Electrochemical dissolution and passivation phenomena of gold cyanidation from roasted ore in the presence of iron oxides

Cette thèse de doctorat est divisée en des études sur l'or pur; la corrosion galvanique; et la polarisation de l'or en présence d'oxydes de fer contenus dans un minerai d'or grillé. La dissolution de l’or diminue en présence de magnétite et, augmente en présence d’hématite et de maghémite. Des produits de corrosion et des couches adsorbées ralentissent la dissolution d’or. Pour les études sur l’or pur, une augmentation du pH de 10 à 11 a réduit de 35 fois la densité de courant, alors qu'elle a augmentée de 32 fois en diminuant l'agitation de 100 à 60 tr/min. Les études potentiostatiques, à trois potentiels anodiques, montrent que l'augmentation de la concentration de cyanure, du pH, et du potentiel diminuent la densité de courant. Des films d'oxydes d'or ont été identifiés par XPS. La mesure du bruit électrochimique est un outil prometteur pour estimer la vitesse de corrosion in situ. Pendant les tests de corrosion galvanique, utilisés en mode ampèremètre zéro-résistance, les électrodes minérales testées ont eu un effet négatif sur la lixiviation de l’or selon l’ordre décroissant : magnétite, magnétite-hématite avec des surfaces égales, et minerai d'or grillé. Cependant, la maghémite et l'hématite ont eu un effet positif. La concentration d'ions solubles et la vitesse de diffusion pourraient retarder ou favoriser la dissolution. L’argent a été identifié par XPS sur la surface de l’or, suggérant, une passivation partielle. À partir des études de polarisation potentiodynamique, l'hématite, en tant que composé système “combiné d'anode Au-hématite”, favorise le courant de corrosion anodique de 12%, alors que la magnétite abaisse le courant (de 11%). Les études de deux cellules séparées ont été réalisées pour révéler l’influence des ions solubles dans la dissolution de l’or. Le balayage du potentiel circuit ouvert jusqu’à vers des valeurs cathodiques en présence d'oxygène atmosphérique et de cyanure montre des vitesses de corrosion, déduites des pentes de Tafel, sont proches des à valeurs industrielles. La vitesse de lixiviation de l'or diminue de 40% en présence de pulpe de magnétite, alors que celle-ci augmente, respectivement de 25% et 10% pour l'hématite et la maghémite. MEB-EDX confirment l'effet négatif de la magnétite par la présence d’une forte accumulation d’oxydes de fer sur la surface de l'or. De faibles quantités d'or ont été identifiées sur les particules de magnétite par XPS. La séparation magnétique des résidus de cyanuration a été suivie la caractérisation électrochimique du concentré et des rejets.This Ph.D. thesis is divided into studies using pure gold; galvanic corrosion; and gold polarization in presence of iron oxides of roasted gold ore. Gold dissolution decreases in the presence of magnetite, and increases in the presence of hematite, and maghemite. The corrosion products and adsorbed layers lead to a slowdown of gold dissolution. For pure gold study, increasing pH from 10 to 11 results in a current density lower by 35 times, while it increases by 32 times with decreasing agitation from 100 to 60 rpm. At three anodic potentials, potentiostatic studies show that increasing cyanide concentration, pH, and potential decrease the current density. Au oxides have been identified by XPS. Electrochemical noise measurement is promising tool with its in-situ corrosion rate estimation. In galvanic corrosion studies, employing zero-resistance ammeter (ZRA) mode, the tested mineral electrodes show a negative effect on gold leaching in decreasing order: magnetite, magnetite-hematite with equal surfaces, and roasted gold ore. However, maghemite and hematite show a positive effect. Concentration of soluble ions and diffusion rate could retard or promote gold dissolution. Silver has been identified by XPS on gold surface suggesting partial passivation. In potentiodynamic polarization studies, hematite, as a part of the combined “Au-hematite anode” system promotes anodic corrosion current by 12%, while magnetite shows negative effect (11%). Two separate container tests have been considered to examine the influence of soluble ions on gold dissolution. Scanning from open circuit potential to more cathodic values in presence of atmospheric oxygen and cyanide shows corrosion rates obtained from Tafel slopes close to industrial practice. Gold leach rate decreases by 40% with magnetite slurry, whereas it increased by 25% and 10% for hematite and maghemite, respectively. SEM-EDS findings have confirmed the negative effect of magnetite due to the high accumulation of iron oxides on the gold surface. Low amounts of gold in magnetite particles are identified by XPS. Magnetic separation of leach tailings has been followed by electrochemical characterisation of the concentrate and the residues

