Enhancing the stability of Ni Fe-layered double hydroxide nanosheet array for alkaline seawater oxidation by Ce doping

Electrocatalytic hydrogen production from seawater holds enormous promise for clean energy generation.Nevertheless,the direct electrolysis of seawater encounters significant challenges due to poor anodic stability caused by detrimental chlorine chemistry.Herein,we present our recent discovery that the incorporation of Ce into Ni Fe layered double hydroxide nanosheet array on Ni foam(Ce-Ni Fe LDH/NF)emerges as a robust electrocatalyst for seawater oxidation.During the seawater oxidation process,CeO_(2)is generated,effectively repelling Cl^(-)and inhibiting the formation of Cl O-,resulting in a notable enhancement in the oxidation activity and stability of alkaline seawater.The prepared Ce-Ni Fe LDH/NF requires only overpotential of 390 m V to achieve the current density of 1 A cm^(-2),while maintaining long-term stability for 500 h,outperforming the performance of Ni Fe LDH/NF(430 m V,150 h)by a significant margin.This study highlights the effectiveness of a Ce-doping strategy in augmenting the activity and stability of materials based on Ni Fe LDH in seawater electrolysis for oxygen evolution.

Ballistic Testing and Thermal Behavior of Cast Double-base Propellant Containing BuNENA

Preparation of cast double-propellant grains depends on the ability of nitrocellulose powder to swell and coalesce into a coherent mass when treated with a suitable solvent.The cast double-base process has been developed into a highly versatile technique for manufacturing solid rocket charges.Propellants manufactured by this process provide a wide range of energies and burning rates.Successful preparation of cast double-base propellant grains has been performed using compatible casting liquid with the casting powder.BuNENA was used as an energetic plasticizer for manufacturing of casting powder.Burning rate measurements have been performed using closed bomb SV-2to investigate the burning behavior along a wide range of operating pressure.Plateau burning had been detected in pressure range(50-70)×105 Pa for the composition included BuNENA.DTA and TGA thermal analysis were conducted to evaluate the thermal behavior of the prepared cast double-base propellants.Results from DTA were used to calculate the apparent activation energy.

Solid base catalysts derived from Ca-M-Al(M = Mg, La, Ce, Y) layered double hydroxides for dimethyl carbonate synthesis by transesterification of methanol with propylene carbonate

Composite solid base catalysts derived from Ca‐M‐Al(M=Mg,La,Ce,Y)layered double hydroxides(LDH)were synthesized,characterized and applied to the transesterification of methanol with propylene carbonate.X‐ray diffraction analyses of the catalysts show that all of the catalysts were in the form of composite oxides.Compared with the Ca‐Al LDH catalyst,the specific surface areas and pore volumes of the catalysts were increased with the introduction of Mg,La or Ce.The catalytic performance of these catalysts increases in the order of Ca‐Y‐Al<Ca‐Al<Ca‐Ce‐Al<Ca‐La‐Al<Ca‐Mg‐Al,which is consistent with the total surface basic amounts of these materials and the formation of especially strong basic sites following modification with Mg and La.The Ca‐Mg‐Al catalyst shows the highest(Ca+Mg):Al atomic ratio,indicating that it likely contains more unsaturated O2?ions,providing it with the highest concentration of very strong basic sites.The recyclability of these catalysts is improved following the addition of Mg,La,Ce or Y,with the Ca‐Mg‐Al maintaining a high level of activity after ten recycling trials.X‐ray diffraction analyses of fresh and used Ca‐Mg‐Al demonstrate that this catalyst is exceptionally stable,which could be of value in practical applications related to heterogeneous catalysis.

Common Base Four-Finger InGaAs/InP Double Heterojunction Bipolar Transistor with Maximum Oscillation Frequency 535 GHz

A common base four-finger InOaAs/InP double heterojunction bipolar transistor with 535 OHz fmax by using the 0.5 μm emitter technology is fabricated. Multi-finger design is used to increase the input current. Common base configuration is compared with common emitter configuration, and shows a smaller K factor at high frequency span, indicating a larger breakpoint frequency of maximum stable gain/maximum available gain （MSG/MAG） and thus a higher gain near the cut-off frequency, which is useful in THz amplifier design.

