Optimization of equimolar reverse constant-temperature mass-diffusion process for minimum entransy dissipation

The mass entransy describes the mass-diffusion ability of the solution system, and the mass-diffusion process with the finite concentration difference always leads to the mass-entransy dissipation. This paper studies the equimolar reverse constant-temperature mass-diffusion process with Fick's law( g∝Δ(c)). The optimal concentration paths for the MED(Minimum Entransy Dissipation) are derived and compared with those for the MEG(Minimum Entropy Generation) and CCR(Constant Concentration Ratio) operations. It is indicated that the strategy of the MED is equivalent to that of the CCD(Constant Concentration Difference) of the same component; whether the MED or the MEG is selected as the optimization objective, the strategy of the CCD is much better than that of the CCR.     

Is there any relation between helium isotope composition of underground fluids and heat flow in continental areas?

The regression formula between³He/⁴He ratio of underground fluids and terrestrial heat flow in continental areas is tested by data sets from the former Soviet Union and the mainland of China. The results show that there is no close relation between the two values. The heat-He relation might estimate the regional heat flow value with ±25% accuracy at best. We propose that the ratio of crust/mantle component of continental heat flow (q _c/q _m) be inversely related to the³He/⁴He ratio of underground fluids. Based on data sets of³He/⁴He ratio andq _c/q _m in the Eurasia and Canadian Shield, we obtain the regression relation betweenq _c/q _m and³He/⁴He:q _c/q _m=0.815?0.300^*log_e (³He/⁴He), in which the unit of³He/⁴He is Ra (atmospheric³He/⁴He ratio). The crust and mantle heat flow components can be taken from surface heat flow andq _c/q _m ratio. Based on this formula and heat flow data in major basins of China, the crustal, mantle heat flow values and the average crustal heat production rates were estimated. The estimated crustal chemical composition of China is in agreement with the result inferred by deep seismic sounding survey. Helium isotope ratio (³He/⁴He) of underground fluids may be a useful parameter for separating crust and mantle components of continental heat flow.     

Morphology study of oriented SmBCO film deposited by MOCVD

c-axis-oriented SmBa_2Cu_3O_7(SmBCO) films have been deposited on(100)- LaA1O_3(LAO)substrate by metal organic chemical vapor deposition(MOCVD) technique.The effects of deposition temperature(T_(dep)) and total pressure(P_(tot)) on the orientation and microstructure of SmBCO films were investigated.The orientation of SmBCO films transformed from α-axis to c-axis with increasing of T_(dep) from 900 to 1 100℃.At T_(dep)=1 050℃,SmBCO films had c-axis orientation and tetragon surface.At P_(tot)~(dep)=400-800 Pa and T_(dep)=1 050 ℃,totally c-axis-oriented SmBCO films were obtained.The R_(dep) of SmBCO films increased firstly and then decreased with increasing P_(tot).The surface of SmBCO films exhibited tetragon morphology at 1 050 ℃ and400 Pa.Maximum thickness of SmBCO film deposited was 1.2μm at P_(tot)= 600 Pa,and the corresponding R_(dep)was 7.2 μm·h~(-1).     

Spontaneous Magnetic Transitions and Corresponding Magnetoelastic Properties of Intermetallic Compounds <Emphasis Type="Italic">R</Emphasis>Mn<Subscript>2</Subscript>Ge<Subscript>2</Subscript> (<Emphasis Type="Italic">R</Emphasis>=Gd,Tb and Dy)

The spontaneous magnetic transitions and corresponding magnetoelastic properties of intermetallic compounds RMn₂Ge₂ (R=Gd, Tb and Dy) were investigated by using the X-ray diffraction method and magnetic measurement. The results showed that the compounds experience two magnetic transitions, namely the second-order paramagnetic to antiferromagnetic transition at temperature T_N (T_N=368, 423 and 443 K for GdMn₂Ge₂, TbMn₂Ge₂ and DyMn₂Ge₂, respectively) and the first-order antiferromagnetic - ferrimagnetic transition at temperature T_t (T_t=96, 80 and 40 K for GdMn₂Ge₂, TbMn₂Ge₂ and DyMn₂Ge₂, respectively) as the temperature decreases. The temperature dependence of the lattice constant a(T) displays a negative magnetoelastic anomaly at the second-order transition point T_N and, at the first-order transition T_t, a increases abruptly for GdMn₂Ge₂ and TbMn₂Ge₂, Δa/a about 10^-3. Nevertheless, the lattice constant c almost does not change at these transition points indicating that such magnetoelastic anomalies are mainly contributed by the Mn-sublattice. The transitions of the magnetoelastic properties are also evidenced on the temperature dependence of magnetic susceptibility χ. The first-order transition behavior at T_t is explained by the Kittel mode of exchange inversion.     

