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1.
The influences of the PbO-B2O3-CuV2O6 （PBC） additives on the microwave dielectric properties of （Pb0.5Ca0.5） （Fe0.5Nb0.5）O3 （PCFN） ceramics were investigated as a function of sintering temperature from 950 ℃ to 1 100 ℃. The sintering temperature of the specimens with the glass could be lowered from 1125 ℃ to 1 025℃ without the degradation of microwave dielectric properties. The microwave results showed that the dielectric constant cr was not significantly different while Qf values decreased with the increase of CuV206 content of PBC glass. For the specimens doped with PB-CV0.1 glass （81% PbO-9% B203-10% CuV2O6） and sintered at 1 025 ℃ for 3 h, the microwave dielectric properties of Qf=4 823 GHz, Cr=107.1 with TCF=＋15.03 ×10^-6/℃ were obtained.  相似文献   

2.
The influence of calcination temperature on TiO2 nanotubes＇ catalysis for TiO2/UV/03 was investigated. TiO2 nanotubes （TNTs） were prepared via the sol-gel method and calcined at 300--700 ℃, which were labeled as TNTs-300, TNTs-400, TNTs-500, TNTs-600 and TNTs-700, respectively. TNTs were characterized by transmission electron microscopy （TEM） and X-ray diffraction （XRD）. It is found that TNTs calcined at 400 ℃ showed the best thermal stability. When the calcination temperature increased from 400 ℃ to 700 ℃, the special structure of tubes was destroyed and gradually converted into nanorods and/or particles. The transformation from anatase to rutile occurred at 600 ℃, and the rutile phase was enhanced when the calcination temperature was increased to over 600 ℃. The calcina- tion temperature＇s influence on TNTs＇ adsorption activity for for TiO2/UV/O3 was investigated in landfill leachate solution chemical oxygen demand （COD） and catalytic activity In landfill leachate solution, the adsorption activity of COD decreased in the reduced order of TNTs-300, TNTs-400, TNTs-500, TNTs-600 and TNTs-700. In photocatalytic ozonation, TNTs-400 showed the best catalytic activity while TNTs-700 exhibited the worst. In other three processes, the COD removal of TNTs-300/UV/O3 was higher than those of TNTs-500/UV/O3 and TNTs-600/UV/O3 in the first 20 rain, and then became close to those of the latter two in the following 40 rain. Compared with TNTs-300 and TNTs- 400, TNTs-600 had the best anti-fouling activity, while TNTs-500 and TNTs-700 had lower anti-fouling activity than the former three. In photocatalytic ozonation, the calcination temperature of 400 ℃ was appropriate when TNTs were obtained at the synthesis temperature of 105 ℃.  相似文献   

3.
Studies on the sintering, microstructure, mechanical properties and low temperature degradation behavior of yttria stabilized-tetragonal zirconia polycrystal （3Y-TZP） were carried out. The results show that the addition of Al2O3 and MgO improve the sintering at low temperatures, and cause exaggerated grain growth and the transformation of tetragonaI-ZrO2 to monoclinic-ZrO2 with corresponding changes in the mechanical properties. The addition of the yttria-free monoclinic zirconia particles change the overall yttria distribution and induce an active transformation toughening mechanism. Furthermore, the dispersed yttria-free ZrO2 can inhibit the tetragonal zirconia transformation, which is beneficial to the improvement of the low temperature degradation behavior of 3Y- TZP ceramics.  相似文献   

4.
A novel metallo-organic chemical vapor deposition (MOCVD) technique has been applied to the preparation of the photocatalytic titanium dioxide supported on activated carbon. The effects of various condition parameters such as carrier gas flow rate, source temperature and deposition temperature on the deposition rate were investigated. The maximum deposition rate of 8.2 mg/(g·h) was obtained under conditions of carrier gas flow rate of 400 ml/min, source temperature of 423 K and deposition temperature of 913 K. The deposition rate followed Arrhenius behavior at temperature of 753 K to 913 K, corresponding to activation energy Ea of 51.09 kJ/mol. TiO2 existed only in anatase phase when the deposition temperature was 773 K to 973 K. With increase of deposition temperature from 1073 K to 1273 K, the rutile content sharply increased from 7% to 70%. It was found that a deposition temperature of 773 K and a higher source temperature of 448 K resulted in finely dispersed TiO2 particles, which were mainly in the  相似文献   

