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Tytuł:
Oscillation criteria for a class of nonlinear differential equations of third order
Autorzy:
Parhi, N.
Das, P.
Powiązania:
https://bibliotekanauki.pl/articles/1311970.pdf
Data publikacji:
1992
Wydawca:
Polska Akademia Nauk. Instytut Matematyczny PAN
Tematy:
third order equations
oscillation
nonoscillation
asymptotic behaviour
Opis:
Oscillation criteria are obtained for nonlinear homogeneous third order differential equations of the form $y''' + q(t)y' + p(t)y^α = 0$ and y''' + q(t)y' + p(t)f(y) = 0, where p and q are real-valued continuous functions on [a,∞), f is a real-valued continuous function on (-∞, ∞) and α > 0 is a quotient of odd integers. Sign restrictions are imposed on p(t) and q(t). These results generalize some of the results obtained earlier in this direction.
Źródło:
Annales Polonici Mathematici; 1992, 57, 3; 219-229
0066-2216
Pojawia się w:
Annales Polonici Mathematici
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Socio-environmental survey of an ecologically important hamlet of Darjeeling district, West Bengal, India
Autorzy:
Bhattacharya, S.
Ghosh, G.
Banerjee, T.
Goswami, S.
Das, P.
Powiązania:
https://bibliotekanauki.pl/articles/11842.pdf
Data publikacji:
2015
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
socio-environmental survey
ecologically important hamlet
management
biodiversity
environment
Darjeeling district
West Bengal
India
Opis:
Forest cover in hills is essential to maintain environmental, economic and ecological balances. North Bengal accounts for 3,086 sq km (26 %) of the 11,876 sq km area of classified forests in the state, and for nearly 5,000 sq km (40 %) of all land under tree cover. Upper Chatakpur is one of the emerging ecotourism spots of north Bengal, located at an altitude of 7887 feet in Darjeeling district. It is a 180 years old ethnic village with 19 houses and a population of about 89, and at an altitude of 7887 ft. It is about 8 km. from Sonada (26° 57' N, 88° 16' E), 22 km. from Darjeeling (26° 2' N, 88° 15' E) and 72 km. from Siliguri (26° 42' N, 88° 25' E). Upper Chatakpur Village situated within Senchal Wildlife Sanctuary, Darjeeling. The sanctuary with an area of 38.88 sq. km has an elevation of 1500-2600 m. The survey work was done in December, 2014 by visiting upper Chatakpur village and the primary data were gathered through field survey and direct contact with common people and authorized centers of the region. Surveys on the topography, demography, agriculture, livestock, water management, education, culture, health, waste management, transport, biodiversity, human animal conflict were done in this area. Medicinal plant diversity was studied in the village area and information was gathered from the local forest department centre. Information regarding the transport system was collected from the local transport office and syndicate. Census report was collected from the Sonada Panchayat Office. Health and education information was collected from the local primary school and the local sub health centre. Information on sustainable agricultural practices and waste management policies is collected through surveys in the village houses and agricultural fields. Biodiversity of Senchal Wildlife Sanctuary was documented by visiting the forest areas. Pictorial documentation was done in every phase of study. In spite of getting so much attention in the recent time, the village is not adequately developed. There is an urgent need for implementing sustainable management systems in the areas for the betterment of the socio-environmental structures. Some of the possible management strategies have been suggested for maintaining the social, environmental, economic and ecological balance of the region.
Źródło:
International Letters of Natural Sciences; 2015, 06
2300-9675
Pojawia się w:
International Letters of Natural Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Gender Difference and Emotional Intelligence in Selected Hospitals - A Study
Autorzy:
Sahu, Tapas Lata
Das, R. P.
Powiązania:
https://bibliotekanauki.pl/articles/1192719.pdf
Data publikacji:
2016
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Emotional Intelligence
Gender Difference
Male and Female Employees
Healthcare Organization
Opis:
Emotions in humans are subjective conscious experience characterized by psycho-physiological expressions and behavioral reactions. It may act as tool, if positively identified by complementing and enriching job performance but if negatively understood can ruin feelings and be a disaster. Emotions in healthcare organizations are important to be taken care of because in the service exchange process emotions of both the service provider and the receiver are directly involved. Although caring and curing patient by these employees is a professional activity but still, the empathetic and sympathetic behavior shown by these professionals influences their performance and success in hospital industry. Moreover, the behavior shown by these employees in the workplace is often discriminated on the basis of their gender as it influences the performance of health professionals. Based on above backdrop, the objective of the current study is to assess whether there exist difference in emotional intelligence of healthcare employees in hospitals with respect to their gender. A standardized questionnaire was used to conduct the study among 300 employees in hospitals with the help of scale developed by Hyde, Pethe and Dhar (2002). Data was analyzed through SPSS and results indicated that the level of emotional intelligence among females is higher than male employees.
