Cut-off value of glycated hemoglobin A1c for detecting diabetic retinopathy in the Chinese population

BACKGROUND Glycated hemoglobin A1c(HbA1c)is considered the most suitable for diabetes mellitus diagnosis due to its accuracy and convenience.However,the effect of HbA1c on diabetic retinopathy(DR)in the Han and Korean populations in Jilin,China,remains inconclusive.AIM To determine the best cut-off of HbA1c for diagnosing DR among the Chinese.METHODS This cross-sectional study included 1933 participants from the Yanbian area of Jilin Province,China.Trained investigators employed a questionnaire-based survey,physical examination,laboratory tests,and fundus photography for the investigation.The best cut-off value for HbA1c was established via the receiver operating characteristic curve.The factors associated with HbA1c-associated risk factors were determined via linear regression.RESULTS The analysis included 887 eligible Chinese Han and Korean participants,591 of whom were assigned randomly to the training set and 296 to the validation set.The prevalence of DR was 3.27% in the total population.HbA1c of 6.2% was the best cut-off value in the training set,while it was 5.9% in the validation set.In both Chinese Han and Korean populations,an HbA1c level of 6.2% was the best cut-off value.The optimal cut-off values of fasting blood glucose(FBG)≥7 mmol/L and<7 mmol/L were 8.1% and 6.2% respectively in Han populations,while those in Korean populations were 6.9%and 5.3%,respectively.Age,body mass index,and FBG were determined as the risk factors impacting HbA1c levels.CONCLUSION HbA1c may serve as a useful diagnostic indicator for DR.An HbA1c level of 6.2% may be an appropriate cut-off value for DR detection in the Chinese population.

Subseasonal Prediction of Early-summer Northeast Asian Cut-off Lows by BCC-CSM2-HR and GloSea5

Northeast Asian cut-off lows are crucial cyclonic systems that can bring temperature and precipitation extremes over large areas.Skillful subseasonal forecasting of Northeast Asian cut-off lows is of great importance.Using two dynamical forecasting systems,one from the Beijing Climate Center(BCC-CSM2-HR)and the other from the Met Office(GloSea5),this study assesses simulation ability and subseasonal prediction skill for early-summer Northeast Asian cut-off lows.Both models are shown to have good ability in representing the spatial structure of cut-off lows,but they underestimate the intensity.The skillful prediction time scales for cut-off low intensity are about 10.2 days for BCC-CSM2-HR and 11.4 days for GloSea5 in advance.Further examination shows that both models can essentially capture the initial Rossby wave train,rapid growth and decay processes responsible for the evolution of cut-off lows,but the models show weaker amplitudes for the three-stage processes.The underestimated simulated strength of both the Eurasian midlatitude and East Asian subtropical jets may lead to the weaker local eddy-mean flow interaction responsible for the cut-off low evolution.

5G Wideband Bandpass Filtering Power Amplifiers Based on a Bandwidth-Extended Bandpass Matching Network

In this paper,a 5G wideband power amplifier(PA)with bandpass filtering response is synthesized using a bandwidth-extended bandpass filter as the matching network(MN).In this structure,the bandwidth(θ_(C))is defined as a variable in the closedform equations provided by the microstrip bandpass filter.It can be extended over a wide range only by changing the characteristic impedances of the structure.Different from the other wideband MNs,the extension of bandwidth does not increase the complexity of the structure(order n is fixed).In addition,based on the bandwidth-extended structure,the wideband design of bandpass filtering PA is not limited to the fixed bandwidth of the specific filter structure.The theoretical analysis of the MN and the design flow of the PA are provided in this design.The fabricated bandpass filtering PA can support almost one-octave bandwidth(2-3.8 GHz),covering the two 5G bands(n41 and n78).The drain efficiency of 47%-60%and output power higher than 40 dBm are measured.Good frequency selectivity in S-parameter measurements can be observed.

