DiffServ实现模型

文中通过分析当前的DiffServ模型及其实现,提出改进方案--基于分层控制的DiffServ模型.模型利用控制分层的思想,将原有的控制平面进一步细化为业务控制平面和模块控制平面.在新的模型中,原本分离的DiffServ各模块,可以通过内部控制消息相互协调,按照动态的QoS策略,共同来保证用户的服务质量(QoS)的需求.     

Effect of additives on the structure characteristics,thermal stability,reducibility and catalytic activity of CeO<Subscript>2</Subscript>–ZrO<Subscript>2</Subscript> solid solution for methane combustion

M _y O _x -modified CeO₂–ZrO₂ (M = Al, Ba, Cu, La, Nd, Pr, Si) solid solutions with the atomic ratio of Zr/Ce = 1 were prepared by the reverse microemulsion method, and the effect of different additives on the structure characteristics, thermal stability, reducibility, and catalytic activity of CeO₂–ZrO₂ solid solution for methane combustion were investigated. According to their different effects, M _y O _x can be classified into three groups. The first group includes SiO₂ and Al₂O₃ which do not vary the crystalline phase of CeO₂–ZrO₂ solid solution but distort the crystal lattice obviously. They are the most effective additives for improving the surface area, thermal stability, and reducibility of CeO₂–ZrO₂, and they can also promote the catalytic activity of Pd/CeO₂–ZrO₂ for methane combustion. The second group includes La₂O₃, Pr₂O₃, and Nd₂O₃, which can also keep the same crystalline phase, distort the crystal lattice, and improve the surface area and thermal stability of the solid solution, but their effects are much weaker and they decrease the reducibility of the solid solution. The third group includes BaO and CuO, whose effects on the property of CeO₂–ZrO₂ are much different. BaO and CuO, especially CuO, can decrease the thermal stability, and reduction extent of CeO₂–ZrO₂. CuO-modified CeO₂–ZrO₂ calcined at 550 °C shows the comparable high activity for the methane combustion, but after being calcined at 900 °C, CuO-modified CeO₂–ZrO₂ would separate into three phases as CeO₂, ZrO₂, and CuO, resulting in the much lower activity for the methane catalytic combustion.     

Assessing dynamic efficiency of air curtain in reducing whole building annual energy usage

The efficiency of air curtain in reducing infiltration and associated energy usage is currently evaluated statically by using an efficiency factor, η _air, based on single steady/static condition, which is often not the case for actual buildings under variable weather conditions and door usages. Based on a new method to consider these dynamic effects on air curtains, this study uses a dynamic efficiency factor η _B in terms of whole building site end-use energy to assess the efficiency of air curtains when compared to single doors (i.e. without air curtains) and vestibule doors. Annual energy simulations were conducted for two reference building models considering their specific door usage schedules in 16 climate zone locations in the North America. The variations of the proposed efficiency factor for different climate zones illustrated the dynamic impacts of weather, building, unit fan energy and door usage frequency on air curtain efficiency. A sensitivity study was also conducted for the operation temperature conditions of air curtain and showed that η _B also considers these operational conditions. It was thus concluded that using whole building site end-use energy to calculate the efficiency factor, ηB, can provide more realistic estimates of the performance of air curtains operations in buildings than the existing static efficiency factor.     

Real-Time Forecasting of Building Fire Growth and Smoke Transport via Ensemble Kalman Filter

Forecasting building fire growth and smoke dispersion is a challenging task but can provide early warnings to first responders and building occupants and thus significantly benefit active building fire protection. Although existent computer simulation models may provide acceptable estimations of smoke temperature and quantity, most simulations are still not able to achieve real-time forecast of building fire due to high computational requirements, and/or simulation accuracy subject to users’ inputs. This paper investigates one of the possibilities of using ensemble Kalman filter (EnKF), a statistical method utilizing the real-time sensor data from thermocouple trees in each room, to estimate the spread of an accidental building fire and further forecast smoke dispersion in real time. A general approach to forecasting building fire and smoke is outlined and demonstrated by a 1:5 scaled compartment fire experiment using a 1.0 kW to 2.8 kW propane burner as fire source. The results indicate that the EnKF method is able to forecast smoke transport in a multi-room building fire using 40 ensemble members and provide noticeable accuracy and lead time. Unlike other methods that directly use measurement data as model inputs, the developed model is able to statistically update model parameters to maintain the forecasting accuracy in real time. The results obtained from the model can be potentially applied to assist mechanical smoke removal, emergency evacuation and firefighting.     

Experimental study on the oil pump driving energy consumption and lubrication safety in a PFI engine under NEDC and WLTC

Journal of Mechanical Science and Technology - We studied the transient driving power of an oil pump for 1.6 L PFI engine in a passenger car under the new European driving cycle (NEDC) and...