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Aerodynamic efficiency is one of the important criteria for racing bicycle helmets, especially in time trial event. The physical characteristics of a bicycle helmet especially its venting geometry, position and number of vents play a crucial role in the aerodynamic efficiency of the helmet. Despite the importance of this, little information on aerodynamic behaviour of racing bicycle helmets is available. In this study, a series of commercially available time trial helmets were investigated in a wind tunnel environment over a range of wind speeds, and yaw and pitch angles to understand their aerodynamic behaviour. In order to obtain as realistic a data as possible, an instrumented mannequin was used in the wind tunnel testing. The experimental findings indicate that the aerodynamic performance of current production time trial helmets varies significantly. The results also show that helmet length as well as vent geometry and vent area have significant effects on aerodynamic drag of a time trial helmet. A time trial helmet having longer length and smooth vents with minimum vent area can reduce aerodynamic drag significantly. 相似文献
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Imidacloprid in processed tea and tea liquor 总被引：1，自引：0，他引：1
Sanyal N Hazra D Pal R Somchaudhury AK Chowdhury A 《Journal of Zhejiang University. Science. B》2006,7(8):619-622
Imidacloprid is a newly introduced broad-spectrum chloronicotinyl insecticide and will find its way in agricultural production, particularly in Asia. However, information on the fate of imidacloprid in crop plants is lacking. The degradation of imidaclopnd in processed CTC tea and tea liquor was investigated in the present study in which imidacloprid was applied at recommended application rate （30.0 g a.i./ha） and twice the recommended application rate （60.0 g a.i./ha） for three consecutive seasons. Imidacloprid was rapidly dissipated in processed tea following first order reaction kinetics at all application rates and had half-lives of 0.9 1-1.16 d with the residue in tea liquor found to be below detectable limit on 3rd day samples. The study revealed that imidacloprid is safe for human consumption and will not pose any residual toxicity problem. 相似文献
24.
Bicycle aerodynamics: an experimental evaluation methodology 总被引：1，自引：1，他引：0
Aerodynamically efficient sports equipment/accessories and athlete body postures are considered to be the fundamental aspect to achieve superior performance. Like other speed sports, the aerodynamic optimisation is more crucial in cycling. A standard full-scale testing methodology for the aerodynamic optimisation of a cyclist along with all accessories (e.g., bicycle, helmet, cycling suit, shoes and goggle) is not well developed, documented, and standardised. This paper describes a design and development of a full-scale testing methodology for the measurement of aerodynamic properties as a function of cyclist body positions along with various accessories over a range of wind speeds. The experimental findings indicate that the methodology can be used for aerodynamic optimisation of all cycling sports. 相似文献
25.
Recent research indicates that Tourette syndrome is more prevalent than was once thought and that teachers in most mainstream schools are likely to encounter pupils displaying the characteristics of Tourette syndrome. Research also indicates that these characteristics, and the range of responses that may be appropriate, are not well understood by school staff. In this article, Dr Uttom Chowdhury, Consultant Child Psychiatrist at the CAMHS Academic Unit in Dunstable and Honorary Child Psychiatrist at the Neurodevelopmental Disorders Clinic at Great Ormond Street Hospital, London, and Dr Deborah Christie, Consultant Clinical Psychologist and Honorary Senior Lecturer at the Department of Child and Adolescent Psychological Services at University College London and Middlesex Hospitals, describe a training day for teachers facilitated by members of the Tic Disorders Clinic at Great Ormond Street Hospital. The day provided a mix of information–giving and discussion of current practice. Uttom Chowdhury and Deborah Christie relate the outcomes of the day to their own professional knowledge and experience and offer an interesting agenda for further developments. 相似文献
26.
Debashish Chowdhury 《Resonance》2007,12(2):39-58
In the first part of this article, we read about Alice’s guided tour through the cellular microfactory. In the second part,
I introduce the methods of studying the materials and mechanisms of the molecular machines through dialogues. The three participants
in this discussion are Alice, her elder brother Alex and her father Albert. The style of presentation here is adapted from
Galileo’s Dialogue Concerning the Two Chief World Systems. Albert, a professor of biophysics, emphasizes the crucial differences between the mechanisms of the natural nano-machines
and those of their macroscopic counterparts. He also points out some practical applications of this interdisciplinary research
in biomedical science and nano-technology.
