Effects of asymmetric coupling and boundary on the dynamic behaviors of a random nearest neighbor coupled system

This study investigates the dynamical behaviors of nearest neighbor asymmetric coupled systems in a confined space.First, the study derivative analytical stability and synchronization conditions for the asymmetrically coupled system in an unconfined space, which are then validated through numerical simulations. Simulation results show that asymmetric coupling has a significant impact on synchronization conditions. Moreover, it is observed that irrespective of whether the system is confined, an increase in coupling asymmetry leads to a hastened synchronization pace. Additionally, the study examines the effects of boundaries on the system's collective behaviors via numerical experiments. The presence of boundaries ensures the system's stability and synchronization, and reducing these boundaries can expedite the synchronization process and amplify its effects. Finally, the study reveals that the system's output amplitude exhibits stochastic resonance as the confined boundary size increases.

A tunable infrared plasmonic polarization filter with asymmetrical cross resonator

A tunable infrared plasmonic polarization filter is proposed and investigated in this paper. The filter is based on the sandwich absorption structure which consists of three layers. The top layer is an array of asymmetrical cross resonator. The middle and bottom layers are dielectric spacer and metal film respectively. By absorbing specific wavelength of the incident light perfectly, the reflection spectrum of the structure shows filter performance. The calculated results show that the absorption wavelength is strongly dependent on the length of branch of the asymmetrical cross resonator which is parallel to the light polarization and independent of the length of the vertical one. Therefore, the asymmetrical cross resonator filter structure opens the way for freely tuning the filtering wavelength for a different light polarization. We can fix a resonant wavelength （absorption wavelength） corresponding to one polarization and change the resonant wavelength for the other polarization by adjusting the corresponding branch length of the asymmetrical cross resonator, or change the two resonant wavelengths of both two polarizations at the same time.

A High-Sensitivity Refractive-Index Sensor Based on Plasmonic Waveguides Asymmetrically Coupled with a Nanodisk Resonator

A high-sensitivity plasmonic refractive-index sensor based on the asymmetrical coupling of two metal-insulator- metal waveguides with a nanodisk resonator is proposed and simulated in the finite-difference time domain. Both analytic and simulated results show that the resonance wavelengths of the sensor have an approximate linear relationship with the refractive index of the materials which are filled into the slit waveguides and the disk- shaped resonator. The working mechanism of this sensor is exactly due to the linear relationship, based on which tile refractive index of the materials unknown can be obtained from the detection of the resonance wavelength. The measurement sensitivity can reach as high as 6.45 × 10-7, which is nearly five times higher than the results reported in the recent literature [Opt. Commun. 300 （2013） 265]. With an optimum design, the sensing value can be further improved, and it can be widely applied into the biological sensing. Tile sensor working for temperature sensing is also analyzed.

Stochastic resonance in an asymmetric bistable system driven by coloured noises

The phenomenon of stochastic resonance is investigated in an asymmetric bistable system with coloured noises. The approximate Fokker Planck equation is derived based on the Novikov theorem and the Fox approach. By applying the two-state theory, the expression of the signal-to-noise ratio is obtained in the adiabatic limit. The effects of the noise parameters on signal-to-ratio are discussed. It is found that the stochastic resonance phenomena appear in most cases and disappear in some special cases.

Asymmetric stochastic resonance under non-Gaussian colored noise and time-delayed feedback

Based on adiabatic approximation theory,in this paper we study the asymmetric stochastic resonance system with time-delayed feedback driven by non-Gaussian colored noise.The analytical expressions of the mean first-passage time(MFPT)and output signal-to-noise ratio(SNR)are derived by using a path integral approach,unified colored-noise approximation(UCNA),and small delay approximation.The effects of time-delayed feedback and non-Gaussian colored noise on the output SNR are analyzed.Moreover,three types of asymmetric potential function characteristics are thoroughly discussed.And they are well-depth asymmetry(DASR),well-width asymmetry(WASR),and synchronous action of welldepth and well-width asymmetry(DWASR),respectively.The conclusion of this paper is that the time-delayed feedback can suppress SR,however,the non-Gaussian noise deviation parameter has the opposite effect.Moreover,the correlation time plays a significant role in improving SNR,and the SNR of asymmetric stochastic resonance is higher than that of symmetric stochastic resonance.Our experiments demonstrate that the appropriate parameters can make the asymmetric stochastic resonance perform better to detect weak signals than the symmetric stochastic resonance,in which no matter whether these signals have low frequency or high frequency,accompanied by strong or weak noise.

