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Abstract

Experiments were carried out on the PF-1000 plasma focus device, with a deuterium filling and with deuterium puffing from a gas-puff nozzle placed on the axis of the anode face. The current was reaching 2 MA. 15 interferometric frames from one shot were recorded with a Nd:YLF laser and a Mach–Zehnder interferometer, with 10–20 ns delay between the frames. As a result, the temporal and spatial distribution of the linear densities and the radial and axial velocities of the moving of plasma in the dense plasma column could be estimated.

Breeding birds of shelterbelts near Sombor (NW Serbia)

In 2008, breeding birds were studied in the shelterbelts surrounded by arable land NW of Sombor (Vojvodina, NW Serbia). Seven 500 m long sections of wooded shelterbelts were selected and surveyed for birds six times between May and July. Sampling plots differed in tree species composition and dominance, in height of trees, and presence and composition of shrub and herb layers. 22 breeding species were found with a mean density of 9.86 ± 1.47 pairs/km of shelterbelt. The mean number of species per shelterbelt was 8.3 ± 1.2. Species richness ranged from 4 (shelterbelt G) to 14 (shelterbelt D) species. Similarity, measured by the Sørensen index, showed strong qualitative similarity (over 70%) between the compared communities in only 19% of all possible pairs of shelterbelts. The most abundant breeding species were Golden Oriole Oriolus oriolus and Greenfinch Carduelis chloris, with overall linear densities of 2.9 and 2.6 pairs/km, respectively. Overall linear densities of a further four species (Red-backed Shrike Lanius collurio, Syrian Woodpecker Dendrocopos syriacus, Whitethroat Sylvia communis and Cuckoo Cuculus canorus) exceeded 1 pair/km. The densities of breeding birds are compared to those obtained during other studies in Europe and elsewhere.

permanently control the successive intermediate products in the spinning process. The quality of the yarns manufactured is best characterized by the distribution irregularity of yarn linear density that also exerts a considerable influence on parameters such as elongation at break, breaking force, degree of twist, and their coefficients of variation [ 1 , 2 ]. Modern apparatuses used for yarn testing make it possible to create digital images of the predicted appearance of woven and knitted fabrics made of the yarn tested, which provides a possibility of a quick

modulus and linear density on the properties of air-jet textured yarns. Textile Research Journal, 66(7), 452-455. [5] Zhang, J., Zhang, Z., Wang, S., & Qin, X. (2007). Investigation on air texturing process for diacetate blending with polyester filaments. Fibers and Polymers, 8(4), 427-431. [6] Zhang, J., Zhang, Z., Wang, S., & Qing, X. (2007). Properties of core-and-effect air textured yarns blended by diacetate and polyester filaments. Fibers and Polymers, 8(1), 84-88. [7] Rengasamy, R. S., Kothari, V. K., & Patnaik, A. (2004). Effect of process variables and feeder

different weft yarns. The results showed that the linear density of the weft yarn influences the heat transfer through the seersucker woven fabrics. The 1/2 fabric variant gives the biggest temperature difference between the hot plate surface and fabric surface. It means that the 1/2 fabric variant ensures the best thermal insulation among all the investigated seersucker woven fabrics. Acknowledgment This work was financed by the National Science Centre. Poland, within the framework of the project titled “Geometrical, mechanical, and biophysical parameterization of three

Abstract

The aim of this study was to analyse the effects of various fabric parameters on the thermal resistance, thermal conductivity, thermal transmittance, thermal absorptivity and thermal insulation of polyester/cotton double layer knitted interlock fabrics. It was found that by increasing fibre content with higher specific heat increases the thermal insulation while decreases the thermal transmittance and absorptivity of the fabric. It was concluded that double layer knitted fabrics developed with higher specific heat fibres, coarser yarn linear densities, higher knitting loop length and fabric thickness could be adequately used for winter clothing purposes.

Abstract

The aim of this study was to develop statistical models for predicting the air permeability and light transmission properties of woven cotton fabrics and determine the level of correlation between the two parameters. Plain woven fabrics were developed with different warp and weft linear densities, ends per inch and picks per inch. After desizing, scouring, bleaching, drying and conditioning, the air permeability and light transmission properties of the fabric samples were determined. Regression analysis results showed statistically significant effect of the fabric ends, picks and warp linear density on both the fabric air permeability and light transmission. Correlation analysis was performed to analyze the relation between the fabric air permeability and light transmission. A linear equation was also formulated to find the fabric air permeability through transmission of light intensity. A fitted line plot between the air permeability and light transmission exhibited significant correlation with R-sq. value of 96.4%. The statistical models for the prediction of fabric air permeability and light transmittance were developed with an average prediction error of less than 7%.

Abstract

The objective of this study was to model the physical and mechanical properties of 100% cotton slub yarns commonly used in denim and other casual wear. Statistical models were developed using central composite experimental design of the response surface methodology. Yarn’s linear density, slub thickness, slub length and pause length were used as the key input variables while yarn strength, elongation, coefficient of mass variation, imperfections and hairiness were used as response/output variables. It was concluded that yarn strength and elongation increased with increase in linear density and pause length, and decreased with increase in slub thickness and slub length. Yarn mass variation and total imperfections increased with increase in slub thickness and pause length, whereas yarn imperfections and hairiness decreased with increase in slub length. It was further concluded that due to statistically significant square and interaction effects of some of the input variables, only the quadratic model instead of the linear models can adequately represent the relationship between the input and the output variables. These statistical models will be of great importance for the industrial personnel to improve their productivity and reduce sampling.

Abstract

Graphene, a carbon allotrope, became a significant area of research with its superior electrical, mechanical, optical properties, etc. There are several methods to obtain graphene oxide from graphite, one of which is the Hummers method. In this study, several modifications and pre-treatments preceding the Hummers method have been employed. Three different graphene oxide fibers have been produced by three different procedures, i.e. fibers obtained by Hummers method with pre-oxidation step, modified Hummers method and modified Hummers method with pre-oxidation step. It has been observed that pre-oxidation has a significant effect on graphene oxide fiber properties produced by wet spinning process (coagulation). Modified Hummers method without pre-oxidation leads to the highest breaking strength and breaking elongation. Reduced fiber linear density, breaking strength and breaking elongation together with increased crimp were observed in graphene fiber due to the addition of pre-oxidation step.

Abstract

Investigations of the influence of the knit structure, i.e. the loop length and the number of yarns in a loop, on flammability and comfortability are presented in this paper. The investigations were carried out using single jersey knits from Delta TA 18 tex × 2 yarns with five variants of a loop length. Single yarn as well as folded yarn from two single yarns was used in the investigations. Comparison of the results of single-layer knits flammability and air permeability with those of multilayer packet was made. The results obtained show that an increase in the loop length of the knit increases their permeability to air and decreases the burning time as well as increase in the number of layers decreases the air permeability and increases the burning time. Moreover, the similar burning time with significantly different permeability to air can be achieved changing the basic knitting parameters, i.e. the loop length and/or the yarn linear density.