Sensitivity analysis of complex embedded real-time systems

The robustness of an architecture to changes is a major concern in the design of efficient and reliable state-of-the-art embedded real-time systems. Robustness is important during design process to identify if and in how far a system can accommodate later changes or updates, or whether it can be reused in a next generation product. In the product life-cycle, robustness helps the designer to perform changes as a result of product updates, integration of new components and subsystems, or modifications of the environment. In this paper we determine robustness as a performance reserve, the slack in performance before a system fails to meet timing requirements. This is measured as design sensitivity. Due to complex component interactions, resource sharing and functional dependencies, one-dimensional sensitivity analysis might not cover all effects that modifications of one system property may have on system performance. One reason is that the variation of one property can also affect the values of other system properties requiring new approaches to keep track of simultaneous parameter changes. In this paper we present a framework for one-dimensional and multi-dimensional sensitivity analysis of real-time systems. The framework is based on compositional analysis that is scalable to large systems. The one-dimensional sensitivity analysis combines a binary search technique with a set of formal equations derived from the real-time scheduling theory. The multi-dimensional sensitivity analysis engine consists of an exact algorithm that extends the one-dimensional approach, and a stochastic algorithm based on evolutionary search techniques.     

Formalizing process-based risk with Value-Focused Process Engineering

Following calls to advance the integration of risk and business process modeling paradigms, this paper formalizes the process of incorporating risk into business process models through the principles of Value-Focused Process Engineering (VFPE). In doing so, the paper aims to extend the existing VFPE modeling notation to reflect a set of necessary constructs required to adequately represent risk in goal-oriented business-process models. The extended set of constructs is proposed to support a formal systems view of process-based risk. Process-based risk is formalized on the one hand, as a product of complex interactions between activity-based elements, and on the other hand, as a natural component of the value creation mechanism of an elementary function or a complex process. The proposed risk-aware VFPE formalism also formulates rules for decomposing risk in process models according to the organizational values, thereby enabling better risk visibility, reducing process complexity, and ensuring continuity of business processes.     

Color image segmentation in HSI space for automotive applications

This article presents a method for classifying color points for automotive applications in the Hue Saturation Intensity (HSI) Space based on the distances between their projections onto the SI plane. Firstly the HSI Space is analyzed in detail. Secondly the projection of image points from a typical automotive scene onto the SI plane is shown. The minimal classes relevant for driver assistance applications are derived. The requirements for the classification of the points into those classes are obtained. Several weighting functions are proposed and a fast form of an euclidean metric is investigated in detail. In order to improve the sensitivity of the weighting function, dynamic coefficients are introduced. It is shown how to compute them automatically in order to get optimal results for the classification. Finally some results of applying the metric to the sample images are shown and the conclusions are drawn.

SI-ATRP Decoration of Magnetic Nanoparticles with PHEMA and Post-Polymerization Modification with Folic Acid for Tumor Cells’ Specific Targeting

Targeted nanocarriers could reach new levels of drug delivery, bringing new tools for personalized medicine. It is known that cancer cells overexpress folate receptors on the cell surface compared to healthy cells, which could be used to create new nanocarriers with specific targeting moiety. In addition, magnetic nanoparticles can be guided under the influence of an external magnetic field in different areas of the body, allowing their precise localization. The main purpose of this paper was to decorate the surface of magnetic nanoparticles with poly(2-hydroxyethyl methacrylate) (PHEMA) by surface-initiated atomic transfer radical polymerization (SI-ATRP) followed by covalent bonding of folic acid to side groups of the polymer to create a high specificity magnetic nanocarrier with increased internalization capacity in tumor cells. The biocompatibility of the nanocarriers was demonstrated by testing them on the NHDF cell line and folate-dependent internalization capacity was tested on three tumor cell lines: MCF-7, HeLa and HepG2. It has also been shown that a higher concentration of folic acid covalently bound to the polymer leads to a higher internalization in tumor cells compared to healthy cells. Last but not least, magnetic resonance imaging was used to highlight the magnetic properties of the functionalized nanoparticles obtained.     

Small Cells in Cellular Networks: Challenges of Future HetNets

Due to their low cost and easy deployment, small cells provide a viable and cost-effective way of improving the cellular coverage and capacity both for homes and enterprises, both in metropolitan and rural areas. Stimulated by their attractive features and advantages, the ongoing development and deployment of small cells by manufacturers and mobile network operators have seen a surge in recent years. Together with macro-cells, they form, what are called Heterogeneous Networks or HetNets. However, the successful rollout and operation of small cells are still facing significan issues. In this paper the need for, challenges and solutions of small cell deployments are analyzed. This analysis is conducted with respect to self-organizing features, interference coordination, energy efficiency and spectrum efficiency. The analysis is complemented with numerical results based on system simulations in Macro-only and HetNet scenarios and also on real measurements performed on an mobile operator network. Results show the clear improvement that a HetNet brings in term of user throughput and also the amunt of spectrum waste that is present in nowadays’ operator networks.     

Robust Index Assignment Using Hadamard Transform for Vector Quantization Transmission over Finite-Memory Contagion Channels

This paper presents a new index assignment (IA) method when vector quantization indices are transmitted over a particular class of Markov binary channels, namely the finite-memory contagion channels. (See F. Alajaji and T. Fuja, IEEE Trans. Inform. Theory, 40:2035-2041, 1994.) For this class of binary channels, the Hadamard transform of the vector formed with noise pattern probabilities obeys well-structured recursions, allowing an efficient evaluation of the channel distortion and also revealing a useful approximation based on the dominant terms in the channel distortion expression. The proposed IA method minimizes the distortion approximation and is very robust to changes in the parameters of the channel model. The same technique applies for both maximum likelihood and mean-squared error decoding methods. The IA algorithm is applied to the transmission of line spectral frequency parameters quantized as in the G.729 standard to show the usefulness of the proposed method.     

Entrapment of fluorescent signaling DNA aptamers in sol-gel-derived silica

We report on the first successful immobilization of a DNA aptamer, in particular, a fluorescence-signaling DNA aptamer, within a sol-gel-derived matrix. The specific aptamer examined in this study undergoes a structural switch in the presence of adenosine triphosphate (ATP) to release a dabcyl-labeled nucleotide strand (QDNA), which in turn relieves the quenching of a fluorescein label that is also present in the aptamer structure. It was demonstrated that aptamers containing a complementary QDNA strand along with either a short complimentary strand bearing fluorescein (tripartite structure) or a directly bound fluorescein moiety (bipartite structure) remained intact upon entrapment within biocompatible sol-gel derived materials and retained binding activity, structure-switching capabilities, and fluorescence signal generation that was selective and sensitive to ATP concentration. Studies were undertaken to evaluate the properties of the immobilized aptamers that were either in their native state or bound to streptavidin using a terminal biotin group on the aptamer, including response time, accessibility, and leaching. Furthermore, signaling abilities were optimized through evaluation of different QDNA constructs. These studies indicated that the aptamers remained in a state that was similar to solution, with moderate leaching, only minor decreases in accessibility to ATP, and an expected reduction in response time due to diffusional barriers to mass transport of the analyte through the silica matrix. Entrapment of the aptamer also resulted in protection of the DNA against degradation from nucleases, improving the potential for use of the aptamer for in vivo sensing. This work demonstrates that sol-gel-derived materials can be used to successfully immobilize and protect DNA-based biorecognition elements and, in particular, DNA aptamers, opening new possibilities for the development of DNA aptamer-based devices, such as affinity columns, microarrays, and fiber-optic sensors.