To simulate the concrete shrinkage in varying temperature and moisture environments, a simulate procedure comprising an analytical process and a finite element analysis is proposed based on the coupled partial differe...To simulate the concrete shrinkage in varying temperature and moisture environments, a simulate procedure comprising an analytical process and a finite element analysis is proposed based on the coupled partial differential equations describing heat and moisture transfer in a porous medium. Using the Laplace transformation method and transfer function to simplify and solve the coupled equations in Laplace domain, the moisture and temperature distribution in time domain are obtained by inverse Laplace transformation. The shrinkage deformations of concrete are numerically simulated by the finite element method （FEM） based on the obtained temperature and moisture distribution. This approach avoids the complex eigenvalues, coupling difficulty and low accuracy found in other solving methods, and also effectively calculates the moisture induced shrinkage which is almost impossible using familiar FEM software. The validity of the simulation procedure is verified by Hundt＇s test data. The results reveal that the proposed approach can be considered a reliable and efficient method to simulate the coupling moisture and temperature shrinkage of concrete.展开更多
An exact solution for simply-supported laminated beams with material properties variable with temperature under a combination of uniform thermo-load and mechanical loads was investigated,based on the two-dimensional(2...An exact solution for simply-supported laminated beams with material properties variable with temperature under a combination of uniform thermo-load and mechanical loads was investigated,based on the two-dimensional(2-D)thermo-elasticity theory.Firstly,the beam was divided into a series of layers with uniform material properties along the interfaces of the beam.The uniform thermo-load acted on each layer was transformed into a combination of the normal surface forces acted at the two ends and the transverse thermo-load.Secondly,the state space method was employed to obtain the general solutions of displacements and stresses in an arbitrary layer.Thirdly,based on the interfacial continuity conditions between adjacent layers,the relations of displacement and stress components between the top and bottom layers of the beam were recursively derived by use of the transfer-matrix method.The unknowns in the solutions can be solved by the mechanical loads acted on the top and bottom surfaces.The convergence of the present solutions was checked.The comparative study of the present solutions with the Timoshenko’s solutions and the finite element(FE)solutions was carried out.The effects of material properties variable with temperature on the thermo-elastic behavior of laminated beams were discussed in detail.展开更多
Experiments of biomass pyrolysis were carried out in a fluidized bed, and dynamic signals of pressure and temperature were recorded. Correlation dimension was employed to characterize the chaotic behavior of pressure ...Experiments of biomass pyrolysis were carried out in a fluidized bed, and dynamic signals of pressure and temperature were recorded. Correlation dimension was employed to characterize the chaotic behavior of pressure and temperature signals. Both pressure and temperature signals exhibit chaotic behavior, and the chaotic behavior of temperature signals is always weaker than that of pressure signals. Chaos transfer theory was advanced to explain the above phenomena. The discussion on the algorithm of the correlation dimension shows that the distance definition based on rhombic neighborhood is a better choice than the traditional one based on spherical neighborhood. The former provides a satisfactory result in a much shorter time.展开更多
AIM:To evaluate the efficacy of Stretta procedure with gastroesophageal reflux disease(GERD)based on symptom control,medication changes and oesophagitis grade.METHODS:Ninety patients with a history of GERD underwent S...AIM:To evaluate the efficacy of Stretta procedure with gastroesophageal reflux disease(GERD)based on symptom control,medication changes and oesophagitis grade.METHODS:Ninety patients with a history of GERD underwent Stretta procedure from June 2007 to March 2010.All patients with GERD diagnosed by the pres-ence of endoscopically evidenced oesophagitis or abnormal esophageal pH testing.We evaluated GERD-health-related quality of life,satisfaction,medication use and endoscopy at baseline,6,12 mo after treatment.Complications of the procedure were analyzed.RESULTS:We found that patients experienced significant changes in symptoms of GERD after Stretta proce-dure.The onset of GERD symptom relief was less than 2 mo(70.0%)or 2 to 6 mo(16.7%).The mean GERD-HRQL score was 25.6(baseline),7.3(6 mo,P<0.01),and 8.1(12 mo,P<0.01).The mean heartburn scorewas 3.3(baseline),and 1.2(12 mo,P<0.05).The percentage of patients with satisfactory GERD control improved from 31.1%at baseline to 86.7%after treat-ment,and patient satisfaction improved from 1.4 at baseline to 4.0 at 12 mo(P<0.01).Medication usage decreased significantly from 100%of patients on pro-ton pump inhibitors therapy at baseline to 76.7%of patients showing elimination of medications or only as needed use of antacids/H2-RA at 12 mo.An improvement in endoscopic grade of oesophagitis was seen in 33 of the 41 patients.All patients had either no erosions or only mild erosive disease(grade A)at 6 mo.CONCLUSION:The experience with Stretta procedure confirms that it is well tolerated,safe,effective and durable in the treatment of GERD.The Stretta procedure provides the drug-refractory patients with a new mini-mally invasive method.展开更多
