Image-guided searching for a landmark

A novel image-guided structure is proposed for searching a helicopter landing apron. The key feature of the structure is the introduction of a stationary camera placed beneath the helicopter so that it can arrive at the correct place on any apron by image-guided searching. The validity of the proposed image-guided structure is verified by means of a practical test on an experimental ball and plate apparatus. The experimental results validate the superiority and practicality of the image-guided search for landmarks.     

Chrysophanol induces necrosis through the production of ROS and alteration of ATP levels in J5 human liver cancer cells

Anthraquinone compounds have been shown to induce apoptosis in different cancer cell types. Effects of chrysophanol, an anthraquinone compound, on cancer cell death have not been well studied. The goal of this study was to examine if chrysophanol had cytotoxic effects and if such effects involved apoptosis or necrosis in J5 human liver cancer cells. Chrysophanol induced necrosis in J5 cells in a dose‐ and time‐dependent manner. Non‐apoptotic cell death was induced by chrysophanol in J5 cells and was characterized by caspase independence, delayed externalization of phosphatidylserine and plasma membrane disruption. Blockage of apoptotic induction by a general caspase inhibitor (z‐VAD‐fmk) failed to protect cells against chrysophanol‐induced cell death. The levels of reactive oxygen species production and loss of mitochondrial membrane potential (ΔΨ_m) were also determined to assess the effects of chrysophanol. However, reductions in adenosine triphosphate levels and increases in lactate dehydrogenase activity indicated that chrysophanol stimulated necrotic cell death. In summary, human liver cancer cells treated with chrysophanol exhibited a cellular pattern associated with necrosis and not apoptosis.     

Mechanical performance and nanoindenting deformation of (AlCrTaTiZr)NCy multi-component coatings co-sputtered with bias

This work develops (AlCrTaTiZr)NC_y multi-component coatings by co-sputtering of AlCrTaTiZr alloy and graphite in an Ar/N₂ mixed atmosphere with the application of different substrate biases. All the (AlCrTaTiZr)NC_y coatings deposited in different conditions exhibited a simple face-centered cubic structure. As the applied substrate bias and graphite-target power increased, the (AlCrTaTiZr)NC_y coatings transformed from a large columnar structure with a [111] preferred orientation to a dense, ultrafine nanocomposite structure. With increasing substrate bias and graphite-target power, the hardness, H/E ratio and H³/E² ratio of the coatings increased from 20 to 35 GPa, from 0.07 to 0.12 and from 0.10 to 0.43 GPa, respectively, attributed to the densification of the coatings, the refinement of grains, the introduction of covalent-like carbide bonds, the formation of nanocomposite structure and the existence of large lattice distortions. Because of the severe distortions in the multi-component coatings caused by the addition of differently-sized atoms, the deformation mechanism was dominated by the activity of low-angle dislocations and/or stacking faults.     

A general strategy for self-assembly of nanosized building blocks on liquid/liquid interfaces

A family of water/oil interfaces is introduced to provide effective platforms for rapid fabrication of large-area self-assembled nanofilms composed of various nanosized building blocks, including nanoparticles (NPs), nanocubes (NC), nanowires (NWs), and nanosheets, at room temperature. As a general interfacial assembly method, NWs and NPs are co-assembled at the liquid/liquid interface. The as-prepared co-assembled Ag NW and Ag NC films show high surface-enhanced Raman spectroscopy (SERS) intensity, the SERS performance being strongly dependent on the number ratio of the two kinds of nanosized building blocks. The results demonstrate that this interfacial system provides a general method for the assembly of various nanosized building blocks with different shapes and dimensionalities, and thus paves an alternative pathway for further applications of macroscopic assemblies with different functionalities.     

Modeling and Design of RF Amplifiers for Envelope Tracking WCDMA Base-Station Applications

Wideband code division multiple access (WCDMA) base-station RF amplifiers using a variety of device technologies including GaN field-effect transistors (FETs), Si LDMOS, and GaAs high-voltage heterojunction bipolar transistors (HVHBTs) are modeled, optimized, and compared for use in wideband envelope tracking (ET) system. A quasi-static approach is employed to effectively model the supply-modulated RF amplifiers, and thus facilitate the design optimization process. A new design methodology for ET RF amplifiers is introduced including identification of optimum fundamental and harmonic terminations. The fundamental and harmonic impedances have been successfully optimized for various RF devices and good agreement has been achieved between the simulation and measurement results. Among the modeled and measured ET RF amplifiers, a GaAs HVHBT exhibits the best overall efficiency of 60% with an average output power of 33 W and a gain of 10 dB for a WCDMA signal with 3.84-MHz bandwidth and 7.7-dB peak-to-average power ratio, while meeting all linearity requirements of the WCDMA standard. Desirable device characteristics for optimum ET operation are also discussed.     

