Discussion on “Adaptive sliding-mode-observer for sensorless induction motor drive using two-time-scale approach”

This short communication is a discussion of the paper entitled “Adaptive sliding-mode-observer for sensorless induction motor drive using two-time-scale approach” by A. Mezouar, M.K. Fellah and S. Hadjeri published in the Simulation Modelling Practice and Theory 16 (2008) 1323–1336. In the discussed paper the authors present a current and flux sliding mode observer for the induction motor that also incorporates an adaptive laws in order to estimate the rotor speed and the inverse of the rotor time constant. However the proposed design for the observer and for the adaptive laws, employs the real value of the rotor time constant and the real value of the rotor speed, which are unknown, and therefore cannot be used in the observer design nor in the adaptive laws design.     

Characteristics and publication patterns of theses from a Peruvian medical school

Background: Many medical schools require a student thesis before graduation. Publishing results in a peer‐reviewed journal could be an indicator of scientific value and acceptability by the scientific community. The publication pattern of theses published by medical students in Peru is unknown. The aim of this study was to assess the characteristics and publication pattern of theses in biomedical‐indexed journals conducted by medical students in a university with the highest research output in Peru. Methods: Data from registered theses between 2000 and 2003 were obtained from the university library. Publication of theses in biomedical journals was assessed in 2008 by a search strategy using PubMed, Google Scholar, LILACS, LIPECS and SciELO. Results: Four hundred and eighty‐two medical theses were registered between 2000 and 2003; 85 (17.6%) were published in biomedical‐indexed journals. Of the published theses, 28 (5.8%) were published in MEDLINE‐indexed journals, 55 (11.4%) in SciELO‐indexed journals, 61 (12.6%) in LILACS‐indexed journals and 68 (14.1%) in LIPECS‐indexed journals. Most of the published theses (80%) were in Spanish and published in Peruvian journals; and 17 theses (20%) were published in foreign journals (all of them indexed in MEDLINE). In addition, 37 (43.5%) belong primarily to internal medicine, and 24 (28.2%) belong primarily to infectious diseases. Medical students were first authors in 71 (83.5%) of the articles. Conclusion: In this study, most of the published theses were in Spanish, published in local journals and indexed in LIPECS. The percentage of published theses in biomedical journals at this university is comparable with others coming from developed countries.     

Influence of surface roughness on the color of dental-resin composites

This study deals with the influence of surface roughness on the color of resin composites. Ten resin composites (microfilled, hybrid, and microhybrid) were each polished with 500-grit, 1 200-grit, 2 000-grit, and 4 000-grit SiC papers. The roughness parameter (R _a) was measured using a Plμ confocal microscope, and field-emission scanning electron microscope (Fe-SEM) images were used to investigate filler morphology. Color was measured using a spectroradiometer and a D65 standard illuminant (geometry diffuse/0° specular component excluded (SCE) mode). Surface roughness decreased with grit number and was not influenced by filler size or size distribution. A significant influence of R _a on lightness (L*) was found. Lightness increased with decreases in roughness, except for specimens that underwent polishing procedure 4 (PP4; 500-grit, 1 200-grit, 2 000-grit, and 4 000-grit SiC papers consecutively). Generally, it was found that surface roughness influenced the color of resin composites. The composites that underwent PP1 (500-grit SiC paper) exhibited significant differences in chroma (C*), hue (h°), and lightness (L*) compared to composites that underwent PP3 (500-grit, 1 200-grit, and 2 000-grit SiC papers consecutively) and PP4. Color difference (ΔE*) between the polishing procedures was within acceptability thresholds in dentistry.     

