Dynamic compressive response of composite square honeycombs

Carbon fibre-epoxy composite square honeycombs, and the parent composite material, were tested in quasi-static compression at a strain rate of 10 -3 s -1 and in dynamic compression at strain rates of 10 3-10 4 s -1 using an instrumented Kolsky bar arrangement. Taken together, these tests provide an assessment of the potential of this composite topology for use as a lightweight sandwich core. The honeycombs had two relative densities, 0.12 and 0.24, and two material orientations, ±45° and 0/90° with respect to the prismatic, loading direction of the honeycomb. Honeycomb manufacture was by slotting, assembling and bonding together carbon fibre/epoxy woven plies of composite sheets of 2 × 2 twill weave construction. The peak value of wall stress in the honeycombs was about one third that of the parent material, for all strain rates. An elastic finite element analysis was used to trace the source of this knock-down in strength: a stress concentration exists at the root of the slots and leads to premature failure by microbuckling. Shock-wave effects were evident at impact velocities exceeding 50 ms -1 for the honeycomb of relative density 0.12. This was traced to stubbing of the buckled cell walls against the face of the Kolsky bar. © 2011 Elsevier Ltd. All rights reserved.

Anisotropy of 2G HTS racetrack coils in external magnetic fields

Pancake or racetrack coils wound with second generation high-temperature superconductors (2G HTSs) are important elements for numerous applications of HTS. The applications of these coils are primarily in rotating machines such as motors and generators where they must withstand external magnetic fields from various orientations. The characterization of 2G HTS coils is mostly focused on AC loss assessment, critical current and maximum magnetic field evaluation. In this study, racetrack coils will be placed in different orientations of external magnetic fields - Jc (Ic) versus angle measurements will be performed and interpreted. Full attention is paid to studies of anisotropy Jc versus angle curves for short samples of 2G HTS tapes. As will be shown, the shape of the Jc versus angle curves for tapes has a strong influence on the Jc (Ic) versus angle curves for coils. In this work, a unique and unpredicted behavior of the Jc versus angle curves for the 2G HTS racetrack coils was found. This will be analyzed and fully explained. © 2013 IOP Publishing Ltd.

Multimode polymer waveguide components for complex on-board optical topologies

Multimode polymer waveguides are an attractive transmission medium for board-level optical links as they provide high bandwidth, relaxed alignment tolerances, and can be directly integrated onto conventional printed circuit boards. However, the performance of multimode waveguide components depends on the launch conditions at the component input, complicating their use in topologies that require the concatenation of multiple multimode components. This paper presents key polymer components for a multichannel optical bus and reports their performance under different launch conditions, enabling useful rules that can be used to design complex interconnection topologies to be derived. The components studied are multimode signal splitters and combiners, 90°-crossings, S-bends, and 90°-bends. By varying the width of the splitter arms, a splitting ratio between 1% and 95% is achieved from the 1 × 2 splitters, while low-loss signal combining is demonstrated with the waveguide combiners. It is shown that a 3 dB improvement in the combiner excess loss can be achieved by increasing the bus width by 50 μm. The worst-case insertion loss of 50 × 100 μm waveguide crossings is measured to be 0.1 dB/crossing. An empirical method is proposed and used to estimate the insertion losses of on-board optical paths of a polymeric four-channel optical bus module. Good agreement is achieved between the predicted and measured values. Although the components and empirical method have been tailored for use in a multichannel optical bus architecture, they can be used for any on-board optical interconnection topology. © 1983-2012 IEEE.

Ontogeny of IgM-producing cells in the mandarin fish Siniperca chuatsi identified by in situ hybridisation

The ontogeny of IgM-producing cells was studied in juvenile mandarin fish Simperca chuatsi, an important fish in China's aquaculture sector. The IgM-producing cells were localised through in situ hybridisation with a probe complementary to the Ig mu-chain in lymphoid-related tissues, including head kidney, spleen, thymus, intestine and gills. In head kidney, transcripts of Ig mu were first detected at 20 days post-hatching (dph) with a few positive signals. and the number of IgM-producing cells increased obviously from 39 dph onwards. At 136 dph, a large amount of positive cells were observed in the entire organ with clusters of these cells located around the blood vessels. In spleen, IgM-producing cells were found from 26 dph onwards, followed by an increase until 67 dph: clusters of positive cells were also detected around blood vessels at 102 dph. In thymus, IgM-producing cells were first observed at 39 dph; thereafter, no obvious increase was detected until 78 dph. The positive cells in thymus were distributed mainly in the outer zone of thymus. A few IgM-producing cells were still observed in thymus of 1-year-old mandarin fish. IgM-producing cells were not detected in the intestine until 87 dph, with several discrete positively stained cells distributed in the lamina propria. IgM-producing cells, scattered mainly in primary gill filaments around blood vessels, were detected in gills from 90 dph. As in other teleosts, these results indicated that the head kidney appears to be the primary organ for IgM production in mandarin fish, and IgM-producing cells exist in all organs examined in the present study, implying their lymphoid role in fish. In addition, it is suggested that vaccination after 20 dph may be much more effective in mandarin fish. (C) 2009 Elsevier B.V. All rights reserved.

