期刊文献+
共找到4,191篇文章
< 1 2 210 >
每页显示 20 50 100
A New Algorithm of Rain Type Classification for GPM Dual-Frequency Precipitation Radar in Summer Tibetan Plateau
1
作者 Yunfei FU Liu YANG +4 位作者 Zhenhao WU Peng ZHANG Songyan GU Lin CHEN Sun NAN 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2024年第11期2093-2111,共19页
In this study, a new rain type classification algorithm for the Dual-Frequency Precipitation Radar(DPR) suitable over the Tibetan Plateau(TP) was proposed by analyzing Global Precipitation Measurement(GPM) DPR Level-2... In this study, a new rain type classification algorithm for the Dual-Frequency Precipitation Radar(DPR) suitable over the Tibetan Plateau(TP) was proposed by analyzing Global Precipitation Measurement(GPM) DPR Level-2 data in summer from 2014 to 2020. It was found that the DPR rain type classification algorithm(simply called DPR algorithm) has mis-identification problems in two aspects in summer TP. In the new algorithm of rain type classification in summer TP,four rain types are classified by using new thresholds, such as the maximum reflectivity factor, the difference between the maximum reflectivity factor and the background maximum reflectivity factor, and the echo top height. In the threshold of the maximum reflectivity factors, 30 d BZ and 18 d BZ are both thresholds to separate strong convective precipitation, weak convective precipitation and weak precipitation. The results illustrate obvious differences of radar reflectivity factor and vertical velocity among the three rain types in summer TP, such as the reflectivity factor of most strong convective precipitation distributes from 15 d BZ to near 35 d BZ from 4 km to 13 km, and increases almost linearly with the decrease in height. For most weak convective precipitation, the reflectivity factor distributes from 15 d BZ to 28 d BZ with the height from 4 km to 9 km. For weak precipitation, the reflectivity factor mainly distributes in range of 15–25 d BZ with height within 4–10 km. It is also shows that weak precipitation is the dominant rain type in summer TP, accounting for 40%–80%,followed by weak convective precipitation(25%–40%), and strong convective precipitation has the least proportion(less than 30%). 展开更多
关键词 satellite precipitation radar rain type classification method Tibetan Plateau strong convective precipitation
下载PDF
Preparation and Characterization of Nanometer TiO_2 by Hydrolysis Precipitation Method 被引量:1
2
作者 方世杰 徐明霞 +1 位作者 郝俊杰 汪成建 《Transactions of Tianjin University》 EI CAS 2002年第2期79-82,共4页
Nanometer TiO 2 powders were obtained from TiOSO 4 and studied by XRD, TEM and BET. The result indicated that pH and heat treatment temperature have great effects on their grain size and crystal phase structu... Nanometer TiO 2 powders were obtained from TiOSO 4 and studied by XRD, TEM and BET. The result indicated that pH and heat treatment temperature have great effects on their grain size and crystal phase structure. Annealed at 500 ℃, nanometer TiO 2 with a specific surface area of 101.39 m 2 ·g -1 and a grain size about 10 nm were obtained(pH=5); and with a specific surface area of 95.48 m 2 ·g -1 and a grain size about 30 nm were obtained(pH=10). The research indicated that crystal phase transformation of rutile at 750 ℃made great promotion in grain size growth. 展开更多
关键词 nanometer Tio 2 hydrolysis precipitation method PH crystal phase transformation
下载PDF
Preparation and Characterization of Nanometer TiO2 by Hydrolysis Precipitation Method 被引量:1
3
作者 方世杰 徐明霞 +1 位作者 郝俊杰 汪成建 《Transactions of Tianjin University》 EI CAS 2002年第2期79-82,共页
Nanometer TiO 2 powders were obtained from TiOSO 4 and studied by XRD, TEM and BET. The result indicated that pH and heat treatment temperature have great effects on their grain size and crystal phase structu... Nanometer TiO 2 powders were obtained from TiOSO 4 and studied by XRD, TEM and BET. The result indicated that pH and heat treatment temperature have great effects on their grain size and crystal phase structure. Annealed at 500 ℃, nanometer TiO 2 with a specific surface area of 101.39 m 2 ·g -1 and a grain size about 10 nm were obtained(pH=5); and with a specific surface area of 95.48 m 2 ·g -1 and a grain size about 30 nm were obtained(pH=10). The research indicated that crystal phase transformation of rutile at 750 ℃made great promotion in grain size growth. 展开更多
