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(Ba, Ca)(Ti, Zr)O3-BiFeO3 lead-free piezoelectric ceramics
Jiagang Wu,Wenjuan Wu,Dingquan Xiao,John Wang,Zhenchun Yang,Zhihang Peng,Qiang Chen,Jianguo Zhu 한국물리학회 2012 Current Applied Physics Vol.12 No.2
Effects of BiFeO3 (BFO) content on the microstructure and electrical properties of Ba0.85Ca0.15Ti0.90Zr0.10O3(BCTZ) ceramics prepared by normal sintering in air were investigated. A stable solid solution is formed between BCTZ and BFO. The grain size gradually becomes smaller, and the ceramics become denser with increasing the BFO content. The Curie temperature, dielectric constant, and dielectric loss of BCTZ ceramics decrease simultaneously with the introduction of BFO. Moreover, the remanent polarization reaches a maximum at x ¼ 0.2 mol%, and the coercive field continuously increases with increasing the BFO content due to the introduction of BFO with a higher coercive field. Improved piezoelectric properties (d33 w 405 pC/N and kp w 0.44) are demonstrated for the BCTZ ceramic with x ¼ 0.2 mol%.
Xiaoyu Chen,Jiagang Wu,Xiaojing Cheng,Bo Wu,Wenjuan Wu,Dingquan Xiao,Jianguo Zhu 한국물리학회 2012 Current Applied Physics Vol.12 No.3
[Li0.03(K0.48Na0.52)0.97](Nb0.97Sb0.03)O3-(Ba0.85Ca0.15)(Ti0.90Zr0.10)O3 [(1-x)LKNNS-xBCTZ] lead-free piezoelectric ceramics were prepared by the conventional solid state method, and effects of BCTZ content on the piezoelectric properties of LKNNS ceramics were mainly investigated. A stable solid solution has been formed between LKNNS and BCTZ, and a morphotropic phase boundary of (1-x)LKNNS-xBCTZ ceramics is identified in the range of 0 < x ≤ 0.02. The Curie temperature of (1-x)LKNNS-xBCTZ ceramics decreases with increasing BCTZ content. A higher εr value and a lower tan d value are demonstrated for the (1-x)LKNNS-xBCTZ ceramic with x = 0.02. The (1-x)LKNNS-xBCTZ ceramic with x = 0.02 has an enhanced electrical behavior of d33w237 pC/N, kpw 48.6%, 3 rw1451, tan d w0.037, and Tcw335 ℃. As a result, (1-x)LKNNS-xBCTZ ceramics are promising candidate materials for the field of lead-free piezoelectric materials.
SP0454, A Putative Threonine Dehydratase, Is Required For Pneumococcal Virulence In Mice
WenJuan Yan,Hong Wang,WenChun Xu,KaiFeng Wu,Run Yao,XiuYu Xu,Jie Dong,YanQing Zhang,Wen Zhong,XueMei Zhang 한국미생물학회 2012 The journal of microbiology Vol.50 No.3
Increasing pressure in antibiotic resistance and the requirement for the design of new vaccines are the objectives of clarifying the putative virulence factors in pneumococcal infection. In this study, the putative threonine dehydratase sp0454 was inactivated by erythromycin-resistance cassette replacement in Streptococcus pneumoniae CMCC 31203 strain. The sp0454 mutant was tested for cell growth, adherence, colonization, and virulence in a murine model. The Δsp0454 mutant showed decreased ability for colonization and impaired ability to adhere to A549 cells. However, the SP0454 polypeptide or its antiserum did not affect pneumococcal CMCC 31203 adhesion to A549 cells. The sp0454 deletion mutant was less virulent in a murine intranasal infection model. Real-time RT-PCR analysis revealed significant decrease of the pneumococcal surface antigen A expression in the sp0454 mutant. These results suggest that SP0454 contributes to virulence and colonization, which could be explained in part by modulating the expression of other virulence factors, such as psaA in pneumococcal infection.
