一种纯追踪模型改进算法

为了提高农业机械自动导航控制系统的精度,根据纯追踪模型和农业机械运动学模型的特点,提出了一种纯追 踪模型改进算法。在重点分析纯追踪模型算法误差原理的基础上,指出纯追踪模型误差主要来源于车体的航向角和转 向角。采用该算法可以校正车体的航向角和转向角,减小车体跟踪规划路径时的横向误差。根据算法推导和电控液压 阀性能等因素得出前视距离L≥3-wT才能取得较好的跟踪效果。Matlah仿真结果表明,该算法比纯追踪算法的精度 提高了30. 24%,最大误差减小了4 cm,标准差也有所减小     

利率期限结构模型改进极大似然估计效率研究

考虑一种改进的极大似然估计算法估计一维利率期限结构模型的未知参数,该方法首先利用Crank-Nicolson差分法求解与该扩散模型相关联的偏微分方程(PDE),获得累积分布函数,然后利用数值微分得到转移密度函数的近似值。数值模拟实验结果表明,当取较小空间步长时,该改进估计法比Euler法具有更高的效率,并考察该改进估计法在中国银行间同业拆借利率的实证分析,实证结果表明,在所考虑的样本区间内,中国利率的长期水平值是0.025 1,且中国货币市场利率粘性系数的值接近于0.5。     

现代农业发展水平评价及其金融支持——以陕西省为例

在界定现代农业概念的基础上,应用改进型熵权法从粮食安全水平、产业化经营水平、现代化生产水平、可持续发展水平和绩效水平五个领域评价了陕西省现代农业发展水平,并建立了农业贷款与现代农业发展水平的分布滞后馍型．研究结果表明,产业化经营水平和现代化生产对陕西现代农业发展影响最大,却呈缓慢发展甚至倒退的局面;现代化生产水平、可持续发展水平与绩效水平严重滞后于产业化经营水平和粮食安全水平;农业贷款是陕西现代农业发展的强动因,农业贷款的远期拉动作用不容忽视。     

Efficient improved estimation of the parameters in two seemingly unrelated regression models

For a system of two seemingly unrelated regression equations, this paper proposes a two-stage covariance improved estimator of the regression coefficients. The new estimator is shown to uniformly dominate the present estimators in terms of generalized mean square error criterion. In addition, we also propose the exact generalized mean square error of new estimator.     

湖南省高质量发展水平的测度研究

文章首先探讨了高质量发展的内涵以及高质量发展指标构建的理论基础,然后基于五大发展理念,采用改进的层次分析法构建了由创新发展、协调发展、绿色发展、开放发展、共享发展5个维度共37项指标构成的中国经济高质量发展评价指标体系,最后以湖南省为例,分析了湖南省2000—2018年19年间5个维度的发展指标以及经济高质量发展综合指标的发展状况。研究发现:2000—2018年19年间湖南省创新发展水平整体呈现快速增长的基本态势;协调发展的增长趋势不明显,面临很大的下行压力;绿色发展水平总体上呈现出显著的“梯型”变化趋势;开放发展水平一直处于上下波动过程中;共享发展水平整体呈现增长趋势。综合来看,2000年以来湖南省高质量发展指数近似呈现线性增长趋势,发展势头良好。“十四五”阶段湖南省应稳固创新发展态势,加强协调发展力度,重视绿色发展前景,加大开放发展水平,保持共享发展稳定增长,从而使高质量水平继续快速发展,早日达成高质量发展目标。     

The Effect of Forest Management Strategy on Carbon Storage and Revenue in Western Washington: A Probabilistic Simulation of Tradeoffs

The objectives of this study are to understand tradeoffs between forest carbon and timber values, and evaluate the impact of uncertainty in improved forest management (IFM) carbon offset projects to improve forest management decisions. The study uses probabilistic simulation of uncertainty in financial risk for three management scenarios (clearcutting in 45‐ and 65‐year rotations and no harvest) under three carbon price schemes (historic voluntary market prices, cap and trade, and carbon prices set to equal net present value (NPV) from timber‐oriented management). Uncertainty is modeled for value and amount of carbon credits and wood products, the accuracy of forest growth model forecasts, and four other variables relevant to American Carbon Registry methodology. Calculations use forest inventory data from a 1,740 ha forest in western Washington State, using the Forest Vegetation Simulator (FVS) growth model. Sensitivity analysis shows that FVS model uncertainty contributes more than 70% to overall NPV variance, followed in importance by variability in inventory sample (3–14%), and short‐term prices for timber products (8%), while variability in carbon credit price has little influence (1.1%). At regional average land‐holding costs, a no‐harvest management scenario would become revenue‐positive at a carbon credit break‐point price of $14.17/Mg carbon dioxide equivalent (CO₂e). IFM carbon projects are associated with a greater chance of both large payouts and large losses to landowners. These results inform policymakers and forest owners of the carbon credit price necessary for IFM approaches to equal or better the business‐as‐usual strategy, while highlighting the magnitude of financial risk and reward through probabilistic simulation.     

改良型生物脱氮除磷水处理综述

现有的城市污水处理厂大多采用A2／O工艺，即英文Anaerobic—Anoxic—Oxic第一个字母的简称（生物脱氮除磷）。此法对污水除磷脱氮较为有效，但由于生物脱氮和生物除磷是相互矛盾的，所以其效果仍不理想。在此介绍一种改良的A2／O工艺，能大大改善污水除磷脱氮效果。     

Improved estimation for the parameters of an inverse gaussian distribution

James-Stein estimators are proposed for the #-parameter of an inverse Gaussian #G# distribution. The estimators of this class have smaller expected quadratic loss than the maximum likelihood estimator usually employed when analysing real sets of data. This problem is also studied for the case of an unknown nuisance parameter. Finally, improved estimators are considered for # in the two sample problem.     

Interval estimation of the common mean

Brown and Cohen (1974) considered the problem of interval estimation of the common mean of two normal populations based on independent random samples. They showed that if we take the usual confidence interval using the first sample only and centre it around an appropriate combined estimate of the common mean the resulting interval would contain the true value with higher probability. They also gave a sufficient condition which such a point estimate should satisfy. Bhattacharya and Shah (1978) showed that the estimates satisfying this condition are nearly identical to the mean of the first sample. In this paper we obtain a stronger sufficient condition which is satisfied by many point estimates when the size of the second sample exceeds ten.