Chalcogenide Ovonic Threshold Switching Selector

Today’s explosion of data urgently requires memory technologies capable of storing large volumes of data in shorter time frames,a feat unattain-able with Flash or DRAM.Intel Optane,commonly referred to as three-dimensional phase change memory,stands out as one of the most promising candidates.The Optane with cross-point architecture is constructed through layering a storage element and a selector known as the ovonic threshold switch(OTS).The OTS device,which employs chalcogenide film,has thereby gathered increased attention in recent years.In this paper,we begin by providing a brief introduction to the discovery process of the OTS phenomenon.Subsequently,we summarize the key elec-trical parameters of OTS devices and delve into recent explorations of OTS materials,which are categorized as Se-based,Te-based,and S-based material systems.Furthermore,we discuss various models for the OTS switching mechanism,including field-induced nucleation model,as well as several carrier injection models.Additionally,we review the progress and innovations in OTS mechanism research.Finally,we highlight the successful application of OTS devices in three-dimensional high-density memory and offer insights into their promising performance and extensive prospects in emerging applications,such as self-selecting memory and neuromorphic computing.

一种在紧框架下求解Analysis Dantzig-selector模型的快速算法

Analysis Dantzig-selector模型是基于经典Dantzig-selector的l_(∞)限制的l_(1)分析模型。本文使用了紧框架下求解此模型的线性化交替方向乘子法,使得每个子问题都有显式解析解,并通过数值实验证明了该方法的有效可行性。

一种解Dantzig-Selector模型的快速分解算法

基于增广拉格朗日法提出了一种快速分解算法求解Dantzig-Selector模型.与经典的乘子交替方向法相比,新算法的每个子问题都具有更简单易行的迭代格式.通过测试两种不同类型的随机数据,相应的数值计算结果表明,算法在CPU运行时间方面有较明显的优势.

Synthesis and Characterisation of Water-Soluble Carboxymethyl-Cyclodextrin Polymer as Capillary Electrophoresis Chiral Selector

The water-soluble carboxymethyl-cyclodextrin polymer (CM-CD polymer) was synthesized and used as capillary electrophoresis chiral selector. Verrapamil and thiopentorusodium were well separated using CM-CD polymer as chiral selector.

Impact of variations of threshold voltage and hold voltage of threshold switching selectors in 1S1R crossbar array

The impact of the variations of threshold voltage（Vth） and hold voltage（Vhold） of threshold switching（TS） selector in1 S1 R crossbar array is investigated. Based on ON/OFF state I–V curves measurements from a large number of Ag-filament TS selectors, Vthand Vholdare extracted and their variations distribution expressions are obtained, which are then employed to evaluate the impact on read process and write process in 32×32 1 S1 R crossbar array under different bias schemes. The results indicate that Vthand Vholdvariations of TS selector can lead to degradation of 1 S1 R array performance parameters,such as minimum read/write voltage, bit error rate（BER）, and power consumption. For the read process, a small Vhold variation not only results in the minimum read voltage increasing but it also leads to serious degradation of BER. As the standard deviation of Vholdand Vthincreases, the BER and the power consumption of 1 S1 R crossbar array under 1/2 bias,1/3 bias, and floating scheme degrade, and the case under 1/2 bias tends to be more serious compared with other two schemes. For the write process, the minimum write voltage also increases with the variation of Vholdfrom small to large value. A slight increase of Vthstandard deviation not only decreases write power efficiency markedly but also increases write power consumption. These results have reference significance to understand the voltage variation impacts and design of selector properly.

Chiral Separation of Erythromycin as a New Chiral Selector on CE

Erythromycin as a new chiral selector was first used for chrial separation of four derivatives of biphenyldimethylester enantiomers on CE. The influence of pH, the chiral selector concentration and organic modifiers were preliminarily studied. Experiments show that the erythromycin as chiral selector is useful to CE.

6-O-(Hydroxypropyltrimethylammonia)-β-cyclodextrin with Low Degree of Substitution: Convenient Preparation and its Application as a Chiral Selector in Capillary Electrophoresis

A cationic cyclodextrin derivative 6-O-（hydroxypropyltrimethylammonia）-β-cyclodextrin （GTA-β-CD） with low degree of substitution was prepared through a convenient method in solid phase. The product could be used as a valuable chiral selector in the capillary electrophoresis （CE） separation of some acidic drug enantiomers such as naproxen, ofloxacin, ibuprofen and warfarin.

部分线性模型下Adaptive Dantzig Selector方法的渐近正态性

变量选择是处理超高维数据过程中重要的部分.本文提出部分线性模型下ADS(Adaptive Dantzig Selector)方法,并证明其渐近正态性.通过数值模拟以及大众点评网数据,验证此方法的可行性以及高精准性.

