The conception of multilevel security (MLS) is commonly used in the study of data model for secure database. But there are some limitations in the basic MLS model, such as inference channels. The availability and data...The conception of multilevel security (MLS) is commonly used in the study of data model for secure database. But there are some limitations in the basic MLS model, such as inference channels. The availability and data integrity of the system are seriously constrained by it′s 'No Read Up, No Write Down' property in the basic MLS model. In order to eliminate the covert channels, the polyinstantiation and the cover story are used in the new data model. The read and write rules have been redefined for improving the agility and usability of the system based on the MLS model. All the methods in the improved data model make the system more secure, agile and usable.展开更多
Extensive testing was carried out to study the effects of rare earth Ce doping on the properties of SnAgCu solder alloys.The addition of 0.03%(mass fraction) rare earth Ce into SnAgCu solder may improve its mechanical...Extensive testing was carried out to study the effects of rare earth Ce doping on the properties of SnAgCu solder alloys.The addition of 0.03%(mass fraction) rare earth Ce into SnAgCu solder may improve its mechanical properties,but slightly lower its melting temperature.The tensile creep behavior of bulk SnAgCuCe solders was reported and compared with SnAgCu solders.It is found that SnAgCuCe solders show higher creep resistance than SnAgCu alloys.Moreover,Dorn model and Garofalo model are successfully used to describe the creep behavior of SnAgCu and SnAgCuCe alloys.The parameters of the two creep constitutive equations for SnAgCu and SnAgCuCe solders are determined from separated constitutive relations and experimental results.Nonlinear least-squares fitting is selected to determine the model constants.The experimental data of the stress-creep strain rate curves are in good agreement with the theoretical ones.展开更多
Objective:To summarize and analyze the clinical and histopathological features of chronic acalculous cholecystitis (CAC) and to investigate the diagnosis and surgical treatment of chronic acalculous cholecystit.Method...Objective:To summarize and analyze the clinical and histopathological features of chronic acalculous cholecystitis (CAC) and to investigate the diagnosis and surgical treatment of chronic acalculous cholecystit.Methods:The study subjects were 39 patients with chronic biliary symptoms but no evidence of stones in the gallbladder by B ultrasonography and magnetic resonance cholopancreatography (MRCP) (CAC group).The CCC group consisted of 66 patients taken randomly from concurrent all patients of chronic calculous cholecystitis (CCC).All patients accepted fibergastroscopy,B ultrasonography,MRCP,laboratory examination preoperatively.We retrospectively analyzed the clinical features,B ultrasonography and MRCP findings,histopathological results and clinical outcomes between the two groups.Results:All the 39 patients were diagnosed by clinical symptoms,B ultrasonography,fatty meal gallbladder contractability studies under ultrasound,fibergastroscopy and magnetic resonance cholangiopancreatography (MRCP),what's more,they were pathologically verified postoperatively.In all patients,there was a complete absence of gallbladder wall contractability.Mucosa epithelial defect was found in 21 patients in CAC group (53.8%) and 16 patients in CCC group (24.2%) respectively (P<0.005).Thickened arteriole wall was found in 29 patients in CAC group (74.4%) and none patient in CCC group (P<0.0001).Thickened gallbladder wall (4 mm or more in thickness) was found in 33 patients in CAC group (84.6%) and 28 patients in CCC group (42.4%) respectively (P<0.005).Bile stasis was found in 23 patients in CAC group (59.0%) and 14 patients in CCC group (21.2%) respectively by ultrasonography preoperatively and confirmed in operation (P<0.005).The outcomes of cholecystectomy,expressed as total or near total relief,was similar in the two groups.No statistically significant differences were observed between patients with CAC (90%) and CCC (80%),the P-value >0.05.Conclusion:Chronic acalculous cholecystitis could be diagnosed by symptoms,ultrasound,fatty meal gallbladder contractability studies under untrasoundand MRCP.The optimal treatment of chronic acalculous cholecystitis characterized by thickened arteriole wall and mucosa epithelial defect is cholecystectomy.展开更多
AIM: To systematically review these minimally invasive approaches to infected pancreatic necrosis. METHODS: We used the MEDLINE database to investigate studies between 1996 and 2010 with greater than 10 patients that ...AIM: To systematically review these minimally invasive approaches to infected pancreatic necrosis. METHODS: We used the MEDLINE database to investigate studies between 1996 and 2010 with greater than 10 patients that examined these techniques. Using a combination of Boolean operators, reports were retrieved addressing percutaneous therapy (341 studies), endoscopic necrosectomy (574 studies), laparoscopic necrosectomy via a transperitoneal approach (148 studies), and retroperitoneal necrosectomy (194 studies). Only cohorts with at least 10 or more patients were included. Non-English papers, letters, animal studies, duplicate series and reviews without original data were excluded, leaving a total of 27 studies for analysis. RESULTS: Twenty-seven studies with 947 patients total were examined (eight studies on percutaneous approach; ten studies on endoscopic necrosectomy; two studies on laparoscopic necrosectomy via a transperitoneal approach; five studies on retroperitoneal necrosectomy; and two studies on a combined percutaneous-retroperitoneal approach). Success rate, complications, mortality, and number of procedures were outcomes that were included in the review. We found that most published reports were retrospective in nature, and thus, susceptible to selection and publication bias. Few reports examined these techniques in a comparative, prospective manner. CONCLUSION: Each minimally invasive approach though was found to be safe and feasible in multiple reports. With these new techniques, treatment of infected pancreatic necrosis remains a challenge. We advocate a multidisciplinary approach to this complex problem with treatment individualized to each patient.展开更多