Stochastic Resonance in an Asymmetric Mono-stable System Subject to Two Periodic Forces and Multiplicative and Additive Noise

在易于二外部周期的力量、趋于增加的一个不对称的单稳态的系统和添加剂噪音的随机的回声(SR ) 的现象被调查。为基本、更高的泛音的 signal-to-noise 比率(SNR ) 是紧张的一个非单调的函数，这被显示出趋于增加并且添加剂噪音，以及系统参数。而且，为基本泛音的 SNR 随系统不对称现象的增加减少，当为更高的泛音的 SNR 是 non-monotonically 表现时，系统不对称现象变化。

Stochastic Resonance in a Harmonic Oscillator Fluctuating Intrinsic Frequency by Asymmetric Dichotomous Noise

The stochastic resonance phenomenon in a harmonic oscillator with fluctuating intrinsic frequency by asymmetric dichotomous noise is investigated in this paper. By using the random average method and Shapiro- Loginov formula, the exact solution of the average output amplitude gain （OAG） is obtained. Numerical results show that OAG depends non-monotonically on the noise characteristics： intensity, correlation time and asymmetry. The maximum OAG can be achieved by tuning the noise asymmetry and or the noise correlation time.

High efficiency and high transmission asymmetric polarization converter with chiral metasurface in visible and near-infrared region

Polarization manipulation of light is of great importance because it could promote development of wireless communications,biosensing,and polarization imaging.In order to use natural light more efficiently,it is highly demanded to design and fabricate high performance asymmetric polarization converters which could covert the natural light to one particular linearly polarized light with high efficiency.Traditionally,polarizers could be achieved by controllers with crystals and polymers exhibiting birefringence.However,the polarizers are bulky in size and the theoretical conversion efficiency of the polarizers is limited to 0.5 with unpolarized light incidence.In this paper,we propose a polarization converter which could preserve high transmission for one linearly polarized light and convert the orthogonal linearly polarized light to its cross-polarized with high transmittance based on a multi-layer chiral metasurface.Theoretical results show that normally incident y-polarized light preserves high transmittance for the wavelength range from 685 nm to 800 nm while the orthogonal normally incident x-polarized light is efficiently converted to the y-polarized light with high transmittance from 725 nm to 748 nm.Accordingly,for unpolarized light incidence,transmittance larger than 0.5 has been successfully achieved in a broadband wavelength range from 712 nm to 773 nm with a maximum transmittance of 0.58 at 732 nm.

限制调频范围的不对称多模式宽输出LLC变换器

频率控制的传统LLC谐振变换器往往受限于开关频率的有效调节范围,难以实现宽输出电压范围,为此,研究了一种限制调频范围的不对称多模式宽输出LLC谐振变换器。采用双谐振腔且对应两变压器变比不同的不对称结构,能够根据原边开关组合的不同,使得双谐振腔分别工作在单半桥、双半桥和半桥+全桥3种不同的模式,从而获得3种不同的电压增益,并且保证每种模式之间归一化增益调节范围不超过1.5,可以在窄开关频率范围内实现宽输出电压范围。建立300 W的实验样机,验证了所提变换器可实现1~3倍的宽输出电压范围,并且实现了原边开关管的零电压开通和副边二极管的零电流关断,具有良好的软开关性能,验证了变换器的可行性。

LLC谐振变换器非对称变占空比软启动设计

LLC谐振变换器在传统启动方法中存在浪涌电流过大的问题,为解决此问题,提出一种非对称变占空比的软启动混合控制策略。通过使两个桥臂的对管脉冲保持一致,同时使上、下开关管占空比保持互补导通,得到一种非对称变占空比的软启动方法,再与降频控制方法相结合组成了软启动混合控制策略。搭建了一台LLC谐振变换器实验样机验证方案的可行性。实验结果表明,所提出的混合控制策略能抑制启动过程中的电流冲击,并能保持初级开关管的零电压开通(ZVS)特性。

