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15 February 2004, Volume 25 Issue 2 Previous Issue    Next Issue
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PCA-DRBFN model in application to estimating dry point of pure benzene in rectifying tower Chang, Yu-Qing (1); Wang, Xiao-Gang (1); Wang, Fu-Li (1) 2004, 25 (2):  103-105.  DOI: - Abstract ( 232 )   HTML   PDF (133KB) ( 662 )   An improved data dimension decreasing method is proposed to reduce the overlapped information in multivariable system, since a number of overlapped information will affect greatly the correct pick-up of PCs (Principal Components) in PCA (Principal Components Analysis). The overlapped information can be found using the correlation coefficients between standardized variables, then they are weighted and integrated altogether. An PCA-DRBFN (Principal Components Analysis-Distributed Radial Basis Function Network) based soft-sensing model is thus developed using the improved method. The model has been applied to the pure benzene rectifying process in a steel plant to estimate the dry point of pure benzene. Simulation results showed that the proposed method and developed model are both favorably versatile. References | Related Articles | Metrics

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Estimate of non-linear modeling parameters based on optimization algorithm of dynamic design variables Yao, Jian-Shi (1); Hou, Xiang-Lin (1); Xu, Xin-He (1) 2004, 25 (2):  106-109.  DOI: - Abstract ( 269 )   HTML   PDF (318KB) ( 1044 )   To minimize the modeling error arising from linearization in traditional estimate of non-linear modeling parameters, a new algorithm based on the optimization of dynamic design variables is presented. The algorithm takes each parameter to be estimated as a design variable to which the related error function is taken as objective function that is formulated involving the constraint conditions on the parameter, thus changing the parameter estimate into optimization problem. A check is carried out to confirm the performance of the optimization algorithm developed. The successful result through a rotary inverted pendulum has verified its higher convergence speed and computation accuracy. It provides an effective solution to the estimate of non-liner modeling parameters. References | Related Articles | Metrics

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Robust H∞ control of singular systems with time-varying uncertainties Dong, Xin-Zhuang (1); Zhang, Qing-Ling (1) 2004, 25 (2):  110-113.  DOI: - Abstract ( 218 )   HTML   PDF (2202KB) ( 812 )   The design of robust H∞ static state feedback and dynamic output feedback controllers are discussed for uncertain singular systems expressed in general foam. Based on the concept of generalized quadratic H∞ performance, by using linear matrix inequality (LMI), it is proved that there must be a robust H∞ static state feedback controller if a robust H∞ dynamic state feedback controller exists. Then, a sufficient and necessary condition is given for the existence of a robust H∞ static state feedback controller with its design. Furthermore, a sufficient condition is presented for the existence of a robust H∞ dynamic output feedback controller with its design. References | Related Articles | Metrics

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New yield equation based on geometric midline of error triangles between Tresca and twin shear stress yield loci Zhao, De-Wen (1); Xie, Ying-Jie (1); Liu, Xiang-Hua (1); Wang, Guo-Dong (1) 2004, 25 (2):  121-124.  DOI: - Abstract ( 203 )   HTML   PDF (247KB) ( 1343 )   The geometric midlines of error triangles or gaps between Tresca and twin shear stress yield loci on π-plane were linked up together to form a third yield locus which reflects a new yield criterion called GM (geometric midline) yield criterion in Haigh Westergaard stress space. The mathematical relationship between the GM criterion and its yield locus on π-plane was given as well as an expression of the rate of plastic work done per unit volume. A precision analysis was made with an actually calculated example. It is showed that the GM criterion is a linear one of which the maximum error relative to Mises criterion is not greater than 2.9% with a mean relative error not greater than 0.95%, and its precision is 1% higher than that of MY criterion. As a linear one, its yield locus is a non-equiangular but equilateral dodecagon intersected with Mises locus. The expression of the rate of plastic work done per unit volume of the criterion is also linear. References | Related Articles | Metrics

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Influence of cold rolling on two-way shape memory effect and martensite transformation of Cu-18Al-10.5Mn alloy Wang, Ji-Jie (1); Fu, Meng (1); Lian, Fa-Zeng (1); Hao, Shi-Ming (1) 2004, 25 (2):  125-128.  DOI: - Abstract ( 263 )   HTML   PDF (181KB) ( 838 )   The cold-rolled Cu-18Al-10.5Mn alloy was investigated for its martensite transformation caused by cold rolling by means of dilatometer, X-ray diffraction and DSC. The results showed that cold rolling process can induce texture of stress-induced martensite and two-way shape memory effect in specific direction. The control of cold rolling reduction can change shapes freely and spontaneously to a certain extent, either forwardly or reversely, and realize the effect of low thermal expansion. The range of martensite transform temperature will be much wider if increasing the reduction. The results of X-ray diffraction in the three sections, i.e. normal to rolling direction (RD) and normal direction (ND), showed that the martensite texture is stress-induced to release the stress due to cold rolling to utmost extent. With the change in temperature, the optimization-oriented stress induces the nuclear growth/disappearance of martensites, which is just the root cause of the anisotropy of reversibly spontaneous change of shapes. References | Related Articles | Metrics

