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31 December 2013, Volume 18 Issue 6 Previous Issue    Next Issue

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Separation Method of Bi-directional Reflected Waves and Oblique Incident Regular Waves LI Jun1* (李 俊), CHEN Gang1,2 (陈 刚), YANG Jian-min1 (杨建民), PENG Tao1 (彭 涛) 2013, 18 (6):  641-645.  doi: 10.1007/s12204-013-1444-8 Abstract ( 796 )   Wave reflection is one of the key problems affecting wave simulation quality in ocean engineering basin. The deep ocean engineering basin is equipped with two-sided segmented wavemakers and two wave absorbing beaches, which are located opposite to wave generators to reduce wave reflection effects. When an oblique longcrested wave is made by two-sided segmented wavemakers in a wave basin, two bi-directional reflected waves with the same azimuth but opposite propagation directions are generated. According to this feature, based on the two-point approach developed by Goda, a method to separate an incident regular wave from two bi-directional reflected waves using three wave gauges is proposed. The validity of this method is proved by numerical composite waves. The results indicate that the method can separate incident wave from reflected waves effectively. The method can be used to determine the reflection coefficient and verify the capacity of wave absorbing beaches in deep ocean engineering basin. References | Related Articles | Metrics

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Three-Dimensional Stability Analysis of Excavation Using Limit Analysis HAN Chang-yu1,2 (韩长玉), CHEN Jin-jian1 (陈锦剑), WANG Jian-hua1 (王建华), XIA Xiao-he1* (夏小和) 2013, 18 (6):  646-649.  doi: 10.1007/s12204-013-1445-7 Abstract ( 730 )   The theory of limit analysis is presented for a three-dimensional stability problem of excavation. In frictional soil, the failure surface has the shape of logarithm helicoid, with the outline profile defined by a logspiral curve. The internal dissipation rate of energy caused by soil cohesion and gravity power of the failure soil is obtained through theoretical derivation. By solving the energy balance equation, the stability factor for the excavation is obtained. Influence of the ratio of width to height, the slope angle, and the top angle on the stability is examined. Numerical results of the proposed algorithm are presented in the form of non dimensional graph. Examples illustrate the practical use of the results. References | Related Articles | Metrics

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Numerical Analysis on Cnoidal Wave Induced Response of Porous Seabed with Definite Thickness XU Yun-feng (徐云峰), XIA Xiao-he* (夏小和), WANG Jian-hua (王建华), CHEN Jin-jian (陈锦剑) 2013, 18 (6):  650-654.  doi: 10.1007/s12204-013-1446-6 Abstract ( 646 )   Severe water waves can induce seabed liquefaction and do harm to marine structures. Dynamic response of seabed with definite thickness induced by cnoidal water waves is investigated numerically. Biot’s consolidation equations are employed to model the seabed response. Parametric studies are carried out to examine the influence of the air content in the pore water and the soil hydraulic conductivity. It has been shown that the air content and soil hydraulic conductivity can significantly affect the pore pressure in seabed. An increase of air content and/or a decrease of soil hydraulic conductivity can change the pore pressure gradient sharply. References | Related Articles | Metrics

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An Improved Dynamic Hysteretic Model for Soils YU Hai-tao1,2,3* (禹海涛), WANG Jian-hua1 (王建华), YUAN Yong2,3 (袁 勇) 2013, 18 (6):  655-659.  doi: 10.1007/s12204-013-1447-5 Abstract ( 746 )   A dynamic hysteretic constitutive model for soil dynamics, Ramberg-Osgood model, is introduced and improved in the paper. Since the model is inherently 1D and is assumed to apply to shear components only, other components of the deviatoric stress and strain and their relations in 3D case could not be fully described. Two parameters, the equivalent shear stress and the equivalent shear strain, are defined to reasonably establish relations between each of stress and strain components respectively. The constitutive equations of the initial Ramberg-Osgood model are extended to generalize the theory into multidimensional cases. Difficulties of the definition of load reversal in 3D are also addressed and solved. The improved constitutive model for soil dynamics is verified by comparisons with different soil dynamic testing data covering both sands and clays. Results show that the dynamic nonlinear hysteretic behaviors of soils can be well predicted with the improved constitutive model. References | Related Articles | Metrics

