生物炭对活性污泥沉降性能和反硝化作用的影响研究

Biochar is a massively produced by-product of biomass pyrolysis to obtain renewable energy and has not been fully used.Incomplete separation of sludge and effluent and insufficient denitrification of sewage are two of main factors that influence the efficiency of activated sludge process.In this work,we proposed a new utilization of biochar and investigated the effect of biochar addition on the performance of settleability and denitrification of activated sludge.Results show that the addition of biochar can improve the settleability of activated sludge by changing the physicochemical characteristics of sludge (e.g.,flocculating ability,zeta-potential,hydrophobicity,and extracellular polymeric substances constituents).Moreover,the dissolved organic carbon released from biochar obtained at lower pyrolysis temperature can improve the nitrate removal efficiency to a certain extent.     

Degree of Flocculation and Interparticles Charges of Conditioned Municipal Activated Sludge using Mixed Polymers

The present research work focuses on a new conditioning and flocculation mechanism of municipal fresh activated sludge using a dual polymer system combining cationic and anionic polyelectrolytes. Various pairs of three different types of polyelectrolytes, low molecular weight cationic polyacrylamide (CPAM-10), high molecular weight cationic polyacrylamide (CPAM-80) and an anionic polyacrylamide (APAM-30), were selected, being used either individually or as cationic-anionic pairs. The results of use of the dual systems indicated that using mixed polymers for conditioning gave lower turbidity with better settling when compared to that of using individual pure polymers. The mixed polymers improved the sludge volume index (SVI) by 62%. The zeta potentials of the supernatant and solid-like samples of conditioned activated sludge were measured. Slight increases in zeta potential, from –12 to –9, of the mixed polymers for all supernatants were observed. On the other hand, zeta measurements showed that the sludge solid-like particles retained their negative charges despite the addition of the individual cationic polymers in the mixture. This phenomenon was explained in terms of the addition of the polyelectrolytes attracting, primarily, the carboxylic groups of the fine suspended sludge particles, while hydrogen bonds between the larger sludge particles resulted in attraction in accordance with the Van der Waals mechanism, and both attractions caused an immediate dewatering that led to flocculation, but with low compactness. As a result of retaining negative charges on the large sludge particles, dissolved metals were partially attracted, causing reduction in conductivities of the supernatants of 10% to 15% for all pairs. Rheological tests showed that the formed flocs had low shear stress resistances, ranging between 0.2 and 0.4 Pa, and weak flocs strength.     

Structural damage assessment in a cantilever beam with a breathing crack using higher order frequency response functions

Vibration measurements offer an effective, inexpensive and fast means of non-destructive testing of structures and various engineering components. There are mainly two approaches to crack detection through vibration testing; open crack model with emphasis on changes in modal parameters and secondly, the breathing crack model focusing on nonlinear response characteristics. The open crack model based on linear response characteristics can identify the crack only at an advanced stage. Researchers have shown that a structure with a breathing crack behaves more like a nonlinear system, similar to that of a bilinear oscillator and the nonlinear response characteristics can very well be investigated to identify the presence of the crack. In the present study, the bilinear restoring force is approximated by a polynomial series and a nonlinear dynamic model of the cracked structure is developed using higher order frequency response functions. The effect of crack severity on the response harmonic amplitudes are investigated and a new procedure is suggested whereby the crack severity can be estimated through measurement of the first and second harmonic amplitudes.     

振动声调制技术下微裂纹的非线性响应分析

采用非线性弹簧模型对振动声调制技术下微裂纹产生的非线性调制效应进行解释。从理论上分析了振动声调制技术下微裂纹产生非线性调制现象的原理,将微裂纹的开合状态等效为非线性弹簧。利用有限元软件构建并仿真微裂纹非线性弹簧模型,分别观察不同激励下裂纹界面的开合状态及混合声波的传播特性。结果表明,微裂纹界面随低频声波呈周期性开合,使得通过裂纹界面的高频声波与低频声波相互调制而产生非线性现象。在以上研究基础上,开展振动声调制实验研究。对比仿真结果,非线性调制系数R在实验条件下和仿真随低频激励幅值的变化趋势相同,证明了该模型的正确性。该模型为振动声调制技术应用于微裂纹的超声非线性检测提供了理论依据。      

