Artificial surfaces of intertwined square spirals:A CPW model

Intertwining planar spirals arranged in doubly periodic arrays enables a substantially subwavelength response of the unit cell smaller than 1/40 of wavelength with large fractional bandwidths. These properties are important for application at low frequencies, conformal curved surfaces, or with compact radiators. It is shown that interleaving counter-wound spiral arms extended into adjacent unit cells dramatically increase the array equivalent capacitance while reducing the inductance. A coplanar waveguide (CPW) model has been developed to analytically estimate the equivalent capacitance and inductance of intertwined spiral array elements in terms of their geometrical parameters. The proposed CPW model is shown to provide an accurate prediction of the fundamental resonance frequency and can be instrumental in the design of the arrays for a specified frequency response. © 2012 IEEE.

Finite Element Analysis of Drilling of Carbon Fibre Reinforced Composites

Despite the increased applications of the composite materials in aerospace due to their exceptional physical and mechanical properties, the machining of composites remains a challenge. Fibre reinforced laminated composites are prone to different damages during machining process such as delamination, fibre pull-out, microcracks, thermal damages. Optimization of the drilling process parameters can reduces the probability of these damages. In the current research, a 3D finite element (FE) model is developed of the process of drilling in the carbon fibre reinforced composite (CFC). The FE model is used to investigate the effects of cutting speed and feed rate on thrust force, torque and delamination in the drilling of carbon fiber reinforced laminated composite. A mesoscale FE model taking into account of the different oriented plies and interfaces has been proposed to predict different damage modes in the plies and delamination. For validation purposes, experimental drilling tests have been performed and compared to the results of the finite element analysis. Using Matlab a digital image analysis code has been developed to assess the delamination factor produced in CFC as a result of drilling. © Springer Science+Business Media B.V. 2011.

Numerical investigation of the effects of drill geometry on drilling induced delamination of carbon fiber reinforced composites

Drilling is a major process in the manufacturing of holes required for the assemblies of composite laminates in aerospace industry. Simulation of drilling process is an effective method in optimizing the drill geometry and process parameters in order to improve hole quality and to reduce the drill wear. In this research we have developed three-dimensional (3D) FE model for drilling CFRP. A 3D progressive intra-laminar failure model based on the Hashin's theory is considered. Also an inter-laminar delamination model which includes the onset and growth of delamination by using cohesive contact zone is developed. The developed model with inclusion of the improved delamination model and real drill geometry is used to make comparison between the step drill of different stage ratio and twist drill. Thrust force, torque and work piece stress distributions are estimated to decrease by the use of step drill with high stage ratio. The model indicates that delamination and other workpiece defects could be controlled by selection of suitable step drill geometry. Hence the 3D model could be used as a design tool for drill geometry for minimization of delamination in CFRP drilling. © 2013 Elsevier Ltd.

Transfers to non-state actors

Background paper for Small Arms Survey, Geneva.

Coordinated Design of Phase Measurement Unit and Power System Stabilisers in Large Scale Power System

This paper presents a case-study of a PMU application with PSS support in a real large scale Chinese power system to suppress inter-area oscillations. The paper uses PMU measured feedback signals from a PSS input signal for dynamic torque analysis (DTA). In the paper, a mathematical model of multi-machine power system is described, followed by formation of the residue and DTA indices. Simulations of the model are used with a large-scale power system model to demonstrate the role of PSS and the equivalence of DTA residue indices.

Thermolyzable polymer networks and star polymers containing a novel, compact, degradable acylal-based dimethacrylate cross-linker: Synthesis, characterization, and thermolysis

A compact, cleavable acylal dimethacrylate cross-linker, 1,1-ethylenediol dimethacrylate (EDDMA), was synthesized from the anhydrous iron(III) chloride-catalyzed reaction between methacrylic anhydride and acetaldehyde. The ability of EDDMA to act as cross-linker was demonstrated by using it for the preparation of one neat cross-linker network, four star polymers of methyl methacrylate (MMA), and four randomly cross-linked MMA polymer networks using group transfer polymerization (GTP). For comparison, the corresponding polymer structures based on the commercially available ethylene glycol dimethacrylate (EGDMA) cross-linker (isomer of EDDMA) were also prepared via GTR The number of arms of the EDDMA-based star polymers was lower than that of the corresponding EGDMA polymers, whereas the degrees of swelling in tetrahydrofuran of the EDDMA-based MMA networks were higher than those of their EGDMA-based counterparts. Although none of the EDDMA-containing polymers could be cleanly hydrolyzed under basic or acidic conditions, they could be thermolyzed at 200 degrees C within 1 day giving lower molecular weight products.

