Strong heterogeneity and complex pore systems of carbonate reservoir rock make its rock physics model building and fluid substitution difficult and complex. However, rock physics models connect reservoir parameters wi...Strong heterogeneity and complex pore systems of carbonate reservoir rock make its rock physics model building and fluid substitution difficult and complex. However, rock physics models connect reservoir parameters with seismic parameters and fluid substitution is the most effective tool for reservoir prediction and quantitative characterization. On the basis of analyzing complex carbonate reservoir pore structures and heterogeneity at seismic scale, we use the gridding method to divide carbonate rock into homogeneous blocks with independent rock parameters and calculate the elastic moduli of dry rock units step by step using different rock physics models based on pore origin and structural feature. Then, the elastic moduli of rocks saturated with different fluids are obtained using fluid substitution based on different pore connectivity. Based on the calculated elastic moduli of rock units, the Hashin-Shtrikman-Walpole elastic boundary theory is adopted to calculate the carbonate elastic parameters at seismic scale. The calculation and analysis of carbonate models with different combinations of pore types demonstrate the effects of pore type on rock elastic parameters. The simulated result is consistent with our knowledge of real data.展开更多
[Objective] To establish the comprehensive evaluation index system of public green area per capita as a quantitative mean of measuring ecological city and livable city. [Method]The GM (1, 1) forecasting model was set ...[Objective] To establish the comprehensive evaluation index system of public green area per capita as a quantitative mean of measuring ecological city and livable city. [Method]The GM (1, 1) forecasting model was set up according to statistics of public green area per capita in Xi’an City during 1996 and 2005, on this basis, the development trend of green area per capita in Xi’an City until 2015 were analyzed in case of no any changing factors or conditions. [Result]Grey forecasting model was established as, (t = 0, 1, …, n); model parameters as a = - 0.031 71, u = 4.139 17. After residual error test and posterior-variance-test, the precision of this model is proved fairly good. [Conclusions]According to this model, public green area per capita in Xi’an City will achieve 7.66 m2 by 2015, which is still far away from the livable city index (16 m2 per capita) and should be paid more attention by the local government, the construction of urban green areas should be further enhanced, more vegetations should be cultivated so as to improve the urban green coverage ratio.展开更多
This paper puts forward a rigorous approach for a sensitivity analysis of stochastic user equilibrium with the elastic demand （SUEED） model. First, proof is given for the existence of derivatives of output variables...This paper puts forward a rigorous approach for a sensitivity analysis of stochastic user equilibrium with the elastic demand （SUEED） model. First, proof is given for the existence of derivatives of output variables with respect to the perturbation parameters for the SUEED model. Then by taking advantage of the gradient-based method for sensitivity analysis of a general nonlinear program, detailed formulae are developed for calculating the derivatives of designed variables with respect to perturbation parameters at the equilibrium state of the SUEED model. This method is not only applicable for a sensitivity analysis of the logit-type SUEED problem, but also for the probit-type SUEED problem. The application of the proposed method in a numerical example shows that the proposed method can be used to approximate the equilibrium link flow solutions for both logit-type SUEED and probit-type SUEED problems when small perturbations are introduced in the input parameters.展开更多
On the basis of rural household survey in 12 provinces of China in 2005,this research built an econometrical model to find the area standard for rural housing land.This standard is expected to facilitate rural housing...On the basis of rural household survey in 12 provinces of China in 2005,this research built an econometrical model to find the area standard for rural housing land.This standard is expected to facilitate rural housing land administration,efficient and intensive housing land use and policy making.This research concludes:1) according to the household survey data,the average area for rural housing land in China is about 235.26 m 2,and the rural housing land mainly includes unused land(42.89%) and house construction land(37.76%) with the average floor-area ratio of 0.42;2) the indexes in the standard concern the factors such as location,landform,house form,household population and cultivated land area per farmer,which all have significant effects on rural housing land use;3) the reasonable area for rural housing land may be 150 m 2 in average before 2020,and the referential standards in different provinces are 120 m 2,130 m 2,140m 2,150 m 2,160 m 2,170 m 2,190 m 2,200 m 2,210 m 2,220 m 2,230 m 2 and 250 m 2 respectively;and 4) if there are less than two persons or more than five persons in a family,these standards need to be decreased or increased by 7%.When the cultivated land area per farmer is lower than the provincial average,the standards have to reduce by 3.5%.展开更多
