浅谈动频法试桩的影响因素

本文系通过桩基的动刚度来求取单桩竖向容许承载力。文中讨论了影响试桩成果的诸因素,并用实测结果加以说明。还提出了排除这些影响的办法。

混合移频静刚度法和直接扰动迭代法

本文对混合移频动柔度法的迭代式进行等价变换 ,从而得到一个“变种” ,该变种不包含混合移频系统的动柔度式FΔ(λ ) ,这便消除了FΔ(λ )带来的近似性。另外 ,对直接扰动法也进行等价变换 ,引出可以省时地用于许多特征向量导数计算的直接扰动迭代法。最后 ,为了供读者参数 ,本文还导出了三种混合移频动柔度法的非迭代式 ,其中有两种恰好是另外两种动柔度法经混合移频后的非迭代式 ,这实际上已将另两种动柔度法也扩展到密集根情况了。

一类多自由度非线性振动系统的多频摄动法

本文把Lindstedt的频率展开思想推广到高维系统,并通过引进自变量的非线性变换,给出一类多自由度非线性自治系统内共振锁相周期解的多频摄动法。最后给出该法的若干应用。

Passive-source multitaper-spectral method based low-frequency data reconstruction for active seismic sources

Passive seismic data contain large amounts of low-frequency information. To effectively extract and compensate active seismic data that lack low frequencies, we propose a multitaper spectral reconstruction method based on multiple sinusoidal tapers and derive equations for multisource and multitrace conditions. Compared to conventional cross correlation and deconvolution reconstruction methods, the proposed method can more accurately reconstruct the relative amplitude of recordings. Multidomain iterative denoising improves the SNR of retrieved data. By analyzing the spectral characteristics of passive data before and after reconstruction, we found that the data are expressed more clearly after reconstruction and denoising. To compensate for the low-frequency information in active data using passive seismic data, we match the power spectrum, supplement it, and then smooth it in the frequency domain. Finally, we use numerical simulation to verify the proposed method and conduct prestack depth migration using data after low-frequency compensation. The proposed power-matching method adds the losing low frequency information in the active seismic data using the low-frequency information of passive- source seismic data. The imaging of compensated data gives a more detailed information of deep structures.

An approach to improving maneuver performance of coning algorithm

Aiming to improve the maneuver performance of the strapdown inertial navigation attitude coning algorithm a new coning correction structure is constructed by adding a sample to the traditional compressed coning correction structure. According to the given definition of classical coning motion the residual coning correction error based on the new coning correction structure is derived. On the basis of the new structure the frequency Taylor series method is used for designing a coning correction structure coefficient and then a new coning algorithm is obtained.Two types of error models are defined for the coning algorithm performance evaluation under coning environments and maneuver environments respectively.Simulation results indicate that the maneuver accuracy of the new 4-sample coning algorithm is almost double that of the traditional compressed 4-sample coning algorithm. The new coning algorithm has an improved maneuver performance while maintaining coning performance compared to the traditional compressed coning algorithm.

Research on the Dividing Method for Present-Day Regional Active Block

In this paper, a new idea that combines Quasi-Accurate Detection of gross errors (QUAD) with discontinuous deformation positive analysis, is brought forward to divide the regional active blocks. The method can improve the demarcation of active blocks for areas lacking with observation data and offer a new train of through for the complete study of the regional deformation of active blocks. In addition, using the Sichuan-Yunnan area as example, the practice process of the method is introduced briefly.

