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    Tytuł:
    Road to Quantum Boxes
    Autorzy:
    Chang, L. L.
    Powiązania:
    https://bibliotekanauki.pl/articles/1946514.pdf
    Data publikacji:
    1996-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.20.Dx
    73.61.-r
    78.66.-w
    Opis:
    Quantum wells and superlattices have evolved over the last two decades to become a prominent multi-disciplinary field in condensed matter science. From the first observation of resonant tunneling to the recent realization of the quantum box, in this work we provide a summary description of the historical development of the field, known today as quantum structures. The focus is on the physics aspect with emphasis on important experimental observations that collectively define the field and set its direction of development.
    Źródło:
    Acta Physica Polonica A; 1996, 90, 4; 603-612
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    How To Construct Support Vector Machines Without Breaching Privacy
    Autorzy:
    Zhan, J.
    Chang, L.
    Matwin, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/92993.pdf
    Data publikacji:
    2006
    Wydawca:
    Uniwersytet Przyrodniczo-Humanistyczny w Siedlcach
    Tematy:
    privacy
    security
    support vector machine (SVM)
    Opis:
    This paper addresses the problem of data sharing among multiple parties in the following scenario: without disclosing their private data to each other, multiple parties, each having a private data set, want to collaboratively construct support vector machines using a linear, polynomial or sigmoid kernel function. To tackle this problem, we develop a secure protocol for multiple parties to conduct the desired computation. In our solution, multiple parties use homomorphic encryption and digital envelope techniques to exchange the data while keeping it private. All the parties are treated symmetrically: they all participate in the encryption and in the computation involved in learning support vector machines.
    Źródło:
    Studia Informatica : systems and information technology; 2006, 1(7); 233-244
    1731-2264
    Pojawia się w:
    Studia Informatica : systems and information technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A Multi-Party Scheme for Privacy : Preserving Clustering
    Autorzy:
    Zhan, J.
    Matwin, S.
    Chang, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/93043.pdf
    Data publikacji:
    2006
    Wydawca:
    Uniwersytet Przyrodniczo-Humanistyczny w Siedlcach
    Tematy:
    privacy
    security
    clustering
    Opis:
    Preserving data privacy while conducting data clustering among multiple parties is a demanding problem. We address this challenging problem in the following scenario: without disclosing their private data to each other, multiple parties, each having a private data set, want to collaboratively conduct k-medoids clustering. To tackle this problem, we develop secure protocols for multiple parties to achieve this dual goal. The solution is distributed, i.e., there is no central, trusted party having access to all the data. Instead, we define a protocol using homomorphic encryption and digital envelope techniques to exchange the data while keeping it private.
    Źródło:
    Studia Informatica : systems and information technology; 2006, 1(7); 217-232
    1731-2264
    Pojawia się w:
    Studia Informatica : systems and information technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Impact of mesh quality on the numerical estimation of saturated water conductivity of pore media
    Autorzy:
    Gackiewicz, B.
    Lamorski, K.
    Slawiński, C.
    Hsu, S.-Y.
    Chang, L.-C.
    Powiązania:
    https://bibliotekanauki.pl/articles/2082923.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Instytut Agrofizyki PAN
    Tematy:
    porous media
    numerical modelling
    hydraulic
    conductivity
    mesh accuracy
    Opis:
    The numerical modelling of transport phenomena in porous media often requires a compromise between grid precision and the accuracy of simulation results. This study demonstrates the impact of errors on the accuracy of the reproduction of the actual pore space by the numerical grid on the estimated values of the saturated water conductivity. Four types of computational grids with varying levels of complexity were prepared for each of the 12 tomographic images of the porous specimens. The specific surfaces and total porosities were calculated for each of the meshes and compared with those parameters calculated for binarized tomographic images. Simulations of steady flow were performed on the computational grids, and the saturated water conductivity values were calculated. It has been shown that an insufficiently accurate mesh only reproduces the largest pore spaces in the analysed sample, which most often leads to an underestimation of the water conductivity coefficient. The following criterion for the optimal accuracy of the computational grid is proposed, it is based on the voxel size of the tomographic images of the porous media: the minimum size of the cell in the mesh used for simulations has to be at most two times the size of the voxel used in the tomographic scans of the porous medium.
