[en] Genetic composition of Poa annua populations showed clinal change along an organic pollution gradient. - The population genetic composition of Poa annua L. was studied by starch electrophoresis along a transect running NE from an organic reagents factory at Shanghai, China. Five enzyme systems were stained. We have reached the following preliminary conclusions: (1) Organic pollution has dramatically changed genotypic frequencies at some loci of Poa annua populations. At polluted sites, significant deviations from Hardy-Weinberg equilibrium were observed on loci Sod-1 and Me due to the excess of heterozygote. Especially in the two nearest sites to pollution source, all the individuals were heterozygous at locus Sod-1. The data suggests that heterozygotes were more tolerant to organic pollution than homozygotes, indicating the fitness superiority of heterozygotes. (2) A tendency towards clinal changes of allele frequencies was found at some polymorphic loci. Frequencies of the common alleles at loci Sod-1, Me and Fe-1 increased as the distance to the pollution source increased. (3) The effective number of alleles per locus, and the observed and expected heterozygosity were much higher in the pollution series than in the clear control site (Botanic Park population), but genetic multiplicity (number of alleles per locus) was lower than for the control. (4) Most genetic variability was found within populations, and only 2.56% were among populations of the polluted series. However, 9.48% of the total genetic variation occurred among populations when including the Botanic Park population. The genetic identity between populations of the pollution series (0.9869-1.0000, mean 0.9941) was higher than those between the pollution series and the Botanic Park population. UPGMA divided the five populations into two groups. One contained the four polluted populations, and the other only contained the Botanic Park population

[en] Highlights: • A novel ISCC scheme with two-stage DSG fields has been proposed and analyzed. • HRSG and steam turbine working parameters have been optimized to match the solar integration. • New scheme exhibits higher solar shares in the power output and solar-to-electricity efficiency. • Thermodynamic performances between new and reference systems have been investigated and compared. - Abstract: Integrated solar combined cycle (ISCC) systems have become more and more popular due to their high fuel and solar energy utilization efficiencies. Conventional ISCC systems with direct steam generation (DSG) have only one-stage solar input. A novel ISCC with DSG system has been proposed and analyzed in this paper. The new system consists two-stage solar input, which would significantly increase solar share in the total power output. Moreover, how and where solar energy is input into ISCC system would have impact on the solar and system overall efficiencies, which have been analyzed in the paper. It has been found that using solar heat to supply latent heat for vaporization of feedwater would be superior to that to be used for sensible heating purposes (e.g. Superheating steam). The study shows that: (1) producing both the high- and low-pressure saturated steam in the DSG trough collector could be an efficient way to improve process and system performance; (2) for a given live steam pressure, the optimum secondary and reheat steam conditions could be matched to reach the highest system thermal efficiency and net solar-to-electricity efficiency; (3) the net solar-to-electricity efficiency could reach up to 30% in the novel two-stage ISCC system, higher than that in the one-stage ISCC power plant; (4) compared with the conventional combined cycle gas turbine (CCGT) power system, lower stack temperature could be achieved, owing to the elimination of the approach-temperature-difference constraint, resulting in better thermal match in the heat recovery steam generator (HRSG) and thus more feedwater could be circulated

[en] Highlights: • An ISCC scheme with two DSG solar fields has been proposed and analyzed. • Thermodynamic analysis of solar multiple was performed to achieve optimum property. • Economic analysis of solar multiple was carried out to give the best cost. • Optimal scheme exhibits higher thermal efficiency and lower electricity cost. - Abstract: Integrated solar combined cycle (ISCC) systems coupled with direct steam generation (DSG) are more promising in terms of system efficiency and electricity cost than current solar-only power generation systems, as ISCC–DSG offers the advantages of higher net thermal efficiency and lower cost. However, the ISCC systems usually have to be operated at part-load conditions with low system efficiency when no or lower insolation than that at design point is available as most of state-of-the-art such systems have no thermal storage equipped. In order to improve system performance and prolong the system full-load operation hours, a proper solar field size represented as the solar multiple is a prime parameter to be determined during the design stage of the ISCC system. A too large solar multiple might cause the collected solar thermal energy to become partially useless without thermal storage and high investment cost, while a smaller one might worsen the part-load performance of the system. This paper presents the thermodynamic and economic analysis for an ISCC system with two pressure level DSG solar fields (ISCC–2DSG), aiming to study the impacts of solar multiples on system performance with or without consideration of thermal storage. In the ISCC–2DSG system, the solar thermal energy produced from two solar fields is only used to supply latent heat for low- and high-pressure water vaporization, respectively. Feedwater preheating and steam superheating are achieved in a HRSG. The annual thermodynamic performance of several such ISCC–2DSG systems, with different solar multiple values but with identical design parameters in the power subsystem, is characterized. Based on these features, the LEC for each system is calculated and compared. An optimum solar field size (solar multiple), which gives the minimum LEC, for the ISCC–2DSG system can be finally obtained.

