ELECTRICALLY FORCED VIBRATION OF A THICKNESS-TWIST MODE PIEZOELECTRIC RESONATOR WITH NON-UNIFORM ELECTRODES

We study the effect of electrodes with varying thickness on thickness-twist vibration of a piezoelectric plate resonator of crystals of 6 mm symmetry. An exact theoretical analysis is performed. Results show that non-uniform electrodes have a strong effect on mode shapes, and suggest the possibility of using nonuniform electrodes for strong energy trapping.

Electric admittance analysis of quartz crystal resonator in thickness-shear mode induced by array of surface viscoelastic micro-beams

The electric admittance of a compound system composed of a thickness-shear mode （TSM） quartz crystal resonator （QCR） and an array of surface viscoelastic micro-beams （MBs） is studied. The governing equations of the MBs are derived from the Timoshenko-beam theory in consideration of shear deformation. The electrical admittance is described directly in terms of the physical properties of the surface epoxy resin （SU-8） MBs from an electrically forced vibration analysis. It is found that both the inertia effect and the constraint effect of the MBs produce competitive influence on the resonant frequency and admittance of the compound QCR system. By further comparing the numerical results calculated from the Timoshenko-beam model with those from the Euler-beam model, the shear deformation is found to lead to some deviation of an admittance spectrum. The deviations are revealed to be evident around the admittance peak（s） and reach the maximum when a natural frequency of the MBs is identical to the fundamental frequency of the QCR. Besides, a higher order vibration mode of the MBs corresponds to a larger deviation at the resonance.

Diffusion Coefficient at Resonance Frequency as Applied to n+/p/p+ Silicon Solar Cell Optimum Base Thickness Determination

The modelling and determination of the geometric parameters of a solar cell are important data, which influence the evaluation of its performance under specific operating conditions, as well as its industrial development for a low cost. In this work, an n+/p/p+ crystalline silicon solar cell is studied under monochromatic illumination in modulation and placed in a constant magnetic field. The minority carriers’ diffusion coefficient (D(ω, B), in the (p) base leads to maximum values (Dmax) at resonance frequencies (ωr). These values are used in expressions of AC minority carriers recombination velocity (Sb(Dmax, H)) in the rear of the base, to extract the optimum thickness while solar cell is subjected to these specific conditions. Optimum thickness modelling relationships, depending respectively on Dmax, ωr and B, are then established, and will be data for industrial development of low-cost solar cells for specific use.

Motility index measured by magnetic resonance enterography is associated with sex and mural thickness

BACKGROUND Recently,a technique has been developed to use magnetic resonance enterography(MRE)for the evaluation of small bowel motility.The hypothesis was that assessment of the motility index(MI)should reflect differences in motility between clinical conditions.AIM To aim of the present observational,cross-sectional study was to evaluate the use of the MI in daily clinical practice.METHODS All consecutive patients aged 18-70 years who were referred for MRE at the Department of Radiology during a 2-year period were asked to participate.Healthy volunteers were included as controls.MRE was prepared and conducted in accordance with clinical routines.On the day of examination,all the participants had to complete the visual analog scale for irritable bowel syndrome(IBS)and IBS-symptom severity scale.Maps of MI were calculated from dynamic MR images.ANOVA was used to evaluate differences in MI between groups,classified as healthy,Crohn’s disease,ulcerative colitis,IBS,other assorted disorders and dysmotility.Logistic and linear regression were applied to the MI values.All medical records were scrutinized for medical history.RESULTS In all,224 examinations were included(inclusion prevalence 76.3%),with 22 controls and 202 patients.There was a significant difference in the MI of the jejunum(P=0.021)and terminal ileum(P=0.007)between the different groups.The MI was inversely associated with the mural thickness of the terminal ileum in men(P<0.001)and women(P=0.063)after adjustments,and tended to be lower in men than in women(P=0.056).Subjectively observed reduction of motility on MRI was accomplished by reduced MI of terminal ileum in men(P<0.001)and women(P=0.030).In women,diarrhea was inversely associated with the MI of the jejunum(P=0.029),and constipation was positively associated with the MI of the terminal ileum(P=0.039).CONCLUSION Although MIs differ across diseases,a lower MI of the terminal ileum is mainly associated with male sex and an increased mural thickness.Symptoms are weakly associated with the MI.

