Path Loss Models for Low-Height Mobiles in Forest and Urban

This paper presents path loss measurements at 2.1 GHz in forest and urban areas. Empirical path loss models have been presented for low-height dual-mobility channels. Three test scenarios are considered for the transmitter (Tx) and receiver (Rx) placed inside the test vehicle or on a test cart pushed at walking speed. Based on measurements, the in-leaf and single-slope path loss models are presented. The path loss exponents for the dual-mobility channels are found to be between 2.1 and 3.4 in urban and 8.0 in forest, with higher reference when antennas are placed inside the vehicle.     

Network Coding Based Converge-Cast Scheme in Wireless Sensor Networks

The converge-cast in wireless sensor networks (WSNs) is widely applied in many fields such as medical applications and the environmental monitoring. WSNs expect not only providing routing with high throughput but also achieving efficient energy saving. Network coding is one of the most promising techniques to reduce the energy consumption. By maximizing the encoding number, the message capacity per package can be extended to the most efficient condition. Thus, many researchers have focused their work on this field. Nevertheless, the packages sent by the outer nodes need to be temporary stored and delayed in order to maximize the encoding number. To find out the balance between inserting the delay time and maximizing the encoding number, a Converge-cast Scheme based on data collection rate prediction (CSRP) is proposed in this paper. To avoid producing the outdated information, a prediction method based on Modifying Index Curve Model is presented to deal with the dynamic data collection rate of every sensor in WSNs. Furthermore, a novel coding conditions based on CDS is proposed to increase the coding opportunity and to solve the collision problems. The corresponding analysis and experimental results indicate that the feasibility and efficiency of the CSRP is better than normal conditions without the prediction.     

Temporal Topic-Based Multi-Dimensional Social Influence Evaluation in Online Social Networks

Analytical applications in online social networks can be generalized as the influence evaluation problem, which targets at finding most influential users. Nowadays social influence evaluation is still an open and challenging issue. Most influence evaluation models focus on the single dimensional evaluation factor but fail to research on the multi-dimensional factors. In this paper, we propose a novel influence evaluation model: the temporal topic influence (TTI) evaluation model, which is a time-aware, content-aware and structure-aware evaluation model. For the aim of multi-dimensional evaluation, we incorporate multi-dimensional measure factors into our model, including the time factor, the topological information and the topic distribution information, etc. We propose a novel concept of user gravitational ability which is inspired by Newton’s law of universal gravitation. It can integrate multi-dimensional factors in an appropriate way. Our experiments are conducted on the Sina Weibo data set. Through the experimental analysis, we prove TTI model can calculate users’ influences effectively and efficiently. The TTI model can distinguish the value of users’ influences. And the TTI model identifies the top-k influential users with higher quality. We also validate the effect of time and topic measure factors in the influence evaluation process.     

WDTF: A Technique for Wireless Device Type Fingerprinting

In this Work, a technique for wireless device type fingerprinting has been introduced. The technique utilizes the information that revealed as a result of the homogeneity in devices of the same make and the heterogeneity in devices of a different make. The diversity in devices of different make is due to different device hardware compositions and the variations in their management capabilities. We apply the statistical technique on network traffic to create unique, reproducible device signatures. We demonstrate the efficacy of our technique on network traffic captured in different scenarios. We have used a total of 300 devices types representing a wide range of device classes. In the experiment, we have used more than 1.5 GB of filtered traffic for analysis and performance evaluation. We measure the performance of the technique by considering the accuracy of device type detection. The results obtained are promising with a higher detection rate than its counterparts.     

Fabrication and Electromagnetic Properties of Conjugated NH<Subscript>2</Subscript>-CuPc@Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>

Conjugated amino-phthalocyanine copper containing carboxyl groups/magnetite (NH₂-CuPc@Fe₃O₄) has been fabricated from FeCl₃·6H₂O and NH₂-CuPc via a simple solvothermal method and its electromagnetic properties investigated. Scanning electron microscopy and transmission electron microscopy revealed that the NH₂-CuPc@Fe₃O₄ was a waxberry-like nanomaterial with NH₂-CuPc molecules effectively embedded in the interior of Fe₃O₄ particles in the form of beads. Introduction of NH₂-CuPc effectively improved the complementarity between the dielectric and magnetic losses of the system, resulting in excellent electromagnetic performance. The minimum reflection loss of the as-prepared composite reached ?33.4 dB at 7.0 GHz for coating layer thickness of 4.0 mm and bandwidth below ?10.0 dB (90% absorption) of up to 3.8 GHz. These results indicate that introduction of NH₂-CuPc results in a composite with potential for use as an electromagnetic microwave absorption material.     