A new DRIE cut-off material in SOG MEMS process

The silicon on glasses process is a common preparation method of micro-electro-mechanical system inertial devices,which can realize the processing of thick silicon structures.This paper proposes that indium tin oxides(ITO)film can serve as a deep silicon etching cut-off layer because ITO is less damaged under the attack of fluoride ions.ITO has good electrical conductivity and can absorb fluoride ions for silicon etching and reduce the reflection of fluoride ions,thus reducing the foot effect.The removal and release of ITO use an acidic solution,which does not damage the silicon structure.Therefore,the selection of the sacrificial layer has an excellent effect in maintaining the shape of the MEMS structure.This method is used in the preparation of MEMS accelerometers with a structure thickness of 100μm and a feature size of 4μm.The over-etching of the bottom of the silicon structure caused by the foot effect is negligible.The difference between the simulated value and the designed value of the device characteristic frequency is less than 5%.This indicates that ITO is an excellent deep silicon etch stopper material.

Multifractal estimation of NMR T_(2) cut-off value in low-permeability rocks considering spectrum kurtosis: SMOTE-based oversampling integrated with machine learning

The transverse relaxation time (T_(2)) cut-off value plays a crucial role in nuclear magnetic resonance for identifying movable and immovable boundaries, evaluating permeability, and determining fluid saturation in petrophysical characterization of petroleum reservoirs. This study focuses on the systematic analysis of T_(2) spectra and T_(2) cut-off values in low-permeability reservoir rocks. Analysis of 36 low-permeability cores revealed a wide distribution of T_(2) cut-off values, ranging from 7 to 50 ms. Additionally, the T_(2) spectra exhibited multimodal characteristics, predominantly displaying unimodal and bimodal morphologies, with a few trimodal morphologies, which are inherently influenced by different pore types. Fractal characteristics of pore structure in fully water-saturated cores were captured through the T_(2) spectra, which were calculated using generalized fractal and multifractal theories. To augment the limited dataset of 36 cores, the synthetic minority oversampling technique was employed. Models for evaluating the T_(2) cut-off value were separately developed based on the classified T_(2) spectra, considering the number of peaks, and utilizing generalized fractal dimensions at the weight <0 and the singular intensity range. The underlying mechanism is that the singular intensity and generalized fractal dimensions at the weight <0 can detect the T_(2) spectral shift. However, the T_(2) spectral shift has negligible effects on multifractal spectrum function difference and generalized fractal dimensions at the weight >0. The primary objective of this work is to gain insights into the relationship between the kurtosis of the T_(2) spectrum and pore types, as well as to predict the T_(2) cut-off value of low-permeability rocks using machine learning and data augmentation techniques.

Lipoprotein (a) Cut-Off in Chronic Kidney Disease Patients with a History of Cardiovascular Disease in Center Hospital University Souro SANOU, Burkina Faso

Patients living with chronic kidney disease (CKD) are at high risk of cardiovascular events. Our aim in this study was to assess the cut-off value for lipoprotein (a) (Lp(a)) in CKD patients with a history of cardiovascular disease (CVD). This was a cross-sectional study. Variables including age, sex, history of CVD, body mass index and CKD stage, were collected during CKD patient’s first admission in the nephrology dialysis department. Blood samples were collected for quantitative determination of Lp(a) by immunoturbidimetric method. They were divided into two groups: CKD patients without history of CVD and CKD patients with history of CVD. Fisher’s exact test was used to assess associations with a significance level of 0.05%. Area under the curve (AUC) and new cut-off value for Lp(a) were identified by drawing Receiver Operating Characteristic (ROC) curve. A total of seventy CKD patients with median age of 43 years [minimum-maximum = 15 - 78 years] were included. Patients with history of CVD were 65.71% (46/70). New Lp(a) cut-off point in CKD patients with history of CVD was 66.50 nmol/L [sensitivity, 87.00%;specificity, 58.30%;AUC = 0.727;p = 0.000]. ROC curve demonstrated good performance of Lp(a) to screen CKD patients with history of CVD. Further research is needed to determine an LPA gene polymorphism’s contribution to increasing risk for CVD at each kidney disease stage.

