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Used car price prediction based on XGBoost and retention rate

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The Journal of China Universities of Posts and Telecommunications 2024年第3期31卷 72-79页

作者： Shen Yutian Chen Jian Dai Min Zhang Sirui Xu Jing Wang Qing college of Mechanical Engineering Yangzhou UniversityYangzhou 225127China college of economics and Management Southeast University Chengxian CollegeNanjing 210088China Shandong Shuncheng Automobile Trade Co. LtdJinan 250000China

In order to improve the accuracy of used car price prediction,a machine learning prediction model based on the retention rate is proposed in this ***,a random forest algorithm is used to filter the variables in the *** main characteristic variables that affect used car prices,such as new car price,service time,mileage and so on,are filtered ***,the linear regression classification method is introduced to classify the test data into high and low retention rate *** that,the extreme gradient boosting(XGBoost)regression model is built for the two datasets *** prediction results show that the comprehensive evaluation index of the proposed model is 0.548,which is significantly improved compared to 0.488 of the original XGBoost ***,compared with other representative machine learning algorithms,this model shows certain advantages in terms of mean absolute percentage error(MAPE),5%accuracy rate and comprehensive evaluation *** a result,the retention rate-based machine learning model established in this paper has significant advantages in terms of the accuracy of used car price prediction.

关键词： random forest data dimensionality reduction extreme gradient boosting(XGBoost) retention rate price prediction

Tamed EM method for a delayed Ait-Sahalia type model driven by Poisson jumps

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Acta Mathematica Sinica,English Series 2024年

作者： Li TAN Sheng Rong WANG School of Statistics and Data Science Jiangxi University of Finance and Economics Key Laboratory of Data Science in Finance and economics Jiangxi University of Finance and Economics college of Modern economics and Management of Jiangxi University of Finance and economics

In this paper, we consider a delayed Ait-Sahalia type model driven by Poisson jumps. The analytical properties including uniqueness, positiveness and boundedness of the true solution to this model are investigated. Since the coefficients are sup-linear, a tamed Euler-Maruyama(EM) method is constructed, and it is shown that the tamed EM solution converges strongly to the true solution.

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Does Green Food Certification promote agri-food export quality?Evidence from China

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Journal of Integrative Agriculture 2024年第3期23卷 1061-1074页

作者： Ping Wei Hongman Liu Chaokai Xu Shibin Wen college of economics and Management China Agricultural UniversityBeijing 100083China School of Public Affairs Zhejiang UniversityHangzhou 310058China

The construction of a food certification system plays a vital role in upgrading export quality, which previous studies have largely overlooked. We match China's industry-level data of Green Food Certification with its HS6-digit export data of agri-food products to quantify the impact of Green Food Certification on export quality. We identify the significant and positive effect of Green Food Certification on export quality. The 2SLS estimation based on instrumental variables and a range of robustness checks confirm the validity and robustness of the benchmark conclusions. Further analysis discloses that Green Food Certification improves export quality by raising agricultural production efficiency and brand premiums. Heterogeneity analysis shows that the effect of Green Food Certification varies across regions, notably improving the quality of agri-food products exported to developed regions and regions with high levels of import supervision. Furthermore, among various product types, Green Food Certification significantly improves the export quality of primary products and products vulnerable to non-tariff measures. The above findings could guide the future development of agri-food quality certification systems, potentially leading to a transformation and promotion of the agri-food trade.

关键词： Green Food Certification agri-food products green transformation export quality food labeling

Comparison of the capacity of biological desulfurization of Thiobacillus ferrooxidans from different sulfur-containing substrates with or without additional ferrous iron

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International Journal of Agricultural and Biological Engineering 2024年第3期17卷 140-143页

作者： Yanjin Wang Xiaopeng Chang Hongge Tao Zhenfeng Wang Quanguo Zhang college of Environment economics Henan Finance UniversityZhengzhou 450046China college of Mechanical and Electrical Engineering Henan Agricultural UniversityZhengzhou 450002China

Thiobacillus ferrooxidans,abbreviated as *** is one of the important microorganisms in the field of biological *** of ferrous iron and sulfur-containing substrates on biological desulfurization of *** were *** show that in the absence of Fe^(2+),*** can utilize three kinds of sulfur-containing substrates of Na_(2)S_(2)O_(3),elemental S and Na_(2)SO_(3) for growth and *** utilization complexity,Na_(2)S_(2)O_(3) was easiest to use,next was elemental S,and Na_(2)SO_(3) was the worst for *** the utilization of ferrous iron and sulfur-containing substrates by ***,the iron oxidation system was first *** the decrease of the Fe^(2+)concentration,the sulfur oxidation system was started,and then the two systems synergistically *** presence of three sulfur-containing substrates had different effects on Fe^(2+)oxidation,and elemental S did not inhibit the oxidation of Fe^(2+),while Na_(2)S_(2)O_(3) and Na_(2)SO_(3) had some inhibition on the oxidation of Fe^(2+),especially the inhibition of Na_(2)SO_(3) was significant,and complete oxidation of ferrous iron needed more *** isolated *** is applied to the removal of H2S gas,aiming to provide a new technological approach for biological removal of H2S.

