Pricing and personal data collection strategies of online platforms in the face of privacy concerns

Electronic Commerce Research - We consider a platform providing free content for users and earning profit from the sale of advertising. The platform can collect and analyze personal data to...     

Mechanically induced rhombohedral to tetragonal phase transition in PMN–PT single crystals by nanoindentation

Understanding the phase transition behavior of the rhombohedral phase (R) and tetragonal phase (T) of the relaxor ferroelectric PMN–PT single crystals under mechanical load is essential for the potential voltage-free controlled ferroelectric-based nanodevices. Relaxor ferroelectric single crystals PMN–PT, under a local inhomogeneous mechanical load, were studied experimentally by the nanoindentation tests and Raman spectroscopy measurements. The observations show that the rhombohedral phase can be transformed successfully to the tetragonal phase under a mechanical stress, and the tetragonal phase in the PMN–PT single crystals presents a structural stability. The phase transition induced by the mechanical stress with different strain rates further indicates that the relaxor ferroelectric single crystals possess a potential mechanical controllability. The present study reveals the phase transition pathway of the relaxor ferroelectric single crystal under inhomogeneous stress and provides the exciting possibility of the control of mechanically induced phase transition for ferroelectrics.     

Optical design of the Lyman alpha based beam emission spectroscopy(LAB)diagnostic on the HL-2A tokamak

In this article, we present the optical design of a novel diagnostic on the HL-2 A tokamak, i.e. the20-channel edge Lyman-alpha beam emission spectroscopy, which is a promising solution for edge density turbulence research on tokamaks, as it offers the possibility of density fluctuation measurement with a 3.3 mm spatial resolution while maintains a high temporal resolution of1 μs. The optical path, including the reflective collection optics, the high-dispersion spectrometer, and the linear detector array, is carefully optimized to obtain a good image quality and a high throughput. The maximum root mean square radius of the collection optics is 64 μm.The detected photon flux is estimated to be about 10~(11) photons/s/channel.     

An inverse problem for non-selfadjoint Sturm–Liouville operator with discontinuity conditions inside a finite interval

This paper is concerned with the inverse problem for non-selfadjoint Sturm–Liouville operator with discontinuity conditions inside a finite interval. Firstly, we give the definitions of generalized weight numbers for this operator which may have the multiple spectrum and then investigate the connections between the generalized weight numbers and other spectral characteristics. Secondly, we obtain the generalized spectral data, which consists of the generalized weight numbers and the spectrum. Then the operator is determined uniquely by the method of spectral mappings. Finally, we give an algorithm for reconstructing the potential function and the coefficients of the boundary conditions and the coefficients of the discontinuity conditions.     

塑料薄膜材料在微藻培养环境中的稳定性和生物附着行为

考察了6种薄膜材料在次氯酸钠(NaClO)溶液、HCl溶液(pH=2)和NaOH溶液(pH=12)中的稳定性及其在普通小球藻培养体系中的生物附着行为。结果表明，聚氯乙烯(PVC)在3种溶液中浸泡后420 nm处的透光率下降约50%，聚氨酯(PU)在NaClO溶液中、乙烯?醋酸乙烯酯(EVA)在NaOH溶液中浸泡后420 nm处的透光率下降10%?15%，聚乙烯(PE)、聚丙烯(PP)和聚对苯二甲酸乙二醇酯(PET)在3种溶液中浸泡后的透光率没有明显变化；6种薄膜材料在普通小球藻培养体系中均有微藻明显附着，浸泡7 d后透光率明显下降，其中PVC表面附着最严重，浸泡7 d后透光率接近0，附着物量随浸泡时间延长而增加，浸泡45 d后达3069 ?g/cm2；其它5种薄膜表面附着物量先增加后降低，PU和EVA在第15 d时、PE, PP和PET在第30 d时附着物量最大，分别为292, 375, 292, 194和236 ?g/cm2。     

高压X射线衍射的脉冲激光加热方法

相对于传统的连续激光加热方法,脉冲激光加热能够显著缩短加热时间,从而有效阻止金刚石样品腔内各组分的化学反应。基于北京同步辐射装置(Beijing synchrotron radiation facility,BSRF)高压实验站原有的连续激光加热系统,建立了可应用于高压X射线衍射实验的脉冲激光加热方法。该方法利用信号发生器对脉冲激光器、测温电荷耦合器件(Charge Coupled Device,CCD)光谱仪以及X射线探测器进行同步控制,实现了脉冲激光对样品加热,并在加热周期内完成温度谱及高压衍射数据的同步采集。利用高压条件下的Pt样品,对脉冲激光加热过程中样品的温度稳定性、重复性以及温度梯度进行了测试,并完成了原位X射线衍射实验。该脉冲激光加热系统的搭建,为在BSRF高压实验站开展原位脉冲激光加热方法研究提供了条件,也为将来在北京高能同步辐射光源上实施相关方法奠定了基础。     

Plasmonic coupling-enhanced in situ photothermal nanoreactor with shape selective catalysis for C-C coupling reaction

Carbon-carbon (C-C) coupling reactions represent one of the most powerful tools for the synthesis of complex natural products, bioactive molecules developed as drugs and agrochemicals. In this work, a multifunctional nanoreactor for C-C coupling reaction was successfully fabricated via encapsulating the core-shell Cu@Ni nanocubes into ZIF-8 (Cu@Ni@ZIF-8). In this nanoreactor, Ni shell of the core-shell Cu@Ni nanocubes was the catalytical active center, and Cu core was in situ heating source for the catalyst by absorbing the visible light. Moreover, benefiting from the plasmonic resonance effect between Cu@Ni nanocubes encapsulated in ZIF-8, the absorption range of nanoreactor was widened and the utilization rate of visible light was enhanced. Most importantly, the microporous structure of ZIF-8 provided shape-selective of reactant. This composite was used for the highly shape-selective and stable photocatalysed C-C coupling reaction of boric acid under visible light irradiation. After five cycles, the nanoreactor still remained high catalytical activity. This Cu@Ni@ZIF-8 nanoreactor opens a way for photocatalytic C-C coupling reactions with shape-selectivity.

     

一种基于双重ddPCR的肉制品中牛源性成分的定量分析方法

将低价肉类原料掺入高价肉制品是一种典型的肉类掺假方式，为准确鉴别牛肉及牛肉制品的真伪，建立一种基于双重微滴式数字聚合酶链式反应（droplet digital polymerase chain reaction，ddPCR）的牛源性成分定量分析方法。通过对14 种动物的Beta-actin单拷贝基因序列进行分析，设计牛源性特异性引物、探针与动物源性成分通用引物、探针并建立双重ddPCR体系，推导出牛源性成分质量与其特异性扩增拷贝数之间的计算公式，对牛源性成分进行定量检测该方法得到牛源性成分质量M牛（mg）与其特异性扩增拷贝数浓度C牛（copies/μL）之间的计算公式为M牛=0.033C牛＋2.37，对已知牛肉质量的混合肉样品与不同部位的牛肉样品进行检测，结果显示牛肉定量检测值与实际质量基本一致。同时拷贝数相对含量可辅助判断肉制品中是否存在非牛源性的其他动物源性成分掺假。对市售样品的检测发现，存在目标肉样含量不达标以及不同程度的动物源性成分等掺假现象，说明该检测方法可为牛肉制品掺假量化判定和混合源性产品分级鉴定提供技术支撑。