In view of the difficulty of automatic adjustment, the recovery lag and the major accident potential of the mine ventilation system, an experimental model of the pipe net was established according to the typical one m...In view of the difficulty of automatic adjustment, the recovery lag and the major accident potential of the mine ventilation system, an experimental model of the pipe net was established according to the typical one mine and one working face ventilation system of Daliuta coal mine. Using the best uniform approximation method of Chebyshev interpolation to fit the fan performance curve, we experimentally determined fan characteristics with different frequencies and establish the data base for the curves. Based on ventilation network monitoring theory, we designed a monitoring system for ventilation network parameter monitoring and fan operating frequency automatic control. Using the absolute methane emission quantity to predict the air quantity requirement of branch and fan frequency, we established a f-ω regulation model based on fan frequency and absolute methane emission quantity. After analysing methane emission and distribution characteristics, using CO_2 to simulate the methane emission characteristics from a working face, we verified the correctness and rationality of the f-ω regulation model. The fan operation frequency is adjusted by the method of air adjustment change with methane emission quantity and the curve searching method after determining air quantity requirements. The results show that the air quantity in a branch strictly changes according to the f-ω regulation model, in the airincreasing dilution by fan frequency regulation, the CO_2 concentration is limited to the set threshold value. The paper verifies the practicability of a frequency regulation system and the feasibility of the frequency adjustment scheme and provides guidance for the construction of automatic frequency conversion control system in coal mine ventilation networks.展开更多
This paper aims to evaluate the feasibility of pressure-dependent models in the design of ship piping systems.For this purpose,a complex ship piping system is designed to operate in firefighting and bilge services thr...This paper aims to evaluate the feasibility of pressure-dependent models in the design of ship piping systems.For this purpose,a complex ship piping system is designed to operate in firefighting and bilge services through jet pumps.The system is solved as pressure-dependent model by the piping system analysis software EPANET and by a mathematical approach involving a piping network model.This results in a functional system that guarantees the recommendable ranges of hydraulic state variables(flow and pressure)and compliance with the rules of ship classification societies.Through this research,the suitability and viability of pressure-dependent models in the simulation of a ship piping system are proven.展开更多
Heat transfer of a capillary evaporator in a loop heat pipe was analyzed through 3D numerical simulations to study the effects of the thermal conductivity of the wick, the contact area between the casing and the wick,...Heat transfer of a capillary evaporator in a loop heat pipe was analyzed through 3D numerical simulations to study the effects of the thermal conductivity of the wick, the contact area between the casing and the wick, and the subcooling in the compensation chamber (CC) on the thermal performance of the evaporator. A pore network model with a distribution of pore radii was used to simulate liquid flow in the porous structure of the wick. To obtain high accuracy, fine meshes were used at the boundaries among the casing, the wick, and the grooves. Distributions of temperature, pressure, and mass flow rate were compared for polytetra-fluoroethylene (PTFE) and stainless steel wicks. The thermal conductivity of the wick and the contact area between the casing and the wick significantly impacted thermal performance of the evaporator heat-transfer coefficient and the heat leak to the CC. The 3D analysis provided highly accurate values for the heat leak;in some cases, the heat leaks of PTFE and stainless steel wicks showed little differences. In general, the heat flux is concentrated at the boundaries between the casing, the wick, and the grooves;therefore, thermal performance can be optimized by increasing the length of the boundary.展开更多
校园用水数据,既有趋势性又有季节性。为了准确地对智能水表收集的用水数据进行异常点分析,从而检测预估管网漏损问题,研究对用水数据进行了相关检验,并选择了合适的自回归差分移动平均模型(Autoregressive Integrated Moving Average M...校园用水数据,既有趋势性又有季节性。为了准确地对智能水表收集的用水数据进行异常点分析,从而检测预估管网漏损问题,研究对用水数据进行了相关检验,并选择了合适的自回归差分移动平均模型(Autoregressive Integrated Moving Average Model,ARIMA)模型。基于Chen-Liu迭代算法,研究利用R软件进行编程,成功识别了用水数据中的异常点位置、类型、异常效应的大小,以及调整后的时间序列等,由此预估管网漏损可能出现的日期和位置。研究发现,基于ARIMA时间序列模型对用水数据进行异常点的检测较为准确,且输出的异常点类型可以区分异常点是人为因素造成还是由管网漏损问题造成,进而预估管网漏损问题,这为供水行业漏损管理模式提供了一种新的方向。展开更多
