Manipulating selenium molecular configuration in N/O dual-doped porous carbon for high performance potassium-ion storage

Potassium-selenium(K-Se)batteries have attracted more and more attention because of their high theoretical specific capacity and natural abundance of K resources.However,dissolution of polyselenides,large volume expansion during cycling and low utilization of Se remain great challenges,leading to poor rate capability and cycle life.Herein,N/O dual-doped carbon nanofibers with interconnected micro/mesopores(MMCFs)are designed as hosts to manipulate Se molecular configuration for advanced flexible K-Se batteries.The micropores play a role in confining small Se molecule(Se_(2–3)),which could inhibit the formation of polyselenides and work as physical barrier to stabilize the cycle performance.While the mesopores can confine long-chain Se(Se_(4–7)),promising sufficient Se loading and contributing to higher discharge voltage of the whole Se@MMCFs composite.The N/O co-doping and the 3D interpenetrating nanostructure improve electrical conductivity and keep the structure integrity after cycling.The obtained Se_(2–3)/Se_(4–7)@MMCFs electrode exhibits an unprecedented cycle life(395 mA h g^(−1) at 1 A g^(−1) after 2000 cycles)and high specific energy density(400 Wh kg^(−1),nearly twice the specific energy density of the Se_(2–3)@MMCFs).This study offers a rational design for the realization of a high energy density and long cycle life chalcogen cathode for energy storage.

Multiplexing modulation design optimization and quality evaluation of BDS-3 PPP service signal

The Precise Point Positioning(PPP)service of BeiDou-3 Navigation Satellite System(BDS-3)is implemented on its Geostationary Earth Orbit(GEO)satellites.However,its signal design is limited by the actual power of satellite and other conditions.Furthermore,the design needs to fully consider the compatibility of diferent service phases.Starting from the actual state of the BDS-3 GEO satellite,this paper studies the multiplexing modulation of the BDS PPP service signal that is based on the Asymmetric Constant Envelope Binary Ofset Carrier(ACE-BOC)technique and proposes several feasible schemes for this signal.Comparison and optimization of these techniques are made from the aspects of transmission efciency,multiplexing efciency,and service forward compatibility.Based on the Type-III ACE-BOC multiplexing modulation technique,phase rotation and intermodulation reconstruction techniques are proposed to suppress the intermodulation interference issue.Finally,a signal based on improved ACE-BOC multiplexing is designed.The quality of the proposed signal was continuously monitored and tested using large-diameter antennas.The evaluation results show that the power spectrum deviation of the signal is 0.228 dB,the correlation loss is 0.110 dB,the S-curve slope deviation is 1.558%on average,the average length diference between the positive/negative chip and the ideal chip is only 0.0006 ns,and the coherence between the carrier and the pseudo code is 0.082°.All quality indicators are satisfactory,indicating that the proposed signal multiplexing modulation technique is an ideal solution that meets all the requirements of the design constraints,and can achieve efcient information broadcasting and forward compatibility of the BDS PPP service.

IOLMaster700与IOLMaster500测量白内障术前眼轴长度的一致性及检出率比较

目的:比较新型扫频源生物测量仪IOLMaster700与传统部分相干光干涉生物测量仪IOLMaster500测量白内障患者眼轴长度(AL)的相关性、一致性及检出率。方法:系列病例研究。选取2017年8-9月于北京同仁医院眼科就诊的年龄相关性白内障患者840例(840眼)纳入研究,分别应用IOLMaster700及IOLMaster500测量AL,2种仪器检出率差异采用χ2检验进行比较,AL的数值差异采用配对t检验进行比较,相关性采用Pearson相关分析,一致性采用Bland-Altman分析。结果:IOLMaster700AL检出率为93.4%,IOLMaster500AL检出率为86.0%,二者差异具有统计学意义(χ2=63.00,P<0.001)。IOLMaster700及IOLMaster500测得的AL结果分别为(23.38±1.02)mm和(23.35±1.01)mm,差值为(0.03±0.04)mm,差异有统计学意义(t=-19.06,P<0.001),2种仪器测得的AL具有高度的相关性(r=1.00,P<0.001),Bland-Altamn分析95%一致性界限范围为0.13(-0.04~0.09)mm,上下限绝对值为0.09mm,一致性较好。结论:新型IOLMaster700与传统IOLMaster500测得的AL相比,具有高度相关性及良好的一致性,其检出率高于IOLMaster500,在白内障患者AL测量中具有一定优势。

