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Energy principle of ferroelectric ceramics and single domain mechanical model

Acta Mechanica Sinica 2007年第5期23卷 531-543页

作者： T.c.wang LNM Institute of MechanicsChinese Academy of SciencesBeijing 100080China

Many physical experiments have shown that the domain switching in a ferroelectric material is a complicated evolution process of the domain wall with the variation of stress and electric field. According to this mechanism, the volume fraction of the domain switching is introduced in the constitutive law of ferroelectric ceramic and used to study the nonlinear constitutive behavior of ferroelectric body in this paper. The principle of stationary total energy is put forward in which the basic unknown quantities are the displacement ui, electric displacement Di and volume fraction pI of the domain switching for the variant I. Mechanical field equation and a new domain switching criterion are obtained from the principle of stationary total energy. The domain switching criterion proposed in this paper is an expansion and development of the energy criterion. On the basis of the domain switching criterion, a set of linear algebraic equations for the volume fraction PI of domain switching is obtained, in which the coefficients of the linear algebraic equations only contain the unknown strain and electric fields. Then a single domain mechanical model is proposed in this paper. The poled ferroelectric specimen is considered as a transversely isotropic single domain. By using the partial experimental results, the hardening relation between the driving force of domain switching and the volume fraction of domain switching can be calibrated. Then the electromechanical response can be calculated on the basis of the calibrated hardening relation. The results involve the electric butterfly shaped curves of axial strain versus axial electric field, the hysteresis loops of electric displacement versus electric filed and the evo- lution process of the domain switching in the ferroelectric specimens under uniaxial coupled stress and electric field loading. The present theoretic prediction agrees reasonably with the experimental results given by Lynch.

关键词： Ferroelectric ceramic Domain switching The volume fraction of domain switching Single domain mechanical model

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Thermal Properties of PHB/PEG Blends

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Journal of Materials Science & Technology 1998年第1期14卷 95-96页

作者： Zhang, QQ Zhang, Y wang, FJ Liu, LR wang, c chinese Acad Med Sci Inst Biomat Engn Tianjin 300192 Peoples R China Peking Union Med coll Tianjin 300192 Peoples R China Univ Utah Salt Lake City UT 84112 USA

Thermal properties of PHB and PHB/PEG blends were investigated by differential scanning calorimetry (DSc) and melt index (MI) test. DSc thermograms indicate that two components of blend are miscible. From the DSc thermogram, we can also conclude that the melting point of PHB descends with the increased content of PEG, this can improve PHB processing properties. From MI data, we may draw the same conclusion.

关键词： Polyesters

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Application of a hybrid gravity-driven membrane filtration and dissolved ozone flotation(MDOF)process for wastewater reclamation and membrane fouling mitigation

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Journal of Environmental Sciences 2019年第7期31卷 17-27页

作者： Xin Jin Wei wang Shuai wang Pengkang Jin Xiaochang c.wang Wushou Zhang Weijun An Yong wang Key Lab of Northwest Water Resource Environment and Ecology MOE Xi'an University of Architecture and Technology Langzheng Environmental Protection Technology co. Ltd.

This study proposed a novel membrane filtration and dissolved ozone flotation integrated(MDOF) process and tested it at pilot scale. Membrane filtration in the MDOF process was operated in gravity-driven mode, and required no backwashing, flushing, or chemical cleaning. Because ozone was added in the MDOF process, ozonation, coagulation, and membrane filtration could occur in a single reactor. Moreover, in situ ozonation occurred in the MDOF process, which differs from the conventional pre-ozonation membrane filtration process. Significant enhancement of turbidity removal was further achieved through the addition of membrane filtration. Membrane fouling was mitigated in the MDOF process compared to the MDAF process. In situ ozonation in the MDOF process decreased the fluorescence intensity and transformed the high MW dissolved organics into small MW compounds. For the fouling layer, the extracellular polymeric substance(EPS) contents and cake layer morphology were analyzed. The results indicated that the contents of EPS decreased. Furthermore, a thinner and more loosely structured cake layer formed in the MDOF process. Because coagulation and ozonation occurred simultaneously in a single reactor, the generation of hydroxyl radicals was enhanced through the catalytic effect of Al-based coagulants on ozone decomposition, which further alleviated membrane fouling in the MDOF process.

