科创中国

抽汽压损是一种不明显的热力损失,使蒸汽的作功能力下降、热经济性降低.假定抽汽口的压力不变,加热器端差不变,分析抽汽压损变化对热力系统的影响.根据抽汽压损的理论分析和热力系统汽水分布方程建立抽汽压损对回热系统抽汽系数影响的数学模型,并结合炯平衡原理和小扰动理论建立抽汽压损对炯损分布的影响的数学模型.以某电厂N1000-25/600/600机组热力系统为例,在TRL工况下,定量计算热力系统炯损变化情况.根据定量计算结果定性分析了抽汽压损对热力系统的影响.

In piezoceramic ultrasonic devices,the piezoceramic stacks may fail permanently or function improperly if their working temperatures overstep the Curie temperature of the piezoceramic material.While the end of the horn usually serves near the melting point of the molten metal and is enclosed in an airtight chamber,so that it is difficult to experimentally measure the temperature of the transducer and its variation with time,which bring heavy difficulty to the design of the ultrasonic molten metal treatment system.To find a way out,conjugate heat transfer analysis of an ultrasonic molten metal treatment system is performed with coupled fluid and heat transfer finite element method.In modeling of the system,the RNG model and the SIMPLE algorithm are adopted for turbulence and nonlinear coupling between the momentum equation and the energy equation.Forced air cooling as well as natural air cooling is analyzed to compare the difference of temperature evolution.Numerical results show that,after about 350 s of working time,temperatures in the surface of the ceramic stacks in forced air cooling drop about 7 K compared with that in natural cooling.At 240 s,The molten metal surface emits heat radiation with a maximum rate of about 19 036 W/m2,while the heat insulation disc absorbs heat radiation at a maximum rate of about 7922 W/m2,which indicates the effectiveness of heat insulation of the asbestos pad.Transient heat transfer film coefficient and its distribution,which are difficult to be measured experimentally are also obtained through numerical simulation.At 240 s,the heat transfer film coefficient in the surface of the transducer ranges from–17.86 to 20.17 W/(m2?K).Compared with the trial and error method based on the test,the proposed research provides a more effective way in the design and analysis of the temperature control of the molten metal treatment system.

Further development of the photovoltaic industry is restricted by the productivity of mono-crystalline silicon technology due to its requirements of low cost and high efficient photocells.The heat shield is not only the important part of the thermal field in Czochralski(Cz)mono-crystalline silicon furnace,but also one of the most important factors influencing the silicon crystal growth.Large-diameter Cz-Si crystal growth process is taken as the study object.Based on FEM numerical simulation,different heat shield structures are analyzed to investigate the heater power,the melt-crystal interface shape,the argon flow field,and the oxygen concentration at the melt-crystal interface in the process of large Cz-Si crystal growth.The impact of these factors on the growth efficiency and crystal quality are analyzed.The results show that the oxygen concentration on the melt-crystal interface and the power consumption of the heater stay high due to the lack of a heat shield in the crystal growth system.Argon circumfluence is generated on the external side of the right angle heat shield.By the right-angle heat shield,the speed of gas flow is lowered on the melt free surface,and the temperature gradient of the free surface is increased around the melt-crystal interface.It is not conducive for the stable growth of crystal.The shape of the melt-crystal interface and the argon circulation above the melt free surface are improved by the inclined heat shield.Compared with the others,the system pulling rate is increased and the lowest oxygen concentration is achieved at the melt-crystal interface with the composite heat shield.By the adoption of the optimized composite heat shield in experiment,the real melt-crystal interface shapes and its deformation laws obtained by Quick Pull Separation Method at different pulling rates agree with the simulation results.The results show that the method of simulation is feasible.The proposed research provides the theoretical foundation for the thermal field design of the large diameter Cz-Si monocrystalline growth.

As the popularization of dual ring fieldbus,the optimized dual ring synchronization methods are still in short.The current synchronization methods are generally established in traditional industrial fieldbus,in which transmission is commonly considered in single track,the two-way transmitting cannot take full effect,and would result in unwanted idle load on equipment lines.In stamp-transferring part,the synchronizing algorithm is not properly processed to diminish the latency,so the real-time performance of entire system cannot be ensured.To support the synchronization control of stations in the CNC system,a real-time time synchronization method for dual ring fieldbus in the CNC system is designed in this paper.In this method a synchronizing message transmission scheme based on dual ring architecture and the synchronization algorithm between master and secondary stations are integrated.In the scheme,the clock models of both master and secondary stations are optimized with corresponding modules and the stamp data transmission based on the dual ring fieldbus is devised exclusively,so the transmitting efficiency improves with less idle work.In the algorithm,all the secondary stations can accomplish the consistent state with master station by updating clock discrepancy information in one communication cycle,and it takes the advantage of two-way transmitting and makes the best use of dual ring structure,so the real-time performance of the system can be promoted while retaining the precision of synchronization.To evaluate the performance,the costs of the method and errors during synchronizing are noted and analyzed based on the actual running environment in the industrial fieldbus.The results show that it reduces communication cost and ensures the smoothness of the system with low lag effects under heavy load.The proposed time synchronization method optimizes the architecture of sync message transmission in dual ring fieldbus,and improves the efficiency of time synchronization in the stations of CNC system.

