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At least 487 records · Page 27

Simulation investigation of multipactor in metal components for space application with an improved secondary emission model

Effects of the secondary electron emission (SEE) phenomenon of metal surface on the multipactor analysis of microwave components are investigated numerically and experimentally in this paper. Both the secondary electron yield (SEY) and the emitted energy spectrum measurements are performed on silver plated samples for accurate description of the SEE phenomenon. A phenomenological probabilistic model based on SEE physics is utilized and fitted accurately to the measured SEY and emitted energy spectrum of the conditioned surface material of microwave components. Specially, the phenomenological probabilistic model is extended to the low primary energy end lower than 20 eV mathematically, since no accurate measurement data can be obtained. Embedding the phenomenological probabilistic model into the Electromagnetic Particle-In-Cell (EM-PIC) method, the electronic resonant multipacting in microwave components can be tracked and hence the multipactor threshold can be predicted. The threshold prediction error of the transformer and the coaxial filter is 0.12 dB and 1.5 dB, respectively. Simulation results demonstrate that the discharge threshold is strongly dependent on the SEYs and its energy spectrum in the low energy end (lower than 50 eV). Multipacting simulation results agree quite well with experiments in practical components, while the phenomenological probabilistic model fit both the SEY and the emission energy spectrum better than the traditionally used model and distribution. The EM-PIC simulation method with the phenomenological probabilistic model for the surface collision simulation has been demonstrated for predicting the multipactor threshold in metal components for space application.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

High-throughput shadow mask printing of passive electrical components on paper by supersonic cluster beam deposition

We report the rapid prototyping of passive electrical components (resistors and capacitors) on plain paper by an additive and parallel technology consisting of supersonic cluster beam deposition (SCBD) coupled with shadow mask printing. Cluster-assembled films have a growth mechanism substantially different from that of atom-assembled ones providing the possibility of a fine tuning of their electrical conduction properties around the percolative conduction threshold. Exploiting the precise control on cluster beam intensity and shape typical of SCBD, we produced, in a one-step process, batches of resistors with resistance values spanning a range of two orders of magnitude. Parallel plate capacitors with paper as the dielectric medium were also produced with capacitance in the range of tens of picofarads. Compared to standard deposition technologies, SCBD allows for a very efficient use of raw materials and the rapid production of components with different shape and dimensions while controlling independently the electrical characteristics. Discrete electrical components produced by SCBD are very robust against deformation and bending, and they can be easily assembled to build circuits with desired characteristics. The availability of large batches of these components enables the rapid and cheap prototyping and integration of electrical components on paper as building blocks of more complex systems.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Performance demonstration of vacuum microwave components critical for the operation of the ITER low-field side reflectometer

Final design studies in preparation for manufacturing have been performed for functional components of the vacuum portion of the ITER Low-Field Side Reflectometer (LFSR). These components consist of an antenna array, electron cyclotron heating (ECH) protection mirrors, phase calibration mirrors, and vacuum windows. Evaluation of these components was conducted at the LFSR test facility and DIII-D. The antenna array consists of six corrugated-waveguide antennas for simultaneous profile, fluctuation, and Doppler measurements. A diffraction grating, incorporated into the plasma-facing miter bend, provides protection of sensitive components from stray ECH at 170 GHz. For in situ phase calibration of the LFSR profile reflectometer, an embossed mirror is incorporated into the adjacent miter bend. Measurements of the radiated beam profile indicate that these components have a small, acceptable effect on mode conversion and beam quality. Baseline transmission characteristics of the dual-disk vacuum window are obtained and are used to guide ongoing developments. Preliminary simulations indicate that a surface-relief structure on the window surfaces can greatly improve transmission. The workability of real-time phase measurements was demonstrated on the DIII-D profile reflectometer. The new automated real-time analysis agrees well with the standard post-processing routine.