An area method for visualizing heat-transfer imperfection of a heat exchanger network in terms of temperature–heat-flow-rate diagrams

The identification of the imperfection originating from finite-temperature-difference heat transfer is an indispensable step for both the performance analysis and the better design of a heat exchanger network(HEN) with the aim of energy saving. This study develops a convenient area method for visualizing the heat-transfer imperfection of a HEN in terms of temperature–heat flow diagrams( T-Q diagrams) by combining the composite curves that have already been used in pinch analysis and the recently developed entransy analysis. It is shown that the area between the hot and cold composite curves and the hot and cold utility lines on a T-Q diagram is just equal to the total entransy dissipation rate during the multi-stream heat transfer process occurred in a HEN, and this area can be used to graphically represent the total heat-transfer imperfection of the HEN. The increase in heat recovery or decrease in energy requirements with decreasing the minimum temperature difference, ΔT_(min), of a HEN can then be attributed to a lower entransy dissipation rate, quantitatively represented by the decrease of the area between the composite curves and the utility lines. In addition, the differences between the T-Q diagram and the pre-existing energy level–enthalpy flow diagram(Ω-H diagram) in the roles of visualizing process imperfection and designing HENs are discussed.     

Studies of antioxidant performance of amine additives in lubricating oil using 3D-QSAR

Available model of 3D-quantitative structure-activity relationship (3D-QSAR, the method of TopomerCoMFA) has been used to establish relationship between antioxidant performances of lubricating oil (trimethylolpropane trioleate, TMPTO) with 15 kinds of amine additives and its molecular structure. Correlation coefficient of the cross-validation (include internal q ² and external q _pred ² ) and conventional correlation coefficient showed the model to be both stable and good predictive. The electron-donating group and larger steric effects group are adopted at the para-position or meta-position of amido on the benzene ring, and suitably decreasing the branch chain near the para-position, these indicate that the antioxidant performance of amine additives can be enhanced. The results not only can help us understanding the rule of antioxidant performance, but also providing guidance(s) to predict antioxidant performance of existing amine additives and to design or modify new amine additives in lubricating oil.     

Structural,anisotropic and thermodynamic properties of Imm2-BCN

Structural, anisotropic, and thermodynamic properties of Imm2-BCN were studied based on density function theory with the ultrasoft psedopotential scheme in the frame of the generalized gradient approximation(GGA). The elastic constants were confirmed that the predicted Imm2-BCN is mechanically stable. The anisotropy of elastic properties were also studied systematically. The anisotropy studies of Young's modulus, shear modulus, linear compressibility, and Poisson's ratio show that the Imm2-BCN exhibits a large anisotropy. Through the quasi-harmonic Debye model, the relations between the equilibrium volume V, thermal expansion α, the heat capacity C_V and CP, the Grüneisen parameter γ, and the Debye temperature Θ_D with pressure P and temperature T were also studied systematically.     

Thermodynamic assessment of solar-aided carbon dioxide conversion into fuels via Tin oxides

The conversion of CO_2 to liquid hydrocarbon fuels using solar energy is gaining attraction as a means to deal with climate change and energy depletion,and assessment for related thermochemical cycles has attracted great interests in recent years.Here,we perform the thermodynamical analysis on solar-aided CO_2 conversion reactions based on Tin oxides.The equilibrium compositions,production purity and CO_2 conversion are obtained.Also,the variations of conversion efficiency with respect to temperature,normal beam solar insolation,mean flux concentration ratio,initial CO_2 to SnO ratio and heat recuperation percentage are revealed.Our results indicate the initial CO_2 to SnO ratio,χ_(ini),has an evident impact on conversion efficiency andχ_(ini)=0.5,T=700 K andχ_(ini)=1,T=950 K,are favourable for solid C and gaseous CO production,respectively.The calculated maximum cycle efficiency with direct work production is 0.340 at T=950 K andχ_(ini)=1,demonstrating the high conversion efficiency of the proposed system.     

