漫反射光谱手工与机器制样方法测试结果与对比分析

矿物含量及其变化有可能蕴藏着环境信息。赤铁矿和针铁矿是常见的两种化合物,在各种类型的沉积物中基本都有分布。在古气候研究中,赤铁矿和针铁矿的含量变化可以用来指示气候的干湿变化。漫反射光谱方法(DRS)可以进行赤铁矿和针铁矿含量测算,具有灵敏度高、速度快、准确度高等特点。这种方法虽然很实用,但是对于样品量比较大的研究来说,其手工磨样速度比较慢,而用机器研磨则会大幅提高样品制备效率,但是机器研磨是否会对分析结果产生影响尚未有研究报道。本文对30个河流相和湖泊相样品进行了漫反射光谱对比分析实验,发现手工和机器磨样在磁性矿物浓度上的变化趋势基本一致,但是两者之间存在一定的差异。因此,如果研究目的是希望从整体变化趋势来反演气候变化的过程,用机器研磨方法可以达到要求且效率明显提高;如果是进行浓度含量等其它方面的研究,则传统的手工方法是优先选择。     

城市交通道路氮氧化物浓度的CART回归树预测研究

提出了基于CART回归树的氮氧化物(NO_x)浓度预测模型,利用杭州市延安路路边空气质量监测站2016年6—9月空气污染物监测数据和同期延安路路段车辆抓拍识别数据,通过数据处理、影响因素分析及CART回归树构造,搭建了NO_x浓度预测模型.实验分析结果表明,相对于支持向量机和BP神经网络预测模型,基于CART回归树的NO_x浓度预测模型的预测精度有大幅度提升,可决系数在0.92以上;同时,对环境条件差异较大的G20会议期间NO_x浓度进行预测分析,结果表明,CART回归树方法的预测精度比其它方法更高,能够适应不同条件下的预测需求.     

基于PCA-AHPSO-SVR的煤层瓦斯含量预测研究

为了提高煤层瓦斯含量预测的准确性和科学性,通过主成分分析方法对影响煤层瓦斯含量的7个因素进行特征提取,消除影响因素之间的相关性,减少维度;用支持向量回归机对提取的因素进行训练,并用改进的自适应混合粒子群算法对SVR的参数进行优化,提出PCA-AHPSO-SVR模型;与PCA-PSO-SVR,PSO-SVR这2个模型在相同环境下进行30次运行比较。研究结果表明:研究提出的PCA-AHPSO-SVR模型较其他2种模型平均准确率分别提高5.51%和9.32%,稳定性更佳,可满足工程实际需求。     

某大型机加车间数控机床噪声暴露特点与分析研究

为研究大型机加车间噪声现状和特点,选取某大型机加车间数控机床开展现场实测,并对噪声测量结果进行分析。结果显示:数控机床产生的噪声是非稳态噪声;数控机床产生的噪声在车间传播,声场分布不均匀;加工某转向工件频率在500～5 300 Hz,峰值频率分别为500,800,2 000,5 000 Hz;对机加数控机床操作岗位工作人员的8 h噪声暴露量进行测量,测量值为89.2 dB(A)。研究结果表明:评价大型机加车间噪声,测量重点应选在机床操作岗位和人行通道;应重点关注被测机床周围20 m内的噪声值;机加工作场所测量时间段的选择取决于作业持续时间。     

硅碳比对机床铸件性能的影响

在一定的碳当量的条件下 ,提高硅碳比 (Si/C) ,可以提高机床铸件的抗拉强度、硬度及硬度均匀性 ,降低残留应力 ,改善铸造性能和机加工性能 ,降低废品率。从而达到提高机床的刚度和精度稳定性的目的     

在数学教学中如何培养学生能力

学生能力的培养是教学活动的中心,本文通过对数学教学过程的总结和分析,就如何培养学生能力问题谈了自己的一些见解,并针对学习能力和理解能力的培养提出了一些措施。     

浅谈CNC板材加工设备在钣金加工中的应用

介绍了数控冲床、数控折弯机、数控激光切割机、数控剪板机等CNC板材加工设备的特点,以及这些先进的设备在钣金加工业中的应用和我国钣金生产的加工技术的发展趋向.     

基于支持向量机的资源型城市可持续发展指标体系研究

资源型城市的可持续发展系统是由自然、经济、社会三个基本层次组成的相互作用且相互依赖的复杂巨系统。支持向量机回归具有非线性、并行分布处理、自学习等特点，可以较为逼真地模拟该系统。本文通过对资源型城市可持续发展指标体系现有主要方法的研究，提出以支持向量机为模型的资源型城市可持续发展指标的分析预测方法，并应用此方法构造支持向量机。绘制指标预测图。对铜陵市国民经济总产值进行了预测。结果表明本预测方法效果较好。     

Resource distributions and diet development by trial-and-error learning

We study interactions between resource distributions, grouping, and diet development in foragers who learn by trial-and-error. We do this by constructing an individual-based model where individuals move and forage in groups in a 2-D space with high resource diversity and learn what to eat. By comparing diet development in different resource distributions, and in gregarious and solitary individuals, we elucidate how these factors affect patterns of diet variation. Our results indicate that different resource distributions have profound effects on learning opportunities, and thereby lead to contrasting phenomena. In uniform environments, local resource depletion by gregarious individuals, in interaction with learning, leads to diet differentiation. In patchy environments, grouping leads to enhanced diet overlap within groups and leads to differences in diet between groups. Surprisingly, mixed environments can generate all these phenomena simultaneously. Our results predict relationships between diet variation, trial-and-error learning, and resource distributions. The phenomena we describe are not evolved strategies, but arise spontaneously when groups of individuals learn to forage in certain resource distributions. This suggests that describing diet specialization or diet homogenization as the result of behavioral strategies may not always be justified.     

Less is more: social learning of predator recognition requires a low demonstrator to observer ratio in Arctic charr (Salvelinus alpinus)

Reintroduction programs for conservation purposes suffer from low post-release survival of captive-bred animals, especially so with fish reintroductions. High mortality is most often due to weakened antipredator skills, which could be enhanced through direct experience with predators and social learning. As yet, the relative efficiency of these learning methods has not been tested, and the significance of the factors determining how efficiently antipredator responses are transmitted socially from experienced (demonstrator) to predator naive (observer) individuals is largely unknown. Using hatchery-bred stock of the endangered Saimaa Arctic charr (Salvelinus alpinus), we show for the first time that: (1) contrary to theoretical predictions, acquired predator recognition was only socially transmitted from predator-experienced to predator-naive fish in groups with a smaller proportion of experienced than naive individuals, and that (2) socially acquired avoidance of the predator odors was as strong as in those fish conditioned with a combination of odors and predator exposure. We conclude that using social transmission procedures in training fish for reintroduction programs may provide considerable ecological, economical and ethical advantages.Communicated by J. Krause