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INTRODUZIONE 引言
Pub Date : 2018-09-11 DOI: 10.4081/incontri.2018.381
Attilio Rigamonti, A. Varlamov
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引用次数: 0
INCREASING THE EFFICIENCY OF INTERNAL COMBUSTION ENGINES: HEAT RECOVERY FROM EXHAUST GASES BY THERMOELECTRIC EFFECT 提高内燃机的效率:利用热电效应从废气中回收热量
Pub Date : 2018-07-31 DOI: 10.4081/incontri.2018.380
M. Sgroi
The concern related to global warming is generating a legislative pressure on reducing CO2 emissions that is forcing automotive industry to find alternative and more efficient solutions to internal combustion engines. In Europe, the current regulation for passenger vehicles limits the CO2 emissions calculated as fleet average to 130 g/km and fix a target value of 95 g/km to be achieved by 2021. Car manufacturers will have to pay heavy penalties for each registered vehicle exceeding the CO2 limits (€95 per exceeding gram by 2019). Concurrently, the regulations on toxic emissions (CO, NOx, unburned hydrocarbons, particulate matter) is also becoming more and more stringent and requires complex and costly abatement systems to respect the strict limitations imposed on NOx and particulate matter emissions. On the other hand, zero emission electric vehicles, based on batteries, are still not mature enough for a replacement of the internal combustion engine in extra-urban applications, since they are not able to guarantee the driving range required by customers. Hydrogen fuelled vehicles, could meet the same performance of conventional cars, but the cost of materials used in the fuel cell stack is preventing the penetration into the market. Therefore, even though characterized by low energy efficiency, the internal combustion engine will remain, in the short-medium term, the reference technology for the transport industry but the environmental regulations will impose its hybridization with electric systems. Hybrid architectures allow circulating in electric mode in urban areas, limiting the local pollution, and increase the efficiency of the car through energy recovery during breaking phases. An energetic analysis of conventional internal combustion engine reveals that about 70% percent of the chemical energy stored in the fuel is converted in to mechanical energy for traction: the remaining part is dissipated as heat in the exhaust gases (30%) and in the cooling circuit (40%). So a great amount of thermal energy (tens of kW) is available on a car and its effective recovery can dramatically increase the efficiency of the system. Hybrid systems facilitate this task, since the produced electric energy can be stored in the battery pack. Thermoelectric generators (TEGs) offer the possibility to directly convert thermal energy into electricity with a reduced complexity and potential low cost. Even though available semiconducting junctions are characterized by low efficiency and limited operating temperatures, coupling a TEG to the internal combustion engine would allow recovering about 1 kW of electric power on a medium size car, with a reduction of CO2 emissions of about 10 g/km.
对全球变暖的担忧正在产生减少二氧化碳排放的立法压力,迫使汽车行业寻找替代内燃机的更有效的解决方案。在欧洲,目前的乘用车法规限制了以车队平均计算的二氧化碳排放量为130克/公里,并确定了到2021年实现95克/公里的目标值。汽车制造商将不得不为每辆超过二氧化碳排放限制的注册车辆支付高额罚款(到2019年每超标95欧元)。同时,对有毒排放物(一氧化碳、氮氧化物、未燃烧的碳氢化合物、颗粒物)的规定也变得越来越严格,需要复杂和昂贵的减排系统来遵守对氮氧化物和颗粒物排放的严格限制。另一方面,基于电池的零排放电动汽车在城市以外的应用中,还不够成熟,无法替代内燃机,无法保证客户所要求的行驶里程。氢燃料汽车可以达到与传统汽车相同的性能,但燃料电池堆所用材料的成本阻碍了氢燃料汽车进入市场。因此,尽管内燃机的特点是能源效率低,但在中短期内,内燃机仍将是交通运输行业的参考技术,但环境法规将强制其与电力系统混合。混合动力架构允许在城市地区以电动模式循环,限制了当地的污染,并通过在中断阶段的能量回收提高了汽车的效率。对传统内燃机的能量分析表明,储存在燃料中的化学能中约有70%转化为机械能用于牵引,其余部分作为热量在废气(30%)和冷却回路(40%)中消散。因此,大量的热能(几十千瓦)可用于汽车,其有效的回收可以大大提高系统的效率。混合动力系统促进了这项任务,因为产生的电能可以储存在电池组中。热电发电机(teg)提供了直接将热能转化为电能的可能性,降低了复杂性和潜在的低成本。尽管现有的半导体结的特点是效率低,工作温度有限,但将TEG与内燃机相结合,将使一辆中型汽车回收约1千瓦的电力,每公里减少约10克的二氧化碳排放。
