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Effects of Cr_2O_3 doping on the electrical properties and the temperature stabilities of PZT binary piezoelectric ceramics

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Rare Metals 2008年第4期27卷 362-366页

作者： LI Jianhua SUN Qingchi School of Electronic and Information and Engineering Tianjin University Tianjin 300072 China. School of Materials Science and Engineering Tianjin University Tianjin 300072 China

The ceramics with Pb1.04Zr0.52Ti0.48O3 ＋ z wt.% Cr2O3 were prepared using the traditional technique. The effects of Cr2O3 doping on the phase structure, the microstructure, and the electrical properties of ceramics were investigated. Meanwhile, the temperature stabilities of the resonant frequency （fx） were studied. The results showed that the △fr/fr,25℃ decreased with the addition of 0.2 wt.% - 0.8 wt.% Cr2O3 as compared with the undoped samples. The minimum value （-0.182%） of △fr/fr,25℃ was obtained for z = 0.6 wt.% Cr2O3 samples that sintered at 1260℃. The values of ε^τ33/ε0 = 1650, tanδ = 0.006, d33 = 328 pC/N, Kp = 0.63, Qm = 2300 were obtained when Cr2O3 was 0.6 wt.%, which exhibited more excellent piezoelectric properties than other compositions such as those with z = 0.2 wt.%, 0.4 wt.%, and 0.8 wt.%, but had a similar value as compared with the tmdoped samples. When the Cr2O3 additive increased, the Curie temperature moved toward low temperature and the changes of resonant frequency changed from positive to negative with increasing temperature.

关键词： ceramics piezoelectric properties temperature stability doping

Progress in modifications and applications of fluorescent dye probe

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Progress in Natural Science:Materials International 2009年第1期19卷 1-7页

作者： Xuening Fei,Yingchun Gu Department of Material Science and Engineering,tianjin Institute of Urban Construction,tianjin 300384,China [a]Department of Material Science and Engineering Tianjin Institute of Urban Construction Tianjin 300384 China

This review summarizes the labeling technology and applications of fluorescent dye probe in biology,especially the characteristics,modification and applications of cyanine *** on the currently available modification methods of fluorescent dye probe,we discuss the studies of enhancing the water-solubility,improving the degree of biocompatibility and target-labeling,increasing the sensitivity and decreasing the toxicity of fluorescent *** also give a brief introduction on the modification method,that the fluorescent dye is directly introduced onto the cell surfaces by amine derivatives or azides to intensify the transferring information of aberrant *** suggest that fluorescent dye modified with chitosan oligosaccharide can obviously increase the degree of biocompatibility and target-labeling,and decrease the degree of toxicity.

关键词： Fluorescent dye probe Cyanine dye Chitosan oligosaccharide Modification

Selections of data preprocessing methods and similarity metrics for gene cluster analysis

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Progress in Natural Science:Materials International 2006年第6期16卷 607-613页

作者： YANG Chunmei, WAN Baikun and GAO Xiaofeng (Department of Biomedical Engineering and Scientific Instrumentations, tianjin University, tianjin 300072, China Motorola (China) Electronics Ltd., tianjin 3.04.7, China) [a]Department of Biomedical Engineering and Scientific Instrumentations Tianjin University Tianjin China [b]Motorola (China) Electronics Ltd. Tianjin China

Clustering is one of the major exploratory techniques for gene expression data analysis. Only with suitable similarity metrics and when datasets are properly preprocessed, can results of high quality be obtained in cluster analysis. In this study, gene expression datasets with external evaluation criteria were preprocessed as normalization by line, normalization by column or logarithm transformation by base-2, and were subsequently clustered by hierarchical clustering, k-means clustering and self-organizing maps (SOMs) with Pearson correlation coefficient or Euclidean distance as similarity metric. Finally, the quality of clusters was evaluated by adjusted Rand index. The results illustrate that k -means clustering and SOMs have distinct advantages over hierarchical clustering in gene clustering, and SOMs are a bit better than k-means when randomly initialized. It also shows that hierarchical clustering prefers Pearson correlation coefficient as similarity metric and dataset normalized by line. Meanwhile, k -means clustering and SOMs can produce better clusters with Euclidean distance and logarithm transformed datasets. These results will afford valuable reference to the implementation of gene expression cluster analysis.

