234 research outputs found
Grounding of Human Environments and Activities for Autonomous Robots
With the recent proliferation of robotic applications in domestic and industrial scenarios, it is vital for robots to continually learn about their environments and about the humans they share their environments with. In this paper, we present a framework for autonomous, unsupervised learning from various sensory sources of useful human āconceptsā; including colours, people names, usable objects and simple activities. This is achieved by integrating state-of-the-art object segmentation, pose estimation, activity analysis and language grounding into a continual learning framework. Learned concepts are grounded to natural language if commentary is available, allowing the robot to communicate in a human-understandable way. We show, using a challenging, real-world dataset of human activities, that our framework is able to extract useful concepts, ground natural language descriptions to them, and, as a proof-of-concept, to generate simple sentences from templates to describe people and activities
Korozija visokohromnog belog gvožÄa u kiseloj sredini
In this work we studied the electrochemical behavior of chromium white cast irons in deaerated aqueous sulphuric acid solutions of the pH 1-3. The measurements of concentrations of dissolved iron and chromium in the solution, as well as the volume of hydrogen evolved were carried out. By comparing the results, it was found that besides the electrochemical corrosion, another, chemical, process occurs at the same time. This process takes place at the surface of the metal, in the contact with the water molecules or hydrogen ions, and produces hydrogen evolution. These results show, that the usual electrochemical determination of the metal corrosion rate must be very critically applied.U ovom radu prouÄavano je elektrohemijsko ponaÅ”anje visokohromnog belog gvožÄa u dearisanim rastvorima sumporne kiseline u oblasti pH 1-3. Provedena su merenja koncentracije rastvorenog gvožÄa i hroma u rastvoru, kao i zapremine izdvojenog vodonika. PoreÄenjem rezultata konstatovano je da pored elektohemijske korozije jednovremeno teÄe i drugi hemijski proces koji se odigrava na povrÅ”ini metala u kontaktu sa molekulima vode ili vodoniÄnim jonima uz izdvajanje vodonika. Ovi rezultati ukazuju da se uobiÄajene metode elektrohemijskog odreÄivanja brzine korozije metala moraju primenjivati vrlo kritiÄki, uz prethodno dokazivanje da su ovakvi hemijski procesi u odnosu na elektohemijske na ispitivanom metalu relativno zanemarljivi
Korozija visokohromnog belog gvožÄa u kiseloj sredini
In this work we studied the electrochemical behavior of chromium white cast irons in deaerated aqueous sulphuric acid solutions of the pH 1-3. The measurements of concentrations of dissolved iron and chromium in the solution, as well as the volume of hydrogen evolved were carried out. By comparing the results, it was found that besides the electrochemical corrosion, another, chemical, process occurs at the same time. This process takes place at the surface of the metal, in the contact with the water molecules or hydrogen ions, and produces hydrogen evolution. These results show, that the usual electrochemical determination of the metal corrosion rate must be very critically applied.U ovom radu prouÄavano je elektrohemijsko ponaÅ”anje visokohromnog belog gvožÄa u dearisanim rastvorima sumporne kiseline u oblasti pH 1-3. Provedena su merenja koncentracije rastvorenog gvožÄa i hroma u rastvoru, kao i zapremine izdvojenog vodonika. PoreÄenjem rezultata konstatovano je da pored elektohemijske korozije jednovremeno teÄe i drugi hemijski proces koji se odigrava na povrÅ”ini metala u kontaktu sa molekulima vode ili vodoniÄnim jonima uz izdvajanje vodonika. Ovi rezultati ukazuju da se uobiÄajene metode elektrohemijskog odreÄivanja brzine korozije metala moraju primenjivati vrlo kritiÄki, uz prethodno dokazivanje da su ovakvi hemijski procesi u odnosu na elektohemijske na ispitivanom metalu relativno zanemarljivi
