Analogs of microgravity: the function of Schlemm's canal, intraocular pressure and autonomic nervous during the head-down tilt test in healthy subjects

AIM:To evaluate the ocular outcomes and to elucidate possible mechanisms underlying intraocular pressure(IOP)change following the head-down tilt(HDT)test.METHODS:The study included 21 participants at the Department of Ophthalmology of Tongji Hospital.Subjects received the test of I-care tonometry,enhanced depth imaging optical coherence tomography and heart rate variability(HRV)analysis before and after 15 min HDT test.The lumen area of Schlemm’s canal(SCAR),IOP,HRV were calculated.RESULTS:IOP increased significantly after 20°head down position from 14.0±3.0 to 17.0±3.3 mm Hg(P<0.001).SCAR decreased from 13449.0±5454.9μm^(2) at sitting condition to 9576.6±4130.9μm^(2) post 15 min HDT test.High frequency(HF)indices increased significantly from 1462±865 Hz at baseline to 2128±824 Hz.Heart rate(HR)decreased significantly from 76±11.48 to 70±11.52 bpm after the HDT.The linear regression analysis showed that the difference of HF and SCAR significantly correlated with each other during the HDT(R^(2)=20%,P=0.04).CONCLUSION:These outcomes perform the first evidence of the activation of autonomic nervous system of HDT may cause the collapse of Schlemm’s canal lumen,which in turn leading to the increased IOP.

基于伪磁梯度张量混合方向tilt梯度的磁源定位方法及其应用:以内蒙古塔木素铀矿床为例

斜磁化磁源的准确定位是磁法勘探有效圈定场源分布及划分断裂构造的重要依据.但受磁化方向影响,总磁异常与地质体分布并无明显对应关系.为此,本文从总磁异常垂向积分出发,推导出了伪磁梯度张量,定义了伪磁梯度张量的混合方向tilt梯度及混合方向解析信号振幅,提出了基于伪磁梯度张量混合方向tilt梯度水平导数组合的场源定位方法.模型试验表明,相对于解析信号振幅、tilt梯度的总水平导数及方向tilt梯度的总水平导数模这3种受磁化方向影响较小的方法,本文提出的磁源定位方法能够更有效地反映出不同磁化方向的磁源位置,具有更强的识别能力和定位精度.在内蒙古塔木素铀矿床的航磁资料应用中,新方法较好地展示出了已知断裂带的展布及出露岩浆岩的分布,同时有效地提取了塔木素铀矿床上方的弱磁异常信息,处理结果为研究区圈定隐伏岩体、划分隐伏断裂及扩大铀矿找矿靶区提供了依据.

基于多CNN的分块镜piston和tip-tilt误差同步检测方法研究

绝大多数大型望远镜采用分块镜的设计方案,为了获得优质的成像效果,需要控制分块望远镜系统的piston和tip-tilt误差。神经网络误差检测方法相较于传统的检测方法具有一定优势,但存在仅检测单一类型误差的局限性。本文提出一种基于卷积神经网络的piston和tip-tilt误差同步检测方法,通过在出瞳面设置具有离散孔的光阑,引发分段镜反射的子波发生干涉-衍射现象,构建包含丰富piston和tip-tilt误差信息的数据集。通过粗测网络和精测网络级联,满足大范围和高精度同步检测的需求。结果表明,该方法实现了对输入光源相干长度内纳米级的piston误差检测,并对10μrad范围内的tip-tilt误差实现了亚微弧度检测;对40 dB的CCD噪声表现出良好的抗干扰性,对面形误差的允差为0.05λ0RMS(λ0=600 nm),同时对六子镜系统具有可扩展性。本文方法光路简单,操作便利,具有实际意义。

