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This paper reviews the background of China’s decision to launch the “China Migrants Dynamic Survey” (CMDS), and examines the ideas and characteristics of CMDSs carried out annually from 2009 through 2018. The paper considers such aspects as project design, questionnaire design, sampling design, and survey implementation, and summarizes why it is necessary to carry out CMDS and the survey’s performance. Based on the need for information that drives migration surveys and research in the new era, and taking into account the experience gained from previous surveys, this paper attempts to set forth several issues that need to be taken into consideration in the design and implementation of future surveys of migrants.

In this paper, the macro–micro interfacial bond behaviour of steel fibres embedded in ultra-high-performance concrete (UHPC) matrix was investigated using a single-fibre pull-out test with the parameters of fibre size, maximum sand grain size and fibre type. Test results showed that the maximum sand grain size (1·18 and 2·36 mm) had a slight effect on the pull-out responses while increasing the maximum sand grain size tended to change the microscopic interfacial failure mode according to observations made using scanning electron microscopy (SEM). Increasing the fibre size led to an increase in the maximum pull-out load, average bond strength and pull-out work but a decrease in the equivalent bond strength. The percentage of end hook contribution to the total pull-out energy ranged from 54·0 to 60·3%, indicating a significant mechanical anchorage contribution. A new evaluation index on the fibre–matrix interfacial bond behaviour was firstly proposed using the concept of the contribution of unit volume from the perspective of structural demands. It was found that, according to the proposed index, hooked-end fibres with a smaller diameter would be a better choice for structural applications.

Curved beams are sometimes used in practical framed structures due to good mechanical properties and artistic design. In a framed structure, curved beams may undergo large displacement and experience nonlinear behavior as same as the other straight slender beam-column members. Thus, a geometrically nonlinear curved beam element plays an important role in the analysis of framed structures with curved beams. However, most existing curved beam elements are not accurate enough and still need several or even dozens of elements to accurately describe the behavior of a curved beam with a large subtended angle. To fill this gap, this paper presents a novel geometrically nonlinear curved beam element based on the element-independent co-rotational (EICR) method. The proposed element can simulate a curved beam using only one single element in the analysis and design of most practical framed structures. Moreover, this element is directly derived in a Cartesian coordinate system and can be directly and conveniently used with straight beam-column elements in nonlinear structural analysis. In this manuscript, the derivation of the proposed geometrically nonlinear curved beam element is detailed and several benchmark problems are proposed to verify its accuracy and efficiency.

Superstructure rotation method (SRM) can optimize bridge construction in terms of reducing impacts on traffic, safety and overall budget. This paper focus on the key scientific problems of the swivel arch bridge, and takes the world’s largest high-speed railway swivel arch bridge on soft soil foundation over Hu-Hang highway as the engineering background. Construction technologies of this project including the installation process, design of the traction system and the precision control method are introduced. Optimum design method of tension force of the tie bars which considering 7 different load conditions during the construction process is proposed. As the key element of the construction of swivel arch bridge, a complete design process of the spherical hinge is present in detail. Exact analytical solution to determine the relationship of radial stress and upper load, which based on the solution of concentrated force acting on the half-plane body in the elastic mechanics, has been firstly put forward and compared with the simplified method recommended by codes. Meanwhile, reasonable ranges of geometric and material parameters have been given and elaborate design flows of the spherical hinge have been presented. Besides, overturning resistance checking design of the spherical hinge during the construction process have been presented also, which are particularly instructive for engineers and designers.

This study proposes a new mix design method for C30 recycled concrete using recycled aggregate crushed from different strength source concrete (SC). The dosages of cement, water, sand, and coarse recycled concrete aggregate (CRCA) are the same as the corresponding components in natural concrete, but the CRCA should be pre-wetted before casting. Its weighted mean strength has a value of 43.1 MPa for two strengths of SC. Compressive and splitting tensile strength tests on recycled concrete with CRCA (100% substituting limestone aggregate) made from two mixed SC with varying strengths, have been implemented to acquire the mix design method. For investigating the influence of CRCA from two strengths of SC on recycled concrete performance, test parameters of mechanical behavior including compressive strength of SC, strength difference between two mixes of SC, and proportion of two mixed CRCA were taken into account. Test results indicate that when one of the two mixed SC strengths is similar to the target strength, two requirements have to be satisfied to achieve the target compressive strength: one of the SC has to be more than 10 MPa higher than the target strength, and the proportion of the higher strength SC is larger than 75% in weight of the total CRCA. The results provide useful information for recycling multiple strength SC.

