Effects of weight on bit on torsional stick-slip vibration of oilwell drill string

Liping Tang,Xiaohua Zhu,Xudong Qian,Changshuai Shi 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.10

The stick-slip phenomenon is a type of dysfunction detrimental to the drilling operation. Field application shows that stick-slip phenomenon is inclined to appear when using a large Weight on bit (WOB). In this paper, effects of the WOB on the stick-slip vibration are investigated. Based on a lumped torsional pendulum model of the drilling system, equation of motion of the drill bit is obtained. By using parameters commonly used in field applications, the bit dynamics are analyzed and the stick-slip vibrations are discussed. During the stick-slip motions, the negative damping effect occurs in the transition from the stick phase to the slip phase. With the increasing WOB, the bit behavior may change from the stable motion to the stick-slip vibration once the WOB reaches the critical value. In case of stickslip vibration, the phase trajectory ultimately converges to a limit cycle which represents periodical bit motion. With increases in the WOB, the limit cycle enlarges. For cases without stick-slip vibrations, the drill bit vibrates damply and finally converges to a state of uniform motion. The results presented in this paper can be applied to interpret some of the field phenomena related to WOB.

High Efficient Consistency Maintenance Strategy of Real-time String Text Editing Systems

Liping Gao,Wenfeng Tang 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.10

The idea of address space transformation provides a new way for concurrency control. During concurrent processing, it retraces the document status back to the state when the operations are generated to maintain consistency. However the previous concurrency processes strategy is based on single characters, the transmission cost during processing is too high, especially when the network is unstable. Due to this problem, this paper presents a consistency maintenance strategy based on string editing operations, and proposes the string splitting mechanism combined with the idea of the address space transformation in order to maintain consistency.

Application of Joint Electro-Chemical Detection for Gas Insulated Switchgear Fault Diagnosis

Liping Li,Ju Tang,Yilu Liu 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.4

The integrity of the gas insulated switchgear (GIS) is vital to the safety of an entire power grid. However, there are some limitations on the techniques of detecting and diagnosing partial discharge (PD) induced by insulation defects in GIS. This paper proposes a joint electro-chemical detection method to resolve the problems of incomplete PD data source and also investigates a new unique fault diagnosis method to enhance the reliability of data processing. By employing ultra-high frequency method for online monitoring and the chemical method for detecting SF6 decomposition offline, the acquired data can form a more complete interpretation of PD signals. By utilizing DS evidence theory, the diagnostic results with tests on the four typical defects show the validity of the new fault diagnosis system. With higher accuracy and lower computation cost, the present research provides a promising way to make a more accurate decision in practical application.

Application of Joint Electro-Chemical Detection for Gas Insulated Switchgear Fault Diagnosis

Li, Liping,Tang, Ju,Liu, Yilu The Korean Institute of Electrical Engineers 2015 Journal of Electrical Engineering & Technology Vol.10 No.4

The integrity of the gas insulated switchgear (GIS) is vital to the safety of an entire power grid. However, there are some limitations on the techniques of detecting and diagnosing partial discharge (PD) induced by insulation defects in GIS. This paper proposes a joint electro-chemical detection method to resolve the problems of incomplete PD data source and also investigates a new unique fault diagnosis method to enhance the reliability of data processing. By employing ultra-high frequency method for online monitoring and the chemical method for detecting SF6 decomposition offline, the acquired data can form a more complete interpretation of PD signals. By utilizing DS evidence theory, the diagnostic results with tests on the four typical defects show the validity of the new fault diagnosis system. With higher accuracy and lower computation cost, the present research provides a promising way to make a more accurate decision in practical application.

A Framework for Enterprise Network Management

최태상,Liping Zhang,Deok Jai Choi,Adrian Tang 한국통신학회 1995 Asia-Pacific Conference on Communications Vol.2 No.1

Control and Measurement System for the Tuning of a PEFP Low-Beta Superconducting RF Cavity

Zhang Liping,Sun An,Yingmin Li,Tang Yazhe,Yong Sub Cho 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.5

The superconducting RF (SRF) cavity is being considered to accelerate the proton beam in the proton engineering frontier project (PEFP) linac and for its post-project. In order to correct for the frequency shift and the field flatness variation of a TM010 mode in a raw PEFP multi-cell (SRF) cavity caused by manufacturing errors and welding shrinkage during its production, a field flatness tuning system has been developed. A new control and measurement system has been successfully developed for the relevant tuning system. The system automatically controls the bead's forward movement to a designated position and back to its original point and it also drives the network analyzer to measure and acquire the data on the SRF cavity while the bead is moving through the SRF cavity. After the bead has past through the cavity, the control and measurement system provides the cavity's field flatness and the tuning frequencies of the individual cells. The experiments in this study revealed that the control and measurement system is reliable. By using this control and measurement system, the field flatness of a PEFP low-beta cavity can be tuned from 75.62 % at 697.925 MHz to 1.43 % at 700 MHz, which can satisfy the control requirement.