Tilt-up建筑波纹钢板屋盖平面内抗震设计方法研究

Tilt-up建筑体系是一种由钢筋混凝土墙板、屋盖、内部承重柱组成的“盒式”受力体系。屋盖作为重要的结构构件,不仅承受平面外荷载,还承受由地震作用产生的水平力。论文分析了屋盖平面内受力机理,介绍了美国ASCE 7规范、IBC规范中Tilt-up结构波纹钢板屋盖平面内抗震设计方法,对华盛顿地区某Tilt-up建筑波纹钢板屋盖进行了设计研究,为我国引入Tilt-up建筑体系提供参考。

Analytical solution for the effective elastic properties of rocks with the tilted penny-shaped cracks in the transversely isotropic background

Seismic prediction of cracks is of great significance in many disciplines,for which the rock physics model is indispensable.However,up to now,multitudinous analytical models focus primarily on the cracked rock with the isotropic background,while the explicit model for the cracked rock with the anisotropic background is rarely investigated in spite of such case being often encountered in the earth.Hence,we first studied dependences of the crack opening displacement tensors on the crack dip angle in the coordinate systems formed by symmetry planes of the crack and the background anisotropy,respectively,by forty groups of numerical experiments.Based on the conclusion from the experiments,the analytical solution was derived for the effective elastic properties of the rock with the inclined penny-shaped cracks in the transversely isotropic background.Further,we comprehensively analyzed,according to the developed model,effects of the crack dip angle,background anisotropy,filling fluid and crack density on the effective elastic properties of the cracked rock.The analysis results indicate that the dip angle and background anisotropy can significantly either enhance or weaken the anisotropy degrees of the P-and SH-wave velocities,whereas they have relatively small effects on the SV-wave velocity anisotropy.Moreover,the filling fluid can increase the stiffness coefficients related to the compressional modulus by reducing crack compliance parameters,while its effects on shear coefficients depend on the crack dip angle.The increasing crack density reduces velocities of the dry rock,and decreasing rates of the velocities are affected by the crack dip angle.By comparing with exact numerical results and experimental data,it was demonstrated that the proposed model can achieve high-precision estimations of stiffness coefficients.Moreover,the assumption of the weakly anisotropic background results in the consistency between the proposed model and Hudson's published theory for the orthorhombic rock.

Research on Transmission Line Tower Tilting and Foundation State Monitoring Technology Based onMulti-Sensor Cooperative Detection and Correction

The transmission line tower will be affected by bad weather and artificial subsidence caused by the foundation and other factors in the power transmission.The tower’s tilt and severe deformation will cause the building to collapse.Many small changes caused the tower’s collapse,but the early staff often could not intuitively notice the changes in the tower’s state.In the current tower online monitoring system,terminal equipment often needs to replace batteries frequently due to premature exhaustion of power.According to the need for real-time measurement of power line tower,this research designed a real-time monitoring device monitoring the transmission tower attitude tilting and foundation state based on the inertial sensor,the acceleration of 3 axis inertial sensor and angular velocity raw data to pole average filtering pre-processing,and then through the complementary filtering algorithm for comprehensive calculation of tilt angle,the system meets the demand for inclined online monitoring of power line poles and towers regarding measurement accuracy,with low cost and power consumption.The optimization multi-sensor cooperative detection and correction measured tilt angle result relative accuracy can reach 1.03%,which has specific promotion and application value since the system has the advantages of unattended and efficient calculation.

Analysis and Research on Aerodynamic Characteristics of Quad Tilt Rotor Aircraft

For the quad tilt rotor aircraft, a computational fluid dynamics method based on multiple reference frames (MRF) was used to analyze the influence of aerodynamic layout parameters on the aerodynamic characteristics of the quad tilt rotor aircraft. Firstly, a numerical simulation method for the interference flow field of the quad tilt rotor aircraft is established. Based on this method, the aerodynamic characteristics of isolated rotors, rotor combinations at different lateral positions on the wing, and rotor rotation directions under different inflow velocities were calculated and analyzed, in order to grasp their aerodynamic interference laws and provide reference for the design and control theory research of such aircraft.

