Compatibilization of Poly(ethylene terephthalate)/Polypropylene Blends with Maleic Anhydride Grafted Polyethylene-Octene Elastomer

Blends of poly(ethylene terephthalate) (PET) and polypropylene (PP) at composition 80/20 with and without a compatibilizing agent were studied. Both materials are widely used in the soft drink bottle industry. The compatibilizing agent was a maleic anhydride grafted polyethylene-octene elastomer (POE-g-MA). The olefinic segment of POE is compatible with PP, whereas the maleic anhydride is affined with PET carbonyl groups. The effectiveness of the compatibilizing agent was evaluated using different techniques, such as Fourier transform IR spectroscopy, mechanical analysis, scanning electron microscopy, dynamic mechanical analysis, and rheological analysis. The results show that the addition of POE-g-MA promotes a fine dispersed-phase morphology, and improves process ability and toughness of these blends. Shifts in the glass-transition temperature of the PET phase and the increase in the melt viscosity of the compatibilized blends indicated enhanced interactions between the discrete PET and PP phases induced by the functional compatibilizer.     

Utility‐based probabilistic call admission control for complete fairness in wireless networks

Resource reservation or the other prioritization strategies adopted by Call Admission Control (CAC) schemes in wireless networks lead to unfair resource allocation to users belonging to different service classes (SCs) due to high divergence among the respective call blocking probabilities (CBPs). In this paper, we propose dynamic optimization of probabilistic CAC (P‐CAC) schemes to assure CAC fairness among users of different SCs in wireless networks. The approach is based on users utility combined with fairness optimization, aiming at dynamically determining the probability value in the P‐CAC scheme. This optimal probability is adjusted to network ongoing traffic, CBPs of each SC, prioritization levels characterizing the SCs supported, and the users risk aversion, which reflects their behavior toward the perceived QoS. The existence and uniqueness of the optimal probability that leads to absolute fairness among the users of a wireless network are proven. Copyright © 2012 John Wiley & Sons, Ltd.     

Spatiotemporal saliency detection and salient region determination for H.264 videos

In this study, a spatiotemporal saliency detection and salient region determination approach for H.264 videos is proposed. After Gaussian filtering in Lab color space, the phase spectrum of Fourier transform is used to generate the spatial saliency map of each video frame. On the other hand, the motion vector fields from each H.264 compressed video bitstream are backward accumulated. After normalization and global motion compensation, the phase spectrum of Fourier transform for the moving parts is used to generate the temporal saliency map of each video frame. Then, the spatial and temporal saliency maps of each video frame are combined to obtain its spatiotemporal saliency map using adaptive fusion. Finally, a modified salient region determination scheme is used to determine salient regions (SRs) of each video frame. Based on the experimental results obtained in this study, the performance of the proposed approach is better than those of two comparison approaches.     

A miniature generator using piezoelectric bender with elastic base

Nowadays green energy devices such as vibration generators attempt to harvest energy from environment. A lot of studies dealing with vibration generators put emphasis on mechanism designs or power generation methods, but few on lowering the resonant frequency of power generation systems. This study proposes that elastic bases attached to vibration generators can lower natural frequencies, so as to make natural frequencies closer to ambient vibration frequency. Therefore, this study investigates miniature electric generators consisting of piezoelectric benders and elastic bases. To install the elastic base, this work uses a spring with prescribed stiffness and a board with given mass between the piezoelectric bender and a vibration source to make the resonant frequency of piezoelectric benders close to the frequency of ambient vibration. Analytical derivation is carried out to obtain optimal mass and stiffness. Accordingly, more electric power can be generated from piezoelectric generators using an elastic base with appropriate mass and stiffness. According to experimental results, using an elastic base increases 376 times generated power compared with no elastic base. In the presence of the elastic base, the power increases 132% when a point mass is added.     

Adaptive joint beamforming and B‐MMSE detection for CDMA signal reception under multipath interference

The combination of antenna array beamforming with multiuser detection can effectively improve the detection efficiency of a wireless system under multipath interference, especially in a fast‐fading channel. This paper studies the performance of an adaptive beamformer incorporated with a block‐wise minimum mean square error(B‐MMSE) detector, which works on a unique signal frame characterized by training sequence preamble and data blocks segmented by zero‐bits. Both beam‐former weights updating and B‐MMSE detection are carried out by either least mean square (LMS) or recursive least square (RLS) algorithm. The comparison of the two adaptive algorithms applied to both beamformer and B‐MMSE detector will be made in terms of convergence behaviour and estimation mean square error. Various multipath patterns are considered to test the receiver's responding rapidity to changing multipath interference. The performance of the adaptive B‐MMSE detector is also compared with that of non‐adaptive version (i.e. through direct matrix inversion). The final performance in error probability simulation reveals that the RLS/B‐MMSE scheme outperforms non‐adaptive B‐MMSE by 1–5 dB, depending on the multipath channel delay profiles of concern. The obtained results also suggest that adaptive beamformer should use RLS algorithm for its fast and robust convergence property; while the B‐MMSE filter can choose either LMS or RLS algorithm depending on antenna array size, multipath severity and implementation complexity. Copyright © 2004 John Wiley & Sons, Ltd.     

An ISM,DEI, and ANP based approach for product family development

Product customization has been used for many years, and with this concept, product families can be designed that are better matched to the needs of customers through the use of market segmentation and modular architecture. This study is composed of two phases: the first phase establishes the modular architecture, and taking a bicycle as the case study, applies the Interpretive Structural Model (ISM) to modularize and cluster parts, and then models the connecting relations between the parts numerically using a Disassembly Effort Index (DEI). The second step involves the development of a product family using cluster analysis to divide the experimental samples and the employment of an Analytic Network Process (ANP) to obtain the optimal weight performance of the modules after establishing the market segmentation model. Results of the case study establish four product families and address construction performance of both the common and independent modules between the product families.     

SNS collaborative learning design: enhancing critical thinking for human–computer interface design

Universal Access in the Information Society - In many cases, classrooms seem to be functioning as well as ever, though the challenges and expectations have changed quite dramatically. This study...     

Carrier dynamics and intervalley scattering in InN

The carrier cooling and the carrier relaxation of an InN thin film illuminated with two excitation energies of 1.53 and 3.06 eV were studied by an ultrafast time-resolved photoluminescence upconversion apparatus. The hot phonon effect could be accounted for longer effective phonon emission times as compared to the theoretical prediction. The rise time and the LO phonon emission time for 3.06 eV excitation were much smaller than those for 1.53 eV excitation. These differences were attributed to the intervalley scattering between the Γ₁ and Γ₃ valleys in InN when carriers were excited with the energy of 3.06 eV. The intervalley scattering times of 250 fs and 2 ps were estimated for the intervalley scattering from the Γ₁ to Γ₃ valley and the reversed scattering process, respectively.     

Formation mechanism of microcrystalline spherical graphite particles in solidified nickel

Nickel is a well known catalyst that can readily transform carbon into graphite at high temperature. In our designed arc-discharge experiments, diamond easily dissolved in melted nickel and became small graphitic flakes. After the melted nickel had cooled and solidified, there were many microcrystalline-sized spherical graphite particles found on the nickel grain boundaries, surprisingly. It is interesting that only at the hotter area would the spherical graphite be found. This leads to our proposed forming mechanism: the spherical graphite particles were formed during the solidification of nickel. Because the temperature and solubility are high at the hotter area (zone A), the crystallization and growth of graphite became transport-controlled, instead of surface-controlled, and therefore the most common shape of the particles was spherical. This phenomenon, as far as we know, has not been previously observed.