Imposing accurate wall boundary conditions in corrective‐matrix‐based moving particle semi‐implicit method for free surface flow

Corrective matrix that is derived to restore consistency of discretization schemes can significantly enhance accuracy for the inside particles in the Moving Particle Semi‐implicit method. In this situation, the error due to free surface and wall boundaries becomes dominant. Based on the recent study on Neumann boundary condition (Matsunaga et al, CMAME, 2020), the corrective matrix schemes in MPS are generalized to straightforwardly and accurately impose Neumann boundary condition. However, the new schemes can still easily trigger instability at free surface because of the biased error caused by the incomplete/biased neighbor support. Therefore, the existing stable schemes based on virtual particles and conservative gradient models are applied to free surface and nearby particles to produce a stable transitional layer at free surface. The new corrective matrix schemes are only applied to the particles under the stable transitional layer for improving the wall boundary conditions. Three numerical examples of free surface flows demonstrate that the proposed method can help to reduce the pressure/velocity fluctuations and hence enhance accuracy further.     

掺锗提高VO2薄膜的相变温度机理研究

二氧化钒(VO₂)作为一种长久以来备受关注的新型可逆相变材料,发展潜力巨大,其相变温度(T_MIT)的调控一直是研究热点。本文主要利用锗离子作为掺杂离子探索其对VO₂薄膜T_MIT的影响,并尝试解释其内部作用机理。在约1 cm²大小抛光的氧化铝薄片上沉积了一系列含不同比例锗离子VO₂薄膜。研究发现锗离子作为掺杂离子确实有利于T_MIT的提高(本课题T_MIT最大可达84.7 ℃)。T_MIT提高的主要原因是锗离子的引入能够强化单斜态V-V二聚体的稳定性,进而增强单斜态的稳定性,使得低温单斜态向四方金红石态转变更加困难。     

白云石制备似立方体状方解石型碳酸钙晶体及其机理研究

以轻烧白云石粉、氯化铵和二氧化碳为原料,在未使用晶型控制剂的情况下,通过蒸氨-沉钙过程制备出了似立方体状碳酸钙。研究了反应温度、溶液中钙离子浓度、通气速率、搅拌速度以及陈化时间对碳酸钙中方解石相含量以及晶体形貌的影响,并探索了沉钙反应的晶型控制机理。结果表明,在反应温度40 ℃、钙离子浓度0.05 mol/L、通碳速率100 mL/min、搅拌速度400 r/min和陈化时间2 h的条件下,制备出形貌规整、粒径分布均匀的似立方体状碳酸钙,平均粒径为5~10 μm。该研究为提升白云石的使用价值、生产高附加价值的碳酸钙产品,以及提高白云石资源的利用率提供理论基础。     

Collective Strategy Condensation: When Envy Splits Societies

Human societies are characterized by three constituent features, besides others. (A) Options, as for jobs and societal positions, differ with respect to their associated monetary and non-monetary payoffs. (B) Competition leads to reduced payoffs when individuals compete for the same option as others. (C) People care about how they are doing relatively to others. The latter trait—the propensity to compare one’s own success with that of others—expresses itself as envy. It is shown that the combination of (A)–(C) leads to spontaneous class stratification. Societies of agents split endogenously into two social classes, an upper and a lower class, when envy becomes relevant. A comprehensive analysis of the Nash equilibria characterizing a basic reference game is presented. Class separation is due to the condensation of the strategies of lower-class agents, which play an identical mixed strategy. Upper-class agents do not condense, following individualist pure strategies. The model and results are size-consistent, holding for arbitrary large numbers of agents and options. Analytic results are confirmed by extensive numerical simulations. An analogy to interacting confined classical particles is discussed.     

Optimisation of the ultrasound-assisted extraction of betalains and polyphenols from Amaranthus hypochondriacus var. Nutrisol

The present study optimised the ultrasound-assisted extraction (UAE) of bioactive compounds from Amaranthus hypochondriacus var. Nutrisol. Influence of temperature (25.86–54.14 °C) and ultrasonic power densities (UPD) (76.01–273.99 mW/mL) on total betalains (BT), betacyanins (BC), betaxanthins (BX), total polyphenols (TP), antioxidant activity (AA), colour parameters (L*, a*, and b*), amaranthine (A), and isoamaranthine (IA) were evaluated using response surface methodology. Moreover, betalain extraction kinetics and mass transfer coefficients (K_La) were determined for each experimental condition. BT, BC, BX, TP, AA, b*, K_La, and A were significantly affected (p < 0.05) by temperature extraction and UPD, whereas L*, a*, and IA were only affected (p < 0.05) by temperature. All response models were significantly validated with regression coefficients (R²) ranging from 87.46 to 99.29%. BT, A, IA, and K_La in UAE were 1.38, 1.65, 1.50, and 29.93 times higher than determined using conventional extraction, respectively. Optimal UAE conditions were obtained at 41.80 °C and 188.84 mW/mL using the desired function methodology. Under these conditions, the experimental values for BC, BX, BT, TP, AA, L*, a*, b*, K_La, A, and IA were closely related to the predicted values, indicating the suitability of the developed quadratic models. This study proposes a simple and efficient UAE method to obtain betalains and polyphenols with high antioxidant activity, which can be used in several applications within the food industry.     

