共查询到20条相似文献,搜索用时 15 毫秒
1.
In this paper, we use random walk theory to describe the length dynamics of microtubules, one of the principal components of the cytoskeleton. We present a simple two-state model (growing and shrinking) of microtubule length evolution that incorporates a variable rate of switching between the states. Using the generating function technique, we calculate the mean length of microtubule, its variance and diffusion coefficient. We also report analytical and computer simulation results for the mean number of positive monomers in microtubule, and find good qualitative agreement with experimental data. 相似文献
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Dorota Nowak-Wo?ny Tomasz Janiczek Witold Mielcarek Juliusz B. Gajewski 《Journal of Electrostatics》2009,67(1):18-21
Modified bismuth oxide (Bi2O3) is of great importance to fuel cells and oxide varistors. The electrical parameters of Bi2O3 vary with its modifying components as well as with its aging temperature. This paper presents an analysis of impedance test results carried out to find an equivalent electric model and the relationship between the model's elements to various additives used to modify Bi2O3 and to changes in aging temperature. The proposed model was tested via computer simulation and the model parameters correlated to individual modifiers. 相似文献
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We describe new planar multiport devices written by spatial solitons that are composed of several nonlinearly coupled components in Kerr-type media. Such devices have no radiation losses at a given wavelength. We demonstrate that, for the same relative angle between the input soliton-induced channels, one can vary the transmission coefficients into the output channels by adjusting the polarizations of multicomponent solitons. We determine analytically the transmission properties and discuss two types of experimental embodiment of the proposed device. 相似文献
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The acoustic effect significantly increases the timing jitter of solitons and the bit-error rates in communication lines. We suggest the transmission of information with fixed-length blocks that contain an equal number of ones and zeros to suppress acoustically induced timing jitter. It is shown theoretically that this approach will significantly enhance the performance of systems with bit rates per channel higher than 20 Gbits/s. 相似文献
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Optimal allocation of amplifiers in a dispersion-managed line for a wavelength-division-multiplexed soliton transmission system 总被引:1,自引:0,他引:1
Optimal allocation of amplifiers in a dispersion-managed line is theoretically derived by means of minimizing the collision-induced frequency shift in a two-channel wavelength-division-multiplexed soliton transmission system. Almost complete cancellation of the frequency shift can be obtained for such a system with any strength of dispersion management. 相似文献
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The effect of the third-order filter term on soliton interactions in optical fibers with guiding filters is theoretically analyzed. We find that this term causes a significant difference to the interaction of solitons through filters among the regimes of without sliding, with up- and down-sliding frequencies of filters. It is shown that the interaction between solitons can be more effectively suppressed by up-sliding filters than that by down-sliding filters in the presence of the third-order filter term. Moreover, the third-order filter term is found to play a positive role in suppressing soliton interactions in the case of non-sliding. 相似文献
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Yong Zhang Donald M. Reeves Karl Pohlmann Jenny B. Chapman Charles E. Russell 《Central European Journal of Physics》2013,11(6):634-645
Tracer transport through fractured media exhibits concurrent direction-dependent super-diffusive spreading along high-permeability fractures and sub-diffusion caused by mass transfer between fractures and the rock matrix. The resultant complex dynamics challenge the applicability of conventional physical models based on Fick’s law. This study proposes a multi-scaling tempered fractional-derivative (TFD) model to explore fractional dynamics for tracer transport in fractured media. Applications show that the TFD model can capture anomalous transport observed in small-scale single fractures, intermediate-scale fractured aquifers, and two-dimensional large-scale discrete fracture networks. Tracer transport in fractured media from local (0.255-meter long) to regional (400-meter long) scales therefore can be quantified by a general fractional-derivative model. Fractional dynamics in fractured media can be scale dependent, owning to 1) the finite length of fractures that constrains the large displacement of tracers, and 2) the increasing mass exchange capacity along the travel path that enhances sub-diffusion. 相似文献
10.
Jicheng Wang Yueke Wang Xueru Zhang Kun Yang Yuxiao Wang Shutian Liu Yinglin Song 《Optik》2011,122(20):1808-1810
A transmission line model for subwavelength metallic grating with single cut is presented. The model is based on analogy between the subwavelength metallic structure and the microwave transmission line theory. The analytical expression for the transmission is derived by the transfer matrix method. To confirm our model, the finite-difference time-domain (FDTD) method simulations are carried out. The influences of the position of the cuts on the higher modes of slit are presented. It is found that the transmission line model gives analytical prediction about the evolution of the transmission spectra. 相似文献
11.
Timing jitter induced by soliton collisions is the leading nonlinear penalty in wavelength-division-multiplexed (WDM) dispersion-managed soliton transmission. Through analysis and numerical simulations we show that consecutive complete collisions together with partial collisions at the system output cause approximately the same amount of timing shift as partial collisions at the system input. We further show that the worst-case timing shift diverges logarithmically with the total number of WDM channels and linearly with the total transmission distance. However, the probability for such worst cases to occur decreases exponentially with channel spacing, total number of WDM channels, and transmission distance. We conclude that only the effects caused by adjacent channels need to be considered in a high channel count WDM system. 相似文献
12.
