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Wyświetlanie 1-12 z 12
Tytuł:
Activating flotation of chalcopyrite using CuSO4 and H2O2 from the cyanide tailings
Autorzy:
Ai, G.
Yan, H.
Qiu, T.
Liu, C.
Powiązania:
https://bibliotekanauki.pl/articles/109562.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
cyanide tailings
chalcopyrite
CuSO4
H2O2
activation mechanism
Opis:
The effects of CuSO4 and H2O2 on the flotation behavior of cyanide chalcopyrite were investigated by flotation tests, microcalorimetry and X-ray photoelectron spectroscopy (XPS). The underlying activation mechanism was studied in the perspective of micro-thermodynamics and surface properties. The flotation results indicated that cyanide chalcopyrite was strongly inhibited by sodium cyanide, with the maximum flotation recovery of 22.5% only. CuSO4 and H2O2 significantly improved the flotation of cyanide chalcopyrite, and the flotation recovery was increased to 92.28% and 84.35%, respectively. The micro-thermodynamics results indicated that the adsorption heat of butyl xanthate on cyanide chalcopyrite surface increased after the addition of CuSO4 and H2O2, as well as the reaction order. CuSO4 and H2O2 can significantly improve the adsorption of butyl xanthate on the surface of cyanide chalcopyrite by decreasing the apparent activation energy by 80.11% and 66.54%, respectively. XPS analysis indicated that the CuCN was generated on the surface of cyanide chalcopyrite, leading to the loss of sulfur and inhibiting the adsorption of collectors. As a result, the flotation of cyanide chalcopyrite was depressed. It is considered that, CuSO4 and H2O2 can improve the flotation of cyanide chalcopyrite by eleminating CuCN from its surface and increasing the concentration of S by 57.02% and 37.48%, respectively.
Źródło:
Physicochemical Problems of Mineral Processing; 2018, 54, 2; 578-589
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Flotation kinetics and thermodynamic behavior of chalcopyrite and pyrite in high alkaline systems
Autorzy:
Yan, H.
Yuan, Q.
Zhou, L.
Qiu, T.
Ai, G.
Powiązania:
https://bibliotekanauki.pl/articles/110078.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
flotation kinetics
pyrite
chalcopyrite
flotation separation
high alkaline
microcalorimetry
Opis:
The monomineral flotation test and microcalorimetry were used to study the flotation kinetics and thermodynamic behavior of chalcopyrite and pyrite in high alkaline systems of lime and NaOH. The results showed that in these systems there were less hydrophilic substances on the chalcopyrite surface, so that the apparent activation energy of sodium butyl xanthate (SBX) adsorption on chalcopyrite surface was low. This promoted the adsorption of SBX and increased the flotation rate and recovery of chalcopyrite. In contrast, the hydrophilic Fe(OH)3 and SO42- formed by oxidation on the pyrite surface increased the adsorption activation energy of SBX. Thus, the flotation rate and recovery of pyrite were lower. Moreover, in the lime high alkaline system, the hydrophilic calcium film generated on the pyrite surface further hindered the adsorption of SBX, thereby further inhibiting pyrite in this environment. In other words, the lime high alkaline environment increased the apparent activation energy difference of SBX adsorption between chalcopyrite and pyrite compared to the NaOH system, facilitating the flotation separation of chalcopyrite and pyrite. The results can help with the theoretical research of flotation separation of other minerals, and provide guidance for developing low alkaline and lime-free pyrite depressants.
Źródło:
Physicochemical Problems of Mineral Processing; 2018, 54, 3; 901-910
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Konečno-èlementnaâ modelʹ èlektronno-lučevoj pajki tverdosplavnyh režuŝih èlementov k opravke
The finite element model for electron beam soldering of carbide cutting elements to a mandrel
Autorzy:
Goranskij, G.G.
