草原补奖政策下牧户家庭收入的影响研究——以内蒙古锡林郭勒盟为例

为探究草原补奖政策对牧户家庭收入的影响,本研究基于锡林郭勒盟219户牧民调研数据,运用分位数回归模型,对牧民收入的影响因素和作用程度进行分析。结果显示：草原补奖政策促进牧民增收,尤其是对低收入牧户家庭增收效果显著;草场使用面积、年初家畜数量、劳动力比例、家畜出生率及出售率对牧民收入具有显著正影响,当草场使用面积、年初家畜数量分别增加1公顷、1羊单位,人均总收入分别提高0.02%,0.15%;劳动力比例、家畜出生率及出售率分别提高1%时,人均总收入分别提高0.65%,0.43%,1.83%;各因素对不同收入家庭的收入影响及作用程度具有差异性,即随着收入水平的提高,劳动力比例增收效果趋于加强,而家畜出生率和出售率的增收效果则趋于减弱。因此,建议引导牧民发展畜牧业适度规模经营、加大畜牧业社会化服务体系建设等以提高牧民收入水平。     

中国产业结构优化升级引致的城镇化效应研究——一个省级面板分位数模型的实证检验

基于2000~2011年我国省级面板数据,采用面板分位数计量模型考察了产业结构引致的城镇化效应。研究发现,第三产业份额的估计参数显著为正,说明产业结构优化带来的城镇化效应是存在的。同时,这种效应对于处于不同分位数上的地区有较大差异：第三产业份额适中的省（市、自治区）,城镇化效应最为明显;第三产业份额相对过高或过低的省（市、自治区）,产业结构优化带来的城镇化效应较弱,估计参数呈现“两头小、中间大”的结果,显著、稳健为“倒U型”结构。     

基于Q-RBF神经网络模型的国产大豆价格预测研究

大豆是重要的经济作物,同时也是我国市场化和国际化程度最高的大宗农产品,对其价格进行预测具有重要意义。采用Q-RBF神经网络模型对国产大豆价格进行预测,该模型具有如下两个特点:(1)通过分位数回归功能来描述大豆在不同价格水平下的分布特征;(2)通过RBF神经网络结构来刻画大豆价格的非线性关系。在模型参数优化时,由于遗传算法是一种全局搜索优化方法,但是搜索速度慢、对初始值具有一定依赖性;而梯度下降法具有收敛快,对初始值没有特定要求等优点,所以本文提出遗传算法与梯度下降法相结合的混合改进算法,其基本思想是利用梯度下降法的局部寻优能力加快遗传算法的收敛速度。采用2010年1月-2015年12月的国产大豆月度价格数据进行预测研究,结果表明,算法收敛速度较快,模型预测精度较高,是可以泛化应用的预测模型。     

改进蚁群算法优化支持向量机的网络入侵检测

利用1999~2012年样本数据,采用空间聚类分析方法研究了中国省域税收收入空间聚类分布格局以及通过分位数回归模型分析了税负水平、税收结构和税收不确定性对我国居民消费水平在不同分位点上产生的区域效应。实证结果表明,在参数异质性假设条件下,税收负担挤入居民消费水平,而税收不确定因素挤出居民消费水平;商品税、所得税与财产税对居民消费水平的影响,在不同税收收入水平下,呈现出具有差异性的区域空间特征。     

Mine waste contamination limits soil respiration rates: a case study using quantile regression

We present an application of a statistical approach, quantile regression (QR), which identifies trends in soil processes otherwise masked by spatial and temporal variability. QR identifies limits on processes and changes in the variance of a response along an environmental gradient. We quantified in situ soil respiration, pH, and heavy metal concentrations across a mine waste contamination gradient that spanned greater than an order of magnitude of metal concentrations. Respiration values were monitored at study sites over 2 years. We used QR to show that soil respiration was limited with respect to both heavy metals and pH, and that both increased metals and increased acidity constrained variation in soil respiration values. Maximum respiration values declined by 48% over the Metals Contamination Index (MCI) range and by 72% over the pH range. The use of QR avoided the necessity of discriminating between multiple sources of variation in a spatially and temporally variable system. It is often unrealistic or too time consuming and expensive to attempt to measure all of the relevant predictor variables in the field. The simpler approach offered by QR is to explore factors that limit a process, recognizing that not all of the factors contributing to a soil function will be measured. An application of this approach to the evaluation of a mine waste remediation procedure is discussed.     

