Attitude Estimation: With or Without Spacecraft Dynamics?

Kalman filter based spacecraft attitude estimation has been used in many space missions and has been widely discussed in literature. While some models in spacecraft attitude estimation include spacecraft dynamics, most do not. To our best knowledge, there is no analysis to determine which model is a better choice. In this paper, we discuss the reasons why spacecraft dynamics should be considered in the Kalman filter based spacecraft attitude estimation problem. We also propose a reduced quaternion spacecraft dynamics model which admits additive noise. Geometry of the reduced quaternion model and the additive noise are discussed. This formulation makes computation easier than the one with full quaternion. Simulations are conducted to justify our claims

Effect of Stress Level on Bending Creep Behavior of Wood During Cyclic Moisture Changes

This study investigated the effect of stress level on bending creep behavior of Japanese cedar (Cryptomerica japonica D. Don) during cyclic moisture changes. Tests were made at 20° with four cyclic relative humidity changes between 65% and 95% under four stress levels: 12.6, 18.5, 24.3, and 30.2 MPa, corresponding to 17, 25, 33, and 42% of short-term breaking stress, respectively. The effect of moisture content (MC) change on elastic compliance and mechano-sorptive (MS) compliance was examined. The results indicated that the total compliance revealed different behavior under various stress levels over the history of cyclic moisture changes and appeared to be greater under higher stress. Elastic compliance increased linearly with MC and affected the behavior of total compliance during MC change. As MC change increased, the MS compliance during the first adsorption and all desorption increased linearly, while during subsequent adsorption revealed a decrease in lower stress and an increase in higher stress. At a given stress level, the first adsorption led to greater MS deformation than did desorption and subsequent adsorption. The elastic parameter KE for MC effect on elastic compliance and the MS parameter KM for relationship between MS compliance and MC increased as quadratic functions of applied stress. The rate of increase in the parameters accelerated above about 25 to 33% stress level. As a result, when MC is cycled, MS compliance increase occurs at lower stress levels relative to creep at constant MC

Bending Creep Behavior of Medium Density Fiberboard and Particleboard During Cyclic Moisture Changes

Bending creep behavior of four types of medium density fiberboard (MDF) and two types of particleboard during cyclic moisture changes was investigated in this study. Tests were made at 20°C with three cyclic relative humidity changes between 65% and 95% under the 10% short-term breaking stress. The effect of moisture content (MC) change on initial compliance and mechano-sorptive (MS) compliance was examined. The results indicated that relative deflection and total compliance of the samples increased over the history of cyclic moisture changes, and their magnitudes varied with board types. Melamine- and phenol-resin bonded boards had smaller relative deflection and total compliance than did urea-resin bonded boards. Both relative deflection and total compliance increased in adsorption and showed reduction in desorption. Initial compliance followed a linear relation with MC and had some influence on total compliance behavior under moisture cycles. MS compliance increased in adsorption while showing slight reduction or increase in desorption. The first adsorption led to the largest MS compliance, followed by subsequent adsorption. With increasing MC change, MS compliance increased linearly in the first adsorption, while it increased nonlinearly in the subsequent adsorption. The MS compliance coefficient KM was product-dependent. Resin type appeared to be an important factor influencing the variations in KM. In this study, urea-resin bonded boards had a greater KM compared to melamine- and phenol-resin bonded boards

Screening hub genes in coronary artery disease based on integrated analysis

Background: Coronary artery disease (CAD) is the leading cause of mortality worldwide. Identifying key pathogenic genes benefits the understanding molecular mechanism of CAD. Methods: In this study, 5 microarray data sets from the blood sample of 312 CADs and 277 healthy controls were downloaded. Limma and metaMA packages were used to identify differentially expressed genes. The functional enrichment analysis of differentially expressed genes was further performed by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes. Additionally, protein–protein interac­tion and transcript factors-target networks were performed based on top 10 up- and down-regulated differentially expressed genes to further study the biological function. Last, real-time quantitative poly­merase chain reaction (RT-qPCR) was used to validate the integrated analysis result. Results: A total of 528 differentially expressed genes were obtained. All differentially expressed genes were significantly involved in signal transduction and the MAPK signaling pathway. Among MAPK signaling pathway, IL1R2, ARRB2 and PRKX were associated with CAD. Furthermore, there were 4 common differentially expressed genes including PLAUR, HSPH1, ZMYND11 and S100A8 in the protein–protein interaction and transcript factors-target networks, which played crucial roles in the development of CAD. In quantitative RT-qPCR, the expression of PRKX, HSPH1 and ZMYND11 was down-regulated and consistent with the integrated analysis. Conclusions: Identified 7 differentially expressed genes (IL1R2, ARRB2, PRKX, PLAUR, HSPH1, ZMYND11 and S100A8) may play crucial roles in the development of CAD

The use of redox potential to estimate free chlorine in fresh produce washing operations : possibilities and limitations

Maintaining free chlorine (FC) residual at appropriate pH values is a control approach used to prevent pathogen cross-contamination during tomato dump tank handling and fresh-cut produce washing operations. Oxidation reduction potential (ORP) is a rapid measurement of oxidant-based sanitizer strength, and has been used to estimate FC residual. However, factors, in addition to FC and pH, which influence ORP are not fully understood. This study examined the relationship between ORP and FC under chlorine demand (CLD) free conditions and during fresh produce washing. An equation predictive of FC was developed in the form logFC = f(ORP, ORP2, ORP.pH). A good correlation between ORP and logFC was maintained when other variables changed, but the resulting ORP-logFC curve changed (slope, intercept). A decrease in pH or temperature led to an increase in ORP. Using tap water to wash the produce instead of distilled water significantly changed the ORP. For different types of tested produce, i.e., fresh-cut carrot, onion, romaine and iceberg lettuce, and for whole tomatoes, increasing the product-to-water ratio (i.e., increasing the organics transferred into the water) led to a decrease in ORP for a specific FC residual. The choice of acidulant during washing also influenced ORP. Overall, the correlation of ORP with logFC is more reliable at the lower end (5 mg/L FC) than at the higher end (100 mg/L FC) of the FC range used in fresh produce washing. However, since the ORP in fresh produce wash water is affected significantly in multiple ways by the wash water and process conditions, the predicted FC values with ORP under certain fresh-cut produce washing conditions cannot be generalized for other conditions