Many structure-property/activity studies use graph theoretical indices, which are based on the topological properties of a molecule viewed as a graph. Since topological indices can be derived directly from the molecul...Many structure-property/activity studies use graph theoretical indices, which are based on the topological properties of a molecule viewed as a graph. Since topological indices can be derived directly from the molecular structure without any experimental effort, they provide a simple and straightforward method for property prediction. In this work the flash point of alkanes was modeled by a set of molecular connectivity indices (Х), modified molecular connectivity indices ( ^mХ^v ) and valance molecular connectivity indices ( ^mХ^v ), with ^mХ^v calculated using the hydrogen perturbation. A stepwise Multiple Linear Regression (MLR) method was used to select the best indices. The predicted flash points are in good agreement with the experimental data, with the average absolute deviation 4.3 K.展开更多
The viscoelastic-plastic creep experiments on soft ore-rock in Jinchuan Mine III were performed under circular increment step load and unload. The experimental data were analyzed according to instantaneous elastic str...The viscoelastic-plastic creep experiments on soft ore-rock in Jinchuan Mine III were performed under circular increment step load and unload. The experimental data were analyzed according to instantaneous elastic strain, visco-elastic strain, instantaneous plastic strain and visco-plastic strain. The result shows that instantaneous deformation modulus tends to increase with the increase of creep stress; soft rocks enhance the ability to resist instantaneous elastic deformation and instantaneous plastic deformation during the multi-level of load and unload in the cyclic process. In respect of specimen JC1099, the ratio of visco-elastic strain to visco-plastic strain varies from 3.15 to 6.58, and the ratio has decreasing tendency with stress increase as a whole; creep deformation tends to be a steady state at low stress level; soft rocks creep usually embodies accelerated creep properties at high stress level. With the damaging variable and the hardening function introduced, a nonlinear creep model of soft rocks is established, in which the decay creep is described by the nonlinear hardening function H of viscidity coefficient. The model can describe the accelerated creep of soft rocks since the nonlinear damaging evolvement variable D of deformation parameter of rocks is introduced. Three stages of soft rocks creep can be described with the uniform creep equation in the nonlinear creep model. With this nonlinear creep model applied to the creep experiments of the ore-rock of Jinchuan Mine III, the nonlinear creep model's curves are in good agreement with experimental data.展开更多
Proposed new cubic equation of state is more accurate than others in result and simple in form. The equation has been tried with 23 pure compounds including both polar and non-polar compounds. Experimental values of t...Proposed new cubic equation of state is more accurate than others in result and simple in form. The equation has been tried with 23 pure compounds including both polar and non-polar compounds. Experimental values of these compounds collected from various journals were compared with proposed model and found to be more accurate than other widely used cubic equations of state like SRK and Peng Robinson. The form of current EOS best suits to PVT data and total error is almost halved for a set of experimental data in the most cases.展开更多
A two-dimensional steady state model was developed and solved numerically to predict the performance of evaporative condensing regenerator.Two-dimensional parameter distributions of air,solution and refrigerant were c...A two-dimensional steady state model was developed and solved numerically to predict the performance of evaporative condensing regenerator.Two-dimensional parameter distributions of air,solution and refrigerant were calculated by the mathematical model.The solution content first increases and then decreases along the solution flow direction.At y/Hr=0.98(where Hr is the height of regenerator),air humidity increases from 1.99% to 2.348% firstly and then decreases.The experimental results were used to validate mathematical model.It is indicated that the simulation results agree with experimental data well.The results not only show that the mathematical model can be used to predict the performance of regenerator,but also has great value in the design and improvement of evaporative condensing regenerator.展开更多
In order to study whether the intemal control of enterprises is effective, this paper studies the relationship between the quality of internal control and the performance of the company in 2012-2015, in which 61 liste...In order to study whether the intemal control of enterprises is effective, this paper studies the relationship between the quality of internal control and the performance of the company in 2012-2015, in which 61 listed companies in China's Shanghai traffic transportation industry are studied. The results show that the quality of internal control has a significant positive correlation with the financial performance of enterprises. In particular, the internal control is significantly correlated with the company's growth ability, and the internal control is positively correlated with the profitability of the company. This research provides empirical data and decision-making basis for the state to deepen the construction of internal control system and strengthen internal control management of enterprises.展开更多