多光子非线性Compton散射对等离子体中电子运动的影响

应用多光子非线性Compton散射模型,研究了多光子非线性Compton散射对激光等离子体中电子运动的影响,提出了将入射激光和Compton散射光形成的耦合光、耦合光与等离子体产生的自生磁场形成的混合场作为加速电子的新机制,对电子动量和能量方程进行了修正和数值模拟。结果表明,当混合场的电场振幅与磁场振幅相等时,回旋共振电子在与混合场作用时间内能被加速到很高的能量;电子加速能量随耦合光幅值的增大而增大,随电子耦合初始角度的增大而周期变小,随电子横向耦合归一化初始速度的增大,开始时较快增加,之后缓慢增加,最后趋于稳定。     

Nonlinear frequency mixing in a resonant cavity: Numerical simulations in a bubbly liquid

The study of nonlinear frequency mixing for acoustic standing waves in a resonator cavity is presented. Two high frequencies are mixed in a highly nonlinear bubbly liquid filled cavity that is resonant at the difference frequency. The analysis is carried out through numerical experiments, and both linear and nonlinear regimes are compared. The results show highly efficient generation of the difference frequency at high excitation amplitude. The large acoustic nonlinearity of the bubbly liquid that is responsible for the strong difference-frequency resonance also induces significant enhancement of the parametric frequency mixing effect to generate second harmonic of the difference frequency.     

Adsorption of heavy metals on sonicated activated sludge

The objective of this work is to assess heavy metals fixation capacity on sonicated activated sludge. Ultrasonic treatment of sludge has lead to its desintegration and changes physico-chemical characteristics such as soluble chemical oxygen demand, proteins or particle size distribution. This study has shown that these modifications have improved significantly the capacity of sludge to fix heavy metals. Indeed, after a sonication of 15min and storage of three days after irradiation, the equilibrium capacity is increased about 45%. The restructuration of sludge during the storage seems to increase the accessibility to active binding sites.     

A fully coupled 3-D mixed finite element model of Biot consolidation

The numerical solution to the Biot equations of 3-D consolidation is still a challenging task because of the ill-conditioning of the resulting algebraic system and the instabilities that may affect the pore pressure solution. Recently new approaches have been advanced based on mixed formulations. In the present paper a fully coupled 3-D mixed finite element model is developed with the aim at alleviating the pore pressure numerical oscillations at the interface between materials with different permeabilities. A solution algorithm is implemented that takes advantage of the block structure of the discretized problem. The proposed model is verified against well-known analytical solutions and successfully experimented with in realistic applications of soil consolidation.     

Many-body effects in the highly excited state of fullerenes

The highly excited state of fullerenes is characterised by a luminescence output which is dependent on the cube of the input intensity. This nonlinear emission is red shifted from the low-level emission and has a long, intensity dependent lifetime. Under similar irradiation conditions, the photoconductive response is seen to increase with the cube of the input intensity and the photocurrent in the highly excited state is observed to be largely independent of temperature, contrasting sharply with the thermally activated behaviour at low excitation densities. The degree of nonlinearity of the observed phenomena exclude an interpretation in terms of intra-molecular processes and the temperature dependence of the photoconductive response is suggestive of a Mott-like transition. The nonlinear behaviour is compared to that of indirect band-gap semiconductors in which the origin of similar nonlinear phenomena in the highly excited state luminescence and photoconductivity are explained in terms of electron-hole droplet formation. The similarities of the behaviours leads to a consideration of exchange and correlation energies in fullerenes, which are calculated according to a phenomenological model. Estimates of the contributions are consistent with a Mott-like transition at high excitation densities and an excess exchange/correlation energy in the highly excited state of 150 meV.     

Mössbauer study of the Fe mineralogy in two different Argentine soils

Two Argentine soils featuring different characteristics and compositions (mollisols and ultisols) have been studied by Mössbauer spectroscopy and X-ray diffraction. The first type has a weakly developed profile with a solum thickness of 40 cm; the Fe oxyhydroxides are present in low concentrations in mixtures with other slightly weathered minerals (e.g., quartz, feldspars, 2 : 1 phyllosilicates, etc.). The second one is a typic kandihumult, which is a highly weathered red coloured, deep soil. The Fe oxyhydroxides are abundant, mixed mainly with kaolinite clay minerals. Analyses of iron mineralogy show hematite and goethite in both soils. Their ratio is low in the first case and high in the last case. Magnetite–maghemite are also present in both situations, but in the mollisol their content is much lower than in the ultisol. The mineralogy found is related to the different lithological characteristics and processes of pedological evolution on both soils.     

