钻具材料疲劳损伤的磁记忆检测试验研究

为及时准确地确定钻具疲劳损伤及应力集中位置,确定疲劳损伤程度,对42CrMo钢缺口试件进行拉扭疲劳试验及磁记忆在线检测。试验中实时采集磁记忆信号的切向分量,分析其梯度变化趋势,并提取Hp(x)max,Hp(x)sub,Kmax,Ksub等4个磁记忆信号特征参量,研究这4个特征参量在整个疲劳循环过程中的变化规律,并比较在线卸载与在线加载检测各特征参量的异同。试验结果表明,在整个疲劳过程中,各磁记忆信号特征参量具有不同的变化规律,很好地诠释了材料的拉扭疲劳过程,表征出不同疲劳阶段材料的应力集中程度。     

铁磁形状记忆合金研究进展与展望(Ⅰ):材料、力学特性

综述了铁磁形状记忆合金(Ferromagnetic Shape Memory Alloy,简写为FSMA)在材料研制和热磁力学特性方面的研究现状,对其存在的问题进行了分析并指出其发展方向.在材料研发方面,介绍了新型合金、Ni-Mn-Ga-X系列合金、复合材料和Ni2MnGa系列合金;在热磁力学特性方面,介绍了形状记忆效...     

延安城市居民红色记忆的建构路径与代际差异

作为贯通于中国现当代社会进步与发展的典型文化现象,红色记忆宏观层面的书写、建构、传承等话题得到了广泛的关注与探讨,但个体层面的红色记忆研究相对空缺并亟待推进。为此,本文以红色资源富集的延安城市核心区为案例地,借助世代研究法,通过对36位当地居民的深度访谈,明晰了红色记忆"宏观—微观"的建构路径与结果,并诠释了延安老中青三代城市居民的红色记忆代际差异。研究发现,宏观层面的记忆要素挖掘、叙事表达与资源活化构筑了居民红色记忆的编码、选择与巩固过程,促使当地居民生成富有时代特色的红色记忆内容,并最终构建了老中青三代权威性、功能性及反思性的差异性红色记忆体系。研究结果折射出记忆建构的社会力量与时代变迁对个体记忆塑造的重要意义,并为规范开展红色记忆实践,推进红色记忆薪火相传提供了理论参照。     

基于长短时记忆网络的水质预测模型研究

在当前水质数据急剧增加的背景下,为了挖掘水质时间序列中的更多信息,提升水质预测的精度,构建了基于缺失值填补算法和长短时记忆网络(LSTM)相结合的水质预测模型。通过缺失值填补算法进行水质数据的缺失值处理,利用LSTM网络分别构建不同水质参数的预测模型,以太湖水质监测数据为样本,对模型进行检验。结果表明,基于缺失值填补算法-LSTM的水质预测模型适应性强,相较传统SVM、BP神经网络、RNN、LSTM模型预测精度更高,对水环境保护具有重要意义。     

WebGIS在作业场所职业危害监管信息系统中的应用

作业场所职业危害监管具有很强的时空特性,将WebGIS应用于作业场所职业危害监管信息系统,可将空间区域信息和职业危害及监管信息相结合,为政府提供方便、快捷、可视化的职业危害监管依据。由于WebGIS系统空间数据量大、服务器过载、网络传输速度慢等问题降低了系统响应速度,限制了在职业危害监管信息系统中的应用。作业场所职业危害监管分为"国家-省级-市级-县级-用人单位"5级逻辑结构,而WebGIS的功能需求分为"国家-省级-市级-县级"4级逻辑结构,笔者将WebGIS的空间数据分为"国家-省级-市级-县级"4级分布式存储,有效地解决了WebGIS的瓶颈问题,提高了系统响应速度,同时也满足作业场所职业危害监管信息系统的功能需求。     

Place attachment,place identity,and place memory: Restoring the forgotten city past

This paper investigates collective memory in inhabitants of two twin cities, Lviv (Ukraine, previously Lwów, Poland) and Wroc?aw (Poland, previously Breslau, Germany). Due to territorial changes in Eastern and Central Europe after World War II, the two cities changed their state belonging and—consequently—their populations. This study focused on memory of residence place and on its relationship with place identity and place attachment.     

