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1. Hierarchical accompanying and inhibiting patterns on the spatial arrangement of taxis' local hotspots

Author

Chen, Xiao-Jian, Dong, Quanhua, Xiao, Changjiang, Huang, Zhou, Wang, Keli, Zhang, Weiyu, and Liu, Yu

Subjects
Computer Science - Computers and Society
Abstract

The spatial arrangement of taxi hotspots indicates their inherent distribution relationships, reflecting spatial organization structure and has received attention in urban studies. Previous studies mainly explore large-scale hotspots by visual analysis or simple indexes, where hotspots usually cover the entire central business district, train stations, or dense residential areas, reaching a radius of hundreds or even thousands of meters. However, the spatial arrangement patterns of small-scale hotspots, reflecting the specific popular pick-up and drop-off locations, have not received much attention. This study quantitatively examines the spatial arrangement of fine-grained local hotspots in Wuhan and Beijing, China, using taxi trajectory data. Hotspots are adaptatively identified with sizes of 90m*90m in Wuhan and 105m*105m in Beijing according to identification method. Findings show popular hotspots are typically surrounded by less popular ones, though regions with many popular hotspots inhibit the presence of less popular ones. We term these configurations as hierarchical accompany and inhibiting patterns. Finally, inspired by both patterns, a KNN-based model is developed to describe these relationships, successfully reproducing the spatial distribution of less popular hotspots based on the most popular ones. These insights enhance understanding of local urban structures and support urban planning.

Published
2023

2. Time series anomaly detection with reconstruction-based state-space models

Author

Wang, Fan, Wang, Keli, and Yao, Boyu

Subjects
Computer Science - Machine Learning, Computer Science - Artificial Intelligence
Abstract

Recent advances in digitization have led to the availability of multivariate time series data in various domains, enabling real-time monitoring of operations. Identifying abnormal data patterns and detecting potential failures in these scenarios are important yet rather challenging. In this work, we propose a novel unsupervised anomaly detection method for time series data. The proposed framework jointly learns the observation model and the dynamic model, and model uncertainty is estimated from normal samples. Specifically, a long short-term memory (LSTM)-based encoder-decoder is adopted to represent the mapping between the observation space and the latent space. Bidirectional transitions of states are simultaneously modeled by leveraging backward and forward temporal information. Regularization of the latent space places constraints on the states of normal samples, and Mahalanobis distance is used to evaluate the abnormality level. Empirical studies on synthetic and real-world datasets demonstrate the superior performance of the proposed method in anomaly detection tasks.

Published
2023
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6. Cost-effectiveness Analysis of Antiepidemic Policies and Global Situation Assessment of COVID-19

Author

Xu, Liyan, Zhang, Hongmou, Deng, Yuqiao, Wang, Keli, Li, Fu, Lu, Qing, Yin, Jie, Di, Qian, Liu, Tao, Yin, Hang, Zhang, Zijiao, Du, Qingyang, Yu, Hongbin, Liu, Aihan, Jiang, Hezhishi, Guo, Jing, Yuan, Xiumei, Zhang, Yun, Liu, Liu, and Liu, Yu

Subjects
Physics - Physics and Society, Quantitative Biology - Populations and Evolution
Abstract

With a two-layer contact-dispersion model and data in China, we analyze the cost-effectiveness of three types of antiepidemic measures for COVID-19: regular epidemiological control, local social interaction control, and inter-city travel restriction. We find that: 1) intercity travel restriction has minimal or even negative effect compared to the other two at the national level; 2) the time of reaching turning point is independent of the current number of cases, and only related to the enforcement stringency of epidemiological control and social interaction control measures; 3) strong enforcement at the early stage is the only opportunity to maximize both antiepidemic effectiveness and cost-effectiveness; 4) mediocre stringency of social interaction measures is the worst choice. Subsequently, we cluster countries/regions into four groups based on their control measures and provide situation assessment and policy suggestions for each group.

