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1.
A system with n independent components which works if and only if a least k of its n components work is called a k-out-of-n system. For exponentially distributed component lifetimes, we obtain point and interval estimators for the scale parameter of the component lifetime distribution of a k-out-of-n system when the system failure time is observed only. In particular, we prove that the maximum likelihood estimator (MLE) of the scale parameter based on progressively Type-II censored system lifetimes is unique. Further, we propose a fixed-point iteration procedure to compute the MLE for k-out-of-n systems data. In addition, we illustrate that the Newton–Raphson method does not converge for any initial value. Finally, exact confidence intervals for the scale parameter are constructed based on progressively Type-II censored system lifetimes. 相似文献
2.
L. H. Yang Randolph Q. Hood J. E. Pask J. E. Klepeis 《Scientific Modeling and Simulation》2007,14(3):337-347
High-Z metals constitute a particular challenge for large-scale ab initio electronic-structure calculations, as they require high resolution due to the presence of strongly localized states and require many eigenstates to be computed due to the large number of electrons and need to accurately resolve the Fermi surface. Here, we report recent findings on high-Z metals, using an efficient massively parallel planewave implementation on some of the largest computational architectures currently available. We discuss the particular architectures employed and methodological advances required to harness them effectively. We present a pair-correlation function for U, calculated using quantum molecular dynamics, and discuss relaxations of Pu atoms in the vicinity of defects in aged and alloyed Pu. We find that the self-irradiation associated with aging has a negligible effect on the compressibility of Pu relative to other factors such as alloying. 相似文献
3.
A topological mechanism of hole localization as two skyrmions in the CuO2 layers of high-T c superconductors is suggested on the basis of a nonlinear σ model. 相似文献
4.
S. L. Liu 《Journal of Superconductivity and Novel Magnetism》2008,21(3):199-203
Based on the Arrhenius equation, a method to calculate the activation energy from the resistance transition is proposed for
high temperature superconductors. This method is applied to the Y-based superconductors. The activation energy is found to
be U(T,H)∼(1−T/T
c
)4.8(H/H
0)−3.8 of YBCO crystal, and U(T,H)∼(1−T/T
c
)3.3(H/H
0)−2.2 of Er doped MTG YBCO crystal, respectively. With the obtained activation energy U(T,H), the lower part of the experimental curve ρ(T,H) and its derivative can be reproduced.
相似文献
5.
Clustering has been recognized as a very important approach for data analysis that partitions the data according to some (dis)similarity criterion. In recent years, the problem of clustering mixed-type data has attracted many researchers. The k-prototypes algorithm is well known for its scalability in this respect. In this paper, the limitations of dissimilarity coefficient used in the k-prototypes algorithm are discussed with some illustrative examples. We propose a new hybrid dissimilarity coefficient for k-prototypes algorithm, which can be applied to the data with numerical, categorical and mixed attributes. Besides retaining the scalability of the k-prototypes algorithm in our method, the dissimilarity functions for either-type attributes are defined on the same scale with respect to their dimensionality, which is very beneficial to improve the efficiency of clustering result. The efficacy of our method is shown by experiments on real and synthetic data sets. 相似文献
6.
N. L. Bazhenov B. E. Zhurtanov K. D. Mynbaev A. P. Astakhova A. N. Imenkov M. P. Mikhaĭlova V. A. Smirnov N. D. Stoyanov Yu. P. Yakovlev 《Technical Physics Letters》2007,33(12):987-989
We have studied electroluminescence in n-GaSb/n-AlGaAsSb/n-GaInAsSb heterostructures with isotype heterojunctions, in which the quantum efficiency of emission is increased due to the additional production of electron-hole pairs as a result of the impact ionization that takes place near the heterointerface. The impact ionization in such heterostructures is possible due to the presence of deep wells in the energy band structure. 相似文献
7.
We consider the problem of designing algorithmic support for k-best routing decisions in train shunting scheduling. A study at the Netherlands Railways revealed that planners like to interact
with the solution process of finding suitable routes. Two types of interaction were required: the possibility of assigning
specific tracks to a route and of preventing the assignment of specific tracks to a route. The paper develops insights in
the structure of the cost matrix in this k-best optimization problem. These dominance results are used in a two stage k-shortest path algorithm to support this task of the shunting planners. The solution approach determines the optimal sequence
of the tracks that manually have been added to the route and determines the k shortest paths in this network. The approach is implemented in a prototype of a support system for shunting planners. The
required calculation times for practical instances of the problem with varying numbers of alternative solutions (k ≤ 8) and intermediate tracks (m ≤ 5) are between 0.1 and 1.4 s. These calculation times are acceptable to provide adequate support to the planners of these
shunting yards.
