The Changes of Baroreflex Sensitivity During Head-up Tilt Test and Its Clinical Significance in the Patients with Vasovagal Syncope

Objective To study thechanges of baroreflex sensitivity (BRS) during head - up tilt test (HUT) in patients with vasovagal syncope (VS), and to examine the relationship between baroreflex sensitivity and neurohormonal factors. Furthermore, to investigate the effects of the changes of BRS on VS. Methods Forty - two patients with unexplained syncope (Among the 42 patients, there were 22 patients with positive HUT and 20 patients with negative HUT respectively) and 20 healthy volunteers (with negative HUT) underwent passive head - up tilt testing, Ante-cubital vein blood samples were taken before and after HUT, or at syncope. The fasting plasma endothelin , serum nitric oxide (NO), serum NE were measured, the BRS was assessed on the basis of the linear regression slope the RR interval versus systolic arterial blood pressure during the increment in blood pressure after intravenous administration of phenylephrine. Results (1) During the syncope, the BRS significantly reduced in HUT(+) group than baseline. At the end of tilt, the level of plasma ET, serum NO in patients with positive HUT significantly increased compared with baseline or normal controls, and the plasma concentration of NE also had the trend of increase. (2) By multiple regression analysis, a significant negative correlation was found between baroreceptor sensitivity and the plasma ET, NO at the end of HUT in patients with positive HUT, but there was no relationship between BRS and NE. Conclusions During the syncope occure, the BRS in patients with VS decreased significantly compared with normal controls. The abnormal plasma ET, NO concen-tration might contribute to the mechanism of VS.

The Changes of Heart Rate Power Spectral Density during Head-up Tilt Test

To study the role of autonomic nervous system in the period of developing syncope induced by head-up tilt test(HUT), we analysed the changes of heart rate power spectral density(HRPSD) in 50 patients with unexplained syncope, including 15 positive patients (Group 1) and 35 negative patients(Group 2), and 15 negative healthy persons(Group 3) in 5 minute periods before and after tilting and 5 minutes before the end of test. HRPSD and their changes in total(T), very low-frequence(VLF), low-frequence(LF), high-frequence(HF) and the ratio of low/high frequence(LF/HF) were similar (P>0.05) 5 minutes before and after tilting among three groups. Five minutes before the end of test, Group 1 had obvious increase of T, VLF, LF and LF/HF while Group 2 and 3 had not such significant changes. There was significant difference(P<0.01) compared Group 1 with Group 2, 3. The results showed that the abnormal regulatory function of autonomic nervous system played an important role in the mechanism of symcope induced by HUT, the positive group had abnormal increase of sympathetic tone and imbalance of sympathetic/parasympathetic neural tone before syncope appeared.

Deceleration Capacity--A Novel Measure for Autonomic Nervous System in Patients with Vasovagal Syncope on Tilt-table Testing

This study was to investigate the changes of autonomic nerve function and hemodynamics in patients with vasovagal syncope(VVS) during head-up tilt-table testing(HUT). HUT was performed in 68 patients with unexplained syncope and 18 healthy subjects served as control group. According to whether bradycardia, hypotension or both took place during the onset of syncope, the patients were divided during the test into three subgroups: vasodepressor syncope(VD), cardioinhibitory syncope(CI) and mixed syncope(MX) subgroups. Heart rate, blood pressure, heart rate variability(HRV), and deceleration capacity(DC) were continuously analyzed during HUT. For all the subjects with positive responses, the normalized low frequency(LFn) and the LF/HF ratio markedly decreased whereas normalized high frequency(HFn) increased when syncope occurred. Syncopal period also caused more significant increase in the power of the DC in positive groups. These changes were more exaggerated compared to controls. All the patients were indicative of a sympathetic surge in the presence of withdrawal vagal activity before syncope and a sympathetic inhibition with a vagal predominance at the syncopal stage by the frequency-domain analysis of HRV. With the measurements of DC, a decreased vagal tone before syncope stage and a vagal activation at the syncopal stage were observed. The vagal tone was higher in subjects showing cardioinhibitory responses at the syncopal stage. DC may provide an alternative method to understand the autonomic profile of VVS patients.