Published
2020

14. Theoretical Study of the Temperature- and Pressure-Dependent Rate Constants for Nine Reactions between COn(n= 0–4), Om(m= 1–3), C2O, and C3O2during the Radiolysis of Carbon Dioxide

Author

Tang, Yuhong, Yang, Yu, Cao, Qi, Wang, Keli, Ma, Dandan, Liu, Beibei, Zhu, Quan, and Ma, Jianyi

Abstract

We investigate the reaction pathways of nine important CO2-related reactions using the revDSD-PBEP86-D3(BJ)/jun-cc-pV(T+d)Z level and simultaneously employ an accurate composite method (jun-Cheap) based on coupled-cluster (CC) theory. Subsequently, the Rice–Ramsperger–Kassel–Marcus/master equation (RRKM/ME) is solved to calculate the temperature- and pressure-dependent rate constants. This work investigates reactions involving transition states that have been overlooked in previous literature, including the dissociation of singlet-state C3O2, the triple channel formation of C2O + CO to form C3O2, and the formation of O3+ CO. The results show that CO3is highly prone to dissociation at high temperatures. Finally, the kinetic data show that over a wide temperature range, our calculations are consistent with previous experimental measurements. The majority of the reaction rate constants studied exhibit significant pressure dependence, while the O3+ CO reaction is pressure-independent at low temperatures. These results are instrumental in the development of detailed kinetic models for the CO2radiolysis reaction network.

Published
2024
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20. Additional file 1 of Quantifying the spatial spillover effects of non-pharmaceutical interventions on pandemic risk

Author

Wang, Keli, Han, Xiaoyi, Dong, Lei, Chen, Xiao-Jian, Xiu, Gezhi, Kwan, Mei-po, and Liu, Yu

Abstract

Additional file 1: Table S1. Best-fit model posterior estimates of key epidemiological parameters for January 6 to March 9, 2020. Table S2. Gamma distributions for monthly reporting delay (Dr). Table S3. Comparison of the results of DIC based on different spatial weight matrices. Table S4. The contribution of direct effects and SSE of all NPIs on COVID-19 cases in 48 regions and Washington D.C. Table S5. The coefficients of different NPI estimates under the dependent variable multiplied by 100. Table S6. The coefficients estimate of direct effects under the dependent variable multiplied by 100. Table S7. The coefficients estimate of spatial spillover effects under the dependent variable multiplied by 100. Table S8. The coefficients estimate of direct effects from spatial panel durbin model. Table S9. The coefficients estimate of spatial spillover effects from spatial panel durbin model. Table S10. The coefficient estimated by our spatial panel model with different weight matrix during Phase A. Table S11. The coefficient estimated by our spatial panel model with different weight matrix during Phase B. Figure S1. The connectivity structure of different spatial weight matrix. Figure S2. Comparison of the change of human mobility estimated by our spatial panel model versus the factual human mobility change of 48 states and Washington D.C. Figure S3. The scatterplot of the change of human mobility estimated by our spatial panel model versus the factual human mobility change in all states. Figure S4. The direct and spatial spillover effect estimates of NPIs in 48 states and Washington D.C. from the spatial panel model. Figure S5. Model fitting to daily case numbers (blue dots) by S-SEIR model in 48 states and Washington D.C. Figure S6. The estimated cases by different model in 48 states (regions) and Washington D.C. Notes: S-SEIR (Direct effects): similar to the S-SEIR model, but only the direct effects of NPIs are considered. S-SEIR (SSE): similar to the S-SEIR model, but only the spatial spillover effects of NPIs are considered. S-SEIR: both the direct and spatial spillover effects are considered. The line and shaded area represent the median and 95% CI, respectively. Figure S7. The estimated national cumulative confirmed cases by changing the intensity of all NPIs in different regions. Figure S8. The national cumulative confirmed cases estimated by changing the intensity of diffferent NPIs in different regions. Figure S9. The estimated national cumulative confirmed cases by restricting the flows of r2, r4, or r5, including all travel flow with these targeted regions (denoted as ’OD’), travel flow from these targeted regions (denoted as ’O’) and travel flow to these targeted regions (denoted as ‘D’). Figure S10. The median differences in national cumulative confirmed cases at t = 30 week are estimated by the complete lockdown (OD), origin-based lockdown (O), destination-based lockdown (D) in r4 or r5 and baseline scenario. Figure S11. The change of intrastate human mobility in each state. Figure S12. The distribution of the dependent variables in different weeks. Figure S13. Estimation results of the change of intrastate human mobility and spatial spillover effects of NPIs by panel SAR model. The matrix during introduction phase is flow weight (8 neighbors) matrix, during lifting phase is the inverse distance matrix with a cut-off distance of 600 km. Figure S14. Estimation results of the change of intrastate human mobility and spatial spillover effects of NPIs by panel SAR model. The matrix during introduction phase is the inverse distance matrix with a cut-off distance of 600 km, and during lifting phase is flow weight (8 neighbors). Figure S15. Estimation results of the change of intrastate human mobility and spatial spillover effects of NPIs by panel SAR model. The matrix during introduction phase is the inverse distance matrix with a cut-off distance of 600 km, and during lifting phase is the inverse distance (the max distance is 800 km). Figure S16. Estimation results from the S-SEIR model, taking changes in actual human mobility as intervention effects. Figure S17. Estimation results from the Sp-SEIR model, the initial seed is the number of cases in the five days from T0 to T0+4. Figure S18. Estimation results from the Sp-SEIR model. During initialization, symptomatic patients are not assigned an initial value. Figure S19. Estimation results from the Sp-SEIR model, the range of movement fixed factor (θ) is from 1 to 10. Figure S20. Estimation results from the Sp-SEIR model. We assume that the infection of asymptomatic patients relative to symptomatic patients also varies over time and region.