Novel aspects for thermal stability studies and shelf life assessment of modified double-base propellants

Modified DB propellants, based on energetic nitramine(RDX) were manufactured by solventless extrusion process. Thermal stability and shelf life assessment of modified DB propellant were investigated. Shelf life assessment was evaluated using Van’t Hoff’s formula and artificial aging at 70℃ up to120 days. Quantification of total heat released and heat flow with aging time was conducted using differential scanning calorimetry(DSC) and thermal activity monitoring(TAMIII) respectively. Modified DB formulation based on 20 wt % RDX demonstrated enhanced thermal stability in terms of controlled heat flow, and slow decomposition reactions at elevated temperature. This formulation demonstrated extended service life up to 56 years compared with reference formulation. These novel finding was ascribed to the high thermal stability of RDX and its compatibility with DB constituents. This manuscript shaded the light on novel and effective approach for thermal stability via monitoring thermal activity with aging.

Chemical stability, thermal behavior, and shelf life assessment of extruded modified double-base propellants

Double base propellant suffers from lack of chemical stability; this could result in self ignition during storing. Modified double base(MDB) propellant based on stoichiometric binary mixture of oxidizermetal fuel(Ammonium perchlorate/Aluminum), and energetic nitramines(HMX) offered enhanced thrust as well as combustion characteristics. This study is devoted to evaluate the impact of such energetic additives on thermal behavior, chemical stability, and shelf life. Extruded MDB formulations were manufactured by extrusion process. Artificial aging at 80℃ for 28 days was conducted. Shelf life assessment was performed using Van't Hoff's equation. Quantification of evolved NOxgases with aging time was performed using quantitative stability tests. MDB formulation based on HMX demonstrated extended service life of 16 years compared with(AP/Al)-MDB which demonstrated 9 years. This finding was ascribed to the reactivity of AP with nitroglycerin with the formation of perchloric acid. Thermal behavior of aged MDB, exhibited an increase in heat released with time; this was ascribed to the autocatalytic thermal degradation during artificial aging. The increase in released heat by 31% was found to be equivalent to evolved NOx gases of 6.2 cm^3/5 g and 2.5 cm^3/1 g for Bergmann-Junk test, and Vacuum stability test respectively. This manuscript shaded the light on a novel approach to quantify evolved NOx gases to heat released with aging time. MDB based on HMX offered balanced ballistic performance,chemical stability, and service life.

Injection modulation of p^+-n emitter junction in 4H-SiC light triggered thyristor by double-deck thin n-base

To overcome hole-injection limitation of p^＋-n emitter junction in 4H-SiC light triggered thyristor, a novel high- voltage 4H-SiC light triggered thyristor with double-deck thin n-base structure is proposed and demonstrated by two- dimensional numerical simulations. In this new structure, the conventional thin n-base is split to double-deck. The hole- injection of p^＋-n emitter junction is modulated by modulating the doping concentration and thickness of upper-deck thin n- base. With double-deck thin n-base, the current gain coefficient of the top pnp transistor in 4H-SiC light triggered thyristor is enhanced. As a result, the triggering light intensity and the turn-on delay time of 4H-SiC light triggered thyristor are both reduced. The simulation results show that the proposed 10-kV 4H-SiC light triggered thyristor is able to be triggered on by 500-mW/cm^2 ultraviolet light pulse. Meanwhile, the turn-on delay time of the proposed thyristor is reduced to 337 ns.

Non-ideal effect in 4H-SiC bipolar junction transistor with double Gaussian-doped base

The non-ideal effect of 4H-SiC bipolar junction transistor （BJT） with a double Gaussian-doped base is characterized and simulated in this paper. By adding a specific interface model between SiC and SiO2, the simulation results are in good agreement with the experiment data. An obvious early effect is found from the output characteristic. As the temperature rises, the early voltage increases, while the current gain gradually decreases, which is totally different from the scenario of silicon BJT. With the same effective Gummet number in the base region, the double Gaussian-doped base structure can realize higher current gain than the single base BJT due to the built-in electric field, whereas the early effect will be more salient. Besides, the emitter current crowding effect is also analyzed. Due to the low sheet resistance in the first highly- doped base epilayer, the 4H-BJT with a double base has more uniform emitter current density across the base-emitter junction, leading to better thermal stability.

