Struvite(MAP)crystallization technology is widely used to treat ammonia nitrogen in waste effluents of its simple operation and good removal efficiency.However,the presence of heavy metal ions in the waste effluents c...Struvite(MAP)crystallization technology is widely used to treat ammonia nitrogen in waste effluents of its simple operation and good removal efficiency.However,the presence of heavy metal ions in the waste effluents causes problems such as slow crystallization rate and small crystal size,limiting the recovery rate and economic value of the MAP.The present study was conducted to investigate the effects of concentrations of three heavy metal ions(Cu^(2+),Zn^(2+),and Pb^(2+))on the crystal morphology,crystal size,average growth rate,and crystallization kinetics of MAP.A relationship was established between the kinetic rate constant Ktcalculated by the chemical gradient model and the concentrations of heavy metal ions.The results showed that low concentrations of heavy metal ions in the solution created pits on the MAP surface,and high level of heavy metal ions generated flocs on the MAP surface,which were composed of metal hydroxides,thus inhibiting crystal growth.The crystal size,average growth rate,MAP crystallization rate,and kinetic rate constant Ktdecreased with the increase in heavy metal ion concentration.Moreover,the Ktdemonstrated a linear relationship with the heavy metal concentration ln(C/C~*),which provided a reference for the optimization of the MAP crystallization process in the presence of heavy metal ions.展开更多
Absolute rate constants for the reaction of ozone with dimethyl sulfide (DMS) were measured in a 200-L Teflon chamber over the temperature range of 283-353 K. Measurements were carried out using DMS in large excess ...Absolute rate constants for the reaction of ozone with dimethyl sulfide (DMS) were measured in a 200-L Teflon chamber over the temperature range of 283-353 K. Measurements were carried out using DMS in large excess over ozone of 10 to 1 or greater. Over the indicated temperature range, the data could be fit to the simple Arrhenius expression as kDMS = (9.96 ± 3.61) × 10^-11 exp (-(7309.7 ± 1098.2)/T) cm^3/(molecule.s). A compared investigation of the reaction between ozone and ethene had a kC2H4 value of (1.35 ± 0.11) × 10^-18 cm^3/(molecule.s) at room temperature.展开更多
Structural and thermodynamic parameters of 16 chloro-phenol compounds in water solution were calculated and fully optimized by using Onsager model in self-consistent reaction field(SCRF) based on the B3LYP/6-311G*...Structural and thermodynamic parameters of 16 chloro-phenol compounds in water solution were calculated and fully optimized by using Onsager model in self-consistent reaction field(SCRF) based on the B3LYP/6-311G** level.These quantum chemical parameters were used as theoretical descriptors to correlate with the experimental biodegradation rate constant(Kb) of 16 compounds by stepwise multiple linear regression.As a result,a three-parameter model including molecular average polarizability(α),entropy(Sθ),and molar heat capacity at constant volume(CVθ) were established for Kb prediction,which was proposed with correlation coefficient R2 = 0.894.α exhibits the most significant effect on Kb.Variance analysis and standard t-value test were applied to validate the model.As expected,this model exhibits good robustness and prediction ability,which can be used in Kb prediction of analogs.展开更多
A simple model for estimating the rate constant between CO2-CO gas and molten slag containing iron oxides was developed using optical basicity only. In this model, the temperature dependence of the rate constant can b...A simple model for estimating the rate constant between CO2-CO gas and molten slag containing iron oxides was developed using optical basicity only. In this model, the temperature dependence of the rate constant can be described by the Arrhenius law, and the activation energy can be expressed with a linear function of the slag's optical basicity. The model was applied to some molten slag systems, such as FeO, FeO-CaO, FeO-SiO2, FeO-Na2O, FeO-CaO-SiO2, FeO-SiO2-P2O5, FeO-SiOE-Na2O, and FeO-CaO-SiOE-P2O5. A comparison between the predicted results and measured data showed that the model worked well.展开更多
Rate constants for the reactions of NO3 and SO4 radicals with oxalic acid and oxalate anions in aqueous solution have been measured using pulse radiolysis and laser flash photolysis.