    Źródło:
    International Agrophysics; 2020, 34, 4; 473-483
    0236-8722
    Pojawia się w:
    International Agrophysics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Paleomagnetic analyses on Badenian–Sarmatian drill cores from the North Carpathian Foredeep (Middle Miocene, Poland)
    Analizy paleomagnetyczne rdzeni wiertniczych z utworów badenu–sarmatu z północnej części zapadliska przedkarpackiego (środkowy miocen, Polska)
    Autorzy:
    Sant, K.
    Leeuw, A. de
    Chang, L.
    Czapowski, G.
    Gąsiewicz, A.
    Krijgsman, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/2061987.pdf
    Data publikacji:
    2015
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Badenian-Sarmatian boundary
    paleomagnetic dating
    Northern Carpathian Foredeep
    granica baden–sarmat
    datowania paleomagnetyczne
    zapadlisko przedkarpackie
    Opis:
    Accurate dating of the Badenian–Sarmatian transition, a boundary between two regional Middle Miocene stages of the semi-isolated Paratethys Sea, is crucial to understand what event caused the corresponding major turnover in faunal assemblage at that point in time. The general opinion is that this event resulted from a sudden isolation of the Eastern Paratethys from ocean water, due to the closure of the Eastern Anatolian seaway to the Indian Ocean, but it remains debated if the final isolation had a tectonic or climatic cause. This pilot study presents paleomagnetic analyses of two drill cores from the North Carpathian Foredeep in Poland that straddle the Badenian–Sarmatian transition. Rock magnetic experiments, including thermomagnetic runs in air on a Curie balance, and hysteresis measurements on a MicroMag, indicate that the dominant magnetic carrier is the iron sulphide greigite. This is in agreement with the observed gyroremanence obtained during alternating field demagnetization above 40 mT. Alternating field and thermal demagnetization results are in good agreement and show a weak, mixed-polarity, signal for most of the Badenian, rapidly shifting to a much stronger and dominantly normal polarity signal in the Sarmatian part of the cores. First order reversal curves diagrams indicate that the greigite in the Sarmatian part is clearly of diagenetic origin, it thus most likely concerns a secondary overprint by the present-day field that cannot be used for magnetostratigraphic correlations. We conclude that the Paratethys-wide paleoenvironmental change that occurred at the Badenian–Sarmatian transition had probably also created different conditions for the formation and/or preservation of magnetic minerals.
    Dokładne datowanie przejścia baden–sarmat, granicy dwóch regionalnych pięter środkowego miocenu na terenie częściowo izolowanego morza Paratetydy, jest istotne dla zrozumienia przyczyny wyraźnej zmiany zespołów faunistycznych, która towarzyszyła temu wydarzeniu. Według powszechnie akceptowanych poglądów wydarzenie to było wynikiem nagłego odcięcia obszaru Paratetydy Wschodniej od otwartego oceanu wskutek zamknięcia cieśnin na terenie wschodniej Anatolii, które stanowiły łącznik z Oceanem Indyjskim. Obecnie przedmiotem dyskusji jest tektoniczna lub klimatyczna przyczyna tego wydarzenia. Paleomagnetyczne badania pilotowe rdzeni z dwóch otworów wiertniczych, położonych w północnej części zapadliska przedkarpackiego na terenie Polski, dotyczą przejściowej, badeńsko-sarmackiej sukcesji osadowej. Badania petromagnetyczne (w tym analizy termomagnetyczne na wadze Curie oraz histerezy na instrumencie MicroMag) wskazują, że dominującym minerałem magnetycznym jest siarczek żelaza – greigit, co potwierdza obecność składowej giromagnetycznej podczas rozmagnesowywania próbek zmiennym polem magnetycznym powyżej 40 mT. Wyniki polowej i termicznej demagnetyzacji są zgodne i wskazują na słaby sygnał, o mieszanej polarności, dla większości sukcesji badeńskiej, wzmocniony i zmieniający charakter na normalny dla części sarmackiej profilu. Odwrócone krzywe pierwszego rzędu dowodzą, że greigit w osadach sarmackich jest minerałem diagenetycznym, co bardziej wskazuje na wtórne nałożenie oddziaływania współczesnego pola magnetycznego i tym samym nie pozwala na przeprowadzenie korelacji magnetostratygraficznych. Autorzy stwierdzają, że zmiana paleośrodowiskowa w Paratetydzie na pograniczu badenu i sarmatu wpłynęła na powstanie i/lub dalsze przemiany minerałów o właściwościach magnetycznych.
