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1.
It has been reported that dislocations with 1/3\( \left\langle {\bar{1}101} \right\rangle \) edge component of the Burgers vector are formed in {1\( \bar{1} \)04}/\( \left\langle {11\bar{2}0} \right\rangle \) low-angle grain boundaries of alumina (α-Al2O3). These dislocations dissociate into two partial dislocations with a stacking fault on the (0001) plane (Tochigi et al. in J Mater Sci 46:4428–4433, 2011). However, the dissociation reaction of these dislocations has not been determined so far. In this study, the structures of the dissociated dislocations and the (0001) stacking fault were investigated by transmission electron microscopy and theoretical calculations. It was revealed that the dissociated dislocations were generated from the 1/3\( \left\langle {\bar{1}101} \right\rangle \) perfect edge dislocation by the reaction of 1/3\( \left\langle {\bar{1}101} \right\rangle \) → 1/18\( \left\langle {\bar{4}223} \right\rangle \) + 1/18\( \left\langle {\bar{2}4\bar{2}3} \right\rangle \). Furthermore, electron energy loss spectroscopy analysis was performed to examine the atomic/electronic structure of the (0001) stacking fault. In the observed spectra, a chemical shift and intensity decrease were found at the oxygen K-edge. Theoretical spectrum analysis using first-principles calculations revealed that the characteristic features of the spectra are originated from the local atomic configurations of the (0001) stacking fault.  相似文献   

2.
The stress-strain curves under tensile deformation in the 〈100〉, 〈110〉, and 〈111〉 directions and under shear deformation in the (001)〈110〉, \((110)\langle \overline {1}10\rangle \), \((111)\langle 1\overline {1}0\rangle \), and \((111)\langle 11\overline {2}\rangle \) slip systems have been systematically calculated by first-principles method to study the ideal strengths of superconducting MgCNi3 and CdCNi3. The ideal strengths in the three tensile directions are found to be reduced in the order of 〈100〉 → 〈110〉 → 〈111〉 and those for the four shear slip systems in the order of \((110)\langle \overline {1}10\rangle \rightarrow (111)\langle 11\overline {2}\rangle \rightarrow (111)\langle 1\overline {1}0\rangle \rightarrow (001)\langle 110\rangle \) for both superconductors. Their lowest ideal tensile strengths are found to be larger than the corresponding highest ideal shear strengths, which could explain why both superconductors have the ductility. The obtained lattice constants and elastic properties coincide well with the the available experimental and theoretical values.  相似文献   

3.
Let \({\mathbb {F}}_{2^m}\) be a finite field of characteristic 2 and \(R={\mathbb {F}}_{2^m}[u]/\langle u^k\rangle ={\mathbb {F}}_{2^m} +u{\mathbb {F}}_{2^m}+\ldots +u^{k-1}{\mathbb {F}}_{2^m}\) (\(u^k=0\)) where \(k\in {\mathbb {Z}}^{+}\) satisfies \(k\ge 2\). For any odd positive integer n, it is known that cyclic codes over R of length 2n are identified with ideals of the ring \(R[x]/\langle x^{2n}-1\rangle \). In this paper, an explicit representation for each cyclic code over R of length 2n is provided and a formula to count the number of codewords in each code is given. Then a formula to calculate the number of cyclic codes over R of length 2n is obtained. Moreover, the dual code of each cyclic code and self-dual cyclic codes over R of length 2n are investigated.  相似文献   

