Prilog istraživanju nesigurnosti digitalnih modela terena kao primarne baze podataka topografskih informacionih sistema

U radu je razmatran uticaj nesigumosti DMT-a na rezultate analiza u kojima se ova baza podataka о prostoru koristi. Za primer je izabrana kvantitativna geomorfološka analiza, odnosno izračunavanje primamih topografskih parametara, kao sto su nagib, aspekt i zakrivljenost terena. Topografski parametri kvantitativno oslikavaju teren i sami po sebi čine bazu podataka о reljefu, koja je sastavni deo Topografskih informacionih sistema (TIS). Računanje vrednosti topografskih parametara je posebno pogodno u DMT-u sa gridnom strukturom podataka. Visine terena u DMT-u su atributi tačaka, koje su osnovni entitet ovih baza. Ovakva struktura podataka DMT-a se naziva 2.5D GIS organizacijom podataka. S obzirom na tu činjenicu analiza nesigumosti DMT-a tretirana je kao ocena atributske tačnosti podataka. Kao osnovna mera tačnosti koristi se srednja kvadratna greška visina u DMT-u, dobijena na osnovu mreže kontrolnih tačaka koje su hijerarhijski veće tačnosti u odnosu na visine u DMT-u. Veoma važan podatak u analizi je i korelativna zavisnost grešaka visina u DMT-u, koja je sračunata kovarijacionom analizom reziduuma visina DMT-a i visina kontrolne mreže tačaka. Na test području "Zlatibor" za DMT dobijen digitalizacijom orohidrografskih oleata osnovne državne karte R= 1:5000 sračunate su srednja kvadratna greška visina i korelaciona dužina grešaka visina, i one iznose 1.3m i 110m, respektivno. Ovi podaci korišćeni su u daljem postupku ocene nesigumosti DMT-a na test području "Zlatibor". U radu su primenjene dve metode za ocenu kvaliteta DMT-a. Prva se zasniva na Monte Karlo metodi stohastičkih simulacija polja grešaka sa srednjom kvadratnom greškom visine i korelacionom dužinom kao ulaznim parametrima. Tako generisana polja grešaka, koja su istih dimenzija i rezolucije kao polazni grid, dodaju se na njega. Na taj način se dobijaju moguée realizacije DMT-a iz kojih se statističkom obradom dobijaju podaci о najverovatnijim vrednostima topografskih parametara i njihovim standardnim greškama za svaku ćeliju grida. U radu je pokazano da se sa relativno malim brojem generisanih simulacija (25) mogu dobiti statistički pouzdani podaci. Druga metoda je analitički postupak ocene nesigumosti DMT-a i zasniva se na Gausovom zakonu о prenosu grešaka. Metoda se svodi na teorijsko izvođenje za greške funkcija topografskih parametara. Praktičan problem koji nastaje uzimanjem u obzir korelisanosti grešaka visina, prevaziđen je jednostavnim numeričkim rešenjem. Rezultati dobijeni na ovaj način potvrđeni su poređenjem sa rezultatima dobijenim stohastičkim simulacijama. Primenom standardnih statističkih postupaka potvrđen je visok stepen saglasnosti rezultata dobijenih ovim metodama, i to za sve topografske paramétré. U radu je posebno razmatran projektni pristup određivanja kontrolnih mreža tačaka u cilju dobijanja pouzdanih rezultata koji su potrebni za ocenu kvaliteta DMT-a. Na jednom klasičnom GIS upitu, kao što je analiza dogledanja terena, pokazano je kakav uticaj može imati nesigumost DMT-a, i kako se taj uticaj može prikazati pomoću karata verovatnoéa, i u drugim primenama DMT-a. DMT sa gridnom strukturom podataka predstavlja pogodnu bazu za proračune kao sto su geomorfometrijske analize. Međutim, njihov glavni nedostatak je ograničena mogućnost nadogradnje u kvalitativnom smislu. Primenom kokriging geostatističke interpolatone metode u radu je prikazano moguće rešenje ovoga problema sa zadovoljavajućim rezultatom. Sa relativno malim brojem naknadno merendi tačaka na terenu (156 tačaka) srednja greška visina u polaznom DMT-u je sa 1.3077? svedena na 1.22m.This work deals with the influence of DTM's uncertainty on the results of analysis where this kind of spatial data base is used. Geomorphometric analysis, more exactly calculation of primary topographic indices (parameters), like slope, aspect and curvature of the terrain, were chosen as a case study. Topographic indices are quantitative characteristics of terrain and they are also a data base of relief, which is a segment of Topographic Information System (TIS). Estimation of the topographic indices is especially suitable with grid DTM's, called digital elevation models (DEM). Terrain heights are attributes of points as basic entities in this kind of spatial date bases. This kind of data structure is well known as 2.5D GIS data bases. In respect to this, uncertainty assessment of DTM is treated as attribute accuracy estimation. A standard deviation of height error is used as a basic accuracy measure, and it is obtained from control network points which are more accurate than in DTM's heights. Very important information in this kind of analysis is correlation dependence of height errors, obtained by covariance analysis of DTM heights and residuums of control point. For DTM obtained by digitalization of contours layer of Base State Map (S = 1:5000) at test area "Zlatibor", standard deviation of height error and correlation distance were calculated to be 1.30m and 110m, respectively. These data have been used in the further procedure of uncertainty assessment of DTM's on the same test area. Two methods for DTM quality assessment were used in this work. The first one is based on the Monte Carlo method of stochastic simulations of error fields, with standard deviation of height error and correlation distance as entry parameters. The error fields, generated by this way, and which are of the same dimension and resolution as the initial grid, were added to it. Thus, the possible realizations of DTM were obtained, and data related to the most probable values of topographic parameters, as well as of their standard errors for the each grid cell, were obtained by statistical data processing. It was shown in this work that with relatively small number of generated simulations (25) statistically reliable data could be acquired. Second method is analytical approach of DTM uncertainty assessment is based on Gaussian law of error propagation. This method is based on theoretical evaluation of error function of topographic parameters. The problem which arises when correlation of heights errors is taken into account could be solved by a simple numerical solution for this method of uncertainty assessment. The results obtained by this way were verified by comparing them with the ones obtained by stochastic simulations. The high level of agreement of the results obtained by these two methods, for all topographic parameters, was confirmed by standard statistical procedures The project procedure for establishing the control networks, with the aim of getting reliable results necessary for DTM quality assessment, was particularly examined in this work. The influence of DTM uncertainty, as well as the method of its presentation (probability maps) in the other DTM applications, were shown in a classical GIS query, such as a viewshed analysis

