Enhanced Wideband Frequency Estimation via FFT: Leveraging Polynomial Interpolation and Array Indexing

Accurate frequency estimation in a wideband digital receiver using the FFT algorithm encounters challenges, such as spectral leakage resulting from the FFT’s assumption of signal periodicity. High-resolution FFTs pose computational demands, and estimating non-integer multiples of frequency resolution proves exceptionally challenging. This paper introduces two novel methods for enhanced frequency precision: polynomial interpolation and array indexing, comparing their results with super-resolution and scalloping loss. Simulation results demonstrate the effectiveness of the proposed methods in contemporary radar systems, with array indexing providing the best frequency estimation despite utilizing maximum hardware resources. The paper demonstrates a trade-off between accurate frequency estimation and hardware resources when comparing polynomial interpolation and array indexing.

L型阵水下目标方位和距离联合最大似然估计

空间目标定位是阵列信号处理领域中的研究热点,广泛应用于雷达、声纳、通信、射电天文、医学诊断、地震遥感等众多领域。传统的水下声源定位仅获取目标声源的深度和距离信息,却无法估计目标的方位信息。针对这一问题,在充分考虑水下声传播模型的基础上,利用L型阵列固有的结构特征,将最大似然估计技术应用到水下目标定位,提出一种基于L型水听器阵列的水下目标方位与距离联合最大似然估计算法。研究表明:最大似然估计法可有效突破传统波束形成分辨力“瑞利限”的限制,提高水下目标定位的分辨能力和精度。计算机仿真分析显示,在单目标和相干双目标的场景中,文中所提出的方法均具有更为尖锐的谱峰及更低的旁瓣水平,可对水下目标进行有效的方位角和距离联合估计。

小数据集下基于DRKDE-ICSO的BN结构学习

为了解决在小数据集条件下进行数据拓展时产生数据高度相似的问题,提出了基于降维核密度估计的小数据集拓展方法,从而得到较为准确的拓展数据。另外,针对鸡群优化算法求解效率低下和收敛性不足的问题,提出改进的鸡群优化算法进行结构学习:在雄鸡的位置更新公式中引入莱维飞行,使鸡群算法具有更强的跳跃能力;采用指数递减的动态调节惯性权重,以加速局部搜索和提高收敛速度;通过引入最优个体引导策略,增加找到较优位置的概率。实验结果表明,所提算法在小数据集条件下,BIC评分、准确率及汉明距离等指标均优于MCMC算法、BPSO算法、CSO算法、ADLCSO-I算法和SA-ICSO算法。

基于高阶幂的单快拍LDACS系统波达方向估计

L波段数字航空通信系统(L band digital aeronautical communication system,LDACS)是未来航空宽带通信重要的基础设施之一,针对LDACS信号容易受到相邻波道大功率测距仪(distance measuring equipment,DME)信号干扰的问题,提出了联合正交投影干扰抑制与单快拍稀疏分解的波达方向(direction of arrival,DOA)估计方法。通过子空间投影抑制DME干扰,然后使用单快拍数据构建伪协方差矩阵,对伪协方差矩阵求高阶幂,之后进行奇异值分解,并利用约束条件求解稀疏解得到期望信号来向的估计值。所提方法使用高阶伪协方差矩阵降低了噪声影响,仅用单快拍就可以准确估计LDACS信号的入射方向。仿真结果表明,改进单快拍高级幂(improved single snapshot high order power,ISS-HOP)L1-SVD算法的估计精度优于ISS-HOP-MUSIC算法。该方法可以有效抑制DME干扰,提高OFDM接收机性能。

