Study of the silver ions cementation after mechanical activation of cementator

Thiosulphate leaching of silver is a proposed alternative to cyanide or thiourea leaching for certain types of refractory silver ores and secondary resources. Traditional method for the recovery of rare metals from various sources by hydrometallurgy is leaching followed by cementation onto zinc powder and electrowinning. Silver cementation is an inexpensive and simple way to deposit thin metal films. Cementation of silver onto zinc powder, treated by mechanical activation, from thiosulphate solutions was studied by measuring Ag+ ions concentration in the solution. The high energy attrition and planetary ball milling in methanol was applied for the mechanical activation of zinc powder. The changes in the particle size distribution and surface area of cementator, occurring during mechanical treatment have been registered. The observed changes in the physicochemical properties illustrate the possibility of applying activation to modify the surface and/or volume properties of zinc powder and its further application in well-known hydrometallurgical process of cementation. The study was also focused on the changes in the concentration of zinc and pH as a function of reaction time. The morphology of cementation products on zinc powder was also investigated

PMR repeater

Cílem této práce je navrhnout a vyrobit jednoduchý opakovač fungující v pásmu 446 MHz zvaném PMR. Tento opakovač se skládá z funkční stanice PMR a opakovacího modulu, který je realizován pomocí zařízení pro záznam a přehrávání zvuku a je řízen mikrokontrolérem Atmel řad AVR. Opakovač dále zaznamenává během provozu maximální a minimální naměřenou teplotu a jeho přesný čas je aktualizován přijímačem DCF. Ten lze také připojit k počítači pomocí sériové linky.The main target of this work is to project and make a simple repeater working in 446 MHz tape called PMR. This repeater is made from functional station PMR and repeating program unit, which was constructed by the help of the system for recording and replaying sound. The repeater is managed by microcontroller Atmel from line AVR. The repeater records minimal and maximal temperature during its operation and its date and time is still actual thanks to transceiver DCF. It is possible to connect the transceiver with a computer by the serial link.

Interconnects modelling for signals transmission

V této práci je řešen problém týkající se integrity signálů a problémy, které způsobuje zvyšující se frekvence v obvodech a zařízeních. Je zde popsána analýza propojovacích modelů, které umožňují přenos signálů ve smíšených analogově – digitálních obvodech a rozdíl mezi analýzou v časové a frekvenční oblasti. Dále jsou zde popsány tři metody výpočtu homogenních přenosových vedení. První metoda je založena na matematickém popisu přenosového vedení a druhá metoda využívá kaskádně řazených a T článků k simulaci modelu homogenního přenosového vedení. Třetí metoda je založená na momentovém přizpůsobení při využiti stavových proměnných. Tyto metody využívají numerickou metodu inverzní Laplaceovy transformace a jsou řešeny v jazyku Matlab. Výsledky a srovnání metod je popsáno v závěru.In this work, there is solution for problem about signal itegrity and problems that causes raising frequence in circuits and machineries. There is describe interconnect analysis of models, which enable transfer of signals in mixed analog – digital circuits and a different between the analyse of an time domain and an s-domain. Next, there are described three methods of the calculation homogenous transmission line.The first method is constructed on mathematic description of transmission line. The second method uses cascade connection and T networks to the simulation model of the homogenous transmission line. The last one is constructed on the moment matching in use of state variables. These methods uses numerical inversion of Laplace transforms and these methods are constructed in programming language Matlab. Its results with the confrontation is described in the ending.

The Effect of Gum Arabic on the Nano / Microstructure and Optical Properties of Precipitated ZnO

The development of the nano/microstructure of ZnO particles precipitated from zinc acetylacetonate showed dependence on the presence of gum arabic. In the absence of gum arabic in near-neutral pH range ZnO rods, some of them hollow, precipitated, whereas in alkaline (NH4OH) medium the multipods (stars) were obtained. A strong effect of gum arabic was noticed both in the near-neutral pH range and in alkaline (NH4OH) medium. In both cases ZnO particles consisted of 1D subunits. The FT-IR spectra of ZnO particles precipitated in the presence of gum arabic showed the IR bands due to the residual content of this biopolymer. Gum arabic formed the corona on ZnO particles and played a key role in the precipitation process from nucleation to the final ZnO product. UV/Vis spectra were also recorded. The PL spectra of ZnO powders dispersed in pure ethanol were very similar. In the presence of ethanol characteristic peaks in the blue emission region were diminishing, thus softening the intrinsic defects responsible for this emission. It was assumed that this effect was due to the covering of oxygen vacancies (VO) at the interface ZnO/C2H5OH with the oxygen atoms present in ethanol. This work is licensed under a Creative Commons Attribution 4.0 International License

Study of de-aggregation of mechanochemically synthesized ZnSe nanoparticles by re-milling in the presence of ZnCl2 solution

Conventional mechanochemical synthesis of zinc selenide, ZnSe nanoparticles was performed in a planetary ball mill by high-energy milling of zinc (Zn) and selenium (Se) powders. Mechanochemically synthesized ZnSe was subsequently re-milled in circulation mill in ZnCl2 solution in order to study de-aggregation, physical-chemical and optical properties of ZnSe nanoparticles. The mechanochemically synthesized and re-milled samples were characterized by X-ray diffraction analysis (XRD) that confirmed the presence of cubic and hexagonal ZnSe phases. Size of crystallites calculated from XRD patterns has decreased from 50 to 19 nm for cubic ZnSe phase and from 145 to 2.5 nm for hexagonal ZnSe phase after re-milling for 110 min in ZnCl2 solution. Size, phase composition, morphology, and crystallinity of ZnSe nanoparticles were studied by transmission electron microscopy (TEM) and selected area electron diffraction (SAED). UV-Vis optical spectroscopy has provided an evidence of blue shift of the re-milled nanocrystalline ZnSe particles from the direct band gap of 2.67 eV characteristic of bulk ZnSe crystals. Colloidal stability of ZnSe nanoparticles dispersions was studied by ? �potential measurements