In this paper,the new theory frame and practical methhod for determining all the minimum solutions of Fuzzy matrix equation and transitive closure of Fuzzy relation is described,and it has been carried out on the mier...In this paper,the new theory frame and practical methhod for determining all the minimum solutions of Fuzzy matrix equation and transitive closure of Fuzzy relation is described,and it has been carried out on the miero-computer quickly and accurately.展开更多
This present paper deals with a mathematical description of linear axial and torsional vibrations. The normal and tangential stress tensor components produced by axial-torsional deformations and vibrations in the prop...This present paper deals with a mathematical description of linear axial and torsional vibrations. The normal and tangential stress tensor components produced by axial-torsional deformations and vibrations in the propeller and intermediate shafts, under the influence of propeller-induced static and variable hydrodynamic excitations are also studied. The transfer matrix method related to the constant coefficients of differential equation solutions is used. The advantage of the latter as compared with a well-known method of transfer matrix associated with state vector is the possibility of reducing the number of multiplied matrices when adjacent shaft segments have the same material properties and diameters. The results show that there is no risk of buckling and confirm that the strength of the shaft line depends on the value of the static tangential stresses which is the most important component of the stress tensor.展开更多
The thawing time of ice and freezed Salomon fish during high pressure assisted thawing process was evaluated by computer simulation using a finite element and the results were compared with those under atmospheric pre...The thawing time of ice and freezed Salomon fish during high pressure assisted thawing process was evaluated by computer simulation using a finite element and the results were compared with those under atmospheric pressure. The apparent specific heat method was adopted to treat the release of latent heat. The effects of different factors on the high pressure assisted thawing process were analyzed. The time reductions of different sample dimensions were estimated and the temperature contour of thawing at different conditions was obtained. The results showed that the temperature gap of phase transition was the main factor, which could shorten the thawing time. Moreover, a second order relationship was obtained between pressure and phase transition time.展开更多
基金The National Natural Science Foundation of China(No50539040)the Trans-Century Training Programme Foundation forthe Talents by the State Education Commission (NoNCET-05-0473)
文摘To simulate the concrete shrinkage in varying temperature and moisture environments, a simulate procedure comprising an analytical process and a finite element analysis is proposed based on the coupled partial differential equations describing heat and moisture transfer in a porous medium. Using the Laplace transformation method and transfer function to simplify and solve the coupled equations in Laplace domain, the moisture and temperature distribution in time domain are obtained by inverse Laplace transformation. The shrinkage deformations of concrete are numerically simulated by the finite element method （FEM） based on the obtained temperature and moisture distribution. This approach avoids the complex eigenvalues, coupling difficulty and low accuracy found in other solving methods, and also effectively calculates the moisture induced shrinkage which is almost impossible using familiar FEM software. The validity of the simulation procedure is verified by Hundt＇s test data. The results reveal that the proposed approach can be considered a reliable and efficient method to simulate the coupling moisture and temperature shrinkage of concrete.
基金Project(2012CB026205)supported by the National Basic Research Program of ChinaProjects(51608264,51778289)supported by the National Natural Science Foundation of ChinaProject(2014Y01)supported by the Transportation Science and Technology Project of Jiangsu Province,China
文摘An exact solution for simply-supported laminated beams with material properties variable with temperature under a combination of uniform thermo-load and mechanical loads was investigated,based on the two-dimensional(2-D)thermo-elasticity theory.Firstly,the beam was divided into a series of layers with uniform material properties along the interfaces of the beam.The uniform thermo-load acted on each layer was transformed into a combination of the normal surface forces acted at the two ends and the transverse thermo-load.Secondly,the state space method was employed to obtain the general solutions of displacements and stresses in an arbitrary layer.Thirdly,based on the interfacial continuity conditions between adjacent layers,the relations of displacement and stress components between the top and bottom layers of the beam were recursively derived by use of the transfer-matrix method.The unknowns in the solutions can be solved by the mechanical loads acted on the top and bottom surfaces.The convergence of the present solutions was checked.The comparative study of the present solutions with the Timoshenko’s solutions and the finite element(FE)solutions was carried out.The effects of material properties variable with temperature on the thermo-elastic behavior of laminated beams were discussed in detail.