MRI ideal-iq技术联合血清学指标在乙型肝炎患者肝纤维化分期中的应用

目的探讨磁共振最小二乘法估计和不对称回波迭代分解水和脂肪的脂肪成像(MRI ideal-iq)技术联合血清学指标在乙型肝炎患者肝纤维化分期中的应用价值。方法选取2021年1月至2023年1月淮南市第一人民医院收治的乙型肝炎患者100例,其中S0~S1期41例、S2期28例、S3期17例和S4期14例。比较4组患者IDEAL-IQ参数、血清学指标[透明质酸(HA)、Ⅳ型胶原(CⅣ)、层联蛋白(LN)]和肝功能[丙氨酸氨基转移酶(ALT)、天门氨酸氨基转移酶(AST)、白蛋白]。ROC分析ideal-iq参数联合血清学指标预测早期肝硬化(S4期)的价值;相关性分析ideal-iq参数、血清学指标与肝纤维化的关系。结果S0~S1期组FF、R2^(*)值、HA、CIV为(1.51±0.33)%、(54.58±8.15)Hz、(139.05±60.57)μg/L、(88.24±24.78)ng/mL,S2期组为(2.01±0.42)%、(69.07±7.44)Hz、(337.56±113.24)μg/L、(106.04±30.21)ng/mL,S3期组为(3.07±0.46)%、(94.55±10.53)Hz、(416.08±124.51)μg/L、(134.07±38.76)ng/mL,S4期组为(4.32±0.53)%、(111.14±11.42)Hz、(583.76±150.54)μg/L、(190.06±42.83)ng/mL,4组间比较差异有统计学意义(F=188.442、178.839、75.985、38.451,均P<0.05);4组间血清LN水平比较差异无统计学意义(P>0.05)。ROC分析显示,FF、R2^(*)值和血清HA、CⅣ水平预测早期肝硬化的曲线下面积分别为0.777、0.782、0.819、0.744,最佳截断值分别为FF≥3.560%,R2^(*)值≥102.950 Hz,HA≥517.210μg/L,CⅣ≥173.895 ng/mL,(均P<0.05),联合预测早期肝硬化的曲线下面积为0.832,敏感度为0.786,均高于单项指标。S0~S1期组ALT、AST、白蛋白为(134.65±37.85)U/L、(74.22±20.57)U/L、(45.15±3.76)g/L,S2期组为(192.08±47.52)U/L、(100.25±30.16)U/L、(43.45±3.01)g/L,S3期组为(214.12±55.63)U/L、(127.13±38.53)U/L、(40.35±5.24)g/L,S4期组为(159.14±43.71)U/L、(101.54±33.48)U/L、(37.42±3.65)g/L,4组间比较差异有统计学意义(F=18.341、14.667、16.786,P<0.05)。经相关性分析发现,FF、R2^(*)值和血清HA、CⅣ水平与肝纤维化分期呈显著正相关(P<0.05);血清LN水平与肝纤维化分期无显著相关性(P>0.05)。结论FF、R2^(*)值和血清HA、CⅣ水平在不同肝纤维化分期患者中均存在显著差异,且二者联合诊断早期肝硬化具有较高敏感度。

