Mathematical and Computer Modelling最新文献

The sample observations of a functional variable are functions that come from the observation of a statistical variable in a continuous argument that in most cases is the time. But in practice, the sample functions are observed in a finite set of points. Then, the first step in functional data analysis is to reconstruct the functional form of sample curves from discrete observations. The sample curves are usually represented in terms of basis functions and the basis coefficients are fitted by interpolation, when data are observed without error, or by least squares approximation, in the other case. The main purpose of this paper is to compare three different approaches for estimating smooth sample curves observed with error in terms of $B$-spline basis: regression splines (non-penalized least squares approximation), smoothing splines (continuous roughness penalty) and $P$-splines (discrete roughness penalty). The performance of these spline smoothing approaches is studied via a simulation study and several applications with real data. Cross-validation and generalized cross-validation are adapted to select a common smoothing parameter for all sample curves with the roughness penalty approaches. From the results, it is concluded that both penalized approaches drastically reduced the mean squared errors with respect to the original smooth sample curves with $P$-splines giving the best approximations with less computational cost.

In view that the selections of box tap and thread making parameters are still groundless and lack scientific evidence, which has caused many practical engineering problems, such as long fishing cycle and low success rate, this study establishes a mathematical model such that fish is fished by the box tap based on the theory of large deformation and principle of virtual work. The analysis and evaluation methods of the whole elastoplasticity process for tapping and fishing are proposed as well in accordance with Johnson and Cook’s experimental model and separation criterion in our study. In addition, the effects of such factors (drilling pressure, rotation speed, box tap strength, taper and pitch) on the thread making capacity of the box tap and the new thread strength of fish have been systemically analyzed. In the case study, the paper derives the safety rotation speed range of tapping, the optimal box tap tape and parameter combination of fishing, and the maximum allowable lifting power. The results obtained in our study show that the analyzing model and evaluation methods are quite reasonable and can be generally applied, which will be of great significance for the enhancement of fishing efficiency in future industry.

This paper presents an efficient approach for determining the solution of linear differential equations. The linear ordinary differential equation is first converted to a Volterra integral equation. By solving the resulting Volterra equation by means of Taylor’s expansion, different approaches based on differentiation and integration methods are employed to reduce the resulting integral equation to a system of linear equations for the unknown and its derivatives. The approximate solution of the linear differential equation is thereby obtained. A test example demonstrates the effectiveness of the method and gives the efficiency and high accuracy of the proposed method.

In this paper, we analyze several adaptive and static data models of arithmetic compression. These models are represented by using Upgraded Petri net as our original class of the Petri nets. After the iterative processes of modeling, simulation and analysis, the models are transformed into an application. The models refer to one-pass and two-pass arithmetic coding where a set of symbols refers to bytes or nibbles. The frequency of a symbol is represented as an unsigned 32-bit integer. Original software for modeling and simulations of Upgraded Petri net, PeM (Petri Net Manager) is developed and used for all models described in this paper. All models are observed in the experiments by using a created application over a standard set of files. Experimental results are presented and compared.

In this paper, we present an analytical method to solve systems of the mixed Volterra–Fredholm integral equations (VFIEs) of the second kind. By using the so called $ħ$-curves, we determine the convergence parameter $ħ$, which plays a key role to control convergence of approximation solution series. Further, we show that the homotopy perturbation method (HPM), which is a well-known tool for solving systems of integral equations, is only the special case of the presented method. Some test examples are given to clarify the efficiency and high accuracy of the method. An efficient error estimation for the approximate solution is also presented for the proposed method.

This paper studies the stability of switched systems with general nonlinear disturbances. By using generalized Gronwall–Bellman inequalities, we obtain stability results for the systems with arbitrary switching laws. Finally, an example is given to illustrate the effectiveness of the results obtained.

To solve the problem caused by the lack of the structure of the nonlinearity in Wiener systems identification, we propose a new approach to identify the linear part and the nonlinear part of a Wiener system in sequence by using the limited information on the nonlinearity. The linear part of the system is identified firstly based on the limited information of the nonlinearity, such as sign information, monotonic information and then, we construct the internal signals to identify the structure and the parameters of the Wiener systems. A novel Particle Swarm Optimization–Rosenbrock (PSO–Rosenbrock) algorithm is developed and the numerical simulation shows that the identification procedure proposed in this paper is effective.

Nowadays, power consumption is a big concern for mobile devices because battery power of mobile devices is one of the most crucial resources. Unfortunately, the performance of battery power fails to meet the power needs of high-end mobile devices. Increased data to be transferred/received through wireless communication incur high power consumption, because the wireless communication interface is one of the most dominant modules of mobile devices in terms of power consumption. Therefore, efficient power management of wireless interfaces should be employed for mobile devices. Dynamic power management is widely employed in order to support multiple power modes such as active modes (e.g., transmit, receive, and idle mode) and inactive modes (e.g., sleep mode and power off). Therefore maximizing the staying time of the wireless interface in an inactive mode is an essential scheme to reduce energy expenditure. However, required overhead energy and time for turning on/off the wireless interface are not negligible. Most of recent works have been trying to enhance the hardware architecture or network/MAC protocols. In this paper, we present an energy-efficient carpool policy that turns on the wireless interface and transmits all awaited data only when the predefined threshold is exceeded. We propose two kinds of thresholds–time and space. For practical evaluation, we conduct not only simulations but also experimental measurements by implementing a test program on a real test bed. Results of simulation and experimental measurements show that our proposed scheme incurs less energy expenditure than legacy power management schemes do.

Traditional research discusses the impact of foreign investment on the technology diffusion effect or environment individually. In fact, foreign capital can promote environmental efficiency of the funded region by improving the local innovation capacity through technology diffusion. This article analyzes the path relationship between foreign investment, innovation capacity and environmental efficiency by using structural equation models, the results of which show that, on the one hand, foreign investment can directly promote local environmental efficiency; on the other hand, it is also effective in enhancing local innovation capacity, which is conducive to the improvement in local environmental efficiency. Finally, corresponding countermeasures are put forward in line with the above results.

Energy consumption is now one of the most important issues for network carriers, since the majority of the energy needed for their operation is consumed in the wireless access and optical transport networks. The continuous growth in the wireless customers and traffic volumes and the consequent energy demand on modern carriers’ broadband infrastructures require reconsidering their energy efficiency, by starting from the formulation of new, more complete and representative network models that should become the foundations for modern energy-aware control plane architectures.

Accordingly, this work presents a novel comprehensive energy model for next-generation wireless access-over-optical-transport networks characterized by hybrid power systems (i.e., multiple dynamically available power sources). The objective is to identify the energy-related information that need to be handled at the control plane layer to support energy-aware networking practices. Such information can be made available to suitable energy-aware routing and wavelength assignment algorithms that may exploit them to optimize the overall network energy-consumption and reducing the associated carbon footprint. The proposed model may be taken as a reference for the implementation of new energy-aware control plane protocols (routing and signaling) that make use of power-related considerations to achieve energy-efficiency and energy-awareness in wavelength-routed network infrastructures.