Korozioni potencijal nerÄajuÄeg Äelika 304 u sumpornoj kiselini
The potentiodynamic study of the electrochemical behavior of austenitic 304 stainless steel in deaerated aqueous sulfuric acid of pH 1 revealed that the steel achieved a stable corrosion potential of ca. - 0.350 V (SCE) independent of whether the electrode had previously been cathodically "activated" or anodically passivated. It was also shown that the experimentally observed anodic peak was not the usually obtained anodic passivation peak, as is the case with a number of metal, but an artifact due to the anodic oxidation of hydrogen absorbed during the previously employed cathodic polarization and hydrogen evolution, intended to activate the initially passive surface, or even hydrogen absorbed on the open circuit potential. It was shown that this potential establishes and electrochemical corrosion potential of the Wagner-Traud type due to the evolution of cathodic hydrogen on a passivated steel surface and anodic metal dissolution through the passive layer. It was impossible to activate 304 stainless steel in sulfuric acid of pH 1 by cathodic polarization, and the usually observed anodic peak obtained under these conditions should not be considered as an active metal dissolution process and a passivation anodic peak, but rather as an artifact due to the electrochemical oxidation of the in the steel absorbed hydrogen.PotenciodinamiÄka ispitivanja elektrohemijskog ponaÅ”anja nerÄajuÄeg Äelika 304 u deaeriranoj sumpornoj kiselini sa pH 1 pokazala su da se na Äeliku uspostavlja stabilan korozioni potencijal od - 0,350 V(ZKE) nezavisno od toga da li je elektroda prethodno katodno tretirana radi "aktivacije", ili je povrÅ”ina bila pasivirana. Pokazano je, takoÄe, da eksperimentalno dobijeni anodni maksimum na potenciodinamiÄkoj krivi pozitivnije od korozionog potencijala nije anodni pasivacioni maksimum koji se obiÄno dobija pri anodnoj polarizaciji veÄeg broja metala u sliÄnim uslovima, veÄ eksperimentalni artefakt koji nastaje zbog anodne oksidacije vodonika apsorbovanog unutar Äelika tokom katodnog "aktiviranja" ili Äak i pri dužem držanju na korozionom potencijalu. Pokazano je da je spontano formirani potencijal otvorenog kola zapravo korozioni potencijal koji nastaje kao meÅ”oviti potencijal Vagner-Traudovog tipa suprotnim delovawem katodne reakcije izdvajanja vodonika na pasivnom sloju i anodnog rastvaranja Äelika kroz pasivni sloj. Nije bilo moguÄno katodnom "aktivacijom" i dugotrajnijom katodnom polarizacijom do znaÄajno negativnih potencijala i vrlo velikih katodnih struja da se pasivni sloj ukloni i postigne aktivno elektrohemijsko rastvaranje metala bez prisustva pasivnog sloja, tj. slobodna metalna povrÅ”ina. Stoga, Äesto eksperimentalno konstatovan anodni maksimum na ovakvim Äelicima ne treba da se interpretira kao anodno rastvaranje sa pasivacionim maksimumom, veÄ kao posledica anodne oksidacije apsorbovanog vodonika u pasivnom Äeliku, a koji se pod ovim uslovima ne može elektrohemijski aktivirati, odn. depasivirati
Uticaj hloridnih jona na potencijal otvorenog kola hroma u deaerisanim rastvorima sumporne kiseline