The effect of controlling strata movement in solid filling mining depends on the filling rate of the goal. However, the mechanical property of the overburden in the backfill stope and the designed size of the backfill...The effect of controlling strata movement in solid filling mining depends on the filling rate of the goal. However, the mechanical property of the overburden in the backfill stope and the designed size of the backfill mining workface should also be considered. In this study, we established a main roof strata model with loads in accordance with the theory of key strata to investigate the stability of the overburden in solid dense filling mining. We analyzed the stress distribution law of the main roof strata based on elastic thin plate theory. The results show that the position of the long side midpoint of the main roof strata failed more easily because of tensile yield, indicating that this position is the area where failure is likely to occur more easily. We also deduced the stability mechanics criterion of the main roof strata based on tensile yield criterion. The factors affecting the stability of the overburden in solid dense filling mining were also analyzed, including the thickness and elasticity modulus of the main roof strata, overlying strata loads, advanced distance and length of workface, and elastic foundation coefficient of backfill body. The research achievements can provide an important theoretical basis for determining the designed size of the solid dense filling mining workface.展开更多
The lack of data concerning the morphology of male cladocerans greatly impedes our understanding of the systematics of cladocerans. This is because the differentiation of males is of significant importance for disting...The lack of data concerning the morphology of male cladocerans greatly impedes our understanding of the systematics of cladocerans. This is because the differentiation of males is of significant importance for distinguishing closely related species. Simocephalus himalayensis himalayensis Chiang & Chen, 1974 (Cladocera, Simocephalus) is an endemic cladoceran species in the Tibetan plateau, China. To date, no information has been available regarding the morphology and biology of its males. In this study, we provide the morphological and biological data of the males that were produced in laboratory populations. The male individuals are about 1.01–1.20 mm long; the margin of antennulae possess two sensory papilla; dorsal valve margin smooth. Two vas deferens are located between the supra-anal angle and the proximal anal teeth. Sperm is round with a diameter of two micrometers. An updated morphological description and reproductive data of the females of this species are also provided.展开更多
α decay half-lives are calculated using the Qα values obtained by Semi-empirical Shell Model in the framework of the Unified Fission Model (UFM) with the Coulomb repulsion, nuclear attraction due to proximity pote...α decay half-lives are calculated using the Qα values obtained by Semi-empirical Shell Model in the framework of the Unified Fission Model (UFM) with the Coulomb repulsion, nuclear attraction due to proximity potential, and rotational energy due to angular momentum transfer of a particle. In addition, the calculated and experimental half-lives of 425 nuclei are compared to check the validity of the model applied on α decay. The calculated half-lives of decay are in good agreement with the experimental data. Finally, some useful predications on the α decay half-lives are provided for future experiments.展开更多
In this article, we take the vector charmonium-like state Y(4660) as a φ' fo(980) bound state (irrespective of the hadro-charmonium and the molecular state) tentatively, and study its mass using the QCD sum ru...In this article, we take the vector charmonium-like state Y(4660) as a φ' fo(980) bound state (irrespective of the hadro-charmonium and the molecular state) tentatively, and study its mass using the QCD sum rules. The numerical value My = 4.71 ±0.26 GeV is consistent with the experimental data. Considering the SU(3) symmetry of the light flavor quarks and the heavy quark symmetry, we also study the bound states φ'a(400-1200), γ′″ fo(980), and γ′″σ(400-1200) with the QCD sum rules, and make reasonable predictions for their masses.展开更多
In this work, we analyze the positive parity of states of odd-A Eu isotopes within the framework of interacting boson fermion model (IBFM-1). The result of an IBFM-1 multilevel calculation with the 3s1/2, 2d3/2, 2d5...In this work, we analyze the positive parity of states of odd-A Eu isotopes within the framework of interacting boson fermion model (IBFM-1). The result of an IBFM-1 multilevel calculation with the 3s1/2, 2d3/2, 2d5/2, and 1g7/2 single panicle orbits is reported for the positive parity states of the odd-A Eu isotopes. A/so, an IBM-1 calculation is presented for the low-lying states in the even-even 152-154Sm core nucleus. The energy levels and B(E2) transition probabilities are calculated and compared with the experimental data. It is found that the calculated positive parity low spin state energy spectra of the odd-A Eu isotopes agree quite well with the experimental data.展开更多
The temperature dependence of the anisotropy parameter of upper critical field γHe2 (T) = Hc2^‖ (T) /Hc2^⊥ (T) and London penetration depth γλ (T) = λ‖(T)/λ⊥ (T) are calculated using two-band Ginz...The temperature dependence of the anisotropy parameter of upper critical field γHe2 (T) = Hc2^‖ (T) /Hc2^⊥ (T) and London penetration depth γλ (T) = λ‖(T)/λ⊥ (T) are calculated using two-band Ginzburg-Landau theory for layered superconductors. It is shown that, with decreasing temperature the anisotropy parameter γHc2 (T) is increased, while the London penetration depth anisotropy γλ(T) reveals an opposite behavior. Results of our calculations are in agreement with experimental data for single crystal MgB2 and with other calculations..Results of an analysis of magnetic field Hc1 in a single vortex between superconducting layers are also presented.展开更多
