Browsing by Author "Li, Ang"
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Item Association of Food Insecurity and Acute Health Care Utilization in Children With End-Stage Kidney Disease(American Medical Association, 2019-09-09) Starr, Michelle C.; Wightman, Aaron; Munshi, Raj; Li, Ang; Hingorani, Sangeeta; Pediatrics, School of MedicineItem The impacts of precipitation increase and nitrogen addition on soil respiration in a semiarid temperate steppe(Wiley, 2017-01) Zhang, Xiaolin; Tan, Yulian; Zhang, Bingwei; Li, Ang; Daryanto, Stefani; Wang, Lixin; Huang, Jianhui; Department of Earth Sciences, School of ScienceSoil respiration, Rs, is strongly controlled by water availability in semiarid grasslands. However, how Rs is affected by precipitation change (either as rainfall or as snowfall) especially under increasing nitrogen (N) deposition has been uncertain. A manipulative experiment to investigate the responses of growing season Rs to changes in spring snowfall or summer rainfall with or without N addition was conducted in the semiarid temperate steppe of China during three hydrologically contrasting years. Our results showed that both spring snow addition and summer water addition significantly increased Rs by increasing soil moisture. The effect of spring snow addition only occurred in years with both relatively lower natural snowfall and later snowmelt time. Summer water addition showed a much stronger effect on Rs by increasing plant root growth and microbial activities, but the magnitude also largely depended on the possible legacy effect of previous year precipitation. Our results indicated that precipitation increase in the form of snowfall had weaker effects than that in the form of rainfall as the former only accounted for less than 30% of total precipitation. Compared with other ecosystem processes, Rs was less responsible for increase in N deposition as it did not increase root productivity and microbial activities in the soils. Our results provided field data constraints for modeling the ecosystem carbon balance under the future global change scenarios in semiarid grasslands.Item Influential Path of Social Risk Factors toward Suicidal Behavior—Evidence from Chinese Sina Weibo Users 2013–2018(MDPI, 2021-03-05) Han, Yujin; Li, He; Xiao, Yunyu; Li, Ang; Zhu, Tingshao; School of Social Work(1) Purpose: The purpose of this study was to determine suicidal risk factors, the relationship and the underlying mechanism between social variables and suicidal behavior. We hope to provide empirical support for the future suicide prevention of social media users at the social level. (2) Methods: The path analysis model with psychache as the mediate variable was constructed to analyze the relationship between suicidal behavior and selected social macro variables. The data for our research was taken from the Chinese Suicide Dictionary, Moral Foundation Dictionary, Cultural Value Dictionary and National Bureau of Statistics. (3) Results: The path analysis model was an adequate representation of the data. With the mediator psychache, higher authority vice, individualism, and disposable income of residents significantly predicted less suicidal behavior. Purity vice, collectivism, and proportion of the primary industry had positive significant effect on suicidal behavior via the mediator psychache. The coefficients of harm vice, fairness vice, ingroup vice, public transport and car for every 10,000 people, urban population density, gross domestic product (GDP), urban registered unemployment rate, and crude divorce rate were not significant. Furthermore, we applied the model to three major economic development belts in China. The model's result meant different economic zones had no influence on the model designed in our study. (4) Conclusions: Our evidence informs population-based suicide prevention policymakers that incorporating some social factors like authority vice, individualism, etc. can help prevent suicidal ideation in China.Item Nitrogen addition amplified water effects on species composition shift and productivity increase(Oxford, 2021-10) Zhang, Xiaolin; Hasi, Muqier; Li, Ang; Tan, Yulian; Daryanto, Stefani; Wang, Lixin; Zhang, Xueyao; Chen, Shiping; Huang, Jianhui; Earth Sciences, School of ScienceAims Water and nitrogen (N) are two key resources in dryland ecosystems, but they may have complex interactive effects on the community structure and ecosystem functions. How future precipitation (rainfall vs snowfall) change will impact aboveground net primary production (ANPP) is far from clear, especially when combined with increasing