抗地震结构的服役费用函数及其建立方法

讨论了服役工程结构的经济性问题 ,包括 :抗地震结构在服役过程中为完成预定功能所需要的经济花费、这些花费同结构抗震可靠度的函数关系以及它们的建立方法。形成的服役费用函数可以作为决策结构最佳抗震设防标准的依据。     

Semi-analytical solutions for a Gray-Scott reaction-diffusion cell with an applied electric field

An ionic version of the Gray-Scott chemical reaction scheme is considered in a reaction-diffusion cell, with an applied electric field, which causes migration of the reactant and autocatalyst in a preferred direction. The Galerkin method is used to reduce the governing partial differential equations to an approximate model consisting of ordinary differential equations. This is accomplished by approximating the spatial structure of the reactant and autocatalyst concentrations. Bifurcation analysis of the semi-analytical model is performed by using singularity theory to analyse the static multiplicity and a stability analysis to determine the dynamic multiplicity. The application of the electric field causes variation in the parameter regions, in which multiple steady-state and oscillatory solutions occur. Moreover, as the reactor is not symmetric, reversal of the direction of the electric field can cause bifurcation in the reactor between high and low conversion states. Comparisons with numerical solutions of governing partial differential equations confirms the accuracy and usefulness of the semi-analytical model.     

Implementation of an Indirect Control Structure for Composition in a Hybrid Distillation Column

In this paper a PID controller is proposed to ensure the fuel ethanol composition at desired value, above 92.5°INPM, at the same time as saving energy through the minimal use of reboiler power. Due to the fact that composition analyzers are expensive and have a high response time, an inference model was developed in which the product composition is inferred from the product temperature and thermodynamics equations, enabling the monitoring and the indirect control a posteriori of this variable. In addition, the inference of composition allows defining the reference value of the product temperature, which ensures the fuel ethanol production at the desired composition.     

Air separation with cryogenic energy storage: Optimal scheduling considering electric energy and reserve markets

The concept of cryogenic energy storage (CES) is to store energy in the form of liquid gas and vaporize it when needed to drive a turbine. Although CES on an industrial scale is a relatively new approach, the technology is well known and essentially part of any air separation unit that utilizes cryogenic separation. In this work, the operational benefits of adding CES to an existing air separation plant are assessed. Three new potential opportunities are investigated: (1) increasing the plant's flexibility for load shifting, (2) storing purchased energy and selling it back to the market during higher‐price periods, and (3) creating additional revenue by providing operating reserve capacity. A mixed‐integer linear programming scheduling model is developed and a robust optimization approach is applied to model the uncertainty in reserve demand. The proposed model is applied to an industrial case study, which shows significant potential economic benefits. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1547–1558, 2015     

Transient convective mass transfer for a fluid sphere dissolution in an alternating electric field

In this study, we considered mass transfer in a binary system comprising a stationary fluid dielectric sphere embedded into an immiscible dielectric liquid under the influence of an alternating electric field. Fluid sphere is assumed to be solvent-saturated so that an internal resistance to mass transfer can be neglected. Mass flux is directed from a fluid sphere to a host medium, and the applied electric field causes a creeping flow around the sphere. Droplet deformation under the influence of the electric field is neglected. The problem is solved in the approximations of a thin concentration boundary layer and finite dilution of a solute in the solvent. The thermodynamic parameters of a system are assumed constant. The nonlinear partial parabolic differential equation of convective diffusion is solved by means of a generalized similarity transformation, and the solution is obtained in a closed analytical form for all frequencies of the applied electric field. The rates of mass transfer are calculated for both directions of fluid motion—from the poles to equator and from the equator to the poles. Numerical calculations show essential (by a factor of 2/3) enhancement of the rate of mass transfer in water droplet-benzonitrile and droplet of carbontetrachloride-glycerol systems under the influence of electric field for a stagnant droplet. The asymptotics of the obtained solutions are discussed.     

Nanoclay dispersion in a miscible blend: an assessment through rheological analysis

In this study, miscible polymer blend nanocomposite of Poly(ethylene oxide)/Poly(methyl methacrylate), (PEO/PMMA), with sodium montmorillonite (Na⁺-MMT) clay were prepared at a constant concentration of nanoparticles via different solution intercalation methods. The resultant nanocomposites possess different structure and dispersion of Na⁺-MMT clays which are assessed through a combination of transmission electron microscopy (TEM) and X-ray diffraction (XRD). The rheology of the neat blend and two different layered silicate nanocomposites were investigated using linear viscoelastic measurements with a parallel plate rheometry at small strain amplitudes. It was found that regardless of the extent of dispersion, the storage and loss modulus increased by incorporating the nanoparticles into the matrix of PEO/PMMA. Moreover, at low frequencies the rheological response of the nanocomposite in which layered silicates benefit from a better dispersion becomes relatively invariant with frequency and represents a mediocre solid-like behavior in comparison to the nanocomposite in which the nanoparticles are intercalated or agglomerated.     

An overall assessment of a new adhesive bonding process for composite materials,with regard to quality and cost

An assessment of innovative adhesive bonding process has been performed with regard to quality and cost. In this frame, the effect of two different atmospheric pressure plasma surface treatment conditions on the fracture toughness behaviour of adhesively bonded joints was experimentally investigated. Furthermore, the mechanical performance of a newly developed aerospace structural adhesive has been characterised experimentally in order to assess the quality of the bonded elements. To assess the feasibility of the new process, a complete cost-estimation analysis of the process has been carried out based on the activity-based costing modelling approach, thus serving to the estimation of the total cost/duration of the process. To this end, the newly developed process is assessed with regard to quality and cost. It could be shown that the new process offers tempting alternatives to the existing adhesive bonding and joining processes used in the aeronautic industry.     