In order to improve the sensitivity of the Compass B1C signal acquisition for the receiver,the principle of constant false alarm rate(CFAR)is applied for the B1C pilot channel acquisition to realize the dynamic adjust...In order to improve the sensitivity of the Compass B1C signal acquisition for the receiver,the principle of constant false alarm rate(CFAR)is applied for the B1C pilot channel acquisition to realize the dynamic adjustment of the threshold of acquisition against the carrier to noise ratio.The non-coherent data/pilot combined acquisition algorithm for B1C signal is analyzed to make full use of the power of the B1C signal under the condition of low carrier to noise ratio.On this basis,to improve the acquisition sensitivity of the receiver,the principle of constant false alarm probability is applied for the non-coherent data/pilot combined acquisition algorithm.Theoretical analysis and simulations show that the non-coherent data/pilot combined acquisition algorithm with CFAR improves the B1C signal acquisition sensitivity of the receiver significantly,and achieves a better Receiver Operating Characteristic compared with the traditional acquisition algorithms.展开更多
A quasi-classical trajectory(QCT) calculation is used to investigate the vector and scalar properties of the D + Br O → DBr + O reaction based on an ab initio potential energy surface(X1A state) with collision ...A quasi-classical trajectory(QCT) calculation is used to investigate the vector and scalar properties of the D + Br O → DBr + O reaction based on an ab initio potential energy surface(X1A state) with collision energy ranging from 0.1 kcal/mol to 6 kcal/mol. The reaction probability, the cross section, and the rate constant are studied. The probability and the cross section show decreasing behaviors as the collision energy increases. The distribution of the rate constant indicates that the reaction favorably occurs in a relatively low-temperature region(T 〈 100 K). Meanwhile, three product angular distributions P(θr), P(φr), and P(θr, φr) are presented, which reflect the positive effect on the rotational angular momentum j' polarization of the DBr product molecule. In addition, two of the polarization-dependent generalized differential cross sections(PDDCSs), PDDCS00 and PDDCS20, are computed as well. Our results demonstrate that both vector and scalar properties have strong energy dependence.展开更多
Basing on the DFT calculations we propose the new theoretical model which describes both the surface tension σ of the short chain n-alkanes at their normal boiling points and their reaction rate constants with hydrox...Basing on the DFT calculations we propose the new theoretical model which describes both the surface tension σ of the short chain n-alkanes at their normal boiling points and their reaction rate constants with hydroxyl radicals OH<span style="white-space:nowrap;">•</span> (at 297 ± 2 K) on the basis of their molecular orbital electronic characteristics. It has been shown that intermolecular dispersion attraction within the surface liquid monolayer of these compounds, as well as their reaction rate constants k with OH<span style="white-space:nowrap;">•</span> radicals are determined by the energies <em>E<sub>orb</sub></em> of the specific occupied molecular orbitals which are the same in the determination of both the above physico-chemical characteristics of the studied n-alkanes. The received regression equations confirm the theoretically found dependences between the quantities of σ and k and the module |<em>E<sub>orb</sub></em>|. For the compounds under study this fact indicates the key role of their electronic structure particularities in determination of both the physical (surface tension) and the chemical (reaction rate constants) properties.展开更多
Noncoherent integration is often ed for approving performance in detection of radar signal. Order-statistics constant false alarm rate (OS-CFAR) detector has some advantages in clutter and multiple target situations. ...Noncoherent integration is often ed for approving performance in detection of radar signal. Order-statistics constant false alarm rate (OS-CFAR) detector has some advantages in clutter and multiple target situations. AnOS-CFAN detector with noncoherent integration after Square law envelope detector is presented and an analysis of detection performance for the chi-Square family of Swerling fluctuating targets is given. Its application to the high frequency(HF) ground wave over-the-horizon (OTH) radar is discussed as well.展开更多