N availability. Methods In this study, we investigated changes in community productivity, abundance and aboveground biomass of two dominant plant functional groups (PFGs), i.e. perennial rhizome grasses (PR) and perennial bunchgrasses (PB) under the impacts of increased precipitation (rainfall vs snowfall) combined with N addition in a semiarid temperate steppe. Important Findings Summer rainfall augmentation marginally increased community ANPP, whereas it significantly increased the abundance and aboveground biomass of PR, but not those of PB. Summer rainfall addition increased the fraction of PR biomass (fPR) while decreased that of PB (fPB). Spring snow addition had no effect on aboveground biomass of either compositional PFG although it marginally increased community ANPP. Nitrogen addition significantly increased community ANPP with greater increase in PR under summer rainfall addition, indicating strong interactive effects on community ANPP largely by enhancing PR biomass. We also found a nonlinear increase in the positive effect of nitrogen addition on productivity with the increased precipitation amount. These findings indicate an amplified impact of precipitation increase on grassland productivity under the accelerated atmospheric N deposition in the future.Item Nitrogen addition results in Medicago sativa switching nitrogen sources(Taylor & Francis, 2021) Wang, Yinliu; Hasi, Muqier; Bu, Dongdong; Li, Ang; Xue, Jianguo; Wang, Changhui; Tian, Qiuying; Niu, Guoxiang; Geng, Qianqian; Wang, Lixin; Huang, Jianhui; Earth Sciences, School of ScienceBackground Nitrogen (N) addition may have strong impacts on legume growth and their biological N fixation (BNF), but how legume N acquisition sources respond to N inputs have yet to be comprehensively assessed.Aims We quantified the effects of N addition on the growth and BNF of Medicago sativa and to assess the response of legume N acquisition to N addition.Methods We grew M. sativa in the greenhouse under gradients of added NH4NO3 and analysed the variables that were relative to growth and BNF, such as N concentration, biomass, δ15N values, nodule number, percentage of N derived from the atmosphere (Ndfa%).Results Nitrogen addition had marginal effects on plant biomass production and foliar N concentration. Foliar δ15N value increased with increasing added N, while Ndfa% decreased. The number of nodules formed also decreased with N addition while the nitrogenase (nifH)genecopies per unit nodule mass was not significantly different with N addition.Conclusions These findings indicate that increasing mineral N availability decreases symbiotic investment into BNF, mainly by reducing nodule formation; this was found to have no significant impact on plant growth because the plant changes its N source from BNF-N to mineral N derived from the soil.Item RCID: Fingerprinting Passive RFID Tags via Wideband Backscatter(IEEE, 2022) Li, Jiawei; Li, Ang; Han, Dianqi; Zhang, Yan; Li, Tao; Zang, Yanchao; Computer and Information Science, Purdue School of ScienceTag cloning and spoofing pose great challenges to RFID applications. This paper presents the design and evaluation of RCID, a novel system to fingerprint RFID tags based on the unique reflection coefficient of each tag circuit. Based on a novel OFDM-based fingerprint collector, our system can quickly acquire and verify each tag’s RCID fingerprint which are independent of the RFID reader and measurement environment. Our system applies to COTS RFID tags and readers after a firmware update at the reader. Extensive prototyped experiments on 600 tags confirm that RCID is highly secure with the authentication accuracy up to 97.15% and the median authentication error rate equal to 1.49%. RCID is also highly usable because it only takes about 8 s to enroll a tag and 2 ms to verify an RCID fingerprint with a fully connected multi-class neural network. Finally, empirical studies demonstrate that the entropy of an RCID fingerprint is about 202 bits over a bandwidth of 20 MHz in contrast to the best prior result of 17 bits, thus offering strong theoretical resilience to RFID cloning and spoofing.Item Suicidal Ideation Risk and Socio-Cultural Factors in China: A Longitudinal Study on Social Media from 2010 to 2018(MDPI, 2021-02) Li, He; Han, Yujin; Xiao, Yunyu; Liu, Xingyun; Li, Ang; Zhu, Tingshao; School of Social WorkMany studies cited the importance of social factors as protective and risk factors for suicide. However, there is a lack of evidence on the influences of cultural and moral values. This study aims to examine the association between cultural