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991.
We consider deterministic and stochastic perturbations of dynamical systems with conservation laws in ℝ3. The Landau-Lifshitz equation for the magnetization dynamics in ferromagnetics is a special case of our system. The averaging
principle is a natural tool in such problems. But bifurcations in the set of invariant measures lead to essential modification
in classical averaging. The limiting slow motion in this case, in general, is a stochastic process even if pure deterministic
perturbations of a deterministic system are considered. The stochasticity is a result of instabilities in the non-perturbed
system as well as of existence of ergodic sets of a positive measure. We effectively describe the limiting slow motion. 相似文献
992.
Laser alloying of Ni–P electroless deposited layer with aluminum substrate was carried out by Nd–YAG pulsed laser. The phase composition and microstructure of the alloyed layers produced by different laser power densities were identified by X-ray diffractionary (XRD), scanning electron microscope (SEM) accompanied by energy dispersion X-ray analysis (EDS) and transmission electron microscope (TEM). Furthermore, the surface roughness of the alloyed layers was characterised by confocal laser scanning microscope (CLSM). The results showed that the characteristic dendritic or lamellar microstructures were observed in the alloyed layers. The phase constituents of the alloyed zones were intermetallic compounds of nickel–aluminum NiAl, Al3Ni and Al3Ni2, as well as some non-equilibrium phases and amorphous phases depending on the employed laser power density. As a result, the microhardness of the alloyed layer with Ni–P amorphous phases formed at laser power density 5.36×109 W/m2 reached to HV0.1 390. 相似文献
993.
Structure and photoluminescence properties of ZnS films grown on porous Si substrates 总被引:1,自引:0,他引:1
ZnS films were deposited on porous silicon (PS) substrates with different porosities. With the increase of PS substrate porosity, the XRD diffraction peak intensity decreases and the surface morphology of the ZnS films becomes rougher. Voids appear in the films, due to the increased roughness of PS structure. The photoluminescence (PL) spectra of the samples before and after deposition of ZnS were measured to study the effect of substrate porosity on the luminescence properties of ZnS/PS composites. As-prepared PS substrates emit strong red light. The red PL peak of PS after deposition of ZnS shows an obvious blueshift. As PS substrate porosity increases, the trend of blueshift increases. A green emission at about 550 nm was also observed when the porosity of PS increased, which is ascribed to the defect-center luminescence of ZnS. The effect of annealing time on the structural and luminescence properties of ZnS/PS composites were also studied. With the increase of annealing time, the XRD diffraction peak intensity and the self-activated luminescence intensity of ZnS increase, and, the surface morphology of the ZnS films becomes smooth and compact. However, the red emission intensity of PS decreases, which was associated with a redshift. White light emission was obtained by combining the luminescence of ZnS with the luminescence of PS. 相似文献
994.
This work considers solving the sup-T{\mathcal{T}} equation constrained optimization problems from the integer programming viewpoint. A set covering-based surrogate approach
is proposed to solve the sup-T{\mathcal{T}} equation constrained optimization problem with a separable and monotone objective function in each of the variables. This
is our first trial of developing integer programming-based techniques to solve sup-T{\mathcal{T}} equation constrained optimization problems. Our computational results confirm the efficiency of the proposed method and show
its potential for solving large scale sup-T{\mathcal{T}} equation constrained optimization problems. 相似文献
995.
The purpose of this paper is to investigate nonemptiness and boundedness of the solution set for a vector equilibrium problem with strict feasibility in reflexive Banach spaces. We introduce the concept of strict feasibility for a vector equilibrium problem, which recovers the existing concepts of strict feasibility introduced for variational inequalities. We prove that a pseudomonotone vector equilibrium problem has a nonempty bounded solution provided that it is strictly feasible in the strong sense. 相似文献
996.
Surface profile inspection of a moving object by using dual-frequency Fourier transform profilometry
The 2π phase ambiguity caused by surface isolations and large height step can be solved by dual-frequency projection grating profilometry. However, in the Fourier transform profilometry (FTP) of a moving object, only one single deformed fringe pattern can be obtained. In order to introduce the dual-frequency technique into the FTP of moving object, a novel experimental system is designed to capture two fringe patterns with different frequency at the same time. A grating structure comprising two regions with different frequencies is projected upon the surface of the detected object. Two line-scan CCD cameras are used to capture the surface images encoded by the two kinds of patterns, respectively. By getting the corresponding image intensity at the same point of the object surface in the two acquired images, the dual-frequency technique is applied to extract the real phase without phase ambiguity. The surface profile of a specimen with a large height step is measured to prove the feasibility of the proposed method. The experimental results show that the proposed method can solve the 2π phase ambiguity problem successfully in the surface profile inspection of a moving object. 相似文献
997.
According to the principle of double-beam interference imaging using an infrared broadband light source, a novel method based on the optical fiber low-coherence Young's interferometer for the measurement of programmable optical fiber delay line is proposed. By measuring the small length increments of delay fiber through the evaluation of the central positions of zero-order interference fringes, we successfully construct a system with a variety of important functions, such as real-time controlling, measurement and displaying. This system offers the benefit that it can be regulated precisely to generate interference stripes once again after the length of fiber segment changes. When the locations of central stripes are moved to coincide with the original markers, the determination of the corresponding fiber optical delay time becomes really simplified, as just by reading out the tinny displacement of the reference arm. Multiple groups of experimental results demonstrate the outstanding performance of the proposed system since it bears a measuring accuracy of μm and a measuring range from 1 mm to 20 cm. 相似文献
998.
The nonlinear response of the experimental system and the saturation of fringe patterns can induce the fluctuating phase error in the projection grating phase-shifting profilometry. Two major factors of the fluctuating phase error are discussed by simulation. The fluctuating phase error caused by the nonlinear response of the system is four times the frequency of the fringe pattern when the conventional four-frame phase extracting algorithm is used. However, such error can be decreased by five-frame algorithm. On the other hand, the fluctuating phase error caused by the fringe saturation is five times the frequency of the fringe pattern by using conventional five-frame phase extracting algorithm. A novel phase recovering algorithm is used to decrease the phase error caused by the saturation. Furthermore, the applicability range of the proposed phase recovering algorithm is analyzed by simulation and experiments with different saturation degree of the fringe pattern and nonlinearity of the measurement system. 相似文献
999.
Chaos synchronization and encoding in coupled semiconductor lasers of multiple modulated time delays
We numerically investigate the synchronization performance of unidirectionally and bidirectionally coupled chaotic semiconductor lasers subject to multiple modulated time delays optical feedbacks. Moreover, by studying the autocorrelation function of the coherent feedback semiconductor laser output, we find that the signatures of time delays can be erased in systems incorporating modulated feedback time delays, which largely improve the system security. Finally, chaos masking switching (CMS) is utilized to examine the communication ability. Numerical results indicate that the messages could be successfully recovered both in unidirectionally and bidirectionally coupled lasers, which confirms the possibility of applying multiple modulated delay system in optical chaos secure communication. 相似文献
1000.
High quality photonic crystal heterostructures with a thin titania planar defect layer between its two constitutional photonic crystals were fabricated and their structural and optical properties were analyzed. The results suggest that the thin planar defect layer is beneficial to separate the two constitutional photonic crystals from each other and to reduce the roughness of the interface. The quality of the resulting photonic crystal heterostructures is improved largely and the main features of the photonic band gaps of the two constitutional photonic crystals are inherited. The predominant optical quality of these heterostructures (e.g. deep double photonic band gaps and steep photonic band edges) may afford new flexibility and functionality for engineered photonic behavior in practical devices such as late-model light-operated switches. 相似文献