A modified one-dimensional transient hygrothermal model for multilayer wall was proposed using air humidity ratio and temperature as the driving potentials.The solution for the governing equations was obtained numeric...A modified one-dimensional transient hygrothermal model for multilayer wall was proposed using air humidity ratio and temperature as the driving potentials.The solution for the governing equations was obtained numerically by implementing the finite-difference scheme.To evaluate the accuracy of the model,a test system was built up to measure relative humidity and temperature within a porous wall and compare with the prediction of the model.The prediction results have good agreement with the experimental results.For the interface close to indoor side,the maximum deviation of temperature between calculated and test data is 1.87 K,and the average deviation is 0.95 K;the maximum deviation of relative humidity is 11.4%,and the average deviation is 5.7%.For the interface close to outdoor side,the maximum deviation of temperature between prediction and measurement is 1.78 K,and the average deviation is 1.1 K;the maximum deviation of relative humidity is 9.9%,and the average deviation is 4.2%.展开更多
A five-site comprehensive mathematical model was developed to simulate the steady-state behavior of industrial slurry polymerization of ethylene in multistage continuous stirred tank reactors. More specifically, the e...A five-site comprehensive mathematical model was developed to simulate the steady-state behavior of industrial slurry polymerization of ethylene in multistage continuous stirred tank reactors. More specifically, the effects of various operating conditions (i.e., inflow rates of catalyst, hydrogen and comonomer) on the molecular structure and properties of polyethylene (i.e.,Mw,Mn, polydispersity index (IPD), melt index, density, etc.) are fully assessed. It is shown that the proposed comprehensive model is capable of simulating the steady-state operation of an industrial slurry stirred tank reactor series. It is demonstrated that changing the catalyst flow rate, changes simultaneously the mean residence-time in both reactors, which plays a significant role on the establishment of polyethylene architecture properties such as molecular mass and IPD. The melt index and density of polyethylene are mainly controlled by hydrogen and comonomer concentration, respectively.展开更多
It is a well known fact that studies on growth primarily take into account human populations, although currently many scientific fields （biology, economics, etc.） also use growth models to reflect behaviours in dive...It is a well known fact that studies on growth primarily take into account human populations, although currently many scientific fields （biology, economics, etc.） also use growth models to reflect behaviours in diverse phenomena. These deterministic models are difficult to apply in real populations since, as we know, the volume of a human population depends intrinsically on a large number of other socio-economic variables, including changes in fertility patterns, improvements in living conditions, individual health factors which produce an increase or decrease in the number of years lived, the state of economic well-being, or changes in migratory fluxes. In this study, we have examined the stochastic Gompertz non-homogenous diffusion process, analysing its transition probability density function and conducting inferences on the parameters of the process through discrete sampling All of the results are applied to the population of Andalusia with data disaggregated by sex during the period of 1981 to 2002, taking purely demographic variables as exogenous factors： life expectancy at birth, foreign immigration to Andalusia and total fertility rate展开更多