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Dynamic modelling for solidification process of CC alloy steel billets Jia, Guang-Lin (1); Qi, Ya-Li (1); Zhang, Guo-Zhi (1); Cheng, Shi-Fu (1) 2004, 25 (2):  129-132.  DOI: - Abstract ( 232 )   HTML   PDF (1335KB) ( 806 )   The porosity, segregation and cracks of continuous casting (CC) alloy steel billets in solidification process were investigated in situ, of which the 200 mm × 200 mm billets of GCrl5 (for use of bearings), 40Cr and 20CrMnTi were taken as specimens. A mathematical model of heat transfer in solidification process is therefore set up, with boundary condition, initial condition, surface heat flux at different cooling sections and physical parameters of different steel grades all determined. In particular the 2-dimensional coordinate system is set up on the billets, thus solving dynamically the problem of temperature field on the whole sectional area of billet in solidification process at different overheated temperatures, drawing speeds, times required and positions. The model shows a fairly good agreement with the measurements in situ as verified through numerical calculation. It will provide a reference for taking measures to improve the quality of billets, such as, adjusting technological parameters in continuous casting process, positioning the electromagnetic stirrer at the final solidification area for billets and determining electromagnetic parameters. References | Related Articles | Metrics

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Influence of three cosolvents on hydrolysis of tetraethyl-orthosilicate Huo, Yu-Qiu (1); Zhai, Yu-Chun (1); Tong, Hua-Nan (1) 2004, 25 (2):  133-135.  DOI: - Abstract ( 1009 )   HTML   PDF (182KB) ( 3321 )   Investigates the influence of such cosolvents as n-butanal, isopropanol and ethanol on the reaction time and yield in the precipitation process and sol-gel process of tetraethyl-orthosilicate hydrolysis. The structure and morphology of powdered SiO2 were studied by TEM and FT-IR. The results showed that the reaction time decreases and yield increases with the increase in alkyl chains during either precipitation process or sol-gel process. In addition, the structure of powdered SiO2 obtained from either process are the same, but the particle sizes of SiO2 powder obtained from different hydrolysis process in which different cosolvents are used are different, ie. Using the cosolvents n-butanol and isopropyl can form smaller particle size than using ethanol. References | Related Articles | Metrics

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Ball milling regime for NiFe2O4 spinel powder Zhang, Shu-Ting (1); Yao, Guang-Chun (1); Liu, Yi-Han (1); Liu, Hai-Shi (2) 2004, 25 (2):  136-138.  DOI: - Abstract ( 249 )   HTML   PDF (132KB) ( 584 )   Investigates the effect of ball milling parameters on the particle size of powdered NiFe2O4 spinel. Based on the ball size that was calculated to meet the requirement for lab test, a series of orthogonal tests were carried out to select parameters appropriate to the ball milling process. Test results showed that the duration of ball milling process is the predominant factor to the particle size, and the ball size grading also has an important effect on the distribution range of particle size. A set of optimum parameters for such a ball milling process is thus recommended as follows. Time required for ball milling: 36 h; ball size grading: 35:40:25; mass ratio of the stuff to mill to the ball: 1:2; and the volumetric percent of water contained in slurry: 75%. References | Related Articles | Metrics

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Effect of anionic surfactant on decomposition of sodium aluminate solution Zhao, Su (1); Bi, Shi-Wen (1); Yang, Yi-Hong (1); Xie, Yan-Li (1) 2004, 25 (2):  139-141.  DOI: - Abstract ( 310 )   HTML   PDF (635KB) ( 702 )   During the seed precipitation process of sodium aluminate solution, adding an anionic surfactant derived from unsaturated fatty acid in the solution can intensify the decomposition process so as to improve the quality of final products. Experimental results indicated that the decomposed portion of sodium aluminate can increase by about 5%, with the average grain size and strength of aluminum hydroxide as final product increase by 2% and about 5%, respectively, if adding in 280 mg/l of the surfactant. The fact implies that there is an obvious physico-chemical change caused by the surfactant added in the solution. With the viscosity, surface tension and conductivity of the solution tested, the functional mechanism of the surfactant is discussed and elucidated. References | Related Articles | Metrics

