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In recent years, indoor positioning system employing Bluetooth has attracted tremendous attention. However, it is investigated that its received channel information is significantly affected by hardware configuration and wireless environments, especially the received dataset of angle of arrival (AOA), which leads to inaccurate channel estimation and positioning. Further-more, AOA estimation at larger angle direction is severely influenced by the variant wireless environment and signal distortion, which has not been resolve in existing literature. In this paper, we propose an advanced I/Q density-based AOA estimation (IQDAE) to deal with the above-mentioned problem, which consists of two sub-schemes. We firstly employ the designed phase difference (PD) filter to convert I/Q signals to phase information and then select the candidate sets by eliminating outliers. Afterward, we conceive a PD density-based classification algorithm to estimate AOA. The experimental results show that the mean absolute error of proposed IQDAE algorithm is comparably smaller than that from the other schemes, including commercial solutions, especially at larger angles. The results indicate that we can effectively increase the service range for the Bluetooth positioning system by adopting the proposed algorithm.

The surface quality of micro-arc oxidation (MAO) in 6061 aluminum alloy was investigated using a variety of process parameters. The tribological properties of the different MAO surfaces were evaluated using the ‘reciprocating pin-on-disk’ method. Different current densities were selected in order to illustrate the formation mechanism of the MAO layer. Wear test results were used to evaluate the wear resistance ability of the various MAO layers for establishing a wear model. The surface morphology, porosity distribution on cross section, and worn surface of the MAO layers were characterized using a scanning electron microscope (SEM). Different material counterparts and contact conditions were applied to simulate a variety of practical scenarios. The results show that the hardness of the MAO layer formed at the 15 A/dm2condition was the highest among the four kinds of specimens, and the MAO layer formed at the 15 A/dm2 condition had the best wear resistance. This can be attributed to the various size and distribution of the pores and the different ratio of $\alpha$ to $\gamma$ phase in the MAO layers when subjected to different parameters during MAO process.

Optical quartz glass has been widely used in consumer electronics. This work investigated the nano grooving of optical quartz glass using a molecular dynamics simulation (MD) method. Moreover, the critical depth of grooving with tool tips of different radius was discussed. The cutting force and the amount of elastic recovery of the grooved depth were evaluated under different cutting conditions. The simulation results showed that the critical depth of grooving and the amount of elastic recovery of the grooved depth were dependent on the radius of the tool tip. A cutting tool with a smaller radius can obtain a smaller critical depth of the groove.

This study tracks the evolution of wear scar under extreme pressure (EP) conditions, using zinc dialkyl dithiophosphates (ZDDP) additives mixed with polyalkylene glycol (PAG) refrigeration oil via a four-ball test method using an AISI 52100 hardened steel as a test ball. The experiments show that the extreme pressure performance of the PAG oil declined significantly when the load was raised to a critical value. However, ZDDP additives mixed with the PAG oil in appropriate ratios can improve the extreme pressure performance of the PAG oil. According to the experimental results, ZDDP additives effectively form tribofilm on the rubbing surface to improve extreme pressure performance during run in process. In particular, some ZDDP tribofilm was detected in the region outside of the rubbing area. This was caused by the effects of the scraped off tribofilm flowing out, then accumulating on the outside of the wear scar. In addition, the high temperature caused ZDDP tribofilm formation near the rubbing region.

This study aim to investigated the effects of physical micro wedge in contacting surface patterns on tribological performance. Different surface patterns fabricated on low carbon steel by a nano-second pulsed laser. The frictional test were conducted using a rotating type tribometer and machine tool slideway oil (Shell Tonna S2 M 32), the frictional behavior were investigated by against copper under starved lubrication conditions, with a constant normal load of 147.15 N and a sliding speed of 0.4189 m/s. The results showed that the surface pattern with physical micro wedge could enhance the micro-hydrodynamic lubrication during a sliding contact, resulting in a decrease in the frictional coefficient approaching to 0.03.