Miniaturized modular manipulator design for high precision assembly and manipulation tasks

In this paper, design and control issues for the development of miniaturized manipulators which are aimed to be used in high precision assembly and manipulation tasks are presented. The developed manipulators are size adapted devices, miniaturized versions of conventional robots based on well-known kinematic structures. 3 degrees of freedom (DOF) delta robot and a 2 DOF pantograph mechanism enhanced with a rotational axis at the tip and a Z axis actuating the whole mechanism are given as examples of study. These parallel mechanisms are designed and developed to be used in modular assembly systems for the realization of high precision assembly and manipulation tasks. In that sense, modularity is addressed as an important design consideration. The design procedures are given in details in order to provide solutions for miniaturization and experimental results are given to show the achieved performances

Maksiller premolar radiküler oluğu: “tehlikeli bölge”midir?

Objectives: To evaluate the presence of radicular groove and dentin thickness on the palatal aspect of the buccal root of maxillary first premolars using cone-beam computed tomography (CBCT). Materials and methods: Images of 312 maxillary first premolars belonging to 187 patients (between 18-69 years, 94 females and 93 males) who were referred to the clinic were retrospectively reviewed. Root canal treatment, periapical lesion, and post-core were excluded. One and three-rooted premolars were also excluded. CBCT images were viewed on the axial plane to detect grooves. The concave area on the palatal aspect of the buccal root was recorded as a groove. Buccal and palatal dentin thicknesses were measured by two observers at the level of 3 mm below furcation. Statistical analyses were performed. Results: Buccal and palatal thicknesses were 1.28(±0.25) and 0.87(±0.13) mm, respectively. According to Student’s t-test, buccal dentin thickness was statistically higher than palatal dentin. The prevalence of groove was 82.05%. While palatal thickness without groove was 0.93(±0.14) mm, palatal thickness corresponding to groove was 0.82(±0.12) mm. One-way ANOVA showed palatal and buccal thickness in group 1 (18-35 years) was statistically lower than group 3 (>65 years). No statistical difference in thickness was observed between sex and left or right side. Conclusions: Palatal thickness related to groove can be considered a “danger zone” for post-core and endodontic treatment. Considering the high prevalence (82.05%) and thin dentin of the groove, more conservative canal and post space preparation and CBCT examination are recommended to avoid perforation.Amaç: Bu çalışmanın amacı maksiller birinci premolardaki bukkal kökün palatinalinde bulunan oluğun prevalansının ve ayrıca bukkal ve palatinal dentin kalınlığının konik-ışınlı bilgisayarlı tomografi kullanarak (KIBT) incelenmesidir Yöntem: Çalışmaya, kliniğe başvuran 187 hastaya ait (18-69 yaş arası, 94 kadın ve 93 erkek) 312 premolar dişin KIBT görüntüsü dahil edildi. Kanal tedavili, post uygulanmış, tek veya üç köklü premolar dişler çalışma dışı bırakıldı. Kök oluğunu tespit edebilmek için KIBT görüntüleri aksiyel kesitte incelendi. Bukkal kökün palatinalindeki konkav alanlar oluk olarak kaydedildi. Bukkal ve palatinal dentin kalınlıkları iki gözlemci tarafından, furkasyonun 3 mm altından ölçüldü. İstatistiksel analiz yapıldı. Bulgular: Bukkal ve palatinal dentin kalınlıkları sırasıyla 1,28(±0,25) ve 0,87(±0,13) olarak bulundu. Student’s ttestine göre, bukkal dentin kalınlığı palatinaldeki dentin kalınlığına göre istatistiksel olarak anlamlı derecede fazla bulundu. Bukkal oluk prevalansı %82,05 olarak kaydedildi. Oluk bulunmayan palatinal dentin kalınlığı 0,93(±0,14) mm iken oluk bulunan palatinal dentin kalınlığı 0,82(±0,12) mm olarak tespit edildi. Tek yönlü ANOVA testine göre, palatinal ve bukkal kalınlık grup 1(18-35 yaş)’de istatistiksel olarak anlamlı derecede grup 3 (>65 yaş)’e göre daha inceydi. Cinsiyet ve sağ-sol arasında dentin kalınlığı açısından bir farklılık gözlenmedi. Sonuçlar: Kök oluğu bulunan bölgedeki dentin kalınlığı kanal tedavisi ve özellikle kök dentininde kayba sebep olan post uygulamaları açısından “tehlikeli bölge” olarak düşünülebilir. Kök oluğunun yüksek prevalansı ve kök oluğundaki ince dentin varlığı düşünüldüğünde, klinikte perforasyon oluşumu engellemek için, işlem öncesi üç boyutlu inceleme ve ayrıca daha konservatif kanal şekillendirmesi ve post boşluğu hazırlığı önerilir

