A Reciprocal Transformation for the Constant Astigmatism Equation

We introduce a nonlocal transformation to generate exact solutions of the constant astigmatism equation $z_{yy} + (1/z)_{xx} + 2 = 0$. The transformation is related to the special case of the famous B\"acklund transformation of the sine-Gordon equation with the B\"acklund parameter $\lambda = \pm1$. It is also a nonlocal symmetry

Possibilities of 3D machining of materials by abrasive water jets

Machining of materials through classical way, i.e. using conventional tools for turning, drilling, milling, grinding and polishing, has some limits that can be overcome applying an abrasive water jet (AWJ). Therefore, some possibilities of 3D machining by AWJ placed on 6 axes robot have been tested. Programming of traverse speeds and tilting angles of cutting head was based on Hlaváč’s theoretical model. Low pressure pump has been used for tests. Because of very low pumping pressure, a selfdesigned and manufactured special mixing chamber was used in the experiments. The article deals with preliminary results and points at the direction of further research

Investigation of significant parameters during abrasive waterjet turning

This paper presents an investigation of abrasive waterjet turning (AWJT). The purpose of the article was to investigate significant parameters of the turning process and to evaluate their impact on the turning product. The influence of the traverse speed, the rotational speed, and the relative position of the jet to the specimen (lateral jet shift) were investigated. Based on the previous research done in this field, the multi-pass tangential turning method was selected. Rotational speed does not seem to have a significant impact on the AWJ turning process. However, the relative position of the jet is a key parameter for improving the efficiency of the process. Increasing the lateral jet shift causes the volume of the material removed to increase until the optimal impact angle is reached. These findings need to be extended in order to adjust AWJT. Without these improvements, a comparison of jet to traditional technologies is inappropriate.Web of Science1416art. no. 438

Abrasive waterjet (AWJ) forces-indicator of cutting system malfunction

Measurements enabling the online monitoring of the abrasive waterjet (AWJ) cutting process are still under development. This paper presents an experimental method which can be applicable for the evaluation of the AWJ cutting quality through the measurement of forces during the cutting process. The force measuring device developed and patented by our team has been used for measurement on several metal materials. The results show the dependence of the cutting to deformation force ratio on the relative traverse speed. Thus, the force data may help with a better understanding the interaction between the abrasive jet and the material, simultaneously impacting the improvement of both the theoretical and empirical models. The advanced models could substantially improve the selection of suitable parameters for AWJ cutting, milling or turning with the desired quality of product at the end of the process. Nevertheless, it is also presented that force measurements may detect some undesired effects, e.g., not fully penetrated material and/or some product distortions. In the case of a proper designing of the measuring device, the force measurement can be applied in the online monitoring of the cutting process and its continuous control.Web of Science147art. no. 168

Abrasive waterjet (AWJ) forces - Potential indicators of machining quality

The necessity of monitoring the abrasive waterjet (AWJ) processes increases with the spreading of this tool into the machining processes. The forces produced on the workpiece during the abrasive waterjet machining can yield some valuable information. Therefore, a special waterjet-force measuring device designed and produced in the past has been used for the presented research. It was tested during the AWJ cutting processes, because they are the most common and the best described up-to-date AWJ applications. Deep studies of both the cutting process and the respective force signals led to the decision that the most appropriate indication factor is the tangential-to-normal force ratio (TNR). Three theorems concerning the TNR were formulated and investigated. The first theorem states that the TNR strongly depends on the actual-to-limit traverse speed ratio. The second theorem claims that the TNR relates to the cutting-to-deformation wear ratio inside the kerf. The third theorem states that the TNR value changes when the cutting head and the respective jet axis are tilted so that a part of the jet velocity vector projects into the traverse speed direction. It is assumed that the cutting-to-deformation wear ratio increases in a certain range of tilting angles of the cutting head. This theorem is supported by measured data and can be utilized in practice for the development of a new method for the monitoring of the abrasive waterjet cutting operations. Comparing the tilted and the non-tilted jet, we detected the increase of the TNR average value from 1.28 +/- 0.16 (determined for the declination angle 20 degrees and the respective tilting angle 10 degrees) up to 2.02 +/- 0.25 (for the declination angle 30 degrees and the respective tilting angle of 15 degrees). This finding supports the previously predicted and published assumptions that the tilting of the cutting head enables an increase of the cutting wear mode inside the forming kerf, making the process more efficient.Web of Science1412art. no. 330

