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β-二酮类化合物分子中存在着酮式与烯醇式的互变异构体,适于与金属离子发生配位作用。通过对各种金属离子的革取性能和机理的研究,表明它们是有效的革取剂,已广泛用于过渡金属和稀土离子的分离和分析中。相应Eu、Tb稀土配合物,具有独特的光致发光和电致发光性能,可以开发成理想的发光材料. 相似文献
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对ZnO单晶材料不同温度下进行了光致发光研究。室温下ZnO单晶有两个发光峰,分别为375nm的紫外发光峰和570nm的可见光发光带。随着温度的降低,出现两个紫外发光峰,分别为自由激子(FX)和束缚激子(D0X)发光峰,并且束缚激子发光峰随着温度降低较自由激子变化明显。较低温度时在370nm到400nm出现多个发光峰,为声子(LO)参与的受主束缚激子(A0X)发光峰。10K时出现四个紫外发光峰,分别为自由激子(FX)、表面激子(SX)和束缚激子(D0X)发光峰。 相似文献
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以混合的Zn粉和金属Ga作为源,通过热蒸发方法合成了高产率ZnO:Ga麦克风微米结构。室温光致发光表明,可见发光峰可能是由于ZnO样品中的表面缺陷态引起的。发光动力学表明,低温光致发光由中性施主束缚激子(D0,X)、中性受主束缚激子(A0,X)和A0,X的一个伴线(A0,X-1LO)组成。随温度的升高各个峰的强度迅速下降。最后被自由激子(FX)取代,成为占主导地位的峰。 相似文献
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研究了纳米硅在3K-250K温度范围的光致发光谱的特性。观测到纳米硅的三个发光峰,其中心波长分别为470nm、479nm和487nm。随着温度的升高,470nm的发光峰呈现蓝移且强度明显增强,479nm的发光峰位不随温度的变化而变化,487nm的发光峰随温度的升高出现微小的红移。基于量子限制效应,提出综合发光模型解释实验结果。 相似文献
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建立了人体血浆多相模型,研究了人体血浆体系中Tb(Ⅲ)物种的分布.结果表明,Tb(Ⅲ)的物种形式随着Tb(Ⅲ)的量浓度的变化而变化.当Tb(Ⅲ)的量浓度低于4.000×10-8mol/L时,大部分Tb(Ⅲ)物种以可溶态存在;当Tb(Ⅲ)的量浓度高于4.000×10-8mol/L而低于1.667×10-2mol/L时,沉淀物种(TbPO4和Tb2(CO3)3)成为Tb(Ⅲ)的主要物种.可溶的Tb(Ⅲ)在量浓度低于1.0×10-4mol/L时,主要与运铁蛋白键合,分布于[Tb(Tf)]中;当Tb(Ⅲ)的量浓度高于1.0×10-4mol/L时,运铁蛋白耗尽,可溶的Tb(Ⅲ)主要分布于[Tb(HSA)],[Tb2(Tf)],[Tb(Ox)]和[Tb(Cit)]等物种中. 相似文献
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依据Sb(Ⅲ)对Cr(Ⅵ)-Ⅰ~--氧化还原反应体系的诱导作用,以Ⅰ_3~--淀粉络合物为指示剂,提出了测定微量锑(Ⅲ)的诱导动力学-停流流动注射光度法.本法线性范围为0～2.6μg/ml Sb(Ⅲ),测定Sb(Ⅲ)的检测限为0.008μg/ml.10 倍量的Sb(Ⅴ)对Sb(Ⅲ)的测定没有影响;测得Sb(Ⅲ)量后,将Sb(Ⅴ)还原为Sb(Ⅲ)并测定总锑量,进而可作锑的价态分布.用本法测定了污染水样中锑的价态分布以及总锑量,样品平均加标回收率为98.1％,相对标准偏差RSD<1.3％. 相似文献
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首次利用材料在超短脉冲激发下的瞬间高载流子密度特性研究了GaNxAs1-x/GaAs量子阱的光学特性。研究首次发现在高于量子阱的Mott迁移边(局域发光的高能端)存在一个非局域特性的新的发光峰。该峰具有与局域发光完全不同的光学性质。通过研究材料的不同温度和激发强度下的发光行为证实该新的发光峰是量子阱的本征能级发光。这一结果为目前人们在Ga(In)NAs材料体系中是否存在Ga(In)NAs合金态或者N是以杂质带的形式存在的争论提供了重要证据。在Ga(In)NAs以及InGaN等材料体系中都观察到PL发光峰随温度升高先红移，然后蓝移，再红移的所谓的“S”形变化。它的来源一直令人们疑惑不解。我们直接证明GaNxAs1-x材料中发光峰的“S”形变化是由于材料中的低能端的局域态随温度的淬灭以及相邻的局域态与非局域态之间在温度的作用下相互竞争的结果。这一结果为能量随温度的“S”形变化提供了最直接的实验证据。通过光荧光谱, 时间分辨光谱研究了低N含量的GaNxAs1-x光学性质。首次发现在低N含量的GaNxAs1-x材料(N%<1%)中，在N的杂质态的高能端(低于GaAs带边)存在一个新的，其光学性质与N的杂质态完全不同的发光峰。实验证明该峰是GaNxAs1-x材料的合金态。这一结果说明在GaNxAs1-x中即便在N含量<0.1%时就已经形成了GaNxAs1-x的合金态。这个结果的重要意义在于它直接证明N在GaAs中能够形成GaNxAs1-x合金，而不是仅仅以N的杂质态存在。这为目前人们所争论的N在GaAs所起的作用，GaNxAs1-x光跃迁的来源，以及Ga(In)NAs的基本能带结构提供了直接的实验证据。最后我们利用选择激发在GaAs1-xSbx/GaAs量子阱中实验上第一次同时观察到空间直接（Type-I）跃迁和间接跃迁(Type-II)。时间分辨荧光寿命谱进一步直接论证了GaAs1-xSbx/GaAs能带排列的Type-II特性。 相似文献
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为提高大型体育赛事的物流管理水平,从大型体育赛事的发展态势分析入手,研究了大型体育赛事物流的概念.将3PL平台引入到大型体育赛事物流管理中,分析了3PL平台的优点 从管理决策层、信息层、3PL平台以及资源层四个层次,构建了以3PL平台为基础的大型体育赛事物流的流程体系.分析出了其未来的发展方向,给出相应建议. 相似文献
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Xujie Lü Constantinos Stoumpos Qingyang Hu Xuedan Ma Dongzhou Zhang Songhao Guo Justin Hoffman Kejun Bu Xiaofeng Guo Yingqi Wang Cheng Ji Haijie Chen Hongwu Xu Quanxi Jia Wenge Yang Mercouri G Kanatzidis Ho-Kwang Mao 《国家科学评论(英文版)》2021,8(9)
