Elastic and mechanical properties of Mg3Rh intermetallic compound:An ab initio study

In this work, density functional theory plane-wave pseudo potential method, with local density approximation (LDA) and generalized gradientapproximation (GGA) are used to investigate the structural, elastic, mechanical and thermodynamic properties of the intermetallic compoundMg3Rh. Comparison of the calculated equilibrium lattice constants and experimental data shows very good agreement. The elastic constants weredetermined from a linear fit of the calculated stress-strain function according to Hooke’s law. From the elastic constants, the bulk modulus B, shearmodulus G, Young’s modulus E, Poisson’s ratio σ, anisotropy factor A, the ratio B/G and the hardness parameter H for Mg3Rh compound areobtained. Our calculated elastic constants indicate that the ground state structure of Mg3Rh is mechanically stable. The calculation results showthat this intermetallic crystal is stiff, elastically anisotropic and ductile material. The sound velocities and Debye temperature are also predictedfrom elastic constants. This is the first quantitative theoretical prediction of these properties.

Generalized Coherent States of a Particle in a Time-Dependent Linear Potential

We derive, with an invariant operator method and unitary transformation approach, that the Schr6dinger equation with a time-dependent linear potential possesses an infinite string of shape-preseving wave-packet states 1φ,λ （t） having classical motion. The qualitative properties of the invariant eigenvalue spectrum （discrete or continuous） are described separately for the different values of the frequency ω of a harmonic oscillator. It is also shown that, for a discrete eigenvalue spectrum, the states 1φ,λ （t） could be obtained from the coherent state 1φ,λ （t）.

Structural and electrical characterization of Cu_(2)ZnSnS_(4) ingot material grown by melting method

In this work,a Cu_(2)ZnSnS_(4)(CZTS)ingot is grown via a melting method,then cooled;the resulting molten stoichiomet-ric mixture is sealed off in a quartz ampoule under vacuum.The CZTS powder chemical composition analyses are determined us-ing energy dispersive spectroscopy,and revealing the slightly Cu-rich and Zn-poor character of the ingot.Powder X-ray diffrac-tion analysis reveals a crystalline structure with a kesterite phase formation,and a preferred orientation of(112)plane.The lat-tice constants of the a-and c-axes,calculated based on the XRD analyses,are a=5.40Åand c=10.84Å.Based on Hall measure-ments at room temperature,we find that the crystal exhibits p-type conductivity,with a high concentration of 1018 cm^(-3),a res-istivity of 1.7Ωcm,and a mobility of 10.69 cm^(2)V-1s-1.Activation energies are estimated based on an Arrhenius plot of conductiv-ity versus 1/T,for a temperature range of 80-350 K,measuring 35 and 160 meV in low-and high-temperature regimes,respect-ively,which is attributed to complex defects(2CuZn+SnZn)and antisite defects(CuZn),respectively.The observed scattering mech-anisms are attributed to ionized impurities and acoustic phonons at low and high temperatures,respectively.The extracted band-gap is 1.37 eV.

Role of Periodic Input Composition and Sweeping Gas for Improvement of Hydrogen Production in a Palladium Membrane Reactor by Partial Oxidation of Methane

The partial oxidation of methane under periodic operation over Ni/y/-Al2O3 catalyst was investigated in a Pd-membrane reactor. The effects of key parameters such as the inlet composition and the sweeping, gas on methane conversion and the hydrogen recovery are numerically estalallshed with two penodtc input ttmctlons. In order to analyze the effect of the inputs modulation, the reaction was performed under low steam to methane ratio at a mod-erate temperature and pressure. It was obtained that to achieve process intensification is to operate the process in a periodic way. The main results show that the periodic input functions can improve the performance of the process compared to the optimal steady state operation. Moreover, there is an optimum amplitude of manipulated inputs leads to a maximum of hydrogen recovery. It is noteworthy that the comparison between the predicted performancevia the sinusoidal and the＇square ways show that the better＇average performance was obtainedwith the square way.

玻璃的冲击损伤(英文)

冲蚀过程是一个与颗粒反复冲击物体表面而移除物质相关的表面现象.本文研究了玻璃的冲蚀坑的几何尺寸和体积,给出了冲蚀移除物质如何依赖于颗粒流动速度、颗粒尺寸和冲击角的理论关系.通过理论与实验结果相比较,定义了一定冲蚀坑尺度的有效域.

Finite temperature thermophysical properties of MgCu intermetallic compound from quasi-harmonic Debye model

The influence of pressure and temperature on the thermodynamic properties of MgCu intermetallic compound was investigated by quasi-harmonic Debye model approximation.The equation of state(EoS)parameters has performed using plane-wave pseudopotential(PW-PP)approach in the framework of the density functional theory(DFT)and the generalized gradient approximation(GGA)for the exchange-correlation functional.Our results agree well with other data of the literature.The finite temperature thermophysical properties under pressure up to 16 GPa and high temperature up to 800 K,respectively were determined.Our results of the thermophysical properties are also agree very well with other data of the literature,where for example at ambient temperature,the deviation between our obtained value(11.05 Cal mol^(−1)K^(−1))of C V,and the theoretical value(11.21 Cal mol^(−1)K^(−1))reported in the literature is only around 1.44%.The finite temperature thermophysical properties were found varied monotonically with either temperature or pressure.Compared with other materials previously studied,similar behaviors were observed.