Debljina dentina u zoni opasnosti i morfologija kanala maksilarnih kutnjaka

Objectives: Dentin thickness in concave areas of the root creates risk for complications such as strip perforation during endodontic treatment. The study aims to examine dentin thickness of the danger (DZ) and safety zone (SZ), canal configuration, and the presence of isthmus in the mesiobuccal root of maxillary molars. Material and methods: Cone-beam Computed Tomography (CBCT) images of 1251 teeth belonging to 642 patients were retrospectively reviewed. The dentin thicknesses at DZ and SZ in maxillary molars with one (MB) or two mesiobuccal canals (MB1, MB2) were measured at the 3 mm apical to the furcation level. Vertucci’s canal configurations and the isthmus rate were recorded. The Chi-square test andThe Student’s t-test were performed. Results: MB2 rate was higher in maxillary first molars (61.68%) than second molars (39.36%). Isthmus rates were 27.3% and 44.11% in first and second molars. DZ thickness was thinner than the dentin thickness in the SZ in both first and second molars with one or two mesial canals (p< 0.05). In teeth with single canal, the mean DZ thickness was 0.88mm. In teeth with two canals, the mean DZ thicknesses were 0.83mm and 0.80mm for MB1 and MB2 canals, respectively. Conclusion: MB2 rate was higher in the first molar (61.68%), and the isthmus rate was higher in the second molar (44.11%). DZ and SZ were thinner in MB2 than in MB1 at the maxillary molars with two mesial canals. The results indicated that more conservative preparation must be applied to the MB2 canal in the maxillary molars.No sponso

Evaluation of the bone thickness of mandibular molars using cone beam computed tomography

Objective: To investigate buccal and lingual bone thicknesses and fenestration rate of mandibular first and second molars using cone-beam computed tomography (CBCT). Methods: A total of CBCT images of 41 patients were selected and overall 120 mandibular molars were investigated. The buccal and lingual alveolar bone widths were measured at apex of the roots. The prevalence of fenestration in mandibular molars was recorded. Statistical analyses were performed. Results: The buccal bone widths of mesial root of second molars were significantly lower than the lingual (p<0.05). The lingual bone widths of mesial and distal root of second molars were lower than the buccal (p<0.05). The lowest thickness of buccal and lingual bone was observed in mesial root of first molar and distal root of second molar. The prevalence of fenestration in mandibular first and second molars was 5% and 10%. Conclusion: The buccal bone widths were lower at the first molar than the second molar. All fenestrations in first molar were in buccal aspect, in second molar were in lingual aspect. Topographical proximity of the buccal side of first molar and the lingual side of second molar to bone plate create a risky region for endodontic treatment or spread of infection.No sponso

A field programmable gate array based modular motion control platform

The expectations from motion control systems have been rising day by day. As the systems become more complex, conventional motion control systems can not achieve to meet all the specifications with optimized results. This creates the necessity of fundamental changes in the infrastructure of the system. Field programmable gate array (FPGA) technology enables the reconfiguration of the digital hardware, thus dissolving the necessity of infrastructural changes for minor manipulations in the hardware even if the system is deployed. An FPGA based hardware system shrinks the size of the hardware hence the cost. FPGAs also provide better power ratings for the systems as well as a more reliable system with improved performance. As a trade off, the development is rather more difficult than software based systems, which also affects the research and development time of the overall system. In this paper a level of abstraction is introduced in order to diminish the requirement of advanced hardware description language (HDL) knowledge for implementing motion control systems thoroughly on an FPGA. The intellectual property library consists of synthesizable hardware modules specifically implemented for motion control purposes. Other parts of a motion control system, like user interface and trajectory generation, are implemented as software functions in order to protect the modularity of the system. There are also several external hardware designs for interfacing and driving various types of actuators