IDEAL-IQ序列在乳腺肿块良恶性鉴别诊断中的应用价值探究

目的 探讨非对称回波最小二乘估算法迭代水脂分离序列(iterative decomposition of water and fat with echo asymmetrical and least-squares estimation quantitation sequence, IDEAL-IQ)来源的R2^(*)值在乳腺良恶性肿瘤鉴别诊断中的价值,并与传统多回波T2^(*)梯度回波(gradient recalled echo, GRE)序列来源的R2^(*)值进行比较。材料与方法 回顾性分析2021年9月至2023年10月在中国医科大学附属第一医院连续收治的42名患者的50个良性肿瘤病灶,在本院影像归档和通信系统(picture archiving and communication systems, PACS)中使用倾向性评分匹配方法匹配肿瘤所在最大层面的最长径,按1∶3的比例纳入150名患者的150个恶性肿瘤病灶。将恶性肿瘤根据预后因子[雌激素受体(estrogen receptor, ER)、孕激素受体(progesterone receptor, PR)以及人表皮生长因子受体2(human epidermal growth factor receptor 2, HER-2)]的阳性/阴性表达情况进行分组。所有患者均接受包含IDEAL-IQ和多回波T2*GRE序列的多参数MRI,测量以下定量参数:IDEAL-IQ序列R2^(*)值(R2^(*)IDEAL)、多回波T2*GRE序列R2^(*)值(R2^(*)GRE)、表观扩散系数(apparent diffusion coefficient, ADC)及肿瘤长径。根据原始资料类型的不同,分别利用单因素分析(独立样本t检验、Mann-Whitney U检验等方法)对比分析各参数的差异。采用Spearman相关性分析R2^(*)IDEAL与R2^(*)GRE及二者与ADC的相关性。采用配对样本t检验比较R2^(*)IDEAL与R2^(*)GRE的差异。采用logistic回归分析建立联合诊断模型,并使用受试者工作特征(receiver operating characteristic, ROC)曲线及曲线下面积(area under the curve,AUC)分析单独及联合参数鉴别乳腺肿瘤良恶性的效能。结果 相关性分析显示乳腺肿瘤患者的R2^(*)IDEAL与R2^(*)GRE呈中度相关(r=0.763,P<0.001),二者与ADC值均呈负性弱相关[r=-0.300(R2^(*)IDEAL),-0.306(R2^(*)GRE),P<0.001]。良性组与恶性组中,R2^(*)IDEAL与R2^(*)GRE均呈中度相关(r=0.745、0.680,P<0.001),二者与ADC均无相关性。两种序列所得的R2^(*)值差异有统计学意义(P<0.001)。R2^(*)IDEAL在良恶性组间差异有统计学意义(P<0.001),管腔HER-2阴性型R2^(*)值最高。对于单一参数,ADC值鉴别良恶性的AUC最高(0.857);对于联合参数,R2^(*)IDEAL+ADC鉴别良性组与管腔阴性组的AUC最高(0.927);差异均有统计学意义(P<0.05)。结论 IDEAL-IQ序列生成的R2^(*)值可用于区分良恶性乳腺肿块,可能成为除ADC外辅助乳腺肿瘤良恶性鉴别的又一无需对比剂参数。

基于双不对称LLC半桥的全桥谐振变换器研究

双不对称LLC半桥的全桥谐振变换器是一种采用定频控制的改进型LLC谐振变换器,具有很高的效率.先指出不对称LLC半桥谐振变换器存在的问题,再详细分析双不对称LLC半桥电路的工作原理、工作模态及参数选择,并根据选择的器件参数对变换器模型进行仿真试验.结果表明,该变换器能减小励磁电流叠加的环流损耗、关断损耗和零电压导通的无容性损耗,大大提高变换效率.

基于Hexverter的AC/AC系统交流不对称故障控制策略研究

六边形模块化多电平换流器(hexagonal modular multilevel converter,Hexverter)作为一种新型的AC/AC功率变换器,在未来海上风电场并网及低频输电技术中有着广阔的应用前景。为了解决Hexverter在电力系统不对称故障工况的稳定运行,文章首先对Hexverter的拓扑结构和工作原理简要介绍,并对其支路电流、支路功率进行分析。然后,研究其AC/AC系统交流侧不对称故障工况下的控制策略,基于理论推导部分得出的Hexverter六个支路间功率分布的规律(即不相邻的三个支路功率分别相等的特征),设计了子模块电容电压均衡控制方法,共包含两部分控制,分别为六个支路间子模块电容电压均衡控制和每个支路内部n个子模块电容电压之间的均衡控制。考虑到支路电流含有两侧交流系统不同频率成分,基于比例谐振控制器,提出了一种对支路电流直接进行控制的方法。最后,通过算例中稳态工况与故障工况研究分别对其工作原理和文中所提出的控制策略有效性进行验证。结果表明,在二次侧交流系统发生BC相短路故障期间,整个系统保持稳定运行,各个子模块电压始终保持均衡,仿真结果验证了文中所提控制策略的有效性。

