基于线路运行介数的过负荷脆弱性评估

提出了一种基于线路运行介数的过负荷脆弱性评估方法。该方法从电网络理论出发,首先推导了线路电流共享因子,定义线路运行介数,在此基础上评估过负荷脆弱性。该方法不仅考虑了网络拓扑结构对脆弱性的影响,同时还考虑了系统运行方式对脆弱性的影响,克服了复杂网络模型中潮流仅按最短路径流动的缺陷,物理意义明确,且符合电力系统的实际情况。IEEE39节点测试系统仿真结果验证了评估方法的正确性与合理性。

基于运行时间的变频型房间空调器季节能效比和潜力温度分析

计算了3台变频型房间空调器基于北京、上海、广州3种运行时间的季节能效比(SEER);采用运行时间频数(RTF)表征空调器运行时间在温度区间上的分布规律;绘制了3台空调器基于3种运行时间的制冷量和耗电量分布图.结果表明:RTF最大值对应的温度越小,SEER越大;RTF在低温段累计速度越快,SEER越大;空调器制冷量和耗电量在温度区间上的分布规律由运行时间决定;基于运行时间的制冷量和耗电量分布图能够直观反映当地的潜力温度,可为空调器性能的优化和选型提供参考依据.

通信枢纽楼能耗运行分析研究

如何在业务量不断增加,电源容量无法扩容的情况下,更好地解决供电能力紧张、机房装机位不足、机房散热等问题,是本论文的研究意义所在。本文通过对S省通信枢纽楼能耗运行分析,给出以上难点的合理化建议和建设指导原则。

Alternate operation characteristics of a solar-ground source heat pump system

In order to investigate the alternate operation characteristics of a solar-ground source heat pump system（SGSHPS）,various alternate operation modes are put forward and defined.A two-dimensional mathematical model with freezing/melting phase changes is developed for the heat transfer analysis of the soil.Based on the numerical solution of the model,the variation trends of underground soil temperature of the SGSHPS operated in various alternate operation modes are discussed.The results indicate that,for the day-night and short-time interval alternate operation modes without solar energy,the operation time fraction of a solar heat source should be confined to from 50% to 58% when operated in an alternate period of 24 h.Meanwhile,the disadvantages of a natural resumption of soil temperature can be overcome effectively by solar energy filling,and an optimal operation effect can be achieved by integrating the mode of solar energy filling with other alternate modes.In addition,the accuracy of the presented model is verified by the experimental data of borehole wall temperatures.The conclusions can provide a reference for the optimization operation of the SGSHPS.

Effects of Spark Ignition Engine Operating Parameters on Its Cyclic Variation ——Modeling and Simulation

An engine cyclic variation model has been built by using the residual gas temperature for the n th cycle as the input of the model, through constant pressure intake process, adiabatic compression process, constant volume combustion process, adiabatic expansion process, adiabatic blow down process and constant pressure exhaust process to approximate the thermodynamic processes in the cylinder, finally the residual gas temperature for the ( n+1) th cycle can be estimated. Because of the adding of engine operating parameters such as engine speed, spark advance, equivalence ratio, intake air pressure, intake air temperature to the model, effects of these parameters on cyclic variation can be estimated quantitatively. Since residual gas temperature fluctuation between cycles reflects the circumstances of engine cyclic variation, parameters to which residual gas temperature is sensitive are most likely used as the means to control cyclic variation. Model simulation shows that for the nearly stiochiometric mixture, cyclic variation is not obvious or even quite stable, but for the lean mixture, under the circumstances of partial load and larger spark advances, engine cyclic variations occur chaotically or with bifurcation.

Relationship between number of passing events and operating parameters in mixed bicycle traffic

This paper investigates the passing events between electric bicycles and conventional bicycles and explores the relationships between passing events and traffic parameters in bicycle facilities.Three exclusive bicycle paths in Nanjing, China,were observed with cameras.Then,the field data including vehicle number,velocity characteristics and passing event features were analyzed in detail.Data analysis and fitting reveal that the speed difference has little impact on the passing event number,as does the bicycle ratio.The Gaussian function can better describe the relationship between the passing event number and bicycle volume （density）.The valid use level of bicycle path width influences the inflexion of the passing events-density fitting curve.The conclusions can be applied for estimating the passing events in mixed bicycle flows and for choosing a suitable width of separate bicycle path.