Syncope as a health risk for soldiers: Influence of medical history and clinical findings on the sensitivity of head-up tilt table testing

Background: Syncope is a relevant health problem in military environments. Reliable diagnosis is challenging. Tilt table testing is an important tool for syncope diagnosis. The aim of this study was to determine whether signs such as prodromal symptoms, co-morbidity, frequency of syncopal events, body length, body mass index, and electrocardiography(ECG) abnormalities can be used to predict the success of tilt table testing at diagnosing syncope.Methods: Data from 100 patients with histories of syncope or pre-syncope, who were diagnosed using head-up tilt table testing, were retrospectively analyzed in a cross-sectional analysis. The diagnostic procedure was based upon a modified version of the Westminster protocol without any pharmacological provocation. Results: Patients showing pathological reaction patterns during tilt table testing suffered from prodromal symptoms, such as dizziness and sweating, significantly more often. The patients reported more injuries resulting from syncopal events and more previous syncopal events, and the prevalence of co-morbidity was greater among patients presenting negative findings during tilt testing. An asthenic-leptosomal physique was not confirmed as a risk factor for syncopal events as is the case for idiopathic arterial hypotension. However, patients with pathological reaction patterns during tilt table testing were significantly taller. This finding was detected for both females and males. No significant predictors were found in the ECG patterns of patients showing syncope during tilt table testing.Conclusions: Frequency of prior syncope and prodromal symptoms, and increased body length with an otherwise good state of health influence the predictive value of tilt table testing for syncope diagnosis. In particular, if these factors are present, tilt table testing should be considered part of the diagnostic algorithm for soldiers with recurrent syncope.

Tilt table test today-state of the art

A tilt table test(TTT) is an inexpensive, noninvasive tool for the differential diagnosis of syncope and orthostatic intolerance and has good diagnostic yield. The autonomic system malfunction which underlines the reflex syncope is manifested as either hypotension or bradycardia, while an orthostatic challenge is applied. The timing of the response to the orthostatic challenge, as well as the predominant component of the response help to differentiate between various forms of neurocardiogenic syncope, orthostatic hypotension and non-cardiovascular conditions(e.g., pseudosyncope). Medications, such as isoproterenol and nitrates, may increase TTT sensitivity. Sublingual nitrates are easiest to administer without the need of venous access. TTT can be combined with carotid sinus massage to evaluate carotid sinus hypersensitivity, which may not be present in supine position. TTT is not useful to access the response to treatment. Recently, implantable loop recorders(ILR) have been used to document cardioinhibitory reflex syncope, because pacemakers are beneficial in many of these patients, especially those over 45 years of age. The stepwise use of both TTT and ILR is a promising approach in these patients. Recently, TTT has been used for indications other than syncope, such as assessment of autonomic function in Parkinson's disease and its differentiation from multiple system atrophy.

Syncope as a health risk for soldiers-influence of medical history and clinical findings on the sensitivity of head-up tilt table testing

Background:Syncope is a relevant health problem in military environments.Reliable diagnosis is challenging.Tilt table testing is an important tool for syncope diagnosis.The aim of this study was to determine whether signs such as prodromal symptoms,co-morbidity,frequency of syncopal events,body length,body mass index,and electrocardiography abnormalities can be used to predict the success of tilt table testing at diagnosing syncope.Methods:Data from 100 patients with histories of syncope or pre-syncope,who were diagnosed using head-up tilt table testing,were retrospectively analyzed in a cross-sectional analysis.The diagnostic procedure was based upon a modified version of the Westminster protocol without any pharmacological provocation.Results:Patients showing pathological reaction patterns during tilt table testing suffered from prodromal symptoms,such as dizziness and sweating,significantly more often.The patients reported more injuries resulting from syncopal events and more previous syncopal events,and the prevalence of co-morbidity was greater among patients presenting negative findings during tilt testing.An asthenic-leptosomal physique was not confirmed as a risk factor for syncopal events as is the case for idiopathic arterial hypotension.However,patients with pathological reaction patterns during tilt table testing were significantly taller.This finding was detected for both females and males.No significant predictors were found in the electrocardiogram patterns of patients showing syncope during tilt table testing.Conclusions:Frequency of prior syncope and prodromal symptoms,and increased body length with an otherwise good state of health influence the predictive value of tilt table testing for syncope diagnosis.In particular,if these factors are present,tilt table testing should be considered part of the diagnostic algorithm for soldiers with recurrent syncope.

