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Open access

Sławomir Kłos and Peter Trebuna

Abstract

This paper proposes the application of computer simulation methods in order to analyse the availability of resources, buffers and the impact of the allocation of workers on the throughput and work-in-progress of a manufacturing system. The simulation model of the production system is based on an existing example of a manufacturing company in the automotive industry. The manufacturing system includes both machining and assembly operations. Simulation experiments were conducted vis-à-vis the availability of the different manufacturing resources, the various allocations of buffer capacities and the number of employees. The production system consists of three manufacturing cells – each cell including two CNC machines – and two assembly stations. The parts produced by the manufacturing cells are stored in buffers and transferred to the assembly stations. Workers are allocated to the manufacturing cells and assembly stations, but the number of workers may be less than number of workplaces and are thus termed ‘multi-workstations’. Using computer simulation methods, the impact of the availability of resources, the number of employees and of the allocation of buffer capacity on the throughput and work-in-progress of the manufacturing system is analysed. The results of the research are used to improve the effectiveness of manufacturing systems using a decision support system and the proper control of resources. Literature analysis shows that the study of the impact of buffer capacities, availability of resources and the number of employees on assembly manufacturing system performance have not been carried out so far.

Open access

Sławomir Kłos and Peter Trebiina

Abstract

This paper proposes the application of the Analytic Hierarchy Process method to support decision making regarding the selection of an Enterprise Resource Planning system in a manufacturing company. The main assumption of the work is that the management of the selection of an ERP system should consider that the most important selection criteria are concerned with the functionality of the ERP system. Besides this, the aspects of total cost of ownership, technical support and implementation time or vendor experience are taken into consideration to guarantee a successful ERP implementation. The proposed procedure of an ERP system selection is dedicated for small and medium manufacturing enterprises. A structure of attributes for the AHP method is proposed on the basis of an analysis and identification of critical success factors. Different kinds of production (make-to-stock, make-to-order and engineer-to-order are taken into consideration). Illustrative examples are also given.

Open access

Sławomir Kłos and Peter Trebuna

Abstract

This paper proposes the application of computer simulation methods to support decision making regarding intermediate buffer allocations in a series-parallel production line. The simulation model of the production system is based on a real example of a manufacturing company working in the automotive industry. Simulation experiments were conducted for different allocations of buffer capacities and different numbers of employees. The production system consists of three technological operations with intermediate buffers between each operation. The technological operations are carried out using machines and every machine can be operated by one worker. Multi-work in the production system is available (one operator operates several machines). On the basis of the simulation experiments, the relationship between system throughput, buffer allocation and the number of employees is analyzed. Increasing the buffer capacity results in an increase in the average product lifespan. Therefore, in the article a new index is proposed that includes the throughput of the manufacturing system and product life span. Simulation experiments were performed for different configurations of technological operations.

Open access

Mingliang Bao, Peter J. Joza, Andrew Masters and William S. Rickert

SUMMARY

A simple, accurate, and reliable method for routine analysis of trace carbonyl compounds, including formaldehyde, acetaldehyde, acetone, propionaldehyde, methyl-ethyl ketone (MEK), butyraldehyde, and crotonaldehyde, in processed tobacco products was developed. One gram of tobacco sample was spiked with a mixture of isotopelabeled carbonyls as internal standards and extracted with water. A portion of aqueous extract was derivatizated with o-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine hydrochloride (PFBHA). The PFBHA derivatives of carbonyls were extracted with hexane and analysed by gas chromatography- mass spectrometry (GC-MS). The accuracy and precision of the method were evaluated with spiked Kentucky Reference Cigarette 3R4F and CORESTA smokeless reference products CRP1, CRP2, CRP3, and CRP4. For the investigated carbonyl compounds, excellent recoveries (95-107%) and precisions (5-10%) were achieved with different spiked tobacco products, with the exception of acrolein, which was found unstable in all tested tobacco products. The linear range of the developed method was from 0.07 to 36 μg/g with limits of quantification ranged from 0.10 to 0.15 μg/g. Using this method, formaldehyde (0.31-6.24 μg/g) and acetaldehyde (0.84-17.7 μg/g) were detected in all tested reference tobacco products. Acetone (0.55-2.12 μg/g) was found in 3R4F, CRP1, CRP2, and CRP3. Detectable levels of propionaldehyde were only found in CRP1 and CRP3. The levels of MEK, butyraldehyde, and crotonaldehyde in all tested reference products were below the method quantification limits. It was found that the effects of storage conditions (storage time, container, and temperature) on yields of carbonyls detected in reference tobacco product samples (3R4F, CRP2, CRP3) were dependent on compound and sample matrix: the concentrations of formaldehyde in all tested reference products gradually increased as the storage time increased, while the concentrations of acetone in 3R4F samples dramatically decreased as the storage time increased. [Beitr. Tabakforsch. Int. 26 (2014) 86-97]

