What is the Computational Value of Finite Range Tunneling?

Quantum annealing (QA) has been proposed as a quantum enhanced optimization heuristic exploiting tunneling. Here, we demonstrate how finite range tunneling can provide considerable computational advantage. For a crafted problem designed to have tall and narrow energy barriers separating local minima, the D-Wave 2X quantum annealer achieves significant runtime advantages relative to Simulated Annealing (SA). For instances with 945 variables, this results in a time-to-99%-success-probability that is $\sim 10^8$ times faster than SA running on a single processor core. We also compared physical QA with Quantum Monte Carlo (QMC), an algorithm that emulates quantum tunneling on classical processors. We observe a substantial constant overhead against physical QA: D-Wave 2X again runs up to $\sim 10^8$ times faster than an optimized implementation of QMC on a single core. We note that there exist heuristic classical algorithms that can solve most instances of Chimera structured problems in a timescale comparable to the D-Wave 2X. However, we believe that such solvers will become ineffective for the next generation of annealers currently being designed. To investigate whether finite range tunneling will also confer an advantage for problems of practical interest, we conduct numerical studies on binary optimization problems that cannot yet be represented on quantum hardware. For random instances of the number partitioning problem, we find numerically that QMC, as well as other algorithms designed to simulate QA, scale better than SA. We discuss the implications of these findings for the design of next generation quantum annealers.Comment: 17 pages, 13 figures. Edited for clarity, in part in response to comments. Added link to benchmark instance

Development and characterization of silicone/phosphorus modified epoxy materials and their application as anticorrosion and antifouling coatings

Epoxy resin is chosen for our present study owing to its exceptional combination of properties such as easy processing, high safety, excellent solvent and chemical resistance, toughness, low shrinkage on cure, good electrical, mechanical and corrosion resistance with excellent adhesion to many substrates. This versatility in formulation made epoxy resins widely applied for surface coatings, adhesives, laminates, composites, potting, painting materials, encapsulant for semiconductor and insulating material for electric devices. There are numerous paint/coating systems based on epoxy resin available for corrosion and fouling prevention. They however are not completely satisfactory in field applications, where high corrosion, fouling and flame resistance are required. The demand for epoxy resin as corrosion/fouling resistant coatings is restricted mainly due to its inferior characteristics like poor impact strength, high rigidity, and moisture absorbing nature besides inadequate flame retardant properties. It is for this reason that silicones and phosphorus-based compounds are used as modifier in this work by intercrosslinking network mechanism (ICN) to obtain epoxy resin with desired properties ideally suitable for field applications for preventing corrosion and fouling with flame retardantancy. The present work involves the development of solvent free silicone/phosphorus modified epoxy coating systems, since solvent free coating systems are widely used for numerous applications due to their lower cost per unit film thickness, freedom from fire and pollution hazard and ability to provide better performance. For the development of coating systems, epoxy resin (X) serves as base material, hydroxyl terminated dimethylsiloxane (HTPDMS) as modifier, aminopropyltriethoxysilane (APS) as crosslinking agent and dibutyltindilaurate (DBTDL) as catalyst. Polyamidoamine (A), aromatic amine adducts (B) and phosphorus-containing diamine (C) were used as curing agents. The study also describes the evaluation of corrosion resistant behaviour of unmodified epoxy and siliconized epoxy coatings by potentiodynamic polarization method, electrochemical impedance spectroscopy (EIS), salt-spray and antifouling tests. The results are discussed.CSIR. National Metallurgical Laboratory. Madras Centre. Fundação para a Ciência e Tecnologia

Comparative structural and mechanical studies on polyamide 6 knitted-reinforced single polymer composites prepared by different reactive processing techniques

