NiCo_2O_4纳米结构阵列的水热合成与氧析出特性研究     

陈传胜  张作胜  陈伟杰  乔浏 《安徽职业技术学院学报》2020,(1):16-19,41

钴酸镍纳米材料具有良好的电催化氧析出反应(Oxygen Evolution Reaction,OER)活性,是一种很有发展潜力的非贵金属电催化材料。文章以碳纤维纸为基底,采用水热合成的方法对纳米结构钴酸镍的生长进行了系统的研究,分别考察了生长温度、前驱体浓度和配比、生长时间对产物的形貌、尺寸、物相结构、OER电化学性能的影响,通过对比分析后发现在生长温度100℃、生长时间5h、镍钴比为2:1时所获得的多孔片状钴酸镍纳米结构具有最佳的OER特性。  相似文献   

MARC to BIBFRAME: Converting the PCC to Linked Data     

Jacquie Samples  Ian Bigelow 《Cataloging & classification quarterly》2020,58(3-4):403-417

Abstract

The Program for Cooperative Cataloging (PCC) has formal relationships with the Library of Congress (LC), Share-VDE, and Linked Data for Production Phase 2 (LD4P2) for work on Bibliographic Framework (BIBFRAME), and PCC institutions have been very active in the exploration of MARC to BIBFRAME conversion processes. This article will review the involvement of PCC in the development of BIBFRAME and examine the work of LC, Share-VDE, and LD4P2 on MARC to BIBFRAME conversion. It will conclude with a discussion of areas for further exploration by the PCC leading up to the creation of PCC conversion specifications and PCC BIBFRAME data.  相似文献   

Early career mathematics teachers: Concepts,methods, and strategies for comparative international research     

《Teaching and Teacher Education》2020

In this article, we report on the challenges entailed in the development of concepts, methods, and strategies for designing and implementing a cross-national research study of the first-years of school-mathematics teaching, including an exploration of how beginning mathematics teachers differ in their preparation, knowledge for teaching, teaching practice, working conditions, and pupil characteristics. The study was designed as a proof-of-concept for a study of teaching and teacher education to be implemented by educationalists, teacher educators, and early career teachers as an ongoing professional endeavor. Primary among the challenges was the development of the sampling design and the construction of measures.  相似文献   

超顺磁性Fe2O3较Fe3O4用于磁共振胃肠造影剂的优劣研究     

桂维玲 《实验室研究与探索》2008,27(11)

用超顺磁性氧化铁制备磁共振造影剂的报道较多,其中的磁粒均为Fe3O4。本文提出了用Fe2O3的可行性,并根据超顺磁性理论推导出两种微粒显示超顺磁现象的临界尺寸理论值分别为24.8nm、31.6 nm,在1.5T磁共振磁场中的临界值为7.1 nm、11.1 nm;根据磁学理论,分析了磁共振造影剂稳定的机理;推导出在磁共振磁场中,两者在造影剂中稳定悬浮的极限尺寸为13.3 nm、14 nm。得出在造影剂中,两者既能稳定悬浮又具有超顺磁性的临界尺寸为7.1 nm、11.1 nm的结论。同时分析了两者用做磁共振胃肠造影剂的优劣点。  相似文献   

An Improvement of MPEG-4 Rate Control Algorithm     

鲁照华李华  刘继兴 《天津大学学报(英文版)》2005,11(1):40-43

Frame skipping in low bit video coding could significantly reduce the visual quality of reconstructed video. At the same time, if the complexity of the video sequence remains high for a long period, then driving up the long term average bit rate, the only resort of MPEG-4 Q2 rate control algorithm results in using a high quantization scale, which shows a poor visual quality of the reconstructed video. This paper analyzes the main causes of frame skipping in current MPEG-4 frame rate control scheme, and presents a new rate control algorithm based on the quadratic R-D model over a CBR channel. Key features of the present work are. 1) the bits allocated to each P-frame or B-frame are in proportion to its distance from the end of this GOP, i.e. more bits are allocated to the frames that are nearer to their reference Ⅰ -frame: 2) the target buffer level is changeable in the GOP, at the end of each GOP( five P-frames or B-frames), the target buffer level is linearly reduced from 1/2 to 1/4 of buffer size, to other frames, the target buffer level is set to 1/2 of buffer size: 3 ) a selective and judicious use of the reduced resolution mode, in addition to a modulation of the quantization scale parameter, is to control the average long term bit rate. Experimental results with different video sequences of varied complexity, encoded at low bit rates show better efficacy of the proposed algorithm than MPEG-4 Q2 rate control scheme, and the experimental results also show that the improved algorithm has significantly reduced the number of frame skipping, increased the overall PSNR, and improved the perceptual quality.  相似文献   

Stakeholders’ test perceptions on test reform     

《Studies in Educational Evaluation》2021

The success of test reform relies considerably on how stakeholders understand and accept the revised test (Green & Andrade, 2010). This study provided an opportunity for students and teachers to share their perceptions of a recently revised English test in China, the Test for English Majors Grade Four (TEM4). In addition, this study examined how stakeholders’ perceptions of the test varied across institutions of different academic rankings. Survey data were collected from 496 students and 79 teachers, of whom 32 students and 12 teachers participated in a post-survey interview. Findings indicate that although stakeholders were overall positive about the revised TEM4, their perceptions were qualified by concerns with content representation and test difficulty. In addition, the data suggest that the revised TEM4 was associated with context-varying washback effects and negative psychological impacts. These findings highlight the important contribution that students' and teachers' perceptions may have in the test reform process.  相似文献   

硼镧共渗对Ti-6Al-4V钛合金空蚀性能的影响          下载免费PDF全文

李海斌张晓波石林爽张曼婷 《福建工程学院学报》2021,(4):360-364

采用固体渗剂包埋渗法对Ti-6Al-4V钛合金进行硼-稀土共渗处理,并利用超声振动空蚀机研究分析试样在去离子水中的空蚀性能。结果表明,硼-稀土共渗在Ti-6Al-4V合金表面获得均匀致密的表面渗层。表面渗层具有很高的显微硬度,与基体冶金结合,其主要由TiB2、TiB化合物层和B原子固溶于α-Ti的扩散层构成。稀土元素La的添加,提高渗硼效率,使试样表面渗层厚度增加,显微硬度显著提高,材料的抗空蚀性能得到显著改善。  相似文献   

营销组合4P范式的不可替代性   总被引：8，自引：0，他引：8  

吴长顺  朱玲 《科技管理研究》2007,27(6):215-217,227

营销组合范式从4P发展至4C、4R,引起学者的热烈反应和广泛讨论。在前人研究的基础上,将4P、4C、4R从产品、定价、渠道、促销四个方面进行对比,得出4P理论是具有实操性的营销组合工具,能为消费者提供实际的价值方案,更符合营销工具的实质,是营销学不可替代的理论根基。  相似文献   

IPV6的现状研究   总被引：4，自引：0，他引：4  

王月明  王瑞励 《内蒙古科技与经济》2006,(10):49-50

本文论述了IPV6的发展背景,IPV6相对于IPV4的新特性;IPV6技术。  相似文献   

土地利用纹理样本数据库的建立     

周秀华  霍宏  方涛  李钢 《中国科技信息》2007,(9):28-30

本文概述了多种数据源,多时相的所有类别的不同表现形式的土地利用纹理样本数据的采集、建库等一系列工作,介绍了土地利用纹理样本库德体系结构,主要功能以及设计方法,并分析了XML、OO4O等关键技术。  相似文献