Scale-effects on mean and standard deviation of the mechanical properties of condensed matter: an energy-based unified approach

The size effects on the mean values of the mechanical properties of condensed matter and on the related variances are analysed by means of a unified approach based on the multiscale character of energy dissipation. In particular, the scaling law for fragmentation energy density is obtained taking into account the self-similarity of fragments. It is based on a generalization of the three classical comminution laws that has been performed to evaluate the energy dissipation, computing volume and surface area of the particles for one- two- and three-dimensional fragmented objects. The result is general and can be applied to different fractal energy dissipation mechanisms, e.g., plasticity. Based on this approach, the scaling laws for mean and standard deviation values of the main mechanical properties of materials can be derived, like Young's and shear elastic moduli, ultimate normal and shear stresses and strains, fracture energy and toughness.     

Finite-difference time-domain simulation of scattering from objectsin continuous random media

A three-dimensional (3D) finite-difference time-domain (FDTD) scheme is introduced to model the scattering from objects in continuous random media. FDTD techniques have been previously applied to scattering from random rough surfaces and randomly placed objects in a homogeneous background, but little has been done to simulate continuous random media with embedded objects where volumetric scattering effects are important. In this work, Monte Carlo analysis is used in conjunction with FDTD to study the scattering from perfectly electrically conducting (PEC) objects embedded in continuous random media. The random medium models under consideration are chosen to be inhomogeneous soils with a spatially fluctuating random permittivities and prescribed correlation functions. The ability of frequency averaging techniques to discriminate objects in this scenarion is also briefly investigated. The simulation scheme described in this work can be adapted and used to help in interpreting the scattered field data from targets in random environments such as geophysical media, biological media, or atmospheric turbulence     

Effects of flux enhancing polymer on the characteristics of sludge in membrane bioreactor process.

A newly developed membrane performance enhancer (MPE) was used to prevent membrane fouling in a membrane bioreactor (MBR) process. It transpired that 1,000 mg/l of MPE reduced polysaccharide levels from 41 mg/I to 21 mg/I on average under the experimental condition. Repeated experiments also confirmed that 50-1,000 mg/l of MPE could reduce membrane fouling significantly and increase the intervals between membrane cleanings. Depending on MPE dosages and experimental conditions, trans-membrane pressure (TMP) increase was suppressed for 20-30 days, while baseline TMP surged within a few days. In addition, MPE allowed MBR operation even at 50,000 mg/l of total solid and reduced permeate COD. However, no evidence of toxicity for sludge was found from respiratory works.     

Ionothermal synthesis of a three-dimensional zinc phosphate with DFT topology using unstable deep-eutectic solvent as template-delivery agent

A three-dimensional zinc phosphate compound with DFT topology, designated as ZnPO₄-EU1, has been synthesized by an ionothermal approach from the system HF-ZnO–P₂O₅-choline chloride-imidazolidone. Ethylenediamine, derived from decomposition of the imidazolidone component of the deep-eutectic solvent (DES) itself, is delivered to the synthesis and serves as an appropriate template for ZnPO₄-EU1. Experiments in which the synthesis conditions were varied showed that ZnPO₄-EU1 may be prepared over a wide molar ratio of P/Zn = 0.55–13.0. Powder X-ray diffraction patterns have been obtained at intervals to track the crystallization process of this material. The experimental data show that Zn₃(PO₄)₂ · 4H₂O (a dense phase) was first isolated from the DES after reaction for 1 h. Subsequently, the pure phase of ZnPO₄-EU1 was obtained with increasing crystallization time from 12 h to 72 h. The experimental results show that the nucleation and crystallization take place with relatively low levels of solvent degradation, demonstrating that zinc phosphate with a three-dimensional framework can be synthesized by in situ generation of an appropriate template using an unstable DES at high temperatures (150–200 °C).     

BC480-22/42支架液压系统的大流量技术改造

分析了BC-480支架在综采工作面使用中液压系统配置低的原因,提出了系统的改造原则和方案,比较了改制前后支架的动作速度.     

