热处理对铜合金模具材料组织和硬度的影响

对研制的新型铜合金模具材料（Cu-14Al-X）的热处理工艺进行了试验研究，分析讨论了固溶时效处理对铜合金模具材料组织和硬度的影响。结果表明，通过固溶时效处理可以显著改善铜合金模具材料的金相组织和硬度，其中时效时间对铜合金模具材料硬度的影响较大。在600℃时效处理时，随时效时间从2h增加到5h，硬度明显提高，5h后达到最高值48.2HRC。硬化的原因是时效过程中γ2相和k相的弥散折出。     

关于教学规律的思考

我国教育学界对教学规律的研究存在在重理论思辨、轻教学实践、落后于时代发展的问题，没有起到对教学实践应有的指导作用。分析我国当前的教学现象，可以发现下列重要的教学规律：教师的教学水平决定教育质量的规律；评价导向规律；内因决定规律；成长差异规律；个别差异规律。     

水工钢闸门使用年限对其结构安全的影响分析

随着使用年限的逐渐延长,水工钢闸门会出现锈蚀、磨损、空蚀、裂纹、变形、连接件松动、活动关节咬死等各种各样的缺陷。在对腐蚀削弱后的断面进行强度复核时,不宜采用使用年限折减的方式修正结构材料的容许应力。     

基于集成的年龄估计方法

近十年来, 由于广泛的应用前景, 关于人脸识别的研究得到了广泛的关注. 但目前有一种影响人脸识别技术的因素尚未被研究者所重视, 那就是年龄变化. 而在适用于年龄变化的人脸识别技术中有一个重要的问题, 即年龄估计. 本文基于典型相关分析和代价敏感学习提出了两种年龄估计算法, 并在此基础上利用集成技术来提高年龄估计的准确性. 最终实验结果验证了本文方法的有效性.     

必要的倔强——论数字时代手绘插画的生存能力

随着数字设备在插画创作中的运用,数字化生存已被越来越多的从业者与学界研究人员注重。但数字化的宏观背景下,随着人们生活生活水平与欣赏能力的提高,怀旧意识的增强,追求生活品质的愿望凸显,以及审美心理中的大众化与个性化的矛盾性共生,因此手绘插画依旧有它顽强的生命力。     

基于一种改进NMF算法的人脸年龄估计方法

基于人脸图像的年龄自动估计是人脸识别领域的一个重要研究方向,同时也是一个难点。对此,提出了一种改进的NMF算法来实现人脸年龄估计,该算法首先对NMF分解的基图像进行判别分析,保留最具判别力的基图像来构造子空间,然后将整体训练集图像向得到的子空间进行投影,并用RBF(radial basis function)神经网络进行训练和测试,提取包含在大多数人脸图像上的年龄信息来进行年龄估计,实验结果表明,该算法获得了较好的测试结果。     

基于信息年龄的变电站业务无线接入选择算法

为更好满足变电站中大规模设备接入和高可靠低时延业务传输需求,提出了一种适用于变电站业务的多频异构无线通信网络接入选择算法。首先构造了一个异构无线网络覆盖下的变电站场景模型,综合考虑变电站业务对于可靠性和有效性的需求。其次为有效提升接收到信息的新鲜程度,以平均信息年龄（Average Age of Information,AAoI）作为无线网络接入选择的优化目标函数,提出了基于信息年龄的变电站业务接入选择优化问题。最后利用深度Q学习（Deep Q-Learning,DQN）方法求解该问题,以获得最佳的接入选择方案。通过对应用实例与试验数据的分析可以看出,所提出的接入选择优化理论和算法,可以降低业务传输时的平均信息年龄,提升数据的新鲜程度。     

Iron working at Zambana el Vato (TN), Italy

ABSTRACT

The workshop of Zambana el Vato (region Trentino, Northern Italy), is dated to the period between the 7th-6th and the 5th century BC. Iron working activities are clearly recognizable from the various finds. Among them there are working slag, heated clay, fragments of hearth or forge, hammerscale and more residues that can be referred to iron technology. A number of selected specimens were sectioned and mounted for photomicroscopy to identify the structure and some of the mounted samples were also examined by scanning electron microscopy (SEM) using both a back scattered electron detector and energy dispersive (EDS) x-ray analysis. This paper presents the results of these studies. The hearths were regularly repaired, as their fragments were found mixed with working slag. The hammerscale samples indicate that there were three iron-working areas. The fragments of forge with traces of tuyeres indicate that bellows were employed. Refining slag was identified among the debris. This is particularly significant as for the moment no iron refining centers are known in this area.     

Optimal imperfect preventive maintenance policy for equipment leased during successive periods

In this paper, we consider randomly failing equipment leased several times during their life cycle with a given warranty period. A mathematical model is developed to determine the optimal efficiency levels of preventive maintenance (PM) to be performed on the equipment between successive lease periods, maximising the expected total profit of the lessor over the equipment life cycle. The model considers the expected leasing revenue as well as the equipment acquisition cost and the average PM and repair costs. PM actions allow reducing the age of the equipment to a certain extent with a corresponding cost depending on the PM level adopted. The efficiency of the PM is determinant of the expected revenue during the next lease period. Given a set of K possible PM levels and the number of lease periods n over the equipment life cycle, K^{n?1 PM} strategies are possible. A genetic algorithm is proposed in order to obtain nearly optimal policies in situations where the number of possibilities K^n?1 is very high. Obtained numerical results are discussed. Small- and big-size instances of the problem are considered in the case of a service company in the oil and gas industry specialised in leasing specific equipment such as separators, to oil companies for production activities with a limited duration of several months like well testing or short production tests.     

Testing Concrete E‐modulus at Very Early Ages Through Several Techniques: An Inter‐laboratory Comparison

The design of concrete structures is based on calculation rules, which often do not take into account the very early age behaviour of the material. However, during this period, structural concrete is subjected to strains due to the hydration process of cement. If these strains are restrained by concrete itself or surrounding boundaries, stresses start to build up that can lead to the formation of cracks. Among the parameters involved in the stress build up, the stiffness evolution is of major importance. This paper reports the use of eight different techniques aimed at stiffness evolution assessment, applied on the same concrete mix, in a round robin experimental test within three laboratories. The observations are compared after having expressed the results at the same equivalent age. Both the loading stress rate and amplitude are observed to have an effect of limited importance on the determination of the quasi‐static elastic modulus, which might be explained by very short term creep. Ultrasonic measurements provide values of E‐modulus that are higher than the values provided by the quasi‐static tests at the time of the concrete setting. Similar mechanisms associated to very short term creep could explain the difference between the quasi‐static and high‐frequency elastic modulus.