小型化低剖面全向滤波天线设计

设计了一个小型化全向微带滤波天线。天线由带通滤波器和微带天线组成,二者共用一个地平面以减小尺寸且采用缝隙耦合方式连接,带通滤波器蚀刻在微带贴片天线的馈线位置处,引入选频滤波功能,在输入馈线前端添加一个横向矩形贴片使整个系统达到良好的阻抗匹配。与传统的微带天线相比,所设计的滤波天线在不改变尺寸大小的基础上引入了选频滤波功能,在通带边缘体现出较高的选择性。仿真与测试结果表明,该滤波天线的阻抗带宽为2.31 GHz~2.56 GHz,且通带内增益平缓,平均增益约为2.1 dBi,在工作频段内呈全向辐射特性。

低噪声水声信号前置放大器设计

水下信息的发送与接收主要通过声信号的传播,水听器作为常用的水声信号接收装置,需要前置放大器来提高所获取信号的质量。文中选用AD8421仪表放大器芯片与OP2177精密运算放大器芯片设计了一种低噪声水声信号前置放大器,该电路增益为26 dB,工作带宽为100 Hz~20 kHz,输出信号为差分形式,同时具有小体积、低功耗的特点。通过连接某型压电水听器,测试了电路工作性能以及对水听器信号的调理效果。实测结果表明,该前置放大器能满足设计技术指标要求,在实际工作中取得了良好的效果。

基于cut-off方法刚性承台下群桩基础优化分析

针对刚性筏板下群桩基础优化设计问题进行分析,通过改变桩长分布来调整各桩的荷载分担,群桩分析采用基于弹性理论的积分方程方法,并通过cut-off方法来反映桩的弹塑性特性,实现群桩基础的弹塑性优化分析,改进了常规弹性分析方法的缺陷。算例分析表明,随着外荷载的不断增加,角桩首先达到极限荷载,对角桩超出极限荷载的部分进行重新分布,继而使得边桩逐渐达到极限承载状态,继续加载直至内桩也达到极限承载状态,从而引起桩筏基础的整体破坏。采用cut-off方法可以改进基础变刚度优化设计,使之与实际情况更为吻合。

基于阶跃阻抗谐振器的四阶频率可调滤波器设计

提出一种基于阶跃阻抗谐振器的紧凑型四阶四零点频率可调滤波器设计。滤波器使用变容二极管加载的阶跃阻抗谐振器(VL-SIR),有效拓宽了滤波器的调谐范围。在VL-SIR之间引入交叉耦合,从而在滤波器通带近端产生一对传输零点,显著提高了滤波器的选择性。同时,引入源和负载端的交叉耦合,在通带远端生成一对传输零点,以提高带外抑制。此外,采用基于VL-SIR的频变耦合结构来实现恒定绝对带宽。仿真结果与实测结果吻合良好。测量结果显示,可调滤波器频率调谐范围为0.78~1.15 GHz,3 dB绝对带宽约为55±3 MHz,滤波器的回波损耗大于10 dB,插入损耗约为2.8~3.3 dB。

利用RIBA试验确定HCV抗体检测的cut-off值及比较分析

目的利用重组蛋白免疫印迹分析(RIBA)实验,制定本实验室所用的日本希森美康公司的HISCL-5000型化学发光免疫分析仪及配套的相关试剂检测丙型肝炎病毒抗体(抗-HCV)的cut-off值。方法在2015年10月至2016年9月所检测的19341例患者标本中收集抗-HCV阳性标本80例,进行RIBA确认实验后进行分析,再利用ROC曲线计算出cut-off值。结果在本室HCV抗体阳性率为0.41%的数据中,RIBA结果可分为3种,其中25例(31.3%)为阴性,18例(22.5%)为不确定,37例(46.2%)为阳性。当截断值为3.95 COI时,灵敏度为81.1%,特异性为95.1%。另外当特异性为100%时,截断值为5.25 COI,灵敏度为73%。结论希森美康HISCL-5000型化学发光免疫分析仪及配套的相关试剂检测丙型肝炎病毒抗体(抗-HCV)与RIBA结果间呈正相关;当cut-off值为3.95 COI时,是一个适合本实验室的cut-off值。