values and suicidal ideation risks detected on an online social media platform. We collected a total of 5.1 billion pieces of Weibo posts from 2010 to 2018 to calculate their suicidal ideation risks as measured by psychache in the Chinese Suicide Dictionary. We calculated the word frequencies of cultural and moral values based on Cultural Value Dictionary and Moral Foundation Dictionary. We collected economic and population data from the China National Bureau of Statistics. Two-way fixed-effect models were performed to analyze the association between culture, economy, and population factors and suicidal ideation risks. The results confirm the relations between high suicidal ideation risk and public concerns of vice under the Chinese context such as harm (β = 0.193, p < 0.01), betrayal (β = 0.096, p < 0.01), and dirty (β = 0.624, p < 0.001). In addition, extremely individualistic or collectivistic values of the public were associated with high suicidal ideation risks. The finding indicated the significant impact of social culture on suicide risk apart from the influence of the social economy and population characteristics. Our evidence informs population-based suicide prevention policymakers that incorporating cultural and moral values can help prevent suicidal ideation in China.Item Water and nitrogen availability co-control ecosystem CO2 exchange in a semiarid temperate steppe(Springer Nature, 2015-10-23) Zhang, Xiaolin; Tan, Yulian; Li, Ang; Ren, Tingting; Chen, Shiping; Wang, Lixin; Huang, Jianhui; Department of Earth Sciences, School of ScienceBoth water and nitrogen (N) availability have significant effects on ecosystem CO2 exchange (ECE), which includes net ecosystem productivity (NEP), ecosystem respiration (ER) and gross ecosystem photosynthesis (GEP). How water and N availability influence ECE in arid and semiarid grasslands is still uncertain. A manipulative experiment with additions of rainfall, snow and N was conducted to test their effects on ECE in a semiarid temperate steppe of northern China for three consecutive years with contrasting natural precipitation. ECE increased with annual precipitation but approached peak values at different precipitation amount. Water addition, especially summer water addition, had significantly positive effects on ECE in years when the natural precipitation was normal or below normal, but showed trivial effect on GEP when the natural precipitation was above normal as effects on ER and NEP offset one another. Nitrogen addition exerted non-significant or negative effects on ECE when precipitation was low but switched to a positive effect when precipitation was high, indicating N effect triggered by water availability. Our results indicate that both water and N availability control ECE and the effects of future precipitation changes and increasing N deposition will depend on how they can change collaboratively in this semiarid steppe ecosystem.Item WearRF-CLA: Continuous Location Authentication with Wrist Wearables and UHF RFID(National Science Foundation, 2022) Li, Ang; Li, Jiawei; Han, Dianqi; Zhang, Yan; Li, Tao; Zhang, Yanchao; Computer and Information Science, Purdue School of ScienceContinuous location authentication (CLA) seeks to continuously and automatically verify the physical presence of legitimate users in a protected indoor area. CLA can play an important role in contexts where access to electrical or physical resources must be limited to physically present legitimate users. In this paper, we present WearRF-CLA, a novel CLA scheme built upon increasingly popular wrist wearables and UHF RFID systems. WearRF-CLA explores the observation that human daily routines in a protected indoor area comprise a sequence of human-states (e.g., walking and sitting) that follow predictable state transitions. Each legitimate WearRF-CLA user registers his/her RFID tag and also wrist wearable during system enrollment. After the user enters a protected area, WearRF-CLA continuously collects and processes the gyroscope data of the wrist wearable and the phase data of the RFID tag signals to verify three factors to determine the user's physical presence/absence without explicit user involvement: (1) the tag ID as in a traditional RFID authentication system, (2) the validity of the human-state chain, and (3) the continuous coexistence of the paired wrist wearable and RFID tag with the user. The user passes CLA if and only if all three factors can be validated. Extensive user experiments on commodity smartwatches and UHF RFID devices confirm the very high security and low authentication latency of WearRF-CLA.