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1
Content available A closed-loop power controller model of series-resonant-inverter-fitted induction heating system
Pal P., Roy D., Datta A., Sadhu P. K., Banerjee A.
Archives of Electrical Engineering
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2016
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Vol. 65, nr 4
827--841
EN
This paper presents a mathematical model of a power controller for a high-frequency induction heating system based on a modified half-bridge series resonant inverter. The output real power is precise over the heating coil, and this real power is processed as a feedback signal that contends a closed-loop topology with a proportional-integral-derivative controller. This technique enables both control of the closed-loop power and determination of the stability of the high-frequency inverter. Unlike the topologies of existing power controllers, the proposed topology enables direct control of the real power of the high-frequency inverter.
2
Bezpieczeństwo ratowników górniczych w zadymionej strefie zagrożenia w aspekcie połączenia zastępu linką ratowniczą
Pal P., Mroziński K.., Dopierała J., Ściuk A.
Bezpieczeństwo Pracy i Ochrona Środowiska w Górnictwie
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2015
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nr 7
11--23
PL
Bezpieczeństwo zastępu w czasie prowadzenia prac ratowniczych w warunkach braku, bądź ograniczonej widoczności, będącej wynikiem silnego zadymienia, jest uzależnione od doświadczenia zastępowego i ratowników. Wchodząc do zadymionej strefy, zastępowy jest zobowiązany do połączenia ratowników w zastępie linką ratowniczą. Nie zastosowanie się do tego obowiązku może prowadzić do tragicznych skutków. W artykule uzasadniono wagę takiego połączenia ratowników oraz zwrócono uwagę na problemy wynikające z zastosowania różnego rodzaju linek ratowniczych. Przedstawiono też sposoby połączenia ratowników w wybranych krajach oraz efekty prac związanych z opracowaniem nowych rozwiązań w tym zakresie, prowadzonych w ramach strategicznego projektu badawczego NCBiR: „Poprawa bezpieczeństwa pracy w kopalniach”.
EN
The safety of mine rescue teams during rescue operations in areas of low or zero visibility due to high smoke concentration depends on the professional experience of the mine rescue officer and the rescuers. Another critical safety component is, among others, connecting the rescue team members with a lifeline. This paper discusses the problems caused by the use of various lifeline types, e.g. rope entanglement or lifeline slack causing it to rest on the floor. This article also presents the methods of connecting the rescuers with rope used in selected countries. The development of new solutions for lifeline use has found that the connection of rescuers with a lifeline made of lengths of band or rope will, under certain conditions, result in effects specific to the properties of the linking element used. Hence, it is not possible to completely eliminate the primary weaknesses of fastening provided by a lifeline. However, a prototype has been created to minimise those weaknesses, by which rescuers are connected with personal retractable flexible bands, each 1.75 m long. The fastening is designed as a retractable gear attached to the waist belt or to the shoulder-mounted apparatus of every rescuer, where the free end of the retractable lifeline in that gear features a snap-hook which attaches to the belt worn by the preceding rescuer. Research is still in progress to develop a solution to keep the lifeline or rope at a constant tension in order to easily locate it and provide freedom of movement to the rescuer.
3
Content available remote Generation of SH-Type waves due to shearing stress discontinuity in a sandy layer overlying an Isotropic and inhomogeneous elastic half-space
Pal P., Mandal D.
Acta Geophysica
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2014
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Vol. 62, no. 1
44--58
EN
The generation of SH-type waves due to sudden application of a stress discontinuity which moves after creation at the sandy layer of finite thickness overlying an isotropic and inhomogeneous elastic halfspace is considered. The displacements are obtained in exact form by the method due to Cagniard modified by De Hoop. The numerical calculations are obtained. Two cases of shearing stress discontinuities are considered for different sandiness parameters. The graphs are drawn to show the effect of sandiness in the displacement components
4
Content available An Examination of Shoulder Postures and Moments of Force Among Different Skill Levels in the Wool Harvesting Industry
Gregory D. E., Pal P., Carman A., Milosavljevic S., Callaghan J. P.