Synthesis and characterization of amphiphilic star copolymers of 2-(dimethylamino) ethyl methacrylate and methyl methacrylate: Effects of architecture and composition

Six amphiphilic star copolymers comprising hydrophilic units of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and hydrophobic units of methyl methacrylate (MMA) were prepared by the sequential group transfer polymerization (GTP) of the two comonomers and ethylene glycol dimethacrylate (EGDMA) cross-linker. Four star-block copolymers of different compositions, one miktoarm star, and one statistical copolymer star were synthesized. The molecular weights (MWs) and MW distributions of all the star copolymers and their linear homopolymer and copolymer precursors were characterized by gel permeation chromatography (GPC), while the compositions of the stars were determined by proton nuclear magnetic resonance (H-1 NMR) spectroscopy. Tetrahydrofuran (THF) solutions of all the star copolymers were characterized by static light scattering to determine the absolute weight-average MW ((M) over bar (w)) and the number of arms of the stars. The R, of the stars ranged between 359,000 and 565,000 g mol(-1), while their number of arms ranged between 39 and 120. The star copolymers were soluble in acidic water at pH 4 giving transparent or slightly opaque solutions, with the exception of the very hydrophobic DMAEMA(10)-b-MMA(30)-star, which gave a very opaque solution. Only the random copolymer star was completely dispersed in neutral water, giving a very opaque solution. The effective pKs of the copolymer stars were determined by hydrogen ion titration and were found to be in the range 6.5-7.6. The pHs of precipitation of the star copolymer solutions/dispersions were found to be between 8.8-10.1, except for the most hydrophobic DMA-EMA(10)-b-MMA(30)-Star, which gave a very opaque solution over the whole pH range. (c) 2006 Elsevier Ltd. All rights reserved.

Three different types of quasi-model networks: synthesis by group transfer polymerization and characterization

Group transfer polymerization (GTP) chemistry was employed for the preparation of polymethacrylate networks of controlled structure (quasi-model networks) of three different types: (a) regular quasi-model networks, in which all polymer chains were linked at their ends, leaving, in principle, no free chain ends, (b) crosslinked star polymer quasi-model networks, in which star polymers were interlinked via half of their chains, letting the other half free (dangling), and (c) shell-crosslinked polymer quasi-model networks, in which the outer part of the network contained polymer arms (dangling chains). Combination of hydrophilic and hydrophobic monomers led to amphiphilic networks whose aqueous swelling behavior was characterized gravimetrically.

Synthesis and characterization of star polymers and cross-linked star polymer model networks with cores based on an asymmetric, hydrolyzable dimethacrylate cross-linker

A hydrolyzable dimethacrylate cross-linker, 2-methyl-2,4-pentanediol dimethacrylate (MPDMA), was synhesized by the reaction of 2-methyl-2,4-pentanediol and methacryloyl chloride in the presence of triethylamine. This cross-linker was used to prepare a neat cross-linker network and three cross-linked star polymer model networks (CSPMNs) of methyl methacrylate (MMA), as well as star-shaped polymers of MMA, by group transfer polymerization (GTP). Gel permeation chromatography (GPC) in tetrahydrofuran (THF) confirmed the narrow molecular weight distributions (MWDs) of the linear polymer precursors, and demonstrated the increase in molecular weight (MW) on each successive addition of cross-linker or monomer. Characterization of the star polymers by static light scattering (SLS) in THF showed that star polymers with MPDMA cores bear a relatively small number of arms, between 7 and 35. All star polymers and polymer networks containing the MPDMA cross-linker were hydrolyzed at room temperature in neat trifluoroacetic acid to yield lower-MW products.

Synthesis and characterization of polymer networks and star polymers containing a novel, hydrolyzable acetal-based dimethacrylate cross-linker

An acid-labile dimethaerylate acetal cross-linker,di(methacryloyloxy-l-ethoxy)methane(DMOEM), was synthesized by the reaction of 2-hydroxyethyl methacrylate and paraformaldehyde using p-toluenesulfonic acid and toluene as catalyst and solvent, respectively. Group transfer polymerization was employed to use this cross-linker in the preparation of nine hydrolyzable polymer structures: one neat cross-linker network, one randomly cross-linked network of methyl methacrylate (MMA), and seven star-shaped polymers of MMA. Gel permeation chromatography (GPC) in tetrahydrofuran (THF) confirmed the narrow molecular weight distributions of the linear polymer precursors to the stars and demonstrated the increase in molecular weight upon the addition of cross-linker for the formation of star-shaped polymers. Characterization of the star polymers in THF using static light scattering and GPC showed that the molecular weights and the number of arms of each star polymer increased with an increase in the molar ratio of cross-linker to initiator and with a decrease in the molar ratio of monomer to initiator. The star polymers with DMOEM cores bore a smaller number of arms than those cross-linked with the non-hydrolyzable commercial cross-linker ethylene glycol dimethacrylate due to the bulkier structure of DMOEM. All DMOEM-containing polymer networks and star polymers were completely hydrolyzed within 48 h using hydrochloric acid in THF.

