Using materials science

The science of the solid state has joined nuclear science and molecular biology as a field of major importance in the latter half of the 20th century. It took particular shape during the genesis of solid-state electronics and the post-transistor era of integrated circuits for telecommunications, computers, and digital signal machines. However, these developments were soon joined by techniques from the ancient fields of metallurgy and ceramics and contributions from the more current fields of synthetic polymers, rubbers, plastics, and modified bioorganic substances. This vast realm was characterized by a National Academy of Sciences study of the 1970's as "materials science and engineering." The public, as well as the scientific and engineering community, are currently concerned about the uses of research and development and the applications of knowledge for national progress. Consideration is given here to how well we are using the science of materials for industrial strength and such governmental objectives as national security and energy economy.     

Perovskite oxides: materials science in catalysis

In a time of growing need for catalysts, perovskites have been rediscovered as a family of catalysts of such great diversity that a broad spectrum of scientific disciplines have been brought to bear in their study and application. Because of the wide range of ions and valences which this simple structure can accommodate, the perovskites lend themselves to chemical tailoring. It is relatively simple to synthesize perovskites because of the flexibility of the structure to diverse chemistry. Many of the techniques of ceramic powder preparation are applicable to perovskite catalysts. In their own right, they are therefore of interest as a model system for the correlation of solid-state parameters and catalytic mechanisms. Such correlations [See figure in the PDF file] have recently been found between the rate and selectivity of oxidation-reduction reactions and the thermodynamic and electronic parameters of the solid. For commercial processes such as those mentioned in the introduction, perovskite catalysts have not yet proven to be practical. Much of the initial interest in these catalysts related to their use in automobile exhaust control. Current interest in this field centers on noble metalsubstituted perovskites resistant to S poisoning for single-bed, dual-bed, and three-way catalyst configurations. The formulations commercially tested to date have shown considerable promise, but long-term stability has not yet been achieved. A very large fraction of the elements that make up presently used commercial catalysts can be incorporated in the structure of perovskite oxides. Conversely, it is anticipated that perovskite oxides, appropriately formulated, will show catalytic activity for a large variety of chemical conversions. Even though this expectation is by no means a prediction of commercial success in the face of competition by existing catalyst systems, it makes these oxides attractive models in the study of catalytic chemical conversion. By appropriate formulation many desirable properties can be tailored, including the valence state of transition metal ions, the binding energy and diffusion of O in the lattice, the distance between active sites, and the magnetic and conductive properties of the solid. Only a very small fraction of possible perovskite formulations have been explored as catalysts. It is expected that further investigation will greatly expand the scope of perovskite catalysis, extend the understanding of solid-state parameters in catalysis, and contribute to the development of practical catalytic processes.     

基于土壤学理论的土地整理研究

从耕地质量评价、"补充耕地的数量、质量实行按等级折算"、土壤形成和演变、土地的养育和涵养功能源于土壤以及实施土壤保护、培肥与改良工程等方面,阐述了土壤学作为土地整理最重要的支撑理论,指出了土壤学在土地整理过程中的应用首先是土壤保护,维护土壤肥力和自动协调功能,实现土地生产力在利用中提高和土地可持续利用;其次是改土培肥,即根除土壤障碍因子,改善土宜条件等,提高土地生产力.在上述研究的基础上,提出了基于土壤学理论的土地整理实践活动,即因区护土和因地改土培肥等.     

分形理论在木材科学领域中的应用

阐述了分形理论的基本概念、分形结构的主要特征以及分维的计算方法,总结了分形理论在木材解剖学、物理学、力学、无损检测及环境学中的应用情况,讨论了利用分形理论对木材细胞壁中纳米纤维的超微构造进行定量表征的可行性。结果表明:木材细胞壁中不同尺寸纤维的结构特征和组合排布关系,符合分形体系所要求的无特征长度和自相似性两大特征,可应用分形的方法对木材细胞壁中纳米纤维的微观构造进行定量表征。     

Electronic publication and the narrowing of science and scholarship

Online journals promise to serve more information to more dispersed audiences and are more efficiently searched and recalled. But because they are used differently than print-scientists and scholars tend to search electronically and follow hyperlinks rather than browse or peruse-electronically available journals may portend an ironic change for science. Using a database of 34 million articles, their citations (1945 to 2005), and online availability (1998 to 2005), I show that as more journal issues came online, the articles referenced tended to be more recent, fewer journals and articles were cited, and more of those citations were to fewer journals and articles. The forced browsing of print archives may have stretched scientists and scholars to anchor findings deeply into past and present scholarship. Searching online is more efficient and following hyperlinks quickly puts researchers in touch with prevailing opinion, but this may accelerate consensus and narrow the range of findings and ideas built upon.