基于扫频源相干光断层成像原理与部分相干光干涉原理的生物测量仪在眼轴测量中的比较

目的:比较基于扫频源相干光断层成像原理的OA2000和基于部分相干光干涉原理的AL-Scan在白内障患者眼轴长度测量中的检出率、差异性及一致性。方法:系列病例研究。纳入2017年11月29日至12月15日在首都医科大学附属北京同仁医院眼科门诊就诊,并拟行白内障手术的白内障患者210例(378眼)为研究对象,使用2种生物测量仪OA2000和AL-Scan检测眼轴长度。分别计算2种仪器的眼轴检出率。采用配对t检验比较2种仪器眼轴测量结果间的差异性。采用Pearson相关分析评价2种仪器测量间的相关性。采用组内相关系数(ICC)及Bland-Altman法评价仪器的一致性。并将研究眼分为眼轴<22mm组、眼轴22~26mm组、眼轴>26mm组,使用Bland-Altman法分别评价每组一致性。结果:OA2000和AL-Scan的眼轴检出率分别为98.4%和90.2%,差异有统计学意义(χ2=56.19,P<0.001)。OA2000和AL-Scan检测眼轴长度分别为(24.532±2.678)mm和(24.526±2.679)mm,差异无统计学意义(t=1.847,P=0.066)。2种仪器测量的眼轴长度结果具有密切相关性(r=1.000,P<0.001),ICC为1.000,Bland-Altamn分析95%一致性界限范围为0.23mm(-0.12~0.11mm)。95%一致性界限范围在眼轴<22mm组、眼轴22~26mm组、眼轴>26mm组分别为0.20mm(-0.10~0.10mm)、0.20mm(-0.09~0.11mm)、0.33mm(-0.16~0.17mm),3组的线外点分别为7.7%、4.5%、8.4%。结论:在白内障患者的眼轴测量中,OA2000比AL-Scan具有更高的眼轴检出率。2种仪器眼轴检测结果的相关性及一致性良好,尤其眼轴范围在22~26mm的患者中一致性表现最佳。2者数据可以相互替代使用。

新型扫频生物测量仪OA-2000与IOLMaster 700测量高度近视白内障患者的一致性

目的:比较OA-2000与IOLMaster 700在高度近视白内障患者生物测量中的一致性。方法:系列病例研究。选择2018年1─2月于北京同仁眼科中心拟行白内障手术的高度近视患者119例(119眼)。分别应用OA-2000和IOLMaster 700进行生物测量,获得角膜厚度(CCT)、前房深度(ACD)、晶状体厚度(LT)、眼轴长度(AL)、角膜曲率(Kf和Ks)、散光及轴向、平均角膜曲率(Km)、角膜横径(WTW)等数据,并通过矢量计算公式计算散光矢量J_(0)和J_(45),通过Barrett UniversalⅡ公式计算人工晶状体(IOL)度数。2种仪器测量参数及IOL度数差异比较采用配对t检验,一致性评估采用组内相关系数(ICC)及Bland-Altman法。结果:2种仪器测量Kf、Ks、Km、J_(0)、J_(45)、AL及IOL度数计算结果的差异均无统计学意义,测量CCT、ACD、LT及WTW差异均有统计学意义(t=-29.95、5.00、12.25、-5.56,均P<0.001)。2种仪器各测量参数及IOL度数计算结果的ICC为0.88~1.00。Bland-Altman分析显示2种仪器测量Kf、Ks、Km、J_(0)、J_(45)、CCT、ACD、LT、AL、WTW及IOL度数95%一致性界限(LoA)最大绝对值分别为:0.37 D、0.41 D、0.32 D、0.27 D、0.25 D、32.6μm、0.08 mm、0.18 mm、0.13 mm、0.73 mm及0.53 D。结论:在高度近视白内障患者中,OA-2000和IOLMaster 700测量Kf、Ks、Km、J_(0)、J_(45)、ACD、LT、AL的一致性好。2种仪器测量参数通过Barrett UniversalⅡ公式计算的IOL度数同样具有较好的一致性,可以相互替换使用。

Performance analysis of SBAS ephemeris corrections and integrity algorithms in China region

Satellite Based Augmentation Systems(SBASs)improve the positioning accuracy and integrity by broadcasting to the civil aviation community the corrections and integrity parameters.A snapshot algorithm based on the minimum variance estimation is investigated in this study to calculate the satellite clock and orbit corrections.A chi-square test is performed on the remaining errors in the corrected ephemeris to guarantee the integrity.User Differential Range Error(UDRE)and scaling matrix contained in Message Type 28 are derived using the covariance information based on the assumption that one of the reference stations failed.A software package is developed and applied in the real data collected at 26 stations.International GNSS(Global Navigation Satellite System)Service(IGS)precise clock and orbit products are taken as the references to assess the accuracy of corrections.For both Global Positioning System(GPS)and BeiDou Navigation Satellite System(BDS),the range accuracy of 0.10 m can be achieved with the employment of the derived corrections.No obvious performance difference between GPS and BDS is found.UDREs for all visible satellites are generated with the maximum index of 12 and minimum index of 3.The geometric range differences calculated with IGS precise products and broadcast ephemeris are employed to assess the integrity of UDRE.It is found that the UDRE is able to bound the residuals with 99.9%confidence which meet the requirement of aviation users.With ionospheric delay corrected by Global Ionosphere Map(GIM),the positioning accuracy of 0.98 m with GPS corrections and 0.80 m with multi-constellation augmentation can be achieved which indicates a significant improvement of GPS standalone results.