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Xu, Q.,Chen, M.,Chen, W.,Liu, H.X.,Kim, B.H.,Ahn, B.K. Elsevier Science 2008 ACTA MATERIALIA Vol.56 No.3
(Na<SUB>0.5</SUB>Bi<SUB>0.5</SUB>)<SUB>0.93</SUB>Ba<SUB>0.07</SUB>TiO<SUB>3</SUB> ceramics with added 0-0.8 wt.% CoO were prepared by a citrate method and the influence of the CoO additive on the structure and electrical properties of the ceramics was investigated. All the specimens maintained a rhombohedral-tetragonal phase coexistence in crystal structure and the addition of CoO caused a remarkably promoted grain growth. Adding CoO led to a disappearance of the response in the dielectric constant (ε<SUB>r</SUB>) to the ferroelectric-antiferroelectric transition and increased the diffuseness of the dielectric constant peak around 230<SUP>o</SUP>C. Polarization-electric field hysteresis loops at varied temperatures revealed that adding CoO served to increase the depolarization temperature (T<SUB>d</SUB>). The addition of CoO tailored the dielectric, piezoelectric and ferroelectric properties at room temperature basically following a hard doped effect. The specimen with 0.8 wt.% CoO added showed a low dissipation factor (tanδ) of 0.8% and a high mechanical quality factor (Q<SUB>m</SUB>) of 297 while retaining a piezoelectric constant (d<SUB>33</SUB>) of 137 pC N<SUP>-1</SUP>.
Xu, X.Q.,Belli, E.,Bodi, K.,Candy, J.,Chang, C.S.,Cohen, R.H.,Colella, P.,Dimits, A.M.,Dorr, M.R.,Gao, Z.,Hittinger, J.A.,Ko, S.,Krasheninnikov, S.,McKee, G.R.,Nevins, W.M.,Rognlien, T.D.,Snyder, P.B. International Atomic Energy Agency 2009 Nuclear fusion Vol.49 No.6
<P>We present edge gyrokinetic simulations of tokamak plasmas using the fully non-linear (full-<I>f</I>) continuum code TEMPEST. A non-linear Boltzmann model is used for the electrons. The electric field is obtained by solving the 2D gyrokinetic Poisson equation. We demonstrate the following. (1) High harmonic resonances (<I>n</I> > 2) significantly enhance geodesic-acoustic mode (GAM) damping at high <I>q</I> (tokamak safety factor), and are necessary to explain the damping observed in our TEMPEST <I>q</I>-scans and consistent with the experimental measurements of the scaling of the GAM amplitude with edge <I>q</I><SUB>95</SUB> in the absence of obvious evidence that there is a strong <I>q</I>-dependence of the turbulent drive and damping of the GAM. (2) The kinetic GAM exists in the edge for steep density and temperature gradients in the form of outgoing waves, its radial scale is set by the ion temperature profile, and ion temperature inhomogeneity is necessary for GAM radial propagation. (3) The development of the neoclassical electric field evolves through different phases of relaxation, including GAMs, their radial propagation and their long-time collisional decay. (4) Natural consequences of orbits in the pedestal and scrape-off layer region in divertor geometry are substantial non-Maxwellian ion distributions and parallel flow characteristics qualitatively like those observed in experiments.</P>
Monitoring and control of wind-induced vibrations of hanger ropes of a suspension bridge
Xu G. Hua,Zheng Q. Chen,Xu Lei,Qin Wen,Hua W. Niu 국제구조공학회 2019 Smart Structures and Systems, An International Jou Vol.23 No.6
In August 2012, during the passage of the typhoon Haikui (1211), large amplitude vibrations were observed on long hangers of the Xihoumen suspension Bridge, which destroyed a few viscoelastic dampers originally installed to connect a pair of hanger ropes transversely. The purpose of this study is to identify the cause of vibration and to develop countermeasures against vibration. Field measurements have been conducted in order to correlate the wind and vibration characteristics of hangers. Furthermore, a replica aeroelastic model of prototype hangers consisting of four parallel ropes was used to study the aeroelastic behavior of hanger ropes and to examine the effect of the rigid spacers on vibration mitigation. It is shown that the downstream hanger rope experiences the most violent elliptical vibration for certain wind direction, and the vibration is mainly attributed to wake interference of parallel hanger ropes. Based on wind tunnel tests and field validation, it is confirmed that four rigid spacers placed vertically at equal intervals are sufficient to suppress the wake-induced vibrations. Since the deployment of spacers on hangers, server hanger vibrations and clash of hanger ropes are never observed.
