A mathematical model for determining elliptical volumes of fluid contents by means of ultrasound

Predložena je formula za izračunavanje elipsoidnih volumena tekućeg sadržaja pomoću ultrazvuka kojim su izmjereni potrebni elementi za proračun. Predložena formula glasi: V = ABCπ/6. Model je ispitan na aparatu koji je za ovu priliku posebno konstruiran. Zbog tehničkih karakteristika aparature područje mjerenja bilo je ograničeno na volumene od 50 do 112 ml. Rezultati 32-ju mjerenja na modelu pokazali su veoma visoku povezanost između proračunatih i pravih vrijednosti koja je iznosila r = 0,979 i veoma točnu procjenu (najmanja razlika između proračunatih i pravih vrijednosti iznosila je 0,1 ml, a najveća 10,0 ml), pa se otvara mogućnost primjene ovog modela u medicinskoj dijagnostičkoj praksi.A mathematical model for calculating elliptical volumes of fluid contents by means of ultrasound is described. The suggested formula is: V = ABCπ/6. The model was investigated on the apparatus which was especially constructed for the purpose. Because of the technical characteristics of the apparatus the measuring range was limited to the volumes from 50 to 112 ml. The results of 32 measurements on the model showed a very high correlation between the calculated and real values (r = 0.979), and a high accuracy of evaluation (the lowest difference between the calculated and real values was 0.1 and the highest 10.0 ml). This opens a possibility of applying the model in medical diagnostic practice

Study of Barium Bismuth Titanate Prepared by Mechanochemical Synthesis

Barium-bismuth titanate, BaBi4Ti4O15 (BBT), a member of Aurivillius bismuth-based layer-structure perovskites, was prepared from stoichiometric amounts of barium titanate and bismuth titanate obtained via mechanochemical synthesis. Mechanochemical synthesis was performed in air atmosphere in a planetary ball mill. The reaction mechanism of BaBi4Ti4O15 and the preparation and characteristics of BBT ceramic powders were studied using XRD, Raman spectroscopy, particle analysis and SEM. The Bi-layered perovskite structure Of BaBi4Ti4O15 ceramic forms at 1100 degrees C for 4 h without a pre-calcination step. The microstructure of BaBi4Ti4O15 exhibits plate-like grains typical for the Bi-layered structured material and spherical and polygonal grains. The Ba2+ addition leads to changes in the microstructure development, particularly in the change of the average grain size

MECHANIZATION COSTS IN FRUIT PRODUCTION

Suvremena voćarska proizvodnja zahtijeva ulaganja u specijalizirane strojeve koja se kreću od oko 327 do gotovo 397 tisuća kuna, što čini od 33,65 do 39,12% ukupnih ulaganja u preporučene, ekonomski održive modele voćarske proizvodnje u našim uvjetima (3-5 ha). Udio mehanizacije u ukupnim troškovima rada po voćnim vrstama je od 10,70 do 16,29%, a u ukupnim satima rada je udio mehanizacije od 8,17 do 14,23%. Cijene sata rada mehanizacije u voćnjacima od 1 ha su od 300,54 do 399,76 kuna, dok su cijene za voćnjak površine 5 ha od 101,04 do 120,89 kuna. Ukupni troškovi mehanizacije su za voćnjak od 1 ha od 24.784 do 37.289 kuna, dok su isti troškovi za voćnjak od 5 ha od 18.719 do 26.835 kuna. Kako se s porastom veličine voćnjaka značajno smanjuju troškovi rada mehanizacije, uočljivo je povećanje koeficijenta parcijalne ekonomičnosti mehanizacije za preko 3 puta (od 3,5 do 3,8 puta) kod površine od 5 ha u odnosu na voćnjake površine 1 ha. Pokazatelji proizvodnosti rada također su od 10,2 do 17,6% veći na većim površinama.The modern fruit-growing production requires investments in specialized mechanization varying from 327,000 to 397,000 kn, which makes from 33.65 to 39.12 % of total investments in recommended, economy sustainable models of fruit-growing production in our conditions (3-5 ha). Mechanization share in total work cost is from 10.70 to 16.29 %, and in the total working hours from 8.17 to 14.23 %. The prices of working hour for mechanization in 1 ha orchards are from 300.54 to 399.76 kn, while the same prices for the 5 ha orchards are from 101.04 to 120.89 kn. The total mechanization cost for 1 ha orchard is from 24,784 to 37,289 kn, while the cost for the 5 ha orchard is from 18,719 t0 26,835 kn. With increasing orchard size the mechanization costs decrease, and mechanization partial economy coefficient increases more than 3 times (from 3.5 to 3.8 times) for the 5 ha orchard in comparison with 1 ha orchard size. Work efficiency indicators are from 10.2 to 17.6 % higher for bigger areas

