Advanced Materials Research Vol. 902

Abstract: Offsetting of measured data, as a basic geometric operation, has already been widely used in many areas, like reverse engineering, rapid prototyping and NC machining. However, measured data always carry typical defects like caves and singular points. A fault-tolerant offset method is proposed to create the high quality offset surface of measured data with such defects. Firstly, we generated an expansion sphere model of measured data with the radius equivalent to the offset length. Secondly, using the computational geometry application of convex hull, we acquire the data of outermost enveloping surface of this expansion sphere model. Finally, we use local MLS projection fitting method to wipe out existing defects, and generate the high-quality triangular mesh surface of the offset model. The offset surface generated by this method is suitable for practical engineering application due to its high efficiency and accuracy.

Abstract: In order to reduce time and cost in mechanical product design wizards development work, the Mechanical Product Design Wizard Rapid Development Platform (MPDW-RDP) was established. According to the Independence Axiom, the system architecture of the MPDW-RDP was obtained, then, the MPDW-RDP had been implemented by taking advantage of existing mature software and components in accordance with the Information Axiom, at last, application case indicated that this system can rapidly develop different kinds of mechanical product design wizard.

Abstract: The parting line design for vehicle door is an indispensable step at the phase of auto-body conceptual design, and also the premise of door kinematic analysis. Combined the CATIA CAA platform characteristics with the hinge layout features, we propose an intelligent and semiautomatic algorithm for parting line design and build a layout and checking module based on CATIA software platform. The present method, which originates from an introduced procedure of hinge layout, could define two envelop curves called K-Lines to judge if the given parting line is reasonable. It calculates the minimum clearance size between doors and surrounding parts on each section by using a transform with some settled parameters. In reverse, when the sizes are set to 0s, a serial of extreme start and end points help the engineer to design two new parting lines. An example is carried out with our module and the position relationship between K-lines and parting line are analyzed. The results show that our method has great feasibility and validity to design the parting line and shorten the design periods.

Abstract: Joint channel coding and spread spectrum modulation technologies bring to wireless networks the tremendous amount of performance improvement, the elimination, and the mitigation of interference. This paper proposes an improved design for irregular accumulate concatenated tree (IACT) codes, which can be viewed as simply precoded by an accumulator. This class of codes belongs to the special turbo-like codes, which combines the advantages of fast encoder structures of turbo codes, and the advantages of parallel high-speed belief-propagation (BP) iterative decoding algorithm of low-density parity-check (LDPC) codes. The improved IACT codes can be coded via a Tanner graph. With these improved codes, we propose a joint IACT coding and frequency hopping orthogonal frequency division multiplexing (FH-OFDM) modulation scheme for wireless networks. We compare the performance of different coding bases such as the irregular concatenated tree (ICT) codes and turbo codes in the scheme by theoretical analysis and simulation. Numerical results are shown that the proposed scheme with these IACT codes has really good performance.

Abstract: Aiming at the safe operation of the wind turbine, a feature extraction method of vibration signal based on the principle of blind source separation was proposed. Blind source and the current state of fault signal was separated and predicated by Using historical data of wind turbine vibration signal as the observation noise, and then fault diagnosis signal mechanical operation was analyzed, the HMM/SVM series fault diagnosis models structure was proposed. By calculating the matching degree of unknown signal and wind power equipment in the state using HMM, the features for SVM was formed to achieve the finally discriminant. The experimental results showed that the fault diagnosis method can precisely and effectively complete the wind power equipment, higher than pure HMM or SVM diagnostic accuracy.

Abstract: In the mechanical design process, the interpretation of geometrical and dimensional tolerances is a common task in a products life cycle because tolerances are of decisive importance in the decisions related to cost and quality. At present, there are numerous approaches and investigations related to the modeling of tolerances in mechanical assemblies, related to Computer Aided Design Systems. The goal of this paper is to show a method to modeling an assembly based on a graph map structure, to guarantee the resolution of dimensional chains and tolerance analysis. In this process, which is based on a graph map structure, the dimensional chains associated to the functional requirements that influence the relative location of the parts are determined. A subset of a belt conveyor as an example, illustrates the proposed method.