An efficient C–P bond formation reaction was developed by virtue of the synergetic catalysis strategy by merging heterogeneous photocatalysis and nickel catalysis.This platform utilizing cadmium sulfide semiconductor...An efficient C–P bond formation reaction was developed by virtue of the synergetic catalysis strategy by merging heterogeneous photocatalysis and nickel catalysis.This platform utilizing cadmium sulfide semiconductors as heterogeneous photocatalysts and nickel complexes as transition metal catalysts provided a variety of organophosphorus compounds from readily available aryl and vinyl halides,as well as aryl triflates,with generally a good-to-excellent reaction efficiency(31 examples,46%-98%yields).The current protocol features mild reaction conditions,a broad substrate scope,recyclability of photocatalysts,and inexpensive catalysts,thus defining the practical and economic proprieties of the present catalyst system.展开更多
In order to study the major performance indicators of the twin-rotor piston engine(TRPE), Matlab/simulink was used to simulate the mathematical models of its thermodynamic processes. With consideration of the characte...In order to study the major performance indicators of the twin-rotor piston engine(TRPE), Matlab/simulink was used to simulate the mathematical models of its thermodynamic processes. With consideration of the characteristics of the working processes in the TRPE, corresponding differential equations were established and then simplified by period features of the TRPE. Finally, the major boundary conditions were figured out. The changing trends of mass, pressure and temperature of working fuel in the working chamber during a complete engine cycle were presented. The simulation results are consistent with the trends of an actual working cycle in the TRPE, which indicates that the method of simulation is feasible. As the pressure in the working chamber is calculated, all the performance parameters of the TRPE can be obtained. The major performance indicators, such as the indicated mean effective pressure, power to weight ratio and the volume power, are also acquired. Compared with three different types of conventional engines, the TRPE has a bigger utilization ratio of cylinder volume, a higher power to weight ratio and a more compact structure. This indicates that TRPE is superior to conventional engines.展开更多
The increase on the competitiveness, the search on the customer satisfaction, the search by reducing waste in the civil construction were facts which helped entrepreneurs and companies to seek new ways of working, bei...The increase on the competitiveness, the search on the customer satisfaction, the search by reducing waste in the civil construction were facts which helped entrepreneurs and companies to seek new ways of working, being lean construction one of the ways to get that. Studies report that the application of the lean tools in construction was carried out in an isolated way. This type of application was pointed as a major factor limiting the extent of achievement in implementing lean principles. The aim of this studies is to identify opportunities to implement the principles of lean production in the service department of a construction company in Goi^is, proposing routines that try to implement the continuous improvement of its processes, eliminating waste, reducing the lead time, allow it to perform the mapping processes, applying the just-in-time and among others, providing services that add value to the customer satisfaction. It was possible to establish the average time for each step, allowing to identify possible improvements in the department, from the perspective of lean principles. The research paper concludes by pointing out the activities for the Department of Post Construction work from building companies, from lean concepts.展开更多
Objective： To introduce the experience and key points of percutaneous reduction combined with bone graft to treat calcaneal fractures. Methods： Percutaneous reduction and internal fixation combined with bone graft w...Objective： To introduce the experience and key points of percutaneous reduction combined with bone graft to treat calcaneal fractures. Methods： Percutaneous reduction and internal fixation combined with bone graft was performed from April 2004 to April 2006 on 15 cases （16 sides） with intra-articular calcaneal fractures including 13 males （14 feet） and 2 females （2 feet） ,with average age of 36. 