Conrad Bertrand Tabi Alidou Mohamadou Timoléon Crépin Kofané 《Physics letters. A》2009,373(29):2476-2483
We study the nonlinear dynamics of DNA which takes into account the twist-opening interactions due to the helicoidal molecular geometry. The small amplitude dynamics of the model is shown to be governed by a solution of a set of coupled nonlinear Schrödinger equations. We analyze the modulational instability and solitary wave solution in the case. On the basis of this system, we present the condition for modulation instability occurrence and attention is paid to the impact of the backbone elastic constant K. It is shown that high values of K extend the instability region. Through the Jacobian elliptic function method, we derive a set of exact solutions of the twist-opening model of DNA. These solutions include, Jacobian periodic solution as well as kink and kink-bubble solitons. 相似文献
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We present a closed form expression to analyse the error performance of a differential phase-shift keying (DPSK) digital modulation format in an optical soliton communication system. In the analysis we include the effect of Gordon-Haus jitter, which is mainly due to the amplified spontaneous emission noise of the amplifiers. Gordon-Haus jitter is found to be less significant when the bit period is 15 times greater than the jitter variance and becomes more significant when the signal-to-noise ratio is greater than 20 dB. Due to a good bit error rate (BER) performance (BER ≈ 10−20at SNR= 21 dB), the DPSK modulation format has a potential application for a high-bit-rate and low-noise soliton communication system. 相似文献
14.
Abstract The bit error rate (BER) performance of an optical soliton communication system is analyzed. Based on the jitter variance equation and the chi-square distribution for the amplified spontaneous emission noise, an analytic expression for the BER calculation is obtained. We have investigated the effects of Gordon-Haus jitter, which is due to the random phase shift of the soliton individual central wavelength induced by the amplified spontaneous emission noise of the amplifiers. Very good agreement has been obtained between our theory and the reported experimental results. 相似文献
15.
We consider a one-dimensional chain of coupled linear and nonlinear oscillators with long-range powerwise interaction. The corresponding term in dynamical equations is proportional to 1//n-m/alpha+1. It is shown that the equation of motion in the infrared limit can be transformed into the medium equation with the Riesz fractional derivative of order alpha, when 0相似文献
16.
The bit error rate (BER) performance of an optical soliton communication system is analyzed. Based on the jitter variance equation and the chi-square distribution for the amplified spontaneous emission noise, an analytic expression for the BER calculation is obtained. We have investigated the effects of Gordon-Haus jitter, which is due to the random phase shift of the soliton individual central wavelength induced by the amplified spontaneous emission noise of the amplifiers. Very good agreement has been obtained between our theory and the reported experimental results. 相似文献
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We introduce an extended nonlinear Schrödinger (ENLS) equation describing the dynamics of modulated waves in a nonlinear discrete electrical transmission line (NLTL) with nonlinear dispersion. We show that this equation admits envelope dark solitary wave with compact support, with width and speed independent of the amplitude, as a solution. Analytical criteria of existence and stability of this solution are derived. In particular, we show that the modulated compact wave may exist in the NLTL depending on the frequency range of the chosen carrier wave, for physically realistic parameters. The stability of compact dark solitary wave is confirmed by numerical simulations of this ENLS equation and the exact equations of the network. 相似文献
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Frydel JA Krzystyniak M Pienkowski D Pietrzak M de Sousa Amadeu N Ratajczyk T Idzik K Gutmann T Tietze D Voigt S Fenn A Limbach HH Buntkowsky G 《Solid state nuclear magnetic resonance》2011,39(3-4):72-80
Transmission line-based multi-channel solid state NMR probes have many advantages regarding the cost of construction, number of RF-channels, and achievable RF-power levels. Nevertheless, these probes are only rarely employed in solid state-NMR-labs, mainly owing to the difficult experimental determination of the necessary RF-parameters. Here, the efficient design of multi-channel solid state MAS-NMR probes employing transmission line theory and modern techniques of electrical engineering is presented. As technical realization a five-channel ((1)H, (31)P, (13)C, (2)H and (15)N) probe for operation at 7 Tesla is described. This very cost efficient design goal is a multi port single coil transmission line probe based on the design developed by Schaefer and McKay. The electrical performance of the probe is determined by measuring of Scattering matrix parameters (S-parameters) in particular input/output ports. These parameters are compared to the calculated parameters of the design employing the S-matrix formalism. It is shown that the S-matrix formalism provides an excellent tool for examination of transmission line probes and thus the tool for a rational design of these probes. On the other hand, the resulting design provides excellent electrical performance. From a point of view of Nuclear Magnetic Resonance (NMR), calibration spectra of particular ports (channels) are of great importance. The estimation of the π/2 pulses length for all five NMR channels is presented. 相似文献