Control methods for arc welding power supplies

Welding is one of the most important process of modern industry. Welding technology is used in the manufacture and repair a wide variety of products from different metals and alloys. In this thesis the different aspects of arc welding were discussed, such as stability and control of welding arc, power supplies for arc welding (especially the welding inverters because it is the most modern welding power source). All parameters of power source have influence on the arc parameters and its by-turn influence on quality. The ways of control for arc welding inverter power sources have been considered. Calculations and modeling in Matlab/Simulink were done for PI control method. All parameters of power source have influence on the arc parameters and its by-turn influence on quality.

A proposal for a repertoire of software testing methods

Nowadays software testing and quality assurance have a great value in software development process. Software testing does not mean a concrete discipline, it is the process of validation and verification that starts from the idea of future product and finishes at the end of product’s maintenance. The importance of software testing methods and tools that can be applied on different testing phases is highly stressed in industry. The initial objectives for this thesis were to provide a sufficient literature review on different testing phases and for each of the phases define the method that can be effectively used for improving software’s quality. Software testing phases, chosen for study are: unit testing, integration testing, functional testing, system testing, acceptance testing and usability testing. The research showed that there are many software testing methods that can be applied at different phases and in the most of the cases the choice of the method should be done depending on software type and its specification. In the thesis the problem, concerned to each of the phases was identified; the method that can help in eliminating this problem was suggested and particularly described.

Sensitive bromatometric assay methods for finasteride in pharmaceuticals

Three sensitive spectrophotometric methods are presented for the determination of finasteride in bulk and in tablets. The methods rely on the use of bromate-bromide reagent and three dyes namely, methyl orange, indigocarmine and thymol blue as reagents. They involve the addition of a measured excess of bromate-bromide reagent to finasteride in acid medium, and after the bromination reaction is judged to be complete, the unreacted bromine is determined by reacting with a fixed amount of either methylorange and measuring the absorbance at 520 nm (method A) or indigocarmine and measuring the absorbance at 610 nm (method B) or thymol blue and measuring the absorbance at 550 nm (method C). In all the methods, the amount of insitu generated bromine reacted corresponds to the amount of finasteride. The absorbance measured at the respective wavelength is found increase linearly with the concentration of finasteride. Beer's law is obeyed in the ranges 0.25- 2.0, 0.5-6.0 and 1-12 µg mL-1 for method A, method B and method C, respectively. The calculated molar absorptivity values are 5.7x10(4), 3.12x10(4) and 1.77x10(4) L mol-1 cm-1 respectively, for method A, method B and method C, and the corresponding Sandell sensitivity values are 0.0065, 0.012 and 0.021 µg cm-2. The limits of detection (LOD) and quantification (LOQ) are also reported for all the methods. Accuracy and, intra-day and inter-day precisions of the methods were established according to the current ICH guidelines. The methods were successfully applied to the determination of finasteride in commercially available tablets and the results were found to closely agree with the label claim. The results of the methods were statistically compared with those of a reference method by applying Student's t-test and F-test. The accuracy and reliability of the methods were further confirmed by performing recovery tests via standard addition procedure.

Energy harvesting methods for wireless sensor nodes in heavy-duty vehicles

The number of autonomous wireless sensor and control nodes has been increasing rapidly during the last decade. Until recently, these wireless nodes have been powered with batteries, which have lead to a short life cycle and high maintenance need. Due to these battery-related problems, new energy sources have been studied to power wireless nodes. One solution is energy harvesting, i.e. extracting energy from the ambient environment. Energy harvesting can provide a long-lasting power source for sensor nodes, with no need for maintenance. In this thesis, various energy harvesting technologies are studied whilst focusing on the theory of each technology and the state-of-the-art solutions of published studies and commercial solutions. In addition to energy harvesting, energy storage and energy management solutions are also studied as a subsystem of a whole energy source solution. Wireless nodes are also used in heavy-duty vehicles. Therefore a reliable, long-lasting and maintenance-free power source is also needed in this kind of environment. A forestry harvester has been used as a case study to study the feasibility of energy harvesting in a forestry harvester’s sliding boom. The energy harvester should be able to produce few milliwatts to power the target system, an independent limit switch.

Simple and sensitive spectrophotometric methods for the determination of acebutolol hydrochloride in bulk sample and pharmaceutical preparations

A direct, extraction-free spectrophotometric method has been developed for the determination of acebutolol hydrochloride (ABH) in pharmaceutical preparations. The method is based on ion-pair complex formation between the drug and two acidic dyes (sulphonaphthalein) namely bromocresol green (BCG) and bromothymol blue (BTB). Conformity to Beer's law enabled the assay of the drug in the range of 0.5-13.8 µg mL-1 with BCG and 1.8-15.9 µg mL-1 with BTB. Compared with a reference method, the results obtained were of equal accuracy and precision. In addition, these methods were also found to be specific for the analysis of acebutolol hydrochloride in the presence of excipients, which are co-formulated in the drug.

Highly sensitive spectrophotometric methods for the determination of olanzapine

Highly sensitive and selective spectrophotometric methods (A and B) were developed for the determination of micro amounts of olanzapine (OLZ). Method A (direct method) is based on the oxidation of olanzapine with a known excess of iodine monochloride (ICl) in an acidic medium. Under the same condition, thymol blue was iodinated by unreacted ICl, and the absorbance of uniodinated thymol blue was measured at 536 nm. The decrease in ICl concentration is a measure of drug concentration. In method B (indirect method), oxidation of OLZ by a known excess of Ce(IV) in sulfuric acid medium followed by the reaction of unreacted Ce(IV) with leuco crystal violet (LCV) to crystal violet (CV), which is measured in an acetate buffer medium ( pH 4.9) at 580 nm. These methods obey the Beer's law in the concentration range of 0.2-1.6 µg mL-1 (method A) and 0.1-1.4 µg mL-1 (method B). The developed procedures have been successfully applied to the determination of OLZ in pure and in dosage forms. The results exhibit no interference from the presence of excipients. The reliability of the methods was established by parallel determination of OLZ against the reference method.