慢性直立不耐受人群血流动力学模式与缺血性卒中发病风险关系的前瞻性研究

目的:探讨慢性直立不耐受(OI)人群血流动力学模式与缺血性卒中发病风险的关联,为早期评估缺血性卒中的发病提供依据。方法:以多阶段随机抽样的方法抽取吉林省长春市3个街道/乡镇≥40岁638名居民作为研究对象,经颅多普勒(TCD)联合直立倾斜试验(HUTT)评估OI人群血流动力学模式,建立OI研究队列;按血流动力学改变模式将患者分为直立位低血压(OH)组、直立位高血压(OHT)组、体位性心动过速综合征(POTS)组和直立性脑低灌注综合征(OCHOs)组;对入选的研究对象每半年随访1次,随访2年;以首次缺血性卒中发病为观察终点,收集研究对象基线资料和随访期间缺血性卒中发病情况,采用Cox比例风险模型分析与缺血性卒中发病风险关联的因素。结果:121例研究对象符合OI诊断标准,其中OH组80例(66.12%),OHT组35例(28.93%),POTS组5例(4.13%),OCHOs组1例(0.82%);随访期间,总体人群确诊新发缺血性脑卒中事件共43例;在控制相关混杂因素后,以非OI者为参照,OI全人群、OH和OHT患者发生缺血性卒中的风险分别增加1.527倍[风险比(HR)=2.527,95%CI:1.269~5.032,P<0.01]、2.268倍(HR=3.268,95%CI:1.603~6.663,P=0.001)和2.153倍(HR=3.153,95%CI:1.213~8.916,P=0.008)。结论:OI与缺血性卒中发病风险增加有关,其中OH组和OHT组患者发病风险增加尤为明显。

Influence of Tilted Angle on Effective Linear Energy Transfer in Single Event Effect Tests for Integrated Circuits at 130 nm Technology Node

A heavy-ion irradiation experiment is studied in digital storage cells with different design approaches in 130？nm CMOS bulk Si and silicon-on-insulator （SOI） technologies. The effectiveness of linear energy transfer （LET） with a tilted ion beam at the 130？nm technology node is obtained. Tests of tilted angles θ=0 ° , 30 ° and 60 ° with respect to the normal direction are performed under heavy-ion Kr with certain power whose LET is about 40？MeVcm 2 /mg at normal incidence. Error numbers in D flip-flop chains are used to determine their upset sensitivity at different incidence angles. It is indicated that the effective LETs for SOI and bulk Si are not exactly in inverse proportion to cosθ , furthermore the effective LET for SOI is more closely in inverse proportion to cosθ compared to bulk Si, which are also the well known behavior. It is interesting that, if we design the sample in the dual interlocked storage cell approach, the effective LET in bulk Si will look like inversely proportional to cosθ very well, which is also specifically explained.

Continuous assessment of cerebral autoregulation by TCD during tilt table testing

[SUMMARY] TTTT is a non-invasive and new investigative examination,and a most important method of clinical diagnosis for many diseases,specially for orthostatic syncope,autonomic failure,intracranial hypertension,neurodegenerative diseases,CVAs and so on.At the same time,TCD technique for non-invasive monitoring of CBFV has also provided a new tool for investigating CA.In clinical circumstance,we may carry on assessment of dynamic CA by TTTT,and this kind of method has been proved to be appropriate to examine patients and monitor.we can choose different tilt positions by tilt-table according to the different demands for clinical diagnosis or researches,and record the different appearances of various index signs,we can take advantage of the technique of transfer function analysis of power spectrum between spontaneous changes in CBF and other factors(such as arterial pressure) to do research on the specific mechanism of impaired CA.