Multiple Framework QoE Model based Energy Efficient Transmission Strategy in LTE Networks

Ge Zhihui,Tang Liping,Li Taoshen,Li Qinghua 보안공학연구지원센터 2016 International Journal of Future Generation Communi Vol.9 No.8

Wireless technology is continuously evolving, and the development of new versions of adaptive protocols and mechanisms are at their peak to achieve high performance in network-based applications and services. LTE networks offer broadband wireless access to users who can benefit from high data rate applications such as video streaming. However, the high energy consumption of these applications has not been considered. The end user quality of experience (QoE) of video delivery over a radio network is mainly influenced by the radio parameters in the radio access network. This paper will present a multiple framework QoE model for video delivery over LTE, denoted as MQoE that measures the overall perceived quality of mobile video delivery from subjective user experience and objective system performance. We propose a QoE-based energy efficient mechanism to reduce smartphones’ power consumption. We have done a series of experiments to verify the efficiency of this model. Experiment results show that MQoE has significant improvement at energy efficiency

Frequency and Length Adjustment of A PEFP Low-Beta Dumbbell

Changyi, Gao,An, Sun,Liping, Zhang,Yazhe, Tang,Yingmin, Li,Kim, Han-Sung,Cho, Yong-Sub The Korean Society of Superconductivity and Cryoge 2008 한국초전도저온공학회논문지 Vol.10 No.2

Superconducting RF cavities are being considered for accelerating a proton beam at 700 MHz in the linac of the Proton Engineering Frontier Project (PEFP) and its post-project. Dumbbell fabrication is a mid-process for manufacturing an elliptical superconducting RF cavity. During the dumbbell fabrication, control of the dumbbell length and the $TM010\;{\pi}$ mode frequencies is necessary to build up a desired cavity. A new formula with a perturbation measurement method is used to measure and calculate the frequencies of the individual half-cells of a PEFP low-beta dumbbell, and to tune the frequency and length of the half-cells. In this article, the tuning method and results of the PEFP low-beta dumbbells have been presented.

Enhanced crystallization and properties of poly(ethylene terephthalate) nanocomposites with zeolites from 3D to 2D topologies

Wei Zhang,Hongbin Zhang,Liping Yang,Yi Tang,Ping Tang 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.109 No.-

To improve the low crystallization rate and long molding cycle of Poly(ethylene terephthalate) (PET), series of PET nanocomposites incorporated small quantities of zeolites with different topologies were blended by melt compounding. The nucleation influence of 3-dimensional zeolites Y, ZSM-5 and 2- dimensional zeolite MCM-22P on the crystallization manner of PET was analyzed by non-isothermal and isothermal crystallization, quantitative evaluation of nanoparticle dispersion and morphology of nanoparticles. The results show that all PET/zeolite nanocomposites exhibit higher crystallization temperature and faster crystallization rate than PET due to large specific surface area of zeolites and their superior dispersion in the PET matrix. Among them, PET/MCM-22P nanocomposites remarkably improved the crystallization behavior, thermal stability and oxygen barrier properties, which is related to the layered morphology of MCM-22P and hydrogen bond interactions between MCM-22P and PET. It is revealed that MCM-22P can provide more heterogeneous nucleation sites for PET by exfoliation in melting compounding. Furthermore, the nucleation mechanism induced by MCM-22P was investigated by the means of Mozhishen method, Avrami equation and theory of Hoffman-Lauritzen. The results indicate that the incorporation of MCM-22P can decrease the free energy of nucleation and fold surface in PET crystallization process, thus improving the crystallinity.

Analysis of mechanical behavior and hysteresis heat generating mechanism of PDM motor

Changshuai Shi,Xiaohua Zhu,Juan Deng,Liping Tang 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.3

Positive displacement motor (PDM), which is prone to high temperature fatigue failure, can be weakened in its application in deep and superdeep well. In order to study the forced state, deformation regularity and thermal hysteresis of PDM motor, the paper established the three-dimensional thermal-mechanical coupled Finite element model (FEM). Based on the theoretical research, experimental study and numerical simulation, the study found that the displacement of stator lining shows a sinusoidal variation under internal pressure, when adapting the general form of sine function to fitting inner contour line deformation function. Then the paper analyzed the hysteresis heat generating mechanism of the motor, learning that hysteresis thermogenous of stator lining occurs due to the viscoelastic of rubber material and cyclic loading of stator lining. A heartburn happens gradually in the center of the thickest part of the stator lining as temperature increases, which means work efficiency and service life of PDM will be decreased when used in deep or superdeep well. In this paper, we established a theory equation for the choice of interference fit and motor linetype optimization design, showing hysteresis heat generating analyzing model and method are reasonable enough to significantly improve PDM’s structure and help better use PDM in deep and surdeep well.