Synthesis and characterization of star polymers and cross-linked star polymer model networks containing a novel, silicon-based, hydrolyzable cross-linker

An acid-labile dimethacrylate cross-linker, dimethyldi(methacryloyloxy-l-ethoxy)silane (DMDMAES), was synthesized by the reaction of 2-hydroxyethyl methacrylate (HEMA) and dichlorodimethylsilane in the presence of triethylamine. Group transfer polymerization (GTP) was employed to use this cross-linker in the preparation of six hydrolyzable polymer structures: one neat cross-linker network, one randomly cross-linked network of methyl methacrylate (MMA), two star-shaped polymers of MMA, and two cross-linked star polymer model networks (CSPMNs) of MMA. A nonhydrolyzable CSPMN of MMA, based on a stable cross-linker, was also synthesized. Gel permeation chromatography (GPC) in tetrahydrofuran (THF) confirmed the narrow molecular weight distributions (MWDs) of the linear polymer precursors and demonstrated the increase in molecular weight (MW) upon each successive addition of cross-linker or monomer. Characterization by static light scattering (SLS) and GPC showed that star polymers with DMDMAES cores bear a relatively small number of arms, around 7. All star polymers and polymer networks were hydrolyzed using hydrochloric acid in THF. While the MWs of the products from the hydrolysis of the star polymers, the neat cross-linker network, and the randomly cross-linked network were as expected, those from the CSPMNs were of a much higher than expected MW, indicating extensive star-star coupling.

Beowulf Hondbona: the Literary Context for Emending Line 1520b

In this article I consider the debate over whether line 1520b ought to be read as the emended “hond sweng” or the scribal “hord swenge.” It is a small point philologically but it raises interesting cultural and literary questions about the attitude of the Beowulf poet to arms and armour, to aggressive and defensive war gear, and to swords in particular. It has widely been assumed that swords are important in Beowulf and yet, the question of what their significance might be has received very little attention. Throughout the poem the hero is plagued by breaking, melting, and failing swords. He borrows, finds, and is given swords but unlike other English and Germanic heroes he is never identified with a single, great sword. I suggest that this is because, ultimately, Beowulf is conceived as a hondbana, a designation which has implications for what kind of a hero he proves to be.

Inclusion of chemotherapy in addition to anthracycline in the treatment of acute promyelocytic leukaemia does not improve outcomes:results of the MRC AML15 trial

Two hundred eighty-five patients, median age 42, with PML-RARa-positive acute promyelocytic leukaemia were randomised to Ara-C-containing 'Medical Research Council (MRC) Chemotherapy'+ATRA (All-trans-retinoic acid) or anthracycline+ATRA (modified 'Spanish') therapy. MRC treatment comprised four courses with ATRA in courses 1-2. Spanish treatment comprised four anthracycline-based courses with ATRA in courses 1-3. In course 3 patients were randomised to gemtuzumab ozogamicin (GO) or not. The Spanish arm received 24-month maintenance. Patients were sequentially molecularly monitored. Quality of life was assessed at baseline, 3, 6, 9, 12, 24 months. Remission rates were similar in both arms (93%): cumulative incidence of haematological relapse (CIHR) was 6% at 5 years; 5 patients relapsed molecularly. Survival post relapse was 80%. There were more deaths in remission in the MRC arm (4% vs 10%: P=0.2). The overall 5-year relapse-free and overall survival was similar between arms (81% vs 82% and 84% vs 83%, respectively). More supportive care and hospitalisation (81.8 vs 63 days, P10 × 10(9)/l) was not prognostic overall, or within treatment arms. Both approaches deliver similar results with minor differences in quality of life. MRC treatment required more hospitalisation. This suggests that additional chemotherapy, Ara-C in particular, is not required.

Delamination and wear in drilling of carbon-fiber reinforced plastic composites using multilayer TiAlN/TiN PVD-coated tungsten carbide tools

This study aims to investigate drilling process in carbon-fiber reinforced plastic (CFRP) composites with multilayer TiAlN/TiN PVD-coated tungsten carbide drill. The effect of process parameters have been investigated in drilling of Hexcel M21-T700GC. Thrust force and torque were measured online throughout the drilling experiments. Delamination were observed using optical microscope and analyzed via a developed algorithm based on digital image processing technique. Surface roughness of each hole was measured using a surface profilometer. In addition, the progression of tool wear in various surfaces of drill was observed using tool microscope and measured using image software. Our results indicate that the thrust force and torque increased with the increasing cutting speed and feed rate. Delamination and average surface roughness that rose with the increase in feed rate, however, decreased with the increasing cutting speed. The average surface roughness tended to increase with the increase in feed rate and decrease with the increasing cutting speed in drilling of carbon-fiber reinforced plastic (CFRP). Feed rate was found as the predominant factor on the drilling outputs. Abrasive wear was observed on both flank and relief surfaces, which created edge wear on cutting edges. No sign of chipping or plastic deformation has been observed on the surfaces of drills. © 2012 The Author(s).