Only few studies have been reported on the flexural behavior of steel-ultra high performance fiber reinforced concrete (UHPFRC) composite beams subjected to negative moment. Addressing this limitation, this paper presents the experimental and analytical studies on the steel-UHPFRC composite beam. Two large-scale beams, including one made of normal-strength concrete (NC) slab and another consisted of UHPFRC slab, experienced four-point bending test to investigate their flexural behavior. In this study, the steel girders and NC/UHPFRC slabs were made composite by embedding the stud shear connections in the pockets that were preformed on the precast slabs. The experimental results showed that the use of UHPFRC slab increased the stiffness and improved the crack control capacity of the composite beam. In addition, the full composite action was achieved in both tested beams, evidencing the sufficiency of the stud shear connectors for the tested conditions. The flexural strength and crack width were calculated through simplified analytical approaches. Good agreement was achieved between the measured and computed values.

External prestressing technology has been successfully adopted for enhancing the load-carrying capacity of beams in bridge engineering. Previous studies on the shear behaviour of externally prestressed concrete (EPC) beams mainly focused on the ultimate shear strength. The post-cracking shear behaviour of EPC beams remains unclear. This study aims to investigate the post-cracking shear behaviour of EPC beams. To this end, nine EPC beams with different design parameters were tested to failure. The investigated parameters included the prestressing condition, shear span to depth ratio, shear reinforcement ratio, and bend angle of external tendons. In contrast to reinforced concrete beams, the EPC beams demonstrated shear tension sliding with concrete spalling failure. The applied prestressing increased the concrete shear contribution by 68%. The percentage of the concrete shear contribution out of the total shear strength of the test beams ranged from 45% to 79%. The post-cracking shear strength reserve ability index, defined as the ratio of the shear strength and shear cracking strength, ranged from 1.72 to 2.96 in the EPC beams. A new ductility index, defined as the ratio of the ultimate deflection and the deflection corresponding to first shear cracking, was used to evaluate the post-cracking deformability of EPC beams. The ductility index of the EPC beams ranged from 3.0 to 7.6, indicating considerable post-cracking deformability. The beam’s stiffness at first shear cracking was 39–81% of the beam’s initial stiffness; the beam’s stiffness at the ultimate state was 18–41% of the beam’s initial stiffness. Finally, the current shear provisions were evaluated by the test results.

An experimental program investigating the flexural behavior of an innovative dovetail ultra-high performance concrete joint for connecting precast ultra-high performance concrete slabs in composite bridges is reported in this study. Test parameters included interface treatment method, joint material, reinforcing bar overlapping form, and prestressing level. Specifically, a new steel wire mesh interface treatment was proposed, which could generate an additional fiber-bridging mechanism in the joint surface. An enhancement of 17.4%, 20.1%, and 50% on flexural cracking strength, ultimate strength, and ductility were obtained by using the steel wire mesh. Joint material showed no significant influence, while prestressing had obvious influence on the flexural behavior of ultra-high performance concrete joints. The post-cracking behavior, ductility performance, and stiffness degradation of the tested specimens were analyzed. Good deformability was obtained for the jointed ultra-high performance concrete slabs as the ratio of deflection to span was about 1/50 at failure. The post-cracking stiffness was retained at about 90% of the initial stiffness, while the ultimate stiffness was retained at about 10% of the initial stiffness. The research findings are useful in popularizing and applying the proposed innovative dovetail ultra-high performance concrete joints in composite bridges.

