13C-NMR study of ethylene/1-hexene and ethylene/1-octene copolymers obtained using homogeneous catalysts

Summary This study employed the ¹³C-NMR spectroscopy to investigate the influence of the increase of the comonomer concentration on the microstruture of ethylene/1-hexene and ethylene/1-octene copolymers obtained by the use of MeSiCp₂ZrCl₂, Cp₂ZrCl₂, Et[Ind]₂ZrCl₂ and [Ind]₂ZrCl₂ catalysts. For both comonomers butyl or hexyl branches were isolated between ethylene blocks. As the -olefin concentration in the copolymer increased, butyl or hexyl branches became closer, some of them, separated by only one or two ethylene units. Incorporation of -olefin in the copolymer was higher for the bridged catalysts, MeSiCp₂ZrCl₂, and Et[Ind]₂ZrCl₂ than for the unbridged ones. The -olefin size did not seem to effect its reactivity towards ethylene.     

Counselors network for intrusion detection

Intrusion detection systems (IDSs) are a fundamental component of defense solutions. In particular, IDSs aim to detect malicious activities on computer systems and networks by relying on data classification models built from a training dataset. However, classifiers' performance can vary for each attack pattern. A common technique to overcome this issue is to use ensemble methods, where multiple classifiers are employed and a final decision is taken combining their outputs. Despite the potential advantages of such an approach, its usefulness is limited in scenarios where (i) multiple expert classifiers present divergent results, (ii) all classifiers present poor results due to lack of representative features, or (iii) detectors have insufficient labeled signatures to train their classifiers for a specific attack pattern. In this work, we introduce the concept of a counselors network to deal with conflicts from different classifiers by exploiting the collaboration among IDSs that analyze multiple and heterogeneous data sources. Empirical results demonstrate the feasibility of the proposed architecture in improving the accuracy of the intrusion detection process.     

Experimental evaluation of dynamic resource orchestration in multi-layer (packet over flexi-grid optical) networks

Network services in 5G will be rolled out as pools of virtual network functions (VNFs) exploiting the advantages of both software-defined networking and network function virtualization. In this context, 5G network services are envisaged as ordered sequences of VNFs resulting in the so-called VNF Forwarding Graphs (VNFFGs). Such VNFs can be allocated over a number of distributed but interconnected data centers (DCs). In this work, a cloud/network orchestrator is discussed to dynamically process and accommodate VNFFG requests over a pool of DCs interconnected by a multi-layer (packet/flexi-grid optical) transport network infrastructure. Two different cloud and network resource allocation algorithms are proposed aiming at: (1) minimizing the distance between the selected DCs and (2) minimizing the load (i.e., consumed cloud resources) of the chosen DCs. In the performance evaluation, the proposed algorithms are experimentally validated and compared on the CTTC ADRENALINE testbed.

     

The first iteration of Grover's algorithm using classical light with orbital angular momentum

We present an experimental realization of the first iteration in Grover's quantum algorithm using classical light and linear optical elements. The algorithm serves to find an entry marked by an oracle in an unstructured database. In our scheme, the quantum states encoding the database are represented by helical modes generated by means of a Spatial Light Modulator, while the marking corresponds to a π phase shift of the hidden mode. The optical implementation of Grover's algorithm then selectively amplifies the intensity of the marked mode such that it can be revealed by a modal decomposition. The core of the algorithm – a geometrical reflection of the point representing all database entries – is implemented in a single step independent of the size of the database. Moreover, we demonstrate experimentally that one iteration of the algorithm is enough to identify the marked entry, as a consequence of using classical states of light.     

The effects of topographic correction and gap filling in imagery on the detection of tropical forest disturbances using a Landsat time series in Myanmar