4.
We measured the out-of-plane (c-axis) thermal conductivity of epitaxially grown \(\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-{\delta }}\) (YBCO) thin films (250 nm, 500 nm and 1000 nm) in the temperature range from 10 K to 300 K using the photothermal reflectance technique. The technique enables us to determine the thermal conductivity perpendicular to a thin film on a substrate by curve fitting analysis of the phase lag between the thermoreflectance signal and modulated heating laser beam in the frequency range from \(10^{2}\,\hbox {Hz}\) to \(10^{6}\,\hbox {Hz}\). The uncertainties of measured thermal conductivity of all samples were estimated to be within \({\pm }9\,\%\) at 300 K, \({\pm }12\,\%\) at 180 K, \({\pm }16\,\%\) at 90 K and \({\pm }20\,\%\) below 50 K. The experimental results show that the thermal conductivity is dependent on the thickness of the thin films across the entire temperature range. We also observed that the thermal conductivity of the present YBCO thin films showed \(T^{1.4}\) to \(T^{1.6}\) glass-like dependence below 50 K, even though the films are crystalline solids. In order to explain the reason for this temperature dependence, we attempted to analyze our results using phonon relaxation times for possible phonon scattering models, including stacking faults, grain boundary and tunneling states scattering models.  相似文献   

5.
\({\upvarepsilon }\)-Polylysine is an effective food preservative. In this paper, the \({\upbeta }\)-relaxation time of \({\upvarepsilon }\)-polylysine aqueous solutions, which represents the rotational speed of a single water molecule, was measured by broadband dielectric spectroscopy at various temperatures and concentrations. The broadband dielectric spectrum of each sample containing water ranging from 35 wt% to 75 wt% at temperatures ranging from \(0\,^{\circ }\hbox {C}\) to \(25\,^{\circ }\hbox {C}\) was measured using a co-axial semirigid cable probe. The measured dielectric spectra of the samples were composed of several Debye relaxation peaks, including a shortest single molecular rotational relaxation time of water, the \({\upbeta }\)-relaxation time, longer than that of pure water. This result represents that \({\upvarepsilon }\)-polylysine suppresses the molecular kinetics of water. It is also found that the \({\upbeta }\)-relaxation time of an \({\upvarepsilon }\)-polylysine solution that contained more than 35 wt% water showed a typical Arrhenius plot in the temperature range from \(0\,^{\circ }\hbox {C}\) to \(25\,^{\circ }\hbox {C}\). The activation energy of each sample depends on the water content ratio of the sample. As indicated by its long \({\upbeta }\)-relaxation time, \({\upvarepsilon }\)-polylysine is expected to possess high abilities of suppressing freezing and ice coarsening.  相似文献   

6.
A quaternary glass system \(\hbox {Na}_{1.4}\hbox {B}_{2.8}\hbox {Si}_{x}\hbox {Pb}_{0.3-x}\hbox {O}_{5.2+x}\), with 0 \(\le \) x \(\le \) 0.3, was prepared and studied by Fourier transform infrared spectroscopy, density and ultrasonic techniques to debate the issue of the role of \(\hbox {SiO}_{2}\) in the structure of lead alkali borate glasses. The results indicate that \(\hbox {SiO}_{2}\) generates an abundance of bridging oxygen atoms, [\(\hbox {BO}_{4}\)] and [\(\hbox {SiO}_{4}\)] structural units and changes the bonds B–O–B and Pb–O–B to Si–O–Si and B–O–Si. The latter bonds have higher bond strength and higher average force constant than the former bonds. Therefore, the glass structure becomes contracted and compacted, which decreases its molar volume and increases its rigidity. This concept was asserted from the increase in the ultrasonic velocity, Debye temperature and elastic moduli with the increase of \(\hbox {SiO}_{2}\) content. The present compositional dependence of the elastic moduli was interpreted in terms of the electron–phonon anharmonic interactions and the polarization of \(\hbox {Si}^{4+}\) cation. A good correlation was observed between the experimentally determined elastic moduli and those computed according to the Makishima–Mackenzie model.  相似文献   