Open circuit potential measurements and cyclic voltammetry of chromium in deaerated aqueous H2SO4 solution of pH 1 without and containing NaCl in the concentration range 0.5 - 4 M revealed that chromium exhibits two stable open circuit potentials having the character of a Wagner-Traud corrosion potential. One, E corr.1, was established on the passive surface formed by exposing Cr previously to air or passivated potentiostacially in a controlled manner, and the second one, E corr,2, at the bare Cr surface obtained by prolonged cathodic activation. There is a small difference in the E corr,1 values as a function of the passive layer properties. Addition of NaCl accelerates the hydrogen evolution reaction on the passive surface to some extent, while the same reaction on the bare surface was not affected by NaCl. On the other hand, presence of NaCl accelerates the anodic reaction on the bare surface, and it activates the dissolution of the passive layer so that the passive currents increase with addition of NaCl. This effect is so large that at concentration of NaCl larger than 3 M, the destruction of the passive layer was so fast that in a matter of seconds the Cr was activated, and the only one stable corrosion potential observed was E corr.2. No pitting of Cr in the presence of NaCl was observed up to the transpassive potentials.Merenja potencijala otvorenog kola, kao i merenja primenom cikliÄne voltametrije u deaerisanim vodenim rastvorima H 2SO4, pH1, bez i sa dodatkom NaCl u koncentracionom opsegu 0,5-4M, otkrila su da hrom pokazuje dva stabilna potencijala otvorenog kola koji imaju osobine Wagner-Traud-ovog korozionog potencijala. Jedan korozioni potencijal, E corr.1 , se uspostavljao na pasiviranoj povrÅ”ini, koja se formira prethodnim izlaganjem Cr vazduhu, ili poteciostatskim pasiviranjem na kontrolisan naÄin, a drugi, E corr.2 , se obrazovao na goloj povrÅ”ini Cr koja je formirana katodnom aktivacijom u dovoljno dugom periodu vremena. Postoji izvesna mala razlika u vrednostima E corr.1 kao funkcija osobina pasivnog sloja. Dodatak NaCl u odreÄenoj meri ubrzava reakciju izdvajanja vodonika na pasiviranoj povrÅ”ini, dok NaCl nema uticaja na istu reakciju na goloj povrÅ”ini Cr. Sa druge strane prisustvo NaCl ubrzava anodnu reakciju na goloj povrÅ”ini hroma i aktivira rastvaranje pasivnog sloja, tako da se struja pasivacije poveÄava sa dodatkom NaCl. Uticaj NaCl je toliko veliki, da pri koncentracijama veÄim od 3M, razaranje pasivnog sloja postaje brzo, da se Cr za vreme od nekoliko sekundi aktivira i tada se uoÄava samo jedan stabilni korozioni potencijal E corr.2 . Nije uoÄena pojava pitinga u prisustvu NaCl, sve do potencijala u transpasivnoj oblasti
Uticaj strukture metalnog hroma na njegovu elektrohemijsku i hemijsku koroziju
It was shown that metallic chromium in aqueous solution of sulfuric acid dissolves in accord with the electrochemical mechanism proposed by Wagner and Traud, but also by a direct chemical reaction of metal with water molecules from the electrolyte, as proposed by Kolotyrkin and coworkers. The experiments in this study were carried out with three different chromium samples: large grain size cast chromium obtained from Merck Co., Germany fine grain metallic chromium rods, obtained from Goodfellows, Pa, USA, and a 121 ŃŃ thick electroplated layer of chromium on steel. It was shown that the rates of electrochemical and chemical corrosion are close to each other and similar on all three materials, while on the electroplated chromium surfaces anodic dissolution was ca. 5 times faster than on other chromium surfaces while catholic hydrogen evolution was ca. 5 times slower than on other chromium surfaces. These differences are obviously the consequences of the differences in the structure of electroplated chromium as contrasted to the other chromium samples. This conclusion is supported by the results obtained with the samples with two large crystal grains of different structure and orientation.Pokazano je da se u vodenim rastvorima sumporne kiseline metalni hrom rastvara elektrohemijskim mehanizmom u skladu sa modelom Vaguera i Trauda ali da se hrom paralelno rastvara i hemijskim mehanizmom po modelu Kolotirkina i saradnika direktnim reagovanjem metala sa molekulima vode iz rastvora. Kao materijal za ispitivanje