Abnormal Alterations of Cortical Thickness in 16 Patients with Type 2 Diabetes Mellitus： A Pilot MRI Study

Objective The aim of this study is to investigate the cerebral cortical thickness changes in type 2 diabetes mellitus （T2DM） using a whole brain cortical thickness mapping system based on brain magnetic resonance imaging （MRI）. Methods High resolution three-dimensional T1-weighted fast spoiled gradient recalled echo MR images were obtained from 16 patients with T2DM, as well as from 16 normal controls. The whole brain cortical thickness maps were generated, and the cortical thickness of each brain region was calculated according to gyral based regions of interest （ROI） using an automated labeling system by the Freesurfer software. We compared mean cortical thickness at each brain region by the analysis of covariance with age and sex as covariates. The regional difference of the cortical thickness over the whole brain was compared by the analysis of surface-based cortical thickness. Results Mean cortical thicknesses analysis showed bilateral cerebrum in the patients with T2DM （left： 2.52±0.07 mm; right： 2.51±0.08 mm） were significant thinner than those in the normal controls （left： 2.56±0.09 mm; right： 2.56±0.09 mm） （both P〈0.05）. Regional cortical thinning in T2DM was demonstrated in the paracentral lobule, postcentral gyrus, lateral occipital gyrus, lingual gyrus, precuneus, superior temporal gyrus, middle temporal gyrus, inferior temporal gyrus and posterior cingulate gyrus, compared to the normal controls. The cortical thickness of left middle cingulate and right inferior temporal gyrus were negatively correlated with the disease course. Conclusion A widespread cortical thinning was revealed in patients with T2DM by the analysis of brain cortical thickness on MR. Our finding supports the idea that T2DM could lead to subtle diabetic brain structural changes.

New measurement of thick target yield for narrow resonance at Ex= 9.17 MeV in the 13C（p, γ）14N reaction

High energy γ-rays can be used in many fields, such as nuclear waste transmutation, flash photographics, and astrophysics. The13 C(p, γ)14 N resonance reaction was used to generate high energy and mono-energetic γ-rays in this work. The thick-target yield of the 9.17-MeV γ-ray from the resonance in this reaction was determined to be(4.7±0.4)×10-9γ/proton,which was measured by a HPGe detector. Meanwhile, the angular distribution of 9.17-MeV γ-ray was also determined.The absolute efficiency of HPGe detector was calibrated using56 Co and152 Eu sources with known radioactive activities and calculated by GEANT4 simulation.

Coupled extension and thickness-twist vibrations of lateral field excited AT-cut quartz plates

In this paper, the coupled extension and thickness- twist vibrations are studied for AT-cut quartz plates under Lateral Field Excitation （LFE） with variations along the x1- direction. Mindlin＇s two-dimensional equations are used for anisotropic crystal plates. Both free and electrically forced vibrations are considered. Important vibration characteristics are obtained, including dispersion relations, frequency spectra, and motional capacitances. It is shown that, to avoid the effects of the couplings between extension and thickness-twist vibrations, a series of discrete values of the length/thickness ratio of the crystal plate need to be excluded. The results are of fundamental significance for the design of LFE resonators and sensors.

Thickness-dependent magnetic anisotropy in obliquely deposited Fe(001)/Pd thin film bilayers probed by VNA-FMR

The thickness-dependent magnetic anisotropy of obliquely deposited Fe(001)/Pd thin films on Mg(001) is investigated by fitting the field-dependent resonant field curve using the Kittel equation.In this study, three Fe film samples with thicknesses of 50 monolayers(ML), 45 ML, and 32 ML deposited at 0°, 45°, and 55°, respectively, are used.The magnetic anisotropy constant obtained from ferromagnetic resonance(FMR) spectra exhibits a dominant fourfold magnetocrystalline anisotropy(MCA) at the normal deposition angle with larger Fe thickness.However, the in-plane uniaxial magnetic anisotropy(UMA) is induced by a higher oblique deposition angle and a smaller thickness.Its hard axis lies between the [100] and [010] directions.The FMR data-fitting analysis yields a precise measurement of smaller contributions to the magnetic anisotropy, such as in-plane UMA.Due to MCA, when the magnetic field is weaker than the saturated field,the magnetization direction does not always align with the external field.The squared frequency-dependent resonant field measurement gives an isotropic Landé g-factor of 2.07.Our results are consistent with previous experiments conducted on the magneto-optical Kerr effect(MOKE) and anisotropic magnetoresistance(AMR) systems.Thus, a vector network analyzer ferromagnetic resonance(VNA-FMR) test-method for finding UMA in obliquely deposited Fe(001)/Pd bilayer ferromagnetic thin films, and determining the magnetic anisotropy constants with respect to the film normal deposition, is proposed.

