广义系统的Hamilton矩阵与H_2代数Riccati方程的稳定化解

研究线性连续广义系统的 Hamilton矩阵及 H2 代数 Riccati方程 .提出一个标准的广义H2 代数 Riccati方程及对应的 Hamilton矩阵 ,给出该 Hamilton矩阵的几个重要性质 .在此基础上 ,得到该广义 H2 代数 Riccati方程的稳定化解存在的一个充分条件并给出求解方法 .此条件具有一般性 ,主要定理是正常系统相应结果的推广 .

重视化解不稳定因素 调整资源开发中的利益关系

目前在社会总体和谐下仍有一些不稳定因素,尤其是水电能源、矿藏等自然资源开发中的利益冲突问题。处理资源开发中的利益矛盾应以科学发展观为指导思想,按照"兼顾、统筹、分享"的原则调整资源开发中的利益关系。

Theoretical Aspects on Doped-Zirconia for Solid Oxide Fuel Cells:from Structure to Conductivity

Solid oxide fuel cells(SOFCs)are regarded to be a key clean energy system to convert chemical energy(e.g.H_(2) and O_(2))into electrical energy with high efficiency,low carbon footprint,and fuel flexibility.The electrolyte,typically doped zirconia,is the"state of the heart"of the fuel cell technologies,determining the performance and the operating temperature of the overall cells.Yttria stabilized zirconia(YSZ)have been widely used in SOFC due to its excellent oxide ion conductivity at high temperature.The composition and temperature dependence of the conductivity has been hotly studied in experiment and,more recently,by theoretical simulations.The characterization of the atomic structure for the mixed oxide system with different compositions is the key for elucidating the conductivity behavior,which,however,is of great challenge to both experiment and theory.This review presents recent theoretical progress on the structure and conductivity of YSZ electrolyte.We compare different theoretical methods and their results,outlining the merits and deficiencies of the methods.We highlight the recent results achieved by using stochastic surface walking global optimization with global neural network potential(SSW-NN)method,which appear to agree with available experimental data.The advent of machine-learning atomic simulation provides an affordable,efficient and accurate way to understand the complex material phenomena as encountered in solid electrolyte.The future research directions for design better electrolytes are also discussed.

Stabilizing CuO photocathode with a Cu_(3)N protection shell

CuO,as a promising photocathode material,suffers from severe photocorrosion in photoelectrochemical water splitting applications.Herein,a Cu_(3)N protection shell was used to protect the CuO photocathode for the first time to effectively suppress the photocorrosion of CuO.Consequently,the Cu_(3)N‐protected CuO photocathode shows improved stability,retaining 80% of its initial current density in a 20‐min test,while only 10%of the initial current density can be retained for the bare photocathode.This work may provide an important strategy for using Cu_(3)N shells to stabilize unstable photocathodes.

Metastable-phaseβ-Fe_(2)O_(3) photoanodes for solar water splitting with durability exceeding 100 h

Planar films of pure and Ti^(4+)-dopedβ-Fe_(2)O_(3)were prepared by a spray pyrolysis method.X-ray diffraction patterns and Raman spectra of the metastableβ-Fe_(2)O_(3)film showed that its thermal stability was significantly improved because of covalent bonds in the interfaces between the film and substrate,while only weak Van der Waals bonds existed at the interfaces within the particle-assembledβ-Fe_(2)O_(3)film prepared by electrophoretic deposition.The as-prepared planar films were thus able to withstand higher annealing temperature and stronger laser irradiation power in comparison with theβ-Fe_(2)O_(3)particle-assembly.Ti^(4+)doping was used to increase the concentration of carriers in the metastableβ-Fe_(2)O_(3)film.Compared with pureβ-Fe_(2)O_(3)photoanodes,the highest saturated photocurrent for water splitting over the Ti^(4+)-dopedβ-Fe_(2)O_(3)photoanode was increased by a factor of approximately three.Theβ-Fe_(2)O_(3)photoanode exhibited photochemical stability for water splitting for a duration exceeding 100 h,which indicates its important potential application in solar energy conversion.