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引用次数: 0
THE RENAISSANCE OF FRICTION: FROM EMPIRISM TO PHYSICS – AT THE NANOSCALE 摩擦的复兴:从经验主义到物理学——在纳米尺度上
Pub Date : 2018-07-31 DOI: 10.4081/INCONTRI.2018.377
E. Tosatti
Friction and its science hold more than a record. One is longevity: from its very origins, mankind has had to reckon with it. Still today, reducing (or increasing) sliding friction remain technological and practical objectives of enormous importance — one can read for example that no less than 5% of all energy produced daily degrades into wasted frictional work. Another record is that despite the involvement of great scientist like Leonardo, who already five centuries ago gave friction its first scientific bases, there is still today no proper theoretical formulation of friction. Theorists like us mostly limit themselves to what P.W.Anderson jokingly defined in a different context “the indignity of numerical simulations”. However, progress in science does not take place because it is necessary, but because it is possible. In the last decades, new mesoscopic and nanoscopic experimental techniques opened new windows on frictional phenomena at the atomic and molecular level. Jump-started by the necessity and by the challenge to understand some of that data, theory and simulation progress is moving on along some lines which I will briefly describe.
摩擦和它的科学不仅仅是一个记录。一个是长寿:从一开始,人类就不得不考虑它。直到今天,减少(或增加)滑动摩擦仍然是非常重要的技术和实践目标——例如,人们可以读到,每天产生的所有能量中,有不少于5%的能量被浪费为摩擦功。另一项记录是,尽管像列奥纳多这样的伟大科学家在五个世纪前就为摩擦提供了第一个科学依据,但至今仍没有关于摩擦的适当理论表述。像我们这样的理论家大多局限于p.w.安德森在另一种情况下开玩笑地定义的“数值模拟的侮辱”。然而,科学的进步并不是因为它是必要的,而是因为它是可能的。在过去的几十年里,新的介观和纳米实验技术为原子和分子水平上的摩擦现象打开了新的窗口。从理解这些数据的必要性和挑战开始,理论和模拟的进展沿着一些我将简要描述的路线进行。
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引用次数: 0
GRAPHENE AS A QUANTUM PLAYGROUND 石墨烯作为量子游乐场
Pub Date : 2018-07-31 DOI: 10.4081/INCONTRI.2018.379
G. Benedek
The modern triathlon “heat-electricity-mechanics” has an indisputable champion, graphene, as a recordman, among all materials in normal conditions, in all three specialties: thermal conductivity, electrical mobility and mechanical strength. On the other hand graphene, being perfectly planar, is the simplest of all possible sp2 pure carbon structures. The graphene family includes curved forms like fullerenes, having gaussian curvature G >0, nanotubes, with G=0 like graphene, and schwarzites with G <0 and vanishing mean curvature. The conjugation of carbon-carbon sp2 bonds makes several global electronic and vibrational properties of graphenes to primarily depend upon the structure topology. Global properties which can be estimated on topological grounds are the growth process, the isomer hierarchy, the vibrational spectrum, the elastic constants, the porosity as a function of the deposition energy, etc. The dynamics of free electrons in graphene is well described by the Dirac quantum-relativistic equation, and some of its consequences like the Zitterbewegung and Klein’s paradox have been proved in graphene. Thus graphene allows for the simulation and validation of fundamental theories in fields hardy accessible to experiments like high-energy physics and cosmology. With some surprising prediction! It is a fact that since the late XIX century topology has become a reference paradigm in many branches of fundamental physics, from Hermann Weyl’s topological theory of electricity and cosmological wormholes, to string theory and present topological field theories in high-energy physics.
