Purpose: To test the effectiveness of sitting surfaces with varied amounts of stability on muscle activity and energy expenditure.Methods: Using a within-participants repeated measures design, 11 healthy young-adult f...Purpose: To test the effectiveness of sitting surfaces with varied amounts of stability on muscle activity and energy expenditure.Methods: Using a within-participants repeated measures design, 11 healthy young-adult females(age = 20.0 ± 1.8 years) were measured using indirect calorimetry to assess energy expenditure, and electromyography to assess muscular activation in trunk and leg musculature under 3different sitting surfaces: flat-firm surface, air-filled cushion, and a stability ball. Data were analyzed using repeated measures analysis of variance with follow-up pairwise contrasts used to determine the specific effects of sitting surface on muscle activation and energy expenditure.Results: Significantly greater energy expenditure was recorded for the stability ball(p = 0.01) and the cushion(p = 0.03) over the flat surface(10.4% and 9.6% greater, respectively), with no differences between the ball and the cushion. Both the ball and the cushion produced higher tibialis anterior activation over the flat surface(1.09 and 0.63 root-mean-square millivolts(RMSmv), respectively), while the stability ball produced higher soleus activity over both cushion and flat surfaces(3.97 and 4.24 RMSmv, respectively). Additionally, the cushion elicited higher adductor longus activity over the ball and flat surfaces(1.76 and 1.81 RMSmv, respectively), but no trunk musculature differences were revealed.Conclusion: Compliant surfaces resulted in higher levels of muscular activation in the lower extremities facilitating increased caloric expenditure.Given the increasing trends in sedentary careers and the increases in obesity, this is an important finding to validate the merits of active sitting facilitating increased caloric expenditure and muscle activation.展开更多
The cooling effects of urban green vegetation cover, which can help decrease LST (land surface temperature) in urban area. When air temperature decreases, the electricity consumption of household will also mitigate ...The cooling effects of urban green vegetation cover, which can help decrease LST (land surface temperature) in urban area. When air temperature decreases, the electricity consumption of household will also mitigate loading. Meanwhile, that lack of assessment of green vegetation coverage impact to LST and electricity consumption, so that it could not clearly quantify the environmental contribution of green coves. In Taipei city, for example, FVC (fractional vegetation cover) value and LST was collected from Aster satellite remote sensing images, and data of household electricity consumption was acquired from Taiwan Power Company. Based on these three factors, it analyzed relative model. In the urban area, fractional vegetation cover might influence with land surface temperature and electricity consumption. The result shows that when the value of fractional vegetation cover is low, the air temperature is high. While fractional vegetation cover is increase, not only the land surface temperature is decreasing but the electricity consumption is also reducing. This study hopes can be the reference materials for the future metropolis plan and to inhibit the spread of urban thermal environment.展开更多
Entransy has been applied and studied in a broad range of heat transfer optimizations recently. Current study proposes the entransy of evaporators to conduct the optimization of heat exchangers in heating, ventilation...Entransy has been applied and studied in a broad range of heat transfer optimizations recently. Current study proposes the entransy of evaporators to conduct the optimization of heat exchangers in heating, ventilation, air conditioning and refrigeration systems. A novel finless bare tube heat exchanger was studied using a validated heat exchanger modeling tool. The capacity based optimization and entransy dissipation based thermal resistance were used and compared. The applicability of using entransy dissipation based thermal resistance in this type of heat exchanger optimization has been discussed. It has been demonstrated that minimizing entransy dissipation and maximizing capacity are equivalent to optimizing evaporators with fixed flow rates and different when optimizing evaporators with variable flow rates and the deviation is negligible when heat exchanger capacity is small(~1 k W) and more obvious as heat exchanger capacity increases. Thus entransy dissipation based thermal resistance could be used as an alternative optimization index to capacity for evaporators with fixed flow rate and small capacity evaporators with variable flow rates and should be used individually with capacity as an optimization index for evaporators with large capacity and variable flow rates.展开更多
Stark-chirped rapid adiabatic passage(SCRAP) is an important technique used for coherent quantum controls. In this paper we investigate how the practically-existing dissipation of the system influences on the efficien...Stark-chirped rapid adiabatic passage(SCRAP) is an important technique used for coherent quantum controls. In this paper we investigate how the practically-existing dissipation of the system influences on the efficiency of the passage, and thus the fidelities of the SCRAP-based quantum gates. With flux-biased Josephson qubits as a specifical example, our results show clearly that the efficiency of the logic gates implemented by SCRAP are robust against the weak dissipation. The influence due to the non-adiabtic transitions between the adiabatic passages is comparatively significantly small. Therefore, the SCRAP-based logic gates should be feasible for the realistic physical systems with noises.展开更多
