提心吊胆的华尔街

The war in Iraq, terrorism, rising oil prices-and now the threat of higher interest rates-are all preying on the market. There comes a point in virtually every bull market when     

An Automated Item Pool Assembly Framework for Maximizing Item Utilization for CAT

Computerized adaptive testing (CAT) has gained deserved popularity in the administration of educational and professional assessments, but continues to face test security challenges. To ensure sustained quality assurance and testing integrity, it is imperative to establish and maintain multiple stable item pools that are consistent in terms of psychometric characteristics and content specifications. This study introduces the Honeycomb Pool Assembly (HPA) framework, an innovative solution for the construction of multiple parallel item pools for CAT that maximizes item utilization in the item bank. The HPA framework comprises two stages—cell assembly and pool assembly—and uses a mixed integer programming modeling approach. An empirical study demonstrated HPA's effectiveness in creating a large number of parallel pools using a real-world high-stakes CAT assessment item bank. The HPA framework offers several advantages, including (a) simultaneous creation of multiple parallel pools, (b) simplification of item pool maintenance, and (c) flexibility in establishing statistical and operational constraints. Moreover, it can help testing organizations efficiently manage and monitor the health of their item banks. Thus, the HPA framework is expected to be a valuable tool for testing professionals and organizations to address test security challenges and maintain the integrity of high-stakes CAT assessments.     

Cell separation and transportation between two miscible fluid streams using ultrasound

This paper presents a two-stream microfluidic system for transporting cells or micro-sized particles from one fluid stream to another by acoustophoresis. The two fluid streams, one being the original suspension and the other being the destination fluid, flow parallel to each other in a microchannel. Using a half-wave acoustic standing wave across the channel width, cells or particles with positive acoustic contrast factors are moved to the destination fluid where the pressure nodal line lies. By controlling the relative flow rate of the two fluid streams, the pressure nodal line can be maintained at a specific offset from the fluid interface within the destination fluid. Using this transportation method, particles or cells of different sizes and mechanical properties can be separated. The cells experiencing a larger acoustic radiation force are separated and transported from the original suspension to the destination fluid stream. The other particles or cells experiencing a smaller acoustic radiation force continue flowing in the original solution. Experiments were conducted to demonstrate the effective separation of polystyrene microbeads of different sizes (3 μm and 10 μm) and waterborne parasites (Giardia lamblia and Cryptosporidium parvum). Diffusion occurs between the two miscible fluids, but it was found to have little effects on the transport and separation process, even when the two fluids have different density and speed of sound.     

Stress analysis of anisotropic thick laminates in cylindrical bending using a semi-analytical approach

Semi-analytical elasticity solutions for bending of angle-ply laminates in cylindrical bending are presented using the state-space-based differential quadrature method (SSDQM). Partial differential state equation is derived from the basic equations of elasticity based on the state space concept. Then, the differential quadrature (DQ) technique is introduced to discretize the longitu- dinal domain of the plate so that a series of ordinary differential state equations are obtained at the discrete points. Meanwhile, the edge constrained conditions are handled directly using the stress and displacement components without the Saint-Venant principle. The thickness domain is solved analytically based on the state space formalism along with the continuity conditions at interfaces. The present method is validated by comparing the results to the exact solutions of Pagano’s problem. Numerical results for fully clamped thick laminates are presented, and the influences of ply angle on stress distributions are discussed.     

Private Demand,Social Equity and Adult Education in Singapore

There are currently two views about the relationship between education and economic development. One rather narrow view treats education as an investment in people — in human capital — that raises productivity and national income just like investments in physical capital. Rational individuals invest in themselves when they see that private returns exceed private cost. Governments should invest in education that gives favourable social rates of returns. Their main function is to respond to the established pattern of demand for education. The second, and broader, view sees education not as a pure investment good, but as a powerful force that increases people's knowledge, changes their values and attitudes, and thus expanding their ability to absorb new technology. In this view, the expansion of educational opportunities is vital to the making of a modern society. Governments should provide education with the objective of creating a fully educated society — a society where everyone has at least six to ten years of formal education. They should create educational and training opportunities ahead of demand, with subsidies and compulsory schooling laws if necessary.     

