Effect of the Ag-doping on the phase structural evolution, dielectric and ferroelectric properties of lead-free niobate ceramics

Huining Wang,Zixin Zhang,QuanSen Yang,Fangfang Wang,Kang Yan 대한금속·재료학회 2022 ELECTRONIC MATERIALS LETTERS Vol.18 No.2

Ionic doping is an important approach to modification of crystal structure and physical properties of the piezoelectric ceramics. In this work, the lead-free piezoelectric ceramic (1- x )K 0.18 Na 0.74 Li 0.08 NbO 3 - x AgNbO 3 (abbreviated as KNLN- x AN, 0 ≤ x ≤ 0.8) was prepared by conventional solid-state reaction method. The effect of the Ag doping on the phase structure, dielectric and ferroelectric properties of the KNLN-based ceramics was investigated by the XRD, DSC, dielectric and ferroelectric characterizations. It is found that all KNLN- x AN ceramics show single phase in perovskite structure because the ionic radii of dopant Ag close to the average ionic size at the A-site in KNLN. The KNLN- x AN exhibits the rhombohedral to orthorhombic phase transition at room temperature and the Curie temperature ( T C ) decreases to low temperature with increasing x value. A narrow tetragonal phase region and a wide orthorhombic phase region form for the compositions with x ≥ 0.4, indicating that the Ag doping stabilizes orthorhombic phase in wide temperature for the KNLN. A ferroelectric anomalies due to high electrical field induced phase transition is found in the sample with x = 0.1. When x = 0.4, high Curie temperature ( T C = 380 °C), large remnant polarization ( P r = 24.4 μC/cm 2 ) and high dielectric constant ( ε r = 10,000 at 1 kHz) at T C are achieved.

A Trust Management Model for Mobile P2P Networks based on Multiple-Fuzzy Theory

Meijuan JIA,Huiqiang WANG,Guangsheng FENG,Fangfang GUO 보안공학연구지원센터 2014 International Journal of Multimedia and Ubiquitous Vol.9 No.12

The characteristics of dynamic, heterogeneity and limited resources of peers result in the existence of selfish behavior in MP2P network, which affect the network performance. To improve the performance of MP2P, a trust management model for peer reputation is established based on multiple-fuzzy theory in this paper. Direct trust, indirect trust, residual energy and active degree of peers are used as the fundamental variables and their weights are determined by using fuzzy theory, and then the reputation of peers is calculated. Peers with high reputation are allowed to participate in the communication and peers with low reputation are not allowed. The experimental simulation results show that the model not only effectively improve the malicious peer detection rate and the query hit rate but also reduce the Cx of the network.

Parameter calibrations and application of micromechanical fracture models of structural steels

Fangfang Liao,Wei Wang,Yiyi Chen 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.42 No.2

Micromechanical facture models can be used to predict ductile fracture in steel structures. In order to calibrate the parameters in the micromechanical models for the largely used Q345 steel in China, uniaxial tensile tests, smooth notched tensile tests, cyclic notched bar tests, scanning electron microscope tests and finite element analyses were conducted in this paper. The test specimens were made from base metal, deposit metal and heat affected zone of Q345 steel to investigate crack initiation in welded steel connections. The calibrated parameters for the three different locations of Q345 steel were compared with that of the other seven varieties of structural steels. It indicates that the toughness index parameters in the stress modified critical strain (SMCS) model and the void growth model (VGM) are connected with ductility of the material but have no correlation with the yield strength, ultimate strength or the ratio of ultimate strength to yield strength. While the damage degraded parameters in the degraded significant plastic strain (DSPS) model and the cyclic void growth model (CVGM) and the characteristic length parameter are irrelevant with any properties of the material. The results of this paper can be applied to predict ductile fracture in welded steel connections.