关键词： gene expression cluster analysis data preprocessing similarity metrics Rand index.

An approach to 3D NURBS modeling of complex fault network considering its historic tectonics

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Progress in Natural Science:Materials International 2006年第5期16卷 546-553页

作者： ZHONG Denghua, LIU Jie and LI Mingchao (School of Civil Engineering, tianjin University, tianjin 300072, China) School of Civil Engineering Tianjin University Tianjin 300072 China

Fault disposal is a research area that presents difficulties in 3D geological modeling and visualization. In this paper, we propose an integrated approach to reconstructing a complex fault network (CFN). Based on the non-uniform rational B-spline (NURBS) techniques, fault surface was constructed, reflecting the regulation of its spatial tendency, and correlative surfaces were enclosed to form a fault body model. Based on these models and considering their historic tectonics, a method was put forward to settle the 3D modeling problem when the intersection of two faults in CFN induced the change of their relative positions. First, according to the relationships of intersection obtained from geological interpretation, we introduced the topological sort to determine the order of fault body construction and rebuilt fault bodies in terms of the order; then, with the disposal method of two intersectant faults in 3D modeling and applying the Boolean operation, we investigated the characteristic of faults at the intersectant part. An example of its application in hydropower engineering project was proposed. Its results show that this modeling approach can increase the computing efficiency while less computer memory is required, and it can also factually and objectively reproduce the CFN in the engineering region, which establishes a theoretical basis for 3D modeling and analysis of complex engineering geology.

关键词： fault network NURBS technique historic tectonics topological sort 3D modeling.

Evaluation of non-azeotropic mixtures containing HFOs as potential refrigerants in refrigeration and high-temperature heat pump systems

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Science China(Technological Sciences) 2010年第7期53卷 1855-1861页

作者： ZHANG ShengJun, WANG HuaiXin & GUO Tao Department of Thermal Energy and Refrigeration Engineering, tianjin University, tianjin 300072, China 1. Department of Thermal Energy and Refrigeration Engineering Tianjin University Tianjin 300072 China

With the increasing environmental concern on global warming, hydrofluoro-olefin (HFOs), possessing low GWP, has attracted great attention of many researchers recently. In this study, non-azeotropic mixtures composed of HFOs (HFO-1234yf, HFO-1234ze(z), HFO-1234ze(e) and HFO-1234zf) are developed to substitute for HFC-134a and CFC-114 in air-conditioning and high-temperature heat pump systems, respectively. The cycle performances were evaluated by an improved theoretical cy-cle evaluation methodology. The results showed that all the mixtures proposed herein were favorable refrigerants with excel-lent thermodynamic cycle performances. M1A presented lower discharge temperature and pressure ratio and higher COPc than that of HFC-134a. The volumetric cooling capacity was similar to HFC-134a. It can be served as a good environmentally friendly alternative to replace HFC-134a. M3H delivered similar discharge temperature as CFC-114 did. And the COPh was 3% higher. It exhibits excellent cycle performance in high-temperature heat pump and is a promising refrigerant to substitute for CFC-114. And the gliding temperature differences enable them to exhibit better coefficient of performance by matching the sink/source temperature in practice. Because the toxicity, flammability and other properties are not investigated in detail, ex-tensive toxicity and flammability testing needs to be conducted before they are used in a particular application.