Wave Functions for Time-Dependent Morse Potentials

The one dimensional Schrodinger equation associated with a time-dependent Morse potentials is studied. We use the invariant operator method （Lewis and Riesenfeld） to obtain approximate solution of the Schrodinger equation in terms of solution of second order ordinary differential equation describes the amplitude of the Morse potentials.

Optimization of Parameters CO<SUB>2</SUB>Laser for Drilling Different Types of Glass

The aim of this work is to study in detail the drilling process on glass by CO2 laser. The study parameters considered in the present experiments are based on the laser beam power of range (30% - 80% of 25 W) and an exposure time for drilling (2 - 8 s). The measured diameters of holes by optical methods are between [300 - 800 μm]. The results obtained by optical observations suggest that ordinary and mineral glasses cannot withstand to a contact of the laser beam and crack during the formation of the drilling hole. The minimum power and duration of exposure are the optimal parameters for drilling the organic glass, we observe no micro-cracks, and again we see that the edges of the holes have a good surface quality with a high aspect ratio.

Complexity Analysis of an Interior Point Algorithm for the Semidefinite Optimization Based on a Kernel Function with a Double Barrier Term

In this paper, we establish the polynomial complexity of a primal-dual path-following interior point algorithm for solving semidefinite optimization（SDO） problems. The proposed algorithm is based on a new kernel function which differs from the existing kernel functions in which it has a double barrier term. With this function we define a new search direction and also a new proximity function for analyzing its complexity. We show that if q1 〉 q2 〉 1, the algorithm has O（（q1 ＋ 1） nq1＋1/2（q1-q2）logn/ε）and O（（q1 ＋ 1）2（q1-q2）^3q1-2q2＋1√n logn/c） complexity results for large- and small-update methods, respectively.

Morphology and Photoelectrochemical Characterization of MEH-PPV/PCBM Composite Film Doped with TiO_2 Nanoparticles

Poly[2-methoxy-5-（20-ethylhexyloxy）-io-phenylenevinylene] （MEH-PPV）, [6,6]-phenyl-C61-butyric acid methyl ester （PCBM） and titanium dioxide （TiO2） nanoparticles （n-type） were dissolved, mixed and deposited by physical methods （spin-coating） on indium tin-oxide （ITO） substrate. The incorporation of the titanium dioxide nanoparticles changed the morphology and increased the roughness of polymers film （MEH-PPV/PCBM）, and the photocurrent density of the composite （MEH-PPV/PCBM ＋n-TiO2） was higher than that of single MEH- PPV/PCBM film. The study showed that the presence of n-TiO2 particles in the polymeric film improves the photoelectrochemical properties of M EH-PPV/PCBM composite.

Decay of a Transmission Problem with Memory and Time-Varying Delay

In this article we consider a transmission problem with memory in a bounded domain and varying delay term in the first equation. Under suitable assumptions on the weight of the damping and the weight of the delay, we show the exponential sta- bility of the solution by introducing a suitable Lyapunov functional.

Nonlinear description of Yang-Mills cosmology： cosmic inflation and the accompanying Hannay's angle

Hannay＇s angle is a classical analogue of the ＂geometrical phase factor＂ found by Berry in his research on the quantum adiabatic theorem. This classical analogue is defined if closed curves of constant action variables return to the same curves in phase space after an adaibatic evolution. Adiabatic evolution of Yang-Mills cosmology, which is described by a time-dependent quartic oscillator, is investigated. Phase properties of the Yang-Mills fields are analyzed and the corresponding Hannay＇s angle is derived from a rigorous evaluation. The obtained Hannay＇s angle shift is represented in terms of several observable parameters associated with such an angle shift. The time evolution of Hannay＇s angle in Yang-Mills cosmology is examined from an illustration plotted on the basis of numerical evaluation,and its physical nature is addressed. Hannay＇s angle, together with its quantum counterpart Berry＇s phase, plays a pivotal role in conceptual understanding of several cosmological problems and indeed can be used as a supplementary probe for cosmic inflation.

Urban landscape structure anatomy:Structure patterns and typology identification in the space-time of Setif City,Algeria

The definition of urban form and its elements raises a wide debate in urban morphology.This study presents a proposal to understand the structuring of the urban landscape of Setif City over 170 years(1848-2018)by abstracting its main elements into permanent structure(PSUL).It corresponds to the street network,more static to the change of the town plan,and flexible structure(FSul),more resilient to change and explains the superimpositions of morphological components(plot,building,and land use).This work aims to identify typological patterns of structures suggested in space-time through the inspection of the growth of the street network and the filling of morphological layers framed by the concept of urbanity.The methodology is based on syntactic(diachronic)morphogenetic analysis,with statistical analyses as unsupervised classification.Results indicate that PSUL presents an accumulation of microincrements produced with a similar degree of coherence in different urban fabrics,which explain the local patterns of street network structuring.The typology of FSul patterns indicates an unbalanced growth by the arrangement between morphological elements,resulting in a variation in the degree of urbanity.