služio je krupnozrni liveni hrom sitnozrni kovani i valjani hrom i elektrolitiÄki istaložena hromna prevlaka. Pokazano je da su brzine elektrohemijske i hemijske korozije meÄusobno sliÄne kod sva tri materijala, dok je elektrohemijska prevlaka imala oko 5 puta bržu anodnu reakciju i skoro 5 puta sporiju katodnu reakciju izdvajanja vodonika. Ove razlike posledica su svakako razlika u strukturi i kristalografskoj orijentaciji hromne prevlake prema rastvoru, Å”to se u izvesnoj meri uoÄava i na primeru krupnozrne livene strukture, gde dva razliÄita velika zrna imaju odreÄene razlike u brzinama ovih elektrohemijskih reakcija, iako u znatno manjoj meri
Non-invasive coronary flow reserve predicts response to exercise in asymptomatic severe aortic stenosis
Uticaj strukture metalnog hroma na njegovu elektrohemijsku i hemijsku koroziju
It was shown that metallic chromium in aqueous solution of sulfuric acid dissolves in accord with the electrochemical mechanism proposed by Wagner and Traud, but also by a direct chemical reaction of metal with water molecules from the electrolyte, as proposed by Kolotyrkin and coworkers. The experiments in this study were carried out with three different chromium samples: large grain size cast chromium obtained from Merck Co., Germany fine grain metallic chromium rods, obtained from Goodfellows, Pa, USA, and a 121 ŃŃ thick electroplated layer of chromium on steel. It was shown that the rates of electrochemical and chemical corrosion are close to each other and similar on all three materials, while on the electroplated chromium surfaces anodic dissolution was ca. 5 times faster than on other chromium surfaces while catholic hydrogen evolution was ca. 5 times slower than on other chromium surfaces. These differences are obviously the consequences of the differences in the structure of electroplated chromium as contrasted to the other chromium samples. This conclusion is supported by the results obtained with the samples with two large crystal grains of different structure and orientation.Pokazano je da se u vodenim rastvorima sumporne kiseline metalni hrom rastvara elektrohemijskim mehanizmom u skladu sa modelom Vaguera i Trauda ali da se hrom paralelno rastvara i hemijskim mehanizmom po modelu Kolotirkina i saradnika direktnim reagovanjem metala sa molekulima vode iz rastvora. Kao materijal za ispitivanje služio je krupnozrni liveni hrom sitnozrni kovani i valjani hrom i elektrolitiÄki istaložena hromna prevlaka. Pokazano je da su brzine elektrohemijske i hemijske korozije meÄusobno sliÄne kod sva tri materijala, dok je elektrohemijska prevlaka imala oko 5 puta bržu anodnu reakciju i skoro 5 puta sporiju katodnu reakciju izdvajanja vodonika. Ove razlike posledica su svakako razlika u strukturi i kristalografskoj orijentaciji hromne prevlake prema rastvoru, Å”to se u izvesnoj meri uoÄava i na primeru krupnozrne livene strukture, gde dva razliÄita velika zrna imaju odreÄene razlike u brzinama ovih elektrohemijskih reakcija, iako u znatno manjoj meri
Hemijska korozija metala i legura
In this paper, phenomena of chemical corrosion of metals and alloys in electrolyte solutions are analyzed. It is shown that iron, chromium and other metals and alloys dissolve much faster than is the corrosion rate determined by electrochemical methods. This means that the chemical dissolution takes place simultaneously with the electrochemical dissolution. The chemical dissolution does not depend on electrode potential. Under some conditions, chemical dissolution of metals is the dominant process of dissolution. Several mechanisms of chemical corrosion are described. Also, the consequences of chemical dissolution of various metals and alloys are discussed, as well as the hydrogen evolution during the chemical dissolution. The process of hydrogen evolution during the chemical