Analysis and optimization of a cross-layer adaptation mechanism for real-time applications in wireless networks

The theoretical analysis of a cross-layer mechanism for improving the quality of service of real-time applications in wireless networks is presented. The mechanism coordinates adaptations of the modulation order at the Physical layer and the media encoding mode at the Application layer, to improve packet loss rate, throughput and mean delay. With the use of Continuous Flow Modeling, the system is considered as a “fluid” queue with inflow and outflow rates representing its traffic generation and service rates, respectively. Each data source is modeled as a Markov chain, from the steady-state of which the optimal adaptation thresholds of the cross-layer mechanism are derived. Extensive performance evaluation results show that the optimized operation of the mechanism attains a significant performance improvement compared to both the sub-optimal case, and a legacy system, which adjusts the modulation order and encoding mode separately and independently of each other.     

Comparison of trapping efficacy for Lasioderma serricorne (F.) adults with electric, pheromone, food attractant and control-adhesive traps

During July, August, September and October 1997, in three tobacco stores in the area of Thessaloniki, four types of adhesive traps: electric (black light), pheromone (serricornin and anhydroserricornin), food attractant and control, were used for trapping Lasioderma serricorne (F.) (Coleoptera: Anobiidae). All traps had the same adhesive area based on 29.5×21 cm² polyethylene sheets. Five replicate comparisons of the four trap types took place. The electric trap caught 8912, the pheromone trap 6608, the food attractant trap 1974 and the control 1231 L. serricorne adults. The electric adhesive trap was significantly more effective than the other traps and the control. The electric trap captured a smaller number of male adults than the pheromone trap but many more females. The ratio between female and male adults was 60.15 : 39.84 for the electric trap, 8.75 : 91.25 for the pheromone trap, 51.57 : 48.42 for the food attractant trap and 43.41 : 56.58 for the control trap.     

A Personal Smart Space approach to realising Ambient Ecologies

One of the main aims of research in the area of ubiquitous or pervasive computing is that of dealing with the rapidly growing number of sensors, devices and artefacts in the user’s environment, which have an increasing amount of intelligence built in and which can communicate via wireless technologies. To assist in this the concept of Ambient Ecologies has been proposed as a metaphor for modelling ubiquitous or pervasive applications based on fixed smart spaces, such as the Smart Home. This paper describes the notion of a Personal Smart Space (PSS) and how it can be used to realise Ambient Ecologies. It goes on to show how, using a PSS approach, one can handle more general situations in which an Ambient Ecology is formed dynamically when two or more PSSs come together wherever this may be. The idea of a PSS is fundamental to the prototype pervasive system that has been developed within the Persist project where it has been used to demonstrate a range of different pervasive applications. In particular this prototype has been used to demonstrate a futuristic situation in the smart home where the total environment is under user control. It is shown how the requisite Ambient Ecologies can be handled by PSSs. The paper concludes with an evaluation of the Persist prototype in which mobile PSSs are used to affect the behaviour of fixed PSSs in their environment.     

Local communities towards a sustainable energy future: needs and priorities

The local authorities demonstrate their willingness to implement sound local sustainable energy policies, especially through their participation in the Covenant of Mayors (CoM). However, in rural environments, namely areas outside of large cities and towns, fulfilling their CoM commitments, especially as regards the local energy planning at the medium- to long-term scale, can come with very different and sometimes challenging constraints. In this context, the main objective of this paper is the assessment of the local communities’ needs and priorities, so as to identify the key parameters that should be taken into consideration during the development of their Sustainable Energy Action Plan. The adopted approach was implemented in rural communities from four countries (Austria, Croatia, Greece and Portugal). From the results obtained, the need for a methodology, appropriately customised to the rural communities’ characteristics, was determined, addressing especially interested stakeholders who are not ‘experts’ in the field.     

Theoretical and experimental analysis of a novel low emissivity water pond in summer

The present study focuses on the research of a new passive roof cooling technique, based on the combination of low emissivity materials and water. A novel roof pond is chosen as the most advantageous in terms of both energy efficiency and less maintenance or functional demands. The pond – referred as “Roof Pond with Gunny Bag” (RPWGB) – is covered by a cloth floating on water level, encouraging evaporative heat losses. A mathematical model describing the energy flux through the RPWGB is developed. The following sensitivity analysis marks the parameters that reduce bottom pond temperature thus improving the efficiency of the system. The experimental study analyses alternative ways to reduce bottom pond temperature. For this purpose, the low emissivity material is placed in different positions, above, below and floating on water level. Heat dissipation occurs by means of radiation losses and water evaporation.     

Characterisation of the bioactive behaviour of sol–gel hydroxyapatite–CaO and hydroxyapatite–CaO–bioactive glass composites

The fabrication and characterization of sol–gel derived hydroxyapatite–calcium oxide (HAp–CaO) material is investigated focusing on the effect of the addition of a bioactive glass on the material bioactive behaviour through the fabrication of a novel HAp–CaO (70 wt.%)–bioactive glass (30 wt.%) composite material. The bioactive behaviour of the materials was assessed by immersion studies in Simulated Body Fluid (SBF) and the alterations of the materials surfaces after soaking periods in SBF were characterized by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). A brittle and weakly crystalline carbonate hydroxyapatite (HCAp) layer was found to develop on the surface of all samples, few hours after immersion in SBF, confirming the high bioactivity of the material. Alterations of the morphology of the developed HCAp layer, which led to a more compact structure, were observed on the surface of composite samples after 7 days of immersion in SBF. The presence of the CaO phase seems to accelerate the formation of HCAp, while the bioactive glass affects both the morphology and cohesion of the developed layer.     