Effect of thermal pole tip protrusion and disk roughness on slider disk contacts

Ultra-high areal density for hard disk drives requires a stable head disk interface at a flying height lower than 8 nm. At such a low flying height, small flying height variations may cause slider/disk contacts. Slider/disk contacts can also occur when a write-current is applied to the write coil since the flying height between slider and disk can be affected by the thermal expansion of the pole tip. In this paper, we investigate the vibration characteristics of sliders during thermally induced contacts using laser Doppler vibrometry. We perform a parametric study of contact events using disks with different surface roughness and lubricant thicknesses, and analyze the slider motion statistically. For a given write current, we observe that the slider vibrations increase with disk roughness and lubricant thickness.     

A study of student satisfaction in a blended e-learning system environment

This study proposes a research model that examines the determinants of student learning satisfaction in a blended e-learning system (BELS) environment, based on social cognitive theory. The research model is tested using a questionnaire survey of 212 participants. Confirmatory factor analysis (CFA) was performed to test the reliability and validity of the measurements. The partial least squares (PLS) method was used to validate the measurement and hypotheses. The empirical findings indicate that computer self-efficacy, performance expectations, system functionality, content feature, interaction, and learning climate are the primary determinants of student learning satisfaction with BELS. The results also show that learning climate and performance expectations significantly affect learning satisfaction. Computer self-efficacy, system functionality, content feature and interaction significantly affect performance expectations. Interaction has a significant effect on learning climate. The findings provide insight into those factors that are likely significant antecedents for planning and implementing a blended e-learning system to enhance student learning satisfaction.     

Efficient adaptive error concealment technique for video decoding system

This paper presents a novel error concealment method for video decoding system. The proposed algorithm adaptively combines the spatial interpolation and the temporal prediction technique based on block variance and interframe correlation, to recover the lost data. The adaptive function depends on the scene change detection, motion distance and spatial information from the nearby blocks of the previous and current frames to determine the weighting of the spatial interpolation and the temporal compensation. Simulations demonstrate that the proposed technique can achieve well subjective and quantitative results, and outperforms all the others against which are compared. Even if the scene changes in the videos, this algorithm also can efficiently recover the damaged blocks for Intra(I), Predictive(P), and Bidirectional (B) frames.     

Fast video segmentation algorithm with shadow cancellation, global motion compensation, and adaptive threshold techniques

Automatic video segmentation plays an important role in real-time MPEG-4 encoding systems. Several video segmentation algorithms have been proposed; however, most of them are not suitable for real-time applications because of high computation load and many parameters needed to be set in advance. This paper presents a fast video segmentation algorithm for MPEG-4 camera systems. With change detection and background registration techniques, this algorithm can give satisfying segmentation results with low computation load. The processing speed of 40 QCIF frames per second can be achieved on a personal computer with an 800 MHz Pentium-III processor. Besides, it has shadow cancellation mode, which can deal with light changing effect and shadow effect. A fast global motion compensation algorithm is also included in this algorithm to make it applicable in slight moving camera situations. Furthermore, the required parameters can be decided automatically, which can enhance the proposed algorithm to have adaptive threshold ability. It can be integrated into MPEG-4 videophone systems and digital cameras.     

Dynamics of ultra low flying sliders during contact with a lubricated disk

In this paper, laser Doppler vibrometry is used to study the motion of a femto slider in the vertical, pitch, roll, off-track and down-track direction due to slider–lubricant interactions. The change in slider dynamics is determined by comparing the laser Doppler vibrometer signals from the slider for time increments of 2 min. The time evolution of this signal is analyzed. The data suggest that slider–lubricant interactions at the head-disk interface have a strong effect on slider dynamics. Spectral analysis of the slider motion indicates that excitation occurs at the same frequency for all degrees of freedom. The excitation frequency is slightly lower than the free vibration frequency, suggesting that lubricant damping plays a role in the excitation of the slider.