corrosion is not subjected to the laws of electrochemical kinetics.U ovom preglednom radu analizirana je hemijska korozija metala i legura u rastvorima elektrolita. Pokazano je da se gvožÄe, hrom i neki drugi metali i legure rastvaraju mnogo brže nego Å”to je njihova brzina korozije odreÄena elektrohemijskim metodama. To znaÄi da se istovremeno sa elektrohemijskim rastvaranjem odvija i hemijsko rastvaranje, koje ne zavisi od potencijala. U nekim uslovima hemijsko rastvaranje metala je dominantan proces rastvaranja. Opisano je viÅ”e mehanizama hemijske korozije. TakoÄe, razmatrane su posledice hemijskog rastvaranja razliÄitih metala i legura, kao i pojava izdvajanja vodonika pri hemijskom rastvaranju. Proces izdvajanja vodonika pri hemijskoj koroziji ne podleže zakonitostima elektrohemijske kinetike
Uticaj strukture metalnog hroma na njegovo elektrohemijsko ponaŔanje
Chromium dissolution in aqueous sulfuric acid solution of pH 1 was studied electrochemically on chromium electrodes with different crystallographic structures. A slow potentiodynamic method was used for the electrochemical measurements in deaerated solutions (purged with nitrogen),while the Cr(III) ions in the solution after the corrosion were determined by atomic absorption spectrometry. Three electrode materials with a very dominant crystallite orientation resembling single crystal structures (i.e., 111 and 110) confirmed by the electron backscattering diffraction (EBSD), were used in the experiments. The (111) structures were somewhat more active electrochemically (both anodic and cathodic) than the (110) structure. However, Cr electrochemically deposited in standard plating bath, assumed from literature data to has also the (111) structure, was more than 4 times active for anodic dissolution and, by the same number, less active for cathodic hydrogen evolution. The concentrations of Cr(III) ions determined in the solution after definite times of corrosion of all the materials showed almost two times larger dissolution rates than observed electrochemically by three different electrochemical methods (Wagner-Traud, Stern-Geary, electrochemical impedance spectroscopy). This is explained by the simultaneous occurrence of potential independent chemical dissolution of Cr, by a direct reaction of metallic Cr with H2O molecules, proposed a long time ago by Kolotyrkin and coworkers. .ProuÄavano je elektrohemijsko rastvaranje hroma u vodenim rastvorima sumporne kiseline (pH 1) sa elektrodama od hroma razliÄite kristalografske strukture. Primenjena je spora potenciodinamiÄka metoda u deaeriranim rastvorima (uz provoÄenje azota) na 25Ā°C, a joni Cr(III) u rastvoru posle odreÄenog vremena korozije odreÄivani su atomskom apsorpcionom spektroskopijom. U eksperimentima su upotrebljena tri elektrodna materijala sa dominantnim kristalnim strukturama koje podseÄaju na mono kristalne (tj. 111 i 110), a Å”to je potvrÄeno EBSD metodom. NaÄeno je da je struktura (111) elektrohemijski aktivnija (i anodno i katodno) od strukture (110). MeÄutim, elektrolitiÄki istaložen Cr iz standardnog kupatila za hromiranje, a koji na osnovu literaturnih podataka ima strukturu (111) bio je oko 4 puta aktivniji u anodnoj reakciji i isto toliko manje aktivan za katodnu reakciju izdvajanja vodonika. AnalitiÄki odreÄivane koncentracije Cr(III) jona u rastvoru posle odreÄenog vremena spontane korozije pokazivale su dva puta veÄe koncentracije nego Å”to bi se oÄekivalo na osnovu brzine elektrohemijske korozije, odreÄivanih metodama Wagner-Traud, Stern-Geary i elektrohemijskom impedansnom spektroskopijom. Ovo je objaÅ”njeno jednovremenim odigravanjem i elektrohemijske reakcije i hemijske reakcije direktnog reagovanja metalnog Cr sa molekulima vode, po mehanizmu predloženom od Kolotirkina i saradnika.
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