本文针对地下管网三维建模及可视化管理中的准确性和效率进行研究。通过使用地面激光扫描、手持同步定位与建图(Simultaneous Localization and Mapping,SLAM)和高清影像采集的多源融合技术,并结合BIM-点云融合建模方法,成功地实现高精...本文针对地下管网三维建模及可视化管理中的准确性和效率进行研究。通过使用地面激光扫描、手持同步定位与建图(Simultaneous Localization and Mapping,SLAM)和高清影像采集的多源融合技术,并结合BIM-点云融合建模方法,成功地实现高精度的拓扑构建和语义信息集成。利用细节层次(Level of Detail,LOD)渲染优化及GPU加速技术搭建一个具有多视角漫游、属性查询及动态更新等可视化平台。通过仿真和实地检测,发现模型的拓扑连接率超过98%,点云与BIM的匹配度高达95%,渲染帧率维持在28 FPS,数据加载时间范围是3.6~3.9 s,而属性查询的响应时间大约是0.44 s。研究表明:该技术体系能对复杂环境进行稳定、高效地三维建模和可视化管理,为地下管网运维、改造等提供可靠的技术支持。展开更多
基金support from the National Key Research and Development Plan (No.2016YFC0801800)the National Natural Science Foundation of China (No.51404263)+2 种基金the National Natural Science Foundation of Jiangsu (No.BK20130203)the Project Funded by the Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutionsthe Fundamental Research Funds for the Central Universities (Nos.2014XT02 and 2014ZDPY03)
文摘In view of the difficulty of automatic adjustment, the recovery lag and the major accident potential of the mine ventilation system, an experimental model of the pipe net was established according to the typical one mine and one working face ventilation system of Daliuta coal mine. Using the best uniform approximation method of Chebyshev interpolation to fit the fan performance curve, we experimentally determined fan characteristics with different frequencies and establish the data base for the curves. Based on ventilation network monitoring theory, we designed a monitoring system for ventilation network parameter monitoring and fan operating frequency automatic control. Using the absolute methane emission quantity to predict the air quantity requirement of branch and fan frequency, we established a f-ω regulation model based on fan frequency and absolute methane emission quantity. After analysing methane emission and distribution characteristics, using CO_2 to simulate the methane emission characteristics from a working face, we verified the correctness and rationality of the f-ω regulation model. The fan operation frequency is adjusted by the method of air adjustment change with methane emission quantity and the curve searching method after determining air quantity requirements. The results show that the air quantity in a branch strictly changes according to the f-ω regulation model, in the airincreasing dilution by fan frequency regulation, the CO_2 concentration is limited to the set threshold value. The paper verifies the practicability of a frequency regulation system and the feasibility of the frequency adjustment scheme and provides guidance for the construction of automatic frequency conversion control system in coal mine ventilation networks.
文摘This paper aims to evaluate the feasibility of pressure-dependent models in the design of ship piping systems.For this purpose,a complex ship piping system is designed to operate in firefighting and bilge services through jet pumps.The system is solved as pressure-dependent model by the piping system analysis software EPANET and by a mathematical approach involving a piping network model.This results in a functional system that guarantees the recommendable ranges of hydraulic state variables(flow and pressure)and compliance with the rules of ship classification societies.Through this research,the suitability and viability of pressure-dependent models in the simulation of a ship piping system are proven.
文摘Heat transfer of a capillary evaporator in a loop heat pipe was analyzed through 3D numerical simulations to study the effects of the thermal conductivity of the wick, the contact area between the casing and the wick, and the subcooling in the compensation chamber (CC) on the thermal performance of the evaporator. A pore network model with a distribution of pore radii was used to simulate liquid flow in the porous structure of the wick. To obtain high accuracy, fine meshes were used at the boundaries among the casing, the wick, and the grooves. Distributions of temperature, pressure, and mass flow rate were compared for polytetra-fluoroethylene (PTFE) and stainless steel wicks. The thermal conductivity of the wick and the contact area between the casing and the wick significantly impacted thermal performance of the evaporator heat-transfer coefficient and the heat leak to the CC. The 3D analysis provided highly accurate values for the heat leak;in some cases, the heat leaks of PTFE and stainless steel wicks showed little differences. In general, the heat flux is concentrated at the boundaries between the casing, the wick, and the grooves;therefore, thermal performance can be optimized by increasing the length of the boundary.
文摘校园用水数据,既有趋势性又有季节性。为了准确地对智能水表收集的用水数据进行异常点分析,从而检测预估管网漏损问题,研究对用水数据进行了相关检验,并选择了合适的自回归差分移动平均模型(Autoregressive Integrated Moving Average Model,ARIMA)模型。基于Chen-Liu迭代算法,研究利用R软件进行编程,成功识别了用水数据中的异常点位置、类型、异常效应的大小,以及调整后的时间序列等,由此预估管网漏损可能出现的日期和位置。研究发现,基于ARIMA时间序列模型对用水数据进行异常点的检测较为准确,且输出的异常点类型可以区分异常点是人为因素造成还是由管网漏损问题造成,进而预估管网漏损问题,这为供水行业漏损管理模式提供了一种新的方向。
文摘本文针对地下管网三维建模及可视化管理中的准确性和效率进行研究。通过使用地面激光扫描、手持同步定位与建图(Simultaneous Localization and Mapping,SLAM)和高清影像采集的多源融合技术,并结合BIM-点云融合建模方法,成功地实现高精度的拓扑构建和语义信息集成。利用细节层次(Level of Detail,LOD)渲染优化及GPU加速技术搭建一个具有多视角漫游、属性查询及动态更新等可视化平台。通过仿真和实地检测,发现模型的拓扑连接率超过98%,点云与BIM的匹配度高达95%,渲染帧率维持在28 FPS,数据加载时间范围是3.6~3.9 s,而属性查询的响应时间大约是0.44 s。研究表明:该技术体系能对复杂环境进行稳定、高效地三维建模和可视化管理,为地下管网运维、改造等提供可靠的技术支持。