Effects of different numerical algorithms on simulation of chemical dissolution-front instability in fluid-saturated porous rocks

Many scientific and engineering problems need to use numerical methods and algorithms to obtain computational simulation results because analytical solutions are seldom available for them.The chemical dissolution-front instability problem in fluid-saturated porous rocks is no exception.Since this kind of instability problem has both the conventional(i.e.trivial)and the unconventional(i.e.nontrivial)solutions,it is necessary to examine the effects of different numerical algorithms,which are used to solve chemical dissolution-front instability problems in fluid-saturated porous rocks.Toward this goal,two different numerical algorithms associated with the commonly-used finite element method are considered in this paper.In the first numerical algorithm,the porosity,pore-fluid pressure and acid/solute concentration are selected as basic variables,while in the second numerical algorithm,the porosity,velocity of pore-fluid flow and acid/solute concentration are selected as basic variables.The particular attention is paid to the effects of these two numerical algorithms on the computational simulation results of unstable chemical dissolution-front propagation in fluid-saturated porous rocks.The related computational simulation results have demonstrated that:1)the first numerical algorithm associated with the porosity-pressure-concentration approach can realistically simulate the evolution processes of unstable chemical dissolution-front propagation in chemical dissolution systems.2)The second numerical algorithm associated with the porosity-velocity-concentration approach fails to simulate the evolution processes of unstable chemical dissolution-front propagation.3)The extra differential operation is the main source to result in the failure of the second numerical algorithm.

Effect of Biodiesel on Oxidation Stability, Detergency and Antiwear Ability of Diesel Oil

Different contents of biodiesel and petrodiesel were incorporated into diesel engine oils. The oxidative stability, detergency and antiwear performance of the formulated diesel oils were evaluated. The results indicated that, compared with petrodiesel, biodiesel was more liable to promote oxidation degradation of diesel oils, leading to worse oxidative stability, detergency and antiwear ability of the oils.

Effect of Complexation with Hydroxylpropyl-β-Cyclodextrin on Solubility, Dissolution Rate and Chemical Stability of Prostaglandin E1

Aim To study the effect of complexation with hydroxylpropyl-β-cyclodextrin(HP-β-CD) on the solubility, dissolution rate and chemical stability of prostaglandin E_1 (PGE_1) ,thereby providing a basis for preparing a stable solid or aqueous preparation of PGE_1 formulatedwith HP-β-CD. Methods The effect of HP-β-CD on the solubility of PGE_1 was studied by phasesolubility method. The formation of inclusion complexes of PGE_1 with HP-β-CD in the aqueoussolution was confirmed by UV spectra, circular dichroism spectroscopy, and that in the solid stateby IR spectra and X-ray diffractome-try. An solid inclusion complex of PGE_1 with HP-β-CD wasprepared by lyophilization. The dissolution rate and stability of the inclusion complex weredetermined and compared with those of PGE_1 alone. Meanwhile, the stability of PGE_1 aqueoussolutions in the presence of HP-β-CD was studied under different pH conditions. Results Thesolubility of PGE_1 increased linearly with increasing HP-β-CD concentration in various pH bufferedsolutions, showing typical A_L-type phase solubility diagrams. The stability and dissolution rateof the solid inclusion complex of PGE_1 were significantly increased, compared with those of purePGE_1 . The stability of PGE_1 in HP-β-CD solutions was also obviously improved under acidic andbasic conditions, but the stabilizing effect was absent under neutral conditions. Conclusions Thesolubility,dissolution rate and chemical stability of PGE_1 are markedly improved by complexationwith HP-β-CD: It is quite possible to prepare a stable PGE_1 inclusion complex-containing soliddosage forms, but almost impossible to obtain a stable aqueous preparation of PGE_1 formulated withHP-β-CD.