Źródło:
World Scientific News; 2016, 59; 1-11
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Emotional Intelligence and Ability to Manage Customer Relationship in Bank Employees of Selected Indian Banks - A Study
Autorzy:
Sahu, Tapas Lata
Das, R. P.
Powiązania:
https://bibliotekanauki.pl/articles/1189944.pdf
Data publikacji:
2016
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Demographic Variables
Emotional Intelligence
Managing Customer Relationships
Opis:
Managing customer relationship is a great challenge in the present era of service revolution. As large numbers of players are now entering into this industry, the intensity of competition is growing among them in very passing day. In the current cut throat competition, customers are becoming very particular to use or not to use services of any organization. Therefore, managing customer relationship is playing dominant role for in almost every service providing organizations, so banks are not an exception. There is a popular belief that higher the emotional intelligence of service provider better will be their ability to manage customer relationship. So the present study is the part of a large study conducted on 300 bank employees working in 5 different banks (both in public and private sector) in the state of Chhattisgarh to assess whether their demographic variables, emotional intelligence and ability to manage customer relationship are related with each other. Data were collected with the help of a schedule to measure emotional intelligence and ability to manage customer relationship and are analyzed with help of ANOVA and Correlations by using SPSS. The study reveals that there exist significant and strong relationship between emotional intelligence, demographic variables and ability to manage customer relationship. Thus, it is concluded that service providers in banks with their high level of emotional intelligence and ability to manage customer relationship can contribute significantly to attract and retain customers and build long term relationship with them.
Źródło:
World Scientific News; 2016, 52; 31-43
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Estimation of Optimum Value of Y-Capacitor for Reducing Emi in Switch Mode Power Supplies
Autorzy:
Jha, M. M.
Naik, K. B.
Das, S. P.
Powiązania:
https://bibliotekanauki.pl/articles/262807.pdf
Data publikacji:
2009
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie
Tematy:
EMI
CM noise
touch current
Y-capacitor
Opis:
Putting a Y-capacitor between the primary ground and secondary ground is a common practice in industry to reduce EMI; but, this capacitor increases touch current. A method is discussed to measure the touch current at circuit design level. An optimum value of Y-capacitor is predicted without exceeding touch current limit. Experimental results of touch current measurements and EMI measurements are analyzed.
Źródło:
Electrical Power Quality and Utilisation. Journal; 2009, 15, 2; 47-50
1896-4672
Pojawia się w:
Electrical Power Quality and Utilisation. Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dielectric Permittivity and Viscoelastic Measurements οf Two Tricomponent Mixtures Consisting οf Laterally Fluorinated Terphenyl Derivatives
Autorzy:
Basak, S.
Dasgupta, P.
Das, B.
Das, M.
Dabrowski, R.
Powiązania:
https://bibliotekanauki.pl/articles/1400143.pdf
Data publikacji:
2013-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
78.20.Fm
87.19.rd
87.19.rf
83.60.Bc
Opis:
Two tricomponent room temperature nematic eutectic mixtures ABC and ABD with laterally fluorinated constituents A and B were prepared as base mixtures for vertically aligned mode LCD's. The physical properties of these mixtures viz. birefringence, dielectric anisotropy, bend elastic constant, relaxation time and rotational viscosities were determined in order to compare with the optimum values required to achieve the target specifications of VA mode materials. The dielectric anisotropy, Δ ε, and optical birefringence, Δ n, of these mixtures were found to be in the range of (-1.3 to -1.4) and (0.13 and 0.14), respectively, at around 20°C. The figure of merit for the ABD mixture has been found to be higher than that of ABC mixture throughout the entire temperature range. The pretilt angle effect in the physical parameters has also been studied. At T=20°C, the response time decreases to 25% and 35% for mixture ABC for 2° and 5° pretilt respectively in comparison to zero pretilt. On the other hand, at the same temperature for the ABD mixture these values are reduced by 16% and 35%, respectively.