Quantum-classical correspondence for the inverted oscillator

While quantum-classical correspondence for a system is a very fundamental problem in modern physics,the understanding of its mechanism is often elusive,so the methods used and the results of detailed theoretical analysis have been accompanied by active debate.In this study,the differences and similarities between quantum and classical behavior for an inverted oscillator have been analyzed based on the description of a complete generalized Airy function-type quantum wave solution.The inverted oscillator model plays an important role in several branches of cosmology and particle physics.The quantum wave packet of the system is composed of many sub-packets that are localized at different positions with regular intervals between them.It is shown from illustrations of the probability density that,although the quantum trajectory of the wave propagation is somewhat different from the corresponding classical one,the difference becomes relatively small when the classical excitation is sufficiently high.We have confirmed that a quantum wave packet moving along a positive or negative direction accelerates over time like a classical wave.From these main interpretations and others in the text,we conclude that our theory exquisitely illustrates quantum and classical correspondence for the system,which is a crucial concept in quantum mechanics.

Mechanical strength of soda-lime glass sandblasted by gravitation

Damage to a glass surface by sandblasting has a remarkable effect on its mechanical properties and strength.In this study,we analyze the superficial deterioration of soda-lime glass and its influence on the mechanical strength.Sandblasting by gravitation from a fixed height causes damages by the free fall of different quantities of sand,which we performed for a selected grain size and at different angles of inclination.To characterize the surface state,we used different roughness measures(the arithmetic mean value of the roughness Ra,the root mean square roughness Rq,and the maximum roughness Rmax)and measured the optical transmission(transmittance)at different points on the specimen surface using a profilometer.To determine the mechanical strength,we proceeded by two methods:first,by a shock ball(falling ball),and then by biaxial bending using circular supports.The effects of the surface damage on the optical transmission and the mechanical strength of the glass are graphically presented and discussed in this paper.

Extracts from Marine Macroalgae and Opuntia ficus-indica Cladodes Enhance Halotolerance and Enzymatic Potential of Diazotrophic Rhizobacteria and Their Impact on Wheat Germination Under Salt Stress

Soil salinity, which affects more than 6% of the earth’s land surface and more than 20% of its irrigated areas, is a major threat to agriculture. Diazotrophic bacteria are among the functional groups of soil microbiota that are threatened by this abiotic stress, as their activity is mostly inhibited by salt stress. Seventy bacterial strains with distinct characteristics were isolated from soils by using N-free Jensen’s selective medium. Based on their ability to produce metabolites of agricultural interest, four strains were selected and identified as Flavobacterium johnsoniae, Pseudomonas putida, Achromobacter xylosoxidans, and Azotobacter chroococcum. The selected strains were grown at different NaCl concentrations (0–600 mmol L^(-1) in N-free broth and 0–2 000 mmol L^(-1) in Luria-Bertani medium) in the presence and absence of glycine betaine (GB), aqueous and hydro-alcoholic extracts from marine macroalgae, Ulva lactuca and Enteromorpha intestinalis, and Opuntia ficus-indica cladodes. The selected bacterial strains, GB, and the aforementioned extracts were tested for their ability to promote the germination of wheat (Triticum durum) seeds at 0–300 mmol L^(-1) NaCl. Compared with the results obtained with the synthetic osmoprotectant GB, the extracts from O. ficus-indica, U. lactuca, and E. intestinalis significantly promoted bacterial growth and seed germination under salt stress.

A comparative study of a direct and pulse electrodeposition method of TiO_(2)films and its effect on photoelectrocatalytic degradation of methyl orange dye

The present study reports the titanium dioxide(TiO_(2))films synthesized from TiCl3 precursor on ITO glass substrates using two electrochemical techniques,namely direct electro-deposition(DE)and pulse electro-deposition(PE).The synthesis potential during the time-on(Ton)period was fixed at-1.5 V.However,the open-circuit potential was applied during the time-off(Toff)period.The effect of the technique of electro-deposition and Toff duration on the properties of TiO_(2)films and their photoelectron-catalytic activity were investigated.The obtained films were investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM),UV-VIS spectrometer,and photocurrent measurement respectively.It is found that the use of the PE technique at different Toff improves the properties of TiO_(2)films compared to the DE technique.The XRD patterns show the anatase phase with a marked preferential orientation along the(101)direction for all samples.From the SEM analysis,it is seen a significant change from big multigrain agglomerates at DE to a dense film structure and small multigrain agglomerates at different Toff.As the Toff decreases from 3 s to 1 s,the photocurrent response rises and reaches a high value of about 12 m A/cm^(2).Compared with DE,and under UV light the photocatalytic property of TiO_(2)film synthesis via PE has been improved in the degradation of methyl orange(MO).Finally,the films deposited at low Toff(Toff=1 s)show a faster degradation of MO.