Showing papers in "Journal of Harbin Engineering University in 2011"

A double zero-watermarking algorithm for 2D vector maps

Abstract: To address the contradiction between robustness and imperceptibility in a traditional watermarking algorithm,a double zero-watermarking algorithm for 2D vector maps was proposed.Based on feature point extraction,for the feature point reflecting the outline of the polyline,the algorithm utilized the feature point relation model established by a BP artificial neural network to construct a zero-watermarking parameter that was robust against simplification and compression attacks.For the non-feature point reflecting the detail of the polyline,the algorithm utilized the matrix singular value decomposition(SVD) to construct a parameter of zero-watermarking that was robust against geometry attacks.This algorithm perfectly depicts the whole character of each polyline,and the construction of double zero-watermarking parameters can improve robustness and achieve a comprehensive protection target for vector maps.Experimental results show that the proposed zero-watermarking has preferable robustness and invisibility,which is suitable for copyright protection of 2D vector maps.

Analysis of dynamic characteristics of a fiber-optic gyroscope based on dynamic Allan variance

Abstract: In order to study the dynamic characteristics of a fiber-optic gyroscope,it was proposed that the dynamic error which had been obtained by testing a fiber-optic gyroscope be analyzed by dynamic Allan variance.According to the principle of window function in the dynamic Allan variance method,the analysis results of the dynamic error were discussed under the different window length conditions.Furthermore,a kind of single sway movement and two kinds of composite sway movement were analyzed by the dynamic Allan variance method and their results were provided.There was fluctuating variation of variance in the analysis figures,by which the various non-stationary factors in the dynamic error such as mutation and periodic variation were accurately reflected,and the different sway states hidden in the dynamic errors were clearly identified.Both the theoretical analysis and experimental results indicate that the dynamic Allan variance method is very applicable for analyzing the dynamic characteristics of a fiber-optic gyroscope.

A robust localization and identification method of noise sources using second-order cone programming

Abstract: In order to improve the robustness of the noise source high-resolution localization and identification method,a new robust minimum variance distortionless response(MVDR) focused beamforming method based on vector sensor array was proposed in this paper.On the basis of previous MVDR focused beamforming,this new method improves its robustness by imposing the inequality norm constraint on the weight vector,and solves the optimal weight vector and spacial spectrum by second-order cone programming.Because this method is robust against the array steering vector mismatch,it can achieve a greater dynamic range,sharper focused peak,and lower background noise level.The validity of this method under mismatched conditions can be verified by theoretical modeling,simulation,and experimental research,and the results provide the theoretical and experimental support for engineering applications.

Design of a nonlinear controller for dynamic ship positioning

Abstract: A vessel suffers from environmental disturbance while keeping its position and throughout offshore operation processes.There is some nonlinearity in the dynamic positioning(DP) control.A new dynamic positioning controller was proposed based on the active disturbance rejection control(ADRC) technique.The controller used a nonlinear state estimator to give an estimation of the vessel speed and the general disturbances,and it applied the nonlinear feedback to compensate for the disturbances.The simulation experiments indicate that the controller has strong anti-disturbance ability and robustness.

Numerical studies of added mass based on the CFD method

Abstract: In order to provide a concrete computation method,to find the affecting factors of computed results,and to explore the effects of shape on flow patterns and consequently added masses,added masses of 3D underwater objects considering viscosity were computed by the dynamic mesh method.These computations were based on general CFD FLUENT code and were made possible by solving Reynolds averaged Navier-Stokes equations.Two shapes were computed,and results were compared with those predicted by the strip theory and slender body assumption.It was shown that the combination of the cutoff cone and cutoff cylinder has a lower resistance force and lower added mass than that of the pure cutoff cone,which has the same length and section of the ends.Different shapes have different requirements on the time step of computation.

