电火花加工在模具制造中的应用

文章介绍了电火花成型加工、电火花线切割加工的工艺原理、加工特点,通过对电火花加工原理和加工特点的介绍,进而介绍了电火花加工在模具制造中广泛应用。     

Examining multi-functionality for crop yield and ecosystem services in five systems of agroecological intensification

Agroecological intensification (AEI) integrates ecological principles and biodiversity management into farming systems with the aims of increasing farm productivity, reducing dependency on external inputs, and sustaining or enhancing ecosystem services. This review develops an analytic framework to characterize the fulfilment of these objectives by documenting the co-occurrence of positive, neutral, and negative outcomes for crop yield and nine regulating ecosystem services. We provide an illustrative examination of the framework, evaluating evidence for yield and ecosystem service outcomes across five AEI systems: conservation agriculture, holistic grazing management, organic agriculture, precision agriculture, and system of rice intensification (SRI). We reviewed 104 studies containing 245 individual comparisons between AEI and contrasting farming systems. In three of the five AEI systems, conservation agriculture, precision agriculture, and SRI, more than half of reviewed comparisons reported ‘win-win’ outcomes, enhancement of both yield and ecosystem services, or ‘win-neutral’ outcomes relative to contrasting farming systems. The review presents substantial evidence that the five AEI systems can contribute to multi-functional agriculture by increasing ecosystem service provision, or reducing negative externalities associated with agriculture, while maintaining or increasing yields. A framework such as the one presented here can help guide decision-makers considering how best to implement multi-functional agriculture so that both crop yield and ecosystem service delivery can be maintained or increased.     

Do Joint Audits Improve or Impair Audit Quality?

Conventional wisdom holds that joint audits would improve audit quality by enhancing audit evidence precision because “Two heads are better than one.” Our paper challenges this wisdom. We show that joint audits by one big firm and one small firm may impair audit quality, because, in that situation, joint audits induce a free‐riding problem between audit firms and reduce audit evidence precision. We further derive a set of empirically testable predictions comparing audit evidence precision and audit fees under joint and single audits. This paper, the first theoretical study of joint audits, contributes to a better understanding of the economic consequences of joint audits on audit quality.     

基于GF-1 PMS影像的柠檬种植面积估算

为应用国产高空间分辨率影像快速、准确估算丘陵区柠檬种植面积,文章基于GF-1 PMS影像使用不同数据预处理及分类法估算柠檬种植面积。通过对影像进行大气校正、数据融合、滤波等处理,分别得到光谱反射率数据、融合影像和纹理特征数据(分辨率分别为8m、2m、2m)。通过可分离性分析,发现荒草地和未成林柠檬的可分性最差,二者在光谱反射率数据、融合影像和纹理图像中的可分性数值均小于1.8,是影响柠檬分类精度的主要因素。基于最大似然法的分类精度评价结果显示,纹理图像数据估算精度好于8m分辨率的多光谱反射率数据和2m分辨率的融合图像,适当的影像预处理有助于提高监督分类精度。对比基于最大似然法的精度,基于面向对象法的柠檬面积估算精度达95.09%,高于监督分类法的,使用GF-1 PMS影像估算柠檬面积最优方法为面向对象法。该研究为应用国产高分辨率遥感数据快速、准确估算丘陵地区果树种植面积提供了相关参考。     

整合式扶贫:一种新的扶贫治理模式的尝试性阐释——以大理州扶贫治理经验为例

通过对扶贫治理研究中的发展主义范式、制度主义范式和政策主义范式比较分析，发现当前部分地区的精准扶贫实践更多遵从在政策主义范式指引下的政策性扶贫路径。这种路径可能导致扶贫效果的"棘轮效应"，造成政策结果的"马太效应"，引发基层政权"异化效应"。考察云南省大理州的扶贫治理实践，我们发现一种整合式扶贫模式，这种模式具有整合论意义上的整体涌现性特征，遵循内生性逻辑、整体性逻辑和综合性逻辑进行运转，提升了国家贫困治理政策的执行绩效，化解了地方政府的政策风险，可以看作是一种贫困治理模式的创新。     

基于精准扶贫的安徽省乡村旅游驱动力分析

[目的]文章选取主成分分析法,首次对安徽省的精准扶贫的乡村旅游的驱动力进行分析,以期对安徽省旅游扶贫工作提供借鉴与指导。[方法]选择主成分分析法(principal component analysis,PCA)和多元线性回归方程,结合SPSS22.0对安徽省基于精准扶贫的乡村旅游驱动力以及影响因子进行分析。[结果]基于精准扶贫的安徽省乡村旅游的主要驱动力是经济驱动、城市环境驱动和健康卫生驱动。其中空气可吸入颗粒年均值对于安徽省精准扶贫的乡村旅游呈负向驱动,乡村饮用水水质达标率、农村卫生厕所普及率、农村居民恩格尔系数、乡村旅游扶贫政策性文件发布数量呈正向驱动,这几个因素是安徽省乡村旅游的主要驱动因子。[结论]今后安徽省基于扶贫的乡村旅游要注重乡村环境的维护、卫生质量的提升、设施设备的完善以及督促各地区政府对发展乡村旅游引起高度重视为入手点,着重提升乡村空气质量、饮用水水质达标率、卫生厕所普及率以及相关政策数量等,以促进乡村旅游在精准扶贫中的成效和带动作用。     

含有曲线的土地面积量算精度分析

土地面积的量算是地籍测量中非常重要的基础工作,在实际工作中,作业人员经常遇到含有曲线的宗地或地块面积量算,本文通过理论分析及公式推导,提出了处理包含曲线宗地的面积量算的方法,对作业人员有一定指导意义。     

Expected Precision of Estimation and Probability of Ruling Out a Hypothesis Based on a Confidence Interval

Interval estimation is an important objective of most experimental and observational studies. Knowing at the design stage of the study how wide the confidence interval (CI) is expected to be and where its limits are expected to fall can be very informative. Asymptotic distribution of the confidence limits can also be used to answer complex questions of power analysis by computing power as probability that a CI will exclude a given parameter value. The CI‐based approach to power and methods of calculating the expected size and location of asymptotic CIs as a measure of expected precision of estimation are reviewed in the present paper. The theory is illustrated with commonly used estimators, including unadjusted risk differences, odds ratios and rate ratios, as well as more complex estimators based on multivariable linear, logistic and Cox regression models. It is noted that in applications with the non‐linear models, some care must be exercised when selecting the appropriate variance expression. In particular, the well‐known ‘short‐cut’ variance formula for the Cox model can be very inaccurate under unequal allocation of subjects to comparison groups. A more accurate expression is derived analytically and validated in simulations. Applications with ‘exact’ CIs are also considered.     

弹性材料3J21微槽的微细电解加工研究

为解决高硬度、高强度弹性材料3J21微结构的成形加工难题,在分析进给速度、微细电极、加工电压、电解液浓度等工艺参数对弹性材料3J21加工精度的影响规律基础上,进行了微槽的微细电解铣削加工工艺实验,加工出了宽度约为40μm的微槽,具有较好的加工质量。     

靶场测控装备状态及故障预测方法

靶场测控装备的管控与状态预测对于确保靶场试验任务的顺利开展有着重要的意义,也是状态/故障处理研究领域的发展方向。结合装备结构关系网络,通过对状态信号的分析,给出了靶场测控设备单元的状态预测方法。依据电子元器件寿命规律,结合状态异常出现的分布函数,重点构建了离散型状态变量的预测模型,提出了相应的预测流程和方法。仿真计算表明,提出的状态及故障预测模型和方法有效,可为提高任务期间装备的可靠性提供判断依据。