Structural and electrical properties of high Curie temperature Aurivillius phase composite ceramics with largely enhanced piezoelectricity

High performance piezoelectric ceramics with high Curie temperatures(TC) are the bottle necks of relevant high temperature devices. In this study, the electrical performance and microstructure of Li and Mn codoped Aurivillius-type composite ceramics with a composition Ca_(0.99-x_Bi_(6.99+x)(Li Mn)_(0.01) Nb Ti_5O_(24)(x = 0–0.8) were systematically investigated. The results indicated that uniform intergrowth structure with a lattice similar to that of the end member CBT could be formed at a low x value(x 0.4). Phase separation occurred when more A-site Ca~(2+) ions were replaced by Bi~(3+) ions. Nevertheless, all composite samples showed d_(33) values about 2 to 3 times of that of the constituent phase Ca Bi_4Ti_4O_(15) and Bi_3 Ti NbO_9 with still a high depolarization temperature. The performance of the samples was found to be related to the density and larger lattice distortion along the polarization a axis. The results also demonstrated that formation of the compound system was an effective way in improving the performance of Aurivillius-type high TC piezoelectric ceramics.     

Elimination of Voids at Interface of <Emphasis Type="Italic">β</Emphasis>-SiC Films and Si Substrate by Laser CVD

Void-free β-SiC films were deposited on Si(001) substrates by laser chemical vapor deposition using hexamethyldisilane (HMDS) as the precursor. The effect of the time of introducing HMDS, i e, the substrate temperature when HMDS introduced (T_in), on the preferred orientation, surface microstructure and void was investigated. The orientation of the deposited SiC films changed from <001> to random to <111> with increasing T_in. The surface showed a layer-by-layer microstructure with voids above T_in ? 773 K, and then transformed into mosaic structure without voids at T_in= 298 K. The mechanism of the elimination of voids was discussed. At T_in =298 K, Si surface can be covered by an ultrathin SiC film, which inhibits the out-diffusion of Si atoms from substrate and prohibites the formation of the voids.     

Azobenzene/graphene hybrid for high-density solar thermal storage by optimizing molecular structure

A large capacity storing solar energy as latent heat in a close-cycle is essentially important for solar thermal fuels. This paper presents a solar thermal molecule model of a photo-isomerizable azobenzene(Azo) molecule covalently bound to graphene. The storage capacity of the Azo depending on isomerization enthalpy(ΔH) is calculated based on density functional theory. The result indicates that the ΔH of Azo molecules on the graphene can be tuned by electronic interaction, steric hindrance and molecular hydrogen bonds(H-bonds). Azo with the withdrawing group on the ortho-position of the free benzene shows a relatively high ΔH due to resonance effect. Moreover, the H-bonds on the trans-isomer largely increase ΔH because they stabilize the trans-isomer at a low energy. 2-hydroxy-4-carboxyl-2′,6′,-dimethylamino-Azo/graphene shows the maximum ΔH up to 1.871 e V(107.14 Wh kg~(-1)), which is 125.4% higher than Azo without functional groups. The Azo/graphene model can be used for developing high-density solar thermal storage materials by controlling molecular interaction.     

Effects of annealing processes on Cu<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Si<Subscript>1-<Emphasis Type="Italic">x</Emphasis></Subscript> thin films

The Cu _x Si_1-x thin films have been grown by pulsed laser deposition (PLD) with in situ annealing on Si (001) and Si (111), respectively. The transformation of phase was detected by X-ray diffraction (XRD). The results showed that the as-deposited films were composed of Cu on both Si (001) and Si (111). The annealed thin films consisted of Cu + η”-Cu₃Si on Si (001) while Cu + η’-Cu₃Si on Si (111), respectively, at annealed temperature (T _a) = 300-600 °C. With the further increasing of T _a, at T _a= 700 °C, there was only one main phase, η”-Cu₃Si on Si (001) while η’-Cu₃Si on Si (111), respectively. The annealed thin films transformed from continuous dense structure to scattered-grain morphology with increasing T _a detected by field emission scanning electron microscope (FESEM). It was also showed that the grain size would enlarge with increasing annealing time (t _a).     

Effects of functionalized silica nanoparticles on characteristics of nanocomposites PES cation exchange membranes

Nanocomposite cation exchange membranes(CEMs) were prepared by adding various loadings of functionalized silica nanoparticles to the sulfonated polyethersulfone(s PES) polymeric matrix. The silica nanoparticles were functionalized by mercaptopropyl(F_1, IEC=0), propylsulfonic acid(F_2, IEC= 2.71), and sulfonic acid(F_3, IEC=2.84). The properties of prepared membranes were investigated by varying the loadings of functionalized silica nanoparticles. Applying functionalized nanoparticles provides additional ion exchange groups and enhances water contents as well as conductivities and permselectivities of the membranes. The maximum IEC of 1.9 meq.g~(-1) was obtained for the membrane having 3 wt% F_3 nanoparticles and the maximum conductivity of 0.237 S·cm~(-1) was achieved for the membrane having 2 wt% F_3 nanoparticles, which were 19.6% and 64% higher than the corresponding values for s PES membrane, respectively. The excellent properties of the nanocomposite cation-exchange membranes make them appropriate candidates for electrodialysis and desalination processes.     