Bayesian Inference of Nucleus Resonance and Neutron Skin

In this proceeding,some highlight results on the constraints of the nuclear matter equation of state(EOS)from the data of nucleus resonance and neutron-skin thickness using the Bayesian approach based on the Skyrme-Hartree-Fock model and its extension have been presented.Typically,the anti-correlation and positive correlations between the slope parameter and the value of the symmetry energy at the saturation density under the constraint of the neutron-skin thickness and the isovector giant dipole resonance have been discussed respectively.It’s shown that the Bayesian analysis can help to find a compromise for the“PREXII puzzle”and the“soft Tin puzzle”.The possible modifications on the constraints of lower-order EOS parameters as well as the relevant correlation when higher-order EOS parameters are incorporated as independent variables have been further illustrated.For a given model and parameter space,the Bayesian approach serves as a good analysis tool suitable for multi-messengers versus multi-variables,and is helpful for constraining quantitatively the model parameters as well as their correlations.

基于HVSR方法的上海市典型场地特征研究

上海市强震台网获取了2020年5月3日日本九州6.0级地震等多次强震记录。通过对地震记录进行分析处理,分别计算了每个强震台站的H/V谱比曲线,结合上海市地质调查研究院的基岩埋深分布图,得到了每个台站的基阶共振频率与沉积层厚度。结果表明:H/V谱比曲线峰值与沉积层厚度存在明显相关性,并且通过数据拟合建立了上海市沉积层厚度与基阶共振频率的经验公式,绘制了上海市场地基本周期分布图,可以为上海市抗震设防提供一定的参考;厚沉积层场地上地震记录的谱比曲线会出现多个峰值,第二个峰值代表了沉积层的高阶共振频率;通过数据拟合得到上海地区剪切波速与沉积层厚度的经验公式。

陕西渭北晚更新世黄土-古土壤结合水膜厚度的试验研究

为深入剖析黄土与古土壤工程性质的影响因素,以陕西渭北晚更新世黄土与古土壤为研究对象,基于核磁共振、比表面积测试并结合理论分析对结合水膜厚度进行研究。试验结果显示:黄土与古土壤的结合水膜厚度存在明显差异,黄土的结合水膜厚度明显大于古土壤,原因在于古土壤孔隙体积及孔径小于黄土,而古土壤中高价阳离子含量大于黄土,同时古土壤颗粒表面分布铁锰质薄膜,其亲水性较弱。分析结合水膜与黄土湿陷性、回弹变形等工程特性间的关系,发现黄土-古土壤的湿陷性随结合水膜厚度的增大而增强,随结合水膜厚度的减小而减弱,结合水膜厚度与卸荷变形系数呈正相关关系。综合分析说明,高价阳离子含量、颗粒表面特性,及孔隙性的不同造成了黄土与古土壤结合水膜厚度的差异,从而导致黄土与古土壤的湿陷性等工程性质有显著区别。