Analysis of nonlinear electric field of hvdc wall bushing with a finite element approach

The present research intends to establish a numerical model, on the basis of a theoretical analysis, for describing and analyzing the electric field of High Voltage Direct Current (HVDC) wall bushing that demonstrates highly nonlinear characteristics. The wall bushing is subjected high voltage with nonlinear electric field and the relationship between the electric field intensity and the resistance of the insulators of the wall bushing is highly nonlinear. With a parameter design language of a Finite Element Analysis software package for carrying out the numerical calculations, the effects of the nonlinearity on the electric field can be well taken into consideration in performing the numerical assessment. A technique utilizing the numerical iteration is developed for quantifying the electric intensity of the electric field. With the model and the iteration technique established, the nonlinear characteristics of the HVDC wall bushing can be investigated with efficiency.     

Characterization of PSD of activated carbons by using slit and triangular pore geometries

A mixed geometry model for activated carbons, representing the porous space as a collection of an undetermined proportion of slit and triangular pores, is developed, evaluated theoretically and applied to the characterization of a controlled series of samples of activated carbon obtained from the same precursor material. A method is proposed for the determination of the Pore Size Distribution (PSD) for such a mixed geometry model, leading to the unique determination of the proportion of pores of the two geometries fitting adsorption data. By using the Grand Canonical Monte Carlo (GCMC) simulation method in the continuum space, families of N2 adsorption isotherms are generated both for slit and triangular geometry corresponding to different pore sizes. The problem of the uniqueness in the determination of the PSD by fitting an adsorption isotherm using the mixed geometry model is then discussed and the effects of the addition of triangular pores on the PSD are analyzed by performing a test where the adsorption isotherm corresponding to the known PSD is generated and used as the “experimental” isotherm. It is found that a pure slit geometry model would widen the PSD and shift it to smaller sizes, whereas a pure triangular geometry model would produce the opposite effect. The slit and triangular geometry families of isotherms are finally used to the fit experimental N₂ adsorption data corresponding to a family of activated carbons obtained from coconut shells through a one-step chemical activation process with phosphoric acid in air, allowing for the determination of the micropore volume, the proportion of slit and triangular pores and the PSD corresponding to the mixed geometry. The same experimental data were fit using both the conventional slit pore model and the mixed geometry model. From the analysis of the effect of different preparation procedures on the resulting PSDs, it is concluded that the proposed mixed geometry model may probably better capture the morphology and energetics of activated carbons prepared by chemical activation under mild temperatures.     

生活垃圾微生物堆肥水溶性有机物光谱特性研究

利用外源微生物(MS,ZJ)进行城市生活垃圾工厂化堆肥,在堆肥前后对水溶性有机物的紫外、红外、荧光光谱进行了分析,探讨外源微生物堆肥对水溶性有机光谱学特性的影响。结果表明,堆肥结束后,不同处理水溶性有机物紫外、红外、荧光光谱形状基本相似,但特征峰强度有明显区别。与CK相比,接种微生物处理堆肥后,水溶性有机物紫外光谱280 nm附近类肩峰明显减弱;红外光谱解析表明,水溶性有机物中小分子糖类物质减少,芳族类物质增加;荧光同步扫描光谱进一步证实,水溶性有机物中多环芳族类化合物增加,其荧光光谱特征峰与污泥中富里酸相似。试验结果证实,接种外源微生物可明显增加堆肥水溶性有机物芳构化程度,各处理芳构化程度依次为：MS+ZJ>ZJ>MS>CK。     