Published
2023
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22. Quantifying the spatial spillover effects of non-pharmaceutical interventions on pandemic risk.

Author

Wang, Keli, Han, Xiaoyi, Dong, Lei, Chen, Xiao-Jian, Xiu, Gezhi, Kwan, Mei-po, and Liu, Yu

Subjects
*PANDEMICS, *ECONOMETRIC models, *COVID-19, *MOBILITY of older people
Abstract

Background: Non-pharmaceutical interventions (NPIs) implemented in one place can affect neighboring regions by influencing people's behavior. However, existing epidemic models for NPIs evaluation rarely consider such spatial spillover effects, which may lead to a biased assessment of policy effects. Methods: Using the US state-level mobility and policy data from January 6 to August 2, 2020, we develop a quantitative framework that includes both a panel spatial econometric model and an S-SEIR (Spillover-Susceptible-Exposed-Infected-Recovered) model to quantify the spatial spillover effects of NPIs on human mobility and COVID-19 transmission. Results: The spatial spillover effects of NPIs explain 61.2 % [ 95 % credible interval: 52.8- 84.4 % ] of national cumulative confirmed cases, suggesting that the presence of the spillover effect significantly enhances the NPI influence. Simulations based on the S-SEIR model further show that increasing interventions in only a few states with larger intrastate human mobility intensity significantly reduce the cases nationwide. These region-based interventions also can carry over to interstate lockdowns. Conclusions: Our study provides a framework for evaluating and comparing the effectiveness of different intervention strategies conditional on NPI spillovers, and calls for collaboration from different regions. [ABSTRACT FROM AUTHOR]

Published
2023
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27. Methods of Social Sensing for Urban Studies

Author

Liu, Yu, Gao, Song, Yuan, Yihong, Zhang, Fan, Kang, Chaogui, Kang, Yuhao, Wang, Keli, Liu, Yu, Gao, Song, Yuan, Yihong, Zhang, Fan, Kang, Chaogui, Kang, Yuhao, and Wang, Keli

Abstract

Analyzing large volumes of big geo-data through social sensing provides new research opportunities in urban studies. Such big geo-data include mobile phone records, social media posts, vehicle trajectories, and street view images. They can be used to extract human behavior patterns and infer the geographical characteristics of cities. This chapter discusses a number of analytical methods for big geo-data in social sensing studies, such as temporal signature analysis, text analysis, and image analysis. These methods can be used for various applications such as estimating urban vibrancy, formalizing place semantics, and modeling intraurban human mobility patterns. We structure the chapter sections from a perspective of first- and second-order properties in spatial statistics .