An explicit analytical model was developed to predict the seismic shear strength of reinforced concrete (RC) bridge columns that failed in different modes including flexure, shear and flexure–shear failure. Shear demand was calculated without iteration based on sectional analysis. The shear capacity was divided into three contributions: the concrete compression zone (CCZ), concrete tension zone, and transverse reinforcements. Rankine's concrete failure criteria were used to determine the contribution of the CCZ, while modified compression field theory was applied to predict the other contributions. The three contributions were found to be dependent on the bottom section curvature based on axial-shear–flexure interaction. Seismic shear strength was obtained with a degraded shear capacity equal to the shear demand. Numerous tests were used to verify the proposed model and to assess the methods proposed in existing codes. Based on the proposed model, an application example and parameter analyses were conducted. The results showed that the proposed model produced better agreement with the test data than the methods of current codes. The contribution of the CCZ dominates RC bridge columns with low transverse reinforcements or high axial load ratios. The influence of the axial load ratio on seismic shear strength can be revealed accurately by the proposed model.

This study presents an experimental and numerical investigation on the static behavior of headed stud shear connectors in ultra-high performance concrete (UHPC) of composite bridges. Four push-out specimens were tested. It was found that no cracking, crushing or splitting was observed on the concrete slab, indicating that UHPC slab exhibited good performance and could resist the high force transferred from the headed studs. The numerical and experimental results indicated that the shear capacity is supposed to be composed of two parts stud shank shear contribution and concrete wedge block shear contribution. The stiffness increment of a stud in UHPC was at least 60% higher than that in normal strength concrete. Even if the stud height was reduced from 6d to 2d, there was no reduction in the shear strength of a stud. Short stud shear connectors with an aspect ratio as small as 2 could develop full strength in UHPC slabs. An empirical load-slip equation taking into account stud diameter was proposed to predict the load-slip response of a stud. The reliability and accuracy of the proposed load-slip equation was verified by the experimental and numerical load-slip curves.

This paper presents an experimental study on the flexural behavior of an innovative CA-UHPC (ultrahigh-performance concrete containing coarse aggregate) slab with high and low reinforcement ratios. A total of eighteen CA-UHPC slabs were tested to failure under the parameters of longitudinal reinforcement ratio, curing method, and maximum aggregate size. Test results indicated that sufficient longitudinal reinforcement should be embedded to prevent the brittle failure and disastrous damage. High ductile failure mode was observed for specimens with high reinforcement ratio compared with specimens with low reinforcement ratio. Instead of extensively crushing as normal strength concrete, delamination failure appeared in the compression zone of the CA-UHPC slabs owing to the fibers’ bridging effect, the yielding of longitudinal reinforcement, and the large expansion of flexural cracks which led to the final failure. The reinforced CA-UHPC slabs demonstrated excellent deformability, and ultimate ratio of deflection to span increased from 1/281 to 1/12 when the reinforcement ratio raised from 0% to 3.45%. Stiffness of the reinforced specimens at the flexural cracking state was about 88% and only approximately 6% at the ultimate state, but nearly 50% of the initial stiffness remained when the longitudinal reinforcements yielded, which indicated superior load resistance ability and excellent postcracking deformability. A new ductility index was proposed to evaluate the postcracking ductility of the CA-UHPC specimens. Finally, test results were compared with the flexural strength predictions of CECS 38-2004, ACI 544.4R, and BS EN 1992.

This article presents an experimental and theoretical investigation on the shear behavior of fiber-reinforced ultra-high-performance concrete beams reinforced with high-strength steel. The test parameters included the fiber volume fraction, fiber type, and stirrup ratio. The test results indicate that the shear failure in ultra-high-performance concrete beams is not brittle and catastrophic but has ductility characteristics. A moderate quantity of stirrups can significantly improve the shear behavior of ultra-high-performance concrete beams, as reflected in the thorough propagation of cracks in both shear span and pure bending zone. The depth of the compression zone considering concrete tension was derived based on the deformation compatibility and force equilibrium equations for both serviceability limit state and ultimate limit state. The comparison of the proposed method and classical beam theory shows that the concrete tension should not be neglected in the serviceability limit state analysis. After cracking, the concrete tension can be neglected for simplicity when the beam is heavily reinforced and should be considered when the beam is lightly reinforced. Then, a shear strength model was established based on Rankine’s failure criteria, the truss model, and Association Francaise de Génie Civil-Sétra. Finally, the proposed shear strength equation was verified by the test results and compared with other shear strength equations.