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Robust Intelligent Control Design for Marine Diesel Engine HUA Hai-de1* (华海德), MA Ning1 (马 宁), MA Jie1 (马 捷), ZHU Xing-yu2 (朱星宇) 2013, 18 (6):  660-666.  doi: 10.1007/s12204-013-1448-4 Abstract ( 756 )   This work deals with the nonlinear control of a marine diesel engine by use of a robust intelligent control strategy based on cerebellar model articulation controller (CMAC). A mathematical model of diesel engine propulsion system is presented. In order to increase the accuracy of dynamical speed, the mathematical model of engagement process based on the law of energy conservation is proposed. Then, a robust cerebellar model articulation controller is proposed for uncertain nonlinear systems. The concept of active disturbance rejection control (ADRC) is adopted so that the proposed controller has more robustness against uncertainties. Finally, the proposed controller is applied to engine speed control system. Both the model of the diesel engine propulsion system and of the control law are validated by a virtual detailed simulation environment. The prediction capability of the model and the control efficiency are clearly shown. References | Related Articles | Metrics

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Full Waveform Inversion Method for Horizontally Inhomogeneous Stratified Media WANG Huan (王 欢), CHE Ai-lan* (车爱兰), GE Xiu-run (葛修润) 2013, 18 (6):  667-672.  doi: 10.1007/s12204-013-1449-3 Abstract ( 685 )   Full waveform inversion method is an approach to grasp the physical property parameters of underground media in geotechnical nondestructive detection and testing field. Using finite-difference time domain (FDTD) method for elastic wave equations, the full-wave field in horizontally inhomogeneous stratified media for elastic wave logging was calculated. A numerical 2D model with three layers was computed for elastic wave propagation in horizontally inhomogeneous media. The full waveform inversion method was verified to be feasible for evaluating elastic parameters in lateral inhomogeneous stratified media and showed well accuracy and convergence. It was shown that the time cost of inversion had certain dependence on the choice of starting initial model. Furthermore, this method was used in the detection of nonuniform grouting in the construction of immersed tube tunnel. The distribution of nonuniform grouting was clearly evaluated by the S-wave velocity profile of grouted mortar base below the tunnel floor. References | Related Articles | Metrics

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Symmetry Based Searching Process for Initial Conditions of Passive Running DENG Qi (邓 奇), WANG Shi-gang* (王石刚), MO Jin-qiu (莫锦秋), LIANG Qing-hua (梁庆华) 2013, 18 (6):  673-678.  doi: 10.1007/s12204-011-1203-7 Abstract ( 750 )   Symmetrical passive running of a simple spring model is commonly used to predict the locomotion of real animals and develop the design strategies for legged systems. If the initial conditions for running can be found automatically, we can expand the ranges of the model parameters freely. To achieve this objective, we derive an efficient searching procedure based on analysis of the symmetries. Using this process, the desired initial states of the passive running are obtained. Existence of the results reveals that the leg symmetries can be used to generate the symmetrical running. Moreover, the leg forces are associated with the running pattern, implying that we should choose suitable motion for the given model characteristics. References | Related Articles | Metrics

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Aerodynamic Characteristics of Airship Zhiyuan-1 LIU Pinga* (刘 平), FU Gong-yia (付功义), ZHU Li-juna (朱利君), WANG Xiao-liangb (王晓亮) 2013, 18 (6):  679-687.  doi: 10.1007/s12204-013-1443-9 Abstract ( 891 )   An airship named “Zhiyuan-1” was designed/fabricated/flied as a technical demonstration for stratospheric airship during 2007—2009 by Shanghai Jiaotong University. The calculation method and procedure of aerodynamic parameters were introduced, and the optimized configuration of the hull and the aerodynamic layout were given in this paper. Wind tunnel tests with different configurations, different pitch angles and different yaw angles were performed to study the wind load characteristics of the rigid model of the airship “Zhiyuan-1” in the 3.2 m wind tunnel at China Aerodynamics Research & Development Center. Also the numerical calculation about the test model was carried out to investigate the aerodynamic behavior. According to the results of wind test and numerical calculation, the excellent hull configuration of the airship “Zhiyuan-1” with lower drag characteristic was confirmed, which is based on optimism of the Michel transition law. And the phenomena of pressure coefficient distribution were discussed according to the results of wind tunnel test and numerical calculation at different flight attitudes. References | Related Articles | Metrics