Źródło:
Acta Physica Polonica A; 2013, 123, 4; 714-719
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Determination of Orientational Order Parameters of Two Tri-Component Mixtures from Optical Birefringence and X-Ray Diffraction Measurements
Autorzy:
Basak, S.
Dasgupta, P.
Das, B.
Das, M.
Dabrowski, R.
Powiązania:
https://bibliotekanauki.pl/articles/1492775.pdf
Data publikacji:
2011-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.05.cp
61.30.-v
42.70.Df
Opis:
Two tri-component mixtures as base mixtures for vertically aligned mode LCD's were prepared. The eutectic compositions were theoretically estimated and experimentally verified from differential scanning calorimetry studies. A room temperature nematic mixture with fairly broad operating range emerged from each of the tri-component mixtures. The optical birefringence of these mixtures at the eutectic composition was measured as a function of temperature. X-ray diffraction measurements were done on these mixtures to obtain the orientational order parameters as a function of temperature. The order parameter values were also determined from birefringence measurements and the results were compared with mean field theory. Structural parameters like intermolecular distance and apparent molecular length have also been determined.
Źródło:
Acta Physica Polonica A; 2011, 120, 6; 1037-1042
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hydromagnetic rarefied fluid flow over a wedge in the presence of surface slip and thermal radiation
Autorzy:
Das, K.
Sharma, R. P.
Duari, P. R.
Powiązania:
https://bibliotekanauki.pl/articles/264410.pdf
Data publikacji:
2017
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
convective flow
heat transfer
surface slip
magnetic field
thermal radiation
przepływ konwekcyjny
przenoszenie ciepła
pole magnetyczne
promieniowanie cieplne
Opis:
An analysis is presented to investigate the effects of thermal radiation on a convective slip flow of an electrically conducting slightly rarefied fluid, having temperature dependent fluid properties, over a wedge with a thermal jump at the surface of the boundary in the presence of a transverse magnetic field. The reduced equations are solved numerically using the finite difference code that implements the 3-stage Lobatto IIIa formula for the partitioned Runge-Kutta method. Numerical results for the dimensionless velocity and temperature as well as for the skin friction coefficient and the Nusselt number are presented through graphs and tables for pertinent parameters to show interesting aspects of the solution.
Źródło:
International Journal of Applied Mechanics and Engineering; 2017, 22, 4; 827-837
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Some classes of modified ratio type estimators in sample surveys
Autorzy:
Swain, A. K. P. C.
Das, Manjula
Powiązania:
https://bibliotekanauki.pl/articles/466061.pdf
Data publikacji:
2015
Wydawca:
Główny Urząd Statystyczny
Tematy:
ratio type estimator
simple random sampling
bias
mean square error
efficiency
Opis:
In this paper some classes of modified ratio type estimators with additive and multiplicative adjustments made to the simple mean per unit estimator and classical ratio estimator are suggested to obtain more efficient ratio type estimators compared to the classical one. Their biases and mean square errors are obtained and compared with first order approximations.
Źródło:
Statistics in Transition new series; 2015, 16, 1; 37-52
1234-7655
Pojawia się w:
Statistics in Transition new series
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Removal/reduction of organic pollutants from aqueous environment
Usunięcie/redukcja zanieczyszczeń organicznych ze środowiska wodnego
Autorzy:
Sarkar, M.
Das, M.
Manna, S.
Acharya, P.