现代铁人三项“热电力学”有一个无可争议的冠军,石墨烯,作为记录者,在所有材料在正常条件下,在所有三个方面:导热性,电迁移率和机械强度。另一方面,石墨烯是完美的平面结构,是所有可能的sp2纯碳结构中最简单的。石墨烯家族包括弯曲形式,如富勒烯,具有高斯曲率G >0,纳米管,具有G=0,如石墨烯,以及G <0和平均曲率消失的schwarzites。碳-碳sp2键的共轭使得石墨烯的一些整体电子和振动性能主要取决于结构拓扑。在拓扑学基础上可以估计的整体性质包括生长过程、同分异构体层次、振动谱、弹性常数、孔隙率作为沉积能量的函数等。狄拉克量子相对论方程很好地描述了石墨烯中自由电子的动力学,它的一些结果,如齐特比空和克莱因悖论,已经在石墨烯中得到了证明。因此,石墨烯可以模拟和验证高能物理学和宇宙学等难以进行实验的领域的基本理论。有一些令人惊讶的预测!事实上,自19世纪晚期以来,拓扑学已成为基础物理学许多分支的参考范式,从赫尔曼·魏尔的电力拓扑理论和宇宙虫洞,到弦理论和现在的高能物理拓扑场论。
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引用次数: 0
THERMAL PROPERTIES OF TPD-BASED ORGANIC GLASSES tpd基有机玻璃的热性能
Pub Date : 2018-07-31 DOI: 10.4081/INCONTRI.2018.378
R. Dettori, L. Colombo
Glassy materials are condensed matter systems showing physical properties in between solids and liquids and retaining information about the thermal history they have been subjected to and the way they have been prepared. Formally, this implies that their configurational energy landscape is a complex multi-dimensional surface, showing quite a few basins with different depths, widths, and shapes: the system can be trapped in any of them, assuming very unlike physical properties. Recently, it has been demonstrated experimentally that a glassy system can be grown by physical vapor deposition of organic molecules on a substrate. The physics of such organic glasses is enriched by a new feature, namely: the anisotropic molecular structure of the basic building blocks used to assemble the film. TPD-based organic glasses have been generated by atomistic simulations that mimic vapor deposition and their thermal properties have been accordingly calculated. Simulations generate a rational phenomenology, providing robust evidence that heat transfer is not isotropic but, rather, correlated to an inherent molecular property, namely the axial structure of the TPD molecule. Furthermore, we present the first theoretical prediction of the specific heat trend versus temperature, showing in the quantum regime an intriguing anomaly with respect to crystalline systems.