5.
1-（2-chlorophenyl） ethanol （CPE） is of health and environmental concern due to its toxicity and its use as an intermediate in pharmaceutical manufacturing. The current work deals with the catalytic reductive dechlorination and detoxification of CPE by Pd/Fe bimetal. CPE was effectively dechlorinated to l-phenyl ethanol （PE） accompanied by the equivalent release of chloride. The extent of CPE dechlorination increased with temperature, Fe dosage and Pd loading. A decrease in solution pH increased CPE dechlorination, resulting presumably from an increase in hydrogen production. Under the specific conditions of 20 g/L Pd/Fe, 0.10% Pd （w/w） and initial pH 5-6, the CPE dechlorination was completed within 145 rain. The dechlorination followed a pseudo-first-order kinetics with an activation energy of 56.7 kJ/mol. The results of toxicity testing showed that CPE was very toxic to Chlorella, whereas PE showed little toxicity. The toxicity of the reaction solution declined gradually and the promoting effects on Chlorella intensified consequently with the dechlorination process. Thus, the reductive dechlorination of CPE to PE by Pd/Fe was a detoxification process. It may be used to effectively reduce the toxicological effects of CPE-contaminated wastewater, thereby enhancing the performance of subsequent biological processes in wastewater treatment.  相似文献   

6.
CuO-doped(K0.5Na0.5)Nb0.9Ta0.1O3 lead-free piezoelectric ceramics have been prepared by conventional sintering technique and the effects of CuO on the phase structure and piezoelectric properties of the ceramics have been studied.The results show that a small amount of CuO can improve the densification of the ceramics,consequently,the electric properties are improved.Good piezoelectric and dielectric properties of d33=125 pC/N,Kp=0.38,εr=700,Qm= 248,and Tc=370°C were obtained for the K0.5Na0.5Nb0.9Ta 0.1O3 ceramics doped with 0.5mol% CuO sintered at 1000℃ for 2h.  相似文献   

7.
ZiO2 was prepared by the hydrolyzation method in （NH4）2SO4-modified TiCl4 solution, and TiO2 photocatalysts were obtained by accelerating the precipitation of TiO2 powder in a high-temperature water bath. The photocatalysts were characterized by Brunauer-Emmett-Teller （BET）, X-ray diffraction （XRD）, Raman spectrum and UV-Vis （Ultraviolet-Visible） spectrometry techniques, and the photocatalytic activity in phenol-contaminated water was investigated. The results showed that photocatalysts calcined at 400 ℃ had a specific surface area of 138.2 m^2/g and an average particle size of 9 nm, and a significant increase in thermal stability of anatase phase. At the calcination temperature of 700 ~C, the crystal form of TiO2 started to change into rutile （anatase： 97%, rutile： 3%）. The activity of TiO2 photocatalysts prepared with （NH4）2SO4-modified TIC14 solution was markedly stronger than that without （NH4）2SOg-modified TIC14 solution. Maximal photocatalytic activity was observed at the mole ratio of Ti：（NH4）2SO4= 1：2, the water-bath temperature of 90℃ and the calcination temperature of 700 ℃.  相似文献   

8.
We investigated the influence of soaking time on the semi-conductivity and nonlinear electrical properties of TiO2- based varistor ceramic samples. We used a single sintering process and fabricated six disk samples of （Sr, Bi, Si, Ta）-doped TiO2- based varistor ceramics sintered at 1 250℃ for 0.5 h, 1.0 h, 2.0 h, 3.0 h, 4.0 h, and 5.0 h, respectively. The samples were characterized by X-ray diffraction, breakdown voltage, and complex impedance. The results show that as the soaking time increases from 0.5 h to 5.0 h, the breakdown voltage drops before rising while the nonlinear coefficient increases and then decreases. We suggest that, considering both grain semi-conductivity and nonlinear electrical properties of the TiO2-based varistor ceramics, the optimal soaking time is between 2.0 h and 3.0 h.  相似文献   

9.
We investigated the photocatalytic degradation of dye wastewater by using titanium dioxide （TiO2） coated on a coal cinder. The coal cinder was used as the carrier, with a thin film of TiO2 coated on it by using the sol-gel method. Using the Congo red as the model pollutant for dye wastewater, we studied the decolorization efficiency, and effects of TiO2 film thickness and roasting temperature on the efficiency. We also evaluated the recycling and regeneration of the immobilized TiO2 （TiO2/cinder）. Results show that the decolorization rate of Congo red solution was more than 98% after 2.h treatment when we used TiO2/cinder calcined at 500 ℃ for 2 h and coated four times as the photocatalyst. At the same time, the TiO2/cinder remained high catalytic activity after being reused and regenerated for many times.  相似文献   