A Study on Group Buying of O2O Mode using Generalized Stochastic Petri Nets

Fangfang Hou,Shuyun Zhang,Yue Wang 보안공학연구지원센터 2015 International Journal of Smart Home Vol.9 No.3

This paper proposes a Group Buying model (paid in advance) of online-to-offline mode using Generalized Stochastic Petri Nets. As the time cost of consumers is getting higher and higher, time efficiency is getting much more important in all aspects of life, especially in catering industry, and one way that can lead to direct communication between store owners and consumers is Group Buying of online-to-offline mode, the center of which is the brand building and service efficiency. Although researches based on both users’ and sellers’ perspective about online buying are very rich, these findings are not entirely applicable for this new e-commerce model, and most of current research on online-to-offline mode use qualitative methods. More importantly, few researchers have concerned about the efficiency of Group Buying process and come up with related solutions to improve it. By constructing a business model of GB and conducting time efficiency and performance analysis on it, we find that the key transitions of the system only take up less than half of the time before the whole process has been completed. And when we shorten the feedback process, the percentage of finishing consumption in physical store in the whole Group Buying model can be improved by 14.5%. Thus, we suggest that suppliers and sellers should be more focused and efficient in encouraging customers review timely as well as giving consumers feedback as soon as possible, since consumer comments are proved to be significantly important for the retailers. Besides, site operators and store sellers can also use other ways like WeChat and microblogging to promote their site linkages and gain more market share.

ZnO/TiO2 core–shell heterojunction for CdS and PbS quantum dot-cosensitized solar cells

Fangfang Gao,Qian Chen,Xiaoshan Zhang,Huan Wang,Tianjiao Huang,Liya Zhou 한국물리학회 2018 Current Applied Physics Vol.18 No.5

ZnO nanorods (NRs) with regular morphology were prepared through hydrothermal method, and the TiO2 shell was assembled onto the surface of ZnO NRs by spin coating to the ZnO/TiO2 core–shell heterojunction. CdS and PbS quantum dots (QDs) were used to cosensitize the ZnO/TiO2 nanostructure by direct adsorption (DA) and successive ionic layer adsorption and reaction, respectively. SEM, TEM, and HRTEM images show that the samples possessed a rough surface and four lattice fringes indicating the successful synthesis of the ZnO/TiO2/ CdS/PbS composite structure. The ZnO/TiO2(10T)/CdS/PbS sample showed a high absorption intensity at a broad range of wavelength to visible light region. The ZnO/TiO2(10T)/CdS/PbS photoelectrode with QDSSCs showed the highest IPCE of 36.04% and photoelectric efficiency (η) of 1.59%; these values increased by approximately 550% and 150% compared with those of unsensitized ZnO (0.29%) and ZnO/TiO2(10T) (1.04%) and about 146% and 120% compared with those of ZnO/TiO2(10T)/CdS and ZnO/TiO2(10T)/PbS, respectively. The fill factor was 0.36, and the photocurrent density (Jsc) and open circuit voltage (Voc) reached the maximum values of 9.73 mA cm−2 and 0.46 V, respectively.

A New Approach to Distributed Control for Multi-agent Systems Based on Approximate Upper and Lower Bounds

Fangfang Zhang,Jinfeng Gao,Huanshui Zhang,Cheng Tan,Wei Wang 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.6

In this paper, the distributed control of the LQR problem for continuous-time multi-agent systems isconsidered. Based on the centralized optimal control, we prove that the solution of the algebraic Riccati equationis the maximal solution of the algebraic Riccati inequality. The algebraic relations of the solutions of the algebraicRiccati equations for different weighted matrices are shown and two distributed controllers are designed: the fullydistributed one and the interconnected distributed one. They can provide an upper bounds and a lower bounds ofthe centralized optimal cost function. The optimal closed-loop feedback control systems for the two distributedcontrollers are also asymptotically stable. Some examples are given to show the correctness of the proposed results.

Distributed Suboptimal Controller Synthesis for Multi-agent Systems

Fangfang Zhang,Wei Wang,Huan-Shui Zhang 제어·로봇·시스템학회 2015 International Journal of Control, Automation, and Vol.13 No.3

In this paper, the distributed suboptimal LQR control problem for discrete-time multi-agent systems is considered. The distributed controllers that each subsystem can sense and/or exchange information with only a subset of its neighbors are designed, which are based on the topological structure of the system. Using the “averaged” optimization approach, the suboptimal feedback gain matrices are presented and the distributed suboptimal controllers are obtained. Under mild conditions, the asymptotical convergence of the modified Riccati equation is proved. Accordingly, the infinite-time distributed suboptimal controllers are presented. Examples are given to show the efficiency of the proposed results.