基于Dantzig Selector的迁移学习——应用于广义线性模型

小样本高维度的n-p问题一直是统计学家的研究热点,不同于传统的变量选择的参数估计方法,在本篇论文中,我们应用迁移学习的相关知识,借用与需要预测数据相关但分布不同的数据,有效的帮助我们解决目标域数据参数的预测问题。我们提出了一种新颖的基于Dantzig selector的两步迁移学习算法,在数值模拟中,我们验证了提出的迁移学习算法在广义线性模型以及不同的协方差数据设计中的稳健性和有效性,这表明提出的算法具有一定的实际应用价值。

Multilayer doped-GeSe OTS selector for improved endurance and threshold voltage stability

Selector devices are indispensable components of large-scale memristor array systems.The thereinto,ovonic threshold switching(OTS)selector is one of the most suitable candidates for selector devices,owing to its high selectivity and scalability.However,OTS selectors suffer from poor endurance and stability which are persistent tricky problems for applica-tion.Here,we report on a multilayer OTS selector based on simple GeSe and doped-GeSe.The experimental results show im-proving selector performed extraordinary endurance up to 1010 and the fluctuation of threshold voltage is 2.5%.The reason for the improvement may lie in more interface states which strengthen the interaction among individual layers.These develop-ments pave the way towards tuning a new class of OTS materials engineering,ensuring improvement of electrical perform-ance.

Hollow fiber liquid-supported membrane technology for enantioseparation of racemic salbutamol by combinatorial chiral selectors

Enantioseparation of salbutamol solute was carried out in liquid-supported membrane by using a polyvinylidene fluoride hollow-fiber module. The enantioselective transport of solute was facilitated by combinatorial chiral selectors, which were dissolved in toluene organic solvent. The effects of molar concentration ratios of salbutamol to combinatorial chiral selectors, and the pH value of buffer solution on enantioseparation were investigated. The results show that when the molar concentration ratio is 2∶1∶1, the maximum separation factor and enantiomer excess are 1.49 and 19.74%, respectively, and the R-enantiomer flux is more than S-enantiomer; the pH value of buffer solution influences the performances of enantioseparartion obviously, and the appropriate range of pH value is 7.07.2.

Ag-GST/HfO_(x)-based unidirectional threshold switching selector with low leakage current and threshold voltage distribution for high-density cross-point arrays

The use of electrochemical-metallization-based volatile threshold switching selectors in cross-point arrays has been widely explored owing to their high on-off ratios and simple structure.However,these devices are unsuitable for cross-point architectures because of the difficulty in controlling the random filament formation that results in large fluctuations in the threshold voltage during operation.In this study,we investigated the unidirectional threshold transition characteristics associated with an Ag/GST/HfO_(x)/Pt-based bilayer selector and demonstrated the occurrence of a low leakage current(<1×10^(-11) A) and low distribution of the threshold voltage(Δ0.11 V).The bilayer structure could control the filament formation in the intermediate state through the insertion of an HfO_(x) tunneling barrier.By stacking a bilayer selector with NiO_(x)based resistive random-access memory,the leakage and programming currents of the device could be significantly decreased.For the crossbar array configuration,we performed equivalent circuit analysis of a one-selector oneresistor(1S1R) devices and estimated the optimal array size to demonstrate the applicability of the proposed structure.The maximum acceptable crossbar array size of the 1S1R device with the Ag/GST/HfO_(x)/Pt/Ti/NiO_(x)/Pt structure was 5.29×10^(14)(N^(2),N=2.3×10^(7)).

Microwave photonic sideband selector based on thin-film lithium niobate platform

We propose and demonstrate an integrated microwave photonic sideband selector based on the thin-film lithium niobate(TFLN)platform by integrating an electro-optic Mach-Zehnder modulator(MZM)and a thermo-optic tunable flat-top microring filter.The sideband selector has two functions:electro-optic modulation of wideband RF signal and sideband selection.The microwave photonic sideband selector supports processing RF signals up to 40 GHz,with undesired sidebands effectively suppressed by more than 25 d B.The demonstrated device shows great potential for TFLN integrated technology in microwave photonic applications,such as mixing and frequency measurement.

Short-term prediction of ammonia levels in goose houses via combined feature selector and random forest

Ammonia concentration(NH3)is a dominant source of environmental pollution in geese housing and profoundly affects the healthy growth of geese.Accurately forecasting NH3 and analyzing its change trends in geese houses is crucial for the survival of geese.A novel forecasting model was proposed by combining feature selector(CFS)and random forest(RF)to improve the prediction accuracy of NH3 in this study.The developed model integrated two modules.First,combining mutual information(MI)and relief-F,we propose that CFS quantify each feature’s importance values and eliminate the low-relation or unrelated features.Second,a random forest model was built using K-fold cross-validation grid search algorithm(CVGS)to obtain the RF hyperparameters to predict NH_(3).The simulation results show that the prediction accuracy was improved when feature selection after quantification based on the CFS was used.The mean square error(MSE),root mean square error(RMSE),and mean absolute percent error(MAPE)for the proposed model were 0.5072,0.6583,and 2.88%,respectively.The NH_(3) prediction model(CFS-CVGS-RF)based on Combined Feature Selector,cross-validation grid search algorithm(CVGS),and Random Forest(RF)exhibited the best prediction accuracy and generalization performance compared with other parallel forecasting models and is a suitable and useful tool for predicting NH3 in geese houses.The results of the research can provide a reference for the machine learning method to monitor the dynamic changes of ammonia in goose houses.