基于经颅多普勒直立倾斜试验分析焦虑抑郁患者自主神经功能的特征

目的:基于经颅多普勒(TCD)直立倾斜试验分析焦虑抑郁患者自主神经功能的特征。方法:选择2021年3月至2023年2月就诊于本院的焦虑抑郁患者80例,作为病例组,另选同期于本院体检的健康者80例,作为对照组。两组均接受TCD、直立倾斜试验与动态心电图(DCG)检查,对比两组W波回调不全发生率、直立倾斜试验血流动力学、TCD脑血流、心率变异性(HRV),Pearson相关性分析直立倾斜试验血流动力学、TCD脑血流与HRV的相关性,绘制ROC曲线分析TCD联合直立倾斜试验预测焦虑抑郁发生的价值。结果:与对照组比较,病例组W波回调不全发生率显著升高,有统计学差异(11.25%VS 0.00%,χ2=5.378,P=0.020);病例组倾斜直立位HR高于对照组,DBP、SV低于对照组(t=6.532、7.944、6.152,P均=0.000);病例组从平卧位至倾斜直立位的DBP、HR、SV变化绝对值高于对照组(t=12.015、6.644、5.635,P均=0.000);病例组倾斜直立位的Vd、Vs、Vm低于对照组,RI、PI高于对照组(t=10.488、3.927、11.256、2.298、5.918,P=0.000、0.000、0.000、0.023、0.000);病例组从平卧位至倾斜直立位的Vd、Vs、Vm、RI、PI变化绝对值高于对照组(t=9.559、10.943、10.775、10.738、28.236,P均=0.000);病例组LF、HF、PNN50、RMSSD、SDNN低于对照组(t=10.992、12.098、12.376、6.078、7.758,P均=0.000);Pearson相关性分析,从平卧位至倾斜直立位的DBP、HR、SV、Vd、Vs、Vm、RI、PI变化绝对值均与LF、HF、PNN50、RMSSD、SDNN呈负相关(r<0,P<0.05);绘制ROC曲线发现,从平卧位至倾斜直立位的DBP、HR、SV、Vd、Vs、Vm、RI、PI变化绝对值及联合预测焦虑抑郁的AUC分别为0.603、0.728、0.802、0.805、0.756、0.710、0.783、0.739、0.949。结论:TCD联合直立倾斜试验可有效预测焦虑抑郁发生,且二者可反映患者自主神经功能特征。

基于不同数据源的数字孪生小流域底板模型精度检验

为解决小流域综合治理规划设计中基础地形数据获取困难等问题,基于合成孔径雷达卫星遥感影像、倾斜摄影影像、光探测测距影像等3种主流遥感数据源,分别建立栖龙湾小流域数字孪生底板模型,进而提取主沟道纵断面、2块梯田样地边界、10个林地样区的郁闭度,与人工解译和实测结果对比进行精度检验,结果表明:以光探测测距影像为数据源的提取精度最高,以倾斜摄影影像为数据源的提取精度次之,以孔径雷达卫星遥感影像为数据源的提取精度最低。鉴于3种数据源小流域底板模型各有优缺点,可根据实际工作需要进行多源数据融合,以改善数字孪生技术在小流域综合治理规划设计中的应用效果。在栖龙湾小流域内选择石坎梯田地块进行合成孔径雷达卫星遥感影像与倾斜摄影影像数据融合、选择科普展览馆进行倾斜摄影影像与光探测测距影像数据融合,均取得良好的效果。

直立倾斜试验操作医师累计工作量对血管迷走性晕厥诊断结果的影响性分析

目的:探讨直立倾斜试验操作医师累计工作量对诊断报告结果的影响。方法:回顾性连续纳入中国医学科学院阜外医院自2016年1月1日至2022年12月31日进行直立倾斜试验检查的操作医师和患者资料。根据从本院开展倾斜试验至研究结束这一阶段医师的累计工作量,将医师分为低累计工作量组(累计50~100例)、中等累计工作量组(累计101~350例)、高累计工作量组(累计1000~4000例;无医师累计工作量在351~999例),以及按医师的的性别、学历、职称分别进行分组,分析不同分组内和不同分组间医师倾斜试验报告诊断率的差异。结果:共纳入22名医师操作的6122例患者,22名医师个体之间的阳性、可疑阳性和阴性报告率差异均具有统计学意义(P均<0.001)。中等累计工作量组平均可疑阳性报告率显著高于低累计工作量组和高累计工作量组(3.21%vs.1.09%vs.1.62%,P=0.001),女性医师可疑阳性报告率高于男性医师(2.25%vs.1.07%,P=0.017),本科学历医师可疑阳性报告率高于研究生学历医师(2.46%vs.1.52%,P=0.013),初级职称医师可疑阳性报告率高于中级和高级职称医师(3.40%vs.1.75%vs.2.53%,P=0.024)。多因素Logistic回归分析显示,不论以阴性还是阳性作参照,中等累计工作量均是可疑阳性报告的影响因素(P均<0.05)。结论:不同操作医师个体之间的倾斜试验诊断报告率存在一定差异,中等累计工作量组操作医师更易出具可疑阳性诊断报告。