Open access

Peter C. Verhoef and Peter S.H. Leeflang

Abstract

What influence do marketing departments have in companies today? Which factors determine this influence? These are the issues discussed in the present article. Empirical evidence based on data from companies in the Netherlands demonstrates that accountability, innovativeness and customer connections are the three major drivers of influence. The need for a strong marketing department within companies is also discussed, supported by empirical data.

Open access

P. Valent, P. Rončák, M. Maliariková and Š. Behan

Abstract

The way land is used has a significant impact on many hydrological processes that determine the generation of flood runoff or soil erosion. Advancements in remote sensing which took place in the second half of the 20th century have led to the rise of a new research area focused on analyses of land use changes and their impact on hydrological processes. This study deals with an analysis of the changes in land use over a period of almost three centuries in the Myjava River catchment, which has an outlet at Šaštín-Stráže. In order to obtain information about the way the land was used in the past, three historical mappings representing various periods were used: the first (1st) military mapping (1764-1787), second (2nd) military mapping (1807-1869), and a military topographic mapping (1953-1957). The historical mappings have been manually vectorised in an ArcGIS environment to identify various land use categories. The historical evolution of land use was further compared with a concurrent land use mapping, which was undertaken in 2010 and exploited remote sensing techniques. The study also quantifies the impact of these changes on the long-term catchment runoff as well as their impact on flows induced by extreme precipitation events. This analysis was performed using the WetSpa distributed hydrological model, which enables the simulation of catchment runoff in a daily time step. The analysis showed that the selected catchment has undergone significant changes in land use, mainly characterized by massive deforestation at the end of the 18th century and land consolidation in the middle of the 20th century induced by communist collectivisation. The hydrological simulations demonstrated that the highest and lowest mean annual runoffs were simulated in the first (1st military mapping) and the last (concurrent land use monitoring) time intervals respectively with the smallest and largest percentages of forested areas.

Open access

Peter K. Dimov, Blagoi I. Marinov, Ilcho S. Ilchev, Zdravko Z. Taralov and Stefan S. Kostianev

Abstract

Introduction: Exogenous hypoxia increases ventilation and contracts the pulmonary vessels. Whether those factors change the values of nitric oxide in exhaled air has not yet been evaluated. Objective: To examine the effect of exogenous normobaric hypoxia on the values of the fraction of nitric oxide in exhaled breath (FeNO). Subjects аnd Methods: Twenty healthy non-smoker males at mean age of 25.4 (SD = 3.7) were tested. The basal FeNO values were compared with those at 7 min. and 15 min. after introducing into the hypoxic environment (hypoxic tent), imitating atmospheric air with oxygen concentration corresponding to 3200 m above sea level. Exhaled breath temperature was measured at baseline and at 10-12 min. of the hypoxic exposition. Heart rate and oxygen saturation were registered by pulse-oximetry. Results: All the subjects had FeNO values in the reference range. The mean baseline value was 14.0 ± 3.2 ppb, and in hypoxic conditions - 15.5 ± 3.8 ppb (7 min.) and 15.3 ± 3.6 ppb (15 min.), respectively, as the elevation is statistically significant (p = 0.011 and p = 0.008). The values of exhaled breath temperature were 33.79 ± 1.55°С and 33.87 ± 1.83°С (p = 0.70) at baseline and in hypoxic conditions, respectively. Baseline oxygen saturation in all subjects was higher than that, measured in hypoxia (96.93 ± 1.29% vs. 94.27 ± 2.53%; p < 0.001). Conclusions: Exogenous hypoxia leads to an increase of FeNO values, but does not affect the exhaled breath temperature.