Supported by the Netherlands Railways, Project “Rintel 4a”. We gratefully acknowledge the management and planners of this
company. Specifically, we would like to thank Dr. L.G. Kroon and the planners of location Zwolle for their willingness to
co-operate. 相似文献
8.
A. P. Astakhova B. E. Zhurtanov A. N. Imenkov M. P. Mikhailova M. A. Sipovskaya N. D. Stoyanov Yu. P. Yakovlev 《Technical Physics Letters》2007,33(1):11-13
Photodiodes sensitive in the wavelength ranges 1–2.5 μm and 1–4.8 μm at room temperature have been created on the basis of n-GaSb/n-GaInAsSb/p-AlGaAsSb double-junction heterostructures of two types. The broadband photosensitivity of the diode structures of both types is indicative of the complete separation of photogenerated electron-hole pairs in the staggered n-p heterojunction (n-GaInAsSb/p-AlGaAsSb). The noise characteristics of photodetectors based on the proposed diode structures have been studied. Prospects of the use of these devices in thermophotovoltaic cells for low-temperature radiation sources are considered. 相似文献
9.
T. S. Khasanshin V. S. Samuilov A. P. Shchemelev 《Journal of Engineering Physics and Thermophysics》2008,81(4):760-765
This paper describes an improved experimental facility for measuring the speed of sound in liquids with an accuracy of up
to 0.1%. Measurements of the speed of sound in liquid n-hexane, n-octane, n-decane, and n-hexadecane at temperatures of 298–433
K and pressures of 0.1–100 MPa have been made. It has been shown that in the possible comparison range the obtained values
of the speed of sound are in good agreement with the literature data.
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 4, pp. 732–736, July–August, 2008. 相似文献
10.
The methylmethacrylate (MMA) incorporated SiO2 thin films having low dielectric constant (k = 2.97) were deposited successfully to realize new interlayer material for the enhancement of electrical performance of on-chip
wiring in very large scale integrated (VLSI) circuits. We have successfully incorporated MMA monomer and eliminated the polymerization
step to lower the dielectric constant of deposited thin film. The presence of peak of C=C bond in Fourier transform infrared
(FTIR) spectra and carbon peak in energy dispersive (EDAX) spectra confirms the incorporation of carbon in the film due to
MMA. The concentration of MMA has great impact on the peak area and full width at half maxima (FWHM) of the Si-O-Si bond,
which decreases the density by low atomic weight elements and consequently decreases the dielectric constant. The surface
morphology analysed by scanning electron microscopic (SEM) image shows excellent uniformity of the film. The refractive index
of 1.31 was measured by ellipsometer for 0.5 ml MMA concentration film. These deposited thin films having low refractive index
and dielectric constant are widely applicable for the optical interconnects and interlayer applications in integrated optical
circuits and VLSI circuits. 相似文献
11.
I. V. Rogozin A. N. Georgobiani M. B. Kotlyarevsky V. I. Demin A. V. Marakhovskii 《Inorganic Materials》2010,46(9):948-952
n-Type ZnO〈Ga〉 films were implanted with 150-keV N+ (As+) ions to a dose of 7 × 1015 cm−2 and then annealed in atomic oxygen at different temperatures. p-Type conductivity was obtained at annealing temperatures in the range 770–870 K. The parameters of the p-type layers were determined by photoluminescence spectroscopy, secondary ion mass spectrometry, and Hall effect measurements.
According to the Hall data, the p-type layers had a resistivity of ∼30 Ω cm, carrier mobility of ∼2 cm2/(V s), and carrier concentration of ∼1018 cm−3. The electroluminescence spectra of the p-n junctions produced by ion implantation showed a band at 440 nm, due to recombination via donor-acceptor pairs. 相似文献
12.