Effects of electrode on resistance switching properties of ZnMn<Subscript>2</Subscript>O<Subscript>4</Subscript> films deposited by magnetron sputtering

ZnMn₂O₄ films for resistance random access memory (RRAM) were fabricated with different device structures by magnetron sputtering. The effects of electrode on I-V characteristics, resistance switching behavior, endurance and retention characteristics of ZnMn₂O₄ films were investigated. The ZnMn₂O₄ films, using p-Si and Pt as bottom electrode, exhibit bipolar resistive switching (BRS) behavior dominated by the space-charge-limited conduction (SCLC) mechanism in the high resistance state (HRS) and the filament conduction mechanism in the low resistance state (LRS), but the ZnMn₂O₄ films using n-Si as bottom electrodes exhibit both bipolar and unipolar resistive switching behaviors controlled by the Poole-Frenkel (P-F) conduction mechanism in both HRS and LRS. Ag/ZnMn₂O₄/p-Si device possesses the best endurance and retention characteristics, in which the number of stable repetition switching cycle is over 1000 and the retention time is longer than 10⁶ seconds. However, the highest R _HRS/R _LRS ratio of 10⁴ and the lowest V _ON and V _OFF of 3.0 V have been observed in Ag/ZnMn₂O₄/Pt device. Though the Ag/ZnMn₂O₄/n-Si device also possesses the highest R _HRS/R _LRS ratio of 10⁴, but the highest values of V _ON,V _OFF, R _HRS and R _LRS, as well as the poor endurance and retention characteristics.     

Preparation and Properties of Sapphire by Edge-defined Film-fed Growth (EFG) Method with Different Growth Directions

Sapphire, belonging to hexagonal crystal system, is typically anisotropic which makes it direction-sensitive. To research the effects of growth directions on properties of sapphire, c-[0001] seed(c-sapphire) and a-[11-20] seed(a-sapphire) were used to prepare sapphire by edge-defined film-fed growth(EFG) method. The samples were analyzed through lattice integrity, dislocation and corrosion performance by double-crystal XRD, OM, AFM, SEM and EDX. It was shown that the lattice integrities of two growth-direction crystals were both well due to the small FWHM values. While the average densities of dislocation in c-sapphire and a-sapphire were 9.2×103 and 3.9×103 cm-2 respectively, the energy of dislocation in c-sapphire was lower than that in a-sapphire. During Strong Phosphoric Acid(SPA) etching, the surface of c-sapphire basically kept smooth but in a-sapphire there were many point-like corrosion pits where aluminum and oxygen atoms lost by 2:1. Our work means that it will be promising for growing c-[0001] seed sapphire by EFG if aided by parameter optimization.     

UV disinfection of Staphylococcus aureus in ballast water: Effect of growth phase on the disinfection kinetics and the mechanization at molecular level

This work aimed to study the inactivate kinetics of Staphylococcus aureus (S. aureus) in artificial seawater by ultraviolet radiation, establish relationships between model parameters and growth phases, and explain the mechanization of UV disinfection by molecular biological detection. Investigations were carried out for the validation of Chick-Watson, Collins-Selleck, Hom and Biphasic models when S. aureus was in stationary phase (t=14 h). The results showed that the Biphasic kinetic model’s R² turned out to be the highest one (R²=0.9892) and RMSE was less than 0.5 (RMSE =0.2699). The Biphasic kinetic model was better fit for ultraviolet disinfection than the other three models under the circumstance of this experiment and chosen to fit the ultraviolet disinfection curves for microorganisms at three growth phases. The sensitivity of microorganisms under ultraviolet radiation was in the following order: in exponential phase > in stationary phase > in lag phase by comparing the indexes of the Biphasic model (k₁ and x). Besides, agarose gel electrophoresis was used in order to directly assess the damage to DNA of microorganisms that were exposed to the different dose of UV irradiation. The results revealed that DNA damage caused by UV radiation was an important reason for the microorganism inactivation and as the UV dose increased, there was greater damage caused in DNA.     