A fully flexible potential model for carbon dioxide has been developed to predict the vapor-liquid coexistence properties using the NVT-Gibbs ensemble Monte Carlo technique(GEMC).The average absolute deviation between...A fully flexible potential model for carbon dioxide has been developed to predict the vapor-liquid coexistence properties using the NVT-Gibbs ensemble Monte Carlo technique(GEMC).The average absolute deviation between our simulation and the literature experimental data for saturated liquid and vapor densities is 0.3% and 2.0%,respectively.Compared with the experimental data,our calculated results of critical properties(7.39 MPa,304.04 K,and 0.4679 g?cm-3) are acceptable and are better than those from the rescaling the potential parameters of elementary physical model(EPM2).The agreement of our simulated densities of supercritical carbon dioxide with the experimental data is acceptable in a wide range of pressure and temperature.The radial distribution function estimated at the supercritical conditions suggests that the carbon dioxide is a nonlinear molecule with the C O bond length of 0.117 nm and the O C O bond angle of 176.4°,which are consistent with Car-Parrinello molecular-dynamics(CPMD),whereas the EPM2 model shows large deviation at supercritical state.The predicted self-diffusion coefficients are in agreement with the experiments.展开更多
By means of the nuclear parton distribution studied only with lepton deep-inelastic scattering experimental data, the J/ψ "normal nuclear absorption" and energy loss effects are studied in a GIauber formalism at HE...By means of the nuclear parton distribution studied only with lepton deep-inelastic scattering experimental data, the J/ψ "normal nuclear absorption" and energy loss effects are studied in a GIauber formalism at HERA and RHIC energies. Assuming that the absorption cross section σabs increases with the charmonium-nucleon center of mass energy, the results reveal a significant dependence of the aabs on rapidity g at RHIC energies. The initial-state energy loss effect, which is found important only at HERA energies, is also considered, and its influence should be eliminated when we studied the absorption effect at low collision energies. Finally, we also present the theoretical prediction for LHC.展开更多
In this paper, the high speed tension experiments have been performed on ultra high strength bulletproof steel. The specimen were cut from B-grade bulletproof steel sheet after hard-module quenching with thickness of ...In this paper, the high speed tension experiments have been performed on ultra high strength bulletproof steel. The specimen were cut from B-grade bulletproof steel sheet after hard-module quenching with thickness of 2.3 mm. The mechanical properties at strain rates of 0.001 s^-1, 0.01 s^-1, 0.1 s^-1 and 1 s^-1 were carried out on MTSS10, while those at higher strain rates of 200 s^-1, 500 s^-1 and i 000 s^-1 were tested on HTM5020 high speed tension tester and Hopkinson bar. The data from the high speed tension experiments were fitted via Johnson-Cook constitutive equation, and the fracture surface of each specimen was analyzed by scanning electron microscope (SEM). The results indicate that, the shoot resistance capability of bulletproof steel is closely related to its strength, thickness and flow behaviors under high strain rate. The shoot resistance will be improved in the case of higher strength and better matching between strength and elongation. The Johnson-Cook constitutive equation fitted via experimental data provides fundament to numerical simulation. With the increase of strain rate, the size and depth of dimple trend to decrease and the depth of dimple changes less in steel with lower strength and higher elongation. The SEM analysis of fracture aspect is of benefit for further understanding of deformation and fracture mode under high strain rate.展开更多
Uranium tetrafluoride, UF4, and thorium tetrafluoride, ThF4, can be used as fuels in molten salt reactors. For the molten salt reactor design and safety analysis, it is essential to know the thermodynamic properties o...Uranium tetrafluoride, UF4, and thorium tetrafluoride, ThF4, can be used as fuels in molten salt reactors. For the molten salt reactor design and safety analysis, it is essential to know the thermodynamic properties of the UF4 and ThF4 materials. However, the experimental data for UF4 and ThF4 P-V-T are scarce in literature. Under this circumstance prediction of the thermodynamic properties can be supported by theoretical calculations to remedy missing experimental data. Within this paper the Song, Mason and lhm's equation of state with modification of Tao and Mason, originally derived for spherical and molecular fluids, is applied for fluid UF4 and ThF4 based on the available experimental data. The equation of state is based on statistical mechanical perturbation theory with the perturbation scheme of Weeks, Chandler, and Andresen. The prediction of constants applied in the equation of state is based on the work of Boushehri et al. using data for heat of vaporization and liquid density at the triple point. The calculation of the heat of vaporization applies the "sigma" method reported by Darken et al. with the vapour pressure data and heat capacities of liquid and vapour of UF4 and ThF4. Finally an extra correction term for the vapour pressure is introduced into the new equation of state. The results show that this equation of state agrees reasonably well with the available experimental data. It can be expected that this equation of state can be applied also for conditions where experimental data are currently missing.展开更多
文摘The conception of multilevel security (MLS) is commonly used in the study of data model for secure database. But there are some limitations in the basic MLS model, such as inference channels. The availability and data integrity of the system are seriously constrained by it′s 'No Read Up, No Write Down' property in the basic MLS model. In order to eliminate the covert channels, the polyinstantiation and the cover story are used in the new data model. The read and write rules have been redefined for improving the agility and usability of the system based on the MLS model. All the methods in the improved data model make the system more secure, agile and usable.