Published
2021

32. Optimization of the average figure-of-merit zTin medium-entropy GeTe-based materials viaentropy engineering

Author

Liu, Xusheng, Wang, Keli, Li, Peng, Tang, Qiqi, Huang, Zhenlong, Lin, Yuan, Wang, Wu, Jiang, Binbin, and He, Jiaqing

Abstract

Entropy engineering has emerged as an effective strategy for improving the figure-of-merit zTby decelerating the phonon transport while maintaining good electrical transport properties of thermoelectric materials. Herein, a high average zTof 1.54 and a maximum zTof 2.1 are achieved in the mid-entropy GeTe constructed by Ag, Sb, and Pb alloying. At room temperature, the mid-entropy GeTe tends to a cubic structure. And the power factor is improved from 7.7 μW·cm−1·K−2to 16.2 μW·cm−1·K−2due to the large increase in effective mass and the optimized carrier concentration. The increasing disorder created by heavy and off-centering Ag, Sb, and Pb atoms induces strong mass/strain fluctuations and phonon scattering to decelerate the phonon transport in GeTe. A low lattice thermal conductivity is obtained in the medium-entropy GeTe-based material. Moreover, a GeTe-based thermoelectric cooler is fabricated with the cooling temperature difference of 66.6 K with the hot end fixed at 363 K. This work reveals the effectiveness of entropy engineering in improving the average zTin GeTe and shows potential application of GeTe as a thermoelectric cooler.

Published
2024
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34. Self-assembled micelles of amphiphilic poly(L-phenylalanine)-b-poly(L-serine) polypeptides for tumor-targeted delivery

Author

Zhao,Ziming, Wang,Yu, Han,Jin, Wang,Keli, Yang,Dan, Yang,Yihua, Du,Qian, Song,Yuanjian, Yin,Xiaoxing, Zhao,Ziming, Wang,Yu, Han,Jin, Wang,Keli, Yang,Dan, Yang,Yihua, Du,Qian, Song,Yuanjian, and Yin,Xiaoxing

Abstract

Ziming Zhao,1,2,* Yu Wang,1,2,* Jin Han,1,2 Keli Wang,1 Dan Yang,1,2 Yihua Yang,1,2 Qian Du,1,2 Yuanjian Song,3 Xiaoxing Yin1,2 1Department of Pharmacy, 2Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, 3Department of Basic Medical Sciences, Xuzhou Medical College, Xuzhou, People’s Republic of China *These authors contributed equally to this work Abstract: The aim of this work was to design, synthesize, and characterize self-assembled micelles based on polypeptides as a potential antitumor drug carrier. Amphiphilic poly(L-phenylalanine)-b-poly(L-serine) (PFS) polypeptides were obtained through the polymerization of N-carboxyanhydride. As a novel hydrophilic segment, poly(L-serine) was utilized to enhance tumor targeting due to a large demand of tumors for serine. PFS could self-assemble into micelles with an average diameter of 110–240 nm and a slightly negative charge. PFS polypeptides adopted random coil in pH 7.4 phosphate-buffered saline and could partly transform to a-helix induced by trifluoroethanol. PFS micelles with a low critical micelle concentration of 4.0 µg mL-1 were stable in pH 5–9 buffers and serum albumin solution. PFS micelles had a loading capacity of 3.8% for coumarin-6 and exhibited a sustained drug release. Coumarin-6 loaded rhodamine B isothiocyanate-labeled PFS micelles were incubated with Huh-7 tumor cells to study the correlation between drugs and carriers during endocytosis. The uptake of drugs was consistent with the micelles, illustrating that the intracellular transport of drugs highly depended on the micelles. PFS micelles diffused in whole cytoplasm while coumarin-6 assumed localized distribution, suggesting that the micelles could release the loaded drugs in particular areas. The internalization mechanism of PFS micelles was involved with clathrin-mediated endocytosis and macropinocytosis. Excess serine inhibited the uptake of PFS micelles, which de

