This paper introduces a field measurement of an indoor thermal environment in rural housing in suburban Beijing from December 2008 to March 2009.The indoor environment parameters such as air temperature,mean radiant t...This paper introduces a field measurement of an indoor thermal environment in rural housing in suburban Beijing from December 2008 to March 2009.The indoor environment parameters such as air temperature,mean radiant temperature（MRT）,airflow velocity and relative humidity are measured.A questionnaire survey of the occupants＇ thermal sensations in these surveyed houses is conducted and their daily activities and clothing conditions are recorded.The results show that the thermal neutral temperature of rural housing is 18.4 ℃,and the lower limit of acceptable temperature range can be extended to 10.9 ℃.The comfortable indoor temperature is affected by the occupants＇ clothing and lifestyle.Therefore,the indoor temperature standards of space heating for suburban housing cannot be simply duplicated from that for urban housing.Compared with occupants in suburban Beijing,it is found that the occupants in rural Hunan province feel colder at the same operative temperature due to the high relative humidity in Hunan province.展开更多
Various dispersion models have been developed to simulate the fate and transport of air emissions from animal housing systems to meet the increasing need for knowledge in this area. However, the accuracy of the models...Various dispersion models have been developed to simulate the fate and transport of air emissions from animal housing systems to meet the increasing need for knowledge in this area. However, the accuracy of the models may be challenged due to the unknown plume rise and plume shape. This paper reports a combination of theoretical and field study of the plum rise and shape of air flow from a ventilation fan commonly used in mechanically ventilated animal houses. The theoretical modeling of the plume shape was conducted using a commercial Computational Fluid Dynamics (CFD) package named FloEFD;the field measurements of the plume field was conducted using five 3D ultrasonic anemometers to simultaneously measure the air flow in the plume at various locations (four heights and five downwind distances). The TECPLOT package was used to visualize the plume flow field based upon anemometer measurements. While the plume shapes were found to be left-shifted by the CFD model and TECPLOT visualization, the magnitudes of the 3D wind velocities from field measurement were found to be significantly larger than those from CFD model. The plume field measurements indicated that the plume of a 0.6 m (24-inch) ventilation fan had a depth about 9 m, a width about ±6 m, and a rise (lifting) beyond the highest measurement point, 4.88 m (16 ft).展开更多
Abstract Objective Higher levels of exposure to extremely low-frequency magnetic fields （ELF-MF） are associated with a slightly increased risk of childhood leukaemia. Compared with more-developed Western countries, ...Abstract Objective Higher levels of exposure to extremely low-frequency magnetic fields （ELF-MF） are associated with a slightly increased risk of childhood leukaemia. Compared with more-developed Western countries, higher exposure levels are evident in the Czech Republic, probably because of the different types of housing. In light of this, we aimed to examine the association between ELF-MF exposure and childhood leukaemia in the Czech Republic. Methods We conducted a paired case-control study. The cases （children with leukaemia） were age- sex- and permanent residence-matched to controls （children without leukaemia）. Although this limited potential bias and confounding, it also limited our number of participants. Results The matched analyses included 79 case-control pairs. No significant association between ELF-MF exposure and childhood leukaemia was observed for exposures over 0.2 μT （odds ratio [0R]=0.93, confidence interval [Cl]=0.45-1.93）, 0.3 μT （0R=0.77, Cl=0.34-1.75）, or 0.4 μT （OR=0.9, Cl=0.37-2.22）. Conclusion Despite higher levels of exposure in Middle and Eastern Europe, no indication of an association between ELF-MF exposure and childhood leukaemia was determined. This in contrast to the findings of previous studies conducted in different countries.展开更多
Prediction of electric field impact on residential houses is required in the design of UHVDC transmission lines.The calculation of electric field distribution on houses is a 3D problem,however,the effectiveness of som...Prediction of electric field impact on residential houses is required in the design of UHVDC transmission lines.The calculation of electric field distribution on houses is a 3D problem,however,the effectiveness of some 2D calculation meth-ods has been validated by specific reduced-scale experimental models.The 2D methods are simple in operation and quick in computation compared with the 3D methods.In this paper,the deviation ranges of 2D electric field calculation results on houses are discussed.Then,a 3D electric field reconstruction method is proposed to correct the 2D results according to the size and location of the houses.The 3D electric field distribution on the houses can be obtained based on efficient 2D calculations,and a direct 3D calculation is avoided.Finally,the validity of the calculation methods is verified by the measurement results of a full-scale experimental system.展开更多
基金The National Natural Science Foundation of China(No.50838003)the National Key Technology R&D Program of China during the 11th Five-Year Plan Period(No.2006BAJ02A06)
文摘This paper introduces a field measurement of an indoor thermal environment in rural housing in suburban Beijing from December 2008 to March 2009.The indoor environment parameters such as air temperature,mean radiant temperature（MRT）,airflow velocity and relative humidity are measured.A questionnaire survey of the occupants＇ thermal sensations in these surveyed houses is conducted and their daily activities and clothing conditions are recorded.The results show that the thermal neutral temperature of rural housing is 18.4 ℃,and the lower limit of acceptable temperature range can be extended to 10.9 ℃.The comfortable indoor temperature is affected by the occupants＇ clothing and lifestyle.Therefore,the indoor temperature standards of space heating for suburban housing cannot be simply duplicated from that for urban housing.Compared with occupants in suburban Beijing,it is found that the occupants in rural Hunan province feel colder at the same operative temperature due to the high relative humidity in Hunan province.