Pobol, A.I
Powiązania:
https://bibliotekanauki.pl/articles/2068493.pdf
Data publikacji:
2020
Wydawca:
Politechnika Częstochowska
Tematy:
finite element model
electron beam processing
carbide tool
model elementów skończonych
obróbka wiązką elektronową
narzędzia z węglika
Opis:
Sozdany obobŝennye konečno-èlementnye (KÈ) modeli èlektronno-lučevoj obrabotki (ÈLO) poverhnostej dlâ materialov s suŝestvenno otličaûŝimisâ teplofizičeskimi svojstvami, pozvolâûŝie proizvoditʹ rasčet i optimizaciû režimov processa. Dlâ izdelij raznoj geometrii, učityvaâ termodinamiku processa i temperaturnye zavisimosti svojstv materialov, upravlââ geometriej èlektronnogo pučka i ciklogrammoj processa, optimizirovany diapazony ènergeti českih parametrov ÈLO. KÈ modelirovanie nagreva poverhnosti pri ÈLO provedeno dlâ detali ploskoj formy stacionarnym istočnikom so skaniruûŝej razvertkoj, a takže pri vozdejstvii v režime linejnogo peremeŝeniâ luča bez skaniruûŝej razvertki. Dlâ optimizacii èlektronno-lučevogo oplavleniâ pri pajke predložena termodinamičeskaâ KÈ modelʹ, učityvaûŝaâ geometričeskie osobennosti rezcovyh vstavok i teplofizičeskie svojstva sostavlâûŝih ih materialov. Pokazano, čto učet temperaturnoj zavisimosti teplofizičeskih svojstv materialov pozvolâet realizovyvatʹ shemy ÈLO s menʹšej prodolžitelʹnostʹû vozdejstviâ pučka bolʹšej moŝnosti.
Generalized finite-element models for the electron-beam treatment of the surface of materials with significantly different thermophysical properties have been created, allowing the calculation and optimization of process conditions. For products of different geometries, taking into account the thermodynamics of the process and the temperature dependences of the properties of materials, controlling the electron beam geometry and the process cycloramas, the ranges of energy parameters of electron beam processing have been optimized. Finite-element modeling of surface heating during electron-beam processing was carried out for a flatshaped part by a stationary source with scanning, as well as when exposed to linear beam movement without scanning. To optimize electron beam reflow during soldering, a thermodynamic finite-element model is proposed that takes into account the geometric features of the cutter inserts and the thermophysical properties of their constituent materials. It is shown that taking into account the temperature dependence of the thermophysical properties of the materials makes it possible to realize electron beam processing schemes with a shorter duration of exposure to a beam of greater power.
Źródło:
Zeszyty Naukowe Politechniki Częstochowskiej. Budownictwo; 2020, 26 (176); 44-55
0860-7214
Pojawia się w:
Zeszyty Naukowe Politechniki Częstochowskiej. Budownictwo
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Konečno-èlementnoe modelirovanie èlektrokontaktnogo spekaniâ pravâŝih fil’er stroitel’noj armatury
Finite-element model of electrocontact sintering of straightening dies for construction fittings
Autorzy:
Goranskij, G.G.
Pobol, A.I
Powiązania:
https://bibliotekanauki.pl/articles/2067681.pdf
Data publikacji:
2019
Wydawca:
Politechnika Częstochowska
Tematy:
mathematical model
electrocontact sintering
straightening dies
modelowanie matematyczne
spiekanie
spiekanie elektrostykowe
Opis:
Razrabotana matematičeskaâ model’ processa èlektrokontaktnogo spekaniâ ÈKS) tverdosplavnyh kompozicij pri izgotovlenii pravâŝih fil’er stroitel’noj armatury. Model’ pozvolâet rassčitat’ uplotnenie pressovki, diagrammu poslojnogo raspredeleniâ plotnosti, diagrammy polej temperatur i davlenij, raspredelenie plotnosti toka po sečeniû pressovki i egoizmenenie v zavisimosti ot otnositel’noj plotnosti. Aprobirovannye v modeli analitičeskie zavisimosti rasprostraneny na proizvol’nuû geometriû fil’er pri pomoŝi konečno-èlementnogo modelirovaniâ s korrektirovkoj svojstv materiala po analitičeskim zavisimostâm, ishodâ iz plotnosti pressovki. Ocenka adekvatnosti modeli provedena po krivoj pressuemosti. Rezul’tatami rasčetov dokazan i èksperimental’no podtveržden èffekt sniženiâ termobaričeskih parametrov kompaktirovaniâ spekaemoj tverdosplavnoj kompozicii pri ee modificirovanii termoaktiviruûŝej dobavkoj, blagodarâ čemu povyšena stojkost’ keramičeskih press-form i na 40% snižen procent koničeskoj poverhnosti zagotovki fil’ery.
A mathematical model of the process of electrocontact sintering of carbide compositions in the manufacture of straightening dies of construction fittings has been developed. The model allows to calculate the compression of the compact, the diagram of the layer-by-layer density distribution, the diagrams of temperature and pressure fields, the distribution of current density over the cross-section of the compact and its change depending on the relative density. The analytical dependences, tested in the model, are extended to arbitrary geometry of the dies, using finite element modeling with adjustment of material properties according to analytical dependencies, based on the density of pressing. An assessment of the adequacy of the model was carried out by the compressibility curve. The results of calculations proved and experimentally confirmed the effect of reducing the thermobaric parameters of compacting the sintered carbide composition, when it is modified with a thermosetting additive, which increased the resistance of ceramic molds and reduced the percentage of rejects by 40%. The tensile radial deformations along the conical surface of the die blank are predicted.