Wenjuan Lou,Huihui Wu,Zuopeng Wen,Hongchao Liang 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.34 No.2
The galloping of iced conductors has long been a severe threat to the safety of overhead transmission lines. Compared with normal transmission lines, the ultra-high-voltage (UHV) transmission lines are more prone to galloping, and the damage caused is more severe. To control the galloping of UHV lines, it is necessary to conduct a comprehensive analysis of galloping characteristics. In this paper, a large-span 1000-kV UHV transmission line in China is taken as a practical example where an 8-bundled conductor with D-shaped icing is adopted. Galerkin method is employed for the time history calculation. For the wind attack angle range of 0°~180°, the galloping amplitudes in vertical, horizontal, and torsional directions are calculated. Furthermore, the vibration frequencies and galloping shapes are analyzed for the most severe conditions. The results show that the wind at 0°~10° attack angles can induce large torsional displacement, and this range of attack angles is also most likely to occur in reality. The galloping with largest amplitudes in all three directions occurs at the attack angle of 170° where the incoming flow is at the non-iced side, due to the strong aerodynamic instability. In addition, with wind speed increasing, galloping modes with higher frequencies appear and make the galloping shape more complex, indicating strong nonlinear behavior. Based on the galloping amplitudes of three directions, the full range of wind attack angles are divided into five galloping regions of different severity levels. The results obtained can promote the understanding of galloping and provide a reference for the anti-galloping design of UHV transmission lines.
Wenjuan Lou,Dengguo Wu,Haiwei Xu 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.7
Aerodynamic damping is a key factor that influences the wind-induced responses of transmission conductors. The inaccurate estimation of aerodynamic damping leads to misunderstanding of conductor response to wind actions. For dynamic response analysis in the frequency domain, the generalized aerodynamic damping matrix used to solve conductor motion is diagonal. This study reanalyzed the conductor generalized aerodynamic damping matrix by considering its horizontal and vertical motions and the coupling effects of different modes. The derived generalized aerodynamic damping was a nondiagonal matrix, and we defined it as nonproportional generalized aerodynamic damping. Variations in the aerodynamic damping ratio and the nonproportionality of generalized aerodynamic damping with wind speed were investigated through numerical studies of single- and triple-span conductors. Triple-span conductors with different span lengths, hanging heights, and initial pretension forces were adopted to discuss the effects of the nonproportionality of generalized aerodynamic damping on estimating the dynamic responses of conductors. Results showed that neglecting the vertical motion of a conductor leads to an overestimation of the aerodynamic damping ratio, especially under high wind speed conditions. The nonproportionality of generalized aerodynamic damping is highest when the incoming wind speed at 10 m is 25 m/s. Ignoring such nonproportionality leads to an overestimation of the resonant responses of conductors but exerts minimal effects on total fluctuating responses mainly contributed by background components. Therefore, for a transmission conductor with a significant resonant response, the nonproportionality effect of generalized aerodynamic damping must be considered. Increasing span length and conductor height or reducing initial pretension force seems to enhance nonproportionality effects on conductor responses.
Research on the Efficiency of Cloud Resource Allocation and Operation Based on DEA Method
Li Wenjuan,Wu Jiyi,Zhang Qifei,Zhao Haili 보안공학연구지원센터 2015 International Journal of Grid and Distributed Comp Vol.8 No.5
In order to compensate for the current lack of assessing cloud resource allocation and business operation from the economical perspective, this paper introduced the Data Envelopment Analysis (DEA) method which is one of the most famous methods in economics into this field. Based on it, it proposed several new methods to evaluate the efficiency of cloud resource allocation and cloud providers’ business operation status through the way of case study.
Bolting, an Important Process in Plant Development, Two Types in Plants
Chen Chen,Wenjuan Huang,Kai Hou,Wei Wu 한국식물학회 2019 Journal of Plant Biology Vol.62 No.3
Bolting refers to the rapid lengthening of the plant stem, and is due to the coordinated effects of developmental and environmental factors. The shoot apical meristem differentiates into the inflorescence meristem and eventually the floral meristem, which then develops into various floral organs during the bolting period. The timing of bolting is critical for plant propagation and reproductive success because it influences seed production, species survival, and crop yield. Therefore, analyses of the causes of bolting and how it occurs may enable researchers to regulate bolting. In this review, two different bolting phenotypes are described, namely inflorescence axis elongation and stem internode elongations. Various factors, such as light, temperature, and endogenous hormones, are integrated to mediate bolting. Moreover, the mechanism underlying bolting, including signal cascades and epigenetic inheritance, are discussed, and appropriate future research directions are proposed.