Mechanical properties of porous titanium compacts prepared by powder sintering

Porous Ti compacts for biomedical applications are successfully fabricated in the porosity range from 5.0 to 37.1 vol% by controlling sintering conditions and Ti powder sizes. Young’s modulus and bending strength at the porosity of around 30 vol% are found to be similar to those of human cortical bone.     

Low-energy ion beam treatment of α-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>(0001) and improvement of photoluminescence of ZnO thin films

A low energy N₂ ^? ion beam impinged on a α-Al₂O₃(0001) single crystal surface in the range of fluence 5×10¹⁵/cm²?1×10¹⁸/cm² at room temperature. After ion bombardment, chemical bonding on the modified sapphire surface was investigated by x-ray photoelectron spectroscopy. Below a fluence of 1×10¹⁵/cm², only a non-bonded N1s peak at the binding energy 398.7 eV was found, but further irradiation up to 2×10¹⁷/cm² induced Al?O?N bonding at around 403 eV. The occurrence of Al?N bonding was identified at ion fluence higher than 5×10¹⁷/cm² at 396.6 eV. II–VI ZnO thin films were grown on an untreated/ion-beam-induced sapphire surface by pulsed laser deposition (PLD) for the investigation of the modified-substrate effect on photoluminescence. The ZnO films grown on modified sapphire containing Al?O?N bonding only, and both Al?O?N and Al?N bonding showed a significant reduction of the peak related to deep-level defects in photoluminescence. These results are explained in terms of the formation of Al?N?O and Al?O?N layers and relaxation of the interfacial strain between Al₂O₃ and ZnO.     

Optimization of casting conditions for heat and abrasion resistant large grey iron castings

Numerical simulation technology was applied for optimizing the casting design and conditions in large cast iron castings for marine engine. By the simulation of mold filling and solidification sequences the problems of the previous casting conditions were analyzed and marked improvements for large cylinder liner parts were derived from these results. Especially the amount and positions of chills were optimized to increase the mechanical properties and to minimize the shrinkage and microporosity in the castings. Ultrasonic testing, penetration testing and mechanical property testing were carried out for the parts with the modified casting conditions. It showed that no defects in the castings were found and the productivity could be distinctly increased. The mechanical properties satisfied also the specification demanded.     

Caustic stress corrosion cracking of alloys 600 and 690 with NaOH concentrations

In order to evaluate the stress corrosion cracking resistance for commercial alloys (C600MA, C600TT, C690TT) and Korean-made alloys (K600MA, K690TT), C-ring tests were performed in a caustic environment of 4, 10, 20, 30, and 50% NaOH solution at 315°C, for 480 h with an applied potential of 125 mV vs. OCP. Different stress corrosion cracking phenomena were observed according to the NaOH concentration. The rate of caustic IGSCC attack did not appear to increase monotonically with caustic concentrations, but peaked at a concentration between 4 and 50% caustic, or approximately 30% NaOH. Intergranular stress corrosion cracking was found for C600MA in 10, 20, and 30% NaOH solutions, while no cracking was observed in the 4 and 50% NaOH solutions. In 30% NaOH solution, transgrnular stress corrosion cracking was detected in C690TT, which may be related with the large amount of plastic strain (150% yield) and the applied potential (125 mV vs. OCP). The overall data clearly indicate that C600MA has the worst SCC resistance while K690TT offers the best resistance. There is also fairly good correlation between the caustic SCC susceptibility and some metallurgical parameters, particularly the grain size and the yield strength at room temperature. Specifically, materials having larger grain size and lower yield strength exhibited higher caustic SCC resistance.     

Single-view-based 3D facial reconstruction method robust against pose variations

The 3D Morphable Model (3DMM) and the Structure from Motion (SfM) methods are widely used for 3D facial reconstruction from 2D single-view or multiple-view images. However, model-based methods suffer from disadvantages such as high computational costs and vulnerability to local minima and head pose variations. The SfM-based methods require multiple facial images in various poses. To overcome these disadvantages, we propose a single-view-based 3D facial reconstruction method that is person-specific and robust to pose variations. Our proposed method combines the simplified 3DMM and the SfM methods. First, 2D initial frontal Facial Feature Points (FFPs) are estimated from a preliminary 3D facial image that is reconstructed by the simplified 3DMM. Second, a bilateral symmetric facial image and its corresponding FFPs are obtained from the original side-view image and corresponding FFPs by using the mirroring technique. Finally, a more accurate the 3D facial shape is reconstructed by the SfM using the frontal, original, and bilateral symmetric FFPs. We evaluated the proposed method using facial images in 35 different poses. The reconstructed facial images and the ground-truth 3D facial shapes obtained from the scanner were compared. The proposed method proved more robust to pose variations than 3DMM. The average 3D Root Mean Square Error (RMSE) between the reconstructed and ground-truth 3D faces was less than 2.6 mm when 2D FFPs were manually annotated, and less than 3.5 mm when automatically annotated.     

Object tracking based on an online learning network with total error rate minimization

This paper presents a visual object tracking system which is tolerant to external imaging factors such as illumination, scale, rotation, occlusion and background changes. Specifically, an integration of an online version of total-error-rate minimization based projection network with an observation model of particle filter is proposed to effectively distinguish between the target object and the background. A re-weighting technique is proposed to stabilize the sampling of particle filter for stochastic propagation. For self-adaptation, an automatic updating scheme and extraction of training samples are proposed to adjust to system changes online. Our qualitative and quantitative experiments on 16 public video sequences show convincing performances in terms of tracking accuracy and computational efficiency over competing state-of-the-art algorithms.