Published
2014

36. The cost of coverage: rural health insurance in China

Author

Vinod K. Diwan, Wang Keli, Dong Hengjin, Lennart Bogg, and Cai Wenwei

Subjects
Economic growth, medicine.medical_specialty, China, genetic structures, Population, Self-insurance, Health care, Infant Mortality, medicine, Humans, education, Curative care, Government budget, Health policy, Preventive healthcare, education.field_of_study, Insurance, Health, business.industry, Delivery of Health Care, Integrated, Health Policy, Rural health, Infant, Models, Theoretical, Health Care Reform, Models, Organizational, Business, Rural Health Services
Abstract

China has undergone great economic and social change since 1978 with far reaching implications for the health care system and ultimately for the health status of the population. The Chinese Medical Reform of the 1980s made cost recovery a primary objective. The urban population is mostly protected by generous government health insurance. A high share government budget is allocated to urban health care. Rural cooperative health insurance reached a peak in the mid-1970s when 90% of the rural population were covered. In the 1980s rural cooperative health insurance collapsed and present coverage is less than 8%. The decline has been accompanied by reports of growing equity problems in the financing of and access to health care. This article is the first in a four-year study of the impact on equity of the changes in Chinese health care financing. The article examines the relationship between rural cooperative health insurance as the explanatory variable and health care expenditure, curative vs. preventive expenditure and tertiary curative care expenditure as dependent variables using a natural experimental design with a 'twin' county as a control. The findings support the hypothesis that cooperative health insurance will induce higher growth of health care expenditure. The findings also support the hypothesis that cooperative health insurance will lead to a shift from preventive medicine to curative medicine and to a higher level of tertiary curative care expenditure. The empirical evidence from the Chinese counties is contradicting World Bank health financing policies.The considerable economic and social change experienced in China since 1978 has far-reaching implications for the country's health care system and its population's health status. The Chinese Medical Reform of the 1980s stressed cost recovery. While the urban population is largely protected by generous government health insurance, rural cooperative health insurance reached a peak in the mid-1970s. Rural cooperative health insurance collapsed during the 1980s, and present coverage is less than 8%. This collapse has been accompanied by reports of growing equity problems in the financing of and access to health care. The authors look at the relationship between rural cooperative health insurance as the explanatory variable and health care expenditure, curative versus preventive expenditure, and tertiary curative care expenditure as dependent variables using a natural experimental design with a twin county as a control. Study findings support the hypothesis that cooperative health insurance will induce higher growth of health care expenditures, a shift from preventive medicine to curative medicine, and a higher level of tertiary curative care expenditure. This empirical evidence contradicts World Bank health financing policies.

Published
1996

38. A description of outpatient drug use in rural China : evidence of differences due to insurance coverage

Author

Dong, Hengjin, Bogg, Lennart, Wang, Keli, Rehnberg, Clas, Diwan, Vinod, Dong, Hengjin, Bogg, Lennart, Wang, Keli, Rehnberg, Clas, and Diwan, Vinod

Abstract

This paper describes the effects of health financing systems (insurance) on outpatient drug use in rural China. 1320 outpatients were interviewed (exit interview) in the randomly selected county, township and village health care facilities in five counties in three provinces of central China. The interview was face to face. Questions were asked by a trained interviewer and were answered by patient him/herself. The main finding was that health insurance appeared to influence drug use in outpatient services. The average number of drugs per visit was 2.56 and drug expenditures per visit was 16.9 yuan. Between insured and uninsured (out-of-pocket) groups, there were significant differences in the number of drugs and drug expenditures per visit. The insured had a lower number of drugs and a higher drug expenditure per visit than the uninsured, implying the use of more expensive drugs per visit than the uninsured. There were also significant differences in the number of drugs and drug expenditures per visit between the types of insurance. One third of the drugs were anti-infectives, most of which were penicillin, gentamycin, and sulfonamides. The results imply that uninsured patients do not receive the same care as the insured do even if they have the same needs. The fee-for-service financing for hospitals and health insurance have changed health providers' and consumers' behaviour and resulted in the increase of medical expenditure., SAREC