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Uniaxial Compressive and Splitting Tensile Tests of Artificially Frozen Soils in Tunnel Construction of Hong Kong HU Xiang-dong1,2* (胡向东), WANG Jin-tai1,2 (王金泰), YU Rui-zhi3 (余睿智) 2013, 18 (6):  688-692.  doi: 10.1007/s12204-013-1450-x Abstract ( 563 )   Three different kinds of artificially frozen soils are tested for artificial ground freezing (AGF) project in the tunnel construction of Stonecutters Island Sewage Treatment Works, Hong Kong. Uniaxial compressive test is conducted and uniaxial compressive strength, modulus of elasticity and Poisson’s ratio are obtained. Meanwhile, relations of all these three parameters and temperature are fitted by linear function. The linear relationship between the above-mentioned parameters and temperature is suitable for engineering practice. Splitting tensile test of frozen soil is conducted to obtain tensile strength and find out failure pattern in test. All the parameters obtained are necessities in design and practice. References | Related Articles | Metrics

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Physical Model Test on the Behavior of Large Slurry Shield-Driving Tunnel in Soft Clay HU Xin-yu1* (胡欣雨), ZHANG Zi-xin2 (张子新) 2013, 18 (6):  693-698.  doi: 10.1007/s12204-013-1451-9 Abstract ( 705 )   As the dimension of the slurry shield is greatly increasing, more and more attention is paid to the face stability of slurry shield-driven tunnel in recently years. A reduced-scale slurry shield model test is carried out based on the background of Qianjiang River Tunnel and Shanghai Yangtze River Tunnel. The results of the model test are presented in this paper with particular emphasis on the slurry shield driving parameters and the critical slurry pressure of the excavating face. It is shown that the behavior of large slurry shield-driving induced by the cutting face is mostly decided by the fluctuation of the slurry pressure in the chamber, and a smaller slurry pressure fluctuation range is presented according to the results of the physical model test. Especially, it is more difficult to control the machine in sandy silt than that in soft clay and muddy clay. The chamber pressure will fluctuate greatly when excavating in high permeability ground, and the gradient of accumulation of the flux difference could be used to evaluate the face balance of the slurry shield excavation. References | Related Articles | Metrics

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Automatic Identification of Cracks from Borehole Image Under Complicated Geological Conditions FENG Shao-kong1,2* (冯少孔), HUANG Tao3 (黄 涛), LI Hong-jie4 (李宏阶) 2013, 18 (6):  699-705.  doi: 10.1007/s12204-013-1452-8 Abstract ( 623 )   Identifying cracks from the spread image of a borehole wall is one of the most common usages of borehole imaging method. The manual identification of cracks is time-consuming and can be easily influenced by objective judgment. In this study, firstly, the image translation from RGB color model to HSV color model is done to highlight the structural plane region, which is closer to the color recognition of human sight; secondly, the Saturation component is filtered for further processing and a twice segmentation method is proposed to improve the accuracy of automatic identification. The primary segmentation is based on the statistics of saturation over a longer borehole section and can give a rough estimation of a crack. Then, the pixels are shifted in the reverse direction to the sine curve estimated and make the centerline of the crack flat. Based on the shifted image, the secondary segmentation is done with a small rectangle region that takes the baseline of the roughly estimated crack as its centerline. The result of the secondary segmentation can give a correction to the first estimation. Through verifying this method with actual borehole image data, the result has shown that this method can identify cracks automatically under very complicated geological conditions. References | Related Articles | Metrics

