Browsing by Author "Kolev D."
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Item A precision determination of the mass of the η meson(2005-07-21) Abdel-Bary M.; Budzanowski A.; Chatterjee A.; Ernst J.; Hawranek P.; Jahn R.; Jha V.; Kilian K.; Kliczewski S.; Kirillov D.; Kolev D.; Kravcikova M.; Kutsarova T.; Lesiak M.; Lieb J.; Machner H.; Magiera A.; Maier R.; Martinska G.; Nedev S.; Piskunov N.; Prasuhn D.; Protić D.; Von Rossen P.; Roy B.J.; Sitnik I.; Siudak R.; Smiechowicz M.; Stein H.J.; Tsenov R.; Ulicny M.; Urban J.; Vankova G.; Wilkin C.Several processes of meson production in proton-deuteron collisions have been measured simultaneously using a calibrated magnetic spectrograph. Among these processes, the η meson is seen clearly as a sharp missing-mass peak on a slowly varying background in the p+d→He3+X reaction. Knowing the kinematics of the other reactions with well determined masses, it is possible to deduce a precise mass for the η meson. The final result, m(η)=547.311±0.028(stat)±0.032(syst)MeV/c2, is significantly lower than that found by the recent NA48 measurement, though it is consistent with values obtained in earlier counter experiments. © 2005 Elsevier B.V. All rights reserved.Item Caratheodory differential equations on cones(2015-01-01) Donchev T.; Kolev D.; Lazi A.; Nosheen A.; Rafaqat M.; Zeinev A.In this paper we prove that almost all, in Baire sense, differential equations with Scorza Dragoni right-hand side, defined on closed convex cone of a Banach space, have unique solution. This solution depends continuously on the right-hand side and on the initial condition. The results are applied to fuzzy differential equations and to differential inclusions.Item Cross section and tensor analysing power of the d d → η α reaction near threshold(2009-04-15) Budzanowski A.; Chatterjee A.; Gebel R.; Hawranek P.; Jahn R.; Jha V.; Kilian K.; Kliczewski S.; Kirillov D.; Kirillov D.; Kolev D.; Kravcikova M.; Lesiak M.; Lieb J.; Machner H.; Magiera A.; Maier R.; Martinska G.; Nedev S.; Piskunov N.; Prasuhn D.; Protić D.; Ritman J.; von Rossen P.; Roy B.J.; Sitnik I.; Siudak R.; Tsenov R.; Urban J.; Vankova G.; Wilkin C.The angular distributions of the unpolarised differential cross section and tensor analysing power Ax x of the over(d, →) d → α η reaction have been measured at an excess energy of 16.6 MeV. The ambiguities in the partial-wave description of these data are made explicit by using the invariant amplitude decomposition. This allows the magnitude of the s-wave amplitude to be extracted and compared with results published at lower energies. In this way, firmer bounds could be obtained on the scattering length of the ηα system. The results do not, however, unambiguously prove the existence of a quasi-bound ηα state. © 2009 Elsevier B.V. All rights reserved.Item Detailed comparison of the pp → π+ pn and pp → π+d reactions at 951 MeV(2005-03-17) Abdel-Bary M.; Budzanowski A.; Chatterjee A.; Ernst J.; Hawranek P.; Hinterberger F.; Jha V.; Kilian K.; Kliczewski S.; Kirillov D.; Kolev D.; Kravcikova M.; Kutsarova T.; Lesiak M.; Lieb J.; Machner H.; Magiera A.; Maier R.; Martinska G.; Nedev S.; Niskanen J.; Piskunov N.; Prasuhn D.; Protić D.; Von Rossen P.; Roy B.J.; Sitnik I.; Siudak R.; Smiechowicz M.; Tsenov R.; Ulicny M.; Urban J.; Vankova G.; Wilkin C.The positively charged pions produced in proton-proton collisions at a beam momentum of 1640 MeV/c were measured in the forward direction with a high resolution magnetic spectrograph. The missing mass distribution shows the bound state (deuteron) clearly separated from the pn continuum. Despite the very good resolution, there is no evidence for any significant production of the pn system in the spin-singlet state. However, the σ(pp→π+pn)/ σ(pp→π+d) cross section ratio is about twice as large as that predicted from S-wave final-state-interaction theory and it is suggested that this is due to D-state effects in the pn system. © 2005 Published by Elsevier B.V.Item Energy efficient