基金Project(BCXJ09-07) supported by Doctoral Dissertation Innovation and Excellence Producing Foundation of Nanjing University of Aeronautics and Astronautics,ChinaProject(CX07B_087z) supported by the Jiangsu General Colleges and Universities Postgraduate Scientific Research Innovative Plan,China
文摘Extensive testing was carried out to study the effects of rare earth Ce doping on the properties of SnAgCu solder alloys.The addition of 0.03%(mass fraction) rare earth Ce into SnAgCu solder may improve its mechanical properties,but slightly lower its melting temperature.The tensile creep behavior of bulk SnAgCuCe solders was reported and compared with SnAgCu solders.It is found that SnAgCuCe solders show higher creep resistance than SnAgCu alloys.Moreover,Dorn model and Garofalo model are successfully used to describe the creep behavior of SnAgCu and SnAgCuCe alloys.The parameters of the two creep constitutive equations for SnAgCu and SnAgCuCe solders are determined from separated constitutive relations and experimental results.Nonlinear least-squares fitting is selected to determine the model constants.The experimental data of the stress-creep strain rate curves are in good agreement with the theoretical ones.
文摘Objective:To summarize and analyze the clinical and histopathological features of chronic acalculous cholecystitis (CAC) and to investigate the diagnosis and surgical treatment of chronic acalculous cholecystit.Methods:The study subjects were 39 patients with chronic biliary symptoms but no evidence of stones in the gallbladder by B ultrasonography and magnetic resonance cholopancreatography (MRCP) (CAC group).The CCC group consisted of 66 patients taken randomly from concurrent all patients of chronic calculous cholecystitis (CCC).All patients accepted fibergastroscopy,B ultrasonography,MRCP,laboratory examination preoperatively.We retrospectively analyzed the clinical features,B ultrasonography and MRCP findings,histopathological results and clinical outcomes between the two groups.Results:All the 39 patients were diagnosed by clinical symptoms,B ultrasonography,fatty meal gallbladder contractability studies under ultrasound,fibergastroscopy and magnetic resonance cholangiopancreatography (MRCP),what's more,they were pathologically verified postoperatively.In all patients,there was a complete absence of gallbladder wall contractability.Mucosa epithelial defect was found in 21 patients in CAC group (53.8%) and 16 patients in CCC group (24.2%) respectively (P<0.005).Thickened arteriole wall was found in 29 patients in CAC group (74.4%) and none patient in CCC group (P<0.0001).Thickened gallbladder wall (4 mm or more in thickness) was found in 33 patients in CAC group (84.6%) and 28 patients in CCC group (42.4%) respectively (P<0.005).Bile stasis was found in 23 patients in CAC group (59.0%) and 14 patients in CCC group (21.2%) respectively by ultrasonography preoperatively and confirmed in operation (P<0.005).The outcomes of cholecystectomy,expressed as total or near total relief,was similar in the two groups.No statistically significant differences were observed between patients with CAC (90%) and CCC (80%),the P-value >0.05.Conclusion:Chronic acalculous cholecystitis could be diagnosed by symptoms,ultrasound,fatty meal gallbladder contractability studies under untrasoundand MRCP.The optimal treatment of chronic acalculous cholecystitis characterized by thickened arteriole wall and mucosa epithelial defect is cholecystectomy.