DSS Scheme for Operation Optimization Problem on Power Plants

Based on the target analysis of the operation optimization for power plants, a novel system scheme called operation optimization decision support system (OODSS) is brought forward. According to the structure and design thinking of decision support system (DSS), the overall structure of the OODSS is studied, and the scheme of the sub systems in the OODSS such as the user interface system, the problem processing system, the database system, the model base system, the expert system (ES) and the data mining sy...

品茗闲话之五──功夫茶与茶道

品茗闲话之五──功夫茶与茶道若海至今流传于广东潮汕、闽南及东南亚一带的“功夫茶”品尝技艺，是中国茶道的一种。客主坐定，主人取来上好茶叶先让宾客传递嗅品，同时将开水冲入空壶，谓之“温壶”，温过壶的水倒入茶船（茶盘），继而用匙将茶叶装至茶壶的２／３，甚至...

梦幻PC:2005年好梦成真——光子带来快速轻便电脑前景

让我们憧憬一下梦幻PC。10年之后,主流电脑可能运行于10GHz(10~4MHz)时钟速度下,机内配有1GB内存和100GB存储介质,全重4盎司,一次充电可运行数周,而显示器分辨率为纤毫毕露的10000×10000像素。

Numerical simulation of a gas pipeline network using computational fluid dynamics simulators

This article describes numerical simulation of gas pipeline network operation using high-accuracy computational fluid dynamics (CFD) simulators of the modes of gas mixture transmission through long, multi-line pipeline systems (CFD-simulator). The approach used in CFD-simulators for modeling gas mixture transmission through long, branched, multi-section pipelines is based on tailoring the full system of fluid dynamics equations to conditions of unsteady, non-isothermal processes of the gas mixture flow. Identification, in a CFD-simulator, of safe parameters for gas transmission through compressor stations amounts to finding the interior points of admissible sets described by systems of nonlinear algebraic equalities and inequalities. Such systems of equalities and inequalities comprise a formal statement of technological, design, operational and other constraints to which operation of the network equipment is subject. To illustrate the practicability of the method of numerical simulation of a gas transmission network, we compare computation results and gas flow parameters measured on-site at the gas transmission enter-prise.

A Novel Strategy for Simulating the Main Fractionator of Delayed Cokers by Separating the De-superheating Process

Delayed coking is an important process in refinery to convert heavy residue oils from crude distillation units （CDUs） and fluid catalytic cracking units （FCCUs） into dry gas, liquefied petroleum gas （LPG）, gasoline, die- sel, gas oils and cokes. The main fractionator, separating superheating reaction vapors from the coke drums into lighter oil products, involves a de-superheating section and a rectifying section, and couldn＇t be simulated as a whole column directly because of non-eouilibrium in the de-suoerheatine section. It is verv imoortant to correctlv simulate the main fractionator for operational parameter and energy-use optimization of delayed cokers. This paper discusses the principle of de-superheating processes, and then proposes a new simulation strategy. Some key issues such as composition prediction of the reaction vapors, selection of thermodynamic methods, estimation of tray efficiency, etc. are discussed. The proposed simulation approach is applied to two industrial delayed cokers with typical technological processes in a Chinese refinery by using PRO/II. The simulation results obtained are well consistent with the actual operation data, which indicates that the presented approach is suitable to simulate the main fraction- ators of delayed cokers or other distillation columns consisting of de-superheating sections and rectifying sections.

Theoretical and Experimental Study on Ground Coupled Heat Pump with Vertical Spiral Coil

The numeric al simulation study on the temperature distribution of underground field for the ground coupled heat pump (GCHP) with vertical spira l coil was carried out by using finite element. The distribution and recovery of undergroun d field temperature under different operation ratio and the optimal operation ratio were simulated.The performance parameters, i.e. inlet and outlet temperature of the ground spiral coil in heating and cooling modes were tested, the heat extracted or emitted by the heat pump to the ground was calculated, and the coefficients of performance (COP) of GCHP at heat ing and cooling modes were analyzed.

