Generalized neural network and wavelet transform based approach for fault location estimation of a transmission line

To maintain the efficient and reliable operation of power systems, it is extremely important that the transmission line faults need to be detected and located in a reliable and accurate manner. A number of mathematical and intelligent techniques are available in the literature for estimating the fault location. However, the results are not satisfactory due to the wide variation in operating conditions such as system loading level, fault inception instance, fault resistance and dc offset and harmonics contents in the transient signal of the faulted transmission line. Keeping in view of aforesaid, a new approach based on generalized neural network (GNN) with wavelet transform is presented for fault location estimation. Wavelet transform is used to extract the features of faulty current signals in terms of standard deviation. Obtained features are used as an input to the GNN model for estimating the location of fault in a given transmission systems. Results obtained from GNN model are compared with ANN and well established mathematical models and found more accurate.     

A novel recursive approach for real-time transient stability assessment based on corrected kinetic energy

Real-time assessment of transient stability is one of the main issues of power system operators in online applications. This paper proposes a novel recursive approach based on corrected kinetic energy which has the capability of real-time assessment and real time computation of transient stability margin in the power system. This approach considers all details of power system by using network preserving model to simulate transient stability. This paper uses a hybrid method based on the new concept of equal area criterion to estimate initial value of critical point of the system and corrected Kinetic Energy Function to estimate high precision value of the critical point. Also, this paper proposes a recursive method which uses large change sensitively (LCS) analysis to correct initial condition point of the system when the topology of system is changed by a disturbance. In order to validate the proposed method, comprehensive case studies have been conducted on IEEE39-bus test system. Comprehensiveness in considering the details, simplicity in implementation and low computational cost are the outstanding features of the proposed approach. Also, simulation results approve that the proposed approach can be used in real-time application without loss of any detail in the transient stability assessment.     

Experimental setup for non-destructive measurement of tunneling currents in semiconductor devices

A new experimental setup used to perform non-destructive measurement of electrical quantities on semiconductor devices is described in this paper. The particular case of tunneling current measurement in n-type semiconductor–oxide–semiconductor (SOS) capacitors, whose dielectrics play a crucial role in non-volatile memories, has been investigated. When the gates of such devices are polarized with a sufficient bias voltage while the other terminals are grounded, tunnel conduction of electrons through the thin oxide layer is allowed. Typical tunneling current measurements obtained with this advanced setup are presented and compared to the results yielded by older standard experimental protocols. An application to the experimental observation of the temperature dependence of the tunneling current is proposed. Conclusions about the benefits of this kind of electrical measurements are then drawn.     

Closed-Form Solutions for the Transient and Steady-State Temperature of a Lumped Mass Coupled to Linear and Radiant Boundaries

Exact closed-form solutions describing the transient and steady-state temperature of a lumped mass, linearly coupled to a fixed-temperature boundary and radiatively coupled to a second fixed-temperature boundary, with a constant impressed heat load, are derived. The results are verified by evaluation of limiting cases and comparison with commercial finite-difference heat transfer software.     

Analogues of perillaketone as highly potent agonists of TRPA1 channel

Transient receptor potential (TRP) channels represent interesting molecular target structures involved in a number of different physiological and pathophysiological systems. In particular, TRPA1 channel is involved in nociception and in sensory perception of many pungent chemesthetic compounds, which are widespread in spices and food plants, including Perilla frutescens. A natural compound from P. frutescens (isoegomaketone) and 16 synthetic derivatives of perillaketone have been prepared and tested in vitro on rTRPA1 expressed in HEK293 cells and their potency, efficacy and desensibilisation activity measured. Most derivatives proved to be high potency agonists of TRPA1, with a potency higher than most natural agonists reported in the literature. These furylketones derivatives, represent a new class of chemical structures active on TRPA1 with many potential applications in the agrifood and pharmaceutical industry.     

Robust stability of homogeneous large-scale bilinear systems with time delays and uncertainties

This paper addresses the problem of stability analysis for homogeneous large-scale uncertain bilinear time-delay systems subjected to constrained inputs. Both nonlinear uncertainties and interval systems are discussed. Several delay-independent criteria are presented to guarantee the asymptotic stability of the overall systems. The main feature of the presented criteria is that although the Lyapunov stability theorem is used, they do not involve any Lyapunov equations that may be unsolvable. Three illustrative numerical examples are presented to verify the effectiveness of the proposed stability criteria.     

Crosstalk noise modeling of multiwall carbon nanotube (MWCNT) interconnects using finite-difference time-domain (FDTD) technique

This paper presents an accurate and efficient model for the transient analysis of multiwall carbon nanotubes (MWCNT) using finite-difference time-domain (FDTD) method. The proposed model can be essentially used to analyze the functional and dynamic crosstalk effects of coupled-two MWCNT interconnect lines. Using the proposed model the voltage and current can be accurately estimated at any point on the interconnect line and furthermore, the model can be extended to coupled-n interconnect lines with a low computational cost. Crosstalk induced propagation delay, peak voltage, and its timing instance are measured using the proposed model and validated by comparing it to the HSPICE simulations. Over a random number of test cases it is observed that the average error in estimating the noise peak voltage on a victim line is less than 1%. The proposed model is extremely useful for accurate estimation of crosstalk induced performance parameters of MWCNT interconnects.     

微电网故障下三相电压型并网变换器瞬态行为分析

三相电压源型变换器(VSC)是交直流混合电力系统中重要的功率接口装置。交直流混合系统存在诸如电网侧故障或直流侧负载变化等扰动,对其中功率接口变换器造成难以预计的影响。着重研究微电网故障时并网变换器的瞬态响应过程及其机理。首先,给出了电网三相电压暂降时三相电压源型变换器的失稳的瞬态响应现象。然后,通过非线性分析揭示了该不稳定现象的物理本质,并通过系统建模计算给出了系统参数空间中的稳定域范围;最后,通过微电网与变换器仿真验证了分析计算的有效性。     

Calibration of dynamic tool–workpiece interface temperature measurement during friction stir welding

The objective of this work is to accurately measure the transient temperatures at the tool–workpiece interface during friction stir welding (FSW) using thermocouples that are embedded in the tool. Temperature sensors embedded in the friction stir (FS) tool provide a non-consumable localized temperature measurement capability that is crucial for process research, development, and control. A modification of the ASTM E-1461 standard for measuring thermal diffusivity with pulses of heat flux is proposed for calibrating the transient response of temperature sensors located near the surface of the FS tool. These tests enable the calculation of each sensor’s time constant, which are used in one-dimensional analytical models of the dynamic response to calculate the true interface temperature. Time constants between 21 and 43 ms are measured for 0.25-mm-diameter, sheathed thermocouples located at the FS tool surface.     

压力脉动作用下管道的流固耦合瞬态分析

针对液压输流管内的压力脉动研究,提出流体压力脉动的计算方法和管道流固耦合分析的计算模型。对流体压力脉动进行编程,得到压力脉动作用产生激振力的变化。建立管道和流体实体模型,采用UDF技术将脉动压力编译到流体中,从而进行流固耦合瞬态力学分析,得到异径管和弯管处流体压力变化以及管道的应力和变形情况。研究结果表明:压力脉动沿管道传播发生衰减,其产生的激振力对弯管破坏较大;弯管段流体产生压力集中,进而引起弯管段变形大于异径管段。将压力脉动加载到管道中,对输流管道研究具有一定参考价值。