血管迷走性晕厥手术治疗的现状与展望

血管迷走性晕厥作为晕厥中最常见的一种形式,心脏抑制型晕厥患者经随机临床试验证实有效的药物疗法有限,可建议使用永久性起搏器治疗。本文梳理了起搏器治疗血管迷走性晕厥中曲折发展经历并总结了原因,根据指南整理了目前适用于起搏治疗的患者类型以及应用的局限性,心脏神经消融术可能成为血管迷走性晕厥患者的另一种选择,但尚需要大样本随机对照试验证实其安全性、有效性以及适用人群。

曲面电视机缓冲包装设计及仿真分析

目的曲面电视机因其独特的屏幕弯曲设计,在运输与装卸过程中更易受到冲击而破裂,进而失去其使用价值。为降低包装设计成本,提升保护性能,通过仿真技术设计并验证一种曲面电视机缓冲包装系统。方法基于缓冲包装理论及实际应用对一款曲面电视机进行缓冲包装设计,使用三维建模软件Solidworks绘制包装件模型,运用有限元分析软件ANSYS Workbench中的显示动力学分析模块,对包装件进行全面的跌落仿真分析(2个面跌落、2个棱跌落和1个角跌落)以及倾倒仿真分析。结果6个工况条件下,屏幕的最大加速度和各零部件应力、应变均在许用范围之内,电视机未发生破损。结论通过仿真分析验证,所设计的缓冲衬垫在保护曲面电视机方面发挥了显著的防护效果。然而,考虑到成本效益和安全性的平衡,包装结构仍需进一步地优化与改进。

摇头倾斜抑制试验和视频头脉冲试验鉴别前庭性偏头痛和梅尼埃病的应用研究

背景 摇头倾斜抑制试验(HSTST)与前庭小脑介导的中枢储存机制有关,视频头脉冲试验(vHIT)对外周前庭疾病的诊断起重要作用。目的 探索HSTST及vHIT在诊断前庭性偏头痛(VM)和梅尼埃病(MD)中的临床应用价值。方法 选取2021年7月—2022年12月就诊于贵阳市第二人民医院神经内科以眩晕或头晕为主诉、诊断为VM及MD的患者。完成病史采集、床旁查体;有听力损害者完善纯音测听检查;所有患者进行前庭功能检查,包括摇头试验(HST)、HSTST、温度试验及vHIT,计算倾斜抑制指数(TSI)。比较HST阳性的VM及MD患者临床特征及检查结果,绘制TSI鉴别HST阳性的VM和MD患者的受试者工作特征(ROC)曲线。结果 研究共纳入VM患者50例,其中HST阳性22例(44.0%),包括水平眼震19例(86.4%),垂直眼震3例(13.6%);MD患者45例,其中HST阳性23例(51.1%),均为水平眼震。对HST阳性的VM及MD的患者分析显示:VM患者女∶男=4.5∶1,MD患者女∶男=1∶1.3,VM患者头痛家族史比例高于MD患者(P<0.05);VM患者伴随呕吐、耳鸣、耳闷感、听力下降症状的比例(31.8%、18.2%、13.6%、13.6%)低于MD患者(73.9%、100.0%、82.6%、100.0%),伴随头痛症状的比例(77.3%)高于MD患者(8.7%)(P<0.05);纯音测听结果显示MD患者听力下降比例高于VM患者(P<0.001);VM与MD患者vHIT结果比较,差异有统计学意义(P<0.05);VM与MD患者的TSI比较[(25.41±12.15)%与(78.71±13.76)%],差异有统计学意义(P<0.05),TSI鉴别HST阳性VM和MD的灵敏度为0.90,特异度为0.95,ROC曲线下面积为0.962(95%CI=0.91~1.00),最佳截断值为0.66。结论 VM主要是中枢机制,HSTST联合v HIT可以作为鉴别VM和MD的辅助检查工具。