基于卷积神经网络的微带滤波器的参数预测

提出了一种基于卷积神经网络的微带带通滤波器的参数预测方法,针对一个三频带带通滤波器进行预测。首先利用HFSS电磁仿真软件训练数据得到S参数的数据集作为真实值数据集,将微带滤波器的S参数作为输入,物理结构参数作为输出,通过卷积神经网络进行训练,最后将目标S参数作为输入进行参数预测。相比于简单的全连接神经网络,卷积神经网络不仅能够大幅度地减少网络参数,还有效避免了过拟合情况的出现,解决了全连接神经网络耗时长的问题,并且由于卷积神经网络对于结构参数的预测是直接的,即使对于初学者也可以节省大量设计时间。仿真结果表明,目标S参数与卷积神经网络预测后得到的S参数拟合程度很高,证明了该方法对微带滤波器物理结构参数的预测有较高的准确率。

基于高频注入法的同步磁阻电机无位置传感器控制

同步磁阻电机是一种结构简单耐用、造价较低的特殊同步电机,近年来逐渐受到关注。将旋转高频电压注入法无位置传感器控制技术应用于同步磁阻电机,研究无带通滤波器同步磁阻电机位置辨识策略,以简化控制算法,降低位置辨识误差,减轻处理器的运算压力。同时在实验中,分奇偶周期分别注入基波电压和高频电压,以充分利用实验电源容量。在Matlab/Simulink环境下搭建仿真模型,同时搭建1.2 kW样机的硬件测试平台,仿真和实验结果都验证了简化的无位置传感器矢量控制算法的有效性和准确性。

一种近似芯片级尺寸的小型化微带点频滤波器

射频滤波器作为具备信号筛选功能的射频器件,对现代通信系统而言具有举足轻重的地位。随着通信技术的不断更新迭代,要求射频滤波器具有小型化以及低成本的特点。目前,利用半导体工艺可制作尺寸极小且性能佳的芯片级滤波器,但研发成本普遍过高。文中使用薄膜工艺,通过对滤波器的结构、材料、性能指标进行综合考量,设计了一款适用于点频源、跳频源模块中使用的微带点频滤波器。通过仿真软件HFSS进行建模仿真并对加工工艺进行误差分析,成功得到了一款通带在12 GHz±15 MHz的微带点频滤波器,其尺寸为2.5 mm×3.5 mm×0.127 mm。测试结果表明,性能曲线达到设计指标,成功验证了设计的可行性。

Classifying moisture sources associated with snowfall in the mountains of Lesotho

An average of eight snowfall events occur each year in the eastern Lesotho Highlands.These snowfall events are typically associated with cut-off low(CoLs)systems and mid-latitude cyclones.However,the moisture sources of the snowfall are unclassified and unclear.The Hybrid Single-Particle Lagrangian Integrated Trajectory(HYSPLIT)model,an air mass back trajectory model,has been used to evaluate moisture source waters locally in southern Africa and internationally in China and Europe.This study uses HYSPLIT to determine the source moisture of snow in Lesotho.A list of all 82 snowfall events in Lesotho spanning 2017 to 2022 was compiled using the Snow Report SA Instagram page,including the date and location of snowfall.A 72-hour back trajectory for each snowfall event was initiated for both Afriski and the whole of Lesotho.This amounts to models of moisture source trajectories for 28 and 82 snowfall days,respectively.These air mass pathways are classified according to their frequency per snowfall event,per month in the snow season,per year and for the full period.From this,associated moisture source regions and dominant air mass trajectories were identified.This study reports that the air mass trajectories associated with Afriski and Lesotho as a whole are very similar.The most common pathway of air mass trajectories transporting snow-bearing moisture to Lesotho was an inland trajectory from the northern regions of southern Africa.This pathway makes up 16.6%of all trajectories reported and is associated with the Angola Low,the Congo Air Boundary and the St.Helena High Pressure.

