Liqin Wang

Pulse baseline wander removal using wavelet approximation

Pulse waveform is the key to the traditional Chinese pulse diagnosis. However, its baseline wander introduced in the acquisition may result in misdiagnosis. Whats more, recent advancements in the pulse variability analysis require more accuracy of baseline estimation. In this paper, a wavelet based cascaded adaptive filter (CAF) was presented to remove this drift. The CAF works in two stages. The first stage is a discrete Meyer wavelet approximation and the second stage is a cubic spline estimation. The experimental results on 50 simulated and 200 real pulse signals demonstrate the powerful effect of CAF both in removing the baseline wander and in preserving the diagnostic information of pulse waveform, comparing with some traditional methods, such as cubic spline estimation, morphology filter and linear-phase FIR least-squares-error digital filter. In addition, this CAF is easy to be accomplished and needs no prior knowledge on pulse and its baseline drift.

Lempel-Ziv Decomposition Based Arrhythmic Pulses Recognition

The computerization of traditional Chinese pulse diagnosis (TCPD) is relatively new in the field of automatic physiological signal analysis and diagnosis. The classification of pulse patterns according to their positions and shapes have been intensively investigated, but until now no research in identifying pulses by their rhythms has been found. This paper introduces a method to distinguish rhythmic and arrhythmic pulse patterns and further, applies the Lempel-Ziv decomposition to classify arrhythmic pulses. In the experiment on 140 clinic pulses, our approach was able to classify pulses by their rhythms with an accuracy of 90.7%

A Spectrum Detection Approach for Bearing Fault Signal Based on Spectral Kurtosis

According to the similarity between Morlet wavelet and fault signal and the sensitive characteristics of spectral kurtosis for the impact signal, a new wavelet spectrum detection approach based on spectral kurtosis for bearing fault signal is proposed. This method decreased the band-pass filter range and reduced the wavelet window width significantly. As a consequence, the bearing fault signal was detected adaptively, and time-frequency characteristics of the fault signal can be extracted accurately. The validity of this method was verified by the identifications of simulated shock signal and test bearing fault signal. The method provides a new understanding of wavelet spectrum detection based on spectral kurtosis for rolling element bearing fault signal.

Image Acquisition and Segmentation for Ceramic Bearing Ball Surface Inspection System

Surface and subsurface defects in ceramic bearing balls significantly affect ball strength and lifetime. A brief review of nondestructive evaluation technologies on hybrid bearing balls was presented. An automatic ceramic bearing ball surface inspection system based on computer image technology was developed. Various surface defects were imaged by microscope and image digitizer on a novel ball surface unfolding mechanism. Top-hat and logarithm transformations were applied to eliminate uneven lighting disturbance. An automatic seeded region growing algorithm based on histogram concavity analyses and Otsus method was developed for defects segmentation. The results show that the experimental system is effective for ceramic ball surface and subsurface defects detection

Transient dynamic analysis of high power density gear transmission

In this paper, the dynamic problem of high power density gear transmission in transient state is studied based on flexible multi-body model. First, the flexible gear transmission multi-body model is built with the detailed formula of contact force and component modes synthesis method. Second, the transient time as dynamic external excitation is undertaken for high power density gear transmission, which has larger flexibility than others. Numerical and theoretical results confirm a significant influence of transient state on the dynamic force and deformation. Furthermore, the reasonable time of gear transmission transient state can be avoided the great impact force, reduce vibration and noise in gear system. Consequently, the transient time of gear transmission is an innegligible excitation factor for gear transmission.

Effect of Bi2O3 coating of whisker on thermal expansion behaviour of aluminium composite reinforced by aluminium borate whisker

Abstract The thermal expansion behaviours of aluminium composites reinforced by ABOw with and without Bi2O3 coating are studied. The results show that the coating could influence the thermal expansion behaviour of composite. The coefficient of thermal expansion (CTE) of the composite with Bi2O3 coating is higher than that of the composite without coating. In addition, the heat treatment influences the thermal expansion behaviours of composite with Bi2O3 coating. The CTEs of the heat treatment composites are lower compared to as cast composite. At the same time, the quenching can boost the CTE of the composite compared with the annealing.

Boundary Tribological Behaviors of Untreated and Surface-Modified M50 Steel Lubricated by Fuel JP-10

ABSTRACT To explore the possibility of using advanced surface engineering techniques (ASETs) to solve the wear problems caused by the poor lubricity of pure, low-viscosity aviation fuel JP-10, polished M50 bearing steel sample surfaces were treated with nitrogen ion implantation, TiAlN coating deposition, and Ta coating deposition followed by high current pulsed electron beam (HCPEB) irradiation, respectively. Boundary tribological behaviors of these ASET-treated and untreated steel samples sliding in pure JP-10 against a Si3N4 ball (ball-on-disc model) were investigated under 2.0 GPa in the atmosphere and the friction tests indicated that significant, reductions, although to different extents, in friction and wear were achieved by these modified surfaces. Simultaneously considering the tribological performance and potential pollution caused by wear debris to JP-10, HCPEB-treated Ta coating with a lowest average friction coefficient of 0.11 and a specific wear rate of around zero was the fittest to offset the inadequate lubricity of JP-10 itself under the laboratory condition.

In situ observation on microstructural development of high-speed steel during carbon partitioning process

ABSTRACT Quenching–partitioning–tempering (Q–P–T) process was applied to treat high-speed steel. Microstructural development and properties were studied using high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy, X-ray diffraction and a drop hammer impact toughness tester. The results of impact toughness test showed that the impact absorption energy increased to 16.2–20.1u2009J along the Q–P–T process, namely 56–93% higher than that of traditional Q–T approach (10.4u2009J). The results of in situ HRTEM showed that the interface of martensite/austenite (α/γ) migrated from martensite towards austenite with the increase of holding time, which led to a reduction of retained austenite. One of the migration planes was (110)α/(111)γ. The cementite precipitation and slight decomposition of retained austenite were observed during carbon partitioning process.

Analysis and Evaluation of Interface Mechanics for Thin Films using the Method of Image

The evaluation of interface mechanics was very useful for the design of thin solid film. According to the method of image, interface stresses and deformations of coating-substrate system were gained. Using this mathematical calculation model, the indentation test data was carried out and the results were analysed. Based on the mechanical model and test, the critical state of interface stresses from elastic deformation to plastic yield was evaluated. From experimental and calculating results, interface shear stress and normal stress had different affecting level for the coating failure under the same surface load. And a fitting relationship equation for the two stresses was also gained to determining the failure value in designing. The method of this paper could be used for thin film interface mechanics design and evaluation.

Performance and Failure Modes of Grease Lubricated Hybrid Ceramic Bearing in High Speed and High Temperature Condition

Ceramic rolling element bearings have promising applications in extreme operating conditions such as high speed, high temperature, and heavy load. In this study, a hybrid silicon nitride ceramic ball bearing lubricated with high temperature grease is presented. The structure and parameters of the bearing are specially designed to satisfy the requirement of grease lubrication, high temperature and high speed conditions. A test rig was developed for the experiments of ceramic bearing performance. The experimental results show that grease lubricated ceramic bearings with fine design have excellent high speed and high temperature performance. By analyzing the operation performance and failure bearing inspection, the failure modes of grease lubricated ceramic bearings is analyzed. Thermal instability caused by the grease insufficient supply is the main factor of failure.Copyright