基于外部气相沉积的S+C+L波段低色散斜率大有效面积非零色散位移光纤的设计与制备

针对现有光纤无法满足宽带光密集波分复用系统传输和S+C+L波段粗波分复用的要求,设计了一种具有中心凹陷的三角形芯+环形的折射率剖面,利用外部气相沉积工艺制备了一种非零色散位移光纤,并通过调整第一芯层的相对折射率和第二芯层与第一芯层的半径比,探究了其对光纤衰减、色散斜率和有效面积等参数的影响。研究发现,当第一芯层的相对折射率逐渐增大且第二芯层与第一芯层半径比逐渐减小时,零色散波长和有效面积逐渐减小。当第一芯层的相对折射率在0.52%~0.53%,芯层半径比在2.6~2.7时,光纤的有效面积接近70μm^(2),零色散波长在1420 nm附近,在1550 nm波段的色散系数大于8 ps·nm^(-1)·km^(-1),色散斜率为0.059 ps·nm^(-2)·km^(-1),可以较好地抑制传输过程中光非线性效应,满足长途干线网与城域网的使用要求。

基于BiLSTM-Attention的F_(10.7)指数预测模型与中国自主数据集的应用

F_(10.7)指数是太阳活动的重要指标,准确预测F_(10.7)指数有助于预防和缓解太阳活动对无线电通信、导航和卫星通信等领域的影响.基于F_(10.7)射电流量的特性,在双向长短时记忆网络(Bidirectional Long Short-Term Memory Network,BiLSTM)基础上融入注意力机制(Attention),提出了一种基于BiLSTM-Attention的F_(10.7)预报模型.在加拿大DRAO数据集上其平均绝对误差(MAE)为5.38,平均绝对百分比误差(MAPE)控制在5%以内,相关系数(R)高达0.987,与其他RNN模型相比拥有优越的预测性能.针对中国廊坊L&S望远镜观测的F_(10.7)数据集,提出了一种转换平均校准(Conversion Average Calibration,CAC)方法进行数据预处理,处理后的数据与DRAO数据集具有较高的相关性.基于该数据集对比分析了RNN系列模型的预报效果,实验结果表明,BiLSTM-Attention和BiLSTM两种模型在预测F_(10.7)指数方面具有较好的优势,表现出较好的预测性能和稳定性.

利用卷积神经网络开展偏振雷达定量降水估测研究

利用偏振升级改造后的广州新一代天气雷达(CINRAD/SAD)水平反射率ZH、差分传播相移率KDP、差分反射率因子ZDR和广东佛山219个地面气象自动站雨量数据,形成不同偏振量组合的8个数据集。基于卷积神经网络(CNN),建立雷达定量降水估测网络架构QPEnet,并将该架构用于雷达定量降水估测(QPE),评估结果表明:数据集通道数N的增加可降低QPEnet的定量降雨估测的均方根误差(RMSE),并提高相关系数(CORR);对于由ZH形成的数据集Z、Z_1~3 km和Z_6 min,随着通道数N的增加,数据集Z、Z_1~3 km和Z_6 min的性能逐步得到提高,数据集Z_1~3 km和Z_6 min的均方根误差(RMSE)分别是4.71和3.78,比数值集Z分别降低了1.3%和18.7%;数据集Z_1~3 km和Z_6 min的CORR分别是0.82和0.88,比数据集Z分别提高了2.5%和10.0%;对于ZH、KDP和ZDR偏振量组成的数据集里面,数据集Z_ZDR_KDP的拟合性能最好,RMSE为3.97,比数据集Z的RMSE降低了14.6%,CORR是0.86,比数据集Z提高了7.5%;分别对0.6~5 mm、5~10 mm、10~20 mm、20~30 mm、30~40 mm、40~50 mm和50 mm以上的7个降水量级的均方根误差(RMSE)、平均偏差比(MBR)、平均误差(AE)和相对误差(RE)等的统计结果表明,数据集Z_6 min降雨精度最高。

基于理性扩展热力学的L-S热声弹性理论框架

本文基于连续介质力学和理性扩展热力学分析流程,将L-S(Lord and Shulman)热弹性理论与声弹性理论相结合,建立L-S热声弹性理论的基本框架,包括运动学、力学与热力学、本构方程与演化方程、基本场方程四部分。在运动学部分,区分了Lagrange描述和Euler描述,以及3种不同的状态和构形,同时针对热声弹性情况定义了两类从自然状态到初始状态的转变过程;在力学与热力学部分,给出了质量守恒定律、动量守恒定律、角动量守恒定律、能量守恒定律以及熵产不等式,从而引出经典不可逆热力学的局限性;在本构方程与演化方程部分,介绍了扩展不可逆热力学原理,并基于理性扩展热力学流程,推导了从自然状态到初始状态、从初始状态到最终状态的热声弹性本构方程与演化方程,将热流作为本构自变量并考虑了热流与应变和温度的相关性;在最后一部分给出了基本场方程的运动方程形式和适用于数值模拟的一阶速度-应力-热流-温度微分方程。