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Viscosity measurement and modeling of slag systems of CuCr alloys prepared through Al thermit-SHS (II) Zhang, Ting-An (1); Dou, Zhi-He (1); Xu, Shu-Xiang (2); Yang, Huan (1) 2004, 25 (2):  142-145.  DOI: - Abstract ( 267 )   HTML   PDF (163KB) ( 483 )   The viscosity model, which has already been built to apply as a reference to the slag systems without SiO2, was used to estimate the viscosities of Al2O3-CaO system. The results showed that the estimated values conform well with the measured values as shown in some known literatures. The ionization factor, L, between A13+ and Ca2+ in the Al2O3-CaO system was determined from the experimental data as shown in known literatures. According to the measurements, the slags have good fluidities around the eutectic point and the viscosities are below 0.5 Pa·s at 1460°C for Al2O3-CaO system. As to Al2O3-CaO-MgO system, the slags were prepared according to compositions of two different eutectic points, and the viscosity of the slag which contains more CaO is lower, ie. lower than 0.03 Pa·s at 1500°C. In addition, the additive MgO can reduce obviously the slag viscosity values of Al2O3-CaO system. References | Related Articles | Metrics

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Experimental study on mesh-wear of involute spur gears Wang, Shu-Ren (1); Yan, Yu-Tao (1); Ding, Jin-Yuan (1) 2004, 25 (2):  146-149.  DOI: - Abstract ( 303 )   HTML   PDF (236KB) ( 1361 )   A mesh-wear test was done on CL-100 Gear Test Machine for a pair of involute spur gears with the intention of providing parametric data for computerized simulation. The high-precision UMC 1000 Triaxial Measuring Instrument was used to measure the tooth profiles before and after the wear-out due to gear meshing. The test results were processed by computer, then the curves of linear wearing values of both rears are plotted by means of the software Mathematica. Comparing the calculated results with tested ones, the former is nearly in conformity with the latter. It is found that the wearing value is minimum in the vicinity of the pitch circle, while it is maximum in the radial distributions of linear wearing values are basically in conformity with that of the speed of a gear's tooth flank relative to other one's tooth flank in meshing process. References | Related Articles | Metrics

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Response characteristics of 3 sulfur/phosphorus system lubricant additives in rapeseed oil Ma, Jiang-Bo (1); Hu, Jun-Hong (1); Ding, Jin-Yuan (1); Ma, Xian-Gui (1) 2004, 25 (2):  150-152.  DOI: - Abstract ( 292 )   HTML   PDF (139KB) ( 684 )   Taking rapeseed oil as base constituent, the three lubricant additives, ie. sulfur-system T321 and T307 and phosphorus-system P120, were investigated separately on a 4-ball friction-wear tester with the intention of how they improve the wearability and extreme pressure characteristics of rapeseed oil. The results showed that they all are beneficial to reduce wear-out and improve the load capacity and resistance to extreme pressure of lubrication film. The SEDX (Spectral Energy Distribution X-ray) analysis of steel ball surfaces revealed that there are tribochemical reactions of the rapeseed oil containing any of the three additives during friction/wear process, thus forming a boundary lubrication film composed of triglyceride and others produced from the reacted additive to improve the wearability and load capacity. References | Related Articles | Metrics

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Modeling, interference checking and simulation of virtual assembly systems Yan, Yun-Hui (1); Zhang, Hai-Yan (1); Yang, Hui-Lin (1); Li, Cheng-Feng (1) 2004, 25 (2):  153-155.  DOI: - Abstract ( 266 )   HTML   PDF (163KB) ( 1180 )   Taking product's feature as core, a modeling procedure is proposed to develop virtual assembly systems with an algorithm given to check interference. By this procedure the solution to sequential assembly scheme can be simplified using a hierarchical assembly model to store all the interactions among parts in a matrix. The algorithm is used to compute effectively relative distance between any parts to be assembled in any direction, i.e., the equivalent interference, and then analyze the assembly possibility of all non-geometric information provided by the modeling procedure. The simulation consists of assembly simulation and kinematics simulation, where the former is performed and monitored interactively using the sequential assembly scheme created by the hierarchical assembly model. The parameterized kinematics simulation enables the users to understand fully the kinematical properties of the machine in assembly and find out the problems in relation to kinematics for convenient design correction. References | Related Articles | Metrics

