An improved positioning model of deep-seafloor datum point at large incidence angle

The inhomogeneous sound speed in seawater causes refraction of sound waves,and the elimination of the refraction effect is essential to the accuracy of underwater acoustic positioning.The raytracing method is an indispensable tool for effectively handling problems.However,this method has a conflict between localization accuracy and computational quantity.The equivalent sound speed profile(ESSP)method uses a simple sound speed profile(SSP)instead of the actual complex SSP,which can improve positioning precision but with residual error.The residual error is especially non-negligible in deep water and at large beam incidence angles.By analyzing the residual error of the ESSP method through a simulation,an empirical formula of error is presented.The data collected in the sailing circle mode(large incidence angle)of the South China Sea are used for verification.The experiments show that compared to the ESSP method,the improved algorithm has higher positioning precision and is more efficient than the ray-tracing method.

Method to determine installing angle of conical point attack pick

In order to obtain the determining method of the installing angle and decrease the performance indices (cutting force and wearing rate) of the pick, the relationships among the installing angles (impact angle, inclination angle and the skew angle) were studied, and the static model of installing angles of the pick was built. The relationships among the impact angle, the tip angle of pick and the kinematics parameters of the pick were built, too. Moreover, the mechanic models of the maximum clearance angle and the wearing angle of the pick were set up. To research the relationships of the installing angles and the change law of the wearing angle along with the kinematics parameters, the simulation was done. In order to verify the correctness of the models, the cutting experiments were done by employing two picks with different pick tip angles. The results indicate that, the cutting force is the smallest when the direction of the resultant force of pick follows its axis, and the relationship derived among the installing angles should be satisfied. In addition, to decrease the cutting force and the wearing of the pick, the tip angle of pick should not be larger than the half of the difference between the minimum wearing angle and the impact angle of the pick, and the clearance angle must not be less than zero.

The point of no return and pectoral angle of Japanese anchovy(Engraulis japonicus) larvae during growth and starvation

At a temperature of 23.0 - 24.8℃, the mixed feeding of Japanese anchovy larvae was initiated 24 h before the yolk-sac was exhausted. The point of no return （PNR） was reached on the 6th day after hatching. On the 4th day after hatching, the pectoral angle appeared in both fed and unfed anchovy larvae although it was more evident and sharper in the starved and the PNR stage larvae than in the fed ones. According to observations of larvae collected in the sea, the pectoral angles were evident not only in the larvae of 3.62 - 7.44 mm in standard length, but also in the larvae of 2.70 mm in standard length with remnants of yolk. The pectoral angles became diffuse when the larvae reached 7.84 mm and vanished at 9.86 mm. The pectoral angle cannot be used as a criterion to distinguish healthy from starving larvae.

Effect of fiber angle on LYP steel shear walls behavior

Steel shear wall(SSW) was properly determined using numerical and experimental approaches.The properties of SSW and LYP(low yield point) steel shear wall(LSSW) were measured.It is revealed that LSSW exhibits higher properties compared to SSW in both elastic and inelastic zones.It is also concluded that the addition of CFRP(carbon fiber reinforced polymers) enhances the seismic parameters of LSSW(stiffness,energy absorption,shear capacity,over strength values).Also,stress values applied to boundary frames are lower due to post buckling forces.The effect of fiber angle was also studied and presented as a mathematical equation.

Numerical simulation on influence of jet angle on jet's characteristics in flowing ambient fluid

Based on the stress-algebraic model, the turbulent buoyant jet with variable density was studied by the relation between density and concentration. A simple expression for buoyancy coefficient was proposed. The governing equations of turbulent buoyant jet with variable density were closed by introducing the expression of β and the relation between density and concentration. Numerical results for the jet axis with density difference agree well with experimental ones. By finite volume method, the 2 - D vertical jet＇s flow field with different jet angles was studied. The analysis of the relation among the vortex center, the position of separation point and jet angles shows that the circumfluenee field is the largest when the jet angle is 90°. The area turbulent kinetic energy ka is proposed and the relationship between mixing intensity and jet angles is analyzed based on it. Results show that the jet angle of is the optimum condition for jet water mixing with environment water;and the reduced rate of difference between the centerline density of jet and the density of ambient water is the largest at the jet angle of 90°.