关键词： hydrofluoro-olefin non-azeotropic mixtures refrigerant air-conditioning system high-temperature heat pump

Integrated modeling of nitrogen oxides formation in diesel engines

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Progress in Natural Science:Materials International 2007年第12期17卷 1476-1481页

作者： Song Jinou, Yao Chunde and Wang Hongfu(State Key Laboratory of Engine, tianjin University, tianjin 300072, China) State Key Laboratory of Engine Tianjin University Tianjin 300072 China

To account for the effects of both chemistry and flow turbulence, the present study proposes an integrated NO sub-model that combines the extended Zel’dovich mechanism and engine CFD computations to simulate the NO histories in a diesel engine. NOx sub-model parameters and pollutant formation mechanisms can be more easily investigated by solving the NOx sub-model. The new NO formation model incorporating the effects of both chemical kinetics and turbulent mixing was applied to simulate a diesel engine with a quiescent combustion chamber, and one with a re-entrant combustion chamber; the premise of the model being the reaction rate is mainly determined by a kinetic timescale and a turbulent timescale. The results indicate that the predicted NO formulation from the new model agrees well with the measured data. As the utilization of fossil fuels continues to increase, the control of NOx emissions is a worldwide concern; and it is imperative to understand fully the NOx reaction processes in combustion systems. This technology has the potential to enhance the application of various combustion techniques used to reduce NOx emissions from practical combustion systems.

关键词： nitrogen oxides (NOx) combustion turbulence diesel.

The mechanism of breakdown in laminar-turbulent transition of a supersonic boundary layer on a flat plate-temporal mode

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Science China(Physics,Mechanics & Astronomy) 2005年第5期48卷 614-625页

作者： HUANG Zhangfeng 1, CAO Wei 1,2 & ZHOU Heng 1,2 1. Department of Mechanics, tianjin University, tianjin 300072, China 2. Liu-Hui Center of Applied Mathematics, Nankai University and tianjin University, tianjin 300072, China 1. Department of Mechanics Tianjin University 300072 Tianjin China 2. Liu-Hui Center of Applied Mathematics Nankai University and Tianjin University 300072 Tianjin China

Temporal mode direction numerical simulation has been done for the transition of a supersonic boundary layer on a flat plate with Mach number 4.5. Analysis of the result showed that during the breakdown process in laminar-turbulent transition, the mechanism causing the mean flow profile to evolve swiftly from laminar to turbulent was that the modification of mean flow profile by the disturbances,when they became larger,led to a remarkable change of its stability characteristics. Though the most unstable T-S wave was of second mode for laminar flow, the first mode waves played the key role in the breakdown process in laminar-turbulent transition.

关键词： supersonic boundary layer, transition, breakdown.

1. 32μm Nd3+: YAG Pulse Laser

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Chinese Journal of Lasers 2002年第2期11卷 3-5页

作者： WANG Zhaoying WU Xing(College of Precision Instrument and Optoelectronics Engineering, tianjin University, tianjin 300072, China) Precision Instrument and Optoelectronics Engineering Tianjin University 天津 300072

Using specially coated mirrors, an output energy of 0.97 J at 1.32 μm from a Nd3+: YAG pulse laser is obtained with pumping energy of 66 J. The repetition rate is 1 pulse/sec and the slope efficiency is 1.7%. The rep... 详细信息

关键词： 1.32 μm specially coated mirrors pulse repetition

Homotopy type of smooth weighted complete intersections

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Science China Mathematics 2010年第6期53卷 1583-1594页

作者： WANG JianBo1,& WANG YuYu2 1Department of Mathematics,tianjin University,tianjin 300072,China 2College of Mathematical Science,tianjin Normal University,tianjin 300387,China 1. Department of Mathematics Tianjin University Tianjin 300072 China2. College of Mathematical Science Tianjin Normal University Tianjin 300387 China

If the total degree d has no prime divisors less than(n+3)/2,then we prove that the homotopy type of complex odd dimensional smooth weighted complete intersection Xn(d;w) is determined by the dimension n,the total degree d,the Euler characteristic and the Kervaire invariant,provided that the weights w =(ω0,...,ωn+r) is pairwise relatively prime.

关键词： weighted projective space weighted complete intersection homotopy type connected sum