Imposing Active Sources during High-Frequency Passive Surface-Wave Measurement

Passive surface-wave utilization has been intensively studied as a means of compensating for the short-age of low-frequency information in active surface-wave measurement, In general, passive surface-wave methods cannot provide phase velocities up to several tens of hertz; thus, active surface-wave methods are often required in order to increase the frequency range, To reduce the amount of field work, we pro-pose a strategy for a high-frequency passive surface-wave survey that imposes active sources during con-tinuous passive surface-wave observation; we call our strategy ＂mixed-source surface-wave （MSW） measurement,＂ Short-duration （within 10 min） passive surface waves and mixed-source surface waves were recorded at three sites with different noise levels： namely, inside a school, along a road, and along a railway, Spectral analysis indicates that the high-frequency energy is improved by imposing active sources during continuous passive surface-wave observation, The spatial autocorrelation （SPAC） method and the multichannel analysis of passive surface waves （MAPS） method based on cross-correlations were performed on the recorded time sequences, The results demonstrate the flexibility and applicability of the proposed method for high-frequency phase velocity analysis, We suggest that it will be constructive to perform MSW measurement in a seismic investigation, rather than exclusively performing either active surface-wave measurement or passive surface-wave measurement,

Method for optimizing manipulator's geometrical parameters and selecting reducers

A geometrical parameters optimization and reducers selection method was proposed for robotic manipulators design. The Lagrangian approach was employed in deriving the dynamic model of a two-DOF manipulator. The flexibility of links and joints was taken into account in the mechanical structure dimensions optimization and reducers selection, in which Timoshenko model was used to discretize the hollow links. Two criteria, i.e. maximization of fundamental frequency and minimization of self-mass/load ratio, were utilized to optimize the manipulators. The NSGA-II (fast elitist nondominated sorting genetic algorithms) was employed to solve the multi-objective optimization problem. How the joints flexibility affects the manipulators design was analyzed and shown in the numerical analysis example. The results indicate that simultaneous consideration of the joints and the links flexibility is very necessary for manipulators optimal design. Finally, several optimal combinations were provided. The effectiveness of the optimization method was proved by comparing with ADAMS simulation results. The self-mass/load ratio error of the two methods is within 10%. The maximum error of the natural frequency by the two methods is 23.74%. The method proposed in this work provides a fast and effective pathway for manipulator design and reducers selection.

Application of the DEM to screening process:a 3D simulation

The discrete element method(DEM) has been widely used to simulate microscopic interactions between particles.Screening is a deeply complicated process when considering the law of motion for the particles,themselves.In this paper,a numerical model for the study of a particle screening process using the DEM is presented.Special attention was paid to the modeling of a vibrating screen that allows particles to pass through,or to rebound,when approaching the screen surface.Inferences concerning screen length and vibrating frequency as they relate to screening efficiency were studied.The conclusions were:three-dimensional simulation of screening efficiency along the screen length follows an exponential distribution;when the sieve vibrates over a certain frequency range the screening efficiency is stable;and,higher vibration frequencies can improve the handling capacity of the screening machine.

Multiple Reader Algorithm for Sports Timing Systems and Its Application at Low Frequency Bandwidth

In sports timing systems,P2P communication is used at low frequency bandwidths(under 135 KHz) between tags and readers in the RFID field.However,in such cases,collisions tend to occur when a reader deals with multiple RFID tags simultaneously.To overcome this issue,a sports timing system including a Multi Reader Controller(MRC)loaded with an advanced multiple reader algorithm and application was created and applied at large-scale citizens' marathon events.In these cases,a large number of people pass over the installed urethane type's antenna mat continually during a short period of time.This study verified the superiority of the improved algorithm and application through the on-thespot application of the multi reader algorithm and application program,which allows us to smoothly measure runners' times through multiaccess reading for rapid collision avoidance.