关键词 nanometer Tio 2 hydrolysis precipitation method PH crystal phase transformation
全文增补中
Preparation and Characterization of Nanocrystalline CeO_2 by Precipitation Method 被引量:18
4
作者 董相廷 李明 +2 位作者 张伟 刘桂霞 洪广言 《Journal of Rare Earths》 SCIE EI CAS CSCD 2002年第6期583-586,共4页
CeO 2 nanocrystalline particulates with different sizes were prepared by precipitation method using ethanol as dispersive and protective reagent. XRD spectra show that the synthesized CeO 2 has cubic crystalline str... CeO 2 nanocrystalline particulates with different sizes were prepared by precipitation method using ethanol as dispersive and protective reagent. XRD spectra show that the synthesized CeO 2 has cubic crystalline structure of space group O 5 H-F M3M, when calcination temperature is in the range of 250~800 ℃. TEM images reveal that CeO 2 particles are spherical in shape. The average size of the particles increases with the increase of calcination temperature. Thermogravimetric analysis indicates that the weight loss of precursor mainly depends on the calcination temperature, and little depends on the calcination time. Measurements of CeO 2 relative density show that the relative density of CeO 2 nanocrystalline powders increases with increasing CeO 2 particle size. 展开更多
关键词 rare earths cerium oxide nanoparticulate precipitation method
下载PDF
Preparation of Rare Earth Hydroxide and Oxide Nanoparticles by Precipitation Method 被引量:8
5
作者 Xiangting DONG Guangyan HONG 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2005年第4期555-558,共4页
A series of rare earth hydroxide and oxide nanoparticles have been prepared by precipitation method with alcohol as the dispersive and protective reagent. Transmission electron microscope (TEM) images indicate that ... A series of rare earth hydroxide and oxide nanoparticles have been prepared by precipitation method with alcohol as the dispersive and protective reagent. Transmission electron microscope (TEM) images indicate that the particles are spherical in shape and smaller than 100 nm in size. The crystallite sizes of cubic Ln2O3 have lanthanide shrinking effect, while average crystal lattice distortion rates possess lanthanide swelling effect. The diffraction peak intensity of heavy rare earth oxide nanometer powders is remarkably stronger than that of light rare earth oxide nanometer powders. The variation of diffraction intensity with atomic number presents an inverted W type, forming a double peak structure. Fourier transform infrared (FTIR) spectrums reveal that Ln2O3 nanopowders have higher surface activity than that of ordinary Ln2O3 powders. The UV-vis spectra show that Ln-O bond of these particles is slightly blue-shifted, and its absorption intensity decreases. 展开更多
关键词 Rare earth Rare earth hydroxide Rare earth oxide NANOPARTICLE precipitation method
下载PDF
Synthesis and Characterization of Y-Doped Mesoporous CeO_2 Using A Chemical Precipitation Method 被引量:5
6
作者 宋晓岚 江楠 +2 位作者 李宇焜 徐大余 邱冠周 《Journal of Rare Earths》 SCIE EI CAS CSCD 2007年第4期428-433,共6页
Using cetyltrimethylammonium bromide (CTAB) as the template agent, cerium nitrate as the cerium resource, yttrium nitrate as the yttrium resource, and ammonium carbonate as the precipitating agent, mesoporous CeO2 p... Using cetyltrimethylammonium bromide (CTAB) as the template agent, cerium nitrate as the cerium resource, yttrium nitrate as the yttrium resource, and ammonium carbonate as the precipitating agent, mesoporous CeO2 powders doped with different yttrium contents were successfully synthesized using a chemical precipitation method, under an alkalescent condition. Properties of the obtained samples were characterized and analyzed with X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDAX), transmission electron microscopy (TEM), infrared (IR) absorbance, and the BET method. For the prepared samples with 20% (molar ratio) Y-doped content, a BET specific surface area of 106. 6 m^2 · g^- 1, with an average pore size of3~27 nm were obtained. XRD patterns showed that the doped samples were with a cubic fluorite structure. TEM micrographs revealed that the doped samples showed a spherical morphology with a diameter ranging from 20 to 30 nm and a round pore shape. IR results indicated that the Ce-O-Ce vibration intensity decreased as the Y-doped content increased. N2 adsorption-desorption isotherms showed that the samples possessed typical mesopore characteristics. The average pore size of the samples decreased alter mesoporous CeO2 was doped with yttrium, and the average pore size decreased largely as the Y-doped content increased. 展开更多
