二阶线性循环数列的几个结论

给出并证明了二阶线性循环数列收敛的充要条件及新数列{an/an-1}收敛的必要条件,得出了两个相关推论,为二阶线性循环数数列的实际应用提供了理论依据与方法。     

Investigation of low-cycle fatigue behavior of austenitic stainless steel for cold-stretched pressure vessels

Cold-stretched pressure vessels from austenitic stainless steels(ASS) are widely used for storage and transportation of liquefied gases,and have such advantages as thin wall and light weight.Fatigue is an important concern in these pressure vessels,which are subjected to alternative loads.Even though several codes and standards have guidelines on these pressure vessels,there are no relevant design methods on fatigue failure.To understand the fatigue properties of ASS 1.4301(equivalents include UNS S30400 and AISI 304) in solution-annealed(SA) and cold-stretched conditions(9% strain level) and the response of fatigue properties to cold stretching(CS),low-cycle fatigue(LCF) tests were performed at room temperature,with total strain amplitudes ranging from -.4% to -.8%.Martensite transformations were measured during the tests.Comparisons on cyclic stress response,cyclic stress-strain behavior,and fatigue life were carried out between SA and CS materials.Results show that CS reduces the initial hardening stage,but prolongs the softening period in the cyclic stress response.Martensite transformation helps form a stable regime and subsequent secondary hardening.The stresses of monotonic and cyclic stress-strain curves are improved by CS,which leads to a lower plastic strain and a much higher elastic strain.The fatigue resistance of the CS material is better than that of the SA material,which is approximately 1?03 to 2?04 cycles.The S-N curve of the ASME standard for ASS is compared with the fatigue data and is justified to be suitable for the fatigue design of cold-stretched pressure vessels.However,considering the CS material has a better fatigue resistance,the S-N curve will be more conservative.The present study would be helpful in making full use of the advantages of CS to develop a new S-N curve for fatigue design of cold-stretched pressure vessels.     

Rethinking Mobile Delivery: Using Quick Response Codes to Access Information at the Point of Need

This article covers the use of Quick Response (QR) codes to provide instant mobile access to information, digital collections, educational offerings, library website, subject guides, text messages, videos, and library personnel. The array of uses and the value of using QR codes to push customized information to patrons are explained. A case is developed for using QR codes for mobile delivery of customized information to patrons. Applications in use at the Libraries of the University of Utah will be reviewed to provide readers with ideas for use in their library.     

Writing for Publication and the Role of the Library: “Do Have a Cow,Man!” (“Don't Have a Cow,Man”-Bart Simpson)

The aim of this small-scale research project was to identify the main concerns of editors, academics, researchers, and librarians involved in the writing for publication (WfP) process. This would provide library and information services (LIS) staff with a clearer understanding of the process to enable them to articulate and develop their own role in supporting this activity. A novel “one thing” approach was used to determine the perspectives of editors, researchers, librarians, and research students on key issues surrounding WfP. The results indicate that there are many opportunities for LIS staff to contribute to the WfP process. One major concern which emerged was just how isolated researchers could feel. Suggestion: Having a CoW (Community of Writers) in the library could provide a potential LIS role. Another best practice to support WfP is also identified.     

Tracking the History of Romani Publications: Challenges Presented by Flawed Data

Romani is a language of northern Indic origin spoken natively by an estimated 2.5 million people, primarily in Eurasia but also in North America. The history of publication patterns in Romani has not been well documented. Extracting data about this history based on available information in large bibliographic databases such as OCLC WorldCat has been hampered by unfortunate misapplication of certain language codes, making it all but impossible to filter search results efficiently using Romani language as a parameter. The author discusses how he was able to correct much of this inaccurate data in OCLC WorldCat.     

突破边界——评彼得-保罗·维贝克的《将技术道德化:物之道德的理解与设计》

彼得-保罗·维贝克的著作《将技术道德化》,是现代技术哲学史上伦理转向的开端。该书揭示了存在于道德和技术人工物相互作用领域中的两个维度:新技术的应用带来了新的伦理问题,以及用经过专门设计的技术来改变人的道德行为。维贝克借此所提出的是一种物质化的伦理学观点。在与行动主体相互结合、相互构成的意义上,各种技术产品对道德抉择及行动也具有影响力,进而技术设计者可以被认为是"实践的伦理学家"。同时,对维贝克为实现技术民主而提出的"建构性的技术评价"进行了商榷。《将技术道德化》为技术哲学中经验转向和伦理转向的融合,做出了有益的尝试。     

Dissertations on Improvement of College Teaching – 1960

This article proposes the use of a new technology to assure student anonymity and reduce bias hazards: identifying students by using bar codes. The limited finding suggests that the use of bar codes for assuring student anonymity could potentially cause students to perceive that grades are assigned more fairly and reassure teachers that they are avoiding identity bias to the greatest extent possible. The authors recommend further implementation of bar code usage to investigate whether students and faculty could achieve positive perceptions as well as whether there are any drawbacks to such use.     

Improving teacher preparation and selection: lessons from the Pennsylvania experience

This paper examines Pennsylvania's teacher preparation and selection processes over the last decade. Teacher test scores are examined across colleges of education, and extreme differences in teacher test scores are found. Also, extreme variations are evident among districts' employed teachers. A unique survey of district employment practices reveals that, on average, 40% of a district's teachers previously attended there as students. An exploratory econometric model indicates that the higher the unemployment rate in a district, the more likely it will hire its former students to teach, and that the greater the fraction of former students now in the district's teacher force, the lower is student achievement. The paper concludes with a discussion of conventional and unconventional strategies to improve the quality of teachers actually hired by school boards.     

振动时效激振频率选择的探讨

振动时效激振频率的选择应综合考虑残余应力的集中程度、振动时效后残余应力分布及降低程度。对于结构简单,残余应力集中的构件,振动时效后要得到较低的残余应力状态,应选用较大的激振力,较低的激振频率。对于结构复杂,残余应力不集中的构件,宜采用较低的激振力和较高的振动频率。     

M68HC08单片机与PC机串行通信的实现

介绍了M68HC08系列单片机与PC机串行通信的实现方法,给出了硬件设计及通用程序实例, 该实例稍加修改即可用于Motorala其它型号的单片机,具有实际参考价值。