All Solution‐Based Fabrication of Copper Oxide Thin Film/Cobalt‐Doped Zinc Oxide Nanowire Heterojunctions

Versatile and intriguing solution‐based processes are utilized to synthesize nanostructured materials for device applications to reduce material production and device fabrication costs. This study presents results on the fabrication and characterization of copper oxide (CuO) coated cobalt‐doped zinc oxide nanowires (Co‐doped ZnO NWs)‐based heterojunction diodes prepared by a two‐step synthesis route through combined hydrothermal growth and sol–gel spin coating. Highly dense, well‐ordered, undoped, and Co‐doped ZnO NWs were successfully grown by hydrothermal method. Complementary CuO thin films were synthesized by sol–gel method and subsequently coated onto both undoped and Co‐doped ZnO NWs through spin‐coating technique. Enhanced diode properties with a rectification ratio of 10³ at ±2 V and an ideality factor of n = 2.4 (in dark) were obtained for Co‐doped ZnO NWs‐based heterojunction diodes. The obtained results demonstrated that the investigated heterojunction diode structure fabricated by facile and cost‐effective solution‐based processes can be a promising candidate for the next generation optoelectronic devices.     

A Survey on TOA Based Wireless Localization and NLOS Mitigation Techniques

Localization of a wireless device using the time-ofarrivals (TOAs) from different base stations has been studied extensively in the literature. Numerous localization algorithms with different accuracies, computational complexities, a-priori knowledge requirements, and different levels of robustness against non-line-of-sight (NLOS) bias effects also have been reported. However, to our best knowledge, a detailed unified survey of different localization and NLOS mitigation algorithms is not available in the literature. This paper aims to give a comprehensive review of these different TOA-based localization algorithms and their technical challenges, and to point out possible future research directions. Firstly, fundamental lower bounds and some practical estimators that achieve close to these bounds are summarized for line-of-sight (LOS) scenarios. Then, after giving the fundamental lower bounds for NLOS systems, different NLOS mitigation techniques are classified and summarized. Simulation results are also provided in order to compare the performance of various techniques. Finally, a table that summarizes the key characteristics of the investigated techniques is provided to conclude the paper.     

Influence of thermal annealing on microstructural,morphological, optical properties and surface electronic structure of copper oxide thin films

In this study, effect of the post-deposition thermal annealing on copper oxide thin films has been systemically investigated. The copper oxide thin films were chemically deposited on glass substrates by spin-coating. Samples were annealed in air at atmospheric pressure and at different temperatures ranging from 200 to 600°C. The microstructural, morphological, optical properties and surface electronic structure of the thin films have been studied by diagnostic techniques such as X-ray diffraction (XRD), Raman spectroscopy, ultraviolet–visible (UV–VIS) absorption spectroscopy, field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The thickness of the films was about 520 nm. Crystallinity and grain size was found to improve with annealing temperature. The optical bandgap of the samples was found to be in between 1.93 and 2.08 eV. Cupric oxide (CuO), cuprous oxide (Cu₂O) and copper hydroxide (Cu(OH)₂) phases were observed on the surface of as-deposited and 600 °C annealed thin films and relative concentrations of these three phases were found to depend on annealing temperature. A complete characterization reported herein allowed us to better understand the surface properties of copper oxide thin films which could then be used as active layers in optoelectronic devices such as solar cells and photodetectors.     

Photoinduced Electron Transfer Between Pyridine Coated Cadmium Selenide Quantum Dots and Single Sheet Graphene

Interest in graphene as a two‐dimensional quantum‐well material for energy applications and nanoelectronics has increased exponentially in the last few years. The recent advances in large‐area single‐sheet fabrication of pristine graphene have opened unexplored avenues for expanding from nano‐ to meso‐scale applications. The relatively low level of absorptivity and the short lifetimes of excitons of single‐sheet graphene suggest that it needs to be coupled with light sensitizers in order to explore its feasibility for photonic applications, such as solar‐energy conversion. Red‐emitting CdSe quantum dots are employed for photosensitizing single‐sheet graphene with areas of several square centimeters. Pyridine coating of the quantum dots not only enhances their adhesion to the graphene surface, but also provides good electronic coupling between the CdSe and the two‐dimensional carbon allotrope. Illumination of the quantum dots led to injection of n‐carrier in the graphene phase. Time‐resolved spectroscopy reveals three modes of photoinduced electron transfer between the quantum dots and the graphene occurring in the femtosecond and picosecond time‐domains. Transient absorption spectra provide evidence for photoinduced hole‐shift from the CdSe to the pyridine ligands, thereby polarizing the surface of the quantum dots. That is, photoinduced electrical polarization, which favors the simultaneous electron transfer from the CdSe to the graphene phase. These mechanistic insights into the photoinduced interfacial charge transfer have a promising potential to serve as guidelines for the design and development of composites of graphene and inorganic nanomaterials for solar‐energy conversion applications.     