SO2 removal from flue gases using the method of Wellman-Lord(2013-11-05) Dzhonova-Atanasova D.; Razkazova-Velkova E.; Ljutzkanov L.; Kolev N.; Kolev D.Investigations are reviewed on development of energy efficient technology for SO2 removal from flue gases of combustion systems by using the method of Wellman-Lord. This method is characterized by absorption of sulfur dioxide with sodium sulfite solution, which reacts to form sodium bisulfite. The absorber is typically a packed column with multiple stages. After evaporation of the solution, SO2 and sodium sulfite are obtained. The latter is dissolved in water from condensation of the steam carrying SO2 from the evaporator. The regenerated solution returns in the absorber. The SO2 removed from the flue gases is obtained as a pure product for use in chemical, food or wine production. Technical and economical assessment of this regenerative method is presented in comparison to the non-regenerative gypsum method, using data from the existing research papers and own experience from investigations on improvement of the Wellman-Lord method and development of innovative gypsum technology.Item Hydro - pyrometallurgical treatment of copper converter flue dust(2017-01-01) Lucheva B.; Iliev P.; Kolev D.The aim of this study is to investigate the possibility of pyrometallurgical recovery of lead and bismuth from preliminary desulfated copper converter flue dust into a metal phase, by carbothermal reduction in a soda ash smelt. Hydrometallurgical treatment of flue dust is actually caustic leaching and it aims to remove the sulfate sulfur. The desulfation degree of the converter flue dust, using 35 g NaOH per 100 g dust, is 80 % and the total impurities concentration in the Na2SO4 solution is below 50 mg l-1. The solid product from the hydrometallurgical step was subjected to pyrometallurgical treatment in a soda ash smelt. The effect of temperature, reducing agent type and amount, soda type and amount, on metal yield as well as the distribution of Pb, Bi, Cd, Ag and Cu among the process products, have been determined. It was found that with the increase of temperature, reducer and soda amounts the metal yield increased, but the copper and silver concentrations in the metal phase also increased. The laboratory experiments showed that it is possible to recover Pb and Bi a in separate product at a temperature of 900oC. The optimum established parameters for carbothermal reduction of desulfated copper converter flue dust are: temperature 900°C, soda amount 50 % of the dust mass, reducer amount 10 % of the dust mass and process duration 30 min. The recovery rates of lead and bismuth at these conditions are 80 % and 65 %, respectively. The obtained alloy consists of 74.87 % Pb, 12.96 % Bi, 0,22 % Cd and 11.63 % Cu. Semi industrial experiments should be carried out to clarify the optimal process parameters, since the furnace type and the method of charge heating will also influence the distribution of the metals among the products of smelting.Item Purification of zinc containing Waelz oxides from chlorine and fluorine(2017-01-01) Iliev P.; Stefanova V.; Lucheva B.; Kolev D.The Waelz oxides (WO) obtained upon processing of zinc containing semi products in Waelz kilns are rich in impurities such as alkalines, chlorides and fluorides. After acid leaching of the WO chlorine and fluorine ions dissolve into the zinc electrolyte, causing corrosion of aluminum cathode and lead anode and sticking of the deposited zinc on the cathode. For normal production operation the WO must contain up to 1000 ppm chlorine and 100 ppm fluorine. In the present study the laboratory tests on alkaline scrubbing of zinc containing WO in sodium carbonate solutions are presented. The effect of sodium carbonate concentration, pulp density and test duration on the degree of fluorine and chlorine purification is investigated. Based on the conducted research it was established that at temperature 363 K, pulp density 300 g l-1, concentration of sodium