Hybrid wavelet measurement matrices for improving compressive imaging

Compressive sensing principle claims that a compressible signal can be recovered from a small number of random linear measurements. However, the design of efficient measurement basis in compressive imaging remains as a challenging problem. In this paper, a new set of hybrid wavelet measurement matrices is proposed to improve the quality of the compressive imaging, increase the compression ratio and reduce the processing time. The performance of these hybrid wavelet matrices for image modeling and reconstruction is evaluated and compared with other traditional measurement matrices such as the random measurement matrices, Walsh and DCT matrices. The compressive imaging approach chosen in this study is the block compressive sensing with smoothed projected Landweber reconstruction technique. The simulation results indicate that the imaging performance of the proposed hybrid wavelet measurement matrices is approximately 2–3 dB better than that obtained using Gaussian matrix especially at higher compression ratios.     

Patch-based reconstruction of surfaces undergoing different types of deformations

We deal with the reconstruction of surfaces that deform under a variety of conditions. The deformation can range from no extension to a certain degree of extensibility. The deformed surface is reconstructed from a single image, given a 3D reference shape. This shape corresponds to the undeformed state of the surface and can be computed using any appropriate technique. In particular, we use homographies defined from two views of the surface. To proceed with the 3D reconstruction of the deformed surface, we assume that the deformations are locally homogeneous and that the overall surface deformation can be obtained by combining the local homogeneous deformations. For this purpose, the surface is split into small patches. For each patch, a mapping between the undeformed and the deformed shapes is computed. The mapping is specified by using the quadratic deformation model Fayad et al. (Proceedings of British Machine Vision Conference (BMVC), 2004). As a result, given the undeformed shape, we define an optimization procedure whose goal is to estimate the 3D positions of deformed points in each image. The optimization is performed on each patch, independently of the others. The experimental results show that this approach allows precise reconstruction of a wide class of real deformations.     

Atomic configuration and charge state of hydrogen at dislocations in silicon

The effect of the introduction of hydrogen upon the vibration spectra and electrical characteristics of samples with dislocation networks at the interface of bonded silicon wafers was studied. In order to improve the sensitivity of measurements and to distinguish the signal from dislocation networks in Raman spectra, thin foils conventionally prepared for transmission electron microscopy were used as the sample under investigation. In the samples with dislocation networks, a Raman peak at 2000 cm^–1 was observed. This peak survived after annealing at a temperature of T = 500°C and was not observed in reference samples. Comparison of the experimental data with currently available theoretical calculations allowed one to attribute the observed peak to neutral hydrogen atoms H⁰ at the center of Si–Si bonds. The peak is metastable in the ideal lattice, but becomes stable in the vicinity of dislocations.     

Galvanomagnetic properties of bismuth films with a thin antimony coating or sublayer

The effect of modification of the surfaces of bismuth thin films with an antimony layer of 10 nm thick was studied. Three types of structures deposited onto mica substrates are compared: a bismuth film, an antimony layer as a sublayer for the bismuth film, and an antimony layer as the coating of the bismuth film. A substantial difference in the galvanomagnetic properties of the obtained structures is revealed in the dependence on the position of the antimony layer in the structure and on the bismuth-film thickness.     

Interference Cancelling Codes for Ultra-Reliable Random Access

Combinatorial code designs (CCDs) are proposed as a means for achieving ultra-reliability in the random access channel. In contrast to traditional access protocols that use random repetition coding, we show that by uniquely allocating repetition patterns to users, successful reception may be guaranteed up to a number of simultaneously active users in small frame sizes. Such codes are particularly robust in the low activity region where mission-critical machine-type communication is expected to operate. We also present deterministic codes designed to work in conjunction with successive interference cancellation to further improve reliability. The optimal IC code for frames of 5 access slots is given. Unlike slotted ALOHA, it is shown to limit packet losses to well below the ultra-reliability threshold (10^?5). These error performance gains come at the cost of a strict limitation on the supported user population (11 users in the case of 5 slots). We therefore consider larger frames of 24 slots, and analyse heuristic, low-complexity CCDs with fixed repetition factors that support up to 2024 users. While these are sub-optimal IC codes, significant gains are still observed compared to random codes.