线性Poisson-Boltzmann方程的虚单元L^(2)误差估计

针对一类线性Poisson-Boltzmann方程的虚单元L^(2)误差估计进行分析.首先引入正则化的线性Poisson-Boltzmann方程,将原问题转化为非奇性Poisson-Boltzmann方程.然后给出L^(2)范数的误差估计.最后在四边形和五边形混合多边形网格上进行数值实验,数值结果验证了理论分析的正确性.

深圳X波段双偏振相控阵雷达降水估测算法效果评估

为验证X波段双偏振相控阵雷达的降水估测能力,利用2020年深圳市X波段双偏振相控阵雷达探测资料和广州市S波段双偏振雷达探测资料,建立基于双偏振雷达参量强弱(即ZH、ZDR和KDP)的本地化混合降水反演方法,对不同降水使用最优的雷达参量进行定量降水估测,统计广东龙门县2016年雨滴谱观测资料,得到降水估测公式中的系数,分析不同时间、空间和降水强度下降水个例,利用本地化降水反演方法产生的定量降水估计结果与雨量计观测资料对比。结果表明,高时空分辨率的X波段相控阵雷达可以提高降水估测精度。X波段相控阵雷达在高时间分辨率下,其估测降水强度变化趋势和自动站观测的降水强度变化趋势一致,并且对降水强度小于40 mm/h的降水估测较为准确。在最大观测范围内,X波段相控阵雷达能观测到低层的气象信息,其降水估测的评估结果优于S波段雷达。X波段相控阵雷达对暴雨以下的降水估测更加准确,对暴雨以上的降水估测结果误差较大,可信度不高。

基于迭代学习和模糊模型的机器人故障估计

针对柔性机器人执行器故障问题,提出了基于迭代学习和模糊模型的机器人故障估计策略。首先,为了处理机器人系统的非线性,将机器人系统转化成Takagi-Sugeno(T-S)模糊系统。其次,基于T-S模糊系统和机器人重复运动特性,设计模糊观测器和模糊迭代学习故障估计算法,实现同时精准估计机器人状态和执行器故障。再次,提出可解条件,保证模糊迭代学习故障估计算法的鲁棒单调收敛性,使迭代估计算法具有良好的暂态行为。最后,利用一个单连杆柔性关节机器人来验证所提方法的有效性。

Unveiling DNA methylation in Alzheimer’s disease:a review of array-based human brain studies

The intricacies of Alzheimer’s disease pathogenesis are being increasingly illuminated by the exploration of epigenetic mechanisms,particularly DNA methylation.This review comprehensively surveys recent human-centered studies that investigate whole genome DNA methylation in Alzheimer’s disease neuropathology.The examination of various brain regions reveals distinctive DNA methylation patterns that associate with the Braak stage and Alzheimer’s disease progression.The entorhinal cortex emerges as a focal point due to its early histological alterations and subsequent impact on downstream regions like the hippocampus.Notably,ANK1 hypermethylation,a protein implicated in neurofibrillary tangle formation,was recurrently identified in the entorhinal cortex.Further,the middle temporal gyrus and prefrontal cortex were shown to exhibit significant hypermethylation of genes like HOXA3,RHBDF2,and MCF2L,potentially influencing neuroinflammatory processes.The complex role of BIN1 in late-onset Alzheimer’s disease is underscored by its association with altered methylation patterns.Despite the disparities across studies,these findings highlight the intricate interplay between epigenetic modifications and Alzheimer’s disease pathology.Future research efforts should address methodological variations,incorporate diverse cohorts,and consider environmental factors to unravel the nuanced epigenetic landscape underlying Alzheimer’s disease progression.

