High performance,low complexity cooperative caching for wireless sensor networks

During the last decade, Wireless Sensor Networks have emerged and matured at such point that they currently support several applications such as environment control, intelligent buildings, target tracking in battlefields. The vast majority of these applications require an optimization to the communication among the sensors so as to serve data in short latency and with minimal energy consumption. Cooperative data caching has been proposed as an effective and efficient technique to achieve these goals concurrently. The essence of these protocols is the selection of the sensor nodes which will take special roles in running the caching and request forwarding decisions. This article introduces two new metrics to aid in the selection of such nodes. Based on these metrics, we propose two new cooperative caching protocols, PCICC and scaPCICC, which are compared against the state-of-the-art competing protocol, namely NICoCa. The proposed solutions are evaluated extensively in an advanced simulation environment and the results confirm that the proposed caching mechanisms prevail over its competitor. The evaluation attests also that the best policy is always scaPCICC, achieving the shortest latency and the least number of transmitted messages.     

On the variational foundations of the substitute shape function technique

In this paper, an element recently developed by Whitcomb (Comput. Struct. 22, 387–398, 1986) along the lines of the so-called substitute shape function technique (SSFT) has been re-examined. It is shown that a varialional basis can be found for this element in the form of a modified version of the variational theorem due to Hellinger and Reissner. On the basis of this theorem, a two-dimensional element has been developed using separate trial functions for the displacements and the shear strain. The element is identical to Whitcomb's element; however, the proposed approach appears to have certain advantages over SSFT.     

On the Performance of TETRA Short Data Service-Transport Layer

This paper presents the results of an extensive measurement survey on the performance of Short Data Service Transport Layer (SDS-TL) of Terrestrial Trunked Radio (TETRA) cellular networks. We developed a novel software measurement platform that runs over the TETRA Peripheral Equipment Interface (PEI), generates SDS-TL traffic, performs measurements, and presents statistics of QoS metrics. The measurement platform was utilized in two measurement campaigns: in the first one, two terminals were co-located in the same TETRA cell, and in the second campaign the terminals were positioned in different cells. Measurements were taken for SDS-TL sizes varying from 10 to 190 bytes (excluding the TL header) with an increment of 5 bytes. For each SDS-TL size, 1,500 messages were exchanged through the measurement platform between the TETRA mobile terminals. We repeated all measurements for three intertransmission intervals, namely 2, 1.5, and 1 s, corresponding to measurement durations-for each set of 1,500 SDS-TL- of ≈ 3,000, 2,250 and 1,500 s, respectively. Hence, 166,500 SDS-TL messages were exchanged between two terminals for each measurement campaign. Results obtained include the end-to-end transmission delay (mean and standard deviation) and the percentage of lost SDS-TL versus the message size for the three intertransmission intervals. The effects of inadequate radio capacity as well as gaps in the radiocoverage can be easily identified through the measurement platform, and we analyze such representative cases.     

The three isentropic exponents of dry steam

The isentropic change of an ideal gas is described by the well known relations pv^k=const, Tv^(k−1) =const and p^(1−k)T^k=const, where the exponent k is defined as the ratio of the constant pressure to the constant volume specific heat, k=c_p/c_v. The same relations are also used for real gases if small or differential isentropic changes are considered. A better examination of the differential isentropic change shows that for p, v, T systems, there are three different isentropic exponents corresponding to each pair formed out of the variables p, v, T. These three exponents noted k_T,p, k_T,v, k_p,v after the corresponding pair of variables used, are interconnected by one relation, and accordingly only two out of the three are independent. The analysis of the present paper leads to the conclusion that calculations encountered in real gas isentropic change, with the exponent k taken as the ratio of the local specific heat values may lead to incorrect results. The numerical values of these exponents for steam, have been calculated and are presented. It can be seen that the deviations obtained, in comparison to the use of conventional k=c_p/c_v values are considerable.     

Surface wave dispersion in large concrete structures

The present paper discusses the repair characterization of large concrete surfaces based on the propagation of low-frequency elastic waves. A common repair method is cement injection. As a result, cracks and voids are eliminated increasing the measured average pulse velocity by about 5%. However, the central frequency of the pulses exhibits higher sensitivity to the repair increasing by about 15%. Additionally, the velocity of longitudinal waves exhibits a dependence on frequency. This dispersion is eliminated after repair being an indication of the repair efficiency, while Rayleigh waves are only slightly dispersive due to their long wavelength which enables them to travel below the shallow defects.     

Composition and antioxidant activity of essential oils from Oregano plants grown wild in Greece

In this study, four samples of essential oils obtained from plant species with a wide distribution in Greece and economic importance for the world-wide spice market and also carvacrol and thymol were tested for their possible antioxidant activity. The four plant species wereOriganum vulgare subsp.hirtum, O. onites, Coridothymus capitatus andSatureja thymbra. The essential oils were chemically characterised by gas chromatography-ion trap detection. All the essential oils examined and also carvacrol and thymol were found to have antioxidant activity when tested on TLC plates and by measuring peroxide values of lard stored at 35° C. The results indicate that the antioxidant effect may be related to the presence of carvacrol and thymol in essential oils.     