脑白质病变及大脑皮层厚度与老年轻型卒中后认知功能障碍的相关性研究

目的探讨老年轻型卒中后认知功能障碍(PSCI)与脑白质病变、大脑皮层厚度的关系。方法回顾性分析158例老年轻型卒中病人的临床资料,根据MoCA评估结果分为非PSCI组和PSCI组(MoCA<26分),比较2组的基线资料、MRI影像改变、大脑皮层厚度,并采用多因素Logistic回归分析老年轻型卒中病人发生PSCI的影响因素。结果PSCI组与非PSCI组的腔隙性缺血灶、脑微出血、DWI阳性病变及血管间隙扩大检出率差异无统计学意义(P>0.05)。PSCI组年龄大于非PSCI组,脑白质病变较非PSCI组严重(P<0.05)。2组的左额下回三角部及右额下回三角部皮质厚度差异无统计学意义(P>0.05),但PSCI组左眶额部、右眶额部、左额中回及右额中回的皮质厚度均明显低于非PSCI组(P<0.05)。多因素分析显示,年龄、中重度脑白质病变均为老年轻型卒中病人发生PSCI的危险因素(OR=1.704、1.826,均P<0.05),前额叶脑皮质厚度(左眶额部、右眶额部、左额中回、右额中回)为老年轻型卒中病人发生PSCI的保护因素(OR=0.820、0.838、0.834、0.827,均P<0.05)。结论年龄、脑白质中重度病变及前额叶脑皮质厚度变薄均与PSCI密切相关,通过头颅MRI检查脑白质及大脑皮质厚度变化,可为临床预测PSCI的发生提供参考依据。

帕金森病伴疼痛患者大脑皮层厚度改变的结构MRI研究

目的基于高分辨率结构MRI技术探讨帕金森病(Parkinson’s disease,PD)伴疼痛患者大脑皮层厚度(cortical thickness,CT)的异常改变及其与疼痛评分的相关性,揭示PD疼痛的神经解剖基础。材料与方法本研究于2020年9月至2022年3月招募了经苏州大学附属第二医院神经内科确诊的82例PD患者及附近社区的29例无痛正常对照(normal control,NC)志愿者。采集所有受试者的人口学、临床资料以及结构MRI图像。采用非运动症状问卷和视觉模拟评分法(Visual Analog Scale,VAS)对PD患者分别进行疼痛筛查和疼痛程度评估。依据VAS评分将PD患者分为PD伴疼痛(PD patients with pain,PDP)组41例和PD不伴疼痛(PD patients without pain,nPDP)组41例。CT分析步骤如下:采用计算解剖学工具箱12(Computational Anatomy Toolbox 12,CAT12)软件包对结构像进行预处理获得全部被试者的全脑CT图;统计分析采用one-way ANOVA及post-hoc事后检验。统计结果采用无阈值聚类增强(threshold-free cluster enhancement,TFCE)及错误发现率(false discovery rate,FDR)进行多重比较校正,阈值设为P<0.05。最后,提取PDP组差异脑区的CT值与VAS评分进行偏相关性分析。结果One-way ANOVA分析发现PDP组、nPDP组及NC组间CT值存在差异的脑区包括右侧额上回、右侧额中回下部及右侧额下回三角部。Post-hoc事后分析显示,与nPDP组相比,PDP组的右侧额中回下部及右侧额下回三角部CT值减低(P=0.033、0.007)。与NC组相比,PDP组的右侧额上回、右侧额中回下部及右侧额下回三角部CT值均减低(P<0.001)。偏相关分析未发现PDP组的右侧额中回下部及右侧额下回三角部CT值与VAS评分存在显著相关(P=0.088)。结论右侧前额叶区域(额中回及额下回)的CT减低可能是PD伴疼痛患者的神经解剖基础,该区域可能通过调节疼痛感知以及与疼痛相关的情绪/情感、认知加工等方面参与了PD疼痛的发生。

压缩感知不同加速因子对心脏磁共振电影序列成像质量的影响

目的 探讨不同加速因子的压缩感知(CS)技术对心脏磁共振电影序列图像质量的影响及临床应用的可行性。资料与方法 前瞻性招募合肥市第一人民医院2021年1—7月40名健康志愿者进行心脏磁共振成像,扫描方案共4组(采用SENSE 2及加速因子分别为3、4、8的CS心脏电影序列),每组成像方案包括四腔心、左心室短轴、左心室两腔心及三腔心序列,对比4种方案的图像质量主观评分、左心室心功能及16节段心肌厚度。结果 以SENSE 2图像为标准评分(5分),CS3、CS4评分均在3分以上,CS8评分均在3分及以下,其中CS3与SENSE 2序列的四腔心及左心室短轴图像质量主观评分差异无统计学意义(P均>0.05);左心室两腔心及三腔心各序列组图像质量主观评分差异均有统计学意义(P均<0.05)。4种成像方案的左心室心功能(左心室射血分数、左心室收缩末期容积、左心室舒张末期容积、左心室每搏输出量、左心室舒张末期心肌质量)(F=0.027、0.182、0.057、0.140、0.545)与心肌厚度(F=0.052~7.366)各组间差异均无统计学意义(P均>0.05)。结论 基于CS技术的心脏电影序列具有良好的应用前景。随着加速因子的增加,扫描时间逐渐减少,相应的图像质量降低,而当加速因子为4(与常规电影序列相比扫描时间减少50%)时,仍能够准确进行左心室心功能及心肌厚度测量,且图像质量基本满足诊断需求。