文摘AIM: To systematically review these minimally invasive approaches to infected pancreatic necrosis. METHODS: We used the MEDLINE database to investigate studies between 1996 and 2010 with greater than 10 patients that examined these techniques. Using a combination of Boolean operators, reports were retrieved addressing percutaneous therapy (341 studies), endoscopic necrosectomy (574 studies), laparoscopic necrosectomy via a transperitoneal approach (148 studies), and retroperitoneal necrosectomy (194 studies). Only cohorts with at least 10 or more patients were included. Non-English papers, letters, animal studies, duplicate series and reviews without original data were excluded, leaving a total of 27 studies for analysis. RESULTS: Twenty-seven studies with 947 patients total were examined (eight studies on percutaneous approach; ten studies on endoscopic necrosectomy; two studies on laparoscopic necrosectomy via a transperitoneal approach; five studies on retroperitoneal necrosectomy; and two studies on a combined percutaneous-retroperitoneal approach). Success rate, complications, mortality, and number of procedures were outcomes that were included in the review. We found that most published reports were retrospective in nature, and thus, susceptible to selection and publication bias. Few reports examined these techniques in a comparative, prospective manner. CONCLUSION: Each minimally invasive approach though was found to be safe and feasible in multiple reports. With these new techniques, treatment of infected pancreatic necrosis remains a challenge. We advocate a multidisciplinary approach to this complex problem with treatment individualized to each patient.
文摘Many structure-property/activity studies use graph theoretical indices, which are based on the topological properties of a molecule viewed as a graph. Since topological indices can be derived directly from the molecular structure without any experimental effort, they provide a simple and straightforward method for property prediction. In this work the flash point of alkanes was modeled by a set of molecular connectivity indices (Х), modified molecular connectivity indices ( ^mХ^v ) and valance molecular connectivity indices ( ^mХ^v ), with ^mХ^v calculated using the hydrogen perturbation. A stepwise Multiple Linear Regression (MLR) method was used to select the best indices. The predicted flash points are in good agreement with the experimental data, with the average absolute deviation 4.3 K.
基金Project(2007CB209400) supported by the Major State Basic Research and Development Program of ChinaProject(50774093) supported by the National Natural Science Foundation of ChinaProject(200801) supported by Open Research Fund of Hunan Provincial Key of Safe Mining Techniques of Coal Mines
文摘The viscoelastic-plastic creep experiments on soft ore-rock in Jinchuan Mine III were performed under circular increment step load and unload. The experimental data were analyzed according to instantaneous elastic strain, visco-elastic strain, instantaneous plastic strain and visco-plastic strain. The result shows that instantaneous deformation modulus tends to increase with the increase of creep stress; soft rocks enhance the ability to resist instantaneous elastic deformation and instantaneous plastic deformation during the multi-level of load and unload in the cyclic process. In respect of specimen JC1099, the ratio of visco-elastic strain to visco-plastic strain varies from 3.15 to 6.58, and the ratio has decreasing tendency with stress increase as a whole; creep deformation tends to be a steady state at low stress level; soft rocks creep usually embodies accelerated creep properties at high stress level. With the damaging variable and the hardening function introduced, a nonlinear creep model of soft rocks is established, in which the decay creep is described by the nonlinear hardening function H of viscidity coefficient. The model can describe the accelerated creep of soft rocks since the nonlinear damaging evolvement variable D of deformation parameter of rocks is introduced. Three stages of soft rocks creep can be described with the uniform creep equation in the nonlinear creep model. With this nonlinear creep model applied to the creep experiments of the ore-rock of Jinchuan Mine III, the nonlinear creep model's curves are in good agreement with experimental data.
文摘Proposed new cubic equation of state is more accurate than others in result and simple in form. The equation has been tried with 23 pure compounds including both polar and non-polar compounds. Experimental values of these compounds collected from various journals were compared with proposed model and found to be more accurate than other widely used cubic equations of state like SRK and Peng Robinson. The form of current EOS best suits to PVT data and total error is almost halved for a set of experimental data in the most cases.
基金Project(PHR201007127) supported by Academic Human Resources Development Fund of Institutions of Higher Learning under the Jurisdiction of Beijing Municipality, China Project(bsbe2010-05) supported by the Opening Funds of State Key Laboratory of Building Safety and Built Environment, China Project supported by the Doctoral Startup Foundation of Beijing University of Civil Engineering and Architecture, China
文摘A two-dimensional steady state model was developed and solved numerically to predict the performance of evaporative condensing regenerator.Two-dimensional parameter distributions of air,solution and refrigerant were calculated by the mathematical model.The solution content first increases and then decreases along the solution flow direction.At y/Hr=0.98(where Hr is the height of regenerator),air humidity increases from 1.99% to 2.348% firstly and then decreases.The experimental results were used to validate mathematical model.It is indicated that the simulation results agree with experimental data well.The results not only show that the mathematical model can be used to predict the performance of regenerator,but also has great value in the design and improvement of evaporative condensing regenerator.
文摘In order to study whether the intemal control of enterprises is effective, this paper studies the relationship between the quality of internal control and the performance of the company in 2012-2015, in which 61 listed companies in China's Shanghai traffic transportation industry are studied. The results show that the quality of internal control has a significant positive correlation with the financial performance of enterprises. In particular, the internal control is significantly correlated with the company's growth ability, and the internal control is positively correlated with the profitability of the company. This research provides empirical data and decision-making basis for the state to deepen the construction of internal control system and strengthen internal control management of enterprises.