A dynamic method is employed to study the reaction mechanisms of CH3CH2OCF3 with the hydrogen trioxy (HOOO) radical. In our paper, the geometries and harmonic vibrational frequencies of all the stationary points and...A dynamic method is employed to study the reaction mechanisms of CH3CH2OCF3 with the hydrogen trioxy (HOOO) radical. In our paper, the geometries and harmonic vibrational frequencies of all the stationary points and minimum energy paths (MEPs) are calculated at the MPW1K/6-31+G(d,p) level of theory, and the energetic information along MEPs is further refined by the CCSD/6-31+G(df, p) level of theory. The rate constants are evaluated with the conventional transition-state theory (TST), the canonical variational transition-state theory (CVT), the microcanonical variational transition-state theory (μVT), the CVT coupled with the small-curvature tunneling (SCT) correction (CVT/SCT), and the μVT coupled with the Eckart tunneling correction μVT/Eckart) based on the ab initio calculations in the temperature range of 200-3000 K. The theoretical results are important in determining the atmospheric lifetime and the feasible pathways for the loss of HFEs.展开更多
The application of Monte Carlo method in estimating rate constants for polymerization was described, A general program for Monte Carlo simulation was determined first according to the elementary reactions, after which...The application of Monte Carlo method in estimating rate constants for polymerization was described, A general program for Monte Carlo simulation was determined first according to the elementary reactions, after which the rate constants could be automatically adjusted and optimized through comparing of experimental and simulated data with an error expression that meeted a given minimum criterion. Such a process made the rate constants to be estimated without kinetic model in advance. The technique was applied to estimate the rate constants of the bulk polymerization of styrene catalyzed by the rare earth catalyst. The esthnated results showed the Monte Carlo method was feasible and effective for estimating rate constants in polymerization engineering.展开更多
In a survival analysis context, we suggest a new method to estimate the piecewise constant hazard rate model. The method provides an automatic procedure to find the number and location of cut points and to estimate th...In a survival analysis context, we suggest a new method to estimate the piecewise constant hazard rate model. The method provides an automatic procedure to find the number and location of cut points and to estimate the hazard on each cut interval. Estimation is performed through a penalized likelihood using an adaptive ridge procedure. A bootstrap procedure is proposed in order to derive valid statistical inference taking both into account the variability of the estimate and the variability in the choice of the cut points. The new method is applied both to simulated data and to the Mayo Clinic trial on primary biliary cirrhosis. The algorithm implementation is seen to work well and to be of practical relevance.展开更多
A new approach was employed to calculate the canonical (thermal) rate constant basedon unified statistical theory. All information for the calculation was obtained from ab initio meth-ods. The flux integral for any po...A new approach was employed to calculate the canonical (thermal) rate constant basedon unified statistical theory. All information for the calculation was obtained from ab initio meth-ods. The flux integral for any point of reaction coordinate was calculated by counting the numberof quantum states and applied to determine the dividing surfaces along the intrinsic reaction coor-dinate (IRC). The classical exchange reaction H2+H, as an example, was investigated. The IRC forthe reaction has been traced and detailed information of IRC was carried out at the QCISD/6-311 G** level .The calculated rate constants are well consistent with the experimental results.展开更多
Coal fly ash is being utilized as a recycling material for catalysis due to its aluminosilicate content. Catalytic conversion of polymeric wastes into synthetic gasoline and diesel through pyrolysis requires applicati...Coal fly ash is being utilized as a recycling material for catalysis due to its aluminosilicate content. Catalytic conversion of polymeric wastes into synthetic gasoline and diesel through pyrolysis requires application of kinetic and thermodynamic principles. This study aimed to identify the catalytic rate constant necessary for rate law involved in reaction mechanisms and activation energy reduction needed for heat transfer rate. Stoichiometric application for balanced total series of elementary reactions is solved for the concentration determination of reactants and products. Unsteady-state in three dimensional directions of thermodynamics is derived for the determination of heat transfer rate, temperatures at any position in a sphere using Gurney and Lurie chart and center temperature in a sphere by Heisler chart. Application principles of rate law and Arrhenius equation can result to thermal conductivity as a function of activation energy leading to synthetic fuel production.展开更多
