Bubble Evolution on Different Carbon Anode Designs in Cryolite Melt

The anode potential has been shown to be highly dependent on anode geometry and orientation in the Hall–Héroult process. This work is an experimental laboratory scale study of the effect of anode geometry and orientation on bubble formation and detachment for four different anode designs: horizontal (surface facing downwards), inverted horizontal (surface facing upwards), vertical, rod (with both vertical and horizontal surface). From polarization curves, it was found that the vertical anode and the inverted horizontal anode operated at lowest potentials. Above 1 A cm−2, the vertical anode showed the lowest potential. As the current increases, the transition towards smaller noise is pronounced for the horizontal anode and to some degree for the vertical anode and inverted horizontal anode. Fast Fourier Transform analysis of chronoamperometric data gave a dominant frequency only for the horizontal anode and the rod anode. The bubble release time corresponded well with the dominant frequency for the rod anode for all current densities and for the horizontal anode at lower current densities. Only random bubble noise was found for the vertical and the inverted horizontal anode and is probably due to a bubble-induced convection effectively removing the bubbles.publishedVersio

Laser beam remelting of stainless steel plate for cladding and comparison with conventional CMT process

Progressing towards circular economy requires smarter and more efficient use of energy and resources. Laser beam can be efficient and flexible tool for melting different metals, commonly used in cladding and additive manufacturing (AM) with a wire and powder feedstock. As an alternative, feedstock in the form of plates and sheets can be used for cladding to achieve corrosion resistant surfaces. Compared to powder or wire, plates are easier to process, less costly to use, and may come as scrap metal. This leads to smarter and more efficient resource utilization. However, processing plates in such way is not mature and requires more in-depth investigation to be competitive with well-established methods. In this work, 2.0 mm thick 316L stainless steel plates were remelted by a high-power fibre laser beam for cladding on carbon steel substrates. It was compared to the conventional cold metal transfer (CMT) welding-based arc cladding which is frequently used due to a low heat input. In the first phase, different defocusing distances were studied to understand the laser remelting process capabilities to optimize the productivity. It was found that a highly defocused laser beam provided unstable melt pool conditions with low track quality. Compared to CMT, the laser remelting provided enhanced productivity, reduced heat input by 50% per pass, and lower distortions. Microhardness testing showed an increase in hardness in the intermediate layer towards the fusion line due to carbon diffusion. Despite a higher delta ferrite formation in laser-remelted tracks, a comparable corrosion protection to CMT was observed. The proposed method is promising for reducing CO2 emissions with respect to reusing scrap metal in the form of plates or use of ordinary plates instead of filler wires which opens possibilities for further enhancements.publishedVersio

The Reassigned Pseudo Wigner-Ville Transform in Electrochemical Noise Analysis

Several different time–frequency transforms from signal processing were used to analyze electrochemical noise data to determine frequency components contained within the noise record and their time evolution. Bilinear time–frequency representations (TFR) based on the Wigner–Ville distribution (WVD) were compared with a special focus on the reassigned smoothed pseudo WVD (RSPWVD). Spectra obtained with WVD were compared with traditional linear time–frequency representations, such as short time Fourier transform and wavelet transform. Comparison to other TFRs showed that the RSPWVD suppressed artifacts, provided better resolution of the time–frequency analysis in both time and frequency domains, and improved the overall readability of a representation. The obtained spectra from RSPWVD were consistent with the results from DWT, but permitted a more comprehensive analysis of transients. Consequently, RSPWVD is suitable for electrochemical noise analysis. In the presence of Cl−, RSPWVD showed that the passivity of Al was compromised, as evidenced by the presence of various current transients in the frequency range from 10−2 to 1 Hz

Ren eller oren revisionsberättelse? : En studie om faktorers påverkan på utfallet av en revisionsberättelse

Revisionsmarknaden har förändrats under den senaste tidsperioden till följd av bland annat skandaler som till exempel Enronskandalen och revisionspliktens avskaffande 2010. När bedrägerier uppstår i företagens redovisning blir dess revisorer oftast anklagade som ansvariga då deras huvudsakliga uppgift är att granska företagens finansiella rapporter. När revisorn har genomfört sin granskning utlämnas en revisionsberättelse som antingen är ren eller oren ifall den innehåller avvikande meningar från företagens påståenden. En ren revisionsberättelse ses som en kvalitetsstämpel. Tidigare forskning har påvisat att ett antal olika faktorer påverkar utfallet av en ren respektive oren revisionsberättelse. Syftet med studien är att undersöka huruvida studiens utvalda faktorer har ett samband med en revisionsberättelse, för att förstå vilka faktorer som främst kan associeras med en oren revisionsberättelse. Utifrån en kvantitativ metod har empiri samlats in från 377 stycken mikro, små samt medelstora företags årsredovisningar som har sitt säte i Stockholms län och därefter har en enkel- samt multipel logistisk regressionsanalys utförts med åtta stycken oberoende variabler. Hypoteser ställdes upp för respektive variabel mot den beroende variabeln; revisionsberättelse. Både den enkla- och multipla logistiska regressionsanalysen påvisade en statistisk signifikans på variablerna; soliditet och räntabilitet på totalt kapital, varpå nollhypotesen kunde förkastas för dessa. Ju lägre soliditet och räntabilitet på totalt kapital desto större sannolikhet att en revisor utlämnar en oren revisionsberättelse.The audit market has changed during the recent period due to scandals such as the Enron scandal and the abolition of auditing obligations 2010. When fraud occurs in the company's financial reports, its auditors are usually accused of being responsible as their main task is to review the companies' financial reports. The auditor gives the firms either an unqualified or qualified auditor’s report. An unqualified auditor’s report is seen as a “quality stamp”. Previous research has shown that a variety of factors affect the outcome of an unqualifiedand qualified auditor’s report. The purpose of this study is to investigate whether the chosen factors of the study are related to an audit report, in order to understand which factors can be associated with a qualified audit report. Based on a quantitative method, empirical data has been collected from 377 micro-, small and medium sized companies' annual reports in Stockholm, and were analyzed using simple and multiple logistic regression analysis with eight different independent variables. A statistical significance on the variables; solvency and return on total assets, is found in both the simple and multiple logistic regression analysis, whereupon the zero hypothesis could be rejected for these. The lower the solvency and return on total assets, the greater the likelihood of an auditor leaving a qualified auditor’s report