关键词： Thiobacillus ferrooxidans ferrous iron sulfur-containing substrate biological desulfurization

Shikimic acid accelerates phase change and flowering in Chinese jujube

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Horticultural Plant Journal 2024年第2期10卷 413-424页

作者： Xianwei Meng Zhiguo Liu Li Dai Weiqiang Zhao Jiurui Wang Lili Wang Yuanpei Cui Ying Li Yinshan Cui Yao Zhang Luyao Wang Fengjiao Yu Jin Zhao Mengjun Liu Research Center of Chinese Jujube Hebei Agricultural UniversityBaodingHebei 071000China college of Horticulture Hebei Agricultural UniversityBaodingHebei 071000China college of Life Science Hebei Agricultural UniversityBaodingHebei 071000China college of Forestry Hebei Agricultural UniversityBaodingHebei 071000China eCollege of Economics and ManagementHebei Agricultural UniversityBaodingHebei 071000China college of economics and Management Hebei Agricultural University

The juvenile-to-adult phase change with first flowering as the indicator plays a crucial role in the lifecycle of fruit trees. However, the molecular mechanisms underlying phase change in fruit trees remain largely unknown. Shikimic acid (ShA) pathway is a main metabolic pathway closely related to the synthesis of hormones and many important secondary metabolites participating in plant phase change. So,whether ShA regulates phase change in plants is worth clarifying. Here, the distinct morphological characteristics and the underlying mechanisms of phase change in jujube (Ziziphus jujuba Mill.), an important fruit tree native to China with nutritious fruit and outstanding tolerance abiotic stresses, were clarified. A combined transcriptome and metabolome analysis found that ShA is positively involved in jujube(Yuhong’×Xing 16’) phase change. The genes in the upstream of ShA synthesis pathway (ZjDAHPS, ZjDHQS and ZjSDH), the contents of ShA and the downstream secondary metabolites like phenols were significantly upregulated in the phase change period. Further, the treatment of spraying exogenous ShA verified that ShA at a very low concentration (60 mg·L^(-1)) can substantially speed up the phase change and flowering of jujube and other tested plants including Arabidopsis, tomato and wheat. The exogenous ShA (60 mg·L^(-1)) treatment in jujube seedlings could increase the accumulation of endogenous ShA, enhance leaf photosynthesis and the synthesis of phenols especially flavonoids and phenolic acids, and promote the expression of genes (ZjCOs, ZjNFYs and ZjPHYs) involved in flowering pathway. Basing on above results, we put forward a propose for the underlying mechanism of ShA regulating phase change, and a hypothesis that ShA could be considered a phytohormone-like substance because it is endogenous, ubiquitous, movable and highly efficient at very low concentrations. This study highlights the critical role of ShA in plant phase change and its phytohormone-like propert

关键词： Ziziphus jujuba Mill. Phase change Flowering Shikimic acid Transcriptome Metabolome

New Rural Community Construction or Retention Development:A Comparative Analysis of Rural Settlement Transition Mechanism in Plain Agriculture Area of China Based on Actor Network Theory

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Chinese Geographical Science 2024年第3期34卷 436-452页

作者： QU Yanbo DONG Xiaozhen MA Wenqiu ZHAO Weiying School of Public Administration and Policy Shandong University of Finance and EconomicsJinan 250014China Institute of Land Science and Policy Shandong University of Finance and EconomicsJinan 250014China college of Engineering China Agricultural UniversityBeijing 100083China

It is an important way to realize rural revitalization and sustainable development to guide rural settlement transition(RST)in an appropriate *** paper uses actor network theory(ANT)to construct a theoretical framework for the study of *** two typical villages with different transition paths in rural areas of North China Plain as examples,this paper reveals the mechanism of RST and makes a comparative *** results show that:1)after identifying problems and obligatory passage point,key actors recruit heterogeneous actors into the actor network by entrusting them with common interests,and realize RST under the system operation.2)Rural settlements under different transition paths have similarities in the problems to be solved,collective actions and policy factors,but there are differences in the transition process,mechanism and *** actor network and mechanism of RST through the path of new rural community construction are more complex and the transition effect is more *** contrast,the degree of RST of retention development path is limited if there is no resource and location advantage.3)Based on the applicable conditions of different paths,this paper designs a logical framework of‘Situation-Structure-Behavior-Result’to scientifically guide the identification of RST paths under the background of rural revitalization.