Weifeng Dai Yan Zhang Zhengzhen Du Minliang Ru Meidong Lang 《Journal of materials science. Materials in medicine》2010,21(6):1881-1890
The macromonomer of 2-hydroxyethyl methyacrylate-caprolactone (HPCL) was synthesized by the ring-opening polymerization (ROP) of ε-caprolactone, which was initiated by 2-hydroxyethyl methyacrylate (HEMA). Then, the graft terpolymers of NIPAAm-co-AAc-co-HEMA-g-PCL (PHNA-CL) with varying mole ratios were subsequently synthesized by free radical polymerization of HEMA-PCL, N-isopropylacrylamide (NIPAAm) and acrylic acid (AAc). PHNA-CL was further self-assembled in different types of solvent. All the as-prepared copolymers were characterized by 1H NMR, FT-IR and GPC. Micellization behaviors of micelles were studied by TEM and DLS. The micelles exhibited a phase transition temperature which can be readily adjusted by changing pH value of the micellization system. Micelle loaded with doxorubicin (DOX) was used to evaluate the drug release behavior. The release of DOX from micelles could be controlled by changing pH value and temperature in buffer solutions. The micelles are potentially to be used as a new anticancer drug carrier for intracellular delivery. 相似文献
13.
A. L. Ivanovskii 《Journal of Superhard Materials》2011,33(2):73-87
The state of the art in the search for novel superhard and (or) incompressible materials on the basis of higher borides of
s, p, d metals has been briefly reviewed. The information has been considered about experimental and theoretical studies of the following
groups of borides: diborides of 4d, 5d heavy metals (Tc, Ru, Rh, Re, Os, and Ir), hexagonal tetraborides with the WB4-type structure, and AMB14 borides (where A, M are s, p metals) as well as of a number of related systems. 相似文献
14.
Liu Yuan Wenshuai Fan Linyingjun Han Changan Guo Zuoqin Yan Meifang Zhu Xiumei Mo 《材料科学前沿(英文版)》2018,12(1):95-104
In this study, natural materials (sodium alginate, dextran, gelatin and carboxymethyl chitosan) were modified to get aldehyde components and amino components. Upon mixing the two-component solutions together, four kinds of Schiff base hydrogels formed successfully within 5-300 s and could seal the wound tissue. The cytotoxicity tests of hydrogel extraction solution confirmed that the hydrogels are nontoxic materials. The adhesive ability was evaluated in vivo by measuring the adhesive strength after sealing the skin incisions on the back of rats. All the hydrogels showed higher adhesive strength than that of commercial fibrin glue and the blank control. The histological staining observation by hematoxylin and eosin staining (HE) and Masson’s trichrome staining (MTC) methods suggested that the hydrogels had good biocompatibility and biodegradation in vivo. They have only normal initial inflammation to skin tissue and could improve the formation of new collagen in the incision section. So, the prepared hydrogels were both safe and effective tissue adhesive, which had the great potentials to be used as skin tissue adhesive. 相似文献
15.
The time-dependent Ginzburg–Landau equation with thermal noise is used to calculate the Nernst signal e
N
, describing the Nernst effect, in type-II superconductor in the vortex-liquid regime. The Gaussian method used is an elaboration
of the Hartree–Fock method. An additional assumption often made in analytical calculations that only the lowest Landau level
significantly contributes to physical quantities of interest in the high-field limit is lifted by including all the Landau
levels. The values of e
N
are in good quantitative agreement with experimental data for temperature close to T
c
on Bi2Sr2CaCu2O8+δ
and Bi2Sr2Ca2Cu3O10+δ
. 相似文献
16.
Wan Y Yu A Wu H Wang Z Wen D 《Journal of materials science. Materials in medicine》2005,16(11):1017-1028
Porous-conductive chitosan scaffolds were fabricated by blending conductive polypyrrole (PPy) particles with chitosan solution
and employing an improved phase separation method. In vitro and in vivo degradation behaviors of these scaffolds were investigated. In the case of in vitro degradation, an enzymatic degradation system was employed and lysozyme was used as a working enzyme. Meanwhile, the degradation
products of scaffolds, glucosamine and N-acetyl-glucosamine, were also analyzed with a HPLC method. In vivo degradation of scaffolds was performed by subcutaneously implanting these scaffolds in rat for prescheduled time intervals.
In the both cases, the weight-loss of scaffolds was monitored during the whole degradation process for evaluating the degradation
of scaffolds. The changes in conductivity of scaffolds afterin vitro or in vivo degradation were also measured using a four-point technique. It was observed that the pore parameters of scaffolds themselves
could significantly influence the degradation behaviors of scaffolds but the PPy content in the scaffolds seemed not to impart
its effect to the degradation of scaffolds. Degradation dynamics of scaffolds and conductivity measurements indicated that
these scaffolds shown fairly different behaviors in their in vitro and in vivo degradation process. According to the results obtained from in vitro and in vivo degradation of scaffolds and based on some requirements of practical tissue engineering application, it was suggested that
the PPy content in the scaffold should be slightly higher than 3 wt.% but lower than 6 wt.%. 相似文献
17.
