Wind microturbines typically have rotor diameters of 2 m or less. This paper presents theoretical expressions that can be used to determine the aerodynamic performance of wind microturbines. A commercially-available t...Wind microturbines typically have rotor diameters of 2 m or less. This paper presents theoretical expressions that can be used to determine the aerodynamic performance of wind microturbines. A commercially-available three-bladed microturbine was tested at the outlet plane of a wind tunnel. The cross-section dimensions of the wind tunnel jet are 2.5 m （horizontal） x 1.5 m （vertical）. The tested microturbine has a diameter of 1.2 m, and it generates a maximum power output of about 300 W. The paper provides the wind tunnel test methodology that was used to determine the mean and fluctuating forces generated by the aforementioned wind microturbine. Both the static and dynamic responses of the turbine were measured, and results from this testing are presented in this paper. These results enable the trends and predictions of the theoretical expressions to be compared with wind tunnel measurements. It is shown that, for this particular microturbine, the behaviours of these test measurements are consistent with the expected theoretical predictions.展开更多
The traffic-induced vibrations of the new CCTV Headquarters building are studied stages. In the first stage when the through experiments in two 30th floor of the northwest tower and the 38th floor of the southeast tow...The traffic-induced vibrations of the new CCTV Headquarters building are studied stages. In the first stage when the through experiments in two 30th floor of the northwest tower and the 38th floor of the southeast tower were finished, the traffic flows on the roads surrounding the building were investigated, and 27 setups of accelerations were measured at the roadside, on the pile cap and on the 9th floor. In the second stage when the whole steel structure was completed, l 5 setups of accelerations were measured at the roadside, on the pile cap and on the 37th and the 48th floors. The accelerations of the building under different traffic flows, in different positions are analyzed in both time domain and frequency domain. The damping ratios are estimated by the upgraded half-power bandwidth method.展开更多
The aim of this paper is to describe and analyse the behaviour of heart rate variability(HRV)during constant-load,high-intensity exercise using a time frequency analysis(Wavelet Transform).Eleven elite cyclists took p...The aim of this paper is to describe and analyse the behaviour of heart rate variability(HRV)during constant-load,high-intensity exercise using a time frequency analysis(Wavelet Transform).Eleven elite cyclists took part in the study(age:18.6±3.0 years;VO_(2max):4.88±0.61 litres·min^(-1)).Initially,all subjects performed an incremental cycloergometer test to determine load power in a constant load-test(379.55±36.02 W;89.0%).HRV declined dramatically from the start of testing(p<0.05).The behaviour of power spectral density within the LF band mirrored that of total energy,recording a significant decrease from the outset LF peaks fell rapidly thereafter,remaining stable until the end of the test.HF-VHF fell sharply in the first 20 to 30 seconds.The relative weighting(%) of HF-VHF was inverted with the onset of fatigue,[1.6%at the start,7.1(p<0.05) at the end of the first phase,and 43.1%(p<0.05) at the end of the test].HF-VHF_(peak) displayed three phases:a moderate initial increase,followed by a slight fall,thereafter increasing to the end of the test.The LF/HF-VHF ratio increased at the start,later falling progressively until the end of the first phase and remaining around minimal values until the end of the test.展开更多
文摘Wind microturbines typically have rotor diameters of 2 m or less. This paper presents theoretical expressions that can be used to determine the aerodynamic performance of wind microturbines. A commercially-available three-bladed microturbine was tested at the outlet plane of a wind tunnel. The cross-section dimensions of the wind tunnel jet are 2.5 m （horizontal） x 1.5 m （vertical）. The tested microturbine has a diameter of 1.2 m, and it generates a maximum power output of about 300 W. The paper provides the wind tunnel test methodology that was used to determine the mean and fluctuating forces generated by the aforementioned wind microturbine. Both the static and dynamic responses of the turbine were measured, and results from this testing are presented in this paper. These results enable the trends and predictions of the theoretical expressions to be compared with wind tunnel measurements. It is shown that, for this particular microturbine, the behaviours of these test measurements are consistent with the expected theoretical predictions.
基金The study is sponsored by the National Natural Science Foundation of China （No. 50538010） and the Flander （Belgium）-China Bilateral Project （,No. BIL 07/07）.
文摘The traffic-induced vibrations of the new CCTV Headquarters building are studied stages. In the first stage when the through experiments in two 30th floor of the northwest tower and the 38th floor of the southeast tower were finished, the traffic flows on the roads surrounding the building were investigated, and 27 setups of accelerations were measured at the roadside, on the pile cap and on the 9th floor. In the second stage when the whole steel structure was completed, l 5 setups of accelerations were measured at the roadside, on the pile cap and on the 37th and the 48th floors. The accelerations of the building under different traffic flows, in different positions are analyzed in both time domain and frequency domain. The damping ratios are estimated by the upgraded half-power bandwidth method.
文摘The aim of this paper is to describe and analyse the behaviour of heart rate variability(HRV)during constant-load,high-intensity exercise using a time frequency analysis(Wavelet Transform).Eleven elite cyclists took part in the study(age:18.6±3.0 years;VO_(2max):4.88±0.61 litres·min^(-1)).Initially,all subjects performed an incremental cycloergometer test to determine load power in a constant load-test(379.55±36.02 W;89.0%).HRV declined dramatically from the start of testing(p<0.05).The behaviour of power spectral density within the LF band mirrored that of total energy,recording a significant decrease from the outset LF peaks fell rapidly thereafter,remaining stable until the end of the test.HF-VHF fell sharply in the first 20 to 30 seconds.The relative weighting(%) of HF-VHF was inverted with the onset of fatigue,[1.6%at the start,7.1(p<0.05) at the end of the first phase,and 43.1%(p<0.05) at the end of the test].HF-VHF_(peak) displayed three phases:a moderate initial increase,followed by a slight fall,thereafter increasing to the end of the test.The LF/HF-VHF ratio increased at the start,later falling progressively until the end of the first phase and remaining around minimal values until the end of the test.