基金Supported by the National Natural Science Foundation of China(No.59776036)
文摘Experiments of biomass pyrolysis were carried out in a fluidized bed, and dynamic signals of pressure and temperature were recorded. Correlation dimension was employed to characterize the chaotic behavior of pressure and temperature signals. Both pressure and temperature signals exhibit chaotic behavior, and the chaotic behavior of temperature signals is always weaker than that of pressure signals. Chaos transfer theory was advanced to explain the above phenomena. The discussion on the algorithm of the correlation dimension shows that the distance definition based on rhombic neighborhood is a better choice than the traditional one based on spherical neighborhood. The former provides a satisfactory result in a much shorter time.
文摘AIM:To evaluate the efficacy of Stretta procedure with gastroesophageal reflux disease(GERD)based on symptom control,medication changes and oesophagitis grade.METHODS:Ninety patients with a history of GERD underwent Stretta procedure from June 2007 to March 2010.All patients with GERD diagnosed by the pres-ence of endoscopically evidenced oesophagitis or abnormal esophageal pH testing.We evaluated GERD-health-related quality of life,satisfaction,medication use and endoscopy at baseline,6,12 mo after treatment.Complications of the procedure were analyzed.RESULTS:We found that patients experienced significant changes in symptoms of GERD after Stretta proce-dure.The onset of GERD symptom relief was less than 2 mo(70.0%)or 2 to 6 mo(16.7%).The mean GERD-HRQL score was 25.6(baseline),7.3(6 mo,P<0.01),and 8.1(12 mo,P<0.01).The mean heartburn scorewas 3.3(baseline),and 1.2(12 mo,P<0.05).The percentage of patients with satisfactory GERD control improved from 31.1%at baseline to 86.7%after treat-ment,and patient satisfaction improved from 1.4 at baseline to 4.0 at 12 mo(P<0.01).Medication usage decreased significantly from 100%of patients on pro-ton pump inhibitors therapy at baseline to 76.7%of patients showing elimination of medications or only as needed use of antacids/H2-RA at 12 mo.An improvement in endoscopic grade of oesophagitis was seen in 33 of the 41 patients.All patients had either no erosions or only mild erosive disease(grade A)at 6 mo.CONCLUSION:The experience with Stretta procedure confirms that it is well tolerated,safe,effective and durable in the treatment of GERD.The Stretta procedure provides the drug-refractory patients with a new mini-mally invasive method.
文摘In this paper,the new theory frame and practical methhod for determining all the minimum solutions of Fuzzy matrix equation and transitive closure of Fuzzy relation is described,and it has been carried out on the miero-computer quickly and accurately.
文摘This present paper deals with a mathematical description of linear axial and torsional vibrations. The normal and tangential stress tensor components produced by axial-torsional deformations and vibrations in the propeller and intermediate shafts, under the influence of propeller-induced static and variable hydrodynamic excitations are also studied. The transfer matrix method related to the constant coefficients of differential equation solutions is used. The advantage of the latter as compared with a well-known method of transfer matrix associated with state vector is the possibility of reducing the number of multiplied matrices when adjacent shaft segments have the same material properties and diameters. The results show that there is no risk of buckling and confirm that the strength of the shaft line depends on the value of the static tangential stresses which is the most important component of the stress tensor.
文摘The thawing time of ice and freezed Salomon fish during high pressure assisted thawing process was evaluated by computer simulation using a finite element and the results were compared with those under atmospheric pressure. The apparent specific heat method was adopted to treat the release of latent heat. The effects of different factors on the high pressure assisted thawing process were analyzed. The time reductions of different sample dimensions were estimated and the temperature contour of thawing at different conditions was obtained. The results showed that the temperature gap of phase transition was the main factor, which could shorten the thawing time. Moreover, a second order relationship was obtained between pressure and phase transition time.