Simulation and testing of the transient temperature field of infrared laser sintering

Abstract: In the process of rapid laser prototyping,the transient sintering temperature affects molding quality directlyIn considering the variation of thermal properties and transformation between solid and liquid states of powder,using the finite element method,a 3-D numerical simulation was conducted by using the analysis system(ANSYS) software for the transient sintering temprature of CO2 infrared laser beams and Al2O3 coated ceramic powdersThe 3-D temperature field was reconstructed according to the measured result of high-speed charge coupled device(CCD)Numerical simulation agreed well with experimental resultsThe result demonstrates that the sintering temperature of Al2O3 coated with ceramic powders is far less than the Al2O3 melting point temperature(1 500℃)When the beam passes by the observation points several times after several returns,the second peak of temperature occurs which is beneficial to molding qualityThis is consistent with a practical sintering mechanism

Research on factors of a flow field affecting catamaran resistance calculation

Abstract: In order to achieve consistent and agreeable results in resistance and other areas of hydrodynamic performance for hulls such as that of a catamaran,viscous computational fluid dynamics(CFD) methods were used,and a practical system of investigating the influential factors such as mesh gridding,choice of numerical methods,and turbulence models which affect the calculation results was developedThrough calculation and analysis,specifically with the CFD FLUENT code,an alternative set of computation parameters was suggestedAlso,the application to a catamaran resulted in better agreement with corresponding model tests

Study on resistance prediction method and resistance reduction mechanism of medium & high speed Deep-Vee ship by stern flap

Abstract: To improve the hydrodynamic performance and resistance prediction accuracy of a Deep-Vee ship,a method to calculate the resistance of a Deep-Vee ship sailing at medium and high speed was presented.This method included the prominent influence of dynamic sinkage and trim through the iterative solution of flow field pressure distribution as well as of the sinkage and trim by adopting Fluent software and a hydrostatic equilibrium calculations.The resistance prediction error is about 2% to 4%.The resistance reduction of Deep-Vee ship by the stern flap was due to a decrease of dynamic trim and reduction of the pressure resistance of the hull,as well as an increase in the virtual appendage of the ship.A proper installation method of stern flap for Deep-Vee ship,which can reduce the total resistance of the tested model by 6.5%,was obtained.

A bionic venation growth algorithm for a stiffener layout in plate/shell structure

Abstract: Rib-stiffening is an efficient way to strengthen plate/shell structure.During probing of rib layout problems,a biological venation organism was observed to be similar to a reinforced plate in its irregular pattern.Global and local regularities of dicotyledonous venation were summarized,and the mechanical force theory on venation morphogenesis was discussed intensively.From this study the mechanical variables involved were extracted.A venation growing algorithm was proposed to allow for two-dimensional reinforcement layout optimization.Strain energy and shear stress were selected as the growth criterion of the main and secondary veins,respectively.The design sensitivity was adopted to measure the influence of the design parameters on mechanical properties.Optimization designs of a typical simple-support plate show the effectiveness of the method in static analysis.

Automatic measurement and assembly of miniature partsbased on machine vision

Abstract: The dimensions of miniature parts differ greatly,resulting in low efficiency during manual assembly and poor consistency of the assembled products.A limited visual field of the camera for high-precision measurements and a large work space cause problems in the application of machine vision.Moreover,the diversity of the parts' finished surface and the deviations of dimensions are some of the uncertain factors that affect the assembly process.A system based on machine vision and a manual intervention method was developed.It used a vision apparatus and precise displacement platforms to realize measurement.An assembly control strategy based on task messages was used to fulfill the three frameworks of software(the behavior layer,task layer,and strategy layer).Finally automatic measurement and precise assembly of miniature parts were realized.The composition of the assembly system,the recognition and positioning of the parts,the realization of the micro-assembly procedure,and the test results of practical assembly were introduced.The results show that the measurement system,the control strategy,and software structure have very good feasibility for measurement and assembly of miniature-parts.