Radiocoloring in planar graphs: Complexity and approximations

The Frequency Assignment Problem (FAP) in radio networks is the problem of assigning frequencies to transmitters, by exploiting frequency reuse while keeping signal interference to acceptable levels. The FAP is usually modelled by variations of the graph coloring problem. A Radiocoloring (RC) of a graph G(V,E) is an assignment function such that |Φ(u)-Φ(v)|2, when u,v are neighbors in G, and |Φ(u)-Φ(v)|1 when the distance of u,v in G is two. The number of discrete frequencies and the range of frequencies used are called order and span, respectively. The optimization versions of the Radiocoloring Problem (RCP) are to minimize the span or the order. In this paper we prove that the radiocoloring problem for general graphs is hard to approximate (unless NP=ZPP) within a factor of n^1/2-ε (for any ), where n is the number of vertices of the graph. However, when restricted to some special cases of graphs, the problem becomes easier. We prove that the min span RCP is NP-complete for planar graphs. Next, we provide an O(nΔ) time algorithm (|V|=n) which obtains a radiocoloring of a planar graph G that approximates the minimum order within a ratio which tends to 2 (where Δ the maximum degree of G). Finally, we provide a fully polynomial randomized approximation scheme (fpras) for the number of valid radiocolorings of a planar graph G with λ colors, in the case where λ4Δ+50.     

Comparative Study between Classic and Newer Methods for the Evaluation of Hemodialysis Adequacy

Aim:  The comparative study of hemodialysis (HD) adequacy of Kt/V measurement between classic method (Daugirdas formula) and urea sensor monitor (online).
Patients and methods:  30 patients with end-stage renal failure undergoing dialysis were studied. A comparative evaluation of HD adequacy during the same session was done with two different methods: (1) blood samples were drawn in the beginning and in the end of HD session for the measurement of blood urea nitrogen (BUN) and after measurement of HD adequacy by 3rd generation Daugirdas formula and (2) urea sensor monitor use for continuous HD adequacy measurement during HD session.
Results:  There was statistically significant correlation of Kt/V Daugirdas with Kt/V online (r = 0.8, p < 0.001). Also there was statistically significant correlation between solute removal index (SRI), Kt/V Daugirdas (r = 0.81, p < 0.001) and Kt/V online (r = 0.92, p < 0.001). From nutrition indices that were measured, the protein catabolic rate (PCR) had marginal negative correlation with the two compared adequacy indices, Kt/V Daugirdas (r = −0.24, p < 0.03), and Kt/V online (r = −0.17, p < 0.03) although the nPCR (normalized PCR) had marginal positive correlation (r = 0.35, p < 0.05) (r = 0.42, p < 0.05).
Conclusions:  The use of online urea sensor monitors contributes to the easy measurement of adequacy and nutrition indices and hence complicated mathematical formulas are not necessary. The results of these measurements are reliable and comparable with classic methods of HD adequacy evaluation.     

Development and study of fully biodegradable composite materials based on poly(butylene succinate) and hemp fibers or hemp shives

The use of natural fibers to reinforce polymers is an established practice, and biocomposites have gained an increased interest in areas such as automotive, construction, and agriculture. The purpose of the present work was the preparation and study of fully biodegradable (“green”) composite materials using poly(butylene succinate) (PBSu) as polymeric matrix and hemp fibers and shives as fillers. Composites containing 15, 30, 50, 60, and 70 wt% of fillers were prepared by melt mixing in a twin screw extruder. The composites were studied using Fourier transform infrared spectroscopy, X‐ray diffraction, and differential scanning calorimeter while the dispersion and interfacial adhesion were studied with scanning electron microscopy. From mechanical properties measurements, it was found that tensile and impact strength are both affected by the type and the amount of the used filler. The degree of crystallinity of PBSu was found to decrease by increasing the filler content, although that both fillers can act as nucleating agents. Finally, the degradation rate during enzymatic hydrolysis and soil burial increased in all biocomposites by increasing the filler content. PBSu/hemp shive composites showed higher biodegradation rates than PBSu/hemp fiber composites. POLYM. COMPOS., 37:407–421, 2016. © 2014 Society of Plastics Engineers     

Kinetics of all-trans-β-carotene degradation on heating with and without phenylalanine

All-trans-β-carotene was heated in liquid paraffin at 210°C for 15 min in the presence and the absence of phenylalanine to assess the effect of the amino acid on the rate of degradation of all-trans-β-carotene. The curve that represents all-trans-β-carotene degradation in both model systems is formed of two distinct parts that correspond, respectively, to the propagation and termination phases of an autocatalytic reaction. The reaction over 1–15 min followed first-order reaction kinetics in both systems, and the rate constant obtained was 2.8 times lower in the presence of phenylalanine. The kinetic behavior and the rate constant for color loss were similar to those for all-trans-β-carotene degradation for each model system.