Stability,detonation properties and pyrolysis mechanisms of polynitrotriprismanes C_6H_(6-n)(NO_2)_n (n=1-6)

To further test whether polynitriprismanes are capable of being potential high energy density materials （HEDMs）, extensive theoretical calculations were carried out to investigate on a series of polynitrotriprismanes （PNNPs）： C6H6-.（NO2）. （n=1-6） Heats of formation （HOFs）, strain energies （SE）, and disproportionation energy （DE） were obtained using B3LYP/6-311＋G（2df, 2p）//B3LYP/6-31G＊ method by designing different isodesmic reactions, respectively. Detonation properties of PNNPs were obtained by the well-known KAMLET-JACOBS equations, using the predicted densities （p） obtained by Monte Carlo method and HOFs. It is found that they increase as the number of nitro groups n varies from 1 to 6, and PNNPs with n〉4 have excellent detonation properties The relative stability and the pyrolysis mechanism of PNNPs were evaluated by the calculated bond dissociation energy （BDE）. The comparison of BDE suggests that rupturing the C--C bond is the trigger for thermolysis of PNNPs. The computed BDE for cleavage of C--C bond （88.5 kJ/mol） further demonstrates that only the hexa-nitrotriprismane can be considered to be the target of HEDMs.

Operational Robustness Studies of Solid Oxide Electrolysis Stacks

Stacks of solid oxide cells which can be run as both electrolysers and fuel cells have been tested for robustness towards simulations of stress conditions which are likely to occur during operation of solid oxide electrolysis systems, for which the energy supply comes from renewable sources, such as wind mills and solar cells. Such conditions are thermo mechanical stress conditions as well as loss of fuel and air supply. The cells have Ni/YSZ （yttria stabilized zirconia） fuel electrodes, YSZ electrolytes, and LSCF （lanthanum strontium cobalt ferrite） oxygen electrodes with a CGO （cerium gadolinium oxide） barrier layer. In the stacks, the cells are separated by chromium rich steel interconnects. The robustness tests of stacks are one step in the development of a SOEC （solid oxide electrolysis cell） core; the core component in a SOEC system, including one or more SOEC stacks, heaters, heat exchangers, insulation, and feed troughs.

3D ordered mesoporous cobalt ferrite phosphides for overall water splitting

Developing low-cost and earth-abundant electrocatalysts with high performance for electrochemical water splitting is a challenging issue. Herein, we report a facile and effective way to fabricate three-dimension(3D) ordered mesoporous Co1-xFexP(x=0, 0.25, 0.5, 0.75) electrocatalyst.Benefiting from 3D ordered mesoporous pore channels and composition optimization, the Co0.75Fe0.25 P exhibits excellent electrocatalytic activities with low overpotentials of 270 and 209 mV at 10 mA cm^-2 for oxygen evolution reaction(OER)and hydrogen evolution reaction(HER), respectively, in the alkaline electrolyte along with a durable electrochemical stability. In addition, as both the cathode and anode, the Co0.75Fe0.25P also exhibits superior electrolysis water splitting performance with only an applied voltage of 1.63 V to attain a current density of 10 m A cm^-2 without obvious decay for 18 h,indicating that the Co0.75Fe0.25P is an efficient electrocatalyst for overall water splitting.

