THE PERSISTENCE OF TRACHYTE-TRACHYANDESITE BUILT INTO PEDESTRIAN-ROADWAY CONSTRUCTION

Prirodni kamen određen kao trahit-trahiandezit s lokaliteta Colli Euganei u blizini Padove u Italiji ugrađen je na kolničko-pješačkoj konstrukciji Tkalćičeve ulice u Zagrebu. Uzorci kamena, prije ugradnjie, podvrgnuti su brojnim određivanjima fizičkih i mehaničkih svojstava (gustoće, volumne mase, upijanja vode, poroznosti, tlačne čvrstoće, otpornosti na habanje struganjem, čvrstoće na savijanje, postojanosti na smrzavanje i na Na2SO4, brzine prolaza ultrazvučnih valova, te mikroskopskim i rendgenskim analizama, fotografiranju elektronskim mikroskopom). Utvrđeno je da oko 30% ugrađenog kamena ne odgovara postojećim važećim ili opće prihvaćenim kriteri¬jima o kakvoći prirodnog kamena. Povećanog je upijanja vode i po¬roznosti, velikog pada tlačnih čvrstoća u vodom zasićenom stanju, nedovoljno otporan na habanje i na Na2SO4, anizotropan, sadrži bu-breće gline iz skupine smektita, te brojne defekte posebice u obliku mikroblokova kao posljedice postdijagenetskih procesa. Premda uzorci pripadaju istoj vrsti stijene, razlike medu kamenim elementima su velike. Makroskopski gledajući materijal je vrlo heterogen. U uzorcima kamena slabije kakvoće nalaze se manje ili više brojni subparalelni smeđi i sivi proslojci debljine približno 1—2 mm s povećanim udjelom sekundarnih minerala željeza, Željezovi oksidi i hidroksidi manje ili više impregniraju dijelove stijene, mrljasto ili trakasto, a ponegdje je intenzivno impregniran i čitav uzorak. Impregnaciju intenziviraju bubreće gline i brojne šupljine duž kojih se kamen osipava.Natural stone defined as trachyte-trachyandesite from the locality Colli Euganei near Padua in Italy is built into roadway-pedestrian construction of the Tkalčićcva street in Zagreb. Stone samples were subjected before in-building, to determinations of physical and mecha¬nical properties (density, bulk density, water absorption, porosity, compressive strength, resistance to abrasion, flexural strength, frost resistance and to Na2SO4, velocity of ultrasonic propagation, micros¬copic and X ray analyses and to photographing by electronic micros¬cope. It was found that about 30% in-built stones do not suit to existing criteria on the quality of natural stone. Water absorption and porosity are increased, compressive strength in the water saturated condition is very decreased, the stone is not enough resistant to wear-out and to Na2S04, it is anisotropic and contains swelling clays of the smectite group and numerous defects especially in form of microblocks as consequences of postdiagenetic processes. Although the samples belong to the same rock type, the differences among stone elements are great. Macroscopically materia! is very heterogeneous. In less qualitative stone samples there are more or less numerous sub-parallel brown and gray partings of the thickness approximately 1 -2 mm with enlarged share of secondary iron minerals. Iron oxides and hydroxides mainly impregnate the rock parts, spotty or stripy; somewhere the complete sample is impregnated intensively. The impregnation is intensified by swelling clays and numerous holes along which stone is crumbling

Distributed Control Design for Balancing the Grid Using Flexible Loads

International audienceInexpensive energy from the wind and the sun comes with unwanted volatility, such as ramps with the setting sun or a gust of wind. Controllable generators manage supply-demand balance of power today, but this is becoming increasingly costly with increasing penetration of renewable energy. It has been argued since the 1980s that consumers should be put in the loop: " demand response " will help to create needed supply-demand balance. However, consumers use power for a reason, and expect that the quality of service (QoS) they receive will lie within reasonable bounds. Moreover, the behavior of some consumers is unpredictable, while the grid operator requires predictable controllable resources to maintain reliability. The goal of this chapter is to describe an emerging science for demand dispatch that will create virtual energy storage from flexible loads. By design, the grid-level services from flexible loads will be as controllable and predictable as a generator or fleet of batteries. Strict bounds on QoS will be maintained in all cases. The potential economic impact of these new resources is enormous. California plans to spend billions of dollars on batteries that will provide only a small fraction of the balancing services that can be obtained using demand dispatch. The potential impact on society is enormous: a sustainable energy future is possible with the right mix of infrastructure and control systems

Metal oxide nanoparticle-based coating as a catalyzer for A-TIG welding

Besides a wide application in corrosion protection, wear resistance increase, providing thermal properties and power conversion, oxide coatings have found an alternative application in welding technology as catalysts of the tungsten inert gas (TIG) welding process. In this paper, the novel approach of fabricating a coating containing nanoparticles based on nanosized SiO$_2$ and TiO$_2$ and their mixtures was applied to the austenitic stainless-steel base metal. It was found that coatings increased depths of penetration, enabling a consumable-free welding. Using this method, the use of several critical and near-critical raw materials (e.g., Si and Cr), as well as the relatively expensive Ni can be completely avoided. The most effective coating in terms of weld penetration consisted of a mixture of nanoparticles, rather than unary oxide coatings based on nanoparticles. A model for liquid weld metal flow is proposed based on the metallographic examination of recrystallized grains and microhardnesses measured near the weld metal, supporting the reversed Marangoni convection theory