In this paper, the effect of every parameter （including p, q, r, λ, τ） on the mean first-passage time （MFPT） is investigated in an asymmetric bistable system driven by colour-correlated noise. The expression of ...In this paper, the effect of every parameter （including p, q, r, λ, τ） on the mean first-passage time （MFPT） is investigated in an asymmetric bistable system driven by colour-correlated noise. The expression of MFPT has been obtained by applying the steepest-descent approximation. Numerical results show that （1） the intensity of multiplicative noise p and the intensity of additive noise q play different roles in the MFPT of the system, （2） suppression appears on the curve of the MFPT with small λ （e.g. λ 〈 0.5） but there is a peak on the curve of the MFPT when λ is big （e.g. λ 〉 0.5）, and （3） with different values of r （e.g. r = 0.1, 0.5, 1.5）, the effort of τ on the MFPT is diverse.展开更多
The treatment of metastatic colorectal cancer(mCRC)has evolved considerably in the last decade,currently allowing most mCRC patients to live more than two years.Monoclonal antibodies targeting the epidermal growth fac...The treatment of metastatic colorectal cancer(mCRC)has evolved considerably in the last decade,currently allowing most mCRC patients to live more than two years.Monoclonal antibodies targeting the epidermal growth factor receptor(EGFR)and vascular endothelial growth factor play an important role in the current treatment of these patients.However,only antibodies directed against EGFR have a predictive marker of response,which is the mutation status of v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog(KRAS).Cetuximab has been shown to be effective in patients with KRAS wild-type mCRC.The CRYSTAL study showed that adding cetuximab to FOLFIRI(regimen of irinotecan,infusional fluorouracil and leucovorin)significantly improved results in the first-line treatment of KRAS wildtype mCRC.However,results that evaluate the efficacy of cetuximab in combination with oxaliplatin-based chemotherapy in this setting are contradictory.On the other hand,recent advances in the management of colorectal liver metastases have improved survival in these patients.Adding cetuximab to standard chemotherapy increases the response rate in patients with wild-type KRAS and can thus increase the resectability rate of liver metastases in this group of patients.In this paper we review the different studies assessing the efficacy of cetuximab in the first-line treatment of mCRC.展开更多
The electronic,mechanical and optical properties of La-and Sc-doped Y2O3 were investigated using firstprinciples calculations.Two doping sites of Sc and La in Y2O3 were modeled.The calculated values of the energy of f...The electronic,mechanical and optical properties of La-and Sc-doped Y2O3 were investigated using firstprinciples calculations.Two doping sites of Sc and La in Y2O3 were modeled.The calculated values of the energy of formation show that the most energetically favorable site for a La atom in Y2O3 is a d-site Y atom,while for Sc a b-site Y atom is the more stable position.The calculated band gap shows a slight decrease with increasing La or Sc concentration.The calculated results for the mechanical and optical properties of Y(2-x)RxO3(R=Sc or La,0<x≤0.1875)show that La-or Sc-doped Y2O3 would have enhanced strength,and thus an ability of resisting external shocks,and increased hardness and mechanical toughness.These improved mechanical properties are achieved without sacrificing the optical properties of the doped compounds.So the doping of La or Sc in Y2O3 is permissible in the preparation of Y2O3 transparent ceramics,of course,doping of La or Sc will benefit the sintering of transparent ceramics.展开更多
The band structure, density of states, Mulliken populations, and frontier orbital of spodumene crystal were calculated using the first-principles method based on the density functional theory（DFT） and further analyz...The band structure, density of states, Mulliken populations, and frontier orbital of spodumene crystal were calculated using the first-principles method based on the density functional theory（DFT） and further analyzed in detail. The calculation results reveal that the O in spodumene is the most active and easily links with H＋in the water, but the active Li is very low, so it is better to add activator to increase the concentrate grade and recovery rate of spodumene in the flotation process. Si–O bonds in spodumene crystal are mainly covalent, since the covalency of Al–O bonds is stronger than that of Li–O bonds,and minerals dissociate along the weakest Li–O bonds. In addition, the study of the frontier orbital indicates that both O and Si atoms have large contribution to the frontier orbital in the spodumene crystal. Oleate and dodecylamine are used as the collectors of spodumene. The results contribute to the understanding of crystal structures of spodumene, and can be used in guiding related practical applications.展开更多
First-principles calculations have been carried out to investigate the structural stabilities, electronic structures and elastic properties of Mg17Al12, Al2Ca and Al4Sr phases. The optimized structural parameters are ...First-principles calculations have been carried out to investigate the structural stabilities, electronic structures and elastic properties of Mg17Al12, Al2Ca and Al4Sr phases. The optimized structural parameters are in good agreement with the experimental and other theoretical values. The calculated formation enthalpies and cohesive energies show that Al2Ca has the strongest alloying ability, and Al4Sr has the highest structural stability. The densities of states （DOS）, Mulliken electronic populations, and electronic charge density difference are obtained to reveal the underlying mechanism of structural stability. The bulk modulus, shear modulus, Young＇s modulus, and Poisson＇s ratio are estimated from the calculated elastic constants. The mechanical properties of these phases are further analyzed and discussed. The Gibbs free energy and Debye temperature are also calculated and discussed.展开更多