This paper presents an experimental study on the static behavior of large stud shear connectors embedded in ultra-high performance concrete (UHPC). Test parameters included stud diameter, stud aspect ratio, concrete strength, and concrete slab thickness. Headed studs of two sizes, 22 mm and 30 mm in diameter, were used in this study. Extensive splitting cracks on concrete slab were detected for the normal strength concrete specimen whereas no cracks were found for the UHPC specimen with 30 mm studs, indicating that UHPC matches well with large studs. The shear strength, shear stiffness and ductility of a stud with 30 mm diameter were approximately 15%, 45% and 60% higher than those of a stud with 22 mm diameter, respectively. Stud aspect ratio and concrete slab thickness showed no obvious influence on the static behavior of the test specimens and short stud shear connectors with an aspect ratio of 2.3 could develop full strength in UHPC slabs. An empirical equation taking into account stud diameter was proposed to predict the shear load-slip curve of headed studs. Lastly, the current stud shear strength design provisions were evaluated using the experimental data.

This paper examines the design and the process used to carry out the China Fertility Survey 2017, a national representative survey that collected data on fertility desire, childbearing behavior, the use of childbearing services, and the determinants of childbearing behavior. The sampling method adopted was three-stage stratified probabilities proportional to size (PPS), and survey implementation made use of Computer Assisted Personal Interviewing (CAPI). CAPI played a significant role in survey design, last-stage sampling, interviewer training, face-to-face interviews, and questionnaire review and quality control. The survey results were compared with relevant data in the Integrated Management Information System for Population and Family Planning to check consistency. Ex post facto weighting was applied to correct sample structure bias. The process used to acquire accurate personal information is summarized. Suggestions based on consideration of sampling frame distortion by population mobility and other factors are put forward in the hope of improving similar sampling surveys in the future.

The study provided a systematic evaluation of the pullout behavior of straight and hooked-end steel fibers embedded in ultra-high performance concrete (UHPC) with various angles using a single fiber pullout test. Three steel fibers, including one straight fiber and two hooked-end fibers, were aligned at 0°, 30°, and 45° with respect to the loading direction. The fibers were pulled out from non-fiberous UHPC matrix with a compressive strength of 151.5 MPa. Experimental results showed that when the fiber embedded angle increased from 0° to 30° and 45°, the average bond strengths of straight fibers were increased by 19.2% and 52.9%, while the average bond strengths of hooked-end fibers were increased by 10.3–13.6% and 16.2–26.1%, respectively. The percentage of end hook contribution to total pullout energy ranged from 50% to 56.8%, indicating significant mechanical anchorage contribution. Two types of fiber failure modes, including fiber pullout failure and fracture failure, were found, depending on fiber angles. From Scanning Electronic Microscopy (SEM) observation, interfacial transition zone failure, fiber surface scratching, and matrix failure were identified. Two new indices, namely energy dissipation index and bond strength index, were proposed to evaluate the fiber-matrix bond behavior. It was found that hooked-end fibers with a smaller diameter could be a better choice for structural application according to the proposed evaluation indices. The proposed indices offered an alternative and practical method to assess the fiber-matrix bond behavior.

This paper presents an experimental study on the punching shear behavior of concrete flat slabs partially reinforced with ultra-high-performance concrete (UHPC). The effects of the area and depth of UHPC on the failure mode and punching shear capacity are investigated. Test results indicate that the application of full-depth UHPC at the punching shear area changed the failure mode from a brittle punching shear failure to a ductile punching shear-flexural failure, while the application of partial-depth UHPC at the punching shear area caused brittle punching shear failure. By using full-depth UHPC, the first crack strength and punching shear strength of the slabs were increased by up to 65% and 117%, respectively. Partial-depth UHPC did not increase the first crack strength and punching shear strength. According to the testing results, the optimal application of UHPC in the flat slabs is to use full-depth UHPC within the area enclosed by a perimeter located at a distance equal to the slab thickness away from the column face. A new energy dissipation ductility index is proposed to characterize the post-peak load energy dissipation ability. Finally, an analytical model based on yield line theory is proposed to estimate the punching shear strength of the flat slabs. The proposed model reached a good agreement with the testing results while the current ACI model, Chinese model and fib MC2010 model under-estimated the punching shear strength of the test specimens.