Prognostic significance and relationship of SMAD3 phosphoisoforms and VEGFR-1 in gastric cancer:A clinicopathological study

BACKGROUND The TGF-β/SMAD3 and VEGFR-1 signaling pathways play important roles in gastric cancer metastasis.SMAD3 phosphorylation is a crucial prognostic marker in gastric cancer.AIM To determine the prognostic value and relationship of SMAD3 phospho-isoforms and VEGFR-1 in gastric cancer.METHODS This was a single-center observational study which enrolled 98 gastric cancer patients and 82 adjacent normal gastric tissues from patients aged 32-84 years(median age 65)between July 2006 and April 2007.Patients were followed up until death or the study ended(median follow-up duration of 28.5 mo).The samples were used to generate tissue microarrays(TMAs)for immunohistochemical(IHC)staining.The expressions of TGF-β1,pSMAD3C(S423/425),pSMAD3L(S204),and VEGFR-1 in gastric cancer(GC)tumor tissue and normal tissue were measured by IHC staining using TMAs obtained from 98 GC patients.Prognosis and survival information of the patients was recorded by Outdo Biotech from May 2007 to July 2015.The relationship between TGF-β1,pSMAD3C(S423/425),pSMAD3L(S204),and VEGFR-1 protein expression levels was analyzed using Pearson's correlation coefficient.The relationship between protein expression levels and clinicopathological parameters was analyzed using the Chi-squared test.A survival curve was generated using the Kaplan-Meier survival analysis.RESULTS TGFβ-1 and VEGFR-1 expression was significantly upregulated in gastric cancer tissue compared to adjacent noncancerous tissue.The positive expression of phosphorylated isoforms of Smad3 varied depending on the phosphorylation site[pSMAD3C(S423/425):51.0%and pSMAD3L(S204):31.6%].High expression of pSMAD-3L(S204)was significantly correlated with larger tumors(P=0.038)and later N stages(P=0.035).Additionally,high expression of VEGFR-1 was closely correlated with tumor size(P=0.015)and pathological grading(P=0.013).High expression of both pSMAD3L(S204)and VEGFR-1 was associated with unfavorable outcomes in terms of overall survival(OS).Multivariate analysis indicated that high expression of pSMAD3L(S204)and VEGFR-1 were independent risk factors for prognosis in GC patients.VEGFR-1 protein expression was correlated with TGF-β1(r=0.220,P=0.029),pSMAD3C(S423/425)(r=0.302,P=0.002),and pSMAD3L(S204)(r=0.201,P=0.047),respectively.Simultaneous overexpression of pSMAD3L(S204)and VEGFR-1 was associated with poor OS in gastric cancer patients.CONCLUSION Co-upregulation of pSMAD3L(S204)and VEGFR-1 can serve as a predictive marker for poor gastric cancer prognosis,and pSMAD3L(204)may be involved in enhanced gastric cancer metastasis in a VEGFR-1-dependent manner.

R^(1+1)中Maxwell-Chern-Simons-Higgs模型解的L^(∞)估计

用能量守恒估计和特征线估计的方法解决(1+1)维Maxwell-Chern-Simons-Higgs模型解的Sobolev范数增长性估计问题,给出模型有限能量解的一阶导数的L^(∞)估计,并通过改进指数增长得到解的H^(2)范数的多项式增长.

由Sălăvgean-q微分算子定义的具有对称共轭点的单叶调和函数类

在单复变函数几何理论的研究中,构造函数类及研究它的几何性质是目前国内外重要的研究课题。本文首先定义了一个Sălăgean-q微分算子,利用该算子,我们构建了一类具有特殊性质的倒结构单叶调和函数,这类函数具有对称共轭点。我们进一步推导出了这类函数的系数条件,并得到了相应的Fekete-Szegö不等式,这一发现有效地拓展了现有的知识范畴。这一成果不仅丰富了单复变函数的理论内容,也为调和函数的研究提供了新的视角和方法。更重要的是,这一研究可能为未来在信号处理、图像处理等领域的实际应用提供新的数学模型和算法基础。

On the Range of Action of Adult Culex pipiens s.l.