Consensus problems of first-order multi-agent systems with multiple time delays are investigated in this paper. We discuss three cases： 1） continuous, 2） discrete, and 3） a continuous system with a proportional pl...Consensus problems of first-order multi-agent systems with multiple time delays are investigated in this paper. We discuss three cases： 1） continuous, 2） discrete, and 3） a continuous system with a proportional plus derivative controller. In each case, the system contains simultaneous communication and input time delays. Supposing a dynamic multi-agent system with directed topology that contains a globally reachable node, the sufficient convergence condition of the system is discussed with respect to each of the three cases based on the generalized Nyquist criterion and the frequency-domain analysis approach, yielding conclusions that are either less conservative than or agree with previously published results. We know that the convergence condition of the system depends mainly on each agent’s input time delay and the adjacent weights but is independent of the communication delay between agents, whether the system is continuous or discrete. Finally, simulation examples are given to verify the theoretical analysis.展开更多
Conventional PI control encounters some problems when dealing with large lag process in the presence of parameter uncertainties.For the typical first-order process,an observerbased linear active disturbance rejection ...Conventional PI control encounters some problems when dealing with large lag process in the presence of parameter uncertainties.For the typical first-order process,an observerbased linear active disturbance rejection control（LADRC） scheme is presented to cope with the difficulties,and a reduced-order observer scheme is proposed further.Some quantitative dynamic results with regard to non-overshoot characteristics are obtained.Finally,the performance boundaries of LADRC and PI control are explicitly compared with each other,which shows that the former is more superior in most cases.展开更多
Aiming at developing p-type semiconductors and modulating the band gap for photoelectronic devices and band engineering, we present the ab initio numerical simulation of the effect of codoping ZnO with Al, N and Mg on...Aiming at developing p-type semiconductors and modulating the band gap for photoelectronic devices and band engineering, we present the ab initio numerical simulation of the effect of codoping ZnO with Al, N and Mg on the crystal lattice and electronic structure. The simulations are based on the Perdew-Burke-Ernzerhof generalised-gradient approximation in density functional theory. Results indicate that electrons close to the Fermi level transfer effectively when Al, Mg, and N replace Zn and O atoms, and the theoretical results were consistent with the experiments. The addition of Mg leads to the variation of crystal lattice, expanse of energy band, and change of band gap. These unusual properties are explained in terms of the computed electronic structure, and the results show promise for the development of next-generation photoconducting devices in optoelectronic information science and technology.展开更多
Generalized stacking-fault energies （GSFEs） of basal-plane stacking faults 11 and 12 in Mg alloys have been studied based on first-principles calculations, where 43 alloying elements were considered. It is found tha...Generalized stacking-fault energies （GSFEs） of basal-plane stacking faults 11 and 12 in Mg alloys have been studied based on first-principles calculations, where 43 alloying elements were considered. It is found that the most contributing features of alloying elements to GSFEs are bulk modulus, equilibrium volume, binding energy, atomic radius and ionization energy. Both bulk modulus and ionization energy exhibit positive relationships with GSFEs, and the others show opposite relationships. Multiple regressions have been performed to offer a quantitative prediction for basal-plane GSFEs in Mg-X systems. GSFEs, alloying effects of elements and the prediction model established within this work may provide guidelines for new Mg alloys design with better ductility.展开更多
The structural, elastic, and electronic properties of NiAI alloyed with rare earth element （REE） Ce have been investigated by using density functional theory （DFT）. It is found that Ce has a strong AI site prefere...The structural, elastic, and electronic properties of NiAI alloyed with rare earth element （REE） Ce have been investigated by using density functional theory （DFT）. It is found that Ce has a strong AI site preference and causes lattice distortion of NiAI. The calculation of elastic constants shows that Ce increased both the hardness and the ductility of NiAI, which could be explained by the formation of new ionic bonds between AI （and Ni） and Ce and the enhancement of covalent bonds in NisAl7Ce. Our results are in good agreement with the available experimental data and other theoretical results.展开更多
The surface segregation of La and its effect on the oxygen adsorption on a Mg （0001） surface for a coverage 0=-0.25 monolayer were performed by using first-principles calculations. The calculated results showed that...The surface segregation of La and its effect on the oxygen adsorption on a Mg （0001） surface for a coverage 0=-0.25 monolayer were performed by using first-principles calculations. The calculated results showed that La atoms preferred occupying surface sites to the bulk sites, which suggested the La surface segregation. When oxygen atoms adsorbed on a pure or La alloyed Mg （0001） surface, certain amount of heat would release, and La alloying made the heat released less, which might increase the ignition point of Mg alloy. Both Mg and La had strong atomic affinity with oxygen, so the oxidation film of Mg-La alloys consisted of MgO, La2O3. The denser La2O3 turned oxide film into free and close structure, and prevented oxygen from passing through the oxidation film. The La-O covalent bonding could explain why La2O3 was compact, and resulted in good ignition-proof of Mg-La alloys.展开更多