Strength and failure characteristics of marble spheres subjected to paired point loads

Failure of irregular rock samples may provide implications in the rapid estimation of rock strength,which is imperative in rock engineering practice.In this work,analytical,experimental and numerical investigations were carried out to study the mechanical properties and failure characteristics of rock spheres under paired point loads.Analytical solutions indicted that with the increase in sample size(contact angle)and decrease in Poisson’s ratio,the uneven tensile stress in theta direction decreased.Then laboratory experiments were carried out to investigate the load characteristics and failure mode of spherical marble samples with different sizes subjected to a pair of diametral point loads.The discrete element method(DEM)was adopted to study the failure process of rock spheres.The effect of the sphere diameter on the point load contact angle was examined in terms of peak load,crushed zone distribution and energy dissipation.Experimental and numerical results showed that the samples primarily fail in tension,with crushed zones formed at both loading points.With increase in the sample size,the contact angle,crushed area and total work increase.As the specimen diameter increases from 30 mm to 50 mm,the peak load on the specimen increases from 3.6 kN to 8.8 kN,and the percentage of crushed zone(ratio of crushing zone to sample radius,d/r)increased from 0.191 to 0.262.The results of the study have implications for understanding the failure of irregular rock specimens under point loading conditions and their size effects.

基于转向架航向角的既有铁路平面线形识别方法研究

轨道平面线形识别是解算轨道不平顺的基础。针对外挂式动态轨道检查仪的实际需要,提出一种基于转向架航向角的铁路平面线形识别方法。首先,通过分段试拟合判定准则自动识别各测点所属线元类型和特征点数量;然后,建立基于转向架航向角的平面线形特征点优化模型;最后,结合云模型改进传统遗传算法的搜索策略提出云遗传算法,实现铁路平面线形精确识别。研究表明,平面线路曲线特征点识别偏差在4 m以内,线形识别准确度均达到97%以上,满足外挂式动态轨道检查仪对轨道不平顺解算的精度要求。

机载LiDAR系统安置角自适应迭代修正算法探讨

安置角参数在机载激光雷达作业中对后期点云数据精度质量有着极大的影响,使其真实地物点位置发生改变,相邻航带点云出现分层,而传统布设地面控制点的标定模式效率低、成本高、要求高、可操作性差,为规避上述诸多弊端,给出一种安置角自适应的标定模型,通过相邻重叠航带内部大量同名特征点的空间位置匹配、安置角参数的迭代运算,利用最小二乘配置方法求解机载激光雷达扫描系统的三个安置角参数,并借助C语言实现算法程序,在测试案例中得到了验证,提升了安置角标定效率,提高了机载激光雷达技术在复杂地形中点云的处理质量、适用性与可操作性。

耳穴压豆联合疏肝中药疗法对肝郁型原发性开角型青光眼患者眼压、视野缺损及眼部血流的影响

目的:观察耳穴压豆联合疏肝中药疗法对肝郁型原发性开角型青光眼(POAG)患者眼压、视野缺损及眼部血流的影响。方法:选取2020年2月~2023年5月本院收治的110例肝郁型POAG患者,简单随机法分为两组。基础组55例(110眼)给予西医基础治疗,中医疗法组55例(110眼)在基础组基础上给予耳穴压豆联合疏肝中药疗法治疗。比较两组昼夜眼压、视野平均缺损、跨筛板压力差(TCLPD)、视野指数(VFI)、视盘光学相干断层扫描(OCT)指标[盘沿面积、垂直C/D比率、视杯体积、视网膜纤维层厚度(RNFLT)]、眼部血流、中医证候评分差异。结果:比较昼夜眼压、视野平均缺损、视盘OCT指标、TCLPD、VFI治疗前水平,无差异(P>0.05);两组治疗后视野平均缺损、TCLPD及7点、14点、21点的眼压均较治疗前降低,中医疗法组昼夜眼压、视野平均缺损、TCLPD更低(P<0.05)。两组治疗后VFI、RNFLT升高,中医疗法组治疗后VFI、RNFLT更高(P<0.05);两组盘沿面积、垂直C/D比率、视杯体积治疗前后比较及两组治疗后比较,均无差异(P>0.05)。比较眼部血流治疗前水平,无差异(P>0.05);两组治疗后视网膜中央动脉和睫状后动脉的舒张末期血流速度(EDV)、收缩期峰值血流速度(PSA)较治疗前升高,中医疗法组更高(P<0.05)。两组治疗后视网膜中央动脉和睫状后动脉的阻力指数(RI)降低,中医疗法组治疗后更低(P<0.05)。比较中医证候评分治疗前水平,无差异(P>0.05);两组治疗后视物昏朦、目珠微张、瞳神稍大、情志不舒、胸胁胀痛、口干口苦、耳鸣、便秘评分降低,中医疗法组治疗后更低(P<0.05)。结论:耳穴压豆联合疏肝中药疗法治疗肝郁型POAG可减轻症状,降低昼夜眼压,改善眼部血流循环,提高视野。