Vertical vibration characteristics of seated human bodies and the parameters of a biodynamic model with three degrees of freedom

Abstract: Vibration tests were conducted on 28 volunteers by means of white noise excitation with a wide frequency range and various levels to more accurately understand the vertical vibration characteristics of seated Chinese human bodiesApparent mass was obtained for each volunteerThe model with 3 degrees of freedom suggested by ISO 5982-2001 was employed to describe the vibration characteristicsAn error function defined in terms of both amplitude and phase information of apparent mass was used to identify all model parameters through optimizationApparent mass predicted by the model with identified parameters for each volunteer agrees very well with those obtained from the experimentsBased on the average of the mass-normalized apparent masses of all volunteers,model parameters were obtained to portray the vertical vibration characteristics of seated Chinese people of standard weight and similar age under various excitation levelsIt was shown that 2 resonance frequencies exist with the vertical vibration responses of the seated Chinese human bodyAccording to the excitation levels,the two frequencies vary within 431~557 Hz or 934~121 Hz,respectivelyThe established biodynamic model can accurately describe the vertical vibration characteristics of the seated human body

Research and realization of an azimuth damping inertial navigation system based on multi-damping coefficient

Abstract: The earth cycle oscillation component of latitude and heading error can decrease the accuracy of inertial navigation system.Based on the actual experiment navigation system,this paper covered a three-order damping network and designed an azimuth damping method with a multi-damping coefficient by means of step-by-step attempts.The network can damp the earth cycle oscillation and adapt to various maneuver motions of the carrier by adopting an automatic compensation technique which can decrease the overshooting error during the state switching.The result of the velocity error simulation shows that the multi-azimuth damping project can damp the earth cycle oscillation and the automatic compensation technique can eliminate the switch overshooting effectively.

An adjustable threshold immune negative selection algorithm based on vaccine theory

Abstract: In order to enhance the detection efficiency of the adjustable threshold immune negative selection algorithm,the abnormal parts of the algorithm monitoring system were improved to realize the adaptive immune response of the adaptive.The vaccine operator and positive selection operator were introduced into this algorithm and the antibody storeroom with a dynamic renovation function was set up.The antibody storeroom can eliminate redundancy during the dynamic renovation process,so the redundancy was eliminated through self-adaptation.The simulation results show that the improved adjustable threshold immune negative selection algorithm has a better self-study function than the previous one.When the same antigen enters a second time,the algorithm's second response period is obviously shorter and the detection efficiency is increased dramatically,while also displaying self-adaptation for the second response.

System identification and control of the electro-hydraulic servo system of a continuous rotary motor

Abstract: Due to the periodic interference problems caused by periodic changes of the friction torque as well as by leakage in the entire system of a continuous rotary electro-hydraulic servo motor,the mathematical model of a continuous rotary motor electro-hydraulic position servo system was establishedThe model was constructed using sine sweep signals as excitation signalsA closed-loop parameter identification experiment of the entire cycle of the continuous rotary motor was carried out by each interval of 10° according to its own structural characteristicsEach of the collected input and output data series and prediction error methods based on a Gauss-Newton optimization algorithm were adopted to identify the parameters of the system modelThe changing range of the system model parameters in the whole cycle was also obtainedAccording to the time-varying of motor system parameters and nonlinear uncertainties,and based on design requirements of a continuous rotary electro-hydraulic servo motor,a QFT(quantitative feedback theory)robust controller with two degrees of freedom was designedThe controller was also based on the differential feed-forward of the input signal,and it adopted the quantitative feedback theory,combining the system model parameter identification resultsThe controller's value was proven through an experiment which showed that the motor meets the performance demand,indicating that this identification and control method is feasible

Study on the tourism industry development mode evolutional model

Abstract: Since China began its open-door policy and reform of economic development,tourism industrial restructuring has only had the goal of "industrial rationalization" and "high-class industrial structure," and has only concentrated on static structural problems while ignoring the dynamic mechanism.To solve these problems,the dynamic mechanism must first be solved.Starting with analysis of collaborative and motion theory and combined with industrial system evolution theory,a theoretical model of the tourism industry development mode was proposed,and then empirical research was done with a structural equation model using the questionnaire of Harbin tourism industry.The empirical research analyzed dynamic mechanisms of government-leading and environment-leading evolutions of the Chinese tourism system;moreover,it validated the hypothesis that an environment-leading adjusted mode can improve the performance of the tourism industry.