Robust State Feedback Control Through Actuators With Generalized Sector Nonlinearities And Saturation

In control systems, actuators often have nonlinear characteristics that can not be neglected. For linear systems driven by actuators satisfying the generalized sector condition, a robust state feedback controller synthesis method is proposed to achieve the ultimate boundedness control. The method is based on the linear matrix inequality approach and is easy to apply. As an important special case of the generalized sector condition, the saturation characteristic of actuators is discussed separately, and non‐conservative results are obtained.     

Hydrocarbon exploration risk evaluation through uncertainty and sensitivity analyses techniques

The evaluation of the exploration risk in the oil industry is a fundamental component of the decision process related to the exploratory phase. In this paper the two basic components of the exploratory risk: trap geometry and trapped hydrocarbon quantities (fluid), are compounded in a single coherent uncertainty and sensitivity approach. The results clarify that the model geometry influences each Petroleum System Modeling step and that the geometric uncertainty is correlated with the fluid uncertainty. The geometric uncertainty evaluation makes use of geostatistical techniques that produce a number of possible realizations of the trap geometry, all compatible with available data. The evaluation of the fluid uncertainty, through a Monte Carlo methodology, allows us to compute the possible quantities of oil and gas, generated in a basin and migrated from the hydrocarbon source location to each single trap. The final result is the probability distribution of oil and gas for each trap in the basin, together with other useful indicators like: the hydrocarbon filling probability map, the closure probability map, the drainage area probability map, the spilling paths probabilities, the trap-filling scenarios.     

Hydrodechlorination of 3-chloropyridine and chlorobenzene in methanol solution over alkali-modified zirconia-supported palladium catalysts

The liquid-phase hydrodechlorination of 3-chloropyridine and chlorobenzene has been studied over alkali-modified zirconia-supported palladium catalysts. The modification of the ZrO₂ with alkali metal carbonates improves the catalytic activity of the final palladium catalyst. Therefore, the larger the ionic radii (Li⁺ < Na⁺ < K⁺), the greater the catalytic activity (TOF) of the palladium catalyst. For 3-chloropyridine, hydrodechlorination proceeds without catalyst deactivation. This is explained as the result of the interaction of reaction products (pyridine and HCl) forming pyridinium chloride, thus avoiding the detrimental effect of HCl on the palladium particles. Catalytic hydrodechlorination of chlorobenzene over Pd catalysts exhibits an initial catalytic activity (TOF) much lower than that of 3-chloropyridine and the Pd catalysts deactivate as the reaction proceeds. Finally, chlorobenzene hydrodehalogenation has also been carried out in the presence of an equimolecular amount of pyridine resulting in a decrease in the initial reaction rate on the one hand, but also in an increase in final conversion on the other.     

广义频率响应函数的鲁棒建模新方法

针对基于非线性谱分析的故障诊断技术的需要,研究了非线性系统的广义频率响应函数的鲁棒在线建模方 法。首先将次元分析算法应用于Volterra级数模型的辨识,并通过对此算法的修正,得到了一种改进的Volterra系统的鲁 棒辨识算法。对其鲁棒性能进行的分析表明,改进算法的鲁棒抗噪性能被明显提高。在此基础上,提出了一种广义频率响 应函数的两步鲁棒建模新方法。仿真实验表明,该方法具有良好的鲁棒收敛性能,能够有效解决GFRF的在线建模问题。     

Comments on “Is the cause of size effect on structural strength fractal or energetic-statistical?” by Ba?ant & Yavari [Engng Fract Mech 2005;72:1-31]

Aim of this letter to the Editor is at replying to the criticisms raised by Ba?ant and Yavari [Ba?ant ZP, Yavari A. Is the cause of size effect on structural strength fractal or energetic - statistical? Engng Fract Mech 2005;72:1-31] against the fractal approach to the size-scale effects on the mechanical properties of materials and the concept of the Multi-Fractal Scaling Law presented by Carpinteri [Carpinteri A. Scaling laws and renormalization groups for strength and toughness of disordered materials. Int J Solids Struct 1994;31:291-302]. These criticisms will be analysed thoroughly, showing how they also contain some mistakes and misunderstandings. The presented elucidations should redirect the discussion to a more correct scientific debate.