Analysis of the Impact of the Space Guide Vane Wrap Angle on the Performance of a Submersible Well Pump

In order to study the influence of the wrap angle relating to the space guide vane of a submersible well pump(250QJ125)on the flow field and pump performance,seven possible configurations have been considered(obtained by changing the blade wrap angle while keeping unchanged all the other parameters).Such configurations have been numerically simulated in the framework of a computational model based on the Reynolds time-averaged N-S equations,the RNG k-εturbulence approach and the SIMPLE algorithm.The impact exerted by different wrap angles of the guide vane on the performance of the pump,the internal losses of the guide vane and the flow field distribution in the bladeless area at the guide vane outlet has been assessed via cross-comparison of all these cases.The results show that the wrap angle has a significant influence:the wrap angle with the highest head is different from that with the highest efficiency,and changes in this angle have a more significant effect on the head than efficiency.A moderate raise of the wrap angle can improve the properties of the flow,reduce turbulence losses and enhance the energy conversion rate inside the guide vane.Different wrap angles can also lead to different fluid circulation modes in the bladeless area from guide vane outlet to impeller inlet,while they have a weak influence on the absolute value of the velocity of the fluid entering the impeller.

Half space object classification via incident angle based fusion of radar and infrared sensors

In this paper,we introduce an incident angle based fusion method for radar and infrared sensors to improve the recognition rate of complex targets under half space scenarios,e.g.,vehicles on the ground in this paper.For radar sensors,convolutional operation is introduced into the autoencoder,a“winner-take-all(WTA)”convolutional autoencoder(CAE)is used to improve the recognition rate of the radar high resolution range profile(HRRP).Moreover,different from the free space,the HRRP in half space is more complex.In order to get closer to the real situation,the half space HRRP is simulated as the dataset.The recognition rate has a growth more than 7%com-pared with the traditional CAE or denoised sparse autoencoder(DSAE).For infrared sensor,a convolutional neural network(CNN)is used for infrared image recognition.Finally,we com-bine the two results with the Dempster-Shafer(D-S)evidence theory,and the discounting operation is introduced in the fusion to improve the recognition rate.The recognition rate after fusion has a growth more than 7%compared with a single sensor.After the discounting operation,the accuracy rate has been improved by 1.5%,which validates the effectiveness of the proposed method.

Investigation of hypersonic flows through a cavity with sweepback angle in near space using the DSMC method

Near space has been paid more and more attentionin recent years due to its military application value.However,flow characteristics of some fundamental configurations(e.g.,the cavity)in near space have rarely been investigated due to rarefied gas effects,which make the numerical simulation methods based on continuous flow hypothesis lose validity.In this work,the direct simulation Monte Carlo(DSMC),one of the most successful particle simulation methods in treating rarefied gas dynamics,is employed to explore flow characteristics of a hypersonic cavity with sweepback angle in near space by considering a variety of cases,such as the cavity at a wide range of altitudes 20-60 km,the cavity at freestream Mach numbers of 6-20,and the cavity with a sweepback angle of 30°-90°.By analyzing the simulation results,flow characteristics are obtained and meanwhile some interesting phenomena are also found.The primary recirculation region,which occupies the most area of the cavity,causes pressure and temperature stratification due to rotational motion of fluid inside it,whereas the pressure and temperature in the secondary recirculation region,which is a small vortex and locates at the lower left corner of the cavity,change slightly due to low-speed movement of fluid inside it.With the increase of altitude,both the primary and secondary recirculation regions contract greatly and it causes them to separate.A notable finding is that rotation direction of the secondary recirculation region would be reversed at a higher altitude.The overall effect of increasing the Mach number is that the velocity,pressure,and temperature within the cavity increase uniformly.The maximum pressure nearby the trailing edge of the cavity decreases rapidly as the sweepback angle increases,whereas the influence of sweepback angle on velocity distribution and maximum temperature within the cavity is slight.