Study on hydrostatic gas lubricated non-contacting mechanical seal

The principle and characteristics of hydrostatic gas lubricated non-contacting mechanical seal （HSGLNMS） are introduced. The flow field of the gas film is established by numerical analysis of end faces of HSGLNMS. The distribution of gas film pressure and seal performance parameters inclu- ding opening force and leakage are obtained. Influence of operating parameters and sealing configu- ration on the sealing performance is studied. HSGLNMS has been designed and manufactured. Its working film thickness and leakage are measured to verify the theoretical analysis. The investigation results show that HSGLNMS demonstrates good speed adaptability, which means that the seal runs successfully with both low and high speed, showing excellent performance. The seal can be regula- ted and controlled online ; the opening force will not be raised greatly with the increasing of the num- ber of throttle orifices, but the leakage of seal increases apparently ; the uniform pressure groove im- proves the sealing performance, for example, opening force and stiffness are raised obviously. While leakage is reduced. Finally, the theoretical analysis is verified by experiment.

Size distribution of wet crushed waste printed circuit boards

A wet impact crusher was used to breakdown waste printed circuit boards （PCB＇s） in a water medium. The relationship between the yield of crushed product and the operating parameters was established. The crushing mechanism was analyzed and the effects of hammerhead style, rotation speed, and inlet water volume on particle size distribution were investigated. The results show that the highest yield of -1 ＋ 0.75 mm sized product was obtained with an inlet water volume flow rate of 5.97 m3/h and a smooth hammerhead turning at 1246.15 r/rain. Cumulative undersize-product yield curves were fitted to a nonlinear function： the fitting correlation coefficient was greater than 0.998. These research results provide a theoretical basis for the highly effective wet crushing of PCB＇s.

A systematic approach for synthesizing a low-temperature distillation system

In this paper, by combining a stochastic optimization method with a refrigeration shaft work targeting method,an approach for the synthesis of a heat integrated complex distillation system in a low-temperature process is presented. The synthesis problem is formulated as a mixed-integer nonlinear programming(MINLP) problem,which is solved by simulated annealing algorithm under a random procedure to explore the optimal operating parameters and the distillation sequence structure. The shaft work targeting method is used to evaluate the minimum energy cost of the corresponding separation system during the optimization without any need for a detailed design for the heat exchanger network(HEN) and the refrigeration system(RS). The method presented in the paper can dramatically reduce the scale and complexity of the problem. A case study of ethylene cold-end separation is used to illustrate the application of the approach. Compared with the original industrial scheme, the result is encouraging.

The integrated monitoring system for running parameters of key mining equipment based on condition monitoring technology

An integrated monitoring system for running parameters of key mining equipmenton the basis of condition monitoring technology and modern communication networktechnology was developed.The system consists of a client computer with functions ofsignal acquisition and processing, and a host computer in the central control room.Thesignal acquisition module of the client computer can collect the running parameters fromvarious monitoring terminals in real-time.The DSP high-speed data processing system ofthe main control module can quickly achieve the numerical calculation for the collectedsignal.The signal modulation and signal demodulation are completed by the frequencyshift keying circuit and phase-locked loop frequency circuit, respectively.Finally, the signalis sent to the host computer for logic estimation and diagnostic analysis using the networkcommunication technology, which is helpful for technicians and managers to control therunning state of equipment.

Simulation of MEG Packed Distillation Column Using an Equilibrium Stage Model-Case Study on Operating Parameters of Farsa Petrochemical Company： Assaluyeh-lran

Two types of equilibrium and non-equilibrium stage models are generally used to simulate the mass transfer of packed distillation column. Using non-equilibrium model requires the calculation of mass transfer coefficients, thus, usually equilibrium-based methods are preferred to be used for simulations of distillation columns. In this paper, packed column distillation of production of Mono Ethylene Glycol in FARSA SHIMI Company （Assaluyeh-Iran）＇s Ethylene Glycol portion has been simulated through using the equilibrium model and solving the related equations. The simulation has been carried out in the MATLAB environment. The column also has been simulated in the Aspen Hysys and Aspen Plus ver. 2006.5 environments. Then, the output has been compared with software results, designing and operating data of the underlying columns which demonstrate good consistency with the model. Having the model validated, the effect of some operating parameters has been analyzed through the model.