Thermodynamic assessment of Ti-Co-Cu ternary system has been carried out by combining first-principle calculation and CALPHAD method. Firstly, formation enthalpies of stable and hypothesized compounds were calculated ...Thermodynamic assessment of Ti-Co-Cu ternary system has been carried out by combining first-principle calculation and CALPHAD method. Firstly, formation enthalpies of stable and hypothesized compounds were calculated by first-principles method. Then, based on reported experimental information, a thermodynamic description of the Ti-Co-Cu ternary system was performed. Solution phases were treated as substitutional solutions of which excess Gibbs energies were formulated by Redlich-Kister polynomial, and the intermediate phases were described with sublattice models. All measured isothermal sections were reasonably reproduced. In addition, liquidus projection of this ternary system was further calculated, which may be useful for relevant materials processing.展开更多
The segregation behavior of alloying elements X（ X = Zr,V,Cr,Mn,Mo,W,Nb,Y） on the ferrite（ 100） /TiC（ 100） interface has been investigated using first principles method,and the work of separation and interface e...The segregation behavior of alloying elements X（ X = Zr,V,Cr,Mn,Mo,W,Nb,Y） on the ferrite（ 100） /TiC（ 100） interface has been investigated using first principles method,and the work of separation and interface energy of ferrite / TiC interfaces alloyed by these elements were also analyzed. The results indicated that all these alloying additives except Y were thermodynamically favorable because of the negative segregation energy,showing that they have the tendency to segregate to the ferrite / TiC interface. When the Fe atom in the ferrite /TiC interface is replaced by Y,Zr,or Nb,the adhesive strength of the interface will be weakened due to the lower separation work,larger interfacial energy,and weaker electron effects. However,the introduction of Cr,Mo,W,Mn and V will improve the stability of the ferrite / TiC interface through strong interaction between these elements and C,and Cr-doped interface is the most stable structure. Therefore,the Cr,Mo,W,Mn and V in ferrite side of the interface can effectively promote ferrite heterogeneous nucleation on TiC surface to form fine ferrite grain.展开更多
In order to improve the efficiency of 3D near-surface velocity model building, we develop a layer-stripping method using seismic first-arrival times. The velocity model within a Common Mid-Point （CMP） gather is assu...In order to improve the efficiency of 3D near-surface velocity model building, we develop a layer-stripping method using seismic first-arrival times. The velocity model within a Common Mid-Point （CMP） gather is assumed to be stratified into thin layers, and the velocity of each layer var- ies linearly with depth. The thickness and velocity of the top layer are estimated using minimum-offset first-arrival data in a CMP gather. Then the top layer is stripped and the second layer becomes a new top layer. After removing the effect of the top layer from the former first-arrival data, the new first-arrival data are obtained and then used to estimate the parameters of the second layer. In this manner, the velocity model, being regarded as that at a CMP location, is built layer-by-layer from the top to the bottom. A 3D near-surface velocity model is then formed using the velocity models at all CMP locations. The tests on synthetic and observed seismic data show that the layer-stripping method can be used to build good near-surface velocity models for static correction, and its computation speed is approximately hundred times faster than that of grid tomography.展开更多
Objective: The aim of this trial was to compare both the efficacy and the safety of a weekly nanoparticle albumin-bound paclitaxel(nab-paclitaxel) plus cisplatin vs. gemcitabine plus cisplatin in patients with advance...Objective: The aim of this trial was to compare both the efficacy and the safety of a weekly nanoparticle albumin-bound paclitaxel(nab-paclitaxel) plus cisplatin vs. gemcitabine plus cisplatin in patients with advanced non-small-cell lung cancer(NSCLC).Methods: A total of 84 participants received either 100 mg/m^2 nab-paclitaxel each week on d 1, 8 and 15 of a 28 day cycle, as well as cisplatin 75 mg/m^2 on d 1 every three weeks(nab-TP arm); or gemcitabine 1,000 mg/m^2 on d 1 and 8, plus cisplatin 75 mg/m^2 on d 1 every three weeks(GP arm). The primary end point was progression-free survival(PFS). The secondary end points were overall response rate(ORR) and overall survival(OS).Results: According to our analysis, the median PFS was 4.8 months for the nab-TP arm vs. 5.2 months for the GP arm(P=0.55). Analysis showed the median OS was 14.6 months for participants who were in the nab-TP arm vs. 15.1 months for those in the GP arm(P=0.94). Besides, nab-TP showed OS advantages over GP in patients harboring epidermal growth factor receptor(EGFR) mutation(26.7 vs. 15.3 months, P=0.046) and patients with a performance status of 0(23.5 vs. 14.7 months, P=0.020). It was found that incidences of drug-related grade 3 or 4 toxicities were comparable between the two treatment arms.Conclusions: Therefore, it can be seen that weekly nab-TP treatment has a similar efficacy and tolerability to GP treatment for patients who are undergoing their first-line treatment for NSCLC. It could be that survival differences among platinum doublets in the context of both EGFR mutation and performance status have the potential to be the basis for our further clinical trials.展开更多