Powiązania:
https://bibliotekanauki.pl/articles/1826240.pdf
Data publikacji:
2003
Wydawca:
Politechnika Koszalińska. Wydawnictwo Uczelniane
Tematy:
zanieczyszczenia organiczne wody
adsorpcja siarczanu
jakość wody
Opis:
The problem of considerable contamination of the aqueous environment with organic pollutants still requires the development of quick and simple methods for the removal, separation and determination of these compounds. The main classes of organic compounds that most of the industries use and discharge into the effluents are phenol, surfactant and dye. All these compounds are troublesome contaminants which pose not only to toxicity and health hazards but also hamper the environmental treatment processes. In chemical industry phenol is considered as an important starting materials for numerous intermediates and finished products. It is used for the production of a wide range of consumer goods and process materials ranging from adhesives, resins, emulsifiers and detergents, plasticizers, herbicides, dyes and flavors. The worldwide production of phenol is estimated to be 5 million tons per year. Phenol and its analogues are known to be toxic to microbes. The sign of acute illness induced by phenols in experimental animals as well as in humans is known. Continuous ingestion of phenol for a prolonged period of time causes mouth sore, diarrhoea, excretion of dark urine and impaired vision at concentration levels 10÷240 ppm. Lethal blood concentration for phenol is around 1.3 g/L. phenols are toxic to several biochemical functions and to fish life. It acts as a substrate inhibitor in the bio-transformation. World Health Organization (WHO) prescribed a concentration 1 ppb as the guideline concentration in drinking water [1]. Disposal of dyeing industry waste water pose one of the major problem, because such effluents contain a number of contaminants including acid or base, dissolve solids, surfactants and color. Out of these, color is the first contaminant to be recognized because it is visible to human eye. The dye causes the harmful action to various aquatic lives. As it is resistant to light it protects the sunlight from penetrating through it and reduces the aesthetic quality of water. Possible methods of color removal include chemical oxidation, froth flotation, coagulation, adsorption, etc. The anionic surfactants generally are removed by the chemical precipitation, foam separation, ultrafiltration and adsorption. Possible means of removal of phenols from waste water include ion exchange, reverse osmosis, chemical oxidation, precipitation, distillation, gas stripping, solvent extraction, adsorption or bio remediation. Removal of SDS, 4-nitrophenol and malachite green by activated carbon is an efficient and acceptable process. But the cost of operation is very high. Therefore, the present study is undertaken using fly ash as the adsorbent. Compared to activated carbon the efficiency of removal is less in case of 4-nitrophenol and SDS. But fly ash, being a waste material, is very cheap; only the carrying cost from the site of thermal plant to the laboratory is needed. Thus the use of fly ash in removing organic pollutants appears to be a cost viable. The simplicity of the technique makes the process quite acceptable.
Obecność organicznych zanieczyszczeń w strumieniu ścieków znacznie degraduje jakość wody. Zarówno własność estetyczne jaki i organizmy wodne stają wobec niebezpieczeństwa związanego z taką degradacją. Usunięcie zanieczyszczeń organicznych szczególnie za pomącą prostych i tanich metod jest wyzwaniem dla naukowców zajmujących się środowiskiem. Obecnie komunikaty naukowe mówią o możliwości zastosowania popiołów lotnych, odpadów stałych powstających w elektrociepłowniach, w usuwaniu albo redukcji ładunków niektórych organicznych zanieczyszczeń. W referacie przedstawiono wyniki badań nad adsorpcją siarczanu dodecylu sodu SDS (anionowy środek powierzchniowo czynny), zieleni malachitowej MG oraz 4-nitrofenolu na popiołach lotnych. Usunięcie SDS, 4-nitrofenolu i zieleni malachitowej na węglu aktywnym jest skutecznym i zadowalającym procesem. Ale koszt tej operacji jest bardzo wysoki. Dlatego, przedsięwzięto obecne badania używając popiołów lotnych jako substancji adsorbująca. W porównaniu do węgla aktywnego efektywność usunięcia na popiołach lotnych jest mniejsza w przypadku 4-nitrofenolu i SDS. Ale popioły lotne, będąc odpadem, są bardzo tanie. W ten sposób użycie popiołów lotnych w usuwaniu organicznych zanieczyszczeń okazuje się być wykonalne pod względem kosztów. Proces jest wykonalny kinetycznie i termodynamicznie, prosty w wykonaniu i tani.
Źródło:
Rocznik Ochrona Środowiska; 2003, Tom 5; 79-86
1506-218X
Pojawia się w:
Rocznik Ochrona Środowiska
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
MIPS sequences: a promising molecular consideration in angiosperm phylogeny and systematics
Autorzy:
Hazra, A.
Nandy, P.
Sengupta, C.
Das, S.
Powiązania:
https://bibliotekanauki.pl/articles/80785.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
myo-inositol-1-phosphate synthase
protein sequence
angiosperm
phylogenesis
maximum likelihood method
multiple sequence alignment
Źródło:
BioTechnologia. Journal of Biotechnology Computational Biology and Bionanotechnology; 2018, 99, 1
0860-7796
Pojawia się w:
BioTechnologia. Journal of Biotechnology Computational Biology and Bionanotechnology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kinetics and mechanism of electron transfer to pyridinium chlorochromate (VI) from sulfur containing amino acid, L-cysteine in aqueous and micellar media
Autorzy:
Senapati, S.
