Fairness-related challenges in mobile opportunistic networking

The fundamental challenge in opportunistic networking, regardless of the application, is when and how to forward a message. Rank-based forwarding techniques currently represent one of the most promising methods for addressing this message forwarding challenge. While these techniques have demonstrated great efficiency in performance, they do not address the rising concern of fairness amongst various nodes in the network. Higher ranked nodes typically carry the largest burden in delivering messages, which creates a high potential of dissatisfaction amongst them. In this paper, we adopt a real-trace driven approach to study and analyze the trade-offs between efficiency, cost, and fairness of rank-based forwarding techniques in mobile opportunistic networks.Our work comprises three major contributions. First, we quantitatively analyze the trade-off between fair and efficient environments. Second, we demonstrate how fairness coupled with efficiency can be achieved based on real mobility traces. Third, we propose FOG, a real-time distributed framework to ensure efficiency–fairness trade-off using local information. Our framework, FOG, enables state-of-the-art rank-based opportunistic forwarding algorithms to ensure a better fairness–efficiency trade-off while maintaining a low overhead. Within FOG, we implement two real-time distributed fairness algorithms; Proximity Fairness Algorithm (PFA), and Message Context Fairness Algorithm (MCFA). Our data-driven experiments and analysis show that mobile opportunistic communication between users may fail with the absence of fairness in participating high-ranked nodes, and an absolute fair treatment of all users yields inefficient communication performance. Finally our analysis shows that FOG-based algorithms ensure relative equality in the distribution of resource usage among neighbor nodes while keeping the success rate and cost performance near optimal.     

Feature extraction in carpal-bone analysis

Hand-bone analysis with image processing techniques using a digital radiograph can be used to assess skeletal age. The analysis consists of two steps: phalangeal and carpal bone analysis. The carpal bone analysis is discussed. First, the carpal bone region of interest (CROI) is defined using a standard thresholding technique to separate the hand from the background. Then, a dynamic thresholding method with variable window sizes is used to differentiate between the bones and the soft tissue. Next, the radius, ulna, and metacarpals intersecting the borders of the CROI are removed by using mathematical morphology. Finally, all objects included in the corrected CROI are separated and described in terms of features. These features describe the size, shape, and location and include some gray-scale pixel value information. On the basis of this analysis, the separation of the noncarpal bone objects from the carpal bone is possible. The feature selection step removes features of low discriminant power and reduces the space dimension. The remaining carpal bone parameters are used for further analysis leading to skeletal age assessment.     

Endogenous Modulation of Extracellular Matrix Collagen during Scar Formation after Myocardial Infarction

Myocardial infarction is remains the leading cause of death in developed countries. Recent data show that the composition of the extracellular matrix might differ despite similar heart function and infarction sizes. Because collagen is the main component of the extracellular matrix, we hypothesized that changes in inflammatory cell recruitment influence the synthesis of different collagen subtypes in myofibroblasts, thus changing the composition of the scar. We found that neutrophils sustain the proliferation of fibroblasts, remodeling, differentiation, migration and inflammation, predominantly by IL-1 and PPARγ pathways (n = 3). They also significantly inhibit the mRNA expression of fibrillar collagen, maintaining a reduced stiffness in isolated myofibroblasts (n = 4–5). Reducing the neutrophil infiltration in CCR1^−/− resulted in increased mRNA expression of collagen 11, moderate expression of collagen 19 and low expression of collagen 13 and 26 in the scar 4 weeks post infarction compared with other groups (n = 3). Mononuclear cells increased the synthesis of all collagen subtypes and upregulated the NF-kB, angiotensin II and PPARδ pathways (n = 3). They increased the synthesis of collagen subtypes 1, 3, 5, 16 and 23 but reduced the expression of collagens 5 and 16 (n = 3). CCR2^−/− scar tissue showed higher levels of collagen 13 (n = 3), in association with a significant reduction in stiffness (n = 4–5). Upregulation of the inflammation-related genes in myofibroblasts mostly modulated the fibrillar collagen subtypes, with less effect on the FACIT, network-forming and globular subtypes (n = 3). The upregulation of proliferation and differentiation genes in myofibroblasts seemed to be associated only with the fibrillar collagen subtype, whereas angiogenesis-related genes are associated with fibrillar, network-forming and multiplexin subtypes. In conclusion, although we intend for our findings to deepen the understanding of the mechanism of healing after myocardial infarction and scar formation, the process of collagen synthesis is highly complex, and further intensive investigation is needed to put together all the missing puzzle pieces in this still incipient knowledge process.     