This Metaheuristics are easy to use and usually get good solutions for complex problems. There were many approaches proposed in improving the performance of the metaheuristics. In the past, we proposed a hierarchical execution architecture of GA to shorten the generation number needed to find final solutions. In this paper, we embed different migration mechanisms in the hierarchical sub- population architecture and compare their performance. Experiments are also made for verifying the effectiveness and efficiency of the proposed migration mechanisms. From the experimental results, it is found that the migration mechanism in the hierarchical sub- population architecture could improve solution quality.

In this work, the green diesel (Hydrotreated Vegetable Oil, HVO) was blended with fossil diesel in different concentration as testing fuels. The tribological performance of the biodiesel was evaluated using a reciprocating cylinder-on-flat wear test rig (Cameron-Plint TE-77) at different temperatures (25°C and 80°C). Energy dispersive spectrometer (EDS) demonstrate that there's no tribofilm generate on the worn surface. When the content of green diesel is more than 20%, the friction coefficient of the specimen is obviously declined at 25°C. The specimen tested in the pure green diesel had the maximum wear depth than that tested in the other mixed fuels. At 80°C, the friction coefficients of the test sample were less than those at 25°C, but the wear depth of test sample increased significantly. When the content of green diesel is more than 20%, the friction coefficient of the specimen is less than 0.3. The experimental results demonstrate that the tribological behavior of the blend fuel content with 10% green diesel was superior to that of the other testing fuels. Friction coefficient of the test sample was decreased as a consequence of increasing biodiesel concentration.

In this study, molecular dynamics (MD) are used to simulate the nanoimprinting behaviors of Ag thin films with impurities using a cuboid diamond punch. The results of the simulation show that the imprinting topography of Ag thin films depends on the slip behaviors of dislocations. In the punch indenting process, dislocations would be interfered by impurities defects. In the drafting process, the forming holes appear spring back and micro plastic recovery phenomenon, and the impurities affect the both behaviors. Although the impurities can result in a bigger springback, a better surface roughness can be obtained.

This study investigates the effect of precipitate interfacial bonding strength on the mechanical behavior of Fe nanowire (NW) under simple tension in the [110] direction by molecular dynamic simulation. The results thus obtained that the weak bonding of interface between the precipitate and the Fe nanowire gets a void that was formed close to the precipitate in the tensile process, and plastic deformation occurred mostly close to the precipitate. Additionally, dislocations cannot shear off the hard precipitate, resulting in gradual void growth. Finally, the nanowire broke down around the precipitate and void. In case of high strength bonding of interface between the precipitate and the Fe nanowire, the dislocations can shear off the precipitate, blocking the motion of the dislocation, increasing precipitation strengthening.

LTE-advanced wireless receivers require high-linearity up-front filtering to prevent corruption of the in-band signals by strong out-of-band (OOB) signals and self-interference from the transmitter. SAW duplexer filters are generally used for this purpose, but supporting the plethora of existing and new bands becomes troublesome with separate filters for each band. In this paper we explore the possibility of combining an isolator with on-chip filtering. However, even with 15dB isolation, the on-chip filter needs to deal with up to +10dBm TX leakage and -15dBm OOB blocking, which requires an extremely high IIP3 around +50dBm and IIP2 around +90dBm. Recently inductorless tunable N-path-filter-based receivers achieved >10dBm compression point and good IIP3 of 20 to 30dBm. In order to further improve the receiver linearity to approach the extremely high IIP3 requirement for a SAW-less receiver, a high-linearity N-path bandpass/notch filter topology and receiver architecture are proposed in this paper.

LTE-advanced wireless receivers require high-linearity up-front filtering to prevent corruption of the in-band signals by strong out-of-band (OOB) signals and self-interference from the transmitter. SAW duplexer filters are generally used for this purpose, but supporting the plethora of existing and new bands becomes troublesome with separate filters for each band. In this paper we explore the possibility of combining an isolator with on-chip filtering. However, even with 15dB isolation, the on-chip filter needs to deal with up to +10dBm TX leakage and −15dBm OOB blocking, which requires an extremely high IIP3 around +50dBm and IIP2 around +90dBm. Recently inductorless tunable N-path-filter-based receivers achieved >10dBm compression point and good IIP3 of 20 to 30dBm. In order to further improve the receiver linearity to approach the extremely high IIP3 requirement for a SAW-less receiver, a high-linearity N-path bandpass/notch filter topology and receiver architecture are proposed in this paper.