呼和浩特市沙尘暴发生规律的初步研究

将呼和浩特市1955-2001年沙尘暴天气分别以月、日、时进行划分,用SPSS统计软件通过分位数图分别进行分析,发现每年沙尘暴天气出现次数符合正态分布,沙尘暴的发生主要集中每年的3~6月,平均每年发生3次以上。除19时、20时外,每天其他时刻发生沙尘暴次数也服从正态分布,每日的19时、20时发生的沙尘暴次数明显与正态分布不相符,这一现象的产生原因值得深入研究。每月沙尘暴出现次数不符合正态分布。     

农机社会化服务对玉米生产效率的影响研究——基于吉林省玉米种植户的调查数据

为探究农机社会化服务对玉米生产效率的作用效果,基于2021年对吉林省玉米种植户的微观调查数据,运用DEA-Tobit模型和分位数回归测算玉米生产效率并分析农机社会化服务对玉米生产效率的影响效果。结果表明,农机社会化服务能够显著提高玉米生产效率,但在不同服务环节上的作用效果有所差别。其中,机耕和机播环节的社会化服务对玉米生产效率具有显著的正向影响,施肥打药和机收环节的农机社会化服务对玉米生产效率影响不显著。对于不同效率水平的玉米种植户,农机社会化服务的作用效果也存在差异。因此,在推广普及农机社会化服务时,要注重规范不同生产环节的农机服务标准,以实现农业规模经营,助力农业现代化转型。     

近30年河南省耕地土壤有机碳的三维变化与关键因素研究

详细的土壤有机碳(Soilorganiccarbon,SOC)时空变化信息是评估土壤固碳能力的基础。但多数研究聚焦耕层SOC,对深层SOC变化的敏感区域、深度区间和关键因素理解不足。基于1982和2010两期土壤调查数据,以分位数随机森林构建环境协变量与SOC关系模型,研究了1982—2010河南耕地土壤0～15 cm、15～30 cm、30～60 cm和60～100 cm的SOC变化。研究表明0～15 cm土层SOC增长主要发生在平原和盆地,增幅为2～4 g·kg^-1;15～30 cm土层SOC增长主要发生在沿黄河潮土区和褐土、水稻土的零星地区,增幅为0～2g·kg^-1;30cm以下土层SOC变化的概率较低;总体上,生物气候因素对SOC变化的影响较土壤质地和pH更大。28年间1 m土体SOC储量增长7.04%、年均增长率为2.43‰;随着SOC增加和全球变暖,下阶段SOC增速较难实现第21届联合国气候变化峰会(the 21^st Conference of the Parties,COP21)倡导的4‰目标。     

Estimating the willingness to pay for green space services in Shanghai: Implications for social equity in urban China

The willingness to pay can be considered as the fiscal dimension of equity in a planning context. The common solution in most western countries for such fiscal inequity is to apply taxation to rebalance; however, there is no equivalent tax category in China, where residential segregation has already occurred and intensified. This paper re-examines the traditional economic aspects of urban green space in relation to size, type and proximity level, and questions whether green fiscal equity appeared in China by exploring how homebuyers in different price ranges value green space services. Specifically, this paper uses the empirical case of Shanghai, China, to test the hypothesis via the quantile hedonic approach. The results show that people at the lowest percentile level paid a higher value for accessing urban public goods than people at the higher income percentiles, and that wealthy people prefer to purchase green space services privately. These results indicate that the traditional social equity problem may not appear in the Chines context, instead urban China’s problem with social quity may be more related to the privatisation of green space provision, which is only accessible to homeowners and the resulting decline of public green space developments, which primarily affects low-income renters.     

A new method for modelling biological variation using quantile functions

We describe a general method for modelling biological variability as a function of time using fruit populations as examples. The method can incorporate variations in the biological age or maturity of fruit or other produce, as well as variations in the biological property being measured. Key developments are the use of quantile functions to describe the stochastic elements of the model, the assignment of probabilities to individual measurements based on their rank order within a sample, the use of individual measurements rather than means in the fitting process, and the fact that a single model equation with a single set of parameters describes the distribution of measurements across an entire population as a function of time. Using a representative fruit sample taken at a specific time and generalised model parameters, the technique allows the prediction of future fruit population distributions and the prediction of the date when a defined percentage of the fruit population meet a particular specification.The model development process demonstrates how to account for both biological age variability and measure (hue) variability simultaneously, the latter including components of measurement uncertainty and variability not related to biological age. Using quantile functions as the stochastic elements provides a wide range of distributional options.The method is described in detail using, as examples, a Complementary Log–Log sigmoid to model changes in ‘Hort16A’ kiwifruit hue angle preharvest, and a Logistic sigmoid to model changes in ‘Tradiro’ tomato skin hue data postharvest.The kiwifruit data comprised ten samples of 90 destructive hue angle measurements taken across the growing season from each of eight maturity areas (MAs). Allowing MA-specific parameter sets, the entire data set was modelled with an adjusted rsd of 0.46°. Further exploration of the sensitivity of model parameters showed that the model parameter t_m, which defines the timing of the ‘maturity’ of each MA, needed to be MA-specific.The tomato colour data comprised 120 fruit measured non-destructively on seven occasions postharvest. Initial model fits using a Normal distribution for the biological age component gave an rsd of 1.05°. The rsd was reduced to 0.61° using a four-parameter generalised lambda quantile function to describe the biological age variability and 0.63° when using a truncated Normal, suggesting that the underlying distribution was not Normal.The models are readily fitted using any statistical or computational package that offers non-linear optimisation including Microsoft Excel with Solver. The technique can be used as effectively with destructive as with non-destructive measurement data, in preharvest and postharvest situations, and can provide visualisation as well as computational tools. It can be applied to any populations that vary with time and where the units of the populations exhibit variability. These modelling techniques have formed the basis for decision support tools that have been operating commercially since 2007.