Chemical assessment of the electric arc furnace slag as construction material: Expansive compounds

To carry out a correct management of electric arc furnace slags (EAS) requires a detailed knowledge of their properties. From a chemical point of view, the EAS are surrounded by some chemical problems related to its volume instability when they are used as construction materials, due to the presence of potentially expansive compounds such as free lime and mainly free MgO. The current work focuses on the chemical assessment of the black slags coming from an electric arc furnace in order to know the possible chemical disadvantages as construction materials. A complete study of chemical and mineralogical compositions, pozzolanic activity and the quantification of main expansive compounds in EAS were realised. The results show that the nature of these slags has a very high crystallinity; total absence of pozzolanic activity and the presence of expansive compounds in slags (Cl⁻, SO₃, free CaO and free MgO) were very low, if not null concentrations.     

Initiation of combustion of a gas mixture by an electric explosion of an electrolyte

Initiation of combustion of a stoichiometric propane-oxygen mixture in a bubble located in an electrolyte near a dielectric or metallic wall is performed in experiments. It is demonstrated that combustion in the bubble is initiated by an electric explosion-breakdown of a thin electrolyte layer along the bubble boundary.     

Optimal design of an activated carbon for an adsorbed natural gas storage system

The Dubinin-Astakhov equation was used to determine the influence of the microporous characteristics of activated carbon on the performances of both charge and discharge of an ANG system. From the dynamic performance criterion as a function of total microporous volume (W_o), average micropore width (L_o), and micropore size dispersion (n), it is possible to identify the optimal activated carbon for methane storage under dynamic conditions by way of the heat and mass transfer limitations. This study shows that the activated carbon must be conductive (with an average micropore width of 1.5 nm) for the charge step only, permeable and sufficiently conductive for the discharge process (with an average micropore width of 2.5 nm). The well-known Maxsorb activated carbon shows the better performance. This theoretical investigation has been validated by experimental results.     

Novel graphite/TiO2 electrochemical cells as a safe electric energy storage system

A graphite/TiO₂ full cell has been developed as a new safety energy storage system using a highly safety process. The crystal structures of the anatase TiO₂ electrode have been investigated with respect to the performance of the electrodes. Due to the large anion intercalation into the graphite positive electrode, the possible charging potential can be raised to around 5.3 V against the Li/Li⁺ electrode, which is a higher charging voltage than lithium-ion batteries (maximum voltage is around 4.3 V vs. Li/Li⁺). In situ XRD measurements have been carried out on both the cathode and anode electrodes of the graphite/TiO₂ cell during the charge process to elucidate the intercalation mechanism.     

Nutrition education: a questionnaire for assessment and teaching

It is generally recognized that there is a need for improved teaching of nutrition in medical schools and for increased education of the general population. A questionnaire, derived in part from a study of physician knowledge, was administered to first year medical students in order to assess their knowledge of various aspects of nutrition and metabolism, and as a teaching tool to transmit information about the subject. The performance of first year students was consistent with a generally educated population but there were surprising deficits in some fundamental areas of nutrition. Results of the questionnaire are informative about student knowledge, and immediate reinforcement from a questionnaire may provide a useful teaching tool. In addition, some of the subject matter can serve as a springboard for discussion of critical issues in nutrition such as obesity and markers for cardiovascular disease. A major barrier to improved teaching of nutrition is the lack of agreement on some of these critical issues and there are apparent inconsistencies in recommendations of government and health agencies. It seems reasonable that improved teaching should address the lack of knowledge of nutrition, rather than knowledge of official guidelines. Student awareness of factual information should be the primary goal.     

Diffusion flame in an electric field with a variable spatial configuration

The influence of an electric field whose intensity vector rotates around the flame axis on the shape of the diffusion flame of propane is experimentally studied. Application of spectrozonal registration makes it possible to obtain information about the radiation intensity distribution at wavelengths of intermediate reaction products (OH, CH, and C₂). Different positions of the peak intensity of the own radiation of the flame at different wavelengths testify to the influence of such an electric field on the mixing processes, namely, mixing is more intense than that in the regime without application of the electric field. This feature may turn out to be useful for increasing the efficiency of combustion of gaseous hydrocarbon fuels.     

Hybrid 1-D dielectric microcavity: Fabrication and spectroscopic assessment of glass-based sub-wavelength structures

Two different 1-D multilayer dielectric microcavities are presented, one activated by Er³⁺ ions fabricated by rf-sputtering and other one containing CdSe@Cd_0.5Zn_0.5S quantum dots obtained by a hybrid radio frequency-sputtering/solution deposition process. The rare-earth activated cavity is constituted by an Er³⁺ -doped SiO₂ active layer inserted between two Bragg reflectors consisting of 10 pairs of SiO₂/TiO₂ layers. Starting from the deposition procedure used for this cavity a fabrication protocol was defined with the aim to combine the high reproducibility allowed by the sputtering deposition for the fabrication of multilayers structures with the ability of fabricate films activated with highly luminescent quantum dots dispersed in polymeric matrix. In this case the cavity was constituted by poly-laurylmethacrylate host matrix containing CdSe@Cd_0.5Zn_0.5S quantum dots inserted between two Bragg reflectors consisting of 10 pairs of SiO₂/TiO₂ layers fabricated by rf-sputtering on SiO₂ substrate. The thicknesses of the films of the Bragg reflectors were tailored in order to reflect the visible radiation at around 650 nm. Transmittance spectra were employed to assess the optical features of the single Bragg gratings and whole samples. Luminescence measurements put in evidence that emissions strongly influenced by the presence of the cavities for both the samples.