Tailoring of K0.8Al0.7Fe0.15Si2.25O6 Leucite Based Dental Ceramic Material

Potassium based ceramic materials composed from leucite in which 5 % of Al is exchanged with Fe and 4 % of hematite was synthesized by mechanochemical homogenization and annealing of K2O-SiO2-Al2O3-Fe2O3 mixtures. Synthesized material was characterized by X-ray Powder Diffraction (XRPD) and Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectroscopy (SEM/EDX). The two methods are in good agreement in regard to the specimen chemical composition suggesting that a leucite chemical formula is K0.8Al0.7Fe0.15Si2.25O6. Rietveld structure refinement results reveal that about 20 % of vacancies exist in the position of K atoms. This work is licensed under a Creative Commons Attribution 4.0 International License

Guanacos’ and domestic livestock’s summer diets comparison in ecotone of “Tierra del Fuego” (Argentina)

At present, it is believed that the population of guanacos has increased in the “Isla Grande de Tierra del Fuego”, arising a conflict with livestock and forestry activities. The aim of this study was to evaluate the use of the guanaco’s food resources, taking into account the presence of different types of domestic livestock, in order to provide a tool which will enable the evaluation of environmental management projects. We conducted the study in different areas, considering the presence/absence of domestic livestock and of guanaco. The diet was analyzed by identifying botanical remains present in the pretreated feces. The relative frequencies of ingested taxa were obtained and analyzed according to their functional groups, being the soft, herbaceous and graminoid grasses the most consumed, where the soft grasses were the most frequently ingested. Tree species only appear in diets of guanacos, in a low frequency, compared to other forms of life. In the case of soft grasses, forbs and Graminoides, the diets differ according to ingested species and intake frequency. These results allow us to establish that the guanaco selects the items to be consumed, changing its diet based on the presence of other herbivores, and has a trophic overlap with domestic livestock, mainly with sheep.Fil: Fernández Pepi, María Gabriela. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; ArgentinaFil: Moretto, Alicia Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Universidad Nacional de Tierra del Fuego; ArgentinaFil: Arriaga, Mirta Olga. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Alvarenga, Eugenia Celeste. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Stampacchio, Monica Liliana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Escobar, Julio Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Zucol, Alejandro Fabián. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; Argentin

Propuesta de un sistema de gestión de almacenes para mejorar la productividad en la Empresa Danper Trujillo S.A.C. 2018

La presente investigación tiene como objetivo el incremento de la productividad en la empresa Danper Trujillo S.A.C. mediante una propuesta de gestión de almacenes que va desde la reestructuración de Layout hasta la implementación de una mejora continua. Para ello se consideró el siguiente enunciado del problema ¿En qué medida una propuesta de gestión de almacenes mejorará la productividad en la empresa Danper Trujillo S.A.C.? Y la hipótesis planteada fue: La Propuesta de un Diseño de Gestión de Almacenes permitirá incrementar la productividad significativamente en la Empresa Danper Trujillo, S.A.C. 2018. Se empleó como técnicas la observación, indicadores de gestión, y conteo ABC las que nos ayudó a determinar las deficiencias en la actual gestión de almacenes. Se consideró como población y muestra al almacén de Danper Trujillo S.A.C. Los resultados del presente trabajo de investigación nos permiten determinar que, implementando una correcta gestión de almacenes, teniendo en cuenta la distribución física de almacenes (Layout), mejora en procesos de recepción, almacenamiento y despacho, el correcto control de materiales según su clasificación y almacén permitió un incremento de la productividad de un 46,97% a 77.75% en la empresa Danper Trujillo S.A.C. Esto nos demuestra que la productividad aumento en un 30.78%The present investigation has like objective the increase of the productivity in the company Danper Trujillo S.A.C. through a warehouse management proposal that goes from the restructuring of the layout to the implementation of a continuous improvement. For them, it was considered as a statement of the problem. To what extent will a proposal for warehouse management improve productivity in the company Danper Trujillo S.A.C.? And the hypothesis was: The Proposal of a Warehouse Management Design will allow to increase productivity significantly in the Company Danper Trujillo, S.A.C. 2018 We was choice techniques the observation, management indicators, and ABC count which helped us to determine the deficiencies in the current management of warehouses. It was considered as a population and shows the warehouse of Danper Trujillo S.A.C. The results of this research work allow us to determine that, by implementing a correct warehouse management, taking into account the physical distribution of warehouses (Layout), improvement in reception, storage and dispatch processes, the correct control of materials according to their classification and warehouse allowed an increase in productivity from 46.97% to 77.75% in the company Danper Trujillo SAC This shows us that productivity increased by 30.78%.Tesi

Incubadora y criadero de yacaré con sistema de energía solar: resultados de la primera campaña

Este trabajo presenta los resultados de la primera campaña de crianza de yacaré realizada en el Refugio de Vida Silvestre “El Cachapé” ubicado en la Provincia de Chaco. El proyecto incorpora una batería de 4 colectores solares de 10 m², una caldera auxiliar a leña que producen agua caliente, un sistema fotovoltaico que genera la electricidad necesaria para la bomba de agua y sistemas de control termostático. El funcionamiento del sistema durante el período de incubación permitió mantener las temperaturas dentro de las estrictas condiciones ambientales, reduciendo la mortalidad a una cifra muy baja. Las temperaturas mantenidas en los piletones en invierno fueron menores que los valores esperados. El trabajo presenta resultados y conclusiones de la primera campaña.Facultad de Arquitectura y Urbanism