Advanced Materials Research Vols. 457-458

Abstract: A complete cast crown allows the operator to modify axial tooth contour. The margin should be smooth and distinct and its width has to allow adequate bulk of metal at the margin. The objective of this study was to evaluate, by finite element analysis, the influence of different degree of taper and marginal designs for cast crown preparations, on the stress distribution in teeth and crowns. As experimental model an upper first molar was used. The geometry of the intact tooth were obtained by 3D scanning. The tooth preparations and the complete cast crowns were designed. Models were exported in a finite element analysis software for structural simulations. Von Mises equivalent stresses were calculated and their distribution was plotted graphically. Numerical simulations provide a biomechanical explanation for stress distribution in prepared teeth and overlying crowns.

Abstract: Mg2Ni-type Mg20Ni10-xMx (M=Cu, Co; x=0, 1, 2, 3, 4) electrode alloys with nanocrystalline and amorphous structure were synthesized by melt-spinning technique. The microstructures of the as-spun alloys were characterized by XRD, SEM and HRTEM. The electrochemical hydrogen storage properties of the experimental alloys were measured. The obtained results show that the as-spun (M=Cu) alloys hold an entire nanocrystalline structure, whereas the as-spun (M=Co) alloys display a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni facilitates the glass formation in the Mg2Ni-type alloy. Furthermore, such substitution results in the formation of secondary phases Mg2Cu and MgCo2 instead of changing the major phase of Mg2Ni. The substitution of M (M=Cu, Co) for Ni markedly improves the electrochemical performances of the alloys, involving the discharge capacity and the cycle stability as well as the high rate discharge ability.

Abstract: Failure of dies and molds is caused by wear and deformation during the metal sheet forming process. Die wear takes various forms, and the contact conditions in die-parts affect the strength of the components. Non-destructive methods that can be related to contact conditions are necessary to study and understand the phenomena caused by the contact stresses. In the present work, a newly developed scanning Hall probe microscope (SHPM) equipped with a GaAs film sensor was used to observe the three-dimensional magnetic fields in tool steel plates before and after contact tests at room temperature in air. It was found that the intensity of three-dimensional magnetic fields is only slightly affected by the spherical Hertzian contact. However, all of the three-dimensional components of the magnetic fields change significantly. The extent of the changes depends not on the distribution of stress under spherical Hertzian contact but on the initial distribution of the magnetic fields.

Abstract: A new type of photonic crystal fiber (PCF) with pentagonal air-core is proposed, which consists of octagonal air holes in the cladding. In addition, five elliptical air holes are embedded in the inner layer to enhance the birefringence characteristic. Characteristics of this PCF are analyzed by using of Finite Element Method (FEM). Numerical results show that this kind of PCF exhibits high birefringence with the level of 0.001 after optimization, which will find application in optical sensing systems.

Abstract: This paper presents a novel method for elimination of cast shadow and water tailing in rainy highway videos. Based on color and texture characteristics of vehicles, background, cast shadow and water tailing region, a fusion method is proposed. First, color correlation is estimated between pixels through dot product of HSI vectors. Second, the texture difference based on gradient of current region and background region is calculated. Then, these two results are fused to both eliminate cast shadow and water tailing region. Experiments show that our method is simple and efficient, also helpful to extract accurate traffic information.

Abstract: Recently many practical downlink multi-user MIMO linear pre-coding methods have been proposed, such as the channel inversion method and the block diagonalization method (BD). Considering the channel inversion method based on MMSE criterion (MMSE-CI) which is confined to a single receives antenna case, the BD has more advantages in multiple antennas cases, however, it has poor performance at the low and medium SNR regime on account of no consideration on the noise. In this paper, an improved MMSE pre-coding method is proposed with multi receive antennas of each user. Based on MMSE-CI, the cooperation of multiple antennas is adopted to further suppress the residual interference during designing the pre-coding matrix, which could increase the signal-to- interference-plus-noise ratio (SINR) at each user’s receiver. The proposed method obtains a better performance than the MMSE-CI and the BD algorithms, and its effectiveness is validated by both theoretical analyses and numerical simulations.

Abstract: A simulation model on working process of certain armored vehicle turbocharged diesel engine is proposed with Hiroyasu combustion model.Then the combustion characteristics of the diesel in 4km altitude is calculated. The combustion process is improved via adjusting optimum advanced injection angle(θi) which performed in plateau area.The results show: when the altitude is from 0m to 4000m, the center of gravity for heat release rate is delayed 7°CA,HRRmax (maximum value of Heat Release Rate) reduces 0.009KJ/°CA, pmax (maximum value of cylinder Pressure ) reduces1.6MPa,Tmax(maximum value of combus -tion temperature ) increases 220°C above. When θi is advanced during possible scope, HRRmax increases 0.008KJ/°CA,pmax increases 1.0MPa,Tmax increase 150°C. In view of the restriction of the pmax and the maximum increase rate of p, the optimum θi is fixed on to advanced 4°CA. The simulation results supply a research foundation for the improvement of diesel performance in Plateau.

Abstract: This study dealt with the formation mechanism and microstructure of titanium carbide particulate reinforced Fe-based composite. The microstructure of the composite was characterized by scanning electron microscopy (SEM), the microstructural study reveled that the TiC particles were distributed uniformly in the iron matrix, and TiC particles had various morphology. The formation mechanism of titanium carbide was also investigated by differential thermal analysis (DTA) and X-ray diffraction(XRD). The experimental results indicated that titanium carbide formed at 1138.2°C.

Abstract: In this paper, we analyze the characteristics of the flexible job-shop scheduling problem(FJSP). A novel genetic algorithm is elaborated to solve the FJSP. An improved chromosome representation is used to conveniently represent a solution of the FJSP. Initial population is generated randomly. The relevant selection, crossover and mutation operation is also designed. It jumped from the local optimal solution, and the search area of solution is improved. Finally, the algorithm is tested on instances of 4 jobs and 6 machines. Computational results prove the proposed genetic algorithm effective for solving the FJSP.

Abstract: Nowadays, most of text CAPTCHAs use character connection as a primary means to avoid being recognized. To recognize this kind of CAPTCHA, a new image analysis model, Concept Component Analysis (CCA), is proposed. Based on the approaching idea in Newton’s iteration, this new model is solved by a multi-population genetic algorithm. Compared with traditional image analysis models, such as PCA, components obtained by CCA have obvious concept meanings. Images can be recognized by solely relying on these components, No classifier is needed. CCA has achieved good recognition results in our experiments. Suggestions for securing text recognition CAPTCHAs are also provided based on experiments results.