Debashish Chowdhury is a professor of Physics at IIT Kanpur. He is a theoretical physicist and the areas of his research interest
are statistical and biological physics. He plays with toy models using mathematical formulae and simulates nature with computers. 相似文献
27.
Chowdhury A. Mushtaque R. Nath Samir R. Choudhury Rasheda K. 《International Review of Education/Internationale Zeitschrift für Erziehungswissenschaft/Revue internationale l'éducation》2003,49(6):601-619
Although equity is a desirable objective of any form of development intervention, including education, not many studies dwell upon this important area. Information on related trends is even more rare. This essay uses field-level data from Bangladesh to examine equity levels and trends in primary education, including enrolment and quality of learning, focusing on equity for different gender, urban or rural, economic and ethnic groups. The study shows that while some disparity between girls and boys has been eliminated, girls are still far behind boys in terms of learning achievement. Children belonging to poorer families and ethnic minority groups lag behind the respective dominant groups in terms of both enrolment and learning achievement. At the same time, there have been some improvements for hitherto excluded groups such as rural girls and children of the poor. These changes are attributed mainly to 'positive discriminatory' steps taken by the government and non-governmental organizations in favour of such groups. If this trend continues, Bangladesh can look forward to establishing itself as a more equitable society than it is now. 相似文献
28.
Using data generated through two nationally representative sample surveys, this paper explores the trends in the level of basic education of Bangladeshi children. The instrument used for the purpose was based on the Declaration of the World Conference on Education for All (WCEFA, Jomtien, 1990). The findings reveal that the level of 'basic education' increased very slowly, 26.7% in 1993 to 29.6% in 1998, less than one percentage point per year. Statistically significant improvement was observed in 'life skills knowledge' and 'writing skills', but not in 'reading' or 'numeracy'. Girls progressed in 'reading', 'writing' and 'life skills', while the boys in 'writing' and 'life skills'. Over the period, the level improved for rural children but decreased for urban children. Bangladesh falls much behind the targets of the Jomtien Conference in 1990; it will have to wait until 2093 AD to reach the WCEFA goal. The country has made good progress in increasing the access to primary education, but a massive drive is necessary to improve the quality of education. 相似文献
29.
Bibliometric cartography of information retrieval research by using co-word analysis 总被引：6，自引：0，他引：6
The aim of this study is to map the intellectual structure of the field of Information Retrieval (IR) during the period of 1987–1997. Co-word analysis was employed to reveal patterns and trends in the IR field by measuring the association strengths of terms representative of relevant publications or other texts produced in IR field. Data were collected from Science Citation Index (SCI) and Social Science Citation Index (SSCI) for the period of 1987–1997. In addition to the keywords added by the SCI and SSCI databases, other important keywords were extracted from titles and abstracts manually. These keywords were further standardized using vocabulary control tools. In order to trace the dynamic changes of the IR field, the whole 11-year period was further separated into two consecutive periods: 1987–1991 and 1992–1997. The results show that the IR field has some established research themes and it also changes rapidly to embrace new themes. 相似文献
30.
Debashish Chowdhury 《Resonance》2005,10(9):63-78
Experimental verification of the theoretical predictions made by Albert Einstein in his paper, published in 1905, on the molecular
mechanisms of Brownian motion established the existence of atoms. In the last 100 years Brownian motion has not only revolutionized
our fundamental understanding of the nature ofthermal fluctuations in physical systems, but it has also explained many counterintuitive phenomena in earth and environmental sciences as well
as in life sciences. This 2-part article begins with a brief historical survey and an introduction to the concepts and theoretical
techniques for studying Brownian motion. Then, in Part 2 a discussion on rotational Brownian motion and Brownian shape fluctuations
of soft materials is followed by an elementary introduction to two of the hottest topics in this contemporary area of interdisciplinary
research, namely,stochastic resonance andBrownian ratchet. 相似文献