6 years （24-61 years）. All patients underwent radiography including lateral and axial views for calcaneus, oblique view for foot and three-dimensional CT imaging reconstruction. According to Sanders classification, there were 12 feet of type Ⅱ （3 type Ⅱa, 3 type Ⅱb and 8 type Ⅱc） and 2 feet of type Illac. The length of calcaneus was recovered through traction by Steinmann pin which passed through calcaneal tubercle perpendicularly and the posterior facet was elevated until reduction by a curve scissors through an 0.5 cm incision along the primary fracture line of lateral calcaneus. The calcaneus was fixed with different cannulated cancellous screws according to the type of fractures. Then bone graft was injected to fill the defect of calcaneus through lateral incision. Results： All patients were followed up for an average of 18.4 months （ranged, 12 to 34 months）. No complication such as wound infection, screw breakage and calcaneum varus was found postoperatively. The average time for bone healing was 10 weeks. The results were excellent in 12 cases, good in 4 cases according to the American Orthopaedic Foot and Ankle Society （AOFAS） hindfoot score. The rate of excellent and good clinical results was 100%. The mean AOFAS hindfoot score in tongue type group （86.5±4.4） was better than in joint depression type group （81.2±1.7, P〈0.05）. Radiography showed basic restoration of Bohler＇s angle, Gissane＇s angle and calcaneal shape. Conclusion： The combination of percutaneous reduction and injectable bone graft is suitable for surgical treatment of Sanders Ⅱ and Ⅲ type calcaneal fractures, with advantages of simple operation, fewer complications and good clinical results.展开更多
A rigorous approach is proposed to model the mean ion activity coefficient for strong electrolyte systems using the Poisson-Boltzmann equation. An effective screening radius similar to the Debye decay length is introd...A rigorous approach is proposed to model the mean ion activity coefficient for strong electrolyte systems using the Poisson-Boltzmann equation. An effective screening radius similar to the Debye decay length is introduced to define the local composition and new boundary conditions for the central ion. The crystallographic ion size is also considered in the activity coefficient expressions derived and non-electrostatic contributions are neglected. The model is presented for aqueous strong electrolytes and compared with the classical Debye-Hfickel （DH） limiting law for dilute solutions. The radial distribution function is compared with the DH and Monte Carlo studies. The mean ion activity coefficients are calculated for 1：1 aqueous solutions containing strong electrolytes composed of alkali halides. The individual ion activity coefficients and mean ion activity coefficients in mixed sol- vents are predicted with the new equations.展开更多
Indoor radon levels were measured in 221 homes in rented accommodation. In addition, buildings were registered for a series of variables describing building characteristics and used materials. The mean year value of t...Indoor radon levels were measured in 221 homes in rented accommodation. In addition, buildings were registered for a series of variables describing building characteristics and used materials. The mean year value of the indoor radon level was 30.7 （1~250） Bq/m3. The indoor radon level exceeded 100 Bq/m3 in 5.9% of the homes. Of the investigated variables, only homes in single-family terraced houses, were statistically significant. Approx： 75% of homes exceeding 100 Bq/m3 indoor radon level had levels between 100 and 200 Bq/m3 and 25% had indoor radon levels exceeding 200 Bq/m3. Significant differences in indoor radon levels were found in homes located in multi-occupant houses. Additionally, the risk of indoor radon levels exceeding 100 Bq/m3 in homes in multi-occupant houses was found to be very low, but the risk was the highest on the ground floor in a building constructed with slab on ground.展开更多
基金sponsored jointly by the National Natural Science Foundation of China(No.41074098)the Key State Science and Technology Project(2011ZX05023-005-005)China University of Petroleum(Beijing) Fund(KYJJ2012-05-08)
文摘Strong heterogeneity and complex pore systems of carbonate reservoir rock make its rock physics model building and fluid substitution difficult and complex. However, rock physics models connect reservoir parameters with seismic parameters and fluid substitution is the most effective tool for reservoir prediction and quantitative characterization. On the basis of analyzing complex carbonate reservoir pore structures and heterogeneity at seismic scale, we use the gridding method to divide carbonate rock into homogeneous blocks with independent rock parameters and calculate the elastic moduli of dry rock units step by step using different rock physics models based on pore origin and structural feature. Then, the elastic moduli of rocks saturated with different fluids are obtained using fluid substitution based on different pore connectivity. Based on the calculated elastic moduli of rock units, the Hashin-Shtrikman-Walpole elastic boundary theory is adopted to calculate the carbonate elastic parameters at seismic scale. The calculation and analysis of carbonate models with different combinations of pore types demonstrate the effects of pore type on rock elastic parameters. The simulated result is consistent with our knowledge of real data.