Metal halide perovskites possess unique atomic and electronic configurations that endow them with high defect tolerance and enable high-performance photovoltaics and optoelectronics. Perovskite light-emitting diodes have achieved an external quantum efficiency of over 20%. Despite tremendous progress, fundamental questions remain, such as how structural distortion affects the optical properties. Addressing their relationships is considerably challenging due to the scarcity of effective diagnostic tools during structural and property tuning as well as the limited tunability achievable by conventional methods. Here, using pressure and chemical methods to regulate the metal off-centering distortion, we demonstrate the giant tunability of photoluminescence (PL) in both the intensity (>20 times) and wavelength (>180 nm/GPa) in the highly distorted halide perovskites [CH3NH3GeI3, HC(NH2)2GeI3, and CsGeI3]. Using advanced in situ high-pressure probes and first-principles calculations, we quantitatively reveal a universal relationship whereby regulating the level of off-centering distortion towards 0.2 leads to the best PL performance in the halide perovskites. By applying this principle, intense PL can still be induced by substituting CH3NH3+ with Cs+ to control the distortion in (CH3NH3)1-xCsxGeI3, where the chemical substitution plays a similar role as external pressure. The compression of a fully substituted sample of CsGeI3 further tunes the distortion to the optimal value at 0.7 GPa, which maximizes the emission with a 10-fold enhancement. This work not only demonstrates a quantitative relationship between structural distortion and PL property of the halide perovskites but also illustrates the use of knowledge gained from high-pressure research to achieve the desired properties by ambient methods. 相似文献
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物流业务外包后,第三方物流(3PL)公司代替企业与顾客互动,这在电子商务中尤为明显,因此第三方物流公司的服务质量是否影响顾客满意度成为一个重要问题。在C2C网络购物环境中,基于物流服务质量模型,建立了第三方物流服务质量与顾客满意度的测评模型(LSQ-CS)。对LSQ-CS模型的实证研究表明:物流交互和运作质量均影响顾客对第三方物流服务商的满意度;成本质量并不影响顾客对第三方物流服务商的满意度;物流交互质量对运作和成本质量产生影响;此外,第三方物流服务质量也影响着顾客对企业的满意度。这一研究结论表明当前物流市场中第三方物流公司应该保证运作质量,提高交互质量,避免低成本恶性竞争;同时除了物流成本外,企业也应根据物流服务质量来选择物流服务商。 相似文献
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长三角城市群协同发展背景下,城市间产业转移频繁,伴随经济和碳排放的连接,对城市碳排放强度产生的影响成为区域低碳发展需要考虑的重要战略问题。本文采用动态偏离-份额模型测度城市间产业转入和转出量。基于空间全局自相关、反距离空间权重和经济地理权重矩阵下的空间杜宾模型,对2005—2017年26个长三角城市的产业转移动态、碳排放强度的时空演变特征进行研究,在空间溢出视角下对城市碳排放强度的影响因素进行分析。结果表明：①碳排放强度存在显著的空间自相关性,具有明显的空间溢出效应。②长三角城市群内频繁转移的产业多数为非能源密集型产业,产业转移并未产生显著“碳减排”效应。值得注意的是,产业转移的经济影响开始显现,产业转移实际上不利于长三角城市群整体碳排放量减少。③人均GDP与碳排放强度呈现“倒U型”,技术水平与碳排放强度呈现“U型”,存在“技术进步的反弹效应”,人口数的增加降低了碳排放强度,二产比重正向作用于碳排放强度。因此在制订碳减排计划时,需要考虑不同区域生产效率、能耗强度、人力资本等因素,做好产业转入、转出的碳排放强度监测,避免盲目进行产业转移;壮大优势产业,改善产业结构,培育新增长点,发展符合城市自身禀赋的低能耗产业。 相似文献
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Achieving value from knowledge has been illusive to the organization despite recent attempts to capitalize on it. An individual's willingness to share his or her knowledge is an essential factor in the organization benefiting from the knowledge it collectively possesses. Yet little is understood regarding what knowledge people are willing to share. This paper describes the development of a new construct, perceived value of knowledge (PVK). PVK's relationship with intentions to share knowledge is illustrated (both qualitatively and quantitatively). The qualitative study illustrates that it may influence the enablers and the barriers to knowledge sharing. The quantitative study found that PVK is positively related to intentions to share knowledge, while Uniqueness of Knowledge (a related but separate construct) is negatively related to intentions to share knowledge. Implications of perceived value of knowledge is discussed. 相似文献
