Effects of cryogenic medium on the weakly compressible flow characteristics of a high-speed centrifugal pump at a low flow rate

Xiaoping Chen,Wenjin Zhang,Shaolong Wang,Zu-chao Zhu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.12

On the basis of the weakly compressible assumption, large-eddy simulation of a high-speed centrifugal pump is performed at a rotational speed of 9685 r/min and flow rate of approximately quarter load (0.23 Qd). Three cryogenic media, namely, liquid methane (MM), liquid nitrogen (MN), and liquid oxygen (MO), are used. Results show that many of the internal flow characteristics derived and validated for normal-temperature water still hold for cryogenic media. Pump efficiency, maximum density deviation, and total entropy generation rate increase with the increase in the reference density. The dominant frequencies of the pressure spectrum are 12 and 6 times the rotation frequency and insensitive to the cryogenic media. The average amplitude of the first-order dominant frequency between MN and MO deviates from that of MM by approximately 10 %. The maximum deviations of the average amplitudes of second-order dominant and axial frequencies are 34.9 % and 32.3 %, respectively. The variation in standard deviation exceeds 40 % for all cryogenic media.

Investigation on characteristics of pulverized coal dense-phase pneumatic conveying under high pressure

Chen Xiaoping,Fan Chunlei,Liang Cai,Pu Wenhao,Lu Peng,Zhao Changsui 한국화학공학회 2007 Korean Journal of Chemical Engineering Vol.24 No.3

of dense-phase pneumatic conveying of pulverized coal were carried out in a test facility witha conveying pressure up to 4 MPa. The influence of fluidization nitrogen flow rate, the flow rate of supplementarysolid mass flow rate was investigated. Test results indicate that with the increase in fluidization nitrogen flow rate, thesolid mass flow rate increases, and the solids to gas ratio increases at first and then declines. When the fluidization ofpulverized coal in the sending vessel becomes intensive, with the increase in supplementary nitrogen flow rate, thesolids to gas ratio declines and the solid mas flow rate increases. And the solid mass flow rate increases linearly withthe increase in presure diference between two hoppers. The experimental results provide a database for the design

Time-dependent behaviour of interactive marine and terrestrial deposit clay

Chen, Xiaoping,Luo, Qingzi,Zhou, Qiujuan Techno-Press 2014 Geomechanics & engineering Vol.7 No.3

A series of one-dimensional consolidation tests and triaxial creep tests were performed on Nansha clays, which are interactive marine and terrestrial deposits, to investigate their time-dependent behaviour. Based on experimental observations of oedometer tests, normally consolidated soils exhibit larger secondary compression than overconsolidated soils; the secondary consolidation coefficient ($C_{\alpha}$) generally gets the maximum value as load approaches the preconsolidation pressure. The postsurcharge secondary consolidation coefficient ($C_{\alpha}$') is significantly less than $C_{\alpha}$. The observed secondary compression behaviour is consistent with the $C_{\alpha}/C_c$ concept, regardless of surcharging. The $C_{\alpha}/C_c$ ratio is a constant that is applicable to the recompression and compression ranges. Compared with the stage-loading test, the single-loading oedometer test can evaluate the entire process of secondary compression; $C_{\alpha}$ varies significantly with time and is larger than the $C_{\alpha}$ obtained from the stage-loading test. Based on experimental observations of triaxial creep tests, the creep for the drained state differs from the creep for the undrained state. The behaviour can be predicted by a characteristic relationship among axial strain rate, deviator stress level and time.