关键词： Dissolved ozone flotation Gravity-driven membrane filtration Membrane fouling In situ ozonation

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Synthesis of Novel Isoxazole-contained Analogues of Losartan

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chinese chemical Letters 2000年第11期11卷 961-962页

作者： wang, JW Jia, J Li, HM wang, c Shandong Univ Sch Chem & Environm Sci Jinan 250100 Peoples R China

A series of novel isoxazole-contained analogues of Losartan were designed and synthesized with 1,3-Dc reaction. The regioselectivity of the reaction was discussed and the compounds are potential antihypertensive.

关键词： analogues of losartan synthesis 1,3-Dc antihyertensin

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Allelopathic effect of Acorus tatarinowii upon algae

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Journal of Environmental Sciences 2001年第4期13卷 481-484页

作者： He, c.-q. wang, c.-k. Dept. of Environmental Science/Eng. Shanghai University Shanghai 200072 China

Besides competing with algae for light and mineral nutrients (i. e. N, P, etc.), the root system of Acorus tatarinowii excretes some chemical substances, which injure and eliminate alga cells, to inhibit the growth of the algae. When the algae cells were treated in 'A. tatarinowii water', some of the chlorophyll a were destroyed and the photosynthetic rate of algae decreased markedly and the ability of alga cells to deoxidize triphenyltetrazolium chloride (TTc) reduced greatly. Then alga cells turned from bright red to bluish green under fluorescence microscope. These showed that the allelopathic effects of A. tatarinowii on algae were obvious and planting A. tatarinowii can control some green algae. The experiment on the extractions of the secretions of the root system showed that the inhibitory effect had a concentration effect. If the concentration of the root secretion was below 30 μl/disc, the inhibitory rate was negative; if it was over 45 μl/disc, the inhibitory rate was positive. This proved that the influence of the root secretion on the same acceptor was a kind of concentration effect. When the concentration of the root secretion was low, it promoted the growth of algae; when the concentration reached a definite threshold value, it restrained the growth of algae. In present case, the threshold value was between 30 μl/disc and 45 μl/disc.

关键词： Algae cells chlorophyll concentration (process) Deoxidants Photosynthesis

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Ballistic current induced effective force on magnetic domain wall

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Nano-Micro Letters 2009年第1期1卷 34-39页

作者： c.wang K.Xia Department of Physics Beijing Normal University

The collective dynamics of magnetic domain wall under electric current is studied in the form of spin transfer torque(STT). The out-of-plane STT induced effective force is obtained based on the Landau-Lifshitz-Gilbert(LLG) equation including microscopic STT terms. The relation between microscopic calculations and collective description of the domain wall motion is established. With our numerical calculations based on tight binding free electron model, we find that the non adiabatic out-of-plane torque components have considerable non-local properties. It turns out that the calculated effective forces decay significantly with increasing domain wall widths.

关键词： Magnetic domain Spin Transfer torque Spintronics First principle study

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Layered Machinable and Electrically conductive Ti_2Alc and Ti_3Alc_2 ceramics:a Review

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Journal of Materials Science & Technology 2010年第5期26卷 385-416页

作者： X.H. wang Y.c. Zhou Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang110016 China

Ti2Alc and Ti3Alc2 are the most light-weight and oxidation resistant layered ternary carbides belonging to the MAX *** review highlights recent achievements on the processing,microstructure,physical,mechanical and chemical properties of these two machinable and electrically conductive ***2Alc and Ti3Alc2 display superior properties such as fracture toughness,electrical and thermal conductivities,and oxidation resistance over their binary *** paper provides a comprehensive overview of the processing-microstructure-property correlations of these two *** fields of applications for Ti2Alc and Ti3Alc2 are *** addition,we point out methods for further improving their properties in some specific applications through appropriate structural design and modification.