Fault activation has been the focus of research community for years.However,the studies of fault activation remain immature,such as the fault activation mode and its major factors under constant normal stiffness(CNS)c...Fault activation has been the focus of research community for years.However,the studies of fault activation remain immature,such as the fault activation mode and its major factors under constant normal stiffness(CNS)conditions associated with large thickness of fault surrounding rock mass.In this study,the rock friction experiments were conducted to understand the fault activation modes under the CNS conditions.Two major parameters,i.e.the initial normal stress and loading rate,were considered and calibrated in the tests.To reveal the response mechanism of fault activation,the local strains near the fault plane were recorded,and the macroscopic stresses and displacements were analyzed.The testing results show that the effect of displacement-controlled loading rate is more pronounced under the CNS conditions than that under constant normal load(CNL)conditions.Both the normal and shear stresses drop suddenly when the stick-slip occurs.The decrease and increase of the normal stress are synchronous with the shear stress in the regular stick-slip scenario,but mismatch with the shear stress during the chaotic stick-slip process.The results are helpful for understanding the fault sliding mode and the prediction and prevention of fault slip.展开更多
In this paper, we propose an entanglement scheme for long-distance, constant-fidelity communication in quantum networks. We discuss the optimal rate of entanglement that allows for constant fidelity in both elementary...In this paper, we propose an entanglement scheme for long-distance, constant-fidelity communication in quantum networks. We discuss the optimal rate of entanglement that allows for constant fidelity in both elementary and muhihop links. We also discuss time complexity and propose the mathematical order of the rate capacity for an entanglement scheme. We propose a recursive entanglement scheme, a simultaneous entanglement scheme, and an adjacent entanglement scheme mathematically analyze these schemes. The rate capacity of the recursive and simultaneous entanglement schemes is Ω(1/e^n), but the adjacent entanglement scheme performs better, providing a rate of lΩ(1/n).展开更多
Bayesian inference is applied in this study to evaluate the posterior distribution of rate consents for a thermal isomerization of α-pinene by considering the uncertainty associated with rate constant parameters and ...Bayesian inference is applied in this study to evaluate the posterior distribution of rate consents for a thermal isomerization of α-pinene by considering the uncertainty associated with rate constant parameters and kinetic model structural error. The kinetic model of the thermal isomerization of α-pinene is shown to have a mathematically ill-conditioned system that makes it difficult to apply gradient-based optimization methods for rate constant evaluation. The Bayesian inference relates the posterior probability distribution of the rate constants to the likelihood probability of modeled concentration of reaction products meeting the experimentally measured concentration and the prior probability distribution of the parameters. A Markov chain Monte Carlo (MCMC) is used to draw samples from posterior distribution while the Bayesian inference relationship is considered. Multinomial random walk Metropolis-Hastings is applied in this study to construct the histograms of rate constants as well as the confidence intervals and the correlation coefficient matrix. Results showed that the Bayesian approach can successfully apply to estimate the confidence interval of rate constants of reaction model by taking into consideration the uncertainty.展开更多
