Meteorological Drought Detection and Forecast Using Standardized Precipitation Index and Univariate Distribution Models: Case Study of Bamako, Mali

As an extended period of unusually dry weather conditions without sufficient rain, drought poses enormous risk on societies. Characterized by the absence of precipitation for long periods of time, often resulting in water scarcity, droughts are increasingly posing significant environmental challenges. Drought is therefore considered an important element in the management of water resources, especially groundwater resources during drought. This study therefore sought to investigate the rainfall variability and the frequency of drought for the period 1991 to 2020 in Bamako based on monthly rainfall data from Bamako-Senou gauge station. The standardized precipitation index (SPI) for 12-month, 6-month and 3-month timescales and the SPI for annual totals were used to characterized drought in the study area (Bamako). Univariate parametric probability distributions such as Normal, Log-normal, Gumbel type I and Pearson type III (P3) distributions were fitted with drought variables (severity and duration) for future planning and management. Non-parametric test such as Mann-Kendall trend test was also used to detect trend in annual rainfall data. The results showed that based on 12-month SPI, Bamako experienced two (02) extreme droughts one in July 2002 (SPI = -2.2165) and another in June 2015 (SPI = -2.0598 QUOTE SPI=-2.0598 ). Drought years represented 46.67% for the overall periods according to the SPI for annual totals. The result further indicated that based on the goodness of fit test, the P3 distribution represents the best fitted distribution to both drought severity and duration over Bamako. Bamako is expected to experience several severe severities with higher and shorter duration in the future. Severities with 1, 2, 6, and 10-month duration had return periods ranged from 2.4 to 3.8 years, while 5, 10, 20, 25, 50, and 100-year return periods had 18.51, 26.08, 33.25, 35.50, 42.38, and 49.14 severities, respectively, and durations associated to these severities were 19.8, 26.9, 33.5, 35.6, 42, and 48.2 months, respectively.

Beamforming and Interference Cancellation for D2D Communication Assisted by Two-Way Decode-and-Forward Relay Node

This paper investigates the device-to-device(D2D) communication underlaying cellular network assisted by a two-way decode-and-forward relay node. We assume the base station(BS) is equipped with M-antenna and serves its own cellular user while the D2D users communicate via a two-way decode-and-forward relay node. Both beamforming(BF) and interference cancellation(IC) strategies at the BS are considered to improve the performance for the cellular link and D2D link, respectively. We first analyze the received signal-to-interference-plus-noise for the cellular link under BF and IC strategies and then derive the exact closed-form expressions for the cellular link. Asymmetric and symmetric cases are discussed for various locations of each user. Finally, the approximations for high signal-to-noise regime are also presented. Numerical results demonstrate the accuracy of the analytical and asymptotic results.

Analysis on Potential Conflict Frequency of Intersected Air Routes in Terminal Airspace Design

In order to obtain accurate conflict risks in terminal airspace design,the concept and calculation model of potential conflict frequency for intersected routes are proposed.Conflict frequency is represented by the product of horizontal conflict frequency and vertical conflict probability.The horizontal conflict frequency is derived from the probability density distribution of conflicts in a period of time.Based on the recorded radar trajectory data,the concept and model of ROUTE distance are proposed,and the probability density function of aircraft height at a specified ROUTE distance is deduced by kernel density estimation.Furthermore,vertical conflict probability and its horizontal distribution are achieved.Examples of three intersected arrival and departure route design schemes are studied.Compared with scheme 1,the conflict frequency values of the other two improved schemes decrease to53% and 24%,respectively.The results show that the model can quantify potential conflict frequency of intersected routes.

Stereo-dynamics of the exchange reaction H_a+LiH_b→LiH_a+H_b and its isotopic variants

The quasi-classical trajectory （QCT） method is used to calculate the stereo-dynamics of the exchange reaction Ha＋LiHb→LiHa＋Hb and its isotopic variants based on an accurate potential energy surface reported by Prudente et al. [Prudente F V, Marques J M C and Maniero A M 2009 Chem. Phys. Lett. 474 18]. The reactive probability of the title reaction is computed. The vector correlations and four polarization-dependent generalized differential cross sections （PDDCSs） at different collision energies are presented. The influences of the collision energy and the reagent rotation on the product polarization are studied in the present work. The results indicate that the product rotational angular momentum j′ is not only aligned, but also oriented along the direction perpendicular to the scattering plane. The product polarization distributions of the title reaction and its isotopic variants exhibit distinct differences which may arise from different mass combinations.

Identification of Wool and Cashmere

The quality number66 wool and the first grade cashmerewere tested and analyzed by using the scanning electronmicroscope(SEM)and the probability distribution of thediameter,the surface scale height and the surface scalethickness of the wool and the cashmere were got,thenthe error identification probability(EIP)of the three pa-rameters were calculated.After verifying that these threeparameters were linear non-related,by using the prob-ability theory,the EIPs of these three parameters weremultiplied,thus,the total EIPs of the wool and the cash-mere were reduced.The result of the experiment verifiedthis conclusion.

高校住房商品化的决策与政策

我国高校普遍存在着住房困难，改革开放十多年来，这一局面曾经得到了很大程度的缓解。然而，在新的形势下，又出现了一系列亟待解决的新问题，教师住房短缺重新成为非常严峻的现实。本文针对天津大学教师住房的现状和存在的主要问题，首先分析了教师住房对学校建设与发展的重要意义，分析了提粗补帖等改革措施的利弊，以及多方集资所取得的成绩和面临的新问题。然后，提出了住房商品化是彻底解决住房困难和实现住房与分房改革的根本途径的观点或，并探讨了这一措施的实际操作方法和政策。最后，作者讨论了住房商品化与学校整体建设与发展的关系，以及对高校体制改革的积极意义。

Survival Probability of Population-size-dependent Branching Processes in Random Environments

The class of population-size-dependent branching processes in independent identically distributed random environments is investigated. Under the critical case and appropriate moment assumption, we establish an asymptotic estimate of the survival probability at generation n.

On SIR epidemic models with generally distributed infectious periods： Number of secondary cases and probability of infection

Recently, Clancy [SIR epidemic models with general infectious period distribution, Statist. Prob. Left. 85 （2014） 1-5] has shown how SIR epidemics in which individuals＇ infection periods are not necessarily exponentially distributed may be modeled in terms of a piecewise-deterministic Markov process （PDMP）. In this paper, we present a more detailed description of the underlying PDMP, from which we analyze the population transmission number and the infection probability of a certain susceptible individual.