Study on the Constitutive Model of Boron Steel 22MnB5 with Different Phase Fractions

Fangfang Liao,Jianping Lin,Ming Wang Fu 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.10

The mechanical properties of boron steel 22MnB5 is determined by phase fractions. In order to obtain the mechanical properties and service performance of car component by simulation accurately, a microstructure based constitutive model needs to be developed. In this paper, different area fractions of martensite, bainite and ferrite in boron steel 22MnB5 were obtained via control of cooling rate and the different microstructures were determined quantitatively by metallographic image processing. A modified Katsuro Inoue’s constitutive model was then proposed, which is a function of effective plastic strain, strain rate and the phase fractions of martensite, bainite and ferrite. On the other hand, crash simulation of B-pillar with tailored mechanical properties was conducted as a case study to investigate the relationship between microstructure and property configuration by using the modified Katsuro Inoue’s model. The relationship among phase fraction, the height of tailored segment, and the internal energies absorbed by different segments, the maximum acceleration and displacement of B-pillar during the collision process was studied, and the empirical equations between microstructure and dynamic response of crash performance were also established and formulated.

Porous WO₃ monolith-based photoanodes for high-efficient photoelectrochemical water splitting

Wang, Yina,Zhang, Fangfang,Zhao, Guoyan,Zhao, Yingao,Ren, Yangyang,Zhang, Huijun,Zhang, Linyu,Du, Jimin,Han, Yumin,Kang, Dae Joon Elsevier 2019 CERAMICS INTERNATIONAL Vol.45 No.6

<P><B>Abstract</B></P> <P>We report a successful fabrication of low-cost, high-efficient, structurally-rigid, porous WO<SUB>3</SUB> photoelectrochemical (PEC) catalysts using polystyrene as the template by a sol-gel method and a high-temperature annealing treatment. The scanning electron microscopy and Brunauer-Emmett-Teller surface analysis results indicate that such WO<SUB>3</SUB> monoliths possess a porous structure and a large specific surface area, which can supply lots of photogenerated charge transfer pathways as well as more surface PEC active sites. Compared with a commercially available WO<SUB>3</SUB>, our highly porous WO<SUB>3</SUB> PEC catalysts show an excellent PEC water splitting activity. Particularly, the porous WO<SUB>3</SUB> photoanodes calcinated in the presence of oxygen atmosphere at 450 °C for 7 h show the best PEC performance exhibiting the photocurrent density of 0.97 mA/cm<SUP>2</SUP> at 1.23 V versus reversible the hydrogen electrode and the incident photon-to-current conversion efficiency up to 48.9% at 420 nm in 0.5 M Na<SUB>2</SUB>SO<SUB>4</SUB> electrolyte under AM 1.5 G irradiation. Such excellent PEC performance is due to the high porosity of the WO<SUB>3</SUB>, promoting the fast transfer and the separation rate of photogenerated carriers during the PEC water splitting process.</P>

Effects of different amylose to amylopectin ratios on rumen fermentation and development in fattening lambs

Zhao, Fangfang,Ren, Wen,Zhang, Aizhong,Jiang, Ning,Liu, Wen,Wang, Faming Asian Australasian Association of Animal Productio 2018 Animal Bioscience Vol.31 No.10

Objective: The objective of this experiment was to examine the effects of different amylose/amylopectin ratios on rumen fermentation and development of fattening lambs. Methods: Forty-eight 7-day-old male Small-tailed Han sheep${\times}$Northeast fine wool sheep were randomly assigned to four treatments of dietary amylose/amylopectin ratios (0.12, 0.23, 0.24, and 0.48 in tapioca starch, corn starch, wheat starch and pea starch diets, respectively). Three lambs from each treatment were slaughtered at 21, 35, 56, and 77 days of age to determine the rumen fermentation and development. Results: Compared with tapioca starch diet, the pea starch diet significantly increased the concentration of ammonia nitrogen in the ruminal fluid of lambs but significantly decreased the bacterial protein content. At 56 and 77 d, the rumen propionate concentration tended to be greatest in the tapioca starch group than in other groups. The rumen butyrate concentration was the greatest in lambs fed on pea starch compared with those fed on other starch diets. Furthermore, the pea starch diet significantly stimulated rumen development by increasing the papillae height, width and surface area in the rumen ventral or dorsal locations in lambs. However, different amylose/amylopectin ratios diets did not significantly affect the feed intake, body weight, average daily gain, the relative weight and capacity of the rumen in lambs with increasing length of trial periods. Conclusion: Lambs early supplemented with a high amylose/amylopectin ratio diet had favourable morphological development of rumen epithelium, which was not conducive to bacterial protein synthesis.