The new theoretical models describe both the solubility S of the shot chain n-alkanes in water at 298.15 K, and their reaction rate constants k with nitronium cation NO<sub>2</sub><sup>+ </sup>...The new theoretical models describe both the solubility S of the shot chain n-alkanes in water at 298.15 K, and their reaction rate constants k with nitronium cation NO<sub>2</sub><sup>+ </sup>at 293.15 K on the basis of their molecular orbital characteristics. It is shown that both the quantities S and k are determined by the energies E<sub>orb</sub> of the specific virtual (for S) and occupied (for k) molecular orbitals of these n-alkanes. The obtained regression equations confirm the theoretically found dependences of S and k on the absolute value of E<sub>orb</sub>. This fact demonstrates that the electronic structure particularities of the studied n-alkanes play a crucial role in both their above-mentioned physicochemical properties.展开更多
基金financial support from the National Natural Science Foundation of China (21838004)Priority Academic Program Development of Jiangsu Higher Education Institutions (PPZY2015A044)Top-notch Academic Programs Project of Jiangsu Higher Education Institution (TAPP)。
文摘Struvite(MAP)crystallization technology is widely used to treat ammonia nitrogen in waste effluents of its simple operation and good removal efficiency.However,the presence of heavy metal ions in the waste effluents causes problems such as slow crystallization rate and small crystal size,limiting the recovery rate and economic value of the MAP.The present study was conducted to investigate the effects of concentrations of three heavy metal ions(Cu^(2+),Zn^(2+),and Pb^(2+))on the crystal morphology,crystal size,average growth rate,and crystallization kinetics of MAP.A relationship was established between the kinetic rate constant Ktcalculated by the chemical gradient model and the concentrations of heavy metal ions.The results showed that low concentrations of heavy metal ions in the solution created pits on the MAP surface,and high level of heavy metal ions generated flocs on the MAP surface,which were composed of metal hydroxides,thus inhibiting crystal growth.The crystal size,average growth rate,MAP crystallization rate,and kinetic rate constant Ktdecreased with the increase in heavy metal ion concentration.Moreover,the Ktdemonstrated a linear relationship with the heavy metal concentration ln(C/C~*),which provided a reference for the optimization of the MAP crystallization process in the presence of heavy metal ions.
基金The National Natural Science Foundation of China(No.20677067,20577064)the National Basic Research Program(973) of China(2005CB422206)
文摘Absolute rate constants for the reaction of ozone with dimethyl sulfide (DMS) were measured in a 200-L Teflon chamber over the temperature range of 283-353 K. Measurements were carried out using DMS in large excess over ozone of 10 to 1 or greater. Over the indicated temperature range, the data could be fit to the simple Arrhenius expression as kDMS = (9.96 ± 3.61) × 10^-11 exp (-(7309.7 ± 1098.2)/T) cm^3/(molecule.s). A compared investigation of the reaction between ozone and ethene had a kC2H4 value of (1.35 ± 0.11) × 10^-18 cm^3/(molecule.s) at room temperature.
基金Supported by the State Key Program of NNSFC (No. 20737001)NNSFC (No. 20977044)
文摘Structural and thermodynamic parameters of 16 chloro-phenol compounds in water solution were calculated and fully optimized by using Onsager model in self-consistent reaction field(SCRF) based on the B3LYP/6-311G** level.These quantum chemical parameters were used as theoretical descriptors to correlate with the experimental biodegradation rate constant(Kb) of 16 compounds by stepwise multiple linear regression.As a result,a three-parameter model including molecular average polarizability(α),entropy(Sθ),and molar heat capacity at constant volume(CVθ) were established for Kb prediction,which was proposed with correlation coefficient R2 = 0.894.α exhibits the most significant effect on Kb.Variance analysis and standard t-value test were applied to validate the model.As expected,this model exhibits good robustness and prediction ability,which can be used in Kb prediction of analogs.
基金supported by the National Natural Science Foundation of China (Nos. 50834007, 50874128, and 50674012)
文摘A simple model for estimating the rate constant between CO2-CO gas and molten slag containing iron oxides was developed using optical basicity only. In this model, the temperature dependence of the rate constant can be described by the Arrhenius law, and the activation energy can be expressed with a linear function of the slag's optical basicity. The model was applied to some molten slag systems, such as FeO, FeO-CaO, FeO-SiO2, FeO-Na2O, FeO-CaO-SiO2, FeO-SiO2-P2O5, FeO-SiOE-Na2O, and FeO-CaO-SiOE-P2O5. A comparison between the predicted results and measured data showed that the model worked well.
文摘Rate constants for the reactions of NO3 and SO4 radicals with oxalic acid and oxalate anions in aqueous solution have been measured using pulse radiolysis and laser flash photolysis.
