布敦岩沥青湿法工艺掺量对 改性沥青混合料性能的影响

为研究采用湿法工艺布敦岩沥青掺量对改性沥青混合料使用性能的影响,采用70号A级道路石油沥青作为基质沥青,制备了最大掺量为基质沥青40%的布敦岩沥青改性沥青.进而采用石灰岩集料,对不同掺量改性沥青进行了AC-20C的沥青混合料马歇尔配合比设计.通过实验室试验,确定了不同掺量布敦岩沥青改性沥青混合料的车辙试验动稳定度、浸水马歇尔试验残留稳定度与冻融劈裂试验残留强度比、弯曲试验破坏应变、渗水系数,还有20℃、15℃抗压回弹模量、15℃劈裂抗拉强度.试验结果与结果分析表明,随着布敦岩沥青掺量的增加,改性沥青混合料的高温稳定性、水稳定性、抗渗性、刚度和强度均不同程度逐渐得到提高.随着布敦岩沥青掺量的增加,改性沥青混合料的低温抗裂性先提高至一峰值,然后略有回落.对于路用沥青混合料,推荐的布敦岩沥青掺量上限为基质沥青的30%.     

基于鲁棒最近邻超圆盘的齿轮箱智能故障诊断

针对超圆盘分类器存在分类精度和分类效率较低等问题,引入松弛变量,并考虑当前类样本和异类样本的约束以避免超圆盘相交,从而得到更合理的类别区域估计,得到鲁棒超圆盘模型（Robust Hyperdisk Model,RHD）,将RHD模型与最近邻分类方法结合,提出一种鲁棒最近邻超圆盘分类器（Robust Nearest Neighbor Hyperdisk Classifiers,RNNHDC）. RNNHDC只需计算未知样本点到各类别RHD的距离,计算效率高,且可以直接用于多分类任务. 最后将RNNHDC应用于齿轮箱故障诊断,在2个不同的齿轮箱数据集上进行实验验证,结果表明,RNNHDC分类精度高、鲁棒性强,可有效用于齿轮箱智能故障诊断.     

Recent advances in magnetic electrospun nanofibers for cancer theranostics application

Cancer theranostics is a recent concept that aims to combine in the same device diagnostic and therapeutic features. Magnetic nanoparticles(m NPs) are commonly used as a critical part of these systems due to their ability to respond to an external magnetic field. Consequently, m NPs can generate heat when an alternating magnetic field is applied and enhance image contrast in magnetic resonance. However, direct administration of m NPs intravenously or directly in the tumor can lead to undesired s...     

WHO总干事谭德塞面临挑战

<正>2019年1月2日,谭德塞(Tedros Adhanom Ghebreyesus)面临着一个生死攸关的决定。这位世界卫生组织(WHO)总干事在刚果民主共和国的布尼亚度过了除夕夜,以提高工作人员的士气——他们正对抗着有史以来第二大的埃博拉疫情。在谭德塞登上飞往乌干达的直升机,去跟乌干达常驻联合国代表鲁贡达·鲁哈卡纳(Ruhakana Rugunda)会面之前,他还必须要做一个决定——是否带走一个名叫查尔斯·卢旺加-基韦瓦(Charles Lwanga-Kikwaya)的刚果小伙子。     

紫罗兰恋爱了

<正>许多科幻作品中都会出现图灵测试。按照维基百科上的定义,图灵测试是图灵于1950年提出的一个关于判断机器是否能够思考的著名思想实验,测试某机器是否能表现出与人等价或无法区分的智能。然而,人之所以为人,不单单是靠智能来定义,还有情感这个重要元素。如果用"具不具备近似于人的情感"为标准来考核人工智能会怎样呢?下面这篇由定居在美国的印度裔女作家吉檀迦利·迪格创作的小说提出了一种设想。     

泥土的起源

<正>在地球的大部分历史中,陆地上几乎不存在任何带有泥土的东西。大约4.58亿年前,泥土终于开始堆积起来,永久改变了地球上的生命。数年前,地质学家尼尔·戴维斯(Neil Davies)前往玻利维亚,在成堆的鱼类化石中寻找答案。他想进一步了解当地那条古老海岸线的信息,这些鱼类在大约4.6亿年前曾沿着那条海岸线畅游,他想了解这些鱼是如何死亡的。     

战前的科学

第二次世界大战深刻影响了人们对科学的看法,远超其他历史事件.特别是在广岛和长崎,科学展现了令人生畏的力量.科学与技术、政府之间的合作有可能会带来严重的风险.我们应该重点发展哪些技术?应该怎样规范科学研究,引导它向特定目标发展?政府又该扮演什么样的角色?二战以来,政府资助并组织了许多大规模研究,掌握了技术应用的方向,比如...     

Comparison of distribution and habitat characteristics between an endemic and a wide-ranging cryptic species of Peromyscus on the Baja California Peninsula

Peromyscus eva and Peromyscus fraterculus are 2 morphologically similar species of the Peromyscus eremicus group occurring on the Baja California Peninsula. Due to the similarity between these 2 species, their ranges have been greatly confused; consequently, the specific habitat characteristics for each group are not well known. The goal of this study was to assess distribution ranges and characteristics of preferred habitats for P. eva and P. fraterculus in more detail. We identified taxonomy of individuals by evaluating genetic patterns produced by restriction fragment length polymorphisms (RFLPs). We evaluated the banding pattern generated by Alu I and Bam HI restriction enzymes in an 850-bp cytochrome b fragment. Consistent differences in number and size of fragments allowed for discrimination of individuals to species. The heterogeneity and evenness indexes showed that the microhabitat of P. fraterculus contained less-diverse soil types and is more homogeneous than the microhabitat of P. eva. In the state of Baja California Sur, P. eva occurs exclusively in the flat areas along the Pacific coast from the Vizcaino Desert to the south, including Margarita Island, with one small population in the Loreto area adjacent to Carmen Island. The habitats occupied by P. eva were heterogeneous (areas with friable, soft sandy soil and a low percentage of small stones). Peromyscus fraterculus occurs mostly in Baja California Norte, with some populations distributed in Baja California Sur, particularly in the western areas of the Vizcaino Desert along the mountain range, in the gulf side of the peninsula south of the city of La Paz, and in a small area on the eastern side of Sierra de Las Cruces. This species was mostly found on hard soil with high medium-size stone content.     

利用同伦微扰法和Adomian分解法求解捕食生态模型

给出了同伦微扰法和Adomian分解法的计算过程,利用同伦微扰法和Adomian分解法求解Bazykin捕食生态模型和一类带有HollingⅡ功能反应和食饵具有似Allee效应的捕食生态模型.数值仿真结果表明,与经典的Rung-Kutta法进行对比,这2种方法可用于近似求解所给模型.     

怎样成为天才?

别误会——是的,我是耶鲁大学教授,但我不是天才.当我第一次对四个已成年的孩子说起,我将要开授一门关于天才的新课程时,他们认为这是他们听到过的最滑稽的事情."你,你压根不是天才!"是的,他们说得没错.那么,为什么在十几年后的今天,我还在教授"天才课程".我新出版的著作《天才成功的隐秘》(2020)还入围了亚马逊年度精选....