Shaking Table Test of Pile-Water-Pier Superstructure

The model test of seismic simulation shaking table is an important method to study the seismic design of bridge structure. In order to evaluate the seismic response and dynamic characteristics of pile-water-pier system for developing more reliable design procedures, shaking table model tests of a submerged bridge pier system, including pile groups-cap-pier and inertia mass, were conducted. Since different similitude laws corresponding to different test objectives affected the validity of test results, the similitude law with the aim to consider the effect of hydrodynamic pressure was proposed and confirmed through an actual example. Based on the test results, the effect of water around model on seismic response under seismic excitation input was analyzed and the failure level was judged by observing the variation of basic frequency. The test results indicate that the transfer function of analytical model with water is different from that without water, the natural frequency without water is always higher than that with water, and the first modal shapes are various. It is also concluded that the similitude law is suitable for practical application and the dynamic characteristics and seismic response of the structure system can be changed because of the existence of the surrounding water, which should be paid much attention in the further investigation.

AN EFFICIENT BIT RATE ALLOCATION ALGORITHM FOR MOTION JPEG2000 TRANSPORT IN TILE ENCODING

An efficient bit rate allocation algorithm for video sequence transmission in motion JPEG2000 is presented. In many cases,the moving portions of video are often the interested regions. Based on tile encoding of JPEG2000,the important regions are discerned by two parameters. One is the complexity of a tile;the other is the motion activity of a tile. Thus an adaptive rate-allocation is re-alized in a lower complexity and the perceptive quality of a frame is improved. Experimental results show the effectiveness of this algorithm.

Surface Motion of Alluvial Valley in Layered Half-Space for Incident Plane P-Waves

The indirect boundary element method (IBEM) is used to study the surface motion of an alluvial valley in layered half-space for incident plane P-waves based on Wolf’s theory. Firstly, the free field response can be solved by the direct stiffness method, and the scattering wave response is calculated by Green’s functions of distributed loads acting on inclined lines in a layered half-space. The method is verified by comparing its results with literature and numerical analyses are performed by taking the amplification of incident plane P-waves by an alluvial valley in one soil layer resting on bedrock as an example. The results show that there exist distinct differences between the wave amplification by an alluvial valley embedded in layered half-space and that in homogeneous half-space and there is interaction between the valley and the soil layer. The amplitudes are relatively large when incident frequencies are close to the soil layer’s resonant frequencies.

A Novel Automatic Method for Removal of Flicker in Video

Intensity flicker is a common form of degradation in archived film. Most algorithms on this distortion are complicated and uncontrolled. This paper presented a discrete mathematical model of flicker, designed a block-based estimation method of the model＇s parameters according to their features of intensity variation in large area. With this estimation result it constructed a compensation model to repair the current frame. This restoration approach is full automatic and the repair process of current frame does not need the information of frames behind it. The algorithm was realized to establish a simple and adjustable repair system. The experimental results show that the proposed algorithm can remove most intensity flicker and preserve tho wanted effects.

Design and validation of real-time dynamic spectrum management in OFDM-based HNPLC systems

Time-varying frequency selective attenuation and colored noises are unfavorable characteristics of power line communication(PLC) channels of the low voltage networks.To overcome these disadvantages,a novel real-time dynamic spectrum management(DSM) algorithm in orthogonal frequency division multiplexing(OFDM)-based high-speed narrow-band power line communication(HNPLC) systems is proposed,and the corresponding FPGA circuit is designed and realized.Performance of the proposed DSM is validated with a large amount of network experiments under practical PLC circumstance.As the noise in each narrow subcarrier is approximately Gaussian,the proposed DSM adopts the BER/SER expression formulized via the AWGN channel to provide a handy and universal strategy for power allocation.The real-time requirement is guaranteed by choosing subcarriers in group and employing the same modulation scheme within each transmission.These measures are suitable for any modulation scheme no matter the system criterion is to maximize data rate or minimize power/BER.Algorithm design and hardware implementation of the proposed DSM are given with some flexible and efficient conversions.The DSM circuit is carried out with Xilinx KC705.Simulation and practical experiments validate that the proposed real-time DSM significantly improves system performance.