The study provided an experimental and theoretical investigation on the bond behavior of reinforcing bars in ultra-high performance concrete (UHPC) via a series of pullout tests. Test parameters included depth of concrete cover, bar embedment length and bar diameter. Failure mode, crack pattern and load-slip response were recorded and discussed under different test parameters. Test results indicated that inadequate concrete cover depth led to splitting failure while short embedment length resulted in concrete cone failure, corresponding to lower bond strengths. The bond strength increased up to 229.8% and the pullout energy increased 401.4% as the concrete cover depth increased from 0.5d to 2d. The development lengths were recommended to be 6d and 8d corresponding to the concrete cover depth of 2d, 1.5d, respectively. A theoretical bond strength model using fiber–matrix discrete concept was proposed and validated by comparing the calculated values with the test results and 343 test data collected from literature. The average ratios of the calculated results to the test results and collected data were 0.996 and 1.039, with a standard deviation of 0.255 and 0.252. The proposed model established the connection between the meso-scale bond property of fibers and matrix and the macro-scale bond strength of steel bars and UHPC, offering an alternative perspective in understanding the bond performance of steel bars in UHPC.

This paper presents the results of experimental and theoretical studies undertaken to assess the flexural performance of high-strength steel-ultra-high-performance fiber reinforced concrete (HSS-UHPFRC) beams. A total of nine HSS-UHPFRC beams were tested, and the influence of fiber volume fraction, fiber type, longitudinal reinforcement ratio, and concrete strength on the flexural response was evaluated. The results indicate that sufficient longitudinal reinforcement should be provided in a UHPFRC beam to avoid abrupt failure and possible catastrophic collapse. After the loss of the fiber bridging effect, corresponding to the fibers being pulled out from the matrix, which occurs one by one with audible sound which is sizzling, redistribution, and homogenization of the concrete stress beside cracks, induced by the dispersed fibers, takes place and more flexural cracks with small spacing appear besides the existing cracks. The beam stiffness was about 85% of the initial beam stiffness at flexural cracking state and was only approximately 25% of the initial beam stiffness at the ultimate state. A constitutive model is proposed, including a bilinear model for compression and a drop-down model for tension, taking into account uniform distribution, embedment length, and orientation of fibers for the multi-scale mechanics analysis. A flexural strength model was subsequently derived on the basis of the proposed mesoscale constitutive model; strain compatibility and force equilibrium were taken into account. The prediction of the ultimate flexural capacity and the overall post-cracking response with the proposed model show a good agreement with the test results.

Lignite chars were prepared in a fixed bed reactor under various oxygen concentrations (0–15 vol%) and pyrolysis temperatures (873 K–1173 K). Characterization techniques such as Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and BET were applied to reveal the impacts of temperature and oxygen concentration on char structure evolution during pyrolysis. Combustion performances of the prepared chars were examined on a thermal gravimetric analyzer, using ignition and burnout temperatures as indexes of char reactivity. On a whole, oxy-pyrolysis char is more reactive than the char derived under inert (N2) atmosphere. Raman analysis indicates that the presence of oxygen during pyrolysis can reduce the extent of char graphitization at high temperatures and favors the removal of oxygen containing groups and aliphatic structures. Pore volume and specific surface area can be improved due to the presence of oxygen in pyrolysis. There is a critical oxygen concentration at high pyrolysis temperatures. Releasing behaviors of sulfur and nitrogen, and their speciation and distributions on the prepared chars were also discussed.

This paper presents a new surface treating technology using silane coupling agent KH-550 to strengthen coarse recycled ceramic vase aggregates (CRCVA) with the purpose of enhancing the bond strengt...