Mosquitoes are an interesting topic due to their medical importance, as they play an active role in the transmission of many pathogens and parasites, acting as vectors for various pathologies that are deadly to humans, such as dengue, yellow fever, chikungunya, West Nile virus, encephalitis and malaria, among many others that are less common. In terms of morbidity and mortality caused by vector-borne diseases, mosquitoes are the most dangerous animals for humanity and, although they also play a role in the ecosystem as a food source for other organisms, their importance for public health cannot be overlooked. As highly efficient vectors, they put more than three billion people at risk, mainly in tropical and subtropical regions as well as in Europe, since heat waves and flooding are becoming more frequent and severe, and summers are getting longer and warmer, accelerating mosquito development, biting rates, and the incubation of the pathogens within their bodies. Female mosquitoes bite to acquire proteins for the development of their ovaries and eggs and, in the process, acquire pathogens and/or parasites from one vertebrate host and transmit them to another, usually after a short period of replication. Three of their four life stages are lived in still freshwater, so it is crucial to understand their range of action when they reach adulthood and leave the water, in order to plan and implement local prevention measures. A set of georeferenced abundance data collected in mainland Portugal over seven years was linked to cartographed water bodies in a geographic information system to estimate the distances at which Culex pipiens s.l. had a significant presence, with criteria based on the size of the catches. The result allows for an estimate of the fly range of those mosquitoes, which can be used to focus countermeasures.

Accurate Diagnosis of SARS-CoV-2 JN.1 by Sanger Sequencing of Receptor-Binding Domain Is Needed for Clinical Evaluation of Its Immune Evasion

Background: Omicron JN.1 has become the dominant SARS-CoV-2 variant in recent months. JN.1 has the highest number of amino acid mutations in its receptor binding domain (RBD) and has acquired a hallmark L455S mutation. The immune evasion capability of JN.1 is a subject of scientific investigation. The US CDC used SGTF of TaqPath COVID-19 Combo Kit RT-qPCR as proxy indicator of JN.1 infections for evaluation of the effectiveness of updated monovalent XBB.1.5 COVID-19 vaccines against JN.1 and recommended that all persons aged ≥ 6 months should receive an updated COVID-19 vaccine dose. Objective: Recommend Sanger sequencing instead of proxy indicator to diagnose JN.1 infections to generate the data based on which guidelines are made to direct vaccination policies. Methods: The RNA in nasopharyngeal swab specimens from patients with clinical respiratory infection was subjected to nested RT-PCR, targeting a 398-base segment of the N-gene and a 445-base segment of the RBD of SARS-CoV-2 for amplification. The nested PCR amplicons were sequenced. The DNA sequences were analyzed for amino acid mutations. Results: The N-gene sequence showed R203K, G204R and Q229K, the 3 mutations associated with Omicron BA.2.86 (+JN.1). The RBD sequence showed 24 of the 26 known amino acid mutations, including the hallmark L455S mutation for JN.1 and the V483del for BA.2.86 lineage. Conclusions: Sanger sequencing of a 445-base segment of the SARS-CoV-2 RBD is useful for accurate determination of emerging variants. The CDC may consider using Sanger sequencing of the RBD to diagnose JN.1 infections for statistical analysis in making vaccination policies.