玄武岩纤维增强复合材料拉挤圆管抗弯性能研究

为使玄武岩纤维增强复合材料(Basalt Fiber Reinforced Polymer,BFRP)拉挤圆管在桥梁工程中得到更广泛地应用,对其抗弯性能进行试验及有限元分析。对2根长度为750 mm的BFRP拉挤圆管进行三点抗弯试验;采用LS-DYNA有限元软件对试验过程进行模拟,验证有限元模拟的正确性;在保持BFRP拉挤圆管总厚度不变的条件下,研究内、外层双向纤维布的铺设厚度和角度对抗弯性能的影响。结果表明:试件从加载至破坏分为线弹性阶段、下降阶段和残余阶段,试件破坏后残余强度较大且卸载后迅速回弹恢复几何形状;有限元模拟试件的荷载~滑移曲线、失效现象和试验结果吻合较好,有限元模拟正确;布置适量厚度的内、外层双向纤维布可以提高试件的抗弯承载力;将内、外层双向纤维布铺设方向由90°变为45°后,抗弯承载力进一步提高,随着外层45°纤维布厚度增加,破坏时的挠度下降。建议制作BFRP拉挤圆管时,布置适量厚度的双向纤维布,角度以45°为宜。

基于投影光瞳分布的星地激光通信波前探测

为了解决星地自由空间光学通信系统中的提前角问题,采用了一种基于光强传输的新型波前探测技术——投影光瞳面分布(Projected Pupil Plane Pattern,PPPP),并通过实验室实验验证了该技术的可行性。PPPP基于TIE光强传输公式,根据不同传输距离下光强分布的变化反解出大气湍流引起的波前畸变。由于PPPP采用的是上行通信激光本身的后向瑞利散射,其测量的大气湍流方向与通信卫星方向一致,因此可以有效解决星地激光通信中的提前角问题。实验模拟了1 m口径的地基望远镜作为上行激光发射装置和后向散射光斑成像设备,通过等效高度分别为10 km和17 km的上行激光后向散射光斑图像来实现对10 km以下大气湍流的波前探测。实验采用的波前畸变模拟装置包括空间光调制器和透明塑料片,实验结果表明,对不同的波前畸变PPPP和通用的夏克-哈特曼波前探测器可以实现相似的波前重构,两者重构相位的残差约为初始相位的30%。

Modified algorithm of combined GPS/GLONASS precise point positioning for applications in open-pit mines

A modified algorithm of combined GPS/GLONASS precise point positioning （GG-PPP） was developed by decreasing the number of unknowns to be estimated so that accurate position solutions can be achieved in the case of less number of visible satellites. The system time difference between GPS and GLONASS （STDGG） and zenith tropospheric delay （ZTD） values were firstly estimated in an open sky condition using the traditional GG-PPP algorithm. Then, they were used as a priori known values in the modified algorithm instead of estimating them as unknowns. The proposed algorithm was tested using observations collected at BJFS station in a simulated open-pit mine environment. The results show that the position filter converges much faster to a stable value in all three coordinate components using the modified algorithm than using the traditional algorithm. The modified algorithm achieves higher positioning accuracy as well. The accuracy improvement in the horizontal direction and vertical direction reaches 69% and 95% at a satellite elevation mask angle of 50°, respectively.