关键词： rural settlement transition(RST) actor network theory(ANT) transition path transition mechanism plain area China

Evaluation of the intracellular lipid-lowering effect of polyphenols extract from highland barley in HepG2 cells

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Food Science and Human Wellness 2024年第1期13卷 454-461页

作者： Yijun Yao Zhifang Li Bowen Qin Xingrong Ju Lifeng Wang college of Food Science and Engineering/Collaborative Innovation Centre for Modern Grain Circulation and Safety Nanjing University of Finance and EconomicsNanjing 210023China

Active ingredients from highland barley have received considerable attention as natural products for developing treatments and dietary supplements against *** practical application,the research of food combinations is more significant than a specific food *** study investigated the lipid-lowering effect of highland barley polyphenols via lipase assay in vitro and HepG2 cells induced by oleic acid(OA).Five indexes,triglyceride(TG),total cholesterol(T-CHO),low density lipoprotein-cholesterol(LDL-C),aspartate aminotransferase(AST),and alanine aminotransferase(ALT),were used to evaluate the lipidlowering effect of highland barley *** also preliminary studied the lipid-lowering mechanism by Realtime fluorescent quantitative polymerase chain reaction(q PCR).The results indicated that highland barley extract contains many components with lipid-lowering effects,such as hyperoside and *** vitro,the lipase assay showed an 18.4%lipase inhibition rate when the additive contents of highland barley extract were 100μg/m *** intracellular lipid-lowering effect of highland barley extract was examined using 0.25 mmol/L OA-induced HepG2 *** results showed that intracellular TG,LDL-C,and T-CHO content decreased by 34.4%,51.2%,and 18.4%,*** and AST decreased by 51.6%and 20.7%compared with the untreated hyperlipidemic HepG2 cells.q PCR results showed that highland barley polyphenols could up-regulation the expression of lipid metabolism-related genes such as PPARγand Fabp4.

关键词： Highland barley Polyphenols extract Lipid-lowering effect HepG2 cells

Specialization and Coordination: New Paradigm, Theory, and Path for Regional Development

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China Economist 2024年第1期19卷 76-85页

作者： Lu Ming Xiang Kuanhu Li Pengfei Li Jiewei Zhong Yuejun Antai college of economics&Management Shanghai Jiao Tong UniversityShanghaiChina School of economics Shanghai UniversityShanghai School of economics and Management Shanghai Maritime UniversityShanghai Faculty of economics and Management East China Normal UniversityShanghai

In its new development stage,China seeks to derive new dynamism from reform and opening up at a higher level to boost consumption and *** process coincides with a further differentiation of comparative advantages across *** activity and population will continue to concentrate in clusters in coastal and central cities amid a continuous outflow of population from remote *** expansion from coastal to interior regions and from central cities to the periphery will promote a new regional development paradigm of“dual centers and periphery”.Therefore,China’s regional development strategy should follow the new theory of seeking relative equilibrium amid development,identify regions of population inflow and outflow,and explore a new development path of regional specialization and *** deepening market reforms and increasing central government coordination,the country is poised to improve the spatial allocation of resources and unleash institutional dividends in the process of developing a unified national market.

关键词： Regional development “dual centers-periphery” comparative advantage population migration

Digital Revolution and Job Quality of Lower Class Workers: Quasi-experimental Evidence from the Broadband China Program

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China & World Economy 2024年第4期32卷 146-178页

作者： Xiumei Wang Ye Jiang Famin Yi School of Business Fuyang Normal UniversityChina Department of economics Dickinson CollegeUSA School of economics and Management South China Agricultural UniversityChina

This study examines the impact of the digital revolution on the job quality of workers with a specific focus on those at the lowest end of the spectrum in China's domestic labor market. Leveraging exogenous timing variations that result from the implementation of the Broadband China Program across different cities, it provides quasi-experimental evidence concerning the effects of the digital revolution on the job quality of lower class workers, particularly rural–urban migrant workers. Using data from China Migrants Dynamic Survey, this study reveals that migrants' comprehensive job quality index increased by 0.0138 (5.33 percent), and its component indices experienced positive effects after the Broadband China Program was implemented. This study also investigates heterogeneous policy treatment effects among workers with diverse demographic and occupational characteristics. Underlying mechanisms are considered, including positive macroeconomic shocks, increased social interactions, and Internet use. In particular, migrants' attitudes toward local settlement became more positive, suggesting that the positive effects of the digital revolution on livelihood lasted for some time. Taking China as an example, this study contributes valuable empirical evidence of how the digital revolution can affect lower class workers' employment or living conditions in a developing country. Related policy implications are also considered.

关键词： Broadband China Program digital revolution job quality lower clas workers rural-urban migrants