航空发动机中介圆柱滚子轴承抗倾斜能力分析及优化设计

针对某航空发动机中介圆柱滚子轴承由于内、外圈倾斜而导致滚子与内圈滚道出现剥落的问题,提出采用内、外圈许用倾斜角评价圆柱滚子轴承的抗倾斜能力,基于该方法分析得到轴承许用倾斜角随着滚子凸度和内圈滚道有效宽度增大而增大,故提出将滚子凸度增大到原结构的3.2倍,内圈滚道有效宽度比原结构增加6%的改进措施,改进后的轴承许用倾斜角提升到优化前的4~9倍,仿真和试验结果表明优化后的轴承能够避免滚子与内圈滚道一端出现应力集中。

基于数字图像技术振动台试验结构位移信息捕捉技术研究

针对振动台试验模型箱位移、围岩错动以及隧道衬砌变形监测的需求,将YOLO-V2、改进Canny边缘检测、Hough变换及倾斜矫正技术相结合,提出了一种倾斜影像的自动矫正技术,实现了将倾斜影像修正为相机光轴垂直于测点运动平面的图像分析;提高了试验数据结果的处理精度,扩大了目标追踪算法在结构位移和变形监测的使用范围。同时通过核相关滤波技术完成对修正后的影像进行追踪,形成一套完整的地震动信号捕捉与监测系统。采用该系统进行了强震作用下穿越断层隧道韧性结构减震抗错性能试验研究,分别对模型箱位移、围岩错动和隧道衬砌变形进行信号识别与捕捉,同时对比分析了高精度拉线式位移计和位移传感器采集的数据,验证了系统的可靠性。结果表明:在监测点位设有标记物时,首先对采集结果进行倾斜矫正后追踪,通过监测结果与位移传感器进行对比,两者的2-范数小于0.005;而在无标记物时对结构表面特征物进行追踪,精度达到了97.5%;试验数据证明通过倾斜影像自动矫正技术来完成非对正对标记物时的影像进行追踪具有较高可靠性。

地震采集仪器倾斜测试(TILT)指标与建模温度关系分析

作为408UL/428XL地震数据采集系统日检测的一个重要组成部分,倾斜度测试是我们检测测线正常与否的系统性指标。文章重点从影响倾斜度测试中建模温度与测试结果的关系出发,提出了一套专门的地震采集仪器倾斜测试指标与检波器及环境的对应关系,并针对野外施工的实际情况提出了一整套关于仪器倾斜测试的现场作业指导方案。

Dependence of single event upsets sensitivity of low energy proton on test factors in 65 nm SRAM

In order to accurately predict the single event upsets （SEU） rate of on-orbit proton, the influence of the proton energy distribution, incident angle, supply voltage, and test pattern on the height, width, and position of SEU peak of low energy protons （LEP） in 65 nm static random access memory （SRAM） are quantitatively evaluated and analyzed based on LEP testing data and Monte Carlo simulation. The results show that different initial proton energies used to degrade the beam energy will bring about the difference in the energy distribution of average proton energy at the surface and sensitive region of the device under test （DUT）, which further leads to significant differences including the height of SEU peak and the threshold energy of SEU. Using the lowest initial proton energy is extremely important for SEU testing with low energy protons. The proton energy corresponding to the SEU peak shifts to higher average proton energies with the increase of the tilt angle, and the SEU peaks also increase significantly. The reduction of supply voltage lowers the critical charge of SEU, leading to the increase of LEP SEU cross section. For standard 6-transitor SRAM with bit-interleaving technology, SEU peak does not show clear dependence on three test patterns of logical checkerboard 55H, all＂ 1＂, and all ＂0＂. It should be noted that all the SEUs in 65 nm SRAM are single cell upset in LEP testing due to proton＇s low linear energy transfer （LET） value.

非对称风-浪荷载下海上风电筒型基础的累积倾角研究

随着筒型基础逐渐成为海上风电基础的常用形式,其在循环荷载作用下的倾角长期发展规律备受关注.基于模型试验与原型无量纲量等效的缩比尺原则,开展了不同工况风-浪荷载耦合作用下筒型基础模型试验,得到了筒型基础在循环荷载作用下的累积倾角发展规律.试验结果表明:影响筒型基础倾角累积速率的参数随着无量纲荷载幅值的增加而增加并与荷载的非对称性无关,部分双向非对称的风-浪耦合加载工况会导致筒型基础产生更为严重的累积倾角.当循环次数和循环荷载幅值一定时,累积倾角与表征荷载非对称性的无量纲参数呈近似线性关系.根据试验数据,建立了预测不同循环荷载条件下筒型基础累积倾角的经验公式.