Trend Analysis in Reference Evapotranspiration Using Mann-Kendall and Spearman’s Rho Tests in Arid Regions of Iran

In this research, temporal trends of reference evapotranspiration (ET0) values were investigated in arid regions of Iran. For this purpose, meteorological observations collected from 11 high quality meteorological sites over a 41-year period (1965–2005) were used and statistically significant ET0 trends in the monthly, seasonal and annual time basis were detected using nonparametric Mann-Kendall (MK) and Spearman’s Rho (SR) tests at the 5% significant level. To eliminate the effect of serial correlation on the test results, the Trend Free Pre-Whitening (TFPW) approach was applied. The results of this study indicated that the ET0 trends for some cities were increasing (positive) however, for some sites, they showed decreasing (negative) trends. The most number of significant ET0 trends on a monthly time scale occurred at Birjand but no significant trend was observed at the Bandarabbas, Sabzevar and Semnan sites. On the annual time scale, Mashhad revealed the highest positive trend (7.5 mm per year). On the other hand, Esfahan showed the highest decreasing (negative) ET0 trend of about −6.38 mm per year. In general, the performances and abilities of the MK and SR tests were consistent at the verified significant level.     

Squeezing and entanglement in multi-qutrit systems

We study squeezing and bipartite entanglement in a multi-qutrit system initially in a coherent state, initiated by the two-axis counter-twisting Hamiltonian in the presence and also absence of a magnetic field. We start with an initial coherent state which is neither squeezed nor entangled; however, it gains both properties as it is evolved by the Hamiltonian. Both squeezing and entanglement show an oscillatory behavior in time and stronger Hamiltonians correspond to smaller oscillation periods. Generation of almost continuous squeezing according to Kitagawa criterion seems feasible; however, off and on squeezing death is observed according to that of Wineland. The entanglement is diminished as the size of the system is increased, implying that the generation of strong entanglement in large multi-qutrit systems, instigated by the counter-twisting Hamiltonian, may not be feasible. Application of a magnetic field may have adverse effect on both squeezing and entanglement.     

Electrochemical preparation and characterization of brain-like nanostructures of Y2O3

Nanostructured Y2O3 was successfully prepared via a two-step and template-free method.Firstly,yttrium hydroxide precursor was galvanostatically grown on the steel substrate from chloride bath by direct and pulse current deposition modes.Direct current deposition was carried out at the constant current density of 0.1 A/dm2 for 600 s.The pulse current was also performed at a typical on-time and off-time(ton=1 s and toff=1 s)with an average current density of 0.05 A/dm2(Ia=0.05 A/dm2)for 600 s.The obtained hydroxide films were then scraped from the substrates and thermally converted into final oxide product via heat-treatment.Thermal behaviors and phase transformations during the heat treatment of the hydroxide powder samples were investigated by differential scanning calorimetry(DSC)and thermogravimetric analysis(TGA).The final oxide products were characterized by means of X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR)and scanning electron microscopy(SEM).The results showed that the well-crystallized Y2O3 with brain-and sphere-like morphology were achievable via pulse and direct deposition modes,respectively.It was concluded that pulse current cathodic electrodeposition offered a facile route for preparation of nanostructured Y2O3.     

高压静电聚结器设计、实验及现场应用

为进一步提高电破乳的效率,通过分析油中水滴在电场力作用下的受力情况,得出影响水滴静电聚结的因素,并设计了绝缘型静电聚结器对油包水乳状液进行室内实验,结果表明,增加电场强度和延长电场停留时间可有效促进分散水滴聚并成大颗粒水滴,提高其在油相中的沉降速率,加快油水分层速度。含水量过高导致油水乳状液电导率激增,不利于乳状液的静电聚结。具有良好的稳定性和耐腐蚀性的绝缘材料可有效防止因局部电流过大导致的电场崩溃。在此基础上开发出的静电聚结器在现场生产中取得了较好效果,在保证分离效果的前提下,能显著降低静电聚结器能耗。     

Distributed fault detection and isolation in time-varying formation tracking UAV multi-agent systems

The problem of distributed fault detection and isolation (DFDI) in conjunction with time-varying formation control of unmanned aerial vehicle (UAV) multi-agent systems with multiple-leader leader–follower structure is studied, in this paper. It is assumed that the communication data of the agents are noisy, and faults may occur in either leaders or followers. The followers are not aware of the main trajectory and just follow the leaders. The first step in this paper is to reduce the communication noise. Besides, if a fault occurs in one of the leaders causing to exit the leader from the main trajectory, the followers should be able to detect the fault, isolate the leader, use the other leaders' data, and keep the main trajectory. Tracking the trajectory by followers in such a case is the second step of this paper. Preserving the time-varying formation despite a fault occurring in one of the followers is the next step. To reach these goals, a distributed array of Kalman filters is used for noise cancellation and data extraction. Next, the combination of state vector data fusion and some type of $\chi$² test are employed for DFDI, in agents. Besides, a controller is implemented in each agent for formation tracking. In this controller, estimated relative position and velocity vectors of the agents are employed to keep the time varying formation while tracking the leaders. The closed-loop stability is studied via Lyapunov stability theorem, and various simulations are carried out to demonstrate the capability of the proposed strategy.