Psychiatric disorders and selected variables among medical students in Belgrade (Yugoslavia)

The mental health of a group of 523 medical freshmen (97% of the respective population) was assessed 1 month after enrollment. Students with psychiatric impairment (84 or 16.1%) were compared with those assessed to be mentally healthy in respect of a number of variables. Cluster, correlation, and principal component analyses revealed that psychiatric disorders were related to the result of the screening test, in a lesser degree to the test anxiety, and not at all to any of the other tested variables (separation from parents, family completeness, education of parents, number of siblings, number of employees in the family, grade point average in high school, and smoking).psychiatric disorders medical students epidemiology multivariate analysis

Mechanisms of inhibitor action - passivation and self-healing

In this chapter, we will briefly review the systematics of corrosion inhibitors and the classical mechanisms of action of corrosion inhibitors, the latter with an emphasis on inhibitors interacting with the material surface. The different roles corrosion inhibitors have in protecting materials surfaces will be described – with examples from applications in the oil and gas sector, but also more general. We will discuss in some detail the interaction of an imidazoline‐based surfactant inhibitor with mild steel and the interaction of 2‐mercaptobenzothiazole (MBT) with copper and zinc. By adsorbing to surfaces, molecules in general block sites for metal dissolution. Good inhibitors furthermore react with dissolution products to form insoluble films, in analogy to the formation of conversion coatings. Furthermore, inhibitors may interfere with the kinetics of the cathodic reaction. Over decades, a challenge for the use of inhibitors has been leaching into the environment of inhibiting molecules. Modern triggered release concepts ensure that inhibitors become available only if a corrosion attack has begun. Such triggered release systems have successfully been used for the self‐healing of coatings, and we will discuss one example of the interaction of a cyclodextrin with MBT to see how this works for inhibitors. Future applications in the oil and gas sector may consider the use of intelligent coatings

Bubble Evolution on Different Carbon Anode Designs in Cryolite Melt

The anode potential has been shown to be highly dependent on anode geometry and orientation in the Hall–Héroult process. This work is an experimental laboratory scale study of the effect of anode geometry and orientation on bubble formation and detachment for four different anode designs: horizontal (surface facing downwards), inverted horizontal (surface facing upwards), vertical, rod (with both vertical and horizontal surface). From polarization curves, it was found that the vertical anode and the inverted horizontal anode operated at lowest potentials. Above 1 A cm−2, the vertical anode showed the lowest potential. As the current increases, the transition towards smaller noise is pronounced for the horizontal anode and to some degree for the vertical anode and inverted horizontal anode. Fast Fourier Transform analysis of chronoamperometric data gave a dominant frequency only for the horizontal anode and the rod anode. The bubble release time corresponded well with the dominant frequency for the rod anode for all current densities and for the horizontal anode at lower current densities. Only random bubble noise was found for the vertical and the inverted horizontal anode and is probably due to a bubble-induced convection effectively removing the bubbles

Primena tehnika in vitro kulture za eliminaciju virusa iz ukrasnih biljaka

Viruses are responsible for numerous epidemics in different crops in all parts of the world. As a consequence of their presence great economic losses are being incurred. In addition to the development of sensitive techniques for detection, identification and characterization of viruses, substantial attention has also been paid to biotechnological methods for their elimination from plants. In this review article, the following biotechnological in vitro culture techniques for virus elimination from ornamental plants are presented: meristem culture, thermotherapy, chemotherapy, cryotherapy or a combination of these methods. The plant species, as well as the type of virus determine the choice of a most suitable method. The state of the art in investigation of virus elimination from Impatiens sp. in Serbia is summarized.Virusi su odgovorni za brojne epidemije na različitim usevima u svim delovima sveta. Posledica njihovog prisustva su velike ekonomske štete, pa osim razvoju osetljivih tehnika za detekciju, identifikaciju i karakterizaciju virusa, velika pažnja se poklanja i biotehnološkim metodama za njihovu eliminaciju. U ovom preglednom radu predstavljene su tehnike in vitro kulture za eliminaciju virusa iz biljnog materijala: kultura meristema, termoterapija, hemoterapija, krioterapija ili kombinacija ovih metoda. Koja će metoda biti primenjena zavisi od biljne vrste, kao i od vrste virusa. U radu je dat pregled istraživanja na eliminaciji virusa iz Impatiens sp. u Srbiji

In vitro sensitivity of Alternaria solani to conventional fungicides and a biofungicide based on tea tree essential oil

A study of in vitro sensitivity of five Alternaria solani isolates to cooper-oxychloride, chlorothalonil, difenoconazole, pyraclostrobin and a biofungicide based on tea tree essential oil was carried out. The isolates were obtained from infected tomato leaves collected from five different locations in Serbia. The tested isolates showed the highest sensitivity to pyraclostrobin with EC50 values ranging from 0.0014 to 0.0041 μg ml-1. The EC50 values of difenoconazole were 0.018-0.037 μg ml-1, chlorothalonil 2.99-4.54 μg ml-1, and cooper-oxychloride 13.27-15.63 μg ml-1. All tested A. solani isolates were the least sensitive to tea tree oil (1323.97-3307.08 μg l-1)