On the parallel lines for nondegenerate conics

Computation of parallel lines (envelopes) to parabolas, ellipses, and hyperbolas is of importance in structure engineering and theory of mechanisms. Homogeneous polynomials that implicitly define parallel lines for the given offset to a conic are found by computing Groebner bases for an elimination ideal of a suitably defined affine variety. Singularity of the lines is discussed and their singular points are explicitly found as functions of the offset and the parameters of the conic. Critical values of the offset are linked to the maximum curvature of each conic. Application to a finite element analysis is shown. Keywords: Affine variety, elimination ideal, Groebner basis, homogeneous polynomial, singularity, family of curves, envelope, pitch curve, undercutting, cam surfaceComment: 40 pages, 10 figures, TOC, 3 appendices, short version of this paper was presented at the 5th Annual Hawaii International Conference on Statistics, Mathematics and Related Fields, January 16 - 18, 2006, Honolulu Hawaii, US

Export Outsourcing and Foreign Direct Investment: Evidence from Taiwanese Exporting Firms

Exporting and FDI have traditionally been two major firm-level responses to globalization. Export outsourcing (EO), a new strategy that gained in importance recently, has now become another alternative. This paper seeks to examine how firms choose between EO and outward FDI by looking into firm-level productivity differences. A special data set is constructed by consolidating two micro data sets of Taiwanese manufacturing firms. The paper contributes in four main ways. First, it provides a causality analysis of labor productivity and EO, whereas previous studies deal only with correlations. Second, it shows that EO can be interpreted as an indirect way of exporting. Third, it points out that outward FDI itself may not help with productivity if it is not linked with EO, which finding contradicts conventional wisdom. Finally, most evidences seem to imply that the intricate Taiwan-China interconnection is a significant factor that facilitates or contributes to all above-mentioned findings.productivity, exports, foreign outsourcing, FDI, firm-level data

PERTS: A Prototyping Environment for Real-Time Systems

PERTS is a prototyping environment for real-time systems. It is being built incrementally and will contain basic building blocks of operating systems for time-critical applications, tools, and performance models for the analysis, evaluation and measurement of real-time systems and a simulation/emulation environment. It is designed to support the use and evaluation of new design approaches, experimentations with alternative system building blocks, and the analysis and performance profiling of prototype real-time systems

Producing approximate answers to database queries

We have designed and implemented a query processor, called APPROXIMATE, that makes approximate answers available if part of the database is unavailable or if there is not enough time to produce an exact answer. The accuracy of the approximate answers produced improves monotonically with the amount of data retrieved to produce the result. The exact answer is produced if all of the needed data are available and query processing is allowed to continue until completion. The monotone query processing algorithm of APPROXIMATE works within the standard relational algebra framework and can be implemented on a relational database system with little change to the relational architecture. We describe here the approximation semantics of APPROXIMATE that serves as the basis for meaningful approximations of both set-valued and single-valued queries. We show how APPROXIMATE is implemented to make effective use of semantic information, provided by an object-oriented view of the database, and describe the additional overhead required by APPROXIMATE

Mentat: An object-oriented macro data flow system

Mentat, an object-oriented macro data flow system designed to facilitate parallelism in distributed systems, is presented. The macro data flow model is a model of computation similar to the data flow model with two principal differences: the computational complexity of the actors is much greater than in traditional data flow systems, and there are persistent actors that maintain state information between executions. Mentat is a system that combines the object-oriented programming paradigm and the macro data flow model of computation. Mentat programs use a dynamic structure called a future list to represent the future of computations

Who Are We and Who Are They? A Comparison of Philosophical Beliefs Between American and Chinese Teacher Education Students

The purpose of this study was to compare and contrast philosophical beliefs commonly shared among American pre-service and in-service teachers and their Chinese counterparts. A total of 100 responses was included in this study. A philosophical inventory with 34 items was used. The causes for the similarities and differences as indicated in the findings were examined. This study pointed out the danger of stereotyping people based on cultural backgrounds. lt also encouraged teacher educators to challenge our own habitual view and vision of our practice

Discovery of a mRNA Mitochondrial Localization Element in Saccharomyces Cerevisiae by Nonhomologous Random Recombination and In Vivo Selection

In budding yeast, over 100 nuclear-encoded mRNAs are localized to the mitochondria. The determinants of mRNA localization to the mitochondria are not well understood, and protein factors involved in this process have not yet been identified. To reveal the sequence determinants for mitochondrial localization in a comprehensive and unbiased manner, we generated highly diversified libraries of 3’ UTR regions from a known mitochondrially localized mRNA by nonhomologous random recombination (NRR) and subjected the resulting sequences to an in vivo selection that links cell survival to mitochondrial mRNA localization. When applied to the yeast ATP2 mRNA, this approach rapidly identified a 50-nt consensus motif, designated Min2, as well as two Min2-homologous regions naturally present downstream of the ATP2 stop codon, which are sufficient when appended to the 3’ end of various reporter mRNAs to induce mitochondrial localization. Sitedirected mutagenesis of Min2 revealed primary and secondary structure elements that contribute to localization activity. In addition, the Min2 motif may facilitate the identification of proteins involved in this mode of establishing cellular asymmetry.Chemistry and Chemical Biolog

Adaptive Guidance: Effects On Self-Regulated Learning In Technology-Based Training

Guidance provides trainees with the information necessary to make effective use of the learner control inherent in technology-based training, but also allows them to retain a sense of control over their learning (Bell & Kozlowski, 2002). One challenge, however, is determining how much learner control, or autonomy, to build into the guidance strategy. We examined the effects of alternative forms of guidance (autonomy supportive vs. controlling) on trainees’ learning and performance, and examined trainees’ cognitive ability and motivation to learn as potential moderators of these effects. Consistent with our hypotheses, trainees receiving adaptive guidance had higher levels of knowledge and performance than trainees in a learner control guidance. Controlling guidance had the most consistent positive impact on the learning outcomes, while autonomy supportive guidance demonstrated utility for more strategic outcomes. In addition, guidance was generally more effective for trainees with higher levels of cognitive ability and autonomy guidance served to enhance the positive effects of motivation to learn on the training outcomes