In this paper, we design a hierarchical execution architecture of genetic algorithms (GAs). We present a variant of genetic algorithms known as Hierarchical GA (HGA) based on the proposed architecture. In HGA, the population is divided into several sub-populations, which are initially placed at the lowest level. When the GA process at the level terminates, the GA process goes up to the next level. Experiments are conducted to verify the performance of the proposed mechanism.

A 12b time-interleaved pipelined SAR ADC is presented. The proposed sampling circuit makes timing skew immune to mismatch of control circuit for time interleaving and reduces the main mismatch source to only sampling switch to achieve very low sampling skew of 60fs rms without calibration. MDAC transfer curve of pipeline stage is folded and OP output is kept half without degrading its gain and bandwidth by the proposed MDAC. The proposed OP loading reset scheme also enhances the settling speed without sacrificing ADC conversion time. Operating at 800MS/s, this ADC consumes 14.6mW from 1V supply and achieves SNDR of 60.8dB with Nyquist input.

In recent years, a lot of 2D textures have been synthesized from input 2D textures. However, the quality problems still exist for many textures. Further improvements are required to extract more reliable texture features. In this paper, we present a texture synthesis approach using cooperative color and grey-level features. For color feature extraction, we extract appearance vectors to replace RGB color values. For grey-level feature extraction, we extract the statistical features including entropy, contrast, and correlation based on the grey level co-occurrence probabilities (GLCPs). Moreover, we introduce cooperative color and GLCP features for neighborhood matching in the synthesis process. We assign different weights for color and grey-level features according to the characteristics of the input texture. The results show that the proposed approach performs well in terms of the synthesis quality.

Context-based services have received an increasing attention due to the prevalence of sensor-rich mobile devices such as smartphones. The idea is to recommend information that would be of interest to a user according to the user's surround context. Although remarkable progress has been made, relatively little research has been made to contextualize music playback based on a large-scale dataset of real-life listening records. This paper presents our recent endeavor in collecting 5,502 real-life listening records with context annotation using Android smartphones in-situ. The user-provided context annotation contains labels selected from 10 user activity categories and 10 user mood categories. Moreover, we also compute a rich set of sensor features to capture the context at which the users listen to music, encompassing location, time, acceleration, proximity, etc. Our evaluation shows that with such context information we are able to significantly improve the performance of music recommendation, using factorization machine as the recommendation engine.

A 8-b 2-b/step asynchronous subranged SAR ADC is presented. It incorporates subranging technique to obtain fast reference settling for MSB conversion. The capacitive interpolation reduces number of NMOS switches and lowers matching requirement of a resistive DAC. The proposed timing scheme avoids the need of specific duty cycle of external clock for defining sampling period in a conventional asynchronous SAR ADC. Operating at 750 MS/s, this ADC consumes 4.5 mW from 1-V supply, achieves ENOB of 7.2 and FOM of 41 fJ/conversion-step. It is fabricated in 28-nm CMOS technology and occupies an active area of 0.004 mm2.

In this paper we propose a flexible 4-moduli set (2p+k, 2p+1, 2p−1, 22p+1) which is profitable to construct a high-speed residue number system (RNS). We derive a simple reverse conversion algorithm for the proposed moduli set by using Chinese Remainder Theorem (CRT). The resulting converter architecture mainly consists of simple adders which are suitable to realize an efficient VLSI implementation. Based on TSMC 0.13um CMOS technology, the proposed reverse converter demonstrates its superiority in terms of area, delay and power over the converter design for the 4-moduli set (2n, 2n−1, 2n+1, 22n+1) under the various dynamic range (DR) requirements. Finally, the chip area, the clock rate and the power consumption of the proposed 32-bit reverse RNS converter are 1227×1227um2, 105MHz and 1.3mW respectively.