The effect of navigational expertise on wayfinding in new environments

Becoming proficient at navigation in urban environments is something that we all aspire to. Here we asked whether being an expert at wayfinding in one environment has any effect on learning new spatial layouts. Licensed London taxi drivers are among the most proficient urban navigators, training for many years to find their way around a complex and irregularly-laid out city. We first tested how well they could learn the layout of an unfamiliar town compared with a group of non-taxi drivers. Second, we investigated how effectively taxi drivers could integrate a new district into their existing spatial representation of London. We found that taxi drivers were significantly better than control participants at executing routes through the new town, and representing it at a map-like survey level. However, the benefits of navigational expertise were not universal. Compared with their performance in the new town, taxi drivers were significantly poorer at learning the layout of a new area that had to be integrated with their existing knowledge of London. We consider reasons for this picture of facilitation and limitation, in particular drawing parallels with how knowledge acquisition occurs in the context of expertise in general.     

免疫粒子群优化在波阻抗反演中的应用

针对标准粒子群优化(PSO)算法易出现早熟而陷入局部最优以及进化后期收敛速度慢等缺陷,引入免疫系统的免疫记忆和抗体浓度选择机制,构造了基于免疫机制的粒子群优化(IPSO)算法,并将其应用到波阻抗反演问题中。免疫记忆能够保留高适应度个体,抗体浓度选择机制进一步保证了粒子的多样性,从而能较好地避免早熟收敛,提高算法的全局搜索能力。对理论模型试算表明,IPSO算法在进行波阻抗反演时不仅收敛速度快,而且具有较高的精确度和抗噪性能。     

面向密闭空间内外温度的时序预测模型

目的 研究密闭空间条件下已知外部温度时间序列对内部实时温度的预测推理问题。方法 选取密闭空间内外温度时序预测典型场景,抽象为多变量时间序列预测问题,分析变量间的关联性和依赖性。借鉴特征融合、注意力机制、多任务模型等思路,结合物理机制与数据特征,基于长短期记忆网络基本网络单元,构建密闭空间内外温度时序预测模型,并在万宁、敦煌、漠河对某型密闭空间进行数据采样,基于三地数据集进行不同模型试验。结果 多变量模型比单变量模型具有更好性能,注意力机制对该场景没有显著性能提升,结合物理机制的模型结构设计充分考虑了变量之间的关联性和依赖性,能显著提升预测精度,双输入双输出的多变量时序预测模型具有相对最高的精度和最稳定的鲁棒性,是面向密闭空间内外温度时序预测的相对最优模型。结论 研究结论可指导密闭空间其他环境特征建模,研究思路可为其他多变量时序建模问题中变量之间的关联性、依赖性分析提供参考。     

Amalgam in Dentistry A Health Hazard for Dental Personnel?

In a cross sectional study done in 1993 among dental personnel in Norrbotten, self-reported prevalence of muscular pain, headache, tremor, insomnia, irritation, impaired memory and depression, as well as information regarding different mercury exposures were collected Mercury exposures were determined as “number of amalgam fillings in teeth,” “years in practice,” “insufficient ventilation at work,” “total number of amalgam removed, produced and polished per day,” and “working in dental clinics.” As controls, physicians and nurses from the same geographical area were selected. The correlation between symptoms and different mercury exposures was calculated using logistic regression. The results suggested a higher prevalence of muscular fatigue and tremor for female dental personnel compared to controls Controls reported a lower prevalence of symptoms with increasing number of amalgam fillings in teeth. There was no correlation between the number of amalgam fillings handled per day and symptoms for dental personnel. Male dental personnel associated muscular fatigue headache, impaired memory, and depression with increased handling of amalgam in the clinic’ whereas the female dental personnel associated the same symptoms with the number of amalgam fillings in teeth. The strongest correlation was found between symptoms and insufficient ventilation at dental clinics for dental personnel.