paper employs one of competent genetic-evolutionary algorithms—a messy genetic algorithm to enhance the efficiency of an optimization procedure. A maximum flexibility is ensured by the formulation of a string and solution representation scheme, a fitness definition, and the integration of a well-developed hydraulic network solver that facilitate the application of a genetic algorithm to the optimization of a water distribution system. Two benchmark problems of water pipeline design and a real water distribution system are presented to demonstrate the application of the improved technique. The results obtained show that the number of the design trials required by the messy genetic algorithm is consistently fewer than the other genetic algorithms.     

Aging Effect on Lanthanum Doped Ferroelectric Lead Titanate Ceramics

Ferroelectric devices are widely applied in many fields, such as energy conversion and communication. The aging effect in ferroelectric materials plays a central role in the reliability of the related equipments. But it is very difficult to understand the origin of aging effect in ferroelectrics because these materials possess different defects and exhibit various aging behavior. The reverse transition temperature in lead titanate doped with lanthanum increases during aging at ferroelectric phase was reported. It is well known that lattice defects, such as vacancies and solute atoms, are ubiquitous in crystalline solids. These point defects affect physical properties in ferroelectrics significantly. The abnormal increase of the reverse transition temperature was discussed in terms of diffusion of point defects during aging. Dielectric performance in the material after aging was measured and discussed as well.     

铁酸钙的形态对烧结矿抗断裂性能的影响

采用维氏压痕试验法,研究了含有不同形态铁酸钙的烧结矿中裂纹的萌生与扩展,考察了铁酸钙的形态对烧结矿抗断裂性能的影响.结果表明:铁酸钙尺寸较大时,烧结矿的抗断裂性能由铁酸钙本体的断裂韧性决定,它的尺寸较小时由其形态决定;铁酸钙的晶粒越细,致使裂纹萌生的临界载荷越大,烧结矿的抗断裂性能越好.烧结生产中生成细晶粒铁酸钙有利于提高烧结矿的抗断裂性能.     

钙对钒渣提钒的影响

分析了攀钢钒渣的物理、化学性质，研究了钒渣焙烧、浸出过程的工艺参数对钒回收率的影响规律，优化工艺条件用于钒氧化物生产。     

Adjoint Sensitivity Analysis of Contaminant Concentrations in Water Distribution Systems

Sensitivity analysis is used to determine how a system state or a model output changes due to a change in the value of a system parameter or a model input. We present the adjoint approach for determining the sensitivity of the concentration of a contaminant in a water distribution system to a change in a system parameter such as the location of the source of contamination, the reaction rate of the contaminant, and others. With the adjoint method, the sensitivity of the model output to any number of parameters can be obtained with one simulation of the adjoint model. If the number of parameters of interest exceeds the number of model outputs for which the sensitivity is desired, the adjoint method is more efficient than traditional direct methods of calculating sensitivities. We develop the adjoint equations for water quality in a water distribution system, verify the adjoint-based sensitivity equation using an analytical example, and demonstrate the numerical calculation of adjoint sensitivities using EPANET.     

Effect of Neodymium on Physiological Activities in Oilseed Rape during Calcium Starvation

The effects of RE on increasing crop productivity and stress tolerance were reported inpast years[' '2). La ion acts as a calcium-influxinhibitor by displacing Ca2 from cell wallsand occupying Ca2 -binding sites on the plasmalemma, as effective as Ca in the deferral ofsenescence. Besides blocking calcium channels, La has been frequently reported to mimicCa2 effect on plant ion transport. Migliaccioet al. found that both Ca2 and La3 stimulated auxin uptake into pea epicotyl segmentsfr…     

Nitrification Modeling in Pilot-Scale Chloraminated Drinking Water Distribution Systems

A suspended growth nitrification model was developed to describe nitrification dynamics in terms of chloramine, ammonia, nitrite, nitrate, and nitrifying bacteria concentrations in pilot-scale chloraminated drinking water systems. The model provided a semimechanistic base to study the regrowth and persistence of nitrifiers in chloraminated distribution systems. Results showed that the developed suspended growth model, without a biofilm nitrification component, was able to simulate and predict nitrification episodes in the pilot-scale systems. In the restricted low nutrient drinking water environment, growth kinetic parameters for nitrifiers were estimated to be significantly lower than ranges reported in the literature. The maximum specific growth rate and ammonia half-saturation constant for ammonia oxidizing bacteria were estimated to be 0.46?day?1and 0.023?mg NH3–N/L, respectively. In addition, an estimated reaction rate of 70±32?L/(mg?HPC?day) between chloramines and soluble microbial products suggests that heterotrophic growth can be a significant contributor to chloramine decay in some chloraminated distribution systems.     

Water Distribution Management in Small West African Canal Systems

The performance and progressive development of irrigation distribution and rotation methods were studied in two government-sponsored systems of Niger, West Africa. Systemwide water distribution was monitored intensively throughout several growing seasons and farmer surveys were conducted at both sites. Characteristics of farmer-managed rotation among tertiary canals and among parcels were examined in relation to farmer response to physical and organizational system constraints. A method for indexing the orderliness of irrigation rotation was developed. Where water deliveries were limited, organizational efforts on behalf of the farmers resulted in functional, orderly rotation and distribution among parcels. Farmers exhibit less incentive to organize efficient and orderly rotation among parcels where access to water is less limited. Several organizational and design factors influence the degree to which farmers are both willing and able to organize functional water distribution among themselves. Also, farmers may circumvent design intentions or management strategies imposed on them by irrigation authorities in order to establish their own more effective water management methods, which tend to better accommodate local labor and production constraints. Technical and organizational considerations related to water distribution and management derived from the study results may serve to facilitate the design and operation of small-holder systems in the Sahel.     

Demand Forecasting for Irrigation Water Distribution Systems

One of the main problems in the management of large water supply and distribution systems is the forecasting of daily demand in order to schedule pumping effort and minimize costs. This paper examines methodologies for consumer demand modeling and prediction in a real-time environment for an on-demand irrigation water distribution system. Approaches based on linear multiple regression, univariate time series models (exponential smoothing and ARIMA models), and computational neural networks (CNNs) are developed to predict the total daily volume demand. A set of templates is then applied to the daily demand to produce the diurnal demand profile. The models are established using actual data from an irrigation water distribution system in southern Spain. The input variables used in various CNN and multiple regression models are (1) water demands from previous days; (2) climatic data from previous days (maximum temperature, minimum temperature, average temperature, precipitation, relative humidity, wind speed, and sunshine duration); (3) crop data (surfaces and crop coefficients); and (4) water demands and climatic and crop data. In CNN models, the training method used is a standard back-propagation variation known as extended-delta-bar-delta. Different neural architectures are compared whose learning is carried out by controlling several threshold determination coefficients. The nonlinear CNN model approach is shown to provide a better prediction of daily water demand than linear multiple regression and univariate time series analysis. The best results were obtained when water demand and maximum temperature variables from the two previous days were used as input data.