文摘[Objective] To establish the comprehensive evaluation index system of public green area per capita as a quantitative mean of measuring ecological city and livable city. [Method]The GM (1, 1) forecasting model was set up according to statistics of public green area per capita in Xi’an City during 1996 and 2005, on this basis, the development trend of green area per capita in Xi’an City until 2015 were analyzed in case of no any changing factors or conditions. [Result]Grey forecasting model was established as, (t = 0, 1, …, n); model parameters as a = - 0.031 71, u = 4.139 17. After residual error test and posterior-variance-test, the precision of this model is proved fairly good. [Conclusions]According to this model, public green area per capita in Xi’an City will achieve 7.66 m2 by 2015, which is still far away from the livable city index (16 m2 per capita) and should be paid more attention by the local government, the construction of urban green areas should be further enhanced, more vegetations should be cultivated so as to improve the urban green coverage ratio.
基金The Scientific Innovation Research of College Graduates in Jiangsu Province(No.CXLX13_110)the Young Scientists Fund of National Natural Science Foundation of China(No.51408253)the Young Scientists Fund of Huaiyin Institute of Technology(No.491713328)
文摘This paper puts forward a rigorous approach for a sensitivity analysis of stochastic user equilibrium with the elastic demand （SUEED） model. First, proof is given for the existence of derivatives of output variables with respect to the perturbation parameters for the SUEED model. Then by taking advantage of the gradient-based method for sensitivity analysis of a general nonlinear program, detailed formulae are developed for calculating the derivatives of designed variables with respect to perturbation parameters at the equilibrium state of the SUEED model. This method is not only applicable for a sensitivity analysis of the logit-type SUEED problem, but also for the probit-type SUEED problem. The application of the proposed method in a numerical example shows that the proposed method can be used to approximate the equilibrium link flow solutions for both logit-type SUEED and probit-type SUEED problems when small perturbations are introduced in the input parameters.
基金Under the auspices of National Natural Science Foundation of China (No. 41001108,40971107)Beijing MunicipalNatural Science Foundation (No. 9113029)
文摘On the basis of rural household survey in 12 provinces of China in 2005,this research built an econometrical model to find the area standard for rural housing land.This standard is expected to facilitate rural housing land administration,efficient and intensive housing land use and policy making.This research concludes:1) according to the household survey data,the average area for rural housing land in China is about 235.26 m 2,and the rural housing land mainly includes unused land(42.89%) and house construction land(37.76%) with the average floor-area ratio of 0.42;2) the indexes in the standard concern the factors such as location,landform,house form,household population and cultivated land area per farmer,which all have significant effects on rural housing land use;3) the reasonable area for rural housing land may be 150 m 2 in average before 2020,and the referential standards in different provinces are 120 m 2,130 m 2,140m 2,150 m 2,160 m 2,170 m 2,190 m 2,200 m 2,210 m 2,220 m 2,230 m 2 and 250 m 2 respectively;and 4) if there are less than two persons or more than five persons in a family,these standards need to be decreased or increased by 7%.When the cultivated land area per farmer is lower than the provincial average,the standards have to reduce by 3.5%.
基金Project(51078127) supported by the National Natural Science Foundation of ChinaProject(JJ201109091631) supported by the Foundation for Young Scientists of Jiangxi Education Department, China
文摘A modified one-dimensional transient hygrothermal model for multilayer wall was proposed using air humidity ratio and temperature as the driving potentials.The solution for the governing equations was obtained numerically by implementing the finite-difference scheme.To evaluate the accuracy of the model,a test system was built up to measure relative humidity and temperature within a porous wall and compare with the prediction of the model.The prediction results have good agreement with the experimental results.For the interface close to indoor side,the maximum deviation of temperature between calculated and test data is 1.87 K,and the average deviation is 0.95 K;the maximum deviation of relative humidity is 11.4%,and the average deviation is 5.7%.For the interface close to outdoor side,the maximum deviation of temperature between prediction and measurement is 1.78 K,and the average deviation is 1.1 K;the maximum deviation of relative humidity is 9.9%,and the average deviation is 4.2%.