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Numerical modeling of flow field of submerged circulative reactor to impinging streams Zhang, Jian-Wei (1); Xu, Cheng-Hai (1); Wu, Yuan (2); Zhang, He-Ping (3) 2004, 25 (2):  156-159.  DOI: - Abstract ( 275 )   HTML   PDF (802KB) ( 701 )   Uses the module FLOTRAN CFD for hydrodynamic computation in the software ANSYS that is versatile to finite element analysis to model and analyze the flow field of the submerged circulative reactor to impinging streams (SCISR). The computation results showed that all the parameters in the flow field are symmetrical to the planes impinged. It was found that there are still dead zones on upper and lower sides of conversion barrel and in impinging zone, but they can be reduced by increasing Reynolds number. In the impinging zone the velocity isolines are intensive, ie., in the zone there is a great velocity gradient which is very beneficial to mix up turbulent motions. A pressure value acquisition device on computer is applied to conduct pressure testing for the flow field and the pressure values measured are compared to that modeled, with a good compliance shown. References | Related Articles | Metrics

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Temperature compensation of SOS pressure sensor Mo, Chang-Tao (1); Chen, Chang-Zheng (2); Zhang, Li-Li (3); Sun, Feng-Jiu (1) 2004, 25 (2):  160-163.  DOI: - Abstract ( 524 )   HTML   PDF (985KB) ( 1020 )   The temperature characteristics of SOS pressure sensor was analyzed and found that the sensor output is linear and easy to be affected by ambient temperature over a wide measuring range. Based on the conjugate gradient algorithm for neural network, a temperature compensation method for sensor is put forward the way the approximability of the algorithm to any nonlinear function is utilized to drill the neural network so as to enable it to be set up at different ambient temperatures, thus allowing the sensor output can be in a nonlinear mapping relation to the voltage values the sensor actually sensed. The simulation results on computer showed that the method can not only eliminate the influence of ambient temperature fluctuation but obtain the expected linear output from the output terminal of neural network. References | Related Articles | Metrics

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Modeling of concrete frost resistance on BP network basis Cheng, Yun-Hong (1); Liu, Bin (1) 2004, 25 (2):  164-166.  DOI: - Abstract ( 240 )   HTML   PDF (115KB) ( 713 )   Three computation models of concrete frost resistance are established on basis of optimized BP algorithm, and each of them has an input layer, hidden layer and output layer. The model(1) is named 3-5-2 type in which 3 input neurons, 5 hidden neurons and 2 output neurons are covered. The models(2) and (3) are both named 3-5-1 type in which 3 input neurons, 5 hidden neurons and 1 output neuron are covered. In models(1) the water/cement ratio, unit cement consumption and sand percentage are taken as inputs, with both loss of weight and loss of strength after thawing as outputs. As to models(2) and (3), the inputs are the same to model(1) but the outputs of model(2) and of model(3) are loss of weight and loss of strength after thawing, respectively. The results of the computation conform well to that of tests. All models developed are realized with Visual Basic 6.0. The modeling shows that optimized BP algorithms are very efficient in quantitative analysis of concrete frost resistance. References | Related Articles | Metrics

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Influence of crack continuity on propagation of en echelon cracks in heterogeneous materials Xu, Tao (1); Tang, Chun-An (1); Wang, Shan-Yong (1); Zhao, Xing-Dong (1) 2004, 25 (2):  167-170.  DOI: - Abstract ( 247 )   HTML   PDF (264KB) ( 719 )   Using a Material Failure Process Analysis (MFPA2D) code, the influence of crack continuity in heterogeneous materials containing two existing parallel flaws under uniaxial loading is numerically studied. The numerical simulation reproduces the stress field in the vicinity of cracks and the processes of propagation and coalescence of cracks during compression. The numerical simulation results showed that, with the decrease of the crack continuity, the stress field between the tips of internal cracks gradually changes from tensile stress to compression stress and the propagation mode of cracks also changes from tensile mode(T), tensile-shear mode(T-S) to compressive mode(C), and the initiation angle between the flaw and the direction of the maximum compression increases gradually as well. In addition, the initiation stress on the tips of cracks is about l/2-1/3 of the failure strength of the specimens. References | Related Articles | Metrics