Das, S.
Mohanty, P.
Patnaik, A.K.
Powiązania:
https://bibliotekanauki.pl/articles/779166.pdf
Data publikacji:
2011
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
kinetyka
przeniesienie elektronu
chlorochromian pirydyny
cysteina
kinetics mechanism
electron transfer
pyridinium chlorochromate
cysteine
micellar media
Opis:
The electron transfer reaction of L-cysteine (RSH) with pyridinium chlorochromate (PCC) has been studied spectrophotometrically over the range 2.0 ≤ 10^3 [RSH] ≤ 6.0; 0.01 ≤ [H+] ≤ 0.2; 298 ≤ T ≤ 318 K and I = 0.3 mol dm-3 (NaClO4). The electron transfer reaction has also been carried out in the presence of anionic, cationic and neutral micelle. The reaction in acid medium is strongly catalyzed by changing [SDS]T (sodium dodecyl sulfate) up to 3 × 10-2 mol dm-3, beyond this concentration of SDS, the rate is retarded. The cationic and neutral micelle has a small effect on the rate. ΔH≠ (kJ mol-1) and ΔS≠ (JK-1 mol-1) values for the k1 and k2 paths are 30.20 ± 0.25, -159.65 ± 0.83 and 29.60 ± 0.62, -127.09 ± 2.17, respectively. The negative activation entropy is indicative of the ordered transition state for the electron transfer reaction. Formation of 2-amino-3-(2-amino-2-carboxy-ethyl) disulfanyl-propanoic acid as product is strongly supported by IR spectra.
Źródło:
Polish Journal of Chemical Technology; 2011, 13, 2; 6-10
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Parameters estimation and life cycle economic analysis of a PV powered tri-cycle in India
Autorzy:
Das, S.
Sadhu, P. K.
Majhi, A.
Ghatak, U.
Bandyopadhya, T.
Powiązania:
https://bibliotekanauki.pl/articles/141519.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
PV
tri-cycle
LCEA
fuel-based
Opis:
This paper is devoted towards life cycle economic analysis (LCEA) of a solar photovoltaic (PV) powered tri-cycle. The paper is meant to propose a more systematic approach in determining the optimum use of scarce resources in order to determine the most cost-effective option of the solar tri-cycle. This analysis is based on the life cycle cost of this solar vehicle, involving its comparison with the customary fuel-based tri-cycle which exhibits the relatively less expenditure of the solar alternative. The economic analysis takes into account the fact that over 20 years, the overall price of solar component, replacement and electricity charges, is much lower as compared to that of a fuel-based tri-cycle in India taking into consideration the fuel cost, maintenance and annual inflation over the same period.
Źródło:
Archives of Electrical Engineering; 2018, 67, 3; 655--665
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Identifying overlapping phylogenetic and geographic roots of HIV - 1 evolution through computational analyses
Autorzy:
Singh, P.K.
Banik, R.
Chakraborty, H.J.
Das, S.G.
Ganguli, S.
Datta, A.
