Leaching kinetics of electric arc furnace dust in nitric acid solutions

Electric arc furnace dust contains mainly ZnO, ZnFe₂O₄, and iron oxides. In this study, chemical composition of ZnO, ZnFe₂O₄, and Fe₂O₃ and leaching kinetics of ZnO, ZnFe₂O₄, and Fe₂O₃ in HNO₃ solutions were investigated. It was seen that the dissolution of ZnO is very fast, therefore the leaching kinetics of ZnO cannot be determined. Kinetic parameters and model equations were derived for the leaching of ZnFe₂O₄ and Fe₂O_3. Leaching kinetics of ZnFe₂O₄ was explained by the pseudohomogeneous reaction model. Activation energy and order of HNO₃ concentration were found to be as 37.5 kJ mol⁻¹ and 0.37, respectively. The model equation was derived as . It was determined that experimental data for the leaching kinetics of Fe₂O₃ best fit with the shrinking core model (SCM). Activation energy and order of HNO₃ concentration were found to be as 51.5 kJ mol⁻¹ and 0.67, respectively The model equation was derived using SCM as _.     

改进的FastICA-SVR结合荧光光谱技术测定1-萘酚、2-萘酚

水作为生命之源与人类的生存息息相关，近年来关于水环境污染的报道越来越多，不容忽视。实验以萘酚的两种同分异构体1-萘酚、2-萘酚的混合物作为研究对象，提出了一种新的算法，通过对混合物的三维荧光光谱进行分析来实现水中萘酚的定性定量分析。利用FS920稳态荧光光谱仪对配制的混合溶液进行扫描得到荧光光谱数据，并对数据进行一系列的预处理去除拉曼散射和瑞利散射的影响。将解决盲源分离(BSS)问题的独立成分分析(ICA)算法应用到荧光光谱定性定量分析问题当中，盲源分离技术就是将测量得到的混合信号作为处理对象进行分解，实现未知系统中源信号的求解，并得到混合矩阵。对混合物中单一物质的识别与测量与盲源分离问题类似。采用基于负熵最大的快速独立成分分析(FastICA)算法对实验数据进行分解，将所有样本的三维荧光光谱数据沿发射波长方向展开成为向量，得到一个大小为(N×M)的矩阵(N为样本数，M为波长数)，将该矩阵作为快速独立成分分析的输入进行独立分量提取，输出分别为单组分物质的展开荧光光谱和混合矩阵。FastICA算法的关键是利用牛顿迭代算法得到解混矩阵，但迭代过程中复杂的求导问题会使计算量增大、迭代速度减慢，针对该算法存在的问题，提出用差分法(又称为双点弦截法)代替求导的解决方法。为了验证算法的可行性，用改进后的算法和原有算法分别对荧光光谱数据进行了五次独立分量提取实验，原有算法平均运行时间为17.78 s，而改进后的算法平均运行时间为3.22 s，比原有算法提高了14.56 s，有效地减少了计算量，改善了FastICA算法的迭代速度并且使其收敛性更加稳定。通过实验结果可以看出改进后的算法得到的光谱更接近真实的光谱。利用快速独立成分分析算法分解得到的混合矩阵与物质浓度相关，这是物质定量分析的依据，但它们之间的关系可能是非线性的，采用能实现非线性拟合的支持向量回归机(SVR)进行回归预测，将混合矩阵和实际浓度矩阵分别作为SVR的输入和输出，利用遗传算法(GA)对支持向量回归机的参数进行优化选择，并选择径向基核函数(RBF函数)作为SVR的核函数，建立回归模型，实现对荧光光谱的定量分析。1-萘酚的拟合相关系数(r)为0.998 6，样品回收率(Recovery rate)为96.75%～104.2%，预测均方根误差(RMSEP)为0.119 μg·L-1；2-萘酚的拟合相关系数为0.998 8，样品回收率为96.8%～105.5%，预测均方根误差为0.1 μg·L-1，预测结果比较令人满意，符合预测要求。实验证明改进的基于负熵最大的FastICA-SVR算法能实现对混合物中1-萘酚、2-萘酚准确有效的识别和测量，并且改进之后加快了算法的分解速度。     

Effect of signals on two-route traffic system with real-time information

We study the effect of signals on the vehicular traffic in the two-route system at the tour-time feedback strategy where the vehicles move ahead through a series of signals. The Nagel–Schreckenberg model is applied to the vehicular motion. The traffic signals are controlled by both cycle time and split. The tour times on two routes fluctuate periodically and alternately. The period increases with decreasing the split. Also, the tour time on each route varies with time by synchronizing with the density. The dependences of tour times and densities on both split and cycle time are clarified.     

Uniform recovery from subgaussian multi-sensor measurements

Parallel acquisition systems are employed successfully in a variety of different sensing applications when a single sensor cannot provide enough measurements for a high-quality reconstruction. In this paper, we consider compressed sensing (CS) for parallel acquisition systems when the individual sensors use subgaussian random sampling. Our main results are a series of uniform recovery guarantees which relate the number of measurements required to the basis in which the solution is sparse and certain characteristics of the multi-sensor system, known as sensor profile matrices. In particular, we derive sufficient conditions for optimal recovery, in the sense that the number of measurements required per sensor decreases linearly with the total number of sensors, and demonstrate explicit examples of multi-sensor systems for which this holds. We establish these results by proving the so-called Asymmetric Restricted Isometry Property (ARIP) for the sensing system and use this to derive both nonuniversal and universal recovery guarantees. Compared to existing work, our results not only lead to better stability and robustness estimates but also provide simpler and sharper constants in the measurement conditions. Finally, we show how the problem of CS with block-diagonal sensing matrices can be viewed as a particular case of our multi-sensor framework. Specializing our results to this setting leads to a recovery guarantee that is at least as good as existing results.     