A BINARY INFINITESIMAL FORM OF TEICHMLLER METRIC AND ANGLES IN AN ASYMPTOTIC TEICHMLLER SPACE

The geometry of Teichmuller metric in an asymptotic Teichmuller space is studled in this article. First, a binary infinitesimal form of Teichmuller metric on AT（X） is proved. Then, the notion of angles between two geodesic curves in the asymptotic Teichmuller space AT（X） is introduced. The existence of such angles is proved and the explicit formula is obtained. As an application, a sufficient condition for non-uniqueness geodesics in AT（X） is obtained.

Angles of Norm ed Linear Spaces and Characterizations of Inner Product Spaces

In [1],a family of angles are defined in normed linear spaces. In this paper,it is shown that if anyone of the angles satisfies certain euclidean triangle congruence properties,the space must be an inner product space.

SCATTERING OF CIRCULAR CAVITY IN RIGHT-ANGLE PLANAR SPACE TO STEADY SH-WAVE

Complex function method and multi-polar coordinate transformation technology are used here to study scattering of circular cavity in right-angle planar space to SH-wave with out-of-plane loading on the horizontal straight boundary. At first, Green function of right-angle planar space which has no circular cavity is constructed; then the scattering solution which satisfies the free stress conditions of the two right-angle boundaries with the circular cavity existing in the space is formulated. Therefore, the total displacement field can be constructed using overlapping principle. An infinite algebraic equations of unknown coefficients existing in the scattering solution field can be gained using multi-polar coordinate and the free stress condition at the boundary of the circular cavity. It can be solved by using limit items in the infinite series which can give a high computation precision. An example is given to illustrate the variations of the tangential stress at the boundary of the circular cavity due to different dimensionless wave numbers, the location of the circular cavity, the loading center and the distributing range of the out-of-plane loading. The results show the efficiency and effectiveness of the mothod introduced here.

Angle measurement technology based on magnetization vector for narrow space applications

With the wide application of laser in the field of skin plastic surgery, micro laser galvanometer scanner has made great progress in this field with its portability. However, the measurement method used to measure the deflection angle of laser galvanometer in the narrow space of scanner with high precision remains to be studied. In this paper, an angle measurement method based on magnetic field is proposed, and the effect of the shapes of permanent magnets(PMs) on the measurement is studied by theoretical and experimental study under the condition that the maximum available space for the PMs is a 10 mm side cube. An angle measuring experimental device is set up, and the contrast experiment is carried out with different PMs which are the same as simulation. The experimental results show that cylindrical PM is more suitable than other PMs, which is consistent with the simulation results, and the maximum nonlinearity error is 0.562%. This method has the advantages of small volume,non-contact measurement, small moment of inertia, good dynamic response and no external excitation for the PMs, so it has a broad application prospect in micro laser galvanometer scanner.

An Angle Structure Descriptor for Image Retrieval

This paper presents an efficient image feature representation method, namely angle structure descriptor(ASD), which is built based on the angle structures of images. According to the diversity in directions, angle structures are defined in local blocks. Combining color information in HSV color space, we use angle structures to detect images. The internal correlations between neighboring pixels in angle structures are explored to form a feature vector. With angle structures as bridges, ASD extracts image features by integrating multiple information as a whole, such as color, texture, shape and spatial layout information. In addition, the proposed algorithm is efficient for image retrieval without any clustering implementation or model training. Experimental results demonstrate that ASD outperforms the other related algorithms.

Development of 3D top coal caving angle model for fully mechanized extra-thick coal seam mining

During high-intensity,fully mechanized mining of extra-thick coal seam,the top coal would cave to a certain 3D form.Based on the data collected during drilling,a 3D model of top coal caving surface space was established to determine the relationship between the location of the stope roof and the caving surface,enabling the mathematical computation of the top caving angle(φ).The drilling method was employed to measure the top caving angle on two extra-thick fully mechanized coal caving faces under the conditions of three geological structures,namely,no geological structure,igneous rock structure,and fault structure.The results show that the value of top caving angle could be accurately estimated on-site with the 9-parameter 3D top coal caving surface model built with the drilling method.This method is a novel on-site measurement that can be easily applied.Our findings reveal that the characteristics of the coal-rock in the two mining faces are different;yet their caving angles follow the ruleφ_(igneous rock structure)<φ_(no geological structure)<φ_(fault structure).Finally,through the data fitting with two indexes(the top coal uniaxial compressive strength and the top caving angle),it is found that the relationship between the two indexes satisfies an exponential decay function.