    Źródło:
    Biuletyn Państwowego Instytutu Geologicznego; 2015, 461; 179--192
    0867-6143
    Pojawia się w:
    Biuletyn Państwowego Instytutu Geologicznego
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Si/ZnO nanorods with Ag nanoparticles/AZO heterostructures in PV applications
    Autorzy:
    Gwóźdź, K.
    Płaczek-Popko, E.
    Gumienny, Z.
    Zielony, E.
    Pietruszka, R.
    Witkowski, B. S.
    Wachnicki, Ł.
    Gierałtowska, S.
    Godlewski, M.
    Chang, L. B.
    Powiązania:
    https://bibliotekanauki.pl/articles/201432.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    solar cells
    ZnO
    Si
    heterojunction
    nanorods
    nanoparticles
    ogniwa słoneczne
    nanopręty
    nanocząstki
    Opis:
    Our studies focus on test structures for photovoltaic applications based on zinc oxide nanorods grown using a low-temperature hydrothermal method on a p-type silicon substrate. The nanorods were covered with silver nanoparticles of two diameters – 20–30 nm and 50–60 nm – using a sputtering method. Scanning electron microscopy (SEM) micrographs showed that the deposited nanoparticles had the same diameters. The densities of the nanorods were obtained by means of atomic force microscope (AFM) images. SEM images and Raman spectroscopy confirmed the hexagonal wurtzite structure of the nanorods. Photoluminescence measurements proved the good quality of the samples. Afterwards an atomic layer deposition (ALD) method was used to grow ZnO:Al (AZO) layer on top of the nanorods as a transparent electrode and ohmic Au contacts were deposited onto the silicon substrate. For the solar cells prepared in that manner the current-voltage (I-V) characteristics before and after the illumination were measured and their basic performance parameters were determined. It was found that the spectral characteristics of a quantum efficiency exhibit an increase for short wavelengths and this behavior has been linked with the plasmonic effect.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2016, 64, 3; 529-533
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An algorithm for finding a common solution for a system of mixed equilibrium problem, quasi-variational inclusion problem and fixed point problem of nonexpansive semigroup
    Autorzy:
    Min, L.
    Chang, S.
    Zuo, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/255589.pdf
    Data publikacji:
    2010
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
    Tematy:
    nonexpansive semigroup
    mixed equilibrium problem
    viscosity approximation method
    quasi-variational inclusion problem
    multi-valued maximal monotone mappings
    alpha-inverse-strongly monotone mapping
    Opis:
    In this paper, we introduce a hybrid iterative scheme for finding a common element of the set of solutions for a system of mixed equilibrium problems, the set of common fixed points for a nonexpansive semigroup and the set of solutions of the quasi-variational inclusion problem with multi-valued maximal monotone mappings and inverse-strongly monotone mappings in a Hilbert space. Under suitable conditions, some strong convergence theorems are proved. Our results extend some recent results in the literature.
    Źródło:
    Opuscula Mathematica; 2010, 30, 4; 465-484
    1232-9274
    2300-6919
    Pojawia się w:
    Opuscula Mathematica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mild Method to Synthesize TATB by Amination of 1,3,5-Trialkoxy-2,4,6-Trinitrobenzene under Phase Transfer Catalysis Conditions
    Autorzy:
    Chang, T.
    Li, B.
    Chen, L.
    Ge, L.
    Lu, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/358103.pdf
    Data publikacji:
    2017
    Wydawca:
    Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
    Tematy:
    TATB
    phase transfer catalysis
    atmospheric amination reaction
    Opis:
    Nucleophilic amination, as a vital step in the synthesis of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) using 1,3,5-trialkoxy-2,4,6-trinitrobenzene (TORTNB) and aqueous ammonia as the starting materials and catalyzed by phase transfer catalysis (PTCs) under mild conditions is described. Various phase transfer catalysts, such as crown ethers, tertiary amines, quaternary ammonium salts, poly ethers and cyclodextrin, and various experimental parameters, such as no. of equivalents of PTC, mole ratio of ammonium hydroxide to the starting material, reaction time, reaction temperature and cycle times of the organic phase were investigated. The crown ethers, especially 18-crown-6, show good catalytic activity and re-usability for the amination of 1,3,5-triethoxy-2,4,6-trinitrobenzene giving a yield of 96.52%. This makes for a safe process and suitable for scale-up, because the reactions are carried out under atmospheric conditions. The material synthesised by the new system was characterized by DSC, SEM and LPS.
    Źródło:
    Central European Journal of Energetic Materials; 2017, 14, 1; 47-59
    1733-7178
    Pojawia się w:
    Central European Journal of Energetic Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Recovery mechanisms of sericite in microcrystalline graphite flotation
    Autorzy:
    Li, H.