The electronic structures and effective masses of the N mono-doped and Al N, Ga-N, In-N codoped ZnO system have been calculated by a first-principle method, and comparisons among different doping cases are made. Accor...The electronic structures and effective masses of the N mono-doped and Al N, Ga-N, In-N codoped ZnO system have been calculated by a first-principle method, and comparisons among different doping cases are made. According to the results, the impurity states in the codoping cases are more delocalised compared to the N mono-doping case, which means a better conductive behaviour can be obtained by codoping. Besides, compared to the Al-N and Ga-N codoping cases, the hole effective mass of In-N codoped system is much smaller, indicating the p-type conductivity can be more enhanced by In N codoping展开更多
Abstract A nonlinear stochastic optimal control strategy for minimizing the first-passage failure of quasi integrable Hamiltonian systems （multi-degree-of-freedom integrable Hamiltonian systems subject to light dampi...Abstract A nonlinear stochastic optimal control strategy for minimizing the first-passage failure of quasi integrable Hamiltonian systems （multi-degree-of-freedom integrable Hamiltonian systems subject to light dampings and weakly random excitations） is proposed. The equations of motion for a controlled quasi integrable Hamiltonian system are reduced to a set of averaged It6 stochastic differential equations by using the stochastic averaging method. Then, the dynamical programming equations and their associated boundary and final time conditions for the control problems of maximization of reliability and mean first-passage time are formulated. The optimal control law is derived from the dynamical programming equations and the control constraints. The final dynamical programming equations for these control problems are determined and their relationships to the backward Kolmogorov equation governing the conditional reliability function and the Pontryagin equation governing the mean first-passage time are separately established. The conditional reliability function and the mean first-passage time of the controlled system are obtained by solving the final dynamical programming equations or their equivalent Kolmogorov and Pontryagin equations. An example is presented to illustrate the application and effectiveness of the proposed control strategy.展开更多
AIM: To evaluate the efficacy of moxifloxacin-based sequential therapy(MBST) versus hybrid therapy as a first-line treatment for Helicobacter pylori(H. pylori) infection.METHODS: From August 2014 to January 2015, 284 ...AIM: To evaluate the efficacy of moxifloxacin-based sequential therapy(MBST) versus hybrid therapy as a first-line treatment for Helicobacter pylori(H. pylori) infection.METHODS: From August 2014 to January 2015, 284 patients with confirmed H. pylori infection were randomized to receive a 14-d course of MBST(MBST group, n = 140) or hybrid(Hybrid group, n = 144) therapy. The MBST group received 20 mg rabeprazole and 1 g amoxicillin twice daily for 7 d, followed by 20 mg rabeprazole and 500 mg metronidazole twice daily, and 400 mg moxifloxacin once daily for 7 d. The Hybrid group received 20 mg rabeprazole and 1 g amoxicillin twice daily for 14 d. In addition, the Hybrid group received 500 mg metronidazole and 500 mg clarithromycin twice daily for the final 7 d. Successful eradication of H. pylori infection was defined as a negative 13C-urea breath test 4 wk after the end of treatment. Patient compliance was defined as "good" if drug intake was at least 85%. H. pylori eradication rates, patient compliance with treatment, and adverse event rates were evaluated.RESULTS: The eradication rates in the intention-totreat(ITT) analysis were 91.4%(128/140; 95%CI: 90.2%-92.9%) in the MBST group and 79.2%(114/144; 95%CI: 77.3%-80.7%) in the Hybrid group(P = 0.013). The eradication rates in the perprotocol(PP) analysis were 94.1%(128/136; 95%CI: 92.9%-95.6%) in the MBST group and 82.6%(114/138; 95%CI: 80.6%-84.1%) in the Hybrid group(P = 0.003). The H. pylori eradication rate in the MBST group was significantly higher than that of the Hybrid group for both the ITT(P = 0.013) and the PP analyses(P = 0.003). Both groups exhibited full compliance with treatment(MBST/Hybrid group: 100%/100%). The rate of adverse events was 11.8%(16/136) and 19.6%(27/138) in the MBST and Hybrid group, respectively(P = 0.019). The majority of adverse events were mild-to-moderate in intensity; none were severe enough to cause discontinuation of treatment in either group.CONCLUSION: MBST was more effective and led to fewer adverse events than hybrid therapy as a first-line treatment for H. pylori infection.展开更多
We investigate the stability, diffusion, and impurity concentration of nitrogen in intrinsic tungsten single crystal employing a first-principles method, and find that a single nitrogen atom is energetically favourabl...We investigate the stability, diffusion, and impurity concentration of nitrogen in intrinsic tungsten single crystal employing a first-principles method, and find that a single nitrogen atom is energetically favourable for sitting at the octahedral interstitial site. A nitrogen atom prefers to diffuse between the two nearest neighboring octahedral interstitial sites with a diffusion barrier of 0.72 eV. The diffusion coefficient is determined as a function of temperature and expressed a.s D（N） = 1.66 ~ 10-7 exp（-O.72/kT）. The solubility of nitrogen is estimated in intrinsic tungsten in terms of Sieverts＇ law. The concentration of the nitrogen impurity is found to be 4.82 ~ 10-16 /~ 3 at a temperature of 600 K and a pressure of 1 Pa. A single nitrogen atom can easily sit in an off-vacancy-centre position close to the octahedral interstitial site. There exists a strong attraction between nitrogen and a vacancy with a large binding energy of 1.40 eV. We believe that these results can provide a good reference for the understanding of the behaviour of nitrogen in intrinsic tungsten.展开更多
基金Project supported by the National Natural Science Foundation of China （Grants Nos 10472091, 10332030 and 10502042） and the Graduate Starting Seed Fund of Northwestern Polytechnical University （Grant No Z200655）.