基金Financial support for this work, provided by the National Natural Science Foundation of China (No.51404013)the Natural Science Foundation of Anhui Province (Nos.1508085ME77 and 1508085QE89)the Open Projects of State Key Laboratory for Geomechanics & Deep Underground Engineering at the China University of Mining and Technology (No.SKLGDUEK1212)
文摘The effect of controlling strata movement in solid filling mining depends on the filling rate of the goal. However, the mechanical property of the overburden in the backfill stope and the designed size of the backfill mining workface should also be considered. In this study, we established a main roof strata model with loads in accordance with the theory of key strata to investigate the stability of the overburden in solid dense filling mining. We analyzed the stress distribution law of the main roof strata based on elastic thin plate theory. The results show that the position of the long side midpoint of the main roof strata failed more easily because of tensile yield, indicating that this position is the area where failure is likely to occur more easily. We also deduced the stability mechanics criterion of the main roof strata based on tensile yield criterion. The factors affecting the stability of the overburden in solid dense filling mining were also analyzed, including the thickness and elasticity modulus of the main roof strata, overlying strata loads, advanced distance and length of workface, and elastic foundation coefficient of backfill body. The research achievements can provide an important theoretical basis for determining the designed size of the solid dense filling mining workface.
基金Supported by the National Natural Science Foundation of China (No.31071880,31030059)National Key Laboratory of Freshwater Ecology and Biotechnology of China (No.2009FB11)Hangzhou Key Laboratory for Animal Adaptation and Evolution,Hangzhou Normal University (No.2010100333T05)
文摘The lack of data concerning the morphology of male cladocerans greatly impedes our understanding of the systematics of cladocerans. This is because the differentiation of males is of significant importance for distinguishing closely related species. Simocephalus himalayensis himalayensis Chiang & Chen, 1974 (Cladocera, Simocephalus) is an endemic cladoceran species in the Tibetan plateau, China. To date, no information has been available regarding the morphology and biology of its males. In this study, we provide the morphological and biological data of the males that were produced in laboratory populations. The male individuals are about 1.01–1.20 mm long; the margin of antennulae possess two sensory papilla; dorsal valve margin smooth. Two vas deferens are located between the supra-anal angle and the proximal anal teeth. Sperm is round with a diameter of two micrometers. An updated morphological description and reproductive data of the females of this species are also provided.
基金Supported by the Natural Science Foundation of China under Grant Nos.10775061,10875152,10875151,and 10975064the Fundamental Research Fund for Physics and Mathematic of Lanzhou University(LZULL200805)+2 种基金the Fundamental Research Funds for the Central Universities(lzujbky-2009-21)the Knowledge Innovation Project of the Chinese Academy of Sciences under Grant Nos.KJCX2-SW-N17,KJCX3-SW-N02Major State Basic Research Development Program under Grant No.2007CB815000
文摘α decay half-lives are calculated using the Qα values obtained by Semi-empirical Shell Model in the framework of the Unified Fission Model (UFM) with the Coulomb repulsion, nuclear attraction due to proximity potential, and rotational energy due to angular momentum transfer of a particle. In addition, the calculated and experimental half-lives of 425 nuclei are compared to check the validity of the model applied on α decay. The calculated half-lives of decay are in good agreement with the experimental data. Finally, some useful predications on the α decay half-lives are provided for future experiments.
基金Supported by National Natural Science Foundation under Grant No.10775051 Program for New Century Excellent Talents in University under Grant No.NCET-07-0282 Project Supported by Chinese Universities Scientific Fund
文摘In this article, we take the vector charmonium-like state Y(4660) as a φ' fo(980) bound state (irrespective of the hadro-charmonium and the molecular state) tentatively, and study its mass using the QCD sum rules. The numerical value My = 4.71 ±0.26 GeV is consistent with the experimental data. Considering the SU(3) symmetry of the light flavor quarks and the heavy quark symmetry, we also study the bound states φ'a(400-1200), γ′″ fo(980), and γ′″σ(400-1200) with the QCD sum rules, and make reasonable predictions for their masses.
基金Supported by the Research Foundation of Kirikkale University and the Scientific and Technological Research Council of Turkey under Grant Nos. BAP-2007-36 and TUBITAK-107T557
文摘In this work, we analyze the positive parity of states of odd-A Eu isotopes within the framework of interacting boson fermion model (IBFM-1). The result of an IBFM-1 multilevel calculation with the 3s1/2, 2d3/2, 2d5/2, and 1g7/2 single panicle orbits is reported for the positive parity states of the odd-A Eu isotopes. A/so, an IBM-1 calculation is presented for the low-lying states in the even-even 152-154Sm core nucleus. The energy levels and B(E2) transition probabilities are calculated and compared with the experimental data. It is found that the calculated positive parity low spin state energy spectra of the odd-A Eu isotopes agree quite well with the experimental data.