Joining of composite materials based on Al-Si alloys by using the GMAW process

The aim of this paper is to presents a procedure of joining composite materials on aluminium base by using the GMAW process. The experiment included welding of the aluminium base composite with three different types of filler materials in the form of wire: AlMg4.5Zr, AlMg5 and AlSi5, and comparative analysis of the macroscopic and microscopic examination results. Base material was A356 Al-Si alloy composite containing 10 wt. % Al2O3. Average size of Al2O3 particles was 35 μm. The A356 matrix alloy was modified with the addition of 0.03 wt. % Sr. Composite was produced by the compocasting process. The results show that composite material with Al-Si matrix can be successfully welded by using the GMAW process. Results of macro and micro analysis show that the most favourable results were obtained by using the AlSi5 wire as filler material

Effect of thixocasting and heat treatment on the tribological properties of hypoeutectic Al-Si alloy

This paper presents results of structural, mechanical and tribological tests of thixocast hypoeutectic Al-Si alloy A356 (EN AlSi7Mg0.3). The pin-on-disc tribometer was used to carry out tribological tests under dry sliding conditions at different loads. Two sets of specimens were used as pin materials. The first one was taken from the original alloy billet and the second one from thixocast alloy. Heat treatment was applied on both sets of specimens. The results showed that, for all applied loads, heat treatment improved tribological properties, while improvements caused by additional thixocasting were not systematic, i.e. lower friction coefficient was noticed just for lower specific loads. Overall better wear resistance of thixocast materials, compared to the originally alloy, was attributed mainly to their higher silicon content. (c) 2007 Elsevier B.V. All rights reserved

A study of the sex ratio of the ticks (Acarina, Ixodidae) of Serbia

A study of the sex ratio of the ten tick species in West, East and South-East Serbia between 1984, and 1990. revealed the following: the relative number of each sex was significantly different from the expected one (1:1) testing to unequal distribution in the total number of collected ticks and within individual species, with the exception of Dermacentor pictus

Effects of age-targeted treatment of intestinal parasite infections in Serbia

A survey of intestinal parasite infections in schoolchildren throughout Serbia revealed an area of endemic infection where 31% of the children examined were found to be infected with Giardia lamblia, Enterobius vermicularis, Ascaris lumbricoides and Trichuris trichiura. All infected children were treated with metronidazole for giardiasis and mebendazole for helminthic infections. A post chemotherapy survey was performed 3 months later to assess the efficacy of treatment, showing a decrease in the prevalence of all species, thus indicating drug efficacy of 66-100%. A second survey, performed 13 months after chemotherapy to assess the rates of reinfection, showed that only Ascaris lumbricoides prevalence returned to the pre-treatment level. The results of this field study prove chemotherapy to be an important tool in the control of intestinal parasite infections

Appearance of a hard layer (alpha-case) on the surface of Ti-6Al-4V surgical implant castings

Light microscopy, scanning electron microscopy (SEM) and X-ray diffraction analysis combined with macro and microhardness measurements were performed to characterize a hard layer (alpha-case) forming on the surface of Ti-6Al-4V surgical implants castings. The thickness of alpha-case was found to be approximately 200 mu m, while its hardness was two times higher than the hardness in the core of castings. No presence of the beta phase was detected in the alpha-case.Current Research in Advanced Materials and Processes, 6th Conference of the Yugoslav-Materials-Research-Society, Sep 13-17, 2004, Herceg Novi, Montenegr

The effect of annealing temperatures and cooling rates on microstructure and mechanical properties of investment cast Ti-6Al-4V alloy

Production of investment castings of titanium alloys was considerably increased during last years due to the significant cost savings compared to complicated machined parts. However, the disadvantage of as-cast titanium alloys is that the heat-treatment remains only a limited option for improvement of their properties. The object of this paper was to study the effect of heat-treatment of investment cast Ti-6Al-4V alloy performing X-ray diffraction analysis, light microscopy and quantitative metallography together with hardness and room temperature tensile tests. The effect of annealing temperatures (above and below beta transus temperature) and cooling rates on microstructure and mechanical properties was discussed in terms of the beta - GT alpha transformation. The results of this paper also show that, besides heat treatment parameters, melting and casting practice together with mold technology strongly influence the properties of castings. (c) 2004 Elsevier Ltd. All rights reserved

Study on bi-layered ceramics powders prepared by the mechanochemical synthesis

Bi-layered structured ferroelectric materials-bismuth titanate, Bi4Ti3O12 (BIT) and barium-bismuth titanate, BaBi4Ti4O15 (BBT) powders were prepared by homogenization and sintering of mixture of stehiometric quantities of bismuth titanate and barium titanate obtained via mechanochemical synthesis. The Bi4Ti3O12 ceramic was obtained at 1000 degrees C for 4 h and BaBi4Ti4O15 ceramic at 1100 degrees C for 4 h. The phase formation and properties of Bi4Ti3O12 and BaBi4Ti4O15 were studied using XRD, Raman spectroscopy, EDS and SEM. Microstructure of Bi4Ti3O12 and BaBi4Ti4O15 exhibits plate-like grains typical for the bi-layered structured material. The Ba2+ addition leads to the change in the microstructure development, particularly in the change of the average grain size. Crow