China Consensus Document on Allergy Diagnostics

Chen Hao,Li Jing,Cheng Lei,Gao Zhongshan,Lin Xiaoping,Zhu Rongfei,Yang Lin,Tao Ailin,Hong Haiyu,Tang Wei,Guo Yinshi,Huang Huaiqiu,Sun Jinlyu,Lai He,Lei Cheng,Liu Guanghui,Xiang Li,Chen Zhuanggui,Ma Ha 대한천식알레르기학회 2021 Allergy, Asthma & Immunology Research Vol.13 No.2

The prevalence of allergic diseases has increased dramatically in recent years in China, affecting the quality of life in 40% of the population. The identification of allergens is the key to the diagnosis of allergic diseases. Presently, several methods of allergy diagnostics are available in China, but they have not been standardized. Additionally, cross-sensitization and co-sensitization make allergy diagnostics even more complicated. Based on 4 aspects of allergic disease (mechanism, diagnosis procedures, allergen detection in vivo and in vitro as well as the distribution map of the most important airborne allergens in China) and by referring to the consensus of the European Society of Allergy and Clinical Immunology, the World Allergy Organization, and the important literature on allergy diagnostics in China in recent years, we drafted this consensus of allergy diagnostics with Chinese characteristics. It aims to standardize the diagnostic methods of allergens and provides a reference for health care givers. The current document was prepared by a panel of experts from the main stream of professional allergy associations in China.

Comparative studies on potential dependent electrochemical impedance spectroscopy of cathode material 0.5Li2MnO3$0.5LiNi0.5Mn0.5O2 for the initial two charging cycles

Chao Chen,Shu Chen,Miao Shui,Xiaoping Xu,Weidong Zheng,Lin Feng,Jie Shu,Yuanlong Ren 한국물리학회 2015 Current Applied Physics Vol.15 No.2

Cathode material 0.5Li2MnO3·0.5LiNi0.5Mn0.5O2 is successfully synthesized by citrate acid assisted sol -gel method and shows pretty good electro-chemical performance. To elucidate the electro-chemical reactions and charge carrier transportation kinetics in the charge-discharge process, series of electrochemical impedance spectra for the first and the second charge process are measured on multiple given state of charges. The rapid augmentation of resistance to electronic conduction and ionic conduction within the voltage range 4.45-4.6 V where the removal of Li2O from Li2MnO3 component takes place gives us more evidence about the complicated “structurally integrated” feature of this material. The relatively large span of the arc responsible for electronic conduction and the extremely large Mn3+ related charge transfer resistance at the beginning of the second charging indicate that after one complete charge-discharge cycle, Li2MnO3 and LiNi0.5Mn0.5O2 domains still reserve its original structure and will keep its structure for the followed cycles.

Stress analysis model for un-bonded umbilical cables

Chen, Xiqia,Fu, Shixiao,Song, Leijian,Zhong, Qian,Huang, Xiaoping Techno-Press 2013 Ocean systems engineering Vol.3 No.2

For the optimization design and strength evaluation of the umbilical cable, the calculation of cross section stress is of great importance and very time consuming. To calculate the cross section stress under combined tension and bending loads, a new integrated analytical model of umbilical cable is presented in this paper. Based on the Hook's law, the axial strain of helical components serves as the tensile stress. Considering the effects of friction between helical components, the bending stress is divided into elastic bending stress and friction stress. For the former, the elastic bending stress, the curvature of helical components is deduced; and for the latter, the shear stress before and after the slipping of helical components is determined. This new analytical model is validated by the experimental results of an umbilical cable. Further, this model is applied to estimate the extreme strength and fatigue life of the umbilical cable used in South China Sea.

Synthesis and Cytotoxicity Evaluation of New 3-substituted 4-(4-methyloxy phenyl)-1H-Pyrrole Derivatives

Xiaoping Zhan,Lan Lan,Yuankui Zhang,Jian Chen,Kai Zhao,Shuai Wang,Yuxuan Xin,Zhenmin Mao 대한화학회 2016 Bulletin of the Korean Chemical Society Vol.37 No.2