    Ou, L.
    Feng, Q.
    Chang, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/110055.pdf
    Data publikacji:
    2015
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    microcrystalline graphite
    sericite
    flotation
    entrainment
    entrapment
    Opis:
    Sericite is the main contaminant of concentrate in commercial microcrystalline graphite ore flotation. It was necessary to identify its recovery mechanisms so that the appropriate solution can be selected. In this study, the influence of sericite on flotation selectivity of microcrystalline graphite ore and its recovery mechanisms were investigated. Artificial mixtures flotation test suggested that sericite seriously reported into concentrate leading to poor flotation selectivity of microcrystalline graphite ore. However, the aggregation/dispersion behavior of artificial mixtures indicated that a large repulsive energy existed between sericite and microcrystalline graphite particles at pH 7.4, and sericite was not likely to report into graphite concentrate by slime coating. The results obtained from contact angle measurements and a technique of Warren showed that the floated sericite reached the froth via a combination of both entrainment and entrapment mechanisms, not via true flotation.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2015, 51, 2; 387-400
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analysis of an N-policy GI/M/1 queue in a multi-phase service environment with disasters
    Autorzy:
    Jiang, T.
    Ammar, S. I.
    Chang, B.
    Liu, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/330836.pdf
    Data publikacji:
    2018
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    N-policy
    GI/M/1 queue
    multiphase service environment
    disaster
    sojourn time
    kolejka GI/M/1
    katastrofa
    czas pobytu
    Opis:
    This paper investigates an N-policy GI/M/1 queue in a multi-phase service environment with disasters, where the system tends to suffer from disastrous failures while it is in operative service environments, making all present customers leave the system simultaneously and the server stop working completely. As soon as the number of customers in the queue reaches a threshold value, the server resumes its service and moves to the appropriate operative service environment immediately with some probability. We derive the stationary queue length distribution, which is then used for the computation of the Laplace– Stieltjes transform of the sojourn time of an arbitrary customer and the server’s working time in a cycle. In addition, some numerical examples are provided to illustrate the impact of several model parameters on the performance measures.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2018, 28, 2; 375-386
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Noise Elimination of Reciprocating Compressors Using FEM, Neural Networks Method, and the GA Method
    Autorzy:
    Chang, Y.-C.
    Chiu, M.-C.
    Xie, J.-L.
    Powiązania:
    https://bibliotekanauki.pl/articles/178126.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    finite element method
    polynomial neural network model
    genetic algorithm
    group method of data handling
    reciprocating compressor
    optimization
    Opis:
    Industry often utilizes acoustical hoods to block noise emitted from reciprocating compressors. However, the hoods are large and bulky. Therefore, to diminish the size of the compressor, a compact discharge muffler linked to the compressor outlet is considered. Because the geometry of a reciprocating compressor is irregular, COMSOL, a finite element analysis software, is adopted. In order to explore the acoustical performance, a mathematical model is established using a finite element method via the COMSOL commercialized package. Additionally, to facilitate the shape optimization of the muffler, a polynomial neural network model is adopted to serve as an objective function; also, a Genetic Algorithm (GA) is linked to the OBJ function. During the optimization, various noise abatement strategies such as a reverse expansion chamber at the outlet of the discharge muffler and an inner extended tube inside the discharge muffler, will be assessed by using the artificial neural network in conjunction with the GA optimizer. Consequently, the discharge muffler that is optimally shaped will decrease the noise of the reciprocating compressor.
    Źródło:
    Archives of Acoustics; 2017, 42, 2; 189-197
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Acid alpha-galactosidase is involved in D-chiro-inositol accumulation during tartary buckwheat germination
    Autorzy:
    Jia, C.-F.
    Hu, W.-H.
    Chang, Z.
    Gao, H.-L.