Strength of GRP-laminates with multiple fragment damages

The strength of glass fibre reinforced vinyl-ester laminates with multiple holes has been investigated experimentally. Different hole pattern configurations have been tested, primarily for unidirectional laminates. Unidirectional laminates have shown very low notch sensitivity and the laminate failure was governed by two competing failure modes; shear off failure and net section tensile failure.

Toxicological Research on Environmental Endocrine Disruptors

Most evidence in terms of endocrine dsiruptors (EDs) mainly originates from studies on reproductive organs. However, in veterbrates, the ability to attain reproductive and development success relays on the intact organization of a complex endocrine system. Disturbances in the regulation of the key hormones and receptors functioning along this system may cause detrimental effects on reproduction and development. Here we reviewed recent studies of EDs on endocrine system. EDs may act on key hormones and receptors along with the hypothalarnic-pituitary-gonald (HPG) axis and lead to reproductive failure. Thyroid disruption may be caused at different levels, for example, the synthesis, transport, binding and cellular uptake along with the hypothalamic-pituitary-thyroid (HPT) axis. Knowledge of model of action EDs is largely via receptors-mediated pathway and alternatively may affect on steroid hormone synthesis. Aquatic hypoxia can influence fish reproduction and thus it is also an endocrine disruptor. Molecular techniques, such as toxicomics, transgenic fish will be employed as powerful tools for environmental EDs risk assessment, as well as in elucidating mechanisms of model action.

Developmental expression of CagMdkb during gibel carp embryogenesis

Midkine (Mdk) genes have been revealed to have different expression patterns in vertebrates and therefore, additional studies on Mdk expression patterns are required in more species. In this study, CagMdkb has been cloned and characterized from a SMART cDNA library of 10-somite stage embryos of Carassius auratus gibelio. Its full length cDNA is 1091 bp and encodes a sequence of 147 amino acids, which shows 97.3% identity to zebrafish Mdkb on the amino acid level. RT-PCR analysis reveals that CagMdkb is first transcribed in gastrula embryos and maintains a relatively stable expression level during subsequent embryogenesis. Western blot analysis reveals a 19 kDa maternal CagMdkb protein band and the zygotic CagMdkb protein is expressed from gastrula stage. At around 10 somite stage, the 19 kDa CagMdkb is processed to another protein band of about 17 kDa, which might be the secreted form with the 21-residue signal peptide removed. With immunofluorescence analysis, maternal CagMdkb protein was found to be localized in each blastamere cell of early embryos. The zygotic CagMdkb positive fluorescence signal was detected from a pair of large neurons at 18-somite stage. At the later stages, CagMdkb protein was also extended to numerous small neurons in the forebrain, midbrain and hindbrain, as well as to nerve fibers in the spinal cord. Co-localization with 3A10 antibody revealed CagMdkb immunoreactivity on developing Mauthner neurons, a member of reticulospinal neurons. In addition, ectopic expression of CagMdkb in early embryos of gibel carp and zebrafish suppressed head formation and CagMdkb function was found to depend on secretory activity. All these findings indicate that CagMdkb plays an important role in neural development during gibel carp embryogenesis and there is functional conservation of Mdkb in fish head formation.

Effects of intraperitoneal injection of cortisol on nonspecific immune functions of Ctenopharyngodon idella

After grass carps Ctenopharyngodon idellus were injected with cortisol, with (CBC) and without (C) a cocoa butter carrier, the effects of both slowly and rapidly acting exogenous cortisol oil their non-specific immune functions were investigated. On the one hand, after injection with CBC, the cortisol concentration and lysozyme activity in fish serum were enhanced and were sustained at high levels for a long period (30 days). The killing activity in the serum declined with time, and phagocytosis of head kidney macrophages diminished significantly (P < 0.05 or P < 0.01). The leukocrit values in the high dose group (31-8 mg cortisol fish(-1)) increased over time, however, with the maximum average being 5.6% at day 30. The spleen mass index in the high dose group was 0.93 x 10(-3) after 30 days, notably lower (P < 0.05) than that in the control group. In addition, a decrease in resistance to Aeronionas hydrophilo infection in cortisol-treated fish was shown, with the final cumulative mortalities being 54.5 and 66.7% in the low and high dose groups, respectively. On the other hand, there was a decrease in both serum cortisol concentration and lysozyme activity of the experimental fish within 2 weeks after injection with C, where plasma bactericidal activities in the high dose group (31-8 mg cortisol fish(-1)) were remarkably lower (P < 0.01) than those in the control group at each sampling, but were increased slightly over time. The results of which were different from those in the CBC trial. Phagocytic activity of head kidney macrophages and spleen mass index decreased significantly (P < 0.05), while there were increases in leukocrit value and cumulative mortality due to A. hydrophila. The results of which were similar to those in the CBC trial. This study indicated that the injection of cortisol depressed the non-specific immune functions of the grass carp and increased its susceptibility to disease. (c) 2005 The Fisheries Society of the British Isles.