Xu, Q.Y.,Wang, C.A.,Zhao, Z.G.,Luo, L. Asian Australasian Association of Animal Productio 2012 Animal Bioscience Vol.25 No.11
An 8-wk experiment was conducted to evaluate the effect of replacing fish meal (FM) with soy protein isolate (SPI) on the growth, digestive enzyme activity and serum biochemical parameters of juvenile Amur sturgeon (Acipenser schrenckii). SPI was used to replace 0, 25, 50, 62.5, 75, 87.5, 100% of dietary FM and 100% replacement supplemented crystalline amino acid. Healthy sturgeon with an average initial weight of $26.38{\pm}0.24$ g were randomly assigned to 24 aquaria (8 treatments with triplicates each) at an initial stocking density of 11 fish per aquarium and cultured for 8 wks. The results showed that 75.00% or more substitution resulted in a poor weight gain rate, feed conversion ratio and survival rate compared to that of fish fed the control diet (p<0.05), whereas no significant differences were observed between diets of 25.00% to 62.50% substitution. Protease, lipase and amylase activity in foregut, mid-gut and hindgut were significantly (p<0.05) decreased by diets where SPI replacement levels were 62.50% or more. Levels of serum total protein (TP) and globulin decreased significantly from 21.03, 10.34 to 14.05, 5.63 g/L with the increasing dietary SPI (p<0.05), but alkaline phosphatase activity significantly increased (p<0.05). In addition, supplemental crystalline amino acid in the FM absence diet did not improve growth performance, intestine digestive enzyme activities and serum biochemical parameters. In conclusion, the results from this study showed adverse effects of inclusion of SPI in diets on growth performance, feed utilization and serum biochemical parameters in juvenile Amur sturgeon. Based on WGR and replacement ratio presented in this report, a 57.64% replacement level was recommended.
Association Analyses with Carcass Traits in the Porcine KIAA1717 and HUMMLC2B Genes
Xu, D.Q.,Xiong, Y.Z.,Liu, M.,Lan, J.,Ling, X.F.,Deng, C.Y.,Jiang, S.W. Asian Australasian Association of Animal Productio 2005 Animal Bioscience Vol.18 No.11
By screening a subtracted cDNA library constructed with mRNA obtained from the longissimus dorsi muscles of F1 hybrids Landrace${\times}$Yorkshire and their Yorkshire female parents, we isolated two partial sequences coding for the H3-K4-specific methyltransferase (KIAA1717) and skeletal muscle myosin regulatory light chain (HUMMLC2B) genes. In the present work we investigated two SNPs, one (C1354T) at the 3' untranslated region (UTR) of KIAA1717 and one (A345G) at the SINE (PRE-1) element of HUMMLC2B, in a resource population derived from crossing Chinese Meishan and Large White pig. The selected pigs were genotyped by means of a PCR-RFLP protocol. Significant associations were observed for the KIAA1717 C1354T polymorphic site with thorax-waist backfat thickness (p<0.05), buttock backfat thickness (p<0.05), average backfat thickness (p<0.05), loin eye height (p<0.05), loin eye area (p<0.05), carcass length to 1$^{st}$ spondyle (p<0.01) and carcass length to 1st rib (p<0.01). HUMMLC2B A345G were significantly associated with loin eye width (p<0.05), loin eye area (p<0.05). Further studies are needed to confirm these preliminary results.
Suboptimal control strategy in structural control implementation
Xu, J.Y.,Li, Q.S.,Li, G.Q.,Wu, J.R.,Tang, J. Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.19 No.1
The suboptimal control rule is introduced in structural control implementation as an alternative over the optimal control because the optimal control may require large amount of processing time when applied to complex structural control problems. It is well known that any time delay in structural control implementation will cause un-synchronized application of the control forces, which not only reduce the effectiveness of an active control system, but also cause instability of the control system. The effect of time delay on the displacement and acceleration responses of building structures is studied when the suboptimal control rule is adopted. Two examples are given to show the effectiveness of the suboptimal control rule. It is shown through the examples that the present method is easy in implementation and high in efficiency and it can significantly reduce the time delay in structural control implementation without significant loss of performance.
Measurement of ηc(1S) , ηc(2S) , and nonresonant η′π+π− production via two-photon collisions
Xu, Q. N.,Adachi, I.,Aihara, H.,Al Said, S.,Asner, D. M.,Atmacan, H.,Aulchenko, V.,Aushev, T.,Ayad, R.,Babu, V.,Badhrees, I.,Bakich, A. M.,Bansal, V.,Barberio, E.,Behera, P.,Berger, M.,Bhardwaj, V.,Bh American Physical Society 2018 Physical Review D Vol.98 No.7
Evaluation of vertical dynamic characteristics of cantilevered tall structures
Li, Q.S.,Xu, J.Y.,Li, G.Q. Techno-Press 2001 Structural Engineering and Mechanics, An Int'l Jou Vol.11 No.4
In this paper, cantilevered tall structures are treated as cantilever bars with varying cross-section for the analysis of their free longitudinal (or axial) vibrations. Using appropriate transformations, exact analytical solutions to determine the longitudinal natural frequencies and mode shapes for a one step non-uniform bar are derived by selecting suitable expressions, such as exponential functions, for the distributions of mass and axial stiffness. The frequency equation of a multi-step bar is established using the approach that combines the transfer matrix procedure or the recurrence formula and the closed-form solutions of one step bars, leading to a single frequency equation for any number of steps. The Ritz method is also applied to determine the natural frequencies and mode shapes in the vertical direction for cantilevered tall structures with variably distributed stiffness and mass. The formulae proposed in this paper are simple and convenient for engineering applications. Numerical example shows that the fundamental longitudinal natural frequency and mode shape of a 27-storey building determined by the proposed methods are in good agreement with the corresponding measured data. It is also shown that the selected expressions are suitable for describing the distributions of axial stiffness and mass of typical tall buildings.