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The light management of phytoplankton can be assessed in situ on time scales shorter than those of the non-photochemical fluorescence quenching (q_n) mechanisms. We adopted fast repetition rate fluorometry to water column studies ...
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The light management of phytoplankton can be assessed in situ on time scales shorter than those of the non-photochemical fluorescence quenching (q_n) mechanisms. We adopted fast repetition rate fluorometry to water column studies in the northwest Pacific Ocean and its adjacent shelf seas. Near-surface depression of the photochemical energy conversion efficiency (PECE) (effective F_q'/F_m' and maximum F_v'/F_m'; F_q' = F_m' - F', F_v' = F_m' - F_o'; F_q' and F_v' are variable fluorescence yields in the light, F_v' is that with maximum photochemical quenching; fluorescence yields in the light: F_m' maximum, F' steady-state, and F_o' minimum) defined specific zones according to whether PECE was depressed by photochemistry (relaxation of photochemical quenching, q_p) or photoprotection/photoinhibition (increase of q_n). q_p seemed to be the main factor depressing PECE, and the depressing effect of q_p on PECE also extended to considerably deeper depths than that of q_n. When moving towards the surface, the q_n effect overrode the q_p effect on the PECE decrease at depths of 8 to 13 m, depending on the station. The vertical trends of F_q'/F_m' and F_v'/F_m' were modelled according to a typical P-E (photosynthesis-irradiance) dependence to supplement the ~(14)C-based P-E data. E(F_q'/F_m') and E(F_v'/F_m') were the light levels at which the vertical trends of F_q'/F_m' and F_v'/F_m', respectively, started to decrease. Although the nutrient regime is the main controller of primary photochemistry in general, the ambient light also becomes the controlling factor on PECE whenever the light level rises above E(F_q'/F_m'). At E(F_v'/F_m'), light ultimately overrides the effect of the nutrient status on PECE. E(F_v'/F_m') also marks the light level at which the photoprotective measures first become necessary. This level is close to the onset of the plateau phase producing the ~(14)C-based light-saturated photosynthetic rate P_(max).
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This article aims at systematically comparing three different designs of experiments (DOE) methodologies used in the optimization of engineering structures. The selected methods are a response surface methodology, an adaptive one-...
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This article aims at systematically comparing three different designs of experiments (DOE) methodologies used in the optimization of engineering structures. The selected methods are a response surface methodology, an adaptive one-factor-at-a-time search methodology, and a Bayesian DOE-based methodology. Six evaluative criteria are defined for the comparison. To perform the study, a simulation-based layout optimization of a four-layer composite laminate is used under a fiber misalignment fabrication error. It is found that each solution method satisfies a particular aspect of the six evaluative criteria and, thus, an application of a multiple criteria decision aid model is suggested to assist the analyst.
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We present an updated all-particle energy spectrum of primary cosmic rays in a wide range from 10~(14) to 10~(17) eV using 5.5 × 10~7 events collected from 2000 November through 2004 October by the Tibet-III air-shower array loca...
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We present an updated all-particle energy spectrum of primary cosmic rays in a wide range from 10~(14) to 10~(17) eV using 5.5 × 10~7 events collected from 2000 November through 2004 October by the Tibet-III air-shower array located 4300 m above sea level (an atmospheric depth of 606 g cm~(-2)). The size spectrum exhibits a sharp knee at a corresponding primary energy around 4 PeV. This work uses increased statistics and new simulation calculations for the analysis. We discuss our extensive Monte Carlo calculations and the model dependencies involved in the final result, assuming interaction models QGSJET01 c and SIB YLL2.1, and heavy dominant (HD) and proton dominant (PD) primary composition models. Pure proton and pure iron primary models are also examined as extreme cases. A detector simulation was also performed to improve our accuracy in determining the size of the air showers and the energy of the primary particle. We confirmed that the all-particle energy spectra obtained under various plausible model parameters are not significantly different from each other, which was the expected result given the characteristics of the experiment at high altitude, where the air showers of the primary energy around the knee reach near-maximum development, with their features dominated by electromagnetic components, leading to a weak dependence on the interaction model or the primary mass. This is the highest statistical and the best systematics-controlled measurement covering the widest energy range around the knee energy region.
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Twenty years ago in a series of amazing discoveries it was found that a large family of ceramic cuprate materials exhibited superconductivity at temperatures above, and in some cases well above, that of liquid nitrogen. Imaginatio...
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Twenty years ago in a series of amazing discoveries it was found that a large family of ceramic cuprate materials exhibited superconductivity at temperatures above, and in some cases well above, that of liquid nitrogen. Imaginations were energized by the thought of applications for zero-resistance conductors cooled with an inexpensive and readily available cryogen. Early optimism, however, was soon tempered by the hard realities of these new materials: brittle ceramics are not easily formed into long flexible conductors; high current levels require near-perfect crystallinity; and — the downside of high transition temperature — performance drops rapidly in a magnetic field. Despite these formidable obstacles, thousands of kilometres of high-temperature superconducting wire have now been manufactured for demonstrations of transmission cables, motors and other electrical power components. The question is whether the advantages of superconducting wire, such as efficiency and compactness, can outweigh the disadvantage: cost. The remaining task for materials scientists is to return to the fundamentals and squeeze as much performance as possible from these wonderful and difficult materials.
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In this study, hemp fibres were treated with alkali, acetyl and silane chemicals. Fibre constituents such as cellulose, hemicellulose and lignin constituents were separated from treated fibres. The chemical and thermal influences ...