[en] Highlights: • The effect of Fe-rich phases on squeeze cast Al–Cu alloys with high Fe content. • Four kinds of Fe-rich phases may present in Al–Cu alloys. • There is great tolerance to Fe impurities in squeeze cast Al–Cu alloys. - Abstract: The microstructures and mechanical properties of gravity die cast and squeeze cast Al–5.0 wt% Cu–0.6 wt% Mn alloys with different Fe content have been studied using tensile test, optical microscope, scanning electron microscope, electron probe micro-analyzer and image analysis. The results show that four kinds of Fe-rich intermetallics may present in the final microstructures of the alloys: Chinese script α-Fe (Al₁₅(FeMn)₃(CuSi)₂) and Al₆(FeMn), needle-like β-Fe(Al₇Cu₂Fe) and Al₃(FeMn) when the Fe content increases from 0.1 wt% to 1.5 wt%. In the gravity die cast alloy with 0.5 wt% Fe, the Chinese script α-Fe presents as the main Fe-rich intermetallics, and a few needle-like β-Fe also exist. When the Fe content increases to 1.0 wt%, the main Fe-rich intermetallics change to needle-like Al₃(FeMn) and Chinese-script Al₆(FeMn). The needle-like β-Fe disappears when the Fe content is 0.5 wt% in the squeeze cast alloy with an applied pressure of 75 MPa. Furthermore, the secondary dendritic arm spacing of α(Al), the percentage of porosity and the volume fraction of the second intermetallics decrease distinctly in the squeeze cast alloy compared to the gravity die cast alloy. There is a peak value of ultimate strength and yield strength for the alloy with 0.5 wt% Fe. The elongations of the alloys decrease gradually with increasing Fe content and the elongation of the squeeze cast alloys is two times more than that of the gravity die cast alloys

[en] Highlights: • The microstructure and thermal properties of Mg−Bi alloys are determined. • The relationship between melting enthalpies and phase composition are studied. • The activation energy of Mg−54%Bi alloy is calculated by multiple DSC technology. • Mg−54%Bi alloy is proposed as a phase change material at high (>420 °C) temperature. - Abstract: Comparing with Al-based phase change material, Mg-based phase change material is getting more and more attention due to its high corrosion resistance with encapsulation materials based on iron. This study focuses on the characterization of Mg−36%Bi, Mg−54%Bi and Mg−60%Bi (wt. %) alloys as phase change materials for thermal energy storage at high temperature. The phase compositions, microstructure and phase change temperatures were investigated by X-ray diffusion (XRD), electron probe micro-analysis (EPMA) and differential scanning calorimeter (DSC) analysis, respectively. The results indicates that the microstructure of Mg−36%Bi and Mg−54%Bi alloys are mainly composed of α-Mg matrix and α-Mg + Mg_3Bi_2 eutectic phases, Mg−60%Bi alloy are mainly composed of the Mg_3Bi_2 phase and α-MgMg_3Bi_2 eutectic phases. The melting enthalpies of Mg−36%Bi, Mg−54%Bi and Mg−60%Bi alloys are 138.2, 180.5 and 48.7 J/g, with the phase change temperatures of 547.6, 546.3 and 548.1 °C, respectively. The Mg−54%Bi alloy has the highest melting enthalpy in three alloys. The main reason may be that it has more proportion of α-Mg + Mg_3Bi_2 eutectic phases. The thermal expansion of three alloys increases with increasing temperature. The values of the thermal conductivity decrease with increasing Bi content. Besides, the activation energy of Mg−54%Bi was calculated by multiple DSC technology.

[en] Hydrophobic/super-hydrophobic nanofilms with improved corrosion resistance were fabricated on the surfaces of Mg–Mn–Ce magnesium alloy by a surface modification technique, named as polymer plating, which has been developed to modify superficial characteristics of magnesium alloys with polymeric nanofilms through synthesized organic compounds of triazine dithiol containing functional groups. The nanofilms were prepared by the electrochemical and polymerization reactions during polymer plating analyzed from characteristics of Fourier transform infrared spectrophotometer, X-ray photoelectron spectroscopy and scanning electron microscopy. The fabricated nanofilms changed the surface wettability of blank magnesium alloy from hydrophilic to hydrophobic with contact angle 119.0° of distilled water with lower surface free energy of 20.59 mJ/m² and even super-hydrophobic with contact angle 158.3° with lowest surface free energy of 4.68 mJ/m² by different functional nanofilms on their surfaces. Alteration of wettability from hydrophilic to hydrophobic and super-hydrophobic resulted from their low surface free energy and surface morphology with micro- and nano-rough structures. The corrosion behaviors from potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) show that the super-hydrophobic nanofilm has higher corrosion resistance and stability in 0.1 mol/L NaCl solution and lower corrosion current density (I_corr) with R_ct increasing two orders of magnitude of 16,500 Ω·cm² compared to that obtained for blank of 485 Ω·cm².