    Powiązania:
    https://bibliotekanauki.pl/articles/59199.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Botaniczne
    Tematy:
    alpha-galactosidase
    D-chiro-inositol
    accumulation
    tartary buckwheat
    Fagopyrum tataricum
    duckwheat zob.tartary buckwheat
    India buckwheat zob.tartary buckwheat
    India wheat zob.tartary buckwheat
    green buckwheat zob.tartary buckwheat
    germination
    gene expression
    Opis:
    Tartary buckwheat seed and especially its sprouts are rich in D-chiroinositol (DCI). The research was to evaluate when DCI was most accumulated in tartary buckwheat sprouts. In addition, we explored the activity and expression pattern of α-galactosidase during tartary buckwheat seed germination. The results showed that DCI contents steadily increased at early stage of germination and reached the highest level of 33.42 μg/seed at 24 h during the 72 h trail. However, the total fagopyritol contents sharply decreased from 214.6 μg/seed to 46 μg/seed at the end of the germination. The activity of acid α-galactosidase increased gradually to the peak of 0.36 nkat/seed at 24 h after the primed seed imbibition. We cloned the gene fragment of α-galactosidase in tartary buckwheat for the first time. The deduced amino acid sequence is 93% identical to that of P. vulgaris. The quantitative PCR result of gene expression pattern was consistent with its enzyme activity during seed germination.
    Źródło:
    Acta Societatis Botanicorum Poloniae; 2015, 84, 1
    0001-6977
    2083-9480
    Pojawia się w:
    Acta Societatis Botanicorum Poloniae
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical Assessment of a One-Mass Spring-Based Electromagnetic Energy Harvester on a Vibrating Object
    Autorzy:
    Chiu, M.-C.
    Chang, Y.-C.
    Yeh, L.-J.
    Chung, C.-H.
    Powiązania:
    https://bibliotekanauki.pl/articles/177720.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    spring
    harvester
    generator
    permanent magnet
    simulated annealing
    optimization
    buckling
    Fatigue
    Opis:
    The paper is an exploration of the optimal design parameters of a space-constrained electromagnetic vibration-based generator. An electromagnetic energy harvester is composed of a coiled polyoxymethylen circular shell, a cylindrical NdFeB magnet, and a pair of helical springs. The magnet is vertically confined between the helical springs that serve as a vibrator. The electrical power connected to the coil is actuated when the energy harvester is vibrated by an external force causing the vibrator to periodically move through the coil. The primary factors of the electrical power generated from the energy harvester include a magnet, a spring, a coil, an excited frequency, an excited amplitude, and a design space. In order to obtain maximal electrical power during the excitation period, it is necessary to set the system’s natural frequency equal to the external forcing frequency. There are ten design factors of the energy harvester including the magnet diameter (Dm), the magnet height (Hm), the system damping ratio (ζsys), the spring diameter (Ds), the diameter of the spring wire (ds), the spring length (ℓs), the pitch of the spring (ps), the spring’s number of revolutions (Ns), the coil diameter (Dc), the diameter of the coil wire (dc), and the coil’s number of revolutions (Nc). Because of the mutual effects of the above factors, searching for the appropriate design parameters within a constrained space is complicated. Concerning their geometric allocation, the above ten design parameters are reduced to four (Dm, Hm, ζsys, and Nc). In order to search for optimal electrical power, the objective function of the electrical power is maximized by adjusting the four design parameters (Dm, Hm, ζsys, and Nc) via the simulated annealing method. Consequently, the optimal design parameters of Dm, Hm, ζsys, and Nc that produce maximum electrical power for an electromagnetic energy harvester are found.
    Źródło:
    Archives of Acoustics; 2016, 41, 1; 119-131
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of Vacuum Hot-Press Process on The Sintered Characteristics and Mechanical Properties of A High-Density Cr-31.2 Mass% Ti Alloy
    Autorzy:
    Chang, S.-H.
    Li, C.-L.
    Huang, K.-T.
    Yang, T.-H.
    Powiązania:
    https://bibliotekanauki.pl/articles/356911.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    Cr-31.2 mass% Ti alloy
    vacuum hot-press sintering
    relative density
    TRS
    electrical conductivity
    Opis:
    In this study, two different compositions of submicron-structured titanium (760 nm) and micron-structured chromium (4.66 μm) powders were mixed to fabricate Cr-31.2 mass% Ti alloys by vacuum hot-press sintering. The research imposed various hot-press sintering pressures (20, 35 and 50 MPa), while the sintering temperature maintained at 1250°C for 1h. The experimental results showed that the optimum parameters of the hot-press sintered Cr-31.2 mass% Ti alloys were 1250°C at 50 MPa for 1h. Also, the relative density reached 99.94%, the closed porosity decreased to 0.04% and the hardness and transverse rupture strength (TRS) values increased to 81.90 HRA and 448.53 MPa, respectively. Moreover, the electrical conductivity is enhanced to 1.58 × 104 S·cm-1 However, the grain growth generated during the high-temperature and high-pressure of the hot-press sintering process resulted in the grain coarsening phenomenon of the Cr-31.2 mass% Ti alloys after 1250°C hot-press sintering at 50 MPa for 1h. In addition, the Cr-31.2 mass% Ti alloys were fabricated with the submicron-structured titanium (760 nm) and chromium (588 nm) powders showed more effective compaction than the micron-structured titanium (760 nm) and chromium (4.66 μm) powders did. The closed porosity decreases to 0.02% and the hardness values increase to 83.23 HRA. However, the agglomeration phenomenon of the Cr phase and brittleness of the TiCr2 Laves phases easily led to a slight decrease in TRS (400.54 MPa).