7.
Quaternary tellurite glasses with composition \(75\hbox {TeO}_{2}\)\(5\hbox {WO}_{3}\)\(15\hbox {Nb}_{2} \hbox {O}_{5}\)\(5\hbox {M}_{x} \hbox {O}_{y}\) in mol%, where \(\hbox {M}_{x}\hbox {O}_{y}\) = (\(\hbox {Na}_{2}\hbox {O}, \, \hbox {Ag}_{2}\hbox {O}\), ZnO, MgO, CuO, NiO, \(\hbox {TiO}_{2}\), \(\hbox {MnO}_{2}\)), were prepared by the normal melt-quenching method. The ultrasonic velocities (longitudinal and shear) were measured in these glasses using the pulse-echo technique at room temperature. Their elastic moduli, microhardness and Debye temperature were calculated and discussed in terms of the modifier’s ionicity and quantitatively in terms of number of bonds per unit volume and the cross-link density. In this study, the values of ultrasonic velocities, elastic moduli, Debye temperature and microhardness were found to be strongly dependent on three factors, namely: (i) modifier’s ionicity; (ii) trigonal pyramid (\(\hbox {TeO}_{3}\))/trigonal bipyramid (\(\hbox {TeO}_{4}\)) ratio; and (iii) glass transition temperature \(T_\mathrm{g}\). We used the Makishima and Mackenzie’s model to calculate the theoretical elastic moduli and to indicate that the experimental values were in good agreement with the theoretical values.  相似文献   

8.
This paper deals with the semi-functional partial linear regression model \(Y={{\varvec{X}}}^\mathrm{T}{\varvec{\beta }}+m({\varvec{\chi }})+\varepsilon \) under \(\alpha \)-mixing conditions. \({\varvec{\beta }} \in \mathbb {R}^{p}\) and \(m(\cdot )\) denote an unknown vector and an unknown smooth real-valued operator, respectively. The covariates \({{\varvec{X}}}\) and \({\varvec{\chi }}\) are valued in \(\mathbb {R}^{p}\) and some infinite-dimensional space, respectively, and the random error \(\varepsilon \) verifies \(\mathbb {E}(\varepsilon |{{\varvec{X}}},{\varvec{\chi }})=0\). Naïve and wild bootstrap procedures are proposed to approximate the distribution of kernel-based estimators of \({\varvec{\beta }}\) and \(m(\chi )\), and their asymptotic validities are obtained. A simulation study shows the behavior (on finite sample sizes) of the proposed bootstrap methodology when applied to construct confidence intervals, while an application to real data concerning electricity market illustrates its usefulness in practice.  相似文献   

9.
10.
To reduce uncertainty of calibrations of contact thermometers using dry block calibrators, a concept was developed at Institute for Process Measurement and Sensor Technology of Technische Universität Ilmenau. This concept uses a multi-zone heating, heat flux sensors and a multiple fixed-point cell. The paper shows the concept and its validation on the basis of a dry block calibrator with a working temperature range of \(70\,^{\circ }\hbox {C}\) to \(430\,^{\circ }\hbox {C}\). The experimental results show a stability of \({\pm } 4\,\hbox {mK}\) for the reference temperature and axial temperature differences in the normalization block less than \({\pm }55\,\hbox {mK}\).  相似文献   

11.
This paper presents a study on the damping ratio \(({\upbeta })\) used in discrete element simulations. Physical experiments are performed by dropping particles from a predetermined height. Two kinds of granular particles, aluminum and steel spheres, are used. The size of these particles are the same. The process of particle depositing under gravity is simulated using the discrete element method. The experimental observation is compared with the numerical result to identify the appropriate \({\upbeta }\). The result indicates that the appropriate damping ratio used in discrete element simulations is between 0.2 and 0.3 %. Various \({\upbeta }\) are then used in the numerical simulations to study the effect of \({\upbeta }\) on the dropping process. The final height of the sample relates to \({\upbeta }\) and the drop height. The effect of \({\upbeta }\) is more profound for small drop height. For greater drop height, the effect of \({\upbeta }\) is negligible.  相似文献   

