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991.
Jessica Granderson Jaspal S. Sandhu Domitila Vasquez Expedita Ramirez Kirk R. Smith 《Biomass & bioenergy》2009,33(2):306-315
This study examined the fuel use and design of an improved woodburning cookstove (plancha), in comparison to traditional cooking over an open woodfire. These cookstoves had been randomly introduced into population households in the Guatemalan Highlands that had previously used open woodfires. This research consisted of: (1) a 12-household Kitchen Performance Test (KPT) over a 4-day period and (2) single-day participant observation in five households. The KPT monitored fuel consumption and the number, age, and gender of people who were cooked for, while the participant observation was used to form a complete understanding of fuel use patterns and to examine the influence of stove condition and cooking behavior. In spite of fairly low variability in the fuel use data (coefficients of variation of about 0.34) the KPT did not show statistically significant differences in fuel use between the two cooking methods. It is possible that increased study power through a larger sample size may have resulted in a statistically significant difference in favor of the plancha, but it is doubtful that the size of the effect would be of any practical significance. Thus, although other studies have shown that the plancha is extremely effective in reducing indoor air pollution in the study area, the KPT did not indicate that it offered any benefits with respect to fuel use. Practical and experimental recommendations for future cookstove efficiency studies are presented, with directions for continued work in this area. 相似文献
992.
Huseyin Sehitoglu Tracy Smith Xinlin Qing Hans J. Maier J. A. Allison 《Metallurgical and Materials Transactions A》2000,31(1):139-151
The stress-strain behavior of cast 319-T6 aluminum-copper alloys with three different secondary dendrite arm spacings (SDASs)
was studied at high temperatures and under thermomechanical deformation, exposing marked cyclic softening. A two state-variable
unified inelastic constitutive model proposed earlier was modified to describe the stress-strain responses of these alloys
by considering the variation of hardening and recovery functions of back-stress and drag stress. The SDAS was incorporated
in the model as a length-scale parameter, and the material constants were determined systematically from experiments on a
cast 319-T6 aluminum with small and large SDASs. The capabilities of the constitutive model were checked by the comparisons
of simulations to experiments in the small-strain regime (<0.005). The results show that the model provides successful simulations
for material response after thermal exposure at high temperature and cyclic transient stress-strain behavior. The causes of
mechanical behaviors at the macro scale are discussed based on microstructural changes during thermal exposure. 相似文献
993.
994.
Political Communication Faces the 21st Century 总被引:1,自引:0,他引:1
995.
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997.
Hetherington M. G. Smith G. D. W. Jakubovics J. P. 《Metallurgical and Materials Transactions A》1986,17(9):1629-1631
Metallurgical and Materials Transactions A - 相似文献
998.
999.
1000.
C. D. Smith 《Journal of Computer Assisted Learning》1986,2(2):102-109
Abstract Two experiments were conducted to examine the effects of a period of training in the use of the turtle graphics aspects of LOGO on both attitudes towards computers and the learning of BASIC and statistics. A group of 15 subjects spent 10 hours learning LOGO . Their performance on subsequent learning of BASIC was significantly better than that of a control group, but no differences were found in attitudes towards computers or in the learning of statistics. 相似文献