文摘A five-site comprehensive mathematical model was developed to simulate the steady-state behavior of industrial slurry polymerization of ethylene in multistage continuous stirred tank reactors. More specifically, the effects of various operating conditions (i.e., inflow rates of catalyst, hydrogen and comonomer) on the molecular structure and properties of polyethylene (i.e.,Mw,Mn, polydispersity index (IPD), melt index, density, etc.) are fully assessed. It is shown that the proposed comprehensive model is capable of simulating the steady-state operation of an industrial slurry stirred tank reactor series. It is demonstrated that changing the catalyst flow rate, changes simultaneously the mean residence-time in both reactors, which plays a significant role on the establishment of polyethylene architecture properties such as molecular mass and IPD. The melt index and density of polyethylene are mainly controlled by hydrogen and comonomer concentration, respectively.
文摘It is a well known fact that studies on growth primarily take into account human populations, although currently many scientific fields （biology, economics, etc.） also use growth models to reflect behaviours in diverse phenomena. These deterministic models are difficult to apply in real populations since, as we know, the volume of a human population depends intrinsically on a large number of other socio-economic variables, including changes in fertility patterns, improvements in living conditions, individual health factors which produce an increase or decrease in the number of years lived, the state of economic well-being, or changes in migratory fluxes. In this study, we have examined the stochastic Gompertz non-homogenous diffusion process, analysing its transition probability density function and conducting inferences on the parameters of the process through discrete sampling All of the results are applied to the population of Andalusia with data disaggregated by sex during the period of 1981 to 2002, taking purely demographic variables as exogenous factors： life expectancy at birth, foreign immigration to Andalusia and total fertility rate
基金the National Science Foundation of China(21822103,21820102003,21772052,21772053,21572074,21472057)the Program of Introducing Talents of Discipline to Universities of China(111 Program,B17019)+1 种基金the Natural Science Foundation of Hubei Province(2017AHB047)the International Joint Research Center for Intelligent Biosensing Technology and Health for support of this research~~
文摘An efficient C–P bond formation reaction was developed by virtue of the synergetic catalysis strategy by merging heterogeneous photocatalysis and nickel catalysis.This platform utilizing cadmium sulfide semiconductors as heterogeneous photocatalysts and nickel complexes as transition metal catalysts provided a variety of organophosphorus compounds from readily available aryl and vinyl halides,as well as aryl triflates,with generally a good-to-excellent reaction efficiency(31 examples,46%-98%yields).The current protocol features mild reaction conditions,a broad substrate scope,recyclability of photocatalysts,and inexpensive catalysts,thus defining the practical and economic proprieties of the present catalyst system.
基金Project(7131109)supported by the National Defense Pre-research Foundation of ChinaProject(51175500)supported by the National Natural Science Foundation of China
文摘In order to study the major performance indicators of the twin-rotor piston engine(TRPE), Matlab/simulink was used to simulate the mathematical models of its thermodynamic processes. With consideration of the characteristics of the working processes in the TRPE, corresponding differential equations were established and then simplified by period features of the TRPE. Finally, the major boundary conditions were figured out. The changing trends of mass, pressure and temperature of working fuel in the working chamber during a complete engine cycle were presented. The simulation results are consistent with the trends of an actual working cycle in the TRPE, which indicates that the method of simulation is feasible. As the pressure in the working chamber is calculated, all the performance parameters of the TRPE can be obtained. The major performance indicators, such as the indicated mean effective pressure, power to weight ratio and the volume power, are also acquired. Compared with three different types of conventional engines, the TRPE has a bigger utilization ratio of cylinder volume, a higher power to weight ratio and a more compact structure. This indicates that TRPE is superior to conventional engines.
文摘The increase on the competitiveness, the search on the customer satisfaction, the search by reducing waste in the civil construction were facts which helped entrepreneurs and companies to seek new ways of working, being lean construction one of the ways to get that. Studies report that the application of the lean tools in construction was carried out in an isolated way. This type of application was pointed as a major factor limiting the extent of achievement in implementing lean principles. The aim of this studies is to identify opportunities to implement the principles of lean production in the service department of a construction company in Goi^is, proposing routines that try to implement the continuous improvement of its processes, eliminating waste, reducing the lead time, allow it to perform the mapping processes, applying the just-in-time and among others, providing services that add value to the customer satisfaction. It was possible to establish the average time for each step, allowing to identify possible improvements in the department, from the perspective of lean principles. The research paper concludes by pointing out the activities for the Department of Post Construction work from building companies, from lean concepts.