Comparison of measurements of anterior chamber angle via anterior segment optical coherence tomography and ultrasound biomicroscopy

BACKGROUND Glaucoma is an irreversible optic neuropathy with the loss of visual field and decrease of vision.The variable clinical manifestations may result in differential diagnostic difficulties.The early screening and diagnosis of glaucoma are currently experiencing a demand for anterior segment analysis tools that can gather more information with one short measurement.Therefore,we analyzed the agreement,difference,and correlation of chamber angle parameters such as angel opening distance at 500μm(AOD500)and trabeculo-iris space area at 500μm^2(TISA500)measured by anterior segment optical coherence tomography(ASOCT)and ultrasound biomicroscopy(UBM).AIM To compare the differences,correlation,and agreement in measuring AOD500 and TISA500 by AS-OCT and UBM.METHODS Both AS-OCT and UBM were performed to measure AOD500 and TISA500 in 45 subjects(72 eyes).All subjects without glaucoma were collected from October 2015 to August 2016 at the Ophthalmology Department of the Fourth Affiliated Hospital of China Medical University.Data of the two groups(AOD500 and TISA500)were compared by nonparametric tests.Pearson correlative analysis and Bland-Altman analysis were used to compare the correlation and agreement.RESULTS There were no significant differences between AS-OCT and UBM in measuring AOD500(P1=0.110,P2=0.633,P3=0.078,and P4=0.474)and TISA500(P1=0.584,P2=0.889,P3=0.297,and P4=0.550)of the four quadrants of the anterior chamber angle.There was a high correlation in measuring AOD500(r1=0.562,r2=0.671,r3=0.635,and r4=0.720;P<0.001)and TISA500(r1=0.584,r2=0.889,r3=0.297,and r4=0.550;P<0.001).There was a good agreement in measuring AOD500 and TISA500 by the two modalities.CONCLUSION There is a high correlation and agreement between AOD500 and TISA500 measurements by AS-OCT and UBM.They are interchangeable under some circumstances.AS-OCT proves to be a better early screening tool for glaucoma.

Moment-angle复形轨道构型空间的欧拉示性数

设I^m为m维标准方体,K'为单纯复形K的重心重分.将K'上的锥形按一定规则逐片线性嵌入I^m的典范单纯剖分中,从而得到K对应的一类方体复形cc(K).根据cc(K)的构造过程,计算了cc(K)的f-向量,即各个维数的胞腔个数.通过投射(D^d)m→J^m的拉回,可定义cc(K)上的moment-angle复形Z_(K.d).将Z_(K,d)放入轨道构型空间的框架中,得到轨道构型空间F_G(Z_(K,d,n)).由F_G(Z_(K,d,n))的组合结构和著名的Inclusion-exclsion原理,给出了轨道构型空间FG(Z_(K,d,n))的欧拉示性数利用f-向量表示的计算公式,并且提供了一种计算Z_(K,d)欧拉示性数的新方法.

View on the Clinical Value of QRS-T Angle

The QRS-T angle,as an index of noninvasive cardioelectric vector,is closely related to the change of heart structure and function.There are different methedologies to measure the QRS-T angle,which can be roughly dividedinto two types:plane angle and space angle.Studies show that the influence factors include two aspects of physiology and pathology of the angle,in pathological ways,the disease such as myocardial hypertrophy,myocardial ischemia,hypertension,ventricular arrhythmia has larger clinical significance.In recent years,the research on the risk stratification of the QRS-T angle on sudden death has made great progress,but there are still some disputes about whether the space angle can be replaced by the plane angle and the range of normal value and so on.