室温铁磁性Sr3YCo4O10.5+δ多晶有序化的烧结工艺及电磁性能

采用固相反应法制备了不同烧结温度(950~1 180 ℃)、烧结时间、烧结次数共7种工艺的Sr₃YCo₄O_10.5+δ多晶块材,通过热分析、XRD、SEM确定了有序化相变和最佳烧结工艺(1 180 ℃/24 h+1 180 ℃/24 h),并研究了多晶的电磁性能。结果表明,964 ℃完全晶化的四方相Sr₃YCo₄O_10.5在1 042 ℃吸氧(δ)完成有序化,生成Sr₃YCo₄O_10.5+δ,而1 100 ℃和1 180 ℃烧结的样品均出现(103)、(215)超结构峰,验证了其结构的有序性。块材均呈半导体电输运行为,二次烧结晶格完整性提高,晶粒长大,300 K时电阻率仅为0.06 Ω·cm,居里温度(T_c)~335 K,零场冷曲线(ZFC)上的Hopkinson峰源于低温时被冻结的磁矩随温度升高转向磁场方向,磁化强度在298 K达到最大,随后受热扰动的影响减小。室温铁磁性源于有序结构导致的中自旋或高自旋态Co³⁺的e_g轨道有序。     

Optimization of biodiesel production via transesterification of soybean oil using α-MoO3 catalyst obtained by the combustion method

A catalyst based on MoO₃ was synthesized by a simple and fast pilot-scale combustion reaction method and applied to the conversion of soybean oil to biodiesel via transesterification. For that, the statistical analysis of the catalyst amount and temperature, factors that influence the process, was evaluated by means of central composite design 2². MoO₃ was characterized in terms of structure by X-ray diffraction (XRD), textural characterization Brunauer-Emmett-Teller (BET), density by helium pycnometry (DE), particle size analysis (DG) and acidity tests by temperature-programmed desorption of ammonia (NH₃-TPD), chemical analysis by X-ray fluorescence (EDX), morphology by scanning electron microscopy (SEM) and catalytic properties. The transesterification products were characterized by gas chromatography (GC), acidity index (AI) and kinematic viscosity (KV). The results indicate the catalyst formation with a surface area of 1.36 m²g^?1, and density of 4.5 g/cm³ which consists of a single crystalline phase of orthorhombic configuration, with total NH₃ acidity of 33.61 μ.mol/g. Morphological characterization revealed that the catalyst is formed by irregular plates of various sizes and shapes, with a wide sizes range of agglomerated particles. In the soybean oil transesterification reactions, the catalyst was active showing 96.9% conversion to ethyl esters. The experimental design was meaningful and predictive, with a reliability level of 95%. The statistical analysis identified temperature as a significant variable for the adopted planning. To conclude, a new single-phase catalyst (α-MoO₃) has been developed and successfully applied to the biodiesel Synthesis from soybean oil. These results have a positive and promising impact for biodiesel production by transesterification of soybean oil against ethanol.     

Pressure-induced novel structure with graphene-like boron-layer in titanium monoboride

The recent discovery of the novel boron-framework in boron-rich metal borides with complex structures and intriguing features under high pressure has stimulated the search into the unique boron-network in the metal monoborides or boron-deficient metal borides at high pressure. Herein, based on the particle swarm optimization algorithm combined with first-principles calculations, we thoroughly explored the structural evolution and properties of TiB up to 200 GPa. This material undergoes a pressure-induced phase transition of $Pnma$ $\to $ $Cmcm$ $\to $ $Pmmm$. Besides of two known phases $Pnma$ and $Cmcm$, an unexpected orthorhombic $Pmmm$ structure was predicted to be energetically favored in the pressure range of 110.88-200 GPa. Intriguingly, the B covalent network eventually evolved from a one-dimensional zigzag chain in $Pnma$-TiB and $Cmcm$-TiB to a graphene-like B-sheet in $Pmmm$-TiB. On the basis of the microscopic hardness model, the calculated hardness ($H_{\rm v}$) values of $Pnma$ at 1 atm, $Cmcm$ at 100 GPa, and $Pmmm$ at 140 GPa are 36.81 GPa, 25.17 GPa, and 15.36 GPa, respectively. Remarkably, analyses of the density of states, electron localization function and the crystal orbital Hamilton population (COHP) exhibit that the bonding nature in the three TiB structures can be considered as a combination of the B-B and Ti-B covalent interactions. Moreover, the high hardness and excellent mechanical properties of the three TiB polymorphs can be ascribed to the strong B-B and Ti-B covalent bonds.     

Solid-state luminescence of Au(I) complexes with external stimuli-responsive properties

In the last decade, the field of stimuli-responsive luminescent materials have been intensely emerged because of the high potential application to functional sensors or photoelectronic devices. In particular, luminescent molecular crystals constructed from Au(I) complexes have produced a wide range of examples of luminescent alterations when some external stimulations, such as heat, mechanical stress, vapor (or solvents), were applied to the solid samples. In this review, we describe the recent progress through a summary of the reported Au(I) complexes based on their utilized stimuli-responsive mechanisms, which are categorized in crystal phase transitions (“crystal-to-amorphous”, “crystal-to-crystal” and “single-crystal-to-single-crystal” transitions) and molecular rotation in crystalline media, respectively.