Distributed Detection With Censoring Sensors Under Physical Layer Secrecy

We consider distributed binary detection problems in which the remote sensors of a network implement a censoring strategy to fulfill energy constraints, and the network works under the attack of an eavesdropper. The attacker wants to discover the state of the nature scrutinized by the system, but the network implements appropriate countermeasures to make this task hopeless. The goal is to achieve perfect secrecy at the physical layer, making the data available at the eavesdropper useless for its detection task. Adopting as performance metric certain Ali-Silvey distances, we characterize the detection performance of the system under physical layer secrecy. Two communication scenarios are addressed: parallel access channels and a multiple access channel. In both cases the optimal operative points from the network perspective are found. The most economic operative solution is shown to lie in the asymptote of low energy regime. How the perfect secrecy requirement impacts on the achievable performances, with respect to the absence of countermeasures, is also investigated.     

Sequential detection of almost-harmonic signals

To detect a purely harmonic signal, it is difficult to beat a fast Fourier transform (FFT). However, when the signal is very long and weak, Parker and White (1999) have shown that a sequential probability ratio test (SPRT) operating on magnitude-square FFT data is far more efficient. Indeed, both from a numerical-error perspective and in terms of robustness against a deviation from a precisely tonal signal, the block-FFT/SPRT idea is very appealing. Here, the approach is extended to the case that the frequency is unknown, and expressions are developed for performance both in terms of detection and of sample number. The approach is applicable to a large number of practical problems, but particular attention is paid to the continuous gravitational wave (GW) example. The computational savings as compared with a fixed test vary as a function of signal strength, block length, bandwidth and operating point; however, gains of a factor of two are easy. That these gains are not more exciting relates mostly to the underlying FFT structure; although many SPRTs "end early," it is difficult to take advantage of that with an efficient FFT algorithm. However, the progressive reduction of the number of working SPRTs implies a substantial reduction of the ensemble of the candidate frequencies with time, which is an appealing feature, particularly in the GW case.     

Effect of Fatty Acid Addition on the Properties of Biopolymer Films Based on Lipophilic Maize Starch and Gelatin

In the presented work, composed layer films based on lipophilic starch and gelatin were produced containing different amounts of fatty acids (palmitic, lauric, myristic, capric, caproic and caprylic); i.e., 5, 15, 25 and 50%, using sorbitol as the plasticizer. All films were prepared by casting in an acrylic plate and their barrier properties (vapor permeability), as well as their mechanical (tensile strength and elongation), physicochemical (water solubility) and physical (opacity and thickness) properties were measured. The addition of fatty acids to the biopolymer films increased their thickness, opacity and elongation. On the other hand, the addition of fatty acids decreased the tensile strength and water vapor permeability of the biopolymer films for all formulations studied. The fatty acid concentration found to be effective in reducing the biopolymer film permeability varied between 15 and 25%.     

Evaluation of nanocomposites containing graphene nanoplatelets: Mechanical properties and combustion behavior

Polypropylene (PP) nanocomposites containing graphene nanoplatelets (GNPs) with different loadings were fabricated via masterbatch compounding–melt blending processing technique. Morphological studies showed that the method employed provided uniform GNPs dispersion in the matrix, orienting the nanoplatelets along the same direction the flow of matter. Enhancements of storage and Young's modulus occurred, increasing GNP content, and the improvement was more obvious when a compatibilizer, the PP‐grafted‐maleic anhydride, was introduced to achieve a better GNP dispersion and distribution within the matrix. For all the nanocomposites, even for those compatibilized, it was not possible to fully exploit the GNP toughening effect since a stiffening and embrittling effect prevailed. Thermogravimetric analysis showed that GNP incorporation has improved the thermal stability of the nanocomposites. In addition, cone calorimetry results showed that GNPs can act as intumescent flame retardant and significantly reduced the heat release rate, thus improving the flame retardancy of the PP matrix. POLYM. ENG. SCI., 59:2062–2071, 2019. © 2019 Society of Plastics Engineers     

Learning style as an influence on the effectiveness of self-paced computer-assisted instruction: Preliminary results

Many have studied the relative effectiveness of self-paced, computer-assisted instruction. An experiment was conducted to investigate whether people of certain who exhibit certain learning styles are more successful using a self-paced instructional package. The preliminary results reported here indicate that differences in learning performance can be identified for different learning style categories (as measured by the Myers Briggs Type Indicator (MBTI).     

Precipitation potential of some BI-univalent electrolytes

Precipitation potentials of chlorides, bromides, and iodides of barium, calcium and magnesium are measured. The phase potentials of these electrolytes have been estimated from the decay curves. True precipitation potentials computed thereby show a linear relationship (for each set of halides) with (i) lattice energy; (ii) ratio of ionic radii of cation and anion; and (iii) ratio of real hydration energies of cation and anion. The sign and relative magnitude of precipitation potentials have also been explained on the basis of ion—water interaction.     

Production of a banana (Musa cavendishii) extract containing no polyphenol oxidase by ultrafiltration

The objective of this research was the production of a banana extract containing no polyphenol oxidase by ultrafiltration. Banana juice was extracted after inhibition of polyphenol oxidase using a solution containing 0.15 g per 100 ml of sodium metabisulphite and 1 g per 100 ml of ascorbic acid in distilled water to avoid initial browning. Polyphenol oxidase was then retained by ultrafiltration using polysulphone membranes with a cut‐off of 20 kDaltons. Two transmembrane pressures, 600 and 800 kPa, were used but 600 kPa was preferred because of the more stable permeate flux which decreased less with time and concentration of extract. © 1999 Society of Chemical Industry