基于Freesurfer自动分割技术评估不同类型颞叶癫痫患者大脑皮层厚度的改变

目的探讨Freesurfer自动分割技术评估成人颞叶癫痫(TLE)大脑皮层厚度的变化。资料与方法回顾性收集2021年1月—2023年9月宁夏医科大学总医院经临床表现和脑电图共同确诊的84例TLE,包括MRI阴性TLE 32例、左侧海马硬化30例、右侧海马硬化22例,招募50例健康志愿者作为对照组,均行轴位T1WI三维磁化强度预备梯度回波序列扫描。使用Freesurfer软件对T1WI图像行大脑皮层分割,比较不同类型TLE患者各皮层厚度的差异。结果MRI阴性TLE组与对照组比较有14个区域皮层厚度均减小,主要集中在双侧额叶和右侧顶叶,差异有统计学意义(P均<0.05);左侧海马硬化组与对照组比较有34个区域皮层厚度均减小,主要集中在双侧额叶、颞叶及顶叶,差异有统计学意义(P均<0.05);右侧海马硬化组与对照组比较有27个区域皮层厚度均减小,主要集中在双侧额叶、顶叶及右侧颞叶,差异有统计学意义(P均<0.05)。结论自动分割技术可评价不同类型TLE患者大脑不同皮层区域厚度的变化,有助于临床进一步了解TLE的发展,为完善治疗方法或术前评估提供参考。

前庭性偏头痛患者大脑皮质厚度异常研究

目的分析前庭性偏头痛(vestibular migraine,VM)患者大脑皮质厚度改变区域,为VM发病机制的研究提供理论依据。方法选择2021年6月—2022年12月于我院神经内科就诊的VM患者27例(设为VM组),同期招募28例健康志愿者作为对照组。所有受试者进行全脑磁共振(MR)扫描,采用基于表面形态学分析(SBM)方法分析并比较两组受试者MR图像中大脑皮质厚度;对VM组患者皮质厚度异常脑区与其病程、头痛发作频率、头晕发作频率、头痛视觉模拟评分(VAS)分值等参数进行Spearman相关性分析。结果与对照组相比,VM组患者左侧顶下小叶皮质厚度明显下降(P_(vertex)<0.01,P_(cluster)<0.05),但左侧顶下小叶皮质厚度与VM病程、头痛发作频率、头晕发作频率、头痛VAS分值均无相关性(P>0.05)。结论前庭性偏头痛患者大脑皮质厚度异常区域位于左侧顶下小叶,左侧顶下小叶可能参与了VM发生的病理生理过程。

组合型亥姆霍兹通风吸声体低频宽带吸声特性研究

为解决低频段通风吸声效果差的问题,提出一种亚波长厚度的颈部嵌入式亥姆霍兹通风超材料吸声体,该结构由中央通风开放区域和周围布置的多谐振器两部分组成。通过精确设计每个共振单元,使吸声体在445~678 Hz频率范围内具有优异的吸声特性,吸声系数均在0.85以上。该结构厚度为40 mm,仅是445 Hz波长的1/20。分析嵌入颈部的吸声机制,指出结构在颈部位置处,会具有很强的黏性来耗散声波能量,且共振频率随着颈部嵌入的长度增加而向低频偏移。随后,通过实验验证通风吸声体的传递损失与计算结果符合良好,目标频段内传递损失平均提高6dB。因此,该功能结构的通风吸声体材料为在低频域实现高吸声能力的可行性得到验证。

