Conspiracy vs science: A large-scale analysis of online discussion cascades

World Wide Web - With the emergence and rapid proliferation of social media platforms and social networking sites, recent years have witnessed a surge of misinformation spreading in our daily life....     

基于超声传感技术在污水旋流池测量中的应用

为了能够准确地测量污水旋流池的液面高度,设计了基于超声传感技术的污水旋流池液面测量方法,通过长时间的运行,测量数据完全满足污水旋流池的生产工艺要求。     

关于虚功原理及用其求解约束反力的分析

从虚功原理的定义入手,分析了在理想约束下以及在光滑约束下的虚功原理的运用,并且运用虚功原理对解决有非理想约束存在时约束反力的求法问题进行了探讨分析。     

消泡剂在发酵工业中的应用

泡沫问题是发酵工业中一个棘手的问题,几乎所用的液体深层发酵都会用到天然或者化学消泡剂。在过去的发酵过程中,泡沫控制一般是依靠经验,关于消泡剂的系统知识较少。本文综述了发酵工业中消泡剂的种类和作用机制,以及消泡剂的应用进展。     

横风作用下复杂路段汽车运行安全的概率评估

应用基于可靠度的概率模型对多风的环境中汽车运行稳定性进行了评估。定义了具有概率特性的基本变量风速、风向、路面摩擦系数、路拱横坡度和汽车速度,分析了各种基本变量的相互关系,以及它们如何影响交通事故的概率,并建立了基于交通事故指数的数学概率模型。结果表明,与风有关的交通事故是几个基本变量综合作用的结果。该研究可以为多风地区的道路设计及交通安全的保障提供一定的理论依据。     

Degradability and biocompatibility of bioglass/poly(amino acid) composites with different surface bioactivity as bone repair materials

Bioglass (BG) possesses excellent bioactivity and has been widely used in the manufacture of biomaterials. In this study, a composite with different surface bioactivity was fabricated via in situ melting polymerization by incorporating BG and poly(amino acid) (PAA) at a suitable ratio. The structure of the composite was characterized by Fourier transform infrared spectroscopy and XRD. The compressive strength of the BG/PAA composites was 139 MPa (BG:PAA = 30:70). The BG/PAA composites were degradable, and higher BG in composite showed higher weight loss after 4 weeks of incubation in simulated body fluid. In addition, the BG/PAA composite maintained adequate residual compressive strength during the degradation period. The SEM results showed the differences in surface bioactivities of the composites directly, and 30BG/PAA composite showed thicker apatite layer and higher Ca/p than 15BG/PAA. in vitro MG-63 cell culture experiments showed that the composite was noncytotoxic and thus allows cells to adhere, proliferate, and differentiate. This indicates that the composite has good biocompatibility. The implantations in the bone defects of rabbits for 4 and 12 weeks were studied. The composites had good biocompatibility and were capable of guiding new bone formation without causing any inflammation. The composite may be successfully used in the development of bone implants.     

Infrared heat treatment of Ti-6Al-4V with electroplated Cu

The objective of this study is to investigate an innovative infrared (IR) technique to enhance adhesion of electroplated copper (Cu) on Ti-6Al-4V without dichromate dipping. The ultimate goal is to develop a Cu coating process on Ti-6Al-4V without hazardous hexavalent chromium (Cr) solution treatments. Cu coatings of around 50 μm were electroplated on Ti-6Al-4V specimens at a current density of 0.03 A/cm² in an acidic Cu solution. To improve adhesion of coatings, IR heat treatments were performed on the Cu-coated samples at different temperatures and durations: 860 °C for 600 s and 875 °C for 20–120 s. This process was accomplished in an attempt to replace the use of dichromate dipping before electroplating. For samples heat treated at 860 °C, no bonding existed, even after 600 s. It is believed that solid-state diffusion prevailed at 860 °C and that 600 s was not enough for sufficient diffusion to occur. Adhesion was poor when samples were heat treated at 875 °C for 20 s. Excellent adhesion was observed when the heat treatment holding time was increased to 40 s. For 90 s, the surface appearance of coatings partially changed from Cu-colored to a grayish color. There was no Cu left on the surface after a 120 s heat treatment. From optical microscopic observations on sample cross sections, an interlayer between the Cu and Ti-6Al-4V formed when heat treated at 875 °C for 40 s and longer. The interlayer thickness increased as the holding time increased, until depletion of Cu. The sheet resistivity of coated specimens was on the order of pure Cu for samples heat treated at 875 °C and less than 90 s. During the 875 °C heat treatment, the following occurred: solid-state diffusion of Cu in Ti-6Al-4V, formation of eutectic solutions, dissolution of Cu and Ti-6Al-4V into the liquid phase, and the formation of intermetallic compounds. The lowest eutectic temperature of 875 °C played a key role in this innovative process of Cu coating on Ti-6Al-4V. This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September 15–17, 2003, in Indianapolis, Indiana and appears on pp. 403–10 of the Proceedings.     

美国高等教育融资方式的特点及启示

美国高等教育经费主要来源于政府、学费、捐赠收入、销售和服务收入以及争取的研究及合同经费。在对美国诸种融资渠道特点进行分析的基础上，借鉴美国融资模式并根据我国国情，提出了切合我国实际的高等教育融资方式，以期对我国高等教育投资体制的改革以启示。     

研究合金定向凝固组织的脉冲磁场设备的研制

介绍了脉冲电磁场发生设备的工作原理 ,设计等。并介绍了其如何与合金的定向凝固设备结合 ,以实现对合金的定向凝固组织在脉冲电磁场作用下的研究。     

硬质合金磨削温度的实验研究

采用半人工和人工热电偶法，对硬质合金YG6和YT30平面磨削的磨削温度进行了实验研究。并对磨削参数与磨削温度的关系，进行了理论分析及实验验证。结果表明：磨削深度和工作台速度增加，磨削温度升高，但工作台速度的改变，对磨削温度的影响较小．