Tilt Angle Optimality Criteria for Stand Alone PV Systems

The conventional approach to optimizing tilt angles for fixed solar panels aims to maximize energy generation over the entire year. However, in the context of a supply controlled electric grid, where solar energy availability varies, this criterion may not be optimal. This study explores two alternative optimization criteria focused on maximizing baseload supply potential and minimizing required storage capacity to address seasonality in energy generation. The optimal tilt angles determined for these criteria differed significantly from the standard approach. This research highlights additional factors crucial for designing solar power systems beyond gross energy generation, essential for the global transition towards a fully renewable energy-based electric grid in the future.

Effects of Head-down Tilt on Nerve Conduction in Rhesus Monkeys

Background： Few studies have focused on peripheral nerve conduction during exposure to microgravity. The -6° head-down tilt （HDT） comprises an experimental model used to simulate the space flight environment. This study investigated nerve conduction characteristics of rhesus monkeys before and alter prolonged exposure to H DT. Methods： Six rhesus monkeys （3-4 years old） were tilted backward 6° from the horizontal. Nerve conduction studies （NCSs） were performed on the median, ulnar, tibial, and fibular motor nerves. Analysis of variance with a randomized block design was conducted to compare the differences in the NCS belbre and 7, 2 l, and 42 days alter the 6° HDT. Results： The proximal amplitude of the CMAP of the median nerve was significantly decreased at 21 and 42 days of HDT compared with the amplitude before HDT （4.38 ± 2.83 vs. 8.40 ±2.66 mV, F = 4.85, P = 0.013 and 3.30± 2.70 vs. 8.40± 2.66 mV, F = 5.93, P = 0.004, respectively）. The distal amplitude of the CMAP of the median nerve was significantly decreased at 7, 21, and 42 days of HDT compared with the amplitude before HDT （7.28 ± 1.27 vs. 10.25 ± 3.40 mV, F= 4.03, P = 0.039; 5.05 ± 2.01 vs. 10.25 ± 3.40 mV, F = 6.25, P = 0.04; and 3.95 ± 2.79 vs. 10.25 ± 3.40 mV, F = 7.35, F=- 0.01; respectively）. The proximal amplitude of the CMAP of the tibial nerve was significantly decreased at 42 days of HDT compared with the amplitude betbre HDT （6.14± 1.94 vs. 11.87± 3.19 mV, F = 5.02, P = 0.039）. Conclusions： This study demonstrates that the compound muscle action potential amplitudes of nerves are decreased under simulated microgravity in rhesus monkeys. Moreover, rhesus monkeys exposed to HDT might be served as an experimental model for the study of NCS under microgravity.

In-fiber photoelectric device based on graphene-coated tilted fiber grating

Graphene and related two-dimensional materials have attracted great research interests due to prominently optical and electrical properties and flexibility in integration with versatile photonic structures.Here,we report an in-fiber photoelec-tric device by wrapping a few-layer graphene and bonding a pair of electrodes onto a tilted fiber Bragg grating(TFBG)for photoelectric and electric-induced thermo-optic conversions.The transmitted spectrum from this device consists of a dense comb of narrowband resonances that provides an observable window to sense the photocurrent and the electrical injection in the graphene layer.The device has a wavelength-sensitive photoresponse with responsivity up to 11.4 A/W,allowing the spectrum analysis by real-time monitoring of photocurrent evolution.Based on the thermal-optic effect of electrical injection,the graphene layer is energized to produce a global red-shift of the transmission spectrum of the TF-BG,with a high sensitivity approaching 2.167×10^(4)nm/A^(2).The in-fiber photoelectric device,therefore as a powerful tool,could be widely available as off-the-shelf product for photodetection,spectrometer and current sensor.

