Papers by Keyword: Time-Domain

Abstract: The portable grounding system plays an important role in the lightning protection system of mobile equipments. But the traditional earth electrodes composed of vertical rods wouldn’t work well or would take a long time to set up in some conditions such as frozen soil, hard clay and so on. In this paper, a new type of portable grounding system which can be quickly spread and folded has been designed. To analyze the TGR’s (Transient Grounding Resistance) time-domain characteristics, the grounding systems have been modeled and simulated with FDTD (Finite Difference Time Domain). The influence rule of electrodes’ number and down-lead’s position to TGR has been studied with numerical analysis and validated with experiments. The results show that the new grounding system works well even on cement floor.

Abstract: Move performance in six-degree-of-freedom is one of the important indexes of hydro-dynamic property of tension leg platform (TLP). This paper discusses the time domain dynamic response characteristics of a tension leg platform in the regular wave. The paper focuses on the effects of the incident wave angles (15 °, 22.5 ° and 45 °), the wave height (6m, 8m and 10m) and the wave period (10s, 12s and 14s) on the movement of tension leg platform, the top tension of the tension leg. The results show that: because of the different sensitivity of the tension leg platform to the incident wave angle, the wave height and the wave period, the motion characteristics is different.

Abstract: A numerical method integrating computational fluid dynamics and computational structural dynamics for predicating wing flutter in time domain is described. A strong coupling employing the dual-time method is adopted. The Newmark algorithm is used to solve flutter equation in modal spaces while the finite-volume algorithm for the Navier-Stokes equations is used to solve the flow. The computed flutter boundaries of AGARD wing 445.6 for frees-tream Mach numbers ranging from 0.499 to 1.141 agree well with the experiment than using the DLM.

Abstract: The dynamic response analysis of the multi-body system with floating base includes the interaction between bodies and flow field as well as the one inside the multi-body system, which needs to use both the time-domain theory about the interaction between the object and the flow field and the method of multi-body system dynamics. With the growing complexity of the upper body, the multi-body system with floating base, whose generalized modeling and analysis become an inevitable trend.Using ADAMS(Automatic Dynamic Analysis of Mechanical System) for multi-body system dynamics analysis has unique advantages. It integrates modeling, solving and visualization technology. It also can realize automatically statics, kinematics and dynamics analysis. In this paper, the feasibility of ADAMS software and some related key issues are discussed, including the system architecture, fluid force analysis, fluid-structure coupling calculation module and ADAMS multi-body dynamics analysis module of data generation and transmission, etc.

Abstract: Aim at some problem in fault diagnose: the characteristic frequency depends on the speed, the spectrum is complex , which are easy to diagnose error when in the variable conditions, and it is often difficult to identify the fault positioning in the frequency domain. the paper puts forward a new method: Variable condition bearing fault diagnosis basing on time-domain and artificial intelligence , not depend on speed and frequency domain. This method use vibration signal, calculates the kurtosis, skewness, rms etc 12 time-domain value, then these character vectors are sent to the neural network classifier to complete fault type pattern recognition, Finally, the same faults are sent to the next neural network for fault positioning and damage extent identification. The experimental result showed that using this method can obtain very good effect.

Abstract: The equipment with higher measuring accuracy is installed at a suitable place in fore and aft to get ship sway data during sailing in wind and wave. The data is classified. The ship sway data prediction model based on PSO-SVM method is provided, and the extreme short time prediction result which meets the demand can be get after multi-steps calculation.

Abstract: In this paper, a specific method is presented for designing program of wave data acquisition and time-domain analysis, which includes brief description of wave height sensor, the basic concepts related to wave data time-domain analysis and specific idea and method of program design. Firstly, computer receives wave data through the serial port. While MSComm control is used for serial prot programming for the most part.Secondly, the methods of the average of some big waves and cumulative rate of value are both used in time-domain analysis of wave data. According to the practical test, the program is stable, expeditious and accurate highly.

Abstract: In this paper, a new time-domain method for detecting structural local damage has been developed, which is based on the measured strain signals. The “pseudo strain energy density (PSED)” is defined and used to build two major damage indexes, the “average pseudo strain energy density” (APSED) and the “average pseudo strain energy density changing rate” (APSEDR). A probability and mathematical statistics technique is utilized to derive a standardized damage index. Afterwards, these indexes are used to establish the damage identification strategies for beam structures and plate structures respectively. Furthermore, the wavelet packet transform is used to pre-process the measured dynamic strain signals. Then, the effectivity of the new damage identification method is confirmed by numerical simulations. Finally, a laboratory beam model experiment is conducted to verify this method examine the feasibility and applicability of the new method.