关键词 mesoporous ceria Y-doped chemical precipitation method SYNTHESIS characterization rare earths
下载PDF
Upconversion luminescence of Y_2O_3:Er^(3+), Yb^(3+) nanoparticles prepared by a homogeneous precipitation method 被引量:11
7
作者 李艳红 张永明 +1 位作者 洪广言 于英宁 《Journal of Rare Earths》 SCIE EI CAS CSCD 2008年第3期450-454,共5页
Y2O3: Er^3+, Yb^3+ nanoparticles were synthesized by a homogeneous precipitation method without and with different concentrations of EDTA 2Na. Upconversion luminescence spectra of the samples were studied under 980... Y2O3: Er^3+, Yb^3+ nanoparticles were synthesized by a homogeneous precipitation method without and with different concentrations of EDTA 2Na. Upconversion luminescence spectra of the samples were studied under 980 nm laser excitation. The results of XRD showed that the obtained Y2O3:Er^3+,Yb^3+ nanoparticles were of a cubic structure. The average crystallite sizes calculated were in the range of 28-40 nm. Green and red upconversion emission were observed, and attributed to ^2H11/2,^4S3/2→^4I15/2 and ^4F9/2→^4I15/2 transitions of the ion, respectively. The ratio of the intensity of green emission to that of red emission drastically changed with a change in the EDTA 2Na concentration. In the sample synthesized without EDTA, the relative intensity of the green emission was weaker than that of the red emission. The relative intensities of green emission increased with the increased amount of EDTA 2Na used. The possible upconversion luminescence mechanisms were discussed. 展开更多
关键词 homogeneous precipitation method Y2O3: Er^3+ Yb^3+ nanoparticles upconversion luminescence rare earths
下载PDF
Influence of different solution methods on microstructure, precipitation behavior and mechanical properties of Al-Mg-Si alloy 被引量:8
8
作者 Guan-jun GAO Chen HE +3 位作者 Yong LI Jia-dong LI Zhao-dong WANG R. D. K. MISRA 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2018年第5期839-847,共9页
The effects of different solution methods on microstructure, mechanical properties and precipitation behavior of Al-Mg-Si alloy were investigated by scanning electron microscope, transmission electron microscope, tens... The effects of different solution methods on microstructure, mechanical properties and precipitation behavior of Al-Mg-Si alloy were investigated by scanning electron microscope, transmission electron microscope, tensile test, and differential scanning calorimetry. The results revealed that the recrystallized grains of the alloy after the solution treatment with hot air became smaller and more uniform, compared with solution treatment with electrical resistance. The texture of the alloy after two solution treatment methods was different. More rotated cube components were formed through solution treatment with electrical resistance, which was better for improving the drawability of the alloy. The strength of the alloy under the solution treatment with hot air was higher before stamping, because of the small uniform grains and many clusters in the matrix. The alloy solution treated with hot air also possessed good bake hardenability, because the transformation occurred on more clusters in the matrix. 展开更多
关键词 Al-Mg-Si alloy solution method recrystallization grain TEXTURE mechanical property precipitation activation energy
下载PDF
Synthesis and luminescence properties of nanocrystalline Gd_3Ga_5O_(12):Eu^(3+) by a homogeneous precipitation method 被引量:3
9
作者 Li Yanhong Lu Haiyan +2 位作者 Zhang Yongming Ma Jing Song Guoyi 《Rare Metals》 SCIE EI CAS CSCD 2012年第6期599-603,共5页