Novel approach to quantify the chemical stability and shelf life of modified double-base propellants

Double-base(DB) propellant is vulnerable to auto-catalytic decomposition reactions during storing with the evolution of nitrogen oxides. Modified DB propellant based on energetic nitramines(RDX) can offer enhanced thrust and action time. This study is devoted to evaluate the impact of RDX on chemical stability and shelf life of DB propellant. Extruded modified DB propellant based on RDX was manufactured by solventless extrusion process. Shelf life assessment was performed using an artificial aging at70 ℃ up to 120 days and employing Van't Hoffs formula. Quantification of evolved NOx gases and stabilizer depletion with aging time was conducted using Bergmann-Junk test and HPLC respectively.Modified DB formulation based on RDX 20 wt % demonstrated enhanced chemical stability and extended service life up to 46 years compared with reference formulation. This finding was ascribed to the high chemical and thermal stability of RDX as well as its compatibility with DB constituents; no side chemical reactions could take place during storing. This manuscript shaded the light on RDX as effective energetic constituent that offered DB propellants with enhanced performance, good chemical stability, and extended service life.

An Improved Double r-iteration IOD Method for GEO UCTs Based on SBSS System

The purpose of initial orbit determination,especially in the case of angles-only data for observation,is to obtain an initial estimate that is close enough to the true orbit to enable subsequent precision orbit determination processing to be successful.However,the classical angles-only initial orbit determination methods cannot deal with the observation data whose Earth-central angle is larger than 360°.In this paper,an improved double r-iteration initial orbit determination method to deal with the above case is presented to monitor geosynchronous Earth orbit objects for a spacebased surveillance system.Simulation results indicate that the improved double r-iteration method is feasible,and the accuracy of the obtained initial orbit meets the requirements of re-acquiring the object.

Theoretical study on the mechanism for the excited-state double proton transfer process of an asymmetric Schiff base ligand

Excited-state double proton transfer(ESDPT)in the 1-[(2-hydroxy-3-methoxy-benzylidene)-hydrazonomethyl]-naphthalen-2-ol(HYDRAVH_(2))ligand was studied by the density functional theory and time-dependent density functional theory method.The analysis of frontier molecular orbitals,infrared spectra,and non-covalent interactions have crossvalidated that the asymmetric structure has an influence on the proton transfer,which makes the proton transfer ability of the two hydrogen protons different.The potential energy surfaces in both S_(0)and S_1 states were scanned with varying O-H bond lengths.The results of potential energy surface analysis adequately proved that the HYDRAVH_(2)can undergo the ESDPT process in the S_1 state and the double proton transfer process is a stepwise proton transfer mechanism.Our work can pave the way towards the design and synthesis of new molecules.

A Study of Estimating the Safe Storage Life, Self-accelerating Decomposition Temperature and Critical Temperature of Thermal Explosion of Double-base Propellant Using Isothermal and Non-isothermal Decomposition Behaviours

A method of estimating the safe storage life （τ）, self-accelerating decomposition temperature （TsADT） and critical temperature of thermal explosion （Tb） of double-base propellant using isothermal and non-isothermal decomposition behaviours is presented. For double-base propellant composed of 56±1wt% of nitrocellulose （NC）, 27±0.5wt% of nitroglycerine （NG）, 8.15±0.15wt% of dinitrotoluene （DNT）, 2.5±0.1wt% of methyl centralite, 5.0±0.15wt% of catalyst and 1.0±0.1wt% of other, the values of r of 49.4 years at 40℃, of TSAOT of 151.35℃ and of Tb of 163.01℃ were obtained.

Synthesis and Properties of Double Calix[4]arene Derivatives Linked by Schiff-base in the Lower Rim

25,27-bis-(2-aminoethoxy)-p-tert-butylcalix[4]arene was linked to double calix[4]arene derivatives by the Schiff-base moiety in its lower rim. They behave strong ability to complex with Ph2+, Cu2+ and Co2+.

Combustion Properties of Metal Particles as Components of Modified Double-Base Propellants

Metal particles such as aluminum（ Al）,magnesium（ Mg）,boron（ B） and nickel（ Ni）,as well as Mg/Al alloy（ Mg/Al = 3/4） are currently the most widely used ingredients in modified doublebase propellants. In this contribution,the combustion properties of the metal species are studied by means of the high-speed photography technique and the non-contact wavelet-based measurement of flame temperature distribution. The combustion process of the Al,Mg and Mg/Al samples shows both gas phase reaction and surface oxidation,which yield volatile and nonvolatile products,corresponding to the oxide and suboxide respectively. However,the combustion of B and Ni shows only gas phase reaction,due to their high melting point as well as high enthalpy of vaporization. In addition to the experiments,a hypothetical combustion model has been proposed to clarify the combustion characteristics of metal species in modified double-base propellants.