İdempotent matrisler ve idempotent matrislerin lineer kombinasyonlarının nonsingülerliği

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Kuadratik formların, özellikle idempotent matrisli kuadratik formların istatistikteorilerinde merkezi bir rol oynadığı iyi bilinmektedir. Bununla birlikte istatistikteorisi ile ilgili detaylar bu çalışmada verilmemektedir.Bu çalışmanın amacı iki aşamalıdır: P1 ve P2 herhangi iki idempotent matris, c1 vec2 skalerler olmak üzere c1P1 + c2 P2 lineer kombinasyonunun nonsingülerliğiyle ilgiliolan ve J. K. Baksalary ve O. M. Baksalary[2] tarafından ele alınan problemiincelemek ve ikinci olarak iki değişmeli idempotent matrisin lineerkombinasyonunun bir involutif matris olduğu tüm durumları karakterize etmeproblemi için tam çözüm ortaya koymaktır. Bir involutif matris daima nonsingülerolduğundan dolayı ikinci durum, birinci durumun özel bir durumu olduğuna dikkatetmek gerekir.Çalışma şöyle düzenlenmiştir. Bazı temel tanımlar ve yardımcı sonuçlar Bölüm 1 deverilmektedir. Bölüm 2 de, idempotent ve tripotent matrislerin lineerkombinasyonları ile ilgili bazı sonuçlar sunulmaktadır. Yukarıda bahsedilen esaskonular Bölüm 3 te tartışılmaktadır.It is well known that quadratic forms, particulary those with idempotent matrices play acentral role in statistical theory. However, it is not given the details of the statisticaltheory here.The purpose of this study is two fold: to investigate the problem considered byBaksalary and Baksalary[2], which deals with the nonsingularity of any linearcombination c1P1 + c2 P2 where P1 and P2 are any two idempotent matrices and c1 andc2 are scalars, and secondly, to established complete solutions to the problem ofcharacterizing all situations in which a linear combinations of two commutingidempotent matrices is an involutive matrix. Notice that the latter is a special case of theformer because of the fact that an involutive matrix is always nonsingular.The study is organized as follows. Some basic definitions and auxiliary results are givenin Chapter 1. In Chapter 2, some results related to the linear combinations of idempotentand tripotent matrices are presented. Main subjects mentioned above are discussed inChapter 3

A versatile and reconfigurable microassembly workstation

In this paper, a versatile and reconfigurable microassembly workstation designed and realized as a research tool for investigation of the problems in microassembly and micromanipulation processes and recent developments on mechanical and control structure of the system with respect to the previous workstation are presented. These developments include: (i) addition of a manipulator system to realize more complicated assembly and manipulation tasks, (ii) addition of extra DOF for the vision system and sample holder stages in order to make the system more versatile (iii) a new optical microscope as the vision system in order to visualize the microworld and determine the position and orientation of micro components to be assembled or manipulated, (iv) a modular control system hardware which allows handling more DOF. In addition several experiments using the workstation are presented in different modes of operation like tele-operated, semiautomated and fully automated by means of visual based schemes

Development of system supervision and control software for a micromanipulation system

This paper presents the realization of a modular software architecture that is capable of handling the complex supervision structure of a multi degree of freedom open architecture and reconfigurable micro assembly workstation. This software architecture initially developed for a micro assembly workstation is later structured to form a framework and design guidelines for precise motion control and system supervision tasks explained subsequently through an application on a micro assembly workstation. The software is separated by design into two different layers, one for real-time and the other for non-realtime. These two layers are composed of functional modules that form the building blocks for the precise motion control and the system supervision of complex mechatronics systems

Lesion Detection on Leaves using Class Activation Maps

Lesion detection on plant leaves is a critical task in plant pathology and agricultural research. Identifying lesions enables assessing the severity of plant diseases and making informed decisions regarding disease control measures and treatment strategies. To detect lesions, there are studies that propose well-known object detectors. However, training object detectors to detect small objects such as lesions can be problematic. In this study, we propose a method for lesion detection on plant leaves utilizing class activation maps generated by a ResNet-18 classifier. In the test set, we achieved a 0.45 success rate in predicting the locations of lesions in leaves. Our study presents a novel approach for lesion detection on plant leaves by utilizing CAMs generated by a ResNet classifier while eliminating the need for a lesion annotation process.Comment: 6 pages, 1 figur