针对传统Buck变换器受最小占空比限制的影响,无法适用于高降压比场合的问题,提出了一种新型无变压器高降压DC-DC变换器。首先,详细地分析了所提变换器的工作模态和开关时序。其次,在控制层面,该变换器应用交错式脉宽调制的开关模式,不...针对传统Buck变换器受最小占空比限制的影响,无法适用于高降压比场合的问题,提出了一种新型无变压器高降压DC-DC变换器。首先,详细地分析了所提变换器的工作模态和开关时序。其次,在控制层面,该变换器应用交错式脉宽调制的开关模式,不但增加了其带载能力,还极大减少了元器件的电压应力。对新型高降压比变换器的工作过程进行分析,同时在理论上进行了参数设计。最后,搭建500/26 V 430 W的样机进行实验,实验结果充分证明了理论的正确性和可行性。展开更多
针对传统单级DC/DC变换器高降压变换困难的以及发电间歇问题及电网惯性不足的问题,文中提出了一种具有虚拟连轴电机特性的高降压比直流固态变压器(DC Electronic Power Transformer,DCEPT)控制方法。控制策略可在维持直流配网稳定的同...针对传统单级DC/DC变换器高降压变换困难的以及发电间歇问题及电网惯性不足的问题,文中提出了一种具有虚拟连轴电机特性的高降压比直流固态变压器(DC Electronic Power Transformer,DCEPT)控制方法。控制策略可在维持直流配网稳定的同时实现对上级高压电网的自主响应与功率支持。为直流并网接口提供惯性支持,有效实现对上级电网的惯性和阻尼支撑。拓扑具有降压比较高、负载响应速度快、具有较好的抗干扰能力。仿真结果验证了所提拓扑方法以及虚拟联轴控制策略的有效性。展开更多
The greenhouse has been increasingly used in the breeding industry. However, the high temperature inside the greenhouse in summer has not been effectively addressed. The spray cooling system sprays tiny droplets into ...The greenhouse has been increasingly used in the breeding industry. However, the high temperature inside the greenhouse in summer has not been effectively addressed. The spray cooling system sprays tiny droplets into the air. Thus the water molecules will be vaporized, absorbing heat and reducing ambient temperature. It is the only cooling method that can be used to cool the uneasily-sealed flexible greenhouse. We developed an energy-storing high pressure spray cooling system. The ordinary water pump is used as the source of high-pressure water. The partial kinetic energy is stored in the energy-storing tubes. When the water pump is stopped, the energy produced by releasing the compressed air can still be used to maintain the spray. And thus the use-cost and systematic wear would be reduced. The cooling system only requires 1 kilowatt hour of power per day. It has been widely used in summer to cool the breeding sheds. After a recent continuous improvement, its functions have been extended to disinfection, removing dust, humidifying and immunizing animals. In addition, it can also be used for the cooling and humidifying of squares, venues and streets in summer. The energy-storing high pressure spray cooling system has a broad application prospect.展开更多
The hydrodynamics and mass transfer of Plum Flower Mini Ring (PFMR), Pall Ring and Intalox Saddle were studied in a 600 mm diameter column with air-oxygen-water system over a wide range of liquid loads. It was shown f...The hydrodynamics and mass transfer of Plum Flower Mini Ring (PFMR), Pall Ring and Intalox Saddle were studied in a 600 mm diameter column with air-oxygen-water system over a wide range of liquid loads. It was shown from the experiments that PFMR had much lower resistance, larger throughput and higher mass transfer efficiency than Pall Ring and Intalox Saddle. It was clear from the comparison that existing equations could not predict the performance of packings very well at high liquid loads. Therefore, new semi-empirical equations of pressure drop, flooding gas velocity and height of transfer unit (HTU) were proposed based on the experimental data.展开更多
The impact of the subtropical high (STH) on precipitation was investigated on a daily timescale using matched NCEP and the Global Precipitation Climatology Project (GPCP) datasets.Comparison of the conditional probabi...The impact of the subtropical high (STH) on precipitation was investigated on a daily timescale using matched NCEP and the Global Precipitation Climatology Project (GPCP) datasets.Comparison of the conditional probability (intensity) of precipitation under STH condi-tions with that under non-STH conditions suggests that the presence of the STH conditions has a limited impact on local precipitation.In the West Pacific Subtropical High (WPSH) and the North Atlantic Subtropical High (NASH),precipitation was only 30% lower under STH conditions than under non-STH conditions.The STH conditions had somewhat more impact on precipitation intensity,but it was still 50% less than the intensity under non-STH conditions (mean of roughly 5 mm d 1).Pre-cipitation under STH conditions was found to be highly correlated with vertical motion.Active updrafts occurring even under STH conditions are essential for frequent oc-currences and moderate intensities of precipitation.展开更多
