Epidemic contact tracing with smartphone sensors

ABSTRACT

Contact tracing is widely considered as an effective procedure in the fight against epidemic diseases. However, one of the challenges for technology based contact tracing is the high number of false positives, questioning its trust-worthiness and efficiency amongst the wider population for mass adoption. To this end, this paper proposes a novel, yet practical smartphone-based contact tracing approach, employing WiFi and acoustic sound for relative distance estimate, in addition to the air pressure and the magnetic field for ambient environment matching. We present a model combining six smartphone sensors, prioritising some of them when certain conditions are met. We empirically verified our approach in various realistic environments to demonstrate an achievement of up to 95% fewer false positives, and 62% more accurate than Bluetooth-only system. To the best of our knowledge, this paper was one of the first work to propose a combination of smartphone sensors for contact tracing.     

Revealing the relationships between alloy structure,composition and plastic deformation in a ternary alloy system by a combinatorial approach

A high-throughput approach based on magnetron co-sputtering of alloy libraries is employed to inves-tigate mechanical properties of crystalline and amorphous alloys in a ternary palladium(Pd)-tungsten(W)-silicon(Si)system with the aim to reveal the difference in plastic deformation response and extract the relevant structure-property relationships of the alloys in the system.It was found that in contrast to crystalline alloys,the amorphous ones,i.e.,metallic glasses,exhibited a much smaller fluctuation range in the plasticity parameters(Er2/H and Wp/Wt),indicating a significant difference in the plastic deformation mechanism controlling the mechanical properties for the respective alloys.We propose that the inho-mogeneous deformation of amorphous alloys localized in thin shear bands is responsible for the weaker compositional dependence of both plasticity parameters,while dislocation gliding in crystalline materials is significantly more dependent on the exact structure,thus resulting in a larger scattering range.Based on the representative efficient cluster packing model,a set of composition-dependent atomic structural models is proposed to figure out the structure-property relationships of amorphous alloys in Pd-W-Si alloy system.     

高电导率银纳米线@聚吡咯@CoNi气凝胶的制备及其电催化析氧性能

针对传统贵金属析氧反应(OER)电催化剂的电导率较低、催化活性较差、成本高等问题,开发高效耐久、低成本且具有高暴露活性表面和优良导电性的电催化剂已迫在眉睫.通过冷冻干燥法合成银纳米线@聚吡咯(AgNWs@PPy)气凝胶,然后使用溶剂热法在AgNWs@PPy气凝胶骨架表面生长纳米CoNi合金,获得了OER电催化性能良好的...     

大连国际会议中心钢屋面稳定性分析

大连国际会议中心是一个大跨空间钢结构,其结构形式复杂,规模大,屋盖结构总的平面投影覆盖面积为25 097.2m2,最大跨度为94.572m。对该屋面结构进行了深入分析,得出了其在特征值屈曲、几何非线性屈曲、弹塑性几何非线性屈曲下的稳定承载力,并对不同分析条件下的稳定承载力进行了比较、分析。     

Tensile Properties of Boronized N80 Steel Tube Cooled by Different Methods

The microstructures and tensile properties of boronized N80 steel pipes by pack boriding under four different cooling conditions were investigated. The boride layer was composed of FeB and Fe₂B phases with a hardness range of 1200-1600 HV. Fan cooling and fan cooling with a graphite bar in the center of the boriding agent were employed to improve the tensile properties. As cooling velocity was increased, the thickness of boride layer and grain size of the steel substrate were consequently reduced, whereas the pearlite volume in steel substrate was increased, resulting in improvement of tensile properties. Boronized N80 steel pipe which was fan cooled with a graphite bar inside possessed the highest ultimate tensile strength and yield strength, in accordance with the mechanical properties required by API SPEC 5L. Fracture surface analysis revealed that the boronized N80 steel showed ductile fracture at room temperature.     

CaC_2在低碳含铝钢脱氧工艺中的应用

针对河北敬业集团板坯连铸生产低碳含铝钢铝消耗高的问题,通过试验确定了用廉价的脱氧剂电石（CaC2）替代铝粉造白渣的技术方案。采用新工艺后,吨钢降低铝制品消耗0.32 kg,节约成本2元,LF工序可减少钢水吸氮2～3 ppm,提高了产品质量。从CaC2在该工艺中的应用原理以及使用效果证明：CaC2能够有效降低铝的消耗,减少钢水的吸氮。     

利用FPGA实现的多通道同步数据采集卡

介绍了一种基于PC104总线的多通道高速同步数据采集卡的设计方法,硬件上采用FPGA进行控制逻辑设置和数据缓存的实现,简化了硬件电路,同时也提高了其使用的简易性和配置的灵活性,具有准确和快速的特点。     

SECANT-FUZZY LINEAR REGRESSION METHOD FOR HARMONIC COMPONENTS ESTIMATION IN A POWER SYSTEM

In order to avoid unnecessary damage of electrical equipments and installations,high quality power should be delivered to the end user and strict control on frequency should be made, Therefore, it is important to estimate the power system's harmonic components with higher accuracy. This paper presents a new approach for estimating harmonic component in a power system using secant - fuzzy linear regression method. In this approach the non - sinusoidal voltage or current waveform is written as I linear function. The coefficient of this function is assumed to be fuzzy number with a membership function that has center and spread value. The time dependent quantity is written as Taylor series with two different time dependent quantities. The objective is to use the sample obtained from the transmission line to find the power system harmonic components and frequencies. We used an experimental voltage signal from a sub power station as a numerical test.     

我国磷资源利用现状与可持续利用的建议

磷是一种不可更新、难以替代的资源,磷的资源危机将对我国社会可持续发展乃至人类的生存构成严重威胁。我国现有磷矿储量能够维持再使用70年左右的时间,如果仅以富磷矿磷储量[w(P2O5)≥30%]计算,富磷矿储量仅能维持使用10～15年。因此,充分认识磷资源,合理开发和利用磷矿,同时寻找新的出路,对保障我国国民经济可持续发展有着重要的战略意义。通过对现阶段我国与世界磷的资源储备、生产状况、品位变化的对比,陈述现阶段我国磷矿资源开发利用所面临的问题,提出磷资源可持续利用的建议。     

当前石油地质研究思维问题--兼答卓勤功同志商榷

石油系统是系统论思维方式在石油地质学中的应用，而系统论本身是把客观事物看成多层次、多要素、多方面相互联系的有机系统，因此，石油系统的层次性是与生俱来的。自石油系统的概念和研究方法引入以来，中国学者一方面探索本土化问题，以寻找更多的油气田；另一方面则探索如何用它把自己的研究成果引向世界，更重要的是石油系统将成为把中国石油经济引向世界的桥梁。