基于激光扫描点云的脚手架杆件角度获取

脚手架变形监测是脚手架安全的基础,施工现场一般采用传感器或全站仪进行点式监测,监测效率和准确性均较低。因此,提出一种基于点云的脚手架杆件角度获取方法。首先采用激光扫描仪对搭设好的脚手架进行扫描,对收集到的脚手架点云数据进行预处理后,基于RANSAC算法拟合脚手架杆件圆柱体,提取不同杆件圆柱体方程与轴线方向向量,计算方向向量间的角度。为验证所提方法的有效性,将脚手架点云模型分别围绕某一轴或某一点旋转不同的理论角度,得到新点云模型,然后采用上述方法计算其与原模型间的角度,与理论角度进行比较。结果显示,计算角度与理论角度间的最大相对误差为125%,平均相对误差为075%,验证了该方法的可靠性,为脚手架变形监测提供新的思路。

踝关节骨折术后踝穴冠状位角度波动与关节功能恢复的关系

背景:踝关节骨折术后的踝穴形态指标会出现相应变化,而其中踝穴冠状位角度变化与踝关节的功能恢复之间存在一定的关联,既往研究大多探讨患者术后踝穴高度恢复,故研究踝关节骨折术后踝穴冠状位角度的波动与关节功能恢复的相关性具有一定参考意义。目的:探讨踝关节骨折术后踝穴冠状位角度变化对关节功能恢复的影响。方法:纳入进行手术治疗的86例踝关节骨折患者为研究对象,根据末次随访美国骨科足踝外科协会踝-后足评分结果分为优良组(n=45)和可差组(n=41),比较两组患者的一般资料。根据踝关节的踝穴位及侧位X射线片对比术后患者患侧和健侧的踝穴形态指标:包括踝穴宽度和深度、冠状位角度及矢状位角度,以及上述指标患侧和健侧之间的差值,并进一步进行组内比较分析。构建联合模型,利用Cox回归分析评估冠状位角度波动与关节功能恢复情况的关系。利用最小绝对收缩选择算子回归法和多因素Logistic回归分析影响患者关节功能恢复的危险因素。按踝穴冠状位角度从低到高等分为5分位数组(Q1-Q5),比较5组患者的临床资料特征,并采用多因素Logistic回归分析踝穴冠状位角度变化与关节功能恢复不良风险的相关性,建立限制性立方样条Logistic回归模型分析其剂量-反应关系。建立回归方程y=1-1/(1+e^(-z))预测模型并进行验证。结果与结论:①患者患侧的踝穴宽度和深度、冠状位角度及矢状位角度均显著大于健侧(P均<0.05);且与优良组患者相比,可差组患者踝穴宽度差值、深度差值、冠状位角度差值及矢状位角度差值均更大(P<0.05);②联合模型显示无论冠状位角度是否在正常范围内,冠状位角度每纵向增加1˚,关节功能恢复不良的风险增加3%;③最小绝对收缩选择算子回归和多因素Logistics回归分析显示,调整潜在混杂因素后发现年龄过大、早期功能锻炼缺乏、无跟骨牵引、内固定物未取出、术后并发症、踝冠状位角度增大均为影响患者关节功能恢复的独立危险因素(P<0.05);④术后3个月内的冠状位角度与关节功能恢复效果不良风险存在独立相关性(OR=1.57,95%CI:1.38-1.76,P=0.002),且术后各时间段冠状位角度从低到高5分位数组趋势性检验差异有统计学意义(P趋势<0.001);⑤限制性立方样条模型分析显示,男性或女性的踝穴冠状位角度变化与关节功能恢复效果不良风险均不存在非线性关系;经Bootstrap自抽样,预测模型区分度、准确度较好;⑥提示踝关节骨折术后踝穴冠状位角度减小对关节功能恢复起到明显的促进作用,因此在踝关节骨折术后重点检测踝穴冠状位角度有助于了解患者关节功能恢复情况。

结合井口对称点的竖井联系测量的应用

竖井联系测量中定向比较困难。为此,利用井口点对称性质,可减弱竖轴倾斜误差、投点误差和对中误差对水平角的影响,测定导线连接角,为隧道内导线建立起始或终止方向。对于两井定向,增加水平角校核条件,仍可采用无定向导线计算。结合某隧道扩建工程,验证该方法的有效性。该方法可结合其他定向方法,为一井定向导入较准确定向,对两井定向也有参考作用。

