Self‑Assembly of Binderless MXene Aerogel for Multiple‑Scenario and Responsive Phase Change Composites with Ultrahigh Thermal Energy Storage Density and Exceptional Electromagnetic Interference Shielding

The severe dependence of traditional phase change materials(PCMs)on the temperature-response and lattice deficiencies in versatility cannot satisfy demand for using such materials in complex application scenarios.Here,we introduced metal ions to induce the self-assembly of MXene nanosheets and achieve their ordered arrangement by combining suction filtration and rapid freezing.Subsequently,a series of MXene/K^(+)/paraffin wax(PW)phase change composites(PCCs)were obtained via vacuum impregnation in molten PW.The prepared MXene-based PCCs showed versatile applications from macroscale technologies,successfully transforming solar,electric,and magnetic energy into thermal energy stored as latent heat in the PCCs.Moreover,due to the absence of binder in the MXene-based aerogel,MK3@PW exhibits a prime solar-thermal conversion efficiency(98.4%).Notably,MK3@PW can further convert the collected heat energy into electric energy through thermoelectric equipment and realize favorable solar-thermal-electric conversion(producing 206 mV of voltage with light radiation intensity of 200 mw cm^(−2)).An excellent Joule heat performance(reaching 105℃with an input voltage of 2.5 V)and responsive magnetic-thermal conversion behavior(a charging time of 11.8 s can achieve a thermal insulation effect of 285 s)for contactless thermotherapy were also demonstrated by the MK3@PW.Specifically,as a result of the ordered arrangement of MXene nanosheet self-assembly induced by potassium ions,MK3@PW PCC exhibits a higher electromagnetic shielding efficiency value(57.7 dB)than pure MXene aerogel/PW PCC(29.8 dB)with the same MXene mass.This work presents an opportunity for the multi-scene response and practical application of PCMs that satisfy demand of next-generation multifunctional PCCs.

We Watch: An Application for Watching Video Across Two Mobile Devices

In recent years, high-resolution video has developed rapidly and widescreen smart devices have become popular. We present an Android application called WeWatch that enables high-resolution video to be shared across two mobile devices when they are close to each other. This concept has its inspiration in machine-to-machine connections in the Internet of Things （loT）. We ensure that the two parts of the video are the same size over both screens and are synchronous. Further, a user can play, pause, or stop the video by moving one device a certain distance from the other. We decide on appropriate distances through experimentation. We implemented WeWatch on Android operating system and then optimize Watch so battery consumption is reduced. The user experience provided by WeWatch was evaluated by students through a questionnaire, and the reviews indicated that WeWatch does improve the viewing experience.

International Experience and Enlightenment of the Regularization Development of Stall Economy

Stall economy can promote the recovery of national economy,relieve the employment pressure of tens of thousands of people,increase people’s happiness,and so on.Many benefits brought by stall economy show its important position and function.In fact,stall economy should be a durable product,not a substitute.We should look at it from a long-term perspective,standardize it and develop it.Combined with the practices and policies of many countries on the standardization of street stall economy,this article puts forward the reference methods for the standardization of street stall economy in the future.The country,society and individuals can enjoy the wealth and value brought by stall economy in the future.

Machine learning for nanohertz gravitational wave detection and parameter estimation with pulsar timing array

Studies have shown that the use of pulsar timing arrays(PTAs)is among the approaches with the highest potential to detect very low-frequency gravitational waves in the near future.Although the capture of gravitational waves(GWs)by PTAs has not been reported yet,many related theoretical studies and some meaningful detection limits have been reported.In this study,we focused on the nanohertz GWs from individual supermassive binary black holes.Given specific pulsars(PSR J1909-3744,PSR J1713+0747,PSR J0437-4715),the corresponding GW-induced timing residuals in PTAs with Gaussian white noise can be simulated.Further,we report the classification of the simulated PTA data and parameter estimation for potential GW sources using machine learning based on neural networks.As a classifier,the convolutional neural network shows high accuracy when the combined signal to noise ratio≥1.33 for our simulated data.Further,we applied a recurrent neural network to estimate the chirp mass(M)of the source and luminosity distance(Dp)of the pulsars and Bayesian neural networks(BNNs)to obtain the uncertainties of chirp mass estimation.Knowledge of the uncertainties is crucial to astrophysical observation.In our case,the mean relative error of chirp mass estimation is less than 13.6%.Although these results are achieved for simulated PTA data,we believe that they will be important for realizing intelligent processing in PTA data analysis.

A study on population dynamics in“Belt&Road”countries and their implications

China’s Belt&Road(“B&R”)initiative has attracted much attention in recent years.Many studies have assessed the potential impacts of this initiative from the economic,political,foreign relations,and military perspectives.However,very little attention has been paid to examine the opportunities and challenges of this new initiative from a demographic perspective.Therefore,this study investigates into the population dynamics of 65 countries in the B&R region,and explores the demographic dynamics of this regional cooperation model.Based on graphic visualization,the demographic heterogeneities within the B&R region,in terms of current stages of demographic transitions,population age structure,and demographic windows of opportunities have been revealed.Furthermore,a model-based cluster analysis has been conducted to classify the B&R countries into two groups.One group consists of countries with younger population,low education access,and larger gender gap in the labor market,while the other group comprises of more aged population and has better performances in economic development,education enrolment,and female labor participation.The demographic windows of opportunities in the former group will remain open for the coming decades;whereas the windows have already closed or is about to close very soon in the latter group.The former group should take lessons from the latter concerning how to better prepare themselves for the demographic transition.Moreover,the curvilinear relationship between wealth and well-being has a complicated structure and the B&R initiative should focus not only on economic development but also on the human well-being.

Gender gap in life expectancy in Hong Kong, 1986-2016

Over the past decades,life expectancy in Hong Kong has been increasing steadily.However,the gender gap in life expectancy has experienced a comparatively high level of plateauing state.Based on data from the Human Mortality Database and the official statistics,an age-and cause-decomposition method was used to analyze contributions of main age groups and major causes of death to the gender gap over the period 1986-2016.The results showed that a female-advantage in the mortality among those aged 25 years and above was mainly responsible for the male-female gap in life expectancy in Hong Kong.In consideration of major causes of death,lower female mortality from non-communicable diseases,particularly malignant neoplasms,and pneumonia at older age groups,was the major contributor to the female-favored life expectancy.Public efforts to reduce excess mortality rates from non-communicable diseases and pneumonia among older male population may help narrow the gender gap in life expectancy in Hong Kong.