Abstract: In recent years, orthogonal frequency division multiplexing (OFDM) technology has drawn widespread attention for its high spectral efficiency, and has doing better on combating multipath interference than traditional technology.The reason why OFDM system has high spectral efficiency is that it takes advantage of the orthogonality between sub-carriers,characteristic of which can eliminate interference of each subcarrier even when the spectrum of them overlapped.It is the demanding of orthogonality between subcarriers to demodulate signals that makes OFDM system extremely sensitive to frequency offset. Even a little frequency offset can bring inter-carrier interference.This paper studied the mechanism of formation of interference among sub-carriers, and proposed a frequency offset estimation algorithm by changing the structure of data symbols so that the data symbols can act as training sequence.The simulation results show that the proposed algorithm performs better than S.C algorithm in many aspects, such as MSE, BER, Constellation and so on.

Abstract: Ship maneuvering model and ocean scene are the core parts of navigation simulator, on the basis of MMGs model, the dual-engine and dual-propelling equipment of the Z-propeller tug were researched, the tugs mechanical model and propulsion model were established, speed, course and path of the tug were calculated with the Runge-Kutta method; virtual ocean was built at the meantime based on waves statistic spectrum and fast fourier transform; at last, data communication between different softwares was realized by means of UDP and ADO protocol, and virtual marine navigation system was established based on the Z-propeller tugs maneuvering model.

Abstract: Environmental perception is a functional area that is severely limited in persons with deafblindness (DB) who belong a category of people with severe disabilities. Monitor is a vibratory aid developed with the aim to improve environmental perception of persons with DB. The aid consists of a mobile phone with an application connected to a microphone and vibrator. Monitor picks up the sounds produced by events by microphone, processes the sound using an algorithm programmed as an application in the mobile phone and then presents the signal via the vibrator to the persons with DB to be sensed and interpreted. In previous laboratory studies, four algorithms (AM, AMMC, TR, and TRHA) were developed based on modulating, and transposing principles. The algorithms were tested by persons with normal hearing/hearing impairment and selected as good candidates to improve vibratory identification of environmental sounds. In this on-going the algorithms are tested by 13 persons with congenital D and five persons with DB using Monitor in a realistic environment, living room, kitchen or office. Forty five recorded environmental sounds were used as test stimuli. The subjects tested the algorithms two times, Test and Retest each including a test session initiated by a training session. The four algorithms were tested in four days at Test and four days at Retest in total eight test days. Each test day began with a training session where a sound was presented as vibrations to be sensed by the person with the aim to remember its pattern and identity. The 45 sounds were grouped in four groups where an specific algorithm was chosen to process an specific sound group in a specific day. At the test session a sound was presented and the person was given 5 randomly chosen sound alternatives to choose the one as represented sound. The algorithms were different for different sound groups during four different test days so all algorithms were used to process all sounds. The algorithms were tested a second time, Retest, in same way as in Test. The mean value of identification of environmental sounds varied between 74.6% and 84.0% at Test and between 86.9% and 90.4% at Retest. The identification results at Retest were significantly improved (p<0.01) for all algorithms after a relatively short time of training indicating a good learning effect. At Test the algorithm AM was significantly better than the algorithms AMMC and TRHA (p< 0.01) and the algorithm TR was better than TRHA (p<0.01). The algorithms AM, AMMC, and TR were selected as good candidates to be implemented in the Monitor to improve environmental perception.

Abstract: Taking ArcEngine as the 2D map symbols marking systems development tool, this study designs a 2D GIS marking desktop application system byusing Ortho vector map as its basic map, and implements such functions as map navigation operation, labelling major targets of earthquake-stricken areas, animation deduction of emergency rescue solutions, and exporting emergency rescue plans, etc.