S, N co-doped carbon nanotube-encapsulated core-shelled CoS2@Co nanoparticles： efficient and stable bifunctional catalysts for overall water splitting

Hydrogen, serving as a clean, sustainable energy source, may be mainly produced from electrolysis water. Herein, we report cobalt disulphide encapsulated in self-catalyzed carbon nanotubes （S, N-CNTs/ CoS2@Co） serving as a bifunctional catalyst, which exhibits excellent hydrogen evolution reaction perfor-mance （10.0 mAcm^-2 at 0.112 V, and low Tafel slope for 104.9 mV dec^-1 ） and oxygen evolution reaction performance （10.0 mAcm^-2 at 1.57 V, and low Tafel slope for 76.1 mV dec^-1）, meanwbile with a strong stability at various current densities. In-depth study reveals that the excellent catalytic properties can be mainly attributed to the increased catalytic sites induced by S, N co-doping, the improved electronic con-ductivity derived from the carbon nanotubes, and Mott-Schottky effect between the metal cobalt and semiconductive cobalt disulfide. Notably, when the bifunctional catalysts are applied to overall water splitting, a low potential of 1.633 V at the current density of 10.0 mAcm^-2 is achieved, which can com-pete with the precious metal catalyst benchmarks in alkaline media, demonstrating its promising prac-ticability in the realistic water splitting application. This work elucidates a practicable way to the design of transition metal and nano-carbon composite catalysts for a broad application in the fields of energy chemistry.

Geometric approach to the stability analysis of the periodic solution in a semi-continuous dynamic system

Integrated pest management （IPM） is a long-term management strategy and has been proved to be more effective in pest control. To well-understand the mechanism and effect of the action of IPM, the geometric theory of the involved semi-continuous dynamic systems is becoming more and more important. In this work, a geometric approach is applied to analyze the stability of the positive order-one periodic solution in semi-continuous dynamic systems. A stability criterion to test the stability of the order-one periodic solution is established. As an application, a stage-structure model involved chemical control is presented to show the efficiency of the proposed method. The sufficient conditions to insure the existence of the periodic solution are provided. In addition, the number and the stability of the periodic solutions are discussed accordingly. The simulations are carried out to verify the results.

Effective conversion of cellobiose and glucose to sorbitol using non-noble bimetallic NiCo/HZSM-5 catalyst

The tandem hydrolysis and hydrogenation of saccharides into sorbitol is an especially attractive reaction in the conversion of biomass. Here, an economical and efficient bimetallic catalyst for the transformation of glucose and cellobiose into sorbitol is reported. Non-precious metal based catalysts such as NiCo, Ni, and Co, were prepared via modified impregnation method, and NiCo/HZSM-5 showed superior performance for the synthesis of sorbitol(86.9% from cellobiose, 98.6% from D-glucose).Various characterizations, such as Brunner-Emmet-Teler(BET), X-ray diffraction(XRD), transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy(XPS), confirmed that NiCo alloy formed and highly dispersed in NiCo/HZSM-5 catalyst. The high performance of fabricated catalyst would be attributed to the formation of nickel-cobalt alloy over HZSM-5 zeolite surface. High temperature and H_2 pressure were favorable for the tandem hydrolysis and hydrogenation reaction. Besides,the reaction pathway was also proposed based on the kinetics study. Cellobitol was detected as the intermediate in the reaction mixture. Furthermore, in the catalytic stability study, it was found that active metal species of NiCo/HZSM-5 were stable. The deactivation of catalyst would be due to the covering of acidic sites over NiCo/HZSM-5.

Solid electrolyte interphase in water-in-salt electrolytes

The water-in-salt strategy successfully expands the electrochemical window of the aqueous electrolyte from1.23 to~3.0 V,which can lead to a breakthrough in the energy output of the aqueous battery system while maintaining the advantage of high safety.The expanded electrochemical window of the water-in-salt electrolytes can be ascribed to the decreased water activity and the solid electrolyte interphase formed on the anode.The solid electrolyte interphase in the aqueous system is not fully understood,and the basic composition,the structure,and the formation mechanism are still cloaked in mystery.This perspective summarizes the published research with emphasis on the most possible formation mechanism and composition of the interphase layer in the aqueous system.Further understanding of the interphase as well as rounded assessment of the water-in-salt electrolyte in practical operating conditions is encouraged.The full understanding of the interface will guide the design of aqueous electrolytes and help to build novel aqueous batteries with high safety and high energy density.