Stochastic resonance in a monostable system driven by square-wave signal and dichotomous noise

This paper investigates the stochastic resonance in a monostable system driven by square-wave signal, asymmetric dichotomous noise as well as by multiplicative and additive white noise. By the use of the properties of the dichotomous noise, it obtains the expressions of the signal-to-noise ratio under the adiabatic approximation condition. It finds that the signal-to-noise ratio is a non-monotonic function of the asymmetry of the dichotomous noise, and which varies non- monotonously with the intensity of the multiplicative and additive noise as well as the system parameters. Moreover, the signal-to-noise ratio depends on the correlation rate and intensity of the dichotomous noise.

Effect of Asymmetry in a Bistable System Subject to Multiplicative Colored Noise

By the method of the stochastic energetics,we investigate the stochastic resonance (SR) phenomenon of anoverdamped Brown particle in an asymmetric bistable potential,driven by external periodical signal and multiplicativenoise.The expressions have been obtained for the quasi-steady-state probability distribution function.It is found thatthe input energy (IE) pumped into the system by the external driving shows an SR-like behavior as a function of thenoise strength,whereas the IE turns to be a monotonic function of the correlation time of the noise.The effect ofpotential asymmetry is also studied on SR and IE.

Experiment and application of parameter-induced stochastic resonance in an over-damped random linear system

This paper investigates the parameter-induced stochastic resonance using experimental methods in an over-damped random linear system with asymmetric dichotomous noise. Non-monotonic dependence of signal-to-noise ratio on the system parameter is observed. Several potential applications of parameter-induced stochastic resonance are given in circuits.

Theoretical Study of the Scattering Resonance State, Reaction Mechanism and Partial Potential Energy Surface of the F+CH4→HF+CH3 Reaction

The partial potential energy surface was constructed by ab initio method [QCISD（T）/6- 311＋＋G（2df,2pd）]for F＋CH4→HF＋CH3 reaction system. It not only explained the reaction mechanism brought forward by Diego Troya by means of quasiclassical trajectory （QCT） but also successfully validated Kopin Liu＇s experimental phenomena about the existence of the reactive resonance. The lifetime of the scattering resonance state was about 0.07 ps. All these were in agreement with the experiments.

石墨烯纳米片阵列的表面等离激元法诺共振

为了在中红外波段获得多阶表面等离激元法诺共振,设计了结构简单、制备方便的非对称石墨烯纳米片二聚体阵列超表面。采用有限元分析方法,对各阶法诺共振峰产生的物理机制,费米能级、纳米片结构及相对位置等因素对法诺共振的影响进行了理论分析。结果表明,随着费米能级的增加,法诺共振发生蓝移;表面等离激元共振效应增强,同时增强了近场的局域效应;随着纳米片二聚体的大小和位置的不对称性增加,法诺线型的非对称性也随之增加;这种结构简单的多阶表面等离激元法诺共振有望在生物传感及相关领域得到广泛应用。该研究为进一步的实验研究提供了理论参考。

非饱和非对称二维随机共振系统的优化及在高速铁路轴承故障诊断中的应用

针对传统双稳杜芬随机共振SR的输出饱和及噪声能量转换不足的问题,引入张角系数控制下的线性分段势阱函数,以抑制SR系统的输出饱和现象,采用非对称势阱函数扩大布朗粒子在单边势阱内的振荡范围,以增加SR输出幅值。结合非线性SR系统最佳耦合方式,构建非饱和-非对称二维SR系统,该系统的4个三维势阱的动力学特性丰富,势阱宽且陡峭度低,布朗粒子的振荡范围较大。采用多尺度简化粒子群优化算法,对构建的非饱和-非对称的二维SR系统进行多参数同步优化,进一步提高粒子在势阱内迁移向上的运动能量。仿真试验与高速铁路轴箱轴承的故障试验结果表明:所提出的优化耦合SR系统,能够显著增强特征信号幅值,提高噪声的利用率,在轴承早期损伤检测中具有突出优势。