作为市场经济体制比较完善的西方发达国家,美国较为完善的税制体系及税务管理体系,对我国的税制改革和征管改革有很多有益的借鉴.本文通过对美国税制、主要税种的介绍,美国税制特征的分析,提出我国税制结构设计以及改进所得税、财产税、社会保障税等方面的启示.

"十二五"时期我国节能工作面临着更加复杂的形势和严峻的挑战,需要在以往工作基础上有所创新和突破.日本是全球能源效率最高的国家之一,节能取得卓越成绩不仅依靠对技术的不懈追求,更依靠对节能更加深入的理解和政策上的大胆尝试.通过将节能融入经济发展战略、"以人为本"的管理手段以及用更加系统整体的眼光重新看待节能技术和产品,加上能源管理师、领跑者等制度上的创新,日本一直保持着全球节能引领者地位.本文简要地回顾和总结了日本近年来节能理念和制度方面的创新,并结合我国"十一五"以来节能工作,提出了针对"十二五"节能工作的政策建议.

足细胞,作为肾小球滤过屏障的一道重要防线,被认为是蛋白尿产生的中心环节,因此近年来备受关注.免疫抑制剂对足细胞损伤的保护作用促使人们寻找除其免疫抑制作用之外对足细胞直接的保护机制.足细胞本身是否具有免疫细胞样的特性?在病理情况下,足细胞又是如何对机体炎症反应作出应答的?上述问题的解答将对足细胞损伤机制研究和探寻治疗干预措施具有重要意义.

The existing research of the active suspension system(ASS) mainly focuses on the different evaluation indexes and control strategies. Among the different components, the nonlinear characteristics of practical systems and control are usually not considered for vehicle lateral dynamics. But the vehicle model has some shortages on tyre model with side-slip angle, road adhesion coefficient, vertical load and velocity. In this paper, the nonlinear dynamic model of lateral system is considered and also the adaptive neural network of tire is introduced. By nonlinear analysis methods, such as the bifurcation diagram and Lyapunov exponent, it has shown that the lateral dynamics exhibits complicated motions with the forward speed. Then, a fuzzy control method is applied to the lateral system aiming to convert chaos into periodic motion using the linear-state feedback of an available lateral force with changing tire load. Finally, the rapid control prototyping is built to conduct the real vehicle test. By comparison of time response diagram, phase portraits and Lyapunov exponents at different work conditions, the results on step input and S-shaped road indicate that the slip angle and yaw velocity of lateral dynamics enter into stable domain and the results of test are consistent to the simulation and verified the correctness of simulation. And the Lyapunov exponents of the closed-loop system are becoming from positive to negative. This research proposes a fuzzy control method which has sufficient suppress chaotic motions as an effective active suspension system.

多智能体(代理)系统(Multi-Agent System,MAS)是基于实体建模的、分布式离散事件驱动的仿真方法,其中实体行为的描述和协同一直是持续研究的难点问题.基于Cougaar体系结构,根据混合型Agent的定义,针对Multi-Agent的实体建模提出了一种通用描述方法,简化了实体Agent建模描述,方便定义Agent之间的关系.设计实现了一个高性能的协同算法,把实体Agent分为总控Agent和仿真Agent两类,通过集中式控制方法进行时钟同步,仿真Agent按需进行时间同步,能够有效降低实际仿真中的硬件资源消耗,实现高效的时间同步.各个Agent的仿真时间推进步长可以自适应变化,取得仿真性能和仿真精度之间的平衡.

Extensive studies on rotor systems with single or coupled multiple faults have been carried out. However these studies are limited to single-span rotor systems. A finite element model for a complex rotor-bearing system with coupled faults is presented. The dynamic responses of the rotor-bearing system are obtained by using the rotor dynamics theory and the modern nonlinear dynamics theory in connection with the continuation-shooting algorithm(commonly used for obtaining a periodic solution for a nonlinear system) for a range of rub-impact clearances and crack depths. The stability and Hopf instability of the periodic motion of the rotor-bearing system with coupled faults are analyzed by using the procedure described. The results indicate that the finite element method is an effective way for determining the dynamic responses of such complex rotor-bearing systems. Further for a rotor system with rub-impact and crack faults, the influences of the clearances are significantly different for different rub-impact stiffness. On the contrary, the influence of crack depths is rather small. The instability speeds of the rotor-bearing system increase due to the presence of the crack fault. The results obtained using the new finite element model, presented for computation and analysis of dynamic responses of the rotor-bearing systems with coupled faults, are in accordance with measurements in experiment. The formulations given can be used for diagnosis of faults, vibration control, and safe and stable operations of real rotor-bearing systems.