文摘In this paper, the effect of every parameter （including p, q, r, λ, τ） on the mean first-passage time （MFPT） is investigated in an asymmetric bistable system driven by colour-correlated noise. The expression of MFPT has been obtained by applying the steepest-descent approximation. Numerical results show that （1） the intensity of multiplicative noise p and the intensity of additive noise q play different roles in the MFPT of the system, （2） suppression appears on the curve of the MFPT with small λ （e.g. λ 〈 0.5） but there is a peak on the curve of the MFPT when λ is big （e.g. λ 〉 0.5）, and （3） with different values of r （e.g. r = 0.1, 0.5, 1.5）, the effort of τ on the MFPT is diverse.
文摘The treatment of metastatic colorectal cancer(mCRC)has evolved considerably in the last decade,currently allowing most mCRC patients to live more than two years.Monoclonal antibodies targeting the epidermal growth factor receptor(EGFR)and vascular endothelial growth factor play an important role in the current treatment of these patients.However,only antibodies directed against EGFR have a predictive marker of response,which is the mutation status of v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog(KRAS).Cetuximab has been shown to be effective in patients with KRAS wild-type mCRC.The CRYSTAL study showed that adding cetuximab to FOLFIRI(regimen of irinotecan,infusional fluorouracil and leucovorin)significantly improved results in the first-line treatment of KRAS wildtype mCRC.However,results that evaluate the efficacy of cetuximab in combination with oxaliplatin-based chemotherapy in this setting are contradictory.On the other hand,recent advances in the management of colorectal liver metastases have improved survival in these patients.Adding cetuximab to standard chemotherapy increases the response rate in patients with wild-type KRAS and can thus increase the resectability rate of liver metastases in this group of patients.In this paper we review the different studies assessing the efficacy of cetuximab in the first-line treatment of mCRC.
基金Project supported by National Natural Science Foundation of China(51372203,51332004,51571166)
文摘The electronic,mechanical and optical properties of La-and Sc-doped Y2O3 were investigated using firstprinciples calculations.Two doping sites of Sc and La in Y2O3 were modeled.The calculated values of the energy of formation show that the most energetically favorable site for a La atom in Y2O3 is a d-site Y atom,while for Sc a b-site Y atom is the more stable position.The calculated band gap shows a slight decrease with increasing La or Sc concentration.The calculated results for the mechanical and optical properties of Y(2-x)RxO3(R=Sc or La,0<x≤0.1875)show that La-or Sc-doped Y2O3 would have enhanced strength,and thus an ability of resisting external shocks,and increased hardness and mechanical toughness.These improved mechanical properties are achieved without sacrificing the optical properties of the doped compounds.So the doping of La or Sc in Y2O3 is permissible in the preparation of Y2O3 transparent ceramics,of course,doping of La or Sc will benefit the sintering of transparent ceramics.
基金financially supported by the National Natural Science Foundation of China (No. 51104070)the Special Funds for Postgraduate Student Innovation Program of Jiangxi University of Science and Technology (No. YC2012-X07)the Special Funds for Postgraduate Student Innovation Program of Jiangxi province (No. YC2013-S183)
文摘The band structure, density of states, Mulliken populations, and frontier orbital of spodumene crystal were calculated using the first-principles method based on the density functional theory（DFT） and further analyzed in detail. The calculation results reveal that the O in spodumene is the most active and easily links with H＋in the water, but the active Li is very low, so it is better to add activator to increase the concentrate grade and recovery rate of spodumene in the flotation process. Si–O bonds in spodumene crystal are mainly covalent, since the covalency of Al–O bonds is stronger than that of Li–O bonds,and minerals dissociate along the weakest Li–O bonds. In addition, the study of the frontier orbital indicates that both O and Si atoms have large contribution to the frontier orbital in the spodumene crystal. Oleate and dodecylamine are used as the collectors of spodumene. The results contribute to the understanding of crystal structures of spodumene, and can be used in guiding related practical applications.