47 OTHER INSTRUMENTATION↗

Developing a space-filling mixture experiment design when the components are subject to linear and nonlinear constraints

This article presents a case study of developing a space-filling design (SFD) for a constrained mixture experiment when the experimental region is specified by single-component constraints (SCCs), linear multiple-component constraints (LMCCs), and nonlinear multiple-component constraints (NMCCs). Traditional methods and software for designing constrained mixture experiments with SCCs and LMCCs (using either optimal design or SFD approaches) are not directly applicable because of the NMCCs. A SFD algorithm in the JMP software was modified to accommodate the nonlinear MCCs; the modification is described in this article. The case study involves high-level waste (HLW) glass that is subject to the formation of nepheline crystals as the glass cools. This can significantly reduce the durability of HLW glass (which is undesirable). The goal of the study was to develop a SFD for the HLW glass compositional region where nepheline may form, and generate data for modeling nepheline formation as a function of HLW glass composition. The HLW glass composition region was specified in terms of eight components with SCCs, two LMCCs, and two NMCCs. The NMCCs were based on a nonlinear logistic regression model for a binary-response nepheline response that was developed from previous data. This article discusses the HLW glass example, the constraints specifying the experimental composition region, and how an existing algorithm for generating SFDs was modified to accommodate the NMCCs. The methodology discussed in this article can be applied to any example in which the experimental region is specified by one or more nonlinear constraints in addition to linear constraints on mixture components and/or non-mixture variables.

Mixture experiment, space-filling experimental des↗

TIME-SERIES SPECTROSCOPY OF THE ECLIPSING BINARY Y CAM WITH A PULSATING COMPONENT

We present the physical properties of the semi-detached Algol-type eclipsing binary Y Cam based on high resolution spectra obtained using the Bohyunsan Optical Echelle Spectrograph. This is the first spectroscopic monitoring data obtained for this interesting binary system, which has a δ Sct-type pulsating component. We obtained a total of 59 spectra over 14 nights from 2009 December to 2011 March. Double-lined spectral features from the hot primary and cool secondary components were well identified. We determined the effective temperatures of the two stars to be T{sub eff,1} = 8000 ± 250 K and T{sub eff,2} = 4629 ± 150 K. The projected rotational velocities are v{sub 1}sin i{sub 1} = 51 ± 4 km s{sup −1} and v{sub 2}sin i{sub 2} = 50 ± 10 km s{sup −1}, which are very similar to a synchronous rotation with the orbital motion. Physical parameters of each component were derived by analyzing our radial velocity data together with previous photometric light curves from the literature. The masses and radii are M{sub 1} = 2.08 ± 0.09 M{sub ⊙}, M{sub 2} = 0.48 ± 0.03 M{sub ⊙}, R{sub 1} = 3.14 ± 0.05 R{sub ⊙}, and R{sub 2} = 3.33 ± 0.05 R{sub ⊙}, respectively. A comparison of these parameters with the theoretical evolution tracks showed that the primary component is located between the zero-age main sequence and the terminal-age main sequence, while the low-mass secondary is noticeably evolved. This indicates that the two components have experienced mass exchange with each other and the primary has undergone an evolution process different from that of single δ Sct-type pulsators.

79 ASTRONOMY AND ASTROPHYSICS↗

STEPWISE FILTER CORRELATION METHOD AND EVIDENCE OF SUPERPOSED VARIABILITY COMPONENTS IN GAMMA-RAY BURST PROMPT EMISSION LIGHT CURVES

Gamma-ray bursts (GRBs) have variable light curves. Although most models attribute the observed variability to one physical origin (e.g., central engine activity, clumpy circumburst medium, or relativistic turbulence), some models invoke two physically distinct variability components. We develop a method, namely, the stepwise filter correlation method, to decompose the variability components in a GRB light curve. Based on a low-pass filter technique, we progressively filter the high-frequency signals from the light curve, and then perform a correlation analysis between each adjunct pair of filtered light curves. Our simulations suggest that if a mock light curve contains a 'slow' variability component superposed on a rapidly varying time sequence, the correlation coefficient as a function of the filter frequency would display a prominent 'dip' feature around the frequency of the slow component. Through simulations, we demonstrate that this method can identify significant clustering structures of a light curve in the frequency domain, and we prove that it can catch superposed signals that are otherwise not easy to retrieve based on other methods (e.g., the power density spectrum analysis method). We apply this method to 266 Burst and Transient Source Experiment bright GRBs. We find that the majority of the bursts have clear evidence of such a superposition effect. We perform a statistical analysis of the identified variability components and discuss the implications for GRB physics.