The relationship between homework and the academic progress of children in Spain during compulsory elementary education: A twin fixed-effects approach

Homework has traditionally been considered positive for students’ academic achievement, to the extent that it makes children more responsible while learning. Nevertheless, making students do a large amount of homework has been one of the most criticised practices in recent years. Parental associations have long held the view that Spanish elementary school pupils spend too much time on homework. This situation is so alarming that it has recently caused a ‘homework strike’, which has been supported by many children's parents. Furthermore, being assigned an excessive amount of homework is a serious problem which extends well beyond Spain. In light of this context, this article aims to provide new evidence on the relationship between homework and academic performance. To carry out this research, rich longitudinal census data, together with a twin fixed-effects approach and value-added models, have been used. In this way, we can control for variables that are the same within twins, allowing us to generate a better understanding of the association between homework time and primary children's academic achievement. Our main finding is that homework is not associated with young people's academic achievement (at least within this specific country context).     

Positive Aging Beyond “Success”: Towards a More Inclusive Perspective of High Level Functioning in Old Age

Successful aging is the ability to maintain low probability of disease and disability, high cognitive and physical functioning, and active engagement with life (Rowe &; Kahn, 1999 Rowe, J. W. &; Kahn, R. L. (1999). Successful aging. New York, NY: Dell Pub. [Google Scholar]). These criteria allow for a minority of people to be classified as being “successful” and overlook the importance of psychological variables in balancing the weight of disease. A total of 1322 seniors (55 + years) were classified on their overall functioning according to core domains (health, psychological, cognitive, biobehavioural, social, personality). Findings support the idea that a broader perspective of aging outcomes, rather than success criteria, may better reflect reality.     

The indigenous worldview of Yupiaq culture: Its scientific nature and relevance to the practice and teaching of science

Is science an invention of European thought, or have legitimate scientific bodies of knowledge and scientific ways of thinking emerged separately in other cultures? Can indigenous knowledge systems contribute to contemporary science teaching? Here we describe evidence from the Yupiaq culture in southwestern Alaska which demonstrates a body of scientific knowledge and epistemology that differs from that of Western science. We contend that drawing from Yupiaq culture, knowledge, and epistemology can provide not only a more culturally relevant frame of reference for teaching science concepts to Yupiaq students, but also a potentially valuable context for more effectively addressing many of the recommendations of U.S. science education reform initiatives. © 1998 John Wiley & Sons, Inc. J Res Sci Teach 35: 133–144, 1998.     

Self-Regulation and School Readiness

RESEARCH FINDINGS: In this article, we review research on the relations of self-regulation and its dispositional substrate, effortful control, to variables involved in school success. First, we present a conceptual model in which the relation between self-regulation/effortful control and academic performance is mediated by low maladjustment and high-quality relationships with peers and teachers, as well as school engagement. Then we review research indicating that effortful control and related skills are indeed related to maladjustment, social skills, relationships with teachers and peers, school engagement, as well as academic performance. PRACTICE OR POLICY: Initial findings are consistent with the view that self-regulatory capacities involved in effortful control are associated with the aforementioned variables; only limited evidence of mediated relations is currently available.     

Activity optimization method in SPECT： A comparison with ROC analysisActivity optimization method in SPECT： A comparison with ROC analysis

A discriminant method for optimizing activity in nuclear medicine studies is validated by comparison with ROC （received operating characteristic）-curves. The method is tested in 21 single photon emission computerized tomography （SPECT）, performed with a cardiac phantom. Three different lesions （Lb L2 and L3） were placed in the myocardium-wall by pairs fbr each SPECT. Three activities （84, 37 or 18.5 MBq） of 99mTc were used as background. Linear discriminant analysis was used to select the parameters that characterize image quality among the measured variables in the images [（Background-to-Lesion （B/Li） and Signal-to-Noise （S/N） ratios）]. Two clusters with different image quality （P=0.021 ） were obtained. The ratios B/Lj, B/L2 and B/L3 are the parameters used to construct the function with 100% of cases correctly classified into the clusters. The value of 37 MBq was the lowest tested activity for which good results for the B/Li ratios were obtained. The result coincides with the applied ROC-analysis （r=0.89）.