Electrochemical Biosensors Based on Micro-fabricated Devices for Point-of-Care Testing: A Review

Point-of-care testing (POCT) is becoming a hot research topic that allows rapid, on-site, and non-professional measurements outside the central laboratory. The micro-fabricated devices prepared by various micro-machining technologies have shown the advantages of low reagent consumption, high-throughput samples, and wearability. This review presents the recent progress of electrochemical biosensors based on various micro-fabricated devices for POCT and the corresponding electrochemical techniques. Signal amplification strategies based on enzyme and nanotechnology are also illustrated for the more sensitive POCT applications of these micro-fabricated devices. Consequently, the trends and challenges of electrochemical biosensors based on micro-fabricated devices in POCT diagnosis are discussed.     

SirX: a selective inversion recovery experiment on X‐nuclei for the determination of the exchange rate of slow chemical exchanges between two sites

Nuclear magnetic resonance spectroscopy has proven to be powerful for the study of dynamic processes. A new pulse sequence, SirX, is designed to provide boundary conditions that simplify the McConnell equations. Both an initial rate approximation and a whole curve fitting to the time course of magnetization can be used to calculate the exchange rate. These methods were used to study the exchange kinetics of N,N‐dimethylacetamide. As compared with the well‐established exchange spectroscopy suitable to studies of slow exchange, SirX has the advantage of being less time consuming and capable of providing more reliable kinetic data. Furthermore, by setting the observation on X‐nuclei with larger chemical shift dispersion as compared with an observation on ¹H resonance, SirX extends the upper limit of a reliable determination of exchange rates. Copyright © 2015 John Wiley & Sons, Ltd.     

Survivability in IP-over-WDM Networks: WDM Lightpath Protection versus IP LSP Protection

Abstract

This article compares the performance of WDM lightpath protection and IP LSP protection schemes for IP-over-WDM networks. A mathematical formulation of the maximum throughput problem is presented and analytical expressions for recovery time are derived for both schemes. The throughputs and recovery times are analyzed and compared. Results show that the IP LSP protection scheme presents higher throughputs then WDM lightpath protection. The IP LSP protection scheme, providing individual IP LSP protection has, however, scalability problems. This scheme presents high recovery times when a failure affects many lightpaths and many hops are allowed for the primary routes of IP LSPs.     

Selective Recovery of Ammonia Nitrogen from Wastewaters with Transition Metal-Loaded Polymeric Cation Exchange Adsorbents

Extracting valuable products from wastewaters with nitrogen-selective adsorbents can offset energy-intensive ammonia production, rebalance the nitrogen cycle, and incentivize environmental remediation. Separating nitrogen (N) as ammonium from other wastewater cations (e.g., K⁺, Ca²⁺) presents a major challenge to N removal from wastewater and N recovery as high-purity products. High selectivity and capacity were achieved through ligand exchange of ammonia with ammine-complexing transition metals loaded onto polymeric cation exchange resins. Compared to commercial resins, metal–ligand exchange adsorbents exhibited higher ammonia removal capacity (8 mequiv g⁻¹) and selectivity (N/K⁺ equilibrium selectivity of 10.1) in binary equimolar solutions. Considering optimal ammonia concentrations (200–300 mequiv L⁻¹) and pH (9–10) for metal–ligand exchange, hydrolyzed urine was identified as a promising candidate for selective TAN recovery. However, divalent cation exchange increased transition metal elution and reduced ammonia adsorption. Ultimately, metal–ligand exchange adsorbents can advance nitrogen-selective separations from wastewaters.     

Work hardening and recovery in fully lamellar TiAl: relative activity of deformation systems

The relative activity of deformation systems during work hardening and thermal recovery has been investigated in fully lamellar TiAl. This has been done by a combination of a series of deformation/static recovery experiments and numerical simulations based on a defect density-based crystal plasticity model. Firstly, active deformation systems in differently oriented polysynthetically twinned crystals/single lamellar colonies have been studied. Subsequently, numerical experiments on a polycolony microstructure have been used to investigate the inhomogeneous microplasticity (i.e. the typical microyield) in fully lamellar TiAl. From this, it has been possible to analyse how changes in the lamella thickness, domain size and colony size influence the onset of macroscopic yield. Based on static recovery experiments with differently oriented polysynthetically twinned crystals, numerical studies have revealed trends in the recovery of work hardening in both polysynthetically twinned crystals and polycolony microstructures.     

Recovery decisions of a producer in a legislative disposal fee environment

The main objectives of the environmental legislation originating from extended producer responsibility (EPR) principle are to lead producers to undertake recovery initiatives for their end-of-use products and to promote environmentally desirable product design. It is still controversial whether current implementations of EPR principle are effective in attaining these objectives. This study seeks to answer the following questions: (1) What is the impact of EPR legislation on the product recovery decisions of producers? (2) How do the redesign opportunities (i.e., design for disassembly) affect the willingness of producers for product recovery? (3) How do the investment needs to start recovery practices and the reluctance of producers to allocate sufficient funds for this purpose affect the optimal recovery decisions? We use stylized economic models to represent the implementation in practice and solving our models we obtain closed form and numerical solutions that help us to see the impact of various parameters on the optimal decisions of a producer. Our findings indicate that redesign opportunities encourage producers for more recovery, however the reluctance of producers to cover the initial investments may substantially reduce the effectiveness of the legislation and the recovery amounts.