High resolution grid of potential incoming solar radiation for Serbia

Solar radiation is a key driving force for many natural processes. At the Earth's surface solar radiation is the result of complex interactions between the atmosphere and Earth's surface. Our study highlights the development and evaluation of a data base of potential solar radiation that is based on a digital elevation model with a resolution of 90 m over Serbia. The main aim of this paper is to map solar radiation in Serbia using digital elevation model. This is so far the finest resolution being applied and presented using this model. The final results of the potential direct, diffuse and total solar radiation as well as duration of insolation databases of Serbia are portrayed as thematic maps that can be communicated and shared easily through the cartographic web map-based service

Adherence measurements and corrosion resistance in primer/hot-dip galvanized steel systems

This paper focuses on the adherence during ageing of a primer (made of polyester resins crosslinked with melamine) applied onto hot-dip galvanized (HDG) steel for coil coating application and its influence on corrosion protection. A chromium-free surface treatment, composed of fluorotitanic acid, phosphoric acid, manganese phosphate, and vinylphenol was applied on the HDG steel to obtain high corrosion resistance and high adherence of a polyester and melamine primer. The influence of the manganese phosphate on the corrosion and adherence was investigated. To measure the adherence between the metal and the primer, a three-point flexure test was set up. The adherence was then linked with corrosion resistance during ageing, using electrochemical impedance spectroscopy