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Analytical Solution to Steady-State Temperature Field of Two Freezing Pipes with Different Temperatures HU Xiang-dong* (胡向东), ZHANG Luo-yu (张洛瑜) 2013, 18 (6):  706-711.  doi: 10.1007/s12204-013-1453-7 Abstract ( 468 )   The existing analytical formulas to calculate the temperature field distribution of artificial frozen soil walls are all based on the conditions that the surface temperatures of all freezing pipes are equivalent. In this paper, analytical solution of steady state temperature field of two freezing pipes with different temperatures is deduced based on thermal potential superposition method. The correctness of the analytical formulas is verified by comparing the temperature field distributions of the analytical formulas and those of the numerical simulations in the same conditions. And discussions are made to analyze the influence of some parameters on temperature field distribution of this condition. References | Related Articles | Metrics

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Wavelet Moment Invariants Extraction of Underwater Laser Vision Image HUANG Shu-ling* (黄蜀玲), PANG Yong-jie (庞永杰), WANG Bo (王 博), WAN Lei (万 磊) 2013, 18 (6):  712-718.  doi: 10.1007/s12204-013-1454-6 Abstract ( 722 )   Wavelet moment invariants are constructed for object recognition based on the global feature and local feature of target, which are brought for the simple background of the underwater objects, complex structure, similar form etc. These invariant features realize the multi-dimension feature extraction of local topology and invariant transform. Considering translation and scale invariant characteristics were ignored by conventional wavelet moments, some improvements were done in this paper. The cubic B-spline wavelets which are optimally localized in space-frequency and close to the forms of Li’s (or Zernike’s) polynomial moments were applied for calculating the wavelet moments. To testify superiority of the wavelet moments mentioned in this paper, generalized regression neural network (GRNN) was used to calculate the recognition rates based on wavelet invariant moments and conventional invariant moments respectively. Wavelet moments obtained 100% recognition rate for every object and the conventional moments obtained less classification rate. The result shows that wavelet moment has the ability to identify many types of objects and is suitable for laser image recognition. References | Related Articles | Metrics

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Experimental Study on Mechanical Properties of Weathered Rock Covered by Loess WANG Ping1,2,3 (王 平), WU Zhi-jian1,2,3* (吴志坚), WANG Jun1,2,3 (王 俊), ZHANG Ze-zhong1,2 (张泽忠), WANG Qian1,2,3 (王 谦) 2013, 18 (6):  719-723.  doi: 10.1007/s12204-013-1455-5 Abstract ( 435 )   Based on dynamic triaxial test, the mechanical properties of the weathered rock covered by loess were studied. The cohesion value of weathered mudstone is far below that of the weathered sandstone, while the internal friction angle values are basically equivalent, about 30?. Compared with the undisturbed sample, the cohesion value of remodeling weathered rock sample decreases significantly. With the increase of moisture content, the strength of weathered mudstone is obviously decreased due to the influence of the water softening effect. This results illustrate that the bearing stratum is not easily affected by external disturbance in comparison to weathered mudstone. In the engineering, in order to ensure the good mechanical properties of the soil, more attention should be paid to keeping the water content constant, even to reducing the water content. The experiments show that the relations between shear stress and strain of weathered rock were nonlinear and the behavior of weathered rock can be expressed by the hyperbolic model. The initial modulus of undisturbed weathered rock, under the same consolidation conditions, is much greater than that of remodeling samples. Meanwhile, the initial dynamic elastic modulus of sandstone is also greater than that of the mudstone. The dynamic shear modulus ratios of the undisturbed sandstone, the undisturbed mudstone, as well as the remodeling mudstone have the normalization characteristics with the increase of dynamic shear strain. The damping ratio of mudstone is larger than that of the sandstone, and the damping ratio of remolding sample is also greater than that of the undisturbed mudstone. The mudstone has the bad mechanical properties as bearing stratum. References | Related Articles | Metrics