基金supported by the Joint Funds of the Ministry of Education of China(No.6141A02022383)the Fundamental Research Funds for the Central Universities of Ministry of Education of China(No.20101195611)
文摘In order to improve the sensitivity of the Compass B1C signal acquisition for the receiver,the principle of constant false alarm rate(CFAR)is applied for the B1C pilot channel acquisition to realize the dynamic adjustment of the threshold of acquisition against the carrier to noise ratio.The non-coherent data/pilot combined acquisition algorithm for B1C signal is analyzed to make full use of the power of the B1C signal under the condition of low carrier to noise ratio.On this basis,to improve the acquisition sensitivity of the receiver,the principle of constant false alarm probability is applied for the non-coherent data/pilot combined acquisition algorithm.Theoretical analysis and simulations show that the non-coherent data/pilot combined acquisition algorithm with CFAR improves the B1C signal acquisition sensitivity of the receiver significantly,and achieves a better Receiver Operating Characteristic compared with the traditional acquisition algorithms.
基金supported by the Jilin University,China(Grant No.419080106440)the Chinese National Fusion Project for the International Thermonuclear Experimental Reactor(ITER)(Grant No.2010GB104003)the National Natural Science Foundation of China(Grant No.10974069)
文摘A quasi-classical trajectory(QCT) calculation is used to investigate the vector and scalar properties of the D + Br O → DBr + O reaction based on an ab initio potential energy surface(X1A state) with collision energy ranging from 0.1 kcal/mol to 6 kcal/mol. The reaction probability, the cross section, and the rate constant are studied. The probability and the cross section show decreasing behaviors as the collision energy increases. The distribution of the rate constant indicates that the reaction favorably occurs in a relatively low-temperature region(T 〈 100 K). Meanwhile, three product angular distributions P(θr), P(φr), and P(θr, φr) are presented, which reflect the positive effect on the rotational angular momentum j' polarization of the DBr product molecule. In addition, two of the polarization-dependent generalized differential cross sections(PDDCSs), PDDCS00 and PDDCS20, are computed as well. Our results demonstrate that both vector and scalar properties have strong energy dependence.
文摘Basing on the DFT calculations we propose the new theoretical model which describes both the surface tension σ of the short chain n-alkanes at their normal boiling points and their reaction rate constants with hydroxyl radicals OH<span style="white-space:nowrap;">•</span> (at 297 ± 2 K) on the basis of their molecular orbital electronic characteristics. It has been shown that intermolecular dispersion attraction within the surface liquid monolayer of these compounds, as well as their reaction rate constants k with OH<span style="white-space:nowrap;">•</span> radicals are determined by the energies <em>E<sub>orb</sub></em> of the specific occupied molecular orbitals which are the same in the determination of both the above physico-chemical characteristics of the studied n-alkanes. The received regression equations confirm the theoretically found dependences between the quantities of σ and k and the module |<em>E<sub>orb</sub></em>|. For the compounds under study this fact indicates the key role of their electronic structure particularities in determination of both the physical (surface tension) and the chemical (reaction rate constants) properties.
基金Supported by the Eleventh Five Year National Key Technology R&D Program (2008BAE58B01)New Century Excellent Talents of Ministry of Education (NCET-07-0577),the People’s Republic of China
文摘实验方程适合的一个运动模型被建议了描述液体排水行为。率常数(k <sub > 液体排水方程的 d </sub>) 能从上述实验方程被获得。在这篇论文,胶体的煤气的 aphrons ( CGA )的稳定性,钠 dodecyl 苯硫酸盐( SDBS )的集中的效果, dodecyl trimethylammonium 溴化物( HTAB )和 polyoxyethylene 山梨糖醇酐 monolaurate ( Tween-20 ),温度,激动人心的速度,激动人心的时间,并且 k <sub 上的盐的各种各样的类型>液体排水的 d </sub>进一步被调查。结果证明 Arrhenius 方程能成功地被用来描述在 k <sub 之间的关系 > d </sub> 和绝对温度(T) ,和表面活化剂,激动人心的速度,激动人心的时间和咸度的集中也在 k <sub 上有大效果 > d </sub> 。最后, CGA 排水机制作为时间的功能从液体排水的率的分析被解释。
文摘Noncoherent integration is often ed for approving performance in detection of radar signal. Order-statistics constant false alarm rate (OS-CFAR) detector has some advantages in clutter and multiple target situations. AnOS-CFAN detector with noncoherent integration after Square law envelope detector is presented and an analysis of detection performance for the chi-Square family of Swerling fluctuating targets is given. Its application to the high frequency(HF) ground wave over-the-horizon (OTH) radar is discussed as well.