The relationship between photometric and spectroscopic oscillation amplitudes from 3D stellar atmosphere simulations

We establish a quantitative relationship between photometric and spectroscopic detections of solar-like oscillations using ab initio, three-dimensional (3D), hydrodynamical numerical simulations of stellar atmospheres. We present a theoretical derivation as proof of concept for our method. We perform realistic spectral line formation calculations to quantify the ratio between luminosity and radial velocity amplitude for two case studies: the Sun and the red giant $\epsilon$ Tau. Luminosity amplitudes are computed based on the bolometric flux predicted by 3D simulations with granulation background modelled the same way as asteroseismic observations. Radial velocity amplitudes are determined from the wavelength shift of synthesized spectral lines with methods closely resembling those used in BiSON and SONG observations. Consequently, the theoretical luminosity to radial velocity amplitude ratios are directly comparable with corresponding observations. For the Sun, we predict theoretical ratios of 21.0 and 23.7 ppm/[m/s] from BiSON and SONG respectively, in good agreement with observations 19.1 and 21.6 ppm/[m/s]. For $\epsilon$ Tau, we predict K2 and SONG ratios of 48.4 ppm/[m/s], again in good agreement with observations 42.2 ppm/[m/s], and much improved over the result from conventional empirical scaling relations which gives 23.2 ppm/[m/s]. This study thus opens the path towards a quantitative understanding of solar-like oscillations, via detailed modelling of 3D stellar atmospheres.Comment: 16 pages, 7 figures, accepted for publication in MNRA

FEDSM2013-16598 NUMERICAL OPTIMAL DESIGN OF IMPELLER BACK PUMP-OUT VANES ON AXIAL THRUST IN CENTRIFUGAL PUMPS

ABSTRACT Axial thrust in centrifugal pu mps attracts extensive attention in order to improve the operating reliability of pu mps. High axial thrust can cause rapid thrust bearing wear and subsequent pump failure o r frequent overhauls. A centrifugal pump (XA65/20) was selected in this study, based on L 16 (4 3 ) orthogonal array and CFD methods. The time -averaged Navier-Stokes equation was calcu lated for a 3D steady flow in the model pump in ANSYS CFX with the standard k-ω turbulence model and standard wall function applied. The structured meshes with different numbers were used for comparison in order to confirm that the computational results were not influenced by the mesh. Meanwhile, the effects of impeller back pump -out vane geometrical parameters, including its thickness S k , its outlet diameter D e and axial clearance δ, on the axial thrust and performances of the model centrifugal pu mp were analy zed. The different orthogonal schemes were obtained on the different values of S k , D e , and δ. Finally, when the parameters of the impeller S k , D e , and δ are 5mm, 100mm, 1.5mm, respectively. The Best Efficiency Point (BEF) of 69.9% was achieved with 60.12m for the designed head and -952.133N for the minimu m total axial force. The corresponding impeller with minimu m total axial fo rce was considered as the optimal scheme and manufactured for experimental test. The external characteristics by CFD have a good agreement with their experimental data, wh ich also better verified the accuracy of the numerical method of axial thrust applied in this research. Back pump-out vane thickness Back pump-out vane outlet diameter Z Back pump-out vane number N (r/min) Rotating speed ρ (kg/m3) Density g (m/s2) Gravity acceleration H (m) Pressure head ω (rad/s) Angular speed p (Pa) Pressure INTRODUCTION One of the most challenging aspects in horizontal pumps design is represented by the accurate evaluation of the axial thrust acting on the rotating shaft. In order to balance axial thrust of centrifugal pu mps, many devices such as balancing disk, balancing dru m, balancing hole and sealing system are used In this paper, the model pu mp of XA65/20 was designed to study its axial thrust and external characteristics with S k , δ an

Degradable mesoporous semimetal antimony nanospheres for near-infrared II multimodal theranostics.

Metallic and semimetallic mesoporous frameworks are of great importance owing to their unique properties and broad applications. However, semimetallic mesoporous structures cannot be obtained by the traditional template-mediated strategies due to the inevitable hydrolytic reaction of semimetal compounds. Therefore, it is yet challenging to fabricate mesoporous semimetal nanostructures, not even mention controlling their pore sizes. Here we develop a facile and robust selective etching route to synthesize monodispersed mesoporous antimony nanospheres (MSbNSs). The pore sizes of MSbNSs are tunable by carefully controlling the partial oxidation of Sb nuclei and the selective etching of the as-formed Sb2O3. MSbNSs show a wide absorption from visible to second near-infrared (NIR-II) region. Moreover, PEGylated MSbNSs are degradable and the degradation mechanism is further explained. The NIR-II photothermal performance of MSbNSs is promising with a high photothermal conversion efficiency of ~44% and intensive NIR-II photoacoustic signal. MSbNSs show potential as multifunctional nanomedicines for NIR-II photoacoustic imaging guided synergistic photothermal/chemo therapy in vivo. Our selective etching process would contribute to the development of various semimetallic mesoporous structures and efficient multimodal nanoplatforms for theranostics