Implication of Climate Change Induced Variation in Wind Extremes on Wind Farm in Mountainous Area of Central China—A Case Study of Hengshan

AbstractWind load is critical to the safety of wind turbines. Wind turbines are designed according to the referrence wind speed of 50-year recurrence interval. The climate change induced variation in extremes of wind could impact safety of wind turbines. Meteorological data from Hengshan weather station in central China is investigated. The wind data of 1973–1992 and 1992–2011 are utilized to estimate the extreme wind of 50-year recurrence interval using method of independent storm and generalized pareto distribution model. It is uncovered that although extreme wind of 50-year recurrence interval escalate a little during the two time spans, it will not affect the safety of wind turbines over there notably

A New Approach to Fault Diagnosis of Power Systems Using Fuzzy Reasoning Spiking Neural P Systems

Fault diagnosis of power systems is an important task in power system operation. In this paper, fuzzy reasoning spiking neural P systems (FRSN P systems) are implemented for fault diagnosis of power systems for the first time. As a graphical modeling tool, FRSN P systems are able to represent fuzzy knowledge and perform fuzzy reasoning well. When the cause-effect relationship between candidate faulted section and protective devices is represented by the FRSN P systems, the diagnostic conclusion can be drawn by means of a simple parallel matrix based reasoning algorithm. Three different power systems are used to demonstrate the feasibility and effectiveness of the proposed fault diagnosis approach. The simulations show that the developed FRSN P systems based diagnostic model has notable characteristics of easiness in implementation, rapidity in parallel reasoning, and capability in handling uncertainties. In addition, it is independent of the scale of power system and can be used as a reliable tool for fault diagnosis of power systems

Mini percutaneous nephrolithotomy is a noninferior modality to standard percutaneous nephrolithotomy for the management of 20-40 mm renal calculi: A Multicenter randomized controlled trial

Background: High quality of evidence comparing mini percutaneous nephrolithotomy (mPNL) with standard percutaneous nephrolithotomy (sPNL) for the treatment of larger-sized renal stones is lacking. Objective: To compare the efficacy and safety of mPNL and sPNL for the treatment of 20–40 mm renal stones. Design, setting, and participants: A parallel, open-label, and noninferior randomized controlled trial was performed at 20 Chinese centers (2016–2019). The inclusion criteria were patients 18–70 yr old, with normal renal function, and 20–40 mm renal stones. Intervention: Percutaneous nephrolithotomy PNL was performed using either 18 F or 24 F percutaneous nephrostomy tracts. Outcome measurements and statistical analysis: The primary outcome was the one-session stone-free rate (SFR). The secondary outcomes included operating time, visual analog pain scale (VAS) score, blood loss, complications as per the Clavien-Dindo grading system, and length of hospitalization. Results and limitations: The 1980 intention-to-treat patients were randomized. The mPNL group achieved a noninferior one-session SFR to the sPNL group by the one-side noninferiority test (0.5% [difference], p < 0.001). The transfusion and embolization rates were comparable; however, the sPNL group had a higher hemoglobin drop (5.2 g/l, p < 0.001). The sPNL yielded shorter operating time (–2.2 min, p = 0.008) but a higher VAS score (0.8, p < 0.001). Patients in the sPNL group also had longer hospitalization (0.6 d, p < 0.001). There was no statistically significant difference in fever or urosepsis occurrences. The study's main limitation was that only 18F or 24F tract sizes were used. Conclusions: Mini mPNL achieves noninferior SFR outcomes to sPNL, but with reduced bleeding, less postoperative pain, and shorter hospitalization. Patient summary: We evaluated the surgical outcomes of percutaneous nephrolithotomy using two different sizes of nephrostomy tracts in a large population. We found that the smaller tract might be a sensible alternative for patients with 20–40 mm renal stones. This multicenter, parallel, open-label, and noninferior randomized controlled trial showed that mini percutaneous nephrolithotomy achieved noninferior stone-free rate with advantages of reduced blood loss, less postoperative pain, and shorter hospitalization. Mini percutaneous nephrolithotomy should be considered a sensible alternative treatment of 20–40 mm renal stones.grants from high-level development funding of Guangzhou Medical Universit

UK Executives' vision on business environment for information scanning, a cross industry study

Business environment scanning contributes a great deal to strategic intelligence gathering. However, earlier studies treat the business environment as a single entity. This study based on a multi-industry survey examined how UK executives perceive the stability of the business environment in which their companies operate, and what environmental sectors are perceived more strategically important than others for information scanning. The effort reveals that UK executives perceive the immediate-task environment information more strategically important than far-general environment information, but the perception of far environment information differs widely from industry to industry. A corporate "radar" system for business environment scanning is proposed to offer practical guidance. Our conclusion is that industry-specific environment sectors should be identified for strategic information scanning

Simplified Analytic Approach of Pole-to-Pole Faults in MMC-HVDC for AC System Backup Protection Setting Calculation

AC (alternating current) system backup protection setting calculation is an important basis for ensuring the safe operation of power grids. With the increasing integration of modular multilevel converter based high voltage direct current (MMC-HVDC) into power grids, it has been a big challenge for the AC system backup protection setting calculation, as the MMC-HVDC lacks the fault self-clearance capability under pole-to-pole faults. This paper focused on the pole-to-pole faults analysis for the AC system backup protection setting calculation. The principles of pole-to-pole faults analysis were discussed first according to the standard of the AC system protection setting calculation. Then, the influence of fault resistance on the fault process was investigated. A simplified analytic approach of pole-to-pole faults in MMC-HVDC for the AC system backup protection setting calculation was proposed. In the proposed approach, the derived expressions of fundamental frequency current are applicable under arbitrary fault resistance. The accuracy of the proposed approach was demonstrated by PSCAD/EMTDC (Power Systems Computer-Aided Design/Electromagnetic Transients including DC) simulations

Multi-Robot Trajectory Planning and Position/Force Coordination Control in Complex Welding Tasks

In this paper, the trajectory planning and position/force coordination control of multi-robot systems during the welding process are discussed. Trajectory planning is the basis of the position/ force cooperative control, an object-oriented hierarchical planning control strategy is adopted firstly, which has the ability to solve the problem of complex coordinate transformation, welding process requirement and constraints, etc. Furthermore, a new symmetrical internal and external adaptive variable impedance control is proposed for position/force tracking of multi-robot cooperative manipulators. Based on this control approach, the multi-robot cooperative manipulator is able to track a dynamic desired force and compensate for the unknown trajectory deviations, which result from external disturbances and calibration errors. In the end, the developed control scheme is experimentally tested on a multi-robot setup which is composed of three ESTUN industrial manipulators by welding a pipe-contact-pipe object. The simulations and experimental results are strongly proved that the proposed approach can finish the welding task smoothly and achieve a good position/force tracking performance