文摘The temperature dependence of the anisotropy parameter of upper critical field γHe2 (T) = Hc2^‖ (T) /Hc2^⊥ (T) and London penetration depth γλ (T) = λ‖(T)/λ⊥ (T) are calculated using two-band Ginzburg-Landau theory for layered superconductors. It is shown that, with decreasing temperature the anisotropy parameter γHc2 (T) is increased, while the London penetration depth anisotropy γλ(T) reveals an opposite behavior. Results of our calculations are in agreement with experimental data for single crystal MgB2 and with other calculations..Results of an analysis of magnetic field Hc1 in a single vortex between superconducting layers are also presented.
基金Supported by the National Natural Science Foundation of China (50573063), the Program for New Century Excellent Talents in University of the State Ministry of Education (NCET-05-0566) and the Specialized Research Fund for the Doctoral Program of Higher Education of China (2005038401).
文摘A fully flexible potential model for carbon dioxide has been developed to predict the vapor-liquid coexistence properties using the NVT-Gibbs ensemble Monte Carlo technique(GEMC).The average absolute deviation between our simulation and the literature experimental data for saturated liquid and vapor densities is 0.3% and 2.0%,respectively.Compared with the experimental data,our calculated results of critical properties(7.39 MPa,304.04 K,and 0.4679 g?cm-3) are acceptable and are better than those from the rescaling the potential parameters of elementary physical model(EPM2).The agreement of our simulated densities of supercritical carbon dioxide with the experimental data is acceptable in a wide range of pressure and temperature.The radial distribution function estimated at the supercritical conditions suggests that the carbon dioxide is a nonlinear molecule with the C O bond length of 0.117 nm and the O C O bond angle of 176.4°,which are consistent with Car-Parrinello molecular-dynamics(CPMD),whereas the EPM2 model shows large deviation at supercritical state.The predicted self-diffusion coefficients are in agreement with the experiments.
文摘By means of the nuclear parton distribution studied only with lepton deep-inelastic scattering experimental data, the J/ψ "normal nuclear absorption" and energy loss effects are studied in a GIauber formalism at HERA and RHIC energies. Assuming that the absorption cross section σabs increases with the charmonium-nucleon center of mass energy, the results reveal a significant dependence of the aabs on rapidity g at RHIC energies. The initial-state energy loss effect, which is found important only at HERA energies, is also considered, and its influence should be eliminated when we studied the absorption effect at low collision energies. Finally, we also present the theoretical prediction for LHC.
文摘In this paper, the high speed tension experiments have been performed on ultra high strength bulletproof steel. The specimen were cut from B-grade bulletproof steel sheet after hard-module quenching with thickness of 2.3 mm. The mechanical properties at strain rates of 0.001 s^-1, 0.01 s^-1, 0.1 s^-1 and 1 s^-1 were carried out on MTSS10, while those at higher strain rates of 200 s^-1, 500 s^-1 and i 000 s^-1 were tested on HTM5020 high speed tension tester and Hopkinson bar. The data from the high speed tension experiments were fitted via Johnson-Cook constitutive equation, and the fracture surface of each specimen was analyzed by scanning electron microscope (SEM). The results indicate that, the shoot resistance capability of bulletproof steel is closely related to its strength, thickness and flow behaviors under high strain rate. The shoot resistance will be improved in the case of higher strength and better matching between strength and elongation. The Johnson-Cook constitutive equation fitted via experimental data provides fundament to numerical simulation. With the increase of strain rate, the size and depth of dimple trend to decrease and the depth of dimple changes less in steel with lower strength and higher elongation. The SEM analysis of fracture aspect is of benefit for further understanding of deformation and fracture mode under high strain rate.
文摘Uranium tetrafluoride, UF4, and thorium tetrafluoride, ThF4, can be used as fuels in molten salt reactors. For the molten salt reactor design and safety analysis, it is essential to know the thermodynamic properties of the UF4 and ThF4 materials. However, the experimental data for UF4 and ThF4 P-V-T are scarce in literature. Under this circumstance prediction of the thermodynamic properties can be supported by theoretical calculations to remedy missing experimental data. Within this paper the Song, Mason and lhm's equation of state with modification of Tao and Mason, originally derived for spherical and molecular fluids, is applied for fluid UF4 and ThF4 based on the available experimental data. The equation of state is based on statistical mechanical perturbation theory with the perturbation scheme of Weeks, Chandler, and Andresen. The prediction of constants applied in the equation of state is based on the work of Boushehri et al. using data for heat of vaporization and liquid density at the triple point. The calculation of the heat of vaporization applies the "sigma" method reported by Darken et al. with the vapour pressure data and heat capacities of liquid and vapour of UF4 and ThF4. Finally an extra correction term for the vapour pressure is introduced into the new equation of state. The results show that this equation of state agrees reasonably well with the available experimental data. It can be expected that this equation of state can be applied also for conditions where experimental data are currently missing.