Nanocrystalline Gd3Ga5O12:Eu3+ with cubic phase was prepared by a urea homogeneous precipitation method. X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), Fourier transform infrared spectrosc... Nanocrystalline Gd3Ga5O12:Eu3+ with cubic phase was prepared by a urea homogeneous precipitation method. X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric and differential thermal analysis (TG-DTA) and photoluminescence spectra were used to characterize the samples. The effects of the initial solution pH value and urea content on the structure of the sample were studied. The XRD results show that pure phase Gd3Ga5O12 can be obtained at pH =6 and pH =8 of the initial solution. The average crystallite size can be calculated as in the range of 24~33 nm. The average crystallite size decreases with increasing molar ratio of urea to metal ion. The results of excitation spectra and emission spectra show that the emission peaks are ascribed to 5D0→7FJ transitions of Eu3+, and the magnetic dipole transition originated from 5D0 →7F1 of Eu3+ is the strongest; the broad excitation bands belong to change transfer band of Eu?O and the host absorption of Gd3Ga5O12. An efficient energy transfer occurs from Gd3+ to Eu3+. 展开更多
关键词 Gd3Ga5O12:Eu3+ nanocrystal urea homogeneous precipitation method LUMINESCENCE
下载PDF
Improvement of humidity resistance of water soluble core by precipitation method 被引量:5
10
作者 Zhang Long Li Yuancai Zhao Wei 《China Foundry》 SCIE CAS 2011年第2期212-217,共6页
Water soluble core has been widely used in manufacturing complex metal components with hollow configurations or internal channels;however,the soluble core can absorb water easily from the air at room temperature.To im... Water soluble core has been widely used in manufacturing complex metal components with hollow configurations or internal channels;however,the soluble core can absorb water easily from the air at room temperature.To improve the humidity resistance of the water soluble core and optimize the process parameters applied in manufacturing of the water soluble core,a precipitation method and a two-level-three-full factorial central composite design were used,respectively.The properties of the cores treated by the precipitation method were compared with that without any treatment.Through a systematical study by means of both an environmental scanning electron microscope(ESEM) and an energy dispersive X-ray(EDX) analyzer,the results indicate that the hygroscopicity can be reduced by 20% and the obtained optimal process conditions for three critical control factors affecting the hygroscopicity are 0.2 g·mL-1 calcium chloride concentration,4% water concentration and 0 min ignition time.The porous surface coated by calcium chloride and the high humidity resistance products generated in the precipitation reaction between calcium chloride and potassium carbonate may contribute to the lower hygroscopicity. 展开更多
关键词 water soluble core precipitation method HYGROSCOPICITY tensile strength
下载PDF
Synthesis and Characterization of Large Surface Area Yttrium Oxide by Precipitation Method 被引量:1
11
作者 崔大立 龙志奇 +2 位作者 张顺利 崔梅生 黄小卫 《Journal of Rare Earths》 SCIE EI CAS CSCD 2004年第6期771-774,共4页
The method for preparing yttrium oxide with large specific surface area was introduced. By means of BET, SEM, TG and DTA analysis, the effects of precipitant, stirring velocity, non-RE impurity in solution, calcinatio... The method for preparing yttrium oxide with large specific surface area was introduced. By means of BET, SEM, TG and DTA analysis, the effects of precipitant, stirring velocity, non-RE impurity in solution, calcination temperature, on the surface area were studied respectively. The Y_2O_3 sample with specific surface area of more than 60 m^2·g^(-1) and L.O.I less than 1% was prepared in the suitable precipitation condition and calcinations temperature when the ammonia used as precipitant. The SEM shows that the Y_2O_3 prepared with large surface area is the aggregation of about 50 nm particles. 展开更多
关键词 surface area yttrium oxide MORPHOLOGY precipitation method rare earths
下载PDF
Precipitation Retrieval from Himawari-8 Satellite Infrared Data Based on Dictionary Learning Method and Regular Term Constraint 被引量:2
12
作者 Wang Gen Ding Conghui Liu Huilan 《Meteorological and Environmental Research》 CAS 2019年第3期61-65,68,共6页