International Journal of Occupational Safety and Ergonomics
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2009
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Vol. 15, No. 4
409--418
EN
The wool harvesting industry employs workers of varying skill levels that differ in both quality and number of harvested fleeces. As it was unknown how skill affected parameters such as joint posture and loading, the current study comparatively examined 140 wool harvesting workers representing 4 skill levels during wool harvesting competitions. Three-dimensional upper limb postures and peak and cumulative shoulder moments were calculated for each worker. Results indicated that elite wool harvesters, in general, used different shoulder postures to perform the harvesting tasks and were thus exposed to different shoulder moments as compared to the lower skill levels. It is plausible that these adopted postures allow the higher class workers to perform their job with higher quality and greater speed as compared to the lower ranked workers. Postural-based training may help improve technique in lower ranked workers and enable these workers to achieve higher ranked status.
5
Content available remote Segmentation of cloud image using the feature of fractal dimension
Pal P., Mukherjee A.
Image Processing & Communications
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2008
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Vol. 13, no 3-4
53-58
EN
Different ways of segmentation for cloud images have been developed. The time complexity of these algorithms become vital for implementation. Implementation of Otsu's method of thresholding for segmentation purpose take reasonable computational time for multiple class problem. In this paper, a fractal based segmentation method is developed. The technique is compared to modified version of Otsu's algorithm with reduced time complexity. The time complexity of the fractal based method is favourable and the results of segmentation are also comparable.
6
Content available remote Removal of noise from sodar data using ABL characteristics guided morphological filter
Pal P., Mukherjee A., Chanda B.
Image Processing & Communications
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2007
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Vol. 12, no 1
5-15
EN
There is potential of using acoustic sounder system to study boundary layer meteorology. The repeatable patterns on sodar-images become necessary and useful to find suitable techniques for computer analysis and interpretation. Image processing and pattern recognition approaches have been explored for SODAR signal processing. Like all real digital images, sodar-images are also degraded with noise, thereby complicating the sodar-patterns. Since the exact mathematical model of the system is not available, challenges exist to minimise the effect of noise present in the sodar-images. This will lead to better extraction of the sodar-patterns from the sodar-images. Noise cleaning algorithm for sodar-images have been considered here based on the morphology of ABL pattern characteristics. The results of this algorithm compare favourably with the existing methods.
7
Content available remote An initialization-free clustering technique based on symmetry
Pal P., Chanda B.
Image Processing & Communications
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2007
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Vol. 12, no 2
17-25
EN
In this paper we propose a clustering technique that extracts sub-clusters based on a simple measure of isotropic symmetry. These sub-clusters are then used as building blocks to form final clusters of any arbitrary shape including concave ones through merging iteratively. The proposed method is tested on multi-spectral satellite imagery and a good result is obtained. Major advantages of this method are its simplicity and being free from initial guess about the cluster centres, shapes and the number of clusters. However, this algorithm is more suitable for mul-tivariate images even with very high spectral resolution.
8
Surface waves in a heterogeneous layer over a liquid saturated poro-elastic solid half space
Pal P.
Acta Geophysica Polonica
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2000
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Vol. 48, nr 2
195-205
EN
Rayleigh waves in a heterogeneous layer over a saturated half space are investigated under plane strain conditions. The dispersion equation is derived using the methods for propagation of free waves in layered media. The effect of heterogeneity on phase velocity is studied by taking different numerical values of heterogeneity factor and the result is shown graphically.
9
Generation of SH waves by a moving stress discontinuity in an anisotropic soil layer over an elastic half space
Pal P., Kumar L.
Acta Geophysica Polonica
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2000
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Vol. 48, nr 4
465-478
EN
The paper considers the generation and propagation of SH waves in an anisotropic soil layer overlying an elastic half space by a moving stress discontinuity. Stress discontinuity moves with non-uniform velocity and is impulsive in nature. Theories of Biot and Weiskopf are used to formulate the problem. Solid displacement component is evaluated on the free surface of soil layer by using Cagniard-De Hoop special reduction technique. Solution is discussed on the basis of Ray theory and some wave front patterns are obtained. The numerical result is calculated for a special case and compared with earlier results.
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