基于光学成像探测的仅测角高轨空间物体接近感知方法

提出一种仅利用任务航天器光学成像探测设备给出的测角信息进行高轨空间物体接近行为感知的方法。首先,分析了空间物体相对任务航天器的方位变化规律,得到物体接近时在任务航天器轨道坐标系下方位角正切值随时间波动幅值逐渐增大;其次,分析了在光学成像探测设备成像过程中,逆光与探测设备灵敏度对空间物体可见性的影响,得到物体可见弧段在每个轨道周期内具有一定的相似性;进一步地,根据物体相对方位及可见性的变化规律,设计了一种空间物体接近行为感知方法,利用物体观测量的轨道周期一致性进行多段观测量关联,拟合方位角正切值随时间波动趋势,预测波动极值并统计极值变化规律,实现物体接近行为感知;最后,仿真验证了该方法具备不依赖距离信息感知高轨空间物体相对任务航天器接近行为的能力,仅利用3个轨道周期内、每周期有效弧段大于30 min的高轨空间物体指向测量信息判断物体相对任务航天器存在接近行为的准确率优于96%。结果证明:该方法通过赋能任务航天器常用光学成像探测设备高效费比地实现航天器自我防护能力有效提升,可普遍用于高轨航天器任务。

弹间干扰对聚能射流成型及射孔穿深的影响规律

射孔是油气开采过程中的重要一环,射孔间距是影响射流成型效果和穿深的主要参数之一,相邻两射孔弹之间会产生弹间干扰,进而影响射流质量和穿深。为探究弹间距对弹间干扰的影响规律,利用LS-DYNA软件,结合ALE(Arbitrary Lagrange-Euler)算法进行算子分离,实现了单元边界的质量、内能和动量的穿透,并以某油田井下射孔为例,建立了射孔弹—射孔枪—套管—水泥环三维模型,分析了弹间干扰对射流成型和射孔穿深的影响规律。研究结果表明:①弹间干扰降低了射孔弹总能量转化为射流能量的效率:弹间距为5.0 mm时,临近射孔弹射流能量转化率减少0.31%,射流轴向速度减小39 m/s,径向速度增大20 m/s;弹间距为3.5 mm时,临近射孔弹射流能量转化率减少2.21%,射流轴向速度减小130 m/s,径向速度增大111 m/s。②弹间干扰减小了对穿深有效的轴向速度,增加了无效的径向速度,径向速度的增大影响射流质量,使得射流趋向发散,降低射孔穿深。③数值模拟结果揭示,随着相位角的减小,射流线之间的距离减小,弹间干扰加强,有效能量转化降低,射孔穿深降低。结论认为,该规律认识给出了弹间干扰对射流成型和射孔穿深的量化影响,可为合理优化射孔孔密和提高射孔弹穿深提供理论依据。

制氢厂房氢泄漏激光检测光路布置优化研究

氢气扩散能力强、燃烧速度快、可燃范围广的特点使其泄漏易发生爆炸事故。对比基于可调谐半导体激光吸收光谱技术的激光传感器布置方式,以降低对氢泄漏的检测时间,获得最佳光路布置间距和角度。利用数值模拟研究了氢气在制氢厂房内的泄漏逸散规律,通过光学仿真确定了激光传感器的最短布置距离,分析了相邻光路间距及光路投影角度两种因素对氢泄漏检测的影响,得到了检测时间短、经济成本相对较低的布置方式。结果表明:相邻光路间距为0.4 m、光路与地面夹角为45°时,检测氢气泄漏时间优于其他方式并且所需激光传感器数量最少。