文摘Objective： To introduce the experience and key points of percutaneous reduction combined with bone graft to treat calcaneal fractures. Methods： Percutaneous reduction and internal fixation combined with bone graft was performed from April 2004 to April 2006 on 15 cases （16 sides） with intra-articular calcaneal fractures including 13 males （14 feet） and 2 females （2 feet） ,with average age of 36. 6 years （24-61 years）. All patients underwent radiography including lateral and axial views for calcaneus, oblique view for foot and three-dimensional CT imaging reconstruction. According to Sanders classification, there were 12 feet of type Ⅱ （3 type Ⅱa, 3 type Ⅱb and 8 type Ⅱc） and 2 feet of type Illac. The length of calcaneus was recovered through traction by Steinmann pin which passed through calcaneal tubercle perpendicularly and the posterior facet was elevated until reduction by a curve scissors through an 0.5 cm incision along the primary fracture line of lateral calcaneus. The calcaneus was fixed with different cannulated cancellous screws according to the type of fractures. Then bone graft was injected to fill the defect of calcaneus through lateral incision. Results： All patients were followed up for an average of 18.4 months （ranged, 12 to 34 months）. No complication such as wound infection, screw breakage and calcaneum varus was found postoperatively. The average time for bone healing was 10 weeks. The results were excellent in 12 cases, good in 4 cases according to the American Orthopaedic Foot and Ankle Society （AOFAS） hindfoot score. The rate of excellent and good clinical results was 100%. The mean AOFAS hindfoot score in tongue type group （86.5±4.4） was better than in joint depression type group （81.2±1.7, P〈0.05）. Radiography showed basic restoration of Bohler＇s angle, Gissane＇s angle and calcaneal shape. Conclusion： The combination of percutaneous reduction and injectable bone graft is suitable for surgical treatment of Sanders Ⅱ and Ⅲ type calcaneal fractures, with advantages of simple operation, fewer complications and good clinical results.
基金Supported by the National Natural Science Foundation of China(21206010)
文摘A rigorous approach is proposed to model the mean ion activity coefficient for strong electrolyte systems using the Poisson-Boltzmann equation. An effective screening radius similar to the Debye decay length is introduced to define the local composition and new boundary conditions for the central ion. The crystallographic ion size is also considered in the activity coefficient expressions derived and non-electrostatic contributions are neglected. The model is presented for aqueous strong electrolytes and compared with the classical Debye-Hfickel （DH） limiting law for dilute solutions. The radial distribution function is compared with the DH and Monte Carlo studies. The mean ion activity coefficients are calculated for 1：1 aqueous solutions containing strong electrolytes composed of alkali halides. The individual ion activity coefficients and mean ion activity coefficients in mixed sol- vents are predicted with the new equations.
文摘Indoor radon levels were measured in 221 homes in rented accommodation. In addition, buildings were registered for a series of variables describing building characteristics and used materials. The mean year value of the indoor radon level was 30.7 （1~250） Bq/m3. The indoor radon level exceeded 100 Bq/m3 in 5.9% of the homes. Of the investigated variables, only homes in single-family terraced houses, were statistically significant. Approx： 75% of homes exceeding 100 Bq/m3 indoor radon level had levels between 100 and 200 Bq/m3 and 25% had indoor radon levels exceeding 200 Bq/m3. Significant differences in indoor radon levels were found in homes located in multi-occupant houses. Additionally, the risk of indoor radon levels exceeding 100 Bq/m3 in homes in multi-occupant houses was found to be very low, but the risk was the highest on the ground floor in a building constructed with slab on ground.
