化学共沉淀法制备单相BiFeO3粉体及其高密度单相陶瓷块材的物理性能

通过对Fe3+-Bi3+-NO-3-H2O体系的热力学分析,确定了Bi3+、Fe3+共沉淀范围为p H=7~12。固定p H=11,采用共沉淀法制备了Bi Fe O3的前驱体,经过煅烧得到了单相Bi Fe O3粉体,并进行了粒度和晶体结构的研究。采用放电等离子烧结(spark plasma sintering,SPS)的方法制备出高密度单相Bi Fe O3陶瓷块材并测试了其介电性能和铁电性能。结果表明,陶瓷块材相对密度为96.7%;陶瓷块材在频率为30 MHz时,介电常数ε’为91.9,介电损耗tanδ为0.017;陶瓷块材在室温时具有铁电性。在电场强度为30 k V/cm时,饱和极化强度Ps’=0.40μC/cm2,剩余极化强度Pr’=0.17μC/cm2,矫顽场强度EC=16 k V/cm。放电等离子烧结(SPS)出的陶瓷块材比传统常压烧结制备的陶瓷块材更加致密,介电和铁电性能更加优良。     

超声法合成CePO4纳米线及发光性能研究

用CeO2作为铈源,采用可重复利用的H3PO4及非模板剂的情况下,用低温超声法成功合成了六方结构的CePO4一维纳米线材料。用X-射线粉末衍射(XRD)、透射电镜(TEM)和荧光分光光度计(FL)测试样品的物相结构、微观形貌、颗粒尺寸和发光性能;并研究超声时间和PO3-4/Ce3+摩尔比对产物的形貌和荧光性能的影响。结果表明:实验所做出的样品全部是六方晶系的结构,形貌都为一维纳米线,其纳米线长50~200nm,宽5~40nm左右;不同超声时间和PO3-4/Ce3+摩尔比的纳米线长径比不同,随超声时间的延长和PO3-4/Ce3+摩尔比增大纳米线出现团聚现象,产物在250~300nm处有宽的激发峰,在378nm处有一个发射峰,是属于Ce3+的5d-4f能级跃迁。     

Ca8Mg（SiO4）4Cl2∶Eu2+,Ce3+,Mn2+绿色荧光粉发光性能及其应用研究

利用高温固相法,合成出Eu2+、Ce3+、Mn2+共掺的Ca8Mg(SiO4)4Cl2系列绿色荧光粉。通过XRD表征了这些荧光粉的结构,通过分子荧光光谱仪研究了它们的室温发光性能。首先调查了Eu2+掺杂的Ca8Mg(SiO4)4Cl2绿色荧光粉发光性能,随后引入Ce3+、Mn2+提高了Ca8Mg(SiO4)4Cl2∶Eu2+在紫外光区的吸收强度及绿光发射强度。最后将筛选出来的荧光粉与InGaN-LED芯片组装制作成单一绿光LED器件,利用Ca7.8215MgSi4O16Cl2∶0.0525Eu2+,0.056Ce3+,0.070Mn2+所制作成的绿光LED器件发光最强,在20mA电流激发下,此LED发很强的绿光,其电致发光光谱所对应的色坐标值为:x=0.26,y=0.55。     

3-Oxodapagliflozin as a Potent and Highly Selective SGLT2 Inhibitor for the Treatment of Type 2 Diabetes

Structural modifications of 3-OH in the glucose moiety of dapagliflozin（1）, an approved potent sodium-dependent glucose transporter 2（SGLT2） inhibitor, led to 3-oxodapagliflozin（16）, a highly potent and more selective SGLT2 inhibitor[IC50（hSGLT1）/IC50（hSGLT2）=2851 for compound 16 vs. 843 for compound 1]. 3-Oxodapagliflozin（16） exhibited in vitro（IC50=1.0nmol/L against hSGLT2 for compound 16 vs. 1.3 nmol/L for compound 1） and in vivo activities comparable to those of dapagliflozin（1）. The bioactivities of 3-oxodapagliflozin （16） warrant its further evaluation as a promising SGLT2 inhibitor for the treatment of type 2 diabetes.     

Comparison of Two Rhodamine-Polyamine Polystyrene Solid-phase Fluorescence Sensors for Hg(II) Detection Based on Theoretical Calculation

Two novel rhodamine-based polystyrene solid-phase fluorescence sensors PS-PA-I and PS-PA-II with different lengths of polyamines were synthesized for Hg(II) determination. The detection mechanism involving the Hg(II) chelation-induced spirocycle open of rhodamine was proposed with the aid of theoretical calculation. The stronger N-Hg bond and the longer polyamine chain in PS-PA-II led to a better selectivity, much higher and more quickly fluorescence response to Hg(II).     

Towards Artificial Cells: Engineering Encapsulated Molecular Signaling with Intelligent DNA Nanomachines

The building and engineering of an artificial molecular signaling system in encapsulated vesicles is a key step towards artificial cells. Recently, Tan et al. reached a new milestone by integrating an intelligent DNA nano- gatekeeper with an artificial vesicle system. The DNA nanogatekeeper driven by adenosine triphosphate(ATP) is able to receive outside stimulus, which in turn switches the diffusion of environmental ions into the integrated vesicle. Most importantly, this system enables triggering downstream signaling cascaded reactions confined in the artificial vesicle, as well as returning feedback to the DNA nanogatekeeper, mimicking real cellular behaviors of reception, transduction and response. This work has been published online in Nature Communications aon February 20, 2020.     

COMPUTER SIMULATION TECHNIQUES FOR A MOBILE SATELLITE COMMUNICATION CHANNEL

This paper gives a brief and systematic presentation of the computer simulation techniques of satellite communications, especially for a mobile satellite channel, based on a summarization of the author's exploration and experience in this area. It includes the equivalent complex baseband notation (ECBN) method, a very convenient mathematical form for software simulation; development of a multi-functional and expandable channel simulation system on a computer from L-band to Ka-band; channel impulse or frequency response estimation in real time by the technique burst-mode link analyser with least-squares algorithm (BMLA/LS), modelling and simulation of the channel fast fading due to multipath and shadowing; acquisition of the equivalent normalized binary signal-to-noise ratio (E_b/N₀) data at the channel input; and bit-error rate (BER) evaluation by the directly error-counting approach and the computational approach at the channel output in simulation.     

连续波多R(·R)测量系统设计

连续波多RR测量体制是某测控系统的主干测量系统,本文从精度、可靠度、与系统内其它设备的协调性、弹地协调等方面完成了系统设计,并从系统的角度提出了对单台设备的主要技术指标要求。     

压控器件的磁隔离驱动电路设计

根据压控器件的特点,设计出了适用于任意占空比的磁隔离驱动电路。通过仿真,进一步得到最优化的实际驱动电路,最后给出了实验波形。