On-line modeling of non-stationary network traffic with schwarz information criterion

Modeling of network traffic is a fundamental building block of computer science. Measurements of network traffic demonstrate that self-similarity is one of the basic properties of the network traffic possess at large time-scale. This paper investigates the change of non-stationary self-similarity of network traffic over time,and proposes a method of combining the discrete wavelet transform (DWT) and Schwarz information criterion (SIC) to detect change points of self-similarity in network traffic. The traffi...     

Parallel-pipelined architecture of H.264 deblocking filter with adaptive dynamic power

In H.264,the computational complexity and memory access of deblocking filter are variable and depend on the video contents. In this paper,a pipelined VLSI architecture of deblocking filter with adaptive dynamic power is proposed. It avoids redundant computations and memory access by precluding the blocks which can be skipped. And the vertical and horizontal edges are simultaneously processed in an advanced scan order to speed up the decoder. As a result,the dynamic power of the proposed architecture can be ...     

Gait analysis in primary total knee arthroplasty with and without patellar resurfacing: A randomized control study

It is still controversial whether or not to resurface patella during primary total knee arthroplasty (TKA). One of the reasons may be insensitive measurement tools. We conducted a randomized controlled study to compare kinematic and kinetic parameters of resurfacing and nonresurfacing patella with the Vicon gait analysis system. The results show that patient post-operative gait of the two groups improved compared to pre-operative gait. Part of gait parameters, knee flexion at heel-strike, double limb support time and maximum adduction angle appeared to be statistically difference in 3 months, but 12 months later, the gait parameters of the two groups had no significant difference. Therefore, it seems that the final function of knee after TKA is not related whether or not to resurface patella.     

Static softening characteristics and static recrystallization kinetics of aluminum alloy A6082 after hot deformation

The static softening behavior of aluminum alloy A6082 was investigated by interrupted hot tests conducted on Gleeble-1500 simulator at deformation temperatures from 573 to 773 K and strain rates from 0.1 to 10 s⁻¹, with a pre-strain from 0.3 to 0.7 and variable inter-pass delay times. The offset method was applied to convert the changes in flow stress between two passes to static softening fraction. The microstructural changes were characterized by the quantitative metallography of quenched specimens. The results showed both static softening and static recrystallization curves exhibited a simple sigmoidal shape; the static softening is related to the static recrystallization in a nonlinear manner with 50% static recrystallized volume fraction corresponding to 80% static softening fraction; an increase in temperature, strain rate or pre-strain yields a decrease in the time for 50% static recrysallized volume fraction, on which the temperature has the most remarkable influence; Si and Mn additions accelerate the process of static recrystallization. Finally, the equations of static recrystallization kinetics of this alloy were developed with a good agreement between the predicted and experimental results.     

Four-degree-of-freedom course stability of an air cushion vehicle

A four-degree-of-freedom mathematical model was established to investigate the course stability of an air cushion vehicle (ACV). The forces of aerodynamic,propeller and rudder were obtained by wind tunnel experiments. A series of constrained model experiments with horizontal-planar-motion-mechanism (HPMM) were conducted to determine the hydrodynamics. The ACV's course stability was analyzed by using Hurwitz deter-mination method with differential equation of perturbation,and the four-degree-of-freedom cours...     

Research of interaction force coefficients based on model test in loading condition

It is very difficult,for the component-type ship mathematical model,to estimate the interaction force coefficients among the hull,propeller and rudder. Some coefficients such as wake fraction and flow straightening coefficient were studied from the model tests in diffierent loading conditions and the normal force of rudder was tested in captive model tests to obtain the coefficients. From these results of the tests,the flow straightening coefficients increase with the increase of trims or drafts. Similarly,...     

Improvement of collaborative optimization

This paper presents a new improved collaborative optimization (CO) model that provides solution capabilities for multiobjective multidisciplinary optimization problems. Reasons that cause computational difficulties in CO algorithm are firstly analyzed. Then a new system level objective function is advised to minimize relative value between the collaborative objective function and single disciplinary objective function. And it eliminates the effect of dimensions and magnitude orders among objectives. A new s...     

Real-time life-cycle modular design method based on game theory for jack-up

AbstractTo study an entity the entire jack-up performs as a total system with close interdependency and high level of integration of a myriad of subsystems supporting each individual function.All subsystems should be arranged in regular geometric space with clear regional division according to their respective functions.The "building block"such as arrangement makes it feasible to apply modular design method while the integration and conflicts among subsystems offer an arena for game theoretic analysis.All the contradictions between subsystems should be resolved bye the designer.Here we present a game theoretic analysis methodology,which based on the basic principles of game theory,through the establishment of matrix-mode game models to describe and analyze engineering design tasks.By using this method the optimization process in various fields of expertise can be effectively coordinated and controlled,and the parallel design patterns can be achieved to some extent.Taking account of the impact of commercial or technical activities in platform’s life cycle,time line is considered in the early stage of design process which provides more convenience for effcient upgrade and reconfiguration.Some second-hand three-legged jack-up upgrade design process is used as an example to illustrate the utility of the method.     

Identification of grinding wheel wear signature by a wavelet packet decomposition method

Grinding is known as the most complicated material removal process and the method for monitoring the grinding wheel wear has its own characteristics comparing with the approaches for detecting the wear on regular cutting tools. Research efforts were made to develop the wheel wear monitoring system due to its significance in grinding process. This paper presents a novel method for identification of grinding wheel wear signature by combination of wavelet packet decomposition (WPD) based energies. The distinctive feature of the method is that it takes advantage of the combinational information of the decomposed frequency components based on the WPD so the extracted features can be customized according to the specific monitored object to get better diagnosis effects. Experiments are researched on monitoring of grinding wheel wear states under different machining conditions. The results show that the energy ratio extracted from the measured vibration signals is consistent with the grinding wheel wear condition evaluated by experiment and the further extracted feature ratio can be used in prediction of wheel wear condition.     

Comparison of gas particle flow prediction from large eddy simulation and Reynolds-averaging Navier-Stokes modeling

In order to account for the effect of particle existence on gas-particle turbulence flow in large-eddy simulation (LES), a new gas-particle turbulent kinetic energy subgrid-scale (SGS) turbulence model is established, and the effect of particle wake is also considered in gas turbulent kinetic energy SGS turbulence model. Simulation of gas-particle turbulence flow in backward-facing step is carried out by LES using present model and by unified second-order moment (USM) model. The prediction statistical results including mean velocity and fluctuation velocity by LES using present model are in reasonable agreement with the experimental results. It is shown that present model is with higher calculating accuracy than USM model, which indicates that the turbulent kinetic energy SGS turbulence model is suitable.