Enrichment of Semi-Volatile Organic Acids from Aqueous Solutions by Multiple-Effect Membrane Distillation

Multiple-effect membrane distillation （MEMD） process for enriching semi-volatile organic acids from their individual aqueous solutions was performed by using a hollow fiber-based air gap membrane distillation （AGMD） module with the function of internal heat recovery. Aqueous solutions of glyoxylic acid, glycolic acid, lactic acid, pyrnvic acid, malonic acid and glutaric acid were used as model feed. For a feed of 1% （mass fraction）, each acid could be enriched for 8--20 times, which depended on the surface tension of the concentrate. The operation performance of MEMD process was characterized by permeation flux J, performance ratio PR and acid rejection rate R. The effects of cold feed-in temperature, heated feed-in temperature, feed-in volumetric flow rate and feed-in concen- tration on MEMD performance were experimentally evaluated. Maximum values of J, PR and R were 4.8 L/（h-m2）, 9.84 and 99.93%, respectively. Moreover, MEMD process demonstrated a fairly good stability in a long-term experiment lasting for 30 d when aqueous solution of 4% （mass fraction） lactic acid was used as a feed.

Orthogonal experiment design of EMI of security monitoring system in coal mines

Security monitoring system of coal mines is indispensable to ensure the safe and efficient production of colliery. Due to the special and narrow underground field of the coal mine, the electromagnetic interference can cause a series of misstatements and false positives on the monitoring system, which will severely hamper the safe production of coal industry. In this paper, first, the frequency characteristics of the interference source on the power line are extracted when equipment runs normally. Then the finite difference time domain method is introduced to analyze the effects of the electromagnetic interference parameters on the security monitoring signal line. And the interference voltage of the two terminal sides on the single line is taken as evaluating indexes. Finally, the electromagnetic interference parameters are optimized by orthogonal experimental design based on the MATLAB simulation on the normal operation of equipment.

Donor safety and remnant liver volume in living donor liver transplantation

AIM:To evaluate the relationship between donor safety and remnant liver volume in right lobe living donor liver transplantation(LDLT).METHODS:From July 2001 to January 2009,our liver transplant centers carried out 197 LDLTs.The clinical data from 151 cases of adult right lobe living donors(not including the middle hepatic vein) were analyzed.The conditions of the three groups of donors were well matched in terms of the studied parameters.The donors' preoperative data,intraoperative and postoperative data were calculated for the three groups:Group 1 remnant liver volume(RLV) < 35%,group 2 RLV 36%-40%,and group 3 RLV > 40%.Comparisons included the different remnant liver volumes on postoperative liver function recovery and the impact of systemic conditions.Correlations between remnant liver volume and post-operative complications were also analyzed.RESULTS:The donors' anthroposomatology data,op-eration time,and preoperative donor blood test indicators were calculated for the three groups.No significant differences were observed between the donors' gender,age,height,weight,and operation time.According to the Chengdu standard liver volume formula,the total liver volume of group 1 was 1072.88 ± 131.06 mL,group 2 was 1043.84 ± 97.11 mL,and group 3 was 1065.33 ± 136.02 mL.The three groups showed no statistically significant differences.When the volume of the remnant liver was less than 35% of the total liver volume,the volume of the remnant had a significant effect on the recovery of liver function and intensive care unit time.In addition,the occurrence of complications was closely related to the remnant liver volume.When the volume of the remnant liver was more than 35% of the total liver volume,the remnant volume change had no significant effect on donor recovery.CONCLUSION:To ensure donor safety,the remnant liver volume should be greater than the standard liver volume(35%) in right lobe living donor liver transplantation.