基金supported by the the National Natural Science Foundation of China(No.21373025 and 20933001)the Research Foundation of Education Bureau of Hebei Province(No.Z2011115)+3 种基金the 111 Project of China(No.B07012)the Natural Science Foundation of Hebei Province(No.B2012105002)the Research Foundation of Tangshan Administration of Science&Technology(131302115b)the Research Foundation of Tangshan normal college(2013A04)
文摘A dynamic method is employed to study the reaction mechanisms of CH3CH2OCF3 with the hydrogen trioxy (HOOO) radical. In our paper, the geometries and harmonic vibrational frequencies of all the stationary points and minimum energy paths (MEPs) are calculated at the MPW1K/6-31+G(d,p) level of theory, and the energetic information along MEPs is further refined by the CCSD/6-31+G(df, p) level of theory. The rate constants are evaluated with the conventional transition-state theory (TST), the canonical variational transition-state theory (CVT), the microcanonical variational transition-state theory (μVT), the CVT coupled with the small-curvature tunneling (SCT) correction (CVT/SCT), and the μVT coupled with the Eckart tunneling correction μVT/Eckart) based on the ab initio calculations in the temperature range of 200-3000 K. The theoretical results are important in determining the atmospheric lifetime and the feasible pathways for the loss of HFEs.
基金Project supported by National Natural Science Foundation of China (Grant No, 20406016)
文摘The application of Monte Carlo method in estimating rate constants for polymerization was described, A general program for Monte Carlo simulation was determined first according to the elementary reactions, after which the rate constants could be automatically adjusted and optimized through comparing of experimental and simulated data with an error expression that meeted a given minimum criterion. Such a process made the rate constants to be estimated without kinetic model in advance. The technique was applied to estimate the rate constants of the bulk polymerization of styrene catalyzed by the rare earth catalyst. The esthnated results showed the Monte Carlo method was feasible and effective for estimating rate constants in polymerization engineering.
文摘In a survival analysis context, we suggest a new method to estimate the piecewise constant hazard rate model. The method provides an automatic procedure to find the number and location of cut points and to estimate the hazard on each cut interval. Estimation is performed through a penalized likelihood using an adaptive ridge procedure. A bootstrap procedure is proposed in order to derive valid statistical inference taking both into account the variability of the estimate and the variability in the choice of the cut points. The new method is applied both to simulated data and to the Mayo Clinic trial on primary biliary cirrhosis. The algorithm implementation is seen to work well and to be of practical relevance.
文摘A new approach was employed to calculate the canonical (thermal) rate constant basedon unified statistical theory. All information for the calculation was obtained from ab initio meth-ods. The flux integral for any point of reaction coordinate was calculated by counting the numberof quantum states and applied to determine the dividing surfaces along the intrinsic reaction coor-dinate (IRC). The classical exchange reaction H2+H, as an example, was investigated. The IRC forthe reaction has been traced and detailed information of IRC was carried out at the QCISD/6-311 G** level .The calculated rate constants are well consistent with the experimental results.