12.
The scaling behavior of dynamic hysteresis was investigated in Bi3.15Nd0.85Ti3O12 bulk ceramics at a frequency of 1–1000 Hz and an external electric field amplitude of 79–221 kV/cm. The scaling behavior at low amplitude (E 0 ≤ 114 kV/cm) takes the form of \(\langle A \rangle \propto f^{ - 0.013} E_{0}^{0.7}\) for low frequency (f ≤ 200 Hz) and \(\langle A \rangle \propto f^{ - 0.013} E_{0}^{0.22}\) for high frequency (f > 200 Hz), where \(\langle A \rangle\) is the area of hysteresis loop and f and E 0 are frequency and amplitude of external electric field, respectively. At high amplitude (E 0 > 114 kV/cm), we obtain \(\langle A \rangle \propto f^{0.011} E_{0}^{1.163}\) at low frequency and \(\langle A \rangle \propto f^{ - 0.015} E_{0}^{0.7}\) at high frequency. At low E 0, the contribution to the scaling relation mainly results from reversible domain switching, while at high E 0 reversible and irreversible domain switching concurrently contribute to the scaling relation.  相似文献   

13.
Alumina and alumina–zirconia mixed oxides were compared as supports to prepare nickel catalysts. The oxides were prepared by the sol–gel method using aluminum tri-sec-butoxide and zirconium (IV) propoxide as precursors, and its physicochemical properties were determined by BET, TGA, DTA, XRD, SEM and TEM. The catalysts of nickel were obtained by the impregnation of the supports with nickel nitrate (10 wt%) and were heat-treated at \(700{^{\circ }}\hbox {C}\). The specific area of the supports and catalysts decreased with the increase in the zirconia content in agreement with the crystalline phase formed. TEM micrographs of nickel catalysts revealed particles in the size range of 10–30 nm. The \(\hbox {Ni/Al}_{2}\hbox {O}_{3}\)\(\hbox {ZrO}_{2}\) catalysts were tested in the steam reforming reaction of ethanol (SRE) at \(500{^{\circ }}\hbox {C}\), and the obtained results suggest that the differences in catalytic activities depended on the content of \(\hbox {ZrO}_{2}\). The selectivity towards \(\hbox {H}_{2}\) was \({\sim }56\%\) for the named catalyst Ni–Al–0.25Zr.  相似文献   

14.
Infrared (IR) transparent ceramics are found to have applications in demanding defence and space missions. In this work, \(\hbox {Y}_{2}\hbox {O}_{3}\)\(\hbox {MgO}\) nanocomposites were synthesised by a modified single-step combustion technique. The characterisation of the as-prepared powder by X-ray diffraction and transmission electron microscopy revealed the presence of cubic phases of ultra-fine nanostructured \(\hbox {Y}_{2}\hbox {O}_{3 }\) and MgO, with an average crystallite size of \({\sim }19 \hbox { nm}\). For the first time the resistive and microwave heatings were effectively coupled for sintering the sample, and it was found that the sintering temperature and soaking time were reduced considerably. The pellets were sintered to 99.2% of the theoretical density at \(1430{^{\circ }}\hbox {C}\) for a soaking duration of 20 min. The well-sintered pellets with an average grain size of \({\sim }200 \hbox { nm}\) showed better transmittance properties relative to pure yttria. The promising percentage transmission of 80% in the UV–visible region and 82% in the mid-IR region shown by \(\hbox {Y}_{2}\hbox {O}_{3}\)\(\hbox {MgO}\) nanocomposites can be tailored and made cost-effective to fabricate high-quality IR windows for strategic defence and space missions.  相似文献   