Reflections on light monitoring: Evaluating museum lighting options for modern and contemporary art

Spectrometric handheld light meters that can provide adequate data for evaluation of replacement bulbs for contemporary art objects are now commercially available. This approach was taken to assess potential replacements for the incandescent street lamps in Chris Burden's Urban Light at LACMA, Los Angeles, USA. These meters are also useful tools for monitoring and characterizing museum lighting, which are currently done with illuminance (lux) meters. The new spectral light meters will enable conservators to tailor lighting recommendations for individual artworks, when spectral information from these meters is combined with damage function data on artists’ materials. The latter information can be obtained for some materials by a small modification to the microfade testing procedure, as exemplified by microfading colored samples Henri Matisse created during the design phase for La Gerbe.     

The changing role of school/media resource libraries in secondary schools in Singapore and the need to implement mandatory standards, 1946–2010: Issues, challenges and opportunities

The aim of this paper is to study the development and evolution of secondary school libraries into Media Resource Libraries (MRLs) in Singapore after the Second World War and the rationale to have mandatory school library standards. It is an historical survey analysing published data about the linkages of libraries and librarianship, school library standards, education and school reforms in Singapore. It analyses historical and current documents on the roles played by stakeholders like the Library Association of Singapore (LAS) and the Ministry of Education (MOE) in the introduction and development of school library standards. The need for school libraries standards was first discussed when the Malayan Library Group (MLG) organised the first course on librarianship for school teachers in 1955, but, with no follow through. The need for school libraries standards was also mentioned by the LAS in 1962 in a memorandum to the Commission of Enquiry into Education to train teacher librarians and adopt school library standards. However, this was left out in the final report of the Commission published in 1964. The need for school library standards was discussed in a school library seminar for 150 teacher librarians in 1970. The first Recommended Minimum Standards for Secondary School Libraries was published two years later by the Standing Committee on Libraries set up by the MOE, but it was not mandatory for schools to adopt the standards. In 1997 the MOE launched its “Thinking School Learning Nation” vision to teach thinking skills. Students were expected to do multidisciplinary project work and be independent users of information. The MOE began to convert school libraries into Media Resource Libraries (MRLs) with print and non-print materials. However, a survey conducted in 2001 on the roles and competencies of 112 Library Coordinators (LCs) or teacher librarians revealed that they lack the skills and knowledge to manage MRLs effectively. This is because subsequent school library standards published in 1983 and 2002 did not require trained and full-time teacher librarians to manage the MRLs. Furthermore, it is essential for the standards to be periodically updated with regards to professional staff, collection development, facilities, Information and Communications Technology (ICT) infrastructure and school library programs. Otherwise, MRLs risk being “hollow shells still considered on the periphery of core educational requirements, and are run by teachers not professionally prepared to do the work” (Hart, 2001, p. 25). The national standards published in the United States from 1918 to 2008 are well researched and provide substantive guidelines to develop school libraries. Therefore, it is essential for the MOE to formulate MRL standards by doing comparative studies of school library standards in other countries. These standards have to be mandatory and fully adopted by the schools. It provides opportunities for stakeholders like the LAS, National Library Board (NLB), the National Institute of Education (NIE), and the Singapore Teachers’ Union, to collaborate in the formulation of these standards and take collective ownership to implement them.     

Developmental dyslexia revisited and projected

There are three parts to this paper. First, I review briefly the signposts from research, theory, and application in developmental dyslexia in the 1960s and the 1970s that have led us from there to here, and show the pitfalls to avoid. Second, I discuss some of the pertinent issues of the 1980s: the role of intelligence in the diagnosis of children with specific reading disabilities, the distribution of reading difficulties and disabilities, and the important place of verbal efficiency. Third, I project to the 1990s to emphasize the challenge of the computer technology as mediated learning and the challenge of “bounded rationality” and “collective rationality” in education. Throughout this survey, the paramount role of knowledgeable and caring teachers is implicit. Portions of this paper were given at the British Dyslexia Association Conference on Dyslexia in Bath in 1989 and The Orton Dyslexia Society Annual Conference in Washington, D.C. in 1990. The writing of the paper was assisted in part by research grant No. 410-89-0128 from the Social Sciences and Humanities Research Council of Canada