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Experimental study on the gold extracted from carbonaceous gold ore leached in heaps by preoxidized roast Wang, Cheng-Gong (1); Zhou, Shi-Jie (1); Zhang, Shu-Min (1); Yang, Hong-Ying (1) 2004, 25 (2):  171-174.  DOI: - Abstract ( 272 )   HTML   PDF (113KB) ( 904 )   The preoxidized roast process and direct leaching in heaps of the roasted ore from a low-sulfur carbonaceous silicified gold mine in Dandong, Liaoning Province were studied experimentally, of which the roasted/oxidized conditions of gold ore and main influencing factors on leaching rate of gold were investigated under different temperatures, atmospheres and times, such as the weight% of NaCN, spraying intensity, grain size of roasted ore and spraying time. As a result, the oxidizing rate and ashing rate of the sulphides and carbonaceous material can be up to 98% and 97%, respectively, if roasting the ore for 1 h (for dearsenification) at 450°C and ventilated with a bit of air to provide 5%-10% of oxygen content in air and, further, roasting it for 2 h at 650°C and ventilated with full air. The leaching rate of gold is 84.8% if the weight% of NaCN is 0.10%-0.15%, spraying intensity 15.0 L/(m2·h), grain size of roasted ore 0-3 mm and spraying time 8-10 days. The basic technological process of direct leaching in heaps of roasted ore is recommended with the intention of laying a foundation for industrial applications. References | Related Articles | Metrics

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Study of failure process in concrete samples by using numerical simulation Zhang, De-Hai (1); Xing, Ji-Bo (2); Zhu, Fu-Sheng (1); Yang, Shun-Cun (3) 2004, 25 (2):  175-178.  DOI: - Abstract ( 321 )   HTML   PDF (274KB) ( 1426 )   A numerical approach based on Beam-Particle Model (BPM2) is developed to the simulation of fracture process of concrete samples under uniaxial compression. Three types of beam have been used in BPM2 to form numerical model of concrete at mesoscale level, and the mechanical properties of every type of beam are randomly initialized according to Weibull distribution so as to reflect the initial heterogeneity of concrete samples at mesoscale level. The results of numerical simulation showed that the initiation and propagation of internal cracks at mesoscale level and their connection with each other in the concrete samples are just the cause of its macro-failure. It has been revealed via a comparison of numerical simulations that the failure modes of concrete samples vary with the initial heterogeneity of distribution of material properties. The fracture mechanism of concrete has been discussed on the basis of the numerical simulation. References | Related Articles | Metrics

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- - 2004, 25 (2):  179-182.  DOI: - Abstract ( 215 )   HTML   PDF (195KB) ( 1029 )   - References | Related Articles | Metrics

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- - 2004, 25 (2):  183-186.  DOI: - Abstract ( 205 )   HTML   PDF (165KB) ( 724 )   - References | Related Articles | Metrics

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- - 2004, 25 (2):  187-189.  DOI: - Abstract ( 225 )   HTML   PDF (129KB) ( 659 )   - References | Related Articles | Metrics

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- - 2004, 25 (2):  190-193.  DOI: - Abstract ( 250 )   HTML   PDF (253KB) ( 857 )   - References | Related Articles | Metrics

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- - 2004, 25 (2):  194-196.  DOI: - Abstract ( 165 )   HTML   PDF (136KB) ( 572 )   - References | Related Articles | Metrics

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Chemisorption-induced multilayer segregation: H/Au-Ag Zhang, Hui (1); Zhang, Guo-Ying (2); Wei, Guo-Zhu (2); Liu, Shi-Yang (2) 2004, 25 (2):  197-200.  DOI: - Abstract ( 325 )   HTML   PDF (1644KB) ( 808 )   The chemisorption of hydrogen on the multilayer surface segregated Au-Ag alloy is investigated using Green function method and the multicoupling self-consistent coherent-potential approximation. The interaction between chemisorption and multilayer surface segregation is discussed in detail. The chemisorption-induced surface segregation can change greatly the surface component of the alloy as well as the chemisorption energy. For H/Au-Ag system, a fluctuation characteristic of the calculated values of chemisorption energy is found if increasing the number of surface layers to calculate. References | Related Articles | Metrics

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Discharge characteristics and jet intensity of nitrogen plasma gun in atmosphere Liu, Jun-You (1); Sun, Feng-Jiu (1); Yan, Ping-Yuan (1); Yan, Wei (1) 2004, 25 (2):  201-204.  DOI: - Abstract ( 244 )   HTML   PDF (162KB) ( 512 )   Aiming at local treatment of material surface by plasma, a glow discharge N2 plasma gun to be used in atmosphere was designed to investigate and analyze theoretically its discharge characteristics and jet intensity. As experimental results, the discharging volt-ampere characteristic curve and effect of jet flux on torch's working voltage/current were discussed on their causes, with an analytic curve-fitting equation given. It was found that the working voltage and current is exponentially increasing and decreasing in relation to jet flux, respectively. Furthermore, the jet from the plasma gun is characterized by expanding first then contracting, with a maximum active sectional area found 5 mm distant from torch tip. The optimal intensity gas jet is 0.2 m3/h. The operation mechanism of the plasma gun was thus discussed further to find out the optimal conditions on which the specimen preparation will be available. References | Related Articles | Metrics