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1. Ensemble learning prediction of soybean yields in China based on meteorological data
LI Qian-chuan, XU Shi-wei, ZHUANG Jia-yu, LIU Jia-jia, ZHOU Yi, ZHANG Ze-xi
Journal of Integrative Agriculture    2023, 22 (6): 1909-1927.   DOI: 10.1016/j.jia.2023.02.011
摘要207)      PDF    收藏

准确预测大豆单产对于农业生产、监测和预警具有重要意义。尽管目前有研究已经使用机器学习算法来基于气象数据预测大豆单产,但尚没有充分探讨如何使用不同的模型来有效地将不同地区的大豆气象单产与大豆单产区分开来。此外,综合利用各种机器学习算法的优势与特点以通过集成学习算法提高大豆预测单产精度的研究也不够深入。通过对中国最主要的两个大豆主产区东北地区和黄淮地区,173个县级行政区域和气象观测站跨度34年的单日气象数据和大豆产量数据进行研究与分析,本文采用K近邻(K-Nearest Neighbors, KNN),随机森林(Random Forest, RF)和支持向量机(Support Vector Machine, SVR)作为3个有效的基模型,建立了基于堆栈集成学习框架的高精度、高可靠性大豆气象单产预测模型。通过5折交叉验证进一步提升了模型泛化能力,并利用主成分分析降维和超参数调优对模型进行了优化。利用173个县的5年滑动预测和4种回归指标进行模型精度评价,表明大豆气象单产堆栈集成学习预测模型具有更高的精度和更强的鲁棒性。基于堆栈集成学习框架173个县大豆单产5年滑动估测表明,模型估测效果能够详细反映出大豆单产的时空分布变化情况,MAPE低于5%。大豆气象单产堆栈集成学习预测模型为准确预测大豆单产提供了新的思路。

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2. Research and application of real-time monitoring and early warning thresholds for multi-temporal agricultural products information
XU Shi-wei, WANG Yu, WANG Sheng-wei, LI Jian-zheng
Journal of Integrative Agriculture    2020, 19 (10): 2582-2596.   DOI: 10.1016/S2095-3119(20)63368-8
摘要133)      PDF    收藏
Monitoring and early warning is an important means to effectively prevent risks in agricultural production, consumption and price.  In particular, with the change of modes of national administration against the background of big data, improving the capacity to monitor agricultural products is of great significance for macroeconomic decision-making.  Agricultural product information early warning thresholds are the core of agricultural product monitoring and early warning.  How to appropriately determine the early warning thresholds of multi-temporal agricultural product information is a key question to realize real-time and dynamic monitoring and early warning.  Based on the theory of abnormal fluctuation of agricultural product information and the research of substantive impact on the society, this paper comprehensively discussed the methods to determine the thresholds of agricultural product information fluctuation in different time dimensions.  Based on the data of the National Bureau of Statistics of China (NBSC) and survey data, this paper used a variety of statistical methods to determine the early warning thresholds of the production, consumption and prices of agricultural products.  Combined with Delphi expert judgment correction method, it finally determined the early warning thresholds of agricultural product information in multiple time, and carried out early warning analysis on the fluctuation of agricultural product monitoring information in 2018.  The results show that: (1) the daily, weekly and monthly monitoring and early warning thresholds of agricultural products play an important early warning role in monitoring abnormal fluctuations with agricultural products; (2) the multi-temporal monitoring and early warning thresholds of agricultural product information identified by the research institute can provide effective early warning on current abnormal fluctuation of agricultural product information, provide a benchmarking standard for China’s agricultural production, consumption and price monitoring and early warning at the national macro level, and further improve the application of China’s agricultural product monitoring and early warning.