玻璃材料是一种凝聚态物质系统,表现出介于固体和液体之间的物理性质,并保留了它们所经受的热历史和制备方式的信息。正式地说,这意味着它们的构型能量景观是一个复杂的多维表面,显示出相当多的不同深度、宽度和形状的盆地:系统可以被困在其中的任何一个盆地中,假设物理性质非常不同。近年来,通过实验证明,有机分子在衬底上的物理气相沉积可以生长出玻璃状体系。这种有机玻璃的物理特性被一个新的特征所丰富,即:用于组装薄膜的基本构建块的各向异性分子结构。通过模拟气相沉积的原子模拟生成了基于tpd的有机玻璃,并计算了其热性能。模拟产生了一个合理的现象,提供了强有力的证据,证明传热不是各向同性的,而是与固有的分子特性相关,即TPD分子的轴向结构。此外,我们提出了比热趋势随温度变化的第一个理论预测,显示了在量子体系中关于晶体系统的一个有趣的异常。
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引用次数: 1
THERMOELECTRICITY AND MODERN TRENDS IN ITS STUDIES 热电学及其研究的现代趋势
Pub Date : 2018-07-31 DOI: 10.4081/INCONTRI.2018.376
A. Varlamov, I. Chikina, D. Peddis
The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa. A thermoelectric device creates voltage when there is a different temperature on each side. Conversely, when a voltage is applied to it, it creates a temperature difference. At the microscopic level of understanding one can say that an applied temperature gradient causes charge carriers in the material to diffuse from the hot side to the cold side. We will start our discussion from the discovery of the phenomenon of thermoelectricity by the Estonian physicist Thomas Johann Seebeck in 1821 and its early manifestations. Today the term “thermoelectric effect” encompasses three separately identified effects: the Seebeck effect, Peltier effect, and Thomson effect. Application of magnetic field considerably increases the variety of possible manifestations of thermoelectricity. The most known among them is the Nernst effect which is nothing else as a thermoelectric effect observed when a conducting sample is subjected to a magnetic field and a temperature gradient perpendicular to each other. The crossed electric and magnetic fields should lead to the drift of a charged particle in the direction perpendicular to both of them. In the case of broken circuit condition such motion of the carriers is prevented by appearance of the temperature gradient in corresponding direction, what is the essence of the Nernst-Ettingshaus effect, reciprocal to the Nernst one. The theory of thermoelectric and thermomagnetic phenomena in metals and semiconductors, based on the quantum theory of solids, was developed in the middle of XX century. It was found that in metals these effects are negligibly small (for Bi the Seebeck coefficient is maximal and is of the order of 7μV/K). The magnitudes of thermoelectric signals considerably increase in semiconductors what allows to use them as the working elements of thermoelectric generators (solid state devices that convert heat flux (temperature differences) directly into electrical energy), for studies of the scattering mechanisms in semiconductors, etc. Today the interest to the thermoelectricity is very high, especially in view of the possibility to design new artificial materials with tuned high thermoelectric properties: graphene, new generation of superconductors, conducting polymers, electrolytes and ferrofluids. Their non-trivial properties will be reviewed in the second part of our presentation.
热电效应是温差与电压的直接转换,反之亦然。热电装置在两侧温度不同时产生电压。相反,当施加电压时,它会产生温差。在微观的理解水平上,人们可以说,施加的温度梯度导致材料中的载流子从热的一面扩散到冷的一面。我们将从爱沙尼亚物理学家托马斯·约翰·塞贝克在1821年发现热电现象及其早期表现开始讨论。今天,“热电效应”一词包含了三种不同的效应:塞贝克效应、珀尔帖效应和汤姆逊效应。磁场的应用大大增加了热电现象的可能表现形式。其中最著名的是能司特效应,这是一种热电效应,当导电样品受到磁场和相互垂直的温度梯度时观察到。交叉的电场和磁场会导致带电粒子沿垂直于两者的方向漂移。在断路条件下,载流子的这种运动被相应方向的温度梯度的出现所阻止,这就是与能斯特效应相反的能斯特-埃廷肖斯效应的本质。在固体量子理论的基础上,发展了金属和半导体中的热电和热磁现象理论。结果发现,在金属中,这些效应可以忽略不计(铋的塞贝克系数最大,约为7μV/K)。半导体中热电信号的大小大大增加,这使得它们可以用作热电发生器(将热流(温差)直接转换为电能的固态器件)的工作元件,用于研究半导体中的散射机制等。今天,人们对热电的兴趣非常高,特别是考虑到设计具有高热电性能的新型人工材料的可能性:石墨烯、新一代超导体、导电聚合物、电解质和铁磁流体。它们的非平凡性质将在我们演讲的第二部分进行复习。