10.
Poly （N-isopropylacrylamide） （PNIPAAm）/carboxymethylated chitosan （CMCH） hydrogels were prepared by irradiating the aqueous solution mixture of NIPAAm and CMCH by 60 Co γ-ray.The effects of feed ratio of NIPAAm and CMCH,temperature,pH and ionic strength on the swelling ratio of PNIPAAm/CMCH hydrogels were studied.The results show that the addition of CMCH shifts the lower critical solution temperature （LCST） of the PNIPAAm hydrogel to higher temperature.The PNIPAAm/CMCH hydrogel displays not only pH-and thermo-sensitivity,but also ion-sensitivity.Differential scanning calorimetry （DSC） was applied for the determination of the LCST of the hydrogel.  相似文献   

11.
This article presents the methodology used by the Finnish Education Evaluation Council in the national evaluation of social and communication skills in vocational education and training. The evaluation concentrates on key competences such as learning-to-learn skills, communication skills, social skills and entrepreneurship （Implementation of Education and Stringfellow, 2005; Recommendation of the European Training 2010, 2004; Winterton, Delemare-Le Deist ＆ Parliament and of the Council of December 18, 2006 on key competencies for lifelong leaming, 2006）. The evaluation focuses particularly on skills required in the labour market. These competences are included in all vocational study programmes as a part of accompanying with other key competences. The authors＇ approach follows the principles of developmental and participative evaluation, applying the Common Quality Assurance Framework （CQAF） model, which has been accepted by the European Commission for the quality management and quality assurance framework for vocational education and training in Europe. Additional methods such as interview and statistical data gathering were used to acquire comprehensive data and ensure extensive participation of each partner involved has key competences. The evaluation material was collected from vocational education and training providers by sector （n=8） and by qualification （n=53）. Every sector and type of examination was included in the evaluation. The evaluation was based on a sample （n=130）. The evaluation data were collected from multiple sources by using multiple methods. The material included written self-evaluation reports by vocational education and training providers （n=130 which equals 95% of VET providers）, quantitative information, interviews organized by the National Board of Education and an evaluation seminar for providers as focus groups. Educational administrators, teachers, students, employers and workplace instructors participated in the self-evaluation of the vocational education and training establishments （multi-professional evaluation）.  相似文献   

12.
In this paper, the Toda equation and the discrete nonlinear Schrdinger equation with a saturable nonlinearity via the discrete ＂ （G′/G＂）-expansion method are researched. As a result, with the aid of the symbolic computation, new hyperbolic function solution and trigonometric function solution with parameters of the Toda equation are obtained. At the same time, new envelop hyperbolic function solution and envelop trigonometric function solution with parameters of the discrete nonlinear Schro¨dinger equation with a saturable nonlinearity are obtained. This method can be applied to other nonlinear differential-difference equations in mathematical physics.  相似文献   

13.
In order to explore effective ways to develop Chinese English learners＇ communicative competence, this study first briefly reviews the advantages of communicative language teaching （CLT） method which widely practiced in the Western countries and analyzes in details its obstacles in Chinese classroom context. Then it offers guidelines for compromising the communicative approach with the traditional Chinese approach. Finally, it puts forward some principles and techniques for English teaching practice in the Chinese environment.  相似文献   

14.
Yunnan officialdom was extremely understaffed in QIAN -Long period, which is very rare in Yunnan history. The study finds that the bureaucratization of Yunnan chieftaincy in YONG - zheng period together with other factors resulted in the crisis of understaffed officials in Yunnan official- dom. QIAN - Long＇ s government took a variety of measures to solve this problem and achieved good re- sults. The understaffed crisis was greatly alleviated in late QIAN - Long time, which guaranteed the reign of effective Governance in Yunnan.  相似文献   

15.
The city of Taipei has been considered as a leading role of information technology education in Taiwan. However, many questions have been waited to be answered. The purpose of this study was to investigate the current situations and problems of primary school teachers＇ technology-instruction integration. By implementing the approach of cognitive motivators and the human performance technology （HPT） theory, this study also investigated the relationships among teachers＇ cognitive motivators （self-efficacy and task values） and their commitment and effort on technology-instruction integration. The researchers delivered 2,952 questionnaires via Internet, e-mail and airmail in January 2008. Finally, 1,549 questionnaires replied back and turned out to be ok. The findings were described as below. The situation of＂high-tech schools, low-access technology＂ also happened in Taipei primary schools. The time teachers devote to use technology into instruction is about 1-3 hour（s） per week and the level of technology implementation to use was low. Besides, teachers＇ self-efficacy and task values have impact on their commitment and effort on technology-instruction integration. Teachers＇ age and the length of teaching presented opposite correlations with their commitment and effort on technology-instruction integration. Teachers have huge difficulty on comprehending and designing computer-animation related multimedia materials to help students clear their abstract learning concept to concrete. In the future, they hope to take more workshops related with multimedia design principles, how to integrate technology with learning areas, and other multimedia related theories.  相似文献   