适配变压器全档位切换暂态分析的有载分接开关电路模型构建

有载分接开关(on-loadtap-changer,OLTC)是换流变压器的核心组件,其可靠切换过程关乎换流变的安全。然而目前国内在运特高压换流变用OLTC完全依赖进口,仿真获取OLTC不同运行状态的暂态特性数据是支撑OLTC关键电气参数设计与国产化制造的基础。经典的OLTC模型仅改变变压器变比或仅模拟单级档位切换过程,难以满足全档位电压调整与各级档位暂态特性数据同步获取的需求,导致OLTC设计优化、参数选型及故障分析缺乏足够的仿真数据支持。该文首先以真空OLTC为研究对象建立切换开关和极性开关等效电路模型,根据OLTC复杂的调压功能建立分层控制系统。其次,在PSCAD中搭建交流仿真系统,获取有载调压过程的暂态特性数据波形,与解析计算得到的电压和电流相比误差小于0.2%,证明该模型满足OLTC电磁暂态仿真研究的精度要求。最后,开展循环调压仿真,获得负载电压数据与波形。结果表明:该文提出的OLTC模型能够接收外部控制信号,进行全档位调压与极性转换仿真分析,能够为OLTC的调压研究、故障溯源分析和过渡电阻设计选型等提供基础模型。

分体分步式换流变有载分接开关研制

特高压直流换流变压器有载分接开关长期承载满负荷运行的方波电流,切换电流di/dt大,熄弧困难,并且动作频繁,基本被国外企业垄断。文中首先针对特高压换流变传统有载分接开关无任何直接有效的电气量监测保护的“黑盒”难题,以及故障极易引起换流变本体损坏,影响特高压直流工程可用率问题,提出了一种分体分步式有载分接开关拓扑,实现换流变有载分接开关核心部件分体布置以及分步闭环控制保护,并分析梳理了工程应用的电气应力;然后进行了切换开关、分接选择器和控制保护装置等关键核心部件的研制;最后搭建基于LC谐振法的切换试验系统,对所研制的分体分步式有载分接开关进行了切换试验、容量试验、温升试验以及绝缘试验。试验结果表明:所研制的分体分步式有载分接开关额定级电压4 kV,最大通过电流1600 A,切换开关外置,无油化设计,内部集成电气测量系统,切换过程能够实现分步操作控制和保护,避免故障扩大化,满足±800 kV/5000 A特高压直流输电换流变压器的工程应用需求。

基于随机共振-反向传播算法的压电选针器渐变失效检测

针对压电式选针器在提花过程中故障特征难以判断的问题,提出了一种基于随机共振-反向传播(SR-BP)算法的压电选针器渐变失效检测方案。研究压电选针器提花过程中驱动件的运动状态及其双向压电效应产生的电信号,对渐变失效状态下的压电陶瓷驱动件内部电信号进行随机共振(SR)故障诊断。提取振动序列的时域及频域参数与SR参数生成训练样本,通过算法使特征参数匹配出最优SR参数,将压电选针器振动信号与噪声信号混入SR参数形成的非线性系统中,观察该系统输出量的时域和频域变化达到快速检测故障的目的。研究结果表明:选针器失效后时域特征在30~350 Hz将发生明显差异,全参数的SR-BP故障检测方法的精确度可达到97.5%,信噪比达到7.36 dB,可有效地对压电选针器进行故障检测。

A comprehensive understanding of grain selection in spiral grain selector during directional solidification

It is of great importance to further investigate grain selection mechanism for the production of single crystal(SX) turbine blade because a single crystal with optimized crystal orientation will enhance service performance of the blade severely.In this paper,single crystals with different deviation angles,i.e.6°,12° and 29°, were obtained using directional solidification under the same casting conditions.It has been found that the grain selection in spiral selector is a coupling process where high order dendrites branch in the front side and primary dendrites disappear in the back side based on the metallographic analysis and electron back scatter diffraction(EBSD).Considering the development of liquid/solid interface by numerical simulation,a combination effect with space expansion,geometrical restriction and grain competition was proposed for spiral grain selection.The space expansion mechanism dominates the process as it provides growth space and driving force for high order dendrites advancing.Thereby,the smaller the take-off angle(θ) is,the larger space and the stronger driving force high order dendrites will get,and the higher efficient the selector will be. The competitive growth between the secondary dendrites plays more contribution than that of primary dendrites,i.e.grain with preferred secondary dendrites instead of preferred primary dendrites could outcompete during grain selection,and this is the reason why spiral grain selector cannot optimize the orientation of the primary dendrites.These findings provide experimental evidence for spatial control of SX growth,and benefit the sophistic casting fields such as turbine blade casting for improved yield.