Quality monitoring at fusion welding of polyethylene high-density pipes

The paper presents the main parameters of fusion welding and their Off - line analysis of Polyethylene high-density (PE-HD) pipes. By direct measurements of voltage and current at the coupler, inductive and the resistant character changes in amplitude modulation waveforms of the measured signal are observed. In early measuring device analyzes the scanned parameters with certain types of fittings and compares them with the tested and measured parameters is done by welding machines. There can be seen the time delay or “dead time” when the system analyzes the parameters and dimensioned regulatory function of the system

Nadzor kvalitete elektrofuzijskog zavarivanja polietilenskih cijevi visoke gustoće

The paper presents the main parameters of fusion welding and their Off - line analysis of Polyethylene high-density (PE-HD) pipes. By direct measurements of voltage and current at the coupler, inductive and the resistant character changes in amplitude modulation waveforms of the measured signal are observed. In early measuring device analyzes the scanned parameters with certain types of fittings and compares them with the tested and measured parameters is done by welding machines. There can be seen the time delay or “dead time” when the system analyzes the parameters and dimensioned regulatory function of the system.U radu se prikazuju glavni parametri fuzijskog zavarivanja te njihova Off – line analiza PE-HD cijevi. Izravnim mjerenjem napona i struje na spojnici induktivnog i djelatnog karaktera uočene su promjene u amplitudnoj modulaciji valnih oblika mjerenih signala. Početkom mjerenja uređaj analizira skenirane parametre sa pojedine vrste spojnice i uspoređuje ih sa ispitanim i izmjerenim parametrima koje je odradio sam uređaj za zavarivanje. Upravo se tu vidi zadrška u vremenu tzv. „mrtvo vrijeme“ kada sustav analizira parametre i dimenzionira sustav regulatorske funkcije

Comparison of extraction agents for metal determination in sediments from artificial lakes and rivers in Serbia

The purpose of this paper was to investigate the effectiveness of three different extraction agents for the extraction of 25 elements from sediment samples collected from 4 artificial lakes and 12 rivers in Serbia (33 samples in total). The extraction efficiency of the agents was evaluated by its ability to extract the highest quantity of the elements. For that purpose, three acids (1M HCl, 2M HNO3 and 0.43M CH3COOH) have been used. Inductively coupled plasma atomic emission spectrometry (ICP-OES) was used for quantitative determination of following elements: Al, As, B, Ba, Be, Bi, Ca, Cd, Cr, Co, Cu, Fe, Hg, K, Li, Mg, Mn, Ni, Na, Pb, Sb, Se, Sr, V, and Zn. The extraction with 1M HCl has shown the best results for the majority of investigated elements (especially Sr, Mn and Ca). Antimony (Sb) was detected only after extraction with 0.43M CH3COOOH, while selenium (Se) could not be detected when 2M HNO3 was applied as extraction agents. The present study could be very useful for choosing a suitable method for specific elements and also can be helpful in the evaluation of the contaminants in freshwater sediments in Serbia. This might contribute to environmental risk assessment of the present elements

Long term grassland vegetation changes: Case study Nature Park Stara Planina (Serbia)

Changes in grassland flora and vegetation Caused by inadequate management, primarily under-grazing and grass-lands abandonment were studied in the south-east region of Serbia - Mt. Stara Planina, the largest mountain massif of the country. This mountain is one of the major centres of tertiary and endemic-relict plant species that remains in ravines, and glacial relics and mountain endemic species. The paper presents an analysis and comparison of previous (about 30 years ago) and current biodiversity of the most common grasslands, such as: ass. Festuco-Agrostietum vulgaris, Agrostio-Asphodeletum albae. Koelerietum montanae, Agrostietum vulgaris, Festucetum spadiceae, Nardetum strictae, Poetum molinerii-Plantaginetum carinatae, Poetum violaceae and Seslerietum coerulantis. Both environmental and human impacts on grassland vegetation were discussed and a proposal of sustainable grassland use and management is given