基金Funded by the National Natural Science Foundation of China(Nos.51204147,51274175)the International Cooperation Project Supported by Ministry of Science and Technology of China(No.2011DFA50520)the Postgraduate Excellent Innovation Project of Shanxi Province(No.20133105)
文摘First-principles calculations have been carried out to investigate the structural stabilities, electronic structures and elastic properties of Mg17Al12, Al2Ca and Al4Sr phases. The optimized structural parameters are in good agreement with the experimental and other theoretical values. The calculated formation enthalpies and cohesive energies show that Al2Ca has the strongest alloying ability, and Al4Sr has the highest structural stability. The densities of states （DOS）, Mulliken electronic populations, and electronic charge density difference are obtained to reveal the underlying mechanism of structural stability. The bulk modulus, shear modulus, Young＇s modulus, and Poisson＇s ratio are estimated from the calculated elastic constants. The mechanical properties of these phases are further analyzed and discussed. The Gibbs free energy and Debye temperature are also calculated and discussed.
基金Project supported in part by the National Natural Science Foundation of China (Grant Nos. 60973114 and 61170249)in part by the Natural Science Foundation of CQCSTC (Grant Nos. 2009BA2024 and cstc2011jjA1320)in part by the State Key Laboratory of Power Transmission Equipment & System Securityand New Technology, Chongqing University (Grant No. 2007DA10512711206)
文摘Consensus problems of first-order multi-agent systems with multiple time delays are investigated in this paper. We discuss three cases： 1） continuous, 2） discrete, and 3） a continuous system with a proportional plus derivative controller. In each case, the system contains simultaneous communication and input time delays. Supposing a dynamic multi-agent system with directed topology that contains a globally reachable node, the sufficient convergence condition of the system is discussed with respect to each of the three cases based on the generalized Nyquist criterion and the frequency-domain analysis approach, yielding conclusions that are either less conservative than or agree with previously published results. We know that the convergence condition of the system depends mainly on each agent’s input time delay and the adjacent weights but is independent of the communication delay between agents, whether the system is continuous or discrete. Finally, simulation examples are given to verify the theoretical analysis.
基金supported by the National Natural Science Foundation of China(60774088)the National High Technology Research and Development Program of China(863 Program)(2009AA04Z132)the Specialized Research Fund for the Doctoral Program of Higher Education of China(20090031110029)
文摘Conventional PI control encounters some problems when dealing with large lag process in the presence of parameter uncertainties.For the typical first-order process,an observerbased linear active disturbance rejection control（LADRC） scheme is presented to cope with the difficulties,and a reduced-order observer scheme is proposed further.Some quantitative dynamic results with regard to non-overshoot characteristics are obtained.Finally,the performance boundaries of LADRC and PI control are explicitly compared with each other,which shows that the former is more superior in most cases.
基金Project supported by the National Basic Research Program of China(Grant No.2011CB606401)
文摘Aiming at developing p-type semiconductors and modulating the band gap for photoelectronic devices and band engineering, we present the ab initio numerical simulation of the effect of codoping ZnO with Al, N and Mg on the crystal lattice and electronic structure. The simulations are based on the Perdew-Burke-Ernzerhof generalised-gradient approximation in density functional theory. Results indicate that electrons close to the Fermi level transfer effectively when Al, Mg, and N replace Zn and O atoms, and the theoretical results were consistent with the experiments. The addition of Mg leads to the variation of crystal lattice, expanse of energy band, and change of band gap. These unusual properties are explained in terms of the computed electronic structure, and the results show promise for the development of next-generation photoconducting devices in optoelectronic information science and technology.
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0701202)the National Natural Science Foundation of China(General Program No.51474149 and Key Program No.51631006)
文摘Generalized stacking-fault energies （GSFEs） of basal-plane stacking faults 11 and 12 in Mg alloys have been studied based on first-principles calculations, where 43 alloying elements were considered. It is found that the most contributing features of alloying elements to GSFEs are bulk modulus, equilibrium volume, binding energy, atomic radius and ionization energy. Both bulk modulus and ionization energy exhibit positive relationships with GSFEs, and the others show opposite relationships. Multiple regressions have been performed to offer a quantitative prediction for basal-plane GSFEs in Mg-X systems. GSFEs, alloying effects of elements and the prediction model established within this work may provide guidelines for new Mg alloys design with better ductility.
基金supported by the National Natural Science Foundation of China under grant No.50871035
文摘The structural, elastic, and electronic properties of NiAI alloyed with rare earth element （REE） Ce have been investigated by using density functional theory （DFT）. It is found that Ce has a strong AI site preference and causes lattice distortion of NiAI. The calculation of elastic constants shows that Ce increased both the hardness and the ductility of NiAI, which could be explained by the formation of new ionic bonds between AI （and Ni） and Ce and the enhancement of covalent bonds in NisAl7Ce. Our results are in good agreement with the available experimental data and other theoretical results.
基金National Natural Science Foundation of China(50671069)Natural Science Foundation of Liaoning Province(20102173)the Experimental Central Director’s Foundation of Shenyang Normal University(Sy201103)
文摘The surface segregation of La and its effect on the oxygen adsorption on a Mg （0001） surface for a coverage 0=-0.25 monolayer were performed by using first-principles calculations. The calculated results showed that La atoms preferred occupying surface sites to the bulk sites, which suggested the La surface segregation. When oxygen atoms adsorbed on a pure or La alloyed Mg （0001） surface, certain amount of heat would release, and La alloying made the heat released less, which might increase the ignition point of Mg alloy. Both Mg and La had strong atomic affinity with oxygen, so the oxidation film of Mg-La alloys consisted of MgO, La2O3. The denser La2O3 turned oxide film into free and close structure, and prevented oxygen from passing through the oxidation film. The La-O covalent bonding could explain why La2O3 was compact, and resulted in good ignition-proof of Mg-La alloys.