The single channel seismic-acoustic signal blind-source separation method based on EEMD

Abstract: With only a single observing channel,the blind source separation methods based on matrix calculating do not workTo deal with this problem,a single channel blind-source separation method for seismic-acoustic signal processing was presentedFirst,the observing signal was decomposed into intrinsic mode matrix by ensemble empirical mode decomposition,transforming the single channel underdetermined problem into the multi-channel positive definite problemThen the input matrix for blind source separation was obtainedFinally,the source was estimated by the blind source separation methodThe simulation results show that this method can separate the source signal from broad frequency and impulsive noise,and works well when the frequencies of different source signals overlapExperimental results show that the signal-to-noise ratio can also be improved for seismic-acoustic background noiseIt proves that this method is effective for processing seismic-acoustic signal

The function and mechanism of an aidant reducer in the deep reduction process of iron ore

Abstract: In view of the problem of large reserves of low-grade refractory ore along with low utilization,a study was conducted on refractory low-grade hematite by using deep reduction roasting-magnetic separation.The results show that under the conditions of using coal as the reducer with a dosage of 30%,JZQ-F1 as the assistant reducer with a dosage of 15%,and roasting at 1200℃ for 40min,the iron ore concentrate with the Fe content of 91.27% and Fe recovery of 91.04% was produced.The mechanisms of JZQ-F1 and JZQ-F2 are also investigated by X-ray Diffraction(XRD) and Scanning Electron Microscope(SEM).The results show that JZQ-F1 can promote the reduction of wustite to metallic iron and inhibit the formation of fayalite.JZQ-F2 can also inhibit the formation of fayalite and react with quartz,and thereby destroy the structure of raw mine,so that the reaction between reducing gas and hematite be easy.

Correlative analysis of shield tunneling data and recognition of geologic features

Abstract: For the purpose of judging geological conditions by excavation parameters and considering the stratums surrounding a certain section of the Tianjin tunnel,a correlative analysis of the tunneling data and the geologic parameters was made based on shield excavation tests on the site of construction.The qualitative method of recognizing the geologic features from the tunneling data was proposed.The shield machine's working data was normalized by the cutting-in per revolution of the shield cutter penetration.Also,the geologic data of different stratums with their weighting coefficients was calculated.The investigation presented the correspondence between the tunneling and geologic data following the above processing.

Development of an actuated exoskeleton with pneumatic muscles for gait rehabilitation training

Abstract: Treadmill training is widely used to improve the walking ability of stroke patients.During treadmill training,the movements of the patient's lower limbs must be assisted by therapists.The manual training provided by therapists is demanding and labor intensive.Therefore,a powered lower limb exoskeleton was developed for gait training.The exoskeleton can provide power for the hip and knee joints during treadmill training.The actuation of the exoskeleton was based on the principles of human joint actuation,and each joint of the exoskeleton was actuated by a pair of pneumatic muscles.The actuation model of the exoskeleton was analyzed on the basis of the pneumatic muscle model.Preliminary experimentation proved that the exoskeleton is effective and safe for gait rehabilitation training.

Effects of loading rate on TA1 rivet deformation in electromagnetic riveting

Abstract: For the riveting of a titanium alloy rivet with high strain rate sensitivity,effects of a loading rate on TA1 rivet deformation,energy efficiency,and the riveting joints between TA1 rivet and steel plate,TA1 rivet and laminates of a composite-steel sheet in electromagnetic riveting(EMR) were investigated through experiments and microstructure analysis.The results show that TA1 riveting can be carried out by two kinds of loading rates with different magnitudes.The increasing loading rate contributes to more remarkable deformation in the adiathermal shear zone.With an appropriate loading rate,a good riveting joint can be obtained between the TA1 rivet and laminates of the composite-steel sheet.The low loading rate of the EMR process enables the transfer of heat generated during the rivet deformation,the postponing of cracks,a fine grain in the region of rivet deformation,and the enhancement of the deformation limit of the rivets.