In order to observe the therapeutic effects of Huanglian Fire-Purging Mixture (黄连清降合剂) on primary hypertension, 46 cases of primary hypertension in the treatment group were treated with Huanglian Fire-Purging Mi...In order to observe the therapeutic effects of Huanglian Fire-Purging Mixture (黄连清降合剂) on primary hypertension, 46 cases of primary hypertension in the treatment group were treated with Huanglian Fire-Purging Mixture to clear away heat from the liver, relieve mental stress, purge fire and remove toxin;and the other 26 cases of primary hypertension in the control group were treated with Niuhuang Bolus for Lowering Blood Pressure (牛黄降压丸). The effect in the treatment group was obviously superior to that in the control group (P＜0.05). The Huanglian Fire-Purging Mixture shows noticeable effects 3-6 hours after medication. The mixture can improve the clinical symptoms, the left ventricular diastolic function and myocardial ischemia, correct dyslipoproteinemia and dysglycemia, and reduce blood viscosity. And it is safe and with no obvious adverse reactions.展开更多
A three-dimensional diesel particulate filter(DPF)simulation model was developed by using AVL software FIRE to study the effects of four factors on soot particle distributions along the axial and radial directions in ...A three-dimensional diesel particulate filter(DPF)simulation model was developed by using AVL software FIRE to study the effects of four factors on soot particle distributions along the axial and radial directions in the DPF after the model accuracy was validated.An orthogonal test method was used to determine the importance and weights of the design of experiments(DoE)factors such as the expanding angle,the number of channels per square inch,and the exhaust mass flow rate.The effects of these factors on the uniformity of the soot particle distributions were also analyzed.The results show that when the soot loading time was 400 s,the soot particles inside the DPF along the axial direction exhibited a bowl shape,which was high on the both ends and low in the middle.The uniformity of the axial distribution of soot particles reduces significantly with an increase in the number of channels per square inch.The uniformity of the radial distribution reduced with an increase in the expanding angle of the divergent tube.Based on the impacts on the axial uniformity,the three most influencing factors in a descending order are the number of channels per square inch,the exhaust mass flow rate,and the expanding angle of the divergent tube.展开更多
文摘针对传统Buck变换器受最小占空比限制的影响,无法适用于高降压比场合的问题,提出了一种新型无变压器高降压DC-DC变换器。首先,详细地分析了所提变换器的工作模态和开关时序。其次,在控制层面,该变换器应用交错式脉宽调制的开关模式,不但增加了其带载能力,还极大减少了元器件的电压应力。对新型高降压比变换器的工作过程进行分析,同时在理论上进行了参数设计。最后,搭建500/26 V 430 W的样机进行实验,实验结果充分证明了理论的正确性和可行性。
文摘针对传统单级DC/DC变换器高降压变换困难的以及发电间歇问题及电网惯性不足的问题,文中提出了一种具有虚拟连轴电机特性的高降压比直流固态变压器(DC Electronic Power Transformer,DCEPT)控制方法。控制策略可在维持直流配网稳定的同时实现对上级高压电网的自主响应与功率支持。为直流并网接口提供惯性支持,有效实现对上级电网的惯性和阻尼支撑。拓扑具有降压比较高、负载响应速度快、具有较好的抗干扰能力。仿真结果验证了所提拓扑方法以及虚拟联轴控制策略的有效性。
基金Supported by Jiangsu Agricultural Science and Technology Innovation Fund[CX(12)1001-04]~~
文摘The greenhouse has been increasingly used in the breeding industry. However, the high temperature inside the greenhouse in summer has not been effectively addressed. The spray cooling system sprays tiny droplets into the air. Thus the water molecules will be vaporized, absorbing heat and reducing ambient temperature. It is the only cooling method that can be used to cool the uneasily-sealed flexible greenhouse. We developed an energy-storing high pressure spray cooling system. The ordinary water pump is used as the source of high-pressure water. The partial kinetic energy is stored in the energy-storing tubes. When the water pump is stopped, the energy produced by releasing the compressed air can still be used to maintain the spray. And thus the use-cost and systematic wear would be reduced. The cooling system only requires 1 kilowatt hour of power per day. It has been widely used in summer to cool the breeding sheds. After a recent continuous improvement, its functions have been extended to disinfection, removing dust, humidifying and immunizing animals. In addition, it can also be used for the cooling and humidifying of squares, venues and streets in summer. The energy-storing high pressure spray cooling system has a broad application prospect.
