There is a common sense that heavy-duty CNC machine strongly depends on its foundation and can be easily affected by many factors.Hydraulic system,the most important part in CNC machine,is a complex and multi-loop sys...There is a common sense that heavy-duty CNC machine strongly depends on its foundation and can be easily affected by many factors.Hydraulic system,the most important part in CNC machine,is a complex and multi-loop system.In order to make up for the shortcomings of traditional fault tree analysis method and traditional GO method,the most effective method named fuzzy GO method is proposed to analyze the reliability of hydraulic system.And then some ideas are provided for system reliability assessment,fault diagnosis and maintenance by qualitative and quantitative analysis.展开更多
A great amount of work addressed methods for predicting the battery lifetime in wireless sensor systems. In spite of these efforts, the reported experimental results demonstrate that the duty-cycle current average met...A great amount of work addressed methods for predicting the battery lifetime in wireless sensor systems. In spite of these efforts, the reported experimental results demonstrate that the duty-cycle current average method, which is widely used to this aim, fails in accurately estimating the battery life time of most of the presented wireless sensor system applications. The aim of this paper is to experimentally assess the duty-cycle current average method in order to give more effective insight on the effectiveness of the method. An electronic metering system, based on a dedicated PCB, has been designed and developed to experimentally measure node current consumption profiles and charge extracted from the battery in two selected case studies. A battery lifetime measurement (during 30 days) has been carried out. Experimental results have been assessed and compared with estimations given by using the duty-cycle current average method. Based on the measurement results, we show that the assumptions on which the method is based do not hold in real operating cases. The rationality of the duty-cycle current average method needs reconsidering.展开更多
Liuzhou City is located in Guangxi Zhuang Autonomous Region of China. It has a warm and rainy climate and belongs to the middle subtropical monsoon climate. It is a rainstorm and flood-prone area. The work of flood dr...Liuzhou City is located in Guangxi Zhuang Autonomous Region of China. It has a warm and rainy climate and belongs to the middle subtropical monsoon climate. It is a rainstorm and flood-prone area. The work of flood drainage and waterlogging prevention is very important. The “minute to minute” rainfall process data of Liuzhou National Meteorological Observation Station from 1975 to 2014 and the Pilgrim & Cordery method were used to estimate the short-time design rainstorm profile of Liuzhou City, and the profiles of the rainfall lasting for 30, 60, 90, 120, 150, and 180 min were obtained. The research shows that the same rain duration and different recurrence period conditions are consistent with the rainstorm profile. The rainfall duration of 30, 60, 90, 120, and 180 min generally shows single-peak rainstorm profile, and the rainfall duration of 150 min shows double-peak rainstorm profile. Most peaks of each short-time design rainstorm profile are at or ahead of the 1/3 part of the entire rainfall process. During the same recurrence period, the rainfall in peak period fluctuated with the increase of the duration, and the intensity of rainfall increased with the prolonging of the recurrence period.展开更多
研究轻型车辆碳排放测算方法,分析车辆碳排放与运行工况关系。基于车辆实际行驶污染物排放(Real Drive Emission,RDE)车载测试数据,以CO_(2)当量CO_(2e)代表碳排放,分析得出碳排放速率随车速、比功率(Vehicle Specific Power,VSP)增大...研究轻型车辆碳排放测算方法,分析车辆碳排放与运行工况关系。基于车辆实际行驶污染物排放(Real Drive Emission,RDE)车载测试数据,以CO_(2)当量CO_(2e)代表碳排放,分析得出碳排放速率随车速、比功率(Vehicle Specific Power,VSP)增大而上升;运用BP(Back Propagation)神经网络算法建立车辆碳排放与车速、加速度、比功率多参数间非线性关系测算模型,计算得出世界轻型车测试循环(World Light Vehicle Test Cycle,WLTC)、新欧洲行驶循环(New European Driving Cycle,NEDC)和中国轻型商用车行驶工况(China Light-duty Vehicle Test Cycle-commercial Car,CLTC-C)3种台架测试循环工况下的碳排放因子。比较发现3种台架测试循环工况下的碳排放因子均高于实际道路行驶碳排放因子,其中WLTC下碳排放因子最高,其次是NEDC,再是CLTC-C,原因是加速度越大、车速越高的测试工况导致碳排放增加。展开更多
针对传统的扰动观察法(perturbation and observation method,P&O)跟踪速度较慢、跟踪精度不高,且容易振荡等问题,提出一种基于改进P&O的光伏最大功率点跟踪(maximum power point tracking,MPPT)控制方法,以占空比为扰动步长,...针对传统的扰动观察法(perturbation and observation method,P&O)跟踪速度较慢、跟踪精度不高,且容易振荡等问题,提出一种基于改进P&O的光伏最大功率点跟踪(maximum power point tracking,MPPT)控制方法,以占空比为扰动步长,将光伏阵列的功率变化率dP/dU和电压偏差变化率ΔU/ΔP引入扰动步长中,通过实时自适应调整占空比,实现更快、更可靠地跟踪最大功率点。仿真结果表明,相较于传统P&O,改进的P&O在同等条件下拥有更好的跟踪速度与跟踪精度。展开更多
文摘There is a common sense that heavy-duty CNC machine strongly depends on its foundation and can be easily affected by many factors.Hydraulic system,the most important part in CNC machine,is a complex and multi-loop system.In order to make up for the shortcomings of traditional fault tree analysis method and traditional GO method,the most effective method named fuzzy GO method is proposed to analyze the reliability of hydraulic system.And then some ideas are provided for system reliability assessment,fault diagnosis and maintenance by qualitative and quantitative analysis.