    Źródło:
    Archives of Metallurgy and Materials; 2018, 63, 4; 1715-1723
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Finite element analysis of three-point bending of a T-beam structural biaxial highly oriented polymer material
    Analiza metodą elementów skończonych zginania trójpunktowego belki teowej wykonanej z wysoko zorientowanego dwuosiowo materiału polimerowego
    Autorzy:
    Wei, C.-L.
    Chang, Y.
    Lee, Y.-C.
    Lee, R.
    Luo, T.-W.
    Chen, J.-H.
    Powiązania:
    https://bibliotekanauki.pl/articles/946988.pdf
    Data publikacji:
    2018
    Wydawca:
    Sieć Badawcza Łukasiewicz - Instytut Chemii Przemysłowej
    Tematy:
    solid phase processing
    highly oriented polymer (HOP)
    orthotropic materials
    T-beam
    three-point bending
    finite element
    proces w fazie stałej
    wysoko zorientowany polimer
    materiały ortotropowe
    belka teowa
    zginanie trójpunktowe
    elementy skończone
    Opis:
    Polymers with biaxial aligned molecular chains are also orthotropic materials, which are characterized by high tensile strength and low shear strength in the length direction. When orthotropic materials are used as structural shapes with poor shear strength, they are likely to undergo premature failure under shear stress. Therefore, in three-point bending, the cross-section of the entire profile not only bears tensile stress and compressive stress in the length direction, but also simultaneously exhibits shear stress. This study analyzes the distribution of tensile stress, compressive stress and shear stress in the length direction of highly oriented polymers (HOP) by finite element analysis to find the most suitable length-to-height ratio for these materials when used as structural shapes. The finite element analysis software, Abaqus, is utilized to simulate HOP T-beam to analyze the load stress of a T-beam. With a fixed cross–section area, as the length of the material changes, its shear strength also changes. Accordingly, the order of occurrence of tensile failure and shear failure can be investigated. The simulation reveals that when the length-to-height ratio is between 4 : 1 and 20 : 1, a zone of stress in which tensile failure and shear failure occur can be found. This result can be exploited in the design and development of structural beam.
    Polimery o dwuosiowo zorientowanych łańcuchach makrocząsteczek są materiałami ortotropowymi, wykazującymi dużą wytrzymałość na rozciąganie oraz niewielką wytrzymałość na ścinanie w kierunku długości. Elementy konstrukcyjne wytworzone z materiału ortotropowego o małej wytrzymałości na ścinanie są podatne na przedwczesne uszkodzenie pod wpływem naprężeń ścinających. Przy zginaniu trójpunktowym w przekroju ich profilu występują zarówno naprężenia rozciągające i ściskające w kierunku podłużnym, jak i naprężenia ścinające. Metodą elementów skończonych analizowano rozkład naprężeń rozciągających, ściskających i ścinających w kierunku podłużnym wysoko zorientowanych polimerów (HOP) w celu określenia optymalnego stosunku długości do wysokości w kształtach konstrukcyjnych. Do symulacji naprężeń obciążeniowych w zginaniu trójpunktowym belki teowej wykorzystano program komputerowy Abaqus. Stwierdzono, że przy stałej powierzchni przekroju poprzecznego belki jej wytrzymałość na ścinanie zmienia się wraz ze zmianą długości. Badano również kolejność występowania uszkodzeń pod wpływem działania sił rozciągających i ścinających. Symulacja wykazała, że przy stosunku długości do wysokości w zakresie od 4 : 1 do 20 : 1 występuje strefa naprężeń, w której mogą się pojawiać uszkodzenia w wyniku rozciągania lub ścinania. Uzyskane wyniki można wykorzystać w projektowaniu i optymalizacji belek konstrukcyjnych.
    Źródło:
    Polimery; 2018, 63, 3; 219-223
    0032-2725
    Pojawia się w:
    Polimery
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-15 z 15

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