16.
当传统文化、民族文化的价值被多元、深入地重新发掘与体认之际,成吉思汗及其所代表的蒙古民族再度成为一个新的社会文化热点。20世纪七、八十年代以来,有关成吉思汗的专著开始不断涌现。大陆、台湾等各地出版社相继出版了多种成吉思汗传记作品。从事不同学术领域研究、不同国籍的学者站在各自不同的角度,密切关注着成吉思汗及蒙元文化的特性,相关文学或学术专著层出不穷。目前,这一研究领域有影响力的专著已达数十种之多,马冀先生的《成吉思汗评传》（内蒙古人民出版社,2005年10月）即是其中之一。  相似文献   

17.
Vanadium oxides condensed films are prepared on glass substrates, using spray pyrolysis （SP） technique. The effects of substrate temperature, vanadium concentra- tion in initial solution and the solution spray rate on the nano-structural, electrical, and optical properties of depos- ited films were investigated. Characterizations of the sam- ples were performed using X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and UV-Vis spec- troscopy methods. The type and concentration of the charge carriers were determined and measured by Hall effect experiment. XRD patterns showed that the prepared films had polycrystalline structure, mostly tetragonal fl-V205 and V409 phases with the preferred orientation along （200） direction. The Hall effect experiment revealed that all samples were n-type, except the ones deposited at substrate temperatures Tsub ： 300 ~C and Tsub = 450 ~C, vanadium concentration 0.1 mol/L and solution spray rate 10 mL/min. The charge carrier concentrations obtained were in the range 1016-1018 cm-3. The lowest sheet resistance （R~） was obtained for the samples prepared at T~ub = 450 ~C, vana- dium concentration 0.05 mol/L and solution spray rate 10 mL/min. It was also found that the optical transparency of the samples changed from 20% to 75% and the optical bandgap of the samples was from 2.22 eV to 2.58 eV, depending on the deposition conditions.  相似文献   

18.
蒋亚娟 《教师》2010,(15):93-94
Teachers＇ questioning is quite significant on motivating learners. When asking questions, teachers need to find a balance between convergent and divergent questions. Wait-time is also very important when questioning. This study was based on a survey of 34 students who were taking academic English language courses in a UK university （the University of Hertfordshire） and also suggested that three to five seconds is the most suitable wait-time for students.  相似文献   

19.
This research is attempting to examine the effectiveness in the application of ICT （information and communication technology） and standardize courseware in ETeMS （English for Teaching Mathematics and Science） or PPSMI （Pengajaran and Pembelajaran Sains and Matematic dalam Bahasa Inggeris） in English program in the Malaysian secondary school system. Five dimensions of secondary school （type of school, demographic, leadership quality, teaching and learning culture, and teachers＇ personal and working experience） were examined to determine the maximizing usage of TEC （technology-enhanced classroom） in the learning program. In general, there is a significant difference among factors stated above with maximizing usage of TEC in teaching and learning of science and mathematics in English program. The learning culture is also closely related. In addition, the school and teaching staff are another two essential factors found to be the strong fundamental of maximizing the usage of technology in TEC teaching and learning with towering quality. This study represents an addition to the extant literature on maximizing the usage of technology-enhanced teaching and learning towards the excellence of education in the secondary school system. The maximizing usage of TEC teaching and learning environment within the secondary school system is pivotal towards achieving high quality human capital and improving the efficiency and integrity of technology-enhanced learning of science and mathematics in English program. This study provides further groundwork to assist existing education managers to improve work quality and deliver the maximizing usage of TEC teaching and learning towards the excellence in secondary education.  相似文献   

20.
The troubled state of affairs in the Federally Administered Tribal Areas （FATA） of Pakistan portends serious repercussions and grave consequences, destined to affect education particularly higher education in the entire tribal belt. Ironically, no extensive study has been conducted, to investigate those dimensions of FATA higher education which have been adversely affected in the aftermath of 9/11. This exploratory study examines those areas which have been badly affected as a result of current turmoil. In fact, the higher education in FATA has its own peculiar dynamics. Inherently, the entire tribal region has very few well-maintained and properly equipped colleges. Lack of adequate educational facilities, multiplied poor security environment has aggravated the entire situation. Law and order situation in the region has undermined the already dilapidated monitoring mechanism of education department. This state of affairs provides breeding ground for extremist propensities and radical tendencies. In reality, very little attention has been devoted to reform the education system in tribal areas. The whole set up needs to be rehabilitated by taking recourse due to the proactive role of international community. The paper concludes with recommendations for policy makers besides offering new avenues for further research.  相似文献   

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