Single polymer laminate composites based on anionic polyamide 6 (PA6) matrix-reinforced by PA6 knitted textile structures (KSPC) were produced by nylon reactive injection molding and powder coating/compression molding (PCCM) processing techniques. The effect of the reinforcement’s structure and the fiber volume fraction on the mechanical properties of the knitted-reinforced PA6 composites resulting from the two methods were investigated and compared. The morphology and the crystalline structure of KSPC materials were studied to identify the main factors determining the tensile properties. The results showed that the PCCM method produced laminate composites with higher Young’s modulus and mechanical strength in tension. Microscopy, differential scanning calorimetry and X-ray diffraction experiments were carried out to correlate the morphology and crystalline structure of the composites and their precursors with the different tensile behavior of KSPC prepared using the two techniques. The microscopy and X-ray scattering studies suggested the formation of a transcrystalline layer at the matrix/reinforcement interface. POLYM. COMPOS., 40:E886–E897, 2019. © 2018 Society of Plastics EngineersThis work was partially financed by FEDER funds through the COMPETE program and by national funds through FCT – Foundation for Science and Technology within the project POCI‐01‐0145‐FEDER‐007136. SDT thanks FCT for his PhD Grant SFRH/BD/94759/2013. NVD thanks for the financial support of FCT in the frames of the strategic project UID/CTM/50025/2013. Finally, ZZD is thankful to FCT for the SFRH/BSAB/130271/2017 personal research grant. All authors gratefully acknowledge the support of the project TSSiPRO‐NORTE‐01‐0145‐FEDER‐000015 funded by the regional operational program NORTE 2020, under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund

Structure–properties relationship in single polymer composites based on polyamide 6 prepared by in-mold anionic polymerization

Single polymer composites (SPCs) based on polyamide 6 (PA6) were prepared by in-mold activated anionic ring-opening polymerization (AAROP) of capro- lactam in the presence of PA6 textile fibers. The influence of the reinforcing fibers content, their surface treatment, as well as of the temperature of AAROP upon the morphol- ogy, crystalline structure, and mechanical properties of the resulting SPCs was followed. The presence of oriented transcrystalline layer (TCL) on the surface of the rein- forcing fibers was demonstrated by means of microscopy methods. Its orientation and polymorph structure were determined by synchrotron wide-angle X-ray scattering. Studies on the mechanical behavior in tension of the SPCs showed a well-expressed growth of the stress at break (70–80 %) and deformation at break (up to 150–190 %) in composites with 15–20 wt% of reinforcements. The best mechanical properties were found in SPCs whose rein- forcing fibers were solvent-pretreated prior to AAROP in order to remove the original finish. In these samples a stronger adhesion at the fiber/matrix interface was proved by scanning electron microscopy of cryofractured samples. This effect was related to a thinner TCL in which the α-to-γ polymorph transition is impeded.Strategic Project LA 25-2011-2012 financed by Fundação para a Ciência e a Tecnologia (FCT) - PortugalHASYLAB at DESY (Grant Number II-07- 011EC)FCT post-doctoral award SFRH/BPD/45252/2008, co-financed by QREN-POPH program of EU

Semi-automatic laboratory equipment for reactive injection molding

Traditional melt processing techniques limit in shape and thickness the parts of fiber-reinforced thermoplastic composites. Producing of thermoplastic hybrid composites through melt intercalation often results in heterogeneous products due to micron-scale agglomerations with a negative effect on the mechanical properties. The in-situ polymerization processes to form the matrix in polymer composites have proved to be a good approach toward the resolution of these issues. In the present work we report on the design and con-struction of a prototype semi-automatic laboratory equipment for reactive injection molding and its application for the preparation of various types of polyamide-6 based composites via in-situ activated anionic polymerization of ε-caprolactam.Fundação para a Ciência e Tecnologia grant SFRH/BPD/45252/2008 co-funded by FS

New records and noteworthy data of plants, algae and fungi in SE Europe and adjacent regions, 11

This paper presents new records and noteworthy data on the following taxa in SE Europe and adjacent regions: red algae Sheathia confusa, parasitic fungus Anthracoidea caryophylleae, mycorrhizal fugus Hydnellum caeruleum, bryoparasitic fungus Octospora erzbergeri, liverwort Cephaloziella baumgartneri, mosses Hamatocaulis vernicosus, Streblotrichum convolutum var. commutatum and Ulota crispula, monocots Ophrys bertolonii subsp. bertolonii, Ophrys scolopax subsp. cornuta and Spiranthes spiralis and dicots Androsace hedraeantha, Hieracium mrazii, Ramonda nathaliae and Triglochin palustris are given within SE Europe and adjacent region