G. N. Mikhailova B. P. Mikhailov V. N. Tokarev A. V. Troitskii V. M. Marchenko 《Inorganic Materials》2007,43(5):557-563
We have analyzed experimental data on the effect of short-term melting followed by recrystallization on the microstructure and critical current density of YBa2Cu3O7 ? x , Bi2Sr2CaCu2O8 ? x , and Bi2Sr2Ca2Cu3O10 ? x high-T c ceramics. The ceramics were melted using different heat sources: infrared lamps, laser radiation, and electric current. A significant increase in the critical current density of Bi2Sr2Ca2Cu3O10 ? x ceramics (by a factor of 40 at 20 K and by a factor of 8 at 77 K) was achieved using cw CO2 laser irradiation. Melting TiC-doped (0.1%) Bi2Sr2Ca2Cu3O10 ? x ceramics with a CO2 laser, followed by annealing, insured an even larger increase in critical current density: by a factor of 35 at 77 K. We have calculated the thickness of the molten layer produced by laser heating of high-T c ceramics. 相似文献
18.
Petra J. Kluger Ralf Wyrwa Jürgen Weisser Julia Maierle Miriam Votteler Claudia Rode Matthias Schnabelrauch Heike Walles Katja Schenke-Layland 《Journal of materials science. Materials in medicine》2010,21(9):2665-2671
Electrospinning is a long-known polymer processing technique that has received more interest and attention in recent years
due to its versatility and potential use in the field of biomedical research. The fabrication of three-dimensional (3D) electrospun
matrices for drug delivery and tissue engineering is of particular interest. In the present study, we identified optimal conditions
to generate novel electrospun polymeric scaffolds composed of poly-d/l-lactide and poly-l-lactide in the ratio 50:50. Scanning electron microscopic analyses revealed that the generated poly(d/l-lactide-co-l-lactide) electrospun hybrid microfibers possessed a unique porous high surface area mimicking native extracellular matrix
(ECM). To assess cytocompatibility, we isolated dermal fibroblasts from human skin biopsies. After 5 days of in vitro culture,
the fibroblasts adhered, migrated and proliferated on the newly created 3D scaffolds. Our data demonstrate the applicability
of electrospun poly(d/l-lactide-co-l-lactide) scaffolds to serve as substrates for regenerative medicine applications with special focus on skin tissue engineering. 相似文献
19.
This article introduces the Impact Factor squared or IF2-index, an h-like indicator of research performance. This indicator reflects the degree to which large entities such as countries and/or their
states participate in top-level research in a field or subfield. The IF2-index uses the Journal Impact Factor (JIF) of research publications instead of the number of citations. This concept is applied
to other h-type indexes and their results compared to the IF2-index. These JIF-based indexes are then used to assess the overall performance of cancer research in Australia and its states
over 8 years from 1999 to 2006. The IF2-index has three advantages when evaluating larger research units: firstly, it provides a stable value that does not change
over time, reflecting the degree to which a research unit participated in top-level research in a given year; secondly, it
can be calculated closely approximating the publication date of yearly datasets; and finally, it provides an additional dimension
when a full article-based citation analysis is not feasible. As the index reflects the degree of participation in top-level
research it may favor larger units when units of different sizes are compared. 相似文献
20.
V VASUDEVAN R RAMESH BABU A REICHER NELCY G BHAGAVANNARAYANA K RAMAMURTHI 《Bulletin of Materials Science》2011,34(3):469-475
Semi-organic nonlinear optical material, L-lysine L-lysinium dichloride nitrate (2C6H15N2O2+_{2}^{+} · H + · NO3-_{3}^{-} · 2Cl − ) was synthesized at room temperature. Single crystals of L-LLDN were grown by slow cooling solution growth technique. The grown crystal was confirmed by powder X-ray diffraction analysis.
The crystalline perfection of the grown single crystal was characterized by high-resolution X-ray diffraction (HRXRD) studies.
The cut-off wavelength was determined by UV-vis transmission spectral analysis. The frequency doubling of the grown crystal
was confirmed by powder second harmonic generation (SHG) measurement. The refractive index and birefringence of the crystal
were determined using He–Ne laser source. Mechanical property of the crystal was determined by Vickers hardness tester. The
frequency and temperature dependence of dielectric constant (ε
r), dielectric loss (tan δ) and a.c. conductivity (σ
ac) were also measured. 相似文献