文摘The hydrodynamics and mass transfer of Plum Flower Mini Ring (PFMR), Pall Ring and Intalox Saddle were studied in a 600 mm diameter column with air-oxygen-water system over a wide range of liquid loads. It was shown from the experiments that PFMR had much lower resistance, larger throughput and higher mass transfer efficiency than Pall Ring and Intalox Saddle. It was clear from the comparison that existing equations could not predict the performance of packings very well at high liquid loads. Therefore, new semi-empirical equations of pressure drop, flooding gas velocity and height of transfer unit (HTU) were proposed based on the experimental data.
基金supported by Special Funds for Public Welfare of China (Grant No.GYHY-QX-2007)the National Natural Science Foundation of China (Grant Nos.40730950,40675027,and 40805007)
文摘The impact of the subtropical high (STH) on precipitation was investigated on a daily timescale using matched NCEP and the Global Precipitation Climatology Project (GPCP) datasets.Comparison of the conditional probability (intensity) of precipitation under STH condi-tions with that under non-STH conditions suggests that the presence of the STH conditions has a limited impact on local precipitation.In the West Pacific Subtropical High (WPSH) and the North Atlantic Subtropical High (NASH),precipitation was only 30% lower under STH conditions than under non-STH conditions.The STH conditions had somewhat more impact on precipitation intensity,but it was still 50% less than the intensity under non-STH conditions (mean of roughly 5 mm d 1).Pre-cipitation under STH conditions was found to be highly correlated with vertical motion.Active updrafts occurring even under STH conditions are essential for frequent oc-currences and moderate intensities of precipitation.
文摘In order to observe the therapeutic effects of Huanglian Fire-Purging Mixture (黄连清降合剂) on primary hypertension, 46 cases of primary hypertension in the treatment group were treated with Huanglian Fire-Purging Mixture to clear away heat from the liver, relieve mental stress, purge fire and remove toxin;and the other 26 cases of primary hypertension in the control group were treated with Niuhuang Bolus for Lowering Blood Pressure (牛黄降压丸). The effect in the treatment group was obviously superior to that in the control group (P＜0.05). The Huanglian Fire-Purging Mixture shows noticeable effects 3-6 hours after medication. The mixture can improve the clinical symptoms, the left ventricular diastolic function and myocardial ischemia, correct dyslipoproteinemia and dysglycemia, and reduce blood viscosity. And it is safe and with no obvious adverse reactions.
基金Project(52066008)supported by the National Natural Science Foundation,ChinaProject(2018FA030)supported by Yunnan Province Fundamental Research Key Project Foundation,China+1 种基金Project(2018ZE001)supported by Yunnan Province Major Science and Technology Project Foundation,ChinaProject(202005AG070057)supported by Yunnan Province Science and Technology Innovation Funds for key Laboratories,China。
文摘A three-dimensional diesel particulate filter(DPF)simulation model was developed by using AVL software FIRE to study the effects of four factors on soot particle distributions along the axial and radial directions in the DPF after the model accuracy was validated.An orthogonal test method was used to determine the importance and weights of the design of experiments(DoE)factors such as the expanding angle,the number of channels per square inch,and the exhaust mass flow rate.The effects of these factors on the uniformity of the soot particle distributions were also analyzed.The results show that when the soot loading time was 400 s,the soot particles inside the DPF along the axial direction exhibited a bowl shape,which was high on the both ends and low in the middle.The uniformity of the axial distribution of soot particles reduces significantly with an increase in the number of channels per square inch.The uniformity of the radial distribution reduced with an increase in the expanding angle of the divergent tube.Based on the impacts on the axial uniformity,the three most influencing factors in a descending order are the number of channels per square inch,the exhaust mass flow rate,and the expanding angle of the divergent tube.