基金financially supported by the National Natural Science Foundation of China (Grant No. 50671122)
文摘Thermodynamic assessment of Ti-Co-Cu ternary system has been carried out by combining first-principle calculation and CALPHAD method. Firstly, formation enthalpies of stable and hypothesized compounds were calculated by first-principles method. Then, based on reported experimental information, a thermodynamic description of the Ti-Co-Cu ternary system was performed. Solution phases were treated as substitutional solutions of which excess Gibbs energies were formulated by Redlich-Kister polynomial, and the intermediate phases were described with sublattice models. All measured isothermal sections were reasonably reproduced. In addition, liquidus projection of this ternary system was further calculated, which may be useful for relevant materials processing.
基金financially sponsored by National Natural Science Foundation of China(51304053)
文摘The segregation behavior of alloying elements X（ X = Zr,V,Cr,Mn,Mo,W,Nb,Y） on the ferrite（ 100） /TiC（ 100） interface has been investigated using first principles method,and the work of separation and interface energy of ferrite / TiC interfaces alloyed by these elements were also analyzed. The results indicated that all these alloying additives except Y were thermodynamically favorable because of the negative segregation energy,showing that they have the tendency to segregate to the ferrite / TiC interface. When the Fe atom in the ferrite /TiC interface is replaced by Y,Zr,or Nb,the adhesive strength of the interface will be weakened due to the lower separation work,larger interfacial energy,and weaker electron effects. However,the introduction of Cr,Mo,W,Mn and V will improve the stability of the ferrite / TiC interface through strong interaction between these elements and C,and Cr-doped interface is the most stable structure. Therefore,the Cr,Mo,W,Mn and V in ferrite side of the interface can effectively promote ferrite heterogeneous nucleation on TiC surface to form fine ferrite grain.
基金supported by the National Natural Science Foundation of China(Nos.41230318,41074077)the Specialized Research Fund for the Doctoral Program of Higher Education(No.20130132110023)the Fundamental Research Funds for the Central Universities of China(No.201413004)
文摘In order to improve the efficiency of 3D near-surface velocity model building, we develop a layer-stripping method using seismic first-arrival times. The velocity model within a Common Mid-Point （CMP） gather is assumed to be stratified into thin layers, and the velocity of each layer var- ies linearly with depth. The thickness and velocity of the top layer are estimated using minimum-offset first-arrival data in a CMP gather. Then the top layer is stripped and the second layer becomes a new top layer. After removing the effect of the top layer from the former first-arrival data, the new first-arrival data are obtained and then used to estimate the parameters of the second layer. In this manner, the velocity model, being regarded as that at a CMP location, is built layer-by-layer from the top to the bottom. A 3D near-surface velocity model is then formed using the velocity models at all CMP locations. The tests on synthetic and observed seismic data show that the layer-stripping method can be used to build good near-surface velocity models for static correction, and its computation speed is approximately hundred times faster than that of grid tomography.
文摘Objective: The aim of this trial was to compare both the efficacy and the safety of a weekly nanoparticle albumin-bound paclitaxel(nab-paclitaxel) plus cisplatin vs. gemcitabine plus cisplatin in patients with advanced non-small-cell lung cancer(NSCLC).Methods: A total of 84 participants received either 100 mg/m^2 nab-paclitaxel each week on d 1, 8 and 15 of a 28 day cycle, as well as cisplatin 75 mg/m^2 on d 1 every three weeks(nab-TP arm); or gemcitabine 1,000 mg/m^2 on d 1 and 8, plus cisplatin 75 mg/m^2 on d 1 every three weeks(GP arm). The primary end point was progression-free survival(PFS). The secondary end points were overall response rate(ORR) and overall survival(OS).Results: According to our analysis, the median PFS was 4.8 months for the nab-TP arm vs. 5.2 months for the GP arm(P=0.55). Analysis showed the median OS was 14.6 months for participants who were in the nab-TP arm vs. 15.1 months for those in the GP arm(P=0.94). Besides, nab-TP showed OS advantages over GP in patients harboring epidermal growth factor receptor(EGFR) mutation(26.7 vs. 15.3 months, P=0.046) and patients with a performance status of 0(23.5 vs. 14.7 months, P=0.020). It was found that incidences of drug-related grade 3 or 4 toxicities were comparable between the two treatment arms.Conclusions: Therefore, it can be seen that weekly nab-TP treatment has a similar efficacy and tolerability to GP treatment for patients who are undergoing their first-line treatment for NSCLC. It could be that survival differences among platinum doublets in the context of both EGFR mutation and performance status have the potential to be the basis for our further clinical trials.