A novel dynamic frame rate control algorithm for H.264 low-bit-rate video coding

The goal of this paper is to improve human visual perceptual quality as well as coding efficiency of H. 264 video at low bit rate conditions by adaptively adjusting the number of skipped frames. The encoding frames are selected according to the motion activity of each frame and the motion accumulation of successive frames. The motion activity analysis is based on the statistics of motion vectors and with consider- ation of the characteristics of H. 264 coding standard. A prediction model of motion accumulation is pro- posed to reduce complex computation of motion estimation. The dynamic encoding frame rate control algorithm is applied to both the frame level and the GOB （Group of Macroblocks ） level. Simulation is done to compare the performance of JM76 with the proposed frame level scheme and GOB level scheme.

Vibration analysis of wind tunnel support

In order to enable a wind tunnel support to have a high enough natural frequency to prevent experiencing mechanical resonance and excessive vibration displacement, five kinds of wind tunnel support structures have been simulated and analyzed individually under five different load conditions by means of a nonlinear finite element numerical method. With natural frequency and three directions vibration displacement given, simulation and analyses indicated that additional supports is more beneficial than heightening the rigidity of steel reinforced concrete in support pillars and adopting steel wrappers on the pillars to increase natural frequency of support structure. Increasing the rigidity of steel reinforced concrete, adopting steel wrappers and providing additional supports are all helpful in reducing three directions vibration Max displacement. and additional supports are comparatively more effective. Therefore, a structure scheme with steel reinforced concrete support pillars, steel wrappers and additional supports should be adopted in practical wind tunnel support construction.

MULTI-EPIPOLAR LINES MATCHING-BASED RAY-SPACE INTERPOLATION FOR FREE VIEWPOINT VIDEO SYSTEM

Ray-space based arbitrary viewpoint rendering without complex object segmentation or model construction is the main technology to realize Free Viewpoint Video(FVV) system for complex scenes. Ray-space interpolation and compression are two key techniques for the solution. In this paper,correlation among multiple epipolar lines in ray-space data is analyzed,and a new method of ray-space interpolation with multi-epipolar lines matching is proposed. Comparing with the pixel-based matching interpolation method and the block-based matching interpolation method,the proposed method can achieve higher Peak Signal to Noise Ratio(PSNR) in interpolating rayspace data and rendering arbitrary viewpoint images.

Automatic detection of respiratory rate from electrocardiogram,respiration induced plethysmography and 3D acceleration signals

Respiratory monitoring is increasingly used in clinical and healthcare practices to diagnose chronic cardio-pulmonary functional diseases during various routine activities.Wearable medical devices have realized the possibilities of ubiquitous respiratory monitoring,however,relatively little attention is paid to accuracy and reliability.In previous study,a wearable respiration biofeedback system was designed.In this work,three kinds of signals were mixed to extract respiratory rate,i.e.,respiration inductive plethysmography(RIP),3D-acceleration and ECG.In-situ experiments with twelve subjects indicate that the method significantly improves the accuracy and reliability over a dynamic range of respiration rate.It is possible to derive respiration rate from three signals within mean absolute percentage error 4.37%of a reference gold standard.Similarly studies derive respiratory rate from single-lead ECG within mean absolute percentage error 17%of a reference gold standard.

A robust system for real-time pedestrian detection and tracking

A real-time pedestrian detection and tracking system using a single video camera was developed to monitor pedestrians. This system contained six modules: video flow capture, pre-processing, movement detection, shadow removal, tracking, and object classification. The Gaussian mixture model was utilized to extract the moving object from an image sequence segmented by the mean-shift technique in the pre-processing module. Shadow removal was used to alleviate the negative impact of the shadow to the detected objects. A model-free method was adopted to identify pedestrians. The maximum and minimum integration methods were developed to integrate multiple cues into the mean-shift algorithm and the initial tracking iteration with the competent integrated probability distribution map for object tracking. A simple but effective algorithm was proposed to handle full occlusion cases. The system was tested using real traffic videos from different sites. The results of the test confirm that the system is reliable and has an overall accuracy of over 85%.