文摘A great amount of work addressed methods for predicting the battery lifetime in wireless sensor systems. In spite of these efforts, the reported experimental results demonstrate that the duty-cycle current average method, which is widely used to this aim, fails in accurately estimating the battery life time of most of the presented wireless sensor system applications. The aim of this paper is to experimentally assess the duty-cycle current average method in order to give more effective insight on the effectiveness of the method. An electronic metering system, based on a dedicated PCB, has been designed and developed to experimentally measure node current consumption profiles and charge extracted from the battery in two selected case studies. A battery lifetime measurement (during 30 days) has been carried out. Experimental results have been assessed and compared with estimations given by using the duty-cycle current average method. Based on the measurement results, we show that the assumptions on which the method is based do not hold in real operating cases. The rationality of the duty-cycle current average method needs reconsidering.
文摘Liuzhou City is located in Guangxi Zhuang Autonomous Region of China. It has a warm and rainy climate and belongs to the middle subtropical monsoon climate. It is a rainstorm and flood-prone area. The work of flood drainage and waterlogging prevention is very important. The “minute to minute” rainfall process data of Liuzhou National Meteorological Observation Station from 1975 to 2014 and the Pilgrim & Cordery method were used to estimate the short-time design rainstorm profile of Liuzhou City, and the profiles of the rainfall lasting for 30, 60, 90, 120, 150, and 180 min were obtained. The research shows that the same rain duration and different recurrence period conditions are consistent with the rainstorm profile. The rainfall duration of 30, 60, 90, 120, and 180 min generally shows single-peak rainstorm profile, and the rainfall duration of 150 min shows double-peak rainstorm profile. Most peaks of each short-time design rainstorm profile are at or ahead of the 1/3 part of the entire rainfall process. During the same recurrence period, the rainfall in peak period fluctuated with the increase of the duration, and the intensity of rainfall increased with the prolonging of the recurrence period.
文摘研究轻型车辆碳排放测算方法,分析车辆碳排放与运行工况关系。基于车辆实际行驶污染物排放(Real Drive Emission,RDE)车载测试数据,以CO_(2)当量CO_(2e)代表碳排放,分析得出碳排放速率随车速、比功率(Vehicle Specific Power,VSP)增大而上升;运用BP(Back Propagation)神经网络算法建立车辆碳排放与车速、加速度、比功率多参数间非线性关系测算模型,计算得出世界轻型车测试循环(World Light Vehicle Test Cycle,WLTC)、新欧洲行驶循环(New European Driving Cycle,NEDC)和中国轻型商用车行驶工况(China Light-duty Vehicle Test Cycle-commercial Car,CLTC-C)3种台架测试循环工况下的碳排放因子。比较发现3种台架测试循环工况下的碳排放因子均高于实际道路行驶碳排放因子,其中WLTC下碳排放因子最高,其次是NEDC,再是CLTC-C,原因是加速度越大、车速越高的测试工况导致碳排放增加。
文摘针对传统的扰动观察法(perturbation and observation method,P&O)跟踪速度较慢、跟踪精度不高,且容易振荡等问题,提出一种基于改进P&O的光伏最大功率点跟踪(maximum power point tracking,MPPT)控制方法,以占空比为扰动步长,将光伏阵列的功率变化率dP/dU和电压偏差变化率ΔU/ΔP引入扰动步长中,通过实时自适应调整占空比,实现更快、更可靠地跟踪最大功率点。仿真结果表明,相较于传统P&O,改进的P&O在同等条件下拥有更好的跟踪速度与跟踪精度。