基于Adaptive Sigma-Point滤波的智能导弹对目标协同定位方法研究

在对智能导弹协同作战过程详细描述的基础上,提出了一种利用多枚智能导弹协同对目标定位的方法。考虑目标运动模型为静止模型和运动模型两种情况,将Sigma-Point滤波方法与过程噪声的自适应估计方法相结合,融合目标运动状态和目标到达角信息,克服了常规Sigma-Point滤波性能依赖于目标运动模型的先验统计信息的缺点。通过比较目标可能存在区域面积的大小,确定了参与协同定位的智能导弹数目和编队构型。仿真研究表明,多枚智能导弹协同对目标定位可以显著提高定位精度和速度。

深海无人航行器双向无线充电系统的涡流损耗分析与效率优化

无线电能传输(WPT)技术在深海无人航行器(AUUS)领域中应用逐渐广泛,相比于空气介质的无线充电而言,海水介质中无线充电产生的涡流损耗严重降低了能量传输效率。该文提出一种采用一次侧和二次侧移相策略的双边LCC水下WPT系统,降低海水介质中的涡流损耗,提高系统效率。通过研究两线圈电流相位差对海水介质的涡流损耗的影响,建立合成感生电场模型,计算合成感生电场的分布和涡流损耗。在其他条件不变时,增大两线圈电流的相位差,会使线圈间各点处的合成感生电场幅值下降,使涡流损耗在总损耗的占比中下降,提高能量传输效率。通过对比在空气介质和海水介质中的损耗与线圈间电流相位差之间的关系,可以得到海水介质中无线充电时的最大效率点的电流相位差。相比于空气介质而言,在海水介质中无线充电的最大效率点处,线圈间的电流相位差增大。在深海双向双边LCC无线充电系统中,仅需增大两侧逆变电压相位差,即可增大线圈间电流相位差,进而提高系统效率。实验中搭建了200 V/3.5 kW级水下无线充电样机,通过增大两侧逆变器之间相位差,实现了91.5%的最大效率传输,比不采用移相策略时的效率提升了0.8%,证实了理论分析结果的正确性与可行性。

深空激光通信终端主要参数的分析与研究

针对深空激光通信的应用环境和特性,分析了通信链路中的关键性能指标,考虑了距离光斑扩散衰减、指向控制精度衰减、大气衰减、太阳辐射、探测器暗电流噪声等因素后,确定了通信速率和通信误码率的具体计算方法。对通信链路进行建模,分析了各个参数的计算方法;通过公式推导分析了发射端望远镜口径(激光束散角)与指向控制精度对最大通信距离的影响,以数值仿真进行佐证并进一步分析了发射端望远镜口径(激光束散角)与指向控制精度的约束关系,提出了深空激光通信参数设计的方法。在此基础上进一步计算了现有激光通信能力在地月空间、地火空间场景下的激光链路性能。

移动式垃圾压缩装置翻转机构的多目标优化

翻转机构的铰点位置直接影响着移动式垃圾压缩装置的整体工作性能和翻转机构各铰点的工作寿命。为提高翻转机构整体工作性能和各铰点的工作寿命,首先,运用Adams软件建立虚拟样机模型并进行仿真,得到翻转机构各铰点的载荷;其次,应用静态应变试验仪对翻转机构进行测试,发现该虚拟样机模型符合实际情况,验证了模型的有效性;在此基础上,进一步分析仿真数据,确定以翻转机构的铰点A、C的最大载荷和最小传动角为优化目标,应用理想点法在Adams软件中构造出一个综合的评价函数,对其进行了优化求解。对比优化前后的数据,翻转机构的铰点A所受最大载荷减小了19.3%,铰点C所受的最大载荷减小了16.2%,最小传动角增大了32.1%。最后,确定了翻转机构各铰点位置的最优设计值,为移动式垃圾压缩装置翻转机构后续设计应用提供参考。

基于激光雷达扫描的观览车摆角测量方法

针对现有的倾角仪在测量大型观览车最大摆角时存在的安装复杂、测量效率低下问题,本文提出了一种结合特征滤波与投影转换的摆角测量方法。该方法综合使用激光雷达与监控相机的数据,实现对大型观览车摆角的非接触式精确测量。首先,通过方向特征滤波器选取摆臂部分的点云;接着,利用形状特征滤波器移除不规则形状的点云;然后,将这些点云投影至二维平面,并用最小二乘法拟合边缘直线来解算摆角。最后,通过等比例模型实验得到该方法角度测量平均误差绝对值为0.29°,最大误差绝对值为0.45°。实验结果表明,该方法能有效提升大型观览车摆角的测量效率并确保测量精度。