A practical method for the minimum weight design of stiffened plates under uniform lateral pressure

A method for the plastic analysis and minimum weight design of grillages and orthogonally stiffened plates subjected to lateral uniform pressure, and under a varying degree of rotational restraint at the supports, is presented. A computer aided design procedure for orthogonally stiffened rectangular plates based on this method is also described. This includes two optimization stages: overall optimization, in which the plastic moments for the beam in each set are found, and stiffener optimization, in which the optimum stiffener geometry is obtained. This design methodology has proved to be very efficient and easy to apply, and it is particularly valuable in the case of ship structures, where the maximum total number of panel stiffeners is in general not large.     

Reactivity of valganciclovir in aqueous solution

The rates of hydrolysis of valganciclovir to ganciclovir and L-valine and isomerization of the R and S diastereomers of valganciclovir in aqueous buffer solution from pH 3.8 to 11.5 were determined at 37 degrees C. The kinetics of hydrolysis were first order for at least two half-lives in neutral and basic solutions. In acidic solutions where less than 10% degradation occurred, the rate of hydrolysis was determined assuming a first-order loss in drug. At 37 degrees C and pH 7.08, the half life is 11 h. The maximum stability at the pH values studied occurred at pH 3.81 with a half life of 220 days. The kinetics of the approach to equilibrium for the isomerization were first order and the ratio of the R:S isomer at equilibrium was 52:48. Isomerization was approximately 10 fold faster than hydrolysis over the pH range studied with a half-life at pH 7.01 of 1 h. The maximum stability toward isomerization (t1/2>533 h) occurs at a pH below 3.8. The pH-rate profile for the hydrolysis and the isomerization reaction are best described by hydroxide ion catalyzed mechanisms. In acidic and neutral solutions, the hydroxide reacts with the protonated form of the drug, while in basic solutions, the hydroxide reacts with the neutral form of the drug.     

Preparation of a selective receptor for ephedrine for the development of an optical spot test for the detection of ephedrine in human urine using stabilized in air lipid films with incorporated receptor

The present technique describes the preparation of a selective receptor for ephedrine and a simple sensitive spot optical test for the rapid one-shot detection of ephedrine in human urine using lipid films with an incorporated receptor that are synthesized by a chemical reaction with a methacrylate polymer on a glass fiber filter. The selective receptor was synthesized using a resorcin[4]arene receptor and by transforming all the -OH groups into methoxy groups. The lipid films without this receptor provided fluorescence under a UV lamp. The use of the receptor in these films quenched this fluorescence, and the color became similar to that of the filters without the lipid films. A drop of aqueous solution of ephedrine provided a "switching on" of the fluorescence, which allows the rapid detection of this stimulant in human urine at the levels of 10(-8) M concentrations. The effect of potent interferences (i.e., proteins, lipids, ascorbic aid, glucose, leucine, glycine, tartrate, citrate, bicarbonate, and caffeine) was examined. The results showed no interferences from these compounds in concentration levels usually found in human urine samples. Dopamine was also investigated as a potent interfering agent, and the results have shown that the transformation of the hydroxy to methoxy groups has altered the selectivity of the receptor. This species does not cause interference at concentration levels lower than 10(-6) M. A drop of urine containing ephedrine provided also a "switching on" of the fluorescence, which allows the rapid detection of this stimulant in human urine at the levels of 10(-8) M concentrations. The reproducibility of the method was checked in approximately 100 samples, and all of them were found to provide similar results. Note that the colors of the filters remain stable for periods of more than 2 months.     

A modified K-means algorithm for circular invariant clustering

Several important pattern recognition applications are based on feature vector extraction and vector clustering. Directional patterns are commonly represented by rotation-variant vectors F/sub d/ formed from features uniformly extracted in M directions. It is often desirable that pattern recognition algorithms are invariant under pattern rotation. This paper introduces a distance measure and a k-means-based algorithm, namely, circular k-means (CK-means) to cluster vectors containing directional information, such as F/sub d/, in a circular-shift invariant manner. A circular shift of F/sub d/ corresponds to pattern rotation, thus, the algorithm is rotation invariant. An efficient Fourier domain representation of the proposed measure is presented to reduce computational complexity. A split and merge approach (SMCK-means), suited to the proposed CK-means technique, is proposed to reduce the possibility of converging at local minima and to estimate the correct number of clusters. Experiments performed for textural images illustrate the superior performance of the proposed algorithm for clustering directional vectors F/sub d/, compared to the alternative approach that uses the original k-means and rotation-invariant feature vectors transformed from F/sub d/.