Double设计在对称化L_2-偏差下的均匀性

二水平部分因子设计在工农业生产、科学实验等领域得到广泛应用,因此有关二水平部分因子设计的研究一直是热点问题.最近,一种称为doubling的方法被用来构造二水平部分因子设计,特别是在构造分辨度为Ⅳ的设计时,这种方法是非常简单但很实用的方法,本文从均匀性的角度来研究double设计,进一步讨论doubling方法的实用性,利用对称化L_2-偏差作为均匀性的测度,发现double设计D(X)的均匀性与初始设计X的均匀性有着密切的联系,给出了double设计在对称化L_2-偏差下的下界.

Double设计在对称化L_2-偏差下两个下界的比较

从列平衡的角度出发,将设计的中心化L2-偏差、对称化L2-偏差、可卷L2-偏差分别用二次型和均衡模式表示,可分别得到两个下界,它们都适合用来评价正交设计的均匀性。以double设计的对称化L2-偏差为例,证明了这两种方法算出的下界是相等的。

Double设计在对称化L_2-偏差下的广义字长型

在工农业生产、科学实验等领域都广泛应用到二水平部分因子设计.最近,在构造二水平部分因子设计时一种称为doubling的方法被使用.特别是在构造分辨度为IV的设计时,doubling是非常简单但很实用的方法.本文利用对称化L2-偏差作为均匀性的测度,得到了double设计D(X)的对称化L2-偏差值与初始设计X的广义字长型之间的关系.利用上述关系,我们断定对于具有广义较小低阶混杂的初始设计X,其对应的double设计D(X)也应该具有较小的对称化L2-偏差值,也就是说,D(X)应该具有较好的均匀性.

Attack on Optical Double Random Phase Encryption Based on the Principle of Ptychographical Imaging

The principle of ptychography is applied in known plain text attack on the double random phase encoding （DRPE） system. We find that with several pairs of plain texts and cipher texts, the model of attack on DRPE can be converted to the model of ptyehographical imaging. Owing to the inherent merits of the ptyehographical imaging, the DRPE system can be breached totally in a fast and nearly perfect way, which is unavailable for currently existing attack methods. Further, since the decryption keys can be seen as an object to be imaged from the perspective of imaging, the ptychographical technique may be a kind of new direction to further analysis of the security of other encryption systems based on double random keys.

Simulation of the plasticizing behavior of composite modified doublebase(CMDB)propellant in grooved calendar based on adaptive grid technology

The frequent occurrence of safety accidents during the calendering process is caused by the flammable and explosive properties of composite modified double-base(CMDB)propellant.Optimization of process parameters with the aid of fluid simulation technology could effectively ensure the safety of the calendering process.To improve the accuracy of the simulation results,material parameters and model structure were corrected based on actual conditions,and adaptive grid technology was applied in the local mesh refinement.In addition,the rheological behavior,motion trajectories and heat transfer mechanisms of CMDB propellant slurry were studied with different gaps,rotational rates and temperatures of two rollers.The results indicated that the refined mesh could significantly improve the contour clarity of boundaries and simulate the characteristics of CMDB propellant slurry reflux movement caused by the convergent flow near the outlet.Compared with the gap,the increased rotational rate of roller could promote the reflux movement and intensify the shear flow of slurry inside the flow region by viscous shear dragging.Meanwhile,under the synergistic effect of contact heat transfer as well as convective heat exchange,heat accumulated near the outlet and diffused along the reflux movement,which led to the countercurrent heat dissipation behavior of CMDB propellant slurry.The plasticizing mechanism of slurry and the safety of calendering under different conditions were explored,which provided theoretical guidance and reference data for the optimization of calendering process conditions.Based on the simulation results,the safety of the CMDB propellant calendering process could be significantly improved with a few tests conducted during a short research and development cycle.

Double perovskite oxides Sr_2Mg_(1-x)Fe_xMoO(6-δ) for catalytic oxidation of methane

The double perovskite oxides Sr2Mg1-xF exMoO6-δ were investigated as catalysts for the methane oxidation.The structural properties of catalysts were characterized in detail by X-ray diffraction,X-ray photoelectron spectroscopy and X-ray absorption spectroscopy.The catalytic property was strongly influenced by the Fe substitution.The relation between catalytic performance and the degree of Fe substitution was examined with regard to the structure and surface characteristics of the mixed oxides.The Fe-containing catalysts exhibited higher activity attributable to the possible（Fe2＋,Mo6＋） and （Fe3＋,Mo5＋）valency pairs,and the highest activity was observed for Sr2Mg0.2Fe0.8MoO6-δ.The enhancement of the catalytic activity may be correlated with the Fe-relating surface lattice oxygen species and was discussed in view of the presence of oxygen vacancies.