Applied Mechanics and Materials Vols. 608-609

Abstract: The article introduced the basic structure and the realization principle of direct digital frequency synthesizer (DDS), and analyzed main properties of DDS system, compared the different ways to achieve frequency synthesis to determine the design scheme in this paper. In addition to the realization of general waveform, the output of the system can realize any hand-painted waveform, improve the shortcomings of the current function generator, and also has the advantages of low cost, low power consumption, short development cycle, flexible design, has the very good practical value and broad application prospect.

Abstract: Based on the important role in aspects of Backfill mining technology in mining to resolve the deep pressure , maintain the slope steady, control the surface sinking and protect the ecological environment, this article probes the relationship between filling material strength to gangue for coarse aggregate ,to coal ash for fine aggregate, to cement and waterglass for binder and influencing factors, and researches the strength properties and the deformation properties of filling objects used for engineering practice, which gets good filling effect. The results showed that the filling material having a high early strength and high elastic modulus, when compressed it performance plastic hardening characteristics; under certain conditions of the concentration by mass and the amount of coal ash, filling mass showing the approximate linear relationship between the compressive strength and natural curing time, Under the same condition, cement + water glass as cementitious material filling mass is significantly higher than only with cement as a cementitious material in the strength.

Abstract: According to existing backfill process of the Jiaojia Gold Mine, this research uses the whole tailings as fill aggregate to replacement grade tailings. The solid concentration of backfill slurry was increased from 68% to 72% and the naphthalene-based superplasticizer was used to achieve gravity well-distributed transport. The effects of naphthalene-based superplasticizer on the sedimentation rate, bleeding rates, fluidity and compressive strength of the whole tailings backfill materials were investigated with different content. The results show that naphthalene-based superplasticizer can slow the sedimentation rate, improve the fluidity of whole tailings backfill slurry and increase the compressive strength. The fluidity of the whole tailings backfill slurry with 0.3% naphthalene superplasticizer is largest and the compressive strength is highest in all of the specimens.

Abstract: This paper has designed a new diamond computer evaluation method by the use of the diamond evaluation model, and the combination of VC programming technology, and the method has been introduced into the evaluation of regional tourism comprehensive competitiveness. In order to achieve the comprehensive evaluation function of new diamond model, we have designed new diamond comprehensive fuzzy evaluation model by using fuzzy evaluation function to, and have the developed computer evaluation system of regional tourism competitiveness by combining VC programming technology. The system uses the market, enterprises and infrastructure the three aspects of evaluation factors to score the tourism competitiveness, which has realized the evaluation of computer automation function. Competitiveness of regional tourism industry in Shandong, Yunnan and Gansu and other areas is respectively scored through the function, and the results indicate that the comprehensive evaluation score of Yunnan is the highest, and that of Gansu is the lowest.

Abstract: In order to evaluate the effect of particle size on FeS Spontaneous Combustion Characters, four different grain diameters of FeS particles (100, 170, 220, 320-mesh) were detected in the experiment. The reaction process at heating rates of 5°C /min in air flow from 30°C to 900°C were studied by TG-DSC and oxidation kinetic analysis. The activation energies of samples were calculated by the Coats-Redfern method. It is found that four reaction mechanisms are involved in FeS spontaneous combustion for different particle sizes; the activation energy values change from 307.4 to 398.05 kJ/mol; larger size particles have higher activation energy values; so grain diameters larger than 100-mesh size samples are less inclined to be oxidized and self-ignited.

Abstract: In this paper, we use foam injection coagulation method to fabricate SiC/mullite porous ceramic with porosity 38-80%. In order to study the performance of the ceramic, we use the principle of cavity to establish the fourteen surfaces model of the SiC/ mullite porous ceramics, and use the ANSYS finite element simulation software to simulate the performance of ceramic, and do simulation on the mechanical properties of the ceramics. In order to study the influence of different wall thickness and curvature on the properties of ceramics, we calculate the structure stress distribution of fourteen surfaces when wall thickness is 0.4 and 0.5mm. When the wall thickness is 0.2mm, we study the structure stress distribution with radius 0.1mm and 0.2mm. So we obtain the influence of wall thickness and curvature radius on the properties of porous ceramics. It provides valuable reference data for the study on porous ceramics.

Abstract: Density Functional Theory (DFT),at the B3LYP/6-311 G(d,p) level of theory and Moller-Plesse Theory (MP2/6-311G (d,p)) has been performed to study the mechanism, potential energy surface of the Diels-Alder reaction in the Synthesis of abietane diterpenes. The obtained results indicate that the reaction is concerted and synchronous processes. The transannular product is formed via a six-member ring transition state; yield of the endo product is higher. And finally, the enthalpie and activation energie of the reaction are given respectively. The reaction is exothermic,which accords well with experimental observation.

Abstract: Based on phthalocyanines --SnO₂ as a photo catalyst, this paper uses the degrading difference of thiophene by various catalysts under ultraviolet and visible light irradiation conditions to compare the catalytic effects of the different phthalocyanine compounds --SnO₂ photosensitive catalysts, and summarize the reasons and laws to influence the catalysts’ catalytic performance, and analyze the kinetic process of photocatalytic oxidation reaction, and initially discuss kinetics of photocatalytic oxidation reaction and its products.

Abstract: A technology for using petroleum deposit’s energy and the principle of medium’s phase change heat transfer to make hollow rod into heat pipe, which transferred heat from bottom to top in wellbore by using it without extra energy is proposed. It can improve the temprature distribution of the fluid at the upper part of wellbore; therefore paraffin deposition and flocculation are improved. In this paper, heat transfer model of liquid film and liquid pool is established by means of the equation of N-S.Based on the principle of micro unit in liquid film’s thermal equilibrium and liquid pool’s heat transfer.By analying the heat transfer coeffcients of this two part,it was found out that gravity heat pipe had better heat transfer performance with increasing the length of liquid film in evaporator,improving the flow rate of inner steam and strengthening nucleate boiling of liquid pool,when the requirement of the continuous circulation of two-phase flow was achieved.

Abstract: Organic/inorganic nanocomposites have been widely focused because of their special properties. By modifying nanoTiO₂ and polylactic acid (PLA) with lactic acid, PLA/TiO₂ nanocomposites was prepared, and the test on the dynamic mechanical property, thermal property, and thermal deformation temperature showed that adding nanoTiO₂ helped improve PLA's mechanics property, thermal decomposition temperature, and thermal deformation temperature to certain extent.