15.
\(\hbox {SrTiO}_{3}\) and Bi-doped \(\hbox {SrTiO}_{3}\) films were fabricated with different device structures using the sol–gel method for non-volatile memory applications, and their resistance-switching behaviour, endurance and retention characteristics were investigated. \(\hbox {SrTiO}_{3}\) and \(\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}\) films grown on Si or Pt have the same phase structure, morphologies and grain size; however, the grain size of the \(\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}\) films grown on Si is slightly larger than those of the \(\hbox {SrTiO}_{3}\) films grown on Si and the \(\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}\) films grown on Pt. The \(\hbox {SrTiO}_{3}\) or \(\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}\) films grown on Si or Pt all exhibit bipolar resistive-switching behaviour and follow the same conductive mechanism; however, the \(\hbox {Ag}/\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}/\hbox {Si}\) device possesses the highest \(R_{\mathrm{HRS}}{/}R_{\mathrm{LRS}}\) of \(10^{5}\) and the best endurance and retention characteristics. The doping of Bi is conducive to enhance the \(R_{\mathrm{HRS}}{/}R_{\mathrm{LRS}}\) of the \(\hbox {SrTiO}_{3}\) films; meanwhile, the Si substrates help improve the endurance and retention characteristics of the \(\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}\) films.  相似文献   

16.
The present paper reports the effect of B- and BN-doped \(\hbox {C}_{60}\) as catalysts for lowering the dehydrogenation energy in \(\hbox {MXH}_{4}\) clusters (M = Na and Li, X = Al and B) using density functional calculations. \(\hbox {MXH}_{4}\) interacts strongly with B-doped \(\hbox {C}_{60}\) and weakly with BN-doped \(\hbox {C}_{60}\) in comparison with pure \(\hbox {C}_{60}\) with binding energy 0.56–0.80 and 0.05–0.34 eV, respectively. The hydrogen release energy \((E_{\mathrm{HRE}})\) of \(\hbox {MXH}_{4}\) decreases sharply in the range of 38–49% when adsorbed on B-doped \(\hbox {C}_{60}\); however, with BN-doped \(\hbox {C}_{60}\) the decrease in the \(E_{\mathrm{HRE}}\) varies in the range of 6–20% as compared with pure \(\hbox {MXH}_{4}\) clusters. The hydrogen release energy of second hydrogen atom in \(\hbox {MXH}_{4}\) decreases sharply in the range of 1.7–41% for BN-doped \(\hbox {C}_{60}\) and decreases in the range of 0.2–11.3% for B-doped \(\hbox {C}_{60}\) as compared with pure \(\hbox {MXH}_{4}\) clusters. The results can be explained on the basis of charge transfer within \(\hbox {MXH}_{4}\) cluster and with the doped \(\hbox {C}_{60}\).  相似文献   

17.
A study was conducted to ascertain the effect of variation in spin speed and baking temperature on \(\upbeta \)-phase content in the spin-coated poly(vinylidene fluoride) (PVDF) thick films (\({\sim }4{-}25\,\upmu \hbox {m}\)). Development of \(\upbeta \)-phase is dependent on film stretching and crystallization temperature. Therefore, to study the development of \(\upbeta \)-phase in films, stretching is achieved by spinning and crystallization temperature is adjusted by means of baking. PVDF films are characterized using Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy. It is observed that crystallization temperature lower than \(60^{\circ }\hbox {C}\) and increase in spin speed increases the \(\upbeta \)-phase content in PVDF films. Crystallization temperature above \(60^{\circ }\hbox {C}\) reduces \(\upbeta \)-phase content and increases \(\upalpha \)-phase content. It was also observed that viscosity of the PVDF solution affects the \(\upbeta \)-phase development in films at a particular spin speed.  相似文献   

