Physical Layer Security for UAV Communications:A Comprehensive Survey

Due to its high mobility and flexible deployment,unmanned aerial vehicle(UAV)is drawing unprecedented interest in both military and civil applications to enable agile and ubiquitous connectivity.Mainly operating in an open environment,UAV communications benefit from dominant line-of-sight links;however,this on the other hand renders the communications more vulnerable to malicious attacks.Recently,physical layer security(PLS)has been introduced to UAV systems as an important complement to the conventional cryptography-based approaches.In this paper,a comprehensive survey on the current achievements of UAV-PLS is conducted.We first introduce the basic concepts including typical static/-mobile UAV deployment scenarios,the unique air-toground channel and aerial nodes distribution models,as well as various roles that a UAV may act when PLS is concerned.Then,we start by reviewing the secrecy performance analysis and enhancing techniques for statically deployed UAV systems,and extend the discussion to the more general scenario where the UAVs’mobility is further exploited.For both cases,respectively,we summarize the commonly adopted methodologies,then describe important works in the litera ture in detail.Finally,potential research directions and challenges are discussed to provide an outlook for future works in the area of UAV-PLS.

Long-chain alkanol-alkyl carboxylic acid-based low-viscosity hydrophobic deep eutectic solvents for one-pot extraction of anthraquinones from Rhei Radix et Rhizoma

Natural long-chain alkanol and alkyl carboxylic acid were used to prepare novel hydrophobic deep eutectic solvents(HDESs).These HDESs are liquid at room temperature and have low viscosity(<12.26 mPa·s),low polarity(lower than that of methanol,ChCl-based deep eutectic solvents and other reported HDESs),and low density(<0.928 g/mL).A simple one-pot method based on a novel HDES-water two-phase extraction system was constructed for the extraction of weak-polarity bioactive components,anthraquinones,from Rhei Radix et Rhizoma.This HDES-based new extraction method does not consume hazardous organic solvents and can obtain a total anthraquinone yield of 21.52 mg/g,which is close to that obtained by the Chinese pharmacopoeia method(21.22 mg/g)and considerably higher than those by other reported HDESs-based extraction methods(14.20-20.09 mg/g,p<0.01).The high extraction yield can be mainly attributed to the severe destruction of the RRR cell walls by the extraction system and the excellent dissolving ability of novel HDESs for anthraquinones.

Analysis of Hypertension Status and Its Influencing Factors in Some Areas of Hubei Province, China

Objective: To know about the current situation of hypertension in some areas of Hubei Province and analyze the influencing factors. Methods: According to the principle of Stratified sampling, we conducted health examination and questionnaire survey for 1500 residents over the age of 18 at observation point of chronic noninfectious diseases at 10 sub-districts (towns) of Wuhan City, Jingzhou City, Huanggang City, Shiyan City, which used descriptive statistics and logistics to regressively analyze Current situation of hypertension and its influencing factors of residents. Results: Prevalence of hypertension of rural and urban residents over 18 is 27.44% in Hubei province. There are many differences among prevalence of hypertension of male and female, distribution of BMI of rural and urban residents and prevalence of hypertension and so on, and it has statistical significance (P-value < 0.05 averagely);logistic regressive analysis result shows that different age, gender, education level, dieting habits (high salt and high oil), family per capita monthly income, BMI have statistical significance on the prevalence of hypertension in urban and rural residents of Hubei Province. Conclusions: The prevalence of hypertension in the residents of five cities and prefectures in Hubei Province is on the trend of rising in ladder form and at a much earlier age. The health education, monitoring and intervention of chronic diseases need to be widely carried out, with emphasis on the intervention of the residents’ eating habits of high salt and oil, smoking, drinking and other bad lifestyle.

Isolation of fucoxanthin from Sargassum thunbergii and preparation of microcapsules based on palm stearin solid lipid core

The objective of this study was to isolate fucoxanthin from Sargassum thunbergii and develop microcapsules with palm stearin as the solid lipid core for stability and efficient oral delivery of fucoxanthin. The microcapsules had smooth surfaces with the volume weighted mean diameter （d4.3） of 19.19 μm. Encapsulation efficiency and loading capacity of microcapsules with fucoxanthin were 98.3% and 0.04%, respectively. Moreover, the fucoxanthin in microcapsules presented higher stability than free fucoxanthin against light, humidity and temperature. Especially, the retention rates of fucoxanthin encapsulated in microcapsules reached 97.20% at 4℃, 92.60% at 25℃, 92.32% with the relative humidity of 33% and 92.60% in the dark. The cumulative amount of fucoxanthin released from microcapsules was 22.92% in simulated gastric fluid （SGF） and 56.55% in simulated intestinal fluid （SIF）.

Water use efficiency data from 2000 to 2019 in measuring progress towards SDGs in Central Asia

Central Asia,located in the hinterland of the Eurasian continent,is characterized with sparse rainfall,frequent droughts and low water use efficiency.Limited water resources have become a key factor restricting the sustainable development of this region.Accurately assessing the efficiency of water resources utilization is the first step to achieve the UN Sustainable Development Goals(SDGs)in Central Asia.However,since the collapse of the Soviet Union,the evalua-tion of water use efficiency is difficult due to low data availability and poor consistency.To fill this gap,this paper developed a Water Use Efficiency dataset(WUE)based on the Moderate Resolution Imaging Spectroradiometer(MODIS)Gross Primary Production(GPP)data and the MODIS evapotranspiration(ET)data.The WUE dataset ranges from 2000 to 2019 with a spatial resolution of 500 m.The agricultural WUE was then extracted based on the Global map of irrigated areas and MODIS land use map.As a complementary,the water use amount per GDP was estimated for each country.The present dataset could reflect changes in water use efficiency of agriculture and other sectors.

Coverage Optimization for UAV-Aided Internet of Things with Partial Channel Knowledge

Due to the high maneuverability of unmanned aerial vehicles(UAVs),they have been widely deployed to boost the performance of Internet of Things(IoT).In this paper,to promote the coverage performance of UAV-aided IoT communications,we maximize the minimum average rate of the IoT devices by jointly optimizing the resource allocation strategy and the UAV altitude.Particularly,to depict the practical propagation environment,we take the composite channel model including both the small-scale and the large-scale channel fading into account.Due to the difficulty in acquiring the random small-scale channel fading,we assume that only the large-scale channel sate information is available.On this basis,we formulate an optimization problem,which is not convex and challenging to solve.Then,an efficient iterative algorithm is proposed using block coordinate descent and successive convex optimization tools.Finally,simulation results are presented to demonstrate the significant performance gain of the proposed scheme over existing ones.