[en] Blended 93W–5.6Ni–1.4Fe powders were sintered via the spark plasma sintering (SPS) technique. Fine-grained 93W–5.6Ni–1.4Fe heavy alloys (W grain size is about 6 µm) with liquid-phase sintered microstructure were obtained by control of the SPS process. After SPS, the alloys show relative density of 0.95 and tungsten–tungsten contiguity of 0.53. The alloys exhibit improved bending strength (about 1580 MPa) and yield strength (about 1050 MPa at room temperature and about 640 MPa at 800 °C), due to their fine-grained structure. The fracture morphology after bending test is mainly characterized as tungsten–tungsten intergranular rupture. A decreased tungsten–matrix interface decohesion is presented due to the improved binding strength of tungsten–matrix by “SPS effect”. The mechanical properties of SPSed 93W–5.6Ni–1.4Fe heavy alloys are dependent on the microstructural parameters such as tungsten grain size, matrix volume fraction and tungsten–tungsten contiguity

[en] We carefully investigated the in-plane magnetization reversal and corresponding magnetic domain structures in Fe/n-GaAs/piezoelectric heterostructure using longitudinal magneto-optical Kerr microscopy. The coexistence of the in-plane <100> cubic and [11^¯0] uniaxial magnetic anisotropy was observed in this system at virgin state. The piezo voltages can effectively manipulate the magnetic properties of the Fe/n-GaAs/piezoelectric heterostructure, where the manipulation of two-jump to one-jump magnetization switching during the magnetic reversal was achieved with magnetic field applied in [100] direction. Our findings on manipulation of ferromagnetization in this heterostructure could be important for future metal-semiconductor spintronic applications. The additional uniaxial anisotropy induced by piezo voltages obtained at ±75 V is ±1.4×10³ J/m³. - Highlights: • In this work, we use piezo voltages not only realize the significant change of coercivity but also effectively manipulate the magnetization transition from one step to two steps during magnetic reversal, indicating that the piezo-voltages can be used to effectively control the magnetization reversal. • The additional uniaxial anisotropy induced by piezo voltages at +/−75 V are +/−1.4×10³ J/m³. This work could be very used for future metal-semiconductor spintronic devices

[en] The erosion behavior of pure Ti_3SiC_2 anode under vacuum discharge was investigated. By means of X-ray diffraction, energy dispersive spectroscopy and micro-Raman spectroscopy, the decomposition of Ti_3SiC_2 into nonstoichiometric TiC_x, amorphous carbon and other by-products was proved. The surface morphology was revealed by scanning electron microscope and 3D super depth digital microscope. Different kinds of craters with diameters varying from a few microns to a few hundred microns were observed on the anode surface after arcing. The smaller craters contain some TiC_x, with a few tens of microns in diameter, are flower-like shaped with a protrusion pointing out from the center of the crater bottom. The larger craters are basically composed of TiC_x, have diameters greater than one hundred microns but without the central protrusions, and are surrounded by collapse-fissures. - Highlights: • Ti_3SiC_2 was proved to be decompose into TiC_x under the influence of the vacuum arc. • The Si element in Ti_3SiC_2 vaporized under the influence of the vacuum arc. • Footpoint mode craters and anode spot mode crater were observed on the anode surface. • The anode spot mode crater is basically composed of TiC_x

[en] In this study, tungsten heavy alloy (WHA) composites were fabricated based on tungsten (W), nickel (Ni), and iron (Fe) system. WHA composites with the composition 93W–4.9Ni–2.1Fe/95W–2.8Ni–1.2Fe–1Al_2O_3 were prepared by liquid-phase sintering and post-heat treatment to meet the requirement for complex mechanical performance. The relationship between the microstructural characteristics (relative density, W-grain size, and W–W contiguity) and mechanical properties was investigated. Variation in the content of W and addition of Al_2O_3 resulted in a significant difference in the microstructure of the two parts of W–Ni–Fe heavy alloy composite. The microstructure of the alloy significantly influenced the tensile properties of the two parts of the W–Ni–Fe heavy alloy composite; however, it did not affect their compressive deformation behaviors