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Analysis on Intensity Zonation in Thick Loess Region ZHANG Ze-zhong1,2 (张泽忠), WU Zhi-jian1,2,3* (吴志坚), CHEN Tuo4 (陈 拓), LEI Tian1,2 (雷 天) 2013, 18 (6):  724-728.  doi: 10.1007/s12204-013-1456-4 Abstract ( 443 )   The earthquakes, which occurred in Haiyuan, Tangshan and Wenchuan, have caused serious damages in the loess area and the abnormal intensity sites are commonly found during the earthquakes. The investigation of the actual earthquake damages and character analysis on sites shows that the topography, loess overburden and underground water level and many other factors affect the intensity. In this paper, the thickness of loess overburden of Tianshui City is achieved by inversion algorithm based on site exploration and microtremor test; the amplification effect of peak ground motion acceleration is calculated using numerical method; a complete formula is obtained through summarizing previous achievements and is used to calculate the abnormal intensity under the multifactorial influence. Finally, a seismic intensity anomaly distribution map is plotted applying the graphic information system (GIS) software in Maiji District, Tianshui City. Through the practical investigation of earthquake disaster, it is found that the figure fits the distribution of actual intensity anomaly very well. References | Related Articles | Metrics

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Temperature Adjustment Mechanism of Composite Embankment with Perforated Ventilation Pipe and Blocky Stone NIU Fu-jun1,3 (牛富俊), SUN Hong2* (孙 红), GE Xiu-run2 (葛修润), ZHANG Jin-zhao3 (章金钊) 2013, 18 (6):  729-732.  doi: 10.1007/s12204-013-1457-3 Abstract ( 583 )   Based on the advantages of perforated ventilation characteristic of perforated ventilation pipe embankment and large porosity of blocky stone embankment, composite embankment with ventilation pipe and blocky stone is more efficient to protect the underlying permafrost. The temperature fields and cooling effect of composite embankment with air doors are simulated by examining the effects of holes’ position drilled in the pipe, diameter in pipe and density of holes. It is shown that the underlying permafrost temperature obviously reduces by composite methods, the location of 0?C isotherm raises significantly, especially permafrost temperature under the center and shoulder of embankment reduces more quickly, the composite embankment with holes drilled in the lower side of pipe is the most efficient, the increase of diameter has a slight influence on the 0?C isotherm’s raising, and the density of holes slightly influences the raising of 0?C isotherm. References | Related Articles | Metrics

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A Synthetic Decoding Method of 3GPP Multimedia Broadcast/Multicast Services Raptor Codes GAO Shou-wei1* (高守玮), WANG Hai-run1 (王海润), LI Jun2 (李 骏), ZHANG Wei-dong3 (张卫东) 2013, 18 (6):  733-737.  doi: 10.1007/s12204-013-1458-2 Abstract ( 740 )   The 3GPP multimedia broadcast/multicast services (MBMS) standard takes Raptor codes as a way of channel coding and puts forward an efficient enhanced Gaussian elimination (EGE) for the Raptor decoder. However, the standard decoding method is not the most efficient. A few of researchers made some changes based on the standard decoding method and achieved considerable performance. In this paper, a synthetic decoding method is presented according to the existing enhanced decoding method and the simulation shows that the synthetic way outperforms any other ways. References | Related Articles | Metrics

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Surface Hardness Evaluation of Components Made by Color Stereolithography GONG Hai-jun (宫海军), WANG Mao-lu* (王懋露), WANG Yang (王 扬) 2013, 18 (6):  738-741.  doi: 10.1007/s12204-013-1459-1 Abstract ( 585 )   Surface hardness value is a commonly used indicator for describing the mechanical property of stereolithography parts. In order to investigate colorants how to influence the surface hardness of colorful resin component, a procedure is proposed to fabricate testing specimens based on color stereolithography technology in this study. Liquid photosensitive resin LPR2001 is mixed with two colorants (phthalocyanine blue and eosin powder) respectively before curing. The phthalocyanine blue powder is insoluble and only dispersive in the solidliquid mixture which results in deposits. Therefore, surface modification is conducted to the phthalocyanine blue powder for improving wettability. By contrast, the eosin powder is dissoluble and does not cause any deposits in the liquid resin. Specimens are produced by laser curing colored resin and tested by MTSR Nano Indenter XP system. The change of hardness values is illustrated at certain mass percentages of colorant. Comparisons and discussions are carried out to explain the colorants’ effect. It is concluded that incorporating colorant to liquid resin results in decreasing the surface hardness of components. But sensibilization effect of the colorants also influences the curing process. Surface modification to the phthalocyanine blue powder is a feasible method to increase the hardness value of color stereolithography components. Dissolvable eosin has an approximate linear effect on surface hardness. References | Related Articles | Metrics