文摘Coal fly ash is being utilized as a recycling material for catalysis due to its aluminosilicate content. Catalytic conversion of polymeric wastes into synthetic gasoline and diesel through pyrolysis requires application of kinetic and thermodynamic principles. This study aimed to identify the catalytic rate constant necessary for rate law involved in reaction mechanisms and activation energy reduction needed for heat transfer rate. Stoichiometric application for balanced total series of elementary reactions is solved for the concentration determination of reactants and products. Unsteady-state in three dimensional directions of thermodynamics is derived for the determination of heat transfer rate, temperatures at any position in a sphere using Gurney and Lurie chart and center temperature in a sphere by Heisler chart. Application principles of rate law and Arrhenius equation can result to thermal conductivity as a function of activation energy leading to synthetic fuel production.
基金supported by the Key Projects of the Yalong River Joint Fund of the National Natural Science Foundation of China(Grant No.U1865203)the National Natural Science Foundation of China(Grant Nos.52109142 and 41941018).
文摘Fault activation has been the focus of research community for years.However,the studies of fault activation remain immature,such as the fault activation mode and its major factors under constant normal stiffness(CNS)conditions associated with large thickness of fault surrounding rock mass.In this study,the rock friction experiments were conducted to understand the fault activation modes under the CNS conditions.Two major parameters,i.e.the initial normal stress and loading rate,were considered and calibrated in the tests.To reveal the response mechanism of fault activation,the local strains near the fault plane were recorded,and the macroscopic stresses and displacements were analyzed.The testing results show that the effect of displacement-controlled loading rate is more pronounced under the CNS conditions than that under constant normal load(CNL)conditions.Both the normal and shear stresses drop suddenly when the stick-slip occurs.The decrease and increase of the normal stress are synchronous with the shear stress in the regular stick-slip scenario,but mismatch with the shear stress during the chaotic stick-slip process.The results are helpful for understanding the fault sliding mode and the prediction and prevention of fault slip.
文摘In this paper, we propose an entanglement scheme for long-distance, constant-fidelity communication in quantum networks. We discuss the optimal rate of entanglement that allows for constant fidelity in both elementary and muhihop links. We also discuss time complexity and propose the mathematical order of the rate capacity for an entanglement scheme. We propose a recursive entanglement scheme, a simultaneous entanglement scheme, and an adjacent entanglement scheme mathematically analyze these schemes. The rate capacity of the recursive and simultaneous entanglement schemes is Ω(1/e^n), but the adjacent entanglement scheme performs better, providing a rate of lΩ(1/n).
文摘Bayesian inference is applied in this study to evaluate the posterior distribution of rate consents for a thermal isomerization of α-pinene by considering the uncertainty associated with rate constant parameters and kinetic model structural error. The kinetic model of the thermal isomerization of α-pinene is shown to have a mathematically ill-conditioned system that makes it difficult to apply gradient-based optimization methods for rate constant evaluation. The Bayesian inference relates the posterior probability distribution of the rate constants to the likelihood probability of modeled concentration of reaction products meeting the experimentally measured concentration and the prior probability distribution of the parameters. A Markov chain Monte Carlo (MCMC) is used to draw samples from posterior distribution while the Bayesian inference relationship is considered. Multinomial random walk Metropolis-Hastings is applied in this study to construct the histograms of rate constants as well as the confidence intervals and the correlation coefficient matrix. Results showed that the Bayesian approach can successfully apply to estimate the confidence interval of rate constants of reaction model by taking into consideration the uncertainty.
文摘The new theoretical models describe both the solubility S of the shot chain n-alkanes in water at 298.15 K, and their reaction rate constants k with nitronium cation NO<sub>2</sub><sup>+ </sup>at 293.15 K on the basis of their molecular orbital characteristics. It is shown that both the quantities S and k are determined by the energies E<sub>orb</sub> of the specific virtual (for S) and occupied (for k) molecular orbitals of these n-alkanes. The obtained regression equations confirm the theoretically found dependences of S and k on the absolute value of E<sub>orb</sub>. This fact demonstrates that the electronic structure particularities of the studied n-alkanes play a crucial role in both their above-mentioned physicochemical properties.