carbonate 100 g l-1 and test duration 180 min, the final concentration of fluorine and chlorine in the treated WO is 90 and 220 ppm, respectively. WO with such concentration of impurities are appropriate for further processing for cathode zinc production.Item Recovery Of gold from electronic waste by iodine-iodide leaching(2017-01-01) Lucheva B.; Iliev P.; Kolev D.Gold recovery by iodine-iodide solution is an effective and environment-friendly method. The aim of this research is to investigate the possibility of iodine-iodide gold recovery from gold-plated metal, which is a waste product of the electronic industry. Leaching experiments were carried out in solutions, containing 25 g l-1 iodine and 100 g l-1 KI, under room temperature, rotating speed of 500 rpm and mass ratio of 1:10. The degree of gold recovery for 1 minute leaching was 97,55 %. The concentrations of copper and nickel in the solution were about 0.05 g l-1, while the iron concentration was equal to that of the gold. It had been found that when gold concentration in the solution reached 1 g l-1, the iodine concentration decreased with 20 %. The optimal parameters of reducing dissolved gold iodide salts to gold metal are determined as 20 g KOH and 4 ml 10 % N2H4.H2O per one liter of the solution. Simultaneously with gold, iron and nickel almost completely precipitated (90 %), while the copper precipitation degree was around 25 %, because a large part of it precipitated as CuI during the leaching. The gold was separated from the precipitate by HNO3 treatment.The overall gold recovery is 94,56 %. Experiments were conducted to regenerate the solution by decreasing pH with H2SO4 and by adding of H2O2, as an oxidizing agent. The achieved regeneration degree was 80 %. The main disadvantage of iodine-iodide leaching is the great consumption of reagents and the need for a significant number of filtrations.Item Search for η-mesic nuclei in a recoil-free transfer reaction(2009-01-05) Budzanowski A.; Chatterjee A.; Hawranek P.; Jahn R.; Jain B.K.; Jha V.; Kailas S.; Kilian K.; Kliczewski S.; Kirillov D.; Kirillov D.; Kolev D.; Kravcikova M.; Lesiak M.; Lieb J.; Liu L.C.; MacHner H.; Magiera A.; Maier R.; Martinska G.; Nedev S.; Piskunov N.; Protić D.; Ritman J.; Von Rossen P.; Roy B.J.; Shukla P.; Sitnik I.; Siudak R.; Tsenov R.; Urban J.; Vankova G.We have studied the reaction p+Al27 → He3+p+π-+X at recoil-free kinematics. An η meson possibly produced in this reaction would be thus almost at rest in the laboratory system and could therefore be bound with high probability, if nuclear η states exist. The decay of such a state through the N*(1535) resonance would lead to a proton-π- pair emitted in opposite directions. For these conditions we find some indication of such a bound state. An upper limit of ≈0.5 nb is found. © 2009 The American Physical Society.Item Selective autoclave recovery of copper and silver from Waelz clinker in ammonia medium(2017-01-01) Iliev P.; Stefanova V.; Lucheva B.; Kolev D.Upon processing of zinc ferrite cakes in Waelz kilns a waste product, called Waelz clinker, is obtained. The copper and silver contents in this product are comparable to those of their ores which turns it into a valuable raw material. In the present work the experimental results on selective autoclave leaching of Waelz clinker in ammonia medium are presented. The effect of main technological parameters on the degree of value metals recovery and iron precipitation is studied. It is established that the highest extend of copper and silver recovery is obtained under the following conditions: temperature 383 K, Po2 0.4 MPa, ammonia concentration 110 g l-1, ammonium sulfate concentration 70 g l-1, pulp density 100 g l-1and test duration 120 min. At these conditions 86,5 % of copper and 68,5 % of silver are solubilized, whereupon over 99 % of iron is hydrolytically precipitated. The composition of the corresponding leach solution is: 1,22 g l-1Cu, 10 mg l-1 Ag, 90 mg l-1 Zn, 30 mg l-1 Fe and 40 mg l-1 Mn.