A Numerical and Experimental Study of the Time Averaged and Transient Flow Downstream of a Butterfly Valve

This research took the DN50 butterfly valve as the research object and studied the flow situation of butterfly valves with different shafts. The resistance characteristics, flow state, characteristics, and flow instability of butterfly valves with different structures were studied by experiments and numerical simulations. Research shows that the edge of the valve disc occurs flow separation, and the drag of the valve disc fluctuates non-periodically with time. Under different opening degrees, the velocity distribution downstream of the valve varies, and the effect of the shaft on the velocity fluctuation is different. Finally, the unstable region of flow downstream of the valve is determined. This study provides a reference for the use and optimization of butterfly valves.

Thermal Processing Map and Microstructure Evolution of Inconel 625 Alloy Sheet Based on Plane Strain Compression Deformation

Plane strain compression tests were used to study the deformation behavior of an Inconel 625 alloy sheet at various temperatures and strain rates. The peak stress was selected to establish the constitutive equation, and the processing maps under different strains were drawn. The results show that the effective stress–strain curve of Inconel 625 has typical dynamic recrystallization (DRX) characteristics. With the increasing deformation temperature and the decreasing strain rate, the softening effect is significantly enhanced. The parameters of the constitutive equation are calculated, and the average error of the constitutive equation is 5.68%. Through the analysis of the processing map, a deformation temperature of 950–960 °C with a strain rate of 0.007–0.05 s−1 were determined as the unstable region, and obvious local plastic-rheological zones were found in the unstable region. The optimum deformation condition was found to be 1020–1060 °C/0.005–0.03 s−1. Through electron backscattered diffraction (EBSD) characterization, it was found that both the increase of temperature and the decrease of strain rate significantly promote the recrystallization process. At a low strain rate, the main recrystallization mechanism is discontinuous dynamic recrystallization (DDRX). It is expected that the above results can provide references for the optimization of the rolling process and microstructure control of an Inconel 625 alloy sheet.

Active Q Flux Concept for Sensorless Control of Synchronous Reluctance Machines

<p>This paper proposes a new scheme to use active flux on q-axis for sensorless control of synchronous reluctance machines (SynRM). Conventionally, “Active Flux” on d-axis is adopted to convert a salient pole machine into a fictitious non-salient pole machine. However, the injected d-axis flux can deteriorate high frequency injection (HFI) sensorless control performance or even run the system into unstable region at low speed. This paper demonstrates active flux on q-axis can support back-EMF sensorless control at high speed and improve low speed HFI performance substantially. A seamless transition from HFI sensorless method to back-EMF voltage method is attained after adopting the proposed active q flux. Experiment results are used to validate the proposed method.</p>

Active Q Flux Concept for Sensorless Control of Synchronous Reluctance Machines

<p>This paper proposes a new scheme to use active flux on q-axis for sensorless control of synchronous reluctance machines (SynRM). Conventionally, “Active Flux” on d-axis is adopted to convert a salient pole machine into a fictitious non-salient pole machine. However, the injected d-axis flux can deteriorate high frequency injection (HFI) sensorless control performance or even run the system into unstable region at low speed. This paper demonstrates active flux on q-axis can support back-EMF sensorless control at high speed and improve low speed HFI performance substantially. A seamless transition from HFI sensorless method to back-EMF voltage method is attained after adopting the proposed active q flux. Experiment results are used to validate the proposed method.</p>

Islamic State Central Africa Province (ISCAP)

The emergence of the Islamic State’s new affiliate—Islamic State Central Africa Province (ISCAP)—in Sub-Saharan Africa, has a devastating effect on the security and political landscape of an already fragile and unstable region. Based mainly on open sources, including think tanks, journals, U.N. reports, and news media, this paper attempts to understand the motivations and operations of the Islamic State fighters of this province and the dangers ISCAP presents to local and international actors.

Voltage Stability Analysis of Nigerian 330kV Power Grid using Static P-V Plots

Nigeria power system has been experiencing total or partial system failures in recent times and voltage instability is a strong factor. The paper seeks to perform the voltage stability analysis, based on static P-V plots, on buses located around and within the South East zone of Nigeria. An injection group containing generators to serve as the source and a sink group as loads to be monitored are created. The generators are assumed to be within their min/max MW limits. The load is increased in the sink group as well as in the source group to maintain the same generation/load balance. Load power and bus voltages (P-V) curves are plotted on the load busbars and the first busbar to reach the voltage collapse and MW transfer limit are determined. From the results obtained, at a load of 100 MW, Makurdi bus recorded a voltage of 0.9301 pu which is already below the regulatory standards of ±5% of the nominal line voltage. It entered the region of instability at a load of 245 MW. This created a situation of system instability and a possible partial system collapse. Subsequently, at a load of 260 MW, the system clearly entered unstable region giving rise to partial system collapse of the network.

Low-Speed Stability Optimization of Full-Order Observer for Induction Motor

In terms of the instability of the full-order observer for the induction motor in the low-speed regenerative mode, the low-speed unstable region which leads to the extension of the commissioning cycle cannot be eliminated by the traditional adaptive law which aims at good system performance. It is proposed that the feedback gain matrix can control both the unstable region and the system performance both. To make a trade-off between the stability and performance by designing the feedback gain matrix is still an open problem. To solve this problem, first we analyze the cause of instability and derive constraints to ensure system stability by establishing a transfer function of the adaptive observing system for the speed. Then, with the derived constraints as the design criteria for the feedback gain matrix, a control strategy combining the weighted adaptive law with the improved feedback gain matrix is proposed to improve the stability at low speed. Finally, by comparing the traditional control strategy with the proposed control strategy through simulations and experiments, we show that the proposed control strategy achieves better performance with higher stability.

Energy Efficient Optimized LEACH and SEP Routing Protocol for WSN

We all know how Wireless Sensor Network (WSN) is making its way in the modern world and how its application is growing effectively. It has been useful technology which helps to transmit and receive the data. In WSN, all information of physical parameter is sensed and processed by the sensor nodes. Along with the growth of technology in WSN, growth of sensor node is also in progress, it means that size of sensor node is getting reduced. Due to this dimension of the battery of the sensor node is also decreases. Hence Power storage of the battery is also reduced which is a demerit in WSN. But in sensor network replacement of battery is not possible. So we can increase the energy efficiency of sensor node by using LEACH protocol. This protocol helps us to increase life span of network. For heterogeneous network, LEACH produces greater unstable region. To the network stable the paper proposes another protocol is Stable Election protocol (SEP). In this paper LEACH and SEP protocol are tested with MATLAB simulation and comparison of both has done.

NORTH CAUCASUS: PROMOTING CONFLICT RESOLUTION STRATEGY IN AN UNSTABLE REGION

The article is devoted to comparative analysis of contemporary political theories of socio-cultural integration policy as a way of constructive conϐlict resolution in the North Caucasus. Latent ethno-political conflicts remain the most noticeable of contemporary challenges and threats to civil solidarity and ethnic peace in this unstable region. The fundamental issue that requires a constructive solution in order to ensure political stability in the North Caucasus region is the promotion of multi-level and inclusive sociocultural integration. This study claims that the escalation of protracted, deep-rooted conϐlicts is the result of large-scale social disintegration as a fundamental threat to the North Caucasus stability. Socio-cultural disintegration is superimposed on ethno-territorial and social polarization: ethno-political particularism, religious traditionalism and large-scale demodernization of the North Caucasus archaize regional identities, hindering the formation of civil society.