基金Project supported by the Special Foundation for Young Scientists of Anhui Province,China (Grant No. 2009SQRZ097ZD)the Foundation of Anhui University of Architecture (Grant No. 20070601)
文摘The electronic structures and effective masses of the N mono-doped and Al N, Ga-N, In-N codoped ZnO system have been calculated by a first-principle method, and comparisons among different doping cases are made. According to the results, the impurity states in the codoping cases are more delocalised compared to the N mono-doping case, which means a better conductive behaviour can be obtained by codoping. Besides, compared to the Al-N and Ga-N codoping cases, the hole effective mass of In-N codoped system is much smaller, indicating the p-type conductivity can be more enhanced by In N codoping
基金The project supported by the National Natural Science Foundation of China(10332030)the Special Fund for Doctor Programs in Institutions of Higher Learning of China(20060335125)
文摘Abstract A nonlinear stochastic optimal control strategy for minimizing the first-passage failure of quasi integrable Hamiltonian systems （multi-degree-of-freedom integrable Hamiltonian systems subject to light dampings and weakly random excitations） is proposed. The equations of motion for a controlled quasi integrable Hamiltonian system are reduced to a set of averaged It6 stochastic differential equations by using the stochastic averaging method. Then, the dynamical programming equations and their associated boundary and final time conditions for the control problems of maximization of reliability and mean first-passage time are formulated. The optimal control law is derived from the dynamical programming equations and the control constraints. The final dynamical programming equations for these control problems are determined and their relationships to the backward Kolmogorov equation governing the conditional reliability function and the Pontryagin equation governing the mean first-passage time are separately established. The conditional reliability function and the mean first-passage time of the controlled system are obtained by solving the final dynamical programming equations or their equivalent Kolmogorov and Pontryagin equations. An example is presented to illustrate the application and effectiveness of the proposed control strategy.
文摘AIM: To evaluate the efficacy of moxifloxacin-based sequential therapy(MBST) versus hybrid therapy as a first-line treatment for Helicobacter pylori(H. pylori) infection.METHODS: From August 2014 to January 2015, 284 patients with confirmed H. pylori infection were randomized to receive a 14-d course of MBST(MBST group, n = 140) or hybrid(Hybrid group, n = 144) therapy. The MBST group received 20 mg rabeprazole and 1 g amoxicillin twice daily for 7 d, followed by 20 mg rabeprazole and 500 mg metronidazole twice daily, and 400 mg moxifloxacin once daily for 7 d. The Hybrid group received 20 mg rabeprazole and 1 g amoxicillin twice daily for 14 d. In addition, the Hybrid group received 500 mg metronidazole and 500 mg clarithromycin twice daily for the final 7 d. Successful eradication of H. pylori infection was defined as a negative 13C-urea breath test 4 wk after the end of treatment. Patient compliance was defined as "good" if drug intake was at least 85%. H. pylori eradication rates, patient compliance with treatment, and adverse event rates were evaluated.RESULTS: The eradication rates in the intention-totreat(ITT) analysis were 91.4%(128/140; 95%CI: 90.2%-92.9%) in the MBST group and 79.2%(114/144; 95%CI: 77.3%-80.7%) in the Hybrid group(P = 0.013). The eradication rates in the perprotocol(PP) analysis were 94.1%(128/136; 95%CI: 92.9%-95.6%) in the MBST group and 82.6%(114/138; 95%CI: 80.6%-84.1%) in the Hybrid group(P = 0.003). The H. pylori eradication rate in the MBST group was significantly higher than that of the Hybrid group for both the ITT(P = 0.013) and the PP analyses(P = 0.003). Both groups exhibited full compliance with treatment(MBST/Hybrid group: 100%/100%). The rate of adverse events was 11.8%(16/136) and 19.6%(27/138) in the MBST and Hybrid group, respectively(P = 0.019). The majority of adverse events were mild-to-moderate in intensity; none were severe enough to cause discontinuation of treatment in either group.CONCLUSION: MBST was more effective and led to fewer adverse events than hybrid therapy as a first-line treatment for H. pylori infection.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.50871009 and 51101135)the National Magnetic Confinement Fusion Program,China(Grant No.2009GB106003)
文摘We investigate the stability, diffusion, and impurity concentration of nitrogen in intrinsic tungsten single crystal employing a first-principles method, and find that a single nitrogen atom is energetically favourable for sitting at the octahedral interstitial site. A nitrogen atom prefers to diffuse between the two nearest neighboring octahedral interstitial sites with a diffusion barrier of 0.72 eV. The diffusion coefficient is determined as a function of temperature and expressed a.s D（N） = 1.66 ~ 10-7 exp（-O.72/kT）. The solubility of nitrogen is estimated in intrinsic tungsten in terms of Sieverts＇ law. The concentration of the nitrogen impurity is found to be 4.82 ~ 10-16 /~ 3 at a temperature of 600 K and a pressure of 1 Pa. A single nitrogen atom can easily sit in an off-vacancy-centre position close to the octahedral interstitial site. There exists a strong attraction between nitrogen and a vacancy with a large binding energy of 1.40 eV. We believe that these results can provide a good reference for the understanding of the behaviour of nitrogen in intrinsic tungsten.