79 ASTRONOMY AND ASTROPHYSICS↗

Optimized principal component analysis on coronagraphic images of the fomalhaut system

We present the results of a study to optimize the principal component analysis (PCA) algorithm for planet detection, a new algorithm complementing angular differential imaging and locally optimized combination of images (LOCI) for increasing the contrast achievable next to a bright star. The stellar point spread function (PSF) is constructed by removing linear combinations of principal components, allowing the flux from an extrasolar planet to shine through. The number of principal components used determines how well the stellar PSF is globally modeled. Using more principal components may decrease the number of speckles in the final image, but also increases the background noise. We apply PCA to Fomalhaut Very Large Telescope NaCo images acquired at 4.05 μm with an apodized phase plate. We do not detect any companions, with a model dependent upper mass limit of 13-18 M {sub Jup} from 4-10 AU. PCA achieves greater sensitivity than the LOCI algorithm for the Fomalhaut coronagraphic data by up to 1 mag. We make several adaptations to the PCA code and determine which of these prove the most effective at maximizing the signal-to-noise from a planet very close to its parent star. We demonstrate that optimizing the number of principal components used in PCA proves most effective for pulling out a planet signal.

79 ASTRONOMY AND ASTROPHYSICS↗

CORRELATIONS IN HORIZONTAL BRANCH OSCILLATIONS AND BREAK COMPONENTS IN XTE J1701-462 AND GX 17+2

We studied the horizontal branch oscillations (HBO) and the band-limited components observed in the power spectra of the transient neutron star low-mass X-ray binary XTE J1701-462 and the persistent ''Sco-like'' Z source GX 17+2. These two components were studied based on the state-resolved spectra. We found that the frequencies of XTE J1701-462 lie on the known correlations (WK and PBK), showing consistency with other types of X-ray binaries (black holes, atoll sources, and millisecond X-ray pulsars). However, GX 17+2 is shifted from the WK correlation like other typical Z sources. We suggest that the WK/PBK main track forms a boundary that separates persistent sources from transient sources. The characteristic frequencies of break and HBO are independent of accretion rate in both sources, though it depends on spectral models. We also report the energy dependence of the HBO and break frequencies in XTE J1701-462 and how the temporal properties change with spectral state in XTE J1701-462 and GX 17+2. We studied the correlation between rms at the break and the HBO frequency. We suggest that HBO and break components for both sources probably arise from a similar physical mechanism: Comptonization emission from the corona. These two components could be caused by the same kind of oscillation in a corona with uneven density, and they could be generated from different areas of the corona. We further suggest that different proportions of the Comptonization component in the total flux cause the different distribution between GX 17+2 and XTE J1701-462 in the rms{sub break}-rms{sub HBO} diagram.

79 ASTRONOMY AND ASTROPHYSICS↗

A 2-component blend of coconut oil-derived fatty acids as an oviposition deterrent against Drosophila suzukii (Drosophilidae: Diptera)

Abstract Coconut free fatty acid (CFFA), a mixture of 8 fatty acids derived from coconut oil, is an effective repellent and deterrent against a broad array of hematophagous insects. In this study, we evaluated the oviposition deterrent activity of CFFA on spotted-wing drosophila (SWD; Drosophila suzukii), a destructive invasive pest of berries and cherries, and identified bioactive key-deterrent compounds. In laboratory 2-choice tests, CFFA deterred SWD oviposition in a dose-dependent manner with the greatest reduction (99%) observed at a 20-mg dose compared with solvent control. In a field test, raspberries treated with 20-mg CFFA received 64% fewer SWD eggs than raspberries treated with the solvent control. In subsequent laboratory bioassays, 2 of CFFA components, caprylic and capric acids, significantly reduced SWD oviposition by themselves, while 6 other components had no effect. In choice and no-choice assays, we found that a blend of caprylic acid and capric acid, at equivalent concentrations and ratio as in CFFA, was as effective as CFFA, while caprylic acid or capric acid individually were not as effective as the 2-component blend or CFFA at equivalent concentrations, indicating the 2 compounds as the key oviposition deterrent components for SWD. The blend was also as effective as CFFA for other nontarget drosophilid species in the field. Given that CFFA compounds are generally regarded as safe for humans, CFFA and its bioactive components have potential application in sustainably reducing SWD damage in commercial fruit operations, thereby reducing the sole reliance on insecticides.