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An Improved Proportionate Normalized Least Mean Square Algorithm for Sparse Impulse Response Identification WEN Hao-xiang* (文昊翔), LAI Xiao-han (赖晓翰), CHEN Long-dao (陈隆道), CAI Zhong-fa (蔡忠法) 2013, 18 (6):  742-748.  doi: 10.1007/s12204-013-1460-8 Abstract ( 614 )   In this paper after analyzing the adaptation process of the proportionate normalized least mean square (PNLMS) algorithm, a statistical model is obtained to describe the convergence process of each adaptive filter coefficient. Inspired by this result, a modified PNLMS algorithm based on precise magnitude estimate is proposed. The simulation results indicate that in contrast to the traditional PNLMS algorithm, the proposed algorithm achieves faster convergence speed in the initial convergence state and lower misalignment in the stead stage with much less computational complexity. References | Related Articles | Metrics

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Serial Cost Allocation in the Cooperative Purchasing Organization ZHANG Tao1,2* (张 涛), GU Tian-zhou3 (顾天舟), Song Xin-shuai1 (宋昕帅), GU Feng1 (顾 锋) 2013, 18 (6):  749-755.  doi: 10.1007/s12204-013-1461-7 Abstract ( 632 )   Under the seller’s quantity discount, buyers self-organize or rely on a third party to aggregate their purchasing quantities to obtain lower prices. Because of the unequal member contributions in the cooperative purchasing organization, the buyers’ strategy is different, the members often fluctuate, and the organizations do not sustain themselves. An effective mechanism is necessary to improve the performance of purchasing groups. We study the various forms of cost allocation mechanism in practice. Different allocation rules may have influence on the buyers’ behavior (i.e., purchasing quantities, whether joining the organization or not). We analyze the serial cost allocation and equilibrium purchasing quantity based on a Nash equilibrium, and the results show that each buyer is worse off when not participating in the existence buying organization of the other buyers. We further find that the serial mechanism just confirms the most efficient Nash equilibrium: reasonable cost allocation rule is necessary for the subjects to identify their optimal strategy. References | Related Articles | Metrics

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volution Assessment of China’s Three Mega-City Regions Based on Entire-Array-Polygon Method LIU Shi-lin* (刘士林), SHENG Rong (盛 蓉), ZHANG Yi-wei (张懿玮), LIU Xin-jing (刘新静), WANG Xiao-jing (王晓静), KONG Duo (孔 铎) 2013, 18 (6):  756-762.  doi: 10.1007/s12204-013-1462-6 Abstract ( 578 )   Mega-city region is the mainstream of global urban development and also the dominant model of the neo urbanization process in China. The Beijing-Tianjin-Hebei area, Yangtze River Delta area and Pearl River Delta area are China’s three largest and most mature mega-city regions, the status of which represents the general level of the urban and regional development in China. Based on entire-array-polygon method, this paper makes a comprehensive evolution assessment of the three mega-city regions in terms of urban population index, urban economy index, urban life index, urban culture index and urban primacy index. In terms of general developing level, the three mega-city regions have progressed to optimize the structure. With their respective advantages and disadvantages, the three mega-city regions initially realize a “diversified” regional layout. The difference and gap among the three mega-city regions are obviously decreasing, which contributes to the regional balance of China metropolitan development. The rankings of the three mega-city regions will be in a continuous adjustment. The Beijing-Tianjin-Hebei area is possible to catch up and take the lead. References | Related Articles | Metrics