High-spectral resolution M-band observations of CO Rot-Vib absorption lines towards the Galactic center

Context. In the near- to mid-infrared wavelength domain, bright continuum sources in the central parsec of the Galactic center (GC) are subject to foreground absorption. These sources therefore represent ideal probes of the intervening material that is responsible for the absorption along the line of sight. Aims. Our aim is to shed light on the location and physics of the absorbing clouds. We try to find out which of the gaseous absorbing materials is intimately associated with the GC and which one is associated with clouds at a much larger distance. Methods. We used the capabilities of CRIRES spectrograph located at ESO Very Large Telescope in Chile to obtain absorption spectra of individual lines at a high spectral resolution of R = 50 000, that is, 5 km s(-1). We observed the (CO)-C-12 R(0), P(1), P(2), P(3), P(4), P(5), P(6), P(7) and P(9) transition lines, applied standard data reduction, and compared the results with literature data. Results. We present the results of CRIRES observations of 13 infrared sources located in the central parsec of the Galaxy. The data provide direct evidence for a complex structure of the interstellar medium along the line of sight and in the close environment of the central sources. In particular we find four cold foreground clouds at radial velocities VLSR of the order of -145, -85, -60, and -40 +/- 15 km s(-1) that show absorption in the lower transition lines from R(0) to P(2) and in all the observed spectra. We also find in all sources an absorption in velocity range of 50-60 km s(-1), possibly associated with the so-called 50 km s(-1) cloud and suggesting an extension of this cloud in front of the GC. Finally, we detect individual absorption lines that are probably associated with material much closer to the center and with the sources themselves, suggesting the presence of cold gas in the local region

The electrochemical deposition of Zn-Mn coating from choline chloride-urea deep eutectic solvent

Electrochemical and microscopic techniques were used for the characterisation of Zn-Mn coatings electrodeposited from choline chloride-urea deep eutectic solvent. Cyclic voltammograms show that there was no discernible Mn reduction peak when only Mn2+ was present in DES solution. The distinct Mn peak developed only upon addition of Zn2+ to the solution, probably due to previous Zn nucleation on the steel substrate. It was found that 22-27 wt-% Mn deposited at current densities of 3-8 mA cm(-2), amounts significantly higher than those obtained from aqueous electrolytes. Since higher deposition current densities resulted in the formation of a porous surface consisting of clusters of nodular crystallites, the optimal deposition c.d was determined to be 3 mA cm(-2)

Корозиона стабилност превлака Zn-Mn легура добијених електрохемијским путем

Zinc alloy coatings electrochemically deposited on steel from electrolytes with different components differ in their composition, homogeneity, porosity, structure and other characteristics that affect their corrosion resistance. Manganese is characterized by a very negative electrochemical potential and very high strength, prompting many researchers to study Zn-Mn alloys for the anti-corrosion purposes in the industry, especially automotive. In this work it was examined the influence of the type of the electrolyte deposition on the current efficiency during electrodeposition of Zn-Mn alloys. Zn-Mn alloys were deposited on steel from chloride, sulphate and pyrophosphate plating baths at different current densities. We have examined the influence of deposition current density on the current efficiency during electrodeposition, appearance of alloy coatings, as well as their corrosion stability. It was shown that Zn-Mn alloys with the best corrosion properties, among all examined ones, were obtained from chloride plating bath at 2 A dm-2.Превлаке легура цинка електрохемијски добијене из електролита са различитим компонентама имају разлике у свом саставу, хомогености, порозности, структури и другим карактеристикама које утичу на њихову корозиону отпорност. Манган се одликује јако негативним електрохемијским потенцијалом и јако великом чврстоћом, што је навело многе истраживаче на испитивања легуре Zn-Mn у антикорозионе сврхе, за потребе у индустрији, нарочито аутомобилској. У овом раду испитиван је утицај врсте електролита на таложење Zn-Mn легура, као и на искоришћење струје приликом електрохемијског таложења. Легуре су таложене на челику из хлоридног, сулфатног и пирофосфатног електролита различитим густинама струје. При задатим условима таложења испитиван је хемијски састав, храпавост, изглед превлака легура, и њиховa корозиона стабилност. Показано је да највећу корозиону стабилност имају легуре добијене таложењем из хлоридног електролита густином струје од 2 A dm-2