In this paper,the application of an algorithm for precipitation retrieval based on Himawari-8 (H8) satellite infrared data is studied.Based on GPM precipitation data and H8 Infrared spectrum channel brightness tempera... In this paper,the application of an algorithm for precipitation retrieval based on Himawari-8 (H8) satellite infrared data is studied.Based on GPM precipitation data and H8 Infrared spectrum channel brightness temperature data,corresponding "precipitation field dictionary" and "channel brightness temperature dictionary" are formed.The retrieval of precipitation field based on brightness temperature data is studied through the classification rule of k-nearest neighbor domain (KNN) and regularization constraint.Firstly,the corresponding "dictionary" is constructed according to the training sample database of the matched GPM precipitation data and H8 brightness temperature data.Secondly,according to the fact that precipitation characteristics in small organizations in different storm environments are often repeated,KNN is used to identify the spectral brightness temperature signal of "precipitation" and "non-precipitation" based on "the dictionary".Finally,the precipitation field retrieval is carried out in the precipitation signal "subspace" based on the regular term constraint method.In the process of retrieval,the contribution rate of brightness temperature retrieval of different channels was determined by Bayesian model averaging (BMA) model.The preliminary experimental results based on the "quantitative" evaluation indexes show that the precipitation of H8 retrieval has a good correlation with the GPM truth value,with a small error and similar structure. 展开更多
关键词 Himawari-8(H8) RETRIEVAL of precipitATION k-nearest NEIGHBOR (KNN) REGULAR TERM constraints DICTIONARY method Bayesian model average (BMA)
下载PDF
Enhanced Photocatalytic Properties of Pure and Cr-Modified ZnS Powders Synthesized by Precipitation Method 被引量:1
13
作者 Bedour A. Mahammed Luma M. Ahmed 《Journal of Geoscience and Environment Protection》 2017年第10期101-111,共11页
Zinc sulfide photocatalysts doped with chromium (1:1)% were synthesized via precipitation technique. Their characteristics were studied by X-ray diffraction (XRD), AFM and Florescence spectrometer. The photocatalytic ... Zinc sulfide photocatalysts doped with chromium (1:1)% were synthesized via precipitation technique. Their characteristics were studied by X-ray diffraction (XRD), AFM and Florescence spectrometer. The photocatalytic reaction was applied under light intensity equal to 1.45 × 10-7 Einstein mol-1 to investigate the kinetics and thermodynamic parameters for photo-decolorization of reactive black 5 dye in collide solution of bare and Cr-doped ZnS. The mean crystal size and particle size for bare ZnS are more than those values for prepared Cr loaded ZnS. 展开更多
关键词 Cr-Loaded ZNS NANOPOWDERS Reactive Black 5 DYE AZO DYE precipitation method
下载PDF
Fluorescence and preparation of Sr_2(P_2O_7 ):Ce,Tb phosphate by co-precipitation method 被引量:8
14
作者 Cheng-Guo Ma Wei Zheng +1 位作者 Li-Guo Jin Li-Min Dong 《Rare Metals》 SCIE EI CAS CSCD 2013年第4期420-424,共5页
The micron-sized Sr2(P2OT):Ce,Tb green phosphors were prepared by being annealed at different temperatures with its precursors synthesized by co-pre-cipitates of (NH4)2HPO4 at ambient temperature. The phase struc... The micron-sized Sr2(P2OT):Ce,Tb green phosphors were prepared by being annealed at different temperatures with its precursors synthesized by co-pre-cipitates of (NH4)2HPO4 at ambient temperature. The phase structure, grain size, surface morphology, and luminescent properties of phosphors were investigated by X-ray diffraction, scanning electron microscope, trans-mission electron microscope, and fluorescence spectrum. The results show that the product of precursor annealed at 1,100 ℃ is Sr2(P2O7):Ce,Tb, which belongs to ortho-rhombic phase. The powder is spherical and the size dis-tribution is in micron grade. The sample with the molar ratio of Sr/Tb/Ce of 100.0:0.4:0.6 shows the best fluores-cence effect annealed at 1,100 ℃ for 3 h. The phosphors produce green fluorescence by being excitated with ultra-violet radiation of 254 nm wavelength, and the main emission peak is at 547 nm. The Sr2(P2O7):Ce,Tb phos-phors synthesized by co-precipitation method of precursors at ambient temperature is a kind of efficient green-emitting phosphors. 展开更多
关键词 PHOSPHORS Co-precipitation method Rareearth phosphate PHOSPHORESCENCE
下载PDF
Synthesis of γ-Al_2O_3 nanoparticles by chemical precipitation method 被引量:1
15