文摘Various dispersion models have been developed to simulate the fate and transport of air emissions from animal housing systems to meet the increasing need for knowledge in this area. However, the accuracy of the models may be challenged due to the unknown plume rise and plume shape. This paper reports a combination of theoretical and field study of the plum rise and shape of air flow from a ventilation fan commonly used in mechanically ventilated animal houses. The theoretical modeling of the plume shape was conducted using a commercial Computational Fluid Dynamics (CFD) package named FloEFD;the field measurements of the plume field was conducted using five 3D ultrasonic anemometers to simultaneously measure the air flow in the plume at various locations (four heights and five downwind distances). The TECPLOT package was used to visualize the plume flow field based upon anemometer measurements. While the plume shapes were found to be left-shifted by the CFD model and TECPLOT visualization, the magnitudes of the 3D wind velocities from field measurement were found to be significantly larger than those from CFD model. The plume field measurements indicated that the plume of a 0.6 m (24-inch) ventilation fan had a depth about 9 m, a width about ±6 m, and a rise (lifting) beyond the highest measurement point, 4.88 m (16 ft).
文摘Abstract Objective Higher levels of exposure to extremely low-frequency magnetic fields （ELF-MF） are associated with a slightly increased risk of childhood leukaemia. Compared with more-developed Western countries, higher exposure levels are evident in the Czech Republic, probably because of the different types of housing. In light of this, we aimed to examine the association between ELF-MF exposure and childhood leukaemia in the Czech Republic. Methods We conducted a paired case-control study. The cases （children with leukaemia） were age- sex- and permanent residence-matched to controls （children without leukaemia）. Although this limited potential bias and confounding, it also limited our number of participants. Results The matched analyses included 79 case-control pairs. No significant association between ELF-MF exposure and childhood leukaemia was observed for exposures over 0.2 μT （odds ratio [0R]=0.93, confidence interval [Cl]=0.45-1.93）, 0.3 μT （0R=0.77, Cl=0.34-1.75）, or 0.4 μT （OR=0.9, Cl=0.37-2.22）. Conclusion Despite higher levels of exposure in Middle and Eastern Europe, no indication of an association between ELF-MF exposure and childhood leukaemia was determined. This in contrast to the findings of previous studies conducted in different countries.
基金This work was supported in part by National Key Research and Development Program under Grant 2016YFB0900900in part by State Grid Corporation of China under Project GY71-18-008.
文摘Prediction of electric field impact on residential houses is required in the design of UHVDC transmission lines.The calculation of electric field distribution on houses is a 3D problem,however,the effectiveness of some 2D calculation meth-ods has been validated by specific reduced-scale experimental models.The 2D methods are simple in operation and quick in computation compared with the 3D methods.In this paper,the deviation ranges of 2D electric field calculation results on houses are discussed.Then,a 3D electric field reconstruction method is proposed to correct the 2D results according to the size and location of the houses.The 3D electric field distribution on the houses can be obtained based on efficient 2D calculations,and a direct 3D calculation is avoided.Finally,the validity of the calculation methods is verified by the measurement results of a full-scale experimental system.