氢质子磁共振波谱中胆碱水平对良性前列腺增生合并膀胱过度活动症的诊断价值分析

目的探讨氢质子磁共振波谱(^(1)H-MRS)分析中胆碱(Cho)水平对良性前列腺增生患者合并膀胱过度活动症(OAB)的诊断价值。方法选取2022年7月至2023年3月合肥市第二人民医院诊治的60例BPH患者作为研究对象。根据膀胱过度活动症自我评价量表(OABSS)将其分为BPH合并OAB组(n=32)与单纯BPH组(n=28)。采用^(1)H-MRS检测两组膀胱壁中Cho、肌酸(Cr)水平,计算Cho/Cr比值。绘制受试者工作特征(ROC)曲线分析相关指标对BPH合并OAB的诊断效能。结果BPH合并OAB组膀胱壁中Cho、Cho/Cr较单纯BPH组显著升高,差异具有统计学意义(P<0.05)。多因素Logistic回归分析结果显示,Cho/Cr、膀胱壁厚度(BWT)是诊断BPH合并OAB的因素。ROC曲线结果显示,Cho/Cr可作为诊断BPH合并OAB的指标,截断值为0.70,Cho/Cr联合BWT诊断的效能更高,灵敏度、特异度分别为84.40%、67.90%,截断值为0.47。结论^(1)H-MRS分析中膀胱壁Cho与BPH合并OAB密切相关,Cho/Cr联合BWT具有良好的诊断价值。

Persistent alterations in gray matter in COVID-19 patients experiencing sleep disturbances:a 3-month longitudinal study

Sleep disturbances are among the most prevalent neuropsychiatric symptoms in individuals who have recovered from severe acute respiratory syndrome coronavirus 2 infections.Previous studies have demonstrated abnormal brain structures in patients with sleep disturbances who have recovered from coronavirus disease 2019(COVID-19).However,neuroimaging studies on sleep disturbances caused by COVID-19 are scarce,and existing studies have primarily focused on the long-term effects of the virus,with minimal acute phase data.As a result,little is known about the pathophysiology of sleep disturbances in the acute phase of COVID-19.To address this issue,we designed a longitudinal study to investigate whether alterations in brain structure occur during the acute phase of infection,and verified the results using 3-month follow-up data.A total of 26 COVID-19 patients with sleep disturbances(aged 51.5±13.57 years,8 women and 18 men),27 COVID-19 patients without sleep disturbances(aged 47.33±15.98 years,9 women and 18 men),and 31 age-and gender-matched healthy controls(aged 49.19±17.51 years,9 women and 22 men)were included in this study.Eleven COVID-19 patients with sleep disturbances were included in a longitudinal analysis.We found that COVID-19 patients with sleep disturbances exhibited brain structural changes in almost all brain lobes.The cortical thicknesses of the left pars opercularis and left precuneus were significantly negatively correlated with Pittsburgh Sleep Quality Index scores.Additionally,we observed changes in the volume of the hippocampus and its subfield regions in COVID-19 patients compared with the healthy controls.The 3-month follow-up data revealed indices of altered cerebral structure(cortical thickness,cortical grey matter volume,and cortical surface area)in the frontal-parietal cortex compared with the baseline in COVID-19 patients with sleep disturbances.Our findings indicate that the sleep disturbances patients had altered morphology in the cortical and hippocampal structures during the acute phase of infection and persistent changes in cortical regions at 3 months post-infection.These data improve our understanding of the pathophysiology of sleep disturbances caused by COVID-19.

基于微波平面传感器的碳纤维复合材料表面薄涂层厚度测量方法

碳纤维增强复合材料已经广泛用于航空航天制造,其表面涂层厚度直接影响部件性能,因此准确测量涂层厚度至关重要。基于材料微扰原理,提出一种利用微带线平面谐振器测量碳纤维增强复合材料表面涂层厚度的方案,该传感器具有尺寸小、成本低等优点。电磁仿真结果表明,谐振频率随着涂层厚度的增加而增大。试验在复合材料表面放置薄膜来模拟涂层,结果与仿真一致,且谐振频率偏移与厚度之间的关系可以用二次多项式进行表征。利用拟合曲线对覆盖层厚度进行预测,误差在实际厚度的±3%以内,而且对较厚覆盖层的预测也比较准确,表明所提出的传感器用于厚度测量的适用性较广。