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引用次数: 0
SEEBECK EFFECT IN COMPLEX FLUIDS & MAGENTA PROJECT (MAGNETIC NANOPARTICLE BASED LIQUID ENERGY MATERIALS FOR THERMOELECTRIC APPLICATIONS) 复杂流体中的塞贝克效应&品红项目(热电应用的磁性纳米颗粒基液体能源材料)
Pub Date : 2018-07-31 DOI: 10.4081/INCONTRI.2018.375
S. Nakamae
Thermoelectric (TE) materials that are capable of converting heat into electricity have been considered as one possible solution to recover the low-grade waste-heat (from industrial waste-stream, motor engines, household electronic appliances or body-heat). Solid semiconductor-based TE-modules were the first to enter the commercial application, and they still dominate the TE-market today. Despite their technical robustness including long life-time, simple use involving no moving parts, TE-technology has long been limited to low-power applications due to their poor efficiency. Closely following the rise of ‘nanotechnology’ in the 1980’s - 90’s, there has been a huge increase in the TE materials research in the past 20 years, which has led to some remarkable improvements in thermal-to-electric energy conversion capacity. However, even the most “promising” materials have not yet reached the minimum ZT requirements. Furthermore, solid TE-materials suffer from a variety of practical obstacles such as small sizes, substantial production costs and the use of scarce and/or toxic raw materials, precluding them from wide-scale applications. Clearly, a technological breakthrough in TE-materials research is needed in order to make the thermoelectric technology environmentally friendly and economically viable for its future use. MAGENTA is a 4-year research & innovation project that aims at bringing a paradigm change in TE-technology by exploiting the magneto-thermoelectric (MTE) property of ionic-liquid (IL) based ferrofluids (FF), i.e., colloidal dispersions consisting of magnetic nanoparticles (MNPs) in non-magnetic ionic liquids. Magnetic nanoparticles are, as the name suggests, a class of nanoparticles (less than 1 mm in diameter) made of magnetic elements such as iron and nickel and their alloys and chemical compounds. They are used in a plethora of technological fields from biomedicine to data storage. However, their use in energy applications remains quite limited so far. Ionic liquids (IL), on the other hand, are enjoying substantial attention in several areas of energy research including thermoelectricity in recent decades. As a thermoelectric material, ILs present many promising features such as high electrical conductivity, large temperature and electrochemical windows, low vapour pressure and toxicity, and raw material abundance. In this presentation, I will discuss MAGENTA’s scientific motivations (how to produce thermoelectric voltage and current using IL based ferrofluids), the methodologies to be used and the project objectives; i.e., 1) to provide founding knowledge of novel MTE phenomena in IL based ferrofluids, and 2) to build application-specific MTE prototypes with tailor-made IL-FFs for their use in targeted industrial sectors (cars and portable electronics). Some encouraging preliminary results on liquid thermoelectric materials obtained by the project partners will also be presented.