Effectiveness of granular matrix sensors in different irrigation treatments and installation depths

Continuous monitoring of soil moisture content plays a key role in irrigation scheduling and yield formation. This study was conducted to derive the technique and efficiency of application of granular matrix sensors (GMSs) in a sprinkler irrigation system of maize (Zea mays L.). Two irrigation (a2 = 60%- 100% of field capacity (FC), a3 = 80%-100% of FC) treatments were imposed during two growing seasons (2010, 2012) and compared with rainfed control plots (a1). GMSs are used as an indirect method for monitoring soil water status at two depths (b1 = 15 cm and b2 = 30 cm) in order to make a decision on when to irrigate. The sensors used in this study were calibrated using a mass-based gravimetric method. In both growing seasons, irrigation treatment and installation depths have a significant influence (P<0.01) on soil water content. Sensors have shown a satisfactory response to wetting and drying periods in irrigation scheduling at 30-cm depth. Yet, due to variability of weather conditions, a slow response to wetting and drying was recorded in periods with intensive rainfall events (2010) and drought conditions with frequent irrigation intervals (2012)

Long term grassland vegetation changes: Case study Nature Park Stara Planina (Serbia)

Changes in grassland flora and vegetation caused by inadequate management, primarily under-grazing and grasslands abandonment were studied in the south-east region of Serbia — Mt. Stara Planina, the largest mountain massif of the country. This mountain is one of the major centres of tertiary and endemic-relict plant species that remains in ravines, and glacial relics and mountain endemic species. The paper presents an analysis and comparison of previous (about 30 years ago) and current biodiversity of the most common grasslands, such as: ass. Festuco-Agrostietum vulgaris, Agrostio-Asphodeletum albae, Koelerietum montanae, Agrostietum vulgaris, Festucetum spadiceae, Nardetum strictae, Poetum molinerii-Plantaginetum carinatae, Poetum violaceae and Seslerietum coerulantis . Both environmental and human impacts on grassland vegetation were discussed and a proposal of sustainable grassland use and management is given

Quantification of morphology of canine circumanal gland tumors: a fractal based study

Circumanal gland tumors are very common neoplasms of dogs. Their classification relies on microscopic examination and is further supported by a few immunohistochemical markers that help indicate their prognosis. However, new additional tests would be highly useful. The purpose of this study was to develop such a test using fractal analysis which is increasingly being applied in science, especially in the field of biomedicine. A total of 53 circumanal gland tumors were chosen from our department archives. After a precise histological classification according to the World Health Organization classification, the number of de novo classified samples was as follows: 15 adenomas, 11 epitheliomas, 21 well differentiated carcinomas, 6 poorly differentiated carcinomas. Ten samples of normal circumanal gland were also included as control. All samples were immunohistochemicaly stained with vimentin. All immunohistochemical reactions were photographed at two different magnifications -100X and 400X and converted to 1 bit in black and white (bitmap) images thus enhancing the positive vimentin reactions. These images were used for the assessment of fractal dimension applying the box counting method and computer software Fractalyse. To determine the significance of results, conventional statistics were performed using Statistica software. The overall vimentin stain score was significantly higher in epitheliomas and carcinomas than in normal circumanal glands (CG) or adenomas. Mean values of fractal dimension estimated at magnification 100X and 400X were as follows: normal CG 1.318 and 1.372, CG adenomas 1.384 and 1.408, CG epitheliomas 1.547 and 1.597, CG well differentiated carcinomas 1.569 and 1.607, CG poorly differentiated carcinomas 1.679 and 1.723. Significant differences (at level of 5%) of these values were observed between individual groups of CG adenomas or normal CG, and epitheliomas or carcinomas. The above results indicate vimentin immunohistochemistry staining and assessment of fractal dimension as an ancillary diagnostic method of choice when discerning between benign and malignant tumors of circumanal glands. Additional development of the method of fractal dimension assesment may yield a possibility for this tool to successfully discern between all of the types of CG tumors.</p