Open access

Steven Moser, Peter Lee and Adrian Podoleanu

Abstract

Zernike modes are commonly used in adaptive optics systems to represent optical wavefronts. However, real-time calculation of Zernike modes is time consuming due to two factors: the large factorial components in the radial polynomials used to define them and the large inverse matrix calculation needed for the linear fit. This paper presents an efficient parallel method for calculating Zernike coefficients from phase gradients produced by a Shack-Hartman sensor and its real-time implementation using an FPGA by pre-calculation and storage of subsections of the large inverse matrix. The architecture exploits symmetries within the Zernike modes to achieve a significant reduction in memory requirements and a speed-up of 2.9 when compared to published results utilising a 2D-FFT method for a grid size of 8×8. Analysis of processor element internal word length requirements show that 24-bit precision in precalculated values of the Zernike mode partial derivatives ensures less than 0.5% error per Zernike coefficient and an overall error of <1%. The design has been synthesized on a Xilinx Spartan-6 XC6SLX45 FPGA. The resource utilisation on this device is <3% of slice registers, <15% of slice LUTs, and approximately 48% of available DSP blocks independent of the Shack-Hartmann grid size. Block RAM usage is <16% for Shack-Hartmann grid sizes up to 32×32.

Open access

Zdenka Stojanovska, Blazo Boev, Zora S. Zunic, Peter Bossew and Svetlana Jovevska

Abstract

The paper deals with the recent survey of indoor radon (Rn) results in schools, where paired CR-39 detectors were simultaneously exposed to different long-term periods, i.e., one detector was exposed during the whole year and the other one in the period of the school year duration. To be able to compare the results obtained, for its analysis, the relative bias and U tests were used. It was found that there are no systematic differences between the results, which points that the exposure of the detector during summer vacations did not affect the estimated average annual radon concentration. The paired results were modelled by a linear function, giving an extremely high coefficient of determination R 2 = 0.99.

Open access

A. Dudlová, P. Juriš, S. Jurišová, P. Jarčuška and V. Krčméry

Summary

Examinations of the set of 2,760 samples of human stools revealed the current epidemiological situation in the occurrence of gastrointestinal parasitoses in Slovakia. Prevalence of gastrointestinal parasitic infection was P = 6.81 % out of which the protozoan infections was P = 2.64 % and helminthiases P = 4.17 %, in the representation of endoparasitic species Entamoeba coli, Giardia intestinalis, Blastocystis hominis, Endolimax nana, Ascaris lumbricoides, Trichuris trichiura and Enterobius vermicularis.

The species with the highest proportion from the protozoa was Entamoeba coli (P = 0.79 %) and from the helminths Ascaris lumbricoides (P = 3.73 %). The highest prevalence of protozoan infections (P = 3.27 %) was found in the age group 8 – 18 yearly and helminthic infections (P = 5.84 %) in the lowest age group of children at the age of 1 month to 7 years. Almost regularly, there was most frequently infection with Endolimax nana, Giardia intestinalis and Ascaris lumbricoides. By comparison of all age categories, a high statistical significance of differences in the prevalence of helminthiases was found, which most frequently infected children aged from 1 month to 7 years (X2, p≤ 0.0001). The statistical significance of differences in the incidence of protozoan infections (X2, p≤ 0.01) and helminthiases (X2, p≤ 0.0001) was recorded between the compared regions of Slovakia (Western, Central and Eastern Slovakia) with the highest prevalence in the eastern region of Slovakia.