Fatigue analysis on multi-spanning pipelines

Abstract: Pipelines are used on the seabed for long periods of time,so the fatigue life of the pipeline is important.In considering this issue,pipeline fatigue life was investigated.The method of calculation of the load was obtained by analysis of the environmental load of a multi-spanning pipeline.Following that,the fatigue models of in-line and cross-flow vortex induced vibration(VIV) were investigated and the fatigue life of multi-spanning pipelines could be obtained.The in-line and cross-flow multi-modes of pipelines were calculated by the finite element method(FEM),making it possible to acquire the dynamic characteristics of the pipelines.In the end,the effects of different span lengths and soil types on the fatigue life of pipelines were illustrated.Consequently,this analysis of pipelines may provide useful information for further investigation on pipelines.

A software reliability growth model considering an S-shaped testing effort function under imperfect debugging

Abstract: Software testing effort and imperfect debugging are two important testing factors which can effectively improve the fitting and prediction power of a software reliability growth model(SRGM)Therefore,for describing the influence of these two factors on reliability in the modeling process more accurately,an S-shaped testing effort function(TEF) was proposed,which is also known as an inflected S-shaped TEF(IS-TEF)This function is suitable and flexible for describing the S-shaped varying trend of the testing effort's increasing rateThen two new NHPP SRGMs(IS-TEFID1 and IS-TEFID2) were presented by incorporating IS-TEF and two forms of imperfect debugging into the exponential-type NHPP SRGM,respectivelyFinally,on two real failure data-sets,a case study was proposed for comparing the two proposed models with several representative SRGMs in terms of fitting and prediction powerThe experimental results indicate that compared with these SRGMs,the proposed IS-TEFID2 yields the best fitting and prediction results for each data-setThat is,incorporating IS-TEF and imperfect debugging into the NHPP SRGM can provide accurate fitting and prediction results

Evaluation of the emergency response capacity of the city public based on the AHP-Entropy integrated method

Abstract: In order to develop and enhance new city emergency ability systems,the emergency reaction capacity of the urban public was considered as an important part of urban emergency preparation.In this paper,an evaluation was made for seven sample cities based on the AHP-Entropy integrated method.This method reflects the expert knowledge,experiences and raw data.The sample cities were chosen according to three standards,namely disaster distribution,city type,and geographic location.They were Heihe,Harbin,Wuhan,Wuwei,Quanzhou,Nanning,and Yangjiang.The evaluation results show that the emergency response of the urban public in Yangjiang and Quanzhou are comparatively high,and Wuhan and Heihe's capacity are lower.The results are shown to conform to reality.

The application of a virtual time reversal mirror to upstream communication of underwater acoustic networks

Abstract: Based on the properties of an underwater acoustic channel,using the uncorrelated character among different users' channel impulse responses(CIR),the single-element virtual time reversal mirror(VTRM) was proposed for application to upstream communication of underwater acoustic networks.The scheme focused on information from desired users and suppressed information from undesired users;in addition,the VTRM mitigated the intersymbol interference caused by a multipath channel and improved the SNR.The simulation results show that a single-element VTRM can separate every user's information as the channel impulse responses(CIR) are uncorrelated,which works favorably toward realizing underwater acoustic networks.

Influence of a nanomaterial on propellant and the function of a nanomaterial for increasing the service life of a gun barrel

Abstract: In order to increase the service life of a gun barrel,a method of modifying powder by adding a nanomaterial to the propellant was applied.The design idea of the nanocomposite was introduced.Taking a kind of double-base ball propellant as a research object,a method of adding the nanomaterial to the propellant was presented.Also,the influence of the nanomaterial on a propellant's manufacturing process,interior ballistics,anti-erosion capability,combustion completion,and combustion capability were researched.A propellant with the nanomaterial which satisfied interior ballistic performance was prepared.Then,the barrel life of two caliber rifles was tested by using the propellant with the nanomaterial and the standard propellant in a high-temperature environment(50℃),a low temperature environment(-45℃) and a normal temperature(20℃) environment,respectively.Lastly,the test results and phenomenon were analyzed.It was proven that the anti-erosion of the propellant with the nanomaterial was improved,and the service life of the gun barrel was prolonged.