热电材料能够将热量转化为电能,被认为是回收低品位废热(来自工业废热流、发动机、家用电子设备或人体热量)的一种可能的解决方案。基于固体半导体的te模块是第一个进入商业应用的模块,它们至今仍主导着te市场。尽管te技术坚固耐用,包括使用寿命长,使用简单,不涉及移动部件,但由于效率低,te技术长期以来一直局限于低功耗应用。紧跟着20世纪80 - 90年代“纳米技术”的兴起,在过去的20年里,TE材料的研究有了巨大的增长,这导致了热电转换能力的一些显着提高。然而,即使是最“有前途”的材料也尚未达到最低ZT要求。此外,固体te材料受到各种实际障碍的影响,例如尺寸小、生产成本高以及使用稀缺和/或有毒原料,使它们无法大规模应用。显然,为了使热电技术在未来的使用中环保和经济可行,需要在te材料研究方面取得技术突破。MAGENTA是一个为期4年的研究和创新项目,旨在通过利用基于离子液体(IL)的铁磁流体(FF)的磁热电(MTE)特性,即由非磁性离子液体中的磁性纳米颗粒(MNPs)组成的胶体分散体,带来te技术的模式变革。磁性纳米颗粒,顾名思义,是一类纳米颗粒(直径小于1毫米),由铁和镍等磁性元素及其合金和化合物构成。它们被用于从生物医学到数据存储的众多技术领域。然而,到目前为止,它们在能源应用中的应用仍然相当有限。另一方面,近几十年来,离子液体在包括热电在内的几个能源研究领域受到了极大的关注。作为一种热电材料,液态硅具有导电性高、温度和电化学窗口大、蒸气压低、毒性小、原料丰富等优点。在这次演讲中,我将讨论MAGENTA的科学动机(如何使用基于IL的铁磁流体产生热电电压和电流),使用的方法和项目目标;即,1)提供基于IL的铁磁流体中新型MTE现象的基础知识,2)使用量身定制的IL- ffs构建特定应用的MTE原型,用于目标工业部门(汽车和便携式电子产品)。还将介绍项目合作伙伴在液体热电材料方面取得的一些令人鼓舞的初步结果。
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引用次数: 0
RETTORE DI TUTTI: PAOLO MANTEGAZZA E LE FACOLTÀ UMANISTICHE 保罗·曼特加扎和文科
Pub Date : 2018-07-18 DOI: 10.4081/INCONTRI.2018.368
A. Padoa-Schioppa
A short survey of the personality and of the multiple achievements of the President, of the University of Milan, whose work has been seminal in developing research, teaching and library structures of students and professors.
简要介绍米兰大学校长的个性和多项成就,他的工作在发展学生和教授的研究、教学和图书馆结构方面具有开创性。
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引用次数: 0
TESTIMONIANZE 证词
Pub Date : 2018-07-18 DOI: 10.4081/incontri.0.410
M. Vitale
Non disponibile.
不可用。
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引用次数: 0
PAOLO MANTEGAZZA E LA FACOLTÀ DI MEDICINA: UNA PRESIDENZA DI CAMBIAMENTO 保罗·曼特加扎和医学院:变革的总统
Pub Date : 2018-07-18 DOI: 10.4081/INCONTRI.2018.366
G. Coggi
The years during which Paolo Mantegazza served as Dean of the Medical Faculty, the Country was involved in a considerably large social turmoil, under the pressure of the so called student revolution, which was spreading through Europe. Such a movement, albeit very often out of control (with dangerous deviations), still was, in its basic and best aspects, the expression of an urgent need for innovation and social change. Mantegazza, who was a very qualified scientist in Pharmacology, perceived by intuition the need for a controlled change in the style and action of his office, and used a “gentle leadership” to carry on consistent innovations in the traditional “academic” policy of the Faculty. His major achievement was twofold: first, he was able to expand the Faculty into city hospitals other than the traditional Main Central University Hospital, thus allowing students to perform clinical practice in a new environment, more patient oriented than the classical one; second, this expansion offered teachers and researchers the opportunity to practice a less formal teaching, paying more attention, both from a clinical, scientific and teaching point of view, to the complexity of the patient and his/her social and personal context, with relevant consequences on the educational approach and to teacher-students relationships.
在Paolo Mantegazza担任医学院院长期间,在席卷欧洲的所谓学生革命的压力下,国家陷入了相当大的社会动荡。这样的运动,虽然经常失去控制(有危险的偏差),但在其基本和最好的方面,仍然是迫切需要创新和社会变革的表现。Mantegazza是一位非常合格的药理学科学家,他凭直觉意识到需要在办公室的风格和行为上进行可控的改变,并使用“温和的领导”对学院传统的“学术”政策进行持续的创新。他的主要成就有两个方面:首先,他能够将学院扩展到传统的中央大学医院以外的城市医院,从而使学生能够在一个新的环境中进行临床实践,比传统的环境更以患者为中心;其次,这种扩展为教师和研究人员提供了实践不那么正式的教学的机会,从临床、科学和教学的角度更加关注患者及其社会和个人背景的复杂性,以及对教育方法和师生关系的相关影响。
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引用次数: 0
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Istituto Lombardo - Accademia di Scienze e Lettere - Incontri di Studio
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