强化生物除磷过程中聚β羟基烷酸酯的红外光谱分析

强化生物除磷是废水生物除磷的主要技术手段。在厌氧与好氧交替运行的反应过程中,污泥中聚β羟基烷酸酯(PHA)经历了厌氧储存和好氧降解的过程,其位于1 740 cm-1吸收峰亦呈现出先增强后减弱的变化。通过比较PHA标准品的红外光谱图,实现了活性污泥PHA的红外特征归属,1 740 cm-1红外吸收峰源于PHA羰基特征吸收。利用高斯分峰法将相互重叠的PHA峰、蛋白质Ⅰ峰和蛋白质Ⅱ峰进行了分离,PHA与蛋白质Ⅰ峰的峰面积比值与PHA测定值有较好相关性,相关系数可达0.873,峰面积比值可反映污泥中PHA的变化趋势。选取1 480~1 780 cm-1区域红外光谱,经过归一化处理并转化为吸光度数据后,结合污泥样品PHA含量的色谱分析结果,应用偏最小二乘法建立了污泥样品红外光谱与PHA含量的关系模型,模型预测值与测量值具有较好的一致性,结合未知浓度活性污泥样品的红外光谱以及该关系模型,可以迅速预测未知污泥样品中的PHA含量。该方法的研究为污泥胞内PHA的快速表征和定量分析提供了新的分析方法。     

Hydromagnetic Carreau Nanoliquid in Frames of Dissipation and Activation Energy

The novel characteristics of magnetic field and entropy generation in mixed convective flow of Carreau fluid towards a stretched surface are investigated.Buongiornio nanoliquid model consists of thermophoresis and Brownian movement aspects is opted for analysis.Energy expression is modeled subject to thermal radiation and viscous dissipation phenomenon.Concentration by zero mass flux condition is implemented.Consideration of chemical reaction and activation energy characterizes the mass transfer mechanism.Total entropy generation rate and Bejan number is formulated.The utilization of transformation variables reduces the PDEs into non-linear ODEs.The obtained nonlinear complex problems are computed numerically through Shooting scheme.The impact of involved variables like local Weissenberg number,magnetic parameter,thermal radiation parameter,Brownian motion parameter,thermophoresis parameter,buoyancy ratio parameter,mixed convection parameter,Prandtl parameter,Eckert number,Schmidt number,non-dimensional activation energy parameter,chemical reaction parameter,Brinkman number,dimensionless concentration ratio variable,diffusive variable and dimensionless temperature ratio variable on velocity,temperature,nanoparticles concentration,entropy generation,Bejan number,surface drag force and heat transfer rate are examined through graphs and tables.     

X-ray determination of the mean Debye-Waller factors and Debye temperatures of KCl-RbCl mixed crystals

Integrated intensities of Bragg reflections have been measured for KCl-RbCl mixed crystals with various compositions and the data used to evaluate the mean Debye-Waller factors and the Debye temperatures. The composition dependence of the Debye-Waller factor is highly nonlinear with positive deviations from linearity while that of the Debye temperature is slightly nonlinear with negative deviations from linearity. Using an empirical relationship between the Debye temperature and the molar volume, the average values of the Gruneisen parameter for some mixed crystal systems are obtained.     

Effect of electric field on activated sludge in water

The results of the study of the effect of a dc electric field on activated sludge of aeration tanks. It is experimentally detected that the specific oxidation rate of organic compounds by activated sludge increases up to 90.5% with electric field processing, and then decreases. The observed effect is substantiated. The results obtained can find wide application in purification of sewage polluted by organic compounds.     

Closed-form internal impedance model and characterization of mixed carbon nanotube bundles for three-dimensional integrated circuits

Based on the complex effective conductivity method, a closed-form expression for the internal impedance of mixed carbon nanotube(CNT) bundles, in which the number of CNTs for a given diameter follows a Gaussian distribution, is proposed in this paper. It can appropriately capture the skin effect as well as the temperature effect of mixed CNT bundles.The results of the closed-form expression and the numerical calculation are compared with various mean diameters, standard deviations, and temperatures. It is shown that the proposed model has very high accuracy in the whole frequency range considered, with maximum errors of 1% and 2.3% for the resistance and the internal inductance, respectively. Moreover,by using the proposed model, the high-frequency electrical characteristics of mixed CNT bundles are deeply analyzed to provide helpful design guidelines for their application in future high-performance three-dimensional integrated circuits.     

新型全光纤高能量飞秒光脉冲源的数值模拟

数值模拟了自相似脉冲的产生与压缩,得到一种产生高能量飞秒光脉冲的新方法.结果表明:利用掺铒光纤对光脉冲进行自相似传输,可得到含线性频率啁啾的高能量自相似光脉冲;自相似光脉冲经过空芯光子带隙光纤的一级线性压缩和高非线性光纤的二级非线性压缩,可获得高峰值功率的飞秒光脉冲;压缩过程中存在最佳光纤长度;喇曼自频移和自陡效应对脉冲压缩产生不利影响.