Tilt-up建筑体系楼盖抗震性能数值模拟研究

对一栋单层Tilt-up厂房进行罕遇地震的弹塑性时程分析,结论如下:(1)在三条地震波作用于结构时,剪力墙作为结构的主要抗侧力构件承担着大部分剪力,符合设计理念;(2)结构的顶点最大位移和层间位移角均小于规范限值,满足要求。

基于倾角反演的隧道断面变形全方位监测方法

倾角传感器具有体积小、使用方便、测量连续等优点,在隧道变形监测领域有着巨大应用潜力,然而,现有基于倾角传感器的监测方法往往只能得到特定监测点的变形,在测量隧道断面整体变形方面还存在明显不足。为此,提出一种新的基于监测点倾角的隧道断面变形全方位监测方法。基于隧道断面曲线的形状特征,构造隧道分段变形插值函数,根据极坐标下隧道倾角与极径的关系,采用分段解析方法提出隧道倾角-变形数学模型,进一步通过协同变形假定,修正隧道测点极角,得到隧道倾角-变形算法;接着,建立隧道三维数值模型,通过均布荷载、对称非均布荷载和非对称荷载3种典型工况,采用误差分析方法分别研究算法的适用性;最后,通过室内试验进一步验证算法在实际应用中的准确性。研究结果表明:对于铁路隧道典型三心圆断面,推导的倾角-变形算法在均布荷载、对称非均布荷载和非对称荷载这3种典型工况下均具有良好的适应性,变形最大绝对误差均小于1 mm,平均相对误差均小于7%;在室内模型试验中,拱顶沉降监测误差小于8%,水平收敛监测误差小于5%,证明了监测方法的准确性。

掏土孔应力扰动法下的塑性区范围研究

针对普通浅层掏土法下倾斜建筑回倾速度慢、沉降不均匀的问题,提出掏土孔应力扰动法。在岩石力学的弹性圈和塑性圈应力解中引入修正系数,得到掏土孔应力扰动法下的塑性区半径计算公式。在进行现场掏土孔周应力扰动试验时,采用地锚反压的形式模拟上部建筑荷载,利用长钉在掏土孔周围进行深度为50 mm的螺旋扰动,通过测量应力扰动前后的孔周土体应力并结合有限元模拟结果,得到实际塑性区范围,验证了塑性区半径公式的正确性。结果表明:当掏土孔半径为100 mm,应力扰动范围为孔径的1/2时,塑性区范围扩大30%~40%,掏土孔应力扰动法对于扩大塑性区范围、加快建筑纠倾速度具有工程应用价值。

不同前倾角度倾转旋翼噪声数值计算分析

基于自由尾迹结合FW-H(Ffowcs Williams-Hawkings)方程的方法建立了倾转旋翼气动噪声计算模型,并采用倾转旋翼模型噪声试验数据验证了计算分析方法的有效性。选取典型过渡路径,进行考虑配平的倾转双旋翼气动噪声特性计算,获得了旋翼桨叶剖面非定常气动载荷以及不同测点气动噪声等计算结果,分析了倾转旋翼在不同前倾角下噪声指向性和噪声声压级的变化。结果表明:由于双旋翼噪声在传播中的叠加和抵消,倾转双旋翼和孤立单旋翼的噪声指向特性存在较大的不同;倾转旋翼噪声随前倾角增加总体上呈现先增加后减小的变化趋势,在前倾角30°附近噪声最强;不同前倾角下噪声声压级和指向性的变化与旋翼桨尖马赫数、气动载荷和桨盘角度等多种因素相关。

倾斜隧道双火源双竖井对自然通风隧道火灾烟气流动特征的影响

为研究城市倾斜隧道发生火灾后的烟气流动特征,通过FDS数值模拟仿真软件模拟了自然通风状态下不同坡度与垂直多竖井耦合作用时的温度分布及烟气运动,分析了由隧道及竖井温度场表现的烟气层吸穿现象、竖井上部开口处烟气速率及质量流率变化。结果表明,水平隧道中,隧道下游处竖井发生烟气层吸穿现象,隧道坡度增大,烟气聚集于下游,隧道下游处竖井内烟气层吸穿现象的消失对竖井排烟效率起正向影响;坡度是自然通风状态下影响竖井排烟效率的主要因素;竖井内烟气流动特征主要由坡度决定,存在临界坡度使竖井内发生边界层分离现象且该现象不会随坡度增大而消失;固定长度段隧道中多竖井的存在一定程度上延缓了由坡度导致的排烟效率下降的过程。