一种联合TDCM和PFA的空间目标大转角ISAR成像方法

空间目标态势感知是当前航天技术领域的研究热点,逆合成孔径雷达(Inverse Synthetic Aperture Radar, ISAR)是空间目标感知的一种有效手段。为了得到利于目标鉴别的高分辨二维ISAR图像,需要通过增大积累转角来提高方位向分辨率。但是,随着转角的增大,平动与转动之间的耦合增大,使得传统的先平动补偿、后利用转动成像的两步式成像方法不再适用。本文提出了一种结合时域信号共轭相乘(Time Domain Conjugate Multiplication, TDCM)处理与极坐标格式算法(Polar Format Algorithm, PFA)的成像算法,首先利用雷达回波的二维相干性,通过TDCM处理进行平动粗补偿,然后借助PFA的插值操作校正大转角引起的散射点越分辨单元走动(Motion Through Resolution Cell, MTRC)并估计目标相对转动参数。通过迭代处理,持续对平动和转动参数进行优化,提升运动补偿效果。仿真验证了所提成像算法的有效性,与传统算法相比,成像聚焦性更好。

近红外空间碎片激光测距探测成功概率影响因素的研究

基于激光雷达方程和天空背景噪声估算公式推导出近红外空间碎片激光测距探测成功概率的计算公式,仿真研究了该公式中大气透过率和天空背景噪声的影响因素,经数据拟合,得到空间碎片激光测距探测成功概率的归一化表达式。在此基础上,仿真分析了太阳高度角、目标天顶角、目标轨道距离和目标横截面积对目标探测成功概率的影响。结果表明:目标探测成功概率随太阳高度角升高而减小,随目标轨道距离的增加而减小,随目标天顶角的增大而减小,当目标天顶角增加到70°时,目标探测成功概率开始急剧下降;目标轨道距离固定的情况下,目标探测成功概率随目标横截面积的增大而增大。该研究对提高空间碎片的观测效率具有一定的应用价值。

碳类粒子对固体推进剂束流发散角度影响的实验研究

以石墨烯和碳粉两种碳类粒子作为掺杂剂定向改性固体推进剂,借助高速摄影技术和自搭建的束流发散角度测量系统,对比并分析不同掺杂比例和工作条件对改性推进剂束流发散角度的影响,确定了掺杂粒子的最优掺杂比例和工作条件。结果表明,石墨烯和碳粉的最优掺杂比例均为7%,且石墨烯的束流发散角度更小,生成稳定等离子体流的响应时间更短。同时,石墨烯更适配于小激光能量供给下的工作条件,而碳粉更适配于大激光能量供给下的工作条件。

基于动态阈值的距离搜索初轨确定

提出一种改进的初轨确定算法,基于动态阈值的距离搜索方法,以改进传统算法在处理数据时初轨成功率和初轨误差。通过动态调整搜索阈值,旨在实现更精准和高效的初轨确定,以满足当前对空间目标初轨确定的需求;利用LEO,MEO和GEO目标的实测角度数据开展算法测试。介绍了基于动态阈值的距离搜索算法的实现过程,基于数据处理的经验,用动态阈值实现初轨参数质量控制环节的轨道筛选。给出了详细的算法实现流程。利用TLE(Two Line El⁃ements)评估了初轨确定参数误差。基于“烛龙”观测网的中低轨目标和中国科学院长春人造卫星观测站的高轨目标的实测角度数据,开展算法测试。结果表明:LEO,MEO和GEO目标短弧初轨确定成功率分别约为94%,75%和89%,半长轴误差均值分别约为9,12和50 km。该算法适用性强、成功率高、定轨精度高,证明了监测数据的质量。

星载迈克尔逊干涉仪扫描角镜装调工艺研究

针对星载迈克尔逊干涉仪悬臂式扫描角镜组件装调维度多、装调精度高、检测困难等技术难点,提出了一种“向量解析+精密微动调整”方法,通过建立装调及检测基准、将角镜组件简化为空间点向量、采用“先法向后平面”的调整顺序、利用专用精密微动装置等措施,实现了空间多自由度角镜组件的高精度调整,角镜顶点位置对称度装调后达到8μm,优于0.01 mm的设计指标要求,有效提高了装调精度,缩短了装调周期。