Applied Mechanics and Materials Vols. 130-134

Abstract: In order to solve the problems of pumping fluctuations and bandwidth limitation to dynamic air fuel ratio (AFR) control for a coal-bed gas engine, adaptive models for air mass flow rate and fuel gas mass flow rate in intake system and exhaust AFR were constructed by a recursive identification method based on the forgetting factor (FF) algorithm. A linear time-varying equation error model was selected as the structure of the adaptive models. Firstly, the throttle position and crankshaft speed signals were used to predict the air and fuel gas flow rates. Secondly, the AFR was predicted in real time according to the estimated air and fuel gas flow rates. The trade-off between tracking ability and noise sensitivity was realized by adjusting a FF. The experiment validations at transient operating conditions of the engine accelerating and decelerating show that, adaptive recursive models of the air and gas flow rates with a larger FF can not only track the averaging values of the flow rates, but also deal with the phase delays introduced by the filter, the AFR adaptive recursive model with a smaller FF can predict transient AFR accurately.

Abstract: Fishing activities as well as other third-party factors can have great impact on the safety of subsea pipelines. Through an investigation into fishing activities in different sea areas in China, combined with theoretical and modeling calculation of the actual influence of the impacting trawl board and anchor on pipelines, a recommended under bed solution of subsea pipeline was worked out. The solution can provide reference in rule-making involving the burial depth of subsea pipelines.

Abstract: A simple technique is introduced to estimate the inter-modal coupling relations of two Statistical Energy Analysis (SEA) subsystems connected via an arbitrary interface. Based on a subsystem modal approach, the dynamic stiffness matrix of a generic built-up system is derived analytically. The coupling stiffness terms between any pair of subsystem modes can then be determined in explicit expressions. Under the proper SEA conditions, e.g. each subsystem has a high modal density and the couplings between SEA subsystems are sufficiently weak, these inter-modal coupling stiffness expressions can be greatly simplified. The results can then be easily accommodated within the standard SEA modeling procedure to predict the SEA response of generic built-up systems in a simple manner. Theoretical applications are made to estimate the SEA coupling loss factors between two subsystems connected by two rigid points.

Abstract: The adsorption of methylene blue (MB) from aqueous solution using a low-cost adsorbent, ginkgo leaf powder, has been studied. The equilibrium data were fitted to Langmuir and Freundlich isotherms and the equilibrium adsorption was best described by the Langmuir isotherm model with maximum monolayer adsorption capacities found to be 39 mg/g. The sorption was analyzed using pseudo-first-order and pseudo-second order kinetic models, and the sorption kinetics was found to follow a pseudo-second order kinetic model. Ginkgo leaf appears as a prospective adsorbent for the removal of methylene blue from aqueous solution.

Abstract: Due to the decline of the world's forest resources, non-wood fiber sources are becoming increasingly important as raw materials in fiber-based industries, One source of such non-wood fiber is S. alterniflora (Common Cordgrass) and related species, which are large-sized grasses, about 1-1.5 m tall, with leaves 20-60 cm in length). These grasses have invaded many coastal areas in China and can result in huge economic losses. Studies have shown that the fiber composition of S. alterniflora is: cellulose 35.9%, hemicellulose 34.2%, lignin 15.9%, ash 2.98%. The length of S. alterniflora fibers, which are shorter and narrower than bamboo fibers, makes it difficult to utilize S. alterniflora in chemical pulps. However, thermomechanical pulping of S. alterniflora stems can be used to prepare pulps which can then be suitably mixed with chemical pulps and used to manufacture a variety of molded pulp products The raw material for the pulp molding products is used S. alterniflora pulp mixing with other chemical pulp like bamboo pulp, off-cuts from the paper making factory, printing factory, corrugated factory and other paper product factories. The pulp molding products can be collected and reused again, which could control the rapid spread invasive species of S. alterniflora effectively. Even if it is abandoned in nature, it will be biodegraded into fertilizer within a few months.

Abstract: The ash characteristics is closely related to the fuel compositions, and chemical reactions happened between the compounds of ash during co-combustion of biomass and coal. Through the phase compositions analysis of ash from co-combustion of biomass and coal, the results show that KCl_(g) mainly reacts with aluminosilicates to form potassium-aluminosilicates and part of KCl_(g) also can be sulfated by SO₂ during co-combustion. In the fuel, CaO and MgO may react with aluminosilicates to form CaAl₂Si₂O₈ and Mg₃Al₂Si₃O₁₂ with low melting temperature, which can reduce the content of potassium-aluminosilicates and drop the ash melting point temperature.

Abstract: A possible mechanism of polaron to bipolaron transition is investigated based on the well known SSH model. We have studied the dynamical process of collision between two positively charged polarons with same spin in the presence of external electric fields. It is found that when the relative velocity of collision is not very large, the collision leads to a direct transition of two polarons to a bipolaron.

Abstract: The grinding wheel will have a property of self-lubricating when the inclusion complexes of β-cyclodextrin (β-CD) and oleic acid are used as filler. The association constants and thermodynamic parameters of inclusion complex of β-CD and oleic acid were determined by competitive inclusion method in aqueous buffer solution (pH = 10.50, c = 0.025 mol/L) at different temperatures using phenolphthalein (PP) as a probe. Furthermore, the stoichiometric ratio of the complex was derived by equimolar series method. The results showed that the stoichiometric ratio of the complex was about 1:1 and the thermodynamic parameters of ΔG, ΔH and ΔS were all negative, which indicated that the formation of the inclusion complex was spontaneous, exothermic and enthalpy-driven. Thermogravimetric analysis revealed that the complex began to have a weight loss at 300°C and could withstand the hardening temperature of resin bond grinding wheel.

Abstract: Ferric salt modified sands were prepared with quartz sand as a carrier and ferric salt coating by the two methods of repeat high-temperature process and repeat alkaline deposition process. The specific surface area of two ferric salt modified sands were detected, and their Pb2+ adsorption capability in different conditions were also described in this paper. The results showed that the specific surface area of ferric chloride and ferric nitrate modified sand was 2.468m2/g and 4.247m2/g respectively, which was 6.910 and 12.612 times more than that of raw quartz sand. In the neutral pH condition, the removal efficiency of Pb2+ by raw quartz sands was approximately 37%, in contrast, the removal efficiency reached 85% by ferric nitrate modified sand and over 90% by ferric chloride modified sand, and it was much higher than that of raw quartz sand.

Abstract: In this experiment quartz sand was chosen as a carrier to be coated by aluminous salt under alkaline condition, and then the specific surface area was tested, and the adsorption capability and Cd²⁺ removal influencing factors of modified sand were studied. The investigation results showed that the specific surface area of modified sand was 75.244m²/g which was 9.38 times of that of original sand; the removal efficiency of Cd²⁺ by aluminous salt modified sand reached 59% contrast to 39% of original sand with pH 7.00. It was also found that the removal efficiency of Cd²⁺ by the aluminous salt modified sand was reduced with the increase of initial concentration of Cd²⁺ solution, and was enhanced with the increase of pH value, the Cd²⁺ removal efficiency was almost 71% with pH 9.0.