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3. Food packing: A case study of dining out in Beijing
WANG Yu, XU Shi-wei, YU Wen, Ahmed Abdul-gafar, LIU Xiao-jie, BAI Jun-fei, ZHANG Dan, GAO Liwei, CAO Xiao-chang, LIU Yao
Journal of Integrative Agriculture    2016, 15 (8): 1924-1931.   DOI: 10.1016/S2095-3119(15)61282-5
摘要1892)      PDF    收藏
  Food waste results in nutritional losses, ecological damage, and environmental pollution. This survey is conducted in Beijing and aims to determine whether food waste can be reduced by food packing when leftovers are produced at the dining table and to identify factors that affect food packing behavior and the use of leftovers. Based on statistical and econometric analyses of the relationship between leftovers packing and possible factors, this study finds that the age, educational level, employment status, farming experience, environmental protection consciousness, food saving advertisement, families with old members, and reasons for dining out significantly influence the food packing behavior of the consumers. Moreover, the dining environment plays an important role in leftovers packing. People with intimate relationships, such as families, friends, classmates, or colleagues, are more willing to take leftovers home. Business partners do the opposite. Finally, almost all packed leftovers (91.59%) are eaten by people and animals. Therefore, packing leftovers is an excellent approach to reduce food waste.
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4. China agricultural outlook for 2015–2024 based on China Agricultural Monitoring and Early-warning System (CAMES)
XU Shi-wei, LI Gan-qiong, LI Zhe-min
Journal of Integrative Agriculture    2015, 14 (9): 1889-1902.   DOI: 10.1016/S2095-3119(15)61149-2
摘要2612)      PDF    收藏
The primary goal of Chinese agricultural development is to guarantee national food security and supply of major agricultural products. Hence, the scientific work on agricultural monitoring and early warning as well as agricultural outlook must be strengthened. In this study, we develop the China Agricultural Monitoring and Early-warning System (CAMES) on the basis of a comparative study of domestic and international agricultural outlook models. The system is a dynamic and multi-market partial equilibrium model that integrates biological mechanisms with economic mechanisms. This system, which includes 11 categories of 953 kinds of agricultural products, could dynamically project agricultural market supply and demand, assess food security, and conduct scenario analysis at different spatial levels, time scale levels, and macro-micro levels. Based on the CAMES, the production, consumption, and trade of the major agricultural products in China over the next decade are projected. The following conclusions are drawn: i) The production of major agricultural products will continue to grow steadily, mainly because of the increase in yield. ii) The growth of agricultural consumption will be slightly higher than that of agricultural production. Meanwhile, a high self-sufficiency rate is expected for cereals such as rice, wheat, and maize, with the rate being stable at around 97%. iii) Agricultural trade will continue to thrive. The growth of soybean and milk imports will slow down, but the growth of traditional agricultural exports such as vegetables and fruits is expected to continue.
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5. Spatial-Temporal Changes in Grain Production, Consumption and Driving Mechanism in China
XU Shi-wei, WU Jian-zhai, SONG Wei, LI Zhi-qiang, LI Zhe-min , KONG Fan-tao
Journal of Integrative Agriculture    2013, 12 (2): 374-385.   DOI: 10.1016/S2095-3119(13)60236-1
摘要1594)      PDF    收藏
The spatial-temporal patterns of grain production and consumption have an important influence on the effective national grain supply on condition of tight balance in the total grain amount in China. In this paper, we analyze the spatial-temporal patterns of grain production, consumption and the driving mechanism for their evolution processes in China. The results indicate that both gravity centers of grain production and consumption in China moved toward the northern and eastern regions, almost in the same direction. The coordination of grain production and consumption increased slightly from 1995 to 2007 but decreased from 2000 to 2007. There is a spatial difference between the major districts of output increase and the strong growth potential in grain consumption, which indicates an increasing difficulty in improving the regional coordination of grain production and consumption. The movement of the gravity center of grain production is significantly correlated with regional differences in grain production policy, different economic development models, and spatial disparity of land and water resource use. For grain consumption, the main driving factors include rapid urbanization, the upgrade of food consumption structure, and distribution of food industries.