基于HMSIW的小型化三模带通滤波器设计

传统的多模谐振器引入多个谐振器,并利用其中两个甚至多个谐振模式来组合构建滤波器通带,但由于其谐振器个数较多而在射频系统中占用了较大的空间。为此,本文提出了基于半圆形半模基片集成波导(HMSIW)的三模带通滤波器,通过引入金属化过孔来扰动半圆形HMSIW谐振腔的谐振模式的电场分布,使得对应的谐振模式的频率也会随之发生偏移,进而使原本谐振频率相差较大的三个谐振模式的频率逐渐靠近,最终组合形成滤波器的通带。该设计无需引入额外的谐振器,能够实现滤波器尺寸减半甚至成倍减少,从而达成小型化的目的。

基于悬置微带结构的无反射滤波器

通过悬置微带传输线结构进行了无反射滤波器的研究和设计。首先利用耦合线结构设计了中心频率为3.92 GHz,插入损耗为0.32 dB,在0.1~10 GHz内回波损耗超过11.6 dB,中心频率处超过38 dB的双端口无反射带通滤波器;又利用λ/4开路谐振器和λ/4短路谐振器作为滤波单元,设计了中心频率为4.25 GHz,回波损耗在1.5~6 GHz内超过11 dB,在中心频率处超过40 dB的双端口无反射带阻滤波器。所提出的这两款无反射滤波器具有无反射频带范围宽、工作频带内S_(11)衰减大、多层自封装等突出优点。

In Situ Atomic Reconstruction Engineering Modulating Graphene-Like MXene-Based Multifunctional Electromagnetic Devices Covering Multi-Spectrum

With the diversified development of big data,detection and precision guidance technologies,electromagnetic(EM)functional materials and devices serving multiple spectrums have become a hot topic.Exploring the multispectral response of materials is a challenging and meaningful scientific question.In this study,MXene/TiO_(2)hybrids with tunable conduction loss and polarization relaxation are fabricated by in situ atomic reconstruction engineering.More importantly,MXene/TiO_(2)hybrids exhibit adjustable spectral responses in the GHz,infrared and visible spectrums,and several EM devices are constructed based on this.An antenna array provides excellent EM energy harvesting in multiple microwave bands,with|S11|up to−63.2 dB,and can be tuned by the degree of bending.An ultra-wideband bandpass filter realizes a passband of about 5.4 GHz and effectively suppresses the transmission of EM signals in the stopband.An infrared stealth device has an emissivity of less than 0.2 in the infrared spectrum at wavelengths of 6-14μm.This work can provide new inspiration for the design and development of multifunctional,multi-spectrum EM devices.

多频连续可调的可重构滤波天线

设计了一种多频连续可调的可重构滤波天线。首先将2个加载变容二极管的1/4波长阶跃阻抗谐振器(Step Impedance Resonator,SIR)带通滤波器与50Ω微带传输线集成,得到一个可重构滤波馈电网络,通过控制6个PIN二极管的通断状态,实现超宽带与窄带模式的切换,同时分析了馈电网络对应的等效电路。另外,设计了一款工作频率覆盖可调滤波器通带范围的分形超宽带天线,并将二者集成实现滤波天线。对该天线设计进行了仿真优化和实物测试,结果表明,该天线能够在WiMAX窄带连续可调、WLAN窄带连续可调和超宽带3种模式下工作,且均具有良好的辐射特性,可广泛应用于多频段无线通信中。

基于FPGA的数字带通滤波器设计与仿真

为快速准确地提取超声导波信号中的目标信息,采用流水线加法树阵列结构设计低阶滤波器,采用直接型低阶叠加实现20阶高精度带通滤波器。运用流水线技术与FPGA片上资源相结合实现对该结构数字算法优化,并将其应用在镍铬合金超声导波测温系统中。结果表明:所设计的滤波器对512点的混频超声导波信号滤波耗时约1047个时钟。该滤波器总体设计简单,可以达到实时滤波的功能。