Entomology↗

Gram-positive bacterial cell wall components inhibit herpes simplex virus infection

The role of the mucosal microbiome in viral infections remains unclear. Genital herpes, caused by herpes simplex virus 1 and 2 (HSV-1 and HSV-2), is among the most prevalent sexually transmitted infections worldwide. Despite evidence linking vaginal Lactobacillus to protection against sexually transmitted viruses, the specific microbial components and mechanisms that mediate this defense are not well understood. Here, we show that multiple cell wall components from diverse gram-positive bacteria, including lactobacilli, inhibit HSV-1 and HSV-2 infection in cells and in a mouse model of genital herpes infection. Peptidoglycan (PG) and lipoteichoic acid (LTA), both major components of the gram-positive bacterial cell wall, significantly reduced HSV infectivity in vitro and improved survival and disease outcomes in mice. We further showed that Lactobacillus crispatus surface layer proteins SlpA and SlpB bind HSV-1 and inhibit infection. Antiviral effects of cell wall components were dose-dependent, relied on intact PG structure, and, in the case of PG and LTA, were independent of TLR2-mediated host signaling. Collectively, our findings identify a species-independent antiviral function for gram-positive bacterial cell wall components against HSV and suggest that the composition of the mucosal microbiome may play an underappreciated role in suppressing mucosal herpes infection in humans.

Adams↗

Analytical thermodynamics of a strongly attractive three-component Fermi gas in one dimension

Ultracold three-component atomic Fermi gases in one dimension are expected to exhibit rich physics due to the presence of trions and different pairing states. Quantum phase transitions from the trion state into a paired phase and a normal Fermi liquid occur at zero temperature. We derive the analytical thermodynamics of strongly attractive three-component one-dimensional fermions with SU(3) symmetry via the thermodynamic Bethe ansatz method in unequal Zeeman splitting fields H{sub 1} and H{sub 2}. We find explicitly that for low temperature the system acts like either a two-component or a three-component Tomonaga-Luttinger liquid dependent on the system parameters. The phase diagrams for the chemical potential and specific heat are presented for illustrative values of the Zeeman splitting. We also demonstrate that crossover between different Tomonaga-Luttinger-liquid phases exhibit singular behavior in specific heat and entropy as the temperature tends to zero. Beyond Tomonaga-Luttinger-liquid physics, we obtain the equation of state which provides a precise description of universal thermodynamics and quantum criticality in three-component, strongly attractive Fermi gases.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Component-specific electromechanical response in a ferroelectric/dielectric superlattice.

The electronic and electromechanical properties of complex oxide superlattices are closely linked to the evolution of the structure and electrical polarization of the component layers in applied electric fields. Efforts to deduce the responses of the individual components of the superlattice to applied fields have focused on theoretical approaches because of the limitations of available experimental techniques. Time-resolved x-ray microdiffraction provides a precise crystallographic probe of each component using the shift in wave vector and change in intensity of superlattice satellite reflections. We report in detail the methods to measure and analyze the x-ray diffraction patterns in applied electric field and their application to a 2-unit-cell BaTiO{sub 3}/4-unit-cell CaTiO{sub 3} superlattice. We find that the overall piezoelectric distortion is shared between the two components. Theoretical predictions of the electromechanical properties of a superlattice with the same composition constrained to tetragonal symmetry are in excellent agreement with the experiments. Lattice instability analysis, however, suggests that the low-temperature ground state could exhibit antiferrodistortive rotations of TiO{sub 6} octahedra within and/or at the interfaces of the CaTiO{sub 3} component.