Enhanced Ferroelectric Polarization in Laser-ablated Bi<Subscript>4</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> Thin Films by Controlling Preferred Orientation

Polycrystalline Bi₄Ti₃O₁₂ thin films with various fractions of a-axis, c-axis and random orientations have been grown on Pt(111)/Ti/SiO₂/Si substrates by laser-ablation under different kinetic growth conditions. The relationship between the structure and ferroelectric property of the films was investigated, so as to explore the possibility of enhancing ferroelectric polarization by controlling the preferred orientation. The structural characterization indicated that the large growth rate and high oxygen background pressure were both favorable for the growth of non-c-axis oriented grains in the Bi₄Ti₃O₁₂ thin films. The films with high fractions of a-axis and random orientations, i e, f (a-sxis) = 28.3% and f (random) = 69.6%, could be obtained at the deposition temperature of 973 K, oxygen partial pressure of 15 Pa and laser fluence of 4.6 J/cm², respectively. It was also noted that the variation of ferroelectric polarization was in accordance with the evolution non-c-axis orientation. A large value of remanent polarization (2Pr = 35.5 μC/cm²) was obtained for the Bi₄Ti₃O₁₂ thin films with significant non-c-axis orientation, even higher than that of rare-earth-doped Bi₄Ti₃O₁₂ films.     

Microstructure and growth kinetics of silicide coatings for TiAl alloy

In order to improve the oxidation resistance of Ti Al alloy, silicide coatings were prepared by pack cementation method at 1273, 1323, and 1373 K for 1-3 hours. Scanning electron microscopy(SEM), energy dispersive spectrometry(EDS) and X-ray diffraction(XRD) were employed to investigate the microstructures and phase constitutions of the coatings. The experimental results show that all silicon deposition coatings have multi-layer structure. The microstructure and composition of silicide coatings strongly depend on siliconizing temperatures. In order to investigate the rate controlling step of pack siliconizing on Ti Al alloy, coating growth kinetics was analyzed by measuring the mass gains per unit area of silicided samples as a function of time and temperature. The results showed that the rate controlling step was gas-phase diffusion step and the growth rate constant(k) ranged from 1.53 mg~2/(cm~4·h~2) to 2.3 mg~2/(cm~4·h~2). Activation energy(Q) for the process was calculated as 109 k J/mol, determined by Arrhenius' equation: k = k0 exp[–Q/(RT)].     

Composition dependence of phase structure and electrical properties of (1−y)Bi1−xNdxFeO3−yBiScO3 ceramics

In this work, we have studied a new lead-free ceramic of(1-y)Bi_(1-x)Nd_xFeO_(3-y)BiScO_3(0.05≤x≤0.15 and 0.05≤y≤0.15) prepared by a conventional solid-state method, and the influences of Nd and Sc content on their phase structure and electrical properties were investigated in detail. The ceramics with 0.05≤x≤0.10 and 0.05≤y≤0.15 belong to an R3 c phase, and the rhombohedral-like and orthorhombic multiphase coexistence is established in the composition range of 0.125≤x≤0.15 and y=0. The electrical properties of the ceramics can be enhanced by modifying x and y values. The highest piezoelectric coefficient(d33~51 p C/N) is obtained in the ceramics with x=0.075 and y=0.125, which is superior to that of a pure BiFeO_3 ceramic. In addition, a lowest dielectric loss(tan δ~0.095%, f=100 k Hz) is shown in the ceramics with x=0.15 and y=0 due to the involvement of low defect concentrations, and the improved thermal stability of piezoelectricity at 20–600oC is possessed in the ceramics. We believe that the ceramics can play a meaningful role in the high-temperature lead-free piezoelectric applications.     

Probabilistic composition of cone-based cardinal direction relations

Composition tables play a significant role in qualitative spatial reasoning (QSR). At present, a couple of composition tables focusing on various spatial relations have been developed in a qualitative approach. However, the spatial reasoning processes are usually not purely qualitative in everyday life, where probability is one important issue that should be considered. In this paper, the probabilistic compositions of cone-based cardinal direction relations (CDR) are discussed and estimated by making some assumptions. Consequently, the form of composition result turns to be {(R ₁,P ₁), (R ₂,P ₂), ..., (R _n ,P _n )}, where P _i is the probability associated with relation R _i . Employing the area integral method, the probabilities in each composition case can be computed with the assumption that the target object is uniformly distributed in the corresponding cone regions.