18.
Kinematic viscosity correlation has been developed for liquid petroleum fractions at 37.78\(\,^{\circ }\hbox {C}\) and \(98.89\,^{\circ }\hbox {C}\) (100 and \(210^{\circ }\hbox {F})\) standard temperatures using a large variety of experimental data. The only required inputs are the specific gravity and the average boiling point temperature. The accuracy of the correlation was compared with several other correlations available in the literature. The proposed correlations proved to be more accurate in predicting the viscosity at 37.78\(\,^{\circ }\hbox {C}\) and \(98.89\,^{\circ }\hbox {C}\) with average absolute deviations of 0.39 and \(0.72\hbox { mm}^{2}/\hbox {s}\), respectively. Another objective was to develop a relation for the variation of viscosity with temperature to predict the viscosity of petroleum fraction at a certain temperature from the knowledge of the viscosity for the same liquid at two other temperatures. The newly developed correlation represents a wide array of temperatures from 20 \(^{\circ }\hbox {C}\) to 150 \(^{\circ }\hbox {C}\) and viscosities from 0.14\(\hbox { mm}^{2}/\hbox {s}\) to 343.64\(\hbox { mm}^{2}/\hbox {s}\). The results have been validated with experimental data consisting of 9558 data points, yielding an overall deviation of \(0.248\hbox { mm}^{2}/\hbox {s}\) and \(\hbox {R}^{2}\) of 0.998. In addition, new formulas were developed to interconvert the viscosity of petroleum fractions from one unit of measure to another based on finding the best fit for a set of experimental data from the literature with \(R^{2}\) as high as 1.0 for many cases. Detailed analysis showed good agreement between the predicted values and the experimental data.  相似文献   

19.
Structural and optical properties of \(\text {WO}_{3}/\text {Ag}/\text {WO}_{3}\) nano-multilayer composites were investigated for heat mirror applications. \(\text {WO}_{3}/\text {Ag}/\text {WO}_{3}\) thin films were fabricated through a physical vapour deposition method by using electron-beam evaporation at the vacuum chamber at 10\(^{-5}\) Torr. \(\text {WO}_{3}\) nano-layer was fabricated at 40 nm. Annealing treatment was carried out at 100, 200, 300 and 400\(^{\circ }\)C for 1 h after the deposition of first layer of \(\text {WO}_{3}\) on the glass. On \(\text {WO}_{3}\) film, Ag nano-layers with 10, 12 or 14 nm thickness were deposited. Individual layers morphology was investigated using atomic force microscopy (AFM) and deduced that a smoother layer can be achieved after the annealing at 300\(^{\circ }\)C. Ellipsometry analysis was executed to determine both layers, Ag film thickness and inter-diffusion between the \(\text {WO}_{3}\)–Ag–\(\text {WO}_{3}\) layers. It was inferred that there was almost no interfering among the \(\text {WO}_{3}\)\(\text {WO}_{3 }\) layers in the samples with 12 and 14 nm Ag thickness; while silver was deposited on the annealed \(\text {WO}_{3}\) layer at 300\(^{\circ }\)C. UV–visible spectrophotometer showed that the annealing treatment of the first \(\text {WO}_{3}\) layer enhanced the transparency of films in the visible region. The innovations of the present study have been based on the annealing of the films and finding an optimum thickness for the Ag film at 12–14 nm. Heat mirrors efficiency was assessed according to the principle of their optical behaviour and optimum performance obtained for 14 nm of Ag film, deposited on annealed tungsten oxide at 300\(^{\circ }\)C.  相似文献   

20.
We report the first calorimetric detection of individual \(\hbox {He}_2^*\) excimers within a bath of superfluid \(^4\hbox {He}\). The detector used in this work is a single superconducting titanium transition edge sensor (TES) with an energy resolution of \({\sim }1~\hbox {eV}\), immersed directly in the helium bath. \(\hbox {He}_2^*\) excimers are produced in the surrounding bath using an external gamma-ray source. These excimers exist either as short-lived singlet or long-lived triplet states. We demonstrate detection (and discrimination) of both states: In the singlet case the calorimeter records the absorption of a prompt \({\approx }15~\hbox {eV}\) photon, and in the triplet case the calorimeter records a direct interaction of the molecule with the TES surface, which deposits a distinct fraction of the \({\approx }15~\hbox {eV}\), released upon decay, into the surface. We also briefly discuss the detector fabrication and characterization.  相似文献   

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