A Fuzzy Bayesian Classifier with Learned Mahalanobis Distance

Recent developments show that naive Bayesian classifier (NBC) performs significantly better in applications, although it is based on the assumption that all attributes are independent of each other. However, in the NBC each variable has a finite number of values, which means that in large data sets NBC may not be so effective in classifications. For example, variables may take continuous values. To overcome this issue, many researchers used fuzzy naive Bayesian classification for partitioning the continuous values. On the other hand, the choice of the distance function is an important subject that should be taken into consideration in fuzzy partitioning or clustering. In this study, a new fuzzy Bayes classifier is proposed for numerical attributes without the independency assumption. To get high accuracy in classification, membership functions are constructed by using the fuzzy C‐means clustering (FCM). The main objective of using FCM is to obtain membership functions directly from the data set instead of consulting to an expert. The proposed method is demonstrated on the basis of two well‐known data sets from the literature, which consist of numerical attributes only. The results show that the proposed the fuzzy Bayes classification is at least comparable to other methods.     

Semiactive Suspension Control of a Light Commercial Vehicle

This paper presents the design and implementation of a semi-active suspension control system for a light commercial vehicle using continuously varying dampers, accelerometers, and an onboard processor. The control algorithms such as sky-hook, ground-hook, and hybrid are designed based on the vertical velocities of each quarter of the car. These velocities are estimated from Kalman filter using quarter car vehicle model. The controllers are implemented in an actual vehicle equipped with the developed semiactive suspensions system and their performance are compared. Sky-hook control improved ride comfort by reducing body accelerations in the 1-3 Hz range, ground-hook control improved road holding by reducing wheel accelerations in the 10-15 Hz range, and hybrid control results were in between the sky-hook and ground-hook results. The main contribution of this paper is the successful implementation of the semiactive suspension control strategies on an actual vehicle with accompanying experimental results.     

Optical response of Ag-Au bimetallic nanoparticles to electron storage in aqueous medium

Composition and structure dependence of the shift in the position of the surface plasmon resonance band upon introduction of NaBH4 to aqueous solutions of gold and silver nanoparticles are presented. Silver and gold nanoalloys in different compositions were prepared by co-reduction of the corresponding salt mixtures using sodium citrate as the reducing agent. After addition of NaBH4 to the resultant nanoalloys, the maximum of their surface plasmon resonance band, ranging between that of pure silver (ca. 400 nm) and of pure gold (ca. 530 nm), is blue-shifted as a result of electron storage on the particles. The extent of this blue shift increases non-linearly with the mole fraction of silver in the nanoparticle, parallel to the trends reported previously for both the frequency and the extinction coefficient of the plasmon band shifts. Gold(core)@silver(shell) nanoparticles were prepared by sequential reduction of gold and silver, where addition of NaBH4 results in relatively large spectral shift in the plasmon resonance band when compared with the nanoalloys having a similar overall composition. The origin of the large plasmon band shift in the core-shell is related with a higher silver surface concentration on these particles. Hence, the chemical nature of the nanoparticle emerges as the dominating factor contributing to the extent of the spectral shift as a result of electron storage in bimetallic systems.     

Statistics of macrocell-synchronous femtocell-asynchronous users? delays for improved femtocell uplink receiver design

In a typical macrocell network, the mobile users are synchronized to the macrocell base station (mBS), where users further away to the mBS transmit their signals earlier. In such a network, the signals of the macrocell users arrive at a femtocell base station (fBS) asynchronously, which may yield interference problems such as inter-carrier-interference in orthogonal frequency domain multiple access (OFDMA) systems. In this letter, statistics of the arrival times of macrocell-synchronous femtocell-asynchronous mobile users' signals to an fBS is derived (conditioned on the fBS-mBS distance), and its implications on the femtocell uplink receiver design are briefly discussed.     

Threshold selection for UWB TOA estimation based on kurtosis analysis

In this letter, a normalized threshold selection technique for time of arrival estimation of ultra-wideband signals is proposed. It exploits the kurtosis of the received signal samples. The dependency between the kurtosis and optimal normalized threshold are investigated via simulations. The proposed technique yields efficient threshold selection, has low complexity and sampling rate requirements, and accounts both the signal to noise ratio and the statistics of individual channel realizations.