Źródło:
Zeszyty Naukowe Politechniki Częstochowskiej. Budownictwo; 2019, 25 (175); 40-49
0860-7214
Pojawia się w:
Zeszyty Naukowe Politechniki Częstochowskiej. Budownictwo
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Belarusian agricultural and ecological tourism within SME sector and its further development in current and modern conditions
Autorzy:
Gribov, G.M.
Lysiuk, A.I.
Powiązania:
https://bibliotekanauki.pl/articles/398931.pdf
Data publikacji:
2012
Wydawca:
Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej
Tematy:
Białoruś
turystyka wiejska
Belarus
rural tourism
Opis:
The article offers brief history of the development of rural tourism in Belarus and identifies the main problems in this sphere. It also shows the results of a sociological study investigating the attitude of residents living in the border regions toward agricultural and ecological tourism. The priorities and the level of attractiveness are also analyzed. The article provides recommendations aimed at optimizing the activity of the actors in the sphere of rural tourism.
Źródło:
Ekonomia i Zarządzanie; 2012, 4, 1; 51-63
2080-9646
Pojawia się w:
Ekonomia i Zarządzanie
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Модифицированные композиции на основе отходов твердого сплава для правящих фильер строительной арматуры
Modified compositions, based on hard alloy wastes, for straightening dies of construction fittings
Autorzy:
Goranskij, G.G.
Zornik, V.I.
Pobol, A.I
Powiązania:
https://bibliotekanauki.pl/articles/2068494.pdf
Data publikacji:
2018
Wydawca:
Politechnika Częstochowska
Tematy:
hard alloy wastes
modification
straightening dies
construction fittings
odpady
okucia budowlane
matryce
Opis:
Целью работы являлось научное обоснование целесообразности модифицирования твердосплавных отходов для коррекции технологических режимов их электроконтактного спекания при изготовле- нии правящих и направляющих фильер строительной арматуры, исследование эволюции строения и свойств композиций, а также эксплуатационных характеристик изделий. Установлено, что введение аморфизированных модификаторов систем Fe–Ni–Mo–Co–Cr–В–Si и Ni–Cr–Si–В в состав композита на основе отходов твердого сплава ВК6 сопровождается легированием матричной фазы ß–Со атомами замещения с бoльшим атомным радиусом (Fe, Mo, Cr, Si) и примесями внедрения (В), приводящим к появлению атомных смещений в окрестностях атомов легирующей примеси и увели- чению искаженности кристаллической решетки ß–Со, что способствует упрочнению спеченного сплава, росту его механических и эксплуатационных свойств. Отмеченный эффект модифицирова- ния твердосплавных отходов позволяет вовлечь их в производство электроконтактным спеканием правящих и направляющих фильер для строительной арматуры, существенно снизив стоимость изделий при высоком уровне их служебных характеристик.
The aim of the work was the scientific substantiation of the feasibility of modifying of hard alloy wastes to correct the technological modes of their electrical contact sintering in the manufacture of the straightening and guide dies of construction fittings; the study the evolution of the structure and properties of the compositions, as well as the operational characteristics of the products. It has been established that the introduction of amorphized modifiers of the systems Fe–Ni–Mo–Co–Cr–B–Si and Ni–Cr–Si–B into the composite, based on the hard alloy WCo6 wastes, is accompanied by doping the matrix ß–Co phase by atoms with more atomic radius (Fe, Mo, Cr, Si) and interstitial impurities (B), leading to the appearance of atomic displacements in the vicinity of dopant atoms and an increase the lattice distortion of ß–Co phase, which contributes to the hardening of the sintered alloy, the growth of its mechanical and operational properties. The noted effect of modifying of hard alloy wastes makes it possible to involve them in the production by electrocontact sintering of the straightening and guide dies for construction fittings, significantly reducing the cost of products at a high level of their performance characteristics.
Źródło:
Zeszyty Naukowe Politechniki Częstochowskiej. Budownictwo; 2018, 24 (174); 95-101
0860-7214
Pojawia się w:
Zeszyty Naukowe Politechniki Częstochowskiej. Budownictwo
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Capybaras, size, shape, and time: A model kit
Autorzy:
Vucetich, M G
Deschamps, C.M.
Olivares, A.I.