有限元分析对骨质疏松条件下L5/S1斜外侧椎间融合与两种后路固定的生物力学研究

目的评估在骨质疏松条件下,行L5/S1节段斜外侧椎间融合术(oblique lateral interbody fusion at L5/S1,OLIF51)及其联合双侧皮质骨轨迹螺钉(cortical bone trajectory screw,CBT)和双侧椎弓根螺钉(bilateral pedicle screw,BPS)的生物力学性能。方法招募1名健康青年男性作为志愿者,获得其腰骶椎三维CT数据,在有限元分析软件中完成L4~S1三维模型,采用前路钛板(titanium plate,TP)固定的OLIF51手术模型、OLIF51+CBT和OLIF51+BPS手术模型的构建,分别命名为A、B、C、D模型。通过赋值、设定条件、施加载荷,分析不同条件下的生物力学特性。结果顺利完成4种有限元模型的构建。4种模型在所有运动中的平均活动度(range of motion,ROM)变化趋势为A模型>B模型>C模型>D模型;其中,与A模型相比,B模型降幅为84.21%~94.42%,C模型降幅为88.12%~96.40%,D模型降幅为90.07%~96.49%(P均<0.05);与B模型相比,C模型降幅为7.41%~52.38%,D模型降幅为27.78%~58.33%(P均<0.05)。3种手术模型在所有运动中的融合器(Cage)平均最大应力变化趋势为B模型>C模型>D模型;其中,与B模型相比,C模型降幅为12.89%~57.62%,D模型降幅为36.43%~73.11%;D模型和C模型相比,除左侧弯外差异均有统计学意义(P均<0.05);D模型降幅为21.83%~37.67%。3种手术模型在所有运动中的内固定平均最大应力变化趋势为B模型>C模型>D模型;与B模型相比,C模型降幅为3.55%~65.47%,D模型降幅为18.58%~84.41%;CBT应力大于BPS应力(P<0.05)。结论在OLIF51手术中,补充后路内固定可以增强融合节段的稳定性并减轻TP上的应力。不建议对骨质疏松症患者单独进行OLIF51手术,使用BPS辅助固定可达到最佳生物力学特性。接受CBT辅助内固定的患者术后需要佩戴支具,并尽量避免融合部位的右侧弯曲运动。

L型氨基酸转运蛋白1的表达对非霍奇金淋巴瘤临床病理特征和预后的影响

目的:检测非霍奇金淋巴瘤(NHL)组织中L型氨基酸转运蛋白1(LAT1)的表达,分析LAT1对患者临床病理特征和预后的影响。方法:收集2017年1月至2019年4月在本院接受治疗的NHL患者92例,免疫组织化学检测NHL组织中LAT1的表达,比较不同病理特征(包括性别、Ann Arbor分期、结外浸润、Ki-67)患者组间LAT1的表达差异,单因素和多因素Cox回归分析影响患者死亡的危险因素,受试者工作曲线(ROC)检测NHL组织中LAT1阳性细胞百分比对患者死亡的预测价值,分析LAT1阳性细胞百分比对患者生存率的影响。结果:LAT1在NHL组织中呈阳性表达,Ann Arbor分期III期和IV期组LAT1高表达率高于I期组,结外浸润组LAT1高表达率高于无结外浸润组,Ki-67阳性表达组LAT1高表达率高于阴性表达组,比较差异均有统计学意义(均P<0.05)。LAT1高表达组治疗3个疗程后的缓解率为70.7%,低于低表达组的91.2%,比较差异有统计学意义(P<0.05)。Ann Arbor分期III期、IV期、结外浸润、Ki-67阳性表达和LAT1表达增加(即LAT1阳性细胞比例评分≥2)为患者死亡的危险因素。LAT1阳性细胞百分比预测NHL死亡的截断值为45.6%,曲线下面积为0.905(95%CI:0.897-0.924)。LAT1高水平组(LAT1阳性细胞百分比≥45.6%)3年生存率为50.00%,低于LAT1低水平组的78.26%(P<0.05)。结论:LAT1在NHL组织中表达水平增加,影响患者的肿瘤分期和结外浸润,是患者死亡的危险因素。

山竹皮氧杂蒽酮超声辅助植物油提取工艺优化及其抗氧化和抑菌能力研究

使用中心复合设计对超声波辅助植物油提取山竹皮氧杂蒽酮工艺进行优化,并研究山竹皮提取物在植物油中的抗氧化能力和抑菌能力。结果:超声波辅助植物油提取山竹皮氧杂蒽酮工艺中最终采用大豆油作为提取溶剂,最佳提取工艺为超声时间2 h、料液比1∶25 g/mL、水浴时间35 min;山竹皮氧杂蒽酮提取物在植物油中具有显著的抗氧化能力和一定抑菌效果,其对枯草芽孢杆菌的抑菌效果最佳。