The influence of Ce-based coatings as pretreatments on corrosion stability of top powder polyester coating on AA6060

Cerium-based conversion coatings (CeCCs) are one of the most prospective alternatives to the widely used chromate conversion coatings (CCCs) due to their anticorrosion efficiency, environmentally friendly nature and low cost. In this work, the CeCCs on AA6060 were prepared by immersion into aqueous cerium salt solutions at room temperature, and subsequently post-treated in heated phosphate solution. The effect of counter ion (nitrate and chloride) on the coating properties was studied testing CeCCs as sole or conversion layers for the top polyester coating. Since the 60 mu m thick polyester coating was applied, an artificial defect of 0.8 mm hole was introduced to faster assess the differences between pretreatments. The system with CCC pretreatment was used as reference. Corrosion properties were investigated in 0.5 M NaCl solution by electrochemical impedance spectroscopy while the adhesion strength was measured by NMPR (N-methyl-2-pyrrolidone) and pull-off tests. As shown, the post-treated chloride-based CeCC offered better protection than crack-free thin nitrate-based CeCC, when used as sole coatings. On the other hand, it was brought to evidence that in combination with top powder polyester coating, the CeCC deposited from nitrate solution exhibited better protection compared to protective system pretreated with chloride-based one. Excellent polyester coating adhesion was found independently on aluminium surface pretreatment. (C) 2013 Elsevier B.V. All rights reserved

Cerium Oxide as Conversion Coating for the Corrosion Protection of Aluminum

CeO2 coatings were formed on the aluminum after Al surface preparation, by dripping the ceria sol, previously prepared by forced hydrolysis of Ce(NO3)(4). The anticorrosive properties of ceria coatings were investigated by the electrochemical impedance spectroscopy (EIS) during the exposure to 0.03% NaCl. The morphology of the coatings was examined by the scanning electron microscopy (SEM). EIS data indicated considerably larger corrosion resistance of CeO2-coated aluminum than for bare Al. The corrosion processes on Al below CeO2 coating are subjected to more pronounced diffusion limitations in comparison to the processes below passive aluminum oxide film, as the consequence of the formation of highly compact protective coating. The results show that the deposition of ceria coatings is an effective way to improve corrosion resistance for aluminum.International Conference ModTech Proceedings, 16th International Conference on Modern Technologies, Quality and Innovation, May 24-26, 2012, Sinaia, Romani

Cerium Oxide as Conversion Coating for the Corrosion Protection of Aluminum

CeO2 coatings were formed on the aluminum after Al surface preparation, by dripping the ceria sol, previously prepared by forced hydrolysis of Ce(NO3)(4). The anticorrosive properties of ceria coatings were investigated by the electrochemical impedance spectroscopy (EIS) during the exposure to 0.03% NaCl. The morphology of the coatings was examined by the scanning electron microscopy (SEM). EIS data indicated considerably larger corrosion resistance of CeO2-coated aluminum than for bare Al. The corrosion processes on Al below CeO2 coating are subjected to more pronounced diffusion limitations in comparison to the processes below passive aluminum oxide film, as the consequence of the formation of highly compact protective coating. The results show that the deposition of ceria coatings is an effective way to improve corrosion resistance for aluminum.International Conference ModTech Proceedings, 16th International Conference on Modern Technologies, Quality and Innovation, May 24-26, 2012, Sinaia, Romani