作者 宋晓岚 曲鹏 +2 位作者 杨海平 何希 邱冠周 《Journal of Central South University of Technology》 EI 2005年第5期536-541,共6页
Highly pure active γ-Al2O3 nanoparticles were synthesized from aluminum nitrate and ammonium carbonate with a little surfactant by chemical precipitation method. The factors affecting the synthesis process were studi... Highly pure active γ-Al2O3 nanoparticles were synthesized from aluminum nitrate and ammonium carbonate with a little surfactant by chemical precipitation method. The factors affecting the synthesis process were studied. The properties of γ-Al2O3 nanoparticles were characterized by DTA, XRD, BET, TEM, laser granularity analysis and impurity content analysis. The results show that the amorphous precursor AI(OH)3 sols are produced by using 0.1 mol/L Al(NO3)3·9H2O and 0.16 mol/L (NH4)2CO3·H2O reaction solutions, according to the volume ratio 1.33, adding 0.024%(volume fraction) surfactant PEG600, and reacting at 40℃, 1000 r/min stirring rate for 15min. Then, after stabilizing for 24 h, the precursors were extracted and filtrated by vacuum, washed thoroughly with deionized water and dehydrated ethanol, dried in vacuum at 80℃ for 8h, final calcined at 800℃ for 1h in the air, and high purity active γ-Al2O3 nanoparticles can be prepared with cubic in crystal system, OH^7-FD3M in space group, about 9 nm in crystal grain size, about 20 nm in particle size and uniform size distribution, 131.35 m^2/g in BET specific surface area, 7 - 11 nm in pore diameter, and not lower than 99.93% in purity. 展开更多
关键词 chemical precipitation method γ-Al2O3 nanoparticles characterization of properties
下载PDF
Effects of synthesis conditions on the structural and electrochemical properties of layered LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2 cathode material via oxalate co-precipitation method 被引量:6
16
作者 TIAN Hua YE Naiqing +1 位作者 LIU Dan LI Wenqun 《Rare Metals》 SCIE EI CAS CSCD 2008年第6期575-579,共5页
The uniform layered LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion batteries was prepared by using (Ni1/3Co1/3Mn1/3)C2O4 as precursor synthesized via oxalate co-precipitation method in air. The effects of calc... The uniform layered LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion batteries was prepared by using (Ni1/3Co1/3Mn1/3)C2O4 as precursor synthesized via oxalate co-precipitation method in air. The effects of calcination temperature and time on the structure and electrochemical properties of the LiNi1/3Co1/3Mn1/3O2 were systemically studied. XRD results revealed that the optimal calcination conditions to prepare the layered LiNi1/3Co1/3Mn1/302 were 950℃ for 15 h. Electrochemical measurement showed that the sample prepared under the such conditions has the highest initial discharge capacity of 160.8 mAh/g and the smallest irreversible capacity loss of 13.5% as well as stable cycling performance at a constant current density of 30 mA/g between 2.5 and 4.3 V versus Li at room temperature. 展开更多
关键词 lithium ion batteries oxalate co-precipitation method cathode materials electrochemical performance
下载PDF
Preparation of Nanocrystalline ZrO_2 by Reverse Precipitation Method
17
作者 董相廷 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2005年第3期1-4,共4页
Nanncrystalline ZrO2 particulates with different sizes were prepared by precipitation method using ethanol as dispersive and protective reagent. XRD patterns show that the synthesized ZrO2 is monnclinic in structure w... Nanncrystalline ZrO2 particulates with different sizes were prepared by precipitation method using ethanol as dispersive and protective reagent. XRD patterns show that the synthesized ZrO2 is monnclinic in structure with space group P21/a when calcination temperature is in the range of 400- 1000 ℃ . It is found that the smaller the particle, the bigger the crystal lattice distortion, the worse the costal growth, and the lower the diffrnction intensity. TEM images reveal that ZrO2 particles are spherical in shape, and the particle size distribution is in narrow range. The mean sizes of the particles increase with the increase of calcination temperatures . It is first to observe tbe streaks of different crystallographic planes. Thermogravimetric analysis indicates that the crystallization temperature of ZrO2 is 461.32 ℃ . Measurement of ZrO2 relative density shows that the relative density of nanocrystalline ZrO2 powders increases witb the increasing of ZrO2 particle sizes. 展开更多