Eleven T-beams, reinforced with high strength steel (HSS), were tested to failure to investigate the effect of shear span to depth ratio, fiber ratio, fiber type, concrete strength and stirrup ratio on the shear behavior, especially post-cracking shear strength and deformability, of ultra-high performance fiber reinforced concrete (UHPFRC) beams. Test results indicated that fibers were efficient not only in enhancing the post-cracking shear strength but also in improving the post-cracking deformability of UHPFRC beams. In addition, fibers could bridge the cracks gap and help in re-distributing and homogenizing the concrete stress beside cracks, allowing more fine and short diagonal shear cracks with small spacing to develop around the existed cracks. A moderate amount of stirrups can effectively restrain shear cracks and allow more parallel diagonal shear cracks to develop and propagate thoroughly within shear span. The UHPFRC beams stiffness at ultimate state was about 50% of beam initial stiffness, which was considerable in strength calculation and ductility analysis, especially in seismic performance evaluation. Lastly, the current shear provisions were evaluated by the experimental results.

The comprehensive studies from materials properties to structural innovations have been conducted aiming at combining the fundamental theory and structural analysis and applications using ultra high-performance concrete (UHPC). Firstly, experimental and theoretical investigations on fiber-UHPC interfacial behavior were performed and two new indices were proposed to evaluate the fiber-matrix interfacial bond behavior from the structural perspective. A mesoscale constitutive model was then proposed, taking into account uniform distribution, embedment length, and orientation of fibers for the multi-scale mechanics analysis. A theoretical method, termed the mesoscale fiber-matrix discrete model (MFDM), was developed to calculate the shear strength of UHPC beams based on the concept of effective fiber distributed region where fibers were efficient at providing shear resistance. The proposed MFDM offered an alternative perspective in understanding the shear behavior of UHPC beams, especially the shear resistance of fibers at a mesoscale level. On the basis of modeling and design methods, five different types of high-performance structural systems for bridges were proposed utilizing UHPC and other innovative construction materials. The structural systems cover various applications including the large stud-UHPC composite structure, light-weight FRP truss-UHPC bridge decks, self-centering precast segmental bridge columns, precast segmental box-girder with large shear key connection. Lastly, some practical engineering applications in China are presented including Vanke pedestrian bridge (the first precast segmental UHPC Arch Bridge in China) and Nanjing 5th Yangtze River Bridge engineering in which the proposed design theory and structural systems were applied

The 5th Nanjing Yangtze River Bridge is a three-tower cable-stayed bridge with a main span of 600 m and a composite cross section consisting of a steel box girder- and precast ultra-high performance concrete (UHPC) deck slab. The precast UHPC slabs are connected using cast-in-place UHPC, and joints between the UHPC slabs are prone to cracking under negative bending moment. This paper investigates the flexural behavior of an innovative dovetail UHPC joint in seven UHPC slabs under negative bending moment. An innovative method using steel wire mesh is presented to enhance the interface between precast and cast-in-place UHPC at the joints. Test parameters of the UHPC slabs included interface treatment method, joint material, reinforcing bar overlapping form, and prestressing level. The steel wire mesh generated fibers that bridge the interface between the precast and cast-in-place UHPC, thus significantly enhancing the mechanical performance of the jointed UHPC slabs: (1) the nominal cracking strength was increased by 2.4 MPa; (2) the post-cracking stiffness was retained at about 80% of the initial stiffness; (3) the ultimate stiffness was retained at about 35% of the initial stiffness; and (4) closely-spaced multiple cracks occurred at the joints. A new ductility index defined as the ratio of the ultimate deflection and the flexural cracking deflection is proposed to characterize the post-cracking ductility. The research findings are useful in understanding and improving the flexural behaviors of UHPC bridge decks subjected to negative bending moment.

A theoretical method, termed the mesoscale fiber-matrix discrete model (MFDM), has been developed that can be used for estimating the shear contribution of steel fibers and calculating shea...

