Perovskite oxynitrides AB(N,O)_(3), a crucial class in materials science, have attracted much attention. By precisely controlling A-and B-site ions and tuning the N/O ratio, new materials with exotic charge states and...Perovskite oxynitrides AB(N,O)_(3), a crucial class in materials science, have attracted much attention. By precisely controlling A-and B-site ions and tuning the N/O ratio, new materials with exotic charge states and intriguing electronic behaviors can be designed and synthesized. In this work, a novel oxynitride perovskite, CeNbO_(2)N, was prepared under high-temperature and high-pressure conditions. The compound crystallizes in an orthorhombic perovskite structure in Pnma symmetry with disordered N/O distribution. The x-ray absorption spectroscopy confirms the presence of a Nb^(4+) state with 4d^(1) electronic configuration in CeNbO_(2)N. As a result, the resistivity of CeNbO_(2)N is sharply reduced compared to its counterpart CeTa^(5+)ON_(2) and other Nb^(5+) compounds. No long-range spin order is found to occur with the temperature down to 2 K in CeNbO_(2)N, while a remarkable negative magnetoresistance effect shows up at lower temperatures, probably due to the magnetic scattering arising from short-range spin correlations.展开更多
再生器是溶液除湿系统中的关键部件之一,提高再生器综合性能是解决极端热湿气候区高湿问题的有效手段。将指标相关法(CRITIC,Criteria Importance Through Intercriteria Correlation)和优劣解距离法(TOPSIS,Technique for Order Prefer...再生器是溶液除湿系统中的关键部件之一,提高再生器综合性能是解决极端热湿气候区高湿问题的有效手段。将指标相关法(CRITIC,Criteria Importance Through Intercriteria Correlation)和优劣解距离法(TOPSIS,Technique for Order Preference by Similarity to Ideal Solution)联合,建立CRITIC-TOPSIS模型,用于再生器运行入口参数(空气质量流量、溶液质量流量、温度)的选择评价。以永暑岛礁地区为例,通过再生器处理模型得到基础数据以及4个指标的评价体系,采用CRITIC法求得权重后使用TOPSIS法对220种运行入口参数的组合方案进行评价得到最优解。结果表明,空气质量流量为0.1 kg/s、溶液质量流量为0.3 kg/s、溶液温度为56℃时得分0.885,为永暑地区再生器综合性能最优解;再生量指标的权重为0.4,可作为永暑地区再生器综合性能的代表性指标。展开更多
为探究国内外公路隧道通风标准中需风量存在差异的原因,解决目前公路隧道通风精准化设计存在的难题,以我国隧道通风设计标准JTG/T D70/2-02—2014《公路隧道通风设计细则》和世界道路协会(PIARC)《Road tunnels:Vehicle emissions and a...为探究国内外公路隧道通风标准中需风量存在差异的原因,解决目前公路隧道通风精准化设计存在的难题,以我国隧道通风设计标准JTG/T D70/2-02—2014《公路隧道通风设计细则》和世界道路协会(PIARC)《Road tunnels:Vehicle emissions and air demand for ventilation》2019标准中关于隧道稀释机动车污染物所需风量计算方法为理论基础,结合江苏省某长江隧道实际工程案例,针对80、60、40、30、20(全程阻滞)、10 km/h(局部阻滞)6种工况,分别计算稀释CO、NO_(2)和VI的近期(2035年)、远期(2045年)所需风量。结果表明:1)两者在计算方法上的不同造成了计算结果的差异,相同背景计算出的稀释污染物设计需风量数值国内标准是国际标准的3.35倍;国内外机动车CO基准排放量的差异是造成稀释CO所需风量差距较大的原因,且NO_(2)对隧道需风量的影响程度已逐渐超过CO。2)采用国内标准计算稀释VI所需风量值在低车速工况下受烟尘设计浓度值和车密度影响较明显。3)随着机动车尾气排放标准逐渐严格和新能源汽车的出现,为了适应我国机动车尾气排放特性,新的基准排放量要考虑的因素需增加。展开更多
基金Project supported by the National Key R&D Program of China (Grant No. 2021YFA1400300)the National Natural Science Foundation of China (Grant Nos. 12425403, 12261131499, 12304268, 12304159, 11934017, and 11921004)+1 种基金the China Postdoctoral Science Foundation (Grant No. 2023M743741)The synchrotron x-ray diffraction experiments were performed at SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (Grant Nos. 2023B1575, 2023B1976, 2024A1506, and 2024A1695)。
文摘Perovskite oxynitrides AB(N,O)_(3), a crucial class in materials science, have attracted much attention. By precisely controlling A-and B-site ions and tuning the N/O ratio, new materials with exotic charge states and intriguing electronic behaviors can be designed and synthesized. In this work, a novel oxynitride perovskite, CeNbO_(2)N, was prepared under high-temperature and high-pressure conditions. The compound crystallizes in an orthorhombic perovskite structure in Pnma symmetry with disordered N/O distribution. The x-ray absorption spectroscopy confirms the presence of a Nb^(4+) state with 4d^(1) electronic configuration in CeNbO_(2)N. As a result, the resistivity of CeNbO_(2)N is sharply reduced compared to its counterpart CeTa^(5+)ON_(2) and other Nb^(5+) compounds. No long-range spin order is found to occur with the temperature down to 2 K in CeNbO_(2)N, while a remarkable negative magnetoresistance effect shows up at lower temperatures, probably due to the magnetic scattering arising from short-range spin correlations.
文摘再生器是溶液除湿系统中的关键部件之一,提高再生器综合性能是解决极端热湿气候区高湿问题的有效手段。将指标相关法(CRITIC,Criteria Importance Through Intercriteria Correlation)和优劣解距离法(TOPSIS,Technique for Order Preference by Similarity to Ideal Solution)联合,建立CRITIC-TOPSIS模型,用于再生器运行入口参数(空气质量流量、溶液质量流量、温度)的选择评价。以永暑岛礁地区为例,通过再生器处理模型得到基础数据以及4个指标的评价体系,采用CRITIC法求得权重后使用TOPSIS法对220种运行入口参数的组合方案进行评价得到最优解。结果表明,空气质量流量为0.1 kg/s、溶液质量流量为0.3 kg/s、溶液温度为56℃时得分0.885,为永暑地区再生器综合性能最优解;再生量指标的权重为0.4,可作为永暑地区再生器综合性能的代表性指标。
文摘为探究国内外公路隧道通风标准中需风量存在差异的原因,解决目前公路隧道通风精准化设计存在的难题,以我国隧道通风设计标准JTG/T D70/2-02—2014《公路隧道通风设计细则》和世界道路协会(PIARC)《Road tunnels:Vehicle emissions and air demand for ventilation》2019标准中关于隧道稀释机动车污染物所需风量计算方法为理论基础,结合江苏省某长江隧道实际工程案例,针对80、60、40、30、20(全程阻滞)、10 km/h(局部阻滞)6种工况,分别计算稀释CO、NO_(2)和VI的近期(2035年)、远期(2045年)所需风量。结果表明:1)两者在计算方法上的不同造成了计算结果的差异,相同背景计算出的稀释污染物设计需风量数值国内标准是国际标准的3.35倍;国内外机动车CO基准排放量的差异是造成稀释CO所需风量差距较大的原因,且NO_(2)对隧道需风量的影响程度已逐渐超过CO。2)采用国内标准计算稀释VI所需风量值在低车速工况下受烟尘设计浓度值和车密度影响较明显。3)随着机动车尾气排放标准逐渐严格和新能源汽车的出现,为了适应我国机动车尾气排放特性,新的基准排放量要考虑的因素需增加。