关键词： MAX phases Ti2Alc Ti3Alc2 Machinable ceramics

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Structure Investigation of Poly(vinyl alcohol)-collagen composite

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Journal of Materials Science & Technology 1997年第3期13卷 179-183页

作者： Zhang, QQ Ren, L Liu, LR wang, c UNIV UTAH CCCDSALT LAKE CITYUT 84112

Naturally derived collagen protein was mixed thoroughly with medical grade poly (vinyl alcohol) (PVA) at the ratio of 90:10 (w/w) and was crosslinked by formaldehyde to form a homogeneous composite membrane. The bulk structure of the membrane was characterized by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM). The membrane surface structure was investigated using Fourier transform-infrared spectroscopy (attenuated total refraction) (FTIR-ATR), electron spectroscopy for chemical analysis (EScA) and contact angle measurement. It was found that collagen and PVA can remain stable. This was supported by the fact that no sign of phase separation had been observed. The use of crosslinking agent can substantially influence the structure of the composite. It is suggested that this new composite deserves further investigation and is potentially usable as a biomedical material.

关键词： Nonmetallic matrix composites

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Kartogenin induces cartilage-like tissue formation in tendon–bone junction

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Bone Research 2014年第1期2卷 61-70页

作者： Jianying Zhang James H-c wang MechanoBiology Laboratory Departments of Orthopaedic Surgery Bioengineering Mechanical Engineering and Materials Science and Physical Medicine and Rehabilitation University of Pittsburgh

Tendon-bone junctions （TBJs） are frequently injured, especially in athletic settings. Healing of TBJ injuries is slow and is often repaired with scar tissue formation that compromises normal function. This study explored the feasibility of using kartogenin （KGN）, a biocompound, to enhance the healing of injured TBJs. We first determined the effects of KGN on the proliferation and chondrogenic differentiation of rabbit bone marrow stromal cells （BMScs） and patellar tendon stern/progenitor cells （PTScs） in vitro. KGN enhanced cell proliferation in both cell types in a concentration-dependent manner and induced chondrogenic differentiation of stem cells, as demonstrated by high expression levels of chondrogenic markers aggrecan, collagen II and Sox-9. Besides, KGN induced the formation of cartilage-like tissues in cell cultures, as observed through the staining of abundant proteoglycans, collagen II and osteocalcin. When injected into intact rat patellar tendons in vivo, KGN induced cartilage-like tissue formation in the injected area. Similarly, when KGN was injected into experimentally injured rat Achilles TBJs, wound healing in the TBJs was enhanced, as evidenced by the formation of extensive cartilage-like tissues. These results suggest that KGN may be used as an effective cell-free clinical therapy to enhance the healing of injured TBJs.

关键词： bone junction BMScs

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Automated Machine Learning Algorithm Using Recurrent Neural Network to Perform Long-Term Time Series Forecasting

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computers, Materials & continua 2024年第3期78卷 3529-3549页

作者： Ying Su Morgan c.wang Shuai Liu Department of Statistics and Data Science University of Central FloridaOrlandoFL32816-2370USA School of Mathematics and Statistics Beijing Technology and Business UniversityBeijing100048China

Long-term time series forecasting stands as a crucial research domain within the realm of automated machine learning(AutoML).At present,forecasting,whether rooted in machine learning or statistical learning,typically relies on expert input and necessitates substantial manual *** manual effort spans model development,feature engineering,hyper-parameter tuning,and the intricate construction of time series *** complexity of these tasks renders complete automation unfeasible,as they inherently demand human intervention at multiple *** surmount these challenges,this article proposes leveraging Long Short-Term Memory,which is the variant of Recurrent Neural Networks,harnessing memory cells and gating mechanisms to facilitate long-term time series ***,forecasting accuracy by particular neural network and traditional models can degrade significantly,when addressing long-term time-series ***,our research demonstrates that this innovative approach outperforms the traditional Autoregressive Integrated Moving Average(ARIMA)method in forecasting long-term univariate time *** is a high-quality and competitive model in time series prediction,and yet it requires significant preprocessing *** multiple accuracy metrics,we have evaluated both ARIMA and proposed method on the simulated time-series data and real data in both short and long ***,our findings indicate its superiority over alternative network architectures,including Fully connected Neural Networks,convolutional Neural Networks,and Nonpooling convolutional Neural *** AutoML approach enables non-professional to attain highly accurate and effective time series forecasting,and can be widely applied to various domains,particularly in business and finance.

关键词： Automated machine learning autoregressive integrated moving average neural networks time series analysis

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