Effects of transient temperature conditions on the divergence of activated sludge bacterial community structure and function

The effect of temperature fluctuations on bacterial community structure and function in lab-scale sequencing batch reactors treating bleached kraft mill effluent was investigated. An increase in temperature from 30 to 45 degrees C caused shifts in both bacterial community structure and function. Triplicate reactors were highly similar for 40 days following startup. After the temperature shift, their community structure and function started to diverge from each other and from the control. A multi-response permutation procedure confirmed that the variability in community structure between transient and control reactors were greater than that among the triplicate transient reactors. The fact that these disturbances manifest themselves in different ways in apparently identical reactors suggests a high degree of variability between replicate systems.     

SET Emulation Under a Quantized Delay Model

Single event transient (SET) fault analysis is usually performed through digital simulation at the gate level. However, this method cannot be used for large fault injection campaigns, since gate level simulation is quite slow. In this paper, we propose an approach to build an FPGA based SET emulator, which implements a quantized delay model of the circuit under evaluation. Experimental results demonstrate that the quantized delay model produces accurate results and can be easily captured in an FPGA. The proposed approach can be automated to increase SET fault analysis performance by three orders of magnitude with respect to simulation.

Multi-machine transient modelling of wind farms: An essential approach to the study of fault conditions in the distribution network

This paper reports the study carried out to asses the dynamic behaviour of a real wind farm during fault conditions in the distribution network. The objective is to obtain a transient model valuable for all kinds of operational conditions. The paper begins with a detailed modelling of the distribution network between the wind farm common busbar and the point of common coupling with the HV transmission system, for all types of short-circuits. The state-space network model, together with the electromagnetic transient model of each wind generator, configure a multi-machine wind farm model, with 572 state variables. Simulation results prove that multi-machine modelling is mandatory in order to tackle the wind farm contribution to symmetric and asymmetric short-circuits.     

Transient analysis of gas flow in a straight pipe

In the present work, numerical simulation has been done to analyze transients in gas flow and pressure in a horizontal straight pipe. For a single gas pipeline, eight representative cases corresponding to different causes of transient behaviour are simulated to predict unsteady state flow and the evolution of pressure profiles. The numerical results show that depending upon the pipe dimensions and operating variables such as pressure and gas flow rate, transient effects in the pipeline may last for a long time and/or over significant length of pipe. The simulations predict an initial surge in gas flow rate greater than the final steady‐state value if the pressure drop across the pipe is increased. Similarly, initial flow rate may decrease below the final steady‐state value if the pressure drop is decreased. In case of complete closure of a valve, oscillations in both pressure and mass flow rate are observed, which gradually decay and the steady state conditions of no flow are ultimately achieved. The present results are compared with a published work from the literature. A reasonably good agreement is found between these two predictions. The present study is of practical significance in safe design and operation of a gas delivery system.     

边界保护的理论基础 第一部分 故障暂态分析

近年来 ,基于单端暂态量的输电线路保护新原理不断涌现出来 ,这种利用故障产生的暂态分量是否透过线路边界的特征构成的具有全线速动的保护称为边界保护 ,边界保护成立的条件有两个 ,其一是区内外故障时 ,暂态分量存在差异 ;其二是该差异有规律性 ,可以被提取并且很明显 ,足以构成保护判据。基于这个目的 ,对输电线路区内外故障时的暂态分量的频谱进行了分析 ,发现并提取该差异 ,为边界保护的研究提供理论基础。全文共分为三个部分 ,第一部分是故障暂态分析 ;第二部分是线路边界折反射系数的频谱分析 ;第三部分是区内外故障暂态分量频谱差异的提取和EMTP仿真。本文是第一部分 ,利用网格法对输电线路在区内、正方向区外和反方向三个典型位置故障时的暂态分量进行分析和比较 ,并发现了不同故障方向时暂态分量的差异和正方向区内外故障的差异 ,前者的差异主要体现在线路边界的反射系数的频谱特征中 ,后者主要体现在线路边界的透射系数的频谱特征中     

Tuning the microstructure and functional properties of metal nanowire arrays via deposition potential

The present study is focused on electrochemical fabrication and characterization of the ordered arrays of one-dimensional Ni nanostructures templated by porous anodic alumina films. A possibility to monitor and control homogeneity of arrays and completeness of the pores filling in the course of potentiostatic deposition is discussed. Current efficiency is determined from independent analytical data and taken into account in the treatment of charge transients. The crystallinity of Ni nanowire arrays as well as the homogeneity and completeness of the replication process are demonstrated to be controlled by deposition potential. Just these structural features affect the magnetic properties of nanowire arrays. The advantages and drawbacks of the quantitative coulometric analysis of current transients are considered.     

秦山一期核电站未能紧急停堆的预期瞬变导致堆芯熔化的进程及事故缓解措施研究

选择失去主给水、失去厂外电和正常运行情况下控制棒失控提升3个典型的导致未能紧急停堆的预期瞬变(ATWS)的初因事故,采用自行研制的基于SCDAP／RELAP5／MOD3．1的核反应堆严重事故分析平台,对秦山一期核电站ATWS初因导致堆芯熔化严重事故进程进行了分析研究,对防止ATWS导致堆芯熔化进程的缓解措施的有效性进行了验证。计算分析结果表明,二回路补水和一回路卸压的事故缓解措施能有效地阻止堆芯熔化进程。     

HVDC换相失败暂态特性及其对差动保护的影响分析和对策

通过CIGRE HVDC标准测试模型,获取了直流系统换相失败时的等值工频电流与换流母线电压之间的关系曲线。推导了交直流互联系统中电流差动保护的判据表达式,并对与直流系统直接相连的输电线路的差动保护进行了分析。分析结果表明,交直流互联运行环境下发生区内故障有可能引发差动保护的拒动。提出了基于幅值判据来识别内部故障。PSCAD/EMTDC仿真结果验证了理论分析的正确性和所提判据的有效性。     

小电流接地电网单相接地故障的暂态特性

针对小电流接地系统单相接地故障接地选线困难的问题,通过理论分析、仿真研究和大量6kV模拟实验验证,深入研究了该型故障的特征,着重研究了电弧接地故障时暂态零序测量电流的特征,以及故障线路与非故障线路暂态零序测量电流之间的关系。结果表明:①电弧接地时,零序电压和各馈线零序电流中都有高频衰减的暂态分量。暂态分量的频率主要与变压器漏抗、电网对地电容和相间电容有关,频率约在0.3～3kHz之间。暂态分量的特征基本不受中性点接地方式的影响。②故障线路与非故障线路的暂态零序电流在频率、衰减速度等特性上相同。非故障线路暂态零序电流的大小与本线路对地电容的大小成正比,而故障线路暂态零序电流等于所有非故障线路暂态零序电流之和,但方向相反。③单相接地故障发生在相电压最大值附近时暂态零序电流最大,发生在相电压过零点附近时最小;暂态零序电流的衰减速度随电弧电阻的增大而加快。这些暂态特性可为研究基于单相接地故障暂态分析的接地选线方法提供理论依据。