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6. Prediction Model of Weekly Retail Price for Eggs Based on Chaotic Neural Network
LI Zhe-min, CUI Li-guo, XU Shi-wei, WENG Ling-yun, DONG Xiao-xia, LI Gan-qiong , YU Hai-peng
Journal of Integrative Agriculture    2013, 12 (12): 2292-2299.   DOI: 10.1016/S2095-3119(13)60610-3
摘要1424)      PDF    收藏
This paper establishes a short-term prediction model of weekly retail prices for eggs based on chaotic neural network with the weekly retail prices of eggs from January 2008 to December 2012 in China. In the process of determining the structure of the chaotic neural network, the number of input layer nodes of the network is calculated by reconstructing phase space and computing its saturated embedding dimension, and then the number of hidden layer nodes is estimated by trial and error. Finally, this model is applied to predict the retail prices of eggs and compared with ARIMA. The result shows that the chaotic neural network has better nonlinear fitting ability and higher precision in the prediction of weekly retail price of eggs. The empirical result also shows that the chaotic neural network can be widely used in the field of short-term prediction of agricultural prices.
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7. Using Quantile Regression Approach to Analyze Price Movements of Agricultural Products in China
LI Gan-qiong, XU Shi-wei, LI Zhe-min, SUN Yi-guo , DONG Xiao-xia
Journal of Integrative Agriculture    2012, 12 (4): 674-683.   DOI: 10.1016/S1671-2927(00)8588
摘要1398)      PDF    收藏
This paper studies how the price movements of pork, chicken and egg respond to those of related cost factors in short terms in Chinese market. We employ a linear quantile approach not only to explore potential data heteroscedasticity but also to generate confidence bands for the purpose of price stability study. We then evaluate our models by comparing the prediction intervals generated from the quantile regression models with in-sample and out-of-sample forecasts. Using monthly data from January 2000 to October 2010, we observed these findings: (i) the price changes of cost factors asymmetrically and unequally influence those of the livestock across different quantiles; (ii) the performance of our models is robust and consistent for both in-sample and out-of-sample forecasts; (iii) the confidence intervals generated from 0.05th and 0.95th quantile regression models are good methods to forecast livestock price fluctuation.
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8. Price Transmission in China’s Swine Industry with an Application of MCM
XU Shi-wei, LI Zhe-min, CUI Li-guo, DONG Xiao-xia, KONG Fan-tao, LI Gan-qiong
Journal of Integrative Agriculture    2012, 12 (12): 2097-2106.   DOI: 10.1016/S1671-2927(00)8748
摘要1210)      PDF    收藏
The paper studies the relationship, adjustment ability, path, efficiency and intensity of price transmission in the swine industry chain in China, which consists of the prices of corn, compound feed for fattening pig, piglet, pig and pork. Monthly prices covering a period of 18 yr (1994-2011) are analyzed using a Market-Chain Cooperated Model (MCM). The empirical results show that there exists a stable long-term cointegration and short-term dynamic relationship in the price system. First, the adjustment speed of each price series is very slow and the transmission path is top-down and one-way significantly. Second, the price from upstream to downstream lags about 2 mon, while there is no lag in price transmission from midstream to downstream. Third, in terms of price transmission intensity, the price of pig impacted greatly on pork price, not only in the current period but also through the whole period. Besides, the price of corn has the largest lagged effects on pork price. According to the above empirical results, we suggest that government should strengthen monitoring and early warning of the swine industry chain, especially the upstream and midstream, attach great importance to the timely adjustment of feed prices and perfect the measures of price subsidy.
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9. Vertical Price Transmission in the China’s Layer Industry Chain: an Application of FDL Approach 
XU Shi-wei, DONG Xiao-xia, LI Zhe-min, LI Gan-qiong
Journal of Integrative Agriculture    2011, 10 (11): 1812-1823.   DOI: 10.1016/S1671-2927(11)60181-8
摘要1614)      PDF    收藏
This paper examines the vertical price relationship between upstream and downstream products in China’s layer industry chain by estimating elasticity coefficients of the price transmission. We use cointegration tests, error correction models and finite distributed lag models to analyze vertical price shifts between corn, layer feed, egg-laying chicken and egg prices. With monthly data from 1994 to 2010, our results show that various prices in China’s layer industry chain are well integrated. In addition, our results indicate that both long-run and short-run price relationships between upstream and downstream products in layer industry chain exist and the long-run equilibrium, to a certain extent, may eliminate the short-run dynamics price deviation. We also found that the influence of corn and feed prices on egg prices is still more remarkable than egg-laying chicken prices. Our findings imply that governments should pay more attention to corn and layer feed prices in order to stabilize egg prices under the conditions of market integration.
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