Semi-supervised clustering-based anonymous data publishing

Abstract: To enhance protection efforts of individual and privacy information,as well as to improve data utility and reduce the time cost,an(α,k)-anonymous model based on semi-supervised clustering was proposed,and an algorithm was designed to achieve this model.Moreover,time complexity of the algorithm was analyzed.The data set,containing numeric and category attributes,was mapped to the same metric space.Therefore,the element of the dissimilarity matrix can denote the distance between the tuples,which results in the same or similar tuples gathering to the same cluster.For high sensitivity attributes,a higher degree of protection was set whereas for low sensitive attributes a lower degree of protection was set,achieving personalized protection of sensitive attributes.Experimental results show that the semi-supervised(α,k)-anonymous model can achieve safe and efficient privacy preservation while simultaneously ensuring the quality of publishing data.

Comparative studies on the temperature stresses in external walls with different thermal insulation models

Abstract: To study the development of the thermal stress in different functional layers of external wall with different thermal insulation modes,based on the calculation results of the temperature field on the external walls with a typical internal or external thermal insulation layer in Beijing,this paper presents an analytical model for temperature stress calculation of the walls under typical constraint condition of walls.Through calculation,the influence of internal and external thermal insulation modes on temperature stress of different functional layers of a composite wall was analyzed and compared with the self-thermal insulated aerated concrete wall.The results show that the thermal stress inside the wall is controlled by the initial temperature(T0),temperature variation(T-T0),and elastic modulus of materials.As T0=15℃,the thermal stress of the wall is in tension in winter and in compression in summer.Therefore,the wall has the potential of cracking in winter and expanding in summer.For the external heat insulation mode,the temperature stress in the structure layer is relatively small due to less temperature variation and gradient in it.For the internal heat insulation mode,the temperature stress in the structure layer is relatively large due to large temperature variation in it.The external heat insulation mode can protect the foundation layer of the wall.Due to heat isolation of the heat insulation layer,the temperature variation of every functional layer other than the heat insulation layer is great,and the corresponding thermal stress is also large during alternation of winter and summer.

Global stability of ship motion in stochastic beam seas

Abstract: In order to improve the safety of ship navigation on the sea,the global stability of a ship in stochastic beam seas was researched using the global bifurcation method,based on the nonlinear dynamics theory.While considering the stochastic excitation term as bounded noise as well as the influence of nonlinear damping and a nonlinear righting moment,a stochastic nonlinear single degree of freedom differential equation for ship rolling was established.The random Melnikov mean-square criterion was used to analyze the global stability of this system and the results were verified by the safe basin method.The research indicates that the bounded noise can simulate the wave excitation quite well,and if the noise exceeds the threshold value,the ship will undergo stochastic chaotic motion.That will lead to instability of the ship and possibly even to capsizing.

The reference plane by wavelets for 3D roughness evaluation of micro wire electrical discharge machining(MWEDM)

Abstract: The two key problems in the evaluation of the reference plane by wavelet for 3D roughness are determining the optimum wavelet base and the base level of wavelet decomposition mainly by experience.The optimum wavelet base was chosen through comparison of reconstruction accuracy after wavelet decomposition of the three-dimensional shape of micro wire electrical discharge machining(MWEDM).According to energy conservation features of wavelet transformation,when decomposing single frequency signals by wavelet transformation,the wavelet decomposition energy follows exponential distribution,thereby determining the base level of the wavelet decomposition of three-dimensional surface roughness.The number of reference plane assessment to extract the reference plane of three-dimensional surface roughness evaluation of MWEDM by wavelet.The experimental test verified the accuracy of this method,which can be extended to the evaluation of three-dimensional surface roughness in machining.

Multi-objective optimization research on preventive maintenance planning and production scheduling

Abstract: In order to reduce the effects of machine failures on the manufacturing cost and time,a multi-objective optimization model was proposed to jointly determine preventive maintenance planning and production scheduling for a single machine.The maintenance cost,makespan,total weighted completion times,and total weighted tardiness were simultaneously considered as objectives.Multi-objective genetic algorithms were developed to solve a joint optimization model for PM planning and production scheduling.Compared with the method of optimization integrating PM planning and production scheduling and the methods separately optimizing PM planning and production scheduling in an example,the proposed multi-objective joint optimization method can save more time at a lower cost.