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主要研究供应商碳配额不足、制造商碳配额富余、零售商碳配额富余情景下,考虑碳排放转移影响的三级供应链企业间最优运营策略问题。运用变分不等式理论构建超网络模型,研究结果表明：(1)网络内生性的碳排放转移率能弥补供应商碳配额不足,有助于确保网络均衡状态下供应商碳排放量在政府规定的碳配额范围之内;(2)随着碳排放转移率的升高,供应链超网络的网络均衡交易数量总体呈现下降趋势,网络均衡交易价格总体呈上升趋势;(3)由于碳排放转移效应的存在,供应链整体的利润下降,供应链企业应警惕碳排放转移带来的影响。 相似文献
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Knowledge transfer processes in IT outsourcing relationships and their impact on shared knowledge and outsourcing performance 总被引：1，自引：0，他引：1
What is the impact of specific knowledge-transfer processes on the level of shared knowledge and, in turn, on outsourcing performance in outsourcing relationships? Drawing on a series of case studies covering IT providers and banks, we investigate several applied knowledge-transfer processes dedicated to the transfer of explicit or tacit knowledge between outsourcing banks and their providers. We examine the differential influence of various types of knowledge transfer on shared knowledge between the parties and on the resulting outsourcing performance. Results depict the differential impact of various knowledge-transfer processes dedicated to the transfer of explicit, or tacit knowledge, respectively, on the development of shared knowledge. Interestingly, the combination of both knowledge-transfer processes dedicated to the transfer of explicit knowledge and those dedicated to the transfer of tacit knowledge proves to be most effective. Furthermore the results indicate that high levels of shared knowledge positively influence outsourcing performance. In addition to previous literature, we found transfer processes for explicit knowledge in an outsourcing context to consist of two dimensions: The content dimension, primarily focused on in literature, and the sender–receiver dimension of transfer processes which are rarely addressed in outsourcing literature. The content dimension embraces mechanisms such as trainings, SLAs and standards that define how content has to be interpreted, whereas the sender–receiver dimension of transfer processes of explicit knowledge defines explicit, documented interaction structures between parties. 相似文献
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本文运用阈值协整模型揭示了我国电力消费与经济增长、产业结构、电力使用效率、电力价格因经济周期性波动而具有的长期非线性关系,主要结论为:(1)我国经济增长对电力消费的阈值效应的机制转移发生在人均GDP增长率等于7.479%和9.184%处;(2)整个样本期间,经济增长显著推动了电力消费增长,电力使用效率的提高则是抑制电力消费增长的主要因素,以退二进三为主导的产业结构调整表现出了对电力消费的节电红利现象,但在不同的经济增长阶段其效应值存在显著差异;(3)当经济增长处于7.479～9.184%的适度增长区间时,产业结构的调整和优化具有最大的节电红利效应;(4)电价的扭曲削弱了价格机制对电力消费的引导和配置作用。 相似文献
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Inspired by nature, improving photosensitization represents a vital direction for the development of artificial photosynthesis. The sensitization ability of photosensitizers (PSs) reflects in their electron-transfer ability, which highly depends on their excited-state lifetime and redox potential. Herein, for the first time, we put forward a facile strategy to improve sensitizing ability via finely tuning the excited state of Ru(II)-PSs (Ru-1–Ru-4) for efficient CO2 reduction. Remarkably, [Ru(Phen)2(3-pyrenylPhen)]2+ (Ru-3) exhibits the best sensitizing ability among Ru-1–Ru-4, over 17 times higher than that of typical Ru(Phen)32+. It can efficiently sensitize a dinuclear cobalt catalyst for CO2-to-CO conversion with a maximum turnover number of 66 480. Systematic investigations demonstrate that its long-lived excited state and suitable redox driving force greatly contributed to this superior sensitizing ability. This work provides a new insight into dramatically boosting photocatalytic CO2 reduction via improving photosensitization. 相似文献