This paper presents a performance-based evolutionary topology optimization method for externally prestressed concrete(EPC) beams in automatically generating optimal strut-and-tie models using the finite element method. The concrete and steel bar elements with least contribution to the stiffness of the EPC beam are removed by calculating the element virtual strain energy. Load transfer mechanism of EPC beam is characterized by remaining elements. The optimal strut-and-tie model is determined from the topology history. A theoretical formula of the shear strength is derived from optimal strut-and-tie model for EPC beams. The model predicts possible modes of failure, which may be broadly classified into shear-type failure and flexural-type failure. 9 EPC beams were casted in place to evaluate the validation of the proposed method. The predictions of the method are compared with the 9 specimen and other available test results of EPC beams from literatures. Case studies are conducted and compared with the resul...

Background: Recent trends show an unprecedented feminisation of migration in China, triggered by the increasing demand for cheap labour in big cities and the availability of women in the labour market. These trends corroborate the evidence that non-agricultural work and remittance from urban labour migrants have become the major sources of rural household income. Objective: This paper investigates the extent of gender inequalities in job participation and wage earning among internal labour migrants in China. We hypothesize that female migrants in cities are economically more disadvantaged than male migrants in the job market. Methods: We use data from the 2010 National Migrant Dynamics Monitoring Survey conducted in 106 cities representing all 31 provinces and geographic regions. The study applies the standard Heckman two-step Probit-OLS method to model job participation and wage-earning, separately for 59,225 males and 41,546 females aged 16-59 years, adjusting for demographic and social characteristics and potential selection effects. Results: Female migrants have much lower job-participation and wage-earning potential than male migrants. Male migrants earn 26Š higher hourly wages than their female counterparts. Decomposition analysis confirms potential gender discrimination, suggesting that 88Š of the gender difference in wages (or 12Š of female migrant wage) is due to discriminatory treatment of female migrants in the Chinese job market. Migrants with rural hukou status have a smaller chance of participation in the job market and they earn lower wages than those with urban hukou, regardless of education advantage. Conclusions: There is evidence of significant female disadvantage among internal labour migrants in the job market in Chinese cities. Household registration by urban and rural areas, as controlled by the hukou status, partly explains the differing job participation and wage earning among female labour migrants in urban China. Comments: Female migrants have higher opportunity costs and family constraints to participate in job market than male migrants. Higher job participation among male migrants suggests that men face stiff competition for jobs in cities and are more likely to accept jobs with a lower wage offer.

To find out the occurrence of cesarean section (CS) and related factors among child-bearing women in China.The survey was conducted during October, 2010 in 40 counties selected from 30 provinces. Size proportional sampling method was employed in sampling. A face to face questionnaire investigation was conducted among 8 420 women who experienced pregnancies from 1978 to 2010. Information on demographic characteristics, history of pregnancy and birth were obtained, and related factors of CS occurrence were analyzed.A total of 11 440 living births have been given by 8 420 women, and 1 725 CS happened. As the time goes on, there is a growing trend of CS occurrence, from 2.0% (14/701) in 1978-1985 to 36.6% (813/2 224) in 2006-2010, and there is a most fast increase from 2001 to 2010. CS rate in Mid-China (42.3%, 257/608) is the highest from 2006 to 2010. And also, the rate of CS requested by the pregnant women or their family members was increasing year by year, from 14.3% (2/14) in 1978-1985 to 43.7% (255/813) in 2006-2010. Women who were above 25 years old (21.4%, 960/4 485) , with an education degree of high school or above (24.5%, 568/2 317), engaged in nonagricultural work (22.4%, 663/2 956), living in eastern provinces of China (18.6%, 757/4 074), fetal malposition (45.4%, 247/544) , with a heavier birth weight(4 000 gram or above) (36.5%, 175/479) , have accepted B ultrasound exam (18.8%, 1 633/8 687) with an increasing of blood pressure (28.0%, 172/614) and convulsion experiences (24.8%, 131/528) during pregnancy were more likely to have CS.The CS rate among child-bearing women in China was rather high, and was related with factors of demographic characteristics(age of childbearing, education, vocation, residence) and some medical factors(neonatal weight, having accepted B ultrasound exam, fetal malposition, an increase of blood pressure and convulsions during pregnancy).