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In this study, hemp fibres were treated with alkali, acetyl and silane chemicals. Fibre constituents such as cellulose, hemicellulose and lignin constituents were separated from treated fibres. The chemical and thermal influences of these constituents on the treated fibres were examined by using scanning electron microscope (SEM), fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Experimental results revealed that, hemicellulose was degraded faster than that of cellulose and lignin. Cellulose exhibited better thermal stability and lignin was degraded in a wide range of temperatures. The hydrophilic nature of the fibres was predominantly caused by the presence of hemicellulose and then lignin constituents. Hemicellulose and lignin were mostly removed by the alkalisation with higher concentrations of NaOH, followed by acetylation. Silane treatment could not remove the hemicellulose and lignin, rather this treatment facilitated coupling with the fibre constituents.
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Nitridation of Cr-bearing alloys can yield low interfacial contact resistance (ICR), electrically conductive and corrosion-resistant CrN or Cr_2N base surfaces of interest for a range of electrochemical devices, including fuel cel...
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Nitridation of Cr-bearing alloys can yield low interfacial contact resistance (ICR), electrically conductive and corrosion-resistant CrN or Cr_2N base surfaces of interest for a range of electrochemical devices, including fuel cells, batteries, and sensors. This paper presents results of exploratory studies of the nitridation of commercially available, high Cr (30-35 wt%) Ni-Cr alloys and a ferritic high Cr (29 wt%) stainless steel for proton exchange membrane fuel cell (PEMFC) bipolar plates. A high degree of corrosion resistance in sulfuric acid solutions designed to simulate bipolar plate conditions and low ICR values were achieved. Oxygen impurities in the nitriding environment were observed to play a significant role in the nitrided surface structures that formed, with detrimental effects for the Ni-Cr base alloys, but beneficial effects for the stainless steel alloy. Positive results from single-cell fuel cell testing are also presented.
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Zirconia doped with 6-8 wt/100 (3.2-4.2 mol/100) yttria (6-8YSZ), the most common thermal barrier coating material, relies mostly on oxygen vacancies to provide the phonon scattering necessary for low thermal conductivity. The pre...
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Zirconia doped with 6-8 wt/100 (3.2-4.2 mol/100) yttria (6-8YSZ), the most common thermal barrier coating material, relies mostly on oxygen vacancies to provide the phonon scattering necessary for low thermal conductivity. The present study examines whether specific substitutional defects-in addition to, or instead of , oxygen vacancies--can provide similar or greater reductions in conductivity. To this end a series of zirconia samples co-doped with varying levels of yttrium (trivalent) and tantalum/niobium (pentavalent) oxides were synthesized, thereby allowing oxygen vacancy and substitutional atom concentration to be varied independently. The results show that Nb-Y and Ta-Y co-doped zirconia samples containing only substi- tutional defects produce stable single-phase tetragonal materials with thermaI conductivities very close to that of the conventional 6-8YSZ. In these samples, Nb~5+ and Td~5+ are similarly effective in lowering thermal conductivity, in contradiction to phonon scattering theories that consider primarily mass effects and thereby predict significantly greater conductivity reduction due to Ta~5+ doping than Nb~5+ doping. Finally, Nb~5+/Ta~5+- Y~3+ doped samples, which contain both oxygen vacancies and substitutional defects, are found not to be stable in single-phase form; however, the thermal conductivities of the two-phase tetragonal + cubic mixtures are again as low as that of the conventional 6-8YSZ.
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The model of a paper machine is very complex and difficult to describe completely by a mathematical model. There are a lot of parameters in both the wet and dry end of the machine and there is a very large time delay in the system...
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The model of a paper machine is very complex and difficult to describe completely by a mathematical model. There are a lot of parameters in both the wet and dry end of the machine and there is a very large time delay in the system which effects the quality of the paper being produced. Although the PID controller is widely used for these types of applications, it is often not tuned very well. In this work, a newly developed algorithm (Munro, The systematic design of PID controllers, IEE Colloquium in Robust Control: Theory, Software and Applications, Austin Court, Birmingham, 1999) is used for tuning the PID controller. Along with this controller, a Smith-predictive controller is applied to the plant and the transient and steady-state behaviours of these controllers are compared. Hardware and software implementations of the closed-loop control are also presented in the paper.
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ZEPLIN II is a two-phase (liquid/gas) xenon dark matter detector searching for WIMP-nucleon interactions. In this paper we describe the data acquisition system used to record the data from ZEPLIN II and the reduction procedures wh...
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ZEPLIN II is a two-phase (liquid/gas) xenon dark matter detector searching for WIMP-nucleon interactions. In this paper we describe the data acquisition system used to record the data from ZEPLIN II and the reduction procedures which parameterise the data for subsequent analysis.
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The requirements of the DⅢ-D physics program have led to the development of many operational control results with direct relevance to ITER. These include new algorithms for robust and sustained stabilization of neoclassical teari...
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The requirements of the DⅢ-D physics program have led to the development of many operational control results with direct relevance to ITER. These include new algorithms for robust and sustained stabilization of neoclassical tearing modes with electron cyclotron current drive, model-based controllers for stabilization of the resistive wall mode in the presence of ELMs, coupled linear-nonlinear algorithms to provide good dynamic axisymmetric control while avoiding coil current limits, and adaptation of the DⅢ-D plasma control system (PCS) to operate next-generation superconducting tokamaks. Development of integrated plasma control (IPC), a systematic approach to model-based design and controller verification, has enabled successful experimental application of high reliability control algorithms requiring a minimum of machine operations time for testing and tuning. The DⅢ-D PCS hardware and software and its versions adapted for other devices can be connected to IPC simulations to confirm control function prior to experimental use. This capability has been important in control system implementation for tokamaks under construction and is expected to be critical for ITER.
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