Raman study of low-temperature-grown Al0.29Ga0.71As/GaAs photorefractive materials

We report on the observation of resonant Raman scattering in low-temperature-grown AlGaAs/GaAs structure. Two kinds of excitation lights, 632.8 and 488 nm laser lines, were used to detect scattering signal from different regions based on different penetration depths. Under the outgoing resonant condition, up to fourth-order resonant Raman peaks were observed in the low-temperature-grown AlGaAs alloy, owing to a broad exciton luminescence in low-temperature-grown AlGaAs alloy induced by intrinsic defects and As cluster after post-annealing. These resonant peaks were assigned according to their fundamental modes. Among the resonant peaks, besides the overtones of the GaAs- or AlAs-like mode, there exist combination bands of these two kinds of modes. In addition, a weak scattering peak similar to the bulk GaAs longitudinal optical mode was observed in low-temperature Raman experiments. We consider the weak signal correlated with GaAs clusters appearing in AlGaAs alloys. The accumulation of GaAs in AlGaAs alloys was enhanced after annealing at high temperatures. A detailed study of the dependence of vibration modes on measuring temperature and post-annealing conditions is given also. In light of our experiments, it is suggested that a Raman scattering experiment is a sensitive microscopic probe of local disorder and, especially performed at low temperature, is a superior method in detecting and analyzing the weak interaction between phonons and electrons.

Anisotropic strain in (100) ZnSe epilayers grown on lattice mismatched substrates

We show that part of the reflectance difference resonance near the E-0 energy of ZnSe is due to the anisotropic in-plane strain in the ZnSe thin films, as films grown on three distinctly different substrates, GaAs, GaP, and ZnS, all show the resonance at the same energy. Such anisotropic strain induced resonance is predicted and also observed near the E-1/E-1+Delta(1) energies in ZnSe grown on GaAs. The theory also predicts that there should be no resonance due to strain at, the E-0+Delta(0) energy, which is consistent with experiments. The strain anisotropy is rather independent of the ZnSe layer thickness, or whether the film is strain relaxed. For ZnSe films with large lattice mismatch with substrates, the resonance at the E-1/E-1+Delta(1) energies is absent, very likely due to the poor crystalline quality of the 20 nm or so surface layer. (C) 2000 American Vacuum Society. [S0734-211X(00)05604-3].

Layered Architecture for Secure E-Commerce Applications

We present a layered architecture for secure e-commerce applications and protocols with fully automated dispute-resolution process, robust to communication failures and malicious faults. Our design is modular, with precise yet general-purpose interfaces and functionalities, and allows usage as an underlying secure service to different e-commerce, e-banking and other distributed systems. The interfaces support diverse, flexible and extensible payment scenarios and instruments, including direct buyer-seller payments as well as (the more common) indirect payments via payment service providers (e.g. banks). Our design is practical, efficient, and ensures reliability and security under realistic failure and delay conditions.

高塬沟壑区董志塬沟头溯源侵蚀典型调查研究

详细调查了董志塬地区的西峰区、宁县以及庆城县的沟头溯源侵蚀情况,并对近年来发生前进的沟头进行了详细的实地测量和地形地貌特点分析,对董志塬沟头溯源侵蚀整体情况做出概括。在此基础上将溯源侵蚀的发生类型划分:水力冲刷型、陷穴诱发型、裂缝诱发型和人为诱发型。针对每种类型进行了典型的实例分析。

Effects of Cu-Wire Surface Fluctuations on Early Failures

Different chemical mechanical polishing （CMP） slurries are used to obtain single-damascene Cu-wires with different surface fluctuations as well as pre-existing surface-defects in wires with rougher surfaces. The presence of such pre-existing defects strongly increases the rate of early failures to almost 100%, reduces electromigration lifetime rapidly to the level of early failures, and changes the multimodal failure distribution into monomodal. The activation energy （0. 74±0.02eV） for the failure mechanism associated with these pre-existing defects confirms a dominant surface diffusion. It shows how a weakest link approximation analysis can he applied to a single wire by dividing the wire into relevant segments and assigning different failure mechanisms to the various segments. The analysis confirms that, although surface-defects are not the fastest early failure mechanism, the ten times higher surface-defectdensity in the rougher wires is responsible for the observed high early-failure rate and unreliable performance.

Anisotropic strain in (100) ZnSe epilayers grown on lattice mismatched substrates

We show that part of the reflectance difference resonance near the E-0 energy of ZnSe is due to the anisotropic in-plane strain in the ZnSe thin films, as films grown on three distinctly different substrates, GaAs, GaP, and ZnS, all show the resonance at the same energy. Such anisotropic strain induced resonance is predicted and also observed near the E-1/E-1+Delta(1) energies in ZnSe grown on GaAs. The theory also predicts that there should be no resonance due to strain at, the E-0+Delta(0) energy, which is consistent with experiments. The strain anisotropy is rather independent of the ZnSe layer thickness, or whether the film is strain relaxed. For ZnSe films with large lattice mismatch with substrates, the resonance at the E-1/E-1+Delta(1) energies is absent, very likely due to the poor crystalline quality of the 20 nm or so surface layer. (C) 2000 American Vacuum Society. [S0734-211X(00)05604-3].