A new series of 3-substituted 4-(4-methyloxy phenyl)-1H-pyrrole derivatives were synthesized and biologically evaluated for potential anticancer activity. Fifteen targeted compounds showed high selectivity toward normal cells and cancer cells: that is, all targeted compounds had no obvious cytotoxicity toward normal human cells (HUVEC and NIH/3T3), but some compounds exhibited broad-spectrum proliferation inhibitory activity against the screened cancer cell lines. Among these pyrrole derivatives, compounds 3b and 3o showed potent anticancer activity against the MG-63 cell line, with IC50 values of 14.9 and 12.7 μM, respectively. Other pyrrole derivatives also showed promising proliferation inhibitory activity, including compound 3d against A375 (IC50 = 18.6 μM), compound 3f and 3j against MGC80-3 (IC50 = 19.9 μM), and compound 3o against MGC80-3 (IC50 = 11.9 μM). Because the developed pyrrole derivatives showed strong anticancer activity and high selectivity, this new series of pyrrole derivatives could be considered as promising lead compounds for further development of potent and safe anticancer agents.

Study on optimization of the circumferential and axial wavy geometrical configuration of hydrodynamic journal bearing

Xiaoping Pang,Jin Chen,Sinan H. Hussain 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.12

This paper is focused on using GA genetic algorithm to find the optimal performance with respect to shape optimization in three dimensions for the hydrodynamic journal bearing. The mathematical model for film thickness was drawn using Fourier series function and axial waviness value (D) to represent the journal bearing in circumferential and axial direction, respectively. The objective was then to determine the Fourier coefficients and axial waviness value (D) that maximized the load capacity subjected to a given set of constraint. Optimized results show that the presence of cos wave in axial direction, with a positive dimensionless amplitude (+ A) and waviness number m = 0.633 , improves the load capacity by (8-10) % over the cylindrical plain bearing with the same arbitrary shape and size; in general, the increasing order of Fourier series (n), an axial dimensionless amplitude and L/D ratio cause the change in load capacity to become more evident.

Numeric and experimental study of generalized geometrical design of a hydrodynamic journal bearing based on the general film thickness equation

Xiaoping Pang,Jin Chen,Sinan H. Hussain 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.10

This paper deals with multi-objective shape optimization related to the geometrical design of a hydrodynamic journal bearing. The aim proposed here is to show that optimum shape design with better performance could surpass the limitations of existing bearing profiles. Attempting to remove the difficulty of selecting the weighting factor in multi-objective journal bearing optimization problems, a modified non-dominant sort in genetic algorithm was used as an optimization tool with a penalty to those solutions that violate constraints. Three kinds of optimized shapes were manufactured and taken as experimental objects. Experimental apparatus was described and some experimental data was presented. The comparison was made for the optimized bearings between numeric values and experimental data. The results show that the new method for shape optimization of hydrodynamic journal bearings based on the general film thickness equation is feasible.

Research on Influence of Matrix Component on the Mechanical Behavior of Multiaxial Warp-knitted Composites

Jiawei Chen,Xiaoping Gao,Ke Zhao,Wei Wu 한국섬유공학회 2022 Fibers and polymers Vol.23 No.11

The mass ratio of curing agent to epoxy resin is one of the important factors affecting the behavior of matrix andcomposites. In this paper, the solution of curing agent to epoxy resin with different mass ratio (0.25, 0.30, 0.35 and 0.40) wasselected as matrix, quadriaxial warp-knitted fabric was selected as reinforcement, and the composites were manufactured byapplying vacuum assisted film infusion. Then the tensile and bending behavior of the composites was experimentallyinvestigated, and the curing degree and failure mechanism of the composites were analyzed with respect to thethermodynamic properties and the microscopic failure morphologies. The optimal mass ratio was obtained by applyingnonlinear fitting and verified by experiment, and a mathematical model was derived to predict the relationship between thestrength and the mass ratio. The results showed that the thermal stability, curing degree, tensile and bending strength of thespecimens increase firstly and then decrease with increase of the mass ratio. According to the tensile and bending strengthresults, the optimum mass ratio were obtained as 0.31 and 0.33 by applying nonlinear fitting to the experiment data. Theresults could lay a theoretical foundation for optimizing the mass ratio of matrix components, and improve the strength ofcomposites.