关键词 ZIRCONIUM zirconium dioxide nanoparticulate precipitation method
下载PDF
Phase-field study for the splitting behaviour of precipitate under applied stress
18
作者 张玉祥 王锦程 +2 位作者 杨玉娟 杨根仓 周尧和 《Chinese Physics B》 SCIE EI CAS CSCD 2008年第9期3523-3530,共8页
This paper employs the phase-field method to study the splitting behaviour of a single coherent particle under an applied uniaxiai stress. It finds that the splitting behaviour is greatly influenced by the initial sha... This paper employs the phase-field method to study the splitting behaviour of a single coherent particle under an applied uniaxiai stress. It finds that the splitting behaviour is greatly influenced by the initial shape of precipitates, the bulk free energy condition, the degree of supersaturation and the ratio of the interfacial energy to the elastic strain energy, etc. The simulated results demonstrate that the aspect ratio of the particle determines whether the splitting can occur and how many split plates can be obtained. The splitting of particle is sensitive to the interracial energy, i.e. the splitting becomes more and more difficult with increasing the ratio of the interracial energy to the elastic strain energy. And increasing the magnitude of the applied stress is favourable to the splitting. The splitting process is also explained from the point of view of the corresponding diffusion potential. 展开更多
关键词 phase-field method SPLITTING precipitate
下载PDF
Preparation and Characteristics of Hydroxyapatite Whiskers by Homogeneous Precipitation Method
19
作者 王友法 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2001年第3期19-22,共4页
Hydroxyapatite whilkers were prepared by the homogeneousprecipitation method. Soluble calci- um ion and phosphate ion wereused as initial materials, they were refluxed respectively at 85 deg.C, 90 deg. C and 95 deg. C... Hydroxyapatite whilkers were prepared by the homogeneousprecipitation method. Soluble calci- um ion and phosphate ion wereused as initial materials, they were refluxed respectively at 85 deg.C, 90 deg. C and 95 deg. C for various lengths of time. A properprecipitation agent was selected to control the releasing speed ofions in the system; it induced the hydroxyapatite crystal to grow indesired way. The pH each solutions were mea- sured continuouslyduring the reaction. 展开更多
关键词 Hydroxyapatite Whiskers Homogeneous precipitation method HYDROLYSIS
下载PDF
Comparison analysis of sampling methods to estimate regional precipitation based on the Kriging interpolation methods: A case of northwestern China
20
作者 JinKui Wu ShiWei Liu +3 位作者 LePing Ma Jia Qin JiaXin Zhou Hong Wei 《Research in Cold and Arid Regions》 CSCD 2016年第6期485-494,共10页
The accuracy of spatial interpolation of precipitation data is determined by the actual spatial variability of the precipitation, the interpolation method, and the distribution of observatories whose selections are pa... The accuracy of spatial interpolation of precipitation data is determined by the actual spatial variability of the precipitation, the interpolation method, and the distribution of observatories whose selections are particularly important. In this paper, three spatial sampling programs, including spatial random sampling, spatial stratified sampling, and spatial sandwich sampling, are used to analyze the data from meteorological stations of northwestern China. We compared the accuracy of ordinary Kriging interpolation methods on the basis of the sampling results. The error values of the regional annual pre-cipitation interpolation based on spatial sandwich sampling, including ME (0.1513), RMSE (95.91), ASE (101.84), MSE (?0.0036), and RMSSE (1.0397), were optimal under the premise of abundant prior knowledge. The result of spatial stratified sampling was poor, and spatial random sampling was even worse. Spatial sandwich sampling was the best sampling method, which minimized the error of regional precipitation estimation. It had a higher degree of accuracy compared with the other two methods and a wider scope of application. 展开更多
关键词 Kriging interpolation method sampling methods spatial sandwich sampling precipitATION northwestern China
下载PDF
上一页 1 2 210 下一页 到第
使用帮助 返回顶部