A new method to improve the electrical properties of KNN-based ceramics: Tailoring phase fraction

Although both the phase type and fraction of multi-phase coexistence can affect the electrical properties of (K,Na)NbO₃ (KNN)-based ceramics, effects of phase fraction on their electrical properties were few concerned. In this work, through changing the calcination temperature of CaZrO₃ powders, we successfully developed the 0.96 K_0.5Na_0.5Nb_0.96Sb_0.04O₃-0.01CaZrO₃-0.03Bi_0.5Na_0.5HfO₃ ceramics containing a wide rhombohedral-tetragonal (R-T) phase coexistence with the variations of T (or R) phase fractions. It was found that higher T phase fraction can warrant a larger piezoelectric constant (d₃₃) and d₃₃ also showed a linear variation with respect to tetragonality ratio (c/a). More importantly, a number of domain patterns were observed due to high T phase fraction and large c/a ratio, greatly benefiting the piezoelectricity. In addition, the improved ferroelectric fatigue behavior and thermal stability were also shown in the ceramics containing high T phase fraction. Therefore, this work can bring a new viewpoint into the physical mechanism of KNN-based ceramics behind R-T phase coexistence.     

Simultaneous degradation of RhB and reduction of Cr(VI) by MIL-53(Fe)/Polyaniline (PANI) with the mediation of organic acid

MIL-53(Fe)/polyaniline (PANI) composite was prepared by in situ depositing PANI on the surface of MIL-53(Fe) and their catalytic performances on the simultaneous removal of RhB and Cr(VI) were investigated. The elimination efficiency of both RhB and Cr(VI) reached more than 98% under pH=2 where hydrochloric acid and citric acid were used to adjust the pH. The results indicated that MIL-53(Fe)/PANI revealed an obvious pH response to the degradation of RhB, while citric acid promoted the Cr(VI) photoreduction. UV-Vis spectra, EIS, and photocurrent response experiments showed that MIL-53(Fe)/PANI had a better light response and carrier migration ability than MIL-53(Fe). The transient absorption spectra also exhibited that the lifetimes of photo-generated carriers were prolonged after the conductive polymer deposition on the MIL-53(Fe) surface. Scavenger experiments demonstrated that the main active species were ·O₂^- and OH. Combined with activity evaluation results, and the possible photocatalytic mechanism of MIL-53(Fe)/PANI on RhB oxidation and Cr(VI) reduction was proposed. The addition of conductive polymer can effectively improve the light response of the catalyst under acidic conditions, and meanwhile citric acid also provided a new mediation for the synergistic degradation of multiple pollutants. Good activity and stability of the catalysts made the scale-up purification of acid water feasible under UV-Vis light.     

北京世园会世界园艺展示区公共景观的实践与思考

对2019年北京世界园艺博览会世界园艺展示区的公共区景观设计背景、公共景观设计逻辑、主题线索的选择及重点设计内容进行了阐述。通过该项目实践,探索国际级专业园林艺术博览会公共区景观设计中,将人的行为事件作为场地设计推动力,将人的主观性与自然的存在性有效融合的方法与途径。结合项目设计重点区域,着重谈论了"种子的故事""蝶恋花"和"老树记忆"3条设计线索的演绎,阐释与表达人与自然的和谐共生关系。希望该项目能传递设计者对于自然、对于生命的尊重与情感的表达,创造出与自然山水和谐共生的现代景观。     

“城市人”视角下社区卫生服务设施的供需匹配分析及规划策略——以武汉市为例

社区卫生服务设施是保障居民健康生活的基础,是健全城市公共服务的重要组成部分。基于"城市人"理论,以使用者和设施运营者"自存-共存"平衡状态下的共识为目标,构建"基于理性的需求共识和物性的规划匹配以及面向典型人居的要素干预"的社区卫生服务设施评价及规划方法。以武汉市为例,采用社会调查、回归分析、最优化分析等方法,辨识社区卫生服务设施"需求方"满意度的共识,并对典型生活圈的要素进行提取和对比,从服务范围、人居属性、道路属性及设施属性等方面提出优化策略。     

中山市奕翠园住宅小区园林规划浅析

中山市奕翠园住宅小区的园林规划设计,充分考虑了人文与自然的统一,以新版岭南水乡的风格为主题,把点、线、面有机的融合为一体,创造出丰富的立体三维园林空间,营造出一个人与自然和谐共存的居住空间。     

LTE和Wi-Fi系统间灵活频谱使用关键技术

针对授权辅助接入,提出了一种适用于LTE-U与Wi-Fi共同使用免授权频段的方法,该方法无需更改Wi-Fi协议就能实现LTE-U与Wi-Fi比例公平使用免授权频谱,有效聚合授权频谱与免授权频谱,提升频谱效率,为用户提供更好的业务体验。     

基于IMCT理论的CaO-SiO2-MgO-Al2O3-Na2O渣系的脱硫热力学模型

 为了精确表征含Na2O渣系的脱硫能力，改善脱硫效果，基于熔渣离子与分子共存理论（IMCT）建立了CaO-SiO2-MgO-Al2O3-Na2O渣系结构单元的作用浓度计算模型和1 753 K时该渣系的脱硫热力学模型。并对渣系的总硫分配比及各自硫分配比的影响因素进行了讨论分析。理论结果表明，除LS， MgS外，随着Al2O3质量分数的增加，该渣系的脱硫能力明显下降，而MgO和Na2O质量分数的增加，对提高渣系的脱硫能力具有明显的促进作用。此外，少量的Na2O即可表现出很强的脱硫效果，这为含有Na2O的冶金二次资源在铁水脱硫过程中的应用以及铁水脱硫渣系的优化提供了必要的理论依据。     

Chemical warfare and survival strategies in bacterial range expansions

Dispersal of species is a fundamental ecological process in the evolution and maintenance of biodiversity. Limited control over ecological parameters has hindered progress in understanding of what enables species to colonize new areas, as well as the importance of interspecies interactions. Such control is necessary to construct reliable mathematical models of ecosystems. In our work, we studied dispersal in the context of bacterial range expansions and identified the major determinants of species coexistence for a bacterial model system of three Escherichia coli strains (toxin-producing, sensitive and resistant). Genetic engineering allowed us to tune strain growth rates and to design different ecological scenarios (cyclic and hierarchical). We found that coexistence of all strains depended on three strongly interdependent factors: composition of inoculum, relative strain growth rates and effective toxin range. Robust agreement between our experiments and a thoroughly calibrated computational model enabled us to extrapolate these intricate interdependencies in terms of phenomenological biodiversity laws. Our mathematical analysis also suggested that cyclic dominance between strains is not a prerequisite for coexistence in competitive range expansions. Instead, robust three-strain coexistence required a balance between growth rates and either a reduced initial ratio of the toxin-producing strain, or a sufficiently short toxin range.     

A Back Look on the Binary Phase Diagrams of Metals from the Mass Action Law and the Coexistence Theory of Metallic Melts

According to the mass action law and the coexistence theory of metallic melts, the mass action concentrations of Cu-Mg, Bi T1 and Ni-Al melts involving compound formation have been calculated. The calculated results show that, except the ultimate case of pure element, when two elements are present in the melts, all structural units (atoms and molecules) without exception will be present in the melts, i.e., their concentrations may change from great to small, but they will not vanish into nothing, and only under such conditions, the calculated results both agree with practice and obey the law of mass action. In view of that over considerable wide composition range, the activities of both elements of the three solid binary alloys mentioned above have been measured, this seems in contradiction with the present relevant phase diagrams, in which the structural units are determined by composition range, so the latter needs further investigation and consideration.