Powiązania:
https://bibliotekanauki.pl/articles/11359.pdf
Data publikacji:
2014
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
phylogenetic root
geographic root
evolution
computational analysis
HIV-1
genome
recombinant strain
AIDS
human disease
acquired immunodeficiency syndrome zob.AIDS
acquired immune deficiency syndrome zob.AIDS
Opis:
HIV-1 or Human Immuno Deficiency Virus-1 is the main causative agent of Acquired Immuno Deficiency Syndrome (AIDS). Human host infected with HIV - 1 extensively harbours many viral variants but very little is known about the difference in pattern[17] of evolution of phylogenetic lineages of HIV-1 non recombinant, normal inter subtype recombinant and main two specific recombinant forms of HIV-1 i.e., Circulating Recombinant Forms (CRFs) and Unique Recombinant Forms (URFs). This study is mainly concerned with study of the difference in evolutionary lineages of non-recombinant and recombinant sequences of HIV-1 genome sequences and identification of geographically rich areas which has reported high degree of HIV-1 occurrence and variety. Total 1550 HIV-1 genome sequences were obtained from HIV Los Alamos Database. The sequences were aligned using MAFFT (Multiple Alignment using Fast Fourier Transform) web server tool. Alignment was carried out using 10 different set of alignment parameter values. After alignment the aligned file was used for constructing N-J phylogenetic tree using Clustal X2 tool. Phylogenetic analysis was performed keeping in mind the category to which the sequence belongs. Upon analysis it was observed that the clade containing the probable ancestor belongs remained constant in all cases of different alignment values. Non recombinant isolates, inter subtype recombinants, CRFs, URFs all followed different patterns of evolution. Non recombinant sequences were found geographically specific and subtype specific to some extent whereas, normal recombinants were subtype specific and less geographically specific. CRFs showed variation among the pattern of their evolution. At some instances the sequences occurred as sister taxa of non-recombinant or normal inter subtype recombinant sequences, while at some instances as sister taxa of other CRFs where they were geographically specific. Three CRFs existed as completely diverged sequences. URFs were four in number; two of them were Indian isolates of while other two were Japanese isolates. URFs were found to be totally geographically specific. Geography wise high rate of variation was observed in India and Japan as these two countries had sequences belonging to all of the above categories. Cameroon and South Africa have very large number isolates and a considerable amount of genetic variation among isolates but they lack URFs.
Źródło:
International Letters of Natural Sciences; 2014, 02
2300-9675
Pojawia się w:
International Letters of Natural Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
In-situ formed, ultrafine Al-Si composite materials: ductility
Autorzy:
Guba, P.
Gesing, A.
Sokolowski, J.
Conle, A.
Sobiesiak, A.
Das, S.
Kasprzak, M.
Powiązania:
https://bibliotekanauki.pl/articles/366887.pdf
Data publikacji:
2019
Wydawca:
Stowarzyszenie Komputerowej Nauki o Materiałach i Inżynierii Powierzchni w Gliwicach
Tematy:
ultrafine Al-Si composite
Al metal matrix
hypereutectic Al alloys
mechanical properties
high ductility
osnowa metalowa
stop nadeutektyczny
właściwości mechaniczne
ciągliwość
Opis:
Purpose: The work objective includes optimization of the casting production and heat treatment processes that will simultaneously maximize the combination of strength, hardness, and ductility for hypereutectic Al-Si compositions with Si volume fractions of as much as 25 vol.%. In addition, such an in-situ formed composite alloy will attain a unique combination of low production cost, high potential recycled content, and functional characteristics suitable for mission critical aerospace and vehicular applications. Design/methodology/approach: The unique High Pressure Die Casting Universal Metallurgical Simulator and Analyser (HPDC UMSA) was used for melting, cyclic melt treatment, and solidification of the hypereutectic Al-Si-X (A390). The produced as-cast structures contained colonies of nano-diameter Si whiskers and other morphologies, and absence of primary silicon particles. Heat treated structures rendered nano and ultrafine metal matrix composites. Findings: New developed as-cast Al-Si materials containing nano-diameter Si whiskers, without primary silicon particles required ultra short time heat treatment to result in nano and ultrafine metal matrix composite, rendering their hardness, strength and wear resistance, and the same time retaining toughness and ductility. Research limitations/implications: The cast samples were produced in laboratory conditions and potential tensile strength was estimated from empirical correlation with micro-hardness measurements. In the future, the comprehensive mechanical properties need to be tested. Practical implications: These ultrafine Si, Al-MMCs can be net-shape formed by modified HPDC technology or consolidated from spray-atomized alloy powder. Originality/value: Optimization of the entire production process for the hypereutectic Al-Si alloy compositions achieved a uniform distribution of ~ 25 vol.% of ultrafine Si particles in ductile FCC-Al matrix further reinforced by age hardening with nano-scale spinodal GP-zones. The associated mechanical property and ductility improvements will open a wide range of critical lightweighting components in transportation: aerospace, terrestrial vehicle and marine to the optimized hypereutectic Al-Si alloys. Presently, these components do not use the commercial HPDC A390 alloys due to their limited ductility and strength. Proposed new technology will allow conversion of various cast airspace alloys with ultrahigh mechanical properties to the automotive applications.
Źródło:
Journal of Achievements in Materials and Manufacturing Engineering; 2019, 92, 1-2; 5-12
1734-8412
Pojawia się w:
Journal of Achievements in Materials and Manufacturing Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 17

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