Dozo, M.T.
Powiązania:
https://bibliotekanauki.pl/articles/22975.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Miocene
allometry
Puerto Madryn Formation
Rodentia
Cardiatherium patagonicum
size
Argentina
tooth development
capybara
time
shape
Hydrochoeridae
Cardiatherium
paleontology
Opis:
The capybaras (Hydrochoeridae) are outstanding rodents for their large size and euhypsodont and multilaminated cheek teeth. Although today they are represented by a single species, it was generally thought that their past diversity was much higher, especially during the late Miocene–early Pliocene. Such diversity is here analyzed taking into account the ontogenetic variation of the p4–m3 in different populations. Numerous isolated teeth of different size found in the upper levels of the Puerto Madryn Formation (late Miocene, Peninsula Valdés, Argentina) were interpreted as members of an ontogenetic series of a new species here described, Cardiatherium patagonicum. They provided clues to evaluate ontogenetic variation and a new framework to analyze the family diversity. In this context, it is proposed that multiple species described from the Ituzaingó Formation (late Miocene, Entre Ríos, Argentina) based on lower teeth, may actually represent specimens of different stages of the ontogenetic trajectory of a single species. Likewise, we found that several nominal taxa from other localities were based on juvenile specimens. According to these results, the diversity of the Hydrochoeridae during the late Miocene and early Pliocene was drastically reduced. The validity of the subfamily Cardiatheriinae is debated. Finally, it is suggested that the whole family should be revised taking into account the ontogenetic variation.
Źródło:
Acta Palaeontologica Polonica; 2005, 50, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Management of potato virus Y (PVY–NTN) causing potato tuber necrotic ringspot disease (PTNRD) in potato by prior treatment with a mild PVY strain
Autorzy:
Abdalla, O.A.
Eraky, A.I.
Mohamed, S.A.
Fahmy, F.G.
Powiązania:
https://bibliotekanauki.pl/articles/65943.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Egypt
pest management
potato virus Y
potato tuber
necrotic ringspot disease
potato
plant protection
mild strain
treatment
Opis:
Potato virus Y (PVY) is one of the most destructive viruses infecting potato in Egypt and worldwide. Recent research has shown that a necrotic PVY-NTN strain is infecting potato in Upper Egypt. Chemical control is not effective to control this viral pathogen. An alternative to control PVY infecting potato is using a mild PVY strain to elicit systemic cross protection in potato plants against infection with a severe necrotic strain of PVY. Results of this study showed that a PVY necrotic strain produced a significant lesser number of local lesions on diagnostic plants (Robinia pseudoacacia L.) when these plants were treated first with a mild PVY strain. Data obtained from greenhouse and field experiments indicated that treatment of potato plants (variety Burna) with a mild PVY strain significantly protected potato from infection with a severe necrotic PVY strain, and resulted in a significant increase in tuber yield compared with infected plants without prior treatment with a mild PVY strain. The highest increase in potato tuber yield was obtained when potato plants were inoculated with a mild PVY strain 3 days before challenging with the severe necrotic PVY strain. This study proved that using a mild strain of PVY can significantly protect potato plants from infection with a severe strain of this virus under both greenhouse and field conditions and can present a potential method to reduce losses due to infection of this virus in Assiut governorate and Upper Egypt.
Źródło:
Journal of Plant Protection Research; 2018, 58, 2
1427-4345
Pojawia się w:
Journal of Plant Protection Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Virulence of geographically different Cryptosporidium parvum isolates in experimental animal model
Autorzy:
Sayed, F.G.
Hamza, A.I.
Galal, L.A.
Sayed, D.M.
Gaber, M.
Powiązania:
https://bibliotekanauki.pl/articles/6602.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Parazytologiczne
Opis:
Cryptosporidium parvum is a coccidian parasite which causes gastrointestinal disease in humans and a variety of other mammalian species. Several studies have reported different degrees of pathogenicity and virulence among Cryptosporidium species and isolates of the same species as well as evidence of variation in host susceptibility to infection. The study aimed to investigate infectivity and virulence of two Cryptosporidium parvum “Iowa isolate” (CpI) and a “local water isolate” (CpW).Thirty-three Swiss albino mice have been divided into three groups: Negative control Group (C), the CpI group infected with “Iowa isolate “and the CpW group infected with C. parvum oocysts isolated from a local water supply. Infectivity and virulence have been measured by evaluating clinical, parasitological and histological aspects of infection. Significant differences were detected regarding oocysts shedding rate, clinical outcomes, and the histopathological picture of the intestine, lung, and brain. It was concluded that the local water isolate is significantly more virulent than the exported one.
