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The sintering behavior of (La0.7Sr0.3)xCrO3 (0.95 x 1.05) is investigated to compare liquid phase sintering phenomena occuring in stoichiometric and non-stoichiometric compositions. Shrinkage analysis revealed marked contrast between the densification characteristics of the A-site enriched (x > 1.00) and A-site depleted (x < 1.00) materials. A-site depleted samples typically exhibited a single liquid phase sintering event at 1250 °C attributed to the melting of an exsoluted SrCrO4 phase. A-site enriched samples indicated two rapid shrinkage events due to the melting of SrCrO4, and a Sr2.67(CrO4)2 phase with a melting temperature of 1450 °C. Sr2.67(CrO4)2 was shown to evolve from a decomposition reaction between SrCrO4 and La2CrO6, detected together in A-site enriched samples from 800–1000 °C. Maximum densities (93% theoretical density) were achieved for (La0.7Sr0.3)xCrO3 x = 1.00 after sintering at 1700 °C for two hours. 相似文献
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36 left-handed and 36 right-handed kindergarten children were asked to print after seeing a series of reversible letters and numbers presented individually on slides or flash cards. Regardless of handedness, both groups of Ss found the left–right orientation cues of the same letters and numbers difficult to recall. This challenges a proposal expressed in the "grammar of action" that claims that certain reversal errors in children's printing result from the inappropriate application of the horizontal motor rule, because although left- and right-handed children use this rule, they do so in different ways and therefore should have produced different errors. Another sample of 86 right-handed children from nursery school through Grade 1 was given the same printing task. Findings from this 2nd sample provide an additional challenge to the grammar of action by showing that reversals of the letter N, which are also thought to result from a misapplication of motor rules, decrease in frequency along with reversals of other letters and numbers, instead of increasing as predicted, during the developmental period when the motor rules that are said to be responsible for reversals of this particular letter become more strongly established. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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谷雨 《传动技术(上海)》2005,19(4):40-48
以推型金属带为基体的无级变速箱(CVT)的动力传递效率低于有级变速箱,大家已往认识到采用CVT改进发动机/负荷匹配新取得的燃料经济性的好处有被取消的趋势.本组三篇论文详细阐述了发生在作为第一级用来取得效率改进的带传动中损耗机理的研究.已经进行试验研究了涉及推型金属V-带CVT空载和低载的转矩损失.本第一篇论文述及发生在金属带CVT由于带推块和带间相对运动造成主要转矩损失的新分析方法.本研究考虑到其他研究中的新发现并改进了金属V-带的设计.本文中采用几种不同的试验方法提供的实验数据推荐了转矩损失的数字模型.本组第二篇论文阐述了由于带轮变形的许多附加转矩损失机理.在第三篇论文中阐述了根据本文的发现提出带滑动损失的分析. 相似文献
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Synthesis, Densification, and Conductivity Characteristics of BICUVOX Oxygen-Ion-Conducting Ceramics
Steven P. Simner Donaji Suarez-Sandoval John D. Mackenzie Bruce Dunn 《Journal of the American Ceramic Society》1997,80(10):2563-2568
Copper-substituted bismuth vanadate (Bi2 V0.9 Cu0.1 O5.35 ), known as BICUVOX, possesses high oxygen ion conductivities at low temperatures. The ionic conductivity of this material at 300°C (∼1 × 10−3 S/cm) is 50 to 100 times greater than any other solid electrolyte in this temperature range. In this paper we report the preparation of sinterable BICUVOX powders by solid-state reaction and conventional ceramic powder processing techniques. Densification studies indicate that optimum densities (>95% theoretical) can be obtained after 10-20 h sintering at 800°C. Ionic conductivity characteristics were evaluated with respect to temperature, sample density, and prolonged isothermal heating. 相似文献
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Atomized silver spheres (≈20–50 μm diameter) were coated with 1 μm thick layers of (La0.6Sr0.4)0.98Co0.2Fe0.8O3 or Sm0.5Sr0.5CoO3 via a mechanofusion dry processing method. The materials were subsequently assessed as solid oxide fuel cell cathodes on anode-supported YSZ electrolytes at 650–750 °C. The materials were subject to significant electrochemical conditioning during initial cell operation, and factors, such as temperature and operating voltage, affecting the conditioning rate are discussed. Post-conditioned power densities (at 0.7 V) were typically 550–650, 400–450 and 300–350 mW cm−2 at 750, 700 and 650 °C, respectively. Though power degradation rates of ≈7.5 and 4.5% (per 1000 h) were observed at 750 and 700 °C, respectively, no degradation was detected over almost 2000 h of testing at 650 °C. 相似文献
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166 children, kindergarten through Grade 2 (mean ages 5 yrs 4 mo to 7 yrs 11 mo), were asked to reproduce the 26 uppercase and 26 lowercase letters and the numbers 1–9. The resulting stroke patterns obtained from the kindergartners supported predictions derived from the starting, progression, and horizontal rules expressed in the "grammar of action." However, other predictions based on the way Ss of these ages are said to resolve conflicts among these rules were not supported. Similarly, predictions regarding the influence of formal printing instruction in school on the subsequent printing stroke patterns used by the 1st and 2nd graders were not confirmed. An alternative to the grammar of action is proposed to explain these various findings and the general uniformity that children show when they print letters and numbers and copy geometric figures. (7 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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We appreciate the fact that Fiedorowicz has chosen to comment on our review of Reading disabilities (see record 2007-03865-001) because this provides us with an opportunity to expand on some of our previous remarks. However, since these positive features already had received coverage in the review by Goodacre (1982), and since over two-thirds of the book dealt with the authors' own research (which was not discussed in any depth by Goodacre), we chose to restrict ourselves mainly to concerns raised by this research. Our response will have the same focus. To begin with, there are a number of misleading statements in Fiedorowicz's letter that distort both the tone and the content of our review. Fiedorowicz contends, contrary to the conclusion that we reached in our review, that "distinct neuropsychological profiles were determined corresponding to each subtype." The second issue raised by Fiedorowicz deals with our concern about the construct validity of the various test items employed in this investigation. The third issue in Fiedorowicz's letter centres on the interpretation of the results reported by Doehring et al. for the Type S subjects. The last issue of any substance in this letter has to do with the label "oral reading deficit" given by the authors to the Type O subjects. In addition to these four issues there is one final point that we believe also merits a reply. In referring rather pessimistically to the matter of treatment in our review, we were merely repeating comments made by the authors themselves in Chapter 11. Because this review was written in August 1983, we were of course unaware of the information in the paper cited by Fiedorowicz, which was not presented until February 1984. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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Reactions to the position paper (M. L. Simner; see record 1994-03519-001) approved by the Canadian Psychological Association on beginning reading instruction were received from 8 ministries (departments) of education. Despite widespread media and public support for the Association's claim that the level of phonics instruction in whole language is insufficient to meet the needs of many beginning readers, the majority of the ministries took issue with this claim. The present article clarifies the Association's stand by drawing attention to the differences between the phonics exercises that research shows should be employed in beginning reading instruction and the phonics exercises that teachers are being encouraged to employ as a result of the ministries' endorsement of whole language. Four additional measures are provided that the Association now asks the ministries to adopt to avoid having more children suffer the consequences of improper beginning reading instruction. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献