This paper introduces a low complexity VLSI hardware architecture for entropy coding with increased throughput, based on the study of the statistical properties of the Context-based Adaptive Variable Length Coding (CAVLC) in AVC/H.264. These enhanced designs are due to the results of the statistical analyses, in which better symbol length prediction was achieved by breaking the recursive dependency among codewords for multi-symbol decoder implementation. The proposed CAVLC decoder can also easily meet real-time requirements for High Definition (HD) (1920×1080) applications, while the clock speed is operated only at 13 MHz under the best case scenario.

A 6-b 1-GS/s subranging ADC with THA is implemented in 90-nm CMOS technology. This circuit incorporates folded input for the fine ADC as well as offset calibration and digital correction techniques, achieving greater than 5.2 ENOB and 40-dB SFDR up to the Nyquist, and 1.1-GHz ERBW with power consumption of only 30 mW.

The moduli set M1=(2n,2n+1-1,2n-1) which is free of 2a+1 modulus is profitable to construct a high-speed residue number system (RNS). In this paper, we derive a reduced-complexity residue-to-binary conversion algorithm for M1 by using new Chinese remainder theorem (CRT). The resulting converter architecture mainly consists of carry-save adders (CSAs), modular adders and multiplexer (MUX) which is suitable for an efficient VLSI implementation. Under the same dynamic range (DR) requirement, the proposed converter design is significantly more efficient than the latest design for M1 with respect to area-time (AT), time-power (TP) and area-time-power (ATP) products. Based on UMC 0.18 um CMOS cell-based technology, the chip area for 16-bit residue-to-binary converter is only 931times931um2 and the working frequency is 135 MHz.

This study focuses on design of an optical ultra-wideband (UWB) pulse system with binary phase shift keying (BPSK) modulation scheme for multi-channel radio-over-fiber (ROF) communication environments. The generated optical Gaussian-like pulses can provide the several GHz bandwidths and improve the fiber dispersion and inter-symbol interference (ISI) problems for high-bit-rate transmissions. Moreover, a peak power detection scheme is adopted by the orthogonal frequency receiver, which can obtain a minimum channel bandwidth for the multi-channel systems. Finally, we set up a practical experimental system to prove our proposed schemes. Modeling analysis and experiment results demonstrate that the proposed system can provide a large capacity and lower interference noise for the multi-channel UWB wireless communications.

This study proposes the biphase impulse generation by a new optical direct sequence-binary phase shift keying (DS-BPSK) modulation scheme for indoor ultrawide-band (UWB) radio-over-fiber communications. Fiber dispersion and inter-symbol interference (ISI) problems can be avoided by properly adjusting pulse width. The simulation and analytical results demonstrate that the presented scheme indeed provides several GHz bandwidths for future high-bit-rate indoor UWB wireless systems.

Recently, a training-based vector channel estimation scheme has been proposed for single-user CDMA systems with aperiodic spreading codes. In this paper, we extend it to the reverse link of multiuser MIMO CDMA system. We also use the generalized MMSE multiuser detector to suppress multiuser interference so then we can get good initial vector channel estimates for each user. In the data transmission period, we combine the generalized MMSE multiuser detector, the maximum likelihood (ML) MIMO detector, and vector channel prediction of next channel vectors. The simulation results show that the vector channel estimation outperforms scalar channel estimation in multiuser MIMO CDMA systems.

A realization of transmitting multiple radar waveforms and coherently combining multiple ambiguity functions is proposed. We propose to use the concept of synchronous code-division multiple access (CDMA) to do so. The spreading sequences are chosen to be orthogonal such as Walsh-Hadamard sequences. Multiple radar waveforms are synchronously transmitted by using orthogonal spreading sequences. Since they are transmitted at the same time and the same frequency, the respective received signals are affected by the same time delay and Doppler frequency shift. Therefore, coherent combining of low-resolution multiple ambiguity functions to get a high-resolution composite ambiguity function is now feasible.

Ion implantation into contact holes has been widely used to dope the specific contact area and to reduce the contact resistance. In this study, mask edge defects were observed at the edge area of small contact holes ( 4), which resulted in multiplied dislocations penetrating into Si substrate for more than 0.3 um after back-end processings. Those dislocations were identified to be Schockley partials dislocations and stair rod dislocations lying on 4 sets of inclined (111)Si planes.