Źródło:
Annals of Parasitology; 2016, 62, 3
0043-5163
Pojawia się w:
Annals of Parasitology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Immunity to hepatitis A virus among working professionals in Poland - results of a 3-year serological survey 2013–2015
Autorzy:
Juszczyk, G.
Czerw, A.I.
Zalecka, B.
Mikos, M.
Banaś, T.
Deptała, A.
Ślusarczyk, J.
Powiązania:
https://bibliotekanauki.pl/articles/2081899.pdf
Data publikacji:
2018
Wydawca:
Instytut Medycyny Wsi
Tematy:
hepatitis A
hepatitis A antibodies seroprevalence
vaccination against hepatitis type A
Opis:
Introduction. Hepatitis A (HA) is caused by infection with the hepatitis A virus (HAV). The differential etiological diagnosis of acute hepatitis is based on a positive result of the serological test detecting IgM class anti-HAV. For epidemiological studies on past infection and seroprevalence of HAV in populations, the tests measuring IgG class anti-HAV or total anti-HAV are used. Since the 1990s, specific prophylaxis is possible by vaccination against HA. In Poland, vaccination is recommended and in majority is performed at own cost. Materials and method. Database was obtained from electronic medical records of the 2 major private health care providers networks (Luxmed and Medicover) operating in Poland. During a 3-year period (2013–2015), 1,124 persons with unknown status of anti-HA vaccination were tested for the presence of total anti-HAV. Objective. The aim of the study was to evaluate the seroprevalence of anti-HAV among working professionals in Poland. Results. Anti-HAV were detected in 603 (53.6%) persons, while 521 (46.3%) tested negative. The study group was divided into 2 subgroups: 25–44 and 45–64-years-old. For detailed statistical analysis, the presence of anti-HAV was considered as a dependent variable, and its predictors were gender, age and the year of the test performance. The presence of anti-HAV was significantly more prevalent in older age group. The lack of specific antibodies was more prevalent in younger age group. Conclusions. Results of the study show increasing susceptibility to HAV infection in the younger age group, compared with the older age group of corporate professional employees in large cities in Poland. Since the epidemiological situation of HA is currently changing with increasing number of symptomatic cases of HA, it is suggested that employers might consider including an additional procedure of vaccination against HA into their private health insurance portfolio.
Źródło:
Annals of Agricultural and Environmental Medicine; 2018, 25, 3; 572-575
1232-1966
Pojawia się w:
Annals of Agricultural and Environmental Medicine
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Work Ability Index (WAI) values in a sample of the working population in Poland
Autorzy:
Juszczyk, G.
Czerw, A.I.
Religioni, U.
Olejniczak, D.
Walusiak-Skorupa, J.
Banas, T.
Mikos, M.
Staniszewska, A.
Powiązania:
https://bibliotekanauki.pl/articles/2082986.pdf
Data publikacji:
2019
Wydawca:
Instytut Medycyny Wsi
Tematy:
work ability
occupational health services
work capacity evaluation
work performance
occupational therapists
Opis:
Introduction. Ability to work is most often defined as a relationship between a person’s resources and requirements specific to a particular type of work. It is the result of interaction between job requirements in terms of physical and mental strain, capabilities and skills of the employee, as well as his/her health condition and own evaluation of functioning in a given organizational and social situation. Objective. The primary objective of the study was to evaluate the current value of the Work Ability Index (WAI) in a sample of employees in Poland. Materials and method. The study sample was selected purposefully from 422,000 employees covered by the largest occupational health provider in Poland. The standard WAI questionnaire provided by CAWI (Computer-Assisted Web Interview) methodology was voluntary and completed anonymously by 688 employees within 12 months (0.16% response rate). The results were statistically analyzed using the Pearson’s chi-squared test and correlation coefficient, independent- sample T test and one-way analysis of variance (p < 0.05). Results. It was found that the average value of WAI was 37.5 ± 7.7, and 37% of the participants represented low to moderate ability to work. The results showed no significant correlation between the WAI value and its 7 compounds and demographic variables. Nonetheless, a dependency between WAI level and industrial branch was observed. Conclusions. Subjects with moderate and low WAI (1/3 of the study population) had particular indications to implement prophylactic actions, especially for the health care employees and civil servants, whose ability to work may be subject to accelerated deterioration.
Źródło:
Annals of Agricultural and Environmental Medicine; 2019, 26, 1; 78-84
1232-1966
Pojawia się w:
Annals of Agricultural and Environmental Medicine
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-12 z 12

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