Published
1999
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39. The cost of coverage : rural health insurance in China

Author

Bogg, Lennart, Dong, Hengjin, Wang, Keli, Cai, Wenwei, Vinod, Diwan, Bogg, Lennart, Dong, Hengjin, Wang, Keli, Cai, Wenwei, and Vinod, Diwan

Abstract

China has undergone great economic and social change since 1978 with far reaching implications for the health care system and ultimately for the health status of the population. The Chinese Medical Reform of the 1980s made cost recovery a primary objective. The urban population is mostly protected by generous government health insurance. A high share government budget is allocated to urban health care. Rural cooperative health insurance reached a peak in the mid-1970s when 90% of the rural population were covered. In the 1980s rural cooperative health insurance collapsed and present coverage is less than 8%. The decline has been accompanied by reports of growing equity problems in the financing of and access to health care. This article is the first in a four-year study of the impact on equity of the changes in Chinese health care financing. The article examines the relationship between rural cooperative health insurance as the explanatory variable and health care expenditure, curative vs. preventive expenditure and tertiary curative care expenditure as dependent variables using a natural experimental design with a 'twin' county as a control. The findings support the hypothesis that cooperative health insurance will induce higher growth of health care expenditure. The findings also support the hypothesis that cooperative health insurance will lead to a shift from preventive medicine to curative medicine and to a higher level of tertiary curative care expenditure. The empirical evidence from the Chinese counties is contradicting World Bank health financing policies., SAREC

Published
1996
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40. Theoretical Study of the Temperature- and Pressure-Dependent Rate Constants for Nine Reactions between CO n ( n = 0-4), O m ( m = 1-3), C 2 O, and C 3 O 2 during the Radiolysis of Carbon Dioxide.

Author

Tang Y, Yang Y, Cao Q, Wang K, Ma D, Liu B, Zhu Q, and Ma J

Abstract

We investigate the reaction pathways of nine important CO 2 -related reactions using the revDSD-PBEP86-D3(BJ)/jun-cc-pV(T+d)Z level and simultaneously employ an accurate composite method (jun-Cheap) based on coupled-cluster (CC) theory. Subsequently, the Rice-Ramsperger-Kassel-Marcus/master equation (RRKM/ME) is solved to calculate the temperature- and pressure-dependent rate constants. This work investigates reactions involving transition states that have been overlooked in previous literature, including the dissociation of singlet-state C 3 O 2 , the triple channel formation of C 2 O + CO to form C 3 O 2 , and the formation of O 3 + CO. The results show that CO 3 is highly prone to dissociation at high temperatures. Finally, the kinetic data show that over a wide temperature range, our calculations are consistent with previous experimental measurements. The majority of the reaction rate constants studied exhibit significant pressure dependence, while the O 3 + CO reaction is pressure-independent at low temperatures. These results are instrumental in the development of detailed kinetic models for the CO 2 radiolysis reaction network.

Published
2024
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41. Facile synthesis of high-performance SiO 2 @Au core-shell nanoparticles with high SERS activity.

Author

Wang K, Wang Y, Wang C, Jia X, Li J, Xiao R, and Wang S

Abstract

This study proposes a facile and general method for fabricating a wide range of high-performance SiO 2 @Au core-shell nanoparticles (NPs). The thicknesses of Au shells can be easily controlled, and the process of Au shell formation was completed within 5 min through sonication. The fabricated SiO 2 @Au NPs with highly uniform size and SERS activity could be ideal SERS tags for SERS-based immunoassay., Competing Interests: The authors report no conflicts of interest in this work., (This journal is © The Royal Society of Chemistry.)

Published
2018
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