Ionic implantation at low energy: application to the shallow junction accomplishment and surface functionalization

The proposed work deals with rapid thermal processing of ionic boron (¹¹B⁺) and boron difluoride (BF₂⁺), implanted in phosphorusdoped Cz-(100) silicon substrates through protecting oxide films, under different technological parameters. After implantation, the samples were rapidly thermally annealed at temperatures ranging from 900 to 1100 °C, in argon ambient gas, for different annealing durations. The rapid thermal annealings (RTAs) are carried out also, for some samples, after oxide mask removal. The total boron, fluorine as well as oxygen concentrations versus depth profiles, before and after annealing steps, in the SiO₂/Cz-(100) silicon systems were determined using secondary ion mass spectrometry (SIMS). Using a background concentration, the junction depth in the substrate has been investigated under different annealing experimental conditions. The kinetic diffusion process of implanted boron into oxide and monocrystalline silicon during rapid thermal treatments has also been investigated. The reported results show that boron diffusion in the BF₂⁺ case is widely reduced during rapid thermal treatments. Discussions of this are based on the effect of both knocked-on oxygen and fluorine on the boron diffusion kinetics.     

Date palm fibers as polymeric matrix reinforcement: DPF/polyester composite properties

Due to increased awareness on the part of end users and pressure from legislators, the composite industry has begun investigating the possibility of increasing the proportion of recycled or biodegradable composite materials. Accordingly, efforts are being deployed to find alternative reinforcement and resin systems that are environmentally friendly while providing the same performance as their synthetic counterparts. Natural fibers offer the potential to act as a reinforcing material for low to medium strength applications. In this study a natural fiber extracted from the date palm tree was used as reinforcement for polymeric matrix composites. Polyester composite specimens reinforced with date palm fibers (DPF) were subjected to various types of mechanical and physical tests in order to assess their performance. Results show that these fibers may yield reasonable properties and could be used for low‐cost applications that require low to medium strength. Tests indicate, however, that additional work is needed to enhance the compatibility between the fiber and the matrix. POLYM. COMPOS., 26:604–613, 2005. © 2005 Society of Plastics Engineers     

Investigation of BF2 implants in silicon through SiO2 films Redistribution of fluorine and boron under rapid thermal annealing

Boron difluoride (BF₂⁺) ions implantation through protecting oxide films was investigated to understand the behaviour of fluorine in damaged region under rapid thermal annealing (RTA) as well as in attempt to form shallow p⁺/n junctions. The implants redistribution profiles as a function of annealing temperatures and time have been monitored by the secondary ion mass spectrometry (SIMS). Implantation induced point-defects are detected by means of deep level transient spectroscopy (DLTS) technique. The effects of both fluorine and the RTA ion-implant damage annihilation on the transient enhanced boron diffusion are investigated. In particular, the fluorine segregation behaviour near the post implantation disturbed/crystalline interface, resulting in clustering and void formation, as well as near the initial oxide/crystalline silicon is closely related to used technological data.     

A novel high dynamic range differential LNA using quartet topology

In some applications such as short-range radars, a large target can desensitize the receiver. A high dynamic range low-noise amplifier (LNA), as a key component of a transmitter/receiver module, can improve the entire system performance. This study presents a high dynamic range differential LNA that uses a differential quartet topology for the first time. The LNA shows more linearity than the conventional differential common source LNAs. For a typical 0.18 µm CMOS technology, it achieves a power gain of about 5.5 dB at 24 GHz, a low noise figure (NF) of 3.5 dB, very good linearity performance, an input-referred third-order intercept point (IIP3) of +?6.3 dBm, and an input-referred 1 dB compression point (P1dB) of ??4.5 dBm.     

An analog circuit model for drive mode of MEMS vibratory gyroscope

Microsystem Technologies - In this paper, an analog circuit model for the drive mode of a two-degree-of-freedom MEMS vibratory gyroscope is presented. This model is implemented on a printed circuit...     

On the performance of voltage stepping for the simulation of adaptive, nonlinear integrate-and-fire neuronal networks

In traditional event-driven strategies, spike timings are analytically given or calculated with arbitrary precision (up to machine precision). Exact computation is possible only for simplified neuron models, mainly the leaky integrate-and-fire model. In a recent paper, Zheng, Tonnelier, and Martinez (2009) introduced an approximate event-driven strategy, named voltage stepping, that allows the generic simulation of nonlinear spiking neurons. Promising results were achieved in the simulation of single quadratic integrate-and-fire neurons. Here, we assess the performance of voltage stepping in network simulations by considering more complex neurons (quadratic integrate-and-fire neurons with adaptation) coupled with multiple synapses. To handle the discrete nature of synaptic interactions, we recast voltage stepping in a general framework, the discrete event system specification. The efficiency of the method is assessed through simulations and comparisons with a modified time-stepping scheme of the Runge-Kutta type. We demonstrated numerically that the original order of voltage stepping is preserved when simulating connected spiking neurons, independent of the network activity and connectivity.     

Investigation of the liquid crystal alignment layer: effect on electrical properties

We investigate the electrical behavior of a symmetric liquid crystal (LC) cell: elecrode-silane-LC-silane-electrode. The silane (chlorodimethyloctadecyl-silane) layer induces a homeotropic orientation of the nematic liquid crystal (NLC) molecules. The wettability technique is used to detect the change of the surface energy of the electrode upon cleaning and silane layer deposition. We report on the dynamic impedance measurements of the nematic liquid crystal cell. It is found that the silane alignment layer has a blocking effect on the liquid crystal (LC) cell. We also study the relaxation behavior of the cell which is later assimilated as an electrical equivalent circuit.