36 MATERIALS SCIENCE↗

Precise response function for the magnetic component of gravitational waves in scalar-tensor gravity

The important issue of the magnetic component of gravitational waves (GWs) has been considered in various papers in the literature. From such analyses, it has been found that such a magnetic component becomes particularly important in the high-frequency portion of the frequency range of ground based interferometers for GWs which arises from standard general theory of relativity (GTR). Recently, such a magnetic component has been extended to GWs arising from scalar-tensor gravity (STG) too. After a review of some important issues on GWs in STG, in this paper we reanalyze the magnetic component in the framework of STG from a different point of view, by correcting an error in a previous paper and by releasing a more precise response function. In this way, we also show that if one neglects the magnetic contribution considering only the low-frequency approximation of the electric contribution, an important part of the signal could be, in principle, lost. The determination of a more precise response function for the magnetic contribution is important also in the framework of the possibility of distinguishing other gravitational theories from GTR. At the conclusion of this paper, an expansion of the main results is also shown in order to recall the presence of the magnetic component in GTR too.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Structure of nitrilotriacetate monooxygenase component B from Mycobacterium thermoresistibile

Mycobacterium tuberculosis belongs to a large family of soil bacteria which can degrade a remarkably broad range of organic compounds and utilize them as carbon, nitrogen and energy sources. It has been proposed that a variety of mycobacteria can subsist on alternative carbon sources during latency within an infected human host, with the help of enzymes such as nitrilotriacetate monooxygenase (NTA-Mo). NTA-Mo is a member of a class of enzymes which consist of two components: A and B. While component A has monooxygenase activity and is responsible for the oxidation of the substrate, component B consumes cofactor to generate reduced flavin mononucleotide, which is required for component A activity. NTA-MoB from M. thermoresistibile, a rare but infectious close relative of M. tuberculosis which can thrive at elevated temperatures, has been expressed, purified and crystallized. The 1.6 Å resolution crystal structure of component B of NTA-Mo presented here is one of the first crystal structures determined from the organism M. thermoresistibile. The NTAMoB crystal structure reveals a homodimer with the characteristic split-barrel motif typical of flavin reductases. Surprisingly, NTA-MoB from M. thermoresistibile contains a C-terminal tail that is highly conserved among mycobacterial orthologs and resides in the active site of the other protomer. Based on the structure, the C-terminal tail may modulate NTA-MoB activity in mycobacteria by blocking the binding of flavins and NADH.

59 BASIC BIOLOGICAL SCIENCES↗

Glycosylation of hyperthermostable designer cellulosome components yields enhanced stability and cellulose hydrolysis

Biomass deconstruction remains integral for enabling second-generation biofuel production at scale. However, several steps necessary to achieve significant solubilization of biomass, notably harsh pretreatment conditions, impose economic barriers to commercialization. By employing hyperthermostable cellulase machinery, biomass deconstruction can be made more efficient, leading to milder pretreatment conditions and ultimately lower production costs. The hyperthermophilic bacterium Caldicellulosiruptor bescii produces extremely active hyperthermostable cellulases, including the hyperactive multifunctional cellulase CbCel9A/Cel48A. Recombinant CbCel9A/Cel48A components have been previously produced in Escherichia coli and integrated into synthetic hyperthermophilic designer cellulosome complexes. Since then, glycosylation has been shown to be vital for the high activity and stability of CbCel9A/Cel48A. Here, we studied the impact of glycosylation on a hyperthermostable designer cellulosome system in which two of the cellulosomal components, the scaffoldin and the GH9 domain of CbCel9A/Cel48A, were glycosylated as a consequence of employing Ca. bescii as an expression host. Inclusion of the glycosylated components yielded an active cellulosome system that exhibited long-term stability at 75 degrees C. The resulting glycosylated designer cellulosomes showed significantly greater synergistic activity compared to the enzymatic components alone, as well as higher thermostability than the analogous nonglycosylated designer cellulosomes. These results indicate that glycosylation can be used as an essential engineering tool to improve the properties of designer cellulosomes. Additionally, Ca. bescii was shown to be an attractive candidate for production of glycosylated designer cellulosome components, which may further promote the viability of this bacterium both as a cellulase expression host and as a potential consolidated bioprocessing platform organism.