文摘Purpose: To test the effectiveness of sitting surfaces with varied amounts of stability on muscle activity and energy expenditure.Methods: Using a within-participants repeated measures design, 11 healthy young-adult females(age = 20.0 ± 1.8 years) were measured using indirect calorimetry to assess energy expenditure, and electromyography to assess muscular activation in trunk and leg musculature under 3different sitting surfaces: flat-firm surface, air-filled cushion, and a stability ball. Data were analyzed using repeated measures analysis of variance with follow-up pairwise contrasts used to determine the specific effects of sitting surface on muscle activation and energy expenditure.Results: Significantly greater energy expenditure was recorded for the stability ball(p = 0.01) and the cushion(p = 0.03) over the flat surface(10.4% and 9.6% greater, respectively), with no differences between the ball and the cushion. Both the ball and the cushion produced higher tibialis anterior activation over the flat surface(1.09 and 0.63 root-mean-square millivolts(RMSmv), respectively), while the stability ball produced higher soleus activity over both cushion and flat surfaces(3.97 and 4.24 RMSmv, respectively). Additionally, the cushion elicited higher adductor longus activity over the ball and flat surfaces(1.76 and 1.81 RMSmv, respectively), but no trunk musculature differences were revealed.Conclusion: Compliant surfaces resulted in higher levels of muscular activation in the lower extremities facilitating increased caloric expenditure.Given the increasing trends in sedentary careers and the increases in obesity, this is an important finding to validate the merits of active sitting facilitating increased caloric expenditure and muscle activation.
文摘The cooling effects of urban green vegetation cover, which can help decrease LST (land surface temperature) in urban area. When air temperature decreases, the electricity consumption of household will also mitigate loading. Meanwhile, that lack of assessment of green vegetation coverage impact to LST and electricity consumption, so that it could not clearly quantify the environmental contribution of green coves. In Taipei city, for example, FVC (fractional vegetation cover) value and LST was collected from Aster satellite remote sensing images, and data of household electricity consumption was acquired from Taiwan Power Company. Based on these three factors, it analyzed relative model. In the urban area, fractional vegetation cover might influence with land surface temperature and electricity consumption. The result shows that when the value of fractional vegetation cover is low, the air temperature is high. While fractional vegetation cover is increase, not only the land surface temperature is decreasing but the electricity consumption is also reducing. This study hopes can be the reference materials for the future metropolis plan and to inhibit the spread of urban thermal environment.
基金supported by the sponsors of the Energy Efficiency and Heat Pumps Consortium and Modeling and Optimization Consortium at the Center for Environmental Energy Engineering(CEEE)of the University of Maryland and Heat Transfer Technologies LLC for manufacturing the heat exchanger prototype
文摘Entransy has been applied and studied in a broad range of heat transfer optimizations recently. Current study proposes the entransy of evaporators to conduct the optimization of heat exchangers in heating, ventilation, air conditioning and refrigeration systems. A novel finless bare tube heat exchanger was studied using a validated heat exchanger modeling tool. The capacity based optimization and entransy dissipation based thermal resistance were used and compared. The applicability of using entransy dissipation based thermal resistance in this type of heat exchanger optimization has been discussed. It has been demonstrated that minimizing entransy dissipation and maximizing capacity are equivalent to optimizing evaporators with fixed flow rates and different when optimizing evaporators with variable flow rates and the deviation is negligible when heat exchanger capacity is small(~1 k W) and more obvious as heat exchanger capacity increases. Thus entransy dissipation based thermal resistance could be used as an alternative optimization index to capacity for evaporators with fixed flow rate and small capacity evaporators with variable flow rates and should be used individually with capacity as an optimization index for evaporators with large capacity and variable flow rates.
基金Supported by the National Science Foundation under Grant Nos.90921010,11174373the National Fundamental Research Program of China under Grant No.2010CB923104+2 种基金National Research Foundation and Ministry of Education,Singapore under Grant No.WBS:R-710-000-008-271the 2013 Doctoral Innovation funds of Southwest Jiaotong Universitythe Fundamental Research Funds for the Central Universities
文摘Stark-chirped rapid adiabatic passage(SCRAP) is an important technique used for coherent quantum controls. In this paper we investigate how the practically-existing dissipation of the system influences on the efficiency of the passage, and thus the fidelities of the SCRAP-based quantum gates. With flux-biased Josephson qubits as a specifical example, our results show clearly that the efficiency of the logic gates implemented by SCRAP are robust against the weak dissipation. The influence due to the non-adiabtic transitions between the adiabatic passages is comparatively significantly small. Therefore, the SCRAP-based logic gates should be feasible for the realistic physical systems with noises.