In this study, we evaluated the effects of topographic correction and gap filling of Landsat Enhanced Thematic Mapper Plus (ETM+) images on the accuracy of forest change detection through a trajectory-based approach. Four types of Landsat time series stacks (LTSS) were generated. These stacks resulted from combinations of topographically corrected and uncorrected imagery combined with gap-filled and unfilled stacks. These combinations of stacks were then used as input into a trajectory-based change detection. The results of change detection from trajectory-based analysis using these LTSS were compared in order to assess the effects of both topographic correction and gap-filling procedures on the ability to detect forest disturbances. The results showed that overall accuracies of change detection were improved after gap filling (10.5% and 7.5%), but were only slightly improved after topographic correction (3.6% and 0.6%). Although the gap-filling process introduced some uncertainty that might have caused false change detection, the number of pixels whose detection of disturbance was enhanced after gap filling exceeded those detecting false change. The results also showed that the topographic correction did not contribute much to improve the change detection in this study area. However, topographic correction has a potential to increase the accuracy of change detection in areas of more rugged terrain and steep slopes. This is because a direct relationship between the slope of the topography with topographic correction and an enhanced detection of disturbance in pixels from year to year was observed in this study. For robust change detection, we recommend that a gap-filling process should be included in the trajectory-based analysis procedures such as the one used in this study where a single image per year is used to characterize change. We also recommend that in areas of rugged terrain, a topographic correction in the image pre-processing should be implemented.     

Fast similarity metric for real-time template-matching applications

In this study, a visual similarity metric based on precision–recall graphs is presented as an alternative to the widely used Hausdorff distance (HD). Such metric, called maximum cardinality similarity metric, is computed between a reference shape and a test template, each one represented by a set of edge points. We address this problem using a bipartite graph representation of the relationship between the sets. The matching problem is solved using the Hopcroft–Karp algorithm, taking advantage of its low computational complexity. We present a comparison between our results and those obtained from applying the partial Hausdorff distance (PHD) to the same test sets. Similar results were found using both approaches for standard template-matching applications. Nevertheless, the proposed methodology is more accurate at determining the completeness of partial shapes under noise conditions. Furthermore, the processing time required by our methodology is lower than that required to compute the PHD, for a large set of points.     

Platinum-sulfated-zirconia. Infrared study of adsorbed pyridine

Pyridine adsorption on sulfated zirconia (SO _2– ⁴ -ZrO₂) provides evidence for infrared bands characteristic of both Brønsted and Lewis acid sites. Samples treated at 100°C retain water and have a higher fraction of Brønsted acidity than when the sample is treated at 400°C. The fraction of Brønsted acid sites observed for SO _2– ⁴ -ZrO₂ is the same in the presence or absence of supported Pt. Based on pyridine adsorption, exposure to gaseous hydrogen at 100 or 150°C did not significantly alter the fraction of Brønsted acid sites following the exposure to hydrogen.     

Sex Attractant Pheromone from the Neotropical Red-Shouldered Stink Bug, <Emphasis Type="Italic">Thyanta perditor</Emphasis> (F.)

Olfactometer bioassays showed that odors from mature Thyanta perditor males attracted females but not males. Furthermore, odors from females did not attract either sex, indicating that like other phytophagous pentatomid bugs, the males produce a sex pheromone. Attraction appeared to peak in late afternoon to evening. The headspace volatiles collected from male and female T. perditor were analyzed by GC-MS and HPLC. A male-specific compound, methyl (2E,4Z,6Z)-decatrienoate (2E,4Z,6Z-10:COOMe), was identified along with a number of other compounds found in extracts from both sexes. Bioassays carried out with 2E,4Z,6Z-10:COOMe showed it was as attractive to females as the crude extract of male volatiles, suggesting that the male-produced sex pheromone consists of 2E,4Z,6Z-10:COOMe as a single component. Consecutive volatiles collections from males showed that 2E,4Z,6Z-10:COOMe began appearing in extracts from males about 9 d after the final molt, as the males became sexually mature.     

Occurrence of volatile chiral compounds in dairy products, especially cheese – A review

The current review lists a total of 126 chiral compounds described in the literature for at least 21 different cheese varieties: 30 alcohols, 8 ketones, 2 aldehydes, 20 esters, 20 lactones, 27 carboxylic acids, 13 hydrocarbons (8 terpenes), 4 furanones, and 2 amines. Of these only a few authentic reference compounds are commercially available. All these data are compiled in seven tables.     

Calculation of the Second Order Settling Time in SISO Linear Systems

This paper clearly defines the second order settling time as a special and most important case of the generalized settling time. A new calculation procedure for second order settling time determination is developed, based on a decomposition of deterministic, random or mixed non-stationary signals in steady-state and transient components. A worked out example illustrates the computation procedure. The derived relations can be implemented in the form of computer programs. Although restricted to SISO linear systems, the procedure developed in this paper covers a lot of practical situations like those encountered in sensors and transducers modeling.