09 BIOMASS FUELS↗

Weibull and Bootstrap-Based Data-Analytics Framework for Fatigue Life Prognosis of the Pressurized Water Nuclear Reactor Component Under Harsh Reactor Coolant Environment

In general, the fatigue life of a safety critical pressure component is estimated using best-fit fatigue life curves (S-N curves). These curves are estimated based on underlying in-air condition fatigue test data. The best-fitting approach requires a large safety factor to accommodate the uncertainty associated with large scatter in fatigue test data. In addition to this safety factor, reactor component fatigue life prognostics requires an additional correction factor that in general is also estimated deterministically. This additional factor known as the environmental correction factor F en is to cater the effect of the harsh coolant environment that severely reduces the life of these components. The deterministic F en factor may also lead to further conservative estimation of fatigue life leading to unnecessary early retirement of costly reactor components. To address the above-mentioned issues, we propose a data-analytics framework which uses Weibull and Bootstrap probabilistic modeling techniques for explicitly quantifying the uncertainty/scatter associated with fatigue life rather than estimating the lives based on a best-fit based deterministic approach. We assume the proposed probabilistic approach would provide the first hand information for assessing the maximum and minimum effects of pressurized water reactor water on the reactor component. In the discussed approach, in addition to the probabilistic fatigue curves, we suggest using a probabilistic environment correction factor F en . Here, we assume the probabilistic fatigue curve and F en would capture the S-N data scatter associated with the bulk effect of material grades, surface finish, strain rate, etc. on the material/component fatigue life.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

Network Uncertainty Quantification for Analysis of Multi-Component Systems

To impact physical mechanical system design decisions and realize the full promise of high-fidelity computational tools, simulation results must be integrated at the earliest stages of the design process. This is particularly challenging when dealing with uncertainty and optimizing for system-level performance metrics, as full-system models (often notoriously expensive and time-consuming to develop) are generally required to propagate uncertainties to system-level quantities of interest. Methods for propagating parameter and boundary condition uncertainty in networks of interconnected components hold promise for enabling design under uncertainty in real-world applications. These methods avoid the need for time consuming mesh generation of full-system geometries when changes are made to components or subassemblies. Additionally, they explicitly tie full-system model predictions to component/subassembly validation data which is valuable for qualification. These methods work by leveraging the fact that many engineered systems are inherently modular, being comprised of a hierarchy of components and subassemblies that are individually modified or replaced to define new system designs. By doing so, these methods enable rapid model development and the incorporation of uncertainty quantification earlier in the design process. The resulting formulation of the uncertainty propagation problem is iterative. We express the system model as a network of interconnected component models, which exchange solution information at component boundaries. We present a pair of approaches for propagating uncertainty in this type of decomposed system and provide implementations in the form of an open-source software library. We demonstrate these tools on a variety of applications and demonstrate the impact of problem-specific details on the performance and accuracy of the resulting UQ analysis. This work represents the most comprehensive investigation of these network uncertainty propagation methods to date.

42 ENGINEERING↗

Designing Cladded Components for High Temperature Nuclear Service: Part II—Design Rules

The challenge of using existing ASME Section III, Division 5, class A metallic materials for the construction of structural components of advanced reactors with corrosive coolants could be mitigated by allowing designers to use cladding to protect the base material from corrosion. However, the existing Section III, Division 5 rules provide no guidance on the evaluation of strain accumulation and creep-fatigue damage in cladded components. The availability of design rules for cladded components that do not require long-term clad material testing could promote the application of the cladding approach to accelerate the deployment schedule of these advanced reactor systems. To avoid long-term properties for the clad materials Part I of this work proposes two approximate design analysis methods for two types of clad materials—soft clads that creep much faster and have lower yield stress than the class A base material, and hard clads that creep much slower and have higher yield stress than the class A base material. The proposed analysis methods approximate the response of a soft clad by treating it as perfectly compliant and of a hard clad by treating it as linear elastic. Based on these approximate design analysis strategies this Part II develops a complete set of design rules for class A components cladded with either soft or hard clad materials. In conclusion, Part II discusses the reasoning behind the proposed design rules and uses example finite element analyses of representative reactor components to illustrate the use of these design methods.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