Possibilities of utilization of digestate solid fraction as an alternative fertilizer

Import 22/07/2015Z hlediska možnosti získávání obnovitelných zdrojů energie se anaerobní digesce v posledních letech stává velice populární. Neopomenutelnou otázkou zůstává, jak efektivně zhodnotit, vedlejší produkt - digestát, jenž vzniká v bioplynových reaktorech. Digestát je dobrým zdrojem rychle uvolnitelného dusíku a může z části nahradit hnojení kejdou nebo i aplikaci minerálních dusíkatých hnojiv. Diplomová práce v teoretické části poskytuje základní přehled problematiky digestátů z pohledu jejich úpravy, skladování, dávkování a aplikace na zemědělskou půdu. V praktické části se autor zaměřuje na využití separátu (pevné složky digestátu) jako alternativního hnojiva pro zemědělské účely. Prezentovány jsou výsledky polního a laboratorního pokusu, včetně výsledků monitoringu půd a rostlin po aplikaci separátu. V další části jsou zhodnoceny hnojivé účinky digestátu s průmyslovým typem hnojiva.From the viewpoint of obtaining renewable energy anaerobic digestion in recent years has become very popular. Inalienable question remains how to effectively evaluate a byproduct - the digestate, which is generated by biogas reactors. Digestate is a good source of nitrogen and quickly releasable can partially replace fertilizing manure or mineral nitrogen fertilizer application. Diploma thesis in theoretical part provides a basic overview of the issues from the perspective of digestate treatment, storage, dispensing and application on agricultural land. In the practical part, the author focuses on the use of digestate fiber as an alternative fertilizer for agricultural purposes. Presented are the results from field and laboratory experiment, including the results of monitoring of soils and plants after application of digesate fiber. The next section evaluates the fertilizing effects of digestate with industrial fertilizer type.Prezenční546 - Institut environmentálního inženýrstvívýborn

Performance Provided to the Flats Occupants

The title of bachelor work is Performance Provided to the Flats Occupants. Main targets are to define separately each service, detect costs progress of each service and their part in total cost and outline of the future progress. This work is divided in two main parts. The first part is theoritical. It contains terms and information, which are used in the bachelor thesis. From this part comes the next one, which is pratical. For this part was choosen flat, which proper Stavební bytové družstvo v Českých Budějovicích. The analysis of progess is make from transcription of months advance payments rent and for services joint with flat from 1th January 1995 to 1th January 2011. Costs in transcriptions are not final. They are advance payments only. Their range depends on last period expenses. Firstly legal regulations were defined. It was found out that housing co-operatives of DBV type don´t have legal resolutions. Last legal resolutions was the law number 85/1995 Sb. For other types of housing co-operatives the same legal resolutions like for not co-operatives flats are used. There was found that two articles (wages and other services) are wrongly classed by house co-operative. Then it was found that the service payments for a flat in the total payments are 64.42%. Their importance is considerable. The largest representation in the services are the costs for heating. Finally estimation of future prices was made. The costs for heating and water tariffs have tendency to rise. Payments for the lift depend on prices of elektricity and it´s consuption

The financial analysis of the selected retail company

This thesis focuses on financial analysis of a chosen commercial enterprise and it covers the period from 2006 to 2010. For financial analysis was chosen enterprise ESSA, spol. s r.o. from České Budějovice. I used these groups of indicators for the analysis: vertical and horizontal analysis, profitability, activity, indebtedness, liquidity, bankruptcy model, creditworthy model