对强震地形变监测预报方法的思考

简要回顾了中国地形变用于强震监测预报领域的发展过程及现状。对几次强震前得到的比较突出的地形变异常进行了分析,收集了大面积形变异常与强震中长期预测、地震前兆分布存在时间有序和空间配套,强震前发现巨幅形变异常,InSAR给出强震前地面垂向形变,强震前地倾斜异常,慢地震和预滑移等方面的研究成果。综合分析认为,强震前震中区附近存在与孕震体尺度相当的巨幅快速地面异常隆升。及时有效地捕捉强震前巨幅快速地面异常隆升的时间有序和空间配套的异常信息,可望针对人口稠密区域未来发生的强震给出具有减灾实效的预测预报意见,值得尝试。基于本研究提出了针对人口稠密的地震重点监视防御区开展高密度、大量程、低精度地倾斜观测的设想,并初步给出了观测方案、基本原理和数据计算处理方法。

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。

桥墩倾斜方向对自浮式防撞装置防护效果影响研究

随着航道上大跨度桥梁的建设愈加广泛,其桥墩在水面附近往往具有一定的倾斜角度。为研究桥墩倾斜方向对自浮式防撞装置防护效果的影响,文章基于装备自浮式防撞装置的2种倾斜方向的桥墩与6000DWT级散货船为研究对象进行非线性有限元仿真碰撞计算,分析桥墩倾斜方向对不同航速船舶撞击下桥墩撞击力、系统能量转换、船艏结构破坏的影响。结果表明:外倾式桥墩受到撞击力更小,其防撞装置通过变形吸收能量更多、防护效果更好。研究成果可为大跨度桥墩设计与防撞装置的开发提供重要的参考价值。

直线型倾转多旋翼植保无人机建模与控制

针对直线型倾转多旋翼植保无人机模型耦合复杂、作业时易受施药执行器干扰等问题,提出了一种模型补偿-线性自抗扰控制算法。首先建立无人机运动学和动力学模型,并分析作业时离心喷头产生的力矩作用影响;然后将作业模型中的固定部分作为已知扰动,引入模型补偿-扩张状态观测器估计内外未知总扰动并动态补偿控制系统,完成位姿控制器设计。仿真结果表明,所提出的算法在作业场景下偏航角度误差小于0.2°,恢复时间小于0.55 s,相比于PID算法和线性自抗扰算法最大角度偏差分别降低3.4°和0.9°,恢复时间减少3.1和0.99 s,具有较强的鲁棒性。飞行实验表明,该无人机可以很好地跟踪植保作业轨迹,最大位置稳态误差小于15 cm,满足植保作业需求。

基于IESPSO的舵机倾转矢量动力系统建模与参数辨识

针对在旋翼动态时产生的外力矩影响下,倾转矢量动力系统中的舵机系统模型辨识精度低、实际响应难以估计的问题,本文将舵机外力矩作为扰动噪声纳入辨识环节,构建系统模型,并提出了一种基于改进生态系统粒子群优化(IESPSO)的倾转旋翼舵机系统参数辨识方法。为确保试验稳定安全进行,本文设计了倾转矢量动力系统辨识平台,进行参数辨识试验。试验结果表明,在旋翼动态时产生的外力矩噪声影响下,IESPSO相对于粒子群优化法、生态系统粒子群优化法与递推最小二乘法,均方根误差降低了1.46%,1.79%与56.37%,辨识精度有明显提升,并具备更快的寻优收敛速度。在修改搜索空间后,IESPSO仍具有较高的寻优精度,避免了在宽搜索空间下无法快速搜索至较优可行解的问题。